Chronic Puromycin Aminonucleoside Research Articles

TRPC6 Inactivation Does Not Protect Against Diabetic Kidney Disease in Streptozotocin (STZ)‐treated Sprague‐Dawley Rats

Glomerular TRPC6 channels are up‐regulated in rodent models of diabetes mellitus, but the role of TRPC6 in driving progression of experimental diabetic nephropathy is controversial. We recently used CRISPR/Cas9 methods to generate Sprague‐Dawley rats with a deletion in exon 2 of the Trpc6 gene that renders the channels non‐functional [1]. In addition, we observed that animals lacking functional TRPC6 were protected in the chronic puromycin aminonucleoside (PAN) model of acquired FSGS [1]. In the present study, 300‐gram adult Trpc6del/del rats and their wild‐type Trpc6wt/wt littermates were examined in the STZ model of type‐1 diabetes using protocols approved by the University of Houston IACUC committee. In our experiments, diabetes was induced by a single intraperitoneal injection of STZ, while controls received vehicle. Animals were not treated with insulin. STZ‐treated rats with severe hyperglycemia (>450 mg/dl) by 5 days after treatment were used for analysis and were monitored for the next 10 weeks. At 4 and 10 weeks after STZ treatment, compared to vehicle‐treated controls, STZ‐treated rats had severe hyperglycemia (745 ± 144 mg/dl, mean ± SD at 10 weeks). They also had elevated plasma triglycerides and total cholesterol, and failed to gain weight. STZ‐treated rats also exhibited markedly increased urine albumin excretion, increased blood urea nitrogen (BUN), and increased plasma creatinine and decreased creatinine clearance, indicating marked declines in renal function in diabetic rats. Two‐way ANOVA analyses of these datasets revealed no differences between Trpc6wt/wt and Trpc6del/del rats in any of these parameters. There was no time in the course of the experiment where we obtained functional data suggesting a protective effect of TRPC6 inactivation on blood glucose, or kidney function in STZ diabetes. Histological analysis carried out 10 weeks after STZ treatment revealed marked glomerular and tubulointerstitial disease in STZ‐treated rats. Mesangial expansion was the prominent feature in glomeruli of STZ‐treated animals, and glomeruli were less disrupted than we previously observed in the chronic PAN model [1]. Blind semi‐quantitative analysis of glomerular histology revealed a significant effect of STZ but no protective effect of TRPC6 inactivation on glomerular pathology. In summary, TRPC6 inactivation does not prevent declines in renal function and appears to have no protective effect in the STZ model of type‐1 diabetes in Sprague‐Dawley rats. This is in marked contrast to our previous work in chronic PAN nephrosis, where TRPC6 inactivation preserves renal function and histology.Support or Funding InformationSupported by NIH grant R01‐DK104708.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Trpc6 inactivation confers protection in a model of severe nephrosis in rats

Mutations in canonical transient receptor potential-6 (TRPC6) channels give rise to rare familial forms of focal and segmental glomerulosclerosis (FSGS). Here we examined a possible role for TRPC6 in the progression of chronic puromycin aminonucleoside (PAN) nephrosis in Sprague-Dawley rats, a classic model of acquired nephrotic syndromes. We used CRISPR/Cas9 technology to delete a 239-bp region within exon 2 of the Trpc6 gene (Trpc6del allele). Trpc6del/del rats expressed detectable Trpc6 transcripts missing exon 2, and TRPC6 proteins could be detected by immunoblot of renal cortex. However, the abundance of Trpc6 transcripts and TRPC6 protein in renal cortex was much lower than in Trpc6wt/wt littermates, and functional TRPC6 channels could not be detected in whole-cell recordings from glomerular cells cultured from Trpc6del/del animals, possibly because of disruption of ankyrin repeats 1 and 2. During the chronic phase of PAN nephrosis, Trpc6del/del rats had reduced urine albumin excretion, reduced serum cholesterol and triglycerides, and improved azotemia compared to wild-type Trpc6wt/wt littermates. Glomerulosclerosis was severe during chronic PAN nephrosis in Trpc6wt/wt rats but was markedly reduced in Trpc6del/del littermates. Trpc6del/del animals also had less severe tubulointerstitial fibrosis as assessed by several biochemical and histological analyses, as well as reduced foot process effacement and glomerular basement thickening compared to Trpc6wtt/wt controls. None of the manipulations in this study affected the abundance of TRPC5 channels in renal cortex. TRPC3 was increased in PAN nephrosis and in Trpc6del/del rats. These data support a role for TRPC6 channels in driving an acquired form of secondary FSGS.Key messagesWe examined aminonucleoside nephrosis in rats with wild type and inactivated TRPC6.TRPC6 channels were inactivated by CRISPR/Cas9 editing of the Trpc6 gene.TRPC6 inactivation reduced albuminuria in the chronic but not the acute phase.TRPC6 inactivation reduced glomerulosclerosis and ultrastructural changes.TRPC6 inactivation also reduced interstitial changes and renal fibrosis.

