Declan P. McKernan

Plasma cytokine profiles in females with irritable bowel syndrome and extra-intestinal co-morbidity.

OBJECTIVES:Irritable bowel syndrome (IBS) is a functional disorder that is associated with a number of extra-intestinal co-morbidities and a pro-inflammatory profile. This study was designed to examine the cytokine profile among a group of IBS patients with the extra-intestinal co-morbidities fibromyalgia, premenstrual dysmorphic disorder, and chronic fatigue syndrome.METHODS:In all, 100 female IBS patients with these co-morbidities, 21 IBS subjects without co-morbidity (“pure” IBS; Rome II), and 54 age-matched female controls took part in the study. Blood was drawn for measurement of the plasma cytokines interleukin (IL)-1β, IL-6, IL-8, IL-10, IL-12p70, IL-13, tumor necrosis factor (TNF)α, and interferon γ. The presence of the selected extra-intestinal manifestations was assessed using standard international criteria.RESULTS:Patients with IBS have increased plasma levels of IL-6 and IL-8; those with these extra-intestinal co-morbidities were found to have, in addition, increased levels of IL-1β and TNFα. No associations were evident between cytokine profiles and the nature of the co-morbidity or number of extra-intestinal co-morbidities present.CONCLUSIONS:Although IBS is characterized by a pro-inflammatory profile featuring the pro-inflammatory cytokines IL-6 and IL-8, IBS patients with certain extra-intestinal co-morbid conditions are distinguished by additional elevations in IL-1β and TNFα.

The probiotic Bifidobacterium infantis 35624 displays visceral antinociceptive effects in the rat

Background  Irritable bowel syndrome (IBS) is characterized by recurrent abdominal pain and altering bowel habit with a high percentage of patients displaying comorbid anxiety. Growing clinical and preclinical evidence suggests that probiotic agents may restore the altered brain–gut communication in IBS. In this study, we evaluated the efficacy of repeated treatment with three different probiotics in reducing visceral pain in visceral normosensitive (Sprague–Dawley [SD]) and visceral hypersensitive (Wistar–Kyoto [WKY]) rat strains.

Altered peripheral toll-like receptor responses in the irritable bowel syndrome

Aliment Pharmacol Ther 2011; 33: 1045–1052

“Killing the Blues”: A role for cellular suicide (apoptosis) in depression and the antidepressant response?

Apoptosis or programmed cell death is a critical regulator of tissue homeostasis and emerging evidence is focused on the role of apoptosis mechanisms in the central nervous system. Generally, apoptosis is necessary to prevent cancerous growths. However, excessive apoptosis in post-mitotic cells such as neurons leads to neurodegeneration. Chronic stress, which can precipitate depression, has been shown to increase the susceptibility of certain populations of neurons to cell death while antidepressant treatment, in general, shows the ability to oppose these effects and promote neuroprotection. Here, we discuss the major players in cell death pathways, the physiological implications of chronic stress and depression, chronic stress models in animals which result in cell death and the different classes of antidepressants and mood stabilizers that have been shown to prevent cell death. We discuss the cellular effects of antidepressants and possible modes of action in preventing apoptosis. Investigations on the role of apoptosis in mediating the molecular, physiological and behavioural effects of antidepressants may help gain a better mechanistic insight into drug action and allow refinement of current therapeutics in order to target these pathways in a specific manner.

Cytokine imbalance in irritable bowel syndrome: a systematic review and meta-analysis

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder of unknown etiology; although infection and inflammation have recently been considered as important etiologic agents. A recent meta‐analysis showed correlations between cytokine [interleukin‐10 (IL‐10) and tumor necrosis factor (TNF)] gene polymorphisms and IBS; however, it is still unknown whether patients with IBS have different cytokine profiles compared to healthy population.

Toll-Like Receptor mRNA Expression Is Selectively Increased in the Colonic Mucosa of Two Animal Models Relevant to Irritable Bowel Syndrome

Background Irritable bowel syndrome (IBS) is largely viewed as a stress-related disorder caused by aberrant brain-gut–immune communication and altered gastrointestinal (GI) homeostasis. Accumulating evidence demonstrates that stress modulates innate immune responses; however, very little is known on the immunological effects of stress on the GI tract. Toll-like receptors (TLRs) are critical pattern recognition molecules of the innate immune system. Activation of TLRs by bacterial and viral molecules leads to activation of NF-kB and an increase in inflammatory cytokine expression. It was our hypothesis that innate immune receptor expression may be changed in the gastrointestinal tract of animals with stress-induced IBS-like symptoms. Methodology/Principal Findings In this study, our objective was to evaluate the TLR expression profile in the colonic mucosa of two rat strains that display colonic visceral hypersensivity; the stress-sensitive Wistar-Kyoto (WKY) rat and the maternally separated (MS) rat. Quantitative PCR of TLR2-10 mRNA in both the proximal and distal colonic mucosae was carried out in adulthood. Significant increases are seen in the mRNA levels of TLR3, 4 & 5 in both the distal and proximal colonic mucosa of MS rats compared with controls. No significant differences were noted for TLR 2, 7, 9 & 10 while TLR 6 could not be detected in any samples in both rat strains. The WKY strain have increased levels of mRNA expression of TLR3, 4, 5, 7, 8, 9 & 10 in both the distal and proximal colonic mucosa compared to the control Sprague-Dawley strain. No significant differences in expression were found for TLR2 while as before TLR6 could not be detected in all samples in both strains. Conclusions These data suggest that both early life stress (MS) and a genetic predisposition (WKY) to stress affect the expression of key sentinels of the innate immune system which may have direct relevance for the molecular pathophysiology of IBS.

Enhanced peripheral toll-like receptor responses in psychosis: further evidence of a pro-inflammatory phenotype.

Low-grade peripheral inflammation is often present in psychotic patients. Toll-like receptors (TLRs) are pattern-recognition molecules that initiate inflammation. Our objective was to investigate the peripheral TLR activity in psychosis. Forty schizophrenia patients, twenty bipolar patients and forty healthy controls (HC) were recruited. Donated whole blood was cultured with TLR agonists for 24 h. Cell supernatants were analysed using a multiplex enzyme-linked immunosorbent assay approach to measure IL-1β, IL-6, IL-8 and tumour necrosis factor-α (TNFα). Plasma was analysed for cytokines, cortisol and acute phase proteins. Here, we show that selective TLR agonist-induced cytokine (IL-1β, IL-6, IL-8 and TNFα) release is enhanced in stimulated whole blood from schizophrenia and bipolar patients compared with HC. An exaggerated release of IL-1β, IL-6 and TNFα following treatment with the TLR2 agonist HKLM was detected in both disorders compared with controls. Enhanced TLR4-induced increases in IL-1β for both disorders coupled with TNFα increases for bipolar patients were observed. TLR8-induced increases in IL-1β for both disorders as well as IL-6 and TNFα increases for bipolar patients were detected. TLR9-induced increases in IL-8 for schizophrenia patients were also observed. No differences in TLR1, TLR3, TLR5, TLR6 or TLR7 activity were detected. Plasma levels of IL-6 were significantly elevated in bipolar patients while TNFα levels were significantly elevated in schizophrenia patients compared with controls. Plasma acute phase proteins were significantly elevated in bipolar patients. These data demonstrate that specific alterations in TLR agonist-mediated cytokine release contribute to the evidence of immune dysfunction in psychotic disorders.

