Fundamental control of grade-specific colorectal cancer morphology by Src regulation of ezrin-centrosome engagement

The phenotypic spectrum of colorectal cancer (CRC) is remarkably diverse, with seemingly endless variations in cell shape, mitotic figures and multicellular configurations. Despite this morphological complexity, histological grading of collective phenotype patterns provides robust prognostic stratification in CRC. Although mechanistic understanding is incomplete, previous studies have shown that the cortical protein ezrin controls diversification of cell shape, mitotic figure geometry and multicellular architecture, in 3D organotypic CRC cultures. Because ezrin is a substrate of Src tyrosine kinase that is frequently overexpressed in CRC, we investigated Src regulation of ezrin and morphogenic growth in 3D CRC cultures. Here we show that Src perturbations disrupt CRC epithelial spatial organisation. Aberrant Src activity suppresses formation of the cortical ezrin cap that anchors interphase centrosomes. In CRC cells with a normal centrosome number, these events lead to mitotic spindle misorientation, perturbation of cell cleavage, abnormal epithelial stratification, apical membrane misalignment, multilumen formation and evolution of cribriform multicellular morphology, a feature of low-grade cancer. In isogenic CRC cells with centrosome amplification, aberrant Src signalling promotes multipolar mitotic spindle formation, pleomorphism and morphological features of high-grade cancer. Translational studies in archival human CRC revealed associations between Src intensity, multipolar mitotic spindle frequency and high-grade cancer morphology. Collectively, our study reveals Src regulation of CRC morphogenic growth via ezrin-centrosome engagement and uncovers combined perturbations underlying transition to high-grade CRC morphology. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Mechanistic Insights into Colorectal Cancer Phenomics from Fundamental and Organotypic Model Studies

Colorectal cancer (CRC) diagnosis and prognostic stratification are based on histopathologic assessment of cell or nuclear pleomorphism, aberrant mitotic figures, altered glandular architecture, and other phenomic abnormalities. This complexity is driven by oncogenic perturbation of tightly coordinated spatiotemporal signaling to disrupt multiple scales of tissue organization. This review clarifies molecular and cellular mechanisms underlying common CRC histologic features and helps understand how the CRC genome controls core aspects of tumor aggressiveness. It further explores a spatiotemporal framework for CRC phenomics based on regulation of living cells in fundamental and organotypic model systems. The review also discusses tissue homeostasis, considers distinct classes of oncogenic perturbations, and evolution of cellular or multicellular cancer phenotypes. It further explores the molecular controls of cribriform, micropapillary, and high-grade CRC morphology in organotypic culture models and assesses relevant translational studies. In addition, the review delves into complexities of morphologic plasticity whereby a single molecular signature generates heterogeneous cancer phenotypes, and, conversely, morphologically homogeneous tumors show substantive molecular diversity. Principles outlined may aid mechanistic interpretation of omics data in a setting of cancer pathology, provide insight into CRC consensus molecular subtypes, and better define principles for CRC prognostic stratification.

Vascular Endothelial Growth Factor Levels in Serum and Plasma following Esophageal Cancer Resection - Relationship to Platelet Count

In patients with cancer circulating vascular endothelial growth factor (VEGF) may be tumor-derived and have prognostic significance. Activated platelets may also be a source of VEGF, releasing it in serum formation. Debate exists as to whether serum or plasma VEGF (S-VEGF, P-VEGF) is the most appropriate surrogate marker of tumor angiogenesis. As healing wounds produce VEGF that can spill over into the circulation, we aimed to investigate the potential confounding effects of cancer surgery on both perioperative S-VEGF and P-VEGF levels and to evaluate their relationship with platelet count. S-VEGF, P-VEGF and platelet counts were measured in 23 patients undergoing esophageal cancer resection. Samples were taken preoperatively and six weeks following surgery. Seven patients were also sampled on postoperative days 1, 5 and 10. VEGF was assayed using a commercial enzyme linked immunosorbent assay. S-VEGF and P-VEGF both rose after surgery (S-VEGF; day 5: 1017 [446–1224] pg/mL and day 10: 1231 [626–2046] pg/mL versus pre-op: 329 [189–599] pg/mL. P-VEGF; day 1: 55 [46–104] pg/mL and day 10: 58 [20–154] pg/mL versus pre-op: 23 [13–46] pg/mL), falling towards pre-operative levels by six weeks. Platelet count correlated with S-VEGF (rho=0.281; p<0.05, Spearman's rank) and P-VEGF (rho=0.330; p<0.01, Spearman's rank). Platelets may contribute to VEGF levels in plasma as well as in serum. The effects of surgery on S-VEGF or P-VEGF levels are mainly transient. Care must be exercised when interpreting circulating VEGF levels in the early postoperative period.

PTEN controls glandular morphogenesis through a juxtamembrane β-Arrestin1/ARHGAP21 scaffolding complex

PTEN controls three-dimensional (3D) glandular morphogenesis by coupling juxtamembrane signaling to mitotic spindle machinery. While molecular mechanisms remain unclear, PTEN interacts through its C2 membrane-binding domain with the scaffold protein β-Arrestin1. Because β-Arrestin1 binds and suppresses the Cdc42 GTPase-activating protein ARHGAP21, we hypothesize that PTEN controls Cdc42 -dependent morphogenic processes through a β-Arrestin1-ARHGAP21 complex. Here, we show that PTEN knockdown (KD) impairs β-Arrestin1 membrane localization, β-Arrestin1-ARHGAP21 interactions, Cdc42 activation, mitotic spindle orientation and 3D glandular morphogenesis. Effects of PTEN deficiency were phenocopied by β-Arrestin1 KD or inhibition of β-Arrestin1-ARHGAP21 interactions. Conversely, silencing of ARHGAP21 enhanced Cdc42 activation and rescued aberrant morphogenic processes of PTEN-deficient cultures. Expression of the PTEN C2 domain mimicked effects of full-length PTEN but a membrane-binding defective mutant of the C2 domain abrogated these properties. Our results show that PTEN controls multicellular assembly through a membrane-associated regulatory protein complex composed of β-Arrestin1, ARHGAP21 and Cdc42.

Vitamin D3 suppresses morphological evolution of the cribriform cancerous phenotype

Development of cribriform morphology (CM) heralds malignant change in human colon but lack of mechanistic understanding hampers preventive therapy. This study investigated CM pathobiology in three-dimensional (3D) Caco-2 culture models of colorectal glandular architecture, assessed translational relevance and tested effects of 1,25(OH)2D3,theactive form of vitamin D. CM evolution was driven by oncogenic perturbation of the apical polarity (AP) complex comprising PTEN, CDC42 and PRKCZ (phosphatase and tensin homolog, cell division cycle 42 and protein kinase C zeta). Suppression of AP genes initiated a spatiotemporal cascade of mitotic spindle misorientation, apical membrane misalignment and aberrant epithelial configuration. Collectively, these events promoted "Swiss cheese-like" cribriform morphology (CM) comprising multiple abnormal "back to back" lumens surrounded by atypical stratified epithelium, in 3D colorectal gland models. Intestinal cancer driven purely by PTEN-deficiency in transgenic mice developed CM and in human CRC, CM associated with PTEN and PRKCZ readouts. Treatment of PTEN-deficient 3D cultures with 1,25(OH)2D3 upregulated PTEN, rapidly activated CDC42 and PRKCZ, corrected mitotic spindle alignment and suppressed CM development. Conversely, mutationally-activated KRAS blocked1,25(OH)2D3 rescue of glandular architecture. We conclude that 1,25(OH)2D3 upregulates AP signalling to reverse CM in a KRAS wild type (wt), clinically predictive CRC model system. Vitamin D could be developed as therapy to suppress inception or progression of a subset of colorectal tumors.

PTEN regulates colorectal epithelial apoptosis through Cdc42 signalling

Background:

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) regulation of the Rho-like GTPase Cdc42 has a central role in epithelial polarised growth, but effects of this molecular network on apoptosis remain unclear.

Methods:

To investigate the role of Cdc42 in PTEN-dependent cell death, we used flow cytometry, in vitro pull-down assays, poly(ADP ribose) polymerase (PARP) cleavage and other immunoblots in isogenic PTEN-expressing and -deficient colorectal cells (HCT116PTEN^+/+, HCT116PTEN^−/−, Caco2 and Caco2 ShPTEN cells) after transfection or treatment strategies.

