A Decreased Response to Resistin in Mononuclear Leukocytes Contributes to Oxidative Stress in Nonalcoholic Fatty Liver Disease.

BACKGROUND: Deregulation of immune response and oxidative stress contribute to nonalcoholic fatty liver disease (NAFLD) pathogenesis. Resistin is a physiological modulator of inflammation and redox homeostasis of different cell types. Increased resistin serum concentration and the direct association between resistin hepatic expression and NAFLD severity suggest that resistin participates in NAFLD pathogenesis. AIMS: To evaluate resistin-induced regulation of redox homeostasis in mononuclear leukocytes from NAFLD patients and controls. METHODS: We evaluated basal and resistin-mediated modulation of reactive oxygen species (ROS) and glutathione content by flow cytometry, and antioxidant enzyme activities by spectrophotometry. RESULTS: Peripheral blood mononuclear cells (PBMC) from NAFLD patients showed higher ROS content and glutathione peroxidase activity and lower glutathione content, superoxide dismutase and glutathione reductase activities than control PBMC. Resistin decreased ROS levels and superoxide dismutase activity and increased glutathione reductase and catalase activities in PBMC from controls but not from patients. Resistin decreased glutathione content in PBMC from control and NAFLD patients, with greater effect on patient cells. Basal and resistin-modulated ROS levels were directly associated with obesity-related risk factors for NAFLD. Hepatic myeloid cells and T-lymphocytes from NAFLD patients showed higher basal ROS content than cells from controls. Resistin decreased ROS levels in hepatic T-lymphocytes from controls but not from patients. CONCLUSIONS: Resistin regulates redox homeostasis in mononuclear leukocytes. A decreased response to resistin in leukocytes from NAFLD patients is associated with an impaired redox homeostasis.

Acute hypobaric hypoxia and cardiac energetic response in prepubertal rats: Role of nitric oxide.

NEW FINDINGS: What is the central question of this study? In adult rat hearts, exposure to hypobaric hypoxia increases tolerance to hypoxia-reoxygenation, termed endogenous cardioprotection. The mechanism involves the nitric oxide system and modulation of mitochondrial oxygen consumption. What is the cardiac energetic response in prepubertal rats exposed to hypobaric hypoxia? What is the main finding and its importance? Prepubertal rats, unlike adult rats, did not increase tolerance to hypoxia-reoxygenation in response acute exposure to hypobaric hypoxia, which impaired cardiac contractile economy. This finding could be related to a failure to increase nitric oxide synthase expression, hence modulation of mitochondrial oxygen consumption and ATP production. ABSTRACT: Studies in our laboratory showed that exposure of rats to hypobaric hypoxia (HH) increased the tolerance of the heart to hypoxia-reoxygenation (H/R), involving mitochondrial and cytosolic nitric oxide synthase (NOS) systems. The objective of the present study was to evaluate how the degree of somatic maturation could alter this healthy response. Prepubertal male rats were exposed for 48 h to a simulated altitude of 4400 m in a hypobaric chamber. The mechanical energetic activity in perfused hearts and the contractile functional capacity of NOS in isolated left ventricular papillary muscles were evaluated during H/R. Cytosolic nitric oxide (NO), production of nitrites/nitrates (Nx), expression of NOS isoforms, mitochondrial O2 consumption and ATP production were also evaluated. The left ventricular pressure during H/R was not improved by HH. However, the energetic activity was increased. Thus, the contractile economy (left ventricular pressure/energetic activity) decreased in HH. Nitric oxide did not modify papillary muscle contractility after H/R. Cytosolic p-eNOS-Ser1177 and inducible NOS expression were decreased by HH, but no changes were observed in NO production. Interestingly, HH increased Nx levels, but O2  consumption and ATP production in mitochondria were not affected by HH. Prepubertal rats exposed to HH preserved cardiac contractile function, but with a high energetic cost, modifying contractile economy. Although this could be related to the decreased NOS expression detected, cytosolic NO production was preserved, maybe through the Nx metabolic pathway, without modification of mitochondrial ATP production and O2  consumption. In this scenario, the treatment was unable to increase tolerance to H/R as observed in adult animals.

