Complex co-localization of chromogranins and neurohormones in the human gastrointestinal tract

Reproductive health of the sow during puerperium

The modern hyperprolific sow is susceptible to metabolic disease and chronic inflammation. The most sensitive phase is parturition, when the sow experiences systemic inflammation and stress, and major changes in metabolism and endocrinology. Resolution of inflammation and stress needs to happen quickly to ensure good reproductive health during puerperium. If the sow fails to adapt to these changes, puerperal disease may occur. The economically most important puerperal disease complex is the postpartum dysgalactia syndrome (PPDS). Other puerperal diseases include infections of the urogenital tract. Diagnosis of PPDS and urogenital disease on-farm is challenging but several diagnostic methods, including clinical examination, behavioral observations, ultrasonography and biomarkers are available. Ultrasonography is an excellent tool for monitoring the health of the urogenital tract, the mammary gland, and uterine involution and guide further diagnostic interventions. Biomarkers such as Chromogranin A, tumor necrosis factor-α, and interleukin-6 represent promising tools to monitor general health and the systemic state of inflammation and oxidative stress of the sow. Nonsteroidal anti-inflammatory drugs, dopamine antagonists, and oxytocin are promising to address the symptoms of PPDS. Reducing of stress, improving nutrition and intestinal health, and supporting animal welfare-friendly husbandry help in the prevention of PPDS.

A LGR5 reporter pig model closely resembles human intestine for improved study of stem cells in disease

Intestinal epithelial stem cells (ISCs) are responsible for intestinal epithelial barrier renewal; thereby, ISCs play a critical role in intestinal pathophysiology research. While transgenic ISC reporter mice are available, advanced translational studies lack a large animal model. This study validates ISC isolation in a new porcine Leucine Rich Repeat Containing G Protein-Coupled Receptor 5 (LGR5) reporter line and demonstrates the use of these pigs as a novel colorectal cancer (CRC) model. We applied histology, immunofluorescence, fluorescence-activated cell sorting, flow cytometry, gene expression quantification, and 3D organoid cultures to whole tissue and single cells from the duodenum, jejunum, ileum, and colon of LGR5-H2B-GFP and wild-type pigs. Ileum and colon LGR5-H2B-GFP, healthy human, and murine biopsies were compared by mRNA fluorescent in situ hybridization (FISH). To model CRC, adenomatous polyposis coli (APC) mutation was induced by CRISPR/Cas9 editing in porcine LGR5-H2B-GFP colonoids. Crypt-base, green fluorescent protein (GFP) expressing cells co-localized with ISC biomarkers. LGR5-H2B-GFPhi cells had significantly higher LGR5 expression (p < .01) and enteroid forming efficiency (p < .0001) compared with LGR5-H2B-GFPmed/lo/neg cells. Using FISH, similar LGR5, OLFM4, HOPX, LYZ, and SOX9 expression was identified between human and LGR5-H2B-GFP pig crypt-base cells. LGR5-H2B-GFP/APCnull colonoids had cystic growth in WNT/R-spondin-depleted media and significantly upregulated WNT/β-catenin target gene expression (p < .05). LGR5+ ISCs are reproducibly isolated in LGR5-H2B-GFP pigs and used to model CRC in an organoid platform. The known anatomical and physiologic similarities between pig and human, and those shown by crypt-base FISH, underscore the significance of this novel LGR5-H2B-GFP pig to translational ISC research.

Case Report: Severe Hypocalcemic Episodes Due to Autoimmune Enteropathy

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare monogenic disorder, associated with endocrine deficiencies and non-endocrine involvement. Gastrointestinal (GI) manifestations appear in approximately 25% of patients and are the presenting symptom in about 10% of them. Limited awareness among pediatricians of autoimmune enteropathy (AIE) caused by destruction of the gut endocrine cells in APECED patients delays diagnosis and appropriate therapy. We describe an 18-year-old female presenting at the age of 6.10 years with hypoparathyroidism, oral candidiasis and vitiligo. The clinical diagnosis of APECED was confirmed by sequencing the autoimmune regulator-encoding (AIRE) gene. Several characteristics of the disease-Hashimoto's thyroiditis, Addison's disease, diabetes mellitus type 1 and primary ovarian insufficiency-developed over the years. She had recurrent episodes of severe intractable hypocalcemia. Extensive GI investigations for possible malabsorption, including laboratory analyses, imaging and endoscopy with biopsies were unremarkable. Revision of the biopsies and chromogranin A (CgA) immunostaining demonstrated complete loss of enteroendocrine cells in the duodenum and small intestine, confirming the diagnosis of AIE. Management of hypocalcemia was challenging. Only intravenous calcitriol maintained calcium in the normal range. Between hypocalcemic episodes, the proband maintained normal calcium levels, suggesting a fluctuating disease course. Repeated intestinal biopsy revealed positive intestinal CgA immunostaining. The attribution of severe hypocalcemic episodes to AIE emphasizes the need for increased awareness of this unique presentation of APECED. The fluctuating disease course and repeated intestinal biopsy showing positive CgA immunostaining support a reversible effect of GI involvement. CgA immunostaining is indicated in patients with APECED for whom all other investigations have failed to reveal an explanation for the malabsorption.

Generation of an enteric smooth muscle cell line from the pig ileum

Smooth muscle cells (SMCs) play an important role in physiology and production in farm animals such as pigs. Here, we report the generation of a pig SMC line. Our original objective was to establish an enteroendocrine cell line from the pig ileum epithelium through lentiviral transduction of the Simian Virus (SV) 40 large T antigen. However, an initial expression analysis of marker genes in nine cell clones revealed that none of them were enteroendocrine cells or absorptive enterocytes, goblet cells, or Paneth cells, some of the major cell types existing in the ileum epithelium. A more detailed characterization of one clone named PIC7 by RNA-seq showed that these cells expressed many of the known smooth muscle-specific or -enriched genes, including smooth muscle actin alpha 2, calponin 1, calponin 3, myosin heavy chain 11, myosin light chain kinase, smoothelin, tenascin C, transgelin, tropomyosin 1, and tropomyosin 2. Both quantitative PCR and RNA-seq analyses showed that the PIC7 cells had a high expression of mRNA for smooth muscle actin gamma 2, also known as enteric smooth muscle actin. A Western blot analysis confirmed the expression of SV40 T antigen in the PIC7 cells. An immunohistochemical analysis demonstrated the expression of smooth muscle actin alpha 2 filaments in the PIC7 cells. A collagen gel contraction assay showed that the PIC7 cells were capable of both spontaneous contraction and contraction in response to serotonin stimulation. We conclude that the PIC7 cells are derived from an enteric SMC from the pig ileum. These cells may be a useful model for studying the cellular and molecular physiology of pig enteric SMCs. Because pigs are similar to humans in anatomy and physiology, the PIC7 cells may be also used as a model for human intestinal SMCs.

Hormonal and metabolic indicators before and after farrowing in sows affected with postpartum dysgalactia syndrome

BACKGROUND

Postpartum dysgalactia syndrome (PDS) in sows is difficult to diagnose and the pathogenesis is obscure. Hormonal changes related to the disease are often difficult to distinguish from those found in the normal transition period from gestation to lactation. The study aimed to investigate metabolic and hormonal changes related to PDS with the goal of identifying potential biomarkers in sows suffering from PDS (PDS+). Selected biomarkers were examined by comparing 38 PDS+ sows with 38 PDS negative (PDS-) sows. The sows were sampled every 24 h from 60 h ante partum (a.p.) to 36 h post partum (p.p.).

RESULTS

Compared to the baseline (60 to 36 h a.p.), cortisol in serum and saliva and fasting blood glucose concentrations increased in PDS+ as well as PDS- sows. C-peptide decreased relative to the baseline in PDS+ sows, and prolactin and 8-epi prostaglandin F2 alpha (8-epi-PGF2α) decreased in PDS- sows. Concentrations of cortisol in serum and saliva, salivary chromogranin A (CgA), fasting blood glucose, C-peptide, and 8-epi-PGF2α differed significantly between PDS+ and PDS- sows, with levels of cortisol in serum and saliva, salivary CgA, and 8-epi-PGF2α in serum being different in the two groups already before parturition. Concentrations of salivary CgA were significantly lower in PDS- sows than in PDS+ sows during the entire study period.

CONCLUSIONS

The results suggest that salivary CgA, cortisol and serum 8-epi-PGF2α may potentially serve as early diagnostic indicators for PDS. The consistently higher salivary CgA concentration in PDS+ sows compared to PDS- sows may indicate that homeostatic disturbances are present between 36 to 60 h before parturition in sows developing PDS. The higher serum and saliva cortisol concentration in PDS+ sows compared to PDS- sows could reflect an early sign of inflammation or stress. The significantly lower C-peptide in PDS+ sows compared to PDS- sows may reflect a lower food intake. Our results contribute to the understanding of the pathogenesis of PDS, and the homeostatic disturbances detected before parturition warrants further investigation. The diagnostic potential of the markers identified in this study should be investigated further in a larger population of sows.

