Soybean isoflavone ameliorates cognitive impairment, neuroinflammation, and amyloid β accumulation in a rat model of Alzheimer's disease

Oxidative stress and neuroinflammatory changes appear to be the early events involved in AD's development and progression. The present study was designed to assess the effect of soybean isoflavone extract (SIFE) against colchicine-induced cognitive dysfunction and oxidative stress in male rats. Fifty adult male Wistar albino rats were divided into five groups: control, ACSF-treated group, soybean isoflavones (SIF)-treated group, colchicine (COL)-treated group, and SIF + COL-treated group. We found that an intracerebroventricular (icv) injection of a single dose of colchicine (7.5 mu g/rat bilaterally) resulted in learning deficits in rats subjected to the Morris water maze task associated with marked oxidative damage and decreased acetyl cholinesterase (AChE) activity. In addition, COL caused significant increase in amyloid beta peptide 1-42 (beta, amyloid 1-42) interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF alpha), cyclooxygenase-2 (COX-2) and TNF-alpha genes expression in the brain, and glial fibrillary acidic protein (GFAP) in cortical astrocytes in the brain cortex. Treatment with SIFE (80 mg/kg b.wt) daily for 14 days followed by a single dose of COL significantly reduced the elevated oxidative stress parameters and restored the reduced antioxidant activities. Besides, the administration of SIFE reversed the overproduction of beta, amyloid 1-42, pro-inflammatory cytokines, and GFAP in the brain. The obtained results were confirmed by histological observations that clearly indicate a neuroprotective effect of SIF against AD.