Sulforaphane Improved Social Communication Impairment in Valproate Induced Autistic Mice with up-Regulation of BDNF and NR2B in Cerebral Cortex
Autism (ASD) is a neurodevelopmental disorder in which the etiology remains speculative. There are various causative agents to trigger the onset of ASD. The histone deacetylase inhibitor, valproic acid (VPA) has been linked with the etiology of ASD. Rodent models with autistic features induced by VPA have been widely used in many researchers in the past decade. Various treatments have been applied to these ASD models but there is no remarkable method to ameliorate the autistic behavior. A recent clinical study has showed that sulforaphane (SFN) enriched broccoli extract could improve social communication of autistic children. However, the mechanism behind remains inconclusive. SFN has been reported to involve in various mechanisms such as DNA acetylation and counteracting oxidative stress. In this study, the effect of sulforaphane on VPA-induced mouse model of ASD and the mechanism behind was investigated.
This study aimed to investigate the effects of SFN toward the amelioration of autistic feature in ASD using a VPA-induced mouse model. Besides, the mechanism of SFN-related pathway will be studied in respect to the pathogenesis of ASD.
Pregnant BALB/c albino mice were injected intraperitoneally with VPA (600 mg/kg) on embryonic day 12.5, the mothers were allowed to give birth. The sham group mice were prepared by giving the mothers PBS intraperitoneally. The autistic feature of male pups were verified on postnatal day 28 by three-chambers sociability test. Mice with autistic feature were randomly assigned into SFN treatment group and control gorup.The SFN treatment group (VPA-SFN) mice was given with SFN (3.854 mg/kg/day) by oral gavage; while the control group were fed with saline (VPA-SAL). Both groups were fed daily for 22 days. The three-chambers sociability test was performed on postnatal days 35, 42 and 49 to assessthe sociability and social novelty of mice. On postnatal day 50, the mice were euthanized and the cerebral cortices were harvested to perform quanitative PCR analysis ofASD-related genes such as brain-derived neurotrophic factor (BDNF), NMDA receptor subunit2B (NR2B).
From the results of three-chambers sociability test, VPA-SAL mice spent less time with the stranger mice, showing impaired sociability (Fig 1A and B.); also, less time preference were showed towards the novel mice, demonstrating a lack of social novelty (Fig. 1C and D). At PND 49, after 3-weeks SFN treatment, VPA-SFN mice spent significantly more time than VPA-SAL mice with the stranger mice by 66.9% (p<0.01) in the first 10 minutes of the test (Fig. 1A), and they showed more time preference towards novel mice by 44.4% (p<0.01) (Fig. 1D). Moreover, from quantitative PCR results (Fig. 2), BDNF and NR2B expressions were significantly lower in VPA-SAL mice when compared with the sham group. SFN treatment significantly increased the expressions of BDNF and NR2B by 2.40 (p<0.01) and 2.68 (p<0.05) folds respectively.