Post by cm5 on May 22, 2016 19:58:34 GMT -5
UVA Irradiation of Human Skin Vasodilates Arterial Vasculature and Lowers Blood Pressure Independently of Nitric Oxide Synthase
Donald Liu, Bernadette O. Fernandez, Alistair Hamilton, Ninian N. Lang, Julie M.C. Gallagher, David E. Newby, Martin Feelisch, Richard B. Weller
JID (Journal of Investigative Dermatology) July 2014 Volume 134, Issue 7, Pages 1839–1846
Below all courtesy of Wikipedia, to place UVA into context----
Name Abbreviation Wavelength (nm) Photon energy (eV, aJ) Notes / alternative names
Ultraviolet A UVA 315–400 3.10–3.94 0.497–0.631 Long wave, black light, not absorbed by the ozone layer
Ultraviolet B UVB 280–315 3.94–4.43 0.631–0.710 Medium wave, mostly absorbed by the ozone layer
Ultraviolet C UVC 100–280 4.43–12. 0.710–1.987 Short wave, germicidal, completely absorbed by the ozone layer and atmosphere
Near ultraviolet NUV 300–400 3.10–4.13 0.497–0.662 Visible to birds, insects and fish
Middle ultraviolet MUV 200–300 4.13–6.20 0.662–0.993
Far ultraviolet FUV 122–200 6.20–12.4 0.993–1.987
Hydrogen Lyman-alpha H Lyman-α 121–122 10.16–10.25, 1.628–1.642 Spectral line at 121.6 nm, 10.20 eV. Ionizing radiation at shorter wavelengths
Vacuum ultraviolet VUV 10–200 0–0, 0–0 Strongly absorbed by atmospheric oxygen, though 150–200 nm wavelengths can propagate through nitrogen
Extreme ultraviolet EUV 10–121 12.4–124 1.99–19.87 Entirely ionizing radiation by some definitions; completely absorbed by the atmosphere
Beneficial effects
UVB induces production of vitamin D in the skin at rates of up to 1,000 IUs per minute. This vitamin helps to regulate calcium metabolism (vital for the nervous system and bone health), immunity, cell proliferation, insulin secretion, and blood pressure.[35]
People with higher levels of vitamin D tend to have lower rates of diabetes, heart disease, and stroke and tend to have lower blood pressure. However, it has been found that vitamin D supplementation does not improve cardiovascular health or metabolism, so the link with vitamin D must be in part indirect. It seems that those who get more sun are generally healthier, and also have higher vitamin D levels. It has been found that ultraviolet light (even UVA) produces nitric oxide (NO) in the skin, and nitric oxide can lower blood pressure. High blood pressure increases the risk of stroke and heart disease. Although long-term exposure to ultraviolet contributes to non-melanoma skin cancers that are rarely fatal, it has been found in a Danish study that those who get these cancers were less likely to die during the study, and were much less likely to have a heart attack, than those who did not have these cancers.[36]
The amount of the brown pigment melanin in the skin increases after exposure to UV radiation at moderate levels depending on skin type; this is commonly known as a sun tan. Melanin is an excellent photoprotectant that absorbs both UVB and UVA radiation and dissipates the energy as harmless heat, protecting the skin against both direct and indirect DNA damage.
Skin damage
Overexposure to UVB radiation not only can cause sunburn but also some forms of skin cancer. However, the degree of redness and eye irritation (which are largely not caused by UVA) do not predict the long-term effects of UV, although they do mirror the direct damage of DNA by ultraviolet.
All bands of UV radiation damage collagen fibers and accelerate aging of the skin. Both UVA and UVB destroy vitamin A in skin, which may cause further damage.[39]
UVB light can cause direct DNA damage.[40] This cancer connection is one reason for concern about ozone depletion and the ozone hole.
The most deadly form of skin cancer, malignant melanoma, is mostly caused by DNA damage independent from UVA radiation. This can be seen from the absence of a direct UV signature mutation in 92% of all melanoma.[41] Occasional overexposure and sunburn are probably greater risk factors for melanoma than long-term exposure.[36] UVC is the highest-energy, most-dangerous type of ultraviolet radiation, and causes adverse effects that can variously be mutagenic or carcinogenic.[42]
In the past, UVA was considered not harmful or less harmful than UVB, but today it is known to contribute to skin cancer via indirect DNA damage (free radicals such as reactive oxygen species). UVA can generate highly reactive chemical intermediates, such as hydroxyl and oxygen radicals, which in turn can damage DNA. The DNA damage caused indirectly to skin by UVA consists mostly of single-strand breaks in DNA, while the damage caused by UVB includes direct formation of thymine dimers or other pyrimidine dimers, and double-strand DNA breakage.[43] UVA is immunosuppressive for the entire body (accounting for a large part of the immunosuppressive effects of sunlight exposure), and is mutagenic for basal cell keratinocytes in skin.[44] (Note---UVA intentionally utilized for treatment of T Cell Lymphoma of the skin, and also in conjunction with oral administration of psoralen for treatment of psoriasis, although less used now with newer, very effective systemic meds for psoriasis. UVB is intentionally utilized for pruritus from renal failure, severe generalized atopic dermatitis, among other conditions. Note-----"Tanning Beds" emit UVA, use is absolutely associated with significant increase in skin damage/as well as aging and significant increase in incidence of melanoma and other skin cancers. There is no regulatory supervision/testing/proof of UVA output, therefore doses can be extreme.)
