Isotretinoin and lymecycline treatments modify the skin microbiota in acne.

Oral retinoids and tetracyclines have a major role in acne treatment. Here, we report for the first time the effect of isotretinoin and lymecycline therapy on the skin microbiota in cheek, back and armpit swab samples of acne vulgaris patients using 16S ribosomal RNA (16S rRNA) gene amplicon sequencing. Propionibacterium acnes was the most common in sebaceous areas of healthy and untreated acne skin and more abundant in back than cheek samples. Five taxa, including a Streptococcus taxon, differed significantly between the cheek samples of healthy controls and acne patients, and acne severity was positively correlated with the abundance of Propionibacterium. Both treatments reduced clinical acne grades and the abundance of Propionibacterium, while the abundance of several other taxa was significantly higher in treated cheek samples compared with untreated ones. Less variation was observed in back samples and none in armpit samples. There were no differences in alpha diversity between control and acne patients in any of the sampled skin areas, but the diversity of the microbiota on the cheek and the back was significantly increased after acne treatments. This study provides insight into the skin microbiota in acne and how it is modulated by systemic acne treatment.

Antimicrobial peptides - a part of innate immunity.

Antimicrobial peptides (AMP) are evolutionary ancient molecules produced by nearly all living organisms, both prokaryotic and eukaryotic cells. More than 2000 AMPs have now been identified. These peptides are produced by most human cell types, such as those in the skin and mucous membranes and blood. Each tissue has a different spectrum of AMPs. Antimicrobial capacity depends on the structural characteristics such as charge and amphiphilicity that allow the insertion and/or penetration of AMP into the membranes of microorganisms or other cells. AMPs may have importance in the pathogenesis of neurodegenerative diseases and type 2 diabetes. The most investigated AMPs are defensins and cathelicidin LL-37.

[New insights in the pathogenesis and treatment of rosacea]. / Uusia näkemyksiä ruusufinnin patogeneesistä ja hoidosta.

The production of cathelicidin, an antimicrobial peptide is strongly increased in rosacea. Cathelicidin activates innate immunity, inflammation and angiogenesis. Cutaneous proteases produce inflammatory fragments of cathelicidin. UV-B irradiation and microbial components increase vitamin D3 and TLR2 expression in keratinocytes leading to an increase of cathelicidin production. Retinoids and doxycycline inhibit inflammation, proteases, angiogenesis and TLR2 expression. A multicenter study 2010 proved that isotretinoin with a dose of 0,3 mg/kg/d for 12 weeks and doxycycline with the dose of 100 mg/d for 14 days followed with 50 mg/d were equally effective. Doxycycline 40 mg/d is also effective in milder cases.

IL-17/Th17 pathway is activated in acne lesions.

The mechanisms of inflammation in acne are currently subject of intense investigation. This study focused on the activation of adaptive and innate immunity in clinically early visible inflamed acne lesions and was performed in two independent patient populations. Biopsies were collected from lesional and non-lesional skin of acne patients. Using Affymetrix Genechips, we observed significant elevation of the signature cytokines of the Th17 lineage in acne lesions compared to non-lesional skin. The increased expression of IL-17 was confirmed at the RNA and also protein level with real-time PCR (RT-PCR) and Luminex technology. Cytokines involved in Th17 lineage differentiation (IL-1ß, IL-6, TGF-ß, IL23p19) were remarkably induced at the RNA level. In addition, proinflammatory cytokines and chemokines (TNF-α, IL-8, CSF2 and CCL20), Th1 markers (IL12p40, CXCR3, T-bet, IFN-γ), T regulatory cell markers (Foxp3, IL-10, TGF-ß) and IL-17 related antimicrobial peptides (S100A7, S100A9, lipocalin, hBD2, hBD3, hCAP18) were induced. Importantly, immunohistochemistry revealed significantly increased numbers of IL-17A positive T cells and CD83 dendritic cells in the acne lesions. In summary our results demonstrate the presence of IL-17A positive T cells and the activation of Th17-related cytokines in acne lesions, indicating that the Th17 pathway is activated and may play a pivotal role in the disease process, possibly offering new targets of therapy.