bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of the acute cardiotoxicity of the antimalarial drug halofantrine in vitro and in vivo in anaesthetized guinea‐pigs
Authors: Batey Andrew J. , Lightbown Ian D. , Lambert James P. , Edwards Geoffrey , Coker Susan J. 
Published: January 2005

Several unrelated drugs have pro‐arrhythmic activity associated with an ability to prolong the QT interval of the ECG. The aim of this work was to examine the effects of the antimalarial drug halofantrine in vivo and in vitro.
In anaesthetized guinea‐pigs consecutive bolus doses of halofantrine (0.3, 1, 3, 10 and 30 mg kg−1, i.v.) at 25 min intervals caused dose‐dependent prolongation of the rate corrected QTc interval and bradycardia. The change in heart rate became significant after administration of 10 mg kg−1 halofantrine (−23±9 beats min−1) whereas the increase in QTc was significant with only 1 mg kg−1 halofantrine (22±10 ms). It was only with the highest dose of halofantrine that the PR interval was increased (from 52±3 to 67±4 ms) and second degree atrioventricular (AV) block (type 1 Mobitz) occurred in all animals. No changes were observed in any parameters in a separate group of guinea‐pigs which received vehicle (dimethylacetamide 60% propylene glycol 40%) at equivalent time points.
The blood concentrations of halofantrine ranged from 0.26±0.17 μM after administration of 0.3 mg kg−1 to 2.79±0.87 μM after 30 mg kg−1, i.v. There was a significant correlation between the blood concentrations of halofantrine and the changes in QTc interval.
In guinea‐pig left papillary muscles the effective refractory period was increased significantly 60 min after addition of halofantrine; from 161±4 to 173±6 ms with 10 μM, 156±8 to 174±6 ms with 30 μM and 165±6 to 179±5 ms with 100 μM halofantrine. However, the vehicle (0.1% Tween 80 in DMSO; final concentration of vehicle in Krebs, 1%) also increased the effective refractory period from 164±5 to 173±6 ms. Similar results were obtained in right ventricular strips but left atrial effective refractory periods were not altered by either the vehicle or halofantrine.
The results of these experiments suggest that any direct effects that halofantrine may have had on the effective refractory period of cardiac muscle cannot be separated from those of the vehicle. The prolongation of QTc and consistent observation of AV block with halofantrine in anaesthetized guinea‐pigs suggest that in vivo models may be more useful for further studies investigating the mechanisms underlying the cardiotoxicity of halofantrine.

British Journal of Pharmacology (1997) 122, 563–569; doi:10.1038/sj.bjp.0701402
Nitric oxide effects on cell growth: GMP‐dependent stimulation of the AP‐1 transcription complex and cyclic GMP‐independent slowing of cell cycling
Authors: Sciorati Clara , Nisticò Giuseppe , Meldolesi Jacopo , Clementi Emilio 
Published: January 2005

The role of nitric oxide (NO) in the control of cell growth is controversial since both stimulation and (more often) inhibition have been demonstrated in various cell types. In order to reinvestigate the problem and identify the sites of NO action, we have employed murine NIH‐3T3 fibroblasts overexpressing epidermal growth factor (EGF) receptors.
The effects of four structurally‐unrelated NO donors: S‐nitroso‐N‐acetyl penicillamine, S‐nitroso‐L‐glutathione, 3‐morpholinosydnonimine and isosorbide dinitrate (0.01–3 mM) on EGF (10 nM)‐stimulated cell growth were estimated by both thymidine incorporation and the colorimetric MTT assay, while those of a messenger generated in response to NO, cyclic GMP, were revealed by the use of 8‐Br cyclic GMP (0.01–3 mM) as well as of blockers of guanylyl cyclase and cyclic GMP‐dependent kinase I.
Studies were focused on: (i) multiple signalling events, including receptor‐induced tyrosine phosphorylations, phosphorylation of mitogen‐activated protein kinase, activation of the AP‐1 transcription complex and deoxyribonucleotide synthesis; (ii) the progression through the cell cycle, dissected out by the use of staurosporine (1 nM), lovastatin (10 μM), mimosine (200 μM), hydroxyurea (1 mM) and nocodazole (1.5 μM).
NO was found to have no effects on the phosphorylation events of the growth factor cascade. In contrast, later processes were modified by the messenger but with opposite effects.
A cyclic GMP‐dependent stimulation of growth was shown to be sustained in part by the activation of the AP‐1 transcription complex, while a predominant, cyclic GMP‐independent inhibition was found to be mediated by both the negative regulation of ribonucleotide reductase and the marked slowing down of the cell cycle occurring at early and late G1 and during the S phase.
Although multiple and apparently conflicting, the effects of NO here described could work coordinately in a general programme of cell growth regulation. In particular, the cyclic GMP‐dependent actions might function as rapid modulatory events, while the effects on cell cycle might operate collectively as a multi‐switch process whenever growth inhibition is required.

