Osteoimmunological impacts of micro/nanoplastics: systemic translocation, inflammatory responses, and bone remodeling disruption.

Ingested environmental micro- and nanoplastics (MNPs) may represent an emerging systemic health concern. Although toxicological research has mainly focused on the gastrointestinal tract, increasing evidence suggests that the highly vascularized bone marrow may also be a relevant site for MNP accumulation. This narrative review proposes a "gut-immune-bone" axis linking intestinal barrier disruption, systemic translocation, and potential deposition within the bone marrow niche. Current experimental evidence, together with limited human detection data, suggests that MNPs may disturb osteoimmunological homeostasis by impairing osteogenesis and promoting macrophage-associated osteoclastogenesis, thereby favoring bone remodeling imbalance. We summarize potential mechanisms, including oxidative stress, nuclear factor-κB (NF-κB) signaling, NOD-like receptor protein 3 (NLRP3) inflammasome activation, gut microbiota dysbiosis, endocrine disruption, and MNP-heavy metal co-exposure. We also discuss susceptible pediatric and geriatric populations and highlight the need to incorporate osteoimmunological endpoints into future MNP risk assessment.