Generation of Axially Chiral Fluoroallenes through a Copper-Catalyzed Enantioselective ß-Fluoride Elimination.

Herein we report the copper-catalyzed silylation of propargylic difluorides to generate axially chiral, tetrasubstituted monofluoroallenes in both good yields (27 examples >80%) and enantioselectivities (82-98% ee). Compared to previously reported synthetic routes to axially chiral allenes (ACAs) from prochiral substrates, a mechanistically distinct reaction has been developed: the enantiodiscrimination between enantiotopic fluorides to set an axial stereocenter. DFT calculations and vibrational circular dichroism (VCD) suggest that ß-fluoride elimination from an alkenyl copper intermediate likely proceeds through a syn-ß-fluoride elimination pathway rather than an anti-elimination pathway. The effects of the C1-symmetric Josiphos-derived ligand on reactivity and enantioselectivity were investigated. Not only does this report showcase that alkenyl copper species (like their alkyl counterparts) can undergo ß-fluoride elimination, but this elimination can be achieved in an enantioselective fashion.

Treatment with the noradrenaline re-uptake inhibitor atomoxetine alone and in combination with the α2-adrenoceptor antagonist idazoxan attenuates loss of dopamine and associated motor deficits in the LPS inflammatory rat model of Parkinson's disease.

The impact of treatment with the noradrenaline (NA) re-uptake inhibitor atomoxetine and the α2-adrenoceptor (AR) antagonist idazoxan in an animal model of Parkinson's disease (PD) was assessed. Concurrent systemic treatment with atomoxetine and idazoxan, a combination which serves to enhance the extra-synaptic availability of NA, exerts anti-inflammatory and neuroprotective effects following delivery of an inflammatory stimulus, the bacterial endotoxin, lipopolysaccharide (LPS) into the substantia nigra. Lesion-induced deficits in motor function (akinesia, forelimb-use asymmetry) and striatal dopamine (DA) loss were rescued to varying degrees depending on the treatment. Treatment with atomoxetine following LPS-induced lesion to the substantia nigra, yielded a robust anti-inflammatory effect, suppressing microglial activation and expression of the pro-inflammatory cytokine TNF-α whilst increasing the expression of neurotrophic factors. Furthermore atomoxetine treatment prevented loss of tyrosine hydroxylase (TH) positive nigral dopaminergic neurons and resulted in functional improvements in motor behaviours. Atomoxetine alone was sufficient to achieve most of the observed effects. In combination with idazoxan, an additional improvement in the impairment of contralateral limb use 7 days post lesion and a reduction in amphetamine-mediated rotational asymmetry 14 days post-lesion was observed, compared to atomoxetine or idazoxan treatments alone. The results indicate that increases in central NA tone has the propensity to regulate the neuroinflammatory phenotype in vivo and may act as an endogenous neuroprotective mechanism where inflammation contributes to the progression of DA loss. In accordance with this, the clinical use of agents such as NA re-uptake inhibitors and α2-AR antagonists may prove useful in enhancing the endogenous neuroimmunomodulatory potential of NA in conditions associated with brain inflammation.

Association between psychological measures with inflammatory anddisease-related markers of inflammatory bowel disease.

OBJECTIVE: This study aimed at investigating the associations between inflammatory mediators, symptoms and psychological disturbances in inflammatory bowel disease (IBD) patients. METHODS: IBD patients and patient controls were examined during a single visit to a gastroenterology clinic. Disease activity was assessed using the Mayo index for ulcerative colitis (UC), inflammatory bowel disease questionnaire (IBDQ), Crohn's disease activity index (CDAI) and Crohn's disease endoscopic index of severity (CDEIS). Gene expression of inflammatory mediators were measured in intestinal biopsies and whole blood samples along with circulating concentrations of interleukin (IL)-6, interferon (IFN)γ, C-reactive protein (CRP), kynurenine and tryptophan. Validated depression, anxiety and quality of life scores were used to assess psychological well-being. RESULTS: Patients who were symptomatic had the highest depression and anxiety scores, together with increased intestinal expression of IL-1ß, IL-6 and matrix metalloproteinase-9, increased circulating IL-6 and CRP, and an increased circulating kynurenine:tryptophan ratio. Increased Hamilton depression (HAM-D) scores in IBD patients were observed independent of the psychological impact of acute symptoms. CONCLUSIONS: Active IBD is associated with symptoms of depression and anxiety and with a raised circulating inflammatory mediator profile. Patients with active IBD exhibiting psychological symptoms should undergo psychological evaluation to ensure the psychological aspects of the condition are considered and addressed.

