Galectin-3 Identifies a Subset of Macrophages With a Potential Beneficial Role in Atherosclerosis

Protective innate immunity against Pneumocystis does not require Stat6-dependent macrophage polarization

Pneumocystis species are respiratory fungal pathogens that cause life-threatening opportunistic infections in immunocompromised hosts. Pneumocystis typically evade pulmonary innate immunity but are efficiently eradicated by a functional adaptive immune response. FVB/NJ mice are unique in that they display protective alveolar macrophage-dependent innate immunity against Pneumocystis, and remain resistant to infection even in the absence of CD4+ T lymphocyte function. FVB/NJ alveolar macrophages (AMs) were found to display an M2-biased phenotype at baseline, which was potentiated after stimulation with Pneumocystis, suggesting that macrophage polarization may dictate the outcome of the Pneumocystis-macrophage interaction. To determine whether Stat6, a key global regulator of M2 polarization, was required for FVB/NJ innate immunity, FVB Stat6-/- mice were generated. FVB Stat6-deficient AMs were markedly impaired in their ability to polarize to an M2 phenotype when stimulated with Th2 cytokines. However, FVB Stat6-/- mice remained highly resistant to infection, indicating that Stat6 signaling is dispensable for innate FVB/NJ resistance. Despite the loss of Stat6 signaling, primary AMs from FVB Stat6-/- mice maintained baseline expression of M2 markers, and also strongly upregulated M2-associated genes following direct stimulation with Pneumocystis. Additional FVB/NJ knockout strains were generated, but only FVB MerTK-/- mice showed a marginally increased susceptibility to Pneumocystis infection. Together, these findings demonstrate that effective FVB/NJ innate immunity against Pneumocystis does not require Stat6 signaling and suggest that alternative pathways regulate M2 bias and macrophage-mediated innate resistance in FVB/NJ mice.

Elevated cerebrospinal fluid galectin-3 and associated cytokines after severe traumatic brain injury in patients

This study aimed to investigate the galectin-3 and associated cytokines levels in the cerebrospinal fluid (CSF) of severe traumatic brain injury (sTBI) patients. Temporal CSF expression of galectin-3 and associated cytokines levels in sTBI patients within 1-week post-injury were studied using the multiplex bead array. STBI patient group was stratified using the Modified Rankin Score (mRS) into 3 groups: mRS 6 (died), mRS 5 (severely disabled) and mRS 1-4 (mild-to-moderately disabled) group. Analysis for bead array data using Kruskal-Wallis test with post hoc Dunn's multiple comparisons test, and temporal changes and correlation analysis using Spearman's correlation were carried out. At day 1 post-injury, CSF galectin-3 and interleukin-6 (IL-6), interleukin-10 (IL-10), cysteine-cysteine motif chemokine ligand-2 (CCL-2), and cysteine-cysteine motif chemokine ligand-20 (CCL-20), but not interleukin-1β (IL-1β) and tumor necrosis factor (TNF-α) levels were significantly elevated in mRS 5 group compared to non-TBI controls. Temporal correlation analysis at 1-7 days showed decreased IL-10 level in the mRS 6 group, decreased IL-10 and CCL-2 levels in mRS 5 group, and decreased IL-6, CCL-2, and CCL-20 levels in the mRS 1-4 group. Receiver operating characteristic curve analyses revealed a significant area under the curve for comparison between mRS 6 and mRS 5 groups for galectin-3 and IL-6. No significant differences in sex, age, Glasgow Coma Scale score, C-reactive protein levels and types of TBI-induced hemorrhages were observed between the groups. CSF galectin-3 and associated cytokines, especially IL-6, CCL-2 and CCL-20 levels were different within sub-groups of sTBI patients, suggesting their potential use in sTBI prognostics.

Galectin-3 protects distal convoluted tubules in rhabdomyolysis-induced kidney injury

Advanced glycation endproducts (AGEs) contribute to cellular damage of various pathologies, including kidney diseases. Acute kidney injury (AKI) represents a syndrome seldom characterized by a single, distinct pathophysiological cause. Rhabdomyolysis-induced acute kidney injury (RIAKI) constitutes roughly 15% of AKI cases, yet its underlying pathophysiology remains poorly understood. Using a murine model of RIAKI induced by muscular glycerol injection, we observed elevated levels of AGEs and the AGE receptor galectin-3 (LGALS3) in the kidney. Immunofluorescence localized LGALS3 to distal nephron segments. According to transcriptomic profiling via next-generation sequencing, RIAKI led to profound changes in kidney metabolism, oxidative stress, and inflammation. Cellular stress was evident in both proximal and distal tubules, as shown by kidney injury markers KIM-1 and NGAL. However, only proximal tubules exhibited overt damage and apoptosis, as detected by routine morphology, active Caspase-3, and TUNEL assay, respectively. In vitro, distal convoluted tubule (DCT) cells challenged with AGEs underwent apoptosis, which was markedly enhanced by Lgals3 siRNA treatment. Thus, in RIAKI, the upregulation of LGALS3 may protect the distal nephron from AGE-mediated damage, while proximal tubules lacking LGALS3 stay at risk. Thus, stimulating LGALS3 in the proximal nephron, if achievable, may attenuate RIAKI.

Galectin-3 inhibition alleviated LPS-induced periodontal inflammation in gingival fibroblasts and experimental periodontitis mice

OBJECTIVES

Clinical studies have confirmed that galectin-3 (Gal-3) levels are significantly elevated in periodontitis patients. The present study aimed to explore the effects of Gal-3 inhibition on periodontal inflammation in vitro and in vivo.

METHODS

Human gingival fibroblasts (HGFs) with or without Gal-3 knockdown were stimulated by lipopolysaccharide (LPS), and a ligation-induced mouse periodontitis model treated with a Gal-3 inhibitor was established. Hematoxylin-eosin (H&E) and immunohistochemistry (IHC) staining were used to evaluate Gal-3 levels in gingival tissues. Quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) were used to detect Gal-3, interleukin (IL)-6, IL-8, and C-C motif ligand 2 (CCL2) expression. Immunofluorescence and western blotting were used to detect NF-κB and ERK signaling pathway activation. Micro-computed tomography was used to analyse the degree of bone loss.

RESULTS

Gal-3 was significantly up-regulated in inflamed gingival tissues and LPS-induced HGFs. Gal-3 knockdown markedly decreased LPS-induced IL-6, IL-8, and CCL2 expression and blocked NF-κB and ERK signaling pathway activation in HGFs. In the mouse periodontitis model, Gal-3 inhibition significantly alleviated IL-1β and IL-6 infiltration in gingival tissue and mitigated periodontal bone loss.

CONCLUSIONS

Gal-3 inhibition notably alleviated periodontal inflammation partly through blocking NF-κB and ERK signaling pathway activation.

Pharmacological Inhibition of MMP-12 Exerts Protective Effects on Angiotensin II-Induced Abdominal Aortic Aneurysms in Apolipoprotein E-Deficient Mice

Human abdominal aortic aneurysms (AAAs) are characterized by increased activity of matrix metalloproteinases (MMP), including MMP-12, alongside macrophage accumulation and elastin degradation, in conjunction with superimposed atherosclerosis. Previous genetic ablation studies have proposed contradictory roles for MMP-12 in AAA development. In this study, we aimed to elucidate if pharmacological inhibition of MMP-12 activity with a phosphinic peptide inhibitor protects from AAA formation and progression in angiotensin (Ang) II-infused Apoe-/- mice. Complimentary studies were conducted in a human ex vivo model of early aneurysm development. Administration of an MMP-12 inhibitor (RXP470.1) protected hypercholesterolemia Apoe-/- mice from Ang II-induced AAA formation and rupture-related death, associated with diminished medial thinning and elastin fragmentation alongside increased collagen deposition. Proteomic analyses confirmed a beneficial effect of MMP-12 inhibition on extracellular matrix remodeling proteins combined with inflammatory pathways. Furthermore, RXP470.1 treatment of mice with pre-existing AAAs exerted beneficial effects as observed through suppressed aortic dilation and rupture, medial thinning, and elastin destruction. Our findings indicate that pharmacological inhibition of MMP-12 activity retards AAA progression and improves survival in mice providing proof-of-concept evidence to motivate translational work for MMP-12 inhibitor therapy in humans.

Identification of immune subsets with distinct lectin binding signatures using multi-parameter flow cytometry: correlations with disease activity in systemic lupus erythematosus

Objectives

Cell surface glycosylation can influence protein-protein interactions with particular relevance to changes in core fucosylation and terminal sialylation. Glycans are ligands for immune regulatory lectin families like galectins (Gals) or sialic acid immunoglobulin-like lectins (Siglecs). This study delves into the glycan alterations within immune subsets of systemic lupus erythematosus (SLE).

