Clcn5 Knockout Mice Exhibit Novel Immunomodulatory Effects and Are More Susceptible to Dextran Sulfate Sodium-Induced Colitis

Abstract

Although the intracellular Cl−/H+ exchanger Clc-5 is expressed in apical intestinal endocytic compartments, its pathophysiological role in the gastrointestinal tract is unknown. In light of recent findings that CLC-5 is downregulated in active ulcerative colitis (UC), we tested the hypothesis that loss of CLC-5 modulates the immune response, thereby inducing susceptibility to UC. Acute dextran sulfate sodium (DSS) colitis was induced in Clcn5 knockout (KO) and wild-type (WT) mice. Colitis, monitored by disease activity index, histological activity index, and myeloperoxidase activity were significantly elevated in DSS-induced Clcn5 KO mice compared with those in WT mice. Comprehensive serum multiplex cytokine profiling demonstrated a heightened Th1–Th17 profile (increased TNF-α, IL-6, and IL-17) in DSS-induced Clcn5 KO mice compared with that in WT DSS colitis mice. Interestingly, Clcn5 KO mice maintained on a high vitamin D diet attenuated DSS-induced colitis. Immunofluorescence and Western blot analyses of colonic mucosa validated the systemic cytokine patterns and further revealed enhanced activation of the NF-κB pathway in DSS-induced Clcn5 KO mice compared with those in WT mice. Intriguingly, high baseline levels of IL-6 and phospho-IκB were observed in Clcn5 KO mice, suggesting a novel immunopathogenic role for the functional defects that result from the loss of Clc-5. Our studies demonstrate that the loss of Clc-5 1) exhibits IL-6–mediated immunopathogenesis, 2) significantly exacerbated DSS-induced colitis, which is influenced by dietary factors, including vitamin D, and 3) portrays distinct NF-κB–modulated Th1–Th17 immune dysregulation, implying a role for CLC-5 in the immunopathogenesis of UC.

Overexpression of the Endosomal Anion/Proton Exchanger ClC-5 Increases Cell Susceptibility toward Clostridium difficile Toxins TcdA and TcdB

“…Vice versa , increased susceptibility to dextran sulfate sodium-induced colitis was found in Clcn5 knockout mice. (Sullivan et al, 2009 ; Alex et al, 2010 ) These data additionally support the notion that human ClC-5 might be involved in the development of C. difficile -induced cytotoxicity and the pathophysiology of CDI. To test this hypothesis, we expressed human ClC-5 in HEK293 and colon HT29 cells and elucidated the effects of this manipulation on the endocytosis and cellular effects of TcdA and TcdB.…”

Myeloid CFTR loss-of-function causes persistent neutrophilic inflammation in cystic fibrosis

“…In addition to CFTR, mammalian cells express voltage‐gated Cl – channels or H + / Cl – exchangers such as ClC family members, 34 calcium‐activated Cl – channels (CaCCs) such as TMEM16A and TMEM16B, 35‐40 ligand‐gated Cl – channels (GABA‐ and glycine‐gated), 41,42 and volume‐regulated Cl – channels, 43 some of which might transport chloride to neutrophil phagosomes 10,11 . For example, ClC3 was identified in phagocytes including neutrophils, 44,45 but the contribution of ClC3 to phagocyte HOCl production has not been explored.…”

FOLH1/GCPII is elevated in IBD patients, and its inhibition ameliorates murine IBD abnormalities

“…Acute colitis was induced by administration of 2.5% (w/v) DSS (MW 40,000–50,000) in the drinking water for 7 days as described previously (56, 57). On day 8, the colon and ileum were removed and feces were flushed clean with cold saline using a syringe and weighed.…”