Inhibition of acetylcholinesterase attenuated retinal inflammation via suppressing NF-κB activation

Elevated inflammatory cytokines contribute to the pathogenesis of various retinal diseases such as diabetic retinopathy, retinal vasculitis and retinitis. However, the underlying mechanism of retinal inflammation remains largely unknown. Recent studies demonstrated that acetylcholinesterase (ACHE) is an inflammatory indicator in central neural system. This study was aimed to dissect the role of ACHE in retinal inflammation, and its mechanism of action. Retinal inflammation was induced by intravitreal injection of tumor necrosis factor-alpha (TNF-alpha) in heterozygous ACHE knockdown mice (ACHE(+/-)) and wild type mice (ACHE(+/+)). Donepezil, a well-known ACHE inhibitor, was administrated by daily gavage. Expression of ACHE and intercellular adherent molecule-1 (ICAM-1), infiltration of CD11b(+) inflammatory cells, retinal leukostasis and vascular leakage was determined in both ACHE(+/-) and ACHE(+/+) mice. ARPE-19 cells, a human retinal pigment epithelial cell line, were cultured for in vitro assay. Knockdown of ACHE was achieved by lipofectamine-mediated siRNA transfection and pharmaceutical suppression of ACHE was manipulated by donepezil. Cellular expression and distribution of ACHE, ICAM-1, and phosphorylation of NF-kappa B, I kappa B and IKK alpha/beta were detected by western-blot analysis or immunocytochemistry. Retinal expression of ACHE was dramatically upregulated, in parallel with increased ICAM-1 expression, enhanced leukostasis and augmented CD11b(+) inflammatory cell infiltration as well as vascular hyperpermeability in ACHE(+/+) mice injected with TNF-alpha. However, TNF-alpha-injected ACHE(+/-) mice showed lower level of ICAM-1, less leukostasis and fewer infiltrated CD11b(+) cells. Moreover, TNF-alpha-induced retinal vascular leakage was significantly reduced in ACHE(+/-) mice. Similarly, TNF-alpha-induced retinal inflammatory response were also attenuated by donepezil intervention. In addition, TNF-alpha treatment resulted in significant induction of ACHE, upregulation of ICAM-1 and nuclear translocation of NF-kappa B, phosphorylation of I kappa B and IKK alpha/beta in ARPE-19 cells. However, inhibition of ACHE reduced TNF-alpha-induced phosphorylation of NF-kappa B, I kappa B and IKK alpha/beta in ARPE-19 cells. The present study reveals a pivotal role of ACHE in retinal inflammation. Inhibition of ACHE attenuates retinal inflammation and retinal leakage likely through suppressing NF-kappa B signaling activation.