Distribution and expression of non-neuronal transient receptor potential (TRPV) ion channels in rosacea

Rosacea in East Asian populations: Clinical manifestations and pathophysiological perspectives for accurate diagnosis

Rosacea is a chronic inflammatory disorder primarily affecting the facial skin, prominently involving the cheeks, nose, chin, forehead, and periorbital area. Cutaneous manifestations encompass persistent facial erythema, phymas, papules, pustules, telangiectasia, and flushing. The pathogenesis of rosacea is associated with various exacerbating or triggering factors, including microbial infestation, temperature fluctuations, sunlight exposure, physical exertion, emotional stress, consumption of hot beverages and spicy foods, and exposure to airborne pollen. These environmental factors interact with genetic predispositions in the development of rosacea. The roles of the lipophilic microbiome, ultraviolet radiation, nociceptive responses, and vascular alterations have been proposed as significant factors in the pathogenesis. These insights contribute to understanding the anatomical specificity of facial involvement and the progressive nature of rosacea. East Asian skin, predominantly classified as Fitzpatrick skin phototypes III to IV, is characterized by relatively diminished skin barrier function and increased sensitivity to irritants. Airborne pollen exposure may particularly act as a trigger in East Asian individuals, possibly mediated through toll-like receptors. The lack of specificity in objective clinical and histopathological findings leads to diagnostic challenges for individuals with colored skin, including East Asians, particularly when erythema is the sole objective manifestation. An alternative diagnostic scheme may thus be necessary. A diagnostic approach emphasizing vascular manifestations and nociceptive symptoms potentially holds promise for individuals with darker skin tones. More research focusing on potential variations in skin physiology across different racial groups is essential to establish more effective diagnostic schemes applicable to both dark and light skin colors.

Therapeutic strategies focusing on immune dysregulation and neuroinflammation in rosacea

Rosacea is a complex inflammatory condition characterized by papulopustular lesions and erythema on the central face for which there is no cure. The development of rosacea is influenced by both external triggers and genetics, but the common pathophysiology is overactivation of the immune system. Here, we review the current data on proinflammatory cytokines and dysregulation of the neurovascular system as targetable components of rosacea. Amelioration of cutaneous and gastrointestinal dysbiosis and other external factors impacts the immune state and has been observed to improve rosacea. While multiple treatments exist, many patients do not achieve their goals for rosacea control and highlights an unmet need for dermatologic care. Current interventions encompass topical/oral drugs, light devices, and avoidance of triggers management. Additional understanding of the underlying pathogenesis may help us develop novel targeted therapeutic strategies to improve rosacea.

Investigation of Choroidal Thickness and Choroidal Vascularity Index in Ocular Rosacea Patients According to Skin Subtypes

BACKGROUND

To compare the choroidal thickness (CT) and choroidal vascularity index (CVI) values in ocular rosacea (OR) patients across skin subtypes of the disease and healthy controls.

METHODS

This prospective study included 90 eyes of 90 mild-moderate OR patients with different skin subtypes (30 phymatous, 30 papulopustular and 30 erythematotelangiectatic) and 30 eyes of 30 age-gender matched healthy volunteers. After obtaining the enhanced depth imaging optical coherence tomography images, the CT was measured at subfoveal, 1500μm nasal and 1500μm temporal to the fovea, and the CVI was calculated using Image J software in the subfoveal, nasal and temporal areas.

RESULTS

There was no CT significant difference between OR patients and healthy controls in all regions (p>0.05). CVI values of OR patients were found to be significantly lower in the subfoveal, nasal and temporal regions compared to healthy controls (p=0.02, p=0.01, p=0.01, respectively). No CT difference was detected between the subtypes and healthy controls in all regions (p>0.05). Subfoveal-CVI was significantly lower in the phymatous subtype than the other subtypes and controls (p<0.05), while nasal and temporal-CVI were significantly lower in the phymatous and papulopustular subtypes than the erythematotelangiectatic subtype and controls.

CONCLUSION

Our study demonstrated no difference between rosacea skin types and healthy controls in terms of CT. Phymatous and papulopustular subtypes were more likely to be affected by chronic inflammation with having lower CVI in most of the regions. Further studies are needed to investigate the association of inflammatory factors with CVI in OR.

Beyond the classic players: Mas-related G protein-coupled receptor member X2 role in pruritus and skin diseases

Chronic spontaneous urticaria (CSU), atopic dermatitis (AD), psoriasis and rosacea are highly prevalent inflammatory skin conditions which impose a significant burden on patients' quality of life. Their pathophysiology is likely multifactorial, involving genetic, immune and environmental factors. Recent advancements in the field have demonstrated the key role of mast cells (MC) in the pathophysiology of these conditions. The Mas-related G protein-coupled receptor X2 (MRGPRX2) has emerged as a promising non-IgE-mediated MC activation receptor. MRGPRX2 is predominately expressed on MC and activated by endogenous and exogenous ligands, leading to MC degranulation and release of various pro-inflammatory mediators. Mounting evidence on the presence of endogenous MRGPRX2 agonists (substance P, cortistatin-14, LL37, PAMP-12 and VIP) and its high expression among patients with CSU, AD, rosacea, psoriasis and chronic pruritus emphasizes the pathogenic role of MRGPRX2 in these conditions. Despite the currently available treatments, there remains a pressing need for novel drug targets and treatment options for these chronic inflammatory skin conditions. Here, we reviewed the pathogenic role of MRGPRX2 and its potential as a novel therapeutic target and provided an update on future research directions.

Unlocking the therapeutic potential of TRPV3: Insights into thermosensation, channel modulation, and skin homeostasis involving TRPV3

Recent insights reveal the significant role of TRPV3 in warmth sensation. A novel finding elucidated how thermosensation is affected by TRPV3 membrane abundance that is modulated by the transmembrane protein TMEM79. TRPV3 is a warmth-sensitive ion channel predominantly expressed in epithelial cells, particularly skin keratinocytes. Multiple studies investigated the roles of TRPV3 in cutaneous physiology and pathophysiology. TRPV3 activation by innocuous warm temperatures in keratinocytes highlights its significance in temperature sensation, but whether TRPV3 directly contributes to warmth sensations in vivo remains controversial. This review explores the electrophysiological and structural properties of TRPV3 and how modulators affect its intricate regulatory mechanisms. Moreover, we discuss the multifaceted involvement of TRPV3 in skin physiology and pathology, including barrier formation, hair growth, inflammation, and itching. Finally, we examine the potential of TRPV3 as a therapeutic target for skin diseases and highlight its diverse role in maintaining skin homeostasis.

Biomarkers in rosacea: A systematic review

Rosacea is a chronic and psychologically ladened disease affecting 1%-3% of people worldwide. The identification and validation of biomarkers in rosacea patients has the potential to improve disease progression, support diagnosis, provide objective measures for clinical trials and aid in management. The objective of this review is to systematically identify all rosacea biomarkers, categorize them by type and identify trends to improve disease expression. Eligibility criteria for this review (PROSPERO CRD42023397510) include randomized controlled trials, case-control studies, cohort studies and other observational studies. No restrictions were placed on patient demographics (age, sex, ethnicity) or language of publication until February 2023. Quality of studies was assessed using the National Institute of Health quality assessment tool. The literature search was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. A total of 805 unique articles were screened based on the applied inclusion and exclusion criteria. After the articles were screened based on title/abstract and full-text, a total of 38 studies were included, reporting on a total of 119 unique biomarkers. The results of this review and current rosacea pathogenic mechanisms provide the greatest support for the innate cathelicidin and inflammasome, Th1 and Th17 pathways. The most commonly reported biomarkers include IL-1β, TNF-α, IL-37, IFN-γ and MMP-9. Biomarkers identified in this study support current theories of rosacea pathogenesis and provide direction for research to further our knowledge. However, more research is needed to identify biomarkers panels that can provide diagnostic utility. This may be difficult due to the heterogeneity of the disease and potential differences between rosacea subtypes.

