Statin attenuates high glucose-induced and diabetes-induced oxidative stress in vitro and in vivo evaluated by electron spin resonance measurement

Nitroxyl Radical as a Theranostic Contrast Agent in Magnetic Resonance Redox Imaging

Significance:In vivo assessment of paramagnetic and diamagnetic conversions of nitroxyl radicals based on cyclic redox mechanism can be an index of tissue redox status. The redox mechanism of nitroxyl radicals, which enables their use as a normal tissue-selective radioprotector, is seen as being attractive on planning radiation therapy. Recent Advances:In vivo redox imaging using nitroxyl radicals as redox-sensitive contrast agents has been developed to assess tissue redox status. Chemical and biological behaviors depending on chemical structures of nitroxyl radical compounds have been understood in detail. Polymer types of nitroxyl radical contrast agents and/or nitroxyl radical-labeled drugs were designed for approaching theranostics. Critical Issues: Nitroxyl radicals as magnetic resonance imaging (MRI) contrast agents have several advantages compared with those used in electron paramagnetic resonance (EPR) imaging, while support by EPR spectroscopy is important to understand information from MRI. Redox-sensitive paramagnetic contrast agents having a medicinal benefit, that is, nitroxyl-labeled drug, have been developed and proposed. Future Directions: A development of suitable nitroxyl contrast agent for translational theranostic applications with high reaction specificity and low normal tissue toxicity is under progress. Nitroxyl radicals as redox-sensitive magnetic resonance contrast agents can be a useful tool to detect an abnormal tissue redox status such as disordered oxidative stress. Antioxid. Redox Signal. 36, 95-121.

Identification of sphingosine 1-phosphate level and MAPK/ERK signaling in pancreatic β cells

PURPOSE

Sphingosine kinase is a lipid kinase that phosphorylates sphingosine to generate sphingosine 1-phosphate (S1P). S1P regulates pancreatic islet β-cell endoplasmic reticulum stress and proliferation. Type 1 and type 2 diabetes share some key pathogenic processes. In this study, we investigated whether secretion of insulin and production of S1P is altered in alloxan and glucose-treated cells from the rat pancreatic β-cell line RIN-5F.

METHODS

RIN-5F cells were treated with 2 mM alloxan and 20 mM glucose for 6 hours or 24 hours before being evaluated by enzyme linked immunosorbent assay (ELISA) and Western blotting.

RESULTS

Insulin secretion and expression was higher in RIN-5F cells treated with glucose compared to control cells. In contrast, alloxan treatment did not affect insulin secretion and expression in RIN-5F cells. Interestingly, compared with normal control levels, S1P/EDG-5 was increased in both alloxan and glucose-treated pancreatic β cell than normal control. Mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) inhibition strongly decreased the expression of insulin and S1P in glucose- or alloxan-treated RIN-5F cells.

CONCLUSION

We observe that production of S1P is increased in both diabetic cell models. In addition, MAPK/ERK signaling regulates secretion of insulin and S1P expression in pancreatic β-cells. Based on the literature and our findings, S1P may be a promising agent for the treatment of insulin-related disorders.

Effect of chronic administration with human thioredoxin-1 transplastomic lettuce on diabetic mice

SCOPE

Human thioredoxin-1 (hTrx-1) is a defensive protein induced by various stresses and exerts antioxidative and anti-inflammatory effects. Previously, we described a transplastomic lettuce overexpressing hTrx-1 that exerts a protective effect against oxidative damage in a pancreatic β-cell line. In this study, we treated diabetic mice (Akita mice) with exogenous hTrx-1 and evaluated the effects.

METHODS AND RESULTS

Treatment with drinking water and single applications of exogenous hTrx-1 did not influence the feeding, drinking behavior, body weight, blood glucose, or glycosylated hemoglobin (HbA1c) levels in Akita mice. However, chronic administration of a 10% hTrx-1 lettuce-containing diet was associated with a significant reduction from the baseline of HbA1c levels compared with mice fed a wild-type lettuce-containing diet. It also resulted in an increased number of goblet cells in the small intestine, indicating that mucus was synthesized and secreted.

CONCLUSION

Our results revealed that the administration of an hTrx-1 lettuce-containing diet improves the baseline level of HbA1c in Akita mice. This effect is mediated through goblet cell proliferation and possibly related to protection against postprandial hyperglycemia by mucus, which results in the improvement of blood glucose control. These findings suggest that the hTrx-1 lettuce may be a useful tool for the continuous antioxidative and antidiabetic efficacies of the hTrx-1 protein.

Mineralcorticoid receptor blockers in chronic kidney disease

There are many experimental data supporting the involvement of aldosterone and mineralcorticoid receptor (MR) activation in the genesis and progression of chronic kidney disease (CKD) and cardiovascular damage. Many studies have shown that in diabetic and non-diabetic CKD, blocking the renin-angiotensin-aldosterone (RAAS) system with conversion enzyme inhibitors (ACEi) or angiotensin II receptor blockers (ARBs) decreases proteinuria, progression of CKD and mortality, but there is still a significant residual risk of developing these events. In subjects treated with ACEi or ARBs there may be an aldosterone breakthrough whose prevalence in subjects with CKD can reach 50%. Several studies have shown that in CKD, the aldosterone antagonists (spironolactone, eplerenone) added to ACEi or ARBs, reduce proteinuria, but increase the risk of hyperkalemia. Other studies in subjects treated with dialysis suggest a possible beneficial effect of antialdosteronic drugs on CV events and mortality. Newer potassium binders drugs can prevent/decrease hyperkalemia induced by RAAS blockade, and may reduce the high discontinuation rates or dose reduction of RAAS-blockers. The nonsteroidal MR blockers, with more potency and selectivity than the classic ones, reduce proteinuria and have a lower risk of hyperkalemia. Several clinical trials, currently underway, will determine the effect of classic MR blockers on CV events and mortality in subjects with stage 3b CKD and in dialysis patients, and whether in patients with type 2 diabetes mellitus and CKD, optimally treated and with high risk of CV and kidney events, the addition of finerenone to their treatment produces cardiorenal benefits. Large randomized trials have shown that sodium glucose type 2 cotransporter inhibitors (SGLT2i) reduce mortality and the development and progression of diabetic and nondiabetic CKD. There are pathophysiological arguments, which raise the possibility that the triple combination ACEi or ARBs, SGLT2i and aldosterone antagonist provide additional renal and cardiovascular protection.

[Mineralcorticoid receptor blockers in chronic kidney disease]

There are many experimental data supporting the involvement of aldosterone and mineralcorticoid receptor (MR) activation in the genesis and progression of chronic kidney disease (CKD) and cardiovascular damage. Many studies have shown that in diabetic and non-diabetic CKD, blocking the renin- angiotensin-aldosterone (RAAS) system with conversion enzyme inhibitors (ACEi) or angiotensin II receptor blockers (ARBs) decreases proteinuria, progression of CKD and mortality, but there is still a significant residual risk of developing these events. In subjects treated with ACEi or ARBs there may be an aldosterone breakthrough whose prevalence in subjects with CKD can reach 50%. Several studies have shown that in CKD, the aldosterone antagonists (spironolactone, eplerenone) added to ACEi or ARBs, reduce proteinuria, but increase the risk of hyperkalemia. Other studies in subjects treated with dialysis suggest a possible beneficial effect of antialdosteronic drugs on CV events and mortality. Newer potassium binders drugs can prevent / decrease hyperkalemia induced by RAAS blockade, and may reduce the high discontinuation rates or dose reduction of RAAS-blockers. The nonsteroidal MR blockers, with more potency and selectivity than the classic ones, reduce proteinuria and have a lower risk of hyperkalemia. Several clinical trials, currently underway, will determine the effect of classic MR blockers on CV events and mortality in subjects with stage 3b CKD and in dialysis patients, and whether in patients with type 2 diabetes mellitus and CKD, optimally treated and with high risk of CV and kidney events, the addition of finerenone to their treatment produces cardiorenal benefits. Large randomized trials have shown that sodium glucose type 2 cotransporter inhibitors (SGLT2i) reduce mortality and the development and progression of diabetic and nondiabetic CKD. There are pathophysiological arguments, which raise the possibility that the triple combination ACEi or ARBs, SGLT2i and aldosterone antagonist provide additional renal and cardiovascular protection.

