For study of the kinetics of endotoxin release from bacterial cells during therapy for gram-negative bacterial sepsis, serial blood samples were obtained from rabbits with Escherichia coli sepsis ...that were treated with either antibiotic or placebo. The concentrations of viable bacteria, free endotoxin, and total endotoxin in each blood sample were quantitated. In animals treated with placebo the concentration of free endotoxin was proportional to the level of bacteremia. In contrast, in animals treated with antibiotic the plasma levelsof free endotoxin increased 10- to 2,000-fold, in spite of decreasing levels of bacteremia. Free endotoxin that was present in the plasma following antibiotic treatment appeared to be derived in part from the breakdown of circulating bacteria and in part from the disintegration of bacteria in tissues other than the blood. The results of this study demonstrate that significant amounts of endotoxin are released from bacterial cells following administration of antibiotics in vivo.
To evaluate the role of antibiotic class in the rate of liberation of endotoxin during therapy for sepsis caused by gram-negative bacteria, we obtained serial blood samples from rabbits with sepsis ...caused by Escherichia coli and treated with chloramphenicol, gentamicin, or moxalactam. The concentrations of viable bacteria, free endotoxin, and total endotoxin in each blood sample were measured. In rabbits treated with chloramphenicol, the geometric mean levels of free endotoxin remained proportional to the geometric mean levels of bacteremia, a result indicating the absence of antibiotic-induced endotoxin liberation. In contrast, levels of free endotoxin increased rapidly while levels of bacteremia declined after treatment with gentamicin or moxalactam, a result indicating antibiotic-induced release of endotoxin. Despite similar rates of bacterial killing, mean levels of free endotoxin were as much as 20-fold higher in rabbits treated with moxalactam than in paired rabbits receiving gentamicin (P < .05). These results indicate that endotoxin liberation during therapy for sepsis caused by gram-negative bacteria is dependent upon the class of antibiotic administered and is not necessarily correlated with the rate of bacterial killing.
The generation of reactive oxygen species (ROS) is inherent to immune responses. ROS are crucially involved in host defense against pathogens by promoting bacterial killing, but also as signaling ...agents coordinating the production of cytokines. Transient Receptor Potential Melastatin 2 (TRPM2) is a Ca²âº-permeable channel gated via binding of ADP-ribose, a metabolite formed under conditions of cellular exposure to ROS. Here, we show that TRPM2-deficient mice are extremely susceptible to infection with Listeria monocytogenes (Lm), exhibiting an inefficient innate immune response. In a comparison with IFNγR-deficient mice, TRPM2â»/â» mice shared similar features of uncontrolled bacterial replication and reduced levels of inducible (i)NOS-expressing monocytes, but had intact IFNγ responsiveness. In contrast, we found that levels of cytokines IL-12 and IFNγ were diminished in TRPM2â»/â» mice following Lm infection, which correlated with their reduced innate activation. Moreover, TRPM2â»/â» mice displayed a higher degree of susceptibility than IL-12-unresponsive mice, and supplementation with recombinant IFNγ was sufficient to reverse the unrestrained bacterial growth and ultimately the lethal phenotype of Lm-infected TRPM2â»/â» mice. The severity of listeriosis we observed in TRPM2â»/â» mice has not been reported for any other ion channel. These findings establish an unsuspected role for ADP-ribose and ROS-mediated cation flux for innate immunity, opening up unique possibilities for immunomodulatory intervention through TRPM2.
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