Identification of agents that reduce renal hypoxia-reoxygenation injury using cell-based screening: purine nucleosides are alternative energy sources in LLC-PK1 cells during hypoxia.

Acute tubular necrosis is a clinical problem that lacks specific therapy and is characterized by high mortality rate. The ischemic renal injury affects the proximal tubule cells causing dysfunction and cell death after severe hypoperfusion. We utilized a cell-based screening approach in a hypoxia-reoxygenation model of tubular injury to search for cytoprotective action using a library of pharmacologically active compounds. Oxygen-glucose deprivation (OGD) induced ATP depletion, suppressed aerobic and anaerobic metabolism, increased the permeability of the monolayer, caused poly(ADP-ribose) polymerase cleavage and caspase-dependent cell death. The only compound that proved cytoprotective either applied prior to the hypoxia induction or during the reoxygenation was adenosine. The protective effect of adenosine required the coordinated actions of adenosine deaminase and adenosine kinase, but did not requisite the purine receptors. Adenosine and inosine better preserved the cellular ATP content during ischemia than equimolar amount of glucose, and accelerated the restoration of the cellular ATP pool following the OGD. Our results suggest that radical changes occur in the cellular metabolism to respond to the energy demand during and following hypoxia, which include the use of nucleosides as an essential energy source. Thus purine nucleoside supplementation holds promise in the treatment of acute renal failure.

Luteolin ameliorates cisplatin-induced acute kidney injury in mice by regulation of p53-dependent renal tubular apoptosis.

BACKGROUND: Cisplatin chemotherapy often causes acute kidney injury in cancer patients. The causative mechanisms of cisplatin-induced acute kidney injury include renal inflammation, activation of p53 tumour suppressor protein and tubular apoptosis. Luteolin, a flavone found in medicinal herbs and plants, has been reported to exhibit anti-inflammatory, antioxidant and anticarcinogenic activities. The purpose of this study was to investigate the anti-apoptotic effect of luteolin on cisplatin-induced acute kidney injury and the molecular mechanism. METHODS: C57BL/6 mice were treated with cisplatin (20 mg/kg) with or without treatment with luteolin (50 mg/kg for 3 days). Renal function, histological changes, degree of oxidative stress and tubular apoptosis were examined. The effects of luteolin on cisplatin-induced expression of renal p53, PUMA-α and Bcl-2 family proteins were evaluated. RESULTS: Treatment of mice with cisplatin resulted in renal damage, showing an increase in blood urea nitrogen and creatinine levels, tubular damage, oxidative stress and apoptosis. Treatment of cisplatin-treated mice with luteolin significantly improved renal dysfunction, reducing tubular cell damage, oxidative stress and apoptosis. Examination of molecules involving apoptosis of the kidney revealed that treatment of cisplatin increased the levels of p53 and its phosphorylation, PUMA-α, Bax and caspase-3 activity that were significantly decreased by treatment with luteolin. CONCLUSION: These results indicate that cisplatin induces acute kidney injury by regulation of p53-dependent renal tubular apoptosis and that luteolin ameliorates the cisplatin-mediated nephrotoxicity through down-regulation of p53-dependent apoptotic pathway in the kidney.

[Aristolochic acid induces renal tubular injury and inhibits expression of bone morphogenetic protein-7 mRNA in renal tissue of rats].

