title: Mechanisms involved in the early increase of serotonin contraction evoked by endotoxin in rat middle cerebral arteries.
abstract: The present study investigated the mechanisms involved in the increased 5-hydroxytryptamine (5-HT) vasoconstriction observed in rat middle cerebral arteries exposed in vitro to lipopolysaccharide (LPS, 10 microg x ml-1) for 1-5 h. Functional, immunohistochemical and Western blot analysis and superoxide anion measurements by ethidium fluorescence were performed. LPS exposure increased 5-HT (10 microm) vasoconstriction only during the first 4 h. In contrast to control tissue, indomethacin (10 microm), the COX-2 inhibitor NS 398 (10 microm), the TXA2/PGH2 receptor antagonist SQ 29548 (1 microm) and the TXA2 synthase inhibitor furegrelate (1 microm) reduced 5-HT contraction of LPS-treated arteries from hour one. The iNOS inhibitor aminoguanidine (0.1 mm) increased 5-HT contraction from hour three of LPS incubation. The superoxide anion scavenger superoxide dismutase (SOD, 100 U ml-1) and the H2O2 scavenger catalase (1000 U ml-1), as well as the respective inhibitors of NAD(P)H oxidase and xanthine oxidase, apocynin (0.3 mm) and allopurinol (0.3 mm), reduced 5-HT contraction after LPS incubation. LPS induced an increase in superoxide anion levels that was abolished by PEG-SOD. Subthreshold concentrations of the TXA2 analogue U 46619, xanthine/xanthine oxidase and H2O2 potentiated, whereas those of sodium nitroprusside inhibited, the 5-HT contraction. COX-2 expression was increased at 1 and 5 h of LPS incubation, while that of iNOS, Cu/Zn-SOD and Mn-SOD was only increased after 5 h. All the three vascular layers expressed COX-2 and Cu/Zn-SOD. iNOS expression was detected in the endothelium and adventitia after LPS. In conclusion, increased production of TXA2 from COX-2, superoxide anion and H2O2 enhanced vasoconstriction to 5-HT during the first few hours of LPS exposure; iNOS and SOD expression counteracted that increase at 5 h. These changes can contribute to the disturbance of cerebral blood flow in endotoxic shock.
authors.affiliation: Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, C/ Arzobispo Morcillo 4, Madrid 28029, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: Hernanz
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Alonso
authors.forename: Ana M
authors.initials: AM
authors.lastname: Briones
authors.forename: Elisabet
authors.initials: E
authors.lastname: Vila
authors.forename: Ulf
authors.initials: U
authors.lastname: Simonsen
authors.forename: Mercedes
authors.initials: M
authors.lastname: Salaices
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D051546:Cyclooxygenase 2; D004357:Drug Synergism; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004731:Endotoxins / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D005947:Glucose / Q000037:antagonists & inhibitors / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000494:pharmacology; D008297:Male; D020768:Middle Cerebral Artery / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D013928:Thromboxane A2 / Q000096:biosynthesis; D014325:Tromethamine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects* / Q000502:physiology
chemical_list: D004731:Endotoxins; D007527:Isoenzymes; C074097:Krebs-Henseleit solution; D008070:Lipopolysaccharides; D017382:Reactive Oxygen Species; D014325:Tromethamine; D013481:Superoxides; D012701:Serotonin; D013928:Thromboxane A2; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D013482:Superoxide Dismutase; D005947:Glucose