AUTHOR=Li Dayu , Hodges Robin , AukrustNaqvi Maria , Bair Jeffrey , Bispo Paulo J. M. , Gilmore Michael S. , Gregory-Ksander Meredith , Dartt Darlene A. 

TITLE=Staphylococcus aureus activates NRLP3-dependent IL-1β secretion from human conjunctival goblet cells using α toxin and toll-like receptors 2 and 1

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=Volume 13 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2023.1265471

DOI=10.3389/fcimb.2023.1265471

ISSN=2235-2988

ABSTRACT=We used cultured human conjunctival goblet cells to determine: (i) whether toxigenic S.aureusinduced activation of the epithelial goblet cells requires two signals to activate the NLRP3 inflammasome, (ii) if one signal is mediated by TLRs 1, 2, or 6; and (iii) if the S. aureus toxin a toxin is another signal for the activation of the inflammasome and secretion of mature IL-1b. Cultured cells were incubated with siRNA to knock down the different TLRs. After stimulation with toxigenic S. aureus RN6390, pro-IL-1b synthesis, caspase-1 activity, and mature IL-1b secretion were measured. In a separate set of experiments, cells were incubated with toxigenic S. aureus RN6390 or mutant S. aureus ALC837 that does not express a toxin with or without exogenous a toxin. A gentamicin protection assay was used to determine if intracellular bacteria were active. We conclude that a toxin from toxigenic S. aureus triggers two separate mechanisms required for the activation of the NLRP3 inflammasome and secretion of mature IL-1b. In the first mechanism a toxin secreted from internalized S. aureus produces a pore, allowing the internalized bacteria and associated PAMPs to interact with intracellular TLR2 and to a lesser extent TLR1. In the second mechanism a toxin forms a pore in the plasma membrane, leading to an efflux of cytosolic K + and influx of Ca 2+ . We conclude that a-toxin by these two different mechanisms triggers the synthesis of pro-IL-1b and NLRP3 components, activation of capase-1, and secretion of mature IL-1b to defend against the bacterial infection.