Serine deficiency exacerbates psoriatic skin inflammation by regulating S-adenosyl methionine-dependent DNA methylation and NF-κB signalling activation in keratinocytes.

BACKGROUND: Serine metabolism is crucial for tumour oncogenesis and immune responses. S-adenosyl methionine (SAM), a methyl donor, is typically derived from serine-driven one-carbon metabolism. However, the involvement of serine metabolism in psoriatic skin inflammation remains unclear. OBJECTIVES: To investigate the association between serine metabolism and psoriatic skin inflammation. METHODS: Clinical samples were collected from patients with psoriasis and the expression of serine biosynthesis enzymes was evaluated. The HaCaT human keratinocyte cell line was transfected with small interfering RNA (siRNA) of key enzyme or treated with inhibitors. RNA sequencing and DNA methylation assays were performed to elucidate the mechanisms underlying serine metabolism-regulated psoriatic keratinocyte inflammation. An imiquimod (IMQ)-induced psoriasis mouse model was established to determine the effect of the SAM administration on psoriatic skin inflammation. RESULTS: The expression of serine synthesis pathway enzymes, including the first rate-limiting enzyme in serine biosynthesis, phosphoglycerate dehydrogenase (PHGDH), was downregulated in the epidermal lesions of patients with psoriasis compared with that in healthy controls. Suppressing PHGDH in keratinocytes promoted the production of proinflammatory cytokines and enrichment of psoriatic-related signalling pathways, including the tumour necrosis factor-alpha (TNF-α) signalling pathway, interleukin (IL)-17 signalling pathway and NF-κB signalling pathway. In particular, PHGDH inhibition markedly promoted the secretion of IL-6 in keratinocytes with or without IL-17A, IL-22, IL-1α, oncostatin M and TNF-α (mix) stimulation. Mechanistically, PHGDH inhibition upregulated the expression of IL-6 by inhibiting SAM-dependent DNA methylation at the promoter and increasing the binding of myocyte enhancer factor 2A. Furthermore, PHGDH inhibition increased the secretion of IL-6 by increasing the activation of NF-κB via SAM inhibition. SAM treatment effectively alleviated IMQ-induced psoriasis-like skin inflammation in mice. CONCLUSIONS: Our study revealed the crucial role of PHGDH in antagonising psoriatic skin inflammation and indicated that targeting serine metabolism may represent a novel therapeutic strategy for treating psoriasis.

Neutrophil extracellular traps promote keratinocyte inflammation via AIM2 inflammasome and AIM2-XIAP in psoriasis.

The infiltration of neutrophils in the epidermis and the release of neutrophil extracellular traps (NETs) are important events in the pathogenesis of psoriasis, but the regulatory roles and internal mechanism of NETs in psoriasis are largely unknown. Here, we demonstrate that NETs can activate the absent-in-melanoma-2 (AIM2) inflammasome in keratinocytes through the p38-MAPK signalling pathway, and targeting NETs with CI-amidine in vivo reduces AIM2 expression and ameliorates imiquimod-induced psoriasis-like phenotype in mice. Notably, NETs-activated AIM2 in keratinocytes not only promotes IL-1ß production through the classical inflammasome pathway but also promotes IFN-γ production via X-linked inhibitor of apoptosis protein (XIAP), thereby mediating the immune responses of keratinocytes. In conclusion, our study demonstrates that the NETs-AIM2 axis exerts multiple pro-inflammatory effects on keratinocytes and may serve as a potential target for psoriasis therapy.

Nuclear-targeted EGF receptor enhances proliferation and migration of human anaplastic thyroid cancer cells.

