Role of nuclear factor-kappa B activation in metalloproteinase-1, -3, and -9 secretion by human macrophages in vitro and rabbit foam cells produced in vivo

Suppression of cerebral aneurysm formation in rats by a tumor necrosis factor-α inhibitor

OBJECT

Although cerebral aneurysmal subarachnoid hemorrhage is a devastating disease for humans, effective medical treatments have not yet been established. Recent reports have shown that regression of some inflammatory-related mediators has protective effects in experimental cerebral aneurysm models. This study corroborated the effectiveness of tumor necrosis factor-α (TNF-α) inhibitor for experimentally induced cerebral aneurysms in rats.

METHODS

Five-week-old male rats were prepared for induction of cerebral aneurysms and divided into 3 groups, 2 groups administered different concentrations of a TNF-α inhibitor (etanercept), and 1 control group. One month after aneurysm induction, 7-T MRI was performed. The TNF-α inhibitor groups received subcutaneous injection of 25 μg or 2.5 μg of etanercept, and the control group received subcutaneous injection of normal saline every week. The TNF-α inhibitor administrations were started at 1 month after aneurysm induction to evaluate its suppressive effects on preexisting cerebral aneurysms. Arterial circles of Willis were obtained and evaluated 3 months after aneurysm induction.

RESULTS

Rats administered a TNF-α inhibitor experienced significant increases in media thickness and reductions in aneurysmal size compared with the control group. Immunohistochemical staining showed that treatment with a TNF-α inhibitor suppressed matrix metalloproteinase (MMP)-9 and inducible nitric oxide synthase (iNOS) expression through the luminal surface of the endothelial cell layer, the media and the adventitia at the site of aneurysmal formation, and the anterior cerebral artery-olfactory artery bifurcation. Quantitative polymerase chain reaction also showed suppression of MMP-9 and iNOS by TNF-α inhibitor administration.

CONCLUSIONS

Therapeutic administration of a TNF-α inhibitor significantly reduced the formation of aneurysms in rats. These data also suggest that TNF-α suppression reduced some inflammatory-related mediators that are in the downstream pathway of nuclear factor-κB.

A novel synthetic oleanane triterpenoid suppresses adhesion, migration, and invasion of highly metastatic melanoma cells by modulating gelatinase signaling axis

A methyl derivative natural triterpenoid amooranin (methyl-25-hydroxy-3-oxoolean-12-en-28-oate, AMR-Me) has been found to possess antiproliferative, proapoptotic, and antiinflammatory effects against established tumor cells. Large-scale synthesis of pure AMR-Me has eliminated the need of the natural phytochemical for further development of AMR-Me as an anticancer drug. Metastatic melanoma is a fatal form of cutaneous malignancy with poor prognosis and limited therapeutic options. It was hypothesized that antitumor pharmacological effect of AMR-Me could be linked to AMR-Me-mediated suppression of the metastatic potential of B16F10 murine melanoma. AMR-Me was assessed for its antimetastatic efficacy by cell adhesion, migration, and invasion assays in B16F10 cells. The signaling crosstalk was explored by gelatin zymography, Western blot, ELISA, and immunocytochemistry. The results elicited that AMR-Me was successful in restricting the adhesion, migration, and invasion of highly metastatic cells. The antimetastatic potential of this compound may be attributed to the reduced expression of membrane type 1 metalloproteinase (MT1-MMP) and matrix metalloproteinases (MMP-2 and MMP-9). AMR-Me was found to downregulate vascular endothelial growth factor (VEGF)/phosphorylated forms of focal adhesion kinase (pFAK397 )/Jun N-terminus kinase (pJNK)/extracellular signal-regulated kinase (pERK). This, in turn, inhibited transcription factor nuclear factor-κB (NF-κB) and transactivation of MMPs. Moreover, the activation of tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) might have influenced the downmodulation of MT1-MMP, MMP-2, and MMP-9. AMR-Me suppresses the activity of MT1-MMP, MMP-2, and MMP-9 by downregulation of VEGF/pFAK397 /pJNK/pERK/NF-κB and activation of TIMP-1 and TIMP-2 in metastatic melanoma cell line, B16F10. AMR-Me has the potential as an effective anticancer drug for metastatic melanoma which is a dismal disease.

A Network Approach to Wound Healing

OBJECTIVE

The wound healing process is well-understood on the cellular and tissue level; however, its complex molecular mechanisms are not yet uncovered in their entirety. Viewing wounds as perturbed molecular networks provides the tools for analyzing and optimizing the healing process. It helps to answer specific questions that lead to better understanding of the complexity of the process. What are the molecular pathways involved in wound healing? How do these pathways interact with each other during the different stages of wound healing? Is it possible to grasp the entire mechanism of regulatory interactions in the healing of a wound?

APPROACH

Networks are structures composed of nodes connected by links. A network describing the state of a cell taking part in the healing process may contain nodes representing genes, proteins, microRNAs, metabolites, and drug molecules. The links connecting nodes represent interactions such as binding, regulation, co-expression, chemical reaction, and others. Both nodes and links can be weighted by numbers related to molecular concentration and the intensity of intermolecular interactions. Proceeding from data and from molecular profiling experiments, different types of networks are built to characterize the stages of the healing process. Network nodes having a higher degree of connectivity and centrality usually play more important roles for the functioning of the system they describe.

RESULTS

We describe here the algorithms and software packages for building, manipulating and analyzing networks proceeding from information available from a literature or database search or directly extracted from experimental gene expression, metabolic, and proteomic data. Network analysis identifies genes/proteins most differentiated during the healing process, and their organization in functional pathways or modules, and their distribution into gene ontology categories of biological processes, molecular functions, and cellular localization. We provide an example of how network analysis can be used to reach better understanding of regulation of key wound healing mediators and microRNAs that regulate them.

INNOVATION

Univariate statistical tests widely used in clinical studies are not enough to improve understanding and optimize the processes of wound healing. Network methods of analysis of patients "omics" data, such as transcriptoms, proteomes, and others can provide a better insight into the healing processes and help in development of better treatment practices. We review several articles that are examples of this emergent approach to the study of wound healing.

CONCLUSION

Network analysis has the potential to considerably contribute to the better understanding of the molecular mechanisms of wound healing and to the discovery of means to control and optimize that process.

Suppression of experimental abdominal aortic aneurysms in the mice by treatment with Ginkgo biloba extract (EGb 761)

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba extract (EGb 761) is widely used to treat cerebral disorders. Clinical trials have demonstrated therapeutic benefits of EGb 761 in various vascular diseases. Because the potential pathophysiological mechanisms appear similar to those involved in aneurysmal degeneration, we postulated that EGb 761 might affect the development and progression of experimental abdominal aortic aneurysm (AAA). This study was aimed to investigate whether EGb 761 influences the development of experimental AAAs, and to explore the underlying mechanisms.

MATERIAL AND METHODS

C57/BL6 mice underwent abluminal application of CaCl2 to the abdominal aorta followed by gavages with either 200mg/kg EGb 761 per day or vehicle. Six weeks after AAA induction, aortic tissue was excised for further examinations.

RESULTS

EGb 761 treatment reduced the aneurysm size compared with vehicle-treated controls. EGb 761 had no effect on hemodynamics or macrophage infiltration in the aortic wall. However, nuclear factor κB protein levels were decreased in the aortas of EGb 761 treated animals. The increased ROS production, SOD and CAT activities, and mRNA expression of p47phox nicotinamide adenine dinucleotide phosphate oxidase were attenuated by EGb 761 treatment. Moreover, administration of EGb 761 preserved the destruction of the wavy morphology of the elastin during AAA formation. Zymographic activity of matrix metalloproteinase (MMP)-9 and MMP-2 was lowered in EGb 761 treated mice.

CONCLUSIONS

These results suggest that treatment with EGb 761 in mice prevented the development of CaCl2-induced AAA. The possible mechanisms include decreased oxidative damage and inflammation, preservation of aortic wall architecture, and altered MMPs activities.

