Effects of a serotonin 5-HT(4) receptor antagonist SB-207266 on gastrointestinal motor and sensory function in humans

BACKGROUND: Serotonin 5-HT(4) receptors are located on enteric cholinergic neurones and may regulate peristalsis. 5-HT(4) receptors on primary afferent neurones have been postulated to modulate visceral sensation. While 5-HT(4) agonists are used as prokinetic agents, the physiological role of 5-HT(4) receptors in the human gut is unknown. AIMS: Our aim was to characterise the role of 5-HT(4) receptors in regulating gastrointestinal motor and sensory function in healthy subjects under baseline and stimulated conditions with a 5-HT(4) receptor antagonist. METHODS: Part A compared the effects of placebo to four doses of a 5-HT(4) receptor antagonist (SB-207266) on the cisapride mediated increase in plasma aldosterone (a 5-HT(4) mediated response) and orocaecal transit in 18 subjects. In part B, 52 healthy subjects received placebo, or 0.05, 0.5, or 5 mg of SB-207266 for 10-12 days; gastric, small bowel, and colonic transit were measured by scintigraphy on days 7-9, and fasting and postprandial colonic motor function, compliance, and sensation during distensions were assessed on day 12. RESULTS: Part A: 0.5, 5, and 20 mg doses of SB-207266 had significant and quantitatively similar effects, antagonising the cisapride mediated increase in plasma aldosterone and acceleration of orocaecal transit. Part B: SB-207266 tended to delay colonic transit (geometric centre of isotope at 24 (p=0.06) and 48 hours (p=0.08)), but did not have dose related effects on transit, fasting or postprandial colonic motor activity, compliance, or sensation. CONCLUSION: 5-HT(4) receptors are involved in the regulation of cisapride stimulated orocaecal transit; SB 207266 tends to modulate colonic transit but not sensory functions or compliance in healthy human subjects.     

Coexpression of 5-HT2A and 5-HT4 receptors coupled to distinct signaling pathways in human intestinal muscle cells

The type and function of 5-hydroxytryptamine (5-HT) receptors on intestinal muscle cells in humans are not known. 5-HT receptors were characterized pharmacologically and by radioligand binding. Contraction, relaxation, inositol 1,4,5-triphosphate (IP₃) and adenosine 3′,5′-cyclic monophosphate (cAMP) formation, and 5-HT binding were measured in dispersed muscle cells and in cells in which only one receptor type was preserved by selective receptor protection. 5-HT binding was completely inhibited by 5-HT and partially by 5-HT_2A (ketanserin), 5-HT₄ (SDZ-205,557), and 5-HT_1p (N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophan amide; 5-HTP-DP) receptor antagonists. 5-HT caused contraction that was inhibited by ketanserin and augmented by SDZ-205,557 and 5-HTP-DP. In the presence of ketanserin, 5-HT caused relaxation of cholecystokinin-contracted cells that was inhibited by SDZ-205,557 and 5-HTP-DP. 5-HT increased IP₃, which was inhibited by ketanserin, and cAMP, which was inhibited by SDZ-205,557 and 5-HTP-DP. In cells with only 5-HT_2A receptors, 5-HT caused contraction only, and residual binding was inhibited by ketanserin. In cells with only receptors, 5-HT caused only relaxation and residual binding was inhibited by SDZ-205,557 and 5-HTP-DP. 5-HT_2A receptors mediating contraction and 5-HT₄ receptors mediating relaxation coexist on human intestinal muscle cells. The 5-HT₄ receptors are closely similar or identical to 5-HT_1p receptors.     

