Altered inflammasome machinery as a key player in the perpetuation of Rett syndrome oxinflammation

Col4a2 Mutations Contribute to Infantile Epileptic Spasm Syndrome and Neuroinflammation

There are more than 70 million people worldwide living with epilepsy, with most experiencing the onset of epilepsy in childhood. Despite the availability of more than 20 anti-seizure medications, approximately 30% of epilepsy patients continue to experience unsatisfactory treatment outcomes. This situation places a heavy burden on patients' families and society. Childhood epilepsy is a significant chronic neurological disease that is closely related to genetics. Col4a2, the gene encoding the α2 chain of type IV collagen, is known to be associated with multiple diseases due to missense mutations. The Col4a2 variant of collagen type IV is associated with various phenotypes, including prenatal and neonatal intracranial hemorrhage, porencephaly, porencephaly with cataracts, focal cortical dysplasia, schizencephaly, strokes in childhood and adolescence, and sporadic delayed hemorrhagic stroke. Although epilepsy is recognized as a clinical manifestation of porencephaly, the specific mechanism of Col4a2-related epileptic phenotypes remains unclear. A total of 8 patients aged 2 years and 2 months to 18 years who were diagnosed with Col4a2-related infantile epileptic spasm syndrome were analyzed. The seizure onset age ranged from 3 to 10 months. Initial EEG results revealed hypsarrhythmia or multiple and multifocal sharp waves, spike waves, sharp slow waves, or spike slow waves. Elevated levels of the cytokines IL-1β (32.23±12.58 pg/ml) and IL-6 (45.12±16.03 pg/ml) were detected in the cerebrospinal fluid of these patients without any signs of infection. Following antiseizure treatment, decreased IL-1β and IL-6 levels in the cerebrospinal fluid were noted when seizures were under control. Furthermore, we aimed to investigate the role of Col4a2 mutations in the development of epilepsy. Through the use of immunofluorescence assays, ELISA, and Western blotting, we examined astrocyte activity and the expression of inflammatory cytokines such as IL-1β, IL-6, and TNF-α after overexpressing an unreported Col4a2 (c.1838G>T) mutant in CTX-TNA cells and primary astrocytes. We found that the levels of the inflammatory factors IL-1β, IL-6, and TNF-α were increased in both CTX-TNA cells (ELISA: p = 0.0087, p<0.001, p<0.001, respectively) and primary astrocytes (ELISA: p = 0.0275, p<0.001, p<0.001, respectively). Additionally, we conducted a preliminary investigation of the role of the JAK/STAT pathway in Col4a2 mutation-associated epilepsy. Col4a2 mutation stimulated astrocyte activation, increasing iNOS, COX-2, IL-1β, IL-6, and TNF-α levels in both CTX-TNA cells and primary astrocytes. This mutation also activated the JAK/STAT signaling pathway, leading to increased phosphorylation of JAK2 and STAT3. Treatment with the JAK/STAT inhibitor WP1066 effectively counteracted this effect in primary astrocytes and CTX-TNA cells. To date, the genes who mutations are known to cause developmental and epileptic encephalopathies (DEEs) are predominantly grouped into six subtypes according to function. Our study revealed that an unreported mutation site Col4a2Mut (c.1838G>T) of which can cause neuroinflammation, may be a type VII DEE-causing gene.

Biochemical and molecular determinants of the subclinical inflammatory mechanisms in Rett syndrome

To date, Rett syndrome (RTT), a genetic disorder mainly caused by mutations in the X-linked MECP2 gene, is increasingly considered a broad-spectrum pathology, instead of just a neurodevelopmental disease, due to the multitude of peripheral co-morbidities and the compromised metabolic pathways, affecting the patients. The altered molecular processes include an impaired mitochondrial function, a perturbed redox homeostasis, a chronic subclinical inflammation and an improper cholesterol metabolism. The persistent subclinical inflammatory condition was first defined ten years ago, as a previously unrecognized feature of RTT, playing a role in the pathology progress and modulation of phenotypical severity. In light of this, the present work aims at reviewing the current knowledge on the chronic inflammatory status and the altered immune/inflammatory functions in RTT, as well as investigating the emerging mechanisms underlying this condition with a special focus on the latest findings about inflammasome system, autoimmunity responses and intestinal micro- and mycobiota. On these bases, although further research is needed, future therapeutic strategies able to re-establish an adequate immune/inflammatory response could represent potential approaches for RTT patients.

