Ninjurin1 Plays a Crucial Role in Pulmonary Fibrosis by Promoting Interaction between Macrophages and Alveolar Epithelial Cells

Unraveling the mechanisms of NINJ1-mediated plasma membrane rupture in lytic cell death and related diseases

Plasma membrane rupture (PMR), the ultimate event during lytic cell death, releases damage-associated molecular patterns (DAMPs) that trigger inflammation and immune responses in the development of various diseases. Recent years have witnessed significant advances in understanding the PMR mediated by ninjurin1 (NINJ1) in different lytic cell death processes. NINJ1 oligomerizes and ruptures the membrane in pyroptosis and other lytic cell death, participating in the pathogenesis of multiple diseases. Although the membrane-permeabilizing function of NINJ1 is well recognized, the role of NINJ1 in different types of lytic cell death and its impact on multiple disease processes have yet to be fully elucidated. This review summarizes the latest advances in the mechanisms of NINJ1-mediated PMR, discusses the membrane-inducing activity of NINJ1 in different lytic cell death, explains the implications of NINJ1 in lytic cell death-related diseases, and lists the inhibitory strategies for NINJ1. We expect to provide new insights into targeting NINJ1 to suppress lytic cell death for therapeutic benefit, which may become a new strategy to control inflammatory cell lysis-related diseases.

Norovirus co-opts NINJ1 for selective protein secretion

Plasma membrane rupture by Ninjurin-1 (NINJ1) executes programmed cell death, releasing large cellular damage-associated molecular patterns (DAMPs). However, the regulation and selectivity of NINJ1-mediated DAMP release remain unexplored. Here, we uncover that murine norovirus (MNoV) strategically co-opts NINJ1 to selectively release the intracellular viral protein NS1, while NINJ1-mediated plasma membrane rupture simultaneously bulk-releases various cellular DAMPs. Host caspase-3 cleaves the precursor NS1/2, leading to NS1 secretion via an unconventional pathway. An unbiased CRISPR screen identifies NINJ1 as an essential factor for NS1 secretion. During infection, NINJ1 is recruited to the viral replication site, where it oligomerizes and forms speckled bodies, directly interacting with NS1. Subsequent mutagenesis studies identify critical amino acid residues of NS1 necessary for its interaction with NINJ1 and selective secretion. Genetic ablation or pharmaceutical inhibition of caspase-3 inhibits oral MNoV infection in mice. This study underscores the co-option of NINJ1 for controlled release of an intracellular viral protein.

NINJ1 in Cell Death and Ferroptosis: Implications for Tumor Invasion and Metastasis

NINJ1 was initially recognized for its role in nerve regeneration and cellular adhesion. Subsequent studies have uncovered its participation in cancer progression, where NINJ1 regulates critical steps in tumor metastasis, such as cell migration and invasion. More recently, NINJ1 has emerged as a multifunctional protein mediating plasma membrane rupture (PMR) in several lytic cell death processes, including apoptosis, necroptosis, and pyroptosis. However, its role in ferroptosis-an iron-dependent form of lytic cell death characterized by lipid peroxidation-remained unclear until 2024. Ferroptosis is a tumor suppression mechanism that may be particularly relevant to detached and metastatic cancer cells. This review explores the role of NINJ1 in tumor invasion and metastasis, focusing on its regulation of ferroptosis via a non-canonical mechanism distinct from other cell deaths. We discuss the process of ferroptosis and its implications for cancer invasion and metastasis. Furthermore, we review recent studies highlighting the diverse roles of NINJ1 in ferroptosis regulation, including its canonical function in PMR and its non-canonical function of modulating intracellular levels of glutathione (GSH) and coenzyme A (CoA) via interaction with xCT anti-porter. Given that ferroptosis has been associated with tumor suppression, metastasis, the elimination of treatment-resistant cancer cells, and tumor dormancy, NINJ1's modulation of ferroptosis presents a promising therapeutic target for inhibiting metastasis. Understanding the dual role of NINJ1 in promoting or restraining ferroptosis depending on cellular context could open avenues for novel anti-cancer strategies to enhance ferroptotic vulnerability in metastatic tumors.

Multifaceted roles of ninjurin1 in immunity, cell death, and disease

Ninjurin1 (NINJ1) is initially identified as a nerve injury-induced adhesion molecule that facilitates axon growth. It is initially characterized to promote nerve regeneration and mediate the transendothelial transport of monocytes/macrophages associated with neuroinflammation. Recent evidence indicates that NINJ1 mediates plasma membrane rupture (PMR) in lytic cell death. The absence or inhibition of NINJ1 can delay PMR, thereby mitigating the spread of inflammation resulting from cell lysis and preventing the progression of various cell death-related pathologies, suggesting a conserved regulatory mechanism across these processes. Further research elucidated the structural basis and mechanism of NINJ1-mediated PMR. Although the role of NINJ1 in PMR is established, the identity of its activating factors and its implications in diseases remain to be fully explored. This review synthesizes current knowledge regarding the structural basis and mechanism of NINJ1-mediated PMR and discusses its significance and therapeutic targeting potential in inflammatory diseases, neurological disorders, cancer, and vascular injuries.

Loss of Ninjurin1 alleviates acetaminophen-induced liver injury via enhancing AMPKα-NRF2 pathway

Acetaminophen (APAP), a widely used pain and fever reliever, is a major contributor to drug-induced liver injury, as its toxic metabolites such as NAPQI induce oxidative stress and hepatic necrosis. While N-acetylcysteine serves as the primary treatment for APAP-induced liver injury (AILI), its efficacy is confined to a narrow window of 8-24 h post-APAP overdose. Beyond this window, liver transplantation emerges as the final recourse, prompting ongoing research to pinpoint novel therapeutic targets aimed at enhancing AILI treatment outcomes. Nerve injury-induced protein 1 (Ninjurin1; Ninj1), initially recognized as an adhesion molecule, has been implicated in liver damage stemming from factors like TNFα and ischemia-reperfusion. Nonetheless, its role in oxidative stress-related liver diseases, including AILI, remains unexplored. In this study, we observed up-regulation of Ninj1 expression in the livers of both human DILI patients and the AILI mouse model. Through the utilization of Ninj1 null mice, hepatocyte-specific Ninj1 KO mice, and myeloid-specific Ninj1 KO mice, we unveiled that the loss of Ninj1 in hepatocytes, rather than myeloid cells, exerts alleviative effects on AILI irrespective of sex dependency. Further in vitro experiments demonstrated that Ninj1 deficiency shields hepatocytes from APAP-induced oxidative stress, mitochondrial dysfunctions, and cell death by bolstering NRF2 stability via activation of AMPKα. In summary, our findings imply that Ninj1 likely plays a role in AILI, and its deficiency confers protection against APAP-induced hepatotoxicity through the AMPKα-NRF2 pathway.

