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

Synaptosomal membrane peroxidation and alteration in its biophysical properties are associated with Aluminium (Al) toxicity that may lead to cognitive dysfunction and Alzheimer's disease (AD) like pathogenesis. Here we investigated the therapeutic potential of Lepedium sativum (LS) as a natural anti-inflammatory, antioxidant and as acetyl cholinesterase inhibitor in treating Al induced AD-like in rat model. We utilized ATR-IR spectroscopy to follow the restoration in the damaged membrane structure of isolated rat cortical synaptosomes and its biophysical properties, electron paramagnetic resonance (EPR) spin trapping to follow NADPH oxidase activity (NOX), and EPR spin labelling in response to LS treatment after Al intoxication. We measured the concentration of Ca2+ ions in rat cortical tissue by inductively coupled plasma (ICP), the brain atrophy/curing and hydrocephalus by magnetic resonance imaging (MRI) besides light microscope histopathology. Our results revealed significant increase in synaptosomal membrane rgidification, order, lipid packing, reactive oxygen species (ROS) production and Ca2+ ion concentration as a result of Al intoxication. The dramatic increase in Ca2+ ion concentration detected in AD group associated with the increase in synaptic membrane polarity and EPR-detected order S-parameter suggest that release of synaptic vesicles into synaptic cleft might be hindered. LS treatment reversed these changes in synaptic membranes, and rescued an observed deficit in the exploratory behaviour of AD group. Our results also strongly suggest that the synaptosomal membrane phospholipids that underwent free radical attacks mediated by AlCl3, due to greater NOX activity, was prevented in the LS group. The results of ATR-IR and EPR spectroscopic techniques recommend LS as a promising therapeutic agent against synaptic membrane alterations opening a new window for AD drug developers.

Synchrotron Fourier transform infrared microspectroscopy (sFTIRM) analysis of Al-induced Alzheimer's disease in rat brain cortical tissue.

Aluminium (Al) is reported to promote beta amyloid (Aß) aggregation, free radical production and disturb acetylcholine metabolism leading to cognitive dysfunction that are strongly associated with Alzheimer's disease (AD). Here we utilized synchrotron Fourier transform infrared microspectroscopy (sFTIRM) to analyse the fine structure of proteins and lipids in the rat cortical brain tissues in response to AlCl3 toxicity and Lepidium sativum (LS) treatment after 42 and 65 days. For statistical analysis, we used principal component analysis (PCA). Our results showed profusion of gauche rotomers form in membrane lipid acyl chains that increases the membrane fluidity and disorder only in AD group indicated by the detected sνCH2 band shift to higher frequency. All half bands width (HBW) values of the decomposed amide I band showed marked decrease in AD group compared to the other tested groups, together with an increase in the amounts of ß-sheets (1641 cm-1) protein and random coil structure (1654 cm-1). These were indicated by a drastic increase in the percentage areas ratios of (1638 cm-1/1654 cm-1) and (1641 cm-1/1654 cm-1) that may be attributed to a stronger the hydrogen bonds that stabilize the protein conformational structure and/or the increase of the ß-strand length due to misfolded Aß formation in response to Al toxicity through transit phase/phases dominated by random coil structure. In curative group, LS treatment reversed these changes and restored the protein and lipid integrities. To conclude, sFTIRM is a powerful tool that shed light on the biomolecular structure of AD-like cortical brain tissue and considered the therapeutic potential of LS as a promising natural AD treatment.