Prdx4 limits caspase-1 activation and restricts inflammasome-mediated signaling by extracellular vesicles

Regulatory role of PDK1 via integrated gene analysis of mitochondria-immune response in periodontitis

AIMS

To investigate the association between mitochondrial events and immune response in periodontitis and related regulatory genes.

MAIN METHODS

Gene expression profiles in gingival tissues were retrieved from the Gene Expression Omnibus. Mitochondria-immune response-related differentially expressed genes (MIR-DEGs) between the healthy and periodontitis samples were determined. WGCNA, GO, and KEGG were used to investigate the function and the enriched pathways of MIR-DEGs. The correlation between MIR-DEGs expression and clinical probing pocket depth was analyzed. The MIR-DEGs were further identified and verified in animal samples. A periodontitis model was established in C57BL/6 mice with silk ligation. Micro-computed tomography was used to assess alveolar bone loss. Western blot, quantitative real-time polymerase chain reaction, and immunohistochemical analyses further validated the differential expression of the MIR-DEGs.

KEY FINDINGS

A total of ten MIR-DEGs (CYP24A1, PRDX4, GLDC, PDK1, BCL2A1, CBR3, ARMCX3, BNIP3, IFI27, and UNG) were identified, the expression of which could effectively distinguish patients with periodontitis from the healthy controls. Enhanced immune response was detected in the periodontitis group with that in the healthy controls, especially in B cells. PDK1 was a critical MIR-DEG correlated with B cell immune response and clinical periodontal probing pocket depth. Both animal and clinical periodontal samples presented higher gene and protein expression of PDK1 than the control samples. Additionally, PDK1 colocalized with B cells in both animal and clinical periodontal tissues.

SIGNIFICANCE

Mitochondria participate in the regulation of the immune response in periodontitis. PDK1 may be the key mitochondria-related gene regulating B-cell immune response in periodontitis.

Redox signaling in cell fate: Beyond damage

This review explores the nuanced role of reactive oxygen species (ROS) in cell fate, challenging the traditional view that equates ROS with cellular damage. Through significant technological advancements in detecting localized redox states and identifying oxidized cysteines, a paradigm shift has emerged: from ROS as merely damaging agents to crucial players in redox signaling. We delve into the intricacies of redox mechanisms, which, although confined, exert profound influences on cellular physiological responses. Our analysis extends to both the positive and negative impacts of these mechanisms on cell death processes, including uncontrolled and programmed pathways. By unraveling these complex interactions, we argue against the oversimplified notion of a 'stress response', advocating for a more nuanced understanding of redox signaling. This review underscores the importance of localized redox states in determining cell fate, highlighting the sophistication and subtlety of ROS functions beyond mere damage.

Dynamic changes in extracellular vesicle-associated miRNAs elicited by ultrasound in inflammatory bowel disease patients

Blood-based biomarkers that reliably indicate disease activity in the intestinal tract are an important unmet need in the management of patients with IBD. Extracellular vesicles (EVs) are cell-derived membranous microparticles, which reflect the cellular and functional state of their site of site of origin. As ultrasound waves may lead to molecular shifts of EV contents, we hypothesized that application of ultrasound waves on inflamed intestinal tissue in IBD may amplify the inflammation-specific molecular shifts in EVs like altered EV-miRNA expression, which in turn can be detected in the peripheral blood. 26 patients with IBD were included in the prospective clinical study. Serum samples were collected before and 30 min after diagnostic transabdominal ultrasound. Differential miRNA expression was analyzed by sequencing. Candidate inducible EV-miRNAs were functionally assessed in vitro by transfection of miRNA mimics and qPCR of predicted target genes. Serum EV-miRNA concentration at baseline correlated with disease severity, as determined by clinical activity scores and sonographic findings. Three miRNAs (miR-942-5p, mir-5588, mir-3195) were significantly induced by sonography. Among the significantly regulated EV-miRNAs, miR-942-5p was strongly induced in higher grade intestinal inflammation and correlated with clinical activity in Crohn's disease. Prediction of target regulation and transfection of miRNA mimics inferred a role of this EV-miRNA in regulating barrier function in inflammation. Induction of mir-5588 and mir-3195 did not correlate with inflammation grade. This proof-of-concept trial highlights the principle of induced molecular shifts in EVs from inflamed tissue through transabdominal ultrasound. These inducible EVs and their molecular cargo like miRNA could become novel biomarkers for intestinal inflammation in IBD.

