Failure of BCL-2 up-regulation in proximal tubular epithelial cells of donor kidney biopsy specimens is associated with apoptosis and delayed graft function

SUMMARY: In renal transplantation, postischemic acute renal failure (ARF) develops in more than 20% of patients. We investigated whether tubular epithelial cells obtained from donor kidneys without subsequent ARF express a different pattern of survival genes, compared with cells from kidneys exhibiting ARF. Donor kidney biopsy specimens were obtained before transplantation from eight recipients of cadaveric kidneys with primary graft function (CAD-PF), eight patients with biopsy-proven ARF without rejection (CAD-ARF), and eight recipients of living donor kidneys with primary graft function (LIV). One thousand proximal tubular epithelial cells per biopsy specimen were isolated by laser capture microdissection. Quantitative analysis of apoptosis and the apoptosis regulatory genes Bcl-2, Bcl-xL, and Bax were performed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick-end labeling staining and real-time PCR, respectively. Primary cultures of human proximal tubular epithelial cells served as calibrator. The number of apoptotic cells was significantly higher in CAD-ARF compared with LIV and CAD-PF (1.5 +/- 1.1% [p < 0.05] vs. 0.3 +/- 0.2% vs. 0.4 +/- 0.2%; mean +/- SD). The apoptosis inhibitors Bcl-2 and Bcl-xL were significantly up-regulated in renal tubular cells of recipients without ARF compared with CAD-ARF. The ratios of Bcl-2/GAPDH normalized to calibrator were as follows: LIV 48 +/- 30, CAD-PF 38 +/- 55, and CAD-ARF 5 +/- 7 (p < 0.05). The corresponding ratios for Bcl-xL were as follows: LIV 6 +/- 6, CAD-PF 5 +/- 3, and CAD-ARF 1 +/- 1 (p < 0.05). No difference in the expression of the proapoptotic Bax could be observed. These data suggest that failure of proximal tubular cells to respond to injury by up-regulation of survival factors from the Bcl-2 family contributes to postischemic ARF in patients after cadaveric renal transplantation.     

Changes in free and esterified cholesterol: hallmarks of acute renal tubular injury and acquired cytoresistance

Acute tubular cell injury is accompanied by plasma membrane phospholipid breakdown. Although cholesterol is a dominant membrane lipid which interdigitates with, and impacts, phospholipid homeostasis, its fate during the induction and recovery phases of acute renal failure (ARF) has remained ill defined. The present study was performed to ascertain whether altered cholesterol expression is a hallmark of evolving tubular damage. Using gas chromatographic analysis, free cholesterol (FC) and esterified cholesterol (CE) were quantified in: 1) isolated mouse proximal tubule segments (PTS) after 30 minutes of hypoxic or oxidant (ferrous ammonium sulfate) injury; 2) cultured proximal tubule (HK-2) cells after 4 or 18 hours of either ATP depletion/Ca(2+) ionophore- or ferrous ammonium sulfate-mediated injury; and 3) in renal cortex 18 hours after induction of glycerol-induced myoglobinuric ARF, a time corresponding to the so-called "acquired cytoresistance" state (ie, resistance to further renal damage). Hypoxic and oxidant injury each induced approximately 33% decrements in CE (but not FC) levels in PTS, corresponding with lethal cell injury ( approximately 50 to 60% LDH release). When comparable CE declines were induced in normal PTS by exogenous cholesterol esterase treatment, proportionate lethal cell injury resulted. During models of slowly evolving HK-2 cell injury, progressive CE increments occurred: these were first noted at 4 hours, and reached approximately 600% by 18 hours. In vivo myoglobinuric ARF produced comparable renal cortical CE (and to a lesser extent FC) increments. Renal CE accumulation strikingly correlated with the severity of ARF (eg, blood urea nitrogen versus CE; r, 0.84). Mevastatin blocked cholesterol accumulation in injured HK-2 cells, indicating de novo synthesis was responsible. Acute tubule injury first lowers, then raises, tubule cholesterol content. Based on previous observations that cholesterol has cytoprotectant properties, the present findings have potential relevance for both the induction and maintenance phases of ARF.     

