Acute intracerebroventricular administration of palmitoylethanolamide, an endogenous peroxisome proliferator-activated receptor-alpha agonist, modulates carrageenan-induced paw edema in mice.

Peroxisome proliferator-activated receptor (PPAR)-α is a nuclear transcription factor. Although the presence of this receptor in different areas of central nervous system (CNS) has been reported, its role remains unclear. Palmitoylethanolamide (PEA), a member of the fatty-acid ethanolamide family, acts peripherally as an endogenous PPAR- α ligand, exerting analgesic and anti-inflammatory effects. High levels of PEA in the CNS have been found, but the specific function of this lipid remains to be clarified. Using carrageenan-induced paw edema in mice, we show that i.c.v. administration of PEA may control peripheral inflammation through central PPAR- α activation. A single i.c.v. administration of 0.01 to 1 g of PEA, 30 min before carrageenan injection, reduced edema formation in the mouse carrageenan test. This effect was mimicked by 0.01 to 1 µg of GW7647 [2-[[4-[2-[[(cyclohexylamino)carbonyl](4-cyclohexylbutyl)amino]ethyl]phenyl]thio]-2-methylpropanoic acid], a synthetic PPAR- α agonist. Moreover, central PEA administration significantly reduced the expression of the proinflammatory enzymes cyclooxygenase-2 and inducible nitric-oxide synthase, and it significantly restored carrageenan-induced PPAR- α reduction in the spinal cord. To investigate the mechanism by which i.c.v. PEA attenuated the development of carrageenan-induced paw edema, we evaluated inhibitor kB- α (IkB- α) degradation and nuclear factor- kB (NF-kB) p65 activation in the cytosolicor nuclear extracts from spinal cord tissue. PEA prevented IkB-α degradation and NF-kB nuclear translocation, confirming the involvement of this transcriptional factor in the control of peripheral inflammation. The obligatory role of PPAR- α in mediating the effects of PEA was confirmed by the lack of the compounds anti-inflammatory effects in mutant mice lacking PPAR-α. In conclusion, our data show for the first time that PPAR-α activation in the CNS can control peripheral inflammation.