氟伐他汀对阿霉素肾病大鼠肾脏清道夫受体A基因表达的影响及肾保护作用

目的：探讨氟伐他汀对阿霉素肾病（AN）大鼠肾脏清道夫受体A（SR-A）基因表达水平的影响及其肾保护作用。方法：将Wistar大鼠随机分为正常对照组、AN组和氟伐他汀治疗组。以尾静脉注射阿霉素制备AN大鼠模型，邻苯三酚自氧化法测定肾组织匀浆超氧化物岐化酶（SOD）活力，硫代巴比妥酸（TBA）法测定肾组织匀浆液丙二醛（MDA）水平，PCR和RT-PCR法检测大鼠肾脏SR-A基因表达水平。结果：AN组尿蛋白排泄量明显高于对照组和氟伐他汀组，电镜下肾小球上皮细胞足突融合，内皮细胞增生，严重者肾小球基膜增厚，模糊不清，内皮细胞呈连拱状。AN组大鼠血清TP和Alb低于正常对照组，而TG、TC、HDL、LDL、ApoA和ApoB则高于正常对照组，其肾组织匀浆MDA值升高，SOD值下降，肾脏SR-A基因表达水平升高；氟伐他汀治疗后血清TP和Alb水平升高，TG、TC、HDL、LDL、ApoA、ApoB水平和MDA值接近正常组（与AN组比较P〈0．05），肾脏SR-A基因表达水平有所下降，电镜下大部分肾小球上皮细胞足突较好，仅见少部分上皮细胞足突融合。结论：AN大鼠肾脏SR-A过度表达与肾脏脂质代谢异常有关，也是造成肾脏病理改变的主要原因之一；氟伐他汀通过抑制脂质过氧化和在转录水平阻抑SR-A的mRNA表达，从而起到非降脂肾保护作用。     

氟伐他汀对糖尿病大鼠肾脏CTGF表达的影响

目的：研究氟伐他汀对糖尿病大鼠肾组织CTGF表达的影响,探讨氟伐他汀肾脏保护作用的机制。方法：SD雄性大鼠54只,随机分为：正常对照组（N组）、糖尿病对照组（D组）、糖尿病氟伐他汀治疗组（4 mg.kg-1.d-1）（F组）。由大鼠尾静脉单次注射链脲佐菌素（60 mg/kg）,造成糖尿病大鼠模型。经氟伐他汀治疗糖尿病大鼠2、4、8周后,分别观察其对大鼠血糖、血胆固醇、血肌酐、24 h尿蛋白定量和肾皮质CTGF表达的影响。结果：与正常对照组相比,糖尿病大鼠24 h尿蛋白定量、血胆固醇及肾组织CTGF表达显著增加;经氟伐他汀治疗后,糖尿病大鼠的24 h尿蛋白定量、胆固醇和CTGF表达下降。结论：糖尿病大鼠肾组织CTGF表达增加,氟伐他汀可能通过下调糖尿病大鼠肾脏CTGF表达而达到部分肾脏保护作用。     

益肾胶囊对糖尿病肾病大鼠足细胞损伤的影响

目的：观察益肾胶囊对糖尿病肾病大鼠足细胞损伤的影响。方法：32只大鼠随机分为正常对照组、糖尿病肾病模型组（模型组）、益肾胶囊组、苯那普利组,每组各8只。益肾胶囊组每日每只灌胃益肾胶囊（2.5g·kg^-1·d^-1）,苯那普利组每日每只灌胃苯那普利（2.5g·kg^-1·d^-1）,正常对照组及模型组每日给予等量的蒸镏水。测定血压、24h尿蛋白定量、血肌酐（Scr）、尿素氮（BUN）,并计算内生肌酐清除率（Ccr）;光镜检查肾组织病理变化,电镜及免疫荧光法检测肾组织及尿液中足细胞变化等。结果：实验24周后,模型组大鼠血压、24h尿蛋白定量、BUN、Scr较正常对照组明显增高（均P〈0.05）,益肾胶囊组和苯那普利组可降低糖尿病肾病大鼠血压、24h尿蛋白定量、BUN、Scr（均P〈0.05）等;模型组足细胞podocalyxin蛋白表达明显低于正常对照组（P〈0.05）,益肾胶囊组及苯那普利组大鼠足细胞podocalyxin蛋白表达较模型组显著增加（P〈0.05）;两治疗组之间比较无统计学差异。正常对照组尿液偶见podocalyxin阳性足细胞,模型组尿液足细胞排泄较正常对照组明显增多（P〈0.05）,益肾胶囊组及苯那普利组,大鼠尿液足细胞排泄减少（P〈0.05）。结论：益肾胶囊可通过减轻糖尿病肾病大鼠足细胞损伤而具有一定的肾保护作用。     