Methods

Evaluation of binding affinities of Galectin-1, Galectin-3, Siglec-1, Aleuria aurantia lectin (AAL, recognizing core fucosylation), and Sambucus nigra agglutinin (SNA, specific for α-2,6-sialylation) was conducted on various immune subsets in peripheral blood mononuclear cells (PBMCs) from control and SLE subjects. Lectin binding was measured by multi-parameter flow cytometry in 18 manually gated subsets of T-cells, NK-cells, NKT-cells, B-cells, and monocytes in unstimulated resting state and also after 3-day activation. Stimulated pre-gated populations were subsequently clustered by FlowSOM algorithm based on lectin binding and activation markers, CD25 or HLA-DR.

Results

Elevated AAL, SNA and CD25+/CD25- SNA binding ratio in certain stimulated SLE T-cell subsets correlated with SLE Disease Activity Index 2000 (SLEDAI-2K) scores. The significantly increased frequencies of activated AALlow Siglec-1low NK metaclusters in SLE also correlated with SLEDAI-2K indices. In SLE, activated double negative NKTs displayed significantly lower core fucosylation and CD25+/CD25- Siglec-1 binding ratio, negatively correlating with disease activity. The significantly enhanced AAL binding in resting SLE plasmablasts positively correlated with SLEDAI-2K scores.

Conclusion

Alterations in the glycosylation of immune cells in SLE correlate with disease severity, which might represent potential implications in the pathogenesis of SLE.

Hypoxia inducible factor-1α regulates microglial innate immune memory and the pathology of Parkinson's disease

Neuroinflammation is one of the core pathological features of Parkinson's disease (PD). Innate immune cells play a crucial role in the progression of PD. Microglia, the major innate immune cells in the brain, exhibit innate immune memory effects and are recognized as key regulators of neuroinflammatory responses. Persistent modifications of microglia provoked by the first stimuli are pivotal for innate immune memory, resulting in an enhanced or suppressed immune response to second stimuli, which is known as innate immune training and innate immune tolerance, respectively. In this study, LPS was used to establish in vitro and in vivo models of innate immune memory. Microglia-specific Hif-1α knockout mice were further employed to elucidate the regulatory role of HIF-1α in innate immune memory and MPTP-induced PD pathology. Our results showed that different paradigms of LPS could induce innate immune training or tolerance in the nigrostriatal pathway of mice. We found that innate immune tolerance lasting for one month protected the dopaminergic system in PD mice, whereas the effect of innate immune training was limited. Deficiency of HIF-1α in microglia impeded the formation of innate immune memory and exerted protective effects in MPTP-intoxicated mice by suppressing neuroinflammation. Therefore, HIF-1α is essential for microglial innate immune memory and can promote neuroinflammation associated with PD.

Single-cell analysis of age-related changes in leukocytes of diabetic mouse hindpaws

Complications associated with Type 1 and Type 2 diabetes, such as diabetic peripheral neuropathy and diabetic foot ulcers, are a growing health-care concern. In addition, this concern increases as diabetic patients age due to their increased susceptibility to complications. To address this growing problem, it is important to understand fluctuations in physiology which lead to pathological changes associated with the metabolic disturbances of diabetes. Our study explores dysregulation of immune cell populations in the hindpaws of healthy and diabetic mice at 12 and 21 weeks of age using single-cell RNA sequencing to provide insight into immune disruptions occurring in the distal limb during chronic diabetes. In 21-week-old Leprdb/db mice, increases were seen in mast cells/basophils, dermal γδ T cells, heterogeneous T cells, and Type 2 innate lymphoid cells. In addition, macrophages represented the largest cluster of immune cells and showed the greatest increase in genes associated with immune-specific pathways. Sub-clustering of macrophages revealed a bias toward angiogenic Lyve1+MHCIIlo macrophages in the hindpaws of 21-week-old diabetic mice, which corresponded to an increase in Lyve1+ macrophages in the hindpaws of 21-week-old diabetic mice on histology. Our results show that in Type 2 diabetes, the immunological function and phenotype of multiple immune cell types shift not only with metabolic disturbance, but also with duration of disease, which may explain the increased susceptibility to pathologies of the distal limb in patients with more chronic diabetes.

Advances in secondary prevention mechanisms of macrovascular complications in type 2 diabetes mellitus patients: a comprehensive review

Type 2 diabetes mellitus (T2DM) poses a significant global health burden. This is particularly due to its macrovascular complications, such as coronary artery disease, peripheral vascular disease, and cerebrovascular disease, which have emerged as leading contributors to morbidity and mortality. This review comprehensively explores the pathophysiological mechanisms underlying these complications, protective strategies, and both existing and emerging secondary preventive measures. Furthermore, we delve into the applications of experimental models and methodologies in foundational research while also highlighting current research limitations and future directions. Specifically, we focus on the literature published post-2020 concerning the secondary prevention of macrovascular complications in patients with T2DM by conducting a targeted review of studies supported by robust evidence to offer a holistic perspective.

Integrating single-cell and spatially resolved transcriptomic strategies to survey the astrocyte response to stroke in male mice

Astrocytes, a type of glial cell in the central nervous system (CNS), adopt diverse states in response to injury that are influenced by their location relative to the insult. Here, we describe a platform for spatially resolved, single-cell transcriptomics and proteomics, called tDISCO (tissue-digital microfluidic isolation of single cells for -Omics). We use tDISCO alongside two high-throughput platforms for spatial (Visium) and single-cell transcriptomics (10X Chromium) to examine the heterogeneity of the astrocyte response to a cortical ischemic stroke in male mice. We show that integration of Visium and 10X Chromium datasets infers two astrocyte populations, proximal or distal to the injury site, while tDISCO determines the spatial boundaries and molecular profiles that define these populations. We find that proximal astrocytes show differences in lipid shuttling, with enriched expression of Apoe and Fabp5. Our datasets provide a resource for understanding the roles of astrocytes in stroke and showcase the utility of tDISCO for hypothesis-driven, spatially resolved single-cell experiments.

Translational Molecular Imaging Tool of Vulnerable Carotid Plaque: Evaluate Effects of Statin Therapy on Plaque Inflammation and American Heart Association-Defined Risk Levels in Cuff-Implanted Apolipoprotein E-Deficient Mice

Identification of high-risk carotid plaques in asymptomatic patients remains a challenging but crucial step in stroke prevention. The challenge is to accurately monitor the development of high-risk carotid plaques and promptly identify patients, who are unresponsive to best medical therapy, and hence targeted for carotid surgical interventions to prevent stroke. Inflammation is a key operator in destabilisation of plaques prior to clinical sequelae. Currently, there is a lack of imaging tool in routine clinical practice, which allows assessment of inflammatory activity within the atherosclerotic plaque. Herein, we have used a periarterial cuff to generate a progressive carotid atherosclerosis model in apolipoprotein E-deficient mice. This model produced clinically relevant plaques with different levels of risk, fulfilling American Heart Association (AHA) classification, at specific timepoints and locations, along the same carotid artery. Exploiting this platform, we have developed smart molecular magnetic resonance imaging (MRI) probes consisting of dual-targeted microparticles of iron oxide (DT-MPIO) against VCAM-1 and P-selectin, to evaluate the anti-inflammatory effect of statin therapy on progressive carotid atherosclerosis. We demonstrated that in vivo DT-MPIO-enhanced MRI can (i) quantitatively track plaque inflammation from early to advanced stage; (ii) identify and characterise high-risk inflamed, vulnerable plaques; and (iii) monitor the response to statin therapy longitudinally. Moreover, this molecular imaging-defined therapeutic response was validated using AHA classification of human plaques, a clinically relevant parameter, approximating the clinical translation of this tool. Further development and translation of this molecular imaging tool into the clinical arena may potentially facilitate more accurate risk stratification, permitting timely identification of the high-risk patients for prophylactic carotid intervention, affording early opportunities for stroke prevention in the future.

CSF1R-dependent macrophages in the salivary gland are essential for epithelial regeneration after radiation-induced injury

The salivary glands often become damaged in individuals receiving radiotherapy for head and neck cancer, resulting in chronic dry mouth. This leads to detrimental effects on their health and quality of life, for which there is no regenerative therapy. Macrophages are the predominant immune cell in the salivary glands and are attractive therapeutic targets due to their unrivaled capacity to drive tissue repair. Yet, the nature and role of macrophages in salivary gland homeostasis and how they may contribute to tissue repair after injury are not well understood. Here, we show that at least two phenotypically and transcriptionally distinct CX3CR1+ macrophage populations are present in the adult salivary gland, which occupy anatomically distinct niches. CD11c+CD206-CD163- macrophages typically associate with gland epithelium, whereas CD11c-CD206+CD163+ macrophages associate with blood vessels and nerves. Using a suite of complementary fate mapping systems, we show that there are highly dynamic changes in the ontogeny and composition of salivary gland macrophages with age. Using an in vivo model of radiation-induced salivary gland injury combined with genetic or antibody-mediated depletion of macrophages, we demonstrate an essential role for macrophages in clearance of cells with DNA damage. Furthermore, we show that epithelial-associated macrophages are indispensable for effective tissue repair and gland function after radiation-induced injury, with their depletion resulting in reduced saliva production. Our data, therefore, provide a strong case for exploring the therapeutic potential of manipulating macrophages to promote tissue repair and thus minimize salivary gland dysfunction after radiotherapy.

