Induction of Apoptosis in Nifedipine-reactive Gingival Fibroblasts Using 18α-glycyrrhetinic Acid

Objectives: The goal of this investigation was to establish the basis of a pharmacotherapy for nifedipine-induced gingival overgrowth. Gingival overgrowth is an oral disease that compromises both oral function and facial appearance. Calcium channel blockers (e.g., nifedipine) and similar treatments can result in increased fibroblast proliferation and the accumulation of collagenous components within the gingiva. Gingival overgrowth has been attributed to the enhanced growth of gingival fibroblasts due to cell cycle alterations and decreased apoptosis during inflammation and exposure to drugs. The compound 18-alpha-glycyrrhetinic acid (18α-GA) elicits cell growth-inhibitory, apoptosis-promoting, and anti-inflammatory effects. In this study, we investigated the effects elicited by 18α-GA on the apoptosis and the regulators of this process in gingival fibroblasts isolated from patients who presented with nifedipine-induced gingival overgrowth (nifedipine-reactive gingival fibroblasts).
Methods: Semi-confluent cells were cultured in DMEM containing 1% foetal bovine serum (DMEM-1) with/without 10 μM 18α-GA for 24 or 48 h. Apoptotic cell numbers, levels of the regulator protein of apoptosis, and caspase activities were measured using ELISA, western blotting, and ELISA, respectively. The proposal for this experiment was approved by the Committee on Studies Involving Human Beings of the Nihon University School of Dentistry at Matsudo (EC 08-006).
Results: 18α-GA significantly increased the apoptotic cell numbers in the nifedipine-reactive gingival fibroblasts cultured in DMEM-1. In addition, 18α-GA significantly decreased the protein levels of Bcl-xL and Bcl-2 and increased the protein levels of cytosolic cytochrome c and cleaved caspase-3 and the activities of caspases 3 and 9.
Conclusions: 18α-GA induced the apoptosis of nifedipine-reactive gingival fibroblasts. In conclusion, 18α-GA may be applied as a pharmacotherapy for nifedipine-induced gingival overgrowth. This work was supported by JSPS KAKENHI Grant Number 25861780.