Chemically induced renal papillary necrosis and upper urothelial carcinoma. Part 1

Renal Papillary Necrosis Appearing as Bladder Cancer on Imaging

A 79-year-old woman with a history of diabetes mellitus and recurrent urinary tract infections (UTIs) presented with acute onset left lower quadrant pain, left-sided back pain, vomiting, and dysuria. Abdominopelvic CT scan revealed left hydroureteronephrosis to the level of the left ureterovesical junction (UVJ) where a bladder mass appeared to be obstructing the left ureteral orifice. The obstruction was ultimately found to be the result of a sloughed renal papilla lodged in the distal ureter, which created an inflammatory mass at the UVJ. Her history of diabetes and frequent UTIs likely predisposed her to the development of renal papillary necrosis (RPN) that resulted in sloughing of a renal papilla, distal ureteral obstruction with subsequent bladder inflammation that mimicked a bladder mass on imaging. RPN is a condition associated with many etiologies and likely represents a common final pathway of several diseases. Although several hypotheses exist, it is primarily thought to be ischemic in nature and is related to the underlying physiology of the renal papillae. We present a case of hydroureteronephrosis and bladder mass secondary to a sloughed renal papilla from RPN.

Proliferative and nonproliferative lesions of the rat and mouse urinary system

The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying lesions observed in the urinary tract of rats and mice. The standardized nomenclature of urinary tract lesions presented in this document is also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous developmental and aging lesions as well as those induced by exposure to test materials. A widely accepted and utilized international harmonization of nomenclature for urinary tract lesions in laboratory animals will decrease confusion among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

Biomarkers of Collecting Duct Injury in Han-Wistar and Sprague-Dawley Rats Treated with N-Phenylanthranilic Acid

N-phenylanthranilic acid is a chloride channel blocker that causes renal papillary necrosis in rats. Studies were conducted in two strains of male rats to evaluate novel biomarkers of nephrotoxicity. Han-Wistar rats were given daily oral doses of 50, 350, or up to 700 mg/kg/day of NPAA, and Sprague-Dawley rats were given 50 or 400 mg/kg/day of NPAA. Rats were euthanized on days 8 and 15. The candidate kidney injury biomarkers renal papillary antigen-1 (RPA-1, for collecting duct injury), clusterin (for general kidney injury), α-glutathione-S-transferase (a proximal tubular marker), and µ-glutathione-S-transferase (a distal tubular marker) were measured in urine by enzyme immunoassay. Characteristic degeneration and necrosis of the collecting duct and renal papilla were observed in Han-Wistar rats at the high dose on day 8 and at the mid and high doses on day 15, and in Sprague-Dawley rats given the high dose on days 8 and 15. Increases in urinary RPA-1, and to a lesser extent urine clusterin, were generally associated with the presence of collecting duct injury and were more sensitive than BUN and serum creatinine. On the other hand, decreases in α-glutathione-S-transferase without proximal tubule lesions in both strains and decreases in µ-glutathione-S-transferase in Sprague-Dawley rats only were not associated with morphological proximal or distal tubule abnormalities, so both were of less utility. It was concluded that RPA-1 is a new biomarker with utility in the detection of collecting duct injury in papillary necrosis in male rats.

Characterization of Renal Papillary Antigen 1 (RPA-1), a Biomarker of Renal Papillary Necrosis

Renal papillary necrosis (RPN) is a relatively common toxicity observed in preclinical drug safety testing. It is also observed in a variety of human diseases. RPN is difficult to diagnose without expensive scanning methods or histopathology. A noninvasive biomarker that could be detected at early stages of kidney damage would be of great value both to preclinical drug safety testing and in the clinic. An antibody raised to an unknown epitope of an antigen in rat kidney papilla was found to be specific for collecting duct cells in the kidney; this was termed renal papillary antigen 1 (RPA-1). In this study, the authors show that RPA-1 is an early biomarker of RPN in two different rat models of toxicity: 2-bromoethanamine (BEA) and N-phenylanthranilic acid (NPAA). RPA-1 can be detected in urine at early stages of toxicity and correlates well with the histopathology observed. We also characterized the biochemical properties of RPA-1 and found that the antigen is a high molecular weight membrane bound glycoprotein, with the epitope likely to be carried on an N-linked carbohydrate structure. This study demonstrates that RPA-1 is an excellent marker of RPN that can be used to detect this toxicity in preclinical safety testing.