(-)-Epicatechin protects thoracic aortic perivascular adipose tissue from whitening in high-fat fed mice.

High adipose tissue (AT) accumulation in the body increases the risk for many metabolic and chronic diseases. This work investigated the capacity of the flavonoid (-)-epicatechin to prevent undesirable modifications of AT in mice fed a high-fat diet. Studies were focused on thoracic aorta perivascular AT (taPVAT), which is involved in the control of blood vessel tone, among other functions. Male C57BL/6J mice were fed for 15 weeks a high-fat diet with or without added (-)-epicatechin (20 mg per kg body weight per d). In high-fat diet fed mice, (-)-epicatechin supplementation: (i) prevented the expansion of taPVAT, (ii) attenuated the whitening of taPVAT (according to the adipocyte morphology, diameter, and uncoupling-protein 1 (UCP-1) levels) and (iii) blunted the increase in plasma glucose and cholesterol. The observed taPVAT modifications were not associated with alterations in the aorta wall thickness, aorta tumor necrosis factor-alpha (TNF-α) and NADPH-oxidase 2 (NOX2) expression, and endothelial nitric oxide synthase (eNOS) phosphorylation levels. In summary, our results indicate (-)-epicatechin as a relevant bioactive protecting from the slow and silent development of metabolic and chronic diseases as they are associated with excessive fat intake.

Effects of quercetin on heart nitric oxide metabolism in l-NAME treated rats.

This study investigated the effects of a quercetin-supplemented diet on the biochemical changes installed in the heart of NO-deficient rats in terms of oxidants production and NO bioavailability determinants. Sprague-Dawley rats were subjected to Nω-nitro-l-arginine methyl ester (l-NAME) treatment (360 mg/L l-NAME in the drinking water, 4 d) with or without supplementation with quercetin (4 g/kg diet). l-NAME administration led to increased blood pressure (BP) (30%), decreased nitric oxide synthase (NOS) activity (50%), and increases in NADPH oxidase (NOX)-dependent superoxide anion production (60%) and p47phox protein level (65%). The co-administration of quercetin prevented the increase in BP and the activation of NOX but did not modify the decrease in NOS activity caused by l-NAME. In addition, quercetin affected oxidative stress parameters as glutathione oxidation, and the activities of oxidant detoxifying enzymes superoxide dismutase, glutathione peroxidase, and catalase. Thus, quercetin administration counteracts l-NAME effects on NO bioavailability determinants in vivo, essentially through controlling NOX-mediated superoxide anion production.

Cardioprotection after acute exposure to simulated high altitude in rats. Role of nitric oxide.

AIM: In previous studies, upregulation of NOS during acclimatization of rats to sustained hypobaric hypoxia was associated to cardioprotection, evaluated as an increased tolerance of myocardium to hypoxia/reoxygenation. The objective of the present work was to investigate the effect of acute hypobaric hypoxia and the role of endogenous NO concerning cardiac tolerance to hypoxia/reoxygenation under ß-adrenergic stimulation. METHODS: Rats were submitted to 58.7 kPa in a hypopressure chamber for 48 h whereas their normoxic controls remained at 101.3 kPa. By adding NOS substrate L-arg, or blocker L-NNA, isometric mechanical activity of papillary muscles isolated from left ventricle was evaluated at maximal or minimal production of NO, respectively, under ß-adrenergic stimulation by isoproterenol, followed by 60/30 min of hypoxia/reoxygenation. Activities of NOS and cytochrome oxidase were evaluated by spectrophotometric methods and expression of HIF1-α and NOS isoforms by western blot. Eosin and hematoxiline staining were used for histological studies. RESULTS: Cytosolic expression of HIF1-α, nNOS and eNOS, and NO production were higher in left ventricle of hypoxic rats. Mitochondrial cytochrome oxidase activity was decreased by hypobaric hypoxia and this effect was reversed by L-NNA. After H/R, recovery of developed tension in papillary muscles from normoxic rats was 51-60% (regardless NO modulation) while in hypobaric hypoxia was 70% ±â€¯3 (L-arg) and 54% ±â€¯1 (L-NNA). Other mechanical parameters showed similar results. Preserved histological architecture was observed only in L-arg papillary muscles of hypoxic rats. CONCLUSION: Exposure of rats to hypobaric hypoxia for only 2 days increased NO synthesis leading to cardioprotection.