A major role for RCAN1 in atherosclerosis progression

Atherosclerosis is a complex inflammatory disease involving extensive vascular vessel remodelling and migration of vascular cells. As RCAN1 is implicated in cell migration, we investigated its contribution to atherosclerosis. We show RCAN1 induction in atherosclerotic human and mouse tissues. Rcan1 was expressed in lesional macrophages, endothelial cells and vascular smooth muscle cells and was induced by treatment of these cells with oxidized LDLs (oxLDLs). Rcan1 regulates CD36 expression and its genetic inactivation reduced atherosclerosis extension and severity in Apoe^−/− mice. This effect was mechanistically linked to diminished oxLDL uptake, resistance to oxLDL-mediated inhibition of macrophage migration and increased lesional IL-10 and mannose receptor expression. Moreover, Apoe^−/−Rcan1^−/− macrophages expressed higher-than-Apoe^−/− levels of anti-inflammatory markers. We previously showed that Rcan1 mediates aneurysm development and that its expression is not required in haematopoietic cells for this process. However, transplantation of Apoe^−/−Rcan1^−/− bone-marrow (BM) cells into Apoe^−/− recipients confers atherosclerosis resistance. Our data define a major role for haematopoietic Rcan1 in atherosclerosis and suggest that therapies aimed at inhibiting RCAN1 expression or function might significantly reduce atherosclerosis burden.

Hypercholesterolemia boosts joint destruction in chronic arthritis. An experimental model aggravated by foam macrophage infiltration

Objective

The aim of this study was to determine whether hypercholesterolemia increases articular damage in a rabbit model of chronic arthritis.

Methods

Hypercholesterolemia was induced in 18 rabbits by administrating a high-fat diet (HFD). Fifteen rabbits were fed normal chow as controls. Chronic antigen-induced arthritis (AIA) was induced in half of the HFD and control rabbits, previously immunized, by intra-articular injections of ovalbumin. After sacrifice, lipid and systemic inflammation markers were analyzed in blood serum. Synovium was analyzed by Krenn score, multinucleated cell counting, immunohistochemistry of RAM11 and CD31, and TNF-α and macrophage chemoattractant protein-1 (MCP-1) gene expression. Active bone resorption was assessed by protein expression of receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG) and quantification of cathepsin K, contact surface and the invasive area of pannus into bone.

Results

Rabbits receiving the HFD showed higher total serum cholesterol, HDL, triglycerides and CRP levels than rabbits fed a normal diet. Synovitis score was increased in HFD, and particularly in AIA and AIA + HFD groups. AIA + HFD synovium was characterized by a massive infiltration of RAM11+ cells, higher presence of multinucleated foam cells and bigger vascularization than AIA. Cathepsin K+ osteoclasts and the contact surface of bone resorbing pannus were also increased in rabbits with AIA + HFD compared with AIA alone. Synovial TNF-α and MCP-1 gene expression was increased in AIA and HFD rabbits compared with healthy animals. RANKL protein expression in AIA and AIA + HFD groups was higher compared with either HFD or normal groups.

Conclusions

This experimental model demonstrates that hypercholesterolemia increments joint tissue damage in chronic arthritis, with foam macrophages being key players in this process.

Exploration of the mechanisms by which 3,4-benzopyrene promotes angiotensin II-induced abdominal aortic aneurysm formation in mice

OBJECTIVE

This study examined the influence of 3,4-benzopyrene (BaP), a compound found in cigarette smoke, on the formation of angiotensin II (Ang II)-induced abdominal aortic aneurysm (AAA) formation in mice and the underlying mechanisms.

METHODS

C57/B6n mice were divided into four groups. The control group received a weekly intraperitoneal injection of medium-chain triglycerides. The Ang II group received a daily Ang II infusion (0.72 mg/kg) and a weekly intraperitoneal injection of medium-chain triglycerides. The Ang II/BaP group received a daily Ang II infusion (0.72 mg/kg) and a weekly intraperitoneal BaP injection (10 mg/kg, dissolved in medium-chain triglycerides). The BaP group received a weekly intraperitoneal BaP injection (10 mg/kg). After 5 weeks, abdominal aortic diameter was determined. Aortic tissues underwent hematoxylin and eosin, Masson, and immunochemistry staining for evaluation of vascular wall structure, collagen, macrophage infiltration, matrix metalloproteinases (MMPs), and apoptosis.

RESULTS

The Ang II infusion and BaP injection induced AAAs in 41.67% of mice vs 25% in the Ang II group (P < .05). The average aortic diameter increased in the Ang II/BaP group compared with the Ang II group (1.40 ± 0.25 vs 1.2 ± 0.23 mm; P < .05). Average aortic muscular cell apoptosis was higher in the Ang II/BaP group (31% ± 12%) than in the Ang II (19% ± 5%; P < .05) or BaP groups (23% ± 4%; P < .05). Aortic macrophage infiltration and expression of MMP-2, MMP-9, MMP-12, and nuclear factor-κB increased (0.56 ± 0.12, 0.47 ± 0.13, 0.49 ± 0.14, 0.49 ± 0.11, and 0.42 ± 0.12, respectively) in the Ang II/BaP group compared with the Ang II group (0.27 ± 0.08, 0.25 ± 0.06, 0.24 ± 0.09, 0.24 ± 0.09, and 0.23 ± 0.06, respectively; P < .05 for all).

CONCLUSIONS

BaP promotes Ang II-induced AAA formation in mice via elevating infiltration of macrophages, activating nuclear factor-κB, upregulating the expression of MMP-2, MMP-9, and MMP-12, and increasing the apoptosis of vascular muscle cells in its synergistic effect with Ang II in aortic wall.

NFATc3 promotes Ca(2+) -dependent MMP3 expression in astroglial cells

Increase in intracellular calcium ([Ca(2+) ]i ) is a key mediator of astrocyte signaling, important for activation of the calcineurin (CN)/nuclear factor of activated T cells (NFAT) pathway, a central mediator of inflammatory events. We analyzed the expression of matrix metalloproteinase 3 (Mmp3) in response to increases in [Ca(2+) ]i and the role of the CN/NFAT pathway in this regulation. Astrocyte Mmp3 expression was induced by overexpression of a constitutively active form of NFATc3, whereas other MMPs and tissue inhibitor of metalloproteinases (TIMP) were unaffected. Mmp3 mRNA and protein expression was also induced by calcium ionophore (Io) and 2'(3')-O-(4-benzoylbenzoyl) adenosine 5'-triphosphate (Bz-ATP) and Mmp3 upregulation was prevented by the CN inhibitor cyclosporin A (CsA). Ca(2+) -dependent astrocyte Mmp3 expression was also inhibited by actinomycin D, and a Mmp3 promoter luciferase reporter was efficiently activated by increased [Ca(2+) ]i , indicating regulation at the transcriptional level. Furthermore, Ca(2+) /CN/NFAT dependent Mmp3 expression was confirmed in pure astrocyte cultures derived from neural stem cells (Ast-NSC), demonstrating that the induced Mmp3 expression occurs in astrocytes, and not microglial cells. In an in vivo stab-wound model of brain injury, MMP3 expression was detected in NFATc3-positive scar-forming astrocytes. Because [Ca(2+) ]i increase is an early event in most brain injuries, these data support an important role for Ca(2+) /CN/NFAT-induced astrocyte MMP3 expression in the early neuroinflammatory response. Understanding the molecular pathways involved in this regulation could provide novel therapeutic targets and approaches to promoting recovery of the injured brain.

The expression and regulation of matrix metalloproteinase-3 is critically modulated by Porphyromonas gingivalis lipopolysaccharide with heterogeneous lipid A structures in human gingival fibroblasts

Background

Porphyromonas gingivalis lipopolysaccharide (LPS) is a crucial virulence factor strongly associated with chronic periodontitis which is the primary cause of tooth loss in adults. It exhibits remarkable heterogeneity containing tetra-(LPS_1435/1449) and penta-(LPS₁₆₉₀) acylated lipid A structures. Human gingival fibroblasts (HGFs) as the main resident cells of human gingiva play a key role in regulating matrix metalloproteinases (MMPs) and contribute to periodontal homeostasis. This study investigated the expression and regulation of MMPs1-3 and tissue inhibitors of MMP-1 (TIMP-1) in HGFs in response to P. gingivalis LPS_1435/1449 and LPS₁₆₉₀ and hexa-acylated E. coli LPS as a reference. The expression of MMPs 1–3 and TIMP-1 was evaluated by real-time PCR and ELISA.

