HEMA effect on ERK and PI3K/AKT survival pathways in HPC

Previous investigations revealed that dental monomers could affect intracellular pathways leading to cell survival or cell death. Mitogen-activated protein kinase (MAPK) and Protein Kinase B (AKT) might mediate cell responses as well as cell survival and apoptosis. Objective: The purpose of this study was to evaluate the effects of HEMA on ERK1/2 and AKT pathways in human primary pulp fibroblasts (HPC). Methods: HPC were treated with various concentrations of HEMA (0-12 mM) for 24h. Then, viability and cell death were determined by flow cytometry using Annexin V and PI staining. ROS production was detected by the increasing fluorescence of the oxidation-sensitive dye 2,7 -dichlorofluorescine diacetate (DCFH-DA) after HEMA treatment. Whole-cell extracts derived from HPC exposed to HEMA for different time periods (0-120 min) were immunoblotted with anti-P-Akt or anti-P-ERK 1/2. Statistical analysis was performed using the Mann-Whitney U-test (p<0.05). Results: Cell viability decreased significantly at 10mM HEMA related to untreated cells. Cell death increased in dose-dependent manner after HEMA exposure. 10mM HEMA treatment resulted in five-fold increase of ROS formation as well as phosphorylation of ERK and AKT. Selective inhibitors of ERK (PD98059) and AKT (LY294002) activation amplified HPC death after HEMA exposure. However, 10mM NAC reduced HEMA-induced ROS production and cell death, and in turn ERK and AKT phosphorylation. Conclusion: Our results suggest that ROS production in HPC is involved in induced cell death, but also in cell survival by modulating ERK and AKT survival pathway.