3,4,5,6-Tetrahydroxyxanthone prevents vascular endothelial cell apoptosis induced by high glucose

Apoptosis of endothelial cells may be an important risk factor contributing to the incidence of vascular complications in diabetes. In the present study, we tested the effect of 3,4,5,6-tetrahydroxyxanthone, a synthetic xanthone derivative, on apoptosis induced in human umbilical vein endothelial cells (HUVEC) by a high glucose concentration. Cell apoptosis was detected using DNA ladder formation and flow cytometric techniques. The expression of Bcl-2 protein was analysed using flow cytometric techniques. Lactate dehydrogenase (LDH) activity and malonyldialdehyde (MDA) content in the medium were measured. Cell viability was assayed by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) method. Exposure of HUVEC to a high glucose concentration (30 mM) for 48 h markedly increased LDH release and MDA content in the medium and induced apoptosis and Bcl-2 protein expression in HUVEC. Pretreatment with 3,4,5,6-tetrahydroxyxanthone (1, 3 or 10 M) or probucol (10 M) significantly decreased the level of LDH and MDA in the medium, reduced apoptosis and increased the expression of Bcl-2 protein in HUVEC. These results suggest that 3,4,5,6-tetrahydroxyxanthone inhibits high-glucose-induced endothelial cell apoptosis by increasing Bcl-2 protein expression in HUVEC.     

Protective effects of cariporide on endothelial dysfunction induced by high glucose

Aim: To explore the effects of cariporide, a selective sodium-hydrogen antiporter inhibitor, on endothelial dysfunction induced by high glucose. Methods: Acetylcholine (ACh)-induced endothelium-dependent relaxation (EDR), sodium nitroprusside (SNP)-induced endothelium-independent relaxation and biochemical parameters including malondialdehyde (MDA), superoxide dismutase (SOD), and nitric oxide (NO) were measured in rat isolated aorta. Results: A 6-h incubation of aortic rings with high glucose (44 mmol/L) resulted in a significant inhibition of EDR, but had no effects on endothelium-independent relaxation. After the 6-h incubation of aortic rings in the co-presence of cariporide (0.01, 0.1, and 1μmol/L) with high glucose, cariporide prevented the inhibition of EDR caused by high glucose in concentration-dependent manners. Similarly, high glucose decreased SOD activity and contents of NO, and increased MDA concentration in aortic tissue. Cariporide (1 μmol/L) significantly resisted the decrease of NO content and SOD activity, and elevation of MDA concentration caused by high glucose in aortic tissues. Mannitol (44 mmol/L) or cariporide (1μmol/L) alone had no effect on EDR, endothelium-independent relaxation and biochemical parameters. Conclusion: Cariporide significantly prevented endothelial dysfunction induced by high glucose. The mechanisms of endothelial dysfunction induced by high glucose may involve the activation of sodium-hydrogen antiporter and the generation of oxygen-free radicals, but it is not related to the change of osmolarity.     

Na+/H+ exchanger inhibitor prevented endothelial dysfunction induced by high glucose

The aims of this study were to examine whether cariporide, a selective Na+/H+ exchanger inhibitor, has protective effects against endothelial dysfunction induced by high glucose in vitro and to investigate the potential mechanisms. Exposure of rat aorta rings to high glucose (44 mmol/L) for 6 hours caused an inhibition of acetylcholine-induced endothelium-dependent relaxation but had no effect on sodium nitroprusside-induced endothelium-independent relaxation. Treatment with cariporide (0.01, 0.1, 1 micromol/L) of aortic rings incubated with high-glucose medium attenuated the impaired endothelium-dependent relaxation in a dose-dependent manner. Furthermore, high glucose resulted in an increase of malondialdehyde and a decrease of superoxide dismutase activity in rat aorta rings, and these effects were reversed by cariporide. In addition, cariporide was able to inhibit the activation of Na+/H+ exchanger induced by high glucose in cultured endothelial cells. These findings suggest that the endothelial dysfunction induced by high glucose in vitro is caused by the activation of Na+/H+ exchanger.     