Results

The MMP-3 mRNA and protein were highly upregulated in P. gingivalis LPS₁₆₉₀- and E. coli LPS-treated cells, whereas no induction was observed in P. gingivalis LPS_1435/1449-treated cells. On the contrary, the expression of MMP-1 and −2 was not significantly affected by P. gingivalis LPS lipid A heterogeneity. The TIMP-1 mRNA was upregulated in P. gingivalis LPS_1435/1449- and E. coli LPS-treated cells. Next, signal transduction pathways involved in P. gingivalis LPS-induced expression of MMP-3 were examined by blocking assays. Blockage of p38 MAPK and ERK significantly inhibited P. gingivalis LPS₁₆₉₀-induced MMP-3 expression in HGFs.

Conclusion

The present findings suggest that the heterogeneous lipid A structures of P. gingivalis LPS differentially modulate the expression of MMP-3 in HGFs, which may play a role in periodontal pathogenesis.

[Evaluation for antithrombotic agents by a thrombotic model in animals]

To investigate cerebral infarction and intracranial hemorrhage (ICH) in relation to antithrombotic agents, we established an animal stroke model induced by using a combination of a photosensitive dye and local green photoillumination. Microplasmin (μPli), a derivative of plasmin lacking the five "kringle" domains, was administered in this model, and its effect was studied using magnetic resonance imaging. μPli treatment reduced cerebral damage 24 h after middle cerebral artery occlusion; it also reduced the expansion of the positive area on perfusion-weighted images between 1 and 24 h and the degree of neurological deficits. Tissue-type plasminogen activator (t-PA), a serine proteinase that converts plasminogen to plasmin, has been approved for treating acute ischemic stroke, but delayed treatment is associated with increased risk of ICH. Plasmin participates in the degradation of fibrin, causing clot lysis, and of various extracellular matrix proteins, either directly or via the activation of matrix metalloproteinases (MMPs). In this study, we observed that MMP-3 is relatively important in the enhanced risk of ICH induced by delayed t-PA treatment for ischemic stroke. In particular, the binding of t-PA with low-density lipoprotein receptor-related protein (LRP) results in the release of MMP-3 by endothelial cells. LRP production is upregulated in endothelial cells exposed to ischemia, and elevated LRP levels have been implicated in the increased ICH risk associated with delayed t-PA treatment. This implies that the t-PA/LRP/MMP-3 pathway may be a suitable target for developing strategies to improve the therapeutic efficacy of t-PA in acute ischemic stroke.

Classical macrophage activation up-regulates several matrix metalloproteinases through mitogen activated protein kinases and nuclear factor-κB

Remodelling of the extracellular matrix (ECM) and cell surface by matrix metalloproteinases (MMPs) is an important function of monocytes and macrophages. Recent work has emphasised the diverse roles of classically and alternatively activated macrophages but the consequent regulation of MMPs and their inhibitors has not been studied comprehensively. Classical activation of macrophages derived in vitro from un-fractionated CD16^+/− or negatively-selected CD16⁻ macrophages up-regulated MMP-1, -3, -7, -10, -12, -14 and -25 and decreased TIMP-3 steady-state mRNA levels. Bacterial lipopolysaccharide, IL-1 and TNFα were more effective than interferonγ except for the effects on MMP-25, and TIMP-3. By contrast, alternative activation decreased MMP-2, -8 and -19 but increased MMP -11, -12, -25 and TIMP-3 steady-state mRNA levels. Up-regulation of MMPs during classical activation depended on mitogen activated protein kinases, phosphoinositide-3-kinase and inhibitor of κB kinase-2. Effects of interferonγ depended on janus kinase-2. Where investigated, similar effects were seen on protein concentrations and collagenase activity. Moreover, activity of MMP-1 and -10 co-localised with markers of classical activation in human atherosclerotic plaques in vivo. In conclusion, classical macrophage activation selectively up-regulates several MMPs in vitro and in vivo and down-regulates TIMP-3, whereas alternative activation up-regulates a distinct group of MMPs and TIMP-3. The signalling pathways defined here suggest targets for selective modulation of MMP activity.

Quercetin, a flavonoid with anti-inflammatory activity, suppresses the development of abdominal aortic aneurysms in mice

Inflammation has been implicated as a contributing factor in the development of abdominal aortic aneurysms (AAA). Quercetin, a natural flavonoid with anti-inflammatory properties, is known for its beneficial effects on vascular disease. In this study, we examined the effects of quercetin to inflammatory cell infiltration, subsequent expression of cytokines and activation of proteases on the expansion of experimental AAA. Aneurysms were induced by abluminal application of calcium chloride in C57/BL6 mice. Quercetin (60 mg/kg) was administered once daily by gavage beginning 2 weeks before AAA induction and continuing for 8 weeks. Mice treated with quercetin exhibited a 32.7% reduction in aortic size compared with vehicle-treated controls. Prevention of AAA was associated with preservation of medial structure, as well as a relative reduction in macrophage and CD3(+) T cell infiltration in aortic tissue, inflammatory cytokines release and nuclear factor κB activation. Quercetin also reduced the expression of matrix metalloproteinase (MMP)-2, MMP-9, cathepsin B, and cathepsin K in aortic tissue. In addition, quercetin treatment increased tissue inhibitors of metalloproteinases (TIMP)-1 gene expression. These data indicate that quercetin may be useful for the prevention and treatment of AAA via blocking the inflammatory response and inhibiting the proteases involved in the pathogenesis of this disease.

Matrix metalloproteinase inhibition therapy for vascular diseases

The matrix metalloproteinases (MMPs) are 23 secreted or cell surface proteases that act together and with other protease classes to turn over the extracellular matrix, cleave cell surface proteins and alter the function of many secreted bioactive molecules. In the vasculature MMPs influence the migration proliferation and apoptosis of vascular smooth muscle, endothelial cells and inflammatory cells, thereby affecting intima formation, atherosclerosis and aneurysms, as substantiated in clinical and mouse knockout and transgenic studies. Prominent counterbalancing roles for MMPs in tissue destruction and repair emerge from these experiments. Naturally occurring tissue inhibitors of MMPs (TIMPs), pleiotropic mediators such as tetracyclines, chemically-synthesised small molecular weight MMP inhibitors (MMPis) and inhibitory antibodies have all shown effects in animal models of vascular disease but only doxycycline has been evaluated extensively in patients. A limitation of broad specificity MMPis is that they prevent both matrix degradation and tissue repair functions of different MMPs. Hence MMPis with more restricted specificity have been developed and recent studies in models of atherosclerosis accurately replicate the phenotypes of the corresponding gene knockouts. This review documents the established actions of MMPs and their inhibitors in vascular pathologies and considers the prospects for translating these findings into new treatments.

Diverse patterns of cyclooxygenase-independent metalloproteinase gene regulation in human monocytes

BACKGROUND AND PURPOSE Matrix metalloproteinase (MMP) production from monocyte/macrophages is implicated in matrix remodelling and modulation of inflammation. However, knowledge of the patterns and mechanisms of gene regulation of MMPs and their endogenous tissue inhibitors (TIMPs) is fragmentary. MMP up-regulation may be a target for cyclooxygenase (COX) and prostaglandin (PG) receptor inhibition, but the extent and mechanisms of COX-independent MMP up-regulation are unclear. EXPERIMENTAL APPROACH We studied MMP mRNA expression and selected protein levels in human peripheral blood monocytes before and after adhesion, upon stimulation with bacterial lipopolysaccharide (LPS), PGE(2) or forskolin and after culturing with monocyte colony-stimulating factor on plastic or human fibronectin for up to 7 days. KEY RESULTS Monocyte adherence for 2 h transiently up-regulated COX-2, MMP-1, MMP-7 and MMP-10 mRNAs, and persistently up-regulated MMP-2, MMP-9, MMP-14 and MMP-19 mRNAs. LPS, PGE(2) or forskolin selectively increased MMP-1, MMP-9, MMP-10, MMP-12 and MMP-14 mRNAs. LPS increased PGE(2) production through COX but up-regulated MMP levels independently of COX. Differential dependence on inhibition of p42/44 and p38 mitogen-activated protein kinases, c-jun N-terminal kinase and inhibitor of κB kinase2 paralleled the diverse patterns of MMP stimulation by LPS. Differentiation on plastic increased mRNA levels of MMP-7, MMP-9, MMP-12 and MMP-14 and TIMP-2 and TIMP-3 independently of COX; fibronectin accelerated MMP but not TIMP up-regulation. CONCLUSIONS AND IMPLICATIONS Adhesion, LPS stimulation and maturation of human monocytes lead to selective, COX-independent MMP and TIMP gene regulation, which is a potential target for selective inhibition by signalling kinase inhibitors.

