Administration of Dexmedetomidine inhibited NLRP3 inflammasome and microglial cell activities in hippocampus of traumatic brain injury rats

The Role of Intravenous Anesthetics for Neuro: Protection or Toxicity?

The primary intravenous anesthetics employed in clinical practice encompass dexmedetomidine (Dex), propofol, ketamine, etomidate, midazolam, and remimazolam. Apart from their established sedative, analgesic, and anxiolytic properties, an increasing body of research has uncovered neuroprotective effects of intravenous anesthetics in various animal and cellular models, as well as in clinical studies. However, there also exists conflicting evidence pointing to the potential neurotoxic effects of these intravenous anesthetics. The role of intravenous anesthetics for neuro on both sides of protection or toxicity has been rarely summarized. Considering the mentioned above, this work aims to offer a comprehensive understanding of the underlying mechanisms involved both in the central nerve system (CNS) and the peripheral nerve system (PNS) and provide valuable insights into the potential safety and risk associated with the clinical use of intravenous anesthetics.

Association of early dexmedetomidine exposure with brain injury biomarker levels following moderate - Severe traumatic brain injury: A TRACK-TBI study

BACKGROUND

Traumatic brain injury (TBI) triggers autonomic dysfunction and inflammatory response that can result in secondary brain injuries. Dexmedetomidine is an alpha-2 agonist that may modulate autonomic function and inflammation and has been increasingly used as a sedative agent for critically ill TBI patients. We aimed to investigate the association between early dexmedetomidine exposure and blood-based biomarker levels in moderate-to-severe TBI (msTBI).

METHODS

We conducted a retrospective cohort study using data from the Transforming Clinical Research and Knowledge in Traumatic Brain Injury Study (TRACK-TBI), which enrolled acute TBI patients prospectively across 18 United States Level 1 trauma centers between 2014-2018. Our study population focused on adults with msTBI defined by Glasgow Coma Scale score 3-12 after resuscitation, who required mechanical ventilation and sedation within the first 48 h of ICU admission. The study's exposure was early dexmedetomidine utilization (within the first 48 h of admission). Primary outcome included brain injury biomarker levels measured from circulating blood on day 3 following injury, including glial fibrillary acidic protein (GFAP), ubiquitin C-terminal hydrolase-L1 (UCH-L1), neuron-specific enolase (NSE), S100 calcium-binding protein B (S100B) and the inflammatory biomarker C-reactive protein (CRP). Secondary outcomes assessed biomarker levels on days 5 and 14. Linear mixed-effects regression modelling of the log-transformed response variable was used to analyze the association of early dexmedetomidine exposure with brain injury biomarker levels.

RESULTS

Among the 352 TRACK-TBI subjects that met inclusion criteria, 50 (14.2 %) were exposed to early dexmedetomidine, predominantly male (78 %), white (81 %), and non-Hispanic (81 %), with mean age of 39.8 years. Motor vehicle collisions (27 %) and falls (22 %) were common causes of injury. No significant associations were found between early dexmedetomidine exposure with day 3 brain injury biomarker levels (GFAP, ratio = 1.46, 95 % confidence interval [0.90, 2.34], P = 0.12; UCH-L1; ratio = 1.17 [0.89, 1.53], P = 0.26; NSE, ratio = 1.19 [0.92, 1.53], P = 0.19; S100B, ratio = 1.01 [0.95, 1.06], P = 0.82; hs-CRP, ratio = 1.29 [0.91, 1.83], P = 0.15). The hs-CRP level at day 14 in the dexmedetomidine group was higher than that of the non-exposure group (ratio = 1.62 [1.12, 2.35], P = 0.012).

CONCLUSIONS

There were no significant associations between early dexmedetomidine exposure and day 3 brain injury biomarkers in msTBI. Our findings suggest that early dexmedetomidine use is not correlated with either decrease or increase in brain injury biomarkers following msTBI. Further research is necessary to confirm these findings.

Targeting NLRP3 Inflammasomes: A Trojan Horse Strategy for Intervention in Neurological Disorders

Recently, a growing focus has been on identifying critical mechanisms in neurological diseases that trigger a cascade of events, making it easier to target them effectively. One such mechanism is the inflammasome, an essential component of the immune response system that plays a crucial role in disease progression. The NLRP3 (nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain containing 3) inflammasome is a subcellular multiprotein complex that is widely expressed in the central nervous system (CNS) and can be activated by a variety of external and internal stimuli. When activated, the NLRP3 inflammasome triggers the production of proinflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18) and facilitates rapid cell death by assembling the inflammasome. These cytokines initiate inflammatory responses through various downstream signaling pathways, leading to damage to neurons. Therefore, the NLRP3 inflammasome is considered a significant contributor to the development of neuroinflammation. To counter the damage caused by NLRP3 inflammasome activation, researchers have investigated various interventions such as small molecules, antibodies, and cellular and gene therapy to regulate inflammasome activity. For instance, recent studies indicate that substances like micro-RNAs (e.g., miR-29c and mR-190) and drugs such as melatonin can reduce neuronal damage and suppress neuroinflammation through NLRP3. Furthermore, the transplantation of bone marrow mesenchymal stem cells resulted in a significant reduction in the levels of pyroptosis-related proteins NLRP3, caspase-1, IL-1β, and IL-18. However, it would benefit future research to have an in-depth review of the pharmacological and biological interventions targeting inflammasome activity. Therefore, our review of current evidence demonstrates that targeting NLRP3 inflammasomes could be a pivotal approach for intervention in neurological disorders.

Inflammasomes at the crossroads of traumatic brain injury and post-traumatic epilepsy

Post-traumatic epilepsy (PTE) is one of the most debilitating consequences of traumatic brain injury (TBI) and is one of the most drug-resistant forms of epilepsy. Novel therapeutic treatment options are an urgent unmet clinical need. The current focus in healthcare has been shifting to disease prevention, rather than treatment, though, not much progress has been made due to a limited understanding of the disease pathogenesis. Neuroinflammation has been implicated in the pathophysiology of traumatic brain injury and may impact neurological sequelae following TBI including functional behavior and post-traumatic epilepsy development. Inflammasome signaling is one of the major components of the neuroinflammatory response, which is increasingly being explored for its contribution to the epileptogenic mechanisms and a novel therapeutic target against epilepsy. This review discusses the role of inflammasomes as a possible connecting link between TBI and PTE with a particular focus on clinical and preclinical evidence of therapeutic inflammasome targeting and its downstream effector molecules for their contribution to epileptogenesis. Finally, we also discuss emerging evidence indicating the potential of evaluating inflammasome proteins in biofluids and the brain by non-invasive neuroimaging, as potential biomarkers for predicting PTE development.

Inflammasomes in neurological disorders - mechanisms and therapeutic potential

Inflammasomes are molecular scaffolds that are activated by damage-associated and pathogen-associated molecular patterns and form a key element of innate immune responses. Consequently, the involvement of inflammasomes in several diseases that are characterized by inflammatory processes, such as multiple sclerosis, is widely appreciated. However, many other neurological conditions, including Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis, stroke, epilepsy, traumatic brain injury, sepsis-associated encephalopathy and neurological sequelae of COVID-19, all involve persistent inflammation in the brain, and increasing evidence suggests that inflammasome activation contributes to disease progression in these conditions. Understanding the biology and mechanisms of inflammasome activation is, therefore, crucial for the development of inflammasome-targeted therapies for neurological conditions. In this Review, we present the current evidence for and understanding of inflammasome activation in neurological diseases and discuss current and potential interventional strategies that target inflammasome activation to mitigate its pathological consequences.

Neuroprotective Effects of CXCR2 Antagonist SB332235 on Traumatic Brain Injury Through Suppressing NLRP3 Inflammasome

The inflammatory process mediated by nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain comprising 3 (NLRP3) inflammasome plays a predominant role in the neurological dysfunction following traumatic brain injury (TBI). SB332235, a highly selective antagonist of chemokine receptor 2 (CXCR2), has been demonstrated to exhibit anti-inflammatory properties and improve neurological outcomes in the central nervous system. We aimed to determine the neuroprotective effects of SB332235 in the acute phase after TBI in mice and to elucidate its underlying mechanisms. Male C57BL/6J animals were exposed to a controlled cortical impact, then received 4 doses of SB332235, with the first dose administered at 30 min after TBI, followed by additional doses at 6, 24, and 30 h. Neurological defects were assessed by the modified neurological severity score, while the motor function was evaluated using the beam balance and open field tests. Cognitive performance was evaluated using the novel object recognition test. Brain tissues were collected for pathological, Western blot, and immunohistochemical analyses. The results showed that SB332235 significantly ameliorated TBI-induced deficits, including motor and cognitive impairments. SB332235 administration suppressed expression of both CXCL1 and CXCR2 in TBI. Moreover, SB332235 substantially mitigated the augmented expression levels and activation of the NLRP3 inflammasome within the peri-contusional cortex induced by TBI. This was accompanied by the blocking of subsequent production of pro-inflammatory cytokines. Additionally, SB332235 hindered microglial activity induced by TBI. These findings confirmed the neuroprotective effects of SB332235 against TBI, and the involved mechanisms were in part due to the suppression of NLRP3 inflammasome activity. This study suggests that SB332235 may act as an anti-inflammatory agent to improve functional outcomes in brain injury when applied clinically.

