Hydroquinone induces oxidative and mitochondrial damage to human retinal Müller cells (MIO-M1)

•The MIO-M1 cell line is derived from human Müller cells, which are glial cells supporting functions for retinal neurons.•Hydroquinone (HQ) is an aromatic organic phenol compound found in high concentrations in cigarette smoke.•HQ-treated cells had lower viability and mitochondrial function with increased ROS activity, which was reversed by 3MA.•HQ damages the MIO-M1 cells through oxidative, mitochondrial and autophagic pathways and not caspase-related apoptosis.•Inhibitors which block the HQ toxicity need to be identified in future studies.

PurposeSmoking is a risk factor in the development of a variety of neuroretinal diseases. Therefore, we have investigated the effects of hydroquinone (HQ), a toxicant that is present in high concentrations in cigarette smoke, on a human retinal Müller cell line (MIO-M1).MethodsMIO-M1 cells were treated for 24 h with four different concentrations of HQ (200 μM, 100 μM, 50 μM, and 25 μM). Assays were used to measure cell viability, reactive oxygen/nitrogen species (ROS/RNS), mitochondrial dehydrogenase activity (WST assay), caspase-3/7 activity and lactate dehydrogenase (LDH) levels. Western blot analyses with anti-LC3 and anti-GAPDH antibodies were performed on HQ-treated samples. Some cultures were treated with 4 μM rapamycin, to induce autophagy, with and without the autophagy inhibitor 3-methyl-adenine (3MA), and levels of ROS/RNS and LDH were measured.ResultsOur findings show that HQ reduced cell viability at four different concentrations tested (200, 100, 50 and 25 μM); decreased mitochondrial function at concentrations of 200 and 100 μM; increased ROS/RNS activity at all the concentrations tested and increased LDH levels at concentrations of 200, 100 and 50 μM. Caspase-3/7 activities were not modified by HQ. However, treatment of these cells with this agent resulted in the appearance of the autophagy associated LC3-II band. Pre-treatment with 3MA reduced the ROS/RNS and LDH levels of the HQ-treated and rapamycin-treated cells.ConclusionOur study suggests that HQ damages the MIO-M1 cells through oxidative, mitochondrial and autophagic pathways and not caspase-related apoptosis.