Heme oxygenase-1 (HO-1) exerts beneficial effects, including angiogenesis and energy metabolism via the hypoxia-inducible factor-1α (HIF-1α) and peroxisome-proliferator-acti-vating receptor-γ coactivator-1α (PGC-1α)/estrogen-related receptor α (ERRα) pathways, respectively, in astrocytes. However, evidence of cross-talk between both pathways in HO metabolite-mediated mitochondrial biogenesis has not been well elucidated. Here, we found that HIF-1α was upregulated in astrocytes after ischemic brain injury following exposure to the carbon monoxide (CO)-releasing compound CORM-2. Experiments with pharmacological inhibitors and target-specific siRNAs revealed that HIF-1α levels were highly correlated with increased PGC-1α and ERRα levels, which were linked to the HO metabolites CO- and bilirubin-induced activation of apical L-type Ca2+ channel and sequential Ca2+-dependent signal transduction. Moreover, HIF-1α was stabilized in a proline hydroxylase-dependent manner by transient induction of intracellular hypoxia via the PGC-1α/ERRα-induced increases in mitochondrial biogenesis and oxygen consumption. HIF-1α knockdown blocked HO-1 system-mediated transcriptional expression of ERRα, but not of PGC-1α, suggesting a possible involvement of HIF-1α in ERRα-mediated mitochondrial biogenesis. These data suggest that the HO-1-derived metabolites, CO and bilirubin, elevate astrocytic mitochondrial function via a HIF-1α/ERRα circuit coupled with L-type Ca2+ channel activation and PGC-1α-mediated oxygen consumption. This circuit may play an important role in repairing neurovascular function after focal ischemic brain injury by stimulating mitochondrial biogenesis.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIP) (2017R1E1A2A01077606 to Y.K.C., 2017R1A2B3004565 to Y.M.K., and 2015M3A9E6028949 to Y.M.K.). This research was also supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (HI17C2160 to Y.K.C.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
© 2018 Choi et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
All Science Journal Classification (ASJC) codes
- Biochemistry, Genetics and Molecular Biology(all)
- Agricultural and Biological Sciences(all)