Mucosal acidosis elicits a unique molecular signature in epithelia and intestinal tissue mediated by GPR31-induced CREB phosphorylation

Abstract

Metabolic changes associated with tissue inflammation result in significant extracellular acidosis (EA). Within mucosal tissues, intestinal epithelial cells (IEC) have evolved adaptive strategies to cope with EA through the up-regulation of SLC26A3 to promote pH homeostasis. We hypothesized that EA significantly alters IEC gene expression as an adaptive mechanism to counteract inflammation. Using an unbiased RNA sequencing approach, we defined the impact of EA on IEC gene expression to define molecular mechanisms by which IEC respond to EA. This approach identified a unique gene signature enriched in cyclic AMP response element-binding protein (CREB)-regulated gene targets. Utilizing loss- and gain-of-function approaches in cultured epithelia and murine colonoids, we demonstrate that EA elicits prominent CREB phosphorylation through cyclic AMP-independent mechanisms that requires elements of the mitogen-activated protein kinase signaling pathway. Further analysis revealed that EA signals through the G protein-coupled receptor GPR31 to promote induction of FosB, NR4A1, and DUSP1. These studies were extended to an in vivo murine model in conjunction with colonization of a pH reporter Escherichia coli strain that demonstrated significant mucosal acidification in the TNFΔARE model of murine ileitis. Herein, we observed a strong correlation between the expression of acidosis-associated genes with bacterial reporter sfGFP intensity in the distal ileum. Finally, the expression of this unique EA-associated gene signature was increased during active inflammation in patients with Crohn’s disease but not in the patient control samples. These findings establish a mechanism for EA-induced signals during inflammation-associated acidosis in both murine and human ileitis.

The Hypoxia-Adenosine Link during Myocardial Ischemia—Reperfusion Injury

“…However, if oxygen levels fall, PHDs are functionally inactivated. In addition, other metabolic changes in the microenvironment [ 32 , 40 , 41 ], or oxygen-independent mechanisms of PHD inhibition, have been demonstrated previously (e.g., elevations of succinate levels) [ 42 , 43 ]. These changes in metabolic supply and demand lead to the stabilization of HIF1A or HIF2A, which form a transcriptionally active complex with the HIF1B subunit [ 44 ].…”

The TNFΔAREmouse as a model of intestinal fibrosis

“…Animal handling: We utilized the C57BL/6-TNF ΔARE previously described 7,11 and wild type littermates that were all bred in house. All animals were maintained and handled according to protocols approved by the Institutional Animal Care and Use Committee (IACUC).…”

Essential role for epithelial HIF-mediated xenophagy in control of Salmonella infection and dissemination

“…Briefly, Caco-2 cells were grown to confluence on Transwell semi-permeable inserts (0.4μm, Corning# 3470). Cells were then washed and placed into Hanks’ Balanced Salt Solution containing Ca 2+ /Mg 2+ and supplemented with 10mM HEPES (HBSS + ) ( Cartwright et al, 2021 ). Cells were then incubated on an Oxodish sensor plate with or without apical STm, and the percent O 2 of the surrounding buffer was measured over time.…”