LILRB4 deficiency aggravates the development of atherosclerosis and plaque instability by increasing the macrophage inflammatory response via NF-κB signaling

LILRB4 as a novel immunotherapeutic target for multiple diseases

Immune checkpoints are critical for maintaining autoimmune homeostasis and are implicated in various autoimmune diseases, with their significance increasingly recognized. Investigating the functions and mechanisms of these checkpoints is essential for the development of more effective treatments. Leukocyte immunoglobulin-like receptor subfamily B member 4 (LILRB4) stands out as a unique immune checkpoint, with limited expression in most normal tissues but prominent presence in various hematological and solid tumors. It is also expressed on numerous immune and stromal cells, functioning as both a "Tumor Immune Checkpoint" and a "Tumor Stromal Immune Checkpoint." Due to its distinct expression profile, LILRB4 plays a pivotal role in tumors, autoimmune diseases, allergic reactions, and the maintenance of immune homeostasis during transplantation and pregnancy. A thorough understanding of its ligands, functions, mechanisms, and ongoing therapeutic strategies targeting LILRB4 will be crucial for the development of advanced therapeutic options. This review examines LILRB4 expression and function across multiple diseases and discusses therapeutic approaches targeting LILRB4 in various contexts. Additionally, the potential of combining current drugs with LILRB4-targeted therapies is explored. Challenges in developing LILRB4-targeting drugs are also addressed, offering valuable insights for future research.

Genetic Susceptibility to Hidradenitis Suppurativa and Predisposition to Cardiometabolic Disease

Importance

Hidradenitis suppurativa (HS) is associated with an increased prevalence of cardiovascular diseases compared with the general population. Any association between polygenic risk for HS, risk of incident cardiometabolic outcomes, and the plasma proteome is unclear.

Objective

To investigate the genetic correlation between HS and cardiometabolic disease.

Design, Setting, and Participants

This cohort study used a polygenic risk score (PRS) for HS to examine the risks of coronary artery disease (CAD) and diabetes and identify changes in the plasma proteome in individuals of European ancestry from the UK Biobank. Participants were enrolled from January 1, 2006, to December 31, 2010. End of follow-up was January 1, 2023. Correlations were assessed between HS susceptibility and cardiometabolic traits using linkage disequilibrium score regression. Odds ratios were assessed in logistic regressions. The risk of incident CAD and diabetes was estimated in cause-specific survival models designed as time-to-event analyses.

Exposure

The PRS for HS.

Main Outcomes and Measures

Main outcomes were CAD and diabetes diagnosis measured by logistic regressions and incident disease measured by Cox proportional hazards regression models adjusted for sex, age, body mass index, and smoking status.

Results

The study included 391 481 individuals (median [IQR] age, 58 [51-64] years; 209 235 [53%] female). Genetic variants for HS correlated significantly with variants associated with CAD, diabetes, and plasma levels of high-density lipoprotein cholesterol, triglycerides, and C-reactive protein. Compared with the low-risk group, a high PRS for HS (≥75th percentile) conferred odds ratios of 1.09 (95% CI, 1.06-1.12; P < .001) for CAD and 1.13 (95% CI, 1.10-1.17; P < .001) for diabetes. Estimates remained consistent when examining only incident CAD and diabetes. The PRS for HS was significantly associated with altered expression of 58 plasma proteins. Integrating this proteomic profile and the PRS for HS in a machine learning model improved prediction of CAD and diabetes compared with a reference model based on sex, age, and body mass index.

Conclusions and Relevance

These findings suggest that a high genetic risk of HS is associated with increased risk of subsequent CAD and diabetes and altered composition of the plasma proteome. Additional investigation into the identified proteins and their potential roles as drug targets is warranted.

Leukocyte Ig-like receptor B4 (Lilrb4a) alleviates cardiac dysfunction and isoproterenol-induced arrhythmogenic remodeling associated with cardiac fibrosis and inflammation

BACKGROUND

Heart failure is usually accompanied by activation of the sympathetic nerve, and excessive activation of the sympathetic nerve promotes cardiac remodeling and cardiac dysfunction. In the isoproterenol (ISO)-induced animal model, it is often accompanied by myocardial hypertrophy, fibrosis, and inflammation. Leukocyte immunoglobulin-like receptor B4a (Lilrb4a), an immunosuppressive regulatory receptor, plays a vital role in cardiovascular disease. However, the effect of Lilrb4a on ventricular arrhythmia in an ISO-induced mouse model remains unclear.

OBJECTIVE

The purpose of this study was to explore the role and molecular mechanism of Lilrb4a in ISO-induced arrhythmogenic remodeling.

