Strain-related susceptibility to nephrotoxicity induced by aspirin and phenylbutazone in rats

Toxicity Induced by Subchronic Dermal Exposure to Paratertiary Butyl Benzoic Acid (pt BBA) in Fischer 344 Rats

The subchronic dermal toxicity of aqueous solutions containing the diethanolamine salt of para-tertiary butyl benzoic acid was determined in Fischer 344 rats. Para-tertiary butyl benzoic acid (pt BBA) has important applications in the manufacture of resins, polymers, and corrosion inhibitors. Male and female rats were exposed topically 5 days/week for up to 13 weeks with dosing solutions that resulted in daily exposures of 0.0, 17.5, 35.0, 70.0, or 140.0 mg/kg pt BBA. These concentrations did not produce overt clinical signs of toxicity and did not cause irritation to dermal exposure sites. However, exposure to the two highest concentrations resulted in decreased weight gain. Exposure at all concentrations resulted in dosage-related increases in relative hepatic and renal weights. Exposure of males to the two highest concentrations caused decreased testis weight. Exposure-related pathologic changes were confined to three organ systems: cytoplasmic vacuolation in the liver; tubular dilation and papillary necrosis of the kidneys; and tubular degeneration in the testes. Accompanying aberations in clinical chemistry values suggested altered hepatic and renal function. In males exposed daily to 70.0 and 140.0 mg/kg pt BBA, the testicular effects were marked, but no effects were detected in rats exposed to 17.5 or 35.0 mg/kg of pt BBA.

Genomic biomarkers for cardiotoxicity in rats as a sensitive tool in preclinical studies

The development of safer drugs is a high priority for pharmaceutical companies. Among the various toxicities caused by drugs, cardiotoxicity is an important issue because of its lethality. In addition, cardiovascular toxicity leads to the attrition of many drug candidates in both preclinical and clinical phases. Although histopathological and blood chemistry examinations are the current gold standards for detecting cardiotoxicity in preclinical studies, the large number of withdrawals from clinical studies owing to safety problems indicate that a more sensitive tool is required. We recently identified 32 genes that were candidate genomic biomarkers for cardiotoxicity in rats. Based on their functions, the present study focused on 8 of these 32 genes (Spp1, Fhl1, Timp1, Serpine1, Bcat1, Lmcd1, Rnd1 and Tgfb2). Diagnostic accuracy for the genes was determined by a receiver-operating characteristic (ROC) analysis using more cardiotoxic and non-cardiotoxic compounds. In addition, an optimized support vector machine (SVM) model that was composed of Spp1 and Timp1 was newly constructed. This new multi-gene model exhibited a much higher diagnostic accuracy than that observed for plasma cardiac troponin I (cTnI), which is one of the most useful plasma biomarkers for cardiotoxicity detection. Furthermore, we determined that this multi-gene model could predict potential cardiotoxicity in rats in the absence of any cardiac histopathological lesions or elevations of plasma cTnI. Overall, this multi-gene model exhibited advantages over classic tools commonly used for cardiotoxicity evaluations in rats. Our current results suggest that application of the model could potentially lead to the production of safer drugs.

Sex-related differences in renal toxicodynamics in rodents

INTRODUCTION

An issue yet to be addressed, in the investigation of the xenobiotic toxicity, is a detailed characterization of the sex differences in toxicological responses. The 'sex issue' is particularly significant in nephrotoxicology as the kidney is a relevant target organ for xenobiotics and few studies have approached this subject in the past. There is a strong need to improve our understanding regarding the influence of sex in toxicology, given their increased requirement to establish the limits of exposure to chemicals in the environment and at work.

AREAS COVERED

In this review, the authors provide the reader with the current knowledge of sex differences in kidney toxicity for rats and mice. To make the review easier to consult, these studies have been organized according to the class of xenobiotic.

EXPERT OPINION

From the analysis of the present knowledge emerges a dramatic need for information on sex differences in xenobiotics toxicity. Although animals are reasonably good predictors of adverse renal effects in patients, there is need to identify alternative methods (e.g. in vitro/ex vivo) to better study sex differences in organ toxicity.

