Effects of sulphite supplementation on vascular responsiveness in sulphite oxidase-deficient rats

1. The aim of the present study was to explore the effect of dietary sulphite supplementation on vascular responsiveness in sulphite oxidase (SO)-deficient rats. 2. Male albino rats were divided into four groups, namely control (n = 8), sulphite-treated (n = 8), SO-deficient (n = 8) and sulphite-treated SO-deficient (n = 8) groups. Sulphite oxidase deficiency was induced by administration of a low-molybdenum diet with concurrent addition of 200 p.p.m. tungsten in the form of sodium tungstate in the drinking water for 9 weeks. Sulphite, in the form of sodium metabisulphite (Na(2)O(5)S(2); 25 mg/kg) was given in the drinking water to sulphite-treated and sulphite-treated SO-deficient groups for the last 6 weeks. The vascular responsiveness of isolated aortic rings to acetylcholine (ACh), sodium nitroprusside (SNP) and histamine was investigated in organ baths. 3. The responsiveness of aortic rings to SNP and histamine did not differ significantly between groups. Conversely, there was a significant decrease in ACh-induced relaxation in aortic rings from the sulphite-treated SO-deficient group compared with the control group (pD(2) 6.2 +/- 0.3 and 7.5 +/- 0.1, respectively; P < 0.05). Incubation of aortic rings in the presence of either l-arginine or superoxide dismutase significantly improved the ACh-induced vasorelaxation in sulphite-treated SO-deficient group (pD(2) 7.2 +/- 0.3 and 7.4 +/- 0.3, respectively). 4. The findings of the present study suggest that the increased production of reactive oxygen species and the resultant increment in l-arginine/nitric oxideconsumption may play a role in the reduced endothelium-dependent vasorelaxation in sulphite-treated SO-deficient rats.     

Effect of glucagon-like peptide-1(7-36) and exendin-4 on the vascular reactivity in streptozotocin/nicotinamide-induced diabetic rats

We investigated the vascular effects of glucagon-like peptide-1 (GLP-1) and Exendin-4 in type 2 diabetic rat aortae. Studies were performed in a normal control group (NC) (0.2 ml i.p. saline, n = 10), streptozotocin (STZ)/nicotinamide diabetic control group (DC) (a single dose of 80 mg/kg STZ i.p. injection 15 min after administration of 230 mg/kg nicotinamide i.p.), GLP-1 (GLPC) control group (1 microg/kg twice daily i.p. for 1 month, n = 10), Exendin-4 control group (EXC) (0.1 microg/kg twice daily i.p. for 1 month, n = 10), GLP-1-treated diabetic group (GLPT) (1 microg/kg twice daily i.p. for 1 month, n = 10), and Exendin-4-treated diabetic group (EXT) (0.1 microg/kg twice daily i.p. for 1 month, n = 10). One month of GLP-1 and Exendin-4 treatment significantly decreased the blood glucose levels of diabetic rats (113 +/- 2 mg/dl, p < 0.001, and 117 +/- 1 mg/dl, p < 0.001, respectively versus 181 +/- 9 mg/dl in the DC group). Sensitivity (pD2) and maximum response (% Max. Relax) of acetylcholine-stimulated relaxations in the DC group (pD2: 6.73 +/- 0.12 and 55 +/- 6, respectively) were decreased compared with the non-diabetic NC group (pD2: 7.41 +/- 0.25, p < 0.05, and 87 +/- 4, p < 0.01). Treating diabetic rats with GLP-1, pD2 values and with Exendin-4, Max. Relax %values of aortic strips to acetylcholine returned to near non-diabetic NC values (pD2: 7.47 +/- 0.15, p < 0.05, and 87 +/- 3, p < 0.01, respectively). Maximal contractile responses (Emax) to noradrenaline in aortic strips from the diabetic DC group (341 +/- 27 mg tension/mg wet weight) were significantly decreased compared with the non-diabetic NC (540 +/- 66 mg tension/mg wet weight, p < 0.001) and the GLPT group (490 +/- 25 mg tension/mg wet weight, p < 0.05). There were no significant differences in pD2 values of aortic strips to noradrenaline from all groups. Emax to KCl in aortic strips from the DC group (247 +/- 10 mg tension/mg wet weight, p < 0.01) was significantly decreased compared with non-diabetic NC group (327 +/- 26 mg tension/mg wet weight). Treating diabetic rats with GLP-1 (GLPT), Emax values of aortic strips to KCl returned to near non-diabetic NC values (271 +/- 12 mg tension/mg wet weight). GLP-1 and (partially) Exendin-4 treatment could improve the increased blood glucose level and normalize the altered vascular tone in type 2 diabetic rats.     

