Reactivation of inflammatory bowel disease in a mouse model of depression

Inflammatory Bowel Disease: A Stressed "Gut/Feeling"

Inflammatory bowel disease (IBD) is a chronic and relapsing intestinal inflammatory condition, hallmarked by a disturbance in the bidirectional interaction between gut and brain. In general, the gut/brain axis involves direct and/or indirect communication via the central and enteric nervous system, host innate immune system, and particularly the gut microbiota. This complex interaction implies that IBD is a complex multifactorial disease. There is increasing evidence that stress adversely affects the gut/microbiota/brain axis by altering intestinal mucosa permeability and cytokine secretion, thereby influencing the relapse risk and disease severity of IBD. Given the recurrent nature, therapeutic strategies particularly aim at achieving and maintaining remission of the disease. Alternatively, these strategies focus on preventing permanent bowel damage and concomitant long-term complications. In this review, we discuss the gut/microbiota/brain interplay with respect to chronic inflammation of the gastrointestinal tract and particularly shed light on the role of stress. Hence, we evaluated the therapeutic impact of stress management in IBD.

The influence of the brain-gut axis in inflammatory bowel disease and possible implications for treatment

Brain-gut interactions affect psychological wellbeing and symptom reporting in functional gastrointestinal disorders; the presence of anxiety or depression is associated with the development of new-onset gastrointestinal symptoms, and the presence of gastrointestinal symptoms is associated with the development of psychological disorders de novo. In inflammatory bowel diseases (IBD), the reporting of irritable bowel syndrome (IBS)-type symptoms by patients with quiescent disease is common, and is associated with psychological disorders, impaired quality of life, and increased health-care use. In IBD, data from observational studies suggest that psychological disorders might be associated with relapse of disease activity, and that inflammatory activity is associated with the development of new psychological disorders, as has been described for functional gastrointestinal disorders such as IBS and functional dyspepsia. The brain-gut axis provides the physiological link between the CNS and gastrointestinal tract that might facilitate these relationships. In IBS, treatments targeting disordered brain-gut axis activity, including psychological therapies and antidepressants, might lead to improved symptoms and quality of life. However, in IBD, the benefit of these treatments is less certain because of a scarcity of interventional studies. Despite the scarcity of trials, observational data suggest that the effect of disordered brain-gut axis activity in IBD is substantial, and scope remains for further well designed trials of psychological therapies and antidepressants, particularly in the subset of patients who have coexistent psychological disorders, or in those who report IBS-type symptoms. Integrating these treatments into a biopsychosocial model of care has the potential to improve both psychological wellbeing and quality of life in some patients with IBD, reducing health-care use and altering the natural history of disease.

Neuroimmune Responses Mediate Depression-Related Behaviors following Acute Colitis

Many patients with visceral inflammation develop pain and psychiatric comorbidities such as major depressive disorder, worsening the quality of life and increasing the risk of suicide. Here we show that neuroimmune activation in mice with dextran sodium sulfate-induced colitis is accompanied by the development of pain and depressive behaviors. Importantly, treatment with the flavonoid luteolin prevented both neuroimmune responses and behavioral abnormalities, suggesting a new potential therapeutic approach for patients with inflammatory bowel diseases.

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Acute colitis triggers long-term events related to depression

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Leukocytes infiltrate into brain vasculature

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Luteolin abolishes leukocyte infiltration and visceral hypersensitivity

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Luteolin abolishes depression-related behaviors

Traumatic stress and the autonomic brain-gut connection in development: Polyvagal Theory as an integrative framework for psychosocial and gastrointestinal pathology

A range of psychiatric disorders such as anxiety, depression, and post-traumatic stress disorder frequently co-occur with functional gastrointestinal (GI) disorders. Risk of these pathologies is particularly high in those with a history of trauma, abuse, and chronic stress. These scientific findings and rising awareness within the healthcare profession give rise to a need for an integrative framework to understand the developmental mechanisms that give rise to these observations. In this paper, we introduce a plausible explanatory framework, based on the Polyvagal Theory (Porges, Psychophysiology, 32, 301-318, 1995; Porges, International Journal of Psychophysiology, 42, 123-146, 2001; Porges, Biological Psychology, 74, 116-143, 2007), which describes how evolution impacted the structure and function of the autonomic nervous system (ANS). The Polyvagal Theory provides organizing principles for understanding the development of adaptive diversity in homeostatic, threat-response, and psychosocial functions that contribute to pathology. Using these principles, we outline possible mechanisms that promote and maintain socioemotional and GI dysfunction and review their implications for therapeutic targets.

Intestinal macrophages and their interaction with the enteric nervous system in health and inflammatory bowel disease

Over the past decades, there has been an increasing understanding of cellular and molecular mechanisms that mediate modulation of the immune system by the autonomic nervous system. The discovery that vagal nerve stimulation (VNS) attenuates endotoxin-induced experimental sepsis paved the way for further studies investigating neuro-immune interaction. In particular, great attention is now given to intestinal macrophages: several studies report the existence of both intrinsic and extrinsic neural mechanisms by which intestinal immune homoeostasis can be regulated in different layers of the intestine, mainly by affecting macrophage activation through neurotransmitter release. Given the important role of inflammation in numerous disease processes, such as inflammatory bowel disease (IBD), cholinergic anti-inflammatory mechanisms are under intense investigation both from a basic and clinical science perspective in immune-mediated diseases such as IBD. This review discusses recent insights on the cross-talk between enteric neurons and the immune system, especially focusing on macrophages, and provides an overview of basic and translational aspects of the cholinergic anti-inflammatory response as therapeutic alternative to reinstall immune homoeostasis in intestinal chronic inflammation.

Neuroimmune Communication in Health and Disease

The immune and nervous systems are tightly integrated, with each system capable of influencing the other to respond to infectious or inflammatory perturbations of homeostasis. Recent studies demonstrating the ability of neural stimulation to significantly reduce the severity of immunopathology and consequently reduce mortality have led to a resurgence in the field of neuroimmunology. Highlighting the tight integration of the nervous and immune systems, afferent neurons can be activated by a diverse range of substances from bacterial-derived products to cytokines released by host cells. While activation of vagal afferents by these substances dominates the literature, additional sensory neurons are responsive as well. It is becoming increasingly clear that although the cholinergic anti-inflammatory pathway has become the predominant model, a multitude of functional circuits exist through which neuronal messengers can influence immunological outcomes. These include pathways whereby efferent signaling occurs independent of the vagus nerve through sympathetic neurons. To receive input from the nervous system, immune cells including B and T cells, macrophages, and professional antigen presenting cells express specific neurotransmitter receptors that affect immune cell function. Specialized immune cell populations not only express neurotransmitter receptors, but express the enzymatic machinery required to produce neurotransmitters, such as acetylcholine, allowing them to act as signaling intermediaries. Although elegant experiments have begun to decipher some of these interactions, integration of these molecules, cells, and anatomy into defined neuroimmune circuits in health and disease is in its infancy. This review describes these circuits and highlights continued challenges and opportunities for the field.

The Effect of Antidepressants on the Course of Inflammatory Bowel Disease

BACKGROUND AND AIMS

Mood may have an important role in the natural history of inflammatory bowel disease (IBD). However, the impact of antidepressant use on prognosis is unknown. We aimed to address this in a longitudinal study in a referral population.

METHODS

We collected demographic data, clinical disease activity and mood using validated questionnaires, and antidepressant use at baseline. Longitudinal disease activity was defined by disease flare or need for glucocorticosteroids, escalation of medical therapy, hospitalisation, or intestinal resection. We compared rates of these over a minimum period of 2 years according to antidepressant use at baseline.

RESULTS

In total, 331 patients provided complete data, of whom 54 (15.8%) were taking an antidepressant at study entry. Older age, female gender, and abnormal mood scores were associated with antidepressant use. During longitudinal follow-up, there was a trend towards lower rates of any of the four endpoints of IBD activity of interest in patients with abnormal anxiety scores at baseline and who were receiving an antidepressant (42.3% versus 64.6%, P = 0.05). Based on univariate Cox regression analysis, there was a trend towards lower rates of escalation of medical therapy among patients receiving antidepressants at baseline (hazard ratio (HR) = 0.59; 95% confidence interval (CI) 0.35-1.00, P = 0.05). None of the differences observed persisted after multivariate Cox regression.