Interleukin-2 protects against endothelial dysfunction induced by high glucose levels in rats

AIMS: Interleukin-2 (IL-2) can modulate cardiovascular functions, but the effect of IL-2 on vascular endothelial function in diabetes is not known. We hypothesized that IL-2 may attenuate endothelial dysfunction induced by high glucose or diabetes. So the aim of this study was to investigate the effect of IL-2 on endothelium-response of aortas incubated with high glucose or from diabetic rats and its underlying mechanism. METHODS: Acetylcholine (ACh)-induced endothelium-dependent relaxation (EDR), sodium nitroprusside (SNP)-induced endothelium-independent relaxation (EIR), superoxide dismutase (SOD) and nitric oxide synthase (NOS) were measured in aortas isolated from non-diabetic rats and exposed to a high glucose concentration and from streptozotocin-induced diabetic rats. RESULTS: Incubation of aortic rings with high glucose (44 mM) for 4 h resulted in a significant inhibition of EDR, but had no effects on EIR. Co-incubation with IL-2 for 40 min prevented the inhibition of EDR caused by high glucose in a concentration-dependent manner. Similarly, high glucose decreased SOD and NOS activity in aortic tissue. IL-2 (1000 U/ml) significantly attenuated the decrease of SOD and NOS activity caused by high glucose. In addition, EDR declined along with the decrease of serum NO level in aortas from STZ-induced diabetic rats. Injection of IL-2 (5000 and 50,000 U kg(-1) d(-1), s.c.) for 5 weeks prevented the inhibition of EDR and the decrease of serum NO levels caused by diabetes. CONCLUSIONS: IL-2 significantly ameliorated the endothelial dysfunction induced by hyperglycemia, in which the activation of the NO pathway and SOD may be involved.     

Methylglyoxal scavengers attenuate endothelial dysfunction induced by methylglyoxal and high concentrations of glucose

BACKGROUND AND PURPOSE

Endothelial dysfunction is a feature of hypertension and diabetes. Methylglyoxal (MG) is a reactive dicarbonyl metabolite of glucose and its levels are elevated in spontaneously hypertensive rats and in diabetic patients. We investigated if MG induces endothelial dysfunction and whether MG scavengers can prevent endothelial dysfunction induced by MG and high glucose concentrations.

EXPERIMENTAL APPROACH

Endothelium-dependent relaxation was studied in aortic rings from Sprague-Dawley rats. We also used cultured rat aortic and human umbilical vein endothelial cells. The MG was measured by HPLC and Western blotting and assay kits were used.

KEY RESULTS

Incubation of aortic rings with MG (30 µM) or high glucose (25 mM) attenuated endothelium-dependent, acetylcholine-induced relaxation, which was restored by two different MG scavengers, aminoguanidine (100 µM) and N-acetyl cysteine (NAC) (600 µM). Treatment of cultured endothelial cells with MG or high glucose increased cellular MG levels, effects prevented by aminoguanidine and NAC. In cultured endothelial cells, MG and high glucose reduced basal and bradykinin-stimulated nitric oxide (NO) production, cGMP levels, and serine-1177 phosphorylation and activity of endothelial NO synthase (eNOS), without affecting threonine-495 and Akt phosphorylation or total eNOS protein. These effects of MG and high glucose were attenuated by aminoguanidine or NAC.

CONCLUSIONS AND IMPLICATIONS

Our results show for the first time that MG reduced serine-1177 phosphorylation, activity of eNOS and NO production. MG caused endothelial dysfunction similar to that induced by high glucose. Specific and safe MG scavengers have potential to prevent endothelial dysfunction induced by MG and high glucose concentrations.     

Tripterine prevents endothelial barrier dysfunction by inhibiting endogenous peroxynitrite formation

Background and purpose:

Tripterine is an inhibitor of heat shock protein 90 and an active component of Tripterygium wilfordii Hook F., which is used in traditional Chinese medicine to treat inflammatory diseases such as rheumatoid arthritis. We hypothesized that tripterine inhibits endogenous peroxynitrite formation and thereby prevents endothelial barrier dysfunction.

Experimental approach:

Effects of tripterine were investigated on endothelial barrier function, inducible nitric oxide synthase (iNOS) expression, nicotinamide adenine dinucleotide phasphate (NADPH) oxidase activity, 3-nitrotyrosine formation, protein phosphatase type 2A (PP2A) activity, activation of extracellular-regulated kinase (ERK), c-Jun terminal kinase (JNK) and Janus kinase (Jak2), and degradation of IκB in microvascular endothelial cells exposed to pro-inflammatory stimulus [lipopolysaccharide (LPS) + interferon γ (IFNγ)] and on vascular permeability in air pouches of mice injected with LPS + IFNγ.

Key results:

LPS + IFNγ caused an increase in monolayer permeability, induction of iNOS and NADPH oxidase type 1 (Nox1) proteins, formation of superoxide, nitric oxide and 3-nitrotyrosine, and increase in PP2A activity in endothelial cells. These effects of LPS + IFNγ were diminished by tripterine (50–200 nM). Further, LPS + IFNγ-induced expression of iNOS and Nox1 was attenuated by the mitogen-activated protein kinase kinase 1/2 (MEK1/2) inhibitor PD98059, the JNK inhibitor SP600125, the Jak2 inhibitor AG490 and the NFκB inhibitor MG132, but not by the p38 mitogen-activated protein kinase inhibitor SB203580. LPS + IFNγ stimulated phosphorylation of ERK, JNK and Jak2, and degradation of IκB, but only Jak2 phosphorylation was sensitive to tripterine (50–200 nM). Further, tripterine diminished the increased vascular permeability in inflamed air pouches.

Conclusion and implications:

Our results indicate that, by preventing Jak2-dependent induction of iNOS and Nox1, tripterine inhibits peroxynitrite precursor synthesis, attenuates the increased activity of PP2A and consequently protects endothelial barrier function.     

Pharmacological neutropenia prevents endothelial dysfunction but not smooth muscle functions impairment induced by middle cerebral artery occlusion

1. The polymorphonuclear neutrophils (PMN) activation and mobilization observed in acute cerebral infarction contribute to the brain tissue damage, but PMN could also be involved in postischemic functional injury of ischemied blood vessel. 2. This study was undertaken to investigate whether pharmacological neutropenia could modify the postischemic endothelial dysfunction in comparison to smooth muscle whose impairment is likely more related to reperfusion and oxidative stress. 3. A cerebral ischemia-reperfusion by endoluminal occlusion of right middle cerebral artery (MCA) was performed 4 days after intravenous administration of vinblastine or 12 h after RP-3 anti-rat neutrophils monoclonal antibody (mAb RP-3) injection into the peritoneal cavity, on male Wistar rats with 1-h ischemia then followed by 24-h reperfusion period. Brain infarct volume was measured by histomorphometric analysis and vascular endothelial and smooth muscle reactivity of MCA was analysed using Halpern myograph. 4. Neutropenia induced a neuroprotective effect as demonstrated by a significant decrease of brain infarct size. In parallel to neuroprotection, neutropenia prevented postischemic impairment of endothelium-dependent relaxing response to acetylcholine. In contrast, smooth muscle functional alterations were not prevented by neutropenia. Ischemia-reperfusion-induced myogenic tone impairment remained unchanged in vinblastine and mAb RP-3-treated rats. Postischemic Kir2.x-dependent relaxation impairment was not prevented in neutropenic conditions. The fully relaxation of smooth muscle response to sodium nitroprusside was similar in all groups. 5. Our results evidenced the dissociate prevention of pharmacologically induced neutropenia on postischemic vascular endothelial and smooth muscle impairment. The selective endothelial protection by neutropenia is parallel to a neuroprotective effect suggesting a possible relationship between the two phenomena.     

木犀草素减轻氧化应激引起的血管内皮损伤

目的：探讨木犀草素对叔丁基过氧化氢致血管内皮损伤的保护作用及相关机制。方法：首先通过制备大鼠胸主动脉环,观察木犀草素对叔丁基过氧化氢所致血管张力变化的影响;再采用叔丁基过氧化氢诱导血管内皮细胞氧化损伤模型,观察木犀草素对其细胞形态学变化及细胞活力的影响,并用RT-PCR检测eNOS和COX-1 mRNA的含量变化。结果：木犀草素能够浓度依赖性地对抗叔丁基过氧化氢导致的血管舒张功能损伤及细胞损伤作用,且浓度依赖性地减弱叔丁基过氧化氢对内皮细胞eNOS mRNA表达抑制的影响。结论：木犀草素是一种有效的舒血管物质,它可以起到抗氧化的作用,减轻氧化应激反应,并可能通过维持eNOS活性等血管内皮途径舒张血管。     

Simvastatin prevents inflammation-induced aortic stiffening and endothelial dysfunction

AIMS

The aim of this study was to determine whether simvastatin would protect against inflammation-induced aortic stiffening and endothelial dysfunction.

