EFFECTS OF NITRIC OXIDE SYNTHESIS INHIBITION ON FK506-INDUCED NEPHROTOXICITY IN RATS

This study was designed to evaluate the role of nitric oxide (NO) in FK506-induced nephrotoxicity by administering an inhibitor of NO synthesis, Nω-nitro-L-arginine methyl ester (L-NAME) to rats treated with FK506. After one week of treatment with FK506 (3.2 mg/kg/day, intramuscularly) and/or L-NAME (5 mg/100 mL of L-NAME in the drinking water), the arterial pressure, urinary NOx, and parameters for renal function were measured, and histological analysis of the kidney was made. In the L-NAME without FK506 group, L-NAME administration effectively inhibited urinary NOx excretion and increased mean arterial pressure (MAP) without any change in renal function. In the FK506 without L-NAME group, FK506 treatment showed increase in urinary NOx excretion and mild renal dysfunction. In the FK506 with L-NAME group, urinary NOx excretion was decreased by L-NAME administration and renal function was significantly worsened than FK506 without L-NAME group. The plasma creatinine, BUN and urinary N-acetyl-β-D-glucosaminidase increased 2-, 3-, and 3-fold, respectively and the creatinine clearance was reduced by 50% as compared with that in the FK506 without L-NAME group. Histological analysis revealed severe interstitial fibrosis and tubular atrophy in the FK506 + L-NAME treatment group. Thus, results suggest that NO synthesis is enhanced in the kidney during FK506-induced nephrotoxicity and that NO synthesis inhibition aggravates FK506-induced nephrotoxicity. NO may play a protective role attributable to the balance of vasoactive substances in FK506-induced nephrotoxicity.     

New morphological changes induced by FK506 in a short period in the rat kidney and the effect of superoxide dismutase and OKY-046 on THEM: the relationship of FK506 nephrotoxicity to lipid peroxidation and change in production of thromboxane A2 in the kidney

Juxtaglomerular (JG) hyperplasia and tubular damage along with a decrease in the urine creatinine level induced by FK506 in rat kidney have already been reported in previous paper by us [6]. In this paper, we document the relationship of FK506 nephrotoxicity to the change in the production of thromboxane (Tx) A₂ and the lipid peroxidation of the cellular membrane in the rat kidney in order to clarify its morphogenesis. The urinary excretion of TxB₂ increased with FK506 administration even on day 1 (P < 0.02). Histologically, OKY-046 (thromboxane synthetase inhibitor) decreased tubular damage, although JG hyperplasia was not eradicated, while biochemically the excretion of TxB₂ decreased significantly (P < 0.02), and both the decrease in the urine creatinine level and the increase in the N-acetyl-β,d -glucosaminidase (NAG) index were relatively smaller. Although the FK506-induced morphological and biochemical changes could not be prevented by the continuous administration of superoxide dismutase (SOD) 30000 U/kg daily, the malondialdehyde content in renal tissue removed 1 h after FK506 administration had increased. These data suggest that FK506 nephrotoxicity is related to the change in the production of TxA₂ and lipid peroxidation of the cellular membrane. However, other mechanisms such as the involvement of sympathomimetic effects of FK506 and other vasoconstrictive factors cannot be rules out.     

钙离子通道阻滞剂在预防他克莫司肾毒性中的作用

目的 观察他克莫司(FK506)肾毒性模型中钙离子代谢的变化情况,探讨钙离子通道阻滞剂地尔硫草(Dil)对FK506肾毒性的预防作用.方法 按公式将肾移植术后FK506、环孢素(CsA)和Dil的首剂治疗剂量换算成大鼠的治疗剂量.雄性SD大鼠24只随机分成对照组、CsA组(25 mg·kg-1·d-1)、FK506组(0.8 mg·kg-1·d-1)和FK506加Dil组(0.8 mg·kg-1·d-1及8 mg·kg-1·d-1),每组6只,用药4周后建立各组大鼠肾毒性模型.观察各组大鼠SCr、血电解质、肾组织的病理改变(HE染色)、电子显微镜F肾脏细胞内超微结构的改变.结果 CsA组和FK506组大鼠SCr值分别为(36.00±2.61)和(34.17±4.54)μmol/L,均高于FK506加Dil组和对照组[(28.50±2.07)和(29.17±3.43)μmol/L,P＜0.05].CsA组和FK506组大鼠血钙浓度分别为(2.00±0.04)和(2.05_4-0.04)mmol/L,均低于FK506加Dil组和对照组(P＜0.05).CsA组和FK506组均可观察到肾小管细胞轻微肿胀及空泡变性、线粒体肿胀及空泡化等病理改变.与FK506组和CsA组相比,FK506加Dil组上述各项指标的变化明显减轻或接近正常.结论 钙离子代谢紊乱可能介导了FK506引起的肾毒性,Dil可用于预防FK506的肾毒性.     

