Cortical Malondialdehyde Research Articles

Lipid peroxidation accompanies cyclosporine nephrotoxicity: Effects of vitamin E

Cyclosporine A (CsA) has been demonstrated to induce renal microsomal lipid peroxidation in vitro. To examine whether CsA induces lipid peroxidation in vivo, uninephrectomized rats were gavaged with vehicle, CsA 12.5 or 25 mg/kg/day for four weeks. CsA-induced reduction in GFR and RBF was associated with a dose-related increase in renal cortical malondialdehyde (MDA) and conjugated diene, as well as a similar increase in arterial MDA. The latter was apparent within two hours of a single intraperitoneal injection of 25 mg/kg CsA and preceded the acute fall in GFR. To address whether lipid peroxidation contributed to CsA nephrotoxicity, rats were gavaged with vehicles, CsA 25 mg/kg/day or CsA plus vitamin E 25 mg/kg/day for eight weeks. Vitamin E, a lipid radical scavenger, inhibited MDA raise and reduced CsA-induced renal damage. Conversely, CsA administration to vitamin E and selenium deficient rats was accompanied by a greater increase in arterial MDA and fall in GFR. These novel findings, that CsA nephrotoxicity is associated with lipid peroxidation and that a chain-breaking antioxidant ameliorates whereas its deficiency exacerbates, indicate a role for lipid peroxidation, presumably free radical-mediated, in CsA toxicity.

Effects of oxygen free radical scavengers on uranium-induced acute renal failure in rats

Study was made to determine whether oxygen free radicals mediate uranium-induced acute renal failure (ARF). Superoxide dismutase (SOD), a superoxide anion scavenger, did not prevent uranium acetate (UA) (5 mg/kg, i.v.)-induced renal injury 48 h after injection. In contrast, dimethylthiourea (DMTU), a hydroxyl radical scavenger, significantly attenuated UA-induced rise in serum creatinine concentration (1.11 ± 0.05 (DMTU) vs. 1.40 ± 0.06 mg/dl (control), p < .05), and tubular necrosis. Dimethyl sulfoxide (DMSO), a hydroxyl radical scavenger, decreased UA-induced tubular damage. UA injection caused no increase in renal cortical malondialdehyde (MDA) content. DMTU and DMSO did not modify intrarenal MDA content. UA administration brought about significant increase in plasma renin activity but not in renal cortical renin content. Treatment with DMTU and DMSO had no effect on plasma renin activity or intrarenal renin content. It follows from these findings that DMTU and DMSO may attenuate UA-induced renal injury. Such a protective effect would not be mediated through modulation of lipid peroxidation or renin activity.

Taurine attenuates renal disease in chronic puromycin aminonucleoside nephropathy

Repeated administration of low doses of puromycin aminonucleoside (PAMN) to rats induces a proteinuric renal disease that resembles focal segmental glomerulosclerosis (FSGS). Reactive oxygen molecules may be involved in the progressive course of this nephropathy. Therefore we evaluated whether taurine, an endogenous antioxidant, could limit the extent of renal injury. Sprague-Dawley rats received low-dose injections of PAMN, 2 mg/100 g body wt, over a 12-wk period. Two groups were studied: 1) controls given tap water (n = 23), and 2) an experimental group that drank 1% taurine-supplemented water (n = 22). Taurine-treated nephrotic rats had a reduction in albuminuria, as assessed by the urinary albumin-to-creatinine ratio (26 +/- 4 vs. 44 +/- 4, P less than 0.0001). After 12 wk, creatinine clearance was 0.33 +/- 0.03 (experimental) vs. 0.17 +/- 0.03 ml.min-1.100 g body wt-1 (control) (P less than 0.001), and inulin clearance (n = 6 pairs) was 0.26 +/- 0.04 (experimental) vs. 0.13 +/- 0.02 ml.min-1.100 g body wt-1 (control) (P less than 0.025). Administration of taurine reduced the percentage of segmentally sclerosed glomeruli (9.8 +/- 1.7 vs. 16.2 +/- 1.8%, P less than 0.02) and the tubulointerstitial injury score (1.36 +/- 0.19 vs. 2.61 +/- 0.25, P less than 0.0025) in experimental vs. control rats. Taurine treatment normalized the elevated renal cortical malondialdehyde level in rats with PAMN nephropathy (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Oxidative and mitochondrial toxic effects of cephalosporin antibiotics in the kidney: A comparative study of cephaloridine and cephaloglycin

