S1PR4-dependent CCL2 production promotes macrophage recruitment in a murine psoriasis model

Sphingosine-1-Phosphate Receptor 4 links neutrophils and early local inflammation to lymphocyte recruitment into the draining lymph node to facilitate robust germinal center formation

The successful development of germinal centers (GC) relies heavily on innate mechanisms to amplify the initial inflammatory cascade. In addition to their role in antigen presentation, innate cells are essential for the redirection of circulating lymphocytes toward the draining lymph node (dLN) to maximize antigen surveillance. Sphingosine-1-Phosphate (S1P) and its receptors (S1PR1-5) affect various aspects of immunity; however, the role of S1PR4 in regulating an immune response is not well understood. Here we use a footpad model of localized TH1 inflammation to carefully monitor changes in leukocyte populations within the blood, the immunized tissue, and the dLN. Within hours of immunization, neutrophils failed to adequately mobilize and infiltrate into the footpad tissue of S1PR4-/- mice, thereby diminishing the local vascular changes thought to be necessary for redirecting circulating cells toward the inflamed region. Neutrophil depletion with anti-Ly6G antibodies significantly reduced early tissue edema as well as the redirection and initial accumulation of naïve lymphocytes in dLN of WT mice, while the effects were less prominent or absent in S1PR4-/- dLN. Adoptive transfer experiments further demonstrated that the lymphocyte homing deficiencies in vivo were not intrinsic to the donor S1PR4-/- lymphocytes, but were instead attributed to differences within the S1PR4-deficient host. Reduced cell recruitment in S1PR4-/- mice would seed the dLN with fewer antigen-respondent lymphocytes and indeed, dLN hypertrophy at the peak of the immune response was severely diminished, with attenuated GC and activation pathways in these mice. Histological examination of the S1PR4-/- dLN also revealed an underdeveloped vascular network with reduced expression of the leukocyte tethering ligand, PNAd, within high endothelial venule regions, suggesting inadequate growth of the dLN meant to support a robust GC response. Thus, our study reveals that S1PR4 may link early immune modulation by neutrophils to the initial recruitment of circulating lymphocytes and downstream expansion and maturation of the dLN, thereby contributing to optimal GC development during an adaptive response.

Tanshinol ameliorates imiquimod-induced psoriasis by inhibiting M1 macrophage polarization through suppression of the notch signaling pathway

BACKGROUND

Psoriasis is a common immune-related chronic inflammatory skin disease, often accompanied by significant itching, and once diseased, the course of the disease lasts for most of the lifetime. Tanshinol (TAN) is an active ingredient of Salvia miltiorrhiza, which possesses pharmacological effects such as anti-inflammatory and antioxidant properties. However, the effects of TAN on psoriasis have not been widely reported. Therefore, the aim of this study was to investigate the therapeutic effects and mechanisms of TAN in psoriasis.

METHODS

An imiquimod (IMQ)-induced psoriasis mouse model was constructed and treated with different doses of TAN to observe the changes in skin lesion phenotype, macrophage polarization, inflammation and Notch signaling pathway in mice. Further removal of macrophages or inhibition or activation of Notch signaling pathway was performed to examine the changes in skin lesion phenotype, macrophage polarization, inflammation and Notch signaling pathway in mice. In addition, in vitro experiments verified that TAN regulates RAW264.7 macrophage polarization and cytokine secretion through the Notch pathway.

RESULTS

The results showed that TAN alleviated IMQ-induced skin lesions and pathological phenotypes in psoriasis mice and inhibited Notch signaling pathway and M1-type macrophage polarization. Moreover, macrophage clearance and Notch signaling pathway activation inhibited the effect of TAN on psoriasis. Further in vitro experiments showed that Notch agonists reversed the effects of TAN on macrophage polarization and inflammatory cytokines.

CONCLUSIONS

Collectively, these findings suggest that TAN may exert a therapeutic effect on psoriasis by inhibiting the Notch signaling pathway and thus M1-type macrophage polarization.

