Necroptosis Signaling Pathways in Stroke: From Mechanisms to Therapies

The role of ferroptosis as a regulator of oxidative stress in the pathogenesis of ischemic stroke

Ferroptosis is a unique form of cell death that was first described in 2012 and plays a significant role in various diseases, including neurodegenerative conditions. It depends on a dysregulation of cellular iron metabolism, which increases free, redox-active, iron that can trigger Fenton reactions, generating hydroxyl radicals that damage cells through oxidative stress and lipid peroxidation. Lipid peroxides, resulting mainly from unsaturated fatty acids, damage cells by disrupting membrane integrity and propagating cell death signals. Moreover, lipid peroxide degradation products can further affect cellular components such as DNA, proteins, and amines. In ischemic stroke, where blood flow to the brain is restricted, there is increased iron absorption, oxidative stress, and compromised blood-brain barrier integrity. Imbalances in iron-transport and -storage proteins increase lipid oxidation and contribute to neuronal damage, thus pointing to the possibility of brain cells, especially neurons, dying from ferroptosis. Here, we review the evidence showing a role of ferroptosis in ischemic stroke, both in recent studies directly assessing this type of cell death, as well as in previous studies showing evidence that can now be revisited with our new knowledge on ferroptosis mechanisms. We also review the efforts made to target ferroptosis in ischemic stroke as a possible treatment to mitigate cellular damage and death.

Transcutaneous electrical acupoint stimulation alleviates cerebral ischemic injury through the TLR4/MyD88/NF-κ B pathway

This study was to explore whether transcutaneous electrical acupoint stimulation (TEAS) treatment could mediate inflammation, apoptosis, and pyroptosis of neuronal cells and microglia activation through the TLR4/MyD88/NF-κB pathway in the early stage of ischemic stroke. TEAS treatment at Baihui (GV20) and Hegu (LI4) acupoints of the affected limb was administered at 24, 48, and 72 h following middle cerebral artery occlusion/reperfusion (MCAO/R), with lasting for 30 min each time. Neurological impairment scores were assessed 2 h and 72 h after ischemia/reperfusion (I/R). TTC staining was used to evaluate the volume of brain infarction. The histopathologic changes of hippocampus were detected by H&E staining. WB analysis was performed to assess the levels of TLR4, MyD88, p-NF-κB p65/NF-κB p65, and inflammation, apoptosis, pyroptosis-related proteins. TLR4 expression was measured using immunohistochemistry. The expression of inflammation-related proteins was also measured using ELISA. Immunofluorescence was used to detect the expression level of Iba1. Our findings demonstrated that TEAS intervention after I/R improved neurological function, reduced the volume of brain infarction, and mitigated pathological damage. Moreover, TEAS reduced the levels of TLR4, MyD88, p-NF-κB p65/NF-κB p65, TNF-α, IL-6, Bax, NLRP3, cleaved caspase-1/pro caspase-1, IL-1β, IL-18, GSDMD, and Iba1 while enhancing Bcl-2 expression. Moreover, the protective effects of TEAS could be counteracted by lipopolysaccharide (LPS, a TLR4 agonist). In conclusion, TEAS can reduce cerebral damage and suppress inflammation, cell death, and microglia activation after ischemic stroke via inhibiting the TLR4/MyD88/NF-κB pathway.

The Role of Stem Cells as Therapeutics for Ischaemic Stroke

Stroke remains one of the leading causes of death and disability worldwide. Current reperfusion treatments for ischaemic stroke are limited due to their narrow therapeutic window in rescuing ischaemic penumbra. Stem cell therapy offers a promising alternative. As a regenerative medicine, stem cells offer a wider range of treatment strategies, including long-term intervention for chronic patients, through the reparation and replacement of injured cells via mechanisms of differentiation and proliferation. The purpose of this review is to evaluate the therapeutic role of stem cells for ischaemic stroke. This paper discusses the pathology during acute, subacute, and chronic phases of cerebral ischaemic injury, highlights the mechanisms involved in mesenchymal, endothelial, haematopoietic, and neural stem cell-mediated cerebrovascular regeneration, and evaluates the pre-clinical and clinical data concerning the safety and efficacy of stem cell-based treatments. The treatment of stroke patients with different types of stem cells appears to be safe and efficacious even at relatively higher concentrations irrespective of the route and timing of administration. The priming or pre-conditioning of cells prior to administration appears to help augment their therapeutic impact. However, larger patient cohorts and later-phase trials are required to consolidate these findings.

Homer1 ameliorates ischemic stroke by inhibiting necroptosis-induced neuronal damage and neuroinflammation

OBJECTIVE

Proinflammatory necroptosis is the main pathological mechanism of ischemic stroke. Homer scaffolding protein 1 (Homer1) is a postsynaptic scaffolding protein that exerts anti-inflammatory effects in most central nervous system diseases. However, the relationship between Homer1 and proinflammatory necroptosis in ischemic stroke remains unclear.

AIM

This study aimed to investigate the role of Homer1 in ischemia-induced necroptosis.

METHODS

C57BL/6 mice were used to establish a model of permanent middle cerebral artery occlusion model (pMCAO). Homer1 knockdown mice were generated using adeno-associated virus (AAV) infection to explore the role of Homer1 and its impact on necroptosis in pMCAO. Finally, Homer1 protein was stereotaxically injected into the ischemic cortex of Homer1flox/flox/Nestin-Cre +/- mice, and the efficacy of Homer1 was investigated using behavioral assays and molecular biological assays to explore potential mechanisms.

RESULTS

Homer1 expression peaked at 8 h in the ischemic penumbral cortex after pMCAO and colocalized with neurons. Homer1 knockdown promoted neuronal death by enhancing necroptotic signaling pathways and aggravating ischemic brain damage in mice. Furthermore, the knockdown of Homer1 enhanced the expression of proinflammatory cytokines. Moreover, injection of Homer1 protein reduced necroptosis-induced brain injury inhibited the expression of proinflammatory factors, and ameliorated the outcomes in the Homer1flox/flox/Nestin-Cre+/- mice after pMCAO.

CONCLUSIONS

Homer1 ameliorates ischemic stroke by inhibiting necroptosis-induced neuronal damage and neuroinflammation. These data suggested that Homer1 is a novel regulator of neuronal death and neuroinflammation.

