Clinical correlates of blood serotonin levels in patients with mastocytosis

Using the Right Criteria for MCAS

PURPOSE OF REVIEW

The current article aims to provide a comprehensive update on diagnostic criteria for mast cell activation syndrome (MCAS), addressing challenges in diagnosing and classifying MCAS and its variants.

RECENT FINDINGS

In recent years, there has been a significant increase in our knowledge regarding the underlying mechanisms responsible for the activation of mast cells (MCs) in various pathological conditions. Furthermore, a set of criteria and a classification for MCASs have been established. MCAS is characterized by the presence of typical clinical symptoms, a substantial elevation in serum tryptase levels during an attack compared to the patient's baseline tryptase levels, and a response to MC mediator-targeting therapy. In this report, a thorough examination was conducted on the contemporary literature relating to MCAS, with a focus on comparing the specificity, sensitivity, and robustness of MCAS-related parameters within proposals for diagnosing and classifying MCAS and its variants. Moreover, the significance of employing specific consensus criteria in the assessment and categorization of MCAS in individual patients was underscored, due to the escalating occurrence of patients receiving a misdiagnosis of MCAS based on nonspecific criteria.

The association between the neuroendocrine system and the tumor immune microenvironment: Emerging directions for cancer immunotherapy

This review summarizes emerging evidence that the neuroendocrine system is involved in the regulation of the tumor immune microenvironment (TIME) to influence cancer progression. The basis of the interaction between the neuroendocrine system and cancer is usually achieved by the infiltration of nerve fibers into the tumor tissue, which is called neurogenesis; the migration of cancer cells toward nerve fibers, which is called perineural invasion (PNI), and the neurotransmitters. In addition to the traditional role of neurotransmitters in neural communications, neurotransmitters are increasingly recognized as mediators of crosstalk between the nervous system, cancer cells, and the immune system. Recent studies have revealed that not only nerve fibers but also cancer cells and immune cells within the TIME can secrete neurotransmitters, exerting influence on both neurons and themselves. Furthermore, immune cells infiltrating the tumor environment have been found to express a wide array of neurotransmitter receptors. Hence, targeting these neurotransmitter receptors may promote the activity of immune cells in the tumor microenvironment and exert anti-tumor immunity. Herein, we discuss the crosstalk between the neuroendocrine system and tumor-infiltrating immune cells, which may provide feasible cancer immunotherapy options.

The roles of serotonin in cell adhesion and migration, and cytoskeletal remodeling

Serotonin is well known as a neurotransmitter. Its roles in neuronal processes such as learning, memory or cognition are well established, and also in disorders such as depression, schizophrenia, bipolar disorder, and dementia. However, its effects on adhesion and cytoskeletal remodelling which are strongly affected by 5-HT receptors, are not as well studied with some exceptions for e.g. platelet aggregation. Neuronal function is strongly dependent on cell-cell contacts and adhesion-related processes. Therefore the role played by serotonin in psychiatric illness, as well as in the positive and negative effects of neuropsychiatric drugs through cell-related adhesion can be of great significance. In this review, we explore the role of serotonin in some of these aspects based on recent findings.

Role of Mast Cells in the Pathogenesis of Pruritus in Mastocytosis

Pruritus can be defined as an unpleasant sensation that evokes a desire to scratch and significantly impairs patients' quality of life. Pruritus is widely observed in many dermatoses, including mastocytosis, a rare disease characterized by abnormal accumulation of mast cells, which can involve skin, bone marrow, and other organs. Increasing evidence highlights the role of mast cells in neurogenic inflammation and itching. Mast cells release various pruritogenic mediators, initiating subsequent mutual communication with specific nociceptors on sensory nerve fibres. Among important mediators released by mast cells that induce pruritus, one can distinguish histamine, serotonin, proteases, as well as various cytokines. During neuronal-induced inflammation, mast cells may respond to numerous mediators, including neuropeptides, such as substance P, neurokinin A, calcitonin gene-related peptide, endothelin 1, and nerve growth factor. Currently, treatment of pruritus in mastocytosis is focused on alleviating the effects of mediators secreted by mast cells. However, a deeper understanding of the intricacies of the neurobiology of this disease could help to provide better treatment options for patients.