Results:

The PTEN knockout or suppression by short hairpin RNA or small interfering RNA (siRNA) inhibited Cdc42 activity, PARP cleavage and/or apoptosis in flow cytometry assays. Transfection of cells with wild-type or constitutively active Cdc42 enhanced PARP cleavage, whereas siRNA silencing of Cdc42 inhibited PARP cleavage and/or apoptosis. Pharmacological upregulation of PTEN by sodium butyrate (NaBt) treatment enhanced Cdc42 activity, PARP cleavage and apoptosis, whereas Cdc42 siRNA suppressed NaBt-induced PARP cleavage. Cdc42-dependent signals can suppress glycogen synthase kinase-β (GSK3β) activity. Pharmacological inhibition of GSK3β by lithium chloride treatment mimicked effects of Cdc42 in promotion of PARP cleavage and/or apoptosis.

Conclusion:

Phosphatase and tensin homologue deleted on chromosome 10 may influence apoptosis in colorectal epithelium through Cdc42 signalling, thus providing a regulatory framework for both polarised growth and programmed cell death.

Enhanced lymphocyte interferon (IFN)-γ responses in a PTEN mutation-negative Cowden disease kindred

Identification of immune modifiers of inherited cancer syndromes may provide a rationale for preventive therapy. Cowden disease (CD) is a genetically heterogeneous inherited cancer syndrome that arises predominantly from germline phosphatase and tensin homologue deleted on chromosome 10 (PTEN) mutation and increased phosphoinositide 3-kinase/mammalian target of rapamycin (PI3K/mTOR) signalling. However, many patients with classic CD diagnostic features are mutation-negative for PTEN (PTEN M-Neg). Interferon (IFN)-γ can modulate the PI3K/mTOR pathway, but its association with PTEN M-Neg CD remains unclear. This study assessed IFN-γ secretion by multi-colour flow cytometry in a CD kindred that was mutation-negative for PTEN and other known susceptibility genes. Because IFN-γ responses may be regulated by killer cell immunoglobulin-like receptors (KIR) and respective human leucocyte antigen (HLA) ligands, KIR/HLA genotypes were also assessed. Activating treatments induced greater IFN-γ secretion in PTEN M-Neg CD peripheral blood lymphocytes versus healthy controls. Increased frequency of activating KIR genes, potentially activating KIR/HLA compound genotypes and reduced frequency of inhibitory genotypes, were found in the PTEN M-Neg CD kindred. Differences of IFN-γ secretion were observed among PTEN M-Neg CD patients with distinct KIR/HLA compound genotypes. Taken together, these findings show enhanced lymphocyte secretion of IFN-γ that may influence the PI3K/mTOR CD causal molecular pathway in a PTEN mutation-negative CD kindred.

Expression of osteopontin coregulators in primary colorectal cancer and associated liver metastases

BACKGROUND

A transcription regulatory complex (TRC) that includes Ets1, Ets2, PEA3 and β-catenin/T-cell factors regulates osteopontin (OPN) that is implicated in colorectal cancer (CRC) dissemination. The consistency of OPN transcriptional control between primary CRC and metastases is unclear. This study investigates expression and prognostic significance of the OPN-TRC in primary human CRC and associated colorectal liver metastases (CRLM).

METHODS

Osteopontin-TRC factors were assayed by digital microscopy in 38 primary CRCs and matched CRLM specimens and assessed against clinical prognosis.

RESULTS

In primary CRC, OPN expression intensity correlated with that of its co-activators, PEA3 (r=0.600; P<0.01), Ets1 (r=0.552; P<0.01), Ets2 (r=0.521; P<0.01) and had prognostic significance. Osteopontin intensity in primary CRC inversely correlated with the interval between diagnosis and resection of CRLM. Overall OPN intensity was lower in CRLM than primary CRC and correlations with co-activators were weaker, for example, Ets1 (P=0.047), PEA3 (P=0.022) or nonsignificant (Ets2). The ratio of OPN expression in CRLM vs primary CRC had prognostic significance.

CONCLUSION

This study supports transcriptional control of OPN by known coregulators in both primary and secondary CRC. Weaker associations in CRLM suggest involvement of other unknown factors possibly from the liver microenvironment or resulting from additional genetic or epigenetic changes that drive tumour metastatic capability in OPN transcriptional control.

Apc(MIN) modulation of vitamin D secosteroid growth control

A central paradox of vitamin D biology is that 1alpha,25-(OH)(2) D(3) exposure inversely relates to colorectal cancer (CRC) risk despite a capacity for activation of both pro- and anti-oncogenic mediators including osteopontin (OPN)/CD44 and E-cadherin, respectively. Most sporadic CRCs arise from adenomatous polyposis coli (APC) gene mutation but understanding of its effects on vitamin D growth control is limited. Here we investigate effects of the Apc(Min/+) genotype on 1alpha,25-(OH)(2) D(3) regulation of OPN/CD44/E-cadherin signalling and intestinal tumourigenesis, in vivo. In untreated Apc(Min/+) versus Apc(+/+) intestines, expression levels of OPN and its CD44 receptor were increased, whereas E-cadherin tumour suppressor signalling was attenuated. Treatment by 1alpha,25-(OH)(2) D(3) or rationally designed analogues (QW or BTW) enhanced OPN but inhibited expression of CD44, the OPN receptor implicated in cell growth. These treatments also enhanced E-cadherin tumour suppressor activity, characterized by inhibition of beta-catenin nuclear localization, T-cell factor 1 and c-myelocytomatosis protein expression in Apc(Min/+) intestine. All secosteroids suppressed Apc(Min/+)-driven tumourigenesis although QW and BTW had lower calcium-related toxicity. Taken together, these data indicate that the Apc(Min/+) genotype modulates vitamin D secosteroid actions to promote functional predominance of E-cadherin tumour suppressor activity within antagonistic molecular networks. APC heterozygosity may promote favourable tissue- or tumour-specific conditions for growth control by vitamin D secosteroid treatment.

The Drosophila ortholog of the endolysosomal membrane protein, endolyn, regulates cell proliferation

Endolyn (CD164) is a sialomucin that regulates the proliferation, adhesion, and migration of human haematopoietic stem and progenitor cells. This molecule is predominately localized in endocytotic compartments, where it may contribute to endolysosomal biogenesis and trafficking. In order to more closely define the function of endolyn from an evolutionary view-point, we first analyzed endolyn orthologs in species ranging from insects, fish, and birds to mammals. The predicted molecular structures of the endolyn orthologs from these species are well conserved, particularly with respect to significant O-linked glycosylation of the extracellular domain, and the high degree of amino acid similarities within their transmembrane and cytoplasmic domains, with the latter possessing the lysosomal target signal, YXXphi. Focusing on Drosophila, our studies showed that the subcellular distribution of endolyn in non-polarized Drosophila S2 cells resembles that of its human counterpart in hematopoietic cells, with its predominant localization being within intracellular vesicles, while a small fraction occurs on the cell surface. Both Y --> A and L --> A mutations in the YHTL motif perturbed the normal subcellular distribution of Drosophila endolyn. Interestingly, embryonic and early larval development was often arrested in endolyn-deficient Drosophila mutants. This may partly be due to the role of endolyn in regulating cell proliferation, since knock-down of endolyn expression in S2 cells resulted in up to 50% inhibition of cell growth, with a proportion of cells undergoing apoptosis. Taken together, these results demonstrate that endolyn is an evolutionarily conserved sialomucin fundamentally involved in cell proliferation in both the human and Drosophila melanogaster.

Methylprednisolone increases urinary nitrate concentrations and reduces subclinical renal injury during infrarenal aortic ischemia reperfusion

OBJECTIVE

This study tests the hypothesis that methylprednisolone may influence eNOS activity in renal arterial and venous vascular beds and impede subclinical renal injury.

SUMMARY BACKGROUND DATA

Acute renal failure is a major complication of cardiovascular surgery. Renal damage arises in part from excessive vasoconstriction mediated by an imbalance of vasoconstrictive ET-1 and vasodilatory NO produced by eNOS. While methylprednisolone may reduce subclinical renal injury as measured by urinary N-acetyl-beta-D-glucosaminidase (beta-NAG), its effects upon eNOS activity in renal arterial and venous vascular beds, reflected by urinary nitrate levels, is unclear.

METHODS

A porcine model of normotensive, euvolemic infrarenal aortic ischaemia-reperfusion was used. Forty-two pigs underwent a 60-minute laparotomy followed by 150 minutes of infrarenal ischemia and 180 minutes of reperfusion. Animals were randomized to receive methylprednisolone 30 mg/kg or placebo after induction of general anesthesia. Urinary beta-NAG levels were assessed as an index of subclinical renal injury, whereas urinary nitrate was assessed as an indicator of eNOS activity in renal arterial and venous vascular beds.