Advanced three-dimensional culture of equine intestinal epithelial stem cells

BACKGROUND

Intestinal epithelial stem cells are critical to epithelial repair following gastrointestinal injury. The culture of intestinal stem cells has quickly become a cornerstone of a vast number of new research endeavours that range from determining tissue viability to testing drug efficacy for humans. This study aims to describe the methods of equine stem cell culture and highlights the future benefits of these techniques for the advancement of equine medicine.

OBJECTIVES

To describe the isolation and culture of small intestinal stem cells into three-dimensional (3D) enteroids in horses without clinical gastrointestinal abnormalities.

STUDY DESIGN

Descriptive study.

METHODS

Intestinal samples were collected by sharp dissection immediately after euthanasia. Intestinal crypts containing intestinal stem cells were dissociated from the underlying tissue layers, plated in a 3D matrix and supplemented with growth factors. After several days, resultant 3D enteroids were prepared for immunofluorescent imaging and polymerase chain reaction (PCR) analysis to detect and characterise specific cell types present. Intestinal crypts were cryopreserved immediately following collection and viability assessed.

RESULTS

Intestinal crypts were successfully cultured and matured into 3D enteroids containing a lumen and budding structures. Immunofluorescence and PCR were used to confirm the existence of stem cells and all post mitotic, mature cell types, described to exist in the horse intestinal epithelium. Previously frozen crypts were successfully cultured following a freeze-thaw cycle.

MAIN LIMITATIONS

Tissues were all derived from normal horses. Application of this technique for the study of specific disease was not performed at this time.

CONCLUSIONS

The successful culture of equine intestinal crypts into 3D "mini-guts" allows for in vitro studies of the equine intestine. Additionally, these results have relevance to future development of novel therapies that harness the regenerative potential of equine intestine in horses with gastrointestinal disease (colic).

Costorage of Enteroendocrine Hormones Evaluated at the Cell and Subcellular Levels in Male Mice

Recent studies reveal complex patterns of hormone coexpression within enteroendocrine cells (EECs), contrary to the traditional view that gut hormones are expressed individually in EECs. Moreover, different hormones have been found in separate subcellular vesicles. However, detailed analysis of relative expression of multiple hormones has not been made. Subcellular studies have been confined to peptide hormones, and have not included the indolamine 5-hydroxytryptamine (5-HT) or the neuroendocrine protein chromogranin A (CgA). In the present work, coexpression of 5-HT, CgA, secretin, cholecystokinin (CCK), ghrelin, and glucagonlike peptide (GLP)-1 in mouse duodenum was quantified at a cellular and subcellular level by semiautomated cell counting and quantitative vesicle measurements. We investigated whether relative numbers of cells with colocalized hormones analyzed at a cell level matched the numbers revealed by examination of individual storage vesicles within cells. CgA and 5-HT were frequently expressed in EECs that contained combinations of GLP-1, ghrelin, secretin, and CCK. Separate subcellular stores of 5-HT, CgA, secretin, CCK, ghrelin, and GLP-1 were identified. In some cases, high-resolution analysis revealed small numbers of immunoreactive vesicles in cells dominated by a different hormone. Thus the observed incidence of cells with colocalized hormones is greater when analyzed at a subcellular, compared with a cellular, level. Subcellular analysis also showed that relative numbers of vesicles differ considerably between cells. Thus separate packaging of hormones that are colocalized is a general feature of EECs, and EECs exhibit substantial heterogeneity, including the colocalization of hormones that were formerly thought to be in cells of different lineages.

Cellular localization of guanylin and uroguanylin mRNAs in human and rat duodenal and colonic mucosa

Guanylin (GUCA2A/Guca2a/GN) and uroguanylin (GUCA2B/Guca2b/UGN) are expressed in the gastrointestinal tract and have been implicated in ion and fluid homeostasis, satiety, abdominal pain, growth and intestinal barrier integrity. Their cellular sources are debated and include goblet cells, entero-/colonocytes, enteroendocrine (EE) cells and tuft cells. We therefore investigated the cellular sources of GN and UGN mRNAs in human and rat duodenal and colonic epithelium with in situ hybridization (ISH) to determine co-expression with Chromogranin A (CHGA/Chga/CgA; enterochromaffin [EC] cells), defensin alpha 6 (DEFA6/Defa6; Paneth cells), mucin 2 (MUC2/Muc2; goblet cells) and selected tuft cell markers. GUCA2A/Guca2a expression was localized to goblet cells and colonocytes in human and rat colon. In human duodenum, GUCA2A was expressed in Paneth cells and was scarce in villous epithelial cells. In rat duodenum, Guca2a was only localized to goblet cells. Guca2b was focally expressed in rat colon. In human and rat duodenum and in human colon, GUCA2B/Guca2b was expressed in dispersed solitary epithelial cells, some with a tuft cell-like appearance. Neither GUCA2A nor GUCA2B were co-expressed with CHGA in human duodenal cells. Consequently, EC cells are probably not the major source of human GN or UGN but other EE cells as a source of GN or UGN are not entirely excluded. No convincing overlap with tuft cell markers was found. For the first time, we demonstrate the cellular expression of GUCA2B in human duodenum. The specific cellular distribution of both GN and UGN differs between duodenum and colon and between human and rat intestines.

Abundance and turnover of GLP-1 producing L-cells in ileal mucosa are not different in patients with and without type 2 diabetes

INTRODUCTION

The gastrointestinal hormone GLP-1 is released from enteroendocrine L-cells and augments postprandial insulin secretion. In patients with type 2 diabetes, the incretin effect is markedly diminished. It is unclear, whether this is due to a reduction in the abundance of L-cells in the intestine.

METHODS

Ileal tissue samples from 10 patients with and 10 patients without diabetes that underwent surgery for the removal of colon tumors were included. Tissue sections were stained for GLP-1, Ki67, TUNEL and chromogranin A.

RESULTS

The number of L-cells was not different between patients with and without diabetes in either crypts (1.81±0.21% vs. 1.49±0.24%, respectively; p=0.31) or villi (1.07±0.16% vs. 0.83±0.10%, respectively; p=0.23). L-cell number was higher in crypts than in villi (p<0.0001). L-cell replication was detected rarely and not different between the groups. L-cell apoptosis was similar in patients with and without diabetes in both crypts (7.84±2.77% vs. 8.65±3.77%, p=0.85) and villi (4.48±2.89% vs. 8.62±4.64%, p=0.42). Chromogranin A staining was found in a subset of L-cells only.

CONCLUSIONS

Intestinal L-cell density is higher in crypts than in villi. Chromogranin A is not a prerequisite for GLP-1 production. L-cell density and turnover are not different between patients with and without diabetes. Thus, alterations in the number of GLP-1 producing cells do not explain the reduced incretin effect in patients with type 2 diabetes.

Research Resource: A Chromogranin A Reporter for Serotonin and Histamine Secreting Enteroendocrine Cells

Chromogranin A (ChgA) is an acidic protein found in large dense-core secretory vesicles and generally considered to be expressed in all enteroendocrine cells of the gastrointestinal (GI) tract. Here, we characterize a novel reporter mouse for ChgA, ChgA-humanized Renilla reniformis (hr)GFP. The hrGFP reporter was found in the monoamine-storing chromaffin cells of the adrenal medulla, where ChgA was originally discovered. hrGFP also was expressed in enteroendocrine cells throughout the GI tract, faithfully after the expression of ChgA, as characterized by immunohistochemistry and quantitative PCR analysis of fluorescence-activated cell sorting-purified cells, although the expression in the small intestine was weak compared with that of the stomach and colon. In the stomach, hrGFP was highly expressed in almost all histamine-storing enterochromaffin (EC)-like cells, at a lower level in the majority of serotonin-storing EC cells and ghrelin cells, in a small fraction of somatostatin cells, but was absent from gastrin cells. In the small intestine, the hrGFP reporter was selectively, but weakly expressed in EC cells, although not in any peptide-storing enteroendocrine cells. In the colon, hrGFP was exclusively expressed in EC cells but absent from the peptide-storing enteroendocrine cells. In contrast, in the pancreas, hrGFP was expressed in β-cells, α-cells, and a fraction of pancreatic polypeptide cells. It is concluded that ChgA-hrGFP in the GI tract functions as an effective reporter, particularly for the large populations of still poorly characterized monoamine-storing enteroendocrine cells. Furthermore, our findings substantiate the potential function of ChgA as a monoamine-binding protein that facilitates the regulated endocrine secretion of large amounts of monoamines from enteroendocrine cells.