Signaling controversy and future therapeutical perspectives of targeting sphingolipid network in cancer immune editing and resistance to tumor necrosis factor-α immunotherapy

Anticancer immune surveillance and immunotherapies trigger activation of cytotoxic cytokine signaling, including tumor necrosis factor-α (TNF-α) and TNF-related apoptosis-inducing ligand (TRAIL) pathways. The pro-inflammatory cytokine TNF-α may be secreted by stromal cells, tumor-associated macrophages, and by cancer cells, indicating a prominent role in the tumor microenvironment (TME). However, tumors manage to adapt, escape immune surveillance, and ultimately develop resistance to the cytotoxic effects of TNF-α. The mechanisms by which cancer cells evade host immunity is a central topic of current cancer research. Resistance to TNF-α is mediated by diverse molecular mechanisms, such as mutation or downregulation of TNF/TRAIL receptors, as well as activation of anti-apoptotic enzymes and transcription factors. TNF-α signaling is also mediated by sphingosine kinases (SphK1 and SphK2), which are responsible for synthesis of the growth-stimulating phospholipid, sphingosine-1-phosphate (S1P). Multiple studies have demonstrated the crucial role of S1P and its transmembrane receptors (S1PR) in both the regulation of inflammatory responses and progression of cancer. Considering that the SphK/S1P/S1PR axis mediates cancer resistance, this sphingolipid signaling pathway is of mechanistic significance when considering immunotherapy-resistant malignancies. However, the exact mechanism by which sphingolipids contribute to the evasion of immune surveillance and abrogation of TNF-α-induced apoptosis remains largely unclear. This study reviews mechanisms of TNF-α-resistance in cancer cells, with emphasis on the pro-survival and immunomodulatory effects of sphingolipids. Inhibition of SphK/S1P-linked pro-survival branch may facilitate reactivation of the pro-apoptotic TNF superfamily effects, although the role of SphK/S1P inhibitors in the regulation of the TME and lymphocyte trafficking should be thoroughly assessed in future studies.

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.

S. epidermidis Rescues Allergic Contact Dermatitis in Sphingosine 1-Phosphate Receptor 2-Deficient Skin

Recent studies have identified a subtype of the S1P-receptor family called sphingosine-1-phosphate receptor 2 (S1PR2), which plays a crucial role in maintaining the skin barrier. It has been observed that S1PR2 and Staphylococcus epidermidis (S. epidermidis) work together to regulate the skin barrier. However, the interaction between these two factors is still unclear. To investigate this, a study was conducted on healthy skin and allergic contact dermatitis (ACD) using 3,4-Dibutoxy-3-cyclobutene-1,2-dione (SADBE) on the ears of S1pr2fl/fl and S1pr2fl/flK14-Cre mice and using 1 × 106 CFU of S. epidermidis to examine its effects on the skin. The results showed that in S. epidermidis-conditioned ACD, the ear thickness of S1pr2fl/flK14-Cre mice was lower than that of S1pr2fl/fl mice, and mRNA expressions of Il-1β and Cxcl2 of S1pr2fl/flK14-Cre mice were lower than that of S1pr2fl/fl mice in ACD with S. epidermidis. Furthermore, the gene expression of Claudin-1 and Occludin in S1pr2fl/flK14-Cre mice was higher than that of S1pr2fl/fl mice in ACD with S. epidermidis. The study concludes that S. epidermidis colonization improves the skin barrier and prevents ACD even when S1P signaling malfunctions.