CONCLUSIONS

Antidepressants may have some beneficial effects on the natural history of IBD, but larger studies with longer follow-up are required. Whether these effects are limited to patients with abnormal mood remains uncertain.

The Intersection of Sex Differences, Tobacco Use, and Inflammation: Implications for Psychiatric Disorders

PURPOSE OF REVIEW

Tobacco use, sex differences, and psychiatric disorders are associated with altered immune function. There are also sex differences in tobacco use and psychiatric disorders. This review summarizes findings from the small, but growing literature examining sex differences in the effects of tobacco use on inflammation and the implications for psychiatric disorders.

RECENT FINDINGS

We identified four studies that tested the interaction between sex and tobacco/nicotine on inflammation. Although males and females generally exhibited differential tobacco-induced immune responses, the pattern varied depending on the sample (rodents vs. humans) and the method to evaluate inflammation. Evidence suggests that sex modulates the effects of tobacco smoke on inflammation. Many inflammation markers associated with sex differences and tobacco use are related to psychiatric disorders. We propose a model in which sex, tobacco use, and inflammation interact to increase risk for psychiatric disorders. Future studies are needed to examine the mechanisms that explain this relationship.

Bi-directionality of Brain-Gut Interactions in Patients With Inflammatory Bowel Disease

BACKGROUND & AIMS

Inflammatory bowel diseases (IBD) are associated with mood disorders, such as anxiety or depression, but it is not clear whether one contributes to development of the other, or if the interaction is bi-directional (anxiety or depression contributes to the progression of IBD, and IBD affects psychological health). We performed a 2-year longitudinal prospective study of patients in secondary to care investigate the bi-directionality of IBD and mood disorders.

METHODS

We collected data from 405 adult patients with a diagnosis of Crohn's disease (CD) or ulcerative colitis (UC) from November 2012 through June 2017. Demographic features, subtypes of IBD, treatments, symptoms, somatization, and fecal level of calprotectin were recorded at baseline. IBD activity was determined at baseline and after the follow-up period (2 years or more) using the Harvey-Bradshaw Index for CD and the Simple Clinical Colitis Activity Index for UC (scores ≥5 used to define disease activity). Anxiety and depression data were collected using the Hospital Anxiety and Depression Scale (HADS), at baseline and after the follow-up period. Objective markers of disease activity, including glucocorticosteroid prescription or flare of disease activity, escalation of therapy, hospitalization secondary to IBD activity, and intestinal resection during follow-up were assessed via case note review. A brain-gut direction of disease activity was defined as development of new IBD activity in patients with quiescent IBD and abnormal HADS scores at baseline. A gut-brain direction of disease activity was defined by subsequent development of abnormal HADS scores in patients with active IBD and normal HADS scores at baseline. We performed multivariate Cox regression controlling for patient characteristics and follow-up duration.

RESULTS

Baseline CD or UC disease activity were associated with an almost 6-fold increase in risk for a later abnormal anxiety score (hazard ratio [HR], 5.77; 95% CI, 1.89-17.7). In patients with quiescent IBD at baseline, baseline abnormal anxiety scores were associated with later need for glucocorticosteroid prescription or flare of IBD activity (HR, 2.08; 95% CI, 1.31-3.30) and escalation of therapy (HR, 1.82; 95% CI, 1.19-2.80). These associations persisted when normal IBD activity index scores and fecal level of calprotectin <250 μg/g were used to define quiescent disease at baseline.

CONCLUSIONS

In a 2-year study of patients with CD or UC, we found evidence for bi-directional effects of IBD activity and psychological disorders. Patients with IBD should be monitored for psychological well-being.

Nicotine and autoimmunity: The lotus' flower in tobacco

Nicotine, the major component of cigarettes, has demonstrated conflicting impact on the immune system: some authors suggest that increases pro-inflammatory cytokines and provokes cellular apoptosis of neutrophils, releasing intracellular components that act as auto-antigens; others claimed that nicotine has a protective and anti-inflammatory effects, especially by binding to α7 subunit of nicotinic acetylcholine receptors. The cholinergic pathway contributes to an anti-inflammatory environment characterized by increasing T regulatory cells response, down-regulating of pro-inflammatory cytokines and a pro-inflammatory cells apoptosis. The effects of nicotine were studied in different autoimmune disease, as multiple sclerosis, type 1 diabetes, rheumatoid arthritis, sarcoidosis, Behçet's disease and inflammatory bowel diseases. The major problems about nicotine are the addiction and the adverse effects of related to each commercialized formulation. We sought in this review to summarize the knowledge accumulated to date concerning the relationship between nicotine and autoimmunity.

Sex Differences and Drug Dose Influence the Role of the α7 Nicotinic Acetylcholine Receptor in the Mouse Dextran Sodium Sulfate-Induced Colitis Model

Introduction

α7 nicotinic acetylcholine receptors (nAChRs) play an important role in vagus nerve-based cholinergic anti-inflammatory effects. This study was designed to assess the role of α7 nAChRs in dextran sodium sulfate (DSS)-induced colitis in male and female mouse. We first compared disease activity and pathogenesis of colitis in α7 knockout and wild-type mice. We then evaluated the effect of several α7 direct and indirect agonists on the severity of disease in the DSS-induced colitis.

Methods

Male and female adult mice were administered 2.5% DSS solution freely in the drinking water for 7 consecutive days and the colitis severity (disease activity index) was evaluated as well as colon length, colon histology, and levels of tumor necrosis factor-alpha colonic levels.

Results

Male, but not female, α7 knockout mice displayed a significantly increased colitis severity and higher tumor necrosis factor-alpha levels as compared with their littermate wild-type mice. Moreover, pretreatment with selective α7 ligands PHA-543613, choline, and PNU-120596 decreased colitis severity in male but not female mice. The anti-colitis effects of these α7 compounds dissipated when administered at higher doses.

Conclusions

Our results suggest the presence of a α7-dependent anti-colitis endogenous tone in male mice. Finally, our results show for the first time that female mice are less sensitive to the anti-colitis activity of α7 agonists. Ovarian hormones may play a key role in the sex difference effect of α7 nAChRs modulation of colitis in the mouse.

Implications

Our collective results suggest that targeting α7 nAChRs could represent a viable therapeutic approach for intestinal inflammation diseases such as ulcerative colitis with the consideration of sex differences.

Traumatic stress-induced persistent changes in DNA methylation regulate neuropeptide Y expression in rat jejunum

BACKGROUND

Stress-induced chronic neuropsychiatric conditions such as anxiety are often co-morbid with gastrointestinal malfunctions. While we find enduring anxiety-like symptoms following minimal traumatic brain injury (MTBI) in rats, gastrointestinal consequences of MTBI remain elusive.

METHODS

In this study, we examined the effects of MTBI on a major gut peptide, neuropeptide Y (NPY) and gut motility. DNA methylation was studied as a possible epigenetic mechanism operative in the regulation of NPY expression in the gut.

KEY RESULTS

Minimal traumatic brain injury reduced the gut motility 48 hours and 30 days after trauma. The expression of DNA methyltransferase isoforms (DNMT1, DNMT3a, and DNMT3b) was altered in the jejunum 48 hours and 30 days after MTBI. However, the mRNA levels of growth arrest and DNA damage 45 (GADD45) isoforms, GADD45a, and GADD45b, which are believed to be involved in active DNA demethylation, initially decreased at 48 hours but subsequently increased after 30 days of trauma. Similarly, DNA hypomethylation at the NPY promoter region in the jejunum was correlated with the increase in NPY mRNA and protein levels 30 days post-trauma. On the other hand, DNA hypomethylation at 48 hours was associated with a decline in NPY expression. Treatment with 5-azacytidine (5-AzaC), a DNMT inhibitor, retarded DNA methylation and restored the NPY mRNA levels in the jejunum of MTBI-induced rats.

