Nitric oxide inhibition increases matrix metalloproteinase-9 expression by rat aortic smooth muscle cells in vitro

Sodium Nitroprusside Stimulation of Elastic Matrix Regeneration by Aneurysmal Smooth Muscle Cells

The chronic overexpression of matrix metalloproteases leading to consequent degradation and loss of the elastic matrix with the reduction in tissue elasticity is central to the pathophysiology of proteolytic disorders, such as abdominal aortic aneurysms (AAAs), which are localized rupture-prone aortic expansions. Effecting tissue repair to alleviate this condition is contingent on restoring elastic matrix homeostasis in the aortic wall. This is naturally irreversible due to the poor elastogenicity of adult and diseased vascular cells, and the impaired ability to assemble mature elastic fibers, more so in the context of phenotypic changes to medial smooth muscle cells (SMCs) owing to the loss of nitric oxide (NO) signaling in the AAA wall tissue. In this study, we report the benefits of the exposure of primary human aneurysmal SMCs (aHASMCs) to NO donor drug, sodium nitroprusside (SNP), in improving extracellular matrix homeostasis, particularly aspects of elastic fiber assembly, and inhibition of proteolytic degradation. SNP treatment (100 nM) upregulated elastic matrix regeneration at both gene (p < 0.05) and protein levels (p < 0.01) without affecting cell proliferation, improved gene, and protein expression of crosslinking enzyme, lysyl oxidase (p < 0.05), inhibited the expression of MMP2 (matrix metalloprotease 2) significantly (p < 0.05) and promoted contractile SMC phenotypes in aHASMC culture. In addition, SNP also attenuated the expression of mitogen-activated protein kinases, a significant player in AAA formation and progression. Our results indicate the promise of SNP for therapeutic augmentation of elastic matrix regeneration, with prospects for wall repair in AAAs. Impact Statement Chronic and naturally irreversible enzymatic degradation and loss of elastic fibers are centric to proteolytic disorders such as abdominal aortic aneurysms (AAAs). This is linked to poor elastogenicity of adult and diseased vascular cells, compromising their ability to assemble mature elastic fibers. Toward addressing this, we demonstrate the phenotype-modulatory properties of a nitric oxide donor drug, sodium nitroprusside on aneurysmal smooth muscle cells, and its dose-specific proelastogenic and antiproteolytic properties for restoring elastic matrix homeostasis. Combined with the development of vehicles for site-localized, controlled drug delivery, this can potentially lead to a new nonsurgical approach for AAA wall repair in the future.

Association of matrix metalloproteinase-9 and nitric oxide with hypertension in obstructive sleep apnea

Background

Patients with obstructive sleep apnea (OSA) are more likely to suffer from hypertension. At the same time, the serum levels of matrix metalloproteinase-9 (MMP-9) and nitric oxide (NO) in patients with OSA are also changed in OSA patients. We investigated the correlation between serum levels of MMP-9, NO in patients with OSA and their association with hypertension in those patients, and the effects of continuous positive airway pressure therapy (CPAP) on these serum biomarkers and blood pressure.

Methods

Serum MMP-9 and NO levels and blood pressure of 57 patients with newly diagnosed OSA and 30 controls were measured; among them, 30 patients with moderate to severe OSA underwent 3-month CPAP treatment.

Results

In comparison to the control group, the MMP-9 serum levels were higher (232.8 ± 103.2 ng/ml versus 161.6 ± 56.5 ng/ml, p < .001*), there was no statistical significance difference among serum NO (26.7 ± 9.1 IU/ml versus 31.0 ± 11.7 IU/ml, p = .06), and MMP-9 was negatively correlated to NO, especially in patients with hypertension (r = -.644, p = .02*). MMP-9, NO, and blood pressure were significantly recovered in the patients with OSA after CPAP treatment for 3 months (p < .05*).

Conclusion

The MMP-9 level and the NO level were altered in OSA patients. The relationship between the two especially in patients with hypertension suggests the potential mechanism of OSA-induced hypertension.

The effect of opine on matrix metalloproteinase expression in mice with breast cancer

Regarding the anti-inflammatory and anti-tumour effects of arginine and its derivatives, this study evaluates matrix metalloproteinase (MMPs) expression in an animal model of breast cancer following administration of octopine. In this study, 40 animals of Balb/C mice were divided into 5 groups: the healthy control, the cancer control, the cancer group receiving 50 mg of octopine, the cancer group receiving 100 mg of octopine and the cancer group receiving 150 mg of octopine for 3 weeks. 4T1 cell line was used to induce cancer. Biopsy specimens were enrolled from mice and MMP-1, MMP-3 and MMP-9 gene expression evaluated using real-time PCR, while these protein amounts were measured using immunohistochemistry and ELISA methods. Data were analysed using one-way ANOVA, Kruskal-Wallis and Mann-Whitney U tests (p < .05). The results showed that 100 mg octopine consumption had significant decreasing effect on MMP-9 expression (p = .02) in the treatment group compared with cancerous non-treated mice. Furthermore, results from immunohistochemistry and ELISA confirmed this effect, the protein amount of MMP-9 was significantly decreased in group treating with 100 mg octopine (.005). The use of octopine has a beneficial effect on reducing MMP-9 in mice breast cancer.

Extracellular Matrix in Aging Aorta

The aging population is booming all over the world and arterial aging causes various age-associated pathologies such as cardiovascular diseases (CVDs). The aorta is the largest elastic artery, and transforms pulsatile flow generated by the left ventricle into steady flow to maintain circulation in distal tissues and organs. Age-associated structural and functional changes in the aortic wall such as dilation, tortuousness, stiffening and losing elasticity hamper stable peripheral circulation, lead to tissue and organ dysfunctions in aged people. The extracellular matrix (ECM) is a three-dimensional network of macromolecules produced by resident cells. The composition and organization of key ECM components determine the structure-function relationships of the aorta and therefore maintaining their homeostasis is critical for a healthy performance. Age-associated remodeling of the ECM structural components, including fragmentation of elastic fibers and excessive deposition and crosslinking of collagens, is a hallmark of aging and leads to functional stiffening of the aorta. In this mini review, we discuss age-associated alterations of the ECM in the aortic wall and shed light on how understanding the mechanisms of aortic aging can lead to the development of efficient strategy for aortic pathologies and CVDs.

Resveratrol and the Interaction between Gut Microbiota and Arterial Remodelling

Arterial remodelling refers to the alteration in the structure of blood vessel that contributes to the progression of hypertension and other cardiovascular complications. Arterial remodelling is orchestrated by the crosstalk between the endothelium and vascular smooth muscle cells (VSMC). Vascular inflammation participates in arterial remodelling. Resveratrol is a natural polyphenol that possesses anti-oxidant and anti-inflammatory properties and has beneficial effects in both the endothelium and VSMC. Resveratrol has been studied for the protective effects in arterial remodelling and gut microbiota, respectively. Gut microbiota plays a critical role in the immune system and inflammatory processes. Gut microbiota may also regulate vascular remodelling in cardiovascular complications via affecting endothelium function and VSMC proliferation. Currently, there is new evidence showing that gut microbiota regulate the proliferation of VSMC and the formation of neointimal hyperplasia in response to injury. The change in population of the gut microbiota, as well as their metabolites (e.g., short-chain fatty acids) could critically contribute to VSMC proliferation, cell cycle progression, and migration. Recent studies have provided strong evidence that correlate the effects of resveratrol in arterial remodelling and gut microbiota. This review aims to summarize recent findings on the resveratrol effects on cardiovascular complications focusing on arterial remodelling and discuss the possible interactions of resveratrol and the gut microbiota that modulate arterial remodelling.

Nobiletin alleviates vascular alterations through modulation of Nrf-2/HO-1 and MMP pathways in l-NAME induced hypertensive rats

Nobiletin alleviates l-NAME-induced vascular dysfunction and remodeling and superoxide production in rats.

Transient external force induces phenotypic reversion of malignant epithelial structures via nitric oxide signaling

Non-malignant breast epithelial cells cultured in three-dimensional laminin-rich extracellular matrix (lrECM) form well organized, growth-arrested acini, whereas malignant cells form continuously growing disorganized structures. While the mechanical properties of the microenvironment have been shown to contribute to formation of tissue-specific architecture, how transient external force influences this behavior remains largely unexplored. Here, we show that brief transient compression applied to single malignant breast cells in lrECM stimulated them to form acinar-like structures, a phenomenon we term 'mechanical reversion.' This is analogous to previously described phenotypic 'reversion' using biochemical inhibitors of oncogenic pathways. Compression stimulated nitric oxide production by malignant cells. Inhibition of nitric oxide production blocked mechanical reversion. Compression also restored coherent rotation in malignant cells, a behavior that is essential for acinus formation. We propose that external forces applied to single malignant cells restore cell-lrECM engagement and signaling lost in malignancy, allowing them to reestablish normal-like tissue architecture.

