Cell-specific expression and signaling of glucocorticoid receptor isoforms over time in critically ill patients with a low inflammatory response

Glucocorticoid (GC) signaling plays a crucial role in immune regulation during critical illness, but cell-specific responses remain poorly understood. While previous studies have predominantly examined glucocorticoid receptor (GCR)-α and GCR-β, the roles of alternative isoforms (GCR-γ, GCR-P) and the downstream effectors GC-induced leucine zipper (GILZ) and dual-specific phosphatase 1 (DUSP1) across different immune cell populations in critical illness remain unexplored. In this prospective, observational study, we enrolled 43 critically ill patients and 25 healthy controls. Longitudinal blood samples were collected at ICU admission (24–48 h) and days 4 (4d), 8 (8d), and 14 (14d). We quantified the mRNA expression of four GCR variants (GCR-α, GCR-β, GCR-γ, and GCR-P) and GC downstream targets (GILZ and DUSP1) in isolated polymorphonuclear cells (PMNs) and peripheral blood mononuclear cells (PBMCs) via RT‒PCR. Serum cortisol, adrenocorticotropic hormone (ACTH), and cytokines (interleukin (IL)-6 and IL-10) were measured concurrently. Statistical analyses included mixed-effects modeling to assess temporal and cell-specific patterns. PMNs exhibited sustained downregulation of GCR-α, GCR-β, and GCR-γ, with preserved GILZ expression, while GCR-P remained stable. In PBMCs, GCR-α, GCR-β, GCR-γ, and GILZ levels showed no significant changes compared to controls, yet GCR-P was upregulated. DUSP1 was downregulated in PMNs and elevated in PBMCs. Negative correlations emerged between IL-6 and both GILZ and DUSP1. All expression patterns remained stable across time points in the subset of patients who completed the 2-week study despite dynamic ACTH changes and persistently elevated cortisol. PMNs show reduced GCR-α/β/γ with preserved GILZ, while PBMCs maintain GCR-α/β/γ but upregulate GCR-P and DUSP1. These findings highlight divergent GC responsiveness between innate and adaptive immune cells, with implications for cortisol’s role in immune regulation during critical illness and may reflect cell-specific effects driven by changes in glucocorticoid receptor signaling.