bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subtype‐specific regulation of the expression and function of muscarinic acetylcholine receptors in embryonic chicken retinal cells
Authors: Goin Juan C. , Nathanson Neil M. 
Published: March 2003

AbstractWe examined the effect of long‐term agonist exposure on muscarinic acetylcholine receptor expression and function in embryonic chicken retinal cells. Long‐term carbachol exposure induced a time‐ and concentration‐dependent decrease in M2, M3 and M4 muscarinic receptor numbers. Kinetic analyses revealed a first‐order process with similar rate constants for all three subtypes. Both the maximal decrease and the agonist potency for regulation of M3 were significantly higher than those for M2 and M4. Upon agonist removal, M2 and M4 numbers returned to control values, but M3 recovery after 24 h was no higher than 40%. Agonist treatment did not alter the levels of receptor mRNAs. Receptor inactivation with a covalent alkylating antagonist demonstrated that the partial M3 protein recovery was not due to a decreased intrinsic basal rate of synthesis, suggesting that it is induced by agonist treatment. Prolonged carbachol exposure induced concomitant decreases in muscarinic‐mediated inhibition of cyclic AMP accumulation which were completely reversed after agonist removal. Sustained receptor activation also promoted significant decreases in muscarinic receptor‐stimulated phosphoinositide turnover, which were only partially reversed after agonist removal. These data demonstrate subtype‐specific regulation of the expression and function of muscarinic receptors in the retina.
Antipsychotic drug treatment induces differential gene expression in the rat cortex
Authors: Kontkanen Outi , Törönen Petri , Lakso Merja , Wong Garry , Castrén Eero 
Published: March 2003

AbstractAntipsychotic drug treatment is known to modulate gene expression in experimental animals. In this study, candidate target genes for antipsychotic drug action were searched using microarrays after acute clozapine treatment (1, 6 and 24 h) in the rat prefrontal cortex. Microarray data clustering with a self‐organizing map algorithm revealed differential expression of genes involved in presynaptic function following acute clozapine treatment. The differential expression of 35 genes most profoundly regulated in expression arrays was further examined using in situ hybridization following acute clozapine, and chronic clozapine and haloperidol treatments. Acute administration of clozapine regulated the expression of chromogranin A, synaptotagmin V and calcineurin A mRNAs in the cortex. Chronic clozapine treatment induced differential cortical expression of chromogranin A, son of sevenless (SoS) and Sec‐1. Chronic treatment with haloperidol regulated the mRNA expression of inhibitor of DNA‐binding 2 (ID‐2) and Rab‐12. Furthermore, the expression of visinin‐like proteins‐1, ‐2 and ‐3 was regulated by chronic drug treatments in various brain regions. Our data suggest that acute and chronic treatments with haloperidol and clozapine modulate the expression of genes involved in synaptic function and in regulation of intracellular Ca2+ in cortex.
CD44 deficiency in mice protects brain from cerebral ischemia injury
Authors: Wang Xinkang , Xu Lin , Wang Hugh , Zhan Yutian , Puré Ellen , Feuerstein Giora Z. 
Published: March 2003

AbstractCD44 is a transmembrane glycoprotein known to be involved in endothelial cell recognition, lymphocyte trafficking, and regulation of cytokine gene expression in inflammatory diseases. In the present study, we demonstrated that the expression of CD44 mRNA was induced in a mouse model of cerebral ischemia. A potential role of CD44 in ischemic brain injury was investigated using CD44‐deficient (CD44–/–) mice. Over 50% (p < 0.05, n = 14) and 78% (p < 0.05, n = 10) reduction in ischemic infarct was observed in CD44–/– mice compared with that of wild‐type mice following transient (30 min ischemia) and permanent (24 h) occlusion of the middle cerebral artery (MCAO), respectively. Similarly, significant improvement was observed in neurological function in CD44–/– mice as evidenced by spontaneous and forced motor task scores. The marked protection from ischemic brain injury in CD44–/– mice was associated with normal physiological parameters, cytokine gene expression, astrocyte and microglia activation as compared with wild‐type mice. However, in CD44–/– mice, significantly lower expression of soluble interleukin‐1β protein was noted after brain ischemia. Our data provide new evidence on the potential role of CD44 in brain tissue in response to ischemia and may suggest that this effect might be associated with selective reduction in inflammatory cytokines such as interleukin‐1β.
The anti‐inflammatory activity of estrogen in glial cells is regulated by the PKC‐anchoring protein RACK‐1
Authors: Viviani Barbara , Corsini Emanuela , Binaglia Marco , Lucchi Laura , Galli Corrado L. , Marinovich Marina 
Published: March 2003

