Histamine H2 receptor (HRH2) (HRH2)

The Histamine H2 receptor (HRH2) is a G protein-coupled receptor (GPCR) that serves as a key mediator of gastric acid secretion and a potent immunomodulator [1, 3]. Primarily located on the parietal cells of the stomach, HRH2 activation by histamine triggers the Gs-adenylyl cyclase pathway, increasing intracellular cAMP and stimulating the proton pump to release hydrochloric acid [5, 12]. Beyond its gastrointestinal role, HRH2 is expressed on various effector and immune cells, including T cells, B cells, and dendritic cells, where it typically exerts immunosuppressive effects [1, 4]. Activation on these cells inhibits the production of Th1-type cytokines (e.g., IFN-gamma) and reduces neutrophil chemotaxis, thereby modulating the inflammatory landscape [1, 5]. Clinically, H2 receptor antagonists (H2RAs) such as famotidine and cimetidine are standard therapies for peptic ulcers and gastroesophageal reflux disease (GERD) [8, 9]. These drugs work by competitively blocking histamine binding, which effectively reduces both basal and stimulated acid production [9, 17]. Recent evidence also suggests that HRH2 signaling in the tumor microenvironment may facilitate cancer progression by suppressing anti-tumor immunity, positioning the receptor as a potential target for adjunctive cancer immunotherapy [2, 15]. Long-term use of H2RAs is associated with certain safety concerns, including vitamin B12 deficiency and an increased risk of certain infections due to prolonged acid suppression [6, 13].

Other names

H2RHH2RHistamine receptor H2

Competitive antagonism of the H2 receptor, inhibiting histamine-induced activation of adenylyl cyclase and the subsequent rise in intracellular cAMP levels.