calcimycin and 3-aminobenzamide

The role of poly (adenosine diphosphate-ribose) synthetase (PARS) in the contractile and relaxant responses of pulmonary arteries injured by ischemia and reperfusion (IR) of splanchnic artery has not been evaluated. We examined these responses by using 3-aminobenzamide, a pharmacological inhibitor of PARS. IR models in rats were induced by clamping the superior mesenteric artery for 60 min, followed by release of the clamp for 60 min. In the 2 treated groups, 5 or 10 mg/kg of 3-aminobenzamide was administered as an IV bolus at 10 min before reperfusion, followed by infusion rates of 5 and 10 mg.kg(-1).h(-1), respectively, during the period of reperfusion (IR + PARS inhibitor 5 and 10 groups). In the vehicle-treated group, 3-aminobenzamide was not given, but IV saline was administered (IR group). In the control group, surgery was performed, but the superior mesenteric artery was not occluded (sham group). The pulmonary arteries were isolated, and effects of drugs were evaluated in vitro. The IR group showed no attenuation of the contractile responses of the pulmonary artery to phenylephrine. The relaxant responses to endothelium-dependent vasodilators, acetylcholine, and A23187 in the IR group were significantly inhibited when compared with the sham group. The reduction in the relaxant response to endothelium-dependent vasodilators was improved in the IR + PARS inhibitor 5 and 10 groups when compared with the IR group. We concluded that IR attenuated the relaxant responses of the pulmonary artery to endothelium-dependent vasodilators and that PARS inhibitors ameliorate the reduction in the relaxant response.

Topics: Acetylcholine; Animals; Benzamides; Calcimycin; Endothelium, Vascular; Enzyme Inhibitors; Male; Mesenteric Artery, Superior; Nitroprusside; Poly(ADP-ribose) Polymerase Inhibitors; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Splanchnic Circulation; Vasodilation

Apoptosis and necrosis are two forms of cell death that are induced under different conditions and that differ in morphological and biochemical features. In this report, we show that, in the presence of oxidative stress, human B lymphoma cells are unable to undergo apoptosis and die instead by a form of necrosis. This was established using the chemotherapy drug VP-16 or the calcium ionophore A23187 to induce apoptosis in Burkitt's lymphoma cell lines and by measuring classical markers of apoptotic death, including cell morphology, annexin V binding, DNA ladder formation, and caspase activation. In the presence of relatively low levels of H2O2 (75-100 microM), VP-16 and A23187 were unable to induce apoptosis in these cells. Instead, the cells underwent non-apoptotic cell death with mild cytoplasmic swelling and nuclear shrinkage, similar to the death observed when they were treated with H2O2 alone. We found that H2O2 inhibits apoptosis by depleting the cells of ATP. The effects of H2O2 can be overcome by inhibitors of poly(ADP)-ribosylation, which also preserve cellular ATP levels, and can be mimicked by agents such as oligomycin, which inhibit ATP synthesis. The results show that oxidants can manipulate cell death pathways, diverting the cell away from apoptosis. The potential physiological ramifications of this finding will be discussed.

Topics: Adenosine Triphosphate; Annexin A5; Apoptosis; Benzamides; Burkitt Lymphoma; Calcimycin; Caspase Inhibitors; Caspases; DNA Fragmentation; Etoposide; Humans; Hydrogen Peroxide; Oligomycins; Oxidative Stress; Protein Binding; Quinazolines; Quinazolinones; Tumor Cells, Cultured

Apoptotic cell death was induced in rat thymocytes on exposure to calcium ionophore A 23187 (100 micron(s)) for 24 h as observed from morphological changes and DNA fragmentation into oligonucleosomal ladder. The cell death was independent of de novo syntheses of protein. However, the involvement of c-Myc, c-Jun, poly ADPR polymerase and antioxidant enzymes CuZn SOD and catalase was observed.

Topics: Animals; Apoptosis; Benzamides; Calcimycin; Cycloheximide; Enzyme Inhibitors; Ionophores; Protein Synthesis Inhibitors; Rats; Rats, Sprague-Dawley; Thymus Gland; Zinc

Activated macrophages synthesize and release numerous tumoricidal soluble factors that can be divided into receptor- or nonreceptor-dependent agents. Tumor necrosis factor (TNF) would be an example of the former. In our experimental model the killing of EL4 thymoma cells by syngeneic activated macrophages involves, but not exclusively, TNF. Our results show that approximately 50% of the anti-EL4 activity expressed by macrophages can be specifically inhibited with rabbit anti-mouse TNF antibody. EL4 variants resistant to the lytic activity of TNF were still susceptible to macrophage-mediated lysis. A tumor-promoting phorbol ester, TPA, rendered TNF-sensitive and -insensitive EL4 cells resistant to M phi-mediated lysis. However, TPA down-regulated TNF-specific binding sites on both TNF-sensitive and -resistant cell surface membranes, suggesting that resistance to TNF involves postligand:receptor events. Tumor cell G-protein involvement (ADP-ribosylation), as a result of TNF-TNF receptor interactions, was investigated. The results showed that pertussis toxin was cytotoxic against TNF-sensitive and -resistant EL4 cells but not against TPA-treated target cells. Inhibitors of ADP-ribosyltransferase inhibited pertussis toxin cytotoxicity and macrophage-mediated lysis but did not interfere with recombinant TNF lytic activity.

Topics: Animals; Antibodies; Benzamides; Calcimycin; Cytotoxicity, Immunologic; Cytotoxins; Down-Regulation; Genetic Variation; Macrophage Activation; Mice; Niacinamide; Pertussis Toxin; Poly(ADP-ribose) Polymerase Inhibitors; Recombinant Proteins; Tetradecanoylphorbol Acetate; Thymoma; Thymus Neoplasms; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha; Virulence Factors, Bordetella

The repair kinetics and sensitivity to inhibitors of DNA strand breaks caused by superoxide anion, hydrogen peroxide, benzoyl peroxide and anthralin have been studied and compared with strand breaks caused by well-studied agents such as ionizing radiation and bleomycin. The latter two agents are generally believed to produce breaks indirectly by producing hydroxyl radicals, a very potent oxidizing species, which attack the phosphodiester backbone of DNA. As expected from earlier results, breaks induced by radiation and bleomycin rapidly disappear during post-treatment incubation as a consequence of the action of cellular DNA repair enzymes. Thus, strand breaks produced by hydroxyl radicals appear to be readily repaired in human leukocytes. By contrast, breaks caused by extracellular superoxide anion appeared not to be readily repaired, implying that some mechanism other than the generation of hydroxyl radicals in the vicinity of the DNA was involved. Inhibitors such as 3-aminobenzamide, cytosine arabinoside and adenine arabinoside affected the apparent rate of repair of radiation and methylmethane sulfonate-induced breaks but there was no indication that they affected superoxide anion-induced breaks. They partially inhibited repair of hydrogen peroxide-induced breaks. Breaks caused by benzoyl peroxide and anthralin were also apparently not repaired. We conclude that hydroxyl radicals are not likely the ultimate DNA strand-breaking species in cells exposed to extracellular superoxide anion and that the observed slow repair of DNA strand breaks may be significant in the mechanism of action of tumor-promoting agents.

Topics: Benzamides; Calcimycin; DNA; DNA Repair; Humans; Hydrogen Peroxide; Hydroxides; Hydroxyl Radical; Neutrophils; Phorbols; Superoxides; Tetradecanoylphorbol Acetate