Age-related trabecular bone loss is associated with a decline in serum Galectin-1 level

DNA methylation of promoter region inhibits galectin-1 expression in BMSCs of aged mice

Senile osteoporosis increases fracture risks. Bone marrow stromal cells (BMSCs) are sensitive to aging. Deep insights into BMSCs aging are vital to elucidate the mechanisms underlying age-related bone loss. Recent advances showed that osteoporosis is associated with aberrant DNA methylation of many susceptible genes. Galectin-1 (Gal-1) has been proposed as a mediator of BMSCs functions. In our previous study, we showed that Gal-1 was downregulated in aged BMSCs and global deletion of Gal-1 in mice caused bone loss via impaired osteogenesis potential of BMSCs. Gal-1 promoter is featured by CpG islands. However, there are no reports concerning the DNA methylation status in Gal-1 promoter during osteoporosis. In the current study, we sought to investigate the role of DNA methylation in Gal-1 downregulation in aged BMSCs. The potential for anti-bone loss therapy based on modulating DNA methylation is explored. Our results showed that Dnmt3b-mediated Gal-1 promoter DNA hypermethylation plays an important role in Gal-1 downregulation in aged BMSCs, which inhibited β-catenin binding on Gal-1 promoter. Bone loss of aged mice was alleviated in response to in vivo deletion of Dnmt3b from BMSCs. Finally, when bone marrow of young wild-type (WT) mice or young Dnmt3bPrx1-Cre mice was transplanted into aged WT mice, Gal-1 level in serum and trabecular bone mass were elevated in recipient aged WT mice. Our study will benefit for deeper insights into the regulation mechanisms of Gal-1 expression in BMSCs during osteoporosis development, and for the discovery of new therapeutic targets for osteoporosis via modulating DNA methylation status.NEW & NOTEWORTHY There is Dnmt3b-mediated DNA methylation in Gal-1 promoter in aged bone marrow stromal cell (BMSC). DNA methylation causes Gal-1 downregulation and osteogenesis attenuation of aged BMSC. DNA methylation blocks β-catenin binding on Gal-1 promoter. Bone loss of aged mice is alleviated by in vivo deletion of Dnmt3b from BMSC.

Reduced form of Galectin-1 Suppresses Osteoclastic Differentiation of Human Peripheral Blood Mononuclear Cells and Murine RAW264 Cells In Vitro

Galectin-1 (Gal-1) is an evolutionarily conserved sugar-binding protein found in intra- and extracellular spaces. Extracellularly, it binds to glycoconjugates with β-galactoside(s) and functions in various biological phenomena, including immunity, cancer, and differentiation. Under extracellular oxidative conditions, Gal-1 undergoes oxidative inactivation, losing its sugar-binding ability, although it exhibits sugar-independent functions. An age-related decrease in serum Gal-1 levels correlates with decreasing bone mass, and Gal-1 knockout promotes osteoclastic bone resorption and suppresses bone formation. However, the effect of extracellular Gal-1 on osteoclast differentiation remains unclear. Herein, we investigated the effects of extracellular Gal-1 on osteoclastogenesis in human peripheral blood mononuclear cells (PBMCs) and mouse macrophage RAW264 cells. Recombinant Gal-1 suppressed the macrophage colony-stimulating factor and receptor activator of nuclear factor-κB ligand-dependent osteoclast formation, actin ring formation, and bone-resorption activity of human PBMCs. Similar results were obtained for RAW264 cells. Gal-1 knockdown increased osteoclast-like cell formation, suggesting that it affected differentiation in an autocrine-like manner. Oxidized Gal-1 slightly affected differentiation, and in the presence of lactose, the differentiation inhibitory effect of galectin-1 was not observed. These findings suggest that extracellular Gal-1 inhibits osteoclast differentiation in a β-galactoside-dependent manner, and an age-related decrease in serum Gal-1 levels may contribute to reduced osteoclast activity and decreasing bone mass.

Proteomic Analysis Based on TMT Regarding the Therapeutic Action of Rhizoma Drynariae on Rats in an Osteoporosis Model

BACKGROUND

Primary osteoporosis has increasingly become one of the risk factors affecting human health, and the clinical effect and action mechanism of traditional Chinese medicine in the treatment of primary osteoporosis have been widely studied. Previous studies have confirmed that in traditional Chinese medicine (TCM), Drynaria rhizome has a role in improving bone density. In this study, a tandem mass tag (TMT)-based proteomic analysis was conducted to derive potential targets for Drynaria rhizome treatment in postmenopausal osteoporosis.

