An alternative approach to drug discovery for Alzheimer’s disease dementia. Future Med Chem. 2012;4:1681-1688. [PMID: 22924506 DOI: 10.4155/fmc.12.109]

Profiling the chemical nature of anti-oxytotic/ferroptotic compounds with phenotypic screening

Because old age is the greatest risk factor for Alzheimer's disease (AD), it is critical to target the pathological events that link aging to AD in order to develop an efficient treatment that acts upon the primary causes of the disease. One such event might be the activation of oxytosis/ferroptosis, a unique cell death mechanism characterized by mitochondrial dysfunction and lethal lipid peroxidation. Here, a comprehensive library of >900 natural compounds was screened for protection against oxytosis/ferroptosis in nerve cells with the goal of better understanding the chemical nature of inhibitors of oxytosis/ferroptosis. Although the compounds tested spanned structurally diverse chemical classes from animal, microbial, plant and synthetic origins, a small set of very potent anti-oxytotic/ferroptotic compounds was identified that was highly enriched in plant quinones. The ability of these compounds to protect against oxytosis/ferroptosis strongly correlated with their ability to protect against in vitro ischemia and intracellular amyloid-beta toxicity in nerve cells, indicating that aspects of oxytosis/ferroptosis also underly other toxicities that are relevant to AD. Importantly, the anti-oxytotic/ferroptotic character of the quinone compounds relied on their capacity to target and directly prevent lipid peroxidation in a manner that required the reducing activity of cellular redox enzymes, such as NAD(P)H:quinone oxidoreductase 1 (NQO1) and ferroptosis suppressor protein 1 (FSP1). Because some of the compounds increased the production of total reactive oxygen species while decreasing lipid peroxidation, it appears that the pro-oxidant character of a compound can coexist with an inhibitory effect on lipid peroxidation and, consequently, still prevent oxytosis/ferroptosis. These findings have significant implications for the understanding of oxytosis/ferroptosis and open new approaches to the development of future neurotherapies.

Fisetin, potential flavonoid with multifarious targets for treating neurological disorders: An updated review

Neurodegenerative disorders pose a significant health burden and imprint a debilitative impact on the quality of life. Importantly, aging is intricately intertwined with the progression of these disorders, and their prevalence increases with a rise in the aging population worldwide. In recent times, fisetin emerged as one of the potential miracle molecules to address neurobehavioral and cognitive abnormalities. These effects were attributed to its actions on several macromolecules and multiple molecular mechanisms. Fisetin belongs to a class of flavonoids, which is found abundantly in several fruits and vegetables. Fisetin has manifested several health benefits in preclinical models of neurodegenerative diseases such as Alzheimer's disease, Vascular dementia, and Schizophrenia. Parkinson's disease, Amyotrophic Lateral Sclerosis, Huntington's disease, Stroke, Traumatic Brain Injury (TBI), and age-associated changes. This review aimed to evaluate the potential mechanisms and pharmacological effects of fisetin in treating several neurological diseases. This review also provides comprehensive data on up-to-date recent literature and highlights the various mechanistic pathways pertaining to fisetin's neuroprotective role.

Natural products targeting mitochondria: emerging therapeutics for age-associated neurological disorders

Mitochondria are the primary source of energy production in the brain thereby supporting most of its activity. However, mitochondria become inefficient and dysfunctional with age and to a greater extent in neurological disorders. Thus, mitochondria represent an emerging drug target for many age-associated neurological disorders. This review summarizes recent advances (covering from 2010 to May 2020) in the use of natural products from plant, animal, and microbial sources as potential neuroprotective agents to restore mitochondrial function. Natural products from diverse classes of chemical structures are discussed and organized according to their mechanism of action on mitochondria in terms of modulation of biogenesis, dynamics, bioenergetics, calcium homeostasis, and membrane potential, as well as inhibition of the oxytosis/ferroptosis pathway. This analysis emphasizes the significant value of natural products for mitochondrial pharmacology as well as the opportunities and challenges for the discovery and development of future neurotherapeutics.

