Antimicrobial Peptide LL-37 Drives Rosacea-Like Skin Inflammation in an NLRP3-Dependent Manner

Distinct temporal profiles of AMPs and cytokines in pleural fluids from open and closed thoracic surgeries and exploration of synergy with antibiotics and wound healing effects

Antimicrobial peptides (AMPs) play a crucial role in immune defense and wound healing. Their expression and function in pleural fluids following different thoracic surgeries remain underexplored. This study aims to compare AMP and cytokine profiles in pleural fluids from patients undergoing open and closed thoracic surgeries and assess their antimicrobial efficacy and wound healing potential. Pleural fluid and blood samples were collected from 24 patients at multiple time points post-surgery. Levels of four AMPs (DEF-1β, Angiogenin, RNase7, LL-37) and five cytokines (IL-1β, IL-2, IL-6, IL-8, TNF-α) were measured. Antimicrobial activity against E. coli and S. aureus was tested, including combinations with cefazolin. Wound healing was assessed using an in vitro scratch assay. DEF-1β was significantly higher in open surgeries, while Angiogenin was elevated in closed surgeries. Pleural fluids exhibited strong antimicrobial activity, enhanced when combined with cefazolin. Wound healing was rapid but transient with open surgery fluids and more sustained with closed surgery fluids. The distinct AMP profiles and synergistic effects with antibiotics suggest that pleural fluid-derived AMPs could enhance postoperative care. Further studies are needed to explore their therapeutic potential.

A non-bactericidal glycine-rich peptide enhances cutaneous wound healing in mice via the activation of the TLR4/MAPK/NF-κB pathway

Although the antibacterial properties of glycine-rich peptides from prokaryotes to eukaryotes have been well characterized, their role in skin wound healing remains poorly understood, especially non-bactericidal glycine-rich peptides. Herein, a novel glycine-rich (46.5%) peptide (Smaragin, SRGSRGGRGGRGGGGRGGRGRSGSGSSIAGGGSRGSRGGSQYA) was identified from the skin of the tree frog Zhangixalus smaragdinus. Unlike other glycine-rich peptides, Smaragin showed no antimicrobial activity in vitro but significantly enhance wound healing in full-thickness dermal wounds in mice. In comparison with other wound healing-promoting peptides, Smaragin did not directly affect the proliferation and migration of keratinocytes, vascular endothelial cells, and fibroblasts. However, it notably increased phagocytes infiltration at the wound site by 0.5-day post-injury. Smaragin was not a direct chemoattractant for phagocytes, but it stimulated macrophages to secrete chemokines CXCL1 and CXCL2, which indirectly enhanced the migration of phagocytes, keratinocytes and vascular endothelial cells. Moreover, Smaragin promoted the polarization of macrophages from a pro-inflammatory M1-type to an anti-inflammatory M2 phenotype at the wound, which is associated with angiogenic activity. As expected, CD31, the most common analyzed marker of angiogenesis, showed a significant increase in vascular network area. Subsequent studies revealed that Smaragin promoted the chemokine level and polarization of macrophages via the TLR4/MAPK/NF-κB pathway, which enhanced the number of phagocytes and the regeneration of the epidermis and blood vessels at the wound, thereby accelerating skin wound healing in mice. These findings highlight the skin healing properties of non-bactericidal glycine-rich peptides and display the potential of Smaragin as a promising candidate for developing effective wound healing therapies.

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.

A novel regulator of NLRP3 inflammasome: Peptides

The NLRP3 inflammasome plays a crucial role as a critical regulator of the immune response and has been implicated in the pathogenesis of numerous diseases. Peptides, known for their remarkable potency, selectivity, and low toxicity, have been extensively employed in disease treatment. Recent research has unveiled the potential of peptides in modulating the activity of the NLRP3 inflammasome. This review begins by examining the structure of the NLRP3 inflammasome, encompassing NLRP3, ASC, and Caspase-1, along with the three activation pathways: canonical, non-canonical, and alternative. Subsequently, we provide a comprehensive summary of peptide modulators targeting the NLRP3 inflammasome and elucidate their underlying mechanisms. The efficacy of these modulators has been validated through in vitro and in vivo experiments on NLRP3 inflammasome regulation. Furthermore, we conduct sequence alignment of the identified peptides and investigate their binding sites on the NLRP3 protein. This work is a foundational exploration for advancing peptides as potential therapeutic agents for NLRP3-related diseases.

Updated insights into the molecular networks for NLRP3 inflammasome activation

Over the past decade, significant advances have been made in our understanding of how NACHT-, leucine-rich-repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasomes are activated. These findings provide detailed insights into the transcriptional and posttranslational regulatory processes, the structural-functional relationship of the activation processes, and the spatiotemporal dynamics of NLRP3 activation. Notably, the multifaceted mechanisms underlying the licensing of NLRP3 inflammasome activation constitute a focal point of intense research. Extensive research has revealed the interactions of NLRP3 and its inflammasome components with partner molecules in terms of positive and negative regulation. In this Review, we provide the current understanding of the complex molecular networks that play pivotal roles in regulating NLRP3 inflammasome priming, licensing and assembly. In addition, we highlight the intricate and interconnected mechanisms involved in the activation of the NLRP3 inflammasome and the associated regulatory pathways. Furthermore, we discuss recent advances in the development of therapeutic strategies targeting the NLRP3 inflammasome to identify potential therapeutics for NLRP3-associated inflammatory diseases. As research continues to uncover the intricacies of the molecular networks governing NLRP3 activation, novel approaches for therapeutic interventions against NLRP3-related pathologies are emerging.

