eugenosedin-a and Hypotension

Eugenosedin-A has been demonstrated to possess alpha/beta-adrenoceptor and serotonergic receptor blocking activities. We have investigated by what mechanisms eugenosedin-A prevents lipopolysaccharide (LPS)-induced hypotension, vascular hyporeactivity, hyperglycaemia, oxidative injury or inflammatory cytokines formation in rats. Intravenous administration of eugenosedin-A, trazodone, yohimbine (1 mg kg(-1)), aminoguanidine or ascorbic acid (15 mg kg(-1)) normalized LPS (10 mg kg(-1))-induced hypotension. Pretreatment with eugenosedin-A or the other agents 30 min before LPS injection reduced aortic hyporeactivity. LPS-induced increases in plasma interleukin-1beta (IL-beta), IL-6, interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and blood glucose levels were significantly inhibited by eugenosedin-A (1 mg kg(-1), i. v.). The same dose of trazodone, a chloropiperazinylbenzene-type antidepressant, and yohimbine, an alpha(2)-adrenoceptor antagonist, reduced IL-1beta and TNF-alpha, but it could not inhibit hyperglycaemia. Aminoguanidine, an inducible nitric oxide synthase (iNOS) inhibitor, and ascorbic acid, an antioxidant, decreased IL-1beta, TNF-alpha contents and hyperglycaemia. Eugenosedin-A and the other agents inhibited Fe(2+)-ascorbic acid-induced peroxidation in rat cortex, indicating that those agents had antioxidant effects, with the exception of aminoguanidine. In free radical scavenged experiments, eugenosedin-A and ascorbic acid eliminated peroxyl radicals. All test agents inhibited the LPS-induced increase of malondialdehyde (MDA) content in rat brain homogenates. When mice were administered an intraperitoneal injection of LPS alone, mortality occurred from 4 to 16 h, after which time all were dead. However, eugenosedin-A significantly prolonged the survival time after LPS injection, suggesting that eugenosedin-A protected against LPS-induced cardiovascular dysfunction, hyperglycaemia, tissue injury and inflammatory cytokine production. This was attributable mainly to the antioxidant and peroxyl radical scavenged effects of eugenosedin-A, and which may be, at least in part, due to its blockade on alpha/beta-adrenergic and serotonergic receptors.

Topics: Animals; Antidepressive Agents, Second-Generation; Antioxidants; Aorta, Thoracic; Blood Glucose; Cytokines; Free Radical Scavengers; Hyperglycemia; Hypotension; In Vitro Techniques; Lipid Peroxidation; Lipopolysaccharides; Mice; Mice, Inbred ICR; Oxidants; Oxidative Stress; Peroxides; Piperazines; Rats; Rats, Wistar; Survival Analysis; Trazodone

Eugenosedin-A is a newly synthesized compound with special serotonergic, alpha- and beta1-adrenergic blocking actions. Intravenous injection of eugenosedin-A significantly caused dose-dependent decreases in the mean arterial blood pressure and heart rate in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). The effects of eugenosedin-A-decreased blood pressure and heart rate in SHR were more potent than in WKY. In in vitro experiments, eugenosedin-A competitively antagonized the serotonin-, norepinephrine- and clonidine-induced vasocontraction in a concentration-dependent manner in isolated thoracic aorta of WKY and SHR. We also observed that eugenosedin-A competitively antagonized the isoproterenol-induced positive inotropic effects in a concentration-dependent manner in the isolated left atrium of WKY and SHR. These findings clearly suggested that eugenosedin-A possesses alpha1/alpha2, beta1 and 5-HT2A receptor-blocking activities. The order of pA2 values in isolated tissues of WKY was 5-HT2A > alpha1/alpha2 > beta1. However, the order of pA2 values in isolated tissues of SHR was alpha1/alpha2 > 5-HT2A > beta1. Similarly, we found that the in vitro functional activity of eugenosedin-A is quite different between WKY and SHR. On the other hand, in the isolated rabbit ear artery sensitized with 16 mmol/l K+, eugenosedin-A antagonized 5-nonyloxytryptamine- and serotonin-induced vasocontractions, indicating that it also blocked 5-HT1B and 5-HT2A receptors. In radioligand binding experiments, eugenosedin-A had significant binding affinities on alpha1/alpha2, beta1, 5-HT1B and 5-HT2A receptors. Finally, we suggest that the hypotensive effects of eugenosedin-A can be attributed to its multiple actions on the blockade of 5-HT1B, 5-HT2A, alpha and beta1 receptors in both WKY and SHR strains.

Topics: Adrenergic alpha-Antagonists; Adrenergic beta-Antagonists; Animals; Aorta, Thoracic; Binding, Competitive; Blood Pressure; Bradycardia; Clonidine; Dose-Response Relationship, Drug; Ear; Electric Stimulation; Heart Atria; Heart Rate; Hypotension; Injections, Intravenous; Isoproterenol; Muscle, Smooth, Vascular; Myocardial Contraction; Norepinephrine; Piperazines; Rabbits; Radioligand Assay; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptor, Serotonin, 5-HT2A; Receptors, Adrenergic, alpha-1; Receptors, Adrenergic, alpha-2; Receptors, Adrenergic, beta-1; Serotonin; Serotonin Antagonists; Species Specificity; Tritium; Tryptamines; Vasoconstriction; Vasodilation