Simian immunodeficiency virus-infected rhesus macaques with AIDS co-develop cardiovascular pathology and encephalitis

Despite effective antiretroviral therapy, HIV co-morbidities remain where central nervous system (CNS) neurocognitive disorders and cardiovascular disease (CVD)-pathology that are linked with myeloid activation are most prevalent. Comorbidities such as neurocogntive dysfunction and cardiovascular disease (CVD) remain prevalent among people living with HIV. We sought to investigate if cardiac pathology (inflammation, fibrosis, cardiomyocyte damage) and CNS pathology (encephalitis) develop together during simian immunodeficiency virus (SIV) infection and if their co-development is linked with monocyte/macrophage activation. We used a cohort of SIV-infected rhesus macaques with rapid AIDS and demonstrated that SIV encephalitis (SIVE) and CVD pathology occur together more frequently than SIVE or CVD pathology alone. Their co-development correlated more strongly with activated myeloid cells, increased numbers of CD14+CD16+ monocytes, plasma CD163 and interleukin-18 (IL-18) than did SIVE or CVD pathology alone, or no pathology. Animals with both SIVE and CVD pathology had greater numbers of cardiac macrophages and increased collagen and monocyte/macrophage accumulation, which were better correlates of CVD-pathology than SIV-RNA. Animals with SIVE alone had higher levels of activated macrophage biomarkers and cardiac macrophage accumulation than SIVnoE animals. These observations were confirmed in HIV infected individuals with HIV encephalitis (HIVE) that had greater numbers of cardiac macrophages and fibrosis than HIV-infected controls without HIVE. These results underscore the notion that CNS and CVD pathologies frequently occur together in HIV and SIV infection, and demonstrate an unmet need for adjunctive therapies targeting macrophages.

CXCL10 deficiency limits macrophage infiltration, preserves lung matrix, and enables lung growth in bronchopulmonary dysplasia

Preterm infants with oxygen supplementation are at high risk for bronchopulmonary dysplasia (BPD), a neonatal chronic lung disease. Inflammation with macrophage activation is central to the pathogenesis of BPD. CXCL10, a chemotactic and pro-inflammatory chemokine, is elevated in the lungs of infants evolving BPD and in hyperoxia-based BPD in mice. Here, we tested if CXCL10 deficiency preserves lung growth after neonatal hyperoxia by preventing macrophage activation. To this end, we exposed Cxcl10 knockout (Cxcl10-/-) and wild-type mice to an experimental model of hyperoxia (85% O2)-induced neonatal lung injury and subsequent regeneration. In addition, cultured primary human macrophages and murine macrophages (J744A.1) were treated with CXCL10 and/or CXCR3 antagonist. Our transcriptomic analysis identified CXCL10 as a central hub in the inflammatory network of neonatal mouse lungs after hyperoxia. Quantitative histomorphometric analysis revealed that Cxcl10-/- mice are in part protected from reduced alveolar. These findings were related to the preserved spatial distribution of elastic fibers, reduced collagen deposition, and protection from macrophage recruitment/infiltration to the lungs in Cxcl10-/- mice during acute injury and regeneration. Complimentary, studies with cultured human and murine macrophages showed that hyperoxia induces Cxcl10 expression that in turn triggers M1-like activation and migration of macrophages through CXCR3. Finally, we demonstrated a temporal increase of macrophage-related CXCL10 in the lungs of infants with BPD. In conclusion, our data demonstrate macrophage-derived CXCL10 in experimental and clinical BPD that drives macrophage chemotaxis through CXCR3, causing pro-fibrotic lung remodeling and arrest of alveolarization. Thus, targeting the CXCL10-CXCR3 axis could offer a new therapeutic avenue for BPD.

The Role of Galectin-3 in Retinal Degeneration and Other Ocular Diseases: A Potential Novel Biomarker and Therapeutic Target

Galectin-3 is the most studied member of the Galectin family, with a large range of mediation in biological activities such as cell growth, proliferation, apoptosis, differentiation, cell adhesion, and tissue repair, as well as in pathological processes such as inflammation, tissue fibrosis, and angiogenesis. As is known to all, inflammation, aberrant cell apoptosis, and neovascularization are the main pathophysiological processes in retinal degeneration and many ocular diseases. Therefore, the review aims to conclude the role of Gal3 in the retinal degeneration of various diseases as well as the occurrence and development of the diseases and discuss its molecular mechanisms according to research in systemic diseases. At the same time, we summarized the predictive role of Gal3 as a biomarker and the clinical application of its inhibitors to discuss the possibility of Gal3 as a novel target for the treatment of ocular diseases.

Characteristics and evaluation of atherosclerotic plaques: an overview of state-of-the-art techniques

Atherosclerosis is an important cause of cerebrovascular and cardiovascular disease (CVD). Lipid infiltration, inflammation, and altered vascular stress are the critical mechanisms that cause atherosclerotic plaque formation. The hallmarks of the progression of atherosclerosis include plaque ulceration, rupture, neovascularization, and intraplaque hemorrhage, all of which are closely associated with the occurrence of CVD. Assessing the severity of atherosclerosis and plaque vulnerability is crucial for the prevention and treatment of CVD. Integrating imaging techniques for evaluating the characteristics of atherosclerotic plaques with computer simulations yields insights into plaque inflammation levels, spatial morphology, and intravascular stress distribution, resulting in a more realistic and accurate estimation of plaque state. Here, we review the characteristics and advancing techniques used to analyze intracranial and extracranial atherosclerotic plaques to provide a comprehensive understanding of atheroma.

The Role of Toll-like Receptor-4 in Macrophage Imbalance in Lethal COVID-19 Lung Disease, and Its Correlation with Galectin-3

To the current data, there have been 6,955,141 COVID-19-related deaths worldwide, reported to WHO. Toll-like receptors (TLRs) implicated in bacterial and virus sensing could be a crosstalk between activation of persistent innate-immune inflammation, and macrophage's sub-population alterations, implicated in cytokine storm, macrophage over-activation syndrome, unresolved Acute Respiratory Disease Syndrome (ARDS), and death. The aim of this study is to demonstrate the association between Toll-like-receptor-4 (TLR-4)-induced inflammation and macrophage imbalance in the lung inflammatory infiltrate of lethal COVID-19 disease. Twenty-five cases of autopsy lung tissues were studied by digital pathology-based immunohistochemistry to evaluate expression levels of TLR-4 (CD 284), pan-macrophage marker CD68 (clone KP1), sub-population marker related to alveolar macrophage Galectin-3 (GAL-3) (clone 9C4), and myeloid derived CD163 (clone MRQ-26), respectively. SARS-CoV-2 viral persistence has been evaluated by in situ hybridation (ISH) method. This study showed TLR-4 up-regulation in a subgroup of patients, increased macrophage infiltration in both Spike-1(+) and Spike-1(-) lungs (p < 0.0001), and a macrophage shift with important down-regulation of GAL-3(+) alveolar macrophages associated with Spike-1 persistence (p < 0.05), in favor of CD163(+) myeloid derived monocyte-macrophages. Data show that TLR-4 expression induces a persistent activation of the inflammation, with inefficient resolution, and pathological macrophage shift, thus explaining one of the mechanisms of lethal COVID-19.

Targeting galectin-3 in inflammatory and fibrotic diseases

Galectin (Gal)-3 is a β-galactoside-binding lectin emerging as a key player in cardiac, hepatic, renal, and pulmonary fibrosis and inflammation, respiratory infections caused by COVID-19, and neuroinflammatory disorders. Here, we review recent information highlighting Gal-3 as a relevant therapeutic target in these specific disease conditions. While a causal link was difficult to establish until now, we discuss how recent strategic breakthroughs allowed us to identify new-generation Gal-3 inhibitors with improved potency, selectivity, and bioavailability, and report their usefulness as valuable tools for proof-of-concept studies in various preclinical models of the aforementioned diseases, with emphasis on those actually in clinical stages. We also address critical views and suggestions intended to expand the therapeutic opportunities provided by this complex target.

Differential effects of sugar and fat on adipose tissue inflammation

Obese individuals experience low grade inflammation initiated within their adipose tissue. However, the early events that lead to the release of these inflammatory factors from adipose tissue are poorly characterized. To separate glucose effects from lipid effects on adipose tissue, we used an adipose-specific TXNIP knockout model where excess basal glucose influx into adipocytes led to modest increase in adiposity without using high fat diet. We found an uncoupling of two events that are generally presumed to be coregulated: (1) an increase of adipose tissue macrophage (ATM) number; and (2) pro-inflammatory activation of ATMs. These two events are associated with different triggering signals: elevated free fatty acids output and extracellular matrix remodeling with increased ATM number, whereas decreased adiponectin level with activated ATM. This separation reflects non-overlapping pathways regulated by glucose and lipids in adipocytes, and neither group alone is sufficient to elicit the full inflammatory response in adipose tissue.

