β-funaltrexamine differentially modulates chemokine and cytokine expression in normal human astrocytes and C20 human microglial cells

Aim: Emerging evidence implicates astrocyte/microglia dysregulation in a range of brain disorders, thereby making glial cells potential therapeutic targets. The novel anti-inflammatory actions of beta-funaltrexamine (β-FNA) are of particular interest. β-FNA is a derivative of naltrexone, and recognized as a selective, irreversible antagonist at the mu -opioid receptor (MOR). However, we discovered that β-FNA has novel anti-inflammatory actions that seem to be mediated through a MOR-independent mechanism. Thus far, we have focused on the acute effects of β-FNA on inflammatory signaling. Methods: The effect of β-FNA treatment on interleukin-1β (IL-1β)-induced inflammatory signaling in normal human astrocytes (NHA) and C20 human microglial cells. Cytokine/chemokine expression was measured using ELISA, and nuclear factor-kappaB (NF-κB) p65 activation was evaluated by immunoblot. Results: IL-1β-induced interferon-γ inducible protein-10 (CXCL10) production in NHA was more sensitive to chronic (3 day) β-FNA as indicated by an approximately 3-fold lower EC50 compared to that observed in acutely treated cells. Chronic β-FNA did not affect IL-1β-induced monocyte chemoattractant protein-1 (CCL2) or IL-6 production in NHA. β-FNA inhibited phosphorylation of NF-κB p65, suggesting that the inhibitory effects may be due in part to reduced NF-κB activation. We showed for the first time that C20 human microglial cells were insensitive to the anti-inflammatory actions of acute β-FNA. Conclusion: β-FNA differentially affects inflammatory cytokine/chemokine expression in human astrocytes and microglia. These findings warrant further investigation into the novel anti-inflammatory actions of β-FNA, with a particular focus on astrocytes. These insights should contribute to the development of strategies to treat brain disorders that involve neuroinflammation.