Apoptotic pathways of oxidative damage to renal tubular epithelial cells

Toxic renal failure induced by gentamicin, glycerol, or cisplatin, as well as ischemic renal failure in vivo and hypoxia/reoxygenation of tubular epithelial cells in vitro, induces the production of reactive oxygen metabolites (ROM). Generation of ROM is responsible for the induction of tubular epithelial cell death, which is mediated by caspases and/or endonucleases. Scavenging of ROM protects tubular epithelium from caspase and endonuclease activation and from cell death. Thus, the inhibition of ROM production combined with the pharmacological control of caspase and endonuclease pathways may provide future modalities in the prevention or treatment of acute renal failure in humans.     

Role of complement in renal tubular damage

Deposition of immunoglobulins, complement proteins C1q, C3c, C3d, C4, C5, C6, C7, C8, C9, and terminal complement complex neoantigens in the renal tubulointerstitium was studied in serial sections by immuno-fluorescence microscopy. Renal tissue from 45 cases with various glomerular diseases, including 8 controls, was studied. The patients were divided into groups; one with tubulointerstitial lesions (24 cases) and the other without (13 cases). The immunoproteins were deposited mainly in the tubular basement membrane and blood vessels. Compared with controls there was a significantly increased staining score for C5 to C9 in the tubular basement membrane in both disease groups. However, the increase in terminal complement complex neoantigens score was significant only in the disease group with tubulo interstitial lesions. The changes in C3d score were not significant. Serial sections showed consistent and heavy ribbon-like deposits of complement proteins C3d, C5 to C9, and terminal complement complex neoantigens in corresponding locations of the segments of tubular basement membrane, mainly in the disease group with tubulointerstitial lesions and especially in the damaged tubules. These findings suggest that in situ activation of the complement cascade leads to the deposition of terminal complement complex neoantigens. Complement activation in the basal area of the tubules may, therefore, be an important pathogenetic mechanism in tubulointerstitial damage.     

NOX1在TNF-α诱导的肺泡上皮细胞氧化损伤和炎症中的作用研究

目的:探索NADPH氧化酶1(NOX1)在肿瘤坏死因子α(TNF-α)诱导的肺泡上皮细胞A549氧化损伤和炎症中的作用。方法:以real-time PCR和Western blot法测定TNF-α处理后肺泡上皮细胞中NOX1的m RNA和蛋白表达水平。在肺泡上皮细胞中转染NOX1 si RNA及其阴性对照,以TNF-α诱导以后,用real-time PCR和Western blot测定细胞中NOX1水平。硫代巴比妥酸法检测细胞中丙二醛(MDA)含量,黄嘌呤氧化法检测细胞中超氧化物歧化酶(SOD)活性,ELISA法检测细胞培养液中的白细胞介素4(IL-4)、白细胞介素6(IL-6)和白细胞介素1β(IL-1β)含量,流式细胞术检测细胞凋亡率,Western blot检测凋亡蛋白cleaved caspase-3的水平。结果:TNF-α诱导处理后A549细胞中NOX1 m RNA和蛋白水平均升高(P 0. 05),NOX1 si RNA转染可以下调细胞中NOX1的m RNA和蛋白表达(P 0. 05),转染si RNA阴性对照对细胞中NOX1的m RNA和蛋白表达没有影响。TNF-α处理后细胞中MDA含量升高,SOD活性降低,细胞分泌的IL-4、IL-6和IL-1β增多,细胞凋亡率和凋亡蛋白cleaved caspase-3水平均升高,与没有经TNF-α处理的细胞比较,差异有统计学意义(P 0. 05)。下调NOX1的细胞经TNF-α诱导后,细胞中MDA含量降低,SOD活性升高,细胞分泌的IL-4、IL-6和IL-1β减少,凋亡率及凋亡蛋白cleaved caspase-3水平降低,与只经过TNF-α诱导处理的细胞比较,差异有统计学意义(P 0. 05)。结论:TNF-α诱导肺泡上皮细胞表达NOX1。下调NOX1表达可减少细胞氧化损伤和炎症因子分泌,减少细胞凋亡。     

