Intracellular Matrix Metalloproteinase-2 Research Articles

N-Terminomic Identification of Intracellular MMP-2 Substrates in Cardiac Tissue.

Proteases are enzymes that induce irreversible post-translational modifications by hydrolyzing amide bonds in proteins. One of these proteases is matrix metalloproteinase-2 (MMP-2), which has been shown to modulate extracellular matrix remodeling and intracellular proteolysis during myocardial injury. However, the substrates of MMP-2 in heart tissue are limited, and lesser known are the cleavage sites. Here, we used degradomics to investigate the substrates of intracellular MMP-2 in rat ventricular extracts. First, we designed a novel, constitutively active MMP-2 fusion protein (MMP-2-Fc) that we expressed and purified from mammalian cells. Using this protease, we proteolyzed ventricular extracts and used subtiligase-mediated N-terminomic labeling which identified 95 putative MMP-2-Fc proteolytic cleavage sites using mass spectrometry. The intracellular MMP-2 cleavage sites identified in heart tissue extracts were enriched for proteins primarily involved in metabolism, as well as the breakdown of fatty acids and amino acids. We further characterized the cleavage of three of these MMP-2-Fc substrates based on the gene ontology analysis. We first characterized the cleavage of sarco/endoplasmic reticulum calcium ATPase (SERCA2a), a known MMP-2 substrate in myocardial injury. We then characterized the cleavage of malate dehydrogenase (MDHM) and phosphoglycerate kinase 1 (PGK1), representing new cardiac tissue substrates. Our findings provide insights into the intracellular substrates of MMP-2 in cardiac cells, suggesting that MMP-2 activation plays a role in cardiac metabolism.

Matrix metalloproteinase-2 proteolyzes mitofusin-2 and impairs mitochondrial function during myocardial ischemia-reperfusion injury.

During myocardial ischemia and reperfusion (IR) injury matrix metalloproteinase-2 (MMP-2) is rapidly activated in response to oxidative stress. MMP-2 is a multifunctional protease that cleaves both extracellular and intracellular proteins. Oxidative stress also impairs mitochondrial function which is regulated by different proteins, including mitofusin-2 (Mfn-2), which is lost in IR injury. Oxidative stress and mitochondrial dysfunction trigger the NLRP3 inflammasome and the innate immune response which invokes the de novo expression of an N-terminal truncated isoform of MMP-2 (NTT-MMP-2) at or near mitochondria. We hypothesized that MMP-2 proteolyzes Mfn-2 during myocardial IR injury, impairing mitochondrial function and enhancing the inflammasome response. Isolated hearts from mice subjected to IR injury (30min ischemia/40min reperfusion) showed a significant reduction in left ventricular developed pressure (LVDP) compared to aerobically perfused hearts. IR injury increased MMP-2 activity as observed by gelatin zymography and increased degradation of troponin I, an intracellular MMP-2 target. MMP-2 preferring inhibitors, ARP-100 or ONO-4817, improved post-ischemic recovery of LVDP compared to vehicle perfused IR hearts. In muscle fibers isolated from IR hearts the rates of mitochondrial oxygen consumption and ATP production were impaired compared to those from aerobic hearts, whereas ARP-100 or ONO-4817 attenuated these reductions. IR hearts showed higher levels of NLRP3, cleaved caspase-1 and interleukin-1β in the cytosolic fraction, while the mitochondria-enriched fraction showed reduced levels of Mfn-2, compared to aerobic hearts. ARP-100 or ONO-4817 attenuated these changes. Co-immunoprecipitation showed that MMP-2 is associated with Mfn-2 in aerobic and IR hearts. ARP-100 or ONO-4817 also reduced infarct size and cell death in hearts subjected to 45min ischemia/120min reperfusion. Following myocardial IR injury, impaired contractile function and mitochondrial respiration and elevated inflammasome response could be attributed, at least in part, to MMP-2 activation, which targets and cleaves mitochondrial Mfn-2. Inhibition of MMP-2 activity protects against cardiac contractile dysfunction in IR injury in part by preserving Mfn-2 and suppressing inflammation.

Multifunctional fluorescent mesoporous carbon nanoprobe for MMP-2-activated cancer cell imaging and targeted photothermal therapy

The integration of cancer imaging with therapy in a simple system is warranted for precise cancer therapy. In this study, carboxyl-functionalized mesoporous carbon nanospheres (MCN) which are efficient photothermal agents and excellent fluorescence quenchers, were used for cancer cell imaging and selective photothermal therapy (PTT) applications. Using MCN, a matrix metalloproteinase-2 (MMP-2)- responsive theranostic nanoprobe was generated by functionalizing an MMP-2-specific fluorescent-labeled PLGVR sequence on the surface of MCN. The nanoprobe not only can be used to detect MMP-2 with a low detection limit of 0.3 pg mL−1, but also can achieve the sensitive intracellular MMP-2 imaging in living cells, validating the differentiation of cancer cells from healthy cells based on the recovered fluorescence intensity. More importantly, selective cancer PTT was achieved using MMP-2-triggered cancer cell imaging. Our in vitro studies showed that by regulating the power density and irradiation time, the nanoprobe can effectively kill cancer cells via PTT. Our strategy opens new avenues for precision medicine, especially phototherapy.