British Journal of Pharmacology (1997) 122, 687–697; doi:10.1038/sj.bjp.0701413
Effects of ibuprofen enantiomers and its coenzyme A thioesters on human prostaglandin endoperoxide synthases
Authors: Neupert Werner , Brugger Roland , Euchenhofer Christian , Brune Kay , Geisslinger Gerd 
Published: January 2005

Ibuprofen enantiomers and their respective coenzyme A thioesters were tested in human platelets and blood monocytes to determine their selectivity and potency as inhibitors of cyclo‐oxygenase activity of prostaglandin endoperoxide synthase‐1 (PGHS‐1) and PGHS‐2.
Human blood from volunteers was drawn and allowed to clot at 37°C for 1 h in the presence of increasing concentrations of the test compounds (R‐ibuprofen, S‐ibuprofen, R‐ibuprofenoyl‐CoA, S‐ibuprofenoyl‐CoA, NS‐398). Immunoreactive (ir) thromboxane B2 (TXB2) concentrations in serum were determined by a specific EIA assay as an index of the cyclo‐oxygenase activity of platelet PGHS‐1.
Heparin‐treated blood from the same donors was incubated at 37°C for 24 h with the same concentrations of the test compounds in the presence of lipopolysaccharide (LPS, 10 μg ml−1). The contribution of PGHS‐1 was suppressed by pretreatment of the volunteers with aspirin (500 mg; 48 h before venepuncture). As a measure of LPS induced PGHS‐2 activity immunoreactive prostaglandin E2 (irPGE2) plasma concentrations were determined by a specific EIA assay.
S‐ibuprofen inhibited the activity of PGHS‐1 (IC50 2.1 μM) and PGHS‐2 (IC50 1.6 μM) equally. R‐ibuprofen inhibited PGHS‐1 (IC50 34.9) less potently than S‐ibuprofen and showed no inhibition of PGHS‐2 up to 250 μM. By contrast R‐ibuprofenoyl‐CoA thioester inhibited PGE2 production from LPS‐stimulated monocytes almost two orders of magnitude more potently than the generation of TXB2 (IC50 5.6 vs 219 μM).
Western blotting of PGHS‐2 after LPS induction of blood monocytes showed a concentration‐dependent inhibition of PGHS‐2 protein expression by ibuprofenoyl‐CoA thioesters.
These data confirm that S‐ibuprofen represents the active entity in the racemate with respect to cyclo‐oxygenase activity. More importantly the data suggest a contribution of the R‐enantiomer to therapeutic effects not only by chiral inversion to S‐ibuprofen but also via inhibition of induction of PGHS‐2 mediated by R‐ibuprofenoyl‐CoA thioester.
The data may explain why racemic ibuprofen is ranked as one of the safest non‐steroidal anti‐inflammatory drugs (NSAIDs) so far determined in epidemiological studies.