METHODS

Aortic pulse wave velocity (aPWV) and flow-mediated dilatation (FMD) were assessed three times, at baseline, after a 14 day administration of simvastatin or placebo and 8 h after Salmonella typhi vaccination in 50 healthy subjects.

RESULTS

Following vaccination there was a significant increase in aPWV in the placebo group (5.80 ± 0.87 vs. 6.21 ± 0.97 m s⁻¹, 95% CI 0.19, 0.62, P = 0.002) but not the simvastatin group (5.68 ± 0.73 vs. 5.72 ± 0.74 m s⁻¹, 95% CI −0.19, 0.27, P = 0.9; P = 0.016 for comparison). Whereas FMD response was reduced in the placebo group (6.77 ± 4.10 vs. 5.27 ± 2.88%, 95% CI −2.49, −0.52, P = 0.02) but not in the simvastatin group (7.07 ± 4.37 vs. 7.17 ± 9.94%, 95% CI −1.1, 1.3. P = 0.9, P < 0.001 for comparison). There was no difference in the systemic inflammatory response between groups following vaccination. However, there was a significant reduction in serum apolipoprotein A-I (Apo A-I) in the placebo, but not in the simvastatin, group.

CONCLUSIONS

Simvastatin prevents vaccination-induced aortic stiffening and endothelial dysfunction. This protective mechanism may be due to preservation of the Apo A-I lipid fraction, rather than pleiotropic anti-inflammatory effects of statins.     

Chronic heart rate reduction by ivabradine prevents endothelial dysfunction in dyslipidaemic mice

BACKGROUND AND PURPOSE: High resting heart rate is a predictor for total and cardiovascular mortality independent of other risk factors in patients with coronary artery disease. We tested the hypothesis that a reduction of resting heart rate with the cardiac pacemaker I(f) current inhibitor ivabradine prevents the endothelial dysfunction associated with dyslipidaemia. EXPERIMENTAL APPROACH: Three-month-old dyslipidaemic (DL) male mice expressing the human ApoB-100 were assigned or not (DL, n=16), to treatment for 3 months with ivabradine (10 mg kg(-1) d(-1), n=17). Wild-type C57Bl/6 mice (WT, n=15) were used as controls. Heart rate was measured at 3, 4.5 and 6 months. Dilatation to acetylcholine (ACh) of isolated cerebral and renal arteries was investigated at 6 months. KEY RESULTS: Heart rate remained stable in anaesthetized WT mice, increased (25%, P<0.05) with age in DL mice but was limited (11%, P<0.05) by ivabradine. At 6 months, left ventricular maximal pressure was similar in all groups. The minimal and end-diastolic left ventricular pressures were increased (P<0.05) in DL (10.2+/-1.0 and 18.7+/-1.4 mm Hg) compared to WT (-0.4+/-0.7 and 6.3+/-1.0 mm Hg) and reduced (P<0.05) by ivabradine (4.2+/-1.3 and 11.5+/-1.5 mm Hg). ACh-induced maximal dilatation was impaired (P<0.05) in renal and cerebral arteries isolated from DL compared to WT (56+/-7 versus 83+/-3% in renal arteries; 22+/-2 versus 42+/-2% in cerebral arteries). Ivabradine completely prevented (P<0.05) this dysfunction in renal and cerebral arteries. CONCLUSIONS AND IMPLICATIONS: Selective heart rate reduction with ivabradine limits cardiac dysfunction and prevents the renovascular and cerebrovascular endothelial dysfunction associated with dyslipidaemia.     

