# Patent

## Title
Inducible nitric oxide synthase binds, S-nitrosylates, and activates cyclooxygenase-2

## Abstract

Cyclooxygenase (COX2) and inducible nitric oxide synthase (iNOS) are two major inflammatory mediators. Inducible NOS specifically binds to COX2 and S-nitrosylates it, enhancing COX2 catalytic activity. Selectively disrupting iNOS—COX2 binding prevents NO-mediated activation of COX2. The synergistic molecular interaction between two inflammatory systems permits assays for developing anti-inflammatory drugs.

## Background
This application claims the benefit of provisional application Ser. No. 60/675,552 filed Apr. 28, 2005, the disclosure of which is expressly incorporated herein.


The invention was made using funds from the U.S. government, grant numbers DA00266 and DA00074 from NIDA. Therefore, the U.S. government retains certain rights in the invention.


TECHNICAL FIELD OF THE INVENTION
This invention is related to the area of drug screening and therapeutics. In particular, it relates to anti-inflammatory agents.
BACKGROUND OF THE INVENTION
Cyclooxygenase-2 (COX2; prostaglandin H2 synthase) and inducible nitric oxide (NO) synthase (iNOS) are two of the principal inflammatory mediators. (1, 2). Following inflammatory stimuli, these two enzymes, which are inactive under basal conditions, undergo new synthesis, respectively manufacturing large quantities of prostaglandins and NO. Needleman and associates had shown that NOS inhibitors can prevent the formation of prostaglandins (Salvemini et al., PNAS 90:7240, 1993). The simplest interpretation of these findings would be that NO, a free radical, gives rise to even more toxic free radicals such as peroxynitrite and hydroxide free radical, which constitute inflammatory stimuli that would lead to induction of COX2 and formation of prostaglandins.
COX2 inhibitors have attained widespread use as anti-inflammatory agents, though they elicit potentially adverse side effects (1, 3-5), while iNOS inhibitors are not presently employed therapeutically. Inflammatory stimuli elicit new synthesis of iNOS and COX2 proteins with similar time courses suggesting that the two systems may interact (6, 7). Stimulants of iNOS such as bradykinin (8) and lipopolysaccharide (LPS) plus interferon γ (IFNγ), components of endotoxin, also enhance prostaglandin formation (9).
There is a continuing need in the art to develop therapies for reducing disease conditions caused by or exacerbated by inflammation.
SUMMARY OF THE INVENTION
According to one embodiment of the invention a method is provided for screening for substances useful for relieving inflammation. A test substance is contacted with a first protein and a second protein under conditions in which the first protein and the second protein bind to each other. The first protein is selected from the group consisting of mammalian iNOS, a fragment of mammalian iNOS from the N-terminal 10% of iNOS sufficient to bind COX2, and a fusion protein comprising said fragment of mammalian iNOS. The second protein is selected from the group consisting of mammalian COX2, a fragment of mammalian COX2 from the C-terminal 20% of COX2 sufficient to bind iNOS, and a fusion protein comprising said fragment of COX2. The amount of free or bound of said first or said second protein is determined. A test substance is identified as a candidate drug for relieving inflammation if it increases the amount of free first or second protein or decreases the amount of bound first or second protein.
Another aspect of the invention is a method of treating inflammation in a patient. An antibody which binds to amino acid residues 1-114 of mammalian iNOS or amino acid residues 484-604 or 488-604 of mammalian COX2 is administered to the patient. Binding of iNOS to COX2 is thereby inhibited in the patient.
Yet another embodiment of the invention is a method of treating inflammation in a patient. A nucleic acid vector encoding a polypeptide comprising a fragment of human iNOS from the N-terminal 10% of INOS sufficient to bind COX2 or a fragment of human COX2 from the C-terminal 20% of COX2 sufficient to bind iNOS, is administered to the patient. Binding of iNOS to COX2 is thereby inhibited in the patient.
A further aspect of the invention is a method of treating inflammation in a patient. A polypeptide comprising a fragment of human iNOS from the N-terminal 10% of iNOS sufficient to bind COX2 or a fragment of human COX2 from the C-terminal 20% of COX2 sufficient to bind iNOS, is administered to the patient. Binding of iNOS to COX2 is thereby inhibited in the patient.
Also provided by the present invention is a combination therapeutic agent. The combination agent comprises an inhibitor of COX2 and a protein binding inhibitory agent selected from the group consisting of: an antibody which binds to amino acid residues 1-114 of human iNOS or amino acid residues 484-604 of human COX2; a polypeptide comprising a fragment of human iNOS from the N-terminal 10% of iNOS sufficient to bind COX2 or a fragment of human COX2 from the C-terminal 20% of COX2 sufficient to bind iNOS; or a nucleic acid vector encoding a polypeptide comprising a fragment of human iNOS from the N-terminal 10% of iNOS sufficient to bind COX2 or a fragment of human COX2 from the C-terminal 20% of COX2 sufficient to bind iNOS.
These and other embodiments which will be apparent to those of skill in the art upon reading the specification provide the art with methods of identifying potential anti-inflammatory agents and with therapeutic anti-inflammatory agents.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A-1H. COX2 and iNOS bind selectively in vitro and in intact cells. (FIG. 1A) RAW264.7 cells were induced with LPS(2 μg/ml)/IFNγ(100 U/ml). COX2 was immunoprecipitated by anti-COX2 antibodies and probed using anti-COX and anti-iNOS antibodies. (FIG. 1B and FIG. 1C) RAW264.7 cells were induced by LPS/IFNγ with or without an iNOS inhibitor 1400W (100 μM) or COX2 inhibitor SC58125 (100 μM). Cell lysates were subjected to immunoprecipitation with anti-COX2 and anti-iNOS antibodies. (FIG. 1D) The fragments of iNOS denoted in red bound to COX2, while fragments labeled purple did not as determined by co-immunoprecipitation. (FIG. 1E) HEK293T cells transfected with COX2 and GST-fused iNOS fragments were immunoprecipitated with GST conjugated beads. Proteins were detected by the addition of GST•HRP and goat anti-COX2 antibodies. (FIG. 1F) HEK293T cells transfected with COX2 and myc-tagged iNOS fragments were immunoprecipitated with anti-myc antibodies. (FIG. 1G) Generated fragments of COX2 which bind to full length iNOS are labeled in red, while those that do not bind are identified in yellow. (FIG. 1H) HEK293T cells transfected with iNOS and myc-tagged COX2 fragments were immunoprecipitated by anti-myc.
