Modulating macrophage polarization by photobiomodulation

Photobiomodulation (PBM), employing low-power lasers and light-emitting diodes (LEDs), has emerged as an innovative therapeutic modality for modulating macrophage polarization. In this review, we summarized the involvement of PBM in macrophage polarization and described the light physical parameters involved with polarization, focusing on its ability to promote the anti-inflammatory M2 phenotype while suppressing the pro-inflammatory M1 phenotype. This review analyzed studies focusing on macrophage polarization induced by low-power light therapy using lasers and LEDs. A search was conducted in the PubMed database to ensure a comprehensive and structured approach, incorporating studies published in English. The search identified experimental studies using red or infrared light, with inclusion based on clear evidence of macrophage polarization. Data were extracted and synthesized from eligible studies to assess outcomes and application contexts. A final selection of 19 studies was included in this review. Studies primarily utilized wavelengths between 630 and 980 nm, with 68.42% of total studies using the 630-890 nm range identified as the optimal "therapeutic window". Near-infrared wavelengths (≥ 780 nm) demonstrated superior tissue penetration capabilities, particularly in neuro-focused applications, while red light (630-660 nm) exhibited marked specificity for immunomodulation in inflammatory conditions. The main results were focused on in vivo studies, and significant energy density variation was observed among studies. PBM cellular mechanisms efficacy includes its modulation of signaling pathways, such as PI3K/AKT/mTOR, NF-κB, and STAT cascades, which are important in regulating macrophage polarization. Combination wavelength therapies further demonstrated synergistic effects, enhancing therapeutic outcomes. PBM is applied in several fields, including accelerated wound healing, neuroprotection, and inflammation resolution, highlighting its versatility as a non-invasive tool in regenerative and anti-inflammatory medicine. Despite promising results, variability in experimental protocols, particularly regarding energy density, underscores the necessity for further research to standardize methodologies and expand exploration of wavelengths beyond 900 nm. This review provides compelling evidence supporting PBM's transformative potential in macrophage modulation, positioning it as an effective strategy for targeted immune regulation and tissue regeneration.