Prevention and complete reversal of cyclosporine A-induced renal vasoconstriction and nephrotoxicity in the rat by fenoldopam

The primary mechanism of cyclosporine A-induced nephrotoxicity involves renal vasoconstriction. In the present study, we have tested the effects of fenoldopam, a dopamine DA1, receptor agonist with renal vasodilator properties, on the changes in renal function induced by acute and subacute administration of cyclosporine A. In inactin-anesthetized rats, acute administration of cyclosporine A (100 mg/kg i.p.) significantly decreased paraaminohippuric acid (PAH) and inulin clearances. Fenoldopam, at a dose (10 micrograms/kg.min) which alone significantly increased PAH and inulin clearances, completely prevented the cyclosporine A-induced reductions in renal function. Similarly, subacute administration of cyclosporine A (20 mg/kg.day for 3 days) resulted in significant reductions in base-line PAH and inulin clearances which were normalized by administration of fenoldopam. These data indicate that administration of fenoldopam can both prevent and completely reverse cyclosporine A-induced renal vasoconstriction and nephrotoxicity.     

Mechanism of cyclosporine A-induced renal vasoconstriction in the rat

The use of the immunosuppressant cyclosporine A (CSA) is limited by its toxicity. Both acute and chronic administration of CSA lead to renal vasoconstriction and decreased renal blood flow and glomerular filtration rate. The present studies were designed to elucidate the mechanism(s) involved in acute CSA-induced changes in renal hemodynamics. Infusion of CSA resulted in a concentration-dependent increase in perfusion pressure in isolated rat kidneys perfused at constant flow. Phenoxybenzamine blunted this response, and therefore a small component of CSA-induced renal vasoconstriction can be attributed to CSA-induced norepinephrine release from nerve terminals in this preparation. The response was antagonized profoundly, but not blocked completely, by nifedipine and methoxyverapamil, consistent with the hypothesis that a large component of CSA-induced vasoconstriction is mediated by Ca++ influx through potential-operated channels in vascular smooth muscle cells, and perhaps in nerve terminals as well. However, CSA-induced activation of such channels cannot account entirely for CSA-induced vasoconstriction because, in the presence of K-depolarization and Ca++ channel blockade, CSA still produced a small increase in renovascular resistance. This latter response was blocked entirely by quinacrine but not by meclofenamate. Neither quinacrine nor meclofenamate alone affected CSA-induced renal vasoconstriction. Therefore, products of phospholipase A2 activity, but not products of the cyclooxygenase pathway, may be involved to some small extent. In conclusion, CSA-induced increases in renovascular resistance are complex and appear to be produced not only by actions on vascular smooth muscle cells per se but also by actions on nerve terminals.     

Arginine feeding modifies cyclosporine nephrotoxicity in rats.

Glycine (G) infusion causes renal vasodilation mediated by nitric oxide (NO). Cyclosporine A (CsA) nephrotoxicity is characterized by preglomerular vasoconstriction and decreased efferent arteriolar tone probably related to reduced NO and angiotensin II, respectively. L-Arginine (ARG) is a precursor to NO. To test the hypothesis that chronic CsA decreases renal NO activity, we compared the glomerular hemodynamic response to glycine infusion in rats after 8 d of CsA (30 mg/kg per d s.c.), CsA and ARG (1.6 g/kg per d p.o.) (A/CsA), and in two groups of pair-fed controls (CON, A/CON). Single nephron GFR (SNGFR), single nephron plasma flow (SNPF), glomerular capillary hydrostatic pressure gradient (delta P), proximal tubular reabsorption (APR), and kidney tissue angiotensin II (AIIk) were measured before and during G. CsA was associated with baseline decrements in SNGFR, SNPF, delta P, and AIIk, and with a blunted hemodynamic response to G. In CON, ARG did not affect baseline hemodynamics or modify the response to G. In CsA, ARG decreased baseline preglomerular resistance and restored the glomerular hemodynamic response to G. G was associated with a significant increase in AIIk in both CON and CsA. These findings suggest that (a) CsA is associated with decreased AIIk, and (b) CsA may diminish NO activity within the kidney, and that this capacity may be partially restored by arginine feeding.     