Involvement of estrogen receptor activation in kaempferol-3-O-glucoside's protection against aging-related cognition impairment and microglial inflammation

Estrogens have been demonstrated to inhibit age-related cognitive decline via binding to estrogen receptors (ERs). As a natural flavonoid component of Cuscuta Chinensis Lam., Kaempferol-3-O-glucoside (K-3-G) not only possesses anti-neuroinflammatory potential but also functions as an agonist for ERα and ERβ. This study aimed to determine whether K-3-G improved cognition during the aging process, with an emphasis on its effect on microglial inflammation. In vivo, K-3-G (5 or 10 mg/kg/day) was orally given to the senescence-accelerated mouse prone 8 (SAMP8) mice from six to eight-month old. In addition to mitigating the memory and learning deficits of SAMP8 mice, K-3-G upregulated the expression of ERα and ERβ in their hippocampal CA1 region, with the higher dose being more effective. Less Iba-1+ microglial cells presented in SAMP8 mice treated with K-3-G. The formation of NLR Family Pyrin Domain Containing 3 (NLRP3) complex, production of pro-inflammatory cytokines and oxidative stress-related markers, as well as expression of pro-apoptotic proteins were reduced by K-3-G. In vitro, BV2 microglial cells exposed to oligomeric amyloid beta (Aβ)1-42 were treated with 100 μM K-3-G. K-3-G showed similar anti-inflammatory effects on BV2 cells as in vivo. K-3-G-induced alterations were partly diminished by fulvestrant, an ER antagonist. Moreover, dual-luciferase reporter system demonstrated that K-3-G induced ER expression by activating the transcription of estrogen-response elements (EREs). Collectively, these findings demonstrate that K-3-G may be a novel therapeutic agent for senescence-related cognitive impairment by inhibiting microglial inflammation through its action on ERs.

Small molecule inhibitors of NLRP3 inflammasome and GSK-3β in the management of traumatic brain injury: A review

Traumatic brain injury (TBI) is a debilitating mental condition which causes physical disability and morbidity worldwide. TBI may damage the brain by direct injury that subsequently triggers a series of neuroinflammatory events. The activation of NLRP3 inflammasome and dysregulated host immune system has been documented in various neurological disorders such as TBI, ischemic stroke and multiple sclerosis. The activation of NLRP3 post-TBI increases the production of pro-inflammatory cytokines and caspase-1, which are major drivers of neuroinflammation and apoptosis. Similarly, GSK-3β regulates apoptosis through tyrosine kinase and canonical Wnt signalling pathways. Thus, therapeutic targeting of NLRP3 inflammasome and GSK-3β has emerged as promising strategies for regulating the post-TBI neuroinflammation and neurobehavioral disturbances. In this review, we discuss the identification & development of several structurally diverse and pharmacologically interesting small molecule inhibitors for targeting the NLRP3 inflammasome and GSK-3β in the management of TBI.

Neuroinflammation: The central enabler of postoperative cognitive dysfunction

The proportion of advanced age patients undergoing surgical procedures is on the rise owing to advancements in surgical and anesthesia technologies as well as an overall aging population. As a complication of anesthesia and surgery, older patients frequently suffer from postoperative cognitive dysfunction (POCD), which may persist for weeks, months or even longer. POCD is a complex pathological process involving multiple pathogenic factors, and its mechanism is yet unclear. Potential theories include inflammation, deposition of pathogenic proteins, imbalance of neurotransmitters, and chronic stress. The identification, prevention, and treatment of POCD are still in the exploratory stages owing to the absence of standardized diagnostic criteria. Undoubtedly, comprehending the development of POCD remains crucial in overcoming the illness. Neuroinflammation is the leading hypothesis and a crucial component of the pathological network of POCD and may have complex interactions with other mechanisms. In this review, we discuss the possible ways in which surgery and anesthesia cause neuroinflammation and investigate the connection between neuroinflammation and the development of POCD. Understanding these mechanisms may likely ensure that future treatment options of POCD are more effective.

Neuroprotective effect of dexmedetomidine on autophagy in mice administered intracerebroventricular injections of Aβ25-35

Alzheimer's disease (AD), one of the most prevalent neurodegenerative diseases is associated with pathological autophagy-lysosomal pathway dysfunction. Dexmedetomidine (Dex) has been suggested as an adjuvant to general anesthesia with advantages in reducing the incidence of postoperative cognitive dysfunction in Dex-treated patients with AD and older individuals. Several studies reported that Dex improved memory; however, evidence on the effects of Dex on neuronal autophagy dysfunction in the AD model is lacking. We hypothesized that Dex administration would have neuroprotective effects by improving pathological autophagy dysfunction in mice that received an intracerebroventricular (i.c.v.) injection of amyloid β-protein fragment 25-35 (Aβ25-35) and in an autophagy-deficient cellular model. In the Y-maze test, Dex reversed the decreased activity of Aβ25-35 mice. Additionally, it restored the levels of two memory-related proteins, phosphorylated Ca2+/calmodulin-dependent protein kinase II (p-CaMKII) and postsynaptic density-95 (PSD-95) in Aβ25-35 mice and organotypic hippocampal slice culture (OHSC) with Aβ25-35. Dex administration also resulted in decreased expression of the autophagy-related microtubule-associated proteins light chain 3-II (LC3-II), p62, lysosome-associated membrane protein2 (LAMP2), and cathepsin D in Aβ25-35 mice and OHSC with Aβ25-35. Increased numbers of co-localized puncta of LC3-LAMP2 or LC3-cathepsin D, along with dissociated LC3-p62 immunoreactivity following Dex treatment, were observed. These findings were consistent with the results of western blots and the transformation of double-membrane autophagosomes into single-membraned autolysosomes in ultrastructures. It was evident that Dex treatment alleviated impaired autolysosome formation in Aβ mice. Our study demonstrated the improvement of memory impairment caused by Dex and its neuroprotective mechanism by investigating the role of the autophagy-lysosomal pathway in a murine Aβ25-35 model. These findings suggest that Dex could be used as a potential neuroprotective adjuvant in general anesthesia to prevent cognitive decline.

Effect of Dexmedotomdine hydrochloride (Percedex®) on functional outcome of patients with moderate and severe traumatic brain injury

Traumatic brain injury (TBI) is considered among the leading causes of morbidity and mortality worldwide being associated with significant social and economic burden. The best sedative regimen in TBI patients is yet to be identified. This study was designed to determine the effects of dexmedotomdine hydrochloride (Percedex®, DEX) on functional outcome of patients with moderate and severe traumatic brain injury (TBI). This was a retrospective cohort study including patients with severe (3-8) and moderate (9-13) TBI referring to a level I trauma center. We studied two groups of patients, those receiving DEX or routine sedation regimen in neurointensive care unit (NICU). The main outcome measures were the Glasgow outcome scale extended (GOSE) at 3 and 6-month. We have also recorded ICU and hospital length of stay (LOS) and the tracheostomy rate. We included 138 patients in two study groups (each including 69). The baseline characteristics were comparable between groups. DEX was associated with lower LOS in hospital (p = 0.002) and NICU (p = 0.003). The GOSE was comparable between two study groups at 3 (p = 0.245) and 6-month (p = 0.497). Multivariate regression analysis revealed that after LOS of NICU and hospital stay adjustment, DEX group experienced significantly improved 6-month GOSE with the average improvement in score of 0.92 compared to the control group (p = 0.041). DEX administration in patients with moderate and severe TBI was associated with decreased NICU and hospital LOS and improved functional outcome at 6-month.

Effect of the Lipoxin Receptor Agonist BML-111 on Cigarette Smoke Extract-Induced Macrophage Polarization and Inflammation in RAW264.7 Cells

Background

Macrophages are known to play a crucial role in the chronic inflammation associated with Chronic Obstructive Pulmonary Disease (COPD). BML-111, acting as a lipoxin A4 (LXA4) receptor agonist, has shown to be effective in protecting against COPD. However, the precise mechanism by which BML-111 exerts its protective effect remains unclear.

