Light Therapy Prior to Surgery Reduces Organ Damage

Exposure to bright blue light for 24 hours before surgery reduces inflammation and organ damage at the cellular level in a mouse model, according to a new study.

Researchers at the University of Pittsburgh School of Medicine (Pittsburgh; PA, USA), Central South University (Hunan, China), and other institutions conducted a study to compare outcomes when mice were exposed to red light, an ambient white fluorescent light, and high-intensity (1,400 lux) blue spectrum (at peak 442 nm bandwidth) light for 24 hours prior to surgical procedures characterized by a period of blood restriction, such as liver resection or organ transplantation.

They found that high-intensity blue light outperformed the red and white light, attenuating cellular and organ injury through at least two cellular mechanisms. The blue light brought about a reduction in the influx of neutrophils, a white blood cell (WBC) involved in inflammation that can lead to organ damage and other problems, as evidenced by reduced myeloperoxidase (MPO). The blue light also inhibited the dying cells from releasing high-mobility group box 1 (HMGB1), a neutrophil chemotactant that triggers inflammation. The researchers then tested whether the blue light was acting through the optical pathway or via some other mechanism, such as a dermal response.

They found that blind mice demonstrated the same healing response, regardless of whether they were exposed to blue or red light, indicating that the protective impact of blue light acts through the optical pathway. The effect seemed to be mediated by a sympathetic (β3 adrenergic) pathway that functioned independently of the significant alterations in melatonin or corticosterone concentrations commonly signifying neutrophil recruitment. The study was published on March 22, 2016, in the Proceedings of the National Academy of Sciences (PNAS).

“There's long been evidence suggesting that light and circadian rhythms profoundly influence our biology, and specifically the physiological response to stress,” said senior author Matthew Rosengart, MD, MPH, of the departments of Surgery and Critical Care Medicine at Pitt. “So while we were expecting to find some correlation with light spectrum and the immune response, we were not expecting results quite so striking. We were incredibly surprised by our results.”

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University of Pittsburgh School of Medicine
Central South University