Ferulic acid ameliorates bisphenol A (BPA)-induced Alzheimer's disease-like pathology through Akt-ERK crosstalk pathway in male rats

Abstract

Objectives: This study investigated the neuroprotective effect of ferulic acid (FA) against bisphenol A (BPA) induced Alzheimer's disease-like pathology in male rats.

Methods: Rats were allocated into four groups, control, BPA, BPA + FA, and FA, respectively, for 40 days. Spatial working memory and recognition memory were evaluated. Moreover, the brain levels of oxidative stress biomarkers, proinflammatory cytokines, extracellular signal-regulated kinase (ERK), and phosphorylated serine/threonine protein kinase (p-Akt) were measured. We also determined the brain neuropathological protein levels, including Beta-Amyloid 1-42, total Tau (tTau), and phosphorylated Tau (pTau) proteins. Furthermore, brain levels of Acetylcholinesterase (AChE) and Beta-secretase (BACE) were assessed. Brain histological investigation and immunohistochemistry determination of glial fibrillar acidic protein (GFAP) were also performed. Moreover, docking simulation was adapted to understand the inhibitory role of FA on AChE, BACE-1, and ERK1/2.

Results: Interestingly, the BPA + FA treated group showed a reversal in the cognitive impairments induced by BPA, which was associated with improved brain redox status. They also exhibited a significant decrease in brain inflammatory cytokines, ERK, and p-Akt levels. Moreover, they revealed a decline in beta-amyloid 1-42 and a significant improvement in tTau expression and pTau protein levels in the brain tissue. Further, the brain levels of AChE and BACE were substantially reduced in BPA + FA rats. The neuroprotective effect of FA was confirmed by restoring the normal architecture of brain tissue, which was associated with decreasing GFAP.

Conclusion: FA could be a potent neuroprotectant agent against AD with a possible prospect for its therapeutic capabilities and nutritional supplement value due to its antioxidant and antiapoptotic properties.

Keywords: AChE; Apoptosis; BPA; Beta-amyloid 1–42; Ferulic acid; Molecular docking; Neurotoxicity; Oxidative stress; Phosphorylated tau protein; Total tau protein.

Fig. 1

Diagram illustrating the experimental procedure. Male rats were allocated to four groups: control, BPA-intoxicated rats, rats co-treated with BPA + FA, and FA group. All agents were given 40 days; after that, behavioral tests, including Y-maze and NOR, were evaluated from the 41st to the 44th. On the 45th day, blood and brain samples were obtained to evaluate changes in biochemical, histological, and immunohistochemistry parameters

Fig. 2

Effect of BPA administration for 40 days on male rats’ spatial working memory and recognition memory. Y-maze test: number of arm entries, b. Y-maze test: spontaneous alternation percentage, c. Novel object recognition test: novel object preference %, and d. Novel object recognition test: Discrimination ratio. Data are expressed as mean standard error of the mean (SEM) (one-way analysis of variance (one-way ANOVA) followed by Tuckey post hoc test for ten rats in each group. * Significantly different from Group I (control group) and ** significantly different from Group II (BPA-intoxicated rats),P < 0.05

Fig. 3

Effect of BPA administration for 40 days on the level of oxidative stress markers in the brain, such as (a) MDA, b GSH, and (c) GSSG. Data are expressed as mean ± standard error of the mean (SEM) (one-way analysis of variance (one-way ANOVA) followed by Tuckey post hoc test for ten rats in each group. * Significantly different from Group I (control group) and ** significantly different from Group II (BPA-intoxicated rats), P < 0.05

Fig. 4

Effect of BPA administration for 40 dayson the brain level of (a). Beta-amyloid, b. tTau. Data, c. p-Akt, d. ERK, as well as pro-inflammatory cytokines, e. Interleukin 1 beta, and f. Tumor necrosis factor-alpha. Data are expressed as mean ± standard error of the mean (SEM) (one-way analysis of variance (one-way ANOVA) followed by Tuckey post hoc test for ten rats in each group. * Significantly different from Group I (control group) and ** significantly different from Group II (BPA- intoxicated rats), P < 0.05