Functional and morphological changes in rat kidney induced by FK506 and its reversal by various vasodilators]

FK506, a newly developed immunosuppressive agent, has recently been used for human liver and kidney transplantation. The present study was carried out to assess the functional and morphological changes by acute or chronic administration of FK506 in heminephrectomized rats. FK506 was given intravenously at the dose of 0.384 mg/kg/hr for 90 min in acute experiment. FK506 was administered by gastric gavage at doses of 1, 2.5, 5 mg/kg for 21 days. Blood and urinary biochemistry were monitored every week. Inulin and PAH clearance studies were conducted during the infusion of FK506 for acute study, and at day 21 for chronic study. Some of the rats were treated with diltiazem (Dilt), captopril or prazosine for 21 days to prevent FK506 nephrotoxicity. Acute infusion of FK506 did not change renal and systemic hemodynamics. Creatinine clearance showed a dose dependent decrease by 10-20% in the rats with chronic administration of FK506. Inulin/PAH clearance indicated a decrease in glomerular filtration rate and renal plasma flow with an increase in renal vascular resistance. The renal histology showed vacuolization in proximal tubuli and media of smooth muscle cells of arterioles. The administration of Dilt functionally and morphologically improved renal impairment induced by FK506. In conclusion, FK506 induces a dose dependent decrease in renal function with significant histological changes in tubuli and arterioles in rat kidney. Intracellular calcium deregulation seems to be involved in FK506-induced nephrotoxicity.     

Renal complications and development of hypertension in the European study of FK 506 and cyclosporin in primary liver transplant recipients

Abstract We examined the occurrence of renal complications and hypertension in 540 primary liver recipients entered into the European liver trial comparing primary FK 506 to a cyclosporin A based immunosuppression regimen (CBIR). No difference in serious renal impairment or mean creatinine levels was observed with similar rates of "kidney failure" (FK 506 9.4% vs. CBIR 7.3%) and dialysis requirements (FK 506 12% vs. CBIR 11%). "Abnormal kidney function", a less serious parameter of renal impairment, was reported in 89 recipients (33 %) in the FK 506 group versus 58 (21%) in the CBIR group ( P <0.01). Development of this complication was associated with elevated intravenous FK 506 dosing schedules, with the mean cumulative dose 43% higher than treated patients with unaffected kidney function. In a later cohort of patients where intravenous dosing was lower, no significant difference in renal complications was detectable. The 6-month prevalence rate of systemic arterial hypertension was noted to be lower in the FK 506-treated patients compared to the CBIR group [33 (17.2%) vs. 47 (25.7%)].     

转化生长因子-β1在他克莫司肾毒性中的作用

目的 观察转化生长因子(TGF)-β1在他克莫司大鼠肾毒性中的作用.方法 将SD大鼠24只随机分成对照组、CsA组、FK506组和FK506+Dil组,用药4周后建立起各组大鼠模型.观察各组大鼠的肾功能,应用免疫组织化学技术检测各组大鼠TGF-β1的表达.结果 FK506组大鼠的血肌酐值为(34.17±4.54)μmol/L,肌酐清除率为(0.58±0.39)ml·min-1·100g-1,与对照组比较差异有统计学意义(P<0.05).FK506组TGF-β1的阳性表达率均为100%(6/6),对照组TGF-β1的阳性表达率为16%(1/6),两者差异有统计学意义(P<0.05). 结论 TGF-β1可能介导了FK506引起的肾毒性.     

