Cellular and molecular mechanisms underlying autism spectrum disorders and associated comorbidities: A pathophysiological review

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders that develop in early life due to interaction between several genetic and environmental factors and lead to alterations in brain function and structure. During the last decades, several mechanisms have been placed to explain the pathogenesis of autism. Unfortunately, these are reported in several studies and reviews which make it difficult to follow by the reader. In addition, some recent molecular mechanisms related to ASD have been unrevealed. This paper revises and highlights the major common molecular mechanisms responsible for the clinical symptoms seen in people with ASD, including the roles of common genetic factors and disorders, neuroinflammation, GABAergic signaling, and alterations in Ca⁺² signaling. Besides, it covers the major molecular mechanisms and signaling pathways involved in initiating the epileptic seizure, including the alterations in the GABAergic and glutamate signaling, vitamin and mineral deficiency, disorders of metabolism, and autoimmunity. Finally, this review also discusses sleep disorder patterns and the molecular mechanisms underlying them.

Melatonin attenuates cerebral hypoperfusion-induced hippocampal damage and memory deficits in rats by suppressing TRPM7 channels

This study was conducted to examine if modulating transporters like transient receptor potential cation channels, subfamily M, member 7 (TRPM7) underlies the hippocampal neuroprotection afforded by melatonin (Mel) in rats exposed to cerebral hypoperfusion (CHP). Experimental groups included control, Mel-treated (1.87 g/kg), CHP, and CHP + Mel (1.87 g/kg)-treated rats. CHP was induced by the permanent bilateral occlusion of the common carotid arteries (2VO) method and treatments were conducted for 7 days, orally. Mel prevented the damage of the dental gyrus and memory loss in CHP rats and inhibited the hippocampal reactive oxygen species (ROS), lipid peroxidation levels of tumor necrosis factor-α (TNF-α), interleukine-6 (IL-6), interleukine-1 beta (IL-1β), and prostaglandin E2 (PGE2). It also reduced the hippocampal transcription of the TRPM7 channels and lowered levels of calcium (Ca²⁺) and zinc (Zn²⁺). Mel Also enhanced the levels of total glutathione (GSH) and superoxide dismutase (SOD) in the hippocampus of the control and CHP-treated rats. In conclusion, downregulation of TRPM7 seems to be one mechanism underlying the neuroprotective effect of Mel against global ischemia and is triggered by its antioxidant potential.

Leaky gut biomarkers in casein- and gluten-rich diet fed rat model of autism

It is proposed that gluten- and casein-rich diets (GRD and CRD) can synergistically exacerbate dysbiosis as comorbidity in autism by worsening leaky gut that affects the brain through the gut–brain axis. In this study, 35 young male rats were divided into 7 groups, Group 1 serves as control; Group 2, clindamycin (CL)-treated; and Group 3, propionic acid (PPA)-induced rodent model of autism. These three groups were fed standard diet until the end of the experiment. Groups 4–7 are rats treated similarly with CL and PPA, then fed on CRD or GRD until the end of the experiment. Serum zonulin, glutathione (GSH), lipid peroxides, and gut microbial composition were measured in the seven studied groups. Data demonstrate the significant increase in serum zonulin as marker of leaky gut in the CL-treated groups fed on CRD or GRD. Lipid peroxides were significantly higher in the serum of GRD-fed rats compared to CRD-fed or normal diet-fed rats. GSH was much lower in CL-treated groups fed on CRD or GRD compared to PPA-treated rats fed on both diets. Both diets differentially affected the diversity of the gut microbiota. This study demonstrates that CRD and GRD exacerbates leaky gut, according to serum zonulin, which was used as marker for increased gut permeability.

Curriculum Mapping and Alignment of the Neuroscience Block in an Undergraduate Medical Education Program: A Delphi Study

BACKGROUND

Curriculum mapping and alignment are complex processes essential for the improvement of curriculum and serve as guidelines for students, faculty, and college administrators. This project aims to map different components of the curriculum in a comprehensive manner to ensure smooth running of the curriculum for the end users.

