Inhibition of macrophage activation by isoquinolinesulfonamides, phenothiazines, and a napthalenesulfonamide

Inhibitory action of 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxam ide (PK 11195) on some mononuclear phagocyte functions

Peripheral benzodiazepine receptors (PBRs) are widely distributed throughout the body, but their functions are unknown. They are found on mononuclear phagocytes, and they are up-regulated in a number of neurological and other disease states. We explored the functional consequences of PBR ligand binding to mononuclear-derived cells using the high-affinity ligands 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxam ide (PK 11195) and 4'-chlorodiazepam (7-chloro-5-(4'-chlorophenyl)-1, 3-dihydro-1-methyl-2H-1,4-benzodiazepin-2-one; Ro 5-4864). The functions were the following: respiratory burst; secretion of glutamate, interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha); toxicity of culture supernatants towards SH-SY5Y human neuroblastoma cells; and expression of the inflammatory surface markers HLA-DR and Fcgamma RII (CDw32). PK 11195 inhibited the respiratory burst response, reduced release of glutamate and IL-1beta, and suppressed secretion of products cytotoxic to neuronal cells. Selectivity was suggested by the failure of PK 11195 to influence TNF-alpha secretion or expression of HLA-DR and CDw32. Powerful ligands of PBRs, such as PK 11195, may be useful inhibitors of selective macrophage functions, retarding both local and systemic inflammation. Since PK 11195 readily enters the brain, it may be beneficial in treating central as well as peripheral inflammatory diseases.

Metabolic activation of chlorpromazine by stimulated human polymorphonuclear leukocytes. Induction of covalent binding of chlorpromazine to nucleic acids and proteins

Human polymorphonuclear leukocytes (PMNs) have been stimulated with either phorbol 12-myristate 13-acetate (PMA), calcium ionophore A23187 or a combination of both to induce the respiratory burst and myeloperoxidase (MPO) release. Chlorpromazine (CPZ) but not chlorpromazine sulfoxide (CPZSO) inhibited the respiratory burst as measured with lucigenin chemiluminescence. The inhibition was due to interference with processes in the cell leading to the respiratory burst and not to scavenging of produced oxygen radicals that provoke the luminescence. CPZ was metabolized by stimulated PMNs. HPLC analysis revealed formation of CPZSO and an unidentified product. Both products result from decay of chlorpromazine radical cation (CPZ+.), indicating formation of this radical intermediate in CPZSO oxidation by stimulated PMNs. CPZ conversion correlated with H2O2 production and MPO release. The largest CPZ conversion was observed with phorbol ester plus A23187 stimulation. The conversion was reduced by catalase and sodium azide, an inhibitor of MPO, with 70% and 40%, respectively. This indicates only partial involvement of extracellularly released MPO in CPZ metabolism by PMNs. Considerable covalent binding of [3H]CPZ to nucleic acids and proteins of intact stimulated PMNs was observed. This binding was larger upon co-stimulation with phorbol ester and A23187. Azide did not reduce covalent binding. This indicates that covalent binding is not mediated by extracellularly released MPO and that CPZ is probably activated intracellularly. Activation of PMNs and production of H2O2 is a prerequisite for both CPZ conversion and covalent binding. This study demonstrates that phagocytic cells might contribute to drug metabolism and drug-induced toxicity.

Mycoplasmas induce transcription and production of tumor necrosis factor in a monocytic cell line, THP-1, by a protein kinase C-independent pathway

We demonstrated that mycoplasmas (MP), previously shown to augment the antitumor activity of murine peritoneal macrophages, also induce cytotoxic activity in a human monocytic cell line, THP-1. THP-1 cells were induced to produce cytotoxic activity by MP in a time- and dose-dependent manner. By using neutralization by antibody against tumor necrosis factor (TNF), the cytotoxic activity was shown to be due to TNF released from the MP-stimulated cells. Studies with inhibitors of second-messenger pathways and Northern RNA blot analysis indicated that a Ca2(+)-dependent, but not protein kinase C-dependent, biochemical pathway is involved in MP-induced TNF production by THP-1 cells and that MP induce TNF production in the cells at the level of transcription. MP, unlike other bacteria, lack cell walls and lipopolysaccharide. The possible involvement of a TNF production mechanism distinct from that triggered by lipopolysaccharide is discussed.

Role of extracellular calcium in chrysotile asbestos stimulation of alveolar macrophages

The purpose of these studies was to determine whether extracellular calcium and calcium channels can influence chrysotile asbestos-stimulated production of superoxide anion by guinea pig alveolar macrophages. Increasing the extracellular calcium concentration from 0.0 to 10.0 mM markedly enhanced the ability of noncytotoxic levels of chrysotile (25 micrograms/ml) to stimulate macrophage production of superoxide anion at 37 degrees C. The primary effect of increasing extracellular calcium was to prolong superoxide anion production. In parallel with these calcium-dependent effects on superoxide anion production, chrysotile also caused an elevation of cytosolic calcium (measured using Fura-2) which increased with increasing extracellular calcium concentrations. A number of organic calcium channel antagonists were tested for their ability to block chrysotile-stimulated superoxide anion production by cells in medium containing physiological levels of calcium. The relative order of potency of these antagonists was verapamil much greater than nimopidine approximately diltiazem approximately nifedipine greater than segontin. In parallel with its effects on superoxide anion production, verapamil also partially blocked the observed chrysotile-stimulated elevation of cytosolic calcium. Taken together, these results suggest that chrysotile can open calcium channels on the macrophage surface, allowing extracellular calcium to enter and contribute to the elevation of cytosolic calcium levels. This elevation of cytosolic calcium in turn serves to prolong chrysotile-stimulated superoxide anion production.