Matrix Metalloproteinase-9 Knockout Mice Research Articles

Levofloxacin alleviates blood-brain barrier disruption following cerebral ischemia and reperfusion via directly inhibiting A-FABP

Reperfusion therapy is currently the most effective treatment for acute ischemic stroke, but often results in secondary brain injury. Adipocyte fatty acid-binding protein (A-FABP, FABP4, or aP2) was shown to critically mediate cerebral ischemia/reperfusion (I/R) injury by exacerbating blood-brain barrier (BBB) disruption. However, no A-FABP inhibitors have been approved for clinical use due to safety issues. Here, we identified the therapeutic effect of levofloxacin, a widely used antibiotic displaying A-FABP inhibitory activity in vitro, on cerebral I/R injury and determined its target specificity and action mechanism in vivo. Using molecular docking and site-directed mutagenesis, we showed that levofloxacin inhibited A-FABP activity through interacting with the amino acid residue Asp76, Gln95, Arg126 of A-FABP. Accordingly, levofloxacin significantly inhibited A-FABP-induced JNK phosphorylation and expressions of proinflammatory factors and matrix metalloproteinase 9 (MMP-9) in mouse primary macrophages. In wild-type mice with transient middle cerebral artery occlusion, levofloxacin substantially mitigated BBB disruption and neuroinflammation, leading to reduced cerebral infarction, alleviated neurological outcomes, and improved survival. Mechanistically, levofloxacin decreased MMP-9 expression and activity, and thus reduced degradation of extracellular matrix and endothelial tight junction proteins. Importantly, the BBB- and neuro-protective effects of levofloxacin were abolished in A-FABP or MMP-9 knockout mice, suggesting that the therapeutic effects of levofloxacin highly depended on specific targeting of the A-FABP-MMP-9 axis. Overall, our study demonstrates that levofloxacin alleviates A-FABP-induced BBB disruption and neural tissue injury following cerebral I/R, and unveils its therapeutic potential for the treatment of ischemic stroke.

Elucidating the role of MMP9 in hyperhomocysteinemia induced degradation of the neurovascular unit

AbstractBackgroundVascular contributions to cognitive impairment and dementia (VCID) is one of the leading causes of dementia. Hyperhomocysteinemia has been identified as a risk factor for VCID though the mechanism behind this connection has yet to be determined. Hyperhomocysteinemia increases inflammation inducing the upregulation of matrix metalloproteinase 9 (MMP9) activity. MMP9 has been shown to degrade several substrates along the neurovascular unit including claudin 5, collagen 4, occludin and β‐dystroglycan. I hypothesize that increased MMP9 activity following the induction of hyperhomocysteinemia leads to the cleavage of important anchoring proteins along the neurovascular unit weakening the integrity of the blood brain barrier which contributes to the progression of VCID pathology.MethodC57BL6 WT and MMP9 knockout mice were placed on a control diet or a diet deficient in vitamins B6, B12 and folate and enriched in methionine to induce hyperhomocysteinemia for 4, 8, 12 and 16 weeks. Western blot analysis was performed to investigate the substrates of MMP9 including claudin, occludin, and β‐dystroglycan.ResultStudies are underway to examine if MMP9 activation contributes to blood brain barrier dysfunction directly by degrading tight junction proteins leading to a weakened endothelial cell barrier and/or indirectly by cleaving proteins responsible for maintaining the connection between astrocytic end feet and the endothelial basement membrane.ConclusionOur findings suggest that increased levels of MMP9 activity may impact several aspects of the neurovascular unit to contribute to VCID pathology. Further investigations focused on inhibition of MMP9 activation could provide the field with an important target for mitigating progression of this disease.

MMP-9 Deletion Attenuates Arteriovenous Fistula Neointima through Reduced Perioperative Vascular Inflammation

