title: Catalpol attenuates MPTP induced neuronal degeneration of nigral-striatal dopaminergic pathway in mice through elevating glial cell derived neurotrophic factor in striatum.
abstract: The protective effect of an iridoid catalpol extracted and purified from the traditional Chinese medicinal herb Rehmannia glutinosa on the neuronal degeneration of nigral-striatal dopaminergic pathway was studied in a chronic 1-methyl-4-phenyl-1,2,3,4-tetrahydropyridine (MPTP)/probenecid C57BL/6 mouse model and in 1-methyl-4-phenylpyridimium (MPP(+)) intoxicated cultured mesencephalic neurons. Rotarod performance revealed that the locomotor ability of mice was significantly impaired after completion of model production and maintained thereafter for at least 4 weeks. Catalpol orally administered for 8 weeks (starting from the second week of model production) dose dependently improved the locomotor ability. HPLC revealed that catalpol significantly elevated striatal dopamine levels without changing the metabolite/dopamine ratios. Nor did it bind to dopamine receptors. Therefore it is unlikely that catalpol resembles any of the known compounds for treating Parkinsonism. Instead, catalpol dose dependently raised the tyrosine hydroxylase (TH) neuron number in substantia nigra pars compacta (SNpc), the striatal dopamine transporter (DAT) density and the striatal glial cell derived neurotrophic factor (GDNF) protein level. Linear regression revealed that both the TH neuron number and DAT density were positively correlated to the GDNF level. In the cultured mesencephalic neurons, MPP(+) decreased the dopaminergic neuron number and shortened the neurite length, whereas catalpol showed protective effect dose dependently. Furthermore, the expression of GDNF mRNA was up-regulated by catalpol to a peak nearly double of normal control in neurons intoxicated with MPP(+) for 24 h but not in normal neurons. The GDNF receptor tyrosine kinase RET inhibitor 4-amino-5-(4-methyphenyl)-7-(t-butyl)-pyrazolo-[3,4-d]pyrimidine (PP1) abolished the protective effect of catalpol either partially (TH positive neuron number) or completely (neurite length). Taken together, catalpol improves locomotor ability by attenuating the neuronal degeneration of nigral-striatal dopaminergic pathway, and this attenuation is at least partially through elevating the striatal GDNF expression.
authors.affiliation: Research Laboratory of Cell Regulation, Shanghai Jiaotong University School of Medicine, Shanghai, PR China.
authors.forename: G
authors.initials: G
authors.lastname: Xu
authors.forename: Z
authors.initials: Z
authors.lastname: Xiong
authors.forename: Y
authors.initials: Y
authors.lastname: Yong
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: Z
authors.initials: Z
authors.lastname: Ke
authors.forename: Z
authors.initials: Z
authors.lastname: Xia
authors.forename: Y
authors.initials: Y
authors.lastname: Hu
mesh_terms: D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism*; D002478:Cells, Cultured; D002908:Chronic Disease; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism; D004195:Disease Models, Animal; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000378:metabolism*; D005960:Glucosides / Q000008:administration & dosage / Q000494:pharmacology*; D057888:Iridoid Glucosides; D039823:Iridoids / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008636:Mesencephalon / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000187:drug effects; D009410:Nerve Degeneration / Q000139:chemically induced / Q000188:drug therapy*; D009434:Neural Pathways / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018696:Neuroprotective Agents / Q000008:administration & dosage / Q000494:pharmacology*; D011339:Probenecid; D013378:Substantia Nigra / Q000187:drug effects / Q000378:metabolism
chemical_list: C495040:Gdnf protein, mouse; D051100:Glial Cell Line-Derived Neurotrophic Factor; D005960:Glucosides; D057888:Iridoid Glucosides; D039823:Iridoids; D018696:Neuroprotective Agents; C078040:catalpol; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D011339:Probenecid; D004298:Dopamine