Stress-Related Immune Markers in Depression: Implications for Treatment.

Major depression is a serious psychiatric disorder; however, the precise biological basis of depression still remains elusive. A large body of evidence implicates a dysregulated endocrine and inflammatory response system in the pathogenesis of depression. Despite this, given the heterogeneity of depression, not all depressed patients exhibit dysregulation of the inflammatory and endocrine systems. Evidence suggests that inflammation is associated with depression in certain subgroups of patients and that those who have experienced stressful life events such as childhood trauma or bereavement may be at greater risk of developing depression. Consequently, prolonged exposure to stress is thought to be a key trigger for the onset of a depressive episode. This review assesses the relationship between stress and the immune system, with a particular interest in the mechanisms by which stress impacts immune function, and how altered immune functioning, in turn, may lead to a feed forward cascade of multiple systems dysregulation and the subsequent manifestation of depressive symptomology. The identification of stress-related immune markers and potential avenues for advances in therapeutic intervention is vital. Changes in specific biological markers may be used to characterize or differentiate depressive subtypes or specific symptoms and may predict treatment response, in turn facilitating a more effective, targeted, and fast-acting approach to treatment.

Clenbuterol activates the central IL-1 system via the ß2-adrenoceptor without provoking inflammatory response related behaviours in rats.

The long-acting, highly lipophilic, ß2-adrenoceptor agonist clenbuterol may represent a suitable therapeutic agent for the treatment of neuroinflammation as it drives an anti-inflammatory response within the CNS. However, clenbuterol is also known to increase the expression of IL-1ß in the brain, a potent neuromodulator that plays a role in provoking sickness related symptoms including anxiety and depression-related behaviours. Here we demonstrate that, compared to the immunological stimulus lipopolysaccharide (LPS, 250µg/kg), clenbuterol (0.5mg/kg) selectively up-regulates expression of the central IL-1 system resulting in a mild stress-like response which is accompanied by a reduction in locomotor activity and food consumption in rats. We provide further evidence that clenbuterol-induced activation of the central IL-1 system occurs in a controlled and selective manner in tandem with its negative regulators IL-1ra and IL-1RII. Furthermore, we demonstrate that peripheral ß2-adrenoceptors mediate the suppression of locomotor activity and food consumption induced by clenbuterol and that these effects are not linked to the central induction of IL-1ß. Moreover, despite increasing central IL-1ß expression, chronic administration of clenbuterol (0.03mg/kg; twice daily for 21days) fails to induce anxiety or depressive-like behaviour in rats in contrast to reports of the ability of exogenously administered IL-1 to induce these symptoms in rodents. Overall, our findings suggest that clenbuterol or other selective ß2-adrenoceptor agonists could have the potential to combat neuroinflammatory or neurodegenerative disorders without inducing unwanted symptoms of depression and anxiety.

Inhibition of stress-induced hepatic tryptophan 2,3-dioxygenase exhibits antidepressant activity in an animal model of depressive behaviour.

The role of hepatic tryptophan 2,3 dioxygenase (TDO) was assessed in the provocation of stress-induced depression-related behaviour in the rat. TDO drives tryptophan metabolism via the kynurenine pathway (KP) and leads to the production of neuroactive metabolites including kynurenine. A single 2 h period of restraint stress in adult male Sprague-Dawley rats provoked an increase in circulating concentrations of the glucocorticoid corticosterone and induction of hepatic TDO expression and activity. Repeated exposure to stress (10 d of 2 h restraint each day) provoked an increase in immobility in the forced swimming test (FST) indicative of depression-related behaviour. Immobility was accompanied by an increase in the circulating corticosterone concentrations, expression and activity of hepatic TDO and increase in the expression of TDO in the cerebral cortex. Increased TDO activity was associated with raised circulating kynurenine concentrations and a reduction in circulating tryptophan concentrations indicative of KP activation. Co-treatment with the TDO inhibitor allopurinol (20 mg/kg, i.p.), attenuated the chronic stress-related increase in immobility in the FST and the accompanying increase in circulating kynurenine concentrations. These findings indicate that stress-induced corticosterone and consequent activation of hepatic TDO, tryptophan metabolism and production of kynurenine provoke a depression-related behavioural phenotype. Inhibition of stress-related hepatic TDO activity promotes antidepressant activity. TDO may therefore represent a promising target for the treatment of depression associated with stress-related disorders in which there is evidence for KP activation.