Effects of genetic obesity on renal structure and function in the Zucker rat

Although hyperphagia and obesity in the Zucker rat strain have been reported to be associated with spontaneous focal glomerulosclerosis (FGS), little is known about the age of onset and the natural history of hypertension, albuminuria, renal function, and glomerular injury in this model. We systematically investigated renal structure and function in obese male Zucker rats. Lean male littermates were used as controls. Obese rats developed glomerular mesangial matrix expansion and albuminuria by 14 weeks of age. These changes occurred despite normal inulin clearance (2.2 +/- 0.6 ml/min obese vs. 2.0 +/- 0.4 ml/min lean, P greater than 0.1) and filtration fraction (0.32 +/- 0.08 obese vs. 0.34 +/- 0.06 lean, P greater than 0.1), suggesting that increased glomerular filtration and renal plasma flow were not a prerequisite for the development of FGS. By 28 weeks of age, FGS was evident in seven of eight obese rats, and at 68 weeks of age all obese rats had marked FGS. Mean systolic blood pressure was elevated by 11 to 25 mm Hg in obese rats at all ages. Although the pathogenesis of glomerular injury is unknown, our data demonstrate that microalbuminuria, mild hypertension, and mesangial matrix expansion precede the development of progressive FGS in obese Zucker rats.     

Long-term effects of cyclosporine on renal function in organ transplant recipients

To evaluate whether cyclosporine nephrotoxicity is progressive, glomerular filtration rate and renal plasma flow were determined by isotopic techniques in 24 cyclosporine-treated organ transplant recipients (12 heart, 1 pancreas, and 11 kidney recipients). The cyclosporine group demonstrated reductions in glomerular filtration rate and renal plasma flow, with higher renal vascular resistance and mean arterial pressure as compared with an azathioprine-treated control group. However, longitudinal studies over a mean time period of 23 months in eight cyclosporine-treated renal transplant recipients showed renal function to remain stable. In the entire group of 24 cyclosporine-treated patients, longer duration of cyclosporine treatment was associated with decreased but stable glomerular filtration rate, increased renal plasma flow, decreased renal vascular resistance, and lower daily doses of cyclosporine. Evaluation of intrarenal resistances demonstrated a greater decrease in efferent than afferent arteriolar resistance, consistent with the fall in plasma renin activity that occurred with time. Short-term treatment of 12 patients with prazosin produced no beneficial effect on renal function, whereas treatment of nine patients with captopril produced a 20% increase in renal plasma flow, with a significant reduction in renal vascular resistance. We conclude that although cyclosporine treatment produces decreased renal function, the loss in renal function is not necessarily progressive. Treatment with captopril may improve the abnormal renal hemodynamics of cyclosporine-treated patients.     

The effect of methylprednisolone on cisplatin-induced nephrotoxicity in rat renal cortical slices

To investigate the protective action of methylprednisolone against cisplatin nephrotoxicity, the effect of in vivo pretreatment with methylprednisolone on the cisplatin-induced reduction inp-aminohippurate (PAH) accumulation and gluconeogenesis was examined using renal cortical slices prepared from Sprague-Dawley rats. The PAH accumulation in the kidney slices prepared from methylprednisolone-pretreated rats was significantly reduced following in vitro incubation with 2 mM cisplatin, to a degree equal to that observed in the slices prepared from untreated rats. However, the inhibitory effect of cisplatin on gluconeogenesis in the renal cortical slices obtained from methylpredimisolone-pretreated rats was significantly smaller than that seen in the slices from untreated rats. Our present studies suggest that in vivo pretreatment with methylprednisolone may contribute to its protective effect against cisplatin nephrotoxicity through the process of gluconeogenesis in renal epithelial cells.     

