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.