Approci fisici per lo studio degli effetti nella stimolazione dell'attività neuronale

Nel presente lavoro di tesi si indaga lo stato dell’arte sui metodi e approcci fisici usati per studiare gli effetti nella stimolazione dell’attività neuronale. È noto infatti che i neuroni comunicano tra loro tramite i collegamenti intercellulari definiti sinapsi e la comunicazione sinaptica avviene attraverso sostanze chimiche, dette neurotrasmettitori, che stimolano, tramite il passaggio dell’impulso nervoso, la cellula successiva. L’impulso nervoso, detto anche potenziale d’azione, si propaga lungo la fibra nervosa e determina delle modificazioni sia chimiche sia elettriche. I neuroni sono polarizzati, poiché presentano fuori dalla membrana cellulare una carica elettrica diversa da quella presente all’interno. La differenza di carica è determinata dagli ioni sodio e potassio presenti in percentuali diverse all’interno e all’esterno del neurone; tali ioni permettono, grazie all’ausilio di sistemi chiamati canali ionici, di trasmettere l’informazione lungo la cellula neuronale. Quando il potenziale d’azione raggiunge la sinapsi, le vescicole presenti sulla sua superficie liberano un neurotrasmettitore che si diffonde rapidamente tramite la fibra postsinaptica e si lega ad alcune molecole specifiche della membrana postsinaptica della cellula recettrice. La reazione con il neurotrasmettitore altera la permeabilità della membrana della fibra postsinaptica, dando origine ad un potenziale d’azione che consentirà la propagazione ulteriore dell’impulso nervoso. La tesi mira ad approfondire gli attuali metodi e approcci, ivi inclusi quelli che impiegano nanotecnologie, ottica e imaging nella prospettiva di individuare ambiti di applicazione, limiti di applicabilità e prospettive future per proporre soluzioni per coprire i gap ad oggi presenti nella comprensione dei meccanismi di stimolazione e il ruolo giocato da ogni parte del neurone. In this thesis we investigate the state of the art of the methods and physical approaches used to study the effects in the stimulation of neuronal activity. In fact, it is known that neurons communicate with each other through intercellular connections called synapses and synaptic communication occurs through chemicals, called neurotransmitters, which stimulate the next cell through the passage of the nerve impulse. The nerve impulse, also called action potential, propagates along the nerve fiber and determines both chemical and electrical changes. Neurons are polarized, since they have a different electrical charge outside the cell membrane from that present inside. The charge difference is determined by the sodium and potassium ions present in different percentages inside and outside the neuron; these ions allow, thanks to the help of structures called ion channels, to transmit information along the neuronal cell. When the action potential reaches the synapse, the vesicles on its surface release a neurotransmitter that rapidly spreads through the postsynaptic fiber and binds to some specific molecules of the postsynaptic membrane of the receptor cell. The reaction with the neurotransmitter alters the permeability of the membrane of the postsynaptic fiber, giving rise to an action potential that will allow further propagation of the nerve impulse. The thesis aims to deepen the current methods and approaches, including those that use nanotechnologies, optics and imaging in the perspective of identifying areas of application, limits of applicability and future perspectives to propose solutions to cover the gaps currently present in the understanding of the mechanisms of stimulation and the role played by each part of the neuron

Mutations in MAPT give rise to aneuploidy in animal models of tauopathy

Tau is a major microtubule-associated protein in brain neurons. Its misfolding and accumulation cause neurodegenerative diseases characterized by brain atrophy and dementia, named tauopathies. Genetic forms are caused by mutations of microtubule-associated protein tau gene (MAPT). Tau is expressed also in nonneural tissues such as lymphocytes. Tau has been recently recognized as a multifunctional protein, and in particular, some findings supported a role in genome stability. In fact, peripheral cells of patients affected by frontotemporal dementia carrying different MAPT mutations showed structural and numerical chromosome aberrations. The aim of this study was to assess chromosome stability in peripheral cell from two animal models of genetic tauopathy, JNPL3 and PS19 mouse strains expressing the human tau carrying the P301L and P301S mutations, respectively, to confirm the previous data on humans. After demonstrating the presence of mutated tau in spleen, we performed standard cytogenetic analysis of splenic lymphocytes from homozygous and hemizygous JNPL3, hemizygous PS19, and relevant controls. Losses and gains of chromosomes (aneuploidy) were evaluated. We detected a significantly higher level of aneuploidy in JNPL3 and PS19 than in control mice. Moreover, in JNPL3, the aneuploidy was higher in homozygotes than in hemizygotes, demonstrating a gene dose effect, which appeared also to be age independent. Our results show that mutated tau is associated with chromosome instability. It is conceivable to hypothesize that in genetic tauopathies the aneuploidy may be present also in central nervous system, possibly contributing to neurodegeneration

