Electroacupuncture of “Jiaji” (EX-B2) improves asthma by reducing airway inflammation and regulating PI3K/AKT/mTOR signaling pathway in rats with allergic asthma

To observe the effect of electroacupuncture (EA) at “Jiaji” (EX-B2) on asthma symptoms, airway inflammation and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling in rats with allergic asthma (AA), so as to explore its mechanisms underlying improvement of AA.

Forty male SD rats were randomly divided into blank control, AA model, EA and medication groups, with 10 rats in each group. The AA model was established by intraperitoneal injection of 1 mL 1% ovalbumin (OVA, grade V) suspension on the 1^st day and 7^th day and inhalation of 1% aerosol OVA (on the 15^th day) for 30 min, once daily for 2 weeks. Rats of the EA group received EA stimulation (2 Hz/15 Hz, 1-2 mA) of bilateral EX-B2 for 20 min, once daily for 2 weeks. Rats of the medication group received intraperitoneal injection of dexamethasone solution (0.5 mg/kg), once daily for 2 weeks. The nasal scratching or tickling (0-3 points) and asthma (0-9 points) behavior were graded, and their summation (behavior score) was used for assessing the severity of asthma. Histopathological changes of the lung tissue were assessed by giving pathological score after H. E. staining. The contents of IL-4, IL-5, IL-13 in the bronchoalveolar lavage fluid (BALF) and lgE in the serum were detected by ELISA. The immunoactivity of Beclin1 and microtubule-associated protein 1A/1B light chain 3B (LC3B) in the lung tissue was detected by immunohistochemistry. The ratio of expression levels of p-PI3K/PI3K, p-AKT/AKT, p-mTOR/mTOR proteins in the lung tissue were detected by Western blot.

Compared with the blank control group, the model group showed an increase in the behavior score (shortness of breath, wheezing and irritability, etc), pathological scores of the lung tissue, contents of IL-4, IL-5 and IL-13 in the BALF and IgE in the serum, the immunoactivity of Beclin1 and LC3B in the lung tissue (P<0.01), and a decrease in the body weight, and the ratio of expression levels of p-PI3K/PI3K, p-AKT/AKT and p-mTOR/mTOR proteins in the lung tissue (P<0.01). In comparison with the model group, the behavior score, pathological score, the contents of IL-4, IL-5, IL-13 and IgE, and the immunoactivity of Beclin1 and LC3B were significantly decreased (P<0.05, P<0.01), while the ratio of expression levels of p-PI3K/PI3K, p-AKT/AKT and p-mTOR/mTOR proteins were considerably increased (P<0.05, P<0.01) in both EA and medication groups. The body weight of rats was increased (P<0.05) in the EA group compared to the model group. No significant differences were found between the EA and medication groups of all the indexes mentioned above.

EA of EX-B2 can improve the symptoms of asthma in rats with AA, which may be associated with its functions in inhibiting the autophagy level of airway epithelial cells in the lung tissue and reducing airway inflammation by regulating PI3K/AKT/mTOR signaling pathway.