Arterial stiffness and functional properties in chronic kidney disease patients on different dialysis modalities: an exploratory study.

BACKGROUND: Abnormalities of vascular function and accumulation of oxidative stress have been associated with chronic kidney disease (CKD). Dialysis modalities, peritoneal dialysis (PD) and haemodialysis (HD) may differentially impact on vascular function and oxidative stress. METHODS: Patients undergoing living donor transplantation were studied for vascular stiffness using pulse wave velocity measurements, and inferior epigastric arteries were harvested to examine in vitro stiffness and functional properties and evidence of oxidative stress. Forty-one patients were studied representing PD (n = 12), HD (n = 14) and non-dialysed recipients (n = 15). RESULTS: We demonstrated differences in stiffness from in vivo and in vitro measurements such that non-dialysis < HD < PD groups. The stiffness measurements did not correlate with duration of CKD nor dialysis duration, but did so with phosphate levels (r = 0.356, P = 0.02). From the in vitro isometric force experiments, HD arteries demonstrated decreased contractility and endothelium-dependent relaxation compared with PD and non-dialysis vessels. Level of oxidative stress (as indicated by the 8-isoprostane level) was 30% higher in HD arteries than in PD arteries. Protein expression of inducible nitric oxide synthase, NADPH subunits and xanthine oxidase was upregulated in HD arteries, while superoxide dismutase was downregulated. The compromised vascular function in HD arteries was improved by pharmacological means that eliminated oxidative stress. CONCLUSIONS: We report associations between vasomotor function and oxidative stress in the vasculature of patients receiving different dialysis therapies. Oxidative stress, which may be differentially augmented during PD and HD, may play an important role in the vascular dysfunction in dialysis populations.

Effectiveness of combination of losartan potassium and doxycycline versus single-drug treatments in the secondary prevention of thoracic aortic aneurysm in Marfan syndrome.

OBJECTIVE: Losartan potassium (INN losartan), an antihypertensive drug, has been shown to prevent thoracic aortic aneurysm in Marfan syndrome through the inhibition of transforming growth factor beta. Recently we reported that doxycycline, a nonspecific inhibitor of matrix metalloproteinases 2 and 9, normalized aortic vasomotor function and suppressed aneurysm growth. We hypothesized that a combination of losartan potassium and doxycycline would offer better secondary prevention treatment than would single-drug therapy to manage thoracic aortic aneurysm. METHODS: A well-characterized mouse model of Marfan syndrome (Fbn1(C1039G/+)) was used. At 4 months of age, when aneurysm had established, mice (n = 15/group) were given doxycycline alone (0.24 g/L), losartan potassium alone (0.6 g/L), or combined (0.12-g/L doxycycline and 0.3-g/L losartan potassium) in drinking water. Littermate Fbn1(+/+) mice served as control. Thoracic aortas at 6 and 9 months were studied. RESULTS: At 9 months, aortic diameter in untreated group was increased by 40% relative to control. Losartan potassium or doxycycline reduced aortic diameter by 10% to 16% versus untreated aortas. Losartan potassium and doxycycline combined completely prevented thoracic aortic aneurysm and improved elastic fiber organization, also downregulating matrix metalloproteinases 2 and 9 and transforming growth factor beta and normalizing aortic contractile and relaxation functions to control values. CONCLUSIONS: Neither losartan potassium nor doxycycline alone completely restored vascular integrity and cell function when given during delayed treatment, indicating the importance of timed pharmacologic intervention. Combined, however, they synergistically offered better aneurysm-suppressing effects than did single-drug medication in the secondary prevention of thoracic aortic aneurysm.

Vasomotor dysfunction in the thoracic aorta of Marfan syndrome is associated with accumulation of oxidative stress.

