Wntl Participates In Inflammation Induced By Lipopolysaccharide Through Upregulating Scavenger ReceptorA And NF-κB

Background:When the body suffers from bacterial infection, the bacteria release of LPS (lipopolysaccharide) which can stimulate the body’s immune inflammatory response. Inflammation stimulated by LPS involves the activation of a variety of inflammatory signaling pathways (including MAPK, NF-KB, etc). LPS mainly binds to the toll-like receptors on the surface of the cell membrane (mainly TLR4) and scavenger receptor class A (SRA) activating downstream signaling molecules-myd88and increasing the number of p65(NF-KB pathways mainly transcription factor) from cytoplasm to nuclear. P65activated the transcription of TNF alpha IL-6and iNOS, further expanding inflammatory signals.Wnt pathways can be divided into three forms including (1) the classical wnt pathways (2)the non-classical wnt pathways and (3)calcium-dependent pathway, belonging to a class of conservative signaling pathways mainly involved in embryonic development, cell proliferation, cancer, etc.Wntl belongs to a member of the classical wnt pathways. Wntl is synthesized by the cell and secreted to the outside of the cell. By binding to the receptor complexes of FZD1LRP5and LRP6on membrane surface, wntl activates the (3-catenin which translocates into the nuclear promoting the activation of transcription factorsTCF1/TCF4which increasing the transcription of related genes. Previous studies have found that wntl in PC12cells increased cell survival through promoting the NF-KB activation. However, whether wntl participates in the inflammatory response caused by LPS is still unknown.Objective:how LPS regulates SRA expression and the detailed mechanism of wntl activating NF-kB. This study aims to explore the role of wnt1in the inflammatory response induced by LPS and the relationship of wntl SRA and NF-kB.Methods:1) Use PMA to activate THP1cells to became macrophage-like cells for later experiments. Then THP1cells were treated with LPS to detect Wntl protein level by western blot.2) After transfection with Wntl siRNA or Wntl over-expression plasmid, the NF-KB, and the secretion of inflammatory cytokines’including IL-6TNF alpha and iNOS in cells were detected by WB and ELISA.3) THP1cells were transfected with wntlsiRNA or wntl over-expression plasmid. Expression of TLR4receptor and SRA receptor was checked by WB. NF-KB protein level was also detected when transfection with wntl over-expression and SRAsiRNA.4) THP1cells were treated with LPS after trasfection with FZD1siRNA or VAX939(beta-catenin inhibitors) to detect the expression of SRA receptor.Results:1) when THP1cells were treated with PMA or LPS, the expression of Wntl protein rised.2) Transfected with wntl siRNA, NF-kB protein level and the secretion of inflammatory cytokines including IL-6, TNF alpha and iNOS in THP-1cells were both decreased. After transfection with wnt1over-expression plasmid, NF-kB expression and the expression of inflammatory factors including IL-6, TNF alpha and iNOS are increased.3) After THP1cells transfected with wntlsiRNA, SRA receptor expression declined, when transfected with wntl over-expression plasmid, SRA expression increased.4) Before treated with LPS, THP1cells were transfected with FZD1siRNA or added with VAX939(beta-catenin inhibitors), SRA receptor protein expression decreased.Conclusions:1The wntl protein participated in NF-KB activation and the secretion of inflammatory cytokines induced by LPS.2Wntl postively regulated the expression of SRA receptor (mediated NF-KB activation by LPS).3Wntl had co-localization with SRA on the cell membrane and also activated NF-KB through SRA receptor.