Genome-wide gene expression analysis reveals molecular insights into the drug-induced toxicity of nephrotoxic agents

Drug-induced nephrotoxicity is frequently reported. However, the mechanisms underlying nephrotoxic medications and their overlapping molecular events, which might have therapeutic value, are unclear. We performed a genome-wide analysis of gene expression and a gene set enrichment analysis to identify common and unique pathways associated with the toxicity of colistin, ifosfamide, indomethacin, and puromycin. Rats were randomly allocated into the treatment or control group. The treatment group received a toxic dose once daily of each investigated drug for 1 week. Differentially expressed genes were found in the drug-treated kidney and liver compared to the control, except for colistin in the liver. Upregulated pathways were mainly related to cell death, cell cycle, protein synthesis, and immune response modulation in the kidney. Cell cycle was upregulated by all drugs. Downregulated pathways were associated with carbon metabolism, amino acid metabolism, and fatty acid metabolism. Indomethacin, colistin, and puromycin shared the most altered pathways in the kidney. Ifosfamide and indomethacin affected molecular processes greatly in the liver. Our findings provide insight into the mechanisms underlying the renal and hepatic adverse effects of the four drugs. Further investigation should explore the combinatory drug therapies that attenuate the toxic effects and maximize the effectiveness of nephrotoxic drugs.

Effect of clofibrate on fatty acid metabolism in the kidney of puromycin-induced nephrotic rats

BACKGROUND

Proteinuria plays an essential role in the progression of tubulointerstitial damage, which causes end-stage renal disease. An increased load of fatty acids bound to albumin reabsorbed into proximal tubular epithelial cells (PTECs) contributes to tubulointerstitial damage. Fibrates, agonists of peroxisome proliferator-activated receptor α (PPARα), have renoprotective effects against proteinuria whereas the effects of these compounds on fatty acid metabolism in the kidney are still unknown. Therefore, the present study examined whether the renoprotective effects of clofibrate were associated with improvement of fatty acid metabolism in puromycin aminonucleoside (PAN)-induced nephrotic rats.

METHODS

Rats were allocated to the control, PAN or clofibrate-treated PAN group. Biochemical parameters, renal injury and changes in fatty acid metabolism were studied on day14.

RESULTS

PAN increased proteinuria, lipid accumulation in PTECs, excretions of N-acetyl-β-D-glucosaminidase (NAG) and 8-hydroxydeoxyguanosine (8OHdG) and the area of caspase 3-positive tubular cells. It decreased renal expressions of medium-chain acyl-CoA dehydrogenase (MCAD), cytochrome P450 (CYP)4A, peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) and estrogen-related receptor α (ERRα) without change of the expression of PPARα. Clofibrate reduced proteinuria, lipid accumulation, NAG excretion and the area of caspase 3-positive tubular cells. However, albumin excretion was not reduced and 8OHdG excretion was increased. Clofibrate minimized changes in MCAD, CYP4A, PGC-1α and ERRα expressions with increased PPARα, very long-chain acyl-CoA dehydrogenase (VLCAD) and long-chain acyl-CoA dehydrogenase (LCAD) expressions.

CONCLUSION

Clofibrate is protective against renal lipotoxicity in PAN nephrosis. This study indicates that clofibrate has renoprotective effects through maintaining fatty acid metabolism in the kidney of PAN-induced nephrotic rats.

NADPH oxidase-mediated upregulation of connexin43 contributes to podocyte injury

The gap junction protein connexin43 (Cx43) was markedly increased in podocytes in a rat model of nephrosis induced by puromycin. However, the mechanisms and roles of the altered Cx43 in podocytes are still unclear. Given that oxidative stress mediates podocyte injury under a variety of pathological situations, we examined the possible involvement of an oxidative stress-related mechanism in the regulation of Cx43. Incubation of podocytes with puromycin led to a time- and concentration-dependent loss of cell viability, which was preceded by an elevation in Cx43 levels. Concomitantly, puromycin also induced NOX4 expression and promoted superoxide (O(2)(·-)) generation. Inhibition of NADPH oxidase with apocynin and diphenyleneiodonium chloride or addition of the superoxide dismutase mimetic tempol completely abrogated, whereas the O(2)(·-) donors menadione and 2,3-dimethoxy-1,4-naphthoquinone reproduced, the effects of puromycin on Cx43 expression and cell injury. Further analysis demonstrated that treatment of podocytes with several structurally different gap-junction inhibitors significantly attenuated the cytotoxicity of puromycin. Our results thus indicate that NADPH oxidase-mediated upregulation of Cx43 contributes to podocyte injury.

Effect of TGF-beta1 antisense oligodeoxynucleotide on renal function in chronic renal failure rats

AIM

The aim of the present study was to investigate the effectiveness of transforming growth factor (TGF)-beta1 antisense oligodeoxynucleotides (ODN) in ameliorating deteriorated kidney function in rats with puromycin-induced chronic renal failure (CRF).

METHODS

Saline, puromycin, puromycin+TGF-beta1 antisense ODN or puromycin+scrambled ODN were administered to unilaterally nephrectomized rats. Renal hemodynamic and excretory measurements were taken in the anaesthetized rats that had undergone surgical procedure.