AbstractIt has recently been suggested that estrogen inhibits glial activation and the release of neurotoxic mediators. The mechanisms involved in this anti‐inflammatory effect are unclear. We found that an nM concentration of 17‐β estradiol inhibits protein kinaseC‐βII translocation induced by lipopolysaccharide in primary astrocytes. Estradiol treatment did not change the total content of kinaseC‐βII or of lipopolysaccharide receptor, but dose‐dependently reduced the levels of receptors for activated C kinases‐1 (RACK‐1), the anchoring protein involved in protein kinase C (PKC) shuttling. This decrease could thus account for the defective protein kinaseC‐βII activation. Pre‐treatment with 1 nmβ‐estradiol, which reduced by ∼35% the expression of RACK‐1, prevented the lipopolysaccharide‐induced expression of tumour necrosis factor‐α mRNA and of the inducible form of nitric oxide (NO) synthase. As a consequence, the production of tumour necrosis factor‐α and NO were decreased. An antisense oligonucleotide for RACK‐1 also reduced tumour necrosis factor‐α and nitric oxide production on lipopolysaccharide stimulation. These results demonstrate that estrogen reduction of the RACK‐1 expression, leading to a defective protein kinase‐C activation counteracts the inflammatory response in astrocytes.
Differences in multidrug resistance phenotype and matrix metalloproteinases activity between endothelial cells from normal brain and glioma
Authors: Régina Anthony , Demeule Michel , Bérubé Alexandra , Moumdjian Robert , Berthelet France , Béliveau Richard 
Published: March 2003

AbstractEndothelial cells (ECs) are new targets for tumor therapy. In this work, we purified endothelial cells from intracerebral and subcutaneous experimental gliomas as well as from normal brain in order to define some of the phenotypical differences between angiogenic and quiescent brain vasculature. We show that the multidrug resistance genes encoding drug efflux pumps at the brain endothelium are expressed differently in normal and tumoral vasculature. We also show that ECs from gliomas present increased activity of gelatinase B (MMP9), key enzyme in the angiogenic process. Importantly, we observe a different phenotype between ECs in the intracerebral and subcutaneous models. Our results provide molecular evidence of phenotypic distinction between tumoral and normal brain vasculature and indicate that the EC phenotype depends on interactions both with tumor cells and also with the microenvironment.
The immunoglobulin‐superfamily molecule basigin is a binding protein for oligomannosidic carbohydrates: an anti‐idiotypic approach
Authors: Heller Martin , von der Ohe Maren , Kleene Ralf , Mohajeri M. Hasan , Schachner Melitta 
Published: March 2003

AbstractRecognition molecules that carry carbohydrate structures regulate cell interactions during development and play important roles in synaptic plasticity and regeneration in the adult. Glycans appear to be involved in these interactions. We have searched for binding proteins for oligomannosidic structures using the L3 antibody directed against high mannose‐type glycans in an anti‐idiotypic approach. A selected monoclonal anti‐idiotype antibody was used for affinity chromatography and identified basigin as a binding protein from mouse brain detergent lysates. Basigin was found to bind to high mannose‐carrying cell recognition molecules, such as myelin‐associated glycoprotein, L1, the β2‐subunit of Na+/K+‐ATPase and an oligomannosidic neoglycolipid. Furthermore, basigin was involved in outgrowth of astrocytic processes in vitro. A striking homology between the first immunoglobulin (Ig)‐like domain of basigin and the fourth Ig‐like domain of NCAM, previously shown to bind to oligomannosidic glycans, and the lectin domain of the mannose receptor confirms that basigin is an oligomannose binding lectin. To our knowledge this is the first report that anti‐idiotypic antibodies can be used to identify binding partners for carbohydrates.
HIV‐Tat protein induces oxidative and inflammatory pathways in brain endothelium
Authors: Toborek Michal , Lee Yong Woo , Pu Hong , Malecki Andrzej , Flora Govinder , Garrido Rosario , Hennig Bernhard , Bauer Hans‐Christian , Nath Avindra 
Published: March 2003

