TWEAK, a multifunctional cytokine in kidney injury

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a cytokine of the TNF superfamily that activates the Fn14 receptor. TWEAK may regulate cell proliferation, cell death, cell differentiation, and inflammation. TWEAK and Fn14 are constitutively present in the kidney. Sources of TWEAK and Fn14 include intrinsic renal cells and infiltrating leukocytes. Basal Fn14 expression is low, but Fn14 is greatly upregulated during kidney injury. TWEAK contributes to kidney inflammation promoting chemokine secretion by renal cells through canonical and non-canonical NFκB activation. TWEAK also promotes tubular cell proliferation. However, TWEAK induces mesangial and tubular cell apoptosis under proinflammatory conditions. These data indicate that TWEAK is a multifunctional cytokine in the kidney, the actions of which are modulated by the cell microenvironment. Confirmation of the role of TWEAK in kidney injury came from functional studies in experimental animal models. The TWEAK/Fn14 pathway contributed to cell death and interstitial inflammation during acute kidney injury, to glomerular injury in lupus nephritis, to hyperlipidemia-associated kidney injury, and to tubular cell hyperplasia following unilateral nephrectomy. Circulating soluble TWEAK (sTWEAK) levels are a potential biomarker of adverse outcomes in chronic kidney disease and urinary sTWEAK is a potential biomarker of lupus nephritis activity. The available evidence suggests that TWEAK may provide diagnostic information and be a therapeutic target in renal injury. Its role in human kidney disease should be further explored.     

The cytokine TWEAK modulates renal tubulointerstitial inflammation

TNF-like weak inducer of apoptosis (TWEAK) is a member of the TNF superfamily of cytokines. In addition to binding and activating the fibroblast growth factor-inducible 14 receptor, TWEAK may regulate apoptosis, proliferation, and inflammation; however, the role of this system in kidney injury is unknown. In vitro, it was found that TWEAK induced the sustained activation of NF-kappaB in a murine tubular epithelial cell line (MCT). NF-kappaB activation was associated with degradation of IkappaB-alpha; translocation of RelA to the nucleus; and increased mRNA and protein expression of monocyte chemoattractant protein-1, RANTES, and IL-6. Similarly, in vivo, the systemic administration of TWEAK induced renal NF-kappaB activation, chemokine and IL-6 expression, and interstitial inflammation in mice. Parthenolide, which prevents IkappaB-alpha degradation, inhibited TWEAK-induced NF-kappaB activation and prevented the aforementioned changes in vitro and in vivo. After folic acid-induced acute kidney injury, fibroblast growth factor-inducible 14 expression increased in mouse tubular epithelium. Neutralization of TWEAK decreased the expression of chemokines in tubular cells and reduced interstitial inflammation. In conclusion, TWEAK has NF-kappaB-dependent proinflammatory effects on tubular epithelial cells in vitro and in vivo. Moreover, blockade of TWEAK reduces tubular chemokine expression and macrophage infiltration, suggesting that TWEAK modulates acute kidney injury by regulating the inflammatory response.     

Cytokine cooperation in renal tubular cell injury: the role of TWEAK

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK, TNFSF12) is a member of the TNF superfamily. TWEAK activates the Fn14 receptor, and may regulate apoptosis, proliferation, and inflammation, processes that play a significant role in pathological conditions. However, there is little information on the function and regulation of this system in the kidney. Therefore, TWEAK and Fn14 expression were studied in cultured murine tubular epithelial MCT cells and in mice in vivo. The effect of TWEAK on cell death was determined. We found that TWEAK and Fn14 expression was increased in experimental acute renal failure induced by folic acid. Cultured tubular cells express both TWEAK and the Fn14 receptor. TWEAK did not induce cell death in non-stimulated tubular cells. However, in cells costimulated with TNFalpha/interferon-gamma, TWEAK induced apoptosis through the activation of the Fn14 receptor. Apoptosis was associated with activation of caspase-8, caspase-9, and caspase-3, Bid cleavage, and evidence of mitochondrial injury. There was no evidence of endoplasmic reticulum stress. A pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-DL-Asp prevented TWEAK-induced apoptosis, but it sensitized cells to necrosis via generation of reactive oxygen species. In conclusion, cooperation between inflammatory cytokines results in tubular cell death. TWEAK and Fn14 may play a role in renal tubular cell injury.     

