Identification and regulation of reticulon 4B (Nogo-B) in renal tubular epithelial cells.

Nogo-B is a member of the reticulon family of proteins that has been implicated in diverse forms of vascular injury. Although Nogo-B is expressed in renal tissues, its localization and function in the kidney have not been examined. Here, we report that Nogo-B is expressed specifically in the epithelial cells of the distal nephron segments in the murine kidney. After unilateral ureteral obstruction (UUO) and ischemia/reperfusion, Nogo-B gene and protein levels increased dramatically in the kidney. This increase was driven in part by injury-induced de novo expression in proximal tubules. Examination of Nogo-B immunostaining in human biopsy specimens from patients with acute tubular necrosis showed similar increases in Nogo-B in cortical tubules. Mice genetically deficient in Nogo-A/B were indistinguishable from wild-type (WT) mice based on histological appearance and serum analyses. After UUO, there was a significant delay in recruitment of macrophages to the kidney in the Nogo-A/B-deficient mice. However, measurements of fibrosis, inflammatory gene expression, and histological damage were not significantly different from WT mice. Thus, Nogo-B is highly expressed in murine kidneys in response to experimental injuries and may serve as a marker of diverse forms of renal injury in tissues from mice and humans. Furthermore, Nogo-B may regulate macrophage recruitment after UUO, although it does not greatly affect the degree of tissue injury or fibrosis in this model.

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.

Comprehensive evaluation of canine renal papillary necrosis induced by nefiracetam, a neurotransmission enhancer.

The effects of nefiracetam, a neurotransmission enhancer, on renal biochemistry and morphology with toxicokinetic disposition were investigated in both in vivo and in vitro systems. In the in vivo studies with rats, dogs, and monkeys, only the dog exhibited renal papillary necrosis. Namely, when beagle dogs were orally administered with 300 mg/kg/day of nefiracetam over 11 weeks, decreased urinary osmotic pressure was noted from week 5, followed by increases in urine volume and urinary lactate dehydrogenase from week 8. The first morphological change was necrosis of ductal epithelia in the papilla in week 8. In toxicokinetics after 3 weeks of repeated oral administration to dogs, nefiracetam showed somewhat high concentrations in serum and the renal papilla as compared with rats and monkeys. As for metabolites, although metabolite-18 (M-18) concentration in the renal papilla of dogs was between that in rats and monkeys, the concentration ratios of M-18 in the papilla to cortex and papilla to medulla were remarkably high. In the in vitro studies, while nefiracetam itself showed no effects on the synthesis of prostaglandin E2 and 6-keto-prostaglandin F1alpha, a stable metabolite of prostaglandin I2, in canine renal papillary slices, only M-18 among the metabolites clearly decreased both prostaglandin syntheses. The basal prostaglandin synthesis in canine renal papillary slices was extremely low relative to those in rats and monkeys. Taken together, certain factors such as basal prostaglandin synthesis, M-18 penetration into the renal papilla leading to an intrarenal gradient, and inhibitory potential of M-18 on prostaglandin synthesis were considered to be crucial for the occurrence of renal papillary necrosis in dogs.

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.

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.

Effects of 2-bromoethanamine on TonEBP expression and its possible role in induction of renal papillary necrosis in mice.

Chronic analgesic abuse has been shown to induce severe renal injury characterized by renal papillary necrosis (RPN), an injury detectable at late stage. While direct toxicity of the drug may exist, the molecular mechanisms underlying analgesics induction of RPN remain unknown. A major limitation to study the pathogenesis of RPN is the required chronic exposure before detection of injury. Here, we employed 2-bromoethanamine (BEA) to simulate rapid papillary toxicity using inner medullary collecting duct (IMCD3) cells. Although exposure to 10µM BEA had no effect on cellular viability under isotonic conditions, a 50% loss in cell viability was observed in the first 24 h when cells were subjected to sublethal hypertonic stress and nearly complete cell death after 48 h suggesting that BEA exerts cytotoxicity only under hypertonic conditions. Because TonEBP is a transcription factor critical for cell survival during hypertonic conditions, we undertook experiments to examine the effect of BEA on TonEBP expression and activity. Exposure of cells to 10µM BEA resulted in a substantial reduction in TonEBP protein expression after 24 h. In addition, TonEBP was not translocated to the nucleus in BEA-treated IMCD3 cells under acute hypertonic stress for transcription of target genes essential for osmolyte accumulation. Finally, we found a substantial decrease in TonEBP expression in medullary kidney tissues of mice injected with a single ip dose of BEA. Our data suggest that TonEBP is a potential target for BEA leading to the process of papillary necrosis in the settings of hypertonic stress.

