Non-cholinergic Effects of Huperzine A: Beyond Inhibition of Acetylcholinesterase

Huperzine-A administration recovers rat ovary function after sympathetic stress

Chronic cold stress affects ovarian morphology and impairs fertility in rats. It causes an ovarian polycystic ovary (PCOS)-like phenotype, which resembles PCOS in women. The mechanism of cold stress action involves increased ovarian noradrenaline (NA) levels, which remain elevated after cessation of cold stress. By contrast, ovarian acetylcholine (ACh) levels are only transiently elevated and returned to control levels after a 28-day post stress period. Because ACh can exert trophic actions in the ovary, we hypothesised that a sustained elevation of ovarian ACh levels by intraovarian exposure to the ACh-esterase blocker huperzine-A (Hup-A) may interfere with cold stress-induced ovarian changes. This possibility was examined in female Sprague-Dawley rats exposed to cold stress (4°C for 3 h day^-1 for 28 days), followed by a 28-day period without stress. To elevate ACh, in a second group Hup-A was delivered into the ovary of cold stress-exposed rats. A third group was not exposed to cold stress. As expected, cold stress elevated ovarian NA, reduced the number of corpora lutea and increased the number of follicular cysts. It increased plasma testosterone and oestradiol but decreased plasma levels of progesterone. In the Hup-A group, ovarian levels of both, NA and ACh, were elevated, there were fewer cysts and normal testosterone and oestradiol plasma levels were found. However, progesterone levels remained low. Most likely, low progesterone was associated with impaired mating behaviour and low pregnancy rate. We propose that elevated intraovarian levels of ACh are involved in the rescue of ovarian function, opening a target to control ovarian diseases affecting follicular development.

Central and Peripheral Metabolic Defects Contribute to the Pathogenesis of Alzheimer's Disease: Targeting Mitochondria for Diagnosis and Prevention

Significance: Epidemiological studies indicate that metabolic disorders are associated with an increased risk for Alzheimer's disease (AD). Metabolic remodeling occurs in the central nervous system (CNS) and periphery, even in the early stages of AD. Mitochondrial dysfunction has been widely accepted as a molecular mechanism underlying metabolic disorders. Therefore, focusing on early metabolic changes, especially from the perspective of mitochondria, could be of interest for early AD diagnosis and intervention. Recent Advances: We and others have identified that the levels of several metabolites are fluctuated in the periphery before their accumulation in the CNS, which plays an important role in the pathogenesis of AD. Mitochondrial remodeling is likely one of the earliest signs of AD, linking nutritional imbalance to cognitive deficits. Notably, by improving mitochondrial function, mitochondrial nutrients efficiently rescue cellular metabolic dysfunction in the CNS and periphery in individuals with AD. Critical Issues: Peripheral metabolic disorders should be intensively explored and evaluated for the early diagnosis of AD. The circulating metabolites derived from mitochondrial remodeling represent novel potential diagnostic biomarkers for AD that are more readily detected than CNS-oriented biomarkers. Moreover, mitochondrial nutrients provide a promising approach to preventing and delaying AD progression. Future Directions: Abnormal mitochondrial metabolism in the CNS and periphery is involved in AD pathogenesis. More clinical studies provide evidence for the suitability and reliability of circulating metabolites and cytokines for the early diagnosis of AD. Targeting mitochondria to rewire cellular metabolism is a promising approach to preventing AD and ameliorating AD-related metabolic disorders.

Alzheimer's Disease Therapeutic Approaches

Alzheimer's disease (AD) was first described and diagnosed by Dr. Alois Alzheimer in 1906 (Hippius and Neundorfer, Dialogues Clin Neurosc 5:101-108, 2003). According to World Health Organization (WHO), AD is the most common cause of dementia, accounting for as many as 60-70% of senile dementia cases and affecting 47.5 million people worldwide (data from 2015) (Dementia Fact Sheet No 362. http://who.int/mediacentre/factsheets/fs362/en/ ). The median survival time after the onset of dementia ranges from 3.3 to 11.7 years (Todd et al. Int J Geriatr Psychiatry 28:1109-1124, 2013). AD is characterized as a severe, chronic, incurable, and progressive neurodegenerative disorder, associated with memory loss and cognition impairment accompanied by abnormal behavior and personality changes (Godyn et al. Pharmacol Rep 68:127-138, 2016). AD is characterized by neuronal death, which usually correlates with the appearance of key neuropathological changes, including acetylcholine deficiency, glutamate excitotoxicity, extracellular deposition of β-amyloid (Aβ plaques), intracellular neurofibrillary tangles by hyperphosphorylated tau protein deposits, neuroinflammation, and widespread neuronal loss (Godyn et al. Pharmacol Rep 68:127-138, 2016; Graham et al. Annu Rev. Med 68:413-430, 2017). The discovery of the degeneration of cholinergic neurons and the reduction of acetylcholine levels in postmortem studies of patients resulted in the use of drugs that leads to the increase of acetylcholine levels in brain (Dubois et al. Lacet Neurol 13:614-629, 2014). At present there is no preventative or curative treatment that interferes with the development of the disease. However, in recent years progress was made in the development of cholinergic drugs which have a positive effect on disease progression. Nowadays, specific drugs that can inhibit the enzyme that degrades acetylcholine are used. The development of new effective drugs involves a difficult and time-consuming process, accompanied by a very high failure rate. In the absence of effective therapies, the estimated number of people with dementia will reach 115 to 131, five million by 2050 (Dubois et al. Lacet Neurol 13:614-629, 2014; Cummings et al. Alzheimers Res Ther 6:37, 2014). Novel therapies and new targets required for developing more effective drugs for the treatment of AD patients are urgently needed.