Development and Application of a Chemical Probe Based on a Neuroprotective Flavonoid Hybrid for Target Identification Using Activity-Based Protein Profiling

Alzheimer's disease (AD) is the most common form of dementia, and up to now, there are no disease-modifying drugs available. Natural product hybrids based on the flavonoid taxifolin and phenolic acids have shown a promising pleiotropic neuroprotective profile in cell culture assays and even disease-modifying effects in vivo. However, the detailed mechanisms of action remain unclear. To elucidate the distinct intracellular targets of 7-O-esters of taxifolin, we present in this work the development and application of a chemical probe, 7-O-cinnamoyltaxifolin-alkyne, for target identification using activity-based protein profiling. 7-O-Cinnamoyltaxifolin-alkyne remained neuroprotective in all cell culture assays. Western blot analysis showed a comparable influence on the same intracellular pathways as that of the lead compound 7-O-cinnamoyltaxifolin, thereby confirming its suitability as a probe for target identification experiments. Affinity pulldown and MS analysis revealed adenine nucleotide translocase 1 (ANT-1) and sarco/endoplasmic reticulum Ca²⁺ ATPase (SERCA) as intracellular interaction partners of 7-O-cinnamoyltaxifolin-alkyne and thus of 7-O-esters of taxifolin.

M. Pinto M, Sousa E. Marine Natural Products, Multitarget Therapy and Repurposed Agents in Alzheimer's Disease

Alzheimer's disease (AD) is a multifactorial disease characterized by the presence of amyloid plaques, neurofibrillary tangles, and nerve cell death that affects, mainly, older people. After decades of investigation, the search for an efficacious treatment for AD remains and several strategies can be and are being employed in this journey. In this review, four of the most promising strategies, alongside with its most promising agents under investigation or development are highlighted. Marine natural products (MNP) are a source of unique chemical structures with useful biological activities for AD treatment. One of the most promising compounds, a marine-derived acidic oligosaccharide (GV-971) just passed phase III clinical trials with a unique mechanism of action. Combination therapy and multitargeted-directed ligand therapy (MTDL) are also two important strategies, with several examples in clinical trials, based on the belief that the best approach for AD is a therapy capable of modulating multiple target pathways. Drug repurposing, a strategy that requires a smaller investment and is less time consuming, is emerging as a strong contender with a variety of pharmacological agents resurfacing in an attempt to identify a therapeutic candidate capable of modifying the course of this disease.

Molecular Insight into the Therapeutic Promise of Flavonoids against Alzheimer's Disease

Alzheimer’s disease (AD) is one of the utmost chronic neurodegenerative disorders, which is characterized from a neuropathological point of view by the aggregates of amyloid beta (Aβ) peptides that are deposited as senile plaques and tau proteins which form neurofibrillary tangles (NFTs). Even though advancement has been observed in order to understand AD pathogenesis, currently available therapeutic methods can only deliver modest symptomatic relief. Interestingly, naturally occurring dietary flavonoids have gained substantial attention due to their antioxidative, anti-inflammatory, and anti-amyloidogenic properties as alternative candidates for AD therapy. Experimental proof provides support to the idea that some flavonoids might protect AD by interfering with the production and aggregation of Aβ peptides and/or decreasing the aggregation of tau. Flavonoids have the ability to promote clearance of Aβ peptides and inhibit tau phosphorylation by the mTOR/autophagy signaling pathway. Moreover, due to their cholinesterase inhibitory potential, flavonoids can represent promising symptomatic anti-Alzheimer agents. Several processes have been suggested for the aptitude of flavonoids to slow down the advancement or to avert the onset of Alzheimer’s pathogenesis. To enhance cognitive performance and to prevent the onset and progress of AD, the interaction of flavonoids with various signaling pathways is proposed to exert their therapeutic potential. Therefore, this review elaborates on the probable therapeutic approaches of flavonoids aimed at averting or slowing the progression of the AD pathogenesis.

Repurposing antimycotic ciclopirox olamine as a promising anti-ischemic stroke agent

Ischemic stroke is a severe disorder resulting from acute cerebral thrombosis. Here we demonstrated that post-ischemic treatment with ciclopirox olamine (CPX), a potent antifungal clinical drug, alleviated brain infarction, neurological deficits and brain edema in a classic rat model of ischemic stroke. Single dose post-ischemic administration of CPX provided a long-lasting neuroprotective effect, which can be further enhanced by multiple doses administration of CPX. CPX also effectively reversed ischemia-induced neuronal loss, glial activation as well as blood–brain barrier (BBB) damage. Employing quantitative phosphoproteomic analysis, 130 phosphosites in 122 proteins were identified to be significantly regulated by CPX treatment in oxygen glucose deprivation (OGD)-exposed SH-SY5Y cells, which revealed that phosphokinases and cell cycle-related phosphoproteins were largely influenced. Subsequently, we demonstrated that CPX markedly enhanced the AKT (protein kinase B, PKB/AKT) and GSK3β (glycogen synthase kinase 3β) phosphorylation in OGD-exposed SH-SY5Y cells, and regulated the cell cycle progression and nitric oxide (NO) release in lipopolysaccharide (LPS)-induced BV-2 cells, which may contribute to its ameliorative effects against ischemia-associated neuronal death and microglial inflammation. Our study suggests that CPX could be a promising compound to reduce multiple ischemic injuries; however, further studies will be needed to clarify the molecular mechanisms involved.