Comparative analysis of short-term and long-term LL-37-induced rosacea-like mouse models: Histopathological features and inflammatory immune responses

BACKGROUND

It is well recognized that developing new animal models, refining the existing mouse models, and thoroughly characterizing their features are essential for gaining a deeper understanding of rosacea pathogenesis and for advancing therapeutic strategies in this direction. Accordingly, we aimed to characterize the pathological features of a long-term LL-37-induced mouse model of rosacea and to compare the disease manifestations and pathophysiological characteristics between short-term and long-term LL-37-induced models. A key focus was to investigate differential gene expression and the underlying mechanisms of immune system dysregulation in these models.

METHODS

We comparatively assessed skin lesion manifestations, the extent of inflammatory infiltration, sebaceous gland alterations, fibrosis, and angiogenesis in both models. Assessments were performed using photographic documentation, hematoxylin-eosin (HE) staining, Van Gieson's (VG) staining, immunohistochemistry, and Western blotting. Furthermore, we employed RNA sequencing to analyze differential gene expression in mouse skin. The RNA sequencing data were validated using immunofluorescence staining and Western blotting, with a specific focus on gene variations and mechanisms related to immune system dysregulation.

RESULTS

Mice subjected to long-term LL-37 induction developed rosacea-like pathological features, including angiogenesis, thickened skin tissue, and sebaceous gland hypertrophy. In the short-term LL-37-induced model, immune dysregulation primarily involved the innate immune response. However, long-term LL-37 induction resulted in significant activation of both innate and adaptive immune responses.

CONCLUSION

The long-term LL-37-induced mouse model offers a valuable animal model for the detailed investigation of the pathological mechanisms driving moderate-to-severe rosacea with prolonged disease duration. Importantly, this model provides a significant experimental foundation for exploring the potential role of immune system dysregulation in rosacea pathogenesis.

Peptide-modified mesoporous silica nanoparticles for the coordinated regulation of macrophage polarization and pyroptosis in the treatment of implant-related infections

Implant-related infections (IRIs) present a significant challenge in clinical treatment because of the formation of biofilms. The complex architecture of biofilms not only impedes antibiotic penetration, fostering the evolution of multidrug resistance in bacteria under minimal selective pressure but also suppresses the antimicrobial activity of macrophages and induces their pyroptosis in large quantities. This excessive pyroptosis impairs the collective immune function of macrophages, enabling pathogens to evade immune system clearance and rendering infection difficult to eradicate. Existing treatment strategies often necessitate extensive surgical debridement, which not only causes significant harm to patients' physiological health and quality of life but also results in limited therapeutic outcomes. To address these challenges, this study developed a mesoporous silica nanoparticle system (MRL) modified with the RGD (Arginine-Glycine-Aspartic acid) tripeptide and loaded with the antimicrobial peptide LL-37. The LL-37 released from MRL can not only directly disrupt bacterial cell membranes, preventing bacteria from developing resistance through conventional mutation mechanisms, but also enhance antimicrobial activity by modulating macrophage polarization toward the M1 phenotype. However, LL-37 may induce and exacerbate macrophage pyroptosis within biofilms. Therefore, we modified the nanoparticles with RGD to increase macrophage viability and reduce their number of deaths, thereby alleviating the immunosuppression caused by excessive macrophage pyroptosis. In vitro and in vivo experiments demonstrated that MRL, while preserving the antimicrobial activity and immunomodulatory function of LL-37, significantly reduced macrophage pyroptosis and protected the collective immune activity of macrophages. Thus, the fine-tuned regulation of immune response was achieved, providing new insights and strategies for the treatment of IRIs.

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.

Neurotransmitter 5-HT Further Promotes LL-37-Induced Rosacea-like Inflammation Through HTR3A

Rosacea is a chronic inflammatory skin disease and is usually accompanied by extensive macrophage infiltration. There is growing evidence suggesting that neurotransmitter 5-hydroxytryptamine (5-HT) plays a crucial role in inflammatory reactions. However, the interaction between 5-HT and rosacea is still unclear. Here, we hypothesized that the inflammation of rosacea is partly caused by 5-HT, and we investigated the underlying mechanism. In this study, we employed a rosacea model induced by LL-37, which is usually applicated as a rosacea stimulator, to investigate the effects of 5-HT on rosacea in vitro and in vivo. In LL-37-(4 μM)-induced THP-1-derived macrophages, 5-HT (400 μM) further promoted the secretion of inflammatory cytokines and polarized macrophages towards M1 phenotype, which could promote an inflammatory response. Further research revealed that exposure to LL-37 and 5-HT (L5) selectively upregulated HTR3A mRNA expression but not HTR2A or HTR7 and induced colocalization of 5-HT with HTR3A. Notably, application of antagonist tropisetron (TPS) and siRNA of HTR3A suppressed L5-induced inflammation. Meanwhile, 5-HT (25 μg each injection a total of three times) deteriorated skin erythema, stimulated dermal inflammatory cell infiltration, and promoted the secretion of inflammatory cytokines in LL-37 (40 μL and 320 μM each injection a total of four times) induced rosacea-like mice, while these undesirable effects were reversed by using TPS. Our findings revealed that neurotransmitter 5-HT further promoted LL-37-induced rosacea-like inflammation through HTR3A. Our study highlights HTR3A as a promising therapeutic target, which warrants further in-depth investigation into its clinical applicability.