METHODS

Lilrb4a knockout mice and Lilrb4a overexpression mice were infused with ISO (15 mg/kg per 24 hours, 4 weeks). Echocardiography and histology evaluations of myocardial hypertrophy and cardiac structural remodeling were conducted. Surface electrocardiography and electrophysiologic examination were used to evaluate cardiac electrical remodeling and susceptibility to ventricular arrhythmias. Quantitative reverse transcriptase-polymerase chain reaction analysis and Western blotting were used to detect the expression levels of ion channel proteins and signal pathway proteins.

RESULTS

The results discovered that ISO induced cardiac hypertrophy, fibrosis, and inflammation and led to electrical remodeling and the occurrence of ventricular arrhythmias. Lilrb4a alleviated cardiac structural and electrical remodeling and protected against the occurrence of ventricular arrhythmias in ISO-induced mice by gain-of-function or loss-of-function approaches. The mechanism is that Lilrb4a inhibited NF-κB signaling and MAPK signaling activation mediated by transforming growth factor kinase 1.

CONCLUSION

Lilrb4a alleviates cardiac dysfunction and ISO-induced arrhythmogenic remodeling associated with cardiac fibrosis and inflammation through the regulation of NF-κB signaling and MAPK signaling activation.

Microglia LILRB4 upregulation reduces brain damage after acute ischemic stroke by limiting CD8+ T cell recruitment

BACKGROUND

Leukocyte immunoglobulin-like receptor B4 (LILRB4) plays a significant role in regulating immune responses. LILRB4 in microglia might influence the infiltration of peripheral T cells. However, whether and how LILRB4 expression aggravates brain damage after acute ischemic stroke remains unclear. This study investigates the role of LILRB4 in modulating the immune response and its potential protective effects against ischemic brain injury in mice.

METHODS AND RESULTS

Microglia-specific LILRB4 conditional knockout (LILRB4-KO) and overexpression transgenic (LILRB4-TG) mice were constructed by a Cre-loxP system. Then, they were used to investigate the role of LILRB4 after ischemic stroke using a transient middle cerebral artery occlusion (tMCAO) mouse model. Spatial transcriptomics analysis revealed increased LILRB4 expression in the ischemic hemisphere. Single-cell RNA sequencing (scRNA-seq) identified microglia-cluster3, an ischemia-associated microglia subcluster with elevated LILRB4 expression in the ischemic brain. Flow cytometry and immunofluorescence staining showed increased CD8+ T cell infiltration into the brain in LILRB4-KO-tMCAO mice. Behavioral tests, cortical perfusion maps, and infarct size measurements indicated that LILRB4-KO-tMCAO mice had more severe functional deficits and larger infarct sizes compared to Control-tMCAO and LILRB4-TG-tMCAO mice. T cell migration assays demonstrated that LILRB4-KD microglia promoted CD8+ T cell recruitment and activation in vitro, which was mitigated by CCL2 inhibition and recombinant arginase-1 addition. The scRNA-seq and spatial transcriptomics identified CCL2 was predominantly secreted from activated microglia/macrophage and increased CCL2 expression in LILRB4-KD microglia, suggesting a chemokine-mediated mechanism of LILRB4.

CONCLUSION

LILRB4 in microglia plays a crucial role in modulating the post-stroke immune response by regulating CD8+ T cell infiltration and activation. Knockout of LILRB4 exacerbates ischemic brain injury by promoting CD8+ T cell recruitment. Overexpression of LILRB4, conversely, offers neuroprotection. These findings highlight the therapeutic potential of targeting LILRB4 and its downstream pathways to mitigate immune-mediated damage in ischemic stroke.

LILRB4 knockdown inhibits aortic dissection development by regulating pyroptosis and the JAK2/STAT3 signaling pathway

Aortic dissection (AD) is a life-threatening condition with a high mortality rate and without effective pharmacological therapies. Our previous study illustrated that leukocyte immunoglobulin-like receptor B4 (LILRB4) knockdown promoted the contractile phenotypic switch and apoptosis of AD cells. This study aimed to further investigate the role of LILRB4 in animal models of AD and elucidate its underlying molecular mechanisms. Animal models of AD were established using 0.1% beta-aminopropionitrile and angiotensin II and an in vitro model was developed using platelet-derived growth factor BB (PDGF-BB). The effects of LILRB4 knockdown on histopathological changes, pyroptosis, phenotype transition, extracellular matrix (ECM), and Janus kinase 2 (JAK2)/signal transducers and activators of transcription 3 (STAT3) pathways were assessed using a series of in vivo and in vitro assays. The effects of the JAK2 inhibitor AG490 on AD cell function, phenotypic transition, and ECM were explored. LILRB4 was highly expressed in AD and its knockdown increased survival rate, reduced AD incidence, and alleviated histopathological changes in the AD mouse model. Furthermore, LILRB4 knockdown promoted contractile phenotype switch, stabilized the ECM, and inhibited pyroptosis. Mechanistically, LILRB4 knockdown inhibited the JAK2/STAT3 signaling pathway. JAK2 inhibitor AG490 inhibited cell viability and migration, enhanced apoptosis, induced G0/G1 cell cycle arrest, and suppressed S-phase progression in PDGF-BB-stimulated human aortic smooth muscle cells. LILRB4 knockdown suppresses AD development by inhibiting pyroptosis and the JAK2/STAT3 signaling pathway.