Tetrahydrocurcumin Ameliorates Tacrolimus-Induced Nephrotoxicity Via Inhibiting Apoptosis

BackgroundCalcineurin inhibitors are effective immunosuppressive agents, but associated adverse effects such as nephrotoxicity may limit efficacy. Tacrolimus (FK506) is an immunosuppressive drug used mainly to lower the risk of organ rejection after allogeneic organ transplant. Adverse effects of FK-506 can prompt patients to end treatment despite the efficacy. In the present study, we investigated the protective effect and mechanism of tetrahydrocurcumin (THC) on FK506-induced renal damage, apoptosis, and oxidative stress to evaluate its possible use for kidney protection.Materials and MethodsThe effect of THC on FK506-induced kidney cell damage was investigated in LLC-PK1 cells. LLC-PK1 cells were pretreated with THC at concentrations of dose for 2 hours followed by addition of FK506 for 24 hours. LLC-PK1 cells were treated with FK506 and THC, and cell viability and glutathione was measured. The number of apoptotic cells was measured using an annexin V/propidium iodide staining with flow cytometry. The effect of apoptosis by THC in LLC-PK1 cells was determined by measuring the caspase-9, caspase-3, B-cell lymphoma-2 (Bcl-2), and Bcl-2-associated X protein levels using Western blotting analyses.ResultsFK506-induced LLC-PK1 renal cell damage was markedly ameliorated by THC treatment. THC protected LLC-PK1 cells by preventing FK506-induced glutathione decrease. THC protects against FK506-induced apoptosis in LLC-PK1 cells. Apoptosis was significantly decreased, and Bcl-2 was elevated in the THC-treated group. Bcl-2-associated X protein, caspase-3, and caspase-9 were decreased in the THC-treated group.ConclusionThese results collectively provide therapeutic evidence that THC ameliorates the FK506-induced renal damage via antioxidant effect and apoptosis inhibition.     

Urinary Enzymes as Biomarkers of Renal Injury in Experimental Nephrotoxicity of Immunosuppressive Drugs

Urinary excretion of N-acetyl-β-D-glucosaminidase (NAG) and of alanine-aminopeptidase (A AP) was studied after administration of cyclosporine A (CSA A), FK 506, or the corresponding vehicles to salt-depleted rats. On days 7, 14, and 28 after treatment for CSA and day 14 after treatment for FK 506, measurements of the urinary enzymes, serum creatinine (S_cr), creatinine clearance (Cl_Cr), and blinded renal histology were done. After 1 week on CSA there was a dramatic increase of 489% in the urinary excretion of AAP (162.6 IU/g Cr, CSA vs. 27.6 IU/g Cr control, p <.03), a significant decrease of 32% in Cl_Cr, a significant increase of 41% in S_Cr, and mild proximal tubular atrophy and vacuolization. After 2 or 4 weeks of CSA treatment there were no more differences in the urinary AAP between CSA and control rats, but the urinary excretion of NAG was increased: 29.6 IU/g Cr, CSA vs. 20.9 IU/g Cr, control, p <.03 on day 14 and 26.9 IU/g Cr, CSA vs. 21.5 IU/g Cr, control, p <. 008 on day 28. At the same time there was a progressive decline of the Cl_Cr, a progressive increase in the S_Cr, and an increase in the severity of the histological lesion. After 14 days of treatment with FK 506 we observed a striking elevation in urinary AAP (62.6 IU/g Cr, FK 506 vs. 36.0 IU/g Cr, control, p <.01) consistent with a significant decrease in Cl_Cr, a significant increase in S_Cr, and a moderate proximal tubular vacuolization and atrophy. Thus, there was an early and significant increase in enzymuria after treatment with both drugs, even in the presence of mild histological lesion, pointing to the values of AAP and NAG as markers of renal injury in CSA and FK experimental nephrotoxicity.     

