Toxicity of Amyloid Beta Proteins on SH-SY5Y Cells and Determination of an Optimal Dose of Methylene Blue That is Nontoxic to the SH-SY5Y Cells

There are many theories that explain the etiology of Alzheimer’s disease but the exact mechanism and pathophysiology of this disease remains unclear. The hallmark of the disease is the identification of amyloid beta plaques in the brains of Alzheimer’s patients during autopsy and tangles of hyper phosphorylated Tau proteins but why and how these compounds mediate their neurotoxicity is still a matter of debate. Knowing the exact mechanisms and the biochemical pathways through which these compounds mediate their neurotoxicity could open a whole new area of research for targeted medical therapy. There have been a lot of studies establishing the neurotoxicity of amyloid beta proteins in different cell lines but there are also studies establishing other factors of neurodegeneration including the tau protein, glutamate toxicity, oxidative stress which makes drawing a conclusion for amyloid beta as the instigator of the disease challenging but there is a general consensus that amyloid beta plays a role in the pathophysiology of Alzheimer’s disease. I investigated the toxicity of amyloid beta proteins on SH-SY5Y cells and also determined an optimal dose of methylene blue that is nontoxic to the SH-SY5Y cells. SH-SY5Y is a human derived cell line used in most labs for scientific research and my decision to use these cells was based on the fact that few studies have been done using these cells to establish amyloid beta toxicity. SH-SY5Y cells were plated on a 96 well plate and allowed to grow to confluency, after which the amyloid beta protein was added to the cell culture and incubated for two days. A cell viability assay was then performed on the cell cultures. My findings showed amyloid beta protein is toxic to SH-SY5Y cells and the toxicity is dose dependent. I was also able to find an optimal dose of methylene blue that is nontoxic to SH-SY5Y cells. Methylene blue has been in clinical use for a long time and some in vivo studies have shown that it can improve cognitive function in rats by increasing the activity of cytochrome c oxidase by up to 25%. With these findings, further investigation into the mechanism through which the amyloid beta protein mediates its toxicity on SH-SY5Y cells can be carried out. Also, using the optimal dose of methylene blue that’s nontoxic to SH-SY5Y cells, I intend to further investigate if methylene blue can reverse the neurotoxic effects of the amyloid beta protein on SH-SY5Y cells.