FIG. 2A-2G. S-nitrosylation of COX2 enhances enzyme activity. (FIG. 2A) COX2 expressed in HEK293T cells is S-nitrosylated in the presence of GSNO (100 μM) as determined by biotin switch assay. (FIG. 2B) LPS/IFNγ treatment of RAW264.7 cells elicits S-nitrosylation of COX2 which is subsequently prevented by the iNOS inhibitor 1400W (100 μM). (FIG. 2C) COX2 enzyme activity was measured from the cell lysate of COX2 transfected HEK293T cells in the presence or absence of SNP (200 μM) and ascorbate (ASC, 500 μM). Bars represent the mean±SE of three independent cell cultures performed in triplicate. (* Student's t-test) (FIG. 2D) Transfected COX2-myc is S-nitrosylated in the presence of SNP (200 μM) and reversed by the addition of 500 μM ASC. (FIG. 2E) COX2-myc expressed in HEK293T cells is S-nitrosylated by various concentration of GSNO. The dose-dependence of GSNO-mediated activation of PGE2 (ng/mL) was measured. Data were pooled from at least three independent determinations each in triplicate. (FIG. 2F) Recombinant human COX2 was treated with SNP (1 mM) and COX2 activities were measured. (n=3, ●=CTL, Vmax=81.3±4.8 nmol/min/mg, Km=16.2±2.2 μM; ∘=1 mM SNP, Vmax=132±6.5 nmol/min/mg, Km=17.0±2.0 μM) (FIG. 2G) Recombinant human COX2 was treated with SNP (1 mM) and its turnover rate (kcat) was measured in the presence of various concentration of sucrose. Data was expressed as Kcat-control over Kcat in each viscosity vs. viscosity ratio.
FIG. 3A-3D. Endogenously generated NO enhances COX2 activity. (FIG. 3A) RAW264.7 cells were activated by LPS/IFNγ at various concentrations of 1400W overnight. The dose dependence of 1400W mediated suppression of PGE2 (ng/mL) and nitrite (μM) levels were then measured. Data were pooled from at least three independent determinations each in triplicate. (* Student's t-test) (FIG. 3B) Combinations of L-NAME (500 μM), L-NAME+L-Arg (1 mM) or D-Arg (1 mM), and D-NAME (500 μM) were added to RAW264.7 cells subjected to LPS/IFNγ. PGE2 levels were measured and the data are pooled from three independent experiments performed each in triplicate. (FIG. 3C) PGE2 and nitrite levels were measured from wild type and iNOS knock-out primary peritoneal macrophages treated with or without LPS/IFNγ. (* Student's t-test) (FIG. 3D) S-nitrosylation of COX2 of wild type primary peritoneal macrophages treated with LPS/IFNγ, is abolished in iNOS knock-out cultures.
FIG. 4A-4D. COX2-myc fragment attenuates iNOS binding to COX2 and NO-mediated activation of PGE2 production. RAW264.7 cells transfected with COX2-myc fragments 1-483 and 484-604 were treated with LPS/IFNγ. (FIG. 4A) Cell lysates were immunoprecipitated with rabbit anti-iNOS antibodies and analyzed with mouse anti-iNOS, goat anti-COX2 and mouse anti-myc antibodies. (FIG. 4B) COX2-myc fragment (484-604) decreases S-nitrosylation of COX2 in RAW264.7 cells. (FIG. 4C) RAW264.7 cells were transfected with the fragments and treated with LPS/IFNγ. PGE2 levels were measured and the data are pooled from three independent experiments performed each in triplicate. (* Student's t-test) (FIG. 4D). PGE2 and COX2 fragments were visualized with confocal microscopy using mouse anti-myc and Rabbit anti-PGE2 antibodies. Images of COX2 (red) and PGE2 (green) were superimposed to show co-localization. Nuclei were visualized using Hoechst staining (blue). In FIG. 4D1 arrows point to two RAW264.7 cells, only one of which is transfected with the COX2 fragment 484-604 (red). In FIG. 4D2, the same two cells are analyzed for presence of endogenous PGE2 produced after activation of RAW264.7 cells by LPS/IFNγ treatment. Immunofluorescent staining shows a reduction in the PGE2 expression level in the COX2-myc 484-604 transfected cell compared to the non-transfected cell (FIG. 4D2). This observation contrasts with FIG. 4D4 whose arrows point to a transfected and non-transfected cell of the COX2 fragment 1-483. Unlike FIG. 4D2, FIG. 4D5 does not show a reduction of PGE2 in the transfected cell as compared to the non-transfected cell.
FIG. 5A-5B. (S1) COX2 and iNOS bind in vivo. (FIG. 5A) HEK293T cells transfected with COX2, and iNOS were subjected to immunoprecipitation with anti-myc antibody and analyzed with mouse anti-iNOS and goat anti-COX2 antibodies. (FIG. 5B) Peritoneal macrophages were obtained either 4 or 22 hours after 3% thioglycolate injection. Cell lystes were immunoprecipitated by rabbit anti-iNOS antibody and analyzed with rat anti-COX2 and mouse anti-iNOS antibodies.
FIG. 6A-6B (S2.) GST-tagged iNOS fragments co-immunoprecipitate with COX2 in vitro. (FIG. 6A) GST-tagged iNOS fragments for amino acid residues 1-500 and 1-525 were respectively combined with full length COX2 and pulled down using GST beads. Purified GST was also combined with COX2 as a control. (FIG. 6B) GST-tagged iNOS fragments for amino acid residues 1-500 and 510-1145 were co-immunoprecipitated with COX2 using GST pull down. These results suggest that interaction between iNOS and COX2 is direct binding.
FIG. 7A-7B (S3.) COX2 is S-nitrosylated by NO in vitro and in vivo. (FIG. 7A) COX2 is selectively S-nitrosylated in the presence of additional NO donors DETA-NO (500 μM), SNP (100 μM), and Spermine-NO (100 μM) using the biotin switch assay. (FIG. 7B) S-nitrosylation of COX2 in RAW264.7 cells treated with LPS/IFNγ was S-nitrosylated using fluorometic detection assay, which was abolished by iNOS specific inhibitor, 1400W.
