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.

Keywords:

• β₂-Adrenoceptor
• clenbuterol
• IL-1β
• CINC-1
• neutrophil
• apoptosis
• striatum
• rat

Acknowledgements

The authors would like to acknowledge grant support from the Health Research Board of Ireland. JY was supported by the Higher Education Authority of Ireland and the Programme for Research in Third Level Institutions MolCellBio program. The authors would also like to thank Professor Daniel Anthony for kindly gifting us the MBS-2 primary antibody from his laboratory and for his input in developing the immunohistochemistry techniques involved in this study.

Disclosure statement

The authors have no conflicts of interest. Financial support and benefit in kind is described in the acknowledgements.