LncRNA SLC8A1-AS1 protects against myocardial damage through activation of cGMP-PKG signaling pathway by inhibiting SLC8A1 in mice models of myocardial infarction

Extensive investigations into long noncoding RNAs (lncRNAs) in various diseases and cancers, including acute myocardial infarction (AMI) have been conducted. The current study aimed to investigate the role of lncRNA solute carrier family 8 member A1 antisense RNA 1 (SLC8A1-AS1) in myocardial damage by targeting solute carrier family 8 member A1 (SLC8A1) via cyclic guanosine 3′,5′-monophosphate-protein kinase G (cGMP-PKG) signaling pathway in AMI mouse models. Differentially expressed lncRNA in AMI were initially screened and target relationship between lncRNA SLC8A1-AS1 and SLC8A1 was then verified. Infarct size, levels of inflammatory factors, biochemical indicators, and the positive expression of the SLC8A1 protein in AMI were subsequently determined. The expression of SLC8A1-AS1, SLC8A1, PKG1, PKG2, atrial natriuretic peptide, and brain natriuretic peptide was detected to assess the effect of SLC8A1-AS1 on SLC8A1 and cGMP-PKG. The respective contents of superoxide dismutase, lactate dehydrogenase (LDH), and malondialdehyde (MDA) were detected accordingly. Microarray data GSE66360 provided evidence indicating that SLC8A1-AS1 was poorly expressed in AMI. SLC8A1 was verified to be a target gene of lncRNA SLC8A1-AS1. SLC8A1-AS1 upregulation decreased levels of left ventricular end-systolic diameter, −dp/ dt _max, interleukin 1β (IL-1β), IL-6, transforming growth factor α, nitric oxide, inducible nitric-oxide synthase, endothelial nitric-oxide synthase, infarct size, LDH activity and MDA content, and increased IL-10, left ventricular end-diastolic pressure and + dp/ dt _max. Furthermore, the overexpression of SLC8A1-AS1 was noted to elicit an inhibitory effect on the cGMP-PKG signaling pathway via SLC8A1. In conclusion, lncRNA SLC8A1-AS1, by downregulating SLC8A1 and activating the cGMP-PKG signaling pathway, was observed to alleviate myocardial damage, inhibit the release of proinflammatory factors and reduce infarct size, ultimately protecting against myocardial damage.     

MicroRNA-375-3p inhibitor suppresses angiotensin II-induced cardiomyocyte hypertrophy by promoting lactate dehydrogenase B expression

Cardiac hypertrophy is a myocardial enlargement due to overload pressure, and the primary cause of heart failure. We investigated the function of miR-375-3p in cardiac hypertrophy and its regulating mechanisms. miR-375-3p was upregulated in hearts of the transverse aortic constriction rat model and angiotensin II (Ang II)-induced primary cardiomyocyte hypertrophy model; the opposite was observed for lactate dehydrogenase B (LDHB) protein expression. miR-375-3p knockdown reduced the surface area of primary cardiomyocytes increased by Ang II treatment and decreased the B-natriuretic peptide (BNP) and β-myosin heavy chain (β-MHC) messenger RNA (mRNA) and protein levels. miR-375-3p was also observed to directly target LDHB. LDHB knockdown increased the surface area of Ang II-treated primary cardiomyocytes and increased the BNP and β-MHC mRNA and protein levels. LDHB knockdown attenuated the effects of miR-375-3p on the surface area of primary cardiomyocytes and BNP and β-MHC levels. Therefore, miR-375-3p inhibitor suppresses Ang II-induced cardiomyocyte hypertrophy by promoting LDHB expression.     

Propofol-mediated cardioprotection dependent of microRNA-451/HMGB1 against myocardial ischemia-reperfusion injury

Administration of propofol at the time of reperfusion has shown to protect the heart from ischemia and reperfusion (I/R) injury. The aim of the present study was to investigate the molecular mechanism underling the cardioprotective effect of propofol against myocardial I/R injury (MIRI) in vivo and in vitro. Rat heart I/R injury was induced by ligation of the left anterior descending (LAD) artery for 30 min followed by 2-hr reperfusion. Propofol pretreatment (0.01 mg/g) was performed 10 min before reperfusion. In vitro MIRI was investigated in cultured cardiomyocytes H9C2 following hypoxia/reoxygenation (H/R) injuries. Propofol pretreatment in vitro was achieved in the medium supplemented with 25 μmol/L propofol before H/R injuries. Propofol pretreatment significantly increased miRNA-451 expression, decreased HMGB1 expression, reduced infarct size, and I/R-induced cardiomyocyte apoptosis in rat hearts undergoing I/R injuries. Knockdown of miRNA-451 48 hr before I/R injury was found to increase HMGB1 expression, infarct size, and I/R-induced cardiomyocyte apoptosis in rat hearts in the presence of propofol pretreatment. These in vivo findings were reproduced in vivo that knockdown of miRNA-451 48 hr before H/R injuries increased HMGB1 expression and H/R-induced apoptosis in cultured H9C2 supplemented with propofol. In addition, luciferase activity assays and gain-of-function studies found that propofol could decrease HMGB1, the target of miRNA-541. Taken together our findings provide a first demonstration that propofol-mediated cardioprotection against MIRI is dependent of microRNA-451/HMGB1. The study provides a novel target to prevent I/R injury during propofol anesthesia.     

