A positive feedback loop between mTORC1 and cathelicidin promotes skin inflammation in rosacea

Antimicrobial Peptide Signaling in Skin Diseases

Antimicrobial peptides (AMPs) are important innate immune molecules at microbe-host interfaces. The biophysical properties of AMPs that facilitate direct killing of microbes have been extensively reviewed. In this article, we focus on how AMPs perform immunomodulatory functions through interaction with host receptors on epithelial, immune, and neuronal cell types. We summarize the current knowledge of known AMPs in the skin, the receptors that respond to AMPs, and the downstream intracellular signaling pathways. In the end, we discuss the roles of AMP signaling systems in skin diseases.

Circadian rhythm disruption promotes M1 macrophages polarization exacerbating the inflammatory response in rosacea

To explore the role of macrophage polarization induced by circadian rhythm disorder (CRD) in the aggravated inflammatory response of rosacea. The rosacesis-like animal model was established by intradermal injection of Cathelicidin antimicrobial peptide LL-37 (LL37) into the back of mice. HE staining, Western blot and immunofluorescence detection were used to investigate the effect of circadian rhythm disorder on the expression of inflammatory factors and macrophage polarization in rosacea. Overexpression of Brain and Muscle ARNT-Like 1 (Oe-Bmal1) was transfected into HaCaT cells and M0 macrophages treated with LL37 in vitro to investigate the role of Muscle ARNT-Like 1 (Bmal1) on rosacea. In LL37-induced rosacea mice, circadian rhythm disruption (CRD) suppressed the expression of circadian clock proteins, including Bmal1, Circadian Locomotor Output Cycles Kaput (Clock), Period Circadian Protein 1 (Per1), Period Circadian Protein 2 (Per2), Nuclear Receptor Subfamily 1 Group D Member 1 (Rev-erbα), and Retinoic Acid Receptor-Related Orphan Receptor Alpha (RORα), and induced the polarization of macrophages in rosacea-like mice towards the M1 phenotype. Subsequently, the expression of inflammatory factors, including Tumor Necrosis Factor-alpha (TNF-α), Interleukin-6 (IL-6), and Interleukin-1 beta (IL-1β), was promoted, which aggravated the inflammatory response of skin lesions. Over-expression of Bmal1 significantly increased the expression level of clock proteins and inhibited the polarization of macrophages to M1 type, consequently inhibiting the expression of inflammatory factors in the cell model of rosacea. Circadian rhythm disorder may aggravate the inflammatory response of rosacea by affecting macrophage polarization, which indicates that paying attention to regular sleep and rest may be necessary for the treatment and management of rosacea.

Linoleic acid improves rosacea through repairing mitochondrial damage in keratinocytes

Rosacea, as a progressive and chronic inflammatory skin disease, lacks safe and effective treatment options. Our previous study reported metabolic disturbance in rosacea patients, containing abnormal lipid metabolism. Building on this, we characterized significant alterations in fatty acid metabolism among rosacea patients, with a notable increase in linoleic acid (LNA) levels. We further demonstrated that LNA prevents rosacea-like dermatitis in LL37-induced rosacea-like mouse model. Our evidence indicated that LNA hyperactivates PPARγ signaling in the epidermis, a phenomenon observed in both rosacea patients and mouse model. Inhibiting PPARγ rescued the effect of LNA in LL37-induced mice. Additionally, our in vivo and in vitro evidence strongly supported the presence of mitochondrial damage in the keratinocytes of rosacea. LNA stimulated PPARγ to reduce the reactive oxygen species production, increasing the generation of ATP and recovering mitochondrial membrane potential. Finally, through a prospective cohort study utilizing UK Biobank data and linkage disequilibrium score regression (LDSC) regression analysis, we further confirmed LNA levels are negatively related to the risk of rosacea, highlighting LNA as a promising therapeutic strategy for rosacea treatment.

Casticin reduces rosacea-related inflammation by inhibiting mast cell activation via Mas-related G protein-coupled receptor X2

BACKGROUND

Rosacea is a chronic inflammatory disease characterized by persistent erythema, papules, and pustules, mainly on the skin of the face. Rosacea is difficult to treat; therefore, identifying new treatments is crucial. Mas-related G protein-coupled receptor X2 (MRGPRX2)-mediated mast cell (MC) activation is essential in the pathogenesis of rosacea. Casticin has been shown to exert anti-inflammatory effects; however, it remains unclear whether it can inhibit MRGPRX2 in treating rosacea. This study determined the therapeutic efficacy of casticin against rosacea by inhibiting MRGPRX2-mediated MC activation.

METHODS

A mouse model of LL37-induced rosacea-like dermatitis was employed. The pathological changes were evaluated using hematoxylin and eosin (H&E) staining, and MCs and CD4+ T cells were observed. Inflammatory mediators were analyzed using ELISA. Mouse skin lesions were collected for transcriptomic sequencing. We used an MRGPRX2-mediated MC degranulation model to evaluate the inhibitory effects of casticin in vitro. Molecular docking analysis, molecular dynamics simulations, and surface plasmon resonance evaluated the binding between casticin and MRGPRX2.

RESULTS

Casticin attenuated the LL37-induced inflammatory phenotype and reactions in rosacea-like dermatitis. RNA-seq data showed that casticin inhibited MC activation in a mouse model of rosacea. Furthermore, casticin significantly reduced CD4 + T-cell infiltration. Moreover, casticin inhibited MC activation as an MRGPRX2 antagonist in vitro and in vivo by influencing the NF-κB signaling pathway.

CONCLUSION

Our study demonstrated that casticin exhibits therapeutic efficacy against rosacea by inhibiting MC activation via MRGPRX2.

Genetic Association Between Serum Calcium, Potassium Levels, and Rosacea: Evidence from a Two-Sample Mendelian Randomization Study

Purpose

Recent advances in epidemiological and genetic studies have provided some insights regarding the pathophysiology of rosacea, but the majority of its underlying mechanisms are still poorly understood. In particular, more data are needed to fully understand the role of micronutrients in rosacea development. This study aimed to explore the causality of associations between Calcium, Copper, Selenium, Zinc, Iron, Potassium and Magnesium with the risk of rosacea.

Patients and Methods

This was a two-sample Mendelian Randomization (MR) study that used data from genome-wide association studies (GWAS) on serum levels of selected micronutrients as exposure and rosacea as the outcome. The analysis primarily employed the Inverse Variance Weighted (IVW) method. Additional methods included weighted median, weighted mode, and MR-Egger regression. Sensitivity analysis included MR-Egger, MR-PRESSO, Cochran's Q, and leave-one-out methods. A total of 301 Instrumental Variables were selected for analysis.

Results

The genetic prediction indicated a statistically significant association between serum Calcium levels and higher rosacea risk (Odds Ratio (OR) = 2.27, 95% Confidence Interval (CI): 2.02-2.55, P < 0.001), further confirmed by all supplementary MR methods. Significant association was also found between serum Potassium levels and lower rosacea risk (OR = 0.36, 95% CI: 0.14-0.93, P = 0.0354), further confirmed by the weighted-median method. Sensitivity analyses showed that the results were robust and not driven by any single factor, with low probability of horizontal pleiotropy.

Conclusion

This study found an evidence of a causal association between genetically predicted serum levels of Calcium and Potassium with the risk of rosacea. The roles of these micronutrients should be further studied in rosacea, especially as a link to neurovascular dysregulation and oxidative stress.

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.