7-O-Esters of taxifolin with pronounced and overadditive effects in neuroprotection, anti-neuroinflammation, and amelioration of short-term memory impairment in vivo

Alzheimer's disease (AD) is a multifactorial disease and the most common form of dementia. There are no treatments to cure, prevent or slow down the progression of the disease. Natural products hold considerable interest for the development of preventive neuroprotectants to treat neurodegenerative disorders like AD, due to their low toxicity and general beneficial effects on human health with their anti-inflammatory and antioxidant features. In this work we describe regioselective synthesis of 7-O-ester hybrids of the flavonoid taxifolin with the phenolic acids cinnamic and ferulic acid, namely 7-O-cinnamoyltaxifolin and 7-O-feruloyltaxifolin. The compounds show pronounced overadditive neuroprotective effects against oxytosis, ferroptosis and ATP depletion in the murine hippocampal neuron HT22 cell model. Furthermore, 7-O-cinnamoyltaxifolin and 7-O-feruloyltaxifolin reduced LPS-induced neuroinflammation in BV-2 microglia cells as assessed by effects on the levels of NO, IL6 and TNFα. In all in vitro assays the 7-O-esters of taxifolin and ferulic or cinnamic acid showed strong overadditive activity, significantly exceeding the effects of the individual components and the equimolar mixtures thereof, which were almost inactive in all of the assays at the tested concentrations. In vivo studies confirmed this overadditive effect. Treatment of an AD mouse model based on the injection of oligomerized Aβ_25-35 peptide into the brain to cause neurotoxicity and subsequently memory deficits with 7-O-cinnamoyltaxifolin or 7-O-feruloyltaxifolin resulted in improved performance in an assay for short-term memory as compared to vehicle and mice treated with the respective equimolar mixtures. These results highlight the benefits of natural product hybrids as a novel compound class with potential use for drug discovery in neurodegenerative diseases due to their pharmacological profile that is distinct from the individual natural components.

The Potential of Flavonoids for the Treatment of Neurodegenerative Diseases

Neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), and amyotrophic lateral sclerosis (ALS), currently affect more than 6 million people in the United States. Unfortunately, there are no treatments that slow or prevent disease development and progression. Regardless of the underlying cause of the disorder, age is the strongest risk factor for developing these maladies, suggesting that changes that occur in the aging brain put it at increased risk for neurodegenerative disease development. Moreover, since there are a number of different changes that occur in the aging brain, it is unlikely that targeting a single change is going to be effective for disease treatment. Thus, compounds that have multiple biological activities that can impact the various age-associated changes in the brain that contribute to neurodegenerative disease development and progression are needed. The plant-derived flavonoids have a wide range of activities that could make them particularly effective for blocking the age-associated toxicity pathways associated with neurodegenerative diseases. In this review, the evidence for beneficial effects of multiple flavonoids in models of AD, PD, HD, and ALS is presented and common mechanisms of action are identified. Overall, the preclinical data strongly support further investigation of specific flavonoids for the treatment of neurodegenerative diseases.

A11, a novel diaryl acylhydrazone derivative, exerts neuroprotection against ischemic injury in vitro and in vivo

There is an urgent need to develop effective therapies for ischemic stroke, but the complicated pathological processes after ischemia make doing so difficult. In the current study, we identified a novel diaryl acylhydrazone derivative, A11, which has multiple neuroprotective properties in ischemic stroke models. First, A11 was demonstrated to induce neuroprotection against ischemic injury in a dose-dependent manner (from 0.3 to 3 μM) in three in vitro experimental ischemic stroke models: oxygen glucose deprivation (OGD), hydrogen peroxide, and glutamate-stimulated neuronal cell injury models. Moreover, A11 was able to potently alleviate three critical pathological changes, apoptosis, oxidative stress, and mitochondrial dysfunction, following ischemic insult in neuronal cells. Further analysis revealed that A11 upregulated the phosphorylation levels of protein kinase B (AKT) and extracellular signal-regulated kinase (ERK) in OGD-exposed neuronal cells, suggesting joint activation of the phosphoinositide 3-kinase (PI3K)/AKT and mitogen-activated protein kinase (MEK)/ERK pathways. In rats with middle cerebral artery occlusion, single-dose administration of A11 (3 mg/kg per day, i.v.) at the onset of reperfusion significantly reduced the infarct volumes and ameliorated neurological deficits. Our study, for the first time, reports the anti-ischemic effect of diaryl acylhydrazone chemical entities, especially A11, which acts on multiple ischemia-associated pathological processes. Our results may provide new clues for the development of an effective therapeutic agent for ischemic stroke.

