NO synthase

L’arbre bronchique constitue une large interface avec le milieu exterieur ce qui en fait notamment une sentinelle immunologique. Par ailleurs, il est soumis a de multiples contraintes physiques (variation de pressions lors du cycle ventilatoire) avec le developpement de pathologies lorsque la reponse a ces contraintes est inadaptee. Au cours de ce travail, nous avons essaye de caracteriser la reponse bronchique des voies aeriennes distales a partir d’un modele isole de bronche humaine soumis a l’application d’un stretch unique ou cyclique tel qu’il est genere lors de la ventilation mecanique. D’un point de vue fonctionnel, le stretch unique ou cyclique s’accompagne d’une modification significative du tonus basal de la bronche avec deux etapes : l’une precoce apparait au cours de l’exposition meme des variations de tension parietale, l’autre est tardive et apparait a l’arret de l’etirement. Concernant l’etape precoce, elle se revele robuste car aucun pre-traitement et particulieremen...

Objective: To assess the role of nitric oxide in the most relevant local and systemic manifestations in mice injected with the venom of the snake Bothrops asper. Mice were pretreated with nitric oxide synthase inhibitors, and the modifi cations of the pathological effects induced by the venom were tested. Results: Inhibition of NO synthesis did not affect acute local myonecrosis and hemorrhage in muscle tissue upon intramuscular injection of venom. Local footpad edema was reduced in mice pretreated with the NO synthase inhibitor L-NAME, and a reduction in the extent of infl ammatory infi ltrate in muscle tissue was observed after envenomation in mice pretreated with L-NAME and aminoguanidine. The most pronounced effect of NOS inhibition by L-NAME was an increment in the lethal activity of the venom, when injected by the intraperitoneal route. Conclusion: Nitric oxide does not seem to play a signifi cant role in the local acute pathological alterations (hemorrhage and myonecrosis) induced by B. asper venom in mice, although it contributes to edema and infl ammatory infi ltrate. Nitric oxide exerts a protective role in the systemic pathophysiological manifestations leading to lethality.

Volatile anesthetics increase levels of the neurotransmitter nitric oxide (NO) and the secondary messenger molecule cyclic guanosine monophosphate (cGMP) in the brain. NO activates the enzyme guanylyl cyclase (GC) to produce cGMP. We hypothesized that the NO-GC-cGMP pathway contributes to anesthesia-induced unconsciousness. Sevoflurane-induced loss and return of righting reflex (LORR and RORR, respectively) were studied in wild-type mice (WT) and in mice congenitally deficient in the GC-1α subunit (GC-1(-/-) mice). Spatial distributions of GC-1α and the GC-2α subunit in the brain were visualized by in situ hybridization. Brain cGMP levels were measured in WT and GC-1(-/-) mice after inhaling oxygen with or without 1.2% sevoflurane for 20 min. Higher concentrations of sevoflurane were required to induce LORR in GC-1(-/-) mice than in WT mice (1.5 ± 0.1 vs. 1.1 ± 0.2%, respectively, n = 14 and 14, P < 0.0001). Similarly, RORR occurred at higher concentrations of sevoflurane in GC-1...

Kava is a traditional Pacific beverage made from the root of Piper methysticum. It is mainly used for its sedative properties due to lipophilic lactones called kavalactones. Various preparations or medications made from this plant can be purchased via the internet. Kava action mechanisms include cell membrane stabilisation, inhibition of intracellular Ca 2+ increase and enzyme inactivation. Chronic or heavy kava consumption results in the skin taking on a scaly aspect. Biologically, an isolated increase in serum gamma-glutamyltransferase is apparent. Cases of sudden death after heavy kava sessions have occurred in Australia, and nine cases in New Caledonia were reported by our forensic laboratory during the 2000−mid-2013 period. No clear explanation has been given. We describe the possible action mechanism. Methods: We monitored 116 heavy kava drinkers. A multiple-probe drug cocktail was used on six other volunteers, all heavy and chronic kava drinkers, before and after kava abstinence to carry out CYP450 phenotyping. Results: The heavy chronic drinkers showed an isolated increase in GGT without any biological or clinical abnormality other than scaly skin. With the multiple-probe drug cocktail an inhibition of the CYP1A2 isoenzyme was demonstrated. In kava dermopathy a lack of epithelial nitric oxide production leading to an increased S-nitroso-glutathione degradation by the epithelial gamma-glutamyltransferase should be considered. Conclusions: As there are close structural and functional similarities between nitric oxide synthase (NOS) and CYP1A2, and as we have formerly demonstrated that kava inhibits CYP1A2, an inhibition of NOS in chronic kava drinkers must be studied to see if ichthyosis can be explained, and if high blood GGT level is a reflection of epithelial cell GGT activity. Furthermore, a decrease in NO bioavailability can cause myocardial and vascular dysfunctions and hypercoagulability, leading to acute coronary syndrome or ischemic stroke. This mechanism should be explored in cases of "post-kava session sudden death".

Recent studies have shown that the epithelial sodium channel (ENaC) is expressed in vascular tissue. However, the role that ENaC may play in the responses to vasoconstrictors and NO production has yet to be addressed. In this study, the contractile responses of perfused pressurized small-diameter rat mesenteric arteries to phenylephrine and serotonin were reduced by ENaC blockade with amiloride (75.1±3.2% and 16.9±2.3% of control values, respectively; P <0.01) that was dose dependent (EC 50 =88.9±1.6 nmol/L). Incubation with benzamil, another ENaC blocker, had similar effects. α, β, and γ ENaC were identified in small-diameter rat mesenteric arteries using RT-PCR and Western blot with specific antibodies. In situ hybridization and immunohistochemistry localized ENaC expression to the tunica media and endothelium of small-diameter rat mesenteric arteries. Patch-clamp experiments demonstrated that primary cultures of mesenteric artery endothelial cells expressed amiloride-sensitive...