CONCLUSIONS & INFERENCES

These results suggest that DNA demethylation could be operative as an epigenetic mechanism in the long-term regulation of NPY gene expression to alter the gut motility during traumatic stress.

Systematic review with meta-analysis: the impact of a depressive state on disease course in adult inflammatory bowel disease

BACKGROUND

Despite a higher prevalence of psychosocial morbidity in Inflammatory Bowel Disease (IBD), the association between depressive state and disease course in IBD is poorly understood.

AIM

To investigate the impact of depressive state on disease course in IBD.

METHODS

We conducted a systematic review in MEDLINE, EMBASE, the Cochrane Database of Systematic Reviews and PsychINFO for prospective studies evaluating the impact of baseline depressive state on subsequent disease course in adult IBD.

RESULTS

Eleven studies matched our entry criteria, representing 3194 patients with IBD. Three reported on patients with ulcerative colitis (UC), four included patients with Crohn's disease (CD) exclusively, and four studies included both UC and CD. Five studies reported an association between depressive state and disease course. None of the UC-specific studies found any association. In three of four CD-specific studies, a relationship between depressive state and worsening disease course was found. In four of five studies including patients in remission at baseline, no association between depressive state and disease course was found. Pooled analysis of IBD studies with patients in clinical remission at baseline identified no association between depressive state and disease course (HR 1.04, 95%CI: 0.97-1.12).

CONCLUSION

There is limited evidence to support an association between depressive state and subsequent deterioration in disease course in IBD, but what data that exist are more supportive of an association with CD than UC. Baseline disease activity may be an important factor in this relationship. Further studies are needed to understand the relationship between mental health and outcomes in IBD.

Cholinergic modulation of the immune system presents new approaches for treating inflammation

The nervous system and immune system have broad and overlapping distributions in the body, and interactions of these ubiquitous systems are central to the field of neuroimmunology. Over the past two decades, there has been explosive growth in our understanding of neuroanatomical, cellular, and molecular mechanisms that mediate central modulation of immune functions through the autonomic nervous system. A major catalyst for growth in this field was the discovery that vagal nerve stimulation (VNS) caused a prominent attenuation of the systemic inflammatory response evoked by endotoxin in experimental animals. This effect was mediated by acetylcholine (ACh) stimulation of nicotinic receptors on splenic macrophages. Hence, the circuit was dubbed the "cholinergic anti-inflammatory pathway". Subsequent work identified the α7 nicotinic ACh receptor (α7nAChR) as the crucial target for attenuation of pro-inflammatory cytokine release from macrophages and dendritic cells. Further investigation made the important discovery that cholinergic T cells within the spleen and not cholinergic nerve cells were the source of ACh that stimulated α7 receptors on splenic macrophages. Given the important role that inflammation plays in numerous disease processes, cholinergic anti-inflammatory mechanisms are under intensive investigation from a basic science perspective and in translational studies of animal models of diseases such as inflammatory bowel disease and rheumatoid arthritis. This basic work has already fostered several clinical trials examining the efficacy of VNS and cholinergic therapeutics in human inflammatory diseases. This review provides an overview of basic and translational aspects of the cholinergic anti-inflammatory response and relevant pharmacology of drugs acting at the α7nAChR.

Modifiable Environmental Factors in Inflammatory Bowel Disease

PURPOSE OF REVIEW

Environmental factors may influence predisposition to develop inflammatory bowel diseases (Crohn's disease, ulcerative colitis) or alter its natural history by modification of both the host immune response and intestinal microbial composition. The purpose of this review is to translate such evidence into clinical practice by a focus on interventional studies that have modified such environmental influences to improve disease outcomes.

RECENT FINDINGS

Several environmental influences have been identified in the recent literature including tobacco use, diet, antibiotics, vitamin D deficiency, stress, appendectomy, and oral contraceptive use. Some risk factors have similar influences on both Crohn's disease and ulcerative colitis while others are disease-specific or have divergent effects. Emerging epidemiologic evidence has confirmed the association of many of these factors with incident disease using prospective data. In addition, laboratory data has supported their mechanistic plausibility and relevance to intestinal inflammation.

Homeostasis of the gut barrier and potential biomarkers

The gut barrier plays a crucial role by spatially compartmentalizing bacteria to the lumen through the production of secreted mucus and is fortified by the production of secretory IgA (sIgA) and antimicrobial peptides and proteins. With the exception of sIgA, expression of these protective barrier factors is largely controlled by innate immune recognition of microbial molecular ligands. Several specialized adaptations and checkpoints are operating in the mucosa to scale the immune response according to the threat and prevent overreaction to the trillions of symbionts inhabiting the human intestine. A healthy microbiota plays a key role influencing epithelial barrier functions through the production of short-chain fatty acids (SCFAs) and interactions with innate pattern recognition receptors in the mucosa, driving the steady-state expression of mucus and antimicrobial factors. However, perturbation of gut barrier homeostasis can lead to increased inflammatory signaling, increased epithelial permeability, and dysbiosis of the microbiota, which are recognized to play a role in the pathophysiology of a variety of gastrointestinal disorders. Additionally, gut-brain signaling may be affected by prolonged mucosal immune activation, leading to increased afferent sensory signaling and abdominal symptoms. In turn, neuronal mechanisms can affect the intestinal barrier partly by activation of the hypothalamus-pituitary-adrenal axis and both mast cell-dependent and mast cell-independent mechanisms. The modulation of gut barrier function through nutritional interventions, including strategies to manipulate the microbiota, is considered a relevant target for novel therapeutic and preventive treatments against a range of diseases. Several biomarkers have been used to measure gut permeability and loss of barrier integrity in intestinal diseases, but there remains a need to explore their use in assessing the effect of nutritional factors on gut barrier function. Future studies should aim to establish normal ranges of available biomarkers and their predictive value for gut health in human cohorts.

The Vagus Nerve in Appetite Regulation, Mood, and Intestinal Inflammation

Although the gastrointestinal tract contains intrinsic neural plexuses that allow a significant degree of independent control over gastrointestinal functions, the central nervous system provides extrinsic neural inputs that modulate, regulate, and integrate these functions. In particular, the vagus nerve provides the parasympathetic innervation to the gastrointestinal tract, coordinating the complex interactions between central and peripheral neural control mechanisms. This review discusses the physiological roles of the afferent (sensory) and motor (efferent) vagus in regulation of appetite, mood, and the immune system, as well as the pathophysiological outcomes of vagus nerve dysfunction resulting in obesity, mood disorders, and inflammation. The therapeutic potential of vagus nerve modulation to attenuate or reverse these pathophysiological outcomes and restore autonomic homeostasis is also discussed.

Negative Effects on Psychological Health and Quality of Life of Genuine Irritable Bowel Syndrome-type Symptoms in Patients With Inflammatory Bowel Disease

BACKGROUND & AIMS

Symptoms compatible with irritable bowel syndrome (IBS) are common in patients with inflammatory bowel disease (IBD), but it is unclear whether this relates to occult IBD activity. We attempted to resolve this issue in a secondary care population by using a cross-sectional study design.

METHODS

We analyzed Rome III IBS symptoms, disease activity indices, and psychological, somatization, and quality of life data from 378 consecutive, unselected adult patients with IBD seen in clinics at St James's University Hospital in Leeds, United Kingdom from November 2012 through June 2015. Participants provided a stool sample for fecal calprotectin (FC) analysis; levels ≥250 μg/g were used to define mucosal inflammation. By using symptom data and FC levels we identified 4 distinct groups of patients: those with true IBS-type symptoms (IBS-type symptoms with FC levels <250 μg/g, regardless of disease activity indices), quiescent IBD (no IBS-type symptoms with FC levels <250 μg/g, regardless of disease activity indices), occult inflammation (normal disease activity indices and FC levels ≥250 μg/g, regardless of IBS symptom status), or active IBD (abnormal disease activity indices with FC levels ≥250 μg/g, regardless of IBS symptom status). We compared characteristics between these groups.

