Endogenous glucocorticoids are required for normal macrophage activation and gastric immunity.

Glucocorticoids are steroid hormones well known for their potent anti-inflammatory effects. However, their immunomodulatory properties are multifaceted. Increasing evidence suggests that glucocorticoid signaling promotes effective immunity and that disruption of glucocorticoid signaling impairs immune function. In this study, we conditionally deleted the glucocorticoid receptor (GR) in the myeloid lineage using the driver (myGRKO). We examined the impact on macrophage activation and gastric immune responses to , the best-known risk factor of gastric cancer. Our results indicate that, compared with wild type (WT), glucocorticoid receptor knockout (GRKO) macrophages exhibited higher expression of proinflammatory genes in steroid-free conditions. However, when challenged in vivo, GRKO macrophages exhibited aberrant chromatin landscapes and impaired proinflammatory gene expression profiles. Moreover, gastric colonization with revealed impaired gastric immune responses and reduced T cell recruitment in myGRKO mice. As a result, myGRKO mice were protected from atrophic gastritis and pyloric metaplasia development. These results demonstrate a dual role for glucocorticoid signaling in preparing macrophages to respond to bacterial infection but limiting their pathogenic activation. In addition, our results support that macrophages are critical for gastric immunity. Signaling by endogenous glucocorticoids primes macrophages toward more robust responses to pathogens. Disruption of glucocorticoid signaling caused dysregulation of the chromatin landscape, blunted proinflammatory gene activation upon bacterial challenge, and impaired the gastric inflammatory response to infection.