Thalidomide Attenuates Skin Lesions and Inflammation in Rosacea-Like Mice Induced by Long-Term Exposure of LL-37

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.

IL-17A-neutralizing antibody ameliorates inflammation and fibrosis in rosacea by antagonizing the CXCL5/CXCR2 axis

Rosacea is a chronic inflammatory skin disorder that can lead to fibrosis. However, the mechanisms underlying fibrosis in the later stages of rosacea have been less thoroughly investigated. Interleukin-17A (IL-17A) has been implicated in both inflammation and organ fibrosis; however, the effectiveness and mechanism of IL-17A-neutralizing antibodies in the later stages of rosacea-related fibrosis remain unclear. In this study, we induced rosacea-like lesions in mice using LL-37 and administered IL-17A-neutralizing antibodies. The results indicated that the IL-17A-neutralizing antibodies alleviated skin damage, reduced skin thickness, and decreased the secretion of inflammatory factors (TNF-α, CAMP, TLR4, P-NF-kB), angiogenesis-related factors (CD31, VEGF), and the TGF-β1 signaling pathway, along with factors associated with epithelial-mesenchymal transition and the deposition of fibrosis-related proteins (COL1) in the rosacea-like mouse models. Furthermore, the IL-17A-neutralizing antibodies effectively diminished the expression of IL-17, IL-17R, CXCL5, and CXCR2 in the skin. Our findings demonstrate that IL-17A-neutralizing antibodies inhibit the activation of the CXCL5/CXCR2 axis in rosacea-like skin tissue, thereby ameliorating inflammation and fibrosis associated with the condition.

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 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.

Thalidomide interaction with inflammation in idiopathic pulmonary fibrosis

The "Thalidomide tragedy" is a landmark in the history of the pharmaceutical industry. Despite limited clinical trials, there is a continuous effort to investigate thalidomide as a drug for cancer and inflammatory diseases such as rheumatoid arthritis, lepromatous leprosy, and COVID-19. This review focuses on the possibilities of targeting inflammation by repurposing thalidomide for the treatment of idiopathic pulmonary fibrosis (IPF). Articles were searched from the Scopus database, sorted, and selected articles were reviewed. The content includes the proven mechanisms of action of thalidomide relevant to IPF. Inflammation, oxidative stress, and epigenetic mechanisms are major pathogenic factors in IPF. Transforming growth factor-β (TGF-β) is the major biomarker of IPF. Thalidomide is an effective anti-inflammatory drug in inhibiting TGF-β, interleukins (IL-6 and IL-1β), and tumour necrosis factor-α (TNF-α). Thalidomide binds cereblon, a process that is involved in the proposed mechanism in specific cancers such as breast cancer, colon cancer, multiple myeloma, and lung cancer. Cereblon is involved in activating AMP-activated protein kinase (AMPK)-TGF-β/Smad signalling, thereby attenuating fibrosis. The past few years have witnessed an improvement in the identification of biomarkers and diagnostic technologies in respiratory diseases, partly because of the COVID-19 pandemic. Hence, investment in clinical trials with a systematic plan can help repurpose thalidomide for pulmonary fibrosis.

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.