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Journal of Lipid Research, Vol. 46, 1953-1961, September 2005
Copyright © 2005 by American Society for Biochemistry and Molecular Biology

On the importance of anandamide structural features for its interactions with DPPC bilayers: effects on PLA₂ activity

S. Ambrosi^*, L. Ragni, A. Ambrosini^*, L. Paccamiccio, P. Mariani, R. Fiorini^*, E. Bertoli^* and G. Zolese^1,*

^* Istituto di Biochimica, Università Politecnica delle Marche, 60131 Ancona, Italy
Istituto di Scienze Fisiche, Università Politecnica delle Marche, 60131 Ancona, Italy
Dipartimento di Biologia Molecolare, Cellulare, Animale (MCA), Università di Camerino, 62032 Camerino, Italy

Published, JLR Papers in Press, June 16, 2005. DOI 10.1194/jlr.M500121-JLR200

¹ To whom correspondence should be addressed. e-mail: g.zolese{at}univpm.it

The acylethanolamide anandamide (AEA) occurs in a variety of mammalian tissues and, as a result of its action on cannabinoid receptors, exhibits several cannabimimetic activities. Moreover, some of its effects are mediated through interaction with an ion channel-type vanilloid receptor. However, the chemical features of AEA suggest that some of its biological effects could be related to physical interactions with the lipidic part of the membrane. The present work studies the effect of AEA-induced structural modifications of the dipalmitoylphosphatidylcholine (DPPC) bilayer on phospholipase A₂ (PLA₂) activity, which is strictly dependent on lipid bilayer features. This study, performed by 2-dimethylamino-(6-lauroyl)-naphthalene fluorescence, demonstrates that the effect of AEA on PLA₂ activity is concentration-dependent. In fact, at low AEA/DPPC molar ratios (from R = 0.001 to R = 0.04), there is an increase of the enzymatic activity, which is completely inhibited for R = 0.1. X-ray diffraction data indicate that the AEA affects DPPC membrane structural properties in a concentration-dependent manner.

Because the biphasic effect of increasing AEA concentrations on PLA₂ activity is related to the induced modifications of membrane bilayer structural properties, we suggest that AEA-phospholipid interactions may be important to produce, at least in part, some of the similarly biphasic responses of some physiological activities to increasing concentrations of AEA.

Abbreviations: AEA, anandamide; d, unit cell dimension; DPPC, dipalmitoylphosphatidylcholine; emGP, emission generalized polarization; exGP, excitation generalized polarization; GP, generalized polarization; Laurdan, 2-dimethylamino-(6-lauroyl)-naphthalene; LUV, large unilamellar vesicle; MLV, multilamellar vesicle; NAE, acylethanolamide; PL, phospholipid; PLA₂, phospholipase A₂; , lag time; Tm, main phase transition temperature

Supplementary key words dipalmitoylphosphatidylcholine • Laurdan • X-ray diffraction • phospholipase A₂

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