Matrix metalloproteinases and diabetic vascular complications

Vascular remodeling after ischemic stroke: mechanisms and therapeutic potentials

The brain vasculature has been increasingly recognized as a key player that directs brain development, regulates homeostasis, and contributes to pathological processes. Following ischemic stroke, the reduction of blood flow elicits a cascade of changes and leads to vascular remodeling. However, the temporal profile of vascular changes after stroke is not well understood. Growing evidence suggests that the early phase of cerebral blood volume (CBV) increase is likely due to the improvement in collateral flow, also known as arteriogenesis, whereas the late phase of CBV increase is attributed to the surge of angiogenesis. Arteriogenesis is triggered by shear fluid stress followed by activation of endothelium and inflammatory processes, while angiogenesis induces a number of pro-angiogenic factors and circulating endothelial progenitor cells (EPCs). The status of collaterals in acute stroke has been shown to have several prognostic implications, while the causal relationship between angiogenesis and improved functional recovery has yet to be established in patients. A number of interventions aimed at enhancing cerebral blood flow including increasing collateral recruitment are under clinical investigation. Transplantation of EPCs to improve angiogenesis is also underway. Knowledge in the underlying physiological mechanisms for improved arteriogenesis and angiogenesis shall lead to more effective therapies for ischemic stroke.

The anti-inflammatory effects of exercise training promote atherosclerotic plaque stabilization in apolipoprotein E knockout mice with diabetic atherosclerosis

Physical exercise is the cornerstone of cardiovascular disease treatment. The present study investigated whether exercise training affects atherosclerotic plaque composition through the modification of inflammatoryrelated pathways in apolipoprotein E knockout (apoE^−/−) mice with diabetic atherosclerosis. Forty-five male apoE^−/− mice were randomized into three equivalent (n=15) groups: control (CO), sedentary (SED), and exercise (EX). Diabetes was induced by streptozotocin administration. High-fat diet was administered to all groups for 12 weeks. Afterwards, CO mice were euthanatized, while the sedentary and exercise groups continued high-fat diet for 6 additional weeks. Exercising mice followed an exercise program on motorizedtreadmill (5 times/week, 60 min/session). Then, blood samples and atherosclerotic plaques in the aortic root were examined. A considerable (P<0.001) regression of the atherosclerotic lesions was observed in the exercise group (180.339±75.613×10³µm²) compared to the control (325.485±72.302×10³ µm²) and sedentary (340.188±159.108×10³µm²) groups. We found decreased macrophages, matrix metalloproteinase-2 (MMP-2), MMP-3, MMP-8 and interleukin-6 (IL-6) concentrations (P<0.05) in the atherosclerotic plaques of the exercise group. Compared to both control and sedentary groups, exercise training significantly increased collagen (P<0.05), elastin (P<0.001), and tissue inhibitor of matrix metalloproteinase-2 (TIMP-2) (P<0.001) content in the atherosclerotic plaques. Those effects paralleled with increased fibrous cap thickness and less internal elastic lamina ruptures after exercise training (P<0.05), while body-weight and lipid parameters did not significantly change. Plasma MMP-2 and MMP-3 concentrations in atherosclerotic tissues followed a similar trend. From our study we can conclude that exercise training reduces and stabilizes atherosclerotic lesions in apoE^−/− mice with diabetic atherosclerosis. A favorable modification of the inflammatory regulators seems to explain those beneficial effects.

The beneficial effects of a direct thrombin inhibitor, dabigatran etexilate, on the development and stability of atherosclerotic lesions in apolipoprotein E-deficient mice : dabigatran etexilate and atherosclerosis

PURPOSE

Dabigatran etexilate (DE) constitutes a novel, direct thrombin inhibitor. Regarding the association of thrombin with atherogenesis, we assessed the effects of DE on the development and stability of atherosclerotic lesions in apolipoprotein-E deficient (ApoE-/-) mice.

MATERIALS-METHODS

Fifty male ApoE-/- mice were randomized to receive western-type diet either supplemented with DE 7.5 mg DE/g chow) (DE-group, n = 25) or matching placebo as control (CO-group, n = 25) for 12 weeks. After this period, all mice underwent carotid artery injury with ferric chloride and the time to thrombotic total occlusion (TTO) was measured. Then, mice were euthanatized and each aortic arch was analyzed for the mean plaque area, the content of macrophages, elastin, collagen, nuclear factor kappaB (NFκB), vascular cell adhesion molecule-1 (VCAM-1), matrix metalloproteinase-9 (MMP-9) and its inhibitor (TIMP-1).

RESULTS

DE-group showed significantly longer TTO compared to CO-group (8.9 ± 2.3 min vs 3.5 ± 1.1 min, p < 0.001) and the mean plaque area was smaller in DE-group than CO-group (441.00 ± 160.01 × 10(3) μm(2) vs 132.12 ± 32.17 × 10(3) μm(2), p < 0.001). Atherosclerotic lesions derived from DE-treated mice showed increased collagen (p = 0.043) and elastin (p = 0.031) content, thicker fibrous caps (p < 0.001) and reduced number of internal elastic lamina ruptures per mm of arterial girth (p < 0.001) when compared to CO-group. Notably, DE treatment seemed to promote plaque stability possibly by reducing concentrations of NFκB, VCAM-1, macrophages and MMP-9 and increasing TIMP-1 within atherosclerotic lesions (p < 0.05).

CONCLUSIONS

DE attenuates arterial thrombosis, reduces lesion size and may promote plaque stability in ApoE-/- mice. The plaque-stabilizing effects of chronic thrombin inhibition might be the result of the favorable modification of inflammatory mechanisms.

The ERK1/2 Inhibitor U0126 Attenuates Diabetes-Induced Upregulation of MMP-9 and Biomarkers of Inflammation in the Retina

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

Role of matrix metalloproteinase-2 and -9 in the development of diabetic retinopathy

Diabetic retinopathy represents the most common causes of vision loss in patients affected by diabetes mellitus. The cause of vision loss in diabetic retinopathy is complex and remains incompletely understood. One of the earliest changes in the development of retinopathy is the accelerated apoptosis of retinal microvascular cells and the formation of acellular capillaries by unknown mechanism. Results of a recent research suggest an important role of matrix metalloproteinases (MMPs) in the development of diabetic retinopathy. MMPs are a large family of proteinases that remodel extracellular matrix components, and under pathological condition, its induction is considered as a negative regulator of cell survival; and in diabetes, latent MMPs are activated in the retina and its capillary cells, and activation of MMP-2 and -9 induces apoptosis of retinal capillary cells. This review will focus on the MMP-2 and MMP-9 in the diabetic retina with special reference to oxidative stress, mitochondria dysfunction, inflammation and angiogenesis, as well as summarizing the current information linking these proteins to pathogenesis of diabetic retinopathy.

Diabetes-related alterations in the enteric nervous system and its microenvironment

Gastric intestinal symptoms common among diabetic patients are often caused by intestinal motility abnormalities related to enteric neuropathy. It has recently been demonstrated that the nitrergic subpopulation of myenteric neurons are especially susceptible to the development of diabetic neuropathy. Additionally, different susceptibility of nitrergic neurons located in different intestinal segments to diabetic damage and their different levels of responsiveness to insulin treatment have been revealed. These findings indicate the importance of the neuronal microenvironment in the pathogenesis of diabetic nitrergic neuropathy. The main focus of this review therefore was to summarize recent advances related to the diabetes-related selective nitrergic neuropathy and associated motility disturbances. Special attention was given to the findings on capillary endothelium and enteric glial cells. Growing evidence indicates that capillary endothelium adjacent to the myenteric ganglia and enteric glial cells surrounding them are determinative in establishing the ganglionic microenvironment. Additionally, recent advances in the development of new strategies to improve glycemic control in type 1 and type 2 diabetes mellitus are also considered in this review. Finally, looking to the future, the recent and promising results of metagenomics for the characterization of the gut microbiome in health and disease such as diabetes are highlighted.

