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Soliman E, Leonard J, Basso EKG, Gershenson I, Ju J, Mills J, de Jager C, Kaloss AM, Elhassanny M, Pereira D, Chen M, Wang X, Theus MH. Efferocytosis is restricted by axon guidance molecule EphA4 via ERK/Stat6/MERTK signaling following brain injury. J Neuroinflammation 2023; 20:256. [PMID: 37941008 PMCID: PMC10633953 DOI: 10.1186/s12974-023-02940-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Accepted: 10/30/2023] [Indexed: 11/10/2023] Open
Abstract
BACKGROUND Efferocytosis is a process that removes apoptotic cells and cellular debris. Clearance of these cells alleviates neuroinflammation, prevents the release of inflammatory molecules, and promotes the production of anti-inflammatory cytokines to help maintain tissue homeostasis. The underlying mechanisms by which this occurs in the brain after injury remain ill-defined. METHODS We used GFP bone marrow chimeric knockout (KO) mice to demonstrate that the axon guidance molecule EphA4 receptor tyrosine kinase is involved in suppressing MERTK in the brain to restrict efferocytosis of resident microglia and peripheral-derived monocyte/macrophages. RESULTS Single-cell RNAseq identified MERTK expression, the primary receptor involved in efferocytosis, on monocytes, microglia, and a subset of astrocytes in the damaged cortex following brain injury. Loss of EphA4 on infiltrating GFP-expressing immune cells improved functional outcome concomitant with enhanced efferocytosis and overall protein expression of p-MERTK, p-ERK, and p-Stat6. The percentage of GFP+ monocyte/macrophages and resident microglia engulfing NeuN+ or TUNEL+ cells was significantly higher in KO chimeric mice. Importantly, mRNA expression of Mertk and its cognate ligand Gas6 was significantly elevated in these mice compared to the wild-type. Analysis of cell-specific expression showed that p-ERK and p-Stat6 co-localized with MERTK-expressing GFP + cells in the peri-lesional area of the cortex following brain injury. Using an in vitro efferocytosis assay, co-culturing pHrodo-labeled apoptotic Jurkat cells and bone marrow (BM)-derived macrophages, we demonstrate that efferocytosis efficiency and mRNA expression of Mertk and Gas6 was enhanced in the absence of EphA4. Selective inhibitors of ERK and Stat6 attenuated this effect, confirming that EphA4 suppresses monocyte/macrophage efferocytosis via inhibition of the ERK/Stat6 pathway. CONCLUSIONS Our findings implicate the ERK/Stat6/MERTK axis as a novel regulator of apoptotic debris clearance in brain injury that is restricted by peripheral myeloid-derived EphA4 to prevent the resolution of inflammation.
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Affiliation(s)
- Eman Soliman
- Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA, 24061, USA
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt
| | - John Leonard
- Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA, 24061, USA
| | | | - Ilana Gershenson
- Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Jing Ju
- Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Jatia Mills
- Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Caroline de Jager
- Translational Biology Medicine and Health Graduate Program, Roanoke, VA, 24001, USA
| | - Alexandra M Kaloss
- Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Mohamed Elhassanny
- Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Daniela Pereira
- Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Michael Chen
- Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Xia Wang
- Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA, 24061, USA
| | - Michelle H Theus
- Department of Biomedical Sciences and Pathobiology, Virginia Tech, Blacksburg, VA, 24061, USA.
- Translational Biology Medicine and Health Graduate Program, Roanoke, VA, 24001, USA.
- Center for Engineered Health, Virginia Tech, Blacksburg, VA, 24061, USA.
- VT-Biomedical Engineering and School of Neuroscience, 970 Washington Street SW, Life Sciences I; Rm 249 (MC0910), Blacksburg, VA, 24061, USA.
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Arefin A, Gage MC. Metformin, Empagliflozin, and Their Combination Modulate Ex-Vivo Macrophage Inflammatory Gene Expression. Int J Mol Sci 2023; 24:ijms24054785. [PMID: 36902218 PMCID: PMC10003317 DOI: 10.3390/ijms24054785] [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: 12/07/2022] [Revised: 02/09/2023] [Accepted: 02/23/2023] [Indexed: 03/06/2023] Open
Abstract
Type-2 Diabetes Mellitus is a complex, chronic illness characterized by persistent high blood glucose levels. Patients can be prescribed anti-diabetes drugs as single agents or in combination depending on the severity of their condition. Metformin and empagliflozin are two commonly prescribed anti-diabetes drugs which reduce hyperglycemia, however their direct effects on macrophage inflammatory responses alone or in combination are unreported. Here, we show that metformin and empagliflozin elicit proinflammatory responses on mouse bone-marrow-derived macrophages with single agent challenge, which are modulated when added in combination. In silico docking experiments suggested that empagliflozin can interact with both TLR2 and DECTIN1 receptors, and we observed that both empagliflozin and metformin increase expression of Tlr2 and Clec7a. Thus, findings from this study suggest that metformin and empagliflozin as single agents or in combination can directly modulate inflammatory gene expression in macrophages and upregulate the expression of their receptors.
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Affiliation(s)
- Adittya Arefin
- Wolfson Institute for Biomedical Research, Division of Medicine, University College London, Gower Street, London WC1E 6BT, UK
| | - Matthew C. Gage
- Department of Comparative Biomedical Sciences, Royal Veterinary College, 4 Royal College Street, London NW1 0TU, UK
- Correspondence:
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Endocytosis of LXRs: Signaling in liver and disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2023; 194:347-375. [PMID: 36631198 DOI: 10.1016/bs.pmbts.2022.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Nuclear receptors are among one of the major transcriptional factors that induces gene regulation in the nucleus. Liver X receptor (LXR) is a transcription factor which regulates essential lipid homeostasis in the body including fatty acid, cholesterol and phospholipid synthesis. Liver X receptor-retinoid X receptor (LXR-RXR) heterodimer is activated by either of the ligand binding on LXR or RXR. The promoter region of the gene which is targeted by LXR is bound to the response element of LXR. The activators bind to the heterodimer once the corepressor is dissociated. The cellular process such as endocytosis aids in intracellular trafficking and endosomal formation in transportation of molecules for essential signaling within the cell. LXR isotypes play a crucial role in maintaining lipid homeostasis by regulating the level of cholesterol. In the liver, the deficiency of LXRα can alter the normal physiological conditions depicting the symptoms of various cardiovascular and liver diseases. LXR can degrade low density lipoprotein receptors (LDLR) by the signaling of LXR-IDOL through endocytic trafficking in lipoprotein uptake. Various gene expressions associated with cholesterol level and lipid synthesis are regulated by LXR transcription factor. With its known diversified ligand binding, LXR is capable of regulating expression of various specific genes responsible for the progression of autoimmune diseases. The agonists and antagonists of LXR stand to be an important factor in transcription of the ABC family, essential for high density lipoprotein (HDL) formation. Endocytosis and signaling mechanism of the LXR family is broad and complex despite their involvement in cellular growth and proliferation. Here in this chapter, we aimed to emphasize the master regulation of LXR activation, regulators, and their implications in various metabolic activities especially in lipid homeostasis. Furthermore, we also briefed the significant role of LXR endocytosis in T cell immune regulation and a variety of human diseases including cardiovascular and neuroadaptive.
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