Implication of the phosphatidylinositol-3 kinase/protein kinase B signaling pathway in the neuroprotective effect of estradiol in the striatum of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mice.
The present experiments sought to determine the implication of estrogen receptors (ERalpha and ERbeta) and their interaction with insulin-like growth factor receptor (IGF-IR) signaling pathways in neuroprotection by estradiol against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity. C57BL/6 male mice were pretreated for 5 days with 17beta-estradiol, an estrogen receptor alpha (ERalpha) agonist, 4,4',4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)tris-phenol (PPT), or an estrogen receptor beta (ERbeta) agonist, 5-androsten-3beta, 17beta-diol (Delta5-diol). On day 5, mice received MPTP (9 mg/kg) or saline injections, and estrogenic treatments were continued for 5 more days. MPTP decreased striatal dopamine, measured by high-performance liquid chromatography, to 59% of control values; 17beta-estradiol and PPT but not Delta5-diol protected against this depletion. MPTP increased IGF-IR measured by Western blot, which was prevented by PPT. The phosphorylation of protein kinase B (Akt) (at serine 473), an essential mediator of IGF-I neuroprotective actions, increased after 17beta-estradiol and tended to increase with PPT but not with Delta5-diol treatments in MPTP mice. Glycogen synthase kinase 3beta (GSK3beta) phosphorylation (at serine 9) was greatly reduced in MPTP mice; this was completely prevented by PPT, whereas 17beta-estradiol and Delta5-diol treatments were less effective. The ratio between the levels of striatal Bcl-2 and BAD proteins, two apoptotic regulators, decreased after MPTP treatment. This effect was effectively prevented only in the animals treated with PPT. In nonlesioned mice, 17beta-estradiol and PPT increased phosphorylation of striatal Akt and GSK3beta, whereas the other markers measured remained unchanged. Delta5-Diol increased GSK3beta phosphorylation less than the PPT treatment. These results suggest that a pretreatment with estradiol promoted dopamine neuron survival by activating ERalpha and increasing Akt and GSK3beta phosphorylation.
D'Astous
Myreille
M
Molecular Endocrinology and Oncology Research Center, Laval University Medical Center, CHUL, 2705 Laurier Boulevard, Quebec City, Quebec, Canada G1V 4G2.
Mendez
Pablo
P
Morissette
Marc
M
Garcia-Segura
Luis Miguel
LM
Di Paolo
Thérèse
T
D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000494:pharmacology*; D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000502:physiology; D047629:Estrogen Receptor beta / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018696:Neuroprotective Agents / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D018696:Neuroprotective Agents; D004958:Estradiol; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt