Diverse Mechanisms and Consequences of Immunoadoption of Neuromediator Systems

Chromogranin A and other enteroendocrine markers in inflammatory bowel disease

Changes in the distribution and products of enteroendocrine cells may play a role in immune activation and regulation of gut inflammation. This review aims at critically evaluating the main enteroendocrine markers in inflammatory bowel diseases (IBD). A narrative review was performed by searching inflammatory bowel diseases and enteroendocrine biomarkers in PubMed. Relevant modifications of some enteroendocrine markers, such as Chromogranin A, and their correlation with disease activity have been reported in patients with inflammatory bowel diseases. Even if data about neuroendocrine markers are sometimes contrasting, they may be potentially useful for the diagnosis and clinical management of these patients.

Metabolic inflammation in inflammatory bowel disease: crosstalk between adipose tissue and bowel

Epidemiological studies show that both the incidence of inflammatory bowel disease (IBD) and the proportion of people with obesity and/or obesity-associated metabolic syndrome increased markedly in developed countries during the past half century. Obesity is also associated with the development of more active IBD and requirement for hospitalization and with a decrease in the time span between diagnosis and surgery. Patients with IBD, especially Crohn's disease, present fat-wrapping or "creeping fat," which corresponds to ectopic adipose tissue extending from the mesenteric attachment and covering the majority of the small and large intestinal surface. Mesenteric adipose tissue in patients with IBD presents several morphological and functional alterations, e.g., it is more infiltrated with immune cells such as macrophages and T cells. All these lines of evidence clearly show an association between obesity, adipose tissue, and functional bowel disorders. In this review, we will show that the mesenteric adipose tissue and creeping fat are not innocent by standers but actively contribute to the intestinal and systemic inflammatory responses in patients with IBD. More specifically, we will review evidence showing that adipose tissue in IBD is associated with major alterations in the secretion of cytokines and adipokines involved in inflammatory process, in adipose tissue mesenchymal stem cells and adipogenesis, and in the interaction between adipose tissue and other intestinal components (immune, lymphatic, neuroendocrine, and intestinal epithelial systems). Collectively, these studies underline the importance of adipose tissue for the identification of novel therapeutic approaches for IBD.

Effect of vasoactive intestinal peptide (VIP) on NKG2D signal pathway and its contribution to immune escape of MKN45 cells

Objective. To investigate VIP effect on the cytotoxicity of NK cell to gastric cancer cells in vitro and the relation between the effect with the NKG2D signal molecules in NK cells. Material and Methods. NK cells were purified from peripheral blood mononuclear cells (PBMC). Before and after NK cells were incubated with VIP or its antagonist (D-p-Cl-Phe6,Leu17)-VIP, we detected the cytotoxicity of NK cells to MKN45 gastric cancer cells by MTT and detected the expressions of NKG2D, DAP10, and NF-κB proteins and mRNAs in NK cells by immunocytochemistry and RT-PCR in those conditions. Then we analyzed the effect of VIP and its antagonist on the cytotocicity of NK cell to gastric cancer cells and on expressions of NKG2D, DAP10, and NF-κB signal molecules in NK cells. Results. VIP could inhibit the cytotoxicity of NK cells to MKN45 cells and could inhibit the expressions of NKG2D, DAP10, and NF-κB in NK cells. However, (D-p-Cl-Phe6, Leu17)-VIP could reverse those effects. Conclusions. The VIP inhibited the cytotoxicity of NK cell to MKN45 cells which might get through inhibiting the expressions of NKG2D signal molecules in NK cells. This may be one mechanism of gastric cancer cells escaping organism immune clearance.

Prenatal programing: at the intersection of maternal stress and immune activation

Exposure to prenatal insults such as maternal stress and pathogenic infections has been associated with an increased risk for neurodevelopmental disorders. The mechanisms by which these programing events occur likely involve complex interactions between the maternal hormonal milieu, the placenta, and the developing fetus, in addition to compounding factors such as fetal sex and gestational stage of development. Despite the diverse biological processes involved, examination of common pathways in maternal stress and immune activation offers intriguing possibilities for elucidation of mechanistic insight. Further, the endocrine and sex-specific placenta is a tissue poised to be a key mediator in fetal programing, located at the intersection of the maternal and embryonic environments. In this review, we will discuss the potential shared mechanisms of maternal stress and immune pathway activation, with a particular focus on the important contribution and role of the placenta.