EGFR在高糖诱导下人肾小管上皮细胞凋亡中的作用

目的观察EGFR信号通路对高糖诱导下人肾小管上皮细胞(HK-2)凋亡的影响和机制。方法体外培养HK-2细胞,将细胞分为4组:对照组、渗透压对照组、高糖组和高糖加EGFR抑制剂AG1478组。用Western blot检测p-EGFR、total EGFR、cleaved caspase-3、BAX、BCL-2及β-actin的蛋白表达,四唑盐比色法(MTT)检测细胞活性,流式细胞术检测细胞凋亡。结果与对照组和渗透压对照组相比,高糖组HK-2细胞EGFR活性、cleaved caspase-3表达、BAX/BCL-2比值和内质网应激(ERS)明显升高,细胞活性降低(P0.01)。EGFR抑制剂AG1478能够明显抑制高糖诱导的HK-2细胞EGFR活化和细胞凋亡(P0.05),提高细胞活性(P0.05),同时抑制内质网应激(P0.05)。结论抑制EGFR活性能够减少高糖诱导的HK-2细胞凋亡,这可能是通过减少内质网应激实现的。     

Embolic tubular epithelial cells in percutaneous renal biopsies

Four percutaneous renal biopsies with intravascular embolic tubular epithelial cells are presented. This unusual finding is presumably the result of the needle biopsy procedure and can be a puzzling and misleading artifact. It is postulated that dislodged tubular epithelial cells are pushed forward into or pulled back into punctured intrarenal arteries and subsequently transported to distant glomeruli.     

淫羊藿苷通过AMPK减轻脂肪酸诱导的肾小管上皮细胞线粒体损伤

目的:探讨淫羊藿苷(icariin,ICA)对脂肪酸诱导的肾小管上皮细胞线粒体损伤的作用及其可能机制.方法:利用ICA干预棕榈酸(palmitic acid,PA)培养的大鼠肾小管上皮NRK52E细胞,实验分组为对照组、PA组、PA+ICA组及AMP活化蛋白激酶(AMP-activated protein kinase...     

ICAM-1反义寡核苷酸对小鼠肾小管上皮细胞ICAM-1表达的影响

目的:探讨ICAM1反义寡核苷酸对小鼠肾小管上皮细胞表达ICAM1的影响,为利用ICAM1反义寡核苷酸类药物治疗肾小管间质病变奠定基础。方法:小鼠ICAM1反义寡核苷酸及其对照物参照文献合成并行全硫代磷酸化修饰。部分ICAM1反义寡核苷酸在其5′端作FITC荧光标记。将ICAM1反义寡核苷酸单独或脂质体转染试剂DOTAP混合后转染至培养的肾小管上皮细胞之中,转染成功后加入IL1β诱导细胞产生ICAM1。采用对照寡核苷酸及不含寡核苷酸的细胞转染液作为实验对照及空白对照。利用免疫组化染色的方法检测细胞ICAM1表达变化并提取细胞总RNA行逆转录PCR及Northern杂交观察ICAM1mRNA的表达的变化。结果:两个不同浓度的ICAM1反义寡核苷酸均可明显阻断IL1β诱导的肾小管上皮细胞ICAM1及ICAM1mRNA的表达;对照的寡核苷酸不能减少IL1β诱导的肾小管上皮细胞ICAM1及ICAM1mRNA的表达。结论:小鼠ICAM1反义寡核苷酸可明显抑制IL1β诱导的小鼠肾小管上皮细胞ICAM1及ICAM1mRNA的表达,提示ICAM1的反义寡核苷酸有可能应用于肾小管间质病变的实验治疗之中。     

HIV-1 infection initiates an inflammatory cascade in human renal tubular epithelial cells

