AQP4 and chronic obstructive pulmonary disease: Compared to the control group, the mRNA level of AQP1 and AQP5 was decreased in the COPD group (P < 0.01) and the mRNA level of AQP1, AQP4, and AQP5 was decreased in the ASSCOPD group (P < 0.01), whereas the mRNA level of AQP1 was decreased in the ASMCOPD group (P < 0.01).