Fisetin Reduces the Impact of Aging on Behavior and Physiology in the Rapidly Aging SAMP8 Mouse

Alzheimer's disease (AD) is rarely addressed in the context of aging even though there is an overlap in pathology. We previously used a phenotypic screening platform based on old age-associated brain toxicities to identify the flavonol fisetin as a potential therapeutic for AD and other age-related neurodegenerative diseases. Based on earlier results with fisetin in transgenic AD mice, we hypothesized that fisetin would be effective against brain aging and cognitive dysfunction in rapidly aging senescence-accelerated prone 8 (SAMP8) mice, a model for sporadic AD and dementia. An integrative approach was used to correlate protein expression and metabolite levels in the brain with cognition. It was found that fisetin reduced cognitive deficits in old SAMP8 mice while restoring multiple markers associated with impaired synaptic function, stress, and inflammation. These results provide further evidence for the potential benefits of fisetin for the treatment of age-related neurodegenerative diseases.

Report on the Symposium "Molecular Mechanisms Involved in Neurodegeneration"

The prevalence of neurodegenerative diseases is currently a major concern in public health because of the lack of neuroprotective and neuroregenerative drugs. The symposium on Molecular Mechanisms Involved in Neurodegeneration held in Varadero, Cuba, updated the participants on the basic mechanisms of neurodegeneration, on the different approaches for drug discovery, and on early research results on therapeutic approaches for the treatment of neurodegenerative diseases. Alzheimer’s disease and in silico research were covered by many of the presentations in the symposium, under the umbrella of the “State of the Art of Non-clinical Models for Neurodegenerative Diseases” International Congress, held from 20 to 24 June 2017. This paper summarizes the highlights of the symposium.

The Anti-Amyloid-β and Neuroprotective Properties of a Novel Tricyclic Pyrone Molecule

There is an urgent unmet need for new therapeutics for Alzheimer's disease (AD), the most common cause of dementia in the elderly. Therapeutic approaches targeting amyloid-β (Aβ) and its downstream toxicities have become major strategies in AD drug development. We have taken a rational design approach and synthesized a class of tricyclic pyrone (TP) compounds that show anti-Aβ and other neuroprotective actions. The in vivo efficacy of a lead TP named CP2 to ameliorate AD-like pathologies has been shown in mouse models. Here we report the selection and initial characterization of a new lead TP70, which exhibited an anti-Aβ therapeutic index even higher than CP2. Moreover, TP70 was able to reduce oxidative stress, inhibit acyl-coenzyme A:cholesterol acyltransferase (ACAT), and upregulate the expression of ATP-binding cassette subfamily A, member 1 (ABCA1), actions considered neuroprotective in AD. TP70 further showed excellent pharmacokinetic properties, including brain penetration and oral availability. When administered to 5xFAD mice via intraperitoneal or oral route, TP70 enhanced the overall solubility and decreased the level of cerebral Aβ, including both fibrillary and soluble Aβ species. Interestingly, TP70 enhanced N-methyl-D-aspartate (NMDA) receptor-mediated excitatory post-synaptic potential (EPSP) in the hippocampal CA1 area, increased the magnitude of NMDA-dependent hippocampal long-term potentiation (LTP), a cellular model of learning and memory, and prevented the Aβ oligomer-impaired LTP. Significantly, a single dose of TP70 administered to aged 5xFAD mice was effective in mitigating the impaired LTP induction, recorded at 24 h after administration. Our results support a potential of TP70 in clinical development for AD in view of its synergistic neuroprotective actions, ability to positively modulate NMDA receptor-mediated hippocampal plasticity, and favorable pharmacokinetic properties in rodents.