Adiponectin Prevents Skin Inflammation in Rosacea by Suppressing S6 Phosphorylation in Keratinocytes

Numerous recent evidence highlights epidemiological connections between rosacea and metabolic disorders. However, the precise path through which metabolic factors impact rosacea risk is still unclear. Therefore, this study aims to investigate the role of adiponectin, a crucial adipokine that regulates metabolic homeostasis, in the pathogenesis of rosacea. We elucidated a detrimental feedback loop between rosacea-like skin inflammation and decreased levels of skin adiponectin. To elaborate, rosacea lesional skin exhibits diminished adiponectin expression compared with nonlesional areas in the same patients. Induction of rosacea-like inflammation reduced adiponectin levels in the skin by generating inflammatory cytokines that suppress adiponectin production from subcutaneous adipocytes. Conversely, complete depletion of adiponectin exacerbated rosacea-like features in the mouse model. Mechanistically, adiponectin deficiency led to heightened S6 phosphorylation, a marker of the mTORC1 signaling pathway, in the epidermis. Adiponectin significantly inhibited S6 phosphorylation in cultured keratinocytes. Notably, replenishing adiponectin whole protein or topically applying an agonist for adiponectin receptor 1 successfully improved rosacea-like features in mice. This study contributes to understanding the role of adiponectin in skin inflammation associated with rosacea pathophysiology, suggesting that restoring adiponectin function in the skin could be a potential therapeutic strategy.

Naturally-occurring carnosic acid as a promising therapeutic agent for skin inflammation via targeting STAT1

BACKGROUND

Psoriasis and rosacea are prevalent chronic inflammatory skin disorders driven by aberrant interactions between skin-resident keratinocytes and immune cells. Natural products represent a largely untapped source of novel therapeutic agents for various diseases. This study aimed to identify an effective natural product for treating psoriasis and rosacea and to elucidate its underlying mechanism of action.

METHODS

Bioinformatics and network pharmacology approaches were employed to identify potential drug candidates for these conditions. Psoriasis-like and rosacea-like inflammation models were established in mice to assess the in vivo therapeutic effects of carnosic acid. In vitro experiments were performed to investigate the molecular mechanisms underlying carnosic acid's anti-inflammatory activity.

RESULTS

Through bioinformatics and network pharmacology, carnosic acid, a plant-derived phenolic diterpene, was identified as a promising candidate for these skin disorders. Functional assays demonstrated that carnosic acid effectively inhibited skin inflammation in both imiquimod-induced psoriasis and LL37-induced rosacea mouse models. Mechanistically, carnosic acid bound directly to STAT1, inhibiting its phosphorylation and subsequent transcriptional activation, which led to a reduction in the production of STAT1-mediated inflammatory factors in keratinocytes. Topical application of carnosic acid significantly alleviated clinical symptoms in both psoriasis and rosacea models.

CONCLUSION

These findings suggest that carnosic acid holds potential as a therapeutic agent for STAT1-mediated skin inflammation.

Unveiling the Molecular Mechanisms of Rosacea: Insights From Transcriptomics and In Vitro Experiments

BACKGROUND

Rosacea is a prevalent inflammatory skin condition, but its molecular mechanisms and treatment responses remain poorly understood.

AIMS

This study aims to investigate the molecular mechanisms underlying rosacea and explore drug response through transcriptomic analysis and in vitro experiments.

PATIENTS/METHODS

We performed high-throughput RNA sequencing to analyze gene expression patterns in rosacea patients. In vitro experiments, including RT-qPCR, Western blot, ELISA, scratch, and Transwell assays, were used to evaluate gene and protein expression and cell behavior in HaCaT cells under simulated rosacea conditions.

RESULTS

Transcriptomic analysis revealed significantly elevated expression of inflammatory-related genes in rosacea patients. In vitro, HaCaT cells exhibited enhanced proliferation and migration abilities, accompanied by increased expression of pro-inflammatory genes and proteins. Specifically, Toll-like receptor 2 (TLR2) and S100A9 proteins were upregulated, potentially promoting these processes.

CONCLUSIONS

Our study elucidates the molecular mechanisms of rosacea, highlighting the role of inflammatory pathways and altered cell behavior in the disease. TLR2 and S100A9 may contribute to disease progression, offering potential targets for future therapeutic strategies.

Ferulic Acid in the Treatment of Papulopustular Rosacea: A Randomized Controlled Study

BACKGROUND

Rosacea is a chronic inflammatory skin disease characterized by flushing, erythema, papules, and pustules on the central face. It affects patient appearance and is noted for its chronicity, recurrence, and resistance to treatment. Effective rosacea treatment requires repairing the skin barrier, reducing inflammation, and promoting vasoconstriction.

AIMS

This study aims to evaluate the efficacy of topical ferulic acid in treating papulopustular rosacea and its impact on skin barrier function.

METHODS

Sixty patients with mild to moderate papulopustular rosacea were selected from the Department of Dermatology at the Affiliated Hospital of Shandong Second Medical University between January 2023 and December 2023. Patients were randomly assigned to either a control group or an observation group, with 30 patients in each group. The observation group applied ferulic acid solution to the affected areas, while the control group used normal saline, both twice daily for 6 weeks. Both groups also received 0.1 g doxycycline hydrochloride tablets orally once daily. Skin lesions and skin barrier function were assessed using VISIA imaging and self-rating scales before and during treatment, and adverse reactions were recorded.

RESULTS

After 6 weeks, both skin lesion assessments and self-assessment scores improved significantly from baseline, with greater improvement in the observation group compared to the control group (p < 0.05). Indicators of skin barrier function and VISIA imaging results demonstrated the efficacy of ferulic acid in treating rosacea. The total effective rate was significantly higher in the observation group (80.00%) compared to the control group (63.33%) (p < 0.05). In the observation group, nine patients (30.00%) experienced a greasy sensation initially, one patient (3.33%) reported tingling and itching, and no serious adverse reactions were observed.

CONCLUSIONS

Ferulic acid is effective as an adjuvant treatment for papulopustular rosacea, significantly improving skin lesions and repairing skin barrier function with minimal adverse reactions.

Isosilybin A exhibits anti-inflammatory properties in rosacea by inhibiting MAPK pathway and M1 macrophage polarization

Rosacea is a chronic inflammatory skin disease, which is prone to flares and requires continuous management and treatment. However, long-term use of drugs can lead to additional adverse drug reactions. Based on the comorbid relationship between rosacea and Parkinson's disease, bioinformatics and network pharmacology analysis were used to identify a safer drug for rosacea. It has been demonstrated that ISA has an ameliorative impact on the symptoms of Parkinson's disease. The results demonstrated that ISA exhibited anti-inflammatory properties, including reducing erythema areas and inflammatory cell infiltration in rosacea-like mice models, and inhibiting the expression of inflammatory factors in cellular inflammation models. Furthermore, the anti-inflammatory effect of ISA was associated with inhibition of the Erk, p38 and NF-κB signaling pathways and inhibition of macrophage polarization to M1 type. In addition, molecular docking and drug affinity responsive target stability experiment results indicated that VEGFA and RELA were the direct targets of ISA in the treatment for rosacea. In conclusion, these results suggested that ISA may be a potential therapeutic agent for rosacea.

FA-PEG Modified ZIF(Mn) Nanoparticles Loaded with Baicalin for Imaging-Guided Treatment of Melanoma in Mice

Background

Melanoma is an aggressive skin tumor with limited therapeutic options due to rapid proliferation, early metastasis, and poor prognosis. Baicalin (BA), a natural flavonoid, shows promise in inducing ferroptosis and apoptosis but faces challenges of poor solubility and bioavailability. To address these issues, we developed a multifunctional drug delivery system: manganese-doped ZIF-8 nanoparticles (ZIF(Mn)) loaded with BA and modified with folic acid (FA) and polyethylene glycol (PEG). FA targets melanoma cells by exploiting folate receptor overexpression, while PEG enhances biocompatibility and systemic circulation. Manganese enables magnetic resonance (MR) imaging for real-time, non-invasive therapy monitoring.

Methods

BA-loaded ZIF(Mn)/FA-PEG nanoparticles were synthesized via a one-pot method, enabling drug encapsulation, Mn²+ incorporation, and surface modification. The nanoparticles were comprehensively characterized (particle size, Zeta potential, FTIR, and XRD). Cytotoxicity and cellular uptake were evaluated in B16-F10 melanoma cells, and in vivo experiments in C57BL/6J mice investigated MR imaging capability, antitumor efficacy, and biosafety.

