Dual presence of chromogranin A-like immunoreactivity in a population of endocrine-like cells and in nerve fibers in the human anal canal

Distribution pattern and molecular signature of cholinergic tuft cells in human gastro-intestinal and pancreatic-biliary tract

Despite considerable recent insight into the molecular phenotypes and type 2 innate immune functions of tuft cells in rodents, there is sparse knowledge about the region-specific presence and molecular phenotypes of tuft cells in the human digestive tract. Here, we traced cholinergic tuft cells throughout the human alimentary tract with immunohistochemistry and deciphered their region-specific distribution and biomolecule coexistence patterns. While absent from the human stomach, cholinergic tuft cells localized to villi and crypts in the small and large intestines. In the biliary tract, they were present in the epithelium of extra-hepatic peribiliary glands, but not observed in the epithelia of the gall bladder and the common duct of the biliary tract. In the pancreas, solitary cholinergic tuft cells were frequently observed in the epithelia of small and medium-size intra- and inter-lobular ducts, while they were absent from acinar cells and from the main pancreatic duct. Double immunofluorescence revealed co-expression of choline acetyltransferase with structural (cytokeratin 18, villin, advillin) tuft cell markers and eicosanoid signaling (cyclooxygenase 1, hematopoietic prostaglandin D synthase, 5-lipoxygenase activating protein) biomolecules. Our results indicate that region-specific cholinergic signaling of tuft cells plays a role in mucosal immunity in health and disease, especially in infection and cancer.

Xenin-immunoreactive cells and extractable xenin in neuroendocrine tumors of duodenal origin

BACKGROUND & AIMS

Xenin is a 25-amino acid peptide produced by specific endocrine cells of the duodenal mucosa. We investigated whether xenin is expressed in neuroendocrine tumors.

METHODS

Seventy-two foregut and midgut neuroendocrine tumors were examined by means of immunohistochemistry, confocal laser microscopy with an antibody against the C-terminus of xenin, and high-pressure liquid chromatography after acidic extraction, assessed by radioimmunoassay.

RESULTS

We found xenin-immunoreactive cells in 23 of 26 duodenal neuroendocrine tumors, including gastrinomas, somatostatinomas, and nonfunctioning and enterochromaffin cell tumors. In these tumors, up to 20% of the endocrine cells were xenin immunoreactive, and xenin immunoreactivity was concentrated in secretory granules. Xenin was coexpressed with chromogranin A. We found no xenin expression in gastrin-, somatostatin-, and serotonin-immunoreactive cells. High-pressure liquid chromatography after acidic extraction revealed 497 +/- 285 pmol of xenin per gram of tissue in 5 duodenal gastrinomas. The other neuroendocrine tumors, such as bronchial carcinoids, gastric enterochromaffin-like cell carcinoids, gastric and ileal enterochromaffin cell carcinoids, insulinomas, and gastrinomas of pancreatic origin, did not contain immunoreactive xenin.

CONCLUSIONS

Xenin is a peptide marker specific to neuroendocrine tumors of the duodenum. This finding may be useful in tumor classification and in the differential diagnosis of neuroendocrine tumors of the upper gut.

Immunohistochemical localization of the pro-peptide processing enzymes PC1/PC3 and PC2 in the human anal canal

The distribution of prohormone/pro-peptide convertases PC1/PC3 and PC2 was investigated in the human anal canal by immunohistochemistry. Both prohormone convertases exhibited region-specific distribution patterns and were observed in neural and neuroendocrine cells and in nonneuroendocrine cellular elements. PC1/PC3 immunoreactivity was present in enteric neurons, subsets of nerve fibers, and neuroendocrine cells, and also in epithelial cells like intestinal stem cells, and a subpopulation of squamous cells. Enteric neurons were PC2 immunoreactive, whereas PC2 immunostaining in nerve fibers was slightly above background levels. Few neuroendocrine cells contained PC2 immunoreactivity, which were located predominantly in the anal transitional zone. In the squamous epithelium, the basal cell layer stained for PC2. The tissue-specific distribution of PC1/PC3 and PC2 indicates region-specific processing of peptides with regulatory functions in the anal canal and further supports the hypothesis that neuropeptides are important regulators of anal functions.