METHODS

The model group (OVX) and experimental group (OVXDF) for menopausal osteoporosis were established using the universally acknowledged ovariectomy method, and the OVXDF group was given 0.48g/kg Rhizoma Drynariae solution by gavage for 12 weeks. After 12 weeks, femurs of rats selected for this study were examined with a bone mineral density (BMD) test, Micro-CT, ELISABiochemical testing, hematoxylin and eosin (HE) staining, and immunohistochemistry. A certain portion of the bone tissue was studied with a TMT-based proteomic analysis and functional and pathway enrichment analysis. Finally, key target genes were selected for Western blotting for validation.

RESULTS

The comparison of the OVXDF and OVX groups indicated that Drynaria rhizome could improve bone density. In the TMT-based proteomic analysis, the comparison of these two groups revealed a total of 126 differentially expressed proteins (DEPs), of which 62 were upregulated and 64 were downregulated. Further, by comparing the differential genes between the OVXDF and OVX groups and between the OVX and SHAM groups, we concluded that the 27 differential genes were significantly changed in the rats selected for the osteoporosis model after Drynaria rhizome intragastric administration. The gene ontology (GO) enrichment analysis of DEPs showed that molecular function was mainly involved in biological processes, such as glucose metabolism, carbohydrate metabolism, immune responses, and aging. A Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of DEPs revealed that multiple differential genes were enriched in the estrogen and peroxisome proliferator-activated receptor (PPAR) signaling pathways. Relationships with nitrogen metabolism, glycerophospholipid metabolism, secretion systems, and tumor diseases were also observed. Western blotting was consistent with the analysis.

CONCLUSIONS

We used TMT-based proteomics to analyze the positive effects of TCM Drynaria rhizome, which can regulate related proteins through the unique roles of multiple mechanisms, targets, and pathways. This treatment approach can regulate oxidative stress, improve lipid metabolism, reduce the inflammatory response mechanism, and improve bone density. These benefits highlight the unique advantages of TCM in the treatment of primary osteoporosis.

Association of C-type lectin-like receptor 2 and galectin-1 with portal vein system thrombosis in HBV-related liver cirrhosis

Background and aims

Hepatitis B virus (HBV) infection is the most common cause of liver cirrhosis. Portal venous system thrombosis (PVST) is a major complication of liver cirrhosis. Recently, it has been shown that C-type lectin-like receptor 2 (CLEC-2) and galectin-1 participate in the activation and aggregation of platelets, thereby promoting the development of thrombosis. This cross-sectional study aims to evaluate the association of serum CLEC-2 and galectin-1 levels with PVST in patients with HBV-related liver cirrhosis.

Methods

Overall, 65 patients with HBV-related liver cirrhosis were included, of whom 23 had PVST and 42 did not have. Serum CLEC-2 and galectin-1 levels were measured using enzyme-linked immunosorbent assay kits. PVST was assessed by contrast-enhanced computed tomography and/or magnetic resonance imaging scans. Subgroup analyses were conducted according to the degree and location of PVST.

Results

Patients with PVST had significantly higher serum CLEC-2 (p = 0.006) and galectin-1 (p = 0.009) levels than those without. Patients with partial/complete PVST or fibrotic cord (p = 0.007; p = 0.002), but not those with mural PVST (p = 0.199; p = 0.797), had significantly higher serum CLEC-2 and galectin-1 levels than those without PVST. Patients with superior mesenteric vein thrombosis had significantly higher serum CLEC-2 (p = 0.013) and galectin-1 (p = 0.025) levels than those without PVST. Patients with main portal vein thrombosis had higher serum CLEC-2 (p = 0.020) and galectin-1 (p = 0.066) levels than those without PVST, but the difference in serum galectin-1 level was not significant between them.

Conclusion

Serum CLEC-2 and galectin-1 levels may be associated with the presence of PVST in HBV-related cirrhotic patients, but this association should be dependent upon the degree of PVST.

