Inhibition of rat liver and kidney arginase by cadmium ion

Biological activities of ginger against cadmium-induced renal toxicity

Our aim was to evaluate the protective and antioxidant effects of ginger extract against cadmium-induced renal toxicity in animal models and to support the use of ginger as anti-renal failure natural remedy. Seventy rats were examined in a 4-week experiment to evaluate the effect of Ginger (Zingiber officinale) at doses of 100 and 200 mg/kg body weight on molecular DNA content, antioxidant status, and renal function in rats intoxicated with cadmium at dose of (5 mg/kg) using biochemical and histological analysis. Renal dysfunction, kidney tissue damage, and oxidative effect were evident in cadmium intoxicated rats as estimated by significant increase in (creatinine, urea), decrease in (creatinine clearance and reabsorption rate of urine albumin), increase in MDA, decrease in total antioxidant status (TAC), reduction in DNA content, and histopathological changes of kidneys' tissues compared to control rats. Treatment with ginger resulted in significant restoring of renal function biomarkers, TAC, molecular DNA, and histological improvements which occurs via free radical scavenging and regenerative mechanisms. The activity of ginger was supported by estimation of bioactive phenolic and falvinods constituents. Twenty-eight polyphenolic compounds were estimated in ginger extract; [6]-gingerol, [6]-shogaol, citral and pyrogallol were the highest amounts in ginger, and supposed to be responsible for its major antioxidant and free radical scavenging activity as shown by In vitro DPPH/β-carotene-linolic acid assay tests. Consequently, ginger extracts could have a potent protective effects against nephrotoxicity induced by various toxicants.

Modulatory effects of methanol extract of Artocarpus altilis (Moraceae) on cadmium-induced hepatic and renal toxicity in male Wistar rats

BACKGROUND

Cadmium (Cd) is an environmental risk factor with an established toxicity in animals. Therefore, natural antioxidants may be protective against Cd-toxicity. The study was designed to investigate the modulatory effects of methanol extract of Artocarpus altilis (AA) on oxidant-antioxidant balance and lipid profile in liver and kidney of Cd-exposed rats while quercetin (QE) served as standard.

METHODS

Total phenolic content (TPC) and 2,2-diphenyl-1-picryldydrazyl (DPPH) radical scavenging activity of AA were assessed in vitro. In vivo, rats were orally treated with AA (200mg/kg) and QE (25mg/kg) daily for three weeks and challenged with two doses of Cd (1.5mg/kg, i.p.) in the last 72h.

RESULTS

The TPC and DPPH scavenging effects of AA were high and comparable with catechin. Cd-intoxication significantly (p<0.05) increased the activities of serum alanine aminotransferase and levels of urea, total bilirubin and creatinine by 94%, 60%, 234% and 76%, respectively. Cd-exposure caused a significant increase (p<0.05) in serum and tissues total cholesterol, triglyceride, low-density lipoprotein-cholesterol and reduction in high-density lipoprotein-cholesterol levels. The levels of hepatic and renal antioxidant parameters: glutathione-s-transferase, superoxide dismutase and reduced glutathione were significantly (p<0.05) decreased in Cd-intoxicated rats with concomitant elevation of lipid peroxidation. Histopathological findings revealed necrosis and distortion of architecture of renal tissue and, periportal infiltration in hepatocytes of Cd-intoxicated rats. Pretreatment with AA and QE restored antioxidant status, lipid profile and attenuated the lesions in the tissues.

CONCLUSIONS

Extract of A. altilis protects against Cd-induced liver and kidney dysfunction via antioxidant and radical scavenging activities.

Grape seed proanthocyanidins ameliorates cadmium-induced renal injury and oxidative stress in experimental rats through the up-regulation of nuclear related factor 2 and antioxidant responsive elements

Cadmium (Cd) preferentially accumulates in the kidney, the major target for Cd-related toxicity. Cd-induced reactive oxygen species (ROS) have been considered crucial mediators for renal injury. The biologically significant ionic form of cadmium (Cd+) binds to many bio-molecules, and these interactions underlie the toxicity mechanisms of Cd. The present study was hypothesized to explore the protective effect of grape seed proanthocyanidins (GSP) on Cd-induced renal toxicity and to elucidate the potential mechanism. Male Wistar rats were treated with Cd as cadmium chloride (CdCl2, 5 mg·kg−1 bw, orally) and orally pre-administered with GSP (100 mg·kg−1 bw) 90 min before Cd intoxication for 4 weeks to evaluate renal damage of Cd and antioxidant potential of GSP. Serum renal function parameters (blood urea nitrogen and creatinine) levels in serum and urine, renal oxidative stress (lipid peroxidation, protein carbonylation, enzymatic, and non-enzymatic antioxidants), inflammatory (NF-κB p65, NO, TNF-α, IL-6), apoptotic (caspase-3, caspase-9, Bax, Bcl-2), membrane bound ATPases, and Nrf2 (HO-1, keap1, γ-GCS, and μ-GST) markers were evaluated in Cd-treated rats. Pretreatment with GSP revealed a significant improvement in renal oxidative stress markers in kidneys of Cd-treated rats. In addition, GSP treatment decreases the amount of iNOS, NF-κB, TNF-α, caspase-3, and Bax and increases the levels Bcl-2 protein expression. Similarly, mRNA and protein analyses substantiated that GSP treatment notably normalizes the renal expression of Nrf2/Keap1 and its downstream regulatory proteins in the Cd-treated rats. Histopathological and ultra-structural observations also demonstrated that GSP effectively protects the kidney from Cd-induced oxidative damage. These findings suggest that GSP ameliorates renal dysfunction and oxidative stress through the activation of Nrf2 pathway in Cd-intoxicated rats.