RESULTS

Fifty-seven of 206 patients with Crohn's disease (27.7%) and 34 of 172 patients with ulcerative colitis (19.8%) had true IBS-type symptoms. Levels of psychological comorbidity and somatization were significantly higher among patients with true IBS-type symptoms than patients with quiescent IBD or occult inflammation. Quality of life levels were also significantly reduced compared with patients with quiescent disease or occult inflammation and were similar to those of patients with active IBD. By using FC levels ≥100 μg/g to define mucosal inflammation, we found a similar effect of IBS-type symptoms on psychological health and quality of life.

CONCLUSIONS

In a cross-sectional study, we identified a distinct group of patients with IBD and genuine IBS-type symptoms in the absence of mucosal inflammation. These symptoms had negative effects on psychological well-being and quality of life to the same degree as active IBD. New management strategies are required for this patient group.

Etiology and Treatment of Pain and Psychosocial Issues in Patients With Inflammatory Bowel Diseases

There is increasing evidence that brain-gut interactions are altered during development of inflammatory bowel diseases (IBDs). Understanding the relationship between the neurobiology, psychological symptoms, and social ramifications of IBD can guide comprehensive care for the whole patient. The most common psychological conditions in patients with IBD are chronic abdominal pain, anxiety, and depression. We review the evidence-based data and rates of these conditions and their respective relationship to IBD and the diagnostic approaches to identify patients with these conditions. Different treatment options for pain and psychosocial conditions are discussed, and new models of team-based IBD care are introduced. Providing the health care provider with tools to diagnose and manage psychological conditions in patients with Crohn's disease or ulcerative colitis is necessary for their total care and should be part of quality-improvement initiatives.

Vedolizumab Therapy Is Associated with an Improvement in Sleep Quality and Mood in Inflammatory Bowel Diseases

INTRODUCTION

Poor sleep, depression, and anxiety are common in patients with inflammatory bowel diseases (IBD) and associated with increased risk of relapse and poor outcomes. The effectiveness of therapies in improving such psychosocial outcomes is unclear but is an important question to examine with increasing selectivity of therapeutic agents.

METHODS

This prospective cohort enrolled patients with moderate-to-severe CD or UC starting biologic therapy with vedolizumab or anti-tumor necrosis factor α agents (anti-TNF). Sleep quality, depression, and anxiety were measured using validated short-form NIH PROMIS questionnaires assessing sleep and mood quality over the past 7 days. Disease activity was assessed using validated indices. Improvement in sleep and mood scores from baseline was assessed, and regression models were used to identify determinants of sleep quality.

RESULTS

Our study included 160 patients with IBD (49 anti-TNF, 111 Vedolizumab) among whom half were women and the mean age was 40.2 years. In the combined cohort, we observed a statistically significant and meaningful decrease in mean scores from baseline (52.8) by week 6 (49.8, p = 0.002). Among vedolizumab users, sleep T-score improved from baseline (53.6) by week 6 (50.7) and persisted through week 54 (46.5, p = 0.009). Parallel reductions in depression and anxiety were also noted (p < 0.05 by week 6). We observed no difference in improvement in sleep, depression, and anxiety between vedolizumab and anti-TNF use at week 6.

CONCLUSIONS

Both vedolizumab and anti-TNF biologic therapies were associated with improvement in sleep and mood quality in IBD.

Intestinal Barrier and Behavior

The intestinal barrier function contributes to gut homeostasis by modulating absorption of water, electrolytes, and nutrients from the lumen into the circulation while restricting the passage of noxious luminal substances and microorganisms. Chronic conditions such as rheumatoid arthritis, inflammatory bowel disease, and celiac disease are associated to intestinal barrier dysfunction. Here, the hypothesis is that a leaky intestinal wall allowing for indiscriminate passage of intraluminal compounds to the vascular compartment could in turn lead to systemic inflammation. An increasing number of studies are now investigating the association between gut permeability and CNS disorders, under the premise that translocation of intestinal luminal contents could affect CNS function, either directly or indirectly. Still, it is unknown whether disruption of intestinal barrier is a causative agent or a consequence in these situations. Here, we discuss the latest evidence pointing to an association between increased gut permeability and disrupted behavioral responses.

Early life adversity in piglets induces long-term upregulation of the enteric cholinergic nervous system and heightened, sex-specific secretomotor neuron responses

BACKGROUND

Early life adversity (ELA) is a risk factor for the later-life onset of gastrointestinal (GI) diseases such as irritable bowel syndrome (IBS); however, the mechanisms are poorly understood. Here, we utilized a porcine model of ELA, early weaning stress (EWS), to investigate the influence of ELA on the development and function of the enteric nervous system (ENS).

METHODS

Female and castrated male (Male-C) piglets were weaned from their sow either at 15 days of age (EWS) or 28 days of age (late weaning control, LWC). At 60 and 170 days of age, ileal mucosa-submucosa preparations were mounted in Ussing chambers and veratridine- and corticotropin releasing factor (CRF)-releasing factor-evoked short circuit current (Isc ) responses were recorded as indices of secretomotor neuron function. Enteric neuron numbers and the expression of select neurotransmitters and their receptors were also measured.

KEY RESULTS

Compared with LWC pigs, female, but not Male-C EWS, pigs exhibited heightened veratridine-induced Isc responses at 60 and 170 days of age that were inhibited with tetrodotoxin and atropine. Ileum from EWS pigs had higher numbers of enteric neurons that were choline acetyltransferase positive. Markers of increased cholinergic signaling (increased acetylcholinesterase) and downregulated mucosal muscarinic receptor 3 gene expression were also observed in EWS pigs.

CONCLUSIONS & INFERENCES

This study demonstrated that EWS in pigs induces lasting and sex-specific hypersensitivity of secretomotor neuron function and upregulation of the cholinergic ENS. These findings may represent a mechanistic link between ELA and lifelong susceptibility to GI diseases such as IBS.

Vagotomy affects the development of oral tolerance and increases susceptibility to develop colitis independently of the alpha-7 nicotinic receptor

Vagotomy (VGX) increases the susceptibility to develop colitis suggesting a crucial role for the cholinergic anti-inflammatory pathway in the regulation of the immune responses. Since oral tolerance and the generation of regulatory T cells (Tregs) are crucial to preserve mucosal immune homeostasis, we studied the effect of vagotomy and the involvement of α7 nicotinic receptors (α7nAChR) at the steady state and during colitis. Therefore, the development of both oral tolerance and colitis (induced by dextran sulfate sodium (DSS) or via T cell transfer) was studied in vagotomized mice and in α7nAChR^-/- mice. VGX, but not α7nAChR deficiency, prevented oral tolerance establishment. This effect was associated with reduced Treg conversion in the lamina propria and mesenteric lymphnodes. To the same extent, vagotomized mice, but not α7nAChR^-/- mice, developed a more severe DSS colitis compared with control mice treated with DSS, associated with a decreased number of colonic Tregs. However, neither VGX nor absence of α7nAChR in recipient mice affected colitis development in the T cell transfer model. In line, deficiency of α7nAChR exclusively in T cells did not influence the development of colitis induced by T cell transfer. Our results indicate a key role for the vagal intestinal innervation in the development of oral tolerance and colitis, most likely by modulating induction of Tregs independently of α7nAChR.