British Journal of Pharmacology (1997) 122, 487–492; doi:10.1038/sj.bjp.0701415
Localization of Fos‐like immunoreactivity induced by the NK3 tachykinin receptor agonist, senktide, in the guinea‐pig brain
Authors: Yip Jane , Chahl Loris A. 
Published: January 2005

The effects of intracerebroventricular (i.c.v.) administration of the NK3 tachykinin receptor agonist, senktide (10 nmol each side), in guinea‐pigs pretreated with the selective NK3 tachykinin receptor antagonist, SR142801 (3 mg kg−1 subcutaneous, s.c., 30 min before senktide), or its less active enantiomer, SR142806 (3 mg kg−1 s.c. 30 min before senktide), on behaviour and on the distribution of Fos‐like immunoreactivity (Fos‐LI) in central neurones were investigated. Guinea‐pigs were chosen for the study since they possess NK3 tachykinin receptors with pharmacological characteristics similar to those in man.
Wet‐dog shakes, but not locomotor activity, elicited by senktide i.c.v. were significantly reduced by SR142801 but not by SR142806, confirming the involvement of NK3 tachykinin receptors in wet‐dog shake behaviour.
Senktide induced increased numbers of Fos‐LI neurones in the following brain areas: frontal, parietal and piriform cortex, the lateral septum, the CA1, CA2, subiculum and dentate gyrus of the hippocampus, most areas in the amygdala, thalamus and hypothalamus, medial geniculate nucleus and the ventral cochlear nucleus. Pretreatment with SR142801, but not with SR142806, before administration of senktide inhibited Fos‐LI expression in the cingulate cortex, dentate gyrus of the hippocampus, some regions of the thalamus, hypothalamus and amygdala and the ventral cochlear nucleus.
The present results are the first demonstration that senktide induces Fos‐LI in widespread areas of the guinea‐pig brain. It is proposed that NK3 tachykinin receptors may play a more extensive role in the control of diverse brain functions, including cortical processing, learning and memory, neuroendocrine and behavioural regulation, than is currently recognized.

British Journal of Pharmacology (1997) 122, 715–725; doi:10.1038/sj.bjp.0701416
Modulation of a recombinant invertebrate γ‐aminobutyric acid receptor‐chloride channel complex by isoflurane: effects of a point mutation in the M2 domain
Authors: Edwards Michelle D. , Lees George 
Published: January 2005

Inhalational anaesthetics modulate ligand‐gated ion channels at clinical concentrations. In this paper we address submolecular mechanisms for γ‐aminobutyric acid (GABA) receptor modulation by isoflurane.
Wild‐type Drosophila melanogaster homo‐oligomeric GABA receptors were characterized and compared with an ion‐channel mutant (alanine substituted to a serine in M2) by means of two‐electrode voltage‐clamp in membrane‐invariant Xenopus oocytes.
Both channel receptor isoforms generated outwardly rectifying, bicuculline‐insensitive currents with reversal potentials characteristic of a chloride current.
As previously shown, the point mutation in the M2 domain conferred a profound resistance to the blocking action of 10 μM picrotoxinin (PTX): circa 7 fold reduction at the GABA EC20.
Isoflurane, 195–389 μM, enhanced GABA conductance in both receptor variants by significantly increasing the affinity of the agonist for its receptor without changing Hill slope or maximal response. Relative potencies were statistically indistinguishable.
Isoflurane concentration‐response curves (on circa GABA EC25) demonstrated that enhancement was effected at around 100–195 μM for both receptor subtypes, but a dramatic divergence was evident at concentrations above 400 μM: wild‐type receptors exhibited concentration‐dependent block, whilst mutant conductances continued to increase over the same concentration range, showing no tendency to saturate (up to 3330 μM).
The above divergence was not attributable to differential desensitization: neither wild‐type nor mutant conductance desensitized significantly (P>0.05) in the absence or presence of anaesthetic.
This work demonstrates that modulatory sites for anaesthetic are present on a relatively primitive insect ion channel.
The depression of GABA response at high isoflurane concentrations, in WT receptors, (typical of a variety of anaesthetic agents) may reflect low affinity channel block via the PTX site.
The non‐saturable enhancement of chloride conductances, when the PTX site is mutated, is not consistent with topical proposals that inhalational anaesthetics (stereoselectively) occupy a finite number of sites on these membrane spanning proteins.