Selecting the Right Criteria and Proper Classification to Diagnose Mast Cell Activation Syndromes: A Critical Review

In recent years, knowledge about mechanisms underlying mast cell activation (MCA) and accumulation in various pathologic conditions increased substantially. In addition, criteria and a classification of MCA syndromes (MCASs) have been set forth. MCAS is defined by typical clinical symptoms, a substantial increase in serum tryptase level during an attack over the patient's baseline tryptase, and a response of the symptoms to drugs targeting mast cells, mediator production, and/or mediator effects. Alternative diagnostic criteria of MCAS have also been suggested, but these alternative criteria often lack specificity and validation. In this report, we critically review the contemporary literature relating to MCAS and compare the specificity, sensitivity, and strength of MCAS-related parameters within proposals to diagnose and classify MCAS and its variants. Furthermore, we highlight the need to apply specific consensus criteria in the evaluation and classification of MCAS in individual patients. This is an urgent and important medical necessity because as an increasing number of patients are being given a misdiagnosis of MCAS based on nonspecific criteria, which contributes to confusion and frustration by patients and caregivers and sometimes may delay recognition and treatment of correct medical conditions that often turn out to be unrelated to MCA.

COMMD8 changes expression during initial phase of wasp venom immunotherapy

BACKGROUND

Hymenoptera venom allergy (HVA) is of great concern because of the possibility of anaphylaxis, which may be fatal. Venom immunotherapy (VIT) is the only disease-modifying treatment in HVA and, although efficient, its mechanism remains partially unknown. Gene expression analysis may be helpful for establishing a proper model of tolerance induction during the build-up phase of VIT. The present study aimed to analyze how the start of VIT changes the expression of 15 selected genes.

METHODS

Forty-five patients starting VIT with a wasp venom allergy were enrolled. The diagnosis was established based on anaphylaxis history (third or fourth grade on the Mueller scale) and positive soluble immunoglobulin E and/or skin tests. Two blood collections were performed in the patient group: before and after 3 months of VIT. One sample was taken in the control group. Gene expression analysis was performed using a reverse transcriptase-polymerase chain reaction with microfluidic cards and normalized to the 18S housekeeping gene.

RESULTS

Commd8 was the only gene that changed expression significantly after the start of VIT (p = 0.012). Its expression decreased towards the levels observed in the healthy controls. Twelve out of 15 genes (commd8, cldn1, cngb3, fads1, hes6, hla-drb5, htr3b, prlr, slc16a4, snx33, socs3 and twist2) revealed a significantly different expression compared to the healthy controls.

CONCLUSIONS

The present study shows that commd8 changes significantly its expression during initial phase of VIT. This gene might be a candidate for VIT biomarker in future studies.

Integrating Pathophysiology in Migraine: Role of the Gut Microbiome and Melatonin

BACKGROUND

The pathoetiology and pathophysiology of migraine are widely accepted as unknown.

METHODS

The current article reviews the wide array of data associated with the biological underpinnings of migraine and provides a framework that integrates previously disparate bodies of data.

RESULTS

The importance of alterations in stress- and pro-inflammatory cytokine- induced gut dysbiosis, especially butyrate production, are highlighted. This is linked to a decrease in the availability of melatonin, and a relative increase in the N-acetylserotonin/melatonin ratio, which has consequences for the heightened glutamatergic excitatory transmission in migraine. It is proposed that suboptimal mitochondria functioning and metabolic regulation drive alterations in astrocytes and satellite glial cells that underpin the vasoregulatory and nociceptive changes in migraine.

CONCLUSION

This provides a framework not only for classical migraine associated factors, such as calcitonin-gene related peptide and serotonin, but also for wider factors in the developmental pathoetiology of migraine. A number of future research and treatment implications arise, including the clinical utilization of sodium butyrate and melatonin in the management of migraine.

