Rapid broad-spectrum analgesia through activation of peroxisome proliferator-activated receptor-alpha.

Abstract

Severe pain remains a major area of unmet medical need. Here we report that agonists of the nuclear receptor PPAR-alpha (peroxisome proliferator-activated receptor-alpha) suppress pain behaviors induced in mice by chemical tissue injury, nerve damage, or inflammation. The PPAR-alpha agonists GW7647 [2-(4-(2-(1-cyclohexanebutyl)-3-cyclohexylureido)ethyl)phenylthio)-2-methylpropionic acid], Wy-14643 [4-chloro-6-(2,3-xylidino)-2-pyrimidinylthioacetic acid], and palmitoylethanolamide (PEA) reduced nocifensive behaviors elicited in mice by intraplantar (i.pl.) injection of formalin or i.p. injection of magnesium sulfate. These effects were absent in PPAR-alpha-null mice yet occurred within minutes of agonist administration in wild-type mice, suggesting that they were mediated through a transcription-independent mechanism. Consistent with this hypothesis, blockade of calcium-operated IK(ca) (K(Ca)3.1) and BK(ca) (K(Ca)1.1) potassium channels prevented the effects of GW7647 and PEA in the formalin test. Three observations suggest that PPAR-alpha agonists may inhibit nocifensive responses by acting on peripheral PPAR-alpha. (i) PEA reduced formalin-induced pain at i.pl. doses that produced no increase in systemic PEA levels; (ii) PPAR-alpha was expressed in dorsal root ganglia neurons of wild-type but not PPAR-alpha-null mice; and (ii) GW7647 and PEA prevented formalin-induced firing of spinal cord nociceptive neurons in rats. In addition to modulating nociception, GW7647 and PEA reduced hyperalgesic responses in the chronic constriction injury model of neuropathic pain; these effects were also contingent on PPAR-alpha expression and were observed following either acute or subchronic PPAR-alpha agonist administration. Finally, acute administration of GW7647 and PEA reduced hyperalgesic responses in the complete Freund's adjuvant and carrageenan models of inflammatory pain. Our results suggest that PPAR-alpha agonists may represent a novel class of analgesics.

• Authors: Jesse LoVerme, Roberto Russo, Giovanna La Rana, Jin Fu, Jesse Farthing, Giuseppina Mattace-Raso, Rosaria Meli, Andrea Hohmann, Antonio Calignano, Daniele Piomelli
• Journal: The Journal of pharmacology and experimental therapeutics (J Pharmacol Exp Ther) Vol. 319 Issue 3 Pg. 1051-61 (Dec 2006) ISSN: 0022-3565 [Print] United States
• PMID: 16997973 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Analgesics
• DNA, Complementary
• Hypolipidemic Agents
• PPAR alpha
• Potassium Channels, Calcium-Activated
• Formaldehyde
• RNA
• fenofibric acid
• Fenofibrate

Topics

• Analgesics (pharmacology)
• Animals
• DNA, Complementary (biosynthesis, genetics)
• Drug Tolerance
• Fenofibrate (analogs & derivatives, pharmacology)
• Formaldehyde
• Hyperalgesia (drug therapy)
• Hypolipidemic Agents (pharmacology)
• Immunoblotting
• Male
• Mice
• Mice, Inbred C57BL
• Mice, Knockout
• Nociceptors (drug effects)
• PPAR alpha (agonists, genetics)
• Pain Measurement (drug effects)
• Potassium Channels, Calcium-Activated (physiology)
• RNA (isolation & purification)
• Rats
• Rats, Sprague-Dawley
• Sciatica (drug therapy)