Revealing Prdx4 as a potential diagnostic and therapeutic target for acute pancreatitis based on machine learning analysis

Acute pancreatitis (AP) is a common systemic inflammatory disease resulting from the activation of trypsinogen by various incentives in ICU. The annual incidence rate is approximately 30 out of 100,000. Some patients may progress to severe acute pancreatitis, with a mortality rate of up to 40%. Therefore, the goal of this article is to explore the key genes for effective diagnosis and treatment of AP. The analysis data for this study were merged from two GEO datasets. 1357 DEGs were used for functional enrichment and cMAP analysis, aiming to reveal the pathogenic genes and potential mechanisms of AP, as well as potential drugs for treating AP. Importantly, the study used LASSO and SVM-RFE machine learning to screen the most likely AP occurrence biomarker for Prdx4 among numerous candidate genes. A receiver operating characteristic of Prdx4 was used to estimate the incidence of AP. The ssGSEA algorithm was employed to investigate immune cell infiltration in AP. The biomarker Prdx4 gene exhibited significant associations with a majority of immune cells and was identified as being expressed in NKT cells, macrophages, granulocytes, and B cells based on single-cell transcriptome data. Finally, we found an increase in Prdx4 expression in the pancreatic tissue of AP mice through immunohistochemistry. After treatment with recombinant Prdx4, the pathological damage to the pancreatic tissue of AP mice was relieved. In conclusion, our study identified Prdx4 as a potential AP hub gene, providing a new target for treatment.

Validation of the interaction between PRDX4 and TXNDC5 in gastric cancer and the significance of the PRDX4 gene in gastric cancer based on a data mining analysis

Background

We successfully screened the important interacting protein peroxiredoxin 4 (PRDX4) of thioredoxin domain-containing protein 5 (TXNDC5) in gastric cancer. However, its specific molecular mechanism in gastric cancer remains unclear. This study aimed to verify the interaction between PRDX4 and TXNDC5 protein molecules in gastric cancer and analyze the expression and functional significance of PRDX4 in gastric cancer using bioinformatics methods.

Methods

The interaction between TXNDC5 and PRDX4 was verified by the coimmunoprecipitation (co-IP) of the total protein of gastric cancer cells, and tissues with high expressions of TXNDC5. The Human Protein Atlas (HPA) database, UCSC Xena (University of California Santa Cruz xenabrowser) platform, the Kaplan-Meier Plotter platform, and the TIMER (Tumor IMmune Estimation Resource) platform were used to analyze the expression and subcellular localization of the PRDX4 molecule in normal human gastric tissue, the difference in expression between gastric cancer tissue and normal gastric tissue, the relationship between the expression of PRDX4 and survival, its functional significance in gastric cancer cells, and its effect on the tumor immune microenvironment (TIME).

Results

The data analysis results showed that the expression of PRDX4 messenger RNA (mRNA) in the gastric cancer tissues was significantly higher than that in the normal tissues (P<0.05). PRDX4 could affect the occurrence and development of tumors by participating in the neutrophil degranulation signaling pathway to regulate tumor immunity. The expression level of PRDX4 has a certain relationship with the TIME; that is, it is mainly negatively correlated with the infiltration of B lymphocytes and CD4+ T lymphocytes (P<0.05). The expression level of PRDX4 was positively correlated with the expression of LILRB2 (leukocyte immunoglobulin-like receptor subfamily B member 2), and negatively correlated with BLTA (B and T lymphocyte attenuation factor) and VISTA (V-type immunoglobulin domain-containing suppressor of T cell activation) (P<0.05).

Conclusions

There is an interaction between PRDX4 and TXNDC5 protein molecules in gastric cancer. PRDX4 gene expression is significantly up-regulated in gastric cancer. It may reduce the infiltration of B lymphocytes and CD4+ T lymphocytes and affect the expression of LILRB2, BLTA, and VISTA immune checkpoints, leading to anti-tumor immunosuppression.

Redox proteomics combined with proximity labeling enables monitoring of localized cysteine oxidation in cells

Reactive oxygen species (ROS) can modulate protein function through cysteine oxidation. Identifying protein targets of ROS can provide insight into uncharacterized ROS-regulated pathways. Several redox-proteomic workflows, such as oxidative isotope-coded affinity tags (OxICAT), exist to identify sites of cysteine oxidation. However, determining ROS targets localized within subcellular compartments and ROS hotspots remains challenging with existing workflows. Here, we present a chemoproteomic platform, PL-OxICAT, which combines proximity labeling (PL) with OxICAT to monitor localized cysteine oxidation events. We show that TurboID-based PL-OxICAT can monitor cysteine oxidation events within subcellular compartments such as the mitochondrial matrix and intermembrane space. Furthermore, we use ascorbate peroxidase (APEX)-based PL-OxICAT to monitor oxidation events within ROS hotspots by using endogenous ROS as the source of peroxide for APEX activation. Together, these platforms further hone our ability to monitor cysteine oxidation events within specific subcellular locations and ROS hotspots and provide a deeper understanding of the protein targets of endogenous and exogenous ROS.