Cephaloridine and cephaloglycin are the two most nephrotoxic cephalosporins released for human use. Cephaloridine has been shown to produce both oxidative and mitochondrial respiratory injury in renal cortex in patterns of dose (or concentration) and time that are consistent with pathogenicity. Cephaloglycin also produces respiratory toxicity, and recent studies have provided evidence that this injury results from an inactivation of mitochondrial anionic substrate transporters. The abilities of cephaloglycin to produce oxidative changes and Cephaloridine to block mitochondrial substrate uptake have not been examined yet. We therefore compared these two cephalosporins with one another and with cephalexin, which is not nephrotoxic, in the production of the following: (1) several components of oxidative stress or damage [depletion of reduced glutathione (GSH) and production of oxidized glutathione (GSSG) in renal cortex, inhibition of glutathione reductase in vitro, and production of the lipid peroxidation products malondialdehyde (MDA) and conjugated dienes (CDs) in renal cortex]; and (2) renal cortical mitochondrial toxicity (to both respiration with, and the transport of, succinate]. Cephaloridine depleted GSH and elevated GSSG in renal cortex, inhibited glutathione reductase, and increased both MDA in whole cortex and CDs in cortical microsomes and mitochondria. While cephaloglycin depleted GSH at least as much as did Cephaloridine, it produced one-fifth as much GSSG and had little or no effect on glutathione reductase activity or on cortical MDA or microsomal CDs; cephaloglycin caused a transient small increase of mitochondrial CDs. Cephalexin produced no oxidative changes except for a slight increase of mitochondrial CDs comparable to that produced by cephaloglycin. Both Cephaloridine and cephaloglycin, but not cephalexin, decreased the unidirectional uptake of, and respiration with, succinate in cortical mitochondria. We conclude that Cephaloridine and cephaloglycin are both toxic to mitochondrial substrate uptake and respiration, but differ significantly in their generation of products of oxidation.

Evidence suggesting a role for hydroxyl radical in glycerol-induced acute renal failure.

Reactive oxygen metabolites, in particular hydroxyl radical, have been shown to be important mediators of tissue injury in several models of acute renal failure. The aim of the present study was to examine the role of hydroxyl radical in glycerol-induced acute renal failure, a model for myoglobinuric renal injury. Rats injected with glycerol alone (8 mg/kg im following dehydration for 24 h) developed significant renal failure compared with dehydrated controls. Rats treated with glycerol and a hydroxyl radical scavenger, dimethylthiourea (DMTU), had significantly lower blood urea nitrogen (BUN) and creatinine. In contrast, urea, which is chemically similar to DMTU but is not a hydroxyl radical scavenger, provided no protection. In addition, DMTU prevented the glycerol-induced rise in renal cortical malondialdehyde content (a measure of lipid peroxidation that serves as a marker of free radical-mediated tissue injury). A second hydroxyl radical scavenger, sodium benzoate, had a similar protective effect on renal function (as measured by both BUN and creatinine). Because the generation of hydroxyl radical in biological systems requires the presence of a trace metal such as iron, we also examined the effect of the iron chelator, deferoxamine on glycerol-induced renal failure. Deferoxamine was also protective. The interventional agents were also associated with a marked reduction in histological evidence of renal damage. The protective effects of two hydroxyl radical scavengers as well as an iron chelator implicate a role for hydroxyl radical in glycerol-induced acute renal failure.

Evidence suggesting a role for hydroxyl radical in gentamicin-induced acute renal failure in rats.