Dynamics and Patterning of 5-Hydroxytryptamine 2 Subtype Receptors in JC Polyomavirus Entry

The organization and dynamics of plasma membrane receptors are a critical link in virus-receptor interactions, which finetune signaling efficiency and determine cellular responses during infection. Characterizing the mechanisms responsible for the active rearrangement and clustering of receptors may aid in developing novel strategies for the therapeutic treatment of viruses. Virus-receptor interactions are poorly understood at the nanoscale, yet they present an attractive target for the design of drugs and for the illumination of viral infection and pathogenesis. This study utilizes super-resolution microscopy and related techniques, which surpass traditional microscopy resolution limitations, to provide both a spatial and temporal assessment of the interactions of human JC polyomavirus (JCPyV) with 5-hydroxytrypamine 2 receptors (5-HT₂Rs) subtypes during viral entry. JCPyV causes asymptomatic kidney infection in the majority of the population and can cause fatal brain disease, and progressive multifocal leukoencephalopathy (PML), in immunocompromised individuals. Using Fluorescence Photoactivation Localization Microscopy (FPALM), the colocalization of JCPyV with 5-HT₂ receptor subtypes (5-HT_2A, 5-HT_2B, and 5-HT_2C) during viral attachment and viral entry was analyzed. JCPyV was found to significantly enhance the clustering of 5-HT₂ receptors during entry. Cluster analysis of infected cells reveals changes in 5-HT₂ receptor cluster attributes, and radial distribution function (RDF) analyses suggest a significant increase in the aggregation of JCPyV particles colocalized with 5-HT₂ receptor clusters in JCPyV-infected samples. These findings provide novel insights into receptor patterning during viral entry and highlight improved technologies for the future development of therapies for JCPyV infection as well as therapies for diseases involving 5-HT₂ receptors.     

From angiotensin IV binding site to AT4 receptor

One of the fragments of the cardiovascular hormone Angiotensin II incited the interest of several research groups. This 3–8 fragment, denoted as Angiotensin IV (Ang IV) causes a number of distinct biological effects (see Introduction), unlikely to be explained by its weak binding to AT₁ and/or AT₂ receptors. Moreover the discovery of high affinity [¹²⁵I]-Ang IV binding sites and their particular tissue distribution led to the concept of the AT₄ receptor. An important breakthrough was achieved by defining the AT₄ receptor as the membrane-bound insulin-regulated aminopeptidase (IRAP). Crucial for the definition as a receptor the binding of the endogenous ligand(s) should be linked to particular cellular and/or biochemical processes. With this respect, cultured cells offer the possibility to study the presence of binding sites in conjunction with ligand induced signaling. This link is discussed for the AT₄ receptor by providing an overview of the cellular effects by AT₄ ligands.     

Role of the 5-HT2AReceptor and α1-adrenoceptor in the Contractile Response of Rat Pulmonary Artery to 5-HT in the Presence and Absence of Nitric Oxide

This study investigated the role of 5-HT_2Areceptors andα₁ -adrenoceptors in the contractile response to 5-HT in the first branch pulmonary artery of the rat and their interaction with endogenous nitric oxide. 5-HT and phenylephrine induced concentration-dependent contractions. Theα₁ -adrenoceptor antagonists prazosin, HV723 and phentolamine produced concentration-dependent rightward shifts of the 5-HT concentration-response curves (CRC) consistent with an action at α₁-adrenoceptors. The 5-HT₂receptor antagonists ritanserin, ketanserin and methysergide produced rightward shifts that were less than would have been predicted for an action solely at 5-HT_2Areceptors. 5-HT and phenylephrine CRCs were shifted to the left by -NAME. Endothelium denudation also increased the tissue sensitivity to 5-HT. In the presence of -NAME, ketanserin produced greater antagonism of the 5-HT CRC but not the phenylephrine CRC. Ketanserin also produced greater antagonism of the 5-HT CRC in endothelium denuded rings compared with endothelium intact rings. These findings indicate (a) that both theα₁ -adrenoceptor class and the 5-HT_2Areceptor is involved in the contractile response to 5-HT; (b) in the presence of endogenous nitric oxide the contractile response to 5-HT is mediated predominently byα₁ -adrenoceptors; (c) inhibition of endogenous nitric oxide potentiates the 5-HT_2Areceptor-mediated component of the contraction.     