Mastocytosis: from a Molecular Point of View

Mast cells (MCs) are physiologically activated by binding of stem cell factor (SCF) to the extracellular domains of the Kit receptor. This binding increases the proliferation and prolongs the survival of normal mature MCs, as well as intensifies the release of mediators. In mastocytosis, somatic mutations of the coding Kit gene cause autocrine dysregulation and lead to constitutive KIT activation even in the absence of its ligand SCF. Clinical symptoms are caused by MC-mediator release and/or infiltration of MCs into tissues. Aberrant KIT activation may result in increased production of MCs in the skin and extracutaneous organs. Depending on the affected organ(s), the disease can be divided into cutaneous mastocytosis (CM), systemic mastocytosis (SM), and localized MC tumors. The updated classification of WHO discriminates between several distinct subvariants of CM and SM. While the prognosis in CM and indolent SM (ISM) is excellent with (almost) normal life expectancy, the prognosis in aggressive SM (ASM) and MC leukemia (MCL) is dismal. The symptoms may comprise urticaria, angioedema, flush, pruritus, abdominal pain, diarrhea, hypotension, syncope, and musculoskeletal pain and are the results of MC infiltration and mediator release into target organs, i.e., the skin, gastrointestinal tract, liver, spleen, lymph nodes, and bone marrow. Mastocytosis differs from a lot of other hematological disorders because its pathology is not only based on the lack of normal function of a specific pathway or of a specific cell type but additionally is a proliferative disease. Currently available treatments of mastocytosis include symptomatic, antimediator and cytoreductive targeted therapies.

Optimization of spirocyclic proline tryptophan hydroxylase-1 inhibitors

As a follow-up to the discovery of our spirocyclic proline-based TPH1 inhibitor lead, we describe the optimization of this scaffold. Through a combination of X-ray co-crystal structure guided design and an in vivo screen, new substitutions in the lipophilic region of the inhibitors were identified. This effort led to new TPH1 inhibitors with in vivo efficacy when dosed as their corresponding ethyl ester prodrugs. In particular, 15b (KAR5585), the prodrug of the potent TPH1 inhibitor 15a (KAR5417), showed robust reduction of intestinal serotonin (5-HT) levels in mice. Furthermore, oral administration of 15b generated high and sustained systemic exposure of the active parent 15a in rats and dogs. KAR5585 was selected for further pharmacological evaluation in disease models associated with a dysfunctional peripheral 5-HT system.

Mast cells' involvement in inflammation pathways linked to depression: evidence in mastocytosis

Converging sources of evidence point to a role for inflammation in the development of depression, fatigue and cognitive dysfunction. More precisely, the tryptophan (TRP) catabolism is thought to play a major role in inflammation-induced depression. Mastocytosis is a rare disease in which chronic symptoms, including depression, are related to mast cell accumulation and activation. Our objectives were to study the correlations between neuropsychiatric features and the TRP catabolism pathway in mastocytosis in order to demonstrate mast cells' potential involvement in inflammation-induced depression. Fifty-four patients with mastocytosis and a mean age of 50.1 years were enrolled in the study and compared healthy age-matched controls. Depression and stress were evaluated with the Beck Depression Inventory revised and the Perceived Stress Scale. All patients had measurements of TRP, serotonin (5-HT), kynurenine (KYN), indoleamine 2,3-dioxygenase 1 (IDO1) activity (ratio KYN/TRP), kynurenic acid (KA) and quinolinic acid (QA). Patients displayed significantly lower levels of TRP and 5-HT without hypoalbuminemia or malabsorption, higher IDO1 activity, and higher levels of KA and QA, with an imbalance towards the latter. High perceived stress and high depression scores were associated with low TRP and high IDO1 activity. In conclusion, TRP metabolism is altered in mastocytosis and correlates with perceived stress and depression, demonstrating mast cells' involvement in inflammation pathways linked to depression.

Mastocytosis in adulthood and neuropsychiatric disorders

Patients with mastocytosis can display various disabling general and neuropsychological symptoms among one third of them, including general signs such as fatigue and musculoskeletal pain, which can have a major impact on quality of life. Neurological symptoms are less frequent and mainly consist of acute or chronic headache (35%), rarely syncopes (5%), acute onset back pain (4%), and in a few cases, clinical and radiological symptoms resembling or allowing the diagnosis of multiple sclerosis (1.3%). Headaches are associated with symptoms related to mast cell activation syndrome (flushes, prurit, and so forth) and more frequently present as migraine (37.5%), with often aura (66%). Depression-anxiety like symptoms can occur in 40% to 60% of the patients and cognitive impairment is not rare (38.6%). The pathophysiology of these symptoms could be linked to tissular mast cell infiltration or to mast cell mediators release or both. The tryptophan metabolism could be involved in mast cell-induced neuroinflammation through indoleamine-2,3-dioxygenase activation. Treatments targeting mast cell may be useful to target neuropsychological features associated with mastocytosis, including tyrosine kinase inhibitors.

