European Journal of Pharmacology (v.513, #3)

Gentisic acid, an aspirin metabolite, inhibits oxidation of low-density lipoprotein and the formation of cholesterol ester hydroperoxides in human plasma by Keiko Ashidate; Mitsunobu Kawamura; Daigo Mimura; Hisako Tohda; Shigeru Miyazaki; Tamio Teramoto; Yorihiro Yamamoto; Yukio Hirata (173-179).
Gentisic acid, an aspirin metabolite, has an antioxidant effect, although its detailed mechanism remains elusive. The present study was designed to determine whether it inhibits low-density lipoprotein (LDL) oxidation and the formation of lipid hydroperoxides in human plasma.The susceptibility of LDL oxidative modification was investigated by a method using 2,2′-azobis or Cu2+. To study the effect of gentisic acid on free radical-induced damage to plasma lipids, cholesterol ester hydroperoxides generated by incubating human fresh plasma with Cu2+ and gentisic acid was analyzed.Gentisic acid inhibited LDL oxidation in a concentration-dependent manner. It significantly inhibited the formation of cholesterol ester hydroperoxides in plasma, and was consumed after the depletion of ascorbic acid and reduced form of coenzyme Q-10 (CoQH2-10), whereas concentrations of other antioxidants remained unchanged. Gentisic acid had a potent free radical scavenging activity with a minimal chelating effect.The potent antioxidant property of gentisic acid may partly account for the anti-atherogenic effects of aspirin.
Keywords: Gentisic acid; Aspirin; Antioxidant; LDL oxidation;

Molecular and pharmacological characterization of serotonin 5-HT2A and 5-HT2B receptor subtypes in dog by Pascal Bonaventure; Diane Nepomuceno; Kirsten Miller; Jingcai Chen; Chester Kuei; Fredrik Kamme; Da-Thao Tran; Timothy W. Lovenberg; Changlu Liu (181-192).
We report the cloning, molecular characterization, and pharmacological characterization of the canine 5-HT2A and 5-HT2B receptors. The canine and human 5-HT2A receptors share 93% amino acid homology. The canine and human 5-HT2B receptors are also highly conserved (87% homology) with the exception of the carboxyl termini where the canine protein is 62 amino acids shorter. Both the canine 5-HT2A and 5-HT2B receptors have high affinity for [3H]5-HT (K D  = 4.50 ± 0.89 nM and 3.10 ± 0.82 nM, respectively) and, in general, the pharmacology of these two receptors matches closely the pharmacology of their human homologs for the 19 serotonergic ligands tested. However, the functional response (Ca2+ mobilization) of the canine 5-HT2B receptor to several agonists was weaker compared to the human 5-HT2B receptor. Using quantitative reverse transcriptase polymerase chain reaction, a high expression level of canine 5-HT2A receptor mRNA was detected in the brain and lower levels in peripheral tissues, whereas the highest levels of canine 5-HT2B receptor mRNA were observed in lungs and smooth muscles. A significant level of canine 5-HT2B receptor mRNA was detected in brain tissue. The availability of the full sequence and pharmacology of the canine 5-HT2A and canine 5-HT2B receptors provides useful information for the interpretation of previous and future pharmacological studies of 5-HT2A/2B ligands in dog.
Keywords: 5-HT2A receptor; 5-HT2B receptor; Canine; Radioligand binding; Cloning;

Putative role of nitric oxide synthase isoforms in the changes of nitric oxide concentration in rat brain cortex and cerebellum following sevoflurane and isoflurane anaesthesia by Nikolajs Sjakste; Jelizaveta Sjakste; Jean-Luc Boucher; Larisa Baumane; Tatjana Sjakste; Maija Dzintare; Dainuvite Meirena; Jelena Sharipova; Ivars Kalvinsh (193-205).
We have previously observed an increase in nitric oxide (NO) content in rat brain cortex following halothane, sevoflurane or isoflurane anaesthesia. This study was undertaken in order to determine whether isoform-specific nitric oxide synthase (NOS) inhibitors and inducers could modify these increases in NO contents. Rats were subjected to isoflurane and sevoflurane anaesthesia with concomitant administration of neuronal nitric oxide synthase (nNOS) inhibitor 7-Nitro-indazole (7-NI), inducible nitric oxide synthase (iNOS) inhibitor 2-amino-5,6-dihydro-6-methyl-4H-1,3-thiazine (AMT) or lipopolysaccharide. NO concentration in different organs was measured by electron paramagnetic resonance (EPR) spectroscopy. 7-NI significantly decreased NO concentration in cerebellum but not in brain cortex, whereas AMT decreased NO in all the organs studied. Anaesthesia significantly increased NO concentration in brain cortex and decreased that in cerebellum. AMT abolished the NO increase in brain cortex. Anaesthesia enhanced the drastic increase in NO concentration in brain cortex after intraventricular lipopolysaccharide administration. Isoflurane was found to inhibit recombinant nNOS and iNOS activities at high concentrations (EC50  = 20 mM). Our data suggest a putative role for iNOS in the increase in NO levels produced by isoflurane and sevoflurane, whereas nNOS activity is probably inhibited during anaesthesia.
Keywords: Nitric oxide; Halogenated volatile anaesthetic; EPR spectroscopy; Inducible and neuronal nitric oxide synthase; Lipopolysaccharide; NOS inhibitor;