Expression of Fas and Fas Ligand on Mouse Renal Tubular Epithelial Cells in the Generalized Shwartzman Reaction and Its Relationship to Apoptosis

Previously we reported that the consecutive injection of lipopolysaccharide (LPS) into LPS-sensitized mice for the generalized Shwartzman reaction (GSR) appeared to induce the injury of renal tubular epithelial cells via apoptosis. The aim of this study was to characterize the mechanism of renal tubular epithelial cell injury in GSR. The expression of Fas and Fas ligand was immunohistochemically detected on renal tubular epithelial cells from GSR-induced mice, although neither Fas nor Fas ligand was found in cells from untreated control mice or in cells from mice receiving a single injection of LPS. GSR-induced renal tubular epithelial cell injury was produced in neither Fas-negative MRL-lpr/lpr mice nor Fas ligand-negative MRL-gld/gld mice. The administration of anti-gamma interferon antibody together with a preparative injection of LPS prevented the expression of Fas and Fas ligand and the apoptosis of renal tubular epithelial cells. A provocative injection of tumor necrosis factor alpha into LPS-sensitized mice augmented Fas and Fas ligand expression and the apoptosis of renal tubular epithelial cells. The administration of tumor necrosis factor alpha to interleukin-12-sensitized mice resulted in Fas and Fas ligand expression and the apoptosis. Sensitization with interleukin-12 together with anti-gamma interferon antibody did not cause the apoptosis of renal tubular epithelial cells. It was suggested that the Fas/Fas ligand system probably plays a critical role in the development of renal tubular epithelial cell injury through apoptotic cell death.     

黄芪甲苷孵育脂肪源性干细胞对顺铂诱导肾小管上皮细胞凋亡的影响

背景：干细胞移植用于治疗急性肾损伤的有效性已经被多个研究证实,但其对肾小管上皮细胞损伤的修复机制尚不明确。 目的：观察黄芪甲苷孵育后的脂肪源性干细胞对顺铂诱导的肾小管上皮细胞凋亡的保护作用及机制。 方法：实验分为4组。2.5 μmol/L顺铂诱导肾小管上皮细胞 24 h,建立肾小管细胞损伤模型(顺铂损伤组);将脂肪源性干细胞与损伤肾小管上皮细胞共培养(脂肪源性干细胞+损伤肾小管上皮细胞组);利用Transwell小室将20 mg/L黄芪甲苷孵育脂肪源性干细胞48 h后与损伤肾小管上皮细胞共培养(黄芪甲苷孵育脂肪源性干细胞+损伤肾小管上皮细胞组);以正常肾小管上皮细胞做对照(正常对照组)。 结果与结论：与肾小管上皮细胞损伤组相比,AV/PI和TUNEL结果均显示脂肪源性干细胞+肾小管上皮细胞组和20 mg/L 黄芪甲苷脂肪源性干细胞+肾小管上皮细胞组肾小管上皮细胞发生凋亡的比例和数量明显减少;ELISA结果表明20 mg/L黄芪甲苷脂肪源性干细胞+肾小管上皮细胞组胰岛素样生长因子1分泌显著提高(P < 0.05);Western blot进一步显示20 mg/L 黄芪甲苷脂肪源性干细胞+肾小管上皮细胞组caspase-3蛋白水平明显下降,而Bcl-2的表达量明显增加(P < 0.05)。表明黄芪甲苷孵育的人脂肪源性干细胞对顺铂诱导的肾小管上皮细胞凋亡具有抑制作用,从而有利于肾小管损伤的早期恢复,其保护机制可能与增加胰岛素样生长因子1分泌,抑制caspase-3表达、上调Bcl-2水平有关。中国组织工程研究杂志出版内容重点：干细胞;骨髓干细胞;造血干细胞;脂肪干细胞;肿瘤干细胞;胚胎干细胞;脐带脐血干细胞;干细胞诱导;干细胞分化;组织工程全文链接：     

