Protective Effect Of Rosiglitazone On The Amyloid-β Protein Oligomers-induced Synaptic Development Impairment And The Potential Mechanism

Objective1. To study the possible inhibitory effect of soluble amyloid-β protein42oligomers(SO Aβ42) on the filopodia density, velocity, length and the spine density of cultured hippocampalneurons in rats during the synaptic development, and realize the potential effect of SO Aβ42on thestage of synaptic developmentat in cultured hippocampal neurons.2. To study the effect ofperoxisome proliferator-activated receptor gamma (PPAR) agonist rosiglitazone on the SO Aβ42-induced impairment of synaptic developmentat, and investigate the role of PPARγ in the effect ofrosiglitazone.3. To study the underlying potential mechanism of the effect of rosiglitazone,provide experimental evidence for further understanding the pathogenesis of Alzheimer’s disease(AD) and exploring the therapy target of AD.Methods Primary hippocampal neuronal cultures from postnatal1-day-old Wistar rats wereprepared, and were cotransfected with farnesylated enhanced green fluorescent protein (F-GFP)and GFP-actin at the day5in vitro (DIV5) to display the morphological details of the dendrites anddendritic protrusions. Neurons in experimental groups were incubated with500nM SO Aβ42for3h at DIV7and DIV15, while the interference groups were preincubated respectively with0.1μM,0.5μM,5μM rosiglitazone or5μM rosiglitazone with additional5μM GW9662for24h beforeincubated with SO Aβ42. Live cell imaging was used to investigate the effects of SO Aβ42androsiglitazone on the density, velocity and length of filopodia at DIV7and the density of spine atDIV15. Then, hippocampal cultured neurons were cotransfected with F-GFP, GFP-actin andmitochondrially targeted red fluorescent protein (MitoRed) at DIV5to display the morphologicaldetails of the dendrites, dendritic protrusions and mitochondria. Neurons in experimental groupswere incubated with500nM SO Aβ42for3h at DIV15, while the interference groups werepreincubated with5μM rosiglitazone for24h before incubated with SO Aβ42. Live cell imagingwas used to investigate the effects of SO Aβ42and rosiglitazone on the distribution ofmitochondria in the dendrites and spines at DIV15.Results1. Incubation of DIV7hippocampal neurons with500nM SO Aβ42alone for3hsignificantly decreased the dendritic filopodia density. Pre-treatment with rosiglitazone for24hrescued the SO Aβ42-induced dendritic filopodi loss in a dose-dependent manner. Neither thelength nor the motility of filopodia was altered in the presence of SO Aβ42alone or rosiglitazone treated with before SO Aβ42incubation.2. Treatment of500nM SO Aβ42for3h significantlyreduced the spine density in DIV15cultured hippocampal neurons, and pre-treatment withrosiglitazone for24h prevented the SO Aβ42-induced spine loss in dose-dependent manner.3. Co-incubation with5μM PPARγ-specific antagonist GW9662and5μM rosiglitazone abolished therescued effect of5μM rosiglitazone on the both SO Aβ42-induced filopodia and spine loss.4.Incubation of500nM SO Aβ42for3h significantly decreased the dendritic mitochondrial index(total mitochondrial length/total dendrite length), the density of discrete dendritic mitochondriaand the percent of spines containing mitochondria of DIV15cultured hippocampal neurons, whichwas rescued by pre-treatment of hippocampal cultures with5μM rosiglitazone for24h. The lengthof discrete dendritic mitochondria was not altered in the presence of SO Aβ42alone or treated withrosiglitazone before SO Aβ42incubation.Conclusions The treatment of SO Aβ42may disturb the stage of synaptic development,which could reduce the synapses formation. Pre-treatment with rosiglitazone can rescue theimpairment of synaptic development induced by SO Aβ42in a dose-dependent manner. Theprotective effect of rosiglitazone on the SO Aβ42-induced impairment of synaptic development islikely mediated by activating PPARγ pathway to prevent the abnormal distribution of dendriticmitochondria induced by SO Aβ42.