Modifications in nitric oxide and superoxide anion metabolism induced by fructose overload in rat heart are prevented by (-)-epicatechin.

Fructose overload promotes functional and metabolic derangements in humans and in animal experimental models. Evidence suggests that dietary flavonoids have the ability to prevent/attenuate the development of metabolic diseases. In this work we investigated the effects of (-)-epicatechin on the modifications induced by fructose overload in the rat heart in terms of nitric oxide and superoxide metabolism. Male Sprague Dawley rats received 10% (w/v) fructose in the drinking water for 8 weeks, with or without (-)-epicatechin (20 mg per kg body weight per day) in the rat chow diet. These conditions of fructose overload did not lead to overt manifestations of heart hypertrophy or tissue remodeling. However, biochemical and molecular changes were observed and could represent the onset of functional alterations. (-)-Epicatechin prevented a compromised NO bioavailability and the development of oxidative stress produced by fructose overload essentially acting on superoxide anion metabolism. In this line, the increase in superoxide anion production, the overexpression of NOX2 subunit p47phox and of NOX4, the decrease in superoxide dismutase activity, and the higher oxidized/reduced glutathione ratio installed by fructose overload were absent in the rats receiving (-)-epicatechin. These results support the hypothesis that diets rich in (-)-epicatechin could prevent the onset and progression of heart dysfunctions associated with metabolic alterations.

Bioactive constituents in liposomes incorporated in orange juice as new functional food: thermal stability, rheological and organoleptic properties.

Liposomes were developed with bioactive constituents (omega-3, omega-6, tocopherol) incorporated in acid food. They were made of soy phosphatidylcholine (SPC) allowing the encapsulation of antioxidant vitamin C (VC) and tocopherol. Stearic acid (SA) or calcium stearate (CaS) was added as a bilayer stabilizer. The structural and oxidative stability of the liposomes were studied considering the heat effect of pasteurization. Size was analyzed by light scattering; shape and structure were studied by optical and transmission electron microscopy, respectively. Membrane packing was studied with merocyanine 540. Surface charge and oxidative stability were analyzed by zeta potential and ORAC method, respectively. The liposomes showed significant stability in all of the parameters mentioned above and an important protective effect over thermolabile VC. To confirm their applicability in food, the rheological behavior and a sensory evaluation of liposomes with vitamin C and bioactive constituents were studied. The sensory evaluation of liposomes in orange juice was performed by the overall acceptability and triangular tests with 40 and 78 potential consumers, respectively. The incorporation of all liposomal formulation did not change the acceptability of orange juice. Noteworthy, SPC and SPC:SA systems had rheological behavior similar to a Newtonian fluid whereas that SPC:CaS presented a pseudoplastic one, both considered excellent for larger scale production. From all the obtained results, we can conclude that these liposomal formulations are suitable for food industry applications, incorporating bioactive constituents and generating functional orange juice that conserves its bioactivity after pasteurization.

(-)-Epicatechin prevents alterations in the metabolism of superoxide anion and nitric oxide in the hearts of L-NAME-treated rats.

The aim of this work was to evaluate the effects of (-)-epicatechin administration in the heart of a rat model with reduced NO production that follows a short-term treatment with L-NAME. Sprague-Dawley rats were treated for 4 d with L-NAME in the absence or presence of (-)-epicatechin in the diet. The redox status in cardiac tissue was improved by (-)-epicatechin administration. L-NAME treatment induced a decrease in NO synthase activity (-62%, p<0.05) and an increase in NADPH-dependent superoxide anion production (+300%, p<0.05) that were totally prevented by (-)-epicatechin administration. These effects of (-)-epicatechin were associated with a higher endothelial NO synthase phosphorylation at an activation site and a reduced expression of the regulatory subunit, p47(phox), suggesting the involvement of posttranslational mechanisms in (-)-epicatechin action. Thus, the (-)-epicatechin treatment would restore NO steady state levels in vivo through effects on both, its synthesis and degradation via the reaction with superoxide anion. The fact that (-)-epicatechin is commonly present in human diet makes this compound a reasonable explanation for the positive cardiovascular effects of a high consumption of fruits and vegetables.

