Alpha-tocopherol decreases superoxide anion release in human monocytes under hyperglycemic conditions via inhibition of protein kinase C-alpha

Homocysteine stimulates phosphorylation of NADPH oxidase p47phox and p67phox subunits in monocytes via protein kinase Cbeta activation

Hyperhomocysteinaemia is an independent risk factor for cardiovascular diseases due to atherosclerosis. The development of atherosclerosis involves reactive oxygen species-induced oxidative stress in vascular cells. Our previous study [Wang and O (2001) Biochem. J. 357, 233-240] demonstrated that Hcy (homocysteine) treatment caused a significant elevation of intracellular superoxide anion, leading to increased expression of chemokine receptor in monocytes. NADPH oxidase is primarily responsible for superoxide anion production in monocytes. In the present study, we investigated the molecular mechanism of Hcy-induced superoxide anion production in monocytes. Hcy treatment (20-100 microM) caused an activation of NADPH oxidase and an increase in the superoxide anion level in monocytes (THP-1, a human monocytic cell line). Transfection of cells with p47phox siRNA (small interfering RNA) abolished Hcy-induced superoxide anion production, indicating the involvement of NADPH oxidase. Hcy treatment resulted in phosphorylation and subsequently membrane translocation of p47phox and p67phox subunits leading to NADPH oxidase activation. Pretreatment of cells with PKC (protein kinase C) inhibitors Ro-32-0432 (bisindolylmaleimide XI hydrochloride) (selective for PKCalpha, PKCbeta and PKCgamma) abolished Hcy-induced phosphorylation of p47phox and p67phox subunits in monocytes. Transfection of cells with antisense PKCbeta oligonucleotide, but not antisense PKCalpha oligonucleotide, completely blocked Hcy-induced phosphorylation of p47phox and p67phox subunits as well as superoxide anion production. Pretreatment of cells with LY333531, a PKCbeta inhibitor, abolished Hcy-induced superoxide anion production. Taken together, these results indicate that Hcy-stimulated superoxide anion production in monocytes is regulated through PKC-dependent phosphorylation of p47phox and p67phox subunits of NADPH oxidase. Increased superoxide anion production via NADPH oxidase may play an important role in Hcy-induced inflammatory response during atherogenesis.

Gliclazide inhibits differentiation-associated biologic events in human monocyte-derived macrophages

We investigated the in vitro effect of gliclazide on human monocyte-derived macrophage scavenger receptor expression and activity, foam cell formation, and lipopolysaccharide-induced cytokine production. Differentiation of human monocytes into macrophages in the presence of gliclazide (1-10 microg/mL) decreased CD36 expression by 20% to 50%, with maximal effect occurring at 2.5 microg/mL (P<.05). This effect was mimicked by vitamin E (50 micromol/L) and N-acetyl-L-cysteine (10 mmol/L). Incubation of the cells with gliclazide and N-acetyl-L-cysteine also reduced CD36 activity by 30% (P<.02). Despite these effects, neither gliclazide nor vitamin E did affect foam cell formation. In contrast, gliclazide significantly reduced lipopolysaccharide-stimulated macrophage tumor necrosis factor alpha and interleukin 6 secretion (P<.05). Overall, these data indicate that gliclazide, at concentrations in the therapeutic range, may regulate some key biologic events associated with the process of monocyte differentiation into macrophages.

High glucose-induced inhibition of 2-deoxyglucose uptake is mediated by cAMP, protein kinase C, oxidative stress and mitogen-activated protein kinases in mouse embryonic stem cells

Abnormally high glucose levels may play an important role in early embryo development and function. In the present study, we investigated the effect of high glucose on 2-deoxyglucose (2-DG) uptake and its related signalling pathway in mouse embryonic stem (ES) cells. 2. 2-Deoxyglucose uptake was maximally inhibited by 25 mmol/L glucose after 24 h treatment. However, 25 mmol/L mannitol and dextran did not affect 2-DG uptake. Indeed, 25 mmol/L glucose decreased GLUT-1 mRNA and protein levels. The glucose (25 mmol/L)-induced inhibition of 2-DG uptake was blocked by pertussis toxin (a G(i)-protein inhibitor; 2 ng/mL), SQ 22,536 (an adenylate cyclase inhibitor; 10(-6) mol/L) and the protein kinase (PK) A inhibitor myristoylated PKI amide-(14-22) (10(-6) mol/L). Indeed, 25 mmol/L glucose increased intracellular cAMP content. 3. Furthermore, 25 mmol/L glucose-induced inhibition of 2-DG uptake was prevented by 10(-4) mol/L neomycin or 10(-6) mol/L U 73,122 (phospholipase C (PLC) inhibitors) and staurosporine or bisindolylmaleimide I (protein kinase (PK) C inhibitors). At 25 mmol/L, glucose increased translocation of PKC from the cytoplasmic fraction to the membrane fraction. The 25 mmol/L glucose-induced inhibition of 2-DG uptake and GLUT-1 protein levels was blocked by SQ 22,536, bisindolylmaleimide I or combined treatment. In addition, 25 mmol/L glucose increased cellular reactive oxygen species and the glucose-induced inhibition of 2-DG uptake were blocked by the anti-oxidants N-acetylcysteine (NAC; 10(-5) mol/L) or taurine (2 yen 10(-3) mol/L). 4. Glucose (25 mmol/L) activated p38 mitogen-activated protein kinase (MAPK) and p44/42 MAPK. Staurosporine (10(-6) mol/L), NAC (10(-5) mol/L) and PD 98059 (10(-7) mol/L) attenuated the phosphorylation of p44/42 MAPK. Both SB 203580 (a p38 MAPK inhibitor; 10(-7) mol/L) and PD 98059 (a p44/42 MAPK inhibitor; 10(-7) mol/L) blocked 25 mmol/L glucose-induced inhibition of 2-DG uptake. 5. In conclusion, high glucose inhibits 2-DG uptake through cAMP, PLC/PKC, oxidative stress or MAPK in mouse ES cells.