Lilrb4 ameliorates ileal injury in rats with hemorrhagic shock and suppresses the activation of NF-κB signaling pathway

Hemorrhagic shock (HS) leads to intestinal damage and subsequent multiple organ dysfunction syndrome. Intestinal barrier dysfunction is the main cause of multiple organ failure associated with HS. Leukocyte immunoglobulin-like receptor B4 (Lilrb4) belongs to the Ig superfamily and is a vital natural immunomodulatory receptor. The purpose of this study was to identify the role and molecular mechanism of Lilrb4 in HS-induced ileal injury. In this work, HS was established by femoral artery cannula and 90 min of HS (blood pressure, 35-40 mmHg), followed by resuscitation. RNA sequencing analysis showed that Lilrb4 was highly expressed in the ileum of HS rats. As observed, HS rats exhibited severe ileal injury, characterized by enlarged subepithelial space, edema, exfoliation and extensive loss of villi. Whereas, lentivirus system-mediated Lilrb4 overexpression considerably mitigated these alterations. HS led to increased release of markers associated with intestinal injury, which was effectively reversed by Lilrb4 overexpression. In addition, after resuscitation, Lilrb4 overexpression inhibited HS-triggered inflammatory response, as evidenced by decreased levels of proinflammatory cytokines. Lilrb4 also inhibited the activation of NF-κB signal induced by HS. Notably, Lilrb4 modulated the balance of regulatory T (Treg)-T helper 17 (Th17) cells in the mesenteric lymph node (MLN), which may also contribute to its protective role in HS progression. In aggregate, these findings confirmed that Lilrb4 overexpression protected against ileal injury caused by HS, indicating that Lilrb4 may be a potential candidate for the treatment of HS.

Downregulation of LILRB4 Promotes Human Aortic Smooth Muscle Cell Contractile Phenotypic Switch and Apoptosis in Aortic Dissection

Aortic dissection (AD) is a severe vascular disease with high rates of mortality and morbidity. However, the underlying molecular mechanisms of AD remain unclear. Differentially expressed genes (DEGs) were screened by bioinformatics methods. Alterations of histopathology and inflammatory factor levels in β-aminopropionitrile (BAPN)-induced AD mouse model were evaluated through Hematoxylin-Eosin (HE) staining and Enzyme-linked immunosorbent assay (ELISA), respectively. Reverse transcription quantitative real-time polymerase chain reaction was performed to detect DEGs expression. Furthermore, the role of LILRB4 in AD was investigated through Cell Counting Kit-8 (CCK-8), wound healing, and flow cytometry. Western blotting was employed to assess the phenotypic switch and extracellular matrix (ECM)-associated protein expressions in platelet-derived growth factor-BB (PDGF-BB)-stimulated in vitro model of AD. In the AD mouse model, distinct dissection formation was observed. TNF-α, IL-1β, IL-8, and IL-6 levels were higher in the AD mouse model than in the controls. Six hub genes were identified, including LILRB4, TIMP1, CCR5, CCL7, MSR1, and CLEC4D, all of which were highly expressed. Further exploration revealed that LILRB4 knockdown inhibited the cell vitality and migration of PDGF-BB-induced HASMCs while promoting apoptosis and G0/G1 phase ratio. More importantly, LILRB4 knockdown promoted the protein expression of α-SMA and SM22α, while decreasing the expression of Co1, MMP2, and CTGF, which suggested that LILRB4 silencing promoted contractile phenotypic transition and ECM stability. LILRB4 knockdown inhibits the progression of AD. Our study provides a new potential target for the clinical treatment of AD.

LILRB4 Checkpoint for Immunotherapy: Structure, Mechanism and Disease Targets

LILRB4, a myeloid inhibitory receptor belonging to the family of leukocyte immunoglobulin-like receptors (LILRs/LIRs), plays a pivotal role in the regulation of immune tolerance. LILRB4 primarily mediates suppressive immune responses by transmitting inhibitory signals through immunoreceptor tyrosine-based inhibitory motifs (ITIMs). This immune checkpoint molecule has gained considerable attention due to its potent regulatory functions. Its ability to induce effector T cell dysfunction and promote T suppressor cell differentiation has been demonstrated, indicating the therapeutic potential of LILRB4 for modulating excessive immune responses, particularly in autoimmune diseases or the induction of transplant tolerance. Additionally, through intervening with LILRB4 molecules, immune system responsiveness can be adjusted, representing significant value in areas such as cancer treatment. Thus, LILRB4 has emerged as a key player in addressing autoimmune diseases, transplant tolerance induction, and other medical issues. In this review, we provide a comprehensive overview of LILRB4, encompassing its structure, expression, and ligand molecules as well as its role as a tolerance receptor. By exploring the involvement of LILRB4 in various diseases, its significance in disease progression is emphasized. Furthermore, we propose that the manipulation of LILRB4 represents a promising immunotherapeutic strategy and highlight its potential in disease prevention, treatment and diagnosis.