RESULTS

It was observed that in the CRF rats, there was a marked reduction in the renal blood flow (RBF), glomerular filtration rate (GFR), severe proteinuria, and almost 6-fold increased fractional excretion of sodium (FE Na+) as compared to that in the control rats (all P<0.05). It was further observed that in the CRF rats, the treatment with TGF-beta1 antisense, but not scrambled ODN, markedly attenuated the reduction of RBF, GFR, and proteinuria and markedly prevented the increase of the FE Na+ (all P<0.05). In addition, the renal hypertrophy in the CRF group (P<0.05 vs non-renal failure control) was markedly attenuated after treatment with TGF-1 antisense ODN (P<0.05). Focal segmental glomerulosclerosis was evident only in the untreated and scrambled ODN-treated CRF groups. An interesting observation of this study was that in the CRF rats, although there was marked attenuating and preventive effects of the TGF-beta1 antisense ODN on the deteriorated renal functions, the antisense treatment did not cause any marked change in the renal expression of TGF-beta1 at the protein level.

CONCLUSION

Collectively, the data obtained suggests that TGF-beta1 antisense ODN possesses beneficial effects in puromycininduced chronic renal failure and that the deterioration in morphology and impaired renal function in this pathological state is in part dependent upon the action of TGF-beta1 within the kidney.

Protective effect of radical scavenger edaravone against puromycin nephrosis

AIM

Recent studies have indicated that reactive oxygen species (ROS) play a role in the pathogenesis of glomerular injury leading to proteinuria in nephrotic syndrome. In the present investigation, we examined the effects of the radical scavenger edaravone administered at various time points to rats with puromycin nephrosis.

MATERIALS AND METHODS

35 Wistar rats were divided into five groups: treatment with puromycin aminonucleoside (PAN) alone, treatment with PAN followed by edaravone in the early period, treatment with PAN followed by edaravone administration in the late period, treatment with PAN and administration of edaravone for the whole experimental period, and untreated controls. On Days 3, 6 and 9, urinary protein excretion was measured. The levels of glomerular thiobarbituric acid-reactive substance (TBArs) were determined in all animals on Day 10.

RESULTS

On Day 9, rats that had been administered edaravone showed reduced urinary protein excretion and reduced glomerular TBArs. In particular, edaravone administration in the late period, during which proteinuria was most acute, had the effect of reducing the severity of proteinuria. Glomerular TBArs were suppressed to the control level. Our results indicate that edaravone exerts a protective effect in the acute phase of PAN nephrosis when administered as antioxidant therapy at the onset of proteinuria.

CONCLUSIONS

Edaravone can ameliorate urinary protein excretion after the onset of proteinuria in nephrotic syndrome.

Resistance to renal damage by chronic nitric oxide synthase inhibition in the Wistar-Furth rat

Chronic nitric oxide synthase inhibition (NOSI) causes chronic kidney disease (CKD) in the Sprague Dawley (SD) rat. We previously showed that the Wistar-Furth (WF) rats are resistant to several models of CKD and maintain renal nitric oxide (NO) production compared with SD rats, whereas low-dose NOSI caused progression of CKD in WF rats. Here, we evaluate the impact of high-dose chronic NOSI in WF and SD rats, as well as intrarenal responses to an acute pressor dose of NOSI in the normal WF. Rats were given N(G)-nitro-l-arginine methyl ester (l-NAME) (150 and 300 mg/l for 6-10 wk) in the drinking water after an initial bolus tail vein injection. Both strains showed significant reductions in total NO production with chronic l-NAME. SD given 150 mg/l l-NAME for 6 wk developed proteinuria and renal injury, whereas WF rats receiving 150 mg/l l-NAME for 6-10 wk or 300 mg/l for 6 wk developed no proteinuria and minimal renal injury. Blood pressure was significantly elevated with chronic NOSI in both strains but was higher in the SD rat. There was little impact on renal nitric oxide synthase expression with l-NAME, except that cortical endothelial nitric oxide synthase abundance increased in WF after 6 wk (150 mg/l). Micropuncture experiments with acute pressor NOSI resulted in similar increases in systemic blood pressure in SD and WF rats, whereas WF rats showed a much smaller increment in glomerular blood pressure compared with SD rats. In conclusion, WF rats do not develop renal injury after chronic NOSI at, or above, a dose that causes significant injury in the SD rat. This protection may be associated with protection from glomerular hypertension.

Chromosomal alterations cause the high rates and wide ranges of drug resistance in cancer cells

Conventional mutation-selection theories have failed to explain (i) how cancer cells become spontaneously resistant against cytotoxic drugs at rates of up to 10(-3) per cell generation, orders higher than gene mutation, even in cancer cells; (ii) why resistance far exceeds a challenging drug-a state termed multidrug resistance; (iii) why resistance is associated with chromosomal alterations and proportional to their numbers; and (iv) why resistance is totally dependent on aneuploidy. We propose here that cancer-specific aneuploidy generates drug resistance via chromosomal alterations. According to this mechanism, aneuploidy varies the numbers and structures of chromosomes automatically, because it corrupts the many teams of proteins that segregate, synthesize, and repair chromosomes. Aneuploidy is thus a steady source of chromosomal variation from which, in classical Darwinian terms, resistance-specific aneusomies are selected in the presence of chemotherapeutic drugs. Some of the thousands of unselected genes that hitchhike with resistance-specific aneusomies can thus generate multidrug resistance. To test this hypothesis, we determined the rates of chromosomal alterations in clonal cultures of human breast and colon cancer lines by dividing the fraction of nonclonal karyotypes by the number of generations of the clone. These rates were about 10(-2) per cell generation, orders higher than mutation. Chromosome numbers and structures were determined in metaphases hybridized with color-coded chromosome-specific DNA probes. Further, we tested puromycin-resistant subclones of these lines for resistance-specific aneusomies. Resistant subclones differed from parental lines in four to seven specific aneusomies, of which different subclones shared some. The degree of resistance was roughly proportional to the number of these aneusomies. Thus, aneuploidy is the primary cause of the high rates and wide ranges of drug resistance in cancer cells.

