Hyperbaric Oxygen Preconditioning Attenuates Hemorrhagic Transformation Through Reactive Oxygen Species/Thioredoxin-Interacting Protein/Nod-Like Receptor Protein 3 Pathway in Hyperglycemic Middle Cerebral Artery Occlusion Rats

Hemorrhagic transformation in patients with large-artery atherosclerotic stroke is associated with the gut microbiota and lipopolysaccharide

JOURNAL/nrgr/04.03/01300535-202407000-00032/figure1/v/2023-11-20T171125Z/r/image-tiff

Hemorrhagic transformation is a major complication of large-artery atherosclerotic stroke (a major ischemic stroke subtype) that worsens outcomes and increases mortality. Disruption of the gut microbiota is an important feature of stroke, and some specific bacteria and bacterial metabolites may contribute to hemorrhagic transformation pathogenesis. We aimed to investigate the relationship between the gut microbiota and hemorrhagic transformation in large-artery atherosclerotic stroke. An observational retrospective study was conducted. From May 2020 to September 2021, blood and fecal samples were obtained upon admission from 32 patients with first-ever acute ischemic stroke and not undergoing intravenous thrombolysis or endovascular thrombectomy, as well as 16 healthy controls. Patients with stroke who developed hemorrhagic transformation (n = 15) were compared to those who did not develop hemorrhagic transformation (n = 17) and with healthy controls. The gut microbiota was assessed through 16S ribosomal ribonucleic acid sequencing. We also examined key components of the lipopolysaccharide pathway: lipopolysaccharide, lipopolysaccharide-binding protein, and soluble CD14. We observed that bacterial diversity was decreased in both the hemorrhagic transformation and non-hemorrhagic transformation group compared with the healthy controls. The patients with ischemic stroke who developed hemorrhagic transformation exhibited altered gut microbiota composition, in particular an increase in the relative abundance and diversity of members belonging to the Enterobacteriaceae family. Plasma lipopolysaccharide and lipopolysaccharide-binding protein levels were higher in the hemorrhagic transformation group compared with the non-hemorrhagic transformation group. lipopolysaccharide, lipopolysaccharide-binding protein, and soluble CD14 concentrations were associated with increased abundance of Enterobacteriaceae. Next, the role of the gut microbiota in hemorrhagic transformation was evaluated using an experimental stroke rat model. In this model, transplantation of the gut microbiota from hemorrhagic transformation rats into the recipient rats triggered higher plasma levels of lipopolysaccharide, lipopolysaccharide-binding protein, and soluble CD14. Taken together, our findings demonstrate a noticeable change in the gut microbiota and lipopolysaccharide-related inflammatory response in stroke patients with hemorrhagic transformation. This suggests that maintaining a balanced gut microbiota may be an important factor in preventing hemorrhagic transformation after stroke.

Ferroptosis: a potential therapeutic target for stroke

Ferroptosis is a form of regulated cell death characterized by massive iron accumulation and iron-dependent lipid peroxidation, differing from apoptosis, necroptosis, and autophagy in several aspects. Ferroptosis is regarded as a critical mechanism of a series of pathophysiological reactions after stroke because of iron overload caused by hemoglobin degradation and iron metabolism imbalance. In this review, we discuss ferroptosis-related metabolisms, important molecules directly or indirectly targeting iron metabolism and lipid peroxidation, and transcriptional regulation of ferroptosis, revealing the role of ferroptosis in the progression of stroke. We present updated progress in the intervention of ferroptosis as therapeutic strategies for stroke in vivo and in vitro and summarize the effects of ferroptosis inhibitors on stroke. Our review facilitates further understanding of ferroptosis pathogenesis in stroke, proposes new targets for the treatment of stroke, and suggests that more efforts should be made to investigate the mechanism of ferroptosis in stroke.

An overview of hyperbaric oxygen preconditioning against ischemic stroke

Ischemic stroke (IS) has become the second leading cause of morbidity and mortality worldwide, and the prevention of IS should be given high priority. Recent studies have indicated that hyperbaric oxygen preconditioning (HBO-PC) may be a protective nonpharmacological method, but its underlying mechanisms remain poorly defined. This study comprehensively reviewed the pathophysiology of IS and revealed the underlying mechanism of HBO-PC in protection against IS. The preventive effects of HBO-PC against IS may include inducing antioxidant, anti-inflammation, and anti-apoptosis capacity; activating autophagy and immune responses; upregulating heat shock proteins, hypoxia-inducible factor-1, and erythropoietin; and exerting protective effects upon the blood-brain barrier. In addition, HBO-PC may be considered a safe and effective method to prevent IS in combination with stem cell therapy. Although the benefits of HBO-PC on IS have been widely observed in recent research, the implementation of this technique is still controversial due to regimen differences. Transferring the results to clinical application needs to be taken carefully, and screening for the optimal regimen would be a daunting task. In addition, whether we should prescribe an individualized preconditioning regimen to each stroke patient needs further exploration.

