Glucagon-Like Peptide 1 Protects against Hyperglycemic-Induced Endothelial-to-Mesenchymal Transition and Improves Myocardial Dysfunction by Suppressing Poly(ADP-Ribose) Polymerase 1 Activity.

Under high glucose conditions, endothelial cells respond by acquiring fibroblast characteristics, that is, endothelial-to-mesenchymal transition (EndMT), contributing to diabetic cardiac fibrosis. Glucagon-like peptide-1 (GLP-1) has cardioprotective properties independent of its glucose-lowering effect. However, the potential mechanism has not been fully clarified. Here we investigated whether GLP-1 inhibits myocardial EndMT in diabetic mice and whether this is mediated by suppressing poly(ADP-ribose) polymerase 1 (PARP-1). Streptozotocin diabetic C57BL/6 mice were treated with or without GLP-1 analog (24 nmol/kg daily) for 24 wks. Transthoracic echocardiography was performed to assess cardiac function. Human aortic endothelial cells (HAECs) were cultured in normal glucose (NG) (5.5 mmol/L) or high glucose (HG) (30 mmol/L) medium with or without GLP-1analog. Immunofluorescent staining and Western blot were performed to evaluate EndMT and PARP-1 activity. Diabetes mellitus attenuated cardiac function and increased cardiac fibrosis. Treatment with the GLP-1 analog improved diabetes mellitus-related cardiac dysfunction and cardiac fibrosis. Immunofluorescence staining revealed that hyperglycemia markedly increased the percentage of von Willebrand factor (vWF)(+)/alpha smooth muscle actin (α-SMA)(+) cells in total α-SMA(+) cells in diabetic hearts compared with controls, which was attenuated by GLP-1 analog treatment. In cultured HAECs, immunofluorescent staining and Western blot also showed that both GLP-1 analog and PARP-1 gene silencing could inhibit the HG-induced EndMT. In addition, GLP-1 analog could attenuate PARP-1 activation by decreasing the level of reactive oxygen species (ROS). Therefore, GLP-1 treatment could protect against the hyperglycemia-induced EndMT and myocardial dysfunction. This effect is mediated, at least partially, by suppressing PARP-1 activation.

Arginase I enhances atherosclerotic plaque stabilization by inhibiting inflammation and promoting smooth muscle cell proliferation.

AIMS: The aim of this study was to investigate the effect of Arginase I (ArgI) on plaque stabilization in unruptured atherosclerotic plaque and explore its mechanism. METHODS AND RESULTS: The atherosclerotic plaque model was established in New Zealand rabbits by balloon injury of abdominal arteries and a high cholesterol (1%) diet. Arginase I overexpression reduced the content of macrophages and lipids and increased that of smooth muscle cells and collagen in the atherosclerotic plaque, thus contributing to decreased plaque vulnerability. Arginase I overexpression decreased the expression of the inflammatory cytokines tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) as well as inducible nitric oxide synthase (iNOS) in plaques. In vitro, ArgI overexpression or iNOS inhibition abolished the secretion of TNF-α and IL-6 induced by lipopolysaccharide in Raw264.7 cells. However, exogenous l-arginine restored the expression of inflammatory cytokines. Arginase I overexpression inhibited the activity of iNOS without changing its expression. Moreover, ArgI co-localized with iNOS in both Raw264.7 cells and human aortic atherosclerotic plaques. In addition, the IL-10 level was increased in plaque with ArgI overexpression. Finally, ArgI promoted aortic vascular smooth muscle cell proliferation, which was associated with increased production of intracellular polyamines. CONCLUSION: ArgI enhances the stability of atherosclerotic plaque by inhibiting the expression of inflammatory cytokines and stimulating smooth muscle cell proliferation.

HMGB1 mediates hyperglycaemia-induced cardiomyocyte apoptosis via ERK/Ets-1 signalling pathway.