Loss of Mitochondrial Dynamics Proteins Mitofusin‐2 and Drp‐1 in Myocardial Ischemia‐Reperfusion Injury Is Prevented by Matrix Metalloproteinase‐2 Preferring Inhibitors

ObjectiveMatrix metalloproteinase‐2 (MMP‐2) is a ubiquitous protease that cleaves several extracellular and intracellular proteins. MMP‐2 is activated intracellularly in response to enhanced oxidative stress resulting from myocardial ischemia/reperfusion (I/R) injury. Oxidative stress impairs mitochondrial function which is regulated by different proteins including mitofusin‐2 (Mfn‐2) and dynamin‐related protein‐1 (Drp‐1) which control mitochondrial dynamics involving fusion and fission, respectively. As both proteins are localized at the mitochondrial outer membrane and MMP‐2 is localized at the mitochondrial‐endoplasmic reticulum associated membrane we hypothesized that MMP‐2 may proteolyze Mfn‐2 and Drp‐1. We therefore investigated whether inhibition of MMP‐2 could protect against the loss of mitochondrial dynamics proteins during I/R injury.MethodsHearts isolated from 3 month old C57BL/6J mice were perfused according to Langendorff at constant pressure and subjected to I/R injury (30 min ischemia and 40 min reperfusion) in absence or presence of MMP‐2 preferring inhibitors ARP‐100 (10 µM) or ONO‐4817 (50 µM) or their vehicle (n=5 hearts per group). Effects on mechanical function were recorded. At the end of reperfusion, the hearts were homogenized and subcellular fractions were prepared. The degradation of troponin I (TnI), an intracellular MMP‐2 target, was measured in the cytosolic fraction as a marker of MMP‐2 activity. Levels of Mfn‐2 and Drp‐1 in the mitochondrial fraction were also measured using western blot. In silico analysis of potential MMP‐2 cleavage sites was performed using Procleave.ResultsARP‐100 or ONO‐4817 significantly increased left ventricular developed pressure compared to vehicle‐treated I/R hearts (% of pre‐ischemic baseline value at R40: IR+vehicle 25.5±3.2, IR+ARP 50.1±3.2, IR+ONO 57.3±1.6%, p<0.05). Similarly, both inhibitors significantly improved the rates of contraction and relaxation (+/‐dP/dt). TnI loss was increased in I/R hearts as shown by a significant reduction in TnI (~30 kDa) and the appearance of an ~22 kDa band. ARP‐100 or ONO‐4817 attenuated TnI loss, indicating MMP‐2 activation. Levels of Mfn‐2 and Drp‐1 in the mitochondrial fraction were significantly reduced in the I/R group and ARP‐100 or ONO‐4817 attenuated this reduction (p<0.05). Similar results were obtained using a different Mfn‐2 antibody that binds to its C‐terminus. In silico analysis of both mouse Mfn‐2 and Drp‐1 sequences showed several potential sites that could be targeted by MMP‐2.ConclusionsDuring myocardial I/R injury, MMP‐2 may affect mitochondrial dynamics by proteolysis of Mfn‐2 and Drp‐1. Inhibition of MMP‐2 activity could protect against cardiac contractile dysfunction in part by preserving these proteins affecting mitochondrial fusion and fission.

Antimetastatic effects of calycosin on osteosarcoma and the underlying mechanism.

Osteosarcoma (OS) refers to a malignant tumor with potential invasiveness and metastasis; however, the current chemotherapy of OS is lacking. Thus, the alternative drug for treating OS is urgent to explore. Calycosin (CC) is evidenced in our previous study to play the anti-OS benefits for suppressing cancer cell proliferation. Consequently, further investigation of CC-medicated anti-invasive and metastatic effects against OS is needed. In the current study, the clinical samples of OS patients were collected for biological and staining assays, such as enzyme-linked immunosorbent assay and polymerase chain reaction. Meanwhile, the cell line and tumor-bearing nude mice were employed in assessing antimetastatic effects of CC against OS through biochemical tests and immunoassays. As a result, the OS patients exhibited upregulated neoplastic expressions of matrix metalloproteinase 2 (MMP2) and proliferating cell nuclear antigen (PCNA), cellular mRNAs and proteins of inhibitor of nuclear factor kappa-B alpha (IκBα), and epithelial cell transforming sequence 2 (ECT2). In cell-line study, CC-treated human OS cells exhibited induced cell apoptosis, reduced cell proliferation, and cellular MMP2 and PCNA concentration, inhibited cell migration, lowered expressions of IκBα ECT2 mRNAs, and proteins. In tumor-bearing nude mice study, CC-treated mice resulted in the dose-dependent reductions of tumor weights and intracellular MMP2 contents. As shown in further assays, neoplastic expressions of interleukin 6 protein, IκBα, ECT2 mRNAs, and proteins were downregulated dose-dependently in CC-treated tumor-bearing mice. In conclusion, these investigative findings suggest that CC may play the potential anti-invasive benefits against OS through suppressing metastasis-associated IκBα/ECT2 molecular pathway.