The Role of the Mesentery in Crohn's Disease: The Contributions of Nerves, Vessels, Lymphatics, and Fat to the Pathogenesis and Disease Course

Crohn's disease (CD) is a complex gastrointestinal disorder involving multiple levels of cross talk between the immunological, neural, vascular, and endocrine systems. The current dominant theory in CD is based on the unidirectional axis of dysbiosis-innate immunity-adaptive immunity-mesentery-body system. Emerging clinical evidence strongly suggests that the axis be bidirectional. The morphologic and/or functional abnormalities in the mesenteric structures likely contribute to the disease progression of CD, to a less extent the disease initiation. In addition to adipocytes, mesentery contains nerves, blood vessels, lymphatics, stromal cells, and fibroblasts. By the secretion of adipokines that have endocrine functions, the mesenteric fat tissue exerts its activity in immunomodulation mainly through response to afferent signals, neuropeptides, and functional cytokines. Mesenteric nerves are involved in the pathogenesis and prognosis of CD mainly through neuropeptides. In addition to angiogenesis observed in CD, lymphatic obstruction, remodeling, and impaired contraction maybe a cause and consequence of CD. Lymphangiogenesis and angiogenesis play a concomitant role in the progress of chronic intestinal inflammation. Finally, the interaction between neuropeptides, adipokines, and vascular and lymphatic endothelia leads to adipose tissue remodeling, which makes the mesentery an active participator, not a bystander, in the disease initiation and precipitation CD. The identification of the role of mesentery, including the structure and function of mesenteric nerves, vessels, lymphatics, and fat, in the intestinal inflammation in CD has important implications in understanding its pathogenesis and clinical management.

The intestinal cholinergic anti-inflammatory pathway

The main task of the immune system is to distinguish and respond accordingly to 'danger' or 'non-danger' signals. This is of critical importance in the gastrointestinal tract in which immune cells are constantly in contact with food antigens, symbiotic microflora and potential pathogens. This complex mixture of food antigens and symbionts are essential for providing vital nutrients, so they must be tolerated by the intestinal immune system to prevent aberrant inflammation. Therefore, in the gut the balance between immune activation and tolerance should be tightly regulated to maintain intestinal homeostasis and to prevent hypersensitivity to harmless luminal antigens. Loss of this delicate equilibrium can lead to abnormal activation of the intestinal immune system resulting in devastating gastrointestinal disorders such as inflammatory bowel disease (IBD). Recent evidence supports the idea that the central nervous system interacts dynamically via the vagus nerve with the intestinal immune system to modulate inflammation through humoral and neural pathways, using a mechanism also referred to as the intestinal cholinergic anti-inflammatory pathway. In this review, we will focus on the current understanding of the mechanisms and neuronal circuits involved in the intestinal cholinergic anti-inflammatory pathway. Further investigation on the crosstalk between the nervous and intestinal immune system will hopefully provide new insights leading to the identification of innovative therapeutic approaches to treat intestinal inflammatory diseases.

Interaction between diet and gastrointestinal endocrine cells

The gastrointestinal endocrine cells are essential for life. They regulate the gastrointestinal motility, secretion, visceral sensitivity, absorption, local immune defense, cell proliferation and appetite. These cells act as sensory cells with specialized microvilli that project into the lumen that sense the gut contents (mostly nutrients and/or bacteria byproducts), and respond to luminal stimuli by releasing hormones into the lamina propria. These released hormones exert their actions by entering the circulating blood and reaching distant targets (endocrine mode), nearby structures (paracrine mode) or via afferent and efferent synaptic transmission. The mature intestinal endocrine cells are capable of expressing several hormones. A change in diet not only affects the release of gastrointestinal hormones, but also alters the densities of the gut endocrine cells. The interaction between ingested foodstuffs and the gastrointestinal endocrine cells can be utilized for the clinical management of gastrointestinal and metabolic diseases, such as irritable bowel syndrome, obesity and diabetes.

Comorbidity between depression and inflammatory bowel disease explained by immune-inflammatory, oxidative, and nitrosative stress; tryptophan catabolite; and gut-brain pathways

The nature of depression has recently been reconceptualized, being conceived as the clinical expression of activated immune-inflammatory, oxidative, and nitrosative stress (IO&NS) pathways, including tryptophan catabolite (TRYCAT), autoimmune, and gut-brain pathways. IO&NS pathways are similarly integral to the pathogenesis of inflammatory bowel disease (IBD). The increased depression prevalence in IBD associates with a lower quality of life and increased morbidity in IBD, highlighting the role of depression in modulating the pathophysiology of IBD.This review covers data within such a wider conceptualization that better explains the heightened co-occurrence of IBD and depression. Common IO&NS underpinning between both disorders is evidenced by increased pro-inflammatory cytokine levels, eg, interleukin-1 (IL-1) and tumor necrosis factor-α, IL-6 trans-signalling; Th-1- and Th-17-like responses; neopterin and soluble IL-2 receptor levels; positive acute phase reactants (haptoglobin and C-reactive protein); lowered levels of negative acute phase reactants (albumin, transferrin, zinc) and anti-inflammatory cytokines (IL-10 and transforming growth factor-β); increased O&NS with damage to lipids, proteinsm and DNA; increased production of nitric oxide (NO) and inducible NO synthase; lowered plasma tryptophan but increased TRYCAT levels; autoimmune responses; and increased bacterial translocation. As such, heightened IO&NS processes in depression overlap with the biological underpinnings of IBD, potentially explaining their increased co-occurrence. This supports the perspective that there is a spectrum of IO&NS disorders that includes depression, both as an emergent comorbidity and as a contributor to IO&NS processes. Such a frame of reference has treatment implications for IBD when "comorbid" with depression.

Toward a better understanding of the central consequences of intestinal inflammation

Inflammatory bowel diseases (IBDs), which include Crohn's disease and ulcerative colitis, are inflammatory diseases of the gastrointestinal tract. Quality of life for IBD patients is negatively affected by associated pain and gastrointestinal dysfunction, but also by serious behavioral symptoms that include depression, anxiety, fatigue, and cognitive dysfunction. Because these behavioral comorbidities are poorly understood, we have investigated them in a rat model of IBD caused by infusion of a hapten (trinitrobenzene sulfonic acid (TNBS)) into the lower colon. TNBS colitis has many similarities to Crohn's disease, and we have found that it is associated with changes in central nervous system function. TNBS-treated animals have lowered seizure thresholds, which resolve following remission, and hippocampal slices from such animals display increased excitability. There are significant changes in excitatory, AMPA receptor-mediated transmission, in part due to increased numbers of AMPA receptors lacking the GluR2 subunit. Long-term potentiation and depression are reduced in colitic animals, and the synaptic alterations are reversed if microglial activation and tumor necrosis factor α synthesis within the brain are blocked.

Behavioral despair associated with a mouse model of Crohn's disease: Role of nitric oxide pathway

Crohn's disease (CD) is associated with increased psychiatric co-morbidities. Nitric oxide (NO) is implicated in inflammation and tissue injury in CD, and it may also play a central role in pathogenesis of the accompanying behavioral despair. This study investigated the role of the NO pathway in behavioral despair associated with a mouse model of CD. Colitis was induced by intrarectal (i.r.) injection of 2,4,6-trinitrobenzenesulfonic acid (10mg TNBS in 50% ethanol). Forced swimming test (FST), pharmacological studies and tissues collection were performed 72 h following TNBS administration. To address a possible inflammatory origin for the behavioral despair following colitis induction, tumor necrosis factor-alpha (TNF-α) level was measured in both the hippocampal and colonic tissue samples. In parallel, hippocampal inducible nitric oxide synthase (iNOS) and nitrite level were evaluated. Pharmacological studies targeting the NO pathway were performed 30-60 min before behavioral test. Colitis was confirmed by increased colonic TNF-α level and microscopic score. Colitic mice demonstrated a significantly higher immobility time in the FST associated to a significant increase of hippocampal TNF-α, iNOS expression and nitrite content. Acute NOS inhibition using either Nω-nitro-l-arginine methyl ester (a non-specific NOS inhibitor) or aminoguanidine hydrochloride (a specific iNOS inhibitor) decreased the immobility time in colitic groups. Moreover, acute treatment with both NOS inhibitors decreased the TNF-α level and nitrite content in the hippocampal samples. This study suggests that the NO pathway may be involved in the behavioral effects in the mouse TNBS model of CD. These findings endow new insights into the gut-brain communication during the development of colonic inflammation, which may ultimately lead to improved therapeutic strategies to combat behavior changes associated with gastrointestinal disorders.