TRPV3 activation by different agonists accompanied by lipid dissociation from the vanilloid site

TRPV3 represents both temperature- and ligand-activated transient receptor potential (TRP) channel. Physiologically relevant opening of TRPV3 channels by heat has been captured structurally, while opening by agonists has only been observed in structures of mutant channels. Here, we present cryo-EM structures that illuminate opening and inactivation of wild-type human TRPV3 in response to binding of two types of agonists: either the natural cannabinoid tetrahydrocannabivarin (THCV) or synthetic agonist 2-aminoethoxydiphenylborane (2-APB). We found that THCV binds to the vanilloid site, while 2-APB binds to the S1-S4 base and ARD-TMD linker sites. Despite binding to distally located sites, both agonists induce similar pore opening and cause dissociation of a lipid that occupies the vanilloid site in their absence. Our results uncover different but converging allosteric pathways through which small-molecule agonists activate TRPV3 and provide a framework for drug design and understanding the role of lipids in ion channel function.

Elevated interleukin-8 expression by skin fibroblasts as a potential contributor to pain in women with Fabry disease

Fabry disease (FD) is a lysosomal storage disorder of X-linked inheritance. Mutations in the α-galactosidase A gene lead to cellular globotriaosylceramide (Gb3) depositions and triggerable acral burning pain in both sexes as an early FD symptom of unknown pathophysiology. We aimed at elucidating the link between skin cells and nociceptor sensitization contributing to FD pain in a sex-associated manner. We used cultured keratinocytes and fibroblasts of 27 adult FD patients and 20 healthy controls. Epidermal keratinocytes and dermal fibroblasts were cultured and immunoreacted to evaluate Gb3 load. Gene expression analysis of pain-related ion channels and pro-inflammatory cytokines was performed in dermal fibroblasts. We further investigated electrophysiological properties of induced pluripotent stem cell (iPSC) derived sensory-like neurons of a man with FD and a healthy man and incubated the cells with interleukin 8 (IL-8) or fibroblast supernatant as an in vitro model system. Keratinocytes displayed no intracellular, but membrane-bound Gb3 deposits. In contrast, fibroblasts showed intracellular Gb3 and revealed higher gene expression of potassium intermediate/small conductance calcium-activated potassium channel 3.1 (KCa 3.1, KCNN4) in both, men and women with FD compared to controls. Additionally, cytokine expression analysis showed increased IL-8 RNA levels only in female FD fibroblasts. Patch-clamp studies revealed reduced rheobase currents for both iPSC neuron cell lines incubated with IL-8 or fibroblast supernatant of women with FD. We conclude that Gb3 deposition in female FD patient skin fibroblasts may lead to increased KCa3.1 activity and IL-8 secretion. This may result in cutaneous nociceptor sensitization as a potential mechanism contributing to a sex-associated FD pain phenotype.

Rosacea: Practical Guidance and Challenges for Clinical Management

Rosacea is a common chronic dermatosis. Clinically, rosacea can present with flushing, erythema, papules, pustules, telangiectasias, phymatous changes, pruritus, burning, and stinging. In 2017, the National Rosacea Society Expert Committee recommended a phenotype-based classification for therapy. In this review, we identify monotherapies and multimodal treatment approaches for the clinical management of rosacea including topical, systemic, laser and light, alternative, and combination therapies.

Rosacea, microbiome and probiotics: the gut-skin axis

Rosacea is an inflammatory skin disease involving diverse symptoms with a variable clinical progress which can severely impact the patient's quality of life as well as their mental health. The pathophysiological model of rosacea involves an unbalanced immune system predisposed to excessive inflammation, in addition to vascular and nervous alterations, being certain cutaneous microorganisms' triggers of the symptoms onset. The gut-skin axis explains a bidirectional interaction between skin and gut microbiota in some inflammatory skin diseases such as atopic dermatitis, psoriasis, or rosacea. The introduction and consolidation of the next-generation sequencing in recent years has provided unprecedented information about the microbiome. However, the characterization of the gut and skin microbiota and the impact of the gut-skin axis in patients with rosacea has been little explored, in contrast to other inflammatory skin diseases such as atopic dermatitis or psoriasis. Furthermore, the clinical evolution of patients with rosacea is not always adequate and it is common for them to present a sustained symptomatology with frequent flare-ups. In this context, probiotic supplementation could improve the clinical evolution of these patients as happens in other pathologies. Through this review we aim to establish and compile the basics and directions of current knowledge to understand the mechanisms by which the microbiome influences the pathogenesis of rosacea, and how modulation of the skin and gut microbiota could benefit these patients.

Rosacea pathogenesis and therapeutics: current treatments and a look at future targets

Rosacea is a chronic inflammatory skin condition associated with a significant health and economic burden from costs and loss of productivity due to seeking medical treatment. The disease encompasses multiple phenotypic manifestations involving a complex and multi-variate pathogenesis. Although the pathophysiology of rosacea is not completely understood, ongoing research is continually elucidating its mechanisms. In this review, current concepts of rosacea pathogenesis will be addressed which involve skin barrier and permeability dysfunction, the innate and adaptive immune systems, and the neurovascular system. More specifically, the cathelicidin pathway, transient potential receptor channels, mast cells, and the NLRP3 inflammasome pathway are various targets of current pharmacologic regimens. Future therapies may seek different mechanisms to act on current treatment targets, like the potential use of JAK/STAT inhibitors in ameliorating skin barrier dysfunction or TLR antagonists in alleviating cathelicidin mediated inflammation. Other potential treatments aim for entirely different molecular targets such as microvesicle particle mediated local and systemic inflammation. Ultimately rosacea is associated with a significant health and economic burden which warrants deeper research into its pathogenesis and resultant new treatment discovery.

Rosacea and seborrheic dermatitis differentially respond to lactic acid sting and capsaicin tests in Chinese women

BACKGROUND

Although rosacea and seborrheic dermatitis share some symptoms of sensitive skin, whether they respond differently to lactic acid sting and capsaicin tests, common tests for diagnosis of sensitive skin, is unknown.

OBJECTIVES

To reveal the cutaneous responses to lactic acid sting (LAST) and capsaicin test (CAT) in females with either rosacea vs. seborrheic dermatitis.

METHODS

A total of 60 patients with rosacea, 20 patients with seborrheic dermatitis and 40 normal controls were enrolled in the study. Their skin sensitivity to stimuli were evaluated following topical application of either 10% lactic acid solution or 0.001% capsaicin solution. Transepidermal water loss (TEWL) rates and erythema indexes were also measured on the face.