Matrix metalloproteinase 9 (MMP-9) expression is upregulated in vascular inflammation and participates in vascular remodeling, including aneurysm dilatation and arterial neointima development. Neointima at the arteriovenous (AV) fistula anastomosis site primarily causes AV fistula stenosis and failure; however, the effects of MMP-9 on perioperative AV fistula remodeling remain unknown. Therefore, we created AV fistulas (end-to-side anastomosis) in wild-type (WT) and MMP-9 knockout mice with chronic kidney disease to further clarify this. Neointima progressively developed in the AV fistula venous segment of WT mice during the four-week postoperative course, and MMP-9 knockout increased the lumen area and attenuated neointima size by reducing smooth muscle cell and collagen components. Early perioperative AV fistula mRNA sequencing data revealed that inflammation-related gene sets were negatively enriched in AV fistula of MMP-9 knockout mice compared to that in WT mice. qPCR results also showed that inflammatory genes, including tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), interleukin-6 (IL-6), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1), were downregulated. In addition, Western blot results showed that MMP-9 knockout reduced CD44 and RAC-alpha serine/threonine-protein kinase (Akt) and extracellular signal-regulated kinases (ERK) phosphorylation. In vitro, MMP-9 addition enhanced IL-6 and MCP-1 expression in vascular smooth muscle cells, as well as cell migration, which was reversed by an MMP-9 inhibitor. In conclusion, MMP-9 knockout attenuated AV fistula stenosis by reducing perioperative vascular inflammation.

A pilot study of microRNA expression profiles of the spinal neuron in matrix metalloproteinase-9 knockout mice

Introduction: Matrix metalloproteinase-9 (MMP9) plays a key role in blood–spinal cord barrier dysfunction. MMP9 blockade leads to improved injured locomotor recovery. However, it is still unknown whether MMP9 deficiency affects gene expression or signal transduction pathways in the spinal neuron. Material and Methods: In this study, we first screen the MMP9 knockdown mice with high superoxide dismutase (SOD) expression and low MMP9 expression by polymerase chain reaction analysis. Then, the gene microarrays were used to screen differentially expressed genes in the spinal neuron from MMP-9 knockout and wild-type mice. There were six groups in this experiment, including three negative control groups: SOD_1, SOD_2, and SOD_3, and three experiment groups: SOD_ MMP9_1, SOD_ MMP9_2, and SOD_ MMP9_3. The gene ontology terms were used to predict the potential functions of these differentially expressed genes, and the Kyoto Encyclopedia of Genes and Genomes was used to analyze the potential functions of these target genes in the pathways. Results: We found that the gene expression in the spinal neuron from MMP9 knockout mice was significantly altered compared to wild-type mice. FoxO signaling, axon guidance, ubiquitin-mediated proteolysis, regulation of actin cytoskeleton, and proteoglycans were changed. Discussion and Conclusion: In summary, MMP9 plays a role in spinal neuron signaling and the underlying mechanism may through affecting several signaling pathways.

Effect of MMP-9 gene knockout on retinal vascular form and function.

Retinal degeneration from inherited gene mutation(s) is a common cause of blindness because of structural and functional alterations in photoreceptors. Accordingly, various approaches are being tested to ameliorate or even cure neuroretinal blinding conditions in susceptible patients by employing neuroprotective agents, gene therapeutics, optogenetics, regenerative therapies, and retinal prostheses. The FVB/NJ mouse strain inherently has a common Pde6b rd1 homozygous allele that renders its progeny blind by the time pups reach weaning age. To study the role matrix metalloproteinase-9 (MMP-9) in retinal structure and function, we examined a global MMP-9 knockout (KO) mouse model that has been engineered on the same FVB/NJ background to test the hypothesis whether lack of MMP-9 activity diminishes neuroretinal degenerative changes and thus helps improve the vision. We compared side-by-side various aspects of the ocular physiology in the wild-type (WT) C57BL/6J, FVB/NJ, and MMP-9 KO strains of mice. The results suggest that MMP-9 KO mice display subdued changes in their retinae as reflected by both structural and functional enhancement in the overall ocular neurophysiological parameters. Altogether, the findings appear to have clinical relevance for targeting conditions wherein MMPs and their overactivities are suspected to play dominant pathophysiological roles in advancing neurodegenerative retinal diseases.

Bone Marrow Niche-Derived Extracellular Matrix-Degrading Enzymes Influence the Progression of B-Cell Acute Lymphoblastic Leukemia

