The Effects of Thymoquinone on Hippocampal Cytokine Level, Brain Oxidative Stress Status and Memory Deficits Induced by Lipopolysaccharide in Rats

Objective: The study objective was to determine the protective effects of thymoquinone (TQ) on brain tissues oxidative stress status, hippocampal cytokine level, and learning and memory deficits induced by lipopolysaccharide (LPS) in rats.

Methods: Animals were randomly divided into the following groups and treated: (1) Control (saline), (2) LPS (1mg/kg i.p.), (3-5) 2, 5 or 10mg/kg TQ extract 30min before LPS injection. The treatment was started since two weeks before the behavioral experiments and continued during the behavioral tests (LPS injected 2h before each behavioral experiment). Finally, the brains were removed for biochemical assessments.

Results: Morris water maze (MWM) test results showed that LPS increased escape latency compared to control group whereas TQ decreased them vs. LPS group. In passive avoidance (PA) test, LPS reduced the latency to enter the dark compartment vs. control group, while TQ treatment attenuated this effect of LPS. Additionally, LPS increased interleukin-6 (IL-6) and tumor necrosis alpha (TNF-α) in the hippocampal tissues. It also elevated malondialdehyde (MDA) and nitric oxide (NO) metabolites and decreased thiol content, superoxide dismutase (SOD) and catalase (CAT) in both hippocampus and cortex vs. control group, while TQ decreased IL-6, TNF-α, MDA and NO metabolites and increased thiol content, SOD and CAT compared to LPS group.

Conclusion: Findings of current study indicated that TQ improved LPS-induced learning and memory impairments induced by LPS in rats by attenuating the hippocampal cytokine levels and brain tissues oxidative damage.