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Blockage of TLR4 or NLRP3 Inhibits IL-1ß Activation in Response to Intermittent Hypoxia

Background: Intermittent hypoxia(IH) leads to a proinflammatory phenotype in the adipose tissue with M1 macrophage polarization1 which plays a key role in the pathogenesis of insulin resistance(IR) in obstructive sleep apnoea. In elucidating the signalling mechanism, we have recently reported that IH activates the interleukin(IL)-1β pathway in primary macrophages2. Here, we tested the hypothesis that toll like receptor(TLR)4 and NLRP3 inflammasome control IH-induced IL-1β signalling. Methods: Bone marrow derived macrophages(BMDM) isolated from lean and obese wild-type C57BL/6 and NLRP3 KO mice were exposed to IH or intermittent normoxia1, in the presence/absence of LPS (10ng/ml) and then stimulated with ATP(5mM) for 1hr. TLR4 inhibitor experiments cells were pretreated with TAK242(2uM) for 30min before the start of the IH protocol. RT-PCR, immunoblotting and ELISA analysis were performed to assess IL-1 β expression and secretion. Results: The IH-induced increase in IL-1β mRNA was reduced by 3-fold and 4-fold in BMDM’s isolated from lean (p=.02) and obese (p=.03). Moreover, TAK242 decreased the IH increase in LPS induced up-regulation of proIL-1β protein expression in lean and obese macrophages. In BMDM’s from lean NLRP3-/- mice the IH stimulated increase in IL-1β mRNA was reduced by 5-fold (p=.18). Furthermore, the LPS induced increase in IL-1 β secretion in IH was decreased by 2-fold (p=.04). However, loss of NLRP3 had no effect on the IH amplified LPS activation of pro-IL-1β protein expression. Blockage of TLR4 or NLRP3 prevents IL-1β activation in primary macrophages suggesting potential therapeutic target for IH-induced IR. 1Murphy et. Al 2017 ERJ49:1601732Fitzpatrick et. Al ERS2019:Abstract17061