title: Rosiglitazone decreases peroxisome proliferator receptor-γ levels in microglia and inhibits TNF-α production: new evidences on neuroprotection in a progressive Parkinson's disease model.
abstract: Thiazolidinedione (TZD) class of peroxisome proliferator receptor gamma (PPAR-γ) agonists display neuroprotective effects in experimental Parkinson's disease (PD) models. Neurons and microglia express PPAR-γ, therefore both of them are potential targets for neuroprotection, although the role of each cell type is not clear. Moreover, receptor-dependent as well as receptor-independent mechanisms have been involved. This study further investigated mechanisms of TZD-mediated neuroprotection in PD. We investigated the rosiglitazone effect in the progressive MPTP/probenecid (MPTPp) model of PD. C57BL/6J mice received MPTP (25 mg/kg) plus probenecid (100 mg/kg) twice per week for 5 weeks. Rosiglitazone (10 mg/kg) was given daily until sacrifice, starting on the fourth week of MPTPp treatment, in presence of an ongoing neurodegeneration with microgliosis. Changes in PPAR-γ levels were measured by immunofluorescence and confocal microscopy in tyrosine hydroxylase (TH)-positive neurons and CD11b-positive microglia of the substantia nigra pars compacta (SNc). Chronic MPTPp treatment induced a PPAR-γ overexpression in both TH-positive neurons and microglia (139.9% and 121.7% over vehicle, respectively). Rosiglitazone administration to MPTPp-treated mice, reverted PPAR-γ overexpression in microglia without affecting TH-positive neurons. Thereafter, changes in CD11b and tumor necrosis factor α (TNF-α) immunoreactivity in microglia were evaluated in the SNc. MPTPp progressively increased CD11b immunoreactivity, conferring to microglia a highly activated morphology. Moreover, TNF-α levels were increased (457.38% over vehicle) after MPTPp. Rosiglitazone administration counteracted the increase in CD11b immunoreactivity caused by MPTPp. Moreover, rosiglitazone reverted TNF-α expression to control levels. Nigrostriatal degeneration was assessed by high pressure liquid chromatography (HPLC) measurement of striatal dopamine, and counting of TH-positive neurons in the SNc. MPTPp treatment caused a severe decline of striatal dopamine and a partial degeneration of the SNc. Rosiglitazone arrested the degenerative process in both areas. Results suggest that PPAR-γ expression in microglia and TNF-α production by these cells are crucial changes by which rosiglitazone exerts neuroprotection in PD.
authors.affiliation: Department of Toxicology, University of Cagliari, and Centre of Excellence for Studies on Neurobiology of Addiction, Via Ospedale 72, 09124 Cagliari, Italy. acarta@unica.it
authors.forename: A R
authors.initials: AR
authors.lastname: Carta
authors.forename: L
authors.initials: L
authors.lastname: Frau
authors.forename: A
authors.initials: A
authors.lastname: Pisanu
authors.forename: J
authors.initials: J
authors.lastname: Wardas
authors.forename: S
authors.initials: S
authors.lastname: Spiga
authors.forename: E
authors.initials: E
authors.lastname: Carboni
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D018450:Disease Progression; D007004:Hypoglycemic Agents / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D047495:PPAR gamma / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020734:Parkinsonian Disorders / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D000077154:Rosiglitazone; D045162:Thiazolidinediones / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D007004:Hypoglycemic Agents; D018696:Neuroprotective Agents; D047495:PPAR gamma; D045162:Thiazolidinediones; D014409:Tumor Necrosis Factor-alpha; D000077154:Rosiglitazone