High molecular weight plasma proteins induce apoptosis and Fas/FasL expression in human proximal tubular cells.

BACKGROUND: In proteinuria, proximal tubular epithelial cells (PTECs) are exposed to abnormally high protein concentrations, eventually leading to tubular atrophy and end-stage renal disease. The mode of cell death leading to tubular atrophy in proteinuria has not been fully established. This study examines the role of protein overload on apoptosis, necrosis and cell proliferation in primary cultures of human PTECs using plasma protein fractions representative of selective and non-selective proteinuria. The involvement of the Fas/Fas ligand (FasL) system was also investigated. METHODS: Plasma was collected from healthy volunteers and fractionated into albumin-rich (30-100 kDa), high molecular weight (100-440 kDa) and combined (30-440 kDa) fractions. PTECs were exposed to 10 mg/ml of the protein fractions for 24, 48 and 72 h. Apoptosis was measured using fluorescein isothiocyanate (FITC)-annexinV and TUNEL. Necrosis was measured using propidium iodide, metabolic activity by MTT and cell proliferation by bromodeoxyuridine incorporation. Fas and FasL expression was analysed by western blotting. RESULTS: Exposure to the 100-440 and 30-440 kDa fractions produced significant increases in apoptosis at all time points, whereas PTECs exposed to the 30-100 kDa fraction were not significantly different from control cells. There were no changes in the rates of necrosis as a result of protein loading. A significant reduction in metabolic activity was observed in PTECs exposed to the 100-440 and 30-440 kDa fractions, but not to the 30-100 kDa fraction. Cell proliferation was significantly reduced by 24 h in cells exposed to the 100-440 and 30-440 kDa fractions. By 48 and 72 h, all the three fractions had inhibited cell proliferation. PTECs exposed to the 100-440 and the 30-440 kDa fractions showed a significant upregulation in the expression of Fas and FasL. Overall, the high molecular weight fraction was more 'toxic' than the albumin-rich or combined fraction. CONCLUSION: Increased apoptosis and decreased cell proliferation are the major mechanisms of cell death in human PTECs in response to protein overload. These effects may be mediated at least in part by overexpression of the Fas/FasL system. The severity of such changes is largely determined by the high molecular weight fraction (100-440 kDa) rather than the albumin-rich fraction.     

Proapoptotic Fas ligand is expressed by normal kidney tubular epithelium and injured glomeruli

Fas ligand (FasL) is a cell membrane cytokine that can promote apoptosis through activation of Fas receptors. Fas receptor activation induces glomerular cell apoptosis in vivo and participates in tubular cell death during acute renal failure. However, there is little information on the expression of FasL in the kidney. This study reports that FasL mRNA and protein are present in normal mouse and rat kidney. In situ hybridization and immunohistochemistry showed that proximal tubular epithelium is the main site of FasL expression in the normal kidney. In addition, increased total kidney FasL mRNA and de novo FasL protein expression by glomerular cells were observed in two different models of glomerular injury : rat immune-complex proliferative glumerulonephritis and murine lupus nephritis. Both full-length and soluble FasL were increased in the kidneys of the mice with nephritis. Cultured murine proximal tubular epithelial MCT cells and primary cultures of murine tubular epithelial cells expressed FasL mRNA and protein. Tubular epithelium-derived FasL induced apoptosis in Fassensitive lymphoid cell lines but not in Fas-resistant lymphoid cell lines. By contrast, MCT cells grown in the presence of the survival factors of serum were resistant to FasL, and only became partially sensitive to apoptosis induced by high concentrations (100 ng/ml) of FasL upon serum deprivation. However, MCT cells stimulated with inflammatory mediators (tumor necrosis factor-alpha, interferon-gamma, and lipopolysaccharide) increased cell surface Fas expression and were sensitized to apoptosis induced by FasL (FasL 55 +/- 5% versus control 8.3 +/- 4.1% apoptotic cells at 24 h, P < 0.05). Cytokine-primed primary cultures of tubular epithelial cells also acquired sensitivity to FasL-induced apoptosis. These results suggest that FasL expression by intrinsic renal cells may play a role in cell homeostasis in the normal kidney and during renal injury.     

