TY - JOUR
T1 - Ischemic preconditioning upregulates inducible nitric oxide synthase in cardiac myocytes
AU - Wang, Yang
AU - Guo, Yiru
AU - Zhang, Shelley X.
AU - Wu, Wen Jian
AU - Wang, Jianxun
AU - Bao, Weike
AU - Bolli, Roberto
N1 - Funding Information:
This study was supported in part by The Commonwealth of Kentucky Research Challenge Trust Fund, National Institutes of Health Grants R01 HL-43151, HL-55757, and HL-68088 (R.B.), American Heart Association Kentucky Affiliate Grant KY-9804557 (Y.G.), and The Jewish Hospital Research Foundation, Louisville, KY, USA.
PY - 2002
Y1 - 2002
N2 - Recent evidence has shown that the cardioprotection afforded by the late phase of ischemic preconditioning (PC) is mediated by upregulation of inducible nitric oxide synthase (iNOS). However, the specific cardiac cell type(s) that express(es) iNOS in response to ischemic PC remains unknown. Thus, mice underwent a sequence of six cycles of 4-min coronary occlusion/4-min reperfusion, which induces late PC, and tissue samples were collected at serial times for measurement of mRNA (Northern) and protein levels (Western). In addition, whole heart samples were cryosectioned for in situ hybridization and immunohistochemistry. The steady-state levels of iNOS mRNA in the ischemic regions started to increase at 1 h after ischemic PC, peaked at 3 h (201 ± 31% of sham, n=5: P<O.01) and remained elevated at 24 h (1774±22% of sham, n=5: P<0.01). In accordance with these data, iNOS protein expression was increased at 24 h (219±41% of sham, n= 5: P<0.01). In contrast, neither endothelial nitric oxide synthase (eNOS) mRNA levels nor its protein expression changed at any time-point. The magnitude of iNOS upregulation after ischemic PC was mild compared with that noted 66 h after permanent coronary occlusion (360±53% of sham) or 8 h after endotoxin (3117±61% of control). After ischemic PC, diffuse iNOS signals were detected with in situ hybridization and immunohistochemistry in the cytoplasmic space of cardiac myocytes and, to a lesser degree, in the wall of large vessels, but were absent in smooth muscle and endothelium of small vessels and in fibroblasts. This pattern contrasted with that observed in mouse hearts subjected to permanent coronary occlusion where strong iNOS signals were concentrated in inflammatory cells but absent in cardiac myocytes. Thus, not only the degree of iNOS expression but also its cellular distribution were profoundly different in reversibly injured (preconditioned) v infarcted myocardium. We conclude that iNOS is rapidly upregulated after ischemic PC and that cardiac myocytes are the main source of ischemic PC-induced iNOS expression. This study demonstrates, for the first time, a differential pattern of iNOS expression in sublethal (PC) v lethal ischemia, which may have important implication for the role of iNOS in these two settings.
AB - Recent evidence has shown that the cardioprotection afforded by the late phase of ischemic preconditioning (PC) is mediated by upregulation of inducible nitric oxide synthase (iNOS). However, the specific cardiac cell type(s) that express(es) iNOS in response to ischemic PC remains unknown. Thus, mice underwent a sequence of six cycles of 4-min coronary occlusion/4-min reperfusion, which induces late PC, and tissue samples were collected at serial times for measurement of mRNA (Northern) and protein levels (Western). In addition, whole heart samples were cryosectioned for in situ hybridization and immunohistochemistry. The steady-state levels of iNOS mRNA in the ischemic regions started to increase at 1 h after ischemic PC, peaked at 3 h (201 ± 31% of sham, n=5: P<O.01) and remained elevated at 24 h (1774±22% of sham, n=5: P<0.01). In accordance with these data, iNOS protein expression was increased at 24 h (219±41% of sham, n= 5: P<0.01). In contrast, neither endothelial nitric oxide synthase (eNOS) mRNA levels nor its protein expression changed at any time-point. The magnitude of iNOS upregulation after ischemic PC was mild compared with that noted 66 h after permanent coronary occlusion (360±53% of sham) or 8 h after endotoxin (3117±61% of control). After ischemic PC, diffuse iNOS signals were detected with in situ hybridization and immunohistochemistry in the cytoplasmic space of cardiac myocytes and, to a lesser degree, in the wall of large vessels, but were absent in smooth muscle and endothelium of small vessels and in fibroblasts. This pattern contrasted with that observed in mouse hearts subjected to permanent coronary occlusion where strong iNOS signals were concentrated in inflammatory cells but absent in cardiac myocytes. Thus, not only the degree of iNOS expression but also its cellular distribution were profoundly different in reversibly injured (preconditioned) v infarcted myocardium. We conclude that iNOS is rapidly upregulated after ischemic PC and that cardiac myocytes are the main source of ischemic PC-induced iNOS expression. This study demonstrates, for the first time, a differential pattern of iNOS expression in sublethal (PC) v lethal ischemia, which may have important implication for the role of iNOS in these two settings.
KW - Gene expression
KW - Infarction
KW - Ischemia
KW - Mouse
KW - Myocardium
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U2 - 10.1006/jmcc.2001.1482
DO - 10.1006/jmcc.2001.1482
M3 - Article
C2 - 11812160
AN - SCOPUS:0036169559
SN - 0022-2828
VL - 34
SP - 5
EP - 15
JO - Journal of Molecular and Cellular Cardiology
JF - Journal of Molecular and Cellular Cardiology
IS - 1
ER -