Perla D. Maldonado

Garlic ameliorates gentamicin nephrotoxicity: relation to antioxidant enzymes

Reactive oxygen species are involved in gentamicin (GM) nephrotoxicity, and garlic is effective in preventing or ameliorating oxidative stress. Therefore, the effect of garlic on GM nephrotoxicity was investigated in this work. Four groups of rats were studied: (i) fed normal diet (CT), (ii) treated with GM (GM), (iii) fed 2% garlic diet (GA), and (iv) treated with GM and 2% garlic diet (GM + GA). Rats were placed in metabolic cages and GM nephrotoxicity was induced by injections of GM (75 mg/kg every 12 h) for 6 d. Lipoperoxidation and enzyme determinations were made in renal cortex on day 7. GM nephrotoxicity was made evident on day 7 by (i) tubular histological damage, (ii) enhanced BUN and urinary excretion of N-acetyl-beta-D-glucosaminidase, and (iii) decreased creatinine clearance. These alterations were prevented or ameliorated in GM + GA group. The rise in lipoperoxidation and the decrease in Mn-SOD and glutathione peroxidase (GPx) activities observed in the GM group, were prevented in the GM + GA group. Cu, Zn-SOD activity and Mn-SOD and Cu,Zn-SOD content did not change. CAT activity and content decreased in the GM, GA, and GM + GA groups. CAT mRNA levels decreased in the GM group. The protective effect of garlic is associated with the prevention of the decrease of Mn-SOD and GPx activities and with the rise of lipoperoxidation in renal cortex.

Antioxidant S-allylcysteine prevents gentamicin-induced oxidative stress and renal damage

Acute renal failure (ARF) is a major complication of gentamicin (GM) treatment, which is effective against gram-negative infections. Since experimental evidence suggests a role of reactive oxygen species (ROS) in GM-induced ARF, in this work we studied the effect of a garlic-derived compound, S-allylcysteine (SAC), which is a free radical scavenger, on GM-induced nephrotoxicity. In rats treated with GM (70 mg/kg/12 h/4 days/s.c.), ARF was evident by the: (i) decrease in creatinine clearance and increase in blood urea nitrogen, (ii) decrease in blood glutathione peroxidase (GPx) activity and increase in urinary excretion of N-acetyl-beta-D-glucosaminidase and total protein, and (iii) necrosis of proximal tubular cells. These alterations were prevented by SAC treatment (250 mg/kg/i.p. 24 h before the first dose of GM and 125 mg/kg/12 h/4 days along GM-treatment). Furthermore, SAC prevented the GM-induced oxidative stress (protein carbonyl groups) and the decrease in manganese superoxide dismutase (Mn-SOD), GPx, and glutathione reductase (GR) activities in renal cortex. In conclusion, SAC ameliorates the GM-induced ARF by a mechanism related, at least in part, to its ability to decrease oxidative stress and to preserve antioxidant enzymes activity in renal cortex.

S-Allylcysteine, a garlic-derived antioxidant, ameliorates quinolinic acid-induced neurotoxicity and oxidative damage in rats.

