Effects of photobiomodulation therapy on pulmonary inflammation in chronic asthma: Dosimetric study in an...

Photobiomodulation therapy (PBMT) has emerged as a non-invasive therapeutic approach with anti-inflammatory and immunomodulatory potential in respiratory diseases. However, the optimal radiant energy required to achieve effective modulation of chronic airway inflammation remains unclear. This study aimed to investigate the effects of photobiomodulation therapy using different radiant energy doses on pulmonary inflammation, airway remodelling, and immune response in a murine model of chronic asthma induced by ovalbumin (OVA). Chronic allergic pulmonary inflammation was established through subcutaneous sensitization with OVA followed by repeated orotracheal challenges over 5 weeks. After each challenge, animals were treated with a 660 nm continuous-wave diode laser at irradiation times of 10, 30, 50, and 75 s, corresponding to radiant energies of 1, 3, 5, and 7.5 J, respectively. Twenty-four hours after the final challenge, pulmonary inflammation was assessed by cellular analysis of bronchoalveolar lavage fluid, cytokine quantification, histomorphometric evaluation of airway remodelling, and immunophenotyping of regulatory T cell populations. Photobiomodulation therapy significantly attenuated pulmonary inflammation by reducing eosinophil, neutrophil, and lymphocyte recruitment, as well as decreasing pro-inflammatory cytokine levels, including interleukin (IL)-4, IL-5, and IL-13. In parallel, PBMT increased levels of the anti-inflammatory cytokine IL-10 and promoted an expansion of regulatory immune cell subsets, including CD4⁺CD25⁺Forkhead box P3 (Foxp3)⁺ and CD4⁺IL-10⁺ cells, indicating a marked immunomodulatory effect. In addition, PBMT reduced mucus production and collagen deposition in the airways, with the most pronounced effects observed at radiant energies of 3 and 5 J. These findings demonstrate that photobiomodulation therapy, particularly at intermediate radiant energy doses, effectively modulates immune responses, attenuates airway remodelling, and reduces chronic pulmonary inflammation in experimental asthma.