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Translational animal models for oral mucositis (OM) are necessary to simulate and assess the bioclinical effects and response in humans. These models should simulate high levels of radiation exposure that leads to oxidative stress and inflammatory‐initiated tissue changes. Hamster models have been extensively studied to observe pathological effects of radiation exposure and help in the development of effective treatments. To successfully evaluate the potential for treatment regimens with consistency and relevance, a radiation‐induced OM hamster model was developed using a clinical linear accelerator utilized by cancer patients daily. The dose exposure to the isolated, everted cheek pouch of a hamster, as well as the progression of injury, pro‐inflammatory marker, histological, and elasticity analyses of the buccal pouch were conducted to verify replicability and reproducibility of the injury model. The findings from this model demonstrated its ability to consistently induce injury and resolution over 28 days using an acute dose of 60 Gy. This model was developed to enhance clinical relevance when evaluating potential efficacious treatments and can now be utilized in efficacy studies to better evaluate developed therapeutics in a preclinical model that is easy to translate to clinical studies..

TNF plays an integral role in inflammatory bowel disease (IBD), as evidenced by the dramatic therapeutic responses in Crohn’s disease (CD) patients induced by chimeric anti-TNF mAbs. However, treatment of CD patients with etanercept, a decoy receptor that binds soluble TNF, fails to improve disease. To explore this discrepancy, we investigated the role of TNF signaling in Wnt/β-catenin–mediated intestinal stem cell and progenitor cell expansion in CD patients, human cells, and preclinical mouse models. We hypothesized that TNF exerts beneficial effects on intestinal epithelial cell (IEC) responses to injury. In CD patients, intestinal stem cell and progenitor cell Wnt/β-catenin signaling correlates with inflammation status. TNF-deficient (Tnf−/−) mice exhibited increased apoptosis, less IEC proliferation, and less Wnt signaling when stimulated with anti-CD3 mAb. Bone marrow (BM) chimera mice revealed that mucosal repair depended on TNF production by BM–derived cells and TNFR expression by radioresistant IECs. Wild-type→Tnfr1/2−/− BM chimera mice with chronic dextran sodium sulfate colitis exhibited delayed ulcer healing, more mucosal inflammation, and impaired Wnt/β-catenin signaling, consistent with the hypothesis that epithelial TNFR signaling participates in mucosal healing. The direct effect of TNF on stem cells was demonstrated by studies of TNF-induced Wnt/β-catenin target gene expression in murine enteroids and colonoid cultures and TNF-induced β-catenin activation in nontransformed human NCM460 cells (TOPFlash) and mice (TOP-GAL). Together, these data support the hypothesis that TNF plays a beneficial role in enhancing Wnt/β-catenin signaling during ulcer healing in IBD. These novel findings will inform clinicians and therapeutic chemists alike as they strive to develop novel therapies for IBD patients.

Cancer cells are known to upregulate aerobic glycolysis to promote growth, proliferation, and survival. However, the role of mitochondrial respiration in tumorigenesis remains elusive. Here we report that inhibition of mitochondrial function by silencing TFAM, a key transcription factor essential for mitochondrial DNA (mtDNA) replication and the transcription of mtDNA-encoded genes, markedly reduced tumor-initiating potential of colon cancer cells. Knockdown of TFAM significantly decreased mitochondrial respiration in colon cancer cells; however, the cellular levels of ATP remained largely unchanged as a result of increased glycolysis. This metabolic alteration rendered cancer cells highly susceptible to glucose deprivation. Interestingly, upregulation of glycolysis was independent of hypoxia-inducible factor-1 (HIF1) as TFAM knockdown cells fail to stabilize HIF1α under hypoxic conditions. Moreover, knockdown of TFAM results in decreased expression of genes-associated cancer stem cells downstream of Wnt/β-catenin signaling. Metabolic analysis reveals that the level of α-ketoglutarate (α-KG) was significantly upregulated in TFAM knockout cells. Silencing of prolyl hydroxylase domain-containing protein 2 (PHD2), a α-KG-dependent dioxyenase, rescued the expression of target genes of both HIF1α and Wnt/β-catenin. Furthermore, intestinal-specific knockout of TFAM prevents tumor formation in Apc-mutant mouse models of colon cancer. Taken together, our findings identify a novel role of mitochondria-mediated retrograde signaling in regulating Wnt signaling and tumor initiation in colon cancer.