NINJ1 Facilitates Abdominal Aortic Aneurysm Formation via Blocking TLR4-ANXA2 Interaction and Enhancing Macrophage Infiltration

Abdominal aortic aneurysm (AAA) is a common and potentially life-threatening condition. Chronic aortic inflammation is closely associated with the pathogenesis of AAA. Nerve injury-induced protein 1 (NINJ1) is increasingly acknowledged as a significant regulator of the inflammatory process. However, the precise involvement of NINJ1 in AAA formation remains largely unexplored. The present study finds that the expression level of NINJ1 is elevated, along with the specific expression level in macrophages within human and angiotensin II (Ang II)-induced murine AAA lesions. Furthermore, Ninj1flox/flox and Ninj1flox/floxLyz2-Cre mice on an ApoE-/- background are generated, and macrophage NINJ1 deficiency inhibits AAA formation and reduces macrophage infiltration in mice infused with Ang II. Consistently, in vitro suppressing the expression level of NINJ1 in macrophages significantly restricts macrophage adhesion and migration, while attenuating macrophage pro-inflammatory responses. Bulk RNA-sequencing and pathway analysis uncover that NINJ1 can modulate macrophage infiltration through the TLR4/NF-κB/CCR2 signaling pathway. Protein-protein interaction analysis indicates that NINJ1 can activate TLR4 by competitively binding with ANXA2, an inhibitory interacting protein of TLR4. These findings reveal that NINJ1 can modulate AAA formation by promoting macrophage infiltration and pro-inflammatory responses, highlighting the potential of NINJ1 as a therapeutic target for AAA.

The role of macrophage polarization and cellular crosstalk in the pulmonary fibrotic microenvironment: a review

Pulmonary fibrosis (PF) is a progressive interstitial inflammatory disease with a high mortality rate. Patients with PF commonly experience a chronic dry cough and progressive dyspnoea for years without effective mitigation. The pathogenesis of PF is believed to be associated with dysfunctional macrophage polarization, fibroblast proliferation, and the loss of epithelial cells. Thus, it is of great importance and necessity to explore the interactions among macrophages, fibroblasts, and alveolar epithelial cells in lung fibrosis, as well as in the pro-fibrotic microenvironment. In this review, we discuss the latest studies that have investigated macrophage polarization and activation of non-immune cells in the context of PF pathogenesis and progression. Next, we discuss how profibrotic cellular crosstalk is promoted in the PF microenvironment by multiple cytokines, chemokines, and signalling pathways. And finally, we discuss the potential mechanisms of fibrogenesis development and efficient therapeutic strategies for the disease. Herein, we provide a comprehensive summary of the vital role of macrophage polarization in PF and its profibrotic crosstalk with fibroblasts and alveolar epithelial cells and suggest potential treatment strategies to target their cellular communication in the microenvironment.

Control of Cell Death in Health and Disease

Apoptosis, necroptosis, and pyroptosis are genetically programmed cell death mechanisms that eliminate obsolete, damaged, infected, and self-reactive cells. Apoptosis fragments cells in a manner that limits immune cell activation, whereas the lytic death programs of necroptosis and pyroptosis release proinflammatory intracellular contents. Apoptosis fine-tunes tissue architecture during mammalian development, promotes tissue homeostasis, and is crucial for averting cancer and autoimmunity. All three cell death mechanisms are deployed to thwart the spread of pathogens. Disabling regulators of cell death signaling in mice has revealed how excessive cell death can fuel acute or chronic inflammation. Here we review strategies for modulating cell death in the context of disease. For example, BCL-2 inhibitor venetoclax, an inducer of apoptosis, is approved for the treatment of certain hematologic malignancies. By contrast, inhibition of RIPK1, NLRP3, GSDMD, or NINJ1 to limit proinflammatory cell death and/or the release of large proinflammatory molecules from dying cells may benefit patients with inflammatory diseases.

Functional Analysis of Membrane-Associated Scaffolding Tight Junction (TJ) Proteins in Tumorigenic Characteristics of B16-F10 Mouse Melanoma Cells

Tight junction (TJ) proteins (Tjps), Tjp1 and Tjp2, are tight junction-associated scaffold proteins that bind to the transmembrane proteins of tight junctions and the underlying cytoskeleton. In this study, we first analyzed the tumorigenic characteristics of B16-F10 melanoma cells, including cell proliferation, migration, invasion, metastatic potential, and the expression patterns of related proteins, after the CRISPR-Cas9-mediated knockout (KO) of Tjp genes. The proliferation of Tjp1 and Tjp2 KO cells significantly increased in vitro. Other tumorigenic characteristics, including migration and invasion, were significantly enhanced in Tjp1 and Tjp2 KO cells. Zonula occludens (ZO)-associated protein Claudin-1 (CLDN-1), which is a major component of tight junctions and functions in controlling cell-to-cell adhesion, was decreased in Tjp KO cells. Additionally, Tjp KO significantly stimulated tumor growth and metastasis in an in vivo mouse model. We performed a transcriptome analysis using next-generation sequencing (NGS) to elucidate the key genes involved in the mechanisms of action of Tjp1 and Tjp2. Among the various genes affected by Tjp KO-, cell cycle-, cell migration-, angiogenesis-, and cell-cell adhesion-related genes were significantly altered. In particular, we found that the Ninjurin-1 (Ninj1) and Catenin alpha-1 (Ctnna1) genes, which are known to play fundamental roles in Tjps, were significantly downregulated in Tjp KO cells. In summary, tumorigenic characteristics, including cell proliferation, migration, invasion, tumor growth, and metastatic potential, were significantly increased in Tjp1 and Tjp2 KO cells, and the knockout of Tjp genes significantly affected the expression of related proteins.

