Autism Spectrum Disorder (ASD) is a group of neurodevelopmental disabilities that has an early onset. The core symptoms of ASD include impairment of social interaction, repetitive behaviors and restricted interest. To date, no effective pharmacological treatment is known to cure the core symptoms of this disorder (Belmonte et al., 2004; Frith & Happé, 2005; Lord, Elsabbagh, Baird, & Veenstra-Vanderweele, 2018; Maenner, Shaw, & Baio, 2020).
Disturbance in the β-catenin wnt (wingless) signaling pathway is considered as one of the mechanisms included in pathology of ASD. Wnt signaling pathway is highly conserved from lower to higher organisms and plays important and various roles in neurodevelopment. Because of the critical role of wnt signaling pathway in synaptogenesis and neurodevelopment, disruption in this pathway has been reported in ASD. Genetic evidence suggests that mutation in the gene of the main components or modulators of canonical β- catenin signaling pathway may involve in ASD pathogenesis (Mulligan & Cheyette, 2016; Okerlund & Cheyette, 2011; Qin, Dai, & Yin, 2016).
Previous studies reported that Valproic acid (VPA) is an environmental factor for ASD. This drug is used in treatment of epilepsy, bipolar disorder and migraine headaches (Horder et al., 2018; Jentink et al., 2010; José, Emilio, Maria, & Glauce, 2012). Prenatal exposure to VPA may increase the risk of autism. Several studies using different animal models have been shown that embryonic exposure to VPA can increase the risk factor for ASD (Chen et al., 2018; Kim et al., 2014; Mabunga, Gonzales, Kim, Kim, & Shin, 2015; Moore et al., 2000; Narita et al., 2010; Nicolini & Fahnestock, 2018; Piazza et al., 2003). Studies have shown that VPA can lead to overactivation of the canonical β- catenin signaling pathway in VPA-induced ASD animal models. It has been reported that Inhibitor of canonical β- catenin signaling pathway can improve the symptoms of ASD in these animal models (Qin & Dai, 2015; Qin et al., 2016; Zhang et al., 2012; Zhang et al., 2015).
Silibinin is a natural flavonoid and main component of silimaryin that is isolated from silybum marianum. Silibinin is widely used, as a traditional herbal, for its strong antihepatotoxic activity against any kind of human liver disorder. It also has anti-cancer, anti-inflammatory and anti-oxidant properties(Deep & Agarwal, 2010; Wing Ying Cheung, Gibbons, Wayne Johnson, & Lawrence Nicol, 2010). Recent studies have shown that chemotherapeutic effects of silibinin is associated with inhibition of canonical β- catenin signaling pathway (Lu et al., 2012; Ramakrishnan et al., 2009; Vaid, Prasad, Sun, & Katiyar, 2011).
Recently, both zebrafish larvae and adult are used as a powerful animal model of ASD in research studies. Zebrafish are genetically tractable, transparent during development and amenable to high-throughput phenotyping, making it a valuable experimental model. Zebrafish has also high physiological and genetical similarities with human (Gerlai, 2010; Hill, Teraoka, Heideman, & Peterson, 2005; Kalueff et al., 2013; Kalueff, Stewart, & Gerlai, 2014; Stewart et al., 2013; Stewart, Nguyen, Wong, Poudel, & Kalueff, 2014).
In the present study, VPA was used to induce autism in zebrafish larvae. Then, the effect of nanosilibinin (NS), ( as an inhibitor of Wnt signaling pathway), on neurobehavioral parameters was evaluated. In addition, the expression of ASD related genes in the brain of zebrafish larvae was investigated.