Improvement of endothelial function by pitavastatin: a meta-analysis

OBJECTIVE

Dyslipidemia is commonly associated with endothelial dysfunction and increased cardiovascular risk. Pitavastatin has been shown to reduce total and low-density lipoprotein cholesterol, to increase high-density lipoprotein (HDL)-cholesterol and improve HDL function. Furthermore, several trials explored its effects on flow-mediated dilation (FMD), as an index of endothelial function. The authors evaluated the effect of pitavastatin therapy on FMD.

METHODS

The authors performed a systematic review and meta-analysis of all clinical trials exploring the impact of pitavastatin on FMD. The search included PubMed-Medline, Scopus, ISI Web of Knowledge and Google Scholar databases. Quantitative data synthesis was performed using a random-effects model, with weighted mean difference (WMD) and 95% confidence interval (CI) as summary statistics.

RESULTS

Six eligible studies comprising 7 treatment arms were selected for this meta-analysis. Overall, WMD was significant for the effect of pitavastatin on FMD (2.45%, 95% CI: 1.31, 3.60, p < 0.001) and the effect size was robust in the leave-one-out sensitivity analysis.

CONCLUSION

This meta-analysis of all available clinical trials revealed a significant increase of FMD induced by pitavastatin.

Characterization of simvastatin acid uptake by organic anion transporting polypeptide 3A1 (OATP3A1) and influence of drug-drug interaction

Human organic anion transporting polypeptide 3A1 (OATP3A1) is predominately expressed in the heart. The ability of OATP3A1 to transport statins into cardiomyocytes is unknown, although other OATPs are known to mediate the uptake of statin drugs in liver. The pleiotropic effects and uptake of simvastatin acid were analyzed in primary human cardiomyocytes and HEK293 cells transfected with the OATP3A1 gene. Treatment with simvastatin acid reduced indoxyl sulfate-mediated reactive oxygen species and modulated OATP3A1 expression in cardiomyocytes and HEK293 cells transfected with the OATP3A1 gene. We observed a pH-dependent effect on OATP3A1 uptake, with more efficient simvastatin acid uptake at pH5.5 in HEK293 cells transfected with the OATP3A1 gene. The Michaelis-Menten constant (K_m) for simvastatin acid uptake by OATP3A1 was 0.017±0.002μM and the V_max was 0.995±0.027fmol/min/10⁵ cells. Uptake of simvastatin acid was significantly increased by known (benzylpenicillin and estrone-3-sulfate) and potential (indoxyl sulfate and cyclosporine) substrates of OATP3A1. In conclusion, the presence of OATP3A1 in cardiomyocytes suggests that this transporter may modulate the exposure of cardiac tissue to simvastatin acid due to its enrichment in cardiomyocytes. Increases in uptake of simvastatin acid by OATP3A1 when combined with OATP substrates suggest the potential for drug-drug interactions that could influence clinical outcomes.

Aldehyde-modified proteins as mediators of early inflammation in atherosclerotic disease

Inflammation is widely accepted to play a major role in atherosclerosis and other cardiovascular diseases. However, the exact mechanism(s) by which inflammation exerts its pathogenic effect remains poorly understood. A number of oxidatively modified proteins have been associated with cardiovascular disease. Recently, attention has been given to the oxidative compound of malondialdehyde and acetaldehyde, two reactive aldehydes known to covalently bind and adduct macromolecules. These products have been shown to form stable malondialdehyde-acetaldehyde (MAA) adducts that are reactive and induce immune responses. These adducts have been found in inflamed and diseased cardiovascular tissue of patients. Antibodies to these adducted proteins are measurable in the serum of diseased patients. The isotypes involved in the immune response to MAA (i.e., IgM, IgG, and IgA) are predictive of atherosclerotic disease progression and cardiovascular events such as an acute myocardial infarction or coronary artery bypass grafting. Therefore, it is the purpose of this article to review the past and current knowledge of aldehyde-modified proteins and their role in cardiovascular disease.

In vivo evaluation of different alterations of redox status by studying pharmacokinetics of nitroxides using magnetic resonance techniques

Free radicals, particularly reactive oxygen species (ROS), are involved in various pathologies, injuries related to radiation, ischemia-reperfusion or ageing. Unfortunately, it is virtually impossible to directly detect free radicals in vivo, but the redox status of the whole organism or particular organ can be studied in vivo by using magnetic resonance techniques (EPR and MRI) and paramagnetic stable free radicals - nitroxides. Here we review results obtained in vivo following the pharmacokinetics of nitroxides on experimental animals (and a few in humans) under various conditions. The focus was on conditions where the redox status has been altered by induced diseases or harmful agents, clearly demonstrating that various EPR/MRI/nitroxide combinations can reliably detect metabolically induced changes in the redox status of organs. These findings can improve our understanding of oxidative stress and provide a basis for studying the effectiveness of interventions aimed to modulate oxidative stress. Also, we anticipate that the in vivo EPR/MRI approach in studying the redox status can play a vital role in the clinical management of various pathologies in the years to come providing the development of adequate equipment and probes.

Atorvastatin counteracts high glucose-induced Krüppel-like factor 2 suppression in human umbilical vein endothelial cells

OBJECTIVE

Krüppel-like factor 2 (KLF2) is a transcription factor that regulates endothelial function and atorvastatin can stabilize atherosclerotic plaque and inhibit inflammation on endothelial cells by attenuating the role of cytokines. The aim of this study is to investigate the effect of high glucose (HG) on KLF2 expression in human umbilical vein endothelial cells (HUVECs) and the underlying mechanisms.

METHODS

HUVECs were isolated from the human umbilical cords from normal pregnancies and exposed to medium containing 25.5 mM D-glucose for 24 hours as the HG induction model (HG group). In the HG plus atorvastatin groups or KLF2 gene transduction, the medium then was collected for the nitric oxide (NO) assay and the cells were harvested for Western blot and for the real-time polymerase chain reaction to observe the expression of KLF2, vascular cell adhesion molecule (VCAM)-1, intercellular adhesion molecule (ICAM)-1, total and phosphorylated endothelial NO synthase (eNOS), p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK)1/2, caspase-3 and cleaved caspase-3 and the role of the p38MAPK and ERK1/2 intracellular signal pathway. The cells' apoptosis was analyzed by flow cytometry.

RESULTS

HG dose-dependently increased apoptosis. The presence of HG inhibited the expression of KLF2 mRNA and protein in HUVECs and atorvastatin treatment increased KLF2 expression, thus counteracted HG-induced suppression of KLF2 expression, and overexpression of KLF2 might protect the cells from apoptosis. HG increased the expression of VCAM-1, ICAM-1, but decreased the nitric oxide release and the expression of p-eNOs/eNos in HUVECs. However, atorvastatin reversed these changes and also attenuated high-glucose induced p38 MAPK and ERK1/2 phosphorylation.

CONCLUSIONS

HG suppressed the KLF2 expression in HUVECs. The suppression was counteracted by atorvastatin treatment, probably via attenuating the activation of the signal pathyway p38 MAPK and ERK1/2.

Increased oxidative stress in obesity: implications for metabolic syndrome, diabetes, hypertension, dyslipidemia, atherosclerosis, and cancer

Obesity, especially of the abdominal type, is a health problem that constitutes metabolic syndrome and increases the incidence of various diseases, including diabetes, hypertension, dyslipidemia, atherosclerosis, and cancer. Various mechanisms linking obesity to these associated diseases have been postulated. One candidate is oxidative stress, which has been implicated in vascular complications of diabetes and in pancreatic -cell failure in diabetes. Notably, obese people without diabetes also display elevated levels of systemic oxidative stress. In addition, levels of oxidative stress are increased in the adipose tissue in obese mice. Treating obese mice with antioxidant agents attenuates the development of diabetes. In 3T3-L1 adipocytes, increases in reactive oxygen species (ROS) occur with lipid accumulation; the addition of free fatty acids elevates ROS generation further. Thus, adipose tissue represents an important source of ROS; ROS may contribute to the development of obesity-associated insulin resistance and type 2 diabetes. Moreover, the levels of oxidative stress present in several other types of cells or tis-sues, including those in the brain, arterial walls, and tumors, have been implicated in the pathogenesis associated with hypertension, atherosclerosis, and cancer. The increased levels of systemic oxidative stress that occur in obesity may contribute to the obesity-associated development of these diseases.