Cerebral microhemorrhages: mechanisms, consequences, and prevention

The increasing prevalence of multifocal cerebral microhemorrhages (CMHs, also known as "cerebral microbleeds") is a significant, newly recognized problem in the aging population of the Western world. CMHs are associated with rupture of small intracerebral vessels and are thought to progressively impair neuronal function, potentially contributing to cognitive decline, geriatric psychiatric syndromes, and gait disorders. Clinical studies show that aging and hypertension significantly increase prevalence of CMHs. CMHs are also now recognized by the National Institutes of Health as a major factor in Alzheimer's disease pathology. Moreover, the presence of CMHs is an independent risk factor for subsequent larger intracerebral hemorrhages. In this article, we review the epidemiology, detection, risk factors, clinical significance, and pathogenesis of CMHs. The potential age-related cellular mechanisms underlying the development of CMHs are discussed, with a focus on the structural determinants of microvascular fragility, age-related alterations in cerebrovascular adaptation to hypertension, the role of oxidative stress and matrix metalloproteinase activation, and the deleterious effects of arterial stiffening, increased pulse pressure, and impaired myogenic autoregulatory protection on the brain microvasculature. Finally, we examine potential treatments for the prevention of CMHs based on the proposed model of aging- and hypertension-dependent activation of the reactive oxygen species-matrix metalloproteinases axis, and we discuss critical questions to be addressed by future studies.

Collateral Growth in the Peripheral Circulation: A Review

Arterial occlusive diseases are a major cause of morbidity and death in the United States. The enlargement of pre-existing vessels, which bypass the site of arterial occlusion, provide a natural way for the body to compensate for such obstructions. Individuals differ in their capacity to develop collateral vessels. In recent years much attention has been focused upon therapy to promote collateral development, primarily using individual growth factors. Such studies have had mixed results. Persistent controversies exist regarding the initiating stimuli, the processes involved in enlargement, the specific vessels that should be targeted, and the most appropriate terminology. Consequently, it is now recognized that more research is needed to extend our knowledge of the complex process of collateral growth. This basic science review addresses five questions essential in understanding current problems in collateral growth research and the development of therapeutic interventions.

Effect of Nitric Oxide on the Expression of Matrix Metalloproteinase and Its Association with Migration of Cultured Trabecular Meshwork Cells

Purpose

To determine the effect of exogenous nitric oxide (NO) on the migration of trabecular meshwork (TM) cells and its association with expression of matrix metalloproteinases (MMPs).

Methods

Primary human TM cells treated with 1 or 10 µM S-nitroso-N-acetyl-penicillamine (SNAP) and examined for changes in adherence. TM cells were seeded onto transwell culture inserts, and changes in their migratory activity were quantified. Reverse transcription polymerase chain reaction was performed to determine the relative changes in mRNA expression of MMPs and tissue inhibitor of metalloproteinases (TIMPs).

Results

Treatment with SNAP did not significantly suppress TM cell adhesion or migration (p > 0.05). Treatment of TM cells with 10 µM SNAP decreased expression of MMP-2 and increased expression of membrane type MMP-1 and TIMP-2. Treatment with interleukin-1α triggered MMP-3 expression but did not exert significant effects on MMP-3 activation in response to SNAP.

Conclusions

These data suggest that NO revealed no significant effect on the migration of TM cells because NO decreased MMP-2 and increased TIMP-2 expression. Although expression of certain MMPs and TIMPs change in response to NO donors, NO may modulate trabecular outflow by changing the cellular production of extracellular matrix without having a significant effect on the migration of TM cells.

The dual role of iNOS in cancer

Nitric oxide (NO) is one of the 10 smallest molecules found in nature. It is a simple gaseous free radical whose predominant functions is that of a messenger through cGMP. In mammals, NO is synthesized by the enzyme nitric oxide synthase (NOS) of which there are three isoforms. Neuronal (nNOS, NOS1) and endothelial (eNOS, NOS3) are constitutive calcium-dependent forms of the enzyme that regulate neural and vascular function respectively. The third isoform (iNOS, NOS2), is calcium-independent and is inducible. In many tumors, iNOS expression is high, however, the role of iNOS during tumor development is very complex and quite perplexing, with both promoting and inhibiting actions having been described. This review will aim to summarize the dual actions of iNOS-derived NO showing that the microenvironment of the tumor is a contributing factor to these observations and ultimately to cellular outcomes.

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NO is pro- and anti-tumorigenic. High concentrations of NO maybe anti-tumorigenic.

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iNOS produces high concentrations of NO and relates to tumor growth or its inhibition.

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iNOS is associated with cytotoxicity, apoptosis and bystander anti-tumor effects.

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Tumor- and stromal-iNOS, and the ‘cell situation’ contribute to anti or pro-tumor effects.

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Dual role of iNOS is influenced by the cell situation and is environment dependent.

Plasminogen activator-1 overexpression decreases experimental postthrombotic vein wall fibrosis by a non-vitronectin-dependent mechanism

BACKGROUND

Factors associated with postthrombotic syndrome are known clinically, but the underlying cellular processes at the vein wall are not well delineated. Prior work suggests that vein wall damage does not correlate with thrombus resolution but rather with plasminogen activator-1 (PAI-1) and matrix metalloproteinase (MMP) activity.

OBJECTIVE

We hypothesized that PAI-1 would confer post venous thrombosis (VT) vein wall protection via a vitronectin (Vn)-dependent mechanism.

METHODS

A stasis model of VT was used with harvest over 2 weeks, in wild-type, Vn(-/-) , and PAI-1-overexpressing mice (PAI-1 Tg).

RESULTS

PAI-1 Tg mice had larger VT at 6 and 14 days, compared to controls, but Vn(-/-) mice had no alteration of VT resolution. Gene deletion of Vn resulted in an increase in, rather than the expected decrease in, circulating PAI-1 activity. While both Vn(-/-) and PAI-1 Tg had attenuated intimal fibrosis, PAI-1 Tg had significantly less vein wall collagen and a compensatory increase in collagen III gene expression. Both Vn(-/-) and PAI-1 Tg vein wall had less monocyte chemotactic factor-1 and fewer macrophages (F4/80), with significantly less MMP-2 activity and decreased TIMP-1 antigen. Ex vivo assessment of transforming growth factor β-mediated fibrotic response showed that PAI-1 Tg vein walls had increased profibrotic gene expression (collagens I and III, MMP-2, and α-smooth muscle actin) compared with controls, opposite of the in vivo response.

CONCLUSIONS

The absence of Vn increases circulating PAI-1, which positively modulates vein wall fibrosis in a dose-dependent manner. Translationally, PAI-1 elevation may decrease vein wall damage after deep vein thrombosis, perhaps by decreasing macrophage-mediated activities.

Nitric oxide-matrix metaloproteinase-9 interactions: biological and pharmacological significance--NO and MMP-9 interactions

Nitric oxide (NO) and matrix metalloproteinase 9 (MMP-9) levels are found to increase in inflammation states and in cancer, and their levels may be reciprocally modulated. Understanding interactions between NO and MMP-9 is of biological and pharmacological relevance and may prove crucial in designing new therapeutics. The reciprocal interaction between NO and MMP-9 have been studied for nearly twenty years but to our knowledge, are yet to be the subject of a review. This review provides a summary of published data regarding the complex and sometimes contradictory effects of NO on MMP-9. We also analyse molecular mechanisms modulating and mediating NO-MMP-9 interactions. Finally, a potential therapeutic relevance of these interactions is presented.

The role of tissue Renin-Angiotensin-aldosterone system in the development of endothelial dysfunction and arterial stiffness

Epidemiological studies support the notion that arterial stiffness is an independent predictor of adverse cardiovascular events contributing significantly to systolic hypertension, impaired ventricular-arterial coupling and diastolic dysfunction, impairment in myocardial oxygen supply and demand, and progression of kidney disease. Although arterial stiffness is associated with aging, it is accelerated in the presence of obesity and diabetes. The prevalence of arterial stiffness parallels the increase of obesity that is occurring in epidemic proportions and is partly driven by a sedentary life style and consumption of a high fructose, high salt, and high fat western diet. Although the underlying mechanisms and mediators of arterial stiffness are not well understood, accumulating evidence supports the role of insulin resistance and endothelial dysfunction. The local tissue renin-angiotensin-aldosterone system (RAAS) in the vascular tissue and immune cells and perivascular adipose tissue is recognized as an important element involved in endothelial dysfunction which contributes significantly to arterial stiffness. Activation of vascular RAAS is seen in humans and animal models of obesity and diabetes, and associated with enhanced oxidative stress and inflammation in the vascular tissue. The cross talk between angiotensin and aldosterone underscores the importance of mineralocorticoid receptors in modulation of insulin resistance, decreased bioavailability of nitric oxide, endothelial dysfunction, and arterial stiffness. In addition, both innate and adaptive immunity are involved in this local tissue activation of RAAS. In this review we will attempt to present a unifying mechanism of how environmental and immunological factors are involved in this local tissue RAAS activation, and the role of this process in the development of endothelial dysfunction and arterial stiffness and targeting tissue RAAS activation.