HIV-associated nephropathy (HIVAN) is the most common cause of chronic renal failure in HIV-infected patients. Tubulointerstitial inflammation is a prominent component of the histopathology of HIVAN. The pathogenesis of HIVAN is a result of infection of renal epithelial cells, but the cellular response to this infection remains poorly defined. In these studies, we used oligonucleotide microarrays to identify differentially expressed genes in renal tubular epithelial cells from a patient with HIVAN at three time points after infection with vesicular stomatitis virus-pseudotyped gag/pol-deleted HIV-1. Very few genes were differentially expressed 12 and 24 hours after infection. Three days after infection, however, 47 genes were upregulated by at least 1.8-fold. The most prominent response of these cells to HIV-1 expression was production of proinflammatory mediators, including chemokines, cytokines, and adhesion molecules. Many of the upregulated genes are targets of interleukin 6 and nuclear factor kappa B regulation, suggesting a central role for these proteins in the response of tubular epithelial cells to HIV-1 infection. Analysis of kidneys from HIV-1 transgenic mice revealed upregulation of many of the proinflammatory genes identified in the microarray studies. These studies provide novel insights into the mechanisms by which HIV-1 infection of tubular epithelial cells leads to tubulointerstitial inflammation and progressive renal injury.     

ICAM—1反义寡核苷酸对小鼠肾小管上皮细胞ICAM—1表达的影响

目的：探讨ＩＣＡＭ－１反应寡核苷酸对小鼠肾小管上皮细胞表达ＩＣＡＭ－１的影响，为利用ＩＣＡＭ－１反义核苷酸类药物治疗肾小管间质病变奠定基础。方法：小鼠ＩＣＡＭ－１反义寡核苷酸及其对照物参照文献合成并行全硫代磷酸化修饰。部分ＩＣＡＭ－１反义寡核苷酸在其５‘端作ＦＩＴＣ荧光标记。将ＩＣＡＭ－１反义寡核苷酸单独或脂质体转染试剂ＤＯＴＡＰ混合反转染至培养的肾小管上皮细胞之中，转染成功后加入ＩＬ－１β诱导细     

人肾小管上皮细胞necroptosis模型的构建

 目的：以体外培养的人肾小管上皮细胞（HK-2细胞）为靶细胞,构建肾小管上皮细胞凋亡样坏死（necroptosis）的模型。方法：采用肿瘤坏死因子 α (tumor nercosis factor α, TNF-α)诱导细胞凋亡,同时采用抗霉素A (antimycin A)耗竭ATP,构建肾小管上皮细胞凋亡的模型,并以caspase-8抑制剂苄氧羰酰-缬氨酰-丙氨酰-天冬氨酰-氟甲基酮(benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone, zVAD-fmk) 阻断凋亡,用necroptosis的特异性抑制剂necrostatin-1（Nec-1）阻断necroptosis,观察细胞在不同的处理下形态学的变化,同时检测细胞存活率及标志物微管相关蛋白1轻链3-Ⅱ（microtubule-associated protein 1 light chain 3-Ⅱ,LC3-Ⅱ）的表达。结果：（1）在TNF-α+zVAD- fmk+antimycin A处理1 h时细胞及细胞器膨胀,电镜下细胞膜碎裂,线粒体变圆、肿胀,嵴逐渐模糊,胞浆中出现大量自噬小体,而Nec-1预处理后细胞的坏死程度较对照组明显改善。（2）在TNF-α+zVAD-fmk+antimycin A 1 h实验组,Nec-1预处理后细胞的存活率显著增加（P<0.05）。（3）TNF-α+zVAD-fmk+antimycin A干预1 h实验组在Nec-1预处理后LC3-Ⅱ的表达量明显下降（P<0.05）。结论：凋亡环境中阻断凋亡可以诱导肾小管上皮细胞necroptosis,抑制剂Nec-1能特异性阻断肾小管上皮细胞发生坏死。     

