Cephaloridine-induced lipid peroxidation initiated by reactive oxygen species as a possible mechanism of cephaloridine nephrotoxicity

How do we fit ferroptosis in the family of regulated cell death?

In the last few years many new cell death modalities have been described. To classify different types of cell death, the term 'regulated cell death' was introduced to discriminate it from 'accidental cell death'. Regulated cell death involves the activation of genetically encoded molecular machinery that couples the presence of some signal to cell death. These forms of cell death, like apoptosis, necroptosis and pyroptosis have important physiological roles in development, tissue repair, and immunity. Accidental cell death occurs in response to physical or chemical insults and occurs independently of molecular signalling pathways. Ferroptosis, an emerging and recently (re)discovered type of regulated cell death occurs through Fe(II)-dependent lipid peroxidation when the reduction capacity of a cell is insufficient. Ferroptosis is coined after the requirement for free ferrous iron. Here, we will consider the extent to which ferroptosis is similar to other regulated cell deaths and explore emerging ideas about the physiological role of ferroptosis.

Xenobiotic transporters and kidney injury

Renal proximal tubules are targets for toxicity due in part to the expression of transporters that mediate the secretion and reabsorption of xenobiotics. Alterations in transporter expression and/or function can enhance the accumulation of toxicants and sensitize the kidneys to injury. This can be observed when xenobiotic uptake by carrier proteins is increased or efflux of toxicants and their metabolites is reduced. Nephrotoxic chemicals include environmental contaminants (halogenated hydrocarbon solvents, the herbicide paraquat, the fungal toxin ochratoxin, and heavy metals) as well as pharmaceuticals (certain beta-lactam antibiotics, antiviral drugs, and chemotherapeutic drugs). This review explores the mechanisms by which transporters mediate the entry and exit of toxicants from renal tubule cells and influence the degree of kidney injury. Delineating how transport proteins regulate the renal accumulation of toxicants is critical for understanding the likelihood of nephrotoxicity resulting from competition for excretion or genetic polymorphisms that affect transporter function.

Engineering of Penicillium chrysogenum for fermentative production of a novel carbamoylated cephem antibiotic precursor

Penicillium chrysogenum was successfully engineered to produce a novel carbamoylated cephalosporin that can be used as a synthon for semi-synthetic cephalosporins. To this end, genes for Acremonium chrysogenum expandase/hydroxylase and Streptomyces clavuligerus carbamoyltransferase were expressed in a penicillinG high-producing strain of P.chrysogenum. Growth of the engineered strain in the presence of adipic acid resulted in production of adipoyl-7-amino-3-carbamoyloxymethyl-3-cephem-4-carboxylic acid (ad7-ACCCA) and of several adipoylated pathway intermediates. A combinatorial chemostat-based transcriptome study, in which the ad7-ACCCA-producing strain and a strain lacking key genes in beta-lactam synthesis were grown in the presence and absence of adipic acid, enabled the dissection of transcriptional responses to adipic acid per se and to ad7-ACCCA production. Transcriptome analysis revealed that adipate catabolism in P.chrysogenum occurs via beta-oxidation and enabled the identification of putative genes for enzymes involved in mitochondrial and peroxisomal beta-oxidation pathways. Several of the genes that showed a specifically altered transcript level in ad7-ACCCA-producing cultures were previously implicated in oxidative stress responses.

Protection against cephalosporin-induced lipid peroxidation and nephrotoxicity by (+)-cyanidanol-3 and vitamin E

The ability of the clinically used cephalosporins: cephalothin, cefotaxime and cefotiam to induce lipid peroxidation (LPO) and renal damage was compared to that of nephrotoxic cephaloridine under in vivo conditions. Glutathione was measured in rat liver or in renal cortex as non-protein sulfhydryls. LPO was measured in plasma, renal cortex and liver by the generation of malondialdehyde or as the increase in renal cortical concentration of conjugated dienes. Impairment of renal function was measured as the decrease in renal cortical accumulation of the organic anion p-aminohippurate (PAH). Administration of cephalosporins to rats as a single dose (2000 mg/kg, ip) induced a significant glutathione-depletion in the renal cortex with cephaloridine, and in the liver with cephaloridine, cephalothin and cefotiam. Treatment of rats with cephaloridine, cephalothin and cefotiam (200, 500, or 1000 mg kg-1 day-1, ip) for 5 days resulted in a dose-dependent increase of LPO in the renal cortex. While cephaloridine induced the highest concentration of conjugated diene, cefotaxime had no effect. Measurements of PAH accumulation in renal cortical slices from cephalosporin-treated rats showed a dose-dependent decrease in the renal cortical accumulation of PAH. Pretreatment with the antioxidants vitamin E or cyanidanol (400 mg kg-1 day-1, ip) 1 h before treatment with cephaloridine, cephalothin or cefotiam (1000 mg kg-1 day-1, ip) for 3 days inhibited cephalosporin-induced LPO and significantly reduced the impairment of renal cortical accumulation of PAH. The potential of different cephalosporins for inducing LPO and reducing PAH accumulation was ranked as follows: cephaloridine > cephalothin > cefotiam > cefotaxime.

Cephaloridine Induces Translocation of Protein Kinase C δ Into Mitochondria and Enhances Mitochondrial Generation of Free Radicals in the Kidney Cortex of Rats Causing Renal Dysfunction

We have previously reported that the enhancement of free radical generation in mitochondria isolated from the kidney cortex of rats exposed to cephaloridine (CER) is probably mediated by the activation of protein kinase C (PKC). We examined which isoenzymes of PKC might be involved in the development of nephrotoxicity induced by CER in rats. The CER-induced renal dysfunction observed 24 h after its injection was prevented by a potent antioxidant DPPD and well-known PKC inhibitors like H-7 and rottlerin. At 1.5 and 3.5 h after the CER injection, the free radical generation was increased markedly and this was associated with translocation of PKCdelta into the mitochondria of renal cortex tissue. Pretreatment of rats with H-7, a PKC inhibitor, significantly inhibited the CER-derived increase in mitochondrial generation of free radicals, suggesting that H-7 probably gets into the mitochondria and inhibits the activity of translocated PKC within the mitochondria. It was also shown that pretreatment of rats with rottlerin, a specific inhibitor of PKCdelta, suppressed the early translocation of PKCdelta into mitochondria and inhibited the CER-derived development of renal dysfunction. These results suggest that the CER-derived early translocation of PKCdelta into mitochondria probably leads to the enhanced production of free radicals through the mitochondrial respiratory chain during the development of the nephrotoxicity caused by CER. Understanding the role of PKCdelta in mitochondria may provide an important clue to the molecular mechanisms of mitochondrial production of reactive oxygen species and the free radical-induced renal failure in rats treated with CER.

