Aimee Two

Antimicrobials from human skin commensal bacteria protect against Staphylococcus aureus and are deficient in atopic dermatitis

Commensal skin bacteria produce previously unknown antimicrobial peptides that can inhibit Staphylococcus aureus colonization of atopic dermatitis subjects. Bacterial biological warfare in atopic dermatitis Normal human skin is colonized by a variety of bacteria, which typically do not perturb the host. However, Staphylococcus aureus is known to aggravate symptoms of atopic dermatitis. Nakatsuji et al. report that other strains of Staphylococcus residing on the skin of healthy individuals produce a novel antimicrobial peptide that can inhibit S. aureus growth. Colonization of pigskin or mice with these protective commensals reduced S. aureus replication. Autologous bacterial transplant in a small number of atopic dermatitis patients drastically reduced S. aureus skin burden. This commensal skin transplant is already approved by the U.S. Food and Drug Administration, with a clinical trial underway. The microbiome can promote or disrupt human health by influencing both adaptive and innate immune functions. We tested whether bacteria that normally reside on human skin participate in host defense by killing Staphylococcus aureus, a pathogen commonly found in patients with atopic dermatitis (AD) and an important factor that exacerbates this disease. High-throughput screening for antimicrobial activity against S. aureus was performed on isolates of coagulase-negative Staphylococcus (CoNS) collected from the skin of healthy and AD subjects. CoNS strains with antimicrobial activity were common on the normal population but rare on AD subjects. A low frequency of strains with antimicrobial activity correlated with colonization by S. aureus. The antimicrobial activity was identified as previously unknown antimicrobial peptides (AMPs) produced by CoNS species including Staphylococcus epidermidis and Staphylococcus hominis. These AMPs were strain-specific, highly potent, selectively killed S. aureus, and synergized with the human AMP LL-37. Application of these CoNS strains to mice confirmed their defense function in vivo relative to application of nonactive strains. Strikingly, reintroduction of antimicrobial CoNS strains to human subjects with AD decreased colonization by S. aureus. These findings show how commensal skin bacteria protect against pathogens and demonstrate how dysbiosis of the skin microbiome can lead to disease.

Rosacea: part I. Introduction, categorization, histology, pathogenesis, and risk factors.

Rosacea is a chronic inflammatory skin condition that affects approximately 16 million Americans. Four distinct subtypes of rosacea have been recognized, with transient and nontransient facial flushing, telangiectasia, and inflammatory papules and pustules being among the more commonly recognized features. Although the exact pathogenesis of rosacea is unknown, dysregulation of the innate immune system, overgrowth of commensal skin organisms, and aberrant neurovascular signaling may all have a role in promoting the clinical features of rosacea.

Staphylococcus epidermidis in the human skin microbiome mediates fermentation to inhibit the growth of Propionibacterium acnes: implications of probiotics in acne vulgaris

Increasing evidence demonstrates that commensal microorganisms in the human skin microbiome help fight pathogens and maintain homeostasis of the microbiome. However, it is unclear how these microorganisms maintain biological balance when one of them overgrows. The overgrowth of Propionibacterium acnes (P. acnes), a commensal skin bacterium, has been associated with the progression of acne vulgaris. Our results demonstrate that skin microorganisms can mediate fermentation of glycerol, which is naturally produced in skin, to enhance their inhibitory effects on P. acnes growth. The skin microorganisms, most of which have been identified as Staphylococcus epidermidis (S. epidermidis), in the microbiome of human fingerprints can ferment glycerol and create inhibition zones to repel a colony of overgrown P. acnes. Succinic acid, one of four short-chain fatty acids (SCFAs) detected in fermented media by nuclear magnetic resonance (NMR) analysis, effectively inhibits the growth of P. acnes in vitro and in vivo. Both intralesional injection and topical application of succinic acid to P. acnes-induced lesions markedly suppress the P. acnes-induced inflammation in mice. We demonstrate for the first time that bacterial members in the skin microbiome can undergo fermentation to rein in the overgrowth of P. acnes. The concept of bacterial interference between P. acnes and S. epidermidis via fermentation can be applied to develop probiotics against acne vulgaris and other skin diseases. In addition, it will open up an entirely new area of study for the biological function of the skin microbiome in promoting human health.

