Cyclophilin D Deficiency Rescues Oxidative Stress-induced Dental Pulp Cells Apoptosis

Objectives: Oxidative stress plays a central role in the apoptosis of dental pulp cell in the process of dental pulpitis or dental pulp is exposure of external stimulation. However, the underlying mechanism remains unclear. Mitochondrial permeability transition pore (mPTP) is regarded as “a master regulator of cell death”, while Cyclophilin D (CypD), a crucial component for mPTP formation, would facilitate an opening of the mPTP. The aim of this study was to determine whether CypD mediated pathway was involved in hydrogen peroxide (H₂O₂)-induced apoptosis of human dental pulp cells (HDPCs).
Methods: HPDCs was exposed to various concentrations of H₂O₂ with or without indicated treatment. Cell viability was evaluated by MTT assays. The apoptosis rate was analyzed by flow cytometry and TUNEL assays. Mitochondrial oxidative stress, membrane potential (MMP) and intracellular calcium level (Ca²⁺) were determined using a fluorescence microscope. ATP level was measured using a specific Assay kit. Protein levels were detected by western blotting.

Results: A significant reduction in cell viability and increased apoptosis was obtained in H₂O₂ treated cells when compared with negative controls (no treatment), in a concentration and time dependent fashion. Meanwhile, H₂O₂ also induced mitochondrial dysfunction reflected by increased mitochondrial oxidative stress, intracellular Ca²⁺ level, decreased MMP and ATP level. Notably, the expression level of CypD increased and mPTP opening occurred obliviously. However, genetic or pharmacological blockade of CypD significantly prevent H₂O₂-mediated cell injury as well as mitochondrial dysfunction.

Conclusions: These findings provide new insights into the role of CypD-dependent mitochondrial pathway in the H₂O₂-induced apoptosis in HDPCs.