Insulin-like growth factor-1 (IGF-1) elicits a variety of effects on the regulation of oxidative stress, a topic that remains shrouded in controversy. This intricate regulation plays a pivotal role in the aging process and its associated diseases. Notably, it centers around the challenge posed by endogenous antioxidant defenses, which often struggle to counteract free radicals-induced damage to various neural cell macromolecules. The interplay between IGF-1 and oxidative stress holds significant implications. Both factors are intertwined in the context of degenerative and inflammatory disruptions within the central nervous system (CNS), giving rise to dysfunctions in neurons and glial cells. These dysfunctions encompass detrimental outcomes such as excitotoxicity, neuronal attrition, and axonal impairment, all of which are closely related to behavioral irregularities. However, the complexities of IGF-1’s impact remain a topic of debate. Divergent research findings present IGF-1 as both an antioxidative agent and a catalyst to produce reactive oxygen species (ROS) in various neuropathologies. This diversity of outcomes has contributed to the ongoing controversy in the field. The present theoretical review undertakes a comprehensive vision, shedding light on the role of IGF-1 as a regulator within the mechanistic framework of oxidative stress responses. This regulatory role serves as the basis for the emergence of progressive neurodegenerative and neuroinflammatory conditions. Particularly compelling is the exploration of IGF-1 as a potential target for promising therapeutic interventions in this domain. However, the review also highlights significant limitations, including the considerations to work with this factor and the need for further research to clarify IGF-1’s role. Future perspectives should focus on refining our understanding of IGF-1’s mechanisms and exploring its therapeutic potential in more detail.

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.