Is antagonism of α3β4 nicotinic receptors a strategy to reduce morphine dependence? by Olga D. Taraschenko; Vishal Panchal; Isabelle M. Maisonneuve; Stanley D. Glick (207-218).
18-Methoxycoronaridine, a synthetic iboga alkaloid congener, has been previously shown to attenuate several signs of morphine withdrawal in rats. The recently discovered action of 18-methoxycoronaridine to block α3β4 nicotinic receptors may be responsible for this effect. To test this hypothesis the effects of non-selective α3β4 receptor antagonists, dextromethorphan, mecamylamine, bupropion, and their combinations, were assessed on of acute naltrexone-precipitated (1 mg/kg i.p.) morphine withdrawal in rats.Dextromethorphan (5–40 mg/kg, s.c.), mecamylamine (0.25–4 mg/kg, i.p.) and bupropion (10–30 mg/kg, i.p.) alone produced variable effects on signs of withdrawal. However, two low-dose combinations, i.e., dextromethorphan (5 mg/kg, s.c.) and mecamylamine (0.25 mg/kg, i.p.), mecamylamine (0.25 mg/kg, i.p.) and bupropion (10 mg/kg, i.p.) as well as the three-drug combination significantly attenuated diarrhea and weight loss; none of the agents administered alone had these effects. The results of the present study provide evidence that α3β4 nicotinic receptors are involved in the expression of at least two signs of opioid withdrawal.
Keywords: Morphine; Naltrexone; Dextromethorphan; Mecamylamine; Bupropion; Opioid withdrawal;

Hydrogen peroxide and endothelium-dependent hyperpolarization in the guinea-pig carotid artery by Pascale Gluais; Gillian Edwards; Arthur H. Weston; Paul M. Vanhoutte; Michel Félétou (219-224).
This study was designed to determine whether or not endothelium-dependent hyperpolarizations evoked by acetylcholine in the isolated guinea-pig carotid artery involve hydrogen peroxide. Membrane potential was recorded in the vascular smooth muscle cells of that artery. Under control conditions, acetylcholine induced endothelium-dependent hyperpolarization of the vascular smooth muscle cells which was not affected by the presence of catalase, superoxide dismutase or their combination. Neither the superoxide dismutase mimetic, tiron nor the thiol-reducing agent N-acetyl-l-cysteine modified the hyperpolarization evoked by 0.1 μM acetylcholine but each produced a partial and significant inhibition of the hyperpolarization induced by 1 μM acetylcholine. Neither 10 nor 100 μM hydrogen peroxide influenced the resting membrane potential of the smooth muscle cells and the higher concentration did not significantly influence the hyperpolarization elicited by acetylcholine. These data indicate that, in the guinea-pig isolated carotid artery, hydrogen peroxide is unlikely to contribute to the endothelium-dependent hyperpolarization evoked by acetylcholine.
Keywords: Endothelium; Smooth muscle; Endothelium-derived hyperpolarizing factor; Hydrogen peroxide; Membrane potential;

Agonism at 5-HT2B receptors is not a class effect of the ergolines by Sven Jähnichen; Reinhard Horowski; Heinz H. Pertz (225-228).
Restrictive cardiac valvulopathies observed in Parkinson patients treated with the ergoline dopamine agonist pergolide have recently been associated with the agonist efficacy of the drug at 5-hydroxytryptamine2B (5-HT2B) receptors. To evaluate whether agonism at 5-HT2B receptors is a phenomenon of the class of the ergolines, we studied 5-HT2B receptor-mediated relaxation in porcine pulmonary arteries to five ergolines which are used as antiparkinsonian drugs. Pergolide and cabergoline were potent full agonists in this tissue (pEC50 8.42 and 8.72). Bromocriptine acted as a partial agonist (pEC50 6.86). Lisuride and terguride, however, failed to relax the arteries but potently antagonized 5-HT-induced relaxation (pK B 10.32 and 8.49). Thus, agonism at 5-HT2B receptors seems not to be a class effect of the ergolines.
Keywords: Pergolide; Cabergoline; Bromocriptine; Lisuride; Terguride; Valvular heart disease; 5-HT2B receptor agonism;

