MiR-134-5p targeting XIAP modulates oxidative stress and apoptosis in cardiomyocytes under hypoxia/reperfusion-induced injury.

MicroRNA-134-5p (MiR-134-5p) has been proposed as a promising novel biomarker for the diagnosis of acute myocardial infarction (AMI). However, the biological role of miR-134-5p in ischemic cardiomyocytes has been little disclosed yet. Expression of miR-134-5p and X-linked inhibitor of apoptosis protein (XIAP) was detected using RT-qPCR and western blot. Oxidative stress and cell apoptosis were determined by enzyme-linked immunosorbent assays, 3-(4, 5-dimethylthiazole-2-y1)-2, 5-biphenyl tetrazolium bromide assay, flow cytometry, western blot, and terminal-deoxynucleoitidyl transferase-mediated nick end labeling (TUNEL). The interaction between miR-134-5p and XIAP was confirmed by luciferase reporter assay. Expression of miR-134-5p was upregulated in serum of AMI patients and hypoxia/reoxygenation (H/R)-induced cardiomyocytes (AC16 and HCM). MiR-134-5p downregulation could inhibit H/R-mediated release of lactic dehydrogenase enzyme (LDH) and malondialdehyde (MDA), and promote superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) levels. Meanwhile, cell viability was increased, while the apoptosis rate and TUNEL positive cells were inhibited by miR-134-5p downregulation in H/R-treated AC16 and HCM cells. Mechanically, XIAP was downregulated and targeted by miR-134-5p in H/R-induced cardiomyocytes in vitro. Overexpression of XIAP inhibited oxidative stress and cell apoptosis in H/R-treated AC16 and HCM cells, which was similar to miR-134-5p knockdown. Moreover, downregulation of XIAP could partially reverse the effect of miR-134-5p knockdown in H/R-induced cardiomyocytes. Knockdown of miR-134-5p protected cardiomyocytes from H/R-induced oxidative stress and apoptosis in vitro through targeting XIAP.

Th17/Treg imbalance modulates rat myocardial fibrosis and heart failure by regulating LOX expression.

AIM: The imbalance of T helper (Th) 17/T regulatory (Treg) is involved in chronic heart failure (HF). The enzyme lysyl oxidase (LOX) contributes to myocardial fibrosis. This study was designed to decipher the regulatory mechanism of Th17/Treg on LOX expression and to validate whether Th17/Treg imbalance regulates myocardial fibrosis by modulating LOX expression. METHODS: Human cardiac fibroblasts (HCFs) were treated with angiotensin II (Ang II) and co-cultured with Th17 cells and Tregs which were polarized from control naïve CD4+ T cells. Th17 cells and Tregs were adoptively transferred into abdominal aortic coarctation-induced chronic HF rats to investigate the efficacy of Th17 and Treg infusions on myocardial fibrosis and HF. RESULTS: Th17/Treg imbalance (increased Th17 cells and decreased Tregs) was observed in HF patients. Th17 cells/Tregs aggravated/attenuated Ang II-induced upregulation of LOX and fibrosis-related indicators (MMP-2/9 and collagen I/III) in HCFs in vitro and abdominal aortic coarctation-induced myocardial fibrosis and HF in rats, by promoting/inhibiting LOX expression. Mechanistically, Th17 cells promoted LOX expression by activating the IL-17/ERK1/2-AP-1 pathway, while Tregs inhibited LOX expression by activating the IL-10/JAK1-STAT3 pathway. CONCLUSION: Increased Th17 cells and decreased Tregs aggravate myocardial fibrosis and HF by inducing LOX expression.

Induction of LOX by TGF-ß1/Smad/AP-1 signaling aggravates rat myocardial fibrosis and heart failure.

This study aims to evaluate the efficacy of lysyl oxidase (LOX) inhibition in regulating rat myocardial fibrosis and chronic heart failure (CHF) and to validate the regulation of LOX by TGF-ß1/Smad2/3 signaling in this process. A rat model of CHF was established by abdominal aortic coarctation. The renin-angiotensin-aldosterone system (RAAS) indexes (PRA, ACE2, Ang II, and ALD), cardiac function indicators (LVEF, LVFS, SAP, DAP, and LVEDP), ventricular remodeling- and fibrosis-related indicators (hydroxyproline, collagen deposition,and MMP-2/9), and morphological changes of myocardial tissues were examined. Rat cardiac fibroblasts (RCFs) were used in vitro assays. CHF patients showed increased LOX activity, accompanied by activated RAAS and TGF-ß1. Furthermore, inhibition of LOX by ß-aminopropionitrile (BAPN) mitigated the RAAS activation and attenuated cardiac dysfunction, ventricular remodeling, myocardial fibrosis, and collagen deposition in CHF rats. Moreover, TGF-ß1 signaling diminished the LOX inhibition-mediated antiheart failure effect. Further assays showed that TGF-ß1/Smad2/3 signaling increased expression of c-jun (AP-1 transcription factor subunit), which transcriptionally induced LOX expression. Additionally, BAPN abrogated the TGF-ß1-mediated increase in cell proliferation and levels of MMP-2/9 and collagen I/III in RCFs. In conclusion, LOX can be induced by TGF-ß1/Smad/AP-1 signaling and LOX inhibition attenuates rat myocardial fibrosis and CHF.