Glycosylation inhibitors efficiently inhibit P-selectin-mediated cell adhesion to endothelial cells

Glycosylation of blood cells during the onset and progression of atherosclerosis and myocardial infarction

Protein glycosylation controls cell-cell and cell-extracellular matrix (ECM) communication in immune, vascular, and inflammatory processes, underlining the critical role of this process in the identification of disease biomarkers and the design of novel therapies. Emerging evidence highlights the critical role of blood cell glycosylation in the pathophysiology of atherosclerosis (ATH) and myocardial infarction (MI). Here, we review the role of glycosylation in the interplay between blood cells, particularly erythrocytes, and endothelial cells (ECs), highlighting the involvement of this critical post/cotranslational modification in settings of cardiovascular disease (CVD). Importantly, we focus on emerging preclinical studies and clinical trials based on glycan-targeted drugs to validate their therapeutic potential. These findings may help establish new trends in preventive medicine and delineate novel targeted therapies in CVD.

Elevated glycosylation of CD36 in platelets is a risk factor for oxLDL-mediated platelet activation in type 2 diabetes

Platelet activation and related cardiovascular complications are the hallmarks of type 2 diabetes (T2D). We investigated the mechanism of platelet activation in T2D using MS-based identification of differentially expressed platelet proteins with a focus on glycosylated forms. Glycosylation is considered one of the common post-translational modifications in T2D, and N/O-linked glycosylation of glycoproteins (GPs)/integrins is known to play crucial roles in platelet activation. Our platelet proteome data revealed elevated levels of GPs GPIbα, GPIIbIIIa, GPIV (CD36), GPV and integrins in T2D patients. T2D platelets had elevated N-linked glycosylation of CD36 at asparagine (Asn)408,417 . Enrichment analysis revealed a close association of glycosylated CD36 with thrombospondin-1, fibrinogen and SERPINA1 in T2D platelets. The glycosylation of CD36 has previously been reported to increase cellular uptake of long-chain fatty acids. Our in silico molecular docking data also showed a favorable binding of cholesterol with glycosylated Asn417 CD36 compared to the non-glycosylated form. We further investigated the CD36:LDL cholesterol axis in T2D. Elevated levels of oxidized-low density lipoprotein (oxLDL) were found to cause significant platelet activation via CD36-mediated stimulation of Lyn-JNK signaling. Sulfo-N-succinimidyl oleate, an inhibitor of CD36, effectively inhibited oxLDL-mediated platelet activation and adhesion in vitro. Our study suggests increased glycosylation of CD36 in T2D platelets as a potential route for oxLDL-mediated platelet activation. The oxLDL:CD36 axis may thus be exploited as a prospective target to develop therapeutics against thrombosis in T2D.

Advances in protein glycosylation and its role in tissue repair and regeneration

After tissue damage, a series of molecular and cellular events are initiated to promote tissue repair and regeneration to restore its original structure and function. These events include inter-cell communication, cell proliferation, cell migration, extracellular matrix differentiation, and other critical biological processes. Glycosylation is the crucial conservative and universal post-translational modification in all eukaryotic cells [1], with influential roles in intercellular recognition, regulation, signaling, immune response, cellular transformation, and disease development. Studies have shown that abnormally glycosylation of proteins is a well-recognized feature of cancer cells, and specific glycan structures are considered markers of tumor development. There are many studies on gene expression and regulation during tissue repair and regeneration. Still, there needs to be more knowledge of complex carbohydrates' effects on tissue repair and regeneration, such as glycosylation. Here, we present a review of studies investigating protein glycosylation in the tissue repair and regeneration process.

Platelets and Defective N-Glycosylation

N-glycans are covalently linked to an asparagine residue in a simple acceptor sequence of proteins, called a sequon. This modification is important for protein folding, enhancing thermodynamic stability, and decreasing abnormal protein aggregation within the endoplasmic reticulum (ER), for the lifetime and for the subcellular localization of proteins besides other functions. Hypoglycosylation is the hallmark of a group of rare genetic diseases called congenital disorders of glycosylation (CDG). These diseases are due to defects in glycan synthesis, processing, and attachment to proteins and lipids, thereby modifying signaling functions and metabolic pathways. Defects in N-glycosylation and O-glycosylation constitute the largest CDG groups. Clotting and anticlotting factor defects as well as a tendency to thrombosis or bleeding have been described in CDG patients. However, N-glycosylation of platelet proteins has been poorly investigated in CDG. In this review, we highlight normal and deficient N-glycosylation of platelet-derived molecules and discuss the involvement of platelets in the congenital disorders of N-glycosylation.