Neuroprotection against glutamate-induced excitotoxicity and induction of neurite outgrowth by T-006, a novel multifunctional derivative of tetramethylpyrazine in neuronal cell models

Alzheimer's disease is a progressive neurodegenerative disorder, characterized by irreversible impairment of memory and cognitive function. The exact causes of Alzheimer's disease still remain unclear and current single target drugs could only offer limited therapeutic effect to the patients. We have previously reported that T-006, a promising anti-Alzheimer's compound derived from Chinese medicinal component tetramethylpyrazine, might protect neurons through inhibiting the overproduction of intracellular reactive oxygen species (ROS) and reactive nitrogen species (RNS). In this study, we further investigated the neuroprotective effects, as well as the molecular pathways involved, of T-006 against glutamate-induced excitotoxicity in rat cerebellar granule neurons (CGNs). T-006 was also found to promote neuronal differentiation in both PC12 cells and primary cultured rat cortical neurons. The results showed that the pretreatment of T-006 (0.01-1 μM) might prevent glutamate-induced neuronal loss in a concentration-dependent manner. T-006 is found to inhibit the over-activation of NMDAR and ensued calcium overload caused by glutamate. The following activation of phosphorylated extracellular signal-regulated kinase (ERK) were also abolished. Moreover, T-006 concurrently prevented the suppression of phosphorylated protein kinase B (Akt) and glycogen synthase kinase 3β (GSK3β). T-006 was also found to promote neurite outgrowth in PC12 cells and primary cortical neurons. In our study, T-006 (0.1-3 μM) dose-dependently stimulated neurite outgrowth in PC12 cells and the efficacy was comparable to nerve growth factor (NGF). Moreover, co-treatment of T-006 and NGF revealed that T-006 could robustly potentiate the NGF-induced neuritogenesis. Further signal transduction studies indicated that T-006 rapidly up-regulated phosphorylation of ERK but did not activate tyrosine kinase receptor A (Trk A). These findings offer deeper understanding of the anti-neurodegenerative activity of T-006 and provide insight into its possible therapeutic potential for AD treatment in light of the multipotent nature of T-006.

How fisetin reduces the impact of age and disease on CNS function

It is becoming increasingly clear that neurological diseases are multi-factorial involving disruptions in multiple cellular systems. Thus, while each disease has its own initiating mechanisms and pathologies, certain common pathways appear to be involved in most, if not all, neurological diseases. Thus, it is unlikely that modulating only a single factor will be effective at either preventing disease development or slowing disease progression. A better approach is to identify small (< 900 daltons) molecules that have multiple biological activities relevant to the maintenance of brain function. We have identified an orally active, novel neuroprotective and cognition-enhancing molecule, the flavonoid fisetin. Fisetin not only has direct antioxidant activity but it can also increase the intracellular levels of glutathione, the major intracellular antioxidant. Fisetin can also activate key neurotrophic factor signaling pathways. In addition, it has anti-inflammatory activity and inhibits the activity of lipoxygenases, thereby reducing the production of pro-inflammatory eicosanoids and their by-products. This wide range of actions suggests that fisetin has the ability to reduce the impact of age-related neurological diseases on brain function.

Human neural stem cells improve cognition and promote synaptic growth in two complementary transgenic models of Alzheimer's disease and neuronal loss

Alzheimer's disease (AD) is the most prevalent age‐related neurodegenerative disorder, affecting over 35 million people worldwide. Pathologically, AD is characterized by the progressive accumulation of β‐amyloid (Aβ) plaques and neurofibrillary tangles within the brain. Together, these pathologies lead to marked neuronal and synaptic loss and corresponding impairments in cognition. Current treatments, and recent clinical trials, have failed to modify the clinical course of AD; thus, the development of novel and innovative therapies is urgently needed. Over the last decade, the potential use of stem cells to treat cognitive impairment has received growing attention. Specifically, neural stem cell transplantation as a treatment for AD offers a novel approach with tremendous therapeutic potential. We previously reported that intrahippocampal transplantation of murine neural stem cells (mNSCs) can enhance synaptogenesis and improve cognition in 3xTg‐AD mice and the CaM/Tet‐DT_A model of hippocampal neuronal loss. These promising findings prompted us to examine a human neural stem cell population, HuCNS‐SC, which has already been clinically tested for other neurodegenerative disorders. In this study, we provide the first evidence that transplantation of research grade HuCNS‐SCs can improve cognition in two complementary models of neurodegeneration. We also demonstrate that HuCNS‐SC cells can migrate and differentiate into immature neurons and glia and significantly increase synaptic and growth‐associated markers in both 3xTg‐AD and CaM/Tet‐DT_A mice. Interestingly, improvements in aged 3xTg‐AD mice were not associated with altered Aβ or tau pathology. Rather, our findings suggest that human NSC transplantation improves cognition by enhancing endogenous synaptogenesis. Taken together, our data provide the first preclinical evidence that human NSC transplantation could be a safe and effective therapeutic approach for treating AD. © 2014 The Authors. Hippocampus Published by Wiley Periodicals, Inc.