Distribution and activation of matrix metalloproteinase-2 in skeletal muscle fibers.

A substantial intracellular localization of matrix metalloproteinase 2 (MMP2) has been reported in cardiomyocytes, where it plays a role in the degradation of the contractile apparatus following ischemia-reperfusion injury. Whether MMP2 may have a similar function in skeletal muscle is unknown. This study determined that the absolute amount of MMP2 is similar in rat skeletal and cardiac muscle and human muscle (~10-18 nmol/kg muscle wet wt) but is ~50- to 100-fold less than the amount of calpain-1. We compared mechanically skinned muscle fibers, where the extracellular matrix (ECM) is completely removed, with intact fiber segments and found that ~30% of total MMP2 was associated with the ECM, whereas ~70% was inside the muscle fibers. Concordant with whole muscle fractionation, further separation of skinned fiber segments into cytosolic, membranous, and cytoskeletal and nuclear compartments indicated that ~57% of the intracellular MMP2 was freely diffusible, ~6% was associated with the membrane, and ~37% was bound within the fiber. Under native zymography conditions, only 10% of MMP2 became active upon prolonged (17 h) exposure to 20 μM Ca2+, a concentration that would fully activate calpain-1 in seconds to minutes; full activation of MMP2 would require ~1 mM Ca2+. Given the prevalence of intracellular MMP2 in skeletal muscle, it is necessary to investigate its function using physiological conditions, including isolation of any potential functional relevance of MMP2 from that of the abundant protease calpain-1.

Atorvastatin Preserves Cardiac Contractility via Reducing Matrix Metalloproteinase-2 Isoforms Expression in a Diabetic Heart Model

Purpose We investigated whether atorvastatin can alleviate diabetic cardiomyopathy (DM CMP) by reducing intracellular matrix metalloproteinase-2 (MMP-2) isoform expression. Methods Rat cardiomyoblasts (H9C2 cells) were tested to determine whether atorvastatin treatment after high glucose could reduce the expression of the two isoforms of MMP-2. For the in vivo study, we used the streptozotocin murine model of Type I DM and age-matched controls. The changes of each MMP-2 isoform in the diabetic mice hearts were determined using quantitative real-time polymerase chain reaction (qRT-PCR). Immunohistochemical stains were conducted to identify MMP-2 isoform expression. Echocardiography was performed to compare and analyze the changes in cardiac function induced by diabetes and atorvastatin. Results Quantitative RT-PCR and immunofluorescence staining showed that the two MMP-2 isoforms strongly induced by high glucose stimulation were attenuated by atorvastatin treatment in H9C2 cells. Although no definite histologic features of diabetic cardiomyopathy were observed in diabetic mice, left ventricular systolic dysfunction observed in diabetic heart was also normalized by atorvastatin treatment by echocardiographic evaluation. These findings accompanied reduced TUNEL staining and mitochondrial morphological change in atorvastatin treated diabetic group. Quantitative RT-PCR and IHC staining showed this abnormal cardiac function was accompanied with the increases in the mRNA levels of the two isoforms of MMP-2 and attenuated with atorvastatin treatment Conclusion Atorvastatin attenuated deterioration of cardiac dysfunction induced by diabetic condition by reducing expression of two isoforms of MMP-2 in vitro and in a Type I diabetes heart model. The roles played by these isoforms and atorvastatin treatment in diabetic cardiomyopathy require further study.

Knockdown of Golgi phosphoprotein 73 blocks the trafficking of matrix metalloproteinase-2 in hepatocellular carcinoma cells and inhibits cell invasion.