Results

BA@ZIF(Mn)/FA-PEG nanoparticles demonstrated excellent stability, a BA loading capacity of 33.50 ± 0.04%, and pH-responsive release, with accelerated drug release under acidic tumor conditions. Mn²+ provided strong T1-weighted MR imaging contrast. Cellular and animal studies showed enhanced uptake, reduced premature drug release, and improved compatibility. Mechanistically, the nanoparticles induced significant ferroptosis and apoptosis in melanoma cells, leading to potent antitumor effects.

Conclusion

The BA@ZIF(Mn)/FA-PEG nanoplatform effectively integrates targeted delivery, imaging guidance, and dual ferroptosis-apoptosis induction, offering a promising strategy for improving melanoma treatment outcomes.

Effect of combined probiotics and doxycycline therapy on the gut-skin axis in rosacea

Rosacea is a chronic inflammatory skin condition marked by facial erythema, telangiectasia, and acne-like eruptions, affecting millions worldwide. While antibiotics remain a common treatment, prolonged use has significant adverse effects and can lead to antibiotic resistance. This study evaluated the impact of combined probiotics and doxycycline treatment on rosacea, emphasizing the gut-skin axis. Sixty rosacea patients were randomly assigned to the probiotic, placebo, or control groups. After a 2-week doxycycline treatment, participants underwent a 3-month intervention with either a placebo, probiotic, or no further treatment. Clinical outcomes were assessed at baseline and after the 14-week intervention. Our results showed that probiotic administration improved facial skin conditions, alleviated inflammation, and reduced facial skin microbiota diversity while enhancing gut microbiota heterogeneity. Multivariate analysis identified microbial markers distinguishing the probiotic group from the control and placebo groups, and some markers were associated with skin health parameters. After the probiotic intervention, some facial skin-associated taxa, such as Aquabacterium sp., UBA4096 sp. 1, UBA4096 sp. 2, and Yimella indica, decreased in abundance. Additionally, the fecal microbiota of the probiotic group was enriched in specific gut microbes, including Streptococcus parasanguinis, Erysipelatoclostridium ramosum, and Coprobacillus cateniformis, while showing a reduced abundance of Bacteroides vulgatus. These changes were associated with reduced facial sebum levels and a lower physician's global assessment score. Finally, fewer antibiotic resistance genes, particularly tetracycline resistance genes, were detected in the probiotic group compared with the control and placebo groups. Our study supports the existence of a gut-skin axis and the application of probiotics in managing rosacea.

IMPORTANCE

This research elucidates rosacea management with novel insights into probiotic use alongside doxycycline, showing dual benefits in symptom relief and inflammation reduction in patients. The study maps probiotic-induced shifts in gut and skin microbiota, underscoring microbial shifts correlating with skin health improvements. Crucially, it deciphers the gut-skin axis modulation by probiotics, proposing a method to curb antibiotic resistance in rosacea therapies. This study furnishes robust evidence for probiotics in rosacea, advancing our grasp of the gut-skin relationship.

Transcriptomic Analyses Predict Enhanced Metabolic Activity and Therapeutic Potential of mTOR Inhibitors in Acne-Prone Skin

Current acne therapies center on preventing new lesions in patients with acne. These therapies were historically found to be beneficial yet were chosen without knowledge of the specific changes in the skin that favor lesion development. A major challenge in developing new treatments is the incomplete understanding of nonlesional (NL), acne-prone skin's molecular characteristics. To address this, we compared RNA-sequencing data from NL skin of 49 patients with acne (denoted as NL acne [NLA]) with those from 19 healthy controls with no acne history. We found 77 differentially expressed genes in NLA (log fold change > 1; P < .05), including genes associated with innate immunity and epidermal barrier function. Notably, K RT 6C, K RT 16, S100A8, S100A9, and lactotransferrin were upregulated, and LCE4A, LCE6A, and CTSE were downregulated. Gene set enrichment analysis revealed that metabolic pathways were enriched in NLA skin, whereas keratinization was negatively enriched. To identify compounds that could shift the gene expression signature of NLA skin toward healthy control skin, we performed connectivity mapping with the Library of Integrated Network-Based Signatures. We identified 187 compounds, particularly mTOR inhibitors, that could potentially normalize the gene expression profile of acne-prone skin to that of healthy skin. Our findings indicate that NLA skin has distinct differences in epidermal differentiation, cellular metabolism, and innate immunity that may promote lesion formation and suggest that mTOR inhibitors could restore NLA skin toward a healthier state, potentially reversing the predisposition to lesion development.

Single-cell transcriptomics reveals aberrant skin-resident cell populations and identifies fibroblasts as a determinant in rosacea

Rosacea is a chronic inflammatory skin disorder, whose underlying cellular and molecular mechanisms remain obscure. Here, we generate a single-cell atlas of facial skin from female rosacea patients and healthy individuals. Among keratinocytes, a subpopulation characterized by IFNγ-mediated barrier function damage is found to be unique to rosacea lesions. Blocking IFNγ signaling alleviates rosacea-like phenotypes and skin barrier damage in mice. The papulopustular rosacea is featured by expansion of pro-inflammatory fibroblasts, Schwann, endothelial and macrophage/dendritic cells. The frequencies of type 1/17 and skin-resident memory T cells are increased, and vascular mural cells are characterized by activation of inflammatory pathways and impaired muscle contraction function in rosacea. Most importantly, fibroblasts are identified as the leading cell type producing pro-inflammatory and vasodilative signals in rosacea. Depletion of fibroblasts or knockdown of PTGDS, a gene specifically upregulated in fibroblasts, blocks rosacea development in mice. Our study provides a comprehensive understanding of the aberrant alterations of skin-resident cell populations and identifies fibroblasts as a key determinant in rosacea development.

Rapamycin Attenuates H2O2-Induced Oxidative Stress-Related Senescence in Human Skin Fibroblasts

BACKGROUND

Oxidative stress plays an important role in the skin aging process. Rapamycin has been shown to have anti-aging effects, but its role in oxidative senescence of skin cells remains unclear. The aim of this study was to explore the effect of rapamycin on oxidative stress-induced skin cell senescence and to illustrate the mechanism.

METHODS

Primary human skin fibroblasts (HSFs) were extracted and a model of H2O2-induced oxidative senescence was constructed, and the effects of rapamycin on their value-added and migratory capacities were detected by CCK-8 and scratch assays. SA-β-gal was utilized to detect senescence, oxidatively closely related factors were also assessed. Gene and protein expressions of senescence, oxidative, and autophagy were detected by western blotting and quantitative-PCR. The data were analyzed by one-way analysis of variance.

RESULTS

Rapamycin (0.1 nmol/L for 48 h) promoted the proliferative and migration of H2O2-treated HSFs (p < 0.05), decreased senescent phenotypes SA-β-gal staining and the expression of P53, and MMP-1 proteins, and increased the expression level of COL1A-1 (p < 0.001). Rapamycin also enhanced the activities of SOD and HO-1, and effectively removed intracellular ROS, MDA levels (p < 0.05), in addition, autophagy-related proteins and genes were significantly elevated after rapamycin pretreatment (p < 0.001). Rapamycin upregulated the autophagy pathway to exert its protective effects.

CONCLUSION

Our findings indicate that rapamycin shields HSFs from H2O2-induced oxidative damage, the mechanism is related to the reduction of intracellular peroxidation and upregulation of autophagy pathway. Therefore, rapamycin has the potential to be useful in the investigation and prevention of signs of aging and oxidative stress.