Protective Effect of Serum Thymic Factor, FTS, on Cephaloridine-Induced Nephrotoxicity in Rats

Serum thymic factor (FTS), a thymic peptide hormone, has been reported to increase superoxide disumutase (SOD) levels in senescence-accelerated mice. In the present study, we examined the effect of FTS on cephaloridine (CER)-induced nephrotoxicity in vivo and in vitro. We previously reported that CER led to extracellular signal-regulated protein kinase (ERK) activation in the rat kidney. So, we also investigated whether FTS has an effect on ERK activation induced by CER. Treatment of male Sprague-Dawley rats with intravenous CER (1.2 g/kg) for 24 h markedly increased BUN and plasma creatinine levels and urinary excretion of glucose and protein, decreased creatinine clearance and also led to marked pathological changes in the proximal tubules, as revealed by electron micrographs. An increase in phosphorylated ERK (pERK) was detected in the nuclear fraction prepared from the rat kidney cortex 24 h after CER injection. Pretreatment of rats with FTS (50 microg/kg, i.v.) attenuated the CER-induced renal dysfunction and pathological damage. FTS also suppressed CER-induced ERK activation in the kidney. In vitro treatment of the established cell line, LLC-PK1 cells, with FTS significantly ameliorated CER-induced cell injury, as measured by lactate dehydrogenase (LDH) leakage. Our results, taken together with our previous report that MEK inhibitors ameliorated CER-induced renal cell injury and ERK activation induced by CER, suggest that FTS participates in protection from CER-induced nephrotoxicity by suppressing ERK activation induced by CER.

Involvement of MEK/ERK pathway in cephaloridine-induced injury in rat renal cortical slices

We have previously reported that free radical-mediated injury induced by cephaloridine (CER) is enhanced by phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, in rat renal cortical slices. We have also shown that PKC activation in mitochondria is involved in CER-induced nephrotoxicity in rats. We investigated the role of a downstream PKC pathway, a MEK/ERK pathway, in free radical-induced injury in rat renal cortical slices exposed to CER. Immediately after preparing slices from rat renal cortex, the slices were incubated in the medium containing MEK inhibitors. ERK1/2 activation was determined by Western blot analysis for phosphorylated ERK (pERK) 1/2 protein in nucleus fraction prepared from the slices exposed to CER. Prominently, CER caused not only increases in lipid peroxidation as an index of free radical generation and in LDH leakage as that of cell injury in the slices, but also marked activation of ERK1/2 in nucleus fraction. PD98059 and U0126, MEK1/2 inhibitors, significantly attenuated CER-induced increases in lipid peroxidation and LDH leakage in the slices. PD98059 also suppressed ERK1/2 activation in nucleus fraction prepared from the slices treated with CER. Inhibition of other MAP kinase pathways, p38 MAP kinase and c-Jun N-terminal kinase (JNK) had no effect on CER-induced increases in lipid peroxidation level and LDH leakage in the slices. The present results suggest that a MEK/ERK pathway down stream of a PKC pathway is probably involved in free radical-induced injury in rat renal cortical slices exposed to CER.

Mitochondrial cytochrome c oxidase as a target site for cephalosporin antibiotics in renal epithelial cells (LLC-PK(1)) and renal cortex

We reported previously that treatment of the pig kidney proximal tubular epithelial cell line LLC-PK(1) with cephaloridine (CLD) decreased the activity of cytochrome c oxidase in the mitochondria of the cells followed by increases in lipid peroxidation and cell necrosis. In this study, we investigated the effects of CLD on the activity of cytochrome c oxidase in mitochondria isolated from LLC-PK(1) cells and purified the enzyme from mitochondria of the rat renal cortex. The activity of cytochrome c oxidase in the isolated mitochondria from LLC-PK(1) cells was significantly decreased from 1 h after addition of 1 mM CLD. Other cephalosporin antibiotics, cefazolin and cefalotin, also decreased the activity of cytochrome c oxidase in the isolated mitochondria. The activity of cytochrome c oxidase purified from the mitochondria of the rat renal cortex was also decreased from 2 h after addition of 1 mM CLD in a non-competitive manner. These results suggest that the direct inhibition of cytochrome c oxidase activity in the mitochondrial electron transport chain by cephlosporins may result from the observed nephrotoxicity.

Enhancement of protein kinase C activity and chemiluminescence intensity in mitochondria isolated from the kidney cortex of rats treated with cephaloridine

The development of nephrotoxicity induced by cephaloridine (CER) has been reported to be due to reactive oxygen species (ROS). Protein kinase C (PKC) has been suggested to modulate the generation of ROS. We investigated the possible participation of ROS generation assessed by chemiluminescence (CL) and PKC activity in rat kidney cortical mitochondria in the development of CER-induced nephrotoxicity. We first evaluated the magnitude of the nephrotoxic damage caused by CER in rats. The plasma parameters and ultrastructural morphology changes were increased markedly 24hr after the treatment of rats with CER. We demonstrated that the treatment of rats with CER clearly evoked not only enhancement of Cypridina luciferin analog (CLA)-dependent CL intensity, but also the activation of PKC in mitochondria isolated from the kidney cortex of rats 1.5 and 3.5 hr after injection of the drug. These changes were detected in advance of those observed in plasma and by electron microscopy. The increase in CLA-dependent CL intensity detected in the kidney cortical mitochondria 1.5 and 3.5 hr after injection of CER was inhibited completely by the addition of superoxide dismutase, suggesting the generation of superoxide anion in these mitochondria during the early stages of CER-induced nephrotoxicity. These results suggest that the activation of PKC and the enhancement of superoxide anion generation in kidney cortical mitochondria precede the increases in plasma parameters and the electron micrographic changes indicative of renal dysfunction in rats treated with CER. Additionally, they suggest a possible relationship between PKC activation in mitochondria and free radical-induced CER nephrotoxicity in rats.

Characterization of 2-amino-4,5-dichlorophenol (2A45CP) in vitro toxicity in renal cortical slices from male Fischer 344 rats

2-Amino-4,5-dichlorophenol (2A45CP) is a major, aromatic ring hydroxylated metabolite of the renal toxicant, 3,4-dichloroaniline. 3,4-Dichloroaniline is nephrotoxic with primary damage located to the proximal tubules. The purpose of this study was to first characterize the in vitro toxicity of 2A45CP in renal cortical slices. Second, the effect of antioxidants and sulfhydryl containing agents on the severity of 2A45CP toxicity was explored since part of the mechanism of toxicity for aminophenols may involve redox cycling. Renal tissue was isolated from male Fischer 344 rats (190--220 g). Renal slices were rinsed three times for 3 min each in 5-ml Krebs buffer. Tissues were then incubated for 90--120 min with varying concentrations of 2A45CP between 0 and 0.5 mM. In a separate series of experiments, the slices (50--100 mg) were preincubated for 30 min with 1 mM dithiothreitol (DTT), 1 mM glutathione (GSH) or 2 mM ascorbic acid prior to exposure to 0, 0.05, 0.1 or 0.25 mM 2A45CP. 2A45CP produced a concentration and time dependent increase in LDH leakage from renal cortical slices. Total glutathione levels were diminished by 0.5 mM 2A45CP within 30 min. Renal slices incubated for 60 and 120 min with 0.05 and 0.1 mM 2A45CP had lower malondialdehyde levels than control. Pretreatment with DTT did not alter 2A45CP toxicity. Pretreatment of renal cortical slices with GSH or ascorbic acid reduced 2A45CP toxicity. These findings indicate that 2A45CP is directly toxic to renal cortical slices and that cytotoxicity is at least partially mediated by a reactive intermediate.