British Journal of Pharmacology (1997) 122, 726–732; doi:10.1038/sj.bjp.0701417
Effect of L‐lysine on nitric oxide overproduction in endotoxic shock
Authors: Liaudet Lucas , Gnaegi Alex , Rosselet Anne , Markert Michèle , Boulat Olivier , Perret Claude , Feihl François 
Published: January 2005

An enhanced production of nitric oxide (NO) from L‐arginine, related to the diffuse expression of an inducible NO synthase (iNOS), contributes to the pathogenesis of endotoxic shock. Since iNOS activity depends on extracellular L‐arginine, we hypothesized that limiting cellular L‐arginine uptake would reduce NO production in endotoxic shock. We investigated the effects of L‐lysine, an inhibitor of L‐arginine uptake through system y+, on NO production, multiple organ dysfunction and lactate levels, in normal and endotoxaemic rats.
Anaesthetized rats challenged with intravenous lipopolysaccharide (LPS, 10 mg kg−1) received a 5 h infusion of either L‐lysine (500 μmol kg−1 h−1, n=12) or isotonic saline (2 ml kg−1 h−1, n=11). In rats treated with saline, LPS produced a large increase in plasma nitrate and L‐citrulline concentrations at 5 h, both markers of enhanced NO production. LPS also caused severe hypotension, low cardiac output and marked hyperlactataemia. All these changes were significantly reduced byL‐lysine administration.
Endotoxaemia also caused a significant rise in the plasma levels of alanine aminotransferase (ALAT), lipase, urea and creatinine, and hence, liver, pancreatic and renal dysfunction. These changes tended to be less pronounced in rats treated with L‐lysine, although the differences did not reach statistical significance.
Similar experiments were conducted in 10 rats challenged with LPS vehicle in place of LPS and then treated with L‐lysine (500 μmol kg−1  h−1, n=5) or saline (2 ml kg−1  h−1, n=5) for 5 h. In these animals, all the haemodynamic and metabolic variables remained stable and not statistically different between both treatment groups, except for a slight rise in ALAT, which was comparable in L‐lysine and saline‐treated rats.
In conclusion, L‐lysine, an inhibitor of cellular L‐arginine uptake, reduces NO production and exerts beneficial haemodynamic effects in endotoxaemic rats. L‐lysine also reduces hyperlactataemia and tends to blunt the development of organ injury in these animals. Contrastingly, L‐lysine has no effects in the absence of endotoxin and thus appears to act as a selective modulator of iNOS activity.

British Journal of Pharmacology (1997) 122, 742–748; doi:10.1038/sj.bjp.0701419
Differential regulation of cyclo‐oxygenase‐2 and 5‐lipoxygenase‐activating protein (FLAP) expression by glucocorticoids in monocytic cells
Authors: Goppelt‐Struebe M. , Schaefer D. , Habenicht A. J. R. 
Published: January 2005

The objective of the present study was to determine the effects of dexamethasone on key constituents of prostaglandin and leukotriene biosynthesis, cyclo‐oxygenase‐2 (COX‐2) and 5‐lipoxygenase activating protein (FLAP). The human monocytic cell line THP‐1 was used as a model system. mRNA and protein levels of COX‐2 and FLAP were determined by Northern and Western blot analyses, respectively.
Low levels of COX‐2 and FLAP mRNA were expressed in undifferentiated THP‐1 cells, but were induced upon differentiation of the cells along the monocytic pathway by treatment with phorbol ester (TPA, 5 nM). Maximal expression was observed after two days.
Coincubation of the undifferentiated cells with dexamethasone (10−9–10−6 M) and phorbol ester prevented induction of COX‐2 mRNA, but did not affect the induction of FLAP mRNA.
Dexamethasone downregulated COX‐2 mRNA and protein in differentiated, monocyte‐like THP‐1 cells. In contrast, FLAP mRNA and protein were upregulated by dexamethasone in differentiated THP‐1 cells. After 24 h, FLAP mRNA levels were increased more than 2 fold. Dexamethasone did not change 5‐lipoxygenase mRNA expression.
Release of prostaglandin E2 (PGE2) and peptidoleukotrienes was determined in cell culture supernatants of differentiated THP‐1 cells by ELISA. Calcium ionophore‐dependent PGE2 synthesis was associated with COX‐2 expression, whereas COX‐1 and COX‐2 seemed to participate in arachidonic acid‐dependent PGE2 synthesis. Very low levels of peptidoleukotrienes were released from differentiated THP‐1 cells upon incubation with ionophore. Treatment with dexamethasone did not significantly affect leukotriene release.
These data provide evidence that prostaglandin synthesis is consistently downregulated by glucocorticoids. However, the glucocorticoid‐mediated induction of FLAP may provide a mechanism to maintain leukotriene biosynthesis through more efficient transfer of arachidonic acid to the 5‐lipoxygenase reaction, in spite of inhibitory effects on other enzymes of the biosynthetic pathway.

