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Diazoxide preconditioning is mediated by mechanistic target of rapamycin (mTOR) and S6 Kinase (S6K)
Author(s) -
Dutta Somhrita,
Rutkai Ibolya,
Walter Korey,
Katakam Prasad,
Busija David
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.777.2
Subject(s) - p70 s6 kinase 1 , pi3k/akt/mtor pathway , diazoxide , protein kinase b , wortmannin , mitochondrion , reactive oxygen species , microbiology and biotechnology , chemistry , biology , phosphorylation , pharmacology , signal transduction , endocrinology , insulin
Diazoxide (DZ), a mitochondrial ATP‐sensitive potassium channel opener, is protective in models of brain ischemia. The cellular signaling pathways activated by DZ preconditioning are not clear. We examined the role of the mTOR pathway in delayed DZ‐induced preconditioning of cultured rat primary cortical neurons. Neurons were treated for three days with 500 µM DZ or feeding medium and then exposed to three hours of continuous normoxia in DMEM with glucose or with oxygen glucose deprivation (OGD) followed by reoxygenation and feeding medium. OGD decreased viability by 50 percent, depolarized mitochondria and reduced mitochondrial respiration, whereas DZ treatment improved viability and mitochondrial respiration, and suppressed reactive oxygen species production, but did not restore mitochondrial membrane potential after OGD. Diazoxide induced neuroprotection was associated with increased phosphorylation of protein kinase B (Akt), mTOR, and the major mTOR downstream substrate, S6 Kinase (S6K). Previously, we have reported that wortmannin and rapamycin abolished the protective effects of DZ. We expanded our study using torin‐1, a structurally distinct mTOR inhibitor, as well as S6K targeted siRNA. Both approaches abolished the protective effects of DZ. Diazoxide effects on mitochondrial membrane potential or reactive oxygen species production were not affected by rapamycin. We conclude that DZ protects against OGD by activation of the Akt‐mTOR‐S6K pathway rather than by reduced ROS production and mitochondrial membrane depolarization. This work was supported by NIH grants HL‐077731, HL‐030260, HL‐065380, and HL‐093554.