1H-Nuclear magnetic resonance pattern recognition studies withN-phenylanthranilic acid in the rat: time- and dose-related metabolic effects

N-Phenylanthranilic acid (NPAA) causes renal papillary necrosis (RPN) in the rat following repeated oral dosing. Non-invasive early detection of RPN is difficult, but a number of potential biomarkers have been investigated, including phospholipid and uronic acid excretion. This study used 1H-nuclear magnetic resonance (NMR) spectroscopic analysis of urine to investigate urinary metabolic perturbations occurring in the rat following exposure to NPAA. Male Alderley Park rats received NPAA (300, 500 or 700 mg kg(-1) day(-1) orally) for 7 days, and urine was collected on days 7-8, 14-15, 21-22 and 28-29. In a separate study, urine was collected on days 1-2, 3-4, 5-6 and 7-8 from rats receiving 500 mg kg(-1) day(-1). Samples were analysed by 1H NMR spectroscopy combined with multivariate data analysis and clinical chemistry. Histopathology and clinical chemistry analysis of terminal blood samples was carried out following termination on days 4, 6, 8 and 29 (4 week time course) and days 2, 4, 6 and 8 (8 day study). Urine analysis revealed a marked, though variable, excretion of beta-hydroxybutyrate, acetoacetate and acetone (ketone bodies) seen on days 3-4, 5-6 and 7-8 of the study. It is postulated that the ketonuria might be secondary to an alteration in fatty acid metabolism due to inhibition of prostaglandin synthesis. In addition, an elevation in urinary ascorbate was observed during the first 8 days of the study. Ascorbate is considered to be a biomarker of hepatic response, probably reflecting an increased hepatic activity due to glucuronidation of NPAA.

A safety assessment of fixed combinations of acetaminophen and acetylsalicylic acid, coformulated with caffeine

Overuse and abuse of phenacetin-containing mixed analgesics has contributed to end-stage renal disease. Combination analgesics, especially those coformulated with caffeine, have been implicated as imparting a greater risk of analgesic-associated nephropathy (AAN) than single or coformulated analgesics without caffeine. This has led to a recommendation that the sale of "two plus caffeine" analgesic mixtures be reclassified from over-the-counter to prescription only availability. There is a rational basis for coformulating acetylsalicylic acid (ASA) and acetaminophen (paracetamol) as this reduces the dose of each, without altering efficacy. The coformulation of caffeine with these analgesics has a significant adjuvant effect and increases analgesic efficacy 1.4-1.6-fold. Currently available animal and human data do not support the notion that the nephrotoxic risk from coformulated ASA and acetaminophen is higher than the risk from either ASA or acetaminophen alone, in equivalent analgesic doses. There are no epidemiological data that implicate caffeine in AAN, and only limited evidence that links excessive acetaminophen usage to renal disease. There is no evidence that caffeine increases analgesics papillotoxicity directly. The presence of caffeine in mixtures of analgesics are no more addictive than other sources of caffeine. There is no evidence to suggest that adding caffeine to analgesic mixtures enhances the potential for promoting analgesic misuse in the general population. Thus distinct therapeutic benefits of ASA, acetaminophen and caffeine appear to outweigh any known risk. It is doubtful if preventing the availability of these products will significantly affect the role of analgesic abuse/overuse in end-stage renal disease. Better risk management would come from a focused educational program, developed in a close collaboration between industry, healthcare professionals and consumer organizations, such a program must warn against the potential dangers of analgesic and non-steroidal anti-inflammatory drug misuse.

A review of epidemiologic studies of nonnarcotic analgesics and chronic renal disease

The relationship of long-term and heavy exposure of nonnarcotic analgesics to the risk of chronic renal disease (CRD) has been the object of intensive clinical, pharmacologic, toxicologic, and epidemiologic research for 4 decades. The clinical evidence of an increased risk has been suggestive but inconclusive. The experimental evidence in animal models has been inconsistent, and in any case it cannot be generalized to humans. The epidemiologic evidence has been unsatisfactory for the most part: most of the early studies had severe methodologic limitations; moreover, they related mainly to phenacetin-containing drugs and did not have useful information on other analgesics. Since 1980, 9 analytical epidemiologic studies have attempted to confirm that a causal relationship exists between phenacetin or other analgesics and CRD. In the aggregate, despite methodologic flaws, this work suggests that excessive use of phenacetin-containing analgesics probably causes renal papillary necrosis and interstitial nephritis. In contrast, there is no convincing epidemiologic evidence that nonphenacetin-containing analgesics (including acetaminophen, aspirin, and mixtures of these two compounds) or that nonsteroidal antiinflammatory drugs cause CRD. Moreover, the nature of dose-response relationships, the types of renal disease possibly caused by analgesics, and the cofactors that might be related both to analgesic use and to the development of CRD in humans are still uncertain, and the pathologic mechanisms of analgesic-induced CRD in humans remain unclear. It may take many years before all the outstanding issues are settled. Until they are, as a matter of good clinical judgment it would be prudent to consider all analgesics as potentially nephrotoxic and, as much as possible, to avoid excessive, protracted use.

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.