Poly I:C-induced activation of the immune response is accompanied by depression and anxiety-like behaviours, kynurenine pathway activation and reduced BDNF expression.

In this study we characterised the ability of the viral mimetic poly I:C to induce a neuroinflammatory response and induce symptoms of depression and anxiety in rats. Furthermore, the ability of poly I:C to deplete central tryptophan and serotonin via induction of indolamine 2,3 dioxygenase (IDO), and also the ability of poly I:C to impact upon expression of the neurotrophin BDNF and its receptor TrkB were examined as potential mechanisms to link inflammation to depression. Poly I:C induced a neuroinflammatory response characterised by increased expression of IL-1ß, IL-6, TNF-α and CD11b in frontal cortex and hippocampus. In the first 24h following poly I:C administration rats displayed sickness behaviour characterised by reduced locomotor activity and weight gain. Anhedonia measured using the saccharin preference test was used as an indicator of depressive behaviour, and poly I:C induced depressive behaviour that persisted for up to 72h following administration. Anxiety was measured using the open field test and anxious behaviour was observed 24h following poly I:C, a time-point when sickness behaviour had resolved. These behavioural changes were accompanied by decreased expression of BDNF and TrkB in hippocampus and frontal cortex. In addition, poly I:C increased central IDO expression and increased concentrations of tryptophan, and its metabolite kynurenine. However this activation of the kynurenine pathway did not result in reduced central serotonin concentrations. These findings suggest that depressive and anxiety-like behaviours elicited by poly I:C are associated with a reduction in BDNF signalling, and activation of the kynurenine pathway, but not a reduction in serotonin.

C-reactive protein predicts fatigue independently of depression in breast cancer patients prior to chemotherapy.

Heightened inflammatory activity has been proposed as a mechanism for the development of cancer-related fatigue (CRF), a common and distressing condition that can negatively affect quality of life. Inflammation is also implicated in the pathogenesis of depression, and depression is a strong predictor of CRF. Thus, the role of the pro-inflammatory cytokine network in CRF may be mediated by depression or both conditions may share similar underlying physiological processes. The current study investigated associations between fatigue, depression and inflammatory cytokine (IFN-γ, IL-6, TNF-α) and CRP concentrations, as well as kynurenine pathway (KP) activation, in 61 breast cancer patients prior to chemotherapy. Changes in inflammatory markers and KP activation over time were also explored, and associations with changes in fatigue and depression were examined. Higher levels of CRP were significantly correlated with fatigue and depression before chemotherapy; nevertheless, CRP predicted fatigue independently of depression. Although greater kynurenine concentrations were associated with increased immune activation, there was no evidence that the KP played a role in fatigue or depression. Furthermore, no relationships emerged between either fatigue or depression and IFN-γ, IL-6, or TNF-α before chemotherapy. Nevertheless, kynurenine levels pre- and post-treatment significantly predicted changes in depression, suggesting that heightened KP activation may contribute to depressive symptoms in patients treated for cancer. In addition, IL-6 significantly covaried with fatigue. These preliminary findings provide some support for the idea that low-grade inflammation contributes to the development of CRF, independently of depression; however, there was no evidence that this is mediated by KP activity.

Cerebrospinal fluid levels of vascular endothelial growth factor correlate with reported pain and are reduced by spinal cord stimulation in patients with failed back surgery syndrome.