MATERIALS AND METHODS

The project addressed the neuroscience block of the undergraduate medicine program. Eight parameters were investigated: competencies (learning outcomes), curriculum themes, block objectives, weekly problems, and objectives of weekly problems, disciplines, delivery, and assessment. The Delphi method was used by ten experts to assess the importance of these parameters. Focus interviews were then conducted with faculty members.

RESULTS

The panel of ten experts reached consensus by agreeing that the eight parameters are important for aligning and mapping the neuroscience block and can be helpful for smooth operation of the curriculum. Mapping and alignment were performed electronically using eight parameters over 8 weeks. Majority of the faculty members appreciated the use of curriculum mapping.

CONCLUSION

Curriculum mapping using electronic software helps in identifying gaps and redundancies and facilitating alignment between learning and assessment and learning objectives and competencies (learning outcomes). Training programs for faculty members and encouragement from leaders are suggested.

Melatonin Improves Memory Deficits in Rats with Cerebral Hypoperfusion, Possibly, Through Decreasing the Expression of Small-Conductance Ca2+-Activated K+ Channels

This study investigated the expression pattern, regulation of expression, and the role of hippocampal small-conductance Ca²⁺-activated K⁺ (SK) channels in memory deficits after cerebral hypoperfusion (CHP) with or without melatonin treatment, in rats. Adults male Wistar rats (n = 20/group) were divided into (1) a sham (2) a sham + melatonin (3) a two-vessel occlusion (2-VO) model, and (4) a 2-VO + melatonin. Melatonin was administered (i.p.) to all rats at a daily dose of 10 mg kg^-1 for 7 days starting at the time of 2-VO-induction. In contrast to 2-VO rats, melatonin increased the latency of the passive avoidance learning test and decreased time to find the hidden platform in Water Morris Test in all tested rats. In addition, it concomitantly downregulated SK1, SK2, and SK3 channels, downregulated mRNA levels of TNFα and IL-1β, enhanced BDNF levels and activity of PKA levels, and restored the levels of cholinergic markers in the hippocampi of the treated-rats. Mechanistically, melatonin significantly prevented CHP-induced activation of ERK1/2, JNK, and P38 MAPK at least by inhibiting ROS generation and enhancing the total antioxidant potential. In cultured hypoxic hippocampal neurons, individual blockage of MAPK signaling by the MEK1/2 inhibitor (U0126), but not by the P38 inhibitor (SB203580) or JNK inhibitor (SP600125), completely prevented the upregulation of all three kinds of SK channels. These data clearly confirm that upregulation of SK channels plays a role in CHP-induced memory loss and indicate that melatonin reverses memory deficits after CHP in rats, at least by, downregulation of SK1, SK2, and SK3 channels in their hippocampi.

Relationship between selenium, lead, and mercury in red blood cells of Saudi autistic children

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that can cause significant social, communication and behavioral challenges. Environmental contribution to ASD is due in large part to the sensitivity of the developing brain to external exposures such as lead (Pb), and mercury (Hg) as toxic heavy metals or due to a poor detoxification ability as the phenotype of this disorder. Selenium (Se) as an antioxidant element that counteracts the neurotoxicity of Hg, and Pb, presumably through the formation of nontoxic complexes. In the present study, Pb, Hg, and Se were measured in red blood cells (RBCs) of 35 children with ASD and 30 age- and gender-matched healthy control children using atomic absorption spectrometry. Receiver Operating Characteristics (ROC) analysis of the obtained data was performed to measure the predictive value of their absolute and relative concentrations. The obtained data demonstrates a significant elevation of Hg and Pb together with a significant decrease in the Se levels in RBCs of patients with ASD when compared to the healthy controls. The ratios of Se to both Pb and Hg were remarkably altered, being indicative of heavy metal neurotoxicity in patients with ASD. In conclusion, the present study indicates the importance of Se for prevention and/or therapy of heavy metal neurotoxicity.

