Introduction
Gastric injury induces metaplasia is based on parietal cells loss and reprogramming chief cells into proliferative, mucin-rich spasmolytic polypeptide-expressing metaplasia (SPEM) cells. Previously, we demonstrated that parietal cell-selective Slc26a9 deficiency in mice promotes the development of SPEM and progress to gastric intraepithelial neoplasia in mice (Liu et al., Cellular oncology; 2022; Deng et al., DDW2023). However, the exact role of Slc26a9 in injury-induced metaplasia is need further investigated.
Aims & Methods
We used immunostaining to characterize the expression pattern of Slc26a9 during murine gastric development, homeostasis, and injury in homeostasis, after conditionial genetic deletion of Slc26a9. Furthermore, to reveal the functional role of Slc26a9, Injury-induced metaplasia was established in Slc26a9fl/fl mice and Slc26a9fl/fl/Atp4b-Cre mice with high-dose tamoxifen.
Results
Mice with parietal cell selective Slc26a9 deficiency first developed spontaneous parietal cell damage, which subsequently led to SPEM. Parietal cell injury was associated with the release of typical pyroptosis factors, including NRLP3, Caspase-1, ASC, GasderminD, IL-1β and IL-18. At the same time, SLC26A9 colocalized with caspase1, NLRP3, GSDMD, and NLRP3 and GSDMD, and produced a large number of reactive oxygen species (ROS), markers of mitochondrial damage, thereby expanding membrane perforation of GSDMD-N fragments and amplifying inflammasome-mediated parietic cell pyrodeath. At the same time, electron microscopy showed that after the knockout of the Slc26a9 gene, the mitochondria of the murine wall cells were obviously swollen, the cell membrane structure was blurred and damaged, the matrix was more dissolved, the ridge was broken and disappeared, and there were many bubble protrusions. This suggests that parietal cell specific SLC26A9 gene deletion may lead to parietal cell scorch death through mitochondrial damage mediated by GSDMD. However, with a large number of parietal cell damage and loss, gastric hypergastrinemia stimulates Tuft cell proliferation and migration to the gastric mucosa for colonization, and secretes a series of alarm hormones such as IL-25, IL-33, HMGB1. Moreover, ILC2 cell secretory factors such as IL-17RA and IL-17RB, GATA3, CD90, CD25 were up-regulated. M2 macrophage polarization-related markers such as Arg1, Fizz1, Ym1, Klf4 and secreted chemokines such as CCL24 and CCL22 were significantly up-regulated. The immunofluorescence staining of F4/80+ and CD163+ was significantly increased. This suggests that the spontaneous injury of parietal cells caused by the deletion of SLC26A9 gene in gastric parietal cells may lead to gastric dysfunction (hypoacid and hypergastrinemia) and mucosal epithelial injury, which may promote the occurrence of SPEM through IL-25 mediating the activation of ILC2 cells to regulate the cellular immune mechanism of macrophage M2 polarization.
Conclusion
Slc26a9 target deletion in parietal cells leads to spontaneous damage and scorch death of parietal cells, which is the core target and cell origin of initiating SPEM. After parietal cell specific Slc26a9 gene deletion leads to spontaneous injury of parietal cells, gastric dysfunction and mucosal injury result in the release of alarm hormone IL-25, which promotes the development of SPEM by activating IL-25-ILC2-macrophage M2 polarization axis. Slc26a9 plays an important protective role in stabilizing gastric epithelial cell differentiation and gastric mucosal immune homeostasis.
Disclosure
No conflict of interest
