n-butanol extract of Pulsatilla decoction alleviates vulvovaginal candidiasis via the regulation of mitochondria-associated Type I interferon signaling pathways

Ethnopharmacological relevance: Vulvovaginal candidiasis (VVC) is a relatively common fungal infectious disease in the female reproductive tract. The pathogenesis of VVC not only involves Candida albicans (C. albicans) infection, but also the improper immune response of the vaginal mucosal immune system to the fungus. As a classical formula, Pulsatilla decoction has been proven to exert protective effect in both clinical and experimental research in VVC. However, the specific mechanism of Pulsatilla decoction in VVC remains elusive. This study investigated the mechanism of n-butanol extract of Pulsatilla decoction (BEPD) in treating VVC from the perspective of type I interferon signaling and related mitochondrial function.

Materials and methods: A VVC-rat model was developed using an estrogen-based method to evaluate the effectiveness of BEPD in treating VVC, and the therapeutic efficacy of BEPD against VVC was comprehensively evaluated by fungal morphology and burden, neutrophil numbers, histopathology, pro-inflammatory and anti-inflammatory cytokines production, and LDH level. Immunohistochemistry (IHC), immune fluorescence (IF), Western Blot (WB) and RT-qPCR assays were conducted to assess type I interferon signaling and mitochondria functions. Candidalysin-induced vaginal epithelial inflammation in vitro, as cellular models, was employed to detect the changes in type I interferon signaling and mitochondria function before and after BEPD-containing serum intervention.

Results: BEPD could significantly improve the inflammation, reduce fungal loads and inhibit fungal growth, balance pro-inflammatory and anti-inflammatory cytokine levels in VVC model rats. The findings from IHC, IF, WB and RT-qPCR revealed that BEPD could promote type I interferon signaling and alleviate mitochondrial functional damage in VVC model rats, and BEPD-containing serum could play the same role in vitro.

Conclusion: The study findings generally demonstrated that BEPD could improve the inflammation and correct the immune imbalance in VVC through regulation of type I interferon signaling and mitochondrial function.