Methods

In order to establish a cell model of inflammation, cigarette smoke extract (CSE) was used on the RAW264.7 cell line. Afterwards, an Enzyme-linked immunosorbent assay (ELISA) kit was employed to measure concentrations of tumor necrosis factor-α (TNF-α), interleukin-1beta (IL-1β), interleukin-18 (IL-18), and interleukin-10 (IL-10) in the cell supernatants of the RAW264.7 cells.In this study, we examined the markers of macrophage polarization using two methods: quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis. Additionally, we detected the expression of Notch-1 and Hes-1 through Western blotting.

Results

BML-111 effectively suppressed the expression of pro-inflammatory cytokines TNF-α, IL-1β, and IL-18, as well as inflammasome factors NLRP3 and Caspase-1, while simultaneously up-regulating the expression of the anti-inflammatory cytokine IL-10 induced by CSE. Moreover, BML-111 reduced the expression of iNOS, which is associated with M1 macrophage polarization, and increased the expression of Arg-1, which is associated with M2 phenotype. Additionally, BML-111 downregulated the expression of Hes-1 and the ratio of activated Notch-1 to Notch-1 induced by CSE. The effect of BML-111 on inflammation and macrophage polarization was reversed upon administration of the Notch-1 signaling pathway agonist Jagged1.

Conclusion

BML-111 has the potential to suppress inflammation and modulate M1/M2 macrophage polarization in RAW264.7 cells. The underlying mechanism may involve the Notch-1 signaling pathway.

The Potential of NLRP3 Inflammasome as a Therapeutic Target in Neurological Diseases

NLRP3 (NLRP3: NOD-, LRR-, and pyrin domain-containing protein 3) inflammasome is the best-described inflammasome that plays a crucial role in the innate immune system and a wide range of diseases. The intimate association of NLRP3 with neurological disorders, including neurodegenerative diseases and strokes, further emphasizes its prominence as a clinical target for pharmacological intervention. However, after decades of exploration, the mechanism of NLRP3 activation remains indefinite. This review highlights recent advances and gaps in our insights into the regulation of NLRP3 inflammasome. Furthermore, we present several emerging pharmacological approaches of clinical translational potential targeting the NLRP3 inflammasome in neurological diseases. More importantly, despite small-molecule inhibitors of the NLRP3 inflammasome, we have focused explicitly on Chinese herbal medicine and botanical ingredients, which may be splendid therapeutics by inhibiting NLRP3 inflammasome for central nervous system disorders. We expect that we can contribute new perspectives to the treatment of neurological diseases.

Voluntary Exercise to Reduce Anxiety Behaviour in Traumatic Brain Injury Shown to Alleviate Inflammatory Brain Response in Mice

Traumatic brain injury is a leading cause of neuroinflammation and anxiety disorders in young adults. Immune-targeted therapies have garnered attention for the amelioration of TBI-induced anxiety. A previous study has indicated that voluntary exercise intervention following TBI could reduce neuroinflammation. It is essential to determine the effects of voluntary exercise after TBI on anxiety via inhibiting neuroinflammatory response. Mice were randomly divided into four groups (sham, TBI, sham + voluntary wheel running (VWR), and TBI + VWR). One-week VWR was carried out on the 2nd day after trauma. The neurofunction of TBI mice was assessed. Following VWR, anxiety behavior was evaluated, and neuroinflammatory responses in the perilesional cortex were investigated. Results showed that after one week of VWR, neurofunctional recovery was enhanced, while the anxiety behavior of TBI mice was significantly alleviated. The level of pro-inflammatory factors decreased, and the level of anti-inflammatory factors elevated. Activation of nucleotide oligomerization domain-like thermal receptor protein domain associated protein 3 (NLRP3) inflammasome was inhibited significantly. All these alterations were consistent with reduced microglial activation at the perilesional site and positively correlated with the amelioration of anxiety behavior. This suggested that timely rehabilitative exercise could be a useful therapeutic strategy for anxiety resulting from TBI by targeting neuroinflammation.

NLRP3 inflammasome in traumatic brain injury: Its implication in the disease pathophysiology and potential as a therapeutic target

Traumatic brain injury (TBI), an acquired brain injury imparted by a mechanical trauma to the head, has significant ramifications in terms of long-term disability and cost of healthcare. TBI is characterized by an initial phase of cell death owing to direct mechanical injury, followed by a secondary phase in which neuroinflammation plays a pivotal role. Activation of inflammasome complexes triggers a cascade that leads to activation of inflammatory mediators such as caspase-1, Interleukin (IL)-18, and IL-1β, eventually causing pyroptosis. NLRP3 inflammasome, a component of the innate immune response, has been implicated in a number of neurodegenerative diseases, including TBI. Recent findings indicate that NLRP3 inhibitors can potentially ameliorate neuroinflammation and improve cognition and motor function in TBI. The NLRP3 inflammasome also holds potential as a predictive biomarker for the long-term sequelae following TBI. Although several therapeutic agents have shown promising results in pre-clinical studies, none of them have been effective in human trials for TBI, to date. Thus, it is imperative that such promising therapeutic candidates are evaluated in clinical trials to assess their efficacy in alleviating neurological impairments in TBI. This review offers an insight into the pathophysiology of TBI, with an emphasis on neuroinflammation in the aftermath of TBI. We highlight the NLRP3 inflammasome and explore its role in the neuroinflammatory cascade in TBI. We also shed light on its potential as a prospective biomarker and therapeutic target for TBI management.

The role of regulatory necrosis in traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability in the population worldwide, of which key injury mechanism involving the death of nerve cells. Many recent studies have shown that regulatory necrosis is involved in the pathological process of TBI which includes necroptosis, pyroptosis, ferroptosis, parthanatos, and Cyclophilin D (CypD) mediated necrosis. Therefore, targeting the signaling pathways involved in regulatory necrosis may be an effective strategy to reduce the secondary injury after TBI. Meanwhile, drugs or genes are used as interference factors in various types of regulatory necrosis, so as to explore the potential treatment methods for the secondary injury after TBI. This review summarizes the current progress on regulatory necrosis in TBI.

Prevention of Dexmedetomidine on Postoperative Delirium and Early Postoperative Cognitive Dysfunction in Elderly Patients Undergoing Thoracoscopic Lobectomy

Objective

To investigate the effect of dexmedetomidine on postoperative cognitive function and delirium in elderly patients undergoing thoracoscopic lobectomy.

Methods

109 elderly patients (age is more than 65 years) who underwent thoracoscopic lobectomy in our hospital from June 2020 to Feb 2022 were randomly divided into the dexmedetomidine (DEX) group (n = 54) and the control group (n = 55). The patients in the experimental group were given dexmedetomidine by intravenous pump, intravenous pump 0.5 μg/kg within 10 minutes, and maintained the speed of 0.5 μg/(kg. h) to 30 min before the operation was ended. The control group was given the same amount of normal saline. Delirium assessment-severity (CAM-S) assessment and Mini-Cog were used to assess the severity levels of POD and POCD 24 h before, 6 hours after, one day after the operation, three days after the operation, and 1 week after the operation. Serum TNF-αα and NSE levels were assessed by using enzyme-linked immunosorbent assay. NRS pain marks were assessed in the DEX group at postanesthesia care unit (PACU) and 24 postoperation. Surgical pierhysmographic index (SPI) evaluation was performed at five time points.

Results

The Mini-Cog scores in the DEX group were markedly enhanced compared with those in the saline group 6 and 24 hours after the operation. The SPI values in the DEX group were markedly reduced within 2 min after intubation and at surgical sutures. Moreover, the CAM scores in the DEX group were markedly reduced 24 hours after the operation. Tumor necrosis factor-α (TNF-α) and neuron-specific enolase (NSE) levels were significantly decreased in the DEX group at T1∼T3.

Conclusion

The use of dexmedetomidine in the thoracoscopic lobectomy in elderly patients could reduce the occurrence and severity of postoperative cognitive dysfunction and delirium.

Neuro-Inflammation Modulation and Post-Traumatic Brain Injury Lesions: From Bench to Bed-Side

Head trauma is the most common cause of disability in young adults. Known as a silent epidemic, it can cause a mosaic of symptoms, whether neurological (sensory-motor deficits), psychiatric (depressive and anxiety symptoms), or somatic (vertigo, tinnitus, phosphenes). Furthermore, cranial trauma (CT) in children presents several particularities in terms of epidemiology, mechanism, and physiopathology-notably linked to the attack of an immature organ. As in adults, head trauma in children can have lifelong repercussions and can cause social and family isolation, difficulties at school, and, later, socio-professional adversity. Improving management of the pre-hospital and rehabilitation course of these patients reduces secondary morbidity and mortality, but often not without long-term disability. One hypothesized contributor to this process is chronic neuroinflammation, which could accompany primary lesions and facilitate their development into tertiary lesions. Neuroinflammation is a complex process involving different actors such as glial cells (astrocytes, microglia, oligodendrocytes), the permeability of the blood-brain barrier, excitotoxicity, production of oxygen derivatives, cytokine release, tissue damage, and neuronal death. Several studies have investigated the effect of various treatments on the neuroinflammatory response in traumatic brain injury in vitro and in animal and human models. The aim of this review is to examine the various anti-inflammatory therapies that have been implemented.