RESULTS

In comparison to normal controls, the positive rate to either LAST or CAT was significantly higher in subjects with rosacea (p < 0.001), but not in that with seborrheic dermatitis. Similarly, individuals with rosacea displayed a higher positive rate to both LAST and CAT than those with seborrheic dermatitis and normal controls (p < 0.001). In parallel, the LAST scores and CAT scores in individuals with rosacea were significantly higher than in that with either seborrheic dermatitis or normal controls (p < 0.001). The baseline TEWL rates and erythema indexes were higher in individual with rosacea than in normal controls (p < 0.001). But the baseline TEWL rates and erythema indexes did not differ significantly between subjects with rosacea and that with seborrheic dermatitis. Moreover, LAST scores and CAT scores correlated positively with TEWL (p < 0.0001). TEWL rates were higher in CAT positive than in CAT negative subjects (p < 0.0001). Finally, erythema index correlated positively with CAT scores (p < 0.0001), but not with LAST scores (p = 0.0842).

CONCLUSIONS

Skin responses to LAST and CAT differ between individuals with rosacea and those with seborrheic dermatitis, possibly due to the differences in epidermal permeability barrier and the neurovascular hyperreactivity. The higher LAST and CAT scores, as well as positive rates of both LAST and CAT can be attributable to inferior permeability barrier and the neurovascular hyperreactivity in subjects with rosacea.

Transient receptor potential vanilloid 4 promotes cutaneous wound healing by regulating keratinocytes and fibroblasts migration and collagen production in fibroblasts in a mouse model

BACKGROUND

Transient receptor potential vanilloid 4 (TRPV4), a cation ion channel, is expressed in different cells, and it regulates the development of different diseases. We recently found a high TRPV4 expression in the wounded skin area. However, the role of TRPV4 in cutaneous wound healing is unknown.

OBJECTIVE

To investigate the role of TRPV4 in cutaneous wound healing in a mouse model.

METHODS

Skin wound healing experiment and histopathological studies were performed between WT and TRPV4 KO mice. The effect of TRPV4 antagonist and agonist on cell migration, proliferation, and differentiation were examined in vitro.

RESULTS

TRPV4 expression was enhanced in wounded area in the skin. TRPV4 KO mice had impaired cutaneous wound healing compared with the WT mice. Further, they had significantly suppressed re-epithelialization and formation of granulation tissue, amount of collagen deposition, and number of α-SMA-positive myofibroblasts in skin wounds. qPCR revealed that the KO mice had decreased mRNA expression of COL1A1 and ACTA2 in skin wounds. In vitro, treatment with selective TRPV4 antagonist suppressed migrating capacity, scratch stimulation enhanced the expression of phospho-ERK in keratinocytes, and TGF-β stimulation enhanced the mRNA expression of COL1A1 and ACTA2 in fibroblasts. Selective TRPV4 agonist suppressed cell migration in keratinocytes, and did not enhance proliferation and migration, but promoted differentiation in fibroblasts.

CONCLUSION

TRPV4 mediates keratinocytes and fibroblasts migration and increases collagen deposition in the wound area, thereby promoting cutaneous wound healing.

Dietary Patterns in Acne and Rosacea Patients-A Controlled Study and Comprehensive Analysis

As the relationship between exposome factors and inflammatory skin diseases is gaining increasing attention, the objective of this study was to investigate dietary patterns among acne and rosacea patients and to establish the disease risk attributable to nutrition. In this cross-sectional, controlled study, patients' dietary habits were assessed via subjective ratings of beneficial and trigger foods, followed by standardized food frequency surveys (FFS). Scores for disease-specific risk stratification based on dietary habits were proposed. Clinical assessments, dermatologic examinations, and laboratory analyses were performed. A total of 296 patients (acne group (AG) n = 120, control group (ACG) n = 32; rosacea group (RG) n = 105, control group (RCG) n = 39) were included. The significant impact of diet on disease severity was self-reported by 80.8% of the AG and 70.5% of the RG. Leading dietary triggers were found in both groups, while beneficial food items were identified more clearly by the AG. FFS revealed significant dietary differences between the AG, RG, and control groups. Disease-specific scores showed greater precision for acne (odds ratio 14.5 AG, 5.5 RG). The AG had higher insulin-like growth factor (IGF)-1 levels correlating with dairy intake (p = 0.006). Overall, this study underlines the influence of diet on acne and rosacea, providing valuable disease-specific scores for dietary risk stratification. Consuming vegetables, legumes, oily fish, olive oil, and nuts, and limiting meat, cheese, and alcohol appear to be beneficial for both acne and rosacea. Future studies can build on these data to further improve preventive and therapeutic strategies.

[Rosacea-the updated S2k guideline]

Rosacea is a common chronic inflammatory dermatosis of the face, clinically characterized by erythema, telangiectasia, papules, pustules, and rhinophyma. In January 2022, the updated guideline on rosacea was published. Groundbreaking innovations include the new clinical classification according to phenotypes, extended diagnostic and therapeutic recommendations for ocular rosacea and implications of the gut microbiome on rosacea. Furthermore, the guideline encompasses a new chapter on the psychosocial aspects of rosacea and detailed recommendations for approved and off-label therapies.

Alpha-Mangostin: A Potent Inhibitor of TRPV3 and Pro-Inflammatory Cytokine Secretion in Keratinocytes

The TRPV3 calcium ion channel is vital for maintaining skin health and has been associated with various skin-related disorders. Since TRPV3 is involved in the development of skin inflammation, inhibiting TRPV3 could be a potential treatment strategy. Alpha-mangostin isolated from Garcinia mangostana L. extract exhibits diverse positive effects on skin health; however, the underlying mechanisms remain obscure. This study investigated the TRPV3-inhibitory properties of alpha-mangostin on TRPV3 hyperactive mutants associated with Olmsted syndrome and its impact on TRPV3-induced cytokine secretion and cell death. Our findings demonstrate that alpha-mangostin effectively inhibits TRPV3, with an IC50 of 0.077 ± 0.013 μM, showing inhibitory effects on both wild-type and mutant TRPV3. TRPV3 inhibition with alpha-mangostin decreased calcium influx and cytokine release, protecting cells from TRPV3-induced death. These results indicate that alpha-mangostin reduced inflammation in TRPV3-activated skin keratinocytes, suggesting that alpha-mangostin could be potentially used for improving inflammatory skin conditions such as dermatitis.

Exploring the Pathogenesis and Mechanism-Targeted Treatments of Rosacea: Previous Understanding and Updates

Rosacea is a chronic inflammatory skin disease characterized by recurrent erythema, flushing, telangiectasia, papules, pustules, and phymatous changes in the central area of the face. Patients with this condition often experience a significant negative impact on their quality of life, self-esteem, and overall well-being. Despite its prevalence, the pathogenesis of rosacea is not yet fully understood. Recent research advances are reshaping our understanding of the underlying mechanisms of rosacea, and treatment options based on the pathophysiological perspective hold promise to improve patient outcomes and reduce incidence. In this comprehensive review, we investigate the pathogenesis of rosacea in depth, with a focus on emerging and novel mechanisms, and provide an up-to-date overview of therapeutic strategies that target the diverse pathogenic mechanisms of rosacea. Lastly, we discuss potential future research directions aimed at enhancing our understanding of the condition and developing effective treatments.