Neuroprotective Effect of Huperzine A on d-Galactose-Induced Hearing Dysfunction

BACKGROUND

Administration of d-galactose (d-gal) has been used to create animal models of neurodegenerative diseases, and huperzine A has been used to treat the neurodegenerative diseases such as Alzheimer disease.

METHODS

An animal model of hearing dysfunction was established by administration of d-gal in the rats, and the effect of huperzine A on d-gal-induced abnormal hearing function and cochlear damage was investigated. Senescence of the cochlear tissues was examined by β-galactase staining, and messenger RNA expression of inflammatory cytokines was quantified by real-time reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

It was found that d-gal significantly increased auditory brainstem response (ABR) threshold and cellular senescence and decreased neurofilament in the cochlear tissues. Huperzine A could significantly attenuate d-gal-induced increase of ABR threshold and cellular senescence as well as reduction of neurofilament. Moreover, huperzine A could inhibit d-gal-induced activation of nuclear factor kappa-B (NF-κB) in Schwann cells and significantly blocked d-gal-stimulated gene expression of pro-inflammatory cytokines including interleukin (IL)-1β, IL-6, and tumor necrosis factor-α.

CONCLUSION

These findings suggested that d-gal causes hearing dysfunction by inflammatory injury of cochlear neurons and that huperzine A could prevent hearing loss by protecting d-gal-induced physical damage of cochlear tissues.

Investigating the potential protective effects of natural product quercetin against imidacloprid-induced biochemical toxicity and DNA damage in adults rats

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Imidacloprid insecticide causes hepatotoxicity, renal damage and DNA damage.

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Quercetin revealed a significant protective action against the toxic effects of Imidacloprid.

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Quercetin counteracts the imidacloprid effects on liver, Kidney and DNA damage to the normal level.

Quercetin (QT) is a natural antioxidant materials that’s possesses different type of pharmacological activities. In the current study, the protective effect QT against imidacloprid (IMD)-induced toxicity in rats was studied. The experiment included thirty-six adult male rats groups treated with QT, IMD (two different doses), their combinations and control non-treated group for 21 consecutive days. Different biochemical analysis (serum liver and kidney enzymes level, cholesterol and Glucose levels) were evaluated. DNA damage using comet assay and histopathological examination of different body organs were also screened. Treatment with IMD increased ALT, AST, serum urea, creatinine, cholesterol and Glucose levels but decreased the levels of serum total protein, albumin and body weight with induction in triacylglycerol and cholesterol levels. Animals treated with QT prior to IMD administration showed normal enzymatic levels which indicating a protective effect of QT. In addition, QT protected the different body organs from the histological changes and DNA damages induced by IMD toxicity. The present results showed the protective effect of QT as a natural material against the IMD induced toxicity at different doses.

Natural Antioxidant Anthocyanins-A Hidden Therapeutic Candidate in Metabolic Disorders with Major Focus in Neurodegeneration

All over the world, metabolic syndrome constitutes severe health problems. Multiple factors have been reported in the pathogenesis of metabolic syndrome. Metabolic disorders result in reactive oxygen species (ROS) induced oxidative stress, playing a vital role in the development and pathogenesis of major health issues, including neurological disorders Alzheimer's disease (AD) Parkinson's disease (PD). Considerable increasing evidence indicates the substantial contribution of ROS-induced oxidative stress in neurodegenerative diseases. An imbalanced metabolism results in a defective antioxidant defense system, free radicals causing inflammation, cellular apoptosis, and tissue damage. Due to the annual increase in financial and social burdens, in addition to the adverse effects associated with available synthetic agents, treatment diversion from synthetic to natural approaches has occurred. Antioxidants are now being considered as convincing therapeutic agents against various neurodegenerative disorders. Therefore, medicinal herbs and fruits currently receive substantially more attention as commercial sources of antioxidants. In this review, we argue that ROS-targeted therapeutic interventions with naturally occurring antioxidant flavonoid, anthocyanin, and anthocyanin-loaded nanoparticles might be the ultimate treatment against devastating illnesses. Furthermore, we elucidate the hidden potential of the neuroprotective role of anthocyanins and anthocyanin-loaded nanoparticles in AD and PD neuropathies, which lack sufficient attention compared with other polyphenols, despite their strong antioxidant potential. Moreover, we address the need for future research studies of native anthocyanins and nano-based-anthocyanins, which will be helpful in developing anthocyanin treatments as therapeutic mitochondrial antioxidant drug-like regimens to delay or prevent the progression of neurodegenerative diseases, such as AD and PD.

