title: SIRT1 regulates lipopolysaccharide-induced CD40 expression in renal medullary collecting duct cells by suppressing the TLR4-NF-κB signaling pathway.
abstract: OBJECTIVE
  Recent evidence indicates that sirtuin1 (SIRT1), an NAD+-dependent deacetylase, exerts a protective effect against inflammatory kidney injury by suppressing pro-inflammatory cytokines production. The co-stimulatory molecule, CD40, is expressed in a variety of inflammatory diseases in the kidney. Here, we aimed to investigate the potential effect of SIRT1 on CD40 expression induced by lipopolysaccharide (LPS) and to disclose the underlying mechanisms in renal inner medullary collecting duct (IMCD) cells.
  
  
  METHODS
  mRNA and protein expressions were identified by quantitative real-time PCR and Western blot respectively. Subcellular localization of SIRT1 and CD40 were respectively detected by immunofluorescence and immunohistochemical staining. Small-interfering RNA (siRNA) was carried out for mechanism study.
  
  
  RESULTS
  LPS reduced SIRT1 expression and up-regulated the expression of CD40, Toll-like receptor 4 (TLR4) and phospho-NF-κBp65 (p-NF-κBp65) in time- and concentration-dependent manners. Moreover, SIRT1 overexpression or activation by SRT1720 diminished the expression of CD40, TLR4 and p-NF-κBp65, which was reversed by SIRT1 siRNA or inhibitors Ex527 and sirtinol in LPS-stimulated IMCD cells. In addition, knockdown of TLR4 decreased the expression of CD40 and p-NF-κBp65 in IMCD cells exposed to LPS. Knockdown of NF-κBp65 or NF-κBp65 inhibition by pyrrolidine dithiocarbamate (PDTC) reduced LPS-induced CD40 expression in IMCD cells. Importantly, the inhibitory effect of SIRT1 on the expression of CD40 and p-NF-κBp65 was augmented by pre-treating with TLR4 siRNA.
  
  
  CONCLUSIONS
  Our data indicate that SIRT1 inhibits LPS-induced CD40 expression in IMCD cells by suppressing the TLR4-NF-κB signaling pathway, which might provide novel insight into understanding the protective effect of SIRT1 in kidney.
authors.affiliation: College of Physical Education, Yanshan University, Qinhuangdao, Hebei 066004, PR China. Electronic address: linqinqin@ysu.edu.cn.
authors.forename: Qin-Qin
authors.initials: QQ
authors.lastname: Lin
authors.affiliation: College of Physical Education, Yanshan University, Qinhuangdao, Hebei 066004, PR China.
authors.forename: Yuan-Wen
authors.initials: YW
authors.lastname: Geng
authors.affiliation: College of Physical Education, Yanshan University, Qinhuangdao, Hebei 066004, PR China.
authors.forename: Zhong-Wei
authors.initials: ZW
authors.lastname: Jiang
authors.affiliation: Institute of Sports and Exercise Biology, Shaanxi Normal University, Xi'an, Shaanxi 710062, PR China. Electronic address: tianzhj@snnu.edu.cn.
authors.forename: Zhen-Jun
authors.initials: ZJ
authors.lastname: Tian
mesh_terms: D000818:Animals; D019013:CD40 Antigens / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D056564:Sirtuin 1 / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000378:metabolism*
chemical_list: D019013:CD40 Antigens; D008070:Lipopolysaccharides; D012333:RNA, Messenger; C498145:Rela protein, rat; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D051996:Transcription Factor RelA; C488368:Sirt1 protein, rat; D056564:Sirtuin 1
keywords: CD40; Inflammation; Inner medullary collecting duct cells; NF-κB; SIRT1; TLR4