Astragaloside IV Alleviates Hypoxia/Reoxygenation-Induced Neonatal Rat Cardiomyocyte Injury via the Protein Kinase A Pathway

Abstract

Background: Astragaloside IV (As-IV) exerts beneficial effects on hypoxia/reoxygenation (H/R)-induced cardiomyocyte injury, possibly through normalization of sarcoplasmic reticulum Ca²⁺ 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 Ser¹⁶ phosphorylated phospholamban (Ser¹⁶-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 Ser¹⁶-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 Ser¹⁶-PLN, thereby restoring SERCA2a function in H/R injury.

Beta-1-Adrenergic Receptors Mediate Nrf2-HO-1-HMGB1 Axis Regulation to Attenuate Hypoxia/Reoxygenation-Induced Cardiomyocytes Injury in Vitro

“…Otherwise, HO-1 has been further demonstrated to be induced by dobutamine and inhibit HMGB1 release during myocardial I/R injury [11]. Importantly, cultured neonatal cardiomyocytes may present with a very stable phenotype and the contractile profile of cultured neonatal cardiomyocytes during H/R has been proved to be comparable with that of in situ adult hearts during I/R [26][27][28][29].…”

Relationship between acute high altitude response, cardiac function injury, and high altitude de-adaptation response after returning to lower altitude*

“…Since the cells generate less ATP after reoxygenation, the cell membrane and sarcoplasmic reticulum calcium and sodium pump functions may be reduced, leading to intracellular calcium overload. The increase in the intracellular calcium concentration can further activate endothelial cells, promoting OFR generation, and leading to further damage [16,17]. But Li Q [18] study shows that endocannabinoids can suppresses calcium overload through inhibition of INCX during perfusion with simulated ischemic solution; the effects may be mediated by CB2 receptor via PTX-sensitive Gi/o proteins.…”

Phospholamban phosphorylation, mutation, and structural dynamics: a biophysical approach to understanding and treating cardiomyopathy

“…Therapeutic strategies include (a) decreasing PLB levels with micro RNA or antibodies (Andino et al 2008; He et al 1999), (b) increasing PLB phosphorylation by inhibiting PP1, the protein phosphatase that dephosphorylates PLB at both S16 and T17 (Fish et al 2013; Miyazaki et al 2012; Oh et al 2013; Pritchard et al 2013; Xu et al 2007; Zhang et al 2012), (c) uncoupling PLB and SERCA2a with drugs, (d) stabilizing the R state of PLB using drugs, (e) stabilizing the PLB pentamer, and (f) administering PLB loss-of-inhibition mutants using gene therapy.…”

“…Drugs and peptides can also increase PLB phosphorylation by inhibiting PP1. The small molecule, astragaloside IV increases PLB phosphorylation through PKA activation (Xu et al 2007; Zhang et al 2012). Decoy peptides for PP1 have also been used to keep PLB phosphorylated.…”

“…Unphosphorylated PLB (U-PLB) inhibits SERCA2a, but phosphorylation at S16 and/or T17 (producing P-PLB) changes the structure of PLB to relieve SERCA2a inhibition. Because insufficient SERCA2a activity is a hallmark of heart failure, SERCA2a activation (by gene therapy (Andino et al 2008; Fish et al 2013; Hoshijima et al 2002; Jessup et al 2011) or drug therapy (Ferrandi et al 2013; Huang 2013; Khan et al 2009; Rocchetti et al 2008; Zhang et al 2012)) is a widely sought goal for treatment of heart failure. This review describes rational approaches to this goal.…”