Protective Effects Of Quercetin From Ginkgo Biloba Leaves Against Excitotoxic Damage In Cortical Astrocytes Of Rats

BackgroundQuercetin is a ubiquitous flavonoid that is present in numerous plants,fruits and vegetable,possessing a broad range of biological properties,its brain protection and antitumor effect have called much attention.Athough quercetin is regarded as diet antioxidant,its connective capacity with metal?iron,copper,zine,etc?plays a key role in its many biological function.On account of divalent metal ions consist of many proteins which are in cells and most are located in the active site of protein,quercetin affects the physiological and biochemical functions of many proteins,leading to be applied widely in disease field,involving different organ system and having many targets.At present,much of the work on stroke prevention and cure has focused on neuron,however,these approaches have repeatedly failed in clinical trials,therefore the” nerve vascular unit” is put forward.It emphasizes the importance of multi-target,interference with neuron,astrocytes and cerebral intravascular microenvironment,which provides basic entry point for cerebral protection of quercetin.Astrocytes which were regarded as the important component of the ” nerve vascular unit”.The activation of astrocytes in brain ischemia presents dual function in promoting neuron survival and aggravating ischemic injury.Besides,quercetin may cross the motif involved in antioxidant,but connect to specific architectural motif then play a role in neuron protection.Its brain protection mechanism except antioxidative effect is to be elucidated.In the paper,we disscuss the protective role of quercetin which is Ginkgo monomer compound in astrocytes against excitotoxin damage induced by Glu-Gly.The purpose is to explore more about the function and mechanism of quercetin in protecting astrocytes' excitotoxin damage which is induced by Glu-Gly,offering necessary reference for quercetin's application.The analysis about brain protective mechanism of quercetin which is one of the ginkgo's monomer compound help explain the contradiction about application of ginkgo leaf medicine in clinic and civilian.MethodCulture primary astrocytes of cerebral cortex in newborn SD rats within 24h;Identifying a strocytes by GFAP as marker;check cells survival activity by MTT assay;Observe cells ultrastructure with transmission electron microscope;Observe quercetin effect on intracellular calcium ion connection with confocal laser scanning microscope,Observe the expression and morphological changes of GFAP by immunohistochemical experiments and immunoflurescense stain.Results1.Compared with normal group,the difference of newborn rats normal cerebral cortex astrocytes survival is not found when the concentration of quercetin between 12.5 100?mol/L,the concentration of quercetin pretreatment on astrocytes between 12.5 50? mol/L can obviously improve the astrocytes survival activity in excitotoxin damage which is induced by glutamate-glycine?P < 0.05?,there is no obvious protective effect about astrocytes survival activity in 75 100?mol/L high concentration group.2.Cell immunohistochemical experiment confirmed that expression of GFAP in quercetin pretreatment group is less than G-G model group and model group is high expression.3.Cell immunofluorescence experiments confirmed again that the GFAP expression of quercetin group is lower than that of G-G group,GFAP of normal group presents network distribution,uniform density.Astrocytes forms retraction and GFAP distribution scattered in G-G model group;compared to G-G model group,the injury of astrocytes reduced and degree of GFAP change attenuated even tended to normal in rats given quercetin.4.Through detection with confocal laser scanning microscope,Ca²⁺ activation reduced than G-G group,the degree of intracellular Ca²⁺ concentration increased is lower than G-G model group,moreover tend to reduce obviously.5.Using transmission electron microscope to observe the ultrastructure of each treatment group of astrocytes,found that mitochondrial morphology is normal without swelling and the crest is clear in quercetin group,while it is irregular with swelling into spherical and crest is fragmentated and staggered even fuzzy in G-G model group.ConclutionQuercetin pretreatment can protect astrocyte excitotoxin damage effectively,It may connect with reducing the intracellular calcium concentration,to reduce the activity of astrocytes and stability mitochondrial activities.