OBJECTIVE: To investigate the pathogenic mechanism of aristolochic acid nephropathy (AAN) by observing the renal tubular injury and the change of the expression of bone morphogenetic protein-7 (BMP-7) mRNA in renal tissue of rats induced by aristolochic acid (AA), an active constituent in Caulis Aristolochiae Manshuriensis (CAM). METHODS: Forty-six male Wistar rats were randomly divided into normal control group (n=20) and AA-treated group (n=26). Rats in AA-treated group were intragastrically administered with AA 20 mg/(kg.d), and rats in control group were treated with equal volume of potable water. At the end of the 4th, 8th and 12th week of administration, the 24 h-urine was collected by metabolic cage for detecting the activity of N-acetyl-beta-D-glucosaminidase (NAG) and the blood samples were obtained from abdominal aorta for detecting serum creatinine (SCr). Pathological change and the degree of injury of the kidneys were observed by microscopy. The expression of proliferative cell nuclear antigen (PCNA) was detected by immunohistochemical method, and mRNA expression of bone morphogenetic protein-7 (BMP-7) in the renal tissue was detected by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: Compared with the normal control group, the activity of NAG and the ratio of SCr vs body weight were markedly increased in rats of the AA-treated group after treatment (P<0.05 and P<0.01). Pathological section of renal tissue showed that most renal tubules had cloudy swelling, and vacuolar degenerating in tubular epithelial cells, with brush border dropping off, and parts of tubular basement membrane were exposed. The degrees of injuries were aggravated depending on treating time. The tubulointerstitial injury (TI) parameter in rats of AA-treated group was higher than that of the normal control group. The positive expression of PCNA was observed in the damaged tubular cells. The proliferation index of PCNA was significantly increased after 4- and 8-week treatment (P<0.01), but was decreased after 12-week treatment (P<0.05). The mRNA expression of BMP-7 was markedly decreased in the AA-treated group compared with the normal control group after 4-week treatment (P<0.05), and decreased with the extension of treatment time. CONCLUSION: AA can induce injury of the renal tubules, impair the cell regeneration, and inhibit the expression of BMP-7 mRNA in renal tissue. This may be one of the pathogenic mechanisms of AAN.

Ischemic acute tubular necrosis models and drug discovery: a focus on cellular inflammation.

Acute renal failure (ARF) is a common cause of mortality and morbidity in hospitalized patients. Ischemia is an important cause of ARF, and ARF caused by ischemic injury is referred to as ischemic acute tubular necrosis (ATN). There is growing evidence from models that ischemic ATN is associated with intrarenal inflammation. Consequently, intrarenal inflammation is an attractive target for the development of novel drug therapies for ARF. This review outlines ischemic ATN models, the pathophysiological roles of inflammatory cells such as T and B cells in ischemic ATN models, and effective T and B cell therapeutic reagents.

[Peritubular capillary injury in Chinese herb guan-mu-tong-induced acute tubular necrosis].

OBJECTIVE: To explore the role and mechanisms of peritubular capillary (PTC) injury in the progression of Chinese Herb guan-mu-tong (GMT, aristolochiae manshuriensis kom) induced acute tubular necrosis (GMT-ATN). METHODS: Renal biopsy tissue from 4 cases of GMT-ATN and 5 cases of antibiotic induced ATN (A-ATN) were included in the study. Tubulointerstitial injury was semi-quantitatively assessed. Immunohistochemical SP method was applied to reveal PTC as well as the expression of vascular endothelial growth factor (VEGF). Ultra microstructure of endothelial cells and basement membrane of PTC was detected by electronic microscopy (EM). 5 cases of minor mesangioproliferative non-IgA glomerulonephritis were selected as a control group. RESULTS: The density of PTC was decreased significantly in GMT-ATN, as compared with the A-ATN and control group (211.08 +/- 56.15 vs 413.54 +/- 66.59, 536.62 +/- 68.38, P < 0.01). Dilated and deformed PTC lumina were noted in GMT-ATN with some endothelial cells and basement membrane partially disrupted. Most endothelial cells were found to be swollen with vacuoles dispersed in the cell plasma. The basement membrane was partially shrunk and thickened. The expression of VEGF in renal tubular epithelial cells (RTEC) was much less in the GMT-ATN than that in A-ATN group 2.1 (0-3.86)% vs [42.5 (31.33-60.25)%, P < 0.01], even though it was higher than that in the control group [23.1 (18.2-39.5)%, P < 0.01]; the expression was correlated with PTC density. Close correlation was also found between RTEC regeneration and PTC density, as well as VEGF expression (r = 0.880 and 0.802 respectively, P < 0.01). CONCLUSIONS: PTC was markedly injured in GMT-ATN; this could be one of the cause for the continuously progressing tubulointerstitial damage. The low expression of VEGF in RTEC might contribute to the PTC injury process.