OBJECTIVES: Spinal cord stimulation (SCS) is an efficacious therapy for chronic neuropathic pain whose precise mechanism of action is unclear. Mediators produced by glial and immune cells are now believed to modulate neuronal transmission and promote chronic neuropathic pain. We postulated a relationship between cerebrospinal fluid (CSF) concentrations of neuroimmune mediators and SCS. MATERIALS AND METHODS: We measured CSF concentrations of the chemokine, monocyte chemotactic protein-1 (MCP-1), and the growth factors, brain-derived neurotrophic factor (BDNF), and vascular endothelial growth factor (VEGF) and tested for relationships with stimulation parameters and clinical response in nine patients with failed back surgery syndrome (FBSS). RESULTS: Patients with FBSS had higher CSF concentrations of BDNF (p = 0.01) and MCP-1 (p = 0.0001) than matched controls. CSF concentrations of BDNF and VEGF correlated with reported pain (p = 0.04). Five minutes of SCS resulted in a reduction in median VEGF concentrations (p = 0.01). CONCLUSIONS: Patients with FBSS have altered CSF levels of BDNF and MCP-1. CSF VEGF correlates with pain and is reduced by SCS. This may offer novel insights into both the mechanism of action of SCS in FBSS and the variation in clinical response that may be encountered.

Tryptophan depletion in depressed patients occurs independent of kynurenine pathway activation.

The kynurenine pathway (KP) and its rate-limiting tryptophan degrading enzyme indolamine 2,3-dioxygenase (IDO) have been implicated in the pathogenesis of depression. IDO expression is driven by inflammatory cytokines, and has been suggested as the link between inflammation and a serotonergic deficit in depression. Studies also indicate that inflammatory cytokines upregulate the serotonin transporter (SERT), representing another mechanism by which inflammation could influence serotonin availability. Here we examined circulating concentrations of inflammatory cytokines (IFN-γ, TNF-α, IL-1ß, IL-6), and the acute phase protein CRP alongside plasma tryptophan, kynurenine, kynurenic acid (KYNA) and 3-hydroxyanthranilic acid (3-HAA) concentrations, and whole blood mRNA expression of IDO, kynurenine aminotransferases (KAT I and II), kynurenine-3-monooxygenase (KMO), kynureninase and SERT in patients with major depressive disorder (MDD) compared with age and sex-matched controls. Whilst no changes in TNF-α or IL-1ß were observed, plasma concentrations of IL-6, IFN-γ and CRP were increased in the depressed cohort. Despite this inflammatory phenotype, IDO expression or plasma kynurenine were not significantly different between MDD patients and controls. In addition, there was no difference between controls and depressives in concentrations of KYNA and 3-HAA, or in expression of enzymes KAT, KMO or kynureninase that drive their production. Nonetheless, a depletion in tryptophan was evident in depressed patients and was correlated with HAM-D scores. In addition, we failed to observe any difference in SERT mRNA expression in the blood cells from patients with MDD relative to controls. These data support the idea that a mild inflammatory signature is evident in MDD and is accompanied by reduced circulating tryptophan concentrations. However, we found no indication of KP activation in the depressed cohort suggesting that an alternative mechanism mediates the depletion of tryptophan observed. Taken together these data question the ability of the mild inflammatory phenotype observed in depression to induce molecules such as IDO and SERT that could negatively impact upon serotonergic functioning.

The ß2-adrenoceptor agonist clenbuterol elicits neuroprotective, anti-inflammatory and neurotrophic actions in the kainic acid model of excitotoxicity.

