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© Copyright 2004 The British Pharmacological Society

136P University of Newcastle
Winter Meeting December 2004

Reduction of paraquat-mediated renal cell injury by the superoxide dismutase mimetics EUK-134 and tempol

Prabal K. Chatterjee, Niraj Shah & Martyn A, Sharpe #, Department of Pharmacology, School of Pharmacy, University of Brighton, BN2 4GJ and #Department of Molecular Pathogenesis, Institute of Neurology, Queen Square, London WC1N 3BG.

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Chatterjee PK
Shah N
Sharpe MA

Paraquat (methyl viologen) nephrotoxicity occurs via generation of reactive oxygen species (ROS), specifically, superoxide anion (Chan et al., 1998). EUK-134 (manganese 3-methoxy N,N¹ bis(salicyclidene) ethylenediamine chloride) is a superoxide dismutase mimetic (SODm) with catalase activity (Chatterjee et al., 2004). Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) also acts as a SODm with ROS-scavenging properties (Chatterjee et al., 1999). The aim of this study was to investigate whether these chemically distinct SODm could reduce renal cell injury caused by paraquat.

Confluent cultures of NRK-52E cells were incubated with (i) Minimum Essential Medium only (‘MEM-only’ group), (ii) NRK-52E cells treated with 10 mM paraquat only (‘PQ-only’ group), (iii) NRK-52E cells treated with 10 mM paraquat and increasing concentrations of EUK-134 (1 to 100 µM, ‘PQ + EUK’ group) or (iv) NRK-52E cells treated with 10 mM paraquat and increasing concentrations of tempol (0.1 to 10 mM, ‘PQ + Tempol’ group) for 2 hours. Cellular injury was assessed spectrophotometrically by measurement of the mitochondrial-dependent conversion of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) into formazan.

Incubation of NRK-52E cells with 10 mM paraquat for 2 hours inhibited mitochondrial respiration significantly (Tables 1, 2). Incubation with 30 and 100 µM EUK-134 reduced significantly the paraquat-mediated inhibition of mitochondrial respiration (Table 1). Tempol, at a concentration of 10 mM, was also able to attenuate significantly the reduction in mitochondrial respiration caused by paraquat (Table 2).

Table 1 Treatment	Cellular injury (% viability)	N	Table 2 Treatment	Cellular injury (% viability)	N
MEM-only	99.82 ±5.70 +	7	MEM-only	99.95 ±7.83 +	8
PQ-only	24.81 ±0.78 «	7	PQ-only	19.11 ±3.71 «	8
PQ + 1µM EUK	29.01 ±2.94 «	7	PQ + 0.1mM Tempol	13.19 ±2.15 «	8
PQ + 3µM EUK	29.90 ±3.01 «	7	PQ + 0.3mM Tempol	16.72 ±2.34 «	8
PQ + 10µM EUK	33.84 ±2.87 «	7	PQ + 1mM Tempol	18.02 ±3.82 «	8
PQ + 30µM EUK	54.24 ±5.95 «+	7	PQ + 3mM Tempol	30.44 ±3.32 «	8
PQ + 100µM EUK	54.47 ±6.90 «+	7	PQ + 10mM Tempol	45.98 ±5.59 «+	8

Effects of EUK-134 (Table 1) and Tempol (Table 2) on paraquat-mediated injury of NRK-52E cells. Data expressed as mean ± s.e.m, «P<0.05 vs. MEM-only group, +P<0.05 vs. PQ-only group, analysed using one-way ANOVA followed by Dunnett’s.

These results suggest that SODm such as EUK-134 and Tempol can reduce renal injury caused by paraquat and could be beneficial as a therapy for paraquat nephrotoxicity.

Chan, B.S.H., et al., (1998) Pharmacol. Ther.79, 193-203.
Chatterjee, P.K., et al.(1999) Kidney Int. 58, 658-673.
Chatterjee, P.K., et al.(2004) Am. J. Nephrol. 24, 165-177.