Biology subjects

Upchurch, G. R.

Publications and source records attributed to Upchurch, G. R..

5 recordsLinked to original sources

bioRxiv2025

Protectin D1/GPR37 signaling enhances macrophage-dependent efferocytosis to attenuate experimental abdominal aortic aneurysm formation

Abdominal aortic aneurysms (AAAs) are chronic inflammatory vascular disorders characterized by progressive aortic dilation and destruction of the vascular wall, often culminating in rupture. Current management is limited to surgical repair, with no approved targeted pharmacologic therapies. In this study, we investigated the immunomodulatory role of Protectin D1 (PD1), a specialized pro-resolving lipid mediator, through G-protein-coupled receptor 37 (GPR37) signaling on macrophages in mitigating AAA progression and preventing aortic rupture. Single cell-RNA sequencing analysis of human tissue demonstrated significant differences in PD1/GPR37 axis-related genes in macrophages in AAAs compared to control aortic tissue. Using an established murine AAA model, PD1 administration significantly attenuated aortic diameter, pro-inflammatory cytokine and matrix metalloproteinase (MMP2) expression, as well as maintained aortic morphology in a GPR37-dependent manner. Importantly, PD1 treatment prevented preformed AAA progression to aortic rupture in another preclinical elastase+BAPN model of aortic rupture, by attenuating aortic diameter, tissue inflammation as well as decreasing macrophage infiltration, preserving elastin integrity, and restoring smooth muscle -actin expression in the aortic wall. Mechanistically, PD1 enhanced macrophage efferocytosis of apoptotic vascular smooth muscle cells in the murine aortic tissue as well as in isolated macrophages via GPR37-dependent manner and attenuated the inflammatory paracrine secretion of macrophage-specific paracrine release of TNF- and IL-{beta}. These findings suggest that PD1/GPR37 signaling on macrophages promotes inflammation-resolution by enhancing efferocytosis of apoptotic SMCs conferring protection against aortic inflammation and remodeling to mitigate AAA formation and rupture. Significance StatementThis study elucidates the protective role of specialized proresolving lipid mediator, Protectin D1, by activating macrophages via GPR37 receptors, to enhance the clearance of apoptotic smooth muscle cells to mitigate aortic inflammation and vascular remodeling during abdominal aortic aneurysm formation. We observed that several key inflammation related genes were associated with PD1/GPR37-dependent signaling in macrophages of human AAAs. Detailed analysis in experimental models delineated the signaling pathway where upregulating macrophage-dependent efferocytosis via immunomodulation by Protectin D1 attenuated aortic inflammation and remodeling, indicating a potential mechanism for therapeutic intervention in the pathobiology of AAAs to prevent aortic rupture.

immunology↗

bioRxiv2024

Pharmacologic Inhibition of Ferroptosis Attenuates Experimental Abdominal Aortic Aneurysm Formation

The pathogenesis of abdominal aortic aneurysm (AAA) formation involves vascular inflammation, thrombosis formation and programmed cell death leading to aortic remodeling. Recent studies have suggested that ferroptosis, an excessive iron-mediated cell death, can regulate cardiovascular diseases, including AAAs. However, the role of ferroptosis in immune cells, like macrophages, and ferroptosis-related genes in AAA formation remains to be deciphered. Single cell-RNA sequencing of human aortic tissue from AAA patients demonstrates significant differences in ferroptosis-related genes compared to control aortic tissue. Using two established murine models of AAA and aortic rupture in C57BL/6 (WT) mice, we observed that treatment with liproxstatin-1, a specific ferroptosis inhibitor, significantly attenuated aortic diameter, pro-inflammatory cytokine production, immune cell infiltration (neutrophils and macrophages), increased smooth muscle cell -actin expression and elastic fiber disruption compared to mice treated with inactivated elastase in both pre-treatment and treatment after a small AAA had already formed. Lipidomic analysis using mass spectrometry shows a significant increase in ceramides and a decrease in intact lipid species levels in murine tissue compared to controls in the chronic AAA model on day 28. Mechanistically, in vitro studies demonstrate that liproxstatin-1 treatment of macrophages mitigated the crosstalk with aortic smooth muscle cells (SMCs) by downregulating MMP2 secretion. Taken together, this study demonstrates that pharmacological inhibition by liproxstatin-1 mitigates macrophage-dependent ferroptosis contributing to inhibition of aortic inflammation and remodeling during AAA formation.

immunology↗

bioRxiv2024

Lipoxin A4/FPR2 signaling mitigates ferroptosis of alveolar epithelial cells via NRF2-dependent pathway during lung ischemia-reperfusion injury

