thiourea and methylamine

The pathogenesis of toxic shock syndrome (TSS) remains unknown. On the basis of experimental data, it has been hypothesized that staphylococcal TSS Toxin 1 (TSST-1) may interact synergistically with low levels of endotoxin and give rise to many of the clinical findings. We have demonstrated previously that lipid A, the biologically active component of lipopolysaccharide (LPS), or endotoxin, induces dose-dependent necrosis of isolated rat renal tubular cells (RTCs). In the present studies, the authors investigated whether this injury could be augmented by TSST-1. The viability of RTCs was assessed by vital dye exclusion. Incubation of freshly isolated rat RTCs with either 1 ng/ml of TSST-1 or 0.1 ng/ml LPS or lipid A had minimal cytotoxicity (less than 6%). Exposure of RTCs to 1 ng/ml TSST-1 for 20 minutes, followed by washing, resulted in a significant enhancement of cytotoxicity when RTCs were exposed to 0.1 ng/ml LPS or lipid A. The sensitization of RTCs by TSST-1 to LPS- or lipid-A-induced injury was prevented by methylamine and chloroquine, two inhibitors of receptor-mediated endocytosis (RME). Chelation of extracellular calcium by 2 mM EGTA also blocked the TSST-1-induced sensitization of RTCs to LPS or lipid A. Inhibition of RTC arachidonic acid metabolism by methylprednisolone, indomethacin, ibuprofen, and piriprost significantly inhibited RTC necrosis induced by TSST-1 and LPS or lipid A by 33-62%. Thiourea and deferoxamine, agents which ameliorate oxidant injury, also inhibited this synergistic injury by 34-67%. Thus, TSST-1 enhanced the cytotoxic effects of LPS/lipid A, and the sensitization of RTCs appeared to involve RME or TSST-1. Oxidative metabolism of arachidonic acid and generation of reactive oxygen species appeared to participate in LPS/lipid-A-mediated RTC death.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Bacterial Toxins; Cell Separation; Cell Survival; Chloroquine; Deferoxamine; Endocytosis; Endotoxins; Enterotoxins; Hydroxides; In Vitro Techniques; Kidney Tubules; Lipid A; Lipopolysaccharides; Male; Methylamines; Necrosis; Rats; Rats, Inbred Strains; Superantigens; Thiourea

Methylamine and chloroquine both 'lysosomotropic' agents (i.e. agents which sequester in lysosomes) caused a dose-related inhibition of mitogen-induced lymphocyte activation in the concentrations which have previously been shown to increase the pH of lysosomes. The dose-response curves of inhibition of mitogen-induced lymphocyte activation for chloroquine and methylamine are very steep and are similar to the dose-response curves obtained with dimaprit and nordimaprit, but very different from the flat dose-response curves previously described for histamine. Approximate IC50 values were methylamine 6.4 mM, dimaprit 0.13 mM, nordimaprit 0.03 mM and chloroquine 18 microM. It is suggested that the mechanism of action of methylamine and chloroquine may be related to their lysosomotropic action and consequent interference with ligand-receptor processing, and that dimaprit and nordimaprit but not histamine may act by a similar mechanism.

Topics: Cells, Cultured; Chloroquine; Chromium Radioisotopes; Concanavalin A; Dimaprit; Histamine; Humans; Lymphocyte Activation; Lymphocytes; Methylamines; Mitogens; Phytohemagglutinins; Thiourea; Thymidine