Inhibition of gene markers of fibrosis with a novel inhibitor of transforming growth factor-beta type I receptor kinase in puromycin-induced nephritis

SB-525334 (6-[2-tert-butyl-5-(6-methyl-pyridin-2-yl)-1H-imidazol-4-yl]-quinoxaline) has been characterized as a potent and selective inhibitor of the transforming growth factor-beta1 (TGF-beta1) receptor, activin receptor-like kinase (ALK5). The compound inhibited ALK5 kinase activity with an IC(50) of 14.3 nM and was approximately 4-fold less potent as an inhibitor of ALK4 (IC(50) = 58.5 nM). SB-525334 was inactive as an inhibitor of ALK2, ALK3, and ALK6 (IC(50) > 10,000 nM). In cell-based assays, SB-525334 (1 microM) blocked TGF-beta1-induced phosphorylation and nuclear translocation of Smad2/3 in renal proximal tubule cells and inhibited TGF-beta1-induced increases in plasminogen activator inhibitor-1 (PAI-1) and procollagen alpha1(I) mRNA expression in A498 renal epithelial carcinoma cells. In view of this profile, SB-525334 was used to investigate the role of TGF-beta1 in the acute puromycin aminonucleoside (PAN) rat model of renal disease, a model of nephritis-induced renal fibrosis. Orally administered doses of 1, 3, or 10 mg/kg/day SB-525334 for 11 days produced statistically significant reductions in renal PAI-1 mRNA. Also, the compound produced dose-dependent decreases in renal procollagen alpha1(I) and procollagen alpha1(III) mRNA, which reached statistical significance at the 10-mg/kg/day dose when compared with vehicle-treated PAN controls. Furthermore, PAN-induced proteinuria was significantly inhibited at the 10-mg/kg/day dose level. These results provide further evidence for the involvement of TGF-beta1 in the profibrotic changes that occur in the PAN model and for the first time, demonstrate the ability of a small molecule inhibitor of ALK5 to block several of the markers that are predictive of fibrosis and renal injury in this model.

Overview on the application of transcription profiling using selected nephrotoxicants for toxicology assessment

Microarrays allow for the simultaneous measurement of changes in the levels of thousands of messenger RNAs within a single experiment. As such, the potential for the application of transcription profiling to preclinical safety assessment and mechanism-based risk assessment is profound. However, several practical and technical challenges remain. Among these are nomenclature issues, platform-specific data formats, and the lack of uniform analysis methods and tools. Experiments were designed to address biological, technical, and methodological variability, to evaluate different approaches to data analysis, and to understand the application of the technology to other profiling methodologies and to mechanism-based risk assessment. These goals were addressed using experimental information derived from analysis of the biological response to three mechanistically distinct nephrotoxins: cisplatin, gentamicin, and puromycin aminonucleoside. In spite of the technical challenges, the transcription profiling data yielded mechanistically and topographically valuable information. The analyses detailed in the articles from the Nephrotoxicity Working Group of the International Life Sciences Institute Health and Environmental Sciences Institute suggest at least equal sensitivity of microarray technology compared to traditional end points. Additionally, microarray analysis of these prototypical nephrotoxicants provided an opportunity for the development of candidate bridging biomarkers of nephrotoxicity. The potential future extension of these applications for risk assessment is also discussed.

Identification of putative gene based markers of renal toxicity

This study, designed and conducted as part of the International Life Sciences Institute working group on the Application of Genomics and Proteomics, examined the changes in the expression profile of genes associated with the administration of three different nephrotoxicants--cisplatin, gentamicin, and puromycin--to assess the usefulness of microarrays in the understanding of mechanism(s) of nephrotoxicity. Male Sprague-Dawley rats were treated with daily doses of puromycin (5-20 mg/kg/day for 21 days), gentamicin (2-240 mg/kg/day for 7 days), or a single dose of cisplatin (0.1-5 mg/kg). Groups of rats were sacrificed at various times after administration of these compounds for standard clinical chemistry, urine analysis, and histological evaluation of the kidney. RNA was extracted from the kidney for microarray analysis. Principal component analysis and gene expression-based clustering of compound effects confirmed sample separation based on dose, time, and degree of renal toxicity. In addition, analysis of the profile components revealed some novel changes in the expression of genes that appeared to be associated with injury in specific portions of the nephron and reflected the mechanism of action of these various nephrotoxicants. For example, although puromycin is thought to specifically promote injury of the podocytes in the glomerulus, the changes in gene expression after chronic exposure of this compound suggested a pattern similar to the known proximal tubular nephrotoxicants cisplatin and gentamicin; this prediction was confirmed histologically. We conclude that renal gene expression profiling coupled with analysis of classical end points affords promising opportunities to reveal potential new mechanistic markers of renal toxicity.