Protection effects of Taurine supplementation against cisplatin-induced nephrotoxicity in rats.

BACKGROUND: Taurine, which is the major intracellular free beta-amino acid, is known to be an antioxidant and a membrane-stabilizing agent. This study was designed to investigate the protective role of taurine supplementation against cisplatin-induced nephrotoxicity. METHODS: Male Wistar rats were divided into six groups and treated as follows: (1) saline-treated control drinking tap water, (2) saline-treated plus taurine-supplemented (1.5% taurine in the drinking water), (3) saline-treated plus taurine-depleted (3% beta-alanine in the drinking water), (4) cisplatin-treated, CDDP 6 mg/kg intraperitoneally, (5) taurine-supplemented plus CDDP-treated and (6) taurine-depleted plus CDDP-treated. Rats were sacrificed 7 days after CDDP treatment, and serum as well as kidneys were isolated and analyzed. RESULTS: CDDP-treated rats showed increased kidney weight as a percentage of total body weight, serum creatinine and BUN levels and decreased serum albumin and calcium levels. Also, CDDP treatment resulted in a depletion of kidney GSH content, a reduction in the kidney glutathione peroxidase (GSH-Px) activity and increased kidney MDA production level. Taurine supplementation attenuated CDDP-induced nephrotoxicity which was manifested by jeopardizing the elevation in serum creatinine and BUN levels and the reduction in serum albumin and calcium levels. Moreover, taurine supplementation restored kidney GSH content and GSH-Px activity and reduced platinum accumulation and MDA production levels in the kidney tissue following CDDP treatment. Histopathological examination of the kidney of CDDP-treated rats revealed tubular atrophy, tubular necrosis and desquamation of renal tubular cells. However, taurine supplementation protected against CDDP-induced histopathological changes. CONCLUSIONS: The data suggest that taurine supplementation effectively attenuates the accumulation of platinum within kidney tissue and counteracts the deleterious effect of CDDP on the renal tubular function.

Secondary oxalosis: a cause of delayed recovery of renal function in the setting of acute renal failure.

Oxalosis, or calcium oxalate deposition in the tissues, may develop in patients with inherited disorders of oxalate metabolism or can occur secondary to other diseases. In this study, a case of renal oxalosis probably secondary to excessive parenteral vitamin C administration in a patient with acute post-traumatic oliguric renal failure is reported. Oxalate deposits may have contributed to further worsening and delayed recovery of renal function. The elimination of the source of excess vitamin C and its presumed effect on oxalate production, together with enhanced removal of oxalate during aggressive dialysis, resulted in prompt recovery of renal function. Secondary oxalosis represents a possible cause of delayed recovery of renal function in patients with acute renal failure who are receiving vitamin C supplementation if excess dosage of that supplementation is given. Vitamin C supplementation, if utilized, should be carefully monitored in patients receiving artificial renal replacement therapy.

Assessment of the possible role of iron and copper in cisplatin-induced nephrotoxicity in the rat.

Nephrotoxic lesions induced by cisplatin in rats are characterized by acute tubular necrosis in the outer stripe of the medulla. The purpose of this study was to examine the potential role of changes in metal binding proteins, and iron and copper content in urine and renal tissue in cisplatin-induced nephrotoxicity. Cisplatin was administered intravenously to groups of 20 rats at single doses of 0, 1, 2.5, and 5 mg/kg and rats were sacrificed at 1, 2, 3 and 6 days after treatment. Increased serum BUN and creatinine were observed at a dose of 5 mg/kg cisplatin on day 2 through day 6. Increased urinary copper excretion coincided with necrosis and increased BUN and creatinine on day 3 in the high-dose group. Evidence of renal injury was apparent histologically as karyomegaly at all dose levels as early as 48 hours after injection of cisplatin, prior to increases in urinary copper levels. No change in the distribution of metal binding proteins (transferrin, ferritin, ceruloplasmin, and metallothionein) evaluated by immunohistochemical staining, was seen. Based upon these results, it is unlikely that changes in metal excretion play a primary role in cisplatin-induced nephrotoxicity however, changes in nuclear function indicated by karyomegaly may be involved in early renal injury.