Snail1/IGF-1信号通路介导高糖诱导的肾小管上皮细胞EMT

目的:观察高糖诱导大鼠肾小管上皮细胞NRK-52E中锌指转录因子Snail1和胰岛素样生长因子1(insulin-like growth factor-1,IGF-1)的表达变化,并初步探讨Snail1与IGF-1在糖尿病肾脏病(diabetic kidney disease,DKD)上皮-间充质转化(epithelial to mesenchymal transition,EMT)过程中的关系。方法:高糖培养大鼠近端肾小管上皮细胞系NRK-52E 72 h后,给予Snail1 siRNA和IGF-1 siRNA处理,分为高糖组、non-targeting(NT)siRNA组、Snail1 RNAi组和IGF-1 RNAi组,并设置对照组。于转染后48和72 h两个时点收获细胞。分别用实时荧光定量PCR检测细胞Snail1、IGF-1、E-钙黏蛋白(E-cadherin)和纤维连接蛋白(fibronectin,FN)的mRNA表达,用免疫荧光方法检测各蛋白的表达。结果:高糖诱导NRK-52E细胞E-cadherin的mRNA和蛋白表达明显降低(P0.01),FN的mRNA和蛋白表达明显升高(P0.01);同时,Snail1和IGF-1的mRNA和蛋白表达也明显升高(P0.01)。Snail1 RNAi组与高糖组比较,细胞中E-cadherin的mRNA和蛋白表达明显升高(P0.01),FN、Snail1和IGF-1的mRNA和蛋白表达明显降低(P0.01),Snail1的mRNA表达减少62.8%。与高糖组比较,IGF-1 RNAi组细胞IGF-1的mRNA表达减少61.1%,E-cadherin的mRNA和蛋白表达明显升高(P0.01),FN的mRNA和蛋白表达明显降低(P0.01)。NT组E-cadherin、FN、Snail1及IGF-1的mRNA和蛋白表达与高糖组比较差异无统计学显著性。Pearson相关性分析显示,NRK-52E细胞中Snail1与IGF-1蛋白的表达呈显著正相关(r=0.852,P0.01)。结论:Snail1及IGF-1的mRNA和蛋白在高糖诱导的肾小管上皮细胞EMT过程中表达升高,且沉默Snail1基因,IGF-1表达随之减少,提示Snail1/IGF-1可能促进DKD时肾小管上皮细胞EMT。     

转化生长因子β1抑制人肾小管上皮细胞的增殖

背景：慢性肾衰竭进展过程中的一个重要病理改变是炎症和纤维化,主要包括肾小球和肾小管的炎症和纤维化。目前大多数研究主要集中于肾小球,对于肾小管病变的研究相对较少。但实际上部分疾病的肾小管病变出现在肾小球病变之前,其对于疾病预后更具有指导意义。 目的：观察转化生长因子β1对人类肾小管上皮细胞HK-2增殖的影响,探索转化生长因子β1在肾小管炎症和纤维化方面的作用。 方法：将传代培养的HK-2细胞分成空白对照组和转化生长因子β1作用组,分别使用DMEM/F12培养液,以及含转化生长因子β1(2,5,10 μg/L)的DMEM/F12培养液培养,在倒置显微镜下观察各组细胞形态的改变,并使用MTT法检测细胞增殖情况。 结果与结论：转化生长因子β1能显著抑制人肾小管上皮细胞的增殖,并促使细胞向纤维样改变,与空白对照组相比差异有显著性意义(P < 0.05),其抑制增殖作用并不随转化生长因子β1质量浓度的增大而显著增强,作用时间可持续至72 h。结果可见转化生长因子β1能够抑制人肾小管上皮细胞的增殖,并具有促进肾间质纤维化的作用。     