Implications of Successful Symptomatic Treatment in Parkinson's Disease for Therapeutic Strategies of Alzheimer's Disease

Alzheimer's disease (AD) has been a devastating neurodegenerative disorder and lacks effective treatment to improve the prognosis for patients. Symptomatic treatment for AD mainly includes two categories: Acetylcholinesterase inhibitors and the N-methyl-d-aspartate (NMDA) receptor antagonist (memantine). They cannot significantly improve the quality of life and extend survival time for AD patients. Worse, almost all clinical trials for disease-modifying drugs have failed, and the reduction of brain β-amyloid (Aβ) deposition by multiple approaches, including inhibitors of β- or γ-secretase, vaccines, and antibodies against Aβ deposition, was found to have little effect on AD progression. A new therapeutic strategy for AD is urgently needed. Parkinson's disease also is a neurodegenerative disease having no effective treatment for modifying the disease. Nevertheless, successful symptomatic treatment using the combined therapies of l-DOPA supplement and modulators of l-DOPA metabolism greatly improves the prognosis for PD patients; the average survival time of the patient has been extended from 3-4 years to 10-15 years although dopaminergic neurons are still progressively decreasing. This provides useful implications for AD therapeutic strategies. AD patients manifest global cognitive decline, prominently represented by memory deficit, especially in the early stages of the disease. Further, the degree of decreased cognitive abilities correlates with cholinergic dysfunction and the hypometabolism of glucose, the dominant energy fuel for brain. Thus, the amelioration of brain cholinergic function and brain energy metabolism may be effective treatment to improve cognitive abilities of AD patients. Here, we highlighted the explorations of symptomatic therapeutics through modulating brain cholinergic function and energy metabolism in AD.

Tacrine(10)-hupyridone, a dual-binding acetylcholinesterase inhibitor, potently attenuates scopolamine-induced impairments of cognition in mice

Tacrine(10)-hupyridone (A10E) was designed as a dual-binding acetylcholinesterase (AChE) inhibitor from the modification of tacrine and a fragment of huperzine A. We have found that A10E effectively inhibited AChE in a mixed competitive manner, with an IC₅₀ of 26.4 nM, which is more potent than those of tacrine and huperzine A. Most importantly, we have shown, for the first time that A10E attenuated scopolamine-induced cognitive impairments without affecting motor function in mice. A10E effectively attenuated impairments of learning and memory to a similar extent as donepezil, an inhibitor of AChE used for treating Alzheimer's disease (AD). In addition, A10E significantly decreased AChE activity in the brain of mice, suggesting that A10E might cross the brain blood-barrier. Taken together, our results demonstrated that A10E, a designed dual-binding AChE inhibitor, could effectively reverse cognitive impairments, indicating that A10E might provide therapeutic efficacy for AD treatment.

Identification of Lycopodium Alkaloids Produced by an Ultraviolet-Irradiated Strain of Paraboeremia, an Endophytic Fungus from Lycopodium serratum var. longipetiolatum

12- epi-Lycopodine (1), a Lycopodium alkaloid, along with lycopodine (2) and huperzine A (3), were discovered in the mycelium of Paraboeremia sp. Lsl3KI076, a UV-irradiated strain of Paraboeremia sp. Lsl3, an endophytic fungus from Lycopodium serratum Thunb. var. longipetiolatum Spring. Additionally, a trace of 1 was isolated from Phlegmariurus nummulariifolius (Blume) Ching, and the structure was elucidated on the basis of spectroscopic data. This is the first report proving that a new naturally occurring Lycopodium alkaloid can be obtained from an endophytic fungus.

Behavioural effects of novel multitarget anticholinesterasic derivatives in Alzheimer's disease

The current pharmacological approach to Alzheimer's disease (AD) treatment, mostly based on acetylcholinesterase inhibitors (AChEIs), is being revisited, especially in terms of the temporal frames and the potential benefits of their noncanonic actions, raising the question of whether inhibitors of AChE might also act in a disease-modifying manner. Besides, in the last decades, the pharmacophoric moieties of known AChEIs have been covalently linked to other pharmacophores in the pursuit of multitarget hybrid molecules that are expected to induce long-lasting amelioration of impaired neurotransmission and clinical symptoms but also to exert disease-modifying effects. Our research consortium has synthesized and defined the pharmacological profile of new AChEIs derivatives of potential interest for the treatment of AD. Among these, huprines and derivatives have been characterized successfully. Huprine X, a reversible AChE inhibitor, designed by molecular hybridization of tacrine and huperzine A, has been shown to affect the amyloidogenic process in vitro, and the AD-related neuropathology in vivo in mice models of the disease. More recently, we have shown that a group of donepezil-huprine heterodimers exerts a highly potent and selective inhibitory action on AChE both in vitro and ex vivo, simultaneously interacting with both peripheral and catalytic binding sites, and inhibiting the β-amyloid aggregation, whereas some levetiracetam-huprine hybrids have been shown to reduce epileptiform activity, neuroinflammation and amyloid burden in an animal model of AD. Here, we summarize the behavioural correlates of these noncanonic actions as assessed in three distinct biological scenarios: middle-age, cognitive deficits associated with ageing and AD-like phenotype in mice. Besides the improvement in the hallmark cognitive symptomatology without inducing side effects, these drugs have shown to be able to modulate emotional and anxiety-like behaviours or to reduce spontaneous seizures, all of them related to the so-called 'behavioural and psychological symptoms of dementia'. Overall, the studies show that these novel multitarget anticholinesterasics exert noncanonic actions providing symptomatic and disease-modifying benefits of potential interest for the management of AD.

