Tag: uv radiation

Sunlight Might Cause New-onset Lupus

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While a large, long-running epidemiologic study was unable to conclude that ultraviolet (UV) radiation in sunlight can cause new-onset systemic lupus erythematosus (SLE), trends in the data suggested that it could, according to findings reported in the journal Arthritis Care & Research.

Participants in the  who were in the upper tertile (third) of estimated UV-B exposure had 28% higher rates of incident SLE during follow-up.

Similar numerical increases in risk with high estimated UV-B exposure were seen for specific lupus subtypes and manifestations, such as SLE with photosensitivity or with anti-Ro/La antibodies, which also fell short of statistical significance, they reported

The study’s relatively small number of new-onset SLE cases – only 297 out of about six million person-years of data – was the likely reason for the broad confidence intervals. The study did also find one lupus subtype with a statistically significant association with UV-B exposure: SLE with malar rash (HR 1.62 for top versus bottom tertile, 95% CI 1.04-2.52).

“We found no overall association between high UV radiation exposure and risk of overall SLE in these large cohorts of women prospectively followed for many years prior to SLE onset,” the researchers acknowledged.

“However, cumulative average UV radiation exposure in the highest tertile was associated with non-significant but suggestive increased risk of the subtype of SLE presenting with cutaneous antibodies, including anti-Ro and/or anti-La antibodies, and/or cutaneous involvement, including malar rash (acute cutaneous lupus) and/or photosensitivity, which tend to co-occur, and are biologically plausible,” they stated.

Photosensitivity is a hallmark of lupus, and sunlight exposure is known to cause disease flareups in people with established SLE. Among the 297 cases of incident SLE that developed in NHS participants, 58% included photosensitivity. Other risk factors include smoking and exposure to silica. Exposure to strong sunlight might be another one, since UV radiation disrupts skin keratinocytes, releasing antigens that could trigger autoimmune attack.

The decades-long American Nurses’ Health Study (NHS) I and II has the medical records of 240 000 participants, mostly female, who completed detailed questionnaires.

However, new-onset SLE is rare enough that, even with that many participants, there weren’t enough cases to be sure whether risk increases in the 30%-50% range were real.

Other major limitations included having to estimate UV exposure from participants’ residence, race serving as an inexact proxy of skin tone, and no data on sunburn history or sunscreen use.

Source: MedPage Today

New Molecules Provide Deeper UV Protection

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Two new molecules that release tiny quantities of hydrogen sulfide have been found to prevent skin from ageing after being exposed to ultraviolet light found in sunlight. The study was published in Antioxidant and Redox Signalling.

For the study, the researchers exposed adult human skin cells and the skin of mice to ultraviolet radiation (UVA). UVA causes skin ageing by turning on collagenases, enzymes which eat away at the natural collagen, causing the skin to lose elasticity, sag and wrinkle. UVA also penetrates deeper into skin than the UV radiation that causes sunburns (UVB), and it also damages cellular DNA, leading to mutations that can contribute to some skin cancers. Typical sun creams sit on top of the skin and absorb UV radiation, but they do not penetrate the skin where the long-lasting damage occurs.

For deeper protection, the researchers came up with a new way to protect the deeper layers of skin using two compounds invented at the University of Exeter: AP39 and AP123. The compounds do not protect the skin in the same way traditional sun creams prevent sunburn, but instead penetrate the skin to correct how skin cells’ energy production and usage was turned off by UVA exposure. This then prevented the activation of skin-degrading collagenase enzymes. 

The compounds used in this study were previously shown to have impressive effects in reducing skin inflammation and skin damage after burn injury and atopic dermatitis (eczema). In an anti-ageing context, they prevented human skin cells in test tube experiments from ageing, but this is the first time the effects of photo-ageing have been seen in animals.

The important observation noted was that the compounds only regulated energy production, PGC-1α and Nrf2 in skin that was exposed to UVA. This suggests a novel approach to treating skin that has already been damaged by UV radiation, and could potentially reverse, as well as limit, that damage.

While further research is needed, there could be medical as well as cosmetic implications from this work, where protecting skin from UV light is important. For example, not only premature skin ageing and skin cancers, but UV light allergies, solar urticaria and rare hereditary skin diseases such as xeroderma pigmentosum. The researchers are currently partway through testing newer and more potent molecules able to do the same task using newer approaches.

Source: University of Exeter