Raloxifene prevents endothelial dysfunction in aging ovariectomized female rats

Lack of an appropriate animal model has delayed the better understanding of mechanisms related to higher cardiovascular risk in women after menopause. The aging female rat may share some menopausal changes observed in women. However, most studies have attempted to mimic menopause by ovariectomizing young (6-12 weeks old) animals without taking into accounts the influence of aging and of declining ovarian function. Therefore, the present study examined changes in vascular reactivity in the aging (15 months old) female rat after ovariectomy and the effects of chronic raloxifene therapy on vascular reactivity and eNOS protein expression. Aortic rings were prepared from the three experimental groups of rats: sham-operated control, ovariectomized and ovariectomized aging rats receiving daily oral administration of raloxifene for 3 months. Aortic rings were suspended in organ baths for the measurement of isometric tension. Rings with endothelium contracted significantly more to phenylephrine after inhibition of nitric oxide/cyclic GMP-signaling pathway by L-NAME or ODQ (as an index of basal nitric oxide release) in control and raloxifene-treated ovariectomized rats than in ovariectomized rats. This effect was abolished upon mechanical removal of the endothelium. Phenylephrine induced greater contractions only in rings with endothelium from ovariectomized rats as compared with control rats and raloxifene treatment normalized this response. In the presence of L-NAME or ODQ, phenylephrine-induced contraction was similar in rings from the three groups. Rings relaxed more to thapsigargin and acetylcholine in raloxifene-treated ovariectomized rats than in ovariectomized rats. There was no significant difference in aortic eNOS protein contents among the different groups. These results suggest that chronic oral administration of raloxifene to aging ovariectomized female rats augmented the bioavailability of endothelial nitric oxide in isolated aortic rings without altering eNOS protein levels.     

eNOS参与铁过载诱导的血管内皮细胞线粒体损伤

目的探讨e NOS及ADMA/DDAHⅡ介导的铁过载对HUVECs细胞线粒体的损伤作用。方法常规培养HUVECs细胞,随机分为正常对照(Ctrl)组、右旋糖酐铁(Iron)组、L-精氨酸(L-Arg)组。48 h后,MTT法检测细胞存活率;HPLC法检测ADMA含量及DDAHⅡ活性;Western blot法检测e NOS表达;比色法检测培养液LDH活性、NO含量、细胞MDA含量以及m PTP开放;流式细胞仪检测心肌细胞ROS含量、线粒体膜电位及细胞凋亡。结果 Iron处理48 h后,HUVECs细胞存活率明显降低,培养液ADMA及LDH活性升高,NO含量减少;细胞e NOS表达下调、DDAHⅡ活性降低;MDA含量与ROS生成明显增加,线粒体膜电位减小,m PTP大量开放,细胞凋亡增加;ADMA生理性对抗剂L-Arg则可明显减弱Iron的上述损伤作用。结论 e NOS参与铁过载诱导的HUVECs细胞线粒体损伤,ADMA/DDAHⅡ机制也可能发挥了作用。     

Eplerenone prevents adverse cardiac remodelling induced by pressure overload in atrial natriuretic peptide-null mice

1. Atrial natriuretic peptide (ANP)-null mice (Nppa(-/-)) exhibit cardiac hypertrophy at baseline and adverse cardiac remodelling in response to transverse aortic constriction (TAC)-induced pressure overload stress. Previous studies have suggested that natriuretic peptides could potentially oppose mineralocorticoid signalling at several levels, including suppression of adrenal aldosterone production, inhibition of mineralocorticoid receptor (MR) activation or suppression of MR-mediated production of pro-inflammatory factors. Thus, we hypothesized that the MR blocker eplerenone would prevent the exaggerated left ventricular (LV) remodelling/fibrosis and dysfunction after TAC in Nppa(-/-). 2. In the present study, Nppa(-/-) and wild-type Nppa(+/+) mice fed eplerenone- or vehicle (oatmeal)-supplemented chow since weaning were subjected to TAC or sham operation. The daily dose of eplerenone administered was approximately 200 mg/kg. At 1 week after TAC, LV size and function were evaluated by echocardiogram and LV cross-sections were stained with picrosirius red for collagen volume measurement. Total RNA was extracted from the LV for real-time polymerase chain reaction analysis of osteopontin. 3. Eplerenone had no effect on baseline hypertrophy observed in sham-operated Nppa(-/-) compared with Nppa(+/+) mice. Eplerenone attenuated the TAC-induced increase in LV weight in both genotypes and completely prevented LV dilation, systolic dysfunction and interstitial collagen deposition seen in Nppa(-/-) mice after TAC. However, serum aldosterone levels were lower in Nppa(-/-) compared with Nppa(+/+) wild types. No interaction between eplerenone and genotype in osteopontin mRNA levels was observed. 4. Eplerenone prevents adverse cardiac remodelling related to pressure overload in ANP-deficient mice, mainly due to an antifibrotic effect. The mechanism whereby ANP deficiency leads to excess hypertrophy, fibrosis and early failure following TAC is increased profibrotic signals resulting from excess or unopposed MR activation, rather than increased levels of aldosterone.     