Ninjurin 2, a Cell Adhesion Molecule and a Target of p53, Modulates Wild-Type p53 in Growth Suppression and Mutant p53 in Growth Promotion

The nerve injury-induced protein 1 (NINJ1) and NINJ2 constitute a family of homophilic adhesion molecules and are involved in nerve regeneration. Previously, we showed that NINJ1 and p53 are mutually regulated and the NINJ1-p53 loop plays a critical role in p53-dependent tumor suppression. However, the biology of NINJ2 has not been well-explored. By using multiple in vitro cell lines and genetically engineered mouse embryo fibroblasts (MEFs), we showed that NINJ2 is induced by DNA damage in a p53-dependent manner. Moreover, we found that the loss of NINJ2 promotes p53 expression via mRNA translation and leads to growth suppression in wild-type p53-expressing MCF7 and Molt4 cells and premature senescence in MEFs in a wild-type p53-dependent manner. Interestingly, NINJ2 also regulates mutant p53 expression, and the loss of NINJ2 promotes cell growth and migration in mutant p53-expressing MIA-PaCa2 cells. Together, these data indicate that the mutual regulation between NINJ2 and p53 represents a negative feedback loop, and the NINJ2-p53 loop has opposing functions in wild-type p53-dependent growth suppression and mutant p53-dependent growth promotion.

Drugging the NLRP3 inflammasome: from signalling mechanisms to therapeutic targets

Diseases associated with chronic inflammation constitute a major health burden across the world. As central instigators of the inflammatory response to infection and tissue damage, inflammasomes - and the NACHT, LRR and PYD domain-containing protein 3 (NLRP3) inflammasome in particular - have emerged as key regulators in diverse rheumatic, metabolic and neurodegenerative diseases. Similarly to other inflammasome sensors, NLRP3 assembles a cytosolic innate immune complex that activates the cysteine protease caspase-1, which in turn cleaves gasdermin D (GSDMD) to induce pyroptosis, a regulated mode of lytic cell death. Pyroptosis is highly inflammatory, partly because of the concomitant extracellular release of the inflammasome-dependent cytokines IL-1β and IL-18 along with a myriad of additional danger signals and intracellular antigens. Here, we discuss how NLRP3 and downstream inflammasome effectors such as GSDMD, apoptosis-associated speck-like protein containing a CARD (ASC) and nerve injury-induced protein 1 (NINJ1) have gained significant traction as therapeutic targets. We highlight the recent progress in developing small-molecule and biologic inhibitors that are advancing into the clinic and serving to harness the broad therapeutic potential of modulating the NLRP3 inflammasome.

Tomo-seq identifies NINJ1 as a potential target for anti-inflammatory strategy in thoracic aortic dissection

BACKGROUND

Thoracic aortic dissection (TAD) is a life-threatening disease caused by an intimal tear in the aorta. The histological characteristics differ significantly between the tear area (TA) and the distant area. Previous studies have emphasized that certain specific genes tend to cluster at the TA. Obtaining a thorough understanding of the precise molecular signatures near the TA will assist in discovering therapeutic strategies for TAD.

METHODS

We performed a paired comparison of the pathological patterns in the TA with that in the remote area (RA). We used Tomo-seq, genome-wide transcriptional profiling with spatial resolution, to obtain gene expression signatures spanning from the TA to the RA. Samples from multiple sporadic TAD patients and animal models were used to validate our findings.

RESULTS

Pathological examination revealed that the TA of TAD exhibited more pronounced intimal hyperplasia, media degeneration, and inflammatory infiltration compared to the RA. The TA also had more apoptotic cells and CD31+α-SMA+ cells. Tomo-seq revealed four distinct gene expression patterns from the TA to the RA, which were inflammation, collagen catabolism, extracellular matrix remodeling, and cell stress, respectively. The spatial distribution of genes allowed us to identify genes that were potentially relevant with TAD. NINJ1 encoded the protein-mediated cytoplasmic membrane rupture, regulated tissue remodeling, showed high expression levels in the tear area, and co-expressed within the inflammatory pattern. The use of short hairpin RNA to reduce NINJ1 expression in the beta-aminopropionitrile-induced TAD model led to a significant decrease in TAD formation. Additionally, it resulted in reduced infiltration of inflammatory cells and a decrease in the number of CD31+α-SMA+ cells. The NINJ1-neutralizing antibody also demonstrated comparable therapeutic effects and can effectively impede the formation of TAD.

CONCLUSIONS

Our study showed that Tomo-seq had the advantage of obtaining spatial expression information of TAD across the TA and the RA. We pointed out that NINJ1 may be involved in inflammation and tissue remodeling, which played an important role in the formation of TAD. NINJ1 may serve as a potential therapeutic target for TAD.

N,N-Dimethyl-3β-hydroxycholenamide attenuates neuronal death and retinal inflammation in retinal ischemia/reperfusion injury by inhibiting Ninjurin 1

BACKGROUND

Retinal ischemia-reperfusion (RIR) injury refers to an obstruction in the retinal blood supply followed by reperfusion. Although the molecular mechanism underlying the ischemic pathological cascade is not fully understood, neuroinflammation plays a crucial part in the mortality of retinal ganglion cells.

METHODS

Single-cell RNA sequencing (scRNA-seq), molecular docking, and transfection assay were used to explore the effectiveness and pathogenesis of N,N-dimethyl-3β-hydroxycholenamide (DMHCA)-treated mice with RIR injury and DMHCA-treated microglia after oxygen and glucose deprivation/reoxygenation (OGD/R).