Effect of celecoxib, a cyclooxygenase-2 inhibitor, on the pathophysiology of adjuvant arthritis in rat by Masahiro Noguchi; Aishi Kimoto; Seiji Kobayashi; Taiji Yoshino; Keiji Miyata; Masao Sasamata (229-235).
We investigated the efficacy of celecoxib, a specific cyclooxygenase (COX)-2 inhibitor, on arthritic pathophysiology and confirmed its gastric safety in adjuvant-induced arthritis rats. Results were compared with those for loxoprofen, a non-selective COX inhibitor. Arthritis was induced by injection of 1 mg of Mycobacterium butyricum in 50 μl of liquid paraffin into the left footpad of Lewis rats. The drugs were given by twice daily oral administration for 10 days beginning 15 days after adjuvant injection, with celecoxib at 0.01–3 mg/kg/day and loxoprofen at 0.01–3 mg/kg/day. Celecoxib significantly inhibited paw swelling, hyperalgesic response, and joint destruction (radiographic and histopathological findings) in these arthritic rats. These effects of celecoxib were superior to those of loxoprofen. Further, the administration of loxoprofen (3 mg/kg/day) caused significant gastric lesions, whereas celecoxib at the same dose did not. These results suggest that COX-2-mediated prostaglandins may play an important role in the progression of pathophysiology in this model and that celecoxib may be a useful therapeutic agent for the treatment of rheumatoid arthritis, with greater safety than non-selective COX inhibitors.
Keywords: Adjuvant-induced arthritis; Cyclooxygenase-2; Non-steroidal anti-inflammatory drug; Celecoxib;

Suppression of lipopolysaccharide-induced expression of inducible nitric oxide synthase by brazilin in RAW 264.7 macrophage cells by In-Kyung Bae; Hye-Young Min; Ah-Reum Han; Eun-Kyoung Seo; Sang Kook Lee (237-242).
Brazilin (7,11b-dihydrobenz[b]indeno[1,2-d]pyran-3,6a,9,10 (6H)-tetrol) isolated from Caesalpinia sappan has been known as a natural red pigment. Many studies suggest that inducible isoform of nitric oxide synthase (NOS) plays an important role in inflammation and carcinogenesis. On this line, we evaluated the inhibitory effect of brazilin on nitric oxide (NO) production and investigated its mechanism of action. As a result, brazilin exhibited the inhibitory effect on lipopolysaccharide (LPS)-stimulated NO production in a dose-dependent manner (IC50  = 24.3 μM). In addition, brazilin suppressed LPS-induced iNOS protein and mRNA expression in RAW 264.7 macrophage cells, indicating that the inhibitory activity of brazilin possibly involved in the regulation of iNOS expression. To further investigate the mechanism responsible for the suppression of iNOS gene expression by brazilin, the effect of brazilin on LPS-induced transcription factors nuclear factor-κB (NF-κB) and activator protein-1 (AP-1) activation was examined. The DNA binding activity of NF-κB and AP-1 stimulated LPS was inhibited by treatment of brazilin in a dose-dependent manner, suggesting that brazilin-mediated inhibition of NO production might be associated with the regulation of transcription factors NF-κB and AP-1. Taken together, these findings suggest that the suppressive effect of iNOS gene expression by brazilin might provide one possible mechanism for its anti-inflammatory and cancer chemopreventive activity.
Keywords: Brazilin; NO (nitric oxide); iNOS (inducible nitric oxide synthase); NF-κB (nuclear factor-κB); AP-1 (activator protein-1); Anti-inflammatory;

Effects of oleoyl-estrone with dexfenfluramine, sibutramine or phentermine on overweight rats by Raquel Ferrer-Lorente; Cristina Cabot; José-Antonio Fernández-López; Xavier Remesar; Marià Alemany (243-248).
We studied the combination of oleoyl-estrone with either dexfenfluramine, sibutramine or phentermine in overweight male rats treated for 10 days in order to determine whether they shared a mechanism of action. Oleoyl-estrone, dexfenfluramine and sibutramine decreased body weight and energy (essentially lipids); losses were higher when combined with oleoyl-estrone. Glycemia was maintained except under phentermine; oleoyl-estrone induced decreases in triacylglycerols, cholesterol, insulin and HOMA (homeostasis model assessment). Combination of oleoyl-estrone and sibutramine resulted in the loss of up to 29% body energy in 10 days. Energy expenditure was maintained. The effects of oleoyl-estrone and dexfenfluramine or sibutramine on appetite were substantially additive. All oleoyl-estrone-treated rats showed increased insulin sensitivity. In conclusion, combined treatment of overweight rats with oleoyl-estrone and sibutramine or dexfenfluramine results in a dramatic loss of weight and fat, whilst maintaining circulating energy homoeostasis.
Keywords: Obesity; Overweight; Energy balance; Oleoyl-estrone; Dexfenfluramine; Sibutramine; Phentermine;

Author Index (249-250).

Keyword Index (251-255).