Golgi phosphoprotein 73 (GP73) has been regarded as a novel serum biomarker for the diagnosis of hepatocellular carcinoma (HCC) in recent years. It has been reported that the upregulation of GP73 may promote the carcinogenesis and metastasis of HCC; however, the mechanisms remain poorly understood. In this study, GP73 correlates positively with matrix metalloproteinase‐2 (MMP‐2) in HCC‐related cells and tissues. Further studies indicate that the knockdown of GP73 blocks MMP‐2 trafficking and secretion, resulting in cell invasion inhibition. Additionally, the knockdown of GP73 induces the accumulation of intracellular MMP‐2, which inhibits the phosphorylation of Src at Y416 and triggers the inhibition of SAPK/JNK and p53‐p21 signalling pathways through a negative feedback loop. Finally, the transactivation of MMP2 was inhibited by the reduction in E2F1. This study reveals that GP73 plays functional roles in the trafficking and equilibrium of epithelial‐mesenchymal transition (EMT)‐related secretory proteins and that GP73 serves as a new potential target for combating the metastasis of HCC.

Doxorubicin induces de novo expression of N-terminal-truncated matrix metalloproteinase-2 in cardiac myocytes.

Anthracyclines, such as doxorubicin, are commonly prescribed antineoplastic agents that cause irreversible cardiac injury. Doxorubicin cardiotoxicity is initiated by increased oxidative stress in cardiomyocytes. Oxidative stress enhances intracellular matrix metalloproteinase-2 (MMP-2) by direct activation of its full-length isoform and (or) de novo expression of an N-terminal-truncated isoform (NTT-MMP-2). As MMP-2 is localized to the sarcomere, we tested whether doxorubicin activates intracellular MMP-2 in neonatal rat ventricular myocytes (NRVM) and whether it thereby proteolyzes two of its identified sarcomeric targets, α-actinin and troponin I. Doxorubicin increased oxidative stress within 12 h as indicated by reduced aconitase activity. This was associated with a twofold increase in MMP-2 protein levels and threefold higher gelatinolytic activity. MMP inhibitors ARP-100 or ONO-4817 (1 μM) prevented doxorubicin-induced MMP-2 activation. Doxorubicin also increased the levels and activity of MMP-2 secreted into the conditioned media. Doxorubicin upregulated the mRNA expression of both full-length MMP-2 and NTT-MMP-2. α-Actinin levels remained unchanged, whereas doxorubicin downregulated troponin I in an MMP-independent manner. Doxorubicin induces oxidative stress and stimulates a robust increase in MMP-2 expression and activity in NRVM, including NTT-MMP-2. The sarcomeric proteins α-actinin and troponin I are, however, not targeted by MMP-2 under these conditions.

Matrix Metalloproteinase Inhibitors Attenuate Doxorubicin‐Induced Heart Failure by Preventing Cardiac Titin Proteolysis

Heart failure remains a major, long‐term complication with doxorubicin (DXR) cancer chemotherapy. We investigated the mechanism of DXR cardiotoxicity in order to develop new strategies to prevent heart injury when treating cancer patients. The cardiotoxicity of DXR is associated with increased oxidative stress in cardiomyocytes. Intracellular matrix metalloproteinase‐2 (MMP‐2) activity is enhanced by oxidative stress by two means: a) direct activation of 72 kDa MMP‐2 by peroxynitrite‐mediated S‐glutathiolation and, b) de novo expression of an N‐terminal truncated isoform (NTT‐MMP‐2). We have shown that MMP‐2 is enriched in the Z‐disc of the sarcomere where it cleaves titin following oxidative stress caused by ischemia‐reperfusion injury. We determined whether MMP‐2 mediated titin proteolysis contributes to DXR‐induced heart failure in vivo. 8‐week old male C57BL/6J mice were treated with DXR weekly (6 mg/kg, i.p.) or saline vehicle (control) ± MMP inhibitors (by daily gavage) doxycycline (15 mg/kg) or ONO‐4817 (60 mg/kg) for 4 weeks. Cardiac function was assessed by M‐mode echocardiography before and after treatment (n=10 mice per group) and then the hearts were collected for biochemical analysis. MMP‐2 mRNA expression, protein levels, and activity were measured by qPCR, Western blot and gelatin zymography, respectively. N2BA and N2B titin isoforms and the primary titin degradation product levels were measured by agarose gel electrophoresis. DXR caused systolic and diastolic dysfunction marked by a significant reduction in left ventricular ejection fraction (64±2% vs. 45±2%, p<0.05), fractional shortening (35±2% vs. 22±1%, p<0.05), and E′/A′ ratio (1.07±0.04 vs. 0.85±0.06, p<0.05) compared to control. Doxycycline or ONO‐4817 prevented these changes. DXR caused significant cardiac remodeling including the thinning of the posterior wall (0.99±0.03 vs 1.16±0.04 mm, p<0.05) and increased left ventricular internal diameter (2.93±0.09 vs 2.55±0.09 mm, p<0.05) during systole, an effect that was prevented by doxycycline, but not ONO‐4817. DXR upregulated NTT‐MMP‐2 mRNA in the heart to 195±16% (p<0.05) of control and increased MMP‐2 protein levels (149±19% vs. control, p<0.05), accompanied by a trend to increased MMP‐2 gelatinolytic activity (200±14% vs. control, p=0.06). These biochemical changes were prevented by doxycycline or ONO‐4817. DXR did not alter cardiac titin isoform expression (N2BA:N2B) in the heart but increased titin degradation (T2/T1 ratio) to 258±7% (p<0.05) which was reduced by ONO‐4817 (169±10%) but not doxycycline (203±16%). MMP‐2 activation contributes to DXR‐induced heart failure in mice by proteolyzing cardiac titin in an MMP‐2‐dependent manner. Moreover, two orally available MMP inhibitors prevented heart failure, suggesting that their use may be a potential prophylactic strategy to prevent heart during cancer chemotherapy.Support or Funding InformationCanadian Institutes of Health Research (to RS); Women and Children's Health Research Institute Graduate Studentship (to BC).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Short term doxycycline treatment induces sustained improvement in myocardial infarction border zone contractility.

