Inhibition of astragaloside IV against isoproterenol-induced myocardial hypertrophy in neonatal rats and its mechanism

Objective: To investigate the protective effect of astragaloside IV (As IV) on myocardial hypertrophy induced by isoproterenol (ISO) and its mechanism. Methods: The primary cultures of neonatal rat cardiac myocytes were cultured for 48 h in vitro. The cardiac myocytes were treated with As IV, IκBα phosphorylation inhibitor BAY11-7082, and β-blockers Propranolol for 30 min, followed by 48 h incubation with ISO 10 μmol/L. The cardiomyocyte volume was measured by computer photograph analysis system. Total protein contents were assayed by the method of Bradford. RT-PCR was used to quantify the mRNA expression of ANP and TLR4; Western blotting was used to quantify the expression of TLR4, p65, and IκBα proteins; ELISA was used to quantify TNF-α and IL-6. Results: Compared with the control group, the cell size, total protein content, ANP and TLR4 mRNA, TLR4, p65, TNF-α and IL-6 were increased, and expression of IκBα protein was decreased in ISO group (P < 0.01). As IV, BAY11-7082, and Propranolol could remarkably down-regulate the over-expression of the cell size, total protein content, ANP and TLR4 mRNA, TLR4, p65, TNF-α, and IL-6, and increase the expression of IκBα protein (P < 0.05). Conclusion: As IV has the protective effect on cardiac hypertrophy induced by ISO, which is partially referring to inhibiting the TLR4/NF-κB signaling pathway and more than attenuating inflammatory effect.