Excitotoxicity is a mechanism of neuronal cell death implicated in a range of neurodegenerative conditions. Systemic administration of the excitotoxin kainic acid (KA) induces inflammation and apoptosis in the hippocampus, resulting in neuronal loss. Evidence indicates that stimulation of glial ß(2)-adrenoceptors has anti-inflammatory and neurotrophic properties that could result in neuroprotection. Consequently, in this study we examined the effect of the ß(2)-adrenoceptor agonist clenbuterol on KA-induced inflammation, neurotrophic factor expression and apoptosis in the hippocampus. Clenbuterol (0.5mg/kg) was administered to rats one hour prior to KA (10mg/kg). Epileptic behaviour induced by KA was assessed for three hours following administration using the Racine scale. Twenty-four hours later TUNEL staining in the CA3 hippocampal subfield and hippocampal caspase-3 activity was assessed to measure KA-induced apoptosis. In addition, expression of inflammatory cytokines (IL-1ß and IFN-γ), inducible nitric oxide synthase (iNOS), kynurenine pathway enzymes indolamine 2,3-dioxygenase (IDO) and kynurenine monooxygenase (KMO), the microglial activation marker CD11b, and the neurotrophins BDNF and NGF were quantified in the hippocampus using real-time PCR. Whilst clenbuterol treatment did not significantly alter KA-induced epileptic behavior it ameliorated KA-induced apoptosis, and this neuroprotective effect was accompanied by reduced inflammatory cytokine expression, reduced expression of iNOS, IDO, KMO and CD11b, coupled with increased BDNF and NGF expression in KA-treated rats. In conclusion, the ß(2)-adrenoceptor agonist clenbuterol has anti-inflammatory and neurotrophic actions and elicits a neuroprotective effect in the KA model of neurodegeneration.

Noradrenaline acting at central beta-adrenoceptors induces interleukin-10 and suppressor of cytokine signaling-3 expression in rat brain: implications for neurodegeneration.

Evidence indicates that the monoamine neurotransmitter noradrenaline elicits anti-inflammatory actions in the central nervous system (CNS), and consequently may play a neuroprotective role where inflammatory events contribute to CNS pathology. Here we examined the ability of pharmacologically enhancing central noradrenergic tone to induce expression of anti-inflammatory cytokines in rat brain. Administration of the noradrenaline reuptake inhibitor reboxetine (15mg/kg; ip) combined with the alpha(2)-adrenoceptor antagonist idazoxan (1mg/kg; ip) induced interleukin-10 (IL-10) expression in rat cortex and hippocampus. In addition, these drug treatments induced IL-10 signaling as indicated by increased STAT3 phosphorylation and suppressor of cytokine signaling-3 (SOCS-3) mRNA expression. In contrast to the profound increase in IL-10 induced by the reboxetine/idazoxan combination, the other two broad spectrum anti-inflammatory cytokines IL-4 and TGF-beta were not induced by this treatment. The ability of combined treatment with reboxetine and idazoxan to induce IL-10 and SOCS3 expression was mediated by beta-adrenoceptor activation, as their induction was blocked by pre-treatment with the beta-adrenoceptor antagonist propranolol. Moreover, administration of the brain penetrant beta(2)-adrenoceptor agonist clenbuterol induced a time- and dose-dependent increase in central IL-10 and SOCS3 expression, and the ability of clenbuterol to induce IL-10 and SOCS-3 expression was blocked by the centrally acting beta-adrenoceptor antagonist, propranolol, and was mimicked by the highly selective beta(2)-adrenoceptor agonist formoterol. In all, these data indicate that increasing central noradrenergic tone induces IL-10 production and signaling in the CNS, which may protect against neurodegeneration.

Sickness behaviour is induced by a peripheral CXC-chemokine also expressed in multiple sclerosis and EAE.

Non-CNS chemokine production may contribute to previously unrecognised components of Multiple Sclerosis (MS) pathology. Here we show that IL-8, a neutrophil chemoattractant, is significantly increased in serum from individuals with MS, and that the rodent homolog of IL-8 (CXCL1) is expressed in the liver in experimental autoimmune encephalomyelitis (EAE), a rodent model of MS. The hepatic expression of CXCL1 in EAE is accompanied by neutrophil recruitment to the liver, and we show that this recruitment is a feature of post mortem liver tissue from MS patients, which is a previously unrecognised phenomenon. We speculated that the presence of peripheral CXC-chemokine expression might contribute to the sickness behaviours associated with MS, which are a significant contributor to morbidity. Peripheral, but not central, administration of CXCL1 to Wistar rats inhibited spontaneous activity in the open field and burrowing behaviour in a dose-dependent manner (5-45 microg). The expression of CXCL1 by the liver and the recruitment of neutrophils can be modelled by the intracerebral injection of IL-1beta. Here, we found that interferon-beta (IFN-beta) pretreatment significantly inhibited hepatic CXCL1 production and neutrophil recruitment to the liver induced by the microinjection of IL-1beta into the brain. Thus while the mechanism by which IFN-beta therapy suppresses disease in MS remains unclear, the data presented here suggests that the inhibition of hepatic chemokine synthesis may be a contributing factor.