Successful drug development despite adverse preclinical findings part 1: processes to address issues and most important findings

Unexpected adverse preclinical findings (APFs) are not infrequently encountered during drug development. Such APFs can be functional disturbances such as QT prolongation, morphological toxicity or carcinogenicity. The latter is of particular concern in conjunction with equivocal genotoxicity results. The toxicologic pathologist plays an important role in recognizing these effects, in helping to characterize them, to evaluate their risk for man, and in proposing measures to mitigate the risk particularly in early clinical trials. A careful scientific evaluation is crucial while termination of the development of a potentially useful drug must be avoided. This first part of the review discusses processes to address unexpected APFs and provides an overview over typical APFs in particular classes of drugs. If the mode of action (MoA) by which a drug candidate produces an APF is known, this supports evaluation of its relevance for humans. Tailor-made mechanistic studies, when needed, must be planned carefully to test one or several hypotheses regarding the potential MoA and to provide further data for risk evaluation. Safety considerations are based on exposure at no-observed-adverse-effect levels (NOAEL) of the most sensitive and relevant animal species and guide dose escalation in clinical trials. The availability of early markers of toxicity for monitoring of humans adds further safety to clinical studies. Risk evaluation is concluded by a weight of evidence analysis (WoE) with an array of parameters including drug use, medical need and alternatives on the market. In the second part of this review relevant examples of APFs will be discussed in more detail.

Strain differences in morphometrical characteristics of rat kidneys

To clarify the strain differences in the morphology of the rat kidneys, we investigated the morphometrical characteristics of the kidneys of Slc:Wistar, Slc:SD, and F344/NSlc rats. The diameter of the renal corpuscles in female F344/N rats is smaller than that in female Wistar rats. Although sex differences (males>females) were shown in SD and F344/N rats, no effects of castration were detected in any of the groups. Strain-dependent differences in the percentage of renal corpuscles with a cuboidal parietal layer were found in both male and female groups. The highest percentage of them was noted in male Wistar rats. Effects of castration were observed in female Wistar and male F344/N rats, and the values after castration were significantly higher than those in the intact animals. As for the number of proximal convoluted tubular nuclei, no strain differences were detected in either the male or female groups. Although a sex difference was found in SD rats (female>male), no effects of castration were detected in any of the groups. In female F344/N rats, numerous numbers of PAS-positive granules, which were observed in the proximal convoluted and straight tubular epithelia, were noted. Orchiectomy induced an increase of these granules in male SD and F344/N rats, but ovariectomy showed no effects on them in any strains. This is the first study to clarify the strain differences in the morphological characteristics of the kidneys in ordinary rat strains.

Renal papillary necrosis

Renal papillary necrosis (RPN) is a significant problem in human beings, especially in England and in Australia where it has been reported to account for 15% to 20% of patients needing renal transplants. Many compounds, including aspirin, phenacetin, phenylbutazone, indomethacin, mefenamic acid, flufenamic acid, fenoprofin, naproxen, and ibuprofen have been linked to renal papillary necrosis in human beings. Although the exact mechanism of RPN is unknown, there are several theories that have good scientific evidence behind them. Study of RPN in animals as models for the disease in human beings is limited by several factors, including anatomical differences between human beings and most animal species as well as technical difficulties in studying the renal papilla.

The role of glucuronidation in N-(3,5-dichlorophenyl)succinimide (NDPS) nephrotoxicity: nephrotoxic potential of NDPS and NDPS metabolites in Gunn, Wistar, and Fischer 344 rats

