N-Glycomics of Human Erythrocytes

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2021-2022

The use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the analysis of carbohydrates and glycoconjugates is a well-established technique and this review is the 12th update of the original article published in 1999 and brings coverage of the literature to the end of 2022. As with previous review, this review also includes a few papers that describe methods appropriate to analysis by MALDI, such as sample preparation, even though the ionization method is not MALDI. The review follows the same format as previous reviews. It is divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of computer software for structural identification. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other general areas such as medicine, industrial processes, natural products and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. MALDI is still an ideal technique for carbohydrate analysis, particularly in its ability to produce single ions from each analyte and advancements in the technique and range of applications show little sign of diminishing.

Autoimmune Hemolytic Anemia Caused by Cold Agglutinin Antibodies in Systemic Lupus erythematosus-a Rare Association: Case Report

Autoimmune hemolytic anemias (AIHAs) are rare and heterogeneous disorders characterized by the destruction of red blood cells by warm or cold antibodies. Hemolytic anemia associated with warm antibodies is the most common, whereas cold antibodies are rare and infrequent in cases published in the scientific literature. Herein, we present the case of a young patient with systemic lupus erythematosus (SLE) and autoimmune hemolytic anemia caused by cold antibodies. Initially, infectious etiology and hematological malignancy were considered, which were ruled out. She required management in the intensive care unit due to severe hematological involvement and responded well to immunomodulatory therapy. This case illustrates the importance of a strong clinical suspicion of AIHA due to cold agglutinins associated with SLE when faced with similar clinical symptoms in order to achieve a timely diagnosis and provide optimal therapy.

O-GlcNAcylation of RIPK1 rescues red blood cells from necroptosis

Necroptosis is a type of cell death with excessive inflammation and organ damage in various human diseases. Although abnormal necroptosis is common in patients with neurodegenerative, cardiovascular, and infectious diseases, the mechanisms by which O-GlcNAcylation contributes to the regulation of necroptotic cell death are poorly understood. In this study, we reveal that O-GlcNAcylation of RIPK1 (receptor-interacting protein kinase1) was decreased in erythrocytes of the mouse injected with lipopolysaccharide, resulting in the acceleration of erythrocyte necroptosis through increased formation of RIPK1-RIPK3 complex. Mechanistically, we discovered that O-GlcNAcylation of RIPK1 at serine 331 in human (corresponding to serine 332 in mouse) inhibits phosphorylation of RIPK1 at serine 166, which is necessary for the necroptotic activity of RIPK1 and suppresses the formation of the RIPK1-RIPK3 complex in Ripk1 ^-/- MEFs. Thus, our study demonstrates that RIPK1 O-GlcNAcylation serves as a checkpoint to suppress necroptotic signaling in erythrocytes.

N-glycans Profiling in Pilocarpine Induced Status Epilepticus in Immature Rats

Status epilepticus (SE) is a common neurological emergency in children and a well-known epileptogenic insult. Neonates are extremely susceptible to seizures in the neonatal period due to the higher vulnerability. Neonatal SE is associated with significant mortality and morbidity. There is an evident need for attention on neonatal SE in research due to the incredibly limited diagnostic and treatment options in current neonatology, and its serious long-term consequences. The aim of the present study was to characterize the glycoprofiles in the pilocarpine-induced SE model in immature rats to assess the overall N-glycans composition. To induce lithium-pilocarpine (Li-Pilo) SE male Wistar rat pups were pretreated with lithium chloride (127 mg/kg, n=11) on the 11th postnatal day. After 24 hours, the lithium pre-treated pups were administered either with pilocarpine intraperitoneally (i.p.) (35 kg/g, n=6) or saline (n=5) in the control group (Control). On the 19th postnatal day, serum was collected and the analytical procedures were done by mass spectrometry (MS) analytics on matrix-assisted laser desorption/ionization in combination with a time-of-flight detector (MALDI-TOF/MS). Analyzed data were processed by FlexAnalysis (Bruker Daltonics) and GlycoWorkbench software. There were 21 N-glycans that were identified, appointed, and sorted with special emphasis on their structure. We have demonstrated the significant changes in terms of N-glycans sialylation in Li-Pilo compared to the Control. We also observed some other remodelation trends in different portions of relative intenstities of N-glycan clusters according to their glycan type. Our preliminary findings have laid the foundation for additional investigation into glycosylation alterations in the SE in immature rats.

Sialylated N-glycans mediate monocyte uptake of extracellular vesicles secreted from Plasmodium falciparum-infected red blood cells

Glycoconjugates on extracellular vesicles (EVs) play a vital role in internalization and mediate interaction as well as regulation of the host immune system by viruses, bacteria, and parasites. During their intraerythrocytic life-cycle stages, malaria parasites, Plasmodium falciparum (Pf) mediate the secretion of EVs by infected red blood cells (RBCs) that carry a diverse range of parasitic and host-derived molecules. These molecules facilitate parasite-parasite and parasite-host interactions to ensure parasite survival. To date, the number of identified Pf genes associated with glycan synthesis and the repertoire of expressed glycoconjugates is relatively low. Moreover, the role of Pf glycans in pathogenesis is mostly unclear and poorly understood. As a result, the expression of glycoconjugates on Pf-derived EVs or their involvement in the parasite life-cycle has yet to be reported. Herein, we show that EVs secreted by Pf-infected RBCs carry significantly higher sialylated complex N-glycans than EVs derived from healthy RBCs. Furthermore, we reveal that EV uptake by host monocytes depends on N-glycoproteins and demonstrate that terminal sialic acid on the N-glycans is essential for uptake by human monocytes. Our results provide the first evidence that Pf exploits host sialylated N-glycans to mediate EV uptake by the human immune system cells.