Capreomycin inhibits the initiation of amyloid fibrillation and suppresses amyloid induced cell toxicity.

Protein aggregation and amyloid fibrillation are responsible for several serious pathological conditions (like type II diabetes, Alzheimer's and Parkinson's diseases etc.) and protein drugs ineffectiveness. Therefore, a molecule that can inhibit the amyloid fibrillation and potentially clear amyloid fibrils is of great therapeutic value. In this manuscript, we investigated the antiamyloidogenic, fibril disaggregating, as well as cell protective effect of an anti-tuberculosis drug, Capreomycin (CN). Aggregation kinetics data, as monitored by ThT fluorescence, inferred that CN retards the insulin amyloid fibrillation by primarily targeting the fibril elongation step with little effect on lag time. Increasing the dose of CN boosted its inhibitory potency. Strikingly, CN arrested the growth of fibrils when added during the elongation phase, and disaggregated mature insulin fibrils. Our Circular Dichroism (CD) results showed that, although CN is not able to maintain the alpha helical structure of protein during fibrillation, reduces the formation of beta sheet rich structure. Furthermore, Dynamic Light Scattering (DLS) and Transmission Electronic Microscopy (TEM) analysis confirmed that CN treated samples exhibited different size distribution and morphology, respectively. In addition, molecular docking results revealed that CN interacts with insulin through hydrophobic interactions as well as hydrogen bonding, and the Hemolytic assay confirmed the non-hemolytic activity of CN on human RBCs. For future research, this study may assist in the rational designing of molecules against amyloid formation.

Ascorbic acid inhibits human insulin aggregation and protects against amyloid induced cytotoxicity.

Protein aggregation into oligomers and fibrils are associated with many human pathophysiologies. Compounds that modulate protein aggregation and interact with preformed fibrils and convert them to less toxic species, expect to serve as promising drug candidates and aid to the drug development efforts against aggregation diseases. In present study, the kinetics of amyloid fibril formation by human insulin (HI) and the anti-amyloidogenic activity of ascorbic acid (AA) were investigated by employing various spectroscopic, imaging and computational approaches. We demonstrate that ascorbic acid significantly inhibits the fibrillation of HI in a dose-dependent manner. Interestingly ascorbic acid destabilise the preformed amyloid fibrils and protects human neuroblastoma cell line (SH- SY5Y) against amyloid induced cytotoxicity. The present data signifies the role of ascorbic acid that can serve as potential molecule in preventing human insulin aggregation and associated pathophysiologies.

Cysteine as a potential anti-amyloidogenic agent with protective ability against amyloid induced cytotoxicity.

Protein aggregation and misfolding have been allied with numerous human disorders and thus inhibition of such occurrence has been center for intense research efforts against these diseases. Here, we investigated anti-fibrillation activity of cysteine and its effect on kinetics of stem bromelain amyloid fibril formation. We established the anti-fibrillation and anti aggregation activities of cysteine by using multiple approaches like turbidity measurements, dye binding assays (ThT and ANS) and structural changes were monitored by circular dichroism (CD) followed by electron microscopy. Our experimental study inferred that cysteine inhibits temperature induced fibrillation of protein in a concentration dependent way. In addition, MDA-MB-231 cell viability of pre-formed amyloid was increased in presence of cysteine as compared to the fibrils alone. Furthermore, dynamic light scattering studies of native, aggregated as well as incubated (amyloids in presence of cysteine) samples indicates that cysteine restores native like structures of stem bromelain. Isothermal titration calorimetric results revealed that hydrogen bonding between cysteine and stem bromelain plays a significant role during inhibition of stem bromelain aggregation. However, thiophilic interaction between thiol group of cysteine and aromatic amino acid residue of stem bromelain may also have noteworthy role in inhibition of amyloid formation.

Attenuation of amyloid fibrillation in presence of Warfarin: A biophysical investigation.

Protein misfolding and aggregation are associated with more than twenty diseases, such as neurodegenerative diseases. The amyloid oligomers and fibrils may induce cell membrane disruption and lead to cell apoptosis. A great number of studies have focused on discovery of amyloid inhibitors which may prevent or treat amyloidosis. In this study, we used human serum albumin (HSA) as an amyloid model to test the anti-amyloid effects of warfarin (WFN), a very well-known drug for treatment of thrombosis and also used by biophysicists to characterize the specific binding site on HSA (site I of subdomain IIA). We have used a combination of different biophysical, spectroscopic and imaging techniques to prove the anti-amyloidogenic behavior of WFN. Our results demonstrated that WFN is capable enough to inhibit the HSA fibrillation. Exposed HSA surface hydrophobicity was decreased by 50% as judged by ANS analysis. Moreover, anti-amyloidegenic behavior of WFN was found to be concentration dependent as supported by decreased ThT fluorescence by 22.4% and 46% at WFN concentrations of 500 and 1000µM, respectively. Circular dichroism technique showed the change in secondary structure of native HSA as well as in presence of WFN. These results suggests that WFN is capable of inhibiting amyloid aggregation, hence, WFN related compounds may thus be further explored for designing effective anti-amyloidosis compounds.

Anti-amyloidogenic behavior and interaction of Diallylsulfide with Human Serum Albumin.

In this work, binding of garlic component-Diallysulfide (DAS) with major human blood transport protein, Human Serum Albumin (HSA) and its anti- amyloidogenic behavior has been studied by utilizing various spectroscopic and molecular docking strategies. The HSA exhibit significant reduction in fluorescence intensity upon interaction with DAS. DAS quenches the fluorescence of HSA in concentration dependent manner with binding affinity of 1.14×103M-1. UV-visible spectroscopy results confirm the formation of DAS-HSA complex and secondary structure of HSA get stabilized upon complexation with DAS as observed by far UV CD spectroscopy and Differential Scanning Calorimetry. The topology of HSA in absence and presence of DAS was monitored through Dynamic Light Scattering (DLS) technique, inferred that protein becomes more compact in presence of DAS. Further, molecular docking study shows that DAS bind to the nearby site II in subdomain III of HSA. Moreover, effect of DAS was studied on HSA fibrillation process. ThT binding, ANS fluorescence assay, CD measurement, DLS and Transmission Electron Microscopy (TEM) results altogether confirm the anti-amyloidogenic property of DAS. This work will provide biophysical insight into the interaction of DAS with HSA and will help in designing more potential therapeutic strategies against protein aggregation by exploiting other related compounds.