Dexamethasone attenuates inflammatory-mediated suppression of ß2-adrenoceptor expression in rat primary mixed glia.

ß2-adrenoceptors are G-protein coupled receptors expressed on both astrocytes and microglia that play a key role in mediating the anti-inflammatory actions of noradrenaline in the CNS. Here the effect of an inflammatory stimulus (LPS + IFN-γ) was examined on glial ß2-adrenoceptor expression and function. Exposure of glia to LPS + IFN-γ decreased ß2-adrenoceptor mRNA and agonist-stimulated production of the intracellular second messenger cAMP. Pre-treatment with the synthetic glucocorticoid and potent anti-inflammatory agent dexamethasone prevented the LPS + IFN-γ-induced suppression of ß2-adrenoceptor mRNA expression. These results raise the possibility that inflammation-mediated ß2-adrenoceptor downregulation in glia may dampen the innate anti-inflammatory properties of noradrenaline in the CNS.

Noradrenaline reuptake inhibitors limit neuroinflammation in rat cortex following a systemic inflammatory challenge: implications for depression and neurodegeneration.

Evidence suggests that noradrenaline has a tonic anti-inflammatory action in the central nervous system (CNS) via its ability to suppress microglial and astrocytic activation, and inhibit production of inflammatory mediators. Consequently it is suggested that noradrenaline may play an endogenous neuroprotective role in CNS disorders where inflammatory events contribute to pathology. Here we demonstrate that acute treatment of rats with the noradrenaline reuptake inhibitors (NRIs) desipramine and atomoxetine elicited anti-inflammatory actions in rat cortex following a systemic challenge with bacterial lipopolysaccharide (LPS). This was characterized by a reduction in cortical gene expression of the pro-inflammatory cytokines interleukin-1beta (IL-1beta) and tumour necrosis factor-alpha (TNF-alpha), the enzyme inducible nitric oxide synthase (iNOS), and the microglial activation markers CD11b and CD40. These anti-inflammatory actions of NRIs were associated with reduced activation of nuclear factor-kappa B (NF-kappaB); a transcription factor that is considered the major regulator of inflammation in the CNS. To determine whether NRI administration directly altered glial expression of these inflammatory markers, primary cortical glial cells were exposed in vitro to the NRIs desipramine or atomoxetine. In vitro treatment with NRIs largely failed to alter mRNA expression of IL-1beta, TNF-alpha, iNOS, CD11b and CD40, following stimulation with LPS. Similarly, LPS-induced TNF-alpha and IL-1beta protein production from glial cells was unaffected by NRI treatment. In contrast, in vitro exposure of cultured glial cells to noradrenaline suppressed IL-1beta, TNF-alpha, iNOS and CD40 expression. These results suggest that in vivo administration of NRIs limit inflammatory events in the brain, probably by increasing noradrenaline availability. Overall, this study has yielded significant insights into the ability of noradrenaline-augmentation strategies to limit neuroinflammation.

Psychological stress increases expression of IL-10 and its homolog IL-19 via beta-adrenoceptor activation: reversal by the anxiolytic chlordiazepoxide.