Decreased contractility in the non-ischemic border zone surrounding a MI is in part due to degradation of cardiomyocyte sarcomeric components by intracellular matrix metalloproteinase-2 (MMP-2). We recently reported that MMP-2 levels were increased in the border zone after a MI and that treatment with doxycycline for two weeks after MI was associated with normalization of MMP-2 levels and improvement in ex-vivo contractile protein developed force in the myocardial border zone. The purpose of the current study was to determine if there is a sustained effect of short term treatment with doxycycline (Dox) on border zone function in a large animal model of antero-apical myocardial infarction (MI). Antero-apical MI was created in 14 sheep. Seven sheep received doxycycline 0.8 mg/kg/hr IV for two weeks. Cardiac MRI was performed two weeks before, and then two and six weeks after MI. Two sheep died prior to MRI at six weeks from surgical/anesthesia-related causes. The remaining 12 sheep completed the protocol. Doxycycline induced a sustained reduction in intracellular MMP-2 by Western blot (3649±643 MI+Dox vs 9236±114 MI relative intensity; p = 0.0009), an improvement in ex-vivo contractility (65.3±2.0 MI+Dox vs 39.7±0.8 MI mN/mm2; p<0.0001) and an increase in ventricular wall thickness at end-systole 1.0 cm from the infarct edge (12.4±0.6 MI+Dox vs 10.0±0.5 MI mm; p = 0.0095). Administration of doxycycline for a limited two week period is associated with a sustained improvement in ex-vivo contractility and an increase in wall thickness at end-systole in the border zone six weeks after MI. These findings were associated with a reduction in intracellular MMP-2 activity.

An intracellular matrix metalloproteinase-2 isoform induces tubular regulated necrosis: implications for acute kidney injury.

Acute kidney injury (AKI) causes severe morbidity, mortality, and chronic kidney disease (CKD). Mortality is particularly marked in the elderly and with preexisting CKD. Oxidative stress is a common theme in models of AKI induced by ischemia-reperfusion (I-R) injury. We recently characterized an intracellular isoform of matrix metalloproteinase-2 (MMP-2) induced by oxidative stress-mediated activation of an alternate promoter in the first intron of the MMP-2 gene. This generates an NH2-terminal truncated MMP-2 (NTT-MMP-2) isoform that is intracellular and associated with mitochondria. The NTT-MMP-2 isoform is expressed in kidneys of 14-mo-old mice and in a mouse model of coronary atherosclerosis and heart failure with CKD. We recently determined that NTT-MMP-2 is induced in human renal transplants with delayed graft function and correlated with tubular cell necrosis. To determine mechanism(s) of action, we generated proximal tubule cell-specific NTT-MMP-2 transgenic mice. Although morphologically normal at the light microscopic level at 4 mo, ultrastructural studies revealed foci of tubular epithelial cell necrosis, the mitochondrial permeability transition, and mitophagy. To determine whether NTT-MMP-2 expression enhances sensitivity to I-R injury, we performed unilateral I-R to induce mild tubular injury in wild-type mice. In contrast, expression of the NTT-MMP-2 isoform resulted in a dramatic increase in tubular cell necrosis, inflammation, and fibrosis. NTT-MMP-2 mice had enhanced expression of innate immunity genes and release of danger-associated molecular pattern molecules. We conclude that NTT-MMP-2 "primes" the kidney to enhanced susceptibility to I-R injury via induction of mitochondrial dysfunction. NTT-MMP-2 may be a novel AKI treatment target.