Cyclo(His-Pro) exerts anti-inflammatory effects by modulating NF-κB and Nrf2 signalling

Cyclo(His-Pro) is an endogenous cyclic dipeptide that exerts oxidative damage protection by selectively activating the transcription factor Nrf2 signalling pathway. Given the existence of a tight interplay of the Nrf2/NF-κB systems and that the pro-inflammatory response is governed by transcription factor NF-κB, here we sought to investigate whether and how cyclo(His-Pro) interferes with the cross-talk between the antioxidant Nrf2/heme oxygenase-1 and the pro-inflammatory NF-κB pathways. By knocking down the Nrf2 gene, we confirmed that cyclo(His-Pro) inhibits NF-κB nuclear accumulation induced by paraquat in rat pheochromocytoma PC12 cells via the Nrf2/heme oxygenase-1 pathway. The protection required functional heme oxygenase-1 activity, since zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, prevented NF-κB inhibition, and the presence of exogenous carbon monoxide and bilirubin afforded cytoprotection against paraquat-induced toxicity by preventing NF-κB activation. Cyclooxygenase-2 and matrix metalloproteinase 3, two gene products governed by NF-κB, were down-regulated by cyclo(His-Pro) and up-regulated in heme oxygenase-1 knock-down cells. We validated the general mechanism underlying the anti-inflammatory effects by treating PC12 and murine microglial BV2 cells with different pro-inflammatory agents. Finally, cyclo(His-Pro) reduced 12-otetradecanoylphorbol-13-acetate-induced oedema in mouse ear inflammation model. Results, by showing that cyclo(His-pro) suppresses the pro-inflammatory NF-κB signalling via the Nrf2-mediated heme oxygenase-1 activation, contribute to the understanding of essential cellular pathways and allow the proposal of cyclo(His-Pro) as an in vivo anti-inflammatory compound.

Suppression of oxLDL-induced MMP-9 and EMMPRIN expression by berberine via inhibition of NF-κB activation in human THP-1 macrophages

Upregulation of matrix metalloproteinases (MMPs) and extracellular matrix metalloproteinase inducer (EMMPRIN) by macrophages leads to atherosclerotic plaque rupture by degradation of the extracellular matrix. NF-κB activation regulates many key inflammatory genes linked to atherosclerosis. In the present study, the function of berberine, a natural extract from Rhizoma coptidis, on MMP-9 and EMMPRIN expression, the role of NF-κB activation in oxLDL-stimulated macrophages, and the possible mechanism in which NF-κB activation is involved were investigated. Berberine inhibited the expression of MMP-9 and EMMPRIN at both mRNA and protein levels. The phosphorylation of IκB-α and nuclear translocation of p65 protein were reduced by berberine, suggesting that NF-κB activation was inhibited by berberine in oxLDL-stimulated macrophages. Overall, berberine suppressed the expression of MMP-9 and EMMPRIN by at least reducing partly the activity of NF-κB in oxLDL-induced macrophages.

Mycobacterium tuberculosis-infected human monocytes down-regulate microglial MMP-2 secretion in CNS tuberculosis via TNFα, NFκB, p38 and caspase 8 dependent pathways

Tuberculosis (TB) of the central nervous system (CNS) is a deadly disease characterized by extensive tissue destruction, driven by molecules such as Matrix Metalloproteinase-2 (MMP-2) which targets CNS-specific substrates. In a simplified cellular model of CNS TB, we demonstrated that conditioned medium from Mycobacterium tuberculosis-infected primary human monocytes (CoMTb), but not direct infection, unexpectedly down-regulates constitutive microglial MMP-2 gene expression and secretion by 72.8% at 24 hours, sustained up to 96 hours (P < 0.01), dependent upon TNF-α. In human CNS TB brain biopsies but not controls the p38 pathway was activated in microglia/macrophages. Inhibition of the p38 MAP kinase pathway resulted in a 228% increase in MMP-2 secretion (P < 0.01). In contrast ERK MAP kinase inhibition further decreased MMP-2 secretion by 76.6% (P < 0.05). Inhibition of the NFκB pathway resulted in 301% higher MMP-2 secretion than CoMTb alone (P < 0.01). Caspase 8 restored MMP-2 secretion to basal levels. However, this caspase-dependent regulation of MMP-2 was independent of p38 and NFκB pathways; p38 phosphorylation was increased and p50/p65 NFκB nuclear trafficking unaffected by caspase 8 inhibition. In summary, suppression of microglial MMP-2 secretion by M.tb-infected monocyte-dependent networks paradoxically involves the pro-inflammatory mediators TNF-α, p38 MAP kinase and NFκB in addition to a novel caspase 8-dependent pathway.

Innate immunity and monocyte-macrophage activation in atherosclerosis

Innate inflammation is a hallmark of both experimental and human atherosclerosis. The predominant innate immune cell in the atherosclerotic plaque is the monocyte-macrophage. The behaviour of this cell type within the plaque is heterogeneous and depends on the recruitment of diverse monocyte subsets. Furthermore, the plaque microenvironment offers polarisation and activation signals which impact on phenotype. Microenvironmental signals are sensed through pattern recognition receptors, including toll-like and NOD-like receptors - the latter of which are components of the inflammasome - thus dictating macrophage behaviour and outcome in atherosclerosis. Recently cholesterol crystals and modified lipoproteins have been recognised as able to directly engage these pattern recognition receptors. The convergent role of such pathways in terms of macrophage activation is discussed in this review.

Role of the NF-κB transcription pathway in the haemozoin- and 15-HETE-mediated activation of matrix metalloproteinase-9 in human adherent monocytes

Haemozoin (HZ, malarial pigment) is a crystalline ferriprotoporphyrin IX polymer derived from undigested host haemoglobin haem, present in late stages of Plasmodium falciparum-parasitized RBCs and in residual bodies shed after schizogony. It was shown previously that phagocytosed HZ or HZ-containing trophozoites increased monocyte matrix metalloproteinase-9 (MMP-9) activity and enhanced production of MMP-9-related cytokines TNF and IL-1beta. Here we show that in human monocytes the HZ/trophozoite phagocytosis effects and their recapitulation by 15(S,R)-hydroxy-6,8,11,13-eicosatetraenoic acid (15-HETE), a potent lipoperoxidation derivative generated by HZ from arachidonic acid via haem catalysis, were mediated via activation of NF-κB transcription pathway. After phagocytosis of HZ/trophozoites or treatment with 15-HETE, the NF-κB complex migrated to the nuclear fraction while the inhibitory cytosolic IκBalpha protein was phosphorylated and degraded. All HZ/trophozoite/15-HETE effects on MMP-9 activity and TNF/IL-1beta production were abrogated by quercetin, artemisinin and parthenolide, inhibitors of IκBalpha phosphorylation and subsequent degradation, NF-κB nuclear translocation, and NF-κB-p65 binding to DNA respectively. In conclusion, enhanced activation of MMP-9, and release of pro-inflammatory cytokines TNF and IL-1beta, a triad of effects involved in malaria pathogenesis, elicited in human monocytes by trophozoite and HZ phagocytosis and recapitulated by 15-HETE, appear to be causally connected to persisting activation of the NF-κB system.

Differential effects of sulfated triterpene glycosides, holothurin A1, and 24-dehydroechinoside A, on antimetastasic activity via regulation of the MMP-9 signal pathway

Two sulfated triterpene glycosides, holothurin A(1) (HA(1)) and 24-dehydroechinoside A (DHEA), isolated from the sea cucumber Pearsonothuria graeffei, are of the holostane type with 18(20)-lactone and identical carbohydrate chains. DHEA has a side chain 23 (24)-double bond, while HA(1) has a hydroxyl group at C-21. In this study, we compared the effects of DHEA and HA(1) on metastasis in vitro and in vivo. The results show that HA(1) and DHEA treatment significantly suppressed adhesion of human hepatocellular liver carcinoma cells (HepG2) to both matrigel and human endothelial cells (ECV-304) and inhibited HepG2 cell migration and invasion in a dose-dependant manner. HA(1) and DHEA reduced tube formation of ECV-304 cells on the matrigel in vitro and attenuated neovascularization in the chick embryo using the chorioallantoic membrane (CAM) assay in vivo. Immunocytochemistry analyses revealed that both HA(1) and DHEA significantly decreased the expression of the matrix metallo-proteinase-9 (MMP-9) and increased the expression level of tissue inhibitor of metalloproteinase-1 (TIMP-1), an important regulator of MMP-9 activation. Western blot analyses demonstrated that HA(1) and DHEA remarkably abolished the expression of vascular endothelial growth factor (VEGF). The expression of nuclear factor-kappa B (NF-κB) was significantly decreased by HA(1), while DHEA treatment had no effect on the down regulation of NF-κB expression. These data suggest that both DHEA and HA(1) exert significant antimetastatic activities by inhibiting MMP-9 and VEGF expression. DHEA-induced antimetastasis was more potent than HA(1). In addition, only HA(1) treatment downregulated the expression level of NF-κB, suggesting that the antimetastatic activity of triterpene glycosides derived from P. graeffei can be either NF-κB-dependent or -independent, depending on their structure.

