TREM-1 triggers necroptosis of macrophages through mTOR-dependent mitochondrial fission during acute lung injury

J Transl Med. 2023 Mar 6;21(1):179. doi: 10.1186/s12967-023-04027-4.

Abstract

Background: Necroptosis of macrophages is a necessary element in reinforcing intrapulmonary inflammation during acute lung injury (ALI). However, the molecular mechanism that sparks macrophage necroptosis is still unclear. Triggering receptor expressed on myeloid cells-1 (TREM-1) is a pattern recognition receptor expressed broadly on monocytes/macrophages. The influence of TREM-1 on the destiny of macrophages in ALI requires further investigation.

Methods: TREM-1 decoy receptor LR12 was used to evaluate whether the TREM-1 activation induced necroptosis of macrophages in lipopolysaccharide (LPS)-induced ALI in mice. Then we used an agonist anti-TREM-1 Ab (Mab1187) to activate TREM-1 in vitro. Macrophages were treated with GSK872 (a RIPK3 inhibitor), Mdivi-1 (a DRP1 inhibitor), or Rapamycin (an mTOR inhibitor) to investigate whether TREM-1 could induce necroptosis in macrophages, and the mechanism of this process.

Results: We first observed that the blockade of TREM-1 attenuated alveolar macrophage (AlvMs) necroptosis in mice with LPS-induced ALI. In vitro, TREM-1 activation induced necroptosis of macrophages. mTOR has been previously linked to macrophage polarization and migration. We discovered that mTOR had a previously unrecognized function in modulating TREM-1-mediated mitochondrial fission, mitophagy, and necroptosis. Moreover, TREM-1 activation promoted DRP1Ser616 phosphorylation through mTOR signaling, which in turn caused surplus mitochondrial fission-mediated necroptosis of macrophages, consequently exacerbating ALI.

Conclusion: In this study, we reported that TREM-1 acted as a necroptotic stimulus of AlvMs, fueling inflammation and aggravating ALI. We also provided compelling evidence suggesting that mTOR-dependent mitochondrial fission is the underpinning of TREM-1-triggered necroptosis and inflammation. Therefore, regulation of necroptosis by targeting TREM-1 may provide a new therapeutic target for ALI in the future.

Keywords: Acute lung injury; Macrophages; Mitochondrial fission; Necroptosis; TREM-1; mTOR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acute Lung Injury*
  • Animals
  • Inflammation
  • Lipopolysaccharides* / pharmacology
  • Macrophages
  • Mice
  • Mitochondrial Dynamics
  • Necroptosis
  • TOR Serine-Threonine Kinases
  • Triggering Receptor Expressed on Myeloid Cells-1

Substances

  • Triggering Receptor Expressed on Myeloid Cells-1
  • 3-(2,4-dichloro-5-methoxyphenyl)-2-sulfanyl-4(3H)-quinazolinone
  • Lipopolysaccharides
  • TOR Serine-Threonine Kinases