Neuropeptides of human thymus in normal and pathological conditions

Human thymus of healthy subjects and patients affected by thymoma-associated Myastenia Gravis were studied in order to visualize and compare the morphological distributive pattern of four neuropeptides: vasoactive intestinal peptide, substance P, neuropeptide Y, and neurotensin. Based on our observations, we formulated hypotheses on their relations in neuro-immunomodulation under physiological and pathophysiological conditions. Immuno-histochemical staining for neuropeptides was performed and morphological and morphometrical analyses were conducted on healthy and diseased thymus. In normal thymus, a specific distributive pattern was observed for the several neuropeptide-positive nerves in different thymus lobular zones. In particular substance P-positive fibers were observed in subcapsular zone, specifically located into parenchyma, where they represent the almost total amount of fibers; neurotensin-positive fibers were observed primarily located in parenchyma than perivascular site of several thymus lobular zones, and more abundant the cortico-medullary and medullary zones. Instead VIP- and NPY-positive fibers were widely distributed in perivascular and parenchymal sites of several thymus lobular zones. In thymoma, the distribution of neuropeptide-positive fibers was quantitatively reduced, while cells immunopositive to VIP and substance P were quantitatively increased and dispersed. Observation of the perivascular and parenchymal distribution of the analyzed neuropeptides suggests evidence that a regulatory function is performed by nerves and cells that secrete neuropeptide into the thymus. The alteration of neuropeptide patterns in thymoma suggests that these neurotransmitters play a role in autoimmune diseases such as Myastenia Gravis.

Neuropeptides, growth factors, and cytokines: a cohort of informational molecules whose expression is up-regulated by the stress-associated slow transmitter PACAP in chromaffin cells

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a co-transmitter with acetylcholine at the adrenomedullary synapse, mediating sustained hormone secretion and regulation of cellular plasticity in response to stress at the level of gene transcription. Here we have extended our investigation of PACAP-regulated neuroendocrine cell-specific genes from PC12 cells to PC12 cells expressing physiological levels of the PAC1hop receptor found on chromaffin cells in vivo. PACAP induces in these PC12_bPAC1hop cells an additional cohort of genes, compared to PC12 cells, enriched in informational molecules including cytokines, neuropeptides, and growth factors. Using two newly developed microarray platforms for expressed bovine transcripts, we further examined PACAP-induced genes in bovine chromaffin cells during a period of exposure (6 h) corresponding to a period of prolonged metabolic or psychogenic stress in vivo during which PACAP is released from the splanchnic nerve onto chromaffin cells. As in PC12_bPAC1hop cells, PACAP induced in bovine chromaffin cells a cohort of genes encoding secretory proteins, identified by tiling for cellular localization using Ingenuity Pathway Analysis, which were highly enriched in informational molecules (secreted proteins acting at extracellular receptors). These included cytokines, growth factors and hormones, as well as converting enzymes, or protease inhibitors modulating converting enzyme function. Several neuropeptide prohormone transcripts not previously shown to be PACAP-regulated in chromaffin cells, such as thyrotropin-releasing hormone, and tachykinin precursor 1, were identified. Identification of this cohort of informational molecule-encoding transcripts suggests a wider, more integrative role for PACAP as a co-transmitter specific to stress transduction in the adrenal medulla.

Evidence for CRHR1 in multiple sclerosis using supervised machine learning and meta-analysis in 12,566 individuals

The primary genetic risk factor in multiple sclerosis (MS) is the HLA-DRB1*1501 allele; however, much of the remaining genetic contribution to MS has yet to be elucidated. Several lines of evidence support a role for neuroendocrine system involvement in autoimmunity which may, in part, be genetically determined. Here, we comprehensively investigated variation within eight candidate hypothalamic-pituitary-adrenal (HPA) axis genes and susceptibility to MS. A total of 326 SNPs were investigated in a discovery dataset of 1343 MS cases and 1379 healthy controls of European ancestry using a multi-analytical strategy. Random Forests, a supervised machine-learning algorithm, identified eight intronic SNPs within the corticotrophin-releasing hormone receptor 1 or CRHR1 locus on 17q21.31 as important predictors of MS. On the basis of univariate analyses, six CRHR1 variants were associated with decreased risk for disease following a conservative correction for multiple tests. Independent replication was observed for CRHR1 in a large meta-analysis comprising 2624 MS cases and 7220 healthy controls of European ancestry. Results from a combined meta-analysis of all 3967 MS cases and 8599 controls provide strong evidence for the involvement of CRHR1 in MS. The strongest association was observed for rs242936 (OR = 0.82, 95% CI = 0.74-0.90, P = 9.7 × 10(-5)). Replicated CRHR1 variants appear to exist on a single associated haplotype. Further investigation of mechanisms involved in HPA axis regulation and response to stress in MS pathogenesis is warranted.

