Experimental adriamycin nephropathy. Fine structure, morphometry, glomerular polyanion, and cell membrane antigens

Urokinase-type plasminogen activator contributes to amiloride-sensitive sodium retention in nephrotic range glomerular proteinuria in mice

AIM

Activation of sodium reabsorption by urinary proteases has been implicated in sodium retention associated with nephrotic syndrome. The study was designed to test the hypothesis that nephrotic proteinuria in mice after conditional deletion of podocin leads to urokinase-dependent, amiloride-sensitive plasmin-mediated sodium and water retention.

METHODS

Ten days after podocin knockout, urine and faeces were collected for 10 days in metabolic cages and analysed for electrolytes, plasminogen, protease activity and ability to activate γENaC by patch clamp and western blot. Mice were treated with amiloride (2.5 mg kg^-1 for 2 days and 10 mg kg^-1 for 2 days) or an anti-urokinase-type plasminogen activator (uPA) targeting antibody (120 mg kg^-1 /24 h) and compared to controls.

RESULTS

Twelve days after deletion, podocin-deficient mice developed significant protein and albuminuria associated with increased body wt, ascites, sodium accumulation and suppressed plasma renin. This was associated with increased urinary excretion of plasmin and plasminogen that correlated with albumin excretion, urine protease activity co-migrating with active plasmin, and the ability of urine to induce an amiloride-sensitive inward current in M1 cells in vitro. Amiloride treatment in podocin-deficient mice resulted in weight loss, increased sodium excretion, normalization of sodium balance and prevention of the activation of plasminogen to plasmin in urine in a reversible way. Administration of uPA targeting antibody abolished urine activation of plasminogen, attenuated sodium accumulation and prevented cleavage of γENaC.

CONCLUSIONS

Nephrotic range glomerular proteinuria leads to urokinase-dependent intratubular plasminogen activation and γENaC cleavage which contribute to sodium accumulation.

AF1q Contributes to Adriamycin-Induced Podocyte Injury by Activating Wnt/β-Catenin Signaling

BACKGROUND/AIMS

Injury of podocytes plays an important role in decline of glomerular filtration and proteinuria. It is well-known that proteinuria is associated with numerous chronic kidney diseases (CKD). However, the underlying mechanism of podocyte injury remains unclear.

METHODS

We used reverse transcription-quantitative PCR (RT-qPCR) to compare the expression level of the ALL1-fused from the chromosome 1q (AF1q) gene in mice and mouse podocytes (MPC5) with or without Adriamycin (ADR) treatment. The effects of AF1q on Wnt/ β-catenin signaling were investigated by determining the expressions of desmin, snail, WT1, nephrin and E-cadherin using western blotting.

RESULTS

We found that AF1q expression was elevated in podocytes treated with ADR than untreated cells. AF1q overexpression directly led to podocytes injury with increased levels of desmin and snail. Luciferase activity of TOPflash reporter was significantly increased in cells with AF1q overexpression than wild type cells whereas deletion of T-cell-factor-7 (TCF7) eliminated this effect. Immunoprecipitation assay evidenced that AF1q interacted with TCF7 and promoted both transcriptional and translational expressions of TCF7. Overexpression of AF1q increased protein expression of β-catenin. However, in podocytes with deletion of TCF7, AF1q was not able to promote β-catenin expression.

CONCLUSION

Our findings demonstrated that aberrant expression of AF1q may activate Wnt/β-catenin signaling and result in podocyte injury.

Podocytes

Podocytes are highly specialized cells of the kidney glomerulus that wrap around capillaries and that neighbor cells of the Bowman’s capsule. When it comes to glomerular filtration, podocytes play an active role in preventing plasma proteins from entering the urinary ultrafiltrate by providing a barrier comprising filtration slits between foot processes, which in aggregate represent a dynamic network of cellular extensions. Foot processes interdigitate with foot processes from adjacent podocytes and form a network of narrow and rather uniform gaps. The fenestrated endothelial cells retain blood cells but permit passage of small solutes and an overlying basement membrane less permeable to macromolecules, in particular to albumin. The cytoskeletal dynamics and structural plasticity of podocytes as well as the signaling between each of these distinct layers are essential for an efficient glomerular filtration and thus for proper renal function. The genetic or acquired impairment of podocytes may lead to foot process effacement (podocyte fusion or retraction), a morphological hallmark of proteinuric renal diseases. Here, we briefly discuss aspects of a contemporary view of podocytes in glomerular filtration, the patterns of structural changes in podocytes associated with common glomerular diseases, and the current state of basic and clinical research.

