title: Myofibrillogenesis regulator-1 attenuates hypoxia/reoxygenation-induced injury by repairing microfilaments in neonatal rat cardiomyocytes.
abstract: Hypoxia/reoxygenation (H/R) injury is characterized by microfilament reorganization in cardiomyocytes. Previous studies have shown that myofibrillogenesis regulator-1 (MR-1) is expressed in the myocardium and promotes actin organization in cardiomyocytes. The purpose of this study was to investigate the role of MR-1 in attenuating hypoxia/reoxygenation injury in cardiomyocytes through promoting restoration of the microfilament. To address this aim, an H/R model of cultured neonatal cardiomyocytes was used to assess filamentous actin (F-actin) and α-actinin organization through immunofluorescence microscopy analysis. RT-PCR was used to detect mRNA levels of MR-1 and myosin regulatory light chain-2 (MLC-2). Western blot analysis was used to detect protein levels of MR-1 and filamentous actin/globular actin (F-/G-actin) as well as MLC-2 and myosin light chain kinase (MLCK) phosphorylation and protein expression. We also explored the effects of overexpressing or knocking down MR-1 on H/R injury and the MLCK/MLC-2/F-actin pathway. We found that H/R induced cardiomyocyte injury and disruption of F-actin and α-actinin with a decrease in the F-/G-actin ratio compared with controls. Compared with the H/R group, MR-1 overexpression attenuated H/R-induced injury and disruption of F-actin and α-actinin in cardiomyocytes with an increase in the F-/G-actin ratio. MR-1 overexpression also up-regulated H/R-induced MLCK and MLC-2 phosphorylation. However, MR-1 knockdown aggravated H/R injury by further disrupting F-actin and α-actinin, as well as decreasing the F-/G-actin ratio. MR-1 knockdown also down-regulated MLCK and MLC-2 phosphorylation induced by H/R injury. These findings suggest that MR-1 attenuates H/R-induced cardiomyocyte injury by promoting microfilament reorganization through the activation of the MLCK/MLC-2 pathway.
authors.affiliation: Department of Pathophysiology, Chinese PLA General Hospital, 100853 Beijing, China. Electronic address: ttqtxt@163.com.
authors.forename: Tianqi
authors.initials: T
authors.lastname: Tao
authors.affiliation: Department of Pathophysiology, Chinese PLA General Hospital, 100853 Beijing, China. Electronic address: xiaoreng-wang@163.com.
authors.forename: Xiaoreng
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Pathophysiology, Chinese PLA General Hospital, 100853 Beijing, China. Electronic address: liumi177@qq.com.
authors.forename: Mi
authors.initials: M
authors.lastname: Liu
authors.affiliation: Department of Pathophysiology, Chinese PLA General Hospital, 100853 Beijing, China. Electronic address: xiuhualiu98@163.com.
authors.forename: Xiuhua
authors.initials: X
authors.lastname: Liu
mesh_terms: D008841:Actin Cytoskeleton / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D000860:Hypoxia / Q000150:complications* / Q000473:pathology; D007124:Immunoenzyme Techniques; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D015427:Reperfusion Injury / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D009124:Muscle Proteins; C576747:Pnkd protein, rat; D012333:RNA, Messenger
keywords: Cardiomyocyte; Hypoxia/reoxygenation; Microfilament; Myofibrillogenesis regulator-1