AbstractImpaired function of the brain vasculature might contribute to the development of HIV‐associated dementia. For example, injury or dysfunction of brain microvascular endothelial cells (BMEC) can lead to the breakdown of the blood–brain barrier (BBB) and thus allow accelerated entry of the HIV‐1 virus into the CNS. Mechanisms of injury to BMEC during HIV‐1 infection are not fully understood, but the viral gene product Tat may be, at least in part, responsible for this effect. Tat can be released from infected perivascular macrophages in the CNS of patients with AIDS, and thus BMEC can be directly exposed to high concentrations of this protein. To study oxidative and inflammatory mechanisms associated with Tat‐induced toxicity, BMEC were exposed to increasing doses of Tat1−72, and markers of oxidative stress, as well as redox‐responsive transcription factors such as nuclear factor‐κB (NF‐κB) and activator protein‐1 (AP‐1), were measured. Tat1−72 treatment markedly increased cellular oxidative stress, decreased levels of intracellular glutathione and activated DNA binding activity and transactivation of NF‐κB and AP‐1. To determine if Tat1−72 can stimulate inflammatory responses in brain endothelium in vivo, expression of monocyte chemoattractant protein‐1 (MCP‐1), an NF‐κB and AP‐1‐dependent chemokine, was studied in brain tissue in mice injected with Tat1−72 into the right hippocampus. Tat1−72 markedly elevated the MCP‐1 mRNA levels in brain tissue. In addition, a double immunohistochemistry study revealed that MCP‐1 protein was markedly overexpressed on brain vascular endothelium. These data indicate that Tat1−72 can induce redox‐related inflammatory responses both in in vitro and in vivo environments. These changes can directly lead to disruption of the BBB. Thus, Tat can play an important role in the development of detrimental vascular changes in the brains of HIV‐infected patients.
Corticotropin‐releasing hormone induces proliferation and TNF‐α release in cultured rat microglia via MAP kinase signalling pathways
Authors: Wang Wei , Ji Ping , Dow Kimberly E. 
Published: March 2003

AbstractWe have previously demonstrated that corticotropin‐releasing hormone (CRH) receptor 1 (CRH‐R1) is functionally expressed in rat microglia. In the present study, we show that CRH, acting on CRH‐R1, promoted cell proliferation and tumour necrosis factor‐α (TNF‐α) release in cultured rat microglia. Exogenous CRH resulted in an increase in BrdU incorporation compared with control cells, which was observed in a range of concentrations of CRH between 10 and 500 nm, with a maximal response at 50 nm. The effect of CRH on BrdU incorporation was inhibited by a CRH antagonist astressin but not by a cAMP‐dependent protein kinase inhibitor H89. Exposure of microglial cells to CRH resulted in a transient and rapid increase in TNF‐α release in a dose–dependent manner. In the presence of astressin, the effects of CRH on TNF‐α release were attenuated. CRH effects on TNF‐α release were also inhibited by specific inhibitors of MEK, the upstream kinase of the extracellular signal‐regulated protein kinase (ERK) (PD98059) or p38 mitogen‐activated protein kinase (SB203580), but not by H89. Furthermore, CRH induced rapid phosphorylation of ERK and p38 kinases. Astressin, PD98059, and SB230580 were able to inhibit CRH‐induced kinase phosphorylation. These results suggest that CRH induces cell proliferation and TNF‐α release in cultured microglia via MAP kinase signalling pathways, thereby providing insight into the interactions between CRH and inflammatory mediators.
Alterations in inducible 72‐kDa heat shock protein and the chaperone cofactor BAG‐1 in human brain after head injury
Authors: Seidberg Neal A. , Clark Robert S. B. , Zhang Xiaopeng , Lai Yichen , Chen Minzhi , Graham Steven H. , Kochanek Patrick M. , Watkins Simon C. , Marion Donald W. 
Published: March 2003

