Genetic deletion of the glucocorticoid receptor in Cx3cr1+ myeloid cells is neuroprotective and improves motor recovery after spinal cord injury

• Published in: Experimental neurology 2022-09, Vol.355, p.114114-114114, Article 114114
• Main Authors: Madalena, Kathryn M., Brennan, Faith H., Popovich, Phillip G.
• Format: Article
• Language: English
• Subjects: Glucocorticoid receptor; Glucocorticoids; Macrophages; Microglia; Spinal cord injury
• ISSN: 0014-4886; 1090-2430
• DOI: 10.1016/j.expneurol.2022.114114

Glucocorticoid receptors (GRs), part of the nuclear receptor superfamily of transcription factors (TFs), are ubiquitously expressed in all cell types and regulate cellular responses to glucocorticoids (e.g., cortisol in humans; corticosterone in rodents). In myeloid cells, glucocorticoids binding to GRs can enhance or repress gene transcription, thereby imparting distinct and context-dependent functions in macrophages at sites of inflammation. In experimental models and in humans, glucocorticoids are widely used as anti-inflammatory treatments to promote recovery of function after SCI. Thus, we predicted that deleting GR in mouse myeloid lineage cells (i.e., microglia and monocyte-derived macrophages) would enhance inflammation at the site of injury and worsen functional recovery after traumatic spinal cord injury (SCI). Contrary to our prediction, the intraspinal macrophage response to a moderate (75 kdyne) spinal contusion SCI was reduced in Cx3cr1-Cre;GRf/f conditional knockout mice (with GR specifically deleted in myeloid cells). This phenotype was associated with improvements in hindlimb motor recovery, myelin sparing, axon sparing/regeneration, and microvascular protection/plasticity relative to SCI mice with normal myeloid cell GR expression. Further analysis revealed that macrophage GR deletion impaired lipid and myelin phagocytosis and foamy macrophage formation. Together, these data reveal endogenous GR signaling as a key pathway that normally inhibits mechanisms of macrophage-mediated repair after SCI. •Glucocorticoid signaling regulates macrophage function in the injured spinal cord.•Glucocorticoid receptor deletion in myeloid cells helps spinal cord injury recovery.•This deletion reduces the intraspinal macrophage response to spinal cord injury.•This reduced macrophage response leads to better motor recovery and neuroprotection.•Glucocorticoid receptor deletion reduces phagocytosis and foamy macrophages.