Expression of Secretogranin III in Chicken Endocrine Cells: Its Relevance to the Secretory Granule Properties of Peptide Prohormone Processing and Bioactive Amine Content

The expression of secretogranin III (SgIII) in chicken endocrine cells has not been investigated. There is limited data available for the immunohistochemical localization of SgIII in the brain, pituitary, and pancreatic islets of humans and rodents. In the present study, we used immunoblotting to reveal the similarities between the expression patterns of SgIII in the common endocrine glands of chickens and rats. The protein-protein interactions between SgIII and chromogranin A (CgA) mediate the sorting of CgA/prohormone core aggregates to the secretory granule membrane. We examined these interactions using co-immunoprecipitation in chicken endocrine tissues. Using immunohistochemistry, we also examined the expression of SgIII in a wide range of chicken endocrine glands and gastrointestinal endocrine cells (GECs). SgIII was expressed in the pituitary, pineal, adrenal (medullary parts), parathyroid, and ultimobranchial glands, but not in the thyroid gland. It was also expressed in GECs of the stomach (proventriculus and gizzard), small and large intestines, and pancreatic islet cells. These SgIII-expressing cells co-expressed serotonin, somatostatin, gastric inhibitory polypeptide, glucagon-like peptide-1, glucagon, or insulin. These results suggest that SgIII is expressed in the endocrine cells that secrete peptide hormones, which mature via the intragranular enzymatic processing of prohormones and physiologically active amines in chickens.

The glucagon-like peptide 2 receptor is expressed in enteric neurons and not in the epithelium of the intestine

Glucagon-like peptide 2 (GLP-2) is a potent intestinotrophic growth factor with therapeutic potential in the treatment of intestinal deficiencies. It has recently been approved for the treatment of short bowel syndrome. The effects of GLP-2 are mediated by specific binding of the hormone to the GLP-2 receptor (GLP-2R) which was cloned in 1999. However, consensus about the exact receptor localization in the intestine has never been established. By physical, chemical and enzymatic tissue fragmentation, we were able to divide rat jejunum into different compartments consisting of: (1) epithelium alone, (2) mucosa with lamina propria and epithelium, (3) the external muscle coat including myenteric plexus, (4) a compartment enriched for the myenteric plexus and (5) intestine without epithelium. Expression of Glp2r; chromogranin A; tubulin, beta 3; actin, gamma 2, smooth muscle, enteric and glial fibrillary acidic protein in these isolated tissue fractions was quantified with qRT-PCR. Expression of the Glp2r was confined to compartments containing enteric neurons and receptor expression was absent in the epithelium. Our findings provide evidence for the expression of the GLP-2R in intestinal compartments rich in enteric neurons and, importantly they exclude significant expression in the epithelium of rat jejunal mucosa.

The effect of ileal interposition surgery on enteroendocrine cell numbers in the UC Davis type 2 diabetes mellitus rat

AIM

To investigate the short-term effect of ileal interposition (IT) surgery on gut morphology and enteroendocrine cell numbers in the pre-diabetic UC Davis type 2 diabetes mellitus (UCD-T2DM) rat.

STUDY DESIGN

Two-month old male UCD-T2DM rats underwent either sham (n=5) or IT (n=5) surgery. Intestines were collected 1.5months after surgery. The jejunum, ileum and colon regions were processed for histochemical and immunohistochemical labeling and stereological analyses of changes in gut morphometry and number of enteroendocrine cells.

RESULTS

Stereological analysis showed that intestinal volume, luminal surface area and the number of all chromogranin A-positive enteroendocrine cells were markedly increased in the IT rats compared with sham-operated animals. Subanalyses of the glucagon-like peptide 2, cholecystokinin, serotonin cells and the neurotensin immunoreactive sub-pool of enteroendocrine cells in the IT region revealed an increase in numbers across phenotypes. However, the density of the different cell types varied.

CONCLUSION

IT surgery in the UCD-T2DM rat leads to rapid alterations in gut morphometry and an increase in the number of enteroendocrine cells. This effect may potentially explain why IT surgery delays the onset of type 2 diabetes in the UCD-T2DM rat.

Grape-seed procyanidins prevent the cafeteria-diet-induced decrease of glucagon-like peptide-1 production

Grape-seed procyanidin extract (GSPE) has been reported to improve insulin resistance in cafeteria rats. Because glucagon-like peptide-1 (GLP-1) is involved in glucose homeostasis, the preventive effects of GSPE on GLP-1 production, secretion, and elimination were evaluated in a model of diet-induced insulin resistance. Rats were fed a cafeteria diet for 12 weeks, and 25 mg of GSPE/kg of body weight was administered concomitantly. Vehicle-treated cafeteria-fed rats and chow-fed rats were used as controls. The cafeteria diet decreased active GLP-1 plasma levels, which is attributed to a decreased intestinal GLP-1 production, linked to reduced colonic enteroendocrine cell populations. Such effects were prevented by GSPE. In the same context, GSPE avoided the decrease on intestinal dipeptidyl-peptidase 4 (DPP4) activity and modulated the gene expression of GLP-1 and its receptor in the hypothalamus. In conclusion, the preventive treatment with GSPE abrogates the effects of the cafeteria diet on intestinal GLP-1 production and DPP4 activity.

Cell lineage identification and stem cell culture in a porcine model for the study of intestinal epithelial regeneration

Significant advances in intestinal stem cell biology have been made in murine models; however, anatomical and physiological differences between mice and humans limit mice as a translational model for stem cell based research. The pig has been an effective translational model, and represents a candidate species to study intestinal epithelial stem cell (IESC) driven regeneration. The lack of validated reagents and epithelial culture methods is an obstacle to investigating IESC driven regeneration in a pig model. In this study, antibodies against Epithelial Adhesion Molecule 1 (EpCAM) and Villin marked cells of epithelial origin. Antibodies against Proliferative Cell Nuclear Antigen (PCNA), Minichromosome Maintenance Complex 2 (MCM2), Bromodeoxyuridine (BrdU) and phosphorylated Histone H3 (pH3) distinguished proliferating cells at various stages of the cell cycle. SOX9, localized to the stem/progenitor cells zone, while HOPX was restricted to the +4/‘reserve’ stem cell zone. Immunostaining also identified major differentiated lineages. Goblet cells were identified by Mucin 2 (MUC2); enteroendocrine cells by Chromogranin A (CGA), Gastrin and Somatostatin; and absorptive enterocytes by carbonic anhydrase II (CAII) and sucrase isomaltase (SIM). Transmission electron microscopy demonstrated morphologic and sub-cellular characteristics of stem cell and differentiated intestinal epithelial cell types. Quantitative PCR gene expression analysis enabled identification of stem/progenitor cells, post mitotic cell lineages, and important growth and differentiation pathways. Additionally, a method for long-term culture of porcine crypts was developed. Biomarker characterization and development of IESC culture in the porcine model represents a foundation for translational studies of IESC-driven regeneration of the intestinal epithelium in physiology and disease.

CD36-dependent signaling mediates fatty acid-induced gut release of secretin and cholecystokinin

Genetic variants in the fatty acid (FA) translocase FAT/CD36 associate with abnormal postprandial lipids and influence risk for the metabolic syndrome. CD36 is abundant on apical enterocyte membranes in the proximal small intestine, where it facilitates FA uptake and FA-initiated signaling. We explored whether CD36 signaling influences FA-mediated secretion of cholecystokinin (CCK) and secretin, peptides released by enteroendocrine cells (EECs) in the duodenum/jejunum, which regulate events important for fat digestion and homeostasis. CD36 was immunodetected on apical membranes of secretin- and CCK-positive EECs and colocalized with cytosolic granules. Intragastric lipid administration to CD36 mice released less secretin (-60%) and CCK (-50%) compared with wild-type mice. Likewise, diminished secretin and CCK responses to FA were observed with CD36 intestinal segments in vitro, arguing against influence of alterations in fat absorption. Signaling mechanisms underlying peptide release were examined in STC-1 cells stably expressing human CD36 or a signaling-impaired mutant (CD36K/A). FA stimulation of cells expressing CD36 (vs. vector or CD36K/A) released more secretin (3.5- to 4-fold) and CCK (2- to 3-fold), generated more cAMP (2- to 2.5-fold), and enhanced protein kinase A activation. Protein kinase A inhibition (H-89) blunted secretin (80%) but not CCK release, which was reduced (50%) by blocking of calmodulin kinase II (KN-62). Coculture of STC-1 cells with Caco-2 cells stably expressing CD36 did not alter secretin or CCK release, consistent with a minimal effect of adjacent enterocytes. In summary, CD36 is a major mediator of FA-induced release of CCK and secretin. These peptides contribute to the role of CD36 in fat absorption and to its pleiotropic metabolic effects.