Cell-free adipose tissue extracts as a novel treatment for rosacea by downregulating TRPV1

Rosacea is a chronic inflammatory skin disease that typically affects the central facial area. Its main clinical symptoms include paroxysmal flushing, telangiectasia, and non-temporary erythema. Cell-free adipose tissue extracts (ATEs) are liquid components extracted from human adipose tissue that contain large amounts of growth factors. Despite the scar-reducing, anti-aging, and wound-healing effects of ATEs, the efficacy of ATEs in rosacea remains unknown. Therefore, the anti-rosacea effects of ATEs were investigated in human cathelicidin peptide (LL-37) induced rosacea mice and capsaicin (CAP)-stimulated HaCaT keratinocytes. In vitro, ATEs significantly reduced TRPV1 expression, intracellular calcium ions influx and the release of inflammatory factors (such as KLK5, IL-6, IL-8 and TNF-α) after intervening in CAP-stimulated cells. The in vivo results revealed that ATEs alleviated rosacea symptoms, such as erythema score, erythema area, transepidermal water loss, abnormal epidermal thickness, mast cell infiltration and telangiectasia upon downregulating TRPV1 and CD31 expression. Moreover, the up-regulated TRPV1 protein expression was also recovered by ATEs administration in vivo and in vitro. Meanwhile, ATEs demonstrated good biocompatibility. In summary, ATEs could be a potential therapeutic agent for rosacea by regulating inflammation and alleviating telangiectasia.

Signaling pathways and targeted therapy for rosacea

Rosacea is a chronic skin inflammatory disease with a global prevalence ranging from 1% to 20%. It is characterized by facial erythema, telangiectasia, papules, pustules, and ocular manifestations. Its pathogenesis involves a complex interplay of genetic, environmental, immune, microbial, and neurovascular factors. Recent studies have advanced our understanding of its molecular basis, focusing on toll-like receptor (TLR) 2 pathways, LL37 expression, mammalian target of rapamycin (mTOR) activation, interleukin (IL)-17 signaling, transient receptor potential vanilloid (TRPV) functions, and the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathways. LL37-associated signaling pathways, particularly involving TLR2 and mTORC1, are critical in the pathogenesis of rosacea. LL37 interacts with signaling molecules such as extracellular signal-regulated kinases 1 and 2 (ERK1/2), nuclear factor kappa B (NF-κB), inflammasomes, C-X-C motif chemokine ligand 8 (CXCL8), mas-related G-protein-coupled receptor X2 (MRGPRX2)-TRPV4, and vascular endothelial growth factor (VEGF). This interaction activates macrophages, neutrophils, mast cells, and vascular endothelial cells, leading to cytokine release including tumor necrosis factor-alpha (TNF-α), IL-6, IL-1β, C motif chemokine ligand (CCL) 5, CXCL9, and CXCL10. These processes contribute to immune response modulation, inflammation, and angiogenesis in rosacea pathophysiology. The IL-17 signaling pathway also plays a crucial role in rosacea, affecting angiogenesis and the production of inflammatory cytokines. In addition, recent insights into the JAK/STAT pathways have revealed their integral role in inflammatory and angiogenic mechanisms associated with rosacea. Rosacea treatment currently focuses on symptom management, with emerging insights into these molecular pathways providing more targeted and effective therapies. Biological agents targeting specific cytokines, IL-17 inhibitors, JAK inhibitors, and VEGF antagonists are promising for future rosacea therapy, aiming for enhanced efficacy and fewer side effects. This review provides a comprehensive overview of the current knowledge regarding signaling pathways in rosacea and potential targeted therapeutic strategies.

Protease-Activated Receptor 2 in inflammatory skin disease: current evidence and future perspectives

Protease-activated receptor-2 (PAR2) is a class-A G protein-coupled receptor (GPCR) activated by serine proteases and is expressed by multiple tissues, including the skin. PAR2 is involved in the skin inflammatory response, promoting Th2 inflammation, delaying skin barrier repair, and affecting the differentiation of keratinocytes. It also participates in the transmission of itch and pain sensations in the skin. Increasing evidence indicates that PAR2 plays an important role in the pathogenesis of inflammatory skin diseases such as acne vulgaris, rosacea, psoriasis, and atopic dermatitis. Additional focus will be placed on potential targeted therapies based on PAR2. The Goal of this review is to outline the emerging effects of PAR2 activation in inflammatory skin disease and highlight the promise of PAR2 modulators.

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.

S100A9 Exacerbates the Inflammation in Rosacea through Toll-Like Receptor 4/MyD88/NF-κB Signaling Pathway

Rosacea is a chronic inflammatory skin disorder characterized by immune response-dependent erythema and pustules. S100A9, a proinflammatory alarmin, has been associated with various inflammation-related diseases. However, the specific role of S100A9 in rosacea remains unexplored. Therefore, our objective was to unravel the role of S100A9 in the pathogenesis of rosacea and its underlying molecular mechanisms. In this study, we show that expression levels of S100A9 were elevated in both the lesions and serum of patients with papulopustular rosacea as well as in lesions of the LL37-induced rosacea-like mouse model. Moreover, the upregulation of S100A9 was correlated with clinical severity and levels of inflammatory cytokines. In addition, we demonstrated that S100A9 promoted the production of proinflammatory factors in HaCaT cells by activating toll-like receptor 4/MyD88/NF-κB signaling pathways. Notably, inhibition of S100A9 suppressed the progression of rosacea-like dermatitis and inflammatory responses in the LL37-induced rosacea-like mouse model through toll-like receptor 4/MyD88/NF-κB signaling pathways. In conclusion, this study illustrated that S100A9 participates in the pathogenesis of rosacea by upregulating toll-like receptor 4/MyD88/NF-κB signaling pathways, thereby promoting rosacea-associated skin inflammation. These results not only expand our understanding of the potential role of S100A9 in the development of rosacea but also offer greater insight toward targeted therapies.

Probiotics suppress LL37 generated rosacea-like skin inflammation by modulating the TLR2/MyD88/NF-κB signaling pathway

Rosacea, a chronic inflammatory dermatological condition, is characterized by facial erythema and pustules. Recent investigations have delved into the interplay between the gut microbiota and rosacea pathogenesis, unveiling promising avenues for therapeutic intervention. In this study, we screened and isolated strains Ligilactobacillus salivarius 23-006 and Lacticaseibacillus paracasei 23-008 from the feces of healthy volunteers and evaluated the intervention effects of probiotics on rosacea by constructing an LL37 induced rosacea-like mouse model. Our results showed that both L. salivarius 23-006 and L. paracasei 23-008 were probiotic strains with favourable properties. In specific, we observed that both L. salivarius 23-006 and L. paracasei 23-008 alleviated skin lesions, reduced skin inflammatory infiltrates, and decreased the expression of inflammatory factors in mice, with the combination of L. salivarius 23-006 and L. paracasei 23-008 having the most significant effect. Moreover, the combination of strains reduced the expression of cathelicidin LL37 and rosacea-associated factors by inhibiting the TLR2/MyD88/NF-κB pathway. The 16S rRNA analysis showed that the combination enhanced the intestinal barrier, restored intestinal microbiota homeostasis, and up-regulated the abundance of Lactobacillus while down-regulating the abundance of Coprococcus and Oscillospira. We also explored the effects of postbiotics of L. salivarius 23-006 and L. paracasei 23-008 on rosacea. While postbiotics could also ameliorate the rosacea-like phenotype in mice via the TLR2/MyD88/NF-κB pathway, the effects were not as pronounced as those observed with probiotic treatment. However, the postbiotics still enhanced the intestinal barrier, up-regulated the Lactobacillus abundance, and modulated the intestinal microbiota. In conclusion, our study revealed that L. salivarius 23-006 and L. paracasei 23-008 improved rosacea by regulating the TLR2/MyD88/NF-κB pathway and intestinal microbiota, providing a theoretical basis for the treatment of rosacea.

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.