Thioredoxin interacting protein, a key molecular switch between oxidative stress and sterile inflammation in cellular response

Tissue and systemic inflammation have been the main culprit behind the cellular response to multiple insults and maintaining homeostasis. Obesity is an independent disease state that has been reported as a common risk factor for multiple metabolic and microvascular diseases including nonalcoholic fatty liver disease (NAFLD), retinopathy, critical limb ischemia, and impaired angiogenesis. Sterile inflammation driven by high-fat diet, increased formation of reactive oxygen species, alteration of intracellular calcium level and associated release of inflammatory mediators, are the main common underlying forces in the pathophysiology of NAFLD, ischemic retinopathy, stroke, and aging brain. This work aims to examine the contribution of the pro-oxidative and pro-inflammatory thioredoxin interacting protein (TXNIP) to the expression and activation of NLRP3-inflammasome resulting in initiation or exacerbation of sterile inflammation in these disease states. Finally, the potential for TXNIP as a therapeutic target and whether TXNIP expression can be modulated using natural antioxidants or repurposing other drugs will be discussed.

GAS6/Axl Signaling Modulates Blood-Brain Barrier Function Following Intravenous Thrombolysis in Acute Ischemic Stroke

Background and Purpose

Recent studies have shown that several proteins, including Axl, are related to hemorrhagic transformation (HT) following intravenous thrombolysis by affecting blood-brain barrier (BBB) function. However, the effects of these proteins on BBB function have been studied primarily in animal models. In this study, we aimed to identify serum protein markers that predict HT following intravenous thrombolysis in patients with acute ischemic stroke (AIS) and verify whether these serum proteins regulate BBB function and HT in animal stroke models.

Methods

First, 118 AIS patients were enrolled in this study, including 52 HT patients and 66 non-HT patients. In Step 1, baseline serum levels of Axl, angiopoietin-like 4, C-reactive protein, ferritin, hypoxia-inducible factor-1 alpha, HTRA2, Lipocalin2, matrix metallopeptidase 9, platelet-derived growth factor-BB, and tumor necrosis factor alpha were measured using a quantitative cytokine chip. Next, sequence mutations and variations in genes encoding the differentially expressed proteins identified in Step 1 and subsequent function-related proteins were detected. Finally, we verified whether manipulation of differentially expressed proteins affected BBB function and HT in a hyperglycemia-induced rat stroke model.

Results

Serum Axl levels were significantly lower in the HT group than in the non-HT group; none of the other protein markers differed significantly between the two groups. Genetic testing revealed that sequence variations of GAS6 (the gene encoding the Axl ligand)-derived long non-coding RNA, GAS6-AS1, were significantly correlated with an increased risk of HT after intravenous thrombolysis. In animal studies, administration of recombinant GAS6 significantly reduced brain infarction and neurological deficits and attenuated BBB disruption and HT.

Conclusions

Lower serum Axl levels, which may result from sequence variations in GAS6-AS1, are correlated with an increased risk of HT after intravenous thrombolysis in stroke patients. Activation of the Axl signaling pathway by the GAS6 protein may serve as a therapeutic strategy to reduce HT in AIS patients.

Survey of Molecular Mechanisms of Hyperbaric Oxygen in Tissue Repair

For more than six decades, hyperbaric oxygen (HBO) has been used for a variety of indications involving tissue repair. These indications comprise a wide range of diseases ranging from intoxications to ischemia-reperfusion injury, crush syndrome, central nervous injury, radiation-induced tissue damage, burn injury and chronic wounds. In a systematic review, the molecular mechanisms triggered by HBO described within the last two decades were compiled. They cover a wide range of pathways, including transcription, cell-to-cell contacts, structure, adhesion and transmigration, vascular signaling and response to oxidative stress, apoptosis, autophagy and cell death, as well as inflammatory processes. By analyzing 71 predominantly experimental publications, we established an overview of the current concepts regarding the molecular mechanisms underlying the effects of HBO. We considered both the abovementioned pathways and their role in various applications and indications.

