Abstract
Purpose: :
To explore the role of microRNA (miR)-155 in Pseudomonas aeruginosa (PA) keratitis.
Methods: :
Ocular infection, isolation of human peripheral blood mononuclear cell (PBMC), isolation of murine peritoneal macrophage (Mϕ), in vivo miR-155 inhibition, cell culture assays, phagocytosis assay, and real time RT-PCR.
Results: :
miR-155 expression levels were significantly up-regulated in PA-infected vs normal human corneas as well as Mϕ derived from PBMC. Furthermore, in vivo studies showed that miR-155 expression was significantly increased in PA-infected corneas of C57BL/6 (B6) mice. Inhibition of miR-155 led to reduced ocular disease after PA infection, by down-regulating pro-inflammatory cytokine (e.g., IL-1β, IFN-γ, IL-6, IL-12) production. In vitro studies also demonstrated that PA challenge induced miR-155 expression in a time- and dose-dependent manner in peritoneal Mϕ and RAW264.7 cells. The induction of miR-155 was dependent on TLR2, TLR4, TLR9, through NF-ΚB, IKK, JNK and PI3K, but not P38 or ERK pathways. Moreover, overexpression of miR-155 significantly decreased Mϕ-mediated phagocytosis and intracellular bacterial killing of PA, by down-regulating expression of mannose receptor (MR) and complement receptor 3 (CR3). miR-155 overexpression also enhanced the production of pro-inflammatory cytokines including IFN-γ, IL-1β, IL-6, IL-12, IL-17A, but reduced anti-inflammatory cytokine IL-10 expression.
Conclusions: :
Induction of miR-155 is dependent on TLR2, TLR4, TLR9, through NF-ΚB, IKK, JNK and PI3K signal pathway after PA infection. miR-155 amplifies ocular inflammation after PA infection by reducing bacterial phagocytosis and enhancing production of pro-inflammatory cytokines.
Keywords: inflammation • immunomodulation/immunoregulation • cornea: basic science