Modulation by cyclic AMP and phorbol myristate acetate of cephaloridine-induced injury in rat renal cortical slices

Intracellular signaling pathways of cAMP and protein kinase C (PKC) have been suggested to modulate the generation of free radicals. We investigated the effects of cAMP and phorbol myristate acetate (PMA), a PKC activator, on cephaloridine (CER)-induced renal cell injury, which has been reported to be due to the generation of free radicals. Incubation of rat renal cortical slices with CER resulted in increases in lipid peroxidation and lactate dehydrogenase (LDH) release and in decreases in gluconeogenesis and p-aminohippurate (PAH) accumulation in rat renal cortical slices, suggesting free radical-induced injury in slices exposed to CER. A derivative of cAMP ameliorated not only the increase in lipid peroxidation but also the renal cell damage induced by CER. This amelioration by a cAMP derivative of lipid peroxidation and renal cell damage caused by CER was blocked by KT 5720, a protein kinase A (PKA) inhibitor. Lipid peroxidation and the indices of cell injury were increased by PMA. PMA also enhanced CER-induced lipid peroxidation and cell damage in the slices. This enhancement by PMA of CER-induced injury was blocked by H-7, a PKC inhibitor. These results indicated that intracellular signaling pathways of cAMP and PKC modulate free radical-mediated nephrotoxicity induced by CER.

Roles of oxygen radical production and lipid peroxidation in the cytotoxicity of cephaloridine on cultured renal epithelial cells (LLC-PK1)

To clarify the mechanism of cephalosporin nephrotoxicity, the cytotoxic effects of cephaloridine (CER), a nephrotoxic cephalosporin antibiotic, on the pig kidney proximal tubular epithelial cell line (LLC-PK1) were studied in culture. CER increased the content of hydrogen peroxide and decreased the activity of catalase in the treated cells, followed by an increase in the content of lipid peroxide and decreases in both glutathione peroxidase activity and in the non-protein sulfhydryl content. The levels of NADPH-dependent hydrogen peroxide and superoxide anion production by microsomes prepared from LLC-PK1 cells, and by NADPH-cytochrome P-450 reductase purified from the rat renal cortex were significantly increased by paraquat. The production of these molecules was antagonized by p-chloromer-curibenzoate, an inhibitor of NADPH-cytochrome P-450 reductase. On the other hand, CER did not significantly affect the production of hydrogen peroxide or superoxide anions. These results suggested that the cytotoxic effect of CER on cultured LLC-PK1 cells was due to the increases in hydrogen peroxide and lipid peroxide levels and not microsomal oxygen radical production, and that the mechanism of this cytotoxicity is very different from that of paraquat which induces microsomal oxygen radical production.

Cephaloridine-induced inhibition of cytochrome c oxidase activity in the mitochondria of cultured renal epithelial cells (LLC-PK(1)) as a possible mechanism of its nephrotoxicity

To clarify the mechanism of cephalosporin nephrotoxicity, the effects of cephaloridine (CLD), a nephrotoxic cephalosporin antibiotic, on the mitochondria of the pig kidney proximal tubular epithelial cell line LLC-PK(1) were studied in culture. The activity of cytochrome c oxidase in the mitochondria of LLC-PK(1) cells was significantly decreased from 9 h after addition of 1.0 mM CLD to the cultured cells. These effects were dose-dependent and accompanied with a significant decrease in the ATP content in the cells, followed by marked morphological changes in the mitochondria. These alterations were observed in the treated cells before the increase in lipid peroxidation. The activities of NADH-cytochrome c reductase and succinate dehydrogenase in the mitochondria and NADPH-cytochrome P450 reductase, NADH-cytochrome b(5) reductase, and 7-ethoxycoumarin O-deethylase in the microsomes of the treated cells were not affected. Superoxide anion production by the mitochondria prepared from LLC-PK(1) cells or NADH-cytochrome c reductase was not affected by addition of CLD (1-10 mM), but adriamycin (0.1 mM) or paraquat (0.1 mM) significantly increased the superoxide anion production. These results suggested that the primary action of CLD is inhibition of cytochrome c oxidase activity in the mitochondrial electron transport chain, which decreases intracellular ATP content in renal tubular epithelial cells and that these effects of CLD are followed by increased lipid peroxidation and cellular injury.

The effects of mannitol, albumin, and cardioplegia enhancers on 24-h rat heart preservation

During 24 h in vitro heart preservation and reperfusion, tissue damage occurs that seriously reduces cardiac function. Prevention of free radical production during preservation and reperfusion of ischemic tissue using free radical scavengers is of primary importance in maintaining optimal heart function in long-term preservation protocols. We examined whether mannitol (68 mM) and albumin (1.4 microM) in combination with other cardioplegia enhancers decreased free radical formation and edema and increased cardiac function during 24-h cold (5 degrees C) heart preservation and warm (37 degrees C) reperfusion in the Langendorff-isolated rat heart. The performance of mannitol-treated hearts was significantly decreased compared with that of hearts without mannitol treatment after 24 h of preservation with regard to recovery of diastolic pressure, contractility (+dP/dt), relaxation (-dP/dt), myocardial creatine kinase release, coronary flow, and lipid peroxidation. Albumin-treated hearts demonstrated higher cardiac function (contractility and coronary flow especially) than hearts not treated with albumin or hearts treated with mannitol, and this appears to be due to the positive effects of increased cellular metabolism and the enhancement of membrane stability.

Toxicity of cephalosporins to fatty acid metabolism in rabbit renal cortical mitochondria

Cephaloglycin (Cgl) and cephaloridine (Cld) are acutely toxic to the proximal renal tubule, in part because of their cellular uptake by a contraluminal anionic secretory carrier and in part through their intracellular attack on the mitochondrial transport and oxidation of tricarboxylic acid (TCA) cycle anionic substrates. Preliminary studies with Cgl have provided evidence of a role of fatty acid (FA) metabolism in its nephrotoxicity, and work with Cld has shown it to be a potent inhibitor of renal tubular cell and mitochondrial carnitine (Carn) transport. Studies were therefore done to examine the effects of Cgl and Cld on the mitochondrial metabolism of butyrate, the anion of a short-chain FA that does not require the Carn shuttle to enter the inner matrix, and the effects of Cgl on the metabolism of palmitoylcarnitine (PCarn), the Carn conjugate of a long-chain FA that does enter the mitochondrion by the Carn shuttle. The following was found: (1) Cgl reduced the oxidation and uptake of butyrate after in vitro (2000 micrograms/mL, immediate effect) and after in vivo (300 mg/kg body weight, 1 hr before killing) exposure; (2) Cld caused milder in vitro toxicity, and no significant in vivo toxicity, to mitochondrial butyrate metabolism; (3) like Cld, Cgl reduced PCarn-mediated respiration after in vivo exposure, but, unlike Cld, it did not inhibit respiration with PCarn in vitro; (4) the Carn carrier was stimulated slightly by in vitro Cgl but was unaffected by in vivo Cgl; (5) in vivo Cgl had no effect on mitochondrial free Carn or long-chain acylCarn concentrations in the in situ kidney; (6) Cgl increased the excretion of Carn minimally compared with the effect of Cld; and (7) cephalexin, a nontoxic cephalosporin, caused mild reductions of respiration with butyrate and PCarn during in vitro exposure, but stimulated respiration with both substrates after in vivo exposure.

CONCLUSIONS

Cgl has essentially the same patterns of in vitro and in vivo toxicity against mitochondrial butyrate uptake and oxidation that both Cgl and Cld have against TCA-cycle substrates. Cld has little or no in vivo toxicity to mitochondrial butyrate metabolism, whereas in vivo Cgl is as toxic as Cld to respiration with PCarn. The greater overall in vivo toxicity of Cgl to mitochondrial FA metabolism, with lower cortical concentrations and AUCs than those of Cld, supports earlier evidence that Cld is less toxic than Cgl at the molecular level.