FIG. 8A-8B(S4.) Biotin switch assay is specific for S-nitrosothiol detection. (FIG. 8A) COX2 transfected in HEK293T cells were treated with either GSNO or H2O2 to generate S-nitrosothiol or sulfenic acid, respectively. It has been known that 10 mM arsenite is a reducing reagent specific for sulfenic acid. Biotin switch assay was performed with either 1 mM ascorbate or 10 mM sodium arsenite. Our results show that ascorbate is specific for S-nitrosylated COX2 not for COX2 with sulfenic modification, which was confirmed by reversing it using sodium arsenite. (FIG. 8B) S-nitrosylation of COX2 in RAW264.7 cells treated with LPS/IFNγ was confirmed using biotin switch assay either with ascorbate or sodium arsenite. Ascorbate treatment reversed COX2 modification in RAW264.7 cells treated with LPS/IFNγ but sodium arsenite did not, showing that COX2 in LPS/IFNγ-treated RAW264.7 cells is mostly S-nitrosylated.
FIG. 9A-9B. (S5.) Oxyhemoglobin blocks S-nitrosylation of COX2 by exogenous NO but not by endogenous NO produced by iNOS in activated RAW264.7 cells. (FIG. 9A) HEK293T cells transfected with COX2-myc were treated with 100 μM GSNO for 3 hours with or without oxyhemoglobin and biotin switch assay was performed. Oxyhemoglobin blocked GSNO-mediated S-nitrosylation of COX2. (FIG. 9B) However, oxyhomoglobin did not prevent S-nitrosylation of COX2 in RAW264.7 cells induced by LPS/IFNγ suggesting that a delivery of NO to COX2 is crucial.
FIG. 10A-10B (S6.) Target of S-nitrosylation of COX2 is located in c-terminus (484-604) and mutation of Cysteine526 to Serine prevents NO-mediated activation of COX2. (FIG. 10A) COX2 has 13 cysteines and we mutated all the cysteines to serine, two of which were not expressed. Single mutation of cysteine to serine did not eliminate S-nitrosylation signal by the biotin switch assay (data shown) suggesting that there are more than one cysteine can be S-nitrosylated. Hence, we performed biotin switch assay using COX2 fragments and demonstrated that the target for S-nitrosylation is located in c-terminal region (484-604). (FIG. 10B) We wondered which of the 13 cysteines of COX2 are critical for the S-nitrosylation elicited augmentation of COX2 activity. COS1 cells were transfected with empty vector, wild type, or mutants of COX2-myc. Cells were treated with (red) or without (black) NO donor for 3 h, at which point PGE2 levels were measured. Mutation of C526 to serine (C526S) abolishes stimulation of PGE2 formation by the NO donor SNP, while C561S fails to influence stimulation. The target cysteine which is responsible for NO-mediated COX2 activation is also located in the region of 484-604. We attempted to study COX2 with mutation of the other 11 cysteines, two of which could not be expressed in COS1 cells while the other 9 mutations had no demonstrable catalytic activity even under control conditions (data not shown). We could not eliminate the possibility that there is more than one S-nitrosylation target but identified the target cysteine responsible for NO-mediated activation of COX2.



DETAILED DESCRIPTION OF THE INVENTION
The inventors have found that iNOS binds directly to COX2 without a scaffold protein. Moreover, we found that iNOS binding to COX2 leads to S-nitrosylation and activation of COX2. We further found that the binding of iNOS to COX2 leads to augmented formation of prostaglandins by COX2. Based on these findings, one can screen and develop novel anti-inflammatory drugs by monitoring the ability of candidate drugs to inhibit the binding of iNOS to COX2. Peptide agents that mimic the portions of the two binding partners that interact with each other, can be used to block the activation of COX2 by iNOS. Similarly antibodies which bind to the interacting portions of the binding partners can be use to inhibit inflammation responses.
For screening assays, any molecules comprising the binding domains of COX2 and iNOS can be used. These include full-length COX2 and iNOS polypeptides, fragments comprising the binding domains of the two full-length polypeptides, fusion proteins comprising the binding domains of the two full length polypeptides. As defined experimentally, the binding domains are within the N-terminal 10% of iNOS and the C-terminal 20% of COX2, as these residues have been found to be sufficient to mediate binding. Fragments contain less than the full-length proteins, typically less than 50%, more typically less than 25%. Fragments of COX2 do not contain the membrane binding domain while fragments of iNOS do not contain the reductase or CaM (calmodulin) domains. Any of these forms of iNOS protein can be used to bind to any form of the COX2 protein. Binding can be determined by measuring one or both of the binding partners, either in the bound or the free form. Increase in the bound form or decrease in the free form indicates binding of the two partners. Conversely, added test compounds which inhibit binding can be characterized by the decrease in bound form or increase in free form of one or both of the binding partners.
For screening assays, the test compound is preferably a small molecule that binds to and occupies, for example, the binding site of the COX2 or iNOS polypeptide, such that normal binding of the two binding partners is prevented. Examples of such small molecules include, but are not limited to, small peptides or peptide-like molecules. Any small organic molecule can be used. Libraries of natural or synthetic compounds can be screened. Small molecules which mimic three dimensional structure of peptides can be designed.
In screening assays, either the COX2 or iNOS polypeptide can comprise a detectable label, such as a fluorescent, radioisotopic, chemiluminescent, or enzymatic label, such as horseradish peroxidase, alkaline phosphatase, or luciferase. Detection of bound COX2 or iNOS polypeptide can then be accomplished, for example, by direct counting of radioemmission, by scintillation counting, or by determining conversion of an appropriate substrate to a detectable product.
Alternatively, inhibition of binding of a human COX2 to an iNOS polypeptide by a test compound can be determined without labeling the interactants. For example, a microphysiometer can be used to detect binding of a human COX2 and iNOS polypeptide. A microphysiometer (e.g., CytosensorTM) is an analytical instrument that measures the rate at which a cell acidifies its environment using a light-addressable potentiometric sensor (LAPS). Changes in this acidification rate can be used as an indicator of the interaction between a human COX2 or iNOS polypeptide (McConnell et al., Science 257, 1906-1912, 1992).
Determining the ability of a mammalian COX2 and an iNOS polypeptide to bind also can be accomplished using a technology such as real-time Bimolecular Interaction Analysis (BIA) (Sjolander & Urbaniczky, Anal. Chem. 63, 2338-2345, 1991,and Szabo et al., Curr. Opin. Struct. Biol. 5, 699-705, 1995). BIA is a technology for studying biospecific interactions in real time, without labeling any of the interactants (e.g., BIAcoreTM). Changes in the optical phenomenon surface plasmon resonance (SPR) can be used as an indication of real-time reactions between biological molecules.
