Does Long-Term Administration of a Beta-Blocker (Timolol) Induce Fibril-Based Cataract Formation In-vivo?

Timolol is a non-selective beta-adrenergic receptor antagonist administered for treating glaucoma, heart attacks and hypertension. In the present study, we set out to determine whether or not timolol can provoke cataract formation, thus the influence of timolol on the amyloid-type aggregation of crystallin was investigated. We then provided experimental evidence of crystallin aggregation and its induction by timolol using different spectroscopic measurements. Turbidimetric measurements as well as ThT fluorescence data indicated that timolol induce extent of crystallin amyloid formation. The kinetic of protein aggregation was also changed in presence of increasing concentrations of the drug suggesting that long-term drug administration may contribute to the development of cataract. Since the consequence of timolol-crystallin interaction has yet to be identified, additional data on it may help us to postpone amyloid cataract formation.

Amyloid fibril formation by native and modified bovine ß-lactoglobulins proceeds through unfolded form of proteins: a comparative study.

The misfolding and extracellular amyloid deposition of specific proteins are associated with a large family of human pathologies, often called protein conformational diseases. Despite the many efforts expended to characterize amyloid formation in vitro, there is no deep knowledge about the environment (in which aggregation occurs) as well as mechanism of this type of protein aggregation. Recently, ß-lactoglobulin (ß-lg) was driven toward amyloid aggregation under specific extreme conditions. In the present study, citraconylation was employed to neutralize the charges on accessible lysine residues of ß-lg and different approaches such as turbidimetry, thermodynamic analysis, extrinsic fluorimetry and theoretical studies have been successfully used to compare the different behaviors of the native and modified proteins. Kinetic analyses of native ß-lg aggregation showed a gradual development of turbidity, whereas the modified ß-lg displayed an increased propensity toward aggregation. Our results clearly demonstrated that the stability of modified ß-lg is markedly reduced, compared to the native one. Using of TANGO and WALTZ algorithms (as well as modelling softwares) which describe aggregation tendencies of different parts of a protein structure, we suggested critical importance of some of the lysine residues in the aggregation process. The results highlighted the critical role of protein stability and elucidated the underlying role of hydrophobic/electrostatic interactions in lactoglobulin-based experimental system.