Quercetin efficiently alleviates TNF-α-stimulated injury via STAT1 and MAPK pathway in H9c2 cells: a protective role of quercetin in Myocarditis.

ABSTRACT This study aimed to evaluate the protective effect of quercetin and its in-depth mechanism in TNF-α-stimulated cardiomyocytes. The differential expression of TNF-α and STAT1 were analyzed based on the GEO database. H9c2 cells were stimulated with TNF-α to simulate myocarditis. CCK-8 assay and flow cytometry assay were performed to detect the cell viability and apoptosis. ELISA was used to measure the levels of pro-inflammatory cytokines (IL-6 and IL-17A) and anti-inflammatory cytokine (IL-10). STAT1 expression was down-regulated by transfection with si-STAT1, and its expression was detected using qRT-PCR and western blot. Western blot was also performed to assess the expression of the MAPK pathway-related factors. Herein, TNF-α was highly expressed in patients with myocarditis, and TNF-α (20 μg/ml) declined the viability of H9c2 cells. Quercetin pre-treatment partially alleviated the decrease of cell viability, the increase of apoptosis and the release of inflammatory cytokines (IL-10, IL-6 and IL-17A) induced by TNF-α. Additionally, TNF-α increased STAT1 expression, but quercetin prevented TNF-α-increased STAT1 level. Remarkably, knockdown of STAT1 enhanced the protective effect of quercetin on TNF-α-injured H9c2 cells. Moreover, quercetin restrained the TNF-α-induced activation of MAPK pathway. Also, the inhibitory effect of quercetin on the pathway was aggravated by STAT1 lacking. In summing, quercetin plays a protective role in TNF-α-stimulated H9c2 cell injury, which may be related to the regulation of STAT1 and MAPK pathway.