Small molecule-driven SIRT3-autophagy-mediated NLRP3 inflammasome inhibition ameliorates inflammatory crosstalk between macrophages and adipocytes

Br J Pharmacol. 2020 Oct;177(20):4645-4665. doi: 10.1111/bph.15215. Epub 2020 Aug 20.

Abstract

Background and purpose: IL-1β produced by macrophages via the NOD-, LRR- and pyrin domain-containing 3 (NLRP3) inflammasome, mediates the inflammatory crosstalk between macrophages and adipocytes. In our previous study, (16S,20S,24R)-12β-acetoxy-16,23-epoxy-24,25-dihydroxy-3β-(β-D-xylopyranosyloxy)-9,19-cyclolanost-22(23)-ene (AEDC), a cycloartane triterpenoid isolated from Actaea vaginata (Ranunculaceae), was found to possess anti-inflammatory effect on LPS-treated RAW264.7 macrophages. This study was designed to investigate whether AEDC modulates macrophage-adipocyte crosstalk to alleviate adipose tissue inflammation.

Experimental approach: The anti-inflammatory effect of AEDC was evaluated on LPS plus ATP-induced THP-1 macrophages and C57BL/6J mice. The expression of autophagy-related and NLRP3 inflammasome complex proteins was analysed by western blots, immunofluorescence staining and co-immunoprecipitation. The pro-inflammatory cytokines levels were determined by ELISA kits. The adipose tissue inflammation was evaluated by histological analysis and immunohistochemical staining.

Key results: AEDC (5 and 10 μM) activated autophagy, which in turn suppressed the NLRP3 inflammasome activation and IL-1β secretion in THP-1 macrophages. AEDC increased the expression of SIRT3 deacetylase and enhanced its deacetylating activity to reverse mitochondrial dysfunction and activate AMP-activated protein kinase, which together induced autophagy. Moreover, AEDC (10 μM) attenuated macrophage conditioned medium-induced inflammatory responses in adipocytes and blocked THP-1 macrophages migration towards 3T3-L1 adipocytes. In inflammation mice, AEDC (5 and 20 mg·kg-1 ) treatment reduced the levels of pro-inflammatory cytokines in serum and epididymal adipose tissue and reduced macrophage infiltration to alleviate adipose tissue inflammation.

Conclusion and implications: AEDC attenuated the inflammatory crosstalk between macrophages and adipocytes through SIRT3-autophagy-mediated NLRP3 inflammasome inhibition, which might used for the treatment of adipose tissue inflammation-related metabolic disorders.

Keywords: IL-1β, macrophages; NLRP3 inflammasome; adipocytes; adipose tissue inflammation; autophagy; cycloartane triterpenoid.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipocytes
  • Animals
  • Autophagy
  • Inflammasomes*
  • Interleukin-1beta
  • Macrophages
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred NOD
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Sirtuin 3*

Substances

  • Inflammasomes
  • Interleukin-1beta
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Nlrp3 protein, mouse
  • Sirt3 protein, mouse
  • Sirtuin 3