The potential value of capsaicin in modulating cognitive functions in a rat model of streptozotocin-induced Alzheimer’s disease

Abstract

Background: Alzheimer's disease (AD) is a progressive neurodegenerative disorder. Objectives: This study aimed to examine the role of capsaicin dietary exposure in ameliorating cognitive functions in experimental rat model of streptozotocin-induced Alzheimer's disease (STZ-induced AD). Methods: Thirty adult albino male rats were distributed randomly into three equal groups. Ten rats, served as negative controls, were treated once with intracerebroventricular (icv) injection and intragastric infusion of saline for 47 days. Twenty rats were treated with a single icv-STZ (3 mg/kg) injection for induction of AD. Behavioral tests were done after 2 weeks to evaluate the development of Alzheimer's model. Rats with retention latency less than 300 s in the passive avoidance test were further subdivided into 2 groups; one group was treated with intragastric infusion of capsaicin (10 mg/kg) for 47 days and the other group was treated similarly with saline as positive controls. Then, behavioral tests were repeated at the end of the experiment. The expression level of β-amyloid 1-42 peptide (Aβ1-42) and tau proteins was measured using ELISA test. Results: The behavioral impairments had been ameliorated by capsaicin treatment. Furthermore, there was improvement in the estimated biochemical parameters as revealed by the significant decline in the mean values of β-amyloid 1-42 peptide (Aβ1-42) and tau proteins in hippocampal homogenate in capsaicin-treated group as compared to the positive controls (p < 0.001 and p = 0.004, respectively). Chorioallantoic membrane (CAM) assay showed inhibition of angiogenesis in chick embryo by 5 μg capsaicin. Conclusions: Our study suggests that capsaicin is a promising agent for food additives and drugs which ameliorates AD through improvement of the behavioral and biochemical alterations detected in STZ-induced AD.

Capsaicin consumption reduces brain amyloid-beta generation and attenuates Alzheimer’s disease-type pathology and cognitive deficits in APP/PS1 mice

“…Further studies are required to make clear whether capsaicin can enhance memory in wild-type animals or healthy humans. Additionally, capsaicin has been reported to ameliorate tau changes and behaviour impairments in Aβ-independent pathway in stress- or drug-induced nonspecific AD models which only display tau pathologies and cognitive impairment but no Aβ plaques 50 – 52 . In our present study, APP/PS1 transgenic AD mouse model was used.…”

“…To evaluate the toxicity of capsaicin, the cells were seeded in 96-well plates (5 × 10 4 cells/ml) and incubated without (control) or with various concentrations of capsaicin (5,10,25,50,75, 100, 125, 150 μM) for 24 h. The cell culture medium was changed immediately before the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay to avoid an interaction between MTT and capsaicin. Then 10 μl MTT (5 mg/ml, Sigma-Aldrich, USA) solution was added for 4 h. The supernatant was then removed, and 100 μl DMSO was added to dissolve the dye crystals.…”

Sinapic Acid Alleviates Oxidative Stress and Neuro-Inflammatory Changes in Sporadic Model of Alzheimer’s Disease in Rats

“…Morris water maze and passive avoidance paradigms are well accepted behavioral tests used in experimental AD research. The widespread conformational validity of the Morris water maze as a measure of spatial navigation and predictive memory, and use of the passive avoidance test, which assesses the basic capability to learn and remember the existence of a shock stimulus, with the advantages of minimal practice and quick learning make both of these behavioral tests suitable to assess cognitive decline in a sporadic AD model [44]. The escape latency or the time required to locate the platform zone was more, whereas the time spent in the target quadrant was less in STZ injected rats, indicating memory impairment.…”

Cognitive dysfunction and anxiety resulting from synaptic downscaling, hippocampal atrophy and ventricular enlargement with intracerebroventricular streptozotocin injection in male Wistar rats

“…Hippocampal homogenate of i.c.v. STZ treated rats also showed elevated expression of Aβ 1-42 by ELISA or western blot technique from 30 th day post-injection (Ahn et al, 2020; Azadfar et al, 2020; Bao et al, 2017; Shalaby et al, 2019). Only in one report reported diffuse amyloid deposition by congored staining on 30 th day post injection of STZ though in this study authors did not focused on the hippocampus proper or related structures (Gupta et al, 2018).…”