Abstract
This study aimed to evaluate the potential neuroprotective effect of royal jelly (RJ) against Cd-induced neuronal damage. Twenty-eight adult mice were placed equally into four groups. The control group received intraperitoneal (IP) injections of normal saline; the cadmium chloride (CdCl2) group was IP-injected 6.5mg/kg (mg per kg of bodyweight) CdCl2; the RJ group was gavaged 85mg/kg RJ; and the RJ+CdCl2 group was orally administered 85mg/kg RJ 2h before receiving IP-injections of 6.5mg/kg CdCl2. All groups were treated for seven consecutive days and the mice were decapitated 24h after the final dose. Cd accumulation was recorded in the cortical homogenates, accompanied by elevated levels of lipid peroxidation, nitric oxide, tumor necrosis factor-alpha, interleukin-1, and the pro-apoptotic mRNA Bax and caspase-3. Meanwhile, significantly decreased levels of detoxifying antioxidant enzymes including GSH-Px, GSH-R, SOD, and CAT, anti-apoptotic mRNA Bcl-2, and monoamines such as norepinephrine, dopamine, and serotonin were also observed, along with reduced gene expression of Nrf2-dependent antioxidants. Interestingly, in mice pretreated with RJ, the assessed parameters remained near normal levels. Our data provide evidence that RJ treatment has the potential to protect cortical neurons in Cd-intoxicated mice via its antioxidant, anti-inflammatory, anti-apoptotic, and neuromodulatory activity.