Ablation of Galectin-12 Inhibits Atherosclerosis through Enhancement of M2 Macrophage Polarization

Expression and secretion of galectin-12 in the context of neutrophilic differentiation of human promyeloblastic HL-60 cells

Galectin-12 is a tissue-specific galectin that has been largely defined by its role in the regulation of adipocyte differentiation and lipogenesis. This study aimed to evaluate the role of galectin-12 in the differentiation and polarization of neutrophils within a model of acute myeloid leukemia HL-60 cells. All-trans retinoic acid and dimethyl sulfoxide were used to induce differentiation of HL-60 cells which led to the generation of two phenotypes of neutrophil-like cells with opposite changes in galectin-12 gene (LGALS12) expression and different functional responses to N-formyl- l-methionyl- l-leucyl- l-phenylalanine. These phenotypes showed significant differences of differentially expressed genes on a global scale based on bioinformatics analysis of available Gene Expression Omnibus (GEO) data sets. We also demonstrated that HL-60 cells could secrete and accumulate galectin-12 in cell culture medium under normal growth conditions. This secretion was found to be entirely inhibited upon neutrophilic differentiation and was accompanied by an increase in intracellular lipid droplet content and significant enrichment of 22 lipid gene ontology terms related to lipid metabolism in differentiated cells. These findings suggest that galectin-12 could serve as a marker of neutrophilic plasticity or polarization into different phenotypes and that galectin-12 secretion may be influenced by lipid droplet biogenesis.

The Role of Macrophages in Atherosclerosis: Participants and Therapists

Currently, atherosclerosis, characterized by the dysfunction of lipid metabolism and chronic inflammation in the intimal space of the vessel, is considered to be a metabolic disease. As the most abundant innate immune cells in the body, macrophages play a key role in the onset, progression, or regression of atherosclerosis. For example, macrophages exhibit several polarization states in response to microenvironmental stimuli; an increasing proportion of macrophages, polarized toward M2, can suppress inflammation, scavenge cell debris and apoptotic cells, and contribute to tissue repair and fibrosis. Additionally, specific exosomes, generated by macrophages containing certain miRNAs and effective efferocytosis of macrophages, are crucial for atherosclerosis. Therefore, macrophages have emerged as a novel potential target for anti-atherosclerosis therapy. This article reviews the role of macrophages in atherosclerosis from different aspects: origin, phenotype, exosomes, and efferocytosis, and discusses new approaches for the treatment of atherosclerosis.

Galectin-12 modulates Kupffer cell polarization to alter the progression of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease is caused by an imbalance in lipid metabolism and immune response to pose a risk factor for liver fibrosis. Recent evidence indicates that M2 macrophages secrete transforming growth factor-β1, which contributes to liver fibrosis. Galectin-12 has been demonstrated to regulate lipid metabolism and macrophage polarization. The purpose of this study is to investigate the role of galectin-12 in the development of nonalcoholic fatty liver disease and fibrosis. Liver tissue from wild-type C57BL/6 mice fed with a high-fat diet containing cholesterol and cholic acid for 4-12 weeks was used to examine galectin-12 expression and its correlation with nonalcoholic fatty liver disease. Furthermore, the effects of galectin-12 on M2 macrophages during the progression of nonalcoholic fatty liver disease were investigated by studying Kupffer cells from galectin-12 knockout mice and doxycycline-inducible Gal12-/-THP-1 cells. Ablation of galectin-12 promoted M2 polarization of Kupffer cells, as indicated by higher levels of M2 markers, such as arginase I and chitinase 3-like protein 3. Furthermore, the activation of signal transducer and activator of transcription 6 was significantly higher in Gal12-/- macrophages activated by interleukin-4, which was correlated with higher levels of transforming growth factor-β1. Moreover, Gal12-/- macrophage-conditioned medium promoted hepatic stellate cells myofibroblast differentiation, which was indicated by higher α-smooth muscle actin expression levels compared with those treated with LacZ control medium. Finally, we demonstrated that galectin-12 knockdown negatively regulated the suppressor of cytokine signaling 3 levels. These findings suggested that galectin-12 balances M1/M2 polarization of Kupffer cells to prevent nonalcoholic fatty liver disease progression.

San Jie Tong Mai Fang Protects Against Atherosclerosis Progression by Regulating Macroautophagy through the PI3K/AKT/mTOR Signaling Pathway