Huperzine A inhibits immediate addictive behavior but not behavioral sensitization following repeated morphine administration in rats

Acetylcholinesterase inhibitors are regarded as promising therapeutic agents to treat addiction. The current study aimed to examine the effects of huperzine A, a cholinesterase inhibitor, on behavioral sensitization induced by repeated morphine administration and relapse induced by contextual conditioning. The present study also assessed whether the state-dependency hypothesis may explain the results. Adult rats were divided into four groups (n=8) and intraperitoneally injected with 0.2, 0.3 or 0.4 mg/kg huperzine A or saline (1 ml/kg, control), for 5 days. The effect of repeated huperzine A administration alone on locomotor activity was assessed. For the experiments that analyzed the development of morphine-induced sensitization, 40 rats were divided into five groups (n=8): Saline+Saline, Saline+Morphine, 0.2, 0.3 and 0.4 mg/kg huperzine A+Morphine. Following a withdrawal period of 7 days, all animals were administered saline or morphine, as appropriate. To test the state-dependency hypothesis, the rats in the Saline+Morphine group were injected with saline and morphine, while the other three groups were administered different doses of huperzine A and morphine. To examine the effect of huperzine A on the expression of morphine-induced sensitization, the rats in huperzine A+Morphine groups were injected with appropriate concentrations of huperzine A, and morphine. The current results indicated that the administration of huperzine A alone did not affect locomotor activity, while higher doses of huperzine A inhibited the addictive behavior induced by morphine at the development phase. Additionally, huperzine A administration during the expression phase of morphine sensitization did not inhibit the relapse induced by administration of saline. Furthermore, 0.4 mg/kg huperzine A inhibited the expression of morphine-induced behavioral sensitization. Therefore, the results of the current study do not support the state-dependency hypothesis.

Therapeutics of Neurotransmitters in Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease, characterized by the loss of memory, multiple cognitive impairments and changes in the personality and behavior. Several decades of intense research have revealed that multiple cellular changes are involved in disease process, including synaptic damage, mitochondrial abnormalities and inflammatory responses, in addition to formation and accumulation of amyloid-β (Aβ) and phosphorylated tau. Although tremendous progress has been made in understanding the impact of neurotransmitters in the progression and pathogenesis of AD, we still do not have a drug molecule associated with neurotransmitter(s) that can delay disease process in elderly individuals and/or restore cognitive functions in AD patients. The purpose of our article is to assess the latest developments in neurotransmitters research using cell and mouse models of AD. We also updated the current status of clinical trials using neurotransmitters' agonists/antagonists in AD.

TSG attenuates LPC-induced endothelial cells inflammatory damage through notch signaling inhibition

Lysophosphatidylcholine (LPC) induces inflammation in endothelial cells (ECs) but the mechanism is not fully understood. The Notch signaling pathway is involved in chronic EC inflammation, but its functions in LPC-induced endothelial inflammatory damage and 2,3,5,4'-tetrahydroxystilbene-2-O-β-d-glucoside's (TSG) protective effect during LPC-induced inflammatory damage in human umbilical vein endothelial cells (HUVECs) is largely unknown. We report that Notch signaling activation contributed to LPC-induced injury in HUVECs, and that TSG protected HUVECs from LPC-induced injury by antagonizing Notch signaling activation by LPC. γ-secretase inhibitor (DAPT), a specific inhibitor of the Notch signaling pathway, and Notch1 siRNA were used to inhibit Notch activity. HUVECs were exposed to LPC in the presence or absence of TSG, DAPT, and Notch1 siRNA. LPC treatment of HUVECs resulted in reduced cell viability, and Notch1 and Hes1 upregulation. Either silencing of Notch1 by siRNA or pharmacological inhibition of Notch signaling by DAPT prevented the loss of cell viability, and induction of apoptosis, and enhanced expression Notch1, Hes1 and MCP-1 by LPC in HUVECs. Similarly, TSG reduced LPC stimulation of Notch1, Hes1, and MCP-1 expression, prevented the release of IL-6 and CRP and rescued HUVECs from LPC-induced cell damage. Our data indicate that the Notch signaling pathway is a crucial mediator of endothelial inflammatory damage and that TSG protects against endothelial inflammatory damage by inhibiting the Notch signaling pathway. Our findings suggest that targeting Notch signaling by natural products such as TSG is a promising strategy for the prevention and treatment of chronic inflammation associated diseases, including atherosclerosis. © 2015 IUBMB Life, 68(1):37-50, 2016.

Involvement of Intracellular and Mitochondrial Aβ in the Ameliorative Effects of Huperzine A against Oligomeric Aβ42-Induced Injury in Primary Rat Neurons

Considerable studies indicate huperzine A is a promising natural product to suppress neuronal damages induced by β-amyloid (Aβ), a key pathogenic event in the Alzheimer’s disease (AD). As an extension, the present study for the first time explored whether the beneficial profiles of huperzine A against oligomeric Aβ₄₂ induced neurotoxicity are associated with the accumulation and detrimental function of intraneuronal/mitochondrial Aβ, on the basis of the emerging evidence that intracellular Aβ is more relevant to AD progression as compared with extracellular Aβ. Huperzine A treatment was shown to significantly attenuate the neurotoxicity of oligomeric Aβ₄₂, as demonstrated by increased neuronal viability. Interestingly, our results proved that exogenous Aβ₄₂ could accumulate intraneuronally in a dose- and time-dependent manner, while huperzine A treatment markedly reduced the level of intracellular Aβ₄₂. Moreover, huperzine A treatment rescued mitochondrial dysfunction induced by oligomeric Aβ₄₂, including adenosine triphosphate (ATP) reduction, reactive oxygen species (ROS) overproduction and membrane potential depolarization. Further study demonstrated that huperzine A also significantly reduced the level of Aβ₄₂ in the mitochondria-enriched subcellular fractions, as well as the Aβ₄₂ fluorescent signals colocalized with mitochondrial marker. This study indicates that interfering intracellular Aβ especially mitochondrial Aβ accumulation, together with ameliorating Aβ-associated mitochondrial dysfunction, may contribute to the protective effects of huperzine A against Aβ neurotoxicity. Above results may shed more light on the pharmacological mechanisms of huperzine A and provide important clues for discovering novel therapeutic strategies for AD.

