Assessment of DNA repair efficiency in the inbred BTBR T+tf/J autism spectrum disorder mouse model exposed to gamma rays and treated with JNJ7777120

Semaglutide ameliorated autism-like behaviors and DNA repair efficiency in male BTBR mice by recovering DNA repair gene expression

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that is marked by impaired social interactions, and increased repetitive behaviors. There is evidence of genetic changes in ASD, and several of these altered genes are linked to the process of DNA repair. Therefore, individuals with ASD must have improved DNA repair efficiency to mitigate risks associated with ASD. Despite numerous milestones in ASD research, the disease remains incurable, with a high occurrence rate and substantial financial burdens. This motivates scientists to search for new drugs to manage the disease. Disruption of glucagon-like peptide-1 (GLP-1) signaling, a regulator in neuronal development and maintains homeostasis, has been associated with the pathogenesis and progression of several neurological disorders, such as ASD. Our study aimed to assess the impact of semaglutide, a new GLP-1 analog antidiabetic medication, on behavioral phenotypes and DNA repair efficiency in the BTBR autistic mouse model. Furthermore, we elucidated the underlying mechanism(s) responsible for the ameliorative effects of semaglutide against behavioral problems and DNA repair deficiency in BTBR mice. The current results demonstrate that repeated treatment with semaglutide efficiently decreased autism-like behaviors in BTBR mice without affecting motor performance. Semaglutide also mitigated spontaneous DNA damage and enhanced DNA repair efficiency in the BTBR mice as determined by comet assay. Moreover, administering semaglutide recovered oxidant-antioxidant balance in BTBR mice. Semaglutide restored the disrupted DNA damage/repair pathways in the BTBR mice by reducing Gadd45a expression and increasing Ogg1 and Xrcc1 expression at both the mRNA and protein levels. This suggests that semaglutide holds great potential as a novel therapeutic candidate for treating ASD traits.

Aflatoxin B1 Exacerbates Genomic Instability and Apoptosis in the BTBR Autism Mouse Model via Dysregulating DNA Repair Pathway

The pathophysiology of autism is influenced by a combination of environmental and genetic factors. Furthermore, individuals with autism appear to be at a higher risk of developing cancer. However, this is not fully understood. Aflatoxin B1 (AFB1) is a potent food pollutant carcinogen. The effects of AFB1 on genomic instability in autism have not yet been investigated. Hence, we have aimed to investigate whether repeated exposure to AFB1 causes alterations in genomic stability, a hallmark of cancer and apoptosis in the BTBR autism mouse model. The data revealed increased micronuclei generation, oxidative DNA strand breaks, and apoptosis in BTBR animals exposed to AFB1 when compared to unexposed animals. Lipid peroxidation in BTBR mice increased with a reduction in glutathione following AFB1 exposure, demonstrating an exacerbated redox imbalance. Furthermore, the expressions of some of DNA damage/repair- and apoptosis-related genes were also significantly dysregulated. Increases in the redox disturbance and dysregulation in the DNA damage/repair pathway are thus important determinants of susceptibility to AFB1-exacerbated genomic instability and apoptosis in BTBR mice. This investigation shows that AFB1-related genomic instability can accelerate the risk of cancer development. Moreover, approaches that ameliorate the redox balance and DNA damage/repair dysregulation may mitigate AFB1-caused genomic instability.

The small molecule Erk1/2 signaling pathway inhibitor PD98059 improves DNA repair in an experimental autoimmune encephalomyelitis SJL/J mouse model of multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disorder in which the myelin sheath covering the central nervous system axons is damaged or lost, disrupting action potential conduction and leading to various neurological complications. The pathogenesis of MS remains unclear, and no effective therapies are currently available. MS is triggered by environmental factors in genetically susceptible individuals. DNA damage and DNA repair failure have been proposed as MS genetic risk factors; however, inconsistent evidence has been found in multiple studies. Therefore, more investigations are needed to ascertain whether DNA damage/repair is altered in this disorder. In this context, therapies that prevent DNA damage or enhance DNA repair could be effective strategies for MS treatment. The overactivation of the extracellular-signal-related kinase 1 and 2 (Erk1/2) pathway can lead to DNA damage and has been linked to MS pathogenesis. In our study, we observed substantially elevated oxidative DNA damage and slower DNA repair rates in an experimentally autoimmune encephalomyelitis animal model of MS (EAE). Moreover, statistical decreases in oxidative DNA strand breaks and faster repair rates were observed in EAE animals injected with the Erk1/2 inhibitor PD98059 (PD). Moreover, the expression of several genes associated with DNA strand breaks and repair changed in EAE mice at both the mRNA and protein levels, as revealed by the RT² Profiler PCR array and verified by RT-PCR and protein analyses. The treatment with PD mitigated these changes and improved DNA repair gene expression. Our results demonstrate clear associations between Erk1/2 activation, DNA damage/repair, and MS pathology, and further suggest that PD therapy may be a promising adjuvant therapeutic strategy.