Toll-like receptor 4 promotes tubular inflammation in diabetic nephropathy

Inflammation contributes to the tubulointerstitial lesions of diabetic nephropathy. Toll-like receptors (TLRs) modulate immune responses and inflammatory diseases, but their role in diabetic nephropathy is not well understood. In this study, we found increased expression of TLR4 but not of TLR2 in the renal tubules of human kidneys with diabetic nephropathy compared with expression of TLR4 and TLR2 in normal kidney and in kidney disease from other causes. The intensity of tubular TLR4 expression correlated directly with interstitial macrophage infiltration and hemoglobin A1c level and inversely with estimated glomerular filtration rate. The tubules also upregulated the endogenous TLR4 ligand high-mobility group box 1 in diabetic nephropathy. In vitro, high glucose induced TLR4 expression via protein kinase C activation in a time- and dose-dependent manner, resulting in upregulation of IL-6 and chemokine (C-C motif) ligand 2 (CCL-2) expression via IκB/NF-κB activation in human proximal tubular epithelial cells. Silencing of TLR4 with small interfering RNA attenuated high glucose-induced IκB/NF-κB activation, inhibited the downstream synthesis of IL-6 and CCL-2, and impaired the ability of conditioned media from high glucose-treated proximal tubule cells to induce transmigration of mononuclear cells. We observed similar effects using a TLR4-neutralizing antibody. Finally, streptozotocin-induced diabetic and uninephrectomized TLR4-deficient mice had significantly less albuminuria, renal dysfunction, renal cortical NF-κB activation, tubular CCL-2 expression, and interstitial macrophage infiltration than wild-type animals. Taken together, these data suggest that a TLR4-mediated pathway may promote tubulointerstitial inflammation in diabetic nephropathy.     

Deficiency of Fibroblast Growth Factor-Inducible 14 (Fn14) Preserves the Filtration Barrier and Ameliorates Lupus Nephritis

TNF ligand superfamily member 12, also known as TNF-related weak inducer of apoptosis (TWEAK), acts through its receptor, fibroblast growth factor-inducible 14 (Fn14), to mediate several key pathologic processes involved in tissue injury relating to lupus nephritis. To explore the potential for renal protection in lupus nephritis by targeting this pathway, we introduced the Fn14 null allele into the MRL-lpr/lpr lupus mouse strain. At 26–38 weeks of age, female Fn14-knockout MRL-lpr/lpr mice had significantly lower levels of proteinuria compared with female wild-type MRL-lpr/lpr mice. Furthermore, Fn14-knockout mice had significantly improved renal histopathology accompanied by attenuated glomerular and tubulointerstitial inflammation. There was a significant reduction in glomerular Ig deposition in Fn14-knockout mice, despite no detectable differences in either serum levels of antibodies or splenic immune cell subsets. Notably, we found that the Fn14-knockout mice displayed substantial preservation of podocytes in glomeruli and that TWEAK signaling directly damaged barrier function and increased filtration through podocyte and glomerular endothelial cell monolayers. Our results show that deficiency of the Fn14 receptor significantly improves renal disease in a spontaneous lupus nephritis model through prevention of the direct injurious effects of TWEAK on the filtration barrier and/or modulation of cytokine production by resident kidney cells. Thus, blocking the TWEAK/Fn14 axis may be a novel therapeutic intervention in immune-mediated proliferative GN.     

TWEAK Signaling Pathway Blockade Slows Cyst Growth and Disease Progression in Autosomal Dominant Polycystic Kidney Disease

BackgroundIn autosomal dominant polycystic kidney disease (ADPKD), cyst development and enlargement lead to ESKD. Macrophage recruitment and interstitial inflammation promote cyst growth. TWEAK is a TNF superfamily (TNFSF) cytokine that regulates inflammatory responses, cell proliferation, and cell death, and its receptor Fn14 (TNFRSF12a) is expressed in macrophage and nephron epithelia.MethodsTo evaluate the role of the TWEAK signaling pathway in cystic disease, we evaluated Fn14 expression in human and in an orthologous murine model of ADPKD. We also explored the cystic response to TWEAK signaling pathway activation and inhibition by peritoneal injection.ResultsMeta-analysis of published animal-model data of cystic disease reveals mRNA upregulation of several components of the TWEAK signaling pathway. We also observed that TWEAK and Fn14 were overexpressed in mouse ADPKD kidney cysts, and TWEAK was significantly high in urine and cystic fluid from patients with ADPKD. TWEAK administration induced cystogenesis and increased cystic growth, worsening the phenotype in a murine ADPKD model. Anti-TWEAK antibodies significantly slowed the progression of ADPKD, preserved renal function, and improved survival. Furthermore, the anti-TWEAK cystogenesis reduction is related to decreased cell proliferation–related MAPK signaling, decreased NF-κB pathway activation, a slight reduction of fibrosis and apoptosis, and an indirect decrease in macrophage recruitment.ConclusionsThis study identifies the TWEAK signaling pathway as a new disease mechanism involved in cystogenesis and cystic growth and may lead to a new therapeutic approach in ADPKD.     