Clinical phenotypic variability in an Italian family bearing the IVS6+ 5_8delGTGA mutation in PGRN gene

Background Frontotemporal dementia (FTD) is a complex presenile disorder characterized by behavioural changes and executive functions, expression of fronto-temporal degeneration. Hereditary FTD accounts for 20-30% of cases and, in the past decade, mutations in the microtubule associated protein tau (MAPT)gene were identified as a main genetic causes of familial FTD. In 2006, mutations in the gene encoding progranulin (PGRN) were reported, to account for a wide part of the familial FTD cases. Clinically, an high phenotypic variability within and among the kindreds is reported in the familial FTD associated with PGRN mutations and occasionally the memory deficits are the first symptoms, resembling Alzheimer's disease (AD). We report an Italian family with dementia associated with a PGRN mutation characterized by a deletion of 4 base pairs inside the intron 6 of the gene, leading to haploin sufficiency In our kindred, all three affected patients carried the mutation, but presented very different clinical phenotypes, evoking FTD, AD and rapidly-progressive dementia mimicking prion disease. Methods Informations on the members of the first, second and third generations were obtained conducting interviews with relatives, while for the three patients studied, the clinical evidence of dementia symptoms and their characterization was documented directly with sequential neurological examinations, cognitive assessments and neuroimaging. Blood sample collection and DNA extraction from peripheral blood lymphocytes for genetic analysis were performed after written informed consent of the patients. Results In our pedigree, the PGRN mutated patients are affected by dementia with three different clinical pictures: FTD, AD and rapidly progressive dementia mimicking prion disease. Neuropsychological examinations supported these diagnoses, documenting generalized deficits of cortical functions in AD patient and deficits in executive functions and in language in FTD patient. Regarding neuroimaging, in the same two cases MRI results do not correspond to the clinical diagnosis. Conclusions These findings confirms the marked heterogeneity of the clinico-radiological features in patients with PGNR mutations and underline the need of considering mutations of this gene as causes of familial dementing diseases with atypical or uncommon features or discrepancies between the clinical and the neuroimaging findings

Nutraceuticals and Physical Activity as Antidepressants: The Central Role of the Gut Microbiota

Major depressive disorder (MDD) is a common mental illness. Evidence suggests that the gut microbiota play an essential role in regulating brain functions and the pathogenesis of neuropsychiatric diseases, including MDD. There are numerous mechanisms through which the gut microbiota and brain can exchange information in a continuous, bidirectional communication. Current research emphasizes the interexchange of signals influenced by the gut microbiota that are detected and transduced in information from the gut to the nervous system involving neural, endocrine, and inflammatory mechanisms, suggesting a relationship between oxidative stress and the pathophysiology of MDD via the hyperactivation of inflammatory responses. Potential sources of inflammation in the plasma and hippocampus of depressed individuals could stem from increases in intestinal permeability. Some nutraceuticals, such as specific probiotics, namely psychobiotics, polyphenols, carotenoids, butyrate, and prebiotics, have been demonstrated to exert an antidepressant activity, but most of them need to be metabolized and activated by gut microorganisms. By inducing changes in the gut microbiota composition, physical exercise might also exert a role in alleviating depression-like symptoms. The mutual relationships among nutraceuticals, exercise, and depression will be discussed, and the potential role of the gut microbiota as a therapeutic target to treat depression will be explored

Macrophage Migration Inhibitory Factor in Fetoplacental Tissues from Preeclamptic Pregnancies with or without Fetal Growth Restriction

