The effect and mechanism of heat shock protein 47 on streptozotocin-induced diabetic cardiomyopathy

Abstract

Objective: To investigate the effect and specific mechanism of heat shock protein 47 (HSP47) on streptozotocin (STZ)-induced diabetic cardiomyopathy (DCM). Methods: A mouse model of type 1 diabetic cardiomyopathy was established by intraperitoneal injection of STZ. After 8 weeks of successful modeling, HSP47 was overexpressed by tail vein injection, and the heart of the mouse was harvested after 6 weeks. Hematoxylin-eosin (HE) staining and Sirius red (PSR) staining were used to detect the cross-sectional area of myocardial cells and myocardial fibrosis, respectively. Immunofluorescence staining with α-smooth muscle actin (α-SMA) and collagen Ⅰ was used to detect the degree of fibrosis activation. The expression level of fibrosis-related proteins was determined by Western blot. Results: The expression level of HSP47 in the myocardium of the diabetic group up-regulated (2.014±0.264 vs 1.004±0.064, P<0.001). The area of myocardial cells in the diabetic group was increased compared with the control group [(235.3±20.7) μm(2) vs (172.8±13.6) μm(2), P<0.001] and the cross-sectional area of myocardial cells in the HSP47 overexpression-diabetes group was further increased [(302.2±41.0) μm(2) vs (235.3±20.7) μm(2), P=0.009], while the mRNA levels of mouse cardiac hypertrophic markers atrial natriuretic peptide (ANP), type B brain natriuretic peptide (BNP), myosin heavy chain β (β-MHC) further upregulated (all P<0.001). Compared with the control group, the myocardial fibrosis content in the diabetic group increased [(7.333±1.127)% vs (4.837±0.775)%, P=0.002] and the left ventricular fibrosis content of the HSP47 overexpressing diabetic group further increased [(9.175±1.008)% vs (7.333±1.127)%, P=0.025] and the mRNA levels of fibrosis index collagenⅠ, collagen Ⅲ, connective tissue growth factor (CTGF) and transforming growth factor β (TGFβ) further up-regulated (all P<0.001). Immunofluorescence results showed that compared with the control group, the expression of collagenⅠ up-regulated in the endothelial stroma of the diabetic group and the content of collagenⅠ in the HSP47 over-expressing diabetic group was higher (P<0.001). Western blot results indicated that the phosphorylation level of Smad3 and the protein levels of α-SMA and TGFβ in HSP47 overexpressing diabetic group increased, compared with those of diabetic group (all P<0.001). Conclusion: HSP47 ameliorates STZ-induced diabetic myocardial fibrosis by activating the TGFβ/Smad3 signaling pathway.