Abstract: “One of the hallmarks of Parkinson’s disease (PD) is the death of dopaminergic neurons, which is suggested to be caused by oxidative stress due to increased levels of iron present in the brain. Furthermore, the brains of Parkinson’s patients have been found to contain intracellular protein deposits, known as Lewy Bodies, that are comprised of alpha-synuclein (αS) and contain a relatively high concentration of iron. As a result of these observations, a complex that could chelate iron, thereby sequestering it in solution, and decrease the aggregation of αS was proposed as a therapeutic agent against Parkinson’s disease. The target complex, C1, was synthesized via click chemistry with a design centered on the incorporation of a sugar molecule, due to the brain’s affinity for glucose, and a pyridine as the coordinator for the targeted metal ion. Once synthesized, C1 was evaluated for its ability to prevent the metal-associated aggregation of αS. Treatment of αS with C1 in the presence of either Fe(II) or Fe(III) saw a reduction in the relative aggregation of the protein. Moreover, when the samples were analyzed using dynamic light scattering (DLS) and transmission electron microscopy (TEM), smaller particles were consistently observed when C1 was included. Taken together, the overall decrease in fluorescence and smaller particle size of αS and iron containing solutions when C1 was added indicates a decrease in αS aggregation, making iron a potential therapeutic target for PD.”
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Great talk! Very interesting and impactful work. I am curious about the iron oxidation state… why are you are looking at both Fe(II) and Fe(III) throughout? I can see that in some of your assays they give different results. Is it known from the literature whether the oxidation state is important or causes different effects in Parkinson’s disease?
Thank you! With looking at Fe(II) and Fe(III) we were primarily just interested to see the difference in results between the two.
Nice talk! In your ThT fluorescence assays, it looks like your data don’t really reach an equilibrated level of fluorescence within 3 days (for example, αS+Fe(III) looks like it’s still increasing at the end of the 3 days), potentially suggesting that the formation of Lewy bodies in the brain is a slow process that could occur over months or even years – that’s a really interesting result! Is that already a documented phenomenon? And do you have any data after 72 hours to see where the aggregation levels end up?
Hello! I have not seen any documentation of the rate at which Lewy bodies form in the brains of those with Parkinson’s disease, however, with this being a progressive disease that worsens overtime, it is likely that Lewy body formation could be a relatively slow process.
For the ThT fluorescence assay, we did stop the experiment at 72 hours so we do not have any data past the 72 hour mark. We made the decision to stop at 72 hours based on literature we had read about the aggregation of alpha-synuclein; It was a surprising result to see the almost linear increase in fluorescence once I began to work up the data. With future derivatives of C1, we will be adjusting this!
Nice talk and a lot of work here! So a few question, while I do see a shift to smaller size with the Fe(III) DLS, I also see an almost equal shift to a species with a larger size – what do you make of that? Also, why do you think you see a difference between the chelation/aggregration of C1 with Fe(II) vs Fe(III)?
For the DLS, my thoughts are that that larger peak may be some complexes that did not coordinate with iron. As seen by the ThT fluorescence graph, the fluorescence/percent relative aggregation for solutions only containing C1 and alpha-synuclein were over 100% relative aggregation.
I think we see a difference between Fe(II) and Fe(III) because they have different solubilities in water (and in the case of our experiment, phosphate buffer saline).