Serotonin modulates insect hemocyte phagocytosis via two different serotonin receptors

Serotonin (5-HT) modulates both neural and immune responses in vertebrates, but its role in insect immunity remains uncertain. We report that hemocytes in the caterpillar, Pieris rapae are able to synthesize 5-HT following activation by lipopolysaccharide. The inhibition of a serotonin-generating enzyme with either pharmacological blockade or RNAi knock-down impaired hemocyte phagocytosis. Biochemical and functional experiments showed that naive hemocytes primarily express 5-HT1B and 5-HT2B receptors. The blockade of 5-HT1B significantly reduced phagocytic ability; however, the blockade of 5-HT2B increased hemocyte phagocytosis. The 5-HT1B-null Drosophila melanogaster mutants showed higher mortality than controls when infected with bacteria, due to their decreased phagocytotic ability. Flies expressing 5-HT1B or 5-HT2B RNAi in hemocytes also showed similar sensitivity to infection. Combined, these data demonstrate that 5-HT mediates hemocyte phagocytosis through 5-HT1B and 5-HT2B receptors and serotonergic signaling performs critical modulatory functions in immune systems of animals separated by 500 million years of evolution.

Decreased tryptophan and increased kynurenine levels in mastocytosis associated with digestive symptoms

The main metabolism pathway of tryptophan is protein formation, but it can also be metabolized into serotonin and kynurenine. Indoleamine 2,3-dioxygenase (IDO) is the enzyme that catalyzes the degradation of tryptophan into kynurenine. Mastocytosis is a heterogeneous disease characterized by mast cell accumulation in various tissues with 57% of patients having gastrointestinal involvement. We studied tryptophan metabolism in mastocytosis patients displaying or not gastrointestinal features and healthy subjects (n = 26 in each group). Mastocytosis patients with digestive symptoms displayed significantly increased kynurenine level and IDO activity as compared to healthy controls and mastocytosis patients without digestive symptoms. This could be linked to mast cell-mediated digestive inflammation among patients with mastocytosis. This work is the first focusing on kynurenine pathway in a mast cell disease and could help to understand the pathogenesis of digestive features in mastocytosis as well as in other mast cell-mediated diseases.

Mast cell activation disease: An underappreciated cause of neurologic and psychiatric symptoms and diseases

Neurologists and psychiatrists frequently encounter patients whose central and/or peripheral neurologic and/or psychiatric symptoms (NPS) are accompanied by other symptoms for which investigation finds no unifying cause and for which empiric therapy often provides little to no benefit. Systemic mast cell activation disease (MCAD) has rarely been considered in the differential diagnosis in such situations. Traditionally, MCAD has been considered as just one rare (neoplastic) disease, mastocytosis, generally focusing on the mast cell (MC) mediators tryptase and histamine and the suggestive, blatant symptoms of flushing and anaphylaxis. Recently another form of MCAD, MC activation syndrome (MC), has been recognized, featuring inappropriate MC activation with little to no neoplasia and likely much more heterogeneously clonal and far more prevalent than mastocytosis. There also has developed greater appreciation for the truly very large menagerie of MC mediators and their complex patterns of release, engendering complex, nebulous presentations of chronic and acute illness best characterized as multisystem polymorbidity of generally inflammatory ± allergic themes--including very wide arrays of central and peripheral NPS. Significantly helpful treatment--including for neuropsychiatric issues--usually can be identified once MCAD is accurately diagnosed. We describe MCAD's pathogenesis, presentation (focusing on NPS), and therapy, especially vis-à-vis neuropsychotropes. Since MCAD patients often present NPS, neurologists and psychiatrists have the opportunity, in recognizing the diagnostic possibility of MCAD, to short-circuit the often decades-long delay in establishing the correct diagnosis required to identify optimal therapy.