We have described that the progression of thoracic aortic aneurysm in Marfan syndrome is accompanied with aortic vascular dysfunction. In the present study, we hypothesized that the impaired contractile function and endothelial-dependent relaxation could be resulted from oxidative stress in the thoracic aorta. Adrenergic contraction and cholinergic relaxation of thoracic aortae from mice (n=40; age=3, 6, 9 months) heterozygous for FBN1 allele (Fbn1(C1039G/+)), a well-defined model of Marfan syndrome, were compared with those from control (n=40). The aortic 8-isoprostane level, an oxidative stress marker, was 32-50% greater in the Marfan group than in the control. Pre-incubation with superoxide dismutase (SOD) improved the phenylephrine-induced contraction and the sensitivity to acetylcholine in Marfan aortae, but not in controls. The phenylephrine-contraction in Marfan aortae was potentiated by 1400 W, an inducible nitric oxide synthase (iNOS) inhibitor, and allopurinol, a xanthine oxidase inhibitor. Acetylcholine-induced relaxation was restored by apocynin, an inhibitor of NAD(P)H oxidase. Protein expression of SOD-1 and SOD-2 was decreased in Marfan aortae, whereas that of xanthine oxidase, iNOS, and the enzymatic subunits of NAD(P)H oxidase was increased. The vasomotor dysfunction in Marfan thoracic aortae could be associated with accumulation of oxidative stress due to unbalanced protein expression of superoxide-producing and superoxide-eliminating enzymes.

Differential microvasculature dysfunction in living kidney donor transplant recipients: nondialyzed versus dialyzed chronic kidney disease patients.

We hypothesized that there was differential vasomotor dysfunction in the microcirculation between nondialyzed and dialyzed chronic kidney disease (CKD) patients. During live donor kidney transplantation procedures, skin arterioles (SkA; internal diameter = 120 +/- 5 microm) from donors (n = 27) and recipients (nondialysis = 15; dialysis = 20) were dissected from the abdominal wall at the incision site. In vivo aortic pulse wave velocity (PWV) was also measured. In the in vitro isometric force measurement, nondialyzed SkA exhibited comparable contraction to donor SkA, whereas dialyzed SkA had 60 and 40-50% increase in contraction in response to depolarization and agonist (that is, phenylephrine, serotonin and endothelin-1) stimulation, respectively. The acetylcholine-induced relaxation in the nondialyzed SkA was decreased by 50% compared with dialyzed SkA. However, pre-incubation with superoxide dismutase greatly enhanced the relaxation response in the nondialyzed, but not in the dialyzed SkA and donor SkA. Pre-incubation with N(G)-nitro-L-arginine methyl ester (L-NAME) elevated the resting tension and left-shifted the concentration response curve of phenylephrine-stimulated contraction in the donor-SkA. L-NAME only increased the resting tension in the nondialyzed vessel. In vitro stiffness positively correlated with PWV (R(2) = 0.302, p = 0.001), and dialyzed SkA was 60% stiffer than nondialyzed and donor SkA. The acetylcholine relaxation was negatively correlated with PWV in donors and recipients (R(2) = 0.282, p = 0.01). In conclusion, we have uniquely demonstrated differential microvasculature dysfunction between nondialyzed and dialyzed CKD patients.

Long-term effects of losartan on structure and function of the thoracic aorta in a mouse model of Marfan syndrome.

BACKGROUND AND PURPOSE: During development of thoracic aortic aneurysms in a mouse model of Marfan syndrome, upregulation of matrix metalloproteinase (MMP)-2 and -9 was accompanied by compromised aortic constriction and endothelium-dependent relaxation. Losartan has been proposed for the prevention of thoracic aortic aneurysm. We hypothesized that losartan would suppress MMP-2/-9 activation and improve aortic vasomotor function in this model. EXPERIMENTAL APPROACH: A well-characterized mouse model of Marfan syndrome (Fbn1(C1039G/+)) was used. Starting at 6 weeks old, Marfan mice were untreated or given losartan (0.6 g.L(-1) in drinking water, n= 30). The littermate Fbn1(+/+) mice served as control. Thoracic aortas were studied at 3, 6 and 9 months by histology and by contractility assays in isolated segments in vitro. KEY RESULTS: Losartan improved elastic fibre organization and increased aortic breaking stress. Losartan reduced the activity and protein expression of MMP-2 and MMP-9 at all ages. Aortic constriction in response to membrane depolarization or phenylephrine was increased by losartan at 3 and 9 months by 100-200%. Active force of aortic smooth muscle was also increased at 6 and 9 months. Acetylcholine-induced endothelium-dependent relaxation was improved by 30% after 3 months of losartan treatment, but such improvement disappeared with longer duration of treatment, accompanied by reduced phosphorylation of endothelial nitric oxide (NO) synthase(Ser1177), Akt(Thr308) and Akt(Ser473), compared with the control. CONCLUSIONS AND IMPLICATIONS: Losartan improved the contractile function of aorta and reduced MMP activation. However, the endothelial NO pathway remained suppressed in the thoracic aorta during losartan treatment, which might limit its long-term benefits in Marfan syndrome.

