Synthetic cannabinoid WIN55,212-2 inhibits generation of inflammatory mediators by IL-1β-stimulated human astrocytes

Activated glial cells have been implicated in the neuropathogenesis of many infectious and inflammatory diseases of the brain. A number of inflammatory mediators have been proposed to play a role in glial cell-related brain damage; e.g., free radicals such as nitric oxide (NO), cytokines, and chemokines. Our laboratory has been interested in the effect of psychoactive drugs and their derivatives on the production of these mediators. Cannabinoids have been shown to possess immunomodulatory as well as psychoactive properties. We previously have shown that interleukin (IL)-1β-stimulated human astrocytes, but not microglia, produce NO. In this study, we investigated the effects of the synthetic cannabinoid WIN55,212-2 on the production of several key inflammatory mediators by human fetal astrocytes activated by IL-1β. Expression of the cannabinoid receptors CB₁ and CB₂ was detected on human astrocytes. WIN55,212-2 (10^-5 M) potently inhibited inducible NO synthase (iNOS) and corresponding NO production by IL-1β-stimulated astrocytes. The CB₁ and CB₂ receptor-specific antagonists SR141716A and SR144528, respectively, partially blocked this suppressive effect. In addition, treatment of astrocytes with WIN55,212-2 downregulated in a concentration-dependent manner IL-1β-induced tumor necrosis factor (TNF)-α release. Treatment with WIN55,212-2 also inhibited production of the chemokines CXCL10, CCL2 and CCL5 by IL-1β-activated astrocytes. These findings indicate that WIN55,212-2 inhibits the production of inflammatory mediators by IL-1β-stimulated human astrocytes and suggest that comparable agents may have therapeutic potential for the management of brain inflammation.