INTRODUCTION: Epidermal growth factor (EGF) has various important physiological functions, which it exerts by binding to the epidermal growth factor receptor (EGFR). Reports show that EGF expression is strongly correlated with the occurrence and development of many types of tumour. To date, however, the relationship between EGF/EGFR and the occurrence and development of thyroid carcinoma remains unclear. MATERIAL AND METHODS: In the current study, we investigated this phenomenon using human anaplastic thyroid carcinoma cell lines (SUN-80). RESULTS: The results indicated that EGF triggered the EGFR-mediated intracellular signalling pathway, including signal transducers and activators of transcription 1/3/5 (STAT1/3/5) and protein kinase B (AKT) in a time- and dose-dependent manner. In addition, results from EGF-induced EGFR internalization and co-localization analyses showed that clathrin, Rab5/7, and EEA1 play critical roles in the intracellular trafficking of EGF/EGFR. Interestingly, EGF triggered EGFR translocation into the nucleus, while nuclear-localized EGFR affected cell cycle distribution, thereby significantly promoting the ration of S phase. Overall, these findings indicated that nuclear EGFR exerts biological activity and physiological functions, including changing cell cycle, which in turn promotes proliferation and migration of SUN-80 cells. CONCLUSION: These findings lay a foundation for further explorations seeking to understand the biological effects of the EGF/EGFR system on the occurrence and development of thyroid cancer.

LCN2 Mediates Skin Inflammation in Psoriasis through the SREBP2‒NLRC4 Axis.

Lipocalins are a family of secreted adipokines that regulate cell lipid metabolism and immune responses. Although we have previously revealed that LCN2 modulates neutrophil activation in psoriasis, the other roles of LCN2 in psoriatic local inflammation have remained elusive. In this study, we found that 24p3R, the well-known specific receptor of LCN2, was highly expressed in the lesional epidermis of patients with psoriasis. Silencing 24p3R (also known as slc22a17) alleviated hyperkeratosis, inflammatory cell infiltration, and overexpression of inflammatory mediators in an imiquimod-induced psoriasis-like mouse model. In vitro, LCN2 enhanced the expression of proinflammatory factors in primary keratinocytes, such as IL-1ß, IL-23, CXCL1, and CXCL10, which was paralleled by enforced cholesterol biosynthetic signaling. Importantly, taking in vivo and in vitro approaches, we discovered the SREBP2, a vital transcriptional factor in cholesterol synthesis pathway, as the critical mediator of LCN2-induced keratinocyte activation, which bound to the promoter region of NLRC4. Suppressing SREBP2 in mice attenuated NLRC4 signaling and psoriasis-like dermatitis. Taken together, this study identifies the critical role of LCN2‒SREBP2‒NLRC4 axis in the pathogenesis of psoriasis and proposes 24p3R or SREBP2 as a potential therapeutic target for psoriasis.

IRAK2 Has a Critical Role in Promoting Feed-Forward Amplification of Epidermal Inflammatory Responses.

Many inflammatory skin diseases are characterized by altered epidermal differentiation. Whether this altered differentiation promotes inflammatory responses has been unknown. Here, we show that IRAK2, a member of the signaling complex downstream of IL-1 and IL-36, correlates positively with disease severity in both atopic dermatitis and psoriasis. Inhibition of epidermal IRAK2 normalizes differentiation and inflammation in two mouse models of psoriasis- and atopic dermatitis-like inflammation. Specifically, we demonstrate that IRAK2 ties together proinflammatory and differentiation-dependent responses and show that this function of IRAK2 is specific to keratinocytes and acts through the differentiation-associated transcription factor ZNF750. Taken together, our findings suggest that IRAK2 has a critical role in promoting feed-forward amplification of inflammatory responses in skin through modulation of differentiation pathways and inflammatory responses.

Synthesis and anti-inflammatory activity of novel steroidal chalcones with 3ß-pregnenolone ester derivatives in RAW 264.7 cells in vitro.