LLC-PK1 epithelia as a model for in vitro assessment of proximal tubular nephrotoxicity

LLC-PK1 cells, an established epithelial cell line derived from pig kidney, were used as a model system for assessment of nephrotoxic side effects of three cephalosporin antibiotics: cephaloridine, ceftazidime, and cefotaxime. Toxic effects of these xenobiotics were monitored on confluent monolayers by light and electron microscopy and by the release of cellular marker enzyme activities into the culture medium. In addition, LLC-PK1 cells were grown on microporous supports, and cephalosporin-induced alteration of epithelial functional integrity was monitored by a novel electrophysiologic approach. For this purpose, an Ussing chamberlike experimental setup was used. The dose-dependent effects on transepithelial ionic permselectivity were monitored under conditions in which defined fractions of the apical culture medium NaCl contents were replaced iso-osmotically by mannitol. This method of determining the functional intactness of the epithelial barrier by measuring dilution potentials was found to be far more sensitive than monitoring cell injury by means of morphology or measurement of enzyme release. As expected from animal experimental data, a dose-dependent disruption of monolayer integrity was detected with all three methodologies applied. Cephaloridine was found the most toxic compound followed by ceftazidime, where a 3-fold, and cefotaxime, where a 10-fold dose of that of cephaloridine was needed to produce cell injury. Measurement of transepithelial dilution potentials was more sensitive as compared to the release of the apical plasma membrane marker enzyme activities alkaline phosphatase and gamma-glutamyltranspeptidase, the cytosolic lactate dehydrogenase, or the mitochondrial glutamate dehydrogenase. The data were compared to the effects of the aminoglycoside antibiotic gentamicin, which at least with respect to its effects on LLC-PK1 morphology and enzyme release, but not transepithelial electrical properties, was already investigated.

Renal cell type specificity of cephalosporin-induced cytotoxicity in suspensions of isolated proximal tubular and distal tubular cells

We have developed an in vitro model for investigation of nephron heterogeneity and cell type-specific patterns of renal injury. To further validate our model and to study biochemical mechanisms of cephalosporin-induced injury, cytotoxicity of three cephalosporins was studied in freshly isolated proximal tubular (PT) and distal tubular (DT) cells from rat kidney. The three cephalosporins [cephaloridine (CPH), cephalexin (CXN), cephalothin (CTN)] were chosen because they exhibit varying degrees of nephrotoxicity in vivo and contain different functional groups. CPH produced greater amounts of lactate dehydrogenase release from PT cells than either CXN or CTN, indicating greater toxicity of CPH, which agrees with in vivo observations. DT cells were not affected by any of the cephalosporins. Thus, the cephem ring is sufficient to produce PT cell injury but the presence of other functional groups modifies toxicity. SKF-525A and alpha-tocopherol protected PT cells from both CPH and CTN, suggesting involvement of cytochrome P-450 metabolism and oxidative stress. Both PT and DT cells exhibited transport of CPH or CXN and transport of CPH into PT cells was inhibitable by probenecid, consistent with action of a specific carrier. Transport alone, therefore, cannot account for the cell type specificity pattern in vitro. Effects on intracellular glutathione status, malondaldehyde formation, and uncoupler-stimulated respiration were also investigated, and these generally correlated with cell type specificity patterns but not always with degree of cytotoxicity. These results validate further the isolated PT and DT cells as in vitro models to study cell type-specific renal injury and show a role for oxidative stress, cytochrome P-450 bioactivation, and mitochondrial dysfunction in cephalosporin-induced PT cell injury.

Urinary porphyrins as biological indicators of oxidative stress in the kidney. Interaction of mercury and cephaloridine

Reduced porphyrins (hexahydroporphyrins, porphyrinogens) are readily oxidized in vitro by free radicals which are known to mediate oxidative stress in tissue cells. To determine if increased urinary porphyrin concentrations may reflect oxidative stress to the kidney in vivo, we measured the urinary porphyrin content of rats treated with mercury as methyl mercury hydroxide (MMH) or cephaloridine, both nephrotoxic, oxidative stress-inducing agents. Rats exposed to MMH at 5 ppm in the drinking water for 4 weeks showed a 4-fold increase in 24-hr total urinary porphyrin content and a 1.3-fold increase in urinary malondialdehyde (MDA), an established measure of oxidative stress in vivo. Treatment with cephaloridine alone (10-500 mg/kg, i.p.) produced a dose-related increase in urinary MDA and total porphyrin levels up to 1.6 and 7 times control values, respectively. Injection of MMH-treated rats with cephaloridine (500 mg/kg) caused a synergistic (20-fold) increase in urinary porphyrin levels, but an additive (1.9-fold) increase in the MDA concentration. Studies in vitro demonstrated that cephaloridine stimulated the iron-catalyzed H2O2-dependent oxidation of porphyrinogens to porphyrins in the absence of either microsomes or mitochondria. Additionally, porphyrinogens were oxidized to porphyrins in an iron-dependent microsomal lipid peroxidation system. Moreover, porphyrinogens served as an effective antioxidant (EC50 approximately 1-2 microM) to lipid peroxidation. These results demonstrate that MMH and cephaloridine synergistically, as well as individually, promote increased oxidation of reduced porphyrins in the kidney and that this action may be mechanistically linked to oxidative stress elicited by these chemicals. Increased urinary porphyrin levels may, therefore, represent a sensitive indicator of oxidative stress in the kidney in vivo.

Cephaloridine-induced nephrotoxicity in the Fischer 344 rat: proton NMR spectroscopic studies of urine and plasma in relation to conventional clinical chemical and histopathological assessments of nephronal damage

The acute toxicological effects of the nephrotoxic antibiotic cephaloridine (CPH, 0-1500 mg/kg) in male Fischer 344 (F344) rats, have been investigated over 48 h using clinical chemistry, histopathology and proton nuclear magnetic resonance (1H NMR) spectroscopy of urine and plasma. High field (400 and 600 MHz)1H NMR urinalysis revealed increased excretion of lactic acid, acetoacetate, alanine, valine, lysine, glutamine and glutamate and a severe, time-dependent glycosuria. A major change observed in urine of CPH-treated animals was the dose-dependent increase in HB which may relate to altered energy metabolism. CPH also caused dose-dependent decreases in the urinary excretion of hippurate, allantoin and protein (conventional assay). This abnormal metabolic profile is consistent with a functional defect in the S1/S2 regions of the proximal tubule, and was confirmed by histology post mortem. Functional changes observed included elevations in blood urea nitrogen (BUN) and urine flow rate (UFR) and dose-related decreases in urine osmolality. Spin-echo 1H NMR spectroscopic analysis of lyophilised plasma, reconstituted with 2H2O revealed an abnormal phase modulation of the methyl signal from free alanine and it is postulated that this is due to the release of transaminases from damaged tissue which via a reversible conversion to pyruvate, cause variable deuteration of alanine at the alpha-CH position. This observation suggests that 1H NMR spectral patterns are also dependent on the level of plasma transaminases and this may provide a novel indicator of tissue damage.

