Alcohol consumption is associated with increased susceptibility to infections and impaired immune responses, the mechanisms if which are not well understood. LPS, a major component of bacterial wall, is recognized by toll-like receptor (TLR) 4 and ? accessory molecule CD14 and triggers a variety of intracellular events that culminates in the production of pro-inflammatory cytokines. Our previous work showed that in monocytes, acute alcohol impairs bacterial lipopolysaccharide (LPS)-induced cellular activation via inhibition of NF?B pathway to result in low pro-inflammatory cytokines production. Recent studies suggest that LPS triggers formation of a large """"""""signalosome"""""""" - a complex of cellular receptors, including TLR4, CD14, FcR, CD36, CD55, CD11b, CD18, Hsp70, Hsp90, and CXCR4. Formation of signalosome requires rigid cholesterolrich membrane platforms, called membrane rafts. We recently identified that disruption of membrane rafts via cholesterol depletion prevents LPS-induced cell activation. Further, we identified that alcohol prevents TLR4 association with rafts. Based on preliminary data, we hypothesize that alcohol may affect the early events of LPStriggered cell activation. We postulate that inhibition cell activation by alcohol depends on the complexity of signal events that take place at the level of membrane rafts. We further hypothesized that acute alcohol targets the LPS-triggered recruitment of signalosome into lipid rafts and thus prevents cell activation. Specifically, we propose that alcohol disrupts the formation of the """"""""signalosome"""""""".
The Specific Aim of this proposal is to determine the influence of alcohol on the integrity of the TLR4 receptor complex (TLR4, CD14, MD2, MyD88, signalosome members) A) by exploring the colocalization with membrane rafts; B) evaluating the association with detergent-resistant membranes (DRMs); C) detecting acquisition/loss of proteins within the TLR4 receptor complex D) studying the formation of TLR4 multimers. Results from these studies should delineate the early molecular events that lead to impaired LPS-induced cellular activation after acute exposure to alcohol. Investigation of the early steps of LPS signaling may identify strategies for interfering with the effects of LPS and design therapeutic approaches for improving immunity against infections. ? ? ?
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| Dolganiuc, Angela; Szabo, Gyongyi (2008) T cells with regulatory activity in hepatitis C virus infection: what we know and what we don't. J Leukoc Biol 84:614-22 |
