脂多糖作用大鼠肺泡巨噬细胞糖皮质激素受体表达及活性变化

目的探讨脂多糖作用大鼠肺泡巨噬细胞24 h内,糖皮质激素受体表达及活性变化特点.方法将原代培养的大鼠肺泡巨噬细胞分为脂多糖致伤组和地塞米松治疗组,采用RT-PCR和Western Blot在mRNA水平和蛋白质水平测定肺泡巨噬细胞糖皮质激素受体;EMSA测定肺泡巨噬细胞核蛋白中糖皮质激素受体活性.结果脂多糖作用后,糖皮质激素受体mRNA表达下调,24 h恢复正常水平;糖皮质激素受体蛋白质表达降低,4 h降至最低,24 h维持在低水平表达;糖皮质激素受体活性在1 h降到最低,24 h未恢复至正常水平.地塞米松治疗组在治疗后期不能有效维持糖皮质激素受体活性.结论脂多糖(100 ng/ml)作用大鼠肺泡巨噬细胞后,糖皮质激素受体蛋白表达降低,可能与mRNA表达降低及蛋白降解加速有关;糖皮质激素受体活性被显著抑制,出现糖皮质激素抵抗.

Changes of glucocorticoid receptor expression and activity in rat alveolar macrophages induced by lipopolysaccharide

Objective To investigate changes of glucocorticoid receptor (GR) expression and activity in rat alveolar macrophages (AMs) induced by lipopolysaccharide (LPS) within 24 h. Methods Primary cultured AMs were divided randomly into LPS treatment group and LPS Dex treatment group. The expressions of GR mRNA and GR protein in AMs at different time points were detected by RT-PCR and Western blot. Electrophoretic mobility shift assay (EMSA) was used to measure the GR activity in AMs. Results The expression level of GR mRNA decreased after LPS treatment, but returned to the normal level at 24 h after LPS treatment. The expression level of GR also decreased and reached the lowest level at 4 h after LPS treatment. GR activity also decreased, reached the lowest level at 1 h after LPS treatment, but was still lower than that in the normal control group at 24 h after treatment. Dexamethasone treatment had no obvious effect on GR activity during the late period of treatment. Conclusion LPS treatment (100 ng/ml) down-regulates the protein expression of GR, which maybe associated with the decreased expression of mRNA and accelerate degradation of GR protein. The activity of GR is inhibited sharply, resulting in glucocorticoid resistance.