Scutellaria baicalensis Attenuated Neurological Impairment by Regulating Programmed Cell Death Pathway in Ischemic Stroke Mice

Stroke is a major global health problem that causes significant mortality and long-term disability. Post-stroke neurological impairment is a complication that is often underestimated with the risk of persistent neurological deficits. Although traditional Chinese medicines have a long history of being used for stroke, their scientific efficacy remains unclear. Scutellaria baicalensis, an herbal component known for its anti-inflammatory and antioxidant properties, has traditionally been used to treat brain disorders. This study investigated the therapeutic effects of the Scutellaria baicalensis extraction (SB) during the acute stage of ischemic stroke using photothrombotic (PTB)-induced and transient middle cerebral artery occlusion (tMCAO) model mice. We found that SB mitigated ischemic brain injury, as evidenced by a significant reduction in the modified neurological severity score in the acute stage of PTB and both the acute and chronic stages of tMCAO. Furthermore, we elucidated the regulatory role of SB in the necroptosis and pyroptosis pathways during the acute stage of stroke, underscoring its protective effects. Behavioral assessments demonstrated the effectiveness of SB in ameliorating motor dysfunction and cognitive impairment compared to the group receiving the vehicle. Our findings highlight the potential of SB as a promising therapeutic candidate for stroke. SB was found to help modulate the programmed cell death pathways, promote neuroprotection, and facilitate functional recovery.

Melatonin modulates the aggravation of pyroptosis, necroptosis, and neuroinflammation following cerebral ischemia and reperfusion injury in obese rats

Obesity is well-established as a common comorbidity in ischemic stroke. The increasing evidence has revealed that it also associates with the exacerbation of brain pathologies, resulting in increasingly severe neurological outcomes following cerebral ischemia and reperfusion (I/R) damage. Mechanistically, pyroptosis and necroptosis are novel forms of regulated death that relate to the propagation of inflammatory signals in case of cerebral I/R. Previous studies noted that pyroptotic and necroptotic signaling were exacerbated in I/R brain of obese animals and led to the promotion of brain tissue injury. This study aimed to investigate the roles of melatonin on pyroptosis, necroptosis, and pro-inflammatory pathways occurring in the I/R brain of obese rats. Male Wistar rats were given a high-fat diet for 16 weeks to induce the obese condition, and then were divided into 4 groups: Sham-operated, I/R treated with vehicle, I/R treated with melatonin (10 mg/kg), and I/R treated with glycyrrhizic acid (10 mg/kg). All drugs were administered via intraperitoneal injection at the onset of reperfusion. The development of neurological deficits, cerebral infarction, histological changes, neuronal death, and glial cell hyperactivation were investigated. This study revealed that melatonin effectively improved these detrimental parameters. Furthermore, the processes of pyroptosis, necroptosis, and inflammation were all diminished by melatonin treatment. A summary of the findings is that melatonin effectively reduces ischemic brain pathology and thereby improves post-stroke outcomes in obese rats by modulating pyroptosis, necroptosis, and inflammation.

Caspofungin Suppresses Brain Cell Necroptosis in Ischemic Stroke Rats via Up-Regulation of Pellino3

PURPOSE

Pellino3, an ubiquitin E3 ligase, prevents the formation of the death-induced signaling complex in response to TNF-α by targeting receptor-interacting protein kinase 1 (RIPK1), and bioinformatics analysis predicted an interaction between Pellino3 and caspofungin, a common antifungal drug used in clinics. This study aimed to explore the effect of caspofungin on brain injury in ischemic stroke and the underlying mechanisms.

METHODS

Ischemic stroke injury was induced in Sprague Dawley rats by occlusion of the middle cerebral artery (MCA) for 2 h, followed by 24 h reperfusion. PC12 cells were deprived of both oxygen and glucose for 8 h and then were cultured for 24 h with oxygen and glucose to mimic an ischemic stroke in vitro.

RESULTS

Animal experiments showed brain injury (increase in neurological deficit score and infarct volume) concomitant with a downregulation of Pellino3, a decreased ubiquitination of RIPK1, and an up-regulation of necroptosis-associated proteins [RIPK1, RIPK3, mixed lineage kinase domain-like protein (MLKL), p-RIPK1, p-RIPK3, and p-MLKL]. Administration of caspofungin (6 mg/kg, i.m.) at 1 h and 6 h after ischemia significantly improved neurological function, reduced infarct volume, up-regulated Pellino3 levels, increased RIPK1 ubiquitination, and down-regulated protein levels of RIPK1, p-RIPK1, p-RIPK3, and p-MLKL. PC12 cells deprived of oxygen/glucose developed signs of cellular injury (LDH release and necroptosis) concomitant with downregulation of Pellino3, decreased ubiquitination of RIPK1, and elevated necroptosis-associated proteins. These changes were reversed by overexpression of Pellino3.

CONCLUSION

We conclude that Pellino3 has an important role in counteracting necroptosis via ubiquitination of RIPK1 and caspofungin can suppress the brain cell necroptosis in ischemic stroke through upregulation of Pellino3.

A deuterohemin peptide protects cerebral ischemia-reperfusion injury by preventing oxidative stress in vitro and in vivo

Cerebral ischemia-reperfusion injury (CIRI) is a brain injury that usually occurs during thrombolytic therapy for acute ischemic stroke and impacts human health. Oxidative stress is one of the major causative factors of CIRI. DhHP-3 is a novel peroxidase-mimicking enzyme that exhibits robust reactive oxygen species (ROS) scavenging ability in vitro. Here, we established in vitro and in vivo models of cerebral ischemia-reperfusion to mechanistically investigate whether DhHP-3 can alleviate CIRI. DhHP-3 could reduce ROS, down-regulate apoptotic proteins, suppress p53 phosphorylation, attenuate the DNA damage response (DDR), and inhibit apoptosis in SH-SY5Y cells subjected to oxygen-glucose deprivation/re-oxygenation (OGD/R) and in the brain of Sprague Dawley rats subjected to transient middle cerebral artery occlusion. In conclusion, DhHP-3 has bioactivity of CIRI inhibition through suppression of the ROS-induced apoptosis.

Combination of machine learning-based bulk and single-cell genomics reveals necroptosis-related molecular subtypes and immunological features in autism spectrum disorder

Background

Necroptosis is a novel form of controlled cell death that contributes to the progression of various illnesses. Nonetheless, the function and significance of necroptosis in autism spectrum disorders (ASD) remain unknown and require further investigation.

