The Role Of HMGB1/TLR-4/IL-33 Signaling Pathway In Mechanism Of Ventilation Induced Lung Injury

BackgroundCyclic stretch is a major etiology factor underlying ventilation induced lung injury(VILI)which mechanism has been proved involving Toll like receptor 4(TLR-4)signaling.Cytokine changes during stretch could induce inflammatory permeability in distal lung and further cause injury.Recently,nucleus cytokine IL-33 has been demonstrated to play a role in VILI,and HMGB1 could regulate IL-33 production during acute respiratory syndrome.In the present study,we for the first time isolated stretch alone in respiratory epithelial cells and examined whether IL-33 changes,if this changes regulated by TLR-4 and HMGB1,and try to find out upstream signaling of IL-33 production,further explore mechanism of VILI.MethodsWe use cyclic(1Hz,～18% elongation)or static(～18% elongation)pattern to stretch MLE-12 cells for indicated time,and detect the IL-33 level in whole cell lysate,cytoplasm and nucleus parts.Then we knockdown TLR-4 expression in stretched MLE-12 cells to see IL-33 changes and other cytokine expression.We also detect HMGB1 secretion in cell culture media and use recombinant HMGB1 and HMGB1 nutralizing antibody treating cells to see if IL-33 level changes after cyclic stretch.At last we treated TLR-4 knockdown cells with recombinant HMGB1 and detect the influence of TLR-4 on HMGB1 induced IL-33 production.ResultsOur results shown that cyclic stretch could increase IL-33 expression and IL-33 mainly located in the nucleus.Cyclic stretch induced IL-33 production and cell injury are TLR-4 dependent.Cyclic stretch could also increase HMGB1 secretion through TLR-4 signaling,in return HMGB1 as endogenous ligand of TLR-4 increased IL-33 production through TLR-4 dependent pathway during cyclic stretch.ConclusionHMGB1/TLR-4/IL-33 axis could be a new molecular mechanism underlying mechanical stretch and VILI.Modulate HMGB1 secretion and TLR-4 activation further regulate IL-33 production may have potential benefits in relieve mechanical stretch induced lung injury.