Schizophrenia patients with a history of childhood trauma have a pro-inflammatory phenotype

BACKGROUND Increasing evidence indicates that childhood trauma is a risk factor for schizophrenia and patients with this syndrome have a pro-inflammatory phenotype. We tested the hypothesis that the pro-inflammatory phenotype in schizophrenia is associated with childhood trauma and that patients without a history of such trauma have a similar immune profile to healthy controls. METHOD We recruited 40 schizophrenia patients and 40 controls, all of whom completed the Childhood Trauma Questionnaire (CTQ). Using enzyme-linked immunosorbent assay (ELISA) techniques, we measured peripheral levels of interleukin (IL)-1β, IL-6, IL-8 and tumour necrosis factor (TNF)-α. These immune parameters were compared in schizophrenia with childhood trauma, schizophrenia without childhood trauma and healthy controls. RESULTS Patients with childhood trauma had higher levels of IL-6 and TNF-α than patients without trauma and healthy controls, and TNF-α levels correlated with the extent of the trauma. Patients with no trauma had similar immune profiles to controls. CONCLUSIONS Childhood trauma drives changes, possibly epigenetic, that generate a pro-inflammatory phenotype.

A Critical role for Bim in retinal ganglion cell death.

Optic nerve transection results in the death of retinal ganglion cells (RGCs) by apoptosis. Apoptosis is regulated by the Bcl‐2 family of proteins, of which the Bcl‐2 homology (BH3) ‐only proteins forms a subset. As BH3‐only proteins have been shown to play a significant role in regulating cell death in the central nervous system, we wished to investigate the role of Bcl‐2 interacting mediator of cell death (Bim), a prominent member of this protein family in the regulation of cell death in the RGC layer using in vitro retinal explants. In this study, we use an innovative retinal shaving procedure to isolate the cells of the ganglion cell layer to use for western blotting. Members of the BH3‐only protein family are down‐regulated during retinal development and are not normally expressed in the adult retina. Using this procedure, we demonstrate that Bim is re‐expressed and its expression is increased over time following axotomy. Expression of Bad and Bik decreases over the same time course, whereas there is no indication that Bid and Puma are re‐expressed. We show that explants from Bim knockout mice are resistant to axotomy‐induced death when compared with their wild‐type counterparts. Genetic deletion of Bim also prevents caspase 3 cleavage. The activity of Bim can be negatively regulated by phosphorylation. We show that the decrease of Bim phosphorylation correlates with a decrease in expression of survival kinases such as pAkt and pERK over the same time course. These results implicate Bim re‐expression as being essential for axotomy‐induced death of RGCs and that phosphorylation of Bim negatively regulates its activity in RGCs.

A Distinct Profile of Tryptophan Metabolism along the Kynurenine Pathway Downstream of Toll-Like Receptor Activation in Irritable Bowel Syndrome.

Irritable bowel syndrome (IBS), a disorder of the brain-gut axis, is characterised by the absence of reliable biological markers. Tryptophan is an essential amino acid that serves as a precursor to serotonin but which can alternatively be metabolised along the kynurenine pathway leading to the production of other neuroactive agents. We previously reported an increased degradation of tryptophan along this immunoresponsive pathway in IBS. Recently, altered cytokine production following activation of specific members of the toll-like receptor (TLR) family (TLR1-9) has also been demonstrated in IBS. However, the relationship between TLR activation and kynurenine pathway activity in IBS is unknown. In this study, we investigated whether activation of specific TLRs elicits exaggerated kynurenine production in IBS patients compared to controls. Whole blood from IBS patients and healthy controls was cultured with a panel of nine different TLR agonists for 24 h. Cell culture supernatants were then analyzed for both tryptophan and kynurenine concentrations, as were plasma samples from both cohorts. IBS subjects had an elevated plasma kynurenine:tryptophan ratio compared to healthy controls. Furthermore, we demonstrated a differential downstream profile of kynurenine production subsequent to TLR activation in IBS patients compared to healthy controls. This profile included alterations at TLR1/2, TLR2, TLR3, TLR5, TLR7, and TLR8. Our data expands on our previous understanding of altered tryptophan metabolism in IBS and suggests that measurement of tryptophan metabolites downstream of TLR activation may ultimately find utility as components of a biomarker panel to aid gastroenterologists in the diagnosis of IBS. Furthermore, these studies implicate the modulation of TLRs as means through which aberrant tryptophan metabolism along the kynurenine pathway can be controlled, a novel potential therapeutic strategy in this and other disorders.