Study on the effects of fangchinoline in regulating T lymphocyte subsets in an animal model of Sjogren's syndrome

Objective·To elucidate the therapeutic effects of fangchinoline (FAN) on Sjogren's syndrome in Nod/LtJ mice, its regulatory effects on T cell subsets, and its potential molecular targets.Methods·The mice were divided into four groups: control group, disease group, hydroxychloroquine (HCQ)-treated group, and FAN-treated group. The HCQ-treated group received oral gavage every other day, and the FAN-treated group received intraperitoneal injections every other day, both for 4 weeks. Body weight, salivary flow rate, submandibular gland index, and splenic index were measured in the fifth week. Levels of anti-Ro/SSA, anti-La/SSB, and immunoglobulin G (IgG) antibodies in the peripheral blood were detected by enzyme-linked immunosorbent assay (ELISA). Lymphocyte infiltration in the submandibular glands was assessed by hematoxylin-eosin (HE) staining. The distribution of splenic T lymphocyte subsets was analyzed by flow cytometry. Potential targets of FAN were identified by target fishing, PAGE enrichment, and mass spectrometry. Molecular docking was performed to analyze binding affinity and predict binding sites.Results·FAN treatment significantly improved salivary flow reduction in Nod/LtJ mice (P=0.046) and markedly alleviated lymphocyte infiltration in the submandibular glands (P=0.044). The levels of anti-Ro/SSA antibodies in peripheral blood were significantly reduced (P=0.041). Flow cytometry results indicated that FAN altered the distribution of splenic T lymphocyte subsets. T helper 1 (Th1) (P=0.014), T helper 17 (Th17) (P=0.011), T follicular helper (Tfh) (P=0.002), and T helper 2 (Th2) (P=0.018) cells were decreased, and regulatory T cells (Treg) (P=0.014) were increased. Furthermore, target fishing coupled with mass spectrometry identified pyruvate kinase M2 (PKM2) as a potential target for FAN. Molecular docking simulations indicated a stable interaction between FAN and PKM2.Conclusion·FAN exerts discernible therapeutic effects on Sjogren's syndrome symptoms in Nod/LtJ mice. These effects are associated with modulation of T lymphocyte subset distribution and may be mediated through PKM2. These findings highlight the promising therapeutic potential of FAN in managing Sjogren's syndrome.