CD36-dependent signaling mediates fatty acid-induced gut release of secretin and cholecystokinin

Genetic variants in the fatty acid (FA) translocase FAT/CD36 associate with abnormal postprandial lipids and influence risk for the metabolic syndrome. CD36 is abundant on apical enterocyte membranes in the proximal small intestine, where it facilitates FA uptake and FA-initiated signaling. We explored whether CD36 signaling influences FA-mediated secretion of cholecystokinin (CCK) and secretin, peptides released by enteroendocrine cells (EECs) in the duodenum/jejunum, which regulate events important for fat digestion and homeostasis. CD36 was immunodetected on apical membranes of secretin- and CCK-positive EECs and colocalized with cytosolic granules. Intragastric lipid administration to CD36 mice released less secretin (-60%) and CCK (-50%) compared with wild-type mice. Likewise, diminished secretin and CCK responses to FA were observed with CD36 intestinal segments in vitro, arguing against influence of alterations in fat absorption. Signaling mechanisms underlying peptide release were examined in STC-1 cells stably expressing human CD36 or a signaling-impaired mutant (CD36K/A). FA stimulation of cells expressing CD36 (vs. vector or CD36K/A) released more secretin (3.5- to 4-fold) and CCK (2- to 3-fold), generated more cAMP (2- to 2.5-fold), and enhanced protein kinase A activation. Protein kinase A inhibition (H-89) blunted secretin (80%) but not CCK release, which was reduced (50%) by blocking of calmodulin kinase II (KN-62). Coculture of STC-1 cells with Caco-2 cells stably expressing CD36 did not alter secretin or CCK release, consistent with a minimal effect of adjacent enterocytes. In summary, CD36 is a major mediator of FA-induced release of CCK and secretin. These peptides contribute to the role of CD36 in fat absorption and to its pleiotropic metabolic effects.

Endocrine cells in human fetal corpus of stomach: appearance, distribution, and density

BACKGROUND

Since reports on endocrine cells and their kinetics in the corpus of the human stomach are limited, the aim of this study was to examine the appearance, localization, density, and the relationship among the endocrine cell types in the corpus of the human stomach during prenatal and early postnatal development.

METHODS

We examined chromogranin A, somatostatin, ghrelin, glucagon, and serotonin expression by immunohistochemistry in 2 embryos, 38 fetuses, and 3 infants in the corpus of human stomach.

RESULTS

Chromogranin A secreting endocrine cells were identified in the corpus at week 10 of gestation. Somatostatin cells were present from the 10th week, ghrelin and serotonin cells from the 11th week, and glucagon cells from the 12th week of gestation. Endocrine cells were present individually or clustered within the glandular base and body during the first trimester, and were present separately within the basal and central parts of glands during the second and third trimesters. Somatostatin cells were the most common type of cells (~46 %) during the first trimester, while ghrelin cells were the most numerous during the second trimester (~34 %), and in infants (~28 %). The percentage of glucagon cells was significant only during the first trimester of pregnancy (5.5 %), and the percentage of serotonin cells was only significant just before birth (4.8 %).

CONCLUSIONS

These results show, for the first time, that the largest number of endocrine cells are present in the corpus during the first trimester of prenatal development. Also, these results suggest that secretory products of endocrine cells play a role in the regulation of homeostasis, growth, and differentiation, and in human stomach function.

Overlap of endocrine hormone expression in the mouse intestine revealed by transcriptional profiling and flow cytometry

The intestine secretes a range of hormones with important local and distant actions, including the control of insulin secretion and appetite. A number of enteroendocrine cell types have been described, each characterized by a distinct hormonal signature, such as K-cells producing glucose-dependent insulinotropic polypeptide (GIP), L-cells producing glucagon-like peptide-1 (GLP-1), and I-cells producing cholecystokinin (CCK). To evaluate similarities between L-, K-, and other enteroendocrine cells, primary murine L- and K-cells, and pancreatic α- and β-cells, were purified and analyzed by flow cytometry and microarray-based transcriptomics. By microarray expression profiling, L cells from the upper small intestinal (SI) more closely resembled upper SI K-cells than colonic L-cells. Upper SI L-cell populations expressed message for hormones classically localized to different enteroendocrine cell types, including GIP, CCK, secretin, and neurotensin. By immunostaining and fluorescence-activated cell sorting analysis, most colonic L-cells contained GLP-1 and PeptideYY In the upper SI, most L-cells contained CCK, approximately 10% were GIP positive, and about 20% were PeptideYY positive. Upper SI K-cells exhibited approximately 10% overlap with GLP-1 and 6% overlap with somatostatin. Enteroendocrine-specific transcription factors were identified from the microarrays, of which very few differed between the enteroendocrine cell populations. Etv1, Prox1, and Pax4 were significantly enriched in L-cells vs. K cells by quantitative RT-PCR. In summary, our data indicate a strong overlap between upper SI L-, K-, and I-cells and suggest they may rather comprise a single cell type, within which individual cells exhibit a hormonal spectrum that may reflect factors such as location along the intestine and exposure to dietary nutrients.

Dual regulatory role for phosphatase and tensin homolog in specification of intestinal endocrine cell subtypes

AIM: To investigate the impact of phosphatase and tensin homolog (Pten) in the specification of intestinal enteroendocrine subpopulations.

METHODS: Using the Cre/loxP system, a mouse with conditional intestinal epithelial Pten deficiency was generated. Pten mutant mice and controls were sacrificed and small intestines collected for immunofluorescence and quantitative real-time polymerase chain reaction. Blood was collected on 16 h fasted mice by cardiac puncture. Enzyme-linked immunosorbent assay was used to measure blood circulating ghrelin, somatostatin (SST) and glucose-dependent insulinotropic peptide (GIP) levels.

RESULTS: Results show an unexpected dual regulatory role for epithelial Pten signalling in the specification/differentiation of enteroendocrine cell subpopulations in the small intestine. Our data indicate that Pten positively regulates chromogranin A (CgA) expressing subpopulations, including cells expressing secretin, ghrelin, gastrin and cholecystokinin (CCK). In contrast, Pten negatively regulates the enteroendocrine subtype specification of non-expressing CgA cells such as GIP and SST expressing cells.

CONCLUSION: The present results demonstrate that Pten signalling favours the enteroendocrine progenitor to specify into cells expressing CgA including those producing CCK, gastrin and ghrelin.

Preferential entry of botulinum neurotoxin A Hc domain through intestinal crypt cells and targeting to cholinergic neurons of the mouse intestine

Botulism, characterized by flaccid paralysis, commonly results from botulinum neurotoxin (BoNT) absorption across the epithelial barrier from the digestive tract and then dissemination through the blood circulation to target autonomic and motor nerve terminals. The trafficking pathway of BoNT/A passage through the intestinal barrier is not yet fully understood. We report that intralumenal administration of purified BoNT/A into mouse ileum segment impaired spontaneous muscle contractions and abolished the smooth muscle contractions evoked by electric field stimulation. Entry of BoNT/A into the mouse upper small intestine was monitored with fluorescent HcA (half C-terminal domain of heavy chain) which interacts with cell surface receptor(s). We show that HcA preferentially recognizes a subset of neuroendocrine intestinal crypt cells, which probably represent the entry site of the toxin through the intestinal barrier, then targets specific neurons in the submucosa and later (90–120 min) in the musculosa. HcA mainly binds to certain cholinergic neurons of both submucosal and myenteric plexuses, but also recognizes, although to a lower extent, other neuronal cells including glutamatergic and serotoninergic neurons in the submucosa. Intestinal cholinergic neuron targeting by HcA could account for the inhibition of intestinal peristaltism and secretion observed in botulism, but the consequences of the targeting to non-cholinergic neurons remains to be determined.

Botulism is a severe and often fatal disease in man and animals characterized by flaccid paralysis. Clostridium botulinum produces a potent neurotoxin (botulinum neurotoxin) responsible for all the symptoms of botulism. Botulism is most often acquired by ingesting preformed botulinum neurotoxin in contaminated food or after intestinal colonization by C. botulinum under certain circumstances, such as in infant botulism, and toxin production in the intestine. The first step of the disease consists in the passage of the botulinum neurotoxin through the intestinal barrier, which is still poorly understood. We investigated the trafficking of the botulinum neurotoxin in a mouse intestinal loop model, using fluorescent HcA (half C-terminal domain of the heavy chain). We observed that HcA preferentially recognizes neuroendocrine intestinal crypt cells, which likely represent the entry site of the toxin through the intestinal barrier, then targets specific neurons, mainly cholinergic neurons, in the submucosa, and later (90–120 min) in the musculosa leading to local paralytic effects such as inhibition of intestinal peristaltism. These results represent an important advance in the understanding of the initial steps of botulism intoxication and can be the basis for the development of new specific countermeasures against botulism.

