Intervening in the S1PR1/STAT3 Signaling Pathway Attenuates Valvular Damage Due to Rheumatic Heart Disease

Abstract Background: Rheumatic heart disease (RHD) 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 involved in valvular damage by promoting the differentiation of T helper 17 (Th17) cells during the development of valvular damage caused by RHD. In this work, we investigated whether altering the S1PR1/STAT3 signaling pathway attenuates valvular damage due to RHD. Methods: Inactivated Group A streptococci (GAS) was used to establish the RHD rat model. Recombinant adeno-associated virus (serotype 9) vectors carrying the S1PR1 overexpression sequence was used to overexpress the expression of S1PR1. STAT3-small interfering RNA (STAT3-siRNA) was used to inhibit the expression of STAT3. Reverse transcription-quantitative PCR (RT-qPCR) was used to detect the mRNA expression of S1PR1, STAT3, collagen type III α1 chain (Col3a1) and fibroblast-specific protein 1 (FSP1). 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). Enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry were used to detect the levels of interleukin (IL)-6 and IL-17. Haematoxylin and eosin (H&E) staining and Sirius red staining were used to evaluate the degree of inflammation and fibrosis in valve tissues.Results: The expression of S1PR1 in valve tissues of RHD model rats was decreased. 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. The degree of valvular inflammation and fibrosis of RHD model rats was increased. Overexpression of S1PR1 and Inhibition of STAT3 overexpressed S1PR1 expression and decreased STAT3 expression respectively and reduced the total amount of p-STAT3, resulting in decreased expression of IL-6, IL-17 and RORγt and reduced the degree of valvular inflammatory and fibrosis. Conclusions: These results suggest that the S1PR1/STAT3 signaling pathway is involved in regulating the Th17 cell-related cytokines during the vavular damage due to RHD, and altering the S1PR1/STAT3 signaling pathway could affect the expression of Th17 cell-related cytokines then attenuate the vavular damage due to RHD.