Multiple exposure to methylmercury aggravates DNA damage in the BTBR T + Itpr3 tf/J autistic mouse model: the role of DNA repair efficiency

Environmental and genetic factors have been recognized to play major roles in the pathogenesis of autism. Here we examined the BTBR T⁺Itpr3^tf/J (BTBR) mice's susceptibility, an autistic model, to the genotoxic effects and DNA repair dysregulation of methylmercury. Micronuclei formation and oxidative DNA damage were analyzed using the micronucleus/fluorescence in situ hybridization test and modified comet assay, respectively. The results showed higher centromeric-positive micronuclei and oxidative DNA damage in BTBR mice exposed to methylmercury than the unexposed mice, which indicates that mutagenesis aggravated in BTBR mice after methylmercury exposure. Lipid peroxides in BTBR mice were significantly elevated, with a decrease in reduced/oxidized glutathione ratio after methylmercury exposure, indicating an augmenting oxidant-antioxidant imbalance. The expression of several genes involved in DNA repair was markedly altered in BTBR mice after methylmercury exposure as evaluated via PCR array and RT-PCR analyses. Declining of the antioxidant defense and dysregulation in DNA repair process after methylmercury exposure may explain the aggravated genotoxic susceptibility of BTBR mice. Thus, autistic individuals exposed to methylmercury must be under regular medical follow-up through standard timetabled medical laboratory inquiry to allow for early recognition of any mutagenic changes. Additionally, strategies that elevate cellular antioxidants/DNA repair efficiency may counteract methylmercury-induced genotoxicity.

Role of the DUB enzyme USP7 in dendritic arborization, neuronal migration, and autistic-like behaviors in mice

Duplication and haploinsufficiency of the USP7 gene are implicated in autism spectrum disorders (ASD), but the role for USP7 in neurodevelopment and contribution to ASD pathogenesis remain unknown. We find that in primary neurons, overexpression of USP7 increases dendritic branch number and total dendritic length, whereas knockdown leads to opposite alterations. Besides, USP7 deubiquitinates the X-linked inhibitor of apoptosis protein (XIAP). The USP7-induced increase in XIAP suppresses caspase 3 activity, leading to a reduction in tubulin cleavage and suppression of dendritic pruning. When USP7 is introduced into the brains of prenatal mice via in utero electroporation (IUE), it results in abnormal migration of newborn neurons and increased dendritic arborization. Importantly, intraventricular brain injection of AAV-USP7 in P0 mice leads to autistic-like phenotypes including aberrant social interactions, repetitive behaviors, as well as changes in somatosensory sensitivity. These findings provide new insights in USP7-related neurobiological functions and its implication in ASD.

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Overexpression of USP7 increases dendritic arborization

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USP7 targets XIAP for deubiquitination and regulates XIAP proteostasis in neurons

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USP7 regulates dendritic remodeling via the XIAP-caspase 3-tubulin pathway

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Prenatal overexpression of USP7 in mice leads to autistic-like behaviors

The MAP kinase inhibitor PD98059 reduces chromosomal instability in the autoimmune encephalomyelitis SJL/J-mouse model of multiple sclerosis

Multiple sclerosis (MS), a disease in which the immune system attacks nerve cells, has been associated with both genetic and environmental risk factors. We observed increased micronucleus (MN) formation in SJL/J mouse experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Most of these MN were due to chromosomal loss. Increased activation of MAP kinases, which leads to disruption of the mitotic spindle and improper segregation of chromosomes, is associated with MS. MAP kinase inhibitors, such as PD98059, may therefore be beneficial for MS. In the EAE model, PD98059 treatment reduced adverse effects, including MN formation, lipid peroxidation, and GSH oxidation. Interventions that mitigate chromosomal instability may have therapeutic value in MS.

