Background: Paroxysmal sympathetic hyperactivity (PSH) is one of the important reasons for the high mortality and morbidity of traumatic brain injury (TBI). We aim to explore the role of the neutrophil extracellular traps (NETs) in the pathogenesis of sympathetic hyperexcitability after TBI and the underlying mechanisms, providing evidence for clinical treatment.Methods: Enzyme-linked immunosorbent assay was used to assess the plasma metanephrine and normetanephrine levels which represented the variation of the sympathetic system after TBI with rat diffuse axonal injury (DAI) model. NETs in the paraventricular nucleus (PVN) and circulating blood were examined using immunofluorescence and flow cytometry. Neutrophils-microglia co-culture system was established to further explore the effect of NETs on PSH and its mechanisms.Results: After TBI, metanephrine and normetanephrine levels began to increase at 9 h and peaked at 72 h. After the injury, the level of NETs kept increasing at 24 and 72 h in the PVN. A positive correlation was found between the concentration of the PVN NETs and blood catecholamine. Flow cytometry of peripheral blood cells revealed that NETs level in the injury group was higher than that in the control group. Immunofluorescence results confirmed the presence of NETs in the PVN after TBI. The positive result of immunoprecipitation suggested a correlation effect between LL37 and P2 × 7. Peptidyl arginine deiminase-4 (PAD4) inhibitor could inhibit the expression levels of MST1, YAP, and IL-1β. The hippo/MST1 pathway inhibitor could inhibit the expression levels of YAP and IL-1β.Conclusion: NETs formation in the PVN might be associated with sympathetic hyperactivity after TBI, which might relate to the activation of microglia cells and increased secretion of IL-1β via the hippo/MST1 pathway.

Messager RNA (mRNA) can be modified in a variety of ways, among which the modification of N6-methyladenosine (m6A) is one of the most common ones. Recent studies have found that the m6A modification in mRNA could functionally regulate the splicing, localization, translation, and stability of mRNA, which might be closely related to multiple diseases. However, the roles of m6A modification in traumatic optic neuropathy (TON) are unknown. Herein, we detected the expression of m6A-related genes via quantitative real-time PCR (qRT-PCR) and performed methylated RNA immunoprecipitation sequencing (MeRIP-seq) as well as RNA-sequencing to analyze the alteration profiles of m6A modification after TON. The results showed that the expression of m6A-related genes (METTL3, WTAP, FTO, and ALKBH5) were all upregulated after TON. In all, 2,810 m6A peaks were differentially upregulated and 689 m6A peaks were downregulated. In addition, the hypermethylated and hypomethylated profiles of mRNA transcripts were also identified. To sum up, our study revealed the differentially expressed m6A modification in the early stage of TON, which may provide novel insights into the mechanism and treatment of TON.

No abstract

Traumatic brain injury (TBI), particularly diffuse axonal injury (DAI), often results in sympathetic hyperactivity, which can exacerbate the prognosis of TBI patients. A key component of this process is the role of neutrophils in causing neuroinflammation after TBI by forming neutrophil extracellular traps (NETs), but the connection between NETs and sympathetic excitation following TBI remains unclear. Utilizing a DAI rat model, the current investigation examined the role of NETs and the HMGB1/JNK/AP1 signaling pathway in this process. The findings revealed that sympathetic excitability intensifies and peaks 3 days post‐injury, a pattern mirrored by the activation of microglia, and the escalated NETs and HMGB1 levels. Subsequent in vitro exploration validated that HMGB1 fosters microglial activation via the JNK/AP1 pathway. Moreover, in vivo experimentation revealed that the application of anti‐HMGB1 and AP1 inhibitors can mitigate microglial M1 polarization post‐DAI, effectively curtailing sympathetic hyperactivity. Therefore, this research elucidates that post‐TBI, NETs within the PVN may precipitate sympathetic hyperactivity by stimulating M1 microglial polarization through the HMGB1/JNK/AP1 pathway.

Background: Traumatic brain injury (TBI) usually accompanies with sympathetic excitation, and paradoxical sympathetic hyperactivity (PSH) may be detrimental to the prognosis of TBI sufferers. Neutrophils can form neutrophil extracellular traps (NETs) to get involved in the neuroinflammation after TBI. As an important form of NETs, HMGB1 were found to activate the expression of AP1, which can increase the formation of IL-1β in microglia. Considering that IL-1β is able to regulate sympathoexcitation, it is reasonable to infer that HMGB1/AP1 signaling plays an important role in sympathoexcitation after TBI. Methods: In this present study, rat model with diffuse axonal injury (DAI) was established. The existance of NETs and the expression level of HMGB1/AP1/IL-1β in the paraventricular nucleus (PVN) after DAI were examined by immunofluorescence and Western blot (WB). The role of HMGB1/AP1 in the activation of microglia, secretion of IL-1β and sympathoexcitaiton were identified in vitro. Moreover, stereotaxic injection of anti-HMGB1 or HMGB1 was conducted to further validate the effect of HMGB1/AP1 pathway on sympathoexcitation after TBI.Results: The indicators of sympathoexcitation, including mean arterial pressure and serum catecholamine, increased and peaked at 72 hours after TBI. The formation of NETs was observed in PVN after injury, whereas, no NETs were found in the control group. And meanwhile, levels of NETs in PVN were higher than that in the para-PVN tissues after the injury. In vitro experiments showed that HMGB1 can promote the activation of microglia as well as increase the expression of AP1 and IL-1β. In vivo experiments suggested HMGB1 have an impact on the expression of AP1 and IL-1β in the PVN, and further controlling the sympathoexcitation after TBI.Conclusion: NETs might mediate sympathoexcitation after TBI through microglial activation in the PVN in a HMGB1/AP1/IL-1β dependent way.