The neuroprotective effect of dexmedetomidine and its mechanism

Dexmedetomidine (DEX) is a highly selective α2 receptor agonist that is routinely used in the clinic for sedation and anesthesia. Recently, an increasing number of studies have shown that DEX has a protective effect against brain injury caused by traumatic brain injury (TBI), subarachnoid hemorrhage (SAH), cerebral ischemia and ischemia–reperfusion (I/R), suggesting its potential as a neuroprotective agent. Here, we summarized the neuroprotective effects of DEX in several models of neurological damage and examined its mechanism based on the current literature. Ultimately, we found that the neuroprotective effect of DEX mainly involved inhibition of inflammatory reactions, reduction of apoptosis and autophagy, and protection of the blood–brain barrier and enhancement of stable cell structures in five way. Therefore, DEX can provide a crucial advantage in neurological recovery for patients with brain injury. The purpose of this study was to further clarify the neuroprotective mechanisms of DEX therefore suggesting its potential in the clinical management of the neurological injuries.

STING mediates neuroinflammatory response by activating NLRP3-related pyroptosis in severe traumatic brain injury

Long-term neurological deficits after severe traumatic brain injury (TBI), including cognitive dysfunction and emotional impairments, can significantly impair rehabilitation. Glial activation induced by inflammatory response is involved in the neurological deficits post-TBI. This study aimed to investigate the role of the stimulator of interferon genes (STING)-nucleotide-binding oligomerization domain-like receptor pyrin domain-containing-3 (NLRP3) signaling in a rodent model of severe TBI. Severe TBI models were established using weight-drop plus blood loss-reinfusion. Selective STING agonist ADU-S100 or antagonist C-176 was given as a single dose after modeling. Further, NLRP3 inhibitor MCC950 or activator nigericin, or caspase-1 inhibitor VX765, was given as an intracerebroventricular injection 30 min before modeling. After that, a novel object recognition test, open field test, force swimming test, western blot, and immunofluorescence assays were used to assess behavioral and pathological changes in severe TBI. Administration of C-176 alleviated TBI-induced cognitive dysfunction and emotional impairments, neuronal loss, and inflammatory activation of glia cells. However, the administration of STING agonist ADU-S100 exacerbated TBI-induced behavioral and pathological changes. In addition, STING activation exacerbated pyroptosis-associated neuroinflammation via promoting glial activation, as evidenced by increased cleaved caspase-1 and GSDMD N-terminal expression. In contrast, the administration of C-176 showed anti-pyroptotic effects. The neuroprotective effects of C-176 were partially reversed by the NLRP3 activator, nigericin. Collectively, glial STING is responsible for neuroinflammation post-TBI. However, pharmacologic inhibition of STING led to a remarkable improvement of neuroinflammation partly through suppressing NLRP3 signaling. The STING-NLRP3 signaling is a potential therapeutic target in TBI-induced neurological dysfunction.

Effect Evaluation of Dexmedetomidine Intravenous Anesthesia on Postoperative Agitation in Patients with Craniocerebral Injury by Magnetic Resonance Imaging Based on Sparse Reconstruction Algorithm

The effect of dexmedetomidine on postoperative agitation of patients with craniocerebral injury was investigated based on magnetic resonance imaging (MRI) with the sparse reconstruction algorithm. Sixty patients with craniocerebral injury who underwent tracheal intubation and craniotomy hematoma removal under general anesthesia in hospital were selected as the research objects. Patients were randomly and averagely divided into the normal saline group (group A) and the dexmedetomidine (DEX) group (group B). DEX was added to patients in group A during anesthesia. Other operations in group B were the same as those in group A, where DEX needed to be used was replaced by an equal amount of the normal saline. All patients received the MRI examination, and the images were processed by using the sparse reconstruction algorithm. After the surgery, some indexes, such as hemodynamics (mean arterial pressure (MAP) and hear rate (HR)), the Riker sedation agitation score, the Ramsay sedation score, and the visual analogue scale (VAS) score were recorded and compared. The results showed that the MRI image quality processed by sparse reconstruction algorithm was observably improved. After reconstruction, the sharpness of the image was significantly improved, and the distinction between lesions and tissues was also increased. The Riker sedation agitation score and the incidence of agitation in group A were greatly lower than those in group B (16% VS 76%, P < 0.05). The Ramsay sedation score of group A was manifestly higher than that of group B. The cases of postoperative nausea, vomiting, chills, delirium, and bradycardia in group A were 2, 1, 1, 0, and 1, respectively. The cases of postoperative nausea, vomiting, chills, delirium, and bradycardia in group B were 3, 9, 6, 5, and 0, respectively. The cases of chills and delirium in group A were observably less than those in group B (P < 0.05). In conclusion, based on the sparse reconstruction algorithm, the MRI technology and DEX had high adoption value in preventing postoperative agitation of patients with craniocerebral injury. Compared with group B, the hemodynamics of patients in group A was more stable.

TI: NLRP3 Inflammasome-Dependent Pyroptosis in CNS Trauma: A Potential Therapeutic Target

Central nervous system (CNS) trauma, including traumatic brain injury (TBI) and traumatic spinal cord injury (SCI), is characterized by high morbidity, disability, and mortality. TBI and SCI have similar pathophysiological mechanisms and are often accompanied by serious inflammatory responses. Pyroptosis, an inflammation-dependent programmed cell death, is becoming a major problem in CNS post-traumatic injury. Notably, the pyrin domain containing 3 (NLRP3) inflammasome is a key protein in the pyroptosis signaling pathway. Therefore, underlying mechanism of the NLRP3 inflammasome in the development of CNS trauma has attracted much attention. In this review, we briefly summarize the molecular mechanisms of NLRP3 inflammasome in pyroptosis signaling pathway, including its prime and activation. Moreover, the dynamic expression pattern, and roles of the NLRP3 inflammasome in CNS post-traumatic injury are summarized. The therapeutic applications of NLRP3 inflammasome activation inhibitors are also discussed.

The potential role of dexmedetomidine on neuroprotection and its possible mechanisms: Evidence from in vitro and in vivo studies

Neurological disorders following brain injuries and neurodegeneration are on the rise worldwide and cause disability and suffering in patients. It is crucial to explore novel neuroprotectants. Dexmedetomidine, a selective α2-adrenoceptor agonist, is commonly used for anxiolysis, sedation and analgesia in clinical anaesthesia and critical care. Recent studies have shown that dexmedetomidine exerts protective effects on multiple organs. This review summarized and discussed the current neuroprotective effects of dexmedetomidine, as well as the underlying mechanisms. In preclinical studies, dexmedetomidine reduced neuronal injury and improved functional outcomes in several models, including hypoxia-induced neuronal injury, ischaemic-reperfusion injury, intracerebral haemorrhage, post-traumatic brain injury, anaesthetic-induced neuronal injury, substance-induced neuronal injury, neuroinflammation, epilepsy and neurodegeneration. Several mechanisms are associated with the neuroprotective function of dexmedetomidine, including neurotransmitter regulation, inflammatory response, oxidative stress, apoptotic pathway, autophagy, mitochondrial function and other cell signalling pathways. In summary, dexmedetomidine has the potential to be a novel neuroprotective agent for a wide range of neurological disorders.

Dexmedetomidine exerts a protective effect on ischemic brain injury by inhibiting the P2X7R/NLRP3/Caspase-1 signaling pathway

Dexmedetomidine (Dex) has been suggested to exert a protective function in ischemic brain injury. In this study, we aimed to elucidate the intrinsic mechanisms of Dex in regulating microglia pyroptosis in ischemic brain injury via the purinergic 2X7 receptor (P2X7R)/NLRP3/Caspase-1 signaling pathway. First, permanent middle cerebral artery occlusion (p-MCAO) rat model was established, followed by the measurement of behavioral deficit, neuronal injury, the volume of brain edema and the infarct size. Dex treatment was suggested to alleviate the neurological deficits in p-MCAO rats and reduce the brain water content and infarct size. Additionally, rat microglia were cultured in vitro and a model of oxygen and glucose (OGD) was established. Microglia cell activity and ultrastructure were detected. Dex could increase cell activity and reduce LDH activity, partially reversing the changes in cell morphology. Furthermore, the activation of P2X7R/NLRP3/Caspase-1 pathway was tested. The obtained findings indicated Dex suppressed microglial pyroptosis by inhibiting the P2X7R/NLRP3/Caspase-1 pathway. Inhibition of P2X7R or NLRP3 could inhibit Caspase-1 p10 expression, improve cell activity, and reduce LDH activity. The same result was verified in vivo experiments. This study indicated that Dex inhibited microglia pyroptosis by blocking the P2X7R/NLRP3/Caspase-1 pathway, thus playing a protective role against ischemic brain injury.

