Roles of vascular endothelial growth factor and dexamethasone in expressions of surfactant protein B and transforming growth factor-β1 in type II alveolar epithelial cells

Abstract

Objective To investigate the effects of vascular endothelial growth factor (VEGF) and dexamethasone on mRNA expressions of surfactant protein B (SP-B) and transforming growth factor-β1 (TGF-β1) of type Ⅱ alveolar epithelial cell (AECⅡ). Methods AECⅡ were isolated and purified from fetal rat lung tissues,then cultured with different dose of VEGF (25,50 and 100 ng/ml) and dexamethasone (25,50,100 and 200 nmol/ml).The mRNA levels of SP-B and TGF-β1 were detected by real-time quantitative polymerase chain reaction (RT-PCR) and expression of TGF-β1 protein was detected by immunocytochemistry.ANOVA or q-test was applied to compare the difference among groups.Results Compared with control group,SP-B mRNA levels in 25 ng/ml VEGF group and 25,50,100 and 200 nmol/ml dexamethasone groups were higher (13.500±3.172,3.547±0.690,5.219±0.782,3.493±0.335,and 3.981 ± 1.133 vs 1.001 ± 0.059,q=-5.286,-4.943,- 7.228,- 9.906 and - 3.525 respectively,P＜0.05) ; TGF-β1 mRNA expression of 25 ng/ml VEGF group,50,100 and 200 nmol/ml dexamethasone group was lower (0.451 ± 0.078,0.579±0.019,0.422 ± 0.020 and 0.769 ± 0.025 vs 1.019±0.226,q=4.110,3.356,4.551 and 1.901 respectively,P＜0.05) ; other groups had no significant differences compared with control group (P＞0.05).Immunocytochemistry showed that the positive rate of TGF-β1 expression in 25 ng/ml VEGF,50,100 and 200 nmol/ml dexamethasone group was 23％,26％,22％ and 29％,respectively,while in the control group,the expression of TGF-β1 was positive in most of the AECⅡ (80％).Conclusions Both VEGF and dexamethasone could increase the expression of SP-B at mRNA level at appropriate concentrations.At the same time,the expression of TGF-β1 is inhibited.It is suggested that both VEGF and dexamethasone might increase the mRNA expression of SP-B by inhibiting the expression of TGF-β1. Key words: Pulmonary alveoli; Pulmonary surfactant-associated protein B; Transforming growth factor beta 1 ; Vascular endothelial growth factor A; Daxamethasone