Increased monocytic activity and biomarkers of inflammation in patients with type 1 diabetes

Type 1 diabetes is associated with increased vascular complications, and monocytes are pivotal cells in atherogenesis. However, there are few data on monocyte function and inflammation in type 1 diabetes. The aim of this study was to compare monocyte function and biomarkers of inflammation in type 1 diabetic subjects without macrovascular disease with that in matched control subjects (n = 52 per group). Fasting blood was obtained for biomarkers of inflammation (C-reactive protein [CRP], plasma-soluble cell adhesion molecules [CAMs], monocyte chemoattractant protein 1, nitrotyrosine, CD40 ligand [CD40L], and monocyte function). High-sensitive CRP, soluble intracellular adhesion molecule (sICAM), sCD40L, and nitrotyrosine levels were significantly elevated in type 1 diabetic subjects compared with in control subjects (P < 0.05). Monocyte superoxide anion release was significantly increased in the resting (37%; P < 0.05) and activated state (26%; P < 0.005) in type 1 diabetic compared with in control subjects. Monocyte interleukin (IL)-6 levels were significantly elevated in type 1 diabetic subjects compared with in control subjects in the resting state (51%; P < 0.05) and after lipopolysaccharide activation (31%; P < 0.01). Monocyte IL-1beta levels were increased in the activated monocytes in type 1 diabetic compared with in control subjects. There were no significant differences in monocyte tumor necrosis factor levels or adhesion between the two groups. Thus type 1 diabetes is a proinflammatory state, as evidenced by increased levels of monocyte IL-6, superoxide anion, and plasma CRP, sICAM, sCD40L, and nitrotyrosine levels. These results have a major implication on our understanding of the role of inflammation in vasculopathies in type 1 diabetes.

Selective Rac-1 Inhibition Protects From Diabetes-Induced Vascular Injury

Diabetes mellitus is a main risk factor for vascular diseases. Vascular injury induced by diabetes mellitus is characterized by endothelial dysfunction attributable to an increased oxidative stress. So far, the molecular mechanisms involved in the vasculotoxic effects of diabetes are only partially known. We examined the effect of diabetes mellitus on oxidative stress and Rac-1 activation, a small G-protein involved in the activation of NADPH oxidase. Our results show that oxidative stress in vessels of different murine models of diabetes mellitus and in endothelial cells treated with high glucose is associated with an increased Rac-1/PAK binding and Rac-1 translocation from cytosol to plasma membrane, thus demonstrating an enhanced Rac-1 activity. More important, selective Rac-1 inhibition by an adenoviral vector carrying a dominant negative mutant of Rac-1 protected from oxidative stress and vascular dysfunction induced by diabetes mellitus. Our study demonstrates that Rac-1 plays a crucial role in diabetes-induced vascular injury, and it could be a target of novel therapeutic approaches to reduce vascular risk in diabetes mellitus.

Oxidative stress and diabetic cardiovascular complications

Diabetes diagnoses are increasing at an alarming rate worldwide. The majority of diabetes-related deaths arise from cardiovascular complications such as myocardial infarction, stroke, and peripheral vascular disease. Oxidative stress has been demonstrated to be present in animal models as well as in patients with diabetes and has been suggested as a possible contributor to the accelerated atherosclerosis seen in diabetics. The generation of reactive oxygen species in diabetes occurs via several mechanisms and is initiated not only by glucose, but also by other substances that are found at elevated levels in diabetic patients. The resulting oxidative stress leads to a number of proatherogenic events. The elucidation of the mechanisms of oxidative stress in diabetes and their relationship with atherosclerosis could potentially identify molecular targets of therapy for this condition and its cardiovascular consequences.

Oxidative stress in leukocytes from young prematurely aging mice is reversed by supplementation with biscuits rich in antioxidants

Aging is associated with a progressive dysregulation of immune responses as a result of increased oxidative stress. Therefore, we have assessed the oxidative stress status of peritoneal leukocytes from young prematurely aging mice (PAM) as compared with non-prematurely aging mice (NPAM), as well as the effects on this oxidative stress of a dietary supplementation with biscuits rich in antioxidants (vitamin C, vitamin E, beta-carotenes, zinc and selenium). We found that, in the peritoneal leukocytes, the levels of several parameters of oxidation such as extracellular superoxide anion (O(2)(-)), Prostaglandin E(2) (PGE(2)), nitric oxide, oxidized glutathione (GSSG) and lipid peroxidation (malondialdehyde, MDA) were higher in PAM as compared with NPAM, whereas the antioxidant defences such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) activities, as well as reduced glutathione (GSH) levels, were decreased. Consequently, young PAM showed an oxidative stress in their leukocytes, which is characteristic of mice of an older chronological age. Antioxidant diet supplementation was able to restore redox homeostasis, increasing the antioxidant and decreasing the oxidant levels. Accordingly, supplementation with adequate levels of antioxidants, from an early age, could be useful to preserve health, especially in prematurely aging populations.

Elevated concentrations of nonesterified fatty acids increase monocyte expression of CD11b and adhesion to endothelial cells

OBJECTIVE

Monocyte proinflammatory activity has been demonstrated in obesity, insulin resistance, and type 2 diabetes, metabolic conditions that are frequently associated with elevated levels of nonesterified fatty acids (NEFA). We therefore tested the hypothesis that NEFA may induce monocyte inflammation.

METHODS AND RESULTS

Monocytes exposed to NEFA for 2 days demonstrated a dose-related increase in intracellular reactive oxygen species (ROS) formation and adhesion to endothelial cells. All of these effects were inhibited by the coaddition of antioxidants such as glutathione or butylated hydroxytoluene, by inhibition of ROS generation by NADPH oxidase inhibitors, and by inhibition of protein kinase C, a recognized stimulator of NAPDH oxidase. Monocytes exposed to NEFA also demonstrated a significant increase in CD11b message expression. Stimulation of monocyte adhesion to endothelial cells by NEFA was inhibited by addition of neutralizing antibodies to either CD11b or CD18. Finally, surface expression of CD11b increased significantly on monocytes as measured by flow cytometry, after their incubation with NEFA.

CONCLUSIONS

These studies indicate that elevated concentrations of NEFA may enhance integrin facilitated monocyte adhesion to endothelial cells and these effects appear mediated, in part, through activation of NADPH oxidase and oxidative stress.

Development of an In Vitro Screening Assay to Test the Antiinflammatory Properties of Dietary Supplements and Pharmacologic Agents

Background: Monocytes and macrophages are critical in atherosclerosis and on stimulation secrete proinflammatory, proatherogenic cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β, which have been shown to be present in atherosclerotic lesions. The aim of this study was to develop a rapid in vitro screening assay to test the antiinflammatory effects of different compounds.

