Paul Scully

Early Life Stress Alters Behavior, Immunity, and Microbiota in Rats: Implications for Irritable Bowel Syndrome and Psychiatric Illnesses

BACKGROUND Adverse early life events are associated with a maladaptive stress response system and might increase the vulnerability to disease in later life. Several disorders have been associated with early life stress, ranging from depression to irritable bowel syndrome. This makes the identification of the neurobiological substrates that are affected by adverse experiences in early life invaluable. METHODS The purpose of this study was to assess the effect of early life stress on the brain-gut axis. Male rat pups were stressed by separating them from their mothers for 3 hours daily between postnatal days 2-12. The control group was left undisturbed with their mothers. Behavior, immune response, stress sensitivity, visceral sensation, and fecal microbiota were analyzed. RESULTS The early life stress increased the number of fecal boli in response to a novel stress. Plasma corticosterone was increased in the maternally separated animals. An increase in the systemic immune response was noted in the stressed animals after an in vitro lipopolysaccharide challenge. Increased visceral sensation was seen in the stressed group. There was an alteration of the fecal microbiota when compared with the control group. CONCLUSIONS These results show that this form of early life stress results in an altered brain-gut axis and is therefore an important model for investigating potential mechanistic insights into stress-related disorders including depression and IBS.

The microbiome-gut-brain axis during early life regulates the hippocampal serotonergic system in a sex-dependent manner

Bacterial colonisation of the intestine has a major role in the post-natal development and maturation of the immune and endocrine systems. These processes are key factors underpinning central nervous system (CNS) signalling. Regulation of the microbiome–gut–brain axis is essential for maintaining homeostasis, including that of the CNS. However, there is a paucity of data pertaining to the influence of microbiome on the serotonergic system. Germ-free (GF) animals represent an effective preclinical tool to investigate such phenomena. Here we show that male GF animals have a significant elevation in the hippocampal concentration of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid, its main metabolite, compared with conventionally colonised control animals. Moreover, this alteration is sex specific in contrast with the immunological and neuroendocrine effects which are evident in both sexes. Concentrations of tryptophan, the precursor of serotonin, are increased in the plasma of male GF animals, suggesting a humoral route through which the microbiota can influence CNS serotonergic neurotransmission. Interestingly, colonisation of the GF animals post weaning is insufficient to reverse the CNS neurochemical consequences in adulthood of an absent microbiota in early life despite the peripheral availability of tryptophan being restored to baseline values. In addition, reduced anxiety in GF animals is also normalised following restoration of the intestinal microbiota. These results demonstrate that CNS neurotransmission can be profoundly disturbed by the absence of a normal gut microbiota and that this aberrant neurochemical, but not behavioural, profile is resistant to restoration of a normal gut flora in later life.

Commensal-Induced Regulatory T Cells Mediate Protection against Pathogen-Stimulated NF-κB Activation

Host defence against infection requires a range of innate and adaptive immune responses that may lead to tissue damage. Such immune-mediated pathologies can be controlled with appropriate T regulatory (Treg) activity. The aim of the present study was to determine the influence of gut microbiota composition on Treg cellular activity and NF-κB activation associated with infection. Mice consumed the commensal microbe Bifidobacterium infantis 35624 followed by infection with Salmonella typhimurium or injection with LPS. In vivo NF-κB activation was quantified using biophotonic imaging. CD4+CD25+Foxp3+ T cell phenotypes and cytokine levels were assessed using flow cytometry while CD4+ T cells were isolated using magnetic beads for adoptive transfer to naïve animals. In vivo imaging revealed profound inhibition of infection and LPS induced NF-κB activity that preceded a reduction in S. typhimurium numbers and murine sickness behaviour scores in B. infantis–fed mice. In addition, pro-inflammatory cytokine secretion, T cell proliferation, and dendritic cell co-stimulatory molecule expression were significantly reduced. In contrast, CD4+CD25+Foxp3+ T cell numbers were significantly increased in the mucosa and spleen of mice fed B. infantis. Adoptive transfer of CD4+CD25+ T cells transferred the NF-κB inhibitory activity. Consumption of a single commensal micro-organism drives the generation and function of Treg cells which control excessive NF-κB activation in vivo. These cellular interactions provide the basis for a more complete understanding of the commensal-host-pathogen trilogue that contribute to host homeostatic mechanisms underpinning protection against aberrant activation of the innate immune system in response to a translocating pathogen or systemic LPS.

Confirming RGS4 as a susceptibility gene for schizophrenia

A recent study identified a putative association between variants in the regulator of G‐protein signalling 4 (RGS4) and schizophrenia, Chowdari et al. [2002: Hum Mol Genet 11: 1373–1380]. RGS4 is both a positional and functional candidate gene for schizophrenia. Chowdari and colleagues identified association at this locus in a number of distinct and ethnically diverse samples, although the pattern of association was not the same in all the samples. Our study attempted to replicate this association in an independent Irish sample of schizophrenia cases and controls. We succeeded in detecting evidence of association at the RGS4 locus. The signal comes from a four‐marker haplotype that is in significant excess in our case sample. The same haplotype is in excess in the Caucasian schizophrenia sample used by Chowdari et al. [2002: Hum Mol Genet 11: 1373–1380]. This study provides further support for the contribution of RGS4 to schizophrenia susceptibility.

