Acupuncture affects the apoptosis of eosinophilic granulocytes in lung tissue of asthmatic rats by regulating the P38MAPK signaling pathway

Abstract

To investigate the effects of acupuncture on phosphorylated P38 mitogen-activated protein kinase (p-P38MAPK), intercellular adhesion molecule-1 (ICAM-1), interferon γ (IFN-γ), and eosinophilic granulocytes (EOS) in lung tissue of asthmatic rats, and to explore the mechanism of acupuncture in regulating the apoptosis of EOS. Clean-grade male Wistar rats were randomly divided into normal, model, dexamethasone and acupuncture groups, 8 rats in each group. The asthmatic model was established by intraperitoneal injection of mixture suspension (1 mL) of 10% ovalbumin and 10% Al(OH)_3+ normal saline, followed by inhalation of atomized 1% ovalbumin solution for 30 min, once daily for 2 weeks to trigger occurrence of asthmatic symptoms. The rats in dexamethasone group were intraperitoneally injected with 0.9 mg/kg dexamethasone since day 15 once a day for two consecutive weeks. In the acupuncture group, bilateral "Feishu" (BL13), "Pishu" (BL20), "Shenshu" (BL23), "Dingchuan" (EX-B1), and "Danzhong" (CV17) were selected for acupuncture treatment once every other day since day 15 for two consecutive weeks. Uniform reinforcing and reducing manipulation was carried out, and the needles were retained for 30 min. The pathological changes of the lung tissue were observed by hematoxylin-eosin (HE) staining. The apoptosis of EOS in the lung tissue of rats was detected by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. The expression of p-P38MAPK in the lung tissue was detected by Western blot. The protein and mRNA levels of ICAM-1 and IFN-γ in the lung tissue were determined by immunohistochemistry and real-time PCR, respectively. The results of HE staining showed that the pulmonary alveoli and surrounding tissues were intact with no inflammatory cell infiltration in the normal group. The model group showed massive exudation of inflammatory materials and thickened pulmonary interstitium. The dexamethasone group and acupuncture group showed less damage of the alveolar structure and only a small number of inflammatory cells around the airway. Compared with the normal group, the apoptosis rate of EOS in lung tissue was decreased (P<0.01), the expression levels of p-P38MAPK and ICAM-1 proteins and mRNAs in the lung tissue were up-regulated (P<0.01), while the expression levels of IFN-γ protein and mRNA in the lung tissue were down-regulated (P<0.01) in the model group. Compared with the model group, the apoptosis rate of EOS in the lung tissue was increased (P<0.05), the expression levels of p-P38MAPK and ICAM-1 proteins and mRNAs in the lung tissue were down-regulated (P<0.01, P<0.05), while the expression levels of IFN-γ protein and mRNA were up-regulated (P<0.05, P<0.01) in the dexamethasone and acupuncture groups. Acupuncture may inhibit the P38MAPK signaling pathway, down-regulate ICAM-1 expression, and up-regulate IFN-γ expression to promote the apoptosis of EOS and reduce EOS aggregation, thus alleviating the inflammatory response of airway in asthma.