Identification of prospective aging drug targets via Mendelian randomization analysis

Aging represents a multifaceted process culminating in the deterioration of biological functions. Despite the introduction of numerous anti-aging strategies, their therapeutic outcomes have often been less than optimal. Consequently, discovering new targets to mitigate aging effects is of critical importance. We applied Mendelian randomization (MR) to identify potential pharmacological targets against aging, drawing upon summary statistics from both the Decode and FinnGen cohorts, with further validation in an additional cohort. To address potential reverse causality, bidirectional MR analysis with Steiger filtering was utilized. Additionally, Bayesian co-localization and phenotype scanning were implemented to investigate previous associations between genetic variants and traits. Summary-data-based Mendelian randomization (SMR) analysis was conducted to assess the impact of genetic variants on aging via their effects on protein expression. Additionally, mediation analysis was orchestrated to uncover potential intermediaries in these associations. Finally, we probed the systemic implications of drug-target protein expression across diverse indications by MR-PheWas analysis. Utilizing a Bonferroni-corrected threshold, our MR examination identified 10 protein-aging associations. Within this cohort of proteins, MST1, LCT, GMPR2, PSMB4, ECM1, EFEMP1, and ISLR2 appear to exacerbate aging risks, while MAX, B3GNT8, and USP8 may exert protective influences. None of these proteins displayed reverse causality except EFEMP1. Bayesian co-localization inferred shared variants between aging and proteins such as B3GNT8 (rs11670143), ECM1 (rs61819393), and others listed. Mediator analysis pinpointed 1,5-anhydroglucitol as a partial intermediary in the influence LCT exhibits on telomere length. Circulating proteins play a pivotal role in influencing the aging process, making them promising candidates for therapeutic intervention. The implications of these proteins in aging warrant further investigation in future clinical research.

Targeting the STAT3/IL-36G signaling pathway can be a promising approach to treat rosacea

BACKGROUND

Rosacea is an inflammatory skin disorder characterized by the release of inflammatory mediators from keratinocytes, which are thought to play a crucial role in its pathogenesis. Despite an incidence of approximately 5.5%, rosacea is associated with a poor quality of life. However, as the pathogenesis of rosacea remains enigmatic, treatment options are limited.

OBJECTIVES

To investigate the pathogenesis of rosacea and explore new therapeutic strategies.

METHODS

Transcriptome data from rosacea patients combined with immunohistochemical staining were used to investigate the activation of STAT3 in rosacea. The role of STAT3 activation in rosacea was subsequently explored by inhibiting STAT3 activation both in vivo and in vitro. The key molecules downstream of STAT3 activation were identified through data analysis and experiments. Dual-luciferase assay and ChIP-qPCR analysis were used to validate the direct binding of STAT3 to the IL-36G promoter. DARTS, in combination with experimental screening, was employed to identify effective drugs targeting STAT3 for rosacea treatment.

RESULTS

STAT3 signaling was hyperactivated in rosacea and served as a promoter of the keratinocyte-driven inflammatory response. Mechanistically, activated STAT3 directly bind to the IL-36G promoter region to amplify downstream inflammatory signals by promoting IL-36G transcription, and treatment with a neutralizing antibody (α-IL36γ) could mitigate rosacea-like inflammation. Notably, a natural plant extract (pogostone), which can interact with STAT3 directly to inhibit its activation and affect the STAT3/IL36G signaling pathway, was screened as a promising topical medication for rosacea treatment.

CONCLUSIONS

Our study revealed a pivotal role for STAT3/IL36G signaling in the development of rosacea, suggesting that targeting this pathway might be a potential strategy for rosacea treatment.

Quercetin attenuates inflammation in rosacea by directly targeting p65 and ICAM-1

AIMS

Rosacea is an inflammatory skin disease with immune and vascular dysfunction. Although there are multiple treatment strategies for rosacea, the clinical outcomes are unsatisfactory.

MAIN METHODS

Combining transcriptome data and the Connectivity Map database quercetin was identified as a novel candidate for rosacea. Next, the therapeutic efficacy of quercetin was substantiated through proteomic analyses, in vivo experiments, and in vitro assays. Additionally, the utilization of DARTS, molecular docking and experimental verification revealed the therapeutic mechanisms of quercetin.

KEY FINDINGS

Treatment with quercetin resulted in the following effects: (i) it effectively ameliorated rosacea-like features by reducing immune infiltration and angiogenesis; (ii) it suppressed the expression of inflammatory mediators in HaCaT cells and HDMECs; (iii) it interacted with p65 and ICAM-1 directly, and this interaction resulted in the repression of NF-κB signal and ICAM-1 expression in rosacea.

SIGNIFICANCE

We show for the first time that quercetin interacted with p65 and ICAM-1 directly to alleviated inflammatory and vascular dysfunction, suggesting quercetin is a novel, promising therapeutic candidate for rosacea.

SERPINB3/B4 Is Increased in Psoriasis and Rosacea Lesions and Has Proinflammatory Effects in Mouse Models of these Diseases

Psoriasis and rosacea are both chronic inflammatory skin disorders resulted from aberrant keratinocyte-immune cell crosstalk, but the common molecular foundations for these 2 conditions are poorly understood. In this study, we reveal that both patients with psoriasis and those with rosacea as well as their mouse models have significantly elevated expressions of SERPINB3/B4 (members of serine protease inhibitor) in the lesional skin. Skin inflammation in mice that resembles both psoriasis and rosacea is prevented by SERPINB3/B4 deficiency. Mechanistically, we demonstrate that SERPINB3/B4 positively induces NF-κB signaling activation, thereby stimulating disease-characteristic inflammatory chemokines and cytokines production in keratinocytes and promoting the chemotaxis of CD4+ T cells. Our results suggest that in keratinocytes, SERPINB3/B4 may be involved in the pathogenesis of both psoriasis and rosacea by stimulating NF-κB signaling, and they indicate a possible treatment overlap between these 2 diseases.

Unveiling the Role of Endoplasmic Reticulum Stress Pathways in Canine Demodicosis

Canine demodicosis is a prevalent skin disease caused by overpopulation of a commensal species of Demodex mite, yet its precise cause remains unknown. Research suggests that T-cell exhaustion, increased immunosuppressive cytokines, induction of regulatory T cells and increased expression of immune checkpoint inhibitors may contribute to its pathogenesis. This study aimed to gain a deeper understanding of the molecular changes occurring in canine demodicosis using mass spectrometry and pathway enrichment analysis. The results indicate that endoplasmic reticulum stress promotes canine demodicosis through regulation of three linked signalling pathways: eIF2, mTOR, and eIF4 and p70S6K. These pathways are involved in the modulation of Toll-like receptors, most notably TLR2, and have been shown to play a role in the pathogenesis of skin diseases in both dogs and humans. Moreover, these pathways are also implicated in the promotion of immunosuppressive M2 phenotype macrophages. Immunohistochemical analysis, utilising common markers of dendritic cells and macrophages, verified the presence of M2 macrophages in canine demodicosis. The proteomic analysis also identified immunological disease, organismal injury and abnormalities and inflammatory response as the most significant underlying diseases and disorders associated with canine demodicosis. This study demonstrates that Demodex mites, through ER stress, unfolded protein response and M2 macrophages contribute to an immunosuppressive microenvironment, thereby assisting in their proliferation.

Oroxylin A suppress LL-37 generated rosacea-like skin inflammation through the modulation of SIRT3-SOD2-NF-κB signaling pathway

Rosacea is a long-term inflammatory skin disease associated with the dysfunction of vascular and immunological systems. Treatment options for rosacea are difficult to implement. Oroxylin A(OA), a traditional Chinese medicine, has anti-inflammation effects in a variety of inflammatory diseases. However, it is not known that whether OA exerts protective effects against LL-37-induced rosacea. In this study, bioinformatics analyses showed that the mechanisms of rosacea and the pharmacological targets of OA were highly overlapped. Subsequently, it was shown that the administration of OA resulted in a notable amelioration of rosacea-like skin lesions, as evidenced by a reduction in immune cell infiltration, modulation of cytokine production, and inhibition of angiogenesis. Plus, it was shown that OA effectively suppressed the generation of ROS generated by LL-37, as well as the subsequent activation of NF-κB signaling pathway. To explore further, we found that OA inhibited LL-37-induced ROS production via SIRT3-SOD2 signaling pathway in keratinocytes. Based on the aforementioned evidence, it can be inferred that OA exhibits a mitigating effect on the inflammatory response in rosacea by modulating the SIRT3-SOD2-NF-κB signaling pathway.

Associations of serum gamma-linolenic acid levels with erythema severity and anxiety/depression status in patients with rosacea

BACKGROUND

The development of rosacea is suggested to be closely associated with lipid metabolism, inflammation, and anxiety/depression. Gamma linolenic acid (GLA) is a key factor participating in lipid metabolism, which is also confirmed to regulate the inflammatory response. However, the associations of serum GLA levels with rosacea severity and psychological status still remain unclear.