Methods and Results: THP-1 cells (human monocytic cell line) were stimulated with different concentrations of lipopolysaccharide (LPS; 0 to 1000 μg/L) and for different times (4, 12, and 24 h), and the secretion of proinflammatory cytokines (IL-1, IL-6, and TNF-α) was assessed. TNF-α secretion was maximum at the lowest LPS concentration (100 μg/L) and at shortest duration of incubation (4 h). Maximum secretion of IL-1β and IL-6 was achieved at 24 h with higher doses of LPS. Treatment of THP-1 with various test compounds such as dietary supplements (α-tocopherol, N-acetylcysteine, catechin and epigallocatechin gallate) as well as pharmacologic agents (statins, peroxisome proliferator-activated receptor-γ agonists, and an angiotensin II receptor blocker) significantly inhibited LPS-stimulated TNF-α release.

Conclusions: The release of TNF-α after stimulation of THP-1 cells with LPS is a valid model system to test novel compounds for potential antiinflammatory effects.

Comparative radical scavenging and antidiabetic activities of methanolic extract and fractions from Achillea ligustica ALL

The yield of methanolic extract and total phenol and non polar content of flowered parts from Achillea ligustica ALL. are reported. GC-MS analysis of the non polar fraction showed that the triterpene moretenol was the major constituent (17.228%) followed by stigmast-6-en-3beta-ol, veridiflorol and beta-amyrin (7.524%, 5.078% 4.470%, respectively). The antioxidant activities of the methanolic extract and its fractions from A. ligustica were carried out using two different in vitro assays, 2,2-diphenyl-1-picrylhydrazyl (DPPH) test and lipid peroxidation of liposomes assay. Methanolic extract showed higher radical scavenging activity on DPPH (IC50 of 50 microg/ml). This activity is probably due to the phenolic fraction which shown an IC50 value of 22 microg/ml. A different result was obtained from the methanolic extract on the lipid peroxidation of liposomes (IC50 of 416 microg/ml). The alpha-amylase inhibition assay was applied to evaluate antidiabetic activity. The methanolic extract showed weak activity (28.18% at 1 mg/ml) while the n-hexane fraction showed 74.96% inhibition at 250 microg/ml.

Vitamin E, oxidative stress, and inflammation

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in the Western world. Its incidence has also been increasing lately in developing countries. Several lines of evidence support a role for oxidative stress and inflammation in atherogenesis. Oxidation of lipoproteins is a hallmark in atherosclerosis. Oxidized low-density lipoprotein induces inflammation as it induces adhesion and influx of monocytes and influences cytokine release by monocytes. A number of proinflammatory cytokines such as interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha) modulate monocyte adhesion to endothelium. C-reactive protein (CRP), a prototypic marker of inflammation, is a risk marker for CVD and it could contribute to atherosclerosis. Hence, dietary micronutrients having anti-inflammatory and antioxidant properties may have a potential beneficial effect with regard to cardiovascular disease. Vitamin E is a potent antioxidant with anti-inflammatory properties. Several lines of evidence suggest that among different forms of vitamin E, alpha-tocopherol (AT) has potential beneficial effects with regard to cardiovascular disease. AT supplementation in human subjects and animal models has been shown to decrease lipid peroxidation, superoxide (O2-) production by impairing the assembly of nicotinamide adenine dinucleotide phosphate (reduced form) oxidase as well as by decreasing the expression of scavenger receptors (SR-A and CD36), particularly important in the formation of foam cells. AT therapy, especially at high doses, has been shown to decrease the release of proinflammatory cytokines, the chemokine IL-8 and plasminogen activator inhibitor-1 (PAI-1) levels as well as decrease adhesion of monocytes to endothelium. In addition, AT has been shown to decrease CRP levels, in patients with CVD and in those with risk factors for CVD. The mechanisms that account for nonantioxidant effects of AT include the inhibition of protein kinase C, 5-lipoxygenase, tyrosine-kinase as well as cyclooxygenase-2. Based on its antioxidant and anti-inflammatory activities, AT (at the appropriate dose and form) could have beneficial effects on cardiovascular disease in a high-risk population.

Activation of protein kinase C alpha is required for TPA-triggered ERK (MAPK) signaling and growth inhibition of human hepatoma cell HepG2

The signaling mechanisms for most of the antiproliferative processes are not fully understood. We have demonstrated that ERK(MAPK) signaling was involved in the induction of both p15(INK4b)and p16(INK4a) CDK inhibitors and growth inhibition of hepatoma cell HepG2 triggered by the tumor promoter tetradecanoyl phorbol acetate (TPA). In this study, the upstream signal mechanism for TPA-induced ERK(MAPK) activation was investigated. In HepG2 cells only one of the cPKC isozymes, PKCalpha, but not cPKCbetaII, nPKCepsilon or aPKCzeta was activated by TPA as demonstrated by its membrane translocation within 10-30 min and down-regulation at 24 h after TPA treatment. Pretreatment of 0.2-2.0 microM Bisindolylmaleimides, an inhibitor of PKC, attenuated the TPA-induced phosphorylation of ERK, gene expressions of p15(INK4b) and p16(INK4a), and growth inhibition of HepG2 cell in a dose-dependent manner. Consistently, transfection of HepG2 with 1.0-3.0 microM antisense (AS) PKCalpha, but not (AS) PKCbetaII, or nPKCepsilon oligonucleotides (ODN), for 36 h prior to TPA treatment also prevented the TPA-induced molecular and cellular effects described above. Taken together, we concluded that PKCalpha is specifically required for TPA-induced ERK(MAPK) signaling to trigger gene expressions of p15(INK4b) and p16(INK4a) leading to HepG2 growth inhibition.

Enhanced superoxide release and elevated protein kinase C activity in neutrophils from diabetic patients: association with periodontitis

Inflammation and oxidative stress are important factors in the pathogenesis of diabetes and contribute to the pathogenesis of diabetic complications. Periodontitis is an inflammatory disease that is characterized by increased oxidative stress, and the risk for periodontitis is increased significantly in diabetic subjects. In this study, we examined the superoxide (O(2)(-))-generating reduced nicotinamide adenine dinucleotide phosphate-oxidase complex and protein kinase C (PKC) activity in neutrophils. Fifty diabetic patients were grouped according to glycemic control and the severity of periodontitis. Neutrophils from diabetic patients with moderate [amount of glycated hemoglobin (HbA(1c)) between 7.0% and 8.0%] or poor (HbA(1c) >8.0%) glycemic control released significantly more O(2)(-) than neutrophils from diabetic patients with good glycemic control (HbA(1c) <7.0%) and neutrophils from nondiabetic, healthy individuals upon stimulation with 4beta-phorbol 12-myristate 13-acetate or N-formyl-Met-Leu-Phe. Depending on glycemic status, neutrophils from these patients also exhibited increased activity of the soluble- and membrane-bound forms of PKC, elevated amounts of diglyceride, and enhanced phosphorylation of p47-phox during cell stimulation. In addition, we report a significant correlation between glycemic control (HbA(1c) levels) and the severity of periodontitis in diabetic patients, suggesting that enhanced oxidative stress and increased inflammation exacerbate both diseases. Thus, hyperglycemia can lead to a novel form of neutrophil priming, where elevated PKC activity results in increased phosphorylation of p47-phox and O(2)(-) release.