Pharmacotherapy of traumatic brain injury: state of the science and the road forward: report of the Department of Defense Neurotrauma Pharmacology Workgroup

Despite substantial investments by government, philanthropic, and commercial sources over the past several decades, traumatic brain injury (TBI) remains an unmet medical need and a major source of disability and mortality in both developed and developing societies. The U.S. Department of Defense neurotrauma research portfolio contains more than 500 research projects funded at more than $700 million and is aimed at developing interventions that mitigate the effects of trauma to the nervous system and lead to improved quality of life outcomes. A key area of this portfolio focuses on the need for effective pharmacological approaches for treating patients with TBI and its associated symptoms. The Neurotrauma Pharmacology Workgroup was established by the U.S. Army Medical Research and Materiel Command (USAMRMC) with the overarching goal of providing a strategic research plan for developing pharmacological treatments that improve clinical outcomes after TBI. To inform this plan, the Workgroup (a) assessed the current state of the science and ongoing research and (b) identified research gaps to inform future development of research priorities for the neurotrauma research portfolio. The Workgroup identified the six most critical research priority areas in the field of pharmacological treatment for persons with TBI. The priority areas represent parallel efforts needed to advance clinical care; each requires independent effort and sufficient investment. These priority areas will help the USAMRMC and other funding agencies strategically guide their research portfolios to ensure the development of effective pharmacological approaches for treating patients with TBI.

A review on Alzheimer's disease pathophysiology and its management: an update

Alzheimer's disease acknowledged as progressive multifarious neurodegenerative disorder, is the leading cause of dementia in late adult life. Pathologically it is characterized by intracellular neurofibrillary tangles and extracellular amyloidal protein deposits contributing to senile plaques. Over the last two decades, advances in the field of pathogenesis have inspired the researchers for the investigation of novel pharmacological therapeutics centered more towards the pathophysiological events of the disease. Currently available treatments i.e. acetylcholinesterase inhibitors (rivastigmine, galantamine, donepezil) and N-methyl d-aspartate receptor antagonist (memantine) contribute minimal impact on the disease and target late aspects of the disease. These drugs decelerate the progression of the disease, provide symptomatic relief but fail to achieve a definite cure. While the neuropathological features of Alzheimer's disease are recognized but the intricacies of the mechanism have not been clearly defined. This lack of understanding regarding the pathogenic process may be the likely reason for the non-availability of effective treatment which can prevent onset and progression of the disease. Owing to the important progress in the field of pathophysiology in the last couple of years, new therapeutic targets are available that should render the underlying disease process to be tackled directly. In this review, authors will discusses the different aspects of pathophysiological mechanisms behind Alzheimer's disease and its management through conventional drug therapy, including modern investigational therapeutic strategies, recently completed and ongoing.

Xanthoceraside ameliorates mitochondrial dysfunction contributing to the improvement of learning and memory impairment in mice with intracerebroventricular injection of aβ1-42

The effects of xanthoceraside on learning and memory impairment were investigated and the possible mechanism associated with the protection of mitochondria was also preliminarily explored in Alzheimer's disease (AD) mice model induced by intracerebroventricular (i.c.v.) injection of Aβ1-42. The results indicated that xanthoceraside (0.08–0.32 mg/kg) significantly improved learning and memory impairment in Morris water maze test and Y-maze test. Xanthoceraside significantly reversed the aberrant decrease of ATP levels and attenuated the abnormal increase of ROS levels both in the cerebral cortex and hippocampus in mice injected with Aβ1-42. Moreover, xanthoceraside dose dependently reversed the decrease of COX, PDHC, and KGDHC activity in isolated cerebral cortex mitochondria of the mice compared with Aβ1-42 injected model mice. In conclusion, xanthoceraside could improve learning and memory impairment, promote the function of mitochondria, decrease the production of ROS, and inhibit oxidative stress. The improvement effects on mitochondria may be through withstanding the damage of Aβ to mitochondrial respiratory chain and the key enzymes in Kreb's cycle. Therefore, the results from present study and previous study indicate that xanthoceraside could be a competitive candidate for the treatment of AD.

Clerodane diterpenes from Polyalthia longifolia var. pendula protect SK-N-MC human neuroblastoma cells from β-amyloid insult

The n-hexane layer of Polyalthia longifolia methanolic extract showed neuroprotective activity, resulting in the isolation of three new clerodane diterpenes.

Therapeutics of Alzheimer's disease: Past, present and future

Alzheimer's disease (AD) is the most common cause of dementia worldwide. The etiology is multifactorial, and pathophysiology of the disease is complex. Data indicate an exponential rise in the number of cases of AD, emphasizing the need for developing an effective treatment. AD also imposes tremendous emotional and financial burden to the patient's family and community. The disease has been studied over a century, but acetylcholinesterase inhibitors and memantine are the only drugs currently approved for its management. These drugs provide symptomatic improvement alone but do less to modify the disease process. The extensive insight into the molecular and cellular pathomechanism in AD over the past few decades has provided us significant progress in the understanding of the disease. A number of novel strategies that seek to modify the disease process have been developed. The major developments in this direction are the amyloid and tau based therapeutics, which could hold the key to treatment of AD in the near future. Several putative drugs have been thoroughly investigated in preclinical studies, but many of them have failed to produce results in the clinical scenario; therefore it is only prudent that lessons be learnt from the past mistakes. The current rationales and targets evaluated for therapeutic benefit in AD are reviewed in this article. This article is part of the Special Issue entitled 'The Synaptic Basis of Neurodegenerative Disorders'.

