Acne—New Thoughts on Inflammation

Isotretinoin normalized Toll receptor 2 (TLR-2) responses, a measure of innate immunity, as reported by Thiboutot and colleagues in the September JID. Both circulating cytokines and cytokines from P. acnes-stimulated macrophages were measured. TLR-2 levels from stimulated macrophages were increased in untreated acne patients; after one week of therapy, these levels decreased. More interestingly, TLR-2 levels remained decreased for six months after stopping  therapy. Il-10, usually considered an anti-inflammatory cytokine, was increased in the patients, and was not affected by isotretinoin.  These studies focused on two of the key elements in acne pathogenesis: P.acnes and inflammation. Innate immunity, a topic of interest as far back as the time of Ilya Ilyich Metchnikoff (1845-1916), is an active focus of acne vulgaris and acne rosacea investigations in several laboratories currently. Hormones are an active area of acne studies , while the morphology of the hair follicle relative to acne, diet, and blood lipids seems dormant. An article in 2005 by Zouboulis et al (including your blogger) explored the pathogenesis of acne in a broad based fashion (2005).

While musing on inflammation and acne, I remembered medical school pathology, where I learned that young servicemen killed during the Korean war were found to have significant amounts of atherosclerosis. Today, fries and burgers would be the immediate culprit assigned by armchair scientists, but could inflammation from acne be implicated?  The role of the inflammation associated with psoriasis and periodontal disease in inducing cardiovascular disease has been a topic of active investigation – and debate —  for over a decade.  In addition, the metabolic syndrome has been documented recently in acne’s first cousin, hidradenitis suppuritiva (acne inversa in the European literature) by Sabat et al (2012).

Galobardes et al reported a study acne and heart disease, including long-term follow-up of male graduates of Glasgow university (followed up in 1968, twenty years after graduation) (2005). Acne was documented by history in the student health service.  All of the issues related to such retrospective studies, including confounding, incomplete data, and antibiotic use, were discussed in a commentary by Ford and Liu (2005). The diagnosis, severity, and duration of acne may be the most important variables in this study.  Alas, the data suggested that acne was a protective factor for death from cardiovascular diseases and coronary artery disease. The studies were undertaken because of the possible androgen effects in acne. Further longitudinal studies may be available, and many of the drug therapies for acne, including isotretinoin, are documented in administrative databases.  In the next few decades, with proper data collection, it may be possible to determine if acne and its treatments influence cardiovascular disease. There may be an effect, but the extent and direction of the effect is yet to be determined.



Dispenza MC, Wolpert EB, Gilliland KL, et al (2012) Systemic isotretinoin therapy normalizes exaggerated TLR-2-mediated innate immune responses in acne patients. J Invest Dermatol doi:10.1038/jid.2012.111

Ford, ES et al Invited commentary: Acne in adolescence—protecting the heart but damaging the prostate late in life? Am J. Epidemiology 161:1102-1006, 2005.

Galobardes, B.  Acne in adolescence and cause-specific mortality: Lower coronary heart disease but higher prostate cancer mortality Am J. Epidemiology 161:1094-1101, 2005.

Sabat R, Chanwangpong A, Schneider-Burrus S, et al. (2012) Increased Prevalence of Metabolic Syndrome in Patients with Acne Inversa. (2012) PLOS One 7:e31810. 2012

Zouboulis CC, Eady A, Philpott M, et al (2005) What is the pathogenesis of acne  Exp Dermatol. 14:143-132

Credit: Image by Karl Harrison (; used with permission. 3-D Model of Isotretinoin Structure

Evidence-Based Nutritional Chemoprevention of Melanoma

Can nutritional supplements prevent melanoma? Interest in the role of nutrition in health dates back at least two and one-half millennia, and many Hippocratic writings emphasize the role of diet. Historically, Scurvy was the scourge of long ocean voyagers, and arctic explorers who ate polar bear liver suffered symptoms of Vitamin A intoxication. Nutritional deficiency studies in rats, emphasizing the morphological and biochemical changes in skin, were common in the first two decades of the JID (1940-1950s).

We now know the molecular basis of the action of most vitamins, and we understand the nuclear receptors of fat soluble vitamins (A and D) and their effects on gene transcription, so the time is ripe for looking at the evidence for and against vitamins’ influence on disease.


