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Cannabinoid Receptor 2 (CB2) Signals via G‑alpha‑s and Induces IL‑6 and IL-10 Cytokine Secretion in Human Primary Leukocytes
journal contribution
posted on 2019-10-19, 12:03 authored by Yurii Saroz, Dan T. Kho, Michelle Glass, Euan Scott Graham, Natasha Lillia GrimseyCannabinoid receptor 2 (CB2) is a promising therapeutic
target for immunological modulation. There is, however, a deficit
of knowledge regarding CB2 signaling and function in human
primary immunocompetent cells. We applied an experimental paradigm
which closely models the in situ state of human primary
leukocytes (PBMC; peripheral blood mononuclear cells) to characterize
activation of a number of signaling pathways in response to a CB2-selective ligand (HU308). We observed a “lag”
phase of unchanged cAMP concentration prior to development of classically
expected Gαi-mediated inhibition of cAMP synthesis.
Application of G protein inhibitors revealed that this apparent lag
was a result of counteraction of Gαi effects by concurrent
Gαs activation. Monitoring downstream signaling events
showed that activation of p38 was mediated by Gαi, whereas ERK1/2 and Akt phosphorylation were mediated by Gαi-coupled βγ. Activation of CREB integrated multiple
components; Gαs and βγ mediated ∼85%
of the response, while ∼15% was attributed to Gαi. Responses to HU308 had an important functional outcomesecretion
of interleukins 6 (IL-6) and 10 (IL-10). IL-2, IL-4, IL-12, IL-13,
IL-17A, MIP-1α, and TNF-α were unaffected. IL-6/IL-10
induction had a similar G protein coupling profile to CREB activation.
All response potencies were consistent with that expected for HU308
acting via CB2. Additionally, signaling and functional
effects were completely blocked by a CB2-selective inverse
agonist, giving additional evidence for CB2 involvement.
This work expands the current paradigm regarding cannabinoid immunomodulation
and reinforces the potential utility of CB2 ligands as
immunomodulatory therapeutics.