Expression of Matrix Metalloproteinase-9 and Tissue Inhibitor of Metalloproteinase-1 after Administration of Endotoxin in Diabetic Rats

Background: An acute lung injury(ALI) is characterized by the recruitment, activation, and apoptosis of inflammatory cells, numerous products released by inflammatory cells such as reactive oxygen species, inflammatory mediators, and a variety of proteolytic enzymes. It was reported that bacterial infections in diabetics showed impaired PMN functions such as reduced PMN respiratory burst and decreased microbicidal activity in inflamed tissue. However, the effect of the proteinase - inhibitor (MMP-9 vs TIMP-1) in ALI in diabetics is unclear. This study evaluated the differences in the expression of MMP-9 and TIMP-1 after the stimulation of endotoxin in a rat model. Methods: Six-week-old male Sprague-Dawley rats were classified into normal, DM, LPS and DM+LPS groups. The peripheral blood, BAL fluids, and lung tissues were obtained from individual rats. The MMP-9 activity was measured by gelatin zymography and the TIMP-1 level was measured by Western blotting. Results: The total BAL cells of the DM-LPS groups were significantly lower than the LPS groups (p < 0.01). The MMP-9 activities in the serum were higher in the DM+LPS groups than in the other groups. The MMP-9 activities in the BAL fluids were significantly higher in the DM+LPS group than in the normal and diabetic rats (p < 0.05). TIMP-1 expressions in the BAL fluids were significantly lower in the DM+LPS group than other groups (p < 0.05). The ratio between MMP-9 and TIMP-1 in the BAL fluids was significantly higher in the DM+LPS groups (p < 0.05). Conclusion: In ALI in diabetics the higher MMP-9 activity and lower TIMP-1 level are believed to prolonged and intensify the course of inflammation.