FK506对糖尿病大鼠早期肾脏肥大的抑制作用及机制

目的 探讨FK506对糖尿病大鼠早期肾脏肥大的抑制作用及机制。 方法 应用链脲菌素(65 mg/kg)腹腔注射建立大鼠糖尿病模型。每日分别给予FK506 0.5、1.0 mg/kg 灌胃，共4周。观察大鼠肾质量/体质量、尿白蛋白排泄率（AER）、Ccr及肾组织病理形态学变化。应用Western印迹和免疫组化方法检测肾组织钙神经蛋白(calcineurin，CaN)、1αⅣ型胶原、α-平滑肌肌动蛋白(α-SMA)及转化生长因子β1(TGF-β1)蛋白表达。 结果 FK506 1.0组大鼠相对肾质量明显低于模型组(P < 0.05)。FK506 0.5与1.0组大鼠AER水平与肾小球平均体积明显低于模型组(P < 0.05、0.01)。FK506 1.0组肾小管间质?鄄损伤指数也明显低于模型组(P < 0.01)。Western印迹显示，模型组肾组织CaN蛋白表达较对照组增加2.4倍；FK506 0.5与1.0 组肾组织CaN蛋白表达比模型组下降38.0%与73.2%。模型组肾组织1αⅣ型胶原、α-SMA及TGF?鄄β1蛋白表达明显高于对照组；FK506组肾组织上述蛋白表达明显低于模型组(P < 0.05、0.01)。 结论 FK506对糖尿病大鼠早期肾脏肥大有明显抑制作用，其机制与下调肾组织增高的CaN表达有关。     

Inhibition of nuclear factor-kappaB activation by pyrrolidine dithiocarbamate prevents chronic FK506 nephropathy

BACKGROUND: Chronic tacrolimus (FK506) nephrotoxicity is characterized by renal fibrosis with interstitial inflammation. Since nuclear factor-kappaB (NF-kappaB) plays a key role in chronic inflammatory diseases including renal disease, the present study was conducted to elucidate the role of NF-kappaB in the pathogenesis of chronic FK506-induced nephropathy. METHODS: FK506 (1 mg/kg/day, SC) was administered daily to rats maintained on low sodium diet for 42 days. Some rats were treated with a putative NF-kappaB inhibitor, pyrrolidine dithiocarbamate (PDTC; 100, 200 mg/kg/day, by gavage). The renal function, renal histology, renal NF-kappaB-DNA binding activity and gene expression profile were examined. RESULTS: FK506 caused a decline in glomerular filtration and induced characteristic renal morphologic changes including arteriolopathy, tubular atrophy and interstitial fibrosis. FK506 markedly activated renal cortical NF-kappaB-DNA binding. PDTC administration inhibited NF-kappaB-DNA binding activity in a dose dependent manner. With higher dose, NF-kappaB-DNA binding activity was decreased to a control level. PDTC had little effect on FK506-induced renal dysfunction. Renal cortical monocyte/macrophage infiltration observed in FK506-treated rats was dramatically suppressed by PDTC. FK506 up-regulated renal cortical gene expression of chemoattractant proteins, monocyte chemoattractant protein-1 (MCP-1) and osteopontin. PDTC significantly blocked MCP-1 gene expression but had no effect on osteopontin gene expression. Tubular atrophy and tubulointerstitial fibrosis, but not arteriolopathy, were significantly attenuated by PDTC. FK506 increased renal mRNA expression of fibrogenic molecules and extracellular matrices that also were attenuated by PDTC treatment. CONCLUSIONS: NF-kappaB plays an important role in mediating cortical monocyte/macrophage infiltration and in the pathogenesis of tubular injury and interstitial fibrosis in experimental FK506-induced chronic nephropathy.     

Comparison of expression of TGF-beta1, its receptors TGFbeta1R-I and TGFbeta1R-II in rat kidneys during chronic nephropathy induced by cyclosporine and tacrolimus

