Neurotoxicity is a form of toxicity in which a biological, chemical, or physical agent produces an adverse effect on the structure or function of the central and/or peripheral nervous system. It occurs when exposure to a substance – specifically, a neurotoxin or neurotoxicant– alters the normal activity of the nervous system in such a way as to cause permanent or reversible damage to nervous tissue. This can eventually disrupt or even kill neurons, which are cells that transmit and process signals in the brain and other parts of the nervous system. Neurotoxicity can result from organ transplants, radiation treatment, certain drug therapies, recreational drug use, exposure to heavy metals, bites from certain species of venomous snakes, pesticides, certain industrial cleaning solvents, fuels and certain naturally occurring substances. Symptoms may appear immediately after exposure or be delayed. They may include limb weakness or numbness, loss of memory, vision, and/or intellect, uncontrollable obsessive and/or compulsive behaviors, delusions, headache, cognitive and behavioral problems and sexual dysfunction. Chronic mold exposure in homes can lead to neurotoxicity which may not appear for months to years of exposure. All symptoms listed above are consistent with mold mycotoxin accumulation.
Donepezil, sold under the brand name Aricept among others, is a medication used to treat dementia of the Alzheimer's type. It appears to result in a small benefit in mental function and ability to function. Use, however, has not been shown to change the progression of the disease. Treatment should be stopped if no benefit is seen. It is taken by mouth or via a transdermal patch.
Memantine is a medication used to slow the progression of moderate-to-severe Alzheimer's disease. It is taken by mouth.
Amyloid beta denotes peptides of 36–43 amino acids that are the main component of the amyloid plaques found in the brains of people with Alzheimer's disease. The peptides derive from the amyloid-beta precursor protein (APP), which is cleaved by beta secretase and gamma secretase to yield Aβ in a cholesterol-dependent process and substrate presentation. Aβ molecules can aggregate to form flexible soluble oligomers which may exist in several forms. It is now believed that certain misfolded oligomers can induce other Aβ molecules to also take the misfolded oligomeric form, leading to a chain reaction akin to a prion infection. The oligomers are toxic to nerve cells. The other protein implicated in Alzheimer's disease, tau protein, also forms such prion-like misfolded oligomers, and there is some evidence that misfolded Aβ can induce tau to misfold.
Beta-secretase 1, also known as beta-site amyloid precursor protein cleaving enzyme 1, beta-site APP cleaving enzyme 1 (BACE1), membrane-associated aspartic protease 2, memapsin-2, aspartyl protease 2, and ASP2, is an enzyme that in humans is encoded by the BACE1 gene. Expression of BACE1 is observed mainly in neurons.
The biochemistry of Alzheimer's disease, the most common cause of dementia, is not yet very well understood. Alzheimer's disease (AD) has been identified as a proteopathy: a protein misfolding disease due to the accumulation of abnormally folded amyloid beta (Aβ) protein in the brain. Amyloid beta is a short peptide that is an abnormal proteolytic byproduct of the transmembrane protein amyloid-beta precursor protein (APP), whose function is unclear but thought to be involved in neuronal development. The presenilins are components of proteolytic complex involved in APP processing and degradation.
RS-67,333 is a drug which has been investigated as a potential rapid-acting antidepressant, nootropic, and treatment for Alzheimer's disease. It is a high-affinity 5-HT4 receptor partial agonist, as well as a sigma receptor ligand of both subtypes to a lesser extent.
Homotaurine is a natural sulfonic acid found in seaweed. It is analogous to taurine, but with an extra carbon in its chain. It has GABAergic activity, apparently by mimicking GABA, which it resembles.
Solanezumab is a monoclonal antibody being investigated by Eli Lilly as a neuroprotector for patients with Alzheimer's disease. The drug originally attracted extensive media coverage proclaiming it a breakthrough, but it has failed to show promise in Phase III trials.
Cholinesterase inhibitors (ChEIs), also known as anti-cholinesterase, are chemicals that prevent the breakdown of the neurotransmitter acetylcholine or butyrylcholine. This increases the amount of the acetylcholine or butyrylcholine in the synaptic cleft that can bind to muscarinic receptors, nicotinic receptors and others. This group of inhibitors is divided into two subgroups, acetylcholinesterase inhibitors (AChEIs) and butyrylcholinesterase inhibitors (BChEIs).
PHA-543,613 is a drug that acts as a potent and selective agonist for the α7 subtype of neural nicotinic acetylcholine receptors, with a high level of brain penetration and good oral bioavailability. It is under development as a possible treatment for cognitive deficits in schizophrenia. It reduces excitotoxicity and protects striatal dopaminergic neurons in rat models. It also potentiates cognitive enhancement from memantine, decreases dynorphin release and inhibits GSK-B3.
