CCR2-high monocyte membrane-coated ginger-derived exosome-like nanoparticles attenuate spinal cord injury by inhibiting ferroptosis-mediated neuronal death and neuroinflammation via Nrf2/GPX4 axis activation.

Background

Ferroptosis and neuroinflammation are critical pathological processes that drive secondary injury and persistent neurological dysfunction following spinal cord injury (SCI). The CCL2/CCR2 axis predominantly recruits CCR2-high monocytes to lesion sites, further exacerbating local neural damage. Ginger-derived exosome-like nanoparticles (GELNs) possess antioxidant, anti-inflammatory, and drug-delivery properties. However, their poor ability to target lesions and insufficiently understood protective mechanisms restrict the translational application of native GELNs in SCI therapy.

Purpose

We fabricated CCR2-high monocyte membrane-coated GELNs (CCR2-MM/GELNs) with biomimetic targeting capabilities with the aim of validating the therapeutic efficacy of CCR2-MM/GELNs against SCI and clarifying whether these nanoparticles alleviate SCI pathology by activating the Nrf2/GPX4 axis and subsequently suppressing ferroptosis-associated neuronal injury and neuroinflammation.

Methods

The physicochemical properties, in vivo distribution, and pharmacokinetic behaviors of CCR2-MM/GELNs were systematically characterized in SCI rat models. Wild-type and GFP-positive bone marrow (BM) chimeric rats were used to verify lesion-targeting efficiency and biological function. Pharmacological inhibition assays using the Nrf2 inhibitor ML385 and the GPX4 inhibitor RSL3 were further performed to confirm the causal role of the Nrf2/GPX4 axis in CCR2-MM/GELNs-mediated neuroprotection.

Results

CCR2-MM/GELNs successfully integrated the intrinsic bioactivity of GELNs and the CCL2/CCR2-dependent targeting property of CCR2 monocytes. These nanoparticles selectively accumulated in neurons, microglia, and astrocytes within spinal cord lesions, maintained high levels of 6-gingerol and 6-shogaol for 14 days post-injury, and exhibited excellent systemic biosafety. Mechanistically, CCR2-MM/GELNs activated Nrf2/GPX4 signaling, upregulated the expression of Nrf2, SLC7A11, glutathione reductase, and GPX4, and restored cellular redox homeostasis by elevating the GSH/GSSG ratio and ameliorating iron overload, ROS accumulation, and lipid peroxidation (MDA and 4-HNE). These beneficial effects rescued mitochondrial dysfunction, mitigated neuronal ferroptosis and axonal demyelination, and promoted neurological functional recovery. Furthermore, CCR2-MM/GELNs suppressed IκB/NF-κB activation, facilitated the phenotypic transformation of microglia and astrocytes from pro-inflammatory M1/A1 phenotypes into protective M2/A2 phenotypes, reduced pro-inflammatory mediators, chemokines, and adhesion molecules, and restrained BM-derived peripheral immune infiltration, all the while elevating anti-inflammatory cytokines and neurotrophic factors. In addition, CCR2-MM/GELNs downregulated MMP-9 expression, restored tight junction protein levels, and alleviated blood-spinal cord barrier disruption. Notably, pharmacological blockade of Nrf2 or GPX4 abrogated all the protective effects of CCR2-MM/GELNs.

Conclusion

CCR2-MM/GELNs can serve as a novel targeted and multifunctional nanotherapeutic platform for SCI treatment. By activating the Nrf2/GPX4 axis, CCR2-MM/GELNs effectively inhibit ferroptosis-induced neuronal death and alleviate excessive neuroinflammation, thereby attenuating secondary spinal cord pathological damage and improving neurological functional recovery. Our findings provide a promising targeted therapeutic strategy for future translational treatment of SCI.