Interactions with the bone marrow microenvironment (BMM) influence the pathophysiology of hematological malignancies. Reciprocally, hematological malignancies remodel the BMM in order to render it more hospitable for malignant progression. Hypothesizing that different leukemias differentially remodel stroma cells in the BMM, we tested differences in the expression of various genes in sorted osteoblastic cells from mice with B-cell acute lymphoblastic (B-ALL), acute myeloid (AML) or chronic myeloid leukemia (CML) or control mice by microarray. This revealed a high expression of various proteases, especially matrix metalloproteinase-9 (MMP-9), in osteoblastic cells isolated from mice with B-ALL. MMP-9 had previously been shown to be produced by leukemia cells.To investigate the physiological relevance of BMM-derived MMP-9 for the progression of B-ALL, we employed the well-established retroviral transduction/transplantation model of BCR-ABL1-dependent B-ALL in MMP-9-deficient or wildtype mice. Deficiency of MMP-9 in the BMM prolonged the survival of mice with B-ALL compared to wildtype mice. Secondary transplantation of bone marrow from wildtype versus MMP-9 knockout (KO) mice with B-ALL led to a significant prolongation of survival of recipients of B-ALL bone marrow from MMP-9 KO mice, suggesting that leukemia-initiating cells are reduced in a MMP-9 KO BMM. In addition, we observed reduced invasion of B-ALL cells into different organs such as spleen, meninges, lungs and liver, which likely underlies the observed prolongation of survival, as well as the reduced degradation of extracellular matrix (ECM) proteins such as laminin and fibronectin in the BMM of MMP-9 deficient mice. Mechanistically, using various in vivo and in vitro assays, as well as mice deficient for the receptor for tumor necrosis factor-α (TNF-α) we have demonstrated that B-ALL cells induce MMP-9-expression in niche cells, such as mesenchymal stem cells (MSC), via a release of high amounts of TNF-α, both in the murine and the human setting. TNF-α-dependent induction of MMP-9 in MSC was mediated via TNF-receptor-1, followed by activation of the downstream target nuclear factor kappa B (NF-kB). Consistently, transplantation of B-ALL-initiating cells, in which TNF-α had been knocked down, led to a significant prolongation of survival in B-ALL mice.Testing whether treatment of mice with B-ALL with an inhibitor of MMP-9 may prolong survival compared to vehicle-treated mice, we indeed found decreased degradation of ECM proteins in the BMM, a decreased leukemia burden in peripheral blood and a significant prolongation of survival. In addition, we observed reduced minimal residual disease in the bone marrow of mice with B-ALL when the mice had been treated with cytarabine and the MMP-9 inhibitor compared to mice treated with cytarabine alone. Experiments on testing the effect of MMP-9 inhibitor treatment on human B-ALL cells in a xenotransplantation model are currently ongoing.In summary, we have demonstrated the role of BMM-derived MMP-9 for B-ALL progression. B-ALL cells self-reinforce the BMM by inducing the production of MMP-9 via the release of TNF-α. Increased production of MMP-9 from the BMM promotes B-ALL progression via increased invasion of leukemic cells into different organs. Our data suggest, that inhibition of MMP-9 may be a feasible strategy as an adjunct to existing therapies. DisclosuresKrause:Glycotope: Consultancy; Glycomimetics Inc. until 06/2016: Consultancy, Research Funding; Merck KgGA in future: Research Funding; European Patent: Patents & Royalties: European Patent No. 16187926.7-1401 “FIBRONECTIN FOR USE IN THE TREATMENT OF LEUKEMIA” .

Elevation of MMP-9 Levels Promotes Epileptogenesis After Traumatic Brain Injury

Posttraumatic epilepsy (PTE) is a recurrent seizure disorder that often develops secondary to traumatic brain injury (TBI) that is caused by an external mechanical force. Recent evidence shows that the brain extracellular matrix plays a major role in the remodeling of neuronal connections after injury. One of the proteases that is presumably responsible for this process is matrix metalloproteinase-9 (MMP-9). The levels of MMP-9 are elevated in rodent brain tissue and human blood samples after TBI. However, no studies have described the influence of MMP-9 on the development of PTE. The present study used controlled cortical impact (CCI) as a mouse model of TBI. We examined the detailed kinetics of MMP-9 levels for 1 month after TBI and observed two peaks after injury (30 min and 6 h after injury). We tested the hypothesis that high levels of MMP-9 predispose individuals to the development of PTE, and MMP-9 inhibition would protect against PTE. We used transgenic animals with either MMP-9 knockout or MMP-9 overexpression. MMP-9 overexpression increased the number of mice that exhibited TBI-induced spontaneous seizures, and MMP-9 knockout decreased the appearance of seizures. We also evaluated changes in responsiveness to a single dose of the chemoconvulsant pentylenetetrazol. MMP-9-overexpressing mice exhibited a significantly shorter latency between pentylenetetrazol administration and the first epileptiform spike. MMP-9 knockout mice exhibited the opposite response profile. Finally, we found that the occurrence of PTE was correlated with the size of the lesion after injury. Overall, our data emphasize the contribution of MMP-9 to TBI-induced structural and physiological alterations in brain circuitry that may lead to the development of PTE.

