Membrane Oxidative-Damage, Key Role in the Cytotoxicity Induced by HEMA

Objectives: To assess the impact of 2-hydroxyethyl methacrylate (HEMA) exposure on the structure and function of biological membranes in primary odontoblast-like cells (OLCs).
Methods: Differentiated OLCs from human dental pulp mesenchymal stem cells, obtained from third molar surgery after informed consent, were exposed to 3, 6, 9 and 12 mM HEMA for 24 h. The viability and integrity of the cell membrane were determined using calcein and lactate dehydrogenase techniques. Intracellular oxidation was evaluated using the 2',7'-dichlorofluorescein probe to detect the production of reactive oxygen species (ROS). Membrane phospholipids peroxidation by ROS was determined by malondialdehyde (MDA) quantification and the impact of oxidative imbalance on the permeability and functionality of the mitochondrial membrane was evaluated measuring the mitochondrial membrane potential change and caspase-3 activity as apoptotic cell death marker.
Results: The membranes play a central role in cellular response to HEMA being primary intracellular targets for the onset of cell dysfunction following exposure. The HEMA induced a decrease in the activity of cytosolic esterases and loss of plasmatic membrane integrity proportionally to a dramatic intracellular ROS increase. HEMA also induced a damage in membrane permeability allowing the release of cytoplasmic and mitochondrial contents, phenomena that were related to lipid peroxidation by ROS toward toxic aldehydes, increasing MDA levels since 3 h post exposure. As the monomer concentration increased, there was a notable decrease in Δψm. This collapse, demonstrated mitochondrial membrane damage that may be related to caspase-3 increased activity and apoptosis activation.
Conclusions: HEMA induced transient increase of intracellular oxygen intermediates, modifying the intracellular redox state, which caused a decrease in cellular metabolism, changes in membrane permeability and integrity, and disruption of mitochondrial physiology. Lipid peroxidation could be considered as one of the main molecular mechanisms involved in oxidative damage to cellular structures in OLCs.