ATR-IR and EPR spectroscopy for following the membrane restoration of isolated cortical synaptosomes in aluminium-induced Alzheimer's disease - Like rat model

Post-exposure self-recovery reverses oxidative stress, ameliorates pathology and neurotransmitters imbalance and rescues spatial memory after time-dependent aluminum exposure in rat brain

Aluminum is a potent neurotoxin, responsible for memory impairment and cognitive dysfunction. The neurotoxic effect of aluminum on cognitive impairment is well documented, however, exposure to aluminum in a time-dependent manner and post-exposure self-recovery still needs to be elaborated. This research aimed to (1) study the time-dependent effect of aluminum exposure by administering a total dose of 5850 mg/kg of Al over two different time periods: 30 and 45 days (130 and 195 mg/kg of AlCl3 respectively), and (2) study 20 days post-exposure self-recovery effect in both aluminum-exposed groups by giving distilled water. Cognitive abilities were investigated through Morris water maze test and hole board test and compared in both exposure and recovery groups. Oxidative stress markers and neurotransmitter levels were measured for both exposure and recovery groups. To understand the mechanism of aluminum exposure and recovery, immunohistochemical analysis of synaptophysin (Syp) and glial fibrillary acidic protein (GFAP) was performed. Results showed cognitive dysfunction, oxidative stress-induced damage, reduced neurotransmitter levels, decreased immunoreactivity of Syp, and increased GFAP. However, these parameters showed a larger improvement in the recovery group where rats were given aluminum for 30 days period in comparison to recovery group followed by 45 days of aluminum exposure. These results suggest that restoration of cognitive ability is affected by the duration of aluminum exposure. The study findings provide us with insight into the adverse effects of aluminum exposure and can be utilized to guide future preventive and therapeutic strategies against aluminum neurotoxicity.

Comparative Study of Time-Dependent Aluminum Exposure and Post-Exposure Recovery Shows Better Improvement in Synaptic Changes and Neuronal Pathology in Rat Brain After Short-Term Exposure

Aluminum is a ubiquitous metal that causes multiple brain pathologies such as, cognitive dysfunction and Alzheimer's disease like symptoms. Exposure to aluminum through drinking water is responsible for hampering learning and memory. This study aimed to compare (1) the time-dependent effect of aluminum exposure (keeping total exposure of 5850 mg/kg same) in two durations, 30 and 45 days, and (2) to compare post-exposure self-recovery effect after 20 days in both (30 and 45 days exposure) groups. Rats were given 130 and 195 mg/kg of AlCl₃·6H₂O for 45 and 30 days respectively, to see the time-dependent exposure effect. At the end of exposure, rats were given distilled water and allowed to self-recover for 20 days to study the recovery. Expression levels of synaptic genes (Syp, SNAP25, Nrxn1/2, PSD95, Shank1/2, Homer1, CamkIV, Nrg1/2 and Kalrn) were measured using qPCR and compared in the exposure and recovery groups. Cellular morphology of the rat brain cortex and hippocampus was also investigated. Damage in lipid and protein profile was measured by employing FTIR. Results showed downregulation of mRNA expression of synaptic genes, plaques deposition, disorganization in lipid and protein profile by increasing membrane fluidity, and disorder and alteration of protein secondary structure after both exposure periods. However, better improvement/recovery in these parameters were observed in recovery group of 30 days aluminum exposure compared to 45 days aluminum exposure group. Taken together, these results suggested that short-term exposure resulted in better restoration of lipid and protein profile after time-dependent exposure of aluminum than prolonged exposure.