New Perspectives on How to Discover Drugs from Herbal Medicines: CAM's Outstanding Contribution to Modern Therapeutics

With tens of thousands of plant species on earth, we are endowed with an enormous wealth of medicinal remedies from Mother Nature. Natural products and their derivatives represent more than 50% of all the drugs in modern therapeutics. Because of the low success rate and huge capital investment need, the research and development of conventional drugs are very costly and difficult. Over the past few decades, researchers have focused on drug discovery from herbal medicines or botanical sources, an important group of complementary and alternative medicine (CAM) therapy. With a long history of herbal usage for the clinical management of a variety of diseases in indigenous cultures, the success rate of developing a new drug from herbal medicinal preparations should, in theory, be higher than that from chemical synthesis. While the endeavor for drug discovery from herbal medicines is "experience driven," the search for a therapeutically useful synthetic drug, like "looking for a needle in a haystack," is a daunting task. In this paper, we first illustrated various approaches of drug discovery from herbal medicines. Typical examples of successful drug discovery from botanical sources were given. In addition, problems in drug discovery from herbal medicines were described and possible solutions were proposed. The prospect of drug discovery from herbal medicines in the postgenomic era was made with the provision of future directions in this area of drug development.

The anti-inflamm-aging and hepatoprotective effects of huperzine A in D-galactose-treated rats

Oxidative stress contributes to a chronic inflammatory process referred to as "inflamm-aging". Acetylcholinesterase inhibitors (AChEI) can enhance cholinergic transmission and act as anti-inflammatory agents via immunocompetent cells expressing α-7 acetylcholine receptors (AChR). The present study explores the possible role of huperzine A, a reversible and selective AChEI, against D-gal-induced oxidative damage, cell toxicity and inflamm-aging in rat livers. In two-month-old rats with normal liver function, an 8-week administration of D-gal (300 mg/kg subcutaneously (s.c.) injected), significantly increased hepatic impairment, ROS generation and oxidative damage, hepatic senescence, nuclear factor-kappa B (NF-κB) activation and inflammatory responses. An 8-week co-administration of both D-gal (300 mg/kg s.c.) and huperzine A (0.1 mg/kg s.c.) not only significantly decreased hepatic function impairment, ROS generation, oxidative damage, but also suppressed inflamm-aging by inhibiting hepatic replicative senescence, AChE activity, IκBα degradation, NF-κB p65 nuclear translocation and inflammatory responses. The expression levels of pro-inflammatory cytokine mRNA and proteins, such as TNFα, IL-1β and IL-6 decrease significantly, and the protein levels of the anti-inflammatory cytokine IL-10 display an obvious increase. These findings indicated that D-gal-induced hepatic injury and inflamm-aging in the rat liver was associated with the development of a pro-inflammatory phenotype in this organ. D-gal induced damage-associated molecular patterns (DAMPs) because oxidative damages might play an important role in D-gal-induced hepatic sterile inflammation. Huperzine A exhibited protective effects against D-gal-induced hepatotoxicity and inflamm-aging by inhibiting AChE activity and via the activation of the cholinergic anti-inflammatory pathway. The huperzine A mechanism might be involved in the inhibition of DAMPs-mediated NF-κB nuclear localization and activation.

Huprine X and huperzine A improve cognition and regulate some neurochemical processes related with Alzheimer's disease in triple transgenic mice (3xTg-AD)

BACKGROUND

Different studies have established that cholinergic neurodegeneration could be a major pathological feature of Alzheimer's disease (AD). Thus, enhancement of the central cholinergic neurotransmission has been regarded as one of the most promising strategies for the symptomatic treatment of AD, mainly by means of reversible acetylcholinesterase inhibitors (AChEIs). The cognitive-enhancing properties of both huprine X, a new AChEI, and the structurally related huperzine A, as well as their effects on the regulation of several neurochemical processes related to AD have been studied in triple transgenic mice (3xTg-AD).

METHODS

Seven-month-old homozygous 3xTg-AD male mice, which received chronic intraperitoneal treatment with either saline, huprine X (0.12 µmol·kg(-1)) or huperzine A (0.8 µmol·kg(-1)) were subjected to a battery of behavioural tests after 3 weeks of treatment and thereafter the brains were dissected to study the neurochemical effects induced by the two AChEIs.

RESULTS

Treatments with huprine X and huperzine A improved learning and memory in the Morris water maze and some indicators of emotionality without inducing important adverse effects. Moreover, huprine X and huperzine A activate protein kinase C/mitogen-activated protein kinase pathway signalling, α-secretases (ADAM 10 and TACE) and increase the fraction of phospho-glycogen synthase kinase 3-β.

CONCLUSION

Results obtained herein using a sample of 3xTg-AD animals strongly suggest that the treatment with the two AChEIs not only improves the cognitive performance of the animals but also induces some neurochemical changes that could contribute to the beneficial effects observed.

