Red light stimulates vasodilation through extracellular vesicle trafficking

Area of Science:

• Physiology
• Biomedical Engineering
• Photomedicine

Background:

• Red light (670 nm) is known to induce vasodilation ex vivo.
• This effect is nitric oxide (NO) dependent but endothelial nitric oxide synthase (eNOS) independent.
• A transferable vasoactive substance, identified as S-nitrosothiols (RSNO), is secreted from the endothelium.

Purpose of the Study:

• To establish that 670 nm red light-mediated vasodilation occurs in vivo.
• To investigate the physiological stability of this light-induced vasodilation.
• To elucidate the mechanism of RSNO release and its role in vasodilation.

Main Methods:

• In vivo studies on murine facialis arteries.
• Analysis of intracellular and extracellular S-nitroso protein levels.
• Investigation of extracellular vesicle (EV) involvement using CD63 expression.
• Microscopy to observe endosome localization and EV exit.

Main Results:

• 670 nm red light induces physiologically stable vasodilation in vivo.
• Light exposure depletes intracellular S-nitroso protein and increases extracellular RSNO.
• RSNO-containing vasodilators are embedded in extracellular vesicles (EVs).
• Red light enhances CD63 expression, endosome localization, and RSNO-EV exit from arteries.

Conclusions:

• Red light (670 nm) initiates a mechanism involving the formation and release of RSNO-containing EVs from the endothelium.
• These EVs trigger smooth muscle cell relaxation, leading to vasodilation.
• This study reveals a novel pathway for light-mediated physiological vasodilation.