Dental Pulp Stem Cells Modulate Inflammasome Pathway and Collagen Deposition of Dermal Fibroblasts

Fibrosis is a pathological condition consisting of a delayed deposition and remodeling of the extracellular matrix (ECM) by fibroblasts. This deregulation is mostly triggered by a chronic stimulus mediated by pro-inflammatory cytokines, such as TNF-α and IL-1, which activate fibroblasts. Due to their anti-inflammatory and immunosuppressive potential, dental pulp stem cells (DPSCs) could affect fibrotic processes. This study aims to clarify if DPSCs can affect fibroblast activation and modulate collagen deposition. We set up a transwell co-culture system, where DPSCs were seeded above the monolayer of fibroblasts and stimulated with LPS or a combination of TNF-α and IL-1β and quantified a set of genes involved in inflammasome activation or ECM deposition. Cytokines-stimulated co-cultured fibroblasts, compared to unstimulated ones, showed a significant increase in the expression of IL-1β, IL-6, NAIP, AIM2, CASP1, FN1, and TGF-β genes. At the protein level, IL-1β and IL-6 release as well as FN1 were increased in stimulated, co-cultured fibroblasts. Moreover, we found a significant increase of MMP-9 production, suggesting a role of DPSCs in ECM remodeling. Our data seem to suggest a crosstalk between cultured fibroblasts and DPSCs, which seems to modulate genes involved in inflammasome activation, ECM deposition, wound healing, and fibrosis.

Gut microbiota profile in CDKL5 deficiency disorder patients

CDKL5 deficiency disorder (CDD) is a neurodevelopmental condition characterized by global developmental delay, early-onset seizures, intellectual disability, visual and motor impairments. Unlike Rett Syndrome (RTT), CDD lacks a clear regression period. Patients with CDD frequently encounter gastrointestinal (GI) disturbances and exhibit signs of subclinical immune dysregulation. However, the underlying causes of these conditions remain elusive. Emerging studies indicate a potential connection between neurological disorders and gut microbiota, an area completely unexplored in CDD. We conducted a pioneering study, analyzing fecal microbiota composition in individuals with CDD (n = 17) and their healthy relatives (n = 17). Notably, differences in intestinal bacterial diversity and composition were identified in CDD patients. In particular, at genus level, CDD microbial communities were characterized by an increase in the relative abundance of Clostridium_AQ, Eggerthella, Streptococcus, and Erysipelatoclostridium, and by a decrease in Eubacterium, Dorea, Odoribacter, Intestinomonas, and Gemmiger, pointing toward a dysbiotic profile. We further investigated microbiota changes based on the severity of GI issues, seizure frequency, sleep disorders, food intake type, impairment in neuro-behavioral features and ambulation capacity. Enrichment in Lachnoclostridium and Enterobacteriaceae was observed in the microbiota of patients with more severe GI symptoms, while Clostridiaceae, Peptostreptococcaceae, Coriobacteriaceae, Erysipelotrichaceae, Christensenellaceae, and Ruminococcaceae were enriched in patients experiencing daily epileptic seizures. Our findings suggest a potential connection between CDD, microbiota and symptom severity. This study marks the first exploration of the gut-microbiota-brain axis in subjects with CDD. It adds to the growing body of research emphasizing the role of the gut microbiota in neurodevelopmental disorders and opens doors to potential interventions that target intestinal microbes with the aim of improving the lives of patients with CDD.

A proteomic approach to investigate the role of the MECP2 gene mutation in Rett syndrome redox regulatory pathways

Mutations in the X-linked methyl-CpG-binding 2 (MECP2) gene lead to Rett Syndrome (RTT; OMIM 312750), a devasting neurodevelopmental disorder. RTT clinical manifestations are complex and with different degrees of severity, going from autistic-like behavior to loss of acquired speech, motor skills and cardiac problems. Furthermore, the correlation between the type of MECP2 mutation and the clinical phenotype is still not fully understood. Contextually, different genotypes can differently affect the patient's phenotype and omics methodologies such as proteomics could be an important tool for a molecular characterization of genotype/phenotype correlation. The aim of our study was focused on evaluating RTT oxidative stress (OS) responses related to specific MECP2 gene mutations by using proteomics and bioinformatics approaches. Primary fibroblasts isolated from patients affected by R133C and R255× mutations were compared to healthy controls (HC). After clustering primary dermal fibroblasts based on their specific MECP2 mutations, fibroblast-derived protein samples were qualitative and quantitative analyzed, using a label free quantification (LFQ) analysis by mass spectrometry (MS), achieving a preliminary correlation for RTT genotype/phenotype. Among the identified proteins involved in redox regulation pathways, NAD(P)H:quinone acceptor oxidoreductase 1 (NQO1) was found to be absent in R255× cells, while it was present in R133C and in HC fibroblasts. Moreover, NQO1 aberrant gene regulation was also confirmed when cells were challenged with 100 μM hydrogen peroxide (H2O2). In conclusion, by employing a multidisciplinary approach encompassing proteomics and bioinformatics analyses, as well as molecular biology assays, the study uncovered phenotypic responses linked to specific MECP2 gene mutations. These findings contribute to a better understanding of the complexity of RTT molecular pathways, confirming the high heterogeneity among the patients.