Colchicine decreases apoptotic cell death in chronic cyclosporine nephrotoxicity

Colchicine has been shown to prevent kidney injury in chronic cyclosporine nephrotoxicity; however, the mechanisms of its action are undetermined. The purpose of this study was to clarify whether colchicine prevents cyclosporine-induced kidney injury by decreasing kidney-cell apoptosis. We also sought to determine whether such an antiapoptotic effect was related to Bcl-2/Bax protein and caspase3 activity. Adult male Sprague-Dawley rats kept on a salt-depleted diet (0.05% sodium) were treated daily for 28 days with cyclosporine (15 mg/kg in 1 mL/kg olive-oil vehicle), colchicine (30 microg/kg in 100% ethanol, diluted with sterile saline solution to a final concentration of 30 microg/mL), or both cyclosporine and colchicine. Kidney function, histomorphologic findings, in situ terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate-biotin nick end-labeling assay, expressions of Bcl-2 and Bax proteins, and caspase-3 enzymatic activity were compared for the different treatment groups. Compared with the vehicle-treated rats, rats given cyclosporine showed a decline in creatinine clearance rate, an increase in serum creatinine concentration, tubulointerstitial fibrosis, and an increase in the number of apoptotic cells (all P <.01). Concomitant administration of colchicine significantly reversed all the above parameters (all P <.05). The decreased expression of Bcl-2 and the ratio of Bcl-2 to Bax protein seen in cyclosporine-treated rat kidneys were significantly increased after colchicine treatment, accompanying a suppression of caspase-3 activity (P <.05). Furthermore, the decreased apoptotic cell death was closely correlated with improved renal tubulointerstitial fibrosis (r = 0.583, P <.05). These findings strongly suggest that a renoprotective effect of colchicine on cyclosporine-induced nephrotoxicity is coassociated with a decrease in apoptotic cells.     

骨髓间充质干细胞诱导肾移植大鼠免疫耐受:与环孢素A效果的比较

背景:前期动物实验结果显示在肾移植前或移植后注射4次1×10~7的间充质干细胞能够诱导免疫耐受,延长移植物的生存时间,但是效果明显弱于环孢素A.目的:在前期实验基础上,通过调整间充质干细胞的给予次数,并比较不同剂量的效果,进一步确定具体给药方案.设计、时间及地点:随机分组,细胞学体内实验,于2008-03/12在南京医科大学动物实验中心完成.材料:以雄性Wistar大鼠为供体,雄性Lewis大鼠为受体,共35对,建立肾移植模型.运用密度梯度离心法由3只健康雄性Wistar大鼠骨髓内分离培养间充质干细胞.方法:建模后,采用抽签法将受体随机分为4组:低、高剂量间充质干细胞组(n=10,11),于开放血流前1周及开放血流时分别静脉注射间充质干细胞1×10~6,1×10~7,此后1次/d,持续2周:环孢素A组(n=8),移植后2 d腹腔注射经PBS液稀释的环孢索A,0.5 mg/(kg·d),1次/d至死亡;无治疗对照组(n=6),移植后直接腹腔内注射PBS液,1次/d至死亡.主要观察指标:移植后第3,5,10,15,25,40天观察血清肌酐水平,移植后第4天各组中随机抽取2只受观察移植肾组织学改变,同时记录移植受体大鼠生存期.结果:受体大鼠35只均成功建立模型进入结果分析.与环孢素A相比,使用1×10~7间充质干细胞治疗对受体大鼠生存期有类似的延长作用.1×10~6间充质干细胞延长受体存活时间作用明显减弱.不同剂量间充质干细胞组移植后第5天肌酐水平较无治疗组及环孢素A治疗组均有一定程度降低(P＜0.05),其他时间点差异均不显著.高剂量间充质干细胞及环孢素A组移植肾间质浸润较其他组有明显改善,绝大多数肾小球及动脉均无特殊改变.无治疗对照组表现出典型的严重急性排斥反应,低剂量间充质干细胞组表现出的排斥反应明显缓和.结论:移植前及移植中给予2剂后,在移植后2周内每日给予1×10~7的间充质干细胞可以达到有效地免疫调节作用,保护移植后早期移植物功能,延长动物的生存期,作用与环孢素A类似.     