Mapping the tumor microenvironment in clear cell renal carcinoma by single-cell transcriptome analysis

Introduction: Clear cell renal cell carcinoma (ccRCC) is associated with unfavorable clinical outcomes. To identify viable therapeutic targets, a comprehensive understanding of intratumoral heterogeneity is crucial. In this study, we conducted bioinformatic analysis to scrutinize single-cell RNA sequencing data of ccRCC tumor and para-tumor samples, aiming to elucidate the intratumoral heterogeneity in the ccRCC tumor microenvironment (TME). Methods: A total of 51,780 single cells from seven ccRCC tumors and five para-tumor samples were identified and grouped into 11 cell lineages using bioinformatic analysis. These lineages included tumor cells, myeloid cells, T-cells, fibroblasts, and endothelial cells, indicating a high degree of heterogeneity in the TME. Copy number variation (CNV) analysis was performed to compare CNV frequencies between tumor and normal cells. The myeloid cell population was further re-clustered into three major subgroups: monocytes, macrophages, and dendritic cells. Differential expression analysis, gene ontology, and gene set enrichment analysis were employed to assess inter-cluster and intra-cluster functional heterogeneity within the ccRCC TME. Results: Our findings revealed that immune cells in the TME predominantly adopted an inflammatory suppression state, promoting tumor cell growth and immune evasion. Additionally, tumor cells exhibited higher CNV frequencies compared to normal cells. The myeloid cell subgroups demonstrated distinct functional properties, with monocytes, macrophages, and dendritic cells displaying diverse roles in the TME. Certain immune cells exhibited pro-tumor and immunosuppressive effects, while others demonstrated antitumor and immunostimulatory properties. Conclusion: This study contributes to the understanding of intratumoral heterogeneity in the ccRCC TME and provides potential therapeutic targets for ccRCC treatment. The findings emphasize the importance of considering the diverse functional roles of immune cells in the TME for effective therapeutic interventions.

Single-cell RNA landscape of cell heterogeneity and immune microenvironment in ligation-induced vascular remodeling in rat

BACKGROUND AND AIMS

Vascular remodeling is a common pathological basis for cardiovascular diseases. Although both immune and non-immune cells have been suggested to contribute to this process, the complex cellular heterogeneity and intercellular interactions remain largely uncharacterized.

METHODS AND RESULTS

In this study, we simulated early and late vascular remodeling by ligating the rat carotid artery for 1 week and 4 weeks, respectively. Using single-cell RNA-sequencing, we characterized gene expression signatures and driver signals of major cell types involved in vascular remodeling. Focused analysis revealed a novel sub-population of Selenbp1hi smooth muscle cells (SMCs) associated with vascular remodeling. Results of intercellular communication analyses predicted several ligand-receptor pairs between immune cells with SMCs and endothelial cells (ECs), implicating SMCs apoptosis and repair, ECs aging and inflammatory responses.

CONCLUSIONS

We present a comprehensive single-cell atlas of vascular cells in early and late stages of ligated rat carotid artery, providing valuable insights into the understanding of the initiation and progression of vascular remodeling.

Macrophages and the development and progression of non-alcoholic fatty liver disease

The liver is the site of first pass metabolism, detoxifying and metabolizing blood arriving from the hepatic portal vein and hepatic artery. It is made up of multiple cell types, including macrophages. These are either bona fide tissue-resident Kupffer cells (KC) of embryonic origin, or differentiated from circulating monocytes. KCs are the primary immune cells populating the liver under steady state. Liver macrophages interact with hepatocytes, hepatic stellate cells, and liver sinusoidal endothelial cells to maintain homeostasis, however they are also key contributors to disease progression. Generally tolerogenic, they physiologically phagocytose foreign particles and debris from portal circulation and participate in red blood cell clearance. However as immune cells, they retain the capacity to raise an alarm to recruit other immune cells. Their aberrant function leads to the development of non-alcoholic fatty liver disease (NAFLD). NAFLD refers to a spectrum of conditions ranging from benign steatosis of the liver to steatohepatitis and cirrhosis. In NAFLD, the multiple hit hypothesis proposes that simultaneous influences from the gut and adipose tissue (AT) generate hepatic fat deposition and that inflammation plays a key role in disease progression. KCs initiate the inflammatory response as resident immune effectors, they signal to neighbouring cells and recruit monocytes that differentiated into recruited macrophages in situ. Recruited macrophages are central to amplifying the inflammatory response and causing progression of NAFLD to its fibro-inflammatory stages. Given their phagocytic capacity and their being instrumental in maintaining tissue homeostasis, KCs and recruited macrophages are fast-becoming target cell types for therapeutic intervention. We review the literature in the field on the roles of these cells in the development and progression of NAFLD, the characteristics of patients with NAFLD, animal models used in research, as well as the emerging questions. These include the gut-liver-brain axis, which when disrupted can contribute to decline in function, and a discussion on therapeutic strategies that act on the macrophage-inflammatory axis.

Integrated multi-omics analyses reveal the altered transcriptomic characteristics of pulmonary macrophages in immunocompromised hosts with Pneumocystis pneumonia

Introduction

With the extensive use of immunosuppressants, immunosuppression-associated pneumonitis including Pneumocystis jirovecii pneumonia (PCP) has received increasing attention. Though aberrant adaptive immunity has been considered as a key reason for opportunistic infections, the characteristics of innate immunity in these immunocompromised hosts remain unclear.

Methods

In this study, wild type C57BL/6 mice or dexamethasone-treated mice were injected with or without Pneumocystis. Bronchoalveolar lavage fluids (BALFs) were harvested for the multiplex cytokine and metabolomics analysis. The single-cell RNA sequencing (scRNA-seq) of indicated lung tissues or BALFs was performed to decipher the macrophages heterogeneity. Mice lung tissues were further analyzed via quantitative polymerase chain reaction (qPCR) or immunohistochemical staining.

Results

We found that the secretion of both pro-inflammatory cytokines and metabolites in the Pneumocystis-infected mice are impaired by glucocorticoids. By scRNA-seq, we identified seven subpopulations of macrophages in mice lung tissues. Among them, a group of Mmp12⁺ macrophages is enriched in the immunocompetent mice with Pneumocystis infection. Pseudotime trajectory showed that these Mmp12⁺ macrophages are differentiated from Ly6c⁺ classical monocytes, and highly express pro-inflammatory cytokines elevated in BALFs of Pneumocystis-infected mice. In vitro, we confirmed that dexamethasone impairs the expression of Lif, Il1b, Il6 and Tnf, as well as the fungal killing capacity of alveolar macrophage (AM)-like cells. Moreover, in patients with PCP, we found a group of macrophages resembled the aforementioned Mmp12⁺ macrophages, and these macrophages are inhibited in the patient receiving glucocorticoid treatment. Additionally, dexamethasone simultaneously impaired the functional integrity of resident AMs and downregulated the level of lysophosphatidylcholine, leading to the suppressed antifungal capacities.

Conclusion

We reported a group of Mmp12⁺ macrophages conferring protection during Pneumocystis infection, which can be dampened by glucocorticoids. This study provides multiple resources for understanding the heterogeneity and metabolic changes of innate immunity in immunocompromised hosts, and also suggests that the loss of Mmp12⁺ macrophages population contributes to the pathogenesis of immunosuppression-associated pneumonitis.

Melatonin inhibits atherosclerosis progression via galectin-3 downregulation to enhance autophagy and inhibit inflammation

Autophagy deficiency in macrophages exacerbates inflammation in atherosclerosis (AS), and recently, galectin-3 (Gal-3) has been implicated as a critical promoter of inflammation in AS. Further, melatonin (Mel) exerts an autophagy-promoting effect in many chronic inflammatory diseases. In this study, we aimed to investigate whether Mel inhibits AS progression by downregulating Gal-3 to enhance autophagy and inhibit inflammation. Thus, we performed in vivo and in vitro experiments using high-fat diet (HFD)-fed ApoE^-/-  mice and THP-1 macrophages, respectively. Smart-seq of AS plaque macrophages revealed that the differentially expressed genes (DEGs) downregulated by Mel were enriched in immune-related processes, and changes in inflammation status were confirmed based on lower levels of proinflammatory factors in Mel-treated HFD-fed ApoE^-/-  mice and THP-1 macrophages. Further, via transcriptome-based multiscale network pharmacology platform (TMNP), the upstream target genes of the smart-seq DEGs were identified, and Gal-3 showed a high score. Gal-3 was downregulated both in vivo and in vitro by Mel treatment. Besides, the enrichment of the target genes predicted via the TMNP method indicated that autophagy considerably affected the DEGs. Mel treatment as well as Gal-3 knockdown downregulated most inflammatory response-related proteins could attribute to enhancing autophagy. Mechanistically, Mel treatment inhibited Gal-3 leading to lowering the activity of the nuclear transcription factor-kappa B (NF-κB) pathway, and promoting the nuclear localization of transcription factor EB (TFEB). However, increased secretion of Gal-3 activated the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway and impaired autophagy via binding to CD98. Thus, Mel promoted autophagy and restrained inflammation by downregulating Gal-3, implying that it holds promise as a treatment for AS.