AbstractThe stress response in injured brain is well characterized after experimental ischemic and traumatic brain injury (TBI); however, the induction and regulation of the stress response in humans after TBI remains largely undefined. Accordingly, we examined injured brain tissue from adult patients (n = 8) that underwent emergent surgical decompression after TBI, for alterations in the inducible 72‐kDa heat shock protein (Hsp70), the constitutive 73‐kDa heat shock protein (Hsc70), and isoforms of the chaperone cofactor BAG‐1. Control samples (n = 6) were obtained postmortem from patients dying of causes unrelated to CNS trauma. Western blot analysis showed that Hsp70, but not Hsc70, was increased in patients after TBI versus controls. Both Hsp70 and Hsc70 coimmunoprecipitated with the cofactor BAG‐1. The 33 and 46, but not the 50‐kDa BAG‐1 isoforms were increased in patients after TBI versus controls. The ratio of the 46/33‐kDa isoforms was increased in TBI versus controls, suggesting negative modulation of Hsp70/Hsc70 protein refolding activity in injured brain. These data implicate induction of the stress response and its modulation by the chaperone cofactor and Bcl‐2 family member BAG‐1, after TBI in humans.
Characterization of amyloid β peptides from brain extracts of transgenic mice overexpressing the London mutant of human amyloid precursor protein
Authors: Pype Stefan , Moechars Dieder , Dillen Lieve , Mercken Marc 
Published: March 2003

AbstractAlzheimer's disease (AD) is marked by the presence of neurofibrillary tangles and amyloid plaques in the brain of patients. To study plaque formation, we report on further quantitative and qualitative analysis of human and mouse amyloid β peptides (Aβ) from brain extracts of transgenic mice overexpressing the London mutant of human amyloid precursor protein (APP). Using enzyme‐linked immunosorbant assays (ELISAs) specific for either human or rodent Aβ, we found that the peptides from both species aggregated to form plaques. The ratios of deposited Aβ1–42/1–40 were in the order of 2–3 for human and 8–9 for mouse peptides, indicating preferential deposition of Aβ42. We also determined the identity and relative levels of other Aβ variants present in protein extracts from soluble and insoluble brain fractions. This was done by combined immunoprecipitation and mass spectrometry (IP/MS). The most prominent peptides truncated either at the carboxyl‐ or the amino‐terminus were Aβ1–38 and Aβ11–42, respectively, and the latter was strongly enriched in the extracts of deposited peptides. Taken together, our data indicate that plaques of APP‐London transgenic mice consist of aggregates of multiple human and mouse Aβ variants, and the human variants that we identified were previously detected in brain extracts of AD patients.
Chromaffin cell death induced by 6‐hydroxydopamine is independent of mitochondrial swelling and caspase activation
Authors: Galindo María F. , Jordán Joaquín , González‐García Carmen , Ceña Valentín 
Published: March 2003

AbstractOur results provide evidence that 6‐hydroxydopamine induced, after auto‐oxidation, toxic levels of hydrogen peroxide (H2O2) that caused bovine chromaffin cell toxicity and death. 6‐Hydroxydopamine (6‐OHDA) treatment markedly reduced, in a dose–response fashion, chromaffin cell viability. Cell death was accompanied by cell shrinkage, nuclear condensation and DNA degradation. Under our experimental conditions, 6‐OHDA auto‐oxidation formed quinones and reactive oxygen species (ROS) that mainly contributed to 6‐OHDA‐induced cytotoxicity in bovine chromaffin cells. Accordingly, different antioxidants, including catalase, vitamin E, Mn(IIItetrakis(4‐benzoic acid)porphyrin chloride (MnTBAP) or ascorbic acid, provided protection against 6‐OHDA‐induced toxicity. Further evidence that 6‐OHDA induces oxidative stress is provided by the fact that this compound decreased total mitochondrial reduced NAD(P)H levels. Our results also suggest that mitochondrial swelling and caspase activation do not play a direct role in 6‐OHDA‐induced death in bovine chromaffin cells.
Pattern of levodopa‐induced striatal changes is different in normal and MPTP‐lesioned mice
Authors: Gross Christian E. , Ravenscroft Paula , Dovero Sandra , Jaber Mohamed , Bioulac Bernard , Bezard Erwan 
Published: March 2003

