Protective Effect of Oral L-arginine Supplementation on Cyclosporine Induced Nephropathy in Rats

Chrysin Ameliorates Cyclosporine-A-Induced Renal Fibrosis by Inhibiting TGF-β1-Induced Epithelial-Mesenchymal Transition

Cyclosporine A (CsA) is a nephrotoxicant that causes fibrosis via induction of epithelial-mesenchymal transition (EMT). The flavonoid chrysin has been reported to have anti-fibrotic activity and inhibit signaling pathways that are activated during EMT. This study investigated the nephroprotective role of chrysin in the prevention of CsA-induced renal fibrosis and elucidated a mechanism of inhibition against CsA-induced EMT in proximal tubule cells. Treatment with chrysin prevented CsA-induced renal dysfunction in Sprague Dawley rats measured by blood urea nitrogen (BUN), serum creatinine and creatinine clearance. Chrysin inhibited CsA-induced tubulointerstitial fibrosis, characterized by reduced tubular damage and collagen deposition. In vitro, chrysin significantly inhibited EMT in LLC-PK₁ cells, evidenced by inhibition of cell migration, decreased collagen expression, reduced presence of mesenchymal markers and elevated epithelial junction proteins. Furthermore, chrysin co-treatment diminished CsA-induced TGF-β₁ signaling pathways, decreasing Smad 3 phosphorylation which lead to a subsequent reduction in Snail expression. Chrysin also inhibited activation of the Akt/ GSK-3β pathway. Inhibition of both pathways diminished the cytosolic accumulation of β-catenin, a known trigger for EMT. In conclusion, flavonoids such as chrysin offer protection against CsA-induced renal dysfunction and interstitial fibrosis. Chrysin was shown to inhibit CsA-induced TGF-β₁-dependent EMT in proximal tubule cells by modulation of Smad-dependent and independent signaling pathways.

Detrimental Effects of Chronic L-Arginine Rich Food on Aging Kidney

The impaired L-arginine/nitric oxide pathway is a well-recognized mechanism for cardiovascular and renal diseases with aging. Therefore, supplementation of L-arginine is widely proposed to boost health or as adjunct therapy for the patients. However, clinical data, show adverse effects and even enhanced mortality in patients receiving long-term L-arginine supplementation. The effects of long-term L-arginine supplementation on kidney aging and the underlying mechanisms remain elusive. Moreover, high protein and high amino acid diet has been thought detrimental for kidney. We therefore investigated effects of chronic dietary L-arginine supplementation on kidney aging. In both young (4 months) and old (18-24 months) mice, animals either receive standard chow containing 0.65% L-arginine or diet supplemented with L-arginine to 2.46% for 16 weeks. Inflammation and fibrosis markers and albuminuria are then analyzed. Age-associated increases in tnf-α, il-1β, and il-6, vcam-1, icam-1, mcp1, inos, and macrophage infiltration, collagen expression, and S6K1 activation are observed, which is not favorably affected, but rather further enhanced, by L-arginine supplementation. Importantly, L-arginine supplementation further enhances age-associated albuminuria and mortality particularly in females, accompanied by elevated renal arginase-II (Arg-II) levels. The enhanced albuminuria by L-arginine supplementation in aging is not protected in Arg-II^-/- mice. In contrast, L-arginine supplementation increases ROS and decreases nitric oxide production in old mouse aortas, which is reduced in Arg-II^-/- mice. The results do not support benefits of long-term L-arginine supplementation. It rather accelerates functional decline of kidney and vasculature in aging. Thus, the long-term dietary L-arginine supplementation should be avoided particularly in elderly population.

Metformin and silymarin afford protection in cyclosporine A induced hepatorenal toxicity in rat by modulating redox status and inflammation

The use of cyclosporine A (CsA) as an immunosuppressive agent is often limited owing to its hepatotoxic and nephrotoxic properties. The present study was designed to evaluate the protective effect of metformin and silymarin in a rat model of CsA induced hepatorenal toxicity. The study included seven groups of Wistar albino rats (n = 6 per group): normal control, experimental control (CsA alone, 25 mg/kg), CsA + metformin (50 and 500 mg/kg), CsA + silymarin (50 and 200 mg/kg) and CsA + vitamin E (100 mg/kg). All the drugs were given daily for a period of 21 days by oral gavage and their effect was evaluated on serum levels of organ function markers (serum glutamate pyruvate transaminase, serum glutamate oxaloacetate transaminase, bilirubin, urea/blood urea nitrogen, creatinine), markers of oxidative stress (thiobarbituric acid reactive substances, glutathione, superoxide dismutase), inflammation (nitrite, myeloperoxidase, tumour necrosis factor-alpha, prostaglandin E₂ ), apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labelling positivity) in addition to tissue histology, cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) immunoreactivity. Administration of metformin and silymarin along with CsA ameliorated functional damage to liver and kidneys in a dose-dependent manner. Significant and comparable improvement in the tissue levels of oxidative stress, inflammation, apoptotic markers was also observed following treatment with both the test drugs. Normalization of histology scores, as well as COX-2 and iNOS immunoreactivity scores, further strengthened these findings. The hepatoprotective and nephroprotective effects of metformin and silymarin were comparable and matched with that of reference drug, vitamin E. The findings of the present study suggest that both metformin and silymarin have a potential for clinical use in patients receiving long-term CsA treatment to maintain their liver and kidney functions.

