Efeitos da fotobiomodulação local e sistêmica sobre a inflamação na lesão pulmonar aguda induzida por LPS

Abstract

Acute lung injury (ALI) is a severe inflammatory condition characterized by the accumulation of inflammatory cells and increased permeability of the alveolar–capillary barrier, frequently associated with sepsis and the development of acute respiratory distress syndrome (ARDS). Photobiomodulation therapy (PBMT) stands out as a non-pharmacological, low-cost approach with no known adverse effects, with well-recognized anti-inflammatory and immunomodulatory actions. This study aimed to evaluate the effects of local and systemic PBMT on the inflammatory response in an experimental model of LPS-induced ALI in C57BL/6 mice. Inflammation was induced by orotracheal instillation of LPS (10 µg/animal), and treatment began 1 hour later, with three applications at 1-hour intervals. A red laser (660 nm, 30 mW, 60 s/point, 60 J/cm²) was applied to the thoracic region (local PBMT), to the tail artery (systemic PBMT), or in a combined manner. Seventy-two hours after induction, bronchoalveolar lavage fluid (BALF), peripheral blood, and femoral lavage samples were analyzed for total cell counts and cytokine assessment (IL-1β, IL-6, IL-17A, TNF-α, CXCL1, and IL-10). The LPS group showed a significant increase in BALF cellularity and peripheral leukocytosis, accompanied by reduced bone marrow cellularity. All PBMT protocols reduced pulmonary cell infiltration, restored femoral cellularity, and normalized circulating leukocyte levels. In BALF, PBMT attenuated IL-6, TNF-α, and CXCL1 levels across all protocols, whereas IL-17A and IL-10 were preferentially increased by the systemic and combined modalities. In bone marrow, IL-6 levels were reduced in all treated groups, and IL-17A and IL-1β were decreased mainly in the combined protocol, while in serum only IL-6 was partially reversed by the combined treatment. These findings indicate that at 72 hours PBMT particularly the systemic and combined modalities can integratively modulate inflammatory cellularity and cytokine axes in pulmonary and hematopoietic compartments, reinforcing its potential as a safe, non-invasive adjuvant therapy for controlling acute pulmonary inflammation and regulating immune homeostasis.