Upregulation of matrix metalloproteinase-2 in the arterial vasculature contributes to stiffening and vasomotor dysfunction in patients with chronic kidney disease.

BACKGROUND: Cardiovascular disease is the leading cause of mortality in chronic kidney disease patients on maintenance dialysis. Given the importance of matrix metalloproteinase-2 (MMP-2) in matrix integrity, vascular cell function, and structural stability, we hypothesized that MMP-2 was elevated in the macrovasculature in dialyzed chronic kidney disease patients compared with chronic kidney disease patients not on dialysis and kidney donors. METHODS AND RESULTS: Arteries from live kidney donors (A(donor); n=30) and recipients (nondialysis [A(nondialyzed)], n=17; dialysis [A(dialyzed)], n=23 [peritoneal dialysis, n=10; hemodialysis, n=13]) were harvested during the transplantation procedure. Compared with A(donor), MMP-2 upregulation was evident in both recipient groups. Protein expression of latent plus active MMP-2 in A(dialyzed) was 2-fold that in A(nondialyzed). MMP-2 activity increased with length of dialysis (r=0.573, P=0.004). In A(dialyzed), medial elastic fiber fragmentation was pronounced, and the ratio of external elastic lamina to media was negatively correlated with MMP-2 activity (r=-0.638, P=0.001). A(dialyzed) was 25% stiffer than A(nondialyzed); this increased stiffness correlated with MMP-2 activity (r=0.728, P<0.0001) and the severity of medial calcium deposition (r=0.748, P=0.001). The contractile function and endothelium-dependent relaxation were reduced by 35% to 55% in A(dialyzed) and were negatively associated with MMP-2 activity (r=-0.608, P=0.002; r=-0.520, P=0.019, respectively). Preincubation with MMP-2 inhibitor significantly improved contractility and relaxation in A(dialyzed). CONCLUSIONS: We describe a strong correlation between MMP-2 activation and elastic fiber disorganization, stiffness, calcification, and vasomotor dysfunction in the arterial vasculature in dialyzed chronic kidney disease patients. These findings may contribute to an improved understanding of mechanisms important in vascular health in chronic kidney disease patients.

Matrix metalloproteinase-2 and -9 exacerbate arterial stiffening and angiogenesis in diabetes and chronic kidney disease.

AIMS: Chronic kidney disease (CKD) and diabetes are the prominent risk factors of cardiovascular disease (CVD). Matrix metalloproteinase (MMP)-2 and -9 regulate vascular structure by degrading elastic fibre and inhibit angiogenesis by generating angiostatin. We hypothesized that MMP-2 and -9 were up-regulated in the arterial vasculature from CKD patients with diabetes, compared with those without diabetes. METHODS AND RESULTS: During living donor transplantation procedures, arteries from donors (n = 8) and recipients (non-diabetic, n = 8; diabetic, n = 8; matched in age, gender, and dialysis treatments) were harvested. Diabetic arteries had increased MMP-2 and -9 activities by 42 and 116% compared with non-diabetic ones. Diabetic arteries were the stiffest, and the stiffness measurement was highly correlated with the summation of MMP-2 + MMP-9 activities (r = 0.738, P = 0.0002). Pulse wave velocity measurements correlated with MMP activity (r = 0.683, P = 0.005). Elastic fibre degradation and calcification were worst in diabetic vessels. The phosphate level, which was 25% higher in diabetic patients, correlated with MMP activity (r = 0.513, P = 0.04) and in vitro stiffness (r = 0.545, P = 0.03), respectively. Angiostatin expression was doubled, whereas vascular endothelial growth factor was 50% reduced in diabetic compared with non-diabetic vessels. Microvascular density in diabetic vessels was 48% of that in non-diabetic ones, and it was strongly associated with MMP activity (r = -0.792, P < 0.0001) and vasorelaxation (r = 0.685, P = 0.0009). CONCLUSION: Using a matched case-control design, we report up-regulation of MMP-2 and -9 in diabetic CKD arteries and correlate those with stiffening, impaired angiogenesis, and endothelial dysfunction. These findings may help to explain the high susceptibility of CVD in diabetic and non-diabetic CKD patients.