The proinflammatory cytokine MIF (macrophage migration inhibitory factor) is involved in physiological and pathological processes in pregnancy. MIF maternal serum levels are increased in preeclampsia (PE). We hypothesize that pregnancy tissues are the source of MIF overexpression in PE. MIF protein was studied in maternal sera, placental tissues, fetal membranes, and umbilical cord of 8 control and 20 PE pregnancies: 10 with normal fetal growth (PE-AGA) and 10 with fetal growth restriction (PE-FGR). MIF levels were significantly higher in PE-AGA membranes than in controls and PE-FGR. In PE-FGR, MIF cord concentrations were higher than in PE-AGA while MIF placental levels were lower than in controls. MIF maternal serum levels were higher in PE, compared to controls, and the difference was mainly due to PE-FGR samples. These data support MIF involvement in PE pathogenesis and suggest that different pregnancy tissues contribute to MIF production in PE with and without fetoplacental compromise

Diet as a system: an observational study investigating a multi-choice system of moderately restricted low-protein diets

BACKGROUND: There is no single, gold-standard, low-protein diet (LPD) for CKD patients; the best compliance is probably obtained by personalization. This study tests the hypothesis that a multiple choice diet network allows patients to attain a good compliance level, and that, in an open-choice system, overall results are not dependent upon the specific diet, but upon the clinical characteristics of the patients. METHODS: Observational study: Three LPD options were offered to all patients with severe or rapidly progressive CKD: vegan diets supplemented with alpha-ketoacids and essential aminoacids; protein-free food in substitution of normal bread and pasta; other (traditional, vegan non supplemented and tailored). Dialysis-free follow-up and survival were analyzed by Kaplan Meier curves according to diet, comorbidity and age. Compliance and metabolic control were estimated in 147 subjects on diet at March 2015, with recent complete data, prescribed protein intake 0.6 g/Kg/day. Protein intake was assessed by Maroni Mitch formula. RESULTS: Four hundreds and forty nine patients followed a LPD in December, 2007- March, 2015 (90% moderately restricted LPDs, 0.6 g/Kg/day of protein, 10% at lower targets); age (median 70 (19–97)) and comorbidity (Charlson index: 7) characterized our population as being in line with the usual CKD European population. Median e-GFR at start of the diet was 20 mL/min, 33.2% of the patients were diabetics. Baseline data differ significantly across diets: protein-free schemas are preferred by older, high-comorbidity patients (median age 76 years, Charlson index 8, GFR 20.5 mL/min, Proteinuria: 0.3 g/day), supplemented vegan diets by younger patients with lower GFR and higher proteinuria (median age 65 years, Charlson index 6, GFR 18.9 mL/min; Proteinuria: 1.2 g/day); other diets are chosen by an intermediate population (median age 71 years, Charlson index 6; GFR 22.5 mL/min; Proteinuria: 0.9 g/day); (p <0.001 for age, Charlson index, proteinuria, GFR). Adherence was good, only 1.1% of the patients were lost to follow-up and protein intake was at target in most of the cases with no differences among LPDs (protein intake: 0.47 (0.26–0.86) g/Kg/day). After adjustment for confounders, and/or selection of similar populations, no difference in mortality or dialysis start was observed on the different LPDs. Below the threshold of e-GFR 15 mL/min, 50% of the patients remain dialysis free for at least two years. CONCLUSION: A multiple choice LPD system may allow reaching good adherence, without competition among diets, and with promising results in terms of dialysis-free follow-up. The advantages with respect to a non-customized approach deserve confirmation in further comparative studies or RCTs

Low-protein diets in diabetic chronic kidney disease (CKD) patients: Are they feasible and worth the effort?

Low-protein diets (LPDs) are often considered as contraindicated in diabetic patients, and are seldom studied. The aim of this observational study was to provide new data on this issue. It involved 149 diabetic and 300 non-diabetic patients who followed a LPD, with a personalized approach aimed at moderate protein restriction (0.6 g/day). Survival analysis was performed according to Kaplan–Meier, and multivariate analysis with Cox model. Diabetic versus non-diabetic patients were of similar age (median 70 years) and creatinine levels at the start of the diet (2.78 mg/dL vs. 2.80 mg/dL). There was higher prevalence of nephrotic proteinuria in diabetic patients (27.52% vs. 13.67%, p = 0.002) as well as comorbidity (median Charlson index 8 vs. 6 p = 0.002). Patient survival was lower in diabetic patients, but differences levelled off considering only cases with Charlson index &gt; 7, the only relevant covariate in Cox analysis. Dialysis-free survival was superimposable in the setting of good compliance (Mitch formula: 0.47 g/kg/day in both groups): about 50% of the cases remained dialysis-free 2 years after the first finding of e-GFR (estimated glomerular filtration rate) &lt; 15 mL/min, and 1 year after reaching e-GFR &lt; 10 mL/min. In patients with type 2 diabetes, higher proteinuria was associated with mortality and initiation of dialysis. In conclusion, moderately restricted LPDs allow similar results in diabetic and non non-diabetic patients with similar comorbidity