Culture of human breast cancer cell line (MDA-MB-231) on fibronectin-coated surface induces pro-matrix metalloproteinase-9 expression and activity

Interaction between cell surface integrin receptors with extracellular matrix (ECM) plays an important role in cell survival, proliferation, and migration including tumor development and invasion. Binding of ECM to integrins initiates intracellular signaling cascades, modulating expression and activity of different matrix metalloproteinases (MMPs) which is important in ECM degradation. The present study investigates fibronectin-integrin-mediated signaling and thereby modulation of MMPs expression and activity in human breast cancer cell line, MDA-MB-231. Culture of MDA-MB-231 cells on fibronectin (FN) induced expression and activity of pro-matrixmetalloproteinase-9 (MMP-9). Appreciable reduction of FN-induced pro-MMP-9 activity was observed in anti-α5 antibody treated cells. Inhibitor studies revealed that inhibitors of phosphatidyl inositiol-3-kinase (PI-3K), and nuclear factor kappa B (NF-κB) inhibited FN-induced pro-MMP-9 activity. FN increased tyrosine phosphorylation of focal adhesion kinase (FAK), integrin linked kinase (ILK), and PI-3K in MDA-MB-231 cells. FN-induced the transactivation of MMP-9 promoter by enhancing DNA binding activity of NF-κB and Sp1. Wound healing assay showed faster migration of MDA-MB-231cells grown on fibronectin-coated as surface as compared to control. Our findings indicated that culture of MDA-MB-231 on fibronectin perhaps send signals via fibronectin-integrin-mediated signaling pathways recruiting FAK, PI-3K, ILK, NF-κB, and modulate expression and activation of pro-MMP-9. These observations may enrich fundamental aspects of cancer biology especially role of α5β1 integrin in regulation of MMPs expression and activity.

Macrophages heterogeneity in atherosclerosis - implications for therapy

Atherosclerosis is a chronic inflammatory disease occurring within the artery wall and is an underlying cause of cardiovascular complications, including myocardial infarction, stroke and peripheral vascular disease. Its pathogenesis involves many immune cell types with a well accepted role for monocyte/macrophages. Cholesterol-loaded macrophages are a characteristic feature of plaques and are major players in all stages of plaque development. As well as modulating lipid metabolism, macrophages secrete inflammatory cytokines, chemokines and reactive oxygen and nitrogen species that drive pathogenesis. They also produce proteases and tissue factor that contribute to plaque rupture and thrombosis. Macrophages are however heterogeneous cells and when appropriately activated, they phagocytose cytotoxic lipoproteins, clear apoptotic bodies, secrete anti-inflammatory cytokines and synthesize matrix repair proteins that stabilize vulnerable plaques. Pharmacological modulation of macrophage activity therefore represents a potential therapeutic strategy for atherosclerosis. The aim of this review is to provide an overview of the current understanding of the different macrophage subsets and their monocyte precursors, and, the implications of these subsets for atherosclerosis. This will present a foundation for highlighting novel opportunities to exploit the heterogeneity of macrophages as important diagnostic and therapeutic targets for atherosclerosis and its associated diseases.

Sustained inflammation due to nuclear factor-kappa B activation in irradiated human arteries

OBJECTIVES

The aim of this study was to investigate gene expression networks related to cardiovascular disease in radiated human arteries.

BACKGROUND

Recent epidemiological studies have shown that radiotherapy is associated with cardiovascular disease years after treatment. However, the molecular mechanisms underlying late effects of radiation are poorly described.

METHODS

Arterial biopsies from radiated and nonradiated human conduit arteries, from the same patient, were simultaneously harvested during microvascular free tissue transfer for cancer-reconstruction in 13 patients, 4 to 500 weeks from radiation treatment. Radiated and nonradiated arteries were compared, with Affymetrix (Santa Clara, California) microarrays on a subset of the material to generate candidate genes. A Taqman (Applied Biosystems, Foster City, California) low-density array of 45 selected genes was designed for analysis of the whole material.

RESULTS

Thirteen genes were synchronously expressed in all patients (p = 0.0015), including CCL8, CCL3, CXCL2, DUSP5, FGFR2, HMOX1, HOXA9, IL-6, MMP-1, PTX3, RDH10, SOD2, and TNFAIP3. A majority of differentially regulated genes related to the nuclear factor-kappa B (NF-kappaB) signaling pathway and were dysregulated even years after radiation. The NF-kappaB activation was confirmed by immunohistochemistry and immunofluorescence.

CONCLUSIONS

In the present study, we found sustained inflammation due to NF-kappaB activation in human radiated arteries. The results are supported by previous in vitro findings suggesting that deoxyribonucleic acid injury, after radiation, activates NF-kappaB. We also suggest that HOXA9 might be involved in the regulation of NF-kappaB activation. The observed sustained inflammatory response can explain cardiovascular disease years after radiation.

Allele-specific regulation of matrix metalloproteinase-3 gene by transcription factor NFkappaB

Background

Matrix metalloproteinase-3 (MMP3) is implicated in the pathogenesis and progression of atherosclerotic lesions. Previous studies suggested that MMP3 expression is influenced by a polymorphism (known as the 5A/6A polymorphism) in the promoter of the MMP3 gene and that this polymorphism is located within a cis-element that interacts with the transcription factor NFκB. In the present study, we sought to investigate whether MMP3 and NFκB were co-localized in atherosclerotic lesions and whether NFκB had differential effects on the two alleles of the MMP3 5A/6A polymorphism.

Methodology/Principal Findings

Immunohistochemical examination showed that MMP3 and both the NFκB p50 and p65 subunits were expressed abundantly in macrophages in atherosclerotic lesions and that MMP3 expression was co-localized with p50 and p65. Chromatin immunoprecipitation experiments showed interaction of p50 and p65 with the MMP3 promoter in macrophages, with greater binding to the 5A allele than to the 6A allele. Reporter gene assays in transiently transfected macrophages showed that the 5A allele had greater transcriptional activity than the 6A allele, and that this allele-specific effect was augmented when the cells were treated with the NFκB activator lipopolysaccharides or co-transfected with p50 and/or p65 expressing plasmids, but was reduced when the cells were treated with the NFκB inhibitor 6-Amino-4-(4-phenoxyphenylethylamino)-quinazoline or transfected with a dominant negative mutant of IkB kinase-β.

Conclusion

These results corroborate an effect of the 5A/6A polymorphism on MMP3 transcription and indicate that NFκB has differential effects on the 5A and 6A alleles.

Salsalate may have broad utility in the prevention and treatment of vascular disorders and the metabolic syndrome

In the high proportion of vascular disorders associated with excessive oxidative stress and production of pro-inflammatory cytokines, activation of NF-kappaB plays a key pathogenic role. Thus, there is considerable evidence that NF-kappaB is a mediator of atherogenesis, plaque destabilization, ischemia-reperfusion damage, cardiac remodeling, atrial fibrillation, and aneurysm formation and rupture; some studies suggest that it may also play a role in the microvascular complications of diabetes. I kappaB kinase-beta (IKK beta) is the upstream kinase that appears to be primarily responsible for NF-kappaB activation in these disorders; moreover, chronic IKK beta activation plays a prominent role in induction of insulin resistance in the metabolic syndrome. Salicylate inhibits IKK beta in concentrations that are achievable with dose schedules traditionally used in treating rheumatoid arthritis (3-4.5 g daily); indeed, this is likely to be the mechanism responsible for salicylate's utility in this disorder. Salicylate, unlike aspirin, is only a very weak, reversible inhibitor of cyclooxygenase in clinical doses, and thus is not associated with the potentially dangerous side effects seen with NSAIDs; fully reversible ototoxicity, the dose-limiting side effect in salicylate therapy, can be avoided in most patients by dosage adjustment. Hence, it is proposed that salicylate may have practical utility in the prevention or management of a wide range of vascular disorders as well as of metabolic syndrome and diabetes; its efficacy in these regards would likely be complemented by effective antioxidant measures, which would lessen the stimulus to NF-kappaB activation while providing benefits independent of NF-kappaB activity. Salsalate, consisting of two salicylate molecules united by an ester bond, is a venerable drug that may be the best tolerated delivery vehicle for salicylate. Appropriate rodent studies should pave the way for clinical trials with salsalate in patients at vascular risk.

