NO-mediated apoptosis

SIN-1 induced higher antiproliferation activity in BCR-ABL+ leukemia K562 cells when compared to normal hemopoietic cells [52]. NO-mediated apoptosis is shown to be inhibited in myeloid leukemia cells by the elevation of intracellular iron. 

In murine macrophages RAW 264.7, NO generated from NO donor [133] or by iNOS [134] provokes apoptosis in response to p53 accumulation. This effect is inhibited by Bcl-2 [135] and shows an increasing expression of Bax. It is suggested by Brtine et al. [136] that NO-mediated apoptosis in macrophages is entirely controlled by the mitochondrial pathway with the implication of p53 accumulation and cytochrome c release. More downstream, NO activates caspase 3 and provokes PARP clivage [137], Those results confirmed the first experiments on peritoneal macrophages [138, 139]. 

O Donnell et al. [70] found that LOX and not cyclooxygenase, cytochrome P-450, NO synthase, NADPH oxidase, xanthine oxidase, ribonucleotide reductase, or mitochondrial respiratory chain is responsible for TNF-a-mediated apoptosis of murine fibrosarcoma cells. 15-LOX activity was found to increase sharply in heart, lung, and vascular tissues of rabbits by hypercholesterolemia [71], Schnurr et al. [72] demonstrated that there is an inverse regulation of 12/15-LOXs and phospholipid hydroperoxide glutathione peroxidases in cells, which balanced the intracellular concentration of oxidized lipids. 

This ceramide-mediated apoptosis was shown to be inhibited by the simultaneous addition of PKC activators (Ni et at, 1994 Obeid et al, 1993), implying that PS may activate the ceramide-mediated apoptotic pathway. However, the inhibitors of interleukin-1 converting enzyme (ICE)-like proteases (Caspase), such as tosyl-L-lysine chloromethyl ketone (TLCK), and tosyl-L-phenylalanine chloromethyl ketone (TPCK) which inhibit ceramide-mediated apoptosis, had no effect on PS-induced apoptosis (Figure 4). Thus, PS-induced apoptotic pathway appears to be distinct from that mediated by ceramide. Further studies are required to clarify the molecular mechanisms underlying the PS-induced apoptosis. 

Mice that lack caspase-1, -11, or -12 do not have a significant decrease in viability and have no overt consequence on their development [57-59,69,72]. In contrast, caspase-3 and/or -9 ablation results in retarded developmental apoptosis and has a tremendous impact on animals viability and phenotype [61, 67]. Similarly, caspase-8 knockout mice die in utero and are characterized by impaired formation of cardiac muscle and marked abdominal congestion with reduction of the number of hematopoietic precursors [65], The size of the heart was reported to be almost normal, but the developing ventricular musculature was thin and sometimes similar to early mesenchyme. The trabeculae were thin and disorganized. Cultured fibroblasts from caspase-8 mice were resistant to death receptor-mediated apoptosis. These findings indicate that caspase-8 plays an important role in death induction by several receptors of Fas/TNF/NGF family. Similarly, Sakamaki et al. [66] described that protease-deficient caspase-8 mutant mice died in utero due to heart rupture which they believe was due to cardiomyocyte apoptosis. 

ABSTRACT In mammals, nitric oxide (NO) is a reactive free radical involved in diverse physiological functions. NO and its redox-related forms NO+ and NO react with di(oxygen) and its derivatives, with metalloproteins and thiol-containing proteins. NO-mediated nitrosation of proteins represents an important cellular regulatory mechanism. Biosynthesis of NO is catalysed by nitric oxide synthase (NOS). Three isoenzymes representing distinct gene products have been identified the inducible NOS isoform, the constitutive neuronal and endothelial isoforms. Inducible and constitutive NOSs have the same structural features, but their activities differ in their dependence to calcium and the rate of NO produced. The principal NO-mediated functions in mammals are endothelium-dependent relaxation, neurotransmission and immune response. The role of NO in the antitumor immune response comprises both regulatory and effector functions at the intra- or inter-cellular level. The first function includes inhibition of lymphocyte proliferation or participation in different transduction pathways. The second fiinction includes pro- or anti-tumoral effects and NO-mediated cell toxicity or cell resistance to apoptosis. 

NO induces apoptosis of murine splenic T lymphocytes [140], and is a mediator of Fas induced apoptosis in hematopoietic cells isolated from bone marrow [141], The origin of this effect could be a decrease of mitochondrial membrane potential and the generation of active oxygen derivatives [142]. 

Therefore, the role of NO in the antitumor immune response, comprises both regulatory and effector functions at the intra- or intercellular level. The first functions includes inhibition of lymphocyte proliferation or participation in different transduction pathways. The second functions include pro- or anti-tumoral effects and NO mediated cell toxicity or cell resistance to apoptosis. 

Hug, H., Enari, M. and Nagata, S. (1994) No requirement of reactive oxygen intermediates in Fas-mediated apoptosis. FEBSUtt. 351 311-313. 

To confirm the noninvolvement of the caspase pathway, cytotoxicity and apoptosis induction were studied in the presence of a caspase-3 inhibitor (Z-DEVD-FMK) and a negative control for the caspase-3 inhibitor (Z-FA-FMK). The negative control only inhibited cysteine protease and had no inhibitory effect on caspase-mediated apoptosis. The presence of a caspase-3 inhibitor, as well as a negative control, did not alleviate the cytotoxicity of 13-MTD and did not prevent induction of apoptosis. 

Fas protein was rarely expressed on thyroid epithelial cells from each group, except that increasing Fas expression was noticed at the 32nd week in the 1000-fold high iodine group. The expression of Fas was related to the duration and the dosage of exposure. No FasL expression was found, no whether matter autoimmune thyroiditis existed or not. FLIP acts as an intracellular apoptosis-suppression protein, which can competitively bind to the Fas-associated death domain (FADD), the apoptosis-mediated protein in the death receptor apoptosis pathway, hence blocking the Fas—FasL mediated apoptosis pathway. 

NO is a known downstream mediator of VEGF receptor activation [43], ROS are able to react with NO forming highly toxic radicals [44] this block of NO-mediated signals could impair VEGF activity. The simultaneous rise in free radicals and decrease in VEGF would clearly be detrimental for endothelial cells and enhance their apoptosis. 

Induction of apoptosis has been shown to result in depletion of cellular levels of the anti-oxidant glutathione, not via its oxidation, but rather by its extrusion from the cell [reviewed in 50]. Conversely, increasing cellular levels of glutathione (by incubation with the glutathione precursor, N-acetylcysteine) was shown to inhibit Fas-mediated apoptosis, but had no effect on spontaneous neutrophil apoptosis [51]. It may be that inhibition of the glutathione pump (e.g. by methionine or cystathionine) may be required to delay spontaneous neutrophil apoptosis following enhancement of cellular glutathione levels [reviewed in 50]. 

Low doses of NO inhibited apoptosis in human B lymphocytes (Mannick et al. 1994, Genaro et al. 1995). In contrast, NO functions as an apoptotic inducer for macrophages, hepatocytes, neurones and ghal cells. The proapoptotic activity of NO is mediated via the release of mitochondrial cytochrome c into the cytosol, the sequential loss of mitochondrial membrane potential, and the activation of members of the caspase family of proteases (Ue-HARA et al. 1999, Brookes et al. 2000, Moriya et al. 2000). CiBELLi et al. (2002) analysed the NO-... 

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