Relation of Cardiotrophin-1 (CT-1) and cardiac transcription factor GATA4 expression in rat's cardiac myocytes hypertrophy and apoptosis

Let-7a regulates expression of β1-adrenoceptors and forms a negative feedback circuit with the β1-adrenoceptor signaling pathway in chronic ischemic heart failure

BACKGROUND

The aim of the present study was to investigate the role of microRNA (miRNA) let-7a in down-regulation of β1-adrenoceptors (β1-AR) and elucidate the underlying mechanism of chronic ischemia heart failure (CIHF) in rats.

METHODS AND RESULTS

CIHF model was established by occlusion of coronary artery for 4 weeks. β1-AR level was obviously down-regulated and let-7a up-regulated in the failing heart 4 weeks after myocardial infarction. Overexpression of let-7a inhibited β1-AR expression in neonatal rat ventricular cells (NRVCs), which was abolished by anti-let-7a antisense inhibitor. The lentivirus vector containing precursor let-7a (len-pre-let-7a) further down-regulated the reduced β1-AR level by CIHF and the effect was reversed by len-AMO-let-7a. Len-negative control did not produce any significant influence on β1-AR expression. Importantly, there exists a negative feedback loop associated with β1-AR regulation through β1-AR/cAMP/PKA/GATA4/let-7a/β1-AR signaling pathway in CIHF. As demonstrated, GATA4 was activated by β1-AR up-regulation through cAMP-PKA signaling pathway in early phase of ischemia, then GATA4 positively regulated let-7a expression which in turn suppressed β1-AR expression.

CONCLUSIONS

Let-7a regulates β1-AR expression and forms a negative feedback loop with β1-AR signaling pathway in ischemic heart failure. This study provides a new insight into the differential expression of β1-AR in early and later phase of myocardial ischemia.

MiR-770-5p inhibits cisplatin chemoresistance in human ovarian cancer by targeting ERCC2

In this study, we examined the role of the miRNA miR-770-5p in cisplatin chemotherapy resistance in ovarian cancer (OVC) patients. miR-770-5p expression was reduced in platinum-resistant patients. Using a 6.128-fold in expression as the cutoff value, miR-770-5p expression served as a prognostic biomarker and predicted the response to cisplatin treatment and survival among OVC patients. Overexpression of miR-770-5p in vitro reduced survival in chemoresistant cell lines after cisplatin treatment. ERCC2, a target gene of miR-770-5p that participates in the NER system, was negatively regulated by miR-770-5p. siRNA-mediated silencing of ERCC2 reversed the inhibition of apoptosis resulting from miR-770-5p downreglation in A2780S cells. A comet assay confirmed that this restoration of cisplatin chemosensitivity was due to the inhibition of DNA repair. These findings suggest that endogenous miR-770-5p may function as an anti-oncogene and promote chemosensitivity in OVC, at least in part by downregulating ERCC2. miR-770-5p may therefore be a useful biomarker for predicting chemosensitivity to cisplatin in OVC patients and improve the selection of effective, more personalized, treatment strategies.

Sodium Ferulate Protects against Angiotensin II-Induced Cardiac Hypertrophy in Mice by Regulating the MAPK/ERK and JNK Pathways

Background and Objective. It has been reported that sodium ferulate (SF) has hematopoietic function against anemia and immune regulation, inflammatory reaction inhibition, inhibition of tumor cell proliferation, cardiovascular and cerebrovascular protection, and other functions. Thus, this study aimed to investigate the effects of SF on angiotensin II- (AngII-) induced cardiac hypertrophy in mice through the MAPK/ERK and JNK signaling pathways. Methods. Seventy-two male C57BL/6J mice were selected and divided into 6 groups: control group, PBS group, model group (AngII), model + low-dose SF group (AngII + 10 mg/kg SF), model + high-dose SF group (AngII + 40 mg/kg SF), and model + high-dose SF + agonist group (AngII + 40 mg/kg SCU + 10 mg/kg TBHQ). After 7 d/14 d/28 days of treatments, the changes of blood pressure and heart rates of mice were compared. The morphology of myocardial tissue and the apoptosis rate of myocardial cells were observed. The mRNA and protein expressions of atrial natriuretic peptide (ANP), transforming growth factor-β (TGF-β), collagen III (Col III), and MAPK/ERK and JNK pathway-related proteins were detected after 28 days of treatments. Results. SF improved the mice's cardiac abnormality and decreased the apoptosis rate of myocardial cells in a time- and dose-dependent manner (all P < 0.05). MAPK/ERK pathway activator inhibited the protective effect of SF in myocardial tissue of mice (P < 0.05). SF could inhibit the expression of p-ERK, p-p38MAPK, and p-JNK and regulate the expressions of ANP, TGF-β, and Col III (all P < 0.05). Conclusion. Our findings provide evidence that SF could protect against AngII-induced cardiac hypertrophy in mice by downregulating the MAPK/ERK and JNK pathways.