Methods

We utilized single-nucleus RNA sequencing (snRNA-seq) data to assess the expression patterns of necroptosis in children with autism spectrum disorder (ASD) based on 159 necroptosis-related genes. We identified differentially expressed NRGs and used an unsupervised clustering approach to divide ASD children into distinct molecular subgroups. We also evaluated immunological infiltrations and immune checkpoints using the CIBERSORT algorithm. Characteristic NRGs, identified by the LASSO, RF, and SVM-RFE algorithms, were utilized to construct a risk model. Moreover, functional enrichment, immune infiltration, and CMap analysis were further explored. Additionally, external validation was performed using RT-PCR analysis.

Results

Both snRNA-seq and bulk transcriptome data demonstrated a greater necroptosis score in ASD children. Among these cell subtypes, excitatory neurons, inhibitory neurons, and endothelials displayed the highest activity of necroptosis. Children with ASD were categorized into two subtypes of necroptosis, and subtype2 exhibited higher immune activity. Four characteristic NRGs (TICAM1, CASP1, CAPN1, and CHMP4A) identified using three machine learning algorithms could predict the onset of ASD. Nomograms, calibration curves, and decision curve analysis (DCA) based on 3-NRG have been shown to have clinical benefit in children with ASD. Furthermore, necroptosis-based riskScore was found to be positively associated with immune activation. Finally, RT-PCR demonstrated differentially expressed of these four NRGs in human peripheral blood samples.

Conclusion

A comprehensive identification of necroptosis may shed light on the underlying pathogenic process driving ASD onset. The classification of necroptosis subtypes and construction of a necroptosis-related risk model may yield significant insights for the individualized treatment of children with ASD.

Necroptosis: A Pathogenic Negotiator in Human Diseases

Over the past few decades, mechanisms of programmed cell death have attracted the scientific community because they are involved in diverse human diseases. Initially, apoptosis was considered as a crucial mechanistic pathway for programmed cell death; recently, an alternative regulated mode of cell death was identified, mimicking the features of both apoptosis and necrosis. Several lines of evidence have revealed that dysregulation of necroptosis leads to pathological diseases such as cancer, cardiovascular, lung, renal, hepatic, neurodegenerative, and inflammatory diseases. Regulated forms of necrosis are executed by death receptor ligands through the activation of receptor-interacting protein kinase (RIPK)-1/3 and mixed-lineage kinase domain-like (MLKL), resulting in the formation of a necrosome complex. Many papers based on genetic and pharmacological studies have shown that RIPKs and MLKL are the key regulatory effectors during the progression of multiple pathological diseases. This review focused on illuminating the mechanisms underlying necroptosis, the functions of necroptosis-associated proteins, and their influences on disease progression. We also discuss numerous natural and chemical compounds and novel targeted therapies that elicit beneficial roles of necroptotic cell death in malignant cells to bypass apoptosis and drug resistance and to provide suggestions for further research in this field.

Insight into Lotusine and Puerarin in Repairing Alcohol-Induced Metabolic Disorder Based on UPLC-MS/MS

Alcohol is an essential element in human culture. However, alcoholism has contributed to numerous health issues, including alcoholic fatty liver and sudden death. We found that the alkaloid lotusine possessed hepato- and neuroprotection against alcohol injuries. Lotusine showed comparable protective effects to puerarin, a widely recognized antagonist against alcohol damage. To better understand the metabolic response to alcohol injury and antagonist molecules, we applied sensitive zebrafish and LC-ESI-MS to collect metabolites related to alcohol, puerarin and lotusine exposure. LC-MS identified 119 metabolites with important physiological roles. Differential metabolomic analysis showed that alcohol caused abnormal expression of 82 metabolites (60 up-regulated and 22 down-regulated). These differential metabolites involved 18 metabolic pathways and modules, including apoptosis, necroptosis, nucleotide and fatty acid metabolism. Puerarin reversed seven metabolite variations induced by alcohol, which were related to necroptosis and sphingolipid metabolism. Lotusine was found to repair five metabolites disorders invoked by alcohol, mainly through nucleotide metabolism and glutathione metabolism. In phenotypic bioassay, lotusine showed similar activities to puerarin in alleviating behavioral abnormalities, neuroapoptosis and hepatic lipid accumulation induced by alcohol exposure. Our findings provided a new antagonist, lotusine, for alcohol-induced damage and explored the roles in repairing abnormal metabolism.

Exosome in Crosstalk between Inflammation and Angiogenesis: A Potential Therapeutic Strategy for Stroke

The endothelial dysfunction, associated with inflammation and vascular permeability, remains the key event in the pathogenesis of cerebral ischemic stroke. Angiogenesis is essential for neuroprotection and neural repair following stroke. The neuroinflammatory reaction plays a vital role in stroke, and inhibition of inflammation contributes to establishing an appropriate external environment for angiogenesis. Exosomes are the heterogeneous population of extracellular vesicles which play critical roles in intercellular communication through transmitting various proteins and nucleic acids to nearby and distant recipient cells by body fluids and circulation. Recent reports have shown that exosomal therapy is a valuable and potential treatment strategy for stroke. In this review, we discussed the exosomes in complex interaction mechanisms of angiogenesis and inflammation following stroke as well as the challenges of exosomal studies such as secretion, uptake, modification, and application.

Zhongfeng Capsules protects against cerebral ischemia-reperfusion injury via mediating the phosphoinositide 3-kinase/Akt and toll-like receptor 4/nuclear factor kappa B signaling pathways by regulating neuronal apoptosis and inflammation

