COX-2 mRNA expression decreases in the subplantar muscle of rat paw subjected to carrageenan-induced inflammation after low level laser therapy

Objective and design: Low level laser therapy (LLLT) has been presented as a novel therapy to treat inflammation. Herein we studied the effect of LLLT on the COX-2 mRNA expression in subplantar tissue taken from rats treated with carrageenan. Material: The groups consisted of 32 rats: A (1) (Saline), A (2) (Carrageenan), A (3) (Carrageenan + laser 660 nm) and A (4) (Carrageenan + laser 684 nm). Treatment: A(3) and A(4) were irradiated in the first hour after carrageenan. Methods: The edema was measured by a plethysmometer and COX-2 mRNA was by RT-PCR. Statistical were evaluated by ANOVA and Tukey-Kramer Test. Results: Carrageenan increased both edema (A(1)= 0.6 +/- 0.04 vs. A(2)= 2.24 +/- 0.08) and COX-2 mRNA (A(1)= 1.1 +/- 0.26 vs. A(2)= 3.52 +/- 0.69). Irradiation reduced the edema (A(3)= 0.84 +/- 0.09; A(4)= 1.31 +/- 0.05) and the COX-2 mRNA (A(3)= 2.16 +/- 0.28; A(4)= 1.86 +/- 0.20). Conclusion: LLLT reduce the expression of COX-2 mRNA.