Neutral sphingomyelinase, NADPH oxidase and reactive oxygen species. Role in acute hypoxic pulmonary vasoconstriction
✍ Scribed by Giovanna Frazziano; Laura Moreno; Javier Moral-Sanz; Carmen Menendez; Lucía Escolano; Constancio Gonzalez; Eduardo Villamor; Jose Luis Alvarez-Sala; Angel L. Cogolludo; Francisco Perez-Vizcaino
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 202 KB
- Volume
- 226
- Category
- Article
- ISSN
- 0021-9541
No coin nor oath required. For personal study only.
✦ Synopsis
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 z (PKCz) 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 (K V ) inhibition and pulmonary vasoconstriction. Consistently, H 2 O 2 , or its analogue t-BHP, decreased K V 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, K V channel inhibition and vasoconstriction. Hypoxia induced p47 phox phosphorylation and its interaction with caveolin-1. Inhibition of nSMase (GW4869) or PKCz prevented p47 phox 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 PKCz sensitive manner. We propose an integrated signalling pathway for HPV which includes nSMase-PKCz-NADPH oxidase as a necessary step required for ROS production and vasoconstriction.