Stimulation of neurogenesis and synaptogenesis by bilobalide and quercetin via common final pathway in hippocampal neurons

Effects of the standardized Ginkgo biloba extract EGb 761® on neuroplasticity

Neuroplasticity, the ability of synapses to undergo structural adaptations in response to functional demand or dysfunctions is increasingly impaired in aging and Alzheimer's disease. EGb761® has been shown in several preclinical reports to increase nearly all aspects of impaired neuroplasticity (long-term potentiation, spine density, neuritogenesis, neurogenesis). While all three fractions of constituents (ginkgolides, flavonoids, bilobalide) seem to be active, the flavonoids and specifically the aglycone isorhamnetin seem to be most relevant.

Terpenoids as potential anti-Alzheimer's disease therapeutics

Alzheimer's disease (AD) is one of the most well-known neurodegenerative diseases and explains 50-60% of dementia in patients. The prevalence rate of AD is positively correlated with age and AD affects ≥ 40% of those over 85 years old. The major AD therapeutics available on the market are acetylcholinesterase inhibitors, such as tacrine and donepezil. New therapeutic agents that can block the disease-inducing mechanisms are essential. Diverse efforts have been made to discover anti-AD agents from natural sources. In this review article, we describe some representative terpenoids such as ginsenosides, gingkolides, and canabinoids as potential anti-AD agents. These compounds exhibit promising in vitro and in vivo biological activities, but are still waiting clinical trials. Additionally, we also discuss some terpenoids including cornel iridoid glycoside, oleanolic acid, tenuifolin, cryptotanshinone, and ursolic acid, which are under investigation for their in vitro and in vivo animal studies.

Effect of Ginkgo biloba special extract EGb 761® on human cytochrome P450 activity: a cocktail interaction study in healthy volunteers

PURPOSE

We assessed the human in vivo metabolic drug interaction profile of Ginkgo biloba extract EGb 761® with respect to the activities of major cytochrome P450 (CYP) enzymes.

METHODS

A single-center, open-label, randomized, three-fold crossover, cocktail phenotyping design was applied. In random order, the following treatments were administered to 18 healthy men and women for 8 days each: placebo twice daily, EGb 761® 120 mg twice daily, and EGb 761® 240 mg in the morning and placebo in the evening. In the morning of day 8, administration was performed together with the orally administered phenotyping cocktail (enzyme, metric): 150 mg caffeine (CYP1A2, paraxanthine/caffeine plasma ratio 6-h postdose), 125 mg tolbutamide (CYP2C9, plasma concentration 24-h postdose), 20 mg omeprazole (CYP2C19, omeprazole/5-hydroxy omeprazole plasma ratio 3-h postdose), 30 mg dextromethorphan (CYP2D6, dextromethorphan/dextrorphan plasma ratio 3-h postdose), and 2 mg of midazolam (CYP3A, plasma concentration 6-h postdose). Formally, absence of a relevant interaction was assumed if the 90% confidence intervals (CIs) for EGb 761®/placebo ratios of the metrics were within the 0.70-1.43 range.

RESULTS

EGb 761®/placebo ratios for phenotyping metrics were close to unity for all CYPs. Furthermore, respective CIs were within the specified margins for all ratios except CYP2C19 for EGb 761® 120 mg twice daily (90% CI 0.681-1.122) and for CYP2D6 for EGb 761® 240 mg once daily (90% CI 0.667-1.281). These findings were attributed to the intraindividual variability of the metrics used. All treatments were well tolerated.

CONCLUSION

EGb 761® has no relevant effect on the in vivo activity of the major CYP enzymes in humans and therefore has no relevant potential to cause respective metabolic drug-drug interactions.

Effects of Ginkgo biloba extract EGb761 on human colon adenocarcinoma cells

AIMS

To investigate the effect of Ginkgo biloba extract (EGb761) on cell proliferation and apoptosis in human colon cancer cells.

METHODS

Human colon cancer cell lines (HT-29) were cultured and incubated with various concentrations (0-320 mg/l) of EGb 761 solution for up to 72 h. Cell viability, cell apoptosis, cell cycle, expression of caspase-3, the mRNA levels of p53, and Bcl-2 were assessed.

RESULTS

EGb 761 inhibited the growth of HT-29 cells in a time-dose-dependent manner. At 80 and 320 mg/L, EGb 761 increased the number of cells in the G0/G1 phase and reduced cells in the G2/M and S phase. EGb 761 treatment also increased the apoptosis ratio of the HT-29 cells. EGb 761 treatment was associated with an increase in caspase-3 activities, reduction in bcl-2 mRNA expression and elevation in p53 mRNA expression.

CONCLUSION

EGb 761 inhibits the progression of human colon cancer cells. Its therapeutic effect may be related to enhanced caspase-3 activities, up-regulation of p53 and down-regulation of bcl-2 genes.