Fas配体诱导淋巴细胞凋亡与肾癌免疫攻击作用

目的　探讨Fas配体 (FasL)诱导淋巴细胞凋亡与肾癌免疫攻击作用的关系。　方法　采用免疫组化技术检测 4 4例肾癌组织FasL表达及肿瘤周围浸润淋巴细胞 (TIL)凋亡情况 ,并应用肾癌细胞株 786 0、GRC 1与JurkatT淋巴细胞共培养检测T细胞凋亡率。SP法检测Ki6 7表达 ,评价肾癌预后。　结果　 (1) 4 4例肾癌组织FasL表达阳性率 4 6 .5 % ,高于正常肾组织的 2 3.2 % ,差别有显著性意义 (P <0 .0 1)。随肾癌分期增加 ,FasL表达阳性率增加。肾癌FasL表达率与Ki6 7表达率呈显著正相关 (r =0 .93,P <0 .0 1)。 (2 )肾癌组织TIL凋亡率为 33.9% ,高于正常肾组织的3.5 % ,差别有显著性意义 (P <0 .0 1)。肾癌FasL表达率与TIL凋亡率呈显著正相关 (r =0 .96 ,P <0 .0 1)。 (3) 786 0FasL表达率 18.6 % ,GRC 1表达率 2 .3% ,二者差别有显著性意义 (P <0 .0 1)。Ju rkat细胞与 786 0细胞共培养的凋亡率 14 .9% ,与GRC 1共培养的凋亡率 1.3% ,二者差别有显著性意义 (P <0 .0 1)。中和抗体NOK 2中和 786 0细胞FasL后 ,与之共培养的Jurkat细胞凋亡率显著减少 (P <0 .0 1)。　结论　肾癌组织FasL表达增高 ,以此诱导淋巴细胞凋亡 ,实现对宿主的免疫攻击。     

Overexpressed exogenous IL-4 And IL-10 paradoxically regulate allogenic T-cell and cardiac myocytes apoptosis through FAS/FASL pathway

BACKGROUND: The authors' previous study has shown that liposome-mediated ex vivo intracoronary interleukin (IL)-4 and IL-10 combined gene therapy suppressed the allo-immune responses and prolonged the cardiac allograft survival by 15 folds. However, the mechanism for promoting long-term allograft survival remains unknown. METHODS: This study tested the hypothesis that this combined cytokine gene targeting may promote alloreactive T-cell apoptosis or prevent apoptosis of cardiac allograft myocytes through Fas/Fas ligand (FasL) pathway. A rabbit functional cervical heterotopic heart transplantation model was used, and plasmid human recombinant IL-4 and IL-10 gene complexed with cationic liposome (GAP/DLRIE) was delivered into cardiac allografts by intracoronary infusion ex vivo. RESULTS: This liposome-mediated IL-4 and IL-10 combined gene therapy significantly increased apoptotic T cells detected by TUNEL staining. The caspase-8 or caspase-3 expressing T cells were also significantly increased. The Fas+ apoptotic T cells dominated in the population of apoptotic CD4+ T cells, but FasL+ CD4+ T-cell population was less effected in the combined gene therapy group. The effect of combined gene therapy on the infiltrative Fas+ CD8+ T-cell population is much less than that on Fas+ CD4+ cells, and there was almost no effect on the FasL+ CD8+ T-cell population. Furthermore, localized IL-4 and IL-10 combined gene therapy protected cardiac allograft myocytes by down-regulating its FasL expression, but not Fas. CONCLUSIONS: These results suggest that this combined gene targeting strategy which induced localized overexpression of exogenous IL-4 and IL-10 may promote alloreactive T-cell apoptosis and prevent myocytes apoptosis through Fas/FasL cell surface interaction, therefore inducing cardiac allograft tolerance.     

