Biomedical subjects

Gabor Kaley

Publications and source records attributed to Gabor Kaley.

At least 19 recordsLinked to original sources

PubMed2006

H2O2 increases production of constrictor prostaglandins in smooth muscle leading to enhanced arteriolar tone in Type 2 diabetic mice.

Our previous study showed that arteriolar tone is enhanced in Type 2 diabetes mellitus (T2-DM) due to an increased level of constrictor prostaglandins. We hypothesized that, in mice with T2-DM, hydrogen peroxide (H(2)O(2)) is involved in the increased synthesis of constrictor prostaglandins, hence enhanced basal tone in skeletal muscle arterioles. Isolated, pressurized gracilis muscle arterioles ( approximately 100 microm in diameter) of mice with T2-DM (C57BL/KsJ-db(-)/db(-)) exhibited greater basal tone to increases in intraluminal pressure (20-120 mmHg) than that of control vessels (at 80 mmHg, control: 25 +/- 5%; db/db: 34 +/- 4%, P < 0.05), which was reduced back to control level by catalase (db/db: 24 +/- 4%). Correspondingly, in carotid arteries of db/db mice, the level of dichlorofluorescein-detectable and catalase-sensitive H(2)O(2) was significantly greater. In control arterioles, exogenous H(2)O(2) (0.1-100 micromol/l) elicited dilations (maximum, 58 +/- 10%), whereas in arterioles of db/db mice H(2)O(2) caused constrictions (-28 +/- 8%), which were converted to dilations (maximum, 16 +/- 5%) by the thromboxane A(2)/prostaglandin H(2) (TP) receptor antagonist SQ-29548. In addition, arteriolar constrictions in response to the TP receptor agonist U-46619 were not different between the two groups of vessels. Endothelium denudation did not significantly affect basal tone and H(2)O(2)-induced arteriolar responses in either control or db/db mice. Also, in arterioles of db/db mice, but not in controls, 3-nitrotyrosine staining was detected in the endothelial layer of vessels. Thus we propose that, in mice with T2-DM, arteriolar production of H(2)O(2) is enhanced, which leads to increased synthesis of the constrictor prostaglandins thromboxane A(2)/prostaglandin H(2) in the smooth muscle cells, which enhance basal arteriolar tone. These alterations may contribute to disturbed regulation of skeletal muscle blood flow in Type 2 diabetes mellitus.

Animals↗

PubMed2006

COX-2 contributes to the maintenance of flow-induced dilation in arterioles of eNOS-knockout mice.

Our previous studies demonstrated that, in gracilis muscle arterioles of male mice deficient in the gene for endothelial nitric oxide synthase (eNOS), flow-induced dilation (FID) is mediated by endothelial PGs. Thus the present study aimed to identify the specific isoform of cyclooxygenase (COX) responsible for the compensatory mediation of FID in arterioles of eNOS-knockout (KO) mice. Experiments were conducted on gracilis muscle arterioles of male eNOS-KO and wild-type (WT) mice. Basal tone and magnitude of FID of arterioles were comparable in the two strains of mice. A role for COX isoforms in the mediation of the responses was assessed by use of valeryl salicylate (3 mM) and NS-398 (10 microM), inhibitors of COX-1 and COX-2, respectively. In eNOS-KO arterioles, valeryl salicylate or NS-398 alone inhibited FID (at maximal flow rate) by approximately 51% and approximately 58%, respectively. Administration of both inhibitors eliminated the dilation. In WT arterioles, inhibition of COX-2 did not significantly affect FID, whereas inhibition of COX-1 decreased the dilation by approximately 57%. The residual portion of the response was abolished by additional administration of Nomega-nitro-L-arginine methyl ester. Western blot analysis indicated a comparable content of COX-1 protein in arterioles of WT and eNOS-KO mice. COX-2 protein, which was not detectable in arterioles of WT mice, was strongly expressed in arterioles of eNOS-KO mice, together with an upregulation of COX-2 gene expression. Immunohistochemical staining confirmed the presence of COX-2 in the endothelium of eNOS-KO arterioles. In conclusion, COX-2-derived PGs are the mediators responsible for maintenance of FID in arterioles of eNOS-deficient mice.