Loss of cerebral cavernous malformation 3 (Ccm3) in neuroglia leads to CCM and vascular pathology

Communication between neural cells and the vasculature is integral to the proper development and later function of the central nervous system. A mechanistic understanding of the interactions between components of the neurovascular unit has implications for various disorders, including cerebral cavernous malformations (CCMs) in which focal vascular lesions form throughout the central nervous system. Loss of function mutations in three genes with proven endothelial cell autonomous roles, CCM1/krev1 interaction trapped gene 1, CCM2, and CCM3/programmed cell death 10, cause familial CCM. By using neural specific conditional mouse mutants, we show that Ccm3 has both neural cell autonomous and nonautonomous functions. Gfap- or Emx1-Cre–mediated Ccm3 neural deletion leads to increased proliferation, increased survival, and activation of astrocytes through cell autonomous mechanisms involving activated Akt signaling. In addition, loss of neural CCM3 results in a vascular phenotype characterized by diffusely dilated and simplified cerebral vasculature along with formation of multiple vascular lesions that closely resemble human cavernomas through cell nonautonomous mechanisms. RNA sequencing of the vascular lesions shows abundant expression of molecules involved in cytoskeletal remodeling, including protein kinase A and Rho-GTPase signaling. Our findings implicate neural cells in the pathogenesis of CCMs, showing the importance of this pathway in neural/vascular interactions within the neurovascular unit.

Mast Cells Are Key Mediators of Cathelicidin-Initiated Skin Inflammation in Rosacea

Rosacea is a chronic inflammatory skin disease whose pathophysiological mechanism is still unclear. However, it is known that mast cell (MC) numbers is increased in the dermis of rosacea patients. MC proteases not only recruit other immune cells, which amplify the inflammatory response, but also cause vasodilation and angiogenesis. MCs are also one of the primary sources of cathelicidin LL-37 (Cath LL-37), an antimicrobial peptide that has been shown to be an enabler of rosacea pathogenesis. Here, we demonstrate that MCs are key mediators of cathelicidin initiated skin inflammation. Following Cath LL-37 injection into the dermis, MC deficient B6.Cg-KitW-sh/HNihrJaeBsmJ (KitW-sh) mice did not develop rosacea-like features. Conversely, chymase (p<0.001), tryptase and Mmp9 (p<0.01) mRNA levels were significantly higher in C57BL/6 Wild Type (WT) mice. Treating WT mice with a MC stabilizer significantly decreased the expressions of Mmp9 and Cxcl2 (p<0.01). Our data was confirmed on Erythematotelangiectatic rosacea subjects that showed a decrease in MMP activity (p<0.05), after eight weeks of topical cromolyn treatment. We conclude that MCs play a central role in the development of inflammation subsequent to Cath LL-37 activation and that down regulation of activated MCs may be a therapy for rosacea treatment.

Rosacea: Part II. Topical and systemic therapies in the treatment of rosacea

Although rosaceas impact on physical health is limited, it has profound effects on a persons psychological well-being. Therefore, treating rosacea can greatly affect a persons quality of life. Patient education regarding trigger avoidance and skin care techniques such as moisturizing and sun protection are important non-pharmacologic first steps in treating rosacea. Pharmacologic interventions range from topical to systemic medications, with the ideal medication choice dependent on the symptoms and severity of each individual patient. Despite this variety of therapeutic options, none of these therapies are completely curative, and therefore further research into the pathophysiology of rosacea is required in order to create more targeted and efficacious treatment options.