The role of the immune system in idiopathic nephrotic syndrome: a review of clinical and experimental studies

Idiopathic nephrotic syndrome (INS) is a multifactorial disease, characterized by proteinuria, hypoalbuminemia, edema and hyperlipidemia. Studies in humans and animal models have associated INS with changes in the immune response. The purpose of this article is to review clinical and experimental findings showing the involvement of the immune response in the pathogenesis of INS. The role of the immune system in INS has been shown by clinical and experimental studies. However, the pattern of immune response in patients with INS is still not clearly defined. Many studies show changes in the dynamics of T lymphocytes, especially the regulatory T cells. Alternatively, there are other reports regarding the involvement of the complement system and B lymphocytes in the pathophysiology of INS. Indeed, none of the immunological biomarkers evaluated were undeniably linked to changes in glomerular permeability and proteinuria. On the other hand, some studies suggest a link between urinary chemokines, such as IL-8/CXCL8 and MCP-1/CCL2, and changes in glomerular permeability and/or the deterioration of glomerulopathies. To understand the pathophysiology of INS, longitudinal studies are clearly needed. The characterization of the profile of the immune response might help the development of specific and individualized therapies, leading to clinical improvement and better prognosis.

The protection of selenium on adriamycin-induced mitochondrial damage in rat

Although adriamycin (ADR) exhibits high anti-tumor efficacy in vitro, its clinical use in cancer chemotherapy is limited due to its high renal toxicity. This study investigated the mechanism of ADR nephropathy and the protective effect of selenium on ADR-induced kidney damage by analyzing of the relationship between selenium and mitochondria. Rats were divided into four groups. The first group was injected with saline i.p. for 21 days, the second group received the 4 mg/kg i.p. ADR every alternate day for 8 days, the third group received the 50 μg/kg i.p. Se for 21 days, and the fourth group received the Se. ADR co-administration i.p. blood pressures were assessed, the mitochondrial membrane potential (MMP) was assessed, and the adenosine triphosphate (ATP) levels were determined. The total antioxidant (TAS) and oxidant status (TOS) in cytosol, the mitochondria of kidney cells, and plasma were measured. Mitochondrial TAS decreased and TOS increased in the ADR group compared to the Se group. ADR-treated rats showed significantly lower MMP than did the control and Se groups. MMP was significantly restored in the Se + ADR group through selenium treatment compared to the ADR group (p < 0.01). In the ADR group, a reduction in ATP content was seen compared to the control and Se groups (p < 0.01). ATP level was significantly restored through treatment with selenium in the Se + ADR group compared to the ADR group (p < 0.01). We concluded that selenium is effective in vivo against ADR-induced kidney damage via the restoration of TAS and TOS, which prevented mitochondrial damage.

Antroquinonol reduces oxidative stress by enhancing the Nrf2 signaling pathway and inhibits inflammation and sclerosis in focal segmental glomerulosclerosis mice

Oxidative stress, inflammation, and fibrosis are involved in the development and progression of focal segmental glomerulosclerosis (FSGS), a common form of idiopathic nephrotic syndrome that represents a therapeutic challenge because it has a poor response to steroids. Antroquinonol (Antroq), a purified compound, is a major active component of a mushroom, namely Antrodia camphorata, that grows in the camphor tree in Taiwan, and it has inhibitory effects on nitric oxide production and inflammatory reactions. We hypothesized that Antroq might ameliorate FSGS renal lesions by modulating the pathogenic pathways of oxidative stress, inflammation, and glomerular sclerosis in the kidney. We demonstrate that Antroq significantly (1) attenuates proteinuria, renal dysfunction, and glomerulopathy, including epithelial hyperplasia lesions and podocyte injury; (2) reduces oxidative stress, leukocyte infiltration, and expression of fibrosis-related proteins in the kidney; (3) increases renal nuclear factor E2-related factor 2 (Nrf2) and glutathione peroxidase activity; and (4) inhibits renal nuclear factor-κB (NF-κB) activation and decreases levels of transforming growth factor (TGF)-β1 in serum and kidney tissue in a mouse FSGS model. Our data suggest that Antroq might be a potential therapeutic agent for FSGS, acting by boosting Nrf2 activation and suppressing NF-κB-dependent inflammatory and TGF-β1-mediated fibrosis pathways in the kidney.