Roles of adiponectin and oxidative stress in obesity-associated metabolic and cardiovascular diseases

The recent increase in populations with obesity is a worldwide social problem, and the enhanced susceptibility of obese people to metabolic and cardiovascular diseases has become a growing health threat. An understanding of the molecular basis for obesity-associated disease development is required to prevent these diseases. Many studies have revealed that the mechanism involves various bioactive molecules that are released from adipose tissues and designated as adipocytokines/adipokines. Adiponectin is an adipocytokine that exerts insulin-sensitizing effects in the liver and skeletal muscle via adenosine monophosphate-activated protein kinase and proliferator-activated receptor α activation. Additionally, adiponectin can suppress atherosclerosis development in vascular walls via various anti-inflammatory effects. In contrast, oxidative stress is a harmful factor that systemically increases during obesity and promotes the development of diabetes, atherosclerosis, and various other diseases. In obese mice, oxidative stress is enhanced in adipose tissue before diabetes development, but not in the liver, skeletal muscle, and aorta, suggesting that in obesity, adipose tissue may be a major source of reactive oxygen species (ROS). ROS suppress adiponectin production in adipocytes. Treatment of obese mice with anti-oxidative agents improves insulin resistance and restores adiponectin production. Recent studies have demonstrated that adiponectin protects against oxidative stress-induced damage in the vascular endothelium and myocardium. Thus, decreased circulating adiponectin levels and increased oxidative stress, which are closely linked to each other, should be deeply involved in obesity-associated metabolic and cardiovascular disease pathogenesis.

Pitavastatin subacutely improves endothelial function and reduces inflammatory cytokines and chemokines in patients with hypercholesterolaemia

BACKGROUND

Pitavastatin is a statin with strong pleiotropic effects, but the effects of pitavastatin on endothelial cell function (ECF) and both inflammatory cytokines and chemokines have not been fully investigated.

MATERIAL AND METHODS

We simultaneously measured brachial artery (BA) flow-mediated vasodilatation (FMD) and nitroglycerin-mediated vasodilatation (NMD), as well as plasma biomarkers of inflammatory cytokines and chemokines, in patients with hypercholesterolaemia and other atherosclerotic risk factors who were treated with pitavastatin. Sixty-five hypercholesterolaemic patients (age, 66±11 years) with conventional coronary risk factors were enrolled. BA FMD, BA NMD and serum biomarkers (tumour necrosis factor, interleukin (IL)-6, IL-10, monocyte chemoattractant protein-1, IL-8, P-selectin, E-selectin, soluble intercellular cell adhesion molecule-1 (s-ICAM1)) were measured before and after 4 weeks of treatment with pitavastatin (2 mg/day).

RESULTS

Pitavastatin treatment resulted in an increase from baseline to post-treatment in FMD (3.22±1.72 vs 3.97±2.18%, p<0.05) but not in NMD. Furthermore, pitavastatin treatment led to a decrease from baseline to post-treatment in E-selectin (51±27 vs 46±29 pg/mL, p<0.05) and s-ICAM1 (276±86 vs 258±91 pg/mL, p<0.05). Changes in FMD in response to pitavastatin treatment did not correlate with those of E-selectin or s-ICAM1.

CONCLUSIONS

Pitavastatin treatment resulted in a subacute improvement in ECF and a decrease in chemokine levels. These results suggest that pitavastatin might improve long-term outcomes in patients with atherosclerotic disorders.

The role of oxidative stress in high glucose-induced apoptosis in neonatal rat cardiomyocytes

Accumulating evidence has demonstrated that apoptosis plays a critical role in the pathogenesis of diabetic cardiomyopathy. However, the exact molecular mechanisms by which hyperglycaemia induces cardiomyocyte apoptosis are not fully understood. The present study was designed to investigate the role of oxidative stress in high glucose-induced apoptosis in cultured neonatal rat cardiomyocytes. The MTT assay was used to detect the viability of cardiomyocytes exposed to different concentrations of glucose. Oxidative stress was evaluated by measuring intracellular reactive oxygen species with 2′,7′-dichlorofluoresce diacetate staining and by detecting malondialdehyde and superoxide dismutase in the supernatant of culture media. Cardiomyocyte apoptosis was determined by flow cytometry and confocal laser scanning microscopy with Annexin V/PI staining. Our results showed that high glucose can induce oxidative stress and promote apoptosis in neonatal rat cardiomyocytes and the antioxidant can protect against high glucose-induced apoptosis, which suggests that oxidative stress is involved in high glucose-induced cardiomyocyte apoptosis. Furthermore, caspase-3 was found to be activated in the process of high glucose-induced oxidative stress, which subsequently contributes to increased apoptosis in neonatal rat cardiomyocytes. In conclusion, our study demonstrates that oxidative stress is involved in high glucose-induced cardiomyocyte apoptosis via activation of caspase-3.

GLP-1 analog liraglutide protects against oxidative stress and albuminuria in streptozotocin-induced diabetic rats via protein kinase A-mediated inhibition of renal NAD(P)H oxidases

Accumulating evidence has implicated that GLP-1 may have a beneficial effect on cardiovascular and renal diseases but the mechanism is not fully understood. Here we show that GLP-1 analog, liraglutide, inhibits oxidative stress and albuminuria in streptozotocin (STZ)-induced type 1 diabetes mellitus rats, via a protein kinase A (PKA)-mediated inhibition of renal NAD(P)H oxidases. Diabetic rats were randomly treated with subcutaneous injections of liraglutide (0.3 mg/kg/12 h) for 4 weeks. Oxidative stress markers (urinary 8-hydroxy-2'-deoxyguanosine and renal dihydroethidium staining), expression of renal NAD(P)H oxidase components, transforming growth factor-β (TGF-β), fibronectin and urinary albumin excretion were measured. In vitro effect of liraglutide was evaluated using cultured renal mesangial cells. Administration of liraglutide did not affect plasma glucose levels or body weights in STZ diabetic rats, but normalized oxidative stress markers, expression of NAD(P)H oxidase components, TGF-β, fibronectin in renal tissues and urinary albumin excretion, all of which were significantly increased in diabetic rats. In addition, in cultured renal mesangial cells, incubation with liraglutide for 48 h inhibited NAD(P)H-dependent superoxide production evaluated by lucigenin chemiluminescence in a dose-dependent manner. This effect was reversed by both PKA inhibitor H89 and adenylate cyclase inhibitor SQ22536, but not by Epac2 inhibition via its small interfering RNA. Liraglutide may have a direct beneficial effect on oxidative stress and diabetic nephropathy via a PKA-mediated inhibition of renal NAD(P)H oxidase, independently of a glucose-lowering effect.

The role of oxidative stress in the pathogenesis of diabetic vascular complications

Oxidative stress has been paid increasing attention to as an important causative factor for diabetic vascular complications. Among possible various sources, accumulating evidence has indicated that NAD(P)H oxidase may be the most important source for reactive oxygen species production in diabetic vascular tissues. The mechanisms underlying activation and up-regulation of NAD(P)H oxidase has been supposed to be mediated by high glucose-induced protein kinase C (PKC) activation. In this review article, activation of local renin-angiotensin II system induced by chymase activation is also shown to amplify such a PKC-dependent activation of NAD(P)H oxidase. Additionally, human evidence showing the beneficial effect of antioxidants on diabetic vascular complications. Bilirubin has been recognized as a strong endogenous antioxidant. Here markedly lower prevalence of vascular complications is shown in diabetic patients with Gilbert syndrome, a congenital hyperbilirubinemia, as well as reduced markers of oxidative stress and inflammation. Lastly, statin, angiotensin II receptor blocker, chymase inhibitor, bilirubin and biliverdin, PKC β isoform inhibitor, and glucagon-like peptide-1 analog, are shown to serve as antioxidants and have some beneficial effect on diabetic vascular complications, via inhibiting PKC-NAD(P)H oxidase activation, supporting the notion that this mechanism may be an effective therapeutic target for preventing diabetic vascular complications.