Serotonin (5-HT1A-receptor) agonist-induced collecting duct vacuolation and renal papillary necrosis in the rat

General anxiety in humans is treated with azaspirodecanedions, which act through a reduction of serotonin transmission. Ipsapirone also represents a serotonin (5-HT1A) receptor agonist and was under development as an anxiolytic drug. Histopathologic evaluation of animal experiments revealed cellular swelling and/or vacuolation of renal papillary and medullary collecting duct (MCD) epithelium in rats but not in dogs or mice. The changes ensued already after 1 wk of dosing and were first localized in the inner MCDs. Longer treatment periods showed that these changes proceeded from proximal to distal, approaching the papillary collecting ducts. The changes were most likely the result of altered hemodynamics in the papillary tip. Swelling resulted in partial or total papillary necrosis in some cases. Furthermore, rats treated with ipsapirone showed a sharp and transient rise in urinary endothelin excretion. Concomitantly, urinary PGE2 levels were elevated. In contrast, no elevated levels of endothelin were detected in urine samples of patients from a volunteer study, leading to the conclusion that the human kidney is not susceptible to the ipsapirone-induced alterations seen in the collecting ducts of rats.

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.

Urinary markers of nephrotoxicity following administration of 2 bromoethanamine hydrobromide a comparison with hexachlorobutadiene

2 bromoethanamine hydrobromide (BEA) has been widely considered to be a target selective nephrotoxin that causes necrosis of the medulla in 24-48 h, but recent reports suggest that early cortical injury is also associated with this lesion. In order to assess the cortical effects of BEA (100 mg kg(-1) bw single ip injection), several urinary markers of renal injury were evaluated over a 7 day period in male Wistar Albino rats. Hexachlorobutadiene (HCBD 150 mg kg(-1) bw in peanut oil ip), a renal toxin which targets selectively for the proximal tubule, was used as a comparison. After BEA treatment, urinary levels of alanine aminopeptidase, gamma-glutamyl-transpeptidase, alkaline phosphatase and glucose increased transiently. Each of the proximal tubule marker enzymes peaked earlier following HCBD treatment and elevation of alanine aminopeptidase and gamma glutamyl transpeptidase was sustained for longer periods than for BEA. Following BEA treatment, lactate dehydrogenase rose prominently on day 1 followed by a return to control values on day 2 and a further rise on day 3 and remained high until the end of the study. BEA also increased the urinary excretion of total protein and albumin. After HCBD treatment, lactate dehydrogenase showed a transient elevation and glucose levels were slightly increased. Based on the present observations the changes induced by BEA administration on urinary markers of renal injury are different from those observed following HCBD treatment. These findings suggest that BEA toxicity also involves other parts of the kidney besides the papilla.

Combination analgesic involvement in the pathogenesis of analgesic nephropathy: the European perspective

Analgesic nephropathy (AN) is a chronic renal disease characterized by renal papillary necrosis and interstitial nephritis caused by excessive consumption of analgesic mixtures. In a recent study, diagnostic criteria for AN, based on a computed tomography scan investigation without contrast, were presented. The observation of a decreased renal mass of both kidneys combined with either bumpy contours or papillary calcifications was found to have a high diagnostic performance. Although several case control studies and two prospective studies demonstrated the association between analgesic abuse and nephropathy, the nephrotoxicity of the different analgesic products had not been clearly established. Analgesic abuse can be defined as a daily consumption of analgesic mixtures over a several-year period. Abuse of single analgesics is rare; it has been clearly demonstrated that abusers prefer analgesic mixtures. In Belgium, the prevalence of AN was positively related to the sales of analgesic mixtures containing two analgesic components plus caffeine and/or codeine. This relationship could not be observed for analgesics containing only one analgesic component plus caffeine and/or codeine. Moreover, during a European multicenter study, nephrotoxicity of different combinations of analgesic mixtures (all containing caffeine and/or codeine) could be documented in the absence of any previous phenacetin consumption. Epidemiologic observations in Sweden, France, and Belgium regarding incidence of AN, sales figures of analgesics, and legislative measurements concerning analgesic consumption supported the previous observations.

Investigation of regional glutathione levels in a model of chemically-induced renal papillary necrosis

The effect of diphenylamine on renal cortical, outer medullary and inner medullary glutathione (GSH) concentrations and the effect of GSH depletion on the nephrotoxicity of diphenylamine were investigated in male Syrian hamsters. A dose-dependent decrease in renal cortical GSH was observed within 1 hr of a single oral dose of diphenylamine (200, 400 or 600 mg/kg body weight), but statistically significant changes in outer medullary or papillary GSH were not observed. Reduction of renal papillary GSH to 29% of basal concentration [by prior treatment with L-buthionine sulfoxime (500 mg/kg body weight, ip)] did not increase the papillotoxicity of a non-toxic dose of diphenylamine (400 mg/kg) administered orally. The findings indicate that diphenylamine-induced renal papillary necrosis in the Syrian hamster is not associated with a decrease in renal papillary or outer medullary GSH nor mediated by oxidative cell injury.