Involvement of skin TRPV3 in temperature detection regulated by TMEM79 in mice

TRPV3, a non-selective cation transient receptor potential (TRP) ion channel, is activated by warm temperatures. It is predominantly expressed in skin keratinocytes, and participates in various somatic processes. Previous studies have reported that thermosensation in mice lacking TRPV3 was impaired. Here, we identified a transmembrane protein, TMEM79, that acts as a negative regulator of TRPV3. Heterologous expression of TMEM79 was capable of suppressing TRPV3-mediated currents in HEK293T cells. In addition, TMEM79 modulated TRPV3 translocalization and promoted its degradation in the lysosomes. TRPV3-mediated currents and Ca²⁺ influx were potentiated in primary mouse keratinocytes lacking TMEM79. Furthermore, TMEM79-deficient male mice preferred a higher temperature than did wild-type mice due to elevated TRPV3 function. Our study revealed unique interactions between TRPV3 and TMEM79, both in vitro and in vivo. These findings support roles for TMEM79 and TRPV3 in thermosensation.

Whole genome sequencing identifies genetic variants associated with neurogenic inflammation in rosacea

Rosacea is a chronic inflammatory skin disorder with high incidence rate. Although genetic predisposition to rosacea is suggested by existing evidence, the genetic basis remains largely unknown. Here we present the integrated results of whole genome sequencing (WGS) in 3 large rosacea families and whole exome sequencing (WES) in 49 additional validation families. We identify single rare deleterious variants of LRRC4, SH3PXD2A and SLC26A8 in large families, respectively. The relevance of SH3PXD2A, SLC26A8 and LRR family genes in rosacea predisposition is underscored by presence of additional variants in independent families. Gene ontology analysis suggests that these genes encode proteins taking part in neural synaptic processes and cell adhesion. In vitro functional analysis shows that mutations in LRRC4, SH3PXD2A and SLC26A8 induce the production of vasoactive neuropeptides in human neural cells. In a mouse model recapitulating a recurrent Lrrc4 mutation from human patients, we find rosacea-like skin inflammation, underpinned by excessive vasoactive intestinal peptide (VIP) release by peripheral neurons. These findings strongly support familial inheritance and neurogenic inflammation in rosacea development and provide mechanistic insight into the etiopathogenesis of the condition.

Skin Inflammation with a Focus on Wound Healing

Significance: The skin is the crucial first-line barrier against foreign pathogens. Compromise of this barrier presents in the context of inflammatory skin conditions and in chronic wounds. Skin conditions arising from dysfunctional inflammatory pathways severely compromise the quality of life of patients and have a high economic impact on the U.S. health care system. The development of a thorough understanding of the mechanisms that can disrupt skin inflammation is imperative to successfully modulate this inflammation with therapies. Recent Advances: Many advances in the understanding of skin inflammation have occurred during the past decade, including the development of multiple new pharmaceuticals. Mechanical force application has been greatly advanced clinically. Bioscaffolds also promote healing, while reducing scarring. Critical Issues: Various skin inflammatory conditions provide a framework for analysis of our understanding of the phases of successful wound healing. The large burden of chronic wounds on our society continues to focus attention on the chronic inflammatory state induced in many of these skin conditions. Future Directions: Better preclinical models of disease states such as chronic wounds, coupled with enhanced diagnostic abilities of human skin, will allow a better understanding of the mechanism of action. This will lead to improved treatments with biologics and other modalities such as the strategic application of mechanical forces and scaffolds, which ultimately results in better outcomes for our patients.

Ocular rosacea: an under-recognized entity

While rosacea is a common dermatologic condition, ocular rosacea is sometimes evident either with cutaneous rosacea or occasionally by itself. Manifesting with such varied symptoms as dry eye, Meibomian gland dysfunction, and corneal erosion, ocular rosacea can be confused with a multitude of other diseases. While ocular rosacea is commonly mild and rarely severe, physicians should still expand their examination to include ocular manifestations of rosacea. In addition, we propose diagnostic criteria for ocular rosacea, stressing the importance of early recognition and treatment.

Novel Insights into the Role of Keratinocytes-Expressed TRPV3 in the Skin

TRPV3 is a non-selective cation channel that is highly expressed in keratinocytes in the skin. Traditionally, keratinocytes-expressed TRPV3 is involved in multiple physiological and pathological functions of the skin, such as itching, heat pain, and hair development. Although the underlying mechanisms by which TRPV3 functions in vivo remain obscure, recent research studies suggest that several cytokines and EGFR signaling pathways may be involved. However, there have also been other studies with opposite results that question the role of TRPV3 in heat pain. In addition, an increasing number of studies have suggested a novel role of TRPV3 in promoting skin regeneration, indicating that TRPV3 may become a new potential target for regulating skin regeneration. This paper not only reviews the role of keratinocytes-expressed TRPV3 in the physiological and pathological processes of itching, heat pain, hair development, and skin regeneration, but also reviews the relationship between TRPV3 gene mutations and skin diseases such as atopic dermatitis (AD) and Olmsted syndrome (OS). This review will lay a foundation for further developing our understanding of the mechanisms by which TRPV3 is involved in itching, heat pain, and hair development, as well as the treatments for TRPV3-related skin diseases.

Biochemical and Structural Insights into FIH-Catalysed Hydroxylation of Transient Receptor Potential Ankyrin Repeat Domains

Transient receptor potential (TRP) channels have important roles in environmental sensing in animals. Human TRP subfamily A member 1 (TRPA1) is responsible for sensing allyl isothiocyanate (AITC) and other electrophilic sensory irritants. TRP subfamily vanilloid member 3 (TRPV3) is involved in skin maintenance. TRPV3 is a reported substrate of the 2-oxoglutarate oxygenase factor inhibiting hypoxia-inducible factor (FIH). We report biochemical and structural studies concerning asparaginyl hydroxylation of the ankyrin repeat domains (ARDs) of TRPA1 and TRPV3 catalysed by FIH. The results with ARD peptides support a previous report on FIH-catalysed TRPV3 hydroxylation and show that, of the 12 potential TRPA1 sequences investigated, one sequence (TRPA1 residues 322-348) undergoes hydroxylation at Asn336. Structural studies reveal that the TRPA1 and TRPV3 ARDs bind to FIH with a similar overall geometry to most other reported FIH substrates. However, the binding mode of TRPV3 to FIH is distinct from that of other substrates.

TRPV3: Structure, Diseases and Modulators

Transient receptor potential vanillin 3 (TRPV3) is a member of the transient receptor potential (TRP) superfamily. As a Ca²⁺-permeable nonselective cation channel, TRPV3 can recognize thermal stimulation (31-39 °C), and it plays an important regulatory role in temperature perception, pain transduction, skin physiology, inflammation, cancer and other diseases. TRPV3 is not only activated by the changes in the temperature, but it also can be activated by a variety of chemical and physical stimuli. Selective TRPV3 agonists and antagonists with regulatory effects and the physiological functions for clinical application are highly demanded. In recent years, significant progress has been made in the study of TRPV3, but there is still a lack of modulators with a strong affinity and excellent selectivity. This paper reviews the functional characteristics of TRPV3 in terms of the structure, diseases and the research on TRPV3 modulators.

TRPV1: A promising therapeutic target for skin aging and inflammatory skin diseases

TRPV1 is a non-selective channel receptor widely expressed in skin tissues, including keratinocytes, peripheral sensory nerve fibers and immune cells. It is activated by a variety of exogenous or endogenous inflammatory mediators, triggering neuropeptide release and neurogenic inflammatory response. Previous studies have shown that TRPV1 is closely related to the occurrence and/or development of skin aging and various chronic inflammatory skin diseases, such as psoriasis, atopic dermatitis, rosacea, herpes zoster, allergic contact dermatitis and prurigo nodularis. This review summarizes the structure of the TRPV1 channel and discusses the expression of TRPV1 in the skin as well as its role of TRPV1 in skin aging and inflammatory skin diseases.

