Condition Focus: Macrophage Polarization — PI3K/AKT/mTOR Pathway Mapping

While the M1→M2 macrophage shift under PBM is well-documented, the specific signalling pathway responsible remained unclear until this 2023 study from Tian and colleagues. Using 980 nm PBM on LPS-activated macrophages, the researchers identified the PI3K/AKT/mTOR cascade as the mechanism through which PBM promotes M2 polarization.

The evidence is rigorous: they demonstrated increased iNOS suppression (M1 marker), Arg1 upregulation (M2 marker), and IL-10 production, all dose-dependent with an optimum at 5 J/cm². Crucially, they confirmed the pathway using specific inhibitors — when PI3K or mTOR was blocked pharmacologically, PBM’s M2-promoting effect was abolished. This inhibitor confirmation elevates the finding from correlational to mechanistic.

The dose-dependency is also instructive: at 0.5 J/cm², the effects were minimal; at 5 J/cm², they were optimal; at 10 J/cm², they did not improve further. This pattern is consistent with the biphasic dose response seen across PBM research and helps explain why parameter selection matters so much in device design.

For gout, the PI3K/AKT/mTOR pathway is particularly relevant because it intersects with NLRP3 regulation. mTOR signalling influences autophagy — the cellular cleanup process that disassembles activated inflammasomes. By activating this pathway in macrophages, PBM may simultaneously promote M2 resolution signals and enhance the autophagic clearance of NLRP3 complexes.

G.O.A.T. for Gout Alignment:
While this study used 980 nm (longer than the G.O.A.T.’s 850 nm), the PI3K/AKT/mTOR pathway is activated across the NIR range. The optimal dose of 5 J/cm² is close to the G.O.A.T.’s target of 4 J/cm², supporting the device’s parameter selection for macrophage-mediated anti-inflammatory effects.

Link to original research here

Editor’s note: The PI3K/AKT/mTOR pathway identified here complements the IL-6/JAK/STAT pathway mapped in the OA joint model by PBM and Chondrocyte Catabolism 2025. For the Notch1-HIF-1α-NF-κB pathway providing a third mapped mechanism, see Ma et al 2022. Wavelength-specific timing effects on macrophage markers are detailed in Fernandes et al 2019. The dose-response pattern connects to the Arndt-Schulz framework in Huang et al 2009.

Related Articles

• PBM Mitigates Chondrocyte Catabolism via Macrophage M1 Polarization – 2025
• PBM Modulates Macrophage via Notch1-HIF-1α-NF-κB: RNA-seq – Ma et al 2022
• Wavelength and Timing in PBM-Induced Macrophage Polarization – Fernandes et al 2019
• Biphasic Dose Response in PBM: Arndt-Schulz Curve – Huang et al 2009
• PBM and Macrophage Polarization: M1→M2 Shift Review – 2025

Key Takeaways

• PI3K/AKT/mTOR identified as the signalling pathway for PBM-induced M2 polarization
• Inhibitor-confirmed mechanism — blocking PI3K or mTOR abolished the M2 shift
• Dose-dependent: 5 J/cm² optimal (close to G.O.A.T.’s 4 J/cm² target)
• mTOR pathway intersects with NLRP3 regulation and autophagy — relevant to gout

Study Overview

Full Citation

Tian T, et al. (2023). Photobiomodulation activates undifferentiated macrophages and promotes M1/M2 macrophage polarization via PI3K/AKT/mTOR signaling pathway. Lasers in Medical Science, 38, 86. View Publication