Bioinformatics and functional experiments reveal that MRC2 inhibits atrial fibrillation via the PPAR signaling pathway.

Background: Atrial fibrillation (AF) is a prevalent cardiac arrhythmia that requires improved clinical markers to increase diagnostic accuracy and provide insight into its pathogenesis. Although some biomarkers are available, new ones need to be discovered to better capture the complex physiology of AF. However, their limitations are still not fully addressed. Bioinformatics and functional studies can help find new clinical markers and improve the understanding of AF, meeting the need for early diagnosis and individualized treatment. Methods: To identify AF-related differentially expressed genes (DEGs), We applied the messenger RNA (mRNA) expression profile retrieved in Series Matrix File format from the GSE143924 microarray dataset obtained from the Gene Expression Omnibus (GEO) database, and then used weighted gene co-expression network analysis (WGCNA) to identify the overlapping genes. These genes were analyzed by enrichment analysis, expression analysis and others to obtain the hub gene. Additionally, the potential signaling pathway of hub gene in AF was explored and verified by functional experiments, like quantitative real-time polymerase chain reaction (qRT-PCR), cell counting kit-8 (CCK-8), flow cytometry, and Western blotting (WB) assay. Results: From the GSE143924 data (410 DEGs) and tan module (57 genes), 10 overlapping genes were identified. A central down-regulated gene in AF, MRC2, was identified through bioinformatics analysis. based on these results, it was hypothesized that the PPAR signaling pathway is related to the mechanism of action of MRC2 in AF. Moreover, over-MRC2 markedly reduced the growth speed of angiotensin II (Ang II)-induced human cardiac fibroblasts (HCFs) and increased apoptosis. Conversely, knockdown of MRC2 promoted HCFs cell proliferation number. Additionally, MRC2 over-expression increased the protein expression level of PPARα, PPARγ, CPT-1, and SIRT3 in Ang II-induced HCFs. Conclusions: While meeting the need for new biomarkers in the diagnosis and prognosis of AF, this study reveals the inherent limitations of current biomarkers. We identified MRC2 as a key player as an inhibitory gene in AF, highlighting its role in suppressing AF progression through the PPAR signaling pathway. MRC2 may not only serve as a diagnostic indicator, but also as a promising therapeutic target for patients with AF, which is expected to be applied in clinical practice and open up new avenues for individualized interventions.

TERT assists GDF11 to rejuvenate senescent VEGFR2+/CD133+ cells in elderly patients with myocardial infarction.

Growth differentiation factor 11 (GDF11) is a transforming growth factor ß superfamily member with a controversial role in rejuvenating old stem cells after acute injury in the elderly population. This study aimed to evaluate the effects of telomerase reverse transcriptase (TERT) on GDF11-mediated rejuvenation of senescent late-outgrowth endothelial progenitor cells (EPCs), defined as VEGFR2+/CD133+ cells, in elderly patients with acute myocardial infarction (AMI). We compared the quantity and capabilities of VEGFR2+/CD133+ cells from old (>60 years), middle-aged (45-60 years), and young (<45 years) AMI patients. The decline in circulating count and survival of VEGFR2+/CD133+ cells with age was accompanied by decrease in their TERT and GDF11 expression levels in patients with AMI. Further, upregulation of TERT could trigger GDF11-mediated rejuvenation of old VEGFR2+/CD133+ cells by renewing their survival and angiogenic abilities through activation of canonical (Smad2/3) and noncanonical (eNOS) signaling pathways. Depletion of GDF11 or TERT caused senescence of young VEGFR2+/CD133+ cells leading to impaired vascular function and angiogenesis in vitro and in vivo, whereas adTERT and rhGDF11 rescued this senescence. TERT cooperates with GDF11 to enhance regenerative capabilities of old VEGFR2+/CD133+ cells. When combined with TERT, GDF11 may represent a potential therapeutic target for the treatment of elderly patients with MI.

Comparison of Various Strategies for the Prognosis and Outcomes of Ischaemic Dilated Cardiomyopathy in Smokers: Complete Revascularisation and Smoking Cessation Produces a Superior Outcome.