OBJECTIVE AND LIMITATIONS OF THE STUDY

The present study aimed to investigate the associations of gamma linolenic acid (GLA), a key factor participating in lipid metabolism and the inflammatory response, with rosacea severity and psychological status. The present study still had some limitations. First, this study is a cross-sectional study and does not provide longitudinal evidence about the relationship between GLA and rosacea; Second, the cohort in this study is also relatively small, and a larger cohort is needed in further investigation to reveal the potential role of lipid metabolism in the pathogenesis of rosacea.

METHODS

A total of 62 rosacea patients were consecutively recruited. Patient's Self-Assessment (PSA) scale and Clinician Erythema Assessment (CEA) as well as 7-item Generalized Anxiety Disorder (GAD-7) and 9-item Patient Health Questionnaire (PHQ-9) were conducted to evaluate the degree of erythema severity and anxiety/depression, respectively. Serum GLA levels were determined by gas chromatography mass.

RESULTS

Lower levels of serum GLA in rosacea patients were observed (p<0.001), and subgroup analysis revealed that patients with higher-level GLA had lower scores of PSA, CEA, GAD-7 and PHQ-9. Moreover, Spearman correlation analysis uncovered that serum GLA levels were negatively associated with PSA, CEA, GAD-7 as well and PHQ-9 scores, respectively. Linear regression model found that serum GLA levels at baseline were a predictive factor for prognosis of clinical outcomes after 1-month conventional treatment.

CONCLUSION

The present study indicates that lower levels of serum GLA in rosacea patients are negatively associated with the degree of erythema and anxiety/depression status.

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.

OPN promotes pro-inflammatory cytokine expression via ERK/JNK pathway and M1 macrophage polarization in Rosacea

Rosacea is a chronic inflammatory dermatosis that involves dysregulation of innate and adaptive immune systems. Osteopontin (OPN) is a phosphorylated glycoprotein produced by a broad range of immune cells such as macrophages, keratinocytes, and T cells. However, the role of OPN in rosacea remains to be elucidated. In this study, it was found that OPN expression was significantly upregulated in rosacea patients and LL37-induced rosacea-like skin inflammation. Transcriptome sequencing results indicated that OPN regulated pro-inflammatory cytokines and promoted macrophage polarization towards M1 phenotype in rosacea-like skin inflammation. In vitro, it was demonstrated that intracellular OPN (iOPN) promoted LL37-induced IL1B production through ERK1/2 and JNK pathways in keratinocytes. Moreover, secreted OPN (sOPN) played an important role in keratinocyte-macrophage crosstalk. In conclusion, sOPN and iOPN were identified as key regulators of the innate immune system and played different roles in the pathogenesis of rosacea.

Treating rosacea with botulism toxin: Protocol for a systematic review and meta-analysis

BACKGROUND

Rosacea is a chronic inflammatory disease usually associated with persistent erythema and periodic flushing. This disease is difficult to treat, and the outcomes are often unsatisfactory and prone to recurrence. In recent years, botulinum toxin has been used as a new treatment for rosacea; however, its efficacy and safety remain under discussion. Although a systematic review of the effectiveness and safety of botulinum toxin has been previously conducted by other researchers, our systematic review and meta-analysis evaluate the efficacy of botulinum toxin from a more comprehensive and detailed perspective to provide evidence for clinicians.

METHODS

Any study using botulinum toxin for the treatment of rosacea was considered for the analysis.

RESULTS

A total of 22 studies were included, 9 of which were randomized controlled trials involving 720 subjects. After treatment, all studies showed varying degrees of improvement in patient signs and symptoms along with reduced Clinician's Erythema Assessment (CEA) scores. The improvement was maintained for several months, and the adverse effects were mild and self-limiting.

CONCLUSION

Botulinum toxin may be an effective treatment for patients with rosacea; however, further clinical evidence is needed to confirm its long-term efficacy and side effects. The study was preregistered with Prospero (CRD42022358911).

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.

Metformin: A Potential Treatment for Acne, Hidradenitis Suppurativa and Rosacea

Metformin is a widely used drug for treatment of diabetes mellitus, due to its safety and efficacy. In addition to its role as an antidiabetic drug, numerous beneficial effects of metformin have enabled its use in various diseases. Considering the anti-androgenic, anti-angiogenic, anti-fibrotic and antioxidant properties of metformin, it may have the potential to improve chronic inflammatory skin diseases. However, further evidence is needed to confirm the efficacy of metformin in dermatological conditions, This review focuses on exploring the therapeutic targets of metformin in acne vulgaris, hidradenitis suppurativa and rosacea, by studying their pathogeneses.

Targeting Aquaporin-3 Attenuates Skin Inflammation in Rosacea

Rosacea is a common inflammatory skin disorder mediated by the dysregulation of both keratinocytes and T cells. Here, we report that aquaporin 3 (AQP3), a channel protein that mediates the transport of water/glycerol, was highly expressed in the epidermis and CD4+ T cells of both rosacea patients and experimental mice. Specifically, AQP3 deletion blocked the development of rosacea-like skin inflammation in model mice with LL37-induced rosacea-like disease. We also present mechanistic evidence showing that AQP3 was essential to the activation of NF-κB signaling and subsequent production of disease-characteristic chemokines in keratinocytes. Moreover, we show that AQP3 was upregulated during T cell differentiation and promotes helper T (Th) 17 differentiation possibly via the activation of STAT3 signaling. Our findings reveal that AQP3-mediated activation of NF-κB in keratinocytes and activation of STAT3 in CD4+ T cells acted synergistically and contributed to the inflammation in rosacea.

TLR7 promotes skin inflammation via activating NFκB-mTORC1 axis in rosacea

Rosacea is a chronic inflammatory skin disease originated from damaged skin barrier and innate/adaptive immune dysregulation. Toll-like receptors (TLRs) sense injured skin and initiate downstream inflammatory and immune responses, whose role in rosacea is not fully understood. Here, via RNA-sequencing analysis, we found that the TLR signaling pathway is the top-ranked signaling pathway enriched in rosacea skin lesions, in which TLR7 is highlighted and positively correlated with the inflammation severity of disease. In LL37-induced rosacea-like mouse models, silencing TLR7 prevented the development of rosacea-like skin inflammation. Specifically, we demonstrated that overexpressing TLR7 in keratinocytes stimulates rapamycin-sensitive mTOR complex 1 (mTORC1) pathway via NFκB signaling. Ultimately, TLR7/NFκ B/mTORC1 axis promotes the production of cytokines and chemokines, leading to the migration of CD4+T cells, which are infiltrated in the lesional skin of rosacea. Our report reveals the crucial role of TLR7 in rosacea pathogenesis and indicatesa promising candidate for rosacea treatments.

The role of macrophages in rosacea: implications for targeted therapies

Introduction

Rosacea, a widespread chronic skin condition, may be influenced by macrophages, key immune cells in the skin, although their exact role is not yet fully understood. This review delves into the function of macrophages, their potential contribution to rosacea pathogenesis, current treatments, and promising macrophage-targeted therapies. It concludes by identifying knowledge gaps and potential areas for future rosacea research.

Method

Leveraging systematic and narrative literature review techniques, we conducted a comprehensive search of databases such as PubMed, Embase, and Web of Science. Utilizing keywords like "rosacea" and "macrophages", we targeted English articles from the last 5 years (2018-2023). We manually checked reference lists of relevant articles for additional studies. We included only articles emphasizing macrophages' role in rosacea and/or the development of related therapies and published within the specified timeframe.

Results

The systematic search of electronic databases yielded a total of 4,263 articles. After applying the inclusion and exclusion criteria, 156 articles were selected for inclusion in this review. These articles included original research studies, review articles, and clinical trials that focused on the role of macrophages in rosacea and/or the development of macrophage-targeted therapies for the disease. The selected articles provided a comprehensive and up-to-date overview of the current state of research on macrophages in rosacea, including their function in the skin, the potential mechanisms through which they may contribute to rosacea pathogenesis, and the current treatments and therapies available for the disease. Additionally, the articles identified gaps in knowledge regarding the role of macrophages in rosacea and suggested potential areas for future research.