Rett and Rett-related disorders: Common mechanisms for shared symptoms?

Rett syndrome is a neurodevelopmental disorder caused by loss-of-function mutations in the methyl-CpG binding protein-2 (MeCP2) gene that is characterized by epilepsy, intellectual disability, autistic features, speech deficits, and sleep and breathing abnormalities. Neurologically, patients with all three disorders display microcephaly, aberrant dendritic morphology, reduced spine density, and an imbalance of excitatory/inhibitory signaling. Loss-of-function mutations in the cyclin-dependent kinase-like 5 (CDKL5) and FOXG1 genes also cause similar behavioral and neurobiological defects and were referred to as congenital or variant Rett syndrome. The relatively recent realization that CDKL5 deficiency disorder (CDD), FOXG1 syndrome, and Rett syndrome are distinct neurodevelopmental disorders with some distinctive features have resulted in separate focus being placed on each disorder with the assumption that distinct molecular mechanisms underlie their pathogenesis. However, given that many of the core symptoms and neurological features are shared, it is likely that the disorders share some critical molecular underpinnings. This review discusses the possibility that deregulation of common molecules in neurons and astrocytes plays a central role in key behavioral and neurological abnormalities in all three disorders. These include KCC2, a chloride transporter, vGlut1, a vesicular glutamate transporter, GluD1, an orphan-glutamate receptor subunit, and PSD-95, a postsynaptic scaffolding protein. We propose that reduced expression or activity of KCC2, vGlut1, PSD-95, and AKT, along with increased expression of GluD1, is involved in the excitatory/inhibitory that represents a key aspect in all three disorders. In addition, astrocyte-derived brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1), and inflammatory cytokines likely affect the expression and functioning of these molecules resulting in disease-associated abnormalities.

Ox-inflammasome involvement in neuroinflammation

Neuroinflammation plays a crucial role in the onset and the progression of several neuropathologies, from neurodegenerative disorders to migraine, from Rett syndrome to post-COVID 19 neurological manifestations. Inflammasomes are cytosolic multiprotein complexes of the innate immune system that fuel inflammation. They have been under study for the last twenty years and more recently their involvement in neuro-related conditions has been of great interest as possible therapeutic target. The role of oxidative stress in inflammasome activation has been described, however the exact way of action of specific endogenous and exogenous oxidants needs to be better clarified. In this review, we provide the current knowledge on the involvement of inflammasome in the main neuropathologies, emphasizing the importance to further clarify the role of oxidative stress in its activation including the role of mitochondria in inflammasome-induced neuroinflammation.

Sustained activation of NLRP3 inflammasome contributes to delayed wound healing in aged mice

The cutaneous wounds in the elderly heal poorly, resulting in medical and economic burdens posed by defect repairing. Age-related delayed wound healing is associated with persistent inflammation and insufficient ECM deposition. The NLRP3 inflammasome has been proven to be a critical regulator of age-related inflammatory diseases, as well as impaired wound healing. Here, we create a 6 mm full-thickness cutaneous wound on the back of young and aged mice. Compared with young mice, aged counterparts display a retardation in wound healing, accompanied by increased activation of NLRP3 inflammasome. The application of the NLRP3 inhibitor (MCC950) ameliorates wound healing in aged mice. MCC950 inhibits sustained inflammation and reduces pyroptotic cell death in fibroblasts by blocking the abnormal activation of the NLRP3 inflammasome. Our findings illuminate that the NLRP3 inflammasome is a previously unrecognized regulator of aged wound healing and may be a potential target for the therapeutic strategy of delayed wound healing with aging.

