Effect of different concentrations of oxygen on inflammatory response in lipopolysaccharide-induced alveolar typeIIcells

Abstract

Objective To investigate the secretion of inflammatory cytokines in lipopolysaccharide(LPS)-induced aveolar epithelium typeⅡcells(AT-Ⅱ) cells exposed to various oxygen concentrations, and the possible mechanism. Methods Primary cultured AT-Ⅱcells were randomly divided into five groups: A, B, C, D, and E, and then placed in sterilized incubators: 37℃, 21% O2, 5% CO 2; 37℃, 21% O2, 5% CO 2; 37℃, 40% O2, 55% N2, 5% CO 2; 37℃, 60% O 2, 35% N2, 5% CO2; 37℃, 90% O 2, 5% N 2, 5% CO 2.Towenty-four h later, the supernatant fluid was used to assay the content of interleukin-8(IL-8) by enzyme linked immunosorbent assay(ELISA).The expression of p38 mitogen-activated protein kinase(p38 MAPK) m RNA and protein was detected in AT-Ⅱcells by reverse transcription-polymerase chain reaction and Western blotting. Results ELISA, reverse transcriptase-polymerase chain reaction(RT-PCR) and Western blotting showed that the content of IL-8 was(40. 22±7. 25),(109. 35±10. 19),(213. 98 ±30. 51),(369. 71±21. 73)and(489. 32±42. 35) ng/L, p38MAPK mRNA expression level was 0. 066±0. 010, 0. 163±0. 008, 0. 228±0. 027, 0. 268±0. 016 and 0. 292±0. 010, and p38MAPK protein expression level was 0. 055±0. 005, 0. 124±0. 006, 0. 182±0. 009, 0. 227±0. 013 and 0. 303±0. 010 in groups A, B, C, D and E respectively.As compared with group A, the content of IL-8 in the supernatant fluid,and the expression of p38MAPK m RNA and protein were significantly increased in groups B, C, D and E(P< 0. 05).As compared with groups B, the content of IL-8 in the supernatant fluid, and the p38 MAPK m RNA and protein expression level in groups C, D and E were gradually increased with the difference being statistically significant(P< 0. 05).In different oxygen concentration groups, with the increases in oxygen concentrations, the content of IL-8 in the supernatant fluid, and the expression of p38MAPK m RNA and protein expression level were gradually increased with the difference being statistically significant(P< 0. 05). Conclusion 40%-90% oxygen could concentrasion-dependently increase the LPS-induced secretion of IL-8 in AT-Ⅱcells probably by up-regulating the intracellular p38 MAPK expression. Key words: Hyperoxia-induced lung injury; Aveolar epithelium typeⅡcells; Lipopolysaccharide; Interleukin-8; p38 mitogen-activated protein kinase