Apolipoprotein A-I Diminishes Acute Lung Injury And Sepsis In Mice Induced By Lipoteichoic Acid

We evaluated the effect of ApoA-Ⅰon the mortality of L-929 cells which were attacked by LTA-activated peritoneal macrophages.Mice macrophages were activated by LTA.Then different doses of ApoA-Ⅰ(with final concentration of 0,10,50,100μg/ml) were incubated with activated macrophages for 3 h,and 10%LFF was added to the 50μg/ml ApoA-Ⅰtreatment group.The supernatant was added to above L-929 cells and incubated for 16 h.MTT was used to detect the mortality of L-929 cells which were attacked by release-out of cytokines in LTA-activated macrophages.We found that ApoA-Ⅰcould significantly inhibit the LTA-induced cell death in the dose-dependent fashion and LFF could enhance the protective effect of ApoA-Ⅰ.We next sought to evaluate whether ApoA-Ⅰcould attenuate LTA-mediated NFκB nuclear translocation,a process necessary after its activation.We found that after LTA.stimulation,NFκB was localized in nucleus in almost all the cells,while the LTA-mediated NFκB nuclear translocation in macrophages was greatly diminished in ApoA-Ⅰtreated cells..Moreover,we investigated the protective effects of ApoA-Ⅰon LTA-induced acute lung injury(ALl).BALB/c mice were challenged by LTA,then followed by ApoA-Ⅰor saline administration,respectively for 24 h.The mice were then sacrificed and tumor necrosis factorα(TNF-α) and interleukin-1β(IL-1β) levels in the serum and bronchoalverolar lavage(BAL) fluid were measured.We found that ApoA-Ⅰcould significantly inhibit LTA-induced increase of IL- 1βand TNF-αlevels in serum (P＜0.01,P＜0.05,respectively),as well as in BAL fluid(P＜0.01,P＜0.05,respectively). The lung histopathological analysis was also performed.We found that ApoA-Ⅰcould attenuate LTA-induced acute lung injury and inflammation.Also we incubated both ApoA-Ⅰand LTA,then,one aliquot was stained with Coomassie blue and another one aliquot was stained with Sudan black B.Finally,both aliquots were loaded on the agarose gel.We found that both staining showed one strip with same migrating distance after electrophoresis,indicating ApoA-Ⅰand LTA can bind together in vitro.These result suggest that(1) ApoA-Ⅰhas beneficial effect on LTA-induced systemic inflammation and ALl;(2) ApoA-Ⅰmay inhibit LTA-induced activation of Apolipoprotein A-Ⅰdiminishes acute lung injury and sepsis in mice induced by Lipoteichoic acid macrophage by following mechanisms:1) ApoA-Ⅰmay bind and neutralize LTA, interrupting the interaction between LTA and macrophage;and 2) ApoA-Ⅰmay disrupt LTA-induced signal transduction in macrophage(the activation and nuclear translocation of NFκB),and then inhibit the cytokine release of the activated cells.