Vascular complications in diabetes mellitus: the role of endothelial dysfunction

The endothelium is a complex organ with a multitude of properties essential for control of vascular functions. Dysfunction of the vascular endothelium is regarded as an important factor in the pathogenesis of diabetic micro- and macro-angiopathy. Endothelial dysfunction in Type I and II diabetes complicated by micro- or macro-albuminuria is generalized in that it affects many aspects of endothelial function and occurs not only in the kidney. The close linkage between microalbuminuria and endothelial dysfunction in diabetes is an attractive explanation for the fact that microalbuminuria is a risk marker for atherothrombosis. In Type I diabetes, endothelial dysfunction precedes and may cause diabetic microangiopathy, but it is not clear whether endothelial dysfunction is a feature of the diabetic state itself. In Type II diabetes, endothelial function is impaired from the onset of the disease and is strongly related to adverse outcomes. It is not clear whether impaired endothelial function is caused by hyperglycaemia or by other factors. Impaired endothelial function is closely associated with and may contribute to insulin resistance regardless of the presence of diabetes. Endothelial dysfunction in diabetes originates from three main sources. Hyperglycaemia and its immediate biochemical sequelae directly alter endothelial function or influence endothelial cell functioning indirectly by the synthesis of growth factors, cytokines and vasoactive agents in other cells. Finally, the components of the metabolic syndrome can impair endothelial function.

Effect of D-alpha-tocopherol on tubular nephron acidification by rats with induced diabetes mellitus

The objective of the present study was to determine if treatment of diabetic rats with D-alpha-tocopherol could prevent the changes in glomerular and tubular function commonly observed in this disease. Sixty male Wistar rats divided into four groups were studied: control (C), control treated with D-alpha-tocopherol (C + T), diabetic (D), and diabetic treated with D-alpha-tocopherol (D + T). Treatment with D-alpha-tocopherol (40 mg/kg every other day, ip) was started three days after diabetes induction with streptozotocin (60 mg/kg, ip). Renal function studies and microperfusion measurements were performed 30 days after diabetes induction and the kidneys were removed for morphometric analyses. Data are reported as means +/- SEM. Glomerular filtration rate increased in D rats but decreased in D + T rats (C: 6.43 +/- 0.21; D: 7.74 +/- 0.45; D + T: 3.86 +/- 0.18 ml min-1 kg-1). Alterations of tubular acidification observed in bicarbonate absorption flux (JHCO3) and in acidification half-time (t/2) in group D were reversed in group D + T (JHCO3, C: 2.30 +/- 0.10; D: 3.28 +/- 0.22; D + T: 1.87 +/- 0.08 nmol cm-2 s-1; t/2, C: 4.75 +/- 0.20; D: 3.52 +/- 0.15; D + T: 5.92 +/- 0.19 s). Glomerular area was significantly increased in D, while D + T rats exhibited values similar to C, suggesting that the vitamin prevented the hypertrophic effect of hyperglycemia (C: 8334.21 +/- 112.05; D: 10,217.55 +/- 100.66; D + T: 8478.21 +/- 119.81 microm(2)). These results suggest that D-alpha-tocopherol is able to protect rats, at least in part, from the harmful effects of diabetes on renal function.

Enhanced oxidative stress in neutrophils from hyperlipidemic guinea pig

Inhibitors of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase are antilipidemic agents (statins) widely used for the prevention of cardiovascular diseases. Recent studies have suggested that the overall benefits of statin therapy cannot be accounted for solely by its antilipidemic effect. To obtain further insight into the mechanism of action of statins, we studied the effect of pitavastatin on the generation of reactive oxygen species (ROS) by peritoneal polymorphonuclear leukocytes (PMN) obtained from control and hyperlipidemic guinea pigs. Flow cytometric analysis revealed that the amount of ROS generated by PMN from the hyperlipidemic animals that had been administered a laurate-containing diet (LD) for 4 weeks was larger than that from the normal diet (ND) group (837% increase, ND; 82.17 arbitrary units, LD; 688.10 arbitrary units, P < 0.01, n = 6). Administration of pitavastatin to the LD group significantly decreased plasma levels of total cholesterol (TC) and low-density lipoprotein (LDL) with a reduction in ROS generation by PMN (19% decrease, LD control; 688.10 arbitrary units, LD + pitavastatin; 556.87 arbitrary units, P < 0.01, n = 6). Western blotting analysis revealed that the expression of protein kinase C alpha (PKC alpha) and betaI was higher in PMN from the LD group than in PMN from the ND group (PKC alpha; 74% increase, PKC betaI; 339% increase, P < 0.05, n = 4, respectively). Furthermore, expression of NADPH oxidase gp91phox in PMN from the LD group was higher than that in PMN from the ND group (18% increase, P < 0.05, n = 4). By administration of pitavastatin to the LD group, the expression of PKC alpha, betaI and gp91phox was suppressed compared with the control LD group (PKC alpha; 41% decrease, PKC beta; 28% decrease, gp91phox; 56% decrease, P < 0.05, n = 4, respectively). These results indicate that PMN from hyperlipidemic animals is associated with an accelerated respiratory burst of ROS by increasing the expression of PKC alpha, betaI and gp91phox, and pitavastatin inhibits this by suppressing the expression of those proteins.

Mitochondrial dysfunction in cardiovascular disease

Whereas the pathogenesis of atherosclerosis has been intensively studied and described, the underlying events that initiate cardiovascular disease are not yet fully understood. A substantial number of studies suggest that altered levels of oxidative and nitrosoxidative stress within the cardiovascular environment are essential in the development of cardiovascular disease; however, the impact of such changes on the subcellular or organellar components and their functions that are relevant to cardiovascular disease inception are less understood. In this regard, studies are beginning to show that mitochondria not only appear susceptible to damage mediated by increased oxidative and nitrosoxidative stress, but also play significant roles in the regulation of cardiovascular cell function. In addition, accumulating evidence suggests that a common theme among cardiovascular disease development and cardiovascular disease risk factors is increased mitochondrial damage and dysfunction. This review discusses aspects relating mitochondrial damage and function to cardiovascular disease risk factors and disease development.