BACKGROUNDPost-lung transplantation (LTx) injury can involve sterile inflammation due to ischemia-reperfusion injury (IRI). We investigated the cell-specific role of ferroptosis (excessive iron-mediated cell death) in mediating lung IRI and determined if specialized pro-resolving mediators such as Lipoxin A4 (LxA4) can protect against ferroptosis in lung IRI. METHODSSingle-cell RNA sequencing of lung tissue from post-LTx patients was analyzed. Lung IRI was evaluated in C57BL/6 (WT), formyl peptide receptor 2 knockout (Fpr2-/-) and nuclear factor erythroid 2-related factor 2 knockout (Nrf2-/-) mice using a hilar-ligation model with or without LxA4 administration. Furthermore, the protective efficacy of LxA4 was evaluated employing a murine orthotopic LTx model and in vitro studies using alveolar type II epithelial (ATII) cells. RESULTSDifferential expression of ferroptosis-related genes was observed in post-LTx patient samples compared to healthy controls. A significant increase in the levels of oxidized lipids and reduction in the levels of intact lipids were observed in mice subjected to IRI compared to shams. Furthermore, pharmacological inhibition of ferroptosis with liproxstatin-1 mitigated lung IRI and lung dysfunction. Importantly, LxA4 treatment attenuated pulmonary dysfunction, ferroptosis and inflammation in WT mice subjected to lung IRI, but not in Fpr2-/- or Nrf2-/-mice, after IRI. In the murine LTx model, LxA4 treatment increased PaO2 levels and attenuated lung IRI. Mechanistically, LxA4-mediated protection involves increase in NRF2 activation and glutathione concentration as well as decrease in MDA levels in ATII cells. CONCLUSIONSLxA4/FPR2 signaling on ATII cells mitigates ferroptosis via NRF2 activation and protects against lung IRI.

immunology↗

bioRxiv2024

Resolvin D2/GPR18 signaling enhances monocytic myeloid-derived suppressor cell function to mitigate abdominal aortic aneurysm formation

Abdominal aortic aneurysm (AAA) formation is a chronic vascular pathology characterized by inflammation, leukocyte infiltration and vascular remodeling. The aim of this study was to delineate the protective role of Resolvin D2 (RvD2), a bioactive isoform of specialized proresolving lipid mediators, via G-protein coupled receptor 18 (GPR18) receptor signaling in attenuating AAAs. Importantly, RvD2 and GPR18 levels were significantly decreased in aortic tissue of AAA patients compared with controls. Furthermore, using an established murine model of AAA in C57BL/6 (WT) mice, we observed that treatment with RvD2 significantly attenuated aortic diameter, pro-inflammatory cytokine production, immune cell infiltration (neutrophils and macrophages), elastic fiber disruption and increased smooth muscle cell -actin expression as well as increased TGF-{beta}2 and IL-10 expressions compared to untreated mice. Moreover, the RvD2-mediated protection from vascular remodeling and AAA formation was blocked when mice were previously treated with siRNA for GPR18 signifying the importance of RvD2/GPR18 signaling in vascular inflammation. Mechanistically, RvD2-mediated protection significantly enhanced infiltration and activation of monocytic myeloid-derived suppressor cells (M-MDSCs) by increasing TGF-{beta}2 and IL-10 secretions that mitigated smooth muscle cell activation in a GPR18-dependent manner to attenuate aortic inflammation and vascular remodeling via this intercellular crosstalk. Collectively, this study demonstrates RvD2 treatment induces an expansion of myeloid-lineage committed progenitors, such as M-MDSCs, and activates GPR18-dependent signaling to enhance TGF-{beta}2 and IL-10 secretion that contributes to resolution of aortic inflammation and remodeling during AAA formation.

immunology↗

bioRxiv2024

MerTK-dependent efferocytosis by monocytic-MDSCs mediates resolution of post-lung transplant injury

ABSTRACTO_ST_ABSRationaleC_ST_ABSPatients with end stage lung diseases require lung transplantation (LTx) that can be impeded by ischemia-reperfusion injury (IRI) leading to subsequent chronic lung allograft dysfunction (CLAD) and inadequate outcomes. ObjectivesWe examined the undefined role of MerTK (receptor Mer tyrosine kinase) on monocytic myeloid-derived suppressor cells (M-MDSCs) in efferocytosis (phagocytosis of apoptotic cells) to facilitate resolution of lung IRI. MethodsSingle-cell RNA sequencing of lung tissue and BAL from post-LTx patients was analyzed. Murine lung hilar ligation and allogeneic orthotopic LTx models of IRI were used with Balb/c (WT), cebpb-/- (MDSC-deficient), Mertk-/- or MerTK-CR (cleavage resistant) mice. Lung function, IRI (inflammatory cytokine and myeloperoxidase expression, immunohistology for neutrophil infiltration), and flow cytometry of lung tissue for efferocytosis of apoptotic neutrophils were assessed in mice. Measurements and Main ResultsA significant downregulation in MerTK-related efferocytosis genes in M-MDSC populations of CLAD patients compared to healthy subjects was observed. In the murine IRI model, significant increase in M-MDSCs, MerTK expression and efferocytosis was observed in WT mice during resolution phase that was absent in cebpb-/- Land Mertk-/- mice. Adoptive transfer of M-MDSCs in cebpb-/- mice significantly attenuated lung dysfunction, and inflammation leading to resolution of IRI. Additionally, in a preclinical murine orthotopic LTx model, increases in M-MDSCs were associated with resolution of lung IRI in the transplant recipients. In vitro studies demonstrated the ability of M-MDSCs to efferocytose apoptotic neutrophils in a MerTK-dependent manner. ConclusionsOur results suggest that MerTK-dependent efferocytosis by M-MDSCs can significantly contribute to the resolution of post-LTx IRI.

immunology↗