Cell signaling pathways for the regulation of GATA4 transcription factor: Implications for cell growth and apoptosis

GATA4 is a member of the GATA family of zinc finger transcription factor, which regulates gene transcription by binding to GATA elements. GATA4 was originally discovered as a regulator of cardiac development and subsequently identified as a major regulator of adult cardiac hypertrophy. GATA4 regulates gene expression of various genes, which are involved in cardiac development and cardiac hypertrophy and heart failure. In addition to the heart, GATA4 plays important roles in the reproductive system, gastrointestinal system, respiratory system and cancer. Positive and negative regulations of GATA4 therefore are important components of biologic functions. The activation of GATA4 occurs via various cell signaling events. Earlier studies have identified protein-protein interactions of GATA4 with other factors. The discovery of interactions of GATA4 with nuclear factor for activated T cells (NFAT) revealed the importance of calcium signaling in the activation of GATA4. GATA4 can also be phosphorylated by mitogen activated protein kinases and protein kinase A. Lysine modifications also occur on the GATA4 molecule including acetylation and sumoylation. Both reactive oxygen-dependent and -independent antioxidant-sensitive pathways for GATA4 activation have also been demonstrated. The GATA4 activity is also regulated by modulating the level of GATA4 expression via transcriptional as well as translational mechanisms. This work summarizes the current understanding of regulatory mechanisms for modulating GATA4 activity.

Cardiotrophin-1 in cardiovascular regulation

Cardiotrophin (CT)-1 was discovered by coupling expression cloning with an embryonic stem cell-based model of cardiogenesis. Comparison of similarity in amino acid sequence and conformational structure indicates that CT-1 is a member of the interleukin (IL)-6 type cytokine family that shares the transmembrane signaling protein, glycoprotein (gp) 130 as a receptor. These cytokines mediate overlapping pleiotropic actions on a variety of cell types including cardiac myocytes, hepatocytes, megakaryocytes, osteoclasts, and neuronal cells. CT-lmediates its hypertrophic and cytoprotective properties through the Janus kinase/signal transducers and activators of transcription (JAK/STAT), mitogen-activated protein (MAP) kinase, phosphatidylinositol (PI) 3 kinase, and nuclear factor kappa B (NFkappaB) pathways. CT-1 gene and protein are distributed not only in the heart, but also in the pulmonary, renal, gastrointestinal, cerebral, and muscular tissues. CT-1 could also be synthesized and secreted from vascular endothelial cells and adipocytes. CT-1 has hypertrophic actions on the cardiac myocytes, skeletal muscle cells, and smooth muscle cells as well as cytoprotective actions on the cardiac myocytes, neuronal cells, and hepatocytes. CT-1 is circulating in the body, and its plasma concentration is increased in various cardiovascular and renal diseases such as hypertension, congestive heart failure, myocardial infarction, valvular heart disease, metabolic syndrome, and chronic kidney disease. Treatment with CT-1 is beneficial in experimental animal models of cardiovascular diseases. CT-1 specifically protects the cardiac myocytes from ischemic damage when CT-1 is given not only prior to the ischemia, but also given at the time of reoxygenation. Current evidence suggests that CT-1 plays an important role in the regulation of the cardiovascular system.