Jean-Marie Vanderwinden

Nitric Oxide Synthase Activity in Infantile Hypertrophic Pyloric Stenosis

BACKGROUND Hypertrophic pyloric stenosis is a common infantile disorder characterized by enlarged pyloric musculature and gastric-outlet obstruction. Its physiopathologic mechanism is not known, but a defect in pyloric relaxation (pylorospasm) has been postulated. Nitric oxide is a mediator of relaxation in the mammalian digestive tract, raising the possibility that pylorospasm could be caused by a defect in nitric oxide production. Since neuronal nitric oxide synthase and NADPH diaphorase are identical, we used the NADPH diaphorase histochemical reaction to study the distribution of nitric oxide synthase in pyloric tissue from patients with infantile hypertrophic pyloric stenosis. METHODS We studied pyloric tissue from nine infants with infantile hypertrophic pyloric stenosis and seven control infants and children. Cryostat sections were processed for NADPH diaphorase histochemical analysis. A polyclonal tau antiserum was used to identify the enteric nervous system by immunohistochemical methods. RESULTS NADPH diaphorase activity was restricted to the enteric nervous system and blood vessels. In the pyloric tissues from the control patients, intense diaphorase activity was present in the nerve fibers of the circular musculature, in the neurons and nerve bundles of the myenteric plexus, and in some nerve fibers of the longitudinal musculature. In the pyloric tissues from patients with infantile hypertrophic pyloric stenosis, the enteric nerve fibers in the hypertrophied circular musculature were enlarged and distorted and did not contain diaphorase activity, whereas the activity in the myenteric plexus and the longitudinal musculature was preserved. CONCLUSIONS We suggest that a lack of nitric oxide synthase in pyloric tissue is responsible for pylorospasm in infantile hypertrophic pyloric stenosis.

Interstitial cells of Cajal in human colon and in Hirschsprung's disease

BACKGROUND & AIMS Subpopulations of interstitial cells of Cajal are regarded as the source of spontaneous slow waves of the gut musculature (pacemaker cells). Their ontogeny remains unclear, but a role of the tyrosine kinase receptor c-kit in their development has recently been recognized. This study examined the interstitial cells in the human colon and in Hirschsprungs disease (aganglionosis). METHODS The distribution of the c-kit receptor was studied using specific antibodies in 5 normal patients, 10 patients with Hirschsprungs disease, and 3 patients with diversion loop enterostomies. c-kit immunohistochemistry was also combined with reduced nicotinamide adenine dinucleotide phosphate diaphorase histochemistry or with c-kit ligand (stem cell factor) immunohistochemistry. Transmission electron microscopy was performed in 1 patient with Hirschsprungs disease. RESULTS c-kit immunoreactivity labeled a network of interstitial cells at the outer edge of the submucosa, in the muscular layers, and around the myenteric plexus. In aganglionic segments, interstitial cells were scarce and its network appeared disrupted. Interstitial cells of Cajal were identified in aganglionic regions by electron microscopy. Interstitial cells of Cajal are identifiable in newborns and exhibit similar distribution in diversion loops independent of contact with luminal nutrients. CONCLUSIONS Our morphological data may explain the abnormal spontaneous electrical activity in aganglionic segments of Hirschsprungs disease and may give new insight into the ontogeny of interstitial cells.

Germline-Activating Mutation in the Kinase Domain of KIT Gene in Familial Gastrointestinal Stromal Tumors

The proto-oncogene KIT encodes the receptor tyrosine kinase KIT. Gain-of-function mutations in the juxtamembrane domain of KIT have been reported in human gastrointestinal stromal tumors. In a family with multiple gastrointestinal stromal tumors and diffuse hyperplasia of myenteric plexus layer, we have identified another mutation of KIT, a single base mutation, resulting in the substitution of Glu for Lys(642) in the kinase I domain, and studied its biological effect in a cellular system. The mouse homologue of the human KIT mutant was generated by site-directed mutagenesis and stably transfected into the interleukin-3-dependent Ba/F3 murine cell line. The oncogenic potential of the mutated KIT was assessed in vitro by a proliferation assay and in vivo by transplantation into nude mice. Transfected Ba/F3 cells grew autonomously in absence of growth factors and formed tumors in nude mice. Substitution of Glu for Lys(642) is an oncogenic mutation in the tyrosine kinase domain of KIT. As germline heterozygous mutation, it causes a diffuse hyperplasia of myenteric interstitial cells of Cajal during embryonic development and occurrence of multiple gastrointestinal stromal tumors at adulthood.

