HO-2 provides endogenous protection against oxidative stress and apoptosis caused by TNF-alpha in cerebral vascular endothelial cells.
Tumor necrosis factor-alpha (TNF-alpha) causes oxidative stress and apoptosis in a variety of cell types. Heme oxygenase (HO) degrades heme to bilirubin, an antioxidant, and carbon monoxide (CO), a cell cycle modulator, and a vasodilator. Newborn pig cerebral microvascular endothelial cells (CMVEC) highly express constitutive HO-2. We investigated the role of HO-2 in protection against TNF-alpha-induced apoptosis in cerebral vascular endothelium. In CMVEC from mice and newborn pigs, 15 ng/ml TNF-alpha alone, or with 10 microg/ml cycloheximide (CHX) caused apoptosis detected by nuclear translocation of p65 NF-kappaB, caspase-3 activation, DNA fragmentation, cell-cell contact destabilization, and cell detachment. TNF-alpha did not induce HO-1 expression in CMVEC. CMVEC from HO-2 knockout mice showed greater sensitivity to apoptosis caused by serum deprivation and TNF-alpha than did wild-type mice. TNF-alpha increased reactive oxygen species generation, including hydrogen peroxide and superoxide radicals, as detected by dihydrorhodamine-123 and dihydroethidium. The TNF-alpha response was inhibited by superoxide dismutase and catalase suggesting apoptosis is oxidative stress related. Inhibition of endogenous HO-2 in newborn pig CMVEC increased oxidative stress and exaggerated apoptosis caused by serum deprivation and TNF-alpha. In HO-1-overexpressing CMVEC (HO-1 selective induction by cobalt portophyrin), TNF-alpha did not cause apoptosis. A CO-releasing compound, CORM-A1, and bilirubin blocked TNF-alpha-induced reactive oxygen species accumulation and apoptosis consistent with the antioxidant and antiapoptotic roles of the end products of HO activity. We conclude that HO-2 is critical for protection of cerebrovascular endothelium against apoptotic changes induced by oxidative stress and cytokine-mediated inflammation.
Basuroy
Shyamali
S
Dept. of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA. sbasuroy@physio1.utmem.edu
Bhattacharya
Sujoy
S
Tcheranova
Dilyara
D
Qu
Yan
Y
Regan
Raymond F
RF
Leffler
Charles W
CW
Parfenova
Helena
H
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects*; D001663:Bilirubin / Q000494:pharmacology; D001921:Brain / Q000166:cytology* / Q000187:drug effects*; D002248:Carbon Monoxide / Q000494:pharmacology; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D015870:Gene Expression / Q000187:drug effects; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051547:Heme Oxygenase-1 / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D013552:Swine; D014409:Tumor Necrosis Factor-alpha / Q000633:toxicity*; D015854:Up-Regulation / Q000187:drug effects
D007527:Isoenzymes; D016328:NF-kappa B; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D002248:Carbon Monoxide; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C105245:heme oxygenase-2; D001663:Bilirubin