Shedding New Light into Lipid Oxidation in GUVs and Bacteria. From Membrane Dynamics to Cell Survival

ISABEL O. L. BACELLAR; SOL R. MARTÍNEZ; MARÍA CECILIA BECERRA; MAURICIO S. BAPTISTA; GONZALO COSA; ANDRES M. DURANTINI

Encuentro; XIII Encuentro Latinoamericano de Fotoquímica y Fotobiología; 2017

Lipid oxidation is a ubiquitous process with important roles in cell biology and consequently in human health. Lipid oxidation may involve a chain autooxidation reaction, may take place via enzymatic pathways or via photooxidation. Chemical modifications to the lipid molecule may be amplified as changes in collective physical properties such as lipid membrane surface area, thickness, porosity, permeability, and segregation. In this presentation, we will describe the use of fluorescence microscopy jointly with a fluorogenic α-tocopherol analogue probe previously developed by us (H2B-PMHC) to study oxidation of lipid membranes in giant unilamellar vesicles (GUVs) mediated by photoinduced generation of singlet oxygen (1O2). Fluorescence microscopy studies with 1O2 photosensitizers on single GUVs embedding H2B-PMHC illustrated rapid activation of the probe followed later by fluctuations of the lipid membrane and expansion. A correlation was observed between the time for antioxidant H2B-PMHC consumption by 1O2 (directly related to the rate of lipid oxidation) and the onset of membrane fluctuations. We also expand our studies from GUVs to bacteria where our microscopy tools enable us to illuminate the spatiotemporal ROS production due to oxidative stress induced by ciprofloxacin in individual bacteria. Discussion on the biological relevance of these processes will be presented.