New aspects of the pathogenesis of rosacea

The Trinity of Skin: Skin Homeostasis as a Neuro-Endocrine-Immune Organ

For a long time, skin was thought to be no more than the barrier of our body. However, in the last few decades, studies into the idea of skin as an independent functional organ have gradually deepened our understanding of skin and its functions. In this review, we gathered evidence that presented skin as a "trinity" of neuro-endocrine-immune function. From a neuro perspective, skin communicates through nerves and receptors, releasing neurotrophins and neuropeptides; from an endocrine perspective, skin is able to receive and secrete most hormones and has the cutaneous equivalent of the hypothalamic-pituitary-adrenal (HPA) axis; from an immune perspective, skin is protected not only by its physical barrier, but also immune cells and molecules, which can also cause inflammation. Together as an organ, skin works bidirectionally by operating peripheral neuro-endocrine-immune function and being regulated by the central nervous system, endocrine system and immune system at the same time, maintaining homeostasis. Additionally, to further explain the "trinity" of cutaneous neuro-endocrine-immune function and how it works in disease pathophysiology, a disease model of rosacea is presented.

Clinical and biological impact of the exposome on the skin

The skin exposome is defined as the totality of environmental exposures over the life course that can induce or modify various skin conditions. Here, we review the impact on the skin of solar exposure, air pollution, hormones, nutrition and psychological factors. Photoageing, photocarcinogenesis and pigmentary changes are well-established consequences of chronic exposure of the skin to solar radiation. Exposure to traffic-related air pollution contributes to skin ageing. Particulate matter and nitrogen dioxide cause skin pigmentation/lentigines, while ozone causes wrinkles and has an impact on atopic eczema. Human skin is a major target of hormones, and they exhibit a wide range of biological activities on the skin. Hormones decline with advancing age influencing skin ageing. Nutrition has an impact on numerous biochemical processes, including oxidation, inflammation and glycation, which may result in clinical effects, including modification of the course of skin ageing and photoageing. Stress and lack of sleep are known to contribute to a pro-inflammatory state, which, in turn, affects the integrity of extracellular matrix proteins, in particular collagen. Hormone dysregulation, malnutrition and stress may contribute to inflammatory skin disorders, such as atopic dermatitis, psoriasis, acne and rosacea.

Rosacea is associated with conjoined interactions between physical barrier of the skin and microorganisms: A pilot study

Background

Rosacea is a common condition characterized by transient or persistent central facial erythema, and often papules and pustules. Currently, the role of bacterium in the development and progression of rosacea remains controversial. This study aimed to investigate the difference in the physiological conditions and microorganisms between the lesional and non‐lesional areas of papulopustular rosacea.

Methods

Twenty‐five French patients with papulopustular rosacea were enrolled in this pilot study. Each patient was subjected to clinical assessment, and the skin barrier function was tested in lesional and non‐lesional areas. In addition, samples from the lesional and non‐lesional areas were collected for bacterial culturing.

Results

Of all subjects included in the study, a lower skin conductivity was measured in lesional areas than in non‐lesional areas (43.5 ± 12.4 vs. 57.2 ± 11.6 U, P < .05), and a higher transepidermal water loss (TEWL) value was found in lesional areas than in non‐lesional areas (17.2 ± 5.9 vs. 14.2 ± 4.1 g/(m² h), P < .05). We found a lower TEWL in lesions in rosacea patients with bacterial dysbiosis than in those with bacterial balance (P < .05). In addition, there were significant differences in the skin conductivity and TEWL between lesional and non‐lesional areas in patients with bacterial dysbiosis (P < .001), and no significant differences were seen in patients with bacterial balance (P < .05).

Conclusion

The results of the present study demonstrate that the physiological features of rosacea are closely associated with the interactions between the host and the microorganisms.