Salud renal y salud en la mujer: Una oportunidad para mejorar las condiciones de las generaciones actuales y futuras

y el impacto de la enfermedad en el paciente y sus familias puede ser devastador. En el 2018 el Día Mundial del Riñón y el Día Internacional de la Mujer coinciden, ofreciéndonos una oportunidad para demostrar el impacto que tiene la salud de la mujer, específicamente su salud renal, en la comunidad y en las generaciones futuras, es importante fomentar el conocimiento sobre aspectos específicos de la enfermedad renal en la mujer y poder aplicarlos de forma extensiva. Las mujeres y niñas representan aproximadamente el 50 % de la población mundial, siendo integrantes fundamentales de la sociedad y de sus familias. Las diferencias de género persisten alrededor del mundo, afectando su acceso a la educación, cuidados de salud y su inclusión en estudios clínicos. Actualmente, el embarazo en la mujer es una etapa única que ofrece la oportunidad de diagnosticar la enfermedad renal, donde las enfermedades renales agudas y crónicas pueden manifestarse, lo cual podría impactar en la salud renal de las generaciones futuras. Existen varias enfermedades autoinmunes y algunos otros factores que afectan más comúnmente a la mujer, con serias consecuencias durante el embarazo para la madre y para el feto. Las mujeres en diálisis en comparación con los hombres tienen complicaciones diferentes; además son más comúnmente donadoras que receptoras del trasplante renal. En esta editorial, nos enfocamos en qué hacemos y en qué no conocemos sobre la mujer, la salud y enfermedad renal, y qué podemos aprender para mejorar sus condiciones en todo el mund

Protective effects of the combination Bifidobacterium longum plus lactoferrin against NSAID-induced enteropathy

Objectives Non-steroidal anti-inflammatory drugs can exert detrimental effects in the lower digestive tract. This study examined the protective effects of a combination of the probiotic Bifidobacterium longum BB536 (Bifidobacterium) with the prebiotic lactoferrin in a rat model of diclofenac-induced enteropathy. Methods Enteropathy was induced in 40-week-old male rats by intragastric diclofenac (4 mg/kg BID, 14 days). Lactoferrin (100 mg/kg BID), Bifidobacterium (2.5\u2022106 CFU/rat BID) or their combination were administered 1 hour before diclofenac. At the end of treatments, the ileum was processed for the evaluation of histological damage, myeloperoxidase (MPO) and malondialdehyde (MDA) levels, as well as the expression of toll-like receptors 2 and 4 (TLR-2/-4) and the activation of downstream signaling molecules (MyD88 and NF-kB p65). Blood hemoglobin and fecal calprotectin were also assessed. Results Diclofenac induced intestinal damage, along with increments of MPO and MDA, overexpression of TLR-2, TLR-4, MyD88 and NF-kB p65, increase in fecal calprotectin and decrease in blood hemoglobin levels. Lactoferrin or Bifidobacterium alone prevented diclofenac-induced enteric damage, and the changes in blood hemoglobin, MPO, MDA, fecal calprotectin and NF-kB p65. Bifidobacterium, but not lactoferrin, decreased TLR-4 expression, while none of them affected MyD88 overexpression. TLR-2 expression was slightly enhanced by all treatments. The combined administration of lactoferrin and Bifidobacterium reduced further the intestinal damage, and restored MPO and blood hemoglobin levels. Conclusions Diclofenac induced ileal mucosal lesions by activation of inflammatory and pro-oxidant mechanisms. These detrimental actions were prevented by the combination of lactoferrin with Bifidobacterium likely through the modulation of TLR-2/-4/NF-kB pro-inflammatory pathways