Dexmedetomidine Ameliorates Perioperative Neurocognitive Disorders by Suppressing Monocyte-Derived Macrophages in Mice With Preexisting Traumatic Brain Injury

BACKGROUND

Traumatic brain injury (TBI) initiates immune responses involving infiltration of monocyte-derived macrophages (MDMs) in the injured brain tissue. These MDMs play a key role in perioperative neurocognitive disorders (PNDs). We tested the hypothesis that preanesthetic treatment with dexmedetomidine (DEX) could suppress infiltration of MDMs into the hippocampus of TBI model mice, ameliorating PND.

METHODS

We first performed bone marrow transplantation from green fluorescent protein-transgenic mice to C57BL/6 mice to identify MDMs. We used only male mice for homogeneity. Four weeks after transplantation, a controlled cortical impact model of TBI was created using recipient mice. Four weeks after TBI, mice received pretreatment with DEX before general anesthesia (GA). Mice performed the Barnes maze test (8-12 mice/group) 2 weeks after GA and were euthanized for immunohistochemistry (4-5 mice/group) or immunoblotting (7 mice/group) 4 weeks after GA.

RESULTS

In Barnes maze tests, TBI model mice showed longer primary latency (mean difference, 76.5 [95% confidence interval, 41.4-111.6], P < .0001 versus Naïve), primary path length (431.2 [98.5-763.9], P = .001 versus Naïve), and more primary errors (5.7 [0.62-10.7], P = .017 versus Naïve) than Naïve mice on experimental day 3. Expression of MDMs in the hippocampus was significantly increased in TBI mice compared to Naïve mice (2.1 [0.6-3.7], P = .003 versus Naïve). Expression of monocyte chemotactic protein-1 (MCP1)-positive areas in the hippocampus was significantly increased in TBI mice compared to Naïve mice (0.38 [0.09-0.68], P = .007 versus Naïve). Immunoblotting indicated significantly increased expression of interleukin-1β in the hippocampus in TBI mice compared to Naïve mice (1.59 [0.08-3.1], P = .035 versus Naïve). In contrast, TBI mice pretreated with DEX were rescued from these changes and showed no significant difference from Naïve mice. Yohimbine, an α2 receptor antagonist, mitigated the effects of DEX (primary latency: 68.3 [36.5-100.1], P < .0001 versus TBI-DEX; primary path length: 414.9 [120.0-709.9], P = .0002 versus DEX; primary errors: 6.6 [2.1-11.2], P = .0005 versus TBI-DEX; expression of MDMs: 2.9 [1.4-4.4], P = .0001 versus TBI-DEX; expression of MCP1: 0.4 [0.05-0.67], P = .017 versus TBI-DEX; expression of interleukin-1β: 1.8 [0.34-3.35], P = .01 versus TBI-DEX).

CONCLUSIONS

Preanesthetic treatment with DEX suppressed infiltration of MDMs in the hippocampus and ameliorated PND in TBI model mice. Preanesthetic treatment with DEX appears to suppress infiltration of MDMs in the hippocampus and may lead to new treatments for PND in patients with a history of TBI.

The effect of dexmedetomidine premedication on postoperative systemic inflammatory response in children undergoing hernia repair surgery: A randomized controlled trial

BACKGROUND

Surgery results in systemic inflammation, which can affect the central nervous system, leading to changes in mood, emotion, and behavior. Our previous study has shown that compared to midazolam, dexmedetomidine premedication effectively decreased children's postoperative anxiety.

AIM

To investigate whether dexmedetomidine infusion before hernia repair alleviates postoperative systemic inflammation in children and whether postoperative anxiety may be associated with postoperative inflammation.

METHODS

This prospective double-blind randomized controlled trial was conducted in 120 children scheduled to undergo elective hernia repair. Before anesthesia induction, all children received an intravenous infusion consisted of dexmedetomidine (n = 40; 0.5 µg/g, group D), midazolam (n = 40; 0.08 mg/kg, group M), or normal saline (n = 40; group C). One-way ANOVA with least significant difference multiple comparison test was used for multigroup comparisons of postoperative plasma levels of inflammatory cytokines and m-YPAS scores. Spearman rank correlation tests were used for analyzing m-YPAS scores with postoperative plasma levels of inflammatory cytokines.

RESULTS

Plasma levels of tumor necrosis factor-alpha (7.0 ± 1.6 vs. 8.1 ± 1.6, mean difference [95% CI]: 1.19 [0.26-2.11], p = .008) (pg/ml) and of interleukin-6 (1.8 ± 1.2 vs. 3.3 ± 1.6, mean difference [95% CI]: 1.49 [0.74-2.25], p < .001) (pg/ml) and neutrophils-to-lymphocyte ratio (1.0 ± 0.5 vs. 1.5 ± 0.7, mean difference [95% CI]: 0.48 [0.17-0.78], p < .001) were significantly lower in group D than in group C. Furthermore, compared to group M, group D showed significantly lower plasma tumor necrosis factor-alpha levels (7.0 ± 1.6 vs. 7.9 ± 1.9, mean difference [95% CI]: 0.96 [0.04-1.88], p = .04) (pg/ml) and interleukin-6 levels (1.8 ± 1.2 vs. 2.9 ± 1.5, mean difference [95% CI]: 1.06 [0.31-1.81], p = .004) (pg/ml), and neutrophil-to-lymphocyte ratio (1.0 ± 0.5 vs. 1.5 ± 0.6, mean difference [95% CI]: 0.42 [0.11-0.72], p = .004). Anxiety scores at postoperative 2 and 4 h in the three groups positively correlated with plasma levels of proinflammatory cytokines.

CONCLUSION

A single preoperative intravenous dexmedetomidine dose in children undergoing same-day surgery reduces postoperative systemic inflammation.

Dexmedetomidine post-conditioning attenuates cerebral ischemia following asphyxia cardiac arrest through down-regulation of apoptosis and neuroinflammation in rats

Background

Neuroprotection strategies after cardiac arrest (CA)/cardiopulmonary resuscitation (CPR) remain key areas of basic and clinical research. This study was designed to investigate the neuroprotective effects of dexmedetomidine following resuscitation and potential mechanisms.

Methods

Anesthetized rats underwent 6-min asphyxia-based cardiac arrest and resuscitation, after which the experimental group received a single intravenous dose of dexmedetomidine (25 μg/kg). Neurological outcomes and ataxia were assessed after the return of spontaneous circulation. The serum levels and brain expression of inflammation markers was examined, and apoptotic cells were quantified by TUNEL staining.

Results

Neuroprotection was enhanced by dexmedetomidine post-conditioning after the return of spontaneous circulation. This enhancement was characterized by the promotion of neurological function scores and coordination. In addition, dexmedetomidine post-conditioning attenuated the serum levels of the pro-inflammatory cytokine tumor necrosis factor (TNF)-α at 2 h, as well as interleukin IL-1β at 2, 24, and 48 h. TUNEL staining showed that the number of apoptotic cells in the dexmedetomidine post-conditioning group was significantly reduced compared with the control group. Further western blot analysis indicated that dexmedetomidine markedly reduced the levels of caspase-3 and nuclear factor-kappa B (NF-κB) in the brain.

Conclusions

Dexmedetomidine post-conditioning had a neuroprotective effect against cerebral injury following asphyxia-induced cardiac arrest. The mechanism was associated with the downregulation of apoptosis and neuroinflammation.

Dexmedetomidine Mitigated NLRP3-Mediated Neuroinflammation via the Ubiquitin-Autophagy Pathway to Improve Perioperative Neurocognitive Disorder in Mice

Background: Surgery and anesthesia-induced perioperative neurocognitive disorder (PND) are closely related to NOD-like receptors (NLR) family, pyrin domain containing 3 (NLRP3) inflammasome microglia inflammatory response. Inhibiting the occurrence of neuroinflammation is an important treatment method to improve postoperative delirium. Fewer NLRP3-targeting molecules are currently available in the clinic to reduce the incidence of postoperative delirium. Dexmedetomidine (DEX), an α2 adrenergic receptor agonist has been shown to have antioxidant and anti-inflammatory activities. The present study showed that DEX reduced the production of cleaved caspase1 (CASP1) and destroyed the NLRP3–PYD And CARD Domain Containing (PYCARD)–CASP1 complex assembly, thereby reducing the secretion of IL-1β interleukin beta (IL-1β). DEX promoted the autophagy process of microglia and reduced NLRP3 expression. More interestingly, it promoted the ubiquitination and degradation of NLRP3. Thus, this study demonstrated that DEX reduced NLRP3-mediated inflammation through the activation of the ubiquitin-autophagy pathway. This study provided a new mechanism for treating PND using DEX.

