Regulation of electroacupuncture on non-canonical pathway of hepatocellular pyroptosis in rats with nonalcoholic fatty liver disease

Abstract

To observe the effect and mechanism of electroacupuncture (EA) on non-canonical pathway of hepatocellular pyroptosis in nonalcoholic fatty liver disease (NAFLD). Sixty male SD rats were randomly divided into a normal diet group (n=15) and a high fat modeling group (n=45). The rats in the high fat modeling group were fed with customized high fat diet for 8 weeks to establish NAFLD model. Thirty successfully modeled rats were selected and randomly divided into a model group (n=10), an EA group (n=10) and a non-acupoint with shallow needling group (n=10), and 10 rats were randomly selected from the normal diet group as the control group additionally. In the EA group, EA was applied at bilateral "Fenglong" (ST 40) and "Ganshu" (BL 18), with disperse-dense wave, in frequency of 4 Hz/20 Hz and in intensity of 3 mA. In the non-acupoint with shallow needling group, shallow needling was delivered at points 5 mm from bilateral "Fenglong" (ST 40) and "Ganshu" (BL 18), the EA stimulation parameters were same as the EA group. The intervention was given once a day, 20 min a time, 5 days a week for 4 weeks in the two groups. After intervention, the liver morphology was observed by oil red "O" staining, the serum levels of lipopolysaccharide (LPS), interleukin (IL)-1β, IL-18 and tumor necrosis factor-α (TNF-α) were detected by ELISA, the protein expression of gasdermin D (GSDMD), GSDMD-N, cysteine aspartic acid specific protease-11 (Caspase-11), IL-1β, IL-18 and TNF-α in liver tissue were detected by Western blot, the mRNA expression of GSDMD, Caspase-11, IL-1β, IL-18 and TNF-α in liver tissue was detected by real-time PCR in rats of each group. In the model group, vacuoles in different size were found in the hepatocellular cytoplasm, and the fat droplets were in schistose accumulation. Compared with the model group, the hepatocellular fat droplets and the degree of hepatic steatosis were reduced in the EA group and the non-acupoint with shallow needling group. Compared with the control group, the serum levels of LPS, IL-1β, IL-18 and TNF-α were increased (P<0.01), the protein and mRNA expression of GSDMD, Caspase-11, IL-1β, IL-18, TNF-α as well as the protein expression of GSDMD-N in the liver tissue were increased (P<0.01) in the model group. Compared with the model group, the serum levels of LPS, IL-1β, IL-18 and TNF-α were decreased (P<0.01), the protein and mRNA expression of GSDMD, IL-1β, IL-18 and TNF-α in the liver tissue were decreased (P<0.01), the protein expression of GSDMD-N and the mRNA expression of Caspase-11 in the liver tissue were decreased (P<0.01) in the EA group and the non-acupoint with shallow needling group. Compared with the model group, the protein expression of Caspase-11 in the liver tissue was decreased (P<0.01) in the EA group. Compared with the non-acupoint with shallow needling group, the serum levels of LPS, IL-1β, IL-18 and TNF-α were decreased (P<0.01), the protein and mRNA expression of GSDMD, Caspase-11, IL-1β and IL-18 in the liver tissue were decreased (P<0.01), the protein expression of GSDMD-N and the mRNA expression of TNF-α in the liver tissue were decreased (P<0.01) in the EA group. EA can inhibit hepatocellular pyroptosis in NAFLD rats, and its mechanism may be related to reducing the serum level of LPS, and down-regulating the expression of the non-canonical pathway related factors i.e. GSDMD, GSDMD-N, Caspase-11, IL-1β, IL-18 and TNF-α.