title: TREM-2 promotes host resistance against Pseudomonas aeruginosa infection by suppressing corneal inflammation via a PI3K/Akt signaling pathway.
abstract: OBJECTIVE
  To explore the role of triggering receptor expressed on myeloid cells 2 (TREM-2) in Pseudomonas aeruginosa (PA) keratitis.
  
  
  METHODS
  BALB/c mice were routinely infected with PA and evaluated at various postinfection time points for corneal expression of TREM-2, by real-time PCR, Western blot, and flow cytometry. Next, BALB/c and C57BL/6 mice were respectively treated with TREM-2 siRNA or agonistic anti-TREM-2 antibody, to determine the role of TREM-2 in PA keratitis. Bacterial load and neutrophil infiltration were tested by plate count and myeloperoxidase assay, respectively. Th1-/Th2-type and proinflammatory cytokine expression were tested by real-time PCR and ELISA after in vivo and in vitro silencing of TREM-2. Moreover, phosphorylated Akt levels were tested by Western blot in murine macrophages after treatment with agonistic anti-TREM-2 antibody. mRNA levels of proinflammatory cytokines were examined in murine macrophages after TREM-2 activation and lipopolysaccharide stimulation, following pretreatment with inhibitors for PI3K or Akt, to determine whether PI3K/Akt is required in TREM-2-mediated immune modulation. In addition, BALB/c mice were treated with wortmannin and analyzed for bacterial load and proinflammatory cytokine expression.
  
  
  RESULTS
  TREM-2 expression was elevated in the infected BALB/c corneas at 3 or 5 days postinfection. Silencing of TREM-2 accelerated disease progression by enhancing bacterial load and corneal inflammation, whereas activation of TREM-2 promoted host resistance to PA keratitis. PI3K/Akt signaling is required in the TREM-2-mediated immune modulation, and inhibition of PI3K resulted in worsened disease after PA corneal infection.
  
  
  CONCLUSIONS
  TREM-2 promoted host resistance to PA infection by suppressing corneal inflammation via activation of the PI3K/Akt pathway.
authors.affiliation: Department of Immunology, Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China.
authors.forename: Mingxia
authors.initials: M
authors.lastname: Sun
authors.forename: Min
authors.initials: M
authors.lastname: Zhu
authors.forename: Kang
authors.initials: K
authors.lastname: Chen
authors.forename: Xinxin
authors.initials: X
authors.lastname: Nie
authors.forename: Qiuchan
authors.initials: Q
authors.lastname: Deng
authors.forename: Linda D
authors.initials: LD
authors.lastname: Hazlett
authors.forename: Yongjian
authors.initials: Y
authors.lastname: Wu
authors.forename: Meiyu
authors.initials: M
authors.lastname: Li
authors.forename: Minhao
authors.initials: M
authors.lastname: Wu
authors.forename: Xi
authors.initials: X
authors.lastname: Huang
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D015169:Colony Count, Microbial; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D015818:Eye Infections, Bacterial / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D005434:Flow Cytometry; D007113:Immunity, Innate; D007634:Keratitis / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D008264:Macrophages / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011552:Pseudomonas Infections / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D011550:Pseudomonas aeruginosa / Q000472:pathogenicity; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D011971:Receptors, Immunologic / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology
chemical_list: D016207:Cytokines; D008562:Membrane Glycoproteins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D011971:Receptors, Immunologic; C498716:Trem2 protein, mouse
keywords: bacteria; cornea; cytokines; inflammation