N-乙酰半胱氨酸对糖尿病肾病大鼠足细胞的保护作用

目的：探讨N-乙酰半胱氨酸（NAC）对糖尿病肾病（DN）大鼠足细胞的保护作用。方法：制备DN大鼠模型,将动物随机分为正常对照组、DN组和NAC组。8周后观察尿蛋白排泄量,免疫荧光方法和Western blotting检测肾皮质nephrin和podocin蛋白表达,透射电镜检测足细胞超微结构变化。结果：（1）与正常对照组比较,DN组和NAC组尿白蛋白排泄率增多（P〈0.01）,nephrin和podocin蛋白表达减少（P〈0.01或P〈0.05）和肾脏病理病变明显;（2）与DN组比较,NAC组尿蛋白排泄减少（P〈0.01）,nephrin和podocin蛋白表达较高（P〈0.01或P〈0.05）和足细胞的病变较轻。结论：NAC对DN大鼠肾脏保护作用,其部分机制与上调nephrin和podocin蛋白表达及改善足细胞病变有关。     

氟伐他汀对5/6肾切除大鼠肾脏皮质细胞外基质积聚的影响

目的观察降脂药氟伐他汀对5/6肾切除大鼠肾皮质细胞外基质(ECM)积聚的影响和探讨其降脂作用外的肾脏保护机制。方法将5/6肾切除大鼠随机分为模型组和氟伐他汀治疗组(治疗组),另设假手术组作为对照。实验期间测定尿蛋白排泄率;氟伐他汀处理(7mg·kg-1·d-1)13周后免疫组化法检测肾小球Ⅳ型胶原(ColⅣ)及纤连蛋白(FN)蛋白表达;酶谱法检测肾皮质基质金属蛋白酶(MMP)-2活性;免疫印迹检测金属蛋白酶组织抑制物(TIMP)-2蛋白表达。结果与假手术组相比,模型组大鼠尿蛋白排泄、肾小球Ⅳ型胶原和FN表达均明显增加(均为P<0.01)。模型组大鼠肾皮质MMP-2活性较假手术组明显降低(P<0.01),而TIMP-2蛋白表达明显上调(P<0.01)。氟伐他汀治疗后这些改变均明显好转。结论氟伐他汀可能通过增加5/6肾切除大鼠肾脏MMP-2活性和降低TIMP-2表达,从而能增加细胞外基质降解和减轻肾小球细胞外基质积聚。     

活性维生素D改变FSGS大鼠肾小球整合素连接激酶的表达

目的观察整合素连接激酶（ILK）在局灶节段性肾小球硬化（FSGS）大鼠肾小球的表达以及活性维生素D[1，25-（OH2D3]对其表达的影响。方法SD大鼠随机分为对照组、模型组和治疗组，每组10只。采用左肾摘除、阿霉素重复注射诱导FSGS大鼠模型。治疗组皮下埋置渗透性微量泵，给予1，25-（OH）：D30．03ng·g^-1·d^-1，连用8周。检测3组大鼠尿蛋白、尿足细胞。血清白蛋白（SA）及半胱氨酸蛋白酶抑制剂（CysC），测定。肾小球硬化指数（GSI），电镜检测每视野足细胞数、足突平均宽度，间接免疫荧光检测肾小球ILK蛋白的表达，WT-1免疫组化染色观察每个肾小球足细胞数目。结果①与对照组相比较，模型组大鼠尿蛋白、尿足细胞、Cyst、GSI明显增加，SA、肾小球足细胞数目减少，足突宽度增加，肾小球ILK表达明显降低；②与模型组相比较，治疗组尿蛋白、尿足细胞排泄明显减少，GSI明显降低，肾小球足细胞数目增多，足突宽度减小，肾小球ILK表达明显增加。结论1，25-（OH2）D3可增加照；S大鼠肾小球ILK的表达，减少足细胞脱落，维持肾小球足细胞数量。     