Conclusion

This literature review emphasizes the important role that macrophages, vital immune cells in the skin, may play in the pathogenesis of rosacea, a common chronic inflammatory skin disorder. The selected studies suggest potential mechanisms by which these cells might contribute to rosacea progression, although these mechanisms are not yet fully understood. The studies also spotlight current rosacea treatments and illuminate the promising potential of new macrophage-focused therapies. Despite these insights, significant gaps persist in our understanding of the precise role of macrophages in rosacea. Future research in this area could provide further insights into the pathogenesis of rosacea and contribute to the development of more effective, targeted therapeutic strategies.

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.

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.

Obesity-induced immunological effects on the skin

There is an increasing prevalence of obesity globally. Equally, the significance of maintaining a healthy body weight for maintaining a healthy skin homoeostasis is gaining greater attention. On this background, there is growing evidence of an adverse influence of excess body weight on the immune system, which has a resultant detrimental effect on the functioning of the skin. The presence of obesity appears to intensify various inflammatory skin disorders. These immune-dermatological consequences in the obese occur because of multiple adverse changes in the skin physiology, endocrine imbalance, metabolic deviations, alterations in circulation, skin microbiome and immunological disruptions. The purpose of this article is to highlight the profound impact of increased fat deposition on cutaneous immunology and its role in the pathophysiology of various chronic inflammatory dermatological conditions. Understanding these immunological modulations will aid in developing therapies targeting the specific inflammatory mediators in the management of obesity-associated chronic immunological skin disease.

mTOR Signaling Pathway in Bone Diseases Associated with Hyperglycemia

The interplay between bone and glucose metabolism has highlighted hyperglycemia as a potential risk factor for bone diseases. With the increasing prevalence of diabetes mellitus worldwide and its subsequent socioeconomic burden, there is a pressing need to develop a better understanding of the molecular mechanisms involved in hyperglycemia-mediated bone metabolism. The mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase that senses extracellular and intracellular signals to regulate numerous biological processes, including cell growth, proliferation, and differentiation. As mounting evidence suggests the involvement of mTOR in diabetic bone disease, we provide a comprehensive review of its effects on bone diseases associated with hyperglycemia. This review summarizes key findings from basic and clinical studies regarding mTOR's roles in regulating bone formation, bone resorption, inflammatory responses, and bone vascularity in hyperglycemia. It also provides valuable insights into future research directions aimed at developing mTOR-targeted therapies for combating diabetic bone diseases.

Supramolecular salicylic acid ameliorates rosacea-like eruptions by suppressing NLRP3-mediated inflammasome activation in mice

BACKGROUND

Rosacea is a chronic inflammatory skin disease with immunological dysfunction. Supramolecular salicylic acid (SSA) has the properties of keratolytic, antibacterial, and anti-inflammatory. However, the mechanism of SSA in the treatment of rosacea is still unclear.

OBJECTIVE

To investigate the efficiencies and molecular mechanisms of SSA in rosacea.

METHODS

Forty mice were randomly divided into four groups (10 in each group): control, LL-37, LL-37 + azelaic acid (AzA), and LL-37 + SSA. Forty μl LL-37 (320 μM) was administered intradermally into the dorsal skin of the mice in the latter 3 groups every 12 h and 4 times altogether (0 h, 12 h, 24 h, 36 h). Twenty % AzA was applied on the eruptions after the first and third LL-37 injection (0 h, 24 h) in LL-37 + AzA group, while 30 % SSA was applied after the first injection (0 h) in LL-37 + SSA group. The redness score and redness area were evaluated. The skin barrier function was measured by the transepidermal water loss (TEWL) and pH. The infiltration of inflammatory cells was evaluated by hematoxylin-eosin staining, and the inflammatory biomarkers were analyzed by RT-PCR and immunohistochemistry.

RESULTS

SSA alleviated LL-37-induced rosacea-like inflammation. The increased TEWL and pH induced by LL-37 were also reversed by SSA. In addition, SSA reduced inflammatory cell infiltration and suppressed the production of Toll-like receptor 2, Matrix metallopeptidase 9, kallikrein 5, LL-37 associated with rosacea, and inhibited LL-37-induced NOD-like receptor family, pyrin domain containing 3 (NLRP3)-mediated inflammasome activation in mice.

CONCLUSIONS

Our findings indicated that SSA ameliorated LL-37-induced rosacea-like lesions by suppressing NLRP3-mediated inflammasome activation in mice.

GBP5 exacerbates rosacea-like skin inflammation by skewing macrophage polarization towards M1 phenotype through the NF-κB signalling pathway

BACKGROUND

Rosacea is a chronic inflammatory skin disease with increased macrophage infiltration. However, the molecular mechanism remains unclear.

OBJECTIVES

To determine the significance of macrophage infiltration, and the correlation between Guanylate-binding protein 5 (GBP5) and polarization of macrophages in rosacea-like inflammation.

METHODS

Here we tested the hypothesis that Guanylate-binding protein 5 (GBP5) aggravates rosacea-like skin inflammation by promoting the polarization of the M1 macrophages through the NF-κB signalling pathway. We depleted macrophage by injecting clodronate-containing liposomes. We next explored the association between GBP5 and macrophage in rosacea tissue through transcriptome analysis and immunofluorescence analysis. We evaluated the severity of rosacea-like skin inflammation when BALB/c mice were injected with GBP5 siRNA intradermally daily for three consecutive days. At last, to study the causality of knocking down GBP5-blunted M1 macrophage polarization, THP-1 cell was treated with GBP5 siRNA.

RESULTS

Macrophage depletion ameliorated rosacea-like skin inflammation in mice, implying the important role of macrophages in rosacea. Based on the transcriptome analysis, Guanylate-binding protein 5 (GBP5) was identified as hub gene that was associated with macrophage infiltration in rosacea. Next, we found that GBP5 expression was significantly upregulated in rosacea tissues and positively correlated with macrophage infiltration, the immunofluorescence analysis revealed the co-localization between GBP5 and macrophages. In vivo, silencing of GBP5 attenuated rosacea-like skin inflammation in the LL-37-induced mouse model and suppressed the expression of M1 signature genes such as IL-6, iNOS and TNF-a. In vitro, knocking down GBP5 significantly blunted the polarization of the M1 macrophages partly by repressing the activation of the NF-κB signalling pathways.

CONCLUSIONS

Together, our study revealed the important role of macrophages in rosacea and identified GBP5 as a key regulator of rosacea by inducing M1 macrophage polarization via NF-κB signalling pathways.

Modified 5-aminolevulinic acid photodynamic therapy suppresses cutaneous squamous cell carcinoma through blocking Akt/mTOR-mediated autophagic flux

Background: We previously found that modified 5-aminolevulinic acid photodynamic therapy (M-PDT) is painless and effective in cutaneous squamous cell carcinoma (cSCC) treatment, however, the regulatory mechanism of M-PDT in cSCC is still unclear.

Objective: To clarify the effect and relevant regulatory mechanism of M-PDT in cSCC.

Methods: The cSCC apoptosis was examined by flow cytometry, TUNEL staining and Cleaved-caspase-3 immunofluorescence, respectively. The autophagy-related characterization was detected by monodansylcadaverine (MDC) staining, transmission electron microscopy (TEM), GFP-LC3B autophagic vacuoles localization and mRFP-EGFP tandem fluorescence-tagged LC3B construct, respectively. The expression of autophagy-related proteins and Akt/mTOR signaling molecules were examined by Western blot. ROS generation was measured by DCFH-DA probe.