The protective effect of hydroxyl radical scavengers and iron chelators has strongly implicated the hydroxyl radical in several models of tissue injury. Based on in vitro studies showing gentamicin-enhanced generation of reactive oxygen metabolites in renal cortical mitochondria, we examined the effect of hydroxyl radical scavengers and iron chelators in gentamicin-induced acute renal failure. Rats treated with gentamicin (G) alone (100 mg/kg, s.c. x 8 d) developed advanced renal failure (BUN 215 +/- 30 mg/dl) compared to saline-treated controls (BUN 16 +/- 1 mg/dl, P less than 0.001). In contrast, rats treated with gentamicin and either dimethylthiourea (DMTU, an hydroxyl radical scavenger, 125 mg/kg, i.p. twice a day) or deferoxamine (DFO, an iron chelator, 20 mg/day by osmotic pump) had significantly lower BUN (G + DMTU 48.8 +/- 8 mg/dl, P less than 0.001, n = 8; G + DFO 30 +/- 7 mg/dl, P less than 0.001, n = 8). In separate experiments, treatment with two other hydroxyl radical scavengers (dimethyl sulfoxide or sodium benzoate) and a second iron chelator (2,3,dihydroxybenzoic acid) had a similar protective effect on renal function (as measured by both BUN and creatinine). In addition, histological evidence of damage was markedly reduced by the interventional agents. Finally, concurrent treatment with DMTU prevented the gentamicin induced increase in renal cortical malondialdehyde content (G: 4.4 +/- 0.2 nmol/mg; G + DMTU: 3.1 +/- 0.2 nmol/mg, P less than 0.0001, n = 8) suggesting that the protective effect of DMTU was related to free radical mechanisms rather than to some other effect. Taken together, these data strongly support a role for hydroxyl radical or a similar oxidant in gentamicin-induced acute renal failure.

Failure of inhibition of lipid peroxidation by vitamin E to protect against gentamicin nephrotoxicity in the rat

We tested the hypothesis that accelerated lipid peroxidation, possibly at the level of the lysosome, is linked causally to the pathogenesis of aminoglycoside nephrotoxicity by investigating whether administration of vitamin E would inhibit lipid peroxidation and prevent or ameliorate gentamicin-induced proximal tubular cell injury. Five groups of rats were injected with either saline, vitamin E (600 mg/kg per day) for 6 days, gentamicin (100 mg/kg per day) for 6 days, vitamin E for 6 days plus gentamicin for 6 days or vitamin E for 12 days and gentamicin for the last 6 days. Gentamicin alone induced a 16% increase in renal cortical phospholipids; vitamin E had no significant effect on this change. Gentamicin alone caused accelerated lipid peroxidation evident by a doubling of renal cortical malondialdehyde to 1.23 nmol/mg protein, and a sharp decline of esterified polyunsaturated fatty acids, especially arachidonic acid which fell 43%. These changes were accompanied by depressions of Superoxide dismutase, catalase, and total glutathione and a shift from reduced to oxidized glutathione. Concurrent treatment of rats with vitamin E plus gentamicin for 6 days had no significant effect on the gentamicin-induced alterations of malondialdehyde, Superoxide dismutase, catalase or the glutathione cascade; however, the shift from polyunsaturated to saturated fatty acids was largely reversed. In rats pretreated with vitamin E for 6 days, gentamicin failed to raise renal cortical malondialdehyde above that of saline-treated rats. The changes in esterified fatty acids were prevented almost entirely, and there were no significant alterations from control of the glutathione cascade. The depressions of Superoxide dismutase and of catalase, however, were not reversed. Vitamin E did not affect the amount of gentamicin accumulated in renal cortex nor did it prevent the gentamicin-induced rise of serum creatinine. Examination of renal cortex by light and electron microscopy revealed that vitamin E did not prevent or even reduce the severity of gentamicin-induced proximal tubular cell lesions and necrosis. These results confirm those we obtained in a previous study with the antioxidant diphenyl-phenylenediamine. The observation that inhibition of lipid peroxidation by two distinct antioxidants failed to prevent proximal tubular cell injury and renal dysfunction associated with gentamicin administration leads us to conclude that lipid peroxidation is a consequence and not a cause of gentamicin-induced nephrotoxicity.