Effects of 3-methyladenine on airway inflammation, airway hyperresponsiveness and mucus secretion in asthmatic mice

Abstract

Objective: To investigate the effects of 3-methyladenine on airway inflammation, airway hyperresponsiveness and mucus secretion in asthmatic mice, and to explore its mechanism. Methods: C57BL/6J female mice were randomly divided into normal control group (PBS), OVA group(OVA), OVA with 3-methyladenine group (OVA+3-MA), and OVA with 4-phenylbutyrate group (OVA+4-PBA). OVA group, OVA+3-MA group and OVA+4-PBA groups were all sensitized and challenged with OVA to establish asthmatic models, while PBS group was given PBS as a control. At 2 h before challenge, OVA+3-MA group was intraperitoneally injected with 3-methyladenine, and OVA+4-PBA group was intraperitoneally injected with 4-phenylbutyrate. Airway hyperresponsiveness, eosinophils, and pathological changes of pulmonary tissue (hematoxylin-eosin, HE staining) were measured to confirm the establishment of asthmatic models. Sections of pulmonary tissue were also stained with Masson and PAS. The expression level of LC3B was measured by immunofluorescence and Western blot. The Beclin1, Muc5ac, Atf6, Chop and Bip proteins in lung tissues were detected by Western blot. Results: The Penh value, and eosinophils in BALF in OVA group was significantly increased compared with PBS group (P<0.05). The Penh value in OVA+3-MA group and OVA+4-PBA group were significantly decreased compared with the OVA group at the concentration of 6.25 g/L, 12.50 g/L, 25.00 g/L, and 50.00 g/L of methacholine (all the P<0.05), and the eosinophils were also significantly decreased compared with the OVA group (P<0.05). Pulmonary histology revealed that OVA group showed high levels of inflammatory cell infiltration of bronchi and lung vessels, alveolar septal thickening, structural destruction, smooth muscle thickening, collagen deposition, and goblet cell hyperplasia. The levels of inflammatory cell infiltration of bronchi and lung vessels, alveolar septal thickening, structural destruction, smooth muscle thickening, collagen deposition, and goblet cell hyperplasia in OVA+3-MA group and OVA+4-PBA group were significantly lower than the OVA group, while the PBS group was normal. Compared with PBS group, the expression of LC3 Ⅱ/Ⅰ, Beclin1, Muc5ac, Atf6, Chop and Bip proteins in lung tissues in the OVA group were significantly increased (1.09±0.04 vs 0.34±0.09, P<0.05; 0.18±0.01 vs 0.06±0.01, P<0.05; 1.90±0.38 vs 0.46±0.11, P<0.05; 1.67±0.18 vs 0.41±0.08, P<0.05; 2.96±0.45 vs 1.11±0.10, P<0.05; 2.07±0.34 vs 0.49±0.17, P<0.05, respectively). Compared with the OVA group the expression of LC3 Ⅱ/Ⅰ, Beclin1, Muc5ac, Atf6, Chop and Bip proteins in lung tissues in the OVA+3-MA group and OVA+4-PBA group were significantly decreased (0.46±0.07 vs 1.09±0.04, 0.63±0.03 vs 1.09±0.04, both P<0.05; 0.11±0.02 vs 0.18±0.01, 0.12±0.02 vs 0.18±0.01, both P<0.05; 0.72±0.22 vs 1.90±0.38, 0.57±0.13 vs 1.90±0.38, both P<0.05; 1.06±0.12 vs 1.67±0.18, 1.02±0.12 vs 1.67±0.18, both P<0.05; 1.67±0.21 vs 2.96±0.45, 1.10±0.15 vs 2.96±0.45, both P<0.05; 1.03±0.11 vs 2.07±0.34, 0.97±0.10 vs 2.07±0.34, both P<0.05). Conclusion: 3-MA was shown to inhibit airway inflammation, airway hyperresponsiveness and mucus secretion in mice with bronchial asthma, and the mechanism may be related to inhibiting autophagy, and then inhibiting endoplasmic reticulum stress.