Leptin protects against 6-hydroxydopamine-induced dopaminergic cell death via mitogen-activated protein kinase signaling.
The death of midbrain dopaminergic neurons in sporadic Parkinson disease is of unknown etiology but may involve altered growth factor signaling. The present study showed that leptin, a centrally acting hormone secreted by adipocytes, rescued dopaminergic neurons, reversed behavioral asymmetry, and restored striatal catecholamine levels in the unilateral 6-hydroxydopamine (6-OHDA) mouse model of dopaminergic cell death. In vitro studies using the murine dopaminergic cell line MN9D showed that leptin attenuated 6-OHDA-induced apoptotic markers, including caspase-9 and caspase-3 activation, internucleosomal DNA fragmentation, and cytochrome c release. ERK1/2 phosphorylation (pERK1/2) was found to be critical for mediating leptin-induced neuroprotection, because inhibition of the MEK pathway blocked both the pERK1/2 response and the pro-survival effect of leptin in cultures. Knockdown of the downstream messengers JAK2 or GRB2 precluded leptin-induced pERK1/2 activation and neuroprotection. Leptin/pERK1/2 signaling involved phosphorylation and nuclear localization of CREB (pCREB), a well known survival factor for dopaminergic neurons. Leptin induced a marked MEK-dependent increase in pCREB that was essential for neuroprotection following 6-OHDA toxicity. Transfection of a dominant negative MEK protein abolished leptin-enhanced pCREB formation, whereas a dominant negative CREB or decoy oligonucleotide diminished both pCREB binding to its target DNA sequence and MN9D survival against 6-OHDA toxicity. Moreover, in the substantia nigra of mice, leptin treatment increased the levels of pERK1/2, pCREB, and the downstream gene product BDNF, which were reversed by the MEK inhibitor PD98059. Collectively, these data provide evidence that leptin prevents the degeneration of dopaminergic neurons by 6-OHDA and may prove useful in the treatment of Parkinson disease.
Weng
Zhongfang
Z
Department of Neurology, and Pittsburgh Institute of Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
Signore
Armando P
AP
Gao
Yanqin
Y
Wang
Suping
S
Zhang
Feng
F
Hastings
Teresa
T
Yin
Xiao-Ming
XM
Chen
Jun
J
D017667:Adipocytes / Q000378:metabolism / Q000473:pathology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D050882:CREB-Binding Protein / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D004195:Disease Models, Animal; D005419:Flavonoids / Q000494:pharmacology; D051380:GRB2 Adaptor Protein; D006801:Humans; D053614:Janus Kinase 2 / Q000378:metabolism; D020738:Leptin / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D016627:Oxidopamine / Q000633:toxicity*; D010300:Parkinson Disease / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D013378:Substantia Nigra / Q000378:metabolism / Q000473:pathology; D013565:Sympatholytics / Q000633:toxicity*
D002395:Catecholamines; D005419:Flavonoids; D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse; D020738:Leptin; D018696:Neuroprotective Agents; D013565:Sympatholytics; D016627:Oxidopamine; D050882:CREB-Binding Protein; C494364:Crebbp protein, mouse; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C505409:Casp3 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one