Effects of a water-soluble curcumin protein conjugate vs. pure curcumin in a diabetic model of erectile dysfunction

INTRODUCTION

Curcumin is involved in erectile signaling via elevation of cyclic guanosine monophosphate (cGMP).

AIM

Assessment of the effects of water-soluble curcumin in erectile dysfunction (ED).

METHODS

One hundred twenty male white albino rats were divided into: 1st and 2nd control groups with or without administration of Zinc protoporphyrin (ZnPP), 3rd and 4th diabetic groups with or without ZnPP, 5th diabetic group on single oral dose of pure curcumin, 6th diabetic group on pure curcumin administered daily for 12 weeks, 7th and 8th diabetic groups on single dose of water-soluble curcumin administered with or without ZnPP, 9th and 10th diabetic groups on water-soluble curcumin administered daily for 12 weeks with or without ZnPP. All curcumin dosage schedules were administered after induction of diabetes.

MAIN OUTCOME MEASURES

Quantitative gene expression of endothelial nitric oxide synthase (eNOS), neuronal NOS (nNOS), inducible NOS (iNOS), heme oxygenase-1 (HO-1), nuclear transcription factor-erythroid2 (Nrf2), NF-Кβ, and p38. Cavernous tissue levels of HO and NOS enzyme activities, cGMP and intracavernosal pressure (ICP).

RESULTS

Twelve weeks after induction of diabetes, ED was confirmed by the significant decrease in ICP. There was a significant decrease in cGMP, NOS, HO enzymes, a significant decrease in eNOS, nNOS, HO-1 genes and a significant elevation of NF-Кβ, p38, iNOS genes. Administration of pure curcumin or its water-soluble conjugate led to a significant elevation in ICP, cGMP levels, a significant increase in HO-1 and NOS enzymes, a significant increase in eNOS, nNOS, HO-1, and Nrf2 genes, and a significant decrease in NF-Кβ, p38, and iNOS genes. Water-soluble curcumin showed significant superiority and more prolonged duration of action. Repeated doses regimens were superior to single dose regimen. Administration of ZnPP significantly reduced HO enzyme, cGMP, ICP/ mean arterial pressure (MAP), HO-1 genes in diabetic groups.

CONCLUSION

Water-soluble curcumin could enhance erectile function with more effectiveness and with more prolonged duration of action.

Reduced expression of adipose triglyceride lipase enhances tumor necrosis factor alpha-induced intercellular adhesion molecule-1 expression in human aortic endothelial cells via protein kinase C-dependent activation of nuclear factor-kappaB

We examined the effects of adipose triglyceride lipase (ATGL) on the initiation of atherosclerosis. ATGL was recently identified as a rate-limiting triglyceride (TG) lipase. Mutations in the human ATGL gene are associated with neutral lipid storage disease with myopathy, a rare genetic disease characterized by excessive accumulation of TG in multiple tissues. The cardiac phenotype, known as triglyceride deposit cardiomyovasculopathy, shows massive TG accumulation in both coronary atherosclerotic lesions and the myocardium. Recent reports show that myocardial triglyceride content is significantly higher in patients with prediabetes or diabetes and that ATGL expression is decreased in the obese insulin-resistant state. Therefore, we investigated the effect of decreased ATGL activity on the development of atherosclerosis using human aortic endothelial cells. We found that ATGL knockdown enhanced monocyte adhesion via increased expression of TNFα-induced intercellular adhesion molecule-1 (ICAM-1). Next, we determined the pathways (MAPK, PKC, or NFκB) involved in ICAM-1 up-regulation induced by ATGL knockdown. Both phosphorylation of PKC and degradation of IκBα were increased in ATGL knockdown human aortic endothelial cells. In addition, intracellular diacylglycerol levels and free fatty acid uptake via CD36 were significantly increased in these cells. Inhibition of the PKC pathway using calphostin C and GF109203X suppressed TNFα-induced ICAM-1 expression. In conclusion, we showed that ATGL knockdown increased monocyte adhesion to the endothelium through enhanced TNFα-induced ICAM-1 expression via activation of NFκB and PKC. These results suggest that reduced ATGL expression may influence the atherogenic process in neutral lipid storage diseases and in the insulin-resistant state.

Novel mechanisms of endothelial dysfunction in diabetes

Diabetes mellitus is a major risk factor for cardiovascular morbidity and mortality. This condition increases the risk of developing coronary, cerebrovascular, and peripheral arterial disease fourfold. Endothelial dysfunction is a major contributor to the pathogenesis of vascular disease in diabetes mellitus patients and has recently received increased attention. In this review article, some recent developments that could improve the knowledge of diabetes-induced endothelial dysfunction are discussed.

Diabetes-induced peroxynitrite impairs the balance of pro-nerve growth factor and nerve growth factor, and causes neurovascular injury

AIMS/HYPOTHESIS

Diabetic retinopathy, the leading cause of blindness in working-age Americans, is characterised by reduced neurotrophic support and increased proinflammatory cytokines, resulting in neurotoxicity and vascular permeability. We sought to elucidate how oxidative stress impairs homeostasis of nerve growth factor (NGF) and its precursor, proform of NGF (proNGF), to cause neurovascular dysfunction in the eye of diabetic patients.

METHODS

Levels of NGF and proNGF were examined in samples from human patients, from retinal Müller glial cell line culture cells and from streptozotocin-induced diabetic animals treated with and without atorvastatin (10 mg/kg daily, per os) or 5,10,15,20-tetrakis (4-sulfonatophenyl)porphyrinato iron (III) chloride (FeTPPs) (15 mg/kg daily, i.p.) for 4 weeks. Neuronal death and vascular permeability were assessed by TUNEL and extravasation of BSA-fluorescein.

RESULTS

Diabetes-induced peroxynitrite formation impaired production and activity of matrix metalloproteinase-7 (MMP-7), which cleaves proNGF extracellularly, leading to accumulation of proNGF and reducing NGF in samples from diabetic retinopathy patients and experimental models. Treatment of diabetic animals with atorvastatin exerted similar protective effects that blocked peroxynitrite using FeTPPs, restoring activity of MMP-7 and hence the balance between proNGF and NGF. These effects were associated with preservation of blood-retinal barrier integrity, preventing neuronal cell death and blocking activation of RhoA and p38 mitogen-activated protein kinase (p38MAPK) in experimental and human samples.

CONCLUSIONS/INTERPRETATION

Oxidative stress plays an unrecognised role in causing accumulation of proNGF, which can activate a common pathway, RhoA/p38MAPK, to mediate neurovascular injury. Oral statin therapy shows promise for treatment of diabetic retinopathy.

Bilirubin and biliverdin protect rodents against diabetic nephropathy by downregulating NAD(P)H oxidase

We recently found a markedly lower prevalence of vascular complications, including kidney disease, in diabetic patients with Gilbert syndrome, a congenital form of hyperbilirubinemia, suggesting a beneficial effect of bilirubin (BIL) on diabetic nephropathy. To directly examine this, we determined whether hereditary hyperbilirubinemic Gunn j/j rats and biliverdin (BVD)-treated diabetic db/db mice were resistant to the development of renal disease. Both rodent models had less albuminuria and complete protection against the progression of mesangial expansion accompanied by normalization of transforming growth factor-β1 and fibronectin expression. Simultaneously, there was normalization of urinary and renal oxidative stress markers, and the expression of nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase subunits in the kidney. In cultured vascular endothelial and mesangial cells, BIL and BVD significantly inhibited NADPH-dependent superoxide production, and both high glucose- and angiotensin II-induced production of reactive oxygen species. Collectively, our findings suggest that BIL and BVD may protect against diabetic nephropathy and may lead to novel antioxidant therapies for diabetic nephropathy.