Robust design of some selective matrix metalloproteinase-2 inhibitors over matrix metalloproteinase-9 through in silico/fragment-based lead identification and de novo lead modification: Syntheses and biological assays

Broad range of selectivity possesses serious limitation for the development of matrix metalloproteinase-2 (MMP-2) inhibitors for clinical purposes. To develop potent and selective MMP-2 inhibitors, initially multiple molecular modeling techniques were adopted for robust design. Predictive and validated regression models (2D and 3D QSAR and ligand-based pharmacophore mapping studies) were utilized for estimating the potency whereas classification models (Bayesian and recursive partitioning analyses) were used for determining the selectivity of MMP-2 inhibitors over MMP-9. Bayesian model fingerprints were used to design selective lead molecule which was modified using structure-based de novo technique. A series of designed molecules were prepared and screened initially for inhibitions of MMP-2 and MMP-9, respectively, as these are designed followed by other MMPs to observe the broader selectivity. The best active MMP-2 inhibitor had IC50 value of 24nM whereas the best selective inhibitor (IC50=51nM) showed at least 4 times selectivity to MMP-2 against all tested MMPs. Active derivatives were non-cytotoxic against human lung carcinoma cell line—A549. At non-cytotoxic concentrations, these inhibitors reduced intracellular MMP-2 expression up to 78% and also exhibited satisfactory anti-migration and anti-invasive properties against A549 cells. Some of these active compounds may be used as adjuvant therapeutic agents in lung cancer after detailed study.

Abstract 17311: Molecular Memory and the Epigenetic Regulation of Cardiac Intracellular Matrix Metalloproteinase-2

Introduction: We have identified an intracellular isoform of MMP-2 generated by oxidative stress activation of a promoter in the first intron of the MMP-2 gene. This generates a N-terminal truncated isoform of MMP-2 (NTT-MMP-2) which is enzymatically active and found in mitochondria. NTT-MMP-2 triggers the mitochondrial permeability transition leading to myocyte regulated necrosis and inflammation. We hypothesized that transient oxidative stress induces durable epigenetic changes in the NTT-MMP-2 alternate promoter resulting in enhanced injury in subsequent episodes of stress (molecular memory). Methods: The intronic promoter was mapped using a combination of PCR-based and intronic/luciferase constructs. In vivo studies used the hypomorphic ApoER61h/h SR-B1-/- murine model (HypoE mice) of diet-induced coronary atherogenesis and myocardial infarction. Chromatin immunopreciptation (ChIP) probed the RNA Pol II, H3K4Me1 and H3K27Me3 epigenetic marks. NTT-MMP-2 was measured by qPCR. Results: NTT-MMP-2 transcription start sites were mapped to two stress-activated basal promoters along with a stress-activated NF-κB enhancer element. HypoE mice were fed a high fat diet (HFD) for 20 days, followed by gene repair of the hypomorphic ApoE alleles and returned to normal diet for 6-15 weeks. NTT-MMP-2 expression at 20 days of HFD was elevated two-three fold as compared to controls, remained elevated after 6 weeks of normal diet and returned to baseline at 15 weeks. ChIP of the intronic promoter revealed association of RNA Pol II at 6 weeks of normal diet and was not detectable at 15 weeks. In contrast, the pro-transcriptional mark H3K4Me1 remained elevated out to 15 weeks; the inhibitory H3K27Me3 mark returned to baseline at 15 weeks. A brief return to HFD (7 days) at 6 weeks increased NTT-MMP-2 expression resulting in myocyte inflammation and necrosis relative to controls exposed to only 7 days of HFD. Conclusions: Transient periods of oxidative stress lead to durable epigenetic changes in the NTT-MMP-2 promoter that facilitate exaggerated responses to otherwise minor levels of oxidative stress. Our findings may provide an explanation for the enhanced injury susceptibility to relatively minor stresses of patients with pre-existing cardiac disease.

Novel intracellular N-terminal truncated matrix metalloproteinase-2 isoform in skeletal muscle ischemia-reperfusion injury.

Ischemia-reperfusion injury (IRI) occurs when blood returns to tissues following a period of ischemia. Reintroduction of blood flow results in the production of free radicals and reactive oxygen species that damage cells. Skeletal muscle IRI is commonly seen in orthopedic trauma patients. Experimental studies in other organ systems have elucidated the importance of extracellular and intracellular matrix metalloproteinase-2 (MMP-2) isoforms in regulating tissue damage in the setting of oxidant stress resulting from IRI. Although the extracellular full-length isoform of MMP-2 (FL-MMP-2) has been previously studied in the setting of skeletal muscle IRI, studies investigating the role of the N-terminal truncated isoform (NTT-MMP-2) in this setting are lacking. In this study, we first demonstrated significant increases in FL- and NTT-MMP-2 gene expression in C2C12 myoblast cells responding to re-oxygenation following hypoxia in vitro. We then evaluated the expression of FL- and NTT-MMP-2 in modulating skeletal muscle IRI using a previously validated murine model. NTT-MMP-2, but not FL-MMP-2 expression was significantly increased in skeletal muscle following IRI. Moreover, the expression of toll-like receptors (TLRs) -2 and -4, IL-6, OAS-1A, and CXCL1 was also significantly up-regulated following IRI. Treatment with the potent anti-oxidant pyrrolidine dithiocarbamate (PDTC) significantly suppressed NTT-MMP-2, but not FL-MMP-2 expression and improved muscle viability following IRI. This data suggests that NTT-MMP-2, but not FL-MMP-2, is the major isoform of MMP-2 involved in skeletal muscle IRI.

