The intervention of S1PR1/STAT3 signaling pathway by inhibiting the expression of STAT3 attenuates the valvular damage due to rheumatic heart disease

Abstract

Background Rheumatic heart disease (RHD) is a social health problem that affects many patients every year, but its pathogenesis is still unclear. Recent studies have found that the sphingosine 1-phosphate receptor 1 (S1PR1)/signal transducer and activator of transcription 3 (STAT3) signaling pathway is activated during the development of valvular damage caused by RHD. STAT3 plays an important role in the differentiation of CD4 + T cells into T helper 17 (Th17) cells, and Th17 cell-related cytokines are involved in the development of RHD. In this work, we investigated whether altering the S1PR1/STAT3 signaling pathway by inhibiting the expression of STAT3 attenuates valvular damage due to RHD. Methods Inactivated Group A streptococci (GAS) and complete Freund’s adjuvant (CFA) were used to establish the RHD rat model. STAT3-small interfering RNA (STAT3-siRNA) was used to directly inhibit the expression of STAT3 in the heart. Histological examination was used to evaluate the degree of inflammation and fibrosis in valve tissues. Enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry were used to detect the levels of interleukin (IL)-6 and IL-17 in serum and valve tissue. Reverse transcription-quantitative PCR (RT-qPCR) was used to detect the mRNA expression of S1PR1 and STAT3. Western blotting (WB) and immunohistochemistry were used to detect the protein expression of S1PR1, STAT3, phosphorylated (p-) STAT3, retinoic acid-related orphan receptor gamma T (RORγt). Results The expression of S1PR1 in valve tissues of RHD model rats was decreased. The degree of valvular inflammation and fibrosis of RHD model rats was increased. The levels of IL-6 and IL-17 in valves and serum of RHD model rats were increased as well as an increase of p-STAT3 in valve tissues. Inhibition of STAT3 by STAT3-siRNA decreased STAT3 expression and reduced the total amount of p-STAT3, resulting in decreased expression of IL-6, IL-17 and RORγt in valves and serum and reduced valvular inflammatory response and fibrosis. Conclusions These results suggest that inhibiting the expression of STAT3 in the heart may reduce the valvular damage caused by rheumatic heart disease.