Detection of cellular responses to toxicants by dielectrophoresis

The dielectrophoretic (DEP) crossover method has been applied to the detection of cell responses to toxicants. Time and dose responses of the human cultured leukemia (HL-60) line were measured for paraquat, styrene oxide (SO), N-nitroso-N-methylurea (NMU) and puromycin. These toxicants were chosen because of their different predominant mechanisms of action, namely membrane free radical attack, simultaneous membrane and nucleic acid attack, nucleic acid alkylation, and protein synthesis inhibition, respectively. For all treatments, the specific membrane capacitance (C(mem)) of the cells decreased while the specific membrane conductance (G(mem)) increased in dose- and time-dependent manners. The DEP responses correlated sensitively with alterations in cell surface morphology, especially folds, microvilli, and blebs, observed by scanning electron microscopy. The DEP method was more sensitive to agents that had a direct action on the membrane than to agents for which membrane alterations were secondary. The responses to paraquat and SO, which directly damaged the cell membrane, could be detected 15 min after exposure, while those for puromycin and NMU, which acted on intracellular targets, could be detected after 30 min. The detection times and dose sensitivity results showed that the DEP method is much faster and more sensitive than conventional cell and higher organism viability testing techniques. The feasibility of producing small instruments for toxicity detection and screening based on cellular dielectric responses is discussed.

Origin of multidrug resistance in cells with and without multidrug resistance genes: chromosome reassortments catalyzed by aneuploidy

Cancer cells and aneuploid cell lines can acquire resistance against multiple unrelated chemotherapeutic drugs that are over 3,000-fold those of normal levels and display spontaneous resistances up to 20-fold of normal levels. Two different mechanisms were proposed for this phenotype: (i) classical mutation of drug metabolizing genes or (ii) chromosome reassortments, catalyzed by cancer- and cell line-specific aneuploidy, which generate, via new gene dosage combinations, a plethora of cancer phenotypes, including drug resistance. To distinguish between these mechanisms, we have asked whether three mouse cell lines can become drug resistant, from which two or three genes have been deleted, and on which multidrug resistance is thought to depend: Mdr1a, Mdr1b, and Mrp1. Because all three lines could acquire multidrug resistance and were aneuploid, whereas diploid mouse cells could not, we conclude that aneuploid cells become drug resistant via specific chromosome assortments, independent of putative resistance genes. We have asked further whether aneuploid drug-resistant Chinese hamster cells revert spontaneously to drug sensitivity in the absence of cytotoxic drugs at the high rates that are typical of chromosome reassortments catalyzed by aneuploidy or at the very low or zero rates (i.e., deletion) of gene mutation. We found that four drug-resistant hamster cell lines reverted to drug sensitivity at rates of about 2-3% per generation, whereas two closely related lines remained resistant under our conditions. Thus, the karyotypic instability generated by aneuploidy emerges as the common source of the various levels of drug resistance of cancer cells: minor spontaneous resistances reflect accidental chromosome assortments, the high selected resistances reflect complex specific assortments, and multidrug resistance reflects new combinations of unselected genes located on the same chromosomes as selected genes.

Alternatively spliced nephrin in experimental glomerular disease of the rat

Nephrin is a novel transmembrane protein of kidney glomerular podocytes, which appears crucially important for the maintenance of the glomerular filtration barrier. According to its predicted structure, nephrin has additional roles in cell-cell adhesion and/or signal transduction. We have previously cloned the rat homologue of nephrin and described its alternatively spliced transcripts alpha and beta. In this study we examined the alterations in expression and regulation of particularly the major alternatively spliced nephrin-alpha giving rise to a variant lacking the membrane spanning domain in the puromycin nephrosis of the rat. A down-regulation of up to 78% was observed of the full length mRNA after 10 d of PAN treatment. The expression changes of nephrin-alpha followed closely the expression of the full length mRNA. Interestingly, we also found nephrin protein in urine at the peak proteinuria samples of this model. These results suggest that soluble nephrin variants may be important markers for proteinuric diseases.

Alterations in the distribution of plasma fibronectin and the ultrastructure of podocytes in the peripheral glomerular loops in nephrotic rats

Glomerular distribution of rat plasma fibronectin was examined during the course of puromycin (PAN)- and daunomycin (DM)-induced nephrosis. In control animals, fibronectin was detected in the mesangial matrix and along the glomerular basement membrane (GBM), closely associated with the plasma membrane of glomerular cells. In peripheral loops, immunoprecipitates were preferentially distributed in the laminae rarae externa and interna. Fibronectin was densely precipitated in a glomerulosclerotic lesion induced by DM at 8 weeks after the injection. In peripheral loops, loss and reconstruction of epithelial foot processes occurred in PAN nephrosis but the change was accompanied by negligible perturbation of fibronectin distribution in the lamina rara externa. In contrast, a remarkable decrease of fibronectin was observed in DM nephrosis, unrelated to the presence or absence of foot processes. The decrease in immunoreactivity for fibronectin in the lamina rara externa seemed to have no association with podocyte attachment to or detachment from the GBM. Plasma fibronectin distributed in the lamina rara externa is not directly involved in the modification of podocyte configuration or podocyte attachment, although its spatial distribution may have some functional significance for preserving the ultrastructure of the GBM.

Intestinal absorption and biliary secretion of cholesterol in rats with nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) results in hypercholesterolemia which is attributed to increased production and decreased removal of cholesterol-rich lipoproteins. Adjustments in intestinal absorption are reportedly involved in cholesterol homeostasis. We, therefore, studied the intestinal absorption and biliary excretion of cholesterol in NS.

