Recent breakthroughs in neuroscience have led to the awareness that we should revise our traditional mode of thinking and studying the CNS, i.e. by isolating the privileged network of "intelligent" ...synaptic contacts. We may instead need to contemplate all the variegate communications occurring between the different neural cell types, and centrally involving the astrocytes. Basically, it appears that a single astrocyte should be considered as a core that receives and integrates information from thousands of synapses, other glial cells and the blood vessels. In turn, it generates complex outputs that control the neural circuitry and coordinate it with the local microcirculation. Astrocytes thus emerge as the possible fulcrum of the functional homeostasis of the healthy CNS. Yet, evidence indicates that the bridging properties of the astrocytes can change in parallel with, or as a result of, the morphological, biochemical and functional alterations these cells undergo upon injury or disease. As a consequence, they have the potential to transform from supportive friends and interactive partners for neurons into noxious foes. In this review, we summarize the currently available knowledge on the contribution of astrocytes to the functioning of the CNS and what goes wrong in various pathological conditions, with a particular focus on Amyotrophic Lateral Sclerosis, Alzheimer's Disease and ischemia. The observations described convincingly demonstrate that the development and progression of several neurological disorders involve the de-regulation of a finely tuned interplay between multiple cell populations. Thus, it seems that a better understanding of the mechanisms governing the integrated communication and detrimental responses of the astrocytes as well as their impact towards the homeostasis and performance of the CNS is fundamental to open novel therapeutic perspectives.
Abstract For decades, astrocytes have been regarded as passive partners of neurons in central nervous system (CNS) function. Studies of the last 20 years, however, challenged this view by ...demonstrating that astrocytes possess functional receptors for neurotransmitters and respond to their stimulation via release of gliotransmitters, including glutamate. Notably, astrocytes react to synaptically released neurotransmitters with intracellular calcium (Ca2+ ) elevations, which result in the release of glutamate via regulated exocytosis and, possibly, other mechanisms. These findings have led to a new concept of neuron–glia intercommunication where astrocytes play an unsuspected dynamic role by integrating neuronal inputs and modulating synaptic activity. The additional observation that glutamate release from astrocytes is controlled by molecules linked to inflammatory reactions, such as the cytokine tumor necrosis factor α (TNFα) and prostaglandins (PGs), suggests that glia-to-neuron signalling may be sensitive to changes in the production of these mediators occurring in pathological conditions. Indeed, a local, parenchymal brain inflammatory reaction (neuroinflammation) characterized by astrocytic and microglial activation has been reported in several neurodegenerative disorders, including AIDS dementia complex, Alzheimer's disease and amyotrophic lateral sclerosis. This transition may be accompanied by functional de-regulation and even degeneration of the astrocytes with the consequent disruption of the cross-talk normally occurring between these cells and neurons. Incorrect neuron–astrocyte interactions may be involved in neuronal derangement and contribute to disease development. The findings reported in this review suggest that a better comprehension of the glutamatergic interplay between neurons and astrocytes may provide information about normal brain function and also highlight potential molecular targets for therapeutic interventions in pathology.
Dihydrofolate reductase inhibitors are an important class of drugs, as evidenced by their use as antibacterial, antimalarial, antifungal, and anticancer agents. Progress in understanding the ...biochemical basis of mechanisms responsible for enzyme selectivity and antiproliferative effects has renewed the interest in antifolates for cancer chemotherapy and prompted the medicinal chemistry community to develop novel and selective human DHFR inhibitors, thus leading to a new generation of DHFR inhibitors. This work summarizes the mechanism of action, chemical, and anticancer profile of the DHFR inhibitors discovered in the last six years. New strategies in DHFR drug discovery are also provided, in order to thoroughly delineate the current landscape for medicinal chemists interested in furthering this study in the anticancer field.
Astrocytes fulfil several functions that collectively contribute to maintain the optimal microenvironment for neuronal function and survival. The multiplicity and complexity of these activities ...clearly indicates that the correct performance of astrocytes is crucial for the physiological functioning of the nervous system, and its derangement may contribute to the occurrence and progression of many neurological disorders. Although rectifying astrocyte malfunction has successfully counteracted disease pathogenesis and outcome in many preclinical settings, the translation of this revolutionary approach into clinical practice urges the development of innovative, safe, and effective systems for both the selective delivery of therapeutics to the astrocytes and astrocyte replacement strategies.