Macrophage-Derived 25-Hydroxycholesterol Promotes Vascular Inflammation, Atherogenesis, and Lesion Remodeling

BACKGROUND

Cross-talk between sterol metabolism and inflammatory pathways has been demonstrated to significantly affect the development of atherosclerosis. Cholesterol biosynthetic intermediates and derivatives are increasingly recognized as key immune regulators of macrophages in response to innate immune activation and lipid overloading. 25-Hydroxycholesterol (25-HC) is produced as an oxidation product of cholesterol by the enzyme cholesterol 25-hydroxylase (CH25H) and belongs to a family of bioactive cholesterol derivatives produced by cells in response to fluctuating cholesterol levels and immune activation. Despite the major role of 25-HC as a mediator of innate and adaptive immune responses, its contribution during the progression of atherosclerosis remains unclear.

METHODS

The levels of 25-HC were analyzed by liquid chromatography-mass spectrometry, and the expression of CH25H in different macrophage populations of human or mouse atherosclerotic plaques, respectively. The effect of CH25H on atherosclerosis progression was analyzed by bone marrow adoptive transfer of cells from wild-type or Ch25h-/- mice to lethally irradiated Ldlr-/- mice, followed by a Western diet feeding for 12 weeks. Lipidomic, transcriptomic analysis and effects on macrophage function and signaling were analyzed in vitro from lipid-loaded macrophage isolated from Ldlr-/- or Ch25h-/-;Ldlr-/- mice. The contribution of secreted 25-HC to fibrous cap formation was analyzed using a smooth muscle cell lineage-tracing mouse model, Myh11ERT2CREmT/mG;Ldlr-/-, adoptively transferred with wild-type or Ch25h-/- mice bone marrow followed by 12 weeks of Western diet feeding.

RESULTS

We found that 25-HC accumulated in human coronary atherosclerotic lesions and that macrophage-derived 25-HC accelerated atherosclerosis progression, promoting plaque instability through autocrine and paracrine actions. 25-HC amplified the inflammatory response of lipid-loaded macrophages and inhibited the migration of smooth muscle cells within the plaque. 25-HC intensified inflammatory responses of lipid-laden macrophages by modifying the pool of accessible cholesterol in the plasma membrane, which altered Toll-like receptor 4 signaling, promoted nuclear factor-κB-mediated proinflammatory gene expression, and increased apoptosis susceptibility. These effects were independent of 25-HC-mediated modulation of liver X receptor or SREBP (sterol regulatory element-binding protein) transcriptional activity.

CONCLUSIONS

Production of 25-HC by activated macrophages amplifies their inflammatory phenotype, thus promoting atherogenesis.

Circulating galectin-3 levels are inversely associated with subclinical cardiovascular disease in obese adults

BACKGROUND

Galectin-3 is a new cytokine that is mainly secreted by activated macrophages. It is involved in apoptosis, inflammation and may play a role in the development of cardiovascular disease (CVD). However, there is little information about the association between circulating galectin-3 and subclinical atherosclerosis in humans.

METHODS AND RESULTS

We measured serum galectin-3 in 483 obese adult subjects (aged 40 years and over) who had the measurement of carotid intima-media thickness (CIMT) recruited from the community. Adults with lower levels of circulating galectin-3 had increased CIMT (p < 0.05). In multivariable linear regression analyses, circulating galectin-3 was independently associated with CIMT. The risks of increased CIMT were significantly decreased by 65.1% (OR (95% CI): 0.349 (0.165-0.739)), adjusting for possible confounding factors. Notably, individuals in the lowest quartile of serum galectin-3 were 1.80 times (p < 0.05) more likely to have increased CIMT than those in the highest quartile in multivariable logistic regression analyses; however, such associations with circulating galectin-3 were not noted for carotid plague.

CONCLUSIONS

These findings propose that circulating galectin-3 concentrations are inversely associated with increased CIMT in obese adults, which may be a potential biomarker of CVD.

Macrophage polarization states in atherosclerosis

Atherosclerosis, a chronic inflammatory condition primarily affecting large and medium arteries, is the main cause of cardiovascular diseases. Macrophages are key mediators of inflammatory responses. They are involved in all stages of atherosclerosis development and progression, from plaque formation to transition into vulnerable plaques, and are considered important therapeutic targets. Increasing evidence suggests that the modulation of macrophage polarization can effectively control the progression of atherosclerosis. Herein, we explore the role of macrophage polarization in the progression of atherosclerosis and summarize emerging therapies for the regulation of macrophage polarization. Thus, the aim is to inspire new avenues of research in disease mechanisms and clinical prevention and treatment of atherosclerosis.

Dynamics of adipose tissue macrophage populations after gastric bypass surgery

OBJECTIVE

This case-control study aimed to analyze the dynamics of macrophage infiltration in subcutaneous adipose tissue following bariatric surgery or conservative treatment of obesity and to clarify whether these features predict the weight loss outcome after the surgery.

METHODS

Subcutaneous tissue samples taken before and 12 months after laparoscopic Roux-en-Y gastric bypass surgery (n = 39) or conservative (n = 43) treatment for obesity were analyzed. Fat cell size was determined, and with CD68 immunohistochemistry, crown-like structures (CLS) were counted and single macrophages were quantitated.

RESULTS

A major decline in CLS density from 4.1 (SD 3.5) to 1.1 (SD 0.8) per 1000 fat cells (p < 0.000) was found, regardless of the degree of weight loss after the surgery. Surgery had no effect on the fraction of infiltrating single-cell macrophages in subcutaneous adipose tissue. The abundance of these macrophage populations before the intervention did not predict the degree of postsurgery weight loss or suboptimal response to the surgery.

CONCLUSIONS

The effect of gastric bypass on adipose tissue inflammatory status associates closely with CLS density even in subjects with suboptimal weight loss. The study suggests that factors related to bypass surgery other than weight loss modify the inflammatory response in adipose tissue.

The interplay of galectins-1, -3, and -9 in the immune-inflammatory response underlying cardiovascular and metabolic disease

Galectins are β-galactoside-binding proteins that bind and crosslink molecules via their sugar moieties, forming signaling and adhesion networks involved in cellular communication, differentiation, migration, and survival. Galectins are expressed ubiquitously across immune cells, and their function varies with their tissue-specific and subcellular location. Particularly galectin-1, -3, and -9 are highly expressed by inflammatory cells and are involved in the modulation of several innate and adaptive immune responses. Modulation in the expression of these proteins accompany major processes in cardiovascular diseases and metabolic disorders, such as atherosclerosis, thrombosis, obesity, and diabetes, making them attractive therapeutic targets. In this review we consider the broad cellular activities ascribed to galectin-1, -3, and -9, highlighting those linked to the progression of different inflammatory driven pathologies in the context of cardiovascular and metabolic disease, to better understand their mechanism of action and provide new insights into the design of novel therapeutic strategies.

Galectin-3 critically mediates the hepatoprotection conferred by M2-like macrophages in ACLF by inhibiting pyroptosis but not necroptosis signalling

We previously documented that M2-like macrophages exert a hepatoprotective effect in acute-on-chronic liver failure (ACLF) by inhibiting necroptosis signalling. Nevertheless, the molecular mechanism behind this hepatoprotection still needs to be further dissected. Galectin-3 (GAL3) has been reported to be critically involved in the pathogenesis of multiple liver diseases, whereas the potential role of GAL3 in ACLF remains to be explored. Herein, we hypothesised that GAL3 plays a pivotal role in the hepatoprotection conferred by M2-like macrophages in ACLF by inhibiting necroptosis. To test this hypothesis, we first assessed the expression of GAL3 in control and fibrotic mice with or without acute insult. Second, loss- and gain-of-function experiments of GAL3 were performed. Third, the correlation between GAL3 and M2-like macrophage activation was analysed, and the potential role of GAL3 in M2-like macrophage-conferred hepatoprotection was confirmed. Finally, the molecular mechanism underlying GAL3-mediated hepatoprotection was dissected. GAL3 was found to be obviously upregulated in fibrotic mice with or without acute insult but not in acutely injured mice. Depletion of GAL3 aggravated hepatic damage in fibrotic mice upon insult. Conversely, adoptive transfer of GAL3 provided normal mice enhanced resistance against acute insult. The expression of GAL3 is closely correlated with M2-like macrophage activation. Through adoptive transfer and depletion experiments, M2-like macrophages were verified to act as a major source of GAL3. Importantly, GAL3 was confirmed to hold a pivotal place in the hepatoprotection conferred by M2-like macrophages through loss- and gain-of-function experiments. Unexpectedly, the depletion and adoptive transfer of GAL3 resulted in significant differences in the expression levels of pyroptosis but not necroptosis signalling molecules. Taken together, GAL3 plays a pivotal role in the hepatoprotection conferred by M2-like macrophages in ACLF by inhibiting pyroptosis but not necroptosis signalling. Our findings provide novel insights into the pathogenesis and therapy of ACLF.

