Pretreatment of acetylsalicylic acid promotes tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis by down-regulating BCL-2 gene expression

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to be selective in the induction of apoptosis in cancer cells with minimal toxicity to normal tissues. However, not all cancers are sensitive to TRAIL-mediated apoptosis. Thus, TRAIL-resistant cancer cells must be sensitized first to become responsive to TRAIL. In this study, we observed that pretreatment by acetylsalicylic acid (ASA) augmented TRAIL-induced apoptotic death in human prostate adenocarcinoma LNCaP and human colorectal carcinoma CX-1 cells. Western blot analysis showed that pretreatment of ASA followed by TRAIL treatment activated caspases (8, 9, and 3) and cleaved poly(ADP-ribose) polymerase, the hallmark feature of apoptosis. Most interestingly, at least 12 h of pretreatment with ASA was prerequisite for promoting TRAIL-induced apoptosis and was related to down-regulation of BCL-2. Biochemical analysis revealed that ASA inhibited NF-kappaB activity, which is known to regulate BCL-2 gene expression, by dephosphorylating IkappaB-alpha and inhibiting IKKbeta activity but not by affecting the HER-2/neu phosphatidylinositol 3-kinase-Akt signal pathway. Overexpression of BCL-2 suppressed the promotive effect of ASA on TRAIL-induced apoptosis and changes in mitochondrial membrane potential. Taken together, our studies suggested that ASA-promoted TRAIL cytotoxicity is mediated through down-regulating BCL-2 and by decreasing mitochondrial membrane potential.     

Role of tumor necrosis factor-related apoptosis-inducing ligand in immune response to influenza virus infection in mice

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis of various tumor cells but not normal cells. However, various cytokines and virus infection differentially regulate TRAIL and TRAIL receptor expression. It has been demonstrated that virus infection changes the pattern of human TRAIL-receptor expression on normal cells, which were resistant to TRAIL-mediated apoptosis, and makes them susceptible to TRAIL-mediated apoptosis. Since previous studies on the function of TRAIL have been performed mainly in vitro, its physiological role in the immune response to virus infection remains unknown. In the present study, we investigated the expression of TRAIL in the lungs of influenza virus-infected mice and the function of TRAIL in the immune response to infection. Influenza virus infection increased TRAIL mRNA expression in the lung. TRAIL protein expression was induced on NK cells in the lung 4 days after infection. At 7 days after infection, TRAIL protein expression was also detected on CD4(+) and CD8(+) T cells. However, NK cells and T cells in the lungs of uninfected mice did not express a detectable level of TRAIL on their cell surfaces. DR5, which is a mouse TRAIL receptor, was also induced to express after virus infection. Expression of both TRAIL and DR5 mRNAs was reduced to normal level at 6 weeks after virus infection. Administration of anti-TRAIL monoclonal antibody, which blocks TRAIL without killing TRAIL-expressing cells, to mice during influenza virus infection significantly delayed virus clearance in the lung. These results suggest that TRAIL plays an important role in the immune response to virus infection.     

Restricted expression of tumor necrosis factor-related apoptosis-inducing ligand receptor 4 in human peripheral blood lymphocytes

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in tumor but not normal cells, thus providing therapeutic possibilities for human cancers. However, it is not fully clear how widespread TRAIL receptors are, or how TRAIL signaling is modulated in normal cells. We characterized cell surface expression of TRAIL receptors in normal healthy donor peripheral blood and report that each of the TRAIL receptors are characteristically expressed on restricted cell populations. TRAIL-R1 is distinctively expressed on B-lymphocytes, TRAIL-R2 on monocytes, TRAIL-R3 on neutrophils and most impressively, CD8+ lymphocytes and NKT lymphocytes but not CD4+ lymphocytes express TRAIL-R4.     

Adipsin, the adipocyte serine protease: gene structure and control of expression by tumor necrosis factor.

We have isolated, mapped and sequenced adipsin, the adipocyte differentiation-dependent serine protease gene. This gene, which is present in a single form in the mouse, spans 1.7 kilobases and contains five exons. While the basic exon structure characteristic of serine protease genes is conserved in adipsin, there is also a fusion of two exons that are separate in other serine proteases. The sequence data also suggests a mechanism of alternative splicing which appears to account for the generation of two adipsin mRNA species differing by only three nucleotides and encoding two different signal peptides. To investigate the control of adipsin expression we have examined the effects of tumor necrosis factor (TNF) on adipocytes. The level of adipsin RNA is dramatically decreased by hormone treatment, but the change occurs more slowly than for other fat cell mRNAs, such as glycerophosphate dehydrogenase. These results show that adipsin is a novel serine protease gene whose expression is regulated by a macrophage-derived factor which modulates expression of other adipocyte-specific RNAs.     

c-fos and tumor necrosis factor gene expression in Leishmania donovani-infected macrophages.

Leishmania donovani is an obligate intracellular protozoan which resides in macrophages and impairs a number of macrophage functions. We have undertaken to study this host cell-parasite interaction by examining the ability of L. donovani to impair the transmission of information from the cell surface to the nucleus and thus influence normal gene expression. We demonstrate that, in response to lipopolysaccharide, expression of both the c-fos and tumor necrosis factor genes was impaired in L. donovani-infected macrophages. Indomethacin reversed the parasite-mediated downregulation of the tumor necrosis factor gene but not the c-fos gene, suggesting that the impaired expression of these two genes occurred through different mechanisms. Direct stimulation of protein kinase C with oleoyl-2-acetoyl-3-glycerol did not abrogate inhibition of c-fos gene expression by L. donovani; however, L929 cell-conditioned medium induced a similar level of c-fos gene expression in both infected and noninfected macrophages. Impairment of c-fos gene expression by L. donovani thus appeared to be selective, depending on the external stimuli used to induce its expression. These data argue that L. donovani was capable of impairing macrophage gene expression in a selective rather than a general manner.     

Role of replication time in the control of tissue-specific gene expression.

Late-replicating chromatin in vertebrates is repressed. Housekeeping (constitutively active) genes always replicate early and are in the early-replicating R-bands. Tissue-specific genes are usually in the late-replicating G-bands and therein almost always replicate late. Within the G-bands, however, a tissue-specific gene does replicate early in those cell types that express that particular gene. While the condition of late replication may simply be coincident with gene repression, we review evidence suggesting that late replication may actively determine repression. As mammals utilize a developmental program to Lyonize (facultatively heterochromatinize) whole X chromosomes to a late-replicating and somatically heritable repressed state, similarly another program seems to Lyonize individual replicons. In frogs, all genes begin embryogenesis by replicating during a very short interval. As the developmental potency of embryonic cells becomes restricted, late-replicating DNA gradually appears. This addition to the repertoire of gene control--i.e., repression via Lyonization of individual replicons--seems to have evolved in vertebrates with G-bands being a manifestation of the mechanism.