Serotonin and Its Role in Colonic Function and in Gastrointestinal Disorders

Serotonin (5-HT) is most commonly thought of as a neurotransmitter in the central nervous system. However, the predominant site of serotonin synthesis, storage, and release is the enterochromaffin cells of the intestinal mucosa. Within the intestinal mucosa, serotonin released from EC cells activates neural reflexes associated with intestinal secretion, motility, and sensation. Two important receptors for serotonin that are located in the neural circuitry of the intestines are the 5-HT₃ and 5-HT₄ receptors; these are the targets of drugs designed to treat gastrointestinal disorders. 5-HT₃ receptor antagonists are used to treat nausea and emesis associated with chemotherapy and for functional disorders associated with diarrhea. 5-HT₄ receptor agonists are used as promotility agents to promote gastric emptying and to alleviate constipation. Because of the importance of serotonin in normal gut function and sensation, a number of studies have investigated potential changes in mucosal serotonin signaling in pathologic conditions. Despite the inconsistencies in the current literature, changes in serotonin signaling have now been demonstrated in inflammatory bowel disease, irritable bowel syndrome, postinfectious irritable bowel syndrome, and idiopathic constipation. Emerging evidence has led to many contradictory theories regarding serotonin signaling and its roles in the pathology of gut disorders. This review summarizes the current medications affecting serotonin signaling and provides an overview of our current knowledge of the changes in serotonin that occur in pathologic conditions. Supported by NIH grant DK62267, Novartis Pharmaceuticals, and NIH P20 COBRE grant RR16435. Reprints are not available.     

Venoconstrictor responses to dihydroergocristine and dihydroergotamine: Evidence for the involvement of 5-HT1 like receptors

Summary Dihydroergocristine (DHEC) and dihydroergotamine (DHE) were investigated on canine saphenous veins in vivo and on canine saphenous veins and basilar arteries in vitro. Following local IV infusion in vivo, the venoconstrictor response to DHEC was about 30% weaker than that produced by DHE. When administered orally, however, both ergot alkaloids elicited similar venoconstrictor effects. In vitro maximal contractile responses to DHEC and DHE of basilar arteries were only 20–30% of those produced by 5-HT, whereas in saphenous veins both DHEC and DHE elicited similar maximal effects as those observed with 5-HT. In saphenous veins, methiothepin antagonized venoconstrictor responses to 5-HT, DHEC, and DHE within the same concentration range, being significantly less potent when tested against noradrenaline. The reverse was true for yohimbine, which was significantly more potent against noradrenaline than againificantly more potent against noradrenaline than against 5-HT, DHEC, and DHE. It is suggested that the venoconstrictor responses to both DHEC and DHE are mediated through 5-HT₁-like receptors.     

Taurocholate-stimulated leukotriene C4 biosynthesis and leukotriene C4-stimulated choleresis in isolated rat liver

Cysteinyl-containing leukotrienes seem to exert a cholestatic effect. However, leukotriene inhibitors were found to reduce bile salt efflux in isolated rat hepatocytes, suggesting a role for leukotrienes in bile flow formation. In the isolated rat liver, the effects of two different concentrations of leukotriene C₄ on bile flow and bile salt excretion are analyzed, as well as the possible effect of taurocholate on the hepatic production of cysteinyl-containing leukotrienes. Leukotriene C₄ (0.25 fmol) increased bile salt excretion (+22.2%; P < 0.05), whereas a much higher dose (0.25 × 10⁶ fmol) showed the known cholestatic effect, reducing bile salt excretion (−25.9%; P < 0.01). These dose-dependent biphasic effects were specific because they could be prevented by the simultaneous administration of cysteinyl-containing leukotriene antagonists. On the other hand, taurocholate administration induced a dose-dependent increase in biliary excretion of cysteinyl-containing leukotrienes. Furthermore, taurocholate increased messenger RNA levels of 5-lipoxygenase, a key enzyme in leukotriene biosynthesis. Taurocholate increase of hepatocyte intracellular calcium was not significant, suggesting that taurocholate effects are not mediated by stimulation of calcium metabolism. These results constitute evidence for the existence of a positive feedback mechanism by which bile salts stimulate the synthesis of leukotrienes that, in turn, stimulate bile salt excretion.     