Extracellular vesicles derived from M2 microglia reduce ischemic brain injury through microRNA-135a-5p/TXNIP/NLRP3 axis

Accumulating evidences have suggested that extracellular vesicles (EVs) are crucial players in the pathogenesis of ischemic brain injury. This study was designed to explore the specific functions of M2 phenotype microglia-derived EVs in ischemic brain injury progression. The expression of microRNA-135a-5p (miR-135a-5p) in M2 microglia-derived EVs was determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), followed by the identification of expression relationship among miR-135a-5p, thioredoxin-interacting protein (TXNIP), and nod-like receptor protein 3 (NLRP3) by dual luciferase reporter gene assay. After construction of an oxygen-glucose deprivation/reperfusion (OGD/R) cell model, the effects of miR-135a-5p on the biological characteristics of HT-22 cells were assessed by cell counting kit 8 (CCK-8) assay and flow cytometry. Finally, a mouse model of transient middle cerebral artery occlusion (tMCAO) was established and cerebral infarction volume was determined by triphenyltetrazolium chloride (TTC) staining and the expression of IL-18 and IL-1β in the brain tissue was determined by enzyme-linked immunosorbent assay (ELISA). We found that M2 microglia-derived EVs had high expression of miR-135a-5p, and that miR-135a-5p in M2 microglia-derived EVs negatively regulated the expression of NLRP3 via TXNIP. Overexpression of miR-135a-5p promoted the proliferation but inhibited the apoptosis of neuronal cells, and inhibited the expression of autophagy-related proteins. M2 microglia-derived EVs delivered miR-135a-5p into neuronal cells to inhibit TXNIP expression, which further inhibited the activation of NLRP3 inflammasome, thereby reducing neuronal autophagy and ischemic brain injury. Hence, M2 microglia-derived EVs are novel therapeutic targets for ischemic brain injury treatment.

Responses of matrix metalloproteinases to hyperbaric oxygen treatment: changing for good or ill?

Background: Hyperbaric oxygen (HBO₂) is currently emerging as a promising therapeutic option for diseases involving impaired tissue repair and remodeling. In this regard, HBO₂ has been shown to modulate signaling pathways responsible for matrix metalloproteinases (MMPs) regulation, which makes the MMPs interesting targets for investigation. However, the understanding regarding how HBO₂ treatment affects the expression and activity of the MMP family members in different tissues and diseases needs to be clarified. The precise roles of MMPs in the physiopathology of various tissue repair disorders also remain unclear. Because of potential off-target systemic effects of the HBO₂ on MMPs, researchers and physicians should carefully consider whether their patients could be affected adversely by HBO₂ exposure. Aims: This narrative review provides an overview of MMP biology (structure, function, and regulation) and summarizes available data showing how MMPs respond to HBO₂ in different tissues and pathologies, also highlighting possible mechanisms.

Melatonin Ameliorates Hemorrhagic Transformation via Suppression of ROS-Induced NLRP3 Activation after Cerebral Ischemia in Hyperglycemic Rats

Melatonin is a strong antioxidant which beneficially protects against middle cerebral artery occlusion (MCAO) followed by hemorrhagic transformation in rats; protection includes the reduction of neurological deficits, infarction, and hematoma volume. The molecular mechanisms underlying these neuroprotective effects in the MCAO model have not been clearly identified. This study examined the influence and involved mechanism of melatonin on inflammation in hemorrhagic transformation following hyperglycemia MCAO rat model. Compared with the MCAO group, MCAO+dextrose (DX) group showed worse neurological function and higher infarction and hematoma volume. Interestingly, the protein expression of Nod-like receptor protein 3 (NLRP3) inflammasome increased in the MCAO+DX group compared with the MCAO group, which indicated that NLRP3 inflammasome may be involved in the DX-induced hemorrhagic transformation following MCAO. Then, three dosages of melatonin were intraperitoneally injected 2 h after MCAO induction. Melatonin treatment attenuated inflammatory response by inhibiting the reactive oxygen species (ROS) and NLRP3 inflammasome, alleviating neuronal injury, and reducing infarction and hematoma volume, finally improving neurological score. Melatonin also repressed cortical levels of proinflammatory cytokine IL-1β, which were increased 24 h after hyperglycemia MCAO. In order to identify the potential mechanisms, we further revealed that nigericin administration reversed the neuroprotective effect of melatonin by promoting NLRP3 inflammasome activation. In general, this present study reveals that melatonin prevents the occurrence of hyperglycemia-enhanced hemorrhagic transformation, and this effect might be beneficial to attenuate neurological dysfunction via suppressing the inflammatory response after MCAO which possibly associated with the inhibition of the ROS/NLRP3 inflammasome pathway.