Intestinal adaptation to small-bowel resection (SBR) after necrotizing enterocolitis expands absorptive surface areas and promotes enteral autonomy. Survivin increases proliferation and blunts apoptosis. The current study examines survivin in intestinal epithelial cells after ileocecal resection. Wild-type and epithelial Pik3r1 (p85α)-deficient mice underwent sham surgery or 30% resection. RNA and protein were isolated from small bowel to determine levels of β-catenin target gene expression, activated caspase-3, survivin, p85α, and Trp53. Healthy and post-resection human infant small-bowel sections were analyzed for survivin, Ki-67, and TP53 by immunohistochemistry. Five days after ileocecal resection, epithelial levels of survivin increased relative to sham-operated on mice, which correlated with reduced cleaved caspase-3, p85α, and Trp53. At baseline, p85α-deficient intestinal epithelial cells had less Trp53 and more survivin, and relative responses to resection were blunted compared with wild-type. In infant small bowel, survivin in transit amplifying cells increased 71% after SBR. Resection increased proliferation and decreased numbers of TP53-positive epithelial cells. Data suggest that ileocecal resection reduces p85α, which lowers TP53 activation and releases survivin promoter repression. The subsequent increase in survivin among transit amplifying cells promotes epithelial cell proliferation and lengthens crypts. These findings suggest that SBR reduces p85α and TP53, which increases survivin and intestinal epithelial cell expansion during therapeutic adaptation in patients with short bowel syndrome.

Nuclear activation of Wnt/β-catenin signaling is required for cell proliferation in inflammation and cancer. Studies from our group indicate that β-catenin activation in colitis and colorectal cancer (CRC) correlates with increased nuclear levels of β-catenin phosphorylated at serine 552 (pβ-Cat552). Biochemical analysis of nuclear extracts from cancer biopsies revealed the existence of low molecular weight (LMW) pβ-Cat552, increased to the exclusion of full size (FS) forms of β-catenin. LMW β-catenin lacks both termini, leaving residues in the armadillo repeat intact. Further experiments showed that TCF4 predominantly binds LMW pβ-Cat552 in the nucleus of inflamed and cancerous cells. Nuclear chromatin bound localization of LMW pβ-Cat552 was blocked in cells by inhibition of proteasomal chymotrypsin-like activity but not by other protease inhibitors. K48 polyubiquitinated FS and LMW β-catenin were increased by treatment with bortezomib. Overexpressed in vitro double truncated β-catenin increased transcriptional activity, cell proliferation and growth of tumor xenografts compared to FS β-catenin. Serine 552-> alanin substitution abrogated K48 polyubiquitination, β-catenin nuclear translocation and tumor xenograft growth. These data suggest that a novel proteasome-dependent posttranslational modification of β-catenin enhances transcriptional activation. Discovery of this pathway may be helpful in the development of diagnostic and therapeutic tools in colitis and cancer.

