New Alzheimer Disease Drugs, Long COVID and the Central Nervous System, and a Nasal Spray for Migraines-Highlights From the 2023 American Academy of Neurology Conference.

This Medical News article discusses research presented at the recent American Academy of Neurology Conference.

Neuroinvasion and Neurotropism by SARS-CoV-2 Variants in the K18-hACE2 Mouse.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) not only affects the respiratory tract but also causes neurological symptoms such as loss of smell and taste, headache, fatigue or severe cerebrovascular complications. Using transgenic mice expressing human angiotensin-converting enzyme 2 (hACE2), we investigated the spatiotemporal distribution and pathomorphological features in the CNS following intranasal infection with SARS-CoV-2 variants, as well as after prior influenza A virus infection. Apart from Omicron, we found all variants to frequently spread to and within the CNS. Infection was restricted to neurons and appeared to spread from the olfactory bulb mainly in basally oriented regions in the brain and into the spinal cord, independent of ACE2 expression and without evidence of neuronal cell death, axonal damage or demyelination. However, microglial activation, microgliosis and a mild macrophage and T cell dominated inflammatory response was consistently observed, accompanied by apoptotic death of endothelial, microglial and immune cells, without their apparent infection. Microgliosis and immune cell apoptosis indicate a potential role of microglia for pathogenesis and viral effect in COVID-19 and the possible impairment of neurological functions, especially in long COVID. These data may also be informative for the selection of therapeutic candidates and broadly support the investigation of agents with adequate penetration into relevant regions of the CNS.

Progressive Worsening of Neurological Manifestations in HIV-Associated Opportunistic Central Nervous System (CNS) Infection Patients After COVID-19 Vaccinations: A Possible Co-Incidence Causality.

BACKGROUND The iceberg phenomenon (in which the most of a problem is invisible) of people living with HIV/AIDS, particularly those with unknown HIV status, has been epidemiologically challenging. Central nervous system (CNS) opportunistic infections in patients with HIV/AIDS are one of the leading causes of morbidity and mortality in people living with HIV/AIDS. There are currently limited data on the immunogenicity, safety, and efficacy of COVID-19 vaccines in people living with HIV/AIDS with its associated opportunistic CNS infections as well as those without antiretroviral treatment. CASE REPORT Two young men with previously unknown HIV status and its related opportunistic infections received their first doses of COVID-19 vaccine (Vero Cell), inactivated. Both patients had the risk factor of having sex with men (men who have sex with men). Fever and first neurological symptoms occurred within the first few days after vaccination. Both patients were hospitalized and were tested positive for HIV for the first time. Both were further diagnosed from brain imaging as having CNS opportunistic infections. A presumptive diagnosis of cerebral toxoplasmosis was established as the working diagnosis according to the laboratory and epidemiological factors. Despite the treatment, neurological and clinical deficits worsened and eventually led to death in both patients. CONCLUSIONS The causality analyses showed that both adverse events had a possible inconsistent causal relationship to COVID-19 vaccination. Our cases may reflect the need for further studies on the safety of COVID-19 vaccines in people with HIV/AIDS-associated CNS opportunistic infection as well as people with HIV/AIDS who never receive antiretroviral treatment (ART).

Eficacia y seguridad sobre el uso de Tiotepa como acondicionamiento mieloablativo, en pacientes pediátricos y adultos con leucemia linfoblástica aguda con compromiso del sistema nervioso central, con donante HLA idéntico para Trasplante de progenitores hematopoyéticos alogénico emparentado / Efficacy and safety on the use of Thiotepa as myeloablative conditioning, in pediatric and adult patients with central nervous system acute lymphoblastic leukemia, HLA-matched donor for Allogeneic Related Hematopoietic Stem Cell Transplantation