Peroxynitrite activates NLRP3 inflammasome and contributes to hemorrhagic transformation and poor outcome in ischemic stroke with hyperglycemia

This study aims to test the hypothesis that peroxynitrite-mediated inflammasome activation could be a crucial player in the blood-brain barrier (BBB) disruption, hemorrhagic transformation (HT) and poor outcome in ischemic stroke with hyperglycemia. We used an experimental rat stroke model subjected to 90 min of middle cerebral artery occlusion plus 24 h or 7 days of reperfusion with or without acute hyperglycemia. We detected the production of peroxynitrite, the expression of NADPH oxidase, iNOS, MMPs and NLRP3 inflammasome in the ischemic brains, and evaluated infarct volume, brain edema, HT, neurological deficit score and survival rates. Our results show that: (1) Hyperglycemia increased the expression of NADPH oxidase subunits p47phox and p67phox, and iNOS, and the production of peroxynitrite. (2) Hyperglycemia increased infarct volume, aggravated the BBB hyperpermeability, induced brain edema and HT, and worsened neurological outcomes. These brain damages and poor outcome were reversed by the treatments of FeTmPyP (a representative peroxynitrite decomposition catalyst, PDC), peroxynitrite scavenger uric acid, and iNOS inhibitor 1400W. Furthermore, the activations of MMPs and NLRP3 inflammasome including pro/active-caspase-1 and IL-1β were inhibited both PDC and 1400W, indicating the roles of peroxynitrite in the inductions of MMPs and NLRP3 inflammasome in the ischemic brains under hyperglycemia. (3) NLRP3 inflammasome inhibitor MCC950, caspase-1 inhibitor VX-765 and IL-1β inhibitor diacerein attenuated brain edema, minimized hemorrhagic transformation and improved neurological outcome, demonstrating the roles of NLRP3 inflammasome in the hyperglycemia-mediated HT and poor outcome in the ischemic stroke rats with acute hyperglycemia. In conclusion, peroxynitrite could mediate activations of MMPs and NLRP3 inflammasome, aggravate the BBB damage and HT, and induce poor outcome in ischemic stroke with hyperglycemia. Therefore, targeting peroxynitrite-mediated NLRP3 inflammasome could be a promising strategy for ischemic stroke with hyperglycemia.

The Emerging Role of TXNIP in Ischemic and Cardiovascular Diseases; A Novel Marker and Therapeutic Target

Thioredoxin interacting protein (TXNIP) is a metabolism- oxidative- and inflammation-related marker induced in cardiovascular diseases and is believed to represent a possible link between metabolism and cellular redox status. TXNIP is a potential biomarker in cardiovascular and ischemic diseases but also a novel identified target for preventive and curative medicine. The goal of this review is to focus on the novelties concerning TXNIP. After an overview in TXNIP involvement in oxidative stress, inflammation and metabolism, the remainder of this review presents the clues used to define TXNIP as a new marker at the genetic, blood, or ischemic site level in the context of cardiovascular and ischemic diseases.

Sodium butyrate attenuated neuronal apoptosis via GPR41/Gβγ/PI3K/Akt pathway after MCAO in rats

Sodium butyrate, a short-chain fatty acid, is predominantly produced by gut microbiota fermentation of dietary fiber and serves as an important neuromodulator in the central nervous system. Recent experimental evidence has suggested that sodium butyrate may be an endogenous ligand for two orphan G protein-coupled receptors, GPR41 and GP43, which regulate apoptosis and inflammation in ischemia-related pathologies, including stroke. In the present study, we evaluated the potential efficacy and mechanism of action of short-chain fatty acids in a rat model of middle cerebral artery occlusion (MCAO). Fatty acids were intranasally administered 1 h post MCAO. Short-chain fatty acids, especially sodium butyrate, reduced infarct volume and improved neurological function at 24 and 72 h after MCAO. At 24 h, the effects of MCAO, increased apoptosis, were ameliorated after treatment with sodium butyrate, which increased the expressions of GPR41, PI3K and phosphorylated Akt. To confirm these mechanistic links and characterize the GPR active subunit, PC12 cells were subjected to oxygen-glucose deprivation and reoxygenation, and pharmacological and siRNA interventions were used to reverse efficacy. Taken together, intranasal administration of sodium butyrate activated PI3K/Akt via GPR41/Gβγ and attenuated neuronal apoptosis after MCAO.

Hemorrhagic Transformation After Tissue Plasminogen Activator Treatment in Acute Ischemic Stroke

Hemorrhagic transformation (HT) is a common complication after thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) in ischemic stroke. In this article, recent research progress of HT in vivo and in vitro studies was reviewed. We have discussed new potential mechanisms and possible experimental models of HT development, as well as possible biomarkers and treatment methods. Meanwhile, we compared and analyzed rodent models, large animal models and in vitro BBB models of HT, and the limitations of these models were discussed. The molecular mechanism of HT was investigated in terms of BBB disruption, rt-PA neurotoxicity and the effect of neuroinflammation, matrix metalloproteinases, reactive oxygen species. The clinical features to predict HT were represented including blood biomarkers and clinical factors. Recent progress in neuroprotective strategies to improve HT after stroke treated with rt-PA is outlined. Further efforts need to be made to reduce the risk of HT after rt-PA therapy and improve the clinical prognosis of patients with ischemic stroke.