Restored nitric oxide bioavailability reduces the severity of acute-to-chronic transition in a mouse model of aristolochic acid nephropathy

Aristolochic Acid (AA) nephropathy (AAN) is a progressive tubulointerstitial nephritis characterized by an early phase of acute kidney injury (AKI) leading to chronic kidney disease (CKD). The reduced nitric oxide (NO) bioavailability reported in AAN might contribute to renal function impairment and progression of the disease. We previously demonstrated that L-arginine (L-Arg) supplementation is protective in AA-induced AKI. Since the severity of AKI may be considered a strong predictor of progression to CKD, the present study aims to assess the potential benefit of L-Arg supplementation during the transition from the acute phase to the chronic phase of AAN. C57BL/6J male mice were randomly subjected to daily i.p. injections of vehicle or AA for 4 days. To determine whether renal AA-induced injuries were linked to reduced NO production, L-Arg was added to drinking water from 7 days before starting i.p. injections, until the end of the protocol. Mice were euthanized 5, 10 and 20 days after vehicle or AA administration. AA-treated mice displayed marked renal injury and reduced NO bioavailability, while histopathological features of AAN were reproduced, including interstitial cell infiltration and tubulointerstitial fibrosis. L-Arg treatment restored renal NO bioavailability and reduced the severity of AA-induced injury, inflammation and fibrosis. We concluded that reduced renal NO bioavailability contributes to the processes underlying AAN. Furthermore, L-Arg shows nephroprotective effects by decreasing the severity of acute-to-chronic transition in experimental AAN and might represent a potential therapeutic tool in the future.

Sildenafil protects against nitric oxide deficiency-related nephrotoxicity in cyclosporine A treated rats

Cyclosporine A (CsA) is the most widely used immunosuppressant in organ transplant surgery and in treatment of autoimmune disease. Nevertheless, animal and clinical studies have demonstrated that nephrotoxicity is the major adverse effect limiting the prolonged CsA therapeutic use. The present study aimed to investigate possible protective effect of sildenafil, a phoshodiestrase-5 inhibitor, on CsA-induced nephrotoxicity and various mechanism(s) underlies this effect. Male Wistar rats were administered CsA (20 mg/kg/day, s.c.) for 21 days alone or in combination with sildenafil (5 mg/kg/day, p.o.). Sildenafil exhibited nephroprotective effects as evidenced by significant decrease in serum creatinine and urea levels, spot urine albumin-creatinine ratio, as well as renal level of malondialdehyde, with a concurrent increase in renal levels of reduced glutathione and nitric oxide along with catalase activity compared to CsA-treated rats. [corrected]. Additionally, immunohistochemical analysis demonstrated that sildenafil treatment markedly reduced inducible nitric oxide synthase, tumor necrosis factor-alpha, and caspase-3 expressions, while expression of endothelial nitric oxide synthase was prominently enhanced. The protective effects of sildenafil were confirmed by renal histopathological examination. Pretreatment with l-nitro-arginine methyl ester (10 mg/kg/day, i.p.), a non-selective nitric oxide synthase inhibitor, reversed the protection afforded by sildenafil. Taken together, the current study highlighted the renoprotective effects of sildenafil against CsA-induced nephrotoxicity in rats, which might be mediated, in part, through nitric oxide pathway as well as antioxidant, anti-inflammatory, and anti-apoptotic activities.

Endothelial nitric oxide synthase gene variation associated with chronic kidney disease after liver transplant

OBJECTIVE

To identify single nucleotide polymorphisms (SNPs) associated with risk of developing chronic kidney disease (CKD), a prevalent comorbidity, after liver transplant (LT).