Diabetes modulates capacitative calcium entry and expression of transient receptor potential canonical channels in human saphenous vein.

Diabetes is associated with a perturbation of signaling pathways in vascular tissue, which causes vasomotor dysfunction such as hypertension. We have previously demonstrated that vessels from diabetic patients were more contractile than those from non-diabetic. However, in human vessels, the receptor-stimulated contraction is mainly due to enzymatic, rather than calcium signaling pathway. In this study, we hypothesized that the differential contractile response between diabetic and non-diabetic human vessels could be due to the receptor signaling to sarcoplasmic reticulum and the regulation of capacitative calcium entry. In saphenous vein samples (n=20) collected from diabetic patients undergoing bypass surgery, the contraction initiated by the addition of the sarco-endoplasmatic reticulum calcium ATPase blocker, cyclopiazonic acid, was significantly higher than that in the vessels from non-diabetic patients (n=26) (84.0+/-14.9% vs 44.2+/-9.2%), and this contraction was inhibited by SKF-96365, an inhibitor of store-operated calcium channels. Pre-incubation with indomethacin reduced the cyclopiazonic acid-induced contraction in the non-diabetic veins, but had no effect on the diabetic ones. The gene expression of transient receptor potential canonical channels (TRPC)4 was upregulated by 22% in the diabetic vessels compared with the non-diabetic ones. However, the protein expression of TRPC1 and TRPC6 was downregulated in the diabetic group by 50%. We concluded that diabetes would modulate the capacitative calcium entry likely through the store-operated calcium channel specifically via the regulation of TRPC.

Long-term doxycycline is more effective than atenolol to prevent thoracic aortic aneurysm in marfan syndrome through the inhibition of matrix metalloproteinase-2 and -9.

Beta-blockers, eg, atenolol, are the cornerstone therapy for thoracic aortic aneurysm (TAA) in patients with Marfan syndrome; however, continued aortic dilatation has been reported. We have demonstrated that matrix metalloproteinase (MMP)-2 and -9 were upregulated during progression of TAA in Marfan syndrome, accompanied with degenerated elastic fibers and vasomotor dysfunction. We hypothesized that doxycycline, a nonspecific inhibitor of MMPs, would ameliorate TAA by attenuating elastic fiber degeneration and improving vasomotor function. A well-characterized mouse model of Marfan syndrome (Fbn1(C1039G/+)) was used. Mice were untreated (n=40), given doxycycline (0.24 g/L, n=30), or given atenolol (0.5 g/L, n=30) in drinking water at 6 weeks of age. The Fbn1(+/+) mice served as control (n=40). At 3, 6, and 9 months, aortic segments from the ascending, arch, and descending portions were used to obtain the "average" value of the whole thoracic aorta. TAA was prevented in the doxycycline group, whereas mild aneurysm was evident in the atenolol group. Doxycycline improved elastic fiber integrity, normalized aortic stiffness, and prevented vessel weakening. The impairment of vasocontraction and endothelium-dependent relaxation in the untreated and atenolol groups were improved by doxycycline. The upregulation of transforming growth factor-beta in the Marfan aorta was suppressed by doxycycline. Doxycycline augmented expression ratios of tissue inhibitors of MMP to MMPs. Intraperitoneally injected neutralizing antibodies against MMP-2 and -9 yielded similar effects to doxycycline. We concluded that long-term treatment with doxycycline, through the inhibition of MMP-2 and -9, is more effective than atenolol in preventing TAA in Marfan syndrome by preserving elastic fiber integrity, normalizing vasomotor function, and reducing transforming growth factor-beta activation.

Mechanical and pharmacological approaches to investigate the pathogenesis of Marfan syndrome in the abdominal aorta.