Galectin-3 Is a Crucial Immunological Disease Marker in Patients with Fungal Keratitis

Fungal keratitis, one of the most common infectious eye diseases in China, often results in a poor prognosis due to a delayed diagnosis and the insufficiency of effective therapy. There is an urgent need to identify specific biomarkers for the disease. In this study, we screened out tear proteins in patients with fungal keratitis by microsphere-based immunoassay analysis. Levels of cytokine expression were determined in both human corneal epithelial cell models in vitro and the corneas of patients by western blot, quantitative polymerase chain reaction (qPCR), and immunofluorescence analysis. Neutrophil activation was examined by flow cytometry analysis. The relationship between the cytokine expression and neutrophils was evaluated by immunofluorescence costaining and correlation analysis. These results demonstrated that the galectin-3 expression level was increased in both cell model and patient samples at the early and late stages of fungal keratitis. The neutrophils were significantly activated during the disease course of fungal keratitis. Meanwhile, colocalization and a positive correlation between galectin-3 and neutrophils were observed, suggesting that galectin-3 may play a crucial role in the recruitment of neutrophils and immune regulation of fungal keratitis. In conclusion, galectin-3 could be a key disease marker implying a beneficial immune response in the pathogenesis of fungal keratitis, which might be a target of therapeutic strategy in the future.

Single-Cell Transcriptome Analysis of the Circle of Willis in a Mouse Cerebral Aneurysm Model

BACKGROUND

The circle of Willis (CoW) is the most common location for aneurysms to form in humans. Although the major cell types of the intracranial vasculature are well known, the heterogeneity and relative contributions of the different cells in healthy and aneurysmal vessels have not been well characterized. Here, we present the first comprehensive analysis of the lineage heterogeneity and altered transcriptomic profiles of vascular cells from healthy and aneurysmal mouse CoW using single-cell RNA sequencing.

METHODS

Cerebral aneurysms (CAs) were induced in adult male mice using an elastase model. Single-cell RNA sequencing was then performed on CoW samples obtained from animals that either had aneurysms form or rupture 14 days post-induction. Sham-operated animals served as controls.

RESULTS

Unbiased clustering analysis of the transcriptional profiles from >3900 CoW cells identified 19 clusters representing ten cell lineages: vascular smooth muscle cells, endothelial cells fibroblasts, pericytes and immune cells (macrophages, T and B lymphocytes, dendritic cells, mast cells, and neutrophils). The 5 vascular smooth muscle cell subpopulations had distinct transcriptional profiles and were classified as proliferative, stress-induced senescent, quiescent, inflammatory-like, or hyperproliferative. The transcriptional signature of the metabolic pathways of ATP generation was found to be downregulated in 2 major vascular smooth muscle cell clusters when CA was induced. Aneurysm induction led to significant expansion of the total macrophage population, and this expansion was further increased with rupture. Both inflammatory and resolution-phase macrophages were identified, and a massive spike of neutrophils was seen with CA rupture. Additionally, the neutrophil-to-lymphocyte ratio (NLR), which originated from CA induction mirrored what happens in humans.

CONCLUSIONS

Our data identify CA disease-relevant transcriptional signatures of vascular cells in the CoW and is searchable via a web-based R/shiny interface.

Ultrasonication, immune activity, and photocrosslinked microgel formation of pectic polysaccharide isolated from root bark of Ulmus davidiana var. japonica (Rehder) Nakai

The root bark of Ulmus davidiana var. japonica (Rehder) Nakai (Japanese elm) has been used for inflammatory disease treatments. In this work, we isolated pectic polysaccharides from the root bark of U. davidiana (UDP) and explored the immune activities of intact and ultrasonicated UDP on human macrophages. The UDP-treated macrophages showed a proinflammatory response, indicating classical activation via Toll-like receptor-mediated recognition. For hydrogel formation, the ultrasonicated UDP was modified with methacrylate groups, then subjected to photocrosslinking. The formed bulk hydrogel was pulverized into microgels by homogenization, and the microgel size was modulated for macrophage phagocytosis. The UDP microgel-treated macrophages displayed microgel internalization and classical activation that involved upregulation of M1 polarization markers (IL6, TNF-α, and CCR7), indicating that the microgel can be used as a carrier for macrophage-targeted drug delivery.

N-Glycosylation and Inflammation; the Not-So-Sweet Relation

Chronic inflammation is the main feature of many long-term inflammatory diseases such as autoimmune diseases, metabolic disorders, and cancer. There is a growing number of studies in which alterations of N-glycosylation have been observed in many pathophysiological conditions, yet studies of the underlying mechanisms that precede N-glycome changes are still sparse. Proinflammatory cytokines have been shown to alter the substrate synthesis pathways as well as the expression of glycosyltransferases required for the biosynthesis of N-glycans. The resulting N-glycosylation changes can further contribute to disease pathogenesis through modulation of various aspects of immune cell processes, including those relevant to pathogen recognition and fine-tuning the inflammatory response. This review summarizes our current knowledge of inflammation-induced N-glycosylation changes, with a particular focus on specific subsets of immune cells of innate and adaptive immunity and how these changes affect their effector functions, cell interactions, and signal transduction.

SREBP1 regulates Lgals3 activation in response to cholesterol loading

Aberrant smooth muscle cell (SMC) plasticity is etiological to vascular diseases. Cholesterol induces SMC phenotypic transition featuring high LGALS3 (galectin-3) expression. This proatherogenic process is poorly understood for its molecular underpinnings, in particular, the mechanistic role of sterol regulatory-element binding protein-1 (SREBP1), a master regulator of lipid metabolism. Herein we show that cholesterol loading stimulated SREBP1 expression in mouse, rat, and human SMCs. SREBP1 positively regulated LGALS3 expression (and vice versa), whereas Krüppel-like factor-15 (KLF15) acted as a negative regulator. Both bound to the Lgals3 promoter, yet at discrete sites, as revealed by chromatin immunoprecipitation-qPCR and electrophoretic mobility shift assays. SREBP1 and LGALS3 each abated KLF15 protein, and blocking the bromo/extraterminal domain-containing proteins (BETs) family of acetyl-histone readers abolished cholesterol-stimulated SREBP1/LGALS3 protein production. Furthermore, silencing bromodomain protein 2 (BRD2; but not other BETs) reduced SREBP1; endogenous BRD2 co-immunoprecipitated with SREBP1's transcription-active domain, its own promoter DNA, and that of L gals 3. Thus, results identify a previously uncharacterized cholesterol-responsive dyad-SREBP1 and LGALS3, constituting a feedforward circuit that can be blocked by BETs inhibition. This study provides new insights into SMC phenotypic transition and potential interventional targets.

Galectins: An Ancient Family of Carbohydrate Binding Proteins with Modern Functions

Galectins are a large family of carbohydrate binding proteins with members in nearly every lineage of multicellular life. Through tandem and en-mass genome duplications, over 15 known vertebrate galectins likely evolved from a single common ancestor extant in pre-chordate lineages. While galectins have divergently evolved numerous functions, some of which do not involve carbohydrate recognition, the vast majority of the galectins have retained the conserved ability to bind variably modified polylactosamine (polyLacNAc) residues on glycans that modify proteins and lipids on the surface of host cells and pathogens. In addition to their direct role in microbial killing, many proposed galectin functions in the immune system and cancer involve crosslinking glycosylated receptors and modifying signaling pathways or sensitivity to antigen from the outside in. However, a large body of work has uncovered intracellular galectin functions mediated by carbohydrate- and non-carbohydrate-dependent interactions. In the cytoplasm, galectins can tune intracellular kinase and G-protein-coupled signaling cascades important for nutrient sensing, cell cycle progression, and transformation. Particularly, but interconnected pathways, cytoplasmic galectins serve the innate immune system as sensors of endolysosomal damage, recruiting and assembling the components of autophagosomes during intracellular infection through carbohydrate-dependent and -independent activities. In the nucleus, galectins participate in pre-mRNA splicing perhaps through interactions with non-coding RNAs required for assembly of spliceosomes. Together, studies of galectin function paint a picture of a functionally dynamic protein family recruited during eons of evolution to regulate numerous essential cellular processes in the context of multicellular life.

miRNA-29a inhibits atherosclerotic plaque formation by mediating macrophage autophagy via PI3K/AKT/mTOR pathway

Background: miR-29a plays a vital role in AS, but the relationship between the miR-29a-targeted PI3K signaling pathway and AS remains unclear. Therefore, this study was carried out.

Methods: Gene expression profiles from the GEO database containing AS samples were analyzed. ApoE^−/− mice and RAW264.7 cells were treated with miR-29a negative control (NC), miR-29a mimic and miR-29a inhibitor to establish the AS model. Then MOVAT staining, TEM, Western blotting, and immunofluorescence staining were adopted for testing target proteins.

