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Objectives: Autism is a complex disorder that is heterogeneous in nature with varying degrees of severity for which no speci?c biological marker has been identified to date. Autism may result from an interaction between genetic, environmental and immunological factors. Risk factors of autism are linked by the mechanisms of inşammation, oxidative stress and nitrosative stress. Immune system dysfunction and cytokine imbalances are well documented in autism. These imbalances may have a pathogenic role or they may be potential markers for autism. Nitric oxide (NO) is involved in immune reactivity and is known to affect brain neurodevelopmental processes. Recent evidence indicates that NO, and cytokines (such as TNF-?) involved in NO production, may be high in children with autism. In this study, we aimed to evaluate the association between NOS3 4a/4b and G894T (Glu298Asp), TNF-? -308G>A polymorphisms and NOS3, TNF-? gene expressions in cases with autism and healthy controls.
Methods: Twelve autistic patients (10 male, 2 female) and 10 healthy controls (8 male, 2 female) were enrolled. Autism diagnosis was performed using gold standard assessments based on Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) (American Psychiatric Association, 2000) criteria by qualified trained clinicians in the Erciyes University School of Medicine, Department of Child Psychiatry. Patients included in the study were not taking any medication and according to their examination there were not any clinically significant infection, neurological and endocrine findings. DNA was isolated from whole blood samples. The genotyping of NOS3 Glu298Asp and TNF-? -308G>A polymorphisms were performed with Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP). The NOS3 intron 4 polymorphism was determined by PCR. Total RNA was extracted with TRIzol Reagent. NOS3 and TNF-? gene expressions were assessed by Quantitative Real-Time PCR (qRT-PCR). Results were evaluated by appropriate statistical methods.
Results: Participants were not statistically different in age or sex ratios. A significant positive correlation was detected between TNF-? and NOS3 gene expression values in patient group (?=0.937,p<0.001) while (?=0.988,p<0.001) in control group. Polymorphisms of the genes were not significantly different among the groups. Additionally expression levels of TNF-? and NOS3 did not show significant differences between the groups.
Conclusion: This finding with the expression of TNF-? is largely dependent on genetic and environmental inşuences. Because of the complexity of NO biosynthesis, epigenetic mechanisms can be responsible for its expression levels in our study. We recommend studying further with oxidative stress markers, cytokine gene serum levels and gene expressions in autism.