Effects Of Matrix Metalloproteinases Research Articles

Matrix Metalloproteinases on Skin Photoaging.

Skin aging is characterized by an imbalance between the generation and degradation of extracellular matrix molecules (ECM). Matrix metalloproteinases (MMPs) are the primary enzymes responsible for ECM breakdown. Intrinsic and extrinsic stimuli can induce different MMPs. However, there is limited literature especially on the summary of skin MMPs and potential inhibitors. We aim to focus on the upregulation of MMP expression or activity in skin cells following exposure to UV radiation. We also would like to offer valuable insights into potential clinical applications of MMP inhibitors for mitigating skin aging. This article presents the summary of prior research, which involved an extensive literature search across diverse academic databases including Web of Science and PubMed. Our findings offer a comprehensive insight into the effects of MMPs on skin aging after UV irradiation, including their substrate preferences and distinct roles in this process. Additionally, a comprehensive list of natural plant and animal extracts, proteins, polypeptides, amino acids, as well as natural and synthetic compounds that serve as inhibitors for MMPs is compiled. Skin aging is a complex process influenced by environmental factors and MMPs. Research focuses on UV-induced skin damage and the formation of Advanced Glycosylation End Products (AGEs), leading to wrinkles and impaired functionality. Inhibiting MMPs is crucial for maintaining youthful skin. Natural sources of MMP inhibitor substances, such as extracts from plants and animals, offer a safer approach to obtain inhibitors through dietary supplements. Studying isolated active ingredients can contribute to developing targeted MMP inhibitors.

The Effect of Alcoholic Essence Satureja Sahandica Bornm L. on the Expression of Metalloproteinases 1, 2, 9 and 13 in a Model Similar to Osteoarthritis

Loss of the extracellular matrix of cartilage is one of the most important and prominent features of osteoarthritis (OA). The ECM has two important components, including the proteoglycan aggrecan and type II collagen, which are the main targets of MMPs and ADAM TSs enzymes. In this paper, the effect of ASSB Compared with dexamethasone and ibuprofen as representatives of steroidal and nonsteroidal anti-inflammatory drugs. One way to prevent irreversible joint damage in OA is to inhibit MMPs. ASSB can improve the condition of patients with osteoarthritis by reducing the expression of the MMPs 9 and 13 gene. <i>Background</i>: OA is a progressive joint disease characterized by cartilage degeneration, cartilage bone regeneration, and synovial membrane inflammation and is exacerbated with age. Given the side effects of conventional OA treatments, including nonsteroidal anti-inflammatory drugs and corticosteroids, it is important to consider new treatments for this disorder. Recently, the effect of matrix metalloproteinases on the pathogenesis of OA has been attracted attention. <i>Objective</i>: The aim of this paper was to evaluate the impact of Alcoholic Satureja Sahandica Bornem L. (ASSB) essence on inhibiting the expression of metalloproteinase gene 1, 2, 9 and 13 in bovine fibroblast-like synoviocytes stimulated by lipopolysaccharide as a model of osteoarthritis. <i>Methods</i>: Synovial cells were isolated from the articular cartilage of the radiocarpal joint of an 8-month-old Holstein cow. After determining the degree of toxicity by MTT Assay, the cells were exposed to stimulation of LPS without or in the presence of dexamethasone, ibuprofen and alcoholic Satureja Sahandica Bornem essence (ASSB). Metalloproteinase gene expression 1, 2, 9 and 13 were measured by RT-PCR and ELISA. The effect of ASSB on migration and cell invasion was investigated by Transwell chambers. <i>Results</i>: The results showed that Satureja Sahandica Bornm (SSB) essential oil significantly reduced the expression of metalloproteinases 9 and 12 in bovine fibroblast-like synovocytes stimulated by lipopolysaccharide. It also suppressed migration and invasion of these cells. However, Satureja Sahandica Bornm L. had no significant impact on the expression of MMPs 1 and 2. <i>Conclusion</i>: Based on our results, ASSB can significantly reduce the activity and inflammatory effect of MMPs 9 and 12 in OA, its potential role as a complement to NSAIDs and common corticosteroids was confirmed. However, cellular modeling does not confirm the beneficial effect of OA in patients.