Peroxisome proliferator-activated receptor-γ activation with angiotensin II type 1 receptor blockade is pivotal for the prevention of blood-brain barrier impairment and cognitive decline in type 2 diabetic mice

We reported previously that an angiotensin II type 1 receptor blocker, telmisartan, improved cognitive decline with peroxisome proliferator-activated receptor-γ activation; however, the detailed mechanisms are unclear. Enhanced blood-brain barrier (BBB) permeability with alteration of tight junctions is suggested to be related to diabetes mellitus. Therefore, we examined the possibility that telmisartan could attenuate BBB impairment with peroxisome proliferator-activated receptor-γ activation to improve diabetes mellitus-induced cognitive decline. Type 2 diabetic mice KKA(y) exhibited impairment of cognitive function, and telmisartan treatment attenuated this. Cotreatment with GW9662, a peroxisome proliferator-activated receptor-γ antagonist, interfered with these protective effects of telmisartan against cognitive function. BBB permeability was increased in both the cortex and hippocampus in KKA(y) mice. Administration of telmisartan attenuated this increased BBB permeability. Coadministration of GW9662 reduced this effect of telmisartan. Significant decreases in expression of tight junction proteins and increases in matrix metalloproteinase expression, oxidative stress, and proinflammatory cytokine production were observed in the brain, and treatment with telmisartan restored these changes. Swollen astroglial end-feet in BBB were observed in KKA(y) mice, and this change in BBB ultrastructure was decreased in telmisartan. These effects of telmisartan were weakened by cotreatment with GW9662. In contrast, administration of another angiotensin II type 1 receptor blocker, losartan, was less effective compared with telmisartan in terms of preventing BBB permeability and astroglial end-foot swelling, and coadministration of GW9662 did not affect the effects of losartan. These findings are consistent with the possibility that, in type 2 diabetic mice, angiotensin II type 1 receptor blockade with peroxisome proliferator-activated receptor-γ activation by telmisartan may help with protection against cognitive decline by preserving the integrity of the BBB.

Potentiation of aspirin-induced cerebroprotection by minocycline: a therapeutic approach to attenuate exacerbation of transient focal cerebral ischaemia

Cerebrovascular disease is a major cause of mortality and disability in adults. Diabetes mellitus increases the risk of cerebral ischaemia and is associated with worse clinical outcome following an event. Upregulation of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) in diabetes appears to play a role in vascular complications of diabetes. We hypothesised that inhibition of MMP-2 and MMP-9 by minocycline can be potentiated by aspirin through inhibition of cyclooxygenase-2 and tissue plasminogen activator, resulting in amelioration of clinical cerebral ischaemia in diabetes. In the present study, cerebral ischaemia/reperfusion injury was induced in streptozotocin diabetic rats by 1 h middle cerebral artery occlusion and 24 h reperfusion. Infarct volume, cerebral oedema, neurological severity score and blood-brain barrier disruption were significantly increased in diabetic animals compared with the normoglycemic control group. The combination of aspirin and minocycline treatment significantly improved these parameters in diabetic animals. Moreover, this therapy was associated with significantly lower mortality and reduction in MMP-2 and MMP-9 levels. Our data indicate that combination of aspirin and minocycline therapy protects from the consequences of cerebral ischaemia in animal models of diabetes and is associated with inhibition of MMP-2 and MMP-9. Therefore, this combination therapy may represent a novel strategy to reduce the neurological complications of cerebral ischaemia in diabetes.

Matrix metalloproteinase inhibitors as investigative tools in the pathogenesis and management of vascular disease

Matrix metalloproteinases (MMPs) are proteolytic enzymes that degrade various components of the extracellular matrix (ECM). MMPs could also regulate the activity of several non-ECM bioactive substrates and consequently affect different cellular functions. Members of the MMPs family include collagenases, gelatinases, stromelysins, matrilysins, membrane-type MMPs, and others. Pro-MMPs are cleaved into active MMPs, which in turn act on various substrates in the ECM and on the cell surface. MMPs play an important role in the regulation of numerous physiological processes including vascular remodeling and angiogenesis. MMPs may also be involved in vascular diseases such as hypertension, atherosclerosis, aortic aneurysm, and varicose veins. MMPs also play a role in the hemodynamic and vascular changes associated with pregnancy and preeclampsia. The role of MMPs is commonly assessed by measuring their gene expression, protein amount, and proteolytic activity using gel zymography. Because there are no specific activators of MMPs, MMP inhibitors are often used to investigate the role of MMPs in different physiologic processes and in the pathogenesis of specific diseases. MMP inhibitors include endogenous tissue inhibitors (TIMPs) and pharmacological inhibitors such as zinc chelators, doxycycline, and marimastat. MMP inhibitors have been evaluated as diagnostic and therapeutic tools in cancer, autoimmune disease, and cardiovascular disease. Although several MMP inhibitors have been synthesized and tested both experimentally and clinically, only one MMP inhibitor, i.e., doxycycline, is currently approved by the Food and Drug Administration. This is mainly due to the undesirable side effects of MMP inhibitors especially on the musculoskeletal system. While most experimental and clinical trials of MMP inhibitors have not demonstrated significant benefits, some trials still showed promising results. With the advent of new genetic and pharmacological tools, disease-specific MMP inhibitors with fewer undesirable effects are being developed and could be useful in the management of vascular disease.

Current role of biomarkers in carotid disease: a systematic review

BACKGROUND AND PURPOSE

Accumulating evidence suggests that carotid plaque vulnerability can be used as a determinant of ischemic stroke risk stratification and carotid intervention. Novel markers of high-risk carotid plaque in patients are needed.

SUMMARY OF REVIEW

Advances in cellular and molecular pathophysiology, the demand for accurately predicting carotid risk, and choosing the optimal prevention strategy are stimulating great interest in the development of novel surrogate markers. Biomarkers in cardiovascular disease are expected to predict the natural history, clinical outcomes, and the efficacy of disease-modifying interventions. We aimed to review the literature regarding clinical data on novel serum biomarkers related to ischemic cerebrovascular events associated with carotid artery disease. We provide background information on the biomarkers related to all aspects of carotid disease: natural history, carotid intervention strategies for symptomatic and asymptomatic patients, perioperative risk prediction, and their therapeutic implications.

CONCLUSION

At present, heterogeneous data support evidence that biological markers can help existing practices to more accurately assess patients at risk for stroke. Randomized-controlled trials for carotid artery disease and carotid intervention, incorporating biomarkers, are needed.

Effect of non-surgical periodontal therapy on C-reactive protein, oxidative stress, and matrix metalloproteinase (MMP)-9 and MMP-2 levels in patients with type 2 diabetes: a randomized controlled study

BACKGROUND

It is well accepted that glycemic control in patients with diabetes mellitus (DM) is affected by systemic inflammation and oxidative stress. The effect of periodontal therapy on these systemic factors may be related to improvement on glycemic status. The aim of the present study is to assess over a period of 6 months the effect of non-surgical periodontal therapy on serum levels of high-sensitivity C-reactive protein (hsCRP), d-8-iso prostaglandin F2a (d-8-iso) as a marker of oxidative stress, and matrix metalloproteinase (MMP)-2 and MMP-9 on patients with type 2 DM.

