Regulation mechanism of MAP kinases on aquaporin 5 mRNA and protein expression in hyperoxic lung injury

Abstract:

Objective：To investigate regulation mechanism of mitogen activated protein kinases（MAPKs） signaling pathway on Aqua－porin 5（AQP5） expression disorder in hyperoxic lung injury（HLI）. Methods：Forty-eight Wistar rats aged three weeks old were ran－domly divided into 8 groups（n=6）：room-air group（A），hyperoxia group（H），hyperoxia + ERK inhibitor PD98059（H+PD），hyperoxia + p38 inhibitor SB203580（H+SB），hyperoxia + JNK inhibitor SP600125（H+SP），and the corresponding inhibitors control groups（A+PD，A+SB，A+SP）. The rats in hyperoxia groups were kept in cabinet with high concentration of oxygen（≥95%），and those in air groups were kept in room air. AQP5 protein expression in lung tissue was detected by Western blot. AQP5 mRNA expression was de－termined by real-time PCR. Results：Lung injury developed in hyperoxia exposure groups，as evidenced by severe alveolar edema，in－flammatory cell infiltration，RBC leakage and alveolar structure destruction. The protein level of AQP5 detected by Western blot was down- regulated in H group and H+ inhibitors（H+PD/SB/SP） groups than in A group（P=0.000），but the expression of AQP5 protein was markedly higher in H+SB and H+SP groups than in H group（P=0.000），and this change was more significant in H+SB group. There was no difference in AQP5 protein expression between H group and H+PD group（P=0.737）. The mRNA level of AQP5 was decreased in H group but was increased in H+SB，H+SP and H groups compared with that of A group（P=0.000）. How－ever，there was no change in AQP5 mRNA level between H+PD and H group（P=0.796）. There was no significant change in AQP5 protein and mRNA expression between A group and A+inhibitors（A+PD/SB/SP） groups. Conclusion：Hyperioxia decreases AQP5 protein and mRNA expression while SB203580 and SP600125 up-regulates AQP5 gene expression. Inhibition of p38 and JNK pathway blocks the effect of hyperoxia on AQP5 expression. These data show that p38 and JNK MAP kinases may involve in the down-regulation of AQP5 genes in HLI.