PKC-delta-dependent activation of oxidative stress in adipocytes of obese and insulin-resistant mice: role for NADPH oxidase

Oxidative stress is thought to be one of the causative factors contributing to insulin resistance and type 2 diabetes. Previously, we showed that reactive oxygen species (ROS) production is significantly increased in adipocytes from high-fat diet-induced obese and insulin-resistant mice (HF). ROS production was also associated with the increased activity of PKC-delta. In the present studies, we hypothesized that PKC-delta contributes to ROS generation and determined their intracellular source. NADPH oxidase inhibitor diphenyleneiodonium chloride (DPI) reduced ROS levels by 50% in HF adipocytes, and inhibitors of NO synthase (L-NAME, 1 mM), xanthine oxidase (allopurinol, 100 microM), AGE formation (aminoguanidine, 10 microM), or the mitochondrial uncoupler (FCCP, 10 microM) had no effect. Rottlerin, a selective PKC-delta inhibitor, suppressed ROS levels by approximately 50%. However, neither GO-6976 nor LY-333531, effective inhibitors toward conventional PKC or PKC-beta, respectively, significantly altered ROS levels in HF adipocytes. Subsequently, adenoviral-mediated expression of wild-type PKC-delta or its dominant negative mutant (DN-PKC-delta) in HF adipocytes resulted in either a twofold increase in ROS levels or their suppression by 20%, respectively. In addition, both ROS levels and PKC-delta activity were sharply reduced by glucose depletion. Taken together, these results suggest that PKC-delta is responsible for elevated intracellular ROS production in HF adipocytes, and this is mediated by high glucose and NADPH oxidase.

Proatherosclerotic mechanisms involving protein kinase C in diabetes and insulin resistance

In diabetes and insulin resistance, activation of protein kinase C (PKC) in vascular cells may be a key link between elevated plasma and tissue concentrations of glucose and nonesterified fatty acids and abnormal vascular cell signaling. Initial studies of PKC activation in diabetes focused on microvascular complications, but increasing evidence supports that PKC plays a role in several mechanisms promoting atherosclerosis. This review explains how PKC is thought to be activated in diabetes and insulin resistance through de novo synthesis of diacylglycerol. Furthermore, the review summarizes studies that implicate PKC in promoting proatherogenic mechanisms or inhibiting antiatherogenic mechanisms, including studies of endothelial dysfunction; gene induction and activation of vascular NAD(P)H oxidase; endothelial nitric oxide synthase expression and function; endothelin-1 expression; growth, migration, and apoptosis of vascular smooth muscle cells; induction of adhesion molecules; and oxidized low-density lipoprotein uptake by monocyte-derived macrophages.

In Vitro Antioxidant Effect and Inhibition of .ALPHA.-Amylase of Two Varieties of Amaranthus caudatus Seeds

This study reports on the biological properties, antioxidant and antidiabetic, of two varieties of Amaranthus caudatus seeds, Oscar blanco and Victor red. Oil, squalene and phenolic contents were also determined. Seeds of both investigated varieties were found to possess very different levels of squalene (2.2% in Oscar blanco variety and 7.5% in Victor red variety). Although the antioxidant activity of A. caudatus var. Oscar blanco and A. caudatus var. Victor red statistically did not differ significantly from each other (IC50 values of ethyl acetate extracts were 0.50 mg/ml and 0.62 mg/ml, respectively), significant differences were noticed in relation to antidiabetic activity (inhibition of alpha-amylase, EC 3.2.1.1) of methanolic extracts that showed 50.5% for A. caudatus var. Oscar blanco and 28% for A. caudatus var. Victor red at concentration of 25 microg/ml.

Hyperglycemia induces monocytic release of interleukin-6 via induction of protein kinase c-{alpha} and -{beta}

Diabetes confers an increased propensity to atherosclerosis. Inflammation is pivotal in atherogenesis, and diabetes is a proinflammatory state. Interleukin (IL)-6, in addition to inducing the acute-phase response, contributes to insulin resistance. Monocytes from type 2 diabetic patients secrete increased IL-6. The aim of this study was to examine molecular mechanisms for increased IL-6 release from monocytes under hyperglycemia. Monocytic cells (THP-1) were cultured in the presence of 5.5 mmol/l (normal) or 15 mmol/l (high) glucose and mannitol. Secreted IL-6, intracellular IL-6, and IL-6 mRNA were significantly increased with hyperglycemia (P < 0.001). Incubation of cells with inhibitors of reactive oxygen species failed to affect high-glucose-induced IL-6 release. Pan-protein kinase C (PKC) inhibitors significantly decreased high-glucose-induced IL-6 release. A specific inhibitor of p38 mitogen-activated protein kinase (MAPK; SB 202190), but not the extracellular signal-regulated kinase inhibitor PD98059, significantly decreased high-glucose-induced IL-6 release. Furthermore, the PKC-alpha/beta2 inhibitor decreased p38MAPK and the resulting high-glucose-induced IL-6 release. Both antisense oligos to PKC-beta and -alpha as well as small interfering RNA (siRNA) to PKC-alpha and -beta resulted in significantly decreased high-glucose-induced IL-6 release. Nuclear factor-kappaB (NF-kappaB) inhibitors significantly decreased IL-6 mRNA and protein. siRNA to PKC-beta and -alpha also significantly decreased NF-kappaB activity and IL-6 release. The combination was not additive to either siRNA alone, suggesting that they work through a common pathway. Thus, IL-6 release from monocytes under hyperglycemia appears to be mediated via upregulation of PKC, through p38MAPK and NF-kappaB, resulting in increased mRNA and protein for IL-6. Thus, inhibition of PKC-alpha and -beta can ameliorate the proinflammatory state of diabetes.

Oxidative Stress and Antioxidant Treatment in Diabetes

The many studies on oxidative stress, antioxidant treatment, and diabetic complications have shown that oxidative stress is increased and may accelerate the development of complications through the metabolism of excessive glucose and free fatty acids in diabetic and insulin-resistant states. However, the contribution of oxidative stress to diabetic complications may be tissue-specific, especially for microvascular disease that occurs only in diabetic patients but not in individuals with insulin resistance without diabetes, even though both groups suffer from oxidative stress. Although antioxidant treatments can show benefits in animal models of diabetes, negative evidence from large clinical trials suggests that new and more powerful antioxidants need to be studied to demonstrate whether antioxidants can be effective in treating complications. Furthermore, it appears that oxidative stress is only one factor contributing to diabetic complications; thus, antioxidant treatment would most likely be more effective if it were coupled with other treatments for diabetic complications.

