Evaluation of the Effects of Thymoquinone on RAGE/NOX4 Expressions and Brain Tissue Morphometry in Experimental Alzheimer’s Disease Induced by Amyloid Beta 1–42 Peptide

Abstract

The onset of Alzheimer’s disease (AD) is attributed to widespread amyloid beta (Aβ) plaque accumulation, tau hyperphosphorylation, oxidative stress, and neuroinflammation. However, the underlying mechanism of AD remains unclear, and no curative treatment currently exists. The aim was to investigate the effect of thymoquinone by suppressing the RAGE/NOX4 pathway in AD. Mice (n = 60) were divided into five groups, and an experimental AD model induced by an Aβ1–42 peptide was established in two groups. We also administered 5 mg/kg thymoquinone (TMQ) to the mice for its properties to slow or treat neurodegeneration in AD. Behavioral tests for memory and emotional states, micro-computed tomography (Micro CT) to assess brain volume, ELISA to measure malondialdehyde (MDA) levels, hematoxylin and eosin staining (H&E) to evaluate neuronal degeneration were used. Immunohistochemical (IHC), Western blot (WB), and real-time polymerase chain reaction (PCR) methods were used to evaluate the inhibitory effect of TMQ on a receptor for advanced glycation end products (RAGE)/nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4) signaling in AD. The results showed that TMQ may have ameliorative effects on memory, spatial learning, learning ability, and anxiety in AD. We showed that TMQ has an antioxidative effect by decreasing MDA levels by the ELSIA method (p < 0.05). There was a marked increase in neuronal degeneration in AD mice compared to other groups (p < 0.05). We concluded that TMQ could ameliorate neuronal degeneration in AD by H&E staining and suppress RAGE/NOX4 signaling by IHC and WB analysis. We concluded that TMQ could be therapeutic in AD by reducing AB expression level by IHC analysis (p < 0.05). Real-time PCR analysis showed that APP (p < 0.05), RAGE, and NOX4 (p < 0.05) gene expressions could be reduced by TMQ. In conclusion, TMQ has a high therapeutic potential in AD and an effective preventive and therapeutic strategy can be developed with more comprehensive studies on TMQ.