METHODS

Sixty participants with type 2 DM and moderate to severe periodontal disease were randomized into intervention (IG) and control (CG) groups. IG received scaling and root planing, whereas CG received supragingival cleaning at baseline and scaling and root planing at 6 months. Participants of both groups were evaluated at baseline and 1, 3, and 6 months. Periodontal data recorded at each visit included probing depth, clinical attachment loss, bleeding on probing, and gingival index. Blood was collected at each visit for the assay of serum glycated hemoglobin A1c (A1c), hsCRP, d-8-iso, MMP-2, and MMP-9.

RESULTS

Although there was a trend to a reduction in hsCRP, d-8-iso and MMP-9 it did not reach statistical significance. MMP-2 levels remained unchanged after periodontal treatment.

CONCLUSION

Effective non-surgical periodontal treatment of participants with type 2 DM and moderate to severe periodontal disease improved significantly A1c levels but did not result in a statistically significant improvement in hsCRP, d-8-iso, MMP-2, and MMP-9 levels.

The importance of defining serum MMP-9 concentration in diabetics as an early marker of the rupture of atheromatous plaque in acute coronary syndrome

Acute coronary syndrome (ACS) is the main cause of mortality in diabetics. Acute myocardial infarction (AMI) in diabetics is much more often than in non-diabetics. MMP-9 activity could ease the formation of atherosclerosis, destabilization and plaque rupture as well as thrombocyte aggregation.

THE AIM OF THIS STUDY IS TO EXAMINE

MMP-9 defining in serum in diabetics; the impact of diabetes mellitus on atherosclerosis and MMP-9 level; relation between serum values of MMP-9 and markers of glycoregulation and lipid status, respectively.

RESULTS

The greatest concentration of both total and active MMP-9 serum has been noted in diabetics group with ACS. Both total and active MMP-9 values, in group with diabetes and ACS showed significantly important difference regarding the values in control group. Total and active MMP-9 showed statistically important correlation between the values of glycated hemoglobine A1c (HbA1c) and inverse correlations with values of subfraction HDL3.Active MMP-9 showed statistically important inverse correlation with value of HDL cholesterol.

IN CONCLUSION

According to the results, it has been thought that active MMP-9 shows a certain degree of atherosclerotic changes on blood vessels better than total MMP-9. MMP-9, active one, could present an early marker of atherosclerosis, especially on coronary blood vessels, in diabetics with type 2.

Kudzu root: traditional uses and potential medicinal benefits in diabetes and cardiovascular diseases

Kudzu root (Gegen in Chinese) is the dried root of Pueraria lobata (Willd.) Ohwi, a semi-woody, perennial and leguminous vine native to South East Asia. It is often used interchangeably in traditional Chinese medicine with thomson kudzu root (Fengen in Chinese), the dried root of P. thomsonii, although the Chinese Pharmacopoeia has separated them into two monographs since the 2005 edition. For more than 2000 years, kudzu root has been used as a herbal medicine for the treatment of fever, acute dysentery, diarrhoea, diabetes and cardiovascular diseases. Both English and Chinese literatures on the traditional applications, phytochemistry, pharmacological activities, toxicology, quality control and potential interactions with conventional drugs of both species have been included in the present review. Over seventy phytochemicals have been identified in kudzu root, with isoflavonoids and triterpenoids as the major constituents. Isoflavonoids, in particular puerarin, have been used in most of the pharmacological studies. Animal and cellular studies have provided support for the traditional uses of kudzu root on cardiovascular, cerebrovascular and endocrine systems, including diabetes and its complications. Further studies to define the active phytochemical compositions, quality standards and clinical efficacy are warranted. Strong interdisciplinary collaboration to bridge the gap between traditional medicine and modern biomedical medicine is therefore needed for the development of kudzu root as an effective medicine for the management of diabetes and cardiovascular diseases.

Matrix metalloproteinases in type 2 diabetes and non-diabetic controls: effects of short-term and chronic hyperglycaemia

INTRODUCTION

The role of matrix metalloproteinases (MMPs) in type 2 diabetes mellitus (DM) is not clear as increased activation of MMPs in the vasculature contrasts with decreased activity of MMPs in the kidneys, contributing to development of nephropathy.

MATERIAL AND METHODS

We measured serum MMP-2 and MMP-9 in 22 subjects with type 2 DM age (mean ± SD) 56.7 ±16.8 years, BMI 31.8 ±4.6 kg/m(2), HbA(1c) 8.45 ±1.78% and in 32 controls, age 39.2 ±16.0 years, BMI 35.2 ±8.5 kg/m(2). In 15 subjects with 2 DM we also measured MMP-2 and MMP-9 at discharge from hospital and after 3 months (n = 8). In controls, MMP-2 and -9 were also measured during 75 g oral glucose tolerance test (OGTT).

RESULTS

Concentrations of MMP-2 and MMP-9 were lower in subjects with type 2 DM (219 ±62 ng/ml vs. 305 ±63 ng/ml and 716 ±469 ng/ml vs. 1285 ±470 ng/ml, for MMP-2 and MMP-9, respectively, p < 0.05). MMP-9 concentrations fell at 120 min of OGTT from 1675 ±372 ng/ml to 1276 ±422 ng/ml (p < 0.05). In diabetic subjects there was a correlation between MMP-9 and HbA(1c) (r = 0.51, p< 0.05). In subjects with diabetes there was a fall of HbA(1c) from 9.77 ±1.76% to 8.36 ±1.54% (p < 0.01), at three months post-discharge. There was no difference in MMP-2, but there was a fall in MMP-9 at three months post-discharge in comparison to concentrations observed at admission (854 ±560 ng/ml vs. 500 ±235 ng/ml, p= 0.02).

CONCLUSIONS

Matrix metalloproteinases in type 2 and MMP-9 concentrations were lower in subjects with 2 DM than in non-diabetic controls. Regulation of MMPs appears to be complex as hyperglycaemia during OGTT results in a decrease in MMP-9, while chronic hyperglycaemia, reflected by HbA(1c), correlates with MMP-9 concentrations in subjects with 2 DM.

Effects of exercise training on the severity and composition of atherosclerotic plaque in apoE-deficient mice

AIM

To investigate the effects of exercise on atherosclerotic plaque composition, the concentration of matrix metalloproteinases (MMPs) in the atherosclerotic plaque and the systemic circulation.

METHODS

Ninety apolipoprotein E-deficient (apoE(-/-)) mice (45 male) were randomized to the following groups (n=15 each): control male/female; sedentary male/female; exercise male/female. Mice were kept on a 16-week high-fat diet. Subsequently, the control groups were sacrificed, while the rest of the animals were placed on a normal diet for 6 more weeks. During the latter period, the exercise groups were trained daily on treadmill. At the end of the study, mice were euthanized, and blood samples as well as aortic root specimens were obtained.

RESULTS

Compared to control and sedentary animals, exercise training reduced atherosclerotic plaques (-30%; p<0.01) and increased elastin and collagen content in both genders (p<0.05). Body weight or lipid profile did not change significantly. Decreased macrophages and MMP-9 as well as increased tissue inhibitor of metalloproteinases 1 (TIMP-1) levels were observed in the atherosclerotic plaques of the exercise-treated groups (p<0.05). Plasma concentrations of MMP-9 decreased, while plasma TIMP-1 levels increased in the exercise compared to control and sedentary groups (p < 0.05).