RESULTS

Methylprednisolone treatment did not influence mean arterial, central venous, or pulmonary artery wedge pressures but suppressed plasma IL-6 levels. After the ischemia-induced rise from preanaesthetic baseline levels, urinary beta-NAG levels declined to significantly lower values in the MP group, indicative of MP renal protection (P < 0.05). Conversely, urinary nitrate levels indicative of vascular e-NOS activity remained significantly and persistently higher in MP-treated animals (P < 0.05).

CONCLUSION

This study, in a porcine model of renal ischaemia-reperfusion injury, shows the benefits of methylprednisolone pretreatment in enhancing urinary nitrate levels indicative of vascular eNOS activity and the reduction of urinary beta-NAG levels, which represent subclinical renal injury.

Overexpression of p65/RelA potentiates curcumin-induced apoptosis in HCT116 human colon cancer cells

Curcumin, the yellow pigment in the spice turmeric, has potent chemopreventive activities that involve diverse molecular pathways. It is widely believed that curcumin pro-apoptotic properties are mediated by downregulation of NF kappa B (NFkappaB). The p65/RelA subunit of NFkappaB may influence cell death, in part by activation of NFkappaB anti-apoptotic target genes including X-linked inhibitor of apoptosis (XIAP), A20, bcl-xL and inhibition of sustained activation of c-Jun N-terminal kinase (JNK). We have shown previously that curcumin inhibits NFkappaB, activates JNK and promotes apoptosis in HCT116 colorectal cancer cells. Here, we show that forced overexpression of p65 does not affect curcumin-induced JNK activation. Indeed, overexpression of p65 enhanced curcumin-mediated apoptosis as assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay and poly(ADP-ribose) polymerase (PARP) cleavage. This potentiating effect of p65 upon curcumin-mediated apoptosis was reversed by transfection of cells with an IkappaB super-repressor (DeltaNIkappaB). Curcumin treatment inhibited expression of NFkappaB anti-apoptotic target genes in mock-transfected and in p65-overexpressing HCT116 cells, although expression levels remained higher in the latter. Taken together, these results show that curcumin-mediated activation of JNK or induction of apoptosis does not require inhibition of p65. Furthermore, curcumin/p65 synergy in promotion of apoptosis cannot be attributed to active repression of NFkappaB anti-apoptotic genes.

Metallothionein crypt-restricted immunopositivity indices (MTCRII) correlate with aberrant crypt foci (ACF) in mouse colon

Metallothionein (MT) crypt-restricted immunopositivity indices (MTCRII) are colonic crypt stem cell mutation markers that may be induced early and in abundance after mutagen treatment. Metallothionein is the endogenous reporter gene for MTCRII, but is not typically implicated in the classical pathway of colorectal tumorigenesis. Hence, the oncological relevance of MTCRII is unclear. This study tests the hypothesis that MTCRII induced by N-methyl-N-nitrosourea (MNU) and lambda carrageenan (lambdaCgN) associate with aberrant crypt foci (ACF) in mouse colon. Undegraded lambdaCgN and MNU were tested alone and in combination against MTCRII and ACF in Balb/c mice, at 20 weeks after the start of treatment. MTCRII were unaffected by lambdaCgN alone. Combined lambdaCgN/MNU treatments induced greater MTCRII (P < 0.01) as well as greater number (P < 0.001) and crypt multiplicity (P < 0.01) of ACF than MNU alone. MTCRII were approximately 10-fold more numerous than ACF, although linear correlations were observed between these parameters (r = 0.732; P < 0.01). MTCRII are induced by lambdaCgN/MNU interactions in sufficient numbers to provide statistical power from relatively small sample sizes and correlate with ACF formation. MTCRII could thus provide the basis for a novel medium-term murine bioassay relevant to early-stage colorectal tumorigenesis.

Chemopreventive properties of curcumin

Inhibition of defined molecular steps of tumorigenesis by natural nontoxic compounds may be an efficient means to tackle the population cancer burden. Extensive research has addressed the chemotherapeutic potential of curcumin (diferuloylmethane), a relatively nontoxic plant-derived polyphenol. This review considers the following properties of curcumin: anticancer effects in animal model systems; metabolism; biological structure and pharmacokinetics; biological properties implicated in chemoprevention; antioxidant properties; influences upon Phase I and II carcinogen-metabolizing enzymes; signal transduction properties and the neoplastic phenotype; apoptosis evasion, cell proliferation, de-differentiation, migration and invasion and clinical studies. This review will summarize the unique properties of curcumin that may be exploited for successful clinical cancer prevention.

Homeostatic regulation of zinc transporters in the human small intestine by dietary zinc supplementation

BACKGROUND

The role of intestinal transporter regulation in optimising nutrient absorption has been studied extensively in rodent and cell line models but not in human subjects.

AIMS

The aim of the present study was to investigate the response in vivo of zinc transporters in the human enterocyte to dietary zinc supplementation.

SUBJECTS

Eighteen patients who had previously undergone ileostomy, all free of any symptoms of inflammatory bowel disease.

METHODS

Subjects took a daily zinc supplement of 25 mg for 14 days in a double blind, placebo controlled, crossover trial. The effect of the supplement on expression in ileal biopsies of the zinc transporters SLC30A1, SLC30A4, SLC30A5, SLC39A1, SLC39A4, and metallothionein was measured by reverse transcription-polymerase chain reaction RT-PCR. Expression of SLC30A1, SLC30A5, and SLC39A4 was also examined by immunoblotting.

RESULTS

The zinc supplement reduced SLC30A1 mRNA (1.4-fold) together with SLC30A1, SLC30A5, and SLC39A4 protein (1.8-fold, 3.7-fold, and to undetectable levels, respectively) in ileal mucosa and increased metallothionein mRNA (1.7-fold). The supplement had no effect on expression of SLC30A4 or SLC39A1 mRNA. Localisation of SLC30A5 at the apical human enterocyte/colonocyte membrane and also at the apical membrane of Caco-2 cells was demonstrated by immunohistochemistry. Commensurate with these observations in zinc supplemented human subjects, SLC30A1, SLC30A5, and SLC39A4 mRNA and protein were reduced in Caco-2 cells cultured at 200 muM compared with 100 muM zinc.

CONCLUSIONS

These observations indicate that, in response to variations in dietary zinc intakes, regulated expression of plasma membrane zinc transporters in the human intestine contributes to maintenance of zinc status.

Modulation of N-methyl-N-nitrosourea-induced crypt restricted metallothionein immunopositivity in mouse colon by a non-genotoxic diet-related chemical

Red meat consumption is associated with endogenous metabolic generation of mutagenic N-nitroso compounds (NOC) and may be implicated in causation of colorectal cancer. Assessment of a biologically relevant dose of NOCs is hampered by imperfect understanding of NOC interactions with other dietary components. This study tests the hypothesis that NOC effects upon mutational biomarkers in mouse colon may be modulated by a non-genotoxic diet-related compound. N-methyl-N-nitrosourea (MNU) and undegraded lambda carrageenan (lambdaCgN) were selected as test chemicals, representing a NOC and a non-genotoxic agent, respectively. Study end-points included (i) DNA adduct formation and (ii) metallothionein (MT) crypt restricted immunopositivity indices (MTCRII) which are considered representative of crypt stem cell mutations. Frequency and size of MT immunopositive foci as well as total number of MT immunopositive crypts were assessed. Biologically effective doses of MNU and lambdaCgN were determined in model validation studies and the agents were then tested alone and in combination. Continuous lambdaCgN treatment for 10 weeks induced significantly greater colonic mucosal injury than a drinking water control. In combined treatment regimens, lambdaCgN treatment did not significantly affect MNU-induced DNA adduct formation. However, combinations of lambdaCgN with MNU significantly increased MTCRII in excess of those induced by MNU alone. Recurrent or continuous lambdaCgN regimens had greater interactive effects with MNU upon MTCRII than short-term lambdaCgN treatment. This study has shown that exposure to a non-genotoxic diet-related compound (lambdaCgN) modulates the effective NOC dosimetry for induction of MT crypt restricted immunopositivity.

Ischaemic preconditioning before lower limb ischaemia–reperfusion protects against acute lung injury

Background

Ischaemic preconditioning (IPC) of skeletal muscle, by exposing it to repeated brief periods of ischaemia and reperfusion (I-R) before a subsequent longer ischaemic period, protects against local damage on reperfusion. In a large animal model of hindlimb I-R it was hypothesized that hindlimb IPC would attenuate the systemic inflammatory response syndrome and prevent acute lung injury associated with limb reperfusion injury.