The effect of Vitamin A and carotenoids (dietary and in pills from bottles) on the incidence of melanoma is actively being studied.  Conducting such epidemiological studies is an arduous  endeavor, requiring active participant involvement, significant funding, and the understanding that rats and molecules are not people.  The ‘holy of holies’ — the randomized controlled trial — is difficult to perform in long-term nutritional studies.  Parts of the VITAL (VITamin And Lifestyle) study include 69,635 individuals (approximately 94% white) from western Washington (including Seattle) who are being followed with respect to nutritional assessment and melanoma incidence (as well as other diseases).  The population is relatively well-educated (86% “some college”); participants reported high levels of  multivitamin and other supplement use, and 27% reported NSAID use. Older individuals reported less supplement use. There were not enough participants to allow all the subgroup analysis that might be desired, a challenge even in relatively large epidemiological studies.

In a recent JID article, Asgari and colleagues report 566 melanomas (256 in situ and 309 invasive) developed in this population over an average of 5.84 years of follow-up.  Agonizingly detailed prospective nutritional histories as well as vitamin and mineral supplement histories are maintained for this cohort.  The reliability of the questionnaires was ascertained by repeated testing and detailed nutritional interviews, and validation was tested by comparing the results of nutritional questionnaires with blood levels of various minerals and nutrients, including beta-carotene. The investigators calculated retinol and carotenoid levels from the nutritional data and stratified them. The statistical models they used corrected for the multiple variables in the study.

Yes, exact daily levels of intake and blood and tissue levels of the nutrients might make the study better, but the perfect should not be the enemy of the doable. This is evidence-based nutritional medicine in the real world.   Beta-carotene, one of 563 dietary carotenoids, has less than a 10% conversion rate to pro-vitamin A, and some common carotenoids such as lutein, lycopene and zeaxanthin are not precursors of vitamin A at all.  In the data presented, carotenoids – whether dietary or in the form of supplements — had no effect on melanoma incidence.

By contrast, increased Retinol levels from supplements were associated with reduced levels of melanoma. Current use of supplements was an important variable, but not past use of supplements. Interestingly, this effect was more prominent in melanomas on sun-exposed areas. The reduction in melanoma incidence in women was responsible for the overall reported melanoma risk reduction.

SO: What to tell the next person who asks about Vitamin A supplementation to prevent melanoma?

Diet per se is not effective in reducing melanoma, and dietary or supplemental carotenoids do not seem to have a protective effect against the disease. The data suggests that some individuals are benefited, as measured by dietary histories, by supplemental retinoids.  Whether the increased levels of vitamin A have deleterious health effects is not clear. Since DNA was collected on some of the VITAL patients, eventually it may be possible to identify subgroups of patients at varying risks for melanoma (and, thereby, subgroups of patients who may benefit more from retinoid supplements).

We would be especially interested in comments from those with experience with large preventive studies, the role of nutrition in skin diseases, and issues issues related to melanoma studies that may confound preventive studies. What other thoughts does this article provoke? Let’s hear from you.

Credit: This image is by Identity Photogr@phy and it is used via a Creative Commons License; the original can be found on Flickr.

Intimate Life of Mosquitoes

Sing to me, Oh wise muses, of foreskins, flaviviruses, saliva, blood, mosquitoes, monkeys, sylvan glens, and Dengue. Surasombatpattana et al’s article immersed me in this common (100,000,000 cases annually) – and serious — tropical disease.  The Centers for Disease Control (CDC) summarizes clinical dengue, including the severe and frequently lethal hemorrhagic form.

Surasombatpattana et al describe cultured foreskin keratinocytes infected with dengue virus and treated with extracts of Aedes aegypti salivary glands; the extracts increased viral titers and decreased secretions by the innate defense system — molecules such as beta defensin 3 and LL-37 (cathelicidin). 

Protective skin molecules may have evolved in response to a variety of organisms that attack through the skin.  Dengue has a predominantly human reservoir and is spread by mosquitoes, most commonly Aedes aegypti poi and Aedes albopictus, from human to human, without any intermediate hosts.  As in a war, the invading mosquito uses weapons against the skin’s innate defense mechanisms.  The mosquito’s salivary glands synthesize a large set of proteins (the “sialome”), which allows for a good blood meal; it includes anticoagulants as well as proteins whose functions are unknown. 

Mosquitoes are short-attention-span feeders; if they do not insert their proboscis into a blood vessel or a hemorrhagic pool within a minute, they “desist” their proboscis and move to another skin site. While probing, mosquitoes inject saliva in the skin; the saliva is not KY jelly for the proboscis, but it prevents blood coagulation and allows more time for vessel penetration. Unsuccessful attempts by the mosquito phlebotomist are common and have been studied in detail. The female mosquito frantically probes the skin, as a large blood meal is required for procreation. The rapid engorging of the stomach after a blood meal is graphically demonstrated online.

