Elevated adenomatous polyposis coli in goblet cells is associated with inflammation in mouse and human colon

NEW FINDINGS

What is the central question of this study? What is the localization and distribution pattern of adenomatous polyposis coli (APC) in intestinal epithelial cells? Does this distribution change in different regions of the colon or in the condition of inflammation? What is the main finding and its importance? Colonic epithelia from mice and humans contain a subset of goblet cells displaying high APC levels. The number of APC^high goblet cells increases in inflamed tissue, which also displays increased GRP78, indicating potential stress from mucin production. In cultured human colon cells, expression of interleukin 1 pathway components (inducers of MUC2 expression) is reduced upon APC depletion raising the potential for APC participation in an inflammatory response.

ABSTRACT

Adenomatous polyposis coli (APC) serves as a gatekeeper of intestinal homeostasis by promoting cellular differentiation and maintaining crypt architecture. Although appreciated as a critical colon tumour suppressor, roles for APC in disease states such as inflammation have yet to be fully delineated. This study aimed to characterize the localization of APC protein in gastrointestinal tissues from human patients with active inflammatory bowel disease and mice with dextran sodium sulfate (DSS)-induced colitis. Fluorescence immunohistochemistry revealed a subset of goblet cells with elevated Apc staining intensity in the small intestines and proximal/medial colons of mice. Upon induction of colitis with DSS, these 'APC^high ' goblet cells remained in the proximal and medial colon, but now were also observed in the distal colon. This phenotype was recapitulated in humans, with APC^high goblet cells observed only in the descending colons of patients with active ulcerative colitis. In cultured human colon cells derived from normal tissue, APC depletion reduced expression of mRNAs encoding the interleukin 1 (IL1) signalling pathway components IL1β and interleukin-1 receptor (IL1R), known regulators of Muc2 expression. Treating cancer cells lacking wild-type APC with IL1β, or induction of full-length APC in these cells led to increases in IL1R and MUC2 expression. Combining IL1β treatment with APC induction led to an increase of MUC2 expression greater than expected for additive affects, suggesting that APC sensitizes cells to IL1 signalling. These findings suggest that APC has novel roles in maintaining proper goblet cell function, thus providing further evidence for APC as an important factor in intestinal tissue homeostasis and disease.

Diaspirin cross-linked hemoglobin: tissue distribution and long-term excretion after exchange transfusion

This report describes the tissue distribution and long-term (14-day) excretion of hemoglobin cross-linked between the alpha-chains (alpha alpha Hb) with carbon 14-labeled bis(3,5-dibromosalicyl)fumarate. Fully conscious, chronically cannulated rats (n = 40) were treated with a 50% isovolemic exchange transfusion (ET) with solutions of 14C-labeled alpha alpha Hb (8.0 gm/dl) and were then monitored for as long as 14 days. Thirteen tissue types were analyzed for radioactivity by liquid scintillation counting. The highest concentration of label was found in the kidney and in tissues of the reticuloendothelial system (i.e., spleen, bone marrow, and liver). The 14C-labeled alpha alpha Hb did not appear to cross the blood-brain barrier, because radioactivity in the brain was barely detectable. The dose of 14C-labeled alpha alpha Hb (2.4 gm Hb/kg) produced an initial plasma Hb level of 4.6 gm/dl, with a half-life in the plasma of 5.0 hours. The peak concentration in kidney, spleen, and liver occurred at 24 hours after ET, when at least 92% of the 14C-labeled alpha alpha Hb in plasma had been cleared. At 48 hours, red casts were seen in a tiny number of renal tubules in some rats. By 14 days, up to 64% of the injected radioactivity had been recovered in urine and about 10% was recovered in feces. Most excretion occurred 24 to 48 hours after ET. This study demonstrated that 2 weeks were required for the metabolic degradation and elimination of a large dose of alpha alpha Hb in rats.