Animals↗

PubMed2006

Bone morphogenetic protein-2 induces proinflammatory endothelial phenotype.

The transforming growth factor-beta superfamily member bone morphogenetic protein-2 (BMP-2) is up-regulated in atherosclerotic arteries; however, its effects on the endothelium are not well characterized. Using microdissected coronary arterial endothelial cells (CAECs) and cultured primary CAECs, we demonstrated endothelial mRNA expression of BMP-2 and BMP-4. The proinflammatory cytokine tumor necrosis factor-alpha and H2O2 significantly increased endothelial expression of BMP-2 but not BMP-4. In organ culture, BMP-2 substantially decreased relaxation of rat carotid arteries to acetylcholine and increased production of reactive oxygen species, events inhibited by pharmacologically blocking protein kinase C (PKC) or NAD(P)H oxidase. BMP-2 activated nuclear factor-kappaB in CAECs, and BMP-2 and BMP-4 substantially increased adhesion of monocytic THP-1 cells, which was reduced by pharmacologically inhibiting p42/44 MAP kinase pathway (also by siRNA down-regulating ERK-1/2) or PKC. Incubation of rat carotid arteries with BMP-2 ex vivo also increased adhesion of mononuclear cells to the endothelium, requiring p42/44 MAP kinase and PKC. Western blotting showed that in CAECs and carotid arteries BMP-2 elicited phosphorylation of p42/44 MAP kinase, which was reduced by blocking MAP kinase kinase and PKC. Collectively, expression of BMP-2 is regulated by proinflammatory stimuli, and increased levels of BMP-2 induce endothelial dysfunction, oxidative stress, and endothelial activation. Thus, the proinflammatory effects of BMP-2 may play a role in vascular pathophysiology.

Acetylcholine↗

PubMed2005

Contribution of 20-HETE to augmented myogenic constriction in coronary arteries of endothelial NO synthase knockout mice.

Previous studies suggested an important role for 20-HETE in the regulation of myogenic responses. Thus, pressure-diameter relationships were investigated in isolated, cannulated coronary arteries (approximately 100 microm) from male endothelial NO synthase knockout (eNOS-KO) and wild-type (WT) mice. All arteries constricted in response to step increases in perfusate pressure from 20 to 100 mm Hg. This constriction was significantly enhanced from 40 to 100 mm Hg in arteries of eNOS-KO compared with those of WT mice. For example, at 60 and 100 mm Hg, respectively, the normalized diameter (expressed as a percentage of the corresponding passive diameter) of arteries of eNOS-KO mice was 10% and 12% smaller than that of WT mice. Removal of the endothelium did not significantly affect the responses of vessels from either strain of mice. However, N-methylsulfonyl-12,12-dibromododec-11-enamide (5x10(-6) M), an inhibitor of cytochrome P-450 (CYP)/omega-hydroxylase, significantly attenuated the greater myogenic constriction of arteries from eNOS-KO mice by approximately 12% at each pressure step but did not significantly affect responses of those from WT mice, leading to a comparable myogenic response in the 2 strains. Western blot analysis demonstrated a comparable CYP4A protein content in coronary arteries of the 2 strains of mice. However, production of 20-HETE, measured by fluorescent high-performance liquid chromatography assay was approximately 2.7-fold greater in eNOS-KO compared to WT mice. Thus, as a function of eNOS deficiency, the enhanced coronary artery constriction to pressure is attributable to an increased activity of omega-hydroxylase, which, consequently, increases the synthesis of 20-HETE in vascular smooth muscle.

Amides↗

PubMed2005

Type 2 diabetic mice have increased arteriolar tone and blood pressure: enhanced release of COX-2-derived constrictor prostaglandins.