Results: We found that M-PDT induced cSCC apoptosis in a dose-dependent manner, and this result was related to autophagic flux blockage. The phenomenon is confirmed by the results that M-PDT could induce autophagosomes accumulation and upregulate LC3-II and p62 expression. M-PDT elevated co-localization of RFP and GFP tandem-tagged LC3B puncta in cSCC cell, reflecting autophagic flux blockage, and this was confirmed by transmission electron microscopy. Furthermore, we noticed that M-PDT induced accumulated autophagosomes-dependent apoptosis via targeting ROS-mediated Akt/mTOR signaling. Suppression of Akt potentiated M-PDT-induced upregulation of LC3-II and p62 levels, whereas Akt activation and ROS inhibition rendered resistance to these events. In addition, we observed that lysosomal dysfunction was involved in M-PDT-triggered accumulated autophagosomes-dependent cSCC apoptosis.

Conclusion: Our data demonstrates that M-PDT inhibits cSCC through blocking Akt/mTOR-mediated autophagic flux.

Dietary supplementation of n-3 PUFAs ameliorates LL37-induced rosacea-like skin inflammation via inhibition of TLR2/MyD88/NF-κB pathway

Rosacea is a facial chronic inflammatory skin disease with dysfunction of immune and neurovascular system and treatments for rosacea are challenging. N-3 polyunsaturated fatty acids (PUFAs), one of essential fatty acids, are needed for health maintenance and exert anti-inflammation and immunomodulatory effects in a series of cutaneous diseases such as atopic dermatitis and photoaging through dietary supplementation. However, the role of n-3 PUFAs on rosacea remains to be elucidated. In this study, KEGG enrichment analysis and GO analysis indicated that the biological process and signaling pathways, including chemokine signaling pathway, regulated by n-3 PUFAs highly overlapped with those in the pathogenic biological process of rosacea, especially the erythema telangiectasia type. Next, mice were randomized to fed with a customized n-3 PUFAs diet. We showed that n-3 PUFAs ameliorated skin erythema, inhibited dermal inflammatory cell infiltration (mast cells, neutrophils, and CD4 +T cells) and suppressed elevated pro-inflammatory cytokines in LL37-induced rosacea-like mice. Besides, n-3 PUFAs were also verified to repress angiogenesis in LL37-induced mice skin. Further investigation revealed that n-3 PUFAs attenuated LL37-induced inflammation via TLR2/ MyD88/ NF-κB pathway both in mice and in keratinocytes. In conclusion, our findings underscore that dietary supplementation of n-3 PUFAs have the potential to become an efficient and safe clinical therapeutic candidate for rosacea.

EGCG identified as an autophagy inducer for rosacea therapy

Background: Rosacea is a common facial skin inflammatory disease featured by hyperactivation of mTORC1 signaling in the epidermis. Due to unclear pathogenesis, the effective treatment options for rosacea remain limited. Methods: Weighted gene co-expression network analysis (WGCNA) analyzed the relationship between epidermis autophagy and mTOR pathways in rosacea, and further demonstrated it through immunofluorescence and qPCR analysis. A potential therapeutic agent for rosacea was predicted based on the key genes of the WGCNA module. In vivo and in vitro experiments were conducted to verify its therapeutic role. Drug-target prediction (TargetNet, Swiss, and Tcmsp) and molecular docking offered potential pharmacological targets. Results: WGCNA showed that epidermis autophagy was related to the activation of mTOR pathways in rosacea. Next, autophagy was downregulated in the epidermis of rosacea, which was regulated by mTOR. In addition, the in vivo experiment demonstrated that autophagy induction could be an effective treatment strategy for rosacea. Subsequently, based on the key genes of the WGCNA module, epigallocatechin-3-gallate (EGCG) was predicted as a potential therapeutic agent for rosacea. Furthermore, the therapeutic role of EGCG on rosacea was confirmed in vivo and in vitro. Finally, drug-target prediction and molecular docking revealed that AKT1/MAPK1/MMP9 could be the pharmacological targets of EGCG in rosacea. Conclusion: Collectively, our findings revealed the vital role of autophagy in rosacea and identified that EGCG, as a therapeutic agent for rosacea, attenuated rosacea-like inflammation via inducing autophagy in keratinocytes.

Damage-associated molecular patterns in vitiligo: igniter fuse from oxidative stress to melanocyte loss

OBJECTIVES

The pathogenesis of vitiligo remains unclear. In this review, we comprehensively describe the role of damage associated molecular patterns (DAMPs) during vitiligo pathogenesis.

METHODS

Published papers on vitiligo, oxidative stress and DAMPs were collected and reviewed via database searching on PubMed, MEDLINE and Embase, etc.

RESULTS

Oxidative stress may be an important inducer of vitiligo. At high oxidative stress levels, damage-associated molecular patterns (DAMPs) are released from keratinocytes or melanocytes in the skin and induce downstream immune responses during vitiligo. Treatment regimens targeting DAMPs can effectively improve disease severity.

DISCUSSION

DAMPs play key roles in initiating host defenses against danger signals, deteriorating the condition of vitiligo. DAMP levels in serum and skin may be used as biomarkers to indicate vitiligo activity and prognosis. Targeted therapies, incorporating HMGB1, Hsp70, and IL-15 could significantly improve disease etiology. Thus, novel strategies could be identified for vitiligo treatment by targeting DAMPs.

Aberrant amino acid metabolism promotes neurovascular reactivity in rosacea

Rosacea is a chronic skin disorder characterized by abnormal neurovascular and inflammatory conditions on the central face. Despite increasing evidence suggesting that rosacea is associated with metabolic disorders, the role of metabolism in rosacea pathogenesis remains unknown. Here, via a targeted metabolomics approach, we characterized significantly altered metabolic signatures in patients with rosacea, especially for amino acid-related metabolic pathways. Among these, glutamic acid and aspartic acid were highlighted and positively correlated with the disease severity in patients with rosacea. We further demonstrated that glutamic acid and aspartic acid can facilitate the development of erythema and telangiectasia, typical features of rosacea, in the skin of mice. Mechanistically, glutamic acid and aspartic acid stimulated the production of vasodilation-related neuropeptides from peripheral neurons and keratinocytes and induced the release of nitric oxide from endothelial cells and keratinocytes. Interestingly, we provided evidence showing that doxycycline can improve the symptoms of patients with rosacea possibly by targeting the amino acid metabolic pathway. These findings reveal that abnormal amino acid metabolism promotes neurovascular reactivity in rosacea and raise the possibility of targeting dysregulated metabolism as a promising strategy for clinical treatment.

Role of MrgprB2 in Rosacea-Like Inflammation in Mice: Modulation by β-Arrestin 2

Cathelicidin LL-37‒mediated activation of mast cells (MCs) has been implicated in the pathogenesis of rosacea, but the receptor involved and the mechanism of its activation and regulation remain unknown. We found that skin biopsies from patients with rosacea display higher frequencies of MCs expressing MRGPRX2 (mouse counterpart MrgprB2) than normal skin. Intradermal injection of LL-37 in wild-type mice resulted in MC recruitment, expression of inflammatory mediators, and development of rosacea-like inflammation. These responses were substantially reduced in MrgprB2‒/‒ mice and abolished in MC deficient Wsh/Wsh mice. β-arrestin 2 is an adaptor protein that regulates G protein-coupled receptor function by receptor desensitization and also by activation of downstream signaling. We found that LL-37‒induced rosacea-like inflammation was significantly reduced in mice with MC-specific deletion of β-arrestin 2 compared with that in control mice. Interestingly, the absence of β-arrestin 2 resulted in enhanced cofilin phosphorylation and substantial inhibition of LL-37‒induced chemotaxis of mouse peritoneal MCs. Furthermore, LL-37‒induced extracellular signal‒regulated kinase 1/2 phosphorylation, NF-κB activation, and proinflammatory cytokine/chemokine production were reduced in β-arrestin 2‒/‒ peritoneal MCs compared with those in wild-type cells. These findings suggest that MRGPRX2/B2 participates in rosacea and that β-arrestin 2 contributes to its pathogenesis by promoting cofilin dephosphorylation, extracellular signal‒regulated kinase 1/2 and NF-κB phosphorylation, MC chemotaxis, and chemokine/cytokine generation.