Abstract
Tauroursodeoxycholic acid (TUDCA), a hydrophilic bile acid containing taurine conjugated with the ursodeoxycholic acid (UDCA), has been known and used from ancient times as a therapeutic compound in traditional Chinese medicine. TUDCA has recently been gaining significant interest as a neuroprotective agent, also exploited in the visual disorders. Among several mechanisms of TUDCA’s protective action, its antioxidant activity and stabilizing effect on mitochondrial and plasma membranes are considered. In this work we investigated antioxidant activity of TUDCA and its impact on structural properties of model membranes of different composition using electron paramagnetic resonance spectroscopy and the spin labeling technique. Localization of TUDCA molecules in a pure POPC bilayer has been studied using a molecular dynamics simulation (MD). The obtained results indicate that TUDCA is not an efficient singlet oxygen (1O2 (1Δg)) quencher, and the determined rate constant of its interaction with 1O2 (1Δg) is only 1.9 × 105 M−1s−1. However, in lipid oxidation process induced by a Fenton reaction, TUDCA reveals substantial antioxidant activity significantly decreasing the rate of oxygen consumption in the system studied. In addition, TUDCA induces slight, but noticeable changes in the polarity and fluidity of the investigated model membranes. The results of performed MD simulation correspond very well with the experimental results.
Highlights
It has been shown that all-trans retinal (atRAL) released from deactivated Rh might temporarily concentrate in photoreceptor outer segments (POSs) membranes, as its reduction to all trans retinol is a limiting step in retinoid cycle [59]
The results of molecular dynamics simulation (MD) simulations show that Tauroursodeoxycholic acid (TUDCA) molecules did not penetrate deeply the lipid bilayer of model membranes but located mostly parallel to
The results of MD simulations show that TUDCA molecules did not penetrate deeply the lipid bilayer of model membranes but located mostly parallel to the membrane surface with their sulphate groups directed towards the water phase
Summary
Present in the biliary bile acids of a number of vertebrates in a small https://www.mdpi.com/journal/membranes acids constitute major components of a bear bile, in which their level reach up to 75% [3,4]. Earlier studies showed antioxidant activity and membrane stabilizing effect of TUDCA in non-cellular models, these studies focused on the interaction of UDCA and TUDCA with other components of the bile [26,27,28]. In light of these reports, interaction of TUDCA with lipid membrane and/or their components seems to be one of the key mechanisms in its neuroprotective action
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