RESULTS

DMHCA could suppress inflammatory gene expression and attenuate neuronal lesions, restoring the retinal structure in vivo. Using scRNA-seq on the retina of DMHCA-treated mice, we provided novel insights into RIR immunity and demonstrated nerve injury-induced protein 1 (Ninjurin1/Ninj 1) as a promising treatment target for RIR. Moreover, the expression of Ninj1, which was increased in RIR injury and OGD/R-treated microglia, was downregulated in the DMHCA-treated group. DMHCA suppressed the activation of the nuclear factor kappa B (NF-κB) pathways induced by OGD/R, which was undermined by the NF-κB pathway agonist betulinic acid. Overexpressed Ninj1 reversed the anti-inflammatory and anti-apoptotic function of DMHCA. Molecular docking indicated that for Ninj1, DMHCA had a low binding energy of - 6.6 kcal/mol, suggesting highly stable binding.

CONCLUSION

Ninj1 may play a pivotal role in microglia-mediated inflammation, while DMHCA could be a potential treatment strategy against RIR injury.

The Ninj1/Dusp1 Axis Contributes to Liver Ischemia Reperfusion Injury by Regulating Macrophage Activation and Neutrophil Infiltration

BACKGROUND & AIMS

Liver ischemia-reperfusion (IR) injury represents a major risk factor in both partial hepatectomy and liver transplantation. Nerve injury-induced protein 1 (Ninj1) is widely recognized as an adhesion molecule in leukocyte trafficking under inflammatory conditions, but its role in regulating sterile inflammation during liver IR injury remains unclear.

METHODS

Myeloid Ninj1-deficient mice were generated by bone marrow chimeric models using Ninj1 knockout mice and wild-type mice. In vivo, a liver partial warm ischemia model was applied. Liver injury and hepatic inflammation were investigated. In vitro, primary Kupffer cells (KCs) isolated from Ninj1 knockout and wild-type mice were used to explore the function and mechanism of Ninj1 in modulating KC inflammation upon lipopolysaccharide stimulation.

RESULTS

Ninj1 deficiency in KCs protected mice against liver IR injury during the later phase of reperfusion, especially in neutrophil infiltration, intrahepatic inflammation, and hepatocyte apoptosis. This prompted ischemia-primed KCs to decrease proinflammatory cytokine production. In vitro and in vivo, using small-interfering RNA against dual-specificity phosphatase 1 (DUSP1), we found that Ninj1 deficiency diminished the inflammatory response in KCs and neutrophil infiltration through DUSP1-dependent deactivation of the c-Jun-N-terminal kinase and p38 pathways. Sivelestat, a neutrophil elastase inhibitor, functioned similarly to Ninj1 deficiency, resulting in both mitigated hepatic IR injury in mice and a more rapid recovery of liver function in patients undergoing liver resection.

CONCLUSIONS

The Ninj1/Dusp1 axis contributes to liver IR injury by regulating the proinflammatory response of KCs, and influences neutrophil infiltration, partly by subsequent regulation of C-X-C motif chemokine ligand 1 (CXCL1) production after IR.

Potential link between the nerve injury-induced protein (Ninjurin) and the pathogenesis of endometriosis

Endometriosis remains a widespread but severe gynecological disease in women of reproductive age, with an unknown etiology and few treatment choices. The menstrual reflux theory is largely accepted as the underlying etiology but does not explain the morbidity or unpleasant pain sensations of endometriosis. The neurological and immune systems are both involved in pain mechanisms of endometriosis, and interlinked through a complex combination of cytokines and neurotransmitters. Numerous pieces of evidence suggest that the nerve injury-inducible protein, Ninjurin, is actively expressed in endometriosis lesions, which contributes to the etiology and development of endometriosis. It may be explored in the future as a novel therapeutic target. The aim of the present review was to elucidate the multifaceted role of Ninjurin. Furthermore, we summarize the association of Ninjurin with the pain mechanism of endometriosis and outline the future research directions. A novel therapeutic pathway can be discovered based on the potential pathogenic variables.

Elevated Serum Ninjurin-1 Is Associated with a High Risk of Large Artery Atherosclerotic Acute Ischemic Stroke

Ninjurin-1 is a novel adhesion molecule which is involved in many inflammatory diseases. Functional blockage of Ninjurin-1 has exerted an atheroprotective effect. The aim of the study is to explore the association between serum Ninjurin-1 and the risk of large artery atherosclerotic acute ischemic stroke. From August 2020 through December 2021, patients with large artery atherosclerotic acute ischemic stroke (LAA-AIS) admitted to the First Hospital Affiliated to Soochow University, and age- and sex-matched controls free of ischemic stroke were recruited. Serum Ninj1 was measured with an enzyme-linked immunosorbent assay. Multivariable logistic regression models were used to calculate the odds ratios and 95% confidence intervals of LAA-AIS associated with serum Ninj1 levels, and receiver operating characteristic (ROC) curves were performed to assess the improvement value of Ninj1 for the prediction of LAA-AIS after adding Ninj1 to established risk factors. Of the 110 patients and 110 age- and sex-matched controls free of ischemic stroke enrolled, serum Ninj1 levels in LAA-AIS patients were significantly higher than that in control group (142.70 ng/ml [IQR: 110.41-163.44] vs 101.62 ng/ml [IQR: 86.63-120.86], p < 0.001). In multivariable analysis, Ninj1 levels were expressed as continuous variable and ordinal variable (tertiles), and it turned out that Ninj1 levels were positively associated with increased risk of LAA-AIS, especially in tertile3 compared with tertile1 (adjusted OR = 12.567, 95%CI: 5.148-30.678, p < 0.001), and the adjusted odds OR per 10 ng/ml increment was 1.541, 95%CI: 1.348-1.763, p < 0.001. Furthermore, adding Ninj1 to a multivariate logistic model including conventional risk factors associated LAA-AIS improved the area under ROC curves from 0.787 to 0.874. Elevated circulating levels of Ninj1 were associated with increased risk of LAA-AIS, indicating that serum Ninj1 may act as a predictor independent of established conventional risk factors.

