Katie J. Ryan

Noradrenaline acting at β-adrenoceptors induces expression of IL-1β and its negative regulators IL-1ra and IL-1RII, and drives an overall anti-inflammatory phenotype in rat cortex

Evidence indicates that noradrenaline elicits anti-inflammatory actions in the central nervous system (CNS), and plays a neuroprotective role where inflammatory events contribute to pathology. Here we examined the ability of pharmacological enhancement of central noradrenergic tone to impact upon activation of the IL-1 system in rat brain. Treatment with the noradrenaline reuptake inhibitor reboxetine combined with the alpha(2)-adrenoceptor antagonist idazoxan induced expression of IL-1beta as well as its negative regulators, IL-1 receptor antagonist (IL-1ra) and IL-1 type II receptor (IL-1RII) in rat cortex. The ability of reboxetine/idazoxan treatment to activate the IL-1 system was mediated by beta-adrenoceptors, as the aforementioned effects were blocked by the beta-adrenoceptor antagonist propranolol. Moreover, administration of the brain penetrant beta(2)-adrenoceptor agonist clenbuterol induced expression of IL-1beta, IL-1ra and IL-1RII in rat brain. This action was selective to the IL-1 system, as other inflammatory cytokines including TNF-alpha, IL-6 or IFN-gamma were not induced by clenbuterol. Induction of IL-1beta was accompanied by activation of NFkappaB and of the MAP kinase ERK, and clenbuterol also induced expression of the IL-1beta-inducible gene CINC-1. The ability of clenbuterol to activate the IL-1 system was blocked by propranolol, and was mimicked by the highly selective beta(2)-adrenoceptor agonist formoterol. Despite the ability of clenbuterol to activate the central IL-1 system, it largely combated the neuroinflammatory response induced by systemic inflammatory stimulus (bacterial lipopolysaccharide; LPS). Specifically, whilst the ability of clenbuterol to induce expression of IL-1RII and IL-1Ra was maintained following the inflammatory challenge, its ability to induce IL-1beta was reduced. In addition, clenbuterol suppressed LPS-induced expression of the inflammatory cytokines TNF-alpha and IL-6, the inflammatory chemokines RANTES and IP-10, the co-stimulatory molecules CD40 and ICAM-1. Thus overall, clenbuterol suppresses the innate inflammatory response in rat brain.

Noradrenaline acting at central β-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.

The β2-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 β(2)-adrenoceptors has anti-inflammatory and neurotrophic properties that could result in neuroprotection. Consequently, in this study we examined the effect of the β(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-1β 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 β(2)-adrenoceptor agonist clenbuterol has anti-inflammatory and neurotrophic actions and elicits a neuroprotective effect in the KA model of neurodegeneration.

Complementary anti-inflammatory actions of the β2-adrenoceptor agonist clenbuterol and the glucocorticoid dexamethasone in rat brain

Systemic administration of the β(2)-adrenoceptor agonist clenbuterol induces expression of IL-1β and its negative regulators, interleukin-1 receptor antagonist (IL-1ra) and the interleukin-1 type II decoy receptor (IL-1RII) in rat brain. Clenbuterol also increases central expression of the broad spectrum anti-inflammatory cytokine interleukin-10 (IL-10) and its downstream signalling molecule, suppressor of cytokine signalling-3 (SOCS-3). Here we examine the impact of combined treatment with clenbuterol (0.5mg/kg) and the glucocorticoid dexamethasone (1mg/kg) on mRNA expression of IL-1β and the IL-1β-inducible gene iNOS, on IκBα mRNA expression and NFκB activation, and on mRNA expression of the anti-inflammatory molecules IL-1ra, IL-1RII, IL-10 and SOCS-3 in rat cortex, striatum and hippocampus. Dexamethasone inhibited induction of IL-1β and iNOS mRNA expression by clenbuterol in all three brain regions, without altering its ability to induce IL-1ra mRNA expression. In the case of IL-1RII, dexamethasone further augmented clenbuterol-induced IL-1RII mRNA expression in hippocampus and striatum. These data highlight a mechanistic dissociation between the ability of β(2)-adrenoceptor activation to induce expression of IL-1β, and its negative regulators IL-1ra and IL-1RII in the brain. Treatment with either dexamethasone or clenbuterol alone independently induced IκBα mRNA expression, and elicited a concomitant decrease in the DNA binding of NFκB in all three brain regions. In the hippocampus and striatum dexamethasone treatment did not influence the ability of clenbuterol to induce IL-10 mRNA expression. In contrast in the cortex, induction of IL-10 and SOCS-3 mRNA expression by clenbuterol administered in combination with dexamethasone was less than induced by clenbuterol alone. Overall these data indicate that combined treatment with dexamethasone and the β(2)-adrenoceptor agonist clenbuterol elicit complementary anti-inflammatory actions in the CNS. Specifically, dexamethasone inhibits expression of pro-inflammatory cytokines, whereas clenbuterol has the added benefit of promoting expression of anti-inflammatory molecules including IL-1ra, IL-1RII, IL-10 and SOCS-3.