Inflammatory reaction and neuronal apoptosis are the major pathophysiological mechanisms involved in cerebral ischemia-reperfusion injury (CI/RI). It has been reported that Zhongfeng Capsules (ZFCs), which contain Panax notoginseng, Hirudo, Red ginseng, Eupolyphaga sinensis, Pangolin scales, Rhubarb, and Radix Salvia miltiorrhizae, have a definite therapeutic effect on CI/RI. However, the specific molecular mechanisms of ZFCs are unclear. In this study, the effects of ZFCs on middle cerebral artery occlusion were investigated in rats. Our results showed that neurological impairment and neuronal apoptosis were alleviated in ZFC-treated rats. Additionally, infarct volume and cerebral edema decreased and there was an improvement in histopathological features. Furthermore, the expression levels of IL-1β, IL-6, and TNF-α were downregulated in ZFC-treated rats. TLR 4, NF-κB, Bax, and Caspase-3 expression also tended to decrease, whereas the expression of Bcl-2, p-PI3K, p-Akt, and I-κBα increased. The results indicate that the ZFCs effectively protected the rats against CI/RI possibly via the TLR4/NF-κB signaling pathway. Additionally, the formulation regulated the transcriptional activity of NF-κB, secretion of downstream inflammatory factors, and the expression of Bcl-2-Bax proteins in the PI3K/Akt pathway. Our findings suggest that ZFCs suppress neuronal apoptosis and inflammatory reaction via the PI3K/Akt and TLR4/NF-κB signaling pathways, respectively. Moreover, activation of the PI3K/Akt pathway may result in the inhibition of proinflammatory cytokine secretion, which may be another mechanism by which ZFCs alleviate CI/RI.

Neuroprotection by Trans-Resveratrol in Rats With Intracerebral Hemorrhage: Insights into the Role of Adenosine A1 Receptors

Given the neuroprotective effects of trans-resveratrol (RV), this study aimed to investigate the involvement of the adenosine A1 receptor (A1R) in RV-mediated neuroprotection in a rat intracerebral hemorrhage (ICH) model induced by intrastriatal injection of collagenase. Rats were divided into 5 groups: (1) control, (2) sham-operated, (3) ICH pretreated with vehicle, (4) ICH pretreated with RV, and (5) ICH pretreated with RV and the A1R antagonist DPCPX. At 48 hours after ICH, the rats were subjected to neurological testing. Brain tissues were assessed for neuronal density and morphological features using routine and immunohistochemical staining. Expression of tumor necrosis factor-α (TNF-α), caspase-3, and RIPK3 proteins was examined using ELISA. A1R, MAPK P38, Hsp90, TrkB, and BDNF genes were examined using RT-qPCR. RV protected against neurological deficits and neuronal depletion, restored the expression of TNF-α, CASP3, RIPK3, A1R, and Hsp90, and increased BDNF/TrkB. DPCPX abolished the effects of RV on neurological outcomes, neuronal density, CASP3, RIPK3, A1R, Hsp90, and BDNF. These data indicate that the neuroprotection by RV involves A1R and inhibits CASP3-dependent apoptosis and RIPK3-dependent necroptosis in the perihematoma region; this is likely to be mediated by crosstalk between A1R and the BDNF/TrkB pathway.

Polyphenols for the Treatment of Ischemic Stroke: New Applications and Insights

Ischemic stroke (IS) is a leading cause of death and disability worldwide. Currently, the main therapeutic strategy involves the use of intravenous thrombolysis to restore cerebral blood flow to prevent the transition of the penumbra to the infarct core. However, due to various limitations and complications, including the narrow time window in which this approach is effective, less than 10% of patients benefit from such therapy. Thus, there is an urgent need for alternative therapeutic strategies, with neuroprotection against the ischemic cascade response after IS being one of the most promising options. In the past few decades, polyphenolic compounds have shown great potential in animal models of IS because of their high biocompatibility and ability to target multiple ischemic cascade signaling pathways, although low bioavailability is an issue that limits the applications of several polyphenols. Here, we review the pathophysiological changes following cerebral ischemia and summarize the research progress regarding the applications of polyphenolic compounds in the treatment of IS over the past 5 years. Furthermore, we discuss several potential strategies for improving the bioavailability of polyphenolic compounds as well as some essential issues that remain to be addressed for the translation of the related therapies to the clinic.

Knowledge Mapping of Necroptosis From 2012 to 2021: A Bibliometric Analysis

Background

Necroptosis, a recently discovered programmed cell death, has been pathologically linked to various diseases and is thus a promising target for treating diseases. However, a comprehensive and objective report on the current status of entire necroptosis research is lacking. Therefore, this study aims to conduct a bibliometric analysis to quantify and identify the status quo and trending issues of necroptosis research in the last decade.

Methods

Articles were acquired from the Web of Science Core Collection database. We used two bibliometric tools (CiteSpace and VOSviewer) to quantify and identify the individual impact and cooperation information by analyzing annual publications, journals, co-cited journals, countries/regions, institutions, authors, and co-cited authors. Afterwards, we identified the trending research areas of necroptosis by analyzing the co-occurrence and burst of keywords and co-cited references.

Results

From 2012 to 2021, a total of 3,111 research articles on necroptosis were published in 786 academic journals by 19,687 authors in 885 institutions from 82 countries/regions. The majority of publications were from China and the United States, of which the United States maintained the dominant position in necroptosis research; meanwhile, the Chinese Academy of Sciences and Ghent University were the most active institutions. Peter Vandenabeele published the most papers, while Alexei Degterev had the most co-citations. Cell Death & Disease published the most papers on necroptosis, while Cell was the top 1 co-cited journal, and the major area of these publications was molecular, biology, and immunology. High-frequency keywords mainly included those that are molecularly related (MLKL, TNF-alpha, NF-κB, RIPK3, RIPK1), pathological process related (cell-death, apoptosis, necroptosis, necrosis, inflammation), and disease related (cancer, ischemia/reperfusion injury, infection, carcinoma, Alzheimer’s disease).

Conclusion

Necroptosis research had a stable stepwise growth in the past decade. Current necroptosis studies focused on its cross-talk with other types of cell death, potential applications in disease treatment, and further mechanisms. Among them, the synergy with ferroptosis, further RIPK1/RIPK3/MLKL studies, its association with inflammation and oxidative stress and translational applications, and the therapeutic potential to treat cancer and neurodegenerative diseases are the trending research area. These might provide ideas for further research in the necroptosis field.

