Inhibition of the NKCC1/NF-κB Signaling Pathway Decreases Inflammation and Improves Brain Edema and Nerve Cell Apoptosis in an SBI Rat Model

Research developments in the neurovascular unit and the blood‑brain barrier (Review)

The neurovascular unit (NVU) is composed of neurons, glial cells, brain microvascular endothelial cells (BMECs), pericytes, and the extracellular matrix. The NVU controls the permeability of the blood-brain barrier (BBB) and protects the brain from harmful blood-borne and endogenous and exogenous substances. Among these, neurons transmit signals, astrocytes provide nutrients, microglia regulate inflammation, and BMECs and pericytes strengthen barrier tightness and coverage. These cells, due to their physical structure, anatomical location, or physiological function, maintain the microenvironment required for normal brain function. In this review, the BBB structure and mechanisms are examined to obtain a better understanding of the factors that influence BBB permeability. The findings may aid in safeguarding the BBB and provide potential therapeutic targets for drugs affecting the central nervous system.

Attenuation of Blood-Brain Barrier Disruption in Traumatic Brain Injury via Inhibition of NKCC1 Cotransporter: Insights into the NF-κB/NLRP3 Signaling Pathway

Following traumatic brain injury (TBI), inhibition of the Na+-K+-Cl- cotransporter1 (NKCC1) has been observed to alleviate damage to the blood-brain barrier (BBB). However, the underlying mechanism for this effect remains unclear. This study aimed to investigate the mechanisms by which inhibiting the NKCC1 attenuates disruption of BBB integrity in TBI. The TBI model was induced in C57BL/6 mice through a controlled cortical impact device, and an in vitro BBB model was established using Transwell chambers. Western blot (WB) analysis was used to evaluate NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome and nuclear factor-kappaB (NF-κB) pathway proteins. Flow cytometry and transendothelial electrical resistance (TEER) were employed to assess endothelial cell apoptosis levels and BBB integrity. ELISA was utilized to measure cytokines interleukin-1β (IL-1β) and matrix metalloproteinase-9 (MMP-9). Immunofluorescence techniques were used to evaluate protein levels and the nuclear translocation of the rela (p65) subunit. The Evans blue dye leakage assay and the brain wet-dry weight method were utilized to assess BBB integrity and brain swelling. Inhibition of NKCC1 reduced the level of NLRP3 inflammasome and the secretion of IL-1β and MMP-9 in microglia. Additionally, NKCC1 inhibition suppressed the activation of the NF-κB signaling pathway, which in turn decreased the level of NLRP3 inflammasome. The presence of NLRP3 inflammasome in BV2 cells led to compromised BBB integrity within an inflammatory milieu. Following TBI, an upregulation of NLRP3 inflammasome was observed in microglia, astrocytes, vascular endothelial cells, and neurons. Furthermore, inhibiting NKCC1 resulted in a decrease in the positive rate of NLRP3 inflammasome in microglia and the levels of inflammatory cytokines IL-1β and MMP-9 after TBI, which correlated with BBB damage and the development of cerebral edema. These findings demonstrate that the suppression of the NKCC1 cotransporter protein alleviates BBB disruption through the NF-κB/NLRP3 signaling pathway following TBI.

Enriched environment may improve secondary brain injury after traumatic brain injury by regulating the TLR2/NF-κB signaling pathway

Background

Traumatic brain injury (TBI) can cause damage to the blood-brain barrier, resulting in neuroinflammatory reactions and brain edema that seriously affect the recovery of neurological function. We hypothesize that an enriched environment (EE) regulates the TLR2/NF-κB signaling pathway and thereby modulates the integrity of the blood-brain barrier to achieve neuroprotective effects.

Objective

This study evaluated the expression of toll-like receptor (TLR)-2 after TBI in a rat model, with the aim of determining whether TLR2/NF-κB improves secondary brain injury by inhibiting the release of inflammatory factors and reducing brain edema.

Methods

We established a TBI model using Sprague-Dawley rats and implemented EE intervention or TLR2 siRNA to reduce TLR2. Western-blot analysis, real-time PCR, immunofluorescence staining, ELISA, TUNEL and FJC staining, wet-dry methods, rotarod testing, and neurological scoring were then applied for analysis.

Results

Our results revealed that TLR2 was activated after TBI in rats and that EE or silencing of TLR2 with TLR2 siRNA reduced the level of inflammation, significantly alleviating brain edema, neuronal apoptosis, and degeneration. TBI exacerbated brain edema and nerve damage caused by TLR2/NF-κB signaling, and EE appeared to regulate neuroinflammation and brain edema by reducing TLR2.

