We investigated whether responsiveness to dinucleotide uridine adenosine tetraphosphate (Up4A) was altered in aortas from type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats compared with those from age-matched control Long-Evans Tokushima Otsuka (LETO) rats at the chronic stage of disease. In OLETF aortas, we observed the following: (1) Up4A-induced contractions were lower than those in the LETO aortas under basal conditions, (2) slight relaxation occurred due to Up4A, but this was not observed in phenylephrine-precontracted LETO aortas, (3) acetylcholine-induced relaxation was reduced (vs. LETO), and (4) prostanoid release (prostaglandin (PG)F2α, thromboxane (Tx)A2 metabolite, and PGE2) due to Up4A was decreased (vs. LETO). Endothelial denudation suppressed Up4A-induced contractions in the LETO group, but increased the contractions in the OLETF group. Under nitric oxide synthase (NOS) inhibition, Up4A induced contractions in phenylephrine-precontracted aortas; this effect was greater in the LETO group (vs. the OLETF group). The relaxation response induced by Up4A was unmasked by cyclooxygenase inhibitors, especially in the LETO group, but this effect was abolished by NOS inhibition. These results suggest that the relaxant component of the Up4A-mediated response was masked by prostanoids in the LETO aortas and that the LETO and OLETF rats presented different contributions of the endothelium to the response.

The aim of this study is to investigate the role of magnolol in preventing 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP-) induced neurodegeneration in mice and 1-methyl-4-phenylpyridinium ion-(MPP+-) induced cytotoxicity to human neuroblastoma SH-SY5Y cells and to examine the possible mechanisms. Magnolol (30 mg/kg) was orally administered to C57BL/6N mice once a day for 4 or 5 days either before or after MPTP treatment. Western blot analysis revealed that MPTP injections substantially decreased protein levels of dopamine transporter (DAT) and tyrosine hydroxylase (TH) and increased glial fibrillary acidic protein (GFAP) levels in the striatum. Both treatments with magnolol significantly attenuated MPTP-induced decrease in DAT and TH protein levels in the striatum. However, these treatments did not affect MPTP-induced increase in GFAP levels. Moreover, oral administration of magnolol almost completely prevented MPTP-induced lipid peroxidation in the striatum. In human neuroblastoma SH-SY5Y cells, magnolol significantly attenuated MPP+-induced cytotoxicity and the production of reactive oxygen species. These results suggest that magnolol has protective effects via an antioxidative mechanism in both in vivo and in vitro models of Parkinson's disease.

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Autoantibody against nicotinic acetylcholine receptor (nAChR) α3 subunit has been implicated in paraneoplastic neurological syndrome. It has been proposed that this autoantibody impairs synaptic transmission, probably by inducing the internalization of nAChR. To confirm this hypothesis, we incubated human embryonic kidney cells exogenously expressing α3 subunit with seropositive serum, and visualized the intracellular localization of IgG and α3 subunits by double-labeled immunofluorescence staining. As a result, co-localization of internalized IgG and α3 subunits was observed as overlapping punctate fluorescent staining. Our results suggest that autoantibodies against nAChR α3 subunit play a pathogenic role in synaptic transmission by inducing nAChR internalization.