inositol-1-4-5-trisphosphate and Shock--Septic

Many exotoxins of Gram-positive bacteria, such as superantigens [staphylococcal enterotoxins, toxic shock syndrome toxin-1 (TSST-1), and streptococcal pyrogenic exotoxins] and anthrax toxin are bioterrorism agents that cause diseases by immunostimulation or cytotoxicity. Glycerol monolaurate (GML), a fatty acid monoester found naturally in humans, has been reported to prevent synthesis of Gram-positive bacterial exotoxins. This study explored the ability of GML to inhibit the effects of exotoxins on mammalian cells and prevent rabbit lethality from TSS. GML (>or=10 microg/mL) inhibited superantigen (5 microg/mL) immunoproliferation, as determined by inhibition of (3)H-thymidine incorporation into DNA of human peripheral blood mononuclear cells (1 x 10(6) cells/mL) as well as phospholipase Cgamma1, suggesting inhibition of signal transduction. The compound (20 microg/mL) prevented superantigen (100 microg/mL) induced cytokine secretion by human vaginal epithelial cells (HVECs) as measured by ELISA. GML (250 microg) inhibited rabbit lethality as a result of TSST-1 administered vaginally. GML (10 microg/mL) inhibited HVEC and macrophage cytotoxicity by anthrax toxin, prevented erythrocyte lysis by purified hemolysins (staphylococcal alpha and beta) and culture fluids containing streptococcal and Bacillus anthracis hemolysins, and was nontoxic to mammalian cells (up to 100 microg/mL) and rabbits (250 microg). GML stabilized mammalian cell membranes, because erythrocyte lysis was reduced in the presence of hypotonic aqueous solutions (0-0.05 M saline) or staphylococcal alpha- and beta-hemolysins when erythrocytes were pretreated with GML. GML may be useful in the management of Gram-positive exotoxin illnesses; its action appears to be membrane stabilization with inhibition of signal transduction.

Topics: Animals; Antigens, Bacterial; Bacterial Toxins; Cells, Cultured; Endothelium, Vascular; Erythrocytes; Exotoxins; Hemolysin Proteins; Hemolysis; Humans; Inositol 1,4,5-Trisphosphate; Laurates; Monoglycerides; Rabbits; Shock, Septic; Superantigens; T-Lymphocytes

Effects of Salmonella enteritidis endotoxin on intracellular Ca2+ mobilization were studied in hepatocytes. Rats were given intravenous injections of saline (control), endotoxin (20 mg/kg), or endotoxin (20 mg/kg) plus diltiazem (1.2 mg/kg). They were killed 5 h later, at which time endotoxin-injected rats showed signs of shock. The involvement of myoinositol 1,4,5-trisphosphate (IP3) and arachidonic acid (AA) in intracellular Ca2+ mobilization was tested using saponin-permeabilized hepatocytes. Added Ca2+ was sequestered by intracellular organelles in the presence of ATP until the medium free Ca2+ concentration was lowered to a near steady-state level. In control cells subsequent addition of 10(-6) M IP3 and AA, respectively, caused a rapid increase in free Ca2+ concentration from 130 +/- 31 to 257 +/- 54 nM (P less than 0.01) and from 111 +/- 21 to 196 +/- 37 (P less than 0.01). By use of experimental conditions designed to permit selective Ca2+ accumulation, it was determined that all of the Ca2+ released by IP3 and AA originated from the endoplasmic reticulum. The intracellular release of Ca2+ by IP3 and AA was significantly attenuated in endotoxic shock. Treatment of endotoxic rats with a calcium channel blocker, diltiazem, effected an increase in free Ca2+ concentration by IP3 from 124 +/- 18 to 240 +/- 41 nM (P less than 0.01) and by AA from 109 +/- 15 to 192 +/- 32 (P less than 0.01). These data suggest that during endotoxic shock there is an attenuation of IP3- and AA-induced intracellular Ca2+ release, which could be prevented by treatment of animals with diltiazem.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Bacterial Toxins; Calcium; Calcium Channel Blockers; Diltiazem; Inositol 1,4,5-Trisphosphate; Inositol Phosphates; Liver; Male; Mathematics; Permeability; Rats; Salmonella enteritidis; Saponins; Shock, Septic