Neuroprotective Effects of a Benzofuran-Containing Selenium in a Mouse Alzheimer's Disease Model: Molecular, Biochemical, and Behavioral Analyses

Abstract

Alzheimer's disease (AD) is a neurodegenerative disorder mainly characterized by progressive cognitive decline, for which effective treatments remain limited, and selenium is known for its neuroprotective actions. Thus, this study evaluated the neuroprotective effects of the compound 2-(((3-trifluoromethyl)phenyl(selenyl)methyl)-2,3-dihydrobenzofuran (TFSeB) in a streptozotocin (STZ)-induced AD model in male Swiss mice. The animals received intracerebroventricular injections of STZ (3 mg/kg, a neurotoxic agent) to induce cognitive deficits, followed by treatment with TFSeB (1 and 5 mg/kg, intragastrically). Behavioral tests revealed that, like positive control (memantine), the compound TFSeB improved memory performance in the Y-maze, novel object recognition, and passive avoidance tests, suggesting its ability to counteract STZ-induced memory impairments. Biochemical analyses showed that the compound reduced oxidative stress markers in the prefrontal cortex and cerebellum of mice exposed to STZ, including TBARS, ROS, and nitrite levels while increasing NPSH. STZ induced an increase in monoamine oxidase B (MAO-B) activity in the hippocampus and cortex, as well as in acetylcholinesterase (AChE) activity in the cortex and cerebellum, which were reverted by TFSeB. Hippocampal RT-qPCR molecular analyses revealed that TFSeB modulated apoptosis-related proteins by increasing BCL-2 and decreasing BAX expression, favoring neuronal survival. Moreover, TFSeB increased brain-derived neurotrophic factor (BDNF) and nuclear factor erythroid 2 (NRF2), targets associated with neuroprotection. The compound also decreased key inflammatory and neurodegenerative markers, including nuclear factor kappa B (NF-κB), interleukin-6 (IL-6), and glycogen synthase kinase 3 beta (GSK3B). In conclusion, the compound TFSeB demonstrates promising protective effects in a STZ-induced AD model by modulating key neurochemical, oxidative, and neuroinflammatory pathways.

Keywords: memory; neuroinflammation; oxidative damage; selenium; streptozotocin.

1

Effects of the compound TFSeB on (A) correct alternation rate and (B) total number of arm entries in the Y-maze test, and (C) crossings and (D) rearings in the open field test (OFT). Values are expressed as the mean ± standard error of the mean (S.E.M.), N = 7–8 animals per group. One-way ANOVA followed by Newman–Keuls post hoc test. (&) p < 0.05 compared with the naive group. (#) p < 0.05 compared with STZ group. Abbreviations: STZstreptozotocin; MEM: memantine (positive control).

2

Effects of the compound TFSeB on short-term-object recognition test (ST-ORT), long-term-object recognition test (LT-ORT) and object location test (OLT). Total exploration time of both objects in ST-ORT (A), LT-ORT (D), and OLT (G), respectively. (B, E, H) Exploration time of the novel object in ST-ORT (B), LT-ORT (E) and OLT (H), respectively. Discrimination index in ORT (C), LT-ORT (F) and OLT (I), respectively. Values are expressed as the mean ± standard error of the mean (S.E.M.), 7–8 animals per group. Statistical analysis was performed by one-way ANOVA followed by Newman–Keuls post hoc test. (&&&) p < 0.001 compared with naive group; (***) p < 0.001 compared with sham group; (###) p < 0.001 compared with STZ group. Abbreviations: STZstreptozotocin; MEM: memantine (positive control).

3

Effects of compound TFSeB on inhibitory avoidance task (A) Latency time to platform descent during training and (B) Latency time on the test day. Data are presented as the mean ± standard error of the mean (SEM), with 7–8 animals per group. Statistical analysis was performed using one-way ANOVA followed by Newman–Keuls post hoc test. (***) p < 0.001 compared with naive group; (&&&) p < 0.001 compared with sham group; (#) p < 0.05, (##) p < 0.01, (###) p < 0.001 compared with STZ group. Abbreviations: STZstreptozotocin; MEM: memantine (positive control).

