Plasma-arc generated light inhibits proliferation and induces apoptosis of human gingival fibroblasts in a dose-dependent manner

Hwang, In-Yong; Son, Young-Ok; Kim, Ji-Hae; Jeon, Young-Mi; Kim, Jong-Ghee; Lee, Choon-Bong; Park, Jong-Sun; Lee, Jeong-Chae

doi:10.1016/j.dental.2007.11.018

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Volume 24, Issue 8 , Pages 1036-1042, August 2008

Plasma-arc generated light inhibits proliferation and induces apoptosis of human gingival fibroblasts in a dose-dependent manner

In-Yong Hwang
- Graduate School of Dentistry, Institute of Oral Biosciences, Chonbuk National University, Chonju 561-756, South Korea
Young-Ok Son
- Division of Biological Science, Chonbuk National University, Chonju 561-756, South Korea
- Research Center of Bioactive Materials, Chonbuk National University, Chonju 561-756, South Korea
Ji-Hae Kim
- Research Center of Bioactive Materials, Chonbuk National University, Chonju 561-756, South Korea
Young-Mi Jeon
- Graduate School of Dentistry, Institute of Oral Biosciences, Chonbuk National University, Chonju 561-756, South Korea
Jong-Ghee Kim
- Graduate School of Dentistry, Institute of Oral Biosciences, Chonbuk National University, Chonju 561-756, South Korea
Choon-Bong Lee
- Graduate School of Dentistry, Institute of Oral Biosciences, Chonbuk National University, Chonju 561-756, South Korea
Jong-Sun Park
- Graduate School of Dentistry, Institute of Oral Biosciences, Chonbuk National University, Chonju 561-756, South Korea
Jeong-Chae Lee
- Graduate School of Dentistry, Institute of Oral Biosciences, Chonbuk National University, Chonju 561-756, South Korea
- Research Center of Bioactive Materials, Chonbuk National University, Chonju 561-756, South Korea
- Corresponding author at: Institute of Oral Biosciences and Research Center of Bioactive Materials, Chonbuk National University, Chonju 561-756, South Korea. Tel.: +82 63 270 4049; fax: +82 63 270 4049.

Received 22 November 2006; received in revised form 27 August 2007; accepted 21 November 2007.

Abstract

Objective

This study examined the effects of blue light exposure on the proliferation and cytotoxicity of human gingival fibroblasts (HGF). Cellular mechanism by which blue light causes cytotoxic effects was also investigated.

Methods

HGF were exposed to the plasma-arc generated blue light with various energy densities ranging from 2 to 48J/cm². After light exposure of the cells, they were processed for analyzing tritium incorporation, succinate dehydrogenase (SDH) activity, trypan blue exclusion, and DNA fragmentation. In addition, possible mechanism of the light-mediated cytotoxicity was investigated through flow cytometric and Western blot analyses.

Results

Blue light exposure significantly inhibited proliferation and SDH activity of HGF in a dose-dependent manner; exposure more than 12J/cm² had a toxic effect on the cells. The blue light-induced cytotoxicity of the cells resulted from apoptosis, as proven by the migration of many cells to the sub-G₁ phase of cell cycle and the appearance of DNA ladders. Additional experiments revealed that blue light induces apoptosis of HGF through mitochondrial stress and poly (ADP ribose) polymerase cleavage.

Significance

This study suggests that plasma-arc generated blue light exerts some harm to cells, particularly damaging effect to DNA, and thus a long curing time more than recommended can cause biological damage on the oral tissue.

Keywords: Blue light, Human gingival fibroblasts, Growth inhibition, Apoptosis