Abnormal lipid metabolism in epidermal Langerhans cells mediates psoriasis-like dermatitis

Exploring the role of autophagy in psoriasis pathogenesis: Insights into sustained inflammation and dysfunctional keratinocyte differentiation

Psoriasis is a common and prevalent chronic papulosquamous cutaneous disorder characterized by sustained inflammation, uncontrolled keratinocyte proliferation, dysfunctional differentiation, and angiogenesis. Autophagy, an intracellular catabolic process, can be induced in response to nutrient stress. It entails the degradation of cellular constituents through the lysosomal machinery, and its association with psoriasis has been well-documented. Nevertheless, there remains a notable dearth of research concerning the involvement of autophagy in the pathogenesis of psoriasis within human skin. This review provides a comprehensive overview of autophagy in psoriasis pathogenesis, focusing on its involvement in two key pathological manifestations: sustained inflammation and uncontrolled keratinocyte proliferation and differentiation. Additionally, it discusses potential avenues for disease management.

Metabolic homeostasis of tissue macrophages across the lifespan

Macrophages are present in almost all organs. Apart from being immune sentinels, tissue-resident macrophages (TRMs) have organ-specific functions that require a specialized cellular metabolism to maintain homeostasis. In addition, organ-dependent metabolic adaptations of TRMs appear to be fundamentally distinct in homeostasis and in response to a challenge, such as infection or injury. Moreover, TRM function becomes aberrant with advancing age, contributing to inflammaging and organ deterioration, and a metabolic imbalance may underlie TRM immunosenescence. Here, we outline current understanding of the particular metabolic states of TRMs across organs and the relevance for their function. Moreover, we discuss the concomitant aging-related decline in metabolic plasticity and functions of TRMs, highlighting potential novel therapeutic avenues to promote healthy aging.

Metabolic dysfunction associated steatotic liver disease in patients with plaque psoriasis: a case-control study and serological comparison

Background

The relationship between plaque psoriasis and both MASLD and lean MASLD has not been sufficiently explored in the current literature.

Method

This retrospective and observational study was carried out from January 2021 to January 2023 at The First Affiliated Hospital of Zhejiang Chinese Medical University. Patients diagnosed with plaque psoriasis and a control group consisting of individuals undergoing routine physical examinations were enrolled. The incidence of MASLD and lean MASLD among these groups was compared. Additionally, patients with plaque psoriasis were divided into those with MASLD, those with lean MASLD, and a control group with only psoriasis for a serological comparative analysis.

Results

The incidence of MASLD in the observation group and the control group was 43.67% (69/158) and 22.15% (35/158), respectively (p < 0.01). Furthermore, the incidence of lean MASLD within the observation group and the control group was 10.76% (17/158) and 4.43% (7/158), respectively (p < 0.01). After controlling for potential confounding variables, plaque psoriasis was identified as an independent risk factor for MASLD with an odds ratio of 1.88 (95% cl: 1.10-3.21). In terms of serological comparison, compared to the simple psoriasis group, we observed a significant elevation in the tumor marker CYFRA21-1 levels in both groups compared to the control group with simple psoriasis (p < 0.01). Moreover, the MASLD group exhibited elevated levels of inflammatory markers and psoriasis score, whereas these effects were mitigated in the lean MASLD group.

Conclusion

The prevalence of MASLD and lean MASLD is higher among patients with psoriasis. Those suffering from psoriasis along with MASLD show increased psoriasis scores and inflammatory markers compared to those without metabolic disorders. MASLD likely worsens psoriasis conditions, indicating the necessity of targeted health education for affected individuals to reduce the risk of MASLD, this education should include guidelines on exercise and diet. In serological assessments, elevated levels of cytokeratin 19 fragment (CYFRA21-1) were noted in both MASLD and lean MASLD groups, implying a potential synergistic role between psoriasis and MASLD.

Cholesterol and low-density lipoprotein as a cause of psoriasis: Results from bidirectional Mendelian randomization

BACKGROUND

Psoriasis is an inflammatory disease that affects many people. However, the causal effect of lipid metabolism on psoriasis has not yet been verified. This study aimed to identify the genetic relationship between serum lipid levels and psoriasis.

METHODS

Bidirectional two-sample Mendelian randomization (MR) was used to analyse the causal relationship between cholesterol and psoriasis. The outcome of the forward causality test was psoriasis. In the analysis of reverse causality, psoriasis was exposed, and 79 single-nucleotide polymorphisms were detected in the genome-wide association study (GWASs) database from the IEU GWASs Project. MR-Egger regression, inverse variance-weighted, weighted median, weighted mode and simple mode were used for the MR analyses.