氟伐他汀对糖尿病大鼠肾组织核因子-κB活性的影响

目的：观察氟伐他汀对实验性2型糖尿病大鼠肾组织中核因子-κB（NF-κB）活化的影响。方法：应用单侧肾切除后饮食加小剂量链脲佐菌素（STZ）方法,制备2型糖尿病肾病（DN）大鼠模型。将实验动物随机分为假手术组、2型糖尿病组及氟伐他汀治疗组（2mg·kg^-1·d^-1）。给药治疗6周后,检测各组动物血糖、血脂、血肌酐（Scr）、24h尿蛋白定量（TP／24h）等指标。采用电泳迁移率变动分析（EMSA）方法检测NF-κB活性变化,采用RT—PCR方法检测单核细胞趋化蛋白-1（MCP-1）mRNAg达水平。结果：小剂量氟伐他汀未影响血糖、血脂。治疗6周后,可明显降低2型DN大鼠肾组织中NF-κB活性,减少MCP-1 mRNA表达,并降低蛋白尿。结论：氟伐他汀对实验性2型糖尿病大鼠具有非依赖降脂的肾脏保护作用,其机制至少部分与降低肾组织中NF-κB活性,下调MCP-1基因表达有关。     

氟伐他汀对糖尿病大鼠肾脏组织蛋白激酶C活性作用的影响

目的:观察氟伐他汀对实验性糖尿病大鼠肾脏组织蛋白激酶C(PKC)活性的影响。方法:建立雄性SD 大鼠糖尿病动物模型,分为正常对照组(A组)、糖尿病组(B组)、氟伐他汀治疗组(C组),分别于第4、6周末收集24h 尿液、血清及肾脏组织标本,测定血胆固醇、甘油三酯、尿白蛋白、肾重/体重、肾脏细胞膜及细胞浆PKC活性,并进行 形态学观察。结果:C组大鼠血胆固醇、甘油三酯、肾重/体重、尿白蛋白及细胞膜PKC活性均高于同期A组,但低于 同期B组(P<0.05);C组大鼠细胞浆PKC活性高于同期B组,但低于同期A组(P<0.05);细胞膜PKC活性与肾重/体 重、尿蛋白排泄率呈正相关(r=0.772,P<0.01;r=0.353,P<0.05);肾脏组织学观察B组银染区及PAS红色染区 明显扩大,基底膜不规则增厚,足突部分融合,系膜区基质增多,C组较B组减轻。结论:氟伐他汀具有降脂、下调PKC 进而保护肾脏的功能。     

益肾胶囊对糖尿病肾病模型肾小球足细胞的影响

目的：观察益肾胶囊对糖尿病肾病（DN）大鼠肾组织病理改变及足细胞超微结构的影响。方法：将60只Wis-tar大鼠随机分为4组：正常对照组（对照组）、DN模型组（模型组）、苯那普利组、益肾胶囊组。于注射链脲佐菌素（STZ）后3d起,苯那普利组每日每只灌胃苯那普利3.125mg.kg-1.d-1,益肾胶囊组每日每只灌胃益肾胶囊625mg.kg-1.d-1,对照组及模型组每日给予等量的蒸镏水。各组分别干预12周,观察24h尿蛋白定量、血肌酐（Scr）、尿素氮（BUN）的变化,同时行肾脏病理检查。结果：12周末,模型组大鼠24h尿蛋白定量、Scr、BUN均高于对照组（P〈0.05）。苯那普利组及益肾胶囊组24h尿蛋白定量、Scr、BUN均低于模型组（P〈0.05）。光镜下模型组大鼠肾小球系膜基质增多,系膜区增宽;电镜下模型组大鼠肾小球基底膜增厚,足细胞排列紊乱,数目减少,足突增宽、融合。苯那普利组及益肾胶囊组肾小球基底膜病变减轻,细胞外基质减少,足细胞数目增多,足突融合减轻。结论：益肾胶囊能降低尿蛋白排泄,改善肾功能,并对足细胞有一定的保护作用,从而延缓大鼠糖尿病大鼠肾脏损害。     

阿托伐他汀辅助治疗早期糖尿病肾病疗效分析

目的观察阿托伐他汀辅助治疗早期糖尿病肾病的临床疗效。方法早期DN患者90例随机分为治疗组和对照组各45例,对照组常规治疗基础上加用盐酸贝那普利,治疗组在对照组基础上加服阿托伐他汀,比较两组患者疗效及不良反应发生率。结果治疗组总有效率88.9%,明显高于对照组60.0%（P〈0.05）;治疗组尿蛋白排泄率、C反应蛋白、24h尿蛋白定量亦比对照组明显改善（P〈0.05）。结论阿托伐他汀联合贝那普利治疗早期DN疗效满意,不良反应少。     

Calcium sensing in podocytes

Besides its primary function in maintaining systemic calcium homeostasis, the calcium-sensing receptor (CaSR) is expressed by many cell types, with different, sometimes opposite, regulatory functions. Novel work from Oh and collaborators shows that activation of CaSR in podocytes has prosurvival effects and protects the cell from puromycin aminonucleoside damage. Given that the cellular consequences of CaSR activation are largely context-dependent, further studies will be required to elucidate its precise role in podocyte physiology and pathophysiology.     