Multi-layered proteogenomic analysis unravels cancer metastasis directed by MMP-2 and focal adhesion kinase signaling

The role of matrix metalloproteinase-2 (MMP-2) in tumor cell migration has been widely studied, however, the characteristics and effects of MMP-2 in clinical sample of metastatic colorectal cancer (CRC) remain poorly understood. Here, in order to unveil the perturbed proteomic signal during MMP-2 induced cancer progression, we analyzed plasma proteome of CRC patients according to disease progression, HCT116 cancer secretome upon MMP-2 knockdown, and publicly available CRC tissue proteome data. Collectively, the integrative analysis of multi-layered proteomes revealed that a protein cluster containing EMT (Epithelial-to-Mesenchymal Transition)-associated proteins such as CD9-integrin as well as MMP-2. The proteins of the cluster were regulated by MMP-2 perturbation and exhibited significantly increased expressions in tissue and plasma as disease progressed from TNM (Tumor, Node, and Metastasis) stage I to II. Furthermore, we also identified a plausible association between MMP-2 up-regulation and activation of focal adhesion kinase signaling in the proteogenomic analysis of CRC patient tissues. Based on these comparative and integrative analyses, we suggest that the high invasiveness in the metastatic CRC resulted from increased secretion of MMP-2 and CD9-integrin complex mediated by FAK signaling activation.

MMP2 and TLRs modulate immune responses in the tumor microenvironment.

The presence of an immunosuppressive tumor microenvironment is a major obstacle in the success of cancer immunotherapies. Because extracellular matrix components can shape the microenvironment, we investigated the role of matrix metalloproteinase 2 (MMP2) in melanoma tumorigenesis. We found that MMP2 signals proinflammatory pathways on antigen presenting cells, and this requires both TLR2 and TLR4. B16 melanoma cells that express MMP2 at baseline have slower kinetics in Tlr2–/– Tlr4–/– mice, implicating MMP2 in promoting tumor growth. Indeed, Mmp2 overexpression in B16 cells potentiated rapid tumor growth, which was accompanied by reduced intratumoral cytolytic cells and increased M2 macrophages. In contrast, knockdown of Mmp2 slowed tumor growth and enhanced T cell proliferation and NK cell recruitment. Finally, we found that these effects of MMP2 are mediated through dysfunctional DC–T cell cross-talk as they are lost in Batf3–/– and Rag2–/– mice. These findings provide insights into the detrimental role of endogenous alarmins like MMP2 in modulating immune responses in the tumor microenvironment.

Effect of matrix metalloproteinases on the longitudinal change in Alzheimer’s disease (AD) pathology and cognitive function in patients with mild cognitive impairment due to AD

AbstractBackgroundMatrix metalloproteinases (MMPs), endopeptidases expressed in brain and immune cells, have been implicated in the pathogenesis of Alzheimer's disease (AD). However, the longitudinal effect of MMPs on AD patients is still unclear.MethodWe used the data of the Alzheimer's Disease Neuroimaging Initiative database. We included 95 ApoE4‐positive patients with mild cognitive impairment (MCI) due to AD confirmed with low Aβ42 and/or high phosphorylated‐tau (p‐tau) in cerebrospinal fluid (CSF). We obtained baseline demographic data and plasma MMP levels including MMP‐1, MMP‐2, MMP‐7, MMP‐9, and MMP‐10, and longitudinal data of Aβ42, total tau, and p‐tau in CSF, MRI‐measured hippocampal volume, and cognitive function evaluated on Mini‐Mental State Examination (MMSE) and AD Assessment Scale‐11 (ADAS‐11) over 4 years. We investigated the effect of baseline MMP levels on longitudinal changes in CSF AD biomarkers, hippocampus volume and cognitive function.ResultThere was no significant association between the baseline MMP levels and the longitudinal change in CSF biomarkers. Baseline MMP‐9 level was associated with a longitudinal decrease of hippocampal volume and deterioration of MMSE and ADAS‐11 scores.ConclusionHigh plasma MMP‐9 level in the patients with MCI due to AD would be a risk of consequent neurodegeneration and cognitive decline.

