WIN55,212-2 inhibits production of CX3CL1 by human astrocytes: Involvement of p38 MAP kinase

CX3CL1 (fractalkine) has been shown not only to be neuroprotective but also may play a role in HIV-1-associated neuropathogenesis. In this study, we found that production of CX3CL1 by human astrocytes stimulated with interleukin (IL)-1β was inhibited in a concentration-dependent manner following pretreatment with the synthetic cannabinoid WIN55,212-2. The CB₂ receptor selective antagonist SR144528 significantly inhibited WIN55,212-2-mediated suppression of CX3CL1, suggesting a CB₂- receptor-related mechanism. IL-1β triggered the activation of p38 and ERK1/2 (p44/42) MAP kinase (MAPK) signaling pathways, but WIN55,212-2 mainly inhibited p38 MAPK phosphorylation. This finding was mirrored in experiments using known inhibitors of these MAPKs, suggesting that the suppression of CX3CL1 production by WIN55,212-2 involves inhibition of signaling via p38 MAPK. Our results support the concept that synthetic cannabinoids have anti-inflammatory properties and that these agents may have therapeutic potential for certain neuroinflammatory disorders.