P-selectin blockade ameliorates lupus nephritis in MRL/lpr mice through improving renal hypoxia and evaluation using BOLD-MRI

BACKGROUND

Lupus nephritis is one of the most common and severe complications of systemic lupus erythematosus, of which poor prognosis is indicated by aggravated renal hypoxia and tubulointerstitial fibrosis. Cell adhesion molecules play a key role in the progression of lupus nephritis tubulointerstitial lesion, including P-selectin, which mediates the rolling of leukocytes and subsequent adhesion and infiltration and then initiates the inflammatory immune response and ischemia and hypoxia injury. However, the effects and mechanisms of P-selectin in lupus nephritis remain to be investigated, and a noninvasive measurement of lupus nephritis tubulointerstitial hypoxia and fibrosis remains to be explored.

METHODS

Thirty-four MRL/lpr mice were randomly divided into the following three groups: MRL/lpr, saline, and anti-P-selectin, which consisted of no treatment, treatment with normal saline, and treatment with anti-P-selectin monoclonal antibody (mAb) from 12 to 16 weeks of age, respectively. Ten male C57BL/6 mice of the same age served as normal controls. 24-h urinary protein, urinary albumin-creatinine ratio, and periodic acid-Schiff were used to assess kidney damage; Western blot or immunohistochemical staining of the hypoxia probe Hypoxyprobe™-1, hypoxia-inducible factor 1α (HIF-1α), and CD31 were used to evaluate hypoxia in renal tissue; and NADPH oxidase subunit gp91phox and p22phox were used to examine renal oxidative stress. The correlation between kidney injury and blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) was calculated to assess the clinical value of BOLD-MRI.

RESULTS

P-selectin is upregulated in lupus nephritis. Blocking P-selectin with mAb alleviated renal tubulointerstitial fibrosis, renal hypoxia, and peritubular capillary loss, without alteration of the levels of lupus activity indicators, anti-dsDNA antibody, or complement C3. BOLD-MRI showed that the reduced R2* values in the renal cortex and medulla of lupus mice were increased when treated with anti-P-selectin mAb as compared with those treated with normal saline, which were negatively correlated with Hypoxyprobe™-1 hypoxia probe and the expression of HIF-1α.

CONCLUSIONS

Early intervention of lupus nephritis with anti-P-selectin mAb can significantly improve the hypoxic state of the kidney and reduce the severity of tubulointerstitial lesions. BOLD-MRI techniques are noninvasive and can dynamically evaluate the changes in renal lesions and intrarenal oxygenation levels before and after treatment in lupus nephritis.

CDG and immune response: From bedside to bench and back

Glycosylation is an essential biological process that adds structural and functional diversity to cells and molecules, participating in physiological processes such as immunity. The immune response is driven and modulated by protein-attached glycans that mediate cell-cell interactions, pathogen recognition and cell activation. Therefore, abnormal glycosylation can be associated with deranged immune responses. Within human diseases presenting immunological defects are congenital disorders of glycosylation (CDG), a family of around 130 rare and complex genetic diseases. In this review, we have identified 23 CDG with immunological involvement, characterized by an increased propensity to-often life-threatening-infection. Inflammatory and autoimmune complications were found in 7 CDG types. CDG natural history(ies) and the mechanisms behind the immunological anomalies are still poorly understood. However, in some cases, alterations in pathogen recognition and intracellular signaling (eg, TGF-β1, NFAT, and NF-κB) have been suggested. Targeted therapies to restore immune defects are only available for PGM3-CDG and SLC35C1-CDG. Fostering research on glycoimmunology may elucidate the involved pathophysiological mechanisms and open new therapeutic avenues, thus improving CDG patients' quality of life.