Cephaloridine-induced renal pathological and biochemical changes in female rabbits and isolated proximal tubules in suspension

Cephaloridine (Cld) is a nephrotoxic cephalosporin antibiotic. The intracellular biochemical changes that occur leading to Cld-induced nephrotoxicity may involve lipid peroxidation and/or mitochondrial injury. The purpose of this report was to examine and correlate the biochemical changes induced by Cld in vivo and in vitro with the observed pathological changes in an attempt to understand better the mechanisms of beta-lactam-induced nephrotoxicity. Cld treatment (500 mg/kg sc) caused elevations in blood urea nitrogen and decreases in the accumulation of p-aminohippurate (PAH) and tetraethylammonium (TEA) by renal cortical slices. Histopathological alterations, characterized by individual cell necrosis of tubular epithelial cells, were first seen 6 hr after treatment in the pars recta of the outer stripe of the medulla. Ultrastructural alterations involved the straight (S2 and S3) segments of the proximal tubules. Mitochondrial morphology was, for the most part, unaffected by Cld exposure. Cld did not cause any significant changes in tissue malondialdehyde (MDA) content in vivo at any of the time points examined, but it did cause a depletion of GSH to approximately 40% of control by 1 hr after dosing that recovered toward control by 6 hr. Significant changes were observed in renal ATP content beginning at 6 hr after treatment; however, this change mirrored the onset of histological evidence of necrosis. In isolated tubules in vitro, the onset of glutathione (GSH) depletion and MDA formation clearly preceded lactate dehydrogenase (LDH) leakage, whereas ATP depletion was a mirror image of cell death. These data demonstrate that isolated proximal tubules in vitro are a reasonable model for Cld nephrotoxicity in vivo. Cld-induced mitochondrial alterations leading to ATP depletion and cell injury were not observed in this study.

Comparative studies of in vitro renal cephaloridine toxicity between normoglycemic and diabetic rats

This study investigated if the attenuation in cephaloridine toxicity associated with streptozotocin (STZ)-induced diabetes can be attributed to a direct cellular effect. Comparative studies examined the direct toxicity of cephaloridine 14 days after (35 mg kg-1, i.p.) STZ or vehicle injection of male Fischer 344 (F344) rats. In vitro cephaloridine toxicity was assessed by measuring lipid peroxidation, renal gluconeogenesis and organic ion accumulation in renal cortical slices. The in vitro toxicity of cephaloridine was reduced in the diabetic group since lipid peroxidation was not increased following a 120-min exposure to cephaloridine. This was in contrast to a concentration- and time-dependent increase in lipid peroxidation in renal tissue derived from normoglycemic animals pre-incubated with 0-5 mM cephaloridine. Renal gluconeogenesis was inhibited in a concentration-dependent manner in the normoglycemic group following a 15-90-min exposure to 0-5 mM cephaloridine. Pyruvate-stimulated gluconeogenesis was diminished in the diabetic group only after a 90-min preincubation. Renal cortical slice accumulation of p-aminohippurate (PAH) and tetraethylammonium (TEA) was decreased in the normoglycemic group. Accumulation of TEA, but not PAH, was decreased (P less than 0.05) in the diabetic group. These results indicate that in vitro cephaloridine toxicity was attenuated by STZ-induced diabetes.

Interactions among nephrotoxicants: N-(3,5-dichlorophenyl)succinimide and cephaloridine

Numerous studies have demonstrated the interactive potential between nephrotoxicants. The purpose of this study was to examine the interactive potential between two model nephrotoxicants, N-(3,5-dichlorophenyl)succinimide (NDPS) and cephaloridine (CPH). Male Fischer 344 rats (4 rats per group) were administered an intraperitoneal (i.p.) injection of CPH (500 mg/kg), NDPS (0.2 mmol/kg) or the appropriate vehicle 1 h prior to administration of an i.p. injection of NDPS (0.2, 0.4, or 1.0 mmol/kg), CPH (500, 750 or 1000 mg/kg) or the appropriate vehicle. Renal function was monitored at 24 and 48 h. Combination of non-nephrotoxic doses of CPH (500 mg/kg) and NDPS (0.2 mmol/kg) did not result in nephrotoxicity, regardless of which compound was administered first. NDPS (0.2 mmol/kg) weakly enhanced the nephrotoxicity observed following CPH (1000 mg/kg) injection but had little effect on CPH (750 mg/kg)-induced renal effects. However, CPH (500 mg/kg) markedly attenuated NDPS (0.4 or 1.0 mmol/kg)-induced nephrotoxicity. These results demonstrate that prior NDPS exposure has little effect on the outcome of CPH-induced renal effects, but prior CPH exposure can markedly alter the renal response to NDPS administration.

Iron- and ascorbic acid-induced lipid peroxidation in renal microsomes isolated from rats treated with platinum compounds

Renal microsomes isolated on day 3 from cisplatin (CDDP, single i.p. injection, 4 or 6 mg/kg)-treated rats were monitored for their susceptibility to lipid peroxidation as compared with microsomes from rats treated with carboplatin (CBDCA, 30 mg/kg), transplatin (TDDP, 6 mg/kg) or CDDP hydrolysis products (4 or 6 mg/kg) or from control animals. Cephaloridine (1 g/kg daily for 4 days, i.p. injection) was used as a positive control. The effect of CDDP on renal microsomal glucose-6-phosphatase activity was investigated in vivo and in vitro. Following treatment with CDDP and CDDP hydrolysis products vs CBDCA and TDDP treatment, microsomes revealed an enhanced susceptibility to lipid peroxidation in a Fe2+ and/or ascorbic acid stimulation system. Increased lipid peroxidation, expressed as an increase in malondialdehyde (MDA) generation, paralleled the alterations in body and kidney weight and the elevations of plasma creatinine and blood urea nitrogen concentrations. Injection of the antioxidant N,N'-diphenyl-p-phenylenediamine (DPPD, 0.5 g/kg, i.p.) at 24 h prior to CDDP treatment abolished the increased vulnerability of renal microsomes to lipid peroxidation. In vivo, only CDDP hydrolysis products exhibited a significant inhibitory effect on renal glucose-6-phosphatase activity. In vitro, rat renal and hepatic microsomal glucose-6-phosphatase activity was decreased by CDDP both time- and concentration-dependently. Nephrotoxicity induced by CDDP and CDDP hydrolysis products might be attributable to iron-dependent lipid peroxidation and microsomes might represent target organelles on a subcellular level.

Nephrotoxicity of cisplatin, carboplatin and transplatin. A comparative in vitro study

The present study was designed to compare the nephrotoxicity induced by the three platinum compounds cisplatin (CDDP), carboplatin (CBDCA) and transplatin (TDDP) in vitro and to obtain information to elucidate the mechanism of platinum compound-induced nephrotoxicity. Rat or rabbit renal cortical slices were incubated for different periods of time in platinum compound-containing media (0.42 or 1.67 mM) and thereafter monitored for platinum content, tetraethylammonium(TEA) and paraaminohippurate(PAH) accumulation and gluconeogenesis. Malondialdehyde(MDA) content of slices was determined as a parameter of lipid peroxidation. Activity of glucose-6-phosphatase of rat renal microsomes was investigated after platinum-compound exposure. In all series of experiments the effect of the antioxidant N,N'diphenyl-p-phenylenediamine (DPPD) was tested. CBDCA showed no effects on all parameters of renal cell function at all concentrations and all time points investigated, except for the activity of glucose-6-phosphatase, which was slightly affected by CBDCA. CBDCA-induced MDA production was lower, compared to CDDP, which showed marked toxic effects on TEA and PAH accumulation, gluconeogenesis and glucose-6-phosphatase activity. The onset of CDDP-induced alterations was dependent on drug concentration. MDA production was reduced by DPPD. Protection against the platinum compound-induced decrease in TEA and PAH accumulation was observed after the use of DPPD. DPPD had no protective effect on CDDP-induced inhibition of gluconeogenesis and glucose-6-phosphatase, which might indicate an effect on gluconeogenesis by direct inhibition of glucose-6-phosphatase. DPPD did not alter uptake of platinum compounds in rat renal cortical slices. TDDP showed different in vitro properties compared to in vivo conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Contraluminal para-aminohippurate (PAH) transport in the proximal tubule of the rat kidney. VI. Specificity: amino acids, their N-methyl-, N-acetyl- and N-benzoylderivatives; glutathione- and cysteine conjugates, di- and oligopeptides