Insights into Nutritional Strategies in Psoriasis

Psoriasis, an autoimmune chronic inflammatory skin condition, has a high incidence in the general population, reaching 2-4%. Its pathogenesis involves an interplay of genetic factors, immune disturbances, and environmental factors. Within the environmental factors that aid the appearance of this autoimmune skin disease, the Western lifestyle and overall diet play important roles in the steady growth in psoriasis prevalence. Furthermore, psoriasis is associated with comorbidities such as psoriatic arthritis, cardiovascular disease, metabolic syndrome, and obesity. Accumulating evidence suggests that obesity is an important risk factor for psoriasis. Moreover, obesity aggravates established psoriasis, and a reduction in the body mass index can improve the clinical outcomes of psoriasis and increase the efficacy of standard psoriasis therapies. The possible connection between this autoimmune disease and obesity relies on the fact that white adipose tissue is an essential endocrine organ that secretes an array of immune mediators and inflammatory and metabolic factors with pro-inflammatory action. Thus, immune-mediated mechanisms in both psoriasis and obesity conditions are common factors. This paper describes the factors that link obesity with skin autoimmune disease and highlights the importance of the stimulatory or regulatory effects of nutrients and food in psoriasis and the possible improvement of psoriasis through nutritional strategies.

Pathogenic sphingosine 1-phosphate pathway in psoriasis: a critical review of its pathogenic significance and potential as a therapeutic target

Sphingosine-1-phosphate (S1P) is a sphingolipid mediator that exerts a variety of biological functions, including immune, cardiovascular, and neurological regulation as well as tumor promotion, through high-affinity G protein-coupled receptors (S1P_1-5). It has been reported that circulating S1P levels remain higher in patients with psoriasis than in healthy individuals and that circulating S1P levels do not decrease after anti-TNF-α treatment in those patients. The S1P-S1PR signaling system plays an important role in inhibiting keratinocyte proliferation, regulating lymphocyte migration, and promoting angiogenesis, thus contributing to the regulation of psoriasis pathogenesis. Here, we review the mechanisms by which S1P-S1PR signaling affects the development of psoriasis and the available clinical/preclinical evidence for targeting S1P-S1PR in psoriasis. S1P-S1PR signaling mechanisms may partially explain the link between psoriasis and its comorbidities. Although the detailed mechanisms remain to be elucidated, S1P may be a new target for future psoriasis remission.

Silence of S1PR4 Represses the Activation of Fibroblast-like Synoviocytes by Regulating IL-17/STAT3 Signaling Pathway

Rheumatoid arthritis (RA) is a chronic inflammatory disease with persistent inflammation and progressive joint damage. However, the underlying pathological mechanisms of RA are still unclear. Fibroblast‑like synoviocytes (FLSs) play an important role in the pathogenesis of RA by the regulation of proliferation and apoptosis, and the release of multiple pro-inflammatory factors. The lipid mediator sphingosine-1-phosphate receptor 4 (S1PR4) is one of the sphingolipid sphingosine-1-phosphate (S1P) receptors, which affects the function of immune cells. However, the role of S1PR4 in the activation of FLSs and the development of RA is unknown. In this study, we found that the expression of S1PR4 was significantly increased in RA-FLSs. The silence of S1PR4 decreases the proliferation, migration, proinflammation, and promotes the apoptosis of RA-FLSs, accompanied with repressing interleukin-17 (IL-17)/signal transducer and activator of transcription 3 (STAT3) signal pathway. However, the regulatory effects of S1PR4 silencing on RA-FLSs were partly abolished by additional recombinant human (rh) IL-17A treatment. Therefore, our study demonstrated that S1PR4 silencing might inhibit proliferation, migration, proinflammation, and promote apoptosis of RA-FLSs partly by repressing IL-17, which suggests that inhibitors for S1PR4 might be a potentially promising strategy for the treatment of RA.

Sphingosine 1-Phosphate as Essential Signaling Molecule in Inflammatory Skin Diseases