Interstitial cells of Cajal in human gut and gastrointestinal disease

This paper reviews the distribution of interstitial cells of Cajal (ICC) in the human gastrointestinal (GI) tract, based on ultrastructural and immunohistochemical evidence. The distribution and morphology of ICC at each level of the normal GI tracts is addressed from the perspective of their functional significance. Alterations of ICC reported in achalasia of cardia, infantile hypertrophic pyloric stenosis, chronic intestinal pseudoobstruction, Hirschsprungs disease, inflammatory bowel diseases, slow transit constipation, and some other disorders of GI motility as well as in gastrointestinal stromal tumors are reviewed, with emphasis on the place of ICC in the pathophysiology of disease. Microsc. Res. Tech. 47:344–360, 1999.

Nitric oxide synthase distribution in the enteric nervous system of Hirschsprung's disease

BACKGROUND Hirschsprungs disease is characterized histologically by aganglionosis and functionally by impaired relaxation of the gut. Nitric oxide has recently been described pharmacologically as a major inhibitory mediator in the gut musculature in laboratory animals. The present study hypothesized that NO could be involved in motility disorders of the human gut. The aim was to study the neuronal enzyme synthetizing NO in the ganglionic and aganglionic human gut. METHODS Reduced nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry and immunohistochemistry with a specific polyclonal antiserum were used to examine NO synthase distribution in the enteric nervous system in six patients with Hirschsprungs disease and five control patients. RESULTS NO synthase was selectively absent in the plexus area and in the musculature of the aganglionic segments, whereas moderate staining was observed in the hypertrophied nerve bundles in the submucosa. In contrast, in the ganglionic segment NO synthase was abundantly present, in a pattern similar to that of the normal colon. CONCLUSIONS These findings suggest the involvement of NO in the physiopathology of Hirschsprungs disease.

Frequency of Ret mutations in long- and short-segment Hirschsprung disease

Hirschsprung disease, or congenital aganglionic megacolon, is a genetic disorder of neural crest development affecting 1:5,000 newborns. Mutations in the RET proto‐oncogene, repeatedly identified in the heterozygous state in both long‐ and short‐segment Hirschsprung patients, lead to loss of both transforming and differentiating capacities of the activated RET through a dominant negative effect when expressed in appropriate cellular systems. The approach of single‐strand conformational polymorphism analysis established for all the 20 exons of the RET proto‐oncogene, and previously used to screen for point mutations in Hirschsprung patients allowed us to identify seven additional mutations among 39 sporadic and familial cases of Hirschsprung disease (detection rate 18%). This relatively low efficiency in detecting mutations of RET in Hirschsprung patients cannot be accounted by the hypothesis of genetic heterogeneity, which is not supported by the results of linkage analysis in the pedigrees analyzed so far. Almost 74% of the point mutations in our series, as well as in other patient series, were identified among long segment patients, who represented only 25% of our patient population. The finding of a C620R substitution in a patient affected with total colonic aganglionosis confirms the involvement of this mutation in the pathogenesis of different phenotypes (i.e., medullary thyroid carcinoma and Hirschsprung). Finally the R313Q mutation identified for the first time in homozygosity in a child born of consanguineous parents is associated with the most severe Hirschsprung phenotype (total colonic aganglionosis with small bowel involvement). Hum Mutat 9:243–249, 1997.

Palmitoylation of CCR5 is critical for receptor trafficking and efficient activation of intracellular signaling pathways.

CCR5 is a CC chemokine receptor expressed on memory lymphocytes, macrophages, and dendritic cells and also constitutes the main coreceptor for macrophage-tropic (or R5) strains of human immunodeficiency viruses. In the present study, we investigated whether CCR5 was palmitoylated in its carboxyl-terminal domain by generating alanine substitution mutants for the three cysteine residues present in this region, individually or in combination. We found that wild-type CCR5 was palmitoylated, but a mutant lacking all three Cys residues was not. Through the use of green fluorescent fusion proteins and immunofluorescence studies, we found that the absence of receptor palmitoylation resulted in sequestration of CCR5 in intracellular biosynthetic compartments. By using the fluorescence recovery after photobleaching technique, we showed that the non-palmitoylated mutant had impaired diffusion properties within the endoplasmic reticulum. We next studied the ability of the mutants to bind and signal in response to chemokines. Chemokines binding and activation of Gi-mediated signaling pathways, such as calcium mobilization and inhibition of adenylate cyclase, were not affected. However, the duration of the functional response, as measured by a microphysiometer, and the ability to increase [35S]guanosine 5′-3-O-(thio)triphosphate binding to membranes were severely affected for the non-palmitoylated mutant. The ability of RANTES (regulated on activation normal T cell expressed and secreted) and aminooxypentane-RANTES to promote CCR5 endocytosis was not altered by cysteine replacements. Finally, we found that the absence of receptor palmitoylation reduced the human immunodeficiency viruses coreceptor function of CCR5, but this effect was secondary to the reduction in surface expression. In conclusion, we found that palmitoylated cysteines play an important role in the intracellular trafficking of CCR5 and are likely necessary for efficient coupling of the receptor to part of its repertoire of signaling cascades.