The TWEAK/Fn14 pathway is required for calcineurin inhibitor toxicity of the kidneys

Calcineurin inhibitor toxicity (CNT) is a frequent occurrence in transplanted renal grafts and autochthone kidneys from patients undergoing long‐term treatment with calcineurin inhibitors, notably cyclosporin A (CsA) and tacrolimus. Here, we show an indispensable role of the tumor necrosis factor superfamily (TNFS) molecule TNF‐related weak inducer of apoptosis (TWEAK) (TNFSF12) in the pathogenesis of acute CNT lesions in mice. A deficiency in TWEAK resulted in limited tubulotoxicity after CsA exposure, which correlated with diminished expression of inflammatory cytokines and reduced intraparenchymal infiltration with immune cells. We further identified tubular epithelial cells of the kidney as major targets of CsA activity and found that Fn14 (tumor necrosis factor receptor superfamily 12A), the receptor for TWEAK, is a highly CsA‐inducible gene in these cells. Correlating with this, CsA pretreatment sensitized tubular epithelial cells specifically to the pro‐inflammatory activities of recombinant TWEAK in vitro. Moreover, injection of rTWEAK alone into mice induced moderate disease similar to CsA, and rTWEAK combined with CsA resulted in synergistic nephrotoxicity. These findings support the importance of tubular epithelial cells as cellular targets of CsA toxicity and introduce TWEAK as a critical contributor to CNT pathogenesis.     

Gene expression of TWEAK/Fn14 and IP-10/CXCR3 in glomerulus and tubulointerstitium of patients with lupus nephritis

Aim: The role of the tumour necrosis factor‐like weak inducer of apoptosis (TWEAK)/Fn14 and interferon‐inducible protein (IP‐10)/CXCR3 axis in the pathogenesis of lupus nephritis were studied. Methods: The mRNA expression of TWEAK, Fn14, IP‐10 and CXCR3 were quantified in the glomerulus and tubulointerstitium of 42 patients with lupus nephritis (LN group) and 10 healthy controls. Results: As compared to controls, LN patients had higher glomerular expression of TWEAK and Fn14, but glomerular CXCR3 expression was lower in the LN group. Similarly, the LN group had higher tubulointerstitial expression of TWEAK and Fn14, but lower tubulointerstitial expression of CXCR3, than controls. Glomerular TWEAK expression of class V nephritis was significantly higher than class IV nephritis. Glomerular expression of CXCR3 significantly correlated with proteinuria (r = ?0.532; P = 0.019), whereas tubulointerstitial CXCR3 significantly correlated with serum creatinine (r = ?0.447; P = 0.029). Conclusion: In patients with lupus nephritis, there is an increase in intra‐renal expression of TWEAK and Fn14, and a decrease in CXCR3 expression. Intra‐renal expression of CXCR3 correlates with proteinuria and renal function. Our findings suggest that the TWEAK/Fn14 and IP‐10/CXCR3 axis may contribute to the pathogenesis of lupus nephritis.     

Direct targeting of fibroblast growth factor-inducible 14 protein protects against renal ischemia reperfusion injury

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is known to have pivotal roles in various inflammatory processes. The TWEAK receptor, fibroblast growth factor-inducible 14 (Fn14), has various unique functions under physiological and pathological conditions; however, the therapeutic potential of its direct targeting remains unknown. Here, we found that Fn14 expression was highly upregulated in ischemic renal tissues and tubular epithelial cells of patient biopsies and experimental animal models of renal injury. To clarify the function of Fn14 in ischemia reperfusion injury, we coincubated renal tubular cells with ITEM-2, an anti-Fn14 blocking monoclonal antibody, and found that it inhibited the production of proinflammatory cytokines and chemokines after injury. Furthermore, Fn14 blockade downregulated the local expression of several proinflammatory mediators, reduced accumulation of neutrophils and macrophages in ischemic tissues, and inhibited tubular cell apoptosis. Importantly, Fn14 blockade attenuated the development of chronic fibrosis after ischemia reperfusion injury and significantly prolonged the survival of lethally injured mice. Thus, we conclude that Fn14 is a critical mediator in the pathogenesis of ischemia reperfusion injury.     