Remarkable sex-specific differences at single-cell resolution in neonatal hyperoxic lung injury

Exposure to supraphysiological concentrations of oxygen (hyperoxia) predisposes to bronchopulmonary dysplasia (BPD), which is characterized by abnormal alveolarization and pulmonary vascular development, in preterm neonates. Neonatal hyperoxia exposure is used to recapitulate the phenotype of human BPD in murine models. Male sex is considered an independent predictor for the development of BPD, but the main mechanisms underlying sexually dimorphic outcomes are unknown. Our objective was to investigate sex-specific and cell-type specific transcriptional changes that drive injury in the neonatal lung exposed to hyperoxia at single-cell resolution and delineate the changes in cell-cell communication networks in the developing lung. We used single-cell RNA sequencing (scRNAseq) to generate transcriptional profiles of >35,000 cells isolated from the lungs of neonatal male and female C57BL/6 mice exposed to 95% [Formula: see text] between PND1-5 (saccular stage of lung development) or normoxia and euthanized at PND7 (alveolar stage of lung development). ScRNAseq identified 22 cell clusters with distinct populations of endothelial, epithelial, mesenchymal, and immune cells. Our data identified that the distal lung vascular endothelium (composed of aerocytes and general capillary endothelial cells) is exquisitely sensitive to hyperoxia exposure with the emergence of an intermediate capillary endothelial population with both general capillaries (gCap) and aerocytes or alveolar capillaries (aCap) markers. We also identified a myeloid-derived suppressor cell population from the lung neutrophils. Sex-specific differences were evident in all lung cell subpopulations but were striking among the lung immune cells. Finally, we identified that the specific intercellular communication networks and the ligand-receptor pairs that are impacted by neonatal hyperoxia exposure.

Extracellular vesicles participate in the pathogenesis of sepsis

Sepsis is one of the leading causes of mortality worldwide and is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. The early diagnosis and effective treatment of sepsis still face challenges due to its rapid progression, dynamic changes, and strong heterogeneity among different individuals. To develop novel strategies to control sepsis, a better understanding of the complex mechanisms of sepsis is vital. Extracellular vesicles (EVs) are membrane vesicles released from cells through different mechanisms. In the disease state, the number of EVs produced by activated or apoptotic cells and the cargoes they carry were altered. They regulated the function of local or distant host cells in autocrine or paracrine ways. Current studies have found that EVs are involved in the occurrence and development of sepsis through multiple pathways. In this review, we focus on changes in the cargoes of EVs in sepsis, the regulatory roles of EVs derived from host cells and bacteria, and how EVs are involved in multiple pathological processes and organ dysfunction in sepsis. Overall, EVs have great application prospects in sepsis, such as early diagnosis of sepsis, dynamic monitoring of disease, precise therapeutic targets, and prevention of sepsis as a vaccine platform.

Essential Roles of Peroxiredoxin IV in Inflammation and Cancer

Peroxiredoxin IV (Prx4) is a 2-Cysteine peroxidase with ubiquitous expression in human tissues. Prx4 scavenges hydrogen peroxide and participates in oxidative protein folding in the endoplasmic reticulum. In addition, Prx4 is secreted outside the cell. Prx4 is upregulated in several cancers and is a potential therapeutic target. We have summarized historical and recent advances in the structure, function and biological roles of Prx4, focusing on inflammatory diseases and cancer. Oxidative stress is known to activate pro-inflammatory pathways. Chronic inflammation is a risk factor for cancer development. Hence, redox enzymes such as Prx4 are important players in the crosstalk between inflammation and cancer. Understanding molecular mechanisms of regulation of Prx4 expression and associated signaling pathways in normal physiological and disease conditions should reveal new therapeutic strategies. Thus, although Prx4 is a promising therapeutic target for inflammatory diseases and cancer, further research needs to be conducted to bridge the gap to clinical application.

Proteomic characterization of a candidate polygenic driver of metabolism in non-small cell lung cancer

Proteome analysis revealed signatures of co-expressed upregulated metabolism proteins highly conserved between primary and non-small cell lung cancer (NSCLC) patient-derived xenograft tumors (Li et al. 2014, Nat. Communications 5:5469). The C10 signature is encoded by seven genes (ADSS, ATP2A2, CTPS1, IMPDH2, PKM2, PTGES3, SGPL1) and DNA alterations in C10-encoding genes are associated with longer survival in a subset of NSCLC. To explore the C10 signature as an oncogenic driver and address potential mechanisms of action, C10 protein expression and protein-protein interactions were determined. In independent NSCLC cohorts, the coordinated expression of C10 proteins was significant and mutations in C10 genes were associated with better outcome. Affinity purification-mass spectrometry and in vivo proximity-based biotin identification defined a C10 interactome involving 667 proteins including candidate drug targets and clusters associated with glycolysis, calcium homeostasis, and nucleotide and sphingolipid metabolism. DNA alterations in genes encoding C10 interactome components were also found to be associated with better survival. These data support the notion that the coordinated upregulation of the C10 signature impinges metabolic processes that collectively function as an oncogenic driver in NSCLC.