Distribution and chemical phenotypes of neuroendocrine cells in the human anal canal

The presence, morphology and distribution of anal neuroendocrine cells were investigated with a panel of antisera and antibodies for neural markers, biogenic amines, and neuropeptides by the sensitive streptavidin-biotin-peroxidase immunocytochemistry, and coexistence patterns of neurochemically characterized neuroendocrine cells were examined by double immunofluorescence cytochemistry. In the colorectal zone, endocrine-like cells were immunoreactive for chromogranin A (CGA), serotonin (5-HT), pancreastatin (PST), peptide tyrosine tyrosine (PYY), glucagon-like peptide-1 (GLP-1), and somatostatin (SOM). Coexistence patterns of endocrine-like cell phenotypes with CGA and GLP-1 were heterogeneous. In the anal transitional zone (ATZ), endocrine-like cells were immunoreactive for CGA, 5-HT and PST. Furthermore, six new phenotypes of endocrine-like cells were characterized by their immunoreactivity for PYY, GLP-1, protein gene product 9.5 (PGP), calcitonin gene-related peptide (CGRP), neurotensin (NT), and SOM. All endocrine-like cell types in the ATZ were immunoreactive for CGA. In the squamous zone and perianal skin, CGA-immunopositive Merkel cells were also immunoreactive for CGRP, PST, NT and PGP. Neuroendocrine cells in the anal canal exhibit epithelial zone-related diversities in their neurochemical phenotypes and coexistence patterns, which may indicate specific regulatory functions. In the epithelium of the ATZ, which is regarded as metaplastic, endocrine-like cells expressed phenotypes characteristic of the neuroendocrine cells of the colorectal zone and the squamous zones, indicating a possible metaplastic origin of these cells.

Chromogranin A and B in neuronal elements in Hirschsprung's disease: an immunocytochemical and radioimmunoassay study

Chromogranin A and B (CAB) occur in several peptide hormone-producing cells and in neurons of the brain. The aim of the present study was to investigate the possible neuronal localization of these chromogranins in the ganglionic and aganglionic bowel in Hirschsprung's disease by immunocytochemistry and radioimmunoassay, using antibodies recognizing either chromogranin A or both chromogranin A and B. Further, the coexistence of chromogranins and other neuronal constituents was studied. CAB were found in nerve fibers and occasionally in nerve cell bodies of submucous and myenteric ganglia in the ganglionic bowel, indicating that at least a population of chromogranin-immunoreactive nerve fibers is intrinsic in origin. CAB-immunoreactive fibers were numerous in the muscle layers of the aganglionic segment. These fibers contained tyrosine hydroxylase (TH), which indicates that they are adrenergic, in both ganglionic and aganglionic bowel. In the muscle layers of aganglionic (but not ganglionic) bowel, chromogranin A coexisted with galanin, neuropeptide Y (NPY), and vasoactive intestinal peptide (VIP). The concentration of CAB in smooth muscle specimens was higher in the aganglionic bowel than in the ganglionic bowel. Thus, chromogranins are present in the human enteric gut hyperinnervating the aganglionic bowel of Hirschsprung's disease.

Immunocytochemical evidence for chromogranin A and B in neuronal elements in human gut

Chromogranins are a family of acidic proteins known to occur in the secretory granules of endocrine cells and neurons in mammals. The aim of the present study was to investigate the possible neuronal localisation of chromogranins in human intestine and their relationship with other neuronal constituents using one antibody recognizing both chromogranin A and B (CAB) and others recognizing only chromogranin A. Immunoreactive CAB was found to occur in mucosal endocrine cells and in neuronal elements of all layers throughout human gut. A few to large number of CAB-immunoreactive nerve fibers were seen in smooth muscles as well as in submucous and myenteric ganglia and they were regularly found around blood vessels. Occasional CAB immunoreactive nerve cell bodies could be demonstrated in both submucous and myenteric ganglia indicating a local origin of some of the immunoreactive fibers. Most of these neurons seemed to lack acetylcholine esterase, and could be classified as non-cholinergic. CAB coexisted with the catecholamine-synthesizing enzyme tyrosine hydroxylase indicating the presence of chromogranins in noradrenergic nerve fibers. The presence of CAB-immunoreactive nerve cell bodies indicates that some CAB-containing fibers are intrinsic in origin. The distribution of chromogranin A and B immunoreactive nerve fibers in all layers of the gut wall suggests multiple targets for neuronal CAB, and/or their processing products.