Sphingolipids are crucial molecules of the mammalian epidermis. The formation of skin-specific ceramides contributes to the formation of lipid lamellae, which are important for the protection of the epidermis from excessive water loss and protect the skin from the invasion of pathogens and the penetration of xenobiotics. In addition to being structural constituents of the epidermal layer, sphingolipids are also key signaling molecules that participate in the regulation of epidermal cells and the immune cells of the skin. While the importance of ceramides with regard to the proliferation and differentiation of skin cells has been known for a long time, it has emerged in recent years that the sphingolipid sphingosine 1-phosphate (S1P) is also involved in processes such as the proliferation and differentiation of keratinocytes. In addition, the immunomodulatory role of this sphingolipid species is becoming increasingly apparent. This is significant as S1P mediates a variety of its actions via G-protein coupled receptors. It is, therefore, not surprising that dysregulation in the signaling pathways of S1P is involved in the pathophysiological conditions of skin diseases. In the present review, the importance of S1P in skin cells, as well as the immune cells of the skin, is elaborated. In particular, the role of the molecule in inflammatory skin diseases will be discussed. This is important because interfering with S1P signaling pathways may represent an innovative option for the treatment of inflammatory skin diseases.

The Role of Sphingolipids in the Pathogenesis of Psoriasis

Psoriasis is a complex, chronic, immunologically mediated disease which involves skin and joints. Psoriasis is commonly connected with numerous other diseases such as liver diseases, metabolic syndrome, impaired glucose tolerance, diabetes mellitus, atherosclerosis, hypertension, and ischemic heart disease. Interestingly, comorbidities of psoriasis are an attention-grabbing issue. Additionally, it can cause impairment of quality of life and may be associated with depressive disorders. Altered levels of ceramides in psoriatic skin may lead to anti-apoptotic and pro-proliferative states, consequently leading to an over-proliferation of keratinocytes and the development of skin lesions. The pathophysiology of psoriasis and its comorbidities is not fully understood yet. Sphingolipids (including ceramides) and their disturbed metabolism may be the link between psoriasis and its comorbidities. Overall, the goal of this review was to discuss the role of sphingolipid disturbances in psoriasis and its comorbidities. We searched the PubMed database for relevant articles published before the beginning of May 2022. The systematic review included 65 eligible original articles.

The Crosstalk between FcεRI and Sphingosine Signaling in Allergic Inflammation

Sphingolipid molecules have recently attracted attention as signaling molecules in allergic inflammation diseases. Sphingosine-1-phosphate (S1P) is synthesized by two isoforms of sphingosine kinases (SPHK 1 and SPHK2) and is known to be involved in various cellular processes. S1P levels reportedly increase in allergic inflammatory diseases, such as asthma and anaphylaxis. FcεRI signaling is necessary for allergic inflammation as it can activate the SPHKs and increase the S1P level; once S1P is secreted, it can bind to the S1P receptors (S1PRs). The role of S1P signaling in various allergic diseases is discussed. Increased levels of S1P are positively associated with asthma and anaphylaxis. S1P can either induce or suppress allergic skin diseases in a context-dependent manner. The crosstalk between FcεRI and S1P/SPHK/S1PRs is discussed. The roles of the microRNAs that regulate the expression of the components of S1P signaling in allergic inflammatory diseases are also discussed. Various reports suggest the role of S1P in FcεRI-mediated mast cell (MC) activation. Thus, S1P/SPHK/S1PRs signaling can be the target for developing anti-allergy drugs.

Chemokine Profile in Psoriasis Patients in Correlation with Disease Severity and Pruritus

Psoriasis (PsO) is a chronic, immune-mediated, inflammatory skin disease associated in most cases with pruritus. Chemokines seem to play a significant role in PsO pathogenesis. The aim of the study was to analyse serum concentrations of CCL2/MCP-1, CCL3/MIP-1α, CCL4/MIP-1β, CCL5/RANTES, CCL17/TARC, CCL18/PARC, CCL22/MDC and CXCL8/IL-8, and their correlation with PsO severity and pruritus intensity. The study included 60 PsO patients and 40 healthy volunteers. Serum concentrations of six (CCL2/MCP-1, CCL3/MIP-1α, CCL5/RANTES, CCL17/TARC, CCL18/PARC and CCL22/MDC) out of eight analysed chemokines were significantly elevated in PsO patients; however, they did not correlate with disease severity. The serum level of CCL5/RANTES was significantly higher in patients with the psoriasis area and severity index (PASI) ≥ 15 (p = 0.01). The serum concentration of CCL17/TARC correlated positively with pruritus assessed using the visual analogue scale (VAS) (R = 0.47; p = 0.05). The study indicated CCL17/TARC as a potential biomarker of pruritus intensity in PsO patients. Chemokines appear to be involved in the development of PsO systemic inflammation. Further detailed studies on the interactions between chemokines, proinflammatory cytokines and immune system cells in PsO are required to search for new targeted therapies.