Results: DEGs were identified from GSE137578, GSE132651, GSE113969, GSE43292, and GSE97210 datasets. It was found that there were targeted binding sites between miR-29a and PIK3CA. Besides, GO and KEGG analysis demonstrated that autophagy was an enriched pathway in AS. Later, PPI network was depicted, and hub genes were then determined. The results revealed that miR-29a suppressed the areas of plaques and lesional macrophages, but had no impact on VSMCs. TEM results showed the organelles pyknosis of lesional macrophages damaged morphological changes. Furthermore, miR-29a amplified the M2-like macrophages but suppressed the polarization of M1-like macrophages in atherosclerotic plaques. According to mouse and RAW 264.7 cell experiments, miR-29a significantly inhibited the protein expressions of PI3K, p-PI3K, p-AKT, and p-mTOR, which were consistent with the increased expressions of autophagy-related proteins, Beclin 1 and LC3II. However, the miR-29a suppression exhibited the contrary results.

Conclusion: MiR-29a elevation induces the increase of autophagy by down-regulating the PI3K/AKT/mTOR pathway in the progression of AS, indicating that miR-29a is a novel therapeutic strategy for AS.

Investigation of Atherosclerotic Plaque Vulnerability

Histochemical and immunohistochemical approaches permit the detection and evaluation of proteins and cell types within murine brachiocephalic artery atherosclerotic plaques, that can be subsequently analyzed to provide inferences on atherosclerotic plaque vulnerability. Here we describe the specific histochemical techniques deployed to examine the expression of elastin, fibrillar collagens, and neutral lipids, alongside immunohistochemistry protocols for the identification of macrophages (CD68) and vascular smooth muscle cells (α-smooth muscle actin). We will also describe how analyses derived from these methods can be combined to determine evidence of previous plaque rupture and susceptibility to rupture.

Predictive mouse model reflects distinct stages of human atheroma in a single carotid artery

Identification of patients with high-risk asymptomatic atherosclerotic plaques remains an elusive but essential step in preventing stroke. However, there is a lack of animal model that provides a reproducible method to predict where, when and what types of plaque formation, which fulfils the American Heart Association (AHA) histological classification of human plaques. We have developed a predictive mouse model that reflects different stages of human plaques in a single carotid artery by means of shear-stress modifying cuff. Validated with over 30000 histological sections, the model generates a specific pattern of plaques with different risk levels along the same artery depending on their position relative to the cuff. The further upstream of the cuff-implanted artery, the lower the magnitude of shear stress, the more unstable the plaques of higher grade according to AHA classification; with characteristics including greater degree of vascular remodeling, plaque size, plaque vulnerability and inflammation, resulting in higher risk plaques. By weeks 20 and 30, this model achieved 80% and near 100% accuracy respectively, in predicting precisely where, when and what stages/AHA types of plaques develop along the same carotid artery. This model can generate clinically-relevant plaques with varying phenotypes fulfilling AHA classification and risk levels, in specific locations of the single artery with near 100% accuracy of prediction. The model offers a promising tool for development of diagnostic tools to target high-risk plaques, increasing accuracy in predicting which individual patients may require surgical intervention to prevent stroke, paving the way for personalized management of carotid atherosclerotic disease.

Human galectin-1 and galectin-3 promote Tropheryma whipplei infection

Tropheryma whipplei, is an actinobacterium that causes different infections in humans, including Whipple's disease. The bacterium infects and replicates in macrophages, leading to a Th2-biased immune response. Previous studies have shown that T. whipplei harbors complex surface glycoproteins with evidence of sialylation. However, the exact contribution of these glycoproteins for infection and survival remains obscure. To address this, we characterized the bacterial glycoprofile and evaluated the involvement of human β-galactoside-binding lectins, Galectin-1 (Gal-1) and Galectin-3 (Gal-3) which are highly expressed by macrophages as receptors for bacterial glycans. Tropheryma whipplei glycoproteins harbor different sugars including glucose, mannose, fucose, β-galactose and sialic acid. Mass spectrometry identification revealed that these glycoproteins were membrane- and virulence-associated glycoproteins. Most of these glycoproteins are highly sialylated and N-glycosylated while some of them are rich in poly-N-acetyllactosamine (Poly-LAcNAc) and bind Gal-1 and Gal-3. In vitro, T. whipplei modulates the expression and cellular distribution of Gal-1 and Gal-3. Although both galectins promote T. whipplei infection by enhancing bacterial cell entry, only Gal-3 is required for optimal bacterial uptake. Finally, we found that serum levels of Gal-1 and Gal-3 were altered in patients with T. whipplei infections as compared to healthy individuals, suggesting that galectins are also involved in vivo. Among T. whipplei membrane-associated proteins, poly-LacNAc rich-glycoproteins promote infection through interaction with galectins. T. whipplei modulates the expression of Gal-1 and Gal-3 both in vitro and in vivo. Drugs interfering with galectin-glycan interactions may provide new avenues for the treatment and diagnosis of T. whipplei infections.

Mitochondrial STAT3 exacerbates LPS-induced sepsis by driving CPT1a-mediated fatty acid oxidation

Rationale: We found that a subset of signal transducer and activator of transcription 3 (STAT3) translocated into mitochondria in phagocytes, including macrophages isolated from individuals with sepsis. However, the role of mitochondrial STAT3 in macrophages remains unclear.

Method: To investigate the function of mitochondrial STAT3 in vivo, we generated inducible mitochondrial STAT3 knock-in mice. A cytokine array analysis, a CBA analysis, flow cytometry, immunofluorescence staining and quantification and metabolic analyses in vivo were subsequently performed in an LPS-induced sepsis model. Single-cell RNA sequencing, a microarray analysis, metabolic assays, mass spectrometry and ChIP assays were utilized to gain insight into the mechanisms of mitochondrial STAT3 in metabolic reprogramming in LPS-induced sepsis.

Results: We found that mitochondrial STAT3 induced NF-κB nuclear localization and exacerbated LPS-induced sepsis in parallel with a metabolic switch from mainly using glucose to an increased reliance on fatty acid oxidation (FAO). Moreover, mitochondrial STAT3 abrogated carnitine palmitoyl transferase 1a (CPT1a) ubiquitination and degradation in LPS-treated macrophages. Meanwhile, an interaction between CPT1a and ubiquitin-specific peptidase 50 (USP50) was observed. In contrast, knocking down USP50 decreased CPT1a expression and FAO mediated by mitochondrial STAT3. The ChIP assays revealed that NF-κB bound the USP50 promoter. Curcumin alleviated LPS-mediated sepsis by suppressing the activities of mitochondrial STAT3 and NF-κB.

Conclusion: Our findings reveal that mitochondrial STAT3 could trigger FAO by inducing CPT1a stabilization mediated by USP50 in macrophages, at least partially.

In Vivo Human Single-Chain Fragment Variable Phage Display-Assisted Identification of Galectin-3 as a New Biomarker of Atherosclerosis

Background

Atherosclerosis is a complex pathology in which dysfunctional endothelium, activated leucocytes, macrophages, and lipid‐laden foam cells are implicated, and in which plaque disruption is driven by many putative actors. This study aimed to identify accurate targetable biomarkers using new in vivo approaches to propose tools for improved diagnosis and treatment.

Methods and Results

Human scFv (single‐chain fragment variable) selected by in vivo phage display in a rabbit model of atherosclerosis was reformatted as scFv fused to the scFv‐Fc (single‐chain fragment variable fused to the crystallizable fragment of immunoglobulin G format) antibodies. Their reactivity was tested using flow cytometry and immunoassays, and aorta sections from animal models and human carotid and coronary artery specimens. A pool of atherosclerotic proteins from human endarterectomies was co‐immunoprecipitated with the selected scFv‐Fc followed by mass spectrometry for target identification. Near‐infrared fluorescence imaging was performed in Apoe^−/− mice after injection of an Alexa Fluor 647–labeled scFv‐Fc‐2c antibody produced in a baculovirus system with 2 additional cysteine residues (ie, 2c) for future coupling to nano‐objects for theranostic applications. One scFv‐Fc clone (P3) displayed the highest cross‐reactivity against atherosclerotic lesion sections (rabbit, mouse, and human) and was chosen for translational development. Mass spectrometry identified galectin‐3, a β‐galactoside‐binding lectin, as the leader target. ELISA and immunofluorescence assays with a commercial anti‐galectin‐3 antibody confirmed this specificity. P3 scFv‐Fc‐2c specifically targeted atherosclerotic plaques in the Apoe^−/− mouse model.

Conclusions

These results provide evidence that the P3 antibody holds great promise for molecular imaging of atherosclerosis and other inflammatory pathologies involving macrophages. Recently, galectin‐3 was proposed as a high‐value biomarker for the assessment of coronary and carotid atherosclerosis.

