D-dopachrome tautomerase contributes to lung epithelial repair via atypical chemokine receptor 3-dependent Akt signaling

TRAPping the effects of tobacco smoking: the regulation and function of Acp5 expression in lung macrophages

Tartrate-resistant acid phosphatase [TRAP, gene acid phosphatase 5 (Acp5; gene name for TRAP)] is highly expressed in alveolar macrophages with proposed roles in lung inflammation and lung fibrosis development. We previously showed that its expression and activity are higher in lung macrophages of smokers and patients with chronic obstructive pulmonary disease (COPD), suggesting involvement in smoke-induced lung damage. In this study, we explored the function of TRAP and regulation of its different mRNA transcripts (Acp5 201-206) in lung tissue exposed to cigarette smoke to elucidate its function in alveolar macrophages. In mice exposed to cigarette smoke or air for 4-6 wk, higher Acp5 mRNA expression in lung tissue after smoking was mainly driven by transcript Acp5-202, which originates from macrophages. The expression of Acp5-202 correlated with transcription factors previously found to drive proliferation of macrophages. Treating fetal liver progenitor-derived alveolar-like macrophages [Max Planck Institute (MPI; macrophages derived from fetal liver progenitors) macrophages] with cigarette smoke extract resulted in more proliferation compared with nontreated cells. In contrast, Acp5-deficient MPI macrophages and MPI macrophages treated with a TRAP inhibitor proliferated significantly less than control macrophages. Mechanistically, this lack of proliferation after TRAP inhibition was associated with higher presence of phosphorylated Beta-catenin (β-catenin; a signaling protein) compared with nontreated controls. Phosphorylation of β-catenin is known to mark it for ubiquitination and degradation by the proteasome, preventing its activity in promoting cell proliferation. In conclusion, our findings provide strong evidence for TRAP stimulating alveolar macrophage proliferation by dephosphorylating β-catenin. By driving proliferation, TRAP likely helps sustain alveolar macrophage populations during smoke exposure, either compensating for their loss due to smoking or increasing their numbers to better manage smoke-induced damage.NEW & NOTEWORTHY This study has uncovered that the enzyme tartrate-resistant acid phosphatase (TRAP) is crucial for alveolar macrophage proliferation through a β-catenin-dependent pathway. Importantly, TRAP influences this important ability of alveolar macrophages through the Acp5-202 mRNA transcript. The increase in TRAP expression following smoke exposure suggests that it plays a key role in promoting cell renewal, potentially helping to mitigate smoke-induced lung damage.

Proinflammatory Cytokines in Chronic Respiratory Diseases and Their Management

Pulmonary homeostasis can be agitated either by external environmental insults or endogenous factors produced during respiratory/pulmonary diseases. The lungs counter these insults by initiating mechanisms of inflammation as a localized, non-specific first-line defense response. Cytokines are small signaling glycoprotein molecules that control the immune response. They are formed by numerous categories of cell types and induce the movement, growth, differentiation, and death of cells. During respiratory diseases, multiple proinflammatory cytokines play a crucial role in orchestrating chronic inflammation and structural changes in the respiratory tract by recruiting inflammatory cells and maintaining the release of growth factors to maintain inflammation. The issue aggravates when the inflammatory response is exaggerated and/or cytokine production becomes dysregulated. In such instances, unresolving and chronic inflammatory reactions and cytokine production accelerate airway remodeling and maladaptive outcomes. Pro-inflammatory cytokines generate these deleterious consequences through interactions with receptors, which in turn initiate a signal in the cell, triggering a response. The cytokine profile and inflammatory cascade seen in different pulmonary diseases vary and have become fundamental targets for advancement in new therapeutic strategies for lung diseases. There are considerable therapeutic approaches that target cytokine-mediated inflammation in pulmonary diseases; however, blocking specific cytokines may not contribute to clinical benefit. Alternatively, broad-spectrum anti-inflammatory approaches are more likely to be clinically effective. Herein, this comprehensive review of the literature identifies various cytokines (e.g., interleukins, chemokines, and growth factors) involved in pulmonary inflammation and the pathogenesis of respiratory diseases (e.g., asthma, chronic obstructive pulmonary, lung cancer, pneumonia, and pulmonary fibrosis) and investigates targeted therapeutic treatment approaches.