An Extra Breath of Fresh Air: Hyperbaric Oxygenation as a Stroke Therapeutic

Stroke serves as a life-threatening disease and continues to face many challenges in the development of safe and effective therapeutic options. The use of hyperbaric oxygen therapy (HBOT) demonstrates pre-clinical effectiveness for the treatment of acute ischemic stroke and reports reductions in oxidative stress, inflammation, and neural apoptosis. These pathophysiological benefits contribute to improved functional recovery. Current pre-clinical and clinical studies are testing the applications of HBOT for stroke neuroprotection, including its use as a preconditioning regimen. Mild oxidative stress may be able to prime the brain to tolerate full extensive oxidative stress that occurs during a stroke, and HBOT preconditioning has displayed efficacy in establishing such ischemic tolerance. In this review, evidence on the use of HBOT following an ischemic stroke is examined, and the potential for HBOT preconditioning as a neuroprotective strategy. Additionally, HBOT as a stem cell preconditioning is also discussed as a promising strategy, thus maximizing the use of HBOT for ischemic stroke.

Hyperbaric oxygen alleviated cognitive impairments in mice induced by repeated cerebral ischemia-reperfusion injury via inhibition of autophagy

AIMS

In this study, we investigate the effect and underlying mechanism of hyperbaric oxygen (HBO) treatment on a model of repeated cerebral ischemia-reperfusion injury (IR).

MAIN METHODS

Eighty rats were randomly separated into sham, vehicle, hyperbaric air (HBA; 0.25 MPa, 60 min), and HBO (0.25 MPa, 60 min) groups. Repeated cerebral IR was induced by ligating the right and left bilateral common carotid arteries for 10 min and then allowing reperfusion for 10 min. This pattern was repeated three times. The neuroprotective effects of HBO were assessed by animal behavior, neuron morphology, inflammatory markers, intracellular calcium ion content, and autophagy-related protein and gene expression.

KEY FINDINGS

Our result showed that HBO improved learning and memory in the navigation trail and probe trail of the Morris water maze, and these findings were supported by the observation data from 2,3,5-Triphenyltet-razolium chloride staining, Nissl staining, and electron microscopic. Importantly, we found that HBO reduced excessive autophagy in the prefrontal cortex, which was evidenced by activating of the mammalian target of the rapamycin (mTOR) and 4E-BP1, as well as suppression of LC3II and ATG5. Moreover, HBO significantly inhibited the cerebral IR-induced inflammatory reaction. Furthermore, HBO treatment modulated autophagy pathway-related factors, including producing a decrease in the intracellular calcium ion concentration and p53 level; meanwhile, the levels of BDNF and p-Akt were increased.

SIGNIFICANCE

Our results indicated that HBO protected against IR-induced neuron injury by attenuating autophagy, inflammation, and calcium overload. These results provide a new mechanism and laboratory evidence for clinical treatment of VD.

[Effects of combined natural hirudin and hyperbaric oxygen therapy on survival of transplanted random-pattern skin flap in rats]

Objective

To investigate the effect of natural hirudin combined with hyperbaric oxygen therapy on the survival of transplanted random-pattern skin flap in rats.

Methods

A random-pattern skin flap in size of 10.0 cm×2.5 cm was elevated on the dorsum of 72 Sprague Dawley rats. Then the 72 rats were randomly divided into 4 groups ( n=18) according to the therapy method. At immediate and within 4 days after operation, the rats were treated with normal saline injection in control group, normal saline injection combined with hyperbaric oxygen treatment in hyperbaric oxygen group, the natural hirudin injection in natural hirudin group, and the natural hirudin injection combined with hyperbaric oxygen treatment in combined group. The flap survival was observed after operation, and survival rate was evaluated at 6 days after operation. The skin samples were collected for histological analysis, microvessel density (MVD) measurement, and evaluation of tumor necrosis factor α (TNF-α) expression level by the immunohistochemical staining at 2 and 4 days after operation.

