Low-level laser therapy (LLLT) attenuates RhoA mRNA expression in the rat bronchi smooth muscle exposed to tumor necrosis factor-alpha.

Low-level laser therapy (LLLT) has been found to produce anti-inflammatory effects in a variety of disorders. Bronchial smooth muscle (BSM) hyperreactivity is associated with increased Ca+2 sensitivity and increased RhoA mRNA expression. In the current study, we investigated if LLLT could reduce BSM contraction force and RhoA mRNA expression in tumor necrosis factor-alpha (TNF-alpha)-induced BSM hyperreactivity. In the study, 112 male Wistar rats were divided randomly into 16 groups, and BSM was harvested and suspended in TNF-alpha baths for 6 and 24 h, respectively. Irradiation with LLLT was performed with a wavelength of 660 nm for 42 s with a dose of 1.3 J/cm2. This LLLT dose was administered once in the 6-h group and twice in the 24-h group. LLLT significantly decreased contraction force in BSM at 6 h (TNF-alpha + LLLT: 11.65+/-1.10 g/100 mg of tissue) (F=3115) and at 24 h (TNF-alpha+ LLLT: 14.15+/-1.1 g/100 mg of tissue) (F=3245, p<0.05) after TNF-alpha, respectively, when compared to vehicle-bathed groups (control). LLLT also significantly decreased the expression of RhoA mRNA in BSM segments at 6 h (1.22+/-0.20) (F=2820, p<0.05) and 24 h (2.13+/-0.20) (F=3324, p<0.05) when compared to BSM segments incubated with TNF-alpha without LLLT irradiation. We conclude that LLLT administered with this protocol, reduces RhoA mRNA expression and BSM contraction force in TNF-alpha-induced BSM hyperreactivity.