NINJ1 triggers extravillous trophoblast cell dysfunction through blocking the STAT3 signaling pathway

BACKGROUND

Trophoblasts are the most important parts of the placenta in early pregnancy. Trophoblast cell dysfunction can induce embryo implantation insufficiency, thereby resulting in multiple diseases, including recurrent spontaneous abortion (RSA). A previous study indicates higher nerve injury-induced protein 1 (NINJ1) RNA levels in the villi tissues of RSA patients.

OBJECTIVE

This study aimed to investigate the effect of NINJ1 on trophoblast behaviors and pregnancy loss.

METHODS

Fresh villi tissues were obtained from with RSA patients and patients with artificial selective abortion for personal reasons, and NINJ1 expression in these tissues was detected. Extravillous trophoblast cell line HTR-8/SVneo was transfected with small-interfering RNA targeting NINJ1 or NINJ1 overexpression vector to perform loss-/gain-of-function experiments. Spontaneous abortion (SA) was induced by mating CBA/J females with DBA/2 males and the pregnant females were intraperitoneally injected with adenovirus vector carrying NINJ1 short hairpin RNA.

RESULTS

NINJ1 mRNA and protein levels were higher in the villi tissues of RSA patients than those of artificial selective abortion patients. NINJ1 knockdown promoted trophoblast cell proliferation, migration and invasion but inhibited cell apoptosis. Moreover, conditioned medium from NINJ1-depleted trophoblasts promoted the angiogenesis of human umbilical vein endothelial cells. NINJ1 knockdown also promoted activation of the signal transducer and activator of transcription 3 (STAT3) signaling pathway in trophoblasts, and STAT3 inhibitor reversed NINJ1 knockdown-induced effects on trophoblast behaviors. Furthermore, pregnancy loss was attenuated by NINJ1 inhibition.

CONCLUSION

NINJ1 contributes to the development of SA and triggers trophoblast cell dysfunction through inhibiting the STAT3 pathway.

Deficiency of Ninjurin1 attenuates LPS/D-galactosamine-induced acute liver failure by reducing TNF-α-induced apoptosis in hepatocytes

Nerve injury‐induced protein 1 (Ninjurin1, Ninj1) is a membrane protein that mediates cell adhesion. The role of Ninj1 during inflammatory response has been widely investigated in macrophages and endothelial cells. Ninj1 is expressed in various tissues, and the liver also expresses high levels of Ninj1. Although the hepatic upregulation of Ninj1 has been reported in human hepatocellular carcinoma and septic mice, little is known of its function during the pathogenesis of liver diseases. In the present study, the role of Ninj1 in liver inflammation was explored using lipopolysaccharide (LPS)/D‐galactosamine (D‐gal)‐induced acute liver failure (ALF) model. When treated with LPS/D‐gal, conventional Ninj1 knock‐out (KO) mice exhibited a mild inflammatory phenotype as compared with wild‐type (WT) mice. Unexpectedly, myeloid‐specific Ninj1 KO mice showed no attenuation of LPS/D‐gal‐induced liver injury. Whereas, Ninj1 KO primary hepatocytes were relatively insensitive to TNF‐α‐induced caspase activation as compared with WT primary hepatocytes. Also, Ninj1 knock‐down in L929 and AML12 cells and Ninj1 KO in HepG2 cells ameliorated TNF‐α‐mediated apoptosis. Consistent with in vitro results, hepatocyte‐specific ablation of Ninj1 in mice alleviated LPS/D‐gal‐induced ALF. Summarizing, our in vivo and in vitro studies show that lack of Ninj1 in hepatocytes diminishes LPS/D‐gal‐induced ALF by alleviating TNF‐α/TNFR1‐induced cell death.

Ninjurin1 deletion in neuron-glial antigen 2-positive pericytes prevents microvessel maturation and delays wound healing

The formation of mature vasculature through angiogenesis is essential for adequate wound healing, such that blood-borne cells, nutrients, and oxygen can be delivered to the remodeling skin area. Neovessel maturation is highly dependent on the coordinated functions of vascular endothelial cells and perivascular cells, namely pericytes (PCs). However, the underlying mechanism for vascular maturation has not been completely elucidated, and its role in wound healing remains unclear. In this study, we investigated the role of Ninjurin-1 (Ninj1), a new molecule mediating vascular maturation, in wound healing using an inducible PC-specific Ninj1 deletion mouse model. Ninj1 expression increased temporarily in NG2-positive PCs in response to skin injury. When tamoxifen treatment induced a decreased Ninj1 expression in PCs, the neovessels in the regenerating wound margins were structurally and functionally immature, but the total number of microvessels was unaltered. This phenotypic change is associated with a reduction in PC-associated microvessels. Wound healing was significantly delayed in the NG2-specific Ninj1 deletion mouse model. Finally, we showed that Ninj1 is a crucial molecule that mediates vascular maturation in injured skin tissue through the interaction of vascular endothelial cells and PCs, thereby inducing adequate and prompt wound healing.

miR-125a-5p attenuates macrophage-mediated vascular dysfunction by targeting Ninjurin1

Ninjurin1 (Ninj1), an adhesion molecule, regulates macrophage function in hyaloid regression, multiple sclerosis, and atherosclerosis. However, its biological relevance and the mechanism underlying its function in vascular network integrity have not been studied. In this study, we investigated the role of Ninj1 in physiological (postnatal vessel formation) and pathological (endotoxin-mediated inflammation and diabetes) conditions and developed a strategy to regulate Ninj1 using specific micro (mi)RNAs under pathological conditions. Ninj1-deficient mice exhibited decreased hyaloid regression, tip cell formation, retinal vascularized area, recruitment of macrophages, and endothelial apoptosis during postnatal development, resulting in delayed formation of the vascular network. Five putative miRNAs targeting Ninj1 were selected using the miRanda algorithm and comparison of expression patterns. Among them, miR-125a-5p showed a profound inhibitory effect on Ninj1 expression, and miR-125a-5p mimic suppressed the cell-to-cell and cell-to-matrix adhesion of macrophages and expression of pro-inflammatory factors mediated by Ninj1. Furthermore, miR-125a-5p mimic inhibited the recruitment of macrophages into inflamed retinas in endotoxin-induced inflammation and streptozotocin-induced diabetes in vivo. In particular, miR-125a-5p mimic significantly attenuated vascular leakage in diabetic retinopathy. Taken together, these findings suggest that Ninj1 plays a pivotal role in macrophage-mediated vascular integrity and that miR-125a-5p acts as a novel regulator of Ninj1 in the management of inflammatory diseases and diabetic retinopathy.

