The Effects Of Copper Ions And Hydrogen On Amyloid Polypeptide Aggregation In Different Sequences

The abnormal folding of amyloid peptides into fibrils and subsequent accumulation into amyloid deposits has been linked to a number of human neurological diseases,such as Type 2diabetes（T2D）,Alzheimer’s disease（AD）and Parkinson’s disease（PD）.Among them,Type 2diabetes is caused by the decrease in the function of insulin to assist glucose to enter the cell metabolism,the relative shortage of insulin secretion,or the decrease in the body’s response to insulin,resulting in the rise of blood sugar,which accounts for about 90%of the total number of diabetic patients.One of the important causes of type 2 diabetes is the human islet amyloid polypeptide accumulates abnormally and deposits.However,metal ions play an important role in the aggregation of amyloid peptides,among which copper ions can specifically bind to h IAPP and regulate the aggregation process of h IAPP.Therefore,copper ions are one of the key factors in the development of Type 2 diabetes and can seriously damage the secondary structure of proteins.The role of copper ions in h IAPP cytotoxicity has been explored from two aspects:inhibiting the formation of fibrils and stimulating the production of reactive oxygen species（ROS）.It has been found that h IAPP and related fragments can produce a large number of reactive oxygen species（ROS）in self-culture,and copper ions can effectively promote this process.However,the mechanism of promotion is not clear,so we have studied it.In addition,in recent years,with the further research on hydrogen（H₂）by the scientific community,it has been found that H₂has certain antioxidant properties,which has certain positive significance for the clinical treatment of Type 2 diabetes and drug research and development.Therefore,we conducted the following research in this paper:Firstly,the effects of copper ions on amyloid accumulation in different sequences were investigated.The interactions between copper ions and several different h IAPP fragments and their mutants were studied spectroscopically.EPR（electron paramagnetic resonance,EPR）experiments and Amplex Red fluorescence experimental analysis show that the copper ion and h IAPP（11-28）interact to produce the amount of H₂O₂is much higher than h IAPP（1-11）and h IAPP（28-37）.In addition,when His18 in h IAPP（11-28）was replaced by Arg（R）or Ser（S）,the level of H₂O₂produced by the interaction between copper ions and h IAPP（11-28）was seriously reduced,indicating that His18 is a key residue of copper ions binding h IAPP（11-28）to promote the generation of H₂O₂.This may be because the supply of electrons to Cu（II）from the peptide leads to the formation of redox active complexes that stimulate the formation of H₂O₂.At the same time,we also used AFM and Th T methods to study the aggregation image and aggregation kinetics of copper ion on h IAPP（11-28）.The results showed that Cu（II）could effectively inhibit the fibrosis process of h IAPP（11-28）,and the inhibition effect was enhanced with the increase of Cu（II）concentration.Secondly,effects of H₂on amyloid accumulation in different sequences.HIAPP produces harmful H₂O₂in the aggregation process,while H₂has a selective antioxidant effect.In this paper,we used several different spectroscopic techniques do some researches about the eliminating effect of H₂on ROS produced by Cu（II）interaction with h IAPP.Amplex Red fluorescence method showed that when copper ions interacted with h IAPP to produce ROS,H₂showed certain ROS scavenging activity.At the same time,the EPR method is also used to carry out relevant research,and the same conclusion is reached,that is,H₂has certain scavenging effect on ROS.