Methods: C57BL/6 mice were pre-administered DEX 3 days in advance, and an abdominal exploration model was used to establish a perioperative neurocognitive disorder model. The anti-inflammatory effect of DEX was explored in vivo by detecting NLRP3-CASP1/IL-1β protein expression and behavioral testing. Primary microglia were stimulated with lipopolysaccharide (LPS) and adenosine triphosphate (ATP) in vitro, the expression of CASP1 and IL-1β was detected in the supernatant of cells, and the expression of autophagy-related proteins microtubule-associated protein 1 light chain 3 beta (MAP1LC3B) and sequestosome 1 (SQSTM1) was examined in the cytoplasm. Meanwhile, Co-immunoprecipitation (Co-IP) was used to detect NLRP3 protein ubiquitination so as to clarify the new mechanism underlying the anti-inflammatory effect of DEX.

Results: Pre-administration of DEX reduced the protein expression of NLRP3, CASP1, and IL-1β in the hippocampus of mice induced by surgery and also improved the impairment of learning and memory ability. At the same time, DEX also effectively relieved the decrease in spine density of the hippocampal brain induced by surgery. DEX decreased the cleaved CASP1 expression, blocked the assembly of NLRP3–PYCARD–CASP1 complex, and also reduced the secretion of mature IL-1β in vitro. Mechanically, it accelerated the degradation of NLRP3 inflammasome via the autophagy–ubiquitin pathway and reduced the green fluorescent protein/red fluorescent protein MAP1LC3B ratio, which was comparable to the effect when using the autophagy activator rapamycin (Rapa). Furthermore, it increased the ubiquitination of NLRP3 after LPS plus ATP stimulated microglia.

Conclusion: DEX attenuated the hippocampal brain inflammation by promoting NLRP3 inflammasome degradation via the autophagy–ubiquitin pathway, thus improving cognitive impairment in mice.

Traumatic Brain Injury: Mechanistic Insight on Pathophysiology and Potential Therapeutic Targets

Traumatic brain injury (TBI) causes brain damage, which involves primary and secondary injury mechanisms. Primary injury causes local brain damage, while secondary damage begins with inflammatory activity followed by disruption of the blood-brain barrier (BBB), peripheral blood cells infiltration, brain edema, and the discharge of numerous immune mediators including chemotactic factors and interleukins. TBI alters molecular signaling, cell structures, and functions. Besides tissue damage such as axonal damage, contusions, and hemorrhage, TBI in general interrupts brain physiology including cognition, decision-making, memory, attention, and speech capability. Regardless of the deep understanding of the pathophysiology of TBI, the underlying mechanisms still need to be assessed with a desired therapeutic agent to control the consequences of TBI. The current review gives a brief outline of the pathophysiological mechanism of TBI and various biochemical pathways involved in brain injury, pharmacological treatment approaches, and novel targets for therapy.

Verbascoside Attenuates Acute Inflammatory Injury Caused by an Intracerebral Hemorrhage Through the Suppression of NLRP3

Intracerebral hemorrhage (ICH) is a devastating cerebrovascular disease with a high mortality rate affecting individuals worldwide. After ICH, persistent inflammation results in the death of brain cells, as well as the promotion of secondary brain injury. Verbascoside (VB), an active component in herbal medicine, possesses antioxidant, anti-inflammatory and neuroprotective properties. Furthermore, previous studies have shown that VB improves recovery of neuronal function after spinal cord injury in rats. In this study, we investigated whether VB limited inflammation induced by ICH through the targeting of NLRP3, which is associated with acute inflammation and apoptosis. Administration of VB reduced neurological impairment and pathological abnormalities associated with ICH, while increasing cell viability of neurons. This was achieved through NLRP3 inhibition and microglial activation. VB treatment decreased neuronal damage when co-cultured with microglia. Furthermore, knockout of NLRP3 eliminated the ability of VB to inhibit inflammation, cell death or protect neurons. Taken together, VB suppressed the inflammatory response following ICH by inhibiting NLRP3.

Astaxanthin provides neuroprotection in an experimental model of traumatic brain injury via the Nrf2/HO-1 pathway

BACKGROUND

Astaxanthin (ATX) is a carotenoid pigment with effective antioxidant, anti-inflammatory, antitumor and immunomodulatory actions. ATX has been proposed to exert neuroprotective effects and attenuate oxidative stress in mice after traumatic brain injury (TBI). The nuclear factor erythroid 2-related factor 2 (Nrf2)-heme oxygenase 1 (HO-1) signaling pathway is stimulated after TBI and activates a compensatory mechanism against TBI. Nevertheless, the effect of ATX on the pathophysiology of TBI in mice is limited. Our present study evaluated the neuroprotection afforded by ATX and the possible role of the Nrf2/HO-1 pathway in experimental TBI.

MATERIALS AND METHODS

Mice were casually separated into 3 groups: the sham, TBI + vehicle, and TBI + ATX (100 mg/kg, intraperitoneally administered) groups. Neurobehaviors of the mice were assessed using the neurological severity scores (NSSs), the forced swimming test (FST) and the rotarod test. Levels of the Nrf2, HO-1, NAD(P)H: quinine oxidoreductase-1 (NQO1), cleaved caspase3 (C-caspase3), and superoxide dismutase1 (SOD1) proteins and levels of the Nrf2 and HO-1 mRNAs were assessed. In addition, Nrf2 nuclear import and apoptosis were measured after TBI.

RESULTS

The ATX treatment significantly improved the neurological status, promoted Nrf2 activation, and upregulated the expression of the Nrf2 and HO-1 mRNAs and the levels of the Nrf2, HO-1, and NQO1 proteins after TBI. The level of the SOD1 protein was decreased after TBI and increased after ATX treatment; however, the difference was not significant. ATX markedly reduced the level of the C-caspase3 protein and the number of TUNEL-positive cells, indicating that it exerted an antiapoptotic effect. Immunofluorescence staining confirmed that ATX promoted Nrf2 nuclear import.

CONCLUSIONS

Based on our study, ATX possibly affords neuroprotection by activating the Nrf2/HO-1 signaling pathway in mice after TBI.

Progenitor cell therapy for acquired pediatric nervous system injury: Traumatic brain injury and acquired sensorineural hearing loss

While cell therapies hold remarkable promise for replacing injured cells and repairing damaged tissues, cell replacement is not the only means by which these therapies can achieve therapeutic effect. For example, recent publications show that treatment with varieties of adult, multipotent stem cells can improve outcomes in patients with neurological conditions such as traumatic brain injury and hearing loss without directly replacing damaged or lost cells. As the immune system plays a central role in injury response and tissue repair, we here suggest that multipotent stem cell therapies achieve therapeutic effect by altering the immune response to injury, thereby limiting damage due to inflammation and possibly promoting repair. These findings argue for a broader understanding of the mechanisms by which cell therapies can benefit patients.

The NLRP3 inflammasome: a potential therapeutic target for traumatic brain injury

Although the precise mechanisms contributing to secondary brain injury following traumatic brain injury are complex and obscure, a number of studies have demonstrated that inflammatory responses are an obvious and early feature in the pathogenesis of traumatic brain injury. Inflammasomes are multiprotein complexes that prompt the stimulation of caspase-1 and subsequently induce the maturation and secretion of proinflammatory cytokines, such as interleukin-1β and interleukin-18. These cytokines play a pivotal role in facilitating innate immune responses and inflammation. Among various inflammasome complexes, the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is the best characterized, a crucial role for NLRP3 has been demonstrated in various brain diseases, including traumatic brain injury. Several recent studies have revealed the contribution of NLRP3 inflammasome in identifying cellular damage and stimulating inflammatory responses to aseptic tissue injury after traumatic brain injury. Even more important, blocking or inhibiting the activation of the NLRP3 inflammasome may have substantial potential to salvage tissue damage during traumatic brain injury. In this review, we summarize recently described mechanisms that are involved in the activation and regulation of the NLRP3 inflammasome. Moreover, we review the recent investigations on the contribution of the NLRP3 inflammasome in the pathophysiology of TBI, and current advances and challenges in potential NLRP3-targeted therapies. A significant contribution of NLRP3 inflammasome activation to traumatic brain injury implies that therapeutic approaches focused on targeting specific inflammasome components could significantly improve the traumatic brain injury outcomes.