Short-term type 1 diabetes alters the mechanism of endothelium-dependent relaxation in the rat carotid artery

The aim of the present study was to examine the effect of an early stage of streptozotocin-induced diabetes on the mechanism(s) of endothelium-dependent relaxation. Diabetes was induced by a single injection of streptozotocin (48 mg/kg iv), and the ACh-induced relaxation of rat carotid arteries was examined 6 wk later. A diabetes-induced increase in superoxide levels, determined by L-012-induced chemiluminescence, from carotid arteries was associated with endothelial nitric oxide (NO) synthase (eNOS) uncoupling and increased catalytic subunit of NADPH oxidase expression. The sensitivity and maximum response to ACh were similar in normal and diabetic rats despite a decrease in NO release detected by 4-amino-5-methylamino-2′,7′-difluorofluorescein. In normal rats, N-nitro-l-arginine (100 μM) plus 1 H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (10 μM), to inhibit NOS and soluble guanylate cyclase (sGC), respectively, abolished ACh-induced relaxation, whereas in diabetic rats, the maximum relaxation to ACh was attenuated (maximum relaxation: 25 ± 5%), but not abolished, by that treatment. The remaining ACh-induced relaxation was abolished by NO scavengers, cupric chloride (to degrade nitrosothiols), or blockers of endothelial K+ channels. Western blot analysis of the carotid arteries indicated that diabetes significantly increased the expression of eNOS but decreased the proportion of eNOS expressed as the dimer. These findings demonstrate that in early diabetes, ACh-induced relaxation is maintained but is resistant to NOS inhibition. In early diabetes, nitrosothiol-mediated opening of K+ channels may act in conjunction with NO stimulation of sGC to maintain endothelium-dependent relaxation despite the increase in vascular superoxide levels.

Diverse effects of statins on angiogenesis: new therapeutic avenues

Angiogenesis is an important process for a variety of physiologic and pathologic conditions. Different angiogenic modulating targets are under extensive investigation both experimentally and clinically. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are the first-line agents used in hypercholesterolemia. They are also characterized by having other benefits apart from their lipid-lowering effects. Among these pleiotropic effects are the pro- and antiangiogenic properties of statins. The pleiotropic effects of statins and how they modulate new blood vessel formation are discussed in this review. The currently available data from both animal and human studies regarding the effects of statins on angiogenesis in ischemic heart disease, stroke, ocular diseases, and cancer are also reviewed. Statins are safe, orally available agents that may acquire novel therapeutic indications through their angiogenic modulating effects.

Oxidative stress in childhood type 1 diabetes: Results from a study covering the first 20 years of evolution

This study aimed to further analyse the potential role of oxidative stress in children and adolescents with type 1 diabetes at clinical onset, during disease progression and when early microvascular complications ( + DC) appeared. Compared with age-matched controls, diabetic patients had greater oxidative damage to lipids, proteins and DNA demonstrated by analysis of plasma and erythrocyte malondialdehyde, carbonyl proteins and leukocyte 8-hydroxy-deoxyguanosine, all of which were significantly raised at onset, decreased during the first 1.5 years of evolution and rose progressively thereafter. Plasma lipid levels were significantly associated with lipid and protein oxidation products. Erythrocyte glutathione and glutathione-peroxidase activity were significantly decreased with the lowest values at onset and in + DC sub-groups. Insulin therapy in the first year improved metabolic and oxidant-antioxidant status and, consequently, hyperglycaemia-derived biomolecular oxidative damage. Diabetes-associated hyperlipidaemia is related to lipid and protein oxidation, thereby supporting the concept of glucotoxicity and lipotoxicity being inter-related. The overall increase in lipid, protein and DNA oxidative damage in diabetic patients with microangiopathy could be pathogenetically relevant in the early development of diabetes-related complications.

Pitavastatin suppresses formation and progression of cerebral aneurysms through inhibition of the nuclear factor kappaB pathway

OBJECTIVE

Recent investigations strongly suggest that the pathophysiology of cerebral aneurysms (CA) is closely associated with chronic inflammation in vascular walls. Nuclear factor kappaB (NF-kappaB) has a key role in the formation and progression of CAs. Because statins exert anti-inflammatory effects in various vascular diseases, we investigated the effect of pitavastatin on NF-kappaB activation and CA formation in experimentally induced CAs in rats.

METHODS

CAs were induced in Sprague-Dawley rats with or without administration of pitavastatin (4 mg/kg/d orally). Size, change of internal elastic lamina, and media thickness of induced CAs were measured in both groups after aneurysm induction. The effects of pitavastatin on NF-kappaB activation in aneurysmal walls were examined by immunohistochemistry and gel shift assay. Expression of downstream genes was analyzed by quantitative polymerase chain reaction and immunohistochemistry. To examine whether pitavastatin has a suppressive effect on preexisting CAs, pitavastatin administration started 1 month after aneurysm induction.

RESULTS

Pitavastatin treatment significantly prevented CA progression (P < 0.01) and NF-kappaB activation in aneurysmal walls. Expression of monocyte chemotactic protein-1, vascular cell adhesion molecule-1, interleukin-1beta, inducible nitric oxide synthase, and matrix metalloproteinase-9 in aneurysmal walls was also inhibited by pitavastatin. Pitavastatin treatment led to media thickening in preexisting CAs.

CONCLUSION

Pitavastatin has a suppressive effect on CA progression through the inhibition of NF-kappaB activation in aneurysmal walls. Moreover, pitavastatin treatment can cause the regression of degenerative changes in preexisting CA walls. Pitavastatin is a promising candidate for a novel preventive agent against subarachnoid hemorrhage.

High ambient glucose augments angiotensin II-induced proinflammatory gene mRNA expression in human mesangial cells: effects of valsartan and simvastatin

BACKGROUND

Hyperglycemia may potentiate the adverse renal effects of angiotensin II (AII). In the kidney, the major target of AII action is the glomerular mesangial cell, where its hemodynamic and proinflammatory action contributes to renal injury. AII action is mediated by several types of cell receptors. Among those, the AT1 receptor has been best studied using specific AII receptor blockers (ARBs). These agents have emerged as major new modalities in the prevention and amelioration of renal disease where the ARB renoprotective anti-inflammatory properties could be more important than previously appreciated. Like the ARBs, statins may also modulate inflammatory responses that are renoprotective and complement their cholesterol-lowering effects.

AIM

The aim of this project was to (i) identify a repertoire of proinflammatory mesangial cell AII-inducible mRNAs; (ii) determine if the AII-induced proinflammatory mRNA responses depend on ambient glucose, and (iii) test the anti-inflammatory effectiveness of an ARB, valsartan, either alone or in combination with a statin, simvastatin.

RESULTS/CONCLUSIONS

Using high-density microarrays and real-time PCR we identified several AII-inducible proinflammatory mesangial genes that exhibited augmented mRNA responses in high-glucose milieu. Valsartan blocked the AII-induced mRNA expression of proinflammatory genes (i.e. MCP-1, LIF and COX-2) maintained in normal and high glucose. These observations add to the mounting evidence that ARBs have anti-inflammatory effects in the kidney, a beneficial effect that may be more important in protecting renal function in diabetic patients. While simvastatin inhibited expression of some mRNAs encoding chemokines/cytokines, it enhanced expression of mRNA encoding COX-2, a key mediator of inflammation. Thus, the non-cholesterol effects of statins on inflammatory responses appear complex.