特异性小干扰RNA沉默CHOP对肾小管上皮细胞凋亡的影响

目的:研究C/EBP同源蛋白(CHOP)对肾小管上皮HK2细胞凋亡的影响。方法:采用qPCR法检测急性肾损伤患者及健康对照者血清中CHOP的mRNA水平。体外培养肾小管上皮HK2细胞,随机分为对照组、阴性组和si-CHOP组,si-CHOP组和阴性组分别转染CHOP小干扰RNA(siRNA)和阴性对照siRNA,通过转化生长因子β1(TGF-β1)诱导细胞损伤。MTT法检测细胞的活力,流式细胞术检测细胞的凋亡率, Western blot检测细胞中细胞核抗原Ki-67、增殖细胞核抗原(PCNA)、caspase-3和cleaved caspase-3的蛋白水平。结果:与健康对照者相比,急性肾损伤患者血清中CHOP的表达量显著增加(P0.05);转染CHOP siRNA显著降低肾小管上皮细胞HK2中CHOP的水平,与对照组相比差异具有统计学意义(P0.05)。敲减CHOP的表达显著增加肾小管上皮HK2细胞的活力(P0.05),降低其凋亡率(P0.05),增加Ki-67和PCNA的表达量(P0.05),下调cleaved caspase-3的蛋白水平(P0.05)。结论:在急性肾损伤患者血清中CHOP的水平增加。敲减CHOP表达通过调节增殖和凋亡相关蛋白的表达抑制肾小管上皮HK2细胞的凋亡。     

Hypertrophy of Actin Bundles in Tubular Cells in Acute Renal Failure

Small bundles of actin filaments are normally present in the basal part of proximal and distal renal tubular cells and are attached to the basal cell membrane. Their functional significance is unknown, but by contracting they may have a function as a modulator of the intratubular pressure. Increased thickness and number of such actin bundles have been thought to occur in various pathologic conditions, including acute renal failure (ARF), but no quantitative data have been provided. In 19 cases of ARF of the ischemic type (“acute tubular necrosis”), the volume of these bundles was determined by morphometry and expressed per unit area underlying basement membrane (BM). It was found that in ARF there is a significant twofold to fourfold increase in actin bundles in proximal and distal tubular cells compared with findings in nine controls.     

Cis-diamminedichloroplatinum (II)-induced acute renal failure in the rat. Correlation of structural and functional alterations

Studies were undertaken to examine the relationship between renal morphologic and functional alterations during the development of cis-diamminedichloroplatinum (II) (CDDP)-induced acute renal failure (ARF). Control and CDDP-treated rats (10 mg/kg, intraperitoneally) were housed in metabolic cages for the purpose of renal function determinations. Renal morphology was studied by light and electron microscopy at 6, 24, 48, 72, and 96 hours following treatment. Six hours following CDDP administration, morphologic alterations consisting of nucleolar segregation, ribosome dispersion, and the formation of aggregates of smooth endoplasmic reticulum were observed throughout the P3 portion of the proximal tubule located in the outer stripe of the outer medulla and medullary rays. These changes became more frequently observed throughout P3 during the course of the study. At 24 and 48 hours, focal changes were also observed involving the P1 and P2 segments of the proximal tubule which make up the pars convoluta. ARF, indicated by a reduced creatinine clearance, was first apparent 48 hours following CDDP administration. The development of ARF was associated with focal, primarily sublethal, cell injury throughout the proximal tubule. By 72 and 96 hours necrosis primarily affecting P3 became widespread, and renal function progressively worsened. The establishment of ARF prior to the development of tubular necrosis suggests that the processes of tubular obstruction and/or tubular fluid backleak are not involved in the initiation of ARF in this model. Instead, the alterations involving P1 and P2 appear to be most important during the early stages of CDDP-induced ARF. The severity of the convoluted tubular injury at 48 hours showed a significant correlation with the degree of renal function impairment. The tubular injury affecting P3 did not correlate with the loss of renal function at any of the time points studied. However, tubular injury in P3 did appear responsible for some degree of renal function impairment at 72 and 96 hours, probably as a result of tubular obstruction and/or tubular fluid backleak.     

Mesenchymal stem cells contribute to the renal repair of acute tubular epithelial injury

