4'-O-methylhonokiol increases levels of 2-arachidonoyl glycerol in mouse brain via selective inhibition of its COX-2-mediated oxygenation

Background and purpose: 4'-o-methylhonokiol (mh) is a natural product showing anti-inflammatory,anti-osteoclastogenic,and neuroprotective effects. mh was reported to modulate cannabinoid cb2 receptors as an inverse agonist for camp production and an agonist for intracellular [ca2+]. it was recently shown that mh inhibits camp formation via cb2 receptors. in this study,the exact modulation of mh on cb2 receptor activity was elucidated and its endocannabinoid substrate-specific inhibition (ssi) of cyclooxygenase-2 (cox-2) and cns bioavailability are described for the first time. methods: cb2 receptor modulation ([35s]gtpγs,camp,and β-arrestin) by mh was measured in hcb2-transfected cho-k1 cells and native conditions (hl60 cells and mouse spleen). the cox-2 ssi was investigated in raw264.7 cells and in swiss albino mice by targeted metabolomics using lc-ms/ms. results: mh is a cb2 receptor agonist and a potent cox-2 ssi. it induced partial agonism in both the [35s]gtpγs binding and β-arrestin recruitment assays while being a full agonist in the camp pathway. mh selectively inhibited pge2 glycerol ester formation (over pge2) in raw264.7 cells and significantly increased the levels of 2-ag in mouse brain in a dose-dependent manner (3 to 20 mg kg-1) without affecting other metabolites. after 7 h from intraperitoneal (i.p.) injection,mh was quantified in significant amounts in the brain (corresponding to 200 to 300 nm). conclusions: lc-ms/ms quantification shows that mh is bioavailable to the brain and under condition of inflammation exerts significant indirect effects on 2-ag levels. the biphenyl scaffold might serve as valuable source of dual cb2 receptor modulators and cox-2 ssis as demonstrated by additional mh analogs that show similar effects. the combination of cb2 agonism and cox-2 ssi offers a yet unexplored polypharmacology with expected synergistic effects in neuroinflammatory diseases,thus providing a rationale for the diverse neuroprotective effects reported for mh in animal models. © 2015 chicca et al.; licensee biomed central.