concanavalin-a and 3-aminobenzamide

Concanavalin A is known to activate T cells and to cause liver injury and hepatitis, mediated in part by secretion of TNFα from macrophages. Poly(ADP-ribose) polymerase-1 (PARP-1) inhibitors have been shown to prevent tissue damage in various animal models of inflammation. The objectives of this study were to evaluate the efficacy and mechanism of the PARP-1 inhibitor 3-aminobenzamide (3-AB) in preventing concanavalin A-induced liver damage.. We tested the in vivo effects of 3-AB on concanavalin A-treated mice, its effects on lipopolysaccharide (LPS)-stimulated macrophages in culture, and its ability to act as a scavenger in in vitro assays.. 3-AB markedly reduced inflammation, oxidative stress, and liver tissue damage in concanavalin A-treated mice. In LPS-stimulated RAW264.7 macrophages, 3-AB inhibited NFκB transcriptional activity and subsequent expression of TNFα and iNOS and blocked NO production. In vitro, 3-AB acted as a hydrogen peroxide scavenger. The ROS scavenger N-acetylcysteine (NAC) and the ROS formation inhibitor diphenyleneiodonium (DPI) also inhibited TNFα expression in stimulated macrophages, but unlike 3-AB, NAC and DPI were unable to abolish NFκB activity. PARP-1 knockout failed to affect NFκB and TNFα suppression by 3-AB in stimulated macrophages.. Our results suggest that 3-AB has a therapeutic effect on concanavalin A-induced liver injury by inhibiting expression of the key pro-inflammatory cytokine TNFα, via PARP-1-independent NFκB suppression and via an NFκB-independent anti-oxidative mechanism.

Topics: Acute Disease; Animals; Anti-Inflammatory Agents; Antioxidants; Benzamides; Cells, Cultured; Concanavalin A; Disease Models, Animal; Hepatitis; Macrophages; Mice; Mitogens; NF-kappa B; Nitric Oxide Synthase Type II; Poly(ADP-ribose) Polymerase Inhibitors; Treatment Outcome; Tumor Necrosis Factor-alpha

6(5H)-phenanthridinone, a recently identified poly(ADP-ribose)polymerase (PARP) inhibitor, is able, at micromolar concentrations, to inhibit concanavalin A-induced lymphocyte proliferation and to potentiate the effect of gamma radiation upon murine spleen cells. When added at the onset of a mixed lymphocyte culture, this compound strongly depresses the induction of primary allogeneic (anti-H2k) cytotoxic T-lymphocytes (CTLs). Lymphokine-activated killer (LAK) induction was also found to be impaired by the PARP inhibitor. Taken together, these results clearly indicate that PARP plays a key-role in immune reactions involving cytotoxicity and that 6(5H)-phenanthridinone could be considered as a potent immunomodulator.

Topics: Acridines; Acridones; Animals; Benzamides; Cells, Cultured; Concanavalin A; Female; Gamma Rays; Immunosuppressive Agents; Interleukin-2; Isoquinolines; Killer Cells, Lymphokine-Activated; Lymphocyte Activation; Lymphocyte Culture Test, Mixed; Lymphocytes; Male; Mice; Mice, Inbred C3H; Mice, Inbred DBA; Phenanthrenes; Poly(ADP-ribose) Polymerase Inhibitors; Recombinant Proteins; Spleen; T-Lymphocytes, Cytotoxic

The two competitive inhibitors of ADP-ribosylation, nicotinamide and 3-aminobenzamide, have been reported to interfere with TNF-induced cell apoptosis, and there is evidence that they inhibit killer-induced target cell lysis as well. There are very few drugs known to specifically interfere with target apoptosis induced by killer cells. We therefore sought to explore the effects these inhibitors have on CTL-mediated cell lysis. Here we show that TcR-mediated transmembrane signaling in CTL, measured by Ca2+ mobilization and generation of inositol phosphates, is inhibited by nicotinamide. The possibility that all cell functions are suppressed by the drug is excluded by the finding that constitutive secretion of BLT serine esterase is not inhibited, whereas stimulated secretion of this enzyme is suppressed. We also show that nicotinamide does not interfere with CTL target cell binding or reorientation of the Golgi apparatus toward the target binding site. It is concluded that nicotinamide inhibits transmembrane signaling in CTL and thereby interferes with delivery of the lethal hit to targets.

Topics: Animals; Benzamides; Calcium; Concanavalin A; Cytotoxicity, Immunologic; Golgi Apparatus; Granzymes; Inositol Phosphates; Lymphocyte Culture Test, Mixed; Mice; Mice, Inbred Strains; Niacinamide; Phosphatidylinositols; Receptors, Antigen, T-Cell; Serine Endopeptidases; Signal Transduction; T-Lymphocytes, Cytotoxic