Blue light (λ=453 nm) nitric oxide dependently induces ß-endorphin production of human skin keratinocytes in-vitro and increases systemic ß-endorphin levels in humans in-vivo.

ß-Endorphin exerts a broad spectrum of physiological activity on mood, immune functions, pain management, reward effects, and behavioral stability. ß-Endorphin is produced in certain neurons within the central and peripheral nervous system but also in the skin, especially in response to ultraviolet radiation. In the present study we have investigated the impact of visible blue light at λ = 453 nm (BL) on ß-endorphin production of primary human skin keratinocytes (hKC) in-vitro as well as on systemic ß-endorphin formation of whole-body exposed subjects in-vivo. We found that BL irradiation significantly enhanced both keratinocytic ß-endorphin production of hKC cultures as well as systemic ß-endorphin concentrations in light exposed healthy subjects. Interestingly, in hKC cultures elevated ß-endorphin formation was paralleled by significantly increased levels of non-enzymatically generated nitric oxide (NO), whereas elevated systemic ß-endorphin values of BL-exposed subjects were accompanied by enhanced systemic concentration of bioactive NO-derivates. These findings point to a pivotal role of NO in the molecular mechanism of the observed BL-induced effects, and indeed, exogenously applied NO was able to significantly enhance ß-endorphin production in hKC cultures. Thus, our finding of BL-induced increases in systemic ß-endorphin concentration in-vivo can be plausibly explained by an event sequence comprising 1.) BL-driven non-enzymatic formation of NO in the exposed skin tissue, 2.) systemic distribution of cutaneously produced NO in the form of bioactive nitroso compounds, 3.) a subsequent NO-dependent induction of ß-endorphin synthesis in epidermal keratinocytes, and 4.) probably also a NO-dependent modulation of ß-endorphin synthesis in specialized neurons within the central and peripheral nervous system.

Blue light exposure decreases systolic blood pressure, arterial stiffness, and improves endothelial function in humans.

AIMS: Previous studies have shown that ultraviolet light can lead to the release of nitric oxide from the skin and decrease blood pressure. In contrast to visible light the local application of ultraviolet light bears a cancerogenic risk. Here, we investigated whether whole body exposure to visible blue light can also decrease blood pressure and increase endothelial function in healthy subjects. METHODS: In a randomised crossover study, 14 healthy male subjects were exposed on 2 days to monochromatic blue light or blue light with a filter foil (control light) over 30 minutes. We measured blood pressure (primary endpoint), heart rate, forearm vascular resistance, forearm blood flow, endothelial function (flow-mediated dilation), pulse wave velocity and plasma nitric oxide species, nitrite and nitroso compounds (secondary endpoints) during and up to 2 hours after exposure. RESULTS: Blue light exposure significantly decreased systolic blood pressure and increased heart rate as compared to control. In parallel, blue light significantly increased forearm blood flow, flow-mediated dilation, circulating nitric oxide species and nitroso compounds while it decreased forearm vascular resistance and pulse wave velocity. CONCLUSION: Whole body irradiation with visible blue light at real world doses improves blood pressure, endothelial function and arterial stiffness by nitric oxide released from photolabile intracutanous nitric oxide metabolites into circulating blood.