β-Funaltrexamine Displayed Anti-Inflammatory and Neuroprotective Effects in Cells and Rat Model of Stroke

Chronic treatment involving opioids exacerbates both the risk and severity of ischemic stroke. We have provided experimental evidence showing the anti-inflammatory and neuroprotective effects of the μ opioid receptor antagonist β-funaltrexamine for neurodegenerative diseases in rat neuron/glia cultures and a rat model of cerebral Ischemia/Reperfusion (I/R) injury. Independent of in vitro Lipopolysaccharide (LPS)/interferon (IFN-γ)-stimulated neuron/glia cultures and in vivo cerebral I/R injury in Sprague–Dawley rats, β-funaltrexamine downregulated neuroinflammation and ameliorated neuronal degeneration. Alterations in microglia polarization favoring the classical activation state occurred in LPS/IFN-γ-stimulated neuron/glia cultures and cerebral I/R-injured cortical brains. β-funaltrexamine shifted the polarization of microglia towards the anti-inflammatory phenotype, as evidenced by decreased nitric oxide, tumor necrosis factor-α, interleukin-1β, and prostaglandin E2, along with increased CD163 and arginase 1. Mechanistic studies showed that the suppression of microglia pro-inflammatory polarization by β-funaltrexamine was accompanied by the reduction of NF-κB, AP-1, cyclic AMP response element-binding protein, along with signal transducers and activators of transcription transcriptional activities and associated upstream activators. The effects of β-funaltrexamine are closely linked with its action on neuroinflammation by switching microglia polarization from pro-inflammatory towards anti-inflammatory phenotypes. These findings provide new insights into the anti-inflammatory and neuroprotective mechanisms of β-funaltrexamine in combating neurodegenerative diseases, such as stroke.