TLR-Independent and P2X7-Dependent Signaling Mediate Alu RNA-Induced NLRP3 Inflammasome Activation in Geographic Atrophy

METHODS. Human and mouse RPE cells were transfected with a plasmid encoding an Alu element (pAlu) or an in vitro-transcribed Alu RNA. Inflammasome priming was assessed by measuring NLRP3 and IL18 mRNA levels by real-time quantitative PCR. Using immunoblotting, we assessed NF-kappa B activation by monitoring phosphorylation of its p65 subunit, and inflammasome activation by monitoring caspase-1 cleavage into its active form. RPE degeneration was induced in mice by subretinal transfection of pAlu or Alu RNA. The NF-kappa B inhibitor BAY 11-7082, the P2X7 receptor antagonist A-740003, and the NLRP3 inflammasome inhibitor glyburide were delivered by intravitreous injections. We studied wild-type (WT) C57Bl/6J, P2rx7(-/-), Nfkb1(-/-), and Tlr23479(-/-) mice. RPE degeneration was assessed by fundus photography and zonula occludens-1 (ZO-1) staining of mouse RPE.