Lipidomic profiling reveals metabolic signatures in psoriatic skin lesions

Modulation of gut propionate and intestinal mucosal protection by Bifidobacterium longum: Mitigating methotrexate side effects without compromising the efficacy of psoriasis therapy

Methotrexate (MTX) is a widely used medication that can also be employed in the treatment of psoriasis. Previous studies have emphasized that MTX can induce dysbiosis of the gut microbiota, leading to intestinal damage. In this study, the serum levels of calprotectin and zonulin were elevated in patients treated with MTX, while no significant increase in patients treated with MTX combined with probiotics. Furthermore, we established an imiquimod (IMQ) induced psoriasis-like dermatitis mouse model and treated it with MTX (50 µL, 0.3 mg/mL) and B. longum (200 µL, 1 × 1011 CFU/mL). The results showed that B. longum treatment reduced FITC-dextran intestinal permeability and lowered serum levels of calprotectin and zonulin. It also decreased the expression and secretion levels of inflammatory factors in intestinal tissues, such as IL-6, TNF-α, and IL-23A, while increasing the expression and secretion of the protective factor IL-10. Moreover, B. longum treatment maintained barrier integrity by increasing the abundance of propionate in the gut, thereby regulating the balance of Th17/Treg cells. In conclusion, this study suggests that incorporating B. longum into the traditional MTX regimen may enhance its effectiveness in treating psoriasis while preserving the integrity of the intestinal mucosa.

Metabolic pathways of eicosanoids-derivatives of arachidonic acid and their significance in skin

The skin is a barrier that protects the human body against environmental factors (physical, including solar radiation, chemicals, and pathogens). The integrity and, consequently, the effective metabolic activity of skin cells is ensured by the cell membrane, the important structural and metabolic elements of which are phospholipids. Phospholipids are subject to continuous transformation, including enzymatic hydrolysis (with the participation of phospholipases A, C, and D) to free polyunsaturated fatty acids (PUFAs), which under the influence of cyclooxygenases (COX1/2), lipoxygenases (LOXs), and cytochrome P450 (CYPs P450) are metabolized to various classes of oxylipins, depending on the type of PUFA being metabolized and the enzyme acting. The most frequently analyzed oxylipins, especially in skin cells, are eicosanoids, which are derivatives of arachidonic acid (AA). Their level depends on both environmental factors and endogenous metabolic disorders. However, they play an important role in homeostasis mechanisms related to the structural and functional integrity of the skin, including maintaining redox balance, as well as regulating inflammatory processes arising in response to endogenous and exogenous factors reaching skin cells. Therefore, it is believed that dysregulation of eicosanoid levels may contribute to the development of skin diseases, such as psoriasis or atopic dermatitis, which in turn suggests that targeted control of the generation of specific eicosanoids may have diagnostic significance and beneficial therapeutic effects. This review is the first systemic and very detailed approach presenting both the causes and consequences of changes in phospholipid metabolism leading to the generation of eicosanoids, changes in the level of which result in specific metabolic disorders in skin cells leading to the development of various diseases. At the same time, existing literature data indicate that further detailed research is necessary to understand a clear relationship between changes in the level of specific eicosanoids and the pathomechanisms of specific skin diseases, as well as to develop an effective diagnostic and therapeutic approach.

Sphingosine 1-phosphate receptor 2 in keratinocytes plays a key role in reducing inflammation in psoriasis

Background

Psoriasis is an inflammatory skin condition where immune cells play a significant role. The importance of the cross-talk between keratinocytes and immune cells in the pathogenesis of psoriasis has recently been reaffirmed. Recent studies have found that several S1PR functional antagonists, other than S1PR2, are effective in improving psoriasis. This study aims to investigate the role of S1PR2 in psoriasis, that has not been investigated before.

Methods

Spatial transcriptomics, RT-qPCR, and flow cytometry were used to map the immune cell landscape and its association with metabolic pathways in an imiquimod (IMQ)-induced psoriasis-like inflammation in S1pr2fl/fl K14-Cre mice that could not sense sphingosine-1-phosphate (S1P) in the epidermis through the S1PR2 receptor.