Emerging role of galectin family in inflammatory autoimmune diseases

Galectin family is a group of glycan-binding proteins. Members in this family are expressed in different tissues, immune or non-immune cells. These molecules are important regulators in innate and adaptive immune response, performing significantly in a broad range of cellular and pathophysiological functions, such as cell proliferation, adhesion, migration, and invasion. Findings have shown that expression of galectins is abnormal in many inflammatory autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis, osteoarthritis, sjögren's syndrome, systemic sclerosis. Galectins also function as intracellular and extracellular disease regulators mainly through the binding of their carbohydrate recognition domain to glycoconjugates. Here, we review the state-of-the-art of the role that different galectin family members play in immune cells, contributing to the complex inflammatory diseases. Hopefully collection of the information will provide a preliminary theoretical basis for the exploration of new targets for treatment of the disorders.

Galectin-3 in T cell-mediated immunopathology and autoimmunity

Galectin-3 (Gal-3) is the only member of galectin family able to form pentamers and heterodimers with chemokines. Its presence in various cells and tissues suggests variety of regulatory functions in physiological conditions, but increasing body of evidence indicates involvement of Gal-3 in pathological cascades of many diseases. Gal-3 exerts different, sometimes opposite, effects in various disorders or in different phases of the same disease. These differences in action of Gal-3 are related to the localization of Gal-3 in the cell, types of receptors through which it acts, or the types of cells that secrete it. As a regulator of immune response and T-cell activity, Gal-3 appears to have important role in development of autoimmunity mediated by T cells. Absence of Gal-3 in C57Bl6 mice favors Th2 mediated inflammatory myocarditis but attenuate fibrosis. Recent data also indicate Gal-3 involvement in development atherosclerosis. In pathogenesis of diabetes type 1 and autoimmune components of diabetes type 2 Gal-3 may have detrimental or protective role depending on its intracellular or extracellular localization. Gal-3 mediates autoimmune hepatic damage through activation of T-cells or natural killer T cells. Gal-3 is an important mediator in neurodevelopment, neuropathology and behavior due to its expression both in neurons and glial cells. All together, assessing the role of Gal-3 in immunopathology and autoimmunity it could be concluded that it is an important participant in pathogenesis, as well as promising monitoring marker and therapeutic target.

The Role of Mitochondria in Immune-Cell-Mediated Tissue Regeneration and Ageing

During tissue injury events, the innate immune system responds immediately to alarms sent from the injured cells, and the adaptive immune system subsequently joins in the inflammatory reaction. The control mechanism of each immune reaction relies on the orchestration of different types of T cells and the activators, antigen-presenting cells, co-stimulatory molecules, and cytokines. Mitochondria are an intracellular signaling organelle and energy plant, which supply the energy requirement of the immune system and maintain the system activation with the production of reactive oxygen species (ROS). Extracellular mitochondria can elicit regenerative effects or serve as an activator of the immune cells to eliminate the damaged cells. Recent clarification of the cytosolic escape of mitochondrial DNA triggering innate immunity underscores the pivotal role of mitochondria in inflammation-related diseases. Human mesenchymal stem cells could transfer mitochondria through nanotubular structures to defective mitochondrial DNA cells. In recent years, mitochondrial therapy has shown promise in treating heart ischemic events, Parkinson's disease, and fulminating hepatitis. Taken together, these results emphasize the emerging role of mitochondria in immune-cell-mediated tissue regeneration and ageing.

Glycans and Glycan-Binding Proteins as Regulators and Potential Targets in Leukocyte Recruitment

Leukocyte recruitment is a highly controlled cascade of interactions between proteins expressed by the endothelium and circulating leukocytes. The involvement of glycans and glycan-binding proteins in the leukocyte recruitment cascade has been well-characterised. However, our understanding of these interactions and their regulation has expanded substantially in recent years to include novel lectins and regulatory pathways. In this review, we discuss the role of glycans and glycan-binding proteins, mediating the interactions between endothelium and leukocytes both directly and indirectly. We also highlight recent findings of key enzymes involved in glycosylation which affect leukocyte recruitment. Finally, we investigate the potential of glycans and glycan binding proteins as therapeutic targets to modulate leukocyte recruitment and transmigration in inflammation.

Imaging atherosclerotic plaques by targeting Galectin-3 and activated macrophages using (89Zr)-DFO- Galectin3-F(ab')2 mAb

Rationale: The high expression of Galectin-3 (Gal3) in macrophages of atherosclerotic plaques suggests its participation in atherosclerosis pathogenesis, and raises the possibility to use it as a target to image disease severity in vivo. Here, we explored the feasibility of tracking atherosclerosis by targeting Gal3 expression in plaques of apolipoprotein E knockout (ApoE-KO) mice via PET imaging. Methods: Targeting of Gal3 in M0-, M1- and M2 (M2a/M2c)-polarized macrophages was assessed in vitro using a Gal3-F(ab')₂ mAb labeled with AlexaFluor®488 and ⁸⁹Zr- desferrioxamine-thioureyl-phenyl-isothiocyanate (DFO). To visualize plaques in vivo, ApoE-KO mice were injected i.v. with ⁸⁹Zr-DFO-Gal3-F(ab')₂ mAb and imaged via PET/CT 48 h post injection. Whole length aortas harvested from euthanized mice were processed for Sudan-IV staining, autoradiography, and immunostaining for Gal3, CD68 and α-SMA expression. To confirm accumulation of the tracer in plaques, ApoE-KO mice were injected i.v. with Cy5.5-Gal3-F(ab')₂ mAb, euthanized 48 h post injection, followed by cryosections of the body and acquisition of fluorescent images. To explore the clinical potential of this imaging modality, immunostaining for Gal3, CD68 and α-SMA expression were carried out in human plaques. Single cell RNA sequencing (scRNA-Seq) analyses were performed to measure LGALS3 (i.e. a synonym for Gal3) gene expression in each macrophage of several subtypes present in murine or human plaques. Results: Preferential binding to M2 macrophages was observed with both AlexaFluor®488-Gal3-F(ab')₂ and ⁸⁹Zr-DFO-Gal3-F(ab')₂ mAbs. Focal and specific ⁸⁹Zr-DFO-Gal3-F(ab')₂ mAb uptake was detected in plaques of ApoE-KO mice by PET/CT. Autoradiography and immunohistochemical analyses of aortas confirmed the expression of Gal3 within plaques mainly in macrophages. Moreover, a specific fluorescent signal was visualized within the lesions of vascular structures burdened by plaques in mice. Gal3 expression in human plaques showed similar Gal3 expression patterns when compared to their murine counterparts. Conclusions: Our data reveal that ⁸⁹Zr-DFO-Gal3-F(ab')₂ mAb PET/CT is a potentially novel tool to image atherosclerotic plaques at different stages of development, allowing knowledge-based tailored individual intervention in clinically significant disease.

The tandem stenosis mouse model: Towards understanding, imaging, and preventing atherosclerotic plaque instability and rupture

The rupture of unstable atherosclerotic plaques is the major cause of cardiovascular mortality and morbidity. Despite significant limitations in our understanding and ability to identify unstable plaque pathology and prevent plaque rupture, most atherosclerosis research utilises preclinical animal models exhibiting stable atherosclerosis. Here, we introduce the tandem stenosis (TS) mouse model that reflects plaque instability and rupture, as seen in patients. The TS model involves dual ligation of the right carotid artery, leading to locally predefined unstable atherosclerosis in hypercholesterolaemic mice. It exhibits key characteristics of human unstable plaques, including plaque rupture, luminal thrombosis, intraplaque haemorrhage, large necrotic cores, thin or ruptured fibrous caps and extensive immune cell accumulation. Altogether, the TS model represents an ideal preclinical tool for improving our understanding of human plaque instability and rupture, for the development of imaging technologies to identify unstable plaques, and for the development and testing of plaque-stabilising treatments for the prevention of atherosclerotic plaque rupture.

Galectin-3 in Cardiovascular Diseases

Galectin-3 (Gal-3) is a β-galactoside-binding protein belonging to the lectin family with pleiotropic regulatory activities and several physiological cellular functions, such as cellular growth, proliferation, apoptosis, differentiation, cellular adhesion, and tissue repair. Inflammation, tissue fibrosis and angiogenesis are the main processes in which Gal-3 is involved. It is implicated in the pathogenesis of several diseases, including organ fibrosis, chronic inflammation, cancer, atherosclerosis and other cardiovascular diseases (CVDs). This review aims to explore the connections of Gal-3 with cardiovascular diseases since they represent a major cause of morbidity and mortality. We herein discuss the evidence on the pro-inflammatory role of Gal-3 in the atherogenic process as well as the association with plaque features linked to lesion stability. We report the biological role and molecular mechanisms of Gal-3 in other CVDs, highlighting its involvement in the development of cardiac fibrosis and impaired myocardium remodelling, resulting in heart failure and atrial fibrillation. The role of Gal-3 as a prognostic marker of heart failure is described together with possible diagnostic applications to other CVDs. Finally, we report the tentative use of Gal-3 inhibition as a therapeutic approach to prevent cardiac inflammation and fibrosis.