Toxicological scoring of Alzheimer's disease drug huperzine in a guinea pig model

Huperzine is a secondary metabolite in lycopods Huprzia and an inhibitor of acetylcholinesterase and antagonist of N-methyl-D-apartate receptor. Huperine is a suitable drug for the treatment of Alzheimer's disease as it is a part of traditional Chinese medicine. Currently, it undergoes clinical trials in the European Union and United States. The toxicological data about huperzine are missing and link between huperzine and oxidative stress has not been extensively investigated. For the above mentioned reasons, we organized experiment on a guinea pig model aimed at the investigation of adverse effects caused by huperzine. Guinea pigs were exposed to (-)-huperzine A in doses 5-625 µg/kg. Animals were sacrificed one day after exposure. Ferric reducing antioxidant power, thiobarbituric acid reactive substances, glutathione reductase, caspase 3 activity and selected biochemical markers (e.g. transaminases, blood urea nitrogen and glucose) were assayed. In frontal, parietal, temporal lobes and cerebellum, we found increase of antioxidants, glutathione reductase and oxidative stress markers in a dose dependent manner. Effects on liver, kidney and spleen were milder. We discuss ambivalent action of huperzine in the body and judge the huperzine action owing to recently reported experiments.

Huperzine a as potential treatment of Alzheimer's disease: an assessment on chemistry, pharmacology, and clinical studies

Alzheimer's disease (AD) is the fourth leading cause of death in adults, characterized by hallmark neuritic plaques and neurofibrillary tangles. Current treatments focus only on symptom relief. As a possible new treatment option for AD, huperzine A's chemistry, pharmacology, and clinical effectiveness are assessed. The chemical synthesis of huperzine A has been optimized, while an in vitro technique has provided a renewable plant source. Pharmacological studies showed that the drug inhibits the enzyme acetylcholinesterase reversibly and selectively. Huperzine A also displayed good pharmacokinetics with a rapid absorption and a wide distribution in the body at a low to moderate rate of elimination. Presently, inadequate toxicity data in human have been reported, yet animal studies demonstrated mild to moderate cholinergic side effects at therapeutic doses. Previous clinical trials have shown improvement in memory function using MMSE, MQ, ADAS-COG, and ADL tests. In an unpublished phase II clinical trial, the ADAS-COG and MMSE tests indicated cognitive enhancement at a dose of 0.4 mg, yet no improvement was observed at a dose of 0.2 mg. The MMSE scores indicated cognitive enhancement at 0.4 mg. Promising data suggested that huperzine A is well tolerated at doses up to 0.4 mg for 24 weeks. Therefore, huperzine A seems to be a potential treatment option for AD.

Huperzine A activates Wnt/β-catenin signaling and enhances the nonamyloidogenic pathway in an Alzheimer transgenic mouse model

Huperzine A (HupA) is a reversible and selective inhibitor of acetylcholinesterase (AChE), and it has multiple targets when used for Alzheimer's disease (AD) therapy. In this study, we searched for new mechanisms by which HupA could activate Wnt signaling and reduce amyloidosis in AD brain. A nasal gel containing HupA was prepared. No obvious toxicity of intranasal administration of HupA was found in mice. HupA was administered intranasally to β-amyloid (Aβ) precursor protein and presenilin-1 double-transgenic mice for 4 months. We observed an increase in ADAM10 and a decrease in BACE1 and APP695 protein levels and, subsequently, a reduction in Aβ levels and Aβ burden were present in HupA-treated mouse brain, suggesting that HupA enhances the nonamyloidogenic APP cleavage pathway. Importantly, our results further showed that HupA inhibited GSK3α/β activity, and enhanced the β-catenin level in the transgenic mouse brain and in SH-SY5Y cells overexpressing Swedish mutation APP, suggesting that the neuroprotective effect of HupA is not related simply to its AChE inhibition and antioxidation, but also involves other mechanisms, including targeting of the Wnt/β-catenin signaling pathway in AD brain.

Site-activated chelators derived from anti-Parkinson drug rasagiline as a potential safer and more effective approach to the treatment of Alzheimer's disease

chelators can modulate β-amyloid accumulation, protect against tau hyperphosphorylation, and block metal-related oxidative stress, and thereby hold considerable promise as effective anti-AD drugs. At present, a growing interest is focusing on increasing the efficacy and targeting of chelators through drug design. To this end, we have developed a new class of multifunctional prochelators from three FDA- approved drugs rasagiline, rivastigmine, and donepezil or tacrine. HLA20 A was designed by merging the important pharmacophores of rasagiline, rivastigmine, and donepezil into our newly developed multifunctional chelator HLA20. M30D was constructed using the key pharmacophoric moieties from rasagiline, rivastigmine, and tacrine. Experiments showed that both compounds possess potent anti-acetylcholinesterase (AChE) activity in vitro with weak inhibition of butyrylcholinesterase (BuChE), and without significant metal-binding activity. M30D was found also to be a highly potent MAO A inhibitor with moderate inhibition of MAO B in vitro. Both HLA20 and M30D can be activated by inhibition of AChE to release active chelators HLA20 and M30, respectively. HLA20 and M30 have been shown to be able to modulate amyloid precursor protein regulation and beta-amyloid reduction, suppress oxidative stress, and passivate excess metal ions (Fe, Cu, and Zn). Compared with the activated chelator HLA20 or M30, both HLA20A and M30D exhibited lower cytotoxicity in SH-SY5Y neuroblastoma cells, substantiating the prochelator strategy for minimizing toxicity associated with poor targeted chelators.

Pharmacokinetic behavior of huperzine A in plasma and cerebrospinal fluid after intranasal administration in rats

The aim of this study was to investigate the pharmacokinetic behavior of huperzine A (Hup A) in plasma and cerebrospinal fluid (CSF) after intranasal administration (0.5 mg/kg) in male Sprague-Dawley rats. A pharmacokinetic study of intravenous Hup A (0.5 mg/kg) was also performed. The concentrations of Hup A in the biological samples were measured by high performance liquid chromatography-mass spectrometry. Blood samples were taken from the tail vein and CSF was sampled by cisternal puncture using a stereotaxic frame. The contribution of the olfactory pathway to the uptake of Hup A into CSF was determined by comparing the AUC(CSF)/AUC(plasma) ratios after intranasal and intravenous administration. The AUC ratios of intranasal to intravenous administration in CSF and plasma were 104% and 118%, respectively. No significant difference was observed between the AUC(CSF)/AUC(plasma) ratios of Hup A after intranasal administration (20%) and after intravenous infusion (23%). This indicated that approximately 20% of the Hup A level in plasma reached the CSF after both nasal and intravenous administration, and that no direct transport of Hup A from nose to CSF was found in rats.

Site-activated multifunctional chelator with acetylcholinesterase and neuroprotective-neurorestorative moieties for Alzheimer's therapy

A novel strategy to develop site-activated multifunctional chelators for targeting multiple etiologies of Alzheimer's disease is reported. The novel prochelator HLA20A with improved cytotoxicity shows little affinity for metal ions until it is activated by binding and inhibiting acetylcholinesterase (AChE), releasing an active chelator HLA20 that modulates amyloid precursor protein (APP) regulation and beta-amyloid (Abeta) reduction, suppresses oxidative stress, and passivates excess metal ions (Fe, Cu, and Zn) in the brain.

Huperzine A protects isolated rat brain mitochondria against beta-amyloid peptide

Our previous work in cells and animals showed that mitochondria are involved in the neuroprotective effect of huperzine A (HupA). In this study, the effects of HupA on isolated rat brain mitochondria were investigated. In addition to inhibiting the Abeta(25-35) (40 microM)-induced decrease in mitochondrial respiration, adenosine 5'-triphosphate (ATP) synthesis, enzyme activity, and transmembrane potential, HupA (0.01 or 0.1 microM) effectively prevented Abeta-induced mitochondrial swelling, reactive oxygen species increase, and cytochrome c release. More interestingly, administration of HupA to isolated mitochondria promoted the rate of ATP production and blocked mitochondrial swelling caused by normal osmosis. These results indicate that HupA protects mitochondria against Abeta at least in part by preserving membrane integrity and improving energy metabolism. These direct effects on mitochondria further extend the noncholinergic functions of HupA.

The novel cholinesterase-monoamine oxidase inhibitor and antioxidant, ladostigil, confers neuroprotection in neuroblastoma cells and aged rats

The current therapeutic advance in which future drugs are designed to possess varied pharmacological properties and act on multiple targets has stimulated the development of the multimodal drug, ladostigil (TV3326; (N-propargyl-(3R) aminoindan-5yl)-ethyl methyl carbamate). Ladostigil combines neuroprotective effects with monoamine oxidase (MAO)-A and MAO-B and cholinesterase (ChE) inhibitory activities in a single molecule, as a potential treatment for Alzheimer's disease (AD) and Lewy body disease. In the present study, we demonstrate that ladostigil (10(-6)-10 muM) dose-dependently increased cell viability, associated with increased activity of catalase and glutathione reductase and decrease of intracellular reactive oxygen species production in a cytotoxic model of human SH-SY5Y neuroblastoma cells exposed to hydrogen peroxide (H(2)O(2)). In addition, ladostigil significantly upregulated mRNA levels of several antioxidant enzymes (catalase, NAD(P)H quinone oxidoreductase 1 and peroxiredoxin 1) in both H(2)O(2)-treated SH-SY5Y cells, as well as in the high-density human SK-N-SH neuroblastoma cultured apoptotic models. In vivo chronic treatment with ladostigil (1 mg/kg per os per day for 30 days) markedly upregulated mRNA expression levels of various enzymes involved in metabolism and oxidation processes in aged rat hippocampus. In addition to its unique combination of ChE and MAO enzyme inhibition, these results indicate that ladostigil displays neuroprotective activity against oxidative stress-induced cell apoptosis, which might be valuable for aging and age-associated neurodegenerative diseases.

Therapeutic strategies for Alzheimer's disease

Therapeutic approaches for Alzheimer's disease (AD) are guided by four disease characteristics: amyloid plaques, neurofibrillar tangles (NFT), neurodegeneration, and dementia. Amyloid plaques are composed largely of 4 kDa beta-amyloid (Abeta) peptides, with the more amyloidogenic, 42 amino acid form (Abeta42) as the primary species. Because multiple, rare mutations that cause early-onset, familial AD lead to increased production or aggregation of Abeta42, amyloid therapeutics aim to reduce the amount of toxic Abeta42 aggregates. Amyloid-based therapies include gamma-secretase inhibitors and modulators, BACE inhibitors, aggregation blockers, catabolism inducers, and anti-Abeta biologics. Tangles are composed of paired helical filaments of hyperphosphorylated tau protein. Tau-based therapeutics include kinase inhibitors, microtubule stabilizers, and catabolism inducers. Therapeutic strategies for neurodegeneration target multiple mechanisms, including excitotoxicity, mitochondrial dysfunction, oxidative damage, and inflammation or stimulation of neuronal viability. Although not disease modifying, cognition enhancers are important to treat the symptom of dementia. Strategies for cognition enhancement include cholinesterase inhibitors, and other approaches to enhance the signaling of cholinergic and glutamatergic neurons. In summary, plaques, tangles, neurodegeneration and dementia guide the development of multiple therapeutic approaches for AD and are the subject of this review.