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

J Neuroinflammation. 2015 May 13;12:89. doi: 10.1186/s12974-015-0307-7.

Abstract

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.

MeSH terms

  • Animals
  • Anti-Inflammatory Agents / pharmacology*
  • Arachidonic Acids / metabolism*
  • Arachidonic Acids / pharmacokinetics
  • Arrestins / metabolism
  • Biphenyl Compounds / pharmacology*
  • Brain / drug effects*
  • Brain / metabolism
  • CHO Cells
  • Cell Line, Transformed
  • Cricetulus
  • Cyclic AMP / metabolism
  • Cyclooxygenase 2 / metabolism*
  • Dose-Response Relationship, Drug
  • Endocannabinoids / metabolism*
  • Endocannabinoids / pharmacokinetics
  • Female
  • Glycerides / metabolism*
  • Glycerides / pharmacokinetics
  • Guanosine 5'-O-(3-Thiotriphosphate) / pharmacokinetics
  • Lignans / pharmacology*
  • Macrophages
  • Mice
  • Silicone Elastomers / pharmacokinetics
  • Sulfur Isotopes / pharmacokinetics
  • Tritium / pharmacokinetics
  • beta-Arrestins

Substances

  • 4-O-methylhonokiol
  • Anti-Inflammatory Agents
  • Arachidonic Acids
  • Arrestins
  • Biphenyl Compounds
  • Endocannabinoids
  • Glycerides
  • Lignans
  • Silicone Elastomers
  • Sulfur Isotopes
  • beta-Arrestins
  • Tritium
  • aminoethyl-aminopropyl-trimethoxysilane
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • glyceryl 2-arachidonate
  • Cyclic AMP
  • Cyclooxygenase 2