METHODS

We studied intestinal absorption (by in vivo perfusion and in vitro everted sac incubation techniques) and biliary secretion (by common bile duct cannulation) of cholesterol in rats with puromycin-induced NS. The results were compared with those obtained from pair-fed control (PF) animals, those given free access to food (NL) or those fed a hypercholerolemic diet (H-chol group). Micellar solutions of Krebs' phosphate buffer containing trace amounts of [14C]inulin and [3H]cholesterol, as well as different concentrations of unlabeled cholesterol, were used for absorption studies.

RESULTS

The NS and H-chol groups showed severe and comparable hypercholesterolemia. No significant difference was found in the rate of biliary cholesterol secretion among the study groups. Likewise, the rates of in vivo and in vitro cholesterol absorptions in the NS and H-chol groups were comparable with one another and similar to those found in the NL and PF groups. The rate of in vitro cholesterol absorption was directly proportional to its concentration in the incubation media at low concentrations. However, the absorption rate showed a pattern consistent with saturable transport at high cholesterol concentrations in all groups.

CONCLUSIONS

We conclude that intestinal absorption and biliary secretion of cholesterol are not appreciably influenced by either nephrotic or diet-induced hypercholesterolemia in rats. The data further suggest that cholesterol absorption may be a saturable process.

Altered drug membrane permeability in a multidrug-resistant Leishmania tropica line

We selected a Leishmania tropica cell line resistant to daunomycin (DNM) that presents a multidrug-resistant (MDR) phenotype characterized by overexpression of a P-glycoprotein of 150 kDa. The resistant line overexpressed an MDR-like gene, called ltrmdr1, located in an extrachromosomal circular DNA. DNM uptake experiments using laser flow cytometry showed a significant reduction in drug accumulation in the resistant parasites. The initial stages of the interaction of DNM with membranes from wild-type and DNM-resistant parasites were defined by a rapid kinetic stopped-flow procedure which can be described by two kinetic components. On the basis of a previous similar kinetic study with tumor cells, we ascribed the fast component to rapid interaction of DNM with membrane surface components and the slow component to passive diffusion of the drug across the membranes. The results reported here indicate that entrance of DNM into wild-type parasites was facilitated in respect to the resistant ones. We propose that resistance to DNM in L. tropica is a multifactorial event involving at least two complementary mechanisms. an altered drug membrane permeability and the overexpression of a protein related to P-glycoprotein that regulates drug efflux.

Dual effects of lisinopril on puromycin aminonucleoside nephrosis in unilaterally nephrectomized rats

The therapeutic effects of angiotensin converting enzyme inhibitor, lisinopril, on puromycin aminonucleoside (PAN)-induced nephrosis were investigated using unilaterally nephrectomized rats. Lisinopril showed potent dual effects on PAN nephrosis. Lisinopril treatment (50 mg/l in drinking water) from day 5 or day 9 reduced urinary protein excretion and suppressed the development of glomerular sclerosis at 8 weeks after PAN injection (150 mg/kg, i.p.), indicating a therapeutic effect on the nephrosis. Recovery of decreased anionic charge sites on the glomerular basement membrane was involved, at least in part, in the therapeutic action of lisinopril against proteinuria. On the other hand, oliguria and progressive azotemia derived from continuous deterioration of the renal function was induced if the treatment of lisinopril was started on the same day as PAN injection. The renal dysfunction induced by simultaneous administration of lisinopril with PAN could be abolished by combination dosing with sarcosine, an angiotensin II (AII)-receptor agonist. These results indicate that lisinopril treatment attenuates proteinuria by ameliorating the anionic charge barrier on the glomerular basement membrane and that it also protects against the development of chronic renal disease with segmental glomerular sclerosis, although AII depletion during the acute nephrotic stage exacerbates the renal damage in PAN nephrosis of unilaterally nephrectomized rats.

Alpha 2u-globulins in the urine of male rats: a reliable indicator for alpha 2u-globulin accumulation in the kidney

Increases in kidney-type-alpha 2u-globulin (alpha G-K, molecular weight approximately 16 kDa) were detected in the urine of male adult rats treated with d-limonene by immunoblotting analysis using an antiserum which distinguishes native-type-alpha 2u-globulin (alpha G-N, molecular weight approximately 19 kDa) from alpha G-K. When male adult rats received d-limonene by gavage (0-300 mg/kg/day) for 14 consecutive days, dose-dependent increases in urinary excretion of alpha G-K were observed at a dosage level of more than 30 mg/kg/day. This was found to be directly correlated with alterations in the concentration of renal alpha G-K as well as the accumulation of hyaline droplets in proximal convoluted tubule (PCT) epithelial cells in the kidneys. Marked elevation of urinary alpha G-K was also noted following oral treatment of adult male rats with 2,2,4-trimethylpentane (TMP), 1,4-dichlorobenzene (DCB), decalin and isophorone (ISP) by gavage (1.5 mmol/kg/day) for 7 consecutive days, again in association with increased concentrations of renal alpha G-K and hyaline droplet accumulation in renal PCT epithelial cells. However, no such increases in urinary alpha G-K were observed for male adult rats treated with nephrotoxic chemicals such as puromycin aminonucleoside (PAN) (15 mg/kg/day, s.c., 14 consecutive days) or hexachloro-1,3-butadiene (HCBD) (100 mg/kg/day, p.o., 5 consecutive days), lacking the ability to cause kidney accumulation of the hyaline droplets and alpha G-K. The findings in this study thus indicate that measurement of urinary alpha G-K can give a reliable estimates not only of the potential to cause renal accumulation of alpha 2u-globulin but also of its magnitude.

Limitations of podocyte adaptation for glomerular injury in puromycin aminonucleoside nephrosis

Glomerular synechiae that occurred in nephrotic rats with a single intraperitoneal injection of puromycin aminonucleoside were analyzed by immunohistochemistry, radiolabeled thymidine ([3H]-thymidine) autoradiography, as well as light, electron and immunoelectron microscopy. To discriminate podocytes from parietal epithelial cells (PEC) and monocytes, monoclonal antibodies (mAb) against podocalyxin and ED1 were used. The cell kinetics of glomerular epithelial cells were autoradiographically assessed with isotope labeling procedures before and during nephrosis (co-labeled), and a mAb against proliferating cell nuclear antigen (PCNA). All the cell types except the podocyte of normal kidneys were labelled with [3H]-thymidine at different rates. Detachment of degenerated podocytes from the outside of the glomerular basement membrane (GBM) is the first step of synechia, and detached sites are confronted by PEC that were hypertrophied and frequently radiolabeled. Evidence that podocytes in glomeruli of nephrotic rats can proliferate was shown by the presence of mitoses, [3H]-thymidine uptake in the co-labeled experiment, and by PCNA staining, but re-epithelialization over bare segments of the GBM with proliferated podocytes is doubtful. It was concluded that glomerular synechia resulted from the limits of podocyte adaptation to glomerular injuries.

Coexpression of a novel glomerular basement membrane matrix material in mesangial cell culture and glomerulosclerosis

After in vivo administration of purified antibody against cultured mesangial cell (anti-MC IgG), glomerular basement membrane (GBM) was selectively bound. The glomerular bound anti-MC IgG exhibited a monospecificity for a 109-kDa antigen extracted from cultured mesangial cells and normal GBM. The antigen was not digestible by collagenase, heparitinase, or chondroitinase and was revealed by immunoelectron microscopy of a normal glomerular component to be predominantly distributed along the lamina rara externa of GBM and to be absent in mesangium. The ample expression of the antigen in puromycin aminonucleoside nephrosis implies that it represents a significant sclerotic material in glomerulonephritis. Abnormal production of GBM components by mesangial cells may play an important role in glomerulosclerosis.

Increased lymphatic hyaluronan output and preserved hyaluronan content of the rat small intestine in prolonged hypoproteinaemia

Nephrotic syndrome was induced in seven rats by daily aminonucleoside injections. Experiments were performed in anaesthesia 6 or 7 d later when protein loss in urine had reduced serum colloid osmotic pressure (COP) to 8.2 +/- 0.9 (SD) mmHg compared with 20.2 +/- 2.2 mmHg in controls (P < 0.01). Due to the decreased COP in the nephrotic rats, lymph flow in the main mesenteric lymphatic was 29.5 +/- 11.5 microliters min-1 compared with 4.2 +/- 2.2 microliters min-1 in the control rats (P < 0.01). The corresponding hyaluronan concentrations were 3.4 +/- 0.9 micrograms ml-1 and 12.0 +/- 3.5 micrograms ml-1, respectively (P < 0.01). Nevertheless lymphatic hyaluronan output was doubled in the nephrotic rats, but this did not affect the hyaluronan content of the small intestine of 192 +/- 58 micrograms g-1 dry wt compared with 215 +/- 69 micrograms g-1 in controls (P > 0.05). During a 20 min intravenous 0.9% saline infusion of 4 ml 100 g-1 rat, the hyaluronan concentration increased to 18.3 (6.0) micrograms ml-1 in mesenteric lymph in controls, whereas the concentration in lymph from the nephrotic rats remained unchanged. Lymphatic output increased, however, in this group as well due to the elevated flow. The amount of hyaluronan cleared daily by the main mesenteric lymphatic in awake rats corresponds to about half the tissue hyaluronan content in the drained area (østgaard & Reed 1993 b).(ABSTRACT TRUNCATED AT 250 WORDS)

Lysosomal iron accumulation and tubular damage in rat puromycin nephrosis and ageing

1. Energy dispersive X-ray spectrometry was used to examine the relationship between proteinuria and increased urinary iron excretion, and structural and functional damage in puromycin nephrosis. 2. After 11-12 days rats treated with puromycin (10 mg/100 g, i.v.i.) had greater proteinuria (211.6 +/- 35.7 mg/day, mean +/- s.e.m.) and urinary iron excretion (15.4 +/- 2.2 micrograms/day) than saline-treated controls (14.5 +/- 1.4 mg/day and 1.1 +/- 0.2 micrograms/day, respectively, both P < 0.001). 3. On day 13, mean lysosomal iron concentration of proximal tubular cells (306.6 +/- 64.5 vs 11.9 +/- 8.6 mg%, P < 0.001), and proximal tubular cell damage assessed semi-quantitatively (1.17 +/- 0.10 vs 0.62 +/- 0.10, P < 0.001) were higher and creatinine clearance (0.15 +/- 0.01 vs 0.29 +/- 0.02 mL/min per g kidney weight, P < 0.001) lower than in control rats. 4. At days 35, 60 and 360 there were no differences in any of the measured parameters between rats treated with puromycin or saline, and in both groups proteinuria, tissue damage and lysosomal iron concentration increased with time. 5. Lysosomal iron accumulation was the only independent predictor of both functional and structural damage. 6. In conclusion, the apparent association between proteinuria and tubulo-interstitial damage in puromycin nephrosis, and with ageing, is best explained by factors associated with accumulation of iron within lysosomes of proximal tubule cells.

