Prevention and Reversal by Enalapril of Target Organ Damage in Angiotensin II Hypertension

Effect of the antihypertensive drug enalapril on oxidative stress markers and antioxidant enzymes in kidney of spontaneously hypertensive rat

Oxidative stress has been suggested to play a role in hypertension and hypertension induced organ damage. This study examined the effect of enalapril, an antihypertensive drug, on oxidative stress markers and antioxidant enzymes in kidney of spontaneously hypertensive rat (SHR) and Nω -nitro-L-arginine methyl ester (L-NAME) administered SHR. Male rats were divided into four groups (SHR, SHR+enalapril, SHR+L-NAME, and SHR+enalapril+L-NAME). Enalapril (30 mg kg⁻¹ day⁻¹) was administered from week 4 to week 28 and L-NAME (25 mg kg⁻¹ day⁻¹) was administered from week 16 to week 28 in drinking water. Systolic blood pressure (SBP) was measured during the experimental period. At the end of experimental periods, rats were sacrificed; urine, blood, and kidneys were collected for the assessment of creatinine clearance, total protein, total antioxidant status (TAS), thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), and catalase (CAT), as well as histopathological examination. Enalapril treatment significantly enhanced the renal TAS level (P < 0.001) and SOD activity (P < 0.001), reduced the TBARS levels (P < 0.001), and also prevented the renal dysfunction and histopathological changes. The results indicate that, besides its hypotensive and renoprotective effects, enalapril treatment also diminishes oxidative stress in the kidneys of both the SHR and SHR+L-NAME groups.

Endogenous antioxidant defense induction by melon superoxide dismutase reduces cardiac hypertrophy in spontaneously hypertensive rats

We assessed the influence of SODB, a melon superoxide dismutase (SOD), on left ventricular (LV) hypertrophy in SHR. SODB (4 or 40U SOD) was given orally for 4 or 28 days to SHR. For each treatment period, LV weight index (LVWI) and cardiomyocytes size were measured. SOD, glutathione peroxidase (GPx) and catalase expressions, and LV production and presence of superoxide anion were determined. Pro-inflammatory markers were also measured. SODB reduced LVWI and cardiomyocytes size after 4 or 28 days. Cardiac SOD and GPx increased by 30-40% with SODB. The presence but not production of superoxide anion was significantly reduced by SODB. No effect of SODB was detected on inflammatory status in any group. The beneficial effect of SODB on cardiac hypertrophy seems to be related to the stimulation of endogenous antioxidant defense, suggesting that SODB may be of interest as a dietary supplementation during conventional antihypertensive therapy.

Exploring the protective role of apocynin, a specific NADPH oxidase inhibitor, in cisplatin-induced cardiotoxicity in rats

Despite the clinical reports, few studies have focused on reducing the cardiotoxicity of cisplatin. In the present study, cardiotoxicity was examined after a single ip injection of cisplatin (7mg/kg) in rats. Apocynin was given in drinking water (600mg/L) for five successive days before and after cisplatin injection. At the end of the experiment, hemodynamic parameters were recorded, animals were sacrificed and serum creatine kinase-MB activity was determined. The whole ventricle was isolated for estimation of tumor necrosis factor-alpha (TNF-α) content, NADPH oxidase, myeloperoxidase and caspase-3 activities in addition to nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and nuclear factor kappa B (NF-κB) gene expressions. Furthermore, oxidative stress markers and antioxidant enzymes were measured in postmitochondrial and mitochondrial fractions. Mitochondrial membrane potential, nuclear DNA fragmentation and cardiomyocyte cross-sectional area were also evaluated. Apocynin was effective against cisplatin-induced decrement in heart rate and blood pressure. Moreover, pretreatment with apocynin notably ameliorated the state of oxidative stress, mitigated inflammation and preserved mitochondrial membrane potential. Apocynin provided also a significant cardioprotection as revealed by alleviating the overexpression of Nrf2, HO-1 and NF-κB, the elevation of caspase-3 activity, the prominent nuclear DNA fragmentation and the decreased cardiomyocyte cross-sectional area. This study highlights the potential role of apocynin in inhibiting cisplatin-induced hemodynamic changes, postmitochondrial and mitochondrial damage as indicated by improvement in the state of oxidative stress, inflammation and apoptosis.

