Colonic gene expression profile in NHE3-deficient mice: evidence for spontaneous distal colitis

Abstract

Na+/H+ exchanger 3 (NHE3) provides a major route for intestinal Na+ absorption. NHE3 has been considered a target of proinflammatory cytokines and enteropathogenic bacteria, and impaired NHE3 expression and/or activity may be responsible for inflammation-associated diarrhea. However, the possibility of loss of NHE3 function reciprocally affecting gut immune homeostasis has not been investigated. In this report, we describe that NHE3-deficient mice spontaneously develop colitis restricted to distal colonic mucosa. NHE3(-/-) mice housed in a conventional facility exhibited phenotypic features such as mild diarrhea, occasional rectal prolapse, and reduced body weight. Genomewide microarray analysis identified not only a large group of transport genes that potentially represent an adaptive response, but also a considerable number of genes consistent with an inflammatory response. Histological examination demonstrated changes in the distal colon consistent with active inflammation, including crypt hyperplasia with an increased number of 5-bromo-2'-deoxyuridine-positive cells, diffuse neutrophilic infiltrate with concomitant 15-fold increase in matrix metalloproteinase 8 expression, an increased number of pSer276-RelA-positive cells, and a significant decrease in periodic acid-Schiff-positive goblet cells. Real-time PCR demonstrated elevated expression of inducible nitric oxide synthase (38-fold), TNF-alpha (6-fold), macrophage inflammatory protein-2 (48-fold), and IL-18 (3-fold) in the distal colon of NHE3(-/-) mice. NHE3(-/-) mice showed enhanced bacterial adhesion and translocation in the distal colon. Colitis was ameliorated by oral administration of broad-spectrum antibiotics. In conclusion, NHE3 deficiency leads to an exacerbated innate immune response, an observation suggesting a potentially novel role of NHE3 as a modifier gene, which when downregulated during infectious or chronic colitis may modulate the extent and severity of colonic inflammation.

Coordinate activation of inflammatory gene networks, alveolar destruction and neonatal death in AKNA deficient mice

“…The fact that no other leukocyte populations appeared to be affected (Supplementary information, Figure S4A and S4B) underscores the plausible contribution of neu- trophils to phenotypes observed for AKNA deficiency. To test whether the observed peripheral neutrophil mobilization indeed leads to enhanced alveolar infiltration, lung tissue sections from WT and KO mice were probed with the neutrophil-specific antibody MCA771GA [32]. Immunohistochemical results in Figure 3A and 3B show that the number of MCA771GA + cells present in the alveolar microenvironment was quantitatively higher in KO mice, further supporting the involvement of neutrophils in the lung pathology observed in AKNA KO mice.…”

The protein disulfide isomerase AGR2 is essential for production of intestinal mucus

“…Similar changes in these genes were recently identified in mice with Muc2 mutations that cause MUC2 misfolding (21). Although we did not detect overt colitis in young mice, 5 of 8 Agr2 Ϫ/Ϫ mice that we followed for 1 year after birth developed rectal prolapse, a condition that is seen in various mouse models of intestinal inflammation (22,23). None of the 7 Agr2 ϩ/ϩ littermate controls developed rectal prolapse (P ϭ 0.03 by Fisher's exact test).…”

“…AGR2-deficient mice were more susceptible to intestinal disease. The Agr2 Ϫ/Ϫ mice that we generated and studied were viable, but with aging they often developed rectal prolapse, a common feature of mouse models of colitis (22,23). Even in the absence of overt spontaneous colitis, microarray analysis did reveal an increase in mast cells, which are important in intestinal innate immunity, and in expression of some proinflammatory cytokines.…”

Reduced colonic microbial diversity is associated with colitis in NHE3-deficient mice

“…In agreement with those clinical observations, our group described the role of NHE3 in the modulation of inflammatory processes and the maintenance of mucosal integrity. NHE3-deficient mice spontaneously develop colitis (16) and are highly susceptible to DSS-induced intestinal injury (12). More recently, we demonstrated the importance of NHE3 in the maintenance of intestinal barrier integrity and in modulating the inflammatory process in IL-10-deficient mice (15).…”

“…Our studies suggest that NHE3 participates in mucosal responses to epithelial damage, acting as a modifier gene determining the extent of the inflammatory responses in the face of intestinal injury. More importantly, spontaneous colitis developed by NHE3 Ϫ/Ϫ mice was associated with enhanced bacteria adhesion and translocation in the distal colon (11,16), which could be significantly reduced by oral treatment with broad-spectrum antibiotics (16), thus highlighting the importance of microbiota in the pathogenesis of inflammation precipitated by the loss of NHE3 activity.…”