ANTECECENTES: Las leucemias en general son los desórdenes malignos oncohematológicos más comunes que afectan a la población. Las leucemias de linaje linfoide son más frecuentes que las leucemias mieloides. Las leucemias linfoides reciben un tratamiento inicial con quimioterapia de inducción, consolidación y posterior mantenimiento. Sin embargo, tenemos leucemias de alto riesgo o leucemias en recaída con compromiso del sistema nervioso central, que luego de haber alcanzado una respuesta adecuada al tratamiento de inducción o reinducción, se debe optimizar el manejo de acondicionamiento para llegar a un trasplante alogénico de células progenitoras hematopoyeticas. A nivel mundial en el año 2018, las leucemias ocuparon la ubicación 15 de los canceres más frecuentemente diagnosticados, con un total de 437,033 casos; y en relación a mortalidad ocupo el lugar 11, con 309,006 fallecimientos. En Perú, en el periodo 2013-2015 ocurrieron 2047 casos nuevos de leucemia entre los residentes de Lima Metropolitana, con una tasa de incidencia estandarizada de 7,1 casos por 100 000 habitantes. Dichas leucemias representan el 2.9% de todas las neoplasias malignas. Con una incidencia total de cáncer en pacientes pediátricos en el periodo 2013-2015 de 209,4 por millón para los niños y 284,7 por millón para las niñas, dando una relación de niños a niñas de 1,2:1. Se tiene que la incidencia de leucemias en pacientes pediátricos ocupa el primer lugar. Más de un tercio (39,8%) de todas las neoplasias malignas en los niños son leucemias. TECNOLOGÍA: Dentro de los esquemas de acondicionamiento tenemos los que son mieloablativos y los no mieloablativos. Sin embargo, al momento no existe un régimen de acondicionamiento estándar. En la presente ETS se considera la evaluación de un agente alquilante, Tiotepa, como parte de uno de los regímenes de tratamiento en pacientes pediátricos y adultos con leucemia linfoblástica aguda de alto riesgo o en recaída con compromiso del sistema nervioso central, que tengan donante HLA idéntico para trasplante de células progenitoras hematopoyéticas alogénico emparentado. El Tiotepa es un agente antineoplásico alquilante, con una acción radiomimética, liberando radicales de etilenimina, similares a la terapia de radiación, rompiendo los enlaces del ADN. Tiene la capacidad de cruzar la barrera hematoencefálica, alcanzando misma concentración en LCR como en plasma. METODOLOGÍA: Se ha realizado una búsqueda sistemática en la base de datos Medline a través de PubMed, y se encontró: un estudio fase 3, prospectivo, multicéntrico, aleatorizado, de no inferioridad y dos estudios observacionales de reportes de casos, donde se realizó comparación sobre el uso de Tiotepa versus Irradiación corporal total (TBI), evidenciando beneficio en sobrevida global y sobrevida libre de eventos para el uso de TBI (Irradiación Corporal Total); sin embargo el acondicionamiento de Fludarabina, Tiotepa y Busulfan/Treosulfan es una alternativa valiosa para pacientes inelegibles para TBI, ya sea por edad del paciente al momento del tratamiento o comorbilidades presentes. Se cuenta con 04 Guías de Práctica Clínica internacionales y locales, que favorecen el uso de Tiotepa como parte de uno de los regímenes de acondicionamiento para trasplante alogénico en leucemias linfoblásticas agudas de alto riesgo, recaídas, o con enfermedad del SNC. DISCUSIÓN: Tomando los criterios para un marco de valor de la Health Technology Assessment International (2018) para la toma de decisiones y formulación de la recomendación, se describe: Se ha encontrado 01 estudio clínico fase 3, multicéntrico, aleatorizado, de no inferioridad, así como 02 estudios retrospectivos de reportes de casos, los cuales han demostrado eficacia y seguridad con el uso Tiotepa, con una sobrevida libre de eventos de alrededor de 40% y una sobrevida global aproximada de 55%. Los pacientes deben tener como 02 condiciones importantes: una de ellas es tener un donante HLA compatible emparentado y la segunda es estar en respuesta completa previo al uso del régimen de acondicionamiento que incluye a tiotepa. Si bien el objetivo de un estudio de no inferioridad era evaluar la eficacia entre el tratamiento experimental (quimioterapia combinada) vs el control activo (TBI), en el estudio de Peters C. et al no se pudo alcanzar el poder condicional para concluir en una no inferioridad debido a no haber llegado a un numero de 1000 pacientes