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Abstract
Background Macrophages play a crucial role in the inflammatory response to human stomach pathogen Helicobacter pylori (H. pylori). 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 H. pylori infection drives NLRP3 inflammasome and macrophage activation remains unclear.
Methods Human gastritis tissues were implemented for the clinical significance of NLRP3. Infection with H. pylori infection was performed using in vitro and in vivo models. Bone marrow-derived macrophages (BMDMs) from wild-type (WT), NLRP3 knockout (NLRP3-KO) and TNFR1 knockout (TNFR1-KO) mice were infected with H. pylori. Western blotting, qRT-PCR, immunofluorescence, immunohistochemistry and Elisa were utilized for functional and mechanistic studies.
Results 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 H. pylori-positive gastritis compared to H. pylori-negative gastritis (IDDF2024-ABS-0116 Figure 1(B)). Infected with PMSS1 and NCTC11637 H. pylori 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 H. pylori-induced M1 macrophage polarization (IDDF2024-ABS-0116 Figure 1(F)). Furthermore, NLRP3 inflammasome activation upon TNFα or H. pylori 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 H. pylori (IDDF2024-ABS-0116 Figure 1(H,I)).
Conclusions This study revealed that NLRP3, mainly expressed in myeloid cells, is a key regulator of H. pylori-induced M1 macrophage activation and gastric inflammation. The TNF-α/TNFR1 axis is essential for NLRP3 inflammasome activation in macrophages by H. pylori infection.