Novel Expansion of Matrix Metalloproteases in the Laboratory Axolotl (Ambystoma mexicanum) and Other Salamander Species

Matrix metalloprotease (MMP) genes encode endopeptidases that cleave protein components of the extracellular matrix (ECM) as well as non-ECM proteins. Here we report the results of a comprehensive survey of MMPs in the laboratory axolotl and other representative salamanders. Surprisingly, 28 MMPs were identified in salamanders and 9 MMP paralogs were identified as unique to the axolotl and other salamander taxa, with several of these presenting atypical amino acid insertions not observed in other tetrapod vertebrates. Furthermore, as assessed by sequence information, all of the novel salamander MMPs are of the secreted type, rather than cell membrane anchored. This suggests that secreted type MMPs expanded uniquely within salamanders to presumably execute catalytic activities in the extracellular milieu. To facilitate future studies of salamander-specific MMPs, we annotated transcriptional information from published studies of limb and tail regeneration. Our analysis sets the stage for comparative studies to understand why MMPs expanded uniquely within salamanders.

Matrix Metalloproteinases as Biomarkers and Treatment Targets in Mesothelioma: A Systematic Review

Metalloproteinases (MMPs) have an important role in tissue remodeling and have been shown to have an effect on tumor progression, invasion, metastasis formation, and apoptosis in several tumors, including mesothelioma. Mesothelioma is a rare tumor arising from pleura and peritoneum and is frequently associated with asbestos exposure. We have performed a systematic search of PubMed.gov and ClinicalTrials.gov databases to retrieve and review three groups of studies: studies of MMPs expression in tumor tissue or body fluids in patients with mesothelioma, studies of MMPs genetic variability, and studies of MMPs as potential novel drug targets in mesothelioma. Several studies of MMPs in mesothelioma tissues reported a link between higher expression levels of commonly studied MMPs and clinical parameters, such as overall survival. Fewer studies have investigated genetic variability of MMP genes. Nevertheless, these studies suggested that certain genetic variants in MMP genes can have either protective or tumor-promoting effects on mesothelioma patients. MMPs have been also reported as novel drug targets, but so far no clinical trials of MMP inhibitors are registered in mesothelioma. In conclusion, MMPs play an important role in mesothelioma, but further studies are needed to elucidate the potentials of MMPs as biomarkers and drug targets in mesothelioma.

The Emerging Role of Epigenetic Mechanisms in the Causation of Aberrant MMP Activity during Human Pathologies and the Use of Medicinal Drugs

Matrix metalloproteinases (MMPs) cleave extracellular matrix proteins, growth factors, cytokines, and receptors to influence organ development, architecture, function, and the systemic and cell-specific responses to diseases and pharmacological drugs. Conversely, many diseases (such as atherosclerosis, arthritis, bacterial infections (tuberculosis), viral infections (COVID-19), and cancer), cholesterol-lowering drugs (such as statins), and tetracycline-class antibiotics (such as doxycycline) alter MMP activity through transcriptional, translational, and post-translational mechanisms. In this review, we summarize evidence that the aforementioned diseases and drugs exert significant epigenetic pressure on genes encoding MMPs, tissue inhibitors of MMPs, and factors that transcriptionally regulate the expression of MMPs. Our understanding of human pathologies associated with alterations in the proteolytic activity of MMPs must consider that these pathologies and their medicinal treatments may impose epigenetic pressure on the expression of MMP genes. Whether the epigenetic mechanisms affecting the activity of MMPs can be therapeutically targeted warrants further research.

Matrix metalloproteinase 7 (MMP-7) and tissue inhibitor of metalloproteinases-2 (TIMP-2) downregulation complements PALG1 oncogene overexpression in pleomorphic adenoma pathogenesis