requeridos (solo se obtuvieron 417 pacientes entre los dos grupos). Con los resultados se vio que en dicho estudio fase 3, el uso de TBI obtuvo una mejor sobrevida libre de eventos y sobrevida global, pero que en ciertos casos los regímenes con tiotepa alcanzan una respuesta significativa y pueden ser una alternativa de tratamiento en los pacientes que son inelegibles a TBI, así como por ser unfit y/o tener infiltración del sistema nervioso central, dadas las propiedades del tiotepa para llegar a niveles adecuados en LCR. La población de nuestra institución cumple con los criterios de inclusión de los estudios evaluados, tanto en población (pediátrica o adulta), como el estatus de la enfermedad (pacientes con LLA de alto riesgo o recaída que tuvieran compromiso del sistema nervioso central). Además, el beneficio de administrar algún régimen que incluya Tiotepa tiene un mejor beneficio en comparación a otros regímenes sin tiotepa, y más en el grupo de pacientes que tengan infiltración del SNC. Dentro de los eventos adversos mencionados en los estudios tenemos a alteraciones en el crecimiento, de la función gonadal, función cognitiva, cataratas o posibilidad de segundas neoplasias. En el INEN entre los años 2014-2022 se tuvo a 09 pacientes que utilizaron régimen con Tiotepa, de los cuales 09 de ellos siguen vivos y en seguimiento continuo. Dentro de los eventos adversos presentados se tuvo 01 caso de retardo en el crecimiento por déficit de hormona de crecimiento y un caso de sospecha por EICH hepático, los demás pacientes sin complicaciones mayores. El impacto económico de esta tecnología para el INEN se ha considerado en relación a la particularidad de la población involucrada, la cual se beneficiaria de dicha tecnología y al ser un grupo limitado de pacientes beneficiados (aproximadamente 1-2 pacientes al año). Luego de la discusión, se comenta que la calidad de la evidencia es baja, sin embargo, el panel concluye que el uso de un régimen de acondicionamiento que incluya Tiotepa es una opción de tratamiento en pacientes pediátricos y adultos con LLA con debut o recaída en el SNC que no puedan utilizar TBI y que cuenten con un donante HLA idéntico emparentado. CONCLUSIONES: Dentro de la población de pacientes pediátricos y adultos con leucemia linfoblástica aguda, existe un grupo de alto riesgo, pacientes en recaída o con compromiso extramedular (incluyendo sistema nervioso central); para lo cual, al alcanzar una remisión completa deben ir a un trasplante de progenitores hematopoyéticos con donante HLA idéntico, requiriendo previamente recibir un régimen de acondicionamiento. Se realizó la búsqueda sistemática (Medline a través de PubMed) y se identificaron 01 estudio aleatorizado fase 3 de no inferioridad, 01 estudio retrospectivo y 01 estudio de reporte de casos, que incluyeron a la población de estudio. Además, se revisó 04 guías de práctica clínica con las recomendaciones de uso de tiotepa como acondicionamiento. Se ha visto que el uso de regímenes con Tiotepa tiene buena difusión por el sistema nervioso central, líquido cefalorraquídeo, alcanzando similares concentraciones que, en plasma, por lo cual es una alternativa de tratamiento en pacientes con compromiso del SNC. La comparación del uso de Tiotepa versus Irradiación corporal total en el estudio fase 3 no se pudo concluir la no inferioridad debió a la pequeña muestra de pacientes (N=417) requiriendo al menos un numero de 1000. Sin embargo, dentro de los halazgos e el estudio se evidencio beneficio en sobrevida global y sobrevida libre de eventos para el uso de TBI, sin embargo, el acondicionamiento con quimioterapia combinada (uso de Fludarabina, Tiotepa y Busulfan/Treosulfan) es una alternativa valiosa para pacientes inelegibles para TBI, ya sea por edad o comorbilidades. En la población del INEN se recomienda el uso de Tiotepa a pacientes (pediátricos o adultos) con leucemia linfoblástica aguda (B o T) con enfermedad de alto riesgo, con enfermedad en SNC al debut o recaída en SNC. En menores de 3 años o en mayores de 3 años con enfermedad en SNC donde no se pueda usar TBI. Dentro de los eventos adversos presentados en los estudios se tuvieron citopenias, infección, mucositis, EICH (agudo o crónico). En nuestra institución, los pacientes que utilizan Tiotepa son aproximadamente 1 a 2 por año. Debiendo tener un monitoreo regular de los pacientes para evaluar respuestas, toxicidades y sobrevida.