C-反应蛋白诱导人肾小管上皮细胞凋亡

目的:探讨与微炎症状态相应的C-反应蛋白(CRP)水平是否诱导肾小管上皮细胞凋亡。方法:以微炎症状态相应的CRP浓度刺激HK-2细胞。采用AnnexinⅤ-FITC、PI染色和流式细胞术检测凋亡细胞的百分率。采用Hoechst 33258染色观察肾小管上皮细胞凋亡的形态学改变。比色法检测细胞caspase-3活性。Real-time PCR检测促凋亡基因bax、抗凋亡基因bcl-2的mRNA表达。结果:CRP呈剂量和时间依赖性地诱导HK-2细胞凋亡,细胞凋亡在CRP浓度为10 mg/L时达高峰,在20 mg/L时则以晚期凋亡和坏死为主。Hoechst 33258细胞核染色显示CRP作用的HK-2细胞呈现染色质浓缩、碎裂或染色质边集等细胞凋亡的特点。CRP增高细胞caspase-3的酶活性、上调促凋亡基因bax的表达和下调抗凋亡基因bcl-2的表达。结论:CRP轻度增高可诱导肾小管上皮细胞凋亡。     

Hyaluronan attenuates transforming growth factor-beta1-mediated signaling in renal proximal tubular epithelial cells

Increased expression of hyaluronan (HA) has been associated with both acute renal injury and progressive renal disease, although the functional significance of this remains unclear. There is overwhelming evidence that transforming growth factor (TGF)-beta1 is critical to the development of progressive renal disease. Recent studies suggest an interaction between HA and TGF-beta signaling in cancer cell biology. The aim of this study was to examine the potential role of HA as a modulator of TGF-beta1 function in renal proximal tubular epithelial cells (PTC). Under resting conditions, co-localization of the principal receptor for HA, CD44, and both the TGF-beta type I and type II receptors was demonstrated by immunoprecipitation and western analysis and further confirmed by immunocytochemistry and confocal microscopy. Stimulation of PTC with TGF-beta1 led to increased synthesis of both type III and type IV collagen assessed by Western analysis. Addition of HA did not alter collagen synthesis, but abrogated TGF-beta1-mediated increase in type III and type IV collagen. This effect was blocked by the addition of a blocking antibody to CD44 and also by inhibition of MAP kinase kinase (MEK) activity. Furthermore HA decreased TGF-beta1 activation of a luciferase-SMAD responsive construct, and decreased translocation of SMAD4 into the cell nucleus. We have previously demonstrated an anti-migratory effect of TGF-beta1 in a scratch wounding model. As with HA antagonism of TGF-beta1 extracellular matrix generation, HA reduced the anti-migratory effect of TGF-beta1 in a CD44-dependent manner. In contrast to the effect of TGF-beta1 on collagen synthesis, which is SMAD-dependent, the anti-migratory effect of TGF-beta1 in this model is known to be dependent of activation of RhoA. In the presence of HA, TGF-beta1-mediated activation of RhoA was also abrogated in a CD44-dependent manner. The results suggest that co-localization of CD44 and TGF-beta receptors facilitate modulation of both SMAD and non-SMAD-dependent TGF-beta1-mediated events by HA. Our results therefore suggest that alteration of HA synthesis may represent an endogenous mechanism to limit renal injury.     

Apoptosis of tubular epithelial cells in rats with chronic renal failure

Tubular injury leading to tubular atrophy and tubular loss is one of the characteristic features of chronic renal failure. To reveal the mechanism of tubular atrophy in chronic renal failure, the involvement of apoptosis was studied byin situ nick end labeling of biotinylated deoxyuridine by terminal deoxy nucleotidyl transferase (TUNEL) as well as by electron microscopy. TUNEL-positive cells and heterophagosomes containing apoptotic body-like structures having nuclear fragments with condensed chromatin were observed in the renal tubular epithelium 8 weeks after nephrectomy. It has become apparent from our study that atrophy of the tubules in chronic renal failure results, to some extent, from cell deletion by apoptosis.     