MMP-9, Vertebrobasilar Ectasia and Vertebral Artery Dominance in Vertigo or Dizziness Patients With Vascular Risk Factors.

Background and Purpose: Although vertebrobasilar ectasia (VBE) is diagnosed with increasing frequency, it is not clear whether this is because of altered hemodynamics caused by the effects of matrix metalloproteinases (MMPs) and/or vertebral artery dominance (VAD). Therefore, we investigate the relationship between plasma levels of MMPs and VBE in patients with vertigo or dizziness who also have vascular risk factors, in order to determine whether high levels of MMPs in VBE are independent of VAD.Methods: We prospectively studied 285 patients with vertigo or dizziness and at least one vascular risk factor. Plasma levels of MMPs, tissue inhibitor of metalloproteinases (TIMPs) and cathepsin L were measured. Subjects were classified as VBE-negative or VBE-positive, who were further classified based on the presence of VAD with magnetic resonance angiography. Acute ischemic stroke was screened by diffusion-weighted imaging, generally after bedside evaluation and the drawing of blood samples. Receiver operating characteristic (ROC) curves were applied to evaluate the utility of these potential biomarkers in predicting risk for ischemic stroke.Results: The prevalence of VBE in patients with vertigo or dizziness was 16.5%. Of the 82 patients with ischemic stroke, 14 strokes involved the cortex or subcortex. MMP-9 levels were significantly higher in the VBE-positive group than in the VBE-negative group (P = 0.022). There was a significant difference in the risk of posterior circulation ischemic stroke between the VBE-positive group and the VBE-negative group (P = 0.002). Levels of MMP-2 and cathepsin L tended to be higher in the VBE-negative group (P = 0.054, P = 0.060, respectively). Compared with the non-VAD subgroup, levels of MMP-2,−3,−9, TIMP-1,−2, and cathepsin L were similar in the VAD subgroup. ROC analysis showed that MMP-9 predicted risk for ischemic stroke (AUC = 0.582, 95%CI, 0.510–0.654, P = 0.030).Conclusions: MMP-9 was associated with VBE and independent of VAD. High levels of MMP-9 may predict risk for ischemic stroke in patients with vertigo or dizziness who also have vascular risk factors.

1400 W improves cardioprotective effect of matrix metalloproteinase 2 and myosin light chain kinase inhibitors in hearts subjected to ischemia/reperfusion injury

1400 W improves cardioprotective effect of matrix metalloproteinase 2 and myosin light chain kinase inhibitors in hearts subjected to ischemia/reperfusion injury

Effect of Matrix Metalloproteinase 3 Gene Silencing and SRY-Related High Mobility Group-Box Gene 9 Gene Overexpression on Human Degeneration Nucleus Pulposus Cells In Vitro

This study aims to detect the biological effects of matrix metalloproteinase 3 (MMP3) and SRY-related high mobility group-box gene 9 (SOX9) gene regulation in the human intervertebral disc degeneration of nucleus pulposus cells mediated by lentiviral vectors in vitro. The culture and development of human degenerated intervertebral disc nucleus pulposus cells was performed. The cell morphology and structure were observed, as identified by hematoxylin and eosin (H&amp;E) staining. The experiment was divided into five groups: blank control group, SOX9 gene overexpression group, MMP3 gene silencing group, SOX9 gene overexpression+MMP3 gene silencing group, and blank vector group. RT-PCR and western blot were performed to detect the influence of MMP3 gene silencing and SOX9 gene overexpression on degenerated human intervertebral disc nucleus pulposus cells, include the secretion of polysaccharide and expression of type II collagen, at the mRNA and protein level. The originally generated degenerated human intervertebral disc nucleus pulposus cells had the same cellular morphology. The MTT assay revealed that the blank group and blank vector group had no statistical significance in cell proliferation. The MMP3 gene silencing and SOX9 gene overexpression could promote the proliferation of degenerated human intervertebral disc nucleus pulposus cells, when compared with the blank control group and blank vector group, and this more obvious in the MMP3 gene silencing group and SOX9 gene overexpression group. RT-PCR and western blot revealed that MMP3 gene silencing and SOX9 gene overexpression can promote cells to secrete polysaccharide and type-II collagen (P &lt; 0.05). MMP3 gene silencing and SOX9 gene overexpression can promote the proliferation of degenerated human intervertebral disc nucleus pulposus cells, and their ability to secrete polysaccharide and type-II collagen.