Results

Our analysis suggests that S1PR2 in keratinocytes plays a major role in psoriasis-like inflammation compared to other S1PRs. It acts as a down-regulator, inhibiting the recruitment of Th17 cells into the skin. In IMQ-induced psoriasis skin, both S1pr2-/- and S1pr2fl/fl K14-Cre mice showed higher expressions of proinflammatory cytokines such as TNF-α, IL-17A, and IL-1β together with higher expressions of MyD88/NF-κB pathway compared to the wild-type mice. Remarkably, in IMQ-treated mice, the deletion of S1pr2 in keratinocytes only resulted in a larger population of Th17 cells in skin-draining lymph nodes. Other S1PR modulators did not improve the worsening of psoriasis-like inflammation caused by S1PR2 deficiency in keratinocytes.

Conclusion

This study reaches two main conclusions: signals from keratinocytes play a central role in creating an immune environment that promotes the development of psoriasis, and stimulating S1PR2, instead of suppressing it, represents a potential therapeutic approach for psoriasis.

Untargeted Lipidomics Analysis to Discover Lipid Profiles and Biomarkers of Rabbit Acne Model and Reveal Action Mechanism of Isotretinoin

Background

Acne vulgaris (AV), a chronic inflammatory pilosebaceous disorder, affects 80-90% of teenagers. This study aimed to discover lipid profiles and biomarkers of the rabbit ear acne model, and investigate the mechanism of isotretinoin in treating acne at the lipid level.

Methods

Untargeted lipidomic analysis using ultra-high performance liquid chromatography system (UHPLC) coupled to q-extraction plus was performed to identify skin lipid metabolites in blank control (groups C), model group (group M) and isotretinoin group (group T). Multivariate statistical analysis was used to process the lipidomics data.

Results

A total of 43 lipid classes comprising 6989 lipid species were identified from the mass spectrometry data. The orthogonal partial least squares discriminant analysis (OPLS-DA) model demonstrated significant separation in skin lipidomic profiles between group M and group C. With variable influence on projection (VIP) > 1.0 and P-value < 0.05, 299 significantly different lipid metabolites were identified. These lipid metabolites consisted mainly of ceramides (Cer) (53.85%), phosphatidylethanolamines (PE) (9.03%), phosphatidylcholines (PC)(5.35%), and sphingomyelin (SM)(4.01%). Combining with AUC ≥ 0.9 as the elected criteria, Cer (d18;1_24:0), zymosterol (ZyE)(33:5), Cer (t43:1), ZyE (33:6), ZyE (24:7), and ZyE (35:6) have "high" accuracy. Isotretinoin treatment normalized 25 lipid metabolites in the acne model.

Conclusion

Our findings provide new insights into the role of lipid metabolism in the pathogenesis of acne and the action mechanism of isotretinoin.

Longitudinal integrative cell-free DNA analysis in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) presents varied manifestations throughout pregnancy and poses a complex clinical challenge. High-depth cell-free DNA (cfDNA) sequencing analysis holds promise in advancing our understanding of GDM pathogenesis and prediction. In 299 women with GDM and 299 matched healthy pregnant women, distinct cfDNA fragment characteristics associated with GDM are identified throughout pregnancy. Integrating cfDNA profiles with lipidomic and single-cell transcriptomic data elucidates functional changes linked to altered lipid metabolism processes in GDM. Transcription start site (TSS) scores in 50 feature genes are used as the cfDNA signature to distinguish GDM cases from controls effectively. Notably, differential coverage of the islet acinar marker gene PRSS1 emerges as a valuable biomarker for GDM. A specialized neural network model is developed, predicting GDM occurrence and validated across two independent cohorts. This research underscores the high-depth cfDNA early prediction and characterization of GDM, offering insights into its molecular underpinnings and potential clinical applications.