Identification of Critical Genes Differentiating Stable and Unstable Atherosclerotic Plaques: A Bioinformatic and Computational Analysis

BACKGROUND

Identification of biomarkers to distinguish between stable and unstable plaque formation would be very useful to predict plaque vulnerability.

METHODS

We downloaded microarray profiles of gene set enrichment (GSE) accession numbers including GSE71226 and GSE20680 (group A: containing healthy vs stable plaque samples) and GSE62646 and GSE34822 (group B: containing stable vs unstable plaque samples) from Gene expression omnibus (GEO) database. Differentially expressed genes were compared in both data sets of each group.

RESULTS

Ten and 12 key genes were screened in groups A and B, respectively. Gene Ontology (GO) enrichment was applied by the plugin "BiNGO" (Biological networks gene ontology tool) of the Cytoscape. The key genes were mostly enriched in the biological process of positive regulation of the cellular process. The protein-protein interaction and co-expression network were analyzed by the STRING (search tool for the retrieval of interacting genes/proteins) and GeneMANIA (gene multiple association network integration algorithm) plugin of Cytoscape, respectively, which showed that Epidermal growth factor (EGF), Heparin-binding EGF like growth factor (HBEGF), and Matrix metalloproteinase 9 (MMP9) were at the core of the network. Further validation of key genes using two datasets showed that Phosphodiesterase 5A (PDE5A) and Protein S (PROS1) were decreased in unstable plaques, while Suppressor of cytokine signaling (SOCS3), HBEGF, and Leukocyte immunoglobulin-like receptor B4 (LILRB4) were increased.

CONCLUSION

The present study used several datasets to identify key genes associated with stable and unstable atherosclerotic plaque.

Bioinformatics-led discovery of liver-specific genes and macrophage infiltration in acute liver injury

Background

Acute liver injury (ALI) is an important global health concern, primarily caused by widespread hepatocyte cell death, coupled with a complex immune response and a lack of effective remedies. This study explores the underlying mechanisms, immune infiltration patterns, and potential targets for intervention and treatment ALI.

Methods

The datasets of acetaminophen (APAP), carbon tetrachloride (CCl4), and lipopolysaccharide (LPS)-induced ALI were obtained from the GEO database. Differentially expressed genes (DEGs) were individually identified using the limma packages. Functional enrichment analysis was performed using KEGG, GO, and GSEA methods. The overlapping genes were extracted from the three datasets, and hub genes were identified using MCODE and CytoHubba algorithms. Additionally, PPI networks were constructed based on the String database. Immune cell infiltration analysis was conducted using ImmuCellAI, and the correlation between hub genes and immune cells was determined using the Spearman method. The relationship between hub genes, immune cells, and biochemical indicators of liver function (ALT, AST) was validated using APAP and triptolide (TP) -induced ALI mouse models.

Results

Functional enrichment analysis indicated that all three ALI models were enriched in pathways linked to fatty acid metabolism, drug metabolism, inflammatory response, and immune regulation. Immune analysis revealed a significant rise in macrophage infiltration. A total of 79 overlapping genes were obtained, and 10 hub genes were identified that were consistent with the results of the biological information analysis after screening and validation. Among them, Clec4n, Ms4a6d, and Lilrb4 exhibited strong associations with macrophage infiltration and ALI.

Potential therapeutic targets of macrophages in inhibiting immune damage and fibrotic processes in musculoskeletal diseases

Macrophages are a heterogeneous cell type with high plasticity, exhibiting unique activation characteristics that modulate the progression and resolution of diseases, serving as a key mediator in maintaining tissue homeostasis. Macrophages display a variety of activation states in response to stimuli in the local environment, with their subpopulations and biological functions being dependent on the local microenvironment. Resident tissue macrophages exhibit distinct transcriptional profiles and functions, all of which are essential for maintaining internal homeostasis. Dysfunctional macrophage subpopulations, or an imbalance in the M1/M2 subpopulation ratio, contribute to the pathogenesis of diseases. In skeletal muscle disorders, immune and inflammatory damage, as well as fibrosis induced by macrophages, are prominent pathological features. Therefore, targeting macrophages is of great significance for maintaining tissue homeostasis and treating skeletal muscle disorders. In this review, we discuss the receptor-ligand interactions regulating macrophages and identify potential targets for inhibiting collateral damage and fibrosis in skeletal muscle disorders. Furthermore, we explore strategies for modulating macrophages to maintain tissue homeostasis.

