Betulonic acid regulates oviduct epithelial cell inflammation through the TLR4, MAPK, and JAK/STAT signalling pathways.

Context: Infertility is a common disease among women of childbearing age and seriously endangers the reproductive health of human beings.

Aims: We aimed to study the active effect and mechanism of betulonic acid (BTA) on tubal inflammatory infertility.

Methods: An inflammatory model was established in isolated rat oviduct epithelial cells. Immunofluorescence of cytokeratin 18 was performed in cells. The therapeutic effect of BTA on cells was observed. Subsequently, we added JAK/STAT inhibitor AG490 and MAPK inhibitor U0126 and measured the levels of inflammatory factors via enzyme-linked immunosorbent assay and qRT-PCR. CCK-8 assay was applied to test cell proliferation, whereas flow cytometry was used to measure apoptosis. The levels of TLR4, IκBα, JAK1, JAK2, JAK3, Tyk2, STAT3, p38, ERK and the phosphorylation of p65 were determined by Western blotting.

Key results: Betulonic acid inhibited the activation of TLR4 and NF-κB signalling pathways, and significantly downregulated IL-1β, IL-6, and TNF-α, with high doses being the most effective. Furthermore, high-dose BTA promoted the proliferation of oviduct epithelial cells and inhibited apoptosis. In addition, BTA inhibited the activation of JAK/STAT signalling pathway to perform effectively in oviduct epithelial cells inflammation. The addition of AG490 led to the inhibition of the JAK/STAT signalling pathway. BTA also inhibited the activation of MAPK signalling pathway in oviduct epithelial cells inflammation. Under U0126 treatment, the inhibition of proteins in MAPK pathway by BTA was weakened.

Conclusions: Therefore, BTA inhibited the TLR, JAK/STAT and MAPK signalling pathways.

Implications: Our study provided a new therapeutic strategy for infertility caused by oviduct inflammation.