Stimulation of central β2-adrenoceptors suppresses NFκB activity in rat brain: A role for IκB

In this study we examined the impact of systemic treatment with the long-acting brain penetrant β2-adrenoceptor agonist clenbuterol on NFκB activity and IκB expression in rat brain. Clenbuterol decreased NFκB activity (p65 DNA binding) in nuclear extracts prepared from rat cortex and hippocampus for up to 8h following a single treatment. This was accompanied by increased expression of IκBα mRNA and protein. The temporal increase in IκB protein expression paralleled the suppression of NFκB activity, suggesting that IκBα mediates the suppression NFκB activity observed. These actions of clenbuterol were prevented by pre-treatment with the non-selective β-adrenoceptor antagonist propranolol, the β2-adrenoceptor antagonist ICI-118,551, but not the β1-adrenoceptor antagonist metoprolol, suggesting that the effects of clenbuterol on IκBα expression and NFκB activity are mediated specifically by the β2-adrenoceptor. In addition, the actions of clenbuterol were mimicked by systemic administration of another highly selective long-acting β2-adrenoceptor agonist formoterol. As neurodegenerative diseases are associated with inflammation we determined if clenbuterol could suppress NFκB activation that occurs in response to an inflammatory stimulus. In this regard we demonstrate that clenbuterol inhibited IκB phosphorylation and IκB degradation and inhibited NFκB activity in hippocampus and cortex of rats following a central injection of the inflammagen bacterial lipopolysaccharide (LPS). In tandem, clenbuterol blocked expression of the NFκB-inducible genes TNF-α and ICAM-1 following LPS administration. Our finding that clenbuterol and formoterol inhibit NFκB activity in the CNS further supports the idea that β2-adrenoceptors may be an attractive target for treating neuroinflammation and combating inflammation-related neurodegeneration.

The β2-adrenoceptor agonist clenbuterol reduces the neuroinflammatory response, neutrophil infiltration and apoptosis following intra-striatal IL-1β administration to rats

Abstract Objectives: Clenbuterol is a brain penetrant β2-adrenoceptor agonist with anti-inflammatory and putative neuroprotective properties. In the present investigation, the effect of clenbuterol was assessed in a rat model of acute brain injury induced by intra-striatal administration of the pro-inflammatory cytokine IL-1β. Methods: Clenbuterol (0.5 mg/kg; i.p.) was administered one hour prior to stereotactically delivered IL-1β (100 ng) into the striatum. Four hours postinjection, rats were anesthetized, blood samples were collected for circulating cytokine and chemokine analysis, and the ipsilateral striatum and liver tissue were harvested for mRNA expression analysis of target genes. Results: Intrastriatal IL-1β provoked an inflammatory response with increased expression of IL-1β and the pro-inflammatory cytokine TNF-α. TNF-α expression was also increased in the liver and circulating concentrations of the chemokine cytokine-induced neutrophil chemoattractant 1 (CINC-1) were raised in response to intrastriatal IL-1β administration. The striatal response was accompanied by NFκB activation and 24 hours postinjection, increased immunoreactivity of the neutrophil marker MBS-2, indicative of cell infiltration and increased TUNEL staining, a cell marker of apoptosis. Treatment with clenbuterol attenuated all IL-1β-induced changes in the striatum including MBS-2 immunoreactivity and TUNEL + staining. Clenbuterol also attenuated IL-1β-induced expression of TNF-α in the liver and the increase in circulating CINC-1 concentrations. Conclusions: The results provide evidence that clenbuterol elicits anti-inflammatory effects, suppresses the peripheral acute phase response and reduces the infiltration of neutrophils and apoptotic response to acute IL-1β–induced brain injury. Suppression of both the central and peripheral response following clenbuterol administration may contribute to its protective properties following brain injury.

Clenbuterol activates the central IL-1 system via the β2-adrenoceptor without provoking inflammatory response related behaviours in rats.

The long-acting, highly lipophilic, β2-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-1β 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 β2-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-1β. Moreover, despite increasing central IL-1β 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 β2-adrenoceptor agonists could have the potential to combat neuroinflammatory or neurodegenerative disorders without inducing unwanted symptoms of depression and anxiety.

Synergistic CNS anti-inflammatory actions of combined treatment with the beta2-adrenoceptor agonist clenbuterol and the glucocorticoid dexamethasone

405 IL-6 is associated with metabolic syndrome in bipolar disorder A. Prossin , M. McInnis , S. Zalcman , V. Ellingrod a,c a Comprehensive Depression Center, Department of Psychiatry, University of Michigan Medical School, 4250 Plymouth Rd, Ann Arbor, MI 48105, United States b Department of Psychiatry, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, United States c College of Pharmacy, University of Michigan, United States Strong associations exist between pro-inflammatory cytokines (i.e. IL-6) and the metabolic syndrome. In Bipolar Disorder (BD), interleukin-6 (IL-6) is associated with depressed mood, but whether this inflammatory marker accounts for the co-morbidity of metabolic syndrome is unclear.Here we explore the relationship between IL-6 and the presence of metabolic syndrome in BD in an attempt to clarify the role of this potential bio-marker in predicting risk of metabolic syndrome. We studied 78 euthymic BD subjects using a cross-sectional design. Serum IL-6 concentrations were determined with standard ELISAs. The subjects were stratified by presence or absence of metabolic syndrome (NCEP-ATP-III criteria). We compared (Student’s t-test) the differences in IL-6 between these two BD subgroups. We investigated the effects of other variables (i.e. number of criteria of metabolic syndrome) on the relationship between IL-6 and metabolic syndrome in BD using correlations. IL-6 was significantly greater in the BDs with metabolic syndrome as compared to those without. IL-6 was significantly correlated to the number of criteria of metabolic syndrome. These results identify IL-6 as a potential diagnostic marker of metabolic syndrome in BD, a previously understudied relationship.Future longitudinal designs will assess the predictive potential of IL-6 in determining risk of metabolic syndrome in patients with BD. Given the previously identified relationships between IL-6 and mood state in BD, this study furthers the understanding of these common ‘‘mind–body” interactions. doi:10.1016/j.bbi.2010.07.155