In order to evaluate the specificity of the renal contraluminal PAH transport system for amino acids, oligopeptides and their conjugates, the inhibitory potency of these substances against contraluminal [3H] PAH influx has been determined. For this, inhibition of 3H-PAH flux from the interstitium into cortical tubular cells of the rat kidney in situ has been measured. Apparent Ki values were evaluated by a computer program assuming competitive inhibition. Unconjugated amino acids (glycine, cysteine, alanine, leucine, phenylalanine, tyrosine, aspartate, glutamate, arginine, ornithine and lysine) do not inhibit [3H] PAH influx. The very hydrophobic tryptophan, however, does. N-alpha-methylation does not change this behaviour. N-alpha-acetylation does not evoke interaction with the PAH transporter when it occurs with glycine, cysteine (to yield mercapturic acid), arginine, ornithine and lysine. However, it renders alanine, leucine, phenylalanine, tryptophan, L-aspartate moderately, and L-glutamate strongly, inhibitory. The acetylated D-isomers of alanine, leucine and phenylalanine exert a higher inhibitory potency compared with the respective L-isomers. N-alpha-benzoylation of L-lysine is ineffective. N-alpha-benzoylation, however, evokes interaction with the PAH transporter, when it occurs with ornithine less than arginine less than histidine less than glycine = leucine less than alanine = phenylalanine = aspartate = glutamate. Dipeptides interact with the PAH transporter according to their hydrophobicity (Nozaki scale down to 0.9, Fauchère scale up to 1.0). N-acetylation does not change this behaviour. Hydrophobicity also renders oligopeptides, as angiotensin II, inhibitory against PAH transport. Similarly the anionic angiotensin I converting enzyme inhibitors Captopril, Enalapril and Ramipril inhibit contraluminal PAH influx.

Thienamycin nephrotoxicity. Mitochondrial injury and oxidative effects of imipenem in the rabbit kidney

The nephrotoxic cephalosoprins cephaloridine and cephaloglycin both produce mitochondrial respiratory toxicity in renal cortex. Recent work has provided evidence that this respiratory toxicity is caused by acylation and inactivation of mitochondrial anionic substrate transporters. While cephaloridine also causes significant lipid peroxidative injury in cortical mitochondria and microsomes, cephaloglycin causes little or no oxidative damage under identical conditions. The recently released thienamycin antibiotic, imipenem, like the toxic cephalosporins, produces acute proximal tubular necrosis which can be prevented completely by prior administration of probenecid. The ability of imipenem to block mitochondrial substrate uptake and respiration and produce oxidative changes has not been examined. We therefore evaluated the effects of imipenem in rabbit renal cortex on the following: (1) mitochondrial function [respiration with and uptake of succinate, and uptake of ADP]; and (2) evidence of oxidative change [depletion of reduced glutathione (GSH), production of oxidized glutathione (GSSG), and production of lipid peroxidative injury, as reflected in microsomal conjugated dienes (CDs)]. The mitochondrial effects of 300 mg/kg body wt of imipenem, given i.v. 1 and 2 hr before killing the animals, were comparable to those of the nephrotoxic cephalosporins. There was significant reduction of respiration with, and unidirectional uptake of, succinate at both times, while mitochondrial ADP transport was comparatively unaffected. Imipenem also depleted GSH and increased GSSG and CDs at 1 hr. These effects, however, were considerably smaller than those of a comparably nephrotoxic dose of cephaloridine, and this evidence of oxidative stress had resolved by 2 hr. We conclude that imipenem and the nephrotoxic cephalosporins have similar effects on mitochondrial substrate uptake and respiration, but differ significantly in their production of oxidative injury.

Isolation of two distinct populations of cells from rat kidney cortex and their use in the study of chemical-induced toxicity

Procedures for the isolation and enrichment of cell populations from suspensions of rat kidney cortical cells were developed. Using Percoll density-gradient centrifugation, two populations of cells were obtained; marker enzymes [alkaline phosphatase and gamma-glutamyltransferase for proximal tubular (PT) cells and hexokinase for distal tubular (DT) cells] and functional responses (stimulation of PT cell oxygen consumption by succinate and inhibition of DT cell oxygen consumption by amiloride) were then employed to identify and assess the purity of the two fractions. The PT cell fraction was estimated to contain 97% PT cells and the DT cell fraction was estimated to contain 88% DT cells. Staining with toluidine blue and light microscopy showed that PT cells contained a brush border, were larger than DT cells, and had more intensely staining nuclei than DT cells. To demonstrate the usefulness of these cell preparations in the study of biochemical mechanisms of renal cell injury, time- and concentration-dependent effects of the PT cell-specific nephrotoxin cephaloridine (CPH) on PT and DT cell trypan blue exclusion were examined. CPH was toxic in PT cells but not in DT cells; viability of PT cells incubated with 0.1 or 1 mM CPH for 2 h was 57 or 34%, respectively, compared to 81% for control cells; viability of DT cells incubated with 0.1 or 1 mM CPH for 2 h was 74 or 71%, respectively, compared to 74% for control cells. This method thus provides highly enriched preparations of freshly isolated PT and DT cells that retain their unique properties and are suitable for studies of biochemical mechanisms of chemical toxicity and nephron heterogeneity.

Contraluminal organic anion and cation transport in the proximal renal tubule: V. Interaction with sulfamoyl- and phenoxy diuretics, and with beta-lactam antibiotics

