Cell recovery during segmental intestinal perfusion in healthy subjects and patients with Crohn's disease

Rapid modulation of Ca2+ uptake in human jejunal enterocytes

The active metabolite of D vitamin, 1,25(OH)2D3, has been suggested to promote acute uptake of calcium through the intestinal lining in cell lines and murine models. In this study, the effects of D vitamin on the cytoplasmic Ca2+ of single human jejunal enterocytes, obtained with LOC-I-GUT technique, was analyzed in vivo in a fluorometric system using fura-2 as the Ca2+-sensing probe. Vitamin-promoted acute Ca2+ influx exhibited dual kinetics, indicating initial release from intracellular Ca2+ pools and fast entry from the extracellular space. Furthermore, providing a chemical clamp of membrane potential close to 0 mV did not activate voltage-sensitive calcium channels in the cellular membrane, neither was the hormone-induced Ca2+ influx affected by verapamil. This advocates that voltage-operated channels like L-type Ca2+ channels do not participate in the process of Ca2+ uptake. In fact, the existence of calcium-release-activated-calcium channels (I(CRAC)) was implied by the findings that irreversible depletion of intracellular Ca2+ stores by thapsigargin promoted Ca2+ entry. In the thapsigargin-treated enterocytes, D vitamin lost its ability to promote calcium entry indicating an important role for intracellular store-operated Ca2+ stores in the acute effects of 1,25(OH)2D3.

Regulation of hyaluronan synthase-2 expression in human intestinal mesenchymal cells: mechanisms of interleukin-1beta-mediated induction

Elevated levels of hyaluronan are associated with numerous inflammatory diseases including inflammatory bowel disease. The purpose of this study was to determine whether a cause and effect relationship might exist among proinflammatory cytokines, IL-1beta, TNF-alpha, IFN-gamma, or transforming growth factor-beta (TGF-beta) and hyaluronan expression in human JDMC and, if so, to identify possible mechanisms involved in the induction of hyaluronan expression. TGF-beta, TNF-alpha, and IFN-gamma had little or no effect on hyaluronan production by these cells. Treatment with IL-1beta induced an approximate 30-fold increase in the levels of hyaluronan in the medium of human jejunum-derived mesenchymal cells. Ribonuclease protection analysis revealed that steady-state transcript levels for hyaluronan synthase (HAS)2 were present at very low levels in untreated cells but increased as much as 18-fold in the presence of IL-1beta. HAS3 transcript levels were also increased slightly by exposure of these cells to IL-1beta. Expression of HAS1 transcripts was not detected under any condition in these cells. IL-1beta induction of hyaluronan expression was inhibited in cells transfected with short interfering RNA corresponding to HAS2 transcripts. Inhibitors of the p38 and ERK1/2 mitogen-activated pathways but not JNK/SAPK blocked the IL-1beta-mediated induction of hyaluronan expression and the increase in HAS2 transcript expression. These results suggest that IL-1beta induction of HAS2 expression involves multiple signaling pathways that act in concert, thus leading to an increase in expression of hyaluronan by jejunum-derived mesenchymal cells.

Influence of changes in lactase activity and small-intestinal mucosal growth on lactose digestion and absorption in preterm infants

BACKGROUND

Feeding intolerance (ie, achieving and maintaining full enteral feedings) is a significant problem in preterm infants. A relation exists between feeding intolerance and incomplete lactose digestion.

OBJECTIVES

We sought to identify the factors relating to lactose digestion and absorption, lactase activity, and small-intestinal mucosal growth.

DESIGN

Lactose digestion and absorption, lactase-specific activity, and lumen-to-mucosa water flux as a measure of small-intestinal mucosal surface area were determined by using the triple-lumen perfusion technique on 2 occasions 3 wk apart in 10 preterm infants (x+/-SEM gestational age: 28.0+/-0.2 wk).

RESULTS

Lactose digestion and absorption and lactase activity doubled between studies (P=0.035 and P=0.041, respectively). The change in digestion and absorption was related to lactase activity (P=0.034, R2=0.38). Lactase activity correlated with gestational age at birth (P=0.012, R2=0.51). The number of days of feeding explained 80% of the variability in small-intestinal mucosal surface area (P=0.001).

CONCLUSIONS

To our knowledge, this is the first study to measure directly lactose digestion and absorption, lactase activity, and small-intestinal surface area in preterm infants. Changes in lactose absorption relate primarily to lactase activity rather than to mucosal growth. We showed directly a relation between enteral feeding and small-intestinal mucosal growth.

Absorption/metabolism of sulforaphane and quercetin, and regulation of phase II enzymes, in human jejunum in vivo

For the first time the human intestinal effective permeability, estimated from the luminal disappearance and intestinal metabolism of phytochemicals, sulforaphane and quercetin-3,4'-glucoside, as well as the simultaneous changes in gene expression in vivo in enterocytes, has been studied in the human jejunum in vivo (Loc-I-Gut). Both compounds as components of an onion and broccoli extract could readily permeate the enterocytes in the perfused jejunal segment. At the physiologically relevant, dietary concentration tested, the average effective jejunal permeability (Peff) and percentage absorbed (+/- S.D.) were 18.7 +/- 12.6 x 10-4 cm/s and 74 +/- 29% for sulforaphane and 8.9 +/- 7.1 x 10-4 cm/s and 60 +/- 31% for quercetin-3,4'-diglucoside, respectively. Furthermore, a proportion of each compound was conjugated and excreted back into the lumen as sulforaphane-glutathione and quercetin-3'-glucuronide. The capacity of the isolated segment to deconjugate quercetin from quercetin-3,4'-diglucoside during the perfusion was much higher than the beta-glucosidase activity of the preperfusion jejunal contents, indicating that the majority (79-100%) of the beta-glucosidase capacity derives from the enterocytes in situ. Simultaneously, we determined short-term changes in gene expression in exfoliated enterocytes, which showed 2.0 +/- 0.4-fold induction of glutathione transferase A1 (GSTA1) mRNA (p < 0.002) and 2.4 +/- 1.2-fold induction of UDP-glucuronosyl transferase 1A1 (UGT1A1) mRNA (p < 0.02). The changes in gene expression were also seen in differentiated Caco-2 cells, where sulforaphane was responsible for induction of GSTA1 and quercetin for induction of UGT1A1. These results show that food components have the potential to modify drug metabolism in the human enterocyte in vivo very rapidly.