Intracellular mechanisms of cyclosporin A-induced tubular cell apoptosis

Tubular cell apoptosis contributes to the pathogenesis of renal injury. However, the intracellular pathways that are active in tubular epithelium are poorly understood. The lethal pathways activated by cyclosporin A (CsA), a nephrotoxin that induces caspase-dependent apoptosis in tubular epithelium, were explored. Fas expression, caspase activation, and mitochondrial injury were assessed by Western blot, flow cytometry, and microscopy in cultured murine tubular epithelial cells exposed to CsA. The influence of FasL antagonists, Bax antisense oligodeoxynucleotides, and caspase inhibitors on cell survival was explored. Tubular cells constitutively express FasL. CsA increased the expression of Fas. However, Fas had no role in CsA-induced apoptosis, as CsA did not sensitize to FasL-induced apoptosis, caspase-8 activity was not increased, and neither blocking anti-FasL antibodies nor caspase-8 inhibition prevented CsA-induced apoptosis. Apoptosis induced by CsA is associated with the translocation of Bax to the mitochondria and Bax antisense oligodeoxynucleotides protected from CsA-induced apoptosis. CsA promoted a caspase-independent release of cytochrome c and Smac/Diablo from mitochondria. CsA also led to a caspase-dependent loss of mitochondrial membrane potential. Caspase-2, caspase-3, and caspase-9 were activated, and specific caspase inhibitor prevented apoptosis and increased long-term survival. Evidence for endoplasmic reticulum stress, such as induction of GADD153, was also uncovered. However, endoplasmic reticulum-specific caspase-12 was not activated. CsA induces changes in several apoptotic pathways. However, the main lethal apoptotic pathway in CsA-exposed tubular epithelial cells involves mitochondrial injury.     

Up-regulation of tissue factor activity on human proximal tubular epithelial cells in response to Shiga toxin

BACKGROUND: The pathophysiology of hemolytic uremic syndrome (HUS) is incompletely established. Based on clinical studies demonstrating the presence of prothrombotic plasma markers in patients with HUS, we hypothesized that Shiga toxin might cause activation of the coagulation pathway by augmenting tissue factor, the major initiator of coagulation. METHODS: Human proximal tubular epithelial cells (PTECs) [human kidney-2 (HK-2 cells)] were exposed to Shiga toxin-1, and expression of tissue factor, cell detachment, protein synthesis, caspase-3 activity, and Shiga toxin-1 binding were examined. Results. HK-2 cells expressed constitutive surface tissue factor activity and increased their tissue factor expression upon exposure to Shiga toxin-1. Shiga toxin-1 bound to HK-2 cells and inhibited protein synthesis. The up-regulation of tissue factor was dose- and time-dependent and strongly correlated with cell detachment and increase in caspase-3 activity caused by Shiga toxin-1 exposure. A general caspase inhibitor simultaneously inhibited HK-2 cell detachment and tissue factor up-regulation while mutant Shiga toxin-1 neither caused cell detachment, protein synthesis inhibition, nor increase in tissue factor activity. Tissue factor activity elicited by Shiga toxin-1 was abrogated by a monoclonal antitissue factor antibody. Calphostin C, a protein kinase C (PKC) inhibitor, partially blocked tissue factor up-regulation, indicating possible involvement of PKC-dependent mechanism. CONCLUSION: These data, taken together, suggest a strong link between Shiga toxin-induced up-regulation of tissue factor activity, cytotoxicity, and apoptosis in HK-2 cells. The proximal tubule is a target of Shiga toxin in HUS, and it seems plausible that injured proximal tubular cells trigger the activation of the coagulation system, the formation of intrarenal platelet-fibrin thrombi, and the development of acute renal failure in HUS.     

Fas/FasL表达和细胞凋亡在人类同种异体移植肾急性排斥中的作用

目的探讨移植肾急性排斥（ＡＲ）时细胞凋亡与Ｆａｓ和Ｆａｓ配体（ＦａｓＬ）表达的作用及其临床意义。方法分别用原位末端标记技术（ＴＵＮＥＬ法）和免疫组织化学方法检测２６例移植肾ＡＲ标本中细胞凋亡和Ｆａｓ／ＦａｓＬ表达情况。结果细胞凋亡和Ｆａｓ／ＦａｓＬ表达主要在ＡＲ移植肾小管上皮发生,且凋亡指数和Ｆａｓ／ＦａｓＬ表达与肾组织病理损伤程度平行,与正常肾对照组和移植肾功能稳定组比较差异显著（Ｐ＜０．０１）。结论肾小管上皮细胞凋亡在ＡＲ所致的移植肾损伤中起重要作用,Ｆａｓ／ＦａｓＬ系统可能参与移植肾ＡＲ,是造成肾小管上皮细胞凋亡的重要因素。ＴＵＮＥＬ法检测细胞凋亡可作为判断移植肾病理变化和预后的重要指标     