Prkdc participates in mitochondrial genome maintenance and prevents Adriamycin-induced nephropathy in mice

Adriamycin (ADR) is a commonly used chemotherapeutic agent that also produces significant tissue damage. Mutations to mitochondrial DNA (mtDNA) and reductions in mtDNA copy number have been identified as contributors to ADR-induced injury. ADR nephropathy only occurs among specific mouse inbred strains, and this selective susceptibility to kidney injury maps as a recessive trait to chromosome 16A1-B1. Here, we found that sensitivity to ADR nephropathy in mice was produced by a mutation in the Prkdc gene, which encodes a critical nuclear DNA double-stranded break repair protein. This finding was confirmed in mice with independent Prkdc mutations. Overexpression of Prkdc in cultured mouse podocytes significantly improved cell survival after ADR treatment. While Prkdc protein was not detected in mitochondria, mice with Prkdc mutations showed marked mtDNA depletion in renal tissue upon ADR treatment. To determine whether Prkdc participates in mtDNA regulation, we tested its genetic interaction with Mpv17, which encodes a mitochondrial protein mutated in human mtDNA depletion syndromes (MDDSs). While single mutant mice were asymptomatic, Prkdc/Mpv17 double-mutant mice developed mtDNA depletion and recapitulated many MDDS and ADR injury phenotypes. These findings implicate mtDNA damage in the development of ADR toxicity and identify Prkdc as a MDDS modifier gene and a component of the mitochondrial genome maintenance pathway.

Late effects of adriamycin single dose on fetal rat kidney-ultrastructural assessment

The purpose of the study was ultrastructural evaluation of long-lasting activity of an antibiotic from anthracycline group-adriamycin (ADR), on fetal kidneys from rat females which 4 weeks before fertilization were given a single dose of adriamycin intraperitoneally. The results showed the damage of glomerular filtration barrier (fusion of podocytes' foot processes) and degenerative lesions in tubular epithelial cells (EC). Those changes were described in literature in the case of adriamycin induced nephrotic syndrome in adult rats. If those lesions are due to increased glomerular permeability for proteins or cytotoxic activity of adriamycin can be decided after further biochemical tests of fetal urine and blood.

Effect of mycophenolate mofetil on the progression of adriamycin nephropathy

In order to assess the effects of mycophenolate mofetil (MMF) on the development of adriamycin-induced nephropathy, the development of this nephropathy in rats treated with MMF was compared to that in non-treated animals (group ADR + V) over 28 weeks. At weeks 8, 16 and 20, 24-h proteinuria of the treated group statistically differed from that of the non-treated group. However, no significant difference in proteinuria was observed thereafter between the groups. At the end of the experiment, there was no significant difference between both groups regarding the frequency of glomerular lesion (Group ADR + V: Md = 35%, P25 = 20%, P75 = 68%; Group ADR + MMF: Md = 27%, P25 = 9.5%, P75 = 54%); tubulointerstitial lesion index (Group ADR + V: Md = 7, P25 = 1.5, P75 = 9; Group ADR + MMF: Md = 8, P25 = 2, P75 = 9); glomerulosclerosis area (group ADR + V = 2779 microm2, P25 = 751.8 microm2, P75 = 3115 microm2; Group ADR + MMF = 1147 microm2, P25 = 3969.7 microm2, P75 = 1560 microm2); and, interstitial fibrosis area (Group ADR + V: Md = 218200 microm2, P25 = 78670 microm2, P75 = 282700 microm2 group ADR + MMF: Md = 136000, P25 = 25010, P75 = 255800 microm2). In conclusion, MMF caused a temporary reduction in proteinuria but did not change the severity of the renal lesion observed after 28 weeks.

Role of ticlopidine on adriamycin-induced nephropathy

The effect of ticlopidine on rats with adriamycin nephropathy was observed during 26 weeks. In the ticlopidine-treated nephrotic animals (TNG), proteinuria was less than in the untreated nephrotic animals (NG), but this difference was significant only at week 6 (TNG = 47.27 +/- 16.52 versus NG = 100.08 +/- 13.83 mg/24 h, p < 0.01) and week 26 (TNG = 157.00 +/- 28.73 versus NG = 217.00 +/- 21.73 mg/24 h, p < 0.01) after ADR injection. NG presented severe tubulointerstitial abnormalities with a tubulointerstitial lesion index of 3+. No difference in glomerular lesions was observed among the groups (NG median = 6%, TNG median = 4% and TCG median = 2%). The tubulointerstitial lesion index of TNG was less intense (median = 2+) but not different from those of the control groups (CG median = 1+; TCG median = 0+) nor NG (median = 3+). We concluded that the treatment with ticlopidine produced some partially beneficial effects but did not prevent the development of adriamycin-induced nephropathy.