Tissue-type plasminogen activator (t-PA) induces stromelysin-1 (MMP-3) in endothelial cells through activation of lipoprotein receptor–related protein

Tissue-type plasminogen activator (t-PA) is approved for treatment of ischemic stroke patients, but it increases the risk of intracranial bleeding (ICB). Previously, we have shown in a mouse stroke model that stromelysin-1 (matrix metalloproteinase-3 [MMP-3]) induced in endothelial cells was critical for ICB induced by t-PA. In the present study, using bEnd.3 cells, a mouse brain–derived endothelial cell line, we showed that MMP-3 was induced by both ischemic stress and t-PA treatment. This induction by t-PA was prevented by inhibition either of low-density lipoprotein receptor–related protein (LRP) or of nuclear factor-κB activation. LRP was up-regulated by ischemic stress, both in bEnd.3 cells in vitro and in endothelial cells at the ischemic damage area in the mouse stroke model. Furthermore, inhibition of LRP suppressed both MMP-3 induction in endothelial cells and the increase in ICB by t-PA treatment after stroke. These findings indicate that t-PA deteriorates ICB via MMP-3 induction in endothelial cells, which is regulated through the LRP/nuclear factor-κB pathway.

Macrophage heterogeneity in atherosclerotic plaques

PURPOSE OF REVIEW

The varied behaviour of macrophages and foam cells during atherosclerosis and its clinical sequelae prompt the question whether all these activities can be the property of a single cell population.

RECENT FINDINGS

Subsets of monocytes with distinct patterns of surface markers and behaviours during inflammation have recently been characterized and shown to have complementary roles during progression of atherosclerosis. A variety of macrophage phenotypes derived from these monocyte subsets in response to mediators of innate and acquired immunity have also been found in plaques. Based on functional properties and genomic signatures, they may have different impacts on facets of plaque development, including fibrous cap and lipid core formation.

SUMMARY

Monocyte and macrophage phenotypic diversity is important in atherogenesis. More work is needed to define consistent marker sets for the different foam cell phenotypes in experimental animals and humans. Cell tracking studies are needed to establish their relationship with monocyte subtypes. In addition, genetic and pharmacological manipulation of phenotypes will be useful to define their functions and exploit the resulting therapeutic potential.

Cranberry proanthocyanidins inhibit MMP production and activity

Matrix metalloproteinases (MMPs) produced by resident and inflammatory cells in response to periodontopathogens play a major role in periodontal tissue destruction. Our aim was to investigate the effects of A-type cranberry proanthocyanidins (AC-PACs) on: (i) the production of various MMPs by human monocyte-derived macrophages stimulated with Aggregatibacter actinomycetemcomitans lipopolysaccharide (LPS), and (ii) the catalytic activity of recombinant MMP-1 and MMP-9. The effects of AC-PACs on the expression of 5 protein kinases and the activity of nuclear factor-kappa B (NF-kappaB) p65 in macrophages stimulated with LPS were also monitored. Our results indicated that AC-PACs inhibited the production of MMPs in a concentration-dependent manner. Furthermore, the catalytic activity of MMP-1 and MMP-9 was also inhibited. The inhibition of MMP production was associated with reduced phosphorylation of key intracellular kinases and the inhibition of NF-kappaB p65 activity. AC-PACs thus show potential for the development of novel host-modulating strategies to inhibit MMP-mediated tissue destruction during periodontitis.

Inhibitory effect of penta-acetyl geniposide on C6 glioma cells metastasis by inhibiting matrix metalloproteinase-2 expression involved in both the PI3K and ERK signaling pathways

Penta-acetyl geniposide [(Ac)(5)GP], an acetylated geniposide product from Gardenia fructus, has been known to have hepatoprotective properties and recent studies have revealed its anti-proliferative and apoptotic effect on C6 glioma cells. In this study, we first report the anti-metastastic effect of (Ac)(5)GP in the rat neuroblastoma line: C6 glioma cells. First (Ac)(5)GP exhibited an inhibitory effect on abilities of adhesion and motility by cell-matrix adhesion assay, wound healing assay and Boyden chamber assay. Second, the decreasing activity of matrix metalloproteinase-2 (MMP-2) was noted by gelatin zymography assay. Further analysis with semi-quantitative RT-PCR showed the mRNA levels of MMP-2 and membrane type I matrix metalloproteinase (MT1-MMP) were significantly reduced, while the tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) was elevated by (Ac)(5)GP treatment. Further (Ac)(5)GP also exerted an inhibitory effect on phosphoinositide 3-kinase (PI3K) protein expression, phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and inhibition of activation of transcription factor nuclear factor kappa B (NF-kappaB), c-Fos, c-Jun. These findings proved (Ac)(5)GP is highly likely to be a inhibiting cancer migration agent to be further developed in the future.

Treponema denticola lipooligosaccharide activates gingival fibroblasts and upregulates inflammatory mediator production

In response to bacterial challenges, fibroblasts, a major constituent of gingival connective tissue, can produce immunoregulatory cytokines and proteolytic enzymes that may contribute to tissue destruction and the progression of periodontitis, a chronic inflammatory disease affecting tooth-supporting tissues, including alveolar bone. The spirochete Treponema denticola is a major etiological agent of periodontitis and can invade oral tissues. The aim of the present study was to investigate the inflammatory response of gingival fibroblasts to T. denticola lipooligosaccharide (LOS). T. denticola LOS induced significant production of various inflammatory mediators by fibroblasts, including interleukin-6, interleukin-8, monocyte chemoattractant protein 1, nitric oxide, and prostaglandin E(2). In addition, the secretion of matrix metalloproteinase 3, an enzyme active on basement membrane components, was also significantly increased. The response of fibroblasts was dose-dependent and much stronger following a 24 h stimulation period. The expression and/or phosphorylation state of several signaling proteins, including Fos, MKK1, MKK2, MKK3/6, NF-kappaB p50, and NF-kappaB p65, was enhanced following stimulation of fibroblasts with T. denticola LOS. In summary, T. denticola LOS induced an inflammatory response in gingival fibroblasts and may thus contribute to the immunopathogenesis of periodontitis and the progression of the disease.

Low tissue inhibitor of metalloproteinases 3 and high matrix metalloproteinase 14 levels defines a subpopulation of highly invasive foam-cell macrophages

OBJECTIVE

An excess of metalloproteinases (MMPs) over tissue inhibitors of metalloproteinases (TIMPs) may favor atherosclerotic plaque rupture. We compared TIMP levels in nonfoamy and foam-cell macrophages (FCM) generated in vivo.

METHODS AND RESULTS

In vivo generated rabbit FCM exhibited 84% reduced TIMP-3 protein compared to nonfoamy macrophages, and immunocytochemistry revealed a TIMP-3 negative subset (28%). Strikingly, only TIMP-3 negative FCM invaded a synthetic basement membrane, and invasion was inhibited by exogenous TIMP-3. TIMP-3 negative FCM also had increased proliferation and apoptosis rates compared to TIMP-3 positive cells, which were retarded by exogenous TIMP-3; this also reduced gelatinolytic activity. TIMP-3 negative FCM were found at the base of advanced rabbit plaques and in the rupture-prone shoulders of human plaques. To explain the actions of low TIMP-3 we observed a 26-fold increase in MT1-MMP (MMP-14) protein in FCM. Adding an MT1-MMP neutralizing antibody reduced foam-cell invasion, apoptosis, and gelatinolytic activity. Furthermore, MT1-MMP overexpressing and TIMP-3 negative FCM were found at the same locations in atherosclerotic plaques.

CONCLUSIONS

These results demonstrate that TIMP-3 is downregulated in a distinct subpopulation of FCM which have increased MMP-14. These cells are highly invasive and have increased proliferation and apoptosis, all properties expected to destabilise atherosclerotic plaques.

