Aspirin-triggered lipoxin induces CB1-dependent catalepsy in mice

Evidence are that inhibition of cyclooxygenase 2 (COX-2) enhances endocannabinoid signaling, indicating a crosstalk between these two eicosanoid pathways. Aspirin, a non-selective COX inhibitor, acetylates COX-2 with generation of a lipoxygenase (LOX) substrate, whose end product is the 15-epi-lipoxin A₄ (15-epi-LXA₄), an aspirin-triggered lipoxin. Our objective was to investigate whether 15-epi-LXA₄ would potentiate in vivo effects of the endocannabinoid anandamide (AEA). Catalepsy was selected as a behavioral parameter and tested 5 min after AEA injection in all experiments. AEA induced dose-dependent (200 pmol/2 μl, i.c.v.) catalepsy. A sub-dose of AEA (10 pmol/2 μl, i.c.v.) was potentiated by aspirin (300 mg/kg, p.o.) via a 5-LOX-dependent step. The cataleptic effect induced by the interaction between sub-doses of 15-epi-LXA₄ (0.01 pmol/2 μl, i.c.v.) and AEA (10 pmol/2 μl, i.c.v.) was prevented by the cannabinoid CB₁ receptors antagonist SR141716A (1 mg/kg, i.p.), but not by the antagonist of lipoxin ALX receptors Boc-2 (10 μg/kg, i.p.). While previous studies have shown that COX inhibition itself may enhance endocannabinoid effects, here we add another piece of evidence revealing that a LOX-derivative produced in consequence of COX-2 acetylation participates in this process.