Dendritic Cells and Macrophages in the Pathogenesis of Psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by scaly indurated erythema. This disease impairs patients’ quality of life enormously. Pathological findings demonstrate proliferation and abnormal differentiation of keratinocytes and massive infiltration of inflammatory immune cells. The pathogenesis of psoriasis is complicated. Among immune cells, dendritic cells play a pivotal role in the development of psoriasis in both the initiation and the maintenance phases. In addition, it has been indicated that macrophages contribute to the pathogenesis of psoriasis especially in the initiation phase, although studies on macrophages are limited. In this article, we review the roles of dendritic cells and macrophages in the pathogenesis of psoriasis.

Sphingosine 1-Phosphate Signaling at the Skin Barrier Interface

Sphingosine 1-phosphate (S1P) is a product of membrane sphingolipid metabolism. S1P is secreted and acts via G-protein-coupled receptors, S1PR1-5, and is involved in diverse cellular functions, including cell proliferation, immune suppression, and cardiovascular functions. Recent studies have shown that the effects of S1P signaling are extended further by coupling the different S1P receptors and their respective downstream signaling pathways. Our group has recently reported that S1P inhibits cell proliferation and induces differentiation in human keratinocytes. There is a growing understanding of the connection between S1P signaling, skin barrier function, and skin diseases. For example, the activation of S1PR1 and S1PR2 during bacterial invasion regulates the synthesis of inflammatory cytokines in human keratinocytes. Moreover, S1P-S1PR2 signaling is involved in the production of inflammatory cytokines and can be triggered by epidermal mechanical stress and bacterial invasion. This review highlights how S1P affects human keratinocyte proliferation, differentiation, immunoreaction, and mast cell immune response, in addition to its effects on the skin barrier interface. Finally, studies targeting S1P-S1PR signaling involved in inflammatory skin diseases are also presented.

A systematic comparison of the effect of topically applied anthraquinone aglycones to relieve psoriasiform lesion: The evaluation of percutaneous absorption and anti-inflammatory potency

The anthraquinones derived from rhubarb are reported to have anti-inflammatory activity. The present study aimed to assess the topical application of rhubarb anthraquinone aglycones for psoriasis treatment. The antipsoriatic effect of five anthraquinones, including aloe-emodin, rhein, emodin, physcion, and chrysophanol, was compared to elucidate a structure-permeation relationship. Molecular modeling was employed to determine the physicochemical properties. Both macrophages (differentiated THP-1) and keratinocytes (HaCaT) were used to examine the anti-inflammatory activity in the cell-based study. The in vitro pig skin absorption showed that chrysophanol was the compound with the highest cutaneous accumulation. Topically applied rhein was detected to be largely delivered to the receptor compartment. The absorption of rhein was increased by 5-fold in the barrier-deficient skin as compared to intact skin. By stimulating macrophages with imiquimod (IMQ) to model the inflammation in psoriasis, it was found that the anthraquinones significantly reduced IL-6, IL-23, and TNF. The cytokine inhibition level was comparable for the five compounds. The anthraquinones suppressed cytokines by inhibiting the activation of MAPK and NF-κB signaling. The anthraquinones also downregulated IL-6, IL-8, and IL-24 in the inflammatory keratinocytes stimulated with TNF. Rhein and chrysophanol were comparable to curtail the STAT3 phosphorylation in keratinocytes induced by the conditioned medium of stimulated macrophages. The IMQ-induced psoriasiform mouse model demonstrated the improvement of scaling, erythema, and epidermal hyperplasia by topically applied rhein or chrysophanol. The epidermal acanthosis evoked by IMQ was reduced with rhein and chrysophanol by 3-fold. The histological profiles exhibit that both anthraquinone compounds diminished the number of macrophages and neutrophils in the lesional skin, skin-draining lymph node, and spleen. Rhein and chrysophanol showed multifunctional inhibition, by regulating several targets for alleviating psoriasiform inflammation.