Doxorubicin‐induced Activation of Intracellular Matrix Metalloproteinase‐2 by Oxidative Stress

Matrix metalloproteinase‐2 (MMP‐2) activity is involved in several heart pathologies resulting from increased oxidative stress including ischemia‐reperfusion injury. In addition to its roles in extracellular matrix remodeling, MMP‐2 is also an intracellular protease with specific intracellular substrates. MMP‐2 mRNA and protein levels are elevated in cancer patients treated with doxorubicin (DXR). Though effective in chemotherapy, DXR's dose‐limiting cardiotoxicity may cause heart failure by activating intracellular MMP‐2. Human fibrosarcoma cells (HT1080 cells) and neonatal rat ventricular myocytes (NRVM) were treated with 0.01‐1 μM DXR for 0.5 and 2 h at 37°C. DXR treatment had no effect on cell viability. MMP‐2 activity and protein levels were measured by gelatin zymography and immunoblotting, respectively. Oxidative stress was measured by changes in mitochondrial aconitase activity. To visualize changes in intracellular MMP‐2 activity in real time, we will use a genetically encoded, fluorescence resonance energy transfer (FRET)‐based biosensor. In HT1080 cells 0.1‐1 μM DXR stimulated a 1.6 fold increase in intracellular MMP‐2 activity after 2 h without changing its protein level. DXR had no effect on MMP‐2 activity in NRVM. The FRET‐based MMP‐2 biosensor detected MMP but not other intracellular proteases, such as calpains and caspases, in vitro. In human cancer cells, acute treatment with DXR activates intracellular MMP‐2. The biosensors are now being expressed in cells to directly study intracellular MMP‐2 activity. The FRET‐based biosensor will allow us to better understand how oxidative stress stimuli affects intracellular MMP‐2 activity and its specific substrates.

Matrix metalloproteinase 2 contributes to pancreatic Beta cell injury induced by oxidative stress.

ObjectiveTo investigate the role of matrix metalloproteinase 2 (MMP2) in pancreatic beta cell injury induced by oxidative stress.MethodsRat pancreatic beta cell line INS-1 cells were treated with advanced glycation end-products (AGE) to induce intracellular oxidative stress. Intracellular MMP2 expression and activity were determined by quantitative reverse transcription polymerase chain reaction (RT-PCR), Western blotting, and zymography, respectively. MMP2 expression and activity were manipulated by over-expression with recombinant MMP2 plasmids or knockdown with either MMP2 specific siRNA or inhibitors, and effects on apoptosis and insulin-secretion were measured by flow cytometry and ELISA.ResultsAGE treatment induced intracellular oxidative stress in INS-1 cells, as indicated by elevated ROS levels, apoptotic cell death, and suppressed insulin secretion. This was accompanied by increased MMP2 expression and activity. However, Antioxidant N-acetylcysteine (NAC) treatment inhibited MMP2 expression and activity, and partially reversed cell apoptosis and insulin secretion dysfunction induced by AGE. Forced expression of MMP2 mimicked the effects of AGE treatment while inhibition of MMP2 either by a specific MMP2 inhibitor or MMP2 siRNA protected oxidative stress induced by AGE.ConclusionMMP2 expression and intracellular activity are increased by oxidative stress, contributing to cellular dysfunction and apoptosis in INS-1 cells after AGE challenge.

Intracellular MMP‐2 Activity in Skeletal Muscle Is Associated With Type II Fibers