Evaluation of animal model congruence to human depression based on large-scale gene expression patterns of the CNS.

Depression is a complex mental health disorder that is difficult to study. A wide range of animal models exist and for many of these data on large-scale gene expression patterns in the CNS are available. The goal of this study was to evaluate how well animal models match human depression by evaluating congruence and discordance of large-scale gene expression patterns in the CNS between almost 300 animal models and a portrait of human depression created from male and female datasets. Multiple approaches were used, including a hypergeometric based scoring system that rewards common gene expression patterns (e.g., up-up or down-down in both model and human depression), but penalizes opposing gene expression patterns. RRHO heat maps, Uniform Manifold Approximation Plot (UMAP), and machine learning were used to evaluate matching of models to depression. The top ranked model was a histone deacetylase (HDAC2) conditional knockout in forebrain neurons. Also highly ranked were various models for Alzheimer's, including APPsa knock-in (2nd overall), APP knockout, and an APP/PS1 humanized double mutant. Other top models were the mitochondrial gene HTRA2 knockout (that is lethal in adulthood), a modified acetylcholinesterase, a Huntington's disease model, and the CRTC1 knockout. Over 30 stress related models were evaluated and while some matched highly with depression, others did not. In most of the top models, a consistent dysregulation of MAP kinase pathway was identified and the genes NR4A1, BDNF, ARC, EGR2, and PDE7B were consistently downregulated as in humans with depression. Separate male and female portraits of depression were also evaluated to identify potential sex specific depression matches with models. Individual human depression datasets were also evaluated to allow for comparisons across the same brain regions. Heatmap, UMAP, and machine learning results supported the hypergeometric ranking findings. Together, this study provides new insights into how large-scale gene expression patterns may be similarly dysregulated in some animals models and humans with depression that may provide new avenues for understanding and treating depression.

Neurofilament light in plasma is a potential biomarker of central nervous system involvement in systemic lupus erythematosus.

