15-Lipoxygenase metabolism of 2-arachidonylglycerol. Generation of a peroxisome proliferator-activated receptor alpha agonist.
The recent demonstrations that cyclooxygenase-2 and leukocyte-type 12-lipoxygenase (LOX) efficiently oxygenate 2-arachidonylglycerol (2-AG) prompted an investigation into related oxygenases capable of metabolizing this endogenous cannabinoid receptor ligand. We evaluated the ability of six LOXs to catalyze the hydroperoxidation of 2-AG. Soybean 15-LOX, rabbit reticulocyte 15-LOX, human 15-LOX-1, and human 15-LOX-2 oxygenate 2-AG, providing 15(S)-hydroperoxyeicosatetraenoic acid glyceryl ester. In contrast, potato and human 5-LOXs do not efficiently metabolize this endocannabinoid. Among a series of structurally related arachidonyl esters, arachidonylglycerols serve as the preferred substrates for 15-LOXs. Steady-state kinetic analysis demonstrates that both 15-LOX-1 and 15-LOX-2 oxygenate 2-AG comparably or preferably to arachidonic acid. Furthermore, 2-AG treatment of COS-7 cells transiently transfected with human 15-LOX expression vectors or normal human epidermal keratinocytes results in the production and extracellular release of 15-hydroxyeicosatetraenoic acid glyceryl ester (15-HETE-G), establishing that lipoxygenase metabolism of 2-AG occurs in an eukaryotic cellular environment. Investigations into the potential biological actions of 15-HETE-G indicate that this lipid, in contrast to its free-acid counterpart, acts as a peroxisome proliferator-activated receptor alpha agonist. The results demonstrate that 15-LOXs are capable of acting on 2-AG to provide 15-HETE-G and elucidate a potential role for endocannabinoid oxygenation in the generation of peroxisome proliferator-activated receptor alpha agonists.
Kozak
Kevin R
KR
Department of Biochemistry, Vanderbilt-Ingram Cancer Center and Center in Molecular Toxicology, Nashville, Tennessee, USA.
Gupta
Rajnish A
RA
Moody
John S
JS
Ji
Chuan
C
Boeglin
William E
WE
DuBois
Raymond N
RN
Brash
Alan R
AR
Marnett
Lawrence J
LJ
D000818:Animals; D001093:Arachidonate 15-Lipoxygenase / Q000502:physiology*; D001095:Arachidonic Acids; D019556:COS Cells; D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D005989:Glycerides / Q000378:metabolism*; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism; D011817:Rabbits; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists*; D013379:Substrate Specificity; D014157:Transcription Factors / Q000819:agonists*; D015533:Transcriptional Activation
D001095:Arachidonic Acids; D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D005989:Glycerides; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; C094503:glyceryl 2-arachidonate; D001093:Arachidonate 15-Lipoxygenase