Inhibitors of c-Jun N-terminal kinases: an update

The c-Jun N-terminal kinases (JNKs) are serine/threonine kinases implicated in the pathogenesis of various diseases. Recent advances in the development of novel inhibitors of JNKs will be reviewed. Significant progress in the design of JNK inhibitors displaying selectivity versus other kinases has been achieved within the past 4 years. However, the development of isoform selective JNK inhibitors is still an open task.

Carthamus, Salvia and Stachys species protect neuronal cells against oxidative stress-induced apoptosis

CONTEXT

Finding effective therapies for neurodegenerative diseases is of utmost importance for the aging population. Plants growing in Iran are rich sources of antioxidants and active phytochemicals.

OBJECTIVE

The protective capacity of plants, with a special focus on those with reported antioxidant or neuroprotective potential or nervous system-related applications in folk medicine, was tested against oxidative stress-induced apoptosis.

MATERIALS AND METHODS

Aerial parts of 20 plants including Carthamus, Salvia, and Stachys species were extracted with 80% methanol and dichloromethane and preincubated with neuronal PC12 cells for 3 h. Oxidative stress and apoptosis were induced by hydrogen peroxide (75 µM, 1 h exposure). Cell viability and intracellular reactive oxygen species (ROS) were measured by MTT and 2',7'-dichlorofluorescein-diacetate (DCFH-DA) assays, respectively, while apoptosis was determined by annexin V-FITC/propidium iodide staining by a flow cytometer.

RESULTS

Eighty percent methanol extracts of Carthamus oxyacantha Bieb. (Asteraceae), Salvia santolinifolia Boiss. (Lamiaceae), and Salvia sclarea L. (Lamiaceae) at the concentration of 100 μg/ml showed significant neuroprotection in the MTT assay by 38.7, 34.7, and 39.5%, respectively, and inhibited intracellular ROS by 48.6, 61.9, and 61.4%, respectively. The first two extracts also significantly inhibited apoptosis. Dichloromethane extracts of C. oxyacantha and Stachys pilifera Benth. (Lamiaceae) at the concentration of 25 μg/ml showed neuroprotection by 27.5 and 26.5%, respectively, and inhibited ROS by 44.5 and 39.4%, respectively.

CONCLUSION

The above-mentioned plants seem to have important biological activities and their further study may lead to the discovery of new natural therapeutics useful against disorders such as Alzheimer and Parkinson diseases.

The development of small molecule angiotensin IV analogs to treat Alzheimer's and Parkinson's diseases

Alzheimer's (AD) and Parkinson's (PD) diseases are neurodegenerative diseases presently without effective drug treatments. AD is characterized by general cognitive impairment, difficulties with memory consolidation and retrieval, and with advanced stages episodes of agitation and anger. AD is increasing in frequency as life expectancy increases. Present FDA approved medications do little to slow disease progression and none address the underlying progressive loss of synaptic connections and neurons. New drug design approaches are needed beyond cholinesterase inhibitors and N-methyl-d-aspartate receptor antagonists. Patients with PD experience the symptomatic triad of bradykinesis, tremor-at-rest, and rigidity with the possibility of additional non-motor symptoms including sleep disturbances, depression, dementia, and autonomic nervous system failure. This review summarizes available information regarding the role of the brain renin-angiotensin system (RAS) in learning and memory and motor functions, with particular emphasis on research results suggesting a link between angiotensin IV (AngIV) interacting with the AT4 receptor subtype. Currently there is controversy over the identity of this AT4 receptor protein. Albiston and colleagues have offered convincing evidence that it is the insulin-regulated aminopeptidase (IRAP). Recently members of our laboratory have presented evidence that the brain AngIV/AT4 receptor system coincides with the brain hepatocyte growth factor/c-Met receptor system. In an effort to resolve this issue we have synthesized a number of small molecule AngIV-based compounds that are metabolically stable, penetrate the blood-brain barrier, and facilitate compromised memory and motor systems. These research efforts are described along with details concerning a recently synthesized molecule, Dihexa that shows promise in overcoming memory and motor dysfunctions by augmenting synaptic connectivity via the formation of new functional synapses.