How Pyroptosis Contributes to Inflammation and Fibroblast-Macrophage Cross-Talk in Rheumatoid Arthritis

About thirty years ago, a new form of pro-inflammatory lytic cell death was observed and termed pyroptosis. Only in 2015, gasdermins were defined as molecules that create pores at the plasma membrane and drive pyroptosis. Today, we know that gasdermin-mediated death is an important antimicrobial defence mechanism in bacteria, yeast and mammals as it destroys the intracellular niche for pathogen replication. However, excessive and uncontrolled cell death also contributes to immunopathology in several chronic inflammatory diseases, including arthritis. In this review, we discuss recent findings where pyroptosis contributes to tissue damage and inflammation with a main focus on injury-induced and autoimmune arthritis. We also review novel functions and regulatory mechanisms of the pyroptotic executors gasdermins. Finally, we discuss possible models of how pyroptosis may contribute to the cross-talk between fibroblast and macrophages, and also how this cross-talk may regulate inflammation by modulating inflammasome activation and pyroptosis induction.

Elevated plasma Ninjurin-1 levels in atrial fibrillation is associated with atrial remodeling and thromboembolic risk

BACKGROUND

Nerve injury-induced protein 1 (Ninj1) is elevated in various inflammatory diseases. The soluble form of Ninj1 yield by matrix metalloproteinase cleavage is a secreted protein and inhibits cell adhesion and inflammation. However, the role of plasma Ninj1 in atrial fibrillation (AF) has not been reported. The present study aimed to investigate the correlation between plasma Ninj1 levels and AF.

METHODS

A total of 96 AF patients [age 66.00 (60.00, 72.00) years, male 56 (58.33%)] and 51 controls without AF [age 65.00 (55.00, 68.00) years, male 21 (41.18%)] were enrolled in this study. Plasma Ninj1 concentrations were detected using enzyme-linked immunosorbent assay. Also, the clinical characteristics, left atrial volume index (LAVI), CHA2DS2-VASc score, and HAS-BLED score were evaluated.

RESULTS

Plasma Ninj1 levels were significantly higher in patients with AF than in controls (P < 0.001). Plasma Ninj1 levels were positively correlated with LAVI (P = 0.019) and CHA2DS2-VASc score (P = 0.024). Logistic regression analysis confirmed that the Ninj1 plasma levels were associated with AF (P = 0.009). The receiver operating characteristic analysis showed that plasma Ninj1 had a predictive value for AF (P < 0.001).

CONCLUSIONS

Plasma Ninj1 levels were elevated in patients with AF, associated with left atrial enlargement and thromboembolic risk in AF.

Comprehensive Analysis of the Transcriptome-Wide m6A Methylation Modification Difference in Liver Fibrosis Mice by High-Throughput m6A Sequencing

N6-Methyladenosine (m6A), a unique and common mRNA modification method in eukaryotes, is involved in the occurrence and development of many diseases. Liver fibrosis (LF) is a common response to chronic liver injury and may lead to cirrhosis and even liver cancer. However, the involvement of m6A methylation in the development of LF is still unknown. In this study, we performed a systematic evaluation of hepatic genome-wide m6A modification and mRNA expression by m6A-seq and RNA-seq using LF mice. There were 3,315 genes with significant differential m6A levels, of which 2,498 were hypermethylated and 817 hypomethylated. GO and KEGG analyses illustrated that differentially expressed m6A genes were closely correlated with processes such as the endoplasmic reticulum stress response, PPAR signaling pathway and TGF-β signaling pathway. Moreover, a total of 90 genes had both a significant change in the m6A level and mRNA expression shown by joint analysis of m6A-seq and RNA-seq. Hence, the critical elements of m6A modification, including methyltransferase WTAP, demethylases ALKBH5 and binding proteins YTHDF1 were confirmed by RT-qPCR and Western blot. In an additional cell experiment, we also observed that the decreased expression of WTAP induced the development of LF as a result of promoting hepatic stellate cell (HSC) activation. Therefore, this study revealed unique differential m6A methylation patterns in LF mice and suggested that m6A methylation was associated with the occurrence and course of LF to some extent.

Transcriptomic Profiling of Adult-Onset Asthma Related to Damp and Moldy Buildings and Idiopathic Environmental Intolerance

A subset of adult-onset asthma patients attribute their symptoms to damp and moldy buildings. Symptoms of idiopathic environmental intolerance (IEI) may resemble asthma and these two entities overlap. We aimed to evaluate if a distinct clinical subtype of asthma related to damp and moldy buildings can be identified, to unravel its corresponding pathomechanistic gene signatures, and to investigate potential molecular similarities with IEI. Fifty female adult-onset asthma patients were categorized based on exposure to building dampness and molds during disease initiation. IEI patients (n = 17) and healthy subjects (n = 21) were also included yielding 88 study subjects. IEI was scored with the Quick Environmental Exposure and Sensitivity Inventory (QEESI) questionnaire. Inflammation was evaluated by blood cell type profiling and cytokine measurements. Disease mechanisms were investigated via gene set variation analysis of RNA from nasal biopsies and peripheral blood mononuclear cells. Nasal biopsy gene expression and plasma cytokine profiles suggested airway and systemic inflammation in asthma without exposure to dampness (AND). Similar evidence of inflammation was absent in patients with dampness-and-mold-related asthma (AAD). Gene expression signatures revealed a greater degree of similarity between IEI and dampness-related asthma than between IEI patients and asthma not associated to dampness and mold. Blood cell transcriptome of IEI subjects showed strong suppression of immune cell activation, migration, and movement. QEESI scores correlated to blood cell gene expression of all study subjects. Transcriptomic analysis revealed clear pathomechanisms for AND but not AAD patients. Furthermore, we found a distinct molecular pathological profile in nasal and blood immune cells of IEI subjects, including several differentially expressed genes that were also identified in AAD samples, suggesting IEI-type mechanisms.