Excitotoxicity elicited by overactivation of N-methyl-D-aspartate receptors is a well-known characteristic of quinolinic acid-induced neurotoxicity. However, since many experimental evidences suggest that the actions of quinolinic acid also involve reactive oxygen species formation and oxidative stress as major features of its pattern of toxicity, the use of antioxidants as experimental tools against the deleterious effects evoked by this neurotoxin becomes more relevant. In this work, we investigated the effect of a garlic-derived compound and well-characterized free radical scavenger, S-allylcysteine, on quinolinic acid-induced striatal neurotoxicity and oxidative damage. For this purpose, rats were administered S-allylcysteine (150, 300 or 450 mg/kg, i.p.) 30 min before a single striatal infusion of 1 microl of quinolinic acid (240 nmol). The lower dose (150 mg/kg) of S-allylcysteine resulted effective to prevent only the quinolinate-induced lipid peroxidation (P < 0.05), whereas the systemic administration of 300 mg/kg of this compound to rats decreased effectively the quinolinic acid-induced oxidative injury measured as striatal reactive oxygen species formation (P < 0.01) and lipid peroxidation (P < 0.05). S-Allylcysteine (300 mg/kg) also prevented the striatal decrease of copper/zinc-superoxide dismutase activity (P < 0.05) produced by quinolinate. In addition, S-allylcysteine, at the same dose tested, was able to reduce the quinolinic acid-induced neurotoxicity evaluated as circling behavior (P < 0.01) and striatal morphologic alterations. In summary, S-allylcysteine ameliorates the in vivo quinolinate striatal toxicity by a mechanism related to its ability to: (a) scavenge free radicals; (b) decrease oxidative stress; and (c) preserve the striatal activity of Cu,Zn-superoxide dismutase (Cu,Zn-SOD). This antioxidant effect seems to be responsible for the preservation of the morphological and functional integrity of the striatum.

On the antioxidant properties of kynurenic acid: Free radical scavenging activity and inhibition of oxidative stress

Kynurenic acid (KYNA) is an endogenous metabolite of the kynurenine pathway for tryptophan degradation and an antagonist of both N-methyl-D-aspartate (NMDA) and alpha-7 nicotinic acetylcholine (α7nACh) receptors. KYNA has also been shown to scavenge hydroxyl radicals (OH) under controlled conditions of free radical production. In this work we evaluated the ability of KYNA to scavenge superoxide anion (O(2)(-)) and peroxynitrite (ONOO(-)). The scavenging ability of KYNA (expressed as IC(50) values) was as follows: OH=O(2)(-)>ONOO(-). In parallel, the antiperoxidative and scavenging capacities of KYNA (0-150 μM) were tested in cerebellum and forebrain homogenates exposed to 5 μM FeSO(4) and 2.5 mM 3-nitropropionic acid (3-NPA). Both FeSO(4) and 3-NPA increased lipid peroxidation (LP) and ROS formation in a significant manner in these preparations, whereas KYNA significantly reduced these markers. Reactive oxygen species (ROS) formation were determined in the presence of FeSO(4) and/or KYNA (0-100 μM), both at intra and extracellular levels. An increase in ROS formation was induced by FeSO(4) in forebrain and cerebellum in a time-dependent manner, and KYNA reduced this effect in a concentration-dependent manner. To further know whether the effect of KYNA on oxidative stress is independent of NMDA and nicotinic receptors, we also tested KYNA (0-100 μM) in a biological preparation free of these receptors - defolliculated Xenopus laevis oocytes - incubated with FeSO(4) for 1 h. A 3-fold increase in LP and a 2-fold increase in ROS formation were seen after exposure to FeSO(4), whereas KYNA attenuated these effects in a concentration-dependent manner. In addition, the in vivo formation of OH evoked by an acute infusion of FeSO(4) (100 μM) in the rat striatum was estimated by microdialysis and challenged by a topic infusion of KYNA (1 μM). FeSO(4) increased the striatal OH production, while KYNA mitigated this effect. Altogether, these data strongly suggest that KYNA, in addition to be a well-known antagonist acting on nicotinic and NMDA receptors, can be considered as a potential endogenous antioxidant.

S-allylmercaptocysteine scavenges hydroxyl radical and singlet oxygen in vitro and attenuates gentamicin-induced oxidative and nitrosative stress and renal damage in vivo