Pyroptosis in Periprosthetic Osteolysis

Periprosthetic osteolysis (PPO) along with aseptic loosening (AL) caused by wear particles after artificial joint replacement is the key factor in surgical failure and subsequent revision surgery, however, the precise molecular mechanism underlying PPO remains unclear. Aseptic inflammation triggered by metal particles, resulting in the imbalance between bone formation by osteoblasts and bone resorption by osteoclasts may be the decisive factor. Pyroptosis is a new pro-inflammatory pattern of regulated cell death (RCD), mainly mediated by gasdermins (GSDMs) family, among which GSDMD is the best characterized. Recent evidence indicates that activation of NLRP3 inflammasomes and pyroptosis play a pivotal role in the pathological process of PPO. Here, we review the pathological process of PPO, the molecular mechanism of pyroptosis and the interventions to inhibit the inflammation and pyroptosis of different cells during the PPO. Conclusively, this review provides theoretical support for the search for new strategies and new targets for the treatment of PPO by inhibiting pyroptosis and inflammation.

Chemical composite of indigenous whole grain scented joha rice varietal prevents type 2 diabetes in rats through ameliorating insulin sensitization by the IRS-1/AKT/PI3K signalling cascade

Preventive measures to lower the prevalence of type-2 diabetes development using dietary phytochemicals are most realistic. A phytochemical composite derived from whole grain scented joha rice (PCKJ), which is indigenous to the North-eastern Region, India, was investigated to understand its preventive efficacy in rats in which type 2 diabetes was induced using a high-fat high-fructose (HFHF) diet and a low dose of streptozotocin, and the findings were correlated with those in L6-myotubes. Studies on cultured L6 myotubes revealed that treatment with PCKJ facilitated glucose uptake and GLUT-4 translocation to the plasma membrane, as evidenced by confocal microscopy and/or cell fractionation studies. Furthermore, the FFA-induced L6 myotubes were identified as having elevated levels of PI3K, p-AKT (Ser473) and GLUT-4, which returned to the basal level upon exposure to PCKJ. The administration of PCKJ (100 mg per kg body weight, oral gavage, 24 weeks) to rats significantly reduced their blood glucose levels along with common lipid and liver biomarkers (LDL, triglycerides, cholesterol, ALT, and AST) compared to the control group. Moreover, immunoblotting analysis showed that upon PCKJ treatment, PI3K, p-AKT and GLUT-4 levels are upregulated in the skeletal tissue of HFHF-fed rats, similar to the in vitro model. The alteration in the levels of inflammatory cytokines IL-6, IL-10 and IFN-γ in diabetic rats returned to normal levels upon exposure to PCKJ. Histological analysis of vital tissues further strengthens the findings of the preventive value of PCKJ against the development of insulin resistance. In conclusion, this study showed the prophylactic effect of PCKJ as a potent chemical composite, which can be used to develop functional foods (nutraceuticals) for ameliorating type-2 diabetes by improving insulin sensitization and thereby glucose metabolism.

Inflammation in pediatric epilepsies: Update on clinical features and treatment options

The role of inflammation is increasingly recognized in triggering or sustaining epileptic activity. In the last decades, increasing research has provided definite evidence to support the link between immunity, inflammatory process, and epilepsy. Neuro- and systemic inflammation play a pivotal role in driving epileptogenesis through different pathogenetic mechanisms: the activation of innate immunity in glia, neurons, and microvasculature, the brain mediated by blood-brain barrier (BBB) impairment, and the imbalance of pro- and anti-inflammatory molecules produced by both arms of immunity. More recently, research has focused on the adverse effects of maternal or early-life immune activation and cytokine imbalance on fetal neurodevelopment and postnatal epilepsy. A complex crosstalk between the immune and nervous system, and a crucial interplay of genetic, epigenetic, and environmental factors may influence structures and functions of the developing brain. A better understanding of the inflammatory process in promoting epilepsy implies that targeting specific pathways may be effective in seizure control. Multiple targets have been identified so far, and several antiseizure interventions are obtained by inhibiting inflammatory signaling or protecting/restoring BBB. All this evidence has changed the field of epilepsy research and neuropharmacology. Further developments and new treatments will rapidly emerge to improve seizure management in inflammation-related epilepsies. This article is part of the Special Issue "Severe Infantile Epilepsies".

The constitutive activation of TLR4-IRAK1- NFκB axis is involved in the early NLRP3 inflammasome response in peripheral blood mononuclear cells of Rett syndrome patients