Methods

Anaesthetized ventilated swine (six per group) were used throughout. After midline laparotomy, animals were randomized to the following three groups: bilateral external iliac artery occlusion for 120 min, followed by reperfusion for 180 min (I-R group); IPC (three cycles of 5 min ischaemia, then 5 min reperfusion of both external iliac arteries) followed by bilateral external iliac artery occlusion for 120 min and reperfusion for 180 min (I-R + IPC group); or laparotomy alone (control group). Acute lung injury was assessed by invasive pulmonary artery pressure (PAP) measurement, arterial to alveolar (A-a) oxygen gradient, lung tissue wet: dry weight ratio, and lung myeloperoxidase (MPO) concentration.

Results

Conclusion

Lower limb I-R induces systemic inflammation and acutely impairs oxygen transport associated with lung neutrophil sequestration. IPC attenuates acute pulmonary hypertension, impairment of oxygen transport, oedema and leucosequestration in planned lower limb I-R.

Phenol sulphotransferase SULT1A1*1 genotype is associated with reduced risk of colorectal cancer

Sulphation is an important detoxification pathway for numerous xenobiotics; however, it also plays an important role in the metabolism and bioactivation of many dietary and environmental mutagens, including heterocyclic amines implicated in the pathogenesis of colorectal and other cancers. A major sulphotransferase (SULT) enzyme in humans, SULT1A1, is polymorphic with the most common variant allele, SULT1A1*2, occurring at a frequency of about 32% in the Caucasian population. This allele codes for an allozyme with low enzyme activity and stability compared to the wild-type (SULT1A1*1) enzyme, and therefore SULT1A1 genotype may influence susceptibility to mutagenicity following exposure to heterocyclic amines and other environmental toxins. Previously, a significant association of SULT1A1*1 genotype with old age has been observed, suggesting a 'chemoprotective' role for the high-activity phenotype. Here we have compared the frequencies of the most common SULT1A1 alleles in 226 colorectal cancer patients and 293 previously described control patients. We also assessed whether SULT1A1 genotype was related to various clinical parameters in the patient group, including Duke's classification, differentiation, site, nodal involvement and survival. There was no significant difference in allele frequency between the control and cancer patient populations, nor was there a significant association with any of the clinical parameters studied. However, when the age-related difference in allele frequency was considered, a significantly reduced risk of colorectal cancer (odds ratio = 0.47; 95% confidence interval = 0.27-0.83; P = 0.009), was associated with homozygosity for SULT1A1*1 in subjects under the age of 80 years. These results suggest that the high activity SULT1A1*1 allozyme protects against dietary and/or environmental chemicals involved in the pathogenesis of colorectal cancer.

Bactericidal/permeability-increasing protein attenuates systemic inflammation and acute lung injury in porcine lower limb ischemia-reperfusion injury

OBJECTIVE

To investigate the role of recombinant bactericidal/permeability-increasing protein (rBPI21) in the attenuation of the sepsis syndrome and acute lung injury associated with lower limb ischemia-reperfusion (I/R) injury.

SUMMARY BACKGROUND DATA

Gut-derived endotoxin has been implicated in the conversion of the sterile inflammatory response to a lethal sepsis syndrome after lower torso I/R injury. rBPI21 is a novel antiendotoxin therapy with proven benefit in sepsis.

METHODS

Anesthetized ventilated swine underwent midline laparotomy and bilateral external iliac artery occlusion for 2 hours followed by 2.5 hours of reperfusion. Two groups (n = 6 per group) were randomized to receive, by intravenous infusion over 30 minutes, at the start of reperfusion, either thaumatin, a control-protein preparation, at 2 mg/kg body weight, or rBPI21 at 2 mg/kg body weight. A control group (n = 6) underwent laparotomy without further treatment and was administered thaumatin at 2 mg/kg body weight after 2 hours of anesthesia. Blood from a carotid artery cannula was taken every half-hour for arterial blood gas analysis. Plasma was separated and stored at -70 degrees C for later determination of plasma tumor necrosis factor (TNF)-alpha, interleukin (IL)-6 by bioassay, and IL-8 by enzyme-linked immunosorbent assay (ELISA), as a markers of systemic inflammation. Plasma endotoxin concentration was measured using ELISA. Lung tissue wet-to-dry weight ratio and myeloperoxidase concentration were used as markers of edema and neutrophil sequestration, respectively. Bronchoalveolar lavage protein concentration was measured by the bicinclinoic acid method as a measure of capillary-alveolar protein leak. The alveolar-arterial gradient was measured; a large gradient indicated impaired oxygen transport and hence lung injury.

RESULTS

Bilateral hind limb I/R injury increased significantly intestinal mucosal acidosis, intestinal permeability, portal endotoxemia, plasma IL-6 concentrations, circulating phagocytic cell priming and pulmonary leukosequestration, edema, capillary-alveolar protein leak, and impaired gas exchange. Conversely, pigs treated with rBPI21 2 mg/kg at the onset of reperfusion had significantly reduced intestinal mucosal acidosis, portal endotoxin concentrations, and circulating phagocytic cell priming and had significantly less pulmonary edema, leukosequestration, and respiratory failure.

CONCLUSIONS

Endotoxin transmigration across a hyperpermeable gut barrier, phagocytic cell priming, and cytokinemia are key events of I/R injury, sepsis, and pulmonary dysfunction. This study shows that rBPI21 ameliorates these adverse effects and may provide a novel therapeutic approach for prevention of I/R-associated sepsis syndrome.

Role of glutathione S-transferase P1, P-glycoprotein and multidrug resistance-associated protein 1 in acquired doxorubicin resistance

While P-glycoprotein (Pgp) and multidrug resistance-associated protein 1 (MRP1) are known to be important in acquired doxorubicin resistance, the role of glutathione S-transferases (GST) remains unclear. Our study assessed roles of these 3 factors in a human drug-sensitive carcinoma cell line (HEp2), a subclone made resistant by prolonged incubation in doxorubicin (HEp2A), and HEp2 cells stably transfected with human GSTP1. Drug-resistant HEp2A cells showed greater total GST activity, GSTP class enzyme expression, Pgp expression, MRP1 transcript expression, drug efflux and at least 13-fold greater resistance to doxorubicin than the parent HEp2 cell line. GSTM class enzyme expression was similar in both cell types, while GSTA class enzymes were not detected. In the resistant HEp2A cells, cytotoxicity was markedly enhanced by the Pgp/MRP inhibitor verapamil at low doxorubicin concentrations. The GST inhibitor curcumin also enhanced cytotoxicity in HEp2A cells when the Pgp/MRP efflux barrier had been reversed by verapamil or overcome by high doxorubicin concentrations. In addition, curcumin had a chemosensitising effect at low doxorubicin concentrations in HEp2 cells. Stable transfection of HEp2 cells with human GSTP1 increases doxorubicin resistance 3-fold over control cells. Our study indicates involvement of GSTP enzymes as well as efflux mechanisms in the acquired doxorubicin-resistance phenotype.

Curcumin modifies Apc(min) apoptosis resistance and inhibits 2-amino 1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induced tumour formation in Apc(min) mice

Curcumin, the active ingredient of the rhizome of Curcuma longa, promotes apoptosis and may have chemopreventive properties. This study investigates the effects of curcumin on apoptosis and tumorigenesis in male Apc(min) mice treated with the human dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Intestinal epithelial apoptotic index in response to PhIP treatment was approximately twice as great in the wild-type C57BL/6 APC(+/+) strain than in Apc(min) mice (3.7% Apc(+/+) versus 1.9% Apc(min); P < 0.001). PhIP promoted tumour formation in Apc(min) proximal small intestine (4.6 tumours per mouse, PhIP treated versus 2.1 tumours per mouse, control untreated; P < 0.05). Curcumin enhanced PhIP-induced apoptosis (4.0% curcumin + PhIP versus 2.1% PhIP alone; P < 0.01) and inhibited PhIP-induced tumorigenesis in the proximal small intestine of Apc(min) mice (2.2 tumours per mouse, curcumin + PhIP versus 4.6 tumours per mouse PhIP alone; P < 0.05). This study shows that the Apc(min) genotype is associated with resistance to PhIP-induced apoptosis in intestinal epithelium. Curcumin attenuates Apc(min) resistance to PhIP-induced apoptosis and inhibits PhIP-induced tumorigenesis in proximal Apc(min) mouse small intestine.

Recombinant bactericidal/permeability-increasing protein attenuates the systemic inflammatory response syndrome in lower limb ischemia-reperfusion injury

OBJECTIVES

Hind limb ischemia-reperfusion (I/R) injury increases gut permeability, and resultant endotoxemia is associated with an amplified systemic inflammatory response syndrome leading to multiple organ dysfunction syndrome. We studied the potential role of recombinant bactericidal/permeability-increasing protein (rBPI(21) ), a novel antiendotoxin therapy, in modulating endotoxin-enhanced systemic inflammatory response syndrome in hind limb I/R injury.

