Infrared LED irradiation photobiomodulation of oxidative stress in human dental pulp cells.
OBJECTIVE
To investigate the effect of infrared light-emitting diode (LED) irradiation on the oxidative stress induced in human dental pulp cells (HDPCs) by lipopolysaccharide (LPS).


METHODS
Human dental pulp cells (HDPCs) were harvested from sound primary teeth that were near exfoliation. Cells were seeded (10(5)  cells cm(-2) ) using α-MEM supplemented with 10% FBS and after 24 h, were placed in contact with LPS (10 μg mL(-1) of culture medium). Immediately afterwards, HDPCs were subjected to a single irradiation with an infrared LED (855 nm) delivering different doses of energy (0, 2, 4, 8, 15 or 30 J cm(-2) ). For each dose, there was a control group without LPS application. Twenty-four hours after irradiation, groups were tested for nitric oxide (NO) quantification, cell viability (MTT assay) and qualitative assessment of reactive oxygen species (ROS). Data were submitted to Kruskal-Wallis and Mann-Whitney tests (α = 0.05).


RESULTS
Lipopolysaccharide (LPS)-induced stress resulted in significant increase in NO production by HDPC without causing damage to cell respiratory metabolism. Irrespective of energy dose delivered, NO production was significantly reduced when LPS-stressed cells were irradiated with infrared LED (2 J cm(-2) , P = 0.003; 95% CI = 5.84-27.71; 4 J cm(-2) , P = 0.001; 95% CI = 7.52-26.39; 8 J cm(-2) , P = 0.0195; 95% CI = -2.86-16.01; 15 J cm(-2) , P = 0.0001; 95% CI = 12.10-30.96; 30 J cm(-2) , P = 0.007; 95% CI = 5.84-24.71). The highest decrease in NO production was observed when 15 J cm(-2) was delivered to cells. Infrared LED irradiation resulted in a decrease in ROS production, whilst HDPC metabolism was not significantly affected.


CONCLUSIONS
Biomodulation of oxidative stress of HPDC can be achieved by irradiation with a single dose of infrared LED. Within the range investigated, 15 J cm(-2) resulted in the least production of NO.
Department of Orthodontics and Pediatric Dentistry, School of Dentistry, University Estadual Paulista (UNESP), Araraquara, SP, Brazil.
L A
LA
Montoro
A P S
AP
Turrioni
F G
FG
Basso
C A
CA
de Souza Costa
J
J
Hebling
D002478:Cells, Cultured; D003782:Dental Pulp / Q000166:cytology / Q000528:radiation effects*; D006801:Humans; D007259:Infrared Rays; D009569:Nitric Oxide / Q000096:biosynthesis; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism
D017382:Reactive Oxygen Species; D009569:Nitric Oxide
cells cultured; lipopolysaccharides; nitric oxide; phototherapy; reactive oxygen species; spectrophotometry infrared