Pan-neuronal expression of chromogranin A in rat nervous system

Sensitive and specific in situ hybridization detection of CGA mRNA, and immunohistochemistry with an antibody recognizing the CGA(316-329) epitope within CGA and its proteolytic fragments were employed to determine whether or not CGA mRNA or protein expression are restricted to specific neuronal subpopulations within the central and peripheral nervous systems. Virtually all neurons in sympathetic, sensory, and parasympathetic ganglia examined, as well as enteric nervous system and spinal cord, expressed both CGA mRNA and the 316-329 (WE-14) CGA epitope. Chromogranin A expression was also ubiquitous within all telencephalic and diencephalic brain nuclei examined, including frontal cortex, striatum, and hippocampus. In addition, CGA mRNA was expressed in nonneuronal cells that appeared to be glia in dorsal root ganglion, spinal cord, and brain. In contrast to earlier reports, neuronal expression of CGA appears to be unrestricted within the central and peripheral nervous systems. Nonneuronal expression of CGA also occurs in the nervous system, albeit at levels much lower than in neuronal cells.

Regional specificities in the distribution, chemical phenotypes, and coexistence patterns of neuropeptide containing nerve fibres in the human anal canal

Despite the pivotal clinical significance of the human anal canal, little is known about its total and specific innervation. This study assessed the comparative distribution and histotopology of nerve fibres immunoreactive for neural markers and a variety of regulatory active neuropeptides in the human anal canal by light microscopic immunohistochemistry. Depending on the epithelial zone and region of the anal canal, the neural elements were differentially immunoreactive for the pan-neural marker protein gene product 9.5, the catecholamine marker tyrosine hydroxylase, the neuroendocrine marker chromogranin A, and various neuropeptides. Protein gene product 9.5-immunoreactive nerve fibres were ubiquitously abundant in the anal canal. In the anal transitional zone, ectopic epithelial types were supplied by the same pattern of peptidergic nerves as the respective type of epithelium in normotopic location. In the dermis of the squamous zone and in the perianal epidermis, unusual distribution patterns of nerve fibres, referred to as areas of high nerve fibre density, were encountered. Double immunohistochemistry revealed region-specific coexistence patterns of neuropeptidergic nerve fibres, and novel peptide coexistence patterns were detected in anal nerve fibres. Subsets of nerve fibres formed close spatial relationships with chromogranin A-positive neuroendocrine cells, most frequently in the anal transitional zone. Chromogranin-A positive cells were shown to be present in the epithelium of perianal eccrine sweat glands. The differential distribution, peptide phenotypes and coexistence patterns of different nerve fibre populations in the human anal canal may reflect topospecific regulatory functions of neurally released neuropeptides in health and disease.

Distribution and coexistence of chromogranin A-, serotonin- and pancreastatin-like immunoreactivity in endocrine-like cells of the human anal canal

The comparative distribution and coexistence of chromogranin A (CGA)-, serotonin (5-hydroxytryptamine; 5-HT)- and pancreastatin (PST)-like immunoreactivity in endocrine-like cells of the human anal canal was investigated by light-microscopic immunocytochemistry. The largest population of colorectal endocrine-like cells consisted of CGA-immunoreactive (ir) cells, followed by the 5-HT-ir and PST-ir cell population. In the anal transitional zone (ATZ), CGA- and 5-HT-immunoreactivity was equally distributed; ir-PST was confined to a smaller endocrine-like cell population. In the squamous zone and the perianal skin, Merkel cells in the basal layer of the epidermis and hair follicles exhibited ir-CGA and ir-PST but no ir-5-HT. Double immunofluorescence on identical sections revealed distinct coexistence patterns. In the colorectal zone, about 2/3 of the CGA-ir endocrine-like cells also stained for 5-HT, whereas in the ATZ epithelium, CGA- and 5-HT-immunoreactivity completely overlapped. No 5-HT-immunoreactivity could be detected in CGA-ir Merkel cells of the squamous zone of the anal canal and the perianal skin. PST-immunoreactivity was present in about 1/3 of the CGA-ir colorectal and anal transitional endocrine-like cells and in about 1/4 of the Merkel-cell population staining for CGA. These chemically heterogeneous phenotypes of the anal endocrine-like and Merkel cells may reflect a specific regulatory role of these cells in the various epithelial linings of the human anal canal and the perianal skin.