Oxidative stress-associated vascular aging is xanthine oxidase-dependent but not NAD(P)H oxidase-dependent

Vascular aging is characterized by endothelial dysfunction that is primarily attributed to increased superoxide production, the exact source of which remains ambiguous. This study compared the NAD(P)H and xanthine oxidase (XO) systems as sources of superoxide and impaired vascular function in aging. Male Sprague Dawley rats, 4-months-old (young) and 18-months-old (Aging), were used. Systolic blood pressure was higher (36 +/- 3%) in the aging group compared with young rats, and this was accompanied by reduced acetylcholine-induced renal vasodilatation. Urinary excretion of nitrite was lower in the aging rats (P < 0.05), and this was associated with reduced nitric oxide synthase (NOS) activity and reduced eNOS and iNOS protein expression in the aorta. Aged rats showed a n approximately twofold increase in free radical generation, as evident by increased plasma 8-isoprostane level, and an approximately fourfold increase in proteinuria compared with the young rats. Vascular NADP(H) oxidase was unchanged between both groups, as was the expression of p67phox or p47phox components of NAD(P)H oxidase. However, XO activity was increased (19 +/- 1%; P < 0.05) as well as XO expression in the aorta of aging rats. These results suggest that increased free radical generation-associated increase in SBP in aging rats is XO but not NAD(P)H oxidase-dependent.     

Inhibition of NAD(P)H oxidase attenuates aggregation of platelets from high-risk cardiac patients with aspirin resistance

Up to one-third of serious vascular events in high-risk patients is attributable to a failure of aspirin (ASA) to suppress platelet aggregation. We hypothesized that inhibition of NAD(P)H oxidase may inhibit aggregation of platelets from ASA-resistant (ASA-R) patients. Thus, platelet-rich plasma was isolated from ASA-sensitive (ASA-S) and ASA-R patients (aspirin resistance was defined as higher than expected aggregation to collagen and epinephrine [> or = 40%] after chronic oral treatment with 100 mg/day ASA). Aggregation to adenosine diphosphate (ADP) (5 and 10 micromol/l), collagen (2 microg/ml) and epinephrine (10 micromol/l) in the absence and presence of the NAD(P)H oxidase inhibitors: diphenylene iodonium (DPI) (1 micromol/l) and apocynin (3 x 10(-4) mol/l) was measured by optical aggregometry. Maximal aggregation of ASA-R platelets to collagen and epinephrine was significantly decreased by DPI and apocynin, whereas they had no effect in ASA-S platelets. Maximal aggregation to ADP was unaffected by NAD(P)H oxidase inhibition in either group. In ASA-R platelets both NADPH-driven O2(.-) production (lucigenin chemiluminescence assay) and expression of gp91phox and p67phox subunits of the NADPH oxidase (Western blotting) tended to increase. Collectively, inhibition of NAD(P)H oxidase effectively suppressed collagen and epinephrine-induced aggregation of platelets from ASA-R patients, which may represent a novel pharmacological target for cardioprotection in high-risk cardiac patients.     

Trichloroethylene decreases heat shock protein 90 interactions with endothelial nitric oxide synthase: implications for endothelial cell proliferation.