Impaired fibrinolytic system in ApoE gene-deleted mice with hyperlipidemia augments deep vein thrombosis

BACKGROUND

Hyperlipidemia increases the level of blood plasminogen activator inhibitor-1 (PAI-1) that is responsible for regulating fibrinolysis by inhibiting both urokinase-type plasminogen activator (u-PA) and tissue-type plasminogen activator (t-PA). While this fibrinolytic pathway is well known, the role of PAI-1 in venous thrombosis (VT) under hyperlipidemic conditions has not been fully established. We sought to determine the effects of PAI-1 in an in vivo hyperlipidemic model of VT.

METHODS

C57BL/6 wild-type (WT) mice, apolipoprotein E gene-deleted mice (ApoE-/-) having hyperlipidemia, and PAI-1 gene-deleted (PAI-1-/-) mice were used in this study. Inferior vena cava (IVC) ligation below the level of the renal veins was performed to create a stasis VT. Endpoints included measuring acute thrombosis (day 2) and chronic thrombosis (days 6 and 14). At euthanasia, blood samples were collected for plasmin and PAI-1 activity. In addition, the IVC and its thrombus were evaluated for thrombus weight (TW), u-PA activity, and differential leukocyte count while the vein wall only was analyzed for monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase (MMP) 2, and MMP-9.

RESULTS

Compared to WT at day 2, ApoE-/-mice demonstrated a statistically significant 14% increase in TW (P < .05) and a significant 41% increase in circulating PAI-1 activity (P < .05), while showing a trend of decreased plasmin activity. In addition, TW in ApoE-/-mice was 45% higher than PAI-1-/-mice at day 2 (P < .05), 33% at day 6 (P < .01), and 41% at day 14 (P < .01). ApoE-/-mice exhibited undetectable levels of u-PA in both vein wall and thrombus, compared to WT, at all time points. Also, vein wall MMP-2 was significantly decreased by 64% at day 6 (P < .01) and 58% at day 14 (P < .05). MMP-9 was significantly decreased by 71% at day 2 (P < .01) and 48% at day 6 (P < .01), in ApoE-/-mice compared to WT mice. In addition, in ApoE-/-mice, MCP-1 was significantly decreased by 38% at day 2 (P < .01) and 67% at day 6 (P < .01) vs WT mice. As expected in ApoE mice, following a decrease in MCP-1, monocyte recruitment was significantly decreased at days 6 (P < .01) and 14 (P < .05).

CONCLUSIONS

A significant increase of circulating PAI-1 levels in hyperlipidemic mice correlated with an early increase in TW due to impaired fibrinolysis. The undetectable levels of u-PA in ApoE-/-mice correlated to a decrease in vein wall MMP-2, MMP-9, MCP-1, and a decrease in monocyte recruitment diminishing thrombus resolution.

Endogenous nitric oxide formation correlates negatively with circulating matrix metalloproteinase (MMP)-2 and MMP-9 levels in black subjects

Deficient formation of endogenous nitric oxide (NO) contributes to cardiovascular diseases, and this may be associated with increased circulating levels of matrix metalloproteinase-9 (MMP-9), as previously shown in white subjects. Because interethnic differences exist with respect to risk factors, prevalence, and severity of cardiovascular diseases, we designed this study to examine whether the circulating levels of nitrites (a marker of endogenous NO formation) are associated with the plasma levels of MMP-9 and MMP-2 in healthy black subjects. We studied 198 healthy subjects self-reported as blacks not taking any medications. Venous blood samples were collected and plasma and whole blood nitrite levels were measured using an ozone-based chemiluminescence assay. Plasma MMP-2 and MMP-9 levels were determined by gelatin zymography. We found a positive correlation between plasma MMP-9 and MMP-2 levels (P < 0.0001, rs = 0.556). Interestingly, we found a negative relationship between the plasma MMP-9 levels and the plasma or whole blood nitrites levels (P = 0.04, rs = -0.149; and P < 0.0001, rs = -0.349, respectively). In parallel, we found similar negative relationships between plasma MMP-2 levels and plasma or whole blood nitrites levels (P = 0.02, rs = -0.172; and P < 0.0001, rs = -0.454, respectively). This is the first study to show that endogenous nitric oxide formation correlates negatively with the circulating levels of both MMP-2 and MMP-9 in black subjects. Our findings suggest a mechanistic link between deficient NO formation and increased MMPs levels, which may promote cardiovascular diseases.

Plasma matrix metalloproteinase (MMP)-9 levels are reduced following low-calorie cranberry juice supplementation in men

OBJECTIVE

Matrix metalloproteinase (MMP)-9, also known as gelatinase B, is implicated in the development of hypertension and atherosclerotic plaque vulnerability to rupture, an important step in the etiology of cardiovascular diseases. Studies have suggested that flavonoid consumption may be cardioprotective, and its favorable impact on circulating MMP-9 concentrations could partly explain this association. The aim of the present study was to determine the effect of consuming increasing daily doses of low-calorie cranberry juice cocktail (CJC) on plasma MMP-9 concentrations of abdominally obese men.

METHODS

Thirty men (mean age +/- SD: 51 +/- 10 years) consumed increasing doses of CJC during 3 successive periods of 4 weeks (weeks 1-4: 125 ml/day, weeks 5-8: 250 ml/day, and weeks 9-12: 500 ml/day). Before the study and after each phase, a series of physical and metabolic variables were measured, including MMP-9.

RESULTS

We found that CJC supplementation significantly decreased plasma MMP-9 concentrations (mean +/- SEM: -36% +/- 9%, p < 0.0005; week 12 vs. baseline) while baseline plasma MMP-9 concentrations strongly correlated with the changes noted over the entire intervention (r = -0.71, p < 0.0001). We also show that the reduction in plasma MMP-9 levels was associated with a change in plasma nitrites/nitrates (NOx) concentration over the entire intervention (r = -0.38, p < 0.05; week 12 vs. baseline). Significant correlations were also noted between changes in plasma MMP-9 levels and those of systolic (r = 0.39, p < 0.05) and diastolic (r = 0.60, p < 0.001) blood pressure during the course of the study (week 12 vs. baseline).

CONCLUSIONS

Our results show that daily CJC consumption is associated with a decrease in plasma MMP-9 concentrations in abdominally obese men. We hypothesize that polyphenolic compounds from cranberries may be responsible for this effect, supporting the notion that the consumption of flavonoid-rich foods can exert cardioprotective effects.

Interleukin-lβ induces migration of rat arterial smooth muscle cells through a mechanism involving increased matrix metalloproteinase-2 activity

BACKGROUND

Interleukin-lβ (IL-lβ) is associated with vascular smooth muscle cell (VSMC) migration during neointimal formation following arterial injury, of which matrix metalloproteinase-2 (MMP-2) may have an important role. We investigated whether IL-lβ stimulated migration and MMP-2 production in VSMC, and, if so, whether migration correlated with MMP-2 activity.

MATERIALS AND METHODS

Modified Boyden chamber assay quantified cultured rat aorta VSMC migration. Methyl-thiazolyl-tetrazolium assay assessed cell growth. Gelatin zymography and Western blotting determined MMP-2 activity and protein levels, respectively.

RESULTS

IL-lβ (0.1 - 10 ng/mL) induced migration of VSMC in a concentration-dependent manner without cell proliferation. VSMC released increasing levels of active MMP-2 in a dose-response fashion at IL-1β 1-10 ng/mL (P < 0.05) while significantly increased levels of latent MMP-2 (pro-MMP-2) were attained more gradually (10 ng/mL, P < 0.05). There was a dose-dependent increase in the ratio of active MMP-2 to pro-MMP-2 in response to IL-1β (1-10 ng/mL, P < 0.05), suggesting extracellular activation of pro-MMP-2. Protein levels on Western blot paralleled enzyme activity, with the synthesis of more active MMP-2 than pro-MMP-2 in response to IL-1β. IL-lβ-stimulated VSMC migration was significantly attenuated by both the pan-selective MMP inhibitor GM6001 and cis-9-octadecenoyl-N-hydroxylamide, a MMP-2-selective inhibitor.

CONCLUSIONS

IL-lβ increases MMP-2 activity in VSMC through increased protein synthesis and activation of pro-MMP-2. VSMC migration induced by IL-lβ requires active MMP-2. IL-lβ may play a role in arterial remodeling following injury.

Thrombus resolution and vein wall injury: dependence on chemokines and leukocytes

Chronic venous insufficiency resulting in post-thrombotic syndrome occurs commonly after acute deep vein thrombosis, and is a prevalent cause of vascular disease morbidity in the community. Therefore, a better understanding of the pathophysiologic mechanisms that promote the development of chronic venous insufficiency could lead to novel approaches to interrupt the natural history and prevent post-thrombotic syndrome. In this paper, we will review the evidence that venous thrombus resolution is an inflammatory process that is dependent on chemokines and leukocytes.