Investigation on urinary proteins and renal mRNA expression in canine renal papillary necrosis induced by nefiracetam.

The occurrence of renal papillary necrosis (RPN), seen only in dogs after repeated oral administration of nefiracetam, a neurotransmission enhancer, at a relatively high dose, is because of inhibition of renal prostaglandin synthesis by the nefiracetam metabolite M-18. In this study, analyses of urinary proteins and renal mRNA expression were performed to investigate the possible existence of a specific protein expressing the characteristics of RPN evoked by nefiracetam. In the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of urinary proteins from male dogs given nefiracetam at 300 mg kg(-1) day(-1) over weeks 5-11, a protein of approximately 40 kDa, which was not seen in control urine, and protein of approximately 30 kDa emerged as distinct bands. Subsequently, clusterin precursor was identified in the former band and tissue kallikrein precursor in the latter by LC-electrospray ionization tandem mass spectrometry (LC-ESI-MS-MS). By quantitative real-time RT-PCR analysis with renal morphological aspects, individual findings showed that renal clusterin mRNA was increased in dogs with severe renal injury, and renal tissue kallikrein also increased, presumably related to hemodynamics. These results demonstrate that changes in renal clusterin mRNA may reflect the progression or severity of RPN, whereas upregulation of tissue kallikrein mRNA may subsequently play a compensating role in the prevention of RPN.

Early pathophysiological features in canine renal papillary necrosis induced by nefiracetam.

To ascertain the early pathophysiological features in canine renal papillary necrosis (RPN) caused by the neurotransmission enhancer nefiracetam, male beagle dogs were orally administered nefiracetam at 300 mg/kg/day for 4 to 7 weeks in comparison with ibuprofen, a non-steroidal anti-inflammatory drug (NSAID), at 50 mg/kg/day for 5 weeks. During the dosing period, the animals were periodically subjected to laboratory tests, light-microscopic, immunohistochemical, and electron-microscopic examinations and/or cyclooxygenase (COX)-2 mRNA analysis. In laboratory tests, a decrease in urinary osmotic pressure and increases in urine volume and urinary lactate dehydrogenase (LDH) level were early biomarkers for detecting RPN. Light-microscopically, nefiracetam revealed epithelial swelling and degeneration in the papillary ducts in week 7, while ibuprofen displayed degeneration and necrosis in the papillary interstitium in week 5. In immunohistochemical staining with COX-2 antibody, nefiracetam elicited a positive reaction within interstitial cells around the affected epithelial cells in the papillary ducts (upper papilla) in week 7, and ibuprofen positively reacted within interstitial cells adjacent to the degenerative and/or necrotic lesions in week 5. Ultrastructurally, nefiracetam exhibited reductions of intracellular interdigitation and infoldings of epithelial cells in the papillary ducts, whereas ibuprofen showed no changes in the identical portions. Thus, the early morphological change in the papilla brought about by nefiracetam was quite different from that elicited by ibuprofen. By the renal papillary COX-2 mRNA expression analysis, nefiracetam exceedingly decreased its expression in week 4, but markedly increased it in week 7, suggesting an induction of COX-2 mRNA by renal papillary lesions. These results demonstrate that the epithelial cell in the papillary ducts is the primary target site for the onset of RPN evoked by nefiracetam.

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.

Carbonic anhydrase independent bicarbonate reabsorption in rats with chronic papillary necrosis.