Protease Degradation of Protein Coronas and Its Impact on Cancer Cells and Drug Payload Release.

The effect of matrix metalloproteinases (MMPs) on preformed protein coronas around spherical gold nanoparticles (AuNPs) was studied. Protein coronas of different compositions (human serum, human serum albumin, and collagen IV) were formed around AuNPs and characterized. The protease MMP-9 had different effects on the corona depending on the corona composition, resulting in different changes to the corona hydrodynamic diameter ( DH). When incubated with PANC-1 cells, the corona showed evidence of both increases as well as decreases in DH. Varying the composition of the corona influenced the MMP-9 activity. Furthermore, the corona was influenced not only by the protease activity of the MMP-9 but also by its ability to exchange with proteins in the preformed corona. This exchange could also occur with proteins in the media. Thus, the net effect of the MMP-9 was a combination of the MMP-9 protease activity and also exchange. Time scales for the exchange varied depending on the nature that make up the protein corona (weakly vs strongly bound corona proteins). Mass spectrometry was used to probe the protein corona composition and supported the exchange and degradation model. Together, these results indicate that the mechanism of protease activity on AuNP coronas involves both rearrangement and exchange, followed by degradation.

The effect of matrix metalloproteinases and adhesion molecules on the prognosis in gastric carcinoma

Background: Matrix metalloproteinases (MMPs), adhesion molecules, and receptors are needed in the process of cancer growth. This study aims to investigate the role of MMP-3, MMP-10, MMP-11, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) in gastric cancer. Materials and Methods: Fifty-two gastric carcinoma cases who underwent gastrectomy were included in the study. The cases were inspected with regard to the presence/absence of lymph node and distant metastases. The selected paraffin blocks were immunohistochemically stained with MMP 3, MMP 10, MMP 11, ICAM (CD 54), and VCAM (CD 106). Results: Most of the cases (n: 50, 94%) with gastric cancer manifested cytoplasmic staining with MMP-11. MMP-10 expression was found in 45 of 52 (86.5%), MMP-3 staining was determined in 43 (82.6%) of gastric carcinomas. Different areas of differentiation within the tumor showed differences in MMP expression in terms of intensity and extensiveness. ICAM-1 expression was found in 47 of 52 (90.4%) cases and with VCAM-1, 46/52 (88.5%) of gastric cancers manifested positive staining. Its expression was found to be higher in the nonmetastatic group both in intestinal and diffuse types. VCAM-1 was diffusely expressed in gastric cancers. However, we did not determine a significant correlation concerning differentiation and lymph node and distant metastasis. Conclusions: MMP-3, MMP-10, MMP-11, ICAM-1, and VCAM-1 are expressed in gastric cancers and are thought to be involved in tumor development. Levels of expression that decrease in parallel to decreasing differentiation in areas of differentiation within tumor corroborate the idea that they are related to tumor progression. Due to its relationship with metastasis, ICAM-1 expression in noncohesive cells supports the idea that ICAM-1 is a significant factor involved in metastasis development in gastric cancers. Decreased MMP-10 and MMP-11 expression in metastases suggest that these enzymes may also be linked to the metastatic potential of gastric cancers.

