Inhibiting post-translational core fucosylation prevents vascular calcification in the model of uremia

EVs-miR-17-5p attenuates the osteogenic differentiation of vascular smooth muscle cells potentially via inhibition of TGF-β signaling under high glucose conditions

Vascular calcification, which is a major complication of diabetes mellitus, is an independent risk factor for cardiovascular disease. Osteogenic differentiation of vascular smooth muscle cells (VSMCs) is one of the key mechanisms underlying vascular calcification. Emerging evidence suggests that macrophage-derived extracellular vesicles (EVs) may be involved in calcification within atherosclerotic plaques in patients with diabetes mellitus. However, the role of macrophage-derived EVs in the progression of vascular calcification is largely unknown. In this study, we investigated whether macrophage-derived EVs contribute to the osteogenic differentiation of VSMCs under high glucose conditions. We isolated EVs that were secreted by murine peritoneal macrophages under normal glucose (EVs-NG) or high glucose (EVs-HG) conditions. miRNA array analysis in EVs from murine macrophages showed that miR-17-5p was significantly increased in EVs-HG compared with EVs-NG. Prediction analysis with miRbase identified transforming growth factor β receptor type II (TGF-β RII) as a potential target of miR-17-5p. EVs-HG as well as miR-17-5p overexpression with lipid nanoparticles inhibited the gene expression of Runx2, and TGF-β RII. Furthermore, we demonstrated that VSMCs transfected with miR-17-5p mimic inhibited calcium deposition. Our findings reveal a novel role of macrophage-derived EVs in the negative regulation of osteogenic differentiation in VSMCs under high glucose conditions.

FUT8-Mediated Core Fucosylation Promotes the Pulmonary Vascular Remodeling in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive cardiopulmonary disease with unclear underlying molecular mechanisms and limited therapeutic options. This study aimed to explore the role of core fucosylation and the only glycosyltransferase FUT8 in PAH. We observed increased core fucosylation in a monocrotaline (MCT)-induced PAH rat model and isolated rat pulmonary artery smooth muscle cells (PASMCs) treated with platelet-derived growth factor-BB (PDGF-BB). We found that 2-fluorofucose (2FF), a drug used to inhibit core fucosylation, improved hemodynamics and pulmonary vascular remodeling in MCT-induced PAH rats. In vitro, 2FF effectively restrains the proliferation, migration, and phenotypic switching of PASMCs and promotes apoptosis. Compared with controls, serum FUT8 concentration in PAH patients and MCT-induced rats was significantly elevated. FUT8 expression appeared increased in the lung tissues of PAH rats, and the co-localization of FUT8 with α-SMA was also observed. SiRNA was used to knockdown FUT8 in PASMCs (siFUT8). After effectively silencing FUT8 expression, phenotypic changes induced in PASMCs by PDGF-BB stimulation were alleviated. FUT8 activated the AKT pathway, while the admission of AKT activator SC79 could partially counteract the negative effect of siFUT8 on the proliferation, apoptotic resistance, and phenotypic switching of PASMCs, which may be involved in the core fucosylation of vascular endothelial growth factor receptor (VEGFR). Our research confirmed the critical role of FUT8 and its mediated core fucosylation in pulmonary vascular remodeling in PAH, providing a potential novel therapeutic target for PAH.

Role of Glycosylation in Vascular Calcification

Glycosylation is an important step in post-translational protein modification. Altered glycosylation results in an abnormality that causes diseases such as malignancy and cardiovascular diseases. Recent emerging evidence highlights the importance of glycosylation in vascular calcification. Two major types of glycosylation, N-glycosylation and O-glycosylation, are involved in vascular calcification. Other glycosylation mechanisms, which polymerize the glycosaminoglycan (GAG) chain onto protein, resulting in proteoglycan (PG), also have an impact on vascular calcification. This paper discusses the role of glycosylation in vascular calcification.

Blocking core fucosylation of epidermal growth factor (EGF) receptor prevents peritoneal fibrosis progression

OBJECTIVE

Peritoneal fibrosis (PF) ultimately causes ultrafiltration failure and peritoneal dialysis (PD) termination, but there are few effective therapies for it. Core fucosylation, which is catalyzed by α1,6-fucosyltransferase (Fut8) in mammals, may play a crucial role in PF development. This study aims to assess the effects of inhibiting core fucosylation of epidermal growth factor (EGF) receptor on PF rats.

