NLRP3 Attenuates Intraocular Inflammation by Inhibiting AIM2-Mediated Pyroptosis Through the Phosphorylated Salt-Inducible Kinase 1/Sterol Regulatory Element Binding Transcription Factor 1 Pathway

OBJECTIVE: The NLRP3 inflammasome has been shown to be involved in the development of uveitis, but the exact mechanism remains elusive. Here, we explored the role of NLRP3 in the development of uveitis.

METHODS: Firstly, Nlrp3 deficiency mice were used to study the role of NLRP3 in experimental autoimmune diseases, such as experimental autoimmune uveitis (EAU) and experimental autoimmune encephalomyelitis (EAE). Then, the gathering of ASC, activation of CASPASE-1 and GSDMD, and secretion of LDH and IL-1β were detected to confirm macrophages pyroptosis and AIM2 activation in the Nlrp3-/- mice. Additionally, RNA sequencing and Chromatin Immunoprecipitation and Polymerase Chain Reaction (ChIP-PCR) were used to investigate the P-SIK1/SREBF1 pathway, which regulates the transcription of Aim2. Finally, overexpression of Nlrp3 was applied to treat EAU.

RESULTS: Surprisingly, our results show that NLRP3 plays an anti-inflammatory role in two models of EAU and EAE. Additionally, macrophages show an increased M1 activation and pyroptosis in Nlrp3-/- mice. Further experiments indicate that this pyroptosis of macrophages was mediated by the upregulated transcription of Aim2 as a result of Nlrp3 deficiency. In mechanistic studies, Nlrp3 deficiency was implicated in downregulation of P-SIK1 and subsequently the upregulation of SREBF1, which binds to Aim2 and then promotes the latter's transcription. Finally, deficiency of Aim2, RNA silencing of Aim2 or Srebf1, and overexpression of Nlrp3 resulted in attenuated inflammation of EAU.

CONCLUSION: Our data show that NLRP3 inhibits AIM2 inflammasome mediated EAU by regulating the P-SIK1/SREBF1 pathway, highlighting the therapeutic potential of targeting Nlrp3. This article is protected by copyright. All rights reserved.