Decreased mobilization of endothelial progenitor cells contributes to impaired neovascularization in diabetes

1. Circulating bone marrow (BM)-derived endothelial progenitor cells (EPCs) play an important role in neovascularization. In the present study, we investigated the mechanisms underlying the reduction in circulating EPCs in a mouse model of diabetes induced by streptozotocin. 2. Compared with non-diabetic controls, diabetic mice had reduced circulating EPCs (0.59 +/- 0.11 vs 0.94 +/- 0.21%, respectively; P < 0.01) and increased plasma endothelial microparticles (18 642 +/- 6809 vs 5692 +/- 1862/mL, respectively; P < 0.01). In a mouse bone marrow (BM) transplantation model, increased adhesion of transplanted BM cells to aortas of diabetic mice was observed compared with control (900 +/- 194 vs 431 +/- 109 cells/mm(2), respectively; P < 0.01). 3. Following hindlimb ischaemia, diabetic mice exhibited suppressed EPC mobilization, a reduction in the expected increase in capillary density and suppressed restoration of transcutaneous oxygen pressure in the ischaemic tissue. Diabetic mice also showed impaired ischaemia-induced upregulation of vascular endothelial growth factor (VEGF), hypoxia-inducible factor (HIF)-1 alpha and interleukin-1 beta, an exaggerated increase in matrix metalloproteinase (MMP)-2 and -9 and a suppressed increase in tissue inhibitor of matrix metalloproteinase (TIMP)-1. On multivariate analysis, VEGF expression was the only independent factor related to circulating EPC count. 4. In conclusion, the data indicate that the decrease in basal circulating EPCs in diabetes may be attributable, in part, to consumptive loss of EPCs due to increased endothelial damage. Impairment of ischaemia-induced EPC mobilization in the diabetic mouse model is associated with altered HIF-1 alpha/VEGF and MMP/TIMP regulation and represents a novel mechanism underlying defective postischaemic neovascularization in diabetes.

Molecular mechanisms of nitric oxide-dependent inhibition of TPA-induced matrix metalloproteinase-9 (MMP-9) in MCF-7 cells

Matrix metalloproteinase-9 (MMP-9) is implicated in the invasion and metastasis of breast cancer cells. We investigated the modulatory effects of nitric oxide (NO) on the 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced MMP-9 expression in MCF-7 cells. Different chemical NO donors inhibited the extracellular content of TPA-induced MMP-9 protein and MMP-9 activity as assessed by gelatin-zymography and ELISA, respectively. Concomitant with the reduction in the extracellular MMP-9 content NO strongly decreased the steady-state levels of MMP-9 mRNA which in turn leads to a lower recruitment of MMP-9 transcripts to polysomes and to a diminished MMP-9 translation. Reporter gene assays revealed that the inhibition in MMP-9 expression by NO is mainly attributed to a 0.67 kb fragment of the 5'-promoter region of the MMP-9 gene but independent of the 3'untranslated region thus indicating that MMP-9 suppression by NO mainly results from transcriptional events. Electrophoretic mobility shift assays (EMSA), showed that NO specifically interferes with the TPA-induced DNA binding affinity of c-Jun and c-Fos without affecting the TPA-induced increase in the levels of the transcription factors. Using pharmacological inhibitors and small interfering (si)RNA we found that PKCdelta is indispensably involved in the TPA-triggered MMP-9 expression. Concomitantly, the TPA-evoked increase in total PKC activity was strongly attenuated in the lysates from NO-treated MCF-7 cells, thus suggesting that NO attenuates TPA-triggered MMP-9 mainly through a direct inhibition of PKCdelta. Modulation of MMP-9 by NO highlights the complex roles of NO in the regulation of MMP-9 in breast cancer cells.

Interleukin-1-mediated hematopoietic cell regulation in the aorta-gonad-mesonephros region of the mouse embryo

Hematopoiesis during development is a dynamic process, with many factors involved in the emergence and regulation of hematopoietic stem cells (HSCs) and progenitor cells. Whereas previous studies have focused on developmental signaling and transcription factors in embryonic hematopoiesis, the role of well-known adult hematopoietic cytokines in the embryonic hematopoietic system has been largely unexplored. The cytokine interleukin-1 (IL-1), best known for its proinflammatory properties, has radioprotective effects on adult bone marrow HSCs, induces HSC mobilization, and increases HSC proliferation and/or differentiation. Here we examine IL-1 and its possible role in regulating hematopoiesis in the midgestation mouse embryo. We show that IL-1, IL-1 receptors (IL-1Rs), and signaling mediators are expressed in the aorta-gonad-mesonephros (AGM) region during the time when HSCs emerge in this site. IL-1 signaling is functional in the AGM, and the IL-1RI is expressed ventrally in the aortic subregion by some hematopoietic, endothelial, and mesenchymal cells. In vivo analyses of IL-1RI-deficient embryos show an increased myeloid differentiation, concomitant with a slight decrease in AGM HSC activity. Our results suggest that IL-1 is an important homeostatic regulator at the earliest time of HSC development, acting to limit the differentiation of some HSCs along the myeloid lineage.

Inverse relationship between markers of nitric oxide formation and plasma matrix metalloproteinase-9 levels in healthy volunteers

BACKGROUND

Nitric oxide (NO) is a major regulator of cardiovascular homeostasis and has anti-atherogenic properties. Reduced NO formation is associated with endothelial dysfunction and with cardiovascular risk factors. Although NO downregulates the expression and activity of the pro-atherogenic enzyme matrix metalloproteinase-9 (MMP-9), no previous clinical study has examined whether endogenous NO formation is inversely associated with the circulating levels of pro-MMP-9, which are associated with cardiovascular events. We examined this hypothesis in 175 healthy male subjects who were non-smokers.

METHODS

To assess NO bioavailability, the plasma concentrations of nitrite, nitrate, and cGMP were determined using an ozone-based chemiluminescence assay and an enzyme immunoassay. Pro-MMP-9 and pro-MMP-2 levels were measured in plasma samples by gelatin zymography.

RESULTS

We found significant negative correlations between pro-MMP-9 levels and plasma nitrite (P=0.035, rs= -0.159), nitrate (P=0.040, rs= -0.158), and cGMP (P=0.011, rs= -0.189) concentrations. However, no significant correlations were found between pro-MMP-2 levels and the plasma concentrations of markers of NO bioavailability (all P>0.05).

CONCLUSIONS

There is an inverse relationship between markers of NO formation and plasma MMP-9 levels. This finding may shed some light on the possible mechanisms involved in the increased cardiovascular risk of apparently healthy subjects with low NO bioavailability or high circulating levels of pro-MMP-9.

Endocannabinoid regulation of matrix metalloproteinases: implications in ischemic stroke

Stroke is a major cause of morbidity and mortality and follows heart disease and cancer as the third leading cause of death in Western societies [1]. Despite many advances in stroke research and pharmacotherapy, clinical treatment of this debilitating disorder is still inadequate. Recent findings from several laboratories have identified the endocannabinoid signaling pathway, comprised of the endocannabinoid agonist anandamide and its pharmacological targets, CB1 and CB2 cannabinoid receptors and associated anandamide receptors, as a physiological system with capacity to mitigate cardiovascular and cerebrovascular disorders through neuronal and endothelial actions. Variability in experimental stroke models and modes of outcome evaluation, however, have provoked controversy regarding the precise roles of endocannabinoid signals in mediating neural and/or vascular protection versus neurovascular damage. Clinical trials of the CB1 antagonist rimonabant demonstrate that modulation of endocannabinoid signaling during metabolic regulation of vascular disorders can significantly impact clinical outcomes, thus providing strong argument for therapeutic utility of endocannabinoids and/or cannabinoid receptors as targets for therapeutic intervention in cases of stroke and associated vascular disorders. The purpose of this review is to provide updated information from basic science and clinical perspectives on endocannabinoid ligands and their effects in the pathophysiologic genesis of stroke. Particular emphasis will be placed on the endocannabinoids anandamide and 2-arachidonylglycerol and CB1 receptor-mediated mechanisms in the neurovascular unit during stroke pathogenesis. Deficiencies in our knowledge of endocannabinoids in the etiology and pathogenesis of stroke, caveats and limitations of existing studies, and future directions for investigation will be addressed.

Nitric oxide and vascular remodeling: Spotlight on the kidney

Extracellular matrix (ECM) remodeling with successive tissue fibrosis is a key feature of chronic cardiovascular diseases, including atherosclerosis and restenosis. The atherogenic changes underlying these pathologies result from chronification of an acute repair response towards injurious and inflammatory stimuli. Thereby functional tissue is replaced by excessive ECM deposition. In the kidney, impaired remodeling is a major cause of perivascular, interstitial, and glomerular fibrosis but also a common complication of chronic hypertension. Experimental evidence points to the matrix metalloproteases (MMPs) and their intrinsic inhibitors, the tissue inhibitors of MMPs as key mediators of atherogenic and fibrotic pathologies. Mechanistically, a deregulation in ECM turnover tightly correlates with an increased production and release of proinflammatory and profibrotic factors including interleukin-1beta, transforming growth factor beta, angiotensin II, and reactive oxygen species. Unlike these factors the pleiotropic messenger molecule nitric oxide (NO) by acting as the major physiological vasodilator has emerged as one of the most atheroprotective factors. However, under inflammatory conditions NO does acquire proatherogenic and profibrotic properties thereby exacerbating tissue fibrosis. In this review, the mechanisms underlying both opposing properties of NO on perivascular ECM remodeling will exemplarily be discussed for renal fibrosis with a particular focus on the MMPs and intrinsic protease inhibitors.

