E. A. Andraska1, J. Alvikas1, D. Mitchell1, M. Rosengart1, M. Neal1 1University Of Pittsburgh, Surgery, Pittsburgh, PA, USA
Introduction: Exposure to differing wavelengths of light affects various physiologic processes such as immune response to sepsis and ischemia reperfusion. Previous data has suggested a role of circadian regulation in fibrinolysis and thrombosis. We hypothesized that varying light exposure prior to induction of deep venous thrombosis (DVT) would attenuate the subsequent immune cell response.
Methods: Mice were exposed to ambient light (N =15, fluorescent white light, 400 lux), blue light (N = 15, 442 nm, 1,400 lux), and red light (N = 15, 617 nm, 1,400 lux) with a 12:12 hour light:dark cycle for 72 hours. After 72 hours of light exposure, mice were subjected to an experimental model of DVT formation that includes complete ligation of the inferior vena cava (IVC). Thrombus and blood samples were harvested for analysis. Neutrophils were isolated from mice exposed to the varying wavelengths of light and the degree of neutrophil extracellular trap activation (NETosis) was measured. Next, the supernatant of activated platelets (releasate) was isolated from the platelets of animals exposed to ambient, red, or blue light and NETosis was measured on ex vivo neutrophils after exposure to the platelet releasate.
Results: Exposure to red light resulted in reduced clot weight compared to blue light-exposed mice (Ambient 16.5±7.7mg, Red 4.2±5.1mg, Blue 19.9±8.7mg; p<0.01, Fig 1A). Immunofluorescence images of thrombus revealed lower cellularity and reduced NET formation in the red-exposed thrombi (Ambient NETs per neutrophil in thrombi 0.16±0.02, Red 0.11±0.09, Blue 0.40±0.08; p<0.01 Red vs. Blue). Isolated neutrophils from red light-exposed mice also showed reduced NETosis ex vivo. Strikingly, platelet releasate from these animals markedly reduced neutrophil activation (Figure 1B).
Conclusion: Taken together, these data suggest that red light exposure results in reduced thrombus burden by attenuating NETosis in venous thrombosis. Fewer NETs are noted in the thrombus and reduced NETosis is seen in neutrophils of red light-exposed animals. Platelets in these animals show reduced activation, suggesting that the mechanism for this phenomenon may be a result of reduced platelet-neutrophil interactions.