p-Coumaric acid, a common dietary polyphenol, protects cadmium chloride-induced nephrotoxicity in rats

The present study was conducted to elucidate the protective role of p-coumaric acid, a common dietary polyphenol against cadmium induced nephrotoxicity in rats. For the purpose of comparison, a standard reference drug silymarin (50 mg/kg b. wt) was used. In this experiment, the animals were divided into four groups, with each consisting of six animals. The animals in Group I animals received saline and served as a control group and those in Group II received cadmium chloride (3 mg/kg b. wt) subcutaneously once daily for 3 weeks, but Group III and IV animals received cadmium chloride followed by p-coumaric acid (100 mg/kg b. wt, oral) and silymarin (50 mg/kg b. wt, oral), respectively, daily for 3 weeks. At the end of the treatment, the animals were sacrificed, and the blood and kidney samples were collected. The results obtained in this study revealed the fact that the levels of lipid peroxidation, lysosomal enzymes, glycoprotein, cadmium and metallothionein were increased in the cadmium chloride alone treated rats and antioxidant status was found to be decreased, when compared to the control group. The levels of kidney functional markers (urea, uric acid and creatinine) were also found to be abnormal in serum and urine of cadmium chloride alone treated rats. On the other hand, the administration of p-coumaric acid along with cadmium chloride significantly protected the biochemical alterations as observed in the cadmium chloride alone treated rats as evidenced by histopathology. Thus, the oral administration of p-coumaric acid significantly protected the cadmium-induced nephrotoxicity in rats.

Unique hepatic cytosolic arginase evolved independently in ureogenic freshwater air-breathing teleost, Heteropneustes fossilis

Hepatic cytosolic arginase (ARG I), an enzyme of the urea cycle operating in the liver of ureotelic animals, is reported to be present in an ammoniotelic freshwater air-breathing teleost, Heteropneustes fossilis which has ureogenic potential. Antibodies available against mammalian ARG I showed no cross reactivity with the H. fossilis ARG I. We purified unique ARG I from H. fossilis liver. Purified ARG I is a homotrimer with molecular mass 75 kDa and subunit molecular mass of 24 kDa. The pI value of the enzyme was 8.5. It showed maximum activity at pH 10.5 and 55°C. The Km of purified enzyme for L-arginine was 2.65±0.39 mM. L-ornithine and N(ω)-hydroxy-L-arginine showed inhibition of the ARG I activity, with Ki values 0.52±0.02mM and 0.08±0.006mM, respectively. Antibody raised against the purified fish liver ARG I showed exclusive specificity, and has no cross reactivity against fish liver ARG II and mammalian liver ARG I and ARG II. We found another isoform of arginase bound to the outer membrane of the mitochondria which was released by 150-200 mM KCl in the extraction medium. This isoform was immunologically different from the soluble cytosolic and mitochondrial arginase. The results of present study support that hepatic cytosolic arginase evolved in this ureogenic freshwater teleost, H. fossilis. Phylogenetic analysis confirms an independent evolution event that occurred much after the evolution of the cytosolic arginase of ureotelic vertebrates.

Inhibition of purified bovine liver glutathione reductase with some metal ions

Glutathione reductase (GR; E.C. 1.6.4.2) is a flavoprotein that catalyzes the NADPH-dependent reduction of oxidized glutathione (GSSG). In this study we tested the effects of Al3+, Ba2+, Ca2+, Li+, Mn2+, Mo6+, Cd2+, Ni2+, and Zn2+ on purified bovine liver GR. In a range of 10 microM-10 mM concentrations, Al3+, Ba2+, Li+, Mn2+, and Mo6+, and Ca2+ at 5 microM-1.25 mM, had no effect on bovine liver GR. Cadmium (Cd2+), nickel (Ni2+), and zinc (Zn2+) showed inhibitory effects on this enzyme. The obtained IC50 values of Cd2+, Ni2+, and Zn2+ were 0.08, 0.8, and 1 mM, respectively. Cd2+ inhibition was non-competitive with respect to both GSSG (Ki(GSSG) 0.221 +/- 0.02 mM) and NADPH (Ki(NADPH) 0.113 +/- 0.008 mM). Ni2+ inhibition was non-competitive with respect to GSSG (Ki(GSSG) 0.313 +/- 0.01 mM) and uncompetitive with respect to NADPH (Ki(NADPH) 0.932 +/- 0.03 mM). The effect of Zn2+ on GR activity was consistent with a non-competitive inhibition pattern when the varied substrates were GSSG (Ki(GSSG) 0.320 +/- 0.018 mM) and NADPH (Ki(NADPH) 0.761 +/- 0.04 mM), respectively.

The inhibitory effect of various indolyl amino acid derivatives on arginase activity in macrophages

Numerous indolyl amino acids and their derivatives inhibited arginase activity. The inhibition was found to be non-competitive, - at least partly - allosteric, and independent on manganese ions in the active site, and it cannot be explained by the dissociation of arginase homotrimers. Indole alone is weakly inhibitory; however, the presence of three-carbon side chains and their net charges is favorable for the inhibition. The binding of the inhibitory compounds caused only minor changes in the steric structure of arginase: a slight increase in alpha-helix content was detected by circular dichroism together with a decrease in parallel pleated sheet and beta-turn sections. A slight alteration in the tertiary structure was also found using tryptophane fluorescence studies, but buried apolar side chains were not transposed to the protein surface. Computer studies that were performed did not provide additional structural information.