In yet another aspect of the invention, a mammalian COX2 or iNOS polypeptide can be used in a two-hybrid assay or three-hybrid assay (see, e.g., U.S. Pat. No. 5,283,317; Zervos et al., Cell 72, 223-232, 1993; Madura et al., J. Biol. Chem. 268, 12046-12054, 1993; Bartel et al., BioTechniques 14, 920-924, 1993; Iwabuchi et al., Oncogene 8, 1693-1696, 1993; and Brent W094/10300), to identify agents which inhibit binding of the COX2 and iNOS polypeptides and thereby modulate COX2 activity.
The two-hybrid system is based on the modular nature of most transcription factors, which consist of separable DNA-binding and activation domains. Briefly, the assay utilizes two different DNA constructs. For example, in one construct, polynucleotide encoding a mammalian COX2 or iNOS polypeptide can be fused to a polynucleotide encoding the DNA binding domain of a known transcription factor (e.g., GAL-4, particularly yeast GAL-4). In the other construct a DNA sequence that encodes the other of COX2 or iNOS can be fused to a polynucleotide that codes for the activation domain of the known transcription factor. When the fusion proteins are able to interact in vivo to form a protein-dependent complex, the DNA-binding and activation domains of the transcription factor are brought into close proximity. This proximity allows transcription of a reporter gene (e.g., LacZ, particularly E. coli LacZ), which is operably linked to a transcriptional regulatory site responsive to the transcription factor. Contacting such cells (typically but not limited to yeast cells) with test substances will permit an assay for binding inhibition. Expression or inhibition of expression of the reporter gene can be detected, thus identifying an agent which inhibits the interaction of COX2 and iNOS polypeptide.
It may be desirable to immobilize either the COX2 or iNOS polypeptide or the test compound to facilitate separation of bound from unbound forms of one or both of the interactants, as well as to accommodate automation of the assay. Thus, either the COX2 or iNOS polypeptide or the test compound can be bound to a solid support. Suitable solid supports include, but are not limited to, glass or plastic slides, tissue culture plates, microtiter wells, tubes, silicon chips, or particles such as beads (including, but not limited to, latex, polystyrene, or glass beads). Any method known in the art can be used to attach the polypeptide or test compound to a solid support, including use of covalent and non-covalent linkages, passive absorption, or pairs of binding moieties attached respectively to the polypeptide or test compound and the solid support. Test compounds can be bound to the solid support in an array, so that the location of individual test compounds can be tracked. Binding of a test compound to a mammalian COX2 or iNOS polypeptide can be accomplished in any vessel suitable for containing the reactants. Examples of such vessels include microtiter plates, test tubes, and microcentrifuge tubes.
In one embodiment, the iNOS polypeptide is a fusion protein comprising a domain that allows the iNOS polypeptide to be bound to a solid support. For example, glutathione-S-transferase fusion proteins can be adsorbed onto glutathione sepharose beads (Sigma Chemical, St. Louis, Mo.) or glutathione derivatized microtiter plates, which are then combined with the test compound or the test compound and the non-adsorbed COX2 polypeptide; the mixture is then incubated under conditions conducive to complex formation (e.g., at physiological conditions for salt and pH). Following incubation, the beads or microtiter plate wells are washed to remove any unbound components. Binding of the interactants can be determined either directly or indirectly, as described above. Alternatively, the complexes can be dissociated from the solid support before binding is determined. In another alternative, the COX2 polypeptide is a fusion protein.
Other techniques for immobilizing proteins on a solid support also can be used in the screening assays of the invention. For example, either an iNOS or COX2 polypeptide or a test compound can be immobilized utilizing conjugation of biotin and streptavidin. Biotinylated iNOS or COX2 polypeptides test compounds can be prepared from biotin-NHS(N-hydroxysuccinimide) using techniques well known in the art (e.g., biotinylation kit, Pierce Chemicals, Rockford, Ill.) and immobilized in the wells of streptavidin-coated 96 well plates (Pierce Chemical). Alternatively, antibodies which specifically bind to an iNOS or COX2 polypeptide, or a test compound, but which do not interfere with a desired binding site, can be derivatized to the wells of the plate. Unbound target or protein can be trapped in the wells by antibody conjugation.
Methods for detecting such complexes, in addition to those described above for the GST-immobilized complexes, include immunodetection of complexes using antibodies which specifically bind to the iNOS or COX2 polypeptide or test compound, enzyme-linked assays which rely on detecting an activity of the iNOS or COX2 polypeptide, and SDS gel electrophoresis under non-reducing conditions.
Screening for test compounds which bind to an iNOS or COX2 polypeptide also can be carried out in an intact cell, in whole animals, or cell-free systems. Any cell which comprises an iNOS or COX2 polypeptide can be used in a cell-based assay system. An iNOS or COX2 polynucleotide can be naturally occurring in the cell or can be introduced using techniques such as those described above. Binding of the test compound to an iNOS or COX2 polypeptide is determined as described above.
Once a test compound has been identified that inhibits the binding of iNOS to COX2, whether in cells, in whole animals, or in a cell-free system, it can be further tested to determine its effect on inflammation. For example, it can be tested for its effect on prostaglandin synthesis or for its effect in any of several animal models of inflammation known in the art. Exemplary animal models include the following mouse strains, without limitation. The mouse strain CD1-Tg(Gadd45β-luc)-Xen (Gadd45β-luc LPTA®) animal model is useful in studying apoptosis, Gadd45β gene regulation, MAP kinase- and NF-κB mediated signaling pathways, and the treatment of inflammatory diseases and cancer. The mouse strain FVB/N-Tg(iNos-luc)Xen (iNos-luc LPTA®) animal model is useful in studying sepsis, arthritis, and anti-inflammatory compounds. The mouse strain FVB/N-Tg(Epx-luc)-Xen (Epx-luc LPTA®) animal model is useful in studying changes in eosinophil production resulting from parasite infection and asthma, and may be used as donor animals for studying bone marrow transplantation. The mouse strain BALB/C-Tg(Saa1-luc)-Xen (Saa1-luc LPTA®) animal model is useful in studying sepsis, arthritis, amyloidosis, and A-SAA-mediated disorders. The mouse strain CD1-Tg(IL2-luc)-Xen (IL2-luc LPTA®) animal model is useful in studying IL-2 gene regulation, inflammatory diseases, and cancer. The mouse strain BALB/C-Tg(Tnfα-luc)-Xen (Tnfα-luc LPTA®) animal model is useful in studying sepsis, arthritis, inflammatory bowel disease, apoptosis, TNFα gene regulation, and the treatment of TNFα-mediated inflammatory diseases. The mouse strain BALB/C-Tg(NFκB-RE-luc)-Xen (NFκB-RE-luc LPTA® animal model is useful in studying sepsis, arthritis, inflammatory bowel disease, apoptosis, tumor development, NFκB gene regulation, and the treatment of inflammatory diseases and cancer. The mouse strain DBA/1,BALB/C-Tg (NFκB-RE-luc [Oslo])-Xen (NFκB-luc (Oslo) LPTA®) animal model is useful in studying sepsis, arthritis, inflammatory bowel disease, apoptosis, tumor development, NFκB gene regulation, and the treatment of inflammatory diseases and cancer. The mouse strain BALB/C-Tg(IkBa-luc)-Xen (IκBα-luc LPTA®) animal model is useful in studying sepsis, arthritis, inflammatory bowel disease, apoptosis, tumor development, transcriptional regulation of IκBα gene and other genes responsive to NFκB, and the treatment of inflammatory diseases and cancer. Any animal model of inflammation can be used.