Cigarette Smoking and Risk of Incident Rosacea in Women

The relationship between smoking and rosacea is poorly understood. We aimed to conduct the first cohort study to determine the association between smoking and risk of incident rosacea. We included 95,809 women from Nurses' Health Study II (1991-2005). Information on smoking was collected biennially during follow-up. Information on history of clinician-diagnosed rosacea and year of diagnosis was collected in 2005. We used Cox proportional hazards models to estimate age- and multivariable-adjusted hazard ratios and 95% confidence intervals for the association between different measures of smoking and risk of rosacea. During follow-up, we identified 5,462 incident cases of rosacea. Compared with never smoking, we observed an increased risk of rosacea associated with past smoking (multivariable-adjusted hazard ratio = 1.09, 95% confidence interval: 1.03, 1.16) but a decreased risk associated with current smoking (hazard ratio = 0.65, 95% confidence interval: 0.58, 0.72). We further found that increasing pack-years of smoking was associated with an elevated risk of rosacea among past smokers (P for trend = 0.003) and with a decreased risk of rosacea among current smokers (P for trend < 0.0001). The risk of rosacea was significantly increased within 3-9 years since smoking cessation, and the significant association persisted among past smokers who had quit over 30 years before.

Effects of Helicobacter pylori treatment on rosacea: A single-arm clinical trial study

Rosacea is a chronic dermatological disease. Helicobacter pylori has been discussed as one of its causative factors. In this clinical trial study, we attempted to evaluate the effect of H. pylori standard eradication protocol on the rosacea clinical course. In this single-arm clinical trial, patients ascertained to have H. pylori infection based on serological studies were assessed to examine existence of rosacea. Patients with concurrent rosacea and H. pylori infection were included in the study and underwent standard H. pylori eradication therapy. Rosacea was evaluated using the Duluth rosacea grading score at the beginning, 2 months later and at the end of the trial (day 180). Of 872 patients positive for H. pylori, 167 patients (19.15%) manifested the clinical features of rosacea. The patients with concurrent rosacea were younger (P < 0.001) and with a female sex predominance (P = 0.03) when compared with rosacea-free patients. Of 167 patients, 150 received H. pylori eradication therapy, demonstrating a 92% (138/150) cure rate. The rosacea Duluth score grading on day 0, 60 and 180 among 138 patients significantly decreased in most of the criteria except for telangiectasias (P = 0.712), phymatous changes (P = 0.535) and the existence of peripheral involvement (P = 0.431). The present study concluded that H. pylori eradication leads to improvement of rosacea.

Rosacea and cardiovascular risk factors: a case control study

BACKGROUND AND OBJECTIVE

Rosacea is an inflammatory skin disease with a chronic course. This study aimed to investigate the risk of cardiovascular disease (CVD) in rosacea patients.

MATERIALS AND METHODS

The study included 60 rosacea patients and 50 age- and gender-matched controls. Demographic data, medical history, presence of cardiovascular risk factors were recorded. Waist circumference, height, and weight were measured, and the body mass index was calculated for each participant. Laboratory investigations, including fasting blood glucose, C-reactive protein (CRP), very low-density lipoprotein, low-density lipoprotein (LDL), high-density lipoprotein, total cholesterol, triglyceride, lipoprotein(a) were performed.

RESULTS

In all, 66% of the rosacea patients were female (mean age: 44.65 ± 12.9 years) and 66% of the controls were female (mean age: 42.3 ± 12.3 years). Median disease duration in the rosacea group was 36 months. High total cholesterol (>200 mg/dL), LDL (>130 mg/dL) and CRP (>0.8 mg/L) levels, a family history of premature CVD, and a history of smoking and alcohol consumption were significantly more common in the rosacea patients compared to controls.

CONCLUSION

Rosacea patients may have a high risk of CVD. As such, we recommend close follow-up of rosacea patients because of the increased risk of CVD. The mechanism underlying this increased risk is unknown, and additional randomized and controlled studies are required for clarification.