OBJECTIVE: Chronic rejection is a major cause of graft dysfunction after kidney transplantation. Long-term treatment with cyclosporine (CsA) or tacrolimus (FK506) results in chronic nephrotoxicity. Transforming growth factor-beta1 (TGFbeta1) and its receptors type I (TR-I) and type II (TR-II) have been known to contribute to this side effect. The expression of TGF-beta1, TR-I, and TR-II in rat kidneys has not been compared during chronic nephropathy induced by CsA or FK506. METHODS: Rat models of chronic CsA- or FK506-induced nephropathy were established using Sandimun Neoral or Prograf administration. The kidneys were dissected and TGF-beta1, TR-I, and TR-II proteins and TR-I and TR-II mRNAs measured by immunohistochemistry and in situ hybridization, respectively, to compare the results of the two groups. RESULTS: The functional and morphologic studies showed that in the rats the nephrotoxic effects of FK506 were not as significant as those of CsA. The results of immunohistochemistry and in situ hybridization showed that the expression of renal TGFbeta1, TR I, TR-II proteins and TR and TR II mRNA in the FK506 group were lower than those in the CsA groups. CONCLUSION: These results showed that both FK506 and CSA display nephrotoxicity, but that the nephrotoxicity of FK506 was less than that of CsA in chronic nephropathy.     

Mechanism of FK 506/520 action on rat renal proximal tubular Na+, K+-ATPase activity.

BACKGROUND: The neurotransmitter in renal sympathetic nerves, norepinephrine (NE), regulates the activity of proximal tubule (PT) Na+,K+-ATPase in a bidirectional manner via stimulation of alpha- and beta-adrenoceptors. The stimulatory alpha-adrenergic pathway is mediated by calcineurin, the target molecule for FK 506 and related compounds. We examined whether the FK 506 analogue FK 520, by interrupting the calcineurin-mediated alpha-adrenergic signaling pathway, enhance the inhibitory beta-adrenergic effect of NE on PT Na+,K+-ATPase activity. METHODS: The effects of three days of treatment with FK 520 were examined on rat renal PT Na+,K+-ATPase activity, measured as ouabain-sensitive ATP hydrolysis in single, microdissected PT segments. Renal function studies, including glomerular filtration rate (GFR) and urinary excretion of N-acetyl-3-D-glucoseaminidase (NAG), were examined using conventional clearance techniques after three days of treatment with FK 506. RESULTS: FK 520 treatment induced a pronounced and dose-dependent decrease in PT Na+,K+-ATPase activity. This effect was completely reversed by the competitive FK 520 antagonist, L 685 818, indicating that the effect was dependent on inhibition of calcineurin. To test whether the FK 520-induced decrease in Na+, K+-ATPase activity was mediated by enhanced beta-adrenoceptor signaling, the FK 520 effect was examined in rats pretreated with a beta-adrenoceptor antagonist (propranolol) or rats subjected to renal denervation. Both of these procedures prevented the FK 520-induced decrease in Na+,K+-ATPase activity. Thus, during FK 520 treatment, renal sympathetic nerves mediate an inhibitory effect on PT Na+,K+-ATPase activity via beta-adrenoceptors. Propranolol pretreatment also prevented FK 506-induced decreases in GFR and urinary excretion of NAG, an index of PT dysfunction. CONCLUSIONS: The results support the hypothesis that the net effect of the neurotransmitter NE on Na+,K+-ATPase activity is dependent on the balance between the alpha- and beta-adrenergic signaling pathways and suggest that agents that interfere with these pathways may, by altering the activity of tubular Na+,K+-ATPase, also alter the function of the renal tubular epithelial cell.     

Renal Blood Flow and Serotonin Metabolism in Tacrolimus Treated Rats

Background: Serotonin (5-HT) is a potent vasoconstrictor and activator of platelets, endothelial cells and vascular smooth muscle cells. The result of activation by serotonin is platelet aggregation and vasoconstriction. The aim of the present study was to evaluate the role of serotonin metabolism as a mediator of tacrolimus (FK 506) nephrotoxicity.
Methods: The whole blood and plasma levels of serotonin and its major metabolite (5-hydroxyindoleacetic acid: 5-HIAA) as well as renal cortical blood flow were investigated in rats administered FK 506 at doses of 4, 6 or 8mg/kg b.w. for 14 consecutive days.
Results: Renal cortical blood flow declined in a dose-dependent manner in the rats given FK 506, whereas serum creatinine remained unaltered following FK 506 administration. Although there was no significant change in serotonin, the whole blood and plasma 5-HIAA levels increased significantly following FK 506 administration.
Conclusion: FK 506 may cause acute nephrotoxicity by decreasing renal blood flow and the increase of 5-HIAA suggests some role of serotonin metabolism in the development of FK 506 nephrotoxicity.     