Analgecine protects against cerebral ischemia-reperfusion through apoptosis inhibition and anti-neuroinflammation in rats

Stroke influence the quality of life of patients and leave big public health issues as acute cerebrovascular disease all over the world. Analgecine (AGC) relieves pain and accelerates repair of nerve injury. This current study aims to observe the pharmacological effects and related mechanisms of AGC in cerebral ischemic stroke among middle cerebral artery ischemia-reperfusion (MCAO) rats. After seven days of AGC administration, motor function was enhanced as evidenced by the prehensile traction test. Morphological ameliorations were observed by immunohistochemistry analysis. The protein expression levels of HSP70, Bcl-2, Bax, TRAF-6, MyD88, BDNF, NGF, pCREB, CREB, pTrkB, TrkB, pAKT and AKT were estimated by western blot. Meanwhile, AGC alleviated MCAO-induced inflammation chiefly by decreasing inflammatory cytokines in rat brain tissues. These results above suggested that MCAO-caused brain infarction was obviously alleviated by AGC. The immunohistochemistry data showed that AGC reduced neuronal injury and apoptosis, and inhibited microglia and astrocytes activation. The protein results suggested the expression of apoptosis-relevant proteins decreased among AGC treated groups and the neurotrophin related proteins were obviously enhanced by CREB/BDNF/TrkB/AKT and HSP70/Bcl-2/Bax pathways. Collectively, the results demonstrated that AGC primarily promoted neuro-nutrition, reduced the injury of nerve apoptosis and ameliorated neuroinflammation. In summary, AGC played a neuroprotective role, which had provided reliable evidence for AGC to be a potential drug in treating stroke.

Heliox Preconditioning Exerts Neuroprotective Effects on Neonatal Ischemia/Hypoxia Injury by Inhibiting Necroptosis Induced by Ca2+ Elevation

Our previous studies have indicated that heliox preconditioning (HePC) may exert neuroprotective effects on neonatal hypoxic-ischemic encephalopathy (HIE). The present study was to investigate whether HePC alleviates neonatal HIE by inhibiting necroptosis and explore the potential mechanism. Seven-day-old rat pups were randomly divided into Sham group, HIE group, HIE + HePC group, HIE + Dantrolene (DAN) group, and HIE + Necrostatin-1 (Nec-1) group. HIE was induced by common carotid artery ligation and subsequent hypoxia exposure. The neurological function, brain injury, and molecular mechanism were evaluated by histological staining, neurobehavioral test, Western blotting, Ca²⁺, immunofluorescence staining, co-immunoprecipitation (Co-IP), and transmission electron microscopy (TEM). Results supported that the expression of necroptosis markers and p-RyR2 in the brain increased significantly after HIE. HePC, DAN, or Nec-1 was found to improve the neurological deficits after H/I and inhibit neuronal necroptosis. Interestingly, both HePC and DAN inhibited the increases in cytoplasmic Ca²⁺ and CaMK-II phosphorylation in the brain secondary to HIE, but Nec-1 failed to affect Ca²⁺. In conclusion, our results suggest HePC may alleviate cytoplasmic Ca²⁺ overload by regulating p-RyR2, which inhibits the necroptosis in the brain, exerting neuroprotective effects on HIE.

Role of Mitophagy in the Pathogenesis of Stroke: From Mechanism to Therapy

Mitochondria can supply adenosine triphosphate (ATP) to the tissue, which can regulate metabolism during the pathologic process and is also involved in the pathophysiology of neuronal injury after stroke. Recent studies have suggested that selective autophagy could play important roles in the pathophysiological process of stroke, especially mitophagy. It is usually mediated by the PINK1/Parkin-independent pathway or PINK1/Parkin-dependent pathway. Moreover, mitophagy may be a potential target in the therapy of stroke because the control of mitophagy is neuroprotective in stroke in vitro and in vivo. In this review, we briefly summarize recent researches in mitophagy, introduce the role of mitophagy in the pathogenesis of stroke, then highlight the strategies targeting mitophagy in the treatment of stroke, and finally propose several issues in the treatment of stroke by targeting mitophagy.

CHIP ameliorates cerebral ischemia-reperfusion injury by attenuating necroptosis and inflammation

Blood reperfusion of ischemic cerebral tissue may cause cerebral ischemia-reperfusion (CIR) injury. Necroptosis and inflammation have been demonstrated to be involved in the disease-related process of CIR injury. The E3 ubiquitin ligase carboxyl terminus of Hsp70-interacting protein (CHIP) can modulate multiple cellular signaling processes, including necroptosis and inflammation. Numerous studies have demonstrated the neuroprotective effects of CHIP on multiple central nervous system (CNS) diseases. However, the effects of CHIP on CIR injury have not been fully explored. We hypothesize that CHIP can exert neuroprotective effects by attenuating necroptosis and inflammation during CIR injury. In the present study, adult wild-type (WT) C57BL/6 mice and CHIP knock-in (KI) mice with a C57BL/6 background and CHIP overexpression in neural tissue underwent middle cerebral artery occlusion (MCAO) surgery to simulate CIR onset. Our data indicated that CHIP expression in the peri-infarct tissue was markedly increased after MCAO surgery. Compared with WT mice, CHIP KI mice significantly improved neurological deficit scores, decreased cerebral infarct volume, and attenuated brain edema and neuronal damage. Meanwhile, CHIP overexpression attenuated necroptosis and inflammation induced by MCAO surgery. These findings indicated that overexpression of CHIP might exert neuroprotective effects by attenuating necroptosis and inflammation during CIR injury, and increasing CHIP levels may be a potential strategy in cerebrovascular disease therapy.

The effect of Camellia sinensis (green tea) with its active compound EGCG on neuronal cell necroptosis in Rattus norvegicus middle cerebral artery occlusion (MCAO) model

OBJECTIVES

To determine the inhibition effect of epigallocatechin gallate (EGCG) and green tea extract on neuronal necroptosis based on necroptosis morphology.

METHODS

In vivo study was performed on male Rattus norvegicus middle cerebral artery occlusion (MCAO) model divided into five groups, MCAO-control groups, EGCG 10 mg/kg BW/day, EGCG 20 mg/kg BW/day, EGCG 30 mg/kg BW/day, and green tea extract 30 mg/kg BW/day for 7 days treatment. MCAO model was made by modification method using Bulldog clamp. After 7 days of treatment, all R. norvegicus were sacrificed. After that, examination using Hematoxylin-Eosin stain was conducted to look at necroptosis morphology in each group.

RESULTS

We found that there are significant differences between control group and the other three groups (EGCG 20 mg/kg BW/day, EGCG 30 mg/kg BW/day, and green tea extract (p<0.05). There is a significant correlation between the number of neuron cell necroptosis and both EGCG and green tea extract (p<0.05). The correlation is negative, which means both EGCG and green tea extract will decrease the number of neuron cell necroptosis. EGCG will decrease neuron cell necroptosis starting from the dose of 20 mg/kg BW/day. EGCG 30 mg/kg BW/day produces the best result compared to other doses.