Effects of vitamin E supplementation on intracellular antioxidant enzyme production in adolescents with type 1 diabetes and early microangiopathy

Defective intracellular antioxidant enzyme production (IAP) has been demonstrated in adults with diabetic nephropathy. To evaluate the effects on IAP of vitamin E administration in adolescents with type 1 diabetes and early signs of microangiopathy, 12 adolescents (aged 11-21 y; diabetes duration 10-18) were studied. Eight had retinopathy [background (four), preproliferative (three), or proliferative (one)], four had persistent microalbuminuria, and seven had both. Skin fibroblasts were obtained by biopsies and cultured in Dulbecco's modified Eagle's medium. CuZn superoxide dismutase (SOD), MnSOD, catalase (CAT), and glutathione-peroxidase (GPX) activity and mRNA expression were measured before and after 3 mo of synthetic vitamin E supplementation (600 mg twice daily); on both occasions, IAP was evaluated at different ex vivo glucose concentrations (5 and 22 mM). Ten adolescents with type 1 diabetes (aged 12-20 y) without angiopathy and eight healthy volunteers (aged 15-22 y) participated as control subjects. Vitamin E serum levels were measured throughout the study. In normal glucose concentrations, CuZnSOD, MnSOD, CAT, and GPX activity and mRNA expression were not different among the groups. In high glucose, CuZnSOD activity and mRNA increased similarly in all groups [angiopathics: 0.96 +/- 0.30 U/mg protein; 9.9 +/- 3.2 mRNA/glyceraldehyde-3-phosphate dehydrogenase). CAT and GPX activity and mRNA did not increase in high glucose only in adolescents with angiopathy (0.35 +/- 0.09; 4.2 +/- 0.1 and 0.52 +/- 0.14; 2.4 +/- 0.9, respectively). MnSOD did not change in any group. Vitamin E supplementation had no effect on any enzymatic activity and mRNA in both normal and hyperglycemic conditions. Adolescents with early signs of diabetic angiopathy have defective IAP and activity, which are not modified by vitamin E.

An alpha-tocopherol dose response study in Paramecium tetraurelia

Vitamin E (D,L-alpha-tocopherol) was administered to Paramecium tetraurelia in doses of 10, 100, 1000 and 10,000mg/l throughout its clonal lifespan. ANOVA revealed significant differences in clonal lifespan between groups, whether lifespan was measured in total fissions, or in days (P<0.05). When mean clonal lifespan was measured in fissions the greatest difference was between the 1000mg/l alpha-tocopherol treatment at 382 fissions, and the ethanol control at 255.5 fissions. The greatest difference in mean clonal lifespan in days survived was between the 10,000mg/l alpha-tocopherol treatment at 292.5 days and the ethanol control at 76 days. ANOVA also revealed significant differences (P<0.05) in the initial cell fission rates between groups. At the 1000 and 10,000mg/l concentrations of alpha-tocopherol, a decrease in cell fission rates was apparent early in the lifespan, but these rates began to increase gradually during the late clonal lifespan. Although no clonal toxicity effects were found in terms of decreasing life-expectancy, the 1000 and 10,000mg/l treatment groups exhibited higher background mortality rates throughout their respective lifespans than did the control groups, which could represent a cytotoxic effect.

Vitamin E reduces cisplatin ototoxicity

OBJECTIVES/HYPOTHESIS

Cisplatin ototoxicity is a major dose-limiting factor in the treatment of several neoplasms. Vitamin E, a slow-acting free radical scavenger, has been shown to ameliorate nephrotoxicity and endothelial cell damage in animals receiving cisplatin. The purpose of the study was to determine the effectiveness of vitamin E as an otoprotectant.

STUDY DESIGN

Prospective, randomized controlled trial in the rat model.

METHODS

Wistar rats (weight, 261-386 g) were sedated using 172.4 mg/kg intramuscular ketamine and 3.4 mg/kg xylazine. Baseline auditory brainstem response (ABR) testing was performed in response to clicks and 8-, 16-, and 32-kHz tone bursts. After auditory thresholds were determined, the animals received intraperitoneal drug administration according to one of three group classifications. Group 1 received 4 g/kg vitamin E followed after 30 minutes by 16 mg/kg cisplatin. Group 2 received 6 mL/kg soybean oil followed after 30 minutes by cisplatin. Group 3 received soybean oil followed after 30 minutes by 16 mL/kg saline. After 3 days' follow-up, ABR testing was performed and threshold changes were recorded. Cochleae were removed and processed for scanning electron microscopy after follow-up auditory testing was carried out.

RESULTS

Group 2 animals showed marked hearing loss with average threshold shifts of 28.75 +/- 2.3 dB for clicks, 30.0 +/- 1.9 dB at 8 kHz, 21.25 +/- 4.0 dB at 16 kHz, and 45.0 +/- 4.2 dB at 32 kHz. No significant loss was observed in group 3 with shifts of 2 +/- 1.3 dB, 3 +/-3.0 dB, -2.2 +/- 3.1 dB, and -1.1 +/- 4.0 dB for clicks and tone bursts at 8, 16, and 32 kHz, respectively. Significant protection was seen in group 1 animals compared with group 2 animals. In the former group, threshold shifts of 12.5 +/- 3.1 dB for clicks, 7.5 +/- 2.5 dB at 8 kHz, 5.0 +/- 3.3 dB at 16 kHz, and 24.4 +/- 5.6 dB at 32 kHz were observed. These findings were supported by the scanning electron microscope observations that severe outer hair cell destruction occurred in group 2 rats, whereas outer hair cells were preserved to a much greater extent in the cochleae of rats in group 1 that were pretreated with vitamin E.

CONCLUSION

Vitamin E appears to have a protective effect against cisplatin ototoxicity.

Vitamin E modulation of C-reactive protein in smokers with acute coronary syndromes

Acute coronary syndromes are characterized by the expression of proinflammatory cytokines such as C-reactive protein (CRP). Sustained upregulation of inflammatory markers is associated with an adverse prognosis. Vitamin E is known to have significant anti-inflammatory properties and has been associated with a reduction in cardiovascular events in some studies of high-risk patients. The mechanism of benefit remains controversial. We conducted a randomized, double-blind placebo controlled trial of vitamin E 400 IU daily for 6 months in 110 patients with acute coronary syndromes. Serum samples were collected at enrollment and at 2, 4, and 6 months. CRP, interleukin-6 and the soluble cell adhesion molecules were measured. Vitamin E levels increased significantly in the treatment group (from 31 micromol/l at baseline to 51 micromol/l, p <.0001) and were unchanged in the placebo group (32 micromol/l at baseline to 34 micromol/l, p = NS). CRP levels fell in both the vitamin E group and the placebo group over the treatment period (from 17.2 +/- 2.9 to 6.1 +/- 0.8 mg/l and from 21.5 +/- 4.9 to 5.9 +/- 0.9 mg/l, p = NS for the difference between active and placebo groups). However, vitamin E treatment was associated with significantly lower 6 month CRP levels in smokers versus smokers on placebo (4.7 +/- 0.71 mg/l vs. 8.26 +/- 1.5 mg/l, p =.02). Vitamin E reduces CRP levels in smokers with acute coronary syndromes for up to 6 months after hospitalization.

