Crotalus helleri venom preconditioning reduces postoperative cerebral edema and improves neurological outcomes after surgical brain injury

Neutrophil Extracellular Traps Regulate Surgical Brain Injury by Activating the cGAS-STING Pathway

Surgical brain injury (SBI), induced by neurosurgical procedures or instruments, has not attracted adequate attention. The pathophysiological process of SBI remains sparse compared to that of other central nervous system diseases thus far. Therefore, novel and effective therapies for SBI are urgently needed. In this study, we found that neutrophil extracellular traps (NETs) were present in the circulation and brain tissues of rats after SBI, which promoted neuroinflammation, cerebral edema, neuronal cell death, and aggravated neurological dysfunction. Inhibition of NETs formation by peptidylarginine deiminase (PAD) inhibitor or disruption of NETs with deoxyribonuclease I (DNase I) attenuated SBI-induced damages and improved the recovery of neurological function. We show that SBI triggered the activation of cyclic guanosine monophosphate-adenosine monophosphate synthase stimulator of interferon genes (cGAS-STING), and that inhibition of the cGAS-STING pathway could be beneficial. It is worth noting that DNase I markedly suppressed the activation of cGAS-STING, which was reversed by the cGAS product cyclic guanosine monophosphate-adenosine monophosphate (cGMP-AMP, cGAMP). Furthermore, the neuroprotective effect of DNase I in SBI was also abolished by cGAMP. NETs may participate in the pathophysiological regulation of SBI by acting through the cGAS-STING pathway. We also found that high-dose vitamin C administration could effectively inhibit the formation of NETs post-SBI. Thus, targeting NETs may provide a novel therapeutic strategy for SBI treatment, and high-dose vitamin C intervention may be a promising translational therapy with an excellent safety profile and low cost.

Tetramethylpyrazine protects mitochondrial function by up-regulation of TFAM and inhibition of neuronal apoptosis in a rat model of surgical brain injury

Objectives

Mitochondrial dysfunction caused by mitochondrial DNA (mtDNA) damage and mutation is widely accepted as one of the pathological processes of neurodegenerative diseases. As an mtDNA binding protein, mitochondrial transcription factor A (TFAM) maintains the integrity of mtDNA through transcription, replication, nucleoid formation, damage perception, and DNA repair. In recent works, the overexpression of TFAM increased the mtDNA copy count, promoted mitochondrial function, and improved the neurological dysfunction of neurodegenerative diseases. The role of TFAM in neurodegenerative diseases has been well explained. However, the role of TFAM after surgical brain injury (SBI) has not been studied. In this work, we aimed to study the role of TFAM in the brain after SBI and its mechanism of action.

Materials and Methods

One hour after the occurrence of SBI, tetramethylpyrazine (TMP) was injected into the abdominal cavity of rats, and the brain was collected 48 hr later for testing. The evaluation included neurobehavioral function test, brain water content measurement, immunofluorescence, western blot, TUNEL staining, FJC staining, ROS test, and ATP test.

Results

After SBI, the content of TFAM on the ipsilateral side increased and reached a peak at about 48 hr. After intraperitoneal injection of TMP in rats, 48 hr after SBI, the concentration of TFAM, Bcl-2, and adenosine triphosphate (ATP) increased; the content of caspase-3, reactive oxygen species (ROS), and cerebral edema decreased; and the nerve function significantly improved.

Conclusion

TMP inhibited cell apoptosis after SBI in rats by up-regulating TFAM and protecting brain tissues.

Possible role of Sox11 in a rat model of surgical brain injury

Objectives

Sox11, one of the SoxC family members, is an important transcription factor during neural development and neurogenesis. However, there is no report about its function in neural apoptosis. This research aims to examine the function of Sox11 in surgical brain injury (SBI).

Materials and Methods

We used 90 Sprague-Dawley rats to develop the SBI models and the siRNA of Sox11 to study the roles of Sox11. Western blot, real-time PCR, immunofluorescence, neuron apoptosis and necrosis, brain edema, and neurological score were determined.

Results

The gene and protein amount of Sox11, compared with the Sham group, were increased after SBI, which reached a peak at 12 hr. In addition, following the application of siRNAs, the amount of Sox11 protein was significantly less than that in the SBI group. On the other hand, neuronal apoptosis, necrosis, and brain edema were significantly increased, while neurological scores were decreased.

Conclusion

These findings demonstrate the role of Sox11 following nerve injury induced by SBI. Inhibition of Sox11 with siRNA may lead to neuronal injury and cell death, aggravating secondary brain injury after SBI.