World health dilemmas: Orphan and rare diseases, orphan drugs and orphan patients

According to global annual estimates hunger/malnutrition is the major cause of death (36 of 62 million). Cardiovascular diseases and cancer (5.44 of 13.43 million) are the major causes of death in developed countries, while lower respiratory tract infections, human immunodeficiency virus infection/acquired immunodeficiency syndrome, diarrhoeal disease, malaria and tuberculosis (10.88 of 27.12 million) are the major causes of death in developing countries with more than 70% of deaths occurring in children. The majority of approximately 800 million people with other rare diseases, including 100000 children born with thalassaemia annually receive no treatment. There are major ethical dilemmas in dealing with global health issues such as poverty and the treatment of orphan and rare diseases. Of approximately 50000 drugs about 10% are orphan drugs, with annual sales of the latter approaching 100 billion USD. In comparison, the annual revenue in 2009 from the top 12 pharmaceutical companies in Western countries was 445 billion USD and the top drug, atorvastatin, reached 100 billion USD. In the same year, the total government expenditure for health in the developing countries was 410 billion USD with only 6%-7% having been received as aid from developed countries. Drugs cost the National Health Service in the United Kingdom more than 20 billion USD or 10% of the annual health budget. Uncontrollable drug prices and marketing policies affect global health budgets, clinical practice, patient safety and survival. Fines of 5.3 billion USD were imposed on two pharmaceutical companies in the United States, the regulatory authority in France was replaced and clinicians were charged with bribery in order to overcome recent illegal practises affecting patient care. High expenditure for drug development is mainly related to marketing costs. However, only 2 million USD was spent developing the drug deferiprone (L1) for thalassaemia up to the stage of multicentre clinical trials. The criteria for drug development, price levels and use needs to be readdressed to improve drug safety and minimise costs. New global health policies based on cheaper drugs can help the treatment of many categories of orphan and rare diseases and millions of orphan patients in developing and developed countries.

Screening and identification of neuroprotective compounds relevant to Alzheimer׳s disease from medicinal plants of S. Tomé e Príncipe

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer׳s disease (AD) neuropathology is strongly associated with the activation of inflammatory pathways, and long-term use of anti-inflammatory drugs reduces the risk of developing the disease. In S. Tomé e Príncipe (STP), several medicinal plants are used both for their positive effects in the nervous system (treatment of mental disorders, analgesics) and their anti-inflammatory properties. The goal of this study was to determine whether a phenotypic, cell-based screening approach can be applied to selected plants from STP (Voacanga africana, Tarenna nitiduloides, Sacosperma paniculatum, Psychotria principensis, Psychotria subobliqua) in order to identify natural compounds with multiple biological activities of interest for AD therapeutics.

MATERIALS AND METHODS

Plant hydroethanolic extracts were prepared and tested in a panel of phenotypic screening assays that reflect multiple neurotoxicity pathways relevant to AD-oxytosis in hippocampal nerve cells, in vitro ischemia, intracellular amyloid toxicity, inhibition of microglial inflammation and nerve cell differentiation. HPLC fractions from the extract that performed the best in all of the assays were tested in the oxytosis assay, our primary screen, and the most protective fraction was analyzed by mass spectrometry. The predominant compound was purified, its identity confirmed by ESI mass spectrometry and NMR, and then tested in all of the screening assays to determine its efficacy.

RESULTS

An extract from the bark of Voacanga africana was more protective than any other plant extract in all of the assays (EC50s≤2.4 µg/mL). The HPLC fraction from the extract that was most protective against oxytosis contained the alkaloid voacamine (MW=704.90) as the predominant compound. Purified voacamine was very protective at low doses in all of the assays (EC50s≤3.4 µM).

CONCLUSION

These findings validate the use of our phenotypic screening, cell-based assays to identify potential compounds to treat AD from plant extracts with ethnopharmacological relevance. Our study identifies the alkaloid voacamine as a major compound in Voacanga africana with potent neuroprotective activities in these assays.

Modulation of p25 and inflammatory pathways by fisetin maintains cognitive function in Alzheimer's disease transgenic mice

Alzheimer's disease (AD) is the most common type of dementia. It is the only one of the top ten causes of death in the USA for which prevention strategies have not been developed. Although AD has traditionally been associated with the deposition of amyloid β plaques and tau tangles, it is becoming increasingly clear that it involves disruptions in multiple cellular systems. Therefore, it is unlikely that hitting a single target will result in significant benefits to patients with AD. An alternative approach is to identify molecules that have multiple biological activities that are relevant to the disease. Fisetin is a small, orally active molecule which can act on many of the target pathways implicated in AD. We show here that oral administration of fisetin to APPswe/PS1dE9 double transgenic AD mice from 3 to 12 months of age prevents the development of learning and memory deficits. This correlates with an increase in ERK phosphorylation along with a decrease in protein carbonylation, a marker of oxidative stress. Importantly, fisetin also reduces the levels of the cyclin-dependent kinase 5 (Cdk5) activator p35 cleavage product, p25, in both control and AD brains. Elevated levels of p25 relative to p35 cause dysregulation of Cdk5 activity leading to neuroinflammation and neurodegeneration. These fisetin-dependent changes correlate with additional anti-inflammatory effects, including alterations in global eicosanoid synthesis, and the maintenance of markers of synaptic function in the AD mice. Together, these results suggest that fisetin may provide a new approach to the treatment of AD.

