Potentiation of the toxicity of mithramycin by bacterial lipopolysaccharide

Human endothelial cell response to lipopolysaccharide, interleukin-1, and tumor necrosis factor is regulated by protein synthesis

In this study we assessed the viability of cultured human umbilical vein endothelial cells (HUVE) treated with bacterial lipopolysaccharide (LPS), recombinant human interleukin-1 (rhIL-1), or recombinant human tumor necrosis factor-alpha (rhTNF-alpha) during inhibition of RNA or protein synthesis. Cytotoxicity was determined by 51Cr activity retained in labeled HUVE monolayers after exposure to LPS, rhIL-1 or rhTNF-alpha, and cycloheximide (Cx) or actinomycin D (Act D). Lipopolysaccharide (150 ng/ml), rhIL-1 (100 pg/ml), or rhTNF-alpha (20 ng/ml) alone was not toxic to HUVE in an 18-hr incubation. Cycloheximide alone (1 microgram/ml for 18 hr) or Act D alone (1 microgram/ml for 6 hr) was also not toxic to HUVE. However, coincubation of HUVE with Cx and LPS (150 ng/ml), rhIL-1 (10 pg/ml), or rhTNF-alpha (20 ng/ml) produced significant cytotoxicity at 18 hr (70 +/- 4% for LPS, 75 +/- 5% for rhIL-1, and 52 +/- 5% for rhTNF-alpha; mean +/- SEM of 18, 16, and 19 separate experiments, respectively). Similarly, coincubation of HUVE with Act D and LPS, rhIL-1, or rhTNF-alpha resulted in 82 +/- 5%, 85 +/- 3%, and 67 +/- 4% cytotoxicity, respectively, at 6 hr (mean +/- SEM of 5 separate experiments for LPS, and 7 separate experiments each for rhIL-1 and rhTNF-alpha). At the highest concentrations of LPS, rhIL-1, or rhTNF-alpha, cytotoxicity during coincubation with Cx or Act D was detected as early as 2 hr and was near maximal by 6 hr. In contrast to LPS, rhIL-1, or rhTNF-alpha, recombinant human interferon-gamma (up to 100 U/ml), or human alpha-thrombin (up to 10 U/ml), produced no cytotoxicity in the presence of Cx. Recombinant human lymphotoxin (up to 50 ng/ml) had a detectable cytotoxic effect in the presence of Cx although it was significantly less than that seen with rhTNF-alpha. Furthermore, coincubation of human fibroblasts and human smooth muscle cells with Cx and LPS, rhIL-1, or rhTNF-alpha produced no cytotoxicity. We conclude that under these culture conditions, LPS, rhIL-1, or rhTNF-alpha produces a lethal injury to HUVE when de novo RNA or protein synthesis is inhibited. These results suggest that LPS, rhIL-1, and rhTNF-alpha may act via a common pathway in endothelial cells and that protein synthesis is important in regulating the response to these stimuli.

Action of bacterial endotoxin and lipid A on mitochondrial enzyme activities of cells in culture and subcellular fractions

Escherichia coli O127:B8 lipopolysaccharide (LPS), prepared by the Westphal procedure, caused a marked decrease in the activities of mitochondrial malate dehydrogenase, succinate dehydrogenase, and adenylate kinase in African green monkey kidney (Vero) cells and primary cultures of mouse liver cells within 2 h after exposure to 10 micrograms of LPS/ml of culture medium. These three enzyme activities leaked into the supernatant fraction, and cytochrome oxidase activity was lost from the mouse liver mitochondrial particulate fraction within 45 min after exposure to 10 micrograms of LPS/mg of protein. Loss malate dehydrogenase activity from isolated mitochondria was also accelerated by LPS from E. coli O26:B6 (Boivin preparation) or Salmonella typhosa O901 (Westphal preparation), and by lipid A from Salmonella minnesota or Shigella sonnei. In addition, LPS and lipid A inhibited state 3 respiration by isolated mitochondria with attendant loss of respiratory control, but adenosine 5'-diphosphate/O ratios were relatively unchanged. Impaired mitochondrial function is an early event after exposure to biologically relevant amounts of LPS or lipid A.