Rett syndrome (RTT), a devastating neurodevelopmental disorder, is caused in 95% of the cases by mutations in the X-chromosome-localized MECP2 gene. To date, RTT is considered a broad-spectrum disease, due to multisystem disturbances affecting patients, associated with mitochondrial dysfunctions, subclinical inflammation and an overall OxInflammatory status. Inflammasomes are multi-protein complexes crucially involved in innate immune responses against pathogens and oxidative stress mediators. The assembly of NLRP3:ASC inflammasome lead to pro-caspase 1 activation, maturation of interleukins (IL)-1β and 18 and proteolytic cleavage of Gasdermin D leading eventually to pyroptosis and systemic inflammation. The possible de-regulation of this system, in parallel with upstream nuclear factor (NF)-κB p65 pathway, were analyzed in peripheral blood mononuclear cells (PBMCs) and plasma isolated from RTT patients and matching controls. RTT PBMCs showed a constitutive activation of the axis TLR4 (Toll-like receptor 4)-IRAK1 (interleukin-1 receptor associated kinase 1)-NF-κB p65, together with augmented ROS generation and enhanced IL-18 mRNA levels and NLRP3:ASC co-localization. The deregulation of inflammasome components was even found in THP-1 cells silenced for MECP2 and importantly, in plasma compartment of RTT subjects, from the earliest stages of the pathology or in correlation with the severity of MeCP2 mutations. Taken together, these data provide new insights into the mechanisms involved in RTT sub-clinical inflammatory status present in RTT patients, thus helping to reveal new targets for future therapeutic approaches.

Extra Virgin Olive Oil Extracts of Indigenous Southern Tuscany Cultivar Act as Anti-Inflammatory and Vasorelaxant Nutraceuticals

Extra virgin olive oil (EVOO) is the typical source of fats in the Mediterranean diet. While fatty acids are essential for the EVOO nutraceutical properties, multiple biological activities are also due to the presence of polyphenols. In this work, autochthonous Tuscany EVOOs were chemically characterized and selected EVOO samples were extracted to obtain hydroalcoholic phytocomplexes, which were assayed to establish their anti-inflammatory and vasorelaxant properties. The polar extracts were characterized via 1H-NMR and UHPLC-HRMS to investigate the chemical composition and assayed in CaCo-2 cells exposed to glucose oxidase or rat aorta rings contracted by phenylephrine. Apigenin and luteolin were found as representative flavones; other components were pinoresinol, ligstroside, and oleuropein. The extracts showed anti-inflammatory and antioxidant properties via modulation of NF-κB and Nrf2 pathways, respectively, and good vasorelaxant activity, both in the presence and absence of an intact endothelium. In conclusion, this study evaluated the nutraceutical properties of autochthonous Tuscany EVOO cv., which showed promising anti-inflammatory and vasorelaxant effects.

TI: NLRP3 Inflammasome-Dependent Pyroptosis in CNS Trauma: A Potential Therapeutic Target

Central nervous system (CNS) trauma, including traumatic brain injury (TBI) and traumatic spinal cord injury (SCI), is characterized by high morbidity, disability, and mortality. TBI and SCI have similar pathophysiological mechanisms and are often accompanied by serious inflammatory responses. Pyroptosis, an inflammation-dependent programmed cell death, is becoming a major problem in CNS post-traumatic injury. Notably, the pyrin domain containing 3 (NLRP3) inflammasome is a key protein in the pyroptosis signaling pathway. Therefore, underlying mechanism of the NLRP3 inflammasome in the development of CNS trauma has attracted much attention. In this review, we briefly summarize the molecular mechanisms of NLRP3 inflammasome in pyroptosis signaling pathway, including its prime and activation. Moreover, the dynamic expression pattern, and roles of the NLRP3 inflammasome in CNS post-traumatic injury are summarized. The therapeutic applications of NLRP3 inflammasome activation inhibitors are also discussed.

MicroRNA Alterations Induced in Human Skin by Diesel Fumes, Ozone, and UV Radiation

Epigenetic alterations are a driving force of the carcinogenesis process. MicroRNAs play a role in silencing mutated oncogenes, thus defending the cell against the adverse consequences of genotoxic damages induced by environmental pollutants. These processes have been well investigated in lungs; however, although skin is directly exposed to a great variety of environmental pollutants, more research is needed to better understand the effect on cutaneous tissue. Therefore, we investigated microRNA alteration in human skin biopsies exposed to diesel fumes, ozone, and UV light for over 24 h of exposure. UV and ozone-induced microRNA alteration right after exposure, while the peak of their deregulations induced by diesel fumes was reached only at the end of the 24 h. Diesel fumes mainly altered microRNAs involved in the carcinogenesis process, ozone in apoptosis, and UV in DNA repair. Accordingly, each tested pollutant induced a specific pattern of microRNA alteration in skin related to the intrinsic mechanisms activated by the specific pollutant. These alterations, over a short time basis, reflect adaptive events aimed at defending the tissue against damages. Conversely, whenever environmental exposure lasts for a long time, the irreversible alteration of the microRNA machinery results in epigenetic damage contributing to the pathogenesis of inflammation, dysplasia, and cancer induced by environmental pollutants.