Increased nitric oxide inactivation by reactive oxygen species in lead-induced hypertension.

BACKGROUND: We have recently found evidence for increased reactive oxygen species (ROS) in rats with lead-induced hypertension. We hypothesized that increased ROS activity may contribute to hypertension by enhancing inactivation of nitric oxide (NO) in this model. METHODS: Rats were treated for 12 weeks with either lead acetate (100 p.p.m.) alone (Pb group) or lead acetate plus vitamin E-fortified food (5000 U/kg rat chow, Pb + E group). The control animals were fed either regular rat chow or a vitamin E-fortified diet. Blood pressure, creatinine clearance, and urinary excretion of stable NO metabolites (NOx) were monitored, and plasma and tissue abundance of nitrotyrosine, which is the footprint of NO oxidation by ROS, were determined. RESULTS: The Pb group showed a marked rise in blood pressure, a significant increase in plasma and kidney, heart, liver, and brain nitrotyrosine abundance, and a substantial fall in urinary NOx excretion. Concomitant administration of high-dose vitamin E in the Pb + E group ameliorated hypertension and normalized both urinary NOx excretion and tissue nitrotyrosine without altering tissue lead content. However, vitamin E supplementation had no discernible effect on either blood pressure or nitrotyrosine abundance in the normal controls. CONCLUSIONS: These findings point to enhanced ROS-mediated inactivation and sequestration of NO, which can potentially contribute to hypertension, tissue damage, and reduced urinary NOx excretion in rats with lead-induced hypertension. The beneficial effects of high-dose vitamin E on blood pressure, tissue nitrotyrosine burden, and urinary NOx excretion support the role of increased ROS activity in the pathogenesis of these abnormalities in this model.     

他克莫司抗同种肾移植排斥反应的临床研究(附136例报道)

目的 研究他克莫司（ＦＫ５０６）在同种肾移植术后抗排斥反应的效果及毒副作用。方法 １３６例肾移植患者在术后２４ｈ开始服用ＦＫ５０６,起始量０．１５ｍｇ．ｋｇ＾－１,ｄ＾－１,同时口服霉酚酸酯（ＭＭＦ）１．０ｇ／ｄ、泼尼松（Ｐｒｅｄ）３０ｍｇ／ｄ。观察ＦＫ５０６的治疗效果、理想的治疗窗及毒副反应。结果 肾移植术后１３６例应用ＦＫ５０６的患者中,肾功能２～７ｄ恢复正常为９６例,８～１５ｄ恢复正常为２３     

Possible role of nitric oxide in the protective effect of resveratrol in 5/6th nephrectomized rats

BACKGROUND: Nitric oxide (NO) plays an important role in the modulation of glomerular disease. The renal protective effect of resveratrol (RVT), a polyphenolic phytoalexin, was investigated in the 5/6th nephrectomized rats. MATERIALS AND METHODS: Resveratrol (5 mg/kg, PO) was administered for 12 weeks to 5/6th nephrectomized (NX) rats together with and without nitro L-arginine methyl ester (L-NAME) (10 mg/kg, IP). We evaluated the effect of these agents on proteinuria, hypertension, renal function, glomerulosclerosis, and urinary excretion of nitric oxide metabolites. RESULTS: 5/6th NX resulted in elevation in systolic blood pressure (SBP), reduced the urinary excretion of NO metabolites, increased urinary protein excretion, and deranged renal function and glomerulosclerosis. Treatment of animals with resveratrol significantly attenuated the increase in SBP, preserved the normal renal function, reduced the urinary protein excretion, increased the urinary excretion of NO metabolites, and prevented the glomerulosclerosis. Co-administration of animals with L-NAME along with resveratrol prevented the protection observed with resveratrol. CONCLUSION: These findings indicate that resveratrol exerts its protective effect in 5/6 NX rats through a nitric oxide pathway.     