Flavonoids and metabolic syndrome.

Increasing evidence indicates that several mechanisms, associated or not with antioxidant actions, are involved in the effects of flavonoids on health. Flavonoid-rich beverages, foods, and extracts, as well as pure flavonoids are studied for the prevention and/or amelioration of metabolic syndrome (MS) and MS-associated diseases. We summarize evidence linking flavonoid consumption with the risk factors defining MS: obesity, hypertriglyceridemia, hypercholesterolemia, hypertension, and insulin resistance. Nevertheless, a number of molecular mechanisms have been identified; the effects of flavonoids modifying major endpoints of MS are still inconclusive. These difficulties are explained by the complex relationships among the risk factors defining MS, the multiple biological targets controlling these risk factors, and the high number of flavonoids (including their metabolites) present in the diet and potentially responsible for the in vivo effects. Consequently, extensive basic and clinical research is warranted to assess the final relevance of flavonoids for MS.

Cocoa flavanols: effects on vascular nitric oxide and blood pressure.

Diets rich in fruits and vegetables have been associated with benefits for human health. Those effects have been partially ascribed to their content in flavonoids, compounds that are present in many edible plants and its derived foods. In humans, a significant number of studies has been developed analyzing the effect of foods and beverages rich in flavonoids on the presence and progression of risk factors associated to cardiovascular diseases, including hypertension. Cocoa derived products, rich in flavanols, have been thoroughly studied and demonstrated to be efficient improving endothelial function and decreasing blood pressure in humans and animals. However, the final chemical species and the mechanism/s responsible for these effects have not been completely defined. In this paper we present data supporting the hypothesis that flavanols could define superoxide anion production and then, establish optimal nitric oxide levels and blood pressure.

Effects of heme oxygenase isozymes on Leydig cells steroidogenesis.

In the present study, we demonstrate the expression of heme oxygenase (HO) isozymes, HO-1 and HO-2 (listed as HMOX1 and HMOX2 in the MGI Database), in MA-10 Leydig tumor cells and its effect on steroidogenesis. The well-known HO inducer, hemin, increased both HO-1 and HO-2 protein levels and HO-specific activity. Induction of HO by hemin inhibited basal, hCG-, and dibutyryl cAMP (db-cAMP)-induced steroidogenesis in a reversible way. When we studied the effect of HO isozymes along the steroid synthesis, we found that steroidogenic acute regulatory protein levels were decreased, and the conversion of cholesterol to pregnenolone was inhibited by hemin treatment, with no changes in the content of cholesterol side-chain cleavage enzyme (P450scc). hCG and db-cAMP also stimulated the expression of HO-1 and HO-2, and HO enzymatic activity in MA-10 cells. Basal and hCG-stimulated testosterone synthesis was also inhibited by hemin in rat normal Leydig cells. Taken together, these results suggest that: i) at least one of HO products (presumably carbon monoxide) inhibits cholesterol transport to the inner mitochondrial membrane and Leydig cell steroidogenesis by binding to the heme group of the cytochrome P450 enzymes, in a similar way as we described for nitric oxide, and ii) hCG stimulation results in the induction of an antioxidant enzymatic system (HO) acting as a cytoprotective mechanism in Leydig cells, as already demonstrated in the adrenal gland.

Cardiac mitochondrial function and tissue remodelling are improved by a non-antihypertensive dose of enalapril in spontaneously hypertensive rats.

