Achyranthes bidentata polysaccharides alleviate severe traumatic brain injury by suppressing the TLR4/MyD88/NF-κB pathway and inhibiting neutrophil extracellular trap formation

Abstract

Objective This study aims to investigate the potential protective effects of Achyranthes bidentata polysaccharides (ABPS) against severe traumatic brain injury (sTBI) and to elucidate the underlying mechanisms. Methods A sTBI model was established using a modified free-fall impact device. Neurological function in sTBI rats treated with different doses of ABPS was evaluated using neurological deficit scoring, brain water content measurement, the open field test, and the rotarod test. Enzyme-linked immunosorbent assay (ELISA) was performed to quantify neutrophil extracellular traps (NETs)-related markers (cell-free DNA (cf-DNA), myeloperoxidase–DNA (MPO–DNA), and neutrophil elastase–DNA (NE–DNA)), pro-inflammatory cytokines (interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α)), and oxidative stress indicators (reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px)) in brain tissues. Western blot analysis was conducted to assess the expression of NETs-associated markers (citrullinated histone H3 (cit-H3) and myeloperoxidase (MPO)), apoptosis-related proteins (B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (Bax)), proteins in the TLR4/MyD88/NF-κB signaling pathway (Toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), nuclear factor-κB (NF-κB) and phosphorylated NF-κB (p-NF-κB)), and peptidylarginine deiminase 4 (PAD4), a key enzyme involved in NETs formation. Immunofluorescence staining was used to detect NETs-related markers (cit-H3,MPO, and neutrophil elastase (NE)) in brain tissues. Neuronal apoptosis was evaluated by TUNEL staining and Western blot analysis. Hematoxylin and eosin (H&E) staining and Nissl staining were performed to assess histopathological changes and the extent of neuronal injury in rat brain tissues. Results ABPS exerted a neuroprotective effect against sTBI-induced brain injury, exhibiting a dose-dependent trend. Functionally, ABPS alleviated neurological damage by attenuating sTBI-induced neuroinflammation, oxidative stress, and neuronal apoptosis. Mechanistically, ABPS mitigated secondary brain injury following sTBI by inhibiting the activation of the TLR4/MyD88/NF-κB signaling pathway and suppressing NET formation. Conclusion ABPS ameliorate secondary brain injury following sTBI by inhibiting activation of the TLR4/MyD88/NF-κB signaling pathway and reducing NET formation, thereby attenuating neuroinflammation, oxidative stress, and neuronal apoptosis. These findings provide novel experimental evidence supporting the potential therapeutic application of ABPS in the treatment of sTBI.