Extensive and prolonged manipulation of the proboscis results in viral deposition, as the mosquito’s salivary glands often contain large amounts of the Dengue virus. These early stages of flavivirus infection and the battleground for the lower epidermis and upper dermis can be exquisitely investigated with today’s methodologies.

Mosquitoes hold no special animosity toward humans, nor do they favor the flavivirus; by probing human skin, they are simply trying to ingest an important blood meal. Likewise, human skin has no special love or obvious need for the mosquito, and it has evolved molecules to make the mosquito’s job more difficult.  Most evolutionary conundrums are like a cold crime scene:  investigation is carried out thousands or millions of years after the key events have occurred, and often after the initial culprits have assumed disguises.  This elegant tango between defense mechanism and host is an old one, and probably began in arboreal jungles where monkeys, virus and mosquitoes were, and still are, in close proximity. The sophisticated stealth approaches — such interfering with the host’s innate immune system — may have started in the forests of Southeast Asia and Central Africa. In these regions there are several species of monkeys that carry sylvan Dengue strains closely related to human Dengue strains. (Vasilakis et al, 2011). The sylvatic disease, when introduced into humans in rural areas, mimics the endogenous human disease and even presents in the hemorrhagic form.

There is a possibility that cross-species Dengue transmission is less than hundreds of years old.  Tree harvesting, fires, drought and other climate changes, and human encroachment on forests can increase the spread of sylvatic dengue into human populations.

Understanding these defense and anti-defense mechanisms in detail holds more than heuristic interest; it may influence control of this disease, since vaccines and mosquito elimination may be only partially effective. The battle is eternal among man, vectors, and organisms, and it always deserves close attention, as the advantage can change rapidly among the species.


Surasombatpattana P, Patramool S, Luplertlop N, et al (2012) Aedes aegypti Saliva Enhances Dengue Virus Infection of Human Keratinocytes by Suppressing Innate Immune Responses. J Invest Dermatol doi:101038/jid.2012.76

Vasilakis N, Cardos J, Hanley K.A., et al (2011) Fever from the forest: prospects for the continued emergence of sylvatic dengue virus and its impact on public health. Nature Reviews Microbiology 9:532-542


Image credit:  This image of Aedes aegypti feeding is from Wikipedia; it was taken by an employee of the USDA and is in the public domain.

Psoriasis, Reproducibility, and the Winner’s Curse

Reproducibility of experimental results is a hallmark of good science. Yet reproduction of results is rarely performed. There is little fame and often little external funding for being the confirmer, being second in the race. Hence the laurels in the Olympics of science are often awarded to those who publish first — or for the more practically minded — patent first.

It is therefore encouraging and stimulating when there is a serious effort to reproduce the results of others, as recently reported by Stuart et al in the JID. But as with all good things, there may be a curse — in this case, the “winner’s curse” should be considered.

The β-defensin gene often has multiple copies (up to 7-12), and previously, higher copy number of the defensin gene was associated with psoriasis. This might explain partially why psoriatic skin is rarely infected with pyogenic organisms.  This finding was re-investigated with patients from both the US and in Europe, with particular attention to the technical details of determining the number of copies, increasing the  number of patients and controls, and utilizing more highly powered statistics. After much analysis an increased prevalence of psoriasis was shown to be associated with increased  copy numbers of the β-defensin gene. However, the odds ratio of the association were not as high as those reported in the initial study. This is not completely unexpected, since subsequent studies and meta-analyses of gene associations with complex diseases often show decreased odds ratios or even odds ratios without statistical significance . This is considered an example of the ”winner’s curse”. That curse requires some explanation.

The term originated in relation to activities such as sealed auctions or bidding on oil fields or baseball players, where the exact monetary value of the product is not known. The winning bid is often higher than that which a rational economist might predict. The statistical mechanisms of this phenomenon have been studied in detail and might be reviewed by  those readers for whom standard sleeping pills are no longer effective. The odds ratio being higher than that which is estimated for future meta-analyses is the ”winner’s curse” for gene association studies. Since the winner often is awarded the next grant based on  statistically significant initial data, this curse is one many researchers might welcome.

In addition to statistical concerns, known and uncontrollable heterogeneity in populations and  heterogeneity of complex diseases such as psoriasis must be considered. I hope our mathematically  and genetically  inclined  readers will take the opportunity to discuss “the curse” and share whether they worry about it affecting their research.

One must marvel that Mendel was smart enough to study single gene traits; however, he may have been the first victim of the curse: it could explain why his findings were undiscovered for decades.