Biotransformation and membrane transport in nephrotoxicity

The kidney is a frequent target organ for toxic effects of xenobiotics. In recent years, the molecular mechanisms responsible for the selective renal toxicity of many nephrotoxic xenobiotics have been elucidated. Accumulation by renal transport mechanisms, and thus aspects of renal physiology, plays an important role in the renal toxicity of some antibiotics, metals, and agents binding to low molecular weight proteins such as alpha(2u)-globulin. The accumulation by active transport of metabolites formed in other organs is involved in the kidney-specific toxicity of certain polyhaloalkanes, polyhaloalkenes, hydroquinones, and aminophenols. Other xenobiotics are selectively metabolized to reactive electrophiles by enzymes expressed in the kidney. This review summarizes the present knowledge on the mechanistic basis of target organ selectivity of these compounds.

Renal papillary necrosis and urinary protein alterations induced in Fischer-344 rats by D-ormaplatin

D-ormaplatin (previously called tetraplatin) produced dose-related renal papillary necrosis when given intravenously to Fischer-344 rats at doses of 2, 4, and 9 mg/kg. The lesions were most severe at 4 days postdosing and had repaired by day 9 in the 2- and 4-mg/kg dose groups. Blood urea nitrogen and the N-acetyl-beta-glucosaminidase (NAG): creatinine ratio were slightly elevated at day 4 while creatinine clearance was decreased. Body weight was reduced in a dose-related manner while kidney weights increased. Total protein excretion in male and female rats was elevated at day 4 postdosing. The evaluation of urinary proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed an increase, primarily in high molecular weight proteins at 4 days postdosing, indicating an increase in glomerular filtration of albumin and transferrin. The morphologic appearance of the glomeruli was normal by light microscopy. At day 4 postdosing, alpha 1-microglobulin was elevated. This correlated with an increase in the NAG: creatinine ratio also seen at this time and the morphologic appearance of the kidney, indicating that the proximal tubules were affected but were not a major site of toxicity. Although the change in urinary proteins occurred at the same time as morphologic alterations in the renal papilla, these findings were not considered to be related. SDS-PAGE provided a useful method for detecting and localizing renal toxicity when used in conjunction with morphologic and clinical chemistry methods.

Relevance of a rat model of papillary necrosis and upper urothelial carcinoma in understanding the role of ochratoxin A in Balkan endemic nephropathy and its associated carcinoma

Ochratoxin A is nephrotoxic and has been implicated in the genesis of Balkan endemic nephropathy (BEN), a condition that leads to end-stage renal disease and upper urothelial tumours. This compound induces renal parenchymal carcinoma in male mice only, and is not considered to be a potent carcinogen nor is there experimental evidence of its propensity to cause upper urothelial carcinoma. There is, however, evidence that exposure to more than one mycotoxin may be an important factor in the clinical spectrum of BEN. Analgesic nephropathy is clinically different, but is also associated with an upper urothelial carcinoma. The combination of urothelial initiation and an acute papillary necrosis in rats produces upper urothelial carcinoma. This two-stage experimental model offers the potential to assess the role of ochratoxin A in BEN-associated upper urothelial carcinoma under experimental conditions.

Renal pelvic carcinoma which shows metastatic potential to distant organs, induced by N-butyl-N-(4-hydroxybutyl)nitrosamine in NON/Shi mice

Renal pelvic carcinoma was induced in mice by giving N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN). Initially, differences in renal pelvic carcinogenesis by BBN were examined in three male mouse strains: NON/Shi, which demonstrate spontaneous hydronephrosis with incidences of 10-30%, and DS/Shi and B6C3F1, which do not exhibit hydronephrosis. When mice of these strains were given 0.05% BBN in the drinking water for 12 weeks followed by water without BBN for 8 weeks, renal pelvic carcinoma morphologically similar to human carcinomas developed in 8 of 23 NON/Shi mice (35%). Metastasis to the lung was found in one of them (13%). B6C3F1 and DS/Shi mice had no pelvic tumors, but the response to urinary bladder carcinogenesis in NON/Shi mice was nearly equal to that in DS/Shi and B6C3F1 mice. These results suggest that renal pelvic carcinogenesis is related to the presence of stagnant urine containing carcinogen in the renal pelvis. In a second experiment, we examined renal pelvic carcinogenesis in NON/Shi mice given BBN for 4 weeks followed by water without BBN for 32 weeks. The incidence of renal pelvic carcinoma (28%) was similar to that in the first experiment, but the incidence of metastasis was markedly elevated to 60%. These results indicate that BBN treatment can induce renal pelvic carcinoma which often metastasizes to the lung in NON/Shi mice.