Alterations in dorsal horn neurones in a rat model of cancer-induced bone pain

Cancer-induced bone pain is a major clinical problem. A rat model based on intra-tibial injection of MRMT-1 mammary tumour cells was used to mimic progressive cancer-induced bone pain. At the time of stable behavioural changes (decreased thresholds to mechanical and cold stimuli) and bone destruction, in vivo electrophysiology was used to characterize natural (mechanical, thermal, and cold) and electrical-evoked responses of superficial and deep dorsal horn neurones in halothane-anaesthetized rats. Receptive field size was significantly enlarged for superficial neurones in the MRMT-1 animals. Superficial cells were characterised as either nociceptive specific (NS) or wide dynamic range (WDR). The ratio of WDR to NS cells was substantially different between sham operated (growth media alone) (26:74%) and MRMT-1 injected rats (47:53%). NS cells showed no significant difference in their neuronal responses in MRMT-1-injected compared to sham rats. However, superficial WDR neurones in MRMT-1-injected rats had significantly increased responses to mechanical, thermal and electrical (A beta-, C fibre-, and post-discharge evoked response) stimuli. Deep WDR neurones showed less pronounced changes to the superficial dorsal horn, however, the response to thermal and electrical stimuli, but not mechanical, were significantly increased in the MRMT-1-injected rats. In conclusion, the spinal cord is significantly hyperexcitable with previously superficial NS cells becoming responsive to wide-dynamic range stimuli possibly driving this plasticity via ascending and descending facilitatory pathways. The alterations in superficial dorsal horn neurones have not been reported in neuropathy or inflammation adding to the evidence for cancer-induced bone pain reflecting a unique pain state.     

不同来源及水平的蛋白质对肾损害大鼠营养状况的影响

目的探讨不同质量的蛋白质对肾损害大鼠营养状况的影响。方法40只正常SD大鼠按体质量从小到大排序,采用随机数字表法分为4组,每组10只,均用腺嘌呤灌胃制作大鼠肾脏损害模型,同时A组(Ca14):为标准对照组,喂饲14%酪蛋白为来源的饲料;B组(SP14):喂饲14%大豆蛋白为来源的饲料;C组(Ca7-SP7):喂饲酪蛋白和大豆蛋白各占7%的混合饲料,蛋白质总量为14%即14%混合蛋白组;D组(Ca7-SP14):喂饲7%酪蛋白和14%大豆蛋白的混合饲料,蛋白质总量为21%即21%混合蛋白组。每10d测量大鼠体质量留尿检测尿蛋白含量,第42天杀鼠取血标本,检测血清总蛋白(TP)、白蛋白(Alb)、球蛋白(G)、胆固醇(Tch)、甘油三酯(TG)。结果大鼠体质量呈缓慢增长趋势,实验结束时B、C两组体质量明显高于A、D两组,有显著性差异(P<0.01);B组尿蛋白含量始终低于其他3组(P<0.05)。4组大鼠间总蛋白、白蛋白及球蛋白没有显著性差异(P>0.05);A组胆固醇、甘油三酯均高于其他3组,有显著性差异(P<0.01)。结论大豆蛋白作为蛋白质来源,在蛋白总量相同的情况下,替代酪蛋白或与酪蛋白适当搭配,能够维持大鼠的营养状况。     

