Extracellular environment as one mediator of blue light-induced mitochondrial suppression.
OBJECTIVE
The current study tested the hypothesis that the extracellular environment mediates mitochondrial suppression of oral epithelial cells and fibroblasts by blue light.


METHODS
We exposed Balb fibroblasts (Balb), normal human epidermal keratinocytes (NHEK), and oral squamous carcinoma cells (OSC2) to blue light (30-120J/cm2) in different cell-culture media and in phosphate buffered saline (PBS). Mitochondrial activity (MTT method) was used to assess cellular response 72 h post-light exposure. Cell-culture media were replaced or supplemented before or after light exposure to assess the variables of exposure time and medium degradation as mediators of blue light-induced effects.


RESULTS
Mitochondrial activity of NHEK was not suppressed by exposure to blue light regardless of extracellular conditions. The mitochondrial activity of OSC2 and Balb cells was suppressed most when cells were exposed to light in cell-culture medium (versus PBS). Blue light suppressed mitochondrial activity more when irradiated medium remained in contact with the cells at least 1h, indicating a time-dependence of the medium effects. Neither a replacement nor a supplementation of medium components reduced blue light-induced mitochondrial suppression.


CONCLUSIONS
Our results suggest that tissue environments influence cellular responses to blue light and that these environments should be considered when assessing any biological effects of blue light during the photopolymerization of restorative resins.
Rotenberg
Shaun
S
Department of Oral Biology and Maxillofacial Biology, Medical College of Georgia, Augusta, GA 30912-1100, USA.
Lewis
Jill B
JB
Lockwood
Petra E
PE
Tseng
Wan Y
WY
Messer
Regina L W
RL
Hsu
Stephen D
SD
Omata
Yo
Y
Wataha
John C
JC
D000818:Animals; D002021:Buffers; D002294:Carcinoma, Squamous Cell / Q000648:ultrastructure; D002460:Cell Line; D045744:Cell Line, Tumor; D004396:Coloring Agents / Q000494:pharmacology; D003470:Culture Media / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004847:Epithelial Cells / Q000528:radiation effects; D005347:Fibroblasts / Q000528:radiation effects; D006801:Humans; D015603:Keratinocytes / Q000528:radiation effects; D008027:Light; D051379:Mice; D008807:Mice, Inbred BALB C; D008928:Mitochondria / Q000528:radiation effects*; D009062:Mouth Neoplasms / Q000648:ultrastructure; D010637:Phenolsulfonphthalein / Q000494:pharmacology; D010710:Phosphates; D017319:Photosensitizing Agents / Q000494:pharmacology; D012256:Riboflavin / Q000494:pharmacology; D012965:Sodium Chloride; D013385:Succinate Dehydrogenase / Q000528:radiation effects; D013997:Time Factors
D002021:Buffers; D004396:Coloring Agents; D003470:Culture Media; D010710:Phosphates; D017319:Photosensitizing Agents; D012965:Sodium Chloride; D013385:Succinate Dehydrogenase; D010637:Phenolsulfonphthalein; D012256:Riboflavin