BackgroundOxidative and nitrosative stress have been involved in gentamicin-induced nephrotoxicity. The purpose of this work was to study the effect of S-allylmercaptocysteine, a garlic derived compound, on gentamicin-induced oxidative and nitrosative stress and nephrotoxicity. In addition, the in vitro reactive oxygen species scavenging properties of S-allylmercaptocysteine were studied.ResultsS-allylmercaptocysteine was able to scavenge hydroxyl radicals and singlet oxygen in vitro. In rats treated with gentamicin (70 mg/Kg body weight, subcutaneously, every 12 h, for 4 days), renal oxidative stress was made evident by the increase in protein carbonyl content and 4-hydroxy-2-nonenal, and the nitrosative stress was made evident by the increase in 3-nitrotyrosine. In addition, gentamicin-induced nephrotoxicity was evident by the: (1) decrease in creatinine clearance and in activity of circulating glutathione peroxidase, and (2) increase in urinary excretion of N-acetyl-β-D-glucosaminidase, and (3) necrosis of proximal tubular cells. Gentamicin-induced oxidative and nitrosative stress and nephrotoxicity were attenuated by S-allylmercaptocysteine treatment (100 mg/Kg body weight, intragastrically, 24 h before the first dose of gentamicin and 50 mg/Kg body weight, intragastrically, every 12 h, for 4 days along gentamicin-treatment).ConclusionIn conclusion, S-allylmercaptocysteine is able to scavenge hydroxyl radicals and singlet oxygen in vitro and to ameliorate the gentamicin-induced nephrotoxicity and oxidative and nitrosative stress in vivo.

Aged garlic extract attenuates gentamicin induced renal damage and oxidative stress in rats

Gentamicin (GM) is an antibiotic whose clinical use is limited by its nephrotoxicity. Experimental evidences suggest a role of reactive oxygen species in GM-induced nephrotoxicity. Therefore, we investigated if aged garlic extract (AGE), an antioxidant, has a protective role in this experimental model. Four groups of male Wistar rats were studied: 1) Control (CT), injected subcutaneously (s.c.) and intraperitoneally (i.p.) with saline, 2) GM, treated s.c. with GM (70 mg/kg/12 hours/4 days), 3) AGE, treated i.p with AGE (1.2 mL/kg/12 hours/6 days), and 4) GM + AGE treated with GM and AGE. The treatment with AGE started two days before the first dose of GM (GM + AGE group) or saline (AGE group). Animals were sacrificed on day 5, and blood, urine, and kidneys were obtained. Nephrotoxicity was made evident by: 1) the increase in blood urea nitrogen and plasma creatinine, 2) the decrease in plasma glutathione peroxidase (GPx) activity and the urinary increase in N-acetyl-beta-D-glucosaminidase activity and total protein, and 3) necrosis of proximal tubular cells. These alterations were prevented or ameliorated by AGE treatment. Furthermore, AGE prevented the GM-induced increase in the renal levels of oxidative stress markers: nitrotyrosine and protein carbonyl groups and the decrease in manganese superoxide dismutase (Mn-SOD), GPx, and glutathione reductase (GR) activities. The protective effect of AGE was associated with the decrease in the oxidative stress and the preservation of Mn-SOD, GPx, and GR activities in renal cortex. These data suggest that AGE may be a useful agent for the prevention of GM-nephrotoxicity.

Diallyl disulfide ameliorates gentamicin-induced oxidative stress and nephropathy in rats

Experimental evidences suggest a role of reactive oxygen species in gentamicin-induced nephropathy in rats. Therefore, we investigated if diallyl disulfide, a garlic-derived compound with antioxidant properties, has a renoprotective effect in this experimental model. Four groups of rats were studied: (1) control, (2) gentamicin treated subcutaneously with gentamicin (70 mg/kg/12 h/4 days), (3) diallyl disulfide treated intragastrically with diallyl disulfide (50 mg/kg/24 h/4 days), and (4) gentamicin + diallyl disulfide treated with gentamicin + diallyl disulfide. Gentamicin induced (a) nephrotoxicity, (b) increase in renal oxidative stress, and (c) decrease in the activity of manganese superoxide dismutase, glutathione peroxidase, and glutathione reductase. Diallyl disulfide ameliorated these changes induced by gentamicin. The mechanism by which diallyl disulfide has a renoprotective effect in gentamicin-induced acute renal failure in rats may be related, at least in part, to the amelioration in the oxidative stress and the preservation in the activity of the antioxidant enzymes in kidney.

