Matta et al have now shown what we all should have seen coming: the chemicals of our most common and effective sunscreens do not just sit on the skin’s surface and soak up damaging ultraviolet rays before these rays can penetrate to deeper layers and injure nuclear DNA. No – these chemicals themselves can penetrate the skin’s barrier and enter the blood stream (and from whence they can theoretically go anywhere in the body). We should have seen this coming because: a) the permeability barrier is a biological construct, and as such, has its limitations and vulnerabilities; and b) previous studies have found some of these ingredients in human urine and breast milk.[Read more…] about Sunscreens In The Blood?
RESEARCH FROM LABS AROUND THE WOLD
As the Earth’s rotation creates alternating hours of light and dark, we adapt our behaviors to harmonize with this daily cycle. An internal ‘clock’ adjusts our metabolism to fit the demands of our usual daytime and nighttime activities. This makes good sense, since our metabolic needs are very different when we are sleeping and fasting, in comparison to what we need when awake, working and eating. Until recently, it was believed that this biological clock resided solely in the brain – in the hypothalamus to be precise – and that the effects of this clock on our metabolism were mediated by hormones, like melatonin and cortisol. In this traditional scheme, light entering the eye, stimulates the retina, transmitting messages along the optic nerve to regulate the activity of the cells in this central clock and their output of these hormones or their activators. That is still true – but it’s not the whole story.
Skin Can Tell Time, Too!
It turns out that nearly all cells have clocks of their own, and melatonin and cortisol released by a central clock are not the only signals to which these ‘peripheral’ clocks are tuned. Now, recent research suggests that the skin may provide the key to understanding our daily or ‘circadian’ rhythms and their importance in medical practice. Epidermis, these authors demonstrate, may be the ideal tissue to study. It possesses a robust peripheral clock, with a set of metabolic pathways having a reliable, diurnal cycle of activity – and it has the added advantage of being readily accessible.
Why is this potentially important? First, in the past physicians could evaluate the timing of a patient’s internal clock only by using difficult to administer and time-consuming assays of blood melatonin levels under standardized laboratory conditions. These assays were not practical for use in clinical settings. But, if Wu, et al, are correct, it should soon be possible to assess the status of a person’s internal clock with a single, easily obtained skin samples, such as plucked hairs or tape-stripped skin.
When Should I Take My Pills, Doctor? Have That Operation? Apply My Creams?
Information about the timing of our internal clocks could be helpful to our doctors, when they prescribe medications or schedule surgery. Other research has shown that ‘circadian’ fluctuations in metabolism impact both the effectiveness of some medications, and the outcomes of surgery. Knowing the status of a patient’s clock might be particularly important for night shift workers, in whom the normal circadian rhythm may well be disrupted. By assessing his or her skin’s clock, physicians might be able to ascertain the best time of day (or night) for a night-time worker to take medications or undergo surgery
The skin’s clock also regulates the repair mechanisms that protect against the development of the types of DNA damage from ultraviolet light linked to skin cancers. Knowing which hours of sunlight are the most risky for producing unrepaired genetic damages that could result in skin cancer for a patient, could help their dermatologist identify the best time for their light treatments – to achieve the desired therapeutic effect with the lowest risk of inducing cancer later on. Our skin’s clock also regulates melanin synthesis – the protein in skin that produces our shades of color. Timing treatments for vitiligo, (a common skin condition of decreased skin pigmentation), around the hours when melanin synthesis is peaking might increase the effectiveness of these therapies. In addition, the knowledge that these clock genes regulate pigment production could lead to new approaches to therapy for this and other pigmentation disorders. Hair is another skin product whose growth is tuned to its biological clock. Clearly, further understanding of the skin’s clocking system may have important therapeutic spin-offs for a variety of skin conditions.
Fourth, and of particular interest to our readers, is the fact that circadian rhythms are also known to modify the efficiency of our skin’s permeability barrier. Knowledge of the timing of a patient’s clock might be predictive of the best time to apply certain topical medications. If the desired effect of the drug requires it to penetrate the permeability barrier, then it might be optimal to apply it when the barrier is less efficient in keeping out foreign chemicals. Conversely, if the benefit takes place on the surface of the skin – as with topical medications directed against ectoparasites, like lice or scabies – then applying the treatment when the barrier is most robust could prevent unwanted side effects, such as neurotoxicity from the scabicide, lindane.
Our Smart Skin
This developing story of the skin’s biological clock can serve as yet another reminder that we should take the skin and what it does for us seriously. In addition, discovery of the skin’s internal clock offers yet another striking example of how the brain and epidermis are closely related, operationally. We now have learned that the skin has retained its own internal clock, which operates in synchrony and employs some of the same genes that regulate the brain’s clock. This should not be surprising if we recall that the brain and epidermis share a mutual embryonic origin. Both are branches from the same tree.
A High Salt Diet Is Bad, Right?
Most of us probably think salt is bad for us. Our doctors will most likely have prescribed a low salt diet if we suffer from high blood pressure or heart disease. Yet, recent studies shed a whole new light on how our bodies adjust to a high salt diet. And maybe its not all bad…
It had always been thought that if we ingest an extra load of salt, our kidneys will immediately try to restore the balance of salt and water in our blood. According to this simplistic concept – when we eat more salt, we drink more water. The imbibed water then flushes out the excess salt, allowing the levels of both salt and water to return to normal.
