Plasma-arc generated light inhibits proliferation and induces apoptosis of human gingival fibroblasts in a dose-dependent manner.
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/cm(2). 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/cm(2) 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-G(1) 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.


CONCLUSIONS
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.
Hwang
In-Yong
IY
Graduate School of Dentistry, Institute of Oral Biosciences, Chonbuk National University, Chonju 561-756, South Korea.
Son
Young-Ok
YO
Kim
Ji-Hae
JH
Jeon
Young-Mi
YM
Kim
Jong-Ghee
JG
Lee
Choon-Bong
CB
Park
Jong-Sun
JS
Lee
Jeong-Chae
JC
D017209:Apoptosis / Q000528:radiation effects*; D015153:Blotting, Western; D049109:Cell Proliferation / Q000528:radiation effects; D002478:Cells, Cultured; D004396:Coloring Agents; D053938:DNA Fragmentation / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004587:Electrophoresis, Agar Gel; D005347:Fibroblasts / Q000166:cytology / Q000528:radiation effects*; D005434:Flow Cytometry; D005881:Gingiva / Q000166:cytology / Q000528:radiation effects*; D006801:Humans; D008027:Light; D008029:Lighting / Q000295:instrumentation*; D008422:Materials Testing; D008928:Mitochondria / Q000528:radiation effects; D011065:Poly(ADP-ribose) Polymerases / Q000528:radiation effects; D011829:Radiation Dosage; D019275:Radiopharmaceuticals; D013385:Succinate Dehydrogenase / Q000032:analysis; D013936:Thymidine; D014316:Tritium; D014343:Trypan Blue
D004396:Coloring Agents; D019275:Radiopharmaceuticals; D014316:Tritium; D013385:Succinate Dehydrogenase; D011065:Poly(ADP-ribose) Polymerases; D014343:Trypan Blue; D013936:Thymidine