Signal transduction in Sj?gren's syndrome T cells. Abnormalities associated with a newly described human A-type retrovirus.

OBJECTIVE. To study the effects of a novel A-type retrovirus, detected in cocultures of lip biopsy specimens from Sj?gren's syndrome (SS) patients and a human T cell line, on the infected T cells. METHODS. Interleukin-2 (IL-2) and IL-6 secretion were measured by bioassay and enzyme-linked immunosorbent assay, respectively, in the infected and noninfected cell lines. Surface antigen expression was determined by flow cytometry, using monoclonal antibodies. Protein kinase C (PKC) activity was measured using an enzyme assay kit, and calcium mobilization was assessed with a fluorescent probe. RESULTS. Infected cells expressed less CD4 and IL-6 receptor, but more HLA-DR, compared with noninfected cells. Infected cells also produced less IL-2 and displayed reduced PKC activation and calcium mobilization. A similar defect in calcium mobilization was detected in T cells from SS patients. CONCLUSION. These data suggest a possible involvement of the newly described retrovirus in T cell abnormalities.     

Platinum-resistance in ovarian cancer cells is mediated by IL-6 secretion via the increased expression of its target cIAP-2

Ovarian carcinoma patients are initially responsive to platinum-based therapy, but eventually become refractory to treatment due to the development of platinum chemoresistance. Elevated levels of interleukin-6 (IL-6) in the sera and ascites of these patients predict poor clinical outcome. Our goal was to analyze the interaction between cisplatin and cisplatin-resistant ovarian cancer cells, and to identify means of circumventing platinum resistance. We studied ovarian carcinoma cell lines and cells drawn from ovarian carcinoma patients. Gene array analyses were performed on ovarian carcinoma cells upon treatment with cisplatin, and the results were validated by ELISA and Western blotting (WB). Cytotoxicity assays were performed on anti-IL-6 Ab-, IL-6-, and cellular inhibitor of apoptosis 2 (cIAP-2) siRNA-treated cells, following cisplatin addition. Our results revealed a highly significant increase in IL-6 and cIAP-2 mRNA and protein levels upon treatment with cisplatin. WB analysis of cisplatin-treated cells exhibited decreased cIAP-2 expression level following anti-IL-6 Ab addition. Furthermore, IL-6 by itself, significantly increased cIAP-2 levels in ovarian carcinoma cells. Finally, cytotoxicity assays showed sensitization to cisplatin following the addition of IL-6 and cIAP-2 inhibitors. In conclusion, cisplatin treatment of ovarian carcinoma cells upregulates IL-6 and cIAP-2 levels while their inhibition significantly sensitizes them to cisplatin. Here, we present cIAP-2 as a novel inducer of platinum resistance in ovarian carcinoma cells, and suggest an axis beginning with an encounter between cisplatin and these cells, mediated sequentially by IL-6 and cIAP-2, resulting in cisplatin resistance. Consequently, we propose that combining IL-6/cIAP-2 inhibitors with cisplatin will provide new hope for ovarian carcinoma patients by improving the current treatment.     

Methyl jasmonate binds to and detaches mitochondria-bound hexokinase

Cellular bio-energetic metabolism and mitochondria are recognized as potential targets for anticancer agents, due to the numerous relevant peculiarities cancer cells exhibit. Jasmonates are anticancer agents that interact directly with mitochondria. The aim of this study was to identify mitochondrial molecular targets of jasmonates. We report that jasmonates bind to hexokinase and detach it from the mitochondria and its mitochondrial anchor-the voltage-dependent anion channel (VDAC), as judged by hexokinase immunochemical and activity determinations, surface plasmon resonance analysis and planar lipid bilayer VDAC-activity analysis. Furthermore, the susceptibility of cancer cells and mitochondria to jasmonates is dependent on the expression of hexokinase, evaluated using hexokinase-overexpressing transfectants and its mitochondrial association. Many types of cancer cells exhibit overexpression of the key glycolytic enzyme, hexokinase, and its excessive binding to mitochondria. These characteristics are considered to play a pivotal role in cancer cell growth rate and survival. Thus, our findings provide an explanation for the selective effects of jasmonates on cancer cells. Most importantly, this is the first demonstration of a cytotoxic mechanism based on direct interaction between an anticancer agent and hexokinase. The proposed mechanism can serve to guide development of a new selective approach for cancer therapy.     

Vergiftungen. Giftnachweis (einschl. Blutalkoholbestimmung)

Ohne Zusammenfassung     

On the interactions between macrophages and developmental stages of Schistosoma mansoni: the cytotoxic mechanisms involved in macrophage-mediated killing of schistosomula in vitro

In an in vitro cytotoxicity assay, mouse adherent peritoneal exudate macrophages (APEM), harvested 8-10 weeks post Schistosoma mansoni infection caused sizable (greater than 90%) specific killing of schistosomula. This cidal effect was not diminished by the addition of scavengers of oxidative burst products to the cytotoxicity assay, albeit macrophages from schistosome-infected mice produced more H2O2 than did macrophages from non-infected mice. Of inhibitors of lysosomal enzyme function and release added to the cytotoxicity assay, trypan blue (1 mg/ml) fully abolished the schistosomulicidal effect; hydrocortisone (100 micrograms/ml) was partly effective, and gold salts (1 mg/ml) were ineffective. A cidal effect was not apparent in the absence of L-arginine nor in the presence of excess (greater than 400 micrograms/ml) L-arginine, L-lysine or L-ornithine. Arginase (5 U/ml) totally abrogated the schistosomulicidal effect. The findings suggest that a macrophage protein of a lysosomal origin, dependent on arginine for its reaction and/or production, may be involved in the in vitro killing of schistosomula by macrophages from S. mansoni-infected mice.