METHODS

PF rats (established by 4.25% glucose dialysate) were treated with either an adenovirus-Fut8 short hairpin RNA (Fut8shRNA) or adenovirus-control. Masson's staining and net ultrafiltration were performed at week six. Fut8 level and core fucosylation of EGF receptor and collagen I in the peritoneal membrane were assessed, and EGF signaling was detected, including signal transducer and activator of transcription 3 (STAT3), nuclear factor kappa B (NF-κB) and their phosphorylation. Monocyte chemoattractant protein-1 (MCP-1) in peritoneal effluent was examined.

RESULTS

Fut8 was upregulated in PF rats but decreased after Fut8shRNA treatment. EGF and EGF receptor expression was upregulated in PF rats, while core fucosylation of EGF receptor decreased after Fut8shRNA treatment. Masson's staining results showed an increase in peritoneal thickness in PF rats but a decrease after Fut8shRNA treatment. Fut8shRNA treatment increased net ultrafiltration, reduced the expression of collagen I and MCP-1 compared to PF rats. Fut8shRNA treatment suppressed phosphorylation of STAT3 and NF-κB in the peritoneal membrane of PF rats.

CONCLUSIONS

Fut8shRNA treatment ameliorated the fibrotic changes in PF rats. A potential mechanism may be that Fut8shRNA treatment inactivated EGF signaling pathway by suppressing the phosphorylation of STAT3 and NF-κB.

Up-regulation of FUT8 inhibits TGF-β1-induced activation of hepatic stellate cells during liver fibrogenesis

Liver fibrosis is a continuous wound healing response caused by chronic liver injury, and the activation of hepatic stellate cells (HSCs) is considered as the main event for it. Core fucosylation catalyzed by FUT8 refers to adding the fucosyl moiety to the innermost GlcNAc residue of N-linked oligosaccharides and is involved in many biological processes such as cell differentiation, migration, and signaling transduction. Aberrant core fucosylation is associated with a variety of diseases including cardiovascular disease, tumors and neuroinflammation, but much less is understood in liver fibrosis. Herein, we reported FUT8 mRNA level was increased in patients with liver fibrosis from GEO database and positively correlated with fibrosis progression. FUT8 expression and the core fucosylation were also elevated in TAA-induced mouse liver fibrosis model, and were mainly distributed in the fibrous septum of mouse liver. TGF-β1, as the most pro-fibrogenic cytokine, could promote the expression of FUT8 and total core fucosylation levels in HSCs in vitro. However, up-regulation of FUT8 in turn inhibited TGF-β1-induced trans-differentiation, migration and pro-fibrogenic signaling pathways in HSCs. In conclusion, our results suggest that the up-regulation of FUT8 inhibits TGF-β1-induced HSC activation in a negative feedback loop, and provide potential new therapeutic strategy for liver fibrosis by targeting FUT8.

Dermal Alterations in Clinically Unaffected Skin of Pseudoxanthoma elasticum Patients

Background: Pseudoxanthoma elasticum (PXE), due to rare sequence variants in the ABCC6 gene, is characterized by calcification of elastic fibers in several tissues/organs; however, the pathomechanisms have not been completely clarified. Although it is a systemic disorder on a genetic basis, it is not known why not all elastic fibers are calcified in the same patient and even in the same tissue. At present, data on soft connective tissue mineralization derive from studies performed on vascular tissues and/or on clinically affected skin, but there is no information on patients’ clinically unaffected skin. Methods: Skin biopsies from clinically unaffected and affected areas of the same PXE patient (n = 6) and from healthy subjects were investigated by electron microscopy. Immunohistochemistry was performed to evaluate p-SMAD 1/5/8 and p-SMAD 2/3 expression and localization. Results: In clinically unaffected skin, fragmented elastic fibers were prevalent, whereas calcified fibers were only rarely observed at the ultrastructural level. p-SMAD1/5/8 and p-SMAD2/3 were activated in both affected and unaffected skin. Conclusion: These findings further support the concept that fragmentation/degradation is necessary but not sufficient to cause calcification of elastic fibers and that additional local factors (e.g., matrix composition, mechanical forces and mesenchymal cells) contribute to create the pro-osteogenic environment.