OBJECTIVES/SPECIFIC AIMS: Intestinal stem cells (ISC) primarily act in the repair of ulcerated epithelium, and their proliferative capacity relies on Wnt/β-catenin signaling. However, the role of GCs on basal epithelial cell signaling has not been fully characterized. The objective of this study was to interrogate a mechanism by which steroids may limit ISC activation. GCs inhibit NFκB signaling, which has been shown to play a role in nuclear β-catenin activation in epithelial cells. We hypothesized that GCs limit Wnt/β-catenin signaling required for ISC activation and epithelial restitution by inhibiting NFκB activation in epithelial cells. METHODS/STUDY POPULATION: To examine the effects of GCs on intestinal epithelial cells, we treated a nontransformed human colonic epithelial cell line (NCM460) with dexamethasone and observed the effects on NFκB and Wnt/β-catenin signaling events. We isolated mouse epithelial cells from the distal colon for stem cell culture as 3D “organoids.” We obtained pure epithelial cell preparations from mucosal biopsies isolated from patients treated at GI clinics at the University of Kentucky Chandler Hospital and VA Medical Center, Lexington. Steroid treated patients with equivalent levels of inflammation, but no mucosal ulceration were used as controls. RESULTS/ANTICIPATED RESULTS: In steroid-treated NCM460 cells, we saw an increase in steroid-responsive genes GILZ and SGK1. We saw a significant decrease in transcripts for Wnt target genes, including Axin2 and cmyc; NFκB target genes, including IFNG and IL6; and the shared NFκB and Wnt pathway co-activator CREBBP, despite unchanged transcript levels for β-catenin (CTNNB1). This data was corroborated in 3D stem cell cultures from cells isolated from mouse colon tissue, which had significant decreases in transcripts for stem cell markers Lgr5 and Ascl2, proliferative markers KI67 and PCNA, and Wnt target Axin2. NCM460s transfected with a lentivirus carrying a TCF/LEF luciferase construct showed a 2.5-fold decrease in TNF-stimulated luciferase activity with dexamethasone treatment. Interestingly, this effect can be rescued by glucocorticoid receptor (GR) blockade with RU-486. Intestinal epithelial cells from patient biopsies showed significant decreases in colitis-induced Axin2, p-LRP6 (a positive marker of Wnt Signaling) and nuclear β-catenin, which correlated with decreased p-p65 protein levels. DISCUSSION/SIGNIFICANCE OF IMPACT: Together, these data suggest that steroid therapy inhibits Wnt/β-catenin signaling at multiple levels, and effects stem cell proliferation in pure stem cell cultures. Decreases in TCF/LEF transcriptional activation (nuclear β-catenin’s DNA binding target) can be reversed with steroid receptor blockade with RU-486, suggesting that a receptor level interaction may be occurring. Interestingly, the required co-activator CBP, shared between NFκB and Wnt pathways, has decreased transcription following steroid treatment, which may provide a mechanism for limited Wnt activation following steroid therapy. Although steroids play a significant role in regulating the amount of inflammatory damage that occurs during IBD treatment, our data suggest that they may be limiting pathways required for effective healing as well.

We questioned how tight junctions contribute to intestinal barrier function during the cell shedding that is part of physiological cell renewal. Intravital confocal microscopy studied the jejunal villus epithelium of mice expressing a fluorescent zonula occludens 1 (ZO-1) fusion protein. Vital staining also visualized the cell nucleus (Hoechst staining) or local permeability to luminal constituents (Lucifer Yellow; LY). In a cell fated to be shed, ZO-1 redistributes from the tight junction toward the apical and then basolateral cell region. ZO-1 rearrangement occurs 15 ± 6 min ( n = 28) before movement of the cell nucleus from the epithelial layer. During cell extrusion, permeation of luminal LY extends along the lateral intercellular spaces of the shedding cell only as far as the location of ZO-1. Within 3 min after detachment from the epithelial layer, nuclear chromatin condenses. After cell loss, a residual patch of ZO-1 remains in the space previously occupied by the departed cell, and the size of the patch shrinks to 14 ± 2% ( n = 15) of the original cell space over 20 min. The duration of cell shedding measured by nucleus movement (14 ± 1 min) is much less than the total duration of ZO-1 redistribution at the same sites (45 ± 2 min). In about 15% of cell shedding cases, neighboring epithelial cells also undergo extrusion with a delay of 5–10 min. With the use of normal mice, ZO-1 immunofluorescent staining of fixed tissue confirmed ZO-1 redistribution and the presence of ZO-1 patches beneath shedding cells. Immunostaining also showed that redistribution of ZO-1 occurred without corresponding mixing of apical and basolateral membrane domains as marked by ezrin or E-cadherin. ZO-1 redistribution is the earliest cellular event yet identified as a herald of physiological cell shedding, and redistribution of tight junction function along the lateral plasma membrane sustains epithelial barrier during cell shedding.

Mucin-type O-linked oligosaccharides (O-glycans) are primary components of the intestinal mucins that form the mucus gel layer overlying the gut epithelium. Impaired expression of intestinal O-glycans has been observed in patients with ulcerative colitis (UC), but its role in the etiology of this disease is unknown. Here, we report that mice with intestinal epithelial cell-specific deficiency of core 1-derived O-glycans, the predominant form of O-glycans, developed spontaneous colitis that resembled human UC, including massive myeloid infiltrates and crypt abscesses. The colitis manifested in these mice was also characterized by TNF-producing myeloid infiltrates in colon mucosa in the absence of lymphocytes, supporting an essential role for myeloid cells in colitis initiation. Furthermore, induced deletion of intestinal core 1-derived O-glycans caused spontaneous colitis in adult mice. These data indicate a causal role for the loss of core 1-derived O-glycans in colitis. Finally, we detected a biosynthetic intermediate typically exposed in the absence of core 1 O-glycan, Tn antigen, in the colon epithelium of a subset of UC patients. Somatic mutations in the X-linked gene that encodes core 1 β1,3-galactosyltransferase-specific chaperone 1 (C1GALT1C1, also known as Cosmc), which is essential for core 1 O-glycosylation, were found in Tn-positive epithelia. These data suggest what we believe to be a new molecular mechanism for the pathogenesis of UC.

