الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
ASD is a neurodevelopmental disorder characterized by impaired social interaction and repetitive stereotyped behavior. It is related to multiple etiological factors including genetic predispositions and environmental exposure to teratogens during the critical stages of brain development that affects different areas leading to functional and behavioral impairments. Unfortunately, the prevalence of ASD is increasing despite the increased advances in clinical and experimental research, and still there is a lack of knowledge to the definite pathogenic mechanisms of ASD due to the clinical diversity of its symptoms.
Numerous lines of evidence pointed out different underlying mechanisms in the pathophysiology of ASD such as, neuroinflammation and redox imbalance. Recently, PPAR-α, tauopathy and gliopathology especially reactive astrogliosis and its impact on synaptic maturation and neuronal development, are considered to have a major role underlying ASD. Thus, a deeper knowledge about the neurobiological basis is warranted to improve the treatment options.
Notably, PPAR-α is considered an attractive therapeutic target in neurodevelopmental disorders due to its neuroprotective effects by regulating genes involved in inflammation and oxidative stress, ameliorating astroglial reactivity and maintaining the structural morphology and functional integrity of several brain areas.
Summary and Conclusion
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In this context, VPA exposure was used as a valid rat model of autism based on the notion that children born to pregnant women taking VPA for seizure management had an elevated risk of developing ASD. Rats exposed to VPA during critical times of brain development was proved to interfere with cell proliferation, differentiation, synaptic maturation and inducing neurodevelopmental delays and behavioral deficits thus, recapitulating the human autistic clinical symptoms and allow to detect novel therapeutic options in ASD.
To date, no treatment exists for autistic core symptoms, and only few medications have been approved by FDA such as risperidone for treatment of irritability associating autism. Unfortunately, RIS treatment is associated with weight gain and obesity that negatively impact patient compliance, being a major reason for drug discontinuation. Recently, MET through activating PPAR-α, has promising effects on ameliorating autistic core symptoms and neurobiological changes beside being effective in mitigating risperidone-induced weight gain that would favor the treatment compliance in autistic patients.
Aim of the work
Our study was designed to detect the potential roles of PPAR-α, reactive astrogliosis and tauopathy in ASD pathophysiology and the effects of chronic treatments with MET and RIS monotherapy vs combination on autistic-like behaviors, neurobiological and histopathological neurodegenerative changes induced by prenatal VPA exposure in male Wistar rats.
Summary and Conclusion
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Study design
Total 60 male Wistar rats were randomly divided into six groups as follow;
1. Prenatal Control group, (n=10).
2. Prenatal VPA group (Model of Autism), (n=10).
3. VPA-vehicle-treated group, (n=10).
4. VPA-MET (100mg/kg/day)-treated group, (n=10).
5. VPA-RIS (1mg/kg/day)-treated group, (n=10).
6. VPA-MET+RIS-treated group, (n=10).
Rats in all groups were subjected to:
1. Behavioral assessments:
- Assessment of autistic-like behaviors (3-CST, MBT, OFT, MWM and TNT).
- Assessment of neurodevelopmental delays (RRT, NGT, day of eye opening, tail deformities and body weight).
2. Biochemical measurements in prefrontal cortex and hippocampal tissue homogenates:
- Biological markers of neuroinflammation (TNF-α, IL-1ß and NF-κB).
- Biological markers of oxidative stress (GSH levels, CAT activity, lipid peroxidation (MDA), ‘NOx’ as nitrite levels).
- PPAR-α expression (PCR).
3. Histopathological and Immuno-histochemical studies of prefrontal cortex and hippocampus area CA1:
- H&E stain: to examine the histological architecture of neurons.
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- Toluidine blue stain: for detection of Nissl’s granules.
- Marsland, Glees and Erikson’s silver stain: for detection of neurofibrillary tangles.
- Caspase-3 immuno-histochemistry: for detection of apoptosis.
- GFAP immune-histochemistry: for detection of astrocytes activity.
The results could be summarized as follows:
At the behavioral level, prenatal VPA exposure exhibited autistic-like behaviors expressed by decreased social interaction (in 3-CST), increased repetitive stereotyped behavior and anxiety (in MBT & OFT), cognitive impairment (in MWM) and decreased pain sensitivity (in TNT), along with decreased body weight compared to control group.
MET and RIS monotherapy and in combination attenuated autistic-like behaviors compared to vehicle group and the effect of MET was comparable to RIS. RIS monotherapy couldn’t significantly improve the cognitive deficits and pain sensitivity in addition to increasing body weight. On the other hand, MET monotherapy and in combination to RIS treatment significantly improved the autistic-like behaviors, cognitive deficits, pain sensitivity in addition to decreasing body weight. Furthermore, combination therapy was superior to RIS monotherapy in decreasing repetitive stereotyped behavior in MBT.
At the molecular level, prenatal VPA exposure significantly exhibited an increase in neuroinflammatory markers (TNF-α, IL-1ß and NF-κB) and induced redox imbalance (GSH and CAT activity with MDA and NOx) in addition to deceased PPAR-α expression in
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prefrontal cortex and hippocampus tissue homogenates compared to control group.
MET and RIS monotherapy and in combination significantly decreased markers of neuroinflammation, restored the redox balance and increased PPAR-α expression compared to vehicle group and the combination was superior to monotherapy in most of the aforementioned parameters. Interestingly, the effect of MET was comparable to RIS.
Histopathological examination revealed that, prenatal VPA exposure subsequently led to neurodegenerative changes and apoptosis, increased NFTs and astrocytes reactivity in both prefrontal cortex and hippocampus area CA1 compared to control group. MET and RIS monotherapy and in combination reduced signs of neurodegeneration, apoptosis, NFTs and astrocytes reactivity compared to vehicle group and the effect of MET was comparable to RIS. Combined MET+RIS treatment was superior to either MET or RIS monotherapy in ameliorating neurodegenerative and apoptotic changes in both examined brain areas.