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) is an acute nephrotoxicant in rats. Although the mechanism of NDPS nephrotoxicity is not clear, our previous studies have strongly suggested that glucuronide conjugation of NDPS metabolite(s) is an important biotransformation reaction leading to the ultimate nephrotoxicant metabolite(s) mediating NDPS nephrotoxicity. In this study, the nephrotoxic potential of NDPS and its nephrotoxicant metabolites, N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (NDHSA), was examined in Gunn rats, which contain a genetic deficiency in bilirubin uridine diphosphate-glucuronosyltransferase (UDPGT), to explore further the role of glucuronidation in NDPS nephrotoxicity. The nephrotoxic potential of NDPS, NDHS, and NDHSA was also examined in Wistar rats, the parent strain for Gunn rats and which generally have normal UDPGT activity. Comparisons were then made with the nephrotoxicity induced by these compounds in Fischer 344 (F344) rats. Age-matched male F344, homozygous (j/j) Gunn, and Wistar rats were used. Rats (four to eight rats/group) of each strain were administered NDPS (0.4 mmol/kg ip), NDHS (0.1 or 0.2 mmol/kg ip), NDHSA (0.1 mmol/kg ip), or vehicle, and renal effects were monitored functionally and morphologically for 48 h. NDPS and its nephrotoxicant metabolites, NDHS and NDHSA, were much weaker nephrotoxicants in Gunn rats than in F344 rats, while Wistar rats were susceptible to the nephrotoxicity induced by NDPS, NDHS, or NDHSA. These results suggest that the lack of NDPS nephrotoxicity observed in Gunn rats is due to the deficiency in UDPGT in this strain rather than the parent Wistar strain being inherently nonresponsive to NDPS nephrotoxicity. Therefore, it appears that glucuronide metabolite(s) of NDHS and/or NDHSA contribute(s) to NDPS nephrotoxicity, although the exact nature of the nephrotoxicant glucuronide metabolite(s) of NDPS remains to be determined.

Renal papillary necrosis--40 years on

Analgesics and nonsteroidal anti-inflammatory drugs (NSAIDs) are well recognized as a major class of therapeutic agent that causes renal papillary necrosis (RPN). Over the last decade a broad spectrum of other therapeutic agents and many chemicals have also been reported that have the potential to cause this lesion in animals and man. There is consensus that RPN is the primary lesion that can progress to cortical degeneration; and it is only at this stage that the lesion is easily diagnosed. In the absence of sensitive and selective noninvasive biomarkers of RPN there is still no clear indication of which compound, under what circumstances, has the greatest potential to cause this lesion in man. Attempts to mimic RPN in rodents using analgesics and NSAIDs have not provided robust models of the lesion. Thus, much of the research has concentrated on those compounds that cause an acute or subacute RPN as the basis by which to study the pathogenesis of the lesion. Based on the mechanistic understanding gleaned from these model compounds it has been possible to transpose an understanding of the underlying processes to the analgesics and NSAIDs. The mechanism of RPN is still controversial. There are data that support microvascular changes and local ischemic injury as the underlying cause. Alternatively, several model papillotoxins, some analgesics, and NSAIDs target selectively for the medullary interstitial cells, which is the earliest reported aberration, after which there are a series of degenerative processes affecting other renal cell types. Many papillotoxins have the potential to undergo prostaglandin hydroperoxidase-mediated metabolic activation, specifically in the renal medullary interstitial cells. These reactive intermediates, in the presence of large quantities of polyunsaturated lipid droplets, result in localized and selective injury of the medullary interstitial cells. These highly differentiated cells do not repair, and it is generally accepted that continuing insult to these cells will result in their progressive erosion. The loss of these cells is thought to be central to the degenerative cascade that affects the cortex. There is still a need to understand better the primary mechanism and the secondary consequences of RPN so that the risk of chemical agents in use and novel molecules can be fully assessed.

Normal ultrastructure of the kidney and lower urinary tract

The mammalian urinary tract includes the kidneys, ureters, urinary bladder, and urethra. The renal parenchyma is composed of the glomeruli and a heterogeneous array of tubule segments that are specialized in both function and structure and are arranged in a specific spatial distribution. The ultrastructure of the glomeruli and renal tubule epithelia have been well characterized and the relationship between the cellular structure and the function of the various components of the kidney have been the subject of intense study by many investigators. The lower urinary tract, the ureters, urinary bladder, and urethra, which are histologically similar throughout, are composed of a mucosal layer lined by transitional epithelium, a tunica muscularis, and a tunica serosa or adventitia. The present manuscript reviews the normal ultrastructural morphology of the kidney and the lower urinary tract. The normal ultrastructure is illustrated using transmission electron microscopy of normal rat kidney and urinary bladder preserved by in vivo perfusion with glutaraldehyde fixative and processed in epoxy resin.