CRISPR/Cas9 Deletion of a Portion of Exon 2 in the Trpc6 Gene Produces a Hypomorphic Variant that Confers Protection in the Chronic Puromycin Aminonucleoside Nephrosis Model in Sprague‐Dawley Rats

Mutations in TRPC6 channels give rise to rare familial forms of focal and segmental glomerulosclerosis (FSGS). Here we examined the role of TRPC6 channels in the chronic puromycin aminonucleoside (PAN) model of acquired FSGS in Sprague‐Dawley rats, using protocols approved by the University of Houston IACUC. In our disease model, animals received two i.p. injections of PAN at 30 day intervals, a protocol that has long been known to induce albuminuria and FSGS lesions in this species. To test our central hypothesis, we used CRISPR/Cas9 methods to delete a 239‐bp fragment in Exon 2 of Trpc6, which resulted in a frame shift that we expected to introduce numerous premature stop codons downstream of the deletion. However as a result of a recently described process known as exon skipping, short Trpc6 transcripts missing Exon 2 were detected by RT‐PCR in Trpc6del/del rats, albeit at considerably lower levels in renal cortex compared to the normal full‐length transcripts seen in Trpc6wt/wt controls. The Exon 2 deletion encodes a portion of an ankyrin‐repeat domain in the N‐terminal of the channel subunit. The function of that domain in the channel protein is not known. Using two different antibodies directed at different motifs downstream of the deletion, we detected very low levels of TRPC6 protein in immunoblots of the renal cortex of Trpc6del/del rats, whereas signal was robust in Trpc6wt/wt controls with both antibodies. In addition, we did not observe ATP‐activated cationic currents mediated by TRPC6 in whole‐cell recordings from glomerular cells resembling podocytes cultured from Trpc6del/del rats, but these currents were readily seen in Trpc6wt/wt controls. Kidney disease in chronic PAN nephrosis (measured 60 days after the first PAN injection) was markedly decreased in Trpc6del/del rats compared to Trpc6wt/wt littermates. This conclusion is based on reduced 24‐hr albumin excretion, reduced serum cholesterol and triglycerides, and improved blood urea nitrogen in Trpc6del/del rats. Trpc6del/del rats also had reduced glomerulosclerosis, less severe tubulointerstitial disease based on biochemical and histological measures, and reduced foot process effacement and glomerular basement thickening in transmission EM compared to Trpc6wt/wt rats. Protection in Trpc6del/del rats was robust but not complete. Thus, most of the quantifiable parameters of disease severity were reduced by about 50% in Trpc6del/del rats compared to wild‐type littermates. We did not discern any difference between renal function or glomerular structure in saline‐treated Trpc6del/del and Trpc6wt/wt rats. We also observed that glomerular TRPC3 abundance in renal cortex was increased in Trpc6del/del rats, although TRPC3 abundance did not increase further in chronic PAN nephrosis. None of the manipulations in this study affected the abundance of TRPC5 channels in renal cortex. These results support TRPC6 family channels as therapeutic targets for acquired forms of FSGS.Support or Funding InformationSupported by NIH grant RO1‐DK104708This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Connective tissue growth factor modulates podocyte actin cytoskeleton and extracellular matrix synthesis and is induced in podocytes upon injury

Structural changes of podocytes and retraction of their foot processes are a critical factor in the pathogenesis of minimal change nephritis and glomerulosclerosis. Here we tested, if connective tissue growth factor (CTGF) is involved in podocyte injury during acute and chronic puromycin aminonucleoside nephrosis (PAN) as animal models of minimal change nephritis, and focal segmental glomerulosclerosis, respectively. Rats were treated once (acute PAN) or for 13weeks (chronic PAN). In both experimental conditions, CTGF and its mRNA were found to be highly upregulated in podocytes. The upregulation correlated with onset and duration of proteinuria in acute PAN, and glomerulosclerosis and high expression of glomerular fibronectin, and collagens I, III, and IV in chronic PAN. In vitro, treatment of podocytes with recombinant CTGF increased amount and density of actin stress fibers, the expression of actin-associated molecules such as podocalyxin, synaptopodin, ezrin, and actinin-4, and activation of focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK). Moreover, we observed increased podocyte expression of mRNA for transforming growth factor (TGF)-β2, TGF-β receptor II, fibronectin, and collagens I, III, and IV. Treatment of cultured podocytes with puromycin aminonucleoside resulted in loss of actin stress fibers and cell death, effects that were partially prevented when CTGF was added to the culture medium. Depletion of CTGF mRNA in cultured podocytes by RNA interference reduced both the number of actin stress fibers and the expression of actin-associated molecules. We propose that the expression of CTGF is acutely upregulated in podocytes as part of a cellular attempt to repair structural changes of the actin cytoskeleton. When the damaging effects on podocyte structure and function persist chronically, continuous CTGF expression in podocytes is a critical factor that promotes progressive accumulation of glomerular extracellular matrix and glomerulosclerosis.