CONCLUSIONS

Camellia sinensis (green tea) with its active compound EGCG decreases neuronal necroptosis morphology in MCAO models.

Baicalein attenuates caspase-independent cells death via inhibiting PARP-1 activation and AIF nuclear translocation in cerebral ischemia/reperfusion rats

It is reported that baicalein can activate PI3K/AKT pathway, inhibit caspase activation and reduce cerebral infarct volume in middle cerebral artery occlusion (MCAO) rats. However, a caspase-independent mechanism initiated by poly (ADP-ribose) polymerase-1 (PARP-1) activation has been reported to make more contribution to cells death after ischemic stroke. In the present study, we established a cerebral ischemia/reperfusion (I/R) rat model through middle cerebral artery occlusion following reperfusion to investigate the mechanisms of ischemic tissue recovery following baicalein treatment. The data showed that baicalein treatment at dose of 100 mg/kg for 7 days significantly inhibited the release of cytokines, activation of PARP-1, nuclear translocation of apoptosis-inducing factor (AIF) and macrophage migration inhibitory factor (MIF) in cerebral I/R rats, therefore decreased cerebral infarct volume and neurological scores. Then, we further investigated the signal transduction mechanisms of ischemic tissue protection by baicalein in vitro. Following oxygen and glucose deprivation (OGD) in SH-SY5Y cells, the mitochondrial AIF was translocated into nucleus after 12 h. The co-immunoprecipitation analysis showed that the interaction between AIF and MIF was activated by OGD and subsequently resulted in MIF nuclear translocation. Also, the baicalein inhibited apoptosis, reduced oxidative stress, protected mitochondrial function and restored mitochondrial membrane potential in OGD cells. The results obtained from both in vivo and in vitro study demonstrated the PARP-1/AIF pathway involved in mechanisms of baicalein to protect the cerebral tissues from ischemic injury.

Inhibition of MLKL-dependent necroptosis via downregulating interleukin-1R1 contributes to neuroprotection of hypoxic preconditioning in transient global cerebral ischemic rats

Background

Our previous study indicated that hypoxic preconditioning reduced receptor interacting protein (RIP) 3-mediated necroptotic neuronal death in hippocampal CA1 of adult rats after transient global cerebral ischemia (tGCI). Although mixed lineage kinase domain-like (MLKL) has emerged as a crucial molecule for necroptosis induction downstream of RIP3, how MLKL executes necroptosis is not yet well understood. In this study, we aim to elucidate the molecular mechanism underlying hypoxic preconditioning that inactivates MLKL-dependent neuronal necroptosis after tGCI.

Methods

Transient global cerebral ischemia was induced by the four-vessel occlusion method. Twenty-four hours before ischemia, rats were exposed to systemic hypoxia with 8% O₂ for 30 min. Western blotting was used to detect the expression of MLKL and interleukin-1 type 1 receptor (IL-1R1) in CA1. Immunoprecipitation was used to assess the interactions among IL-1R1, RIP3, and phosphorylated MLKL (p-MLKL). The concentration of intracellular free calcium ion (Ca²⁺) was measured using Fluo-4 AM. Silencing and overexpression studies were used to study the role of p-MLKL in tGCI-induced neuronal death.

Results

Hypoxic preconditioning decreased the phosphorylation of MLKL both in neurons and microglia of CA1 after tGCI. The knockdown of MLKL with siRNA decreased the expression of p-MLKL and exerted neuroprotective effects after tGCI, whereas treatment with lentiviral delivery of MLKL showed opposite results. Mechanistically, hypoxic preconditioning or MLKL siRNA attenuated the RIP3-p-MLKL interaction, reduced the plasma membrane translocation of p-MLKL, and blocked Ca²⁺ influx after tGCI. Furthermore, hypoxic preconditioning downregulated the expression of IL-1R1 in CA1 after tGCI. Additionally, neutralizing IL-1R1 with its antagonist disrupted the interaction between IL-1R1 and the necrosome, attenuated the expression and the plasma membrane translocation of p-MLKL, thus alleviating neuronal death after tGCI.

Conclusions

These data support that the inhibition of MLKL-dependent neuronal necroptosis through downregulating IL-1R1 contributes to neuroprotection of hypoxic preconditioning against tGCI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02141-y.

Virtual reality for limb motor function, balance, gait, cognition and daily function of stroke patients: A systematic review and meta-analysis

AIMS

To explore the beneficial effects of virtual reality (VR) interventions on upper- and lower-limb motor function, balance, gait, cognition and daily function outcomes in stroke patients.

DESIGN

A systematic review and meta-analysis of randomized controlled trials.

DATA SOURCES

English databases (PubMed, EMBASE, the Cochrane Library, CINAHL, Web of Science, Physiotherapy Evidence Database, ProQuest Dissertations and Theses) and Chinese databases (Chinese BioMedical Literature Service System, WANFANG, CNKI) and the Clinical Trial Registry Platform were systematically searched from inception until December 2019. Additionally, reference lists of the included studies were manually searched.

REVIEW METHODS

The methodological quality of studies was scored with the Cochrane 'risk-of-bias tool' and PEDro scale from the Physiotherapy Evidence Database by two independent evaluators.

RESULTS

In total, 87 studies with 3540 participants were included. Stroke patients receiving VR interventions showed significant improvements in Fugl-Meyer assessment of Upper Extremity, Action Research Arm Test, Wolf Motor Function Test, Fugl-Meyer Assessment of Lower Extremity, Functional Ambulation Classification, Berg Balance Scale, Time Up and Go, Velocity, Cadence, Modified Barthel Index and Functional Independence Measure. However, differences between VR intervention and traditional rehabilitation groups were not significant for Box-Block Test, 10 m Walk Test, Auditory Continuous Performance Test, Mini-Mental State Examination and Visual Continuous Performance Test.

CONCLUSION

This review suggests that VR interventions effectively improve upper- and lower-limb motor function, balance, gait and daily function of stroke patients, but have no benefits on cognition.

IMPACT

This review identified the positive effects of VR-assisted rehabilitation on upper- and lower-limb motor function, balance, gait and daily function of stroke patients. And, we verified the duration of VR intervention affects some health benefits. The benefit of VR on cognitive function requires further investigation through large-scale multicentre RCTs.