The present study was designed to indirectly localize the tubular sites of carbonic anhydrase independent bicarbonate reabsorption in the rat. Papillary necrosis was induced in rats by intravenous administration of bromoethyleneamine hydrobromide (BEA) 6 weeks prior to the study, in order to assess the role of deep nephrons in this process. Acetazolamide alone, acetazolamide plus amiloride, and acetazolamide, amiloride plus furosemide were infused into rats with intact papillae (groups I, III, V) and rats with BEA-induced papillary necrosis (groups II, IV, VI). Our results show that chronic papillary necrosis does not alter carbonic anhydrase independent bicarbonate reabsorption, since the fractional excretion of bicarbonate (FEHCO3) was not significantly higher when acetazolamide was infused into animals with BEA-induced papillary necrosis as compared to those rats with intact papillae (FEHCO3 group I vs. group II: NS). The addition of amiloride hydrochloride, a blocker of distal acidification at the administered doses, increased FEHCO3 significantly in both, animals with intact papillae and those with papillary necrosis, to a similar degree. The addition of furosemide to acetazolamide and amiloride further induced a significant increase in FEHCO3 only in the group of animals with papillary necrosis (FEHCO3 group V 43.0 +/- 2.9% vs. group VI 52.1 +/- 0.9%; p less than 0.05). It appears from our study that deeper nephrons and papillary structures are not indispensable for carbonic anhydrase independent bicarbonate reabsorption in the rat on a chronic basis. The cortical collecting duct appears to have a significant capacity to reabsorb bicarbonate independent of carbonic anhydrase which can be blocked by amiloride.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesic renal papillary necrosis.

Analgesic nephropathy is well recognised. This is a retrospective review of 19 patients with the disease, who presented at Groote Schuur Hospital over a 4-year period. The diagnosis was made on historical and clinical grounds and on the radiological manifestations of papillary necrosis. The mean age was 49 years (26 - 74) with a sex ratio of 3,8 female : 1 male. The period of abuse varied between 3 and 20 years. Aspirin, phenacetin, codeine, and antipyrine were the compounds mainly ingested. If the abuse is stopped, renal deterioration can be halted. However, factors which lead to dehydration and infection tend to cause further decompensation. As a means of preventing this disease greater control over analgescis is needed.

Functional characterization of drug-induced experimental papillary necrosis.

The functional expression of papillary necrosis was investigated with a model of drug-induced papillary necrosis. Bromoethylamine hydrobromide (BEA) administration to rats uniformly resulted in the development of papillary necrosis. All studies were performed 24 hours after BEA administration with the exception of the electrolyte balance studies, which were performed during the 72 hours after the induction of papillary necrosis. GFR was not different between BEA-treated and sham rats. BEA-treated rats had a significantly lower maximal urine osmolality and free water reabsorption than did sham rats. Renal tissue concentrations of sodium, potassium, and water were not different between BEA-treated and sham rats. During water diuresis, free water clearance was not significantly different between the two groups. During sodium bicarbonate administration, maximal bicarbonate reabsorption and urine-blood Pco2 gradient (at comparable urine bicarbonate concentrations) were not significantly different between the two groups. During sodium sulfate infusion, there was no difference in minimum urine pH, ammonium excretion, and net acid excretion between chronically acidotic BEA-injected and sham rats. In rats on "zero" sodium intake, BEA administration resulted in a significant increase in urine flow and sodium excretion, whereas sham rats remained in sodium balance. In rats with restriction of both sodium and chloride, BEA administration resulted in a significant wastage of sodium, chloride, and calcium. There was no difference in potassium excretion between BEA-treated and sham rats during hydropenia, bicarbonate administration, sodium sulfate infusion, or ingestion of a normal potassium diet. When potassium intake was restricted to "zero," BEA-treated rats developed potassium wastage; when potassium intake was increased to 21 mEq/day, BEA-treated rats had a significantly lower potassium excretion than did sham rats. These findings may result from alterations in collecting duct transport, but damage to deep medullary structures may also contribute.

Changes in collagenases and TGF-beta precede structural alterations in a model of chronic renal fibrosis.