Enhancement of susceptibility to Fas-mediated apoptosis of TH1 cells by nonmitogenic anti-CD3epsilon F(ab')2

BACKGROUND: Anti-CD3epsilon F(ab')2 are nonmitogenic for naive T cells but can induce apoptosis of antigen-activated T cells in vitro and in vivo. We studied the mechanisms by which nonmitogenic anti-CD3epsilon F(ab')2 antibodies induce T cell death. METHODS: OVA-responsive T cell lines were generated by immunization in vivo and restimulation in vitro. Fas or Fas ligand (FasL) expression was tested by surface staining with specific mAbs. The apoptotic DNA and cell cycle phase were tested by staining DNA with propidium iodide. Interferon-gamma was measured by ELISA, whereas interleukin (IL)-2 and IL-4 were detected by bioassays. RESULTS: Restimulation with anti-CD3epsilon F(ab')2 induced apoptosis of antigen-activated wild-type T cells, but not Fas or FasL-defective T cells. Anti-CD3epsilon F(ab')2 induced death of cells expressing high levels of Fas and FasL, and preferentially deleted T helper (Th)1 cells but spared Th2 cells. Soluble anti-CD3epsilon F(ab')2 did not regulate Fas or induce FasL expression, indicating that the ability of anti-CD3epsilon F(ab')2 to induce T cell apoptosis depends on a distinct mechanism. T cells in S/G2 were found relatively resistant to Fas-mediated apoptosis, but anti-CD3epsilon F(ab')2 rendered those T cells exquisitely sensitive to Fas-mediated apoptosis. CONCLUSIONS: Anti-CD3epsilon F(ab')2 induces apoptosis of cycling CD4+ T cells through activation of the Fas/FasL pathway. Anti-CD3epsilon F(ab')2 does not regulate Fas or FasL expression but induces susceptibility to Fas-mediated apoptosis of cycling T cells. Anti-CD3epsilon F(ab')2 can induce death of polarized Th1 cells, but not Th2 cells, thus potentially skewing the repertoire of antigen-activated T cells toward the Th2 phenotype. These features predict that nonmitogenic anti-CD3epsilon F(ab')2-like antibodies can be useful to prevent or reverse pathogenic immune responses mediated by Th1 cells.     

MicroRNA-503 regulates high-glucose induced apoptosis of renal tubular epithelial cells by targeting Bcl-2

Objective To investigate the expression vibration of microRNA-503(miR-503) and its effect on target gene Bcl-2, caspase enzyme activity and apoptosis of human renal tubular epithelial cells (HK-2) induced by high glucose, and to clarify the pathogenesis of renal tubular injury induced by high glucose. Methods HK-2 cells were cultured in normal glucose group (NG), mannitol hypertonic control group (MA), and high glucose group (HG). The morphology of apoptotic cells was observed using inverted microscope. The expression of miR-503 was determined using real-time quantitative PCR. The apoptosis rate of HK-2 cells was detected by Annexin Ⅴ-FITC double dye using flow cytometry instrument. The expression of Bcl-2 and cleaved caspase-9 were detected by Western blotting. Results In the high glucose and mannitol groups HK-2 cell, an obviously increased apoptotic rate was observed under inverted microscope compared with normal glucose group (P＜0.05). MA and HG up-regulated miR-503 expression (P＜0.01), down-regulated anti-apoptotic protein Bcl-2 expression (P＜0.05) and up-regulated cleaved caspase-9 (P＜0.05). Conclusions The expression of miR-503 increases in HK-2 cells cultured by high glucose and mannitol. MiR-503 promotes apoptosis of HK-2 cells via activating mitochondrial apoptotic pathways and enhancing cleaved caspase-9 for Bcl-2 insufficiency. The tubular toxicity of high glucose is partly due to osmotic pressure. The miR-503 may be involved in diabetic tubular injury and may be a new therapeutic target of DN.     

复方苦参注射液诱导胃癌细胞凋亡的机制

目的探讨复方苦参注射液对胃癌SGC-7901细胞凋亡的影响及其可能机制。方法体外培养胃癌细胞系SGC-7901，四甲基偶氮唑盐（MTT）法测定药物对SGC-7901细胞生长的抑制作用；透射电镜下观察肿瘤细胞的超微结构变化；应用流式细胞术（FCM）检测肿瘤细胞凋亡情况和Fas、FasL蛋白的表达；分光光度法检测半胱氨酸天冬氨酸蛋白酶（caspase）-3活性的变化。结果不同浓度复方苦参注射液对SGC-7901细胞生长均有一定的抑制作用。0．5g／L、1．0g／L和1．5g／L复方苦参注射液组SGC-7901细胞凋亡率分别为39．80％、58．11％和79．00％，呈明显的量效关系；复方苦参注射液组以早期凋亡细胞为主，氟尿嘧啶对照组以晚期凋亡细胞为主。Fas蛋白表达及FasL蛋白表达与凋亡均呈显著正相关：Fas蛋白表达及FasL蛋白表达之间呈显著正相关。复方苦参注射液组caspase．3酶活性随着药物浓度而升高，且酶活性变化与细胞凋亡率变化呈正相关。结论复方苦参注射液可有效诱导胃癌SGC-7901细胞凋亡，其机制可能与上调Fas／FasL蛋白表达、激活caspase-3酶有关。     

The Fas ligand/Fas system in renal injury.

The FasL-Fas system regulates renal cell apoptosis, as well as the immune and inflammatory responses. Evidence that FasL and Fas participate in renal injury may be summarized along modified Koch's postulates (Table 1): (i) FasL is expressed by renal cells and during renal injury, (ii) activation of the Fas receptor promotes apoptosis of cultured renal cells, (iii) Fas agonists induce glomerular injury but they may also decrease renal injury by limiting injurious immunological responses, (iv) mice with disrupted FasL/Fas systems are protected from tubular cell injury during ischaemia reperfusion, although they develop autoimmune glomerulonephritis if other genetic predisposing factors are present. FasL/Fas must be considered a new target for therapeutic intervention in renal injury. Therapeutic modulation of Fas should aim not only at protecting intrinsic glomerular or tubular epithelial cells from death, but also at modulating the immune, inflammatory, and fibrogenic responses. Possible therapeutic interventions include Fas agonists, soluble Fas receptors, or other antagonists, and targetting of Fas to undesired cells, such as fibroblasts, in order to decrease their numbers in a physiological manner through apoptosis. Any therapeutic attempt should carefully take into account the possible effects of interference with Fas in other 1833 cell systems. Given the complexities of the FasL/Fas system, further studies are warranted.     

Local anesthetics induce human renal cell apoptosis

Renal cell apoptosis contributes significantly to the pathogenesis of acute renal failure. Local anesthetics induce apoptosis in neuronal and lymphocytic cell lines. We examined the effects of chronic (48 h) local anesthetic treatment (lidocaine, bupivacaine and tetracaine) on human proximal tubular (HK-2) cells. Apoptosis induction was assessed by detecting poly(ADP)-ribose polymerase fragmentation, caspase activation, terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) staining, DNA laddering and by cellular morphology. Cell death was quantified by measuring neutral red dye uptake and lactate dehydrogenase released into the cell culture medium. All 3 local anesthetics caused concentration-dependent cell death, induced HK-2 cell apoptosis and potentiated TNF-alpha induced apoptosis. Local anesthetics induced HK-2 cell apoptosis by activation of caspases 3, 6, 7, 8 and 9. ZVAD-fmk, a pan-caspase inhibitor, blocked the local anesthetic induced HK-2 cell apoptosis. Local anesthetics also inhibited the activities of anti-apoptotic kinases protein kinase B (Akt) and extracellular signal regulated mitrogen-activated protein kinase. Local anesthetic's pro-apoptotic effects are independent of sodium channel inhibition as tetrodotoxin, a selective voltage-gated sodium channel blocker, failed to mimic local anesthetic-mediated induction or potentiation of HK-2 cell apoptosis. We conclude that local anesthetics induce human renal cell apoptotic signaling by caspase activation and via inhibition of pro-survival signaling pathways.     

Fas and Fas-ligand expression in human pancreatic cancer

OBJECTIVE: To investigate Fas and FasL expression in pancreatic tissues and cultured pancreatic cancer cell lines, and to assess the ability of anti-Fas antibodies to induce apoptosis. SUMMARY BACKGROUND DATA: Activation of the Fas receptor by Fas-ligand (FasL) results in apoptosis, and dysregulation of this pathway may contribute to abnormal cell proliferation. METHODS: Northern blotting and immunohistochemistry were used to compare Fas and FasL expression in normal and cancerous tissues. DNA 3'-OH end labeling was used to detect apoptotic cells. The effects of Fas activation on cell growth and signaling pathways were investigated in culture. RESULTS: Pancreatic cancers exhibited increased Fas RNA levels, whereas FasL mRNA levels were similar in both groups. Despite the colocalization of Fas and FasL in the cancer cells, an apoptotic signal was present in approximately 10% of these cells in only 2 of 16 cancer samples. Fas and FasL were coexpressed in all four cell lines, whereas Fas-associated phosphatase 1 was below the level of detection in all cell lines. Only COLO-357 cells underwent apoptosis after Fas activation. Apoptosis was associated with enhanced activation of jun kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). In the presence of actinomycin D, Fas antibody also induced apoptosis in the other three cell lines. CONCLUSIONS: These results suggest that pancreatic cancer cells are resistant to Fas-mediated apoptosis by mechanisms excluding receptor downregulation or Fas-associated phosphatase upregulation and raise the possibility that Fas-mediated apoptosis may be dependent on the activation of the JNK/p38 MAPK pathway in these cells.     

The evaluation of Fas/Fas ligand system in renal cell carcinoma--the effect of preoperative interferon-alpha therapy

OBJECTIVES: In order to investigate the effect of preoperative interferon (IFN)-alpha on Fas/Fas ligand (FasL) system, we examined Fas and FasL expression and the occurrence of apoptotic cell death in a preoperative therapy group, and in a control group using surgically resected renal cell carcinoma (RCC) tissues. METHODS: Ten cases were served as the preoperative therapy group, and sixteen cases as the control group. IFN-alpha was administered at five megaunits daily intramuscularly for two weeks in the preoperative therapy group. Immunohistochemistry for Fas and FasL, and terminal-deoxynucleotidyl-transferase (TdT)-mediated digoxigenin-dUTP nick end-labeling (TUNEL) were employed. We defined the labeling index (LI) as percentage of Fas- or FasL-positive cells in carcinomatous cells, and apoptotic index (AI) as percentage of TUNEL-positive cells in carcinomatous cells. RESULTS: Significant correlations were found between the LIs of Fas and AIs in all 26 cases. LIs of Fas and AIs of the preoperative therapy group were significantly higher than those of the control group. FasL expression was detected in nine out of ten cases in the preoperative therapy group, and in fourteen out of sixteen cases in the control group. There were no significant differences in LIs of FasL between two groups. CONCLUSION: These data suggest that apoptosis via the Fas/FasL system is functional, and that preoperative IFN-alpha treatment may up-regulate the Fas/FasL system in RCC. On the other hand, we need to investigate about an immune-escape mechanism through the FasL expression considering the relatively frequent expression of FasL in our results in RCC from now.     

Fas/FasL在异源融合瘤诱导结肠癌细胞早期凋亡中的作用

目的 探讨Fas/FasL通路在人异源树突状细胞（dendritic cell,DC）/结肠癌细胞融合瘤诱导结肠癌细胞凋亡中的作用.方法 使用50%聚乙二醇（PEG）将健康人外周血来源DC与结肠癌细胞SW480融合,用其致敏T淋巴细胞,采用流式细胞术检测致敏细胞毒性T淋巴细胞（CTL）对结肠癌细胞凋亡的影响;使用免疫组化法分别检测SW480细胞Fas分子的表达以及T淋巴细胞活化前后FasL的表达情况.结果 结肠癌SW480细胞的早期凋亡率为46.88%;结肠癌SW480细胞高表达Fas分子用融合瘤致敏T细胞后,其FasL分子的表达明显增加.结论 异源树突状细胞融合瘤可能通过Fas/FasL通路来诱导结肠癌细胞的早期凋亡.     

A novel strategy for preventing human CD8+ cytotoxic T lymphocyte-mediated cytotoxicity against pig endothelial cells by overexpression of pig cellular FLICE-like inhibitory protein (c-FLIP) gene

Human CD8+ cytotoxic T lymphocyte (CTL)-mediated cytotoxicity in xenograft recipients is an important obstacle for successful xenotransplantation of pig organs into humans. In our previous study, we demonstrated that xenocytotoxicity of human CD8+ CTL detrimental to pig endothelial cells (PEC) is mediated mainly by the Fas/FasL apoptotic pathway. Furthermore, we developed new methods to prevent this CTL killing by extracellular remodeling using overexpression of human decoy Fas antigen and membrane-bound human FasL on pig xenograft cells. The cellular FLICE-inhibitory protein (c-FLIP), a caspase-8 inhibitor that lacks the cysteine domain, is a negative regulator of death receptor-mediated apoptosis. c-FLIP proteins exist as long (c-FLIP(L)) and short (c-FLIPs) splice variants, both capable of protecting cells from death receptor-mediated apoptosis. In this report, we have demonstrated that both pig c-FLIPs and pig c-FLIP(L) significantly inhibit human CD8+ CTL-mediated xenocytotoxicity toward stably transfected PEC, although the expression level of pig Fas antigen on cell surface was not changed. These data suggested that intracellular remodeling with overexpression of pig c-FLIP in xenograft cells may decrease the innate cellular responses against xenografts, facilitating long-term xenograft survival.     

Role of E-selectin in cell apoptosis induced by allogeneic blood perfusion in isolated mouse lung

BACKGROUND: In a model of mouse isolated lung, we have recently demonstrated that E-selectin is involved in the activation of endothelial cells induced by allogeneic blood perfusion. In the present study, we explored the signaling pathway of apoptosis induced by E-selectin triggering. METHODS: Lungs were perfused for 3 hours with fresh blood in the absence or presence of an anti-E-selectin monoclonal antibody, or a protein kinase C (PKC), protein tyrosine phosphatase (PTP), or protein tyrosine kinase (PTK) inhibitor. The number of apoptotic cells in lung sections was determined by a TUNEL method. mRNAs for Fas, FasL and caspase-8, and for Bad, Bax, Bcl-w, Bcl-xL and caspase-9, for the FasL and the mitochondrial cytochrome-c pathways of apoptosis, respectively, and mRNA for the effector caspase-3 were quantified in lung tissues by RT-PCR. PTP and Src-PTK activities were also measured. RESULTS: After 3 hours of allogeneic perfusion, we observed a significant increase in: 1) the number of apoptotic cells in lung sections, 2) mRNA levels of FasL, Bcl-xL, caspase-8 and caspase-3, and 3) PTP activity (P < 0.05 compared with isogeneic perfusion). Surprisingly, mRNA levels of the proapoptotic genes Bad and Bax were significantly decreased (P < 0.05). PTK activity and caspase-9 mRNA level were not affected. Blocking anti-E-selectin mAbs and inhibitors for PKC, PTP, and PTK resulted in a significant reduction of apoptosis. CONCLUSIONS: In our model, the engagement of E-selectin induced by endothelial cell allogeneic activation appeared to be a prerequisite for lung apoptosis, which involved FasL and increase of PTP activity. Blockade of apoptosis with selective inhibitors may be a promising approach to the treatment/prevention of lung graft injury.     

Fas on renal parenchymal cells does not promote autoimmune nephritis in MRL mice

BACKGROUND: Although Fas on pancreatic islets promotes autoimmune diabetes in mice, the role of Fas expression on kidney parenchymal cells during autoimmune disease is unknown. METHODS: To determine whether Fas on renal parenchymal cells promotes autoimmune renal destruction, we compared apoptosis and pathology in Fas-intact and Fas-deficient kidneys in an autoimmune milieu. For this purpose, we transplanted single, normal kidneys from MRL-++ (Fas-intact) mice (3 months of age) into age-matched, congenic MRL-Faslpr (Fas-deficient) recipients after removal of nephritic kidneys. These Fas-intact kidneys were compared with Fas-deficient nephritic kidneys. RESULTS: There is a progressive increase of FasL on kidney-infiltrating cells and Fas and FasL on renal parenchymal cells in MRL-++ kidneys during engraftment (0, 2, 4-6, and 8 weeks). By comparison, we detected an increase in FasL in MRL-Faslpr kidneys (3 to 5 months of age), whereas Fas was not detectable. The engagement of T cells bearing FasL with Fas expressing tubular epithelial cells (TECs) induced TEC apoptosis in vitro. However, apoptosis and pathology were similar in kidneys (MRL-++, 8 weeks postengraftment vs. MRL-Faslpr, 5 months) with equivalent amounts of FasL-infiltrating cells or FasL TECs, regardless of Fas on renal parenchymal cells. CONCLUSION: The expression of Fas on renal parenchymal cells does not increase apoptosis or promote renal disease in MRL-++ mice. We speculate that the autoimmune milieu evokes mechanisms that mask, counter, or pre-empt Fas-FasL-initiated apoptosis in MRL kidneys.     