CONCLUSIONS

Exercise training had a favorable effect on the size and composition of the atherosclerotic plaque in apoE(-/-) mice, associated with suppressed MMP activity.

An update on markers of carotid atherosclerosis in patients with Type 2 diabetes

Carotid atherosclerosis constitutes an important cause of ischemic brain attack and stroke, accounting for up to 40% of cases of ischemic cerebrovascular disease. Type 2 diabetes mellitus is an independent risk factor for stroke and its recurrence. Thus, identifying diabetic patients who are at high risk of developing stroke is of great clinical importance. Noninvasive measurements of surrogate markers of atherosclerosis, such as novel serum biomarkers, can be helpful in detecting subclinical carotid disease, especially among individuals at the highest cardio-/cerebro-vascular risk. Previous studies have proposed an expanding body of serum biomarkers, such as C-reactive protein, fibrinogen, adipokines, cytokines and growth factors, as novel indicators of carotid atherosclerosis development that predict carotid-related clinical outcomes. Furthermore, those biomarkers are expected to assess the efficacy of both pharmaceutical and interventional strategies. Accordingly, it is increasingly clear that measuring biomarkers may improve the definition of cerebrovascular risk profile in patients with Type 2 diabetes mellitus.

Diabetes impairs arteriogenesis in the peripheral circulation: review of molecular mechanisms

Patients suffering from both diabetes and PAD (peripheral arterial disease) are at risk of developing critical limb ischaemia and ulceration, and potentially requiring limb amputation. In addition, diabetes complicates surgical treatment of PAD and impairs arteriogenesis. Arteriogenesis is defined as the remodelling of pre-existing arterioles into conductance vessels to restore the perfusion distal to the occluded artery. Several strategies to promote arteriogenesis in the peripheral circulation have been devised, but the mechanisms through which diabetes impairs arteriogenesis are poorly understood. The present review provides an overview of the current literature on the deteriorating effects of diabetes on the key players in the arteriogenesis process. Diabetes affects arteriogenesis at a number of levels. First, it elevates vasomotor tone and attenuates sensing of shear stress and the response to vasodilatory stimuli, reducing the recruitment and dilatation of collateral arteries. Secondly, diabetes impairs the downstream signalling of monocytes, without decreasing monocyte attraction. In addition, EPC (endothelial progenitor cell) function is attenuated in diabetes. There is ample evidence that growth factor signalling is impaired in diabetic arteriogenesis. Although these defects could be restored in animal experiments, clinical results have been disappointing. Furthermore, the diabetes-induced impairment of eNOS (endothelial NO synthase) strongly affects outward remodelling, as NO signalling plays a key role in several remodelling processes. Finally, in the structural phase of arteriogenesis, diabetes impairs matrix turnover, smooth muscle cell proliferation and fibroblast migration. The review concludes with suggestions for new and more sophisticated therapeutic approaches for the diabetic population.

Effects of high glucose and thiamine on the balance between matrix metalloproteinases and their tissue inhibitors in vascular cells

Pericyte survival in diabetic retinopathy depends also on interactions with extracellular matrix (ECM) proteins, which are degraded by matrix metalloproteinases (MMP). Elevated glucose influences ECM turnover, through expression of MMP and their tissue inhibitors, TIMP. We reported on reduced pericyte adhesion to high glucose-conditioned ECM and correction by thiamine. We aimed at verifying the effects of thiamine and benfotiamine on MMP-2, MMP-9 and TIMP expression and activity in human vascular cells with high glucose. In HRP, MMP-2 activity, though not expression, increased with high glucose and decreased with thiamine and benfotiamine; TIMP-1 expression increased with high glucose plus thiamine and benfotiamine; MMP-9 was not expressed. In EC, MMP-9 and MMP-2 expression and activity increased with high glucose, but thiamine and benfotiamine had no effects; TIMP-1 expression was unchanged. Neither glucose nor thiamine modified TIMP-2 and TIMP-3 expression. TIMP-1 concentrations did not change in either HRP or EC. High glucose imbalances MMP/TIMP regulation, leading to increased ECM turnover. Thiamine and benfotiamine correct the increase in MMP-2 activity due to high glucose in HRP, while increasing TIMP-1.

Enhanced tyrosine nitration of prostacyclin synthase is associated with increased inflammation in atherosclerotic carotid arteries from type 2 diabetic patients

Prostacyclin synthase (PGIS) is tyrosine nitrated in diseased animals. Whether PGIS nitration occurs in human diabetic atherosclerotic arteries has not been reported. The present study was designed to determine PGIS nitration and its association with the inflammatory response in atherosclerotic carotid arteries from patients with or without type 2 diabetes, and carotid plaques were obtained from patients who underwent carotid endarterectomy. PGIS nitration, nitric oxide synthases, adhesion molecules, myeloperoxidase, osteopontin, and matrix metalloproteinase (MMP) were measured by using immunohistochemistry and Western blotting. In low stenosis areas, diabetes enhanced reactive nitrogen species production, as evidenced by increases in 3-nitrotyrosine and PGIS nitration. In parallel, diabetes dramatically increased inflammatory markers including intracellular adhesion molecule-1, vascular adhesion molecule-1, and osteopontin. In both diabetic and nondiabetic patients, MMP-2 and MMP-9 protein levels were significantly increased in the arteries with high stenosis as compared with those with low stenosis. Moreover, diabetes enhanced inducible nitric oxide synthase expression in the plaques from low stenosis areas and up-regulated myeloperoxidase expression in the plaques from both high and low stenosis areas. These data demonstrate that diabetes preferentially increases PGIS nitration that is associated with excessive vascular inflammation in atherosclerotic carotid arteries from patients with type 2 diabetes, suggesting a possible role of tyrosine nitration of PGIS in the development of atherosclerosis in patients with diabetes.

GPCR agonist-induced transactivation of the EGFR upregulates MLC II expression and promotes hypertension in insulin-resistant rats

AIMS

The presence of metabolic abnormalities such as insulin resistance and elevated levels of various vasoconstrictor G-protein-coupled receptor (GPCR) agonists contributes to the development of hypertension. Recent studies have suggested a link between disease progression and activation of growth factor receptor signalling pathways such as the epidermal growth factor receptor (EGFR) by matrix metalloproteinases (MMPs). We hypothesized that excessive stimulation of GPCRs such as alpha(1)-adrenergic receptors activates MMP-dependent EGFR transactivation and contributes to the development of hypertension by promoting increased synthesis of contractile proteins in vascular smooth muscle (VSM).

METHODS AND RESULTS

We tested this concept in experiments using insulin-resistant VSM cells (VSMCs) and fructose hypertensive rats (FHRs), a model of acquired systolic hypertension and insulin resistance. We found that insulin resistance and agonist stimulation increased the expression and activity of MMPs (MMP-2 and MMP-7), the EGFR, contractile proteins such as myosin light chain kinase and MLC II, and their transcriptional activators including P90 ribosomal kinase (P90RSK) and serum response factor, possibly via the activation of extracellular signal-regulated kinase (ERK1/2) in VSMCs. Further, in insulin-resistant VSMCs and arteries from FHRs, disruption of MMP-EGFR signalling either by a pharmacological or small interfering RNA approach normalized the increased expression and activity of contractile proteins and their transcriptional activators and prevented the development of hypertension in FHRs.