Urinary 11β-PGF2α and N-methyl histamine correlate with bone marrow biopsy findings in mast cell disorders

BACKGROUND

The utility of measuring histamine and prostaglandin metabolites in the urine of patients with mastocytosis has not been critically examined in a large series of patients. This study examined the relationship between the extent of increase in urinary excretion of 11β-prostaglandinF2α and N-methyl histamine, with serum tryptase, whole blood serotonin, and bone marrow findings including morphology, percentage involvement, and abnormal mast cell phenotype.

METHODS

This was a retrospective analysis of 90 patients who were continuously enrolled in the study for a period of 6 years (2008-2014). We recorded serum tryptase, whole blood serotonin, levels of urinary mast cell metabolites 11β-prostaglandinF2α and N-methyl histamine (NMH), and bone marrow findings.

RESULTS

Urinary mast cell metabolites 11β-prostaglandinF2α and N-methyl histamine correlated with levels of serum tryptase, mast cell burden in the bone marrow, the presence of mast cell aggregates, and atypical mast cells on bone marrow biopsy. Whole blood serotonin did not have a significant correlation with the serum tryptase or mast cell burden in the bone marrow. Urinary NMH was significantly different between c-kit D816V-positive and c-kit D816V-negative patients, while 11β-prostaglandinF2α was not. Urinary 11β-prostaglandinF2α 24-h excretion >3500 ng and NMH levels >400 μg/gm Cr corresponded with the high degree of bone marrow biopsies positive for atypical mast cells, the presence of aggregates, and c-kit mutation.

CONCLUSIONS

Easily obtained and quantified urinary metabolites of histamine (greater than twice the upper limit of normal) and prostaglandin D2 (>3.4 times the upper limit of normal) correlate well with bone marrow findings of mastocytosis.

Mast Cell Serotonin Immunoregulatory Effects Impacting on Neuronal Function: Implications for Neurodegenerative and Psychiatric Disorders

Mast cells (MCs) are derived from hemopoietic precursor cells, undergo their maturation in peripheral tissues, and play a significant role in both the innate and adaptive immune response. Cross-linking of the FcεRI on MCs initiates activation of several cytoplasmic protein tyrosine kinases which rapidly lead to phosphorylation and recruitment of adaptor molecules. These effects trigger the release of preformed mediators stored in the cytoplasmic granules, including histamine, serotonin and tryptase, as well as newly synthesized mediators, such as cytokines/chemokines, prostaglandins, leukotrienes, and growth factors. Serotonin (5-HT) is a bioactive monoamine, which has seven specific cell surface membrane bound receptors which are coupled to G-proteins, plays an important role in the central and peripheral nervous system, and is one of the key mediators in signaling between nervous and immune systems. Serotonin is not stored in all MC types but is implicated in MC adhesion, chemotaxis, tumorigenesis, and tissue regeneration through smooth muscle differentiation of stromal cells. Recent evidence indicates that serotonin has immunoregulatory actions that may be important in neuropsychiatric conditions. Chemokines, RANTES/CCL5, MCP-1/CCL2, and related molecules, constitute the C-C class of chemokine supergene family, play a role in regulating T helper-cell cytokine production and MC trafficking, and are involved in histamine and serotonin generation and MC functions. Pro-inflammatory cytokines such as interleukin-1-β and tumor necrosis factor which mediate MC response, are capable of activating p38 MAPK, and might increase serotonin generation through p38 MAPK activation. Here, we review the relationship between MCs and serotonin and its role in inflammatory diseases and neuroimmune interactions.

Serotonin mediated immunoregulation and neural functions: Complicity in the aetiology of autism spectrum disorders

Serotonergic system has long been implicated in the aetiology of autism spectrum disorders (ASD), since platelet hyperserotonemia is consistently observed in a subset of autistic patients, who respond well to selective serotonin reuptake inhibitors. Apart from being a neurotransmitter, serotonin functions as a neurotrophic factor directing brain development and as an immunoregulator modulating immune responses. Serotonin transporter (SERT) regulates serotonin level in lymphoid tissues to ensure its proper functioning in innate and adaptive responses. Immunological molecules such as cytokines in turn regulate the transcription and activity of SERT. Dysregulation of serotonergic system could trigger signalling cascades that affect normal neural-immune interactions culminating in neurodevelopmental and neural connectivity defects precipitating behavioural abnormalities, or the disease phenotypes. Therefore, we suggest that a better understanding of the cross talk between serotonergic genes, immune systems and serotonergic neurotransmission will open wider avenues to develop pharmacological leads for addressing the core ASD behavioural deficits.