Inhibition of the p‑SPAK/p‑NKCC1 signaling pathway protects the blood‑brain barrier and reduces neuronal apoptosis in a rat model of surgical brain injury

Surgical brain injury (SBI) can disrupt the function of the blood‑brain barrier (BBB), leading to brain edema and neurological dysfunction. Thus, protecting the BBB and mitigating cerebral edema are key factors in improving the neurological function and prognosis of patients with SBI. The inhibition of WNK lysine deficient protein kinase/STE20/SPS1‑related proline/alanine‑rich kinase (SPAK) signaling ameliorates cerebral edema, and this signaling pathway regulates the phosphorylation of the downstream Na⁺‑K⁺‑Cl^‑ cotransporter 1 (NKCC1). Therefore, the purpose of the present study was to investigate the role of SPAK in SBI‑induced cerebral edema and to determine whether the SPAK/NKCC1 signaling pathway was involved in SBI via regulating phosphorylation. An SBI model was established in male Sprague‑Dawley rats, and the effects of SPAK on the regulation of the NKCC1 signaling pathway on BBB permeability and nerve cell apoptosis by western blotting analysis, immunofluorescence staining, TUNEL staining, Fluoro‑Jade C staining, and brain edema and nervous system scores. The results demonstrated that, compared with those in the sham group, phosphorylated (p)‑SPAK and p‑NKCC1 protein expression levels were significantly increased in the SBI model group. After inhibiting p‑SPAK, the expression level of p‑NKCC1, neuronal apoptosis and BBB permeability were significantly reduced in SBI model rats. Taken together, these findings suggested that SBI‑induced increases in p‑SPAK and p‑NKCC1 expression exacerbated post‑traumatic neural and BBB damage, which may be mediated via the ion‑transport‑induced regulation of cell edema.

Biological effects of selective COX-2 inhibitor NS398 on human glioblastoma cell lines

Background

Cyclooxygenase-2 (COX-2), an inflammation-associated enzyme, has been implicated in tumorigenesis and progression of glioblastoma (GBM). The poor survival of GBM was mainly associated with the presence of glioma stem cells (GSC) and the markedly inflammatory microenvironment. To further explore the involvement of COX-2 in glioma biology, the effects of NS398, a selective COX-2 inhibitor, were evaluated on GSC derived from COX-2 expressing GBM cell lines, i.e., U87MG and T98G, in terms of neurospheres' growth, autophagy, and extracellular vesicle (EV) release.

Methods

Neurospheres' growth and morphology were evaluated by optical and scanning electron microscopy. Autophagy was measured by staining acidic vesicular organelles. Extracellular vesicles (EV), released from neurospheres, were analyzed by transmission electron microscopy. The autophagic proteins Beclin-1 and LC3B, as well as the EV markers CD63 and CD81, were analyzed by western blotting. The scratch assay test was used to evaluate the NS398 influence on GBM cell migration.

Results

Both cell lines were strongly influenced by NS398 exposure, as showed by morphological changes, reduced growth rate, and appearance of autophagy. Furthermore, the inhibitor led to a functional change of EV released by neurospheres. Indeed, EV secreted by NS398-treated GSC, but not those from control cells, were able to significantly inhibit adherent U87MG and T98G cell migration and induced autophagy in recipient cells, thus leading to effects quite similar to those directly caused by NS398 in the same cells.

Conclusion

Despite the intrinsic diversity and individual genetic features of U87MG and T98G, comparable effects were exerted by the COX-2 inhibitor NS398 on both GBM cell lines. Overall, our findings support the crucial role of the inflammatory-associated COX-2/PGE2 system in glioma and glioma stem cell biology.

Surgically-induced brain injury: where are we now?

Neurosurgical procedures cause inevitable brain damage from the multitude of surgical manipulations utilized. Incisions, retraction, thermal damage from electrocautery, and intraoperative hemorrhage cause immediate and long-term brain injuries that are directly linked to neurosurgical operations, and these types of injuries, collectively, have been termed surgical brain injury (SBI). For the past decade, a model developed to study the underlying brain pathologies resulting from SBI has provided insight on cellular mechanisms and potential therapeutic targets. This model, as seen in a rat, mouse, and rabbit, mimics a neurosurgical operation and causes commonly encountered post-operative complications such as brain edema, neuroinflammation, and hemorrhage. In this review, we elaborate on SBI and its clinical impact, the SBI animal models and their clinical relevance, the importance of applying therapeutics before neurosurgical procedures (i.e., preconditioning), and the new direction of applying venom-derived proteins to attenuate SBI.