Luminescence experiments involved in the mechanism of streptozotocin diabetes and cataract formation

Streptozotocin (STZ)-induced diabetes is linked to excessive nitric oxide (NO), and possibly peroxynitrite (OONO(-)) and/or other nitrogen oxides, e.g. nitrogen trioxide (N(2)O(3)), which damages DNA of pancreatic beta cells, causing death and loss of insulin. Simultaneous injection of carboxy-PTIO (CPTIO) and STZ prevents diabetes and cataract formation in rats, whereas 4-hydroxy-Tempo (4HT) does not. CPTIO oxidizes nitric oxide to nitrite, which prevents production of the diabetogenic toxin. Peroxynitrite may not be involved, since 4HT (converts O(2)(-) to H(2)O(2)) injected with STZ produces diabetes. All six of the control rats injected with STZ became diabetic and developed cataracts after 3 months. Eight rats injected with STZ and CPTIO were non-diabetic with no cataracts up to a year. This work establishes the idea that excessive nitric oxide is a primary initiator in STZ diabetes. Luminescence experiments using OONO(-) generation from SIN-1 with L-012 indicates that 4HT is an effective inhibitor, while CPTIO is ineffective. Experiments with dilute solutions of nitrogen trioxide added to ladder or plasmid DNA reveal extensive nicking of DNA, thereby raising the possibility that other oxides of nitrogen could be involved with the damage to DNA. It can be concluded that diabetes can be prevented by oxidizing excessive NO from STZ.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Therapeutic interventions and oxidative stress in diabetes

Many therapeutic agents that are used in patients with diabetes mitigate oxidative stress. These agents are of particular interest because oxidative stress is elevated in diabetes and is thought to contribute to vascular dysfunction. Agents that merely quench already formed reactive oxygen species have demonstrated limited success in improving cardiovascular outcomes. Thus, although vitamin E, C, and alpha lipoic acid appeared promising in animal models and initial human studies, subsequent larger trials have failed to demonstrate improvement in cardiovascular outcomes. Drugs that limit the production of oxidative stress are more successful in improving vascular outcomes in patients with diabetes. Thus, although statins, ACE inhibitors, ARBs and thiazolinediones are used for varied clinical purposes, their increased efficacy in improving cardiovascular outcomes is likely related to their success in reducing the production of reactive oxygen species at an earlier part of the cascade, thereby more effectively decreasing the oxidative stress burden. In particular, statins and ACE inhibitors/ ARBs appear the most successful at reducing oxidative stress and vascular disease and have potential for synergistic effects.

Changes in oxidant-antioxidant status in young diabetic patients from clinical onset onwards

Oxidative stress has been implicated as a mechanism underlying hyperglycaemia-associated cellular damage and could play a role in the development of diabetes-related complications. This study aimed to evaluate the significance of changes in oxidant-antioxidant status in 176 child and adolescent diabetic patients at clinical onset, during disease progression and when early microvascular complications appeared. Indicative lipid and protein oxidation markers and antioxidant defence activity were measured in plasma and correlated with clinical data, diabetes duration, long-term glycometabolic control and serum lipids. Compared with their respective age-matched controls, diabetic patients had greater oxidative damage to lipids and proteins, demonstrated through the analysis of hydroperoxides, lipoperoxides and oxidation protein products, all of which were significantly raised at onset, decreased during the first 1.5 years of evolution and rose progressively thereafter. Plasma levels of oxidizable lipids were significantly associated with lipid and protein oxidation products. Overall, plasma antioxidant capacity was significantly and consistently lower from clinical onset onwards. These results suggest that insulin therapy in the first year improved metabolic and oxidant homeostasis and consequently hyperglycaemia-derived biomolecular oxidative damage. Diabetes-associated hyperlipidaemia is related to lipid and protein oxidation processes, which supports the concept of glucose toxicity and lipotoxicity being interrelated. The greatest increase in lipid and protein oxidative damage biomarkers in young diabetic patients with premature microangiopathy points to oxidative stress as a possible contributing mechanism of microvascular dysfunction. Consequently, tight lipid and glycometabolic control may have therapeutic potential by diminishing oxidative tissue-damaging effects of hyperglycaemia.

Asymmetric dimethylarginine may be a missing link between cardiovascular disease and chronic kidney disease

Decreased nitric oxide (NO) production and/or impaired NO bioavailability may occur in patients with chronic kidney disease (CKD), and could contribute to the elevation of blood pressure, cardiovascular disease (CVD) and the progression of renal injury in these patients. However, the underlying molecular mechanisms for reduced NO action in patients with CKD remains to be elucidated. Asymmetric dimethylarginine (ADMA) is a naturally occurring L-arginine analogue found in plasma and various types of tissues, acting as an endogenous NO synthase inhibitor in vivo. Further, plasma level of ADMA is elevated in patients with CKD and found to be a strong biomarker or predictor for future cardiovascular events. In addition, plasma level of ADMA could predict the progression of renal injury in these patients as well. These findings suggest that elevation of ADMA may be a missing link between CVD and CKD. In this review, we discuss the molecular mechanisms for the elevation of ADMA and its pathophysiological role for CVD in high-risk patients, especially focusing on patients with CKD.

Aldosterone nongenomically produces NADPH oxidase-dependent reactive oxygen species and induces myocyte apoptosis

The roles of aldosterone in the progression of heart failure have not been fully elucidated. This study examined whether aldosterone nongenomically activates reactive oxygen species (ROS) production, causing myocyte apoptosis. Addition of aldosterone to neonatal rat cardiac myocytes caused the activation of NADPH oxidase and intracellular ROS production in a dose-dependent manner (10-(9)-10(-7) mol/L). NADPH oxidase activation was evident as soon as 5 min after aldosterone treatment. Neither an inhibitor for nuclear transcription (actinomycin D) nor an inhibitor of new protein synthesis (cycloheximide) blocked this rapid activation, and specific binding of aldosterone to plasma membrane fraction was inhibited by eplerenone, suggesting a nongenomic mechanism. Aldosterone did not affect the mRNA or protein levels of NOX2, which is a major subunit of NADPH oxidase in myocytes, after 48 h. Nuclear staining with DAPI showed that aldosterone (10(-7) mol/L) increased the myocyte apoptosis (2.3 fold, p<0.001), coincident with the activation of caspase-3 (1.4 fold, p<0.05), compared with the serum-deprived control after 48 h. Aldosterone also induced phosphorylation of apoptosis signal-regulating kinase 1 (ASK1). These effects of aldosterone on myocyte ROS accumulation, ASK1 activation, and apoptosis were abolished by eplerenone, a mineralocorticoid receptor (MR) antagonist, apocynin, an inhibitor of NADPH oxidase activation, and tempol, a free radical scavenger, but by neither RU486, a glucocorticoid receptor antagonist, nor butylated hydroxyanisol (BHA), a mitochondrial ROS scavenger. In conclusion, aldosterone-mediated ROS production is blocked by eplerenone and induced by the nongenomic activation of NADPH oxidase, leading to myocyte apoptosis associated with ASK1 activation. These proapoptotic actions of aldosterone may play a role in the progression of heart failure.

Effect of pitavastatin on type 2 diabetes mellitus nephropathy in KK-Ay/Ta mice

It is generally considered that 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) have renoprotective effects via a pathway independent of their cholesterol-lowering cascade. In the kidneys of diabetic nephropathy, monomeric endothelial nitric oxide synthase (eNOS) is thought to be overexpressed; and its dimerization is suppressed. In the present study, we investigated the expression of eNOS and oxidative stress in type 2 diabetes mellitus KK-Ay/Ta mice treated with pitavastatin, one of the statins. The KK-Ay/Ta mice were divided into 3 groups and given pitavastatin intraperitoneally starting at 8 weeks of age for 8 weeks: pitavastatin 3 mg/(kg d) (n=5), pitavastatin 10 mg/(kg d) (n=5), and a control group (n=10). The urinary albumin-creatinine ratio (ACR), urinary 8-hydroxy-2'-deoxyguanosine, body weight, fasting blood glucose, hemoglobin A1c, total cholesterol, and triglyceride were measured; and the intraperitoneal glucose tolerance test was performed. The eNOS, nitrotyrosine, and p47 phox were evaluated by immunohistochemical analyses and/or Western blot analyses. Guanosine triphosphate cyclohydrolase 1 messenger RNA expression in the kidneys was evaluated using a real-time polymerase chain reaction assay. Pitavastatin improved the levels of urinary ACR and 8-hydroxy-2'-deoxyguanosine, intraperitoneal glucose tolerance test, and hemoglobin A1c. Protein levels of monomeric eNOS, nitrotyrosine, and p47 phox in the kidneys were decreased in the pitavastatin-treated groups. Guanosine triphosphate cyclohydrolase 1 messenger RNA expression was significantly increased in the pitavastatin groups. There were no significant changes in body weight, levels of fasting blood glucose, serum total cholesterol, triglyceride, and blood pressure among all groups. Pitavastatin improved urinary ACR apparently because of suppression of eNOS uncoupling and its antioxidant effect in the kidneys of KK-Ay/Ta mice.