1H NMR spectroscopic and histopathological studies on propyleneimine-induced renal papillary necrosis in the rat and the multimammate desert mouse (Mastomys natalensis)

The renal papillary toxin, propyleneimine (PI), was administered at 20 or 30 microliters/kg i.p. to male Sprague Dawley (SD) rats (n = 5), Fischer 344 (F344) rats (n = 4), and to multimammate desert mice (Mastomys natalensis, n = 4). Urine was collected at time points up to 4 days p.d. and the toxicological response of the different animal models to PI compared using 1H NMR spectroscopy of urine, renal histopathology, and urinary assays for alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and gamma-glutamyl transpeptidase (gamma GT). The renal papillae of both F344 and SD rats showed extensive necrotic lesions 4 days post-dosing and in some cases sloughing of the papilla. However, only slight renal papillary necrosis (RPN) was observed in Mastomys treated with 20 microliters/kg PI and, although slight to moderate damage was observed at 30 microliters/kg, PI-treated Mastomys showed substantially less RPN than either group of PI-treated rats. 1H NMR urinalysis showed that PI treatment caused a decrease in the urinary concentrations of succinate (0-24 hr p.d.) and citrate (24-48 hr p.d.) and an increase in creatine (0-48 hr p.d.) in all animal models. Trimethylamine-N-oxide (24-48 hr) and 2-oxoglutarate concentrations decreased initially following the administration of PI and then rose above control levels. The 1H NMR-detected urinary biochemical effects of PI in all three models were similar. However, taurine concentrations were elevated in the urine of Mastomys following PI treatment, perhaps indicating a degree of liver damage, whereas taurinuria was not seen in either SD or F344 rats. These observations are discussed in relation to the potential mechanism of PI-toxicity.

Comparative studies on the nephrotoxicity of 2-bromoethanamine hydrobromide in the Fischer 344 rat and the multimammate desert mouse (Mastomys natalensis)

Renal papillary necrosis (RPN) was induced in Fischer 344 (F344) rats (n = 4) using 2-bromoethanamine hydrobromide (BEA) dosed at 150 mg/kg, and in multimammate desert mice (Mastomys natalensis) at 150 and 250 mg/kg (n = 4 per group). Control rats and Mastomys were dosed with 0.9% saline (n = 4 per group). Urine was collected at regular intervals for up to 4 days post-dosing and analysed for low MW metabolites using high resolution 1H NMR spectroscopy. The urinary activity of lactate dehydrogenase, gamma-glutamyl transpeptidase and alkaline phosphatase was determined using conventional biochemical assays. On termination, histopathological examination of papillae was performed showing the development of extensive lesions in F344 rats at 150 mg/kg BEA. Mastomys appeared much more resistant to BEA and showed normal renal histology at 150 mg/kg and patchy lesions at 250 mg/kg BEA. Enzyme analysis of control urine showed F344 rats to have > 1000% higher gamma-glutamyl transpeptidase activity than Mastomys. 1H NMR spectroscopic analysis showed that BEA caused a substantial decrease in urinary concentrations of succinate and citrate (0-24 h p.d.) and an increase in creatine (0-96 h p.d.) in both animal models. A decrease in the urinary concentration of 2-oxoglutarate with a subsequent increase by 72-96 h p.d. was also noted in both animal models. Glutaric and adipic aciduria were also induced in both F344 rats and Mastomys 0-24 h post-BEA treatment, indicative of an enzyme deficiency in the acyl CoA dehydrogenases. Urinary taurine levels were elevated in Mastomys following the administration of BEA, indicating some degree of liver toxicity. Urinary taurine was not elevated in F344 rats following BEA administration, demonstrating further species difference in BEA toxicity.