An atypical atherogenic chemokine that promotes advanced atherosclerosis and hepatic lipogenesis

Atherosclerosis is the underlying cause of myocardial infarction and ischemic stroke. It is a lipid-triggered and cytokine/chemokine-driven arterial inflammatory condition. We identify D-dopachrome tautomerase/macrophage migration-inhibitory factor-2 (MIF-2), a paralog of the cytokine MIF, as an atypical chemokine promoting both atherosclerosis and hepatic lipid accumulation. In hyperlipidemic Apoe-/- mice, Mif-2-deficiency and pharmacological MIF-2-blockade protect against lesion formation and vascular inflammation in early and advanced atherogenesis. MIF-2 promotes leukocyte migration, endothelial arrest, and foam-cell formation, and we identify CXCR4 as a receptor for MIF-2. Mif-2-deficiency in Apoe-/- mice leads to decreased plasma lipid levels and suppressed hepatic lipid accumulation, characterized by reductions in lipogenesis-related pathways, tri-/diacylglycerides, and cholesterol-esters, as revealed by hepatic transcriptomics/lipidomics. Hepatocyte cultures and FLIM-FRET-microscopy suggest that MIF-2 activates SREBP-driven lipogenic genes, mechanistically involving MIF-2-inducible CD74/CXCR4 complexes and PI3K/AKT but not AMPK signaling. MIF-2 is upregulated in unstable carotid plaques from atherosclerotic patients and its plasma concentration correlates with disease severity in patients with coronary artery disease. These findings establish MIF-2 as an atypical chemokine linking vascular inflammation to metabolic dysfunction in atherosclerosis.

Lung organoids in COPD: recent advances and future prospects

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory airway disease that is characterized by progressive airflow limitation, a high prevalence, and a high mortality rate. However, the specific mechanisms remain unclear, partly due to the lack of robust data from in vitro experimental models and animal models that do not adequately represent the structure and pathophysiology of the human lung. The recent advancement of lung organoid culture systems has facilitated new avenues for the investigation of COPD. Lung organoids are in vitro models derived from adult stem cells, human pluripotent stem cells, or embryonic stem cells, established through three-dimensional culture. They exhibit a high degree of homology and genetic consistency with human tissues and can better mimic human lungs in terms of function and structure compared to other traditional models. This review will summarise the generation process of lung organoids from different cell sources and their application in COPD research, and provide suggestions for future research directions.

Dexmedetomidine Regulates Macrophage Phenotype Remodeling Through AMPK/SIRT1 to Alleviate Inflammatory Mediators and Lung Injury

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is associated with high morbidity and mortality in the intensive care unit (ICU) and can cause excessive inflammation. Dexmedetomidine (DEX) is a drug that exerts anti-inflammatory effects. Identifying the anti-inflammatory mechanism of DEX in the context of ALI/ARDS possesses potential significance for the prevention and treatment of ARDS. In this study, DEX was used to treat mouse models of cecal ligation and puncture (CLP) and lipopolysaccharide (LPS)-stimulated cells. Immunofluorescence, western blot analysis, and flow cytometry were used to detect macrophage phenotypic markers in mice, and western blot analysis, real-time qPCR (RT-qPCR), ELISA, and immunofluorescence were used to detect macrophage phenotype markers in RAW264.7 cells. Flow cytometry was used to detect phenotypic markers of bone marrow-derived macrophages (BMDM). Culture medium collected from macrophages was used to cultivate human non-small cell adenocarcinoma epithelial cells (A549) to detect their aquaporins 1 (AQP1) expression and apoptosis status. Western blot analysis was used to detect the activation of the AMP-activated protein kinase (AMPK)/sirtuin 1(SIRT1) signaling pathway both in vivo and in vitro. The regulatory effect of DEX on macrophage phenotype remodeling was detected by knocking down AMPK expression in cells using AMPK shRNA. The results showed that in both in vivo and in vitro experiments, DEX downregulated the expression of M1 markers (tumor necrosis factor-α [TNF-α], nitric oxide synthase [iNOS], and cluster of differentiation [CD]-86) and upregulated the expression of M2 markers (arginase-1 [ARG-1], interleukin [IL]-10, and CD206) in macrophages. The culture medium of macrophages treated with DEX alleviated the edema and apoptosis of A549 cells. DEX activates the AMPK/SIRT1 signaling pathway in macrophages. After AMPK knockdown, the ability of DEX to regulate macrophage phenotype remodeling decreased. Together, this study suggests that DEX regulates macrophage phenotype remodeling by activating the AMPK/SIRT1 pathway, thereby reducing ALI/ARDS.

The synthesis of 1,2,3-triazoles as binders of D-dopachrome tautomerase (D-DT) for the development of dual-targeting inhibitors

Despite recent advances in the treatment of cancer, the issue of therapy resistance remains one of the most significant challenges in the field. In this context, signaling molecules, such as cytokines have emerged as promising targets for drug discovery. Examples of cytokines include macrophage migration inhibitory factor (MIF) and its closely related analogue D-dopachrome tautomerase (D-DT). In this study we aim to develop a new chemical class of D-DT binders and subsequently create a dual-targeted inhibitor that can potentially trigger D-DT degradation via the Proteolysis Targeting Chimera (PROTAC) technology. Here we describe the synthesis of a novel library of 1,2,3-triazoles targeting D-DT. The most potent derivative 19c (IC50 of 0.5 ± 0.04 μM with high selectivity toward D-DT) was attached to a cereblon (CRBN) ligand through aliphatic amides, which were synthesized by a remarkably convenient and effective solvent-free reaction. Enzyme inhibition experiments led to the discovery of the compound 10d, which exhibited moderate inhibitory potency (IC50 of 5.9 ± 0.7 μM), but unfortunately demonstrated no activity in D-DT degradation experiments. In conclusion, this study offers valuable insight into the SAR of D-DT inhibition, paving the way for the development of novel molecules as tools to study D-DT functions in tumor proliferation and, ultimately, new therapeutics for cancer treatment.

Single-cell RNA sequencing reveals the MIF/ACKR3 receptor-ligand interaction between neutrophils and nucleus pulposus cells in intervertebral disc degeneration

OBJECTIVES

To unravel the heterogeneity and function of microenvironmental neutrophils during intervertebral disc degeneration (IDD).

METHODS

Single-cell RNA sequencing (scRNA-seq) was utilized to dissect the cellular landscape of neutrophils in intervertebral disc (IVD) tissues and their crosstalk with nucleus pulposus cells (NPCs). The expression levels of macrophage migration inhibitory factor (MIF) and ACKR3 in IVD tissues were detected. The MIF/ACKR3 axis was identified and its effects on IDD were investigated in vitro and in vivo.

RESULTS

We sequenced here 71520 single cells from 5 control and 9 degenerated IVD samples using scRNA-seq. We identified a unique cluster of neutrophils abundant in degenerated IVD tissues that highly expressed MIF and was functionally enriched in extracellular matrix organization (ECMO). Cell-to-cell communication analyses showed that this ECMO-neutrophil subpopulation was closely interacted with an effector NPCs subtype, which displayed high expression of ACKR3. Further analyses revealed that MIF was positively correlated with ACKR3 and functioned via directly binding to ACKR3 on effector NPCs. MIF inhibition attenuated degenerative changes of NPCs and extracellular matrix, which could be partially reversed by ACKR3 overexpression. Clinically, a significant correlation of high MIF/ACKR3 expression with advanced IDD grade was observed. Furthermore, we also found a positive association between MIF+ ECMO-neutrophil counts and ACKR3+ effector NPCs density as well as higher expression of the MIF/ACKR3 signaling in areas where these two cell types were neighbors.

CONCLUSIONS

These data suggest that ECMO-neutrophil promotes IDD progression by their communication with NPCs via the MIF/ACKR3 axis, which may shed light on therapeutic strategies.

Protective effect of Xixin-Ganjiang herb pair for warming the lungs to dissolve phlegm in chronic obstructive pulmonary disease rats based on integrated network pharmacology and metabolomics

Xixin-Ganjiang herb pair (XGHP) is a classic combination for warming the lungs to dissolve phlegm and is often used to treat a variety of chronic lung diseases; it can treat the syndrome of cold phlegm obstruction of lungs. First, ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to examine the composition of XGHP, and network pharmacology was used to predict its potential core targets and signaling pathways in the current study. Second, a rat model of chronic obstructive pulmonary disease (COPD) was established for assessing the anti-COPD activity of XGHP, and metabolomics was used to explore the biomarkers and metabolic pathways. Finally, the sample was validated using molecular docking and Western blotting. The integration of metabolomics and network pharmacology results identified 11 targets, 3 biomarkers, 3 pathways, and 2 metabolic pathways. Western blotting showed that XGHP effectively regulated the expression of core proteins via multiple signaling pathways (downregulation of toll-like receptor 4 [TLR4] and upregulation of serine/threonine-protein kinase 1 [p-AKT1] and nitric oxide synthase 3 [NOS3]). Molecular docking results showed that the 10 potentially active components of XGHP have good affinity with tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), matrix metalloproteinase 9 (MMP-9), TLR4, p-AKT1, and NOS3. Our findings suggest that XGHP may regulate glucolipid metabolism, improve energy supply, and inhibit inflammatory responses (TNF-α, IL-6, and MMP-9) via the PI3K-Akt signaling pathway and HIF-1 signaling pathway in the management of COPD.

ACKR3 in olfactory glia cells shapes the immune defense of the olfactory mucosa

Barrier-forming olfactory glia cells, termed sustentacular cells, play important roles for immune defense of the olfactory mucosa, for example as entry sites for SARS-CoV-2 and subsequent development of inflammation-induced smell loss. Here we demonstrate that sustentacular cells express ACKR3, a chemokine receptor that functions both as a scavenger of the chemokine CXCL12 and as an activator of alternative signaling pathways. Differential gene expression analysis of bulk RNA sequencing data obtained from WT and ACKR3 conditional knockout mice revealed upregulation of genes involved in immune defense. To map the regulated genes to the different cell types of the olfactory mucosa, we employed biocomputational methods utilizing a single-cell reference atlas. Transcriptome analysis, PCR and immunofluorescence identified up-regulation of NF-κB-related genes, known to amplify inflammatory signaling and to facilitate leukocyte transmigration, in the gliogenic lineage. Accordingly, we found a marked increase in leukocyte-expressed genes and confirmed leukocyte infiltration into the olfactory mucosa. In addition, lack of ACKR3 led to enhanced expression and secretion of early mediators of immune defense by Bowman's glands. As a result, the number of apoptotic cells in the epithelium was decreased. In conclusion, our research underlines the importance of sustentacular cells in immune defense of the olfactory mucosa. Moreover, it identifies ACKR3, a druggable G protein-coupled receptor, as a promising target for modulation of inflammation-associated anosmia.

The C-terminal Region of D-DT Regulates Molecular Recognition for Protein-Ligand Complexes

Systematic analysis of molecular recognition is critical for understanding the biological function of macromolecules. For the immunomodulatory protein D-dopachrome tautomerase (D-DT), the mechanism of protein-ligand interactions is poorly understood. Here, 17 carefully designed protein variants and wild type (WT) D-DT were interrogated with an array of complementary techniques to elucidate the structural basis of ligand recognition. Utilization of a substrate and two selective inhibitors with distinct binding profiles offered previously unseen mechanistic insights into D-DT-ligand interactions. Our results demonstrate that the C-terminal region serves a key role in molecular recognition via regulation of the active site opening, protein-ligand interactions, and conformational flexibility of the pocket's environment. While our study is the first comprehensive analysis of molecular recognition for D-DT, the findings reported herein promote the understanding of protein functionality and enable the design of new structure-based drug discovery projects.

Revealing molecular and cellular heterogeneity in hypopharyngeal carcinogenesis through single-cell RNA and TCR/BCR sequencing

Introduction

Hypopharyngeal squamous cell carcinoma (HSCC) is one of the malignant tumors with the worst prognosis in head and neck cancers. The transformation from normal tissue through low-grade and high-grade intraepithelial neoplasia to cancerous tissue in HSCC is typically viewed as a progressive pathological sequence typical of tumorigenesis. Nonetheless, the alterations in diverse cell clusters within the tissue microenvironment (TME) throughout tumorigenesis and their impact on the development of HSCC are yet to be fully understood.

Methods

We employed single-cell RNA sequencing and TCR/BCR sequencing to sequence 60,854 cells from nine tissue samples representing different stages during the progression of HSCC. This allowed us to construct dynamic transcriptomic maps of cells in diverse TME across various disease stages, and experimentally validated the key molecules within it.

Results

We delineated the heterogeneity among tumor cells, immune cells (including T cells, B cells, and myeloid cells), and stromal cells (such as fibroblasts and endothelial cells) during the tumorigenesis of HSCC. We uncovered the alterations in function and state of distinct cell clusters at different stages of tumor development and identified specific clusters closely associated with the tumorigenesis of HSCC. Consequently, we discovered molecules like MAGEA3 and MMP3, pivotal for the diagnosis and treatment of HSCC.

Discussion

Our research sheds light on the dynamic alterations within the TME during the tumorigenesis of HSCC, which will help to understand its mechanism of canceration, identify early diagnostic markers, and discover new therapeutic targets.

The Role of Macrophage Migration Inhibitory Factor (MIF) and D-Dopachrome Tautomerase (D-DT/MIF-2) in Infections: A Clinical Perspective

Macrophage migration inhibitory factor (MIF) and its homolog, D-dopachrome tautomerase (D-DT), are cytokines that play critical roles in the immune response to various infectious diseases. This review provides an overview of the complex involvement of MIF and D-DT in bacterial, viral, fungal, and parasitic infections. The role of MIF in different types of infections is controversial, as it has either a protective function or a host damage-enhancing function depending on the pathogen. Depending on the specific role of MIF, different therapeutic options for MIF-targeting drugs arise. Human MIF-neutralizing antibodies, anti-parasite MIF antibodies, small molecule MIF inhibitors or MIF-blocking peptides, as well as the administration of exogenous MIF or MIF activity-augmenting small molecules have potential therapeutic applications and need to be further explored in the future. In addition, MIF has been shown to be a potential biomarker and therapeutic target in sepsis. Further research is needed to unravel the complexity of MIF and D-DT in infectious diseases and to develop personalized therapeutic approaches targeting these cytokines. Overall, a comprehensive understanding of the role of MIF and D-DT in infections could lead to new strategies for the diagnosis, treatment, and management of infectious diseases.

Human Lung Organoids-A Novel Experimental and Precision Medicine Approach

The global burden of respiratory diseases is very high and still on the rise, prompting the need for accurate models for basic and translational research. Several model systems are currently available ranging from simple airway cell cultures to complex tissue-engineered lungs. In recent years, human lung organoids have been established as highly transferrable three-dimensional in vitro model systems for lung research. For acute infectious and chronic inflammatory diseases as well as lung cancer, human lung organoids have opened possibilities for precise in vitro research and a deeper understanding of mechanisms underlying lung injury and regeneration. Human lung organoids from induced pluripotent stem cells or from adult stem cells of patients' samples introduce tools for understanding developmental processes and personalized medicine approaches. When further state-of-the-art technologies and protocols come into use, the full potential of human lung organoids can be harnessed. High-throughput assays in drug development, gene therapy, and organoid transplantation are current applications of organoids in translational research. In this review, we emphasize novel approaches in translational and personalized medicine in lung research focusing on the use of human lung organoids.

CXCL12-CXCR4/CXCR7 Axis in Cancer: from Mechanisms to Clinical Applications

Cancer is a multi-step disease caused by the accumulation of genetic mutations and/or epigenetic changes, and is the biggest challenge around the world. Cytokines, including chemokines, exhibit expression changes and disorders in all human cancers. These cytokine abnormalities can disrupt homeostasis and immune function, and make outstanding contributions to various stages of cancer development such as invasion, metastasis, and angiogenesis. Chemokines are a superfamily of small molecule chemoattractive cytokines that mediate a variety of cellular functions. Importantly, the interactions of chemokine members CXCL12 and its receptors CXCR4 and CXCR7 have a broad impact on tumor cell proliferation, survival, angiogenesis, metastasis, and tumor microenvironment, and thus participate in the onset and development of many cancers including leukemia, breast cancer, lung cancer, prostate cancer and multiple myeloma. Therefore, this review aims to summarize the latest research progress and future challenges regarding the role of CXCL12-CXCR4/CXCR7 signaling axis in cancer, and highlights the potential of CXCL12-CXCR4/CXCR7 as a biomarker or therapeutic target for cancer, providing essential strategies for the development of novel targeted cancer therapies.

CircRNA_0026344 via miR-21 is involved in cigarette smoke-induced autophagy and apoptosis of alveolar epithelial cells in emphysema

Cigarette smoke (CS), a main source of indoor air pollution, is a primary risk factor for emphysema, and aberrant cellular autophagy is related to the pathogenesis of emphysema. Circular RNAs (circRNAs) affect the expression of mRNAs via acting as microRNA (miRNA) sponges, but their role in emphysema progression is not established. In the present investigation, CS, acting on alveolar epithelial cells, caused higher levels of miR-21, p-ERK, and cleaved-caspase 3 and led to lower levels of circRNA_0026344 and PTEN, which induced autophagy and apoptosis. miR-21 suppressed the expression of PTEN, which was involved in the regulation of autophagy and apoptosis. Further, in alveolar epithelial cells, overexpression of circRNA_0026344 blocked cigarette smoke extract (CSE)-induced autophagy and apoptosis, but this blockage was reversed by upregulation of miR-21 with a mimic. These results demonstrated that, in alveolar epithelial cells, CS decreases circRNA_0026344 levels, which sponge miR-21 to inhibit the miR-21 target, PTEN, which, in turn, activates ERK and thereby promotes autophagy and apoptosis, leading to emphysema. Thus, for emphysema, circRNA_0026344 regulates the PTEN/ERK axis by sponging miR-21, which is associated with the CS-induced autophagy and apoptosis of alveolar epithelial cells. In sum, the present investigation identifies a novel mechanism for CS-induced emphysema and provides information useful for the diagnosis and treatment of CS-induced emphysema.

NanoB2 to monitor interactions of ligands with membrane proteins by combining nanobodies and NanoBRET

The therapeutic potential of ligands targeting disease-associated membrane proteins is predicted by ligand-receptor binding constants, which can be determined using NanoLuciferase (NanoLuc)-based bioluminescence resonance energy transfer (NanoBRET) methods. However, the broad applicability of these methods is hampered by the restricted availability of fluorescent probes. We describe the use of antibody fragments, like nanobodies, as universal building blocks for fluorescent probes for use in NanoBRET. Our nanobody-NanoBRET (NanoB2) workflow starts with the generation of NanoLuc-tagged receptors and fluorescent nanobodies, enabling homogeneous, real-time monitoring of nanobody-receptor binding. Moreover, NanoB2 facilitates the assessment of receptor binding of unlabeled ligands in competition binding experiments. The broad significance is illustrated by the successful application of NanoB2 to different drug targets (e.g., multiple G protein-coupled receptors [GPCRs] and a receptor tyrosine kinase [RTK]) at distinct therapeutically relevant binding sites (i.e., extracellular and intracellular).

2,5-Pyridinedicarboxylic acid is a bioactive and highly selective inhibitor of D-dopachrome tautomerase

Macrophage migration inhibitory factor (MIF) and D-dopachrome tautomerase (D-DT) are two pleotropic cytokines, which are coexpressed in various cell types to activate the cell surface receptor CD74. Via the MIF/CD74 and D-DT/CD74 axes, the two proteins exhibit either beneficial or deleterious effect on human diseases. In this study, we report the identification of 2,5-pyridinedicarboxylic acid (a.k.a. 1) that effectively blocks the D-DT-induced activation of CD74 and demonstrates an impressive 79-fold selectivity for D-DT over MIF. Crystallographic characterization of D-DT-1 elucidates the binding features of 1 and reveals previously unrecognized differences between the MIF and D-DT active sites that explain the ligand's functional selectivity. The commercial availability, low cost, and high selectivity make 1 the ideal tool for studying the pathophysiological functionality of D-DT in disease models. At the same time, our comprehensive biochemical, computational, and crystallographic analyses serve as a guide for generating highly potent and selective D-DT inhibitors.

Hallmarks of Cancer Affected by the MIF Cytokine Family

New diagnostic methods and treatments have significantly decreased the mortality rates of cancer patients, but further improvements are warranted based on the identification of novel tumor-promoting molecules that can serve as therapeutic targets. The macrophage migration inhibitory factor (MIF) family of cytokines, comprising MIF and DDT (also known as MIF2), are overexpressed in almost all cancer types, and their high expressions are related to a worse prognosis for the patients. MIF is involved in 9 of the 10 hallmarks of cancer, and its inhibition by antibodies, nanobodies, or small synthetic molecules has shown promising results. Even though DDT is also proposed to be involved in several of the hallmarks of cancer, the available information about its pro-tumoral role and mechanism of action is more limited. Here, we provide an overview of the involvement of both MIF and DDT in cancer, and we propose that blocking both cytokines is needed to obtain the maximum anti-tumor response.

D-dopachrome tautomerase in cardiovascular and inflammatory diseases-A new kid on the block or just another MIF?

