Effects of hyperoxia on expression of lung β-defensin-2 mRNA in rats

Abstract

Objective To investigate the effects of hyperoxia on the expression of β-defensin-2 mRNA in the lungs in rats. Methods Forty 21-day old male SD rats weighing 50-60 g were randomly divided into 5 groups ( n = 8 each): control group breathing room air (group C) and 4 hyperoxia groups breathing high concentration of oxygen (92%-94% O2 ) for 12, 24, 48 and 72 h respectively (group H1-4 ). The animals were sarificed at the end of O2 breathing. The lungs were removed for microscopic examination and determination of wet/dry lung weight ratio and expression of β-defensin-2 mRNA (by RT-PCR), total NF-κB p65 protein and NF-κB p65 protein in cell nucleus (by Western blot analysis). The level of activation of NF-κB was calculated. Results The W/D lung weight ratio was significantly higher in group H3 and H4than in group C. The lung injury scores were significantly increased and β-defensin-2 mRNA expression was significantly down-regulated in group H1-4 as compared with groups in a duration of hyperoxia dependent manner. The level of activation of NF-κB was up-regulated in group H1-4 compared with group C and peaked at 48 h of hyperoxia (group H3 ). Conclusion Inhalation of high concentration of O2 can induce lung injury by down-regulating lung β-defensin 2 mRNA expression. NF-κB signal transductinn pathway may not be involved in the underlying mechanism. Key words: Oxygen inhalation therapy; beta-Defensins; Lung