The effects of Nigella sativa l. and thymoquinone on experimental alzheimer's disease model of rats

Alzheimer's disease is a neurodegenerative disorder characterized by progressive deterioration of cognitive functions. Amyloid plaques formed by the accumulation of Aβ peptides, are typical hallmarks of the disease. These peptides are known to induce inflammatory processes and play a role in disease progression. Nigella sativa and thymoquinone may have therapeutic potential for the disease by virtue of their anti-inflammatory properties. In this study, we aimed to evaluate the effect of NS oil and thymoquinone in a dose dependent manner against the decrease in cognitive function and neuroinflammation in the disease model of rats. Alzheimer's disease model was induced by bilateral intrahippocampal injection of Aβ1-42 in adult male rats. Treatment groups received 0.5 ml/kg, 1 ml/kg, 2 ml/kg NS oil or 3 mg/kg, 10 mg/kg, 30 mg/kg thymoquinone while Control and Alzheimer's Disease groups received corn oil by gastric gavage daily. After treatments that started 7 days before and continued 10 days after Aβ1-42 injection Passive Avoidance and Morris Water Maze tests were performed. Learning and memory decline induced by Aβ1-42 administration is reversed by 1 ml/kg 2 ml/kg NS oil and 3 mg/kg, 10 mg/kg and 30 mg/kg thymoquinone delivery. The increase in astrocytes and microglia activity in Alzheimer's disease group was attenuated in all treatment groups except 0.5 ml/kg NS oil group. We found that the increase in proinflammatory cytokine TNF-α and IL-1β levels induced by injecting Aβ in the hippocampus was supressed in treatment groups. No significant differences in serum fatty acid levels that could be related to disease or treatment was found. According to our experimental results, NS and thymoquinone administration prevented degeneration in memory and learning by inhibiting the increase in pro-inflammatory cytokine levels and astroglial and microglial activation caused by Aβ1-42 injection. These results suggest that the beneficial effects of NS and thymoquinone on learning and memory may be associated with their anti-neuroinflammatory effect.