Effects of edaravone against glomerular injury in rats with chronic puromycin aminonucleoside nephrosis

Effects of edaravone against glomerular injury in rats with chronic puromycin aminonucleoside nephrosis

Reduced podocyte expression of α3β1 integrins and podocyte depletion in patients with primary focal segmental glomerulosclerosis and chronic PAN-treated rats

Integrins attach cells to extracellular matrix (ECM) and mediate signals from ECM to cells or from cells to ECM. They regulate cell functions, including adhesion, migration, cell cycle regulation, and differentiation. Podocytes may detach from the glomerular basement membrane (GBM) and be excreted in the urine, and proteinuria is found in patients with primary focal segmental glomerulosclerosis (FSGS); both may be associated with loss of alpha3beta1integrins. In this study, we have examined the podocyte number in patients with primary FSGS and normal controls, and the alpha3- and beta1-integrin subunits expression of podocytes in patients with primary FSGS and chronic puromycin aminonucleoside (PAN)-treated rats by the morphometric, immunoperoxidase histochemical, and immunoelectron microscopic examination. We also measured their expression serially in rats that received repeated PAN injection. The results showed that the podocyte number was significantly decreased in patients with primary FSGS than in normal control (P < 0.05). The immunostaining score showed that both alpha3- and beta1-integrin subunits on podocytes in patients with primary FSGS were significantly lower than in normal controls (both P < 0.01). The number of immuno-gold particles of alpha3- and beta1-integrins at the effaced foot process area of patients with primary FSGS were also significantly decreased than that of normal controls (both P < 0.05). The immunostaining score of both alpha3- and beta1-integrin subunits was negatively correlated with the degree of glomerular sclerosing score and the amount of daily protein loss, and they were positively correlated with the number of podocytes. Chronic 12-week PAN-treated rats showed similar findings with decreased immunostaining expression and immuno-gold particles of alpha3-integrin on podocytes than in normal control (both P < 0.05). The chronic PAN-treated rats also showed a trend toward gradually decreased immunostaining expression of alpha3-integrin subunit on podocyte during the progress from normal to FSGS state. These studies indicate that podocyte expression of alpha3- and beta1-integrin subunits is significantly reduced in humans with primary FSGS and chronic PAN-treated rats, before the morphological changes of FSGS are observed. The decreased podocyte expression of alpha3beta1 integrins is closely related with podocyte depletion, glomerular sclerosis, and daily protein loss in patients with primary FSGS.

Antifibrotic effect of the Chinese herbs, Astragalus mongholicus and Angelica sinensis, in a rat model of chronic puromycin aminonucleoside nephrosis

Nephrotic syndrome has long been treated in China with two herbs, Astragalus mongholicus and Angelica sinensis, which may have antifibrotic effects. Methods: Rats with chronic puromycin-induced nephrosis were treated with Astragalus and Angelica 3 mL/d (n=7) or enalapril 10 mg/kg/d (n=7). Normal control rats (n=7) received saline rather than puromycin, and an untreated control group (n=7) received puromycin but no treatment. After 12 weeks, stained sections of the glomerulus and tubulointerstitium were evaluated for injury. Immunohistochemistry staining measured extracellular matrix components, transforming growth factor-β1 (TGFβ1), osteopontin, ED-1-positive cells, and α-actin. TGFâ1 mRNA was assessed by in situ hybridization. Renin, ACE activity, angiotensin, and aldosterone were measured by radioimmunoassay or colorimetry. In the untreated rats, chronic renal injury progressed to marked fibrosis at 12 weeks. Astragalus and Angelica significantly reduced deterioration of renal function and histologic damage. Expressions of type III and IV collagen, fibronectin, and laminin also decreased significantly. This anti-fibrotic effect was similar to that of enalapril. The herbs had no effect on the renin-angiotensin system but did reduce the number of ED-1-positive, and α-actin positive cells and expression of osteopontin compared to untreated controls. The combination of Astragalus and Angelica retarded the progression of renal fibrosis and deterioration of renal function with comparable effects of enalapril .These effects were not caused by blocking the intrarenal renin-angiotensin system, but associated with suppression of the overexpression of TGFâ 1 and osteopontin, reduction of infiltrating macrophages, and less activation of renal intrinsic cells.