Synthesis of Sialyl LewisX Glycomimetics Bearing a Bicyclic 3- O,4- C-Fused Galactopyranoside Scaffold

Reported herein is the synthesis of sialyl Lewis^X analogues bearing a trans-bicyclo[4.4.0] dioxadecane-modified 3- O,4- C-fused galactopyranoside scaffold that locks the carboxylate pharmacophore in either the axial or equatorial position. This novel series of bicyclic galactopyranosides are prepared through a stereocontrolled intramolecular cyclization reaction that has been evaluated both experimentally and by density functional theory calculations. The cyclization precursors are obtained from β-d-galactose pentaacetate in a nine-step sequence featuring a highly diastereoselective equatorial alkynylation and Cu(I) catalyzed formation of the acetylenic α-ketoester moiety. Preliminary biological evaluations indicate improved activity as P-selectin antagonists for the axially configured analogues as compared to their equatorial counterparts.

Serum of sickle cell disease patients contains fetal hemoglobin silencing factors secreted from leukocytes

BACKGROUND

The mechanisms that regulate fetal hemoglobin (HbF) expression in sickle cell disease (SCD) remain elusive. We previously showed that steady-state SCD patients with high HbF levels due to a γ-globin gene mutation demonstrate strong inverse correlations between HbF levels and leukocyte counts, suggesting that leukocytes play a role in regulating HbF in SCD.

MATERIALS AND METHODS

To further investigate the role of leukocytes in HbF expression in SCD, we examined the presence of HbF silencing factors in the serum of 82 SCD patients who received hydroxyurea (HU) therapy.

RESULTS

HU-mediated HbF induction was associated with elevated total hemoglobin levels and improved red blood cell parameters, but there was no correlation with reticulocyte or platelet counts. Importantly, we again found that HU-induced HbF levels correlated with reductions in both neutrophils and lymphocytes/monocytes, indicating that these cell lineages may have a role in regulating HU-mediated HbF expression. Our in vitro studies using CD34+-derived primary erythroblasts found that patient serum preparations include HbF silencing factors that are distinct from granulocyte-macrophage colony-stimulating factor, and the activity of such factors decreases upon HU therapy.

CONCLUSION

Together, these results demonstrate the importance of leukocyte numbers in the regulation of HbF levels for SCD patients both in steady state and under HU therapy, and that leukocytes secrete HbF silencing factors that negatively affect HbF expression in erythroid-lineage cells in SCD.

Alternatively-Activated Macrophages Upregulate Mesothelial Expression of P-Selectin to Enhance Adhesion of Ovarian Cancer Cells

Peritoneal metastasis of high-grade serous ovarian cancer (HGSOC) occurs when tumor cells suspended in ascites adhere to mesothelial cells. Despite the strong relationship between metastatic burden and prognosis in HGSOC, there are currently no therapies specifically targeting the metastatic process. We utilized a coculture model and multivariate analysis to examine how interactions between tumor cells, mesothelial cells, and alternatively-activated macrophages (AAM) influence the adhesion of tumor cells to mesothelial cells. We found that AAM-secreted MIP-1β activates CCR5/PI3K signaling in mesothelial cells, resulting in expression of P-selectin on the mesothelial cell surface. Tumor cells attached to this de novo P-selectin through CD24, resulting in increased tumor cell adhesion in static conditions and rolling underflow. C57/BL6 mice treated with MIP-1β exhibited increased P-selectin expression on mesothelial cells lining peritoneal tissues, which enhanced CaOV3 adhesion ex vivo and ID8 adhesion in vivo Analysis of samples from patients with HGSOC confirmed increased MIP-1β and P-selectin, suggesting that this novel multicellular mechanism could be targeted to slow or stop metastasis in HGSOC by repurposing anti-CCR5 and P-selectin therapies developed for other indications.Significance: This study reports novel insights on the peritoneal dissemination occurring during progression of ovarian cancer and has potential for therapeutic intervention.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/13/3560/F1.large.jpg Cancer Res; 78(13); 3560-73. ©2018 AACR.