OBJECTIVE: Type 2 diabetes mellitus (T2-DM) is frequently associated with vascular dysfunction and elevated blood pressure, yet the underlying mechanisms are not completely understood. We hypothesized that in T2-DM, the regulation of peripheral vascular resistance is altered because of changes in local vasomotor mechanisms. METHODS AND RESULTS: In mice with T2-DM (C57BL/KsJ-(db-)/db-), systolic and mean arterial pressures measured by the tail cuff method were significantly elevated compared with those of control (db+/db-) animals (db/db, 146+/-5 and 106+/-2 mm Hg versus control, 133+/-4 and 98+/-4 mm Hg, respectively; P<0.05). Total peripheral resistance, calculated from cardiac output values (measured by echocardiography) and mean arterial pressure were significantly elevated in db/db mice (db/db, 25+/-6 versus control, 15+/-1 mm Hg[middot]mL(-1)[middot]min(-1)). In isolated, pressurized gracilis muscle arterioles (diameter approximately 80 microm) from db/db mice, stepwise increases in intraluminal pressure (from 20 to 120 mm Hg) elicited a greater reduction in diameter than in control vessels at each pressure step (at 80 mm Hg, db/db, 66+/-4% versus control, 79+/-3%). The passive diameters of arterioles (obtained in Ca2+-free solution) and the calculated myogenic index were not significantly different in the 2 groups. The presence of the prostaglandin H2/thromboxane A2 receptor antagonist SQ29548 did not affect arteriolar diameters of control mice but reduced the enhanced arteriolar tone of db/db mice back to control levels (at 80 mm Hg, 80+/-4%). The inhibitor of cyclooxygenase-1 (COX-1), SC-560, did not affect the basal tone of arterioles, whereas NS-398, an inhibitor of COX-2, caused a significant shift in the arteriolar pressure-diameter curve of vessels from db/db mice (at 80 mm Hg, 76+/-3%) but not in those of control mice. Also, in aortas of db/db mice, expression of COX-2 was enhanced compared with controls. CONCLUSIONS: Collectively, these findings suggest that in mice with T2-DM, the basal tone of skeletal muscle arterioles is increased because of an enhanced COX-2-dependent production of constrictor prostaglandins. These alterations in microvascular prostaglandin synthesis may contribute to the increase in peripheral resistance and blood pressure in T2-DM.

Animals↗

PubMed2005

PECAM-1 mediates NO-dependent dilation of arterioles to high temporal gradients of shear stress.

OBJECTIVE: In response to changes in wall shear stress (WSS) the vascular endothelium releases several factors, among others nitric oxide. On the basis of studies of endothelial cells in culture, suggesting that platelet endothelial cell adhesion molecule-1 (PECAM-1) is specifically involved in sensing and coupling high temporal gradients of fluid shear stress with activation of eNOS, we hypothesized that dilations of isolated skeletal muscle arterioles from PECAM-1 knockout mice (PECAM-KO) will be reduced to rapid increases in WSS elicited by increases in perfusate flow. METHODS AND RESULTS: Small and large step increases in flow resulted in substantial dilations in arterioles of WT mice (45+/-4%), but they were markedly reduced in arterioles of PECAM-KO mice (22+/-5%). The initial slope of dilations, when WSS increased rapidly, was greater in vessels of WT than those of PECAM-KO mice (slopes: 0.378 and 0.094, respectively), whereas the second phase of dilations, when flow/shear stress was steady, was similar in the 2 groups (slopes: 0.085 and 0.094, respectively). Inhibition of eNOS significantly reduced the initial phase of dilations in arterioles from WT, but not from those of PECAM-KO mice. The calcium ionophore A23187 elicited similar NO-mediated dilation in both WT and PECAM-KO mice. CONCLUSIONS: In isolated arterioles of PECAM-KO mice activation of eNOS and consequent dilation by agonists is maintained, but the dilation to high temporal gradients of wall shear stress elicited by increases in perfusate flow is reduced. Thus, we propose that PECAM-1 plays an important role in the ability of the endothelium to sense and couple high temporal gradients of wall shear stress to NO-mediated arteriolar dilation during sudden changes in blood flow in vivo.

