Alkylamides from Echinacea are a new class of cannabinomimetics. Cannabinoid type 2 receptor-dependent and -independent immunomodulatory effects

J Biol Chem. 2006 May 19;281(20):14192-206. doi: 10.1074/jbc.M601074200. Epub 2006 Mar 17.

Abstract

Alkylamides (alkamides) from Echinacea modulate tumor necrosis factor alpha mRNA expression in human monocytes/macrophages via the cannabinoid type 2 (CB2) receptor (Gertsch, J., Schoop, R., Kuenzle, U., and Suter, A. (2004) FEBS Lett. 577, 563-569). Here we show that the alkylamides dodeca-2E,4E,8Z,10Z-tetraenoic acid isobutylamide (A1) and dodeca-2E,4E-dienoic acid isobutylamide (A2) bind to the CB2 receptor more strongly than the endogenous cannabinoids. The Ki values of A1 and A2 (CB2 approximately 60 nM; CB1 >1500 nM) were determined by displacement of the synthetic high affinity cannabinoid ligand [3H]CP-55,940. Molecular modeling suggests that alkylamides bind in the solvent-accessible cavity in CB2, directed by H-bonding and pi-pi interactions. In a screen with 49 other pharmacologically relevant receptors, it could be shown that A1 and A2 specifically bind to CB2 and CB1. A1 and A2 elevated total intracellular Ca2+ in CB2-positive but not in CB2-negative promyelocytic HL60 cells, an effect that was inhibited by the CB2 antagonist SR144528. At 50 nM, A1, A2, and the endogenous cannabinoid anandamide (CB2 Ki >200 nM) up-regulated constitutive interleukin (IL)-6 expression in human whole blood in a seemingly CB2-dependent manner. A1, A2, anandamide, the CB2 antagonist SR144528 (Ki <10 nM), and also the non-CB2-binding alkylamide undeca-2E-ene,8,10-diynoic acid isobutylamide all significantly inhibited lipopolysaccharide-induced tumor necrosis factor alpha, IL-1beta, and IL-12p70 expression (5-500 nM) in a CB2-independent manner. Alkylamides and anandamide also showed weak differential effects on anti-CD3-versus anti-CD28-stimulated cytokine expression in human whole blood. Overall, alkylamides, anandamide, and SR144528 potently inhibited lipopolysaccharide-induced inflammation in human whole blood and exerted modulatory effects on cytokine expression, but these effects are not exclusively related to CB2 binding.

MeSH terms

  • Animals
  • Blotting, Western
  • CHO Cells
  • Cell Separation
  • Cricetinae
  • Echinacea / metabolism*
  • Flow Cytometry
  • HL-60 Cells
  • Humans
  • Kinetics
  • Models, Biological
  • Models, Molecular
  • Plant Extracts / metabolism
  • Receptor, Cannabinoid, CB2 / chemistry*
  • Receptors, Cannabinoid / chemistry*
  • Receptors, Cannabinoid / metabolism

Substances

  • Plant Extracts
  • Receptor, Cannabinoid, CB2
  • Receptors, Cannabinoid