Occludin S408 phosphorylation regulates interactions between occludin, ZO-1, and select claudins to define tight junction molecular structure and barrier function., Although the C-terminal cytoplasmic tail of the tight junction protein occludin is heavily phosphorylated, the functional impact of most individual sites is undefined. Here, we show that inhibition of CK2-mediated occludin S408 phosphorylation elevates transepithelial resistance by reducing paracellular cation flux. This regulation requires occludin, claudin-1, claudin-2, and ZO-1. S408 dephosphorylation reduces occludin exchange, but increases exchange of ZO-1, claudin-1, and claudin-2, thereby causing the mobile fractions of these proteins to converge. Claudin-4 exchange is not affected. ZO-1 domains that mediate interactions with occludin and claudins are required for increases in claudin-2 exchange, suggesting assembly of a phosphorylation-sensitive protein complex. Consistent with this, binding of claudin-1 and claudin-2, but not claudin-4, to S408A occludin tail is increased relative to S408D. Finally, CK2 inhibition reversed IL-13–induced, claudin-2–dependent barrier loss. Thus, occludin S408 dephosphorylation regulates paracellular permeability by remodeling tight junction protein dynamic behavior and intermolecular interactions between occludin, ZO-1, and select claudins, and may have therapeutic potential in inflammation-associated barrier dysfunction.

Anion secretion by colonic epithelium is dependent on apical CFTR-mediated anion conductance and basolateral ion transport. In many tissues, the NKCC1 Na+-K+-2Cl−cotransporter mediates basolateral Cl−uptake. However, additional evidence suggests that the AE2 Cl−/HCO3−exchanger, when coupled with the NHE1 Na+/H+exchanger or a Na+-HCO3−cotransporter (NBC), contributes to HCO3−and/or Cl−uptake. To analyze the secretory functions of AE2 in proximal colon, short-circuit current ( Isc) responses to cAMP and inhibitors of basolateral anion transporters were measured in muscle-stripped wild-type (WT) and AE2-null (AE2−/−) proximal colon. In physiological Ringer, the magnitude of cAMP-stimulated Iscwas the same in WT and AE2−/−colon. However, the Iscresponse in AE2−/−colon exhibited increased sensitivity to the NKCC1 inhibitor bumetanide and decreased sensitivity to the distilbene derivative SITS (which inhibits AE2 and some NBCs), indicating that loss of AE2 results in a switch to increased NKCC1-supported anion secretion. Removal of HCO3−resulted in robust cAMP-stimulated Iscin both AE2−/−and WT colon that was largely mediated by NKCC1, whereas removal of Cl−resulted in sharply decreased cAMP-stimulated Iscin AE2−/−colon relative to WT controls. Inhibition of NHE1 had no effect on cAMP-stimulated Iscin AE2−/−colon but caused a switch to NKCC1-supported secretion in WT colon. Thus, in AE2−/−colon, Cl−secretion supported by basolateral NKCC1 is enhanced, whereas HCO3−secretion is diminished. These results show that AE2 is a component of the basolateral ion transport mechanisms that support anion secretion in the proximal colon.

The NBC1 Na+/HCO3- cotransporter is expressed in many tissues, including kidney and intestinal epithelia. NBC1 mutations cause proximal renal tubular acidosis in humans, consistent with its role in HCO3- absorption in the kidney. In intestinal and colonic epithelia, NBC1 localizes to basolateral membranes and is thought to function in anion secretion. To test the hypothesis that NBC1 plays a role in transepithelial HCO3- secretion in the intestinal tract, null mutant (NBC1-/-) mice were prepared by targeted disruption of its gene (Slc4a4). NBC1-/- mice exhibited severe metabolic acidosis, growth retardation, reduced plasma Na+, hyperal-dosteronism, splenomegaly, abnormal dentition, intestinal obstructions, and death before weaning. Intracellular pH (pH(i)) was not altered in cAMP-stimulated epithelial cells of NBC1-/- cecum, but pH(i) regulation during sodium removal and readdition was impaired. Bioelectric measurements of NBC1-/- colons revealed increased amiloride-sensitive Na+ absorption. In Ringer solution containing both Cl- and HCO3-, the magnitude of cAMP-stimulated anion secretion was normal in NBC1-/- distal colon but increased in proximal colon, with the increase largely supported by enhanced activity of the basolateral NKCC1 Na+-K+-2Cl- cotransporter. Anion substitution studies in which carbonic anhydrase was inhibited and transepithelial anion conductance was limited to HCO3- revealed a sharp decrease in both cAMP-stimulated HCO3- secretion and SITS-sensitive current in NBC1-/- proximal colon. These results are consistent with the known function of NBC1 in HCO3- absorption in the kidney and demonstrate that NBC1 activity is a component of the basolateral mechanisms for HCO3- uptake during cAMP-stimulated anion secretion in the proximal colon.