Animals↗

PubMed2005

Transcriptional basis for exercise limitation in male eNOS-knockout mice with age: heart failure and the fetal phenotype.

Endothelium-derived nitric oxide (NO) is pivotal in regulating mitochondrial O(2) consumption (Vo(2)) and glucose uptake in mice. The aim of this study was to investigate the mechanism of age- and genotype-related exercise limitation in male endothelial NO synthase (eNOS)-knockout (KO, n = 16) and wild-type (WT, n = 19) mice. Treadmill testing was performed at 12, 14, 16, 18, and 21 mo of age. Vo(2), CO(2) production, respiratory exchange ratio, and maximal running distance were determined during treadmill running. There were good linear correlations for increase of speed with increase of Vo(2). The difference between KO and WT mice was not significant at 12 mo but was significant at 18 mo. Linear regression showed that KO mice consumed more O(2) at the same absolute and relative workloads, suggesting that Vo(2) was not inhibited by NO in KO mice. KO mice performed 30-50% less work than WT mice at each age (work = vertical distance x weight). In contrast to WT mice, the work performed by KO mice significantly decreased from 17 +/- 1.4 m.kg at 12 mo to 9.4 +/- 1.7 m.kg at 21 mo. Running distance was significantly decreased from 334 +/- 27 m at 12 mo to 178 +/- 38 m at 21 mo, and maximal Vo(2), CO(2) production, and respiratory exchange ratio per work unit were significantly higher in KO than in WT mice. Gene arrays showed evidence of a fetal phenotype in KO mice at 21 mo. In conclusion, age- and genotype-related exercise limitations in maximal work performed and maximal running distance in male eNOS-KO mice indicated that fetal phenotype and age were related to onset of heart failure.

Aging↗

PubMed2005

Regulation of bone morphogenetic protein-2 expression in endothelial cells: role of nuclear factor-kappaB activation by tumor necrosis factor-alpha, H2O2, and high intravascular pressure.

BACKGROUND: Recent studies suggest that bone morphogenetic protein-2 (BMP-2), a transforming growth factor-beta superfamily member cytokine, plays an important role both in vascular development and pathophysiological processes, including endothelial activation that is likely to contribute to the development of coronary atherosclerosis, yet the factors that regulate arterial expression of BMP-2 are completely unknown. We tested the hypothesis that BMP-2 expression in endothelial cells is governed by an H2O2 and nuclear factor (NF)-kappaBeta-dependent pathway that can be activated by both proinflammatory and mechanical stimuli. METHODS AND RESULTS: The proinflammatory cytokine tumor necrosis factor (TNF)-alpha induced NF-kappaBeta activation and elicited significant increases in BMP-2 mRNA and protein in primary coronary arterial endothelial cells and human umbilical vein endothelial cells that were prevented by NF-kappaBeta inhibitors (pyrrolidine dithiocarbamate and SN-50), silencing of p65 (siRNA), or catalase. Administration of H2O2 also elicited NF-kappaBeta activation and BMP-2 induction. In organ culture, exposure of rat arteries to high pressure (160 mm Hg) elicited H2O2 production, nuclear translocation of NF-kappaBeta, and upregulation of BMP-2 expression. Although high pressure upregulated TNF-alpha, it appears that it directly regulates BMP-2 expression, because upregulation of BMP-2 was also observed in vessels of TNF-alpha knockout mice. CONCLUSIONS: Vascular BMP-2 expression can be regulated by H2O2-mediated activation of NF-kappaBeta both by inflammatory stimuli and by high intravascular pressure.

Animals↗

PubMed2005

Limited exercise capacity in heterozygous manganese superoxide dismutase gene-knockout mice: roles of superoxide anion and nitric oxide.

