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[Effect of the proteasome inhibitor MG-132 on hyperoxic lung injury and its mechanism in rats].

OBJECTIVE
To observe the effects of proteasome inhibitor MG-132 on hyperoxic lung injury in rats and explore the mechanism.


METHODS
Thirty SD rats were randomly divided into 3 groups, namely the normoxic group, hyperoxic group, and hyperoxic with MG-132 treatment group, and rat models of hyperoxic exposure-induced lung injury were established in the latter two groups. After pathological grading of the lung injury under optical microscope and determination of the wet/dry weight ratio of the lung tissue, the expressions of ubiquitin protein and nuclear factor-kappaB (NF-kappaB) p56 and the activity of proteasome 20S and myeloperoxidase (MPO) were detected. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) expressions in the lung tissue were also detected.


RESULTS
The rats with hyperoxic exposure showed obvious pulmonary edema and increased wet/dry weight ratio of the lung tissue (P<0.01), which were significantly alleviated with MG-132 treatment (P<0.01). Compared with the normoxic group, hyperoxic exposure resulted in significant lung pathologies (P<0.01), which was reduced after MG-132 treatment. Immunohistochemistry and Western blotting demonstrated increased expression of ubiquitin protein in the lung tissue after hyperoxic exposure (P<0.01), which was lowered by MG-132 treatment (P<0.01). Proteasome 20S activity was obviously enhanced in the hyperoxic group (P<0.01) but lowered by MG-132 treatment (P<0.01). Hyperoxic exposure also caused obviously enhanced MPO activity and expressions of NF-kappaB, TNF-alpha, and IL-6 (P<0.01), which were all reduced by MG-132 treatment (P<0.05).


CONCLUSION
MG-132 alleviates hyperoxic lung injury probably by inhibiting the NF-kappaB/inflammatory factor pathways.