Cathelicidin LL-37 in periodontitis: current research advances and future prospects - A review

LL-37 is the sole member of the cathelicidin family of antimicrobial peptides in humans, primarily produced by phagocytic leukocytes and epithelial cells, mediating a wide range of biological responses. Discovered in human neutrophils, LL-37 is known for its broad-spectrum antimicrobial activity and immunomodulatory functions. In periodontitis, LL-37 is mainly expressed in gingival epithelium, gingival sulcus fluid, and saliva. Emerging evidence from several studies suggests that LL-37 is significant in the development of periodontitis, exhibiting antimicrobial, immunomodulatory, and tissue regenerative effects. Several studies have quantified the levels of LL-37 in gingival crevicular fluid (GCF), revealing elevated levels in patients with periodontitis compared to healthy controls. This review summarizes the expression and roles of LL-37 in periodontitis, providing new perspectives and insights into its pathogenesis and potential treatments. Additionally, this review aims to identify potential areas for future research, including therapeutic applications and biomarker development.

Novel Thermosensitive Hydrogel Encapsulated Carvedilol for the Treatment of Rosacea

BACKGROUND

Carvedilol can be used in the treatment of rosacea. However, their oral administration often results in a series of adverse effects.

PURPOSE

A novel thermosensitive hydrogel was developed to improve the administration of carvedilol in the treatment of rosacea and to evaluate its safety and efficacy.

METHODS

The thermosensitive hydrogel was formulated using varying ratios of poloxamer 407 (P407) and poloxamer 188 (P188), with carvedilol being encapsulated during the process. The gel temperature and time of the hydrogel were observed, its phase transition was assessed through the inverted tube test, its microstructure was examined using scanning electron microscopy (SEM), and its characteristic functional groups were identified with Fourier transform infrared spectrometry (FTIR). The hydrogel's therapeutic efficacy on a rosacea-like phenotype in mice was evaluated through in vitro experiments.

RESULTS

It is observed that the microstructure of the hydrogel possesses a porous structure, with pores uniformly arranged in a square lattice measuring 8-12 μm in diameter. Thermosensitive hydrogel encapsulated carvedilol (Car-P40724/P1881) had favorable drug release rate and swelling properties. Live/dead cell assays indicated minimal toxicity of the hydrogel to HaCaT cells, and the carvedilol encapsulated with hydrogel possessed a better therapeutic effect on the rosacea-like phenotype in mice.

CONCLUSION

Car-P40724/P1881 was not significantly cytotoxic and possessed good cellular biocompatibility. Furthermore, it exhibits a good therapeutic effect on rosacea-associated facial flushing and erythema. It possesses some anti-inflammatory properties and exhibits great potential for future use in rosacea treatment.

Human antimicrobial/host defense peptide LL-37 may prevent the spread of a local infection through multiple mechanisms: an update

BACKGROUND

Human cathelicidin LL-37 shows activity towards both gram-positive and gram-negative bacteria, and it is also active against some types of viruses. Besides its antimicrobial effects, the peptide modulates innate immunity through binding and inactivation of bacterial endotoxins and promoting chemotaxis of immune cells.

RESULTS

LL-37 is reported to interact with plasma membrane receptors and mediate import of Ca2+. Importantly, LL-37 has both anti- and pro-inflammatory effects. LL-37 is cytotoxic to many different human cell types, particularly infected cells, when administered to the cells at final concentrations of 1-10 µM. In psoriatic lesions very high concentrations (300 µM) of the peptide are detected, and in periodontitis, gingival crevicular fluid contains about 1 µM LL-37, implying high concentrations of the peptide at the site of infection/inflammation which can affect host cell viability locally.

CONCLUSIONS

Altogether, LL-37 may inhibit and prevent the infection from spreading by direct anti-bacterial and anti-viral effects, but also via anti- and pro-inflammatory mechanisms, and through killing already infected and weakened host cells at the site of infection/inflammation.

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.

Association between Air Quality Index and the risk of rosacea: a nationwide population-based cohort study

BACKGROUND

Air pollution is associated with several inflammatory skin disorders. However, the association between air quality and rosacea remains unclear.

OBJECTIVES

To investigate the association between the Air Quality Index (AQI) and incidence of rosacea.

METHODS

In total, 21 709 479 participants without rosacea before 2008 were recruited from the Taiwan National Health Insurance Research Database. The long-term average AQI value for each participant was acquired from the Taiwan Air Quality Monitoring System Network and calculated from 1 January 2008 until the diagnosis of rosacea, withdrawal from the National Health Insurance programme, or 31 December 2018.

RESULTS

We observed a significant association between AQI and the incidence of rosacea, with each unit elevation in the AQI increasing the risk of rosacea by 5%. We then categorized participants equally into four groups by quantiles (Q) of AQI values, with mean AQI values of: Q1, 69.0 (SD 6.4); Q2, 79.0 (SD 2.3); Q3, 89.9 (SD 3.6); and Q4, 103.9 (SD 6.8). Compared with the Q1 group, the Q2, Q3 and Q4 cohorts exhibited 1.82-fold, 4.48-fold and 7.22-fold increased risk of rosacea, respectively. Additionally, exposure to particulate matter (PM)2.5 (airborne particulate matter with a diameter ≤ 2.5 μm), sulfur dioxide (SO2) and carbon monoxide increased the risk of rosacea, whereas exposure to PM10 (airborne PM with a diameter ≤ 10 μm) was associated with a lower risk.

CONCLUSIONS

This study supported a significant dose-response relationship between AQI and the incidence of rosacea.