BACKGROUND: Neuropsychiatric manifestations (NP) are common in systemic lupus erythematosus (SLE). However, the pathophysiological mechanisms are not completely understood. Neurofilament light protein (NfL) is part of the neuronal cytoskeleton. Increased NfL concentrations, reflecting neurodegeneration, is observed in cerebrospinal fluid (CSF) in several neurodegenerative and neuroinflammatory conditions. We aimed to explore if plasma NfL could serve as a biomarker for central nervous system (CNS) involvement in SLE. METHODS: Sixty-seven patients with SLE underwent neurological examination; 52 underwent lumbar puncture, while 62 underwent cerebral magnetic resonance imaging (MRI). We measured selected auto-antibodies and other laboratory variables postulated to have roles in NP pathophysiology in the blood and/or CSF. We used SPM12 software for MRI voxel-based morphometry. RESULTS: Age-adjusted linear regression analyses revealed increased plasma NfL concentrations with increasing creatinine (ß = 0.01, p < 0.001) and Q-albumin (ß = 0.07, p = 0.008). We observed higher plasma NfL concentrations in patients with a history of seizures (ß = 0.57, p = 0.014), impaired motor function (ß = 0.36, p = 0.008), increasing disease activity (ß = 0.04, p = 0.008), and organ damage (ß = 0.10, p = 0.002). Voxel-based morphometry suggested an association between increasing plasma NfL concentrations and the loss of cerebral white matter in the corpus callosum and hippocampal gray matter. CONCLUSION: Increased plasma NfL concentrations were associated with some abnormal neurological, cognitive, and neuroimaging findings. However, plasma NfL was also influenced by other factors, such as damage accrual, creatinine, and Q-albumin, thereby obscuring the interpretation of how plasma NfL reflects CNS involvement. Taken together, NfL in CSF seems a better marker of neuronal injury than plasma NfL in patients with SLE.

SARS-CoV-2 Psychiatric Sequelae: A Review of Neuroendocrine Mechanisms and Therapeutic Strategies.

From the earliest days of the coronavirus disease 2019 (COVID-19) pandemic, there have been reports of significant neurological and psychological symptoms following Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection. This narrative review is designed to examine the potential psychoneuroendocrine pathogenic mechanisms by which SARS-CoV-2 elicits psychiatric sequelae as well as to posit potential pharmacologic strategies to address and reverse these pathologies. Following a brief overview of neurological and psychological sequelae from previous viral pandemics, we address mechanisms by which SARS-CoV-2 could enter or otherwise elicit changes in the CNS. We then examine the hypothesis that COVID-19-induced psychiatric disorders result from challenges to the neuroendocrine system, in particular the hypothalamic-pituitary-adrenal stress axis and monoamine synthesis, physiological mechanisms that are only further enhanced by the pandemic-induced social environment of fear, isolation, and socioeconomic pressure. Finally, we evaluate several FDA-approved therapeutics in the context of COVID-19-induced psychoneuroendocrine disorders.

Safety, Tolerability, and Pharmacokinetics of FAAH Inhibitor BIA 10-2474: A Double-Blind, Randomized, Placebo-Controlled Study in Healthy Volunteers.

This study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of BIA 10-2474, a fatty acid amide hydrolase (FAAH) inhibitor, after first administration to healthy male and female participants. Participants (n = 116) were recruited into this phase I, double-blind, randomized, placebo-controlled, single ascending dose and multiple ascending dose (10-day) study. The primary outcome was the safety and tolerability of BIA 10-2474. Secondary outcomes were pharmacokinetics of BIA 10-2474 and pharmacodynamics, considering plasma concentrations of anandamide and three other fatty acid amides (FAAs) and leukocyte FAAH activity. Single oral doses of 0.25-100 mg and repeated oral doses of 2.5-50 mg were evaluated. BIA 10-2474 was well tolerated up to 100 mg as a single dose and up to 20 mg once daily for 10 days. In the cohort receiving repeated administrations of 50 mg, there were central nervous system adverse events in five of six participants, one with fatal outcome, which led to early termination of the study. BIA 10-2474 showed a linear relationship between dose and area under plasma concentration-time curve (AUC) across the entire dose range and reached steady state within 5-6 days of administration, with an accumulation ratio, based on AUC0-24h , of <2 on Day 10. BIA 10-2474 was rapidly absorbed with a mean terminal elimination half-life of 8-10 hours (Day 10). BIA 10-2474 caused reversible, dose-related increases in plasma FAAs. In conclusion, we propose that these data, as well as the additional data generated since the clinical trial was stopped, do not provide a complete mechanistic explanation for the tragic fatality.

Central nervous system outcomes of COVID-19.