Culture methods of glomerular podocytes

Podocytes (glomerular visceral epithelial cells) cover the exterior surface of the glomerular capillaries and contribute to the glomerular filtration membrane. Failure of podocyte function is involved in the progression of chronic glomerular disease; accordingly, research interest into podocyte biology is driven by the need for better protection and perhaps recovery of these cells in renal diseases. This review aims at summarizing available techniques for podocyte cell cultures from both the past and present, with special attention to the currently used methods. The establishment of classical primary cultures is based on isolation of glomeruli by differential sieving. Plating of glomeruli onto a collagen surface is followed by an outgrowth of cobblestone-like cells that, after replating, differentiate into arborized, mature podocytes. Currently, the majority of research studies use immortalized podocytic cell lines most often derived from transgenic mice bearing a conditional immortalizing gene. The podocytes can also be collected and cultured from healthy or diseased animal or patient urine. The urinary podocytes obtained from subjects with active glomerulopathies display higher proliferation potential and viability in vitro, perhaps due to disease-induced transdifferentiation. Finally, a list of phenotypic markers useful for identification and characterization of the cultured podocytic elements is provided.     

The Renin-Angiotensin-aldosterone system in podocytes

The renin-angiotensin-aldosterone system (RAAS) plays a critical role in kidney function and its inhibition reduces proteinuria and preserves kidney function in patients with chronic kidney disease. Recent studies have shown that podocytes generate many components of the RAAS and they express receptors of RAAS, including angiotensin II, mineralocorticoid, and prorenin receptors. Crucial functions of podocytes, such as contraction, apoptosis, autophagocytosis, and cytoskeletal organization, have been shown to be regulated by the angiotensin II type 1 receptors. An activation of the glomerular RAAS and protection from podocyte injury by RAAS inhibitors have been shown in many glomerular diseases. Exploring the interaction between the local RAAS and the signaling involved in RAAS activation in podocytes will lead to new therapeutic strategies of podocyte protection.     

The role of podocytes in proteinuria

SUMMARY:   Glomerular visceral epithelial cells, also known as podocytes, are highly specialized epithelial cells that cover the outer layer of the glomerular basement membrane. Podocytes consist of cell bodies, major processes and foot processes (FP) of neighbouring cells, with the filtration slits bridged by the slit membrane between them. The function of podocytes is largely based on their specialized cell architecture and functions such as stabilization of glomerular capillaries and participation in the barrier function of the glomerular filter. Therefore, they form the final barrier to protein loss, which explains why podocyte injury is typically associated with marked proteinuria. Under pathological conditions, podocytes exhibit various changes. Among these changes, FP effacement represents the most characteristic change in cell shape of podocytes. FP effacement is dependent on disruption of the actin cytoskeletal network in the podocytes, The mechanisms of organization and re-organization of actin in the FP of podocytes are discussed in this review.     

Podocyte injury damages other podocytes

Loss of podocytes promotes glomerulosclerosis, but whether this results from a continued primary insult or a secondary mechanism triggered by the initial loss of podocytes is unknown. We generated chimeric mice in which only a subpopulation of podocytes expressed hCD25, which is the receptor for the immunotoxin LMB2. In addition, genetic labeling of hCD25-negative cells with human placental alkaline phosphatase allowed the study of these two distinct podocyte populations. Administration of LMB2 did not cause podocyte injury in hCD25-negative control mice. In contrast, LMB2 severely damaged or sloughed off the subpopulation of hCD25-positive podocytes within the chimeric glomeruli. Moreover, hCD25-negative podocytes, which were immune to the initial toxin injury, developed injury as early as 4 d after LMB2 injection, evidenced by foot process effacement, upregulation of desmin, and downregulation of nephrin, podocin, and podocalyxin. Furthermore, the magnitude of secondary injury correlated with the magnitude of primary injury, supporting the concept of an amplified cascade of podocyte injury. In conclusion, podocyte damage can propagate injury by triggering secondary damage of "remnant" intact podocytes, even when the primary insult is short-lived. This transmission of podocyte injury may form a vicious cycle leading to accelerated podocyte deterioration and glomerulosclerosis.     