Acute renal failure (ARF) is a common disease with high morbidity and mortality. Recovery from ARF is dependent on the replacement of necrotic tubular cells with functional tubular epithelium. Recent advancement in developmental biology led to the discovery of immature mesenchymal stem cells (MSCs) in bone marrow and several established organs and to the definition of their potential in the recovery from tissue injury. We investigated the effect of MSCs infusion on the recovery from ARF induced by intramuscle injection of glycerol in C57/BL6 mice. In this model, ARF is associated with an extensive necrosis of tubular epithelial cells due to myoglobin- and hemoglobin-induced injury. MSCs were obtained from bone marrow of transgenic mice expressing green fluorescent protein (GFP). MSC GFP-positive cells (MSC-GFP(+)) injected intravenously homed to the kidney of mice with glycerol-induced ARF but not to the kidney of normal mice. MSC-GFP(+) localized in the context of the tubular epithelial lining and expressed cytokeratin, indicating that MSCs engrafted in the damaged kidney, differentiated into tubular epithelial cells and promoted the recovery of morphological and functional alterations. Moreover, MSCs enhanced tubular proliferation as detected by the increased number of proliferating cell nuclear antigen (PCNA) positive cells. A significant contribution of the engrafted MSCs in the regeneration of tubular epithelial cells was shown by the presence of a consistent number of GFP(+) tubular cells 21 days after the induction of injury. In conclusion, these results indicated a tropism of MSCs for the injured kidney and a potential contribution of these cells to tubular regeneration and to the recovery from ARF.     

TLR4/NLRP3炎症复合体介导对比剂诱导的肾小管上皮细胞炎症和损伤

目的:探讨Toll样受体4(TLR4)/Nod样受体蛋白3(NLRP3)炎症复合体是否介导了对比剂(CM)引起的肾小管上皮细胞炎症和损伤。方法:本研究运用碘普罗胺作用于大鼠肾小管上皮细胞NRK-52E建立损伤模型。应用CCK-8法测定细胞存活率;Western blot测定TLR4、NLRP3、凋亡相关斑点样蛋白(ASC)、caspase-1和cleaved caspase-3的蛋白水平;ELISA法检测炎症因子白细胞介素1β(IL-1β)和IL-18的水平;Hoechst 33258核染色法检测凋亡率;JC-1染色法测定线粒体膜电位。用小干扰RNA沉默NLRP3表达。结果:CM可降低NRK-52E细胞的存活率并上调cleaved caspase-3的蛋白水平(P0.05);此外,CM可上调细胞TLR4/NLRP3炎症复合体的表达并促进炎症因子IL-1β和IL-18的分泌(P0.05)。沉默NLRP3可以对抗CM诱导的炎症因子分泌;TLR4抑制剂TAK-242及沉默NLRP3能减轻CM引起的细胞凋亡和线粒体功能损伤。结论:TLR4/NLRP3炎症复合体参与了CM致急性肾损伤的发病机制,并介导了CM诱导的肾小管上皮细胞损伤和炎症。     

Analysis of glial cell line-derived neurotrophic factor-inducible zinc finger protein 1 expression in human diseased kidney

The glial cell line-derived neurotrophic factor (GDNF)-RET signaling pathway plays an important role in kidney development. We have previously identified a novel zinc finger protein, glial cell line-derived neurotrophic factor-inducible zinc finger protein 1 (GZF1), whose expression was induced in the human neuroblastoma cell line TGW expressing RET by GDNF stimulation and was also detected in mouse metanephric kidney. In the present study, we examined the immunohistochemical expression of GZF1 in normal human kidney and various kidney diseases including chronic kidney disease, acute kidney injury, and cancers, and assessed the clinical significance of GZF1 expression. In the normal kidney, GZF1 was highly expressed only in the proximal tubular epithelial cells that were also positive for angiotensin-converting enzyme. We also evaluated GZF1 expression in various kidney diseases including membranous nephropathy, minimal change nephrotic syndrome with or without acute kidney injury, immunoglobulin A nephropathy, diabetic nephropathy, acute tubular necrosis, and antineutrophil cytoplasmic antibody-related glomerulonephritis. We found that decreased expression of GZF1 was associated with an increase in tubulointerstitial damage and serum creatinine levels. In addition, GZF1 expression was undetectable or very low in most cases of renal cell carcinomas and Wilms tumors. These findings suggest that GZF1 represents a new marker for renal proximal tubules and that there is an inverse correlation between the expression level of GZF1 and tubular function.     