Classification and functions of enteroendocrine cells of the lower gastrointestinal tract

With over thirty different hormones identified as being produced in the gastrointestinal (GI) tract, the gut has been described as 'the largest endocrine organ in the body' (Ann. Oncol., 12, 2003, S63). The classification of these hormones and the cells that produce them, the enteroendocrine cells (EECs), has provided the foundation for digestive physiology. Furthermore, alterations in the composition and function of EEC may influence digestive physiology and thereby associate with GI pathologies. Whilst there is a rapidly increasing body of data on the role and function of EEC in the upper GI tract, there is a less clear-cut understanding of the function of EEC in the lower GI. Nonetheless, their presence and diversity are indicative of a role. This review focuses on the EECs of the lower GI where new evidence also suggests a possible relationship with the development and progression of primary adenocarcinoma.

Short-chain fatty acid level and field cancerization show opposing associations with enteroendocrine cell number and neuropilin expression in patients with colorectal adenoma

BACKGROUND

Previous reports have suggested that the VEGF receptor neuropilin-1 (NRP-1) is expressed in a singly dispersed subpopulation of cells in the normal colonic epithelium, but that expression becomes dysregulated during colorectal carcinogenesis, with higher levels in tumour suggestive of a poor prognosis. We noted that the spatial distribution and morphology if NRP-1 expressing cells resembles that of enteroendocrine cells (EEC) which are altered in response to disease state including cancer and irritable bowel syndrome (IBS). We have shown that NRP-1 is down-regulated by butyrate in colon cancer cell lines in vitro and we hypothesized that butyrate produced in the lumen would have an analogous effect on the colon mucosa in vivo. Therefore we sought to investigate whether NRP-1 is expressed in EEC and how NRP-1 and EEC respond to butyrate and other short-chain fatty acids (SCFA - principally acetate and propionate). Additionally we sought to assess whether there is a field effect around adenomas.

METHODOLOGY

Biopsies were collected at the mid-sigmoid, at the adenoma and at the contralateral wall (field) of 28 subjects during endoscopy. Samples were fixed for IHC and stained for either NRP-1 or for chromogranin A (CgA), a marker of EEC. Stool sampling was undertaken to assess individuals' butyrate, acetate and propionate levels.

RESULT

NRP-1 expression was inversely related to SCFA concentration at the colon landmark (mid-sigmoid), but expression was lower and not related to SCFA concentration at the field. Likewise CgA+ cell number was also inversely related to SCFA at the landmark, but was lower and unresponsive at the field. Crypt cellularity was unaltered by field effect. A colocalisation analysis showed only a small subset of NRP-1 localised with CgA. Adenomas showed extensive, weaker staining for NRP-1 which contrastingly correlated positively with butyrate level. Field effects cause this relationship to be lost. Adenoma tissue shows dissociation of the co-regulation of NRP-1 and EEC.

CONCLUSION

NRP-1 is inversely associated with levels of butyrate and other SCFA in vivo and is expressed in a subset of CgA expressing cells. EEC number is related to butyrate level in the same way.

Immunohistochemical and biochemical studies with region-specific antibodies to chromogranins A and B and secretogranins II and III in neuroendocrine tumors

This short review deals with our investigations in neuroendocrine tumors (NETs) with antibodies against defined epitopes of chromogranins (Cgs) A and B and secretogranins (Sgs) II and III. The immunohistochemical expression of different epitopes of the granin family of proteins varies in NE cells in normal human endocrine and non-endocrine organs and in NETs, suggesting post-translational processing. In most NETs one or more epitopes of the granins were lacking, but variations in the expression pattern occurred both in benign and malignant NETs. A few epitopes displayed patterns that may be valuable in differentiating between benign and malignant NET types, e.g., well-differentiated NET types expressed more CgA epitopes than the poorly differentiated ones and C-terminal secretoneurin visualized a cell type related to malignancy in pheochromocytomas. Plasma concentrations of different epitopes of CgA and CgB varied. In patients suffering from carcinoid tumors or endocrine pancreatic tumors the highest concentrations were found with epitopes from the mid-portion of CgA. For CgB the highest plasma concentrations were recorded for the epitope 439-451. Measurements of SgII showed that patients with endocrine pancreatic tumors had higher concentrations than patients with carcinoid tumors or pheochromocytomas. SgIII was not detectable in patients with NETs.

Secretogranin III in human neuroendocrine tumours: a comparative immunohistochemical study with chromogranins A and B and secretogranin II

BACKGROUND

Different epitopes of the granin family of proteins, chromogranin (Cg) A, CgB and secretogranin (Sg) II, have been demonstrated in normal human pancreas, gastrointestinal tract, adrenal medulla and in several neuroendocrine tumours (NETs). SgIII has been recently reported in endocrine pancreas. The aim of the present study was to examine the expression of SgIII in different NETs and compare it with the expression of CgA, CgB and SgII epitopes.

MATERIAL AND METHODS

Tissue specimens from 47 NETs were analyzed. Antibodies to CgA 250-284, CgB 244-255, SgII 172-186 (C-terminal secretoneurin) and SgIII 348-361 were used for immunostaining.

RESULTS

SgIII was expressed in 41 of 47 NETs. The expression of SgIII agreed well with that of CgA, CgB and SgII, with exceptions of phaeochromocytomas, where more CgB and SgII immunoreactive cells were observed and parathyroid adenomas, which were only stained by CgA. In rectal NETs more cells expressed SgIII than CgA.

CONCLUSIONS

This is the first report on SgIII expression in various NETs. A majority of tumours studied displayed SgIII immunostaining, which indicates a functional relationship with the other granins.

Granins and granin-related peptides in neuroendocrine tumours

This review focus on neuroendocrine tumours (NETs), with special reference to the immunohistochemical analysis of granins and granin-related peptides and their usefulness in identifying and characterizing the great diversity of NET types. Granins, their derived peptides, and complex protein-processing enzyme systems that cleave granins and prohormones, have to some extent cell-specific expression patterns in normal and neoplastic NE cells. The marker most commonly used in routine histopathology to differentiate between non-NETs and NETs is chromogranin (Cg) A, to some extent CgB. Other members of the granin family may also be of diagnostic value by identifying special NET types, e.g. secretogranin (Sg) VI was only found in pancreatic NETs and phaeochromocytomas. SgIII has recently arisen as an important NET marker; it was strongly expressed in NETs, with some exceptions--phaeochromocytomas expressed few cells and parathyroid adenomas none. Some expression patterns of granin-related peptides seem valuable in differentiating between some benign and malignant NETs, some may also provide prognostic information, among which: well-differentiated NET types expressed more CgA epitopes than the poorly differentiated ones, except insulinomas, where the opposite was noted; medullary thyroid carcinomas containing few cells immunoreactive to a CgB antibody were related to a bad prognosis; C-terminal secretoneurin visualized a cell type related to malignancy in phaeochromocytomas. Further research will probably establish new staining patterns with marker functions for granins in NETs which may be of histopathological diagnostic value.

A fuller understanding of pancreatic neuroendocrine tumours combined with aggressive management improves outcome

BACKGROUND

Neuroendocrine tumours of the pancreas (PNETs) represent 1-2% of all pancreatic tumours. The terms 'islet cell tumours' and 'carcinoids' of the pancreas should be avoided. The aim of this review is to offer an overview of the history and diagnosis of PNETs followed by a discussion of the available treatment options.

METHODS

A search on PubMed using the keywords 'neuroendocrine', 'pancreas' and 'carcinoid' was performed to identify relevant literature over the last 30 years.

RESULTS

The introduction of a revised classification of neuroendocrine tumours by the World Health Organisation (WHO) in 2000 significantly changed our understanding of and approach to the management of these tumours. Advances in laboratory and radiological techniques have also led to an increased detection of PNETs. Surgery remains the only treatment that offers a chance of cure with increasing number of non-surgical options serving as beneficial adjuncts. The better understanding of the behaviours of PNETs together with improvements in tumour localisation has resulted in a more aggressive management strategy with a concomitant improvement in symptom palliation and a prolongation of survival.

CONCLUSION

Due to their complex nature and the wide range of therapeutic options, the involvement of specialists from all necessary disciplines in a multidisciplinary team setting is vital to provide optimal treatment of this disease.

