title: PPARγ activation blocks development and reduces established neuropathic pain in rats.
abstract: Peroxisome proliferator-activated receptor gamma (PPARγ) is emerging as a new pharmacotherapeutic target for chronic pain. When oral (3-30 mg/kg/day in chow for 7 wk) or twice-daily intraperitoneal (1-10 mg/kg/day for 2 wk) administration began before spared nerve injury (SNI), pioglitazone, a PPARγ agonist, dose-dependently prevented multiple behavioral signs of somatosensory hypersensitivity. The highest dose of intraperitoneal pioglitazone did not produce ataxia or reductions in transient mechanical and heat nociception, indicating that inhibitory effects on hypersensitivity were not secondary to adverse drug-induced behaviors or antinociception. Inhibitory effects on hypersensitivity persisted at least one week beyond cessation of pioglitazone administration, suggestive of long-lasting effects on gene expression. Blockade of PPARγ with GW9662, an irreversible and selective PPARγ antagonist, dose-dependently reduced the inhibitory effect of pioglitazone on hypersensitivity, indicating a PPARγ-dependent action. Remarkably, a single preemptive injection of pioglitazone 15 min before SNI attenuated hypersensitivity for at least 2 weeks; this was enhanced with a second injection delivered 12 h after SNI. Pioglitazone injections beginning after SNI also reduced hypersensitivity, albeit to a lesser degree than preemptive treatment. Intraperitoneal pioglitazone significantly reduced the nerve injury-induced up-regulation of cd11b, GFAP, and p-p38 in the dorsal horn, indicating a mechanism of action involving spinal microglia and/or astrocyte activation. Oral pioglitazone significantly reduced touch stimulus-evoked phospho-extracellular signal-related kinase (p-ERK) in lamina I-II, indicating a mechanism of action involving inhibition of central sensitization. We conclude that pioglitazone reduces spinal glial and stimulus-evoked p-ERK activation and that PPARγ activation blocks the development of and reduces established neuropathic pain.
authors: Department of Physiology, University of Kentucky Research Foundation, Lexington, KY 40536, USA.
authors: J
authors: J
authors: Morgenweck
authors: R B
authors: RB
authors: Griggs
authors: R R
authors: RR
authors: Donahue
authors: J E
authors: JE
authors: Zadina
authors: B K
authors: BK
authors: Taylor
mesh_terms: D000813:Anilides / Q000494:pharmacology; D000818:Animals; D001259:Ataxia / Q000139:chemically induced; D039481:CD11b Antigen / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006930:Hyperalgesia / Q000188:drug therapy / Q000503:physiopathology / Q000517:prevention & control; D008297:Male; D009437:Neuralgia / Q000188:drug therapy / Q000503:physiopathology* / Q000517:prevention & control; D047495:PPAR gamma / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology*; D000077205:Pioglitazone; D020671:Posterior Horn Cells / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D045162:Thiazolidinediones / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: C457499:2-chloro-5-nitrobenzanilide; D000813:Anilides; D039481:CD11b Antigen; D005904:Glial Fibrillary Acidic Protein; D047495:PPAR gamma; D045162:Thiazolidinediones; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000077205:Pioglitazone