BackgroundDiabetic cardiomyopathy (DCM), a fatal cardiovascular complication of diabetes mellitus, often leads to progressive heart failure, however its pathogenesis remains unclear. Corin, a cardiac serine protease, is responsible for converting pro-atrial natriuretic peptide (pro-ANP) to biologically active atrial natriuretic peptide (ANP). It has been well established that corin deficiency is associated with the progression of hypertension, cardiac hypertrophy and heart failure. However, because the involvement of corin-mediated pro-ANP processing in DCM has not been clarified, this study aims to investigate the role of corin in the pathogenesis of DCM.MethodsDiabetes mellitus was induced by a single intraperitoneal injection of streptozotocin (STZ 65 mg/kg) to Sprague–Dawley rats (180–220 g). DCM was confirmed by monitoring continuously transthoracic echocardiography every 4 weeks and hemodynamic measurements at 20 weeks. Myocardial disorder and fibrosis were detected by HE staining and Masson’s trichrome staining. The mRNA and protein levels of corin and ANP in rat hearts and cardiomyocytes were determined by quantitative real-time PCR, western blotting and immunohistochemical staining, respectively. H9c2 cardiomyoblasts proliferation was detected by MTT colorimetric assay and viable cell counting with trypan blue. The effect of Corin-siRNA H9c2 cardiomyoblasts on EA.hy926 cells migration was measured by the wound healing scratch assay.ResultsThe corin and ANP expression in mRNA and protein levels was decreased in DCM rat hearts. Corin and ANP levels of neonatal rat cardiomyocytes and H9c2 cardiomyoblasts treated with high glucose were significantly lower than that of normal glucose treated. Precisely, corin and ANP levels decreased in DCM rats at 12, 16, 20 and 33 weeks; neonatal cardiomyocytes and H9c2 cardiomyoblasts treated with high glucose at 36, 48 and 60 h demonstrated significant reduction in corin and ANP levels. Corin-siRNA H9c2 cardiomyoblasts showed decreased proliferation. Culture supernatants of Corin-siRNA H9c2 cardiomyoblasts prevented endothelial cell line EA.hy926 migration in the wound healing scratch assay. Furthermore, iso-lectin expression in arteriole and capillary endothelium was down-regulated in DCM rats.ConclusionsOur results indicate that corin plays an important role in cardioprotection by activating pro-atrial natriuretic peptide pathway in DCM. Corin deficiency leads to endothelial dysfunction and vascular remodeling.Electronic supplementary materialThe online version of this article (doi:10.1186/s12933-015-0298-9) contains supplementary material, which is available to authorized users.

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Diabetic nephropathy (DN) is a serious complication of diabetes and can cause an increased mortality risk. It was previously reported that NLR family pyrin domain containing 3 (NLRP3) inflammasome is involved in the pathogenesis of diabetes. However, the underlying mechanism is not clearly understood. In the present study, the effects of spleen tyrosine kinase (Syk) and c-Jun N-terminal kinase (JNK) on the NLRP3 inflammasome were examined in vivo and in vitro. Sprague-Dawley rats were injected intraperitoneally with streptozotocin (65 mg/kg) to induce diabetes. HK2 cells and rat glomerular mesangial cells (RGMCs) were examined to detect the expression of JNK and NLRP3 inflammasome-associated proteins following treatment with a Syk inhibitor or Syk-small interfering (si)RNA in a high glucose condition. In the present study, it was revealed that the protein and mRNA expression levels of NLRP3 inflammasome-associated molecules and the downstream mature interleukin (IL)-1β were upregulated in vivo and in vitro. The Syk inhibitor and Syk-siRNA suppressed high glucose-induced JNK activation, and subsequently downregulated the activation of the NLRP3 inflammasome and mature IL-1β in HK2 cells and RGMCs. Furthermore, high glucose-induced apoptosis of HK2 cells was reduced by the Syk inhibitor BAY61-3606. Therefore, the present results determined that high glucose-induced activation of the NLRP3 inflammasome is mediated by Syk/JNK activation, which subsequently increased the protein expression level of IL-1β and mature IL-1β. The present study identified that the Syk/JNK/NLRP3 signaling pathway may serve a vital role in the pathogenesis of DN.

Biodegradable polymer poly-D,L-lactide-polyethylene glycol (PLA-PEG) was synthesized with stannous octoate (SnOc 2 ) as catalyst by a cationic ring-opening polymerization. The molecular weight of PLA-PEG is the highest at a content of 0.1% SnOc 2 . The PLA-PEG microspheres carrying protein were prepared by a solvent evaporation composite emulsion technique with a narrow size range (1-2 mm). The sizes of PLA-PEG microspheres increased with the increase of the molecular weight of PLA-PEG. The PEG in PLA-PEG (10%) significantly improved the size control of the microspheres of the PLA family as a drug carrier matrix. Polyvinyl alcohol (PVA) aqueous solution was used as dispersion medium for microsphere preparation. The concentration of the PVA solution can affect the size of the PLA-PEG microspheres. The differential scanning calorimetry data showed that the PLA-PEG microspheres can efficiently encapsulate the protein and that the crystalline of the microspheres carrying protein was lower than that of the nonprotein-loading microspheres. The amount of protein carried in the PLA-PEG microspheres was related to the nature of the protein itself.

Diabetic nephropathy (DN) is one of the leading causes of mortality in diabetic patients, but its pathogenesis is unclear. We aimed to study the role of the pro-ANP convertase Corin in the pathogenesis of DN. Corin and ANP expression in DN rat kidneys and high-glucose-treated HK-2 cells was analyzed by real-time PCR, western blotting, and immunohistochemical staining. The effect of Corin-siRNA or ANP-siRNA HK-2 cells on EA.hy926 cell migration was determined by scratch-wound healing assay. The expression of mitogen-activated protein kinase (MAPK) and endothelial NO synthase (eNOS) in EA.hy926 cells treated with conditioned medium from Corin-siRNA-or ANP-siRNA-transfected HK-2 cells was determined by western blotting. We found a significant reduction in Corin and ANP expression in DN rat kidneys. These results were recapitulated in HK-2 cells treated with high glucose.EA.hy926 cells treated with conditioned medium from Corin-deficient HK-2 cells had inhibited migration, increased MAPK activity, and decreased eNOS activity.Similar effects were observed with ANP-siRNA transfection. Finally, adding ANP to the Corin-deficient HK-2 conditioned medium rescued the above defects, indicating that Corin mediates its effects through ANP. In conclusion, Corin plays a renoprotective role through pro-ANP processing, and defects in Corin cause endothelial dysfunction through MAPK and eNOS signaling in DN. K E Y W O R D SCorin, diabetic nephropathy, endothelial dysfunction, eNOS, MAPK 96 |