Establishment of particulate matter-induced lung injury model in mouse

BACKGROUND

Particulate matter (PM) is one of the principal causes of human respiratory disabilities resulting from air pollution. Animal models have been applied to discover preventive and therapeutic drugs for lung diseases caused by PM. However, the induced severity of lung injury in animal models using PM varies from study to study due to disparities in the preparation of PM, and the route and number of PM administrations. In this study, we established an in vivo model to evaluate PM-induced lung injury in mice.

RESULTS

PM dispersion was prepared using SRM2975. Reactive oxygen species were increased in MLE 12 cells exposed to this PM dispersion. In vivo studies were conducted in the PM single challenge model, PM multiple challenge model, and PM challenge with ovalbumin-induced asthma using the PM dispersion. No histopathological changes were observed in lung tissues after a single injection of PM, whereas mild to moderate lung inflammation was obtained in the lungs of mice exposed to PM three times. However, fibrotic changes were barely seen, even though transmission electron microscopy (TEM) studies revealed the presence of PM particles in the alveolar macrophages and alveolar capillaries. In the OVA-PM model, peribronchial inflammation and mucous hypersecretion were more severe in the OVA+PM group than the OVA group. Serum IgE levels tended to increase in OVA+PM group than in OVA group.

CONCLUSIONS

In this study, we established a PM-induced lung injury model to examine the lung damage induced by PM. Based on our results, repeated exposures of PM are necessary to induce lung inflammation by PM alone. PM challenge, in the presence of underlying diseases such as asthma, can also be an appropriate model for studying the health effect of PM.

Methodology for characterization of platinum-based drug's targeted delivery nanosystems

Conventional anticancer therapies exploiting platinum-based drugs rely principally on the intravascular injection of the therapeutic agent. The anticancer drug is distributed throughout the body by the systemic blood circulation undergoing cellular uptake, rapid clearance and excretion. Consequently, only a small portion of the platinum-based drug reaches the tumor site, which is associated with severe side effects. For this reason, targeted delivery systems are of great need since they offer enhanced and selective delivery of a drug to cancerous cells making the therapy safe and more effective. Up to date, a variety of the Pt-based drug targeted delivery systems (Pt-based DTDSs) utilizing nanomaterials have been developed and tested using a range of analytical techniques that provided essential information on their synthesis, stability, biodistribution and cytotoxicity. Here we summarize those experimental techniques indicating their applicability at different stages of the research, as well as pointing out their strengths, advantages, drawbacks and limitations. Also, the existing strategies and approaches are critically reviewed with the objective to reveal and give rise to the development of the analytical methodology suitable for reliable Pt-based DTDSs characterization which would eventually result in novel therapies and better patients' outcomes.

The Role of Ninjurin1 and Its Impact beyond the Nervous System

Ninjurin1 (Ninj1) is a double-transmembrane cell surface protein that could promote nerve regeneration in the process of the peripheral nervous system injury and repairment. Nonetheless, the accurate function of Ninj1 in the central nervous system and outside the nervous system is not completely clear. According to the recent studies, we found that Ninj1 is also aberrantly expressed in various pathophysiological processes in vivo, including inflammation, tumorigenesis, and vascular, bone, and muscle homeostasis. These findings suggest that Ninj1 may play an influential role during these pathophysiological processes. Our review summarizes the diverse roles of Ninj1 in multiple pathophysiological processes inside and outside the nervous system. Ninj1 should be considered as an important and novel therapeutic target in certain diseases, such as inflammatory diseases and ischemic diseases. Our study provided a better understanding of Ninj1 in different pathophysiological processes and thereby provided the theoretical support for further research.

Deciphering the cellular mechanisms underlying fibrosis-associated diseases and therapeutic avenues

Fibrosis is the excessive deposition of extracellular matrix components, which results in disruption of tissue architecture and loss of organ function. Fibrosis leads to high morbidity and mortality worldwide, mainly due to the lack of effective therapeutic strategies against fibrosis. It is generally accepted that fibrosis occurs during an aberrant wound healing process and shares a common pathogenesis across different organs such as the heart, liver, kidney, and lung. A better understanding of the fibrosis-related cellular and molecular mechanisms will be helpful for development of targeted drug therapies. Extensive studies revealed that numerous mediators contributed to fibrogenesis, suggesting that targeting these mediators may be an effective therapeutic strategy for antifibrosis. In this review, we describe a number of mediators involved in tissue fibrosis, including aryl hydrocarbon receptor, Yes-associated protein, cannabinoid receptors, angiopoietin-like protein 2, high mobility group box 1, angiotensin-converting enzyme 2, sphingosine 1-phosphate receptor-1, SH2 domain-containing phosphatase-2, and long non-coding RNAs, with the goal that drugs targeting these important mediators might exhibit a beneficial effect on antifibrosis. In addition, these mediators show profibrotic effects on multiple tissues, suggesting that targeting these mediators will exert antifibrotic effects on different organs. Furthermore, we present a variety of compounds that exhibit therapeutic effects against fibrosis. This review suggests therapeutic avenues for targeting organ fibrosis and concurrently identifies challenges and opportunities for designing new therapeutic strategies against fibrosis.