Single-cell RNA sequencing is redefining the concept of astrocyte diversity at the molecular level. The clarification of astrocyte heterogeneity has important implications for the comprehension of central nervous system (CNS) physiopathology.Astrocytes have emerged as primary players in the mechanisms of neurodegeneration and the progression of several neurological disorders.Viral vectors, nanoformulations, and peptide-based treatments for the selective targeting of harmful pathways in astrocytes are being developed and hold potential for the treatment of neurological disorders in preclinical modelsEngrafted healthy astrocytes can survive in a pathological milieu and improve the phenotype of animal models of CNS disorders. This raises the expectation of astroglial cell transplantation as a valuable therapeutic tool.
Abstract The identification of novel molecular targets crucially involved in motor neuron degeneration/survival is a necessary step for the development of hopefully more effective therapeutic ...strategies for amyotrophic lateral sclerosis (ALS) patients. In this view, S1R, an endoplasmic reticulum (ER)-resident receptor with chaperone-like activity, has recently attracted great interest. S1R is involved in several processes leading to acute and chronic neurodegeneration, including ALS pathology. Treatment with the S1R agonist PRE-084 improves locomotor function and motor neuron survival in presymptomatic and early symptomatic mutant SOD1-G93A ALS mice. Here, we tested the efficacy of PRE-084 in a model of spontaneous motor neuron degeneration, the wobbler mouse (wr) as a proof of concept that S1R may be regarded as a key therapeutic target also for ALS cases not linked to SOD1 mutation. Increased staining for S1R was detectable in morphologically spared cervical spinal cord motor neurons of wr mice both at early (6th week) and late (12th week) phases of clinical progression. S1R signal was also detectable in hypertrophic astrocytes and reactive microglia of wr mice. Chronic treatment with PRE-084 (three times a week, for 8 weeks), starting at symptom onset, significantly increased the levels of BDNF in the gray matter, improved motor neuron survival and ameliorated paw abnormality and grip strength performance. In addition, the treatment significantly reduced the number of reactive astrocytes whereas, that of CD11b + microglial cells was increased. A deeper evaluation of microglial markers revealed significant increased number of cells positive for the pan-macrophage marker CD68 and of CD206 + cells, involved in tissue restoration, in the white matter of PRE-084-treated mice. The mRNA levels of TNF-α and IL-1β were not affected by PRE-084 treatment. Thus, our results support pharmacological manipulation of S1R as a promising strategy to cure ALS and point to increased availability of growth factors and modulation of astrocytosis and of macrophage/microglia as part of the mechanisms involved in S1R-mediated neuroprotection.
Astrocytes have emerged as critical elements for the maintenance and function of the central nervous system. The expression on their cell membrane of RAGE and TLR4 receptors makes astrocytes ...susceptible to High-mobility group box 1 (HMGB1), a nuclear protein typically released in the extracellular milieu by living cells experiencing physiological stress conditions or by damaged cells. Here, we show that the interaction of HMGB1 with normal spinal cord astrocytes induces the astrocytic production of neurotrophic factors, particularly brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF). Multiple investigations suggest a role for HMGB1 in amyotrophic lateral sclerosis (ALS). Yet, no mechanistic information on the implication of HMGB1 signaling in this disorder is currently available. We demonstrate that non-transgenic and transgenic SOD1
spinal motor neurons exhibit only a basal nucleus-to-cytoplasm shuttling of the HMGB1 protein. Conversely, in SOD1
ALS mouse spinal cords, HMGB1 significantly translocates from the nucleus to the cytoplasm of motor neurons, thereby suggesting that it may be eventually released in the extracellular environment during the progression of the disease. We postulate that extracellular HMGB1 can paracrinally interact with the neighboring astrocytes in an attempt to counteract the neurodegenerative process. Yet, at variance with normal cells, SOD1
-expressing astrocytes show impaired capacity to raise BDNF and GDNF levels upon HMGB1 stimulation. Our data suggest that HMGB1 have a potential to promote neuroprotective actions by healthy astrocytes. However, this neurotrophic response is disrupted in ALS astrocytes. This indicates that diseased astroglial cells may exacerbate motor neuron degeneration in ALS because of the loss of their neurosupportive functions.