Soy protein diet ameliorates renal nitrotyrosine formation and chronic nephropathy induced by puromycin aminonucleoside

It has been shown that reactive oxygen species are involved in chronic puromycin aminonucleoside (PAN) induced nephrotic syndrome (NS) and that a 20% soy protein diet reduces renal damage in this experimental model. The purpose of the present work was to investigate if a 20% soy protein diet is able to modulate kidney nitrotyrosine formation and the activity of renal antioxidant enzymes (catalase, glutathione peroxidase, Cu,Zn- or Mn-superoxide dismutase) which could explain, at least in part, the protective effect of the soy protein diet in rats with chronic NS induced by PAN. Four groups of rats were studied: (1) Control rats fed 20% casein diet, (2) Nephrotic rats fed 20% casein diet, (3) Control rats fed 20% soy protein diet, and (4) Nephrotic rats fed 20% soy protein diet. Chronic NS was induced by repeated injections of PAN and rats were sacrificed at week nine. The soy protein diet ameliorated proteinuria, hypercholesterolemia, and the increase in serum creatinine and blood urea nitrogen observed in nephrotic rats fed 20% casein diet. Kidney nitrotyrosine formation increased in nephrotic rats fed 20% casein diet and this increase was ameliorated in nephrotic rats fed 20% soy protein diet. However, the soy protein diet was unable to modulate the antioxidant enzymes activities in control and nephrotic rats fed 20% soy protein diet. Food intake was similar in the two diet groups. The protective effect of a 20% soy protein diet on renal damage in chronic nephropathy induced by PAN was associated with the amelioration in the renal nitrotyrosine formation but not with the modulation of antioxidant enzymes.

2-Hydroxyestradiol attenuates renal disease in chronic puromycin aminonucleoside nephropathy.

It has been previously shown that 2-hydroxyestradiol (2-OHE) attenuates the development of renal disease in genetic nephropathy associated with obesity and the metabolic syndrome. The purpose of this study was to test the hypothesis that 2-OHE, irrespective of its effects on metabolic status and/or obesity, exerts direct renoprotective effects in vivo. First, the effects of increasing doses of 2-OHE on mesangial cell growth, proliferation, and collagen synthesis in isolated rat glomerular mesangial cells were evaluated in vitro. Second, the effects of 12-wk administration of 2-OHE (10 micro g/h per kg) on renal function and structure in chronic puromycin aminonucleoside (PAN)-induced nephropathy in rats were evaluated in vivo. 2-OHE concentration-dependently (0.001 to 1 micro mol/L; P < 0.001) inhibited serum (2.5%)-induced cell growth ((3)H-thymidine incorporation), collagen synthesis ((3)H-proline incorporation), and cell proliferation (cell number). Importantly, the inhibitory effects of 2-OHE (0.1 micro mol/L) were not blocked by ICI182780 (50 micro mol/L), an estrogen receptor antagonist. In vivo, chronic administration of PAN (75 mg/kg + 5 x 20 mg/kg) over 12 wk induced severe chronic renal disease. Chronic treatment with 2-OHE significantly (P < 0.05) attenuated PAN-induced decrease in glomerular filtration, reduced proteinuria, and the elevated BP, and it had no effect on PAN-induced increase in plasma cholesterol and triglycerides levels. 2-OHE had no effects on plasma testosterone levels in male nephropathic animals. Immunohistochemical staining for collagen IV and proliferating cell nuclear antigen (PCNA) in glomeruli and transforming growth factor-beta (TGF-beta) in renal tubular cells were significantly higher in PAN nephropatic rats versus control animals with intact kidneys. PAN also markedly increased glomerular and interstitial macrophage infiltration (ED1(+) cells). 2-OHE had no effects on renal tubular cell TGF-beta, but it significantly reduced glomerular PCNA and collagen IV and glomerular and interstitial macrophage infiltration. In summary, this study provides the first evidence that 2-OHE exerts direct renoprotective effects in vivo. These effects are mediated by estrogen receptor-independent mechanisms and are due, at least in part, to the inhibition of some of the key proliferative mechanisms involved in glomerular remodeling and sclerosis.