Role of angiotensin II-induced renal functional changes in mesangial deposition of exogenous ferritin in rats

The relationship between acute angiotensin II (AII)-induced functional changes of the kidney and mesangial localization of macromolecules was investigated in rats utilizing native horse spleen ferritin as an exogenous tracer. One group of rats received a 30-minute infusion of a pressor dose of AII. Ten minutes before sacrifice they were injected with a single intravenous dose of ferritin. In the other group the injection of ferritin was followed by an 80-minute infusion of AII. Serial measurements of systolic blood pressure (BP), inulin clearance (CIN), p-aminohippuric acid (PAH) clearance (CPAH), filtration fraction (FF), and excretion of albumin (UAlb V) and ferritin (UFe V) were obtained. Although AII-treated rats showed significant increases of BP, FF, UAlb V and UFe V over controls, they were not different from controls with respect to plasma ferritin concentrations, renal delivery of ferritin, CPAH, and CIN. Semiquantitative evaluation of renal tissue by immunofluorescence and electron microscopy revealed that at 10 minutes no differences in the early and mild deposition of ferritin in the mesangium were appreciable. In contrast, at 80 minutes, AII-treated rats had markedly enhanced mesangial localization of ferritin when compared with controls. In the animals infused with AII for 80 minutes, the amount of glomerular ferritin deposition correlated strongly with UAlb V and UFe V. Combining the results of both, AII and controls at 80 minutes, these correlations were still present, in addition to weaker yet significant correlations of glomerular ferritin with BP and absolute changes of FF during the treatment period. The results show that, over a time interval of 80 minutes, AII augments the mesangial accumulation of ferritin in the presence of normal tracer delivery to the kidney. The enhanced mesangial localization of ferritin is observed under circumstances where overall increases in glomerular capillary permeability to albumin and ferritin are present. Although the precise mechanisms underlying these effects are not identified, AII-induced changes of glomerular microcirculatory forces and permeability properties of the glomerular capillary appear to be involved.     

IL-18对肾小管上皮细胞表型转化的影响

目的：研究IL-18对体外培养肾小管上皮细胞表型转化的影响，以明确IL-18在慢性肾脏疾病中的可能作用机制。方法：应用体外细胞培养技术培养人肾小管上皮细胞侏（HK-2）。应用RT-PCR技术检测α-平滑肌肌动蛋白（α-SMA）、转化生长因子-β1（TGF-β1）mRNA水平，用免疫细胞化学方法（ICC）及Western blot技术分别检测IL-18对HK-2细胞表达仪-SMA蛋白的影响。结果：（1）IL-18可促进HK-2细胞表达α-SMA、TGF-β1 mRNA，且两者之间呈正相关（P〈0．05）。（2）IL-18增加α-SMA阳性HK-2细胞百分数（P〈0．05）。（3）IL-18使HK-2细胞α-SMA蛋白表达水平增加。结论：IL-18可剂量和时间依赖性地促进肾小管上皮细胞转分化为肌成纤维细胞，促进肾间质纤维化。     

STAT蛋白在抑瘤素M诱导的肾小管上皮细胞损伤中的作用

目的探讨STAT蛋白在抑瘤素M(oncostatin M,OSM)诱导的肾小管上皮细胞表型转化及分泌功能中的作用。方法体外培养人肾近曲小管上皮细胞,分为对照组(C组)、OSM(20 ng/ml)组(OSM组)、OSM+雷帕霉素(100 ng/ml)组(OSM+R组)和OSM+氟达拉滨(100 ng/ml)组(OSM+F组)。培养72 h后收集细胞及上清液,透射电镜观察细胞超微结构改变;免疫细胞化学和Western blot法检测CK18、α-SMA蛋白表达;采用Western blot法检测信号转导及转录激活因子(STAT1、STAT3、pSTAT1、p-STAT3)的表达;酶联免疫吸附实验测定细胞上清液中Ⅰ型胶原(collagenⅠ,ColⅠ)和纤维连接蛋白(fibronectin,FN)的分泌。结果与对照组相比,细胞经OSM刺激后CK18的表达下调,而α-SMA的表达上调并分泌过多的细胞外基质蛋白ColⅠ和FN;此外,OSM还可磷酸化激活STAT1和STAT3。OSM的上述作用可被雷帕霉素和氟达拉滨所阻断。结论 OSM具有促纤维化特性,而STAT1和STAT3信号活化在OSM介导的纤维化进程中发挥同等重要的作用。     