Cysteine-Rich LIM-Only Protein 4 (CRP4) Promotes Atherogenesis in the ApoE-/- Mouse Model

Vascular smooth muscle cells (VSMCs) can switch from their contractile state to a synthetic phenotype resulting in high migratory and proliferative capacity and driving atherosclerotic lesion formation. The cysteine-rich LIM-only protein 4 (CRP4) reportedly modulates VSM-like transcriptional signatures, which are perturbed in VSMCs undergoing phenotypic switching. Thus, we hypothesized that CRP4 contributes to adverse VSMC behaviours and thereby to atherogenesis in vivo. The atherogenic properties of CRP4 were investigated in plaque-prone apolipoprotein E (ApoE) and CRP4 double-knockout (dKO) as well as ApoE-deficient CRP4 wildtype mice. dKO mice exhibited lower plaque numbers and lesion areas as well as a reduced content of α-smooth muscle actin positive cells in the lesion area, while lesion-associated cell proliferation was elevated in vessels lacking CRP4. Reduced plaque volumes in dKO correlated with significantly less intra-plaque oxidized low-density lipoprotein (oxLDL), presumably due to upregulation of the antioxidant factor peroxiredoxin-4 (PRDX4). This study identifies CRP4 as a novel pro-atherogenic factor that facilitates plaque oxLDL deposition and identifies the invasion of atherosclerotic lesions by VSMCs as important determinants of plaque vulnerability. Thus, targeting of VSMC CRP4 should be considered in plaque-stabilizing pharmacological strategies.

Peroxiredoxin 4 regulates tumor-cell-like characteristics of fibroblast-like synoviocytes in rheumatoid arthritis through PI3k/Akt signaling pathway

Peroxiredoxin-4 (PRDX4), a member of PRDX family, which played an important role in scavenging reactive oxygen species (ROS). The up-regulation of PRDX4 in synovial tissue and synovial fluid from rheumatoid arthritis (RA) patients has been reported. However, the biological functions of PRDX4 in fibroblast-like synoviocytes (RA-FLS) remains unclear. In this research, we reveal that expression of PRDX4 was notably increased in RA synovial tissue, especially in hyperplastic synovial tissue. PRDX4 silencing significantly inhibited the tumor cell-like behaviors and mRNA expression of matrix metalloproteinases (MMPs) in RA-FLS. Furthermore, overexpression of PRDX4 markedly activated PI3K/Akt signaling pathway, which can be reverted by Akt inhibitor MK-2206. These observations identified elevated PRDX4 may regulates the tumor cell-like biological characteristic of RA-FLS via Pi3k/Akt pathway. Targeting PRDX4 and its downstream signaling pathway might provide a potential diagnostic markers and therapeutic target for RA.

The Role of Peroxiredoxins in the Regulation of Sepsis

Oxidative stress, a result of a disturbance in redox homeostasis, is considered to be one of the main aggravating events in the pathogenesis of immune disorders. Peroxiredoxins (Prdxs) are an enzyme family that catalyzes the reduction of peroxides, including hydrogen peroxide, lipid peroxides, and nitrogen peroxides. Although the maintenance of cellular redox homeostasis through Prdxs is essential for surviving in adverse environments, Prdxs also participate in the regulation of cellular signal transduction by modulating the activities of a panel of molecules involved in the signal transduction process. Although Prdxs were discovered as intracellular anti-oxidative enzymes, recent research has revealed that Prdxs also play important roles in the extracellular milieu. Indeed, Prdxs have been shown to have the capacity to activate immune cells through ligation with innate immune receptors such as toll-like receptors (TLRs). In this review, we will summarize the intracellular as well as extracellular roles of Prdxs for and against the pathogenesis of inflammatory disorders including sepsis, hemorrhagic shock, and drug-induced liver injury.

Engineering Extracellular Vesicles Restore the Impaired Cellular Uptake and Attenuate Intervertebral Disc Degeneration

Extracellular vesicles (EVs) are potential alternatives for mesenchymal stem cells (MSCs) in the treatment of musculoskeletal degenerative diseases, including intervertebral disc degeneration (IDD). Usually, EVs are internalized and then deliver bioactive molecules that impart phenotypic changes in recipient cells. For effective utilization of EVs in the IDD therapy, understanding the mechanism of EV uptake is of vital importance. In this study, we found that EVs delivered antioxidant proteins to protect against pyroptosis of nucleus pulposus cells (NPCs). In particular, the therapeutic effect of EVs decreased in TNF-α-treated NPCs due to the impaired caveolae-mediated endocytosis pathway. Transcriptome sequencing and functional verification revealed that caveolae associated protein 2 (Cavin-2) played an important role in the uptake process of EVs. We then constructed the Cavin-2-modified engineering EVs via the gene-editing of parental MSCs. These kinds of modified EVs presented an improved uptake rate in TNF-α-treated NPCs, which effectively ameliorated the cell death of NPCs in a three-dimensional hydrogel culture model and retarded the progression of IDD in the ex vivo organ culture model. Collectively, these findings illustrate the mechanism of EV uptake in NPCs and explore the application of engineering EVs in the treatment of IDD.