Determination of plasma heparin level improves identification of systemic mast cell activation disease

Diagnosis of mast cell activation disease (MCAD), i.e. systemic mastocytosis (SM) and idiopathic systemic mast cell activation syndrome (MCAS), usually requires demonstration of increased mast cell (MC) mediator release. Since only a few MC mediators are currently established as biomarkers of MCAD, the sensitivity of plasma heparin level (pHL) as an indicator of increased MC activation was compared with that of serum tryptase, chromogranin A and urinary N-methylhistamine levels in 257 MCAD patients. Basal pHL had a sensitivity of 41% in MCAS patients and 27% in SM patients. Non-pharmacologic stimulation of MC degranulation by obstruction of venous flow for 10 minutes increased the sensitivity of pHL in MCAS patients to 59% and in SM patients to 47%. In MCAS patients tryptase, chromogranin A, and N-methylhistamine levels exhibited low sensitivities (10%, 12%, and 22%, respectively), whereas sensitivities for SM were higher (73%, 63%, and 43%, respectively). Taken together, these data suggest pHL appears more sensitive than the other mediators for detecting systemic MC activity in patients with MCAS. The simple, brief venous occlusion test appears to be a useful indicator of the presence of pathologically irritable MCs, at least in the obstructed compartment of the body.

Oxidative stress markers are increased in patients with mastocytosis

BACKGROUND

Mastocytosis is characterized by clonal proliferation of mast cells limited to the skin (cutaneous mastocytosis: CM and mastocytosis in the skin: MIS) and/or involving internal organs (systemic mastocytosis: SM). Oxidative stress occurring in various inflammatory and neoplastic disorders causes molecular damage with the production of advanced oxidation protein products (AOPPs) and advanced glycation end products (AGEs). We evaluated these markers of oxidative stress in patients with CM/MIS and SM and correlated their levels with the presence of symptoms related to mast cell activation.

METHODS

Serum levels of AOPPs and AGEs in 34 patients with mastocytosis (23 CM/MIS and 11 SM) and 27 healthy controls were measured by spectrofluorimetric and spectrophotometric methods. Serum tryptase levels were measured by immunofluorescence.

RESULTS

Serum AOPPs, but not AGEs, were significantly higher in patients with mastocytosis as compared to healthy controls. While serum tryptase levels were higher in patients with SM as compared to those with CM/MIS, there was no difference in AOPP and AGE concentrations between these two groups of patients. Patients with recurrent mediator-related symptoms had lower AOPPs and AGEs as compared to patients without symptoms. AOPPs and AGEs were inversely correlated with the severity of symptoms, and in patients with symptoms, AOPPs correlated with tryptase levels.

DISCUSSION

Our data show that mastocytosis is associated with a state of increased oxidative stress that, in patients with mediator-related symptoms, correlates with mast cell burden as assessed by tryptase. Patients with symptoms presumably have an adaptive response resulting in lower blood levels of AOPPs and AGEs.

The expression of melanoma inhibitory activity on mast cells in child patients with cutaneous mastocytosis

BACKGROUND

Cutaneous mastocytosis is a disorder characterized by the proliferation of mast cells in the skin. Melanoma inhibitory activity (MIA) is a serum marker for malignant melanoma. However, it has not been known on MIA expression of cutaneous mastocytosis.

METHODS

We investigated the expression of MIA in 4 child patients with cutaneous mastocytosis immunohistochemically and serum MIA level in 1 patient by enzyme-linked immunosorbent assay.

RESULTS

Histopathological examination revealed diffuse mast cell infiltration in the dermis. MIA was positive for infiltrating mast cells in all patients. Serum level of MIA was elevated in 1 patient.

CONCLUSION

Although it was difficult to assess the significance of elevated serum levels of MIA in child patients, MIA was expressed on infiltrating mast cells in our study. Based on our findings, mast cell-derived MIA might be related to the formation of pigmented regions in cutaneous mastocytosis.