Down-regulation of matrix metalloproteinase-9 expression by nitric oxide in lipopolysaccharide-stimulated rat primary astrocytes

Immunologically activated astrocytes over-express matrix metalloproteinase-9 (MMP-9) and nitric oxide (NO). Because they have both beneficial and detrimental effects on the pathophyiological outcomes of several neurological diseases, their expression should be tightly regulated in the CNS. NO can modify the activity of other proteins either by directly modifying protein structure or regulating the expression of target proteins. In this study, we investigated the role of NO on the expression of MMPs in rat primary astrocytes. Rat primary astrocytes were stimulated with lipopolysaccharide (LPS), resulting in the over-expression of both MMP-9 and NO. Inhibition of NO production using nitric oxide synthase inhibitor, Nomega-nitro-l-arginine methyl ester (l-NAME), further increased MMP-9 expression, suggesting NO inhibits MMP-9 expression. In line with this observation, exogenous addition of NO donor, sodium nitroprusside (SNP) or S-nitroso-N-acetylpenicillamine (SNAP), inhibited MMP-9 expression in astrocytes. The inhibitory effect of NO was mediated by the down-regulation of mRNA and protein levels of MMP-9 but not by the direct modification of the enzymatic activity of MMP-9. The effect of NO on MMP-9 expression was mimicked by dibutyryl-cGMP and inhibited by PKG inhibitor KT5823, suggesting NO regulates MMP-9 expression via guanylate cyclase-PKG pathway. Finally, SNP or dibutyryl-cGMP inhibited the activation of ERK1/2 in LPS-stimulated astrocytes, which is an essential regulator of MMP-9 expression in astrocytes. The regulation of MMP-9 expression by NO may confer additional levels of fine-tuning of the level of MMP-9 during brain inflammatory conditions.

Matrix metalloproteinase 2-induced venous dilation via hyperpolarization and activation of K+ channels: relevance to varicose vein formation

BACKGROUND

Varicose veins are a common disorder of extensive venous dilation and remodeling with an as-yet unclear mechanism. Studies have shown increased plasma and tissue levels of matrix metalloproteinases (MMPs) in human varicose veins and animal models of venous hypertension. Although the effects of MMPs are generally attributed to extracellular matrix degradation, their effects on the mechanisms of venous contraction/relaxation are unclear. Our preliminary experiments have demonstrated that MMP-2 causes inhibition of phenylephrine-induced venous contraction. The purpose of this study was to determine whether MMP-induced inhibition of venous contraction involves an endothelium-dependent and/or -independent pathway.

METHODS

Circular segments of the inferior vena cava (IVC) were isolated from male Sprague-Dawley rats and suspended between two wire hooks in a tissue bath, and the effects of MMP-2 on phenylephrine- and KCl-induced contraction were measured. To study the role of endothelium-derived vasodilators, experiments were performed in the presence and absence of endothelium; N(G)-l-nitro-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthesis; indomethacin, an inhibitor of prostacyclin synthesis; cromakalim, an activator of adenosine triphosphate-sensitive K+ channels (K(ATP)); and iberiotoxin, a blocker of large-conductance Ca2+-dependent K+ channels (BK(Ca)) and smooth muscle hyperpolarization.

RESULTS

In endothelium-intact IVC segments, phenylephrine (10(-5) mol/L) caused significant contraction that slowly declined to 82.0% in 30 minutes. The addition of MMP-2 (1 microg/mL) caused a gradual decrease of phenylephrine contraction to 39.5% at 30 minutes. In endothelium-denuded IVC, MMP-2 induced a greater reduction of phenylephrine contraction, to 7.6%. In the presence of L-NAME (10(-4) mol/L), MMP-2 caused a marked decrease in phenylephrine contraction, to 4.4%. Large MMP-2-induced inhibition of phenylephrine contraction was also observed in IVC treated with L-NAME plus indomethacin. MMP-2 caused relaxation of phenylephrine contraction in IVC pretreated with cromakalim (10(-7) mol/L), an activator of K(ATP) channels. MMP-2-induced inhibition of phenylephrine contraction was abrogated in the presence of iberiotoxin (10(-8) mol/L), a blocker of BK(Ca). MMP-2 did not inhibit venous contraction during membrane depolarization by 96 mmol/L KCl, a condition that prevents outward K+ conductance and cell hyperpolarization.

CONCLUSIONS

MMP-2 causes significant IVC relaxation that is potentiated in the absence of endothelium or during blockade of endothelium-mediated nitric oxide and prostacyclin synthesis. The lack of effects of MMP-2 on KCl contraction and in iberiotoxin-treated veins suggests MMP-2-induced smooth muscle hyperpolarization and activation of BK(Ca) channels--a novel effect of MMP that may play a role in the early stages of venous dilation and varicose vein formation.

Interleukin-1β and Interleukin-6 Stimulate Matrix Metalloproteinase-9 Secretion in Cultured Myenteric Glia

Western blotting of culture media of myenteric glia stained positive for GFAP revealed increased secretion of matrix metalloproteinase-9 (MMP-9) in interleukin-1beta (IL-1beta) stimulated cells (10 ng/mL) versus control (142 +/- 19 versus 42 +/- 19, P < 0.05). Interleukin-6 (IL-6) stimulated cells also showed increased expression of MMP-9 (10 ng/mL) versus control (69 +/- 14 versus 4 +/- 2, P < 0.01). Control and cytokine-stimulated cells secreted MMP-2 constituitively. Gelatin zymography demonstrated that products were biologically active. Cytoplasmic staining for MMP-9 was detected in IL-1beta and IL-6-stimulated cells but was negligible in controls. Cultured myenteric glia are responsive to IL-1beta and IL-6 stimulation by secreting MMPs into the extracellular environment.

Factors in the pathogenesis of Dupuytren's contracture

This article reviews the basic science elements involved in the pathogenesis of Dupuytren's disease. Dupuytren's contracture is effected by a multitude of complex processes at the cellular level and the exact relative contribution of each is unknown. Various investigators have proposed different theories and documented individual findings regarding the pathophysiology of Dupuytren's contracture. The current report attempts to summarize many of these findings together in a schema of pathogenesis.

The nitric oxide donor DETA-NONOate decreases matrix metalloproteinase-9 expression and activity in rat aortic smooth muscle and abdominal aortic explants

Our objective was to examine the role of an exogenous nitric oxide (NO) donor, DETA-NONOate (DETA), on matrix metalloproteinase (MMP)-9, MMP-2, and tissue inhibitor of matrix metalloproteinases (TIMP)-1 expression and activity in interleukin (IL)-1beta-induced rat aortic smooth muscle cells (RA-SMCs) and rat aortic explants (RAEs). RA-SMCs were incubated with IL-1beta (2 ng/ml), an inflammatory cytokine known to induce MMP-9 expression, and increasing concentrations of DETA (0, 1.0, 10, 100 microM; n = 3/group) for 48 hr. RAEs were incubated with IL-1beta (2 ng/mL) and increasing concentrations of DETA (0, 5.0, 50, 100, and 500 microM; n = 3/group) for 48 hr. Media were collected and assayed for NO(x) by the Griess reaction and MMP-9 activity by zymography. Messenger RNA (mRNA) was extracted from cells and analyzed for MMP-9, MMP-2, and TIMP-1 expression levels by quantitative real-time reverse-transcriptase polymerase chain reaction. All statistical analyses were performed by analysis of variance. In RA-SMCs and RAEs, DETA administration resulted in a dose-dependent increase in media NOx concentration (RA-SCM p < 0.01, RAE p < 0.01) and a concurrent decrease in both MMP-9 expression (RASMC p = 0.01, RAE p = 0.01) and activity (RASMC p = 0.04, RAE p = 0.006). There were no significant differences seen in MMP-2 and TIMP-1 expression or activity in response to DETA exposure. DETA decreased IL-1beta-induced MMP-9 expression and activity in both RA-SMCs and RAEs in a dose-dependent fashion. In addition, DETA administration had no effect on MMP-2 or TIMP-1 expression or activity in vitro. These data suggest that NO donors may be beneficial in decreasing MMP-9 levels and might serve to inhibit MMP-9-dependent vessel wall remodeling seen during abdominal aortic aneurysm formation.

