23Abbreviations used in this paper: Helicobacter pylori, H. pylori; adrenomedullin, ADM; interleukin, IL; 24 interferon, IFN; receptor activity modifying protein, RAMP; phosphoinositide 3-kinase, PI3K; signal 25 transducers and activators of transcription, STAT; wild-type, WT; knockout, KO; post infection, p.i.; 26 haematoxylin and eosin, H&E.Abstract 2 Adrenomedullin (ADM) is a multifunctional peptide that is expressed by many surface epithelial cells, 3 but its relevance to H. pylori-induced gastritis is unknown. Here, we found that gastric ADM 4 expression was elevated in gastric mucosa of H. pylori-infected patients and mice. In H. 5 pylori-infected human gastric mucosa, ADM expression was positively correlated with the degree of 6 gastritis, accordingly, blockade of ADM resulted in decreased inflammation within the gastric 7 mucosa of H. pylori-infected mice. During H. pylori infection, ADM production was promoted via 8 PI3K-AKT signaling pathway activation by gastric epithelial cells in a cagA-dependent manner, and 9 resulted in increased inflammation within the gastric mucosa. This inflammation was characterized 10 by the increased IFN-γ-producing T cells, whose differentiation was induced via the phosphorylation 11 of AKT and STAT3 by ADM derived from gastric epithelial cells. ADM also induced macrophages to 12 produce IL-12, which promoted the IFN-γ-producing T-cell responses, thereby contributing to the 13 development of H. pylori-associated gastritis. Accordingly, blockade of IFN-γ or knockout of IFN-γ 14 decreased inflammation within the gastric mucosa of H. pylori-infected mice. This study identifies a 15 novel regulatory network involving H. pylori, gastric epithelial cells, ADM, macrophages, T cells, and 16 IFN-γ, which collectively exert a pro-inflammatory effect within the gastric microenvironment.17 18 Author summary 19 H. pylori infect almost half the world's population. Once infected, most of people carry the bacteria 20 lifelong if left untreated, so that persistent H. pylori infection can lead to chronic gastritis, peptic 21 ulceration and ultimately gastric cancer. H. pylori infection is accompanied with increased 22 inflammation in gastric mucosa, but the mechanisms of chronic gastritis induced by H. pylori 23 infection remains poorly understood. We studied a multifunctional peptide known as adrenomedullin 24 (ADM) in gastric epithelial cells, which was known as a key factor of regulating gastrointestinal 25 physiology and pathology. Here, we found that gastric ADM expression was elevated in gastric 26 mucosa of H. pylori-infected patients and mice, and was positively correlated with the degree of 27 gastritis. ADM production was promoted via PI3K-AKT signaling pathway activation by gastric 28 epithelial cells in a cagA-dependent manner. Blockade of ADM during H. pylori infection resulted in 29 decreased gastric inflammation that was characterized by the increased IFN-γ-producing T cells 30 which was induced via the phosphorylation of AKT and STAT3 by ADM derived from gastric 1 epitheli...