Movement disorders in patients with Rett syndrome: A systematic review of evidence and associated clinical considerations

AIM

This systematic review identified and thematically appraised clinical evidence of movement disorders in patients with Rett syndrome (RTT).

METHOD

Using PRISMA criteria, six electronic databases were searched from inception to April 2021. A thematic analysis was then undertaken on the extracted data to identify potential themes.

RESULTS

Following the thematic analysis, six themes emerged: (i) clinical features of abnormal movement behaviors; (ii) mutational profile and its impact on movement disorders; (iii) symptoms and stressors that impact on movement disorders; (iv) possible underlying neurobiological mechanisms; (v) quality of life and movement disorders; and (vi) treatment of movement disorders. Current guidelines for managing movement disorders in general were then reviewed to provide possible treatment recommendations for RTT.

CONCLUSION

Our study offers an enriched data set for clinical investigations and treatment of fine and gross motor issues in RTT. A detailed understanding of genotype-phenotype relationships of movement disorders allows for more robust genetic counseling for families but can also assist healthcare professionals in terms of monitoring disease progression in RTT. The synthesis also showed that environmental enrichment would be beneficial for improving some aspects of movement disorders. The cerebellum, basal ganglia, alongside dysregulation of the cortico-basal ganglia-thalamo-cortical loop, are likely anatomical targets. A review of treatments for movement disorders also helped to provide recommendations for treating and managing movement disorders in patients with RTT.

MeCP2 deficiency exacerbates the neuroinflammatory setting and autoreactive response during an autoimmune challenge

Rett syndrome is a severe and progressive neurological disorder linked to mutations in the MeCP2 gene. It has been suggested that immune alterations may play an active role in the generation and/or maintenance of RTT phenotypes. However, there is no clear consensus about which pathways are regulated in vivo by MeCP2 in the context of immune activation. In the present work we set to characterize the role of MeCP2 during the progression of Experimental Autoimmune Encephalomyelitis (EAE) using the MeCP2308/y mouse model (MUT), which represents a condition of "MeCP2 function deficiency". Our results showed that MeCP2 deficiency increased the susceptibility to develop EAE, along with a defective induction of anti-inflammatory responses and an exacerbated MOG-specific IFNγ expression in immune sites. In MUT-EAE spinal cord, we found a chronic increase in pro-inflammatory cytokines gene expression (IFNγ, TNFα and IL-1β) and downregulation of genes involved in immune regulation (IL-10, FoxP3 and CX3CR1). Moreover, our results indicate that MeCP2 acts intrinsically upon immune activation, affecting neuroimmune homeostasis by regulating the pro-inflammatory/anti-inflammatory balance in vivo. These results are relevant to identify the potential consequences of MeCP2 mutations on immune homeostasis and to explore novel therapeutic strategies for MeCP2-related disorders.

Impaired mitochondrial quality control in Rett Syndrome

Rett Syndrome (RTT) is a rare neurodevelopmental disorder caused in the 95% of cases by mutations in the X-linked MECP2 gene, affecting almost exclusively females. While the genetic basis of RTT is known, the exact pathogenic mechanisms that lead to the broad spectrum of symptoms still remain enigmatic. Alterations in the redox homeostasis have been proposed among the contributing factors to the development and progression of the syndrome. Mitochondria appears to play a central role in RTT oxidative damage and a plethora of mitochondrial defects has already been recognized. However, mitochondrial dynamics and mitophagy, which represent critical pathways in regulating mitochondrial quality control (QC), have not yet been investigated in RTT. The present work showed that RTT fibroblasts have networks of hyperfused mitochondria with morphological abnormalities and increased mitochondrial volume. Moreover, analysis of mitophagic flux revealed an impaired PINK1/Parkin-mediated mitochondrial removal associated with an increase of mitochondrial fusion proteins Mitofusins 1 and 2 (MFN1 and 2) and a decrease of fission mediators including Dynamin related protein 1 (DRP1) and Mitochondrial fission 1 protein (FIS1). Finally, challenging RTT fibroblasts with FCCP and 2,4-DNP did not trigger a proper apoptotic cell death due to a defective caspase 3/7 activation. Altogether, our findings shed light on new aspects of mitochondrial dysfunction in RTT that are represented by defective mitochondrial QC pathways, also providing new potential targets for a therapeutic intervention aimed at slowing down clinical course and manifestations in the affected patients.

