During infection, membrane components are shed from bacteria in complexes that include LPS and two bacterial membrane lipoproteins: murein lipoprotein (MLP), and peptidoglycans associated lipoprotein (PAL). This renewal proposal seeks to study the physical interactions that each of these bacterial membrane components have with each other and with host lipoproteins, and the relative contribution of each in activation of cellular and systemic inflammatory responses that are mediated through Toll-like receptors (TLRs). Our central hypothesis is that MLP and PAL contribute to the pathogenesis of sepsis, and that their activity in vivo may be altered by interactions with each other, with LPS, and with host proteins and lipoproteins. Whereas most previous work has studied chemically purified or synthetic TLR agonists, this work will study natural forms of MLP and PAL wherever possible. The first specific aim is to study the kinetics of release of MLP and PAL from the bacterial cell wall into bacterial membrane complexes and into low density forms in serum. In vitro studies will utilize human serum. In vivo studies will be performed in two models of infection in mice: peritoneal E. coli infection and cecal ligation and puncture. The physical association of MLP and PAL with subsets of lipoprotein particles containing LPS and apoA 1 and the distribution of MLP and PAL in organs and cells in tissues will be studied over time. The second specific aim is to compare the effects of serum released forms of MLP and PAL with chemically purified forms of each in vitro and in vivo. Effects will be evaluated using both macrophages and endothelial cells because these cells integrate the inflammaory response in sepsis. Bacterial strains deficient in MLP and PAL, and mice deficient in TLR2 and TLR4, will be used to distinguish the contributions of cellular activation by each bacterial lipoprotein and by LPS. Our third specific aim is to study the effect of anti-MLP IgG on the processes above and on survival in the two models. The experiments are designed to evaluate the importance that physiologically relevant forms of MLP and PAL play in the pathophysiology of sepsis during infection.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM059694-05
Application #
6870107
Study Section
Surgery, Anesthesiology and Trauma Study Section (SAT)
Program Officer
Somers, Scott D
Project Start
2000-03-01
Project End
2008-11-30
Budget Start
2005-02-01
Budget End
2005-11-30
Support Year
5
Fiscal Year
2005
Total Cost
$362,031
Indirect Cost
Name
Massachusetts General Hospital
Department
Type
DUNS #
073130411
City
Boston
State
MA
Country
United States
Zip Code
02199
Zeng, Melody Y; Cisalpino, Daniel; Varadarajan, Saranyaraajan et al. (2016) Gut Microbiota-Induced Immunoglobulin G Controls Systemic Infection by Symbiotic Bacteria and Pathogens. Immunity 44:647-658
Lin, Tian; Sammy, Fatima; Yang, Huan et al. (2012) Identification of hemopexin as an anti-inflammatory factor that inhibits synergy of hemoglobin with HMGB1 in sterile and infectious inflammation. J Immunol 189:2017-22
Warren, H Shaw; Fitting, Catherine; Hoff, Eva et al. (2010) Resilience to bacterial infection: difference between species could be due to proteins in serum. J Infect Dis 201:223-32
Lin, Tian; Kwak, Young Ho; Sammy, Fatima et al. (2010) Synergistic inflammation is induced by blood degradation products with microbial Toll-like receptor agonists and is blocked by hemopexin. J Infect Dis 202:624-32
Liang, Xueya; Lin, Tian; Sun, Guangjie et al. (2009) Hemopexin down-regulates LPS-induced proinflammatory cytokines from macrophages. J Leukoc Biol 86:229-35
Warren, H Shaw (2009) Peroxisome proliferator-activated receptor-gamma agonists, control of bacterial outgrowth, and inflammation. Crit Care Med 37:773-4
Warren, H Shaw (2009) Editorial: Mouse models to study sepsis syndrome in humans. J Leukoc Biol 86:199-201
Bagchi, Aranya; Herrup, Elizabeth A; Warren, H Shaw et al. (2007) MyD88-dependent and MyD88-independent pathways in synergy, priming, and tolerance between TLR agonists. J Immunol 178:1164-71
Valentine, Catherine H; Hellman, Judith; Beasley-Topliffe, Laura K et al. (2006) Passive immunization to outer membrane proteins MLP and PAL does not protect mice from sepsis. Mol Med 12:252-8
Liang, Michael D; Bagchi, Aranya; Warren, H Shaw et al. (2005) Bacterial peptidoglycan-associated lipoprotein: a naturally occurring toll-like receptor 2 agonist that is shed into serum and has synergy with lipopolysaccharide. J Infect Dis 191:939-48

Showing the most recent 10 out of 16 publications