Mechanisms by which Stress Affects the Experimental and Clinical Inflammatory Bowel Disease (IBD): Role of Brain-Gut Axis

BACKGROUND

Stress of different origin is known to alter so called "braingut axis" and contributes to a broad array of gastrointestinal disorders including inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and other functional gastrointestinal diseases. The stressful situations and various stressors including psychosocial events, heat, hypo- and hyperthermia may worsen the course of IBD via unknown mechanism. The aims of this paper were to provide an overview of experimental and clinical evidences that stress activates the brain-gut axis which results in a mucosal mast cells activation and an increase in the production of proinflammatory cytokines and other endocrine and humoral mediators.

METHODS

Research and online content related to effects of stress on lower bowel disorders are reviewed and most important mechanisms are delineated.

RESULTS

Brain conveys the neural, endocrine and circulatory messages to the gut via brain-gut axis reflecting changes in corticotrophin releasing hormone, mast cells activity, neurotransmission at the autonomic nerves system and intestinal barrier function all affecting the pathogenesis of animal colitis and human IBD. Stress triggers the hypothalamus-pituitary axis and the activation of the autonomic nervous system, an increase in cortisol levels and proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin-8, interleukin-1beta and interleukin-6.

CONCLUSION

The acute or chronic stress enhances the intestinal permeability weakening of the tight junctions and increasing bacterial translocation into the intestinal wall. An increased microbial load in the colonic tissue, excessive cytokine release and a partially blunted immune reactivity in response to stress result in its negative impact on IBD.

Psychological status in Iranian patients with ulcerative colitis and its relation to disease activity and quality of life

BACKGROUND

Psychological profile of inflammatory bowel disease patients is not well studied in Iran. We investigated the psychological status of Iranian patients with ulcerative colitis (UC) and its relationship with disease activity and quality of life (QOL).

MATERIALS AND METHODS

A cross-sectional study was conducted on adult UC patients. The Lichtiger Colitis Activity Index, Hospital Anxiety and Depression Scale, General Health Questionnaire-12, and WHOQOL-BREF, were completed by the patients.

RESULTS

From 120 studied patients, 35 (29.2%), 48 (40.0%), and 46 (38.3%) had significant anxiety, depression, and psychological distress, respectively. Anxiety, depression, and psychological distress were strongly correlated with disease activity (r = 0.357 to 0.439, P < 0.01). Disease activity was negatively correlated with all QOL dimensions (r = -0.245 to -0.550, P < 0.01). Anxiety, depression, and psychological distress were also negatively correlated with all QOL domains (r = -0.356 to -0.789, P < 0.01). In the regression models, anxiety was independently associated with active disease (β = 4.150, P = 0.049). Furthermore, disease activity was associated with the physical health (β = -0.371, P < 0.001). For almost all of the QOL domains, depression and psychological distress were independent predictors (β = -0.296 to -0.453, P < 0.001).

CONCLUSION

Anxiety, depression, and psychological distress are highly frequent in UC patients of our society and are strongly associated with disease activity. Depression and psychological distress are important predictors of poor QOL in these patients. Further prospective studies, as well as clinical trials, are warranted in this regard.

The Neuromodulation of the Intestinal Immune System and Its Relevance in Inflammatory Bowel Disease

One of the main tasks of the immune system is to discriminate and appropriately react to “danger” or “non-danger” signals. This is crucial in the gastrointestinal tract, where the immune system is confronted with a myriad of food antigens and symbiotic microflora that are in constant contact with the mucosa, in addition to any potential pathogens. This large number of antigens and commensal microflora, which are essential for providing vital nutrients, must be tolerated by the intestinal immune system to prevent aberrant inflammation. Hence, the balance between immune activation versus tolerance should be tightly regulated to maintain intestinal homeostasis and to prevent immune activation indiscriminately against all luminal antigens. Loss of this delicate equilibrium can lead to chronic activation of the intestinal immune response resulting in intestinal disorders, such as inflammatory bowel diseases (IBD). In order to maintain homeostasis, the immune system has evolved diverse regulatory strategies including additional non-immunological actors able to control the immune response. Accumulating evidence strongly indicates a bidirectional link between the two systems in which the brain modulates the immune response via the detection of circulating cytokines and via direct afferent input from sensory fibers and from enteric neurons. In the current review, we will highlight the most recent findings regarding the cross-talk between the nervous system and the mucosal immune system and will discuss the potential use of these neuronal circuits and neuromediators as novel therapeutic tools to reestablish immune tolerance and treat intestinal chronic inflammation.

Blocking peripheral serotonin synthesis by telotristat etiprate (LX1032/LX1606) reduces severity of both chemical- and infection-induced intestinal inflammation

Mucosal inflammation is accompanied by an alteration in 5-HT. Intestinal 5-HT synthesis is catalyzed by tryptophan hydroxylase 1 (Tph1) and we have shown that mice deficient in this rate-limiting enzyme have reduced severity of intestinal inflammation in models of chemical-induced experimental colitis. Here, we investigated the effect of blocking peripheral 5-HT synthesis in generation of intestinal inflammation by a using peripheral Tph inhibitor, telotristat etiprate (LX1606), in models of intestinal inflammation. LX1606 was given orally either prophylactically or therapeutically to mice with dextran sulfate sodium (DSS)-induced colitis or with infection with Trichuris muris. Severity of intestinal inflammation was measured by assessment of disease activity scores, histological damage, and MPO and inflammatory cytokine levels. LX1606 significantly reduced intestinal 5-HT levels and delayed onset and severity of DSS-induced acute and chronic colitis. This was associated with decreased MPO and proinflammatory cytokine levels compared with vehicle-treated controls. In the infection-induced inflammation model, treatment with LX1606 enhanced worm expulsion as well as increased IL-10 production and goblet cell numbers. LX1606-treated mice had significantly lower MPO and IL-1β levels compared with controls postinfection. Our results demonstrate that peripheral 5-HT plays an important role in intestinal inflammation and in the generation of immune responses. Pharmacological reduction of peripheral 5-HT may serve as a potential strategy for modulating various intestinal inflammatory disorders.

Epidemiology and risk factors for IBD

IBD, comprising Crohn's disease and ulcerative colitis, is a chronic immunologically mediated disease at the intersection of complex interactions between genetics, environment and gut microbiota. Established high-prevalence populations of IBD in North America and Europe experienced the steepest increase in incidence towards the second half of the twentieth century. Furthermore, populations previously considered 'low risk' (such as in Japan and India) are witnessing an increase in incidence. Potentially relevant environmental influences span the spectrum of life from mode of childbirth and early-life exposures (including breastfeeding and antibiotic exposure in infancy) to exposures later on in adulthood (including smoking, major life stressors, diet and lifestyle). Data support an association between smoking and Crohn's disease whereas smoking cessation, but not current smoking, is associated with an increased risk of ulcerative colitis. Dietary fibre (particularly fruits and vegetables), saturated fats, depression and impaired sleep, and low vitamin D levels have all been associated with incident IBD. Interventional studies assessing the effects of modifying these risk factors on natural history and patient outcomes are an important unmet need. In this Review, the changing epidemiology of IBD, mechanisms behind various environmental associations and interventional studies to modify risk factors and disease course are discussed.

Relationship between brain-gut axis and inflammatory bowel disease

Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), is a chronic relapsing inflammatory disease affecting the gastrointestinal tract. The incidence of IBD has increased dramatically year by year in China. Currently, the IBD research is focused on genetically predisposed factors, immune response, environmental triggers and infections. However, the etiology of IBD is still unclear. Recently, more attention has been paid to the research of neural regulation affecting the progression of IBD. Previous research has revealed that psycho-neuro-endocrine-immune modulation through the brain-gut axis plays a crucial role in the pathogenesis of IBD. It is important to explore other psychotherapies applied to adjutant therapy in IBD. This review reviews the recent advances in understanding the relationship between the brain-gut axis and inflammatory bowel disease.

