Effects of Barbiturates on the Expression of the Inducible Nitric Oxide Synthase in Vascular Smooth Muscle

Abstract

Certain cytokines stimulate the expression of the inducible nitric oxide synthase (iNOS) in vascular smooth muscle cells (VSMCs) and in many other cell types. The large amounts of nitric oxide (NO) generated by iNOS in the vascular wall contribute to the unrelenting hypotension in septic shock. Because septic patients are often treated with barbiturates, we examined the effect of these anesthetic agents on the expression of iNOS in VSMCs. The induction of iNOS was elicited either in cultured rat aortic SMCs [interleukin-1beta (IL-1beta), 60 U/ml for 24 h] or in endothelium-denuded segments of the rabbit carotid artery [IL-1beta (100 U/ml) for 7 h]. The activity of iNOS was assessed by the accumulation of nitrite in the conditioned medium of cultured VSMCs and by the hyporeactivity of carotid arteries to phenylephrine. Moreover, iNOS protein abundance was determined by Western blot analysis, iNOS messenger RNA (mRNA) by reverse transcription followed by the polymerase chain reaction (PCR), and activation of the transcription factor NF-kappaB by gel electrophoretic mobility-shift analysis of nuclear extracts from VSMCs. The IL-1beta-stimulated increase in nitrite formation, iNOS protein, and mRNA abundance in VSMCs was significantly augmented in the presence of thiopental (100 microM), whereas methohexital, hexobarbital, pentobarbital, and phenobarbital were without effect. The potentiating effect of thiopental was observed only when the barbiturate was administered during the first 2 h of the 24-h incubation period of cultured VSMCs with IL-1beta. Thiopental did not affect the IL-1beta-stimulated activation of NF-kappaB in VSMCs. This barbiturate also significantly augmented the hyporeactivity to phenylephrine in carotid arteries exposed to IL-1beta, an effect that was abolished by N(G)-nitro-L-arginine. Exposure of either cultured or native VSMCs to thiopental alone did not stimulate iNOS expression. These findings demonstrate that the thiobarbiturate thiopental, but not oxybarbiturates, augments the IL-1beta-stimulated synthesis of NO in both cultured and native VSMCs. This effect of thiopental is the result of an increased expression of iNOS, involving most likely mechanisms distinct from NF-kappaB activation. The use of thiopental for long-term treatment of septic patients might possibly potentiate the biosynthesis of NO in the vascular wall and thus cause a further deterioration of the hemodynamic state.

Ketamine suppresses endotoxin-induced NF-κB expression

“…23,25,26 It is interesting that thiopental (a commonly used intravenous anesthetic for neurologic surgery) augments proinflammatory cytokine-induced iNOS expression and subsequent cellular NO production and release. 27 The common clinical dosages for ketamine in humans range from 0.5 to 10 mg·kg -1 iv, 28 with resultant plasma concentrations of 60-80 µM. 28,29 Therefore, the concentrations of ketamine used for the invitro and vivo portions of these experiments are similar to the concentrations used clinically.…”

Anesthetic modulation of immune reactions mediated by nitric oxide

“…Transcription factors: NF-kB, nuclear factor-κB; IRF-1, interferon regulatory factor-1; STAT-1a, signal transducer and activator of transcription-1α; CREB, cyclic AMPresponsive element binding protein; AP-1, activating protein-1; LPS, lipopolysaccharide; cGMP, cyclic guanosine monophosphate by thiopental, indicating that thiopental may suppress iNOS-induced cyclic GMP formation in vascular smooth muscle, without affecting NO production [17]. Of interest, IL-1β-stimulated increases in nitrite formation, iNOS protein, and mRNA abundance in cultured rat aortic smooth muscle cells were augmented in the presence of thiopental, whereas methohexital, hexobarbital, pentobarbital, and phenobarbital were without effect; thiopental did not affect the IL-1β-stimulated activation of nuclear factor-κB (NF-κB); also, this barbiturate augmented hyporeactivity to phenylephrine in rabbit carotid arteries exposed to IL-1β, an effect that was abolished by L-NA [18], These effects of thiopental could be the result of increased iNOS expression, most likely involving mechanisms distinct from NF-κB activation. Propofol inhibited NF-κB activation in LPSstimulated human umbilical vein endothelial cells [19].…”

Anästhetika und Stickstoffmonoxid (NO) - Interaktionen und ihre Bedeutung für die Anästhesie

“…Kim und Fulco [56] zeigten, daß das Ausmaß der Induzierbarkeit der Cytochrom P450-abhängigen Monooxygenasen vom Grad der Lipophilie abhängt. Ebenso kam es nach 7-stündiger Inkubation deendothelialisierter Gefäßringe der A. carotis des Kaninchens mit Thiopental (100 µM) zu einer Zunahme der IL-1β-induzierten, NO-vermittelten Abschwächung der konstringierenden Wirkung von Phenylephrin [50]. Da aber nur Thiopental die IL-1β-induzierte Expression der iNOS verstärkte, U/ml)-induzierte Nitritfreisetzung, ein Maß für die iNOS-Aktivität, während Methohexital, Pheno-, Hexo-und Pentobarbital ohne Wirkung blieben [50].…”

“…Die Beurteilung des Propofol in seinen Auswirkungen auf eine Verstärkung der iNOS-Expression und -aktivität wird durch den Zusatz des Lösungsmittels mit möglichen Eigeneffekten erschwert [51]. Die Beurteilung des Propofol in seinen Auswirkungen auf eine Verstärkung der iNOS-Expression und -aktivität wird durch den Zusatz des Lösungsmittels mit möglichen Eigeneffekten erschwert [51].…”