Serotonin signalling in the gut--functions, dysfunctions and therapeutic targets

Serotonin (5-HT) has been recognized for decades as an important signalling molecule in the gut, but it is still revealing its secrets. Novel gastrointestinal functions of 5-HT continue to be discovered, as well as distant actions of gut-derived 5-HT, and we are learning how 5-HT signalling is altered in gastrointestinal disorders. Conventional functions of 5-HT involving intrinsic reflexes include stimulation of propulsive and segmentation motility patterns, epithelial secretion and vasodilation. Activation of extrinsic vagal and spinal afferent fibres results in slowed gastric emptying, pancreatic secretion, satiation, pain and discomfort, as well as nausea and vomiting. Within the gut, 5-HT also exerts nonconventional actions such as promoting inflammation and serving as a trophic factor to promote the development and maintenance of neurons and interstitial cells of Cajal. Platelet 5-HT, originating in the gut, promotes haemostasis, influences bone development and serves many other functions. 5-HT3 receptor antagonists and 5-HT4 receptor agonists have been used to treat functional disorders with diarrhoea or constipation, respectively, and the synthetic enzyme tryptophan hydroxylase has also been targeted. Emerging evidence suggests that exploiting epithelial targets with nonabsorbable serotonergic agents could provide safe and effective therapies. We provide an overview of these serotonergic actions and treatment strategies.

Friend or foe: high bone mineral density on routine bone density scanning, a review of causes and management

A finding of high BMD on routine DXA scanning is not infrequent and most commonly reflects degenerative disease. However, BMD increases may also arise secondary to a range of underlying disorders affecting the skeleton. Although low BMD increases fracture risk, the converse may not hold for high BMD, since elevated BMD may occur in conditions where fracture risk is increased, unaffected or reduced. Here we outline a classification for the causes of raised BMD, based on identification of focal or generalized BMD changes, and discuss an approach to guide appropriate investigation by clinicians after careful interpretation of DXA scan findings within the context of the clinical history. We will also review the mild skeletal dysplasia associated with the currently unexplained high bone mass phenotype and discuss recent advances in osteoporosis therapies arising from improved understanding of rare inherited high BMD disorders.

5-HT and the immune system

The classical neurotransmitter, serotonin (5-HT), plays an important role outside of the central nervous system in immune signaling. Here I review recent studies describing 5-HT uptake in dendritic cells and B lymphocytes, 5-HT synthesis in T lymphocytes, and the role of specific 5-HT receptor subtypes in innate and adaptive immune cells. Furthermore, a recent paper describing the immune phenotype of 5-HT deficient mice is discussed.

Changes in gene expression caused by insect venom immunotherapy responsible for the long-term protection of insect venom-allergic patients

BACKGROUND

Insect venom immunotherapy (VIT) is the only causative treatment of insect venom allergy (IVA). The immunological mechanism(s) responsible for long-term protection achieved by VIT are largely unknown. A better understanding is relevant for improving the diagnosis, prediction of anaphylaxis, and monitoring and simplifying treatment of IVA.

OBJECTIVE

To find genes that are differentially expressed during the maintenance phase of VIT and after stopping, to get clues about the pathways involved in the long-term protective effect of immunotherapy.

METHODS

Whole genome gene expression analysis was performed on RNA samples from 50 patients treated with VIT and 43 healthy controls. Patients were divided into three groups: (1) before the start of VIT; (2) on maintenance phase of VIT for at least 3 years still receiving injections; and (3) after VIT.

RESULTS

Of all 48,804 probes present in the array, 48,773 transcripts had sufficient data for further analysis. The list of genes that were differentially expressed (at least log2 FC > 2; P < .05 corrected for multiple testing) during the maintenance phase of VIT as well as after successful VIT contains 89 entities. The function of these genes affects cell signaling, cell differentiation, and ion transport.

CONCLUSION

This study shows that a group of genes is differentially expressed both during and after VIT in comparison with gene expression in patients before VIT. Although the results of this study should be confirmed prospectively, the relevance of these findings is supported by the fact that they are related to putative mechanisms of immunotherapy.