In order to study the interaction of sulfamoyl- and phenoxy diuretics as well as of beta-lactam antibiotics with the contraluminal anion and cation transport systems the inhibitory potency of these substances against the influx of 3H-para-aminohippurate, 14C-succinate, 35S-sulfate and 3H-N1-methylnicotinamide into cortical tubular cells have been determined. 1.) 2-, 3- and 4-sulfamoylbenzoate inhibit contraluminal PAH influx. N-dipropyl substitution to yield probenecid or ring-substitution to yield furosemide and piretanide augment the inhibitory potency. However, hydrochlorothiazide and acetazolamide exert only a moderate inhibitory potency. Succinate transport was inhibited by furosemide only. Sulfate transport was inhibited by furosemide and 3-sulfamoyl-4-phenoxybenzoate as well as by probenecid, piretanide, hydrochlorothiazide and acetazolamide. 2.) Phenoxyacetate, -propionate, and -butyrate exert increasing inhibition against PAH transport. The weed-killers 2,4-dichloro-, and 2,4,5-trichlorophenoxyacetate (2,4 D and 2,4,5 T) had a similar inhibitory potency, while ethacrynic acid showed a lower and the uricosuric tienilic acid a higher inhibitory potency. None of the compounds of this group interact with contraluminal succinate transport, and only the multiring-substituted compounds 2,4 D, 2,4,5 T, ethacrynic and tienilic acid interact slightly with the sulfate transporter. 3.) The monocarboxylic penicillins benzylpenicillin and phenoxymethylpenicillin as well as the dicarboxylic ticarcillin interact with the contraluminal PAH transport. The aminopenicillin ampicillin had a lower, and apalcillin a higher inhibitory potency than monocarboxylic penicillin. Benzylpenicillin showed small inhibition against succinate transport and ticarcillin against sulfate transport. 4.) The monocarboxylic cephalosporine, 6315 S Shionogi, and the aminocephalosporines, cephalexin and cefadroxil, showed an app. Ki.PAH as the comparable penicillins. The zwitterions cephaloridine and cefpirome did not interact with the PAH transporter, but with the organic cation (NMN) transporter. Amongst the amino-thiazol-containing compounds cefotaxime, ceftriaxone, and cefodizime, increasing interaction with the PAH transporter was seen dependent of a second ionizable anionic group. Compounds with two ionizable anionic groups (cefsulodin, ceftriaxone, cefodizime) exert also a small inhibitory potency against sulfate transport. None of the cephalosporins interacted with the dicarboxylate transporter. The interaction pattern of the tested compounds is in accordance with the specificity requirements for the contraluminal transporters depending on electrical charge and hydrophobicity.

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.

Minimum essential structural requirements for lactam antibiotic action

A mechanism of action encompassing mono- and bicyclic beta-lactams has been proposed previously, which stresses the importance of formation of an electron transfer (ET) entity (conjugated iminium) as a requirement for antibiotic activity, in association with enzyme inactivation. Additional evidence in support of this contention is now provided. Reduction potentials for several cephalosporins and pyrazolidinones, all of which contain an oximino functionality in the side chain, were observed in the range of -0.6 to -0.7 V. Comparison is made with related compounds lacking imine. Agents containing side chain hydrazone, oxamazins (mono beta-lactams), and lactivicin are discussed based on the ET approach.

Cytoprotective effect of isotonic mannitol at low oxygen tension

The beneficial effect of mannitol infusion in postischemic kidneys remains unresolved. Contradictory reports may have originated from at least 3 different mechanisms: a) arterial vasodilation, b) osmotic support of hypoxic cellular volume regulation, and c) scavenging of hydroxyl radicals in the reoxygenation period. To exclude vascular effects we tested at 37 degrees C in hypoxic (PO2 less than 1 mmHg) and reoxygenated isolated tubular cells of rat kidney cortex cellular function, i.e. intracellular K+ accumulation (K+), posthypoxic lactate gluconeogenesis (GNG), loss of membrane-bound tau-Glutamyltransferase (tau GT), and formation of a lipid peroxidation product, malondialdehyde (MDA). Mannitol (M) was added to a Ringer incubation medium in variable concentration either without (hypertonic M) or with omission of equiosmolar amounts of NaCl (isotonic M). K+ and GNG were significantly supported, and tau GT-loss markedly suppressed in a range of 10-50 mmol/l hypertonic and isotonic M. At higher concentrations no improvement (isotonic) or even deleterious effects (hypertonic) of M occurred. Beneficial effects of lower concentrations of M (10 mmol/l) were not correlated to anaerobic glycolysis, and 1 as well as 10 mmol/l M induced a comparable and significant reduction in posthypoxic MDA-formation. This effect was most pronounced when M was only added in hypoxia, indicating leakiness of cellular membranes in hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Specific alterations of rat renal microsomal proteins induced by cephaloridine

In order to elucidate the molecular mechanisms of cephaloridine (CPH) nephrotoxicity, the effect of cephaloridine treatment on the protein composition of different subcellular fractions from rat kidney cortex was investigated. After intravenous treatment of male Wistar rats with 250-1200 mg/kg/d CPH for 1-3 days, kidneys were removed and the homogenate from renal cortex was separated into lysosomal, cytosolic and microsomal fractions. The polypeptide composition of the different subfractions was analyzed by one-dimensional SDS-gel electrophoresis and quantified by densitometry. Significant differences in the polypeptide composition between treated and non-treated animals were seen in the microsomal fraction. CPH-treatment induced a polypeptide with an apparent molecular weight of 44,000 and decreased the content of cytochrome P-450 isoenzymes in the microsomal fraction. Solubilization experiments showed that the CPH-induced microsomal polypeptide of molecular weight 44,000 is a peripheral membrane protein rather than an integral membrane protein. The induction of this protein by CPH was dose- and time-dependent. Preliminary experiments using the kidney slice technique indicate that the induction of this polypeptide correlates with the nephrotoxicity measured as decrease in renal cortical accumulation of organic ions. Thus, the results of the present study indicate that treatment of rats with CPH resulted in the induction of a microsomal polypeptide of molecular weight 44,000 which could be a sensitive parameter of cephaloridine nephrotoxicity.

Cisplatin-induced lipid peroxidation and decrease of gluconeogenesis in rat kidney cortex: different effects of antioxidants and radical scavengers

The present in vitro study was performed to investigate the effect of the nephrotoxic anticancer agent cisplatin (CP) on lipid peroxidation, on pyruvate-stimulated gluconeogenesis and on p-aminohippurate (PAH) accumulation in rat renal cortical slices. In addition, the inhibitory effects of the antioxidants and radical scavengers N,N'-diphenyl-p-phenylenediamine (DPPD), (+)-cyanidanol-3 or alpha-tocopherol on CP-induced lipid peroxidation and CP-induced decrease of gluconeogenesis and the inhibitory effect of DPPD on CP-induced decrease of PAH accumulation were evaluated. Slices were incubated in a CP-containing medium for different periods of time (7.5-300 min) and at different concentrations (0.025-1.5 mg/ml). Lipid peroxidation was monitored by measuring the production of malondialdehyde (MDA). Accumulation of PAH was expressed as slice to medium concentration ratio. Pyruvate-stimulated gluconeogenesis, measured as glucose production, was determined after a subsequent 60- or 15-min incubation in a pyruvate-containing, CP-free medium. CP led to a time- and concentration-dependent increase in MDA production, a time- and concentration-dependent decrease of pyruvate-stimulated gluconeogenesis and a time-dependent decrease of PAH accumulation in renal cortical slices. Decrease of gluconeogenesis preceded MDA production and decrease of PAH accumulation. Antioxidants reduced CP-induced MDA production and CP-induced decrease of accumulation of PAH, but did not reverse CP-induced decrease of gluconeogenesis. This might indicate, that the generation of free radicals and subsequent lipid peroxidation may play a role, at least in part, in inducing CP nephrotoxicity. There could be more than one mechanism of CP-induced nephrotoxicity, since decrease of gluconeogenesis preceded MDA production and decrease of PAH accumulation and could not be inhibited by antioxidants and radical scavengers.

