Molecular genetic characterization of alternatively spliced CD44 transcripts in human stomach carcinoma.

CD44 is a member of cell surface glycoproteins which are involved in cell-matrix adhesion and tumor metastasis. Certain types of tumors express complex CD44 isoforms generated by alternative splicing of 2v-10v exons, and their expression appears to promote metastasis of tumor cells. Using a nested RT-PCR, we analyzed expression of CD44 variants in 26 stomach carcinoma, 21 matched normal tissues, and 2 carcinoma cell lines. We observed frequent and complex patterns of CD44 variant expression in tumor tissues. While exons 6v and 7v expression was detected in most normal and tumor tissues, exon 9v was most rarely detected. Exon 5v showed a significantly frequent expression in carcinoma, suggesting that its expression might contribute to the malignant progression. While exon 9v was frequently observed in diffuse-type tumors, the other 8 variant exons including 6v showed more frequent expression in intestinal-type tumors. Exons 9v and 10v were predominantly expressed in advanced tumor tissues and exon 8v was expressed more frequently in tumors of lymph node metastasis. We believe that series with a longer follow-up now need to be tested to clarify the association between CD44 splice variant expression and distant metastasis or long-term prognosis.     

氧化型低密度脂蛋白抗体对单个核细胞CD36 mRNA表达的影响

目的:通过观察氧化型低密度脂蛋白(OX-LDL)抗体对单个核细胞CD36 mRNA表达的影响,探讨OX-LDL抗体影响泡沫细胞形成的可能机制。方法:U937细胞和新西兰兔外周血单个核细胞分别被分成4组:空白对照组(普通培养基孵育)、OX-LDL刺激组(培养基中添加50μg/L的兔抗人OX-LDL多克隆抗体)、抗体干预组(培养基中添加50μg/L的兔抗人OX-LDL多克隆抗体及100μg/L的纯化人OX-LDL)及单纯抗体组(培养基中添加100μg/L的纯化人OX-LDL),经培养24 h后,利用半定量RT-PCR技术分析CD36的mRNA表达水平。结果:无论在U937细胞或兔单个核细胞中,OX-LDL刺激组及抗体干预组CD36 mRNA的表达量均显著高于对照组,而经抗体干预后,CD36 mRNA表达量在U937细胞和在兔单个核细胞分别降低了约64.80%和35.18%,种属间差异有统计学意义。结论:抗OX-LDL抗体可以抑制单个核细胞CD36抗原的表达,从而抑制泡沫细胞形成过程中OX-LDL向细胞内的聚集。     

白细胞介素18受体在人类外周血单个核细胞及肾组织表达的研究

目的 :进一步明确白细胞介素 (IL 18)在肾组织免疫性损伤中的作用。方法 :应用半定量逆转录 多聚酶链反应(RT PCR)技术检测 16例正常人 ,16例原发性系膜增生性肾小球肾炎 (MsPGN)患者以及 18例狼疮性肾炎 (LN)患者外周血单个核细胞 (PBMC)白细胞介素 18受体 (IL 18R)α链mRNA的表达量 ,并用免疫组化方法检测 6例正常肾组织 ,16例MsPGN)患者及 18例LN患者肾组织IL 18Rα链蛋白表达量。结果 :MsPGN患者PBMCIL 18RmRNA表达量较正常组有所增高 ,但未达统计学意义 (P >0 0 5 ) ,LN患者PBMCIL 18RmRNA表达量较正常人显著增高 (P <0 0 0 1) ;正常肾组织存在较弱的IL 18R表达 ,MsPGN患者肾组织IL 18R表达量较正常肾组织有所增强 ,但未达统计学差异 ,而LN患者肾组织IL 18R的表达量较正常肾组及MsPGN组均显著增强 (P <0 0 0 1) ,但Pearson相关分析发现LN患者PBMC及肾组织IL 18R表达量均不与血清肌酐 (Scr)水平及 2 4小时尿蛋白排泌量 (2 4h UPE)存在相关关系。结论 :IL 18信号在全身系统及肾组织局部的免疫调节中起一定的作用 ;IL 18在肾功能未严重损害MsPGN患者的发病过程中可能所起作用不大 ;LN患者不但存在IL 18的过量产生 ,而且存在着IL 18过度作用的问题 ,抑制过强的IL 18作用信号可能是LN治疗的新途径。     

Macrophage recognition and phagocytosis of apoptotic fibroblasts is critically dependent on fibroblast-derived thrombospondin 1 and CD36

The induction of fibroblast apoptosis and their clearance by phagocytes is essential for normal wound healing and prevention of scarring. However, little is known about the clearance of apoptotic fibroblasts and whether apoptotic cells are active participants in the recruitment and activation of phagocytes. In this study, we provide the first evidence that apoptotic fibroblasts actively release increased amounts of thrombospondin (TSP1) to actively recruit macrophages. Expression of TSP1 and its receptor CD36 was increased on the surface of apoptotic fibroblasts. By chemical cross-linking and immunoprecipitation we show that TSP1 and CD36 were directly associated. This was confirmed by confocal microscopy. Blockade of either CD36 or TSP1 on apoptotic fibroblasts inhibited phagocytosis. Blockade of alpha v beta 3 integrins as well as CD36 and TSP1 on macrophages inhibited phagocytosis. In contrast, phosphatidylserine or lectins were not involved. These findings suggest that apoptotic fibroblasts release TSP1 as a signal to recruit macrophages while the up-regulated expression of the CD36/TSP1 complex on their cell surface may form a ligand bridging the fibroblast to a complex consisting of alpha v beta 3/CD36/TSP1 on macrophages. These results establish fundamental mechanisms for the clearance of apoptotic fibroblasts and may provide insights into the processes involved in normal wound repair.     

PVR (CD155) and Nectin-2 (CD112) as ligands of the human DNAM-1 (CD226) activating receptor: involvement in tumor cell lysis

The capability of NK lymphocytes to kill tumor cells depends on different receptors/ligands interactions. In order to identify the cellular ligands recognized by "orphan" triggering receptors, mice were immunized with NK susceptible target cells. mAbs were selected that inhibited NK cytotoxicity and recognized two different molecules of 70 and 60-65 kDa. Tryptic digestion and mass spectra analysis of purified proteins identified these molecules as PVR and Nectin-2, respectively. PVR-Fc and Nectin-2-Fc chimeric molecules stained COS-7 cells expressing the DNAM-1 activating receptor and conversely, PVR and Nectin-2 CHO-K cell transfectants were stained by DNAM-1-Fc. Thus, both PVR and Nectin-2 represent specific ligands for DNAM-1. Importantly, the specific interaction between DNAM-1 (in NK cells) and PVR or Nectin-2 (in target cells) enhanced the NK-mediated lysis of tumor cells that was downregulated by mAb-mediated masking of the receptor or its ligands.     

Distribution of adenosine A2 receptor mRNA in the human brain.

The distribution of the messenger RNA coding for the recently cloned adenosine A₂ receptor was studied in the human brain using in situ hybridization histochemistry. A₂ receptor mRNA is exclusively detected in the medium-sized neurons of the caudate, putamen and accumbens nuclei but not elsewhere in the brain. This highly selective distribution of adenosine A₂ receptor mRNA in human dorsal and ventral striatum, similar to that of adenosine A₂ binding sites reported in rodents, suggests a major role in the basal ganglia physiology.     

Up-regulation of Fas ligand (FasL) mRNA expression in peripheral blood mononuclear cells (PBMC) after major surgery

FasL, which is expressed mainly on activated lymphocytes, can induce apoptosis (programmed cell death) of cells which express Fas. Fas/FasL interaction is primarily beneficial in maintaining immunological and physiological homeostasis by eliminating unnecessary cells. Dysregulation of the interaction, however, leads to tissue damage. We investigated how Fas/FasL levels changed after major surgery. The major aim of this study was to elucidate the involvement of the Fas/FasL system in postoperative inflammation. The investigation involved 10 patients admitted to the intensive care unit after surgery. Although the percentage of Fas⁺ cells and the amount of Fas expression tended to increase, there was no significant difference between pre- and post-operative samples. In contrast, the levels of FasL mRNA were dramatically up-regulated after operation. Post-operative C-reactive protein (CRP) levels increased and correlated well with FasL levels (r = 0.91, P < 0.01). Lymphocyte counts decreased after operation and were inversely proportional to FasL levels (r = 0.58, P < 0.05). These results suggest that the enhanced FasL expression is likely to be related to systemic inflammatory responses induced during the perioperative period. FasL up-regulation may be involved in the aggravation of tissue damage, including lymphocytopenia, in the early post-operative period.     

Synonymous mutations in the human dopamine receptor D2 (DRD2) affect mRNA stability and synthesis of the receptor

Although changes in nucleotide sequence affecting the composition and the structure of proteins are well known, functional changes resulting from nucleotide substitutions cannot always be inferred from simple analysis of DNA sequence. Because a strong synonymous codon usage bias in the human DRD2 gene, suggesting selection on synonymous positions, was revealed by the relative independence of the G+C content of the third codon positions from the isochoric G+C frequencies, we chose to investigate functional effects of the six known naturally occurring synonymous changes (C132T, G423A, T765C, C939T, C957T, and G1101A) in the human DRD2. We report here that some synonymous mutations in the human DRD2 have functional effects and suggest a novel genetic mechanism. 957T, rather than being 'silent', altered the predicted mRNA folding, led to a decrease in mRNA stability and translation, and dramatically changed dopamine-induced up-regulation of DRD2 expression. 1101A did not show an effect by itself but annulled the above effects of 957T in the compound clone 957T/1101A, demonstrating that combinations of synonymous mutations can have functional consequences drastically different from those of each isolated mutation. C957T was found to be in linkage disequilibrium in a European-American population with the -141C Ins/Del and TaqI 'A' variants, which have been reported to be associated with schizophrenia and alcoholism, respectively. These results call into question some assumptions made about synonymous variation in molecular population genetics and gene-mapping studies of diseases with complex inheritance, and indicate that synonymous variation can have effects of potential pathophysiological and pharmacogenetic importance.