British Journal of Pharmacology (1997) 122, 619–624; doi:10.1038/sj.bjp.0701425
Neuroprotective efficacy of ebselen, an anti‐oxidant with anti‐inflammatory actions, in a rodent model of permanent middle cerebral artery occlusion
Authors: Takasago T. , Peters E. E. , Graham D. I. , Masayasu H. , Macrae I. M. 
Published: January 2005

The aim of this study was to investigate whether delayed treatment with the anti‐oxidant and anti‐inflammatory agent ebselen reduces the volume of infarction in a rodent model of permanent focal cerebral ischaemia.
Ebselen (10 or 30 mg kg−1) or vehicle was administered by gavage 30 min and 12 h after the induction of cerebral ischaemia by permanent occlusion of the left middle cerebral artery (MCA). Animals were killed 24 h following MCA occlusion, and the volumes of ischaemic damage in the ebselen and control groups were evaluated by quantitative histopathology.
Ebselen was quickly absorbed following oral (gavage) administration and reached peak levels in the plasma by 1 h post‐administration (plasma selenium level of 0.68±0.04 and 0.84±0.1 μg ml−1 for 10 and 30 mg kg−1, respectively, compared to control level of 0.51±0.02 μg kg−1).
Treatment with the lower dose of ebselen (10 mg kg−1) significantly (P<0.01) reduced the volume of infarction in the cerebral hemisphere and cerebral cortex (by 31.8% and 36.7%, respectively compared with the placebo group).
The neuroprotective efficacy of the higher dose ebselen (30 mg kg−1) was less than that of the lower dose ebselen (10 mg kg−1). The volume of ischaemic damage in the cerebral hemisphere was reduced by 23.7% (P<0.02), and cerebral cortex by 27.5% (P<0.01).
Both doses of ebselen (10, 30 mg kg−1) had no therapeutic efficacy on the caudate nucleus, where ischaemia was most severe, in this model.
Free radical‐mediated injury is normally associated with reperfusion of ischaemic tissue. The present results suggest that oxidative injury is also a significant contributor to brain damage in models of maintained (permanent) ischaemia and that ebselen is effective in attenuating this free radical‐induced damage.

British Journal of Pharmacology (1997) 122, 1251–1256; doi:10.1038/sj.bjp.0701426
Involvement of nitric oxide in the inhibition of angiogenesis by interleukin‐2
Authors: Sakkoula Eleni , Pipili‐Synetos Eva , Maragoudakis M. E. 
Published: January 2005

Interleukin‐2 (IL‐2), an immunoregulatory cytokine possessing antitumour activity, is an inducer of nitric oxide (NO) synthesis in mice and man. In this study, the possibility that IL‐2 possesses antiangiogenic properties that account for its antitumour effects in vivo was examined. IL‐2 caused a dose‐dependent inhibition of angiogenesis in the chick embryo chorioallantoic membrane (CAM). This inhibition was completely reversed by the NO synthase inhibitor NG‐nitro‐L‐arginine methylester (L‐NAME). Furthermore, IL‐2 was capable of stimulating NO synthase activity in the CAM in vitro and this effect was suppressed by L‐NAME. Addition of IL‐2 to human umbilical vein endothelial cells (HUVECs) in culture, had no effect on their growth characteristics. These results suggest that IL‐2 may be an important antiangiogenic molecule causing its effect via nitric oxide synthesis. The antiangiogenic activity of IL‐2 may be, at least in part, responsible for its antitumour properties.British Journal of Pharmacology (1997) 122, 793–795; doi:10.1038/sj.bjp.0701436
Analysis of the pulmonary hypertensive effects of the isoprostane derivative, 8‐iso‐PGF2α, in the rat
Authors: John Gareth W. , Valentin Jean‐Pierre 
Published: January 2005

