Plasma Levels of Alpha and Gamma Synucleins in Autism Spectrum Disorder: An Indicator of Severity

The Role of Alpha-Synuclein in Neurodevelopmental Diseases

Neurodevelopmental disorders are a group of diseases with cognitive, motor, and emotional development deficits. Alpha-synuclein (α-syn) is a synaptic protein involved in transmission and neurodevelopment. This protein was previously shown to be associated with several disorders, including Parkinson's disease. Furthermore, a close link between neurodevelopmental disorders and Parkinson's has also been found. Changes in synaptic function have been noticed in neurodevelopmental disorders, including autism spectrum disorder. Impaired neurogenesis and related cognitive problems have been associated with altered expression of α-syn. Various studies reported α-syn in different body fluids and tissues such as blood and serum. Alpha-synuclein can help in better understanding the pathogenesis of neurodevelopmental diseases and facilitating their early diagnosis. This review aims to go over the recent advances in the role of α-syn in the pathophysiology of neurodevelopmental disorders, including autism spectrum disorder, attention deficit hyperactivity disorder, and motor and social impairment, and its value as a diagnostic biomarker.

Decreased levels of alpha synuclein in families with autism spectrum disorder and relationship between the disease severity

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorders that begin in early childhood. Mutations in α-synuclein (SNCA) gene have been shown to result in the accumulation of α-synuclein, which occurs in many neurodegenerative diseases. Our aim was to determine the changes in the expression profile and protein level of this gene by comparing the autistic children with their healthy siblings, their mothers and healthy controls in order to elucidate the possible contribution of the SNCA gene to the etiology of ASD. 50 autistic patients, their mothers, siblings and 25 healthy controls and their mothers were enrolled to determine SNCA gene expression and serum α-synuclein levels. It was determined that α-synuclein serum levels decreased in the autistic patients. Similarly, it was found that SNCA gene expression and serum α-synuclein levels were significantly decreased in the mothers of the patients. Significant negative correlation was observed between the SNCA gene and protein expression amounts in the 6-8 age of the patients. This family-based study is the first in the literature, with both gene expression and serum levels of α-synuclein. The relationship between ASD severity and α-synuclein level needs to be confirmed in larger-scale studies.

Alpha-Synuclein in Peripheral Tissues as a Possible Marker for Neurological Diseases and Other Medical Conditions

The possible usefulness of alpha-synuclein (aSyn) determinations in peripheral tissues (blood cells, salivary gland biopsies, olfactory mucosa, digestive tract, skin) and in biological fluids, except for cerebrospinal fluid (serum, plasma, saliva, feces, urine), as a marker of several diseases, has been the subject of numerous publications. This narrative review summarizes data from studies trying to determine the role of total, oligomeric, and phosphorylated aSyn determinations as a marker of various diseases, especially PD and other alpha-synucleinopathies. In summary, the results of studies addressing the determinations of aSyn in its different forms in peripheral tissues (especially in platelets, skin, and digestive tract, but also salivary glands and olfactory mucosa), in combination with other potential biomarkers, could be a useful tool to discriminate PD from controls and from other causes of parkinsonisms, including synucleinopathies.

A Disintegrin and Metalloproteinase Protein 8 (ADAM 8) in Autism Spectrum Disorder: Links to Neuroinflammation

Background

Converging lines of evidence confirmed neuroinflammation's role in autism spectrum disorder (ASD) etiological pathway. A disintegrin and metalloproteinase 8 (ADAM8) play major roles in inflammatory and allergic processes in various diseases.

Aim

This study aimed to investigate ADAM8 plasma levels in autistic children compared to healthy controls. Also, to discover the association between ADAM8, disease severity, and neuroinflammation in ASD.

Methodology

This case-control study included children with ASD (n=40) and aged-matched healthy controls (n=40). The plasma levels of the ADAM 8 were determined using enzyme-linked immunosorbent assay (ELISA). The assessment of ASD severity and social and sensory behaviors were categorized as mild, moderate and severe. Correlations among ADAM8 plasma levels and ASD severity scores [Childhood Autism Rating Scale (CARS), Social Responsiveness Scale (SRS) and Short Sensory Profile (SSP)] were obtained by Spearman correlation coefficient (r).

