Photobiomodulation Activates Coordinated Signaling Networks to Modulate Inflammation, Adaptive Stress, and Tissue Healing via Redox-Mediated NFκB–TGF-β1–ATF-4 Axis

Highlights: What are the main findings? Photobiomodulation evokes intra- and extracellular redox mechanisms. NFκB coordinates PBM-activated TGF-β–ATF-4 signaling. What are the implications of the main findings? Anti-inflammatory clinical responses to PBM therapy can be better rationalized. Framework for integration of adaptive stress and tissue healing responses by PBM. Photobiomodulation (PBM) therapy has been effectively used to relieve pain and inflammation and promote tissue healing and regeneration in a broad range of ailments. Prior work has focused on intracellular mitochondrial cytochrome c oxidase, while extracellular latent TGF-β1 activation had been noted. This work investigated the role of PBM-generated redox signaling and integration in normal oral keratinocytes, using Western blots and pathway-specific small molecule inhibitors. We observed that PBM primarily generates ROS intracellularly within mitochondria, which then diffuse extracellularly to activate latent TGF-β1. This activation triggers ATF-4 expression through both canonical (Smad3) and non-canonical (p38, ERK) TGF-β signaling pathways. We observed a critical role for NFκB as an essential integrator, coordinating these responses as evidenced by the loss of ATF-4 expression following NFκB inhibition (BAY II) after both PBM and TGF-β1 treatments. Proteomic pathway analysis revealed that PBM downregulates inflammatory and apoptotic pathways while activating stress-adaptive responses in the NFκB pathway. A core set of PBM-induced redox, NFκB, and TGF-β signaling targets was identified. These findings suggest that optimal PBM treatment responses require a coordinated action of multiple signaling pathways that optimize cellular adaptation to stress and promote tissue repair rather than protracted inflammation and cell death.