Agonism of the glutamate receptor GluK2 suppresses dermal mast cell activation and cutaneous inflammation

Activation of dermal mast cells through the Mas-related G protein-coupled receptor B2 receptor (MrgprB2 in mice and MrgprX2 in humans) is a key component of numerous inflammatory skin diseases, including dermatitis and rosacea. Sensory neurons actively suppress mast cell activation through the regulated release of glutamate, resulting in reduced expression of Mrgprb2 as well as genes associated with proteins found in mast cell granules. To determine whether exogenous glutamate receptor agonism could suppress mast cell function, we determined that mast cells have relatively selective expression of the glutamate receptor ionotropic, kainate 2 (GluK2). A GluK2-specific agonist, SYM2081, effectively inhibited mast cell degranulation in response to MrgprB2 agonism in both murine mast cells and human skin explants in vitro as well as in vivo after both intradermal and topical administration of SYM2081 to mice. Analyses of transcriptomic datasets from SYM2081-treated mast cells using standard differential expression approaches and an interpretable machine learning technique revealed a previously unrecognized cellular program coordinately regulated by GluK2 agonism. GluK2 agonism suppressed the expression of Mrgprb2 and genes associated with mast cell proliferation. Suppression of mast cell proliferation by SYM2081 exposure was confirmed on the basis of reduced Ki-67 expression and BrdU incorporation in vitro and in vivo. Last, pretreatment with SYM2081 reduced skin inflammation in murine models of dermatitis and rosacea. Thus, agonism of GluK2 represents a promising approach to suppress mast cell activation and may prove beneficial as therapy for inflammatory diseases in which mast cell activation is pathogenic.

Tranilast alleviates skin inflammation and fibrosis in rosacea-like mice induced by long-term exposure to LL-37

Rosacea, a prevalent chronic facial inflammatory condition, afflicts millions worldwide. Its multifaceted pathogenesis poses challenges for effective treatment. Tranilast (TR), an analog of a tryptophan metabolite, has demonstrated anti-inflammatory and anti-fibrotic properties across various diseases. Yet, its potential in rosacea treatment remains understudied. Here, we induced rosacea-like symptoms in mice via prolonged LL-37 injections and administered TR intervention. Our findings reveal that TR mitigated skin lesions, reduced skin thickness, and suppressed inflammatory cell infiltration within the dermis of LL-37 mice. Notably, TR downregulated the expression of rosacea-associated inflammatory cytokines (TNF-α, IL-6, IL-1β, and IL-18) and the antimicrobial peptide CAMP, while also inhibiting NLRP3 inflammasome activation and the TLR4 signaling pathway. Furthermore, TR attenuated LL-37-induced fibrosis and hindered the transforming growth factor-β1 (TGF-β1)/Smad2/3 pathway. In summary, our study underscores TR's therapeutic potential in rosacea by mitigating both skin inflammation and fibrosis, thereby offering a promising treatment avenue for this condition.

Macrophages in inflammatory skin diseases and skin tumors

Macrophages, as specialized, long-lasting phagocytic cells of the innate immune system, have garnered increasing attention due to their wide distribution and various functions. The skin, being the largest immune organ in the human body, presents an intriguing landscape for macrophage research, particularly regarding their roles in inflammatory skin diseases and skin tumors. In this review, we compile the latest research on macrophages in conditions such as atopic dermatitis, psoriasis, systemic sclerosis, systemic lupus erythematosus, rosacea, bullous pemphigoid, melanoma and cutaneous T-cell lymphoma. We aim to contribute to illustrating the pathogenesis and potential new therapies for inflammatory skin diseases and skin tumors from the perspective of macrophages.

Antimicrobial Peptide CATH-2 Attenuates Avian Pathogenic E. coli-Induced Inflammatory Response via NF-κB/NLRP3/MAPK Pathway and Lysosomal Dysfunction in Macrophages

Cathelicidins have anti-inflammatory activity and chicken cathelicidin-2 (CATH-2) has shown to modulate immune response, but the underlying mechanism of its anti-inflammation is still unclear. Therefore, in this study, we investigated the anti-inflammatory activity of CATH-2 on murine peritoneal macrophages during avian pathogenic E. coli (APEC) infection. The results showed that CATH-2 priming significantly reduced the production of IL-1β, IL-6, IL-1α, and IL-12. In addition, CATH-2 significantly attenuated APEC-induced caspase-1 activation and the formation of an adaptor (ASC) of NLRP3 inflammasome, indicating that CATH-2 inhibits APEC-induced NLRP3 inflammasome activation. Furthermore, CATH-2 remarkably inhibited NF-κB and MAPK signaling pathways activation. Moreover, CATH-2 significantly inhibited mRNA expression of cathepsin B and inhibited lysosomal acidification, demonstrating that CATH-2 disrupts lysosomal function. In addition, promoting lysosomal acidification using ML-SA1 hampered the anti-inflammatory effect of CATH-2 on APEC-infected cells. In conclusion, our study reveals that CATH-2 inhibits APEC-induced inflammation via the NF-κB/NLRP3/MAPK pathway through the dysfunction of lysosome.

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.

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.

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.

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.

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.