We analysed the pulmonary hypertensive effects of the F2‐isoprostane derivative, 8‐iso‐prostaglandin F2α (8‐iso‐PGF2α), in comparison with those of the high efficacy thromboxane A2/prostanoid (TP) receptor agonist, U‐46619, in pentobarbitone‐anaesthetized, open‐chest rats (n=4–15 per group).
8‐iso‐PGF2α produced dose‐dependent increases in mean pulmonary arterial pressure, with an ED50 of 39.0 (31.4–50.6) μg kg−1, i.v. (geometric mean with 95% confidence limits in parentheses) compared to 1.4 (1.1–2.3) μg kg−1, i.v., for U‐46619. The maximum responses evoked by U‐46619 and 8‐iso‐PGF2α were not statistically significantly different (21.0±1.0 and 25.8±1.9 mmHg at 10 μg kg−1 of U‐46619 and 630 μg kg−1 of 8‐iso‐PGF2α, respectively).
The TP receptor antagonist, SQ 29,548 (0.63 mg kg−1, i.v. + 0.63 mg kg−1 h−1) fully antagonised both U‐46619 and 8‐iso‐PGF2α‐induced pulmonary hypertensive responses.
Further experiments were carried out to determine whether 8‐iso‐PGF2α antagonized the pulmonary hypertensive responses evoked by U‐46619, or those induced by itself, as would be predicted for a partial agonist. However, ED10 or ED25 doses of 8‐iso‐PGF2α (10 or 20 μg kg−1, i.v.) failed to reduce the pulmonary hypertensive responses induced either by U‐46619 or by itself.
The data suggest that in the pulmonary vascular bed of the rat, 8‐iso‐PGF2α acts as an agonist of high intrinsic activity at SQ 29,548‐sensitive (probably TP) receptors.

British Journal of Pharmacology (1997) 122, 899–905; doi:10.1038/sj.bjp.0701441
PNU‐107484A with α isoform‐dependent functional changes in αxβ2γ2 subtypes of rat recombinant GABAA receptors
Authors: Im Haesook K. , Im Wha Bin , Carter Donald B. , Schwartz Theresa M. , Bundy Gordon L. , Von Voigtlander Philip F. 
Published: January 2005

We discovered a novel γ‐aminobutyric acidA (GABAA) receptor ligand displaying seemingly opposite functionalities, depending on the α isoform of the αxβ2γ2 subtypes. PNU‐107484A enhanced GABA‐induced Cl− currents in the α1β2γ2 subtype, but inhibited the currents in the α3β2γ2 and α6β2γ2 subtypes, and its half‐maximal concentrations in the subtypes were 3.1±0.5, 4.2±1, and 3.5±0.2 μM, respectively, without showing much dependency on α isoforms.
In the α1β2 subtype, the drug at concentrations up to 40 μM showed no effect on GABA‐induced Cl− currents, suggesting the requirement of the γ subunit for its action.
PNU‐107484A behaved like a positive allosteric modulator of the α1β2γ2 subtype with its binding site distinct from those for benzodiazepines, barbiturates and neurosteroids. With the α3β2γ2 subtype, the drug behaved like a non‐competitive inhibitor of GABA, thus blocking Cl− currents by GABA alone or in the presence of pentobarbitone and neurosteroids.
It appears that PNU‐107484A is a unique GABAA receptor ligand with α isoform‐dependent functionalities, which may provide a basis for development of α isoform‐selective ligands, and it could be useful as a probe to investigate the physiological roles of the various α isoform subtypes.

British Journal of Pharmacology (1997) 122, 821–824; doi:10.1038/sj.bjp.0701450