Effect of matrix metalloproteinase 8 inhibitor and chlorhexidine on the cytotoxicity, oxidative stress and cytokine level of MDPC-23

ObjectiveThis study investigated the effect of matrix metalloproteinase-8 inhibitor I (MMP8-I) and chlorhexidine (CHX) on the viability, oxidative stress and cytokine secretion of MDPC-23 under short-term (30min) and long-term (3 days) culture. MethodsMDPC-23 were treated with MMP8-I or CHX for 30min, 1day, 2days and 3days to detect the proliferation by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay. In the following assays, MDPC-23 treated with 0.0003% CHX were referred to CHX group, treated with 8μM MMP8-I were MMP8-I group. Cells without additional treatment were regarded as control group. The cell cycle, reactive oxygen species (ROS) level, and apoptosis were assessed by flow cytometry. The cytokine level was quantified by enzyme-linked immunosorbent assay (ELISA). ResultsIn 30min, CHX at concentrations higher than 0.0003% dilution inhibited cell proliferation when compared to the control group. MMP8-I (0.1–500μM) showed no obvious cytotoxicity to MDPC-23, and MMP8-I (1000μM) inhibited cell proliferation. In 3 days, CHX (0.0003%) significantly inhibited cell growth, while MMP8-I (8μM) had no cytotoxicity. In the CHX group, the S phase population was decreased, and cellular ROS were increased in 3 days. In the MMP8-I group, the change of S phase population and cellular ROS was not significant compared with the control group. Cell apoptosis was not elevated in the MMP8-I group, while the apoptosis rate was increased in the CHX group both in 30min and 3 days. In 30min, CHX treatment significantly increased the secretion of interleukin (IL)-1β and IL-8, but slightly increased the secretion of IL-10, while MMP8-I caused no change in cytokines. In 3 days, CHX treatment significantly increased the secretion of IL-1β, IL-6, and IL-8, and inhibited the secretion of IL-10. MMP8-I treatment caused the increase of IL-6. SignificanceCompared with CHX, MMP8-I at low concentration did not result in cytotoxicity, oxidative stress, or the disorder of immune response.

Neutralization of matrix metalloproteinase-9 potentially enhances oncolytic efficacy of tanapox virus for melanoma therapy.

Matrix metalloproteinases (MMPs), which are involved in degradation of extracellular matrix, are critical regulators in tumor progression, metastasis and angiogenesis. Although induction of MMPs is frequently observed during the viral infection, the effect of MMPs on viral replication varies between viruses. MMP-9, for instance, is upregulated and promotes the replication of some viruses, such as herpes simplex virus, but inhibits the replication of others. Here, we report that infection with tanapox virus (TPV) promotes the expression of MMP-9 in the melanoma cells. In addition, we show that MMP-9 exerts an anti-viral effect on TPV replication and plays a protective role in TPV-infected melanoma cells in vitro. Moreover, the neutralization of MMP-9 in melanoma cells remarkably enhances the TPV infection and leads to a significant reduction in cell survival. In summary, this study contributes to understanding of the role played by MMP-9 in TPV infectivity and provides more insights for using TPV as cancer virotherapy in future studies. Since TPV has shown substantial oncolytic efficacy in promoting melanoma tumor regression in animal models, identifying mechanisms that suppress MMP-9 expression upon TPV infection can potentially improve its use as a melanoma virotherapy.

Effects of matrix metalloproteinases on the fate of mesenchymal stem cells.

Mesenchymal stem cells (MSCs) have great potential as a source of cells for cell-based therapy because of their ability for self-renewal and differentiation into functional cells. Moreover, matrix metalloproteinases (MMPs) have a critical role in the differentiation of MSCs into different lineages. MSCs also interact with exogenous MMPs at their surface, and regulate the pericellular localization of MMP activities. The fate of MSCs is regulated by specific MMPs associated with a key cell lineage. Recent reports suggest the integration of MMPs in the differentiation, angiogenesis, proliferation, and migration of MSCs. These interactions are not fully understood and warrant further investigation, especially for their application as therapeutic tools to treat different diseases. Therefore, overexpression of a single MMP or tissue-specific inhibitor of metalloproteinase in MSCs may promote transdifferentiation into a specific cell lineage, which can be used for the treatment of some diseases. In this review, we critically discuss the identification of various MMPs and the signaling pathways that affect the differentiation, migration, angiogenesis, and proliferation of MSCs.