Matrix metalloproteinase-3 induction in rat brain astrocytes: focus on the role of two AP-1 elements

Many brain cells secrete MMPs (matrix metalloproteinases), and increased or misregulated MMP levels are found in neurodegenerative disorders. Here we report that MMP-3 transcription and protein secretion were increased in rat brain astrocytes stimulated with lipopolysaccharide, gangliosides or interferon-gamma. Sequential deletion of the MMP-3 promoter revealed that sequences between -0.5 kb and the start codon were crucial for the transcriptional induction of MMP-3. In addition, experiments using pharmacological inhibitors of individual mitogen-activated protein kinases revealed that MMP-3 induction and promoter activity involved Jun N-terminal kinase, a representative upstream signal of AP-1 (activator protein-1). Sequence analyses of the region of the MMP-3 promoter 500 bp from the start codon indicated the presence of three AP-1 binding sequences. Among them, electrophoretic-mobility-shift assays as well as site-directed mutagenesis of individual AP-1 sequences revealed that distal and middle, but not proximal, sequences largely mediated its induction. Together, these results indicate that AP-1 could control MMP-3 induction in brain astrocytes and that its regulation through specific AP-1 elements could be exploited in the treatment of brain pathologies in which increased expression of MMP-3 plays crucial roles.

Metalloproteinases and vulnerable atherosclerotic plaques

Plaque rupture is the main cause of myocardial infarctions and strokes. Ruptured plaques have thin, highly inflamed, and collagen-poor fibrous caps that contain elevated levels of proteases, including metalloproteinases (MMPs), which might weaken plaque caps and promote rupture. On the other hand, MMPs facilitate migration and proliferation vascular smooth muscle cells, which should promote fibrous cap stability. Given the dual effects of MMPs, therapies should selectively target harmful MMPs or the processes that cause MMP activity to rise to destructive levels.

Rapid expression and activation of MMP-2 and MMP-9 upon exposure of human breast cancer cells (MCF-7) to fibronectin in serum free medium

Interactions between tumour cells and the extracellular matrix (ECM) strongly influence tumour development, affecting cell survival, proliferation and migration. Many of these interactions are mediated through a family of cell surface receptors named integrins. Fibronectin and its integrin receptors play important roles in tumour development. The alpha5beta 1 integrin interacts with the central cell adhesive region of fibronectin and requires both the RGD and synergy sites for maximal binding. Matrix metalloproteinases (MMPs) are a family of zinc dependent endopeptidases. They are capable of digesting the different components of the ECM and basement membrane. The ECM gives structural support to cells and plays a central role in cell adhesion, differentiation, proliferation and migration. Binding of ECM to integrins modulates expression and activity of the different MMPs. Our experimental findings demonstrate that cultivation of human breast cancer cells, MCF-7, in serum free medium in the presence of fibronectin upregulates the activity of MMP-2 and MMP-9. Blocking of alpha5beta 1 integrin with anti-alpha5 monoclonal antibody inhibits the fibronectin-induced MMP activation response appreciably. This strongly indicates alpha5beta 1 mediated signalling events in activation of MMP-2 and MMP-9. Phosphorylation of FAK and PI-3 kinase and the nuclear translocation of ERK and NF-kappaB upon fibronectin binding demonstrate possible participation of the FAK/PI-3K/ERK signalling pathways in the regulation of MMP-2 activity.

NF-κB Is a Key Mediator of Cerebral Aneurysm Formation

Background— Subarachnoid hemorrhage caused by the rupture of cerebral aneurysm (CA) remains a life-threatening disease despite recent diagnostic and therapeutic advancements. Recent studies strongly suggest the active participation of macrophage-mediated chronic inflammatory response in the pathogenesis of CA. We examined the role of nuclear factor-κB (NF-κB) in the pathogenesis of CA formation in this study.

Methods and Results— In experimentally induced CAs in rats, NF-κB was activated in cerebral arterial walls in the early stage of aneurysm formation with upregulated expression of downstream genes. NF-κB p50 subunit–deficient mice showed a decreased incidence of CA formation with less macrophage infiltration into the arterial wall. NF-κB decoy oligodeoxynucleotide also prevented CA formation when it was administered at the early stage of aneurysm formation in rats. Macrophage infiltration and expression of downstream genes were dramatically inhibited by NF-κB decoy oligodeoxynucleotide. In human CA walls, NF-κB also was activated, especially in the intima.

Conclusions— Our data indicate that NF-κB plays a crucial role as a key regulator in the initiation of CA development by inducing some inflammatory genes related to macrophage recruitment and activation. NF-κB may represent a therapeutic target of a novel medical treatment for CA.

Insulin facilitates monocyte migration: a possible link to tissue inflammation in insulin-resistance

Mononuclear cells (MNCs) are the primary cell type involved in the pro-inflammatory state of obesity-linked insulin-resistance, and atherosclerosis. Increased serum levels of MMP-9 are reported in insulin-resistant type 2 diabetic patients. Here we demonstrate insulin facilitating human monocytic THP-1 cell chemotaxis via prolonged Erk1/2-dependent induction of MMP-9. In vivo, significantly increased serum levels of MMP-9 were found in obesity-induced hyperinsulinemic C57BL/J6 mice, which were diminished by treatment with the anti-diabetic PPARgamma-ligand pioglitazone. In line with this, pioglitazone inhibited Erk1/2-phosphorylation and subsequent insulin-dependent MMP-9 synthesis in THP-1 cells. Thus, insulin increases MMP-9 gelatinolytic activity in monocytic cells, which results in accelerated chemotaxis. Hyperinsulinemia is associated with enhanced MMP-9 serum levels, potentially facilitating monocyte migration to and infiltration of adipose tissue and the arterial wall, thereby contributing to the increased cardiovascular risk in obese, hyperinsulinemic patients.

Interferon-gamma regulation of TNFalpha-induced matrix metalloproteinase 3 expression and migration of human glioma T98G cells

Induction of proinflammatory cytokines in response to malignant cells is an integral component of immune response to control tumor development. However, recent evidences have suggested that tumor cells may evade the immune system and exploit inflammatory responses to enhance its own growth. An exemplary example is the highly invasive and tumor necrosis factor (TNF)alpha-resistant glioblastoma, whose growth is associated with TNFalpha expression. We thus examined whether the tumor takes advantage of TNFalpha overexpression to enhance its invasiveness. To delineate the contribution of inflammation in tumor migration, we demonstrated that the role of proinflammatory cytokines on matrix metalloproteinases-3 (MMP-3) expression, and its consequent effects on the invasiveness of a human glioma cell-line, T98G. By using Matrigel Invasion Chamber, T98G cell migration was significantly enhanced in response to TNFalpha. In contrast, interferon-gamma (IFN gamma) reduced both basal and TNFalpha-enhanced cell invasion. To investigate the mechanisms involved, we demonstrated that TNFalpha upregulated mRNA and protein expression of MMP-3 in T98G cells, whereas IFN gamma downregulated the MMP-3 expression. The role of MMP-3 in glioma invasiveness was further confirmed by transfecting MMP-3 siRNA in T98G to abrogate the TNFalpha-enhanced cell invasion. To delineate the mechanisms further, we showed that IFN gamma exerts an inhibitory effect on the binding of TNFalpha-activated Ets-1 and NF kappa B to their respective enhancer elements found in MMP-3 promoter. In summary, our results indicated that TNFalpha enhances the invasiveness of T98G glioma cells through MMP-3 induction, and such enhancement of cell migration can be inhibited by IFN gamma.

Role of endothelial shear stress in the natural history of coronary atherosclerosis and vascular remodeling: molecular, cellular, and vascular behavior

Although the entire coronary tree is exposed to the atherogenic effect of the systemic risk factors, atherosclerotic lesions form at specific arterial regions, where low and oscillatory endothelial shear stress (ESS) occur. Low ESS modulates endothelial gene expression through complex mechanoreception and mechanotransduction processes, inducing an atherogenic endothelial phenotype and formation of an early atherosclerotic plaque. Each early plaque exhibits an individual natural history of progression, regression, or stabilization, which is dependent not only on the formation and progression of atherosclerosis but also on the vascular remodeling response. Although the pathophysiologic mechanisms involved in the remodeling of the atherosclerotic wall are incompletely understood, the dynamic interplay between local hemodynamic milieu, low ESS in particular, and the biology of the wall is likely to be important. In this review, we explore the molecular, cellular, and vascular processes supporting the role of low ESS in the natural history of coronary atherosclerosis and vascular remodeling and indicate likely mechanisms concerning the different natural history trajectories of individual coronary lesions. Atherosclerotic plaques associated with excessive expansive remodeling evolve to high-risk plaques, because low ESS conditions persist, thereby promoting continued local lipid accumulation, inflammation, oxidative stress, matrix breakdown, and eventually further plaque progression and excessive expansive remodeling. An enhanced understanding of the pathobiologic processes responsible for atherosclerosis and vascular remodeling might allow for early identification of a high-risk coronary plaque and thereby provide a rationale for innovative diagnostic and/or therapeutic strategies for the management of coronary patients and prevention of acute coronary syndromes.