双侧供肾大鼠肾移植模型的建立

目的:大鼠肾移植动物模型是免疫和移植相关研究的重要实验工具,但即往的大鼠肾移植模型大多以单侧肾脏为供肾,手术时间较长,实验经济性不高.拟建立双侧供肾大鼠肾移植模型,并进行改良,以期缩短手术时间及实验费用.方法:①实验于2007-05/08于大坪医院实验动物中心完成,实验方法符合医学伦理学要求.②共选用大鼠90只,按随机数字表法分为2组,双侧供肾组Wistar供体大鼠18只,SD受体大鼠36只,采用原位低温灌洗,同时取供者双肾作为供肾;单侧供肾组Wistar供体大鼠18只,SD受体大鼠18只,取供者左侧肾脏为供肾.③以硬膜外导管为支架行供肾静脉与受者肾静脉端端吻合,供肾动脉带腹主脉瓣与受者腹主动脉行端侧吻合,供肾输尿管膀胱瓣与受者的膀胱吻合.受者术中预置右侧肾脏血管体外结扎线,术后3 d结扎.④术后1,5,7 d由受体大鼠尾静脉分别抽取静脉血1 mL测肌酐.结果:①双侧供肾组手术成功率为91.7%,大鼠死亡的原因主要为血管吻合口出血、感染、休克、血栓形成以及膀胱漏尿致弥漫性腹膜炎等;单侧供肾组手术成功率为88.9%.②除取肾时间外两组其余手术耗时差异无显著性意义(P > 0.05).③两组受体大鼠组内比较术后血肌酐含量均持续升高(P < 0.01),两组差异无显著性意义(P > 0.05).结论:双侧供肾大鼠同种异体肾移植模型建立方法可靠、稳定,并能降低实验成本,缩短手术时间.     

A prospective comparative study of gentamicin- and amikacin-induced nephrotoxicity in patients with normal baseline renal function

The aim of this study was to compare the nephrotoxic potential of amikacin (AK) and gentamicin (GM) in patients with normal baseline renal function. This study was a 1-year, non-interventional prospective study of patients administered either GM or AK. The study was carried out at the internal medicine department of Al-Watani governmental study. Nephrotoxicity was defined as a serum creatinine (SCr) increase of ≥0.5 mg/dL from the basal (normal) SCr level. The two groups (GM, n  = 45 and AK, n  = 49) were similar in population composition, and underlying pathological and infectious processes requiring antimicrobials. No significant difference in age was found between patients in the GM and AK groups, P  = 0.83. Patients in the GM group received comparatively lower doses than those in the AK group (mean = 2.5 mg/kg/day and 14.4 mg/kg/day, respectively) but the duration of treatment was similar. Sixteen of 45 patients receiving GM (35.6%) and eight of 49 patients receiving AK (16.3%) developed nephrotoxicity, P  = 0.033. Single daily dosing with GM, regardless of the total daily dose, produced less nephrotoxicity than multiple dosing. In contrast, AK given at a total dose of 1 g daily, showed no benefit of single dosing compared with multiple dosing. In patients with initial normal renal function, GM was significantly more nephrotoxic than AK. Multiple dosing of GM was more nephrotoxic than single dosing. AK-induced nephrotoxicity was not significantly dependent on dosing frequency.     

Effect of nifedipine on renal haemodynamics in an animal model of cyclosporin A nephrotoxicity

1. This study investigates the effect of nifedipine on cyclosporin A nephrotoxicity in the spontaneously hypertensive rat. 2. Cyclosporin A, administered daily by subcutaneous injection at 25 mg/kg body weight for 14 days, induced a significant reduction in glomerular filtration rate (35.3%) and effective renal plasma flow (45.0%), and an increase in renal vascular resistance (219%). Using this regimen, tubular, glomerular or vascular morphological damage was not evident on light microscopy. 3. The administration of nifedipine simultaneously with cyclosporin A from day 1 prevented the characteristic decline in renal function and increase in renal vascular resistance. However, the administration of nifedipine to spontaneously hypertensive rats previously exposed to cyclosporin A for 7 days failed to improve renal haemodynamics. 4. This study suggests that the beneficial effect conferred by nifedipine on cyclosporin A nephrotoxicity is present only when treatment is initiated simultaneously with cyclosporin A.     

