Astragaloside IV alleviates hypoxia/reoxygenation-induced neonatal rat cardiomyocyte injury via the protein kinase a pathway.
BACKGROUND
Astragaloside IV (As-IV) exerts beneficial effects on hypoxia/reoxygenation (H/R)-induced cardiomyocyte injury, possibly through normalization of sarcoplasmic reticulum Ca(2+) ATPase (SERCA2a) function. The exact mechanisms remain unknown. This study was designed to investigate the role of protein kinase A (PKA) in the protective effect of As-IV on SERCA2a function.


METHODS
Cultured cardiomyocytes from neonatal rats were exposed to 6 h of hypoxia followed by 3 h of reoxygenation (H/R) with or without As-IV treatment. Myocyte injury was determined by the creatine kinase (CK)-MB fraction in supernatant. Myocardial SERCA2a activity and PKA kinase activity were assessed. PKA subunit mRNA expression and Ser(16) phosphorylated phospholamban (Ser(16)-PLN) protein expression were detected by real-time PCR and Western blot, respectively.


RESULTS
The administration of As-IV significantly decreased CK-MB release and restored SERCA2a activity in H/R cardiomyocytes. The mRNAs of PKA subunits, PKA-RIα, PKA-RIIα, PKA-RIIβ, PKA-Cα and PKA-Cβ, were downregulated in H/R cardiomyocytes. However, PKA-Cα mRNA expression was significantly increased after As-IV treatment. Meanwhile, there was a tendency to recovery of the H/R-induced PKA kinase activity decrease after As-IV treatment. The expression of Ser(16)-PLN protein, which is specifically phosphorylated by PKA, was upregulated in As-IV-treated H/R cardiomyocytes.


CONCLUSIONS
These results suggest that the cardioprotection of As-IV may be through the upregulation of PKA and Ser(16)-PLN, thereby restoring SERCA2a function in H/R injury.
Research Institute of Cardiovascular Disease, First Affiliated Hospital of Nanjing Medical University, Nanjing, PR China.
Da-Wei
DW
Zhang
Zhi-Ping
ZP
Bian
Jin-Dan
JD
Xu
Heng-Fang
HF
Wu
Chun-Rong
CR
Gu
Bin
B
Zhou
Xiang-Jian
XJ
Chen
Di
D
Yang
D000818:Animals; D000831:Animals, Newborn; D002316:Cardiotonic Agents / Q000494:pharmacology*; D015687:Cell Hypoxia / Q000187:drug effects*; D002478:Cells, Cultured; D052279:Creatine Kinase, MB Form / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000473:pathology; D021122:Protein Subunits / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015427:Reperfusion Injury / Q000188:drug therapy* / Q000378:metabolism; D012503:Saponins / Q000494:pharmacology*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D014315:Triterpenes / Q000494:pharmacology*
C506948:Atp2a2 protein, rat; D002316:Cardiotonic Agents; D021122:Protein Subunits; D012333:RNA, Messenger; D012503:Saponins; D014315:Triterpenes; C052064:astragaloside A; D017868:Cyclic AMP-Dependent Protein Kinases; D052279:Creatine Kinase, MB Form; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases