Macrophage autophagy deficiency-induced CEBPB accumulation alleviates atopic dermatitis via impairing M2 polarization

Multiple omics-based machine learning reveals specific macrophage sub-clusters in renal ischemia-reperfusion injury and constructs predictive models for transplant outcomes

BACKGROUND

Ischemia-reperfusion injury (IRI) is closely associated with numerous severe postoperative complications, including acute rejection, delayed graft function (DGF) and graft failure. Macrophages are central to modulating the aseptic inflammatory response during the IRI process. The objective of this study is to conduct an analysis of the developmental and differentiation characteristics of macrophages in IRI, identify distinct molecules subtypes of IRI, and establish robust predictive strategies for DGF and graft survival.

METHOD

We analyzed scRNA-Seq data from GEO database to identify macrophage sub-clusters specific to renal IRI, and use the hdWGCNA algorithm to screen gene modules closely associated with this sub-cluster. Integrating these module genes with the results from bulk RNA-Seq differential analysis to obtain hub genes, and delineating the different IRI molecular subtypes through consensus clustering based on the expression profiles of hub genes. Innovatively, the gene expression matrix was transformed into a unique graphic pixel module and applied advanced computer vision processing algorithms to construct a DGF predictive model. Additionally, we also employed 111 combinations of 10 machine learning algorithms to develop a predictive signature for graft survival. Finally, we validated the expression of the key gene ANXA1 in a mouse IRI model using qRT-PCR, WB, and IHC.

RESULT

This study successfully identified a subset of macrophages closely associated with renal IRI, and cell communication and pseudo-time analysis implied that they may be instrumental in both the maintenance and exacerbation of the IRI process. Utilizing the expression patterns of hub genes, recipients can be clustered into two subtypes (CI and C2) with unique clinical and molecular features. We innovatively applied deep learning algorithms to construct a model for DGF prediction, which can effectively mitigate batch effects among IRI recipients. Compared to other existing models, our model demonstrated superior performance with AUC of 0.816 and 0.845 in the training and validation set. Furthermore, we also used the random survival forest algorithm to develop a high-precision predictive signature for graft failure. The mouse IRI model confirmed a marked upregulation of ANXA1 mRNA and protein expression in renal tissue following IRI.

CONCLUSION

This study successfully revealed the macrophage sub-cluster closely associated with renal IRI. Two distinct IRI subgroups with different characteristics were identified and robust strategies were constructed for predicting DGF and graft survival, which can offer potential therapeutic targets for the treatment of IRI and reference for early prevention of various postoperative complications.

The alleviating effect of Bai-Ju essence on atopic dermatitis through anti-inflammatory and skin barrier repair mechanisms

Bai-Ju essence (BJE) is a bioactive formulation composed of medicinal plant extracts, utilized in skincare products for its therapeutic potential. Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by epidermal barrier dysfunction and immune dysregulation. This study aimed to evaluate BJE anti-inflammatory and skin-protective effects, and its potential mechanisms in treating AD. The ability of BJE to restore the epidermal barrier was assessed in HaCaT cells. In LPS-induced RAW264.7 cells, the anti-inflammatory potential of BJE was evaluated by measuring NO, IL-6, PGE2, and TNF-α. Western blot analysis was used to assess the regulation of the MAPK pathway. An in vivo AD-like mouse model was established using MC903, and measurements of body weight, ear thickness, and AD symptoms were recorded. Histological analysis quantified mast cell infiltration, while western blot determined FLG, LOR, and ELOVL6 expression. ELISA was used to measure TNF-α, IgE, IL-4, and IL-13 levels. Flow cytometry assessed the effect of BJE on Th cell phenotypes. BJE significantly enhanced skin barrier protein expression (CERS2, LOR, HAS-1, HAS-2, FLG) in HaCaT cells. It significantly reduced the levels of NO, IL-6, PGE2, and TNF-α in LPS-treated RAW264.7, demonstrating its anti-inflammatory potential. Mechanistically, BJE inhibited MAPK activation. BJE decreased ear thickness, improved skin lesions, and relieved AD symptoms in AD-like mice. In addition, BJE effectively suppressed mast cell infiltration and hyperkeratosis. BJE also decreased levels of TNF-α, IgE, IL-4, and IL-13 while increasing LOR, ELOVL6, and FLG expressions. Furthermore, BJE modulated Th1, Th2, and Th17 cell proportions. BJE promoted epidermal barrier repair in HaCaT, suppressed the LPS-induced inflammation in RAW264.7, enhanced the skin barrier integrity in AD-like mice, and exhibited immunomodulatory effects by restoring Th cell balance. These findings highlighted the therapeutic potential of BJE in AD through its dual action of anti-inflammation and skin barrier restoration.

Macrophage ATG16L1 promotes liver regeneration after partial hepatectomy

Background & Aims

Autophagy plays an important role in liver regeneration. However, most studies are limited to hepatocytes, and the function and mechanism of macrophage autophagy in liver regeneration remain unclear. This study investigated the role of the essential autophagy gene encoding autophagy-related 16-like 1 (ATG16L1), which regulates the macrophage phenotype in liver regeneration.

Methods

We generated FloxP-Atg16l1 (Atg16l1 FL/FL ), Lyz2-Cre Atg16l1 knockout (KO) (Atg16l1 M-KO ), and myeloid-specific Atg16l1-overexpression-knock-in (Atg16l1 OE ) mice. These mice were subjected to 70% partial hepatectomy to demonstrate the role of ATG16L1 in macrophages during liver regeneration.

Results

ATG16L1 expression was significantly upregulated in macrophages during the early stages of liver regeneration. ATG16L1 deletion in macrophages substantially delayed liver regeneration in mice and caused a marked imbalance in Ly6Chi and Ly6Clo macrophage proportions in the liver. RNA-sequencing analysis revealed that, compared with macrophages isolated from Atg16l1 FL/FL mice, those from Atg16l1 M-KO mice exhibited significant downregulation of genes associated with oxidative phosphorylation and upregulation of proinflammatory gene expression. Mechanistically, ATG16L1 loss impaired mitophagy in macrophages, leading to the accumulation of mitochondrial damage and a metabolic shift that promoted proinflammatory macrophage polarization. ATG16L1 deficiency not only promoted macrophage mitochondrial (mt)DNA release and cyclic GMP-AMP synthase-stimulator of interferon genes (STING) activation, but also suppressed STING degradation. Sustained STING hyperactivation and subsequent increased release of downstream interferons further contributed to the inhibition of liver regeneration. Notably, pharmacological activation or genetic overexpression of ATG16L1 significantly enhanced liver regeneration in mice.

Conclusions

ATG16L1 has a pivotal role in liver regeneration by affecting the phenotype and function of macrophages. Thus, targeting ATG16L1 in macrophages could present a novel strategy for promoting liver regeneration.

Impact and implications

The autophagy-related gene ATG16L1 mediates mitophagy, facilitating the clearance of damaged mitochondria in macrophages following partial hepatectomy and maintaining a reparative macrophage phenotype. ATG16L1 deficiency triggers excessive STING activation and inhibits its degradation, thereby suppressing liver regeneration. Thus, targeting ATG16L1 in macrophages could represent a novel strategy to promote liver regeneration.

Decoding Macrophage Dynamics: A Pathway to Understanding and Treating Inflammatory Skin Diseases

Psoriasis and atopic dermatitis (AD) are both chronic inflammatory skin diseases. Their pathogenesis remains incompletely understood. The polarization states of macrophages, as a crucial part of the innate immune system, are influenced by various factors such as cytokines, inflammatory mediators, and epigenetics. Research has demonstrated that macrophages play a "double-edged sword" role in the pathological process of inflammatory skin diseases: they both drive inflammation progression and participate in tissue repair. This article summarizes the roles of macrophages in the inflammatory development and tissue homeostasis of psoriasis and atopic dermatitis. It explores the impact of different factors on macrophages and inflammatory skin diseases. In conclusion, understanding the classification and plasticity of macrophages is crucial for a deeper understanding of the pathogenesis of psoriasis and AD and the development of personalized treatments.

Plasma from hypertensive pregnancy patients induce endothelial dysfunction even under atheroprotective shear stress

Preeclampsia (PE) is a challenge in maternal healthcare due to its complex nature, characterized by high blood pressure, protein in the urine, and damage to various organs. There is evidence linking PE to endothelial dysfunction (ED), triggered by substances released from an oxygen-deprived placenta. Previous in vitro studies have not considered the impact of in vivo elements, such as the different patterns of blood flow, and laminar (LSS) vs. oscillatory (OSS) shear stress, on the development of ED. We investigated the impact of plasma from healthy pregnant women (HP), subjects with gestational hypertension (GH), and PE patients on global gene expression of human coronary endothelial cells (HCAECs) under LSS and OSS. Our findings revealed a unique transcriptional profile of endothelial cells induced by plasma incubation in LSS. Notably, OSS resulted in similar transcriptomes irrespective of plasma treatment. Under LSS, GH plasma resulted in a proliferative profile, whereas PE plasma was linked to pro-inflammatory and antioxidant profiles compared to HP plasma. Our findings demonstrate that shear stress levels influence the endothelial cell transcriptome in response to plasma from hypertensive pregnancy patients. Both PE and GH can induce endothelial dysfunction under atheroprotective LSS, with a more significant effect observed with PE-derived plasma.

An S100A8/A9 Neutralizing Antibody Potently Ameliorates Contact Hypersensitivity and Atopic Dermatitis Symptoms

Contact hypersensitivity and atopic dermatitis are pervasive inflammatory skin diseases with similar symptoms, and their global prevalence is steadily increasing. Many compounds and biotics have been developed to target molecules critical to the etiology or pathogenesis of contact hypersensitivity and atopic dermatitis. However, these molecules are sometimes ineffective or lose their potency during the therapeutic course. Therefore, innovative medicines are still needed for the treatment of intractable cases. We focused on S100A8/A9, a heterodimer complex of S100A8 and S100A9 that is abundant in the extracellular milieu of inflammatory skin lesions. Although S100A8/A9 is primarily recognized as a diagnostic marker protein, we have previously shown that it also plays a crucial role in contact hypersensitivity and atopic dermatitis progression. This insight inspired us to develop its inhibitory antibody, leading to the ground-breaking Ab45. In this study, we demonstrated that Ab45 effectively prevented disease symptoms in various models and that its disease-ameliorating activity likely involved the downregulation of several disease-relevant molecules, including Il-23a, Il-36g, S100a8, and S100a9. We also created a humanized version of Ab45, HuAb45, which exhibited similar effectiveness. These antibodies show great promise for the treatment of contact hypersensitivity and atopic dermatitis and possibly for other inflammatory skin diseases.

Isoliquiritigenin alleviates neuropathic pain by reducing microglia inflammation through inhibition of the ERK signaling pathway and decreasing CEBPB transcription expression

BACKGROUND

Natural compounds are invaluable for their therapeutic effects in treating various diseases. Isoliquiritigenin (ISL) stands out due to its potent anti-inflammatory and antioxidative properties, offering significant therapeutic effects in many diseases. However, there is currently no existing literature on the role of ISL in neuropathic pain treatment.

METHODS

We used lipopolysaccharide to stimulate BV-2 microglia in order to evaluate the inhibitory effects of ISL on neuroinflammation. Proteomics data and protein-protein interaction network analysis were used to identify differential proteins expressed in BV-2 microglia treated with ISL. This allowed for the identification of targets impacted by ISL action. Additionally, we assessed the analgesic efficacy of ISL in a mouse model of chronic constriction injury of the sciatic nerve (CCI) and investigated its inhibitory influence on pro-inflammatory cytokine production and spinal microglia activation.

RESULTS

Our results indicate that ISL efficiently inhibits BV-2 microglia activation and pro-inflammatory cytokine expression. Furthermore, CEBPB has been recognized as a possible target for ISL activity. Crucially, microglia activation was successfully reduced by CEBPB knockdown. Functional recovery tests carried out later on validated that ISL works by specifically inhibiting the ERK/CEBPB signaling pathway. In vivo studies showed that giving mice ISL reduces the mechanical and thermal pain caused on by chronic contraction injuries.

CONCLUSION

The analgesic effect of ISL on neuropathic pain primarily stems from its ability to inhibit the activation of spinal microglia and neuroinflammation. This mechanism may be attributed to the capacity of ISL to suppress microglial activation, reduce the expression of pro-inflammatory cytokines by inhibiting the ERK signaling pathway, and decrease transcriptional expression of CEBPB.

Cannabichromene as a Novel Inhibitor of Th2 Cytokine and JAK/STAT Pathway Activation in Atopic Dermatitis Models

Cannabichromene (CBC) is one of the main cannabinoids found in the cannabis plant, and although less well known than tetrahydrocannabinol (THC) and cannabidiol (CBD), it is gaining attention for its potential therapeutic benefits. To date, CBC's known mechanisms of action include anti-inflammatory, analgesic, antidepressant, antimicrobial, neuroprotective, and anti-acne effects through TRP channel activation and the inhibition of inflammatory pathways, suggesting that it may have therapeutic potential in the treatment of inflammatory skin diseases, such as atopic dermatitis (AD), but its exact mechanism of action remains unclear. Therefore, in this study, we investigated the effects of CBC on Th2 cytokines along with the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathways involved in AD pathogenesis. We used a 2,4-Dinitrochlorobenzene (DNCB)-induced BALB/c mouse model to topically administer CBC (0.1 mg/kg or 1 mg/kg). The results showed that skin lesion severity, ear thickness, epithelial thickness of dorsal and ear skin, and mast cell infiltration were significantly reduced in the 0.1 mg/kg CBC-treated group compared with the DNCB-treated group (p < 0.001). In addition, real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis showed a significant decrease in the mRNA expression of Th2 cytokines (TSLP, IL-4, IL-13) and inflammatory mediators (IFN-γ, IL-1β, IL-6, IL-17, IL-18, and IL-33) (p < 0.05). Western blot analysis also revealed a significant decrease in JAK1, JAK2, STAT1, STAT2, STAT3, and STAT6 protein expression (p < 0.05). These results suggest that CBC is a promising candidate for the treatment of AD and demonstrates the potential to alleviate AD symptoms by suppressing the Th2 immune response.

Macrophages in inflammatory skin diseases and skin tumors

Macrophages, as specialized, long-lasting phagocytic cells of the innate immune system, have garnered increasing attention due to their wide distribution and various functions. The skin, being the largest immune organ in the human body, presents an intriguing landscape for macrophage research, particularly regarding their roles in inflammatory skin diseases and skin tumors. In this review, we compile the latest research on macrophages in conditions such as atopic dermatitis, psoriasis, systemic sclerosis, systemic lupus erythematosus, rosacea, bullous pemphigoid, melanoma and cutaneous T-cell lymphoma. We aim to contribute to illustrating the pathogenesis and potential new therapies for inflammatory skin diseases and skin tumors from the perspective of macrophages.

Atopic dermatitis: pathogenesis and therapeutic intervention

The skin serves as the first protective barrier for nonspecific immunity and encompasses a vast network of skin-associated immune cells. Atopic dermatitis (AD) is a prevalent inflammatory skin disease that affects individuals of all ages and races, with a complex pathogenesis intricately linked to genetic, environmental factors, skin barrier dysfunction as well as immune dysfunction. Individuals diagnosed with AD frequently exhibit genetic predispositions, characterized by mutations that impact the structural integrity of the skin barrier. This barrier dysfunction leads to the release of alarmins, activating the type 2 immune pathway and recruiting various immune cells to the skin, where they coordinate cutaneous immune responses. In this review, we summarize experimental models of AD and provide an overview of its pathogenesis and the therapeutic interventions. We focus on elucidating the intricate interplay between the immune system of the skin and the complex regulatory mechanisms, as well as commonly used treatments for AD, aiming to systematically understand the cellular and molecular crosstalk in AD-affected skin. Our overarching objective is to provide novel insights and inform potential clinical interventions to reduce the incidence and impact of AD.

Evaluating the Causal Association between Circulating Plasma Proteins, 731 Immune Cell Phenotypes, and Atopic Dermatitis: A Mediation Mendelian Randomization Study

INTRODUCTION

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by eczematous lesions and severe itching. However, its pathogenesis has not yet been fully elucidated. The aim of this study was to investigate the causal relationship between plasma proteins and AD, as well as to identify and quantify the potential roles of immune cell phenotypes as mediators.

METHODS

We utilized summary-level data from genome-wide association studies and conducted a two-sample Mendelian randomization (MR) analysis involving 4,907 circulating plasma proteins, 731 immune cell phenotypes, and AD. Initially, we conducted bidirectional univariate MR analyses to forecast causal effects linking circulating plasma proteins and AD. Subsequently, we employed a two-step MR analysis to scrutinize the immune cell phenotypes that could mediate these effects. The inverse variance weighted was the main method employed for MR analysis, while the Cochran's Q test and MR-Egger intercept test were used to assess the presence of heterogeneity and pleiotropy, respectively. We then determined whether our results could be influenced by individual single-nucleotide polymorphisms using the "leave-one-out" test.

RESULTS

Positive correlations were observed between KRT1, IL18R1, and SEMA6A and the risk of AD, whereas BDH2, ADAMTS3, ANKRD1, TIAM1, MID2, and IFNA16 all showed negative correlations with the risk of AD. Mediation analysis indicated that CD8 on CM CD8br cells acted as a mediator between IFNA16 and AD, with a mediation effect proportion of 11.2%. In addition, sensitivity analyses did not reveal significant heterogeneity or level pleiotropy.

CONCLUSION

Our findings indicated the presence of a one-way causal relationship between the circulating plasma protein IFNA16 and AD. This study also explored immune cell phenotypes that may serve as mediators, offering novel insights into the etiology, pathogenesis, and potential clinical interventions in AD. Nevertheless, these findings need to be validated by clinical and laboratory studies.

Mechanisms of autophagy and their implications in dermatological disorders

Autophagy is a highly conserved cellular self-digestive process that underlies the maintenance of cellular homeostasis. Autophagy is classified into three types: macrophage, chaperone-mediated autophagy (CMA) and microphagy, which maintain cellular homeostasis through different mechanisms. Altered autophagy regulation affects the progression of various skin diseases, including psoriasis (PA), systemic lupus erythematosus (SLE), vitiligo, atopic dermatitis (AD), alopecia areata (AA) and systemic sclerosis (SSc). In this review, we review the existing literature focusing on three mechanisms of autophagy, namely macrophage, chaperone-mediated autophagy and microphagy, as well as the roles of autophagy in the above six dermatological disorders in order to aid in further studies in the future.

Macrophages and autophagy: partners in crime

Macrophages and autophagy are intricately linked, both playing vital roles in maintaining homeostasis and responding to disease. Macrophages, known for their 'eating' function, rely on a sophisticated digestion system to process a variety of targets, from apoptotic cells to pathogens. The connection between macrophages and autophagy is established early in their development, influencing both differentiation and mature functions. Autophagy regulates essential immune functions, such as inflammation control, pathogen clearance, and antigen presentation, linking innate and adaptive immunity. Moreover, it modulates cytokine production, ensuring a balanced inflammatory response that prevents excessive tissue damage. Autophagy also plays a critical role in macrophage polarization, influencing their shift between pro-inflammatory and anti-inflammatory states. This review explores the role of autophagy in macrophages, emphasizing its impact across various tissues and pathological conditions, and detailing the cellular and molecular mechanisms by which autophagy shapes macrophage function.