Presence of TRPV3 in macrophage lysosomes helps in skin wound healing against bacterial infection

Transient Receptor Potential Vanilloid subtype 3 (TRPV3) is a non-selective cation channel that is known to be activated by physiological temperature and endogenous ligands. Involvement of TRPV3 in different skin functions has been reported. In this work, we demonstrate that activation of TRPV3 by FPP, an endogenous ligand enhances skin wound healing and bacterial clearance there. We report for the first time that TRPV3 is endogenously expressed in macrophages and activation of TRPV3 results in efficient bacterial clearance. At the subcellular level, TRPV3 is present in the lysosome and also in the nucleolus. We demonstrate that pharmacological modulation of TRPV3 protects lysosomal functions at hyperthermic shock conditions. The localization of TRPV3 at the nucleolus is specific, more in case of LPS-treatment and dynamic with respect to the cell signalling. We demonstrate that at certain conditions, the nucleolar localization of TRPV3 is correlated with the presence of TRPV3 at the lysosome and with the cellular stress in general. We propose that TRPV3 act as a lysosomal regulator and sensor for cellular stress. These findings may have broad implications in understanding the cellular stress and TRPV3-induced channelopathies and may have clinical relevance to skin infection treatment.

Role of Transient Receptor Potential Vanilloid 1 in Sonic Hedgehog-Dependent Taste Bud Differentiation

Taste bud cell differentiation is extremely important for taste sensation. Immature taste bud cells cannot function during taste perception transmission to the nerve. In this study, we investigated whether hedgehog signaling affected taste bud cell differentiation and whether transient receptor potential vanilloid 1 (TRPV1) played a key role in dry mouth. The induction of dry mouth due to salivary gland resection (SGR) was confirmed on the basis of reduced salivation and disrupted fungiform papillae. The expression of keratin 8 (K8) of taste bud cells, neurofilament (NF), sonic hedgehog (Shh), and glioma-associated oncogene homolog 1 (Gli1) around taste bud cells was downregulated; however, the expression of TRPV1, P2X purinoceptor 3 (P2X3), and hematopoietic stem cell factor (c-Kit) was upregulated at the NF ends in the dry mouth group. To investigate the effect of TRPV1 defect on dry mouth, we induced dry mouth in the TRPV-/- group. The K8, NF, and P2X3 expression patterns were the same in the TRPV1 wild-type and TRPV1-/- dry mouth groups. However, Shh and c-Kit expression decreased regardless of dry mouth in the case of TRPV1 deficiency. These results indicated that TRPV1 positively regulated proliferation during taste bud cell injury by blocking the Shh/Gli1 pathway. In addition, not only cell proliferation but also differentiation of taste bud cells could not be regulated under TRPV1-deficiency conditions. Thus, TRPV1 positively regulates taste bud cell innervation and differentiation; this finding could be valuable in the clinical treatment of dry mouth-related taste dysfunction.

Cannabinoid Compounds as a Pharmacotherapeutic Option for the Treatment of Non-Cancer Skin Diseases

The endocannabinoid system has been shown to be involved in various skin functions, such as melanogenesis and the maintenance of redox balance in skin cells exposed to UV radiation, as well as barrier functions, sebaceous gland activity, wound healing and the skin's immune response. In addition to the potential use of cannabinoids in the treatment and prevention of skin cancer, cannabinoid compounds and derivatives are of interest as potential systemic and topical applications for the treatment of various inflammatory, fibrotic and pruritic skin conditions. In this context, cannabinoid compounds have been successfully tested as a therapeutic option for the treatment of androgenetic alopecia, atopic and seborrhoeic dermatitis, dermatomyositis, asteatotic and atopic eczema, uraemic pruritis, scalp psoriasis, systemic sclerosis and venous leg ulcers. This review provides an insight into the current literature on cannabinoid compounds as potential medicines for the treatment of skin diseases.

TRPV4 Activation Increases the Expression of CD207 (Langerin) of Monocyte-Derived Langerhans Cells without Affecting their Maturation

Langerhans cells (LCs) are the sole professional antigen-presenting cell normally found in the human epidermal compartment. Research into their physiological role is hindered by the fact that they are invariably activated during isolation from the skin. To overcome this challenge, we turned to a monocyte-derived LC (moLC) model, which we characterized with RNA sequencing, and compared the transcriptome of moLCs with that of donor-matched immature dendritic cells. We found that moLCs express markers characteristic of LC2 cells as well as TRPV4. TRPV4 is especially important in the skin because it has been linked to the conservation of the skin barrier, immunological responses, as well as acute and chronic itch, but we know little about its function on LCs. Our results show that TRPV4 activation increased the expression of Langerin and led to increased intracellular calcium concentration in moLCs. Regarding the functionality of moLCs, we found that TRPV4 agonism had a mitigating effect on their inflammatory responses because it decreased their cytokine production and T-cell activating capability. Because TRPV4 has emerged as a potential therapeutic target in dermatological conditions, it is important to highlight LCs as, to our knowledge, a previously unreported target of these therapies.

Mechanisms of rosacea pathogenesis. A phenotypic approach to therapeutic tactics

Rosacea is a widespread disease worldwide, affecting 5.5% of the human population and accompanied by a significant deterioration in the patient's quality of life. Currently, there are two classifications of rosacea, the first of which is based on a subtype approach (erythematous-telangiectatic, papulo-pustular, phimatous and ophthalmological subtypes), or on an individual analysis of the presented phenotype of rosacea. New data on the pathophysiology of rosacea have emerged, which show that genetic factors and environmental components can cause the initiation and exacerbation of rosacea due to a violation of the regulation of the innate and adaptive immune system. In addition, trigger factors can directly interact with the cutaneous nervous system and, with the help of neurovascular and neuroimmune active neuropeptides, lead to the manifestation of rosacea foci. The main mechanisms of rosacea pathogenesis are currently: activation of the immune system, disorders of neuro-immune regulation, genetic predisposition. New pathogenetic mechanisms of rosacea make it possible to continue the diagnostic search and therapeutic approaches with the personalization of management tactics for each patient, depending on the prevalence of clinical features of the course of the disease. It is necessary to evaluate the advantages and disadvantages of subtypical and phenotypic approaches to rosacea classification and choose the most optimal one. The article presents arguments on this issue, and also suggests assessing the need to switch to a new classification in order to improve the effectiveness of therapy and improve the quality of life of patients.

The temperature-sensitive receptors TRPV4 and TRPM8 have important roles in the pruritus of rosacea

BACKGROUND

Certain sensations are the secondary phenotypes of rosacea and affect patients' quality of life. Transient receptor potential (TRP) channels may be involved in its occurrence. However, there is a lack of research independently discussing itch in rosacea.

OBJECTIVES

Our study aimed to investigate risk factors for pruritus in rosacea patients and to discover the molecular mechanism of pruritus.

METHODS

A binary logistic regression model was used to identify significant variables affecting pruritus in 782 rosacea patients. The LL-37 was injected intradermally into the face of mice to establish the animal model. qRT-PCR, immunohistochemistry and immunofluorescence were used to analyse the expression differences in pruritus-related molecules in mouse skin and the corresponding trigeminal ganglion (TG) between pruritus and nonpruritus groups.

