The Effects And Potential Mechanism Of Total Flavonoids Of Selaginella Pulvinata And Amentoflavone Against Cognitive Impairment

Cognition is the process of human brain for acquiring and processing ofinformation, translating into psychological action, and finally gaining and applyingknowledge. Cognition is a group of mental processes that includes attention, memory,producing and understanding language, learning, reasoning, problem solving, anddecision making. Cognitive impairment (CI) refers to the dysfunction of the cognitioninduced by any reasons. It includes several steps, from mild cognitive impairment todementia. All factors that can directly or indirectly lead to chronic damnification tothe cortical structure and function of the brain will cause CI, for example, abnormitiesof neurotransmitters like dopamine, acetylcholine, noradrenaline and their receptors,abnormal aggregation and modification of protein in the brain, neural degenerativedisease, chronic ischemia injury to the cerebrum induced by disorder of energy supply,oxidosis, free radical injury, excitatory toxicity, and some diseases that will causeinsufficiency of cerebral blood supply. CI is in fact the primary stage of seniledementia, it is common in the people over60years old. CI will soon develop intodementia (or Alzheimer’s disease) if it is not treated properly. Therefore, CI is the beststage for preventing, intervening and curing senile dementia. In recent years, the harmand importance of CI have been recognized, attributed to the research development ofcognitive impairment.At present, CI is mostly treated in the same way as Alzheimer’s disease or seniledementia in clinic. The possible reseasons are considered, such as cholinergic nerve,β-amyloid protein, inflammation, aluminium poisoning, calcium imbalance, metabolicdisturbance, free radical insult and mitochondrial dysfunction, and the related drugsare prescribed. The CI condition of the patients can be controlled or relieved to someexetent after the drugs being administered. There is a medicine that is effective andwidely accepted, named Ginaton. It is made of leaf extract of Ginkgo Biloba. Themain constituents in leaf extract of Ginkgo Biloba are flavonoids, and mostly are bioflavonoids. It is proved that leaf extract of Ginkgo Biloba has many good effects,such as improving blood volume of cerebral vascular, reducing the resistance ofcerebral vascular, ameliorating blood circulation, protecting the brain cells fromischemia, clearing oxyradical, improving immunity and against aging. The efficacy ofleaf extract of Ginkgo Biloba enlightened us that the bioflavonoids in other plants mayhave analogous effects.We screened flavonoids extracted from different plants. Total flavonoids ofSelaginella Pulvinata (TFSP) showed good effects on anti-oxidant and improving CIin animal model. The results in the literaures showed that total flavonoids ofSelaginella tamariscina had the ability of anti oxidation, anti diabetes, improvinghuman umbilical vein endothelia cells proliferation and VEGF expression. Flavonoidsof Selaginella moellendorfii Hieron inhibit the expression of COX-2and proliferationof HT-29. Biflavones of Selaginella Pulvinata have the effects of clearing diphenylpicryl hydrazinyl radical, inhibiting lactate dehydrogenase release and damages ofendothelial cells induced by lysophosphatidylcholine, and decreasing the activity ofxanthinoxidase in vitro. There is not a report about the effect of TFSP on CI so far. Wedetected the effects of TFSP on different step of learning and memory in mice model.TFSP and AF promote the proliferation of SH-SY5Y, protect the cell insulted byhydrogen peroxide, okadaic acid and Aβ25-35, and they repair the damaged cell tosome extent. On the basis of the above research, the possible mechanism of AF onameliorating CI was explored from endoplasmic reticulum stress (ERS),mitochondrial dysfunction and oxidative stress.The animal experiment results showed, TFSP had significant therapeutic actionon the impairment of memory acquisition, memory consolidation and memoryevocation induced by scopolamine hydrobromide, sodium nitrite and45%alcoholrespectively. TFSP inhibited the acetylcholine reduction in the brain induced byscopolamine hydrobromide, increased the activity of acetylcholinesterase and cholineacetyltransterase. It suggested that TFSP resisted the memory acquisition impairmentinduced by scopolamine hydrobromide through its influence on enzyme activities of cholinergic system and antagonizing scopolamine’s blockage on M-cholinergicreceptor. Sodium nitrite caused peroxidation injury to the mice cerebral tissue andbrought about the memory consolidation impairment. TFSP activated theantioxidative enzyme and suppressed the accumulation of hyperoxide in the brain.TFSP might improve the memory consolidation through anti-oxidation. D-galactosecaused the systemic aging of the mice, including the withering of the immune organs,the accumulation of hyperoxide and free radical in the body and the activitydepression of antioxidative enzyme. TFSP suppressed the systemic aging of the micethrough antioxidation and improving the immunity.On the basis of animal experiments, we studied the efficacy of TFSP and AF oncell model in vitro. Within the concentration range, TFSP and AF moderatelypromoted the proliferation of SH-SY5Y. Hydrogen peroxide, okadaic acid and Aβ25-35brought the cell to death when they were incubated with SH-SY5Y cell together. Thatmeans hydrogen peroxide, okadaic acid and Aβ25-35could be the damage factors in thestudy. We learned from the IC50of the three factors that okadaic acid was the mostpoisonous factor to the cell. Our results indicating, AF showed protection andrepairment to the cell damage caused by hydrogen peroxide, okadaic acid and Aβ25-35,especially to the insult induced by hydrogen peroxide. It is inferred that AF mightexert the action of improving memory consolidation through resistance to oxidativestress injury (resisting hydrogen peroxide injury).Since ERS, mitochondrial dysfunction and oxidative stress were three mainpossible paths that could cause CI, we determined the expression of three proteinclosely related with ERS (cysteinylaspartate specific proteinase-12, glucose regulatedprotein78and CCAAT/enhancer binding protein homologous protein; caspase-12,Grp78and Chop) induced by okadaic acid in SH-SY5Y treated with AF. AF regulatedcaspase-12to some extent that increased by okadaic acid in SH-SY5Y. Grp78andChop had no significant change in SH-SY5Y after treated with okadaic acid and AF,suggesting that the protective effect of AF on the cell may not attribute to ERS. Wefound that AF partially recovered the mitochondrial transmembrance potential and inhibited the cell apoptosis induced by okadaic acid. That indicated AF might exertprotective effect by regulating the mitochondrial dysfunction. Hyperphosphorylationof tau was detected induced by okadaic acid, while AF had the effect ofdephosphorylation on phosphorelated tau, suggesting that AF might protect the nervecell through resisting phosphorylation of protein and maintaining the structure andfunction of the microtube. The inevitable result of mitochondrial dysfunction is theincrease of oxidative stress, the accumulation of free radical and hyperoxide in celland the activity depression of antioxidative enzyme. AF displayed strong antioxidativeactivity on SH-SY5Y in oxidative stress. It suggested that anti oxidative stress mightbe the main important mechanism for AF protecting SH-SY5Y cell insulted byokadaic acid.We studied the effect of TFSP on the memory impairment mice model for thefirst time, and investigated the possible mechanism of TFSP and AF on improving CI.That supplied a valuable clue for further research of TFSP and AF in cell biology andmolecular biology, and provided experimental medicine foundation for theexploitation and utilization of TFSP.