BACKGROUND: We have reported that there is a limitation of exercise capacity in mice with defects in the expression of endothelial nitric oxide (NO) synthase, which is associated with a greater increase in whole-body oxygen consumption (VO2). We hypothesized that in states in which superoxide anion (O2-) is increased, especially in the mitochondria, whole-body VO2 will be increased because of the inactivation of NO, and consequently, exercise capacity will be reduced. METHODS AND RESULTS: Heterozygous manganese superoxide anion dismutase (SOD2) gene-knockout mice (SOD2+/-), in which SOD2 activity is reduced by 30% to 80%, and wild-type control mice (SOD2+/+) were treadmill-tested to measure indices defining exercise capacity. Tempol was given to each mouse for 7 days by an intraperitoneal injection to scavenge O2- before a second treadmill testing. VO2 and carbon dioxide production (VCO2) at rest were increased in SOD2+/-. The work (vertical distance run x body weight) to exhaustion was decreased in SOD2+/-. When the maximum VO2 and VCO2 were corrected to per work unit, they were increased in SOD2+/-. Tempol normalized basal VO2 and VCO2 and improved the work to exhaustion and corrected VO2 and VCO2 in SOD2+/-. VO2 of skeletal muscle was measured in vitro. Bradykinin-induced reduction in VO2 in vitro was attenuated in SOD2+/-, and was acutely restored by Tempol. There was a decrease in SOD2 protein level and a concomitant increase in lucigenin-detectable O2- production in skeletal muscle from SOD2+/-. CONCLUSIONS: These results suggest that exercise capacity is reduced in conditions in which superoxide anion is increased, and this is associated with a greater increase in whole-body oxygen consumption in SOD2+/- compared with SOD2+/+.

Animals↗

PubMed2005

Increased superoxide leads to decreased flow-induced dilation in resistance arteries of Mn-SOD-deficient mice.

The role of mitochondrial manganese-superoxide dismutase (Mn-SOD) in the maintenance of vascular function has not yet been studied. Thus we examined flow- and agonist-induced dilations in isolated mesenteric arteries (approximately 90 microm in diameter) of Mn-SOD heterozygous (Mn-SOD+/-) and wild-type (WT) mice. Increases in flow elicited dilations in all vessels, but the magnitude of the dilation was significantly less in vessels of Mn-SOD+/- mice than in those of WT mice (64 vs. 74% of passive diameter). N(omega)-nitro-L-arginine methyl ester inhibited the dilation in vessels of WT mice but had no effect on vessels of Mn-SOD+/- mice. Tempol or tiron (superoxide scavengers) increased flow-induced dilation in vessels of Mn-SOD+/- mice. Acetylcholine- and sodium nitroprusside-induced, but not adenosine-induced, dilations were also decreased in arteries of Mn-SOD+/- mice. Superoxide levels in the arteries of Mn-SOD+/- mice were significantly increased. Western blot analysis confirmed a 50% reduction of Mn-SOD protein in the vessels of Mn-SOD+/- mice. A 41% reduction in endothelial nitric oxide synthase (eNOS) protein and a 37% reduction in eNOS activity were also found in the vessels of Mn-SOD+/- mice. Whereas there was no difference in eNOS protein in kidney homogenates of WT and Mn-SOD+/- mice, a significant reduction of nitric oxide synthase activity was found in Mn-SOD+/- mice, which could be restored by the administration of tiron. We conclude that an increased concentration of superoxide due to reduced activity of Mn-SOD, which inactivates nitric oxide and inhibits eNOS activity, contributes to the impaired vasodilator function of isolated mesenteric arteries of Mn-SOD+/- mice. These results suggest that Mn-SOD contributes significantly to the regulation of vascular function.

Animals↗

PubMed2005

Epoxyeicosatrienoic acids are released to mediate shear stress-dependent hyperpolarization of arteriolar smooth muscle.