New kids in the block: the role of FasL and Fas in kidney damage.

Fas ligand (FasL) is a lethal cytokine that promotes apoptosis through cross-linking of the Fas receptor, although it also has other, less well understood functions. The FasL/Fas system regulates immune and inflammatory responses. Evidence that FasL and Fas participate in kidney damage can be summarized as follows: 1) FasL is expressed by renal cells and its expression increases during kidney damage; 2) activation of the Fas receptor promotes apoptosis of non-stimulated or cytokine-primed renal cells in culture; 3) Fas agonists kill mesangial cells and induce glomerular injury in vivo, but can also reduce kidney damage by limiting injurious immunological responses; 4) mice with disrupted FasL/Fas systems are protected from acute tubular cell injury, although they develop autoimmune glomerulonephritis if other genetic predisposing factors are present. These facts imply that the FasL/Fas system can be considered a new target for therapeutic intervention in kidney damage. However, any therapeutic approach must consider interference with Fas in other cell systems. The complexities of the FasL/Fas system in the kidney are still far from clear.     

低渗非离子造影剂对肾小管上皮细胞凋亡的作用及其机制

目的 探讨低渗非离子型造影剂碘必乐诱导体外培养的人肾小管上皮细胞（HK-2细胞）凋亡的作用及机制。 方法 体外培养的HK-2细胞,分为阴性对照组、不同剂量（1.16、4.63、18.5、74、296 gI/L）的碘必乐作用组（作用时间为6 h）。通过流式细胞仪、Hoechst 33258染色观察细胞凋亡的比例和形态学变化;Western印迹方法检测凋亡蛋白天冬氨酸半胱氨酸蛋白酶3（caspase-3）的表达水平,并选取作用最强的剂量（296 gI/L）刺激2、4、6、12 h,观察caspase-3表达变化。选取不同剂量碘必乐作用1 h,与阴性对照组比较,观察细胞外信号调节激酶（ERK）和p38丝裂原活化蛋白激酶（MAPK）信号通路磷酸化水平的变化,并观察不同剂量p38MAPK抑制剂SB203580对碘必乐诱导的caspase-3和Bcl-2表达的影响。 结果 流式细胞仪检测结果示74、296 gI/L碘必乐作用下细胞凋亡率较阴性对照显著升高（均P < 0.05）。Hoechst 33258染色结果示296 gI/L碘必乐可致明显的细胞凋亡形态学改变,凋亡细胞核呈致密浓染或核碎裂。Western印迹检测方法表明,碘必乐以剂量和时间依赖方式诱导细胞内caspase-3表达,以296 gI/L作用12 h表达最强;各剂量碘必乐作用下细胞内ERK1/2磷酸化水平与阴性对照组的差异均无统计学意义（均P > 0.05）,而一定剂量的碘必乐处理组细胞内p38MAPK磷酸化水平较阴性对照组显著升高（均P < 0.05）。应用p38MAPK特异性抑制剂（30 μmol/L）预处理2 h可以阻断细胞内p38MAPK信号通路的磷酸化,抑制碘必乐诱导的细胞内caspase-3表达并部分上调Bcl-2表达,与碘必乐阳性对照组的差异均有统计学意义（P < 0.05）。 结论 低渗非离子型造影剂碘必乐以剂量和时间依赖方式诱导体外培养的HK-2细胞凋亡,其机制可能与上调caspase-3和下调抗凋亡蛋白Bcl-2有关,而p38MAPK信号通路的激活可能参与了该过程的调控。