Tiam1/Rac1 signaling pathway mediates palmitate-induced, ceramide-sensitive generation of superoxides and lipid peroxides and the loss of mitochondrial membrane potential in pancreatic β-cells

The phagocytic NADPH oxidase [NOX] has been implicated in the generation of superoxides in the pancreatic β-cell. Herein, using normal rat islets and clonal INS 832/13 cells, we tested the hypothesis that activation of the small G-protein Rac1, which is a member of the NOX holoenzyme, is necessary for palmitate [PA]-induced generation of superoxides in pancreatic β-cells. Incubation of isolated β-cells with PA potently increased the NOX activity culminating in a significant increase in the generation of superoxides and lipid peroxides in these cells; such effects of PA were attenuated by diphenyleneiodonium [DPI], a known inhibitor of NOX. In addition, PA caused a transient, but significant activation [i.e., GTP-bound form] of Rac1 in these cells. NSC23766, a selective inhibitor of Rac1, but not Cdc42 or Rho activation, inhibited Rac1 activation and the generation of superoxides and lipid peroxides induced by PA. Fumonisin B-1 [FB-1], which inhibits de novo synthesis of ceramide [CER] from PA, also attenuated PA-induced superoxide and lipid peroxide generation and NOX activity implicating intracellularly generated CER in the metabolic effects of PA; such effects were also demonstrable in the presence of the cell-permeable C2-CER. Further, NSC23766 prevented C2-CER-induced Rac1 activation and production of superoxides and lipid peroxides. Lastly, C2-CER, but not its inactive analogue, significantly reduced the mitochondrial membrane potential, which was prevented to a large degree by NSC23766. Together, our findings suggest that Tiam1/Rac1 signaling pathway regulates PA-induced, CER-dependent superoxide generation and mitochondrial dysfunction in pancreatic β-cells.     

大肠癌裸鼠移植瘤实验模型的建立及T细胞淋巴瘤侵袭和转移诱导蛋白1封闭载体的治疗作用

目的 通过建立大肠癌SW620细胞裸鼠皮下移植瘤模型,观察T细胞淋巴瘤侵袭和转移诱导蛋白1( Tiam1)封闭载体在动物体内的治疗作用.方法 构建编码一条短发夹RNA的Tiam1质粒表达封闭载体,并用之转染SW620细胞;应用Hoechst 33342荧光染色技术观察细胞形态学变化.将皮下接种SW620细胞的裸鼠分为3组,每组8只,在接种后第2周分别瘤内注射生理盐水(对照组)、HK错配链(HK组)和Tiam1封闭载体(Tiam1组).第16天处死各组裸鼠,取出移植瘤移重.结果 通过DNA测序证实封闭载体构建成功.SW620细胞经Tiam1封闭载体转染后,细胞核可见凋亡小体.对照组平均移植瘤重量(2.84±0.27)g,HK组(2.89±0.18)g,Tiam1组(1.47±0.20)g,Tiam1组与其他2组比较差异有统计学意义(P＜0.01),而HK组和对照组之间比较差异无统计学意义(P＞0.05).结论 所构建的Tiam1封闭载体能有效抑制大肠癌裸鼠皮下移植瘤生长.     

ESTABLISHMENT OF A HUMAN T-LYMPHOMA CELL LINE（H-TL90） AND ANALYSIS OF ITS BIOLOGICAL CHARACTERISTICS

We established a human T-lymphoma cell line from the cancerous ascites of a male patient with prostate cancer which was named H-TL90. This cell line was characterized by its histological features, and by chromosomal and immunological analysis. Immunophenotypic analysis revealed that the cells expressed surface antigen CD3^- CD4^- CD7^ CD8^-. Biological analysis revealed that the cell can promote lymphocyte proliferation. This suggested that the cell line has an autosecretion function. Cytogenetic analysis revealed that H-TL90 was a hyperdlploid with 47 chromosomes and had characteristic translocation between chromosome 3 and 11, and the deletion of the long arm of chromosome 6. These results demonstrated the H-TL90 cell line can be a useful modal for the study of human T-lymphoma.     

Prolactin receptor signaling: shared components with the T-cell antigen receptor in Nb2 lymphoma cells

Previously, we reported that activation of the human prolactin receptor (PRLR) produced a protein phosphorylation pattern strikingly similar to that provoked by Concanavalin A (Con A), an activator of the T-cell antigen receptor (TCR). These results suggested that certain signaling components of the TCR may be shared by the activated PRLR. Additional studies here assessed the levels of TCR expression following PRLR stimulation and the effect of TCR activation on PRL-stimulated proliferation in lactogen-dependent pre-T Nb2-11 lymphoma cells. The results indicated that the TCR was expressed on the surface of approx 4% of exponentially proliferating and prolactin- (PRL) treated cells. In contrast, approx 45% of quiescent cells, cultured in the absence of PRL for 24 h, expressed the TCR at the cell surface, suggesting that lactogen withdrawal may up-regulate TCR cell-surface expression. Moreover, TCR activation with anti-CD3 antibodies attenuated PRL-stimulated Nb2-11 cell proliferation in a concentration-dependent manner. In other experiments, immunoprecipitation and immunoblotting of Nb2-11 lysates revealed that activation of the PRLR resulted in rapid tyrosyl phosphorylation of ZAP-70, a critical TCR-associated tyrosine kinase. In addition, ZAP-70 was found to associate transiently with the putative guanine nucleotide exchange factor and substrate, Vav, in PRL-treated cells. ZAP-70 was also found to associate constitutively with the PRLR; PRL stimulation provoked the transient recruitment of Vav to the complex. These observations suggest that PRL signaling reflects the transient formation of a PRLR-ZAP-70-Vav complex and its immunomodulatory actions involve diverse interactions that affect TCR expression and signaling mechanisms.     

Hemophagocytic Syndrome in Epstein-Barr Virus-Associated T-Lymphoproliferative Disorders: Disease Spectrum, Pathogenesis, and Management

The Epstein-Barr virus (EBV) has been shown to infect T lymphocytes and is associated with two recently recognized human. T-lymphoproliferative disorders: childhood EBV-associated hemophagocytic syndrome (VAHS) representing a primary or active EBV infection of T cells in young children, and the EBV-containing T cell lymphoma in adults predominantly affecting the nose, skin and gastrointestinal tract. In both diseases, hemophagocytic syndrome (HS) accounts for the major cause of mortality. The patients developing HS share common clinicopathologic features such as fever, skin lesions, lung infiltrates, hepatosplenomegaly with jaundice, cytopenias, and coagulopathy. The liver, spleen, lymph nodes, and bone marrow usually show florid histiocytic proliferation with hemophagocytosis in addition to the proliferation of atypical T lymphocytes or immunoblasts.

The HS in T cell lymphoma may develop simultaneously with initial lymphoma presentation, at tumor relapse, or even during remission. The cytokines, in particular tumor necrosis factor-alpha, released from the EBV-infected T lymphocytes are presumed to cause the histiocytic activation and the subsequent hemophagocytic process. Chemotherapy or antiviral agents fail to arrest the hemophagocytic process in both diseases. Immunomodulatory treatment incorporating etoposide and intravenous immunoglobulin, however, has been effective in the control of the progression of the hemophagocytic process in a substantial number of VAHS patients. Preliminary data suggest that bone marrow transplantation may be a promising way for eliminating both the virus and the proliferating T cells. Further investigations are mandatory for combating this aggressive hemophagocytic process in EBV-associated T lymphoproliferative disorders.     

Large-Cell T-Lymphoma with Hypersegmented Nuclei

Clinical, morphological, cytochemical and immunological features in a case of T-lymphoma in a 67-year-old man are presented. Clinically, a predilection for lymph nodes was observed with a subsequent tumour-like spread to the liver, lungs and, to a minor extent, to the bone marrow. The skin, the spleen and the thymus were spared. Morphologically, the neoplastic lymphoid cells were characterized by their large size and particularly by their hypersegmented nuclei with a relatively coarse chromatin and large nucleoli. Cytochemically, a T-cell-like staining pattern in the acid phosphatase and in the acid α-naphthyl acetate esterase stains was absent. The neoplastic lymphocytes demonstrated a strong binding with sheep erythrocytes in suspension and in cryostat tissue sections. The morphological features of this lymphoma appear distinct from other non-Hodgkin's lymphomas. The similarities and the differences of our case in relation to some recently described cases of peripheral T-lymphomas comprising large cells with hyperlobated nuclei, are discussed.     

儿童肉芽肿性皮肤松弛症

肉芽肿性皮肤松弛症系一种罕见的T细胞性淋巴瘤,临床表现为皮肤松弛、斑块、结节。病理特点为皮肤的淋巴样细胞浸润及巨大的多核细胞性肉芽肿伴弹性纤维消失。本文报告1例男性患儿,10岁发病,15岁死亡。     

N,N-bis(cyclohexanol)amine aryl esters inhibit P-glycoprotein as transport substrates

P-Glycoprotein (Pgp) inhibition by three sets of four isomers of N,N-bis(cyclohexanol)amine aryl esters was assessed on rhodamine 123 (R123) efflux in human MDR1-gene transfected mouse T-lymphoma L5178 cells and on Sf9 ATPase activity. The most active compounds inhibited Pgp with IC₅₀ values much lower than those of either cyclosporin A (CSA) or GF120918. As to R123 efflux inhibition, the role of the bond present in the second aryl moiety appeared important since the triple bond derivatives (3a–d) were the most powerful as compared to the double bond (2a–d) and the single bond (1a–d) counterparts. Concentration–inhibition curves of 2c and 3d exhibited a biphasic behaviour suggesting the existence of two binding sites in the recognition domain of Pgp. Persistence of inhibition by these compounds resulted to be intermediate between that caused by CSA and GF120918. R123 exhibited positive interaction with CSA, 1d, 1c, 2d, 2c and 3c, the concentration–inhibition curves being shifted leftward when R123 concentration was increased, while it exhibited negative interaction with 3d and no effect with GF120918. Sf9 ATPase activity was stimulated in an increasing order of potency by 2c, 3c, 2d, CSA, epirubicin and 3d. In a decreasing order of potency 3d, 2c, GF120918, CSA, 2d and 3c inhibited at sub-nanomolar concentrations epirubicin-stimulated ATPase activity. In conclusion, isomeric geometry and restriction of molecular flexibility of N,N-bis(cyclohexanol)amine aryl esters were crucial for their presentation to and inhibition of Pgp as transport substrates, R123 and epirubicin cooperating with them to this inhibition.