Renal and cardiac benefits of renin-angiotensin system inhibition exceed blood pressure (BP) reduction and seem to involve mitochondrial function. It has been shown that RAS inhibition prevented mitochondrial dysfunction in spontaneously hypertensive rats (SHR) kidneys. Here, it is investigated whether a non-antihypertensive enalapril dose protects cardiac tissue and mitochondria function. Three-month-old SHR received water containing enalapril (10 mg/kg/day, SHR+Enal) or no additions (SHR-C) for 5 months. Wistar-Kyoto rats (WKY) were normotensive controls. At month 5, BP was similar in SHR+Enal and SHR-C. In SHR+Enal and WKY, heart weight and myocardial fibrosis were lower than in SHR-C. Matrix metalloprotease-2 activity was lower in SHR+Enal with respect to SHR-C and WKY. In SHR+Enal and WKY, NADH/cytochrome c oxidoreductase activity, eNOS protein and activity and mtNOS activity were higher and Mn-SOD activity was lower than in SHR-C. In summary, enalapril at a non-antihypertensive dose prevented cardiac hypertrophy and modifies parameters of cardiac mitochondrial dysfunction in SHR.

Involvement of nitric oxide synthase in the mechanism of histamine-induced inhibition of Leydig cell steroidogenesis via histamine receptor subtypes in Sprague-Dawley rats.

This study was conducted to shed light on the so far unexplored intracellular mechanisms underlying negative modulation of Leydig cell steroidogenesis by histamine (HA). Using the MA-10 cell line and highly purified rat Leydig cells as experimental models, we examined the effect of the amine on biochemical steps known to be modulated by HA or involved in LH/hCG action. In agreement with previous findings, HA at 10 microM showed a potent inhibitory effect on hCG-stimulated steroid synthesis, regardless of the gonadotropin concentration used. Moreover, HA decreased not only LH/hCG-induced cAMP production but also steroid synthesis stimulated by the permeable cAMP analog dibutyryl cAMP (db-cAMP). Considering the post-cAMP sites of HA action, it is shown herein that HA markedly inhibited db-cAMP-stimulated steroidogenic acute regulatory (STAR) protein expression, as well as steps catalyzed by P450-dependent enzymes, mainly the conversion of cholesterol to pregnenolone by cholesterol side-chain cleavage enzyme (CYP11A). The antisteroidogenic action of HA was blocked by addition of the phospholipase C (PLC) inhibitor U73122, and HA significantly augmented inositol triphosphate (IP3) production, suggesting a major role for the PLC/IP3 pathway in HA-induced inhibition of Leydig cell function. Finally, HA increased nitric oxide synthase (NOS) activity, and the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) markedly attenuated the effect of the amine on steroid synthesis. On the basis of our findings, HA antagonizes the gonadotropin action in Leydig cells at steps before and after cAMP formation. NOS activation is the main intracellular mechanism by which HA exerts its antisteroidogenic effects.

Renal mitochondrial impairment is attenuated by AT1 blockade in experimental Type I diabetes.

To investigate whether ANG II type 1 (AT(1)) receptor blockade could protect kidney mitochondria in streptozotocin-induced Type 1 diabetes, we treated 8-wk-old male Sprague-Dawley rats with a single streptozotocin injection (65 mg/kg ip; STZ group), streptozotocin and drinking water containing either losartan (30 mg.kg(-1).day(-1); STZ+Los group) or amlodipine (3 mg.kg(-1).day(-1); STZ+Amlo group), or saline (intraperitoneally) and pure water (control group). Four-month-long losartan or amlodipine treatments started 30 days before streptozotocin injection to improve the antioxidant defenses. The number of renal lesions, plasma glucose and lipid levels, and proteinuria were higher and creatinine clearance was lower in STZ and STZ+Amlo compared with STZ+Los and control groups. Glycemia was higher in STZ+Los compared with control. Blood pressure, basal mitochondrial membrane potential and mitochondrial pyruvate content, and renal oxidized glutathione levels were higher and NADH/cytochrome c oxidoreductase activity was lower in STZ compared with the other groups. In STZ and STZ+Amlo groups, mitochondrial H(2)O(2) production rate was higher and uncoupling protein-2 content, cytochrome c oxidase activity, and renal glutathione level were lower than in STZ+Los and control groups. Mitochondrial nitric oxide synthase activity was higher in STZ+Amlo compared with the other groups. Mitochondrial pyruvate content and H(2)O(2) production rate negatively contributed to electron transfer capacity and positively contributed to renal lesions. Uncoupling protein-2 content negatively contributed to mitochondrial H(2)O(2) production rate and renal lesions. Renal glutathione reduction potential positively contributed to mitochondria electron transfer capacity. In conclusion, AT(1) blockade protects kidney mitochondria and kidney structure in streptozotocin-induced diabetes independently of blood pressure and glycemia.