COX2 and iNOS for use in any of the methods or compositions of the invention can be from any species, particularly from mammals, such as rat, mouse, rabbit, dog, cat, and most particularly from humans. These proteins are well known in the art and a version of these proteins from any individual can be used even though the version of the protein from that individual may vary slightly from that which is documented in a protein sequence database. Exemplary sequences which can be used are those which are documented at GenBank as P35228 and P35354. Other COX2 sequences which can be used include those from P. troglodytes, C. familiaris, M musculus, R. norvegicus, and G. gallus, horse and sheep. Exemplary sequences include AAH52900 (mouse), NP—000954 (human), NP—058928 (Rattus norvegicus), P79208 (sheep), O62698 (bovine), O19183 (horse), and NP—001003354 (Canis familiaris). Other iNOS sequences which can be used include those from C. familiaris, M. musculus, R. norvegicus, and G. gallus. Exemplary sequences include NP—001003186, NP—035057, and NP—990292, respectively. All referenced protein and/or gene sequences are incorporated by reference herein as they exist on Apr. 28, 2006.
Treatment modalities based on the discovery of binding of iNOS and COX2 include administration of a polypeptide, administration of a nucleic acid encoding a polypeptide, and administration of an antibody. The nucleic acid can be a naturally occurring genomic or cDNA sequence or can be any sequence which encodes the desired protein. Each of these is designed to inhibit binding of the two binding partners. Both the polypeptides and the antibodies bind to the portion of the binding partners that interact, thereby inhibiting the interaction. Inhibition of the interaction inhibits the iNOS-mediated S-nitrosylation of COX2 which activates COX2. Polypeptides delivered directly or indirectly via nucleic acids can be fragments of fusion proteins comprising a binding domain or sufficient amounts of a binding domain to bind and interferen with COX2/iNOS binding.
Inflammation which can be treated according to the present invention includes any which is exacerbated by prostaglandin synthesis. These include, without limitation, chronic inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease, systemic lupus erythematosus, multiple sclerosis, type 1 diabetes, rheumatoid arthritis, chronic obstructive pulmonary disease (COPD), asthma, allergic rhinitis, cardiovascular disease, psoriasis. Inflammatory diseases of the brain include abscess, meningitis, encephalitis and vasculitis. Any of these diseases can be treated according to the methods of the present invention.
Antibodies for use in the present invention can be monoclonal or polyclonal. They can gain their specificity by purification or by limitation of the inducing immunogen. The antibodies will bind to the N-terminal 10% of iNOS or to the C-terminal 20% of COX2. Administration of antibodies can be by any means known in the art, but typically the antibodies are administered by injection, such as intrathecal, intraventricular, intravascular (intravenous or intraarterial), subcutaneous, intramuscular, intraperitoneal, intrapleural, by perfusion through a regional catheter, or by direct intralesional injection. When administering antibodies by injection, the administration may be by continuous infusion or by single or multiple boluses. Polypeptides and polynucleotides can be administered by similar means.
In general, the dosage of administered antibodies will vary depending upon such factors as the patient's age, weight, height, sex, general medical condition, and previous medical history. Preferably, a saturating dose of antibody is administered to a patient. Antibodies can be administered as whole IgG, F(ab′)2, F(ab)2, Fab′, or Fab.
Typically, it is desirable to provide the recipient with a dosage of antibody that is in the range of from about 50 to 500 milligrams of antibody, although a lower or higher dosage also may be administered as circumstances dictate. Effective in vivo dosages of an antibody are in the range of about 5 mg to about 50 mg/kg, about 50 mg to about 5 mg/kg, about 100 mg to about 500 mg/kg of patient body weight, and about 200 to about 250 mg/kg of patient body weight. High doses of antibody may cause anaphylaxis due to complement activation with endogenous antibodies. This side effect, however, can be prevented by administration of oligosaccharides that bind with endogenous antibodies, as detailed below.
The antibodies of the present invention can be formulated according to known methods to prepare pharmaceutically useful compositions, whereby antibodies are combined in a mixture with a pharmaceutically acceptable carrier. A composition is said to be a “pharmaceutically acceptable carrier” if its administration can be tolerated by a recipient patient. Sterile phosphate-buffered saline is one example of a pharmaceutically acceptable carrier. Other suitable carriers are well-known to those in the art. See, for example, Remington's Pharmaceutical Sciences, 19th Ed. (Mack Publishing Co. 1995), and Gilman's The Pharmacological Basis of Therapeutics, 7th Ed. (MacMillan Publishing Co. 1985).
For purposes of therapy, an antibody and a pharmaceutically acceptable carrier are administered to a patient in a therapeutically effective amount. A combination of an antibody and a pharmaceutically acceptable carrier is said to be administered in a “therapeutically effective amount” if the amount administered is physiologically significant. An agent is physiologically significant if its presence results in a detectable change in the physiology of a recipient patient. In the present context, an agent is physiologically significant if its presence results in the modulation of an immune response or malignant T cell malignancy growth.