4

Effects of the compound TFSeB on MAO-B activity in different brain regions: (A) cortex, (B) cerebellum, (C) hypothalamus, and (D) hippocampus. Values are presented as the mean ± standard error of the mean (SEM), with 7–8 animals per group (A, B, and C) or 5 animals per group for (D). Statistical analysis was performed using one-way ANOVA followed by Newman–Keuls post hoc test. (&) p < 0.05 compared with the naive group; (*) p < 0.05 and (***) p < 0.001 compared with the sham group; (#) p < 0.05 and (###) p < 0.001 compared with the STZ group. Abbreviations: STZstreptozotocin; MEM: memantine (positive control).

5

Effects of the compound TFSeB on AChE activity in the (A) cortex and (B) cerebellum. Values are expressed as the mean ± standard error of the mean (SEM), with 7–8 animals per group. Statistical analysis was performed using one-way ANOVA followed by Newman–Keuls post hoc test. (&) p < 0.05 and (&&&) p < 0.001 compared with the naive group. (*) p < 0.05 and (***) p < 0.001 compared with the sham group. (#) p < 0.05 and (###) p < 0.001 compared with the STZ group. Abbreviations: STZstreptozotocin; MEM: memantine (positive control).

6

Effects of the compound TFSeB on redox markers (TBARS, ROS, NOx, and NPSH) in the cortex and cerebellum. (A) and (B) represent TBARS levels in the cortex and cerebellum, respectively. (C) and (D) show ROS levels in the cortex and cerebellum. (E) and (F) illustrate NOx levels in the cortex and cerebellum, while (G) and (H) depict NPSH levels in the cortex and cerebellum. Values are expressed as the mean ± standard error of the mean (SEM), with 7–8 animals per group. Statistical analysis was performed using one-way ANOVA followed by the Newman–Keuls post hoc test. (&) p < 0.05, (&&) p < 0.01, and (&&&) p < 0.001 compared with the naive group; (*) p < 0.05, (**) p < 0.01, and (***) p < 0.001 compared with the sham group; (#) p < 0.05, (##) p < 0.01, and (###) p < 0.001 compared with the STZ group. Abbreviations STZstreptozotocin; MEMmemantine (positive control).

7

Effects of the compound TFSeB (5 mg/kg) on hippocampal gene expression: mRNA levels of (A) BAX, (B) BCL2, (C) TNF-α, (D) NF-κB, (E) IL-6, (F) CAT, (G) SOD, (H) NRF2, (I) GSK3b, and (J) BDNF. Data are presented as the mean ± standard error of the mean (SEM); n = 4 per group. Statistical analysis was conducted using one-way ANOVA followed by the Newman–Keuls post hoc test (*) p < 0.05, (**) p < 0.01, and (***) p < 0.001 represent comparisons with the sham group; (#) p < 0.05, (##) p < 0.01, and (###) p < 0.001 represent comparisons with the STZ group, except for NRF2, which was analyzed using an unpaired t test (**) p < 0.01.

8

Effects of the compound TFSeB on (A) ALT, (B) AST, (C) Urea, (D) Blood glucose on day 0, (E) Blood glucose on day 25, and (F) Weight Variation. Data are presented as the mean ± standard error of the mean (SEM), with 7–8 animals per group. No significant differences were observed between groups. Statistical analysis was performed using one-way ANOVA followed by the Newman–Keuls post hoc test. Abbreviations: STZstreptozotocin; MEM: memantine (positive control).

1. General Synthesis of 2-(((3-Trifluoromethyl)­phenyl­(selenyl)­methyl)-2,3-dihydrobenzofuran (TFSeB)

9

Experimental design and chemical structure of the compound TFSeB. ICV: intracerebroventricular injection; STZ: streptozotocin; OFT: open field test; LT-ORT: long-term object recognition test; ST-ORT: short-term object recognition test; OLT: object location test.