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Cao Y, Rische CH, Bochner BS, O’Sullivan JA. Interactions between Siglec-8 and endogenous sialylated cis ligands restrain cell death induction in human eosinophils and mast cells. Front Immunol 2023; 14:1283370. [PMID: 37928558 PMCID: PMC10623328 DOI: 10.3389/fimmu.2023.1283370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 10/06/2023] [Indexed: 11/07/2023] Open
Abstract
Sialic acid-binding immunoglobulin-like lectin (Siglec)-8 is a sialoside-binding receptor expressed by eosinophils and mast cells that exhibits priming status- and cell type-dependent inhibitory activity. On eosinophils that have been primed with IL-5, GM-CSF, or IL-33, antibody ligation of Siglec-8 induces cell death through a pathway involving the β2 integrin-dependent generation of reactive oxygen species (ROS) via NADPH oxidase. In contrast, Siglec-8 engagement on mast cells inhibits cellular activation and mediator release but reportedly does not impact cell viability. The differences in responses between cytokine-primed and unprimed eosinophils, and between eosinophils and mast cells, to Siglec-8 ligation are not understood. We previously found that Siglec-8 binds to sialylated ligands present on the surface of the same cell (so-called cis ligands), preventing Siglec-8 ligand binding in trans. However, the functional relevance of these cis ligands has not been elucidated. We therefore explored the potential influence of cis ligands of Siglec-8 on both eosinophils and mast cells. De-sialylation using exogenous sialidase profoundly altered the consequences of Siglec-8 antibody engagement on both cell types, eliminating the need for cytokine priming of eosinophils to facilitate cell death and enabling Siglec-8-dependent mast cell death without impacting anti-Siglec-8 antibody binding. The cell death process licensed by de-sialylation resembled that characterized in IL-5-primed eosinophils, including CD11b upregulation, ROS production, and the activities of Syk, PI3K, and PLC. These results implicate cis ligands in restraining Siglec-8 function on eosinophils and mast cells and reveal a promising approach to the selective depletion of mast cells in patients with mast cell-mediated diseases.
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Affiliation(s)
- Yun Cao
- Division of Allergy and Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Clayton H. Rische
- Division of Allergy and Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
- Department of Biomedical Engineering, Northwestern University McCormick School of Engineering, Evanston, IL, United States
| | - Bruce S. Bochner
- Division of Allergy and Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Jeremy A. O’Sullivan
- Division of Allergy and Immunology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
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Fastenau C, Wickline JL, Smith S, Odfalk KF, Solano L, Bieniek KF, Hopp SC. Increased α-2,6 sialic acid on microglia in amyloid pathology is resistant to oseltamivir. GeroScience 2023; 45:1539-1555. [PMID: 36867284 PMCID: PMC10400525 DOI: 10.1007/s11357-023-00761-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 02/22/2023] [Indexed: 03/04/2023] Open
Abstract
Terminal sialic acid residues are present on most glycoproteins and glycolipids, but levels of sialylation are known to change in the brain throughout the lifespan as well as during disease. Sialic acids are important for numerous cellular processes including cell adhesion, neurodevelopment, and immune regulation as well as pathogen invasion into host cells. Neuraminidase enzymes, also known as sialidases, are responsible for removal of terminal sialic acids in a process known as desialylation. Neuraminidase 1 (Neu1) cleaves the α-2,6 bond of terminal sialic acids. Aging individuals with dementia are often treated with the antiviral medication oseltamivir, which is associated with induction of adverse neuropsychiatric side effects; this drug inhibits both viral and mammalian Neu1. The present study tested whether a clinically relevant antiviral dosing regimen of oseltamivir would disrupt behavior in the 5XFAD mouse model of Alzheimer's disease amyloid pathology or wild-type littermates. While oseltamivir treatment did not impact mouse behavior or modify amyloid plaque size or morphology, a novel spatial distribution of α-2,6 sialic acid residues was discovered in 5XFAD mice that was not present in wild-type littermates. Further analyses revealed that α-2,6 sialic acid residues were not localized the amyloid plaques but instead localized to plaque-associated microglia. Notably, treatment with oseltamivir did not alter α-2,6 sialic acid distribution on plaque-associated microglia in 5XFAD mice which may be due to downregulation of Neu1 transcript levels in 5XFAD mice. Overall, this study suggests that plaque-associated microglia are highly sialylated and are resistant to change with oseltamivir, thus interfering with microglia immune recognition of and response to amyloid pathology.
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Affiliation(s)
- Caitlyn Fastenau
- Department of Pharmacology, University of Texas Health Science Center San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
| | - Jessica L Wickline
- Department of Pharmacology, University of Texas Health Science Center San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
| | - Sabrina Smith
- Department of Pharmacology, University of Texas Health Science Center San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
| | - Kristian F Odfalk
- Department of Pharmacology, University of Texas Health Science Center San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
| | - Leigh Solano
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
| | - Kevin F Bieniek
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
- Department of Pathology and Laboratory Medicine, University of Texas Health Science Center San Antonio, San Antonio, TX, USA
| | - Sarah C Hopp
- Department of Pharmacology, University of Texas Health Science Center San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA.
- Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases, University of Texas Health Science Center San Antonio, San Antonio, TX, USA.
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