Enhanced hepatic insulin signaling in the livers of high altitude native rats under basal conditions and in the livers of low altitude native rats under insulin stimulation: a mechanistic study

This study was designed to investigate the role of the liver in lowering fasting blood glucose levels (FBG) in rats native to high (HA) and low altitude (LA) areas. As compared with LA natives, besides the improved insulin and glucose tolerance, HA native rats had lower FBG, at least mediated by inhibition of hepatic gluconeogenesis and activation of glycogen synthesis. An effect that is mediated by the enhancement of hepatic insulin signaling mediated by the decreased phosphorylation of TSC induced inhibition of mTOR function. Such effect was independent of activation of AMPK nor stabilization of HIF1α, but most probably due to oxidative stress induced REDD1 expression. However, under insulin stimulation, and in spite of the less activated mTOR function in HA native rats, LA native rats had higher glycogen content and reduced levels of gluconeogenic enzymes with a more enhanced insulin signaling, mainly due to higher levels of p-IRS1 (tyr612).

Increase of cytosolic phospholipase A2 as hydrolytic enzyme of phospholipids and autism cognitive, social and sensory dysfunction severity

BACKGROUND

Autism is neurodevelopmental disorder that is characterized by developmental, behavioral, social and sensory abnormalities. Researchers have focused in last years in immunological alteration and inflammation as a hot subject in autism field. This work aims to study the alteration in phospholipids (PE, PS, and PC) together with the change in cPLA2 concentration as the main phospholipid hydrolytic enzyme in autistic patients compared to control. It was also extended to find a correlation between these biomarkers and severity of autism measured as childhood autism rating scale (CARS), Social responsiveness scale (SRS), and Short sensory profile (SSP).

METHODS

Phospholipids (PE, PS, PC) and cPLA2 as biochemical parameters were determined in the plasma of 48 Saudi autistic male patients, categorized as mild-moderate and severe as indicated by their Childhood Autism Rating Scale (CARS), social responsiveness scale (SRS) and short sensory profile (SSP) and compared to 40 age- and gender-matched control samples.

RESULTS

The reported data demonstrate significantly lower levels of PE, PS, and PC together with a significant increase in cPLA2. While association between severity of autism and impaired phospholipid concentration was completely lacked, an association between cPLA2 and impaired sensory processing was observed.

CONCLUSIONS

The impaired phospholipid level and remarkable increased in cPLA2 concentration asserted their roles in the etiology of autism. Receiver operating characteristic analysis together with predictiveness diagrams proved that the measured parameters could be used as predictive biomarkers of clinical symptoms and provide significant guidance for future therapeutic strategy to re-establish physiological homeostasis.

Changes in sympathetic neurovascular function following spinal cord injury

The effects of spinal cord injury (SCI) on sympathetic neurovascular transmission have generally been ignored. This review describes changes in sympathetic nerve-mediated activation of arterial vessels to which ongoing sympathetic activity has been reduced or silenced following spinal cord transection in rats. In all vessels studied in rats, SCI markedly enhanced their contractile responses to nerve activity. However, the mechanisms that augment neurovascular transmission differ between the rat tail artery and mesenteric artery. In tail artery, the enhancement of neurovascular transmission cannot be attributed to changes in sensitivity of the vascular muscle to α₁- or α₂-adrenoceptor agonists. Instead the contribution of L-type Ca²⁺ channels to activation of the smooth muscle by nerve-released noradrenaline is greatly increased following SCI. By contrast, mesenteric arteries from SCI rats had increased sensitivity to phenylephrine but not to methoxamine. While both phenylephrine and methoxamine are α₁-adrenoceptor agonists, only phenylephrine is a substrate for the neuronal noradrenaline transporter. Therefore the selective increase in sensitivity to phenylephrine suggests that the activity of the neuronal noradrenaline transporter is reduced. While present evidence suggests that sympathetic vasoconstrictor neurons do not contribute to the normal regulation of peripheral resistance below a complete SCI in humans, the available evidence does indicate that these experimental findings in animals are likely to apply after SCI in humans and contribute to autonomic dysreflexia.

