Background: Increasing evidence demonstrate N-acetylcysteine amide (NACA) provides neuroprotection and attenuated oxidative stress in rats following traumatic brain injury (TBI). The nuclear factor erythroid 2-related factor 2 (Nrf2)–antioxidant response element (ARE) signal pathway is activated after TBI and provides a protective effect against TBI. However, the function and mechanism of NACA in mice after TBI remain unknown. This study was to evaluate the neuroprotection of NACA and the potential action of the Nrf2-ARE pathway in a weight-drop mouse model of TBI.
Materials and methods: Four groups of animals were randomly divided into sham, TBI, TBI+vehicle, and TBI+NACA (100 mg/kg, administered intraperitoneally). The protein levels of Nrf2, heme oxygenase-1 (HO-1), NAD(P)H: quinine oxidoreductase-1 (NQO1), cleaved caspase-3 and the mRNA levels of HO-1 and NQO1 were detected. The neurobehavior, neuronal degeneration, apoptosis and oxidative stress were also assessed.
Results: Treatment with NACA significantly improved neurologic status at days 1 and 3 following TBI. Moreover, NACA promoted Nrf2 activation a day after TBI. The protein and mRNA levels of HO-1 and NQO1 were upregulated by NACA. Meanwhile, NACA treatment significantly reduced the level of malondialdehyde (MDA) and enhanced the activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx), which indicated NACA attenuated oxidative stress following TBI. NACA prominently reduced the protein level of cleaved caspase-3 and TUNEL-positive cells, indicating its antiapoptotic effect. Additionally, Fluoro-Jade C staining showed NACA alleviated neuronal degeneration a day after TBI. 
Conclusions: Our study reveals that NACA potentially provides neuroprotection via the activation of the Nrf2-ARE signaling pathway after TBI in mice.
Keywords: N-acetylcysteine amide, traumatic brain injury, nuclear factor erythroid 2-related factor 2, heme oxygenase-1 (HO-1), NAD(P)H: quinine oxidoreductase-1, oxidative stress