Intestinal immune activation in presumed post-infectious functional dyspepsia

Functional dyspepsia (FD) symptoms may develop after an acute gastroenteritis. In post-infectious (PI) irritable bowel syndrome, persisting low-grade colonic inflammation and increased enterochromaffine cells (EC) counts have been reported. The aim was to compare signs of inflammation and EC hyperplasia on duodenal biopsies in presumed PI-FD and unspecified-onset (U-)FD. Duodenal biopsies were obtained in 12 U-FD and 12 PI-FD (on average 13 months after the acute event) patients. The presence of intra-epithelial, intravillar, and the number of CD3, CD4, CD8 and CD68+ cells per crypts, and the mean number of Chromogranine A (CA) positive cells per villus were compared. We also measured gastric emptying and assessed proximal stomach function with a barostat. Data are shown as mean +/- SEM. Focal aggregates of T cells and focal CD8+ aggregates, were found in PI-FD but not in U-FD patients (respectively 5/12 vs 0/12, P = 0.02 and 5/9 vs 0/11, P < 0.01). In patients with focal aggregates, gastric emptying was delayed (189 +/- 37 min vs 98 +/- 11 min, P = 0.002). The number of CD4+ cells per crypt (0.52 +/- 1.6 vs 1.22 +/- 2.18, P = 0.04), and the number of intravillar CD4+ cells (0.5 +/- 0.2 vs 2.7 +/- 0.7, P = 0.01) were reduced, while the number of CD68+ cells per crypt was increased (0.64 +/- 0.13 vs 0.40 +/- 0.05, P = 0.03) in PI-FD. The number of EC and CA were comparable. PI-FD is associated with persisting focal T-cell aggregates, decreased CD4+ cells and increased macrophage counts surrounding the crypts. This may indicate impaired ability of the immune system to terminate the inflammatory response after acute insult.

Classification of tumours

Tumours are classified according to the most differentiated cells with the exception of carcinomas where a few tumour cells show neuroendocrine differentiation. In this case these cells are regarded as redifferentiated tumour cells, and the tumour is not classified as neuroendocrine. However, it is now clear that normal neuroendocrine cells can divide, and that continuous stimulation of such cells results in tumour formation, which during time becomes increasingly malignant. To understand tumourigenesis, it is of utmost importance to recognize the cell of origin of the tumour since knowledge of the growth regulation of that cell may give information about development and thus possible prevention and prophylaxis of the tumour. It may also have implications for the treatment. The successful treatment of gastrointestinal stromal tumours by a tyrosine kinase inhibitor is an example of the importance of a correct cellular classification of a tumour. In the future tumours should not just be classified as for instance adenocarcinomas of an organ, but more precisely as a carcinoma originating from a certain cell type of that organ.

SREBP-2 regulates gut peptide secretion through intestinal bitter taste receptor signaling in mice

Bitter taste-sensing G protein-coupled receptors (type 2 taste receptors [T2Rs]) are expressed in taste receptor cells of the tongue, where they play an important role in limiting ingestion of bitter-tasting, potentially toxic compounds. T2Rs are also expressed in gut-derived enteroendocrine cells, where they have also been hypothesized to play a role in limiting toxin absorption. In this study, we have shown that T2R gene expression in both cultured mouse enteroendocrine cells and mouse intestine is regulated by the cholesterol-sensitive SREBP-2. In addition, T2R stimulation of cholecystokinin (CCK) secretion was enhanced directly by SREBP-2 in cultured cells and in mice fed chow supplemented with lovastatin and ezetimibe (L/E) to decrease dietary sterol absorption and increase nuclear activity of SREBP-2. Low-cholesterol diets are naturally composed of high amounts of plant matter that is likely to contain dietary toxins, and CCK is known to improve dietary absorption of fats, slow gastric emptying, and decrease food intake. Thus, these studies suggest that SREBP-2 activation of bitter signaling receptors in the intestine may sensitize the gut to a low-fat diet and to potential accompanying food-borne toxins that make it past the initial aversive response in the mouth.

Chromogranin A-, serotonin-, synaptophysin- and vascular endothelial growth factor-positive endocrine cells and the prognosis of colorectal cancer: an immunohistochemical and ultrastructural study

BACKGROUND AND AIM

Endocrine differentiation in colorectal adenocarcinoma has been reported but its significance as a prognostic marker remains uncertain. The aim of the present study was to analyze the prognostic significance of endocrine differentiation in colorectal cancer.

METHODS

The presence of endocrine cells (EC) was determined in 137 colorectal cancers using light and electron immunohistochemistry and the immunogold method with chromogranin A, serotonin and synaptophysin. Vascular endothelial growth factor (VEGF) expression in tumor biopsies was also analyzed applying anti-VEGF antibodies.

RESULTS

EC labeled with at least one of the studied markers were detected in 47 (34.3%) primary colorectal cancers (30% chromogranin A-positive, 33% synaptophysin-positive and 18% serotonin-positive). In 23% of tumor biopsies, VEGF-positive EC were also detected. The immunostaining on serial sections showed that some chromogranin A-, synaptophysin- or serotonin-positive EC also contained VEGF immune deposits. By the immunogold method, the presence of VEGF was localized to the granules of EC. Tumors with VEGF-positive EC appeared to have significantly higher vascularization, detected as systematic microvessel density (28.89 vs 15.22 vessels/mm(2), P = 0.044, Mann-Whitney U-test) compared to those without VEGF-positive EC. Ultrastructurally, EC in the tumor tissue displayed some features different from those in the normal colon. The survival analyses revealed that patients with EC in primary tumor tissues had a worse prognosis after surgical therapy than those without endocrine cell differentiation (P < 0.05, log-rank test).

CONCLUSIONS

Endocrine differentiation is not an uncommon event in primary colorectal cancer and it could be a useful marker for a worse prognosis after the surgical therapy. Tumors positive for VEGF and containing VEGF-positive EC have higher vascularization, which probably also contributes to the unfavorable prognosis of patients.

Expression of PCSK1 (PC1/3), PCSK2 (PC2) and PCSK3 (furin) in mouse small intestine

The family of serine proteases known as the proprotein convertases subtilisin/kexin type (PCSK) is responsible for the cleavage and maturation of many precursor hormones. Over its three successive regions, the duodenum, the jejunum and the ileum, the small intestine (SI) expresses over 40 peptide hormones necessary for normal intestinal physiology. Most of these hormones derive from proteolytic cleavage of their cognate inactive polypeptide precursors. Members of the PCSK family of proteases have been implicated in this process, although details of enzyme-substrate interactions are largely lacking. As a first step towards elucidating these interactions, we have analyzed by immunohistochemistry the regional distribution of PCSK1, PCSK2 and PCSK3 in mouse SI as well as their cellular co-localization with substance P (SP), cholecystokinin (CCK), glucose-dependent insulinotropic polypeptide (GIP) and somatostatin (SS), 4 peptide hormones known to result from PCSK-mediated processing. Results indicate that PCSK1 is found in all three regions of the SI while PCSK2 and PCSK3 are primarily expressed in the upper two, the duodenum and the jejunum. In these proximal regions, PCSK1 was detectable in 100% of SP-positive (+) cells, 85% of CCK+ cells and 50% of GIP+ cells; PCSK2 was detectable in 40% of SS+ cells and 35% of SP+ cells; PCSK3 was detectable in 75% of GIP+ cells and 60% of SP+ cells. These histological data suggest that the 3 PCSKs may play differential and overlapping roles in prohormone processing in the three regions of the SI.

Immunoreactivity against Goblet cells in patients with inflammatory bowel disease

BACKGROUND

A number of autoantibodies have been reported in inflammatory bowel disease (IBD). The aim of this study was to investigate to what extent sera from patients with IBD contain autoantibodies directed against normal human gastrointestinal mucosa.

METHODS

Samples of sera from 50 patients with IBD and 50 healthy subjects were used for immunostaining of normal and affected human gastrointestinal tissues.

RESULTS

Eighty-four percent of the sera from IBD patients showed immunoreactivity against goblet cells in the appendix compared with 8% of the sera from healthy subjects. Goblet cell reactivity of IBD patient sera varied between regions in the gastrointestinal tract. Sera from healthy subjects only reacted with goblet cells in the appendix. In the colon and the appendix, goblet cell reactivity of IBD sera was generally weak at the base of the crypts and gradually increased toward the lumen. Three IBD sera samples reacted with gastrin cells in the antrum. In colon biopsies from patients with ulcerative colitis, immunoreactivity against the remaining goblet cells showed an inverse correlation with inflammatory activity.

CONCLUSIONS

These findings suggest that immunoreactivity against goblet cells may be of central importance in the pathogenesis of IBD. Identification of goblet cell antigens could lead to a better understanding of IBD and provide a new diagnostic tool.

Elevated cocaine- and amphetamine-regulated transcript immunoreactivity in the circulation of patients with neuroendocrine malignancy

CONTEXT

Cocaine- and amphetamine-regulated transcript (CART) codes for a peptide widely distributed in nervous and endocrine tissues. CART immunoreactivity (CART-LI) has been detected in human insulinomas.

OBJECTIVE

The objective of the study was to investigate the measurement of plasma CART-LI as a tumor marker of neuroendocrine malignancy.

DESIGN AND SUBJECTS

Plasma CART-LI levels were measured in 401 patients with a range of diagnoses: neuroendocrine malignancy (n = 131), after removal of neuroendocrine malignancy (n = 27), without any form of tumor or renal impairment (n = 192), with renal impairment (n = 17) and with nonneuroendocrine tumors (n = 34). Chromatography methods were used to investigate CART-LI circulating in human plasma.

