Modulation of matrix metalloproteinase-9 and tissue inhibitor of matrix metalloproteinase-1 in sepsis

Previous studies demonstrated that hepatic matrix metalloproteinase-9 (MMP-9) activity increased following cecal ligation and puncture (CLP) in rats, indicating liver injury in sepsis. The activity of MMP-9 in degrading extracellular matrix is controlled by activation of proenzymes and inhibition of tissue inhibitor of MMPs (TIMP-1). To further assess the proteolytic cascade imbalance in sepsis, hepatic MMP-9 and TIMP-1 expressions were examined in CLP rats. In this study, sepsis was induced in rats by CLP, and at 10 and 20 h after sepsis induction, liver samples were collected and MMP-2, MMP-9, and TIMP-1 gene and protein expressions were evaluated by real time PCR and Western blot analysis, respectively. Gene expression of MMP-9 was increased by 6.4-fold and 3.0-fold at 10 h and 20 h after CLP as compared to sham group, respectively. Likewise, MMP-9 protein expression was also significantly increased at both time points. In contrast, MMP-2 gene expression was not altered at 10 h and 20 h after CLP as compared to sham controls. Interestingly, TIMP-1 gene expression was elevated to 89-fold and 46-fold from sham levels at 10 h and 20 h after CLP, respectively. Similarly, TIMP-1 protein levels were also significantly increased at both time points. In addition, MMP-9/TIMP-1 protein ratio was lower at both 10 h and 20 h after CLP compared to sham rats. Results demonstrated an imbalance between MMP and TIMP, with a more evident role for MMP-9 than MMP-2, and high value of TIMP-1 was particularly evident in CLP rats. Our results indicate that MMP-9 and TIMP-1 expressions are increased and they may serve as useful markers to predict the outcome of sepsis.