Conclusions

Inhibition of TLR2 with EE might constitute a successful approach in the management of TBI.

Aquaporins in sepsis- an update

Aquaporins (AQPs), a family of membrane proteins that facilitate the transport of water and small solutes, have garnered increasing attention for their role in sepsis, not only in fluid balance but also in immune modulation and metabolic regulation. Sepsis, characterized by an excessive and dysregulated immune response to infection, leads to widespread organ dysfunction and significant mortality. This review focuses on the emerging roles of aquaporins in immune metabolism and their potential as therapeutic targets in sepsis, with particular attention to the modulation of inflammatory responses and organ protection. Additionally, it explores the diverse roles of aquaporins across various organ systems, highlighting their contributions to renal function, pulmonary gas exchange, cardiac protection, and gastrointestinal barrier integrity in the context of sepsis. Recent studies suggest that AQPs, particularly aquaglyceroporins like AQP3, AQP7, AQP9, and AQP10, play pivotal roles in immune cell metabolism and offer new therapeutic avenues for sepsis treatment. In the context of sepsis, immune cells undergo metabolic shifts to meet the heightened energy demands of the inflammatory response. A key adaptation is the shift from oxidative phosphorylation (OXPHOS) to aerobic glycolysis, where pyruvate is converted to lactate, enabling faster ATP production. AQPs, particularly aquaglyceroporins, may facilitate this process by transporting glycerol, a substrate that fuels glycolysis. AQP3, for example, enhances glucose metabolism by transporting glycerol and complementing glucose uptake via GLUT1, while also regulating O-GlcNAcylation, a post-translational modification that boosts glycolytic flux. AQP7 could further contributes to immune cell energy production by influencing lipid metabolism and promoting glycolysis through p38 signaling. These mechanisms could be crucial for maintaining the energy supply needed for an effective immune response during sepsis. Beyond metabolism, AQPs also regulate key immune functions. AQP9, highly expressed in septic patients, is essential for neutrophil migration and activation, both of which are critical for controlling infection. AQP3, on the other hand, modulates inflammation through the Toll-like receptor 4 (TLR4) pathway, while AQP1 plays a role in immune responses by activating the PI3K pathway, promoting macrophage polarization, and protecting against lipopolysaccharide (LPS)-induced acute kidney injury (AKI). These insights into the immunoregulatory roles of AQPs suggest their potential as therapeutic targets to modulate inflammation in sepsis. Therapeutically, AQPs present promising targets for reducing organ damage and improving survival in sepsis. For instance, inhibition of AQP9 with compounds like HTS13286 or RG100204 has been shown to reduce inflammation and improve survival by modulating NF-κB signaling and decreasing oxidative stress in animal models. AQP5 inhibition with methazolamide and furosemide has demonstrated efficacy in reducing immune cell migration and lung injury, suggesting its potential in treating acute lung injury (ALI) in sepsis. Additionally, the regulation of AQP1 through non-coding RNAs (lncRNAs and miRNAs) may offer new strategies to mitigate organ damage and inflammatory responses. Moreover, AQPs have emerged as potential biomarkers for sepsis progression and outcomes. Altered expression of AQPs, such as AQP1, AQP3, and AQP5, correlates with sepsis severity, and polymorphisms in AQP5 have been linked to better survival rates and improved outcomes in sepsis-related acute respiratory distress syndrome (ARDS). This suggests that AQP expression could be used to stratify patients and tailor treatments based on individual AQP profiles. In conclusion, AQPs play a multifaceted role in the pathophysiology of sepsis, extending beyond fluid balance to crucial involvement in immune metabolism and inflammation. Targeting AQPs offers novel therapeutic strategies to mitigate sepsis-induced organ damage and improve patient survival. Continued research into the metabolic and immune functions of AQPs will be essential for developing targeted therapies that can be translated into clinical practice.

Broadening horizons: ferroptosis as a new target for traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide, with ~50 million people experiencing TBI each year. Ferroptosis, a form of regulated cell death triggered by iron ion-catalyzed and reactive oxygen species-induced lipid peroxidation, has been identified as a potential contributor to traumatic central nervous system conditions, suggesting its involvement in the pathogenesis of TBI. Alterations in iron metabolism play a crucial role in secondary injury following TBI. This study aimed to explore the role of ferroptosis in TBI, focusing on iron metabolism disorders, lipid metabolism disorders and the regulatory axis of system Xc-/glutathione/glutathione peroxidase 4 in TBI. Additionally, we examined the involvement of ferroptosis in the chronic TBI stage. Based on these findings, we discuss potential therapeutic interventions targeting ferroptosis after TBI. In conclusion, this review provides novel insights into the pathology of TBI and proposes potential therapeutic targets.