Protective effects of apocynin on cisplatin-induced ototoxicity in an auditory cell line and in zebrafish

Cisplatin is a very effective anticancer drug and generates reactive oxygen species (ROS) such as superoxide anions that can deplete antioxidant protective molecules in the cochlea. These processes result in the death of cochlear hair cells by induction of apoptosis. Apocynin, which is used as a specific nicotinamide adenine dinucleotide phosphate oxidase inhibitor, has a preventive effect for intracellular ROS generation. In this study, the effect of apocynin was investigated in a cochlear organ of Corti-derived cell line, HEI-OC1 cells, and in transgenic zebrafish (Brn3C: EGFP). To investigate the protective effects of apocynin, HEI-OC1 cells were treated with various concentrations of apocynin and a 20 µm concentration of cisplatin, simultaneously. An in vivo study of transgenic zebrafish (Brn3C: EGFP) was used to investigate the protective effects of apocynin on cisplatin-induced hair cell death. In an in vitro study, apocynin appeared to protect against cisplatin-induced apoptotic features on Hoechst 33258 staining in the HEI-OC1 cells. Treatment of the HEI-OC1 cells with 100 µm of apocynin, significantly decreased caspase-3 activity. Treatment of the cells with a 100 µm concentration of apocynin and a 20 µm concentration of cisplatin significantly decreased the intracellular ROS production. In the in vivo study, apocynin significantly decreased the TUNEL reaction and prevented cisplatin-induced hair cell loss of the neuromasts in the transgenic zebrafish at low concentrations (125 and 250 µm). These findings suggest that apocynin has antioxidative effects and prevents cisplatin-induced apoptotic cell death in HEI-OC1 cells as well as in zebrafish.

Mechanisms underlying sex differences in progressive renal disease

Men with nondiabetic renal disease exhibit a faster rate of decline in renal function compared with women. To investigate this sex difference in renal disease progression, our research group has been studying the renal wrap (RW) model of hypertension in rats. Compared with RW female rats, the glomerulosclerosis index, mean glomerular volume, and proteinuria were greater (3.1-, 1.7-, and 1.8-fold, respectively) in RW males under conditions in which no differences in the degree of hypertension were detected, suggesting that sex differences may exist in the mechanisms underlying renal injury, independent of blood pressure. Gonadal steroids contribute to these sex differences, because orchidectomy attenuated and ovariectomy exacerbated the severity of renal injury, whereas dihydrotestosterone and 17beta-estradiol (E(2)) replacement prevented these respective effects. Chronic renal disease is associated with impairment in nitric oxide (NO) signaling and elevated levels of superoxide. Sex differences were observed in RW-induced changes in renal nitric oxide synthesis (NOS) protein abundance. Whereas RW had no effect on NOS in the female kidney, endothelial NOS was elevated and neuronal NOS was decreased in the male kidney, suggesting that renal injury may cause dysfunction in NO metabolism in the male. Sex differences in superoxide signaling were also observed. Renal cortical nicotinamide adenine dinucleotide phosphate oxidase activity was 1.3-fold higher in RW males than in RW females, and ovariectomy increased enzyme activity 1.4-fold, whereas E(2) replacement prevented this effect. These changes in enzyme activity were mirrored by changes in protein abundance of the p22(phox) regulatory subunit. Our findings suggest that E(2) may protect the female kidney from hypertension-associated renal disease by attenuating injury-induced superoxide production.

Protective effects of apocynin against cisplatin-induced oxidative stress and nephrotoxicity

Cis-diamminedichloroplatinum (II) (cisplatin) is an effective chemotherapeutic agent successfully used in the treatment of a wide range of tumors; however, nephrotoxicity has restricted its clinical use. Several studies have shown that reactive oxygen species are involved in cisplatin-induced nephrotoxicity, including hydrogen peroxide, hydroxyl radical and superoxide anion (O(2)(-)). The source of O(2)(-) in cisplatin-induced renal damage has not been established. The aim of this study was to investigate if NADPH oxidase is involved in cisplatin-induced nephrotoxicity using apocynin, a widely used NADPH oxidase inhibitor. Rats were studied 3 days after a single injection of cisplatin (7.5mg/kg, i.p.). Apocynin was given in the drinking water (2g/L) 7 days before and 3 days after cisplatin injection. Apocynin treatment was able to ameliorate the renal histological damage and the increase in blood urea nitrogen, serum creatinine, and urinary excretion of total protein, N-acetyl-beta-d-glucosaminidase and glutathione-S-transferase induced by cisplatin. In addition, the protective effect of apocynin was associated with the amelioration of cisplatin-induced oxidative and nitrosative stress. Our data suggest that O(2)(-) derived from NADPH oxidase triggers some of the side effects due to cisplatin administration.

Simvastatin reverses target organ damage and oxidative stress in Angiotensin II hypertension: comparison with apocynin, tempol, and hydralazine

The ability of the 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor simvastatin to reverse established cardiovascular and renal alterations and oxidative stress was assessed in angiotensin II (AngII) hypertension. Sprague-Dawley rats infused with AngII (200 ng/kg per minute for 17 days) were concomitantly treated or not for the last 7 days with simvastatin, apocynin, tempol, and hydralazine (60, 60, 30, and 15 mg/kg per day, respectively). Only hydralazine lowered AngII hypertension. Simvastatin and apocynin lowered cardiac hypertrophy by 52% and 54% and reversed the marked rise in albuminuria by 25% and 70%. Neither tempol nor hydralazine affected cardiac mass or albuminuria. None of the treatments modified the AngII-induced increase in carotid media thickness. The rise in cardiac superoxide anion production (lucigenin-enhanced chemiluminescence method) induced by AngII was reversed by all treatments. Enhanced plasma concentration of advanced oxidation protein products (spectrophotometry using chloramine T) was unaffected by simvastatin and tempol, but it was reversed by apocynin and hydralazine. Our results indicate that simvastatin reverse established cardiac and renal alterations in AngII hypertension independently of arterial pressure. It is suggested that oxidative stress participates in the maintenance of target organ damage and that antioxidant properties are involved in the beneficial influence of the statin.