Prolonged elevated levels of c-kit+ progenitor cells after a myocardial infarction by beta 2 adrenergic receptor priming

Endogenous progenitor cells may participate in cardiac repair after a myocardial infarction (MI). The beta 2 adrenergic receptor (ß2-AR) pathway induces proliferation of c-kit+ cardiac progenitor cells (CPC) in vitro. We investigated if ß2-AR pharmacological stimulation could ameliorate endogenous CPC-mediated regeneration after a MI. C-kit+ CPC ß1-AR and ß2-AR expression was evaluated in vivo and in vitro. A significant increase in the percentage of CPCs expressing ß1-AR and ß2-AR was measured 7 days post-MI. Accordingly, 24 hrs of low serum and hypoxia in vitro significantly increased CPC ß2-AR expression. Cell viability and differentiation assays validated a functional role of CPC ß2-AR. The effect of pharmacological activation of ß2-AR was studied in C57 mice using fenoterol administered in the drinking water 1 week before MI or sham surgery or at the time of the surgery. MI induced a significant increase in the percentage of c-kit+ progenitor cells at 7 days, whereas pretreatment with fenoterol prolonged this response resulting in a significant elevated number of CPC up to 21 days post-MI. This increased number of CPC correlated with a decrease in infarct size. The immunofluorescence analysis of the heart tissue for proliferation, apoptosis, macrophage infiltration, cardiomyocytes surface area, and vessel density showed significant changes on the basis of surgery but no benefit due to fenoterol treatment. Cardiac function was not ameliorated by fenoterol administration when evaluated by echocardiography. Our results suggest that ß2-AR stimulation may improve the cardiac repair process by supporting an endogenous progenitor cell response but is not sufficient to improve the cardiac function.     

Angiotensin-converting enzyme inhibitors attenuated advanced glycation end products-induced renal tubular hypertrophy via enhancing nitric oxide signaling

Advanced glycation end products (AGE) and angiotensin II were closely correlated with the progression of diabetic nephopathy (DN). Nitric oxide (NO) is a protective mediator of renal tubular hypertrophy in DN. Here, we examined the molecular mechanisms of angiotensin-converting enzyme inhibitor (ACEI) and NO signaling responsible for diminishing AGE-induced renal tubular hypertrophy. In human renal proximal tubular cells, AGE decreased NO production, inducible NOS activity, guanosine 3′,5′-cyclic monophosphate (cGMP) synthesis, and cGMP-dependent protein kinase (PKG) activation. All theses effects of AGE were reversed by treatment with ACEIs (captopril and enalapril), the NO donor S-nitroso-N-acetylpenicillamine (SNAP), and the PKG activator 8-para-chlorophenylthio-cGMPs (8-pCPT-cGMPs). In addition, AGE-enhanced activation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK) were clearly reduced by captopril, enalapril, SNAP, and 8-pCPT-cGMPs. The abilities of ACEIs and NO/PKG activation to inhibit AGE-induced hypertrophic growth were verified by the observation that captopril, enalapril, SNAP, and 8-pCPT-cGMPs decreased protein levels of fibronectin, p21 ^Waf1/Cip1, and receptor for AGE. The results of the present study suggest that ACEIs significantly reduced AGE-increased ERK/JNK/p38 MAPK activation and renal tubular hypertrophy partly through enhancement of the NO/PKG pathway.     

Stem cell therapy: A novel approach for myocardial infarction

Myocardial infarction (MI) is a major cause of morbidity and mortality worldwide. Until recently, it was thought that myocardium was not able to repair itself, but studies have now shown that resident cardiac stem cells have regenerative capacity, and stem cell therapy may be a novel approach for cardiac muscle repair and regeneration. Stem cell-derived paracrine factors have been shown to regulate ventricular remodeling, inflammation, apoptosis, cardiomyocytes regeneration, and neovascularization in regions of infarcted cardiac tissue. In this review, we summarize the evidence from cellular, animal, and clinical studies supporting the potential clinical significance of stem cell therapy as a novel therapeutic approach for the treatment of MI.     