Inhibition of gelatinase B/MMP-9 does not attenuate colitis in murine models of inflammatory bowel disease

One third of patients with inflammatory bowel disease (IBD) inadequately respond to anti-TNF treatment and preclinical data suggest that matrix metalloproteinase-9 (MMP-9) is a novel therapeutic target. Here we show that IBD clinical and histopathological parameters found in wild type mice challenged with three different models of colitis, acute and chronic dextran sodium sulphate (DSS), and acute 2,4,6-trinitrobenzenesulfonic acid-induced colitis are not attenuated in MMP-9 knockout mice. We find similar colonic gene expression profiles in wild type and MMP-9 knockout mice in control and acute DSS conditions with the exception of eleven genes involved in antimicrobial response during colitis. Parameters of chronic colitis are similar in wild type and MMP-9 knockout mice. Pharmacological inhibition of MMP-9 with bio-active peptides does not improve DSS colitis. We suggest that MMP-9 upregulation is a consequence rather than a cause of intestinal inflammation and we question whether MMP-9 represents a disease target in IBD.

Matrix Metalloproteinase-9 and Synaptic Plasticity in the Central Amygdala in Control of Alcohol-Seeking Behavior

BackgroundDysfunction of the glutamatergic system has been implicated in alcohol addiction; however, the molecular underpinnings of this phenomenon are still poorly understood. In the current study we have investigated the possible function of matrix metalloproteinase-9 (MMP-9) in alcohol addiction because this protein has recently emerged as an important regulator of excitatory synaptic plasticity. MethodsFor long-term studies of alcohol drinking in mice we used IntelliCages. Dendritic spines were analyzed using Diolistic staining with DiI. Whole-cell patch clamp was used to assess silent synapses. Motivation for alcohol in human subjects was assessed on the basis of a Semi-Structured Assessment for the Genetics of Alcoholism interview. ResultsMice devoid of MMP-9 (MMP-9 knockout) drank as much alcohol as wild-type animals; however, they were impaired in alcohol seeking during the motivation test and withdrawal. The deficit could be rescued by overexpression of exogenous MMP-9 in the central nucleus of the amygdala (CeA). Furthermore, the impaired alcohol seeking was associated with structural alterations of dendritic spines in the CeA and, moreover, whole-cell patch clamp analysis of the basal amygdala to CeA projections showed that alcohol consumption and withdrawal were associated with generation of silent synapses. These plastic changes were impaired in MMP-9 knockout mice. Finally, C/T polymorphism of MMP-9 gene at position –1562, which upregulates MMP-9 expression, correlated with increased motivation for alcohol in alcoholics. ConclusionsIn aggregate, our results indicate a novel mechanism of alcohol craving that involves MMP-9–dependent synaptic plasticity in CeA.

Matrix metalloproteinase 9-dependent Notch signaling contributes to kidney fibrosis through peritubular endothelial-mesenchymal transition.

ABSTRACT Background: Endothelial cells are known to contribute to kidney fibrosis via endothelial–mesenchymal transition (EndoMT). Matrix metalloproteinase 9 (MMP-9) is known to be profibrotic. However, whether MMP-9 contributes to kidney fibrosis via EndoMT is unknown. Methods: Primary mouse renal peritubular endothelial cells (MRPECs) were isolated and treated by recombinant human transforming growth factor beta 1 (rhTGF-β1) with or without MMP-9 inhibitor or by recombinant human MMP-9 (rhMMP-9) alone. Kidney fibrosis was induced by unilateral ureteral obstruction (UUO) in MMP-9 knockout (KO) and wide-type (WT) control mice. The effects of MMP-9 on EndoMT of MRPECs and kidney fibrosis were examined. Results: We showed that MRPECs underwent EndoMT after rhTGF-β1 treatment or in UUO kidney as evidenced by decreased expression of endothelial markers, vascular endothelial cadherin (VE-cadherin) and CD31, and increased levels of mesenchymal markers, α-smooth muscle actin (α-SMA) and vimentin. The expression of fibrosis markers was also up-regulated significantly after rhTGF-β1 treatment in MRPECs. The EndoMT and fibrosis markers were significantly less in rhTGF-β1-treated MMP-9 KO MRPECs, whereas MMP-9 alone was sufficient to induce EndoMT in MRPECs. UUO kidney of MMP-9 KO mice showed significantly less interstitial fibrosis and EndoMT in MRPECs. Notch signaling shown by Notch intracellular domain (NICD) was increased, while Notch-1 was decreased in rhTGF-β1-treated MRPECs of MMP-9 WT but not MMP-9 KO mice. Inhibition of MMP-9 or Notch signaling prevented rhTGF-β1- or rhMMP-9-induced α-SMA and NICD upregulation in MRPECs. UUO kidney of MMP-9 KO mice had less staining of Notch signaling transcription factor Hey-1 in VE-cadherin-positive MRPECs than WT controls. Conclusions: Our results demonstrate that MMP-9-dependent Notch signaling plays an important role in kidney fibrosis through EndoMT of MRPECs.