Colchicine reduces extracellular vesicle NLRP3 inflammasome protein levels in chronic coronary disease: A LoDoCo2 biomarker substudy

BACKGROUND AND AIMS

Colchicine reduces the risk of cardiovascular events in patients with coronary disease. Colchicine has broad anti-inflammatory effects and part of the atheroprotective effects have been suggested to be the result of NLRP3 inflammasome inhibition. We studied the effect of colchicine on extracellular vesicle (EV) NLRP3 protein levels and inflammatory markers, high sensitivity-CRP (hs-CRP) and interleukin (IL)-6, in patients with chronic coronary disease.

METHODS

In vitro, the NLRP3 inflammasome was stimulated in PMA-differentiated- and undifferentiated THP-1 cells. In vivo, measurements were performed in serum obtained from 278 participants of the LoDoCo2 trial, one year after randomization to colchicine 0.5 mg once daily or placebo. EVs were isolated using precipitation. NLRP3 protein presence in EVs was confirmed using iodixanol density gradient centrifugation. Levels of NLRP3 protein, hs-CRP and IL-6 were measured using ELISA.

RESULTS

In vitro, NLRP3 inflammasome stimulation showed an increase of EV NLRP3 protein levels. EV NLRP3 protein levels were lower in patients treated with colchicine (median 1.38 ng/mL), compared to placebo (median 1.58 ng/mL) (p = 0.025). No difference was observed in serum NLRP3 protein levels. Serum hs-CRP levels were lower in patients treated with colchicine (median 0.80 mg/L) compared to placebo (median 1.34 mg/L) (p < 0.005). IL-6 levels were lower in patients treated with colchicine (median 2.07 ng/L) compared to placebo (median 2.59 ng/L), although this was not statistically significant (p = 0.076).

CONCLUSIONS

Colchicine leads to a reduction of EV NLRP3 protein levels. This indicates that inhibitory effects on the NLRP3 inflammasome might contribute to the atheroprotective effects of colchicine in coronary disease.

Oxidation of peroxiredoxin-4 induces oligomerization and promotes interaction with proteins governing protein folding and endoplasmic reticulum stress

Peroxiredoxins (PRDXs) catalyze the reduction of hydrogen peroxide (H₂O₂). PRDX4 is the only peroxiredoxin located within the endoplasmic reticulum (ER) and is the most highly expressed H₂O₂ scavenger in the ER. PRDX4 has emerged as an important player in numerous diseases, such as fibrosis and metabolic syndromes, and its overoxidation is a potential indicator of ER redox stress. It is unclear how overoxidation of PRDX4 governs its oligomerization state and interacting partners. Herein, we addressed these questions via nonreducing Western blots, mass spectrometry, and site-directed mutagenesis. We report that the oxidation of PRDX4 in lung epithelial cells treated with tertbutyl hydroperoxide caused a shift of PRDX4 from monomer/dimer to high molecular weight (HMW) species, which contain PRDX4 modified with sulfonic acid residues (PRDX4-SO₃), as well as of a complement of ER-associated proteins, including protein disulfide isomerases important in protein folding, thioredoxin domain-containing protein 5, and heat shock protein A5, a key regulator of the ER stress response. Mutation of any of the four cysteines in PRDX4 altered the HMW species in response to tertbutyl hydroperoxide as well as the secretion of PRDX4. We also demonstrate that the expression of ER oxidoreductase 1 alpha, which generates H₂O₂ in the ER, increased PRDX4 HMW formation and secretion. These results suggest a link between SO₃ modification in the formation of HMW PRDX4 complexes in cells, whereas the association of key regulators of ER homeostasis with HMW oxidized PRDX4 point to a putative role of PRDX4 in regulating ER stress responses.

Peroxiredoxins wear many hats: Factors that fashion their peroxide sensing personalities

Peroxiredoxins (Prdxs) sense and assess peroxide levels, and signal through protein interactions. Understanding the role of the multiple structural and post-translational modification (PTM) layers that tunes the peroxiredoxin specificities is still a challenge. In this review, we give a tabulated overview on what is known about human and bacterial peroxiredoxins with a focus on structure, PTMs, and protein-protein interactions. Armed with numerous cellular and atomic level experimental techniques, we look at the future and ask ourselves what is still needed to give us a clearer view on the cellular operating power of Prdxs in both stress and non-stress conditions.