Targeted Deletion of CCR2 Impairs Deep Vein Thombosis Resolution in a Mouse Model

CCR2 is required for monocyte recruitment in many inflammatory processes, as well as conferring Th1 lymphokine responses. Deep vein thrombosis (DVT) resolution represents a specific inflammatory response whereby the thrombus must be dissolved for restoration of blood flow. Using a stasis model of DVT in the mouse, we investigated the role of CCR2 on DVT resolution. Genetic deletion of CCR2 (CCR2-/-) was associated with larger thrombi at early and later time points, increased thrombus collagen, fewer thrombus monocytes (F4/80), and significantly impaired neovascularization. IL-2 and IFN-gamma were significantly reduced in early CCR2-/- thrombi, whereas MCP-1 was significantly increased, and Th2 lymphokines were unaffected. Supplementation of CCR2-/- mice with IFN-gamma normalized early thrombus resolution without increasing monocyte influx. Neither Ab depletion of IFN-gamma nor genetic deletion of IFN-gamma impaired early DVT resolution. Early fibrinolysis was not impaired in CCR2-/- mice, but a significant reduction in both matrix metalloproteinase (MMP)-2 and MMP-9 activity was observed. However, only MMP-9 activity was restored with administration of IFN-gamma. We conclude that an early CCR2-dependent Th1 lymphokine response predominates in normal DVT resolution, mediates this in part by MMP-9 activation, but is not solely dependent on IFN-gamma.

Endocannabinoids and reactive nitrogen and oxygen species in neuropathologies

Neuropathologies that affect our population include ischemic stroke and neurodegenerative diseases of immune origin, including multiple sclerosis. The endocannabinoid system in the brain, including agonists anandamide (arachidonyl ethanolamide) and 2-arachidonoylglycerol, and the CB1 and CB2 cannabinoid receptors, has been implicated in the pathophysiology of these disease states, and can be a target for therapeutic interventions. This review concentrates on cellular signal transduction pathways believed to be involved in the cellular damage.

Reduced expression of vascular endothelial growth factor paralleled with the increased angiostatin expression resulting from the upregulated activities of matrix metalloproteinase-2 and -9 in human type 2 diabetic arterial vasculature

Impaired angiogenesis could contribute to the increased incidence of coronary and peripheral artery disease in diabetic patients. Angiogenesis is initiated by vascular endothelial growth factor (VEGF), a potent angiogenic cytokine, and suppressed by angiostatin, which is generated by matrix metalloproteinase (MMP)-2 and -9 through proteolytic cleavage of plasminogen. We hypothesized that MMP-2 and -9 were upregulated in the diabetic vasculature, resulting in increased angiostatin production and reduced blood vessel formation. In diabetic internal mammary artery samples (n=32) collected from patients undergoing coronary artery bypass grafting surgery, capillary density was only 30% of that in the nondiabetic vessels (n=32), whereas VEGF expression was reduced by 48%. Diabetes upregulated the expression and the gelatinolytic activity of MMP-2 and -9. Active MMP-2 and -9 were released from diabetic arteries, but not from nondiabetic vessels, during phenylephrine-induced vasoconstriction. Diabetes enhanced transcription and protein expression of tissue inhibitor of MMP (TIMP)-1 but had an opposite effect on TIMP-2. In diabetic vessels angiostatin was increased by 62% and was positively correlated with the activities of MMP-2 and -9 (r2=0.806 and 0.742, respectively). This report indicated a strong correlation between the upregulation of MMP-2 and MMP-9 and the increased angiostatin expression in the human diabetic arterial vasculature. The enhanced angiostatin production with a reduced VEGF formation may explain the pathogenesis of impaired angiogenesis in diabetes mellitus.

Endothelial mechanotransduction, nitric oxide and vascular inflammation

Numerous aspects of vascular homeostasis are modulated by nitric oxide and reactive oxygen species (ROS). The production of these is dramatically influenced by mechanical forces imposed on the endothelium and vascular smooth muscle. In this review, we will discuss the effects of mechanical forces on the expression of the endothelial cell nitric oxide synthase, production of ROS and modulation of endothelial cell glutathione. We will also review data that exercise training in vivo has a similar effect as laminar shear on endothelial function and discuss the clinical relevance of these basic findings.

Drug-induced liver injury: summary of a single topic clinical research conference

Idiosyncratic drug induced liver injury (DILI) remains poorly understood. It is assumed that the affected individuals possess a rare combination of genetic and non genetic factors that, if identified, would greatly improve understanding of the underlying mechanisms. This single topic conference brought together basic scientists, translational investigators, and clinicians with an interest in DILI. The goal was to define high priority areas of investigation that will soon be made possible by The Drug-Induced Liver Injury Network (DILIN). Since 2004 DILIN has been collecting clinical data, genomic DNA and some tissues from patients who have experienced bone fide DILI. The presentations spanned many different areas of DILI, and included novel data concerning mechanisms of hepatotoxicity, new "omics" approaches, and the challenges of improving causation assessment.

Effects of progesterone on iNOS, COX-2, and collagen expression in the cervix

This study examines the relationship between inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in the control of cervical ripening and parturition under normal (normal term pregnancy) and abnormal (preterm labor and prolongation of pregnancy) conditions by (a) measuring changes in the collagen both visually and quantitatively, (b) localizing and characterizing iNOS and COX-2 under normal conditions, and (c) characterizing the changes in iNOS and COX-2 under abnormal conditions. Cervices are obtained from estrus and timed pregnant Sprague-Dawley rats (n=4-10 per group). Preterm labor is induced with Onapristone (3 mg/rat; progesterone antagonist) and the prolongation of pregnancy with progesterone (2.5 mg, twice daily). Collagen changes are measured and visualized with the picrosirius polarization method. RT-PCR is used to characterize the mRNA expression (p<0.05), and immunohistochemistry is used to localize the protein expression for iNOS and COX-2. The organization and birefringence of the collagen during pregnancy decreased and is supported by changes in the luminosity (p<0.001). The iNOS and COX-2 enzymes were localized in cervical smooth muscle, vascular smooth muscle, and epithelium. Under normal conditions, iNOS mRNA levels decreased as COX-2 mRNA levels increased demonstrating an inverse correlation (Spearman r = -0.497; p=0.00295). Onapristone stimulated preterm labor, increasing the iNOS and COX-2 mRNA (p<0.05). The increase demonstrated a positive correlation (Spearman r = 0.456; p=0.03). Progesterone prolonged pregnancy, decreasing the iNOS and COX-2 mRNA (p=0.036). In conclusion, there may be an interaction between the nitric oxide and prostaglandin pathways in cervical ripening and parturition.

Gender differences in rat aortic smooth muscle cell matrix metalloproteinase-9

BACKGROUND

A predilection exists for men to develop abdominal aortic aneurysms (AAAs), but the reasons for this gender predisposition are not known. Matrix metalloproteinase-9 (MMP-9) has been implicated in both human and experimental AAAs. This investigation tested the hypothesis that male and female gender differences exist in the production of MMP-9 by rat aortic smooth muscle cells (RASMCs).

STUDY DESIGN

In the first set of experiments, cultured male and female RASMCs were stimulated with interleukin-1 beta (IL-1beta) at 2 ng/mL. Messenger RNA was extracted from the RASMCs and gene expression of MMP-9 and tissue inhibitor of metalloproteinase-1 (TIMP-1), an MMP-9 inhibitor, was measured by quantitative real-time polymerase chain reaction. Cell culture media were collected for measurement of MMP-9 protein levels and MMP-9 activity by Western blotting and gelatin zymography, respectively. In the second set of experiments, male RASMCs were treated with 17-beta-estradiol (10(-10) to 10(-6) mol/L) and MMP-9 activity was measured. In the third set of experiments, male rats were pretreated with estradiol, and MMP-9 activity was measured in the media from explanted aortas.

RESULTS

MMP-9 gene expression was 10-fold higher in male versus female RASMCs (p=0.003). MMP-9 protein levels (p=0.005) and gelatinolytic activities (p=0.01) were also greater in male than female RASMCs. TIMP-1 expression was fourfold higher in male versus female RASMCs (p<0.001). Estradiol-treated male RASMCs did not exhibit a decrease in MMP-9 activity. But aortic explants from male rats pretreated with 17-beta-estradiol had 60% less MMP-9 activity than explants from male controls (p=0.03).

CONCLUSIONS

MMP-9 and TIMP-1 are greater in male than in female RASMCs. These findings support the tenet that gender-related differences in MMP-9 may contribute to AAA formation.

Inducible nitric oxide synthase (iNOS) in tumor biology: the two sides of the same coin

Inducible nitric oxide synthase (iNOS) is one of three key enzymes generating nitric oxide (NO) from the amino acid l-arginine. iNOS-derived NO plays an important role in numerous physiological (e.g. blood pressure regulation, wound repair and host defence mechanisms) and pathophysiological (inflammation, infection, neoplastic diseases, liver cirrhosis, diabetes) conditions. iNOS is the synthase isoform most commonly associated with malignant disease. Nevertheless, the role of iNOS during tumor development is highly complex, and incompletely understood. Both promoting and deterring actions have been described, presumably depending upon the local concentration of iNOS within the tumor microenvironment. In particular, pivotal effects such as malingnant transformation, angiogenesis, and metastasis are modulated by iNOS. On the other hand, NO derived from macrophages has a potentially cytotoxic/cytostatic effect upon tumor cells. Hence, therapeutical interference with iNOS activity is of considerable interest, especially in tumors where metastatic activity, host defence mechanisms and the level of differentiation seem to be correlated to iNOS expression. This review will aim to summarize the dual actions of iNOS as simultaneous tumor promoter and suppressor.