But some recent studies, including observations on astronauts, whose intake and outgo could be monitored carefully, show that this is not what happens when we increase our salt intake.[Read more…] about Could A High Salt Diet Actually Be Beneficial?
Clinicians have known for decades that people with atopic dermatitis (eczema) are prone to Staph. infections (Staphylococcus aureus) on their skin. And we have also known that treatment of the infection can be critical to improving their eczema. Even when the rash is not obviously infected, nearly always Staph can be recovered from the patches of eczema.
In other words, even when the skin lesions of atopic dermatitis are not obviously infected, they are colonized, often heavily, by Staph. aureus.
The role of Staph in atopic dermatitis has become a hot topic with the recent focus on the normal skin microbiome and its disruption in disease. Like the gut, skin is normally colonized by a large number of microorganisms. Prominent among its ‘normal flora’ are several good varieties of Staphylococcus. These ‘good’ Staph growing on normal skin are usually able to keep the ‘bad’ Staph. (Staph.aureus, that is) at bay.
The ‘bad’ Staph. are known to produce a variety of toxins and proteases (enzymes that digest proteins) that can weaken the barrier and stir up the immune system – both of which are key components in the ‘pathogenesis’ (causation) of atopic dermatitis (or ‘eczema’). This leads to the obvious question: does colonization of the skin with Staph. aureus lead to the development of eczema?
Could Staph. aureus be the ‘egg’ that hatches the atopic dermatitis ‘chicken’?
A recent study out of Lausanne, Switzerland provides evidence that this could indeed by the case. Because most cases of atopic dermatitis develop in the first 2 years of life, these authors took a cohort of 149 newborns and followed them for 2 years or until a clinical diagnosis of atopic dermatitis was established. Some of the infants were considered high risk, because of a family history of ‘atopy’ (or allergy). At birth and then at regular intervals, the skin was cultured at two sites and the infants examined for signs of eczema.
They found a positive association between colonization of the skin by Staph. aureus and the development of atopic dermatitis. And most intriguingly, that this colonization preceded the development of eczema by two months on average. They also found, conversely, that colonization with a ‘good’ strain of Staph. (Staph. hominis) declined on the atopic dermatitis skin.
These studies suggest that its not that atopic dermatitis skin provides a fertile field for the growth of Staph. aureus, but that these ‘bad’ Staph. could indeed be provoking the eczema to develop in the first place.
It has also been known for decades that not only are the lesions of atopic dermatitis colonized – even the clinically uninvolved areas of skin, as well as often the nasal mucosa, of eczema patients will harbor Staph. Aureus – without showing any signs of infection. And we’ve also known that the uninvolved skin of eczema patients is not entirely normal, either. Its often drier (low moisture content), has an impaired skin barrier, and shows subtle signs of eczema under the microscope.
These authors did not measure other skin functions, particularly the skin’s barrier function, to see whether a defective skin barrier (our prediction) is the real ‘egg’ here. In other studies we have shown that the skin’s permeability barrier is intimately linked to its antimicrobial barrier. Whatever disrupts the permeability barrier will also affect its antimicrobial barrier. These barriers are joined hand in glove.
Thus, it is entirely possible that an impaired skin barrier leads to colonization with ‘bad’ Staph. which in turn promotes the development of atopic dermatitis. Hopefully, the next large prospective study will measure both barrier function and Staph. colonization to sort out which of these two scenarios is the most likely.
A Korean company, GPower Inc., has developed a small, hand-held device, called the GPSkin device, that can accurately and quickly measure both the barrier status and moisture content (hydration) of the stratum corneum. At the recent IID meeting, Eric Simpson and his co-worker, Erin Grinich, both from Oregon Health Science University, reported that the GPSkin apparatus is as reliable in measuring barrier function and hydration as other standard, but much more cumbersome and expensive instruments. Another useful feature is the accompanying software, which collects the information, and assists with interpretations of the data.
A big problem for investigators interested in studying the barrier status of normal humans, and in patients with diseases, like atopic dermatitis and psoriasis, has been both the cost and complexity of the devices that are currently in use to measure barrier function. When you consider both the ease of use and widespread deployment of other medical devices – such as those that measure the blood levels of oxygen or sugar across the skin – it’s rather surprising that the capability to measure water movement and water content have not kept pace. Now, simple to use but reliable devices, such as the GPSkin, promise to make this hurdle a thing of the past.
Not only could the GPSkin device be useful for dermatologic research, but dermatologists, allergists and pediatricians also could find it helpful in their clinical practices to determine how well their atopic dermatitis patients are responding to treatment. Nurses and physicians in the intensive care nursery could also find it useful in assessing the maturation of the skin barrier in their premature babies. The ease of use the GPSkin apparatus means that it could even be used by patients to assess changes in their disease activity. Practitioners in skin care salons might also employ the device to determine whether their clients need certain types of barrier repair therapy, or whether the products they are currently using are doing the job – or not. This is particularly important as there is mounting evidence that many of the products commonly used for skin care are actually harmful to skin.
With the availability of simple to use and reliable devices, such as GPSkin, that can measure water loss and skin hydration, the assessment of these epidermal functions should become routine in both the research setting and in clinical practice and is likely to lead to improvements in the care of both normal and inflamed skin.