Silica-coated magnetic nanoparticles labeled endothelial progenitor cells alleviate ischemic myocardial injury and improve long-term cardiac function with magnetic field guidance in rats with myocardial infarction

Low retention of endothelial progenitor cells (EPCs) in the infarct area has been suggested to be responsible for the poor clinical efficacy of EPC therapy for myocardial infarction (MI). This study aimed to evaluate whether magnetized EPCs guided through an external magnetic field could augment the aggregation of EPCs in an ischemia area, thereby enhancing therapeutic efficacy. EPCs from male rats were isolated and labeled with silica-coated magnetic iron oxide nanoparticles to form magnetized EPCs. Then, the proliferation, migration, vascularization, and cytophenotypic markers of magnetized EPCs were analyzed. Afterward, the magnetized EPCs (1 × 10⁶) were transplanted into a female rat model of MI via the tail vein at 7 days after MI with or without the guidance of an external magnet above the infarct area. Cardiac function, myocardial fibrosis, and the apoptosis of cardiomyocytes were observed at 4 weeks after treatment. In addition, EPC retention and the angiogenesis of ischemic myocardium were evaluated. Labeling with magnetic nanoparticles exhibited minimal influence to the biological functions of EPCs. The transplantation of magnetized EPCs guided by an external magnet significantly improved the cardiac function, decreased infarction size, and reduced myocardial apoptosis in MI rats. Moreover, enhanced aggregations of magnetized EPCs in the infarcted border zone were observed in rats with external magnet-guided transplantation, accompanied by the significantly increased density of microvessels and upregulated the expression of proangiogenic factors, when compared with non-external-magnet-guided rats. The magnetic field-guided transplantation of magnetized EPCs was associated with the enhanced aggregation of EPCs in the infarcted border zone, thereby improving the therapeutic efficacy of MI.     

Functional suppression of Epiregulin impairs angiogenesis and aggravates left ventricular remodeling by disrupting the extracellular-signal-regulated kinase1/2 signaling pathway in rats after acute myocardial infarction

Acute myocardial infarction (AMI), a severe consequence of coronary atherosclerotic heart disease, is often associated with high mortality and morbidity. Emerging evidence have shown that the inhibition of the extracellular-signal-regulated kinase (ERK) signaling pathway appears to protect against AMI. Epiregulin (EREG) is an autocrine growth factor that is believed to activate the MEK/ERK signaling pathway. Therefore, the aim of the present study was to determine the expression patterns of EREG in AMI and to further study its effects on AMI induced experimentally in rats focusing on angiogenesis and left ventricular remodeling. Microarray-based gene expression profiling of AMI was used to identify differentially expressed genes. To understand the biological significance of EREG and whether it is involved in AMI disease through the ERK1/2 signaling pathway, rats after AMI were treated with small interfering RNA (siRNA) against EREG, an ERK1/2 pathway inhibitor, PD98059, or both of them. The microarray data sets GSE66360 and GSE46395 showed that EREG was robustly induced in AMI. Both siRNA-mediated depletion of EREG and PD98059 treatment were shown to significantly increase infarct size and left ventricular cardiomyocyte loss and enhance left ventricular remodeling. In addition, we also found that the ERK1/2 signaling pathway was inhibited following siRNA-mediated EREG inhibition and PD98059 could enhance the effects of EREG inhibition on AMI. In conclusion, these findings highlight that the silencing of EREG inhibits angiogenesis and promotes left ventricular remodeling by disrupting the ERK1/2 signaling pathway, providing a novel therapeutic target for limiting AMI.     

Galangin ameliorates cardiac remodeling via the MEK1/2–ERK1/2 and PI3K–AKT pathways

Cardiac remodeling is associated with inflammation and apoptosis. Galangin, as a natural flavonol, has the potent function of regulating inflammation and apoptosis, which are factors related to cardiac remodeling. Beginning 3 days after aortic banding (AB) or Sham surgery, mice were treated with galangin for 4 weeks. Cardiac remodeling was assessed according to echocardiographic parameters, histological analyses, and hypertrophy and fibrosis markers. Our results showed that galangin administration attenuated cardiac hypertrophy, dysfunction, and fibrosis response in AB mice and angiotensin II-treated H9c2 cells. The inhibitory action of galangin in cardiac remodeling was mediated by MEK1/2–extracellular-regulated protein kinases 1/2 (ERK1/2)–GATA4 and phosphoinositide 3-kinase (PI3K)–protein kinase B (AKT)–glycogen synthase kinase 3β (GSK3β) activation. Furthermore, we found that galangin inhibited inflammatory response and apoptosis. Our findings suggest that galangin protects against cardiac remodeling through decreasing inflammatory responses and apoptosis, which are associated with inhibition of the MEK1/2–ERK1/2–GATA4 and PI3K–AKT–GSK3β signals.