Methods of assessing oxidant injury in renal tubular epithelial cells in vitro

Summary Reactive oxygen molecules mediate renal injury in several diseases including glomerulonephritis, ischemic-reperfusion injury, and toxic nephropathies. Several in vivo animal studies document a role for reactive oxygen molecules in causing tissue injury. In vitro methods to determine the mechanisms and effects of reactive oxygen molecule injury will further aid in understanding the pathogenesis of several renal diseases. We describe methods to study cell injury in an in vitro cell culture system of renal tubular epithelial cells exposed to reactive oxygen molecules generated by hypoxanthine-xanthine oxidase or glucose-glucose oxidase. Methods to determine ATP levels and [³H]adenine release as an early response (15 to 90 min) to oxidant stress are described.⁵¹Chromium release representing cell detachment and cell lysis which are late responses (3 to 5 h) are also detailed. Methods of assessing oxidant injury in in vitro systems will allow the precise mechanisms of cell injury to be determined and will allow for the potential development of strategies to prevent or alleviate such injury. Supported by grants from the American Heart Association, Indiana Affiliate, and the James Whitcomb Riley Memorial Association with funds contributed by the Mayflower Classic.     

Human renal tubular epithelial cells suppress alloreactive T cell proliferation

Renal tubular epithelial cells (TECs) are one of the main targets of alloreactive T cells during acute rejection. We hypothesize that TECs modulate the outcome of alloimmunity by executing immunosuppressive effects in order to dampen the local inflammation. We studied whether TECs possess immunosuppressive capacities and if indoleamine 2,3-dioxygenase (IDO) might play a role in suppressing T cell alloreactivity. Next, we studied the role of programmed death ligand 1 (PD-L1) and intercellular adhesion molecule-1 (ICAM-1 with regard to TEC-related immunomodulatory effects. CD3/CD28 and alloactivated peripheral blood mononuclear cells were co-cultured with activated TECs. We analysed CD4⁺ and CD8⁺ T cell proliferation and apoptosis in the absence or presence of IDO inhibitor 1-methyl-L-tryptophan (1-L-MT), anti-PD-L1 and anti-ICAM-1. Further, we examined whether inhibition of T cell proliferation was cell–cell contact-dependent. We found that TECs dose-dependently inhibited CD4⁺ and CD8⁺ T cell proliferation (P < 0·05). Activated TECs showed significantly increased IDO activity and up-regulated PD-L1 and ICAM-1 expression. Suppressed CD4⁺ and CD8⁺ T cell proliferation was only partially restored or failed to restore using 1-L-MT. Activated TECs increased early and late apoptosis of proliferating CD4⁺ and CD8⁺ T cells; only CD4⁺ T cell apoptosis was statistically affected by 1-L-MT. Transwell experiments revealed that TEC-mediated immunosuppression is cell–cell contact-dependent. We found that anti-ICAM-1 affected only CD4⁺ T cell apoptosis and not T cell proliferation. Our data show that TECs suppress both CD4⁺ and CD8⁺ T cell proliferation contact dependently. Interestingly, inhibition of proliferation and enhancement of apoptosis of T cell subsets is differentially regulated by indoleamine 2,3-dioxygenase and ICAM-1, with no evidence for the involvement of PD-L1 in our system.