Recent studies from our laboratory indicate that psychological stress is a potent inducer of the anti-inflammatory cytokine interleukin (IL)-10, raising the possibility that the IL-10 family of cytokines may be key mediators of stress-induced immunosuppression. In this study we examined the impact of psychological stress (restraint stress) on expression of IL-10, and the novel IL-10 family members IL-19, IL-20 and IL-24 in mouse spleen following an in vivo challenge with lipopolysaccharide (LPS). We found that stressor exposure significantly augmented LPS-induced IL-10 expression. Similarly, IL-19 expression was induced by LPS, and this was significantly enhanced by restraint stress. In contrast, expression of IL-24 was not significantly altered by LPS or stress, and expression of IL-20 was largely not detectable in vivo in either saline or LPS-treated animals. Consistent with a role for sympathetic nervous system (SNS) activation in stress-induced immune regulation, the sympathetic neurotransmitter noradrenaline increased LPS-induced IL-10 and IL-19 expression in splenocytes and dendritic cells, and the ability of noradrenaline to induce expression of these cytokines was blocked by pre-treatment with the beta-adrenoceptor antagonist propranolol. Similarly, pre-treatment of mice with the peripherally acting beta-adrenoceptor antagonist nadolol completely blocked the stress-induced increase in IL-10 and IL-19 mRNA expression. Finally, pre-treatment with the benzodiazepine anxiolytic chlordiazepoxide prevented the stress-induced increase in IL-10 and IL-19 expression. Taken together, these data demonstrate that psychological stress induces expression of the IL-10 and its homolog IL-19 via activation of beta-adrenoceptors, and the ability of stress to induce these cytokines is prevented by treatment with the anxiolytic chlordiazepoxide. The findings suggest that stress enhances the production of immunosuppressive cytokines, which may impact on stress-related disease processes.

Psychological stress suppresses innate IFN-gamma production via glucocorticoid receptor activation: reversal by the anxiolytic chlordiazepoxide.

Studies in humans and in animals indicate that psychological stress can modulate immune responses. Here we demonstrate that exposure to psychological stress (restraint stress) suppresses innate interferon (IFN)-gamma production in mice following an in vivo lipopolysaccharide (LPS) challenge. IFN-gamma signaling was also impaired by stress, as indicated by reduced STAT1 phosphorylation and reduced expression of the IFN-gamma-inducible genes, inducible nitric oxide synthase (iNOS) and IFN-gamma-inducible protein 10 (IP-10/CXCL10). Furthermore, restraint stress suppressed production of the IFN-gamma inducing cytokine interleukin (IL)-12 and increased production of the anti-inflammatory cytokine IL-10, which can inhibit both IL-12 and IFN-gamma production. However, using IL-10 knockout mice, we demonstrate that IL-10 does not mediate the suppressive effect of restraint stress on innate IFN-gamma production. Restraint stress increased corticosterone concentrations in serum and spleen, and consistent with a role for glucocorticoids in the immunosuppressive actions of stress, pre-treatment with the glucocorticoid receptor antagonist mifepristone completely blocked the stress-related suppression of innate IFN-gamma production. Addition of exogenous IL-12 to LPS-stimulated spleen cells reversed the suppressive effect of both restraint stress and corticosterone on IFN-gamma production. These data suggest that reduced IL-12 production is a key event in stress-induced suppression of innate IFN-gamma production. Finally, we demonstrate that pre-treatment with the anxiolytic drug chlordiazepoxide prevents the suppressive effect of stress on innate IFN-gamma production, and also attenuates the stress-induced increase in circulating corticosterone concentrations.

Interaction of the immune-inflammatory and the kynurenine pathways in rats resistant to antidepressant treatment in model of depression.

The kynurenine pathway (KP), a major route of tryptophan catabolism, may be associated with the pathophysiology of depressive disorders. KP is responsible for ca. 99% of brain tryptophan metabolism via its degradation to kynurenine (KYN) catalyzed by indoleamine 2,3-dioxygenase (IDO). Some cytokines, such as interferon-γ (IFN-γ) and interleukin (IL)-6 are potent inducers of IDO. KYN is further converted by kynurenine aminotransferase (KAT) to the more neuroprotective kynurenic acid or by kynurenine 3-monooxygenase (KMO) to neurotoxic 3-hydroxykynurenine. The aim of the present study was to delineate whether the administration of imipramine (IMI) to rats subjected to chronic mild stress (CMS) may reverse behavioral changes induced by CMS in association with changes in immune-inflammatory markers and KP. We confirmed that the CMS procedure modeled one of the main symptoms of depression, i.e. anhedonia, and administration of IMI for 5 weeks resulted in a significant reduction in anhedonia in a majority of animals (CMS IMI-R animals), whereas 20% of animals did not respond to IMI treatment (CMS IMI-NR animals). We established that CMS procedure increased IFN-γ and IDO mRNA and decreased KAT II mRNA expression in the rat cortex. In the cortex and hippocampus, IMI treatment and non-responsiveness to IMI (in CMS IMI-NR animals) were associated with increased IL-6 mRNA expression. In the spleen, CMS increased production of IFN-γ and IL-6 proteins, while these cytokines were decreased by IMI in CMS IMI-R animals. Chronic IMI administration to CMS rats decreased IDO and KMO mRNA and protein expression and increased KAT II/KMO mRNA and protein ratio in IMI responders (CMS IMI-R) in comparison to CMS rats. In CMS IMI-NR rats, a significant increase in IDO mRNA expression and protein level in comparison with IMI responders was observed. Our findings indicate that resistance to therapeutic action of IMI could be explained by a deficiency of the inhibitory properties of IMI on IDO, KMO and KYN synthesis in the cortex. We conclude that the antidepressant activity of IMI may, at least in part, be explained by modulatory activities on the KAT II/KMO ratio in brain areas.