Production of an inhibitor of rat mesangial cell growth by the glomerulus and its alteration in puromycin nephrosis

Mesangial cell proliferation is found in many forms of progressive renal disease. This proliferation may be due to dysregulation of mesangial cell growth. The studies presented here test the hypothesis that the normal glomerulus produces a regulator of mesangial cell growth. Conditioned media (CM) from primary glomerular cultures were able to inhibit rat mesangial cell growth in a dose- and time-dependent fashion, from 30.0 +/- 3.8 to 86.6 +/- 3.9% growth inhibition. The growth inhibitor in glomerular CM appears to have a molecular weight of less than 3,000. Glomerular CM caused significantly more growth inhibition than did 3T3 fibroblast CM, 77.9 +/- 2.8% growth inhibition by 10% glomerular CM versus 21.2 +/- 5.4% by 10% 3T3 CM (P < 0.001). The growth inhibition was completely reversible. Glomerular CM had no effect on the growth of 3T3 fibroblasts. Treatment of the glomerular CM with either trypsin or neutral protease had no effect on its growth inhibitory activity. Glomerular CM obtained from rats with puromycin aminonucleoside nephrosis caused significantly less growth inhibition than did control glomerular CM; at a concentration of 10% CM, control glomerular CM had 65.1 +/- 1.9% growth inhibition and puromycin had 45.4 +/- 2.1% (P < 0.001). Thus, the rat glomerulus produces a small, nonprotein inhibitor of rat mesangial cell growth and the activity of this inhibitor is reduced in puromycin nephrosis. Impairment of mesangial cell growth regulation may be important in the pathogenesis of progressive renal disease.

The effect of dilazep on puromycin-induced rat renal mitochondrial dysfunction

The effect of tetrahydro-1 H-1,4 (5H)-dipropanol bis(3,4,5-trimethoxybenzoate)hydrochloride monohydrate (dilazep, Comelian) on puromycin-induced rat renal damage was investigated. In vivo study: Rats were divided into 3 groups, the control group; untreated, the puromycin group; puromycin (150 mg/kg) was injected intraperitoneally once, the dilazep + puromycin group; puromycin (150 mg/kg) was injected 1 h after intraperitoneal dilazep injection (2 mg/kg), and dilazep (2 mg/kg) was injected every 12 h until the end of the experiment. In each group, 84 h after puromycin injection, kidneys were isolated and renal mitochondria were prepared. The endogenous phospholipase activity in kidney homogenate was determined by high performance liquid chromatography. The activities of three segments (NADH-cytochrome c reductase, succinate-cytochrome c reductase and cytochrome c oxidase) of the electron-transport chain in mitochondria were measured enzymatically. In the puromycin group, phospholipase activity was increased and activities of all of three segments of the electron-transport chain were decreased. In the dilazep + puromycin group, premedication with dilazep prevented activation of phospholipase and maintained mitochondrial electron-transport activity. In vitro study: Mitochondria prepared from intact rat kidney were incubated with phospholipase C. Activities of the mitochondrial electron-transport chain were deteriorated by phospholipase C. These results indicated that activation of endogenous phospholipase, which digests membrane phospholipids, essential components in maintaining mitochondrial electron-transport activity, is responsible for the puromycin-induced renal damage. Premedication with dilazep prevented the damage by inhibition of the activation of phospholipase.

Effects of puromycin on rat embryos in vitro

Somite-staged rat embryos were exposed to varying concentrations of puromycin for 48 h in vitro. Medium concentrations below 0.92 microM had no significant effects, while concentrations above 1.84 microM were lethal. Between these extremes, there were concentration dependent increases in the incidence of malformations in a close relationship to growth retardation.

Blockade of beta 1- but not of beta 2-adrenergic receptors replicates propranolol's suppression of the cerebral spread of an engram in mice

Bitemporal injections of puromycin that primarily affect the hippocampal-entorhinal area induce amnesia of aversive maze-learning in mice for 3 days after training but are ineffective 6 or more days after training. At these later times, additional puromycin sites covering widespread forebrain areas are necessary to induce amnesia, a result that we attribute to the cerebral spread of the engram during the 6-day period. We have reported that blockade of about 60% of cerebral beta-adrenergic receptors by a single, subcutaneous injection of (-)-propranolol, a nonselective beta-receptor antagonist, inhibited engram spread for 60-90 days, at which time engram spread spontaneously occurred. In the present experiments using single doses of antagonists that appeared to block 60% of beta 2- or beta 1-adrenergic receptors, it was found that the selective beta 2 antagonist ICI 118,551 was without effect on engram spread, whereas the selective beta 1 antagonist betaxolol inhibited the spread for at least 3 months. Propranolol's effect consequently appears to be accounted for by its blockade of beta 1 receptors.

The frequency and distribution of apoptosis induced by three non-carcinogenic agents in mouse colonic crypts

The appearance of apoptotic cells has been used as an index of carcinogen-induced damage inflicted on the colonic epithelium. We report here that 3 potent biological toxins, colchicine, puromycin and diphtheria toxin which have not been shown to be carcinogenic cause a dose-related increase in apoptotic cells in the colonic epithelium of the mouse. The distribution of apoptosis along the crypt length is characteristic for each of the agents studied.