The worldwide pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected an estimated 200 million people with over 4 million deaths. Although COVID-19, the disease caused by the SARS-CoV-2 virus, is primarily a respiratory disease, an increasing number of neurologic symptoms have been reported. Some of these symptoms, such as loss of smell or taste, are mild and non-life threatening, while others, such as stroke or seizure, are more critical. Many of these symptoms remain long after the acute illness has passed, a phenomenon known as "long COVID" or postacute sequelae of SARS-CoV-2 infection (PASC). Neurological symptoms can be difficult to study due to the complexity of the central and peripheral nervous system. These neurologic symptoms can be difficult to identify and quantitate. This narrative review will describe approaches for assessing neurologic manifestations of COVID-19, with examples of the data they provide, as well as some directions for future research to aid in understanding the pathophysiology of COVID-19-related neurological implications.

The Spatiotemporal Coupling: Regional Energy Failure and Aberrant Proteins in Neurodegenerative Diseases.

The spatial and temporal coordination of each element is a pivotal characteristic of systems, and the central nervous system (CNS) is not an exception. Glial elements and the vascular interface have been considered more recently, together with the extracellular matrix and the immune system. However, the knowledge of the single-element configuration is not sufficient to predict physiological or pathological long-lasting changes. Ionic currents, complex molecular cascades, genomic rearrangement, and the regional energy demand can be different even in neighboring cells of the same phenotype, and their differential expression could explain the region-specific progression of the most studied neurodegenerative diseases. We here reviewed the main nodes and edges of the system, which could be studied to develop a comprehensive knowledge of CNS plasticity from the neurovascular unit to the synaptic cleft. The future goal is to redefine the modeling of synaptic plasticity and achieve a better understanding of neurological diseases, pointing out cellular, subcellular, and molecular components that couple in specific neuroanatomical and functional regions.

Central nervous system physiology.

This is the second chapter of the series on the use of clinical neurophysiology for the study of movement disorders. It focusses on methods that can be used to probe neural circuits in brain and spinal cord. These include use of spinal and supraspinal reflexes to probe the integrity of transmission in specific pathways; transcranial methods of brain stimulation such as transcranial magnetic stimulation and transcranial direct current stimulation, which activate or modulate (respectively) the activity of populations of central neurones; EEG methods, both in conjunction with brain stimulation or with behavioural measures that record the activity of populations of central neurones; and pure behavioural measures that allow us to build conceptual models of motor control. The methods are discussed mainly in relation to work on healthy individuals. Later chapters will focus specifically on changes caused by pathology.

Involvement of central sensory pathways in subjects with restless legs syndrome: A neurophysiological study.

In patients with restless legs syndrome (RLS) a motor cortical disinhibition has been reported in transcranial magnetic stimulation (TMS) studies, but the neuronal excitability in other cortical areas has been poorly explored. The aim of this study was the functional evaluation of thalamo-cortical circuits and inhibitory cortical responses in the sensory cortex in RLS. We assessed the high-frequency somatosensory evoked potentials (HF-SEP) in sixteen subjects suffering from RLS of different degrees of severity. In patients with severe or very severe RLS we found a significant desynchronization with amplitude reduction of both pre- and post-synaptic HF-SEP bursts, which suggest an impairment in the thalamo-cortical projections and in the cortical inhibitory interneurons activity, respectively. The assessment of the central sensory pathways by means of HF-SEP may shed light on the pathophysiological mechanisms of RLS.

Combined Preconditioning Reduces the Negative Influence of Cerebral Ischemia on the Morphofunctional Condition of CNS.

We studied the influence of combined preconditioning (compound pQ-4 and moderate hypoxia) on morphometrical parameters of neuronal populations in hippocampal fields CA1 and CA3 in rats after bilateral ligation of the common carotid artery. Preconditioning produced a neuroprotective effect, improved survival of pyramidal neurons in the early and delayed periods of modeled ischemia, prevented the formation of necrotic and apoptotic neurons and hyperactivation of microglia, and protected endotheliocytes. The positive influence of preconditioning factors on the morphometric parameters of the brain under ischemic conditions agrees with the results of behavioral tests (open field and elevated plus maze) that demonstrated increased locomotor activity and exploratory behavior of animals.