Induction of indolamine 2,3-dioxygenase and kynurenine 3-monooxygenase in rat brain following a systemic inflammatory challenge: a role for IFN-gamma?

Inflammation-mediated dysregulation of the kynurenine pathway has been implicated as a contributor to a number of major brain disorders. Consequently, we examined the impact of a systemic inflammatory challenge on kynurenine pathway enzyme expression in rat brain. Indoleamine 2,3-dioxygenase (IDO) expression was induced in cortex and hippocampus following systemic lipopolysaccharide (LPS) administration. Whilst IDO expression was paralleled by increased circulating interferon (IFN)-gamma concentrations, IFN-gamma expression in the brain was only modestly altered following LPS administration. In contrast, induction of IDO was associated with increased central tumour necrosis factor (TNF)-alpha and interleukin (IL)-6 expression. Similarly, in cultured glial cells LPS-induced IDO expression was accompanied by increased TNF-alpha and IL-6 expression, whereas IFN-gamma was not detectable. These findings indicate that IFN-gamma is not required for LPS-induced IDO expression in brain. A robust increase in kynurenine-3-monooxygenase (KMO) expression was observed in rat brain 24h post LPS, without any change in kynurenine aminotransferase II (KAT II) expression. In addition, we report that constitutive expression of KAT II is approximately 8-fold higher than KMO in cortex and 20-fold higher in hippocampus. Similarly, in glial cells constitutive expression of KAT II was approximately 16-fold higher than KMO, and expression of KMO but not KAT II was induced by LPS. These data are the first to demonstrate that a systemic inflammatory challenge stimulates KMO expression in brain; a situation that is likely to favour kynurenine metabolism in a neurotoxic direction. However, our observation that expression of KAT II is much higher than KMO in rat brain is likely to counteract potential neurotoxicity that could arise from KMO induction following an acute inflammation.

Absence of the 7-repeat variant of the DRD4 VNTR is associated with drifting sustained attention in children with ADHD but not in controls.

Many genetic studies have demonstrated an association between the 7-repeat (7r) allele of a 48-base pair variable number of tandem repeats (VNTR) in exon 3 of the DRD4 gene and the phenotype of attention deficit hyperactivity disorder (ADHD). Previous studies have shown inconsistent associations between the 7r allele and neurocognitive performance in children with ADHD. We investigated the performance of 128 children with and without ADHD on the Fixed and Random versions of the Sustained Attention to Response Task (SART). We employed time-series analyses of reaction-time data to allow a fine-grained analysis of reaction time variability, a candidate endophenotype for ADHD. Children were grouped into either the 7r-present group (possessing at least one copy of the 7r allele) or the 7r-absent group. The ADHD group made significantly more commission errors and was significantly more variable in RT in terms of fast moment-to-moment variability than the control group, but no effect of genotype was found on these measures. Children with ADHD without the 7r allele made significantly more omission errors, were significantly more variable in the slow frequency domain and showed less sensitivity to the signal (d') than those children with ADHD the 7r and control children with or without the 7r. These results highlight the utility of time-series analyses of reaction time data for delineating the neuropsychological deficits associated with ADHD and the DRD4 VNTR. Absence of the 7-repeat allele in children with ADHD is associated with a neurocognitive profile of drifting sustained attention that gives rise to variable and inconsistent performance.