METHODS

In this prospective, randomized, controlled, experimental animal study, 48 male Wistar rats, weighing 300 to 350 g, were randomized to a control group (sham) and five groups undergoing 3 hours bilateral hind limb ischemia with 2 hours reperfusion (I/R) (n = 8 per group). The control and untreated I/R groups received thaumatin, a control-protein preparation, at 2 mg/kg. Treatment groups were administered rBPI(21) intravenously at 1, 2, or 4 mg/kg body weight at the beginning of reperfusion; an additional group was administered rBPI(21) intravenously at 2 mg/kg after 1 hour of reperfusion. Plasma interleukin-6 concentration was estimated by bioassay as a measure of systemic inflammation. Plasma endotoxin concentration was determined by use of an amebocyte lysate chromogenic assay. Crossreactive immunoglobulin G and M antibodies to the highly conserved inner core region of endotoxin were measured by use of an enzyme-linked immunosorbent assay. The lung tissue wet-to-dry weight ratio and myeloperoxidase concentration were used as markers of edema and neutrophil sequestration, respectively.

RESULTS

I/R provoked highly significant elevation in plasma interleukin-6 concentrations (1351.20 pg/mL [860.16 - 1886.40 pg/mL]) compared with controls (125.32 pg/mL [87.76-157.52 pg/mL; P <.0001]), but treatment with rBPI(21) 2 mg/kg at onset of reperfusion (715.89 pg/mL [573.36-847.76 pg/mL]) significantly decreased interleukin-6 response compared with the nontreatment group ( P <.016). I/R increased plasma endotoxin concentrations significantly (21.52 pg/mL [6.20-48.23 pg/mL]), compared with control animals (0.90 pg/mL [0.00-2.30 pg/mL; P <.0001]), and treatment with rBPI(21) 4 mg/kg at reperfusion significantly decreased endotoxemia (1.30 pg/mL [1.20-2.20 pg/mL]), compared with the untreated group ( P <.001). The lung tissue myeloperoxidase level was significantly increased in the untreated I/R group (208.18% [128.79%-221.81%]), compared with in controls (62.00% [40.45%-80.92%; P <.0001]), and attenuated in those treated with rBPI(21) 2 mg/kg (129.54% [90.49%-145.78%; P <.05]). Data represent median and interquartile range, comparisons made with the nonparametric Mann-Whitney U test.

CONCLUSIONS

These findings show that hind limb ischemia-reperfusion injury is associated with endotoxemia, elevations in plasma interleukin-6, and pulmonary leukosequestration. Treatment with rBPI(21) after ischemia reduces endotoxemia, the interleukin-6 response, and attenuates pulmonary leukosequestration in response to hind limb reperfusion injury.

Circulating neutrophil priming and systemic inflammation in limb ischaemia-reperfusion injury

BACKGROUND

Recruitment and activation of neutrophils is a key step in the development of local and systemic injury in lower limb ischaemia-reperfusion. We hypothesis that increased circulating neutrophil priming is responsible for systemic inflammation.

METHODS

Anaesthetised ventilated swine (n = 6 per group) underwent mid-line laparotomy and were randomised to control group or bilateral external iliac artery occlusion for two hours followed by two and a half hours reperfusion (I/R group). Using luminol, respiratory burst activity was assayed with a BioOrbit Luminometer to detect whole blood chemiluminescence (CL) by stimulation with phorbol 1,2-myristate 1,3-acetate (PMA) in the absence or presence of tumour necrosis factor (TNF) respectively. PMN priming is expressed as the ratio of whole blood CL in the presence of TNF to that without. We measured plasma interleukin(IL)-6 and tumour necrosis factor alpha by bioassay as a measure of systemic inflammation. The alveolar-arterial (A-a) gradient was measured using the formula [(A-a)gradient = fraction inspired O2 x 710-(arterial pCO2/0.8)-arterial pO2], it is a measure of lung function, a large gradient being indicative of impaired oxygen transport and hence lung injury.

RESULTS

Lower limb I/R caused significantly greater PMN priming, 0.83 +/- 0.14, compared to control group, 0.22 +/- 0.04, (p < 0.001). Plasma IL-6, a reliable indicator of systemic inflammation, was significantly increased in I/R group after two and a half hours of reperfusion, 1295.0 (833.9-2073.0) pg/L, compared to control, 382.9 (367.4-568.3) pg/L, (p < 0.005). Plasma tumour necrosis factor alpha was significantly elevated after one hour of reperfusion in the I/R group, 86.8 (48.7-106.6) pg/ml, compared to the control group, 32.7 (0.9-42.8) pg/ml, (p < 0.01). (A-a) gradient was significantly increased after IRI, 407.97 +/- 53.13, compared to the control, 183.19 +/- 45.75, (p < 0.005). Mean pulmonary artery pressure was significantly greater after IRI, 38.80 +/- 4.87 mmHg, compared to control, 27.86 +/- 1.92 mmHg, (p < 0.005). Data represents mean +/- standard error mean or median (interquartile range), statistical comparisons using one-way Anova with Student's "t"-test and Kruskall-Wallis Anova with the Mann-Whitney U test.

CONCLUSIONS

Priming of neutrophils increases their circulating respiratory burst activity and ability to induce tissue injury. Systemic PMN priming during hind limb ischaemia-reperfusion injury is associated with the systemic inflammatory response syndrome.

Cyclin D3 expression, cell proliferation and pathological stage of human primary colorectal cancer

Cyclin D3 promotes cell cycle progression but its expression and prognostic significance in human colorectal cancer is unknown. This study assayed cyclin D3 expression against cell cycle phase fraction and Duke's stage in 35 fresh human primary colorectal cancers. DNA content, cell cycle phase fraction and cyclin D3 expression were assessed by flow cytometry in disaggregated tumors. Cyclin D3 expression and S-phase fraction were independently related to Duke's stage. In Duke's stage C tumors, a higher proportion of cells expressed cyclin D3 (14.4 vs. 8.8%, mean; p < 0.05 by Mann-Whitney U test) and were in DNA synthesis (S) phase (21.1 vs. 9.7%, mean; p < 0.05 by Mann-Whitney U test). Neoplastic deregulation of cyclin D3 expression may provide a selective growth advantage which is related to stage in human colorectal cancer.

A mouse model of intestinal stem cell function and regeneration

We present here an in vivo mouse model for intestinal stem cell function and differentiation that uses postnatal intestinal epithelial cell aggregates to generate a differentiated murine small intestinal mucosa with full crypt-villus architecture. The process of neomucosal formation is highly similar to that of intestinal regeneration. Both in vivo grafting and primary culture of these cells reveal two different epithelial cell populations, which display properties consistent with intestinal epithelial transit amplifying and stem cell populations. Using this model system with a mixture of wild-type and transgene marked cells, we have shown that neomucosae originally develop from single aggregates, but that over time the mucosae fuse to form chimaeric mucosae. Despite fusion, the chimaeric mucosae maintain crypt clonality and villus polyclonality, demonstrating that clonal segregation persists during intestinal epithelial regeneration.

Metabolic proficiency and benzo[a]pyrene DNA adduct formation in APCMin mouse adenomas and uninvolved mucosa

Tumour formation may involve interactions between genetic factors and environmental carcinogens. Adenoma formation in APCMin/+ mice is associated homozygous adenomatous polyposis coli (APC) gene mutation, but the effects on carcinogen susceptibility are unknown. This study tests the hypothesis that APCMin/+ adenoma formation is accompanied by changes in metabolic proficiency and carcinogen susceptibility. Cytochrome P450 (CYP)1A1/1A2, glutathione S-transferase (GST)alpha, mu and pi classes and DNA adduct formation were assayed in adenomas and uninvolved mucosa from APCMin/+ mice, before and after benzo[a]pyrene (B[a]P) treatment. In untreated adenomas and mucosa, CYP1A1/1A2 and B[a]P-DNA adducts were undetected but GSTalpha, mu and pi class enzymes were constitutively expressed. In adenomas, B[a]P only induced CYP1A1/1A2 to low level while GSTalpha and pi class enzymes were unaffected. A GST mu band which was absent from mucosa, was induced in adenomas. In mucosa, B[a]P induced CYP1A1/1A2 and GSTalpha and pi, to high levels. B[a]P-DNA adduct levels were 56 +/- 15/10(8) nucleotides (median +/- SE) in adenomas versus 89 +/- 19/10(8) nucleotides in mucosa (P < 0.0001). APCMin adenomas show reduced bioactivation capacity and sustain less DNA damage from B[a]P exposure, than APCMin uninvolved mucosa. These properties could influence mutagenesis and subsequent neoplastic transformation of adenomas.