糖尿病肾病患者肾小管上皮细胞NF-κB及炎性介质表达的临床病理意义

目的 观察糖尿病肾病（DN）患者肾小管上皮细胞NF-κB及炎性介质表达的临床病理意义。 方法 选择经肾活检确诊的23例糖尿病肾病患者肾组织为DN组,以免疫组化法检测肾组织NF-κB p50、p65、单核细胞趋化蛋白（MCP）1、骨调素（OPN）等炎性介质及纤连蛋白（FN）、?琢平滑肌肌动蛋白（?琢-SMA）表达;原位杂交法检测NF-κB p65 mRNA表达,并进行半定量评分;选择10例肾癌切除术患者为对照组,取离癌组织大于5 cm处肾皮质,检测指标同DN组。采用Spearman等级相关法分析炎性介质表达与小管间质病理改变、尿N-乙酰-β-氨基葡萄糖苷酶（NAG）、尿蛋白量（24 h）、肾小球滤过率（eGFR）之间的相关性。 结果 组织学检查显示,各期DN组患者多存在明显的肾小管上皮细胞变性、灶状萎缩、间质炎性细胞浸润及纤维化。免疫组化与原位杂交结果显示,对照组患者NF-κB、OPN和MCP-1在肾组织无明显表达,FN主要表达于肾小球,?琢-SMA主要表达于肾血管;DN组患者随着尿白蛋白水平的增加,NF-κB、OPN和MCP-1在肾小管表达显著增加,主要表达于结构相对正常的小管上皮细胞,在炎性细胞大量聚集及明显纤维化处表达较少;同时,肾间质?琢-SMA、FN表达也有明显增加,但主要表达于炎性介质阳性表达的小管周围及炎性细胞浸润与纤维化较明显的肾间质,二者均不表达于肾小管上皮细胞。相关分析显示,DN组患者肾小管NF-κB p65蛋白的表达与NF-κB p50蛋白、p65 mRNA表达呈正相关,r分别为0.792和0.763,均P < 0.01;与肾小管MCP-1、OPN表达呈正相关,r分别为0.825和0.869,均P < 0.01;与间质?琢-SMA、FN表达呈正相关,r分别为0.327和0.432,均P < 0.01;与尿蛋白量（24 h）、eGFR、尿NAG水平均相关,r分别为 0.710、-0.728、0.930,均P < 0.01。 结论 DN患者肾小管NF-κB及多种炎性介质表达明显上调,多分布于结构相对正常的肾小管上皮细胞。NF-κB及炎性介质的表达与蛋白尿、肾功能下降及肾间质纤维化等临床及病理表现密切相关,提示它们可能参与了人类DN的发生和发展。     