Nifedipine prevents apoptosis of endothelial cells induced by oxidized low-density lipoproteins

Calcium channel blockade has been shown to inhibit experimental atherosclerosis, and early clinical trials suggest that it also reduces atherosclerosis in humans. However, the mechanisms underlying the direct protective effect of calcium channel blockade on endothelial cell injury are not fully understood. The apoptosis of endothelial cells induced by oxidized low-density lipoproteins (oxLDL) may provide a mechanistic clue to the "response-to-injury" hypothesis of atherogenesis. Here we report that the calcium channel blocker, nifedipine, prevents the apoptosis of human umbilical venous endothelial cells (HUVECs) induced by oxLDL via downregulation of the endothelial receptor for oxidized LDL (LOX-1) and inhibition of CPP32-like protease activity. The incubation of HUVEC with oxLDL increased LOX-1 mRNA levels and CPP32-like protease activity, and induced apoptosis. Preincubation of HUVEC with nifedipine before incubation with oxLDL significantly suppressed the increase in LOX-1 mRNA levels and CPP32-like protease activity, preventing apoptosis in a dose-dependent manner. These results suggest that nifedipine blocks the suicide pathway leading to the apoptosis of endothelial cells by decreasing LOX-1 mRNA levels and CPP32-like protease activity. Thus, nifedipine seems to play a protective role against the "response-to-injury" hypothesis of atherogenesis.     

Tetrahydrobiopterin prevents endothelial dysfunction and restores adiponectin levels in rats

Oxidative stress induces endothelial dysfunction and hypoadiponectinemia. We previously reported that supplementation with tetrahydrobiopterin (BH4), one of the most potent naturally occurring reducing agents and an essential cofactor of enzymatic NO synthase (NOS), ameliorates endothelial dysfunction and reverses hypoadiponectinemia as a result of oxidative stress in rats. To further confirm this hypothesis, we investigated the effects of treatment with BH4 on endothelium-dependent relaxation and adiponectin levels during oxidative stress in fructose-fed rats, which provide an animal model for the metabolic syndrome. Ingestion of a fructose diet for 8 weeks significantly impaired endothelium-dependent arterial relaxation in aortic strips and decreased plasma adiponectin levels, as well as adiponectin mRNA levels within adipose tissue. However, oral supplementation with BH4 (10 mg/kg day) over the final 4 weeks leads to a significant partial reversal of impaired endothelium-dependent arterial relaxation, as well as normalization of plasma adiponectin and fat adiponectin mRNA levels. Moreover, BH4 treatment of the fructose-fed rats significantly reduced the lipid peroxidation content of aorta, heart, liver, and kidney tissues, which were increased in fructose-fed rats. This effect of BH4 treatment may be due to its function as a cofactor for eNOS, as well as its anti-oxidative effects. Thus, BH4 might show promise for the treatment of oxidative stress-induced disorders, including the metabolic syndrome.     

Heat stress increases endothelium-dependent relaxations and prevents reperfusion-induced endothelial dysfunction

1. Heat stress has been widely used to stimulate the expression of stress proteins and is associated with various cardiovascular changes, including anti-ischaemic effects. However, the effect of heat stress on endothelial function is less clear. 2. Heat stress was induced in anaesthetized rats by increasing body temperature to 42 degrees C for 15 min. Twenty-four hours later, segments of rat aorta and mesenteric and coronary arteries were mounted in organ chambers. 3. Heat stress markedly increased relaxation to acetylcholine (ACh) in all three blood vessels studied, without affecting the response to the nitric oxide (NO) donor sydnonimine-1. 4. Heat stress also increased aortic relaxation to histamine and the calcium ionophore A23187. 5. In the aorta, an inhibitor of NO synthesis abolished the response to ACh in both control and heat stressed-rings, whereas a cyclo-oxygenase inhibitor had no effect. 6. Heat stress also prevented completely the impaired response to ACh in coronary arteries isolated from rats subjected to myocardial ischaemia and reperfusion. 7. Thus, heat stress increases the stimulated release of NO the rat aorta and mesenteric and coronary arteries and prevents reperfusion-induced injury at the level of the coronary endothelium.     