Endotoxin toxicity in rats with 6-sulfanilamidoindazole arthritis

Seven oral administrations of 6-sulfanilamidoindazole (6-SAI) to 10- to 12-month-old rats sensitized the animals to endotoxin, with dosages as small as 2.5 microgram causing death in 80% of animals. Endotoxin in a dosage of 3,000 microgram was not lethal for nonmedicated control animals. 6-SAI-treated 1-month-old rats were not as sensitive to endotoxin as aged animals. The sulfonamide-induced sensitivity to endotoxin could not be passively transferred and could not be explained by blockade of the reticuloendothelial system or impairment of endotoxin detoxification. 6-SAI administration was associated with both depletion of liver glycogen and lowering of blood glucose concentration without changes in blood lactic acid concentration. Disseminated intravascular coagulation is believed to be involved in the pathogenesis of shock and death as evidenced by: (i) concomitant decreases in plasma fibrinogen concentration and elevations in fibrin degradation products after endotoxin challenge; (ii) protection against lethal actions of endotoxin by pretreatment with heparin. Treatment of 6-SAI-medicated rats with glucocorticoids before endotoxin challenge protected the animals against lethal doses of endotoxin and prevented deposition of fibrin thrombi in the glomerular capillaries.

Enhanced susceptibility of mice to combinations of delta 9-tetrahydrocannabinol and live or killed gram-negative bacteria

Combinations of delta 9-tetrahydrocannabinol (delta 9-THC) and bacterial endotoxin were shown to be hyperadditively toxic for mice. A variety of purified lipopolysaccharide (LPS) preparations elicted enhanced mortality in combination with delta 9-THC. Escherichia coli O26:B6 LPS (Boivin preparation) at an essentially nonlethal dose of 2.5 mg/kg reduced the dose of delta 9-THC required to kill 50% of the treated mice from ca. 350 to 150 mg/kg. Inbred BALB, DBA, and C3H/HeCr mice, noninbred ICR mice, and hybrid CDF1 and BDF1 mice were hyperreactive to combinations of delta 9-THC and LPS. Moreover, a variety of heat-killed intestinal and gram-negative bacteria, live E. coli, and complexes of lipid A with a variety of proteins substituted for LPS in the synergistic toxicity of LPS and delta 9-THC. Extracts of marijuana also elicited hyperreactivity to LPS. The hyperadditive lethality of combinations of delta 9-THC and LPS was markedly less in mice rendered refractory to LPS or delta 9-THC by repeated administration of LPS or delta 9-THC, respectively.

Enhanced toxicity for mice of combinations of bacterial lipopolysaccharide and vincristine

Sublethal doses of vincristine (VNC) and bacterial lipopolysaccharide (LPS) administered simultaneously to adult male mice resulted in markedly enhanced mortality. All of 10 strains of Pseudomonas aeruginosa tested, 4 of 7 strains of Bacteroides, and 6 of 10 strains of Listeria monocytogenes were able to substitute for purified LPS in enhancing mortality in VNC-treated mice. Inoculation of mice with each of 10 strains of Pseudomonas, each of 7 strains of Bacteroides, and about half of the 10 strains of Listeria tested elicited increased resistance to the lethal action of purified LPS. The patterns of responses of mice receiving a lethal combination of 2 mg of LPS/kg and 1 mg of VNC/kg resembled those of mice receiving a lethal dose of 10 mg of VNC/kg alone or 15 mg of LPS/kg alone with respect to (i) serum glutamic pyruvate transaminase activity, (ii) hematocrit values, and (iii) thrombocytopenia. The patterns of responses of mice receiving a lethal combination of LPS and VNC resembled those of mice receiving a lethal dose of LPS alone with respect to (i) hypothermia, (ii) retention of sulfobromophthalein, (iii) fibrinogen level, (iv) prothrombin activity, (v) blood urea nitrogen levels, and (vi) time of death. These data are consistent with the proposition that the combination of VNC and LPS produces a fatal renal failure. Histological studies confirmed that there was extensive renal damage in mice treated with lethal doses of LPS alone or a lethal combination of LPS and VNC.