O-GlcNAc-Mediated Regulation of Galectin Expression and Secretion in Human Promyelocytic HL-60 Cells Undergoing Neutrophilic Differentiation

In this study, we have tested the hypothesis that the expression and secretion of galectins are driven through mechanisms globally impacted by homeostatic regulation involving the post-translational modification of intracellular proteins with O-linked N-acetylglucosamine (O-GlcNAc). We showed that neutrophilic differentiation of HL-60 cells induced by all-trans retinoic acid (ATRA) and 6-diazo-5-oxo-L-norleucine (DON) was associated with a significant drop of cellular O-GlcNAc levels in serum-contained and serum-free cell culture media. Galectin gene and protein expression profiles in HL-60 cells were specifically modified by ATRA and by inhibitors of O-GlcNAc cycle enzymes, however overall trends for each drug were similar between cells growing in the presence or absence of serum except for LGALS9 and LGALS12. The secretion of four galectins (-1, -3, -9, and -10) by HL-60 cells in a serum-free medium was stimulated by O-GlcNAc-reducing ATRA and DON while O-GlcNAc-elevating thiamet G (O-GlcNAcase inhibitor) failed to change the basal levels of extracellular galectins. Taken together, these results demonstrate that O-GlcNAc homeostasis is essential not only for regulation of galectin expression in cells but also for the secretion of multiple members of this protein family, which can be an important novel aspect of unconventional secretion mechanisms.

Galectin-1 deletion in mice causes bone loss via impaired osteogenic differentiation potential of BMSCs

Bone formation is dependent on the osteoblasts which are differentiated from bone marrow stromal cells (BMSCs). In addition to potent proliferation, self-renewal, and pluripotent differentiation, BMSCs have been extensively studied due to their low immunogenicity and immunomodulatory effects. Recently, galectin-1 (Gal-1) has been proposed as a potent mediator of immunomodulatory properties of BMSCs. Previous study demonstrated that Gal-1 showed age-related decline in mice serum and serum Gal-1 was positively associated with bone mass in mice. The current study makes attempts to elucidate the functional role of Gal-1 in skeletal system by investigating the regulation of Gal-1 expression during BMSCs osteogenic differentiation and the molecular mechanisms underlying the effects of Gal-1 on BMSCs osteogenic differentiation. In Gal-1 null (-/-) mice, bone loss was observed due to bone formation attenuation. In in vitro experiments, Gal-1 supported the osteogenic differentiation of BMSCs by binding to CD146 to activate Lrp5 expression and Wnt/β-catenin signaling pathway. Meanwhile, there was positive feedback regulation via Wnt/β-catenin signaling to maintain Gal-1 high-level expression during osteogenic differentiation of BMSCs. More importantly, Gal-1 down-regulation in BMSCs and attenuation of osteogenic differentiation potential of BMSCs were observed in aged mice compared with young mice. Gal-1 over-expression could enhance osteogenic differentiation potential of aged BMSCs. Our study will benefit not only for deeper insights into the functional role of Gal-1 but also for finding new targets to modulate BMSCs osteogenic differentiation.

Progressive skeletal defects caused by Kindlin3 deficiency, a model of autosomal recessive osteopetrosis in humans

The cellular and molecular mechanisms of bone development and homeostasis are clinically important, but not fully understood. Mutations in integrins and Kindlin3 in humans known as Leukocyte adhesion deficiencies (LAD) cause a wide spectrum of complications, including osteopetrosis. Yet, the rarity, frequent misdiagnosis, and lethality of LAD preclude mechanistic analysis of skeletal abnormalities in these patients. Here, using inducible and constitutive tissue-specific Kindlin3 knockout (K3KO) mice, we show that the constitutive lack of embryonic-Kindlin3 in myeloid lineage cells causes growth retardation, edentulism, and skull deformity indicative of hydrocephaly. Micro-CT analysis revealed craniosynostosis, choanal stenosis, and micrognathia along with other skeletal abnormalities characteristic of osteopetrosis. A marked progression of osteosclerosis occurs in mature to middle-aged adults, resulting in the narrowing of cranial nerve foramina and bone marrow cavities of long bones. However, postnatal-Kindlin3 is less critical for bone remodeling and architecture. Thus, myeloid Kindlin3 is essential for skeletal development and its deficiency leads to autosomal recessive osteopetrosis (ARO). The study will aid in the diagnosis, management, and treatment choices for patients with LAD-III and ARO.

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.