RIP3 mediates TCN-induced necroptosis through activating mitochondrial metabolism and ROS production in chemotherapy-resistant cancers

Resisting cell death is one of the hallmarks of cancer. Necroptosis is a form of non-caspase dependent necrotic cell death mediated by receptor-interacting protein kinase-1/3 (RIP1/3), which represents another mode of programmed cell death besides apoptosis. RIP3 also acts as an energy metabolism regulator associated with switching cell death from apoptosis to necroptosis. Trichothecin (TCN) is a sesquiterpenoid originating from endophytic fungi and shows potent anti-tumor bioactivity. Our current findings reveal that RIP3 mediates TCN-induced necroptosis through up-regulating PYGL and PDC-E1α to promote mitochondria energy metabolism and ROS production. RIP3 might be involved in sensitizing tumor cells to chemotherapy induced by TCN. Therefore, activating RIP3 to initiate necroptosis contributes to the bioactivity of TCN. Moreover, TCN could be exploited for therapeutic gain through up-regulating RIP3 to sensitize cancer chemotherapy.

A narrative review of the role of necroptosis in liver disease: a double-edged sword

Acute and chronic liver injuries lead to hepatocyte death and turnover. When injuries become chronic, continuous cell death and transformation lead to chronic inflammation, fibrosis, cirrhosis, and eventually carcinoma. A therapeutic strategy of great significance for liver disease is to control hepatocyte death in acute and chronic injuries. This strategy prevents hepatocytes from causing liver failure and inhibits both secondary inflammation and fibrosis. Both apoptosis and necrosis have been proven to occur in the liver, but the role of necroptosis in liver diseases is controversial. Necroptosis, which has features of necrosis and apoptosis, is a regulatory process that occurs in some cell types when caspases are inhibited. The signaling pathway of necroptosis is characterized by the activation of receptor-interacting proteins kinase (RIPK) and mixed lineage kinase domain-like (MLKL). Necroptosis is associated with a variety of inflammatory diseases and has been the focus of research in recent years. The incidence of necroptosis in liver tissues has been studied recently in several liver injury models, but the results of the studies are not consistent. The purpose of this review is to summarize the published data on the involvement of necroptosis in liver injury, focusing on the controversies, issues remaining to be discussed, and potential therapeutic applications in this area.

Bisphenol AF elevates procoagulant platelets by inducing necroptosis via RIPK1-inflammasome axis

Bisphenol AF, an analogue of Bisphenol A, is an important raw material used in the production of plastic and rubber substances like plastic bottles and containers, toys, and medical supplies. Increased contamination of air, water, dust, and food with BPA/BPAF, poses an enormous threat to humans, globally. BPAF/BPA are endocrine-disrupting chemicals that mimic estrogen hormone, thus increasing the risks of various metabolic and chronic disorders. Exposure of human blood cells to BPA/BPAF induces oxidative stress and genotoxicity. However, its effects on platelets, which play central roles in hemostasis and thrombosis, are not well-documented. In this study, we demonstrate that BPAF induces RIPK1-inflammasome axis-mediated necroptosis in platelets, increasing procoagulant platelet levels in vivo and in vitro. We also show that BPAF-induced rise in procoagulant platelets worsens pulmonary thromboembolism in vivo. The elevated procoagulant platelets are shown to increase platelet-neutrophil/monocyte aggregates that mediate pathogenesis of CVD, thrombosis, and chronic inflammatory diseases. Our results demonstrate the toxic effects of BPAF on platelets and how it propagates the clinical complications by elevating procoagulant platelet numbers. Altogether, our study sends a cautionary message against extensive use of BPAF in the plastic and rubber industries, resulting in frequent human exposure to it, thus endangering platelet functions.

The immune response of T cells and therapeutic targets related to regulating the levels of T helper cells after ischaemic stroke

Through considerable effort in research and clinical studies, the immune system has been identified as a participant in the onset and progression of brain injury after ischaemic stroke. Due to the involvement of all types of immune cells, the roles of the immune system in stroke pathology and associated effects are complicated. Past research concentrated on the functions of monocytes and neutrophils in the pathogenesis of ischaemic stroke and tried to demonstrate the mechanisms of tissue injury and protection involving these immune cells. Within the past several years, an increasing number of studies have elucidated the vital functions of T cells in the innate and adaptive immune responses in both the acute and chronic phases of ischaemic stroke. Recently, the phenotypes of T cells with proinflammatory or anti-inflammatory function have been demonstrated in detail. T cells with distinctive phenotypes can also influence cerebral inflammation through various pathways, such as regulating the immune response, interacting with brain-resident immune cells and modulating neurogenesis and angiogenesis during different phases following stroke. In view of the limited treatment options available following stroke other than tissue plasminogen activator therapy, understanding the function of immune responses, especially T cell responses, in the post-stroke recovery period can provide a new therapeutic direction. Here, we discuss the different functions and temporal evolution of T cells with different phenotypes during the acute and chronic phases of ischaemic stroke. We suggest that modulating the balance between the proinflammatory and anti-inflammatory functions of T cells with distinct phenotypes may become a potential therapeutic approach that reduces the mortality and improves the functional outcomes and prognosis of patients suffering from ischaemic stroke.

Roadmap for Stroke: Challenging the Role of the Neuronal Extracellular Matrix

Stroke is a major challenge in modern medicine and understanding the role of the neuronal extracellular matrix (NECM) in its pathophysiology is fundamental for promoting brain repair. Currently, stroke research is focused on the neurovascular unit (NVU). Impairment of the NVU leads to neuronal loss through post-ischemic and reperfusion injuries, as well as coagulatory and inflammatory processes. The ictal core is produced in a few minutes by the high metabolic demand of the central nervous system. Uncontrolled or prolonged inflammatory response is characterized by leukocyte infiltration of the injured site that is limited by astroglial reaction. The metabolic failure reshapes the NECM through matrix metalloproteinases (MMPs) and novel deposition of structural proteins continues within months of the acute event. These maladaptive reparative processes are responsible for the neurological clinical phenotype. In this review, we aim to provide a systems biology approach to stroke pathophysiology, relating the injury to the NVU with the pervasive metabolic failure, inflammatory response and modifications of the NECM. The available data will be used to build a protein–protein interaction (PPI) map starting with 38 proteins involved in stroke pathophysiology, taking into account the timeline of damage and the co-expression scores of their RNA patterns The application of the proposed network could lead to a more accurate design of translational experiments aiming at improving both the therapy and the rehabilitation processes.

