Adenosine controls tissue fluid and pH homeostasis through transcriptional regulation of SLC26A3

Abstract

Inflammatory bowel disease (IBD) affects 1.5 million individuals and their families in the United States, with rates of diagnosis on the rise and no effective cures. A hallmark of IBD is the presence of crypt abscesses, accumulation of neutrophils in the lumen of intestinal crypts. It has been well established that activated neutrophils release high levels of adenine nucleotides, which is quickly converted to adenosine. In the setting of acute inflammation, such adenosine is made available to can activate epithelial adenosine receptors to regulate multiple cellular functions. As a starting point, we performed an unbiased microarray profiling of epithelial transcripts in response to adenosine stimulation. This profiling identified to prominent induction of SLC26A3, a member of the solute carrier family of genes that serves as a chloride – bicarbonate exchanger. Using a combination of RT‐qPCR, western blots, and a promoter assay in T83 IEC, we show that SLC26A3 is a cAMP/CREB‐regulated gene. We also investigated the role of SLC26A3 in the adenosine response. It has been well established that in IECs adenosine elevates cAMP levels through the adenosine A2B receptor. These elevated cAMP levels trigger the activation of the CFTR and apical efflux of chloride. To investigate the role of SLC26A3 in functional adenosine responses, we utilized CRISPR to knockdown SLC26A3 and an ORF‐lentiviral vector to overexpress SLC26A3. Elevated levels of SLC26A3 prevented adenosine‐induced fluid transport while knockdown of SLC26A3 increased fluid transport. Moreover, intracellular pH changes in response to adenosine correlated with loss and gain of SLC26A3 expression, likely related to chloride‐bicarbonate exchange with elevated intracellular cAMP. Finally, we compared the expression of SLC26A3 in colon biopsies from healthy and patients with active ulcerative colitis. This analysis revealed that SLC26A3 is repressed with active inflammation and residual protein expression is abnormally localized within colonic tissues. These results identify adenosine‐regulated SLC26A3 as a relevant epithelial protein that contributes to tissue pH homeostasis. Targeted regulation of SLC26A3 may serve as a new therapeutic approach in mucosal inflammation.Support or Funding InformationNIH R01‐DK095491This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.