Heparin-binding epidermal growth factor-like growth factor is expressed in the adhesive lesions of experimental focal glomerular sclerosis

In this study, we attempted to determine whether heparin-binding epidermal growth factor-like growth factor (HB-EGF) was up-regulated in two chronic models of proteinuria. Chronic passive Heymann nephritis (PHN) and puromycin aminonucleoside (PAN) models were induced in Sprague-Dawley rats. HB-EGF expression was studied by Northern blotting, in situ hybridization, and immunohistochemistry. The chronic PAN model was associated with the development of glomerular lesions of focal glomerular sclerosis (FGS), severe interstitial fibrosis, and renal failure. Lesions of FGS were seen in approximately 80% of glomeruli at all time points, with a slight increase in the number of glomeruli showing extensive adhesion between 40 and 90 days. Northern blots of whole kidney tissue showed a 3- to 5.8-fold increased expression of HB-EGF mRNA in the chronic PAN group. Increased mRNA and protein were localized by in situ hybridization and immunohistochemistry to tubules, glomerular epithelial cells (GECs), and cells of Bowman's capsule. HB-EGF mRNA and protein were strongly expressed by epithelial cells involved in the formation of the lesions of FGS. By contrast, in chronic PHN, there was a small increase in HB-EGF, and the extensive lesions of FGS did not develop despite continued, heavy proteinuria. These data suggest that HB-EGF may contribute to formation of the lesions of FGS, perhaps through stimulation of abortive mitogenesis in GECs or an adhesive interaction between transmembrane HB-EGF and the exposed glomerular basement membrane.

SUPPRESSION OF RENAL INFLAMMATION WITH VITAMINS A AND E IN ASCENDING PYELONEPHRITIS IN RATS

We evaluated the effects of vitamin A and E supplementation alone or in combination with non-steroidal anti-inflammatory drugs (NSAIDs) on the development of inflammation in an animal model of ascending pyelonephritis. Ascending pyelonephritis was induced in adult rats by surgical bladder inoculation with P-pili-forming Escherichia coli. Treatment of pyelonephritic rats was initiated at 72 hours post-infection. Treatment groups included no treatment, or a five day regimen of antibiotic only, antibiotic plus vitamins A and E, or antibiotic, vitamins and either of two NSAIDs. Kidneys were harvested at six weeks post-infection and assessed for histopathologic inflammation. Antibiotic treatment of pyelonephritic rats with vitamins A and E alone or in combination with NSAIDs resulted in significantly less kidney inflammation, as compared with untreated rats or rats treated with antibiotic alone. There was no significant difference in inflammation between animals treated with vitamins alone or vitamins plus NSAIDs. Antibiotic therapy and diet supplementation with vitamins A and E can significantly reduce the inflammation associated with ascending pyelonephritis, suggesting a potential use in the medical management of reflux nephropathy in children.

Suppressed Activities of Cathepsins and Metalloproteinases in the Chronic Model of Puromycin Aminonucleoside Nephrosis

Glomerulosclerosis and tubulointerstitial fibrosis are the hallmarks of chronic renal diseases. In the present study, we have investigated the potential involvement of various proteinases in these alterations in the model of puromycin aminonucleoside (PAN) nephrosis. Two groups of male Wistar rats were given either three or seven injections of PAN (2.0 mg/100 g body weight) over a 4– and 12–week period, respectively. The two control groups received saline injections. Activities of cathepsins (B, H and L) were determined in isolated glomeruli and proximal tubules. Moreover, collagenaselike and gelatinaselike activities were analyzed in isolated glomeruli. Three weeks after weekly PAN injection, the rats developed heavy proteinuria (140.8±22.0 vs. 13.5±3.29 mg/day; p<0.001), and at week 11 protein excretion reached 606.6±23.00 vs. 22.8±1.5 mg/day. Renal morphology revealed minimal glomerular mesangial changes at the 4th week after PAN administration. At the 12th week a marked mesangial matrix accumulation as well as severe tubulointerstitial infiltration and fibrosis associated with tubular dilation and atrophy were observed. Glomerular cathepsins B, H, and L and gelatinaselike activities decreased at the 4th week after the first PAN injection and remained at this low level throughout the entire study period. Glomerular collagenaselike activity decreased at the 4th week (p<0.05) and was still mildly lower than that of the control group at the 12th week, but without significance. In the isolated proximal tubules, the activities of cathepsins B, H, and L showed the same pattern of decreases as those found in the glomeruli over the whole experimental period. Taken together, our data in the model of chronic PAN nephrosis suggest that the suppressed activities of cathepsins as well as the decreased gelatinase– and collagenaselike activities participate in the accumulation of extracellular matrix and thereby may contribute to the development of glomerulosclerosis and tubulointerstitial fibrosis.

Osteopontin in chronic puromycin aminonucleoside nephrosis.