Necroptotic-Apoptotic Regulation in an Endothelin-1 Model of Cerebral Ischemia

The primary forms of cell death seen in ischemic stroke are of two major types: a necrotic/necroptotic form, and an apoptotic form that is frequently seen in penumbral regions of injury. Typically apoptotic versus necroptotic programmed cell death is described as competitive in nature, where necroptosis is often described as playing a backup role to apoptosis. In the present study, we examined the relationship between these two forms of cell death in a murine endothelin-1 model of ischemia-reperfusion injury in wildtype and caspase-3 null mice with and without addition of the pharmacologic RIPK1 phosphorylation inhibitor necrostatin-1. Analyses of ischemic brain injury were performed via both cellular and volumetric assessments, electron microscopy, TUNEL staining, activated caspase-3 and caspase-7 staining, as well as CD11b and F4/80 staining. Inhibition of caspase-3 or RIPK1 phosphorylation demonstrates significant neural protective effects which are non-additive and exhibit significant overlap in protected regions. Interestingly, morphologic analysis of the cortex demonstrates reduced apoptosis following RIPK1 inhibition. Consistent with this, RIPK1 inhibition reduces the levels of both caspase-3 and caspase-7 activation. Additionally, this protection appears independent of secondary inflammatory mediators. Together, these observations demonstrate that the necroptotic protein RIPK1 modifies caspase-3/-7 activity, ultimately resulting in decreased neuronal apoptosis. These findings thus modify the traditional exclusionary view of apoptotic/necroptotic signaling, revealing a new form of interaction between these dominant forms of cell death.

Protective effect of (Xenical+GSF) against I/R-induced blood brain barrier disruption, ionic edema, lipid deregulation and neuroinflammation

Ischemic stroke is a leading cause of mortality worldwide that occurs following the reduction or interruption of blood brain supply, characterized by a cascade of early events as oxidative stress and ensuing neuro-inflammation, energy failure and the burst of intracellular Ca++ resulting in activation of phospholipases and large increase in FFA including arachidonic acid, ultimately leading to nervous cell death. Grape Seed Flour (GSF) is a complex polyphenolic mixture harboring antioxidant, anti-inflammatory and neuroprotective properties. Orlistat (Xenical ™,Xe) is a gastro-intestinal lipase inhibitor and an anti-obesity agent. In an earlier study we reported the higher efficiency in neuroprotection against HFD-induced brain lipotoxicity when combining the two drugs (GSF + Xe). As a result repurposing Xe as an adjunct to GSF therapy against stroke appeared relevant and worthy of investigation. I/R insult disrupted the blood brain barrier (BBB) as assessed by EB dye extravasation, increased water and Na⁺ within the brain. Ultrastructurally I/R altered the brain blood capillaries at the vicinity of hippocampus dentate gyrus area as assessed by transmission and scanning electron microscopy. I/R altered lipid metabolism as revealed by LDL/HDL ratio, lipase activity, and FFA profiles. Moreover, I/R induced neuro-inflammation as assessed by down-regulation of anti-inflammatory CD 56 and up-regulation of pro-inflammatory CD 68 antigen. Importantly almost all I/R-induced disturbances were retrieved partially upon Xe or GSF on their own, and optimally when combining the two drugs. Xe per se is protective against I/R injury and the best neuroprotection was obtained when associating low dosage Xe with high dosage GSF, enabling neuroprevention and cell survival within hippocampus dentate gyrus area as revealed by increased staining of Ki 67 proliferation biomarker.

Regulated Necrosis in Pulmonary Disease. A Focus on Necroptosis and Ferroptosis

To date, increasing evidence suggests the possible involvement of various types of cell death in lung diseases. The recognized regulated cell death includes necrotic cell death that is immunogenic, releasing damage-associated molecular patterns and driving tissue inflammation. Necroptosis is a well-understood form of regulated necrosis that is executed by RIPK3 (receptor-interacting protein kinase 3) and the pseudokinase MLKL (mixed lineage kinase domain-like protein). Ferroptosis is a newly described caspase-independent form of regulated necrosis that is characterized by the increase of detrimental lipid reactive oxygen species produced via iron-dependent lipid peroxidation. The role of these two cell death pathways differs depending on the disease, cell type, and microenvironment. Moreover, some experimental cell death models have demonstrated shared ferroptotic and necroptotic cell death and the synergistic effect of simultaneous inhibition. This review examines the role of regulated necrotic cell death, particularly necroptosis and ferroptosis, in lung disease pathogenesis in the context of recent insights into the roles of the key effector molecules of these two cell death pathways.

The Role of Mitochondria in Inflammation: From Cancer to Neurodegenerative Disorders

The main features that are commonly attributed to mitochondria consist of the regulation of cell proliferation, ATP generation, cell death and metabolism. However, recent scientific advances reveal that the intrinsic dynamicity of the mitochondrial compartment also plays a central role in proinflammatory signaling, identifying these organelles as a central platform for the control of innate immunity and the inflammatory response. Thus, mitochondrial dysfunctions have been related to severe chronic inflammatory disorders. Strategies aimed at reestablishing normal mitochondrial physiology could represent both preventive and therapeutic interventions for various pathologies related to exacerbated inflammation. Here, we explore the current understanding of the intricate interplay between mitochondria and the innate immune response in specific inflammatory diseases, such as neurological disorders and cancer.

Necroptosis: a crucial pathogenic mediator of human disease

Necroptosis is a genetically regulated form of necrotic cell death that has emerged as an important pathway in human disease. The necroptosis pathway is induced by a variety of signals, including death receptor ligands, and regulated by receptor-interacting protein kinases 1 and 3 (RIPK1 and RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL), which form a regulatory necrosome complex. RIPK3-mediated phosphorylation of MLKL executes necroptosis. Recent studies, using animal models of tissue injury, have revealed that RIPK3 and MLKL are key effectors of injury propagation. This Review explores the functional roles of RIPK3 and MLKL as crucial pathogenic determinants and markers of disease progression and severity in experimental models of human disease, including acute and chronic pulmonary diseases; renal, hepatic, cardiovascular, and neurodegenerative diseases; cancer; and critical illness.