Sphingosine 1-Phosphate Receptor 4 Promotes Nonalcoholic Steatohepatitis by Activating NLRP3 Inflammasome

BACKGROUND & AIMS

Sphingosine 1-phosphate receptors (S1PRs) are a group of G-protein-coupled receptors that confer a broad range of functional effects in chronic inflammatory and metabolic diseases. S1PRs also may mediate the development of nonalcoholic steatohepatitis (NASH), but the specific subtypes involved and the mechanism of action are unclear.

METHODS

We investigated which type of S1PR isoforms is activated in various murine models of NASH. The mechanism of action of S1PR4 was examined in hepatic macrophages isolated from high-fat, high-cholesterol diet (HFHCD)-fed mice. We developed a selective S1PR4 functional antagonist by screening the fingolimod (2-amino-2-[2-(4- n -octylphenyl)ethyl]-1,3- propanediol hydrochloride)-like sphingolipid-focused library.

RESULTS

The livers of various mouse models of NASH as well as hepatic macrophages showed high expression of S1pr4. Moreover, in a cohort of NASH patients, expression of S1PR4 was 6-fold higher than those of healthy controls. S1pr4^+/- mice were protected from HFHCD-induced NASH and hepatic fibrosis without changes in steatosis. S1pr4 depletion in hepatic macrophages inhibited lipopolysaccharide-mediated Ca⁺⁺ release and deactivated the Nod-like receptor pyrin domain-containning protein 3 (NLRP3) inflammasome. S1P increased the expression of S1pr4 in hepatic macrophages and activated NLRP3 inflammasome through inositol trisphosphate/inositol trisphosphate-receptor-dependent [Ca⁺⁺] signaling. To further clarify the biological function of S1PR4, we developed SLB736, a novel selective functional antagonist of SIPR4. Similar to S1pr4^+/- mice, administration of SLB736 to HFHCD-fed mice prevented the development of NASH and hepatic fibrosis, but not steatosis, by deactivating the NLRP3 inflammasome.

CONCLUSIONS

S1PR4 may be a new therapeutic target for NASH that mediates the activation of NLRP3 inflammasome in hepatic macrophages.

Psoriasiform Inflammation Is Associated with Mitochondrial Fission/GDAP1L1 Signaling in Macrophages

While psoriasis is known as a T cell- and dendritic cell-driven skin inflammation disease, macrophages are also reported to play some roles in its development. However, the signaling pathway of activated macrophages contributing to psoriasis is not entirely understood. Thus, we aimed to explore the possible mechanisms of how macrophages initiate and sustain psoriasis. The differentiated THP1 cells, stimulated by imiquimod (IMQ), were utilized as the activated macrophage model. IMQ was also employed to produce psoriasis-like lesions in mice. A transcriptomic assay of macrophages revealed that the expressions of pro-inflammatory mediators and GDAP1L1 were largely increased after an IMQ intervention. The depletion of GDAP1L1 by short hairpin (sh)RNA could inhibit cytokine release by macrophages. GDAP1L1 modulated cytokine production by activating the phosphorylation of mitogen-activated protein kinases (MAPKs) and nuclear factor (NF)-κB pathways. Besides GDAP1L1, another mitochondrial fission factor, Drp1, translocated from the cytosol to mitochondria after IMQ stimulation, followed by the mitochondrial fragmentation according to the immunofluorescence imaging. Clodronate liposomes were injected into the mice to deplete native macrophages for examining the latter’s capacity on IMQ-induced inflammation. The THP1 cells, with or without GDAP1L1 silencing, were then transplanted into the mice to monitor the deposition of macrophages. We found a significant THP1 accumulation in the skin and lymph nodes. The silencing of GDAP1L1 in IMQ-treated animals reduced the psoriasiform severity score from 8 to 2. After depleting GDAP1L1, the THP1 recruitment in the lymph nodes was decreased by 3-fold. The skin histology showed that the GDAP1L1-mediated macrophage activation induced neutrophil chemotaxis and keratinocyte hyperproliferation. Thus, mitochondrial fission can be a target for fighting against psoriatic inflammation.

