Effects of calycosin on isoprenaline-induced cardiac hypertrophy

Objective To explore the effects of calycosin (CA) on isoprenaline (ISO) - induced cardiac hypertrophy. Methods Thirty C57 mice were randomly divided into the control group (n=10) , ISO group (n=10) , and CA+ISO group (n=10) . The mice in ISO group received intraperitoneal injection with ISO (50 mg·kg-1·d-1) , those in CA+ISO group received intraperitoneal injection with ISO (50 mg·kg-1·d-1) and intragastric gavage with CA (50 mg·kg-1·d-1) , and those in control group received intraperitoneal injection with normal saline (50 ml·kg-1·d-1) . At 14 days after the treatment, the mice were measured for body mass (BM) , sacrificed and harvested for cardiac specimens. The heart mass (HM) , tibial length (TL) and myocardial cell cross-sectional area were measured. Real-time quantitative PCR was used to determine the mRNA expression of atrial natriuretic peptide (ANP) and β-myosin heavy chain (β-MHC) . Immunoblotting was used to investigate the molecular pathway related to cardiac hypertrophy. Primary cultured rat cardiac myocytes were divided into the control group, ISO group and ISO+CA group. The control group was added with PBS, ISO group treated with ISO (10 μmol/L) , and ISO+CA group added with ISO (10 μmol/L) and different concentrations of CA (1, 10, 50, 100 μmol/L) . After 48 h, the myocardial cells were collected and determined for ANP mRNA expression by real-time quantitative PCR, and the area of myocardial cell was measured by immunofluorescence staining. Results Compared with the control group, the cardiac volume, HM/BM and HM/TL ratios, and cross-sectional area of myocardial cells were increased in those of the ISO group (all P<0.05) . Compared with the ISO group, CA treatment was shown to reduce the cardiac volume, the ratios of HM/BM and HM/TL, and the cross-sectional area of myocardial cells (all P<0.05) . Real-time quantitative PCR showed that the expressions of ANP and β-MHC mRNA were up-regulated in ISO-treated mice as compared with the control group, whereas CA treatment significantly inhibited the ISO-induced up-regulation of ANP and β-MHC mRNA expressions (all P<0.05) . Immunoblotting showed that the phosphorylation levels of protein kinase B (AKT) , glycogen synthase kinase 3β (GSK3β) and extracellular signal-regulated kinase (ERK) were significantly upregulated in the cardiac tissues of ISO-treated mice, and the activation of these signal pathways was significantly inhibited by CA (all P<0.05) . At 48 h after ISO treatment, the primary cultured rat cardiac myocytes showed significantly increased area and up-regulated level of ANP mRNA expression (both P<0.05) . Compared with the ISO group, CA treatment at concentration of 10, 50 and 100 μmol/L significantly reduced the ANP mRNA expressions in the cardiac myocytes; moreover, the myocyte area was significantly reduced with 100 μmol/L CA treatment (all P<0.05) . Conclusion CA may inhibit ISO-induced cardiac hypertrophy. Key words: Calycosin; Isoprenaline; Cardiomyopathy, hypertrophic