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.

Potential mechanism of TMEM2/CD44 in endoplasmic reticulum stress‑induced neuronal apoptosis in a rat model of traumatic brain injury

Traumatic brain injury (TBI) can lead to the disruption of endoplasmic reticulum (ER) homeostasis in neurons and induce ER stress. Transmembrane protein 2 (TMEM2) may regulate ER stress through the p38/ERK signaling pathway, independent of the classic unfolded protein response (UPR) pathway. The present study examined the expression of TMEM2 following TBI in a rat model, in an aim to determine whether the mitogen‑activated protein kinase (MAPK) signaling pathway is controlled by TMEM2/CD44 to mitigate secondary brain injury. For this purpose, 89 Sprague‑Dawley rats were used to establish the model of TBI, and TMEM2 siRNA was used to silence TMEM2. Western blot analysis, immunofluorescence, TUNEL assay and Fluoro‑Jade C staining, the wet‑dry method and behavioral scoring were used for analyses. The results revealed that TMEM2 was activated following TBI in rats. The silencing of TMEM2 resulted in a significant increase in the levels of p38 and ERK (components of MAPK signaling), while brain edema, neuronal apoptosis and degeneration were significantly aggravated. TBI increased TMEM2/CD44‑aggravated brain edema and neurological impairment, possibly by regulating ERK and p38 signaling. TMEM2/CD44 may thus be a target for the prevention and control of TBI.

The role of SLC12A family of cation-chloride cotransporters and drug discovery methodologies

The solute carrier family 12 (SLC12) of cation-chloride cotransporters (CCCs) comprises potassium chloride cotransporters (KCCs, e.g. KCC1, KCC2, KCC3, and KCC4)-mediated Cl- extrusion, and sodium potassium chloride cotransporters (N[K]CCs, NKCC1, NKCC2, and NCC)-mediated Cl- loading. The CCCs play vital roles in cell volume regulation and ion homeostasis. Gain-of-function or loss-of-function of these ion transporters can cause diseases in many tissues. In recent years, there have been considerable advances in our understanding of CCCs' control mechanisms in cell volume regulations, with many techniques developed in studying the functions and activities of CCCs. Classic approaches to directly measure CCC activity involve assays that measure the transport of potassium substitutes through the CCCs. These techniques include the ammonium pulse technique, radioactive or nonradioactive rubidium ion uptake-assay, and thallium ion-uptake assay. CCCs' activity can also be indirectly observed by measuring γ-aminobutyric acid (GABA) activity with patch-clamp electrophysiology and intracellular chloride concentration with sensitive microelectrodes, radiotracer 36Cl-, and fluorescent dyes. Other techniques include directly looking at kinase regulatory sites phosphorylation, flame photometry, 22Na+ uptake assay, structural biology, molecular modeling, and high-throughput drug screening. This review summarizes the role of CCCs in genetic disorders and cell volume regulation, current methods applied in studying CCCs biology, and compounds developed that directly or indirectly target the CCCs for disease treatments.

Rosiglitazone inhibits acyl-CoA synthetase long-chain family number 4 and improves secondary brain injury in a rat model of surgical brain injury

Ferroptosis is a recently discovered non-apoptotic form of cellular death. Acyl-CoA synthetase long-chain family number 4 (ACSL4) is necessary for iron-dependent cellular death, and reactive oxygen species (ROS) produced by ACSL4 are the executioners of ferroptosis. Rosiglitazone improves ferroptosis by inhibiting ACSL4. There is no research indicating whether ACSL4 plays a role in cell death after surgical brain injury (SBI). This study aimed to investigate the role of ACSL4 in SBI via the ferroptosis pathway. Ninety male Sprague-Dawley rats were examined using a model of SBI. Subsequently, the inhibitory effect of rosiglitazone on ACSL4 was assessed via western blot, real-time polymerase chain reaction (PCR), immunofluorescence, fluoro-jade C staining, Perl's staining, ROS assay, and neurological scoring. The results showed that compared with the Sham group, the protein levels of ACSL4 and transferrin were significantly increased after SBI. Administration of rosiglitazone significantly reduced neuronal necrosis, iron deposition, brain water content and ROS in brain tissue and ameliorated neurological deficits at 48 h after SBI, which was concomitant with decreased transferrin expression. These findings demonstrate that SBI-induced upregulation of ACSL4 may be partly mediated by the ferroptosis pathway, which can be reversed by rosiglitazone administration.