Female protection in progressive renal disease is associated with estradiol attenuation of superoxide production

BACKGROUND

Several types of renal disease progress at a faster rate in men compared with women, but the reasons for this sex difference are not well understood. Chronic renal disease is associated with elevated levels of toxic reactive oxygen species (ROS). Superoxide, the major ROS in the kidney, is generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase.

OBJECTIVE

To determine if female protection from renal disease progression is consistent with 17beta-estradiol (E2) attenuation of superoxide production, this study was conducted to assess superoxide production in the renal cortex of male and female control and renal wrap (RW) rats, as well as in ovariectomized rats treated with vehicle or E2.

METHODS

Sprague-Dawley rats were divided into 2 sham operation male (Sham-M) and female (Sham-F) control groups, and 4 RW hypertensive groups: RW-M; RW-F; RW ovariectomized females treated with vehicle (RW-OVX); and RW ovariectomized females treated with E2, supplied as a 0.24 mg/60-day release pellet (RW-OVX+E2). All groups were maintained on a high-sodium (4% NaCl) diet for 6 weeks.

RESULTS

Mean (SEM) markers of renal injury and oxidative stress, including urinary protein (mg/24 h: RW-M, 298 [31] vs RW-F, 169 [22]; P < 0.001), microalbuminuria (RW/Sham arbitrary units [AU]/24 h: M, 8.78 [0.58] vs F, 4.31 [1.0]; P < 0.005), and malondialdehyde (nmol/24 h: RW-M, 167 [23] vs RW-F, 117 [8.5]; P < 0.05) levels, as well as mean glomerular volume (microm3 x 10(6): RW-M, 2.25 [0.16] vs RW-F, 1.25 [0.04]; P < 0.001) and the glomerulosclerotic index (AU: RW-M, 2.64 [0.19] vs RW-F, 1.10 [0.09]; P < 0.001) were greater in both control and RW males compared with females in the same treatment groups. Though RW surgery increased mean arterial pressure in both male and female rats, no sex difference was observed. Under these conditions, mean (SEM) renal cortical NADPH oxidase activity was 1.3-fold higher in RW males compared with RW females (relative light units [RLU]/180 sec: RW-M, 4080 [240] vs RW-F, 3200 [260]; P < 0.05). Ovariectomy increased NADPH oxidase activity by 1.4-fold (RLU/180 sec: RW-OVX, 4520 [184]; P < 0.01) under conditions in which the mean glomerular volume and glomerulosclerotic index were both increased by 1.5-fold, whereas E2 replacement (RLU/180 sec: RW-OVX+E2, 2745 [440]) prevented these effects. Furthermore, the effects on NADPH oxidase activity were mirrored by changes in the protein abundance of NADPH oxidase subunit p22P(phox).

CONCLUSION

These results suggest that E2 protects the female kidney in part by attenuating injury-induced increases in renal superoxide production.

Interaction of Endothelial Nitric Oxide and Angiotensin in the Circulation

Discovery of the unexpected intercellular messenger and transmitter nitric oxide (NO) was the highlight of highly competitive investigations to identify the nature of endothelium-derived relaxing factor. This labile, gaseous molecule plays obligatory roles as one of the most promising physiological regulators in cardiovascular function. Its biological effects include vasodilatation, increased regional blood perfusion, lowering of systemic blood pressure, and antithrombosis and anti-atherosclerosis effects, which counteract the vascular actions of endogenous angiotensin (ANG) II. Interactions of these vasodilator and vasoconstrictor substances in the circulation have been a topic that has drawn the special interest of both cardiovascular researchers and clinicians. Therapeutic agents that inhibit the synthesis and action of ANG II are widely accepted to be essential in treating circulatory and metabolic dysfunctions, including hypertension and diabetes mellitus, and increased availability of NO is one of the most important pharmacological mechanisms underlying their beneficial actions. ANG II provokes vascular actions through various receptor subtypes (AT1, AT2, and AT4), which are differently involved in NO synthesis and actions. ANG II and its derivatives, ANG III, ANG IV, and ANG-(1-7), alter vascular contractility with different mechanisms of action in relation to NO. This review article summarizes information concerning advances in research on interactions between NO and ANG in reference to ANG receptor subtypes, radical oxygen species, particularly superoxide anions, ANG-converting enzyme inhibitors, and ANG receptor blockers in patients with cardiovascular disease, healthy individuals, and experimental animals. Interactions of ANG and endothelium-derived relaxing factor other than NO, such as prostaglandin I2 and endothelium-derived hyperpolarizing factor, are also described.