Decreased incidence of diphenylamine-induced renal papillary necrosis in Syrian hamsters given dimethylsulphoxide

The renal papillotoxicity of diphenylamine dissolved in dimethylsulphoxide (DMSO) was investigated in male Syrian hamsters, male Sprague-Dawley rats and female Mongolian gerbils. When diphenylamine in DMSO was administered orally to male Syrian hamsters (400, 600 or 800 mg/kg body weight/day for up to 9 days), the incidence of renal papillary necrosis was almost zero. Hamsters pretreated with DMSO (0.5 ml/100 g body weight/day) and 1 hr later given 400, 600 or 800 mg diphenylamine in peanut oil/kg body weight/day for 3 consecutive days had significantly reduced incidences of renal papillary necrosis (0/10, 0/10 and 1/10 in the low-, mid- and high-dose groups, respectively) when compared with hamsters given similar doses of diphenylamine but not pretreated with DMSO (5/10, 7/10 and 5/10 in the low-, mid- and high-dose groups, respectively). Focal, apex-limited renal papillary necrosis was observed in two Sprague-Dawley rats given 800 mg diphenylamine in DMSO/kg body weight/day orally for 9 days. Focal, intermediate renal papillary necrosis was observed in two additional rats administered 800 mg diphenylamine in DMSO/kg/day orally for 9 days. Renal papillary necrosis was not observed in any of the Mongolian gerbils. The results of these studies suggest that DMSO protects against diphenylamine-induced renal papillary necrosis in male Syrian hamsters.

Renal and urinary lipid changes associated with an acutely induced renal papillary necrosis in rats

A single dose of 2-bromoethanamine hydrobromide (BEA; 100 mg/kg body weight) given ip to male Wistar rats causes an acute renal papillary necrosis in 24 hr. Oil Red O (ORO) lipid staining is normally confined to the polyunsaturated lipid droplets of the medullary interstitial cells, but ORO-positive material was present in the endothelial cells of the vasa recta 7 hr after BEA treatment. At 24 hr (by which time papillary necrosis had developed), there were also markedly increased quantities of lipid in the cells of the collecting ducts and covering epithelia. At 48 hr totally necrosed areas stained heavily with ORO, and lipid deposits were particularly numerous in the hyperplastic urothelia adjacent to the necrosed region. Epithelial and endothelial accumulation of lipid material also extended into areas of the juxtamedulla and cortex, which appeared normal by routine haematoxylin and eosin staining. Lipid staining is more selective and sensitive for identifying papillary necrosis than routine histology, because neither hexachlorobutadiene-, aminoglycoside-, cis-platin- nor polybrene-induced lesions produce similar histochemical changes. This suggests that the capillary and epithelial deposits of lipid material are pathognomonic for the development of renal papillary necrosis. An increase in urinary triglycerides following BEA treatment supports the biochemical basis of these ORO changes as a neutral lipid accumulation.

Bioactivation of xenobiotics by prostaglandin H synthase

Prostaglandin H synthase (PHS) catalyzes the oxidation of arachidonic acid to prostaglandin H2 in reactions which utilize two activities, a cyclooxygenase and a peroxidase. These enzymatic activities generate enzyme- and substrate-derived free radical intermediates which can oxidize xenobiotics to biologically reactive intermediates. As a consequence, in the presence of arachidonic acid or a peroxide source, PHS can bioactivate many chemical carcinogens to their ultimate mutagenic and carcinogenic forms. In general, PHS-dependent bioactivation is most important in extrahepatic tissues with low monooxygenase activity such as the urinary bladder, renal medulla, skin and lung. Mutagenicity assays are useful in the detection of compounds which are converted to genotoxic metabolites during PHS oxidation. In addition, the oxidation of xenobiotics by PHS often form metabolites or adducts to cellular macromolecules which are specific for peroxidase- or peroxyl radical-dependent reactions. These specific metabolites and/or adducts have served as biological markers of xenobiotic bioactivation by PHS in certain tissues. Evidence is presented which supports a role for PHS in the bioactivation of several polycyclic aromatic hydrocarbons and aromatic amines, two classes of carcinogens which induce extrahepatic neoplasia. It should be emphasized that the toxicities induced by PHS-dependent bioactivation of xenobiotics are not limited to carcinogenicity. Examples are given which demonstrate a role for PHS in pulmonary toxicity, teratogenicity, nephrotoxicity and myelotoxicity.