Apoptosis is a key event involved in diabetic cardiomyopathy. The expression of high mobility group box 1 protein (HMGB1) is up-regulated in diabetic mice. However, the molecular mechanism of high glucose (HG)-induced cardiomyocyte apoptosis remains obscure. We aimed to determine the role of HMGB1 in HG-induced apoptosis of cardiomyocytes. Treating neonatal primary cardiomyocytes with HG increased cell apoptosis, which was accompanied by elevated levels of HMGB1. Inhibition of HMGB1 by short-hairpin RNA significantly decreased HG-induced cell apoptosis by reducing caspase-3 activation and ratio of Bcl2-associated X protein to B-cell lymphoma/leukemia-2 (bax/bcl-2). Furthermore, HG activated E26 transformation-specific sequence-1 (Ets-1), and HMGB1 inhibition attenuated HG-induced activation of Ets-1 via extracellular signal-regulated kinase 1/2 (ERK1/2) signalling. In addition, inhibition of Ets-1 significantly decreased HG-induced cardiomyocyte apoptosis. Similar results were observed in streptozotocin-treated diabetic mice. Inhibition of HMGB1 by short-hairpin RNA markedly decreased myocardial cell apoptosis and activation of ERK and Ets-1 in diabetic mice. In conclusion, inhibition of HMGB1 may protect against hyperglycaemia-induced cardiomyocyte apoptosis by down-regulating ERK-dependent activation of Ets-1.

In Situ Manipulation of Dendritic Cells by an Autophagy-Regulative Nanoactivator Enables Effective Cancer Immunotherapy.

Cellular immunotherapeutics aim to employ immune cells as anticancer agents. Ex vivo engineering of dendritic cells (DCs), the initial role of an immune response, benefits tumor elimination by boosting specific antitumor responses. However, directly activating DCs in vivo is less efficient and therefore quite challenging. Here, we designed a nanoactivator that manufactures DCs through autophagy upregulating in vivo directly, which lead to a high-efficiency antigen presention of DCs and antigen-specific T cells generation. The nanoactivator significantly enhances tumor antigen cross-presentation and subsequent T cell priming. Consequently, in vivo experiments show that the nanoactivators successfully reduce tumor growth and prolong murine survival. Taken together, these results indicate in situ DCs manipulation by autophagy induction is a promising strategy for antigen presentation enhancement and tumor elimination.

Inhibition of myocyte-specific enhancer factor 2A improved diabetic cardiac fibrosis partially by regulating endothelial-to-mesenchymal transition.

Cardiac fibrosis is an important pathological process of diabetic cardiomyopathy, the underlying mechanism remains elusive. This study sought to identify whether inhibition of Myocyte enhancer factor 2A (MEF2A) alleviates cardiac fibrosis by partially regulating Endothelial-to-mesenchymal transition (EndMT). We induced type 1 diabetes mellitus using the toxin streptozotocin (STZ) in mice and injected with lentivirus-mediated short-hairpin RNA (shRNA) in myocardium to inhibit MEF2A expression. Protein expression, histological and functional parameters were examined twenty-one weeks post-STZ injection. We found that Diabetes mellitus increased cardiac MEF2A expression, aggravated cardiac dysfunction and myocardial fibrosis through the accumulation of fibroblasts via EndMT. All of these features were abolished by MEF2A inhibition. MEF2A gene silencing by shRNA in cultured human umbilical vein endothelial cells (HUVECs) ameliorated high glucose-induced phenotypic transition and acquisition of mesenchymal markers through interaction with p38MAPK and Smad2. We conclude that inhibition of endothelial cell-derived MEF2A might be beneficial in the prevention of diabetes mellitus-induced cardiac fibrosis by partially inhibiting EndMT through interaction with p38MAPK and Smad2.

Prohibitin overexpression improves myocardial function in diabetic cardiomyopathy.

Prohibitin (PHB) is a highly conserved protein implicated in various cellular functions including proliferation, apoptosis, tumor suppression, transcription, and mitochondrial protein folding. However, its function in diabetic cardiomyopathy (DCM) is still unclear. In vivo, type 2 diabetic rat model was induced by using a high-fat diet and low-dose streptozotocin. Overexpression of the PHB protein in the model rats was achieved by injecting lentivirus carrying PHB cDNA via the jugular vein. Characteristics of type 2 DCM were evaluated by metabolic tests, echocardiography and histopathology. Rats with DCM showed severe insulin resistance, left ventricular dysfunction, fibrosis and apoptosis. PHB overexpression ameliorated the disease. Cardiofibroblasts (CFs) and H9c2 cardiomyoblasts were used in vitro to investigate the mechanism of PHB in altered function. In CFs treated with HG, PHB overexpression decreased expression of collagen, matrix metalloproteinase activity, and proliferation. In H9c2 cardiomyoblasts, PHB overexpression inhibited apoptosis induced by HG. Furthermore, the increased phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 was significantly decreased and the inhibited phosphorylation of Akt was restored in DCM. Therefore, PHB may be a new therapeutic target for human DCM.