Vascular and neural dysfunction in Zucker diabetic fatty rats: a difficult condition to reverse

AIM

We had previously demonstrated that vascular and neural dysfunction in Zucker diabetic fatty (ZDF) rats is progressive. In this study, we sought to determine whether monotherapy of ZDF rats can reverse the vascular and nerve defects.

METHODS

ZDF rats at 16 weeks of age were treated for 12 weeks with the angiotensin-converting enzyme inhibitor enalapril, the antioxidant alpha-lipoic acid, the HMG-CoA reductase inhibitor rosuvastatin or the PPARgamma agonist rosiglitazone. Vasodilation of epineurial arterioles was measured by videomicroscopy. Endoneurial blood flow (EBF) was measured by hydrogen clearance, and nerve conduction velocity was measured following electrical stimulation of motor or sensory nerves.

RESULTS

Motor nerve conduction velocity (MNCV), sensory nerve conduction velocity (SNCV) (70 and 77% of control, respectively), EBF (64% of control), and vascular relaxation in response to acetylcholine (50% of control) and calcitonin gene-related peptide (CGRP; 73% of control) are impaired in ZDF rats at 28 weeks of age compared with lean littermate controls. Treatment with enalapril and alpha-lipoic acid attenuated the decrease in MNCV and SNCV. Enalapril, alpha-lipoic acid and rosiglitazone treatment of ZDF rats were partially effective in improving endothelium-dependent vascular dysfunction as measured by vascular relaxation in response to acetylcholine. The same drugs also attenuated the decrease in EBF. However, impairment in vascular relaxation in response to CGRP was improved with only alpha-lipoic acid or rosuvastatin treatment. The increase in superoxide and nitrotyrosine levels in vascular tissue was attenuated by all treatments.

CONCLUSIONS

The efficacy of monotherapy treatment of ZDF rats using different classes of drugs for vascular and neural dysfunction once complications have developed did not achieve expected levels. This could be because of the complex aetiology of vascular and neural disease in type 2 diabetes.

Changes in oxidant-antioxidant status in young diabetic patients from clinical onset onwards

Oxidative stress has been implicated as a mechanism underlying hyperglycaemia-associated cellular damage and could play a role in the development of diabetes-related complications. This study aimed to evaluate the significance of changes in oxidant-antioxidant status in 176 child and adolescent diabetic patients at clinical onset, during disease progression and when early microvascular complications appeared. Indicative lipid and protein oxidation markers and antioxidant defence activity were measured in plasma and correlated with clinical data, diabetes duration, long-term glycometabolic control and serum lipids. Compared with their respective age-matched controls, diabetic patients had greater oxidative damage to lipids and proteins, demonstrated through the analysis of hydroperoxides, lipoperoxides and oxidation protein products, all of which were significantly raised at onset, decreased during the first 1.5 years of evolution and rose progressively thereafter. Plasma levels of oxidizable lipids were significantly associated with lipid and protein oxidation products. Overall, plasma antioxidant capacity was significantly and consistently lower from clinical onset onwards. These results suggest that insulin therapy in the first year improved metabolic and oxidant homeostasis and consequently hyperglycaemia-derived biomolecular oxidative damage. Diabetes-associated hyperlipidaemia is related to lipid and protein oxidation processes, which supports the concept of glucose toxicity and lipotoxicity being interrelated. The greatest increase in lipid and protein oxidative damage biomarkers in young diabetic patients with premature microangiopathy points to oxidative stress as a possible contributing mechanism of microvascular dysfunction. Consequently, tight lipid and glycometabolic control may have therapeutic potential by diminishing oxidative tissue-damaging effects of hyperglycaemia.

Pitavastatin, an HMG-CoA reductase inhibitor, exerts eNOS-independent protective actions against angiotensin II induced cardiovascular remodeling and renal insufficiency

Angiotensin II (Ang II) plays a pivotal role in cardiovascular remodeling leading to hypertension, myocardial infarction, and stroke. Pitavastatin, an HMG-CoA reductase inihibitor, is known to have pleiotropic actions against the development of cardiovascular remodeling. The objectives of this study were to clarify the beneficial effects as well as the mechanism of action of pitavastatin against Ang II-induced organ damage. C57BL6/J mice at 10 weeks of age were infused with Ang II for 2 weeks and were simultaneously administered pitavastatin or a vehicle. Pitavastatin treatment improved Ang II-induced left ventricular hypertrophy and diastolic dysfunction and attenuated enhancement of cardiac fibrosis, cardiomyocyte hypertrophy, coronary perivascular fibrosis, and medial thickening. Ang II-induced oxidative stress, cardiac TGFbeta-1 expression, and Smad 2/3 phosphorylation were all attenuated by pitavastatin treatment. Pitavastatin also reduced Ang II-induced cardiac remodeling and diastolic dysfunction in eNOS-/- mice as in wild-type mice. In eNOS-/- mice, the Ang II-induced cardiac oxidative stress and TGF-beta-Smad 2/3 signaling pathway were enhanced, and pitavastatin treatment attenuated the enhanced oxidative stress and the signaling pathway. Moreover, pitavastatin treatment reduced the high mortality rate and improved renal insufficiency in Ang II-treated eNOS-/- mice, with suppression of glomerular oxidative stress and TGF-beta-Smad 2/3 signaling pathway. In conclusion, pitavastatin exerts eNOS-independent protective actions against Ang II-induced cardiovascular remodeling and renal insufficiency through inhibition of the TGF-beta-Smad 2/3 signaling pathway by suppression of oxidative stress.

Oxidative stress, AGE, and atherosclerosis

Numerous reports on the molecular mechanism of atherogenesis indicate an increase in oxidative stress, formation of advanced glycoxidation end products (AGEs), chronic inflammation, and activated cellular response particularly in diabetic patients. To elucidate the initiating and early accelerating events this review will focus on the molecular causes of the induction of these stress factors, their interactions, and their contribution to atherogenesis. Metabolic factors such as elevated free fatty acids, high glucose levels or AGEs induce reactive oxygen species (ROS) in vascular cells leading to ongoing AGE formation and to gene induction of proinflammatory cytokines. Vice versa, numerous cytokines found elevated in obesity and diabetes may also induce oxidative stress thus a circulus vitious may be initiated and accelerated. Increased production of ROS, mainly from mitochondria and NAD(P)H oxidase, stimulates signaling cascades including protein kinase C and mitogen-activated protein kinase pathway leading to nuclear translocation of transcription factors such as nuclear factor-kappaB (NF-kappaB), activator protein 1, and specificity protein 1. Subsequently, the expression of numerous genes including cytokines is rapidly induced, which, in turn, may act on vascular cells promoting the deleterious effects. From animal models of accelerated atherosclerosis a causal role of NAD(P)H oxidase and the AGE/RAGE/NF-kappaB axis to atherogenesis is suggested. Because all factors involved form a highly interwoven network of interactions, the blockade of ROS or AGE formation at different sites may interrupt the vicious cycle. Promising candidate agents are, currently on trial. Most important to clinical practice, a number of drugs commonly used in the treatment of diabetes, hypertension, or cardiovascular disease, such as angiotensin-converting enzyme inhibitors, AT(1) receptor blockers, 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors (statins), and thiazolidindiones have shown promising 'preventive' intracellular antioxidant activity in addition to their primary pharmacological actions.

Ageing and atherosclerosis: Mechanisms and therapeutic options

Atherosclerosis is the cause of most heart attacks and strokes, and is par excellence, a disease of ageing. Whilst disease prevalence and incidence increases with increasing decade of life, there is also evidence of accelerated cellular ageing in atherosclerosis. Such evidence includes impaired cell proliferation, early culture senescence and cell cycle markers of senescence in vitro and in vivo. Cell senescence is also characterised by loss of telomeres from the ends of chromosomes. Cellular ageing increases with disease severity, acting as a marker for disease, but also directly promotes atherosclerosis. Cellular ageing appears to be due to both abnormal proliferation of cells in an attempt to repair vessel damage, and a response to the damage itself. This review summarises the evidence of vascular cell senescence in atherosclerosis, the causes and consequences of accelerated cellular ageing in atherosclerosis, and identifies potential therapeutic options for both prevention and treatment.