CONCLUSION

Our data suggest that the MMP-EGFR pathway could be a potential target in the treatment of hypertension in insulin resistance and/or hyperglycaemic conditions such as type 2 diabetes.

The Impact of Valvular Oxidative Stress on the Development of Venous Stasis Ulcer Valvular Oxidative Stress and Venous Ulcers

Background: It is widely believed that venous ulcers result from venous insufficiency related to venous valve damages. To further investigate the pathogenesis of venous ulcers, we compared the influence of oxidative stress in venous valvular tissue on stasis ulcer formation in patients with venous ulcers secondary to superficial venous reflux disease. Methods: Thirty-nine consecutive patients with superficial venous reflux who underwent saphenectomy were included in the study. Patients were divided into 2 groups: with healed venous ulcers (group 1, n = 15) and without ulcers (group 2, n = 24). All patients were preoperatively evaluated with duplex ultrasound scanning and their blood samples were obtained to examine leukocyte count, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and C-reactive protein (CRP) levels. All patients underwent standard above-knee saphenectomy. Extracted saphenous vein segments were from the saphenofemoral junction, the first valve along. The biochemical analysis of the valve tissues included matrix metalloproteinase (MMP)-9, MMP-2, IL-6, TNF-α, superoxide dismutase (SOD), malondialdehyde (MDA), and nitric oxide (NO) studies. Results: There was no significant difference between patients in terms of age, gender, hospital stay, and preoperative blood levels of leukocyte, IL-6, TNF-α, and CRP (P > .05). Biochemical examination of valve tissue showed that the levels of MMP-9, MMP-2, IL-6, TNF-α, SOD, MDA, and NO in patients with healing venous ulcer were higher than those of the second group. Conclusion: A higher oxidative stress in the valvular tissue may contribute to venous stasis ulcer formation.

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.

Aldose reductase regulates high glucose-induced ectodomain shedding of tumor necrosis factor (TNF)-alpha via protein kinase C-delta and TNF-alpha converting enzyme in vascular smooth muscle cells

Chronic low-grade inflammation has emerged as a key contributor to the cardiovascular complications of diabetes, however, the mechanisms by which diabetes increases inflammation remain poorly understood. Here, we report that exposure to high glucose (HG) stimulates ectodomain shedding of TNF-alpha from rat aortic smooth muscle cells in culture. Our results show that exposure to HG decreases membrane-associated TNF-alpha. This decrease in unprocessed TNF-alpha was prevented by the aldose reductase (AR) inhibitor sorbinil and AR small interference RNA. Treatment with HG, but not equimolar mannitol or 3-O-methyl glucose, resulted in phosphorylation and activation of TNF-alpha converting enzyme (TACE) (ADAM17), which were attenuated by sorbinil or AR-specific small interference RNA. HG-induced TACE phosphorylation and TNF-alpha processing were also prevented by TNF-alpha protease inhibitor-1, an inhibitor of TACE. Inhibition of protein kinase C (PKC)-delta by rottlerin prevented HG-induced TACE activation and the accumulation of unprocessed TNF-alpha. Treatment with sorbinil decreased elevated levels of circulating TNF-alpha in streptozotocin-treated diabetic rats. Sorbinil treatment also decreased the expression of TNF-alpha, matrix metalloproteinase-2, matrix metalloproteinase-9, and increased tissue inhibitor of metalloproteinase-3 in vascular smooth muscle cells treated with HG and in balloon-injured carotid arteries of diabetic rats. These results indicate that HG-induced TNF-alpha shedding could be attributed to TACE activation, which is regulated, in part, by PKC-delta and AR. Therefore, inhibition of TACE by TNF-alpha protease inhibitor-1, or pharmacological inhibition of PKC-delta or AR may represent useful strategies for treating vascular inflammation associated with diabetes.

Deep vein thrombosis resolution is impaired in diet-induced type 2 diabetic mice

OBJECTIVE

Type 2 diabetes mellitus results in a procoagulant and thrombogenic state that could predispose diabetic individuals to develop venous thrombosis. We sought to determine whether diet-induced type 2 diabetes mellitus affects deep venous thrombosis (DVT) resolution in a murine model.

METHODS

C57Bl/6 mice were fed a low-fat or a high-fat diet (n = 10) for 10 weeks, after which DVT was created in the inferior vena cava (IVC) by a combination of low flow and endothelial damage. The IVC and thrombus were harvested at 1 and 2 weeks. Thrombus resolution and neovascularization were investigated through transfemoral angiography (n = 10), thrombus size (n = 4) and weight (n = 10), and nitric oxide synthase 3 immunoquantification (n = 4). Macrophage content was assessed by CD68 immunoreactivity (n = 4). The fibrinolytic system (urokinase plasminogen activator [uPA] and plasminogen activator inhibitor-1 [PAI-1]) was analyzed by Western immunoblotting (n = 6) and immunohistochemistry (n = 4). Total collagen was stained by Sirius red. Matrix metalloproteinases (MMP)-2 and MMP-9 activities were evaluated by zymography and their expressions by Western immunoblotting (n = 6) and immunohistochemistry (n = 4).

RESULTS

Diabetic mice had significantly larger and heavier thrombi at 1 and 2 weeks (P < .05), threefold less neovascularization (P < .05), and 35-fold increase in macrophage content (P < .01), than control mice 2 weeks after surgery. IVC recanalization was documented in 90% of 2-week control mice and in 10% of 2-week diabetic mice (P < .01). Increased vein wall collagen and less uPA and more PAI-1 expressions with a decreased uPA/PAI-1 ratio (31%, P < .01) were documented at 2 weeks in diabetic mice. MMP-2 and MMP-9 activities and expressions were significantly increased in diabetic mice at 1 and 2 weeks (P < .05) compared with control mice.

CONCLUSION

Diet-induced type 2 diabetes may impair DVT resolution through altered inflammatory, fibrinolytic, and MMP responses.

The oral anti-diabetic agent, gliclazide, inhibits oxidized LDL-mediated LOX-1 expression, metalloproteinase-9 secretion and apoptosis in human aortic endothelial cells

The mechanisms linking diabetes to plaque rupture and thrombotic occlusion remain largely speculative, yet matrix metalloproteinases (MMP) and endothelial apoptosis may represent central elements. Binding of oxidized low-density lipoprotein (oxLDL) to endothelial lectin-like oxidized LDL receptor-1 (LOX-1) induces oxidative stress, MMP expression and apoptosis. In the present study, we examined the effect of gliclazide, a second generation sulfonylurea with antioxidant properties, on LOX-1 expression and LOX-1-mediated MMP-9 expression and apoptosis in oxLDL-treated human aortic endothelial cells (HAECs). Incubation of HAECs with oxLDL increased LOX-1 expression and enhanced MMP-9 production by these cells. Treatment with an anti-LOX-1 antibody or with antioxidants, including gliclazide, inhibited these effects. Induction of LOX-1 and LOX-1-mediated MMP-9 production involved endothelin-1 production and nuclear factor-kappaB activation. These biological parameters were inhibited by gliclazide and anti-LOX-1 antibody treatment. In HAECs, oxLDL induced apoptosis, an effect associated with reduced protein kinase B (PKB) activity. Anti-LOX-1 antibody, antioxidants including gliclazide, as well as caspase inhibitors prevented oxLDL-induced apoptosis. The anti-apoptotic effect of gliclazide was associated with an increase in PKB activity and a decrease in caspase-3 and -9 activities. These results demonstrate that gliclazide inhibits endothelial LOX-1 expression and prevents LOX-1-mediated proatherogenic effects associated with endothelial dysfunction and plaque rupture.

