Glycine receptors in circulating white blood cells regulated by neuroinflammation

Introduction Neuroinflammation is involved in a wide range of neurological disorders, yet the lack of minimally invasive biomarkers hampers early diagnosis and therapeutic monitoring. Glycine receptors (GlyRs), classically known as inhibitory neurotransmitter receptors in the central nervous system, are increasingly recognized as regulators of immune signaling. Here, we identify GlyRs as novel peripheral indicators of neuroinflammation. Methods and results We demonstrate that GlyRα1, α2, and α3 subunits are constitutively expressed in human and murine immune cells, with GlyRα2 predominating across peripheral tissues and the brain. Using ex vivo and in vivo mouse models, we found that the expression of GlyRα1, α2, and α3 in macrophages and circulating white blood cells (WBCs) was not directly mediated by inflammatory cytokine signaling in the brain or WBCs. Neuroinflammation upregulates GlyRα1 and α3 expression in the brain, spleen, bone marrow, and circulating WBCs. Immunostaining revealed GlyRα3 to the membrane and GlyRα1/2 to both the membrane and cytoplasm of WBCs. GlyR expression was also observed in the bone marrow, the spleen (macrophage-rich red pulp), and the neurons. Notably, GlyRα1 and α3 expression in WBCs was significantly elevated in neuroinflammation compared to control and systemic inflammation models. Changes in GlyR expression were not correlated with the expression of pro-inflammatory cytokines in the brain and WBCs. LPS-induced microglial (Iba1 + ) activation paralleled the upregulation of WBC GlyR, suggesting a reciprocal modulation between central and peripheral compartments. Conclusion Together, these findings define a brain-glycinergic signaling-blood axis that maintains homeostatic protectivity. GlyR subunits, particularly GlyRα1 and α3, represent a neuropathology-induced modulation of GlyR signaling in peripheral immune cells.