Abstract
The endolipid N-palmitoylethanolamine (PEA) shows a pleiotropic pattern of bioactivities, whose mechanistic characterization is still unclear and whose pharmacological potential is substantially limited by rapid metabolization by the amido hydrolyzing enzymes fatty acid amide hydrolases and N-acylethanolamine-hydrolyzing acid amidase. To overcome this problem, we have synthesized a new series of PEA homologs and characterized their activity on two in vitro models of neurodegeneration (oxidative stress, excitotoxicity). PEA partially prevented tert-butylhydroperoxide (t-BOOH; 100 μM; 3 h)-induced cell death (maximal effect, 26.3 ± 7.5% in comparison with t-BOOH-untreated cells at 30 μM), whereas it was ineffective against the l-glutamate (1 mM; 24 h)-induced excitotoxicity at all concentrations tested (0.01–30 μM). Oxyhomologation of the amide bond, although leading to an increased enzymatic stability, also potentiated neuroprotective activity, especially for N-palmitoyl-N-(2-hydroxyethyl)hydroxylamine (EC50 = 2.1 μM). These effects were not mediated by cannabinoid/vanilloid-dependent mechanisms but rather linked to a decreased t-BOOH-induced lipoperoxidation and reactive oxygen species formation and l-glutamate-induced intracellular Ca2+ overload. The presence of the hydroxamic group and the absence of either redox active or radical scavenger moieties suggest that the improved neuroprotection is the result of increased metal-chelating properties that boost the antioxidant activity of these compounds.
Footnotes
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This work was supported by the Fondi Regionali per la Ricerca Scientifica Applicata (CIPE 2004) (Turin, Italy).
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.106.112987.
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ABBREVIATIONS: NAE, N-acylethanolamines; AEA, N-arachidonoylethanolamine; PEA, N-palmitoylethanolamine; SR144528, N-((1S)-endo-1,3,3-trimethyl bicyclo heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide); FAAH, fatty acid amide hydrolase; AMT, anandamide membrane transporter; (+)-MK 801, (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine; AM251, N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide; AM630, (6-iodo-2-methyl-1-[2-(4-morpholinyl-)ethyl]-1H-indol-3-yl)(4-methoxyphenyl)methanone; DMEM, Dulbecco's modified Eagle's medium; t-BOOH, tert-butylhydroperoxide; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; PBS, phosphate-buffered saline; LDH, lactic acid dehydrogenase; TBARS, thiobarbituric acid-reacting substance(s); Fr, fluorescence ratio; RT, reverse transcriptase; PCR, polymerase chain reaction; NMDA, N-methyl-d-aspartate.
- Received August 25, 2006.
- Accepted October 25, 2006.
- The American Society for Pharmacology and Experimental Therapeutics