Pretreatment effect of resveratrol on streptozotocin-induced diabetes in rats

This study was planned to investigate the pretreatment effect of resveratrol on streptozotocin-induced diabetic rats. The control group consisted of 10 male albino Sprague-Dawley rats, 10-12 weeks of age, weighing approximately 295 g. The first experimental group consisted of 15 albino Sprague-Dawley rats, 10-12 weeks of age, weighing approximately 305 g. This group was administered streptozotocin (55 mg/kg, intraperitoneally). The second experimental group (n = 15) was administered resveratrol (0.5 ml/day) 10 days before streptozotocin induction. A training period was performed for all groups before the experimental procedure, and systolic arterial blood pressures and heart rates were recorded daily. At the end of the 10th day, blood samples of control and experimental groups were drawn. Total nitrite, nitrite, nitrate, malondialdehyde (MDA), copper, and zinc concentrations in plasma were measured both in control and experimental groups. Additionally, superoxide dismutase, catalase activities, and copper and zinc concentrations in red cell were determined in each group. At the end of the study, increases in catalase activity, nitric oxide level, and zinc concentrations and decreases in lipid peroxidation product MDA and copper concentrations were found in the resveratrol-pretreated diabetic group when compared to the diabetic group.

Pitavastatin ameliorates albuminuria and renal mesangial expansion by downregulating NOX4 in db/db mice

Recent studies have uncovered various pleiotrophic effects of 3-hydroxy-3-methylglutaryl coenzyme A reductase-inhibiting drugs (statins). Several studies have identified a beneficial effect of statins on diabetic nephropathy; however, the molecular mechanisms are unclear. In this study, we show that statin ameliorates nephropathy in db/db mice, a rodent model of type 2 diabetes, via downregulation of NAD(P)H oxidase NOX4, which is a major source of oxidative stress in the kidney. Pitavastatin treatment for 2 weeks starting at 12 weeks of age significantly reduced albuminuria in the db/db mice concomitant with a reduction of urinary 8-hydroxy-2'-deoxyguanosine and 8-epi-prostaglandin F(2alpha). Immunohistochemical analysis found increased amounts of 8-hydroxy-2'-deoxyguanosine and NOX4 protein in the kidney of db/db mice. Quantitative reverse transcription-polymerase chain reaction also showed increased levels of NOX4 mRNA. Pitavastatin normalized all of these changes in the kidneys of diabetic animals. Additionally, 12-week treatment with the statin completely normalized the levels of transforming growth factor-beta1 and fibronectin mRNA as well as the mesangial expansion characteristic of diabetic nephropathy. Our study demonstrates that pitavastatin ameliorates diabetic nephropathy in db/db mice by minimizing oxidative stress by downregulating NOX4 expression. These findings may provide insight into the mechanisms of statin therapy in early stages of diabetic nephropathy.

Hyperglycemia in acute ischemic stroke: a vascular perspective

Admission hyperglycemia complicates approximately one-third of acute ischemic strokes and is associated with a worse clinical outcome. Both human and animal studies have showed that hyperglycemia is particularly detrimental in ischemia/reperfusion. Decreased reperfusion blood flow has been observed after middle cerebral artery occlusion in acutely hyperglycemic animals, suggesting the vasculature as an important site of hyperglycemic reperfusion injury. This paper reviews biochemical and molecular pathways in the vasculature that are rapidly affected by hyperglycemia and concludes that these changes result in a pro-vasoconstrictive, pro-thrombotic and pro-inflammatory phenotype that renders the vasculature vulnerable to reperfusion injury. Understanding these pathways should lead to the development of rational therapies that reduce hyperglycemic reperfusion injury and thus improve outcome in this large subset of acute ischemic stroke patients.

Improved endothelial function and reduced platelet activation by chronic HMG-CoA-reductase inhibition with rosuvastatin in rats with streptozotocin-induced diabetes mellitus

Diabetes is associated with endothelial dysfunction and platelet activation, both of which may contribute to increased cardiovascular risk. We investigated whether the hydroxy-3-methyl-glutaryl CoA reductase inhibitor rosuvastatin improves endothelial function and reduces platelet activation in diabetic rats. Therefore, male Wistar rats were injected with streptozotocin (STZ, 50mg/kg i.v.) to induce insulin-deficient diabetes. Treatment with rosuvastatin (20mg/[kg day]) or vehicle was initiated 2 weeks after injection of STZ and continued for 2 weeks. Thereafter, platelet activation was assessed in fresh whole blood and vascular function was characterized in isolated aortic segments in organ bath chambers. Endothelium-dependent relaxation induced by acetylcholine was significantly attenuated in diabetic rats and improved by treatment with rosuvastatin (maximum relaxation, % of precontraction-control: 99.8+/-0.2, STZ-vehicle: 80.7+/-2.9, STZ-rosuvastatin: 98.9+/-0.7; p<0.01). Similarly, treatment with rosuvastatin significantly reduced fibrinogen-binding to activated GPIIb/IIIa (mean fluorescence-control: 161.0+/-6.9, STZ-vehicle: 207.8+/-15.9, rosuvastatin: 173.6+/-5.3; p<0.05) and P-Selectin surface expression on platelets (mean fluorescence-control: 76.5+/-7.3, STZ-vehicle: 92.1+/-5.5, rosuvastatin: 75.2+/-6.5; p<0.05), while both markers of platelet activation were increased in diabetic rats. Therefore, rosuvastatin treatment normalizes endothelial function and reduces platelet activation in diabetic rats. These effects may contribute to the reduction of cardiovascular events by statins in diabetic patients.

Diabetes, metallothionein, and zinc interactions: a review

Epidemiological evidence, associating diabetes with zinc (Zn) deficiencies, has resulted in numerous research studies describing the effects of Zn and associated metallothionein (MT), on reducing diabetic complications associated with oxidative stress. MT has been found to have a profound effect on the reduction of oxidative stress induced by the diabetic condition. Over expression of MT in various metabolic organs has also been shown to reduce hyperglycaemia-induced oxidative stress, organ specific diabetic complications, and DNA damage in diabetic experimental animals, which have been further substantiated by the results from MT-knockout mice. Additionally, supplementation with Zn has been shown to induce in vivo MT synthesis in experimental animals and to reduce diabetes related complications in both humans and animal models. Although the results are promising, some caution regarding this topic is however necessary, due to the fact that the majority of the studies done have been animal based. Hence more human intervention trials are needed regarding the positive effects of MT and Zn before firm conclusions can be made regarding their use in the treatment of diabetes.

Dietary caloric restriction improves the redox status at the onset of diabetes in hepatocytes of streptozotocin-induced diabetic rats

Enhanced production of free radicals and oxidative stress induced by hyperglycemia play a central role in the pathogenesis of diabetes and its complications. This study assessed the attenuation by dietary caloric restriction on the oxidative and lipid peroxidative effects of diabetes in the liver through reduction in body and organ weights and concomitant metabolic changes. Three-month-old male Wistar rats were subjected to ad libitum feeding and 30% caloric restriction for 9 weeks before induction of diabetes by intraperitoneal injection of 35 mg/kg body weight streptozotocin. The animals were sacrificed 2 weeks after streptozotocin treatment depicting the onset of diabetes. Caloric restriction significantly reduced the organ weights (p<0.01), malondialdehyde (p<0.01) and catalase activity (p<0.01), but significantly increased glutathione reductase activity (p<0.01), and GSH/GSSG ratios (p<0.05). Caloric restriction also non-significantly reduced reactive oxygen species, superoxide dismutase and oxidized glutathione but increased glutathione peroxidase activity and reduced glutathione levels in the diabetic rats. Our data indicate a decrease in lipid peroxidation, improvement in the antioxidant defense systems and restoration of the redox status in the liver by caloric restriction. Therefore, this could provide a non-invasive antioxidant therapy early in diabetes to prevent the development of the complications associated with the disease.