Trichloroetheylene (TRI) is an environmental pollutant that has been linked to congenital heart defects (CHD). Endothelial nitric oxide synthase (eNOS) generation of nitric oxide (NO) plays an important role in endothelial cell proliferation, which is considered essential for normal blood vessel growth and development. We hypothesized that TRI alters the balance of NO and superoxide anion (O2-) to impair endothelial cell proliferation. Proliferating endothelial cells were pretreated with TRI (5 microM) and then stimulated with the calcium ionophore, A23187 (5 microM), to determine changes in endothelial cell and eNOS function with respect to NO and O2- generation. Immunoblots of eNOS, phospho-eNOS at serine 1179 (S1179), and the levels of associated heat shock protein 90 (hsp90) were used to define the activation state of eNOS. The effects of TRI (0.05-100 microM) on vascular endothelial growth factor (VEGF, 0.58 nM) induced endothelial cell proliferation were determined from cell counts. TRI decreased A23187-stimulated nitrite + nitrate production from 1.99 +/- 0.90 to 0.89 +/- 0.51 pmol/mg protein (p < 0.05; n = 6). In controls, Lomega-nitroargininemethylester (L-NAME) increased A23187-stimulated O2- production from 0.130 +/- 0.089 to 0.214 +/- 0.071 nmol/min/mg protein (p < 0.05; n = 5). In TRI-treated cultures, however, L-NAME decreased A23187-stimulated O2- production from 0.399 +/- 0.121 to 0.199 +/- 0.055 nmol/min/mg protein (p < 0.05; n = 5). TRI decreased hsp90 associated with eNOS by 46.7% and inhibited VEGF-stimulated endothelial cell proliferation by 12 to 35%. These data show that TRI alters hsp90 interactions with eNOS and induces eNOS to shift from NO to O2- generation. Our findings provide new insight into how TRI alters endothelial and eNOS function to impair VEGF-stimulated endothelial proliferation. Such changes in endothelial function may play an important role in the development of congenital heart defects.     

Contribution of different Nox homologues to cardiac remodeling in two-kidney two-clip renovascular hypertensive rats: effect of valsartan.

Growing evidences have shown that hypertension, cardiac hypertrophy and fibrosis were associated with an overactivity of NAD(P)H oxidase. It is unknown, however, which isoform of NAD(P)H oxidase yields O(2)*(-) formation in heart and aorta in two-kidney, two-clip (2K2C) hypertensive rats in vivo and thus is responsible for the development of cardiac remodeling. We examined the pathological change of NAD(P)H oxidase homologues and tested the effect of valsartan on the cardiac remodeling in 2K2C renovascular hypertensive rats. Four weeks after male Sprague-Dawley rats accepted 2K2C or sham operation, 2K2C hypertensive (>160 mmHg) rats were divided into vehicle-treated (2K2C) and valsartan (30 mg kg(-1) per day, for 6 weeks)-treated (2K2C+Val) groups, which were compared with sham-operated controls (Sham). At week 10, 2K2C hypertensive rats showed increased serum level of angiotensin II (Ang II), MDA and blood pressure (BP), obvious cardiac hypertrophy and fibrosis, increased O(2)*(-) production and NAD(P)H oxidase activity and expression in aorta and heart. The heart in 2K2C hypertensive rats preferred to use NADH as substrate while the aorta used both NADH and NADPH. Valsartan treatment decreased BP, ameliorated cardiac hypertrophy and fibrosis, decreased O(2)*(-) production and NAD(P)H oxidase activity in aorta and heart. Nox2 and Nox4 protein expression increased in heart, while Nox1 and Nox4 increased in aorta in 2K2C hypertensive rats, which were all normalized after valsartan treatment. In conclusion, these data indicate that different Nox expression might account for substrate preference and the formation of O(2)*(-) by NAD(P)H oxidase resulting from elevated Ang II in the 2K2C model contributes to the development of renovascular hypertension and subsequent cardiac remodeling.     

Characterization of changes in mechanical responses to histamine in omental resistance arteries in pre-eclampsia

Changes in the effect of histamine on the smooth muscle of resistance arteries in pre-eclampsia were investigated by measuring isometric contractions in endothelium-denuded strips of omental resistance arteries from pre-eclamptic and normotensive pregnant women (pregnancy-term matched). Histamine (0.03 -1 microM) caused concentration-dependent relaxation of the contraction induced by 9, 11-epithio-11,12-methano-thromboxane A(2) (STA(2)) in strips from both groups. Sensitivity (for pre-eclampsia: pD(2)=6.66+/-0.04, n=5 and for normotensive pregnant women: pD(2)=7.07+/-0.03, n=10, P<0.001) was lower and the maximum response (90.6+/-0.6% vs 95.5+/-1.1%, P<0.05) was smaller in strips from pre-eclamptic women. Although 8-bromoadenosine-3', 5'-cyclic monophosphorothioate (Sp-isomer: Sp-8-Br-cAMPS, 0.1 - 0.3 mM), a phosphodiesterase (PDE)-resistant activator of adenosine-3',5'-cyclic monophosphate (cyclic AMP)-dependent protein kinase, concentration-dependently attenuated the contraction induced by STA(2) in strips from both groups, the sensitivity (for pre-eclampsia: pD(2)=3.68+/-0.04, n=5 and for normotensive pregnant women: 3.94+/-0.09, n=7, P:=0.02) was lower and the maximum response (64.2+/-2.4% vs 74.9+/-4.4%, P:<0.05) was smaller in pre-eclampsia. In beta-escin-skinned strips, the pD(2) value for the contraction-inducing effect of Ca(2+) did not differ significantly between the two groups (for pre-eclampsia, n=6; for normotensive pregnant women, n=6). Thus, omental resistance arteries from human subjects with pre-eclampsia showed (i) a weaker H(2)-receptor-mediated relaxation to histamine and (ii) a weaker cyclic AMP-analogue-induced relaxation, suggesting that the reduced action of histamine may be partly due to a decreased effect of cyclic AMP.     

