Zinc plays an important role in neuronal signaling and neurotransmission. However, dyshomeostasis of this metal or its accumulation in the brain has been linked with neurological disorders such as Alzheimer's disease and Parkinson's disease. In this study, the neuroprotective effects of Ecklonia maxima (KPM), Gracilaria gracilis (GCL), Ulva lactuca (ULT) and Gelidium pristoides (MNP) in Zn -induced neurotoxicity in HT-22 cells was examined. Cells were treated with Zinc sulphate and/or aqueous - ethanol extracts and cell viability, apoptosis, acetylcholinesterase activity, including some antioxidant enzymes (catalase and superoxide dismutase activity) and glutathione (GSH) levels were determined. Malondialdehyde and nitric oxide levels produced in the Zn and/or seaweed extract treated cells were also determined. Prior treatment with the seaweed extracts improved cell viability and inhibited Zn - induced cell death. Acetylcholinesterase activity was significantly high in Zn treated cells compared to the control. Pre-treatment with the seaweed extracts triggered a decrease in acetylcholinesterase activity in Zn - treated cells. Furthermore, treatment with Zn caused a significant reduction in GSH levels as well as a decrease in superoxide dismutase and catalase activities. In contrast, the seaweed extract increased antioxidant enzyme activities and GSH levels. An increase in malondialdehyde and nitric oxide levels was also reversed after treatment with the seaweed extracts. These results suggest that the seaweed extracts improved cholinergic transmission disrupted by Zn - induced neurotoxicity and protected the cells against oxidative damage and neuroinflammation. The neuroprotective effects of the seaweed extracts could be linked to their bioactive constituents. Hence these seaweeds are potential sources of active ingredients with neuroprotective potentials and could be used for the development of functional foods and/or nutraceuticals.
Keywords: Acetylcholinesterase; Neurodegeneration; Oxidative stress; Seaweeds; Zinc.