Dexamethasone Upregulates the Expression of Aquaporin4 by Increasing SUMOylation in A549 Cells.

Dexamethasone can alleviate the severity of bronchial and alveolar edema and therefore is widely applied in the treatment of various exudative diseases including pulmonary edema. However, the effectiveness of dexamethasone is still being questioned and its mechanism is not fully understood. Aquaporins (AQPs) are mainly responsible for the transmembrane transport of water, which is tightly associated with pulmonary edema. Small ubiquitin-like modifiers (SUMOs) are considered to play a protective role in some pathological conditions. In this study, we demonstrated that dexamethasone can upregulate the expression of AQPs in A549 cells by inducing SUMOylation. We found that a low dose of dexamethasone significantly upregulated the levels of SUMOylation and AQP expression in A549 cells, accompanied by a translocation of SUMOs from the cytoplasm to the nucleus. We also explored the possible relation between SUMOylation and AQPs. Knockdown of SUMO2/3 by RNA interference decreased the level of AQP4 in A549 cells after dexamethasone stimulation. Together, our findings demonstrated that AQP4 expression was upregulated in A549 cells exposed to dexamethasone, and SUMOylation may participate in the regulation of AQP4.