Proteolytic regulation of synaptic plasticity in the mouse primary visual cortex: analysis of matrix metalloproteinase 9 deficient mice.

The extracellular matrix (ECM) is known to play important roles in regulating neuronal recovery from injury. The ECM can also impact physiological synaptic plasticity, although this process is less well understood. To understand the impact of the ECM on synaptic function and remodeling in vivo, we examined ECM composition and proteolysis in a well-established model of experience-dependent plasticity in the visual cortex. We describe a rapid change in ECM protein composition during Ocular Dominance Plasticity (ODP) in adolescent mice, and a loss of ECM remodeling in mice that lack the extracellular protease, matrix metalloproteinase-9 (MMP9). Loss of MMP9 also attenuated functional ODP following monocular deprivation (MD) and reduced excitatory synapse density and spine density in sensory cortex. While we observed no change in the morphology of existing dendritic spines, spine dynamics were altered, and MMP9 knock-out (KO) mice showed increased turnover of dendritic spines over a period of 2 days. We also analyzed the effects of MMP9 loss on microglia, as these cells are involved in extracellular remodeling and have been recently shown to be important for synaptic plasticity. MMP9 KO mice exhibited very limited changes in microglial morphology. Ultrastructural analysis, however, showed that the extracellular space surrounding microglia was increased, with concomitant increases in microglial inclusions, suggesting possible changes in microglial function in the absence of MMP9. Taken together, our results show that MMP9 contributes to ECM degradation, synaptic dynamics and sensory-evoked plasticity in the mouse visual cortex.

Matrix metalloproteinases-9 deficiency impairs liver regeneration through epidermal growth factor receptor signaling in partial hepatectomy mice

BackgroundLiver regeneration is a complex process regulated by many complex mechanisms involving cytokines, growth factors, metabolic networks, and so forth. Previous investigations have demonstrated that matrix metalloproteinase-9 (MMP-9) is an essential factor in liver regeneration. The present study aimed to explore the role of MMP-9 in epidermal growth factor receptor (EGFR) signaling and related proliferation signaling factors in a mouse partial hepatectomy (PH) model. Materials and methodsMMP-9 knockout (KO) and wild-type mice were used to establish the PH model. Liver regeneration was analyzed based on proliferation cell nuclear antigen immunohistochemistry and liver weight to body weight ratio. Also, EGFR ligands, EGFR, and downstream factors were measured by quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and Western blot. ResultsMMP-9 KO mice showed a delayed hepatic regenerative response after PH. EGFR ligands, including heparin-binding epidermal growth factor and amphiregulin, were expressed at significantly lower levels between days 1 and 3 posthepatectomy in MMP-9 KO mice. MMP-9 KO mice also inhibited and delayed EGFR activation after PH. After PH, the expression of STAT3, NF-κB, and cyclinD1, all downstream of EGFR, was similar to EGFR activation. ConclusionsOur data provide new evidence supporting a critical role of MMP-9 in liver regeneration after PH through activation of EGFR signaling.

Abstract 116: Matrix Metalloproteinase-9 Deletion Attenuates Blood-Brain Barrier Disruption and Consequent Injury in White Matter After Subarachnoid Hemorrhage