RESULTS

The upper limit of normal calculated for CART-LI was 150 pmol/liter. Mean circulating plasma CART-LI among neuroendocrine tumor patients was 440 pmol/liter, 56% of subjects having levels greater than 150 pmol/liter. Measuring CART-LI in addition to chromogranin (Cg)-A improved the sensitivity for neuroendocrine malignancy from 85 to 91%, whereas combined use of CgA and CgB had a joint sensitivity of 89%. Of 38 patients with pancreatic neuroendocrine tumors, 71% had plasma CART-LI levels greater than 150 pmol/liter, increasing to 95% in those classified with progressive disease (n = 20, mean CART-LI 625 pmol/liter), compared with 80% for CgA. Chromatographic analysis suggests that circulating CART-LI is present as one major form, which may correspond to CART (62-102) or another unknown form.

CONCLUSIONS

We demonstrate CART-LI as a specific tumor marker in patients with a range of neuroendocrine tumors. Used in combination with CgA, CART-LI measurement has the potential to improve sensitivity in diagnosis and follow-up of neuroendocrine tumors, in particular progressive pancreatic neuroendocrine tumors.

Immunohistochemical staining of human islet cells with region-specific antibodies against secretogranins II and III

Chromogranins and secretogranins belong to the granin family of proteins, which are expressed in neuroendocrine and nervous tissue. In earlier publications we have described the development of region-specific antibodies against CgA and CgB. In this study we describe antibodies to SgII and SgIII and their usefulness for immunohistochemical staining. Peptides homologous to defined parts of secretogranins II and III were selected and synthesized. Antibodies were raised and immunostainings were performed on normal human pancreas. The SgII 154-165 (N-terminal secretoneurin), SgII 172-186 (C-terminal secretoneurin) and SgIII antibodies immunostained all insulin-immunoreactive cells, most of the glucagon cells and some of the pancreatic polypeptide cells. The SgII 225-242 antibody immunostained only the insulin-containing cells. None of the antibodies immunostained the somatostatin cells. This study is the first observation of the expression of SgIII in human tissues, where we show expression of SgIII in three of the four major islet cell types in human pancreas.

Increased presence of serotonin-producing cells in colons with diverticular disease may indicate involvement in the pathophysiology of the condition

INTRODUCTION

Serotonin is an important neuroendocrine transmitter participating in the control of colonic motor activity through neural and biochemical mechanisms in the Enteric Nervous System (ENS). A possible pathophysiological factor for diverticular disease (DD) is altered colonic motility. The study compared the distribution of serotonin cells (SC) in the colonic mucosa of patients with diverticular disease to controls.

METHODS

Sixteen paraffin specimens with sigmoid diverticular disease were selected and sections of bowel without diverticula from the same specimen were used as its own control. The resection margins from sixteen colonic specimens excised for sigmoid cancer were additional controls. Immunocytochemical staining for serotonin cells was performed on 4-mum tissue sections with polyclonal antibody (NCL-SEROTp). The number of serotonin-positive cells per ten microscopic fields (x200) was assessed in all groups and the staining distribution was defined as low (0-33%), moderate (>33-66%) and high (>66%) according to the percentage of the entire cell containing contrast material. The control specimens were blinded before analysis. Student's t test was used for statistical analysis and significance level was set as P < 0.05.

RESULTS

The mean number of serotonin-positive cells per ten fields in the colonic mucosa of specimens with diverticular disease was significantly higher [252.44 (SD 90.64)] than the specimen's own control [147.31 (SD 50.16)] and at normal resection margins of cancer specimens [228.38 (SD 120.10)]. The paired analysis between diverticular disease specimens and its own control (paired t test) showed significant differences for moderate (P = 0.008), high (P = 0.001) and total (P = 0.002) number of serotonin cells. There was no evidence of significance between mean DD and cancer values.

DISCUSSION

Increased presence of SCs and the higher proportion of high and moderate staining cells (indicating increased hormone content) indicate the possible role of serotonin in DD. This may be contributing to the pathogenesis of the condition by altered colonic motility in the affected segments in a similar way as in irritable bowel syndrome.

Endocrine tumours of the gastrointestinal tract-selected topics

This review provides an update on the pathogenesis and histopathological diagnosis of endocrine tumours of the gastrointestinal tract, concentrating on three different varieties whose careful assessment by pathologists is of particular clinical significance. These are the four types of enterochromaffin-like cell tumour of the gastric corpus, the periampullary somatostatin-containing D-cell tumour of the duodenum, and the frequently chromogranin A-negative L-cell tumour of the appendix and large intestine. In addition, the value of pathological factors in predicting the behaviour of gastrointestinal endocrine tumours and selecting therapy is discussed, and the crucial role of the pathologist in the multidisciplinary team management of these neoplasms is emphasized.

Colocalization of the alpha-subunit of gustducin with PYY and GLP-1 in L cells of human colon

In view of the importance of molecular sensing in the function of the gastrointestinal (GI) tract, we assessed whether signal transduction proteins that mediate taste signaling are expressed in cells of the human gut. Here, we demonstrated that the alpha-subunit of the taste-specific G protein gustducin (Galpha(gust)) is expressed prominently in cells of the human colon that also contain chromogranin A, an established marker of endocrine cells. Double-labeling immunofluorescence and staining of serial sections demonstrated that Galpha(gust) localized to enteroendocrine L cells that express peptide YY and glucagon-like peptide-1 in the human colonic mucosa. We also found expression of transcripts encoding human type 2 receptor (hT2R) family members, hT1R3, and Galpha(gust) in the human colon and in the human intestinal endocrine cell lines (HuTu-80 and NCI-H716 cells). Stimulation of HuTu-80 or NCI-H716 cells with the bitter-tasting compound phenylthiocarbamide, which binds hT2R38, induced a rapid increase in the intracellular Ca2+ concentration in these cells. The identification of Galpha(gust) and chemosensory receptors that perceive chemical components of ingested substances, including drugs and toxins, in open enteroendocrine L cells has important implications for understanding molecular sensing in the human GI tract and for developing novel therapeutic compounds that modify the function of these receptors in the gut.

Enteroendocrine cell counts correlate with visceral hypersensitivity in patients with diarrhoea-predominant irritable bowel syndrome

The objective of this study was to determine whether or not the number of enteroendocrine cells (ECs) in the gut is related to visceral hypersensitivity in patients with diarrhoea-predominant irritable bowel syndrome (D-IBS). Twenty-five subjects with D-IBS (mean, 43.1 years; 16 women, nine men) were recruited into our study, along with 13 healthy controls (mean, 40.7 years; nine women, four men). Maximally tolerable pressures were evaluated via barostat testing, and the levels of ECs were immunohistochemically identified and quantified via image analysis. The numbers of ECs between the D-IBS subjects and the controls were not significantly different in the terminal ileum, ascending colon and rectum. However, the maximally tolerable pressures determined in the D-IBS subjects were significantly lower than those of the control subjects (P < 0.01), and we detected a significant relationship between the maximally tolerable pressures and the numbers of ECs in the rectum (r = -0.37, P < 0.01). Rectal sensitivity was enhanced to a greater degree in D-IBS patients exhibiting an elevated level of rectal ECs. This study provides some evidence to suggest that ECs play an important role in visceral hypersensitivity.

Secretin and autism: a basic morphological study about the distribution of secretin in the nervous system

For the first time, the relationship between secretin and autism has been demonstrated by one of us. Intravenous administration of secretin in autistic children caused a fivefold higher pancreaticobiliary fluid secretion than in healthy ones and, at least in some of the patients, better mental functions were reported after the secretin test. Because the precise localization of secretin in the brain is still not completely known, the abovementioned observation led us to map secretin immunoreactivity in the nervous system of several mammalian species. In the present work, the distribution of secretin immunoreactivity in cat and human nervous systems was compared with that of rats using an immunohistochemical approach. Secretin immunoreactivity was observed in the following brain structures of both humans and in colchicine-treated rats: (1) Purkinje cells in the cerebellar cortex; (2) central cerebellar nuclei; (3) pyramidal cells in the motor cortex; and (4) primary sensory neurons. Additionally, secretin immnoreactive cells were observed in the human hippocampus and amygdala and in third-order sensory neurons of the rat auditory system. In cats, secretin was only observed in the spinal ganglia. Our findings support the view that secretin is not only a gastrointestinal peptide but that it is also a neuropeptide. Its presence or the lack of its presence may have a role in the development of behavioral disorders.