Results

ASD children (n=40), including severe autism (n=21) and mild-to-moderate autism (n=19), showed significantly (p ≤ 0.05) lower plasma levels of ADAM8 [4683 (2885-5229); 4663 (4060-5000); 4632 (2885-5229)], respectively, than those of healthy controls [5000 (4047-5000)] [median (IQR) pg/mL]. However, there was no significant difference between the ADAM8 levels of children with severe and mild-to-moderate autism (p = 0.71). Moreover, ADAM8 plasma levels were not significantly correlated with the severity of ASD measured by behavioral scales [CARS (r= -0.11, p=0.55), SRS (r=0.11, p= 0.95), SSP (r=-0.23, p=0.23)].

Conclusion

The low ADAM8 plasma levels in children with ASD possibly indicated that ADAM8 might be implicated in the pathogenesis of ASD but not in the severity of the disease. These results should be interpreted with caution until additional studies are carried out with larger populations to decide whether the reduction in plasma ADAM8 levels is a mere consequence of ASD or if it plays a pathogenic role in the disease.

The possible role of sodium leakage channel localization factor-1 in the pathophysiology and severity of autism spectrum disorders

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social, stereotypical, and repetitive behaviors. Neural dysregulation was proposed as an etiological factor in ASD. The sodium leakage channel (NCA), regulated by NLF-1 (NCA localization factor-1), has a major role in maintaining the physiological excitatory function of neurons. We aimed to examine the level of NLF-1 in ASD children and correlate it with the severity of the disease. We examined the plasma levels of NLF-1 in 80 ASD and neurotypical children using ELISA. The diagnosis and severity of ASD were based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), Childhood Autism Rating Score, Social Responsiveness Scale, and Short Sensory Profile. Then, we compared the levels of NLF-1 with the severity of the disease and behavioral and sensory symptoms. Our results showed a significant decrease in the plasma levels of NLF-1 in ASD children compared to neurotypical children (p < 0.001). Additionally, NLF-1 was significantly correlated with the severity of the behavioral symptoms of ASD (p < 0.05). The low levels of NLF-1 in ASD children potentially affect the severity of their behavioral symptoms by reducing neuron excitability through NCA. These novel findings open a new venue for pharmacological and possible genetic research involving NCA in ASD children.

Influence of Auditory Integrative Training on Casein Kinase 2 and Its Impact on Behavioral and Social Interaction in Children with Autism Spectrum Disorder

Considerable disturbances in post-translational protein phosphorylation have recently been discovered in multiple neurological disorders. Casein kinase-2 (CK2) is a tetrameric Ser/Thr protein kinase that phosphorylates a large number of substrates and contributes in several cellular physiological and pathological processes. CK2 is highly expressed in the mammalian brain and catalyzes the phosphorylation of a large number of substrates that are crucial in neuronal or glial homeostasis and inflammatory signaling processes across synapses. In this study, we investigated the impact of auditory integration therapy (AIT) for the treatment of sensory processing abnormalities in autism on plasma CK2 levels. A total of 25 ASD children, aged between 5 and 12 years, were enrolled and participated in the present research study. AIT was performed for two weeks, for a period of 30 min, twice a day, with a 3 h interval between sessions. Before and after AIT, the Childhood Autism Rating Scale (CARS), Social Responsiveness Scale (SRS), and Short Sensory Profile (SSP) scores were calculated, and plasma CK2 levels were assayed using an ELISA test. The CARS and SRS indices of autism severity improved as a result of AIT, which could be related to the decreased level of plasma CK2. However, the mean value of the SSP scores was not significantly increased after AIT. The relationship between CK2 downregulation and glutamate excitotoxicity, neuro-inflammation, and leaky gut, as etiological mechanisms in ASD, was proposed and discussed. Further research, conducted on a larger scale and with a longer study duration, are required to assess whether the cognitive improvement in ASD children after AIT is related to the downregulation of CK2.

The Synucleins and the Astrocyte

Synucleins consist of three proteins exclusively expressed in vertebrates. α-Synuclein (αS) has been identified as the main proteinaceous aggregate in Lewy bodies, a pathological hallmark of many neurodegenerative diseases. Less is understood about β-synuclein (βS) and γ-synuclein (γS), although it is known βS can interact with αS in vivo to inhibit aggregation. Likewise, both γS and βS can inhibit αS's propensity to aggregate in vitro. In the central nervous system, βS and αS, and to a lesser extent γS, are highly expressed in the neural presynaptic terminal, although they are not strictly located there, and emerging data have shown a more complex expression profile. Synapse loss and astrocyte atrophy are early aspects of degenerative diseases of the brain and correlate with disease progression. Synucleins appear to be involved in synaptic transmission, and astrocytes coordinate and organize synaptic function, with excess αS degraded by astrocytes and microglia adjacent to the synapse. βS and γS have also been observed in the astrocyte and may provide beneficial roles. The astrocytic responsibility for degradation of αS as well as emerging evidence on possible astrocytic functions of βS and γS, warrant closer inspection on astrocyte-synuclein interactions at the synapse.

