Effect of Low-Level Laser Therapy (LLLT) in Pulmonary Inflammation in Asthma Induced by House Dust Mite (HDM): Dosimetry Study

Abstract

Asthma is characterized by chronic inflammation in the airways. Several models have been proposed for the discovery of new therapies. Low-Level Laser Therapy (LLLT) is relatively new and effective, very low cost, with no side effects. However, there is still no consensus on the optimal dose to be used. In this sense, the objective of the present study was to evaluate the best dose in an experimental model of asthma induced by House Dust Mite (HDM). Balb/c mice received administration of 100 ug/animal HDM and LLLT applications (diode laser: 660 nm, 100 mW and four different energies 1J, 3J, 5J, and 7.5J) for 16 days. After 24 hours, we studied inflammatory, functional, and structural parameters. The results showed that LBI was able to modulate the pulmonary inflammation observed by reducing the number of cells in Bronchoalveolar Lavage Fluid (BALF) as well as reducing the percentage of neutrophils, eosinophils and T lymphocytes. On the other hand, LLLT increased the level of IL-10 and reduced levels of IL-4, IL-5 and IL-13 in BALF. LLLT was able to reduce the production of mucus, peribronchial eosinophils, collagen deposition, bronchoconstriction index, and bronchial and muscular thickening in the airways. We concluded that the use of LLLT in the treatment of chronic inflammation of the airways attenuated the inflammatory process and functional and structural parameters. We emphasize, in general, that the 1J and 3J laser presented better results. Thus, photobiomodulation may be considered a promising tool for the treatment of chronic pulmonary allergic inflammation observed in asthma.

Figure 1

Effect of LLLT on the total number of cells (a) and the number of macrophages (b), lymphocytes (c), neutrophils (d), and eosinophils (e) recovered from the BALF. The groups used in the experiment were Basal (unmanaged animals), asthmatics (HDM) (animals immunized and challenged with HDM), LLLT (animals only treated with LLLT), and HDM+LLLT (animals sensitized and challenged with HDM and subsequently treated with LLLT). The results refer to the use of 10 mice in each experimental group. Values expressed as mean and standard deviation. # p <0.001 when compared to Basal group; θ p <0.001, ϕ p <0.01, and δ p <0.05 when compared to the asthmatic group (HDM) and ns (not significant); ∗ p<0,05 and ∗∗∗ p<0,001 when compared HDM+LLLT (3J) group with the other groups treated with other doses.

Figure 2

Effect of LLLT on IL-4 (a), IL-5 (b), IL-10 (c), and IL-13 (d) levels in BALF supernatant. Values expressed as mean and standard deviation. The groups used in the experiment are described in Figure 1. The results refer to the use of 10 mice in each experimental group. # p <0.001 and $\stackrel{\ast }{\#}$ p <0.01 when compared to the Basal group; θ p <0.001, Δ p <0.01, and ϕ p <0.05 when compared to the asthmatic group (HDM) and ns (not significant); ∗ p<0,05 and ∗∗∗ p<0,001 when compared HDM+LLLT (3J) group with the other groups treated with other doses.

Figure 3

Effect of LLLT on the quantification of peribronchial eosinophils. The lungs were fixed, prepared, and stained with LUNA for the analysis of eosinophils in the airways. The animals were irradiated with LLLT 3x/week for 5 weeks, 1 hour after challenge with HDM. Increase of × 400. Values expressed as mean and standard deviation. The groups used in the experiment are described in Figure 1. The results refer to the use of 10 mice in each experimental group. # p <0.001 when compared to the Basal group and θ p <0.001 when compared to the asthmatic group (HDM) and ns (not significant); ∗ p<0,05 and ∗∗∗ p<0,001 when compared HDM+LLLT (3J) group with the other groups treated with other doses.

Figure 4

Effect of LLLT on the production of mucus in the airways. The lungs were fixed, prepared, and stained with PAS (Periodic Acid Schif) for the analysis of mucus in the airways. The animals were irradiated with LLLT 3x/week for 5 weeks, 1 hour after challenge with HDM. Increase of × 200. Values expressed as mean and standard deviation. The groups used in the experiment are described in Figure 1. The results refer to the use of 10 mice in each experimental group. # p <0.001 when compared to the Basal group and Δ p <0.01 when compared to the asthmatic group (HDM) and ns (not significant); ∗ p<0,05 and ∗∗ p<0,01 when compared HDM+LLLT (3J) group with the other groups treated with other doses.

Figure 5

Effect of LLLT on the production of collagen in the airways. The lungs were fixed, prepared, and stained with PSR for analysis of collagen in the airways. The animals were irradiated with LLLT 3x/week for 5 weeks, 1 hour after challenge with HDM. Increase of × 200. Values expressed as mean and standard deviation. The groups used in the experiment are described in Figure 1. The results refer to the use of 10 mice in each experimental group. # p <0.001 when compared to the Basal group and Δ p <0.01 when compared to the asthmatic group (HDM) and ns (not significant) and ∗ p<0,05 when compared HDM+LLLT (3J) group with the other groups treated with other doses.

Figure 6

Effect of LLLT on bronchoconstriction index. The lungs were fixed, prepared and stained with HE for analysis of bronchoconstriction index in the airways. Increase of × 400. Values expressed as mean and standard deviation. The groups used in the experiment are described in Figure 1. The results refer to the use of 10 mice in each experimental group. # p <0.001 when compared to the Basal group and θ p <0.001, Δ p <0.01, and ϕ p <0.05 when compared to the asthmatic group (HDM); ∗ p<0,05 when compared HDM+LLLT (3J) group with the other groups treated with other doses.

Figure 7

Effect of LLLT on bronchial thickening and airway smooth muscle thickening. The lungs were fixed, prepared and stained with HE for the above analyzes. Increase of × 400. Values expressed as mean and standard deviation. The groups used in the experiment are described in Figure 1. The results refer to the use of 10 mice in each experimental group. # p <0.001 when compared to the Basal group and θ p <0.001 when compared to the asthmatic group (HDM) and ns (not significant) when compared HDM+LLLT (3J) group with the other groups treated with other doses.