title: Adhesion of monocytes to periodontal fibroblasts requires activation of NOD1/2- and TLR4-mediated LFA-1 and VLA-4.
abstract: OBJECTIVE
  The aim of this study was to investigate the roles of nucleotide-binding oligomerization domain-containing protein 1/2 (NOD1/2) and Toll-like receptor 4 (TLR4) in mediating the adhesion of monocytes to periodontal fibroblasts through leucocyte function-associated antigen-1 (LFA-1) and very late antigen-4 (VLA-4).
  
  
  METHODS
  The expression of NOD1, NOD2, and TLR4 was detected in the gingival tissue of patients with chronic periodontitis by immunohistochemistry. Then the adhesion of cells of human monocytic cell line U937 to human gingival fibroblasts (hGFs) and human periodontal ligament cells (hPDLCs) was investigated after U937 cells were treated with the agonists of NOD1, NOD2, and TLR4 for 24 h, or transfected with small interfering RNAs (siRNAs) targeting NOD1, NOD2, and TLR4 for 48 h. Meanwhile, the expression of LFA-1 and VLA-4 was examined in U937 cells through real-time polymerase chain reaction (PCR), Western blot, and flow cytometry. To confirm the roles of LFA-1 and VLA-4 involved in the process of adhesion, the adhesion blockade assay was performed using the corresponding blocking antibodies against these adhesion molecules.
  
  
  RESULTS
  The immunostaining results showed that NOD1, NOD2, and TLR4 were highly expressed in the gingival tissue of patients with periodontitis, especially in the monocyte-infiltrated area. The activation of these receptors by agonists upregulated the expression of LFA-1 and VLA-4 in U937 cells, and it increased the affinity of U937 cells to hGFs or hPDLCs. On the other hand, knockdown of these receptors by specific siRNAs resulted in the opposite results. In addition, blocking either LFA-1 or VLA-4 in U937 cells significantly attenuated the agonist-triggered adhesion of U937 to periodontal fibroblasts (P<0.001).
  
  
  CONCLUSIONS
  These results suggested that NOD1/2 and TLR4 mediated monocyte-periodontal fibroblast adhesion via the modulation of LFA-1 and VLA-4.
authors: Department of Periodontology, Peking University School and Hospital of Stomatology, Beijing, China.
authors: Jianru
authors: J
authors: Liu
authors: Department of Periodontology, Peking University School and Hospital of Stomatology, Beijing, China.
authors: Wenyi
authors: W
authors: Liu
authors: Department of Periodontology, Peking University School and Hospital of Stomatology, Beijing, China.
authors: Ying
authors: Y
authors: Xie
authors: Central Laboratory, Peking University School and Hospital of Stomatology, Beijing, China. Electronic address: kqwangyx@gmail.com.
authors: Yixiang
authors: Y
authors: Wang
authors: Department of Periodontology, Peking University School and Hospital of Stomatology, Beijing, China. Electronic address: kqouyangxy@bjmu.edu.cn.
authors: Xiangying
authors: X
authors: Ouyang
mesh_terms: D000328:Adult; D015153:Blotting, Western; D002448:Cell Adhesion / Q000502:physiology*; D002478:Cells, Cultured; D055113:Chronic Periodontitis / Q000378:metabolism*; D005260:Female; D005347:Fibroblasts / Q000502:physiology*; D005434:Flow Cytometry; D005881:Gingiva / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D039041:Integrin alpha4beta1 / Q000378:metabolism*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D053474:Nod1 Signaling Adaptor Protein / Q000378:metabolism*; D053473:Nod2 Signaling Adaptor Protein / Q000378:metabolism*; D010513:Periodontal Ligament / Q000166:cytology / Q000378:metabolism; D034741:RNA, Small Interfering; D060888:Real-Time Polymerase Chain Reaction; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D039041:Integrin alpha4beta1; D016169:Lymphocyte Function-Associated Antigen-1; C119067:NOD1 protein, human; C429018:NOD2 protein, human; D053474:Nod1 Signaling Adaptor Protein; D053473:Nod2 Signaling Adaptor Protein; D034741:RNA, Small Interfering; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4
keywords: Adhesion; Monocyte; NOD1/2; Periodontal fibroblast; TLR4