Tacrolimus Induces Glomerular Injury via Endothelial Dysfunction Caused by Reactive Oxygen Species and Inflammatory Change

Background/Aims: The immunosuppressive drug tacrolimus (FK506) is used clinically to reduce the rejection rate in patients with kidney transplantation; however, the resultant nephrotoxicity remains a serious problem. In the present study we attempted to elucidate the mechanisms of glomerular injury induced by FK506 and the renoprotective effects of the angiotensin II receptor blocker telmisartan. Methods: Seven-week-old male Wistar rats were divided into three groups: vehicle group, FK506 group, and FK506 + telmisartan group. After 8 weeks, we assessed kidney function and renal morphological changes including oxidative stress. We also assessed the effect of FK506 in human glomerular endothelial cells (hGECs) with regard to reactive oxygen species (ROS). Results: FK506 induced ROS production via activation of NAD(P)H oxidase in the glomeruli. Expression of ICAM mRNA was increased in glomeruli from the FK506 group. These effects resulted in macrophage infiltration into the glomeruli. FK506 directly promoted NAD(P)H oxidase activity and accelerated production of ROS in hGECs. Conversely, cotreatment with telmisartan inhibited both NAD(P)H oxidase activity and production of ROS. Conclusion: These findings suggest that glomerular injury resulting from FK506 is caused by oxidative stress mediated by activation of NAD(P)H oxidase and that telmisartan exerts a renoprotective effect via antioxidative activity.     

Hydrogen peroxide mediates FK506-induced cytotoxicity in renal cells

BACKGROUND: The nephrotoxicity induced by immunosuppressant FK506 remains a serious clinical problem, and the underlying mechanism has not been completely understood. The present study was undertaken to determine the role of hydrogen peroxide in FK506-mediated cytotoxicity in a porcine renal proximal tubular cell line, LLC-PK1 cells, and human embryonic kidney (HEK293) cells. METHODS: Cytotoxicity was estimated by crystal violet and lactate dehydrogenase release assays. The activity of reactive oxygen species (ROS) was detected by flow cytometry. FK506-induced cell death was examined in the presence of the hydrogen peroxide scavenger, catalase, or a scavenger of hydroxyl radicals, sodium benzoate. As a control, FK506-induced cell death was also measured in the presence of superoxide anion inhibitor, 4,5-dihydroxy-1,2-benzene disulfonic acid (Tiron), TEMPO, or overexpressed human manganese superoxide dismutase (MnSOD). Catalase was also used in tumor necrosis factor-alpha (TNF-alpha)-induced cell injury to determine whether the enzyme specifically protected cells against FK506-mediated cytotoxicity. RESULTS: FK506 induced cell death in a dose-dependent manner and coincided with a dose-dependent increase in ROS activity. Abrogation of FK506-mediated ROS by catalase and N-acetylcysteine blunted FK506-induced cell death. Furthermore, overexpression of catalase, sodium benzoate, and deferoxamine inhibited the cytotoxic effect of FK506. In contrast, Tiron, TEMPO, or overexpression of human MnSOD failed to show cytoprotection. In fact, TEMPO or expression of MnSOD enhanced the effect of FK506. Catalase did not significantly affect TNF-alpha-induced cell injury. CONCLUSION: Catalase is uniquely required in cellular protection against FK506 cytotoxicity, which suggests an important role for hydrogen peroxide in the cellular actions of FK506.     

FK 506 reduces the injury experienced following renal ischemia and reperfusion.

The effect of FK 506 pretreatment on renal ischemia and reperfusion (I/R) injury was investigated. Adult male rats were assigned to one of two groups (20 animals each). Group 1 (controls) received 0.5 mL saline while group 2 received FK 506 (0.3 mg/kg) intravenously 24 h prior to the induction of renal ischemia. After a 60-min period of ischemia of the right kidney, a left nephrectomy was performed. Blood for BUN, creatinine, and tumor necrosis factor (TNF) was obtained prior to ischemia and on days 1, 2, 3, 5, 7, and 10. All surviving animals were sacrificed at day 10. FK 506 pretreatment reduced the serum levels of BUN (p less than .02), creatinine (p less than .02) and TNF (p less than .05) as compared to that seen in controls. Based upon these data, it appears that: (a) renal ischemia induces the release of TNF; (b) FK 506 pretreatment inhibits TNF production; and (c) FK 506 reduces renal injury association with I/R.