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A Western Diet Increases Serotonin Availability in Rat Small Intestine

Diet-induced obesity is associated with changes in gastrointestinal function and induction of a mild inflammatory state. Serotonin (5-HT) containing enterochromaffin (EC) cells within the intestine respond to nutrients and are altered by inflammation. Thus, our aim was to characterize the uptake and release of 5-HT from EC cells of the rat ileum in a physiologically relevant model of diet-induced obesity. In chow-fed (CF) and Western diet-fed (WD) rats electrochemical methods were used to measure compression evoked (peak) and steady state (SS) 5-HT levels with fluoxetine used to block the serotonin reuptake transporter (SERT). The levels of mRNA for tryptophan hydroxylase 1 (TPH1) and SERT were determined by quantitative PCR, while EC cell numbers were determined immunohistochemically. In WD rats, the levels of 5-HT were significantly increased (SS: 19.2 ± 3.7 μm; peak: 73.5 ± 14.1 μm) compared with CF rats (SS: 12.3 ± 1.8 μm; peak: 32.2 ± 7.2 μm), while SERT-dependent uptake of 5-HT was reduced (peak WD: 108% of control versus peak CF: 212% control). In WD rats, there was a significant increase in TPH1 mRNA, a decrease in SERT mRNA and protein, and an increase in EC cells. In conclusion, our data show that foods typical of a Western diet are associated with an increased 5-HT availability in the rat ileum. Increased 5-HT availability is driven by the up-regulation of 5-HT synthesis genes, decreased re-uptake of 5-HT, and increased numbers and/or 5-HT content of EC cells which are likely to cause altered intestinal motility and sensation in vivo.

Expression and localization of pannexin‐1 hemichannels in human colon in health and disease

Pannexin‐1 (Panx1) proteins can function as channels for adenosine triphosphate (ATP) release, but there have been limited studies investigating their potential role in the human intestine. The aim of this study was to characterize Panx1 expression and distribution in the human colon and its potential involvement in inflammatory bowel diseases (IBD).

Distinct differences in tachykinin gene expression in ulcerative colitis, Crohn’s disease and diverticular disease: a role for hemokinin-1?

Background  In the intestine, the tachykinins substance P (SP) and neurokinin A (NKA) are found in neurons and have key roles in motility, secretion, and immune functions. A new tachykinin, hemokinin (HK‐1), has been identified in non‐neuronal cells in recent years and its role in intestinal inflammation is unclear. We aimed to examine the expression of genes encoding tachykinin peptides and receptors in colon from patients with ulcerative colitis (UC), Crohn’s disease (CD), and acute diverticular disease (DD).

Diethylnitrosamine- and partial hepatectomy-induced decrease in α2u-globulin mRNA level in the rat liver

Changes in gene expression in the rat liver were investigated by analyzing cDNA libraries for liver mRNAs from adult male rats injected with a chemical carcinogen diethylnitrosamine (DEN). Differential screening using normal and DEN-treated liver cDNAs as probes demonstrated that some of the mRNA species had noticeably lower abundance in the DEN-treated liver than in the untreated liver. Surprisingly, most of those clones were found to code for α2u-globulin (A2uG), an abundant protein in the male rat liver. Further analysis by in situ hybridization revealed that the decrease in the A2uG mRNA level occurred in the area where liver cells were proliferating due to DEN treatment and/or partial hepatectomy (PH). The findings indicate coincidence of cell proliferation with a decrease in the A2uG gene expression in the adult male rat liver, implying that the A2uG-related change favors chemical carcinogen-induced cell growth.