Cardiovascular Actions of the Peroxisome Proliferator-Activated Receptor-Alpha (PPAR?) Agonist Wy14,643

This review examines the various effects of Wy14,643, a hypolipidemic agent that activates peroxisome proliferator-activated receptor-alpha (PPARalpha), on the cardiovascular system. An emphasis has been placed on the specific cellular processes affected by Wy14,643 as they relate to vascular and cardiac function. Although the topic of this discussion is limited to vascular and cardiac tissues, the importance of circulating lipids on cardiovascular disease requires that a description of the indirect actions of this compound on liver metabolism also be included. Finally, the pharmacology of Wy14,643 is discussed within the context of PPARalpha-dependent and -independent mechanisms.

Matrix metalloproteinases: influence on smooth muscle cells and atherosclerotic plaque stability

Atherosclerotic plaque rupture, with subsequent occlusive thrombosis, is the underlying cause of most cases of sudden cardiac death. Matrix metalloproteinases (MMPs) are thought to mediate the progression of stable atherosclerotic lesions to an unstable phenotype that is prone to rupture through the destruction of strength-giving extracellular matrix (ECM) proteins. Smooth muscle cells secrete and deposit ECM proteins and are, therefore, considered protective against atherosclerotic plaque destabilization. However, similar to inflammatory cells (e.g., macrophages), smooth muscle cells release numerous MMPs that are capable of digesting ECM proteins. Thus, the interaction of smooth muscle cells and MMPs in atherosclerotic plaques is complex and not fully understood. Recently, research into the roles of MMPs and their endogenous inhibitors (tissue inhibitors of metalloproteinases), and their effects on smooth muscle behavior during plaque destabilization has been aided by the development of reproducible animal models of plaque instability. A plethora of studies has demonstrated that MMPs directly modulate smooth muscle behavior with both beneficial and deleterious effects on atherosclerotic plaque stability, in addition to their canonical effects on ECM remodeling. Consequently, broad-spectrum MMP inhibition may inhibit plaque-stabilizing mechanisms, such as smooth muscle cell growth, while conversely retarding ECM destruction and subsequent rupture. Hence the development of selective MMP inhibitors, that spare inhibitory effects on smooth muscle cell function, may be useful therapies to prevent plaque rupture and in this regard MMP-12 appears to be a particularly attractive target.

Genomics of Foam Cells and Nonfoamy Macrophages From Rabbits Identifies Arginase-I as a Differential Regulator of Nitric Oxide Production

Objective— Conversion of macrophages to foam cells is a critical step in the initiation and progression of atherosclerosis. We sought to identify genes differentially regulated in foam cells, since these are likely to include new targets for intervention.

Methods and Results— We used suppression subtraction hybridization to compare foam cells and nonfoamy macrophages isolated from subcutaneous granulomas of rabbits fed a cholesterol-rich or normal chow diet and confirmed upregulation of 3 genes, including matrix metalloproteinase-12 (mRNA 2.0-fold, P <0.005; protein 3.9-fold, P <0.03). Arginase-I mRNA showed the biggest decrease among 11 downregulated genes in foam cells (2.7-fold, P <0.001) and was accompanied by significantly reduced arginase enzymatic activity (60-fold, P <0.01). Arginase-I competes for substrate L-arginine with nitric oxide synthase and consequently nitric oxide production was significantly increased (3-fold, P <0.02) in foam cells compared with nonfoamy macrophages despite no difference in nitric oxide synthase isoenzyme expression. We validated upregulation of matrix metalloproteinase-12 and downregulation of arginase-1 in foam cells of rabbit and human atherosclerotic plaques.

Conclusions— Our study identified several differentially expressed genes in foam cells and nonfoamy macrophages derived from live rabbits. The altered pattern of gene expression in foam cells is likely to influence atherosclerosis formation and stability.

Native and fragmented fibronectin oppositely modulate monocyte secretion of MMP-9

Monocytes remodel the extracellular matrix (ECM) by secreting proteins composing the ECM such as fibronectin (FN) and degrading proteases such as matrix metalloproteinase-9 (MMP-9), which cleaves FN into fragments. The effects of FN and its fragmented products on the expression of monocyte MMP-9 are controversial and largely unknown. We showed that in human monocytes, the proinflammatory cytokine TNF-alpha induced MMP-9 secretion and increased fragmentation of FN into distinct fragments. When primary monocytes or the U937 monocytic cell line were incubated on a plastic substrate, plastic-coated with native FN, and plastic-coated with fragmented FN (frag-FN), native FN inhibited TNF-alpha-induced proMMP-9 secretion by twofold (P<0.01) compared with plastic or frag-FN. Exploration of the dynamics of inflammation by incubating cells sequentially on the three substrates showed that frag-FN opposed the inhibitory effect of native FN. Inhibition of proMMP-9 by native FN was exerted at the translational level, as no change in MMP-9 mRNA, intracellular protein accumulation, or proteomic degradation was observed, and when degradation was blocked, no de novo translation of MMP-9 could be measured. We also showed that the reduction of MMP-9 secretion by native FN was responsible for attenuated migration of U937 cells (P<0.05). We suggest that in the inflammatory tissue, intact, native FN has a homeostatic role in harnessing MMP-9 activity. However, as fragmented products accumulate locally, they alleviate the inhibition and enable faster migration of the monocytes through the degraded ECM.

Interleukin-4 inhibition of interleukin-1-induced expression of matrix metalloproteinase-3 (MMP-3) is independent of lipoxygenase and PPARgamma activation in human gingival fibroblasts

Background

Interleukin 4 (IL-4) has been shown to suppress interleukin-1 (IL-1) induced expression of matrix metalloproteinase-3 (MMP-3) in human synovial and gingival fibroblasts, but the mechanism of suppression has not been determined. Activators of peroxisome proliferator-activated receptor-γ (PPARγ) have been shown to inhibit cytokine induced expression of MMPs in other cell types, and IL-4 has been shown to activate PPARγ by stimulating production of ligands through the lipoxygenase pathway. It has been suggested that PPARγ may inhibit expression of MMPs by competing with transcription factor AP-1 for binding to a putative composite binding element in the promoters. The objective of this study was to determine whether the suppressive effects of IL-4 on the IL-1 induced expression of MMP-3 involve activation of lipoxygenase and/or PPARγ.

Results

Western blotting revealed the presence of PPARγ in nuclear extract of HGF. IL-1 induced binding of nuclear extract to the putative composite PPRE/AP-1 site was diminished in the presence of pioglitazone, but there was no evidence of any change in the composition of the retarded complexes, and no evidence of PPARγ binding to this site. Nordihydroguaiaretic acid (NDGA), a non-selective lipoxygenase inhibitor, and MK886, a specific inhibitor of 5-lipoxygenase, induced MMP-3 expression synergistically with IL-1. However IL-4 was still able to inhibit MMP-3 expression in the presence of NDGA or MK886 and IL-1. Activation of PPARγ with pioglitazone not only failed to inhibit IL-1 induced expression of MMP-3 mRNA, but rather super-induced MMP-3 in the presence of IL-1. PPARγ antagonist GW9662 failed to abolish the suppressive effects of IL-4. Another PPARγ activator, 15-deoxy-Delta12,14prostaglandin J2 (15dPGJ2), also super-induced MMP-3 mRNA, and this was due at least in part to increased transcription.

Conclusion

IL-4 suppression of IL-1-induced MMP-3 expression in HGF is independent of lipoxygenase activity and activation of PPARγ. Super-induction of MMP-3 by pioglitazone may have important implications for patients using pioglitazone to treat type II diabetes in the presence of chronic inflammation.