PACAP-cytokine interactions govern adrenal neuropeptide biosynthesis after systemic administration of LPS

We have examined induction of neuropeptide expression in adrenal medulla after treatment of mice with lipopolysaccharide (LPS), a model for septic shock, which activates both immune and stress responses in vivo. Messenger RNAs encoding vasoactive intestinal polypeptide (VIP) and galanin, both modulators of steroidogenesis in neighboring adrenal cortex, are up-regulated at 24 h (eight-fold for VIP and two-fold for galanin) after LPS injection, and remain elevated for the following 24 h. Up-regulation of VIP and galanin by LPS is abrogated in pituitary adenylate cyclase-activating polypeptide (PACAP)-deficient mice, suggesting an interaction between LPS, or LPS-induced cytokines, and PACAP released in adrenal medulla from the splanchnic nerve. Treatment of cultured chromaffin cells with 100 nM PACAP and 10 nM tumor necrosis factor-alpha (TNF-alpha), a cytokine whose production is elevated by LPS, results in long-term synergistic up-regulation of VIP and galanin mRNA. PACAP blocks the earlier induction by TNF-alpha of mRNA encoding inhibitor of NF-kappaB alpha (I kappaB alpha), normally a negative autoregulator of TNF-alpha signaling through nuclear factor-kappaB (NF-kappaB), without affecting the induction of TNF-alpha-induced protein 3 (TNFAIP3), another NF-kappaB-dependent gene induced by TNF-alpha in chromaffin cells. By acting downstream of NF-kappaB to inhibit I kappaB alpha gene induction by TNF-alpha, PACAP may block I kappaB alpha-dependent negative autoregulation of TNF-alpha signaling through NF-kappaB, prolonging TNF-alpha-dependent signaling to neuropeptide-encoding genes in chromaffin cells. This mechanism may also underlie PACAP-dependent neuropeptide gene induction by LPS in vivo.

Stress-related modulation of inflammation in experimental models of bowel disease and post-infectious irritable bowel syndrome: role of corticotropin-releasing factor receptors

The interaction between gut inflammatory processes and stress is gaining increasing recognition. Corticotropin-releasing factor (CRF)-receptor activation in the brain is well established as a key signaling pathway initiating the various components of the stress response including in the viscera. In addition, a local CRF signaling system has been recently established in the gut. This review summarize the present knowledge on mechanisms through which both brain and gut CRF receptors modulate intestinal inflammatory processes and its relevance towards increased inflammatory bowel disease (IBD) activity and post-infectious irritable bowel syndrome (IBS) susceptibility induced by stress.

Neuropeptides and inflammatory bowel disease

PURPOSE OF REVIEW

Inflammatory bowel disease (IBD) is a chronic intestinal inflammatory condition, the pathophysiology of which is not well understood. It has, however, become increasingly evident that interactions between the enteric nervous system and the immune system play an important role in the cause of IBD. Both the enteric nervous system and the central nervous system can amplify or modulate the aspects of intestinal inflammation through secretion of neuropeptides or small molecules. The purpose of this study is to present recent data on the role that neuropeptides play in the pathophysiology of IBD.

RECENT FINDINGS

The best studied of the neuropeptides thought to play a role in the pathogenesis of IBD include substance P, corticotropin-releasing hormone, neurotensin, and vasoactive intestinal peptide; small molecules include acetylcholine and serotonin. Recently discovered functions of each of these neuropeptides with a discussion of implications of the data for therapy are reviewed.

SUMMARY

Although the available data suggest an important role for neuropeptides in the pathophysiology of intestinal inflammation, there does yet not appear to be a function that can be taken as established for any of these molecules. The complexity of neuroimmune-endocrine systems, conflicting study results and dual mechanisms of action, warrant further research in this field. Clarification of the molecular mechanisms of action of neuropeptides and on immune and inflammatory reactions will likely yield new treatment options in the future.