Protective effects of memantine and epicatechin on catechol-induced toxicity on Müller cells in vitro

This study evaluates the toxic effects of catechol (a component from cigarette smoke) on Müller cells (MIO-M1) in vitro, and investigates the inhibitors memantine and epicatechin to determine if they can reverse the catechol toxic effects. MIO-M1 cells were exposed to varying concentrations of catechol with or without memantine or epicatechin. Cell viability (CV) was measured by a trypan blue dye-exclusion assay. Caspase-3/7 activity was measured by fluorochrome assay. The production of reactive oxygen/nitrogen species (ROS/RNS) was measured with 2',7'-dichlorodihydrofluorescein diacetate dye assay. Mitochondrial membrane potential (DeltaPsim) was measured using JC-1 assay. Intracellular ATP content was determined by the ATPLite kit. MIO-M1 cells showed significant decrease in cell viability, increased caspase-3/7 activity, elevated ROS/RNS levels, decreased DeltaPsim value, and decreased intracellular ATP content after exposure to catechol 150, 300, and 600 microM compared with control. Pre-treatment with memantine 10 microM or epicatechin 15 microM reversed loss of cell viability in catechol 150 microM-treated cultures (22.3%, p<0.01 and 17.8%, p<0.05), respectively. Similarly, pre-treatment with memantine 10 microM and epicatechin 15 microM prior to catechol resulted in decreased caspase-3/7 activities (77% and 64.2%, p<0.001), decreased ROS/RNS levels (82.3% and 79%, p<0.001), increased DeltaPsim value (76.4% and 72.2%, p<0.001), and increased ATP levels (46.6% and 40.4%, p<0.001) compared to 150 microM catechol-treated cultures. Catechol, a component of smoking, can diminish cell viability and mitochondrial function in MIO-M1 cells in vitro. However, memantine and epicatechin can partially reverse the cytotoxic effect of catechol. Their administration may reduce or prevent Müller cells degeneration in AMD or other retinal degenerative disorders.