Background Kinesiophobia is an excessive, irrational and debilitating fear of physical movement and activity resulting from a feeling of vulnerability to painful injury or re-injury. The Tampa Scale for kinesiophobia (TSK) is a patient-reported outcome (PRO) measure designed to help identify kinesiophobia. The original version of the TSK had 17 items. A 13-item version was later found to have better psychometric properties and was used in the present study. Although the TSK-13 has been widely studied, one shortcoming is the lack of clinically meaningful score categories. The objective of the present study was to develop severity levels to help aid clinical interpretation of TSK-13 scores. Methods After creating four proposed TSK-13 severity ranges, a sample of chronic musculoskeletal pain disorder (CMPD) patients (N = 912) was grouped by TSK-13 scores into: Subclinical (score = 13–22, n = 100; 11%), mild (23–32, n = 271; 30%), moderate (33–42, n = 385; 42%) and severe (43–52, n = 156; 17%) levels of kinesiophobia. These severity groups were then validated by their associations with objective lifting performance (presumed to be highly related to one's level of kinesiophobia) and other PRO questionnaires, assessing depressive symptoms, pain intensity, pain-related anxiety and perceived disability, which all have been shown in previous research to be associated with TSK scores. Results The TSK-13 severity level groups were significantly associated with all lifting performance and PRO variables (p

Wnt/β-catenin signaling is required for crypt structure maintenance. We previously observed nuclear accumulation of Ser-552 phosphorylated β-catenin (pβ-Cat(Ser-552)) in intestinal epithelial cells (IEC) during colitis and colitis-associated cancer. Data here delineate a novel multiprotein cytosolic complex (MCC) involved in β-catenin signaling in the intestine. The MCC contains p85α, the class IA subunit of PI3K, along with β-catenin, 14-3-3ζ, Akt, and p110α. MCC levels in IEC increase in colitis and colitis-associated cancer patients. IEC-specific p85α-deficient (p85(ΔIEC)) mice develop more severe dextran sodium sulfate colitis due to delayed ulcer healing and reduced epithelial β-catenin activation. In colonic IEC, p85α deficiency did not alter PI3K signaling. In vitro shRNA depletion of individual complex members disrupts the MCC and reduces β-catenin signaling. Despite worse colitis, p85(ΔIEC) mice have reduced tumor burden after azoxymethane/dextran sodium sulfate treatment. Together the data indicate that the β-catenin MCC is needed for mucosal repair and carcinogenesis. This novel MCC may be an attractive therapeutic target in preventing cancer in colitis patients.

Previous studies suggest an interdependent relationship between liver and intestine for cholesterol elimination from the body. We hypothesized that a combination of ursodiol (Urso) and ezetimibe (EZ) could increase biliary secretion and reduce cholesterol reabsorption, respectively, to promote cholesterol excretion. Treatment with Urso increased hepatic ABCG5 ABCG8 (G5G8) protein and both biliary and fecal sterols in a dose-dependent manner. To determine whether the drug combination (Urso-EZ) further increased cholesterol excretion, mice were treated with Urso alone or in combination with two doses of EZ. EZ produced an additive and dose-dependent increase in fecal neutral sterol (FNS) elimination in the presence of Urso. Finally, we sequentially treated wide-type and G5G8-deficient mice with Urso and Urso-EZ to determine the extent to which these effects were G5G8 dependent. Although biliary and FNS were invariably lower in G5G8 KO mice, the relative increase in FNS following treatment with Urso alone or the Urso-EZ combination was not affected by genotype. In conclusion, Urso increases G5G8, biliary cholesterol secretion, and FNS and acts additively with EZ to promote fecal sterol excretion. However, the stimulatory effect of these agents was not G5G8 dependent.