The interaction between the renin-angiotensin system and peroxisome proliferator activated receptors: a hypothesis including the participation of mitochondria in aging.

The objective of improving health is intimately associated with preventing and delaying age-related diseases. Nutritional and pharmacological approaches aimed at retarding aging are uncovering mechanisms, whose definitive roles in cell and tissue physiology need to be defined. In this article we hypothesize that peroxisome proliferator activated receptor (PPAR)-modulation is a pivotal process that underlies the association between mitochondria and the renin-angiotensin system (RAS) in aging. This hypothesis is based on several lines of evidence suggesting that: a) mitochondrial function and oxidant production are active participants in the aging process; b) PPARs, by regulating mitochondrial function and uncoupling proteins (UCP), seem to play a major role in the age-retarding effects of caloric restriction; c) RAS inhibition delays the deleterious effects of aging and also upregulates PPARs; and d) a number of physiological and molecular events that occur in experimental caloric restriction, and experimental and clinical RAS inhibition, involve changes in mitochondrial functions.

Mitochondrial function and nitric oxide metabolism are modified by enalapril treatment in rat kidney.

The renal and cardiac benefits of renin-angiotensin system (RAS) inhibition in hypertension exceed those attributable to blood pressure reduction, and seem to involve mitochondrial function changes. To investigate whether mitochondrial changes associated with RAS inhibition are related to changes in nitric oxide (NO) metabolism, four groups of male Wistar rats were treated during 2 wk with a RAS inhibitor, enalapril (10 mg x kg(-1) x day(-1); Enal), or a NO synthase (NOS) inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME) (1 mg x kg(-1) x day(-1)), or both (Enal+L-NAME), or were untreated (control). Blood pressure and body weight were lower in Enal than in control. Electron transfer through complexes I to III and cytochrome oxidase activity were significantly lower, and uncoupling protein-2 content was significantly higher in kidney mitochondria isolated from Enal than in those from control. All of these changes were prevented by L-NAME cotreatment and were accompanied by a higher production/bioavailability of kidney NO. L-NAME abolished mitochondrial NOS activity but failed to inhibit extra-mitochondrial kidney NOS, underscoring the relevance of mitochondrial NO in those effects of enalapril that were suppressed by L-NAME cotreatment. In Enal, kidney mitochondria H(2)O(2) production rate and MnSOD activity were significantly lower than in control, and these effects were not prevented by L-NAME cotreatment. These findings may clarify the role of NO in the interactions between RAS and mitochondrial metabolism and can help to unravel the mechanisms involved in renal protection by RAS inhibitors.

Renal mitochondrial dysfunction in spontaneously hypertensive rats is attenuated by losartan but not by amlodipine.