PATIENTS AND METHODS

This study consists of a cohort of adult (> or =18 years) primary-LT recipients who had normal renal function before LT and who survived 1 year or more after LT at a high-volume US LT program between January 1, 1990, and December 31, 2000. Patients with adequate renal function (estimated glomerular filtration rate, > or =40 mL/min per 1.73 m(2) during follow-up; n=308) and patients with incident CKD (estimated glomerular filtration rate, <40 mL/min per 1.73 m(2) after LT; n=92) were identified. To investigate the association of 6 candidate genes with post-LT CKD, we selected SNPs that have been associated with renal function in the literature. Hazard ratios were estimated using Cox regression, adjusted for potential confounding variables.

RESULTS

The variant allele (298Asp) of the Glu298Asp SNP in the endothelial nitric oxide synthase gene (NOS3) was significantly associated with CKD after LT (P=.05; adjusted for multiple comparisons). The 5-year incidence of CKD was 70% among patients homozygous for the NOS3 variant allele (298Asp) compared with 42% among those not homozygous for the NOS3 variant allele. Specifically, homozygosity for the NOS3 variant allele conferred a 2.5-fold increased risk of developing CKD after LT (P=.005, adjusted for confounding variables).

CONCLUSION

Homozygosity for the variant allele of NOS3 (298Asp) is associated with CKD after LT and may be useful for identifying recipients at higher risk of post-LT CKD.

Cyclosporine A: impact on mitochondrial function in endothelial cells

INTRODUCTION

Although cyclosporine A (CSA) is considered to be an efficient immunosuppressive compound in transplantation, vascular side effects like arterial hypertension, neurologic complications and other adverse reactions occur. Interference of CSA with mitochondrial function may be responsible for these side effects.

METHODS

We evaluated the effect of CSA on mitochondrial and glycolytic function by measuring fatty acid oxidation (FAO), activities of respiratory chain complexes (RC) and citratesynthase (CS), lactate/pyruvate-ratios, energy-rich phosphates as well as activities of some glycolytic enzymes in human umbilical vein endothelial cells.

RESULTS

After 48 h of CSA incubation, global FAO, RC-complexes 1 + 3; 4 and 5 as well as CS were compromised while energy charges were not reduced. Lactate/pyruvate-ratios increased; cellular lactate dehydrogenase (LDH)-, hexokinase- and phosphofructokinase-activities were not impaired by CSA. Moderate cellular toxicity, assessed by LDH leakage, appeared only at the highest CSA concentration.

CONCLUSION

Part of CSA toxicity may arise from alterations in mitochondrial function as judged by impaired FAO and respiratory chain enzymes. To some extent, energy balance seems to be maintained by cytosolic energy production. Although only demonstrated for endothelial cells, it is conceivable that such effects will alter energy metabolism of different organs with high oxidative energy demands.

Experimental models for nephropathy

Nephropathy is a leading cause of morbidity and mortality and its prevalence is continuously increasing in industrialised nations. Nephropathy is characterised to varying degrees by nodular glomerulosclerosis, glomerular basement membrane thickness and mesangial expansion, leading to a decline in glomerular filtration rate, persistent elevated albuminuria, elevated arterial blood pressure and fluid retention. Hyperglycaemia, hyperlipidaemia and hypertension are considered to be the major risk factors implicated in the progression of nephropathy.Various signalling systems, such as vasoconstrictor peptides, inflammatory mediators, growth factors and adhesion molecules, are involved in the pathogenesis of nephropathy.At present, no promising therapy is available to treat patients with nephropathy due to lack of understanding of signalling culprits involved in the pathogenesis of nephropathy. Animal models are being developed to better understand the disease pathogenesis and develop drugs for nephropathy. In the present review, we have discussed various animal models for nephropathy, which may open vistas for developing new drugs to treat nephropathy.

Lycopene, a Carotenoid, Attenuates Cyclosporine-Induced Renal Dysfunction and Oxidative Stress in Rats

The aim of this study was to investigate the possible protective role of antioxidant treatment with lycopene on cyclosporine A-induced nephrotoxicity using biochemical and histopatological approaches. Adult male Sprague-Dawley rats were randomly divided into four groups. The control group received physiological saline; animals in the lycopene group received only lycopene (10 mg/kg); animals in the cyclosporine A group received only cyclosporine A (15 mg/kg) and animals in cyclosporine plus lycopene group received cyclosporine and lycopene for 21 days. The effects of lycopene on cyclosporine A-induced nephrotoxicity were evaluated by plasma creatinine, urea, sodium and calcium concentrations; kidney tissue thiobarbituric acid reactive species, reduced glutathione (GSH), glutathione peroxidase (GSH-Px) and catalase activities and histopatological examinations. Administration of cyclosporine A to rats induced a marked renal failure, characterized with a significant increase in plasma creatinine and urea concentrations. Cyclosporine A also induced oxidative stress as indicated by increased kidney tissue concentrations of thiobarbituric acid reactive species and GSH, and reduced activities of GSH-Px and catalase. Moreover, the kidneys of cyclosporine A-treated rats showed tubular necrosis, degeneration, dilatation, thickened basement membranes, luminal cast formation and inter-tubular fibrosis. Lycopene markedly reduced elevated plasma creatinine, urea levels and counteracted the deleterious effects of cyclosporine A on oxidative stress markers. In addition, lycopene ameliorated cyclosporine A-induced pathological changes including tubular necrosis, degeneration, thickened basement membranes and inter-tubular fibrosis when compared to the alone cyclosporine A group. These data indicate that the natural antioxidant lycopene might have protective effect against cyclosporine-induced nephrotoxicity and oxidative stress in rat.

