Matrix metalloproteinases-2 and 9 do not play a role in the growth of preneoplastic liver lesions in F344 rats

Hydrogen peroxide-mediated downregulation of matrix metalloprotease-2 in indomethacin-induced acute gastric ulceration is blocked by melatonin and other antioxidants

Gastric mucosal damage is directly associated with extracellular matrix degradation in which matrix metalloproteinases (MMPs) play a crucial role. Remodeling of connective tissues and loss of tissue integrity due to the action of MMPs are reported in several inflammatory diseases, including gastric ulcer. Indomethacin-induced gastric ulceration involves the generation of reactive oxygen species (ROS) and a reduction in MMP-2 transcription and translation. Our aim was to identify the mechanism for suppression of MMP-2 activity by ROS during acute ulceration and further to examine the possible actions of antioxidants, especially melatonin, during healing. Melatonin (N-acetyl-5-methoxytryptamine) blocked hydroxyl radical and nitrite anion generation, protein oxidation, mucosal cell disruption, and MMP-2 downregulation. In addition, suppression of MMP-2 activity by H2O2 in a dose- and time-dependent manner in vitro is blocked by melatonin, omeprazole, and curcumin. We observed that melatonin and other antioxidants (e.g., curcumin and omeprazole) offered gastroprotection in vivo by upregulation of suppressed MMP-2 expression and activity at the level of secretion and synthesis. Moreover, antioxidants reversed the suppression of MMP-2 expression by upregulation of MT1-MMP and downregulation of TIMP-2. Hence, we hypothesize that antioxidants exerted protection against H2O2-mediated inactivation and downregulation of MMP-2 expression during onset of indomethacin-induced ulceration.

Redox-dependent matrix metalloproteinase-1 expression is regulated by JNK through Ets and AP-1 promoter motifs

Reactive oxygen species have been shown to play an important role in the regulation of distinct signaling cascades, many of which act upon the production of matrix metalloproteinases (MMP). Using a series of redox-engineered cell lines we have previously demonstrated that MMP-1 expression is sensitive to the alterations in the steady state production of H2O2 (Ranganathan, A. C., Nelson, K. K., Rodriguez, A. M., Kim, K. H., Tower, G. B., Rutter, J. L., Brinckerhoff, C. E., Epstein, C. J., Huang, T. T., Jeffrey, J. J., and Melendez, J. A. (2001) J. Biol. Chem. 276, 14264-14270). In the present study, we investigate the molecular mechanisms involved in the H2O2-mediated induction of MMP-1. Mutational analysis of an MMP-1 promoter indicates that both the single nucleotide polymorphism creating an Ets binding site at -1607 and a proximal AP-1 site at -1602 are required for maximal H2O2-dependent transcription. The redox-sensitive MMP-1 protein expression requires activation of both ERK1/2 and JNK pathways. Importantly, JNK signaling is largely responsible for the H2O2 sensitivity of the MMP-1 promoter, whereas ERK1/2 contributes to both its basal and H2O2 dependence. H2O2 control of Ets-1 expression was ERK1/2-dependent whereas that of c-Jun requires both ERK1/2 and JNK signaling. Chromatin immunoprecipitation assays indicate that binding of the histone acetyltransferase, p300, and the transcription factors Ets-1 and c-Jun to the MMP-1 promoter is redox sensitive. The redox sensitivity of MMP-1 expression is also associated with an increase in the abundance of oxidatively inactivated protein-tyrosine phosphatases. Targeted cytosolic or mitochondrial scavenging of H2O2 prevented all of the aforementioned signals. These studies provide substantial insight into the mechanisms underlying the redox-dependent control of MMP-1 and may lead to the development of novel targeted antioxidant-based inhibitory therapies for controlling MMP-1 expression during degenerative disease processes.

Mitochondrial redox control of matrix metalloproteinases

Reactive oxygen species (ROS) are constantly generated in aerobic organisms during normal metabolism and in response to both internal and external stimuli. Imbalances in the production and removal of ROS have been hypothesized to play a causative role in numerous disease pathologies such as cancer, ischemia/reperfusion injury, and degenerative diseases such as photoaging, atherosclerosis, arthritis, and neurodegeneration. A feature often associated with these diseases is a malfunctioning of the connective tissue remodeling process due to increased activity of extracellular matrix-degrading metalloproteinases (MMPs). This review summarizes the evidence that implicates ROS as key regulators of MMP production and the importance of these interactions in disease pathologies.

Low molecular weight inhibitors of matrix metalloproteinases can enhance the expression of matrix metalloproteinase-2 (gelatinase A) without inhibiting its activation

BACKGROUND

In the current study, the authors investigated the effects of synthetic low molecular weight inhibitors of matrix metalloproteinases (MMPs) on the expression and activation of MMP-2 in a three-dimensional tissue system.

METHODS

Rabbit periosteal explants were cultured with or without various concentrations of the MMP inhibitors CT1166, CT1399, or CT1746, and conditioned media and tissue extracts were analyzed for the expression and activity of MMP-2.

RESULTS

The data showed that blocking the activity of all MMPs with relatively high inhibitor concentrations completely prevented the conversion of pro-MMP-2 into its active form and that the level of protein was decreased. Selective inhibition of the activity of gelatinases (MMP-2 and MMP-9) by using low inhibitor concentrations, however, induced a higher level of active MMP-2 and increased its expression significantly.

CONCLUSIONS

The current observations indicate that selective inhibitors of MMPs affect the expression and activity of MMP-2, thus providing clues regarding the differing effects such inhibitors appear to have when applied in vivo.