Alzheimer’s disease (AD) is a progressive and incurable neurodegenerative disorder, with an unknown etiology and a multifactorial pathophysiology characterized by protein misfolding, neuroinflammation, and neuronal loss. There are three well-discussed main hypotheses for the pathophysiology of AD, which are related to i) the accumulation of amyloid β (Aβ) protein aggregates in the extracellular space, ii) deposition of hyperphosphorylated tau fragments as neurofibrillary tangles, and iii) dysregulation of hemostasis of some neurotransmitters involved in the disease, such as acetylcholine (ACh) and glutamate. The association of all these factors is responsible for installing oxidative stress and neuroinflammation, which contribute to progressive neuronal death in specific brain regions. More recently, other remarkable pathological characteristics have been described, involving changes in all levels of cellular components, especially in the action and function of protein kinases. These enzymes are crucial for cellular regulation since they play a pivotal role in the phosphorylation of protein substrates by transferring a phosphate group from the ATP molecule to threonine, serine, or tyrosine residues. In more recent studies, some kinases have been especially reported by their role in inflammatory and oxidative processes associated to AD, such as cAMP-dependent protein kinase A (PKA), cyclin-dependent protein kinase 5 (CDK5), glycogen synthase kinase 3β (GSK-3β), and the microtubule affinity regulatory kinases (MARKs). Under homeostatic conditions, protein kinases act as cellular signals, directing physiological responses, but in AD pathogenesis, these enzymes have an exacerbated activity in the brain, justifying the need for a better comprehension of their function and role, and how new kinase inhibitors could lead to innovative drugs. In this context, this brief review aimed to compile the literature data related to the most recent efforts and strategies in Medicinal Chemistry in the discovery of new kinase inhibitors, opening new ways to AD therapeutics.

Alzheimer’s disease (AD) is the leading cause of dementia worldwide. The disease is characterized by the abnormal accumulation of amyloid β (Aβ) protein creating neuritic plaques, hyperphosphorylated tau (p-tau) protein forming intracellular tangles, and neuronal degeneration. Pathological changes related to abnormal Aβ and p-tau accumulation may begin more than fifteen years before the clinical diagnosis of AD is made. The glymphatic system is the brain’s waste clearance pathway that prevents the accumulation of these abnormal proteins and macromolecules. Glymphatic clearance is negatively affected by physiological conditions such as sleep deprivation, and pathological conditions such as traumatic brain injury and hemorrhagic strokes. These physiological and pathological conditions are strong risk factors for AD. In conclusion, impaired glymphatic clearance is an important pathogenetic mechanism for AD.

Alzheimer’s disease continuum has been described as the progressive stages of the disease over a long period. This progression can be categorized into three main stages: preclinical, mild cognitive impairment (MCI), and dementia. It has been suggested that there is a bidirectional relationship between the preclinical stage and MCI, but not between dementia and the earlier stages. The stage of MCI should be further analyzed, especially in cases where there is a reversion from MCI to a normal cognitive condition. The mechanisms behind this reversion deserve further investigation to differentiate true reversion from compensatory mechanisms. Analyzing reversion in greater detail could help identify potential therapies aimed at preventing or delaying the onset of dementia. As indicated, the primary focus has been on research indicating that MCI can revert to normal cognition. This reversion can occur by addressing risk factors through lifestyle changes, although a novel mechanism involving a transient functional compensation process in response to cognitive impairment should be also taken into account.

Excitotoxicity represents a neuropathological process, describing the toxic actions of excitatory neurotransmitters, where the excessive or prolonged activation of glutamate receptors triggers a cascade of events leading to neuronal injury or death. Under conditions of reduced energy availability and increased oxidative stress neurons become particularly vulnerable to excitotoxicity and a large body of available evidence indicates that excitotoxicity represents a central mechanism in the pathogenesis of acute and degenerative diseases of the central nervous system. Astrocytes represent key elements in the regulation of glutamate homeostasis by their opposing functions of glutamate uptake and release, and microglial cells play an important role in the response to damage. Depending on the phenotype they assume when activated, microglial cells can trigger immune defense or neuroprotective processes. To perform their functions both glial cell populations monitor the extracellular space through a panel of receptors. Furthermore, a variety of signaling pathways also contribute to the modulation of the glutamatergic transmission, acting on specific cell receptors expressed by neurons, astrocytes, and microglia. In the last decades, evidence has been provided that receptors of almost all families can establish structural receptor-receptor interactions, leading to the formation of heteroreceptor complexes at the cell membrane of neurons and glial cells. The cooperativity that emerges in the actions of ligands of the monomers forming these assemblies provides the cell decoding apparatus with flexible dynamics in terms of recognition and signal transduction and allows an integration of the incoming signals already at the membrane level. Available data on possible modulatory roles played by heteroreceptor complexes in excitotoxic processes will be here reviewed and discussed. From the pharmacological standpoint, these findings may offer possibilities to explore novel therapeutic strategies targeting receptor complexes to address disorders of the central nervous system associated with dysregulation of glutamatergic signaling.

The central nervous system (CNS) is one of the most complex physiological systems, and treatment of CNS disorders represents an area of major medical need. One critical aspect of the CNS is its lack of regeneration, such that damage is often permanent. The damage often leads to neurodegeneration, and so strategies for neuroprotection could lead to major medical advances. The G protein-coupled receptor (GPCR) family is one of the major receptor classes, and they have been successfully targeted clinically. One class of GPCRs is those activated by bioactive lysophospholipids as ligands, especially sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA). Research has been increasingly demonstrating the important roles that S1P and LPA, and their receptors, play in physiology and disease. In this review, I describe the role of S1P and LPA receptors in neurodegeneration and potential roles in neuroprotection. Much of our understanding of the role of S1P receptors has been through pharmacological tools. One such tool, fingolimod (also known as FTY720), which is a S1P receptor agonist but a functional antagonist in the immune system, is clinically efficacious in multiple sclerosis by producing a lymphopenia to reduce autoimmune attacks; however, there is evidence that fingolimod is also neuroprotective. Furthermore, fingolimod is neuroprotective in many other neuropathologies, including stroke, Parkinson’s disease, Huntington’s disease, Rett syndrome, Alzheimer’s disease, and others that are discussed here. LPA receptors also appear to be involved, being upregulated in a variety of neuropathologies. Antagonists or mutations of LPA receptors, especially LPA₁, are neuroprotective in a variety of conditions, including cortical development, traumatic brain injury, spinal cord injury, stroke and others discussed here. Finally, LPA receptors may interact with other receptors, including a functional interaction with plasticity related genes.

Neuroinflammation can be caused by disease, aging, infection, brain injury, toxicity, or stress. It is a contributory factor in the neuropathology of serious conditions that include multiple sclerosis (MS), Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis (ALS), and autoimmune encephalomyelitis (EAE). The neuroinflammatory response involves the activation of microglia, astrocytes, the endothelial cells of the blood-brain barrier, and peripherally-derived immune cells. The endocannabinoid system is composed of the natural cannabinoids, anandamide and 2-arachidonoyl glycerol (2-AG), enzymes regulating their synthesis/catabolism, and the cannabinoid CB₁ and CB₂ receptors. It regulates multiple systems in the body including inflammation and endocannabinoid system dysregulation is involved in numerous inflammatory conditions. The Cannabis sativa plant produces over 100 phytocannabinoids, some of which interact with the endocannabinoid system. The major phytocannabinoids are delta-9-tetrahydrocannabinol (delta-9-THC), cannabidiol (CBD), and cannabigerol (CBG). Compelling evidence is emerging that many phytocannabinoids have anti-inflammatory and antioxidant properties. Phytocannabinoids including delta-9-THC, CBD, and CBG bind to a wide variety of targets in the endocannabinoid and/or other systems, which probably accounts for their diversity of effects in non-clinical and clinical studies. The benefits of certain phytocannabinoids have been proven by regulatory approval for medical use of CBD (Epidiolex^®), chemically synthesized delta-9-THC (Marinol^® and Syndros^®) and 1:1 delta-9-THC/CBD (Sativex^®). Furthermore, the widely recognized therapeutic properties of Cannabis have been a key driver in legalizing the medical use of Cannabis in 38 USA states. In this review, the potential of phytocannabinoids as effective treatments in neuroinflammatory disorders is discussed based on a critical evaluation of the non-clinical and clinical evidence. We focused on delta-9-THC, CBD, and CBG because they are the most abundant phytocannabinoids in Cannabis sativa and a substantial body of scientific data exists to describe their respective pharmacological mechanisms.