RESULTS

The incidence of pruritus in rosacea was 42.46%, and the incidence of other symptoms increased with pruritus. Temperature effects were prominently related to the itch sensation of rosacea. Intradermal injection of LL-37 not only caused rosacea-like facial lesions but also induced a behavioural pattern indicative of pruritus. Increased expression of the temperature-sensitive receptors TRPV4 and TRPM8 was found in pruritic mouse skin and TG and human skin samples.

CONCLUSIONS

In rosacea patients, pruritus occurs frequently along with burning, flushing and sensitivity, most likely due to changes in temperature. The temperature-sensitive receptors TRPV4 and TRPM8 are both involved in the mechanism of pruritus in rosacea.

Current research and clinical trends in rosacea pathogenesis

Background

Rosacea is a common and complex chronic inflammatory skin disorder, the pathophysiology and etiology of which remain unclear. Recently, significant new insights into rosacea pathogenesis have enriched and reshaped our understanding of the disorder. A systematic analysis based on current studies will facilitate further research on rosacea pathogenesis.

Objective

To establish an international core outcome and knowledge system of rosacea pathogenesis and develop a challenge, trend and hot spot analysis set for research and clinical studies on rosacea using bibliometric analysis and data mining.

Methods

A search of the WoS, and PubMed, MEDLINE, Embase and Cochrane collaboration databases was conducted to perform visual bibliometric and data analysis.

Results

A total of 2,654 studies were used for the visualization and 302 of the 6,769 outcomes for data analysis. It reveals an increased trend line in the field of rosacea, in which its fast-growing pathogenesis attracted attention closely related to risk, comorbidity and therapeutic strategies. The rosacea pathogenesis has undergone the great development on immunology, microorganisms, genes, skin barriers and neurogenetics. The major of studies have focused on immune and microorganisms. And keyword visualization and data analyses demonstrated the cross-talk between cells or each aspect of pathogenesis, such as gene-gene or gene-environment interactions, and neurological mechanisms associated with the rosacea phenotype warrant further research.

Limitations

Inherent limitations of bibliometrics; and reliance on research and retrospective studies.

Conclusions

The understanding of rosacea's pathogenesis has been significantly enhanced with the improved technology and multidisciplinary integration, but high-quality, strong evidence in favor of genomic and neurogenic requires further research combined with a better understanding of risks and comorbidities to guide clinical practice.

TRPV1 in chronic pruritus and pain: Soft modulation as a therapeutic strategy

Chronic pain and pruritus are highly disabling pathologies that still lack appropriate therapeutic intervention. At cellular level the transduction and transmission of pain and pruritogenic signals are closely intertwined, negatively modulating each other. The molecular and cellular pathways involved are multifactorial and complex, including peripheral and central components. Peripherally, pain and itch are produced by subpopulations of specialized nociceptors that recognize and transduce algesic and pruritogenic signals. Although still under intense investigation, cumulative evidence is pointing to the thermosensory channel TRPV1 as a hub for a large number of pro-algesic and itchy agents. TRPV1 appears metabolically coupled to most neural receptors that recognize algesic and pruritic molecules. Thus, targeting TRPV1 function appears as a valuable and reasonable therapeutic strategy. In support of this tenet, capsaicin, a desensitizing TRPV1 agonist, has been shown to exhibit clinically relevant analgesic, anti-inflammatory, and anti-pruritic activities. However, potent TRPV1 antagonists have been questioned due to an hyperthermic secondary effect that prevented their clinical development. Thus, softer strategies directed to modulate peripheral TRPV1 function appear warranted to alleviate chronic pain and itch. In this regard, soft, deactivatable TRPV1 antagonists for topical or local application appear as an innovative approach for improving the distressing painful and itchy symptoms of patients suffering chronic pain or pruritus. Here, we review the data on these compounds and propose that this strategy could be used to target other peripheral therapeutic targets.

Association between frontal fibrosing Alopecia and Rosacea: Results from clinical observational studies and gene expression profiles

Background

In recent years, frontal fibrosing alopecia (FFA), a type of scarring alopecia, has attracted increasing attention. Several studies have reported the frequent occurrence of rosacea in FFA; however, the association between FFA and rosacea and the underlying pathogenesis have not been thoroughly clarified. Thus, this study aimed to quantify these relationships and investigate their shared molecular mechanisms.

Methods

We evaluated the association between FFA and rosacea by analyzing clinical data from nine observational studies. We then analyzed the gene expression profiles of FFA and rosacea. First, differential expression analysis and weighted gene co-expression network analysis were used to identify the common differentially expressed genes (DEGs). Later, we conducted a functional enrichment analysis and protein-protein interaction network and used seven algorithms to identify hub genes. Then, we performed a correlation analysis between the hub genes and the gene set variation analysis scores of common pathways in the gene set enrichment analysis (GSEA). The results were validated using different datasets. Finally, transcription factors were predicted and verified, and CIBERSORT and single-sample GSEA were used to estimate the infiltrating immune cells.

Results

Patients with FFA had significantly higher odds for rosacea (pooled odds ratio [OR], 2.46; 95% confidence interval [CI], 1.78–3.40), and the pooled prevalence of rosacea in patients with FFA was 23% (95% CI, 14–23%). Furthermore, we identified 115 co-DEGs and 13 hub genes (CCR5, CCL19, CD2, CD38, CD83, CXCL8, CXCL9, CXCL10, CXCL11, CXCR4, IRF1, IRF8, and PTPRC). Seven pathways showed a high correlation with these hub genes. In addition, one TF, STAT1, was highly expressed in both diseases, and the results of the immune infiltration analysis indicated the importance of M1 macrophages and effector memory CD8+ T cells.

Conclusion

This study contributes to the understanding of the relationship between FFA and rosacea, and based on the hub genes, we reveal the potential pathologies shared by the two diseases. This finding provides new insights of underlying molecular mechanisms and it may inspire future research on this comorbidity.

Structural mechanism of TRPV3 channel inhibition by the anesthetic dyclonine

Skin diseases are common human illnesses that occur in all cultures, at all ages, and affect between 30% and 70% of individuals globally. TRPV3 is a cation-permeable TRP channel predominantly expressed in skin keratinocytes, implicated in cutaneous sensation and associated with numerous skin diseases. TRPV3 is inhibited by the local anesthetic dyclonine, traditionally used for topical applications to relieve pain and itch. However, the structural basis of TRPV3 inhibition by dyclonine has remained elusive. Here we present a cryo-EM structure of a TRPV3-dyclonine complex that reveals binding of the inhibitor in the portals which connect the membrane environment surrounding the channel to the central cavity of the channel pore. We propose a mechanism of TRPV3 inhibition in which dyclonine molecules stick out into the channel pore, creating a barrier for ion conductance. The allosteric binding site of dyclonine can serve as a template for the design of new TRPV3-targeting drugs.

TRPV2: A Key Player in Myelination Disorders of the Central Nervous System

Transient potential receptor vanilloid 2 (TRPV2) is widely expressed through the nervous system and specifically found in neuronal subpopulations and some glial cells. TRPV2 is known to be sensitized by methionine oxidation, which results from inflammation. Here we aim to characterize the expression and regulation of TRPV2 in myelination pathologies, such as hypomyelination and demyelination. We validated the interaction between TRPV2 and its putative interactor Opalin, an oligodendrocyte marker, in mixed glial cultures under pro- and anti-inflammatory conditions. Then, we characterized TRPV2 time-course expression in experimental animal models of hypomyelination (jimpy mice) and de-/remyelination (cuprizone intoxication and experimental autoimmune encephalomyelitis (EAE)). TRPV2 showed upregulation associated with remyelination, inflammation in cuprizone and EAE models, and downregulation in hypomyelinated jimpy mice. TRPV2 expression was altered in human samples of multiple sclerosis (MS) patients. Additionally, we analyzed the expression of methionine sulfoxide reductase A (MSRA), an enzyme that reduces oxidated methionines in TRPV2, which we found increased in inflammatory conditions. These results suggest that TRPV2 may be a key player in myelination in accordance with the recapitulation hypothesis, and that it may become an interesting clinical target in the treatment of demyelination disorders.