Crystalluria, medullary matrix crystal deposits and bladder calculi associated with an acutely induced renal papillary necrosis

A single (100 mg/kg) intraperitoneal dose of 2-bromoethanamine hydrobromide induced renal papillary necrosis (RPN) acutely in rodents and caused a transient crystalluria between 4 and 8 h after dosing. These crystals comprised struvite or magnesium ammonium phosphate (MAP) as assessed by shape, solubility, infra-red spectrum and X-ray microprobe analysis. Acid-soluble, bi-refringent crystals were also present within the renal medullary matrix during the same time period as the crystalluria. The presence of the MAP was associated with loss of the anionic renal medullary mucopolysaccharides staining. A total of 5/64 rats with a 2-bromoethanamine-induced renal papillary necrosis and monitored for up to 160 days had bladder calculi that were predominantly MAP. These data suggest that medullary mucopolysaccharide matrix disruption associated with RPN leads to a release of previously bound cations, super-saturation and the nucleation of crystalline MAP. These processes could also be implicated in the formation of MAP bladder calculi.

Diphenylamine-induced renal papillary necrosis and necrosis of the pars recta in laboratory rodents

The nephrotoxicity of diphenylamine, the parent compound of the mefenamate family of nonsteroidal anti-inflammatory drugs, was evaluated in male Syrian hamsters, male Sprague-Dawley rats, and male Mongolian gerbils. Total renal papillary necrosis was observed in four of ten, seven of ten, and six of ten male Syrian hamsters orally treated with diphenylamine at respective doses of 400 mg/kg body weight/day, 600 mg/kg body weight/day, and 800 mg/kg body weight/day. Total renal papillary necrosis was also observed in five of ten and four of ten male Syrian hamsters intraperitoneally treated with diphenylamine at respective doses of 600 mg/kg body weight/day and 800 mg/kg body weight/day. Focal intermediate renal papillary necrosis was induced in two hamsters orally given diphenylamine at 600 mg/kg body weight/day and in two of ten hamsters intraperitoneally given diphenylamine at 800 mg/kg body weight/day. Apex-limited necrosis of the medullary interstitial cells and vasa recta and degeneration of the renal interstitial matrix occurred in two Sprague-Dawley rats orally administered diphenylamine at 800 mg/kg body weight/day. Degeneration and necrosis of the pars recta was induced in seven of ten hamsters intraperitoneally given diphenylamine at 400 mg/kg body weight/day. Gross and microscopic renal lesions were not observed in any Mongolian gerbils. It was concluded that the Syrian hamster is more susceptible to the papillotoxic effects of diphenylamine than the Sprague-Dawley rat and the Mongolian gerbil. Renal papillary necrosis in the Syrian hamster treated orally with diphenylamine is reproducible, is of short onset, and is induced in a high proportion of the hamsters (70-90%).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of acetaminophen on pig kidneys with a 2-bromoethanamine-induced papillary necrosis

Large White pigs were used to investigate the effects of acetaminophen (paracetamol) on normal kidneys or those with an existing renal papillary necrosis. Pairs of young female animals were treated with either a single iv dose of 50 mg/kg 2-bromoethanamine (BEA), 100 mg/kg/day acetaminophen po for 28 days, or a combination of BEA followed by the acetaminophen treatment. Two pigs served as untreated controls. Kidney length, diameter and parenchymal thickness were measured by ultrasound scans, and glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) assessed by 99mTc-DTPA and 131I-hippuran renography prior to treatment and on day 26. Acetaminophen only caused no renal pathology. Despite the lack of a gross RPN, hyperplasia of the pelvic and ureteric urothelia (with extensive vacuolation) was observed following BEA, but BEA followed by acetaminophen for 28 days did not enhance the lesion. The BEA and BEA-acetaminophen groups (but not acetaminophen only) showed an increased ERPF compared with age-matched controls, but there was no significant difference in the overall GFR between the groups.

High resolution light microscopic morphological and microvascular changes in an acutely induced renal papillary necrosis

Morphological changes were followed in semi-thin glycolmethacrylate sections, after treating male Wistar rats with a single ip dose of 2-bromoethanamine (BEA) hydrobromide (100 mg/kg) to induce renal papillary necrosis. Medullary interstitial cells had irregular nuclei at 4 hr and focal necrosis by 8 hr which spread from the papilla tip to the cortico-medullary junction from 12 hr. Increased mucopolysaccharide staining was observed in the papilla tip at 4 hr, and was lost from those regions where necrosis had developed by 48 hr. Endothelial platelet adhesion, first seen at 8 hr, was very marked at 18 hr, but affected capillaries in necrotic regions only, up to 144 hr. The absence of extravasated Monastral Blue B demonstrated the integrity of the medullary microvascular endothelia. The distal nephron showed degenerative changes at 12 hr and cell exfoliation at 18 hr. Cortical changes were confined to PAS-positive casts in the collecting duct and loop of Henle from 8 hr and dilatation of distal and proximal tubules at 8 and 72 hr, respectively. There was active repair at the junction between viable and necrotic tissue in the papilla from 24 hr with mitoses in the collecting ducts and loops of Henle. Normally the urothelium is less than 3-4 cells thick, but upper urothelial proliferation followed BEA administration. Hyperplasia was especially marked at the mouth of the ureter and in the pelvis opposite the region of necrosis (7-8 cells thick at 18 hr) and had only partially resolved by 144 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme histochemical changes in an acutely induced renal papillary necrosis