Extracellular Vesicles and Their Role in the Spatial and Temporal Expansion of Tumor-Immune Interactions

Extracellular vesicles (EVs) serve as trafficking vehicles and intercellular communication tools. Their cargo molecules directly reflect characteristics of their parental cell. This includes information on cell identity and specific cellular conditions, ranging from normal to pathological states. In cancer, the content of EVs derived from tumor cells is altered and can induce oncogenic reprogramming of target cells. As a result, tumor-derived EVs compromise antitumor immunity and promote cancer progression and spreading. However, this pro-oncogenic phenotype is constantly being challenged by EVs derived from the local tumor microenvironment and from remote sources. Here, we summarize the role of EVs in the tumor–immune cross-talk that includes, but is not limited to, immune cells in the tumor microenvironment. We discuss the potential of remotely released EVs from the microbiome and during physical activity to shape the tumor–immune cross-talk, directly or indirectly, and confer antitumor activity. We further discuss the role of proinflammatory EVs in the temporal development of the tumor–immune interactions and their potential use for cancer diagnostics.

Cell Surface Processing of CD109 by Meprin β Leads to the Release of Soluble Fragments and Reduced Expression on Extracellular Vesicles

Cluster of differentiation 109 (CD109) is a glycosylphosphatidylinositol (GPI)-anchored protein expressed on primitive hematopoietic stem cells, activated platelets, CD4+ and CD8+ T cells, and keratinocytes. In recent years, CD109 was also associated with different tumor entities and identified as a possible future diagnostic marker linked to reduced patient survival. Also, different cell signaling pathways were proposed as targets for CD109 interference including the TGFβ, JAK-STAT3, YAP/TAZ, and EGFR/AKT/mTOR pathways. Here, we identify the metalloproteinase meprin β to cleave CD109 at the cell surface and thereby induce the release of cleavage fragments of different size. Major cleavage was identified within the bait region of CD109 residing in the middle of the protein. To identify the structural localization of the bait region, homology modeling and single-particle analysis were applied, resulting in a molecular model of membrane-associated CD109, which allows for the localization of the newly identified cleavage sites for meprin β and the previously published cleavage sites for the metalloproteinase bone morphogenetic protein-1 (BMP-1). Full-length CD109 localized on extracellular vesicles (EVs) was also identified as a release mechanism, and we can show that proteolytic cleavage of CD109 at the cell surface reduces the amount of CD109 sorted to EVs. In summary, we identified meprin β as the first membrane-bound protease to cleave CD109 within the bait region, provide a first structural model for CD109, and show that cell surface proteolysis correlates negatively with CD109 released on EVs.

ACT1 Is Required for Murine IL-23-Induced Psoriasiform Inflammation Potentially Independent of E3 Ligase Activity

Psoriasis is a debilitating skin disease characterized by epidermal thickening, abnormal keratinocyte differentiation, and proinflammatory immune cell infiltrate into the affected skin. IL-17A plays a critical role in the etiology of psoriasis. ACT1, an intracellular adaptor protein and a putative ubiquitin E3 ligase, is essential for signal transduction downstream of the IL-17A receptor. Thus, IL-17A signaling in general, and ACT1 specifically, represent attractive targets for the treatment of psoriasis. We generated Act1 knockout and Act1 L286G knockin (ligase domain) mice to investigate the potential therapeutic effects of targeting ACT1 and its U-box domain, respectively. Act1 knockout, but not Act1 L286G knockin, mice were resistant to increases in CXCL1 plasma levels induced by subcutaneous injection of recombinant IL-17A. Moreover, in a mouse model of psoriasiform dermatitis induced by intradermal IL-23 injection, Act1 knockout, but not Act1 L286G knockin, was protective against increases in ear thickness, keratinocyte hyperproliferation, expression of genes for antimicrobial peptides and chemokines, and infiltration of monocytes and macrophages. Our studies highlight the critical contribution of ACT1 to proinflammatory skin changes mediated by the IL-23/IL-17 signaling axis and illustrate the need for further insight into ACT1 E3 ligase activity.

Role of Peroxiredoxins in Protecting Against Cardiovascular and Related Disorders

Peroxiredoxin (Prx) refers to a family of thiol-dependent peroxidases that decompose hydrogen peroxide, lipid hydroperoxides, as well as peroxynitrite, and protect against oxidative and inflammatory stress. There are six mammalian Prx isozymes (Prx1-6), classified as typical 2-Cys, atypical 2-Cys, or 1-Cys Prxs based on the mechanism and the number of cysteine residues involved during catalysis. In addition to their well-established peroxide-scavenging activity, some Prxs also participate in the regulation of various cell signaling pathways. Extensive animal studies employing primarily gene knockout models provide substantial evidence supporting a critical protective role of Prxs in various disease processes involving oxidative and inflammatory stress. This review surveys recent research findings, published primarily in influential journals, on the involvement of various Prx isozymes in protecting against cardiovascular injury and related disorders, including diabetes, metabolic syndromes, and sepsis, whose pathophysiology all intimately involves oxidative stress and inflammation.