BACKGROUND: Occurrence of disease complications in the abdominal aorta in Marfan syndrome, a connective tissue disorder caused by mutations in the gene encoding fibrillin-1, is relatively rare. We hypothesized that Marfan syndrome could affect the structure, vasomotor function and mechanical property of the abdominal aorta. METHODS AND RESULTS: Abdominal aorta from mice at 3, 6, 9 and 12 months of age, heterozygous for the Fbn1 allele encoding a cysteine substitution (Fbn1(C1039G/+), Marfan mice, n = 50), were compared with those from age-matched control littermates (n = 50). Marfan abdominal aorta demonstrated pronounced elastic fiber degradation and disorganization, concomitant with an increased aortic stiffness during aging. In the isometric force measurement, vasoconstriction in response to membrane depolarization or phenylephrine stimulation was similar in both Marfan and control abdominal aorta. However, Marfan abdominal aorta was less sensitive to the inhibition of the phenylephrine-induced contraction by indomethacin and SQ-29548, during which the release of thromboxane A(2) was one half of that of the controls. Nevertheless, the protein expression of cyclooxygenase-1 and cyclooxygenase-2 detected by Western immunoblotting was not different between the 2 strains. CONCLUSIONS: We demonstrated that Marfan syndrome affected abdominal aorta with respect to matrix elastic fiber organization, aortic stiffness and release of thromboxane A(2).

Arterialization of a vein graft promotes cell cycle progression through Akt and p38 mitogen-activated protein kinase pathways: impact of the preparation procedure.

BACKGROUND: Vein arterialization following bypass surgery often leads to graft occlusion, but the underlying cellular mechanisms have been poorly studied. OBJECTIVES: Cell cycle progression and the activation of proliferation signalling were compared in arterialized grafts prepared either according to the conventional procedure or using pharmacological relaxation with the native vein. METHODS: Using the porcine carotid-jugular bilateral interposition graft model on one side, a segment of porcine jugular vein was prepared for grafting using the conventional procedure, with pressure distention at 300 mmHg; the segment grafted on the other side was treated with a combination of pharmacological vasodilators. Both veins were grafted into the carotid artery for two weeks. RESULTS: On the immunolabelling of proliferation cell nuclear antigen, a greater number of proliferating cells was found in the conventionally prepared grafts compared with pharmacologically prepared grafts. Cyclin D1 expression and phosphorylation of retinoblastoma increased after implantation, coinciding with nuclear accumulation of beta-catenin, activation of the Akt and mitogen-activated protein kinase cascades, and upregulated phosphatase and tensin homologue phosphorylation. Replacement of distention with pharmacological relaxation reduced the increase in cyclin D1 expression, phosphorylation of retinoblastoma, Akt-Thr(308), glycogen synthase kinase 3 beta and p38, but not extracellular signal-regulated kinases. This technique preserved the active phosphatase and tensin homologue, as well as the expression of cyclin-dependent kinase inhibitor p21(Cip1), while elevating the expression of p27(Kip1). CONCLUSIONS: It was concluded that two-week arterial implantation stimulates proliferation signalling and promotes the cell cycle in vein grafts. Replacement of the conventional preparation procedures with pharmacological vasorelaxation restricts the activation of proliferation and cell cycle progression, and can be beneficial for improving vein graft patency.

Loss of elastic fiber integrity and reduction of vascular smooth muscle contraction resulting from the upregulated activities of matrix metalloproteinase-2 and -9 in the thoracic aortic aneurysm in Marfan syndrome.

Thoracic aortic aneurysm (TAA) is the life-threatening complication of Marfan syndrome (MFS), a connective tissue disorder caused by mutations in the fibrillin-1 gene. TAA is characterized by degradation of elastic fiber, suggesting the involvement of matrix metalloproteinase (MMP)-2 and -9, the activation of which is regulated by TIMP (tissue inhibitor of MMP) types 1 and 2. We hypothesized that MMP-2 and -9 were upregulated during TAA formation in Marfan syndrome, causing loss of elastic fibers and structural integrity. We studied mice, from 3 to 12 months, heterozygous for a mutant Fbn1 allele encoding a cysteine substitution in fibrillin-1 (Fbn1(C1039G/+), designated as "Marfan" mice) (n=120), the most common class of mutation in Marfan syndrome. The littermates, Fbn1(+/+) served as controls (n=120). In Marfan aneurysmal thoracic aorta, mRNA and protein expression of MMP-2 and -9 were detected at 3 months and peaked at 6 months of age, accompanied by severe elastic fiber fragmentation and degradation. From 3 to 9 months, the MMP-2/TIMP-2 ratio increased by 43% to 63% compared with the controls. Dilated thoracic aorta demonstrated increased elasticity but distention caused a pronounced loss of contraction, suggesting weakening of the aortic wall. Breaking stress of the aneurysmal aorta was 70% of the controls. Contraction in response to depolarization and receptor stimulation decreased in the aneurysmal thoracic aorta by 50% to 80%, but the expression of alpha-smooth muscle actin between the 2 strains was not significantly different. This report demonstrates the upregulation of MMP-2 and -9 during TAA formation in Marfan syndrome. The resulting elastic fiber degeneration with deterioration of the aortic contraction and mechanical properties may explain the pathogenesis of TAA.