Effect of rosuvastatin treatment on plasma visfatin levels in patients with primary hyperlipidemia

Visfatin is a novel adipokine involved in the process of atherosclerosis. We assessed the effect of rosuvastatin on plasma visfatin levels in patients with primary hyperlipidemia. Eighty hyperlipidemic patients without evidence of cardiovascular disease were randomized to receive either rosuvastatin 10 mg/day or therapeutic lifestyle changes intervention. Plasma visfatin levels were determined at baseline and after 12-weeks post-randomization. Rosuvastatin induced a significant decrease in plasma visfatin levels (17.1+/-2.1 versus 15.5+/-2.0 ng/ml, P=0.03). This effect correlated with baseline visfatin levels (r=0.51, P<0.01) and was independent of any lipid-lowering actions of rosuvastatin.     

Genetic polymorphisms of oxidative and antioxidant enzymes and arsenic-related hypertension

The association of 4 genetic polymorphisms, NAD(P)H oxidase, manganesesuperoxide dismutase (MnSOD), catalase, and endothelial nitric oxide synthase (e-NOS), was assessed with arsenic-related hypertension risk among 79 hypertensive cases and 213 controls in an arseniasis-hyperendemic area of Taiwan. Overall, MnSOD polymorphism significantly increased the risk of hypertension regardless of arsenic exposure. NADPH oxidase and eNOS polymorphisms were significantly associated with hypertension risk in the high arsenic exposure group; however, catalase polymorphism was not associated with hypertension. Groups were further stratified by triglyceride levels to evaluate whether the cumulative arsenic exposure combined the three polymorphisms together. The adjusted adds ratios (ORs) of at least two risk factors of the cumulative arsenic exposure and MnSOD, NADPH oxidase, and eNOS three-polymorphism combination versus any one risk factor of them were 0.8 (95% CI 0.3-2.3) for individuals with low triglyceride levels (<110 mg/dl) and 2.5 (95% CI 1.0-6.01) for high-triglyceride groups (>110 mg/dl), respectively. These results suggested that the NADPH oxidase, MnSOD, and e-NOS polymorphisms, but not catalase, might play a role in the development of arsenic-related hypertension, especially in subjects with high triglyceride levels.     

Higher activity of polymorphic NAD(P)H:quinone oxidoreductase in liver cytosols from blacks compared to whites

In human liver, the two-electron reduction of quinone compounds, such as menadione is catalyzed by cytosolic carbonyl reductase (CBR) and NAD(P)H:quinone oxidoreductase (NQO1) activities. We assessed the relative contributions of CBR and NQO1 activities to the total menadione reducing capacity in liver cytosols from black (n=31) and white donors (n=63). Maximal menadione reductase activities did not differ between black (13.0+/-5.0 nmol/min mg), and white donors (11.4+/-6.6 nmol/min mg; p=0.208). In addition, both groups presented similar levels of CBR activities (CBR(blacks)=10.9+/-4.1 nmol/min mg) versus CBR(whites)=10.5+/-5.8 nmol/min mg; p=0.708). In contrast, blacks showed higher NQO1 activities (two-fold) than whites (NQO1(blacks)=2.1+/-3.0 nmol/min mg versus NQO1(whites)=0.9+/-1.6 nmol/min mg, p<0.01). To further explore this disparity, we tested whether NQO1 activity was associated with the common NQO1(*)2 genetic polymorphism by using paired DNA samples for genotyping. Cytosolic NQO1 activities differed significantly by NQO1 genotype status in whites (NQO1(whites[NQO1*1/*1])=1.3+/-1.7 nmol/min mg versus NQO1(whites[NQO1*1/*2+NQO1*2/*2])=0.5+/-0.7 nmol/min mg, p<0.01), but not in blacks (NQO1(blacks[NQO1*1/*1])=2.6+/-3.4 nmol/min mg versus NQO1(blacks[NQO1*1/*2])=1.1+/-1.2 nmol/min mg, p=0.134). Our findings pinpoint the presence of significant interethnic differences in polymorphic hepatic NQO1 activity.     