RGFP966 exerts neuroprotective effect via HDAC3/Nrf2 pathway after surgical brain injury in rats

Histone deacetylase 3 (HDAC3) restores chromatin nucleosomes to a transcriptional repression state, thereby inhibiting gene expression. Studies have found that HDAC3 expression is upregulated in a variety of pathological states of the central nervous system and related to its neurotoxicity. However, the role of HDAC3 in surgical brain injury (SBI) has not been thoroughly explored.

OBJECTIVE

To observe the role of HDAC3 in SBI and the outcome of SBI after its suppression.

METHODS

Rat SBI model was used, and intraperitoneal injection of RGFP966 (HDAC3 specific inhibitor) was used to detect the changes of HDAC3 expression and neuronal apoptosis indexes in the surrounding cortex of SBI rats, and the cerebral edema and neurological outcome of rats were observed.

RESULTS

The expression of HDAC3 in the peripheral cortex of SBI rats was increased, and RGFP966 inhibited the upregulation of HDAC3 and saved the nerve cells around the damaged area. In addition, RGFP966 increased the expression of anti-oxidative stress proteins such as heme oxygenase-1 (HO-1) and superoxide dismutase 2 (SOD2). At the same time, the expression of apoptotic marker protein cleaved-caspase-3 (cle-caspase-3) was decreased, while the expression level of apoptotic protective marker protein B-cell lymphoma 2 (Bcl-2) was increased. In addition, this research demonstrated that in the RGFP966 rat SBI model, the expression level of antioxidant modifier nuclear factor-erythroid 2-related factor 2 (Nrf2) was increased.

CONCLUSION

RGFP966 might activate HDAC3/Nrf2 signaling pathway by inhibiting HDAC3, regulated oxidative stress and nerve cell apoptosis induced by SBI in rat SBI model, reduced brain edema, and had a protective effect on nerve injury. It might be a potential target of SBI pathology.

A Wholistic View of How Bumetanide Attenuates Autism Spectrum Disorders

The specific NKCC1 cotransporter antagonist, bumetanide, attenuates the severity of Autism Spectrum Disorders (ASD), and many neurodevelopmental or neurodegenerative disorders in animal models and clinical trials. However, the pervasive expression of NKCC1 in many cell types throughout the body is thought to challenge the therapeutic efficacy of bumetanide. However, many peripheral functions, including intestinal, metabolic, or vascular, etc., are perturbed in brain disorders contributing to the neurological sequels. Alterations of these functions also increase the incidence of the disorder suggesting complex bidirectional links with the clinical manifestations. We suggest that a more holistic view of ASD and other disorders is warranted to account for the multiple sites impacted by the original intra-uterine insult. From this perspective, large-spectrum active repositioned drugs that act centrally and peripherally might constitute a useful approach to treating these disorders.

Downregulation of TREM2/NF-кB signaling may damage the blood-brain barrier and aggravate neuronal apoptosis in experimental rats with surgically injured brain

Surgical brain injury (SBI) is unavoidable in neurosurgery, and could aggravate secondary brain injury. Post-brain injury, multiple inflammatory factors are released, resulting in neuroinflammation and cell apoptosis, with subsequent brain edema and nerve function injury. TREM2, an immune protein mainly expressed in microglia, is an important link for nerve cells to participate in the inflammatory response. TREM2 and nuclear factor кB (NF-кB) are indeed closely associated with the release of inflammatory cytokines following brain injury. This work aimed to determine the inflammatory function of TREM2 in SBI, and to investigate whether TREM2 regulates interleukin-1 beta (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α) release through the NF-кB p65 signaling pathway. We established a rat model of SBI, and performed Western blotting (WB), immunofluorescence (IF) and enzyme-linked immunosorbent assay (ELISA) for further analysis. Next, brain edema and neurological score analyses were performed. Finally, whether TREM2 regulating NF-кB p65 signaling affects blood-brain barrier (BBB) permeability and nerve cell apoptosis was examined. We found that post-SBI, TREM2 was upregulated, and inflammation and brain injury were aggravated. After TREM2 downregulation, NF-кB p65 production, inflammation and brain injury were enhanced, suggesting that TREM2 may play a protective role by inhibiting NF-кB p65 production after SBI. Overall, these findings suggest that TREM2 in SBI may have protective effects on postoperative nerve and BBB damage, possibly in part via the NF-κB p65 pathway.

