title: Myofibrillogenesis regulator-1 attenuated hypoxia/reoxygenation-induced apoptosis by inhibiting the PERK/Nrf2 pathway in neonatal rat cardiomyocytes.
abstract: The purpose of this study was to investigate the role of myofibrillogenesis regulator-1 (MR-1) in cardiomyocyte apoptosis induced by hypoxia/reoxygenation (H/R), through protein kinase R-like ER kinase (PERK)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. To address this aim, an H/R model of neonatal rat cardiomyocytes was used. MR-1 was overexpressed using an adenoviral vector system and knocked down using MR-1 specific siRNA. Apoptosis was assessed by using Annexin V/PI double staining, terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling assay, and the Bcl-2/Bax ratio. Western blotting was used to detect the protein levels of MR-1, glucose-regulated protein 78 (GRP78), total and phosphorylated PERK, Nrf2, activating transcription factor 4 (ATF4), C/EBP homologous protein (CHOP), Bcl-2 and Bax. Immunofluorescence staining was used to assess the subcellular location of Nrf2. We found that H/R induced significant apoptosis in neonatal rat cardiomyocytes. MR-1 overexpression attenuated H/R-induced apoptosis, decreased GRP78 (P < 0.01) and CHOP expression (P < 0.05), and increased the Bcl-2/Bax ratio (P < 0.01). MR-1 overexpression suppressed H/R-induced PERK phosphorylation, Nrf2 nuclear translocation, and ATF4 expression (P < 0.01). While MR-1 knockdown aggravated H/R-induced apoptosis, increased expression of GRP78 and CHOP (P < 0.05), and decreased the Bcl-2/Bax ratio (P < 0.01). MR-1 knockdown significantly increased H/R-induced PERK phosphorylation (P < 0.05), Nrf2 nuclear translocation, and ATF4 expression (P < 0.01). These findings suggest that MR-1 alleviates H/R-induced cardiomyocyte apoptosis through inhibition of the PERK/Nrf2 pathway.
authors.affiliation: Department of Pathophysiology, Chinese PLA General Hospital, Beijing, 100853, China.
authors.forename: Tian-Qi
authors.initials: TQ
authors.lastname: Tao
authors.forename: Xiao-Reng
authors.initials: XR
authors.lastname: Wang
authors.forename: Mi
authors.initials: M
authors.lastname: Liu
authors.forename: Fei-Fei
authors.initials: FF
authors.lastname: Xu
authors.forename: Xiu-Hua
authors.initials: XH
authors.lastname: Liu
mesh_terms: D051701:Activating Transcription Factor 4 / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects; D015687:Cell Hypoxia; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D009124:Muscle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D018384:Oxidative Stress; D010100:Oxygen / Q000494:pharmacology; D061251:Primary Cell Culture; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000235:genetics*; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism; D019076:Transgenes; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP
chemical_list: D051701:Activating Transcription Factor 4; D006360:Heat-Shock Proteins; D009124:Muscle Proteins; D051267:NF-E2-Related Factor 2; D010100:Oxygen; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D051742:Transcription Factor CHOP; D019892:eIF-2 Kinase; C497110:Atf4 protein, rat; C497251:Ddit3 protein, rat; C051684:GRP78 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP; C495637:Nfe2l2 protein, rat; C576747:Pnkd protein, rat