HIV-Associated Neurotoxicity: The Interplay of Host and Viral Proteins.

HIV-1 can incite activation of chemokine receptors, inflammatory mediators, and glutamate receptor-mediated excitotoxicity. The mechanisms associated with such immune activation can disrupt neuronal and glial functions. HIV-associated neurocognitive disorder (HAND) is being observed since the beginning of the AIDS epidemic due to a change in the functional integrity of cells from the central nervous system (CNS). Even with the presence of antiretroviral therapy, there is a decline in the functioning of the brain especially movement skills, noticeable swings in mood, and routine performance activities. Under the umbrella of HAND, various symptomatic and asymptomatic conditions are categorized and are on a rise despite the use of newer antiretroviral agents. Due to the use of long-lasting antiretroviral agents, this deadly disease is becoming a manageable chronic condition with the occurrence of asymptomatic neurocognitive impairment (ANI), symptomatic mild neurocognitive disorder, or HIV-associated dementia. In-depth research in the pathogenesis of HIV has focused on various mechanisms involved in neuronal dysfunction and associated toxicities ultimately showcasing the involvement of various pathways. Increasing evidence-based studies have emphasized a need to focus and explore the specific pathways in inflammation-associated neurodegenerative disorders. In the current review, we have highlighted the association of various HIV proteins and neuronal cells with their involvement in various pathways responsible for the development of neurotoxicity.

Irritable Bowel Syndrome, Depression, and Neurodegeneration: A Bidirectional Communication from Gut to Brain.

Patients with irritable bowel syndrome (IBS) are increasingly presenting with a wide range of neuropsychiatric symptoms, such as deterioration in gastroenteric physiology, including visceral hypersensitivity, altered intestinal membrane permeability, and gastrointestinal motor dysfunction. Functional imaging of IBS patients has revealed several abnormalities in various brain regions, such as significant activation of amygdala, thinning of insular and anterior cingulate cortex, and increase in hypothalamic gray matter, which results in poor psychiatric and cognitive outcomes. Interrelations between the enteric and central events in IBS-related gastrointestinal, neurological, and psychiatric pathologies have compelled researchers to study the gut-brain axis-a bidirectional communication that maintains the homeostasis of the gastrointestinal and central nervous system with gut microbiota as the protagonist. Thus, it can be disrupted by any alteration owing to the gut dysbiosis or loss of diversity in microbial composition. Available evidence indicates that the use of probiotics as a part of a balanced diet is effective in the management of IBS and IBS-associated neurodegenerative and psychiatric comorbidities. In this review, we delineate the pathogenesis and complications of IBS from gastrointestinal and neuropsychiatric standpoints while also discussing the neurodegenerative events in enteric and central nervous systems of IBS patients and the therapeutic potential of gut microbiota-based therapy established on clinical and preclinical data.

Chronic Pain in the Elderly: Mechanisms and Distinctive Features.

BACKGROUND: Chronic pain is a major issue affecting more than 50% of the older population and up to 80% of nursing homes residents. Research on pain in the elderly focuses mainly on the development of clinical tools to assess pain in patients with dementia and cognitive impairment or on the efficacy and tolerability of medications. In this review, we searched for evidence of specific pain mechanisms or modifications in pain signals processing either at the cellular level or in the central nervous system. METHODS: Narrative review. RESULTS: Investigation on pain sensitivity led to conflicting results, with some studies indicating a modest decrease in age-related pain sensitivity, while other researchers found a reduced pain threshold for pressure stimuli. Areas of the brain involved in pain perception and analgesia are susceptible to pathological changes such as gliosis and neuronal death and the effectiveness of descending pain inhibitory mechanisms, particularly their endogenous opioid component, also appears to deteriorate with advancing age. Hyperalgesia is more common at older age and recovery from peripheral nerve injury appears to be delayed. In addition, peripheral nociceptors may contribute minimally to pain sensation at either acute or chronic time points in aged populations. CONCLUSIONS: Elderly subjects appear to be more susceptible to prolonged pain development, and medications acting on peripheral sensitization are less efficient. Pathologic changes in the central nervous system are responsible for different pain processing and response to treatment. Specific guidelines focusing on specific pathophysiological changes in the elderly are needed to ensure adequate treatment of chronic pain conditions.