Growth dysregulation and p53 accumulation in human primary colorectal cancer

p53 accumulation is common in colorectal cancer, but effects on growth homeostasis are unclear. In this study, DNA content, cell cycle phase fractions and DNA strand-breaks consistent with apoptosis were assessed by flow cytometry in 42 fresh primary colorectal tumours and matched normal mucosa. p53 accumulation was assessed in 37 fixed tumour sections, by immunohistochemistry. In normal mucosa, 10.3 +/- 6.6% (mean +/- s.d.) cells were in DNA synthesis phase while 28.7 +/- 17.9% showed apoptosis. A relationship suggestive of growth homeostasis, was observed between these parameters (r = 0.8; P < 0.05). In cancers, a greater number of cells were in DNA synthesis phase (15.6 +/- 12.9% tumour vs mucosa 10.3 +/- 6.6%; P < 0.02) while fewer showed apoptosis than normal mucosa (18.5 +/- 17.0% tumour vs mucosa 28.7 +/- 17.9%; P < 0.01). DNA synthesis and apoptosis fractions were unrelated in cancers, suggesting growth dysequilibrium. p53 accumulation was detected in 59% (22/37) tumours and was associated with reduced apoptosis compared to p53-negative tumours or mucosa (14.8 +/- 15% p53 accumulation vs 26.3 +/- 18% p53-negative; P < 0.05; vs 28.7 +/- 17.9% mucosa; P < 0.05). p53 accumulation was unrelated to DNA synthesis phase fractions. p53 accumulation is accompanied by reduced apoptosis which may accentuate growth dysequilibrium in colorectal cancer.

Expression of growth regulatory genes in a SCID mouse-human model of intestinal epithelial regeneration

Analysis of human intestinal epithelial regeneration has been limited. This study has used a novel SCID mouse-human model to test the hypothesis that distinct stages of human intestinal epithelial regeneration are accompanied by differential expression of growth regulatory genes. Disaggregated epithelium, which included crypt cell aggregates, was isolated from human fetal small intestine and transplanted subcutaneously in SCID mice. This method induced a coordinated regeneration response and enabled temporal separation of cell populations at different stages of histogenesis and cytodifferentiation. Graft epithelium was identified using a specific anti-human monoclonal antibody (MAb 5D3) against cytokeratins 8 and 18. Functional epithelial lineages were identified by appropriate markers. Growth regulatory genes relevant to proliferation and apoptosis, including Bcl-2, p53 and Ki67, were assayed at different stages of regeneration. During early regeneration, Bcl-2, p53, and Ki67 were expressed throughout the epithelial compartment. On completion of regeneration, these genes were expressed only in crypt epithelium and were absent from villi. This study has established a novel SCID mouse-human model of intestinal epithelial regeneration. During early regeneration, increased Bcl-2 and Ki67 expression may indicate suppression of apoptosis and enhanced proliferation respectively, consistent with expansion of the stem cell fraction. The p53 gene may influence pathways of differentiation during regeneration, analogous to its role during development.

Dipyridamole potentiates antipurine antifolate activity in the presence of hypoxanthine in tumor cells but not in normal tissues in vitro

The cytotoxicity of the antifolate inhibitors of de novo purine biosynthesis, lometrexol (LTX) and LY309887, can be abolished by hypoxanthine (HPX) salvage. The nucleoside transport inhibitor, dipyridamole (DP) can prevent HPX rescue from LTX growth inhibition in a cell line-specific manner. The studies described here have shown that, excluding colon and hematological malignancies, DP prevents HPX rescue from LTX growth inhibition in approximately one-third of cell lines with otherwise limited tissue specificity. The clinical dose-limiting toxicities of antipurine antifolates are to the bone marrow and gastrointestinal tract. In vitro models of these normal tissues were established, and the effect of DP on HPX rescue from LY309887 treatment was studied. Growth inhibition assays are not feasible in these primary cultures; therefore, an alternative assay, cellular ATP depletion, was validated in four tumor cell lines as a marker of de novo and salvage purine synthesis. In LY309887-treated cells, DP prevented HPX-mediated maintenance of ATP levels only in cell lines in which DP inhibited HPX rescue from antifolate cytotoxicity. Hence, ATP depletion is a reliable indicator of sensitivity of HPX transport to DP when direct cell growth measurement is impractical. In primary cultures of human hematopoetic progenitor cells and mouse small intestine, coincubation with HPX prevented LY309887-mediated ATP depletion, which was not blocked by DP. These data suggest that DP would not prevent HPX rescue from antipurine antifolate growth inhibition in sensitive normal tissues, whereas activity against certain solid human tumors would be maintained.

Is functional dyspepsia largely explained by gastro-oesophageal reflux disease?

Functional dyspepsia is a chronic disorder of unknown aetiology. The lack of endoscopic abnormalities in patients with this disorder has led many physicians to believe that gastro-oesophageal reflux disease may be responsible for most symptoms. Our group has addressed this issue, by pathophysiological studies in a large cohort of Dundee patients with persistent dyspeptic symptoms. Peptic ulcer and gallstones were excluded in all patients by appropriate tests. Ambulatory pH monitoring showed oesophageal acid reflux that lay above the conventional diagnostic threshold in approximately 20% of patients. This subset was diagnosed as having gastro-oesophageal reflux disease. In the remainder, moderate or severe reflux-like symptoms were reported by approximately 44% patients, who were categorized as reflux-like functional dyspepsia. Reflux symptoms were mild or absent in 36% patients, who were categorized as non-reflux-like dyspepsia. While oesophageal pH profiles lay within the conventional normal range in both of these functional dyspepsia subgroups, patients with reflux-like functional dyspepsia had significantly greater acid exposure values, including total oesophageal acid exposure time, percentage time at a pH of less than 4.0, DeMeester scores and pain reflux event correlation. Hence patients with reflux-like functional dyspepsia have oesophageal acid exposure that lies below the diagnostic threshold for gastro-oesophageal reflux disease but exceeds that of patients with non-reflux dyspepsia. The high pain/reflux event correlation in reflux-like functional dyspepsia suggests that subthreshold oesophageal acid exposure may be associated with troublesome reflux symptoms.

Effects of cisapride on symptoms and postcibal small-bowel motor function in patients with irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome is a common cause of abdominal pain and discomfort and may be related to disordered gastrointestinal motility. Our aim was to assess the effects of long-term treatment with a prokinetic agent, cisapride, on postprandial jejunal motility and symptoms in the irritable bowel syndrome (IBS).

METHODS

Thirty-eight patients with IBS (constipation-predominant, n = 17; diarrhoea-predominant, n = 21) underwent 24-h ambulatory jejunal manometry before and after 12 week's treatment [cisapride, 5 mg three times daily (n = 19) or placebo (n = 19)].

RESULTS

In diarrhoea-predominant patients significant differences in contraction characteristics were observed between the cisapride and placebo groups. In cisapride-treated diarrhoea-predominant patients the mean contraction amplitude was higher (29.3 +/- 3.2 versus 24.9 +/- 2.6 mm Hg, cisapride versus placebo (P < 0.001); pretreatment, 25.7 +/- 6.0 mm Hg), the mean contraction duration longer (3.4 +/- 0.2 versus 3.0 +/- 0.2 sec, cisapride versus placebo (P < 0.001); pretreatment, 3.1 +/- 0.5 sec), and the mean contraction frequency lower (2.0 +/- 0.2 versus 2.5 +/- 0.4 cont./min, cisapride versus placebo (P < 0.001); pretreatment, 2.5 +/- 1.1 cont./min] than patients treated with placebo. No significant differences in jejunal motility were found in the constipation-predominant IBS group. Symptoms were assessed by using a visual analogue scale before and after treatment. Symptom scores relating to the severity of constipation were lower in cisapride-treated constipation-predominant IBS patients [score, 54 +/- 5 versus 67 +/- 14 mm, cisapride versus placebo (P < 0.05); pretreatment, 62 +/- 19 mm]. Diarrhoea-predominant IBS patients had a higher pain score after cisapride therapy [score, 55 +/- 15 versus 34 +/- 12 mm, cisapride versus placebo (P < 0.05); pretreatment, 67 +/- 19 mm].

CONCLUSION

Cisapride affects jejunal contraction characteristics and some symptoms in IBS.