We hypothesized that shear stress stimulates the release of epoxyeicosatrienoic acids (EETs) from arteriolar endothelium, which directly hyperpolarize smooth muscle. To test this hypothesis, a perfusion system, consisting of two separate, serially connected chambers (A and B), was used. A donor vessel, isolated from gracilis muscle of female NO-deficient mice and rats, was cannulated in chamber A. In chamber B, an endothelium-denuded detector vessel isolated from mesentery of these animals was cannulated. In the presence of indomethacin, 5, 10, and 20 dyne/cm2 shear stress elicited dilation of donor vessels, followed by dilation of detector vessels. Changes in membrane potential of the detector vessel smooth muscle cells in response to the perfusate from 5 and 10 dyne/cm2 shear stress-stimulated donor vessels was also recorded (by approximately -12 to -15 and -20 to -30 mV, respectively). Exposing detector vessels to 30 mmol/L KCl or pretreating them with iberiotoxin abolished their hyperpolarization and dilation to the flow of perfusate. Pretreatment of donor vessels with PPOH, an inhibitor of cytochrome P-450/epoxygenase, eliminated dilator responses in both donor and detector vessels, as well as the hyperpolarization of detector vessels. GC-MS analysis showed increasing release of EETs into the perfusate collected from 1, 5, and 10 dyne/cm2 shear stress-stimulated arterioles, which was abolished by PPOH. Thus, EETs, released from endothelial cells of donor vessels stimulated with shear stress, hyperpolarize smooth muscle of downstream detector vessels, confirming their identity as endothelium-derived hyperpolarizing factors and suggesting that gap junctional communication may not be necessary for shear stress-stimulated EDHF-mediated vasodilation.

8,11,14-Eicosatrienoic Acid↗

PubMed2005

Role of oxidative and nitrosative stress, longevity genes and poly(ADP-ribose) polymerase in cardiovascular dysfunction associated with aging.

Epidemiological studies demonstrated that even in the absence of other risk factors (e.g. diabetes, hypertension, hypercholesterolemia), advanced age itself significantly increases cardiovascular morbidity. Although aging is inevitable, cardiovascular gerontologists recognize that a better understanding of the aging process in the not-so-distant future will lead to pharmacological interventions that considerably delay the functional decline of the cardiovascular system. Since the original publishing of the free radical theory of aging, an increased production of reactive oxygen species has been implicated both in the aging process and the development of age-related cardiovascular diseases. This review focuses on the role of oxidative and nitrosative stress in cardiovascular dysfunction in aging, downstream mechanisms including activation of NF- kappaB, and the role of poly(ADP-ribose)polymerase (PARP) and longevity genes that are linked to regulation of cellular redox status and oxidative stress resistance (p66(shc), sirtuins, FOXO transcription factors).

Aging↗

PubMed2004

Mechanical compression elicits NO-dependent increases in coronary flow.

Our previous studies have demonstrated that a decrease in arteriolar diameter that causes endothelial deformation elicits the release of nitric oxide (NO). Thus we hypothesized that cardiac contraction, via deformation of coronary vessels, elicits the release of NO and increases in coronary flow. Coronary flow was measured at a constant perfusion pressure of 80 mmHg in Langendorff preparations of rat hearts. Hearts were placed in a sealed chamber surrounded with perfusion solution. The chamber pressure could be increased from 0 to 80 mmHg to generate extracardiac compression. To minimize the impact of metabolic vasodilatation and rhythmic changes in shear stress, nonbeating hearts, by perfusing the hearts with a solution containing 20 mM KCl, were used. After extracardiac compression for 10 or 20 s, coronary flow increased significantly, concurrent with an increased release of nitrite into the coronary effluent and increased phosphorylation of endothelial NO synthase in the hearts. Inhibition of NO synthesis eliminated the compression-induced increases in coronary flow. Shear stress-induced dilation could not account for this increased coronary flow. Furthermore, in isolated coronary arterioles, without intraluminal flow, the release of vascular compression elicited a NO-dependent dilation. Thus this study reveals a new mechanism that, via coronary vascular deformation, elicited by cardiac contraction, stimulates the endothelium to release NO, leading to increased coronary perfusion.