Transcriptomic analysis of skin immunity genes in the Chinese spiny frog (Quasipaa spinosa) after Proteus mirabilis infection

Recently, populations of Chinese spiny frogs (Quasipaa spinosa), an important amphibian species in China, have decreased, mainly due to a disease caused by the gram-negative bacteria Proteus mirabilis. To elucidate the immune response of the frogs, this study aimed to identify novel candidate genes functionally associated with P. mirabilis infection-induced "rotting skin" disease. Chinese spiny frogs were infected with P. mirabilis, and the skin transcriptome was sequenced using the MGISEQ-2000 platform. A total of 233,965 unigenes were obtained by sequencing, of which 27.23 % were known genes. Screening of differentially expressed genes (DEGs) indicated 210 unigenes differentially expressed after P. mirabilis infection, of which 132 unigenes were up-regulated, and 78 unigenes were down-regulated. Using Kyoto Encyclopedia of Genes and Genomes enrichment analysis, DEGs were identified as enriched in signal pathways, such as oxidative phosphorylation, apoptosis, and the Janus kinase-signal transducer and activator of transcription pathway. Of the DEGs, there was a significant upregulation of the colony stimulating factor 2 receptor beta common subunit, interleukin 2 receptor subunit gamma, cathelicidin antimicrobial peptide, interleukin-17 receptor E, receptor-interacting serine/threonine-protein kinase 3, and pulmonary surfactant-associated protein D immune genes following P. mirabilis infection. Conversely, scavenger receptor cysteine-rich domain-containing group B protein, tumor protein p53 inducible nuclear protein 2, suppressor of cytokine signaling 2, and metalloreductase STEAP3 were significantly downregulated. In conclusion, the first skin transcriptome database of Chinese spiny frogs was established, and several immune genes were identified to elucidate the pathogenic mechanism of "skin rot" in Chinese spiny frogs and other cultured frogs.

Rosacea: Pathogenesis and Therapeutic Correlates

Rosacea is a chronic inflammatory condition of which there is no cure. The pathogenesis of rosacea is likely multifactorial, involving genetic and environmental contributions. Current understanding suggests that pro-inflammatory pathways involving cathelicidins and inflammasome complexes are central to rosacea pathogenesis. Common rosacea triggers modulate these pathways in a complex manner, which may contribute to the varying severity and clinical presentations of rosacea. Established and emerging rosacea treatments may owe their efficacy to their ability to target different players in these pro-inflammatory pathways. Improving our molecular understanding of rosacea will guide the development of new therapies and the use of combination therapies.

The transcriptomic landscape of canonical activation of NLRP3 inflammasome from bone marrow-derived macrophages

The NLRP3 inflammasome has gained significant attention due to its participation in diverse cellular processes. Nevertheless, the detailed framework of the canonical NLRP3 inflammasome assembly still remains unrevealed. This study aims to elucidate the transcriptomic landscape of the various stages involved in the canonical activation of the NLRP3 inflammasome in BMDMs by integrating RNA-seq, bioinformatics, and molecular dynamics analyses. The model for the canonical activation of the NLRP3 inflammasome was confirmed through morphological observations, functional assessments (ELISA and LDH), and protein detection (western blot). Subsequently, cells were subjected to RNA sequencing following three groups: control, priming (LPS 500 ng/ml, 4 h), and activation (LPS 500 ng/ml, 4 h; ATP 5 mM, 1 h). A total of 9116 differentially expressed genes (DEGs) were identified, which exerted regulatory effects on various pathways, including cell metabolism, ion fluxes, post-translational modifications, and organelles. Subsequently, six hub genes (Sirt3, Stat3, Syk, Trpm2, Tspo, and Txnip) were identified via integrating literature review and database screening. Finally, the three-dimensional structures of these six hub proteins were obtained using the MD-optimized RoseTTAFold and Gromacs simulations (at least 200 ns). In summary, our research offers novel insights into the transcriptomic-level understanding of the assembly of the canonical NLRP3 inflammasome.

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).

Pyroptosis-related gene signature elicits immune response in rosacea

Rosacea is a complex chronic inflammatory skin disorder with high morbidity. Pyroptosis is known as a regulated inflammatory cell death. While its association with immune response to various inflammatory disorders is well established, little is known about its functional relevance of rosacea. So, we aimed to explore and enrich the pathogenesis involved in pyroptosis-related rosacea aggravations. In this study, we evaluated the pyroptosis-related patterns of rosacea by consensus clustering analysis of 45 ferroptosis-related genes (FRGs), with multiple immune cell infiltration analysis to identify the pyroptosis-mediated immune response in rosacea using GSE65914 dataset. The co-co-work between PRGs and WGCNA-revealed hub genes has established using PPI network. FRG signature was highlighted in rosacea using multi-transcriptomic and experiment analysis. Based on this, three distinct pyroptosis-related rosacea patterns (non/moderate/high) were identified, and the notably enriched pathways have revealed through GO, KEGG and GSEA analysis, especially immune-related pathways. Also, the XCell/MCPcount/ssGSEA/Cibersort underlined the immune-related signalling (NK cells, Monocyte, Neutrophil, Th2 cells, Macrophage), whose hub genes were identified through WGCNA (NOD2, MYD88, STAT1, HSPA4, CXCL8). Finally, we established a pyroptosis-immune co-work during the rosacea aggravations. FRGs may affect the progression of rosacea by regulating the immune cell infiltrations. In all, pyroptosis with its mediated immune cell infiltration is a critical factor during the development of rosacea.

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.

