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Diazoxide acts more as a PKC‐ ɛ activator, and indirectly activates the mitochondrial K ATP channel conferring cardioprotection against hypoxic injury
Author(s) -
Kim MY,
Kim M J,
Yoon I S,
Ahn J H,
Lee S H,
Baik E J,
Moon CH,
Jung YS
Publication year - 2006
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0706922
Subject(s) - diazoxide , protein kinase c , rottlerin , mitochondrion , biology , microbiology and biotechnology , cytosol , chemistry , endocrinology , biochemistry , phosphorylation , enzyme , insulin
Background and purpose: Diazoxide, a well‐known opener of the mitochondrial ATP‐sensitive potassium (mitoK ATP ) channel, has been demonstrated to exert cardioprotective effect against ischemic injury through the mitoK ATP channel and protein kinase C (PKC). We aimed to clarify the role of PKC isoforms and the relationship between the PKC isoforms and the mitoK ATP channel in diazoxide‐induced cardioprotection. Experimental approach: In H9c2 cells and neonatal rat cardiomyocytes, PKC‐ɛ activation was examined by Western blotting and kinase assay. Flavoprotein fluorescence, mitochondrial Ca 2+ and mitochondrial membrane potential were measured by confocal microscopy. Cell death was determined by TUNEL assay. Key results: Diazoxide (100 μM) induced translocation of PKC‐ɛ from the cytosolic to the mitochondrial fraction. Specific blockade of PKC‐ɛ by either ɛV1‐2 or dominant negative mutant PKC‐ɛ (PKC‐ɛ KR) abolished the anti‐apoptotic effect of diazoxide. Diazoxide‐induced flavoprotein oxidation was inhibited by either ɛV1‐2 or PKC‐ɛ KR transfection. Treatment with 5‐hydroxydecanoate (5‐HD) did not affect translocation and activation of PKC‐ɛ induced by diazoxide. Transfection with wild type PKC‐ɛ mimicked the flavoprotein‐oxidizing effect of diazoxide, and this effect was completely blocked by ɛV1‐2 or 5‐HD. Diazoxide prevented the increase in mitochondrial Ca 2+ , mitochondrial depolarization and cytochrome c release induced by hypoxia and all these effects of diazoxide were blocked by ɛV1‐2 or 5‐HD. Conclusions and Implications: Diazoxide induced isoform‐specific translocation of PKC‐ɛ as an upstream signaling molecule for the mitoK ATP channel, rendering cardiomyocytes resistant to hypoxic injury through inhibition of the mitochondrial death pathway. British Journal of Pharmacology (2006) 149 , 1059–1070. doi: 10.1038/sj.bjp.0706922