Clusterin (6. Renal Toxicity)

Gentamycin

Adult lewis rats were treated with 100 mg/kg/day of gentamicin sulfate for 12 days. Urine, serum, and tissue levels of clusterin protein were measured, as were urinary n-acetyl beta-glucosaminidase (NAG) and serum creatinine levels. Induction of renal injury by gentamicin was detectable within 4 days by increased levels of urinary n-acetyl beta-glucosaminidase (from 280 +/-66 (mean +/-SD) to 910 +/-210 nmol/mg creatinine), and within 9 days of initiating gentamicin treatment by increased serum creatinine (from 0.5 +/- 0.1 to 1.2 +/-0.4 mg/dl). Paralleling these changes, renal, urinary, and serum levels of clusterin increased 10-, 116-, and 3-fold (P less than 0.05). Treatment with gentamicin sulfate did not increase clusterin levels in the seminal vesicle, ventral prostate, testis, or epididymis. The measurement of urinary or serum clusterin may play a role in the early detection of renal injury ^Ref .

LLC-PK(1) cells were incubated with varying concentrations of gentamicin in serum-free media, and cytotoxicity was quantified by lactate dehydrogenase release and confirmed by vital dye exclusion. A dose-dependent increase in cytotoxicity occurred with gentamicin concentrations up to 27 mg/ml. Clusterin decreased cytotoxicity in a dose- and time-dependent manner at 6, 12, and 24 h, whereas albumin, used as a control protein, had no effect. In contrast to the aminoglycoside model, when cells were injured by depletion of ATP, clusterin had only a minimally protective effect. LLC-PK(1) cells did not express megalin, a receptor that can mediate the uptake of both clusterin and aminoglycosides into proximal tubule cells. Uptake of gentamicin into LLC-PK(1) cells was observed despite the absence of megalin. In conclusion, clusterin specifically protects against gentamicin-induced renal tubular cell injury by a megalin-independent mechanism ^Ref .

Cyclosporine A

A study examined the expression of the clusterin gene in the kidney during the development of cyclosporine (CyA)-induced nephrotoxicity in the rat using in situ hybridization histochemistry. Female Sprague-Dawley rats (170 g) were divided into experimental or control groups and were given intraperitoneal injections of CyA (25 mg/kg) or vehicle respectively for 2, 4 and 6 weeks. Kidneys from animals sacrificed at these times were fixed in 4% paraformaldehyde and embedded in paraffin. Tissue sections were hybridized using either a sense or antisense riboprobe complementary to clusterin mRNA which was labelled with 32P-UTP. Clusterin gene expression was detected in scattered tubules in kidneys from control animals. Expression of clusterin in cortical collecting ducts of CyA-treated animals was evident at 2 weeks and increased substantially at 4 and 6 weeks. Clusterin expression was also seen in afferent arterioles, the glomerular capsule and transitional epithelium of the renal pelvis of kidney sections from rats treated with CyA for 6 weeks. No labelling above background was seen at any time with the sense probe. Renin immunostaining in afferent arterioles of kidney sections from animals treated with CyA showed a marked increase after 4 and 6 weeks of CyA treatment ^Ref .

Puromycin

Male Wistar rats (weighing 251 +/- 16 g) were treated with puromycin aminonucleoside (PAN: 15 mg/100 g body wt, subcutaneously; n = 7) or vehicle (control; n = 8). The kidneys were harvested 6 d after treatment, when rats were nephrotic. Clusterin mRNA was markedly induced in the kidneys of nephrotic rats (8.5-fold versus control). Immunohistoche­mistry studies demonstrated clusterin primarily in tubules in the cortex and medulla. Many of the tubules staining for clusterin were dilated but had no other differentiating morphologic features. Increased numbers of proliferating tubular cells were seen at 6 d, but there was no correlation between these cells and clusterin staining. In contrast to the extent and pattern of clusterin staining, vimentin was seen in only sporadic, dilated tubules, in addition to its expected glomerular localization. An increase in clusterin mRNA was not seen 1, 2, or 4 d after PAN injection. In conclusion, tubular epithelial cell induction of clusterin occurs in the kidneys of nephrotic rats. The appearance of clusterin precedes the development of tubulointerstitial disease and may be a response to the proteinuria ^Ref .

