title: Effects of low-level laser therapy on the oxidative metabolism and matrix proteins in the rat masseter muscle.
abstract: OBJECTIVE
  This study aims to analyze the effects of low-level laser therapy (LLLT) on the oxidative activity and the expression/activity of metalloproteinases of the masseter muscle.
  
  
  BACKGROUND
  Currently in dentistry LLLT has been used on patients with muscular disorders, such as the temporomandibular disorders (TMDs) but its effect at the cellular level has not been fully elucidated.
  
  
  METHODS
  Thirty male Wistar rats divided into 6 groups (n=5) received 10 laser irradiations (780 nm, 5 mmW, CW laser, illuminated area 0.04 cm(2), power density 125 mW/cm(2)), with different energy densities (group I-0; group II-0.5; group III-1.0; group IV-2.5; group V-5.0; and group VI-20 J/cm(2)). Muscles were processed for nicotinamide adenine dinucleotide diaphorase (NADH) and sucinate dehydrogenase (SDH) activities and zymography. The photomicrographs were evaluated by the point counting method using a test system and ImageJ software; and by the ANOVA statistical test. The proteinases' secretion/activity was qualitatively analyzed by zymography.
  
  
  RESULTS
  LLLT significantly increased (p<0.05) masseter muscle oxidative metabolism shown by the increased area of intermediary fibers in the NADH (groups IV, V, and VI) and SDH (group V) reactions. The same metabolic pattern was observed among the groups in both reactions. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) zymography detected only the MMP-2 expression/activity for the untreated-control group (group I). The exposure to LLLT increased the activity of MPP-2 in group VI and the activity of MMP-9 in all groups exposed to different energy densities of laser irradiation (groups II, III, IV, V, and VI).
  
  
  CONCLUSIONS
  Thus, LLLT stimulated the oxidative metabolism and the expression of matrix metalloproteinase (MMPs) of the masseter muscle, which may indicate a matrix remodeling process. However, group VI did not show the best results for oxidative metabolism, probably indicating that the dosage they were given was high for this protocol.
authors: Department of Morphology, Stomatology, and Physiology, Faculty of Dentistry of Ribeirao Preto, University of Sao Paulo, Avenida do Cafe s/n - Monte Alegre, Ribeirao Preto, Brazil.
authors: Fernando José
authors: FJ
authors: Dias
authors: João Paulo Mardegan
authors: JP
authors: Issa
authors: Fabiana Testa Moura de Carvalho
authors: FT
authors: Vicentini
authors: Maria José Vieira
authors: MJ
authors: Fonseca
authors: Juliane Carneiro
authors: JC
authors: Leão
authors: Selma
authors: S
authors: Siéssere
authors: Simone Cecílio Hallak
authors: SC
authors: Regalo
authors: Mamie Mizusaki
authors: MM
authors: Iyomasa
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D019069:Cell Respiration; D004591:Electrophoresis, Polyacrylamide Gel; D028022:Low-Level Light Therapy / Q000379:methods*; D008297:Male; D008406:Masseter Muscle / Q000201:enzymology / Q000528:radiation effects*; D009243:NAD / Q000378:metabolism*; D010784:Photomicrography; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013385:Succinate Dehydrogenase / Q000378:metabolism*
chemical_list: D009243:NAD; D013385:Succinate Dehydrogenase