Predicting factors of postoperative relapse in T2-4N0M0 colorectal cancer patients via harvesting a minimum of 12 lymph nodes

Background and aim  The aim of this retrospective study was to determine which clinicopathological factors influenced the incidence of postoperative relapse and overall survival rates after radical resection of T_2-4N₀M₀ colorectal cancer (CRC) patients via harvesting a minimum of 12 lymph nodes. Materials and methods  Between January 2001 and June 2006, a total of 342 T_2-4N₀M₀ CRC patients who underwent radical resection were retrospectively analyzed in Kaohsiung Medical University Hospital. Of these 342 patients, 155 were observed by harvesting a minimum of 12 lymph nodes. These 155 patients were followed up intensively, and their outcomes were investigated retrospectively. Results  Of 155 patients, 83 were men (53.5%) and 72 (46.5%) were women. The mean age was 65.5 ± 11.1 years (range, 24–89 years). The median follow-up period was 49 months (range, 19–80 months). The present data showed invasive depth (P = 0.012), vascular invasion (P < 0.001), and perineural invasion (P = 0.009) as significantly prognostic factors for postoperative 5-year relapse rate by Kaplan–Meier analysis. Likewise, invasive depth (P = 0.013), vascular invasion (P < 0.001), and perineural invasion (P = 0.008) were significant factors for postoperative 5-year survival rate. Meanwhile, using a Cox proportional hazards analysis, depth of tumor invasion (P = 0.026) and vascular invasion (P = 0.001) were the independent predictors for postoperative relapse. Furthermore, the presence of vascular invasion was considerably correlated to the higher postoperative relapse rate and the poorer overall survival rates by survival analyses (P < 0.0001). Conclusions  Besides the conventional depth of tumor invasion, this study highlights the potential for using vascular invasion as a means of identifying a subgroup of T_2-4N₀M₀ CRC patients with adequate lymph node harvest at higher risk who would potential benefit from adjuvant therapy after surgery.     

Evaluation of 5-HT7 receptor expression in the placentae of normal and pre-eclamptic women

In this study, by examining 5-HT₇ receptor expression in placentae from pre-eclamptic and normal pregnancies, we aimed to discover a new step of pathophysiological cascade for preeclampsia. Patients whose blood pressure over the 140/90?mmHg were included when study after 20 weeks of gestation. 5-HT₇ receptor expression was investigated on the placentae obtained after birth by real time PCR (RT-PCR) analysis. Pre-natal–post-natal, systolic–diastolic blood pressure values, proteinuria and renal function indicators as BUN and creatinine levels of pre-eclamptic pregnant women were higher than the healthy group. Similarly, 5-HT₇ receptor expression determined in healthy placentae increased 8-fold in pre-eclamptic women. This study, for the first time we showed 5-HT₇ receptor expression in normal placenta and increased expression in pre-eclamptic placenta.     

Effect of different prokinetic agents and a novel enterokinetic agent on postoperative ileus in rats

BACKGROUND/AIM: The effects of different prokinetic agents, the motilide erythromycin and the substituted benzamides metoclopramide and cisapride, were investigated in a rat model of postoperative ileus. These effects were compared with that of granisetron, a 5-hydroxytryptamine (5-HT(3)) receptor antagonist, and a novel enterokinetic agent, prucalopride, a 5-HT(4) receptor agonist. METHODS: Different degrees of inhibition of gastrointestinal transit, measured by the migration of Evans blue, were achieved by skin incision, laparotomy, or laparotomy plus mechanical stimulation of the gut. RESULTS: Metoclopramide decreased the transit after laparotomy with or without mechanical stimulation, whereas cisapride increased it after all three operations. Granisetron had no effect on the transit after the three operations when given alone. Prucalopride tended to increase the transit after laparotomy with or without mechanical stimulation when given alone. However, statistical significance was only reached when prucalopride was combined with granisetron. Erythromycin, a motilin receptor agonist, did not improve postoperative ileus in the rat. CONCLUSIONS: Cisapride, but not metoclopramide or erythromycin, is able to improve postoperative ileus in the rat. The results suggest that a combination of 5-HT(3) receptor antagonist and 5-HT(4) receptor agonist properties may be required to obtain a beneficial effect on surgery induced ileus in the rat. Furthermore, they indirectly indicate that stimulation of the excitatory mechanisms is not able to overcome the inhibitory influence of the neural reflex pathways activated during abdominal surgery.     