Bovine P-selectin mediates leukocyte adhesion and is highly polymorphic in dairy breeds

Bovine P-selectin (SELP) mediates leukocyte rolling and primes leukocyte adhesion to endothelium, both essential for leukocyte recruitment to an infection site. We investigated SELP-mediated adhesion between bovine peripheral blood leukocytes (PBLs) and cultured bovine aortic endothelial cells pre-activated with lipopolysaccharide (LPS). We examined gene polymorphism for bovine selectins SELP, l-selectin (SELL) and E-selectin (SELE) and compared their SNP frequency between five dairy breeds (Holstein, Friesian, Jersey, Ayrshire and Brown Swiss). LPS treatment caused a rapid (10min) and slower (4h) enhancement of PBL adhesion (P<0.01). Antibody blocking of SELP inhibited LPS induced cell adhesion. SELP was highly polymorphic, with 9 of the 13 SNPs in its exons, whereas only three synonymous SNPs in SELL and one in SELE. The resulting amino acid changes for the three missense SELP SNP were located in the lectin domain and in two consensus repeat (CR) regions, CR2 and CR5. The Val475Met variant locus in the CR4 and CR5 linking region was very close to a predicted N-acetyl-d-glucosamine glycosylation site, which is likely to influence SELP function. The AA genotype was under-represented, only being found in 1% of 373 heifers genotyped from the 5 breeds (P=0.056), suggesting that AA homozygous animals carrying the Val475Met substitution for SELP may have compromised development. Our study thus confirmed that SELP mediates the attachment of PBL to endothelium and provides novel evidence that its high polymorphism is likely to affect biological function. This may potentially influence leukocyte migration and fertility, both key to successful performance in dairy cows.

Nitric Oxide-cGMP Signaling Stimulates Erythropoiesis through Multiple Lineage-Specific Transcription Factors: Clinical Implications and a Novel Target for Erythropoiesis

Much attention has been directed to the physiological effects of nitric oxide (NO)-cGMP signaling, but virtually nothing is known about its hematologic effects. We reported for the first time that cGMP signaling induces human γ-globin gene expression. Aiming at developing novel therapeutics for anemia, we examined here the hematologic effects of NO-cGMP signaling in vivo and in vitro. We treated wild-type mice with NO to activate soluble guanylate cyclase (sGC), a key enzyme of cGMP signaling. Compared to untreated mice, NO-treated mice had higher red blood cell counts and total hemoglobin but reduced leukocyte counts, demonstrating that when activated, NO-cGMP signaling exerts hematopoietic effects on multiple types of blood cells in vivo. We next generated mice which overexpressed rat sGC in erythroid and myeloid cells. The forced expression of sGCs activated cGMP signaling in both lineage cells. Compared with non-transgenic littermates, sGC mice exhibited hematologic changes similar to those of NO-treated mice. Consistently, a membrane-permeable cGMP enhanced the differentiation of hematopoietic progenitors toward erythroid-lineage cells but inhibited them toward myeloid-lineage cells by controlling multiple lineage-specific transcription factors. Human γ-globin gene expression was induced at low but appreciable levels in sGC mice carrying the human β-globin locus. Together, these results demonstrate that NO-cGMP signaling is capable of stimulating erythropoiesis in both in vitro and vivo settings by controlling the expression of multiple lineage-specific transcription factors, suggesting that cGMP signaling upregulates erythropoiesis at the level of gene transcription. The NO-cGMP signaling axis may constitute a novel target to stimulate erythropoiesis in vivo.

P-selectin gene polymorphism associates with pulmonary hypertension in congenital heart disease

OBJECTIVE

To investigate the relationship between P-selectin gene polymorphism and congenital heart disease (CHD) with pulmonary hypertension (PAH).

METHODS

58 CHD patients with PAH (PAH-CHD), 43 CHD patients without PAH and 205 healthy subjects were included in this study. The concentration of plasma P-selectin was determined by ELISA kits; the direct sequencing of PCR products was used to analyze the P-selectin genotypes.

RESULTS

The concentration of plasma P-selectin was markedly higher in PAH-CHD patients than that in CHD subjects and controls, while no difference was observed between CHD group and control. A significant difference of P-selectin genotype -825T/C polymorphism was observed between patients with PAH-CHD and healthy subjects (P<0.05). Logistic analysis showed that the subjects with haplotypes A-G and G-G had lower risk of PAH-CHD compared with the ones with haplotype A-A (OR=0.47, 95% CI=0.24-0.92). In the subjects of PAH-CHD and control, plasma P-selectin concentration was higher in subjects with -825TT genotype than the ones with haplotypes T-C and C-C (P<0.05).

CONCLUSION

P-selectin probably involves in the development of PAH-CHD. The polymorphism of -825T/C is associated with the risk of PAH-CHD, and may be one of its risk factors.