TREM1 Enhances Macrophage Proinflammatory Response to LPS by Promoting NF-κB Activation via an IL-26-mediated...

Lipopolysaccharide (LPS)-induced inflammation in macrophages involves complex signaling pathways. This investigation explored the regulatory roles of triggering receptor expressed on myeloid cells-1 (TREM1) and interleukin (IL)-26 in the Janus kinase/signal transducer and activator of transcription (JAK/STAT) and nuclear factor-kappa B (NF-κB) p65 pathways in LPS-stimulated RAW 264.7 macrophages. RAW 264.7 cells were treated with LPS to assess TREM1 expression. TREM1 or IL-26 was silenced using short hairpin RNA (shRNA), while IL-26 was overexpressed via plasmid transfection. The JAK2 inhibitor AG490 was used to block JAK/STAT signaling. Western blot, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and enzyme-linked immunosorbent assay (ELISA) were employed to analyze the protein and mRNA levels of inflammatory markers and signaling molecules. Results showed that LPS upregulated TREM1 expression. In addition, TREM1 knockdown suppressed p65 activation and reduced inflammatory cytokine levels. Moreover, silencing TREM1 inhibited IL-26 and JAK/STAT phosphorylation (p-JAK1, p-JAK2, p-STAT1, and p-STAT3). Similarly, IL-26 knockdown or AG490 treatment attenuated p65 activation and inflammation. Furthermore, IL-26 overexpression reversed the anti-inflammatory effects of TREM1 silencing. Overall, TREM1 promoted LPS-induced macrophage inflammation via IL-26-mediated JAK/STAT and NF-κB pathway activation, suggesting that TREM1 and IL-26 are potential therapeutic targets.