L-arginine supplementation prevents the development of endothelial dysfunction in hyperglycaemia

Diabetes mellitus leads to the development of endothelial dysfunction which finally contributes to diabetic angiopathy. We investigated the effects of hyperglycaemia on nitric oxide (NO) liberation and a possible influence of L-arginine supplementation. Porcine endothelial aortic cells (PAEC) were cultured in Medium 199 containing 0.33 mmol/l L-arginine. During the entire third culture passage (= 4 days) cells were either exposed to 5 or 20 mmol/l D-glucose with or without additional 3 mmol/l L-arginine. For osmotic control, cells were exposed to 15 mmol/l mannitol. NO liberation was measured under basal conditions and after stimulation with 1 mmol/l ATP using the spectrophotometrical methemoglobin assay. Cells released 35 +/- 8 pmol NO/1 x 10(6) cells/10 min under basal conditions while hyperglycaemia led to a significant reduction in NO release to 16 +/- 6 pmol/1 x 10(6) cells/10 min. In osmotic control, NO release was unchanged (37 +/- 10 pmol/1 x 10(6) cells/10 min). Stimulation with 1 mmol/l ATP led to a significant increase in NO release to 103 +/- 11 pmol/1 x 10(6) cells/10 min (normoglycaemia) which was unchanged in osmotic controls. Under normoglycaemic conditions, additional L-arginine supplementation did not influence NO release from PAEC. In hyperglycaemia (0.33 mmol/l L-arginine) ATP stimulated NO release was reduced (48 +/- 8 pmol/1 x 10(6) cells/10 min, p < 0.05), which was completely prevented by 3 mmol/l L-arginine treatment (98 +/- 15 pmol/ 1 x 10(6) cells/10 min). Hyperglycaemia (but not enhanced osmotic pressure) leads to endothelial dysfunction with reduced NO release which is completely prevented by L-arginine. L-Arginine utilisation may be impaired in hyperglycaemia and L-arginine supplementation might be an interesting additional therapeutic tool in diabetic patients.     

The effect of pitavastatin calcium on endothelial dysfunction induced by hypercholesterolemia

Objective: To investigate whether endothelial function can be improved by the treatment of pitavastatin calcium via its antioxidant properties in hypercholesteremia patients.

Methods: Forty patients with hypercholesteremia were randomized to receive pitavastatin calcium 1 or 2 mg/day for 8 weeks. Among them, four people were lost in the follow-up period. Before and after treatment, clinical and biochemical characteristics, markers of oxidative stress (plasma 8-iso-prostaglandin F_2α and serum gp91phox) were determined and concomitantly endothelium-dependent brachial artery flow-mediated dilation (FMD) was measured by ultrasound examination. Thirty healthy subjects were chosen as controls.

Results: For individuals with hypercholesteremia, total cholesterol, low-density lipoprotein cholesterol (LDL-C) and serum gp91phox were significantly increased (p < 0.001 for all) and plasma 8-iso-prostaglandinF2α (8-iso-PGF2α) was significantly higher (p < 0.05), while FMD was obviously impaired (p < 0.001). Total cholesterol, LDL-C and serum gp91phox were significantly reduced (p < 0.001 for all), plasma 8-iso-PGF2α was lower and FMD was significantly improved after pitavastatin calcium treatment compared with those before treatment in any group (p < 0.05 for both). However, there was no significant difference between the 1-mg and 2-mg pitavastatin calcium groups post-therapy.

Conclusions: Endothelial dysfunction induced by hypercholesteremia can be ameliorated by pitavastatin calcium treatment, which occurs in part through its antioxidative properties.