Effect of quinolinic acid on endogenous antioxidants in rat corpus striatum

The response of endogenous antioxidants to the N-methyl-D-aspartate (NMDA) receptor agonist and excitotoxin, quinolinic acid (QUIN), was investigated in rat corpus striatum. Animals treated with QUIN (240 nmol/microl), were sacrificed at 120 min after a single intrastriatal injection to examine the alterations in the levels of both reduced (GSH) and oxidized (GSSG) glutathione, and the activities of the antioxidant enzymes, superoxide dismutase (SOD) and glutathione peroxidase (Gpx). Changes in the rate of lipid peroxidation (LP) were also measured after exposure to different doses of QUIN (60, 120, 240 and 480 nmol/microl) as an index of oxidative stress. When compared to control, lipid peroxidation was increased at QUIN doses of 240 and 480 nmol/microl. Striatal levels of GSH and GSSG were decreased and increased, respectively, after QUIN injection; whereas GPx activity was unchanged. Cytosolic copper/zinc SOD (CuZn-SOD) activity decreased after treatment, while mitochondrial manganese SOD (Mn-SOD) was unchanged. The alterations observed on these antioxidant systems suggest that QUIN toxicity is mediated by specific mechanisms leading to oxidative stress.

The Antioxidant Mechanisms Underlying the Aged Garlic Extract- and S-Allylcysteine-Induced Protection

Aged garlic extract (AGE) is an odorless garlic preparation containing S-allylcysteine (SAC) as its most abundant compound. A large number of studies have demonstrated the antioxidant activity of AGE and SAC in both in vivo—in diverse experimental animal models associated to oxidative stress—and in vitro conditions—using several methods to scavenge reactive oxygen species or to induce oxidative damage. Derived from these experiments, the protective effects of AGE and SAC have been associated with the prevention or amelioration of oxidative stress. In this work, we reviewed different antioxidant mechanisms (scavenging of free radicals and prooxidant species, induction of antioxidant enzymes, activation of Nrf2 factor, inhibition of prooxidant enzymes, and chelating effects) involved in the protective actions of AGE and SAC, thereby emphasizing their potential use as therapeutic agents. In addition, we highlight the ability of SAC to activate Nrf2 factor—a master regulator of the cellular redox state. Here, we include original data showing the ability of SAC to activate Nrf2 factor in cerebral cortex. Therefore, we conclude that the therapeutic properties of these molecules comprise cellular and molecular mechanisms at different levels.

HO-1 induction attenuates renal damage and oxidative stress induced by K2Cr2O7.

Heme oxygenase (HO) is the rate-limiting enzyme in the degradation of heme; its inducible isozyme HO-1 protects against some types of acute tissue injury. The expression and functional role of HO-1 in rats with renal injury induced by potassium dichromate (K(2)Cr(2)O(7)) was investigated in this work. Rats were studied 24 h after a single injection of K(2)Cr(2)O(7). To address the possible protective effect of HO-1 in this experimental model, this enzyme was induced by an injection of stannous chloride (SnCl(2)) 12 h before K(2)Cr(2)O(7) administration. The functional role of HO-1 in K(2)Cr(2)O(7) + SnCl(2)-treated animals was tested by inhibiting HO activity with an injection of zinc (II) protoporphyrin IX (ZnPP) 18 h before K(2)Cr(2)O(7). In K(2)Cr(2)O(7)-treated rats: (i) renal HO-1 content, measured by Western blot, increased 2.6-fold; and, (ii) renal nitrotyrosine and protein carbonyl content, markers of oxidative stress, increased 3.5- and 1.36-fold, respectively. Renal damage and oxidative stress were ameliorated and HO-1 content was increased in the K(2)Cr(2)O(7) + SnCl(2) group. The attenuation of renal injury and oxidative stress was lost by the inhibition of HO activity in K(2)Cr(2)O(7) + SnCl(2) + ZnPP-treated animals. Our data suggest that HO-1 overexpression induced by SnCl(2) is responsible for the attenuation of renal damage and oxidative stress induced by K(2)Cr(2)O(7).