Neutrophil Depletion Inhibits Experimental Abdominal Aortic Aneurysm Formation

Background— Neutrophils may be an important source of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9), two matrix-degrading enzymes thought to be critical in the formation of an abdominal aortic aneurysm (AAA). The purpose of this investigation was to test the hypothesis that neutrophil depletion would limit experimental AAA formation by altering one or both of these enzymes.

Methods and Results— Control, rabbit serum–treated (RS; n=27) or anti-neutrophil-antibody–treated (anti-PMN; n=25) C57BL/6 mice underwent aortic elastase perfusion to induce experimental aneurysms. Anti-PMN–treated mice became neutropenic (mean, 349 cells/μL), experiencing an 84% decrease in the circulating absolute neutrophil count ( P <0.001) before elastase perfusion. Fourteen days after elastase perfusion, control mice exhibited a mean aortic diameter (AD) increase of 104±14% ( P <0.0001), and 67% developed AAAs, whereas anti-PMN–treated mice exhibited a mean AD increase of 42±33%, with 8% developing AAAs. The control group also had increased tissue neutrophils (20.3 versus 8.6 cells per 5 high-powered fields [HPFs]; P =0.02) and macrophages (6.1 versus 2.1 cells per 5 HPFs, P =0.005) as compared with anti-PMN–treated mice. There were no differences in monocyte chemotactic protein-1 or macrophage inflammatory protein-1α chemokine levels between groups by enzyme-linked immunosorbent assay. Neutrophil collagenase (MMP-8) expression was detected only in the 14-day control mice, with increased MMP-8 protein levels by Western blotting ( P =0.017), and MMP-8–positive neutrophils were seen almost exclusively in this group. Conversely, there were no statistical differences in MMP-2 or MMP-9 mRNA expression, protein levels, enzyme activity, or immunostaining patterns between groups. When C57BL/6 wild-type (n=15) and MMP-8–deficient mice (n=17) were subjected to elastase perfusion, however, ADs at 14 days were no different in size (134±7.9% versus 154±9.9%; P =0.603), which suggests that MMP-8 serves only as a marker for the presence of neutrophils and is not critical for AAA formation.

Conclusions— Circulating neutrophils are an important initial component of experimental AAA formation. Neutrophil depletion inhibits AAA development through a non–MMP-2/9–mediated mechanism associated with attenuated inflammatory cell recruitment.

Vein wall remodeling after deep vein thrombosis involves matrix metalloproteinases and late fibrosis in a mouse model

HYPOTHESIS

Deep venous thrombosis (DVT) confers vein wall injury associated with fibrosis and extracellular matrix (ECM) turnover, likely mediated by matrix proteases. This study investigated the expression of proteases and collagen involved in early vein wall remodeling.

METHODS

In the mouse, DVT was produced by ligation of the infrarenal inferior vena cava (IVC) or sham operation, and tissue was harvested at 4, 8, and 12 days. The vein wall tissue was processed for real-time reverse transcriptase-polymerase chain reaction (6 to 8 per time point), Western immunoblotting (5 per time point), and gelatin zymography (5 per time point). Analysis of variance was used for multiple comparisons, and a P < .05 was significant.

RESULTS

Thrombus resolution was documented by a 38% decrease in the thrombosed IVC weight from day 4 to day 12 (P = .007). Total vein wall collagen increased over time, with a corresponding increase in procollagen I and III, and expression peaked at 12 days (24-fold and 6.1-fold, respectively, P < .02). Matrix metalloproteinase-2 (MMP-2) gene expression was 23-fold greater at 12 days after thrombus formation compared with sham or 4 days after thrombosis (P < .05). Total MMP-2 activity was also significantly elevated at 12 days compared with sham (P < .05). MMP-9 expression was 19-fold and 27-fold higher at days 4 and 8, respectively, relative to sham (P < .05), with no difference in activity. MMP-14 expression was twofold to 3.6-fold greater at day 12 compared with earlier time points and shams (P < .001), but no differences in protein levels were found. Urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) protein levels were not significantly different from sham over time; however, the ratio of uPA to PAI-1 was decreased through 8 days.

CONCLUSIONS

Vein wall remodeling after DVT is similar to wound healing and is associated with increased procollagen gene expression and total collagen. It is also associated with increased early MMP-9 expression, followed by MMP-2 expression and activity after DVT resolution.

CLINICAL RELEVANCE

Deep vein thrombosis is an often neglected problem that long term is associated with the postphlebitic syndrome of limb swelling, pain, and often ulceration. The basic mechanisms of the vein wall damage that results have not been delineated. The following study describes the vein wall matrix metalloproteinase gene and activity response induced over time in the vein wall after DVT. Additionally, the corresponding collagen upregulation and proximate plasmin system mediators are determined. With this knowledge, potential therapies to reduce vein wall injury directly might be possible.

Suppression of experimental aortic aneurysms: comparison of inducible nitric oxide synthase and cyclooxygenase inhibitors

The rat model of abdominal aortic aneurysm (AAA) is associated with inflammation, destruction of extracellular matrix, and production of both inducible nitric oxide synthase (iNOS) and matrix metalloproteinase-9 (MMP-9). Indomethacin, a nonselective cyclooxygenase inhibitor, may prevent AAA formation by inhibiting cyclooxygenase-2 (COX-2) activity. We hypothesized that indomethacin, rofecoxib (selective COX-2 inhibitor), and 1400 W (selective iNOS activity inhibitor) would decrease aneurysm formation in the rat model. Forty-six male Wistar rats underwent intraaortic elastase infusion in two parallel studies based on medication delivery route. Sixteen rats were randomized to rofecoxib or water by gastric lavage. Thirty rats were randomized to subcutaneous saline, indomethacin, or 1400 W. Heart rate, blood pressure and aortic diameters were measured. Western Blot and mRNA analysis for MMP-9 and iNOS was performed on postoperative day 7 aortic segments. Elastin degradation and inflammation were evaluated by immunohistochemistry. Elastase infusion produced AAA in all rats. 1400 W significantly limited aneurysm expansion (p = 0.01) whereas treatment with indomethacin and rofecoxib did not. Only 1400 W significantly increased blood pressure (p < 0.001). Indomethacin alone statistically decreased MMP-9 (p < 0.011). 1400 W resulted in greater conservation of aortic elastin than indomethacin (p = 0.025). All groups demonstrated statistically similar expression of iNOS. In conclusion, selective iNOS activity inhibitor, 1400 W, significantly decreased aneurysm size and preserved aortic elastin without altering MMP-9 levels. Indomethacin significantly decreased MMP-9 expression without decreasing aneurysm size. Rofecoxib did not significantly decrease MMP-9 expression or aneurysm size. Inhibition of iNOS limits aneurysmal expansion by mechanisms other than MMP-9 inhibition. MMP-9 inhibition by indomethacin is not sufficient to limit aneurysm expansion in our model.

Dual role of matrix metalloproteinases (matrixins) in intimal thickening and atherosclerotic plaque rupture

Intimal thickening, the accumulation of cells and extracellular matrix within the inner vessel wall, is a physiological response to mechanical injury, increased wall stress, or chemical insult (e.g., atherosclerosis). If excessive, it can lead to the obstruction of blood flow and tissue ischemia. Together with expansive or constrictive remodeling, the extent of intimal expansion determines final lumen size and vessel wall thickness. Plaque rupture represents a failure of intimal remodeling, where the fibrous cap overlying an atheromatous core of lipid undergoes catastrophic mechanical breakdown. Plaque rupture promotes coronary thrombosis and myocardial infarction, the most prevalent cause of premature death in advanced societies. The matrix metalloproteinases (MMPs) can act together to degrade the major components of the vascular extracellular matrix. All cells present in the normal and diseased blood vessel wall upregulate and activate MMPs in a multistep fashion driven in part by soluble cytokines and cell-cell interactions. Activation of MMP proforms requires other MMPs or other classes of protease. MMP activation contributes to intimal growth and vessel wall remodeling in response to injury, most notably by promoting migration of vascular smooth muscle cells. A broader spectrum and/or higher level of MMP activation, especially associated with inflammation, could contribute to pathological matrix destruction and plaque rupture. Inhibiting the activity of specific MMPs or preventing their upregulation could ameliorate intimal thickening and prevent myocardial infarction.

Dipyridamole selectively inhibits inflammatory gene expression in platelet-monocyte aggregates

BACKGROUND

Drugs that simultaneously decrease platelet function and inflammation may improve the treatment of cardiovascular disorders. Here, we determined whether dipyridamole and aspirin, a combination therapy used to prevent recurrent stroke, regulates gene expression in platelet-monocyte inflammatory model systems.