Excess Potassium Promotes Autophagy to Maintain the Immunosuppressive Capacity of Myeloid-Derived Suppressor Cells Independent of Arginase 1

Potassium ions (K+) are critical electrolytes that regulate multiple functions in immune cells. Recent studies have shown that the elevated concentration of extracellular potassium in the tumor interstitial fluid limits T cell effector function and suppresses the anti-tumor capacity of tumor-associated macrophages (TAMs). The effect of excess potassium on the biology of myeloid-derived suppressor cells (MDSCs), another important immune cell component of the tumor microenvironment (TME), is unknown. Here, we present data showing that increased concentrations of potassium chloride (KCl), as the source of K+ ions, facilitate autophagy by increasing the expression of the autophagosome marker LC3β. Simultaneously, excess potassium ions significantly decrease the expression of arginase I (Arg I) and inducible nitric oxide synthase (iNOS) without reducing the ability of MDSCs to suppress T cell proliferation. Further investigation reveals that excess K+ ions decrease the expression of the transcription factor C/EBP-β and alter the expression of phosphorylated kinases. While excess K+ ions downregulated the expression levels of phospho-AMPKα (pAMPKα), it increased the levels of pAKT and pERK. Additionally, potassium increased mitochondrial respiration as measured by the oxygen consumption rate (OCR). Interestingly, all these alterations induced by K+ ions were abolished by the autophagy inhibitor 3-methyladenine (3-MA). Our results suggest that hyperosmotic stress caused by excess K+ ions regulate the mitochondrial respiration and signaling pathways in MDSCs to trigger the process of autophagy to support MDSCs' immunosuppressive function by mechanisms independent of Arg I and iNOS. Overall, our in vitro and ex vivo findings offer valuable insights into the adaptations of MDSCs within the K+ ion-rich TME, which has important implications for MDSCs-targeted therapies.

Nur77 Mediates Anaphylaxis by Regulating miR-21a

Nur77 belongs to the NR4A subfamily of orphan nuclear hormone receptors. It has been shown to play important roles in metabolism, cancer progression, cellular differentiation, and the regulation of immune process. However, there has yet to be research reporting on the role of Nur77 in allergic inflammations such as anaphylaxis. This study aimed to identify molecules that could mediate allergic inflammations. To this end, we performed RNA sequencing analysis employing bone marrow-derived mast cells (BMMCs). Antigen (DNP-HSA) stimulation increased the expression levels of transcription factors such as Nr4a3 (NOR1), Nr4a1 (Nur77), and Nr4a2 (Nurr1). We focused our study on Nur77. Antigen stimulation increased the expression of Nur77 in a time- and dose-dependent manner in rat basophilic leukemia cells (RBL2H3). The downregulation of Nur77 prevented both antigen-induced increase in β-hexosaminidase activity as well as hallmarks of allergic reactions such as HDAC3, COX2, and MCP1 in RBL2H3 cells. Nur77 was necessary for both passive cutaneous anaphylaxis (PCA) and passive systemic anaphylaxis (PSA). TargetScan analysis predicted that miR-21a would be a negative regulator of Nur77. miR-21a mimic negatively regulated PCA and PSA by inhibiting the hallmarks of allergic reactions. ChIP assays showed that c-JUN could bind to the promoter sequences of Nur77. Antigen stimulation increased the expression of c-JUN in RBL2H3 cells. Altogether, our findings demonstrate the regulatory role played by Nur77-miR-21a loop in allergic inflammations such as anaphylaxis, making this the first report to present the role played by Nur77 in an allergic inflammation. Our results suggest that Nur77 and miR-21 might serve as targets for developing anti-allergy drugs.