Results

Partial necrosis occurred in each group after operation, and the flap in combined group had the best survival. The survival rate of flap was significantly higher in hyperbaric oxygen group, natural hirudin group, and combined group than that in control group, and in combined group than in hyperbaric oxygen group and natural hirudin group ( P<0.05). There was no significant difference between hyperbaric oxygen group and natural hirudin group ( P>0.05). At 2 days, more microvascular structure was observed in hyperbaric oxygen group, natural hirudin group, and combined group in comparison with control group; while plenty of inflammatory cells infiltration in all groups. At 4 days, the hyperbaric oxygen group, natural hirudin group, and the combined group still showed more angiogenesis. Meanwhile, there was still infiltration of inflammatory cells in control group, inflammatory cells in the other groups were significantly reduced when compared with at 2 days. At 2 days, the MVD was significantly higher in hyperbaric oxygen group, natural hirudin group, and combined group than that in control group ( P<0.05); the expression of TNF-α was significantly lower in hyperbaric oxygen group, natural hirudin group, and combined group than that in control group ( P<0.05). There was no significant difference in above indexes between hyperbaric oxygen group, natural hirudin group, and combined group ( P>0.05). At 4 days, the MVD was significantly higher in hyperbaric oxygen group, natural hirudin group, and combined group than that in control group, in natural hirudin group and combined group than in hyperbaric oxygen group ( P<0.05). The expression of TNF-α was significantly lower in hyperbaric oxygen group, natural hirudin group, and combined group than that in control group, in combined group than in natural hirudin group and hyperbaric oxygen group ( P<0.05).

Conclusion

Hyperbaric oxygen and natural hirudin therapy after random-pattern skin flap transplantation can improve the survival of flaps. Moreover, combined therapy is seen to exhibit significant synergistic effect. This effect maybe related to promotion of angiogenesis and the reduction of inflammation response.

Thioredoxin-Interacting Protein (TXNIP) in Cerebrovascular and Neurodegenerative Diseases: Regulation and Implication

Neurological diseases, including acute attacks (e.g., ischemic stroke) and chronic neurodegenerative diseases (e.g., Alzheimer's disease), have always been one of the leading cause of morbidity and mortality worldwide. These debilitating diseases represent an enormous disease burden, not only in terms of health suffering but also in economic costs. Although the clinical presentations differ for these diseases, a growing body of evidence suggests that oxidative stress and inflammatory responses in brain tissue significantly contribute to their pathology. However, therapies attempting to prevent oxidative damage or inhibiting inflammation have shown little success. Identification and targeting endogenous "upstream" mediators that normalize such processes will lead to improve therapeutic strategy of these diseases. Thioredoxin-interacting protein (TXNIP) is an endogenous inhibitor of the thioredoxin (TRX) system, a major cellular thiol-reducing and antioxidant system. TXNIP regulating redox/glucose-induced stress and inflammation, now is known to get upregulated in stroke and other brain diseases, and represents a promising therapeutic target. In particular, there is growing evidence that glucose strongly induces TXNIP in multiple cell types, suggesting possible physiological roles of TXNIP in glucose metabolism. Recently, a significant body of literature has supported an essential role of TXNIP in the activation of the NOD-like receptor protein (NLRP3)-inflammasome, a well-established multi-molecular protein complex and a pivotal mediator of sterile inflammation. Accordingly, TXNIP has been postulated to reside centrally in detecting cellular damage and mediating inflammatory responses to tissue injury. The majority of recent studies have shown that pharmacological inhibition or genetic deletion of TXNIP is neuroprotective and able to reduce detrimental aspects of pathology following cerebrovascular and neurodegenerative diseases. Conspicuously, the mainstream of the emerging evidences is highlighting TXNIP link to damaging signals in endothelial cells. Thereby, here, we keep the trend to present the accumulative data on CNS diseases dealing with vascular integrity. This review aims to summarize evidence supporting the significant contribution of regulatory mechanisms of TXNIP with the development of brain diseases, explore pharmacological strategies of targeting TXNIP, and outline obstacles to be considered for efficient clinical translation.

Suppression of NLRP3 attenuates hemorrhagic transformation after delayed rtPA treatment in thromboembolic stroke rats: Involvement of neutrophil recruitment

BACKGROUND

Inflammation and neutrophils play pivotal roles in hemorrhagic transformation (HT) after recombinant tissue plasminogen activator (rtPA) treatment in stroke; however, the contribution of Nod-like receptor protein 3 (NLRP3), a key component of the innate immune system, is not yet known. This study aimed to explore the role of NLRP3 in the delayed rtPA-induced HT and its association with the neutrophil recruitment.