Benefits of Gut Microbiota Reconstitution by Beta 1,3-1,6 Glucans in Subjects with Autism Spectrum Disorder and Other Neurodegenerative Diseases

BACKGROUND

Aureobasidium pullulans (black yeast) AFO-202 strain-produced beta glucan, Nichi Glucan, has been shown to improve the behavior and sleep pattern along with an increase in α-synuclein and melatonin in children with autism spectrum disorder (ASD).

OBJECTIVE

In this randomized pilot clinical study, we have evaluated the gut microbiota of subjects with ASD after consumption of Nichi Glucan.

METHODS

Eighteen subjects with ASD were randomly allocated: six subjects in the control group (Group 1): conventional treatment comprising remedial behavioral therapies and L-carnosine 500 mg per day, and 12 subjects (Group 2) underwent supplementation with Nichi Glucan 0.5 g twice daily along with the conventional treatment for 90 days.

RESULTS

Whole genome metagenome (WGM) sequencing of the stool samples at baseline and after intervention showed that among genera of relevance, the abundance of Enterobacteriaceae was decreased almost to zero in Group 2 after intervention, whereas it increased from 0.36% to 0.85% in Group 1. The abundance of Bacteroides increased in Group 1, whereas it decreased in Group 2. The abundance of Prevotella increased while the abundance of Lactobacillus decreased in both Group 1 and Group 2. Among species, a decrease was seen in Escherichia coli, Akkermansia muciniphila CAG:154, Blautia spp., Coprobacillus sp., and Clostridium bolteae CAG:59, with an increase of Faecalibacterium prausnitzii and Prevotella copri, which are both beneficial.

CONCLUSION

AFO-202 beta 1,3-1,6 glucan, in addition to balancing the gut microbiome in children with ASD and its role in effective control of curli-producing Enterobacteriaceae that leads to α-synuclein misfolding and accumulation, may have a prophylactic role in Parkinson's and Alzheimer's diseases as well.

Synucleins: New Data on Misfolding, Aggregation and Role in Diseases

The synucleins are a family of natively unfolded (or intrinsically unstructured) proteins consisting of α-, β-, and γ-synuclein involved in neurodegenerative diseases and cancer. The current number of publications on synucleins has exceeded 16.000. They remain the subject of constant interest for over 35 years. Two reasons explain this unchanging attention: synuclein's association with several severe human diseases and the lack of understanding of the functional roles under normal physiological conditions. We analyzed recent publications to look at the main trends and developments in synuclein research and discuss possible future directions. Traditional areas of peak research interest which still remain high among last year's publications are comparative studies of structural features as well as functional research on of three members of the synuclein family. Another popular research topic in the area is a mechanism of α-synuclein accumulation, aggregation, and fibrillation. Exciting fast-growing area of recent research is α-synuclein and epigenetics. We do not present here a broad and comprehensive review of all directions of studies but summarize only the most significant recent findings relevant to these topics and outline potential future directions.

Immune Dysregulation in Autism Spectrum Disorder: What Do We Know about It?

Autism spectrum disorder (ASD) is a group of complex multifactorial neurodevelopmental disorders characterized by a wide and variable set of neuropsychiatric symptoms, including deficits in social communication, narrow and restricted interests, and repetitive behavior. The immune hypothesis is considered to be a major factor contributing to autism pathogenesis, as well as a way to explain the differences of the clinical phenotypes and comorbidities influencing disease course and severity. Evidence highlights a link between immune dysfunction and behavioral traits in autism from several types of evidence found in both cerebrospinal fluid and peripheral blood and their utility to identify autistic subgroups with specific immunophenotypes; underlying behavioral symptoms are also shown. This review summarizes current insights into immune dysfunction in ASD, with particular reference to the impact of immunological factors related to the maternal influence of autism development; comorbidities influencing autism disease course and severity; and others factors with particular relevance, including obesity. Finally, we described main elements of similarities between immunopathology overlapping neurodevelopmental and neurodegenerative disorders, taking as examples autism and Parkinson Disease, respectively.