Paneth cells of intestinal crypts contribute to host defense by producing antimicrobial peptides that are packaged as granules for secretion into the crypt lumen. Here, we provide evidence using light and electron microscopy that postsecretory Paneth cell granules undergo limited dissolution and accumulate within the intestinal crypts of cystic fibrosis (CF) mice. On the basis of this finding, we evaluated bacterial colonization and expression of two major constituents of Paneth cells, i.e., α-defensins (cryptdins) and lysozyme, in CF murine intestine. Paneth cell granules accumulated in intestinal crypt lumens in both untreated CF mice with impending intestinal obstruction and in CF mice treated with an osmotic laxative that prevented overt clinical symptoms and mucus accretion. Ultrastructure studies indicated little change in granule morphology within mucus casts, whereas granules in laxative-treated mice appear to undergo limited dissolution. Protein extracts from CF intestine had increased levels of processed cryptdins compared with those from wild-type (WT) littermates. Nonetheless, colonization with aerobic bacteria species was not diminished in the CF intestine and oral challenge with a cryptdin-sensitive enteric pathogen, Salmonella typhimurium, resulted in greater colonization of CF compared with WT intestine. Modest downregulation of cryptdin and lysozyme mRNA in CF intestine was shown by microarray analysis, real-time quantitative PCR, and Northern blot analysis. Based on these findings, we conclude that antimicrobial peptide activity in CF mouse intestine is compromised by inadequate dissolution of Paneth cell granules within the crypt lumens.

Aim To assess dietary myo-inositol in reducing stem cell activation in colitis, and validate pβ-cateninS552 as a biomarker of recurrent dysplasia. Methods We examined the effects of dietary myo-inositol treatment on inflammation, pβ-cateninS552 and pAkt levels by histology and western blot in IL-10-/- and dextran sodium sulfate-treated colitic mice. Additionally, we assessed nuclear pβ-cateninS552 in patients treated with myo-inositol in a clinical trial, and in patients with and without a history of colitis-induced dysplasia. Results In mice, pβ-cateninS552 staining faithfully reported the effects of myo-inositol in reducing inflammation and intestinal stem cell activation. In a pilot clinical trial of myo-inositol administration in patients with a history of low grade dysplasia (LGD), two patients had reduced numbers of intestinal stem cell activation compared to the placebo control patient. In humans, pβ-cateninS552 staining discriminated ulcerative colitis patients with a history of LGD from those with benign disease. Conclusion Enumerating crypts with increased numbers of pβ-cateninS552 - positive cells can be utilized as a biomarker in colitis-associated cancer chemoprevention trials.

AIM: To investigate the intestinal functions of the NKCC1 Na+-K+-2Cl cotransporter (SLC12a2 gene), differential mRNA expression changes in NKCC1-null intestine were analyzed. METHODS: Microarray analysis of mRNA from intestines of adult wild-type mice and gene-targeted NKCC1-null mice (n = 6 of each genotype) was performed to identify patterns of differential gene expression changes. Differential expression patterns were further examined by Gene Ontology analysis using the online Gorilla program, and expression changes of selected genes were verified using northern blot analysis and quantitative real time-polymerase chain reaction. Histological staining and immunofluorescence were performed to identify cell types in which upregulated pancreatic digestive enzymes were expressed. RESULTS: Genes typically associated with pancreatic function were upregulated. These included lipase, amylase, elastase, and serine proteases indicative of pancreatic exocrine function, as well as insulin and regenerating islet genes, representative of endocrine function. Northern blot analysis and immunohistochemistry showed that differential expression of exocrine pancreas mRNAs was specific to the duodenum and localized to a subset of goblet cells. In addition, a major pattern of changes involving differential expression of olfactory receptors that function in chemical sensing, as well as other chemosensing G-protein coupled receptors, was observed. These changes in chemosensory receptor expression may be related to the failure of intestinal function and dependency on parenteral nutrition observed in humans with SLC12a2 mutations. CONCLUSION: The results suggest that loss of NKCC1 affects not only secretion, but also goblet cell function and chemosensing of intestinal contents via G-protein coupled chemosensory receptors.

