Biology subjects

Ridley, A. J.

Publications and source records attributed to Ridley, A. J..

4 recordsLinked to original sources

bioRxiv2025

Pulmonary macrophage subsets display distinct metabolic responses to polarising stimuli in vivo

Macrophage activation is underpinned by metabolic changes required to fight infection, resolve inflammation and enable effective wound healing. While metabolic control of macrophage activation is increasingly understood in culture systems in vitro, it remains poorly understood in more complex in vivo settings, like the lung. Here we applied novel flow cytometry based immunometabolic techniques to profile immune cell metabolism in the murine lung. We revealed a surprising role for glucose in naive alveolar macrophages (AMs) that was retained by AMs polarised in vivo with either interleukin-4 (IL-4) or lipopolysaccharide (LPS). We identified that naive interstitial macrophages (IMs) were dependent on mitochondrial and glucose metabolism, IMs polarised with IL-4 failed to induce metabolic alterations but displayed a glycolytic phenotype following LPS exposure as they adopted an M1 like metabolic profile. We also demonstrated that AMs were metabolically less responsive than IMs to intranasal delivery of LPS, but upregulated glycolysis and metabolic features of M2 polarisation (defined in vitro) in response to intranasal IL-4, including oxidative phosphorylation (OXPHOS), fatty acid oxidation (FAO) and arginine metabolism. Finally, we identified AM M2 polarisation as highly sensitive to glucose inhibition ex vivo. Thus, lung macrophage subsets display distinct metabolic responses to polarising stimuli in vivo. HighlightsO_LINaive alveolar macrophages require glucose metabolism despite residing in a low glucose environment. C_LIO_LIAlveolar macrophages are more responsive to IL-4 in vivo than LPS upregulating oxidative metabolism, lipid metabolism and glycolysis. C_LIO_LIInterstitial macrophages adopt a glycolytic phenotype characteristic of M1 BMDMs in vitro following in vivo LPS administration. C_LIO_LIAlternatively activated alveolar macrophages are extremely sensitive to glucose inhibition ex vivo. C_LI

immunology↗

bioRxiv2025

Heparan sulfate glycosaminoglycans mediate CXCL4 (PF4) transport across the blood-brain barrier and effects on neurogenesis

CXCL4 (PF4) is a chemokine stored in platelets that has pleiotropic effects across biological settings. These effects include driving of inflammation and fibrosis as well as reversal of the effects of ageing. We have recently demonstrated that CXCL4 function is driven, independently of known chemokine receptors, through binding to glycosaminoglycan (GAG) side chains on proteoglycans within the cell surface glycocalyx. In this study, we have used intravital imaging and radioactive tracer studies, in combination with an exogenous inhibitor and a GAG-binding CXCL4 mutant, to demonstrate that CXCL4 can enter the brain parenchyma of mice by binding to proteoglycans within the cell surface of the endothelial glycocalyx of the blood-brain barrier (BBB). Furthermore, we have also demonstrated that CXCL4 directly promotes neurogenesis in vitro, which is mediated by its ability to oligomerise and bind to GAGs. These findings provide a molecular mechanism for CXCL4 uptake and function within the brain. Furthermore, these data have important implications for understanding CXCL4 during health and disease that may enable development of CXCL4-related therapeutics for inflammatory diseases and ageing.

neuroscience↗

bioRxiv2022

Chemokines form complex signals during inflammation and disease that can be decoded by extracellular matrix proteoglycans

Chemokine driven leukocyte recruitment is a key component of the immune response and is central to a wide range of diseases. However, there has yet to be a clinically successful therapeutic approach that targets the chemokine system during inflammatory disease; possibly due to the supposed redundancy of the chemokine system. A range of recent studies have demonstrated that the chemokine system is in fact based on specificity of function. Here we have generated a resource to analyse chemokine gene (ligand and receptor) expression across different species, tissues and diseases; revealing complex expression patterns whereby multiple chemokine ligands that mediate recruitment of the same leukocyte type are expressed in the same context, e.g. the CXCR3 ligands CXCL9, 10 and 11. We use biophysical approaches to show that CXCL9, 10 and 11 have very different interactions with extracellular matrix glycosaminoglycans (GAGs) which is exacerbated by specific GAG sulphation. Finally, in vivo approaches demonstrate that GAG-binding is critical for CXCL9 driven recruitment of specific T cell subsets (e.g. CD4+) but not others (e.g. CD8+), independent of CXCR3 expression. Our data demonstrate that chemokine expression is complex and that multiple ligands are likely needed for robust leukocyte recruitment across tissues and diseases. We also demonstrate that ECM GAGs facilitate decoding of these complex chemokine signals so that they are either primarily presented on GAG-coated cell surfaces or remain more soluble. Our findings represent a new mechanistic understanding of chemokine mediated immune cell recruitment and identify novel avenues to target specific chemokines during inflammatory disease.

immunology↗

bioRxiv2022

Chemokine CXCL4 interactions with extracellular matrix proteoglycans mediate wide-spread non-receptor mediated immune cell recruitment

Leukocyte recruitment from the vasculature into tissues is a crucial component of the immune system, but is also key to inflammatory disease. Chemokines are central to this process but have yet to be therapeutically targeted during inflammation, due to a lack of mechanistic understanding. Specifically, CXCL4 (PF4) has no established receptor that explains its function. Here we use biophysical, in vitro and in vivo techniques to determine the mechanism underlying CXCL4 mediated leukocyte recruitment. We demonstrate that CXCL4 binds to glycosaminoglycan (GAG) sugars within the endothelial extracellular matrix resulting in increased vascular permeability and non-specific recruitment of a range of leukocytes. Furthermore, GAG sulphation confers selectivity onto chemokine localisation. These findings represent a new understanding of chemokine biology, providing novel mechanisms for future therapeutic targeting. One sentence summaryCXCL4 binds to extracellular matrix proteoglycans resulting in increased vascular permeability and recruitment of a wide range of different leukocytes via a non-canonical mechanism.

immunology↗