BACKGROUND: To study the role of collagenases and transforming growth factor-beta (TGF-beta) in the genesis of interstitial fibrosis, we used the model of bromoethylamine (BEA)-induced papillary necrosis, which is known to lead over a period of 1 to 12 months to interstitial fibrosis and renal insufficiency. METHODS: Rats were injected with BEA, and urine and kidney tissue (cortex and medulla) were collected after 1, 2, 3, 7, and 30 days. One kidney was perfused and fixed for morphological studies and immunostained for collagen type I, III, and IV. The other kidney was used to prepare cortex and medulla extracts for gelatinases (by fluorometric and zymographic techniques), tissue inhibitors of metalloproteinase-1 (TIMP-1), and TIMP-2 (by enzyme-linked immunosorbent assay, ELISA) and TGF-beta1 (by ELISA). RESULTS: Albuminuria and interstitial fibrosis were present in BEA rats by day 7, which continued until day 30. Immunocytochemical staining for collagen types showed that collagen III and IV increased in the interstitium by day 30, but collagen I remained unchanged. Gelatinase activity in the medulla decreased by 57% compared with control by day 2 and remained low until day 30. In the cortex, gelatinase activity remained unchanged between 0 and 7 days after BEA but decreased by 72% by day 30. TIMP-1 and TIMP-2 were decreased by 80% compared with day 0 in both the medulla (by day 1) and cortex (by day 2) and remained low up to day 30. TGF-beta1 immunoreactivity increased progressively until day 2 in the medulla (16-fold higher than control) and day 3 in the cortex (8-fold higher than control) and returned to control level by day 3 in the medulla and by day 30 in the cortex. Two days after BEA injection, the mRNA for TGF-beta1 was increased eightfold in the cortex and 12-fold in the medulla, and it remained high for up to 30 days. CONCLUSIONS: The fibrosis that follows papillary necrosis is associated with both high TGF-beta1 expression and depressed gelatinolytic activity.

Variability in the renal clearance of cephalexin in experimental renal failure.

This study forms a part of an investigation into the extent to which the type of renal damage influences the renal clearance of drugs. We have already demonstrated an effect of different types of experimental renal failure (ERF) on the renal clearance of two cations: cimetidine, a drug that is filtered and secreted by the nephron, and lithium, which is filtered and reabsorbed by more than one segment of the nephron. In this report the renal clearance of cephalexin (CLCEX) is investigated, a drug that has a different mode of renal elimination, since it is filtered, secreted, and reabsorbed by the proximal tubules. The aim was to extend our earlier studies to an organic anion, and to provide an opportunity to evaluate the feasibility of using the renal clearance of N-1-methylnicotinamide (NMN) to predict the renal clearance of anionic drugs in renal failure. Different models of site-specific ERF have been developed in the rat; proximal tubular necrosis (induced by cisplatin), papillary necrosis (induced by 2-bromoethylamine), and glomerulonephritis (induced by sodium aurothiomalate or by antiglomerular basement membrane antibodies). Glomerular function (GFR) was assessed by the clearance of inulin (CLNULIN), and tubular function was assessed by the clearance of endogenous NMN (CLNMN). OUr results show that even if the models of ERF used were not absolutely site-specific, glomerular function and tubular function did not decrease to the same extent in the different ERF. Therefore, glomerulo-tubular imbalance existed, which is incompatible with the "intact nephron hypothesis," i.e., the site of the damage along the nephron and not only the degree of renal dysfunction, is a potential source of variability in the clearance of certain drugs. The renal clearance of cephalexin was estimated more accurately by CLNMN than GFR (r = 0.90). We conclude that the clearance of the endogenous cation NMN can be used to predict the renal clearance of drugs that are not only filtered by the glomeruli but also secreted and/or reabsorbed by the proximal tubules, and in the limited examples investigated appears to apply to both anionic and cationic compounds. In this respect the GFR alone was not an adequate parameter for the prediction of the renal clearance of such drugs.

Experimental papillary necrosis of the kidney. IV. Medullary plasma flow.

To test the thesis that vasoconstriction plays a significant role in the pathogenesis of papillary necrosis caused by bromoethylamine hydrobromide (BEA), medullary plasma flow was determined in rats treated with BEA. Medullary blood flow was normal (1/2) to 1 hour after BEA treatment, and was actually elevated 6 hours after BEA. There was no increase in plasma levels of prostaglandins A and E, which would have been expected if there had been medullary ischemia. Pretreatment with reserpine, which inhibited the development of papillary necrosis, had little effect on medullary plasma flow. These observations do not support the notion that vasoconstriction is the mechanism by which BEA causes papillary necrosis.

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.