CI-1017 is a muscarinic acetylcholine receptor agonist which is selective for and is approximately equipotent at the M1 and M4 receptors, with 20-30-fold lower affinity for the M2, M3, and M5 subtypes It is the (R)-enantiomer of the racemic compound PD-142,505.
Rudolph Emile 'Rudy' Tanzi is the Joseph P. and Rose F. Kennedy Professor of Neurology at Harvard University, Vice-chair of Neurology, Director of the Genetics and Aging Research Unit, and co-director of the Henry and Allison McCance Center for Brain Health at Massachusetts General Hospital (MGH). Dr. Tanzi has been investigating the genetics of neurological disease since the 1980s when he participated in the first study that used genetic markers to find a disease gene. Dr. Tanzi co-discovered all three familial early-onset Alzheimer's disease (FAD) genes and several other neurological disease genes including that responsible for Wilson’s disease. As the leader of the Cure Alzheimer's Fund Alzheimer's Genome Project, Dr. Tanzi has carried out multiple genome wide association studies of thousands of Alzheimer's families leading to the identification of novel AD candidate genes, including CD33 and the first two rare mutations causing late-onset AD in the ADAM10 gene. His research on the role of zinc and copper in AD has led to clinical trials at Prana Biotechnology. He is also working on gamma secretase modulators for the prevention and treatment of Alzheimer's. He also serves as Chair of the Cure Alzheimer's Fund Research Leadership Group and Director the Cure Alzheimer's Fund Alzheimer's Genome Project™.
Nitromemantine is a derivative of memantine developed in 2006 for the treatment of Alzheimer's disease. It has been shown to reduce excitotoxicity mediated by over-activation of the glutamatergic system, by blocking NMDA receptors.
A cholinergic neuron is a nerve cell which mainly uses the neurotransmitter acetylcholine (ACh) to send its messages. Many neurological systems are cholinergic. Cholinergic neurons provide the primary source of acetylcholine to the cerebral cortex, and promote cortical activation during both wakefulness and rapid eye movement sleep. The cholinergic system of neurons has been a main focus of research in aging and neural degradation, specifically as it relates to Alzheimer's disease. The dysfunction and loss of basal forebrain cholinergic neurons and their cortical projections are among the earliest pathological events in Alzheimer's disease.
The ion channel hypothesis of Alzheimer’s disease (AD), also known as the channel hypothesis or the amyloid beta ion channel hypothesis, is a more recent variant of the amyloid hypothesis of AD, which identifies amyloid beta (Aβ) as the underlying cause of neurotoxicity seen in AD. While the traditional formulation of the amyloid hypothesis pinpoints insoluble, fibrillar aggregates of Aβ as the basis of disruption of calcium ion homeostasis and subsequent apoptosis in AD, the ion channel hypothesis in 1993 introduced the possibility of an ion-channel-forming oligomer of soluble, non-fibrillar Aβ as the cytotoxic species allowing unregulated calcium influx into neurons in AD.
Early long-term potentiation (E-LTP) is the first phase of long-term potentiation (LTP), a well-studied form of synaptic plasticity, and consists of an increase in synaptic strength. LTP could be produced by repetitive stimulation of the presynaptic terminals, and it is believed to play a role in memory function in the hippocampus, amygdala and other cortical brain structures in mammals.
Phenserine is a synthetic drug which has been investigated as a medication to treat Alzheimer's disease (AD), as the drug exhibits neuroprotective and neurotrophic effects.
Neurotrophin mimetics are small molecules or peptide like molecules that can modulate the action of the neurotrophin receptor. One of the main causes of neurodegeneration involves changes in the expression of neurotrophins (NTs) and/or their receptors. Indeed, these imbalances or changes in their activity, lead to neuronal damage resulting in neurological and neurodegenerative conditions. The therapeutic properties of neurotrophins attracted the focus of many researchers during the years, but the poor pharmacokinetic properties, such as reduced bioavailability and low metabolic stability, the hyperalgesia, the inability to penetrate the blood–brain barrier and the short half-lives render the large neurotrophin proteins not suitable to be implemented as drugs.
Buntanetap is an orally-administered small molecule inhibitor of several neurotoxic proteins that is under investigation in the treatment of Alzheimer's disease, frontotemporal dementia, chronic traumatic encephalopathy and Parkinson's disease. It is the (+) enantiomer of phenserine, as the (-) enantiomer also has unwanted anticholinergic effects. It is currently in phase III trials for the treatment of Parkinson's.
