Commentary on "Platelet Studies in Autism Spectrum Disorder Patients and First-Degree Relatives"

Plasma levels of nerve growth factor in Egyptian autistic children: Relation to hyperserotonemia and autoimmunity

Hyperserotonemia and brain-specific autoantibodies are detected in some autistic children. Nerve growth factor (NGF) stimulates the proliferation of B lymphocytes with production of antibodies and also increases mast cell serotonin release. This work was the first to investigate the relationship between plasma NGF and both hyperserotonemia and the frequency of serum anti-myelin basic protein (anti-MBP) auto-antibodies in 22 autistic children aged between 4 and 12 years and 22 healthy-matched controls. Levels of NGF, serotonin and anti-MBP were significantly higher in autistic children than healthy control children (P < 0.001). There was a significant positive correlation between NGF and serotonin levels in autistic patients (P < 0.01). In contrast, there was a non-significant correlation between NGF and anti-MBP levels (P > 0.05). In conclusions, serum NGF levels were elevated and significantly correlated to hyperserotonemia found in many autistic children.

Evaluation of Platelet Parameters in Children with Autism Spectrum Disorder: Elongated Collagen-Adenosine Diphosphate and Collagen-Epinephrine Closure Times

Changes related to the serotonin system play a key role in the etiology of autism spectrum disorder (ASD). Although we know that platelets are associated with the serotonin system, their relation to ASD has not yet been elucidated. In this study, we aim to investigate platelet parameters in children with ASD. Forty patients with ASD according to Diagnostic and Statistical Manual of Mental Disorders 5 (DSM-5) and 30 healthy controls were included in the study. A complete blood count was done to measure parameters relating to platelet morphology. Moreover, prothrombin time (PT) and activated partial thromboplastin time (aPTT) were evaluated. Lastly, platelet functions were assessed with a platelet functions analyzer 100 (PFA-100) device by measuring collagen-ADP and collagen-epinephrine (EPI) closure times. There was not a significant difference between the groups in terms of platelet count, mean platelet volume (MPV), platelet distribution width, plateletcrit, PT, or aPTT parameters for ASD patients when compared to the control group (P > 0.05). However, MPV in severe ASD, as quantified by the Childhood Autism Rating Scale, was found to be significantly lower when compared to mild to moderate ASD (P = 0.047). Moreover, in terms of platelet functions, the elongation in collagen-ADP and collagen-EPI closure times were significantly higher for the ASD group (P = 0.044). These results may suggest an impairment in platelet functions rather than in platelet morphology for children with ASD. Considering these results, further investigation of thrombocyte functions in the ASD may lead to a better understanding of the pathogenesis of ASD and to the development of our limited knowledge of this disorder. Autism Res 2019, 12: 1069-1076. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Serotonin is a chemical that is found in brain as wells as in blood cells that function in blood clotting in the human body. There are problems related to serotonin in brains of people who have autism. Thus, blood clotting cells may also be affected in people who have autism. In this study, we compare blood clotting functions of children with autism with that of healthy controls.

Serotonin and serotonin transporter levels in autistic children

OBJECTIVES

To assess the possible correlation between serotonin and serotonin transporter (SERT) with the autism severity and investigate the association between these parameters in autistic children to assess their possible role for diagnosis of autism severity.

METHODS

A comparative cross-sectional study was carried out in the Chemistry and Biochemistry Department, College of Medicine, Al-Nahrain University, Baghdad, Iraq while the samples were taken from 60 male autistic children recruited to the Department of Pediatrics at Al-Sader Hospital, Baghdad, Iraq between November 2014 amd April 2015. Levels of serotonin and serotonin transporters (SERT) were determined in 60 male autistic Iraqi patients classified into mild, moderate and severe (20 for each). These levels were compared with those of 26 healthy control children. Results: Levels of serotonin and SERT were significantly increased in autistic children than that of gender and age-matched controls. Serotonin levels were 80.63± 21.83 ng/ml in mild, 100.39±23.07 ng/ml moderate, and 188.7±31.72 ng/ml severe autistic patients. Serotonin transporter levels were 10.13±4.51 ng/ml in mild, 13.15±4.71 ng/ml moderate, and 16.32±6.7 ng/ml in  severe autistic patients. The increase of both serotonin and SERT levels were associated with severity of autism. Receiver operating characteristic (ROC) analysis  can be used for diagnostic and prognostic purposes.

CONCLUSIONS

High serotonin and SERT levels may indicate that these biomarkers have a role in the autism pathogenesis and support the possibility of using serotonin and SERT to diagnose autism severity.

Loss of Serotonin Transporter Function Alters ADP-mediated Glycoprotein αIIbβ3 Activation through Dysregulation of the 5-HT2A Receptor

Reduced platelet aggregation and a mild bleeding phenotype have been observed in patients chronically taking selective serotonin reuptake inhibitors (SSRIs). However, it remains unclear how SSRIs, which inhibit the plasma membrane serotonin transporter (SERT), modulate hemostasis. Here, we examine how sustained inhibition of SERT activity alters serotonergic signaling and influences platelet activation and hemostasis. Pharmaceutical blockade (citalopram dosing) or genetic ablation (SERT(-/-)) of SERT function in vivo led to reduced serotonin (5-hydroxytryptamine (5-HT)) blood levels that paralleled a mild bleeding phenotype in mice. Transfusion of wild-type platelets to SERT(-/-) mice normalized bleeding times to wild-type levels, suggesting that loss of SERTs causes a deficiency in platelet activation. Although SERT(-/-) platelets displayed no difference in P-selectin or αIIbβ3 activation upon stimulation with thrombin, ADP-mediated αIIbβ3 activation is reduced in SERT(-/-) platelets. Additionally, synergistic potentiation of αIIbβ3 activation by ADP and 5-HT is lost in SERT(-/-) platelets. Acute treatment of wild-type platelets with 5-HT2A receptor (5-HT2AR) antagonists or SSRIs revealed that functional 5-HT2ARs, not SERTs, are necessary for the synergistic activation of αIIbβ3 by dual 5-HT/ADP stimulation. Pharmacological studies using radiolabeled guanosine 5'-3-O-([(35)S]thio)triphosphate and [(3)H]ketanserin revealed that platelets isolated from SERT(-/-) or citalopram-treated mice have reduced activation of G-proteins coupled to 5-HT2ARs and receptor surface expression. Taken together, these data demonstrate that sustained SERT loss of function reduces 5-HT2AR surface expression that is critical for the synergistic activation of αIIbβ3 by 5-HT and ADP. These results highlight an antiplatelet strategy centered on blocking or desensitizing 5-HT2AR to attenuate ADP-mediated αIIbβ3 activation.