Unbiased Profiling of the Human Proinsulin Biosynthetic Interaction Network Reveals a Role for Peroxiredoxin 4 in Proinsulin Folding

The β-cell protein synthetic machinery is dedicated to the production of mature insulin, which requires the proper folding and trafficking of its precursor, proinsulin. The complete network of proteins that mediate proinsulin folding and advancement through the secretory pathway, however, remains poorly defined. Here we used affinity purification and mass spectrometry to identify, for the first time, the proinsulin biosynthetic interaction network in human islets. Stringent analysis established a central node of proinsulin interactions with endoplasmic reticulum (ER) folding factors, including chaperones and oxidoreductases, that is remarkably conserved in both sexes and across three ethnicities. The ER-localized peroxiredoxin PRDX4 was identified as a prominent proinsulin-interacting protein. In β-cells, gene silencing of PRDX4 rendered proinsulin susceptible to misfolding, particularly in response to oxidative stress, while exogenous PRDX4 improved proinsulin folding. Moreover, proinsulin misfolding induced by oxidative stress or high glucose was accompanied by sulfonylation of PRDX4, a modification known to inactivate peroxiredoxins. Notably, islets from patients with type 2 diabetes (T2D) exhibited significantly higher levels of sulfonylated PRDX4 than islets from healthy individuals. In conclusion, we have generated the first reference map of the human proinsulin interactome to identify critical factors controlling insulin biosynthesis, β-cell function, and T2D.

Harnessing Omics Approaches on Advanced Preclinical Models to Discovery Novel Therapeutic Targets for the Treatment of Metastatic Colorectal Cancer

Metastatic colorectal cancer (mCRC) remains challenging because of the emergence of resistance mechanisms to anti-epidermal growth factor receptor (EGFR) therapeutics, so more effective strategies to improve the patients’ outcome are needed. During the last decade, the application of a multi-omics approach has contributed to a deeper understanding of the complex molecular landscape of human CRC, identifying a plethora of drug targets for precision medicine. Target validation relies on the use of experimental models that would retain the molecular and clinical features of human colorectal cancer, thus mirroring the clinical characteristics of patients. In particular, organoids and patient-derived-xenografts (PDXs), as well as genetically engineered mouse models (GEMMs) and patient-derived orthotopic xenografts (PDOXs), should be considered for translational purposes. Overall, omics and advanced mouse models of cancer represent a portfolio of sophisticated biological tools that, if optimized for use in concert with accurate data analysis, could accelerate the anticancer discovery process and provide new weapons against cancer. In this review, we highlight success reached following the integration of omics and experimental models; moreover, results produced by our group in the field of mCRC are also presented.

Joint Reconstituted Signaling of the IL-6 Receptor via Extracellular Vesicles

Interleukin-6 (IL-6) signaling is a crucial regulatory event important for many biological functions, such as inflammation and tissue regeneration. Accordingly, several pathological conditions are associated with dysregulated IL-6 activity, making it an attractive therapeutic target. For instance, blockade of IL-6 or its α-receptor (IL-6R) by monoclonal antibodies has been successfully used to treat rheumatoid arthritis. However, based on different signaling modes, IL-6 function varies between pro- and anti-inflammatory activity, which is critical for therapeutic intervention. So far, three modes of IL-6 signaling have been described, the classic anti-inflammatory signaling, as well as pro-inflammatory trans-signaling, and trans-presentation. The IL-6/IL-6R complex requires an additional β-receptor (gp130), which is expressed on almost all cells of the human body, to induce STAT3 (signal transducer and activator of signal transcription 3) phosphorylation and subsequent transcriptional regulation. In contrast, the IL-6R is expressed on a limited number of cells, including hepatocytes and immune cells. However, the proteolytic release of the IL-6R enables trans-signaling on cells expressing gp130 only. Here, we demonstrate a fourth possibility of IL-6 signaling that we termed joint reconstituted signaling (JRS). We show that IL-6R on extracellular vesicles (EVs) can also be transported to and fused with other cells that lack the IL-6R on their surface. Importantly, JRS via EVs induces delayed STAT3 phosphorylation compared to the well-established trans-signaling mode. EVs isolated from human serum were already shown to carry the IL-6R, and thus this new signaling mode should be considered with regard to signal intervention.