An overview of disease models for NLRP3 inflammasome over-activation

Introduction: Inflammatory reactions, including those mediated by the NLRP3 inflammasome, maintain the body's homeostasis by removing pathogens, repairing damaged tissues, and adapting to stressed environments. However, uncontrolled activation of the NLRP3 inflammasome tends to cause various diseases using different mechanisms. Recently, many inhibitors of the NLRP3 inflammasome have been reported and many are being developed. In order to assess their efficacy, specificity, and mechanism of action, the screening process of inhibitors requires various types of cell and animal models of NLRP3-associated diseases.Areas covered: In the following review, the authors give an overview of the cell and animal models that have been used during the research and development of various inhibitors of the NLRP3 inflammasome.Expert opinion: There are many NLRP3 inflammasome inhibitors, but most of the inhibitors have poor specificity and often influence other inflammatory pathways. The potential risk for cross-reaction is high; therefore, the development of highly specific inhibitors is essential. The selection of appropriate cell and animal models, and combined use of different models for the evaluation of these inhibitors can help to clarify the target specificity and therapeutic effects, which is beneficial for the development and application of drugs targeting the NLRP3 inflammasome.

Dexmedetomidine inhibits inflammatory response and autophagy through the circLrp1b/miR-27a-3p/Dram2 pathway in a rat model of traumatic brain injury

Circular RNAs (circRNAs) have a regulatory function on inflammation and autophagy, of which rno-circRNA_010705 (circLrp1b) appears to be significantly up-regulated following traumatic brain injury (TBI). Dexmedetomidine (DEX) shows improvement effects in TBI by inhibiting NLRP3/caspase-1. However, whether circLrp1b plays critical roles in DEX-mediated TBI attenuation and the underlying mechanisms remain unclear. After TBI was established in rats by controlled cortical impact (CCI) to cause brain trauma, they received an intracerebroventricular injection of lentiviral vector, followed by intraperitoneal injection of DEX. Administration of DEX ameliorated autophagy in rats following TBI, accompanied by up-regulated circLrp1b and Dram2 and down-regulated miR-27a-3p. DEX promoted the effects of circLrp1b in attenuating TBI-induced neurologic impairment, autophagy, and inflammation, which was significantly reversed by inhibition of miR-27a-3p or Dram2 overexpression. Mechanistically, northern blot and luciferase reporter assays indicated that circLrp1b up-regulated Dram2 expression by functioning as a sponge for miR-27a-3p to promote autophagy involved in TBI, which was reversed by DEX treatment. Collectively, this study demonstrated that DEX inhibits inflammatory response and autophagy involved in TBI in vivo through inactivation of the circLrp1b/miR-27a-3p/Dram2 signaling pathway.

The Role of NLRP3 Inflammasome in the Pathogenesis of Traumatic Brain Injury

Traumatic brain injury (TBI) represents an important problem of global health. The damage related to TBI is first due to the direct injury and then to a secondary phase in which neuroinflammation plays a key role. NLRP3 inflammasome is a component of the innate immune response and different diseases, such as neurodegenerative diseases, are characterized by NLRP3 activation. This review aims to describe NLRP3 inflammasome and the consequences related to its activation following TBI. NLRP3, caspase-1, IL-1β, and IL-18 are significantly upregulated after TBI, therefore, the use of nonspecific, but mostly specific NLRP3 inhibitors is useful to ameliorate the damage post-TBI characterized by neuroinflammation. Moreover, NLRP3 and the molecules associated with its activation may be considered as biomarkers and predictive factors for other neurodegenerative diseases consequent to TBI. Complications such as continuous stimuli or viral infections, such as the SARS-CoV-2 infection, may worsen the prognosis of TBI, altering the immune response and increasing the neuroinflammatory processes related to NLRP3, whose activation occurs both in TBI and in SARS-CoV-2 infection. This review points out the role of NLRP3 in TBI and highlights the hypothesis that NLRP3 may be considered as a potential therapeutic target for the management of neuroinflammation in TBI.

Neuroinflammation Mediated by NLRP3 Inflammasome After Intracerebral Hemorrhage and Potential Therapeutic Targets

Intracerebral hemorrhage (ICH) is the most fatal subtype of stroke; there is still a lack of effective treatment. Microglia are a major component of the innate immune system, and they respond to acute brain injury by activating and forming classic M1-like (pro-inflammatory) or alternative M2-like (anti-inflammatory) phenotype. The existence of the polarization indicates that the role of microglia in disease's progression and recovery after ICH is still unclear, perhaps involving microglial secretion of anti-inflammatory or pro-inflammatory cytokines and chemokines. The NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome is considered to be the main participant in neuroinflammation. Recent evidence has shown that NLRP3 inflammasome can be activated after ICH, resulting in inflammatory cascade reactions and aggravating brain injury. Furthermore, previous studies have reported that NLRP3 inflammasome is mainly present in microglia, so we speculate that its activation may be strongly associated with microglial polarization. Many scholars have investigated the role of brain injury caused by NLRP3 inflammasome after ICH, but the precise operating mechanisms remain uncertain. This review summarized the activation mechanism of NLRP3 inflammasome after ICH and the possible mechanism of NLRP3 inflammasome promoting neuroinflammation and aggravating nerve injury and discussed the relevant potential therapeutic targets.

The NLRP3 inflammasome in traumatic brain injury: potential as a biomarker and therapeutic target

There is a great clinical need to identify the underlying mechanisms, as well as related biomarkers, and treatment targets, for traumatic brain injury (TBI). Neuroinflammation is a central pathophysiological feature of TBI. NLRP3 inflammasome activity is a necessary component of the innate immune response to tissue damage, and dysregulated inflammasome activity has been implicated in a number of neurological conditions. This paper introduces the NLRP3 inflammasome and its implication in the pathogenesis of neuroinflammatory-related conditions, with a particular focus on TBI. Although its role in TBI has only recently been identified, findings suggest that priming and activation of the NLRP3 inflammasome are upregulated following TBI. Moreover, recent studies utilizing specific NLRP3 inhibitors have provided further evidence that this inflammasome is a major driver of neuroinflammation and neurobehavioral disturbances following TBI. In addition, there is emerging evidence that circulating inflammasome-associated proteins may have utility as diagnostic biomarkers of neuroinflammatory conditions, including TBI. Finally, novel and promising areas of research will be highlighted, including the potential involvement of the NLRP3 inflammasome in mild TBI, how factors such as biological sex may affect NLRP3 activity in TBI, and the use of emerging biomarker platforms. Taken together, this review highlights the exciting potential of the NLRP3 inflammasome as a target for treatments and biomarkers that may ultimately be used to improve TBI management.

Dexmedetomidine Protects SK-N-SH Nerve Cells from Oxidative Injury by Maintaining Iron Homeostasis

Ferroptosis is characterized by the accumulation of iron-derived reactive oxygen species (ROS). Ferroptosis causes neuronal death in multiple neurological disorders. Dexmedetomidine (Dex), an extensively used anesthetic, has neuroprotective effects against ROS, but its effect on iron metabolism remains unknown. In this study, SK-N-SH cells were treated with Dex for 24 h before treatment with 100 µM tert-butyl hydroperoxide (t-BHP; an ROS inducer) for 1 h. Afterward, intracellular ROS and labile ferrous iron [Fe(II)] levels were assessed. Dex hindered the increase in cellular ROS and labile Fe(II) levels caused by t-BHP, although Dex alone had no effect on labile Fe(II) level. t-BHP increased the expression of iron importers, transferrin receptor-1 and divalent metal transporter-1, and iron regulatory protein 1 and 2. These effects were abrogated by Dex treatment and SP-1 knockdown. t-BHP increased the phosphorylation of c-Jun N-terminal kinase (JNK) and signal transducer and activator of transcription 4 (STAT4), the primary up-stream activators of SP-1, but Dex decreased this. This study, for the first time, revealed that the antioxidative effect of Dex is partly associated to the inhibition of intracellular iron accumulation induced by t-BHP. Dex regulates iron metabolism by regulating iron importers and exporters through JNK/Sp1 and Stat4/Sp1 signaling. It is worth investigating whether Dex can protect neurons from ferroptosis.