Spatial N-glycomics of the human aortic valve in development and pediatric endstage congenital aortic valve stenosis

Congenital aortic valve stenosis (AS) progresses as an obstructive narrowing of the aortic orifice due to deregulated extracellular matrix (ECM) production by aortic valve (AV) leaflets and leads to heart failure with no effective therapies. Changes in glycoprotein and proteoglycan distribution are a hallmark of AS, yet valvular carbohydrate content remains virtually uncharacterized at the molecular level. While almost all glycoproteins clinically linked to stenotic valvular modeling contain multiple sites for N-glycosylation, there are very few reports aimed at understanding how N-glycosylation contributes to the valve structure in disease. Here, we tested for spatial localization of N-glycan structures within pediatric congenital aortic valve stenosis. The study was done on valvular tissues 0-17 years of age with de-identified clinical data reporting pre-operative valve function spanning normal development, aortic valve insufficiency (AVI), and pediatric endstage AS. High mass accuracy imaging mass spectrometry (IMS) was used to localize N-glycan profiles in the AV structure. RNA-Seq was used to identify regulation of N-glycan related enzymes. The N-glycome was found to be spatially localized in the normal aortic valve, aligning with fibrosa, spongiosa or ventricularis. In AVI diagnosed tissue, N-glycans localized to hypertrophic commissures with increases in pauci-mannose structures. In all valve types, sialic acid (N-acetylneuraminic acid) N-glycans were the most abundant N-glycan group. Three sialylated N-glycans showed common elevation in AS independent of age. On-tissue chemical methods optimized for valvular tissue determined that aortic valve tissue sialylation shows both α2,6 and α2,3 linkages. Specialized enzymatic strategies demonstrated that core fucosylation is the primary fucose configuration and localizes to the normal fibrosa with disparate patterning in AS. This study identifies that the human aortic valve structure is spatially defined by N-glycomic signaling and may generate new research directions for the treatment of human aortic valve disease.

Inhibition of vascular calcification by microRNA-155-5p is accompanied by the inactivation of TGF-β1/Smad2/3 signaling pathway

Vascular calcification (VC) is a vital factor for cardiovascular morbidity and mortality. Accumulating data suggest that microRNA (miR) is implicated in the VC. The main purpose of this study is to study the influence of miR-155-5p overexpression on VC development in vitro and in vivo. Immunofluorescence staining, real-time PCR, alizarin red staining, alkaline phosphatase (ALP) activity assay, western blot, luciferase assay, hematoxylin-eosin (HE), Masson's trichrome staining, and calcium content assay were used in this research. The results showed that miR-155-5p was decreased in the rat vascular smooth muscle cells (rVSMCs) undergoing calcification in vitro. MiR-155-5p overexpression reversed the increase of calcification and ALP activity in calcified cells. Further, overexpression of miR-155-5p inhibited the transforming growth factor-β1 (TGF-β1)/Smad2/3 signaling pathway, as evidenced by decreased protein expression of TGF-β1, pSmad-2 and pSmad-3 in rVSMCs. MiR-155-5p was showed to target Smad2 directly. Moreover, miR-155-5p upregulation reduced vascular thickening, fibrosis and calcium content of aorta abdominalis in CaCl₂-mediated VC model. Collectively, our results suggest that miR-155-5p overexpression may inhibit VC development through suppressing TGF-β1/Smad2/3 signaling pathway in vivo and in vitro, indicating that miR-155-5p may act as a potential therapeutic target for VC-related disease.

TGF-β receptors: In and beyond TGF-β signaling

Transforming growth factor β (TGF-β) plays an important role in normal development and homeostasis. Dysregulation of TGF-β responsiveness and its downstream signaling pathways contribute to many diseases, including cancer initiation, progression, and metastasis. TGF-β ligands bind to three isoforms of the TGF-β receptor (TGFBR) with different affinities. TGFBR1 and 2 are both serine/threonine and tyrosine kinases, but TGFBR3 does not have any kinase activity. They are necessary for activating canonical or noncanonical signaling pathways, as well as for regulating the activation of other signaling pathways. Another prominent feature of TGF-β signaling is its context-dependent effects, temporally and spatially. The diverse effects and context dependency are either achieved by fine-tuning the downstream components or by regulating the expressions and activities of the ligands or receptors. Focusing on the receptors in events in and beyond TGF-β signaling, we review the membrane trafficking of TGFBRs, the kinase activity of TGFBR1 and 2, the direct interactions between TGFBR2 and other receptors, and the novel roles of TGFBR3.