A stereological evaluation of secretin and gastric inhibitory peptide-containing mucosal cells of the perinatal small intestine of the pig

Stereological methods were used to quantify secretin and gastric inhibitory peptide (GIP)-immunoreactivity (GIP-IR) in paraffin sections of the duodenum, jejunum and ileum of fetal and neonatal piglets. In addition, sections were processed for GLP-1-immunohistochemistry. The volume density of the tunica mucosa increased after birth, giving rise to a decreased volume density of the tela submucosa and tunica muscularis. Generally known region-specific morphological distinctions were reflected in differing volume densities of the various layers. The highest volume density of GIP-IR epithelial cells was observed in the jejunum of the neonate. In contrast, the volume density of secretin-IR epithelial cells was highest in the duodenum of both fetal and neonatal piglets. The volume occupied by GIP-IR and secretin-IR epithelial cells increased in the jejunum after birth. Additionally, ileal secretin-IR epithelial cells were more numerous in the neonatal piglet. In conclusion, the quantitative and qualitative presence of GIP-IR and secretin-IR epithelial cells agree with earlier reports of their presence and co-localization between GIP-IR and GLP-1-IR, in the pig small intestine. Furthermore, the differences suggest that age- and region-related functional demands are temporally and probably causally related with the morphological diversification of the intestine and its endocrine cells.

Neuroendocrine cell markers for pancreatic islets and tumors

The authors review the application of a variety of neuroendocrine cell markers to identify pancreatic islet cells and tumors. In the past, several empiric histochemical techniques had been used to demonstrate neuroendocrine cells, particularly the Grimelius argyrophilic stain. The development of immunohistochemistry made it possible to demonstrate specific cell products such as regulatory peptides, thus allowing the classification of pancreatic neuroendocrine tumors with a view to clinical symptoms. However, it is not always possible to visualize regulatory peptides in these tumors. It is therefore important to use broad-spectrum neuroendocrine cell markers to identify the neuroendocrine nature. These markers are proteins localized in the secretory granules (core- or membrane-related), in the cytosol, or in the cellular membrane. The markers most commonly used in routine histopathology are the secretory granule proteins chromogranin A and synaptophysin and the cytosolic enzyme neuronspecific enolase. Other new markers (e.g., synaptic vesicle protein 2) are of general diagnostic value. Region-specific antibodies to chromogranin A can be valuable in differentiating between benign and malignant neuroendocrine tumors. Some markers may be related to the functioning characteristics of pancreatic neuroendocrine tumors, such as prohormone convertases. In addition, markers giving further complementary information have been identified, such as five somatostatin receptor subtypes, the expression of which varies markedly in pancreatic neuroendocrine tumors. Antibodies against all somatostatin receptor subtypes are now commercially available, and immunohistochemical investigation of its expression should be routinely applied when considering treatment with somatostatin analogs.

The role of Hoxa3 gene in parathyroid gland organogenesis of the mouse

Mice with a targeted deletion of the Hoxa3 gene have defects of derivatives of the third branchial arch and pouch. To address the role of the Hoxa3 gene in parathyroid organogenesis, we examined the third pharyngeal pouch development by immunohistochemistry (IHC) using the secretory protein (SP)-1/chromogranin A antiserum, which recognizes the parathyroid from its initial formation onward. At embryonic day (E) 11.5, the SP-1/chromogranin A-immunoreactive primary rudiment of the parathyroid appeared in the cranial region of the third pharyngeal pouch of wild-type embryos. In Hoxa3-null mutants, the third pharyngeal pouch was normally formed but failed to differentiate into the parathyroid rudiment, showing no immunoreactivity for SP-1/chromogranin A. Classic studies using chick-quail chimeras have demonstrated that the ectomesenchymal neural crest cells are required for proper development of the pharyngeal pouch-derived organs, including the thymus and parathyroid glands. To visualize the migration and development of mesenchymal neural crest cells in Hoxa3 mutants, the heterozygotes were crossed with connexin43-lacZ transgenic mice in which beta-galactosidase expression was specific to the neural crest cells. In Hoxa3 homozygotes and in wild types, ectomesenchymal neural crest cells densely populated the pharyngeal arches, including the third one, and surrounded the third pouch epithelium. These results indicate that lack of the Hoxa3 gene affects the intrinsic ability of the third pharyngeal pouch to form the parathyroid rudiment and has no detectable effect on the migration of neural crest cells.

Ultrastructural immunohistochemical localization of gastrin, somatostatin and serotonin in endocrine cells of human antral gastric mucosa

Five types of endocrine cells are found in the human antral gastric mucosa: gastrin (G) cells, somatostatin (D) cells, enterochromaffin (EC) cells and cells with an unknown secretory product (D1 cells and P cells). The content of secretory granules, gastrin, somatostatin and serotonin, was evaluated using electron microscopic immunohistochemistry and was compared with the granular content in G cells, D cells and EC cells as determined by routine electron microscopy. Semi-quantitative scoring of the granular content was performed on a scale 1-4 (empty-full). The content of gastrin (2.5 +/- 0.2) and somatostatin (3.3 +/- 0.2) in the granules was not different from the granular content in G cells (2.5 +/- 0.3; p > 0.05) and D cells (3.5 +/- 0.2; p > 0.05). Gastrin was also found in G cells in a nongranular form. The content of serotonin in granules (2.8 +/- 0.3) was smaller than the granular content in EC cells (3.7 +/- 0.2; p < 0.05). In intermediate-full and intermediate-empty granules, serotonin was localized in the periphery of granules whereas the granular content in EC cells was localized in an eccentric or central pattern. The granular content of D1 cells and P cells was 3.8 +/- 0.2, and 3.4 +/- 0.2, respectively. It is concluded that gastrin and somatostatin immunostaining in granules of G cells and D cells reflects the granular content in G cells and D cells, respectively, whereas serotonin immunostaining does not agree with the granular content of EC cells.

Individual subtypes of enteroendocrine cells in the mouse small intestine exhibit unique patterns of inositol 1,4,5-trisphosphate receptor expression

Enteroendocrine cells are a complex population of intestinal epithelial cells whose hormones play critical roles in regulating gastrointestinal and whole-animal physiology. There are many subpopulations of enteroendocrine cells based on the major hormone(s) produced by individual cells. Intracellular calcium plays a critical role in regulating hormone release. Inositol 1,4,5-trisphophate (IP3) receptors regulate calcium mobilization from endoplasmic reticulum-derived calcium stores in many endocrine and excitatory cells and are expressed in the intestine. However, the specific subtypes of enteroendocrine cells that express these receptors have not been reported. Immunohistochemical (IHC) studies revealed that enteroendocrine cells did not express detectable levels of type 2 IP3 receptors, whereas nearly all enteroendocrine cells that produced chromogranin A and/or serotonin expressed type 1 and type 3 IP3 receptors. Conversely, enteroendocrine cells that produced glucose-dependent insulinotropic polypeptide, glucagon-like peptide-1, cholecystokinin, or somatostatin did not express detectable levels of any IP3 receptors. Subsets of enteroendocrine cells that produced substance P or secretin expressed type 1 (33% or 18%, respectively) and type 3 (10% or 62%, respectively) IP3 receptors. Thus, different subtypes of enteroendocrine cells, as well as individual cells that express a particular hormone, exhibit remarkable heterogeneity in the molecular machineries that regulate hormone release in vivo. These results suggest that therapeutic agents can be developed that could potentially inhibit or promote secretion of hormones from specific subtypes of enteroendocrine cells.

Somatostatin and D cells in patients with gastritis in the course of Helicobacter pylori eradication: a six-month, follow-up study

BACKGROUND/AIMS

As well as causing chronic gastritis, Helicobacter pylori predisposes patients to peptic ulcer disease and gastric cancer, and induces gastric functional disorders. The aim of our study was to investigate the effects of H. pylori eradication therapy on the morphological and functional recovery of gastric antral and corpus D cells in patients with chronic gastritis during 6 months of follow-up.

PATIENTS AND METHODS

Forty consecutive, dyspeptic patients referred for endoscopy (31 with H. pylori infection and nine controls; mean age 49 years; 17 men, 23 women) entered the study. All patients had histological signs of gastritis but no signs of peptic ulcer or gastric cancer. Antrum (n=8) and corpus (n=6) biopsy specimens were collected for routine histology, radioimmunoassay tissue somatostatin levels, immunohistochemistry and electron microscopy, prior to and 6 months after therapy. Basal plasma somatostatin levels were determined prior to eradication, plus 6 weeks and 6 months after therapy. Eradication therapy consisted of amoxicillin, metronidazole and omeprazole.

RESULTS

Basal somatostatin plasma values in antral and corpus tissue were lower in infected patients than in the H. pylori-negative controls at the beginning of the study. A significant increase occurred after successful eradication therapy, together with an increase in the number of D cells in both regions. Changes in the D-cell ultrastructure in antral and corpus mucosa after eradication therapy suggest an increase in somatostatin synthesis and secretion.

CONCLUSIONS

The structural and functional restoration of D cells following eradication therapy indicates possible recovery of the diseased mucosa.