DC‐SIGN reacts with TLR‐4 and regulates inflammatory cytokine expression via NF‐κB activation in renal tubular epithelial cells during acute renal injury

In the pathological process of acute kidney injury (AKI), innate immune receptors are essential in inflammatory response modulation; however, the precise molecular mechanisms are still unclear. Our study sought to demonstrate the inflammatory response mechanisms in renal tubular epithelial cells via Toll‐like receptor‐4 (TLR‐4) and dendritic cell‐specific intercellular adhesion molecule 3‐grabbing non‐integrin 1 (DC‐SIGN) signalling. We found that DC‐SIGN exhibited strong expression in renal tubular epithelial cells of human acute renal injury tissues. DC‐SIGN protein expression was increased significantly when renal tubular epithelial cells were exposed to lipopolysaccharide (LPS) for a short period. Furthermore, DC‐SIGN was involved in the activation of p65 by TLR‐4, which excluded p38 and c‐Jun N‐terminal kinases (JNK). Interleukin (IL)‐6 and tumour necrosis factor (TNF)‐α expression was decreased after DC‐SIGN knock‐down, and LPS induced endogenous interactions and plasma membrane co‐expression between TLR‐4 and DC‐SIGN. These results show that DC‐SIGN and TLR‐4 interactions regulate inflammatory responses in renal tubular epithelial cells and participate in AKI pathogenesis.     

Regeneration of kidney tubular epithelial cells

Conclusion The mechanisms that regulate regeneration of kidney epithelial cells after acute tubular necrosis are poorly understood. Repair of the nephron can take place in the adverse systemic metabolic setting caused by failure of renal function. This clinical observation suggests that factors released at the site of the tubular insult can mediate repair. Studies carried out in this and other laboratories show that kidney epithelial cells can release and respond to polypeptide growth factors which may thereby contribute to renal regeneration by autocrine and paracrine mechanisms. Specific growth factors secreted by cells and deposited in the tubular basement membrane prior to injury may subsequently participate in nephron repair. In addition, adenine nucleotides released from injured or dying cells at the injury site or provided exogenously could stimulate surviving renal epithelial cells at the edges of the wound to migrate along the basement membrane to rapidly reepithelialize the nephron and subsequently initiate mitogenesis to replace cells lost by necrosis.The nephrotoxic effect of many agents used in cancer chemotherapy and the older age of patients undergoing complicated surgical procedures has increased the incidence of ARF, whereas the mortality rate has not changed since the early 1950s [22]. Thus there is considerable need for innovative therapeutic strategies. An important goal of future research efforts is to identify new growth factors that facilitate migration, differentiation, and proliferation of renal epithelial cells at sites of tubular necrosis. Isolation and use of these agents in combination with dialysis and nutritional support could speed renal regeneration and thereby improve the outcome in patients with this condition.Abbreviations ARF acute renal failure - ECM extracellular matrix - EGF epidermal growth factor - FGF fibroblast growth factor - IGF insulin-like growth factor - MGSA melanocyte growth-stimulating activity - PDGF platelet-derived growth factor - IGF transforming growth factor     

Differential cellular immunolocalization of renal tumour necrosis factor-alpha production during ischaemia versus endotoxaemia

Both renal ischaemia and endotoxaemia provoke renal dysfunction and cellular injury. Although the clinical manifestation of each insult is similar (global renal dysfunction), ischaemia and endotoxaemia induce different patterns of cellular injury. Tumour necrosis factor-alpha (TNF-alpha) has been implicated in both types of renal injury; however, it remains unknown whether differential cellular TNF-alpha expression accounts for these changes. We hypothesized that renal glomerular cells and tubular cells differentially express TNF-alpha in response to ischaemia compared with endotoxaemia. To investigate this hypothesis, male Sprague-Dawley rats were anaesthetized and exposed to various time-periods of renal ischaemia, with or without reperfusion (sham operation=negative control), or lipopolysaccharide (LPS) 0.5 mg/kg intraperitoneally (i.p.). The kidneys were harvested following renal injury, and rat TNF-alpha protein expression was determined (by enzyme-linked immunosorbent assay), as were TNF-alpha bioactivity (by WEHI-164 cell clone cytotoxicity assay) and TNF-alpha cellular localization (by immunohistochemistry). TNF-alpha protein expression and TNF-alpha bioactivity peaked following 1 hr of ischaemia and 2 hr of reperfusion (48 +/- 11 pg/mg of protein, P < 0.05, and 12 +/- 0.5 x 10-3 units/mg of protein, P < 0.05, respectively). The concentration of TNF-alpha increased to a similar extent following exposure to LPS; however, while TNF-alpha production following ischaemia-reperfusion injury localized predominantly to renal tubular epithelial cells, animals exposed to LPS demonstrated a primarily glomerular distribution of TNF-alpha production. Hence, the cellular localization of renal TNF-alpha production appears to be injury specific, i.e. renal tubular cells are the primary source of TNF-alpha following an ischaemic insult, whereas LPS induces glomerular TNF-alpha production. The cellular source of TNF-alpha following different insults may have therapeutic implications for targeted inhibition of TNF-alpha production.     