Polynucleotides can be administered in any vector, whether viral or non-viral designed for delivery and expression of inserted nucleic acid sequences. Polynucleotides and/or proteins can be further formulated in liposomes or cationic vesicles or particles for added stability. Viral vectors include adenovirus vectors, adeno-associated virus vectors, retrovirus vectors, lentivirus vectors. Non-viral vectors include plasmid vectors. Exemplary types of viruses include HSV (herpes simplex virus), AAV (adeno associated virus), HIV (human immunodeficiency virus), BIV (bovine immunodeficiency virus), and MLV (murine leukemia virus). Nucleic acids can be administered in any desired format that provides sufficiently efficient delivery levels, including in virus particles, in liposomes, in nanoparticles, and complexed to polymers.
Inducible NOS and COX2 physiologically bind, bringing NO in proximity with COX2, facilitating its S-nitrosylation and activation. Earlier findings that NOS inhibition decreases prostaglandin formation suggested a relationship between the two systems(10, 26), but might have reflected a generally diminished stressful stimulus to the COX2 system rather than a direct intermolecular linkage. Because NO is a labile molecule which can be rapidly inactivated within cells by the high physiologic concentrations of glutathione or other reducing agents, it is possible that many of NO's physiologic actions will require delivery of NO to its targets(15). Other instances of NO delivery have primarily involved nNOS acting via scaffold proteins. Thus, a scaffold protein CAPON links nNOS to Dexras1 and provides NO to S-nitrosylate Dexras1 and act as its guanine nucleotide exchange factor(27). Similarly the scaffold protein PSD95 links nNOS to N-Methyl-D-aspartate (NMDA) receptors where NO S-nitrosylates and inactivates NMDA receptors(28). In contrast to these examples, iNOS binds directly to COX2 with no intervening scaffold protein. A similar direct delivery of a regulatory metabolite via protein-protein interactions involves the binding of glyceraldehyde-3-phosphate dehydrogenase(GAPDH) to inositol 1,4,5-trisphosphate (IP3) receptors with NADH formed by GAPDH selectively augmenting calcium release activity of IP3 receptors(29).
The molecular synergism between iNOS and COX2 may represent a major mechanism of inflammatory responses. Inhibitors of iNOS do relieve fever and pain, classically associated with prostaglandin production which may reflect the iNOS—COX2 interaction, though such actions are sufficiently indirect that one cannot draw strong conclusions(30, 31).
Our findings have therapeutic relevance. Thus drugs which block the iNOS—COX2 interaction might have anti-inflammatory action. Moreover, such agents might synergize with COX2 inhibitor drugs permitting lower doses with less side-effects. While it has been speculated that adverse cardiovascular effects of COX2 inhibitors reflect inhibition of PGE2 formation, this has not been directly established so that other actions of the drugs might be involved(32).
The above disclosure generally describes the present invention. All references disclosed herein are expressly incorporated by reference. A more complete understanding can be obtained by reference to the following specific examples which are provided herein for purposes of illustration only, and are not intended to limit the scope of the invention.
EXAMPLE 1
Materials and Methods
Materials and Methods
Cells. HEK293T, COS1 and RAW 264.7 murine macrophages were obtained from the American Type Culture Collection (Manassas, Va.). They were grown in a humid atmosphere of 95% air and 5% CO2 at 37° C. in Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum, L-glutamine (300 ug/ml), penicillin (100 U/ml), and streptomycin (100 μg/ml).
Preparation of peritoneal macrophages. Peritoneal macrophages were obtained following intraperitoneal injection of 1.5 ml of 3% sterile thioglycolate medium. After 4 days mice were sacrificed and macrophages were harvested as described(1).
Plasmid Constructions. Full length human cyclooxygenase2-encoding gene (gene bank sequence NM—000963) was purchased from ATCC in pCMV•SPORT6 vector. The sequence was amplified by PCR using primers harboring Sal1/Not1 restriction sites and cloned into the pCMV-Myc vector (Clontech, Palo Alto, Calif.). The murine inducible nitric oxide synthase (accession number NM—010927) cloned into the pcDNA3.1+vector (Invitrogen, Carlsbad, Calif.).
Immunoprecipitation. For co-immunoprecipitation experiments, 1×106 HEK293T cells were plated in 10 cm2 culture dishes (Invitrogen, Carlsbad, Calif.). Cells were transfected with 4 μg pCMV•Myc-COX2, 2 ug pcDNA3.1-iNOS, or empty pCMV•Myc vector using LipofectAMINE PLUS (Invitrogen, Carlsbad, Calif.) according to the manufacturer's protocol. After 48 h, cells were harvested and lysed in ice-cold lysis buffer (100 mM Tris pH 7.4, 150 mM NaCl, 10% glycerol, 1% Triton X-100,and complete protease inhibitors). The supernatants (800 ul) from the HEKT cell extracts were pre-cleaned for non-specific binding with 50 ul protein A-Sepharose, then mixed overnight at 4° C. with 2 ug/ml anti-Myc antibody (Roche, Alameda, Calif.). After the addition of 80 μl of protein A-Sepharose, the immunoprecipitates were mixed for another 1 h at 4° C. The mixture was washed three times with the buffer described above and the pellet boiled in 10 ul SDS-loading dye, which was subjected to 6% SDS PAGE gel run in MOPS buffer. The proteins were then transferred to nitrocellulose membrane. The bands were visualized by ECL reagent (Pierce, Milwaukee, Wis.) as described by the manufacturer.
Site Directed Mutagenesis. The QuickChange site-directed mutagenesis system (Stratagene, La Jolla, Calif.) was employed per manufacturer's instructions to alter the thirteen cysteine residues in COX2 to serine. Each mutant was verified via automated sequencing by the Hopkins Core Facility.
S-nitrosylation assay. Cells were homogenized by 26G needle in HEN (250 mM Hepes-NaOH pH 7.7, 1 mM EDTA, 0.1 mM Neocuproine) buffer and then centrifuged at 1000 g for 10 min at 4° C. Cells lysates (240 μg) was added 4 vol of blocking buffer (9 vol of HEN buffer plus 1 vol 25% SDS, adjusted to 20 mM MMTS with a 2 M stock prepared in dimethylformamide (DMF)) at 50° C. for 20 min with frequent vortexing. The MMTS was then removed by desalting three times with the MicroBioSpin6 column (Bio-Rad, Hercules, Calif.) pre-equilibrated in HEN buffer. To the eluate was added biotin-HPDP prepared fresh as a 4 mM stock in DMSO from a 50 mM stock suspension in DMF. Sodium ascorbate was added to a final concentration of 1 mM. After incubation for 1 h at 25° C., biotinylated proteins were precipitated by streptavidin-agarose beads. The streptavidin-agarose was then pelleted and washed 5 times using HENS buffer. The biotinylated proteins were eluted by SDS-PAGE sample buffer and subjected to Western-blot analysis.