Hyperglycemia and hyperlipidemia are associated with endothelial dysfunction during the development of type 2 diabetes.

Diabetes mellitus impairs endothelial function, which can be considered as the hallmark in the development of cardiovascular diseases. Hyperglycemia, hyperinsulinemia, and hyperlipidemia are believed to contribute to endothelial dysfunction. In the present study, we investigated the possible links among these plasma metabolic markers and endothelial function in a mouse model during the development of type 2 diabetes. C57BL/6J-Lepob/ob mice at 8, 12, and 16 weeks were used to study endothelial function during the establishment of type 2 diabetes. Endothelial function was accessed in vitro in the thoracic aorta by measuring acetylcholine (ACh)-stimulated vasodilatation. Blood plasma was obtained for the measurements of glucose, insulin, triglycerides, and cholesterol levels. Correlation and multiple regression analysis revealed strong negative associations between the ACh responsiveness and the plasma levels of glucose, insulin, and lipid profiles at the age of 8 weeks. Associations were observed at neither older age nor in C57BL/6J mice. In conclusion, the increase in plasma levels of glucose, insulin, and lipids is associated with the impairment of the endothelial function during the early stage of the development of type 2 diabetes. The loss of correlation at an older age suggests multifactorial regulation of endothelial function and cardiovascular complications at later stages of the disease.

Enhanced cell cycle entry and mitogen-activated protein kinase-signaling and downregulation of matrix metalloproteinase-1 and -3 in human diabetic arterial vasculature.

Diabetic patients have a strong predilection for atherosclerosis and postangioplasty restenosis. Accelerated cell proliferation and excessive extracellular matrix deposition are believed to contribute to the development of atherosclerotic plaques and neointima. We investigated the effect of diabetes on cell cycle, proliferation signaling, and the activation of matrix metalloproteinases (MMPs). Segments of internal mammary arteries from 26 type 2 diabetic and 26 non-diabetic patients undergoing coronary artery bypass grafting surgery were compared. Increased levels of cyclin D1 mRNA (by 135+/-14%) and protein expression (by 93.8+/-7.0%), retinoblastoma protein phosphorylation (by 45.9+/-4.8%), and beta-catenin nuclear localization (by 176+/-16%) indicated the enhanced cell cycle entry in the diabetic arteries. Diabetes increased phosphorylation of extracellular signal-regulated kinase-1/2 and p-38-mitogen-activated protein kinase (MAPK) by 76.0+/-6.8 and 62.3+/-4.3%. Increased collagen deposition was evidenced in the diabetic arteries. mRNA levels of MMP-1 and MMP-3 were decreased in the diabetic tissue to 55 and 82%, respectively, compared to the non-diabetic group; protein levels were also decreased accompanied with decreased enzymatic activities by 21 and 50%, respectively. In conclusion, enhanced cell cycle entry, increased MAPK signaling, and downregulated MMP-1 and MMP-3 were characteristic of diabetic arterial vasculature, and could contribute to the progressive atherosclerosis and postangioplasty restenosis in diabetic patients.

Pharmacologic relaxation of vein grafts is beneficial compared with pressure distention caused by upregulation of endothelial nitric oxide synthase and nitric oxide production.

