Aggregation Of Amyloid Proteins And Amyloid Inhibitors

Background: It is well know that amyloidogenic protein can misfold and aggregateinto amyloid fibrils which can further form amyloid deposition in many tissues and organs.Currently these amyloid depositions are found in many diseases, including Alzheimer’sdisease, Parkinson’s disease and type2diabetes. Amyloid depositions of human isletamyloid polypeptide (hIAPP) have been found in patients with type2diabetes. Reportshave shown that the aggregation process of amyloidogenic protein is mostly accompaniedwith cytotoxicy. Therefore, more and more small molecular inhibitors of amyloidogenicproteins have been found in order to develop drugs for treatment of amyloid disease. Forexample, our previous studies have demonstrated that the three polyphenols derived fromcoffee can significantly inhibit the aggregation of islet amyloid polypeptide. However, dueto complex environment in vivo, the inhibitory effect of small molecular may be affected byother molecular in vivo, such as sugars and amino acid. Purpose: In this experiment, wewill investigate the inhibition of silibinin on aggregation and cytoprotective of hIAPP. Wealso study the effect of the three polyphenols derived from coffee on the aggregation oflysozyme in two different buffers (glycine buffer and PBS buffer). Method: In this study,we detect the effect of silibilin on the oligomerization of hIAPP, and MTT assay to detectthe effect of silibilin on hIAPP-induced cytotoxicity. we used thioflavin T fluorescencespectrometry and dot blot experiments were used to test the strength of human lysozymeaggregation; transmission electron microscopy was used to render the morphology ofamyloid aggregation; circular dichroism spectroscopy was used to detect the changes of the secondary structure during the process of human lysozyme aggregation. Results: Ourresults showed that the oligomerization and cytotoxicity of hIAPP were inhibited bysilibilin dose dependently. Caffeine, caffeic acid and chlorogenic acid had a weakinhibitory effect on lysozyme aggregation in PBS buffer whereas a significantly strengtheneffect on lysozyme aggregation was found in glycine buffer. Conclusion: Silibinin may beused as a potential therapeutic agent for T2DM. The environment in vivo may affect theinhibitory effect of small molecule inhibitors, which may pave the way for the developmentof the effective drugs to prevent and treat amyloid disease.