Objective: To investigate the role of autophagy in SA pathogenesis.
Method: We enrolled 33 SA patients, 14 non-severe asthma (NSA) patients and 33 normal healthy controls (NC). Autophagy was evaluated in sputum granulocytes and peripheral blood cells (PBCs) using Western blot, confocal microscopy, transmission electron microscopy, and flow cytometry. To induce autophagy in vitro, HL-60 cells and primary eosinophil cells were treated with interleukin (IL)-5; A549 cells and primary airway epithelial cells were treated with IL-1β.
Results: Increased expression of microtubule-associated protein light chain (LC3)-II was noted in the sputum granulocytes and PBCs from SA group compared to NSA and NC groups. In confocal microscopy, autophagosomes were observed in the eosinophils from sputum granulocytes and PBCs of SA patients. IL-5 induced autophagy in HL-60 cells with increased eosinophil cationic protein expression. When IL-5 was treated on primary eosinophils of SA patients, autophagy expression increased which were not affected by dexamethasone. After treatment of IL-1β on A549 cells and primary airway epithelial cells, autophagy expression and IL-8 production increased which were attenuated by autophagy inhibitors including E64D+Pepstatin A, 3-MA and LY294002, but not by dexamethasone. Atg5-knockdown or Beclin1-knockdown of A549 cells significantly decreased the IL-8 production as well as the LC3-II. Autophagy expression in peripheral eosinophils from SA patients were significantly higher than those from NC (P=0.013).
Conclusion: We suggest that autophagy play a pivotal role in SA pathogenesis. The autophagy modulation may be a novel therapeutic target for conventional therapy-resistant SA patients.