OBJECTIVE: Pressure distention of veins during preparation for bypass surgery is believed to impair vascular integrity and reduce graft patency. We previously suggested a combination of pharmacologic vasodilatators as an alternative to distention. Vascular homeostasis is largely regulated by nitric oxide. We investigated the role of distention in comparison with pharmacologic vasorelaxation in the regulation of nitric oxide synthases, nitric oxide bioavailability, and vascular reactivity in vein grafts. METHODS: In a porcine model the internal jugular vein from either side received pressure distention or the combination of vasodilators (alpha-adrenergic antagonist, phenoxybenzamine, 10 micromol/L; Rho-kinase inhibitor, HA-1077 [fasudil], 50 mumol/L; calcium blocker, nicardipine, 1 micromol/L) and then was grafted into the carotid artery. Regulation of nitric oxide synthase, as well as nitrate and nitrite levels, were examined in vein grafts after 2 weeks of implantation. RESULTS: Distention of jugular veins resulted in reduction of vasoconstriction in response to depolarization and agonist stimulation. Arterial grafting doubled inducible nitric oxide synthase expression in both grafts but caused a pronounced upregulation of endothelial nitric oxide synthase protein (by 57.3% +/- 5%) only in drug-treated grafts, whereas in distended grafts the endothelial nitric oxide synthase level was decreased by 27.5% +/- 2.7%. The downregulated endothelial nitric oxide synthase level in the distended grafts was accompanied by a 45.2% +/- 3.1% reduction of phospho-endothelial nitric oxide synthase Ser1177 levels and by a significant reduction in nitric oxide synthase activity (12.1% +/- 1.2%) and nitrate production (48.9% +/- 5.6%) in comparison with that seen in drug-treated grafts. CONCLUSIONS: Pharmacologic preparation of the vein grafts results in upregulation of endothelial nitric oxide synthase and increased nitric oxide production in the vein grafts after arterial implantation. This might provide greater clinical benefit than conventional pressure-distention methods.

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.

Pressure distention compared with pharmacologic relaxation in vein grafting upregulates matrix metalloproteinase-2 and -9.

OBJECTIVE: Autogenous vein bypasses are a common and effective method to treat occlusive disease. During surgical preparation, veins are routinely pressure distended to overcome vasospasm and twists. Distention, however, is believed to promote vascular remodeling and contribute to decreased graft patency. Pharmacologic vasorelaxation with a combination of effective vasodilators has been suggested as an alternative to pressure distention. The extracellular matrix (ECM)-degrading matrix metalloproteinases (MMPs) have been implicated in vascular remodeling and neointima formation. The purpose of the present study was to compare the effects of pressure distention with pharmacologic vasorelaxation on graft remodeling and regulation of MMP-2 and MMP-9 in porcine vein grafts. METHODS: Carotid artery bypass utilizing internal jugular veins was performed in eight female white pigs. Jugular veins were randomized to receive pressure distention (300 mm Hg for 2 minutes) or a combination of vasodilators (the alpha-adrenergic antagonist phenoxybenzamine, 10 micromol/L; the Rho-kinase inhibitor HA-1077 [fasudil], 50 micromol/L; and the calcium-channel blocker nicardipine, 1 micromol/L) for 30 minutes and then were grafted into the carotid arteries. Two weeks after surgery, vein graft samples were analyzed for vessel intimal and medial area, lumen diameter, and ECM composition. Molecular analysis using reverse transcription-polymerase chain reaction, Western immunoblotting, gelatin zymography, and reverse zymography were performed to study the expression and activation of MMP-2 and MMP-9, and tissue inhibitors of MMP (TIMP)-1 and TIMP-2. RESULTS: Pressure distention irreversibly overstretched the porcine jugular vein and increased MMP-2 and MMP-9 proteolytic activity by 40% and 77%, respectively. Two weeks of vein grafting in the carotid arterial bed induced vessel wall thickening, ECM modification, and neointima formation, which were more pronounced in the distended grafts (P < .05) and accompanied by an increase in MMP expression and activity. Distended grafts demonstrated higher percentages of active MMP-9 (17.8% +/- 1.0%) and higher activities of latent (35.5% +/- 3.3%) and active MMP-2 (69.6% +/- 8.8%) than the pharmacologically treated grafts. Protein expression of TIMP-1 and TIMP-2 was downregulated after arterial grafting, but the pharmacologically treated grafts expressed significantly more TIMP-1 protein (by 36.8% +/- 4.1%) than the distended ones. The activities of TIMPs were markedly decreased after grafting, contributing to the upregulated MMP activity. CONCLUSIONS: Pressure distention of vein grafts before implantation, compared with pharmacologic vasodilatation, stimulates neointima formation and augments MMP activities. Pharmacologic vasorelaxation may be clinically superior to distention in attenuating graft remodeling and possibly improving graft patency. CLINICAL RELEVANCE: Autogenous vein bypasses are a common and effective method to treat occlusive disease. This study demonstrated that pressure distention, a common preparatory procedure in bypass surgery, upregulates extracellular matrix-degrading matrix metalloproteinases, which predisposes vein grafts to extensive remodeling and contributes to neointima formation and graft occlusion. The topical application of a combination of vasodilators to the vein graft before implantation may be clinically superior to pressure distention in attenuating graft remodeling and may possibly improve graft patency and reduce secondary surgical interventions.

