SLC26A3 Deficiency Alters the Colonic Lamina Propria Lymphocytes

SLC26A3 or Down Regulated in Adenoma (DRA) is the key anion transporter involved in electroneutral NaCl absorption in the mammalian intestine. DRA knockout (KO) mice exhibit diarrheal phenotype and greater susceptibility to experimental colitis. A recent genome wide association study (GWAS) identified SLC26A3 polymorphism leading to lower DRA expression as a risk factor for ulcerative colitis. Additionally, we have shown that genetic deficiency of DRA in mice results in compromised barrier integrity and increased gut permeability. These studies render DRA to have a more complex involvement in IBD, beyond its transporter function. Enhanced intestinal permeability is associated with activation of mucosal immune system and may contribute to alterations in lamina propria lymphocytes consisting of innate (innate lymphoid cells ILC1, ILC2, ILC3) and adaptive immune system (Th1, Th2, Tregs and Th17). Thus, we sought to determine the total levels of lamina propria lymphocytes both innate and adaptive, to decipher their involvement in intestinal pathology observed in DRA KO mice. Ileal and colonic lamina propria lymphocytes were isolated from Wild type (WT) and DRA KO mice (n=7). Fluorescence Assisted Cell Sorting (FACS) analysis was carried out in these mice to determine the various subtypes of CD127 + ILCs and TCRb + /CD4 + Th Cells. Isolated lymphocytes were also stimulated to secrete cytokines using phorbol 12‐myristate 13‐acetate/PMA (50 ng/mL) and ionomycin (500 ng/mL) and were further analyzed with FACS. Our results demonstrated that GATA3 + colonic Th2 cells were significantly increased along with the corresponding CD127 + /GATA3 + ILC2 in DRAKO mice compared to WT mice. These cells partake in mediating intestinal fibrosis and collagen deposition which are highly upregulated in DRAKO mice colons. However, tuft cell hyperplasia which may contribute to increased ILC2 was not observed in DRA KO mice. Similarly, the anti‐inflammatory CD127 + /RORgt + ILC3, which are important in maintaining intestinal epithelial integrity and intestinal cell homeostasis were significantly down‐regulated showing lower secretion of the important cytokine IL‐22 in DRAKO mice colons. However, the FOXP3 + Treg levels increased in colon of KO mice. The differences in lymphoid cells were mainly detected in the colon (where DRA expression is higher) and were less evident in the ileum. Overall, our data indicate that loss of DRA transporter results in altered intestinal lamina propria lymphocytes in the colon which may in part contribute to the higher susceptibility of DRA KO mice to inflammatory and infectious insults. Support or Funding Information NIH/NIDDK, Department of Veterans Affairs