Improvement of behavioural pattern and alpha-synuclein levels in autism spectrum disorder after consumption of a beta-glucan food supplement in a randomised, parallel-group pilot clinical study

Background

Autism spectrum disorders (ASDs) are a wide range of behavioural disabilities for which there are no definite interventional modalities available. Remedial therapies remain the only option but with varying outcomes. We have evaluated the Childhood Autism Rating Scale (CARS) and alpha-synuclein levels in this parallel-group, multiple-arm pilot clinical study after supplementation with a biological response modifier beta-glucan food supplement (Nichi Glucan).

Methods

Six subjects with ASD (n=6) Gr. 1 underwent conventional treatment comprising remedial behavioural therapies and L-carnosine 500 mg per day, and 12 subjects (n=12) Gr. 2 underwent supplementation with the Nichi Glucan 0.5 g two times per day along with the conventional treatment.

Results

There was a significant decrease in the CARS score in all of the children of the Nichi Glucan Gr.2 compared with the control (p=0.034517). Plasma levels of alpha-synuclein were significantly higher in Gr. 2 (Nichi Glucan) than in the control group Gr. 1 (p=0.091701).

Conclusion

Improvement of the behavioural pattern CARS score and a correlating alpha-synuclein level, followed by a safe beta-glucan food supplement, warrants further research on other parameters, such as gut-microbiota evaluation, and relevant neuronal biomarkers which is likely to cast light on novel solutions.

Alpha-Synuclein, cyclooxygenase-2 and prostaglandins-EP2 receptors as neuroinflammatory biomarkers of autism spectrum disorders: Use of combined ROC curves to increase their diagnostic values

BACKGROUND

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairments in social interaction and restricted and repetitive behaviors. Neuroinflammation and abnormal lipid mediators have been identified in multiple investigations as an acknowledged etiological mechanism of ASD that can be targeted for therapeutic intervention.

METHODS

In this study, multiple regression and combined receiver operating characteristic (ROC) curve analyses were used to determine the relationship between the neuroinflammatory marker α-synuclein and lipid mediator markers related to inflammation induction, such as cyclooxygenase-2 and prostaglandin-EP2 receptors, in the etiology of ASD. Additionally, the study aimed to determine the linear combination that maximizes the partial area under ROC curves for a set of markers. Forty children with ASD and 40 age- and sex-matched controls were enrolled in the study. Using ELISA, the levels of α-synuclein, cyclo-oxygenase-2, and prostaglandin-EP2 receptors were measured in the plasma of both groups. Statistical analyses using ROC curves and multiple and logistic regression models were performed.

RESULTS

A remarkable increase in the area under the curve was observed using combined ROC curve analyses. Moreover, higher specificity and sensitivity of the combined markers were reported.

CONCLUSIONS

The present study indicates that measurement of the predictive value of selected biomarkers related to neuroinflammation and lipid metabolism in children with ASD using a ROC curve analysis should lead to a better understanding of the etiological mechanism of ASD and its link with metabolism. This information may facilitate early diagnosis and intervention.

Neuropathological Findings in a Case of Parkinsonism and Developmental Delay Associated with a Monoallelic Variant in PLXNA1

BACKGROUND

PLXNA1 encodes for Plexin-A, a transmembrane protein expressed in the developing nervous system. Mutations in this gene have been associated with developmental delay but have not been previously associated with the development of parkinsonism.

OBJECTIVES

To describe the case of a 38-year-old patient with developmental delay who developed parkinsonism later in life.

METHODS

Post-mortem exome sequencing was performed with confirmation by Sanger sequencing. Brain autopsy was also performed.

RESULTS

Post-mortem exome sequencing on the proband identified a heterozygous predicted nonsense PLXNA1 variant (c.G3361T:p.Glu1121Ter). Pathology demonstrated arhinencephaly with brainstem heterotopia, diffuse Lewy body disease, and frontotemporal lobar dementia-tau.

CONCLUSIONS

This case of a patient with developmental delay and parkinsonism with PLXNA1 mutation highlights a need for assessing long-term outcomes of individuals with neurodevelopmental disorders, as well as the need for genetic testing in adults. It also suggests that the link between PLXNA1 and α-synuclein should be explored in the future. © 2021 International Parkinson and Movement Disorder Society.