Increased expression of osteopontin (OPN) associated with interstitial monocyte infiltration has been demonstrated in the early phase of a variety of experimental renal diseases. Whether these changes occur in the chronic phase of progressive glomerular disease is unknown. Chronic puromycin aminonucleoside nephrosis (PAN) was induced in 16 rats by the injection of a single bolus of PA into the internal jugular vein, which results in a triphasic disease characterized by minimal glomerular change and marked proteinuria, peaking at about 10 to 14 d and subsiding by 28 d, followed by a quiescent 4-wk period of no or minimal proteinuria and then the development of progressive focal glomerulosclerosis (FGS) and increasing proteinuria. Fifteen rats injected similarly with normal saline served as controls. At 11 d after injection, PA rats demonstrated significantly greater urinary protein excretion (P = 0.0107), cortical tubular OPN expression (P = 0.0086), and intraglomerular (P = 0.0009) and interstitial (P = 0.0212) monocyte infiltration than did the controls. At 42 d, no significant differences between the two groups with respect to the above parameters were detected. At 98 d, PA rats had FGS and showed a definite trend to increased proteinuria, cortical tubular OPN, and intraglomerular monocyte infiltration. Although the cortical interstitial monocyte count was not elevated in PA rats compared with controls, there were significantly more monocytes around OPN-positive cortical tubules than around OPN-negative ones (P = 0.0011). Cortical tubular OPN expression correlated well with urinary protein excretion (r = 0.932, P < 0.0001), cortical tubular proliferating cell nuclear antigen (r = 0.796, P < 0.0001), and intraglomerular monocyte count (r = 0.552, P = 0.0013). The results are consistent with a monocyte chemoattractant role for OPN and suggest that OPN is upregulated in the chronic phase of PAN and that this increase in expression is a result of glomerular events.

Dietary antioxidant inhibits lipoprotein oxidation and renal injury in experimental focal segmental glomerulosclerosis

Lipid peroxidation may be involved in the pathogenesis of focal segmental glomerulosclerosis (FSGS). In the present study we examined whether lipid-soluble antioxidants, probucol and vitamin E, could inhibit renal injury in rats with chronic puromycin aminonucleoside (PA) nephrosis and dietary hypercholesterolemia by protecting lipoproteins from oxidation. Male Sprague-Dawley rats received six intraperitoneal injections of PA over a 10 week period and were fed a high cholesterol (HC) diet (PA-HC) or the same diet supplemented with either 1% probucol or vitamin E (100 IU/kg) for 32 weeks. For comparison, a group of rats received PA injections and a normal diet (PA-normal) with or without probucol or vitamin E. Another group rats received saline injections instead of PA and were fed a HC diet (Sal-HC) with or without probucol or vitamin E. At the end of the experiment, proteinuria, FSGS and tubulointerstitial lesions were present in the untreated rats with PA-HC or PA-normal. The magnitude of these lesions was significantly greater in the PA-HC rats than the PA-normal. In contrast to the PA-HC group with hypercholesterolemia, the PA-normal group did not show hypercholesterolemia from week 16 onwards. The rats with PA-HC alone showed significantly higher renal cortical malondialdehyde (MDA) levels and greater susceptibility of plasma very low density lipoprotein (VLDL) + low density lipoprotein (LDL) to the copper-mediated oxidation than the rats with PA-normal or Sal-HC alone. The administration of probucol or vitamin E in the rats with PA-HC significantly reduced the susceptibility of plasma VLDL + LDL to in vitro oxidation, renal cortical MDA level, proteinuria, mesangial volume density and magnitude of FSGS and interstitial lesions. Immunohistochemical staining of renal tissue showed focal segmental distribution of oxidized LDL (Ox-LDL) in the glomeruli of rats with PA-HC. Administration of probucol or vitamin E reduced the intensity of Ox-LDL staining. The staining with ED1 demonstrated that infiltrating glomerular macrophages were significantly more prevalent in the untreated rats with PA-HC than PA-normal or Sal-HC. Treatment with probucol or vitamin E significantly reduced the number of glomerular macrophages in the rats with PA-HC. These results suggest that alimentary hypercholesterolemia aggravates the renal damage in association with increased renal lipid peroxides in chronic PA nephrosis, and that dietary probucol or vitamin E attenuates renal injury in rats with PA-HC possibly by making lipoproteins resistant to oxidation and by inhibiting intraglomerular macrophage infiltration.

Inhibition of progression of chronic puromycin aminonucleoside nephrosis by probucol, an antioxidant.