METHODS

Rats were subjected to thromboembolic focal cerebral ischemia and delayed rtPA treatment at 4 h after ischemia to mimic HT. NLRP3 short hairpin RNAs (shRNA) were administered 72 h before ischemia. Additionally, rabbit anti-rat neutrophil serum (inducing neutropenia) was administered before cerebral ischemia. The infarct volume, edema volume, neurological deficit, hemorrhages, blood-brain barrier (BBB) integrity and brain neutrophil recruitment were evaluated at 24 h after cerebral ischemia.

RESULTS

Our results demonstrated that delayed rtPA treatment at 4 h after ischemia promoted the expression of NLRP3 in neurons, microglia and endothelial cells, degradation of BBB components, and HT. NLRP3 knockdown significantly attenuated NLRP3 expression, BBB disruption, and HT. It also improved neurological functions and reduced neutrophil recruitment. Rabbit anti-rat neutrophil serum, like NLRP3 shRNA, reduced hemorrhage score and hemorrhage volumes after rtPA treatment. Furthermore, the anti-rat neutrophil serum combined with NLRP3 shRNA didn't further increase the protective effect on HT compared to rabbit anti-rat neutrophil serum used alone.

CONCLUSIONS

Together, our data suggest that NLRP3 inhibition can reduce neutrophil recruitment, which may contribute to the inhibitory effect on HT.

Acupuncture inhibits TXNIP-associated oxidative stress and inflammation to attenuate cognitive impairment in vascular dementia rats

AIMS

Oxidative stress and inflammation have been implicated in the pathogenesis of vascular dementia (VD). Thioredoxin-interacting protein (TXNIP) plays a vital role in oxidative stress and NOD-like receptor protein 3 (NLRP3) inflammasome activation. There is evidence that acupuncture has an antioxidative and neuroprotective effect in VD. In this study, we investigated whether acupuncture can attenuate cognitive impairment via inhibiting TXNIP-associated oxidative stress and inflammation in VD rats.

METHODS

Both common carotid arteries were occluded (2-vessel occlusion [2VO]) in rats to model VD. The neuroprotective effect of acupuncture was assessed by the Morris water maze and Nissl staining. Oxidative stress was assessed by detecting levels of reactive oxygen species, DNA oxidation, and antioxidase. Western blot, real-time PCR, and immunofluorescence were used to detect the expression of TXNIP, NLRP3, caspase-1, and IL-1β. A TXNIP siRNA intraventricular injection was applied to investigate whether acupuncture mimicked the effect of TXNIP inhibitor.

RESULTS

Our findings demonstrated that VD rats treated with acupuncture had reduced hippocampal neuronal loss and oxidative stress. The upregulation of TXNIP, NLRP3, caspase-1, and IL-1β induced by 2VO was also reversed by acupuncture. Furthermore, TXNIP siRNA had a similar effect as acupuncture on cognition, hippocampal neurons, and ROS production in VD rats.

CONCLUSION

In conclusion, our study suggests that the neuroprotective effects of acupuncture in VD are mediated through reducing expression of TXNIP-associated oxidative stress and inflammation.

Resveratrol Attenuates Early Brain Injury after Experimental Subarachnoid Hemorrhage via Inhibition of NLRP3 Inflammasome Activation

Previous studies have demonstrated resveratrol (RSV) has beneficial effects in early brain injury (EBI) after subarachnoid hemorrhage (SAH). However, the beneficial effects of RSV and the underlying mechanisms have not been clearly identified. The nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation plays a crucial role in the EBI pathogenesis. The aim of this study was to investigate the role of RSV on the NLRP3 inflammasome signaling pathway and EBI in rats after SAH. A prechiasmatic cistern injection model was established in rats, and the primary cultured cortical neurons were stimulated with oxyhemoglobin (oxyHb) to induce SAH in vitro. It showed that the NLRP3 inflammasome components, including NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), caspase-1, mature interleukin-1β (IL-1β), and interleukin-18 (IL-18) were upregulated after SAH, and the enhanced NLRP3 after SAH was mainly located in microglia. Treatment with 60 or 90 mg/kg RSV after SAH dramatically inhibited the expression of NLRP3, but there was no significant difference in the expression of NLRP3 between the SAH + 60 mg/kg RSV and SAH + 90 mg/kg RSV groups. In addition, treatment with 30 mg/kg RSV did not significantly reduced the expression of NLRP3. We next evaluated the neuroprotective effects of RSV against SAH. We determined that SAH-induced NLRP3 inflammasome activation was significantly inhibited in the SAH + 60 mg/kg RSV group. Meanwhile, 60 mg/kg RSV administration could markedly inhibit microglia activation and neutrophils infiltration after SAH. Concomitant with the decreased cerebral inflammation, RSV evidently reduced cortical apoptosis, brain edema, and neurobehavioral impairment after SAH. In vitro experiments, RSV treatment also clearly protected primary cortical neurons against oxyHb insults, including reduced the proportion of neuronal apoptosis, alleviated neuronal degeneration, and improved cell viabilities. These in vitro data further confirm that RSV has an efficient neuroprotection against SAH. Taken together, these in vivo and in vitro findings suggested RSV could protect against EBI after SAH, at least partially via inhibiting NLRP3 inflammasome signaling pathway.