Fig. 5

Effect of BPA administration for 40 dayson the brain level of (a). AChE, b. BACE, and c. pTau. Data are expressed as mean ± standard error of the mean (SEM) (one-way analysis of variance (one-way ANOVA) followed by Tuckey post hoc test for ten rats in each group. * Significantly different from Group I (control group) and ** significantly different from Group II (BPA- intoxicated rats), P < 0.05

Fig. 6

a: h Brain tissue of male adult Wistar rats. H&E.X400. The cerebral cortex of (a) Control rats (Group I) and (d) ferulic acid-administered rats (Group IV) showed normal structure and distribution of neurons, neuroglia, and neuropil. b Cerebral cortex of Bisphenol A (BPA) administered rats (Group II) showed pyknotic degenerated neurons (yellow arrow) with pericellular spaces (yellow arrowhead) and neuropil vacuolation (green arrowhead). c The cerebral cortex of BPA-administered rats plus ferulic acid (Group III) revealed marked recovery in the form of maintenance of the normal architecture of some pyramidal neurons (black arrow), except a few neurons appeared pyknotic with pericellular spaces (yellow arrow). The hippocampus of (e) Control rats (Group I) and (h) ferulic acid-administered rats (Group IV) showed the normal structure of molecular (M), pyramidal (P), and polymorphic (PL) cell layers, respectively. Molecular (M) and polymorphic (PL) cell layers are composed of scattered neurons (yellow arrow) and neuroglia (yellow arrowhead). The pyramidal cell layer (P) is formed of linearly arranged triangular-shaped neurons with vesicular nuclei (black arrow). f Hippocampus of Bisphenol A (BPA) administered rats (Group II) exhibited pyknotic neuroglia with perineural space (green arrowheads) in both molecular (M) and polymorphic (PL) layers. The pyramidal cell layer had disarranged pyramidal neurons (black line), some pyramidal cells appeared pyknotic with pericellular spaces (yellow arrows), and other neurons had nuclei with chromatolysis (yellow arrowhead). There was neuropil vacuolation (black arrowhead). g Hippocampus of BPA-administered rats plus ferulic acid (Group III) showed marked maintenance of nearly normal architecture of the three layers. Molecular (M) and polymorphic (PL) layers had normal glial cells (yellow arrowheads), except a few glial cells appeared pyknotic with perineural space (black arrowheads). The pyramidal cell layer (P) revealed normal linear arranged (yellow line) triangular-shaped neurons with vesicular nuclei (yellow arrow), but few neurons appeared irregular in shape with darkly stained cytoplasm and pericellular space (circle)

Fig. 7

Immunohistochemically GFAP stained cerebral cortex and hippocampus sections (X400). Cerebral cortex and hippocampus (a & e) of Control rats (Group I) and (d & h) ferulic acid-administered rats (Group IV) showed weak positive glial fibrillar acidic protein (GFAP) immunoexpression in astrocyte body and processes. b Cerebral cortex and (f) hippocampus of BPA-administered rats (Group II) revealed strong positive immunoreaction in astrocyte body and processes compared to control rats. c Cerebral cortex and (g) hippocampus of BPA-administered rats plus ferulic acid (Group III) showed moderate GFAP immunoreactivity in astrocyte body and processes versus the BPA group

Fig. 8

The effect of Bisphenol A (BPA), BPA plus ferulic acid, ferulic acid on the percent area covered by GFAP-positive immunoreactive cells within brain tissue of rats. Results are presented as mean ± SEM. Compared with control: *P˂0.05, compared with BPA: **P˂0.05

Fig. 9

(A) 2D binding mode, (B) surface map, and (C) 3D binding mode of ferulic acid in the active site of the Human Acetylcholinesterase (AChE) (PDB ID: 4EY6)

Fig. 10

(A) 2D binding mode, (B) surface map, and (C) 3D binding mode of ferulic acid in the active site of Beta-Secretase 1 (BACE-1) (PDB ID: 7N66)

Fig. 11

(A) 2D binding mode, (B) surface map, and (C) 3D binding mode of ferulic acid in the active site of the extracellular signal-regulated kinase 1/2 (ERK1/2) (PDB ID: 6G97)