Photostimulation of mitochondria: a Raman microspectroscopy approach

Photostimulation increases growth and metabolism in healthy cells while photobiomodulation (PBM) typically reverses a pathological state. A wide variety of molecular mechanisms involved in photostimulation and photobiomodulation have been described, including alterations in cell signaling, ion channels, reactive oxygen species (ROS), and mitochondrial metabolism. However, the core underlying process of how photon absorption directly leads to these mechanisms remains unclear. Since perturbations in mitochondrial bioenergetics are likely to occur in both photostimulation and PBM, techniques that non-invasively monitor the mitochondria in real-time are particularly appealing tools for investigating these immediate/early mechanisms. Confocal Raman microscopy is one such possible technique. Here we present a novel Raman spectroscopy-based approach that allows for real-time, continuous, non-invasive monitoring of the metabolic state of the mitochondria. Specifically, we monitored the reduction/oxidation (RedOx) state of endogenous mitochondrial cytochrome c before and after exposure to low-energy laser light and recorded real-time dynamics in response to the addition of substrate. This represents a promising new technique for tracking endogenous mitochondria activity with great utility for probing the molecular mechanisms in the immediate and early phases of photostimulation and PBM.