LILRB4, an immune checkpoint on myeloid cells

Leukocyte immunoglobulin-like receptor B4 (LILRB4) is an inhibitory receptor in the LILR family mainly expressed on normal and malignant human cells of myeloid origin. By binding to ligands, LILRB4 is activated and subsequently recruits adaptors to cytoplasmic immunoreceptor tyrosine inhibitory motifs to initiate different signaling cascades, thus playing an important role in physiological and pathological conditions, including autoimmune diseases, microbial infections, and cancers. In normal myeloid cells, LILRB4 regulates intrinsic cell activation and differentiation. In disease-associated or malignant myeloid cells, LILRB4 is significantly correlated with disease severity or patient survival and suppresses T cells, thereby participating in the pathogenesis of various diseases. In summary, LILRB4 functions as an immune checkpoint on myeloid cells and may be a promising therapeutic target for various human immune diseases, especially for cancer immunotherapy.

NK cells require immune checkpoint receptor LILRB4/gp49B to control neurotropic Zika virus infections in mice

Immune cells express an array of inhibitory checkpoint receptors that are upregulated upon activation and limit tissue damage associated with excessive response to pathogens or allergens. Mouse leukocyte immunoglobulin like receptor B4 (LILRB4), also known as glycoprotein 49B (gp49B), is an inhibitory checkpoint receptor constitutively expressed in myeloid cells and upregulated in B cells, T cells, and NK cells upon activation. Here, we report that expression of LILRB4, which binds Zika virus (ZIKV), was increased in microglia and myeloid cells infiltrating the brains of neonatal mice with ZIKV-associated meningoencephalitis. Importantly, while C57BL/6 mice developed transient neurological symptoms but survived infection, mice lacking LILRB4/gp49B (LILRB4 KO) exhibited more severe signs of neurological disease and succumbed to disease. Their brains showed increased cellular infiltration but reduced control of viral burden. The reduced viral clearance was associated with altered NK cell function in the absence of LILRB4/gp49B. In naive animals, this manifested as reduced granzyme B responses to stimulation, but in ZIKV-infected animals, NK cells showed phenotypic changes that suggested altered maturation, diminished glucose consumption, reduced IFN-γ and granzyme B production, and impaired cytotoxicity. Together, our data reveal LILRB4/gp49B as an important regulator of NK cell function during viral infections.

Pathophysiological pathways related to high plasma GDF-15 concentrations in patients with heart failure

AIMS

Elevated concentrations of Growth Differentiation factor 15 (GDF-15) in patients with heart failure (HF) have been consistently associated with worse clinical outcomes, but what disease mechanisms high GDF-15 concentrations represent remains unclear. Here, we aim to identify activated pathophysiological pathways related to elevated GDF-15 expression in patients with HF.

METHODS AND RESULTS

In 2279 patients with HF, we measured circulating levels of 363 biomarkers. Then, we performed a pathway over-representation analysis to identify key biological pathways between patients in the highest and lowest GDF-15 concentration quartiles. Data were validated in an independent cohort of 1705 patients with HF. In both cohorts, the strongest up-regulated biomarkers in those with high GDF-15 were fibroblast growth factor 23 (FGF-23), death receptor 5 (TRAIL-R2), WNT1-inducible-signaling pathway protein 1 (WISP-1), TNF Receptor Superfamily Member 11a (TNFRSF11A), leukocyte immunoglobulin-like receptor subfamily B member 4 (LILRB4), and Trefoil Factor 3 (TFF3). Pathway over-representation analysis revealed that high GDF-15 patients had increased activity of pathways related to inflammatory processes, notably positive regulation of chemokine production; response to interleukin 6 (IL-6); tumour necrosis factor (TNF) and death receptor activity; and positive regulation of T cell differentiation and inflammatory response. Furthermore, we found pathways involved in regulation of insulin-like growth factor (IGF) receptor signalling and regulatory pathways of tissue, bones, and branching structures. GDF-15 quartiles significantly predicted all-cause mortality and HF hospitalization.

CONCLUSION

Patients with HF and high plasma concentrations of GDF-15 are characterized by increased activation of inflammatory pathways and pathways related to IGF-1 regulation and bone/tissue remodelling.

Characterization of the Leucocyte Immunoglobulin-like Receptor B4 (Lilrb4) Expression in Microglia

Simple Summary

In the present study, we provide a detailed characterization of Lilrb4 expression in microglia and peripheral myeloid cells. Our data demonstrate that LILRB4 is a marker for microglia activation, as evidenced by upregulation after lipopolysaccharide treatment and inhibition of microglial TGFβ signaling. Moreover, we provide evidence that microglia express low levels of Lilrb4 in vivo and high levels in vitro, and we clearly demonstrate that LILRB4 is also expressed by bone marrow-derived monocytes and, to a greater extent, by peritoneal macrophages, defining LILRB4 as a surface marker of myeloid cells and not as a microglia-specific marker.

