G3BP2 is involved in isoproterenol-induced cardiac hypertrophy through activating the NF-κB signaling pathway.

The RasGAP SH3 domain-binding proteins (G3BPs) are a family of RNA-binding proteins that can co-ordinate signal transduction and post-transcriptional gene regulation. G3BPs have been shown to be involved in mediating a great diversity of cellular processes such as cell survival, growth, proliferation and apoptosis. But the potential roles of G3BPs in the pathogenesis and progression of cardiovascular diseases remain to be clarified. In the present study, we provide the first evidence that suggests the participation of G3BP2 in cardiac hypertrophy. In cultured neonatal rat cardiomyocytes (NRCMs), treatment with isoproterenol (ISO, 0.1-100 µmol/L) significantly elevated the mRNA and protein levels of G3BP2. Similar results were observed in the hearts of rats subjected to 7D-injection of ISO, accompanied by obvious heart hypertrophy and elevated the expression of hypertrophy marker genes ANF, BNP and ß-MHC in heart tissues. Overexpression of G3BP2 in NRCMs led to hypertrophic responses evidenced by increased cellular surface area and the expression of hypertrophy marker genes, whereas knockdown of G3BP2 significantly attenuated ISO-induced hypertrophy of NRCMs. We further showed that G3BP2 directly interacted with IκBα and promoted the aggregation of the NF-κB subunit p65 in the nucleus and increased NF-κB-dependent transcriptional activity. NF-κB inhibition with PDTC (50 µmol/L) or p65 knockdown significantly decreased the hypertrophic responses in NRCMs induced by ISO or G3BP2 overexpression. These results give new insight into the functions of G3BP2 and may help further elucidate the molecular mechanisms underlying cardiac hypertrophy.

(-)-Epicatechin-3-gallate (a polyphenol from green tea) potentiates doxorubicin-induced apoptosis in H9C2 cardiomyocytes.

OBJECTIVE: The effect of epicatechin-3-gallate (ECG), a polyphenol that is present in green tea, on doxorubicin (DOX) cytotoxicity in H9C2 cardiomyocytes and its underlying mechanisms were investigated. RESULTS: Pretreatment with ECG (20 and 30 µM) significantly increased DOX-induced apoptosis to 16-18% in H9C2 cardiomyocytes. The Bax/Bcl-2 ratio increased significantly after 1 h pretreatment with ECG. ECG also enhanced the phosphorylation of AMP-activated protein kinase (AMPK) which was induced by DOX in a dose-dependent manner. CONCLUSION: Pretreatment with ECG sensitized H9C2 cells to DOX-mediated apoptosis through modulation of proteins involved in apoptosis and AMPK.

High doses of (-)-epigallocatechin-3-gallate from green tea induces cardiac fibrosis in mice.

OBJECTIVE: Tea is the most consumed beverage in the world. (-)-Epigallocatechin-3-gallate (EGCG), a major green tea polyphenol, is effective in the prevention of several chronic diseases, and is marketed as part of many dietary supplements. We have now examined the myocardiotoxic effect of high doses of EGCG in mice. RESULTS: EGCG (500 and 1000 mg/kg·d) induced cardiac collagen synthesis and fibrosis-related protein expression, such as connective tissue growth factor (CTGF) and fibronectin (FN) in mice. Moreover, EGCG decreased the protein expression of p-AMPK and increased the levels of p-p70S6 K and p-S6. CONCLUSION: This is the first evidence that high oral doses of EGCG could induce cardiac fibrosis, and shed new light on the understanding of EGCG-mediated myocardiotoxicity.

Genetically predicted vitamin C levels significantly affect patient survival and immunotypes in multiple cancer types.

Background: Recent observational studies and meta-analyses have shown that vitamin C reduces cancer incidence and mortality, but the underlying mechanisms remain unclear. We conducted a comprehensive pan-cancer analysis and biological validation in clinical samples and animal tumor xenografts to understand its prognostic value and association with immune characteristics in various cancers. Methods: We used the Cancer Genome Atlas gene expression data involving 5769 patients and 20 cancer types. Vitamin C index (VCI) was calculated using the expression of 11 genes known to genetically predict vitamin C levels, which were classified into high and low subgroups. The correlation between VCI and patient overall survival (OS), tumor mutational burden (TMB), microsatellite instability (MSI), and immune microenvironment was evaluated, using Kaplan-Meier analysis method and ESTIMATE (https://bioinformatics.mdanderson.org/estimate/). Clinical samples of breast cancer and normal tissues were used to validate the expression of VCI-related genes, and animal experiments were conducted to test the impact of vitamin C on colon cancer growth and immune cell infiltration. Results: Significant changes in expression of VCI-predicted genes were observed in multiple cancer types, especially in breast cancer. There was a correlation of VCI with prognosis in all samples (adjusted hazard ratio [AHR] = 0.87; 95% confidence interval [CI] = 0.78-0.98; P = 0.02). The specific cancer types that exhibited significant correlation between VCI and OS included breast cancer (AHR = 0.14; 95% CI = 0.05-0.40; P < 0.01), head and neck squamous cell carcinoma (AHR = 0.20; 95% CI = 0.07-0.59; P < 0.01), kidney clear cell carcinoma (AHR = 0.66; 95% CI = 0.48-0.92; P = 0.01), and rectum adenocarcinoma (AHR = 0.01; 95% CI = 0.001-0.38; P = 0.02). Interestingly, VCI was correlated with altered immunotypes and associated with TMB and MSI negatively in colon and rectal adenocarcinoma (P < 0.001) but positively in lung squamous cell carcinoma (P < 0.05). In vivo study using mice bearing colon cancer xenografts demonstrated that vitamin C could inhibit tumor growth with significant impact on immune cell infiltration. Conclusion: VCI is significantly correlated with OS and immunotypes in multiple cancers, and vitamin C might have therapeutic potential in colon cancer.