Objective: The detailed mechanism of white matter injury after subarachnoid hemorrhage (SAH) remains unclear. We hypothesized that blood-brain barrier (BBB) disruption occurs in white matter after SAH and it leads to consequent injury. In this study, we investigated the potential role of matrix metalloproteinase-9 (MMP9) in SAH-induced white matter injury. Methods: SAH was induced by endovascular perforation in male wild-type (WT) C57BL/6 and MMP9 knockout (MMP9-/-) mice. The following three experiments were devised: 1) to determine BBB disruption and MMP9 activation/expression in white matter, mice underwent MRI at 24 h after SAH. They were then euthanized for immunostaining, transmission electron microscopy and MMP zymography; 2) to investigate the role of MMP9 in BBB disruption, lesion volumes on MRI were compared between WT and MMP9-/- mice at 24 h after SAH; 3) WT and MMP9-/- mice underwent MRI at 1 and 8 days after SAH induction to detect time-dependent changes, and were euthanized at 8 days after SAH. Removed brains were used to investigate myelin integrity and axonal damage in the white matter. Results: In WT mice with SAH, albumin leakage along the white matter was increased (p<0.05; vs. sham) and was consistent with T2-hyperintensity on MRI (r=0.97, p<0.01). In microvessels, tight junction detachment and swollen astrocyte endfeet were demonstrated by electron microscopy. MMP9 activity was elevated in white matter at 24 h after SAH (vs. sham; p<0.05), and MMP9 was mainly expressed in astrocytes and oligodendrocyte precursors. The volume of T2-hyperintensity in the white matter in WT mice with SAH was 6.2 ± 3.0 mm3 (p<0.001; vs. WT sham), while that in MMP9-/- mice with SAH was significantly smaller (1.0 ± 1.4 mm3; p<0.01). At 8 days after SAH, decreased myelin integrity and an increased density of damaged axons were observed in WT with SAH mice compared to normal control mice (p<0.05; for each), while T2-hyperintensity on MRI in the white matter almost disappeared. MMP9-/- mice developed less of those injuries than WT mice at 8 days after SAH (p<0.05; for each). Conclusions: SAH causes BBB disruption and consequent injury in the white matter, and MMP9 plays an important role for those pathologies. MMP9 could be a therapeutic target for SAH-induced white matter injury.

MMP9 Deficiency Increased the Size of Experimentally Induced Apical Periodontitis

IntroductionApical periodontitis is an inflammation and destruction of periapical tissues. Matrix metalloproteinase-9 (MMP-9) is thought to be involved in periapical lesion formation and progression. The aim of this study was to evaluate the lesion progression in MMP-9 knockout (KO) mice compared with that in control mice (wild type [WT]). MethodsThe pulps of mouse mandibular first molars were exposed; animals were killed at 0, 7, 14, 21, and 28 days after surgery. Hematoxylin-eosin–stained sections were observed for the description of pulpal, apical, periapical features, and the periapical lesion size. The periapical lesion size was further measured with micro–computed tomographic imaging. The number of osteoclasts was also counted by tartrate-resistant acid phosphatase histoenzymology. Real-time polymerase chain reaction and immunohistochemistry were used to analyze the expression levels of receptor activator of NF-κB (RANK), receptor activator of NF-κB ligand (RANKL), osteoprotegerin (OPG), interleukin-1 beta (IL-1β), tumor necrosis factor alpha (TNF-α), MMP-2, and MMP-8. ResultsThere was a significant difference (P < .05) between the 2 types of animals regarding the periapical lesion size, which was larger in MMP-9 KO animals. No significant differences (P > .05) were found between WT and MMP-9 KO mice related to the osteoclast number as well as the pulpal, apical, and periapical features. More neutrophil cells were observed in MMP-9 KO animals than WT mice (P < .05). The expression levels of RANK, RANKL, OPG, IL-1β, TNF-α, MMP-2, and MMP-8 were found up-regulated in MMP-9 KO mice (P < .05). ConclusionsMMP-9 KO animals developed larger periapical lesions with greater inflammatory response, indicating an important role of MMP-9 in the host's immune and inflammatory response to root canal and periradicular infection.

Protective effect of melatonin against transient global cerebral ischemia-induced neuronal cell damage via inhibition of matrix metalloproteinase-9

