[Effects of hypoxia on the expression of glucocorticoid receptor and the anti-inflammatory action of dexamethasone in human alveolar epithelial cells].

OBJECTIVE

To study the changes in the expression levels of two isoforms of glucocorticoid receptor (GRα and GRβ) and the anti-inflammatory effect of dexamethasone in human alveolar epithelial cell under hypoxic conditions.

METHODS

Human alveolar epithelial cell line A549 was used as the model. Cells were cultured under normoxic (37°C, 950 mL/L air, 50 mL/L CO(2);) or hypoxic (37°C, 950 mL/L N(2);, 250 mL/L CO(2);) conditions for 24, 48 and 72 h, respectively. The expression levels of GRα and GRβ proteins in the cells were determined by Western blotting. Lipopolysaccharide (LPS, 10 μg/mL) and the different concentrations of dexamethasone (DEX, 10(-8);-10(-6); mol/L) were added together into the culture medium under normoxic or hypoxic conditions. 48 h later, radioimmunoassay (RIA) was used to measure the level of IL-8 in the culture supernatants.

RESULTS

The GRα protein level of the normoxia group was not significantly different from that of the hypoxia group at 24 h time point (P>0.05). But at the 48 h and 72 h time points, the GRα protein level of the hypoxia groups was lower than that of the corresponding normoxia groups (P<0.05, P<0.01, respectively). The GRα protein levels decreased progressively in the hypoxia groups (P<0.05), while the levels were not significantly different among the corresponding normoxia groups (P>0.05); The GRβ protein levels of the 24, 48, and 72 h hypoxia groups were not different from those in the corresponding normoxia groups (P>0.05). At 48 h after 10(-7); or 10(-6); mol/L DEX was added, IL-8 levels in the culture supernatants of the hypoxia groups were higher than those in the corresponding normoxia groups (P<0.05).

CONCLUSIONS

Hypoxia can down-regulate the GRα protein level in a time-dependent manner in A549 cells and impair the anti-inflammatory effect of DEX.