脂多糖对人近端肾小管上皮细胞IL-18及其受体复合物表达的影响

观察脂多糖(LPS)对体外培养人近端肾小管上皮细胞IL-18及其受体表达的影响,以初步探讨IL-18在肾小管-间质炎症损伤过程中的作用。以不同浓度LPS(0.01、0.1、1、5、10μg/ml)处理人近端肾小管上皮细胞株(HK-2)24 h、36 h及48 h,然后应用RT-PCR及ELISA测定IL-18及其受体α链(IL-18Rα)和β链(IL-18Rβ)mRNA及蛋白的表达水平变化。静息培养的HK-2细胞表达IL-18 m RNA和蛋白、IL-18Rα和IL-18Rβm RNA,LPS促进HK-2细胞IL-18 mRNA和蛋白的表达及IL-18Rα和IL-18RβmRNA的表达,并呈剂量和时间依赖趋势。肾小管上皮细胞可能既是IL-18的产生者,又是IL-18的靶细胞之一,炎症状态下肾小管上皮细胞通过IL-18自分泌方式参与肾小管-间质的炎症损伤过程。     

Expression of silencer of death domains and death-receptor-3 in normal human kidney and in rejecting renal transplants

We have previously reported the pattern of cellular expression of tumor necrosis factor receptors (TNFR) in human kidney and their altered expression in transplant rejection. We have extended our studies to examine the expression of Silencer of Death Domains (SODD), a protein that binds to the cytoplasmic portion of TNFR1 to inhibit signaling in the absence of ligand. In normal human kidney SODD is expressed in glomerular endothelial cells where it colocalizes with TNFR1. During acute rejection both SODD and TNFR1 are lost from glomeruli, but we found strong expression of SODD on the luminal surface of tubular epithelial cells. This occurs in the absence of detectable TNFR1 expression, suggesting that SODD could interact with other proteins at these sites. Several other members of the TNF superfamily, including Fas and death receptors (DR)-3, -4, and -5, also contain intracellular death domains, but SODD only interacts with the death domain of DR3. We therefore studied the expression of DR3 in human kidney, and report that this death receptor is up-regulated in renal tubular epithelial cells and endothelial cells of some interlobular arteries, in parallel with SODD, during acute transplant rejection. In less severe rejection episodes, DR3 and SODD were more focally induced, generally at sites of mononuclear cell infiltrates. In ischemic allografts, eg, with acute tubular necrosis but no cellular rejection, DR3 was induced on tubular epithelial cells and on glomerular endothelial cells. These data confirm that TNF receptor family members are expressed in a regulated manner during renal transplant rejection, and identify DR3 as a potential inducible mediator of tubular inflammation and injury.     

Tubular ultrastructure in acute renal failure in man: Epithelial necrosis and regeneration

Summary It is not clear whether tubular cell necrosis is present or not in acute renal failure (ARF) of ischaemic type (acute tubular necrosis). In order to get quantitative data, using precisely defined criteria for tubular cell necrosis, 25 renal biopsies from 24 patients with ARF (11 obtained in the active phase, 14 in the early recovery period) were compared with 12 control biopsies. In all 1959 proximal cells and 1603 distal cells were analysed by electron microscopy. Cellular disintegration was very rare in all groups. Shrinkage necrosis (apoptosis) was not present in the proximal tubules of the controls and was rare in ARF (1.6–2.1%). In the distal tubules of controls 2.7% of all cells showed shrinkage necrosis. The incidence in ARF was not significantly increased. Non-replacement sites in distal tubules (probablyloci where cells have recently been desquamated) were significantly increased in number (5.2%) in the active phase in ARF compared to controls and recovery. The relative number of regenerating cells was not increased.These data show that there is no widespread necrosis of tubular cells in ARF. The increased incidence in distal tubules of focal, denuded areas of the basement membrane in the active phase of ARF indicates a slightly increased desquamation of cells and/or a failure to cover such sites by adjacent cells. This process is not restricted to the brief induction phase of ARF but continues during the whole active phase.     

