Hypoxia differentially regulates stress proteins in cultured cardiomyocytes: role of the p38 stress-activated kinase signaling cascade, and relation to cytoprotection.
OBJECTIVE
Stress proteins (heat shock proteins, HSPs) are molecular chaperones that have been shown to enhance the survival of cells exposed to environmental stress. We sought to investigate the effects of hypoxia on the levels of HSP27 and heme oxygenase-1 (HO-1 or HSP32) in an established model of rat neonatal cardiac myocytes in culture.


METHODS
Myocytes were subjected to hypoxia (<0.5% O(2) for 16 h). Studies of cell viability and nuclear morphology showed no evidence of cell death under these conditions.


RESULTS
Messenger RNA analysis demonstrated constitutive expression of HSP27 and low levels of HO-1. Hypoxia strongly induced HO-1 mRNA without affecting HSP27 mRNA. In parallel to mRNA levels, hypoxia increased HO-1 protein level without affecting HSP27. To further assess the signaling pathways implicated in HO-1 induction, we used inhibition experiments. The tyrosine kinase inhibitor tyrphostin and the mitogen-activated protein kinase inhibitor PD98059 did not prevent HO-1 induction, while the protein kinase C inhibitor chelerythrine partially blocked this response. The p38 stress-activated kinase inhibitor SB203580 was the most potent in suppressing hypoxia-induced HO-1. In vitro kinase assays, cell labeling and immunoprecipitation showed activation of signaling pathways downstream of p38 stress-activated kinase as revealed by an increase in phosphorylation of MAPKAPK-2/3 kinases and HSP27.


CONCLUSIONS
These data show a differential pattern of hypoxia-induced HSP expression and implicate the stress kinase in HO-1 induction. Thus, selective regulation of HSP levels may play a role in the cardioprotective mechanisms that participate in the adaptive response to hypoxia-induced stress.
Kacimi
R
R
Cardiology Section, VA Medical Center, 4150 Clement Street, San Francisco, CA 94121, USA.
Chentoufi
J
J
Honbo
N
N
Long
C S
CS
Karliner
J S
JS
D000470:Alkaloids; D000704:Analysis of Variance; D000818:Animals; D053119:Benzophenanthridines; D015687:Cell Hypoxia; D002470:Cell Survival; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics / Q000378:metabolism*; D051547:Heme Oxygenase-1; D007093:Imidazoles / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D009206:Myocardium / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010617:Phenanthridines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011960:Receptors, Estrogen / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D020032:Tyrphostins / Q000494:pharmacology
D000470:Alkaloids; D053119:Benzophenanthridines; D004791:Enzyme Inhibitors; D005419:Flavonoids; D006360:Heat-Shock Proteins; D007093:Imidazoles; D010617:Phenanthridines; D011725:Pyridines; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D020032:Tyrphostins; C016299:chelerythrine; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D020929:Mitogen-Activated Protein Kinase Kinases; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one