Expression and localization of pannexin-1 and CALHM1 in porcine bladder and their involvement in modulating ATP release

ATP release from urinary bladder is vital for afferent signaling. The aims of this study were to localize calcium homeostasis modulator 1 (CALHM1) and pannexin-1 expression and to determine their involvement in mediating ATP release in the bladder. To determine gene expression and cellular distribution, PCR and immunohistochemistry were performed, respectively, in the porcine bladder. CALHM1 and pannexin-1-mediated ATP release in response to hypotonic solution (0.45% NaCl)-induced stretch, and extracellular Ca2+ depletion ([Ca2+]0) was measured in isolated urothelial, suburothelial, and detrusor muscle cells. CALHM1 and pannexin-1 mRNA and immunoreactivity were detected in urothelial, suburothelial, and detrusor muscle layers, with the highest expression on urothelium. Hypotonic stretch caused a 2.7-fold rise in ATP release from all three cell populations (P < 0.01), which was significantly attenuated by the pannexin-1 inhibitor, 10Panx1, and by the CALHM1 antibody. Brefeldin A, a vesicular transport inhibitor, and ruthenium red, a nonselective CALHM1 channel blocker, also significantly inhibited stretch-mediated ATP release from urothelial cells. [Ca2+]0 caused a marked, but transient, elevation of extracellular ATP level in all three cell populations. CALHM1 antibody and ruthenium red inhibited [Ca2+]0-induced ATP release from urothelial cells, but their effects on suburothelial and detrusor cells were insignificant. 10Panx1 showed no significant inhibition of [Ca2+]0-induced ATP release in any types of cells. The results presented here provide compelling evidence that pannexin-1 and CALHM1, which are densely expressed in the porcine bladder, function as ATP release channels in response to bladder distension. Modulation of extracellular Ca2+ may also regulate ATP release in the porcine bladder through voltage-gated CALHM1 ion channels.

W1933 Expression of PYY is Unchanged in Rat Small Intestine During a High-Fat Diet

Purpose: Aging is associated with important changes in gastrointestinal function and in the levels of intestinal hormones secreted. Enterochromaffin cells containing serotonin (5-HT) and melatonin may play a major role in maintaining gut function during aging. Our aim was to characterise the mucosal availability of 5-HT and melatonin in the ileum and colon of a mouse model of aging. Methods: Female young mice (2-5 month; n=6), aged mice (~21 months; n=6) and aged mice treated with melatonin (~21 months; n=6; 10mg/kg/day) were examined. Electrochemical methods were used to measure 5-HT and melatonin (MEL) concentrations near the mucosal surface of ileum and distal colon. Amperometry was used to record compression evoked 5-HT while cyclic voltammetry was used to identify peaks for 5-HT and MEL. Differential pulse voltammetry (DPV: 500/800mV) was used to measure 5-HT and MEL steady state levels. Exogenous 5-HT and MEL were used to calibrate the carbon fibre electrodes and convert current into concentration. Paired or unpaired data were compared with a t test or a one way ANOVA (P<0.05) using a Tukey-Kramer post-hoc test. Results: Amperometry studies showed that young mice had peak compression evoked release of 5-HT from combined colon and ileum of 4.9±1.5 μM while aged mice had a enhanced release of 8.1±2.9 μM and aged mice treated with melatonin were significally depressed compared to aged mice (4.3±1.0 μM; P=004). Steady state levels of 5-HT after compression from combined tissue were 5.7±1.8 μM in young tissue while aged mice (4.8±0.6 μM) and aged mice treated with melatonin were no different from young mice (3.2±0.6 μM). DPV studies showed that young mice had concentrations of 5-HT of 4.1±1.1 μM in the ileum and 5.9±2.4 μM in the colon. Concentrations of MEL were 5.3±1.6 μM in the ileum and 4.7±1.5 μM in the colon (all n=6). Compared to young mice, the steady state levels of 5HT and MEL were increased in aged mice (combined ileum and colon: 5-HT=144% and MEL=127% of young mice). In contrast, the melatonin-treated mice had lower steady state levels compared to young mice (5-HT=89% andMEL=74%).When aged mice were compared directly with aged mice treated with melatonin, there was a significant decrease in both 5HT and MEL in the treated combined tissues (P=0.001); however, when ileum and colon were examined separately only MEL was significantly decreased in the ileum (P=0.04; n= 6) and colon (P=0.02; n=6) of treated mice. Conclusions: Our data show that the availability of 5-HT and melatonin are increased in aged mice and that melatonin treatment suppresses natural gastrointestinal production of 5-HT and melatonin in the aged mouse intestine.