Confirmation and refinement of an ‘at-risk’ haplotype for schizophrenia suggests the EST cluster, Hs .97362, as a potential susceptibility gene at the Neuregulin-1 locus

Two recent association studies have implicated the neuregulin-1 gene (NRG1) at chromosome 8p21–22 as a susceptibility gene for schizophrenia. Stefansson et al identified three ‘at-risk’ haplotypes (HapA, B and C) which spanned the NRG1 locus and shared a common core haplotype. Subsequently, they demonstrated evidence that the core haplotype was associated with schizophrenia in an independent Scottish sample. To confirm and refine this haplotype we investigated the NRG1 locus in an independent Irish case–control sample. We did not find the core haplotype to be associated in our sample. However, we identified a refined 2-marker haplotype (HapBIRE) that shared common alleles with one of the Icelandic ‘at-risk’ haplotypes and is in significant excess in the Irish cases (19.4%) vs controls (12.3%) (P=0.013). This refined ‘at-risk’ haplotype is also in significant excess in the Scottish case sample (17.0% vs 13.5%; P=0.036). Interestingly, this refined ‘at-risk’ haplotype is positioned close to an EST cluster of unknown function (Hs.97362) within intron 1 of NRG1.

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.

Schizophrenia and the city: A review of literature and prospective study of psychosis and urbanicity in Ireland

Urbanicity has been repeatedly associated with increased incidence of schizophrenia. This article (a) presents results of a prospective study of urbanicity and schizophrenia in Ireland and (b) reviews the literature relating to urbanicity and schizophrenia. We prospectively compared incidence of schizophrenia and other psychoses in urban and rural catchment areas (over 4years and 7years, respectively) using face-to-face, DSM-III-R diagnostic interviews. Incidence of schizophrenia in males was higher in urban compared to rural areas, with an age-adjusted incidence rate ratio (IRR) of 1.92 (1.52-2.44) for males and 1.34 (1.00-1.80) for females. Incidence of affective psychosis was lower in urban compared to rural areas for males (IRR 0.48; 0.34-0.67) and females (IRR 0.60; 0.43-0.83). These findings are consistent with the literature, which provides persuasive evidence that risk for schizophrenia increases with urban birth and/or upbringing, especially among males. Register-based studies support this conclusion more consistently than studies using face-to-face diagnostic interviews, the difference being related to power. The mechanism of association is unclear but may relate to biological or social/environmental factors or both, acting considerably before psychotic symptoms manifest. There is a diversity of potential candidates, including air pollution, cannabis and social exclusion. Urbanicity may have a synergistic effect with genetic vulnerability. Future research is likely to focus on the relationship between urbanicity and neural maldevelopment, the possibility of rural protective factors (e.g. social capital, low social fragmentation), urbanicity in developing countries, cultural variables and geographical location, and associations between urbanicity and other disorders (e.g. affective psychosis).

Disturbance of the gut microbiota in early-life selectively affects visceral pain in adulthood without impacting cognitive or anxiety-related behaviors in male rats

Disruption of bacterial colonization during the early postnatal period is increasingly being linked to adverse health outcomes. Indeed, there is a growing appreciation that the gut microbiota plays a role in neurodevelopment. However, there is a paucity of information on the consequences of early-life manipulations of the gut microbiota on behavior. To this end we administered an antibiotic (vancomycin) from postnatal days 4-13 to male rat pups and assessed behavioral and physiological measures across all aspects of the brain-gut axis. In addition, we sought to confirm and expand the effects of early-life antibiotic treatment using a different antibiotic strategy (a cocktail of pimaricin, bacitracin, neomycin; orally) during the same time period in both female and male rat pups. Vancomycin significantly altered the microbiota, which was restored to control levels by 8 weeks of age. Notably, vancomycin-treated animals displayed visceral hypersensitivity in adulthood without any significant effect on anxiety responses as assessed in the elevated plus maze or open field tests. Moreover, cognitive performance in the Morris water maze was not affected by early-life dysbiosis. Immune and stress-related physiological responses were equally unaffected. The early-life antibiotic-induced visceral hypersensitivity was also observed in male rats given the antibiotic cocktail. Both treatments did not alter visceral pain perception in female rats. Changes in visceral pain perception in males were paralleled by distinct decreases in the transient receptor potential cation channel subfamily V member 1, the α-2A adrenergic receptor and cholecystokinin B receptor. In conclusion, a temporary disruption of the gut microbiota in early-life results in very specific and long-lasting changes in visceral sensitivity in male rats, a hallmark of stress-related functional disorders of the brain-gut axis such as irritable bowel disorder.

No evidence for association of the dysbindin gene [DTNBP1] with schizophrenia in an Irish population-based study

A recent family-based association study identified a putative association between variants in the dystrobrevin binding protein 1 (dysbindin) gene (DTNBP1) and schizophrenia. This study used a sample of 270 Irish pedigrees multiply affected with schizophrenia. We attempted to replicate these findings in an independent Irish sample of 219 schizophrenia cases and 231 controls. No evidence was found to suggest an association between the DTNBP1 gene and schizophrenia in our sample. Possible reasons for these findings are discussed.

Increased tumor necrosis factor-alpha concentrations with interleukin-4 concentrations in exacerbations of schizophrenia.

Several studies have indicated that cytokines may be involved in the pathophysiology of schizophrenia. Previous studies, however, have yielded contradictory results; in this study we assess the plasma levels of both T-helper-1 (Th1) and T-helper-2 (Th2) cytokines in patients with acute exacerbations of schizophrenia. Plasma concentrations of interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-alpha) and soluble receptor of interleukin-6 (sIL-6R) were measured with high sensitivity, enzyme-linked immunosorbent assays (ELISA) in patients with acute exacerbations of schizophrenia as compared with healthy controls. Patients with an acute exacerbation of schizophrenia had significantly increased production of TNF-alpha and significantly reduced production of IL-4 as compared with healthy subjects. No significant difference was observed in IL-6, sIL-6R, IL-8 and IL-10. Acute exacerbations of schizophrenia are associated with increased TNF-alpha concentrations (Th1) with concomitantly reduced concentrations of IL-4 (Th2) and a resulting increased TNF-alpha/IL-4 ratio.