Age-dependent change of metabolic capacity and genotoxic injury in rat intestine

The ontogeny of intestinal phase I and II xenobiotic metabolising enzymes and influence on susceptibility to genotoxic injury, are unclear. This study assessed expression of cytochrome P450 monooxygenases (CYP1A, CYP2B, CYP2C, CYP3A, CYP4A), glutathione-S-transferase (GSTA1/2, GSTA3, GSTA4, AND GSTM1), and uridine diphosphate glucuronosyl transferase (UGT) in rat intestine, between fetal life and maturity. Enzyme induction and DNA adduct formation were assessed after 3-methylcholanthrene (MC) exposure. Untreated rat intestine expressed CYP2B, GSTA1/2, GSTA4 and UGT at all stages of maturation, although CYP2B and GSTA1/2 increased in postnatal life. MC induced new expression of CYP1A, GSTA3 and enhanced expression of GSTA1/2 and UGT. Age-dependent differences of enzyme induction and DNA adduct formation between pre- and postnatal intestine and during postnatal maturation, were observed. Rat intestinal epithelium shows variable competence for MC metabolism and sustains disparate levels of DNA adducts during pre- and postnatal development.

Metabolic competence and susceptibility of intestinal epithelium to genotoxic injury during regeneration

The carcinogenic potency of many mutagens is increased in conditions of tissue regeneration. This involves fundamental changes of cellular division and differentiation, in intestinal epithelium. However, effects on epithelial capacity for carcinogen metabolism and susceptibility to genotoxic injury are unknown. Using a novel rat model, this study assessed expression of cytochrome P450 mono-oxygenases (Cyps), glutathione S-transferases (GSTs) and uridine diphosphoglucuronosyl transferase (UGT) in intestinal epithelium during sequential stages of regeneration. Enzyme induction and DNA adduct formation were also assessed after benzo[a]pyrene (BaP) exposure. Control assays were carried out in normal intestinal epithelium. Fewer phase I and II xenobiotic metabolizing enzymes were expressed in regenerating intestinal epithelium than in normal control intestinal epithelium (GSTA3, UGT in regeneration vs Cyp2B, GSTA1/2, GSTA4, GSTP1, UGT in control). Benzo[a]pyrene induced GSTA3 and UGT in regeneration vs Cyp1A, Cyp2B, GSTA1/2, GSTA3, GSTA4, GSTP1 and UGT in control normal intestinal epithelium. Benzo[a]pyrene induced low levels of GSTA3 in early regenerating intestinal epithelium but induction increased by >2-fold at late stage regeneration. Higher levels of benzo[a]pyrene 7,8-diol-9,10-epoxide (BPDE) DNA adducts were formed at early stages of regeneration, than at later stages. Intestinal epithelium displayed reduced metabolic competence and differential susceptibility to genotoxic injury from BaP, during regeneration.

Zamifenacin (UK-76, 654) a potent gut M3 selective muscarinic antagonist, reduces colonic motor activity in patients with irritable bowel syndrome

BACKGROUND

Zamifenacin is a new potent gut M3 selective muscarinic antagonist developed for possible use in irritable bowel syndrome.

METHODS

In this multicentre, double-blind, parallel group, placebo-controlled study, the effect of a single dose of zamifenacin 10 mg or 40 mg on both fasting (30 min) and fed (60 min) colonic motor activity was assessed in 36 patients with irritable bowel syndrome (aged 25-68 years; 19 male). Colonic motility was recorded using a five-channel solid-state catheter introduced by colonoscopy to a depth of 35 cm in an unprepared colon.

RESULTS

Zamifenacin 40 mg profoundly reduced colonic motility, particularly after the meal (P < 0.05). This was reflected by a significant reduction in the mean amplitude of contractions, number of contractions, percentage duration of contractions, activity index and the motility index (P < 0.05). A smaller reduction in all the motility parameters was obtained with 10 mg zamifenacin, but these changes were not statistically significant. Three patients each on placebo and zamifenacin reported side-effects, but these were mild and transient.

CONCLUSION

A single 40 mg dose of zamifenacin significantly reduces colonic motility in irritable bowel syndrome patients without significant antimuscarinic effects. The results of this study confirm that the concept of developing selective antimuscarinic agents may be a promising approach to the treatment of irritable bowel syndrome. Not only would such compounds benefit from not having the usual side-effects of anticholinergics but they might also offer much more in the way of dose flexibility.

Large-scale ambulatory study of postprandial jejunal motility in irritable bowel syndrome

BACKGROUND

The relationship of small-bowel dysmotility to dietary intake in irritable bowel syndrome (IBS) is obscure.

METHODS

This study evaluated postprandial jejunal motility in IBS patients classified as constipation-predominant (n = 25) or diarrhoea-predominant (n = 35) and compared results against 18 volunteers. Twenty-four-hour ambulatory jejunal manometry was carried out in all subjects, and recordings were analysed by microcomputer and visual assessment.

RESULTS

By means of analysis of variance (fitting factors for channels, meals, and time periods) postprandial contraction frequency was greater in both patient groups compared with normal (constipation-predominant versus normal, diarrhoea-predominant versus normal; P < 0.001). In the constipation-predominant cohort, contraction amplitudes were lower (constipation-predominant versus normal; P < 0.002). Discrete cluster contractions occurred with similar frequency and duration in both patient and volunteer groups.

CONCLUSIONS

Quantitative differences of postprandial jejunal contraction characteristics have been shown between patients with IBS and healthy volunteers. Contraction frequency is greater than normal in both diarrhoea- and constipation-predominant categories, whereas contraction amplitudes are lower in constipation-predominant patients.

Influence of cell interactions in a novel model of postnatal mucosal regeneration

BACKGROUND AND AIMS

Conventional models of postnatal mucosal regeneration are cumbersome and limited: a novel model is described here. In addition, the influence of cell interactions on mucosal regeneration is examined within the model.

METHODS

Postnatal rat small intestinal mucosa was digested by enzymes to yield heterotypic cell aggregates (CA). CA colony forming ability, growth, and limited cytodifferentiation were assessed in vitro. CA were transplanted subcutaneously and retrieved for histological examination at staggered intervals to assess neomucosal morphogenesis and cytodifferentiation in vivo. Cell interactions in CA were disrupted by enzymes, thus producing cell suspensions (CS). Regeneration by CA and CS were compared.

RESULTS

CA produced proliferative colonies in vitro and showed a temporal sequence of neomucosal morphogenesis and differentiation in vivo. CA colonies were more numerous within 24 hours of primary culture and had greater cellularity by 96 hours than CS colonies. Alkaline phosphatase was expressed only by 258 of 696 CA colonies (37%). CA subcutaneous grafts (48 of 56 (87%)) regenerated small intestinal neomucosa while CS were unsuccessful.

CONCLUSION

These methods provide a model of mucosal regeneration which includes constituent processes of colony formation, growth, neomucosal morphogenesis, and cytodifferentiation. Preservation of cell interactions within CA seems advantageous to regeneration within the model.

The GLUT5 hexose transporter is also localized to the basolateral membrane of the human jejunum

The intestine is a major site of expression of the human GLUT5 hexose transporter, which is thought to be localized exclusively to the brush border membrane (BBM) where its major role is likely to be in the absorption of fructose. In this study we present novel biochemical and morphological evidence showing that the GLUT5 transporter is also expressed in the basolateral membrane (BLM) of the human intestine. BBM and BLM were isolated by fractionation of human jejunum. BBM were enriched with alkaline phosphatase activity by over 9-fold relative to a crude jejunal homogenate and contained immunoreactive sucrase-isomaltase and GLUT5 proteins. By contrast the BBM fraction was substantially depleted of immunoreactive a1 subunits of the Na,K-ATPase and GLUT2 glucose transporters which were abundantly present in the BLM fraction. This BLM fraction was enriched by over 11-fold in potassium-stimulated phosphatase activity relative to the crude homogenate; BLM also reacted to immunological probes for GLUT5 but showed no observable reactivity with antibodies directed against sucrase-isomaltase. Quantitative immunoblotting revealed that the BBM and BLM contained near equal amounts of GLUT5 per mg of membrane protein. Immunogold localization of GLUT5 on ultrathin sections of human jejunum showed that GLUT5 was present in both apical BBM and BLM. This gold labelling was absent when antiserum was pre-incubated with the antigenic peptide corresponding to a specific C-terminal sequence of human GLUT5. Quantitative analyses of the number of gold particles per unit length of BBM and BLM indicated that the mean density of gold labelling was marginally greater in the BBM (0.399 gold particles/micrometer) than in the BLM (0.293 gold particle/micrometer). The localization of GLUT5 in the BLM of the human jejunum may suggest that it specifically participates in the transfer of fructose across the basal membrane of the enterocyte.