Cisplatin

Sprague-Dawley rats were treated with intravenous cisplatin (6 mg/kg) or vehicle. Serum creatinine concentrations were measured and kidneys harvested at 1, 2, and 5 days. Marked induction of clusterin mRNA was seen only at 5 days, a time when serum creatinine concentration was the highest. Histology of kidney tissue 5 days after cisplatin administration revealed marked tubular necrosis localized to the outer stripe of the outer medulla, a region rich in proximal tubules. Immunohistoche­mistry and in situ hybridization at 5 days demonstrated clusterin primarily in the inner stripe of the outer medulla. In conclusion, expression of clusterin follows renal injury with cisplatin at a time corresponding to the morphologic evidence of tubular necrosis and cell detachment; quite surprisingly, such expression occurs at a site distant from the primary injury ^Ref .

Glycerol

In glycerol-induced acute renal failure, a model of rhabdomyolysis, clusterin mRNA was markedly increased 24 hours after injection of glycerol (control 97 +/- 21 versus glycerol 3644 +/- 134 optical density units; p < 0.001). Immunohistochemical clusterin was also increased in glycerol-treated rats with tubules in both cortex and medulla staining for clusterin. In vitamin e and selenium deficiency, clusterin mRNA was increased 9 weeks after initiation of the deficient diet (control 97 +/- 13 versus deficient 1137 +/- 403 optical density units; p < 0.04) as were the number of tubules staining for clusterin. Since renal injury is instigated in the glycerol model by muscle damage, we tested the effect of muscle extract on clusterin expression in vitro. A homogenate of skeletal muscle induced clusterin mRNA and this induction was not associated with disruption of cell membranes and was not inhibited by cycloheximide treatment, but was blocked by actinomycin D. Since increased generation of hydrogen peroxide is a pivotal biochemical lesion in both in vivo models, we tested the effect of peroxide to induce clusterin in vitro; no such induction occurred. Thus, renal tubular clusterin expression was increased in both acute glycerol-induced renal failure and chronic vitamin E and selenium deficiency, two in vivo models of oxidant injury to the kidney. In vitro induction of clusterin can occur and can be dissociated from cell injury ^Ref .

Nefiracetam

the occurrence of renal papillary necrosis (RPN), seen only in dogs after repeated oral administration of nefiracetam, a neurotransmission enhancer, at a relatively high dose, is because of inhibition of renal prostaglandin synthesis by the nefiracetam metabolite M-18. By Western blot and quantitative real-time RT-PCR analysis with renal morphological aspects, individual findings showed that renal clusterin mRNA was increased in dogs with severe renal injury. Changes in renal clusterin mRNA may reflect the progression or severity of RPN ^Ref .

In a study, a single cell suspension of renal epithelial (LLC-PK1) cells was treated with purified human clusterin, resulting in time- and dose-dependent cell aggregation. Electron microscopy of the cell aggregates demonstrated cell junction and lumen formation. To determine the effect of clusterin on cell adhesion, tissue culture plates were coated with clusterin, fibronectin, PBs, or albumin. Clusterin and fibronectin promoted cell adhesion to the same extent. The adhesion to clusterin was dose dependent and specific, as a monoclonal antibody against clusterin inhibited cell adhesion to clusterin but not fibronectin. Perterbations of the cytoskeleton may underlie the alterations in cell attachment which occur in renal injury. Induction of clusterin mRNA was seen after disruption of both microtubules and microfilaments and after inhibition of cell-substratum interactions. In conclusion, clusterin is a potent renal epithelial cell aggregation and adhesion molecule. It is speculated that clusterin functions to promote cell-cell and cell-substratum interactions which are perturbed in the setting of renal injury, thereby preserving the integrity of the renal epithelial barrier ^Ref .

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