Up-regulation of Akt and eNOS induces vascular smooth muscle cell differentiation in hypertension in vivo

Recent studies have shown that angiotensin II type 1 (AT1) receptor-mediated Akt activation induces vascular smooth muscle cell (VSMC) dedifferentiation in vitro. However, the critical signal transductions affecting the VSMC phenotype remain unclear in vivo. We examined whether signal transduction through AT1 receptor-mediated reactive oxygen species (ROS) could regulate the VSMC phenotype in stroke-prone spontaneously hypertensive rats (SHRSPs). Male SHRSPs were randomized and treated for 6 weeks with a vehicle, an ACE inhibitor cilazapril, or an AT1 receptor antagonist E4177. The 2 drugs showed equipotent effects on the blood pressure, aortic morphology, and collagen deposition. Both drugs also significantly reduced aortic NAD(P)H oxidase activity and p38MAPK and ERK expression, whereas p-Akt, eNOS, and SM2 were significantly increased in SHRSP aortas. Furthermore, E4177 was more effective than cilazapril at inducing VSMC differentiation by reducing NAD(P)H oxidase activity, and up-regulating p-Akt, eNOS, and SM2. Thus, an ACE inhibitor and an AT1 receptor antagonist inhibited VSMC dedifferentiation through inhibition of NAD(P)H oxidase activity and up-regulation of eNOS and Akt in SHRSP aortas, suggesting that in contrast to the in vitro experiments, AT1 receptor-mediated NAD(P)H oxidase-generated ROS, eNOS, and Akt might be crucial determinants for the VSMC phenotype in hypertension in vivo.     

Simvastatin preserves cardiac function in genetically determined cardiomyopathy

Endothelial dysfunction characterizes heart failure (HF). Simvastatin (Sim) increases endothelial nitric oxide (NO) independent of lipid-lowering. We evaluated the effect of Sim on cardiac function, apoptosis, and NO availability in HF. Five-month-old cardiomyopathic (CM) hamsters were divided into 2 groups: Sim (20 mg/kg, 6 weeks, n = 6) and Untreated (n = 6). Age-matched normal hamsters served as controls (n = 6). Serial echocardiograms were performed to measure LV function. Myocardial apoptosis, eNOS, and capillary density were measured at 6 weeks. Cardiomyopathic hamsters had lower LV shortening fraction (SF) compared with controls (17 +/- 3% vs 59 +/- 2%), higher LV end-diastolic volume (30 +/- 3 vs 6 +/- 2 mL/m2), and lower LV mass/volume ratio (0.5 +/- 0.04 vs 0.72 +/- 0.02 mg/ml, P < 0.001). During follow-up, SF decreased (9 +/- 2%) and LV volume increased (38 +/- 1 mL/m2) in untreated hamsters (P < 0.05 from baseline) but did not change significantly in the Sim group (P < 0.05 vs untreated). Myocardial caspase-3 activity was higher and apoptotic nuclear density was lower in Sim compared with untreated CM hamsters (0.072 +/- 0.02% vs 0.107 +/- 0.03%, P < 0.01). Myocardial capillary density was highest in the Sim group (P < 0.05). eNOS expression was not different between groups. Sim retards the progression of HF in CM hamsters. This may be related to an increase in coronary microvasculature, increase in NO availability, and decreased apoptosis.     