Sodium nitroprusside and l-arginine attenuates ferric nitrilotriacetate-induced oxidative renal injury in rats

The role of nitric oxide (NO) in acute renal failure (ARF) is debatable. In the present study, we investigated the effect of acute administration of NO donor, Sodium nitroprusside (SNP), L-Arginine (L-Arg) and NO synthase inhibitor, N(omega)-L-arginine methyl ester (L-NAME) in Fe-NTA induced renal toxicity. Rats were pretreated with SNP (2.5 mg/kg i.p), L-Arg (125 mg/kg, i.p.) and L-NAME (10 mg/kg, i.p.) prior to administration of Fe-NTA (8 mg iron/kg body weight, i.p.) to determine the urea and creatinine levels along with biochemical analysis of oxidative stress. Fe-NTA administration markedly increased the BUN and serum creatinine level which was coupled with a marked lipid peroxidation, decreased levels of reduced glutathione and total nitric oxide levels of rat kidneys coupled with significant morphological alterations. It also resulted in the significant increase in tumor necrosis factor-alpha (TNF-alpha) in serum. Concomitant treatment with SNP and L-Arg significantly reduced the serum creatinine and BUN levels, reduced lipid peroxidation in a significant manner, restored levels of reduced glutathione, increased total nitric oxide levels and restored the normal morphology. Pretreatment with SNP and L-Arg attenuated the levels of TNF-alpha in serum in a significant manner. Prior administration of L-NAME reversed the protective effects produced by SNP and L-Arg. Present findings strongly suggest that nitric oxide plays a significant role in the pathophysiology of iron-induced renal failure and administration of NO donors can be valuable in the treatment of ARF.

Nitric oxide/cytochrome P450 interactions in cyclosporin A-induced effects in the rat

INTRODUCTION

The present study evaluated the contribution of 20-hydroxyeicosatetraenoic acid (20-HETE) and its interaction with nitric oxide (NO) in cyclosporin A-induced nephrotoxicity and hypertension.

METHODS AND RESULTS

The treatment of rats with cyclosporin A (25 mg/kg) for 7 days increased the renal microsomal conversion of arachidonic acid (AA) to 20-HETE (93 +/- 6%, P < 0.05), increased systolic blood pressure (SBP), reduced the urinary excretion of nitrite (53 +/- 8%, P < 0.05), induced renal damage as indicated by a marked increase in protein excretion (163 +/- 14%, P < 0.05), increased renal vasoconstrictor responses to AA (82 +/- 5%, P < 0.05) but not endothelin-1 or phenylephrine, and decreased vasodilator responses to bradykinin (42 +/- 10%, P < 0.05) and sodium nitroprusside (SNP; 56 +/- 13%, P < 0.05) in the renal preglomerular vessel treated with indomethacin and NO synthase inhibitor. The pretreatment of rats with HET0016 (10 mg/kg) or 1-aminobenzotriazole (50 mg/kg), inhibitors of cytochrome P450 (CYP450) activity, attenuated or prevented cyclosporin A-induced increases in 20-HETE production, SBP, and protein excretion, as did L-arginine (4 g/l), a substrate for NO synthase. L-Arginine but not HET0016 or 1-aminobenzotriazole blunted the cyclosporin A-induced decrease in nitrite excretion. Similarly, L-arginine blunted the enhanced vasoconstriction by AA as did HET0016 or 1-aminobenzotriazole. However, cyclosporin A-blunted dilator responses to bradykinin and SNP were not affected by L-arginine, HET0016, or 1-aminobenzotriazole.

CONCLUSIONS

These data suggest that cyclosporin A-induced nephrotoxicity can be accounted for by reduced NO production and a consequent increase in 20-HETE. The cyclosporin A-induced nephrotoxicity is thus an ideal model for evaluating NO/CYP450 interactions.