Stem Cells: Innovative Therapeutic Options for Neurodegenerative Diseases?

Neurodegenerative diseases are characterized by the progressive loss of structure and/or function of both neurons and glial cells, leading to different degrees of pathology and loss of cognition. The hypothesis of circuit reconstruction in the damaged brain via direct cell replacement has been pursued extensively so far. In this context, stem cells represent a useful option since they provide tissue restoration through the substitution of damaged neuronal cells with exogenous stem cells and create a neuro-protective environment through the release of bioactive molecules for healthy neurons, as well. These peculiar properties of stem cells are opening to potential therapeutic strategies for the treatment of severe neurodegenerative disorders, for which the absence of effective treatment options leads to an increasingly socio-economic burden. Currently, the introduction of new technologies in the field of stem cells and the implementation of alternative cell tissues sources are pointing to exciting frontiers in this area of research. Here, we provide an update of the current knowledge about source and administration routes of stem cells, and review light and shadows of cells replacement therapy for the treatment of the three main neurodegenerative disorders (Amyotrophic lateral sclerosis, Parkinson's, and Alzheimer's disease).

Opioid Specific Effects on Central Processing of Sensation and Pain: A Randomized, Cross-Over, Placebo-Controlled Study.

Moderate to severe pain is often treated with opioids, but central mechanisms underlying opioid analgesia are poorly understood. Findings thus far have been contradictory and none could infer opioid specific effects. This placebo-controlled, randomized, 2-way cross-over, double-blinded study aimed to explore opioid specific effects on central processing of external stimuli. Twenty healthy male volunteers were included and 3 sets of assessments were done at each of the 2 visits: 1) baseline, 2) during continuous morphine or placebo intravenous infusion and 3) during simultaneous morphine + naloxone or placebo infusion. Opioid antagonist naloxone was introduced in order to investigate opioid specific effects by observing which morphine effects are reversed by this intervention. Quantitative sensory testing, spinal nociceptive withdrawal reflexes (NWR), spinal electroencephalography (EEG), cortical EEG responses to external stimuli and resting EEG were measured and analyzed. Longer lasting pain (cold-pressor test - hand in 2° water for 2 minutes, tetanic electrical), deeper structure pain (bone pressure) and strong nociceptive (NWR) stimulations were the most sensitive quantitative sensory testing measures of opioid analgesia. In line with this, the principal opioid specific central changes were seen in NWRs, EEG responses to NWRs and cold-pressor EEG. The magnitude of NWRs together with amplitudes and insular source strengths of the corresponding EEG responses were attenuated. The decreases in EEG activity were correlated to subjective unpleasantness scores. Brain activity underlying slow cold-pressor EEG (1-4Hz) was decreased, whereas the brain activity underlying faster EEG (8-12Hz) was increased. These changes were strongly correlated to subjective pain relief. This study points to evidence of opioid specific effects on perception of external stimuli and the underlying central responses. The analgesic response to opioids is likely a synergy of opioids acting at both spinal and supra-spinal levels of the central nervous system. Due to the strong correlations with pain relief, the changes in EEG signals during cold-pressor test have the potential to serve as biomarkers of opioid analgesia. PERSPECTIVE: This exploratory study presents evidence of opioid specific effects on the pain system at peripheral and central levels. The findings give insights into which measures are the most sensitive for assessing opioid-specific effects.