Effects of Matrix Metalloproteinase on Tumour Growth and Morphology via Haptotaxis

A tumour invasion model has been developed to examine the influence of diffusible matrix metalloproteinases (MMPs) and the mediated proteolysis of non-diffusible, membrane type MMPs (MT-MMPs) on tumour growth and morphology via haptotaxis. Our results are the first to explore the influence of localized degradation of extracellular matrix (ECM) by MT-MMPs on the morphology of tumours growing in nutrient-rich and nutrient-poor microenvironments. Two-dimensional numerical simulation, using a level-set-based tumour host interface-capturing method, reveals that haptotaxis due to ECM degradation by MMP causes greater instability than with ECM degradation by MT-MMP in low-nutrient environments, even at low proliferation rates; whereas the resulting morphologies are similar for high apoptosis rates. Our simulation results show that while haptotaxis leads to completely different tumour growth rates and morphologies depending on proliferation and apoptosis rates in low-nutrient environment, there are no significant variations when we compare the haptotaxis due to ECM degradation by MMP and MT-MMP, except for low proliferation rates. Focusing on the differences between MMP and MT-MMP mediated effects; our study has important implications in MMP-target validation and MMP-inhibitor-drug development for anti-cancer clinical trials.

Effects of Matrix Metalloproteinases on the Performance of Platelet Fibrin Gel Spiked With Cardiac Stem Cells in Heart Repair: Effects of MMPs on Cell-Gel in Heart Repair

Effects of Matrix Metalloproteinases on the Performance of Platelet Fibrin Gel Spiked With Cardiac Stem Cells in Heart Repair: Effects of MMPs on Cell-Gel in Heart Repair

Immunohistochemical localisation and effect of matrix metalloproteinases and their inhibitors on canine spontaneous periodontitis

Periodontitis is commonly observed in dogs. In human medicine, it is well documented that matrix metalloproteinases (MMPs) are involved in the destruction of the periodontium. Therefore, the aim of this...

Corrigendum to “Effects of matrix metalloproteinase 13 on vascular smooth muscle cells migration via Akt–ERK dependent pathway” [Tissue Cell 47 (1) (2015) 115–121

Abstract Migration of vascular smooth muscle cells (VSMCs) is an early event of atherosclerosis, which is mediated mainly by matrix metalloproteinase (MMP) 2 and 9. Because MMP13 is associated with tumor cells migration, we hypothesized that MMP13 participates in VSMC migration induced by certain stimuli such as platelet-derived growth factor (PDGF) and angiotensin II (Ang II). We found that the mRNA level of MMP13 in rat aortic smooth muscle cells (RAoSMCs) was increased by both PDGF and Ang II. We observed the significant decrease of migration in PDGF- or Ang II-treated RAoSMCs by MMP13 specific inhibitor treatment. Silencing of MMP13 by a specific small interfering RNA (siRNA) significantly decreased expression of the active form of MMP13, which is followed by the decreased migration of PDGF- or Ang II-treated RAoSMCs. Interestingly, we observed synergistic inhibitory effects on migration by treatment with MMP2 and 13 or MMP9 and 13 inhibitors compared with that in single treatments. Moreover, we found that cordycepin, a known inhibitor of VSMC migration, caused significant downregulation of MMP2, 9, and 13 expression in PDGF-treated RAoSMCs. We further show that the expression level of MMP13 was significantly decreased by the treatment of Akt or ERK specific inhibitor in PDGF-treated RAoSMCs. Together, our data strongly suggest that MMP13 involves VSMCs migration via an Akt and ERK-dependent regulation.

