UVA irradiation of human skin vasodilates arterial vasculature and lowers blood pressure independently of nitric oxide synthase.
Level 2 - randomized trial
Randomized controlled experimental physiological trial in humans
PubMed 24445737 · doi:10.1038/jid.2014.27
What was done
In 24 healthy volunteers, skin was exposed to two standard erythemal doses of UVA radiation. Researchers measured systemic blood pressure, circulating nitrate, and nitrite concentrations. An acute dietary intervention was evaluated to assess whether systemic nitrate availability influenced the response. Forearm blood flow was measured during UVA exposure with nitric oxide synthase (NOS) inhibition, and confocal fluorescence microscopy on human skin samples was used to image and localize cutaneous nitric oxide release.
What was found
UVA irradiation lowered blood pressure, decreased circulating nitrate, and increased circulating nitrite concentrations (exact values not reported in the abstract). Acute dietary nitrate modulation did not affect these hemodynamic changes. UVA-induced forearm vasodilation occurred independently of NOS activity. Imaging showed UVA-triggered nitric oxide release was dose-dependent, NOS-independent, and localized primarily to the upper epidermis.
Why it matters
This trial demonstrates that UVA exposure can acutely lower blood pressure independently of vitamin D by mobilizing stored epidermal nitric oxide into the bloodstream. This provides a mechanistic explanation for seasonal and latitudinal variations in blood pressure and cardiovascular disease.
Limits
The abstract reports no exact numerical changes or confidence intervals for the blood pressure drop. The sample size is small (n = 24) and limited to healthy volunteers, leaving long-term cardiovascular outcomes and effects in hypertensive patients unmeasured.
Cited by
- supports UVA light mobilizes stored nitric oxide from the dermis of the skin into the bloodstream.
- supports Randomized controlled human trials by Dr. Richard Weller demonstrate that shining UVA light on skin increases blood nitric oxide levels and lowers blood pressure.