Animals↗

PubMed2004

Response of tyrosine hydroxylase and GTP cyclohydrolase I gene expression to estrogen in brain catecholaminergic regions varies with mode of administration.

The effect of different dose, mode and duration of estradiol administration was examined in the different brain catecholaminergic areas in ovariectomized (OVX) female rats. We determined changes in mRNA levels of tyrosine hydroxylase (TH), rate-limiting enzyme in catecholamine (CA) biosynthesis of GTP cyclohydrolase I (GTPCH), rate-limiting enzyme in biosynthesis as well as of tetrahydrobiopterin (BH4), and concentration of BH4, which is an essential cofactor for TH, tryptophan hydroxylase and nitric oxide synthase. Short-term administration of estradiol benzoate (EB) by five injections of 15 or 40 microg/kg 12 h apart led to increase in TH and GTPCH mRNA levels in dopaminergic and noradrenergic cell bodies of the ventral tegmental area (VTA), substantia nigra (SN), locus coeruleus (LC) and the nucleus of solitary tract (NTS) depending on dose of administration. Estrogen-elicited alterations in BH4 concentrations were mostly correlated with changes in GTPCH mRNA levels, except in SN. Long-term administration of estradiol by injections (EB: 25 microg/kg, 16 injections 26 h apart; 50 microg/kg, 16 injections 48 h apart) or pellets (0.1 mg 17 beta-estradiol, 14 days) were not very effective in modulating mRNA levels for both genes in most locations except the NTS. Long-term injections of EB elevated GTPCH mRNA levels throughout the NTS and in microvessels. Administration of estradiol by pellets led to decline of TH mRNA in rostral-medial and elevation in caudal parts of the NTS. Thus, estradiol has a complex and differential effect on TH and GTPCH gene expression in a tissue specific manner and depends on the mode of administration.

Analysis of Variance↗

PubMed2004

Microvascular dysfunction after transient high glucose is caused by superoxide-dependent reduction in the bioavailability of NO and BH(4).

We hypothesized that transient high-glucose concentration interferes with mediation by nitric oxide (NO) of flow-induced dilation (FID) of arterioles due to enhanced production of superoxide. In isolated, pressurized (80 mmHg) rat gracilis muscle arterioles ( approximately 130 microm) after transient high-glucose treatment (tHG; incubation with 30 mM glucose for 1 h), FID was reduced (maximum: control, 38 +/- 4%; after tHG, 17 +/- 3%), which was not further diminished by the NO synthase (NOS) inhibitor N(omega)-nitro-l-arginine methyl ester (l-NAME; 18 +/- 2%). Correspondingly, an enhanced polyethylene-glycol-SOD (PEG-SOD)-sensitive superoxide production was detected after tHG in carotid arteries by dihydroethydine (DHE) staining. Presence of PEG-SOD during tHG prevented the reduction of FID (41 +/- 3%), which could be inhibited by l-NAME (20 +/- 4%). Administration of PEG-SOD after tHG did not prevent the reduction of FID (22 +/- 3%). Sepiapterin, a precursor of the NO synthase cofactor tetrahydrobiopterin (BH(4)), administered during tHG did not prevent the reduction of FID (maximum, 15 +/- 5%); however, it restored FID when administered after tHG (32 +/- 4%). Furthermore, inhibition of either glycolysis by 2-deoxyglucose or mitochondrial complex II by 2-thenoyltrifluoroacetone reduced the tHG-induced DHE-detectable enhanced superoxide production in carotid arteries and prevented FID reduction in arterioles (39 +/- 5 and 35 +/- 2%). Collectively, these findings suggest that in skeletal muscle arterioles, a transient elevation of glucose via its increased metabolism, elicits enhanced production of superoxide, which decreases the bioavailability of NO and the level of the NOS cofactor BH(4), resulting in a reduction of FID mediated by NO.

Animals↗

PubMed2004

Proinflammatory phenotype of coronary arteries promotes endothelial apoptosis in aging.