Sunburn effect (as measured by the UV Index) is the product of the sunlight spectrum (radiation intensity) and the erythemal action spectrum (skin sensitivity) across the range of UV wavelengths.
UVB light can cause direct DNA damage. UVB radiation excites DNA molecules in skin cells, causing aberrant covalent bonds to form between adjacent pyrimidine bases, producing a dimer. Most UV-induced pyrimidine dimers in DNA are removed by the process known as nucleotide excision repair that employs about 30 different proteins.[40] Those pyrimidine dimers that escape this repair process can induce a form of programmed cell death (apoptosis) or can cause DNA replication errors leading to mutation.
As a defense against UV radiation, the amount of the brown pigment melanin in the skin increases when exposed to moderate (depending on skin type) levels of radiation; this is commonly known as a sun tan. The purpose of melanin is to absorb UV radiation and dissipate the energy as harmless heat, blocking the UV from damaging skin tissue. UVA gives a quick tan that lasts for days by oxidizing melanin that was already present and triggers the release of the melanin from melanocytes. UVB yields a tan that takes roughly 2 days to develop because it stimulates the body to produce more melanin. The photochemical properties of melanin make it an excellent photoprotectant. However, sunscreen chemicals cannot dissipate the energy of the excited state as efficiently as melanin and therefore the penetration of sunscreen ingredients into the lower layers of the skin increases the amount of reactive oxygen species.[45]
Sunscreen prevents the direct DNA damage which causes sunburn. Most of these products contain an SPF rating to show how well they block UVB rays. The SPF rating, however, offers no data about UVA protection.
Some sunscreen lotions now include compounds such as titanium dioxide which helps protect against UVA rays. Other UVA blocking compounds found in sunscreen include zinc oxide and avobenzone.
Donald Liu, Bernadette O. Fernandez, Alistair Hamilton, Ninian N. Lang, Julie M.C. Gallagher, David E. Newby, Martin Feelisch, Richard B. Weller
JID (Journal of Investigative Dermatology) July 2014 Volume 134, Issue 7, Pages 1839–1846
The incidence of hypertension and cardiovascular disease (CVD) correlates with latitude and rises in winter. The molecular basis for this remains obscure. As nitric oxide (NO) metabolites are abundant in human skin, we hypothesized that exposure to UVA may mobilize NO bioactivity into the circulation to exert beneficial cardiovascular effects independently of vitamin D. In 24 healthy volunteers, irradiation of the skin with two standard erythemal doses of UVA lowered blood pressure (BP), with concomitant decreases in circulating nitrate and rises in nitrite concentrations. Unexpectedly, acute dietary intervention aimed at modulating systemic nitrate availability had no effect on UV-induced hemodynamic changes, indicating that cardiovascular effects were not mediated via direct utilization of circulating nitrate. UVA irradiation of the forearm caused increased blood flow independently of NO synthase (NOS) activity, suggesting involvement of pre-formed cutaneous NO stores. Confocal fluorescence microscopy studies of human skin pre-labeled with the NO-imaging probe diaminofluorescein 2 diacetate revealed that UVA-induced NO release occurs in a NOS-independent, dose-dependent manner, with the majority of the light-sensitive NO pool in the upper epidermis. Collectively, our data provide mechanistic insights into an important function of the skin in modulating systemic NO bioavailability, which may account for the latitudinal and seasonal variations of BP and CVD.
Name Abbreviation Wavelength (nm) Photon energy (eV, aJ) Notes / alternative names
Ultraviolet A UVA 315–400 3.10–3.94 0.497–0.631 Long wave, black light, not absorbed by the ozone layer
Ultraviolet B UVB 280–315 3.94–4.43 0.631–0.710 Medium wave, mostly absorbed by the ozone layer
Ultraviolet C UVC 100–280 4.43–12. 0.710–1.987 Short wave, germicidal, completely absorbed by the ozone layer and atmosphere
Near ultraviolet NUV 300–400 3.10–4.13 0.497–0.662 Visible to birds, insects and fish
Middle ultraviolet MUV 200–300 4.13–6.20 0.662–0.993
Far ultraviolet FUV 122–200 6.20–12.4 0.993–1.987
Hydrogen Lyman-alpha H Lyman-α 121–122 10.16–10.25, 1.628–1.642 Spectral line at 121.6 nm, 10.20 eV. Ionizing radiation at shorter wavelengths
Vacuum ultraviolet VUV 10–200 0–0, 0–0 Strongly absorbed by atmospheric oxygen, though 150–200 nm wavelengths can propagate through nitrogen
Extreme ultraviolet EUV 10–121 12.4–124 1.99–19.87 Entirely ionizing radiation by some definitions; completely absorbed by the atmosphere
Beneficial effects
UVB induces production of vitamin D in the skin at rates of up to 1,000 IUs per minute. This vitamin helps to regulate calcium metabolism (vital for the nervous system and bone health), immunity, cell proliferation, insulin secretion, and blood pressure.[35]
People with higher levels of vitamin D tend to have lower rates of diabetes, heart disease, and stroke and tend to have lower blood pressure. However, it has been found that vitamin D supplementation does not improve cardiovascular health or metabolism, so the link with vitamin D must be in part indirect. It seems that those who get more sun are generally healthier, and also have higher vitamin D levels. It has been found that ultraviolet light (even UVA) produces nitric oxide (NO) in the skin, and nitric oxide can lower blood pressure. High blood pressure increases the risk of stroke and heart disease. Although long-term exposure to ultraviolet contributes to non-melanoma skin cancers that are rarely fatal, it has been found in a Danish study that those who get these cancers were less likely to die during the study, and were much less likely to have a heart attack, than those who did not have these cancers.[36]
The amount of the brown pigment melanin in the skin increases after exposure to UV radiation at moderate levels depending on skin type; this is commonly known as a sun tan. Melanin is an excellent photoprotectant that absorbs both UVB and UVA radiation and dissipates the energy as harmless heat, protecting the skin against both direct and indirect DNA damage.
