IDDF2024-ABS-0116 Helicobacter pylori infection promoted m1 macrophage polarization and gastric inflammation by activation of NLRP3 inflammasome via TNF/TNFR1 axis

<h3>Background</h3> Macrophages play a crucial role in the inflammatory response to human stomach pathogen <i>Helicobacter pylori (H. pylori).</i> M1 macrophages, also called classically activated macrophages, produce proinflammatory cytokines. NLRP3 inflammasome has emerged as an important component of inflammatory processes. However, the molecular mechanism by which <i>H. pylori</i> infection drives NLRP3 inflammasome and macrophage activation remains unclear. <h3>Methods</h3> Human gastritis tissues were implemented for the clinical significance of NLRP3. Infection with <i>H. pylori</i> infection was performed using <i>in vitro</i> and <i>in vivo</i> models. Bone marrow-derived macrophages (BMDMs) from wild-type (WT), NLRP3 knockout (NLRP3-KO) and TNFR1 knockout (TNFR1-KO) mice were infected with <i>H. pylori</i>. Western blotting, qRT-PCR, immunofluorescence, immunohistochemistry and Elisa were utilized for functional and mechanistic studies. <h3>Results</h3> Single cell RNA sequencing (ScRNA-seq) analysis of human gastric tissues, followed by validation, indicated that NLRP3 was primarily expressed in myeloid cells (IDDF2024-ABS-0116 Figure 1(A)) and was significantly increased in <i>H. pylori</i>-positive gastritis compared to <i>H. pylori</i>-negative gastritis (IDDF2024-ABS-0116 Figure 1(B)). Infected with PMSS1 and NCTC11637 <i>H. pylori</i> strains induced NLRP3 inflammasome activation in vitro (THP1 cells) and in the insulin-gastrin (INS-GAS) transgenic mouse model (IDDF2024-ABS-0116 Figure 1(C-E)). Deletion of NLRP3 in BMDMs showed marked inhibition of <i>H. pylori</i>-induced M1 macrophage polarization (IDDF2024-ABS-0116 Figure 1(F)). Furthermore, NLRP3 inflammasome activation upon TNFα or <i>H. pylori</i> stimulation, was partially blocked by TNFα or TNFR inhibitor (IDDF2024-ABS-0116 Figure 1(G)). Deletion of TNFR1 in BMDMs significantly impaired NLRP3 inflammasome activation and M1 macrophages induced by <i>H. pylori</i> (IDDF2024-ABS-0116 Figure 1(H,I)). <h3>Conclusions</h3> This study revealed that NLRP3, mainly expressed in myeloid cells, is a key regulator of <i>H. pylori</i>-induced M1 macrophage activation and gastric inflammation. The TNF-α/TNFR1 axis is essential for NLRP3 inflammasome activation in macrophages by <i>H. pylori</i> infection.