The homeostatic role of neuropeptide Y in immune function and its impact on mood and behaviour

Neuropeptide Y (NPY), one of the most abundant peptides in the nervous system, exerts its effects via five receptor types, termed Y1, Y2, Y4, Y5 and Y6. NPY's pleiotropic functions comprise the regulation of brain activity, mood, stress coping, ingestion, digestion, metabolism, vascular and immune function. Nerve-derived NPY directly affects immune cells while NPY also acts as a paracrine and autocrine immune mediator, because immune cells themselves are capable of producing and releasing NPY. NPY is able to induce immune activation or suppression, depending on a myriad of factors such as the Y receptors activated and cell types involved. There is an intricate relationship between psychological stress, mood disorders and the immune system. While stress represents a risk factor for the development of mood disorders, it exhibits diverse actions on the immune system as well. Conversely, inflammation is regarded as an internal stressor and is increasingly recognized to contribute to the pathogenesis of mood and metabolic disorders. Intriguingly, the cerebral NPY system has been found to protect against distinct disturbances in response to immune challenge, attenuating the sickness response and preventing the development of depression. Thus, NPY plays an important homeostatic role in balancing disturbances of physiological systems caused by peripheral immune challenge. This implication is particularly evident in the brain in which NPY counteracts the negative impact of immune challenge on mood, emotional processing and stress resilience. NPY thus acts as a unique signalling molecule in the interaction of the immune system with the brain in health and disease.

IBS-like symptoms in patients with ulcerative colitis

Ulcerative colitis (UC) and irritable bowel syndrome (IBS) are chronic gastrointestinal disorders that, until recently, have been considered dichotomous conditions falling on either side of a functional-organic divide. However, persistent gastrointestinal symptoms, akin to those of IBS, are observed in up to one in three patients with quiescent UC. Whether these lower gastrointestinal symptoms are secondary to coexistent IBS or occult UC disease activity is uncertain, but when objective evidence of disease activity is lacking, escalation of conventional pharmacotherapy in such patients is often ineffective. The etiologies of both UC and IBS remain unclear, but dysregulation of the enteric nervous system, an altered microbiome, low-grade mucosal inflammation, and activation of the brain–gut axis is common to both; this suggests that some overlap between the two conditions is plausible. How best to investigate and manage IBS-type symptoms in UC patients remains unclear. Studies that have assessed patients with UC who meet criteria for IBS for subclinical inflammation have been conflicting in their results. Although evidence-based treatments for IBS exist, their efficacy in UC patients reporting these types of symptoms remains unclear. Given the disturbances in gut microbiota in UC, and the possible role of the brain–gut axis in the generation of such symptoms, treatments such as probiotics, fecal transfer, antidepressants, or psychological therapies would seem logical approaches to use in this group of patients. However, there are only limited data for all of these therapies; this suggests that randomized controlled trials to investigate their efficacy in this setting may be warranted.

Evaluation of anti-colitic effect of fluvoxamine against acetic acid-induced colitis in normal and reserpinized depressed rats

High prevalence of psychological comorbidities such as depression and anxiety in patients with inflammatory bowel disease (IBD) supports the premise that adding an anti-depressant drug with known anti-inflammatory effect to the medical treatment have beneficial effect in the course of the underlying disease. Colitis was induced by intracolonic instillation of 2 ml of 4% v/v acetic acid solution in rats. Anti-colitic effect of fluvoxamine was evaluated in two categories: A: normal rats, B: reserpinized (6 mg/kg, i.p.) depressed rats. In group A, fluvoxamine (2.5, 5, 10 mg/kg, i.p.) was administered 2 h after induction of colitis and in group B: reserpine (6 mg/kg, i.p.) was administered 1 h prior to colitis induction and then fluvoxamine (2.5, 5, 10 mg/kg, i.p.) was administered 2 h after colitis induction. Dexamethasone (1 mg/kg) was used as reference drug. All the treatments continued daily for five days. The effect was assessed on the basis of macroscopic score, biochemical (myeloperoxidase) changes and histopathological studies. Results showed that fluvoxamine (2.5 and 5 mg/kg) and dexamethasone treatment markedly reduced disease severity in both reserpinized and non-reserpinized rats as indicated by reduction in macroscopic and microscopic colonic damages while reserpine adversely exacerbated the colitis damage. Myeloperoxidase activity which was increased following colitis induction was also decreased. The findings of this study elucidate the anti-colitic and anti-inflammatory properties of fluvoxamine and so introduced it as a good candidate to treat depressive symptoms in people comorbid to IBD.

Macrophages and depression - a misalliance or well-arranged marriage?

Depression is a severe medical condition with multiple manifestations and diverse, largely unknown etiologies. The immune system, particularly macrophages, plays an important role in the pathology of the illness. Macrophages represent a heterogeneous population of immune cells that is dispersed throughout the body. The central nervous system is populated by several types of macrophages, including microglia, perivascular cells, meningeal and choroid plexus macrophages and pericytes. These cells occupy different brain compartments and have various functions. Under basal conditions, brain macrophages support the proper function of neural cells, organize and preserve the neuronal network and maintain homeostasis. As cells of the innate immune system, they recognize and react to any disturbances in homeostasis, eliminating pathogens or damaged cells, terminating inflammation and proceeding to initiate tissue reconstruction. Disturbances in these processes result in diverse pathologies. In particular, tissue stress or malfunction, both in the brain and in the periphery, produce sustained inflammatory states, which may cause depression. Excessive release of proinflammatory mediators is responsible for alterations of neurotransmitter systems and the occurrence of depressive symptoms. Almost all antidepressive drugs target monoamine or serotonin neurotransmission and also have anti-inflammatory or immunosuppressive properties. In addition, non-pharmacological treatments, such as electroconvulsive shock, can also exert anti-inflammatory effects. Recent studies have shown that antidepressive therapies can affect the functional properties of peripheral and brain macrophages and skew them toward the anti-inflammatory M2 phenotype. Because macrophages can affect outcome of inflammatory diseases, alleviate sickness behavior and improve cognitive function, it is possible that the effects of antidepressive treatments may be, at least in part, mediated by changes in macrophage activity.

Correlation between depression, anxiety, and polymorphonuclear cells' resilience in ulcerative colitis: the mediating role of heat shock protein 70

Background

To investigate whether anxiety and depression levels are associated with Heat Shock Protein 70 (HSP70) induction in the colon of patients with ulcerative colitis (UC).

Methods

The design was cross-sectional. Clinical activity was assessed by the Rachmilewitz Index (CAI). Three psychometric questionnaires were used: Zung Depression Rating Scale (ZDRS), Spielberg State-Trait Anxiety Inventory (STAI), Hospital Anxiety and Depression Scale (HADS). Colon biopsies were obtained from each affected anatomical site. Severity of inflammation was assessed by eosin/hematoxylin. Constitutive (HSP70c) and inducible (HSP70i) HSP70 expression were immunohistochemically studied.

Results

29 UC patients were enrolled (69% men). Mean age was 46.5 years (SD: 19.5). Inflammation severity was moderate in 17 patients, severe in 6, and mild in 6. The mean number of years since diagnosis was 7.9 (SD: 6.5). The mean CAI was 6.4 (SD: 3.1). In active UC, there was downregulation of HSP70c in inflamed epithelium, without significant HSP70 induction. In 22/29 cases of active cryptitis, polymorphonuclear cells (PMN) clearly expressed HSP70i, with weak, focal positivity in the other 7 cases. Except for the hospital anxiety scale, scores in all psychometric tools were higher in patients with strong HSP70i immunoreactivity in the PMN. Logistic regression showed a strong positive relationship between HSP70i immunoreactivity in the PMN cells and scores in the trait anxiety, ZDRS, and hospital depression scales, (Odds ratios 1.3, 1.3, and 1.5; P = 0.018, 0.023, and 0.038; Wald test, 5.6, 5.2, and 4.3 respectively) and a weaker but significant positive correlation with the CAI (Odds ratio 1.654; P = 0.049; Wald test 3.858).

Conclusion

HSP70 is induced in PMN cells of UC patients and its induction correlates with depression and anxiety levels.