Redox Regulation of Nucleotide-Binding and Oligomerization Domain-Like Receptors Inflammasome

Significance: Inflammasomes are multimeric complexes that, as part of the innate immune response, sense a wide range of pathogenic and sterile stimuli. They consist of three components, namely a sensor protein, an adaptor, and procaspase-1, which once activated result in secretion of proinflammatory interleukin (IL)-1β and IL-18 and, eventually, in a gasdermin D-dependent lytic cell death called pyroptosis. Recent Advances: Since their discovery 20 years ago, the molecular mechanisms underlying the regulation of inflammasomes have been extensively studied. Oxidative stress appears as a major contributor to modulate inflammasomes, especially NLRP3 as well as NLRP1, NLRP6, and NLRC4. Growing evidence supports the idea that the positive feedback between redox imbalance and inflammasome-driven inflammation fuels an OxInflammatory state in a variety of human pathologies. Critical Issues: The current knowledge about the redox signaling pathways involved in inflammasomes activation and functions are here highlighted. In addition, we discuss the role of this complex molecular network interaction in the onset and progression of pathological conditions including neurological and metabolic diseases as well as skin disorders, also with an insight on COVID-19-related pathology. Finally, the therapeutic strategies able to mitigate the redox-mediated inflammasome activation with synthetic and natural compounds as well as by acting on inflammasome-related post-translational modifications and microRNAs are also addressed. Future Directions: Further investigations leading to a deeper understanding of the reciprocal interaction between inflammasomes and reactive oxygen species will help identify other molecular targets for modulating their hyperactivated state, and to design novel therapeutics for chronic OxInflammatory conditions. Antioxid. Redox Signal. 39, 744-770.

The Role of NLRP3 in Regulation of Antimicrobial Peptides and Estrogen Signaling in UPEC-Infected Bladder Epithelial Cells

The NLRP3 inflammasome, estrogen and antimicrobial peptides have all been found to have a vital role in the protection of the bladder urothelium. However, the interdependence between these protective factors during a bladder infection is currently unknown. Our aim was to investigate the role of NLRP3 in the regulation of antimicrobial peptides and estrogen signaling in bladder epithelial cells during a UPEC infection. Human bladder epithelial cells and CRISPR/Cas9-generated NLRP3-deficient cells were stimulated with the UPEC strain CFT073 and estradiol. The gene and protein expression were evaluated with microarray, qRT-PCR, western blot and ELISA. Microarray results showed that the expression of most antimicrobial peptides was reduced in CFT073-infected NLRP3-deficient cells compared to Cas9 control cells. Conditioned medium from NLRP3-deficient cells also lost the ability to suppress CFT073 growth. Moreover, NLRP3-deficient cells had lower basal release of Beta-defensin-1, Beta-defensin-2 and RNase7. The ability of estradiol to induce an increased expression of antimicrobial peptides was also abrogated in NLRP3-deficient cells. The decreased antimicrobial peptide expression might be linked to the observed reduced expression and activity of estradiol receptor beta in NLRP3-deficient cells. This study suggests that NLRP3 may regulate the release and expression of antimicrobial peptides and affect estrogen signaling in bladder epithelial cells.

Cathelicidin (LL-37) causes expression of inflammatory factors in coronary artery endothelial cells of Kawasaki disease by activating TLR4-NF-κB-NLRP3 signaling

BACKGROUND

Kawasaki disease (KD) is a type of vasculitis with an unidentified etiology. Cathelicidin (LL-37) may be involved in the development of the KD process; therefore, further research to investigate the molecular mechanism of LL-37 involvement in KD is warranted.

METHODS

Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, NLRP3, and LL-37 in the sera of healthy subjects, children with KD, and children with pneumonia. Subsequently, human recombinant LL-37 or/and toll-like receptors 4 (TLR4)-specific inhibitor TAK-242 stimulated human coronary artery endothelial cells (HCAECs), CCK-8 was used to detect cell proliferation, flow cytometry to detect apoptosis, transmission electron microscopy to observe cytoskeletal changes, Transwell to measure cell migration ability, ELISA to detect inflammatory factor levels, Western blot analysis to analyze protein levels of toll-like receptors 4 (TLR4) and NF-κB p-65, and quantitative real-time polymerase chain reaction (qRT-PCR) to determine LL-37, NLRP3 mRNA levels.

RESULTS

In this study, we found that the level of LL-37 was highly expressed in the serum of children with KD, and after LL-37 stimulation, apoptosis was significantly increased in HCAECs, and the expression levels of TLR4, NLRP3 and inflammatory factors in cells were significantly enhanced. Intervention with the TLR4-specific inhibitor TAK-242 significantly alleviated the LL-37 effects on cellular inflammation, TLR4, NLRP3 promotion effect.

CONCLUSIONS

Our data suggest that LL-37 induces an inflammatory response in KD coronary endothelial cells via TLR4-NF-κB-NLRP3, providing a potential target for the treatment of KD.

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.

cGAMP the travelling messenger

2'3'-cGAMP is a key molecule in the cGAS-STING pathway. This cyclic dinucleotide is produced by the cytosolic DNA sensor cGAS in response to the presence of aberrant dsDNA in the cytoplasm which is associated with microbial invasion or cellular damage. 2'3'-cGAMP acts as a second messenger and activates STING, the central hub of DNA sensing, to induce type-I interferons and pro-inflammatory cytokines necessary for responses against infection, cancer or cellular stress. Classically, detection of pathogens or danger by pattern recognition receptors (PRR) was thought to signal and induce the production of interferon and pro-inflammatory cytokines in the cell where sensing occurred. These interferon and cytokines then signal in both an autocrine and paracrine manner to induce responses in neighboring cells. Deviating from this dogma, recent studies have identified multiple mechanisms by which 2'3'-cGAMP can travel to neighboring cells where it activates STING independent of DNA sensing by cGAS. This observation is of great importance, as the cGAS-STING pathway is involved in immune responses against microbial invaders and cancer while its dysregulation drives the pathology of a wide range of inflammatory diseases to which antagonists have been elusive. In this review, we describe the fast-paced discoveries of the mechanisms by which 2'3'-cGAMP can be transported. We further highlight the diseases where they are important and detail how this change in perspective can be applied to vaccine design, cancer immunotherapies and treatment of cGAS-STING associated disease.

