Influence of small molecules on the photo-stability of water soluble porcine lens proteins.

Abstract

The eye lens is a biconvex structure composed of lens fibres, cells that lack of blood and nerve supply and of any organelle, allowing for a high concentration of water soluble proteins that determine the lens transparency and refractive index. The lens water soluble protein pool in mammals is composed of α-, β-, and γ-crystallins, the latter being involved in calcium homeostasis and having structural importance, the first playing a crucial role in preventing protein aggregation and the consequent lens obfuscation, which leads to the clinical outcome of cataract. Among different factors, oxidative stress, free radicals, and reactive oxygen species (ROSs) generated by the exposure to UV light are widely recognized to cause cataract formation. Taking advantage of synchrotron radiation circular dichroism, fluorescence, and circular dichroism spectroscopies, in the present study we investigate the influence of different small molecules with the potential to either quench ROS generation or to stabilize protein conformation. Therefore, ascorbic acid, an excellent antioxidant agent already present in the eye aqueous humour, has been tested along with ceftriaxone, mannitol and trehalose, which osmolyte activity was demonstrated interfering with model proteins misfolding. Our results showed that ascorbic acid strongly inhibits the ROS production without, however, preserving the native protein structure, whereas mannitol had no effect on the ROS production but retained better the secondary structure of WS proteins. Collectively, the use of a mixture of ascorbic acid and mannitol could be used to better protect eye lens proteins from ROS damage preventing the cataract onset.