METHODS AND RESULTS

Human platelets and monocytes were pretreated with dipyridamole, aspirin, or both inhibitors. The cells were stimulated with thrombin or activated by adhesion to collagen, and gene expression was measured in the target monocytes. Thrombin-stimulated platelets increased monocyte chemotactic protein-1 (MCP-1) expression by monocytes. Dipyridamole but not aspirin attenuated nuclear translocation of NF-kappaB and blocked the synthesis of MCP-1 at the transcriptional level. Dipyridamole delayed maximal synthesis of interleukin-8 but did not alter cyclooxygenase-2 accumulation. Adherence to collagen and platelets also increased the expression of matrix metalloproteinase-9 (MMP-9) in monocytes, a response that was inhibited by dipyridamole. In this case, however, dipyridamole did not block transcription or distribution of MMP-9 mRNA to actively translating polysomes, indicating that it regulates the expression of MMP-9 protein at a postinitiation stage of translation. Dipyridamole also blocked MCP-1 and MMP-9 generated by lipopolysaccharide-treated monocytes, indicating that at least part of its inhibitory action is unrelated to its antiplatelet properties.

CONCLUSIONS

These results indicate that dipyridamole has selective antiinflammatory properties that may contribute to its actions in the secondary prevention of stroke.

Tamoxifen up-regulates catalase production, inhibits vessel wall neutrophil infiltration, and attenuates development of experimental abdominal aortic aneurysms

BACKGROUND

Selective estrogen receptor modulators (SERMs), similar to estrogens, possess vasoprotective effects by reducing release of reactive oxygen species. Little is known about the potential effects of SERMs on the pathogenesis of abdominal aortic aneurysms (AAAs). This study's objective was to investigate the growth of experimental AAAs in the setting of the SERM tamoxifen.

METHODS

In the first set of experiments, adult male rats underwent subcutaneous tamoxifen pellet (delivering 10 mg/kg/day) implantation (n = 14) or sham operation (n = 16). Seven days later, all animals underwent pancreatic elastase perfusion of the abdominal aorta. Aortic diameters were determined at that time, and aortas were harvested 7 and 14 days after elastase perfusion for immunohistochemistry, real-time polymerase chain reaction, Western blot analysis, and zymography. In the second set of experiments, a direct irreversible catalase inhibitor, 3-amino-1,2,4-triazole (AT), was administered intraperitoneally (1 mg/kg) daily to tamoxifen-treated (n = 6) and control rats (n = 6), starting on day 7 after elastase perfusion. Aortic diameters were measured on day 14. In a third set of experiments, rats were perfused with catalase (150 mg/kg) after the elastase (n = 5), followed by daily intravenous injections of catalase (150 mg/kg/day) administered for 10 days. A control group of rats (n = 7) received 0.9% NaCl instead of catalase.

RESULTS

Mean AAA diameters were approximately 50% smaller in tamoxifen-treated rats compared with sham rats 14 days after elastase perfusion (P = .002). The tamoxifen-treated group's aortas had a five-fold increase in catalase mRNA expression (P = .02) on day 7 and an eight-fold increase in catalase protein on day 14 (P = .04). Matrix metalloprotroteinase-9 activity was 2.4-fold higher (P = .01) on day 7 in the aortas of the controls compared to the tamoxifen-treated group's aortas. Tamoxifen-treated rats had approximately 40% fewer aortic polymorphonuclear neutrophils compared to controls on day 7 (P = .05). Administration of the direct catalase inhibitor AT to tamoxifen-treated rats partially reversed the aneurysm inhibitory effect of tamoxifen by nearly 30% (P = .02). In contrast, catalase administration inhibited AAA formation by 44% (P = .002).

CONCLUSIONS

The selective estrogen receptor modulator tamoxifen inhibits the development of AAAs in male rats in association with an up-regulation of catalase and inhibition of aortic wall neutrophil infiltration.

Early MT-1 MMP expression following elastase exposure is associated with increased cleaved MMP-2 activity in experimental rodent aortic aneurysms

OBJECTIVE

The objective of this study was to determine the significance of membrane type 1 matrix metalloproteinase (MT1-MMP) activation of MMP-2 in experimental abdominal aortic aneurysms.

METHODS

Rat aortas were perfused with either saline as a control or elastase, and harvested on 2, 4, or 7 days after perfusion (n = 5 per treatment group/day). Aortic MT1-MMP and MMP-2 expression and protein were determined by real time polymerase chain reaction and Western blotting, respectively. Aortic explants were used to measure MMP-2 activity by zymography. Rat aortic smooth muscle cells in vitro were exposed to increasing doses of elastase and analyzed for MT-1 MMP expression.

RESULTS

Aneurysms formed in 80% of the elastase-perfused aortas at 7 days, whereas none formed in the saline-perfused aortas. Significantly increased MT1-MMP expression was observed only on day 4, when levels were 6.5-fold higher in elastase-perfused aortas compared with saline-perfused aortas (P < .01). By day 7, MT1-MMP protein was present only in the elastase-perfused aortas (P = .02). By immunohistochemistry, MT1-MMP was detectable only in the elastase-perfused group at day 7. Cleaved MMP-2 activity (P = .045) was increased in elastase-perfused aortas compared with saline perfused aortas at day 7. In rat aortic smooth muscle cells, MT-1 MMP expression increased in response to elastase (P = .02).

CONCLUSION

The rodent aortic aneurysm model exhibits upregulation of MT1-MMP expression and protein with subsequent increased conversion of MMP-2 from the latent to the cleaved form.

Nitric oxide inhibits matrix metalloproteinase-2 expression via the induction of activating transcription factor 3 in endothelial cells

Nitric oxide (NO) has been shown to inhibit migration of cells in which various matrix metalloproteinases (MMPs) are involved. The underlying molecular mechanisms of this inhibition remain elusive. Endothelial cells (ECs) constitutively produce MMP-2. The effect of NO on MMP-2 expression was examined. A dose-dependent inhibition of MMP-2 mRNA level was demonstrated in ECs treated with NO. ECs infected with adenovirus carrying endothelial NO synthase (Ade-NOS) reduced MMP-2 expression. The inhibitory effect of NO on MMP-2 expression was a transcriptional event because NO reduced MMP-2 promoter activity. NO treatment of ECs consequently suppressed MMP-2 secretion revealed by zymographic assay. Functional analysis of MMP-2 promoter (1716 base pairs) indicated that the p53-binding site (-1659 to -1629) was crucial for MMP-2 promoter activity. Activating transcription factor 3 (ATF3) has been reported to act as a transcriptional repressor for p53. ECs treated with NO induced ATF3 expression. Consistently, Ade-NOS-infected ECs showed an increase of ATF3 level. Moreover, ECs either over-expressed ATF3 or, when treated with an ATF3 activator (MG-132; carbobenzoxy-l-leucyl-l-leucyl-l-leucinal), resulted in a repression of MMP-2 promoter activity. Because of MMP-2 suppression by NO, ECs treated with NO inhibited endothelial migration, a phenomenon similar to that of ECs treated with MMP-2 antibody or MG-132. These results indicate that NO-attenuating endothelial migration is mediated at least in part by its reduction of MMP-2 expression via the up-regulation of ATF3. This study provides a molecular basis that supports the notion that NO acts as a negative regulator in endothelial migration.

Deep vein thrombosis resolution is modulated by monocyte CXCR2-mediated activity in a mouse model

OBJECTIVE

To determine the role of CXCR2, the receptor for cysteine-X-cysteine (CXC) chemokines, and its primary effector cell, the neutrophil (PMN), on deep venous thrombosis (DVT) resolution.

METHODS AND RESULTS

DVT in BALB/c, anti-CXCR2 antibody-treated, and BALB/c CXCR2(-/-) mice were created by infrarenal inferior vena cava (IVC) ligation and the thrombus harvested at various time points over 21 days. The CXCR2(-/-) mice had significantly larger thrombi at early time points (days 2 to 8), and significantly decreased intrathrombus PMNs, monocytes, and neovascularization as compared with controls. Thrombus KC/CXCL1 was significantly higher at 2 days in CXCR2-/- thrombi as measured by enzyme-linked immunosorbent assay. Fibrin content was significantly higher, with less uPA gene expression at 4 days in CXCR2-/- thrombi. Late fibrotic maturation of the thrombus was delayed in the CXCR2-/- mice, with significantly decreased 8 day MMP-2 activity, whereas MMP-9 activity was elevated as compared with controls. Similar impairment in DVT resolution was found at 8 days with anti-CXCR2 inhibition. However, systemic neutropenia, unlike CXCR2 deletion, did not increase the thrombus size as compared with controls.

CONCLUSIONS

Normal DVT resolution involves CXCR2-mediated neovascularization, collagen turnover, and fibrinolysis, and it is probably primarily monocyte-dependent.