To quantitatively analyze the effects of acoustic neurostimulation on the symptoms of depression, anxiety, stress, and sleep quality in healthy workers. Eleven physiological and psychological variables (V1–V11) representing stress levels, sleep quality, and cortisol levels were acquired from a recent article (https://doi.org/10.37349/ent.2023.00064) that analyzed the effects of brainwave entrainment (BWE) techniques—binaural beats (BB), isochronic tones (IT), or a combination of the two (BB + IT). Principal component analysis (PCA) was used to create principal components to analyze the contribution of each variable to the efficacy. A thermodynamic cycle and equations based on a Venn diagram were used to understand the differences in treatment effectiveness in individual and combined auditory stimulations. PCA reduced the dimensionality of variables from eleven to three. PC1 represented auditory treatment efficacy, while neither PC2 nor PC3 did. All eleven variables had a negative correlation to PC1, with stress (V3) showing the most negative correlation and salivary cortisol level (V11) showing the least. Treatments using BB were more effective than treatments with IT or BB + IT. PCA successfully aided in the analysis of auditory treatment efficacies. All examined variables, especially the stress scale (V3), had a negative correlation in treatment efficacy, aligning with the results of the original paper. Analysis using the thermodynamic cycle and Venn diagram based on PCA provided an explanation why a combined treatment (BB + IT) was less effective than BB alone in the collective consideration of all eleven variables. This study demonstrates that the thermodynamic cycle and Venn diagram in conjunction with PCA are useful analytical tools for the quantitative analysis of multi-factor systems.

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by both non-motor and motor symptoms, due to the loss of dopamine-producing neurons in the brain. Monoamine oxidase-B (MAO-B) inhibitors are essential in the treatment of PD, as they increase dopamine levels and could potentially slow down the progression of the disease. MAO-B inhibitors block the ability of the enzyme to degrade dopamine in the brain. MAO-B inhibitors work by inhibiting this enzyme, which raises dopamine levels and helps reduce motor symptoms, such as akinesia and stiffness in the muscles. In addition to their impact on dopamine levels, MAO-B inhibitors may possess neuroprotective properties. Research indicates that these inhibitors can shield neurons from the harmful byproducts of dopamine breakdown, such as dihydroxy acetaldehyde and hydrogen peroxide. This neuroprotective effect could potentially slow the progression of PD and protect against neuronal damage. MAO-B inhibitors are effective in treating both advanced and early stages of PD. They are recommended as initial treatments for individuals with early PD and can also be used as supplementary therapy in advanced PD to assist in managing motor complications. Additionally, MAO-B inhibitors have shown promise for the treatment of non-motor symptoms of PD, such as fatigue and sleep disturbances. MAO-B inhibitors are an important class of drugs for the treatment of PD, offering both symptomatic relief and potential disease-modifying effects. The goal of ongoing research and development of MAO-B inhibitors is to enhance their safety and selectivity profiles, which could lead to improved treatment approaches for PD and other neurodegenerative disorders.

A novel concept has been recently put forward in the mind/body interface (https://doi.org/10.37349/ent.2024.00074). The new concept has led to a new word: vitaction. Vitactions offer benefits to the brain and mind comparable to the advantages vitamins provide for the body’s overall health. The field of vitactions is as it was the vitamin field one century ago, i.e., without tools to make a complete classification. I propose to classify vitactions into five categories according to the behaviours necessary to maintain balanced brain functionality. A deficit of vitactions would contribute to the enormous prevalence in developed countries of diseases ranging from type 2 diabetes to neuropsychiatric diseases. The concept should help to identify which vitactions are deficient and to outline how they can be progressively implemented to improve the quality of life. The parallelism vitactions/vitamins also extends to overdosing; both hypervitaminosis and hypervitactinosis may be detrimental. This perspective article argues that vitactions should be considered at the practical and the scientific research levels, and that a balanced vitamin and vitaction supply is essential for a better life. In addition, reasons for proposing a synonym, “vitactin”, are given.

Peripheral nerve injuries (PNIs) constitute a significant concern as they predominantly affect young and productive age groups of the population, causing social and economic pressure on patients. PNIs are a global problem that can result in disability because of the disruption of nerve function. PNI leads to a reduction in nerve conduction velocity, which worsens or impairs the mobility of the innervated area. Managing PNI remains a major clinical challenge. Coenzyme Q10 (CoQ10) is a lipid-soluble antioxidant first identified in 1957. It is an important antioxidant necessary for the organs to maintain their normal function and the body’s chemical processes. It scavenges free radicals and reduces oxidative stress. Studies showed that antioxidants such as CoQ10 a potent antioxidant, help the regeneration of PNIs. It has been observed to increase the myelination process in nerve fibres and promote nerve regeneration in rats after injury. Therefore, this review handles the current positive effects of CoQ10 on peripheral nerve regeneration following injury.