Importance of reflux symptoms in functional dyspepsia

The relation between symptom severity in gastro-oesophageal reflux disease (GORD) and quantitated oesophageal acid reflux is variable. Furthermore, when oesophageal acid exposure lies within the conventional normal range, the cause of the symptoms is unknown. This prospective study evaluated 24 hour ambulatory oesophageal pH profiles in relation to objective symptom scores in 100 dyspeptic patients who were free from ulcer and gall stones. Twenty patients had raised oesophageal acid exposure and reflux symptoms consistent with GORD, and 80 had oesophageal pH profiles within the conventional normal range. Forty four of the 80 had severe or moderate reflux symptoms and were classified as having reflux like functional dyspepsia (RFD); 36 had minimal or absent reflux symptoms, and were categorised as having non-reflux dyspepsia (NFD). While oesophageal pH profiles lay within the conventional normal range in both functional dyspepsia subgroups, patients with RFD had consistently greater acid exposure values as follows: mean (SEM) total oesophageal acid exposure time, RFD 16.2 (2.56) min v NFD 9.05 (2.0) min (p < 0.03); percentage of time with pH < 4, RFD 1.4 (0.2) v NFD 0.8 (0.2) (p < 0.03); DeMeester scores, RFD 12.8 (0.5) v NFD 11.4 (0.4) (p < 0.03). The RFD group had a pain/reflux event correlation of 23.8 (5.3)% v 8.1 (3.7)% for the NFD group (p < 0.01). This study shows that patients with RFD have oesophageal acid exposure that lies below the diagnostic threshold for GORD, but exceeds that of patients with NFD. The high pain/reflux event correlation in RFD, suggests that subthreshold oesophageal acid exposure may be associated with troublesome reflux symptoms.

Does neomucosa induced by small bowel stem cell transplantation have adequate function?

Small intestinal epithelium digests and absorbs nutrients. Crypt stem cell transplantation can generate neomucosa with normal morphology, but the digestive and absorptive capacities of this neomucosa are unknown. This study evaluates stem cell induced neomucosal brush border digestive enzyme activity and nutrient transport function. Rodent small intestinal epithelial stem cells were isolated by enzymatic digestion, then grafted to inbred recipients. Grafts were retrieved at 25 days, and apical brush border membrane vesicles prepared for quantitative assays. Neomucosal lactase, sucrase, aminopeptidase N, and alkaline phosphatase activity was determined by incubation with enzyme specific substrate. Neomucosal sodium dependent D-glucose transport was evaluated by incubation with D-[U-14C] glucose. Comparative assays were performed in age-matched control intestine. Neomucosal digestive enzyme activities and D-glucose transport were all similar in neomucosa and control small intestine.

Generation of neomucosa in vivo by transplantation of dissociated rat postnatal small intestinal epithelium

A novel method to study the generation of rat small intestinal mucosa, by transplantation of disaggregated postnatal rat small intestinal epithelium is described. Cellular aggregates, comprised of epithelium with attached proliferative cells and closely associated stromal tissue, were isolated from postnatal rat small intestine by enzymatic digestion, then grafted immediately to the subcutaneous plane of adult recipients. On graft retrieval after 14 days, 39% of cellular transplants to nude mice, and 84% of cellular transplants to inbred rats had developed into small intestine-like structures. These structures were comprised of a circumferential layer of epithelium surrounding a central mucin filled lumen. This neomucosal layer exhibited well formed crypts and villi, and contained all epithelial stem cell lineages i.e. absorptive enterocytes, goblet cells, Paneth's cells and entero-endocrine cells. Proliferative activity within this neomucosa was confined to crypt regions as in normal postnatal small intestine. Developmental maturation within the regenerated neomucosa was demonstrated by organotypic morphogenesis, i.e. formation of mature crypts and villi, and progressive cytodifferentiation with increased numbers of goblet cells, entero-endocrine cells and Paneth's cells. Altered patterns of brush border enzyme expression further confirmed a temporal progression of development within neomucosal enterocytes. It is concluded that after "extensive" mucosal disaggregation, postnatal small intestinal epithelial progenitor cells retain the capacity for organotypic regeneration of neomucosa when transplanted to ectopic sites in adult recipients. These small aggregates of epithelium and stroma are capable of generating the topographical signals necessary for the three dimensional regeneration of this tissue. Furthermore, the multipotent generative potential of the stem cells within these cellular aggregates is maintained with production of all progeny.

Active transport of benzo[a]pyrene in apical membrane vesicles from normal human intestinal epithelium

Transport of the carcinogen benzo[a]pyrene in apical membrane vesicles (AMV) from normal human intestine, was investigated. Benzo[a]pyrene transport was found in AMV throughout the small intestine, but was greatest in colon. Evidence suggesting involvement of P-Glycoprotein (P-Gp), included (1) comparable transport of P-Gp substrate doxorubicin, (2) transport stimulation by ATP and (3) transport suppression by the P-Gp inhibitor, verapamil.

Generation of neomucosa in vivo by transplantation of dissociated rat postnatal small intestinal epithelium

A novel method to study the generation of rat small intestinal mucosa, by transplantation of disaggregated postnatal rat small intestinal epithelium is described. Cellular aggregates, comprised of epithelium with attached proliferative cells and closely associated stromal tissue, were isolated from postnatal rat small intestine by enzymatic digestion, then grafted immediately to the subcutaneous plane of adult recipients. On graft retrieval after 14 days, 39% of cellular transplants to nude mice, and 84% of cellular transplants to inbred rats had developed into small intestine-like structures. These structures were comprised of a circumferential layer of epithelium surrounding a central mucin filled lumen. This neomucosal layer exhibited well formed crypts and villi, and contained all epithelial stem cell lineages i.e. absorptive enterocytes, goblet cells, Paneth's cells and entero-endocrine cells. Proliferative activity within this neomucosa was confined to crypt regions as in normal postnatal small intestine. Developmental maturation within the regenerated neomucosa was demonstrated by organotypic morphogenesis, i.e. formation of mature crypts and villi, and progressive cytodifferentiation with increased numbers of goblet cells, entero-endocrine cells and Paneth's cells. Altered patterns of brush border enzyme expression further confirmed a temporal progression of development within neomucosal enterocytes. It is concluded that after "extensive" mucosal disaggregation, postnatal small intestinal epithelial progenitor cells retain the capacity for organotypic regeneration of neomucosa when transplanted to ectopic sites in adult recipients. These small aggregates of epithelium and stroma are capable of generating the topographical signals necessary for the three dimensional regeneration of this tissue. Furthermore, the multipotent generative potential of the stem cells within these cellular aggregates is maintained with production of all progeny.

Progressive morphogenesis in vivo after transplantation of cultured small bowel epithelium

An experimental model for the primary culture and transplantation of late foetal rat small intestinal epithelium is described. Multicellular aggregates of mucosal epithelium containing pre-crypt proliferative cells were isolated from 20-day foetal rat intestine by enzymatic disaggregation. Cellular aggregates, which we refer to as "epithelial organoids," attached readily in culture, proliferated, and spread to produce coalescing colonies within 10 days. Enterocytes were maintained in culture for 3 days, removed as cell sheets, and incubated overnight with foetal mesenchyme. Fourteen recombinant preparations were then grafted to the renal subcapsular space of adult nude mice. Four of six grafts retrieved after 1 wk had developed. Histology demonstrated the formation of simple tubular structures lined by a polarized columnar epithelium. At 14 days, two of eight grafts had developed and demonstrated temporal progression of morphogenesis. Histology showed rudimentary crypts and villi lined by different epithelial cell types, including enterocytes and goblet cells. Small bowel proliferative cells within "epithelial organoids" from 20-day foetal intestine, may be maintained in primary culture for up to four days. After short term primary culture, these proliferative cells retain the capacity for progressive organotypic morphogenesis and pluripotent cytodifferentiation, after transplantation to adult recipients.

Colonic mucosal replacement by syngeneic small intestinal stem cell transplantation

A novel method of colonic mucosal replacement by transplantation of disaggregated small intestinal epithelium is described. Thirty-one inbred rats had the ascending colon isolated, and surgical mucosectomy was performed on the "free" loop. Epithelial cell aggregates were isolated from postnatal small intestine using collagenase and dispase digestion, then 20 microL of the cell suspension was "seeded" over the denuded colonic muscle of 25 recipient rats. Six control rats had surgical mucosectomy only. All loops were retrieved after 14 days for histologic examination. Stem cell lineage studies were used with selective staining protocols to identify enterocytes, goblet cells, entero-endocrine cells, and Paneth cells. A neomucosa with typical small bowel morphology including crypts and villi and all four stem cell lineages was regenerated by transplanted cells on the colonic muscle in 19 of 25 (76%) recipients. Control loops showed no epithelial regrowth confirming total mucosectomy. With appropriate stromal support, transplanted small intestinal stem cells have the capacity to re-epithelialize denuded colonic muscle with small bowel neomucosa.