Nox4 NADPH oxidase-derived reactive oxygen species, via endogenous carbon monoxide, promote survival of brain endothelial cells during TNF-α-induced apoptosis.
We investigated the role of reactive oxygen species (ROS) in promoting cell survival during oxidative stress induced by the inflammatory mediator tumor necrosis factor-α (TNF-α) in cerebral microvascular endothelial cells (CMVEC) from newborn piglets. Nox4 is the major isoform of NADPH oxidase responsible for TNF-α-induced oxidative stress and apoptosis in CMVEC. We present novel data that Nox4 NADPH oxidase-derived ROS also initiate a cell survival mechanism by increasing production of a gaseous antioxidant mediator carbon monoxide (CO) by constitutive heme oxygenase-2 (HO-2). TNF-α rapidly enhanced endogenous CO production in a superoxide- and NADPH oxidase-dependent manner in CMVEC with innate, but not with small interfering RNA (siRNA)-downregulated Nox4 activity. CORM-A1, a CO-releasing compound, inhibited Nox4-mediated ROS production and enhanced cell survival in TNF-α-challenged CMVEC. The ROS-induced CO-mediated survival mechanism requires functional interactions between the protein kinase B/Akt and extracellular signal-related kinase (ERK)/p38 MAPK signaling pathways activated by TNF-α. In Akt siRNA-transfected CMVEC and in cells with pharmacologically inhibited Akt, Erk1/2, and p38 mitogen-activated protein kinase (MAPK) activities, CORM-A1 was no longer capable of blocking Nox4 activation and apoptosis caused by TNF-α. Overall, Nox4 NADPH oxidase-derived ROS initiate both death and survival pathways in TNF-α-challenged CMVEC. The ROS-dependent cell survival pathway is mediated by an endogenous antioxidant CO, which inhibits Nox4 activation via a mechanism that includes Akt, ERK1/2, and p38 MAPK signaling pathways. The ability of CO to inhibit TNF-α-induced ERK1/2 and p38 MAPK activities in an Akt-dependent manner appears to be the key element in ROS-dependent survival of endothelial cells during TNF-α-mediated brain inflammatory disease.
Dept. of Physiology, University of Tennessee Health Science Center, 894 Union Ave., Memphis, TN 38163, USA.
Shyamali
S
Basuroy
Dilyara
D
Tcheranova
Sujoy
S
Bhattacharya
Charles W
CW
Leffler
Helena
H
Parfenova
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D001880:Boranes / Q000008:administration & dosage; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002248:Carbon Monoxide / Q000378:metabolism*; D002254:Carbonates / Q000008:administration & dosage; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D055806:Microvessels / Q000187:drug effects / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013552:Swine / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism* / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D001880:Boranes; D002254:Carbonates; D007527:Isoenzymes; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; C503854:sodium boranocarbonate; D002248:Carbon Monoxide; D006419:Heme Oxygenase (Decyclizing); C105245:heme oxygenase-2; D019255:NADPH Oxidases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases