人支气管上皮细胞c-Ha-rasV12G基因转染细胞系促癌剂检测模型的建立

目的:建立一个新的促癌剂检测模型.方法:采用电穿孔法,将人类突变的c-Ha-rasV12G 基因转入人支气管上皮细胞BEAS-2B中,将获得的G418抗性(G418r)单克隆细胞株用佛波醇酯(PMA)处理,并选用克隆形成率、锚着独立性生长及血清抗性等表型改变对受试细胞进行了恶性程度检测.结果:(1) 在促癌剂PMA作用下,BEAS-2B基因转染细胞发生了恶性转化;(2)表达突变ras基因的上皮细胞,在大剂量PMA (>1 μmol)的急性刺激(24 h)下,可诱导细胞死亡;(3) 随着细胞恶性程度的增加,某些促癌剂的促细胞分化作用将减弱,并有生长刺激作用.结论:该模型可用于促癌剂的检测及促癌作用机制研究.     

HIV-1 gp41 binding to human T- and B-lymphocytes and monocytes is modulated by phorbol myristate acetate (PMA)

HIV-1 gp41 independently of CD4 binds to human T cells, B cells and monocytic cells. Since PMA downmodulates CD4 (HIV receptor) expression and inhibits HIV-1 dependent syncytia formation, we wanted to examine whether PMA could affect gp41 binding protein expression on human cells. The strong binding of HIV-1 recombinant soluble gp41 (rsgp41; Env aa539–684) to monocytes (CD14⁺) and B-lymphocytes (CD19⁺) and B lymphoblastoid cells (Raji) could be clearly decreased by treating the cells with PMA for 48 h, while the weak binding to T lymphocytes was slightly increased by this treatment. The PMA inhibitory- and enhancing-effects could be avoided by pretreatment with staurosporine (protein kinase C inhibitor). The PMA treatment of Raji and U937 (monocytic) cells resulted in a 50–60% decrease of gp41 binding proteins (gp41bps) detectable in cell lysates of these cells in comparison with lysates of buffer-treated cells, while in the case of H9-cells PMA treatment resulted in an increase of available gp41bps by about 35% in comparison with buffer-treated H9. Staurosporine pre-treatment could prevent these effects of PMA. Further studies of rsgp41-eluates from these buffer-treated or PMA-treated cells demonstrated that PMA modulated mainly expression of rsgp41bps of 37, 45, 50 and 62 kDa. These results indicate that PMA exerts different effects on human T, B and monocytic cells. Production by and expression on cells of HIV-1 gp41bps appear to depend on protein kinase C, supporting that the four proteins on human cells may act as receptor proteins for HIV-1 gp41.     

Toxic effects of several mercury compounds on SHand non-SH enzymes

The toxic effects of several mercury compounds on the activities of horse liver alcohol dehydrogenase (an SH-enzyme) and bovine pancreatic trypsin (a non-SH enzyme) have been studied.Non-competitive type inhibition of the alcohol dehydrogenase activity was observed, and the K_i values were calculated to be of the order of 10^?7 M, 10^?6 M and 10^?5 M for mercuric chloride, monosubstituted and disubstituted mercury compounds, respectively.On the other hand, competitive type inhibition of the activity of trypsin was found, and the K_i values were of the order of 10^?6 M and 10^?4 -10^?5 M for mercuric chloride and monosubstituted mercury compounds, respectively (the disubstituted compound could not be tested for technical reasons). These results indicate that the enzymatic activities depend on the level of substitution of mercury compounds, and the SH-enzyme was found to be more sensitive to every mercury compound tested than the non-SH enzyme.These findings may reflect the degrees of toxicity of these mercury compounds in mammalian tissues.     

低剂量X射线全身照射后淋巴细胞对调节因子反应性的变化

肾上腺素（Ｅ）和去甲肾上腺素（ＮＥ）分别在高于１ｎｍｏｌ／Ｌ和１０ｎｍｏｌ／Ｌ浓度时增强淋巴细胞的增殖反应，而皮质酮（ＣＳ）则呈现双相效应，在低于０．１ｎｍｏｌ／Ｌ时促进，高于１０ｎｍｏｌ／Ｌ时抑制此反应。ＣＳ分别与Ｅ或ＮＥ或二者以各自的无效浓度（０．１ｎｍｏｌ／Ｌ）合用时使淋巴细胞的增殖反应显著增强，而且此种增强效应在７５ｍＧｙ Ｘ射线全身照射后进一步上调。乙酰豆蔻佛波酯（ＰＭＡ）和Ａ２３１８亦     

Overexpression of PKCepsilon sensitizes LNCaP human prostate cancer cells to induction of apoptosis by bryostatin 1

Phorbol 12-myristate 13-acetate (PMA)-induced apoptosis of androgen sensitive LNCaP human prostate cancer cells is a well known phenomenon that involves prolonged translocation of multiple protein kinase C (PKC) isozymes to nonnuclear membranes. We have shown recently that PMA-induced death of C4-2 cells, androgen hypersensitive derivatives of LNCaP cells, requires both PKCdelta and a redundant pathway that includes PKCs alpha and epsilon. In contrast, it has been reported that overexpression of murine PKCepsilon in LNCaP cells renders those cells resistant to PMA-induced death, as well as androgen insensitive. Here we report that inducible or constitutive overexpression of human PKCepsilon does not alter the sensitivity of LNCaP cells to either PMA or androgen, nor does it alter expression of caveolin-1 or phosphorylated Rb, reported effects of overexpression of murine PKCepsilon. Moreover, overexpression of very high amounts of PKCepsilon sensitized LNCaP cells to induction of apoptosis by bryostatin 1, a non tumor-promoting activator and down-regulator of PKC isozymes that blocks PMA-induced apoptosis of parental LNCaP cells, mimicked our previous results with overexpression of PKCalpha in LNCaP cells. Given reports that overexpression of PKCepsilon is frequent in human prostate tumors, our results may have important implications for a potential prostate cancer therapy.