Electroacupuncture at "Zusanli"(ST36) protects intestinal mucosal immune barrier by suppre-ssing apoptosis of intestinal lymphocytes and regulating expression of Bcl-2 and Bax in sepsis rats

Abstract

To observe the effect of electroacupuncture (EA) at "Zusanli" (ST36) on apoptosis of intestinal T lymphocytes, translocation of intestinal bacteria and expression of intestinal Bcl-2 and Bax proteins and intestinal mucosal immune barrier in sepsis rats, so as to explore its underlying mechanism in relieving sepsis. SD rats were randomly divided into sham operation (n=6), model (n=15), non-meridian and non-acupoint (non-acupoint, n=15) and acupoint EA(n=15) groups by using random number table method. The sepsis model was established by using cecal ligation and perforation(CLP) method. EA (2 Hz, 2 mA) was applied to bilateral ST36 or non-acupoint for 30 min one hour after modeling, once every day for 3 days. The rats' general conditions and fatality rate in 3 days after modeling were recorded. The liver, spleen and mesenteric lymph nodes were taken for bacterial culture to detect the translocation rate of intestinal bacteria. The small intestinal tissue was taken for observing histopathological changes (Chiu's score: 0-5 points) after HE staining, and for determining the expression levels of Bcl-2 and Bax proteins using Western blot. The intestinal mucosa was sampled for detecting the apop-tosis (apoptotic index) of lymphocytes by using terminal deoxynucleoitidyl transferase-mediated deoxyuridine triphosphate biotin nick end labeling (TUNEL) assay, and the counts of CD4+ and CD8+T cells using flow cytometry. The contents of IL-4 in the small intestine and that of secretory IgA (sIgA) in the small intestinal mucus were determined by using ELISA. After modeling, of the 15 rats in each of the 3 groups, 7, 7 and 2 in the model, non-acupoint and EA groups were dead in the first 3 days, with the fatality rate being 46.67% (7/15), 46.67% (7/15) and 13.33% (2/15), respectively (being obviously lower in the EA group than in the former two groups, P<0.05). Compared with the sham operation group, the incidence of intestinal bacterial translocation, apoptotic index, Chiu's score, and Bax expression were significantly increased (P<0.05), and the percentages of CD4+ and CD8+T cells, IL-4 and sIgA contents and Bcl-2 expression considerably decreased (P<0.05) in the model group. In comparison with the model group, modeling-induced increase of incidence of bacterial translocation, apoptotic index and Bax expression, and decrease of percentages of CD4+ and CD8+T cells, IL-4 and sIgA contents and Bcl-2 expression were reversed (P<0.05) in the EA group. EA at ST36 can reduce death rate and intestinal bacteria translocation incidence in sepsis rats, which may be related to its functions in regulating the expression of intestinal Bcl-2 and Bax proteins and inhibiting the apoptosis of intestinal mucosal T lymphocytes, thereby protecting the immune barrier function of intestinal mucosa to reduce the intestinal permeability.