基于NOD2信号通路探讨NADPH抑制剂对肾脏缺血再灌注损伤的影响

目的基于抑制核苷酸寡聚化结构域蛋白-2(nucleotide-binding oligomerization domain-2,NOD2)信号通路,探讨NADPH抑制剂对大鼠肾脏缺血再灌注损伤(ischemia/reperfusion injury,IRI)的影响及作用机制。方法将雄性Wistar大鼠切除右肾,并随机分为4组:①肾脏缺血再灌注(I/R)组:给予等量生理盐水预处理后夹闭左肾动脉制备IRI模型;②I/R组+氯化二碘联苯(diphenylene iodonium,DPI)组:给予DPI预处理后夹闭左肾动脉制备IRI模型;③I/R组+4-羟基-3甲氧基苯乙酮(4-hydroxy-3-methoxyacetophenone,Apocynin)组:给予Apocynin预处理后夹闭左肾动脉制备肾脏IRI模型;④假手术(Sham)组:给予等量生理盐水处理后不予夹闭左肾动脉。试验结束24 h后收集各组大鼠血及肾组织标本,采用Western blot法分别对NOD2、核因子κB(nuclear factor-κB,NF-κB)、半胱氨酸蛋白酶(Caspase-1)的表达进行检测;采用实时定量PCR法对NOD2 mRNA的表达进行检测;采用HE染色法观察肾脏组织学改变;采用免疫组织化学法检测肾组织炎症因子IL-1β的表达。结果与Sham组比较,I/R组的大鼠肾组织NOD2、NF-κB蛋白、Caspase-1表达显著增加(P<0.05);NOD2 mRNA表达显著增加(P<0.05);I/R组肾脏病理表现为肾小管上皮细胞水肿、坏死,脱落于管腔,肾间质炎性细胞浸润,肾小管损伤评分明显增加(P<0.05)。与I/R组相比,I/R+Apocynin组和I/R+DPI组的NOD2、NF-κB蛋白、Caspase-1表达均显著减少(P<0.05),NOD2 mRNA表达显著减少(P<0.05),肾脏病理显示急性肾小管坏死程度减轻,肾小管损伤评分显著减低(P<0.05)。结论抑制氧化应激可通过阻断NOD2受体信号通路来减轻肾脏IRI过程。     

Characterization of CXCL16 and ADAM10 in the normal and transplanted kidney

The chemokine CXCL16 plays an important role in the recruitment of leukocytes to sites of inflammation influencing the course of experimental glomerulonephritis. Here we show that human kidneys highly express CXCL16 in the distal tubule, connecting tubule and principal cells of the collecting duct with weak expression in the thick ascending limb of Henle. Beside the membrane localization, a soluble form of CXCL16 can be proteolytically released which acts as a chemotactic factor. In human renal tissue the expression pattern of the disintegrin-like metalloproteinase ADAM10 is similar to that of CXCL16, suggesting ADAM10 can potentially cleave CXCL16 in vivo. When we tested this in primary tubular cells we found that blockade of ADAM10 activity inhibited the IFN-gamma induced release of soluble CXCL16. Acute tubular damage in renal allografts was associated with elevated urinary CXCL16 and this correlated with focally increased apical CXCL16 expression in the distal tubules and collecting ducts. Renal allograft biopsies, with a histopathological diagnosis of acute interstitial rejection, showed increased basolateral ADAM10 expression together with high numbers of infiltrating T cells. Our results suggest that CXCL16 and ADAM10 are involved in the recruitment of T cells to the kidney and play an important role in inflammatory kidney diseases.     

Chemokines in renal injury

The main function of chemokines is to guide inflammatory cells in their migration to sites of inflammation. During the last 2 decades, an expanding number of chemokines and their receptors have driven broad inquiry into how inflammatory cells are recruited in a variety of diseases. Although this review focuses on chemokines and their receptors in renal injury, proinflammatory IL-17, TGFβ, and TWEAK signaling pathways also play a critical role in their expression. Recent studies in transgenic mice as well as blockade of chemokine signaling by neutralizing ligands or receptor antagonists now allow direct interrogation of chemokine action. The emerging role of regulatory T cells and Th17 cells during renal injury also forges tight relationships between chemokines and T cell infiltration in the development of kidney disease. As chemokine receptor blockade inches toward clinical use, the field remains an attractive area with potential for unexpected opportunity in the future.     

The inflammatory cytokines TWEAK and TNFα reduce renal klotho expression through NFκB

Proinflammatory cytokines contribute to renal injury, but the downstream effectors within kidney cells are not well understood. One candidate effector is Klotho, a protein expressed by renal cells that has antiaging properties; Klotho-deficient mice have an accelerated aging-like phenotype, including vascular injury and renal injury. Whether proinflammatory cytokines, such as TNF and TNF-like weak inducer of apoptosis (TWEAK), modulate Klotho is unknown. In mice, exogenous administration of TWEAK decreased expression of Klotho in the kidney. In the setting of acute kidney injury induced by folic acid, the blockade or absence of TWEAK abrogated the injury-related decrease in renal and plasma Klotho levels. TWEAK, TNFα, and siRNA-mediated knockdown of IκBα all activated NFκB and reduced Klotho expression in the MCT tubular cell line. Furthermore, inhibition of NFκB with parthenolide prevented TWEAK- or TNFα-induced downregulation of Klotho. Inhibition of histone deacetylase reversed TWEAK-induced downregulation of Klotho, and chromatin immunoprecipitation showed that TWEAK promotes RelA binding to the Klotho promoter, inducing its deacetylation. In conclusion, inflammatory cytokines, such as TWEAK and TNFα, downregulate Klotho expression through an NFκB-dependent mechanism. These results may partially explain the relationship between inflammation and diseases characterized by accelerated aging of organs, including CKD.     