3-Aminobenzamide alleviates elevated DNA damage and DNA methylation in a BTBR T+Itpr3tf/J mouse model of autism by enhancing repair gene expression

Little is known about genetic and epigenetic alterations in autism spectrum disorder. Moreover, the efficiency of DNA repair in autism must be improved to correct these alterations. We examined whether 3-aminobenzamide (3-AB) could reverse these alterations. We conducted experiments to clarify the molecular mechanism underlying these ameliorations. An assessment of genetic and epigenetic alterations by a modified comet assay showed elevated levels of oxidative DNA strand breaks and DNA hypermethylation in BTBR T⁺Itpr3^tf/J (BTBR) mice used as a model of autism. Oxidative DNA strand breaks and DNA methylation were further quantified fluorometrically, and the results showed similar changes. Conversely, 3-AB treated BTBR mice showed a significant reduction in these alterations compared with untreated mice. The expressions of 43 genes involved in DNA repair were altered in BTBR mice. RT² Profiler PCR Array revealed significantly altered expression of seven genes, which was confirmed by RT-PCR analyses. 3-AB treatment relieved these disturbances and significantly improved Ogg1 and Rad1 up-regulation. Moreover, autism-like behaviors were also mitigated in BTBR animals by 3-AB treatment without alterations in locomotor activities. The simultaneous effects of reduced DNA damage and DNA methylation levels as well as the regulation of repair gene expression indicate the potential of 3-AB as a therapeutic agent to decrease the levels of DNA damage and DNA methylation in autistic patients. The current data may help in the development of therapies that ultimately provide a better quality of life for individuals suffering from autism.

Evaluation of DNA repair efficiency in autistic children by molecular cytogenetic analysis and transcriptome profiling

Data regarding DNA repair perturbations in autism, which might increase the risk of malignancy, are scarce. To evaluate whether DNA repair may be disrupted in autistic children, we assessed the incidence of endogenous basal DNA strand breaks as well as the efficiency of repairing DNA damage caused by γ-ray in lymphocytes isolated from autistic and healthy children. The incidence of DNA damage and the kinetics of DNA repair were determined by comet assay, while the incidence of residual DNA damage was evaluated by structural chromosomal aberration analysis. Transcriptome profiling of 84 genes associated with DNA damage and repair-signaling pathways was performed by RT² Profiler PCR Array. The array data were confirmed by RT-PCR and western blot studies. Our data indicate that the incidence of basal oxidative DNA strand breaks in autistic children was greater than that in nonautistic controls. Lymphocytes from autistic children displayed higher susceptibility to damage by γ-irradiation and slower repair rate than those from nonautistic children. Although the total unstable chromosomal aberrations were unaffected, lymphocytes from autistic children were more susceptible to chromosomal damage caused by γ-ray than those from nonautistic children. Transcriptomic analysis revealed that several genes associated with repair were downregulated in lymphocytes from autistic individuals and in those exposed to γ-irradiation. This may explain the increased oxidative DNA damage and reduced repair rate in lymphocytes from autistic individuals. These features may be related to the possible correlation between autism and the elevated risk of cancer and may explain the role of the disruption of the DNA repair process in the pathogenesis of autism.

The histamine-4 receptor antagonist JNJ7777120 prevents immune abnormalities by inhibiting RORγt/T-bet transcription factor signaling pathways in BTBR T+ Itpr3tf/J mice exposed to gamma rays

Autism is a neurodevelopmental disorder characterized by deficits and qualitative impairments in communication and implicit skill learning. Its prevalence is higher than previous estimates, and treatments have limited efficacy and are costly. Here, we assessed the therapeutic potential of JNJ77777120 (JNJ), a histamine-4 receptor (H4R) antagonist, using BTBR T⁺ Itpr3^tf/J (BTBR) mice, a confirmed model of autism, and C57BL/6J (C57) mice, a commonly chosen reference strain. We first examined the effects of JNJ treatment on BTBR mice exposed to gamma-rays (irradiation-exposed) using a three-chambered apparatus. We further investigated the possible molecular mechanisms through which JNJ administration modulates IL-17A-, RORγT-, IL-22-, T-bet-, STAT3-, ICOS-, and Foxp3-producing CD8⁺ T cells in the spleens of irradiation-exposed BTBR mice. The effects of JNJ administration on the mRNA and protein expression of IL-17A, RORγT, IL-22, T-bet, STAT-3, pSTAT3, IL-10, and Foxp3 in brain tissue were also explored. Results showed that JNJ treatment with irradiation exposure increased social interactions in BTBR mice compared to that in irradiation-exposed BTBR mice. Additionally, JNJ-treated and irradiation-exposed BTBR mice exhibited decreases in IL-17A-, RORγT-, IL-22-, T-bet-, and STAT3-producing CD8⁺ T cells and increases in ICOS- and Foxp3-producing CD8⁺ T cells. Moreover, JNJ treatment and irradiation exposure in BTBR mice regulated the mRNA and protein expression levels of IL-17A, RORγT, IL-22, T-bet, STAT3, pSTAT-3, IL-10, and Foxp3 in the brain tissue. These results suggest that JNJ is useful for the treatment of autism, as this H4R antagonist could block inflammatory cytokine production and transcription factor signaling.