Physical exercise alleviates debilities of normal aging and Alzheimer's disease

Both healthy aging and the pathologic incidence of disorders associated with aging involve an array of debilities. Physical exercise harnesses implicit and inherent biologic characteristics amenable to the putative interventional influences under clinical, institutional or laboratory conditions. The neurodegenerative and pathophysiologic progressions that constitute Alzheimer's disease (AD), amnestic mild cognitive impairment (aMCI), normal aging, and different animal models of AD have shown the existence of several putative mechanisms. A large variety of moderating factors have demonstrated that the ever-proliferating plethora of neurotrophic factors, neurogenesis as observed through generality of expression and neuronal arborization. The insistent efficacy of brain vascular angiogenesis may delay also the comorbid incidence of depressive disorders with dementia pathology. The pathogenesis of aging may be contained by selective treatments: these diverse conditions, linked to the basis of the aging concept, have been shown, to greater or lesser extents, to respond to a variety of scheduled applications of physical exercise. The range of reports that provide accounts of the mechanisms mediating the positive progressive response to exercise intervention is far-ranging; these studies indicate that subtle changes at molecular, neuronal, vascular and epigenetic levels may exert notable consequence at functional expression and, perhaps most essentially, offer convincing expectancy of significant benefits.

Effects of Ginkgo biloba extract on promotion of neurogenesis in the hippocampal dentate gyrus in C57BL/6 mice

Ginkgo biloba leaf extract (Gb) has been known to improve blood flow and preclude the tissue from free radical damage. Effects of Gb were examined by using Ki67, a specific proliferative marker for cellular proliferation, and doublecortin (DCX), a marker for immature neurons, indicating degree of neuroblast differentiation in the hippocampal dentate gyrus (DG) of adult C57BL/6 mice. The mice were fed with Gb at 40 and 100 mg/kg once daily for 28 days. The increase of Ki67- and DCX-immunoreactive cells in the DG was increased in a dose-dependent manner. Especially, the group having 100 mg/kg Gb showed a significant increase of DCX-immunoreactive neuroblasts with well-developed tertiary dendrites. Expression of DCX protein in the Gb groups was also significantly increased upon compared with the vehicle group. The results suggested that repeated intake of Gb would enhance cell proliferation and neuroblast differentiation in the mouse DG.

Ginkgo biloba extract ameliorates oxidative phosphorylation performance and rescues abeta-induced failure

BACKGROUND

Energy deficiency and mitochondrial failure have been recognized as a prominent, early event in Alzheimer's disease (AD). Recently, we demonstrated that chronic exposure to amyloid-beta (Abeta) in human neuroblastoma cells over-expressing human wild-type amyloid precursor protein (APP) resulted in (i) activity changes of complexes III and IV of the oxidative phosphorylation system (OXPHOS) and in (ii) a drop of ATP levels which may finally instigate loss of synapses and neuronal cell death in AD. Therefore, the aim of the present study was to investigate whether standardized Ginkgo biloba extract LI 1370 (GBE) is able to rescue Abeta-induced defects in energy metabolism.

METHODOLOGY/PRINCIPAL FINDINGS

We used a high-resolution respiratory protocol to evaluate OXPHOS respiratory capacity under physiological condition in control (stably transfected with the empty vector) and APP cells after treatment with GBE. In addition, oxygen consumption of isolated mitochondria, activities of mitochondrial respiratory enzymes, ATP and reactive oxygen species (ROS) levels as well as mitochondrial membrane mass and mitochondrial DNA content were determined. We observed a general antioxidant effect of GBE leading to an increase of the coupling state of mitochondria as well as energy homeostasis and a reduction of ROS levels in control cells and in APP cells. GBE effect on OXPHOS was even preserved in mitochondria after isolation from treated cells. Moreover, these functional data were paralleled by an up-regulation of mitochondrial DNA. Improvement of the OXPHOS efficiency was stronger in APP cells than in control cells. In APP cells, the GBE-induced amelioration of oxygen consumption most likely arose from the modulation and respective normalization of the Abeta-induced disturbance in the activity of mitochondrial complexes III and IV restoring impaired ATP levels possibly through decreasing Abeta and oxidative stress level.

CONCLUSIONS/SIGNIFICANCE

Although the underlying molecular mechanisms of the mode of action of GBE remain to be determined, our study clearly highlights the beneficial effect of GBE on the cellular OXPHOS performance and restoration of Abeta-induced mitochondrial dysfunction.

Oroxylin A, a flavonoid, stimulates adult neurogenesis in the hippocampal dentate gyrus region of mice

Previously, we reported the cognitive enhancing effects of oroxylin A in unimpaired mice and its memory ameliorating activity in various memory impaired mice. To elucidate the mechanism mediating the cognitive effects of oroxylin A, this study examined the consequences of oroxylin A administration on neurogenesis in the hippocampal dentate gyrus using immunostaining for 5-bromo-2-deoxyuridine (BrdU) incorporation. In addition, we determined whether the new cells adopted a neuronal or glial fate by examining the co-localization of BrdU staining with neuronal or glial markers. Administration of oroxylin A in a dose-dependent and time-dependent manner increased the number of BrdU-incorporating cells. Moreover, the percentage of BrdU-incorporating cells co-localized with neuronal markers, neuronal nuclei, was significantly increased by the oroxylin A administration. These results suggest that the increased neurogenesis induced by the administration of oroxylin A could be, at least in part, associated with its positive effects on cognitive processing.