XCHT alleviates the pancreatic fibrosis via VDR/NLRP3 signaling pathway in a mouse model of CP

Xiao Chai Hu Tang (XCHT) derived from the classic medical book Shang Han Lun (Treatise on Febrile Diseases) in the Eastern Han Dynasty, which has been widely used in China and other Asian countries for the treatment of inflammation and fibrosis of chronic pancreatitis (CP), but the therapeutic mechanism of XCHT in pancreatic fibrosis remains unclear.This study aimed to evaluate the intervention effects and explore pharmacological mechanism of XCHT on inflammation and fibrosis in cerulein-induced CP model.Fifty male C57BL/6 mice were randomly divided into five main groups, 10 animals in each: Control, CP model (50 μg/kg cerulein), high dose XCHT-treated CP group (60 g/kg XCHT), medium dose XCHT-treated CP group (30 g/kg XCHT) and low dose XCHT-treated CP group (15 g/kg XCHT). Different doses of XCHT were given to mice by gavage twice a day for 2 weeks after the CP model induction. Pancreatic tissues were harvested and the pancreatic inflammation and fibrosis were evaluated by histological score, Sirius red staining, and alpha-smooth muscle actin (α-SMA) immunohistochemical staining. ELISA, IHC and RT-qPCR were performed to detect the expression of Vitamin D3 (VD3) and Vitamin D receptor (VDR) in serum and pancreatic tissues, respectively. The expressions of NLRP3 inflammasome related genes and molecules were assayed by WB, IHC and RT-qPCR.The pathohistological results demonstrated that XCHT markedly inhibited the fibrosis and chronic inflammation of cerulein-induced CP, indicated by reduction of collagen I, collagen III, α-SMA, and NLRP3 expressions. XCHT significantly increased VD3 and VDR expression while reduced the pancreatic NLRP3 expression. Correspondingly, XCHT decreased the levels of NLRP3 downstream targets IL-1β, TNF-α and IL-6.These results revealed that XCHT suppressed the pancreatic fibrosis and chronic inflammation in cerulein-induced CP model by enhancing the VD3/VDR expression and inhibiting the secretion of NLRP3-assoicated inflammatory factors.