Effects of Ultrashort Wave Therapy on Inflammation and Macrophage Polarization after Acute Lung Injury in Rats

Acute lung injury (ALI) features dysregulated pulmonary inflammation. Ultrashort waves (USWs) exert anti‐inflammatory effects but no studies have evaluated their activity in ALI. Herein, we used an in vivo lipopolysaccharide (LPS)‐induced ALI model to investigate whether the anti‐inflammatory activity of USWs is mediated by altering the polarization of M1 to M2 macrophages. Twenty‐four male Sprague–Dawley rats were randomly divided into control, untreated ALI, and ALI treated with USW groups ( n = 8 in each group). ALI was induced by intratracheal LPS instillation. Rats in the USW group were treated for 15 min at 0, 4, and 8 h after a single LPS intratracheal instillation. Histopathologic examination, wet/dry lung weight ratio, enzyme‐linked immunosorbent assay, quantitative real‐time polymerase chain reaction, and western blot analyses were performed to evaluate the degree of lung injury and to determine macrophage phenotypes. Histopathologic examination disclosed attenuation of ALI, with reduced alveolar hemorrhage and neutrophilic infiltration in the USW group. Serum levels of tumor necrosis factor‐α (TNF‐α) and interleukin‐1β (IL‐1β) were significantly decreased after USW therapy. Moreover, the messenger RNA (mRNA) expressions of TNF‐α and IL‐1β were significantly decreased in the USW group, whereas the mRNA expression of Arginase 1 ( Arg1 ) and the protein expression of mannose receptor significantly increased in comparison with the untreated ALI group. We conclude that USW therapy may attenuate inflammation in LPS‐induced ALI through the modulation of macrophage polarization. © 2021 Bioelectromagnetics Society.