Obstructive nephropathy in the mouse: progressive fibrosis correlates with tubulointerstitial chemokine expression and accumulation of CC chemokine receptor 2- and 5-positive leukocytes

The infiltration of leukocytes plays a major role in mediating tubulointerstitial inflammation and fibrosis in chronic renal disease. CC chemokines participate in leukocyte migration and infiltration into inflamed renal tissue. Because CC chemokine-directed leukocyte migration is mediated by target cell expression of a group of CC chemokine receptors, this study examined the expression of CC chemokines and their receptors during initiation of tubulointerstitial fibrosis after unilateral ureteral obstruction in C57BL/6 mice. Obstructed kidneys developed hydronephrosis, tubular cell damage, interstitial inflammation, and fibrosis. From days 2 to 10, a progressive interstitial influx of F4/80+ macrophages and CD3+ lymphocytes occurred (macrophages, 4-fold; lymphocytes, 20-fold at day 10, compared with contralateral control kidneys). In parallel, the number of activated fibroblast-specific protein 1+ fibroblasts and interstitial collagen IV accumulation increased from days 2 to 10. The mRNA expression of CC chemokines (predominantly monocyte chemoattractant protein-1 [MCP-1]/CCL2, RANTES/CCL5) and their receptors CCR1, CCR2, CCR5 increased progressively from days 2 to 10. By in situ hybridization, a prominent interstitial mRNA expression of MCP-1 and RANTES and their receptors CCR2 and CCR5 localized to interstitial mononuclear cell infiltrates. MCP-1 and RANTES expression was also seen in tubular epithelial cells. Fluorescence-activated cell sorter analysis of single-cell suspensions from obstructed kidneys revealed a prominent expression of CCR2 and CCR5 by infiltrating macrophages, whereas most lymphocytes expressed CCR5 only. These data demonstrate an increased expression of MCP-1/CCL2 and RANTES/CCL5 at sites of tubulointerstitial damage and progressive fibrosis during unilateral ureteral obstruction that correlates with simultaneous accumulation of interstitial macrophages and T lymphocytes expressing the respective surface receptors CCR2 and CCR5. The chemokine receptor-mediated leukocyte influx into the tubulointerstitium could offer a new potential target for therapeutic intervention in progressive renal tubulointerstitial fibrosis.     

血管紧张素Ⅱ灌注诱导大鼠肾脏血管紧张素转换酶2表达改变

目的 研究血管紧张素Ⅱ(AngⅡ)灌注后大鼠肾脏血管紧张素转换酶2(ACE2)表达的改变及其意义。 方法 雄性SD大鼠随机分为AngⅡ灌注组(400 ng&#8226;kg-1&#8226;min-1)、生理盐水灌注组和健康对照组，每组6只。测定28 天内大鼠血压及尿蛋白量变化。于第28天处死动物取肾，观察组织学改变，并用免疫组化、RT-PCR及Western印迹法检测ACE2表达及分布变化；凝胶电泳迁移率分析法(EMSA)检测核因子(NF)-κB的DNA结合活性变化。 结果 (1) AngⅡ灌注组大鼠血压升高，并出现明显蛋白尿。AngⅡ灌注后第28天，部分肾小球出现轻中度系膜增生，少数有节段性硬化；部分肾小管上皮细胞变性、坏死或萎缩，间质灶性炎性细胞浸润。(2) 健康大鼠肾脏ACE2主要分布于肾小管，以近端肾小管刷状缘分布最多。AngⅡ灌注后第28天，肾皮质ACE2 mRNA及蛋白表达均明显下降(P均< 0.05)，NF-κB结合活性显著增加(P < 0.05)。相关分析表明，ACE2表达与NF-κB结合活性之间呈负相关(r = -0.64，P < 0.01)。 结论 AngⅡ灌注可致大鼠肾脏ACE2表达明显下降，后者与肾损害的程度密切相关。肾脏ACE2表达下降可能是AngⅡ引起肾损害的重要机制     