Pleomorphic adenoma (PA) is the most common neoplasm of salivary glands and consists of epithelial and mesenchymal components. Although a benign lesion, it harbors a potential for recurrence and malignant transformation. Also, due to its histological diversity and unpredictive behavior PA can represent both diagnostic and therapeutic challenge. Matrix metalloproteinases (MMPs) are well known modifiers of extracellular matrix (ECM) PA component and in conjunction with their endogenous tissue inhibitors (TIMPs) may influence PA tumor biology. PLAG1 oncogene also has an important role in PA; however, neither the exact mechanisms of its influence nor its interactions with other genes are completely elucidated. The aims of this study were to assess the expression of PLAG1, MMP-2, MMP-7, MMP-9, TIMP-1 and TIMP-2 genes in PAs, and find a possible association of gene expression levels with clinical/epidemiological parameters of PA patients. Relative mRNA levels were assessed using Quantitative real-time PCR analyses in 15 PAs of the parotid gland and 5 normal salivary glands (NSGs). A statistically significant overexpression of PLAG1 was observed in PA compared to NSG samples (P=0.010); PA had 5.48 times higher mRNA levels than NSG. Out of the three analyzed MMP genes, significantly lower levels of MMP-7 were found in PA patients (P=0.026). TIMP2 was also downregulated in PA samples, compared to NSGs (P=0.040). MMP-7 and TIMP-2 mRNA levels were decreased 2.95 and 2.85 times respectively, in PA samples. No association was found between gene expression and clinical/epidemiological PA parameters. Our results suggest that PLAG1 overexpression with concomitant MMP7 and TIMP2 downregulation may contribute to PA development.

Abnormal Hypermethylation of CpG Dinucleotides in Promoter Regions of Matrix Metalloproteinases Genes in Breast Cancer and its Relation to Epigenomic Subtypes and HER2 Overexpression

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) substantially contribute to the regulation of intercellular interactions and thereby play a role in maintaining the tissue structure and function. We examined methylation of a subset of 5’-cytosine-phosphate-guanine-3’ (CpG) dinucleotides in promoter regions of the MMP2, MMP11, MMP14, MMP15, MMP16, MMP17, MMP21, MMP23B, MMP24, MMP25, MMP28, TIMP1, TIMP2, TIMP3, and TIMP4 genes by methylation-sensitive restriction enzyme digestion PCR. In our collection of 183 breast cancer samples, abnormal hypermethylation was observed for CpGs in MMP2, MMP23B, MMP24, MMP25, and MMP28 promoter regions. The non-methylated status of the examined CpGs in promoter regions of MMP2, MMP23B, MMP24, MMP25, and MMP28 in tumors was associated with low HER2 expression, while the group of samples with abnormal hypermethylation of at least two of these MMP genes was significantly enriched with HER2-positive tumors. Abnormal methylation of MMP24 and MMP25 was significantly associated with a CpG island hypermethylated breast cancer subtype discovered by genome-wide DNA bisulfite sequencing. Our results indicate that abnormal hypermethylation of at least several MMP genes promoters is a secondary event not directly functional in breast cancer (BC) pathogenesis. We suggest that it is elevated and/or ectopic expression, rather than methylation-driven silencing, that might link MMPs to tumorigenesis.

Intravenous antagomiR-494 lessens brain-infiltrating neutrophils by increasing HDAC2-mediated repression of multiple MMPs in experimental stroke

Background: Neutrophil infiltration and phenotypic transformation are believed to contribute to neuronal damage and clinical outcome in ischemic stroke. Emerging evidence suggests that HDAC2 is an epigenetic regulator of inflammatory cells. Here, we investigated whether miR-494 affects HDAC2-mediated neutrophil infiltration and phenotypic shift. Methods: The miR-494 levels in neutrophils from AIS patients were detected by real-time PCR. C57BL/6J mice were subjected to transient middle cerebral artery occlusion, and the N1/N2 neutrophil shift was examined. Cortical neurons were subjected to oxygen-glucose deprivation and stimulated with supernatant from differently treated neutrophils or were cocultured with neutrophils; neuronal injury was detected, and ChIP-Seq was performed to clarify which genes are the binding targets of HDAC2. Finally, a transwell assay was conducted to examine neutrophil migration. Results: Compared to the control subjects, AIS patients had increased neutrophil expression of miR-494, and in AIS patients, elevated miR-494 expression in neutrophils was a predictor of worse neurological outcomes. MiR-494 correlates with the upregulation of adhesion molecules in neutrophils of AIS patients. Systemically administered antagomiR-494 partly shifts neutrophils into the N2 phenotype in MCAO mice. AntagomiR-494-treated neutrophils exert a neuroprotective role in vitro. ChIP-seq revealed that HDAC2 targets multiple MMP genes in neutrophils of AIS patients. Further in vitro and in vivo experiments showed that antagomiR-494 repressed expression of MMP genes, including MMP7, MMP10, MMP13, and MMP16, to reduce the number of brain-infiltrating neutrophils by regulating HDAC2. Conclusion: MiR-494 may serve as an alternative predictive biomarker of the outcome of AIS patients, and antagomiR-494 treatment decreased the expression of multiple MMPs and the infiltration of neutrophils partly by targeting HDAC2.