Macrophage elastase (MMP-12): a pro-inflammatory mediator?

As many metalloproteinases (MMPs), macrophage elastase (MMP-12) is able to degrade extracellular matrix components such as elastin and is involved in tissue remodeling processes. Studies using animal models of acute and chronic pulmonary inflammatory diseases, such as pulmonary fibrosis and chronic obstrutive pulmonary disease (COPD), have given evidences that MMP-12 is an important mediator of the pathogenesis of these diseases. However, as very few data regarding the direct involvement of MMP-12 in inflammatory process in the airways were available, we have instilled a recombinant form of human MMP-12 (rhMMP-12) in mouse airways. Hence, we have demonstrated that this instillation induced a severe inflammatory cell recruitment characterized by an early accumulation of neutrophils correlated with an increase in proinflammatory cytokines and in gelatinases and then by a relatively stable recruitment of macrophages in the lungs over a period of ten days. Another recent study suggests that resident alveolar macrophages and recruited neutrophils are not involved in the delayed macrophage recruitment. However, epithelial cells could be one of the main targets of rhMMP-12 in our model. We have also reported that a corticoid, dexamethasone, phosphodiesterase 4 inhibitor, rolipram and a non-selective MMP inhibitor, marimastat could reverse some of these inflammatory events. These data indicate that our rhMMP-12 model could mimic some of the inflammatory features observed in COPD patients and could be used for the pharmacological evaluation of new anti-inflammatory treatment. In this review, data demonstrating the involvement of MMP-12 in the pathogenesis of pulmonary fibrosis and COPD as well as our data showing a pro-inflammatory role for MMP-12 in mouse airways will be summarized.

Role of tissue inhibitors of metalloproteinases (TIMPs) in colorectal carcinoma

Increased production of matrix metalloproteinases (MMPs) has been associated with increases in invasive and metastatic potential in many types of human carcinoma. Tissue inhibitors of metalloproteinase (TIMP)-1 inhibits most interstitial collagenases and MMP-9. TIMP-2 binds specifically and noncovalently to the pro-form of MMP-2 and inhibits its enzyme activity. In this study, we examined TIMP-1 and TIMP-2 expressions in relation to clinicopathological variables in colorectal carcinoma with in situ hybridization and immunohistochemistry. TIMP-1 and TIMP-2 expressions were localized overwhelmingly to pericancer stromal cells, while malignant and normal mucosal cells were weak or negative. Strong stromal TIMP-1 immunoreactivity correlated with Dukes' stage (p=0.022), status of lymph node metastasis (p=0.044) and poor survival (p= 0.005). The degree of immunohistochemical staining of TIMP-2 did not correlate with all clinicopathological variables. The correlation between enhanced TIMP-1 expression and advanced stage and poor survival suggest a growth promoting activity of TIMP-1 in colorectal carcinoma.