Enhanced inflammatory responses in alpha-tocopherol transfer protein null mice

The liver preferentially secretes alpha-tocopherol into plasma under the control of the hepatic alpha-tocopherol transfer protein (alpha-TTP). alpha-TTP-null mice (Ttpa(-/-) mice) are vitamin E deficient, therefore were used for investigations of in vivo responses to sub-normal tissue alpha-tocopherol concentrations during inflammation. Increased basal oxidative stress in Ttpa(-/-) mice was documented by increased plasma lipid peroxidation, and superoxide production by bone marrow-derived neutrophils stimulated in vitro with phorbol 12-myristate 13-acetate. Lipopolysaccharide (LPS) injected intraperitoneally induced increases in lung and liver HO-1 and iNOS, as well as plasma NO(x) in Ttpa(+/+) mice. LPS induced more modest increases in these markers in Ttpa(-/-) mice, while more marked increases in plasma IL-10 and lung lavage TNF alpha were observed. Taken together, these results demonstrate that alpha-tocopherol is important for proper modulation of inflammatory responses and that sub-optimal alpha-tocopherol concentrations may derange inflammatory-immune responses.

Molecular mechanisms of high glucose-induced cyclooxygenase-2 expression in monocytes

The cyclooxygenase (COX)-2 enzyme has been implicated in the pathogenesis of several inflammatory diseases. However, its role in diabetic vascular disease is unclear. In this study, we evaluated the hypothesis that diabetic conditions can induce COX-2 in monocytes. High glucose treatment of THP-1 monocytic cells led to a significant three- to fivefold induction of COX-2 mRNA and protein expression but not COX-1 mRNA. High glucose-induced COX-2 mRNA was blocked by inhibitors of nuclear factor-kappaB (NF-kappaB), protein kinase C, and p38 mitogen-activated protein kinase. In addition, an antioxidant and inhibitors of mitochondrial superoxide, NADPH oxidase, and glucose metabolism to glucosamine also blocked high glucose-induced COX-2 expression to varying degrees. High glucose significantly increased transcription from a human COX-2 promoter-luciferase construct (twofold, P < 0.001). Promoter deletion analyses and inhibition of transcription by NF-kappaB superrepressor and cAMP-responsive element binding (CREB) mutants confirmed the involvement of NF-kappaB and CREB transcription factors in high glucose-induced COX-2 regulation. In addition, isolated peripheral blood monocytes from type 1 and type 2 diabetic patients had high levels of COX-2 mRNA, whereas those from normal volunteers showed no expression. These results show that high glucose and diabetes can augment inflammatory responses by upregulating COX-2 via multiple signaling pathways, leading to monocyte activation relevant to the pathogenesis of diabetes complications.

Oxidative Stress and Antioxidant Supplementation in the Management of Diabetic Cardiovascular Disease

The diabetic state confers an increased propensity to accelerated atherogenesis. In addition to the established risk factors, there is evidence for increased oxidative stress in diabetes. Increased oxidative stress is manifested by increased lipid peroxidation, increased F2-isoprostanes, increased nitrotyrosine, and increased DNA damage. Also, in diabetics, there is increased superoxide release. With regard to diabetes, antioxidants such as α-tocopherol, α-lipoate, and ascorbic acid supplementation have been shown to be beneficial. Most importantly, α-tocopherol therapy, especially at high doses, clearly shows a benefit with regard to low-density lipoprotein oxidation, isoprostanes, and monocyte superoxide release. Thus, it appears that, in diabetes, antioxidant therapy could alleviate the increased attendant oxidative stress and emerge as an additional therapeutic modality.

High glucose-suppressed endothelin-1 Ca2+ signaling via NADPH oxidase and diacylglycerol-sensitive protein kinase C isozymes in mesangial cells

High glucose (HG) is the underlying factor contributing to long term complications of diabetes mellitus. The molecular mechanisms transforming the glomerular mesangial cell phenotype to cause nephropathy including diacylglycerol-sensitive protein kinase C (PKC) are still being defined. Reactive oxygen species (ROS) have been postulated as a unifying mechanism for HG-induced complications. We hypothesized that in HG an interaction between ROS generation, from NADPH oxidase, and PKC suppresses mesangial Ca2+ signaling in response to endothelin-1 (ET-1). In primary rat mesangial cells, growth-arrested (48 h) in 5.6 mM (NG) or 30 mm (HG) glucose, the total cell peak [Ca2+]i response to ET-1 (50 nM) was 630 +/- 102 nM in NG and was reduced to 159 +/- 15 nM in HG, measured by confocal imaging. Inhibition of PKC with phorbol ester down-regulation in HG normalized the ET-1-stimulated [Ca2+]i response to 541 +/- 74 nM. Conversely, an inhibitory peptide specific for PKC-zeta did not alter Ca2+ signaling in HG. Furthermore, overexpression of conventional PKC-beta or novel PKC-delta in NG diminished the [Ca2+]i response to ET-1, reflecting the condition observed in HG. Likewise, catalase or p47phox antisense oligonucleotide normalized the [Ca2+]i response to ET-1 in HG to 521 +/- 58 nM and 514 +/- 48 nM, respectively. Pretreatment with carbonyl cyanide m-chlorophenylhydrazone or rotenone did not restore Ca2+ signaling in HG. Detection of increased intracellular ROS in HG by dichlorofluorescein was inhibited by catalase, diphenyleneiodonium, or p47phox antisense oligonucleotide. HG increased p47phox mRNA by 1.7 +/- 0.1-fold as measured by reverse transcriptase-PCR. In NG, H2O2 increased membrane-enriched PKC-beta and -delta, suggesting activation of these isozymes. HG-enhanced immunoreactivity of PKC-delta visualized by confocal imaging was attenuated by diphenyleneiodium chloride. Thus, mesangial cell [Ca2+]i signaling in response to ET-1 in HG is attenuated through an interaction mechanism between NADPH oxidase ROS production and diacylglycerol-sensitive PKC.

