Anti-inflammatory effect of low-level laser and light-emitting diode in zymosan-induced arthritis.
OBJECTIVE
The aim of this work was to investigate the effect of low-level laser therapy (LLLT) and light-emitting diode (LED) on formation of edema, increase in vascular permeability, and articular joint hyperalgesia in zymosan-induced arthritis.


BACKGROUND
It has been suggested that low-level laser and LED irradiation can modulate inflammatory processes.


METHODS
Arthritis was induced in male Wistar rats (250-280 g) by intra-articular injection of zymosan (1 mg in 50 microL of a sterile saline solution) into one rear knee joint. Animals were irradiated immediately, 1 h, and 2 h after zymosan administration with a semiconductor laser (685 nm and 830 nm) and an LED at 628 nm, with the same dose (2.5 J/cm(2)) for laser and LED. In the positive control group, animals were injected with the anti-inflammatory drug dexamethasone 1 h prior to the zymosan administration. Edema was measured by the wet/dry weight difference of the articular tissue, the increase in vascular permeability was assessed by the extravasation of Evans blue dye, and joint hyperalgesia was measured using the rat knee-joint articular incapacitation test.


RESULTS
Irradiation with 685 nm and 830 nm laser wavelengths significantly inhibited edema formation, vascular permeability, and hyperalgesia. Laser irradiation, averaged over the two wavelengths, reduced the vascular permeability by 24%, edema formation by 23%, and articular incapacitation by 59%. Treatment with LED (628 nm), with the same fluence as the laser, had no effect in zymosan-induced arthritis.


CONCLUSIONS
LLLT reduces inflammatory signs more effectively than LED irradiation with similar irradiation times (100 sec), average outputs (20 mW), and energy doses (2 J) in an animal model of zymosan-induced arthritis. The anti-inflammatory effects of LLLT appear to be a class effect, which is not wavelength specific in the red and infrared parts of the optical spectrum.
Laboratory of Inflammation, Institute of Research and Development, University of Vale do Paraíba, Sáo José dos Campos, Brazil.
Núbia Cristina Rodrigues
NC
de Morais
Ana Maria
AM
Barbosa
Mariana Lima
ML
Vale
Antonio Balbin
AB
Villaverde
Carlos José
CJ
de Lima
José Carlos
JC
Cogo
Stella Regina
SR
Zamuner
D000818:Animals; D001169:Arthritis, Experimental / Q000139:chemically induced / Q000532:radiotherapy*; D008027:Light; D028022:Low-Level Light Therapy; D008297:Male; D010789:Phototherapy / Q000379:methods*; D051381:Rats; D015054:Zymosan
D015054:Zymosan