A proteomics approach to further highlight the altered inflammatory condition in Rett syndrome

Rett syndrome (RTT) is a progressive neurodevelopmental disorder caused by mutations in the X-linked MECP2 gene. RTT patients show multisystem disturbances associated with perturbed redox homeostasis and inflammation, which appear as possible key factors in RTT pathogenesis. In this study, using primary dermal fibroblasts from control and RTT subjects, we performed a proteomic analysis that, together with data mining approaches, allowed us to carry out a comprehensive characterization of RTT cellular proteome. Functional and pathway enrichment analyses showed that differentially expressed proteins in RTT were mainly enriched in biological processes related to immune/inflammatory responses. Overall, by using proteomic data mining as supportive approach, our results provide a detailed insight into the molecular pathways involved in RTT immune dysfunction that, causing tissue and organ damage, can increase the vulnerability of affected patients to unknown endogenous factors or infections.

Identification of a De Novo Xq26.2 Microduplication Encompassing FIRRE Gene in a Child with Intellectual Disability

Long non-coding RNAs (lncRNAs), defined as transcripts of ≥200 nucleotides not translated into protein, have been involved in a wide range of regulatory functions. Their dysregulations have been associated with diverse pathological conditions such as cancer, schizophrenia, Parkinson’s, Huntington’s, Alzheimer’s diseases and Neurodevelopmental Disorders (NDDs), including autism spectrum disorders (ASDs). We report on the case of a five-year-old child with global developmental delay carrying a de novo microduplication on chromosome Xq26.2 region characterized by a DNA copy-number gain spanning about 147 Kb (chrX:130,813,232-130,960,617; GRCh37/hg19). This small microduplication encompassed the exons 2-12 of the functional intergenic repeating RNA element (FIRRE) gene (chrX:130,836,678-130,964,671; GRCh37/hg19) that encodes for a lncRNA involved in the maintenance of chromatin repression. The association of such a genetic alteration with a severe neurodevelopmental delay without clear dysmorphic features and congenital abnormalities indicative of syndromic condition further suggests that small Xq26.2 chromosomal region microduplications containing the FIRRE gene may be responsible for clinical phenotypes mainly characterized by structural or functioning neurological impairment.

Organic features of autonomic dysregulation in paediatric brain injury - Clinical and research implications for the management of patients with Rett syndrome

Rett Syndrome (RTT) is a complex neurodevelopmental disorder with autonomic nervous system dysfunction. The understanding of this autonomic dysregulation remains incomplete and treatment recommendations are lacking. By searching literature regarding childhood brain injury, we wanted to see whether understanding autonomic dysregulation following childhood brain injury as a prototype can help us better understand the autonomic dysregulation in RTT. Thirty-one (31) articles were identified and following thematic analysis the three main themes that emerged were (A) Recognition of Autonomic Dysregulation, (B) Possible Mechanisms & Assessment of Autonomic Dysregulation and (C) Treatment of Autonomic Dysregulation. We conclude that in patients with RTT (I) anatomically, thalamic and hypothalamic function should be explored, (II) sensory issues and medication induced side effects that can worsen autonomic function should be considered, and (III) diaphoresis and dystonia ought to be better managed. Our synthesis of data from autonomic dysregulation in paediatric brain injury has led to increased knowledge and a better understanding of its underpinnings, leading to the development of application protocols in children with RTT.

The MeCP2E1/E2-BDNF-miR132 Homeostasis Regulatory Network Is Region-Dependent in the Human Brain and Is Impaired in Rett Syndrome Patients

Rett Syndrome (RTT) is a rare and progressive neurodevelopmental disorder that is caused by de novo mutations in the X-linked Methyl CpG binding protein 2 (MECP2) gene and is subjected to X-chromosome inactivation. RTT is commonly associated with neurological regression, autistic features, motor control impairment, seizures, loss of speech and purposeful hand movements, mainly affecting females. Different animal and cellular model systems have tremendously contributed to our current knowledge about MeCP2 and RTT. However, the majority of these findings remain unexamined in the brain of RTT patients. Based on previous studies in rodent brains, the highly conserved neuronal microRNA “miR132” was suggested to be an inhibitor of MeCP2 expression. The neuronal miR132 itself is induced by Brain Derived Neurotrophic Factor (BDNF), a neurotransmitter modulator, which in turn is controlled by MeCP2. This makes the basis of the MECP2-BDNF-miR132 feedback regulatory loop in the brain. Here, we studied the components of this feedback regulatory network in humans, and its possible impairment in the brain of RTT patients. In this regard, we evaluated the transcript and protein levels of MECP2/MeCP2E1 and E2 isoforms, BDNF/BDNF, and miR132 (both 3p and 5p strands) by real time RT-PCR, Western blot, and ELISA in four different regions of the human RTT brains and their age-, post-mortem delay-, and sex-matched controls. The transcript level of the studied elements was significantly compromised in RTT patients, even though the change was not identical in different parts of the brain. Our data indicates that MeCP2E1/E2-BDNF protein levels did not follow their corresponding transcript trends. Correlational studies suggested that the MECP2E1/E2-BDNF-miR132 homeostasis regulation might not be similarly controlled in different parts of the human brain. Despite challenges in evaluating autopsy samples in rare diseases, our findings would help to shed some light on RTT pathobiology, and obscurities caused by limited studies on MeCP2 regulation in the human brain.