Physical inactivity is common in patients with chronic kidney disease (CKD) and is an important modifiable risk factor for mortality, morbidity, and reduced quality of life. The present single-centre ...pilot study evaluated the possibility of performing structured physical exercise using a specific walking model, Fitwalking, in a population of patients with CKD and, according to the American College of Rheumatology guidelines, also in a population with immuno-rheumatological disease.INTRODUCTIONPhysical inactivity is common in patients with chronic kidney disease (CKD) and is an important modifiable risk factor for mortality, morbidity, and reduced quality of life. The present single-centre pilot study evaluated the possibility of performing structured physical exercise using a specific walking model, Fitwalking, in a population of patients with CKD and, according to the American College of Rheumatology guidelines, also in a population with immuno-rheumatological disease.Patients were recruited from nephrology, haemodialysis, peritoneal dialysis, transplantation, and immuno-rheumatology outpatient clinics. After general and functional clinical evaluation and exercise prescription at the Department of Sports Medicine, we performed scientifically proven tests on CKD (6-min walk test and sit-to-stand test), before and after the Fitwalking technique training course, and again after 6 and 12 months, evaluated its effectiveness and identify any critical issues.METHODSPatients were recruited from nephrology, haemodialysis, peritoneal dialysis, transplantation, and immuno-rheumatology outpatient clinics. After general and functional clinical evaluation and exercise prescription at the Department of Sports Medicine, we performed scientifically proven tests on CKD (6-min walk test and sit-to-stand test), before and after the Fitwalking technique training course, and again after 6 and 12 months, evaluated its effectiveness and identify any critical issues.We enrolled 80 patients (41 males, 51.2%), with a mean age of 53 ± 12 years; the clinical data showed statistically significant improvements in systolic, average, and differential blood pressure, average speed, and physical strength. Participants also adapted to muscle fatigue, experienced a reduction in BMI with stable lean mass and reduced fat mass, and reported improved perceptions of physical and mental health, and quality of life.RESULTSWe enrolled 80 patients (41 males, 51.2%), with a mean age of 53 ± 12 years; the clinical data showed statistically significant improvements in systolic, average, and differential blood pressure, average speed, and physical strength. Participants also adapted to muscle fatigue, experienced a reduction in BMI with stable lean mass and reduced fat mass, and reported improved perceptions of physical and mental health, and quality of life.All enrolled patients successfully completed the process. A specific prescription was used that provided health education and allowed for the implementation of structured physical activity that could be performed safely and independently even after the training period. The activity was sustainable thanks to the training of in-house medical and nursing staff, demonstrating that it is possible to overcome this type of barrier to physical activity in CKD and in immuno-rheumatological patients.CONCLUSIONAll enrolled patients successfully completed the process. A specific prescription was used that provided health education and allowed for the implementation of structured physical activity that could be performed safely and independently even after the training period. The activity was sustainable thanks to the training of in-house medical and nursing staff, demonstrating that it is possible to overcome this type of barrier to physical activity in CKD and in immuno-rheumatological patients.
Despite indisputable progress in the molecular and genetic aspects of amyotrophic lateral sclerosis (ALS), a mechanistic comprehension of the neurodegenerative processes typical of this disorder is ...still missing and no effective cures to halt the progression of this pathology have yet been developed. Therefore, it seems that a substantial improvement of the outcome of ALS treatments may depend on a better understanding of the molecular mechanisms underlying neuronal pathology and survival as well as on the establishment of novel etiological therapeutic strategies. Noteworthy, a convergence of recent data from multiple studies suggests that, in cellular and animal models of ALS, a complex pathological interplay subsists between motor neurons and their non-neuronal neighbours, particularly glial cells. These observations not only have drawn attention to the physiopathological changes glial cells undergo during ALS progression, but they have moved the focus of the investigations from intrinsic defects and weakening of motor neurons to glia–neuron interactions. In this review, we summarize the growing body of evidence supporting the concept that different glial populations are critically involved in the dreadful chain of events leading to motor neuron sufferance and death in various forms of ALS. The outlined observations strongly suggest that glial cells can be the targets for novel therapeutic interventions in ALS.
Sigma1 Receptor (S1R) is involved in oxidative stress, since its activation is triggered by oxidative or endoplasmic reticulum stress. Since specific aquaporins (AQP), called peroxiporins, play a ...relevant role in controlling H2O2 permeability and ensure reactive oxygen species wasted during oxidative stress, we studied the effect of S1R modulators on AQP-dependent water and hydrogen peroxide permeability in the presence and in the absence of oxidative stress. Applying stopped-flow light scattering and fluorescent probe methods, water and hydrogen peroxide permeability in HeLa cells have been studied. Results evidenced that S1R agonists can restore water permeability in heat-stressed cells and the co-administration with a S1R antagonist totally counteracted the ability to restore the water permeability. Moreover, compounds were able to counteract the oxidative stress of HeLa cells specifically knocked down for S1R. Taken together these results support the hypothesis that the antioxidant mechanism is mediated by both S1R and AQP-mediated H2O2 permeability. The finding that small molecules can act on both S1R and AQP-mediated H2O2 permeability opens a new direction toward the identification of innovative drugs able to regulate cell survival during oxidative stress in pathologic conditions, such as cancer and degenerative diseases.
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