老年人外周血淋巴细胞CD28及CD95表达变化研究

目的通过对老年人与成年人外周血淋巴细胞CD28及CD95表达水平的比较性研究,观察淋巴细胞凋亡在免疫衰老中的作用。方法采用免疫荧光标记流式细胞术,分析成年组(20~59岁)与老年组(60~90岁)各20例的外周血淋巴细胞表型水平。结果老年组CD28 CD95-[(8.80±4.86)%]及CD28 细胞[(36.32±10.38)%]明显低于成年组[(23.09±3.48)%、(52.29±4.90)%](P<0.01),而CD28-CD95 [(53.23±8.28)%]、CD95 [(80.25±7.19)%]及CD28-细胞[(63.68±10.38)%]明显高于成年组[(33.58±4.72)%、(63.18±4.12)%、(47.71±4.90)%](P<0.01)。结论老年人CD28 表达随年龄增长而下降,CD28-及CD95 表达随年龄增长而上升。提示淋巴细胞凋亡在免疫衰老中可能具有重要作用。     

Inhibition of Fas-mediated Apoptosis by Antigen: Implications for Lymphomagenesis

Apoptotic deletion of expanded B cell populations is essential in avoidance of autoimmune disease and immune regulation of some B cell malignancies. The role of CD4+ T cells in B cell apoptosis is evident from the high incidence of B cell tumors and autoimmunity in patients with T cell diseases such as the acquired immune deficiency syndrome (AIDS). We have previously demonstrated that in Epstein-Barr Virus (EBV) negative Burkitt's lymphoma (BL), a tumor derived from proliferating centroblasts of the germinal center, the malignant lymphocytes can be induced to express Fas (CD95) by ligation of CD40 at the B cell surface. Upon CD40 engagement, BL cells are sensitized to T-cell derived death signals provided by Fas ligand (FasL, CD95L). HBL-3 is a cell line derived from an AIDS-related BL in which the tumor IgM binds the human erythrocyte "i" antigen. To determine whether Fas-mediated apoptosis of BL cells is reduced in the context of antigen to which the tumor IgM binds, we stimulated HBL-3 cells with CD40 ligand (CD40L, CD154) in the presence and absence of human erythrocytes expressing the "i" antigen, and measured Fas-mediated apoptosis upon exposure to an agonistic anti-Fas antibody. We observed that HBL-3 cells were sensitized to Fas-mediated death by exposure to CD40L. When i+ RBCs were present, Fas-mediated apoptosis in HBL-3 cells was reduced by greater than 30%. In contrast, there was no reduction in Fas-mediated apoptosis in the presence of i &#109 (I+) RBCs. These findings demonstrate that Fas-mediated deletion of BL cells is inhibited upon surface IgM engagement by antigen for which the malignant clone has affinity.     

Amyloid-β oligomer synaptotoxicity is mimicked by oligomers of the model protein HypF-N

Protein misfolded oligomers are thought to be the primary pathogenic species in many protein deposition diseases. Oligomers by the amyloid-β peptide play a central role in Alzheimer's disease pathogenesis, being implicated in synaptic dysfunction. Here we show that the oligomers formed by a protein that has no link with human disease, namely the N-terminal domain of HypF from Escherichia coli (HypF-N), are also synaptotoxic. HypF-N oligomers were found to (i) colocalize with post-synaptic densities in primary rat hippocampal neurons; (ii) induce impairment of long-term potentiation in rat hippocampal slices; and (iii) impair spatial learning of rats in the Morris Water Maze test. By contrast, the native protein and control nontoxic oligomers had none of such effects. These results raise the importance of using HypF-N oligomers as a valid tool to investigate the pathogenesis of Alzheimer's disease, with advantages over other systems for their stability, reproducibility, and costs. The results also suggest that, in the context of a compromised protein homeostasis resulting from aggregation of the amyloid β peptide, a number of oligomeric species sharing common synaptotoxic activity can arise and cooperate in the pathogenesis of the disease.     

Overexpression of PDZ1 domain prevents apoptosis of rat hippocampal neurons induced by kainic acid

In our previous studies, Tat-GluR6-9c (a glutamate receptor 6 C-terminus peptide fused the TAT protein transduction sequence) not only inhibited the activation of MLK3 (mixed lineage kinase 3) and JNK (c-Jun N-terminal kinase) via the GluR6·PSD-95 (postsynaptic density protein 95)·MLK3 signaling module but also diminished neuronal death induced by kainic acid or transient cerebral ischemia in rat hippocampus. Here, we investigate whether overexpression of the PDZ1 domain of PSD-95 protein could suppress the binding of GluR6 with PSD-95 and the activation of MLK3, MKK7 (mitogen-activated kinase kinase 7) and JNK1/2, and rescused neuronal cell death induced by kainic acid. Our results showed that overexpression of the PDZ1 domain of PSD-95 protein could prevent nuclear accumulation and abrogate neuronal cell death in SD (Sprague–Dawley) rat hippocampal neuronal cells. Further studies indicated that overexpression of PDZ1 could inhibit the enhancement of binding of GluR6 to PSD-95 and prevent the activation of MLK3, MKK7 and JNK1/2 induced by kainic acid. Taken together, the essential role of the PDZ1 domain of PSD-95 in apoptotic cell death in neurons provides an experimental foundation for gene therapy of neurodegenerative diseases with overexpression of the PDZ1 domain.     

Aggressive NK cell leukaemia after splenectomy: association with CD95-resistant memory T-cell proliferation and recalcitrant clinical course of haemophagocytic syndrome

We describe a 44-yr-old Japanese woman with persistent polyclonal T-cell proliferation and recalcitrant clinical course of haemophagocytic syndrome (HPS). T cells bearing αβ T-cell receptors (TCR) expressed increased amounts of CD95 and of CD45RO, which are phenotypically memory T cells. The TCR repertoire was broad and diverse. Regardless of CD95 expression, these cells were resistant to CD95-mediated apoptosis. Aggressive natural killer cell leukaemia (ANKL) without an association with Epstein–Barr virus was detected 1 month after therapeutic splenectomy that followed 3 yr of immunosuppressive therapy against HPS. The immunophenotype of these leukaemia cells was CD56, CD16^dim, CD7, CD45RA and they expressed some CD2, CD8 and HLA-DR. Moreover, hyperdiploid clones with complex chromosomal abnormalities were also detected. Latent NK-cell malignancy seemed to cause the CD95-resistant memory T-cell proliferation and splenectomy resulted in overt ANKL progression. There should be careful consideration of the risks versus benefits of splenectomy in HPS, in light of the possibility of fatal leukaemia/lymphoma progression.     

Endoscopic duodenal stent versus surgical gastrojejunostomy for gastric outlet obstruction in patients with advanced pancreatic cancer

Background

Malignant gastric outlet obstruction (GOO) often develops in patients with advanced pancreatic cancer (APC). It is not clear whether endoscopic duodenal stenting (DS) or surgical gastrojejunostomy (GJJ) is preferable as palliative treatment.

Bile salt-induced apoptosis involves NADPH oxidase isoform activation

BACKGROUND & AIMS: Hydrophobic bile salts trigger a rapid oxidative stress response as an upstream event of CD95 activation and hepatocyte apoptosis. METHODS: The underlying mechanisms were studied by Western blot, immunocytochemistry, protein knockdown, and fluorescence resonance energy transfer microscopy in rat hepatocytes and human hepatoma cell line 7 (Huh7). RESULTS: The rapid oxidative stress formation in response to taurolithocholate-3-sulfate (TLCS) was inhibited by diphenyleneiodonium, apocynin, and neopterin, suggestive for the involvement of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases. TLCS induced a rapid serine phosphorylation of the regulatory subunit p47phox, which was sensitive to inhibition of sphingomyelinase and protein kinase Czeta (PKCzeta). Inhibitors of p47phox phosphorylation and p47phox protein knockdown abolished the TLCS-induced oxidative stress response and blunted subsequent CD95 activation. Consequences of TLCS-induced oxidative stress were c-Jun-N-terminal kinase activation and Yes-dependent activation of the epidermal growth factor receptor (EGFR), followed by EGFR-catalyzed CD95 tyrosine phosphorylation, formation of the death-inducing signaling complex, and execution of apoptosis. As shown by fluorescence resonance energy transfer experiments in Huh7 cells, TLCS induced a c-Jun-N-terminal kinase-dependent EGFR/CD95 association in the cytosol and trafficking of this protein complex to the plasma membrane. Inhibition of EGFR tyrosine kinase activity by AG1478 allowed for cytosolic EGFR/CD95 association, but prevented targeting of the EGFR/CD95 complex to the plasma membrane. Both processes, and TLCS-induced Yes and EGFR activation, were sensitive to inhibition of sphingomyelinase, PKCzeta, or NADPH oxidases. CONCLUSIONS: The data suggest that hydrophobic bile salts activate NADPH oxidase isoforms with the resulting oxidative stress response triggering activation of the CD95 system and apoptosis.     

MORT1/FADD is involved in liver regeneration

AIM: To explore the role of the adaptor molecule in liver regeneration after partial hepatectomy (PH).METHODS: We used transgenic mice expressing an N-terminal truncated form of MORT1/FADD under the control of the albumin promoter. As previously shown,this transgenic protein abrogated CD95- and CD120a-mediated apoptosis in the liver. Cyclin A expression was detected using Western blotting. ELISA and RT-PCR were used to detect IL-6 and IL-6 mRNA, respectively. DNA synthesis in liver tissue was measured by BrdU staining.RESULTS: Resection of 70% of the liver was followed by a reduced early regenerative response in the transgenic group at 36 h. Accordingly, 36 h after hepatectomy, cyclin A expression was only detectable in wild-type animals. Consequently, the onset of liver mass restoration was retarded as measured by MRI volumetry and mortality was significantly higher in the transgenic group.CONCLUSION: Our data demonstrate for the first time an involvement of the death receptor molecule MORT1/FADD in liver regeneration, beyond its well described role as part of the intracellular death signaling pathway.     

Estrogen receptor α is not a candidate gene for metabolic syndrome in Caucasian elderly subjects

Objective

Variants of estrogen receptor α (ERα) have been associated with obesity, dyslipidemia, diabetes and blood pressure. The Middle East registers some of the highest rate of metabolic syndrome worldwide. The aim of this study is to investigate the relationship between metabolic syndrome, a clustered combination of these metabolic factors, and polymorphisms PvuII and XbaI of ERα in Lebanese Caucasian elderly overweight subjects.

Material/Methods

250 Caucasian Lebanese unrelated elderly men and women, median age 71 years, were studied. ERα intronic polymorphisms variants, PvuII and XbaI diplotypes and genotypes, were examined. Associations with metabolic syndrome, defined by the American Heart Association/National Heart, Lung, and Blood Institute (AHA/NHLBI), and its components, namely high density lipoprotein (HDL), fasting glucose levels, blood pressure, and waist circumference were evaluated in regression models.

Results

ER α diplotypes and genotypes distributions were similar between participants with and without metabolic syndrome, in the overall group of subjects, and by gender. No consistent associations between the diplotypes and genotypes tested and metabolic syndrome, or its components, could be detected.

Conclusions

Genetic variants in ERα were not associated with metabolic syndrome or its components, in a group of 250 Lebanese Caucasian elderly participants, a group with a high prevalence of metabolic syndrome.