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.

Long-Term Administration of LL-37 Can Induce Irreversible Rosacea-like Lesion

Rosacea is a chronic inflammatory skin disease whose late manifestations have not yet been clearly reported in animal models. The objective of this study is to describe the skin lesions and major histopathological changes in a rosacea-like phenotype in mice induced by prolonged LL-37 administration and furthermore, to assess the potential of long-term LL-37 administration in inducing irreversible rosacea-like skin lesion models. Balb/c mice were continuously injected intradermally with LL-37 every 12 h to induce a rosacea-like phenotype. After LL-37 injections were administered for 20 consecutive days, the area of rosacea-like lesions gradually expanded in the first 13 days, then entered a stable phase. Haematoxylin and eosin (H&E) and Van Gieson's staining showed a high degree of inflammatory cell aggregation, thickening of the epidermis and dermis, and collagen deposition in large quantities. The results of immunofluorescence staining and Western blotting showed that the expression of α-SMA, TNF-α, vimentin, and COL1 in the skin of mice was significantly upregulated. Short-term LL-37 administration induced rosacea-like lesions that only featured the aggregation of inflammatory factors and thickening of the epidermis, whereas no collagen hyperplasia was observed, and a full recovery was noticed. However, rosacea-like skin lesions induced by long-term LL-37 administration did not completely recover. Our study compares rosacea-like lesions induced by short-term versus long-term LL-37 administration, and the results suggest that irreversible rosacea-like lesions can be induced by long-term LL-37 administration.

Quality of life measurement in rosacea. Position statement of the European Academy of Dermatology and Venereology Task Forces on Quality of Life and Patient Oriented Outcomes and Acne, Rosacea and Hidradenitis Suppurativa

The European Academy of Dermatology and Venereology (EADV) Task Forces (TFs) on Quality of Life (QoL) and Patient-Oriented Outcomes and Acne, Rosacea and Hidradenitis Suppurativa (ARHS) do not recommend the use of any generic instrument as a single method of Health Related (HR) QoL assessment in rosacea, except when comparing quimp (quality of life impairment) in rosacea patients with that in other non-dermatologic skin diseases and/or healthy controls. The EADV TFs on QoL and Patient-Oriented Outcomes and ARHS recommend the use of the dermatology-specific HRQoL instrument the Dermatology Life Quality Index (DLQI) and the rosacea-specific HRQoL instrument RosaQoL in rosacea patients. The DLQI minimal clinically important difference may be used as a marker of clinical efficacy of the treatment and DLQI score banding of 0 or 1 corresponding to no effect on patients' HRQoL could be an important treatment goal. This information may be added to consensuses and guidelines for rosacea.

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.

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.

Efficient Induction of Antigen-Specific CD8+ T-Cell Responses by Cationic Peptide-Based mRNA Nanoparticles

A major determinant for the success of mRNA-based vaccines is the composition of the nanoparticles (NPs) used for formulation and delivery. Cationic peptides represent interesting candidate carriers for mRNA, since they have been shown to efficiently deliver nucleic acids to eukaryotic cells. mRNA NPs based on arginine-rich peptides have previously been demonstrated to induce potent antigen-specific CD8+ T-cell responses. We therefore compared the histidine-rich amphipathic peptide LAH4-L1 (KKALLAHALHLLALLALHLAHALKKA) to the fully substituted arginine variant (LAH4-L1R) for their capacity to formulate mRNA and transfect dendritic cells (DCs). Although both peptides encapsulated mRNA to the same extent, and showed excellent uptake in DCs, the gene expression level was significantly higher for LAH4-L1. The LAH4-L1–mRNA NPs also resulted in enhanced antigen presentation in the context of MHC I compared to LAH4-L1R in primary murine CD103+ DCs. Both peptides induced DC maturation and inflammasome activation. Subsequent ex vivo stimulation of OT-I splenocytes with transfected CD103+ DCs resulted in a high proportion of polyfunctional CD8+ T cells for both peptides. In addition, in vivo immunization with LAH4-L1 or LAH4-L1R–mRNA NPs resulted in proliferation of antigen-specific T cells. In conclusion, although LAH4-L1 outperformed LAH4-L1R in terms of transfection efficiency, the immune stimulation ex vivo and in vivo was equally efficient.

Celastrol inhibits LL37-induced rosacea by inhibiting Ca2+/CaMKII-mTOR-NF-κB activation

Rosacea is a common chronic facial inflammatory disease that affects millions of people worldwide. Due to the unclear etiology of rosacea, effective treatments are limited. Celastrol, a plant-derived triterpene, has been reported to alleviate inflammation in various diseases. However, whether celastrol exerts protective effects in rosacea remains to be elucidated. In this study, weighted gene co-expression network analyses (WGCNA) were performed. Hub modules closely related to rosacea clinical characteristics were identified and found to be involved in inflammation- and angiogenesis-related signaling pathways. Then, the pharmacological targets of celastrol were predicted using the TargetNet and Swiss Target Prediction databases. A GO analysis indicated that the biological process regulated by celastrol highly overlapped with the pathogenic biological processes in rosacea. Next, we showed that celastrol ameliorated erythema, skin thickness and inflammatory cell infiltration in the dermis of LL37-treated mice. Celastrol suppressed the expression of rosacea-related inflammatory cytokines and inhibited the Th17 immune response and cutaneous angiogenesis in LL37-induced rosacea-like mice. We further demonstrated that celastrol attenuated LL37-induced inflammation by inhibiting intracellular-free calcium ([Ca²⁺]_i)-mediated mTOR signaling in keratinocytes. Chelating intracellular Ca²⁺ with BAPTA/AM potentiated celastrol-induced repression of LL37-induced p-S6 elevation. The mTOR agonist MHY1485 dramatically reinforced LL37-induced rosacea-like characteristics, while celastrol attenuated these outcomes. Moreover, celastrol inhibited LL37-activated NF-κB in a mTOR signaling-dependent manner. In conclusion, our findings underscore that celastrol may be a rosacea protective agent by inhibiting the LL37-activated Ca²⁺/CaMKII-mTOR-NF-κB pathway associated with skin inflammation disorders.