Roles of Epithelial and Mesenchymal TRP Channels in Mediating Inflammatory Fibrosis

The maintenance of normal vision is dependent on preserving corneal transparency. For this to occur, this tissue must remain avascular and its stromal architecture needs to be retained. Epithelial transparency is maintained provided the uppermost stratified layers of this tissue are composed of terminally differentiated non-keratinizing cells. In addition, it is essential that the underlying stromal connective tissue remains avascular and scar-free. Keratocytes are the source of fibroblasts that are interspersed within the collagenous framework and the extracellular matrix. In addition, there are sensory nerve fibers whose lineage is possibly either neural crest or mesenchymal. Corneal wound healing studies have been undertaken to delineate the underlying pathogenic responses that result in the development of opacification following chemical injury. An alkali burn is one type of injury that can result in severe and long- lasting losses in ocular transparency. During the subsequent wound healing process, numerous different proinflammatory cytokines and proteolytic enzymes undergo upregulation. Such increases in their expression levels induce maladaptive expression of sustained stromal inflammatory fibrosis, neovascularization, and losses in the smooth optical properties of the corneal outer surface. It is becoming apparent that different transient receptor potential channel (TRP) isoforms are important players in mediating these different events underlying the wound healing process since injury upregulates both their expression levels and functional involvement. In this review, we focus on the involvement of TRPV1, TRPA1 and TRPV4 in mediating some of the responses that underlie the control of anterior ocular tissue homeostasis under normal and pathological conditions. They are expressed on both different cell types throughout this tissue and also on corneal sensory nerve endings. Their roles have been extensively studied as sensors and transducers of environmental stimuli resulting from exposure to intrinsic modulators and extrinsic ligands. These triggers include alteration of the ambient temperature and mechanical stress, etc., that can induce pathophysiological responses underlying losses in tissue transparency activated by wound healing in mice losses in tissue transparency. In this article, experimental findings are reviewed about the role of injury-induced TRP channel activation in mediating inflammatory fibrotic responses during wound healing in mice.

Rosacea and Dry Eye Disease

Ocular rosacea is a chronic potentially sight-threatening inflammatory condition, which can occur in approximately 20% of patients without skin involvement. However, an accurate diagnosis of ocular rosacea has not been defined yet due to its rather nonspecific symptoms and clinical findings. Therefore, this article updates the current recommendations for diagnosis and treatment of ocular rosacea and the previously published consensus recommendations from the ROSCO expert panel on the management of rosacea.

The impact of clinical nutrition on inflammatory skin diseases

The influence of nutrition on the pathophysiology and clinical severity of inflammatory facial dermatoses such as acne, rosacea, seborrheic dermatitis, and perioral dermatitis has been controversially discussed for years. As part of a modern treatment approach, clinicians should provide patients with information on how their choice of diet might impact their dermatologic diagnosis and could potentially enhance therapeutic outcome. Recently, the concept of a gut-skin axis has gained momentum in the understanding of inflammatory dermatoses, with nutrition considered a contributing factor in this context. For example, gastrointestinal symptoms in rosacea patients may indicate a dysbiosis of the gut microbiome, treatment of which may also improve severity of the skin disease. New research efforts were recently made for acne patients addressing the clinical effects of omega-3 fatty acids and probiotics. In contrast, due to the limited data available, no comparable specific dietary recommendations can yet be made for seborrheic or perioral dermatitis. However, there are promising signs that clinical nutrition and dermatology will be more extensively interlinked in the future, both clinically and scientifically.

The Effect of Capsaicin on Neuroinflammatory Mediators of Rosacea

Background

Rosacea is a chronic inflammatory skin disease with a pathophysiological mechanism that remains unclear. Recently, dysregulation of the sensory nerve system has been implicated in the development of this condition.

Objective

This study aimed to investigate the effect of capsaicin on neuroinflammatory mediators in rosacea. In addition, this study aimed to evaluate the attenuating effects of capsazepine, a transient receptor potential vanilloid type 1 (TRPV1) antagonist.

Methods

We obtained skin tissue from both rosacea patients and normal individuals for an in vivo study. In addition, normal human epidermal keratinocytes (NHEKs) were cultured, and treated with capsaicin and capsazepine for an in vitro study. Quantitative changes in neuroinflammatory mediators were evaluated by semi-quantitative reverse transcription-polymerase chain reaction (PCR), real-time PCR, enzyme-linked immunosorbent assay, and immunofluorescence staining.

Results

The data showed the increase of TRPV1, TRPV4, cathelicidin (LL37) and tumor necrosis factor-α (TNF-α) in skin tissue by real-time PCR. In addition, the data showed that cathelicidin (LL37), kallikrein-5 (KLK-5), TNF-α, vascular endothelial growth factor (VEGF), interleukin (IL)-1α, IL-1β, IL-8, and protease-activated receptor 2 (PAR2) increased in capsaicin-treated NHEKs. Capsazepine attenuated the expression of TRPV1 and other mediators, except for IL-8, in capsaicin-treated NHEKs.

Conclusion

We confirmed that TRPV1, TRPV4, cathelicidin (LL37) and TNF-α are increased in rosacea skin, and that capsaicin is associated with increase of neuroinflammatory mediators such as LL37, KLK-5, TNF-α, VEGF, IL-1α, IL-1β, IL-8, and PAR2. Modulators or inhibitors of neuroinflammatory mediators including TRPV1 could be potential therapeutic option in the treatment of patients with rosacea.

Rosacea and Diet: What is New in 2021?

OBJECTIVE

Rosacea is a common inflammatory cutaneous condition with a complex yet unknown etiopathogenesis. Diet and certain food items are known to trigger or worsen rosacea symptoms, but conflicting and often inconsistent advice is given to patients regarding this link. We provide an up-to-date literature review on the relationship between rosacea and diet.

METHODS

Using the keywords "alcohol," "diet," "flushing," "food," "inflammation," "rosacea," "skin-gut axis" and "spice" we systemically searched the databases PubMed, MEDLINE and EMBASE for English-language articles in July 2020.

RESULTS

The most frequently reported triggers implicated in rosacea include alcohol, spicy food, cinnamaldehyde-containing foods (e.g., tomatoes, citrus fruits, chocolate), hot drinks, and histamine-rich foods (e.g., aged cheese, wine, processed meats). Some food items appear to play a protective role, such as omega-3, which appears to protect against ocular rosacea. The relationship between certain food items and the subtype of rosacea is varied, with inconsistent results shown in the few studies that examined this. As an example, alcohol worsens flushing and fatty food triggers both erythematotelangiectatatic and phymatous rosacea in susceptible individuals.

CONCLUSION

While several food types appear to be associated with exacerbation of rosacea, there are no recommendations that can be applied to all patients. Further studies are needed to examine the exact link between diet and rosacea subtypes.