Abstract

As resident innate immune cells of the CNS, microglia play important essential roles during physiological and pathological situations. Recent reports have described the expression of Lilrb4 in disease-associated and aged microglia. Here, we characterized the expression of Lilrb4 in microglia in vitro and in vivo in comparison with bone marrow-derived monocytes and peritoneal macrophages in mice. Using BV2 cells, primary microglia cultures as well as ex vivo isolated microglia and myeloid cells in combination with qPCR and flow cytometry, we were able to provide a comprehensive characterization of Lilrb4 expression in distinct mouse myeloid cells. Whereas microglia in vivo display low expression of Lilrb4, primary microglia cultures present high levels of surface LILRB4. Among the analyzed peripheral myeloid cells, peritoneal macrophages showed the highest expression levels of Lilrb4. Moreover, LPS treatment and inhibition of microglial TGFβ signaling resulted in significant increases of LILRB4 cell surface levels. Taken together, our data indicate that LILRB4 is a reliable surface marker for activated microglia and further demonstrate that microglial TGFβ signaling is involved in the regulation of Lilrb4 expression during LPS-induced microglia activation.

Single systemic transfer of a human gene associated with exceptional longevity halts the progression of atherosclerosis and inflammation in ApoE knockout mice through a CXCR4-mediated mechanism

Aims

Here, we aimed to determine the therapeutic effect of longevity-associated variant (LAV)-BPIFB4 gene therapy on atherosclerosis.

Methods and results

ApoE knockout mice (ApoE^−/−) fed a high-fat diet were randomly allocated to receive LAV-BPIFB4, wild-type (WT)-BPIFB4, or empty vector via adeno-associated viral vector injection. The primary endpoints of the study were to assess (i) vascular reactivity and (ii) atherosclerotic disease severity, by Echo-Doppler imaging, histology and ultrastructural analysis. Moreover, we assessed the capacity of the LAV-BPIFB4 protein to shift monocyte-derived macrophages of atherosclerotic mice and patients towards an anti-inflammatory phenotype. LAV-BPIFB4 gene therapy rescued endothelial function of mesenteric and femoral arteries from ApoE^−/− mice; this effect was blunted by AMD3100, a CXC chemokine receptor type 4 (CXCR4) inhibitor. LAV-BPIFB4-treated mice showed a CXCR4-mediated shift in the balance between Ly6C^high/Ly6C^low monocytes and M2/M1 macrophages, along with decreased T cell proliferation and elevated circulating levels of interleukins IL-23 and IL-27. In vitro conditioning with LAV-BPIFB4 protein of macrophages from atherosclerotic patients resulted in a CXCR4-dependent M2 polarization phenotype. Furthermore, LAV-BPIFB4 treatment of arteries explanted from atherosclerotic patients increased the release of atheroprotective IL-33, while inhibiting the release of pro-inflammatory IL-1β, inducing endothelial nitric oxide synthase phosphorylation and restoring endothelial function. Finally, significantly lower plasma BPIFB4 was detected in patients with pathological carotid stenosis (>25%) and intima media thickness >2 mm.

Conclusion

Transfer of the LAV of BPIFB4 reduces the atherogenic process and skews macrophages towards an M2-resolving phenotype through modulation of CXCR4, thus opening up novel therapeutic possibilities in cardiovascular disease.

Leukocyte immunoglobulin-like receptor subfamily B: therapeutic targets in cancer

Inhibitory leukocyte immunoglobulin-like receptors (LILRBs 1–5) transduce signals via intracellular immunoreceptor tyrosine-based inhibitory motifs that recruit phosphatases to negatively regulate immune activation. The activation of LILRB signaling in immune cells may contribute to immune evasion. In addition, the expression and signaling of LILRBs in cancer cells especially in certain hematologic malignant cells directly support cancer development. Certain LILRBs thus have dual roles in cancer biology—as immune checkpoint molecules and tumor-supporting factors. Here, we review the expression, ligands, signaling, and functions of LILRBs, as well as therapeutic development targeting them. LILRBs may represent attractive targets for cancer treatment, and antagonizing LILRB signaling may prove to be effective anti-cancer strategies.

Identification of Phomoxanthone A and B as Protein Tyrosine Phosphatase Inhibitors

Phomoxanthone A and B (PXA and PXB) are xanthone dimers and isolated from the endophytic fungus Phomopsis sp. By254. The results demonstrated that PXB and PXA are noncompetitive inhibitors of SHP2 and PTP1B and competitive inhibitors of SHP1. Molecular docking studies showed that PXB and PXA interact with conserved domains of protein tyrosine phosphatases such as the β5-β6 loop, WPD loop, P loop, and Q loop. PXA and PXB could significantly inhibit the cell proliferation in MCF7 cells. Our results indicated that these two compounds do not efficiently inhibit PTP1B and SHP2 activity. RNA sequencing showed that PXA and PXB may inhibit SHP1 activity in MCF7 cells leading to the upregulation of inflammatory factors. In addition to PTP inhibition, PXA and PXB are multitarget compounds to inhibit the proliferation of tumor cells. In conclusion, both compounds show inhibition of cancer cells and a certain degree of inflammatory stimulation, which make them promising for tumor immunotherapy.