ABSTRACT

Many studies have confirmed that macrophage autophagy injury negatively impacts the pathogenesis of atherosclerosis (AS). Meanwhile, the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway affects AS progression by regulating macrophage autophagy. We previously reported that the herbal formula San Jie Tong Mai Fang (SJTMF) elicits lipid regulatory and anti-inflammatory properties. Hence, the current study used an ApoE -/- high-fat diet-fed mouse model to determine whether SJTMF elicits protective effects against AS progression by means of the regulation of macrophage autophagy through the PI3K/AKT/mTOR signaling pathway. Our results show that SJTMF reduced the number of atherosclerotic plaques, foam cell formation, and intimal thickness in mouse aorta. In addition, SJTMF improved blood lipid metabolism and inflammatory levels in mice. We also observed that SJTMF caused macrophages to be polarized toward the M2 phenotype through the inhibition of the PI3K/AKT/mTOR signaling pathway. In addition, the abundances of LC3-II/I and beclin1 proteins-key autophagy molecules-were increased, whereas that of p62 was decreased, resulting in the promotion of macrophage autophagy. Taken together, these findings indicate that SJTMF may regulate the polarization of macrophages by inhibiting the PI3K/AKT/mTOR signaling pathway, thereby reducing atherosclerotic plaque damage in ApoE -/- mice, thereby promoting macrophage autophagy and eliciting a significant antiarteriosclerosis effect. Hence, SJTMF may represent a promising new candidate drug for the treatment of AS.

Evaluation of Plasma Concentrations of Galectins-1, 2 and 12 in Psoriasis and Their Clinical Implications

Psoriasis is a complex disease that nowadays is considered not only a dermatosis but a kind of systemic disorder associated with many accompanying diseases. Metabolic complications leading to cardiovascular incidences are the cause of increased mortality in psoriatic patients. Galectins (gal) are beta-galactoside-binding lectins that exert different functions, including engagement in metabolic processes. Our aim was to assess the concentrations of gal-1, 2 and 12 in psoriatics, to establish their potential clinical implications, including in metabolic complications. Plasma galectins were assessed by ELISA in 60 psoriatic patients and 30 controls without dermatoses and a negative family history of psoriasis. Plasma concentrations of all galectins were significantly higher in patients than controls (gal-1 with p < 0.001, gal-2 and 12 with p < 0.05). There were no correlations between galectins concentrations and psoriasis severity in PASI or disease duration (p > 0.05). Gal-1 and 12 were significantly negatively correlated with GFR (p < 0.05, p < 0.01, respectively) and gal-2 with HDL (p < 0.05). Gal-2 was significantly positively correlated with CRP (p < 0.05) and gal-12 with fasting glucose (p < 0.01). Based on the results and given the reported role of galectins in metabolic disorders we may conclude that gal-1, 2 and 12 could be potentially engaged in metabolic complications in psoriatics, most probably in atherosclerosis. Gal-2 could be perhaps further investigated as a marker of metabolically induced inflammation in psoriasis, gal-1 and gal-12 as predictors of renal impairment in psoriatics due to metabolic disorders. Potentially, gal-12 could be considered in the future as a marker of carbohydrate metabolism disorders in psoriatics.

The interrelation of galectins and autophagy

Autophagy is a vital physiological process that maintains intracellular homeostasis by removing damaged organelles and senescent or misfolded molecules. However, excessive autophagy results in cell death and apoptosis, which will lead to a variety of diseases. Galectins are a type of animal lectin that binds to β-galactosides and can bind to the cell surface or extracellular matrix glycans, affecting a variety of immune processes in vivo and being linked to the development of many diseases. In many cases, galectins and autophagy both play important regulatory roles in the cellular life course, yet our understanding of the relationship between them is still incomplete. Galectins and autophagy may share common etiological cofactors for some diseases. Hence, we summarize the relationship between galectins and autophagy, aiming to draw attention to the existence of multiple associations between galectins and autophagy in a variety of physiological and pathological processes, which provide new ideas for etiological diagnosis, drug development, and therapeutic targets for related diseases.

Galectin functions in cancer-associated inflammation and thrombosis

Galectins are carbohydrate-binding proteins that regulate many cellular functions including proliferation, adhesion, migration, and phagocytosis. Increasing experimental and clinical evidence indicates that galectins influence many steps of cancer development by inducing the recruitment of immune cells to the inflammatory sites and modulating the effector function of neutrophils, monocytes, and lymphocytes. Recent studies described that different isoforms of galectins can induce platelet adhesion, aggregation, and granule release through the interaction with platelet-specific glycoproteins and integrins. Patients with cancer and/or deep-venous thrombosis have increased levels of galectins in the vasculature, suggesting that these proteins could be important contributors to cancer-associated inflammation and thrombosis. In this review, we summarize the pathological role of galectins in inflammatory and thrombotic events, influencing tumor progression and metastasis. We also discuss the potential of anti-cancer therapies targeting galectins in the pathological context of cancer-associated inflammation and thrombosis.

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.

A sweet spot for macrophages: Focusing on polarization

Macrophages are a type of functionally plastic cells that can create a pro-/anti-inflammatory microenvironment for organs by producing different kinds of cytokines, chemokines, and growth factors to regulate immunity and inflammatory responses. In addition, they can also be induced to adopt different phenotypes in response to extracellular and intracellular signals, a process defined as M1/M2 polarization. Growing evidence indicates that glycobiology is closely associated with this polarization process. In this research, we review studies of the roles of glycosylation, glucose metabolism, and key lectins in the regulation of macrophages function and polarization to provide a new perspective for immunotherapies for multiple diseases.