Increased Frequency of Circulating Classical Monocytes in Patients with Rosacea

Purpose

Monocyte subsets, including classical, intermediate and non-classical monocytes, are involved in the pathogenesis of inflammatory or autoimmune diseases. The pathogenic role of monocytes in the peripheral blood mononuclear cells (PBMCs) of patients with rosacea remains unclear. This study aimed to assess frequencies of monocyte subsets in PBMCs from rosacea patients before and after clinical treatment.

Patients and Methods

We applied flow cytometry to examine frequencies of monocyte subsets in 116 patients with rosacea, while patients with 26 systemic lupus erythematosus (SLE), 28 acne and 42 normal healthy subjects without skin problems (HC) were recruited as controls. Expression of C–C chemokine receptor 2 (CCR2) on monocytes and plasma levels of CC-chemokine ligand 2 (CCL2), high mobility group box-1 (HMGB-1), interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) were measured in HC and rosacea patients before and after treatment.

Results

The frequency of classical monocytes, but not intermediate or non-classical monocytes, was higher in rosacea as compared with HC, which decreased after treatment. Frequencies of monocyte subsets showed no gender difference, while increased with age in patients but not in HC. Frequencies of classical monocytes in patients with erythematotelangiectatic rosacea (ETR) and ETR-papulopustular rosacea (PPR) overlap were significantly higher than HC or patients with only PPR or phymatous rosacea (PhR). There was a significant higher expression of CCR2 in classical monocytes, with higher plasma levels of CCL2, HMGB-1, IL-1β and TNF-α in patients than in HC, which all significantly decreased after treatment.

Conclusion

Our data indicated a possible association between abnormal classical monocytes frequencies and rosacea.

Structural mechanism of TRPV3 channel inhibition by the plant-derived coumarin osthole

TRPV3, a representative of the vanilloid subfamily of TRP channels, is predominantly expressed in skin keratinocytes and has been implicated in cutaneous sensation and associated with numerous skin pathologies and cancers. TRPV3 is inhibited by the natural coumarin derivative osthole, an active ingredient of Cnidium monnieri, which has been used in traditional Chinese medicine for the treatment of a variety of human diseases. However, the structural basis of channel inhibition by osthole has remained elusive. Here we present cryo-EM structures of TRPV3 in complex with osthole, revealing two types of osthole binding sites in the transmembrane region of TRPV3 that coincide with the binding sites of agonist 2-APB. Osthole binding converts the channel pore into a previously unidentified conformation with a widely open selectivity filter and closed intracellular gate. Our structures provide insight into competitive inhibition of TRPV3 by osthole and can serve as a template for the design of osthole chemistry-inspired drugs targeting TRPV3-associated diseases.

Cannabinoids interaction with transient receptor potential family and implications in the treatment of rosacea

With the recent interest in medical marijuana, research into cannabinoids is regaining wider attention. Cannabinoids are collectively a group of active compounds that can be produced by animals (endocannabinoids), plants (phytocannabinoids), or synthetically. By acting on a number of different receptors like cannabinoids receptors and transient receptor potential ion channel family, cannabinoids are known to modulate cutaneous inflammation, pain, and itch. Rosacea is a highly prevalent disease and can be associated with a significant degree of morbidity associated with its symptom. Transient receptor potential ion channels are known to be triggered in rosacea and may underlie a portion of rosacea's pathophysiology. This article aims to detail the transient receptor potential channel pathways in rosacea and the known effects of cannabinoids on these pathways and further discussing the potential role of cannabinoids in treating rosacea.

Nonantibiotic Properties of Tetracyclines in Rosacea and Their Clinical Implications

Rosacea is one of the most common inflammatory skin diseases in the United States, with a complex pathophysiology. One of the major components of the pathophysiology of rosacea is an abnormal immune detection and response to stimuli. Tetracyclines and their derivatives, including minocycline and doxycycline, have anti-inflammatory properties independent of their antibacterial activity that correlate with certain aspects of the pathophysiology, and these drugs are often used by dermatologists to treat rosacea. Biological actions of tetracyclines correlating with rosacea include anti-inflammatory and antioxidative activities, inhibitory effects on angiogenesis, and proteolysis. The objective of this review is to re-establish the current understanding of tetracyclines and their mechanism of action as they relate to the pathophysiology and treatment of rosacea for clinicians. This includes reviewing the inflammatory aspects of rosacea that correlate with the known nonantibiotic properties of tetracyclines and providing the most up-to-date clinical evidence supporting the use of tetracyclines to treat rosacea. Given the evolving and multifactorial nature of pathophysiology, this review offers clinicians a unified picture that includes research on the links between rosacea pathophysiology and clinical presentation, the nonantibiotic properties of tetracyclines that relate to pathophysiologic pathways in rosacea, and the potential for clinical application of tetracyclines in rosacea therapy.

Usage of Synthetic Peptides in Cosmetics for Sensitive Skin

Sensitive skin is characterized by symptoms of discomfort when exposed to environmental factors. Peptides are used in cosmetics for sensitive skin and stand out as active ingredients for their ability to interact with skin cells by multiple mechanisms, high potency at low dosage and the ability to penetrate the stratum corneum. This study aimed to analyze the composition of 88 facial cosmetics for sensitive skin from multinational brands regarding usage of peptides, reviewing their synthetic pathways and the scientific evidence that supports their efficacy. Peptides were found in 17% of the products analyzed, namely: acetyl dipeptide-1 cetyl ester, palmitoyl tripeptide-8, acetyl tetrapeptide-15, palmitoyl tripeptide-5, acetyl hexapeptide-49, palmitoyl tetrapeptide-7 and palmitoyl oligopeptide. Three out of seven peptides have a neurotransmitter-inhibiting mechanism of action, while another three are signal peptides. Only five peptides present evidence supporting their use in sensitive skin, with only one clinical study including volunteers having this condition. Noteworthy, the available data is mostly found in patents and supplier brochures, and not in randomized placebo-controlled studies. Peptides are useful active ingredients in cosmetics for sensitive skin. Knowing their efficacy and synthetic pathways provides meaningful insight for the development of new and more effective ingredients.

Efficacy and safety of non-insulated fractional microneedle radiofrequency for treating difficult-to-treat rosacea: a 48-week, prospective, observational study

Rosacea is a common chronic facial inflammatory skin disease. However, treatment for "difficult-to-treat rosacea" cases has not been established. This 48-week, prospective, observational study analyzed patients who underwent three non-insulated fractional microneedle radiofrequency (NFMRF) sessions at 2-month intervals. Therapy efficacy, epidermal barrier function, and side effects were evaluated. 34 subjects completed the trial. NFMRF resulted in CEA score reduction from 2.65 ± 0.59 to 1.56 ± 0.50 (P < 0.001) and mean DLQI reduction from 16.70 ± 3.55 to 10.48 ± 2.92 (P < 0.001). The successes of CEA (44.12 vs. 2.94%), IGA (91.67 vs. 25.00%), and flushing (58.82 vs. 26.47%) were observed. Among 34 patients, 22 reported "excellent" or "good" improvement and 30 were "very" or "relatively" satisfied. Skin barrier results revealed that hemoglobin content significantly decreased from 376.47 ± 71.29 at visit 0 to 161.32 ± 52.86 at visit 3. 2 of 30 patients followed-up at 6 months had a relapse at 18 and 20 weeks, respectively. No serious side effects were observed. NFMRF alone results in visible improvement and has great efficacy for difficult-to-treat rosacea without compromising patient safety or damaging the skin barrier.