RESULTS

The level of triglyceride, lipase member N, chylomicrons, extremely large very low-density lipoprotein (VLDL) particles, high-density lipoprotein (HDL) cholesterol levels, cholesterol esters in large HDL, cholesterol esters in medium HDL and cholesterol esters in medium VLDL have not affected the development of psoriasis. However, total cholesterol, total free cholesterol, low-density lipoprotein (LDL) cholesterol levels, cholesterol esters in large VLDL and cholesterol esters in medium LDL were unidirectional causal effects on psoriasis.

CONCLUSION

Bidirectional two-sample MR analysis indicated that high levels of total cholesterol, total free cholesterol, LDL cholesterol, cholesterol esters in large VLDL and cholesterol esters in medium LDL are genetic risk factors for psoriasis.

The roles of tissue resident macrophages in health and cancer

As integral components of the immune microenvironment, tissue resident macrophages (TRMs) represent a self-renewing and long-lived cell population that plays crucial roles in maintaining homeostasis, promoting tissue remodeling after damage, defending against inflammation and even orchestrating cancer progression. However, the exact functions and roles of TRMs in cancer are not yet well understood. TRMs exhibit either pro-tumorigenic or anti-tumorigenic effects by engaging in phagocytosis and secreting diverse cytokines, chemokines, and growth factors to modulate the adaptive immune system. The life-span, turnover kinetics and monocyte replenishment of TRMs vary among different organs, adding to the complexity and controversial findings in TRMs studies. Considering the complexity of tissue associated macrophage origin, macrophages targeting strategy of each ontogeny should be carefully evaluated. Consequently, acquiring a comprehensive understanding of TRMs' origin, function, homeostasis, characteristics, and their roles in cancer for each specific organ holds significant research value. In this review, we aim to provide an outline of homeostasis and characteristics of resident macrophages in the lung, liver, brain, skin and intestinal, as well as their roles in modulating primary and metastatic cancer, which may inform and serve the future design of targeted therapies.

IL-17A Orchestrates Reactive Oxygen Species/HIF1α-Mediated Metabolic Reprogramming in Psoriasis

Immune cell-derived IL-17A is one of the key pathogenic cytokines in psoriasis, an immunometabolic disorder. Although IL-17A is an established regulator of cutaneous immune cell biology, its functional and metabolic effects on nonimmune cells of the skin, particularly keratinocytes, have not been comprehensively explored. Using multiomics profiling and systems biology-based approaches, we systematically uncover significant roles for IL-17A in the metabolic reprogramming of human primary keratinocytes (HPKs). High-throughput liquid chromatography-tandem mass spectrometry and nuclear magnetic resonance spectroscopy revealed IL-17A-dependent regulation of multiple HPK proteins and metabolites of carbohydrate and lipid metabolism. Systems-level MitoCore modeling using flux-balance analysis identified IL-17A-mediated increases in HPK glycolysis, glutaminolysis, and lipid uptake, which were validated using biochemical cell-based assays and stable isotope-resolved metabolomics. IL-17A treatment triggered downstream mitochondrial reactive oxygen species and HIF1α expression and resultant HPK proliferation, consistent with the observed elevation of these downstream effectors in the epidermis of patients with psoriasis. Pharmacological inhibition of HIF1α or reactive oxygen species reversed IL-17A-mediated glycolysis, glutaminolysis, lipid uptake, and HPK hyperproliferation. These results identify keratinocytes as important target cells of IL-17A and reveal its involvement in multiple downstream metabolic reprogramming pathways in human skin.

Insights into Autophagic Machinery and Lysosomal Function in Cells Involved in the Psoriatic Immune-Mediated Inflammatory Cascade

Impaired autophagy, due to the dysfunction of lysosomal organelles, contributes to maladaptive responses by pathways central to the immune system. Deciphering the immune-inflammatory ecosystem is essential, but remains a major challenge in terms of understanding the mechanisms responsible for autoimmune diseases. Accumulating evidence implicates a role that is played by a dysfunctional autophagy-lysosomal pathway (ALP) and an immune niche in psoriasis (Ps), one of the most common chronic skin diseases, characterized by the co-existence of autoimmune and autoinflammatory responses. The dysregulated autophagy associated with the defective lysosomal system is only one aspect of Ps pathogenesis. It probably cannot fully explain the pathomechanism involved in Ps, but it is likely important and should be seriously considered in Ps research. This review provides a recent update on discoveries in the field. Also, it sheds light on how the dysregulation of intracellular pathways, coming from modulated autophagy and endolysosomal trafficking, characteristic of key players of the disease, i.e., skin-resident cells, as well as circulating immune cells, may be responsible for immune impairment and the development of Ps.

