Han, Yifan

Abstract Neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease, are devastating diseases in the elderly world, which are closely associated with progressive neuronal loss induced by a variety of genetic and/or environmental factors. Unfortunately, currently available treatments for neurodegenerative disorders can only relieve the symptoms but not modify the pathological processes. Over the past decades, our group by collaborating with Profs. Yuan‐Ping Pang and Paul R. Carlier has developed three series of homo/hetero dimeric acetylcholinesterase inhibitors derived from tacrine and/or huperzine A. The representative dimers bis(3)‐Cognitin (B3C), bis(12)‐hupyridone, and tacrine(10)‐hupyridone might possess disease‐modifying effects through the modulation of N ‐methyl‐ d ‐aspartic acid receptors, the activation of myocyte enhancer factor 2D gene transcription, and the promotion of neurotrophic factor secretion. In this review, we summarize that the representative dimers, such as B3C, provide neuroprotection against a variety of neurotoxins via multiple targets, including the inhibitions of N ‐methyl‐ d ‐aspartic acid receptor with pathological‐activated potential, neuronal nitric oxide synthase, and β‐amyloid cascades synergistically. More importantly, B3C might offer disease‐modifying potentials by activating myocyte enhancer factor 2D transcription, inducing neuritogenesis, and promoting the expressions of neurotrophic factors in vitro and in vivo. Taken together, the novel dimers might offer synergistic disease‐modifying effects, proving that dimerization might serve as one of the strategies to develop new generation of therapeutics for neurodegenerative disorders. image

SummaryAimsFibrillar aggregates of β‐amyloid protein (Aβ) are the main constituent of senile plaques and considered to be one of the causative events in the pathogenesis of Alzheimer's disease (AD). Compounds that could inhibit Aβ fibrils formation, disaggregate preformed Aβ fibrils as well as reduce their associated neurotoxicity might have therapeutic values for treating AD. In this study, the inhibitory effects of bis (heptyl)‐cognitin (B7C), a multifunctional dimer derived from tacrine, on aggregation and neurotoxicity of Aβ1‐40 were evaluated both in vitro and in vivo.MethodsThioflavin T fluorescence assay was carried out to evaluate Aβ aggregation, MTT and Hoechst‐staining assays were performed to investigate Aβ‐associated neurotoxicity. Fluorescent probe DCFH‐DA was used to estimate the accumulation of intracellular reactive oxygen stress (ROS). Morris water maze was applied to determine learning and memory deficits induced by intracerebroventricular infusion of Aβ in rats.ResultsB7C (0.1–10 μM), but not tacrine, effectively inhibited Aβ fibrils formation and disaggregated preformed Aβ fibrils following co‐incubation of B7C and Aβ monomers or preformed fibrils, respectively. In addition, B7C markedly reduced Aβ fibrils‐associated neurotoxicity in SH‐SY5Y cell line, as evidenced by the increase in cell survival, the decrease in Hoechst‐stained nuclei and in intracellular ROS. Most encouragingly, B7C (0.1 and 0.2 mg/kg), 10 times more potently than tacrine (1 and 2 mg/kg), inhibited memory impairments after intracerebroventricular infusion of Aβ in rats, as evidenced by the decrease in escape latency and the increase in the spatial bias in Morris water maze test along with upregulation of choline acetyltransferase activity and downregulation of acetylcholinesterase activity.ConclusionThese findings provide not only novel molecular insight into the potential application of B7C in treating AD, but also an effective approach for screening anti‐AD agents.

SummaryAimsNeurodegenerative disorders are caused by progressive neuronal loss in the brain, and hence, compounds that could promote neuritogenesis may have therapeutic values. In this study, the effects of bis(heptyl)‐cognitin (B7C), a multifunctional dimer, on neurite outgrowth were investigated in both PC12 cells and primary cortical neurons.MethodsImmunocytochemical staining was used to evaluate the proneuritogenesis effects, and Western blot and short hairpin RNA assays were applied to explore the underlying mechanisms.ResultsB7C (0.1–0.5 μM) induced robust neurite outgrowth in PC12 cells, as evidenced by the neurite‐bearing morphology and upregulation of growth‐associated protein‐43 expression. In addition, B7C markedly promoted neurite outgrowth in primary cortical neurons as shown by the increase in the length of β‐III‐tubulin‐positive neurites. Furthermore, B7C rapidly increased ERK phosphorylation. Specific inhibitors of alpha7‐nicotinic acetylcholine receptor (α7‐nAChR) and MEK, but not those of p38 or JNK, blocked the neurite outgrowth as well as ERK phosphorylation induced by B7C. Most importantly, genetic depletion of α7‐nAChR significantly abolished B7C‐induced neurite outgrowth in PC12 cells.ConclusionB7C promoted neurite outgrowth through the activation of α7‐nAChR/ERK pathway, which offers novel insight into the potential application of B7C in the treatment of neurodegenerative disorders.

SummaryBackgroundNeuronal loss via apoptosis in CNS is the fundamental mechanism underlying various neurodegenerative diseases. Compounds with antiapoptotic property might have therapeutic effects for these diseases. In this study, bis(propyl)‐cognitin (B3C), a novel dimer that possesses anti‐AChE and anti‐N‐methyl‐d‐aspartate receptor activities, was investigated for its neuroprotective effect on K+ deprivation‐induced apoptosis in cerebellar granule neurons (CGNs).MethodsCerebellar granule neurons were switched to K+ deprived medium with or without B3C. 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium assay, fluorescein diacetate (FDA)/propidium iodide (PI) staining, Hoechst staining, and DNA laddering assays were applied to detect cytotoxicity and apoptosis. Additionally, the expression of p‐VEGFR‐2, p‐Akt, p‐glycogen synthase kinase 3β (GSK3β), and p‐extracellular signal‐regulated kinase (ERK) was examined in CGNs.ResultsSwitching CGNs to K+ deprived medium resulted in remarkable apoptosis, which could be substantially blocked by B3C treatment (IC50, 0.37 μM). Moreover, a rapid decrease in p‐Tyr1054‐VEGFR‐2 was observed after the switch. B3C significantly reversed the inhibition of p‐Tyr1054‐VEGFR‐2 as well as Akt and ERK pathways. VEGFR‐2 inhibitor PTK787/ZK222584, as well as PI3‐K inhibitor LY294002 and MEK inhibitor PD98059, each abolished the neuroprotective effect of B3C.ConclusionsOur results demonstrate that B3C blocks K+ deprivation‐induced apoptosis in CGNs through regulating VEGFR‐2/Akt/GSK3β and VEGFR‐2/ERK signaling pathways, providing a molecular insight into the therapeutic potential of B3C for the treatment of neurodegenerative diseases.