A Role for the Brain RAS in Alzheimer's and Parkinson's Diseases

The brain renin-angiotensin system (RAS) has available the necessary functional components to produce the active ligands angiotensins II (AngII), angiotensin III, angiotensins (IV), angiotensin (1-7), and angiotensin (3-7). These ligands interact with several receptor proteins including AT1, AT2, AT4, and Mas distributed within the central and peripheral nervous systems as well as local RASs in several organs. This review first describes the enzymatic pathways in place to synthesize these ligands and the binding characteristics of these angiotensin receptor subtypes. We next discuss current hypotheses to explain the disorders of Alzheimer's disease (AD) and Parkinson's disease (PD), as well as research efforts focused on the use of angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), in their treatment. ACE inhibitors and ARBs are showing promise in the treatment of several neurodegenerative pathologies; however, there is a need for the development of analogs capable of penetrating the blood-brain barrier and acting as agonists or antagonists at these receptor sites. AngII and AngIV have been shown to play opposing roles regarding memory acquisition and consolidation in animal models. We discuss the development of efficacious AngIV analogs in the treatment of animal models of AD and PD. These AngIV analogs act via the AT4 receptor subtype which may coincide with the hepatocyte growth factor/c-Met receptor system. Finally, future research directions are described concerning new approaches to the treatment of these two neurological diseases.

Modulation of 5-lipoxygenase in proteotoxicity and Alzheimer's disease

The accumulation of intracellular β amyloid (Aβ) may be one of the factors leading to neuronal cell death in Alzheimer's disease (AD). Using a pyrazole called CNB-001, which was selected for its ability to reduce intracellular Aβ, we show that the activation of the eIF2α/ATF4 arm of the unfolded protein response is sufficient to degrade aggregated intracellular Aβ. CNB-001 is a potent inhibitor of 5-lipoxygenase (5-LOX), decreases 5-LOX expression, and increases proteasome activity. 5-LOX inhibition induces eIF2α and PERK (protein kinase R-like extracellular signal-regulated kinase) phosphorylation, and HSP90 and ATF4 levels. When fed to AD transgenic mice, CNB-001 also increases eIF2α phosphorylation and HSP90 and ATF4 levels, and limits the accumulation of soluble Aβ and ubiquitinated aggregated proteins. Finally, CNB-001 maintains the expression of synapse-associated proteins and improves memory. Therefore, 5-LOX metabolism is a key element in the promotion of endoplasmic reticulum dysfunction, and its inhibition under conditions of stress is sufficient to reduce proteotoxicity both in vivo and in vitro.

J-147 a Novel Hydrazide Lead Compound to Treat Neurodegeneration: CeeTox™ Safety and Genotoxicity Analysis

J-147 is a broad spectrum neuroprotective phenyl hydrazide compound with significant neurotrophic properties related to the induction of brain-derived neurotrophic factor (BDNF). Because this molecule is pleiotropic, it may have substantial utility in the treatment of a wide range of neurodegenerative diseases including acute ischemic stroke (AIS), traumatic brain injury(TBI), and Alzheimer’s disease(AD) where both neuroprotection and neurotrophism would be beneficial. Because of the pleiotropic actions of J-147, we sought to determine the safety profile of the drug using multiple assay analysis.

For CeeTox analyses, we used a rat hepatoma cell line (H4IIE) resulted in estimated C_Tox value (i.e.: sustained concentration expected to produce toxicity in a 14 day repeat dosing study) of 90 μM for J-147. The CeeTox panel shows that J-147 produced some adverse effects on cellular activities, in particular mitochondrial function, but only with high concentrations of the drug. J-147 was also not genetoxic with or without Aroclor-1254 treatment.

For J-147, based upon extensive neuroprotection assay data previously published, and the CeeTox assay (C_Tox value of 90 μM) in this study, we estimated in vitro neuroprotection efficacy (EC₅₀ range 0.06–0.115 μM)/toxicity ratio is 782.6–1500 fold and the neurotrophism (EC₅₀ range 0.025 μM)/toxicity ratio is 3600, suggesting that there is a significant therapeutic safety window for J-147 and that it should be further developed as a novel neuroprotective-neurotrophic agent to treat neurodegenerative disease taking into account current National Institute of Neurological Disorders and Stroke (NINDS) RIGOR guidelines.