Delayed maturation of the interstitial cells of Cajal: A new diagnosis for transient neonatal pseudoobstruction. Report of two cases☆☆☆

The case histories of two neonates presenting with intestinal pseudoobstruction are presented. One boy infant was premature and the girl infant was full term. Both patients needed a defunctioning ileostomy, and biopsy findings of the intestine in both patients showed a lack of interstitial cells of Cajal (ICC). At the time of closure of the ileostomies to restore intestinal continuity, repeat biopsy results showed a normal pattern of distribution of ICC. Delay in the development of ICC in the gastrointestinal tract may be a cause of intestinal pseudoobstruction in the newborn.

Cellular distribution of the new growth factor pleiotrophin (HB-GAM) mRNA in developing and adult rat tissues.

SummaryPleiotrophin (PTN), also known as HBGAM, belongs to an emerging cytokine family unrelated to other growth factors. We report here the first comprehensive study using in situ hybridization on the cellular distribution of this new heparin-binding growth factor mRNA in rat tissues. PTN mRNA was developmentally expressed in many — but not all — neuroectodermal and mesodermal lineages, whilst no PTN mRNA was detected in endoderm, ectoderm and trophoblast. PTN mRNA was found in the nervous system throughout development, with a post-natal peak of expression. In the adult nervous system, significant expression persisted in hippocampal CA1 pyramidal neurons and in cortical neurons, but also in different non-neuronal cells types in various locations (olfactory nerve, cerebellar astrocytes, pituicytes, Schwann cells surrounding the neurons in sensory ganglia). PTN mRNA was also found during development in the mesenchyme of lung, gut, kidney and reproductive tract, in bone and cartilage progenitors, in dental pulp, in myoblasts, and in several other sites. Expression was differently regulated in each location, but usually faded around birth. In the adult, PTN mRNA was still present in the meninges, the iris, the Leydig cells of the testis and in the uterus. PTN mRNA was also strongly expressed in the basal layers of the tongue epithelium, which is the only epithelium and ectodermal derivative to express PTN mRNA, and this only after birth. PTN is known to be a growth factor for perinatal brain neurons and a mitogen for fibroblasts in vitro. Recently, trophic effects on epithelial cells and a role as a tumour growth factor have been reported. The mechanisms of regulation and the functions of PTN are however still uncertain. Its expression pattern during development suggests important roles in growth and differentiation. Moreover, the presence of PTN mRNA in several adult tissues and the up-regulation of PTN mRNA expression in the gravid uterus indicate that PTN also has physiological functions during adulthood.

p53 up-regulated modulator of apoptosis (PUMA) activation contributes to pancreatic beta-cell apoptosis induced by proinflammatory cytokines and endoplasmic reticulum stress.

Type 1 diabetes is an autoimmune disorder characterized by chronic inflammation and pancreatic β-cell loss. Here, we demonstrate that the proinflammatory cytokine interleukin-1β, combined with interferon-γ, induces the expression of the Bcl-2 homology 3 (BH3)-only activator PUMA (p53 up-regulated modulator of apoptosis) in β-cells. Transcriptional activation of PUMA is regulated by nuclear factor-κB and endoplasmic reticulum stress but is independent of p53. PUMA activation leads to mitochondrial Bax translocation, cytochrome c release, and caspase-3 cleavage resulting in β-cell demise. The antiapoptotic Bcl-XL protein is localized mainly at the mitochondria of the β-cells and antagonizes PUMA action, but Bcl-XL is inactivated by the BH3-only sensitizer DP5/Hrk in cytokine-exposed β-cells. Moreover, a pharmacological mimic of the BH3-only sensitizer Bad, which inhibits Bcl-XL and Bcl-2, induces PUMA-dependent β-cell death and potentiates cytokine-induced apoptosis. Our data support a hierarchical activation of BH3-only proteins controlling the intrinsic pathway of β-cell apoptosis in the context of inflammation and type 1 diabetes.