Effect of manidipine on gene expression and protein level of oxidative stress-related proteins: p22phox and HO-1: relevance for antihypertensive and anti-remodeling effects

Oxidative stress (OxSt) is a major damaging factor in arterial hypertension and its long-term complications. This is why considerable attention is paid to the possible effects of antihypertensive drugs on OxSt. Manidipine is a dihydropiridine calcium channel blocker with reported nephroprotective activities, but no information is available on its effect on OxSt and related mechanisms.This study assessed the effect of manidipine on normal subjects' monocyte gene and protein expression of OxSt-related proteins such as p22(phox), a NAD(P)H oxidase system subunit, critical in generating O2-, and heme oxygenase-1 (HO-1), induced by and protective from OxSt, and compared manidipine with the ACE inhibitor captopril and the calcium channel blocker nifedipine, in the presence and absence of sodium arsenite (NaAsO2) as an inducer of OxSt.Co-incubation of manidipine with NaAsO2 dose-dependently decreased p22(phox) mRNA production from basal: 0.87 +/- 0.1 d.u., 0.69 +/- 0.06 and 0.66 +/- 0.09 at 100, 300 and 500 nM respectively versus 0.99 +/- 0.2, P < 0.04, while HO-1 mRNA production was increased by the same concentrations of the drug: 0.87 +/- 0.1 d.u., 0.92 +/- 0.1, 0.98 +/- 0.1 respectively versus 0.63 +/- 0.07; P < 0.03. Monocyte p22(phox) mRNA production was reduced both by manidipine and captopril: 0.48 +/- 0.04 d.u. and 0.43 +/- 0.08, respectively versus 0.58 +/- 0.07, P < 0.006, while no changes were induced by nifedipine (0.61 +/- 0.07, P = ns). Manidipine increased monocyte HO-1 mRNA production (1.6 +/- 0.4 versus 1.2 +/- 0.4, P < 0.008), while nifedipine and captopril showed no effect (1.2 +/- 0.3 and 1.1 +/- 0.3, respectively). The effects of M on p22(phox) and HO-1 gene expression in the presence of OxSt were also paralleled by the same effects at protein level. In conclusion, manidipine decreases p22(phox) and increases HO-1 mRNA production and protein level. The manidipine-induced increase of HO-1 gene and protein expression seems to be a peculiar effect of this drug since it is not observed with captopril and nifedipine. This effect, together with the reduction of p22(phox) mRNA production, could play a role in its protective mechanism against OxSt.     

Sirolimus, but not the structurally related RAD (everolimus), enhances the negative effects of cyclosporine on mitochondrial metabolism in the rat brain.

Clinical studies have shown enhancement of cyclosporine toxicity when co-administered with the immunosuppressant sirolimus. We evaluated the biochemical mechanisms underlying the sirolimus/cyclosporine interaction on rat brain metabolism using magnetic resonance spectroscopy (MRS) and compared the effects of sirolimus with those of the structurally related RAD. Two-week-old rats (25 g) were allocated to the following treatment groups (all n=6): I. control, II. cyclosporine (10 mg kg(-1) d(-1)), III. sirolimus (3 mg kg(-1) d(-1)), IV. RAD (3 mg kg(-1) d(-1)), V. cyclosporine+sirolimus and VI. cyclosporine+RAD. Drugs were administered by oral gavage for 6 days. Twelve hours after the last dose, metabolic changes were assessed in brain tissue extracts using multinuclear MRS. Cyclosporine significantly inhibited mitochondrial glucose metabolism (glutamate: 78+/-6% of control; GABA: 67+/-12%; NAD(+): 76+/-3%; P<0.05), but increased lactate production. Sirolimus and RAD inhibited cytosolic glucose metabolism via lactate production (sirolimus: 81+/-3% of control, RAD: 69+/-2%; P<0.02). Sirolimus enhanced cyclosporine-induced inhibition of mitochondrial glucose metabolism (glutamate: 60+/-4%; GABA: 59+/-8%; NAD(+): 45+/-5%; P<0.02 versus cyclosporine alone). Lactate production was significantly reduced. In contrast, RAD antagonized the effects of cyclosporine (glutamate, GABA, and NAD(+), not significantly different from controls). The results can partially be explained by pharmacokinetic interactions: co-administration increased the distribution of cyclosporine and sirolimus into brain tissue, while co-administration with RAD decreased cyclosporine brain tissue concentrations. In addition RAD, but not sirolimus, distributed into brain mitochondria. The combination of cyclosporine/RAD compares favourably to cyclosporine/sirolimus in regards to their effects on brain high-energy metabolism and tissue distribution in the rat.     