Uremic toxins overload accelerates renal damage in a rat model of chronic renal failure

Uremic toxins have been suggested to promote progression of chronic renal failure by damaging tubular cells. Previous in vitro studies have indicated that some uremic toxins induce oxidative stress and activate NF-kappaB to upregulate plasminogen activator inhibitor-1 in tubular cells. These mechanisms may promote tubulointerstitial fibrosis. The present study examined whether uremic toxins induce glomerular and tubulointerstitial damage in vivo. Two uremic toxins, hippuric acid (HA) or indoleacetic acid (IAA), were tested in two independent experiments (HA-treated rats vs. non-HA-treated controls, IAA-treated rats vs. non-IAA-treated controls). The uremic toxins were administered to subtotally nephrectomized rats. Renal functions were measured periodically and glomerular sclerosis and interstitial fibrosis were examined at the end of the experimental period (18 and 24 weeks, respectively, after subtotal nephrectomy for HA and IAA treatments). Glomerular filtration rate (inulin clearance) at the end of the study period was significantly lower in uremic toxin-treated rats than in control rats (HA-treated rats: 0.090 +/- 0.004 ml/min/100 g body weight vs. non-HA-treated controls: 0.125 +/- 0.013, IAA-treated rats: 0.068 +/- 0.006 versus non-IAA-treated controls: 0.100 +/- 0.013; both p < 0.05). Beta-N-acetyl-glucoseamidase excretion was significantly higher in uremic toxin-treated rats than in control rats (HA-treated: 0.55 +/- 0.05 U/day vs. control: 0.39 +/- 0.04 at week 18, IAA-treated: 0.35 +/- 0.02 vs. control: 0.26 +/- 0.07 at week 16; both p < 0.05). Glomerular sclerosis index was significantly higher in uremic toxin-treated rats than in control rats (HA-treated: 0.85 +/- 0.16 versus control: 0.48 +/- 0.10, IAA-treated: 1.13 +/- 0.25 vs. control: 0.57 +/- 0.10; both p < 0.05). Significant enlargement of interstitial fibrosis was observed in indoleacetic acid-treated rats. These results indicate that overload of uremic toxins accelerates the loss of kidney function, glomerular sclerosis and tubulointerstitial injury in a rat model of chronic renal failure. The present study suggests the potential benefit of early intervention to remove various uremic toxins in delaying the onset of end-stage renal failure in patients with progressive renal disease.     

肥大细胞在腺嘌呤致慢性肾功能衰竭模型大鼠肾组织中的浸润

背景:近年研究提示肥大细胞的浸润与人类多种肾病患者的肾间质纤维化关系密切。肥大细胞是否参与了腺嘌呤致慢性肾功能衰竭大鼠模型肾间质纤维化?作者未检索到此类报道。目的:探讨肥大细胞在腺嘌呤致慢性肾功能衰竭大鼠模型肾组织中的分布特点及其与肾间质纤维化之间的关系。方法:46只雄性Wistar大鼠,随机分成对照组和模型组。模型组予腺嘌呤灌胃,剂量为150mg/(kg·d);对照组以等量生理盐水灌胃。分别于不同时间点检测血尿指标,并对肾组织进行苏木精-伊红染色、Masson染色及肾小管间质纤维化评分;采用甲苯胺蓝和免疫组化方法观察肥大细胞在肾脏的分布及浸润数量,并分析它们与肾间质纤维化的相关性。结果与结论:模型组大鼠随着灌胃时间的延长,尿蛋白/尿肌酐、血清肌酐和血清尿素氮持续升高,肾间质纤维化评分也逐渐增加,不同时间点之间及其与对照组比较,差异均有显著性意义(P<0.01);肥大细胞主要分布在模型鼠的肾小管间质、肾小球囊外及血管周围,间质纤维化较重区域浸润较多,其浸润数量随着模型鼠肾损害的加重逐渐增加,不同时间点之间比较,差异均有显著性意义(P<0.01),并且与肾间质纤维程度呈显著正相关(r=0.96,P<0.001)。提示肥大细胞可能促进了腺嘌呤致慢性肾功能衰竭大鼠模型肾间质纤维化的进展。