New Insights for BPIFB4 in Cardiovascular Therapy

Aging is the most relevant risk factor for cardiovascular diseases which are the main cause of mortality in industrialized countries. In this context, there is a progressive loss of cardiovascular homeostasis that translates in illness and death. The study of long living individuals (LLIs), which show compression of morbidity toward the end of their life, is a valuable approach to find the key to delay aging and postpone associate cardiovascular events. A contribution to the age-related decline of cardiovascular system (CVS) comes from the immune system; indeed, it is dysfunctional during aging, a process described as immunosenescence and comprises the combination of several processes overpowering both innate and adaptative immune system. We have recently discovered a longevity-associated variant (LAV) in bactericidal/permeability-increasing fold-containing family B member 4 (BPIFB4), which is a secreted protein able to enhance endothelial function through endothelial nitric oxide synthase (eNOS) activation and capable to protect from hypertension, atherosclerosis, diabetic cardiopathy, frailty, and inflammaging. Here, we sum up the state of the art of the mechanisms involved in the main pathological processes related to CVD (atherosclerosis, aging, diabetic cardiopathy, and frailty) and shed light on the therapeutic effects of LAV-BPIFB4 in these contexts.

Leukocyte immunoglobulin-like receptor B4 protects against cardiac hypertrophy via SHP-2-dependent inhibition of the NF-κB pathway

Cardiac hypertrophy is a complex pathological process, and the molecular mechanisms underlying hypertrophic remodeling have not been clearly elucidated. Leukocyte immunoglobulin-like receptor B4 (lilrb4) is an inhibitory transmembrane protein that is necessary for the regulation of various cellular signaling pathways. To investigate whether lilrb4 plays a role in cardiac hypertrophy, we performed aortic banding in lilrb4 knockout mice, lilrb4 cardiac-specific transgenic mice, and their wild-type littermates. Cardiac hypertrophy was evaluated by echocardiographic, hemodynamic, pathological, and molecular analyses. We found that lilrb4 was expressed both in myocardial tissue and on cultured cardiomyocytes under basal conditions, but the expression was obviously decreased in mouse hearts following aortic banding and in cardiomyocytes treated with angiotensin II. Lilrb4 disruption aggravated cardiac hypertrophy, fibrosis, and dysfunction in response to pressure overload. Conversely, the cardiac overexpression of lilrb4 led to the opposite effects. Moreover, lilrb4 overexpression inhibited angiotensin II-induced cardiomyocyte hypertrophy in vitro. Mechanistically, we determined that the cardioprotective effect of lilrb4 was mediated through an interaction with SHP-2, the preservation of phosphorylated SHP-2, and the inhibition of the NF-κB pathway. In addition, SHP-2 knockdown in cardiomyocytes eliminated the inhibitory effects of lilrb4 on angiotensin II-induced hypertrophy and NF-κB activation. Our results suggest that lilrb4 protects against pathological cardiac hypertrophy via the SHP-2-dependent inhibition of the NF-κB pathway and may act as a potential therapeutic target for cardiac hypertrophy. KEY MESSAGES: Lilrb4 expression is decreased by hypertrophic stimuli. Lilrb4 protects against pathological cardiac hypertrophy. Lilrb4 interacts with SHP-2 and inhibits NF-κB pathway.

Nonalcoholic Fatty Liver Disease: An Update on the Diagnosis

Nonalcoholic fatty liver disease (NAFLD) is a common liver disease and a major cause of related complications such as cirrhosis and hepatocellular carcinoma (HCC). NAFLD progresses through the stages of simple steatosis, nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and HCC. However, NAFLD usually cannot be diagnosed in a timely manner, which is largely attributed to the asymptomatic features of NAFLD patients and the lack of an effective and accurate noninvasive screening approach. Although liver biopsy has been recognized as a gold standard for diagnosing NAFLD, this approach is not suitable for screening and monitoring NAFLD because of its high cost and invasiveness. Several noninvasive screening and diagnostic systemic assessments have been developed in recent years for NAFLD evaluation. Here we summarize the current status and methods for NAFLD diagnosis, including both noninvasive (imaging, biomarkers) and invasive (liver biopsy) assessments. We further discuss the advantages and disadvantages of these developed diagnostic approaches for NAFLD.