AbstractWhile levodopa‐induced neurochemical changes have been studied in animal models of Parkinson's disease, very little is known regarding the effects of levodopa administration in normal animals. The present study investigates the effects normal and MPTP‐lesioned mice chronically treated with two different doses of levodopa. We assess changes in striatal dopamine (DA) receptor binding, striatal DA receptor mRNA levels and striatal neuropeptide precursor levels (preproenkephalin‐A [PPE‐A]; preprotachykinin [PPT]; preproenkephalin‐B [PPE‐B]). The extent of the lesion was measured by striatal DA transporter binding and stereological estimation of the number of tyrosine hydroxylase immunoreactive neurones in the substantia nigra pars compacta (SNc). In non‐lesioned animals, chronic levodopa treatment induced an increase in PPE‐A mRNA, whereas both D3R binding and PPE‐B mRNA levels were dramatically increased in the lesioned animals in a dose dependent manner. The present results show that chronic levodopa administration may induce pathophysiological changes, even in the absence of a lesion of the nigro‐striatal pathway, suggesting that the sensitization process involves predominantly the indirect striatofugal pathway in non‐lesioned animals, whereas the direct pathway is primarily involved in lesioned animals.
Site‐directed mutagenesis of rabbit LAT1 at amino acids 219 and 234
Authors: Boado Ruben J. , Li Jian Yi , Pardridge William M. 
Published: March 2003

AbstractThe availability of amino acids in the brain is regulated by the blood–brain barrier (BBB) large neutral amino acid transporter type 1 (LAT1) isoform, which is characterized by a high affinity (low Km) for substrate large neutral amino acids. The hypothesis that brain amino acid transport activity can be altered with single nucleotide polymorphisms was tested in the present studies with site‐directed mutagenesis of the BBB LAT1. The rabbit has a high Km LAT1 large neutral amino acid transporter, as compared to the low Km neutral amino acid transporter at the human or rat BBB. The rabbit LAT1 was cloned from a rabbit brain capillary cDNA library. Alignment of the amino acid sequences of rabbit, human, and rat LAT1 revealed two radical amino acid residues that differ in the rabbit relative to the rat or human LAT1. The G219D mutation had a modest effect on the Km and Vmax of tryptophan transport via cloned rabbit LAT1 in frog oocytes, but the W234L variant reduced the Km by 64% and the Vmax by 96%. Conversely, LAT1 transport of either tryptophan or phenylalanine was nearly normalized when the double mutation W234L/G219D variant was produced. These studies show that marked changes in the affinity and capacity of the LAT1 are caused by single nucleotide polymorphisms and that phenotype can be restored with a double mutation.
cAMP‐induced differentiation of human neuronal progenitor cells is mediated by nuclear fibroblast growth factor receptor‐1 (FGFR1)
Authors: Stachowiak E. K. , Fang X. , Myers J. , Dunham S. , Stachowiak M. K. 
Published: March 2003

AbstractActivation of cAMP signaling pathway and its transcriptional factor cyclic AMP response element binding protein (CREB) and coactivator are key determinants of neuronal differentiation and plasticity. We show that nuclear fibroblast growth factor receptor‐1 (FGFR1) mediates cAMP‐induced neuronal differentiation and regulates CREB and CREB binding protein (CBP) function in α‐internexin‐expressing human neuronal progenitor cells (HNPC). In proliferating HNPC, FGFR1 was associated with the cytoplasm and plasma membrane. Treatment with dB‐cAMP induced nuclear accumulation of FGFR1 and caused neuronal differentiation, accompanied by outgrowth of neurites expressing MAP2 and neuron‐specific neurofilament‐L protein and enolase. HNPC transfected with nuclear/cytoplasmic FGFR1 or non‐membrane FGFR1(SP‐/NLS), engineered to accumulate exclusively in the cell nucleus, underwent neuronal differentiation in the absence of cAMP stimulation. In contrast, FGFR1/R4, with highly hydrophobic transmembrane domain of FGFR4, was membrane associated, did not enter the nucleus and failed to induce neuronal differentiation. Transfection of tyrosine kinase‐deleted dominant negative receptor mutants, cytoplasmic/nuclear FGFR1(TK‐) or nuclear FGFR1(SP‐/NLS)(TK‐), prevented cAMP‐induced neurite outgrowth. Nuclear FGFR1 localized in speckle‐like domains rich in phosphorylated histone 3 and splicing factors, regions known for active RNA transcription and processing, and activated the neurofilament‐L gene promoter. FGFR1(SP‐/NLS) transactivated CRE, up‐regulated phosphorylation and transcriptional activity of CREB and stimulated the activity of CBP several‐fold. Thus, cAMP‐induced nuclear accumulation of FGFR1 provides a signal that triggers molecular events leading to neuronal differentiation.