KIBRA modulates directional migration of podocytes

Asymmetric delivery and distribution of macromolecules are essential for cell polarity and for cellular functions such as differentiation, division, and signaling. Injury of podocytes, which are polarized epithelial cells, changes the dynamics of the actin meshwork, resulting in foot process retraction and proteinuria. Although the spatiotemporal control of specific protein-protein interactions is crucial for the establishment of cell polarity, the mechanisms controlling polarity-dependent differentiation and division are incompletely understood. In this study, yeast two-hybrid screens were performed using a podocyte cDNA library and the polarity protein PATJ as bait. The protein KIBRA was identified as an interaction partner of PATJ and was localized to podocytes, tubular structures, and collecting ducts. The last four amino acids of KIBRA mediated binding to the eighth PDZ domain of PATJ. In addition, KIBRA directly bound to synaptopodin, an essential organizer of the podocyte cytoskeleton. Stable knockdown of KIBRA in immortalized podocytes impaired directed cell migration, suggesting that KIBRA modulates the motility of podocytes by linking polarity proteins and cytoskeleton-associated protein complexes.     

Permanent genetic tagging of podocytes: fate of injured podocytes in a mouse model of glomerular sclerosis

Injured podocytes lose differentiation markers. Therefore, the true identity of severely injured podocytes remains unverified. A transgenic mouse model equipped with a podocyte-selective injury induction system was established. After induction of podocyte injury, mice rapidly developed glomerulosclerosis, with downregulation of podocyte marker proteins. Proliferating epithelial cells accumulated within Bowman's space, as seen in collapsing glomerulosclerosis. In this study, the fate of injured podocytes was pursued. Utilizing Cre-loxP recombination, the podocyte lineage was genetically labeled with lacZ in an irreversible manner. After podocyte injury, the number of lacZ-labeled cells, which were often negative for synaptopodin, progressively declined, correlating with glomerular damage. Parietal epithelial cells, but not lacZ-labeled podocytes, avidly proliferated. The cells proliferating within Bowman's capsule and, occasionally, on the outer surface of the glomerular basement membrane were lacZ-negative. Thus, when podocytes are severely injured, proliferating parietal epithelial cells migrate onto the visceral site, thereby mimicking proliferating podocytes.     

Old friends form alliance against podocytes

Wang and colleagues identify the activation of Wnt signaling as an important downstream event in transforming growth factor-β-mediated podocyte injury. Supported by other recent studies, canonical Wnt signaling is emerging as a critical stress pathway in podocytes and may be exploited for therapeutic strategies in the treatment of glomerulopathies.     

The role of podocytes in glomerular pathobiology

Podocytes are unique cells with a complex cellular organization. With respect to their cytoarchitecture, podocytes may be divided into three structurally and functionally different segments: cell body, major processes, and foot processes (FPs). The FPs of neighboring podocytes regularly interdigitate, leaving between them the filtration slits that are bridged by an extracellular structure, known as the slit diaphragm (SD). Podocytes cover the outer aspect of the glomerular basement membrane (GBM). They therefore form the final barrier to protein loss, which explains why podocyte injury is typically associated with marked proteinuria. Chronic podocyte injury may lead to podocyte detachment from the GBM. Our knowledge of the molecular structure of the SD has been remarkably improved in the past few years. Several molecules, including nephrin, CD2AP, FAT, ZO-1, P-cadherin, Podocin, and Neph 1-3 have all been shown to be associated with the SD complex, and some of these molecules are critical for its integrity. Podocytes are injured in many forms of human and experimental glomerular disease. The early events are characterized either by alterations in the molecular composition of the SD without visible changes in morphology or, more obviously, by a reorganization of FP structure with the fusion of filtration slits and the apical displacement of the SD. Based on recent insights into the molecular pathology of podocyte injury, at least four major causes have been identified that lead to the uniform reaction of FP effacement and proteinuria: (1) interference with the SD complex and its lipid rafts; (2) direct interference with the actin cytoskeleton; (3) interference with the GBM or with podocyte-GBM interaction; and (4) interference with the negative surface charge of podocytes. There is also evidence, in focal segmental glomerular sclerosis (FSGS) and in idiopathic nephrotic syndrome in humans and rats, that podocyte damage may be caused by circulating albuminuric factors. Ongoing studies in many laboratories are aiming at an understanding of the dynamic relationship between SD proteins, the actin cytoskeleton, and the dynamics of FP structure in nephrotic syndrome and FSGS. These studies should provide us with a better understanding of the biological mechanism underlying the podocyte response to injury. Such studies will potentially translate into more refined treatment and the prevention of proteinuria and progressive glomerular disease.