AimsMelatonin possesses various pharmacological effects including neuroprotective effects against brain ischemia. Post-ischemic increases in matrix metalloproteinase-9 (MMP-9) expression and activity mainly contribute to neuronal damage by degradation of the extracellular matrix. This study was designed to examine whether melatonin has a neuroprotective effect and an influence on MMP-9 in transient global brain ischemia. Main methodsMice were subjected to 20min of global brain ischemia and sacrificed 72h later. Melatonin (30mg/kg) was administered 30min before and 2h after ischemia as well as once daily until sacrifice. Key findingsHippocampal pyramidal cell damage after ischemia was significantly decreased by melatonin. As observed by zymography, melatonin inhibited the increase of MMP-9 activity after ischemia. In the brain sections, the increased gelatinase activity was mainly observed in the hippocampus after ischemia and melatonin also reduced gelatinase activity. The laminin and NeuN expression levels were reduced in the hippocampal CA1 and CA2 regions after ischemia, and melatonin reduced laminin degradation and neuronal loss. A TUNEL assay demonstrated that there were TUNEL-positive cells in the hippocampus and the number of TUNEL-positive cells was significantly decreased by melatonin. There was no difference in the ischemia-induced hippocampal neuronal damage between the vehicle- and melatonin-treated groups of MMP-9 knock-out mice. SignificanceThese data demonstrate that melatonin suppressed the occurrence of neuronal injury, which might be partly due to its inhibitory effects on MMP-9 in addition to its anti-oxidative effects. MMP-9 may be an important key target of melatonin in neuroprotection against global ischemia.

Leukocyte-derived MMP9 is crucial for the recruitment of proinflammatory macrophages in experimental glomerulonephritis

Matrix metalloproteinase 9 (MMP9) is a conditionally expressed enzyme and is upregulated in glomerulonephritis. Its function in these diseases, however, remains to be fully elucidated. The induction of nephrotoxic serum nephritis (NTN) in wild-type mice resulted in an upregulation of MMP9, followed by leukocyte infiltration, albuminuria, and subsequent renal failure. MMP9 deficiency ameliorated the course of NTN as indicated by reduced histological injury and reduced infiltration of proinflammatory macrophages. The chemotaxis of MMP9-deficient macrophages in vitro was impaired. Intrarenal macrophages isolated from the kidneys of nephritic MMP9 knockout mice still displayed the typical features of a proinflammatory phenotype and were indistinguishable from wild type-derived cells. Bone marrow transplantation restored renal tissue injury and macrophage recruitment when wild type-derived donor cells were transplanted onto MMP9-deficient mice prior to the induction of NTN. Thus, leukocyte-derived MMP9 mediates the recruitment of proinflammatory macrophages into kidneys during experimental crescentic glomerulonephritis.

TheERK1/2Inhibitor U0126 Attenuates Diabetes-Induced Upregulation of MMP-9 and Biomarkers of Inflammation in the Retina

This study was conducted to determine the expression of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) in a time-dependent manner and the effect of extracellular-signal-regulated kinases-1/2 (ERK1/2) inhibition on the expressions of MMP-9, TIMP-1, and inflammatory biomarkers in the retinas of diabetic rats. The expression of MMP-9 was quantified by zymography, and the mRNA level of MMP-9 and TIMP-1 was quantified by RT-PCR. The expression of inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) was examined by Western blot analysis. MMP-9 expression was significantly higher in diabetic rat retinas compared to controls at all time points.TIMP-1 expression was nonsignificantly upregulated at 1week of diabetes and was significantly downregulated at 4 and 12 weeks of diabetes. Intravitreal administration of the ERK1/2 inhibitor U0126 prior to induction of diabetes decreased ERK1/2 activation, attenuated diabetes-induced upregulation of MMP-9, iNOS, IL-6, and TNF-α and upregulated TIMP-1 expression. In MMP-9 knockout mice, diabetes had no effect on retinal iNOS expression and its level remained unchanged. These data provide evidence that ERK1/2 signaling pathway is involved in MMP-9, iNOS, IL-6, and TNF-α induction in diabetic retinas and suggest that ERK1/2 can be a novel therapeutic target in diabetic retinopathy.

Synaptic cell adhesion molecule‐2 and collapsin response mediator protein‐2 are novel members of the matrix metalloproteinase‐9 degradome

The elucidation of entire sets of protease substrates ("proteodegradomes") is important for understanding proteolytic pathways, their networks, and their role in the regulation of cell function. Matrix metalloproteinase-9 (MMP-9) is an extracellularly operating protease that is expressed and released in the brain in response to enhanced neuronal activity. Under physiological conditions, MMP-9 is involved in neuronal plasticity, including long-term potentiation, learning, and memory. This function may be related to its activity at the synapse. Under pathological conditions (e.g., during excitotoxicity, stroke, and traumatic brain injury), when the concentration of glutamate is persistently increased, MMP-9 is detrimental to brain tissue. To assess the MMP-9 degradome, we used synaptoneurosomal fractions isolated from the hippocampus of wildtype and MMP-9 knockout mice. To induce MMP-9 activity, the synaptoneurosomal fractions were treated with 50 μM glutamate for 30 min at 37°C. To investigate MMP-9 targets, two-dimensional fluorescence difference gel electrophoresis was performed. This approach enabled the accurate analysis of differences in protein abundance between samples. The differential spots that contained potential MMP-9 substrates were excised from the gel, and proteins of interest were identified using mass spectrometry. Two novel MMP-9 targets were identified: synaptic cell adhesion molecule-2 and collapsin response mediator protein-2. The MMP-9-driven processing of the newly identified substrates was confirmed by western blot in primary hippocampal neurons after stimulation with either N-methyl-D-aspartate or glutamate or incubation with recombinant autoactivating MMP-9 and use of a specific inhibitor.