Co-amplification of double minute chromosomes, multiple drug resistance, and cell surface P-glycoprotein in DNA-mediated transformants of mouse cells

A genetic system comprised of mammalian cell mutants which demonstrate concomitant resistance to a number of unrelated drugs has been described previously. The resistance is due to reduced cell membrane permeability and is correlated with the presence of large amounts of a plasma membrane glycoprotein termed P-glycoprotein. This system could represent a model for multiple drug resistance which develops in cancer patients treated with chemotherapeutic drugs. We demonstrate here that the multiple drug resistance phenotype can be transferred to mouse cells with DNA from a drug-resistant mutant and then amplified quantitatively by culture in media containing increasing concentrations of drug. The amount of P-glycoprotein was correlated directly with the degree of drug resistance in the transformants and amplified transformants. In addition, the drug resistance and expression of P-glycoprotein of the transformants were unstable and associated quantitatively with the number of double minute chromosomes. We suggest that the gene for multiple drug resistance and P-glycoprotein is contained in these extrachromosomal particles and is amplified by increases in double minute chromosome number. The potential use of this system for manipulation of mammalian genes in general is discussed.

Studies on the half-life and the distribution of stearoyl-CoA desaturase in the housefly

The half-life of the stearoyl-CoA desaturase was determined by using houseflies injected with puromycin. The LD50 for puromycin was determined to be 1.55 micrograms/mg body wt for both sexes. By following the decay in specific activity of the desaturase after puromycin injection, the half-life of this enzyme in 4-day-old females was calculated to be 9.35 hr, while in 1-day-old females it was 3.38 hr. The inhibition curve for the 3-day-old males never reached 100%, and a biphasic curve was observed. The early phase resulted in a half-life of the desaturase of 2.41 hr, while the latter phase had a half-life of 8.45 hr. In general, it appeared that the half-life of the desaturase increased with age in either sex. Studies on the distribution of desaturase activity within the housefly showed that most of the activity was present in the integument; however, in the female, the onset of ovarian development seemed to shift the distribution of desaturase from the integument, towards the internal tissues. In the male, there appeared to be equal amounts of desaturase in integument and the fat body plus internal tissues at day 2, but by day 5 most of the activity was associated with the integument. The high specific activity and high percentage of total desaturase activity associated with integument coupled with the shift of distribution of desaturase in females during the onset of ovarian development may be indicative of a close correlation of the desaturase with alkene synthesis and possibly sex pheromone production.

Planarians as a model system for in vitro teratogenesis studies

Free-living flatworms such as planarians are inexpensive to culture, maintain, and use for toxicologic testing in the laboratory. A considerable number of basic studies by ourselves and others indicate that, in simplified miniature, they possess many features of biochemical and physiologic organization similar to higher animals such as mammals. These include a well-developed brain with a varied behavioral repertoire including complex maneuvers of prey capture and learning, with a number of the same neurotransmitters used in mammalian brain. They are sensitive to a variety of the same toxicants. Undifferentiated totipotent stem cells, i.e., "neoblasts," which are capable of mitosis and differentiation into any of the various specialized cell types, permit regeneration of complete planarians from fragments. They also provide new cells to replace those lost in the normal cellular turnover of nonregenerating planarians. Both regeneration of surgical fragments and aberrant remodeling of whole planarians model important features of embyrogenesis and are potentially useful for assaying teratogens. Results are described from studies in which various representative teratogenic toxicants were tested in these two different planarian paradigms. The potential of planarian cephalic regeneration for behavioral teratogenesis investigations is also indicated.

An ultrastructural study of the mechanisms of proteinuria in aminonucleoside nephrosis

Sprague-Dawley rats injected i.v. with a single dose of puromycin aminonucleoside (PAN) developed massive proteinuria five days later. Electron microscopic studies of perfusion-fixed glomeruli showed that loss of epithelial foot processes and their replacement by flattened expanses of epithelial cytoplasm began at two days and was extensive by four days after the injection of PAN. At and after five days (correlating with the onset and persistence of massive proteinuria), areas of focal loss of the epithelial covering on the outside of the glomerular basement membrane (GBM) were observed in 30% of glomeruli. Intravenously administered ferritin was distributed normally in most sections of the GBM of nephrotic animals, but abnormally deep penetration of particles was observed in GBM segments that lacked an external covering of epithelium. The same changes were found following in situ fixation of superficially placed glomeruli of Munich-Wistar rats with PAN nephrosis. We propose that the massive, early proteinuria in PAN nephrosis may be primarily due to a glomerular epithelial lesion, leading to scattered focal defects in the external covering of the GBM. Increased bulk flow of glomerular filtrate across the GBM in such areas may explain the highly selective proteinuria found in this form of the nephrotic syndrome.

Glycolysis in normal and nephrotic rat kidney

Experimental nephrosis was induced in rats by administering the aminonucleo side of puromycin, which inhibits protein synthesis in cell-free and whole-cell preparations.Slices of renal cortex from nephrotic rats incubated for 2 hours in Krebs–Ringer phosphate buffer with glucose as substrate accumulated two to three times more lactate and pyruvate than did slices from normal rats under aerobic but not under anaerobic conditions. Nephrotic cortex metabolizing endogenous substrate similarly accumulated three times as much pyruvate as normal cortex, but no accumulation of lactate occurred in either normal or nephrotic cortex in the absence of glucose. These changes were not observed in nephrotic medulla, nor were they accompanied by any change in oxygen consumption, glucose uptake, or glutamic–pyruvic transaminase activity. Decreased dry weight of the nephrotic slices was accompanied by a similar small decrease in their protein content. It is postulated that there is a decreased activity of enzymes metabolizing pyruvate in the cortex of aminonucleoside-treated rats.