Physiological concentrations of bilirubin control inflammatory response by inhibiting NF-κB and inflammasome activation

Bilirubin, as the final product of heme metabolism, has both toxic and beneficial effects on humans depending on its serum concentration. So far, whether and how physiological concentrations of bilirubin influence inflammation is largely unknown. In the current study, we established inflammatory cell models of murine peritoneal macrophages (PMs) and bone marrow-derived macrophages (BMDMs) by stimulating the cells with either lipopolysaccharide (LPS) alone or with various inflammasome stimuli. In addition, a model of mouse sepsis induced by intraperitoneal injection of LPS was also employed. We found that bilirubin, although used at physiological concentrations, could control inflammation both in vitro and in vivo. In vitro, bilirubin inhibited caspase-1 maturation and IL-1β secretion in NLRP3, AIM2, and NLRC4 inflammasomes. Besides, bilirubin inhibited the secretion of TNF-α and IL-6 in LPS-primed macrophages by reduced phosphorylation of IκB-α and p65, indicating the inhibition of the NF-κB pathway. In vivo, bilirubin significantly inhibited the release of IL-1β and TNF-α, resulting in an increased survival rate of mice with LPS-induced sepsis. Our study demonstrates a protective role of physiological concentrations of bilirubin against inflammation, the mechanisms of which involve the inhibition of the NF-κB signaling pathway as well as control of the activation of inflammasomes. Bilirubin could therefore be considered an endogenous regulatory molecule modulating inflammation. In defined doses, bilirubin could be applied as a potential medication against inflammation and inflammasome-related diseases.

Oxidants, Antioxidants and Thiol Redox Switches in the Control of Regulated Cell Death Pathways

It is well appreciated that biological reactive oxygen and nitrogen species such as hydrogen peroxide, superoxide and nitric oxide, as well as endogenous antioxidant systems, are important modulators of cell survival and death in diverse organisms and cell types. In addition, oxidative stress, nitrosative stress and dysregulated cell death are implicated in a wide variety of pathological conditions, including cancer, cardiovascular and neurological diseases. Therefore, much effort is devoted to elucidate the molecular mechanisms linking oxidant/antioxidant systems and cell death pathways. This review is focused on thiol redox modifications as a major mechanism by which oxidants and antioxidants influence specific regulated cell death pathways in mammalian cells. Growing evidence indicates that redox modifications of cysteine residues in proteins are involved in the regulation of multiple cell death modalities, including apoptosis, necroptosis and pyroptosis. In addition, recent research suggests that thiol redox switches play a role in the crosstalk between apoptotic and necrotic forms of regulated cell death. Thus, thiol-based redox circuits provide an additional layer of control that determines when and how cells die.

Electrophiles Against (Skin) Diseases: More Than Nrf2

The skin represents an indispensable barrier between the organism and the environment and is the first line of defense against exogenous insults. The transcription factor NRF2 is a central regulator of cytoprotection and stress resistance. NRF2 is activated in response to oxidative stress by reactive oxygen species (ROS) and electrophiles. These electrophiles oxidize specific cysteine residues of the NRF2 inhibitor KEAP1, leading to KEAP1 inactivation and, subsequently, NRF2 activation. As oxidative stress is associated with inflammation, the NRF2 pathway plays important roles in the pathogenesis of common inflammatory diseases and cancer in many tissues and organs, including the skin. The electrophile and NRF2 activator dimethyl fumarate (DMF) is an established and efficient drug for patients suffering from the common inflammatory skin disease psoriasis and the neuro-inflammatory disease multiple sclerosis (MS). In this review, we discuss possible molecular mechanisms underlying the therapeutic activity of DMF and other NRF2 activators. Recent evidence suggests that electrophiles not only activate NRF2, but also target other inflammation-associated pathways including the transcription factor NF-κB and the multi-protein complexes termed inflammasomes. Inflammasomes are central regulators of inflammation and are involved in many inflammatory conditions. Most importantly, the NRF2 and inflammasome pathways are connected at different levels, mainly antagonistically.

Prdx4 limits caspase-1 activation and restricts inflammasome-mediated signaling by extracellular vesicles

Inflammasomes are cytosolic protein complexes, which orchestrate the maturation of active IL‐1β by proteolytic cleavage via caspase‐1. Although many principles of inflammasome activation have been described, mechanisms that limit inflammasome‐dependent immune responses remain poorly defined. Here, we show that the thiol‐specific peroxidase peroxiredoxin‐4 (Prdx4) directly regulates IL‐1β generation by interfering with caspase‐1 activity. We demonstrate that caspase‐1 and Prdx4 form a redox‐sensitive regulatory complex via caspase‐1 cysteine 397 that leads to caspase‐1 sequestration and inactivation. Mice lacking Prdx4 show an increased susceptibility to LPS‐induced septic shock. This effect was phenocopied in mice carrying a conditional deletion of Prdx4 in the myeloid lineage (Prdx4‐ΔLysMCre). Strikingly, we demonstrate that Prdx4 co‐localizes with inflammasome components in extracellular vesicles (EVs) from inflammasome‐activated macrophages. Purified EVs are able to transmit a robust IL‐1β‐dependent inflammatory response in vitro and also in recipient mice in vivo. Loss of Prdx4 boosts the pro‐inflammatory potential of EVs. These findings identify Prdx4 as a critical regulator of inflammasome activity and provide new insights into remote cell‐to‐cell communication function of inflammasomes via macrophage‐derived EVs.