Yoon Kyung Choi1,2, Ji-Hee Kim1, Dong-Keun Lee1, Kwang-Soon Lee1, Moo-Ho Won3, Dooil Jeoung4, Hansoo Lee5, Kwon-Soo Ha1, Young-Guen Kwon6, Young-Myeong Kim1. 1. 1 Department of Molecular and Cellular Biochemistry, Kangwon National University , Chuncheon, Republic of Korea. 2. 2 Department of Bioscience and Biotechnology, Konkuk University , Seoul, Republic of Korea. 3. 3 Department of Neurobiology, School of Medicine, Kangwon National University , Chuncheon, Republic of Korea. 4. 4 Department of Biochemistry, Kangwon National University , Chuncheon, Republic of Korea. 5. 5 Department of Life Sciences, College of Natural Sciences, Kangwon National University , Chuncheon, Republic of Korea. 6. 6 Department of Biochemistry, College of Life Science and Biotechnology, Yonsei University , Seoul, Republic of Korea.
Abstract
AIMS: The heme oxygenase-1 (HO-1)/carbon monoxide (CO) pathway induced in astrocytes after ischemic brain injury promotes vascular endothelial growth factor (VEGF) expression to maintain and repair neurovascular function. Although HO-1-derived CO has been shown to induce hypoxia-inducible factor-1α (HIF-1α)-dependent VEGF expression, the underlying mechanism independent of HIF-1α remains to be elucidated. RESULTS: HO-1 and VEGF were coexpressed in astrocytes of ischemic mouse brain tissues. Experiments with specific siRNAs and pharmacological activators/inhibitors of various target genes demonstrated that astrocytes pre-exposed to the CO-releasing compound, CORM-2, or transfected with HO-1 increased HIF-1α-independent VEGF expression via sequential activation of the following signal cascades; Ca2+/calmodulin-dependent protein kinase kinase β-mediated AMP-activated protein kinase (AMPK)α activation, AMPKα-induced increases in nicotinamide phosphoribosyltransferase (NAMPT) expression and cellular NAD+ level, sirtuin 1 (SIRT1)-dependent peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) stabilization and activation, and PGC-1α/estrogen-related receptor (ERR)α-mediated VEGF expression. All of these sequential events were blocked by an L-type voltage-gated Ca2+ channel inhibitor and Ca2+ chelators, but not by other Ca2+ channel inhibitors. INNOVATION: HO-1-derived CO elicits Ca2+ influx by activating L-type Ca2+ channels, which is a key player in HIF-1α-independent VEGF expression by activating the AMPKα-NAMPT-SIRT1-PGC-1α/ERRα pathway. CONCLUSION: Our results provide new mechanistic insight into the possible role for L-type Ca2+ channels in HO-1/CO-induced angiogenesis. Antioxid. Redox Signal. 27, 21-36.
AIMS: The heme oxygenase-1 (HO-1)/carbon monoxide (CO) pathway induced in astrocytes after ischemic brain injury promotes vascular endothelial growth factor (VEGF) expression to maintain and repair neurovascular function. Although HO-1-derived CO has been shown to induce hypoxia-inducible factor-1α (HIF-1α)-dependent VEGF expression, the underlying mechanism independent of HIF-1α remains to be elucidated. RESULTS:HO-1 and VEGF were coexpressed in astrocytes of ischemicmouse brain tissues. Experiments with specific siRNAs and pharmacological activators/inhibitors of various target genes demonstrated that astrocytes pre-exposed to the CO-releasing compound, CORM-2, or transfected with HO-1 increased HIF-1α-independent VEGF expression via sequential activation of the following signal cascades; Ca2+/calmodulin-dependent protein kinase kinase β-mediated AMP-activated protein kinase (AMPK)α activation, AMPKα-induced increases in nicotinamide phosphoribosyltransferase (NAMPT) expression and cellular NAD+ level, sirtuin 1 (SIRT1)-dependent peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) stabilization and activation, and PGC-1α/estrogen-related receptor (ERR)α-mediated VEGF expression. All of these sequential events were blocked by an L-type voltage-gated Ca2+ channel inhibitor and Ca2+ chelators, but not by other Ca2+ channel inhibitors. INNOVATION: HO-1-derived CO elicits Ca2+ influx by activating L-type Ca2+ channels, which is a key player in HIF-1α-independent VEGF expression by activating the AMPKα-NAMPT-SIRT1-PGC-1α/ERRα pathway. CONCLUSION: Our results provide new mechanistic insight into the possible role for L-type Ca2+ channels in HO-1/CO-induced angiogenesis. Antioxid. Redox Signal. 27, 21-36.