Atopic Dermatitis and Psoriasis: Similarities and Differences in Metabolism and Microbiome

Atopic dermatitis and psoriasis are common chronic inflammatory diseases of high incidence that share some clinical features, including symptoms of pruritus and pain, scaly lesions, and histologically, acanthosis and hyperkeratosis. Meanwhile, they are both commonly comorbid with metabolic disorders such as obesity and diabetes, indicating that both diseases may exist with significant metabolic disturbances. Metabolomics reveals that both atopic dermatitis and psoriasis have abnormalities in a variety of metabolites, including lipids, amino acids, and glucose. Meanwhile, recent studies have highlighted the importance of the microbiome and its metabolites in the pathogenesis of atopic dermatitis and psoriasis. Metabolic alterations and microbiome dysbiosis can also affect the immune, inflammatory, and epidermal barrier, thereby influencing the development of atopic dermatitis and psoriasis. Focusing on the metabolic and microbiome levels, this review is devoted to elaborating the similarities and differences between atopic dermatitis and psoriasis, thus providing insights into the intricate relationship between both conditions.

PRDM16 regulates γδT17 cell differentiation via controlling type 17 program and lipid-dependent cell fitness

γδT17 cells are a subset of γδT cells producing IL-17, which is crucial for protection against bacterial and fungal infections. It has recently been shown that γδT17 cells have enriched lipid storage and lipid metabolism. However, the regulation of γδT17 cell function and differentiation with respect to lipids remains unknown. Here, we report that PRDM16 is a critical regulator of γδT17 cell differentiation, controlling type 17 immunity gene expression program and lipid-dependent cell fitness. We demonstrated that γδT17 cells have higher lipid-dependent cell fitness, which is negatively correlated with the expression of Prdm16. Loss of Prdm16 enhances the function and differentiation of γδT17 cells, and increases their fitness in lipid-rich environments. Specifically, loss of Prdm16 exacerbates development of psoriasis in the skin, a lipid-rich organ, and Prdm16 controls lipid-mediated differentiation of Vγ4+ γδT17 cells, which are the major source of IL-17 during the onset of psoriasis. Our study highlights the potential impact of PRDM16 on lipid-dependent fitness and protective immune function of γδT cells and also on the immunotherapy of psoriasis and inflammatory diseases.

Signaling pathways and targeted therapies for psoriasis

Psoriasis is a common, chronic, and inflammatory skin disease with a high burden on individuals, health systems, and society worldwide. With the immunological pathologies and pathogenesis of psoriasis becoming gradually revealed, the therapeutic approaches for this disease have gained revolutionary progress. Nevertheless, the mechanisms of less common forms of psoriasis remain elusive. Furthermore, severe adverse effects and the recurrence of disease upon treatment cessation should be noted and addressed during the treatment, which, however, has been rarely explored with the integration of preliminary findings. Therefore, it is crucial to have a comprehensive understanding of the mechanisms behind psoriasis pathogenesis, which might offer new insights for research and lead to more substantive progress in therapeutic approaches and expand clinical options for psoriasis treatment. In this review, we looked to briefly introduce the epidemiology, clinical subtypes, pathophysiology, and comorbidities of psoriasis and systematically discuss the signaling pathways involving extracellular cytokines and intracellular transmission, as well as the cross-talk between them. In the discussion, we also paid more attention to the potential metabolic and epigenetic mechanisms of psoriasis and the molecular mechanistic cascades related to its comorbidities. This review also outlined current treatment for psoriasis, especially targeted therapies and novel therapeutic strategies, as well as the potential mechanism of disease recurrence.

The Role of Sphingolipids and Sphingosine-1-phosphate-Sphingosine-1-phosphate-receptor Signaling in Psoriasis

Psoriasis is a long-lasting skin condition characterized by redness and thick silver scales on the skin's surface. It involves various skin cells, including keratinocytes, dendritic cells, T lymphocytes, and neutrophils. The treatments for psoriasis range from topical to systemic therapies, but they only alleviate the symptoms and do not provide a fundamental cure. Moreover, systemic treatments have the disadvantage of suppressing the entire body's immune system. Therefore, a new treatment strategy with minimal impact on the immune system is required. Recent studies have shown that sphingolipid metabolites, particularly ceramide and sphingosine-1-phosphate (S1P), play a significant role in psoriasis. Specific S1P-S1P-receptor (S1PR) signaling pathways have been identified as crucial to psoriasis inflammation. Based on these findings, S1PR modulators have been investigated and have been found to improve psoriasis inflammation. This review will discuss the metabolic pathways of sphingolipids, the individual functions of these metabolites, and their potential as a new therapeutic approach to psoriasis.