Compromised arterial function in human type 2 diabetic patients.

Diabetes is associated with a perturbation of signaling pathways in vascular tissue, which causes vasomotor dysfunction such as hypertension and accelerated atherosclerosis. In the present study, the mechanisms of vasomotor dysfunction, Akt (Thr308 and Ser473) phosphorylation and expression of endothelial NO (nitric oxide) synthase, and inducible NO synthase were investigated in human diabetic internal mammary arteries. The phospho-Akt (Thr308) level in arteries from diabetic patients was reduced to about one-half of the level in nondiabetic patients, suggesting impaired insulin signaling in human diabetic vascular tissue. Augmented vasoconstriction was observed in diabetic arteries, due in part to deficiency of basal and stimulated NO production. This correlated with decreased endothelial NO synthase expression and activity in diabetic vessels. The sensitivity of diabetic vessels to the NO donor, sodium nitroprusside, was reduced as well, suggesting that NO breakdown and/or decreased sensitivity of smooth muscle to NO are also responsible for abnormal vasoconstriction. In addition, the abnormal vasoconstriction in diabetic vessels was not completely abolished in the presence of Nomega-nitro-L-arginine methyl ester, revealing that NO-independent mechanisms also contribute to vasomotor dysfunction in diabetes. In conclusion, diabetes downregulates the Akt-signaling pathway and compromises human arterial function through a decrease in NO availability as well as through NO-independent mechanisms.

Platelet-leukocyte aggregation induced by PAR agonists: regulation by nitric oxide and matrix metalloproteinases.

Platelet-leukocyte aggregation (PLA) links haemostasis to inflammation. The role of nitric oxide (NO) and matrix metalloproteinases (MMP-1, -2, -3, -9) in PLA regulation was studied. Homologous human platelet-leukocyte suspensions were stimulated with thrombin (0.1-3 nM) and other proteinase activated receptor-activating peptides (PAR-AP), including PAR1AP (0.5-10 microM), PAR4AP (10-70 microM), and thrombin receptor-activating peptide (1-35 microM). PLA was studied using light aggregometry with simultaneous measurement of oxygen-derived free radicals, dual colour flow cytometry, and phase-contrast microscopy. The release of NO was measured using a porphyrinic nanosensor, while MMPs were investigated by Western blot, substrate degradation assays, immunofluorescence microscopy, and flow cytometry. The levels of P-selectin and microparticles (MP) in PLA were measured by flow cytometry. PLA was also characterized using pharmacological agents: S-nitroso-glutathione (GSNO, 0.01-10 microM), 1H-Oxadiazole quinoxalin-1-one (ODQ, 1 microM), N(G)-L-nitro-L-arginine methyl ester (L-NAME, 100 microM) and compounds that modulate the actions of MMPs such as phenanthroline (100 microM), monoclonal anti-MMP antibodies, and purified MMPs. PAR agonists concentration-dependently induced PLA, an effect associated with the release of microparticles (MP) and the translocation of P-selectin to the platelet surface. NO and radicals were also released during PLA. Inhibition of NO bioactivity by the concomitant release of free radicals or by the treatment with L-NAME or ODQ stimulated PLA, while pharmacological administration of GSNO decreased PLA. PAR agonist-induced PLA resulted in the liberation of MMP-1, -2, -3, and -9. During PLA, MMPs were present on the cell surface, as shown by flow cytometry and immunofluorescence. PLA led to the activation of latent MMPs to active MMPs, as shown by Western blot and substrate degradation assays. Inhibition of MMPs actions by phenanthroline and by the antibodies attenuated PLA. In contrast, purified active, but not latent, MMPs amplified thrombin-induced PLA. It is concluded that NO and MMP-1, -2, -3, and -9 play an important role in regulation of PAR agonist-induced PLA.