The Role Of Urokinase Type Plasminogen Activator In Mouse Experimental Emphysema

Emphysema is terminal stage of chronic obstructive lung disease, with serious damage of collagen and elastin protein component. It manifest with over-aerify and amplify of terminal bronchiole (including bronchioli respiratorii, ductuli alveolares, saccus alveolaris, alveolar). The enzyme of lung matrix degradation includes fibrolysis enzyme and matrix metalloproteinases. MMP-2 and MMP-9 mainly depredate collagen, MMP-12 mainly depredate elastin. Tissue inhibitor of metalloproteinase (TIMP-1) is the most important inhibitor of matrix metalloproteinase, can bind with MMP-2 and MMP-9. Reduce the activity of MMPs and reduce interstitial lung damage and promote repair.Urokinase type plasminogen activator (u-PA) plays a significant role as an important protein factor in serine protease family, not only in the transforming of plasminogen (plg) to plasmin (plm), but also in the extracelluar matrix impairing and repairing process and the cell signal transduction. u-PA can activate MMPs enzyme, and promote degradation of extracellular matrix components.For observeing the roles of urokinase type plasminogen activator (u-PA) gene in mice experimental senile emphysema changes and its possible mechanism. we choosed same aged wild type (WT) mice and u-PA gene knock out (KO) mice what were fed under the criterion of SPF. At 15th day (younger age group) and 4^th month (senior group), mice were anaesthetised and anatomized for further experiments.HE staining of wild type mice and u-PA gene knock out mice showed that there was no significant difference for younger group between u-PA gene KO mice and WT mice. In senior group, WT mice showed significant alveolar expansion and interstitial lung damage, by contrast, u-PA gene deletion had more complete alveolar wall structure and no significant increase of alveolar space. For further analysis of the reasons for these differences, we use image analysis software image pro plus v5.0 analyzed the sections of weigert elastic fiber-dyeing (positive stained part of the total high power field), the result showed that u-PA gene deleted mice had higer elastin content than wild type mice in senior group.(P<0.05) Real time PCR testing Elastin, MMP-12 and the expression of TIMP-1 mRNA level, the results showed that, in senior group, u-PA gene KO mice has higher Elastin and TIMP-1 mRNA content (P<0.01). In the younger group, there was no significant difference.The results suggested that, u-PA gene deletion reduce the mice-emphysema-like changes, its molecular mechanism may be that u-PA gene deletion leading to Elastin and EIMP-1 mRNA expression increased, then, elastin increase in lung. Emphysema is terminal stage of chronic obstructive lung disease, with serious damage of collagen and elastin protein component. It manifest with over-aerify and amplify of terminal bronchiole (including bronchioli respiratorii, ductuli alveolares, saccus alveolaris, alveolar). The enzyme of lung matrix degradation includes fibrolysis enzyme and matrix metalloproteinases. MMP-2 and MMP-9 mainly depredate collagen, MMP-12 mainly depredate elastin. Tissue inhibitor of metalloproteinase (TIMP-1) is the most important inhibitor of matrix metalloproteinase, can bind with MMP-2 and MMP-9. Reduce the activity of MMPs and reduce interstitial lung damage and promote repair.Plasminogen activator inhibitor 1(PAI-1) is the main inhibitor of t-PA and other plasminogen activators (PA). The activity between PAI-1 and PAs is the most sufficient one in all PA inhibitors. PAI-1 combine with u-PA, t-PA and inhibit theirs enzyme activity, reduce the activation of plasminogen and MMPs. Then, increase collagen and elastin deposition, promote tissue repair.Here, we first use PAI-1 gene knockout mice on the role of PAI-1 in development of elderly emphysema. We compared 1day, 3 month and 6 month old PAI-1 gene knockout mice and wild type mice lung sections. The result showed that there was obvious lung space structure damage in old age PAI-1 gene KO mice. For further analysis of the reasons for these differences, we applied hydroxyproline assay determination of collagen protein content in lung, the result showed that PAI-1 gene deletion has higher collagen content though with sever lung interstitial damage. Weigert elastic fibers stained with image pro plus v5.0 image analysis semi-quantitative of lung elastin, the result showed that there was significant elastin decrease in PAI-1 senior age mice. In order to analysis the reasons of collagen and elastin change in PAI-1 gene KO mice lung, we had gelatin zymography trial, western blot test, immunohistochmistry and immunofluorescence. The result showed that PAI-1 gene deletion increased the MMP-12 secretion in lung interstitial and decreased the MMP-2, MMP-9 activity. Real-time PCR test of Collagen and Elatin, TIMP-1, MMP-12 relative mRNA level, the results showed that PAI-1 gene deletion can increase the expression of MMP-12. In senior PAI-1 gene KO mice, there is higher elatin mRNA expression.Through the analysis of PAI-1 in mice age-related emphysema-like changes, we believe, PAI-1 gene deletion increased the level of MMP-12 expression, MMP-12 led to the increased elastin degradation, and finally caused to the damage of lung matrix and emphysema. Thought, there are increased expression of Elastin and TIMP-1 mRNA, it can not fully compensate the lung damage caused by PAI-1 deletion. PAI-1 play an important role in the intergrity of lung space structure.