Background:Amyloid-β(Aβ)metabolic imbalance is the pivotal pathogenesis leading to Alzheimer’s disease(AD).In sporadic AD,decreased clearance of Aβimportantly contributes to the onset and progression.Astrocytes,th...Background:Amyloid-β(Aβ)metabolic imbalance is the pivotal pathogenesis leading to Alzheimer’s disease(AD).In sporadic AD,decreased clearance of Aβimportantly contributes to the onset and progression.Astrocytes,the most abundant cell type in the brain,are mainly responsible for maintaining neuronal homeostasis.Most recently,it has been demonstrated that astrocytes play an important role in regulating Aβmetabolism.Icariin(ICA),a flavonoid glucoside extracted from the traditional Chinese herb Epimedium brevicornu,has been shown to produce protective effects against AD by decreasing Aβproduction.However,it remains unclear whether ICA regulates cellular Aβclearance in the astrocytes.Objective:To examine the regulatory effects of ICA on Aβremoval by astrocytes and explore the mechanisms of its actions.Methods:Uptake and subsequent degradation of Aβby astrocytes were evaluated using a combination of enzyme-linked immunosorbent assay(ELISA)and laser confocal microscopy.The effects of oligomer Aβ(oAβ1-42)and/or ICA on the expressions of sirt6 in the primary astrocytes were examined using western blotting and q-PCR assays.The expression of autophagy markers including P62 and LC3-Ⅱ,and phosphorylated-mTOR were measured by western blotting.In order to determine whether sirt6 is involved in the intracellular Aβmetabolism,sirt6 was knocked down using lentiviral vectors containing sirt6-shRNAs and autophagy levels were assessed by western blotting.Results:①In primary astrocytes,ICA not only significantly increased Aβinternalization but also obviously accelerated its degradation in a concentration-dependent manner.②Treatment of astrocytes with Aβ1-42 at 1μmol·L-1 significantly down-regulated the expression of sirt6,which was rescued by ICA.In addition,ICA at 20μmol·L-1 significantly increased the expression of LC3-Ⅱand markedly decreased the expression of P62 and phosphorylated-mTOR in primary astrocytes.③Sirt6 knockdown in primary astrocytes resulted in decreased cellular Aβuptake and degradation.Simultaneously,silencing of sirt6 in astrocytes increased P62 levels and reduced LC3-Ⅱand phosphorylated-mTOR levels.Conclusion:Taken together,our results demonstrate that sirt6 plays an important role in Aβmetabolism in astrocytes via induction of autophagy.ICA is a potential drug for treatment of AD as it upregulates cellular sirt6.展开更多
Solitons and bifurcations for the generalized Tzitzéica type equation are studied by using the theory of dynamical systems and Hamilton function. With the help of Maple and bifurcation theory of differential equa...Solitons and bifurcations for the generalized Tzitzéica type equation are studied by using the theory of dynamical systems and Hamilton function. With the help of Maple and bifurcation theory of differential equations, the bifurcation parameter conditions and all the bifurcation phase portraits are obtained. Because the same energy value of the Hamiltonian function is corresponding to the same orbit, thus the periodic wave solutions, bright soliton and dark soliton solutions are defined.展开更多
文摘Background:Amyloid-β(Aβ)metabolic imbalance is the pivotal pathogenesis leading to Alzheimer’s disease(AD).In sporadic AD,decreased clearance of Aβimportantly contributes to the onset and progression.Astrocytes,the most abundant cell type in the brain,are mainly responsible for maintaining neuronal homeostasis.Most recently,it has been demonstrated that astrocytes play an important role in regulating Aβmetabolism.Icariin(ICA),a flavonoid glucoside extracted from the traditional Chinese herb Epimedium brevicornu,has been shown to produce protective effects against AD by decreasing Aβproduction.However,it remains unclear whether ICA regulates cellular Aβclearance in the astrocytes.Objective:To examine the regulatory effects of ICA on Aβremoval by astrocytes and explore the mechanisms of its actions.Methods:Uptake and subsequent degradation of Aβby astrocytes were evaluated using a combination of enzyme-linked immunosorbent assay(ELISA)and laser confocal microscopy.The effects of oligomer Aβ(oAβ1-42)and/or ICA on the expressions of sirt6 in the primary astrocytes were examined using western blotting and q-PCR assays.The expression of autophagy markers including P62 and LC3-Ⅱ,and phosphorylated-mTOR were measured by western blotting.In order to determine whether sirt6 is involved in the intracellular Aβmetabolism,sirt6 was knocked down using lentiviral vectors containing sirt6-shRNAs and autophagy levels were assessed by western blotting.Results:①In primary astrocytes,ICA not only significantly increased Aβinternalization but also obviously accelerated its degradation in a concentration-dependent manner.②Treatment of astrocytes with Aβ1-42 at 1μmol·L-1 significantly down-regulated the expression of sirt6,which was rescued by ICA.In addition,ICA at 20μmol·L-1 significantly increased the expression of LC3-Ⅱand markedly decreased the expression of P62 and phosphorylated-mTOR in primary astrocytes.③Sirt6 knockdown in primary astrocytes resulted in decreased cellular Aβuptake and degradation.Simultaneously,silencing of sirt6 in astrocytes increased P62 levels and reduced LC3-Ⅱand phosphorylated-mTOR levels.Conclusion:Taken together,our results demonstrate that sirt6 plays an important role in Aβmetabolism in astrocytes via induction of autophagy.ICA is a potential drug for treatment of AD as it upregulates cellular sirt6.
文摘Solitons and bifurcations for the generalized Tzitzéica type equation are studied by using the theory of dynamical systems and Hamilton function. With the help of Maple and bifurcation theory of differential equations, the bifurcation parameter conditions and all the bifurcation phase portraits are obtained. Because the same energy value of the Hamiltonian function is corresponding to the same orbit, thus the periodic wave solutions, bright soliton and dark soliton solutions are defined.