Dysregulation of matrix metalloproteinases and their tissue inhibitors is related to abnormality of left ventricular geometry and function in streptozotocin-induced diabetic minipigs

This study aimed to characterize matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in relation to changes in left ventricle (LV) geometry and function in a porcine model with streptozotocin (STZ)-induced diabetes. In 15 Chinese Guizhou minipigs with STZ-induced diabetes (diabetic group) and 15 age-matched normal controls (control group), Doppler tissue imaging was performed at 6 months of diabetes. Serum MMP-2, -9, TIMP-1, -4 and B-type natriuretic peptide (BNP) were determined. Expression of MMPs, TIMPs, urokinase type-plasminogen activator (uPA), its receptor (uPAR) and plasminogen activator inhibitor-1 (PAI-1) in aortic intima and LV myocardium was evaluated, with gelatinolytic activities of tissue MMP-2, -9 accessed by zymography. Left ventricle end-diastolic septum thickness (P < 0.05) and mass (P < 0.05) were increased, whereas peak systolic mitral annulus velocity (Sm, P < 0.001), LV systolic (P = 0.01) and diastolic strain (P < 0.001) were significantly decreased in diabetic group than in controls. Diabetic group showed higher expression of TIMP-1, -4 in aortic intima and LV myocardium (P < 0.01 or P < 0.05), with increased collagen content and elevated serum BNP level (P = 0.004) and lower gelatinolytic activities of tissue MMP-2, -9 (all P < 0.05). Semi-quantitative RT-PCR of those diabetic tissues revealed elevated mRNA levels of major TIMPs, uPA, uPAR and PAI-1. Reduction of serum MMP-2 and -9 levels was observed in diabetic group vs. control group (both P < 0.05). This study features elevated levels of TIMP-1, -4, uPA, uPAR and PAI-1, and decreased activities of MMP-2, -9 in aorta and myocardium in STZ-induced diabetic minipigs, indicating that MMP-TIMP dysregulation is associated with LV hypertrophy, cardiac dysfunction and increased cardiovascular fibrosis in diabetes.

The influence of type I diabetes mellitus on the expression and activity of gelatinases (matrix metalloproteinases-2 and -9) in induced periodontal disease

BACKGROUND AND OBJECTIVE

Periodontal disease corresponds to a group of lesions that affect the tooth-supporting tissues present in the dental follicle. Although bacterial plaque is important, the immune response also contributes to the destruction of periodontal tissues. Diabetes mellitus is closely associated with the development, progression and severity of periodontal disease because it not only affects extracellular matrix organization but also the tissue response to inflammation. The objective of the present investigation was to study the influence of diabetes on experimental periodontal disease by evaluating the degradation of extracellular matrix through the analysis of matrix metalloproteinase (MMP)-2 and MMP-9 expression and activity, using immunofluorescence, zymography and real-time reverse transcription-polymerase chain reaction.

MATERIAL AND METHODS

Wistar rats were divided into normal and diabetic groups and evaluated 0, 15 and 30 d after the induction of periodontal disease by ligature.

RESULTS

MMP-2 and -9 were detected in epithelial cells, in the blood vessel endothelium and in connective tissue cells. The same profile of enzymatic expression of MMP-2 and -9 was observed in normal and diabetic animals, with a peak in activity at day 15 of inflammation. However, in diabetic animals, MMP-2 gelatinolytic activity was reduced after the inflammatory stimulus, whereas that of MMP-9 was increased. MMP-2 gene expression decreased with inflammation in both normal groups and groups with diabetes. In contrast, MMP-9 expression increased in normal animals and decreased in diabetic animals after inflammation.

CONCLUSION

The results suggest the involvement of MMP-2 and -9 in the dynamics of periodontal disease and that variation in their expression levels results in differences in tissue organization and wound healing in normal and diabetic animals.

Beneficial effects of rosiglitazone on novel cardiovascular risk factors in patients with Type 2 diabetes mellitus

AIM

Impaired exercise capacity, adiponectin, MMPs and TIMPs have all been implicated in the development of cardiovascular disease. The aim of our study was to determine the effects of rosiglitazone on these factors in diabetic patients.

METHODS

Seventy individuals with Type 2 diabetes were assigned randomly to either a rosiglitazone group (8 mg/day, RG) or a control group (CG) for 6 months. All participants took gliclazide 160 mg plus metformin 1700 mg in stable dose. None of the individuals had diabetic complications or had previously participated in an exercise programme. Anthropometric parameters, VO2 peak, oxygen pulse, glycaemic indices, lipid profile, adiponectin, insulin resistance, blood pressure and serum MMP-9, TIMP-1, TIMP-2 levels were assessed at baseline and at the end of the study. After Bonferroni adjustment, a P-value < 0.017 was assumed to be statistically significant.

RESULTS

Rosiglitazone treatment significantly increased VO2 peak (P < 0.0001), the duration of the exercise test (P < 0.0001), oxygen pulse (P = 0.010) and TIMP-2 levels (P = 0.008) in comparison with CG. Insulin resistance, hyperglycaemia, diastolic blood pressure and MMP-9 levels were also reduced (P < 0.017). Fat mass, lipid profile, TIMP-1 levels and MMP9 : TIMP-1 ratio were unaltered after rosiglitazone treatment. There were no significant changes in these parameters in control subjects. In univariate analysis, the rosiglitazone-induced increment of VO2 peak was associated with alterations in plasma adiponectin (r = 0.691), HOMA-IR (r = -0.782) and HbA(1c) (r = -0.676) (P < 0.017). These relationships retained significance after multiple regression analysis (P = 0.005).

CONCLUSIONS

Rosiglitazone treatment increases cardiorespiratory fitness and modulates favourably serum adiponectin, MMP-9 and TIMP-2 levels. Whether these effects produce cardiovascular benefits in the long term requires further investigation.

The relationship between serum levels of vascular calcification inhibitors and carotid plaque vulnerability

OBJECTIVE

Osteopontin (OPN) and osteoprotegerin (OPG) are well-known vascular calcification inhibitors, which have been recently demonstrated to correlate with inflammation and cardiovascular events incidence. The aim of this cross-sectional study is to survey whether OPN and OPG are involved in carotid plaque vulnerability. For this reason, we assessed serum OPN and OPG levels in patients with carotid stenosis, and we explored their relationship with carotid plaque echogenicity and subsequent cerebrovascular ischemic events.

METHODS

A total of 164 Whites were selected from a large cohort of 297 subjects to participate. In particular, 114 patients (61 men, 53 women), aged 55 to 80, had recently-diagnosed ICA stenosis higher than 50%. A group of 50 age-, sex-, and body mass index (BMI)-matched healthy individuals served as healthy controls. Patients with renal failure, hypothyroidism, osteoporosis, and lipid-lowering therapy were excluded. Images of both carotids were obtained from all participants using a high-resolution color duplex ultrasound and the gray-scale median (GSM) score was calculated. Brain computed tomography (CT), and magnetic resonance imaging (MRI) scans when CT was questionable, were performed on all patients with carotid stenosis. Clinical parameters, lipid and glycemic indexes, hsCRP, fibrinogen, white blood cells (WBC) count, OPN, and OPG were measured. Independent t test, one-way ANOVA, Pearson correlation, and multiple regression analysis were used for statistical analysis.

RESULTS

Among patients with carotid stenosis, 60 had history of ipsilateral stroke or TIA and positive CT or MRI findings (group A), while 54 had no neurological symptoms and negative CT and MRI scan (group B). Overall, patients with carotid stenosis showed worse lipid profile and increased waist circumference, blood pressure, hsCRP, fibrinogen, WBC count, OPN, and OPG levels compared with healthy subjects (group C) (P <.05). Statistical analysis revealed that group A had significantly lower levels of GSM than group B (57.41 +/- 38.19 vs 76.32 +/- 36.72; P = .008) and higher levels of hsCRP, OPN, and OPG than groups B and C (P < .05). Concerning the latter, biochemical markers group B showed only elevated OPG levels compared with group C (P = .038). Notably, GSM was considerably associated with serum OPN and OPG and waist circumference in patients with carotid atherosclerosis in univariate (r = -0.333; P = .032, r = -0.575; P < .001, r = -0.590; P =.006, respectively) and multiple regression analysis (R(2) = 0.445; P =.006).

CONCLUSIONS

The present study demonstrated elevated serum OPN and OPG levels in patients with carotid stenosis and documented an independent association between these biochemical markers, GSM and carotid-induced symptomatology. Therefore bone-matrix proteins combined with GSM could be potential markers for vulnerable carotid plaques.

Matrix metalloproteinases and their inhibitors in vascular remodeling and vascular disease

Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes that degrade various components of the extracellular matrix (ECM). Members of the MMP family include collagenases, gelatinases, stromelysins, matrilysins and membrane-type MMPs. ProMMPs are cleaved into active forms that promote degradation of ECM proteins. Also, recent evidence suggests direct or indirect effects of MMPs on ion channels in the endothelium and vascular smooth muscle, and on other mechanisms of vascular relaxation/contraction. Endogenous tissue inhibitors of metalloproteinases (TIMPs) reduce excessive proteolytic ECM degradation by MMPs. The balance between MMPs and TIMPs plays a major role in vascular remodeling, angiogenesis, and the uterine and systemic vasodilation during normal pregnancy. An imbalance in the MMPs/TIMPs activity ratio may underlie the pathogenesis of vascular diseases such as abdominal aortic aneurysm, varicose veins, hypertension and preeclampsia. Downregulation of MMPs using genetic manipulations of endogenous TIMPs, or synthetic pharmacological inhibitors such as BB-94 (Batimastat) and doxycycline, and Ro-28-2653, a more specific inhibitor of gelatinases and membrane type 1-MMP, could be beneficial in reducing the MMP-mediated vascular dysfunction and the progressive vessel wall damage associated with vascular disease.

Evaluation of metalloproteinase 2 and 9 levels and their inhibitors in diabetic and healthy subjects

OBJECTIVES

We hypothesized that molecules active in vascular remodeling (i.e. MMPs and their TIMPs) could be modified in diabetic patients, as indirect markers of the diabetes related generalized abnormality of vascular activity. To test this hypothesis, we measured the plasma levels of MMP-2, MMP-9, TIMP-1, and TIMP-2 in type 2 diabetic patients and in healthy subjects.

METHODS

We enrolled 181 diabetic patients and 165 controls. We measured body mass index (BMI), glycosylated hemoglobin (HbA(1c)), fasting plasma glucose (FPG), fasting plasma insulin (FPI), homeostasis model assessment index (HOMA index), systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C), high density lipoprotein-cholesterol (HDL-C), triglycerides (Tg), lipoprotein(a) [Lp(a)], plasminogen activator inhibitor-1 (PAI-1), homocysteine (Hct) fibrinogen (Fg), high sensitivity C-reactive protein (hs-CRP), and plasma levels of MMP-2, MMP-9, TIMP-1, and TIMP-2.

RESULTS

A significant increase (P<0.0001) of BMI, HbA(1c), FPG, FPI, HOMA index, SBP, DBP, TC, LDL-C, Tg, Lp(a), PAI-1, Hct, Fg, and hs-CRP was present in the diabetic group, with a significant decrease (P<0.0001) of HDL-C levels compared to healthy subjects. MMP-2 and MMP-9 levels were significantly higher (P<0.0001) in diabetic patients. Significant TIMP-1, and TIMP-2 increase was also observed (P<0.0001) in the diabetic group.

CONCLUSION

Plasma levels of MMP-2, MMP-9, TIMP-1, and TIMP-2 are increased in diabetic patients which may reflect abnormal extracellular matrix (ECM) metabolism.

Modulation of the proteolytic activity of matrix metalloproteinase-2 (gelatinase A) on fibrinogen

The proteolytic processing of bovine fibrinogen by MMP-2 (gelatinase A), which brings about the formation of a product unable to form fibrin clots, has been studied at 37 degrees C. Catalytic parameters, although showing a somewhat lower catalytic efficiency with respect to thrombin and plasmin, indeed display values indicating a pathophysiological significance of this process. A parallel molecular modelling study predicts preferential binding of MMP-2 to the beta-chain of fibrinogen through its haemopexin-like domain, which has been directly demonstrated by the inhibitory effect in the presence of the exogenous haemopexin-like domain. However, the removal of this domain does not impair the interaction between MMP-2 and fibrinogen, but it dramatically alters the proteolytic mechanism, producing different fragmentation intermediates. The investigation at various pH values between 6.0 and 9.3 indicates a proton-linked behaviour, which is relevant for interpreting the influence on the process by environmental conditions occurring at the site of an injury. Furthermore, the action of MMP-2 on peroxynitrite-treated fibrinogen has been investigated, a situation possibly occurring under oxidative stress. The chemical alteration of fibrinogen, which has been shown to abolish its clotting activity, brings about only limited modifications of the catalytic parameters without altering the main enzymatic mechanism.

Contributions of inflammation and cardiac matrix metalloproteinase activity to cardiac failure in diabetic cardiomyopathy: the role of angiotensin type 1 receptor antagonism

We investigated the effect of the angiotensin type 1 (AT-1) receptor antagonist, irbesartan, on matrix metalloproteinase (MMP) activity and cardiac cytokines in an animal model of diabetic cardiomyopathy. Diabetes was induced in 20 C57/bl6 mice by injection of streptozotocin (STZ). These animals were treated with irbesartan or placebo and were compared with nondiabetic controls. Left ventricular (LV) function was measured by pressure-volume loops with parameters for systolic function (end systolic elastance [Ees]) and diastolic function (cardiac stiffness) 8 weeks after STZ treatment. The cardiac protein content of interleukin (IL)1beta and transforming growth factor (TGF)beta1 were measured by enzyme-linked immunosorbent assay. The total cardiac collagen content and collagen type 1 and 3 were measured by histochemistry, and MMP-2 activity was measured by gelatin zymography. LV dysfunction was documented by impaired Ees and diastolic stiffness in STZ mice compared with controls. This was accompanied by increased TGFbeta, IL1beta, and fibrosis and decreased MMP-2 activity. Treatment with irbesartan attenuated LV dysfunction, IL1beta, TGFbeta, and cardiac fibrosis compared with untreated diabetic animals and normalized MMP activity. These findings present evidence that AT-1 receptor antagonists attenuate cardiac failure by decreasing cardiac inflammation and normalizing MMP activity, leading to normalized cardiac fibrosis in STZ-induced diabetic cardiomyopathy.

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.

