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

The long-acting, highly lipophilic, beta(2)-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-1 beta 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, 250 mu g/kg), clenbuterol (0.5 mg/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 beta(2)-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-1 beta. Moreover, despite increasing central IL-1 beta expression, chronic administration of clenbuterol (0.03 mg/kg; twice daily for 21 days) 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 beta(2)-adrenoceptor agonists could have the potential to combat neuroinflammatory or neurodegenerative disorders without inducing unwanted symptoms of depression and anxiety. Copyright (C) 2016 Elsevier Inc. All rights reserved.