DNBS/TNBS colitis models: providing insights into inflammatory bowel disease and effects of dietary fat

Inflammatory Bowel Diseases (IBD), including Crohn's Disease and Ulcerative Colitis, have long been associated with a genetic basis, and more recently host immune responses to microbial and environmental agents. Dinitrobenzene sulfonic acid (DNBS)-induced colitis allows one to study the pathogenesis of IBD associated environmental triggers such as stress and diet, the effects of potential therapies, and the mechanisms underlying intestinal inflammation and mucosal injury. In this paper, we investigated the effects of dietary n-3 and n-6 fatty acids on the colonic mucosal inflammatory response to DNBS-induced colitis in rats. All rats were fed identical diets with the exception of different types of fatty acids [safflower oil (SO), canola oil (CO), or fish oil (FO)] for three weeks prior to exposure to intrarectal DNBS. Control rats given intrarectal ethanol continued gaining weight over the 5 day study, whereas, DNBS-treated rats fed lipid diets all lost weight with FO and CO fed rats demonstrating significant weight loss by 48 hr and rats fed SO by 72 hr. Weight gain resumed after 72 hr post DNBS, and by 5 days post DNBS, the FO group had a higher body weight than SO or CO groups. Colonic sections collected 5 days post DNBS-treatment showed focal ulceration, crypt destruction, goblet cell depletion, and mucosal infiltration of both acute and chronic inflammatory cells that differed in severity among diet groups. The SO fed group showed the most severe damage followed by the CO, and FO fed groups that showed the mildest degree of tissue injury. Similarly, colonic myeloperoxidase (MPO) activity, a marker of neutrophil activity was significantly higher in SO followed by CO fed rats, with FO fed rats having significantly lower MPO activity. These results demonstrate the use of DNBS-induced colitis, as outlined in this protocol, to determine the impact of diet in the pathogenesis of IBD.

Nicotine attenuates activation of tissue resident macrophages in the mouse stomach through the β2 nicotinic acetylcholine receptor

Background

The cholinergic anti-inflammatory pathway is an endogenous mechanism by which the autonomic nervous system attenuates macrophage activation via nicotinic acetylcholine receptors (nAChR). This concept has however not been demonstrated at a cellular level in intact tissue. To this end, we have studied the effect of nicotine on the activation of resident macrophages in a mouse stomach preparation by means of calcium imaging.

Methods

Calcium transients ([Ca²⁺]_i) in resident macrophages were recorded in a mouse stomach preparation containing myenteric plexus and muscle layers by Fluo-4. Activation of macrophages was achieved by focal puff administration of ATP. The effects of nicotine on activation of macrophages were evaluated and the nAChR involved was pharmacologically characterized. The proximity of cholinergic nerves to macrophages was quantified by confocal microscopy. Expression of β2 and α7 nAChR was evaluated by β2 immunohistochemistry and fluorophore-tagged α-bungarotoxin.

Results

In 83% of macrophages cholinergic varicose nerve fibers were detected at distances <900nm. The ATP induced [Ca²⁺]_i increase was significantly inhibited in 65% or 55% of macrophages by 100µM or 10µM nicotine, respectively. This inhibitory effect was reversed by the β2 nAChR preferring antagonist dihydro-β-eryhtroidine but not by hexamethonium (non-selective nAChR-antagonist), mecamylamine (α3β4 nAChR-preferring antagonist), α-bungarotoxin or methyllycaconitine (both α7 nAChR-preferring antagonist). Macrophages in the stomach express β2 but not α7 nAChR at protein level, while those in the intestine express both receptor subunits.

Conclusion

This study is the first insitu demonstration of an inhibition of macrophage activation by nicotine suggesting functional signaling between cholinergic neurons and macrophages in the stomach. The data suggest that the β2 subunit of the nAChR is critically involved in the nicotine-induced inhibition of these resident macrophages.

The vagal innervation of the gut and immune homeostasis

The central nervous system interacts dynamically with the immune system to modulate inflammation through humoral and neural pathways. Recently, in animal models of sepsis, the vagus nerve (VN) has been proposed to play a crucial role in the regulation of the immune response, also referred to as the cholinergic anti-inflammatory pathway. The VN, through release of acetylcholine, dampens immune cell activation by interacting with α-7 nicotinic acetylcholine receptors. Recent evidence suggests that the vagal innervation of the gastrointestinal tract also plays a major role controlling intestinal immune activation. Indeed, VN electrical stimulation potently reduces intestinal inflammation restoring intestinal homeostasis, whereas vagotomy has the reverse effect. In this review, we will discuss the current understanding concerning the mechanisms and effects involved in the cholinergic anti-inflammatory pathway in the gastrointestinal tract. Deeper investigation on this counter-regulatory neuroimmune mechanism will provide new insights in the cross-talk between the nervous and immune system leading to the identification of new therapeutic targets to treat intestinal immune disease.

Depression, antidepressant medications, and risk of Clostridium difficile infection

BACKGROUND

An ancillary finding in previous research has suggested that the use of antidepressant medications increases the risk of developing Clostridium difficile infection (CDI). Our objective was to evaluate whether depression or the use of anti-depressants altered the risk of developing CDI, using two distinct datasets and study designs.

METHODS

In Study 1, we conducted a longitudinal investigation of a nationally representative sample of older Americans (n = 16,781), linking data from biennial interviews to physician and emergency department visits, stays in hospital and skilled nursing facilities, home health visits, and other outpatient visits. In Study 2, we completed a clinical investigation of hospitalized adults who were tested for C. difficile (n = 4047), with cases testing positive and controls testing negative. Antidepressant medication use prior to testing was ascertained.

RESULTS

The population-based rate of CDI in older Americans was 282.9/100,000 person-years (95% confidence interval (CI)) 226.3 to 339.5) for individuals with depression and 197.1/100,000 person-years for those without depression (95% CI 168.0 to 226.1). The odds of CDI were 36% greater in persons with major depression (95% CI 1.06 to 1.74), 35% greater in individuals with depressive disorders (95% CI 1.05 to 1.73), 54% greater in those who were widowed (95% CI 1.21 to 1.95), and 25% lower in adults who did not live alone (95% CI 0.62 to 0.92). Self-reports of feeling sad or having emotional, nervous or psychiatric problems at baseline were also associated with the later development of CDI. Use of certain antidepressant medications during hospitalization was associated with altered risk of CDI.

CONCLUSIONS

Adults with depression and who take specific anti-depressants seem to be more likely to develop CDI. Older adults who are widowed or who live alone are also at greater risk of CDI.

Targeted inhibition of serotonin type 7 (5-HT7) receptor function modulates immune responses and reduces the severity of intestinal inflammation

Mucosal inflammation in conditions ranging from infective acute enteritis or colitis to inflammatory bowel disease is accompanied by alteration in serotonin (5-hydroxytryptamine [5-HT]) content in the gut. Recently, we have identified an important role of 5-HT in the pathogenesis of experimental colitis. 5-HT type 7 (5-HT7) receptor is one of the most recently identified members of the 5-HT receptor family, and dendritic cells express this receptor. In this study, we investigated the effect of blocking 5-HT7 receptor signaling in experimental colitis with a view to develop an improved therapeutic strategy in intestinal inflammatory disorders. Colitis was induced with dextran sulfate sodium (DSS) or dinitrobenzene sulfonic acid (DNBS) in mice treated with selective 5-HT7 receptor antagonist SB-269970, as well as in mice lacking 5-HT7 receptor (5-HT7(-/-)) and irradiated wild-type mice reconstituted with bone marrow cells harvested from 5-HT7(-/-) mice. Inhibition of 5-HT7 receptor signaling with SB-269970 ameliorated both acute and chronic colitis induced by DSS. Treatment with SB-269970 resulted in lower clinical disease, histological damage, and proinflammatory cytokine levels compared with vehicle-treated mice post-DSS. Colitis severity was significantly lower in 5-HT7(-/-) mice and in mice reconstituted with bone marrow cells from 5-HT7(-/-) mice compared with control mice after DSS colitis. 5-HT7(-/-) mice also had significantly reduced DNBS-induced colitis. These observations provide us with novel information on the critical role of the 5-HT7 receptor in immune response and inflammation in the gut, and highlight the potential benefit of targeting this receptor to alleviate the severity of intestinal inflammatory disorders such as inflammatory bowel disease.