[Effect of electroacupuncture on intestinal flora in COPD rats based on gut-lung axis theory]

To observe the effect of electroacupuncture (EA) on the intestinal flora in rats with chronic obstructive pulmonary disease (COPD) and explore its possible mechanism based on the gut-lung axis theory.

A total of 30 male SD rats of SPF grade were randomly divided into a normal control (NC) group, a model group and an EA group, 10 rats in each one. In the model group and the EA group, COPD model was established by intratracheal instillation of lipopolysaccharide combined with cigarette fumigation. In the EA group, EA was applied at bilateral "Feishu" (BL13) and "Zusanli" (ST36), with disperse-dense waves, in frequency of 4 Hz/20 Hz, current of 1-3 mA, 20 min a time, once a day for 14 days continuously. Before and after modeling, as well as after intervention, body weight was observed; after intervention, the lung function indexes (forced expiratory volume in 0.1 second [FEV_0.1], FEV_0.1/forced vital capacity [FVC]%, forced expiratory volume in 0.3 second [FEV_0.3] and FEV_0.3/FVC%) were measured, serum levels of inflammatory factors (tumor necrosis factor-α[TNF-α], interleukin-6[IL-6], interleukin-1β[IL-1β] and interleukin-10[IL-10]) were detected by ELISA, histopathology of lung and colon tissues was observed by HE staining, the intestinal flora were analyzed by 16S rRNA, and the correlations between lung function and intestinal flora were analyzed.

Compared with the NC group, in the COPD group, the body weight and lung function indexes were reduced (P<0.01); the lung and colon tissues were damaged, the mean linear intercept (MLI) of alveolus and inflammatory cell numbers of 100 μm² in lung tissue were increased (P<0.01); the serum levels of TNF-α, IL-6 and IL-1β were increased (P<0.01, P<0.05), and the serum level of IL-10 was decreased (P<0.01); α-diversity indexes of intestinal flora were increased (P<0.01); the relative abundance of Bacteroidetes, Proteobacteria and Oscillospira, Bacteroides, Coprococcus was increased (P<0.01), the relative abundance of Firmicutes, Actinobacteria, Tenericutes, TM7 and Lactobacillus, Allobaculum, Bifidobacterium, YRC22 was decreased (P<0.01, P<0.05); 31 different expressed metabolic pathways were identified between the two groups. Compared with the COPD group, in the EA group, the body weight and lung function indexes were increased (P<0.01); the damage of lung and colon tissues was improved, the MLI of alveolus was decreased (P<0.05); the serum levels of TNF-α, IL-6 and IL-1β were decreased (P<0.05), and the serum level of IL-10 was increased (P<0.05); α-diversity indexes of intestinal flora were decreased (P<0.01); the relative abundance of Bacteroidetes, Proteobacteria and Oscillospira, Bacteroides, Coprococcus was decreased (P<0.01, P<0.05), the relative abundance of Firmicutes, Actinobacteria, Tenericutes, TM7 and Lactobacillus, Allobaculum, Bifidobacterium, YRC22 was increased (P<0.01); 35 different expressed metabolic pathways were identified between the two groups. The lung function was positive related with Actinobacteria, Tenericutes, TM7 and YRC22, and was negative related with Bacteroidetes, Proteobacteria and Oscillospira, Bacteroides, Coprococcus.

EA may ameliorate lung function and tissue injury of COPD by regulating intestinal flora dysbiosis and inflammatory response, suggesting an anti-inflammatory effect mediated via "gut-lung" axis.