Abstract 2463: Protease nexin 1 modulates prostate adenocarcinoma by regulating the Hedgehog pathway in humans and mice

Abstract Prostate adenocarcinoma is the most frequent cancer and is the second leading cause of cancer death of men in the Western world. Aberrant activation of the Hedgehog (Hh) pathway is implicated in the growth and progression of prostate cancer. We show that the Hh pathway is inhibited by the serine protease inhibitor, protease nexin 1 (PN1), an extracellular matrix (ECM) protein highly expressed in normal prostate. We demonstrate here that PN1 regulates Hh signalling by reduction of the Hh ligand, Sonic (SHH), and its downstream effectors in tissue culture and in vivo. Conversely, matrix metalloproteinase 9 (MMP9) enhances Hh signalling through degradation of PN1. MRI imaging was used to determine variation in tumour formation in an orthotopic prostate tumour model using PN1 and MMP9 knock-out mice. In PN1-/- animals, SHH was increased and tumor growth was stimulated. In contrast, PN1 levels were elevated in MMP9-/- mice while Hh signalling was reduced with concomitant decreased tumor growth. Finally, genetic alterations in Hh pathway genes identified by comparative genomic hybridization (CGH) from intermediate risk prostate cancer patients correlated with a worse clinical outcome (HR=2.67, p=0.00067), indicating the importance of this pathway in human cancer. Our data identify PN1 as a novel regulator of SHH and its downstream targets allowing PN1 levels to influence prostate tumor growth. Regulation of the PN1-Hh pathway could constitute a significant therapeutic advance in treating cancers that exhibit high expression of Hh markers. These data also provide a mechanism through which MMP-9 can regulate hedgehog pathway signalling in tissues rich in PN1. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2463. doi:1538-7445.AM2012-2463

The MMP-9/TIMP-1 Axis Controls the Status of Differentiation and Function of Myelin-Forming Schwann Cells in Nerve Regeneration

BackgroundMyelinating Schwann cells (mSCs) form myelin in the peripheral nervous system. Because of the works by us and others, matrix metalloproteinase-9 (MMP-9) has recently emerged as an essential component of the Schwann cell signaling network during sciatic nerve regeneration.Methodology/Principal FindingsIn the present study, using the genome-wide transcriptional profiling of normal and injured sciatic nerves in mice followed by extensive bioinformatics analyses of the data, we determined that an endogenous, specific MMP-9 inhibitor [tissue inhibitor of metalloproteinases (TIMP)-1] was a top up-regulated gene in the injured nerve. MMP-9 capture followed by gelatin zymography and Western blotting of the isolated samples revealed the presence of the MMP-9/TIMP-1 heterodimers and the activated MMP-9 enzyme in the injured nerve within the first 24 h post-injury. MMP-9 and TIMP-1 co-localized in mSCs. Knockout of the MMP-9 gene in mice resulted in elevated numbers of de-differentiated/immature mSCs in the damaged nerve. Our comparative studies using MMP-9 knockout and wild-type mice documented an aberrantly enhanced proliferative activity and, accordingly, an increased number of post-mitotic Schwann cells, short internodes and additional nodal abnormalities in remyelinated nerves of MMP-9 knockout mice. These data imply that during the first days post-injury MMP-9 exhibits a functionally important anti-mitogenic activity in the wild-type mice. Pharmacological inhibition of MMP activity suppressed the expression of Nav1.7/1.8 channels in the crushed nerves.Conclusion/SignificanceCollectively, our data established an essential role of the MMP-9/TIMP-1 axis in guiding the mSC differentiation and the molecular assembly of myelin domains in the course of the nerve repair process. Our findings of the MMP-dependent regulation of Nav channels, which we document here for the first time, provide a basis for therapeutic intervention in sensorimotor pathologies and pain.