Leukocyte immunoglobulin-like receptor B4 deficiency exacerbates acute lung injury via NF-κB signaling in bone marrow-derived macrophages

Acute lung injury (ALI) is an acute inflammatory disease. Leukocyte immunoglobulin-like receptor B4 (LILRB4) is an immunoreceptor tyrosine-based inhibitory motif (ITIM)-bearing inhibitory receptor that is implicated in various pathological processes. However, the function of LILRB4 in ALI remains largely unknown. The aim of the present study was to explore the role of LILRB4 in ALI. LILRB4 knockout mice (LILRB4 KO) were used to construct a model of ALI. Bone marrow cell transplantation was used to identify the cell source of the LILRB4 deficiency-aggravated inflammatory response in ALI. The effect on ALI was analyzed by pathological and molecular analyses. Our results indicated that LILRB4 KO exacerbated ALI triggered by LPS. Additionally, LILRB4 deficiency can enhance lung inflammation. According to the results of our bone marrow transplant model, LILRB4 regulates the occurrence and development of ALI by bone marrow-derived macrophages (BMDMs) rather than by stromal cells in the lung. The observed inflammation was mainly due to BMDM-induced NF-κB signaling. In conclusion, our study demonstrates that LILRB4 deficiency plays a detrimental role in ALI-associated BMDM activation by prompting the NF-κB signal pathway.

The key genes, phosphoproteins, processes, and pathways affected by efavirenz-activated CYP46A1 in the amyloid-decreasing paradigm of efavirenz treatment

Efavirenz (EFV) is an anti-HIV drug, and cytochrome P450 46A1 (CYP46A1) is the major brain cholesterol hydroxylase. Previously, we discovered that EFV activates CYP46A1 and improves behavioral performance in 5XFAD mice, an Alzheimer's disease model. Herein, the unbiased omics and other approaches were used to study 5XFAD mice in the amyloid-decreasing paradigm of CYP46A1 activation by EFV. These approaches revealed increases in the brain levels of postsynaptic density protein 95, gephyrin, synaptophysin, synapsin, glial fibrillary acidic protein, and CYP46A1 and documented altered expression and phosphorylation of 66 genes and 77 proteins, respectively. The data obtained pointed to EFV effects at the synaptic level, plasmin-depended amyloid clearance, inflammation and microglia phenotype, oxidative stress and cellular hypoxia, autophagy and ubiquitin-proteasome systems as well as apoptosis. These effects could be realized in part via changes in the Ca²⁺-, small GTPase, and catenin signaling. A model is proposed, in which CYP46A1-dependent lipid raft rearrangement and subsequent decrease of protein phosphorylation are central in EFV effects and explain behavioral improvements in EFV-treated 5XFAD mice.-Petrov, A. M., Mast, N., Li, Y., Pikuleva, I. A. The key genes, phosphoproteins, processes, and pathways affected by efavirenz-activated CYP46A1 in the amyloid-decreasing paradigm of efavirenz treatment.

Insights into the Epidemiology, Pathogenesis, and Therapeutics of Nonalcoholic Fatty Liver Diseases

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease which affects ≈25% of the adult population worldwide, placing a tremendous burden on human health. The disease spectrum ranges from simple steatosis to steatohepatitis, fibrosis, and ultimately, cirrhosis and carcinoma, which are becoming leading reasons for liver transplantation. NAFLD is a complex multifactorial disease involving myriad genetic, metabolic, and environmental factors; it is closely associated with insulin resistance, metabolic syndrome, obesity, diabetes, and many other diseases. Over the past few decades, countless studies focusing on the investigation of noninvasive diagnosis, pathogenesis, and therapeutics have revealed different aspects of the mechanism and progression of NAFLD. However, effective pharmaceuticals are still in development. Here, the current epidemiology, diagnosis, animal models, pathogenesis, and treatment strategies for NAFLD are comprehensively reviewed, emphasizing the outstanding breakthroughs in the above fields and promising medications in and beyond phase II.

Aged Mouse Cortical Microglia Display an Activation Profile Suggesting Immunotolerogenic Functions

Microglia are the resident immune cells of the central nervous system (CNS) and participate in physiological and pathological processes. Their unique developmental nature suggests age-dependent structural and functional impairments that might contribute to neurodegenerative diseases. In the present study, we addressed the age-dependent changes in cortical microglia gene expression patterns and the expression of M1- and M2-like activation markers. Iba1 immunohistochemistry, isolation of cortical microglia followed by fluorescence-activated cell sorting and RNA isolation to analyze transcriptional changes in aged cortical microglia was performed. We provide evidence that aging is associated with decreased numbers of cortical microglia and the establishment of a distinct microglia activation profile including upregulation of Ifi204, Lilrb4, Arhgap, Oas1a, Cd244 and Ildr2. Moreover, flow cytometry revealed that aged cortical microglia express increased levels of Cd206 and Cd36. The data presented in the current study indicate that aged mouse cortical microglia adopt a distinct activation profile, which suggests immunosuppressive and immuno-tolerogenic functions.