Fluorometric detection of S-nitrosothiols. The methods were modified according to Cook et al.(2) RAW264.7 cells were treated with LPS/IFNγ for overnight and COX2 was immunoprecipitated by donkey anti-rat COX2 antibodies. After that the samples were reacted with 100 μM 2,3-diaminonaphthalene (DAN) in the presence of 100 μM of HgCl2 and incubated in darkness for 30 min at room temperature. The generated fluorescent compound 2,3-napththyltrazole (NAT) was then measured at an excitation wavelength of 375 nm and an emission wavelength of 450 nm.
COX2 enzymatic assay. Recombinant human COX2 was obtained from Cayman Biochemical Inc. COX2 was treated with NO donor, SNP for 30 min and was then passed through a spin column (Bio-Rad, Hercules, Calif.) to remove excess NO. COX2 enzymatic activity was measured with a COX assay kit (Cayman Biochemical Inc, Ann Arbor, Mich.) according to the manufacturer's instructions.
Measurement of PGE2. Cells were washed with worm PBS (×2) and incubated in the phenol free Dulbecco's modified Eagle's medium supplemented with 20 μM arachidonic acid and 3% albumin for 20 min. Media was collected and PGE2 production was measured with a PGE2 ELISA kit from Assay Design (Ann Arbor, Mich.) according to the manufacturer's instructions.
Immunohistochemistry. RAW264.7 cells were transfected with deletion constructs of COX2. Cells were fixed in 4% paraformaldehyde in PBS for 5 min, permeablized in 0.1% Triton X-100 for 10 s, and then rinsed twice in PBS. Coverslips were then blocked in 10% goat serum at room temperature for 1 h and incubated with PGE2 (Cayman Biochemical Inc, Ann Arbor, Mich.) and myc antibodies for 24 hr at 4° C. Rhodamine or fluorescein-conjugated secondary antibodies (Jackson Immunochemicals, West Grove, Pa.) were then added at 10 μg/ml for 1 hr at room temperature as indicated. Coverslips were mounted in ProLong (Molecular Probes, Eugene, Oreg.). Confocal microscopy, in which the immunofluorescent staining is superimposed on phase contrast images, employed a Noran OZ (Noran Instruments, Middleton, Wis.) confocal laser-scanning system, fitted to an Olympus IX-50 fluorescence microscope.
Viscosity studies. Viscosity experiments were performed with sucrose (0-31% w/w) as described previously (3, 4).

    1. Nunoshiba, T., deRojas-Walker, T., Wishnok, J. S., Tannenbaum, S. R. & Demple, B. Activation by nitric oxide of an oxidative-stress response that defends Escherichia coli against activated macrophages. Proc Natl Acad Sci USA 90, 9993-7 (1993).
    2. Cook, J. A., Kim, S. Y., Teague, D., Krishna, M. C., Pacelli, R., Mitchell, J. B., Vodovotz, Y., Nims, R. W., Christodoulou, D., Miles, A. M., Grisham, M. B., & Wink, D. A. Convenient colorimetric and fluorometric assays for S-nitrosothiols. Anal Biochem 238, 150-158 (1996).
    3. Cole, P. A., Burn, P., Takacs, B., Walsh, C. T. Evaluation of the catalytic mechanism of recombinant human Csk (C-terminal Src kinase) using nucleotide analogs and viscosity effects. J Bio Chem 269, 30880-30887 (1994).
    4. Brouwer, A. C., and Kirsch, J. F. Investigation of diffusion-limited rates of chymotrypsin reactions by viscosity variation. Biochem 21, 1302-1307 (1982)


EXAMPLE 2
iNOS and COX2 Bind in Vivo in Cells and Whole Animals
For initial studies we employed RAW264.7 cells, a macrophage cell line in which LPS and IFNγ massively activate both iNOS and COX2. In LPS/IFNγ treated cells immunoprecipitation with COX2 antibodies leads to co-precipitation of iNOS (FIG. 1A). Coprecipitation of COX2 and iNOS is also evident in HEK293T cells transfected with both proteins (FIG. 5A).
To examine interactions between the two enzymes in intact organisms, we injected mice with thioglycollate, an inflammatory stimulus which typically produces peritonitis or pleuritis, and observed coprecipitation of iNOS and COX2 (FIG. 5B).
To determine whether catalytic activity of the enzymes influences their binding interactions, we co-precipitated the two proteins with iNOS antibodies or COX2 antibodies and examined the effect of the iNOS-selective inhibitor 1400W (FIG. 1B) or the COX2 selective inhibitor SC58125 (FIG. 1C). Co-precipitation of iNOS and COX2 is unaffected by either iNOS or COX2 inhibitors. The binding of iNOS and COX2 is selective, as we do not detect immunoprecipitation of COX1 with iNOS (data not shown).
EXAMPLE 3
Mapping the Binding Sites on the Two Interacting Proteins
To map the binding sites, we employed selective deletions of iNOS (FIG. 1D-F) and COX2 (FIG. 1G and H) sequences. Amino acids 1-114 appear to be the minimal portion of iNOS mediating binding, while amino acids 484-604 of COX2 are required. The binding area of iNOS occurs within the oxygenase domain, while the C-terminal portion of COX2 that mediates binding includes a COX2 domain which does not exist in COX1.
EXAMPLE 4
NO Donors Elicit S-nitrosylation of COX2
The two major mechanisms whereby NO influences its targets are stimulation of guanylyl cyclase by direct binding of NO to iron in heme at the active site of guanylyl cyclase(11, 12) or S-nitrosylation of protein targets on appropriate cysteines(13-15). Since COX2 possesses heme at its active site(16), this would be a potential target. However, NO binding to heme in COX does not alter its activity(17).
COX2 also contains 13 cysteines whose roles are not fully understood(18, 19). Hence, we explored the possibility of S-nitrosylation of COX-2 by NO, examining multiple NO donors including nitrosoglutathione (GSNO) (FIG. 2A), sodium nitroprusside (SNP), spermine-NO and DETA-NONOate (FIG. 7A). Utilizing the biotin switch method(20), we demonstrate that all four NO donors elicit S-nitrosylation of COX2 in HEK293T cells transfected with COX2-myc (FIG. 2A).