Appropriate function of the intestinal epithelial barrier is critical for maintaining a balance between potentially noxious luminal contents of the gut and the mucosal immune system. Defects in barrier function are associated with both Crohn’s disease and ulcerative colitis, and are also present in some healthy first-degree relatives. Impaired barrier function is associated with increased risk of Crohn’s disease relapse of patients in clinical remission. The tight junction, which seals the space between adjacent epithelial cells, is the primary determinant of permeability in the absence of epithelial injury, e.g., ulceration. The tight junction is formed by a complex of occludin, claudins, ZO-1, and the actin cytoskeleton; the interactions between components are dynamically regulated to modify paracellular flux. The functional properties of the tight junction are regulated both by physiological stimuli and by cytokines, e.g., TNF, IFNγ (gamma), and IL-13. Under pathological conditions, increased paracellular permeability in response to cytokine production may allow luminal material to access the lamina propria, further activating immune responses and continuing the cycle of barrier dysfunction and inflammation. This model predicts that the tight junction may play a central role in inflammatory bowel disease by balancing the mucosal immune response with the luminal microbiota. As such, the potential of the tight junction as a target for therapeutic intervention should be considered.

Chloride intracellular channel 5 (CLIC5) and other CLIC isoforms have been implicated in a number of biological processes, but their specific functions are poorly understood. The association of CLIC5 with ezrin and the actin cytoskeleton led us to test its possible involvement in gastric acid secretion. Clic5 mutant mice exhibited only a minor reduction in acid secretion, Clic5 mRNA was expressed at only low levels in stomach, and Clic5 mutant parietal cells were ultrastructurally normal, negating the hypothesis that CLIC5 plays a major role in acid secretion. However, the mutants exhibited gastric hemorrhaging in response to fasting, reduced monocytes and granulocytes suggestive of immune dysfunction, behavioral and social disorders suggestive of neurological dysfunction, and evidence of a previously unidentified metabolic defect. Wild-type and mutant mice were maintained on normal and high-fat diets; plasma levels of various hormones, glucose, and lipids were determined; and body composition was studied by quantitative magnetic resonance imaging. Clic5 mutants were lean, hyperphagic, and highly resistant to diet-induced obesity. Plasma insulin and glucose levels were reduced, and leptin levels were very low; however, plasma triglycerides, cholesterol, phospholipids, and fatty acids were normal. Indirect calorimetry revealed increased peripheral metabolism and greater reliance on carbohydrate metabolism. Because Clic5 mutants were unable to maintain energy reserves, they also exhibited increased susceptibility to fasting-induced torpor, as indicated by telemetric measurements showing episodes of reduced body temperature and heart rate. These data reveal a requirement for CLIC5 in the maintenance of normal systemic energy metabolism.

Acid secretion in gastric parietal cells requires highly coordinated membrane transport and vesicle trafficking. Histologically, consensus defines acid secretion as the ratio of the volume density (Vd) of canalicular and apical membranes (CAMs) to tubulovesicular (TV) membranes, a value which varies widely under normal conditions. Examination of numerous achlorhydric mice made it clear that this paradigm is discrepant when used to assess most mice with genetic mutations affecting acid secretion. Vd of organelles in parietal cells of 6 genetically engineered mouse strains was obtained to identify a stable histological phenotype of acid secretion. We confirmed that CAM to TV ratio fairly represented secretory activity in untreated and secretion-inhibited wild-type (WT) mice and in NHE2−/− mice as well, though the response was significantly attenuated in the latter. However, high CAM to TV ratios wrongly posed as active acid secretion in AE2−/−, GHKA−/−, and NHE4−/− mice. Achlorhydric genotypes also had a significantly higher Vd of basolateral membrane than WT mice, and reduced Vd of mitochondria and canaliculi. The Vd of mitochondria, and ratio of the Vd of basolateral membranes/Vd of mitochondria were preferred predictors of the level of acid secretion. Alterations in acid secretion, then, cause significant changes not only in the Vd of secretory membranes but also in mitochondria and basolateral membranes.