Simvastatin acts synergistically with ACE inhibitors or amlodipine to decrease oxygen consumption in rat hearts

Statin drugs, which are cholesterol-lowering agents, can upregulate endothelial nitric oxide synthase (eNOS) in isolated endothelial cells independent of lipid lowering. We investigated the effect of short-term simvastatin administration on NO-mediated regulation of myocardial oxygen consumption (MV(O2)) in tissue from rat hearts. Male Wistar rats were divided into (a) control group (n = 14), and (b) simvastatin group (n = 10, 20 mg/kg/day by oral gavage). After 2 weeks, left ventricular myocardium was isolated to measure MV(O2) using a Clark-type oxygen electrode, and aortic plasma nitrates and nitrites (NOx) were measured. Baseline plasma NOx levels (19+/-2.6 in control vs. 20+/-2.5 microM/L in simvastatin) and baseline MV(O2) (288+/-23 in control vs. 252+/-11 nmol/g/min; p = 0.09) were not significantly different between the two groups. NO-dependent regulation of MV(O2) in response to bradykinin, ramipril, or amlodipine was augmented in simvastatin rats compared with controls (p < 0.05). Decrease of MV(O2) from baseline in response to highest doses in control versus simvastatin groups was as follows-bradykinin, -28+/-5% vs. -44+/-6%; ramipril, -35+/-5% vs. -50+/-8%; and amlodipine, -32+/-9% vs. -42+/-3%. Response to highest dose of NO donor S-nitroso N-acetyl penicillamine (SNAP) was not significantly different in the two groups (-55+/-5% vs. -52+/-7%). Treatment with Nw-nitro-L-arginine methyl ester, inhibitor of NO synthesis, attenuated the effect of bradykinin, ramipril, and amlodipine on MV(O2) (p < 0.05). In conclusion, short-term administration of simvastatin in rats potentiates the ability of angiotensin-converting enzyme (ACE) inhibitors and amlodipine to cause NO-mediated regulation of MV(O2).     

Interaction between osmotic and oxidative stress in diabetic precataractous lens: studies with a sorbitol dehydrogenase inhibitor

Both sorbitol accumulation-linked osmotic stress and "pseudohypoxia" [increase in NADH/NAD+, similar to that in hypoxic tissues, and attributed to increased sorbitol dehydrogenase (1-iditol:NAD+ 5-oxidoreductase; EC 1.1.1.14; SDH) activity] have been invoked among the mechanisms underlying oxidative injury in target tissues for diabetic complications. We used the specific SDH inhibitor SDI-157 [2-methyl-4(4-N,N-dimethylaminosulfonyl-1-piperazino)pyrimid ine] to evaluate the role of osmotic stress versus "pseudohypoxia" in oxidative stress occurring in diabetic precataractous lens. Control and diabetic rats were treated with or without SDI-157 (100 mg/kg/day for 3 weeks). Lens malondialdehyde (MDA) plus 4-hydroxyalkenals (4-HA), MDA, GSH, and ascorbate levels, as well as the GSSG/GSH ratios, were similar in SDI-treated and untreated control rats, thus indicating that SDI-157 was not a prooxidant. Intralenticular osmotic stress, manifested by sorbitol levels, was more severe in SDI-treated diabetic rats (38.2+/-6.8 vs 21.2+/-3.5 micromol/g in untreated diabetic and 0.758+/-0.222 micromol/g in control rats, P<0.01 for both), while the decrease in the free cytosolic NAD+/NADH ratio was partially prevented (120+/-16 vs 88+/-11 in untreated diabetic rats and 143+/-13 in controls, P<0.01 for both). GSH and ascorbate levels were decreased, while MDA plus 4-HA and MDA levels were increased in diabetic rats versus controls; both antioxidant depletion and lipid aldehyde accumulation were exacerbated by SDI treatment. Superoxide dismutase (superoxide:superoxide oxidoreductase; EC 1.15.1.1), GSSG reductase (NAD[P]H:oxidized-glutathione oxidoreductase; EC 1.6.4.2), GSH transferase (glutathione S-transferase; EC 2.5.1.18), GSH peroxidase (glutathione:hydrogen-peroxide oxidoreductase; EC 1.11.1.9), and cytoplasmic NADH oxidase activities were increased in diabetic rats versus controls, and all the enzymes but GSH peroxidase were up-regulated further by SDI. In conclusion, sorbitol accumulation and osmotic stress generated oxidative stress in diabetic lens, whereas the contribution of "pseudohypoxia" was minor. SDIs provide a valuable tool for exploring mechanisms of oxidative injury in sites of diabetic complications.