Enzyme histochemistry was assessed in semi-thin glycolmethacrylate sections after 100 mg/kg 2-bromoethanamine (BEA) hydrobromide had been given ip to male Wistar rats to induce renal papillary necrosis. Changes in the proximal tubular marker enzymes alkaline phosphatase (Alk Phos), gamma-glutamytranspeptidase (GGT) and adenosine triphosphatase (ATPase) were not apparent before 8 hr, but there was a progressive loss up to 144 hr. The proteinaceous PAS-positive casts in the loops of Henle and the collecting ducts stained for Alk Phos and GGT (from 12 hr) and for ATPase (from 18 hr). Acid phosphatase (Acid Phos) staining was increased in the proximal tubule lysosomes from 18 hr. There was a marked increase in Alk Phos in all hyperplastic upper urothelial cells from 8 to 24 hr, and a mosaic of staining remained in the pelvis adjacent to the necrosed papilla at 144 hr. At 12 hr, there was an increase in the staining of the pelvic, ureter and bladder vascular endothelial ATPase, the intensity and area of which increased progressively from 18 hr and almost occluded the capillary lumens in the worst affected areas by 144 hr. These data show several distinct series of pathological changes after the administration of BEA. The subtle degenerative changes in the proximal tubule followed the papillary lesion, but exfoliated brush border and proximal tubular cells were important components of the protein casts in the distal nephron. Similarly, the intense Alk Phos staining in the hyperplastic regions of the upper urothelium and the increased pelvic, ureteric and bladder endothelial ATPase staining suggested they develop as a consequence of the papillary lesion.

Detection of chemically induced renal injury: the cascade of degenerative morphological and functional changes that follow the primary nephrotoxic insult and evaluation of these changes by in-vitro methods

A diversity of chemicals cause discrete lesions in the kidney by a number of different mechanisms, and similar types of chemicals may give rise to more than one target cell injury. Screening for these lesions in vivo may be unreliable if a single noninvasive or invasive criterion is used. Instead, evidence of nephrotoxicity must be based on an array of tests, applied over a period of time. These should include biochemical, pathological and histochemical tests conducted in tandem. A primary toxic injury to the kidney may give rise to recovery, to permanently altered functional reserve or to a clinically identifiable effect, such as acute or chronic renal failure or malignancy. These clinical effects occur as a result of a cascade of degenerative changes which are a consequence of a primary lesion but also affect other parts of the kidney. A number of factors can modulate the progression of the primary insult to the end-effect. In-vitro nephrotoxicity screening is also difficult, but a rational approach can be based on current understanding of how chemicals target for and damage cells in anatomically well-defined regions of the kidney. In-vitro techniques can provide answers to specific questions about the mechanisms by which chemicals damage these discrete cell types. It is essential that a number of different in-vitro systems be developed in parallel to address the mechanistic aspects and screening of nephrotoxicity properly. Data generated in vitro must be related to the situation in vivo and used to devise reliable noninvasive tests for assessing nephrotoxicity in man.

Epidemiology and mechanistic basis of analgesic-associated nephropathy

End-stage renal failure (ESRF) due to analgesic nephropathy is still a common clinical condition in several countries, but the prevalence in dialysis patients shows large geographical differences. The frequency of ESRF of unknown aetiology is the inverse of that linked to analgesic abuse, and data suggest that the occurrence of analgesic nephropathy may be underestimated. The study of analgesic nephropathy is difficult because the earliest damage to the kidney is a renal papillary necrosis (RPN), which cannot easily be diagnosed. Continued analgesic abuse generally leads to a progressive secondary cortical degeneration which is easier to diagnose. If analgesic abuse is stopped at an early enough stage in nephropathy, clinical symptoms stabilize or improve, and ESRF may be averted. A high incidence of upper urothelial carcinoma (UUC) is also observed in individuals with a history of analgesic abuse, but it is still not clear if the two have a related pathogenesis. Study of the mechanism of RPN in animals administered analgesics and nonsteroidal antiinflammatory drugs (NSAID) has been difficult owing to their extrarenal toxicity. Several model compounds cause identical clinical changes and have as their selective target the renal medullary interstitial cells; subsequently, other changes (including cortical and glomerular degeneration) develop as a secondary cascade. A number of mechanisms have been proposed to explain RPN (e.g., counter-current concentrating mechanism, ischaemic injury, altered prostaglandin metabolism, immunological changes), but peroxidative metabolism of papillotoxic chemicals within the interstitial cells seems to be the most likely cause. Analgesic abuse is a costly socioeconomic condition for which there is currently no clinical treatment. If it is diagnosed early enough, severe renal degeneration can be prevented. Additional epidemiological information is needed to establish the causative role of analgesics and other chemicals, in order to determine the relative risk of each. Additional animal experiments are needed in order to clarify the molecular pathogenesis of RPN and UUC, to differentiate the stages in progression to ESRF and to develop more sensitive and selective diagnostic criteria.