Increased blood-brain barrier permeability and altered tight junctions in experimental diabetes in the rat: contribution of hyperglycaemia and matrix metalloproteinases

AIMS/HYPOTHESIS

Although diabetes mellitus is associated with peripheral microvascular complications and increased risk of neurological events, the mechanisms by which diabetes disrupts the blood-brain barrier (BBB) are not known. Matrix metalloproteinase (MMP) activity is increased in diabetic patients, is associated with degradation of tight junction proteins, and is a known mediator of BBB compromise. We hypothesise that diabetes leads to compromise of BBB tight junctions via stimulation of MMP activity.

MATERIALS AND METHODS

Diabetes was induced in the rat with streptozotocin. At 14 days after injection, BBB function was assessed by in situ brain perfusion. Tight junction proteins were assessed by immunoblot and immunofluorescence. Plasma MMP activity was quantified by fluorometric gelatinase assay and gel zymography.

RESULTS

In streptozotocin-treated animals, permeability to [(14)C]sucrose increased concurrently with decreased production of BBB tight junction proteins occludin (also known as OCLN) and zona occludens 1 (ZO-1, also known as tight junction protein 1 or TJP1). Insulin treatment, begun on day 7, normalised blood glucose levels and attenuated BBB hyperpermeability to [(14)C]sucrose. Neither acute hyperglycaemia in naive animals nor acute normalisation of blood glucose in streptozotocin-treated animals altered BBB permeability to [(14)C]sucrose. Plasma MMP activity was increased in streptozotocin-treated animals.

CONCLUSIONS/INTERPRETATION

These data indicate that diabetes increases BBB permeability via a loss of tight junction proteins, and that increased BBB permeability in diabetes does not result from hyperglycaemia alone. Increased plasma MMP activity is implicated in degradation of BBB tight junction proteins and increased BBB permeability in diabetes. Peripheral MMP activity may present a novel target for protection of the BBB and prevention of neurological complications in diabetes.

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.

Lercanidipine reduces matrix metalloproteinase-9 activity in patients with hypertension

Increased levels of metalloproteinase (MMP)-9 have been shown in hypertensive patients. Lercanidipine is a calcium channel blocker with antioxidant actions. We examined whether lercanidipine produces antioxidant effects and reduces MMP-9 activity in hypertensive patients in a placebo-controlled, crossover, single-blinded design study including 18 healthy volunteers (control group), and 14 hypertensive patients without (N = 7) or with (N = 7) diabetes mellitus. Hypertensive patients were randomized to treatment with placebo (15 days) or lercanidipine 20 mg/d (15 days). Arterial blood pressure was evaluated with ambulatory blood pressure monitoring. Plasma thiobarbituric acid reactive species (TBA-RS) levels were measured to assess oxidative stress, and plasma MMP-2 and MMP-9 were assayed by gel zymography before and after treatment with placebo or lercanidipine. Plasma concentrations of tissue inhibitor of metalloproteinases (TIMP)-1 were measured by ELISA. Lercanidipine reduced mean arterial pressure by 7% in hypertensive patients without diabetes (P < 0.05), but not in hypertensive patients with diabetes. It significantly decreased plasma TBA-RS levels in hypertensive patients without and with diabetes (95% confidence interval [CI], -26 to -46%, P = 0.048, and -22 to -33%, P = 0.036, respectively). In addition, lercanidipine decreased activated MMP-9 in hypertensive patients without and with diabetes (95% CI, -19 to -47%, P = 0.047, and -80 to -96%, P = 0.010, respectively). No effects were seen on MMP-2. No significant differences or changes in plasma TIMP-1 concentrations were found. Therefore, we demonstrate for the first time that lercanidipine consistently decreased MMP-9 activity and reduced oxidative stress in hypertensive patients, thus suggesting a mechanism probably involved in the pleotropic actions of lercanidipine.

Oxidative stress in diabetes: A mechanistic overview of its effects on atherogenesis and myocardial dysfunction

Diabetes is a major risk factor for atherosclerosis. Atherogenesis involves endothelial dysfunction, activation and injury, inflammation, and smooth muscle cell migration and proliferation. Platelet activation in the narrowed arteries is the most proximate event in the culmination of an acute event such as acute myocardial infraction and stroke. Hyperglycemia is associated with all these adverse events in the process of genesis of atherosclerosis. The effect of diabetes (hyperglycemia) is mediated in large part by the state of enhanced oxidative stress, which is not counter-balanced by endogenous antioxidants. This paper reviews the ignition of oxidative stress in diabetes and the mediation of events leading to atherogenesis.

Elevated circulating levels of matrix metalloproteinase-9 in type 1 diabetic patients with and without retinopathy

OBJECTIVE

Tissue expression pattern of matrix metalloproteinases (MMPs) and their inhibitors TIMPs indicate that microvascular complications of diabetes mellitus are associated with extracellular matrix remodelling. We investigated whether circulating levels of MMP-9 and TIMP-1 are altered in diabetic retinopathy and whether they might serve as biological markers of ocular complications in type 1 diabetes.

RESEARCH DESIGN AND METHODS

We recruited 47 type 1 diabetic patients free of vascular complications (n=40) or with retinopathy (n=14). Patients with macroangiopathy, neuropathy and nephropathy were excluded. A group of nondiabetic control subjects (n=35) was also constituted for comparative purposes. Peripheral blood levels of MMP-9 and TIMP-1 were determined using immunoenzymatic assays.

RESULTS

Type 1 diabetic subjects exhibited significantly higher circulating levels of both MMP-9 and MMP-9/TIMP-1 ratio, as well as a tendency to increased serum TIMP-1 levels relative to nondiabetic controls (p<0.001). Diabetic patients with retinopathy also displayed elevated systemic values of MMP-9 and MMP-9/TIMP-1 ratio when compared to patients without retinopathy (p<0.05). Logistic regression analysis identified diabetes duration firstly (P<0.01), and MMP-9 serum levels secondly (P<0.01) as significant and independent variables associated with the existence of retinopathy.

CONCLUSIONS

Our data suggest that peripheral blood MMP-9 levels might serve as surrogate biomarkers of retinopathy in type 1 diabetic patients free of other vascular complications.

Contribution of Plasma Matrix Metalloproteinases to Development of Left Ventricular Hypertrophy and Diastolic Dysfunction in Hypertensive Subjects

Matrix metalloproteinases (MMPs) are involved in the regulation of the extracellular matrix (ECM) of the myocardium and thus the pathogenesis of vascular and cardiac hypertrophy. In this study, we investigated contribution of plasma matrix metalloproteinases to development of left ventricular hypertrophy (LVH) and diastolic dysfunction in hypertensive subjects. Hypertensive patients with (n = 27) and without LVH (n = 23) were included. All participants underwent a complete transthoracic echocardiographic examination, including recordings of the mitral annular early, late, systolic and diastolic velocities by Doppler imaging. Plasma concentrations of MMP-3 and MMP-9 were determined by the one-step sandwich enzyme immunoassay method. Plasma MMP-3 and MMP-9 concentrations were significantly higher in patients with LVH than those without LVH (2.4 +/- 1.2 vs 1.5 +/- 0.7 ng/ml, p = 0.006 and 5.2 +/- 2.8 vs 3.3 +/- 1.7 ng/ml, p = 0.003, respectively). MMP-3 and MMP-9 levels were also correlated with left ventricular posterior wall thickness and Doppler indices of diastolic dysfunction. Our findings have suggested that increased MMP levels may contribute to LVH and left ventricular diastolic dysfunction. Therefore, treatment of hypertension with MMP lowering drugs, such as angiotensin converting enzyme inhibitors and angiotensin receptor blockers, may have favorable effects on LVH and left ventricular diastolic dysfunction.