High glucose augments the angiotensin II-induced activation of JAK2 in vascular smooth muscle cells via the polyol pathway

Angiotensin II (Ang II), protein kinase C (PKC), reactive oxygen species (ROS) generated by NADPH oxidase, the activation of Janus kinase 2 (JAK2), and the polyol pathway play important parts in the hyperproliferation of vascular smooth muscle cells (VSMC), a characteristic feature of diabetic macroangiopathy. The precise mechanism, however, remains unclear. This study investigated the relation between the polyol pathway, PKC-beta, ROS, JAK2, and Ang II in the development of diabetic macroangiopathy. VSMC cultured in high glucose (HG; 25 mm) showed significant increases in the tyrosine phosphorylation of JAK2, production of ROS, and proliferation activities when compared with VSMC cultured in normal glucose (5.5 mm (NG)). Both the aldose reductase specific inhibitor (zopolrestat) or transfection with aldose reductase antisense oligonucleotide blocked the phosphorylation of JAK2, the production of ROS, and proliferation of VSMC induced by HG, but it had no effect on the Ang II-induced activation of these parameters in both NG and HG. However, transfection with PKC-beta antisense oligonucleotide, preincubation with a PKC-beta-specific inhibitor (LY379196) or apocynin (NADPH oxidase-specific inhibitor), or electroporation of NADPH oxidase antibodies blocked the Ang II-induced JAK2 phosphorylation, production of ROS, and proliferation of VSMC in both NG and HG. These observations suggest that the polyol pathway hyperactivity induced by HG contributes to the development of diabetic macroangiopathy through a PKC-beta-ROS activation of JAK2.

Overexpression of skin protein kinase C-alpha in anagen hair follicles during induced growth of mouse hair

A role for protein kinase C (PKC)-alpha has been implicated in the growth of mouse hair. Topical application of PKC activators, hair plucking, allergic contact dermatitis and skin irritation can all enhance growth of mouse hair, and a significant increase in PKC-alpha level in whole mouse skin in mature anagen has been demonstrated in these processes. Overexpression of PKC-alpha in anagen hair follicles has also been reported in natural growth of mouse hair. It is known that overexpression of PKC-alpha is associated with the acceleration of cell growth. Therefore, we postulated that overexpression of PKC-alpha in mature anagen may relate to enhancement of hair growth. The distribution of PKC-alpha in hair follicles during induced growth of mouse hair has not previously been studied. In this study, hair growth in C57BL/6 mice was induced by plucking the telogen hairs on one side of the back. The undepilated contralateral side served as a control. Expression of PKC-alpha in hair follicles during the hair growth cycle induced was evaluated by immunohistochemistry using cryosections and a specific polyclonal anti-PKC-alpha immunoglobulin G (IgG) antibody. No PKC-alpha was detected in telogen hair follicles or in the hair follicles at 1 day post-depilation, when the induced hair cycle was in early anagen. At 4 days after plucking, when the induced hair cycle was in mid-anagen, intense staining for PKC-alpha was found in hair papillae. At 10 and 17 days after depilation, when the induced hair cycle was in mature anagen and early catagen, respectively, all outer root sheath (ORS) cells and outer connective sheaths of hair follicles were stained positive. Because no PKC-alpha was detected in telogen hair follicles in this study, down-regulation of PKC-alpha in early anagen could not be observed. However, consistent with our previous findings, overexpression of PKC-alpha was found in mid-anagen and mature anagen. As overexpression of PKC-alpha has been shown to be associated with acceleration of cell growth, our results support the notion that PKC-alpha may play an important role in growth of hair follicle cells in induced growth of hair. As PKC levels are known to increase in hyperglycaemia, overexpressed PKC-alpha in mature anagen hair follicles may be related to the putative function of the ORS in mobilizing glycogen stores for anagen growth.

High glucose-induced expression of proinflammatory cytokine and chemokine genes in monocytic cells

Monocyte activation and adhesion to the endothelium play important roles in inflammatory and cardiovascular diseases. These processes are further aggravated by hyperglycemia, leading to cardiovascular complications in diabetes. We have previously shown that high glucose (HG) treatment activates monocytes and induces the expression of tumor necrosis factor (TNF)-alpha via oxidant stress and nuclear factor-kB transcription factor. To determine the effects of HG on the expression of other inflammatory genes, in the present study, HG-induced gene profiling was performed in THP-1 monocytes using cytokine gene arrays containing 375 known genes. HG treatment upregulated the expression of 41 genes and downregulated 15 genes that included chemokines, cytokines, chemokines receptors, adhesion molecules, and integrins. RT-PCR analysis further confirmed that HG significantly increased the expression of monocyte chemoattractant protein-1 (MCP-1), TNF-alpha, beta(2)-integrin, interleukin-1beta, and others. HG treatment increased transcription of the MCP-1 gene, MCP-1 protein levels, and adhesion of THP-1 cells to endothelial cells. HG-induced MCP-1 mRNA expression and monocyte adhesion were blocked by specific inhibitors of oxidant stress, protein kinase C, ERK1/2, and p38 mitogen-activated protein kinases. These results show for the first time that multiple inflammatory cytokines and chemokines relevant to the pathogenesis of diabetes complications are induced by HG via key signaling pathways.

Activation of Protein Kinase C and Nicotinamide Adenine Dinucleotide Phosphate Oxidase in Leukocytes of Spontaneously Hypertensive Rats

The involvement of oxidative stress in polymorphonuclear leukocytes (PMN) in the pathogenesis of hypertension remains to be elucidated. We analyzed the generation of reactive oxygen species (ROS) by the circulating and peritoneally infiltrating PMN from spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY). Flow cytometric analysis revealed that ROS generation by PMN from SHR was higher than that from WKY before (at 6 weeks of age) and after (at 16 weeks of age) the onset of hypertension. In vivo, ROS generation by PMN from SHR, but not that by PMN from WKY, was significantly suppressed by 10-week treatment with 50 mg/kg/day carvedilol, and this treatment did not affect blood pressure. Western blotting analysis revealed that protein kinase C alpha (PKCalpha), but not PKCbetaI or betaII, was activated more strongly in PMN from SHR than in PMN from WKY. Furthermore, expression of p47phox of nicotinamide adenine dinucleotide phosphate oxidase, but not of p67phox, in PMN from SHR was higher than that in PMN from WKY. These results suggest that ROS generation by PMN is principally enhanced in SHR through activation of PKCalpha and p47phox.