Mechanisms involved in the unbalanced redox homeostasis in osteoblastic cellular model of Alkaptonuria

Alkaptonuria (AKU) is a rare metabolic disease correlated with the deficiency of homogentisate 1,2-dioxygenase and leading to an accumulation of the metabolite homogentisic acid (HGA) which can be subjected to oxidation and polymerization reactions. These events are considered a trigger for the induction of oxidative stress in AKU but, despite the large description of an altered redox status, the underlying pathogenetic processes are still unstudied. In the present study, we investigated the molecular mechanisms responsible for the oxidative damage present in an osteoblast-based cellular model of AKU. Bone, in fact, is largely affected in AKU patients: severe osteoclastic resorption, osteoporosis, even for pediatric cases, and an altered rate of remodeling biomarkers have been reported. In our AKU osteoblast cell model, we found a clear altered redox homeostasis, determined by elevated hydrogen peroxide (H₂O₂) levels and 4HNE protein adducts formation. These findings were correlated with increased NADPH oxidase (NOX) activity and altered mitochondrial respiration. In addition, we observed a decreased activity of superoxide dismutase (SOD) and reduced levels of thioredoxin (TRX) that parallel the decreased Nrf2-DNA binding. Overall, our results reveal that HGA is able to alter the cellular redox homeostasis by modulating the endogenous ROS production via NOX activation and mitochondrial dysfunctions and impair the cellular response mechanism. These findings can be useful for understanding the pathophysiology of AKU, not yet well studied in bones, but which is an important source of comorbidities that affect the life quality of the patients.

Compromised immune/inflammatory responses in Rett syndrome

Mutations in X-linked gene methyl-CpG-binding protein 2 (MECP2), a key transcriptional regulator, account for most cases of Rett syndrome (RTT), a devastating neurodevelopmental disorder with no known cure. Despite extensive research to elucidate MeCP2 functions, the mechanisms underlying RTT pathophysiology are still unclear. In addition to a variety of neurological symptoms, RTT also includes a plethora of additional phenotypical features including altered lipid metabolism, redox imbalance, immune dysfunction and mitochondrial abnormalities that explain its multisystemic nature. Here, we provide an overview of the current knowledge on the potential role of dysregulated inflammatory and immune responses in RTT. The findings show that abnormalities of humoral and cell-mediated immunity together with chronic low-grade inflammation in multiple organs represent not only clinical manifestations of RTT but rather can contribute to its development and deteriorating course. A future research challenge could be to target therapeutically immune dysfunction as a novel means for RTT management.

Alterations of mitochondrial bioenergetics, dynamics, and morphology support the theory of oxidative damage involvement in autism spectrum disorder

Autism spectrum disorder (ASD) has been hypothesized to be a result of the interplay between genetic predisposition and increased vulnerability to early environmental insults. Mitochondrial dysfunctions appear also involved in ASD pathophysiology, but the mechanisms by which such alterations develop are not completely understood. Here, we analyzed ASD primary fibroblasts by measuring mitochondrial bioenergetics, ultrastructural and dynamic parameters to investigate the hypothesis that defects in these pathways could be interconnected phenomena responsible or consequence for the redox imbalance observed in ASD. High levels of 4-hydroxynonenal protein adducts together with increased NADPH (nicotinamide adenine dinucleotide phosphateoxidase) activity and mitochondrial superoxide production coupled with a compromised antioxidant response guided by a defective Nuclear Factor Erythroid 2-Related Factor 2 pathway confirmed an unbalanced redox homeostasis in ASD. Moreover, ASD fibroblasts showed overactive mitochondrial bioenergetics associated with atypical morphology and altered expression of mitochondrial electron transport chain complexes and dynamics-regulating factors. We suggest that many of the changes observed in mitochondria could represent compensatory mechanisms by which ASD cells try to adapt to altered energy demand, possibly resulting from a chronic oxinflammatory status.