Skin damage
Overexposure to UVB radiation not only can cause sunburn but also some forms of skin cancer. However, the degree of redness and eye irritation (which are largely not caused by UVA) do not predict the long-term effects of UV, although they do mirror the direct damage of DNA by ultraviolet.
All bands of UV radiation damage collagen fibers and accelerate aging of the skin. Both UVA and UVB destroy vitamin A in skin, which may cause further damage.[39]
UVB light can cause direct DNA damage.[40] This cancer connection is one reason for concern about ozone depletion and the ozone hole.
The most deadly form of skin cancer, malignant melanoma, is mostly caused by DNA damage independent from UVA radiation. This can be seen from the absence of a direct UV signature mutation in 92% of all melanoma.[41] Occasional overexposure and sunburn are probably greater risk factors for melanoma than long-term exposure.[36] UVC is the highest-energy, most-dangerous type of ultraviolet radiation, and causes adverse effects that can variously be mutagenic or carcinogenic.[42]
In the past, UVA was considered not harmful or less harmful than UVB, but today it is known to contribute to skin cancer via indirect DNA damage (free radicals such as reactive oxygen species). UVA can generate highly reactive chemical intermediates, such as hydroxyl and oxygen radicals, which in turn can damage DNA. The DNA damage caused indirectly to skin by UVA consists mostly of single-strand breaks in DNA, while the damage caused by UVB includes direct formation of thymine dimers or other pyrimidine dimers, and double-strand DNA breakage.[43] UVA is immunosuppressive for the entire body (accounting for a large part of the immunosuppressive effects of sunlight exposure), and is mutagenic for basal cell keratinocytes in skin.[44] (Note---UVA intentionally utilized for treatment of T Cell Lymphoma of the skin, and also in conjunction with oral administration of psoralen for treatment of psoriasis, although less used now with newer, very effective systemic meds for psoriasis. UVB is intentionally utilized for pruritus from renal failure, severe generalized atopic dermatitis, among other conditions. Note-----"Tanning Beds" emit UVA, use is absolutely associated with significant increase in skin damage/as well as aging and significant increase in incidence of melanoma and other skin cancers. There is no regulatory supervision/testing/proof of UVA output, therefore doses can be extreme.)
Sunburn effect (as measured by the UV Index) is the product of the sunlight spectrum (radiation intensity) and the erythemal action spectrum (skin sensitivity) across the range of UV wavelengths.
UVB light can cause direct DNA damage. UVB radiation excites DNA molecules in skin cells, causing aberrant covalent bonds to form between adjacent pyrimidine bases, producing a dimer. Most UV-induced pyrimidine dimers in DNA are removed by the process known as nucleotide excision repair that employs about 30 different proteins.[40] Those pyrimidine dimers that escape this repair process can induce a form of programmed cell death (apoptosis) or can cause DNA replication errors leading to mutation.
As a defense against UV radiation, the amount of the brown pigment melanin in the skin increases when exposed to moderate (depending on skin type) levels of radiation; this is commonly known as a sun tan. The purpose of melanin is to absorb UV radiation and dissipate the energy as harmless heat, blocking the UV from damaging skin tissue. UVA gives a quick tan that lasts for days by oxidizing melanin that was already present and triggers the release of the melanin from melanocytes. UVB yields a tan that takes roughly 2 days to develop because it stimulates the body to produce more melanin. The photochemical properties of melanin make it an excellent photoprotectant. However, sunscreen chemicals cannot dissipate the energy of the excited state as efficiently as melanin and therefore the penetration of sunscreen ingredients into the lower layers of the skin increases the amount of reactive oxygen species.[45]
Sunscreen prevents the direct DNA damage which causes sunburn. Most of these products contain an SPF rating to show how well they block UVB rays. The SPF rating, however, offers no data about UVA protection.
Some sunscreen lotions now include compounds such as titanium dioxide which helps protect against UVA rays. Other UVA blocking compounds found in sunscreen include zinc oxide and avobenzone.