Macrophage migration inhibitory factor (MIF) as well as its more recently described structural homolog D-dopachrome tautomerase (D-DT), now also termed MIF-2, are atypical cytokines and chemokines with key roles in host immunity. They also have an important pathogenic role in acute and chronic inflammatory conditions, cardiovascular diseases, lung diseases, adipose tissue inflammation, and cancer. Although our mechanistic understanding of MIF-2 is relatively limited compared to the extensive body of evidence available for MIF, emerging data suggests that MIF-2 is not only a functional phenocopy of MIF, but may have differential or even oppositional activities, depending on the disease and context. In this review, we summarize and discuss the similarities and differences between MIF and MIF-2, with a focus on their structures, receptors, signaling pathways, and their roles in diseases. While mainly covering the roles of the MIF homologs in cardiovascular, inflammatory, autoimmune, and metabolic diseases, we also discuss their involvement in cancer, sepsis, and chronic obstructive lung disease (COPD). A particular emphasis is laid upon potential mechanistic explanations for synergistic or cooperative activities of the MIF homologs in cancer, myocardial diseases, and COPD as opposed to emerging disparate or antagonistic activities in adipose tissue inflammation, metabolic diseases, and atherosclerosis. Lastly, we discuss potential future opportunities of jointly targeting MIF and MIF-2 in certain diseases, whereas precision targeting of only one homolog might be preferable in other conditions. Together, this article provides an update of the mechanisms and future therapeutic avenues of human MIF proteins with a focus on their emerging, surprisingly disparate activities, suggesting that MIF-2 displays a variety of activities that are distinct from those of MIF.

Atypical chemokine receptor 3 induces colorectal tumorigenesis in mice by promoting β-arrestin-NOLC1-fibrillarin-dependent rRNA biogenesis

Atypical chemokine receptor 3 (ACKR3) has emerged as a key player in various biological processes. Its atypical "intercepting receptor" properties have established ACKR3 as the major regulator in the pathophysiological processes in many diseases. In this study, we investigated the role of ACKR3 activation in promoting colorectal tumorigenesis. We showed that ACKR3 expression levels were significantly increased in human colon cancer tissues, and high levels of ACKR3 predicted the increased severity of cancer. In Villin-ACKR3 transgenic mice with a high expression level of CKR3 in their intestinal epithelial cells, administration of AOM/DSS induced more severe colorectal tumorigenesis than their WT littermates. Cancer cells of Villin-ACKR3 transgenic mice were characterised by the nuclear β-arrestin-1 (β-arr1)-activated perturbation of rRNA biogenesis. In HCT116 cells, cotreatment with CXCL12 and AMD3100 selectively activated ACKR3 and induced nuclear translocation of β-arr1, leading to an interaction of β-arr1 with nucleolar and coiled-body phosphoprotein 1 (NOLC1). NOLC1, as the phosphorylated protein, further interacted with fibrillarin, a conserved nucleolar methyltransferase responsible for ribosomal RNA methylation in the nucleolus, thereby increasing the methylation in histone H2A and promoting rRNA transcription in ribosome biogenesis. In conclusion, ACKR3 promotes colorectal tumorigenesis through the perturbation of rRNA biogenesis by the β-arr1-induced interaction of NOLC1 with fibrillarin.

A Cross-Kingdom View on the Immunomodulatory Role of MIF/D-DT Proteins in Mammalian and Plant Pseudomonas Infections

Gram-negative Pseudomonas bacteria are largely harmless saprotrophs, but some species can be potent pathogens of both plants and mammals. Macrophage migration inhibitory factor (MIF) and its homolog D-dopachrome tautomerase (D-DT, also referred to as MIF-2) are multifunctional proteins that in addition to their intracellular functions also serve as extracellular signaling molecules (cytokines) in orchestrating mammalian immune responses. It recently emerged that plants also possess MIF-like proteins, termed MIF/D-DT-like (MDL) proteins. We here provide a comparative cross-kingdom view on the immunomodulatory role of MIF and MDL proteins during Pseudomonas infections in mammals and plants. Although in both kingdoms the lack of MIF/MDL proteins is associated with a reduction in bacterial load and disease symptoms, the underlying molecular principles seem to be different. We provide a perspective for future research activities to unravel additional commonalities and differences in the MIF/MDL-mediated adjustment of antibacterial immune activities.

Thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione Derivative Inhibits d-Dopachrome Tautomerase Activity and Suppresses the Proliferation of Non-Small Cell Lung Cancer Cells

The homologous cytokines macrophage migration inhibitory factor (MIF) and d-dopachrome tautomerase (d-DT or MIF2) play key roles in cancers. Molecules binding to the MIF tautomerase active site interfere with its biological activity. In contrast, the lack of potent MIF2 inhibitors hinders the exploration of MIF2 as a drug target. In this work, screening of a focused compound collection enabled the identification of a MIF2 tautomerase inhibitor R110. Subsequent optimization provided inhibitor 5d with an IC50 of 1.0 μM for MIF2 tautomerase activity and a high selectivity over MIF. 5d suppressed the proliferation of non-small cell lung cancer cells in two-dimensional (2D) and three-dimensional (3D) cell cultures, which can be explained by the induction of cell cycle arrest via deactivation of the mitogen-activated protein kinase (MAPK) pathway. Thus, we discovered and characterized MIF2 inhibitors (5d) with improved antiproliferative activity in cellular models systems, which indicates the potential of targeting MIF2 in cancer treatment.

Macrophage migration inhibitory factor family proteins are multitasking cytokines in tissue injury

The family of macrophage migration inhibitory factor (MIF) proteins in humans consist of MIF, its functional homolog D-dopachrome tautomerase (D-DT, also known as MIF-2) and the relatively unknown protein named DDT-like (DDTL). MIF is a pleiotropic cytokine with multiple properties in tissue homeostasis and pathology. MIF was initially found to associate with inflammatory responses and therefore established a reputation as a pro-inflammatory cytokine. However, increasing evidence demonstrates that MIF influences many different intra- and extracellular molecular processes important for the maintenance of cellular homeostasis, such as promotion of cellular survival, antioxidant signaling, and wound repair. In contrast, studies on D-DT are scarce and on DDTL almost nonexistent and their functions remain to be further investigated as it is yet unclear how similar they are compared to MIF. Importantly, the many and sometimes opposing functions of MIF suggest that targeting MIF therapeutically should be considered carefully, taking into account timing and severity of tissue injury. In this review, we focus on the latest discoveries regarding the role of MIF family members in tissue injury, inflammation and repair, and highlight the possibilities of interventions with therapeutics targeting or mimicking MIF family proteins.

MIF but not MIF-2 recruits inflammatory macrophages in an experimental polymicrobial sepsis model

Excessive inflammation drives the progression from sepsis to septic shock. Macrophage migration inhibitory factor (MIF) is of interest because MIF promoter polymorphisms predict mortality in different infections, and anti-MIF antibody improves survival in experimental models when administered 8 hours after infectious insult. The recent description of a second MIF superfamily member, D-dopachrome tautomerase (D-DT/MIF-2), prompted closer investigation of MIF-dependent responses. We subjected Mif-/- and Mif-2-/- mice to polymicrobial sepsis and observed a survival benefit with Mif but not Mif-2 deficiency. Survival was associated with reduced numbers of small peritoneal macrophages (SPMs) that, in contrast to large peritoneal macrophages (LPMs), were recruited into the peritoneal cavity. LPMs produced higher quantities of MIF than SPMs, but SPMs expressed higher levels of inflammatory cytokines and the MIF receptors CD74 and CXCR2. Adoptive transfer of WT SPMs into Mif-/- hosts reduced the protective effect of Mif deficiency in polymicrobial sepsis. Notably, MIF-2 lacks the pseudo-(E)LR motif present in MIF that mediates CXCR2 engagement and SPM migration, supporting a specific role for MIF in the recruitment and accumulation of inflammatory SPMs.

4-Iodopyrimidine Labeling Reveals Nuclear Translocation and Nuclease Activity for Both MIF and MIF2*

Macrophage migration inhibitory factor (MIF) and its homolog MIF2 (also known as D‐dopachrome tautomerase or DDT) play key roles in cell growth and immune responses. MIF and MIF2 expression is dysregulated in cancers and neurodegenerative diseases. Accurate and convenient detection of MIF and MIF2 will facilitate research on their roles in cancer and other diseases. Herein, we report the development and application of a 4‐iodopyrimidine based probe 8 for the selective labeling of MIF and MIF2. Probe 8 incorporates a fluorophore that allows in situ imaging of these two proteins. This enabled visualization of the translocation of MIF2 from the cytoplasm to the nucleus upon methylnitronitrosoguanidine stimulation of HeLa cells. This observation, combined with literature on nuclease activity for MIF, enabled the identification of nuclease activity for MIF2 on human genomic DNA.