CB2
cannabinoid receptors (CB2) are a promising therapeutic target that lacks unwanted side effects of CB1 activation. However, the cell types expressing CB2 that mediate these effects remain poorly understood. We used transgenic mice with CB2 promoter-driven expression of
enhanced green fluorescent protein (EGFP) to study cell types that express CB2 and suppress neuropathic nociception in a mouse model of
chemotherapy-induced
peripheral neuropathy. Structurally distinct CB2 agonists (
AM1710 and
LY2828360) suppressed
paclitaxel-induced mechanical and cold
allodynia in CB2EGFP reporter mice with established neuropathy. Antiallodynic effects of
AM1710 were blocked by
SR144528, a CB2 antagonist with limited CNS penetration. Intraplantar
AM1710 administration suppressed
paclitaxel-induced neuropathic nociception in CB2EGFP but not CB2 knockout mice, consistent with a local site of antiallodynic action.
mRNA expression levels of the anti-inflammatory
cytokine interleukin-10 were elevated in the lumbar spinal cord after intraplantar
AM1710 injection along with the proinflammatory
cytokine tumor necrosis factor alpha and
chemokine monocyte chemoattractant protein-1. CB2EGFP, but not wildtype mice, exhibited anti-GFP immunoreactivity in the spleen. However, the anti-GFP signal was below the threshold for detection in the spinal cord and brain of either vehicle-treated or
paclitaxel-treated CB2EGFP mice. EGFP fluorescence was coexpressed with CB2 immunolabeling in stratified patterns among epidermal keratinocytes. EGFP fluorescence was also expressed in dendritic cells in the dermis, Langerhans cells in the epidermis, and Merkel cells. Quantification of the EGFP signal revealed that Langerhans cells were dynamically increased in the epidermis after
paclitaxel treatment. Our studies implicate CB2 expressed in previously unrecognized populations of skin cells as a potential target for suppressing
chemotherapy-induced neuropathic nociception.