Long-term exposure to the anti-inflammatory agent phenylbutazone induces kidney tumors in rats and liver tumors in mice

Long-term toxicity and carcinogenicity of phenylbutazone, a nonsteroidal anti-inflammatory drug, were evaluated in F344/N rats and B6C3F1 mice. In 2-year studies, phenylbutazone was given in corn oil by gavage 5 days per week to groups of 50 rats of each sex at doses of 0, 50, or 100 mg/kg body weight, and to groups of 50 mice at doses of 0, 150, or 300 mg/kg body weight. Body weights and survival were similar among groups. Major target organs are kidneys in rats and liver in mice. Kidney: inflammation, papillary necrosis, and mineralization in both sexes of rats, and hyperplasia and dilatation of the pelvis epithelium, and cysts in female rats. Uncommon tubular cell tumors of the kidney were found in 13 exposed rats: 5 in the 50 mg group and 4 in the 100 mg group of males; 4 in dosed female rats; none in controls. In female rats, dose-related increases in hyperplasia of the pelvis transitional epithelium, and 2 carcinomas were discovered. Urinary bladder: papillomas of the transitional epithelium were seen in 2 low-dose male and in 1 low-dose female rats. Forestomach: ulcers in rats, with acanthosis, hyperkeratosis, and basal cell hyperplasia in female rats; however, no neoplasms were associated with these lesions. Liver: primarily in male mice exposed to phenylbutazone, hemorrhage, centrilobular cytomegaly and karyomegaly, fatty metamorphosis, cellular degeneration, and coagulative necrosis were seen; clear cell foci were observed in male mice. In summary, under the conditions of these 2-year oral intubation studies, phenylbutazone is associated with renal carcinogenicity in rats, as evidenced by increases in tubular cell neoplasms in both sexes. Evidence of carcinogenicity for male mice was shown by increased incidences and multiplicity of liver tumors. No carcinogenic activity was found for female mice.

Nephrotoxicity screening in rats: a validation study

A validation of our non-invasive screening test for the detection of renal damage (Zbinden et al. 1988) is presented. The test is based on repetitive, quantitative urine analysis in groups of six female Sprague-Dawley rats treated on 5 consecutive days with low doses of test substances. Higher doses were administered in the following weeks until nephrotoxic effects or signs of general toxicity were observed. Thirteen reference substances (hexachloro-1:3-butadiene [HCBD], cisplatin, carboplatin, suramin, chloroform, neomycin, rifampicin, phenacetin, phenylbutazone, methicilline, sodium oxalate, ethylene glycol and furosemide) were used. The percentage of rats reaching the test criteria, i.e., pathologic values defined on the basis of measured control values, was determined. In the controls, the overall percentage of rats reaching or exceeding the test criteria was 4.48%, a value that is close to the expected 5%. Evidence of nephrotoxicity was found with all reference compounds. Elevated excretion of cells and occurrence of cylinders were the most sensitive indicators of renal damage. Hematuria was the most frequent finding. Of the other urine constituents measured the enzyme malate dehydrogenase (MDH) was frequently increased. Water consumption, urine volume, pH and specific gravity were occasionally, and protein, glucose, electrolytes, amino acids and gamma-glutamyl-transpeptidase (GGT) were only rarely changed. It is concluded that the screening which is based on quantitative and repeated urine analysis is a useful procedure to detect nephrotoxic chemicals acting by a variety of mechanisms. The histopathological examination of the kidneys contributed useful information of the nature of the toxic effects, but as a screening tool it is less sensitive than quantitative urine analysis.

Nephrotoxicity screening in rats; general approach and establishment of test criteria

The concept of a nephrotoxicity screening test that is based on quantitative assessment of urine collected under standardized conditions for 15.5 h is presented. One to eight urine collections were performed in large numbers of untreated female Sprague-Dawley rats. Normal values for water consumption, urine volume, pH, and excretion of protein, gamma-glutamyltranspeptidase, malate dehydrogenase, electrolytes, glucose, amino acids, leukocytes, erythrocytes, epithelia, unspecified cells and cylinders were determined. Test criteria were established based on the statistical distribution of these measurements. In rats repeatedly placed in metabolism cages, a statistically significant decrease in leukocyte excretion and an increase in excretion of epithelia and unspecified cells were observed. All other variables did not change with time.