The Effects of Dexmedetomidine in a Rat Model of Sepsis-Induced Lung Injury are Mediated Through the Adenosine Monophosphate-Activated Protein Kinase (AMPK)/Silent Information Regulator 1 (SIRT1) Pathway

BACKGROUND This study aimed to investigate the effects of dexmedetomidine in a rat model of sepsis-induced lung injury and the role of the adenosine monophosphate-activated protein kinase (AMPK) gene and silent information regulator 1 (SIRT1) gene signaling pathway. MATERIAL AND METHODS Sixty 28-week-old healthy male Sprague-Dawley rats were randomly divided into three groups, the sham group, the model group, and the dexmedetomidine-treated group. The rat model of sepsis-induced lung injury was developed by surgical cecal ligation and puncture. Lung tissues examined histologically in the three study groups. Cell apoptosis was measured using the TUNEL assay, and the expression of inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin-1ß (IL-1ß), and IL-10 were measured in rat lung tissue by enzyme-linked immunosorbent assay (ELISA). Apoptosis-associated proteins and AMPK/SIRT1 pathway-associated protein expression levels were detected using Western blot. RESULTS Dexmedetomidine significantly increased the survival rate and reduced the body temperature of rats in the model group with sepsis-induced lung injury, reduced lung injury, significantly reduced apoptosis in lung tissues, and reduced the expression levels of TNF-alpha, and IL-1ß, and increased the levels of IL-10. Dexmedetomidine significantly reduced the expression of caspase-3 in the rat lung tissue (P<0.01), and significantly increased the expression of Bcl-2/Bax and the phosphorylation levels of AMPK, SIRT1, nuclear factor-kappaB (NF-kappaB), and forkhead box class O 3a (FOXO3a). CONCLUSIONS In a rat model of sepsis-induced lung injury, dexmedetomidine reduced lung damage by activating the AMPK/SIRT1 signaling pathway and reduced the expression of inflammatory cytokines and cell apoptosis.

Dexmedetomidine Attenuates Neuroinflammatory-Induced Apoptosis after Traumatic Brain Injury via Nrf2 signaling pathway

Objective

Dexmedetomidine (DEX) exhibits neuroprotective effects as a multifunctional neuroprotective agent in numerous neurological disorders. However, in traumatic brain injury (TBI), the molecular mechanisms of these neuroprotective effects remain unclear. The present study investigated whether DEX, which has been reported to exert protective effects against TBI, could attenuate neuroinflammatory‐induced apoptosis and clarified the underlying mechanisms.

Methods

A weight‐drop model was established, and DEX was intraperitoneally injected 30 min after inducing TBI in rats. The water content in the brain tissue was measured. Terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling (TUNEL) assays were performed on histopathological tissue sections to evaluate neuronal apoptosis. Enzyme‐linked immunosorbent assay and PCR were applied to detect the levels of the inflammatory factors, TNF‐α, IL‐1β, IL‐6, and NF‐κB.

Results

TBI–challenged rats exhibited significant neuronal apoptosis, which was characterized via the wet‐to‐dry weight ratio, neurobehavioral functions, TUNEL assay results and the levels of cleaved caspase‐3, Bax upregulation and Bcl‐2, which were attenuated by DEX. Western blot, immunohistochemistry, and PCR results revealed that DEX promoted Nrf2 expression and upregulated expression of the Nrf2 downstream factors, HO‐1 and NQO‐1. Furthermore, DEX treatment markedly prevented the downregulation of inflammatory response factors, TNF‐α, IL‐1β and NF‐κB, and IL‐6.

Interpretation

Administering DEX attenuated inflammation‐induced brain injury in a TBI model, potentially via the Nrf2 signaling pathway.

Dexmedetomidine exerts dual effects on human annulus fibrosus chondrocytes depending on the oxidative stress status

Dexmedetomidine (Dex) is an anesthetic widely used in lumbar discectomy, but its effect on chondrocytes remains unclear. Dex is speculated to promote cartilage degeneration by activating α-2 adrenergic receptor. However, the antioxidative and anti-inflammatory effects of Dex implied the potential chondrocyte protective effect under stress conditions. The present study aimed to determine the effect of Dex on chondrocytes under non-stress and stress conditions. Chondrocytes were isolated from human annulus fibrosus (AF) tissues and oxidative stress was induced by treatment with 1 mM hydrogen peroxide (H₂O₂). Chondrocytes were treated with Dex alone or in combination with H₂O₂. Treatment with Dex alone decreased mRNA expression of COL2A1 and increased that of MMP-3 and MMP-13, thus contributing to cartilage degeneration. However, Dex prevented H₂O₂-induced death and degeneration of chondrocytes partly by enhancing antioxidant capacity. Mechanistically, Dex attenuated H₂O₂-mediated activation of NF-κB and NACHT, LRR, and PYD domains-containing protein 3 (NLRP3), both of which play key roles in inflammation and inflammatory damage. Dex inactivated NLRP3 through the suppression of NF-κB and JNK signals. Co-treatment with Dex and H₂O₂ increased protein level of XIAP (X-linked inhibitor-of-apoptosis, an anti-apoptosis protein), compared with H₂O₂ treatment alone. H₂O₂ treatment increased the expression of neural precursor cell expressed developmentally down-regulated protein 4 (NEDD4) that is a ubiquitin ligase targeting XIAP. However, Dex decreased the amount of NEDD4 adhering to XIAP, thus protecting XIAP protein from NEDD4-mediated ubiquitination and degradation. Given that surgery inevitably causes oxidative stress and inflammation, the protective effect of Dex on chondrocytes during oxidative stress is noteworthy and warrants further study.

The Pathway of Let-7a-1/2-3p and HMGB1 Mediated Dexmedetomidine Inhibiting Microglia Activation in Spinal Cord Ischemia-Reperfusion Injury Mice

Microglial cell activation after spinal cord ischemia-reperfusion injury (SCIRI) commonly causes the secondary nerve motion function injury. This study aims to study the mechanism by which the drug dexmedetomidine (DEX) inhibits microglial cell activation and improves motion function of SCIRI mice. Mice SCIRI model was established, and microglia from spinal cord were isolated and cultured for subsequent molecule analysis of let-7a-1-3p, let-7a-2-3p, HMGB1, TNF-α, and IL-6. DEX was given by intraperitoneal injection. Mice motion function was evaluated by Basso mouse score. In vitro microglial cells were subjected to oxygen and glucose deprivation/reoxygenation (OGD/R) to imitate ischemia-reperfusion injury stimulation. DEX injection improves the mouse motion function in SCIRI model and upregulates let-7a-1/2-3p expression in the isolated activated microglia from SCIRI mice. In OGD/R-stimulated microglia, DEX treatment also caused the inactivation of cells, the upregulation of let-7a-1/2-3p expression, and the downregulation of HMGB1 expression. While the co-silencing of let-7a-1/2-3p in microglia in addition to DEX treatment restored the activation of microglia. HMGB1 is a targeted gene for let-7a-1/2-3p and negatively regulated by them. HMGB1 knockdown abrogates the pro-activation impact on microglial cell by let-7a-1/2-3p silencing. DEX inhibits the activation of microglial cell in the spinal cord of SCIRI mice, mediated by the let-7a-1/2-3p/HMGB1 pathway.

The role of NF-κB-mediated JNK pathway in cognitive impairment in a rat model of sleep apnea

Background

The aim of this study is to determine the role of nuclear factor kappa B (NF-κB)-mediated c-Jun N-terminal kinase (JNK) pathway in cognitive impairment induced by chronic intermittent hypoxia (CIH).

Methods

Ninety-six male Sprague-Dawley rats were randomly divided into 8 groups: sham group, sustained hypoxia (SH) group, CIH group, CIH + melatonin group, CIH + vitamin E group, CIH + DMSO group, CIH + BAY 11-7082 group and CIH + normal saline (NS) group. Rats were exposed to normoxia, CIH (21% O₂ for 60 s and 10% O₂ for 60 s, cyclically repeated for 10 h/day) or SH (10% O₂ for 10 h/day) for 14 days. Afterwards, Morris water maze test was conducted, and serum and hippocampus tissues were subjected to molecular biological and biochemical analyses.

Results

Compared with the Sham and SH group, oxidative stress was induced by CIH in rat hippocampus with the high level of malondialdehyde (MDA) and 8-iso-PGF2α and the low level of superoxide dismutase (SOD) and glutathione (GSH). Activated NF-κB and its downstream products including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and inducible nitric oxide synthase (iNOS) were highly expressed in CIH rats. These changes were attenuated by pretreatment of the rats with melatonin and vitamin E. CIH also resulted in hippocampus neuron apoptosis with increased caspase 3 level, dUIP nick end labeling (TUNEL)-positive neurons number and cognitive impairment verified by prolonged latency and shortened time in the target quadrant in Morris water maze test. JNK and its downstream transcriptional factors including c-Jun, activating transcription factor 2 (ATF2), and JunD were all significantly phosphorylated in CIH rats. However, pretreatment of NF-κB inhibitor BAY 11-7082 inhibited the activation of NF-κB under CIH condition and also significantly reduced the phosphorylation of JNK as well as c-Jun, ATF2, and JunD. Moreover, hippocampus neuron apoptosis and cognitive impairment were significantly improved with the pretreatment of BAY 11-7082 in rats subjected to CIH.

Conclusions

These findings suggest that NF-κB-mediated JNK pathway is at least partially implicated in CIH-induced hippocampus neuron apoptosis and cognitive impairment. Inhibition of NF-κB activation provided a therapeutic potential for cognitive impairment in sleep apnea (SA).