THE EFFECT OF MYCOPHENOLATE MOFETIL AND POLYPHENOLIC BIOFLAVONOIDS ON RENAL ISCHEMIA REPERFUSION INJURY AND REPAIR:

Upregulation of rat renal cortical organic anion transporter (OAT1 and OAT3) expression in response to ischemia/reperfusion injury

BACKGROUND/AIMS

Renal organic anion transporters (OAT1 and OAT3) localized in the basolateral membrane mediate the uptake of organic anions from the blood into proximal tubules. This study aimed to examine the effects of renal ischemia/reperfusion injury (IRI) on the expression of cortical renal OAT1 and OAT3 and the functional impact.

METHODS

Male rats underwent a right nephrectomy and clamping of the left renal pedicle for 50 min or sham operation, followed by reperfusion for 1, 2, 4 and 6 days. The expression of OAT1 and OAT3 was detected by RT-PCR, immunohistochemistry and Western blot analysis. Na(+)-K(+)-ATPase activity was also estimated.

RESULTS

The renal clearance of para-aminohippurate was significantly decreased on day 1 in IRI rats compared with sham-operated rats and returned to normal when the tubular injury recovered. There were significant increases in the mRNA and protein levels of OAT1 and OAT3 in renal cortex homogenates and basolateral membranes on day 1 after IRI, while on days 2 and 4 after IRI, the renal expression of OAT1 and OAT3 decreased gradually but was still significantly higher than that of the sham-operated rats. The Na(+)-K(+)-ATPase activity in renal cortex homogenates decreased significantly on day 1 after IRI but gradually increased on days 2, 4 and 6.

CONCLUSIONS

Renal para-aminohippurate clearance was depressed in response to IRI; however, the expressions of renal cortex OAT1 and OAT3 were significantly elevated in the early stage of IRI which may have substantial impact on renal excretion of some drugs and toxic compounds.

Reversal of Experimental Myoglobinuric Acute Renal Failure in Rats by Quercetin, a Bioflavonoid

The occurrence of acute renal failure (ARF) following rhabdomyolysis has been put at between 10 and 40% of cases, and accounts for between 3 and 15% of all cases of ARF. Reactive oxygen intermediates have been demonstrated to play an etiological role in myoglobinuric renal failure. This study was performed to explore the protective effect of quercetin, a bioflavonoid, in an experimental model of myoglobinuric ARF in rats. Four groups of rats were employed in this study: group 1 served as control, group 2 was given 50% glycerol (8 ml/kg, i.m.), group 3 was given glycerol + quercetin (2 mg/kg, i.p.), and group 4 was given glycerol + DMSO (the solvent for quercetin, 5 ml/kg, i.p.). Renal injury was assessed by measuring serum creatinine, blood urea nitrogen, creatinine and urea clearance. The oxidative stress was measured by renal malondialdehyde levels, reduced glutathione levels and by enzymatic activity of catalase, glutathione reductase, and superoxide dismutase. Glycerol administration resulted in a marked renal oxidative stress, significantly deranged the renal functions as well as renal cytoarchitecture. All these factors were significantly improved by quercetin treatment. Because of its radical-scavenging and iron-chelating properties, quercetin protected the kidney against the glycerol-induced oxidative stress and resultant renal dysfunction. Based on these results, this study confirms the role of oxidative stress and demonstrates the renoprotective potential of quercetin in this rhabdomyolysis-mimicking model.

Protective Effect of Quercetin on the Evolution of Cisplatin-Induced Acute Tubular Necrosis

BACKGROUND

The mechanism of cisplatin-induced nephrotoxicity is unknown, but has been associated with renal lipid peroxidation. The bioflavonoid quercetin may be a potential alternative to reduce cisplatin-induced nephrotoxicity. The aim of this study was to evaluate the effect of quercetin on the evolution of cisplatin-induced acute tubular necrosis.

METHODS

One hundred and three male Wistar rats were injected with cisplatin (5 mg/kg, i.p.), 43 of them received quercetin (50 mg/kg, by gavage) before cisplatin injection. Blood and urine were collected 5 and 20 days after the injection for the determination of plasma creatinine, urine volume and osmolality. The kidneys were removed for the determination of renal malondialdehyde (MDA) and for histological and immunohistochemical studies. The renal expression of fibronectin, alpha-smooth muscle actin, vimentin, Jun N-terminal kinase, nuclear factor-kappaB, and macrophages during the evolution of the acute tubular necrosis induced by cisplatin and the histological changes observed in the kidneys were analyzed.

RESULTS

Cisplatin-treated rats presented a transitory increase in plasma creatinine levels, tubular cell necrosis and increased immunostaining for vimentin, alpha-SM-actin, fibronectin, ED1, NF-kappaB, and p-JNK in the renal cortex and outer medulla. These alterations were less intense in animals treated with quercetin.

CONCLUSION

Quercetin treatment attenuated the functional, histological and immunohistochemical alterations induced by cisplatin.

Dietary quercetin augments activator protein-1 and does not reduce nuclear factor-kappa B in the renal cortex of rats with established chronic glomerular disease

BACKGROUND/AIMS

Quercetin, a naturally occurring dietary flavonoid, is a potent in vitro inhibitor of the transcription factors, nuclear factor (NF)-kappa B and activator protein (AP)-1. Here we investigated the efficacy of quercetin to suppress renal cortical NF-kappa B/AP-1 activation and tubulointerstitial injury, in vivo, in a nephrotic rat model of chronic glomerular disease.

METHODS

Adult male Wistar rats with (n = 27) or without (n = 15) Adriamycin nephropathy (AN) were stratified into six groups (according to proteinuria and endogenous creatinine clearance, measured on day 10) and pair-fed a semipurified diet supplemented with or without quercetin (0.5, 2%) from day 14 to 36.

RESULTS

Quercetin-fed rats had minimal weight gain during the study (p < 0.05). In AN, proteinuria, the decline in endogenous creatinine clearance, hypercholesterolaemia and cortical tubulointerstitial injury were not reduced by quercetin. Quercetin had no effect on renal cortical NF-kappa B activation, but unexpectedly exacerbated the induction of AP-1 in AN (by 67%, p < 0.05). In normal rats, quercetin increased proteinuria (by 75%, p < 0.05), renal cortical AP-1 activation (by 198%, p = 0.06), and malondialdehyde production (by 110%, p < 0.05).

CONCLUSION

These data suggest that supplementation of the diet with quercetin is not an effective therapeutic strategy alone to reduce NF-kappa B/ AP-1 activation in chronic glomerular diseases, and paradoxically could be associated with adverse renal effects.