Sepsis is the leading cause of mortality in the intensive care unit. A common and serious sequel of systemic bacterial infections, sepsis accounts for some 200,000 fatalities annually in the US alone, a figure higher than that attributable to AIDS and breast cancer combined. The pathogenesis of septic shock is a consequence of the host response to bacterial components. In the Gram-negative organism, lipopolysaccharide, found on the outer membrane, plays a major role in inducing the systemic inflammatory response that ultimately leads to the shock state. Although the clinical outcome of Gram-negative and Gram-positive infections are indistinguishable, until very recently, the causative factor in the Gram-positive organism was unknown. Compelling evidence now points to a major role for lipoteichoic acid, an integral component of the cell wall in Gram-positive organisms. In the course of our continuing efforts in identifying small-molecules that would specifically bind and neutralize Gram-negative lipopolysaccharide, we have found that certain classes of compounds also inhibit lethality in murine models of Gram-positive shock. In this proposal, we aim to initiate preliminary screening of select compounds based on the leads we have already obtained. We will first compare the biological activities of isolated, homogeneous, lipoteichoic acid and petidoglycan and verify that lipoteichoic acid is toxic on a molar basis comparable to that of reference lipopolysaccharide. Of the many classes of compounds screened in the past for anti-endotoxin activity, useful leads have been found in three classes: (1) the lipopolyamines (2) dendrimers, and (3) bis-amidines. Focused libraries of these compounds will be subjected to two levels of screening. In the primary screen, the inhibition of key cytokines induced by lipoteichoic acid in human peripheral blood mononuclear cells will be quantified. Active compounds will be subjected to a secondary screen in which upstream cellular events (cytokine mRNA transcription) will be examined. This is to demonstrate that inhibition of cytokine release, if observed, is attributable to the blockade of the cellular recognition of lipoteichoic acid.
| Kimbrell, Matthew R; Warshakoon, Hemamali; Cromer, Jens R et al. (2008) Comparison of the immunostimulatory and proinflammatory activities of candidate Gram-positive endotoxins, lipoteichoic acid, peptidoglycan, and lipopeptides, in murine and human cells. Immunol Lett 118:132-41 |