In cystic fibrosis, impaired secretion resulting from loss of activity of the cystic fibrosis transmembrane conductance regulator (CFTR) causes dehydration of intestinal contents and life-threatening obstructions. Conversely, impaired absorption resulting from loss of the NHE3 Na+/H+ exchanger causes increased fluidity of the intestinal contents and diarrhea. To test the hypothesis that reduced NHE3-mediated absorption could increase survival and prevent some of the intestinal pathologies of cystic fibrosis, Cftr/Nhe3 double heterozygous mice were mated and their offspring analyzed. Cftr-null mice lacking one or both copies of the NHE3 gene exhibited increased fluidity of their intestinal contents, which prevented the formation of obstructions and increased survival. Goblet cell hyperplasia was eliminated, but not the accumulation of Paneth cell granules or increased cell proliferation in the crypts. Microarray analysis of small intestine RNA from Cftr-null, NHE3-null, and double-null mice all revealed downregulation of genes involved in xenobiotic metabolism, including a cohort of genes involved in glutathione metabolism. Expression of energy metabolism genes was altered, but there were no changes in genes involved in inflammation. Total intracellular glutathione was increased in the jejunum of all of the mutants and the ratio of reduced to oxidized glutathione was reduced in Cftr-null mutants, indicating that CFTR deficiency affects intestinal glutathione metabolism. The data establish a major role for NHE3 in regulating the fluidity of the intestinal contents and show that reduced NHE3-mediated absorption reverses some of the intestinal pathologies of cystic fibrosis, thus suggesting that it may serve as a potential therapeutic target.

The NBC1 Na+/HCO3- cotransporter is expressed in many tissues, including kidney and intestinal epithelia. NBC1 mutations cause proximal renal tubular acidosis in humans, consistent with its role in HCO3- absorption in the kidney. In intestinal and colonic epithelia, NBC1 localizes to basolateral membranes and is thought to function in anion secretion. To test the hypothesis that NBC1 plays a role in transepithelial HCO3- secretion in the intestinal tract, null mutant (NBC1-/-) mice were prepared by targeted disruption of its gene (Slc4a4). NBC1-/- mice exhibited severe metabolic acidosis, growth retardation, reduced plasma Na+, hyperal-dosteronism, splenomegaly, abnormal dentition, intestinal obstructions, and death before weaning. Intracellular pH (pH(i)) was not altered in cAMP-stimulated epithelial cells of NBC1-/- cecum, but pH(i) regulation during sodium removal and readdition was impaired. Bioelectric measurements of NBC1-/- colons revealed increased amiloride-sensitive Na+ absorption. In Ringer solution containing both Cl- and HCO3-, the magnitude of cAMP-stimulated anion secretion was normal in NBC1-/- distal colon but increased in proximal colon, with the increase largely supported by enhanced activity of the basolateral NKCC1 Na+-K+-2Cl- cotransporter. Anion substitution studies in which carbonic anhydrase was inhibited and transepithelial anion conductance was limited to HCO3- revealed a sharp decrease in both cAMP-stimulated HCO3- secretion and SITS-sensitive current in NBC1-/- proximal colon. These results are consistent with the known function of NBC1 in HCO3- absorption in the kidney and demonstrate that NBC1 activity is a component of the basolateral mechanisms for HCO3- uptake during cAMP-stimulated anion secretion in the proximal colon.

Image of an intraepithelial lymphocyte (IEL) from a CLIC5 mutant mouse small intestine. The CLIC (Chloride Intracellular Channel) family of proteins is expressed in a wide variety of cell types, and several isoforms are known to cycle between soluble and membranebound forms. As well as being widely expressed, the CLICs are involved in diverse functions, including tubulogenesis, immune cell activation, apoptosis and calcium handling. CLIC5 has been shown to associate with cytoskeletal proteins in placental microvilli and inner ear cells, and is required for proper maintenence of hair cell steriocilia. It has also been localized to the cytosol of human intestinal epithelial cells, though its function there remains unclear. The study in which this particular “IEL” was found, involved a search to see what function CLIC5 played in the modulation of tubulovesicles and microvillar apical membranes in the process of acid secretion. In particular, the relative amounts and structural characteristics of these two membrane types was quantified in parietal cells.

SUMMARY The interaction of the steroid anaesthetic agent CT1341 with selected muscle relaxants and volatile agents has been investigated in man. In four patients the effect at the neuromuscular junction was examined. No effect was seen with CT1341 alone and there was no clinically significant interaction with tubocurarine, pancuronium or suxamethonium. A further forty patients in six groups were anaesthetized using CT1341 and either pancuronium or tubocurarine with controlled respiration. One of the volatile agents, halothane, trichloroethylene or methoxyflurane, was then administered and the resulting effect on electrocardiogram, systolic and diastolic blood pressure, pulse rate and nasopharyngeal temperature noted. Three patients given methoxyflurane developed a marked sinus tachycardia which could be evidence of drug interaction. No other effect was observed.