Macrophage Motility in Wound Healing Is Regulated by HIF-1α via S1P Signaling

Accumulating evidence indicates that the molecular pathways mediating wound healing induce cell migration and localization of cytokines to sites of injury. Macrophages are immune cells that sense and actively respond to disturbances in tissue homeostasis by initiating, and subsequently resolving, inflammation. Hypoxic conditions generated at a wound site also strongly recruit macrophages and affect their function. Hypoxia inducible factor (HIF)-1α is a transcription factor that contributes to both glycolysis and the induction of inflammatory genes, while also being critical for macrophage activation. For the latter, HIF-1α regulates sphingosine 1-phosphate (S1P) to affect the migration, activation, differentiation, and polarization of macrophages. Recently, S1P and HIF-1α have received much attention, and various studies have been performed to investigate their roles in initiating and resolving inflammation via macrophages. It is hypothesized that the HIF-1α/S1P/S1P receptor axis is an important determinant of macrophage function under inflammatory conditions and during disease pathogenesis. Therefore, in this review, biological regulation of monocytes/macrophages in response to circulating HIF-1α is summarized, including signaling by S1P/S1P receptors, which have essential roles in wound healing.

2,4-Dimethoxy-6-Methylbenzene-1,3-diol, a Benzenoid From Antrodia cinnamomea, Mitigates Psoriasiform Inflammation by Suppressing MAPK/NF-κB Phosphorylation and GDAP1L1/Drp1 Translocation

Antrodia cinnamomea exhibits anti-inflammatory, antioxidant, and immunomodulatory activities. We aimed to explore the antipsoriatic potential of 2,4-dimethoxy-6-methylbenzene-1,3-diol (DMD) derived from A. cinnamomea. The macrophages activated by imiquimod (IMQ) were used as the cell model for examining the anti-inflammatory effect of DMD in vitro. A significantly high inhibition of IL-23 and IL-6 by DMD was observed in THP-1 macrophages and bone marrow-derived mouse macrophages. The conditioned medium of DMD-treated macrophages could reduce neutrophil migration and keratinocyte overproliferation. DMD could downregulate cytokine/chemokine by suppressing the phosphorylation of mitogen-activated protein kinases (MAPKs) and NF-κB. We also observed inhibition of GDAP1L1/Drp1 translocation from the cytoplasm to mitochondria by DMD intervention. Thus, mitochondrial fission could be a novel target for treating psoriatic inflammation. A psoriasiform mouse model treated by IMQ showed reduced scaling, erythema, and skin thickening after topical application of DMD. Compared to the IMQ stimulation only, the active compound decreased epidermal thickness by about 2-fold. DMD diminished the number of infiltrating macrophages and neutrophils and their related cytokine/chemokine production in the lesional skin. Immunostaining of the IMQ-treated skin demonstrated the inhibition of GDAP1LI and phosphorylated Drp1 by DMD. The present study provides insight regarding the potential use of DMD as an effective treatment modality for psoriatic inflammation.

Putative Genes and Pathways Involved in the Acne Treatment of Isotretinoin via Microarray Data Analyses