Chromosomal Location-Dependent Nonstochastic Onset of Odor Receptor Expression

As odorant receptors (ORs) are thought to be critical determinants of olfactory sensory neuron (OSN) axon targeting and organization, we examined the spatiotemporal onset of mice ORs expression from the differentiation of OSNs in the olfactory placode to an aging olfactory epithelium. ORs were first detected in the placode at embryonic day 9 (E9), at the onset of OSN differentiation but before axon extension. By E13, 22 of 23 ORs were expressed. Onset of individual OR expression was diverse; levels and patterns of expression were unique for each OR. Regional distribution of ORs within zones of the olfactory epithelium appeared stable across development; adult-like patterns were observed by E13. Finally, analysis of OR expression and chromosomal location suggests that ORs are not stochastically expressed; they show evidence of coordinated expression. Collectively, these studies demonstrate that ORs are not equally represented in the “olfactome” across an animals lifespan.

Reduction in serine protease activity correlates with improved rosacea severity in a small, randomized pilot study of a topical serine protease inhibitor.

Individuals with rosacea express high baseline levels of cathelicidin and kallikrein 5 (KLK5) (Yamasaki, et al, 2007). The significance of elevated KLK5 is that this trypsin-like serine protease controls the cleavage of the cathelicidin precursor protein into LL-37 (Yamasaki et al, 2007; Yamasaki et al, 2006). LL-37 is both pro-inflammatory and angiogenic (Koczulla et al, 2003; Lande et al, 2004; Morizane et al, 2012). Based on these findings, we hypothesized that inhibition of KLK5 may improve the clinical signs of rosacea by decreasing LL-37 production.

The Cutaneous Microbiome and Aspects of Skin Antimicrobial Defense System Resist Acute Treatment with Topical Skin Cleansers

The human skin microbiome has been suggested to play an essential role in maintaining health by contributing to innate defense of the skin. These observations have inspired speculation that the use of common skin washing techniques may be detrimental to the epidermal antibacterial defense system by altering the microbiome. In this study, several common skin cleansers were used to wash human forearms and the short-term effect on the abundance of the antimicrobial peptide LL-37 and the abundance and diversity of bacterial DNA was measured. Despite small but significant decreases in the amount of LL-37 on the skin surface shortly after washing, no significant change in the bacterial community was detected. Furthermore, Group A Streptococcus did not survive better on the skin after washing. In contrast, the addition of antimicrobial compounds such as benzalkonium chloride or triclocarban to soap before washing decreased the growth of Group A Streptococcus applied after rinse. These results support prior studies that hand washing techniques in the health care setting are beneficial and should be continued. Additional research is necessary to better understand the effects of chronic washing and the potential impact of skin care products on the development of dysbiosis in some individuals.

Propionic acid and its esterified derivative suppress the growth of methicillin-resistant Staphylococcus aureus USA300

Previously, we demonstrated that Propionibacterium acnes, a human skin commensal bacterium, ferments glycerol into short-chain fatty acids, including propionic acid. Propionic acid suppressed the growth of Staphylococcus aureus USA300, a community-acquired methicillin-resistant bacterium, in vitro and in vivo. In this study, it is demonstrated that the anti-USA300 activity of propionic acid persisted after buffering the acid with 4-(2-hydroxyethyl)-1- piperazineethanesulfonic acid. This suggests that the growth suppression of USA300 mainly resulted from the antimicrobial activity of propionic acid per se and not from the acidity of the medium. In addition, proprionic acid significantly reduced the intracellular pH of USA300 and exhibited broad-spectrum antimicrobial activity against Escherichia coli and Candida albicans. P. acnes showed a higher tolerance to propionic acid. Next, an esterified derivative of propionic acid was synthesised. Propionic acid and the esterified derivative were equivalent in their efficacy to suppress the growth of USA300 in vitro. The esterified derivative thus provides an alternative to propionic acid as an antimicrobial agent against S. aureus.