Contribution of CXCL16/CXCR6 pathway activated by inflammation to atherosclerosis in patients with end-stage renal disease

Objective To investigate the effects of CXC chemokine ligand 16 (CXCL16)/CXC chemokine receptor 6 (CXCR6) pathway on cholesterol accumulation of atherosclerosis in the radial artery of end-stage renal disease (ESRD) patients under inflammatory stress and further investigate its potential mechanisms modulated by purinergic receptor P2X ligand-gated ion channel 7 (P2X7R). Methods According to plasma C-reactive protein (CRP), forty ESRD patients were divided into control group (CRP＜3.0 mg/L, n=15) and inflammation group (CRP≥3.0 mg/L, n=25). Biochemical index and lipid spectrum of patients were measured. Tissues from the radial artery of patients receiving arteriovenostomy were removed surgically. Foam cell formation was observed by hematoxylin-eosin (HE) and cholesterol accumulation was assessed by filipin staining. CXCL16/CXCR6 pathway related protein expression, P2X7R protein expression and the expression of monocyte chemotactic protein 1 (MCP-1), tumor necrosis factor α (TNF-α) and CD68 were detected by immunohistochemistry staining and immunofluorescence staining. Results Compared with that in control group, protein expression of MCP-1 and TNF-α in radial arteries were increased in inflammation group accompanied with macrophage infiltration (P＜0.05). Further more, there was significantly increased foam cell formation in continuous cross-sections of radial arteries in inflammation group, which was closely correlated with increased protein expression of CXCL16, CXCR6 and a disintegrin and metalloproteinase (ADAM)-10 (P＜0.05). CXCL16 expression was positively correlated with CRP level (r=0.79, P＜0.05) and P2X7R expression (r=0.65, P＜0.05). Conclusion Inflammation contributes to foam cell formation in the radial artery of ESRD patients by activating the CXCL16/CXCR6 pathway, and promotes atherosclerosis, which is possibly regulated by P2X7R activation.     

Effects of 1,25-dihydroxyvitamin D3 on macrophage chemo taxis inhibitory factor and nuclear factor-κB/P65 in obstructive nephropathy rats

Objective To investigate the expression of macrophage migration inhibitory factor(MIF) and nuclear factor-κB/P65 (NF-κB/P65) in the kidneys of unilateral ureteral occlusion (UUO) model rats and the effect of 1,25-dihydroxyvitamin D3 on the expression. Method The cell model of obstructive nephropathy was established by renal tubular epithelial cells treated with TGF- beta 1. Thirty healthy adult male SD rats were randomly divided into 3 groups: sham operation group (n=10), UUO group (n=10) and 1,25-dihydroxyvitamin D3 group (n=10, UUO rats treated with 1,25-dihydroxyvitamin D3 by lavage 2 days before operation)．The rats in sham group and UUO group were treated with equal normal saline by lavage. Serum creatinine (Scr) and histopathological changes were tested at week 2. The expressions of collagen Ⅳ (ColⅣ), macrophage marker antigen ED-1, MIF and NF-κB/P65 in renal issue were measured by immunohistochemistry. The MIF mRNA was detected by real-time PCR and the protein expressions of MIF, NF-κB inhibitor α (IKBα) and p-IKBα were measured by Western blotting. In renal tubular epithelial cells (NRK52E) the expressions of MIF and NF-κB were detected by immunocytochemistry, and the the protein expression of MIF and the activation of IKBα were teasted by Western blotting. Results Compared with those in sham group, in model group rats had increaced Scr, tubulointerstitial damage area and expressions of ED-1 and ColⅣ, and up-regulated mRNA and protein expressions of MIF (all P＜0.05). Moreover, the amount of NF-κB/P65 nuclear positive cells and p-IKBα expression were significantly increased while the expression of IKBα decreased in model group (all P＜0.05). NRK52E cells had higher expressions of MIF, NF-κB and p-IKBα, and lower IKBα in model group than those in control group (all P＜0.05). After the application of 1,25-dihydroxyvitamin D3, those above effects were inhibited (all P＜0.05). The results of cell model and animal model were in agreement. Conclusions The expressions of MIF and the activation of NF-κB/P65 in UUO rats increased significantly. 1,25-dihydroxyvitamin D3 may ameliorate the progression of renal tubulointerstitial inflammation and renal fibrosis by intervening the expression of MIF, inducing phosphorylation of IKBα and decreasing the activation of NF-κB/P65.     