Acne is the eighth most common disease worldwide. Disease burden of acne such as anxiety, reduced self-esteem, and facial scarring lowers the life quality of acne patients. Isotretinoin is the most potent treatment for moderate-severe acne. However, the adverse events of isotretinoin especially teratogenicity limit its use. This study aims at investigating the therapeutical mechanisms of isotretinoin using bioinformatics analysis. Differentially expressed genes (DEGs) were filtered from microarray datasets GSE10432, GSE10433, and GSE11792. Functional and pathway enrichment analyses of DEGs were performed. Protein–protein interaction (PPI) network and module analyses were also conducted based on DEGs. Using isotretinoin for 1 week, LCN2, PTGES, and GDF15 were upregulated and might mediate sebocytes apoptosis and thus decreased sebum production; CCL2 originated from activated TNF signaling pathway and S100A7 could be related with “acne-flare”. While treating with isotretinoin for 8 weeks, key genes were downregulated, including HMGCS1, HMGCR, FDFT1, MVD, IDI1, and FDPS, which may be associated with decreased sebum synthesis; HMGCS1, HMGCR, and FDFT1 also probably associated with apoptosis of sebocytes. There were only two common genes including ACSBG1 and BCAT2 which worked in both 1 week and 8 weeks and could associate with decreased sebum synthesis and apoptosis of sebocytes, respectively. These results indicate potential therapeutics and side effect mechanisms of isotretinoin in the acne treatment and provide a research direction to further investigate the therapeutic mechanism of isotretinoin and thus develop retinoid-like compounds with similar curative effect and without teratogenicity.

Investigation on the Mechanism of Qubi Formula in Treating Psoriasis Based on Network Pharmacology

Objective

To elucidate the pharmacological mechanisms of Qubi Formula (QBF), a traditional Chinese medicine (TCM) formula which has been demonstrated as an effective therapy for psoriasis in China.

Methods

The Traditional Chinese Medicine Systems Pharmacology (TCMSP) database, BATMAN-TCM database, and literature search were used to excavate the pharmacologically active ingredients of QBF and to predict the potential targets. Psoriasis-related targets were obtained from Therapeutic Target Database (TTD), DrugBank database (DBD), MalaCards database, and DisGeNET database. Then, we established the network concerning the interactions of potential targets of QBF with well-known psoriasis-related targets by using protein-protein interaction (PPI) data in String database. Afterwards, topological parameters (including DNMC, Degree, Closeness, and Betweenness) were calculated to excavate the core targets of Qubi Formula in treating psoriasis (main targets in the PPI network). Cytoscape was used to construct the ingredients-targets core network for Qubi Formula in treating psoriasis, and ClueGO was used to perform GO-BP and KEGG pathway enrichment analysis on these core targets.

Results

The ingredient-target-disease core network of QBF in treating psoriasis was screened to contain 175 active ingredients, which corresponded to 27 core targets. Additionally, enrichment analysis suggested that targets of QBF in treating psoriasis were mainly clustered into multiple biological processes (associated with nuclear translocation of proteins, cellular response to multiple stimuli (immunoinflammatory factors, oxidative stress, and nutrient substance), lymphocyte activation, regulation of cyclase activity, cell-cell adhesion, and cell death) and related pathways (VEGF, JAK-STAT, TLRs, NF-κB, and lymphocyte differentiation-related pathways), indicating the underlying mechanisms of QBF on psoriasis.

Conclusion

In this work, we have successfully illuminated that Qubi Formula could relieve a wide variety of pathological factors (such as inflammatory infiltration and abnormal angiogenesis) of psoriasis in a "multicompound, multitarget, and multipathway" manner by using network pharmacology. Moreover, our present outcomes might shed light on the further clinical application of QBF on psoriasis treatment.

Druggable Sphingolipid Pathways: Experimental Models and Clinical Opportunities

Intensive research in the field of sphingolipids has revealed diverse roles in cell biological responses and human health and disease. This immense molecular family is primarily represented by the bioactive molecules ceramide, sphingosine, and sphingosine 1-phosphate (S1P). The flux of sphingolipid metabolism at both the subcellular and extracellular levels provides multiple opportunities for pharmacological intervention. The caveat is that perturbation of any single node of this highly regulated flux may have effects that propagate throughout the metabolic network in a dramatic and sometimes unexpected manner. Beginning with S1P, the receptors for which have thus far been the most clinically tractable pharmacological targets, this review will describe recent advances in therapeutic modulators targeting sphingolipids, their chaperones, transporters, and metabolic enzymes.