Exosomes, the message transporters in vascular calcification

Vascular calcification (VC) is caused by hydroxyapatite deposition in the intimal and medial layers of the vascular wall, leading to severe cardiovascular events in patients with hypertension, chronic kidney disease and diabetes mellitus. VC occurrences involve complicated mechanism networks, such as matrix vesicles or exosomes production, osteogenic differentiation, reduced cell viability, aging and so on. However, with present therapeutic methods targeting at VC ineffectively, novel targets for VC treatment are demanded. Exosomes are proven to participate in VC and function as initializers for mineral deposition. Secreted exosomes loaded with microRNAs are also demonstrated to modulate VC procession in recipient vascular smooth muscle cells. In this review, we targeted at the roles of exosomes during VC, especially at their effects on transporting biological information among cells. Moreover, we will discuss the potential mechanisms of exosomes in VC.

Blocking Posttranslational Core Fucosylation Ameliorates Rat Peritoneal Mesothelial Cell Epithelial-Mesenchymal Transition

Background:

Core fucosylation (CF), catalyzed by α-1,6 fucosyltransferase (Fut8) in mammals, plays an important role in pathological processes through posttranslational modification of key signaling receptor proteins, including transforming growth factor (TGF)-β receptors and platelet-derived growth factor (PDGF) receptors. However, its effect on peritoneal fibrosis is unknown. Here, we investigated its influence on epithelial-mesenchymal transition (EMT) of rat peritoneal mesothelial cells (PMCs) in vitro induced by a high-glucose (HG) culture solution.

Methods:

Rat PMCs were first cultured in a HG (2.5%) culture solution to observe the CF expression level (fluorescein isothiocyanate-lens culinaris agglutinin), we next established a knockdown model of rat PMCs in vitro with Fut8 small interfering RNA (siRNA) to observe whether inhibiting CF decreases the messenger RNA (mRNA) expression and protein expression of Fut8 and reverses EMT status. Rat PMCs were randomly divided into control group, mock group (transfected with scrambled siRNA), Fut8 siRNA group, HG group, HG + mock group, and HG + Fut8 siRNA group. Finally, we examined the activation of TGF-β/Smad2/3 signaling and PDGF/extracellular signal-regulated kinase (ERK) signaling to observe the influence of CF on them.

Results:

CF, Fut8 mRNA, and protein expression were all significantly upregulated in HG- induced EMT model than those in the control rat PMCs (P < 0.05). Fut8 siRNA successfully blocked CF of TGF-β receptors and PDGF receptors and attenuated the EMT status (E-cadherin and α-SMA and phenotypic changes) in HG-induced rat PMCs. In TGF-β/Smad2/3 signaling, Fut8 siRNA did not suppress the protein expression of TGF-β receptors and Smad2/3; however, it significantly suppressed the phosphorylation of Smad2/3 (relative expression folds of HG + Fut8 group vs. HG group: 7.6 ± 0.4 vs. 15.1 ± 0.6, respectively, P < 0.05). In PDGF/ERK signaling, Fut8 siRNA did not suppress the protein expression of PDGF receptors and ERK, but it significantly suppressed the phosphorylation of ERK (relative expression folds of HG + Fut8 group vs. HG group: 8.7 ± 0.9 vs. 15.6 ± 1.2, respectively, P < 0.05). Blocking CF inactivated the activities of TGF-β and PDGF signaling pathways, and subsequently blocked EMT.

Conclusions:

These results demonstrate that CF contributes to rat PMC EMT, and that blocking it attenuates EMT. CF regulation is a potential therapeutic target of peritoneal fibrosis.

Glycosylation as a Main Regulator of Growth and Death Factor Receptors Signaling

Glycosylation is a very frequent and functionally important post-translational protein modification that undergoes profound changes in cancer. Growth and death factor receptors and plasma membrane glycoproteins, which upon activation by extracellular ligands trigger a signal transduction cascade, are targets of several molecular anti-cancer drugs. In this review, we provide a thorough picture of the mechanisms bywhich glycosylation affects the activity of growth and death factor receptors in normal and pathological conditions. Glycosylation affects receptor activity through three non-mutually exclusive basic mechanisms: (1) by directly regulating intracellular transport, ligand binding, oligomerization and signaling of receptors; (2) through the binding of receptor carbohydrate structures to galectins, forming a lattice thatregulates receptor turnover on the plasma membrane; and (3) by receptor interaction with gangliosides inside membrane microdomains. Some carbohydrate chains, for example core fucose and β1,6-branching, exert a stimulatory effect on all receptors, while other structures exert opposite effects on different receptors or in different cellular contexts. In light of the crucial role played by glycosylation in the regulation of receptor activity, the development of next-generation drugs targeting glyco-epitopes of growth factor receptors should be considered a therapeutically interesting goal.