Matrix metalloproteinase 2 (MMP-2) is a proteolytic enzyme implicated in motility, differentiation, and regeneration of skeletal muscle fibers through processing of extracellular substrates. Although MMP-2 has been found to be localized intracellularly in cardiomyocytes where the enzyme is thought to contribute to post-ischemic loss of contractility, little is known about intracellular MMP-2 activity in skeletal muscle fibers. In the present study we demonstrate intracellular MMP-2 in normal skeletal muscle by immunohistochemical staining. Immunogold electron microscopic analyses indicated that the enzyme was concentrated in Z-lines of the sarcomers, in the nuclear membrane, and in mitochondria. By use of in situ zymography, we found that gelatinolytic activity in muscle fibers was co-localized with immunofluorecent staining for MMP-2. Staining for MMP-9, the other member of the gelatinase group of the MMPs, was negative. The broad-spectrum metalloprotease inhibitor EDTA and the selective gelatinase inhibitor CTT2, but not the cysteine inhibitor E64, strongly reduced the gelatinolytic activity. The intracellular gelatinolytic activity was much more prominent in fast twitch type II fibers than in slow twitch type I fibers, and there was a decrease in intracellular gelatinolytic activity and MMP-2 expression in muscles from mice exposed to high intensity interval training. Together our results indicate that MMP-2 is part of the intracellular proteolytic network in normal skeletal muscle, especially in fast twitch type II fibers. Further, the results suggest that intracellular MMP-2 in skeletal muscle fibers is active during normal homeostasis, and affected by the level of physical activity.

Intracellular matrix metalloproteinase-2 (MMP-2) regulates human platelet activation via hydrolysis of talin

Matrix metalloproteinase (MMP) activity is generally associated with normal or pathological extracellular processes such as tissue remodelling in growth and development or in tumor metastasis and angiogenesis. Platelets contain at least three MMPs, 1, 2 and 9 that have been reported to stimulate or inhibit agonist-induced platelet aggregation via extracellular signals. The non-selective Zn+2 chelating MMP inhibitor, 1,10-phenanthroline, and the serine protease inhibitor, AEBSF, were found to inhibit all tested agonist-induced platelet aggregation reactions. In vitro analysis demonstrated that 1,10-phenanthroline completely inhibited MMP-1,2,and 9 but had little to no effect on calpain activity while the converse was true with AEBSF. We now demonstrate that MMP-2 functions intracellularly to regulate agonist-induced platelet aggregations via the hydrolytic activation of talin, the presumed final activating factor of glycoprotein (GP)IIb/IIIa integrin (the inside-out signal). Once activated GPIIb/IIIa binds the dimeric fibrinogen molecule required for platelet aggregation. The active intracellular MMP-2 molecule is complexed with JAK 2/STAT 3, as demonstrated by the fact that all three proteins are co-immunoprecipitated with either anti-JAK 2, or anti-STAT 3 antibodies and by immunofluorescence studies. The MMP-2 platelet activation pathway can be synergistically inhibited with the non-selective MMP inhibitor, 1,10-phenanthroline, plus a JAK 2 inhibitor. This activation pathway is distinct from the previously reported calpain-talin activating pathway. The identification of a new central pathway for platelet aggregation presents new potential targets for drug regulation and furthers our understanding of the complexity of platelet activation mechanisms.

Moderate inhibition of myocardial matrix metalloproteinase-2 by ilomastat is cardioprotective

Pharmacological inhibition of matrix metalloproteinase-2 (MMP-2) is a promising target for acute cardioprotection against ischemia/reperfusion injury. Therefore, here we investigated if the MMP inhibitor ilomastat administered either before ischemia or before reperfusion is able to reduce infarct size via inhibition of MMP-2, the most abundant MMP in the rat heart.Infarct-size limiting effect of ilomastat (0.3–6.0μmol/kg) was tested in an in vivo rat model of myocardial infarction induced by 30min coronary occlusion/120min reperfusion. Ilomastat at 0.75 and 1.5μmol/kg decreased infarct size significantly as compared to the vehicle-treated (dimethyl sulfoxide) group (from 66.1±4.6% to 45.3±7.0% and 46.7±5.5% of area at risk, p<0.0.5, respectively), when administered 5min before the onset of ischemia. Ilomastat at 6.0μmol/kg significantly reduced infarct size from its control value of 65.4±2.5% to 52.8±3.7% of area at risk (p<0.05), when administered 5min before the onset of reperfusion. Area at risk was not significantly affected by ilomastat treatments. To further assess the cytoprotective effect of ilomastat, primary cardiomyocytes isolated from neonatal rats were subjected to 240min simulated ischemia followed by 120min simulated reperfusion in the presence of ilomastat (5nM–5μM). Ilomastat at 500nM and 5μM significantly increased cell viability when compared to vehicle treated group. To assess the in situ MMP-2 inhibitory effect of ilomastat, in separate experiments in situ zymography was performed in cardiomyocytes. The cytoprotective concentration of ilomastat (500nM) showed a moderate (approximately 25%) inhibition of intracellular MMP-2 in ischemic/reperfused cardiomyocytes. In these cells, MMP-2 immunostaining showed a 90% colocalization with the in situ gelatinolytic activity.We conclude that the MMP inhibitor ilomastat reduces infarct size when administered either before the onset of ischemia or before the onset of reperfusion in vivo. Furthermore, this is the first demonstration that a moderate inhibition of intracellular MMP-2 is sufficient to confer cardiocytoprotection.