The Research Of The Phosphorylation Of P38 MAPK And Expression Of MMP-2,MMP-9,TIMP-1 MRNA In Acute Hyperoxia-induced Lung Injury In Neonatal Rats

Objective: 1. To establish the model of neonatal rats with hyperoxia-induced lung injury. 2. Observation of P38 mitogen-activated protein kinase (P38 MAPK) and matrix metalloproteinase -2,9 (matrix metalloproteinases, MMP-2, 9) and its specific tissue inhibitor -1 (tissue inhibitor of metalloproteinases-1, TIMP-1 ) mRNA expression level changes in acute hyperoxia-induced lung injury. 3. To investigate the influence of P38 MAPK activation on inflammation and MMP-2, MMP-9, TIMP-1 mRNA expression in acute hyperoxia-induced lung injury.Methods: seventy-two SD rats aged from three days to five days were randomly devided into three groups:Ⅰair(air group): the rats were exposed to air in the same room;Ⅱhyperoxia+saline (hperoxia group): the rats were exposed continuously to 85%～95% oxygen, were given equivalent volume of normal saline;Ⅲhyperoxia+SB203580 (intervention group):the rats were exposed continuously to 85%～95% oxygen, were given tail vein injection of SB203580(a specific P38 MAPK inhibiter, made in Sigma, United States, 0. 5 mg/kg)at the same time every day. Half animals of each group were lavaged at 3,7 days after douched, the others were killed and the lung was removed. The left lung was used for histologic examination. WBC in bronchoalveolar lavage fluids (BALF) was determinated; the part of right lung was made into homogenate ,then measured the level of p-P38 MAPK protein, MMP-2,MMP-9,TIMP-1 mRNA and total protein content (TP); the remaining was weighed ,then heated in 60℃. The W/D lung weight ratio was calculated; the left lung was sectioned for HE staining and the pathological changes of lung tissue was Observated. Results:1. Pathologic changes in lung: at 3rd day, we could find obvious bleeding and inflammatory cells in alveolar space in hyperoxia group; and at 7th day, the damage was more serious: the lung compartment was enlarged, and the framework was disordered. In SB203580- intervention group, there were less inflammatory changes and no significant enlargement of lung compartment.2. Lung wet weight/dry weight rate: At 3rd day, the ratio was higher in hyperoxia group than air groups(p<0.01); and at 7th day, it was more higher in hyperoxia groups (p<0.01), while in SB203580- intervention groups, it was lower than in hyperoxia groups(At 3rd day, p<0.05; at 7th day,p<0.01).3. TP: At 3rd day, the TP content was higher in hyperoxia group than air groups (p<0.05); and at 7th day, it was more higher in hyperoxia groups (p<0.05), while in SB203580- intervention groups, it was little lower than in hyperoxia groups at 3rd day (p>0.05), and at 7th day it was significantly lower (p<0.01).4. WBC in BALF: At 3rd day, the WBC in BALF was higher in hyperoxia group than air groups(p<0.01); and at 7th day, it was more higher in hyperoxia groups (p<0.01), while in SB203580- intervention groups, it was lower than in hyperoxia groups(p<0.01).5. Expression of p-P38 MAPK protein in mice lung tissue: The expression of p-P38 MAPK protein was weak in air groups. It was higher in hyperoxia groups than air groups (P<0.01). In SB203580- intervention group, it was lower than in hyperoxia group(p<0.01).6. Expression of MMP-2,MMP-9,TIMP-1 mRNA in mice lung tissue:The expression of MMP-2,MMP-9,TIMP-1 mRNA was weak in air group. MMP-2,MMP-9 mRNA was significantly higher in hyperoxia group than air group (P<0.01),TIMP-1 mRNA was higher in hyperoxia group than air group (P<0.05). In SB203580- intervention group, MMP-2,MMP-9 mRNA was significantly lower than in hyperoxia group(p<0.01), TIMP-1 mRNA was lower than in hyperoxia group(p<0.05).Conclusions: P38MAPK play an important role in the development of hyperoxia-induced acute lung injury in rats. In hyperoxia-induced acute lung injury, by inhibiting the phosphorylation of P38 MAPK, SB203580 can relieve inflammatory reaction, and reduce the expression of MMP-2,MMP-9,TIMP-1 mRNA. It indicates that the phosphorylation of P38 MAPK may take part in the control of inflammatory reaction and the expression of MMP-2,MMP-9,TIMP-1 mRNA in hyperoxia-induced acute lung injury.