The NLRP3 Inflammasome: An Important Driver of Neuroinflammation in Hemorrhagic Stroke

Hemorrhagic stroke is a devastating clinical event with no effective medical treatment. Neuroinflammation, which follows a hemorrhagic stroke, is an important element that involves both acute brain injury and subsequent brain rehabilitation. Therefore, delineating the key inflammatory mediators and deciphering their pathophysiological roles in hemorrhagic strokes is of great importance in the development of novel therapeutic targets for this disease. The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a multi-protein complex that is localized within the cytoplasm. This NOD-like receptor orchestrates innate immune responses to pathogenic organisms and cell stress through the activation of caspase-1 and the maturation of the proinflammatory cytokines such as interleukin-1β (IL-1β) and IL-18. Mounting evidence has demonstrated that when the NLRP3 inflammasome is activated, it exerts harmful effects on brain tissue after a hemorrhagic stroke. This review article summarizes the current knowledge regarding the role and the underlying mechanisms of the NLRP3 inflammasome in the pathophysiological processes of hemorrhagic strokes. A better understanding of the function and regulation of the NLRP3 inflammasome in hemorrhagic strokes will provide clues for devising novel therapeutic strategies to fight this disease.

Hyperbaric Oxygen Reduces Infarction Volume and Hemorrhagic Transformation Through ATP/NAD+/Sirt1 Pathway in Hyperglycemic Middle Cerebral Artery Occlusion Rats

BACKGROUND AND PURPOSE

Energy depletion is a critical factor leading to cell death and brain dysfunction after ischemic stroke. In this study, we investigated whether energy depletion is involved in hyperglycemia-induced hemorrhagic transformation after ischemic stroke and determined the pathway underlying the beneficial effects of hyperbaric oxygen (HBO).

METHODS

After 2-hour middle cerebral artery occlusion, hyperglycemia was induced by injecting 50% dextrose (6 mL/kg) intraperitoneally at the onset of reperfusion. Immediately after it, rats were exposed to HBO at 2 atmospheres absolutes for 1 hour. ATP synthase inhibitor oligomycin A, nicotinamide phosphoribosyl transferase inhibitor FK866, or silent mating type information regulation 2 homolog 1 siRNA was administrated for interventions. Infarct volume, hemorrhagic volume, and neurobehavioral deficits were recorded; the level of blood glucose, ATP, and nicotinamide adenine dinucleotide and the activity of nicotinamide phosphoribosyl transferase were monitored; the expression of silent mating type information regulation 2 homolog 1, acetylated p53, acetylated nuclear factor-κB, and cleaved caspase 3 were detected by Western blots; and the activity of matrix metalloproteinase-9 was assayed by zymography.

RESULTS

Hyperglycemia deteriorated energy metabolism and reduced the level of ATP and nicotinamide adenine dinucleotide and exaggerated hemorrhagic transformation, blood-brain barrier disruption, and neurological deficits after middle cerebral artery occlusion. HBO treatment increased the levels of the ATP and nicotinamide adenine dinucleotide and consequently increased silent mating type information regulation 2 homolog 1, resulting in attenuation of hemorrhagic transformation, brain infarction, as well as improvement of neurological function in hyperglycemic middle cerebral artery occlusion rats.

CONCLUSIONS

HBO induced activation of ATP/nicotinamide adenine dinucleotide/silent mating type information regulation 2 homolog 1 pathway and protected blood-brain barrier in hyperglycemic middle cerebral artery occlusion rats. HBO might be promising approach for treatment of acute ischemic stroke patients, especially patients with diabetes mellitus or treated with r-tPA (recombinant tissue-type plasminogen activator).

Hyperbaric oxygen preconditioning: a reliable option for neuroprotection

Brain injury is the leading cause of death and disability worldwide and clinically there is no effective therapy for neuroprotection. Hyperbaric oxygen preconditioning (HBO-PC) has been experimentally demonstrated to be neuroprotective in several models and has shown efficiency in patients undergoing on-pump coronary artery bypass graft (CABG) surgery. Compared with other preconditioning stimuli, HBO is benign and has clinically translational potential. In this review, we will summarize the results in experimental brain injury and clinical studies, elaborate the mechanisms of HBO-PC, and discuss regimes and opinions for future interventions in acute brain injury.