BACKGROUND: Various therapies have been used to improve the symptoms and prognosis of patients with coronary artery disease. However, comparative studies showing more suitable choices for patients with ischaemic dilated cardiomyopathy (IDCM) and who smoke cigarettes are lacking. METHODS: A total of 338 patients were divided into four groups according to whether they received complete revascularisation (CR), and/or underwent smoking cessation (SC). They were followed prospectively for 12 months. The major adverse cardiac and cerebrovascular events (MACCEs: all-cause mortality, non-fatal MI, non-fatal stroke, repeat revascularisation, and AHF) were the primary endpoint, and decompensation necessitating hospitalisation and the combined endpoint thereof were secondary endpoints. RESULTS: During a mean follow-up of 12 months, the prevalence of MACCEs was significantly lower in patients receiving CR plus SC (CRSC) than in patients receiving CR only (CR), SC only (SC), and neither R nor SC (NoRSC) (CRSC 4.4% vs. CR 11.9, p<0.05; vs. SC 26.5%, p<0.001; vs. NoRSC 34.5%, p<0.001, respectively). At 12 months, CR plus SC induced the greatest clinical benefits of the secondary outcomes in the CRSC group (49.1% relative increase in LVEF; 89.8% decrease in NT-proBNP level; 30.9% decrease in LVEDD; 38.3% decrease in LVESD; 51.4% decrease in LVEDVi; 51.2% decrease in LVESVi; 96.4% decrease in hs-cTnT level; 93.5% decrease in CK-MB level; 91.1% decrease in hs-CRP level; 94.0% decrease in IL-6 level; 1.9-fold increase in eNOS level; 1.8-fold increase in NO level; 1.3-fold increase in NOS level, all p<0.001). Absence of revascularisation brought about fewer benefits, and those who continued smoking had worse outcomes. CONCLUSIONS: The combination of CR and SC could be an optimal therapeutic regimen for patients with IDCM who smoke because it improves myocardial blood perfusion and endothelial function.

Hypoxia-stimulated cardiac fibroblast production of IL-6 promotes myocardial fibrosis via the TGF-ß1 signaling pathway.

Interlukin-6 (IL-6) is a multifunctional cytokine produced by several cell types that has a role in fibrosis. Fibroblasts (FBs) maintain this underlying pathogenic change through regulation of IL-6 production; however, its potential functional role in regulating surrounding cellular structural changes during ischemic myocardial remodeling remains unexplored. Here, we generated FBs, cardiomyocytes (CMs), and blood vascular endothelial cells (ECs) from the ventricles of neonatal rats. IL-6 was then overexpressed in FBs and the cells were treated with IL-6 receptor inhibitor (IL6RI), TGF-ß1 receptor inhibitor (TßRI), or MMP2/MMP9 inhibitor (MMPI) using monoculture or coculture models under hypoxic conditions. The results indicate that overexpression of IL-6 is sufficient to induce myofibroblastic proliferation, differentiation, and fibrosis, probably via increased TGF-ß1-mediated MMP2/MMP3 signaling. The use of IL6RI, TßRI, or MMPI diminished these effects. In addition, IL-6 activated the apoptosis-associated factors Caspase3 and Smad3, and decreased the expression of anti-apoptotic factor Bcl2, resulting in apoptosis of CMs under hypoxic coculture: IL6RI or TßRI inhibited these effects. Unexpectedly, IL-6-overexpressing FBs significantly increased the angiogenesis of ECs, which involved significant increases in the expression of proangiogenic growth factors. Treatment of FBs with IL6RI or TßRI in coculture with ECs reduced the levels of secreted proangiogenic growth factors, and the angiogenesis of ECs was significantly downregulated. Thus, IL-6 functions in ischemic myocardial remodeling through multifunctional reprogramming of hypoxia-associated FBs towards fibrosis via upregulation of the TGF-ß1 signaling pathway.

Cardioprotection by PI3K-mediated signaling is required for anti-arrhythmia and myocardial repair in response to ischemic preconditioning in infarcted pig hearts.

Although the phosphatidyl-inositol-3-kinase (PI3K)/Akt pathway is essential for conferring cardioprotection in response to ischemic preconditioning (IP), the role of PI3K/Akt signaling in the infarcted heart for mediating the anti-arrhythmic effects in response to IP remains unclear. We explored the involvement of PI3K/Akt in the IP-like effect of connexin 43 and proangiogenic factors with particular regard to its role in protecting against ischemia-induced arrhythmia, heart failure, and myocardial remodeling. Groups of pigs were administered phosphate-buffered saline (PBS) or LY294002 solution. Before induction of myocardial infarction (MI), pigs were grouped according to whether or not they underwent IP. Next, all animals underwent MI induction by ligation of the left anterior descending (LAD) coronary artery. Myocardial tissues from the pig hearts at 7 days after MI were used to assess myocardium myeloperoxidase and reaction oxygen species, infarct size, collagen content, blood vascular density, expression of Akt, connexin 43, and proangiogenic growth factors, using spectrophotometer, histology, immunohistochemistry, real-time RT-PCR, and western blot. At 7 days after MI, IP significantly reduced animal mortality and malignant ventricular arrhythmia, myocardial inflammation, infarct size, and collagen content, and improved cardiac function and remodeling; use of the PI3K inhibitor LY294002 diminished these effects. In parallel with a decline in Akt expression and phosphorylation by MI, LY294002 injection resulted in significant suppression of connexin 43 and proangiogenic factor expression, and a reduction of angiogenesis and collateral circulation. These findings demonstrate that the cardioprotective effects of IP on antiventricular arrhythmia and myocardial repair occur through upregulation of PI3K/Akt-mediated connexin 43 and growth factor signaling.