Comparative toxicities of cephalosporin antibiotics in a rabbit kidney cell line (LLC-RK1)

The rabbit kidney cell line LLC-RK1 was tested for its ability to discriminate the toxicities of six cephalosporin antibiotics according to their in vivo nephrotoxic potentials in rabbits. With the exception of cephalothin, which was markedly toxic to kidney cells in vitro, a good correlation between in vitro toxicity and in vivo nephrotoxicity was obtained, yielding the following toxicity rank order: ceftazidime less than cefazolin approximately cefoperazone less than cephaloglycin approximately cephaloridine. The addition of a kidney microsomal S9 fraction to the cell cultures desacetylated cephalothin as occurs in vivo and detoxified this antibiotic, providing it with the proper toxicity relative to the other cephalosporins. When compared with parent structures, desacetylated derivatives of other cephalosporins such as cephapirin were similarly found to be less toxic to LLC-RK1 cells. The acetylated cephalosporin cephaloglycin was not detoxified by the kidney S9 fraction and was desacetylated three to four times slower than cephalothin by renal esterases. Thus, the rate and extent of desacetylation of cephalosporins may play a role in their in vivo nephrotoxic potential. Our results further suggest that LLC-RK1 cells will provide a useful model for evaluating the potential nephrotoxicity of new cephalosporin antibiotics before in vivo studies.

Nephrotoxic potential of first-, second-, and third-generation cephalosporins

First-, second-, and third-generation cephalosporins were investigated for their peroidative and nephrotoxic potential. Renal cortical slices from male Wistar rats were incubated at 37 C for 1 h in a phosphate-buffered medium containing the cephalosporin (1.25, 2.5, 5 or 10 mg/ml). In another series of experiments 5 mg/ml cephalosporin was incubated under the same conditions for 30, 60, 90 and 120 min. Subsequently, slices were incubated for 60 or 90 min in a bicarbonate- or phosphate-buffered medium containing pyruvate or tetraethylammonium (TEA) to determine gluconeogenesis and TEA accumulation, respectively. The peroxidative potential was determined at the end of the first incubation by measuring the increase in the malondialdehyde (MDA) content in renal cortical slices. The nephrotoxic potential was determined at the end of the second incubation by measuring the decrease in accumulation of the organic ion (TEA) and decrease of pyruvate-stimulated gluconeogenesis in renal cortical slices. First-generation cephalosporins, cephaloridine and cephalothin showed a time- and concentration-dependent increase in MDA content and a decrease in TEA accumulation and gluconeogenesis by renal cortical slices. Cefazolin, another first generation cephalosporin, showed a weak peroxidative and practically no nephrotoxic potential. In the group of second-generation cephalosporins, cefotiam showed a weak peroxidative potential comparable to that of cefoxitin but had a much greater nephrotoxic potential which was similar to that of cephaloridine. The third-generation cephalosporins, cefotaxime and cefoperazone showed a low peroxidative and no nephrotoxic potential.(ABSTRACT TRUNCATED AT 250 WORDS)

Biochemical mechanisms of cephaloridine nephrotoxicity

Large doses of the cephalosporin antibiotic, cephaloridine, produce acute proximal tubular necrosis in humans and in laboratory animals. Cephaloridine is actively transported into the proximal tubular cell by an organic anion transport system while transport across the lumenal membrane into tubular fluid appears restricted. High intracellular concentrations of cephaloridine are attained in the proximal tubular cell which are critical to the development of nephrotoxicity. There is substantial evidence indicating that oxidative stress plays a major role in cephaloridine nephrotoxicity. Cephaloridine depletes reduced glutathione, increases oxidized glutathione and induces lipid peroxidation in renal cortical tissue. The molecular mechanisms mediating cephaloridine-induced oxidative stress are not well understood. Inhibition in gluconeogenesis is a relatively early biochemical effect of cephaloridine and is independent of lipid peroxidation. Furthermore, cephaloridine inhibits gluconeogenesis in both target (kidney) and non-target (liver) organs of cephaloridine toxicity. Since glucose is not a major fuel of proximal tubular cells, it is unlikely that cephaloridine-induced tubular necrosis is mediated by the effects of this drug on glucose synthesis.

A survey of chemicals inducing lipid peroxidation in biological systems

A great number of drugs and chemicals are reviewed which have been shown to stimulate lipid peroxidation in any biological system. The underlying mechanisms, as far as known, are also dealt with. Lipid peroxidation induced by iron ions, organic hydroperoxides, halogenated hydrocarbons, redox cycling drugs, glutathione depleting chemicals, ethanol, heavy metals, ozone, nitrogen dioxide and a number of miscellaneous compounds, e.g. hydrazines, pesticides, antibiotics, are mentioned. It is shown that lipid peroxidation is stimulated by many of these compounds. However, quantitative estimates cannot be given yet and it is still impossible to judge the biological relevance of chemical-induced lipid peroxidation.

Effect of cisplatin on in vitro production of lipid peroxides in rat kidney cortex

Cisplatin (cis-diamminedichloroplatinum II), an antitumor agent with a dose-limiting adverse effect of nephrotoxicity, increased lipid peroxidation in a time- and concentration-dependent manner in rat renal slices incubated in vitro. The addition of an antioxidant, N-N'-diphenyl-p-phenylenediamine (DPPD), to the incubation medium completely inhibited this increase. We also studied the in vitro effects of agents that modify cisplatin nephrotoxicity on lipid peroxidation in the slices caused by cisplatin. Mannitol, which protects against cisplatin nephrotoxicity, almost completely inhibited the increase in lipid peroxidation caused by cisplatin. Methionine, which potentiates cisplatin nephrotoxicity, made the slices more susceptible to peroxidation. The decrease with cisplatin in p-aminohippurate (PAH) accumulation in incubated kidney cortical slices, the accumulation being a representative biochemical process in the transport ability of renal cells, was partially inhibited when DPPD was in the medium. The results suggested that cisplatin directly affected renal tissues in which free radicals generated by cisplatin may interact with membrane lipids to cause the production of lipid peroxides that damage membrane function. Compounds that modify cisplatin nephrotoxicity such as mannitol and methionine may act by affecting the production of renal lipid peroxides by cisplatin.

Mechanisms mediating cephaloridine inhibition of renal gluconeogenesis

Incubation of renal cortical slices with cephaloridine (CPH) markedly inhibits pyruvate-supported gluconeogenesis, an effect which is independent of CPH-induced lipid peroxidation. CPH was found to inhibit pyruvate-supported gluconeogenesis in a time-and concentration-dependent manner. Pyruvate-supported gluconeogenesis was inhibited as early as 10 min following incubation of renal cortical slices with 5 mM CPH. Similarly, endogenous gluconeogenesis was impaired following CPH treatment. CPH depressed the renal cortical slice content of ATP by 50%, but only following 90 and 120 min of drug exposure, suggesting that mitochondrial dysfunction does not mediate the inhibition of gluconeogenesis by CPH. To identify the intracellular site(s) of CPH inhibition of gluconeogenesis, the effects of CPH on glucose production were evaluated using substrates catalyzed by rate-limiting reactions. CPH inhibited renal cortical slice gluconeogenesis when the following substrates were used: pyruvate (mitochondrial), oxaloacetate and fructose-1,6-diphosphate (FDP) (postmitochondrial), and glucose-6-phosphate (G6P, endoplasmic reticulum). Inhibition of G6P-supported gluconeogenesis occurred within 5 min of incubation with 5 mM CPH. Direct addition of CPH to microsomal suspensions inhibited G6Pase activity in a concentration-dependent fashion. By contrast, addition of CPH to cytosolic fractions did not affect FDPase activity. CPH increased the Km and decreased the Vmax of G6Pase, indicating mixed competitive and noncompetitive inhibition. These data indicate that the profound inhibition of renal cortical slice gluconeogenesis by CPH is mediated by inhibition of microsomal G6Pase activity.