Journal Article

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

Lanis, Jordi M., Mu, Andrew, Cartwright, Ian M., Colgan, Sean P., Onyiah, Joseph C., Gerich, Mark E., Dowdell, Alexander S., Welch, Nichole, Hall, Caroline H. T., Tabor, Jeffrey J., Schaefer, Rachel E. M., Kostelecky, Rachael E., Brink, Kathryn R.

2021

Overview

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.

• Publisher: National Academy of Sciences
• Subject: Acidification / Acidosis / Acidosis - genetics / Acidosis - metabolism / Acidosis - pathology / AMP / Animal models / Animals / Antiporters - genetics / Antiporters - metabolism / Biological Sciences / Cell Biology / Colonization / Crohn Disease - genetics / Crohn Disease - metabolism / Crohn Disease - pathology / Crohn's disease / Cyclic AMP / Cyclic AMP response element-binding protein / Cyclic AMP Response Element-Binding Protein - genetics / Cyclic AMP Response Element-Binding Protein - metabolism / Disease Models, Animal / Dual Specificity Phosphatase 1 - genetics / Dual Specificity Phosphatase 1 - metabolism / E coli / Epithelial cells / Epithelium / FosB protein / Gene expression / Gene Expression Regulation / Gene sequencing / Homeostasis / Humans / Ileitis / Ileitis - genetics / Ileitis - metabolism / Ileitis - pathology / Ileum / Ileum - metabolism / Ileum - pathology / In vivo methods and tests / Inflammation / Intestinal Mucosa - metabolism / Intestinal Mucosa - pathology / Intestine / Kinases / MAP kinase / Mice / Mice, Inbred C57BL / Mitogen-Activated Protein Kinases - genetics / Mitogen-Activated Protein Kinases - metabolism / Molecular modelling / Mucosa / Nuclear Receptor Subfamily 4, Group A, Member 1 - genetics / Nuclear Receptor Subfamily 4, Group A, Member 1 - metabolism / Organoids - metabolism / Organoids - pathology / pH effects / Phosphorylation / Protein kinase / Proteins / Proto-Oncogene Proteins c-fos - genetics / Proto-Oncogene Proteins c-fos - metabolism / Receptors, G-Protein-Coupled - genetics / Receptors, G-Protein-Coupled - metabolism / Sequence Analysis, RNA / Signal Transduction / Sulfate Transporters - genetics / Sulfate Transporters - metabolism