Recent breakthroughs and future directions in drugging aquaporins

Aquaporins facilitate the passive transport of water, solutes, or ions across biological membranes. They are implicated in diverse pathologies including brain edema following stroke or trauma, epilepsy, cancer cell migration and tumor angiogenesis, metabolic disorders, and inflammation. Despite this, there is no aquaporin-targeted drug in the clinic and aquaporins have been perceived to be intrinsically non-druggable targets. Here we challenge this idea, as viable routes to inhibition of aquaporin function have recently been identified, including targeting their regulation or their roles as channels for unexpected substrates. Identifying new drug development frameworks for conditions associated with disrupted water and solute homeostasis will meet the urgent, unmet clinical need of millions of patients for whom no pharmacological interventions are available.

Effects and mechanisms of CTRP3 overexpression in secondary brain injury following intracerebral hemorrhage in rats

C1q/TNF-related protein-3 (CTRP3) is a novel adipokine that serves an important role in oxidative stress, anti-apoptosis, anti-inflammation and immune regulation. The aim of the present study was to investigate the protective role of CTRP3 against intracerebral hemorrhage (ICH)-induced brain injury. A model of autologous arterial blood-induced ICH was constructed in rats. Intracerebral infusion of a lentivirus carrying the CTRP3 gene was used to induce CTRP3 overexpression in the brain. The effects and mechanisms of CTRP3 overexpression on brain injury were investigated by detecting brain edema, blood-brain barrier (BBB) integrity, neurological function and inflammatory-associated factors 3 days after ICH. The present results demonstrated that CTRP3 overexpression ameliorated ICH-induced neurological dysfunction, decreased brain edema, maintained BBB integrity and attenuated inflammation. The protective effect of CTRP3 overexpression was associated with increased activation of silent information regulator 1 (SIRT1). In conclusion, the present study demonstrated that CTRP3 overexpression protected against ICH-induced brain injury in rats, potentially via activating the SIRT1 signaling pathway.

Cochlear Inflammaging in Relation to Ion Channels and Mitochondrial Functions

The slow accumulation of inflammatory biomarker levels in the body-also known as inflammaging-has been linked to a myriad of age-related diseases. Some of these include neurodegenerative conditions such as Parkinson's disease, obesity, type II diabetes, cardiovascular disease, and many others. Though a direct correlation has not been established, research connecting age-related hearing loss (ARHL)-the number one communication disorder and one of the most prevalent neurodegenerative diseases of our aged population-and inflammaging has gained interest. Research, thus far, has found that inflammatory markers, such as IL-6 and white blood cells, are associated with ARHL in humans and animals. Moreover, studies investigating ion channels and mitochondrial involvement have shown promising relationships between their functions and inflammaging in the cochlea. In this review, we summarize key findings in inflammaging within the auditory system, the involvement of ion channels and mitochondrial functions, and lastly discuss potential treatment options focusing on controlling inflammation as we age.

Synovial Fluid of Patient With Rheumatoid Arthritis Enhanced Osmotic Sensitivity Through the Cytotoxic Edema Module in Synoviocytes

Rheumatoid arthritis (RA) is an autoimmune disease that causes inflammation of the synovial membrane ultimately leading to permanent damage in the affected joints. For this study, synovial fluids from 16 patients diagnosed with either RA or osteoarthritis (OA) were used to examine volume regulation and cooperative water channels, both of which are involved in the cytotoxic edema identified in RA-fibroblast-like synoviocytes (FLS). The osmolarity and inflammatory cytokine interleukin (IL)-6 of synovial fluids from RA patients were mildly enhanced compared to that from OA patients. RA-FLS demonstrated the enhanced property of regulatory volume increase in response to IL-6 and synovial fluids from RA patients. Although there was no difference in the protein expression of the volume-associated protein sodium–potassium–chloride cotransporter1 (NKCC1), its activity was increased by treatment with IL-6. Membrane localization of NKCC1 was also increased by IL-6 treatment. Additionally, both the protein and membrane expressions of aquaporin-1 were increased in RA-FLS by IL-6 stimulation. The IL-6-mediated enhanced osmotic sensitivity of RA-FLS likely involves NKCC1 and aquaporin-1, which mainly constitute the volume-associated ion transporter and water channel elements. These results suggest that RA-FLS provide enhanced electrolytes and concomitant water movement through NKCC1 and aquaporin-1, thereby inducing cellular swelling ultimately resulting in cytotoxic edema. Attenuation of cytotoxic edema and verification of its related mechanism will provide novel therapeutic approaches to RA treatment within the scope of cytotoxic edema.

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.