Previously we demonstrated that aging in coronary arteries is associated with proinflammatory phenotypic changes and decreased NO bioavailability, which, we hypothesized, promotes vascular disease by enhancing endothelial apoptosis. To test this hypothesis we characterized proapoptotic alterations in the phenotype of coronary arteries of aged (26 mo old) and young (3 mo old) F344 rats. DNA fragmentation analysis and TUNEL assay showed that in aged vessels there was an approximately fivefold increase in the number of apoptotic endothelial cells. In aged coronary arteries there was an increased expression of TNFalpha, TNFbeta, and caspase 9 (microarray, real-time PCR), as well as increased caspase 9 and caspase 3 activity, whereas expression of TNFR1, TNFalpha-converting enzyme (TACE), Bcl-2, Bcl-X(L), Bid, Bax, caspase 8, and caspase 3 were unchanged. In vessel culture (18 h) incubation of aged coronary arteries with a TNF blocking antibody or the NO donor S-nitroso-penicillamine (SNAP) decreased apoptotic cell death. Incubation of young arteries with exogenous TNFalpha increased caspase 9 activity and elicited endothelial apoptosis, which was attenuated by SNAP. Inhibition of NO synthesis in cultured young coronary arteries also induced apoptotic cell death and potentiated the apoptotic effect of TNFalpha. Thus we propose that age-related upregulation of TNFalpha and caspase 9 and decreased bioavailability of NO promote endothelial apoptosis in coronary arteries that may lead to impaired endothelial function and ischemic heart disease in the elderly.

ADAM Proteins↗

PubMed2004

Reduced release of nitric oxide to shear stress in mesenteric arteries of aged rats.

We hypothesized that aging is characterized by a reduced release of nitric oxide (NO) in response to shear stress in resistance vessels. Mesenteric arterioles and arteries of young (6 mo) and aged (24 mo) male Fischer 344 rats were isolated and cannulated. Shear stress (15 dyn/cm(2))-induced dilation was significantly reduced and shear stress (1, 5, 10, and 15 dyn/cm(2))-induced increases in perfusate nitrite were significantly smaller at all shear stress levels in vessels of aged rats. Inhibition of NO synthesis abolished shear stress-induced release of nitrite. Furthermore, shear stress (15 dyn/cm(2))-induced release of nitrate was significantly higher and total nitrite (nitrite plus nitrate) was significantly lower in vessels of aged rats. Tiron or SOD significantly increased nitrite released from vessels of aged rats, but this was still significantly less than that in young rats. Superoxide production was increased and the activity of SOD was decreased in vessels of aged rats. There were no differences in endothelial NO synthase (eNOS) protein and basal activity or in Cu/Zn-SOD and Mn-SOD proteins in vessels of the two groups, but extracellular SOD was significantly reduced in vessels of aged rats. Maximal release of NO induced by shear stress plus ACh (10(-5) M) was comparable in the two groups, but phospho-eNOS in response to shear stress (15 dyn/cm(2)) was significantly reduced in vessels of aged rats. These data suggest that an increased production of superoxide, a reduced activity of SOD, and an impaired shear stress-induced activation of eNOS are the causes of the decreased shear stress-induced release of NO in vessels of aged rats.

Aging↗

PubMed2004

Vascular inflammation in aging.

Although epidemiologic studies have revealed that high plasma cholesterol or high homocysteine levels, as well as diabetes, hypertension and smoking are important risk factors for atherosclerotic vascular disease, the deleterious effects of these conditions can be delayed or significantly attenuated by therapeutic interventions. Since the population in the Western world is aging, advancing age itself became one of the most significant risk factors for the development of atherosclerosis. Atherosclerosis is a chronic inflammatory disease, however, the mechanisms by which advanced age per se promotes vascular inflammation are not well understood. In the present review the authors propose a model for age-related alterations in cytokine expression, increased oxidative stress and decreased bioavailability of NO that underlie a pro-inflammatory phenotype of aged vessels promoting the development of atherosclerosis in the elderly.

Aging↗