Boosting Piezo/Photo-Induced Charge Transfer of CNT/Bi4O5I2 Catalyst for Efficient Ultrasound-Assisted Degradation of Rhodamine B

Strain-induced internal electric fields present a significant path to boosting the separation of photoinduced electrons and holes. In addition, piezo-induced positive/negative pairs could be released smoothly, taking advantage of the excellent electroconductibility of some conductors. Herein, the hybrid piezo-photocatalysis is constructed by combining debut piezoelectric nanosheets (Bi₄O₅I₂) and typical conductor multiwalled carbon nanotubes (CNT). The photocatalytic degradation efficiency that the hybrid CNT/Bi₄O₅I₂ exhibits was remarkably increased by more than 2.3 times under ultrasonic vibration, due to the piezo-generated internal electric field. In addition, the transient photocurrent spectroscopy and electrochemical impedance measurement reveal that the CNT coating on Bi₄O₅I₂ enhances the piezo-induced positive/negative migration. Therefore, the piezocatalytic activity of CNT/Bi₄O₅I₂ could be improved by three times, compared with pure Bi₄O₅I₂ nanosheets. Our results may offer promising approaches to sketching efficient piezo-photocatalysis for the full utilization of solar energy or mechanical vibration.     

Transport and Electrochemical Properties of Li4Ti5O12-Li2TiO3 and Li4Ti5O12-TiO2 Composites

The study demonstrates that the introduction of the electrochemically inactive dielectric additive Li₂TiO₃ to LTO results in a strong decrease in the grain boundary resistance of LTO-Li₂TiO₃ (LTC) composites at a low concentration of Li₂TiO₃. With the increase in the concentration of Li₂TiO₃ in LTC composites, the grain boundary resistance goes through a minimum and increases again due to the growth of the insulation layer of small Li₂TiO₃ particles around LTO grains. For LTO-TiO₂ (LTT) composites, a similar effect was observed, albeit not as strong. It was found that LTC composites at low concentration of Li₂TiO₃ have unusually high charge–discharge capacity exceeding the theoretical value for pure LTO. This effect is likely to be caused by the occurrence of the electrochemical activity of Li₂TiO₃ in the vicinity of the interfaces between LTO and Li₂TiO₃. The increase in the capacity may be qualitatively described in terms of the model of two-phase composite in which there is the interface layer with a high capacity. Contrasting with LTC composites, in LTT composites, no capacity enhancement was observed, which was likely due to a noticeable difference in crystal structures of LTO and TiO₂ preventing the formation of coherent interfaces.     

Differential functional effects of two 5-HT4 receptor isoforms in adult cardiomyocytes

Serotonin 5-HT4 receptors are present in human atrial myocytes and have been proposed to contribute to the generation of atrial fibrillation. However, 5-HT4 receptors have so far been only found in human and pig atria and are absent from the heart of small laboratory animals, such as rat, guinea pig, rabbit and frog, which limits the experimental settings for studying their functional properties. In this study, we developed an adenovirus expression system to examine the properties of two human 5-HT4 receptor splice variants, h5-HT4(b) and h5-HT4(d), expressed in adult cardiomyocytes devoid of native 5-HT4 receptors. When expressed in the HL-1 murine cell line of atrial origin, both receptors caused specific binding of the 5-HT4 selective antagonist GR113808 and activated adenylyl cyclase in the presence of serotonin (5-HT, 1 microM). When expressed in freshly isolated adult rat ventricular cardiomyocytes, a stimulation of the L-type Ca2+ current (ICa,L) by 5-HT (100 nM) was revealed. Both effects were blocked by GR113808. In HL-1 cells, the h5-HT4(d) receptor was found to be more efficiently coupled to adenylyl cyclase than the h5-HT4(b). Pertussis toxin treatment (250 ng/ml for 5 h) potentiated the stimulatory effect of 5-HT on ICa,L in rat myocytes expressing the h5-HT4(b) but not the h5-HT4(d) receptor, indicating a likely coupling of the (b) isoform to both Gs and Gi/o proteins. Adenoviral expression of h5-HT4 receptor isoforms in adult cardiac myocytes provides a valuable means for the exploration of the receptor signaling cascades in normal and pathological situations.     

