Dear Colleagues,

Photobiomodulation (PBM) therapy is based on exposing cells to non-ionizing low level light radiation with a wavelength generally ranging from 600 to 1400 nm which results in biological consequences after absorption by endogenous chromophores. Over the past few decades, biomedical research relating to photobiomodulation has been constantly increasing, indicating a growing interest in its therapeutic potential.

Both in vitro and in vivo studies have evaluated the effect of PBM in Parkinson’s disease models. A neuroprotective effect of the dopaminergic neurons, a reduction in astrogliosis and a GDNF striatal expression increase have been demonstrated in toxin induced and transgenic animal models.

The translation of these studies to clinical utilization requires adaptations, so that PBM can reach intracerebral regions. Implanted medical devices have been developed to bring light directly into the brain. Less invasive approaches through transcranial illumination have a methodological advantage. Nevertheless, the low probability of reaching the deeper intracerebral regions to the areas of main pathology in the brainstem limits their use. In all cases, PBM seems to be well tolerated, with minimal or no side-effects or toxicity.

The main mechanism of action of PBM involves the stimulation of mitochondria and reduction of oxidative stress. However, the mechanism of action is not yet fully understood and the role of a systemic component remains to be assessed. The effects of PBM treatment are also modulated by the illumination parameters with an obvious hormetic effect.

Considering its ease of use, utilization of PBM at the bedside via an external application has mainly been evaluated. Pilot and exploratory studies with small numbers of patients provide encouraging early observations, but rigorous clinical trials need to be undertaken. As a better understanding of the mechanisms of action ensues, further studies have the potential to optimize the use of PBM at the bedside.

Dr. Cecile Moro

Guest Editor