A striking similarity exists between the pathogenetic properties of group A streptococci and those of activated mammalian professional phagocytes (neutrophils, macrophages). Both types of cells are endowed by the ability to adhere to target cells; to elaborate oxidants, hydrolases, and membrane-active agents (hemolysins, phospholipases); and to freely invade tissues and destroy cells. From the evolutionary point of view, streptococci might justifiably be considered the forefathers of “modern” leukocytes. Our earlier findings that synergy between a streptococcal hemolysin (streptolysin S, SLS) and a streptococcal thiol-dependent proteinase and between cytotoxic antibodies + complement and streptokinase-activated plasmin readily killed tumor cells, led us to hypothesize that by analogy to the pathogenetic mechanisms of streptococci, the mechanisms of tissue destruction initiated by activated leukocytes in inflammatory sites, as well as in tissues undergoing episodes of ischemia and reperfusion, might also be the result of the synergistic effects among leukocyte-derived oxidants, phospholipases, proteinases, cytokines, and cationic proteins. The current report extends our previous synergy studies with endothelial cells to two additional cell types-monkey kidney epithelial cells and rat beating heart cells. Monolayers of51Cr-labeled cells that had been treated by combinations of sublytic amounts of hydrogen peroxide (generated either by glucose oxidase, xanthine-xanthine oxidase, or by paraquat) and with sublytic amounts of a variety of membrane-active agents (streptolysin S, phospholipases A2 and C, lysophosphatides, histone, chlorhexidine) were killed in a synergistic manner (double synergy). Crystalline trypsin markedly enhanced cell killing by combinations of oxidant and the membrane-active agents (triple synergy). Injury to the cells was characterized by the appearance of large membrane blebs that detached from the cells and floated freely in the media, looking like lipid droplets. Cytotoxicity induced by the various combinations of agonists was depressed, to a large extent, by scavengers of hydrogen peroxide (catalase, dimethyl thiourea, and by Mn2+) but not by SOD or by deferoxamine. When cationic agents were employed together with hydrogen peroxide, polyanions (heparin, polyanethole sulfonate) were also found to inhibit cell killing. It is proposed that in order to effectively combat the deleterious toxic effects of leukocyte-derived agonists on cells and tissues, antagonistic “cocktails” comprised of cationized catalase, cationized SOD, dimethylthiourea, Mn2+ + glycine, proteinase inhibitors, putative inhibitors of phospholipases, and polyanions might be concocted. The current literature on synergistic phenomena pertaining to mechanisms of cell and tissue injury in inflammation is selectively reviewed.

Human neutrophils (PMNs) stimulated by sub-toxic concentrations of cetyltrimethyl ammonium bromide (CETAB) (37 μmol/L) generated intense luminol-dependent chemiluminescence (LDCL) and moderate non-amplified chemiluminescence (CL), but, paradoxically, generation of superoxide (as assayed by cytochrome c reduction, lucigenin-dependent chemiluminescence, nitroblue tetrazolium reduction test (NBT), spin trapping or hydrogen peroxide (Thurman reaction) and also oxygen uptake, were not observed. LDCL generation, however, was dependent on the viability of the PMNs. On the other hand, CETAB failed to induce CL in PMNs obtained from two children with an X-linked chronic granulomatous disease of childhood. CETAB inhibited superoxide generation by PMNs stimulated by phorbol-12-myristate-13-acetate (PMA), histone or polyhistidine-opsonized streptococci. It also inhibited NBT reduction in PMNs stimulated by PMA or by cationized streptococci. Generation of LDCL by CETAB-stimulated PMNs was inhibited by azide, cyanide, thiourea, dimethylthiourea, histidine, cimetidine, chloroquine, nordihydroguaiaretic acid and bromophenacyl bromide and partially so, about 50%, by superoxide dismutase (SOD), by TEMPOL (a SOD mimetic) and H-7, a protein kinase c inhibitor, but not by catalase, desferrioxamine, taurine or methionine. PMNs stimulated by CETAB in the presence of azide generated a large peak of LDCL when treated with horseradish peroxidase (HRP), suggesting that hydrogen peroxide, perhaps of intracellular origin, was involved. Such enhanced HRP-stimulated light emission was inhibited by catalase and by desferrioxamine, suggesting that the HRP-catalysed reaction also depended on some source of trace metals. CETAB also markedly enhanced CL generated by a cell-free mixture of hydrogen peroxide and HRP, which was quenched to a large extent by catalase, dimethylthiourea or desferrioxamine, again suggesting that light emission might be linked with trace metals present in the salt solutions employed. It is postulated that CETAB-induced CL in human PMNs is the result of the interaction of hydrogen peroxide, presumably of intracellular source, a trace metal, and a peroxidase (myeloperoxidase). This phenomenon might be unrelated to the classical respiratory burst, which is always accompanied by oxygen consumption, and to the generation of a variety of oxygen-derived species linked with the activation of the NADPH oxidase present in the cell membrane.