Induction of proinflammatory cytokines and nitric oxide by Trypanosoma cruzi in renal cells

Chagas disease is typically associated with cardiac involvement. During the acute phase of murine infection with Trypanosoma cruzi, severe acute myocarditis can develop. Prior to cardiac alteration, however, infected mice present with renal inflammatory infiltration causing acute kidney injury due to an ischemia/reperfusion lesion. Thus, the present study was undertaken in order to evaluate whether the parasites or some of their components would directly affect renal cells. As such, this study employed kidney cell lines (mesangial, epithelial, and proximal tubular) that mimic different regions of the renal system. Mesangial cells are more resistant to infection, showing reduced parasite internalization relative to epithelial and proximal tubular cells. Upon infection, mesangial cells produced more nitric oxide, tumor factor necrosis-α, and interferon-γ and showed decreased viability when compared to the other cell lines. These results indicate that the resistance of mesangial cells to infection may be related to the increased expression of nitric oxide and proinflammatory cytokines. Conversely, the high levels of nitric oxide produced by these cells caused impairment of cell integrity and viability. Higher nitric oxide concentrations promote cellular injury and can be involved in the genesis of ischemia/reperfusion lesions in acute kidney injury.     

乙肝病毒X蛋白通过激活JAK2/STAT3信号通路调节肾小管上皮细胞凋亡

 目的：观察乙肝病毒X蛋白(HBx)对肾小管上皮细胞凋亡的作用,并探讨其在乙型病毒肝炎相关性肾炎(HBVGN)发病中的分子机制。方法：将构建好的HBx真核表达载体pcDNA3.1(+)-HBx转染至体外培养的人肾近曲小管上皮细胞(HK-2细胞)中。Western blotting法检测转染后目的蛋白的表达及JAK2/STAT3信号通路的活化。细胞免疫荧光检测STAT3及p-STAT3表达水平。CCK-8法检测细胞增殖活性。Hoechst 33342染色观察细胞的形态学改变。透射电镜观察细胞的超微结构及凋亡。Annexin V/PI双染流式细胞术检测细胞凋亡率。结果：转染目的基因HBx后,p-JAK2及p-STAT3表达水平均显著增加;同时,细胞增殖明显受抑。透射电镜、Hoechst 33342染色及Annexin V/PI双染流式细胞术检测发现HBx促进HK-2细胞凋亡。AG490（JAK2/STAT3信号通路阻断剂）孵育后能够部分阻断JAK2/STAT3信号通路,减少HBx所致细胞凋亡。结论：HBx通过激活JAK2/STAT3信号通路导致肾小管上皮细胞凋亡,可能参与了HBV直接损伤肾组织的致病机制。     

Abnormal iron deposition in renal cells in the rat with chronic angiotensin II administration.

Acute experimental iron loading causes iron to accumulate in the renal tissue. The accumulation of iron may play a role in enhancing oxidant-induced tubular injury by producing increased amounts of reactive oxygen species. From findings in cells from heme oxygenase-1 (HO-1)-deficient mice, HO-1 is postulated to prevent abnormal intracellular iron accumulation. Recently, it has been reported that HO-1 is induced in the renal tubular epithelial cells, in which iron is deposited after iron loading, and that this HO-1 induction may be involved in ameliorating iron-induced renal toxicity. We previously showed that chronic administration of angiotensin II to rats induces HO-1 expression in the tubular epithelial cells. These observations led us to investigate whether there is a link between iron deposition and HO-1 induction in renal tubular cells in rats undergoing angiotensin II infusion. In the present study, rats were given angiotensin II for continuously 7 days. Prussian blue staining revealed the distinct deposits of iron in the proximal tubular epithelial cells after angiotensin II administration. Electron microscopy demonstrated that iron particles were present in the lysosomes of these cells. Histologic and immunohistochemical analyses showed that stainable iron and immunoreactive ferritin and HO-1 were colocalized in the tubular epithelial cells. Treatment of angiotensin II-infused rats with an iron chelator, deferoxamine, blocked the abnormal iron deposition in kidneys and also the induced expression of HO-1 and ferritin expression. Furthermore, deferoxamine treatment suppressed the angiotensin II-induced increase in the urinary excretion of protein and N-acetyl-beta-D-glucosaminidase, a marker of tubular injury; however, deferoxamine did not affect the angiotensin II-induced decrease in glomerular filtration rate. These results suggest that angiotensin II causes renal injury, in part, by inducing the deposition of iron in the kidney.