Chaihu Guizhi Decoction (CGD) Ameliorates Chronic Pancreatitis (CP) -induced Mechanical Allodynia by Inhibiting Microglia P2X7R-NLRP3 Inflammasome Activation

Abstract

Abstract Background We have previously shown that P2X7R/NLRP3-mediated signaling pathway plays an important role in CP chronic inflammation and fibrosis. Inspired by the traditional Chinese medicine(TCM) theory “Chaihu Guizhi Decoctio(CGD)for the treatment of Sudden pain in the heart or abdomen". Targeting in central sensitization(CS) may explain the treatment of Chaihu Guizhi Decoction (CGD) on CP-induced pain. Methods Fifty male SD rats were randomly and equally divided into two groups based on table of random numbers: TNBS group (n = 40) and sham group (n = 10). At 4w after TNBS model, rats in TNBS (n = 40) and sham group (n = 10) were each further divided for drug injection: TNBS-CGD medium dose(n = 10) and TNBS-CGD high dose group(n = 10):The rats were intragastrically treated with CGD(8g,16g.kg− 1,2W, twice a day). TNBS-BBG group(n = 10), the rats were repeated intraperitoneal injection of BBG (P2X7R inhibitor, dissolved in normal saline, 100 ug/10 mL per rat) or sham operated rats (n = 10) were given 0.9% saline solution.After behavioral tests, at 6 weeks, all the rats including TNBS, and sham rats were sacrificed for further experiments. Pancreatic histology was evaluated with hematoxylin and eosin staining, The expression of PGP9.5, α-SMA, NLRP3 and P2X7R proteins and their molecular effects were detected by immunohistochemical staining, immunofluorescence, Western blot. Results Behavioral study indicated that compared to the sham, CGD significantly decreased TNBS-induced mechanical allodynia at 2w after administration and this effect was dose-dependent(response frequencies: 71 ± 20% vs 28 ± 13%). CGD alleviated pancreatic injury in chronic pancreatitis rat, including atrophy, inflammatory cells infltration, fibrosis, the infiltration of inflammatory cells around pancreatic nerves (PGP9.5)and α-SMA expressions (2.5 ± 0.7 vs 1.5 ± 0.6,3.1 ± 0.8 vs 1.6 ± 0.7,3.2 ± 1.0 vs 1.8 ± 1.3, 20.6 ± 4.2 vs 3.0 ± 1.4, 23.8 ± 7.8% vs 4.9 ± 1.6% ). Western blot, IHC and IF data showed that CGD could significantly block expressions P2X7R,NLRP3 protein (P2X7R: 5.1 ± 0.5% vs 3.2 ± 0.1%,NLRP3:28.0 ± 4.3% vs 12.3 ± 1.5%). Conclusions Our findings indicated that CGD could be a novel and effective treatment for CP-induced chronic pain.