Effects of two 5-hydroxytryptamine agonists on head-weaving behaviour in streptozotocin-diabetic mice

Summary The potencies of 5-methoxy-N, N-dimethyltryptamine (central 5-hydroxytryptamine 1 receptor agonist) and 8-hydroxy-2-(di-n-propylamino) tetralin (central 5-hydroxytryptamine 1A receptor agonist) in eliciting head-weaving behaviour were studied in streptozotocin-diabetic mice and a group of control animals. Both drugs induced head-weaving behaviour in the streptozotocin-diabetic mice and control animals, but the potencies of these 5-hydroxytryptamine 1 agonists were reduced in the streptozotocin-diabetic mice. The numbers of head weaves elicited in the streptozotocindiabetic and control animals by the two drugs were suppressed by pre-treatment with propranolol (5-hydroxytryptamine 1A receptor antagonist) and methysergide (5-hydroxytryptamine 1 and 2 receptor antagonist), but not by ketanserin (5-hydroxytryptamine 2 receptor antagonist), confirming the involvement of the 5-HT_1A receptor. Pre-treatment with nicotinamide before administering streptozotocin prevented streptozotocin-induced hyperglycaemia and restored the inhibition of head-weaving behaviour observed in streptozotocin-diabetic mice. Insulin injection, which partially prevented streptozotocin-induced hyperglycaemia, completely prevented reduction of the number of head weaves elicited by 5-methoxy-N, N-dimethyltryptamine in streptozotocin-diabetic mice. These results suggest that the reduced response to 5-HT₁ agonists in streptozotocindiabetic mice may be caused by the depletion of insulin.     

Gene expression of interstitial collagenase (matrix metalloproteinase 1) in gastrointestinal tract cancers

Collagenolytic proteinases play an important pathological role in the invasion and metastasis of cancer cells. However, little is known about the role of interstitial collagenase (matrix metalloproteinase-1; MMP-1) in this process. To investigate the expression of the MMP-1 gene in cancer tissues, anin situ hybridization study was carried out in gastrointestinal tract cancers (one esophageal cancer, five gastric cancers, and four colorectal cancers), using a³⁵S-labeled MMP-1 cDNA probe. The MMP-1 gene was expressed in the stromal cells of fibrous tissue around cancer nests, especially at the margin of invasion and/or within the cancer nest; however, no definite expression within cancer cells was observed. Expression of the MMP-1 gene in the stromal cells was more common in well differentiated gastric adenocarcinoma than in poorly differentiated adenocarcinomas. These findings indicate that expression of the MMP-1 gene is greater in stromal cells that are closely associated with cancer cells, suggesting a pathophysiological role of MMP-1 in the invasion and metastasis of cancer cells.     

巨噬细胞修饰低密度脂蛋白对细胞受体活性的影响及前列腺素E2的作用

为研究低密度脂蛋白经细胞修饰后对细胞受体的影响及前列腺素Ｅ２的作用，利用免疫细胞化学和生物亲和素－酶联免疫吸附法分析检测小鼠腹腔巨噬细胞清道夫受体、小鼠皮肤纤维母细胞低密度脂蛋白受体的结合活性，结果发现修饰组的巨噬细胞浆及胞膜有强阳性黄褐色颗粒，而药物组仅中度着色；     

Presence of quinolone resistance to qnrB1 genes and blaOXA-48 carbapenemase in clinical isolates of Klebsiella pneumoniae in Spain

A study is presented on the presence of quinolone resistance qnrB1 genes in clinical isolates belonging to the largest series of infections caused by OXA-48-producing Klebsiella pneumoniae in a single-centre outbreak in Spain. Evidence is also provided, according to in vitro results, that there is a possibility of co-transfer of plasmid harbouring bla_OXA-48 with an other plasmid harbouring qnrB1 in presence of low antibiotic concentrations of fluoroquinolones, showing the risk of multi-resistance screening.     

CHADS2 versus CHA2DS2-VASc score in assessing the stroke and throm-boembolism risk stratification in patients with atrial fibrillation: a systematic review and meta-analysis

Objective To perform a systematic review and meta-analysis of the predictive abilities of CHADS2 and CHA2DS2-VASc in stroke and thromboembolism risk stratification of atrial fibrillation (AF) patients....