Differential mechanisms of hepatic vascular dysregulation with mild vs. moderate ischemia-reperfusion.
Endotoxemia produces hepatic vascular dysregulation resulting from inhibition of endothelin (ET)-stimulated NO production. Mechanisms include overexpression of caveolin-1 (Cav-1) and altered phosphorylation of endothelial nitric oxide (NO) synthase (NOS; eNOS) in sinusoidal endothelial cells. Since ischemia-reperfusion (I/R) also causes vascular dysregulation, we tested whether the mechanisms are the same. Rats were exposed to either mild (30 min) or moderate (60 min) hepatic ischemia in vivo followed by reperfusion (6 h). Livers were harvested and prepared into precision-cut liver slices for in vitro analysis of NOS activity and regulation. Both I/R injuries significantly abrogated both the ET-1 (1 microM) and the ET(B) receptor agonist (IRL-1620, 0.5 microM)-mediated stimulation of NOS activity. 30 min I/R resulted in overexpression of Cav-1 and loss of ET-stimulated phosphorylation of Ser1177 on eNOS, consistent with an inflammatory response. Sixty-minute I/R also resulted in loss of ET-stimulated Ser1177 phosphorylation, but Cav-1 expression was not altered. Moreover, expression of ET(B) receptors was significantly decreased. This suggests that the failure of ET to activate eNOS following 60-min I/R is associated with decreased protein expression consistent with ischemic injury. Thus hepatic vascular dysregulation following I/R is mediated by inflammatory mechanisms with mild I/R whereas ischemic mechanisms dominate following more severe I/R stress.
Lee
Sang Ho
SH
Department of Biology, University of North Carolina at Charlotte, Charlotte, NC 28223, USA.
Culberson
Cathy
C
Korneszczuk
Katarzyna
K
Clemens
Mark G
MG
D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D002147:Calmodulin / Q000378:metabolism; D051242:Caveolin 1 / Q000378:metabolism; D019332:Endothelin-1 / Q000494:pharmacology; D016232:Endothelins / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000097:blood; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D044022:Receptor, Endothelin A / Q000378:metabolism; D044023:Receptor, Endothelin B / Q000378:metabolism; D015427:Reperfusion Injury / Q000097:blood / Q000378:metabolism / Q000503:physiopathology*
D002147:Calmodulin; D051242:Caveolin 1; D019332:Endothelin-1; D016232:Endothelins; D018841:HSP90 Heat-Shock Proteins; D010446:Peptide Fragments; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; C074308:sovateltide; D007770:L-Lactate Dehydrogenase; D052250:Nitric Oxide Synthase Type III; D000410:Alanine Transaminase