Azelaic acid reduced senescence-like phenotype in photo-irradiated human dermal fibroblasts: possible implication of PPARγ

Azelaic acid (AzA) has been used for the treatment for inflammatory skin diseases, such as acne and rosacea. Interestingly, an improvement in skin texture has been observed after long-time treatment with AzA. We previously unrevealed that anti-inflammatory activity of AzA involves a specific activation of PPARγ, a nuclear receptor that plays a relevant role in inflammation and even in ageing processes. As rosacea has been considered as a photo-aggravated disease, we investigated the ability of AzA to counteract stress-induced premature cell senescence (SIPS). We employed a SIPS model based on single exposure of human dermal fibroblasts (HDFs) to UVA and 8-methoxypsoralen (PUVA), previously reported to activate a senescence-like phenotype, including long-term growth arrest, flattened morphology and increased synthesis of matrix metalloproteinases (MMPs) and senescence-associated β-galactosidase (SA-β-gal). We found that PUVA-treated HDFs grown in the presence of AzA maintained their morphology and reduced MMP-1 release and SA-β-galactosidase-positive cells. Moreover, AzA induced a reduction in ROS generation, an up-modulation of antioxidant enzymes and a decrease in cell membrane lipid damages in PUVA-treated HDFs. Further evidences of AzA anti-senescence effect were repression of p53 and p21, increase in type I pro-collagen and abrogation of the enhanced expression of growth factors, such as HGF and SCF. Interestingly, PUVA-SIPS showed a decreased activation of PPARγ and AzA counteracted this effect, suggesting that AzA effect involves PPARγ modulation. All together these data showed that AzA interferes with PUVA-induced senescence-like phenotype and its ability to activate PPAR-γ provides relevant insights into the anti-senescence mechanism.

Rosacea: The cytokine and chemokine network

Rosacea is one of the most common dermatoses of adults. Recent studies have improved our understanding of the pathophysiology of rosacea. Current concepts suggest that known clinical trigger factors of rosacea such as UV radiation, heat, cold, stress, spicy food, and microbes modulate Toll-like receptor signaling, induce reactive oxygen species, as well as enhance antimicrobial peptide and neuropeptide production. Downstream of these events cytokines and chemokines orchestrate an inflammatory response that leads to the recruitment and activation of distinct leukocyte subsets and induces the characteristic histopathological features of rosacea. Here we summarize the current knowledge of the cytokine and chemokine network in rosacea and propose pathways that may be of therapeutic interest.

Azelaic acid modulates the inflammatory response in normal human keratinocytes through PPARgamma activation

Azelaic acid (AzA), a nine-carbon dicarboxylic acid, is an agent for the topical treatment of acne. It has also been shown to be effective in rosacea; however, the mechanism of action has not been clarified. Because inflammation is a common feature of both conditions, we investigated the effects of azelaic acid on the inflammatory response of normal human keratinocytes to ultraviolet B light, which is a photosensitizer agent in rosacea. AzA, at 20 mM, a concentration achievable following topical application of a 15% gel, suppresses ultraviolet B light-induced interleukins-1beta, -6 and tumor necrosis factor-alpha mRNA expression and protein secretion. Mechanistically, azelaic acid significantly reduced the ultraviolet B light-induced nuclear translocation of nuclear factor kB p65 subunit and the phosphorylation of the p38 mitogen and stress-activated protein kinase. Moreover, as peroxisome proliferators-activated receptor gamma, (PPARgamma) which has a crucial role in the control of inflammation, is activated by fatty acids and products of lipid peroxidation, we further investigated the effect of azelaic acid on the expression of this nuclear receptor. AzA induced peroxisome proliferators-activated receptor-gamma mRNA and its transcriptional activity. The PPARgamma antagonist GW9662 abrogated the inhibitory effects of AzA on the UVB-induced pro-inflammatory cytokines release and on the cell proliferation. Our study provides new insights into the molecular mechanisms of the activity of azelaic acid and lands additional evidences for its therapeutic effects on inflammatory skin diseases, such as rosacea.