To identify new potential anti-inflammatory agents, we herein report the synthesis of novel steroidal chalcones with 3ß-pregnenolone esters of cinnamic acid derivatives using pregnenolone as the starting material. The structures of the newly synthesised compounds were confirmed by 1H NMR, 13C NMR, HRMS and infrared imaging. All the derivatives were examined to determine their in vitro anti-inflammatory profiles against LPS-induced inflammation in RAW 264.7 cells; the derivates were evaluated by the quantification of the pro-inflammatory mediator nitric oxide (NO) in the cell culture supernatant based on the Griess reaction, which measures nitrite levels, followed by an in vitro cytotoxicity study. Among these novel derivatives, compound 11e [3ß-3-phenyl acrylate-pregn-5-en-17ß-yl-3' -(p-fluoro)-phenylprop-2'-en-1'-one] was identified as the most potent anti-inflammatory agent, which showed significant anti-inflammatory activity by inhibiting the LPS-induced pro-inflammatory mediator NO in a dose-dependent manner without any cytotoxicity. Moreover, compound 11e markedly inhibited the expression of pro-inflammatory cytokines, including inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α), and cyclooxygenase-2 (COX-2), in LPS-induced RAW 264.7 cells. Further studies confirmed that compound 11e significantly suppressed the transcriptional activity of NF-κB in activated RAW 264.7 cells. Molecular docking study revealed the strong binding affinity of compound 11e to the active site of the pro-inflammatory proteins, which confirmed that compound 11e acted as an anti-inflammatory mediator. These results indicated that steroidal chalcones with 3ß-pregnenolone esters of cinnamic acid derivatives might be considered for further research in the design of anti-inflammatory drugs, and compound 11e might be a promising therapeutic anti-inflammatory drug candidate.

Neutrophils Enhance Cutaneous Vascular Dilation and Permeability to Aggravate Psoriasis by Releasing Matrix Metallopeptidase 9.

Neutrophil infiltration and papillary vessel dilation are hallmarks of the initiation phase of psoriatic lesions. However, how neutrophils aggravate psoriasis development during transendothelial migration and the interaction between neutrophils and cutaneous vascular endothelial cells are less well-understood. In this study, we reported that neutrophils and cutaneous vascular endothelial cells activated each other when neutrophils migrated through the cutaneous endothelial barrier. In addition, neutrophil infiltration into skin lesions caused vascular remodeling including cutaneous vasodilation and enhanced vascular permeability in vivo and in vitro. Microarray gene profile data showed that matrix metallopeptidase (MMP)-9 was overexpressed in psoriatic neutrophils, and zymography assay further validated the bioactivity of MMP-9 secreted by psoriatic neutrophils. Moreover, MMP-9 activated vascular endothelial cells through the extracellular signal‒regulated kinase 1/2 and p38-MAPK signaling pathways, enhancing CD4+ T-cell transmigration in vitro. Correspondingly, an MMP-9 inhibitor significantly reduced cutaneous vasodilation, vascular permeability, and psoriatic symptoms in an imiquimod- or IL-23‒induced psoriasiform mouse model. Overall, our study demonstrates that neutrophil-derived MMP-9 induces cutaneous vasodilation and hyperpermeability by activating cutaneous vascular endothelial cells, thus facilitating psoriatic lesion development, which increases our knowledge on the role of neutrophils in the pathogenesis of psoriasis.

Aryl Hydrocarbon Receptor in Cutaneous Vascular Endothelial Cells Restricts Psoriasis Development by Negatively Regulating Neutrophil Recruitment.

Vascular endothelial cells (VECs) that line the interiors of blood vessels participate in physiological and inflammatory processes. All skin cell types express the aryl hydrocarbon receptor (AhR), which is involved in the pathogenesis of psoriasis. However, the role of the cutaneous VEC AhR in the pathogenesis of psoriasis remains elusive. In the present study, we found that AhR protein expression and activation were downregulated in psoriatic VECs. Furthermore, cutaneous VEC-specific AhR-knockout (AhRcVECs-KO) mice were established. Using imiquimod and IL-23-induced psoriasis models, we found that skin inflammation was exacerbated with excessive neutrophil recruitment in AhRcVECs-KO mice. Furthermore, neutrophil neutralization alleviates exacerbated inflammation in imiquimod-treated AhRcVECs-KO mice. In addition, cutaneous VECs in AhRcVECs-KO mice exhibited increased dilation and activation compared with those in control mice. Finally, AhR-deficient microvascular endothelial cells stimulated by proinflammatory cytokines showed increased ICAM-1 expression in vivo and in vitro, which may have facilitated neutrophil recruitment. In summary, our study demonstrates that AhR in dermal VECs restricts psoriasis development by negatively regulating neutrophil recruitment, thereby providing insight into the pathogenesis of psoriasis.