Nephrotoxicity: a rational approach to target cell injury in vitro in the kidney

1. The kidney is a complex organ in which there is cellular heterogeneity. Many nephrotoxic chemicals target preferentially for discrete cell types, but adjacent, morphologically different cells are unaffected. This selectivity has made the assessment of nephrotoxicity in vivo (and the study of underlying mechanisms) difficult. Discrete renal injury can, however, be exploited in vitro, to study the interactions between the toxic compound and the target cell. 2. Several in vitro models have been used to study the potential interaction between the target cells and chemicals, including perfusion of the isolated kidney, renal slices, freshly isolated fragments, primary cultures and continuous cell lines. Where appropriate, isolated organelles and purified enzymes can also be used. 3. The target cell toxicity in vivo of adriamycin, 2-bromoethanamine and hexachlorobutadiene N-acetyl cysteine conjugate is selectively maintained towards glomerular epithelial, medullary interstitial and proximal tubular cells, respectively, in vitro, showing that the "in vivo-in vitro gap" can be bridged. Characteristics unique to each of these renal cell types, such as the selective uptake of a toxin, enzyme systems for generating biologically reactive intermediates, and the presence of lipid droplets (rich in polyunsaturated fatty acid) and peroxidase activity have been identified, and one or more of these may explain the mechanisms of selective injury in discrete regions of the kidney.

Lysosomal storage of sulfated glycosaminoglycans in renal interstitial cells of rats treated with tilorone

This investigation provides histochemical evidence for lysosomal storage of sulfated glycosaminoglycans (GAGs) in the interstitial cells of the renal cortex and in macrophage-like cells of the renal medullary zones of rats chronically treated with the drug tilorone. This compound is known to interfere with lysosomal degradation of sulfated GAGs; therefore cells that develop GAG-storage can be assumed to be involved in the turnover of GAGs. In view of this consideration, the most remarkable and still unexplained finding was that the intrinsic interstitial cells in the papilla, which is known to be particularly rich in sulfated GAGs, did not show the cytological symptoms of lysosomal GAG-storage. The present findings may stimulate further studies focused on the cellular sites of turnover of the sulfated GAGs present in the renal medullary interstitium.

The effect of long-term administration of aspirin and sodium saccharin on the rat kidney

In a study primarily designed to evaluate the inhibitory effects of aspirin on N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT)-initiated and saccharin-promoted bladder carcinogenesis, significant renal lesions were observed. Thus, administration in the diet of aspirin and sodium saccharin to F344 male rats for 68 weeks resulted in significant lesions of the renal papilla. In contrast to the bladder, aspirin enhanced the frequency and severity of the proliferative action of sodium saccharin on the epithelium of the renal papilla (p less than 0.05 compared to rats treated with either compound alone). The majority of rats administered the two chemicals together demonstrated moderate to severe urothelial hyperplasia of the renal papilla. Columnar metaplasia of the papillary epithelium also occurred frequently in rats fed the combination of chemicals. The rats treated with a combination of sodium saccharin and aspirin had a high incidence of renal papillary necrosis which was also present to a lesser extent among rats treated with aspirin only. Papillary calcification was also frequently observed in the rats fed the combination of aspirin and sodium saccharin. Sodium saccharin or aspirin alone reduced the light microscopic incidence and severity of rat nephropathy, a common finding in aging rats. It would appear that the hyperplastic and renal papillary toxic effects of aspirin and sodium saccharin are independent responses, and that the administration of the two chemicals together greatly accentuates these responses.

The mechanisms of target cell injury by nephrotoxins

Hexachlorobutadiene-N-acetylcysteine (HCBD-NAC), adriamycin and 2-bromoethanamine hydrobromide are three renal toxins that have shown in vivo a highly selective target cell toxicity--to the proximal tubules, the glomerular epithelial cells and the medullary interstitial cells, respectively. To study some aspects of the mechanisms of this selective toxicity, the three types of target cell were isolated from the kidneys of Wistar rats, and cultures of the cells or tissue fragments were exposed to various concentrations of the three toxins. Using fluorescence microscopy combined with enzyme and histochemical probes, the selective target-cell toxicity of the three compounds already established in vivo was demonstrated also in vitro. Moreover, the in vitro toxic effect of HCBD-NAC was ameliorated by probenecid, as is the case in vivo. Several functional characteristics specific to each of the target cells, such as the selective uptake of a toxin, the presence of lipid droplets and the level of peroxidative enzyme activity, have been identified as probable factors in the occurrence of the target cell necrosis.