Matrix metalloproteinases and hypertrophic cardiomyopathy

Prognosis of patients with hypertrophic cardiomyopathy (HCMP) to a great extent is determined by clinical variant of the disease. As the system of matrix metalloproteinases (MMPs) plays an important role in development and progression of the processes of fibroformation and tissue remodeling polymorphisms of modifier genes regulating its components can influence clinical course of HCMP. Among possible markers of prognostication of the course of cardiovascular diseases the role of MMPs and their tissue inhibitors has been discussed. With the aim of studying effects of MMPs on the course of HCMP we conducted this investigation in which we included 58 patients and a group of healthy volunteers (control group) with comparable sex and age. In all participants (n=112) we determined polymorphism of MMP-3 - rs3025058 and markers of fibroformation (MMP-3, TIMP-1, TIMP-2, and collagen IV). We found that unfavorable allele variant MMP-3 1171 was associated with hypertrophy of interventricular septum. We also established that levels of TIMP-1 in the group of patients with HCMP were significantly lowered in comparison with those in control group. Concentration of marker MMP-3 was elevated in the group of patients with variant "atrial fibrillation" compared with groups of stable course and progressing course. We revealed medium degree reverse correlation between MMP-3 marker and thickness of left ventricular posterior wall and direct correlation of this parameter with coefficient of asymmetry. Polymorphism MMP-3 - 1171 produced an impact on the level of TIMP-1 marker. The data obtained by us confirm effect of the system of MMPs on formation of hypertrophic remodeling of the heart in HCMP.

Hypoxia induces connexin 43 dysregulation by modulating matrix metalloproteinases via MAPK signaling

Connexin 43 (Cx43) is a major structural protein found in the gap junctions of the ventricular myocardium and a major determinant of its electrical properties. The effects of matrix metalloproteinases (MMPs), the mitogen-activated protein kinase (MAPK) signaling pathway, transcription factor NF-kB, and activator protein-1 (AP-1)/c-Jun on the regulation of Cx43 gene expression in H9c2 cardiomyocytes were assessed. The MAPK signaling pathway (MEK/ERK1/2 and PI3K) and transcription factors NF-kB and AP-1/c-Jun were inhibited, then Cx43 expression was assessed using Western blot analysis, and MMP-9 activity was assessed using gelatin zymography. Hypoxia decreased the Cx43 protein level by approximately 30–50 %. Doxycycline (10 μg/mL), an inhibitor of MMP, markedly attenuated the hypoxia-induced downregulation of Cx43 protein expression at 6 h. The hypoxia-induced decrease in Cx43 protein expression was significantly reversed by U0126 (10 μM), a MEK/ERK1/2 inhibitor, at 6 and 12 h; LY294002 (30 μM), a PI3K inhibitor, downregulated Cx43 expression. Hypoxia-induced MMP-9 activation was inhibited by treatment with LY294002, U0126, and, most especially, U0126. JSH-23 (30 μM), an NF-kB inhibitor, and SP600125 (10 μM), an AP-1/c-Jun inhibitor, attenuated the loss of Cx43. These results suggest that MAPK signaling and the activities NF-kB and MMPs play an important roles in the regulation of Cx43 expression.

Bovine Respiratory Syncytial Virus and Histophilus somni Interaction at the Alveolar Barrier

Our previous studies showed that Histophilus somni and bovine respiratory syncytial virus (BRSV) act synergistically in vivo to cause more severe bovine respiratory disease than either agent alone causes. Since H. somni surface and secreted immunoglobulin binding protein A (IbpA) causes retraction of bovine alveolar type 2 (BAT2) cells and invasion between BAT2 cells in vitro, we investigated mechanisms of BRSV-plus-H. somni infection at the alveolar barrier. BRSV treatment of BAT2 cells prior to treatment with IbpA-rich H. somni concentrated culture supernatant (CCS) resulted in increased BAT2 cell rounding and retraction compared to those with either treatment alone. This mimicked the increased alveolar cell thickening in calves experimentally infected with BRSV followed by H. somni compared to that in calves infected with BRSV or H. somni alone. BRSV-plus-H. somni CCS treatment of BAT2 cells also enhanced paracellular migration. The effect of matrix metalloproteinases (MMPs) was investigated as well because microarray analysis revealed that treatment with BRSV plus H. somni synergistically upregulated BAT2 cell expression of mmp1 and mmp3 compared to that in cells treated with either agent alone. Enzyme-linked immunosorbent assay (ELISA) confirmed that MMP1 and MMP3 protein levels were similarly upregulated. In collagen I and collagen IV (targets for MMP1 and MMP3, respectively) substrate zymography, digestion was increased with supernatants from dually treated BAT2 cells compared with those from singly treated cells. Enhanced breakdown of collagen IV in the basal lamina and of fibrillar collagen I in the adjacent interstitium in the dual infection may facilitate dissemination of H. somni infection.