Radiation Potentiates Monocyte Infiltration into Tumors by Ninjurin1 Expression in Endothelial Cells

Radiation is a widely used treatment for cancer patients, with over half the cancer patients receiving radiation therapy during their course of treatment. Considerable evidence from both preclinical and clinical studies show that tumor recurrence gets restored following radiotherapy, due to the influx of circulating cells consisting primarily of monocytes. The attachment of monocyte to endothelial cell is the first step of the extravasation process. However, the exact molecules that direct the transmigration of monocyte from the blood vessels to the tumors remain largely unknown. The nerve injury-induced protein 1 (Ninjurin1 or Ninj1) gene, which encodes a homophilic adhesion molecule and cell surface protein, was found to be upregulated in inflammatory lesions, particularly in macrophages/monocytes, neutrophils, and endothelial cells. More recently Ninj1 was reported to be regulated following p53 activation. Considering p53 has been known to be activated by radiation, we wondered whether Ninj1 could be increased in the endothelial cells by radiation and it might contribute to the recruiting of monocytes in the tumor. Here we demonstrate that radiation-mediated up-regulation of Ninj1 in endothelial cell lines such as human umbilical vein endothelial cells (HUVECs), EA.hy926, and immortalized HUVECs. Consistent with this, we found over-expressed Ninj1 in irradiated xenograft tumors, and increased monocyte infiltration into tumors. Radiation-induced Ninj1 was transcriptionally regulated by p53, as confirmed by transfection of p53 siRNA. In addition, Ninj1 over-expression in endothelial cells accelerated monocyte adhesion. Irradiation-induced endothelial cells and monocyte interaction was inhibited by knock-down of Ninj1. Furthermore, over-expressed Ninj1 stimulated MMP-2 and MMP-9 expression in monocyte cell lines, whereas the MMP-2 and MMP-9 expression were attenuated by Ninj1 knock-down in monocytes. Taken together, we provide evidence that Ninj1 is a key molecule that generates an interaction between endothelial cells and monocytes. This result suggests that radiation-mediated Ninj1 expression in endothelial cells could be involved in the post-radiotherapy recurrence mechanism.

Linking indirect effects of cytomegalovirus in transplantation to modulation of monocyte innate immune function

Cytomegalovirus (CMV) is an important cause of morbidity and mortality in the immunocompromised host. In transplant recipients, a variety of clinically important "indirect effects" are attributed to immune modulation by CMV, including increased mortality from fungal disease, allograft dysfunction and rejection in solid organ transplantation, and graft-versus-host-disease in stem cell transplantation. Monocytes, key cellular targets of CMV, are permissive to primary, latent and reactivated CMV infection. Here, pairing unbiased bulk and single cell transcriptomics with functional analyses we demonstrate that human monocytes infected with CMV do not effectively phagocytose fungal pathogens, a functional deficit which occurs with decreased expression of fungal recognition receptors. Simultaneously, CMV-infected monocytes upregulate antiviral, pro-inflammatory chemokine, and inflammasome responses associated with allograft rejection and graft-versus-host disease. Our study demonstrates that CMV modulates both immunosuppressive and immunostimulatory monocyte phenotypes, explaining in part, its paradoxical "indirect effects" in transplantation. These data could provide innate immune targets for the stratification and treatment of CMV disease.

Detrimental Role of Nerve Injury-Induced Protein 1 in Myeloid Cells under Intestinal Inflammatory Conditions

Nerve injury-induced protein 1 (Ninjurin1, Ninj1) is a cell-surface adhesion molecule that regulates cell migration and attachment. This study demonstrates the increase in Ninj1 protein expression during development of intestinal inflammation. Ninj1-deficient mice exhibited significantly attenuated bodyweight loss, shortening of colon length, intestinal inflammation, and lesser pathological lesions than wild-type mice. Although more severe inflammation and serious lesions are observed in wild-type mice than Ninj1-deficient mice, there were no changes in the numbers of infiltrating macrophages in the inflamed tissues obtained from WT and Ninj1-deficient mice. Ninj1 expression results in activation of macrophages, and these activated macrophages secrete more cytokines and chemokines than Ninj1-deficient macrophages. Moreover, mice with conditional deletion of Ninj1 in myeloid cells (Ninj1^fl/fl; Lyz-Cre+) alleviated experimental colitis compared with wild-type mice. In summary, we propose that the Ninj1 in myeloid cells play a pivotal function in intestinal inflammatory conditions.

Terrestrosin D from Tribulus terrestris attenuates bleomycin-induced inflammation and suppresses fibrotic changes in the lungs of mice

Context: Terrestrosin D (TED), from Tribulus terrestris L. (Zygophyllaceae), exhibits anti-tumour and anti-inflammatory activities. However, its effects on bleomycin (BLM)-induced pulmonary inflammation and the subsequent fibrotic changes remain unclear. Objective: To examine the anti-inflammatory and anti-fibrotic effects of TED against BLM in murine pulmonary tissues. Materials and methods: Male SPF mice received saline (control), TED (10 mg/kg), BLM (2.5 mg/kg), or BLM (2.5 mg/kg) + TED (10 mg/kg) group. BLM was administered as a single intranasal inoculation, and TED was intraperitoneally administered once daily. After 2 and 6 weeks of treatment, cell number and differentiation (Giemsa staining) and TNF-α, IL-6, IL-8, TGF-β1, and PDGF-AB levels (ELISA) were determined in the bronchoalveolar lavage fluid (BALF). Hydroxyproline (Hyp) content in the left pulmonary tissue was also determined (ELISA). The right pulmonary tissue was H&E-stained and assessed for the severity of pulmonary fibrosis using the Ashcroft scoring method. Compared with the BLM group, TED decreased inflammatory cell infiltration; number of macrophages (p < 0.05), neutrophils (p < 0.05), lymphocytes (p < 0.05); percentage of macrophages in the monocyte-macrophage system (p < 0.05), and levels of TNF-α (p < 0.01), IL-6 (p < 0.01), IL-8 (p < 0.05), TGF-β1 (p < 0.05), and PDGF-AB (p < 0.05) in the BALF. TED also reduced Hyp content (p < 0.05) in the pulmonary tissue and attenuated the BLM-induced deterioration in lung histopathology. Discussion and conclusions: TED can inhibit BLM-induced inflammation and fibrosis in the lungs of mice, which may be related to reduced inflammatory and fibrotic markers. These results could be further tested in humans through clinical studies.