Oxidants have been shown to be involved in the initiation of chronic puromycin aminonucleoside nephrosis in rats, but it is uncertain whether they have a role in the progression of this disease. Rats given a single internal jugular venous bolus of puromycin aminonucleoside (PA) develop early nephrotic syndrome that subsides after about 28 days followed by a 4-wk period of minimal proteinuria and then the development of focal glomerulosclerosis and increasing proteinuria. Fifty-two rats on a high-cholesterol diet were divided into four groups. Two groups of 16 animals each received a single internal jugular venous bolus of PA. One of these groups was started on the dietary antioxidant, probucol (1% wt/wt), 4 days after the PA injection and continued on it until termination. The remaining rats were given an internal jugular venous injection of an equivolume of normal saline. Five of these animals were also started on dietary probucol 4 days after the saline injection. At 11 days postinjection all animals given PA, whether on probucol or not, developed marked proteinuria with histologically minimal glomerular change and significant increases in intraglomerular monocyte and proliferating cell nuclear antigen counts. Forty-two days after PA injection all PA-injected rats had minimal urinary protein injection and no glomerular changes. At 98 days postinjection rats given PA without probucol developed focal glomerulosclerosis and significant proteinuria compared with PA-injected rats on probucol and those injected with saline (P < 0.05). The probucol-fed PA-injected rats showed no glomerular disease and their urinary protein excretion rates were very similar to those of the saline controls. The results indicate that probucol inhibits the progression of chronic puromycin aminonucleoside nephrosis and are consistent with the suggestion that oxidants are involved in the progression of this entity.

The effect of recombinant human insulin-like growth factor-I on chronic puromycin aminonucleoside nephropathy in rats.

We recently demonstrated that recombinant hGH exacerbates renal functional and structural injury in chronic puromycin aminonucleoside (PAN) nephropathy, an experimental model of glomerular disease. Therefore, we examined whether recombinant human (rh) IGF-I is a safer alternative for the treatment of growth failure in rats with chronic PAN nephropathy. The glomerulopathy was induced by seven serial injections of PAN over 12 wk. Experimental animals (n = 6) received rhIGF-I, 400 micrograms/d, whereas control rats (n = 6) received the vehicle. rhIGF-I improved weight gain by 14% (p < 0.05), without altering hematocrit or blood pressure in rats with renal disease. Urinary protein excretion was unaltered by rhIGF-I treatment in rats with chronic PAN nephropathy. After 12 wk, the inulin clearance was higher in rhIGF-I-treated rats, 0.48 +/- 0.08 versus 0.24 +/- 0.06 mL/min/100 g of body weight in untreated PAN nephropathy animals, p < 0.05. The improvement in GFR was not associated with enhanced glomerular hypertrophy or increased segmental glomerulosclerosis, tubulointerstitial injury, or renal cortical malondialdehyde content. In rats with PAN nephropathy, administration of rhIGF-I increased IGF-I and GH receptor gene expression, without altering the steady state level of IGF-I receptor mRNA. In normal rats with intact kidneys, rhIGF-I administration (n = 4) did not alter weight gain, blood pressure, proteinuria, GFR, glomerular planar area, renal cortical malondialdehyde content, or glomerular or tubulointerstitial damage, compared with untreated animals (n = 4). rhIGF-I treatment reduced the steady state renal IGF-I mRNA level but did not modify gene expression of the IGF-I or GH receptors. We conclude that: 1) administration of rhIGF-I improves growth and GFR in rats with chronic PAN nephropathy and 2) unlike rhGH, long-term use of rhIGF-I does not worsen renal functional and structural injury in this disease model.

Dietary vitamin E supplementation ameliorates renal injury in chronic puromycin aminonucleoside nephropathy.

Chronic puromycin aminonucleoside nephropathy (PAN) is an experimental analog of focal segmental glomerulosclerosis. Progressive renal damage in this model is partly mediated by excessive production of oxidant species. Whether dietary supplementation with vitamin E, an endogenous lipophilic antioxidant, ameliorates the severity of chronic PAN was tested. PAN was induced by seven serial injections of the glomerular epithelial cell toxin puromycin aminonucleoside, 2 mg/100 g body wt per dose, over a 12-wk period. Experimental animals (N = 8) received vitamin E-enriched chow (100 IU/kg), whereas control PAN rats (N = 10) were fed standard rodent diet containing vitamin E (30 IU/kg of chow). The administration of vitamin E had no effect on somatic growth or blood pressure; however, rats with PAN fed the vitamin E-enriched diet had an increased hematocrit. In addition, the experimental diet resulted in a 50% reduction in urinary total protein and albumin excretion and stabilization of the serum albumin, cholesterol, and triglyceride concentrations (P < 0.01). The inulin clearance was 69% higher in the vitamin E-supplemented animals (P < 0.001). Tubular function, namely, phosphate reabsorption and beta 2-microglobulin excretion, was improved in rats with chronic PAN treated with the vitamin E-enriched diet. There was a significant decrease in glomerulosclerosis and glomerular planar area, and tubulointerstitial scarring was diminished in vitamin E-treated animals with chronic PAN (P < 0.01). These beneficial effects on renal structure and function were associated with reduced malondialdehyde content in the kidney and liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Recombinant human growth hormone exacerbates chronic puromycin aminonucleoside nephropathy in rats

