Ginsenoside Rg1 attenuates mechanical stress-induced cardiac injury via calcium sensing receptor-related pathway

Background Ginsenoside Rg1 (Rg1) has been well documented to be effective against various cardiovascular disease. The aim of this study is to evaluate the effect of Rg1 on mechanical stress-induced cardiac injury and its possible mechanism with a focus on the calcium sensing receptor (CaSR) signaling pathway. Methods Mechanical stress was implemented on rats through abdominal aortic constriction (AAC) procedure and on cardiomyocytes and cardiac fibroblasts by mechanical stretching with Bioflex Collagen I plates. The effects of Rg1 on cell hypertrophy, fibrosis, cardiac function, [Ca2+]i, and the expression of CaSR and calcineurin (CaN) were assayed both on rat and cellular level. Results Rg1 alleviated cardiac hypertrophy and fibrosis, and improved cardiac decompensation induced by AAC in rat myocardial tissue and cultured cardiomyocytes and cardiac fibroblasts. Importantly, Rg1 treatment inhibited CaSR expression and increase of [Ca2+]i, which similar to the CaSR inhibitor NPS2143. In addition, Rg1 treatment inhibited CaN and TGF-β1 pathways activation. Mechanistic analysis showed that the CaSR agonist GdCl3 could not further increase the [Ca2+]i and CaN pathway related protein expression induced by mechanical stretching in cultured cardiomyocytes. CsA, an inhibitor of CaN, inhibited cardiac hypertrophy, cardiac fibrosis, [Ca2+]i and CaN signaling but had no effect on CaSR expression. Conclusion The activation of CaN pathway and the increase of [Ca2+]i mediated by CaSR are involved in cardiac hypertrophy and fibrosis, that may be the target of cardioprotection of Rg1 against myocardial injury.
Graphical abstract The mechanism of cardioprotection by Ginsenoside Rg1 via downregulation of CaSR. AAC induces overload of [Ca2+]i through CaSR/IP3R pathway. The increased [Ca2+]i leads to activation of CaN signaling pathway, resulting in cardiac hypertrophy and fibrosis. Ginsenoside Rg1 inhibits cardiac hypertrophy and fibrosis through inhibiting [Ca2+]i and downregulation of CaSR, CaN and TGF-β1 signaling pathways.Image 1