Mussel-Inspired Microgel Encapsulated NLRP3 Inhibitor as a Synergistic Strategy Against Dry Eye

The inflammatory response mediated by oxidative stress is the main pathogenesis of dry eye, but clinical observations have shown that scavenging oxygen-free radicals alone has limited therapeutic effect. Moreover, the unique anatomy and physiology of the ocular surface result in low bioavailability of drugs, and higher concentration is required to achieve the desired efficacy, which, however, may bring systemic side effects. These problems pose a challenge, but the revelation of the ROS-NLRP3-IL-1β signaling axis opens up new possibilities. In this investigation, an NLRP3 inhibitor was successfully encapsulated in polydopamine-based microgels and used for dry eye treatment. It was demonstrated that the well-designed microgels exhibited good biocompatibility, prolonged drug retention time on the ocular surface, and effective inhibition of corneal epithelial damage and cell apoptosis. In addition, due to the synergistic effect, the NLRP3 inhibitor–loaded microgels could exert enhanced oxygen radical scavenging and inflammation-inhibiting effects at a lower dose than monotherapy. These findings suggest that polydopamine-based microgels have advantages as ocular surface drug delivery platforms and have promising applications in oxidative damage–related inflammatory diseases in synergy with anti-inflammatory drugs.

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

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

N-Succinyl-S-Farnesyl-L-Cysteine (SFC): A Novel Isoprenylcysteine Analog with In Vitro Anti-Inflammatory Activity and Clinical Skin Protecting Properties

Over the past 15 years, small molecule isoprenylcysteine (IPC) analogs have been identified as a potential new class of topical anti-inflammatories. Clinical studies have demonstrated that IPCs are both safe and effective in promoting healthy skin when applied topically. This work aims to demonstrate N-Succinyl-S-farnesyl-L-cysteine (SFC) as a novel IPC molecule that provides a broad spectrum of benefits for skin. Human promyelocytic cell line HL-60, human dermal microvascular endothelial cells (HDMECs), human dermal fibroblasts (HDFs), and normal human epidermal keratinocytes (NHEKs) were exposed in culture to various inducers to trigger reactive oxygen species, cytokines, or collagenase production. A 49-subject randomized double-blind, vehicle-controlled, split face trial was performed with 1% SFC gel, or 5% niacinamide and vehicle applied for 12 weeks to evaluate anti-wrinkle and anti-aging endpoints. We demonstrated that SFC inhibited GPCR and TLR-induced pro-inflammatory cytokine release in NHEKs and HDMECs from several inflammatory inducers such as UVB, chemicals, cathelicidin, and bacteria. SFC successfully reduced GPCR-induced oxidation in differentiated neutrophils. Moreover, photoaging studies showed that SFC reduced UVA-induced collagenase (pro-MMP-1) production in HDFs. Clinical assessment of 1% SFC gel demonstrated improvement above the vehicle for wrinkle reduction, hydration, texture, and overall appearance of skin. N-Succinyl-S-farnesyl-L-cysteine (SFC) is a novel anti-inflammatory small molecule and is the first farnesyl-cysteine IPC shown to clinically improve appearance and signs of aging, while also having the potential to ameliorate inflammatory skin disorders.

Cathelicidin LL-37 Ignites Primed NLRP3 Inflammasomes in Rosacea

Microbes and commensal mites contribute to the development of inflammation and neurovascular dysregulation in rosacea. Cathelicidin family proteins are epithelial antimicrobial peptides expressed in higher-order mammals. In humans, mature LL-37 is cleaved from its precursor in response to microbial infection, UV light, and injury. In their new article in the Journal of Investigative Dermatology, Yoon et al. expand on existing evidence supporting LL-37 proinflammatory activity in lipopolysaccharide (LPS)- and UV-primed models of rosacea. They show in vitro that LL-37 promotes NLRP3-mediated inflammasome activation through lysosomal destabilization in the presence of LPS and that the injection of LL-37 in vivo leads to skin inflammation that is abrogated by direct NLRP3 inhibition and homozygous knockout in a murine model.

Antimicrobial peptides: mechanism of action, activity and clinical potential

The management of bacterial infections is becoming a major clinical challenge due to the rapid evolution of antibiotic resistant bacteria. As an excellent candidate to overcome antibiotic resistance, antimicrobial peptides (AMPs) that are produced from the synthetic and natural sources demonstrate a broad-spectrum antimicrobial activity with the high specificity and low toxicity. These peptides possess distinctive structures and functions by employing sophisticated mechanisms of action. This comprehensive review provides a broad overview of AMPs from the origin, structural characteristics, mechanisms of action, biological activities to clinical applications. We finally discuss the strategies to optimize and develop AMP-based treatment as the potential antimicrobial and anticancer therapeutics.