Growth failure is a cardinal feature of chronic renal failure in children. Administration of recombinant human growth hormone (rhGH) ameliorates this problem but may adversely affect the kidney and hasten the progression to end-stage renal disease. We conducted experiments to examine the impact of rhGH on the severity of chronic puromycin aminonucleoside (PAMN) nephropathy in rats. The glomerulopathy was induced by serial injections of PAMN over a 12 week period. Experimental animals (N = 6) received rhGH, 0.5 mg per dose, three times weekly, while control rats (N = 6) received hormone vehicle. rhGH had no effect on weight gain, hematocrit, or blood pressure in rats with the experimental renal disease. Urinary protein excretion increased approximately 50% in rhGH-treated rats with chronic PAMN nephropathy compared to untreated animals between four to eight weeks of the observation period. After 12 weeks, the inulin clearance was significantly lower in rhGH-treated rats, 0.26 +/- 0.05 versus 0.50 +/- 0.06 ml/min/100 g body wt in control PAMN animals, P < 0.05. Compared to untreated rats with PAMN nephropathy, administration of rhGH increased the extent of segmental glomerulosclerosis from 11 +/- 3 to 46 +/- 9% (P < 0.005) and elevated the tubulointerstitial injury score from 0.5 +/- 0.1 to 1.4 +/- 0.4 (P < 0.05). Furthermore, glomerular hypertrophy was enhanced in animals with chronic PAMN nephropathy given rhGH, as evidenced by a larger glomerular planar area, 9.2 +/- 0.3 x 10(-3) versus 11.9 +/- 0.5 x 10(-3) mm2, P < 0.005.(ABSTRACT TRUNCATED AT 250 WORDS)

Meprin activity in rats with experimental renal disease

Activity of renal meprin, a membrane-bound proteinase in the proximal tubule brush border, was measured in normal rats and in two disease groups: chronic puromycin aminonucleoside nephropathy for 12 weeks and streptozocin-induced diabetes for 6 months. Enzyme activity in kidney homogenates was assayed using azocasein as substrate. The mean activity of meprin was 3.22±0.34 U/g kidney weight in normal rats. In diabetic animals, enzyme activity was 8.58±2.11 U/g kidney weight, P<0.01. In contrast, meprin activity was decreased in rats with puromycin-induced glomerulopathy, 2.13±0.17 U/g kidney weight, P<0.01. These findings indicate that meprin activity is elevated in experimental diabetes. Diminished activity of this luminal membrane enzyme in puromycin aminonucleoside nephropathy may contribute to renal injury in this disease model associated with massive urinary protein excretion.

Taurine attenuates renal disease in chronic puromycin aminonucleoside nephropathy

Repeated administration of low doses of puromycin aminonucleoside (PAMN) to rats induces a proteinuric renal disease that resembles focal segmental glomerulosclerosis (FSGS). Reactive oxygen molecules may be involved in the progressive course of this nephropathy. Therefore we evaluated whether taurine, an endogenous antioxidant, could limit the extent of renal injury. Sprague-Dawley rats received low-dose injections of PAMN, 2 mg/100 g body wt, over a 12-wk period. Two groups were studied: 1) controls given tap water (n = 23), and 2) an experimental group that drank 1% taurine-supplemented water (n = 22). Taurine-treated nephrotic rats had a reduction in albuminuria, as assessed by the urinary albumin-to-creatinine ratio (26 +/- 4 vs. 44 +/- 4, P less than 0.0001). After 12 wk, creatinine clearance was 0.33 +/- 0.03 (experimental) vs. 0.17 +/- 0.03 ml.min-1.100 g body wt-1 (control) (P less than 0.001), and inulin clearance (n = 6 pairs) was 0.26 +/- 0.04 (experimental) vs. 0.13 +/- 0.02 ml.min-1.100 g body wt-1 (control) (P less than 0.025). Administration of taurine reduced the percentage of segmentally sclerosed glomeruli (9.8 +/- 1.7 vs. 16.2 +/- 1.8%, P less than 0.02) and the tubulointerstitial injury score (1.36 +/- 0.19 vs. 2.61 +/- 0.25, P less than 0.0025) in experimental vs. control rats. Taurine treatment normalized the elevated renal cortical malondialdehyde level in rats with PAMN nephropathy (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)