Keratinocyte FABP5-VCP complex mediates recruitment of neutrophils in psoriasis

One of the hallmarks of intractable psoriasis is neutrophil infiltration in skin lesions. However, detailed molecular mechanisms of neutrophil chemotaxis and activation remain unclear. Here, we demonstrate a significant upregulation of epidermal fatty acid binding protein (E-FABP, FABP5) in the skin of human psoriasis and psoriatic mouse models. Genetic deletion of FABP5 in mice by global knockout and keratinocyte conditional (Krt6a-Cre) knockout, but not myeloid cell conditional (LysM-Cre) knockout, attenuates psoriatic symptoms. Immunophenotypic analysis shows that FABP5 deficiency specifically reduces skin recruitment of Ly6G+ neutrophils. Mechanistically, activated keratinocytes produce chemokines and cytokines that trigger neutrophil chemotaxis and activation in an FABP5-dependent manner. Proteomic analysis further identifies that FABP5 interacts with valosin-containing protein (VCP), a key player in NF-κB signaling activation. Silencing of FABP5, VCP, or both inhibits NF-κB/neutrophil chemotaxis signaling. Collectively, these data demonstrate dysregulated FABP5 as a molecular mechanism promoting NF-κB signaling and neutrophil infiltration in psoriasis pathogenesis.

Advances in dendritic cell targeting nano-delivery systems for induction of immune tolerance

Dendritic cells (DCs) are the major specialized antigen-presenting cells (APCs), play a key role in initiating the body's immune response, maintain the balance of immunity. DCs can also induce immune tolerance by rendering effector T cells absent and anergy, and promoting the expansion of regulatory T cells. Induction of tolerogenic DCs has been proved to be a promising strategy for the treatment of autoimmune diseases, organ transplantation, and allergic diseases by various laboratory researches and clinical trials. The development of nano-delivery systems has led to advances in situ modulation of the tolerance phenotype of DCs. By changing the material composition, particle size, zeta-potential, and surface modification of nanoparticles, nanoparticles can be used for the therapeutic payloads targeted delivery to DCs, endowing them with great potential in the induction of immune tolerance. This paper reviews how nano-delivery systems can be modulated for targeted delivery to DCs and induce immune tolerance and reviews their potential in the treatment of autoimmune diseases, organ transplantation, and allergic diseases.

Metabolic adaption of mucosal macrophages: Is metabolism a driver of persistence across tissues?

Macrophages play essential roles in tissue homeostasis, defense, and repair. Their functions are highly tissue-specific, and when damage and inflammation stimulate repopulation by circulating monocytes, the incoming monocytes rapidly acquire the same, tissue-specific functions as the previous, resident macrophages. Several environmental factors are thought to guide the functional differentiation of recruited monocytes, including metabolic pressures imposed by the fuel sources available in each tissue. Here we discuss whether such a model of metabolic determinism can be applied to macrophage differentiation across barrier sites, from the lung to the skin. We suggest an alternative model, in which metabolic phenotype is a consequence of macrophage longevity rather than an early driver of tissue-specific adaption.

Crosstalk between cholesterol metabolism and psoriatic inflammation

Psoriasis is a chronic autoinflammatory skin disease associated with multiple comorbidities, with a prevalence ranging from 2 to 3% in the general population. Decades of preclinical and clinical studies have revealed that alterations in cholesterol and lipid metabolism are strongly associated with psoriasis. Cytokines (tumor necrosis factor-α (TNF-α), interleukin (IL)-17), which are important in the pathogenesis of psoriasis, have been shown to affect cholesterol and lipid metabolism. Cholesterol metabolites and metabolic enzymes, on the other hand, influence not only the biofunction of keratinocytes (a primary type of cell in the epidermis) in psoriasis, but also the immune response and inflammation. However, the relationship between cholesterol metabolism and psoriasis has not been thoroughly reviewed. This review mainly focuses on cholesterol metabolism disturbances in psoriasis and their crosstalk with psoriatic inflammation.