核因子κB反义寡核苷酸对转化生长因子β1诱导人肾小管上皮细胞转分化的影响

目的 探讨在转化生长因子β1（TGF-β1）诱导下，核因子κB（NF-κB）反义寡核苷酸对体外培养的人肾小管上皮细胞（HK-2）转分化的影响。 方法 采用脂质体介导的方法将NF-κB反义寡核苷酸（AS-ODN）导入细胞，以TGF-β1（10 μg/L）刺激HK-2细胞24 h后，用RT-PCR方法检测细胞中NF-κB mRNA及α平滑肌肌动蛋白（α-SMA）mRNA表达，用荧光光谱法分析α-SMA蛋白的表达，并以倒置相差显微镜观察细胞转分化过程的形态变化。 结果 TGF-β1诱导24 h后，HK-2细胞中NF-κB mRNA的表达显著上调，为空白对照组的8倍以上（P < 0.01）。NF-κB反义寡核苷酸导入细胞后，可显著抑制TGF-β1诱导的HK-2细胞的 NF-κB mRNA表达，比TGF-β1组减少75％（P < 0.05），同时，α-SMA mRNA和蛋白表达亦较TGF-β1组均明显下调（P < 0.05）。 结论 NF-κB反义寡核苷酸可抑制TGF-β1诱导肾小管上皮细胞NF-κB的表达，抑制肾小管上皮细胞转分化，可能有利于肾间质纤维化的防治。     

Apocynin和DPI通过抑制NOD1信号通路在缺血性AKI中的保护作用

目的NOD样受体可促发炎症反应,夹竹桃麻素(apocynin)和二苯基碘鎓(DPI)均为氧化酶抑制剂。本研究观察在缺血性急性肾损伤中抑制氧化应激产生是否能通过NOD1信号通路减轻肾间质炎症反应与细胞凋亡。 方法将雄性Wistar大鼠随机分为4组：假手术(Sham)组、肾脏缺血再灌注(I/R)组、I/R ＋夹竹桃麻素(apocynin)组、I/R ＋二苯基碘鎓(DPI)组。通过Western印记法分别对肾组织核苷酸结合寡聚域样受体1(NOD1)、半胱天冬酶(caspase-1)及细胞核因子-κB(NF-κB)蛋白的表达进行检测;实时定量PCR法对NOD1mRNA的表达进行检测;HE染色法观察肾脏组织学改变;免疫组织化学法检测肾组织肿瘤坏死因子(TNF-ɑ)的表达;TUNEL法检测肾组织细胞凋亡。采用SPSS 22.0统计软包对实验数据进行统计学处理。 结果与Sham组比较,I/R组大鼠肾组织NOD1、caspase-1、NF-κB、TNF-ɑ蛋白表达增加(t＝16.81, t＝ 7.28, t＝ 11.08, t＝ 10.11;P<0.05);NOD1mRNA表达增加(t＝－7.93, P<0.05);HE染色表现为急性肾小管坏死,肾小管损伤评分明显增加(t＝－11.0, P<0.05);TUNEL染色显示缺血区凋亡细胞数目增加(t＝－18.38, P<0.05)。与I/R组比较,I/R＋ apocynin组的NOD1、caspase-1、NF-κB、TNF-ɑ蛋白表达减少(t＝－10.9, t＝－7.6, t＝－4.9, t＝－9.7;P<0.05);NOD1mRNA表达减少(t＝8.49, P<0.05);HE染色后者较前者急性肾小管坏死减轻,肾小管损伤评分减低(t＝－12, P<0.05);TUNEL染色显示缺血区凋亡细胞数目减少(t＝－11.3, P<0.05)。与I/R组比较,I/R＋DPI组的NOD1、caspase-1、NF-κB、TNF-ɑ蛋白表达减少(t＝－11.4, t＝－6.8, t＝－5.4, t＝－10.6, P<0.05);NOD1mRNA表达减少(t＝7.5, P<0.05);HE染色后者较前者急性肾小管坏死减轻,肾小管损伤评分减低(t＝－11, P<0.05);TUNEL染色显示缺血区凋亡细胞数目减少(t＝－10.8, P<0.05)。 结论抑制氧化应激可阻断NOD1样受体依赖的炎症途径与细胞凋亡,从而减轻肾缺血再灌注损伤。