Effect of angiotensin II type 2 receptor blockade on activation of mitogen-activated protein kinases after ischemia-reperfusion in isolated working rat hearts.
BACKGROUND
The stress-responsive mitogen-activated protein kinases (MAPKs) (p38-MAPK, c-Jun NH2-terminal kinase [JNK-1 and JNK-2], and extracellular signal regulated kinases [ERK-1 and ERK-2]) might be involved in angiotensin II (AII)-induced ischemia-reperfusion injury. Cardioprotection induced by AII type 1 (AT1) and type 2 (AT2) receptor blockade during ischemia-reperfusion is associated with protein kinase Cepsilon (PKCepsilon), nitric oxide, and cyclic guanosine monophosphate (cGMP) signaling. Our aim was to assess the effect of selective AT1 and AT2 receptor blockade with losartan and PD123,319, respectively, on MAPK expression after ischemia-reperfusion in isolated working rat hearts.


METHODS
Groups of six hearts were subjected to global ischemia (30 minutes) followed by reperfusion (30 minutes) and exposed to no drug/no ischemia-reperfusion (control), ischemia-reperfusion/no drug, and ischemia-reperfusion with losartan (1 microM), or PD123,319 (0.3 microM) and additional groups. AT1/AT2 receptor expression, MAPKs, PKCepsilon, and cGMP, and changes in mechanical function were measured. Western blotting was done on left ventricular tissue for AT1/AT2, p38/phosphorylated-p38 (p-p38), phosphorylated (p)-JNK-1/-2, phosphorylated (p)-ERK-1/-2, and PKCepsilon proteins; Northern blots for AT1/AT2 mRNA; and enzyme immunoassay for cGMP.


RESULTS
Compared with controls, ischemia-reperfusion induced significant left ventricular dysfunction, decreased AT2 protein and mRNA, increased p-p38 and p-JNK-1/-2, did not change p-ERK-1/-2 or PKCepsilon, and decreased cGMP. PD123,319 improved left ventricular recovery after ischemia-reperfusion, increased AT2 protein and mRNA, mildly increased p-p38, normalized p-JNK-1, did not change p-ERK-1/-2, and increased PKCepsilon and cGMP. Losartan did not change p-p38, increased p-JNK-1, and did not change pERK-1/-2, PKCepsilon, or cGMP.


CONCLUSIONS
The overall results suggest that the activation of p38-MAPK and JNK might be linked to AII signaling and play a significant role in acute ischemia-reperfusion injury as well as in the cardioprotective effect of AT2 receptor blockade.
Kumar
Dinender
D
Cardiovascular Research Center, Department of Medicine, University of Wisconsin, Madison, Wisconsin, USA.
Menon
Vijayan
V
Ford
William R
WR
Clanachan
Alexander S
AS
Jugdutt
Bodh I
BI
D057912:Angiotensin II Type 2 Receptor Blockers; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology; D006152:Cyclic GMP / Q000378:metabolism; D004195:Disease Models, Animal; D015773:Enalaprilat / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006321:Heart / Q000187:drug effects*; D019808:Losartan / Q000494:pharmacology; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects*; D008955:Models, Cardiovascular; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000187:drug effects; D051744:Protein Kinase C-epsilon; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000201:enzymology*
D057912:Angiotensin II Type 2 Receptor Blockers; D000959:Antihypertensive Agents; D012333:RNA, Messenger; C497257:Prkce protein, rat; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon; D020928:Mitogen-Activated Protein Kinases; D015773:Enalaprilat; D006152:Cyclic GMP; D019808:Losartan