Neutral sphingomyelinase, NADPH oxidase and reactive oxygen species. Role in acute hypoxic pulmonary vasoconstriction

8 páginas, 5 figuras.-- et al.The molecular mechanisms underlying hypoxic pulmonary vasoconstriction (HPV) are not yet properly understood. Mitochondrial electron transport chain (ETC) and NADPH oxidase have been proposed as possible oxygen sensors, with derived reactive oxygen species (ROS) playing key roles in coupling the sensor(s) to the contractile machinery. We have recently reported that activation of neutral sphingomyelinase (nSMase) and protein kinase C ζ (PKCζ) participate in the signalling cascade of HPV. Herein, we studied the significance of nSMase in controlling ROS production rate in rat pulmonary artery (PA) smooth muscle cells and thereby HPV in rat PA. ROS production (analyzed by dichlorofluorescein and dihydroethidium fluorescence) was increased by hypoxia in endothelium-denuded PA segments and their inhibition prevented hypoxia-induced voltage-gated potassium channel (KV) inhibition and pulmonary vasoconstriction. Consistently, H2O2, or its analogue t-BHP, decreased KV currents and induced a contractile response, mimicking the effects of hypoxia. Inhibitors of mitochondrial ETC (rotenone) and NADPH oxidase (apocynin) prevented hypoxia-induced ROS production, KV channel inhibition and vasoconstriction. Hypoxia induced p47phox phosphorylation and its interaction with caveolin-1. Inhibition of nSMase (GW4869) or PKCζ prevented p47phox phosphorylation and ROS production. The increase in ceramide induced by hypoxia (analyzed by immunocytochemistry) was inhibited by rotenone. Exogenous ceramide increased ROS production in a PKCζ sensitive manner. We propose an integrated signalling pathway for HPV which includes nSMase-PKCζ-NADPH oxidase as a necessary step required for ROS production and vasoconstriction.This work was supported by the Spanish Ministerio de Ciencia e Innovación (research grants SAF2008-03948, AGL2007-66108 to F.P.V., BFU2007-61848 to C.G. and Predoctoral FPI grant to C.M.), the Spanish Ministerio de Educacion (Predoctoral FPU grant to J.M.-S.) and Fundación Mutua Madrileña (to A.C. and F.P.V.).Peer reviewe

Carnosine protects pancreatic beta cells and islets against oxidative stress damage

Islet transplantation is a valid therapeutic option for type 1 diabetes treatment. However, in this procedure one of the major problems is the oxidative stress produced during pancreatic islet isolation. The aim of our study was to evaluate potential protective effects of L-carnosine and its isomer D-carnosine against oxidative stress. We evaluated the carnosine effect on cell growth, cell death, insulin production, and the main markers of oxidative stress in rat and murine stressed beta cell lines as well as in human pancreatic islets. Both isomers clearly inhibited hydrogen peroxide induced cytotoxicity, with a decrease in intracellular reactive oxygen and nitrogen species, prevented hydrogen peroxide induced apoptosis/necrosis, nitrite production, and reduced glucose-induced insulin secretion. In addition, NF-κB expression/translocation and nitrated protein induced in stressed cells was significantly reduced. Furthermore, both isomers improved survival and function, and decreased reactive oxygen and nitrogen species, and nitrite and nitrotyrosine production in human islets cultured for 1, 3, and 7 days. These results seem to indicate that both L and D-carnosine have a significant cytoprotective effect by reducing oxidative stress in beta cell lines and human islets, suggesting their potential use to improve islet survival during the islet transplantation procedure. [Display omitted] •Oxidative stress induces impairment of β-cell vitality and functions.•β-cells treated with carnosine improved their resistance to oxidative stress.•A similar effect of carnosine was observed in human islets.•Carnosine improves insulin production in β-cells damaged by oxidative stress