We wondered whether physiological induction of NO formation leads to S-nitrosylation of COX2. In RAW264.7 cells treated with LPS/IFNγ we observe S-nitrosylation of COX2 which is prevented by the iNOS specific inhibitor 1400W using the biotin switch assay (FIG. 2B) as well as the fluorometric method (FIG. 7B). To ensure specificity of the biotin switch method, we have observed that H2O2 does not elicit S-nitrosylation (FIG. 8A). We ruled out the possibility that sulfenic acid modification is detected by the biotin switch assay by demonstrating that arsenite, which reverses sulfenic acid modifications but not S-nitrosylation, fails to provide the biotin switch signal afforded by ascorbate utilizing GSNO with purified COX2 or LPS/IFNγ treatment of RAW 264.7 cells (FIG. 8B).
As NO is freely diffusible, in some instances there may be no need to deliver NO directly to targets, as some actions of NO are prevented by hemoglobin, which can sequester freely diffusible NO(21). We examined the effects of hemoglobin on S-nitrosylation of COX2 under varying conditions. In HEK293T cells transfected with COX2,hemoglobin prevents the S-nitrosylation elicited by GSNO (FIG. 9A) whereas it fails to alter S-nitrosylation of COX2 in RAW264.7 cells activated by LPS/IFNγ (FIG. 9B). Thus in the more physiologic macrophage cell line, the S-nitrosylation of COX2 generated by an inflammatory stimulus does not appear to be elicited by freely diffusible NO.
EXAMPLE 5
S-nitrosylation of COX2 Activates Enzyme Activity
To determine whether S-nitrosylation of COX2 alters enzyme activity, we examined COX2 enzyme activity in HEK293T cells transfected with COX2-myc. The NO donor SNP, added to cell lysates, elicits a substantial augmentation of COX2 activity, which reflects S-nitrosylation, as ascorbic acid, which reverses S-nitrosylation(20, 22), prevents the increase (FIG. 2C and D).
The reversal by ascorbate of COX2 activation by NO donors is not merely a reflection of ascorbate influences on enzymes substrates or intermediate products, as ascorbate fails to affect COX2 activity in preparations not treated by SNP. A relationship of S-nitrosylation and COX2 activation is further supported by the closely similar concentration-response relationship between the effects of the NO donor GSNO on S-nitrosylation and on COX2 activity (FIG. 2E).
NO activates COX2 by increasing its apparent Vmax without changing its Km (FIG. 2E). The higher concentration of SNP required to activate COX2 in vitro compared to intact cells accords with earlier studies showing greater potency of NO donors in intact cells(23, 24). To ascertain the kinetic basis for NO activation of COX2,we conducted enzyme assays with increasing concentrations of sucrose to augment viscosity and slow down enzyme kinetics (FIG. 2G). As expected, with increasing viscosity, the ratio of control enzyme activity to the activity in more viscous solutions increases. This increase is diminished in SNP samples consistent with SNP accelerating the release of product from the enzyme.
EXAMPLE 6
Identification of Cysteine Residue(s) Nitrosylated
We wondered which of the 13 cysteines of COX2 are critical for the augmentation of COX2 activity elicited by S-nitrosylation. In RAW 264.7 cells transfected with the N-terminal 483 amino acids or the C-terminal 120 amino acids of COX2, LPS/IFNγ treatment leads to S-nitrosylation of the C-terminal fragment (which contains 3 cysteines) but not the N-terminal fragment (FIG. 10A). To ascertain which of these 3 cysteines is responsible for augmented COX2 activity we mutated each of them to serine. The C526S mutation prevents activation of COX2 activity by the NO donor SNP, while the C561S mutation does not (FIG. 10B). The C555S mutation abolishes enzyme activity so the effects of NO stimulation cannot be assessed. Individual mutation of the 13 cysteines in COX2 does not detectably diminish total S-nitrosylation of the enzyme (data not shown), which suggests that multiple cysteines can be S-nitrosylated but only C526 is responsible for enzyme activation by NO.
EXAMPLE 7
The Influence of NO on PGE2 Formation
To clarify the influence of NO on PGE2 formation in a more physiologic preparation, we employed RAW264.7 cells. The formation of PGE2 in response to LPS/IFNγ is inhibited by the iNOS inhibitor 1400W with 50% reduction of PGE2 formation at drug concentrations which provide 50% inhibition of iNOS activity (FIG. 3A). Specificity of the NO association is evident by inhibition of PGE2 formation with the active L-isomer of the NOS inhibitor nitro-argininemethylester (L-NAME) but not by D-NAME; the effects of L-NAME are reversed by added L-arginine (FIG. 3B). Thus, about 50% of induced COX2 activity is determined by S-nitrosylation.
As RAW264.7 cells are a continuous macrophage cell line which may not behave the same as macrophages in intact organisms, we also tested peritoneal macrophages obtained from iNOS knockout mice. PGE2 formation from macrophages of LPS/IFNγ-treated mice is profoundly reduced in the iNOS knockout mice in parallel with a similar reduction in nitrite formation by the macrophages (FIG. 3C) and a decrease in S-nitrosylated COX2 (FIG. 3D). These observations concur with findings of decreased urinary PGE2 in iNOS knockout mice(25).
EXAMPLE 8
Fragment of COX2 (Amino Acids 484-604) Abolishes the Co-precipitation of iNOS and COX2
We hypothesized that the augmentation of PGE2 formation by iNOS activation reflects binding of iNOS to COX2 to deliver NO in appropriate proximity for S-nitrosylation. To explore this possibility we utilized dominant-negative constructs to block iNOS—COX2 binding using the fragment of COX2,amino acids 484-604,which binds iNOS (FIG. 4A). Transfection of 484-604 into RAW264.7 cells abolishes the co-precipitation of iNOS and COX2 and is associated with precipitation of 484-604 together with iNOS (FIG. 4A). Moreover, this interference of binding between COX2 and iNOS by 484-604 decreases S-nitrosylation of COX2 in RAW264.7 cells (FIG. 4B). The dominant-negative transfection also reduces PGE2 formation by more than 50%, whereas transfection of a fragment comprising amino acids 1-483, which does not bind iNOS, fails to influence PGE2 formation (FIGS. 4C and D).
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## Claims

1. A method of treating inflammation in a patient, comprising:
administering to the patient a polypeptide consisting of a fragment of human COX2 from the C-terminal 20% of COX2 sufficient to bind iNOS, wherein the fragment comprises a domain of human COX2 which is not present in human COX1, whereby binding of iNOS to COX2 is inhibited in the patient.

2. The method of claim 1 wherein the polypeptide consists of amino acid residues 484-604 of COX2.