Bazerman, MX and Samuelson, WF (1983) I won the auction but don’t want the prize. J. Conflict Resolution 27:618-634

Goring, HHH , Terwilliger, JD and Blangero J (2001) Large upward Bias in Estimation of locus-specific effects from Genomewide Scans. Am J. Hum Genet 69:1357-1369

Stuart PE, Hüffmeier U, Nair RP (2012) Association of β-Defensin Copy Number and Psoriasis in Three Cohorts of European Origin. J Invest Dermatol doi:10.1038/jid.2012.191


Image: ©

Urea: The Little Molecule that Could

Credit: wikipedia Urea molecule and its discoverer, Friedrich Wöhler

Urea is a magical, symmetrical molecule, and reading Grether-Beck et al’s article transported me back in time, like Gil in Woody Allen’s movie “Midnight in Paris”.  I visited two seminal years in urea’s history:  1828 and 1954.

In 1828 Friedrich Wohler synthesized urea in vitro, delivering a fatal blow to the concept of “vitalism” that suggested that life, and molecules that were products of living creatures, required more than chemistry (i.e., a vital force) for their synthesis.

Urea is easily quantified, and it was a focus for those studying the composition of sweat and epidermis.  The 1954 state-of-the art thinking about urea and the skin is stated in Rothman’s text, Physiology and Biochemistry of the Skin.  Imagine yourself a member of Rothman’s department at the University of Chicago, as were Fred Malkinson and Eugene Van Scott – two distinguished and current members of the Society for Investigative Dermatology. 

Remember:  In 1954, there was no molecular biology, no transgenic or knock-out animals, and no knockdown molecules. The Krebs-Henseleit urea cycle was described in 1932, and urea was known to be a synthesized by the liver to remove toxic ammonia resulting from protein catabolism. Clinicians used urea to treat multiple skin diseases (wounds just after the First World War and hand eczema in the 1930s) in addition to standby treatments such as tars and salicylic acid. Topical steroids were the new therapeutic superstar on the block. There was interest about urea’s high levels in the epidermis and sweat compared to those in the blood, and there was much speculation about the mechanisms responsible.

Fast forward to today and the experiments described by Grether-Beck. Two main groups of urea transporting molecules (UT-A1 and UT-A2) exist in the epidermis. These molecules have been knocked out in mice without obvious changes in epidermal structure or function. By contrast, knockouts of other epidermal molecules (e.g., p 63) are often associated with compromised neonatal epidermal barrier function, fluid loss, and death. Part of the reason may be that other molecules that transport urea, such as aquaphorin 3, may be quantitatively more important than the specific urea transporters in the epidermis.

One of the urea transporters of the UT-A2 group is the Kidd blood group.  Humans lacking this protein have a grossly normal epidermis.

[Personal time machine moment: in 1957 I was working in a blood bank performing blood typing and was intrigued by the genetics of blood groups and writing my first article on the genetics of blood groups for the Columbia college medical student society magazine. What goes around comes around.]

Today, following the topical application of urea to the skin of healthy volunteers Grether-Beck report increased levels of the epidermal urea transporters, as well as increases in the antimicrobial properties of the epidermis. These results will no doubt inspire more detailed studies of urea metabolism in the epidermis and the investigation of new, urea-containing topicals.

In 1954 there was also high interest in the enzyme arginase, the terminal enzyme of the urea cycle, which converts arginine to ornithine (a precursor of polyamines) and urea.  Arginase is measured at very high levels in normal human epidermis, but especially so in neoplastic epidermis. After a decades-long drought in studies of epidermal arginase, it appears a comeback is in progress.

Arginine is a substrate for inducible nitric oxide synthase (iNOS); its role as an immune modulator is the topic of a burgeoning research industry, and this will no doubt lead to further studies of arginase’s epidermal role (Munder, 2009). Connecting biochemistry and immunology illustrates the challenge of retaining broad knowledge while delving deeper and deeper into one’s personal scientific studies.

As the two hundredth anniversary of its in vitro synthesis approaches, urea will no doubt remain of interest to basic and clinical skin researchers and we expect future studies to seek optimal formulations of urea-containing drugs and explanations of how this small and simple molecule mediates its physiological and potential pharmaceutical roles in the epidermis.

I invite you to share your own time-travel moments with us.



Grether-Beck S, Felsner I, Brenden H, et al (2012):  Urea Uptake Enhances Barrier Function and Antimicrobial Defense in Humans by Regulating Epidermal Gene Expression.  J Invest Dermatol doi:10.1038/jid.2012.42

Munder,M (2009) Arginase:an emerging key player in the mammalian immune system. Br. J Pharm. 158:638-651