Descriptive characteristics of children with autism at Autism Treatment Center, KSA

Autism characteristics in sixty children (aged from 2 to 8) were assed. Their behavioral symptoms were evaluated using the Autism Treatment Evaluation Checklist (ATEC). ATEC has four main domains of autistic disorders (Speech/Language/Communication, Sociability, Sensory/Cognitive Awareness, and Health/Physical/Behavior) in children with clinical diagnosis by Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and Childhood Autism Rating Scale (CARS) of autism spectrum disorder (ASD). Utilizing ATEC checklist, our study describes significant behavioral observations between autistic children which could effectively contribute to better understanding and treatment during their early intervention stage.

Spinal cord injury increases the reactivity of rat tail artery to angiotensin II

Studies in individuals with spinal cord injury (SCI) suggest the vasculature is hyperreactive to angiotensin II (Ang II). In the present study, the effects of SCI on the reactivity of the rat tail and mesenteric arteries to Ang II have been investigated. In addition, the effects of SCI on the facilitatory action of Ang II on nerve-evoked contractions of these vessels were determined. Isometric contractions of artery segments from T11 (tail artery) or T4 (mesenteric arteries) spinal cord-transected rats and sham-operated rats were compared 6–7 weeks postoperatively. In both tail and mesenteric arteries, SCI increased nerve-evoked contractions. In tail arteries, SCI also greatly increased Ang II-evoked contractions and the facilitatory effect of Ang II on nerve-evoked contractions. By contrast, SCI did not detectably change the responses of mesenteric arteries to Ang II. These findings provide the first direct evidence that SCI increases the reactivity of arterial vessels to Ang II. In addition, in tail artery, the findings indicate that Ang II may contribute to modifying their responses following SCI.

Prominent contribution of L-type Ca2+ channels to cutaneous neurovascular transmission that is revealed after spinal cord injury augments vasoconstriction

In patients with spinal cord injury (SCI), somatosympathetic reflexes produce exaggerated decreases in skin blood flow below the lesion. This hypoperfusion appears to result from an increased responsiveness of cutaneous arterial vessels to neural activation. Here we investigated the mechanisms that underlie SCI-induced enhancement of neurovascular transmission in a cutaneous vessel, the rat tail artery. Isometric contractions of arterial segments from T11 spinal cord transected and sham-operated rats were compared 6 wk postoperatively. SCI more than doubled the amplitudes of contractions of arteries in response to moderate frequencies of nerve stimulation (0.1 to 1 Hz). In arteries from SCI rats, but not those from sham-operated rats, the L-type Ca(2+) channel blocker nifedipine (1 μM) reduced the amplitudes of nerve-evoked contractions. Furthermore, while the sensitivity to the agonists phenylephrine (α(1)-adrenoceptor selective) and clonidine (α(2)-adrenoceptor selective) did not differ significantly between arteries from SCI and sham-operated rats, nifedipine had a greater inhibitory effect on contractions to both agents in arteries from SCI rats. Although sensitivity to clonidine was unchanged, SCI selectively reduced the contribution of postjunctional α(2)-adenceptors to nerve-evoked contractions. In arteries from unoperated rats, the L-type channel agonist BAY K 8644 (0.1 μM) produced a similar enhancement of nerve-evoked contraction to that produced by SCI and also selectively reduced the contribution of α(2)-adrenceptors to these responses. Together the findings demonstrate that the SCI-induced enhancement of neurovascular transmission in the rat tail artery can largely be accounted for by an increased contribution of L-type Ca(2+) channels to activation of the vascular smooth muscle.