Acute changes in systemic blood pressure and urine output of conscious rats following exchange transfusion with diaspirin-crosslinked hemoglobin solution

This report describes acute changes in systemic blood pressure and urine output observed after a 50-percent isovolemic exchange transfusion (ET) with diaspirin-crosslinked hemoglobin (alpha alpha Hb). Stroma-free Hb was crosslinked between the alpha chains by using a 14C-labeled diaspirin, bis(3,5-dibromosalicyl)fumarate. Forty conscious, chronically cannulated rats underwent ET with 14C-labeled alpha alpha Hb solution (8.0 g/dL [80 g/L]). This resulted in systemic hypertension for 3 to 4 hours after ET (mean arterial pressure rose from 120 to 145 torr at 1 to 2 hours after ET) and mild bradycardia for 2 to 3 hours (heart rate decreased from 420 to 335 beats/min [bpm] before stabilizing at 360 +/- 10 bpm). This was accompanied by significant diuresis immediately after ET (5- 6-fold increase in urine output, which normalized after 12 hours), and mild hemoglobinuria. The total amount of Hb recovered in the urine was < 5 percent of the injected dose. Reversed-phase high-performance liquid chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis confirmed the presence of crosslinked alpha alpha Hb molecules in the urine. Renal excretion of radioactivity was significantly greater, with 20 percent of total radioactivity being eliminated within 24 hours. The plasma half-life for alpha alpha Hb was 5 hours (administered dose, 2.4 g Hb/kg body weight). Thus, infusion of alpha alpha Hb caused a transient systemic hypertension, and intramolecular crosslinking alone was not enough to exclude completely the filtration of alpha alpha Hb by the kidneys.

The role of the kidneys in the excretion of chemically modified hemoglobins

Stroma-free hemoglobin (SFHb) can be chemically modified to prolong the intravascular retention (prevent renal filtration), and to improve oxygen delivering capability for use as a red cell substitute. Hb derivatives radioactively tagged with tritium [3H] or 14C were used to study their metabolic fate following clearance from the circulation. Fully conscious, chronically cannulated rats were treated by exchange transfusion (ET). Hb solutions tested were: PLPHb (Hb monovalently reacted with pyridoxal 5'-phosphate); HbXL (Hb crosslinked beta-beta with 2-nor-2-formylpyridoxal 5'-phosphate, or with bis-pyridoxal tetraphosphate); alpha alpha Hb (Hb cross-linked between the alpha-chains using bis-3,5-dibromosalicyl fumarate); and polyHb (polymerized with glutaraldehyde or o-raffinose). Plasma retention (T1/2) was significantly affected by dose and the degree of cross-linking. Urine flow rates all increased transiently above normal. In rats treated with any 64 kDa interdimerically cross-linked Hb, mild hemoglobinuria was evident and kidney tissue had the highest label concentration at all time points (1, 5, 10, 24, 48 hr, 7 d, and 14 days post-ET). For polymerized Hb derivatives, the amount of radioactivity in urine and kidneys was inversely related to the MW of the polyHb molecules. In all rats, regardless of the Hb derivative tested, the majority of radioactivity (dpm's) was excreted in urine. About 75% of all renal excretion of radioactivity occurred from 12-60 hours post-ET. This provided evidence that catabolism of cross-linked Hb's began early, and that the kidneys are primarily responsible for excreting smaller degradation fragments.

Pharmacokinetic studies in the rat on a o-raffinose polymerized human hemoglobin

We have studied the plasma half-life (T 1/2), oxygen-binding affinity (P50), organ distribution, and excretion of the individual molecular weight (MW) components of human hemoglobin polymerized with periodate-oxidized, ring-opened raffinose (oR poly-Hb), following transfusion in the rat. The model was an isovolemic 50% exchange transfusion in the conscious, chronically catheterized rat. Total plasma Hb levels yielded a (T 1/2) of 10 to 11 hr for oR poly-Hb. The T 1/2 values of individual MW components of the poly-Hb as determined by size-exclusion HPLC were approximately: 4 hr for the monomeric fraction (Hb)1, 9 hr for the dimer (Hb)2, and 15 hr for the fraction representing trimers to nanomers (Hb)3-9. The P50 values of plasma samples containing oR poly-Hb (collected from 0-24 hr after exchange) remained unchanged at 28 +/- 3 mmHg. oR stabilized and polymerized Hb were not excreted via the kidneys. Hepatic and renal distribution as well as plasma and renal clearance were determined by liquid scintillation counting using individual tritium [3H] labelled MW components purified from [3H]-oR poly-Hb: (Hb)1/2, (Hb)1, (Hb)2, (Hb)3&4, and (Hb) greater than 9. In kidney, uptake (determined by the relative concentration of radioactivity) decreased with increasing MW of the labelled component. Conversely, in liver, uptake increased with increasing MW. Plasma and renal clearance results were consistent with those obtained by HPLC analysis. Hematocrit levels returned from a 20% post-transfusion level to normal pre-transfusion levels (44%) within 10 days after the exchange.