Mitochondrial dysfunction is associated with cardiovascular damage; however, data on a possible association with kidney damage are scarce. Here, we aimed at investigating whether 1) kidney impairment is related to mitochondrial dysfunction; and 2) ANG II blockade, compared with Ca2+ channel blockade, can reverse potential mitochondrial changes in hypertension. Eight-week-old male spontaneously hypertensive rats (SHR) received water containing losartan (40 mg.kg-1.day-1, SHR+Los), amlodipine (3 mg.kg-1.day-1, SHR+Amlo), or no additions (SHR) for 6 mo. Wistar-Kyoto rats (WKY) were normotensive controls. Glomerular and tubulointerstitial damage, systolic blood pressure, and proteinuria were higher, and creatinine clearance was lower in SHR vs. SHR+Los and WKY. In SHR+Amlo, blood pressure was similar to WKY, kidney function was similar to SHR, and renal lesions were lower than in SHR, but higher than in SHR+Los. In kidney mitochondria from SHR and SHR+Amlo, membrane potential, nitric oxide synthase, manganese-superoxide dismutase and cytochrome oxidase activities, and uncoupling protein-2 content were lower than in SHR+Los and WKY. In SHR and SHR+Amlo, mitochondrial H2O2 production was higher than in SHR+Los and WKY. Renal glutathione content was lower in SHR+Amlo relative to SHR, SHR+Los, and WKY. In SHR and SHR+Amlo, glutathione was relatively more oxidized than in SHR+Los and WKY. Tubulointerstitial alpha-smooth muscle actin labeling was inversely related to manganese-superoxide dismutase activity and uncoupling protein-2 content. These findings suggest that oxidant stress is associated with renal mitochondrial dysfunction in SHR. The mitochondrial-antioxidant actions of losartan may be an additional or alternative way to explain some of the beneficial effects of AT1-receptor antagonists.

Concerted action of the renin-angiotensin system, mitochondria, and antioxidant defenses in aging.

Angiotensin-converting enzyme inhibitors (ACEi) and AT-1 receptor blockers (ARB) are two types of drugs that inhibit the renin-angiotensin system (RAS), and can attenuate the progression to cardiac and/or renal functional impairment, secondary to diverse pathologies. Some of the beneficial effects of ACEi and ARB occur independently of the ability of these drugs to reduce arterial blood pressure. Both, in animals, and in humans, we observed an enhancement of antioxidant defenses that occurred after treatment with ACEi. Based on these results, we postulate that some of the beneficial health effects associated to RAS inhibition can be ascribed to the prevention of oxidant-mediated damage. Furthermore, considering that: (i). RAS inhibition attenuates certain age-associated degenerative changes; (ii). aging was postulated to result from the accumulation of oxidant-mediated damage; and (iii). mitochondria are a major source of oxidants, we studied potential associations among RAS inhibition, mitochondrial function and production of oxidants and nitric oxide, and aging. The results obtained suggest, that RAS inhibitors, i.e. enalapril and losartan, can protect against the effects of aging by attenuating oxidant damage to mitochondria, and in consequence, they preserve mitochondrial function. The mechanism(s) explaining such attenuation of oxidant damage can relay on a reduction of the ANG-II-dependent generation of superoxide and/or an increased detoxification of reactive nitrogen and oxygen species by recomposition of antioxidant defense levels.

Enalapril and losartan attenuate mitochondrial dysfunction in aged rats.

Renin-angiotensin system (RAS) inhibition can attenuate the effects of aging on renal function and structure; however, its effect on mitochondrial aging is unknown. To investigate whether an angiotensin-converting enzyme inhibitor (enalapril) or an angiotensin II receptor blocker (losartan) could mitigate age-associated changes in kidney mitochondria, male Wistar rats (14 mo old) received during 8 mo water containing either enalapril (10 mg/kg/day) (Enal), or losartan (30 mg/kg/day) (Los), or no additions (Old). Four-month-old untreated rats (Young) were also studied. In Old rats mitochondrial respiratory control, ADP/O, nitric oxide synthase activity, and uncoupling protein 2 levels were lower (46, 42, 27, and 76%, respectively), and Mn-SOD activity was higher (70%) than in Young, Enal, and Los rats. In Old rats mitochondrial hydrogen peroxide production was higher than in both Young (197%) and Enal or Los (40%) rats. In Old rats, kidney GSH/GSSG was lower than in both Young (80%) and Enal (57%) or Los (68%) rats. In Old rats electron microscopy showed effacement of microvilli in tubular epithelial cells, ill-defined mitochondrial cristae, lower mitochondrial numbers, and enhanced number of osmiophilic bodies relative to Young, Enal, or Los rats. In conclusion, enalapril and losartan can protect against both age-related mitochondrial dysfunction and ultrastructural alterations, underscoring the role of RAS in the aging process. An association with oxidative stress modulation is suggested.