12/15-Lipoxygenase Inhibition or Knockout Reduces Warfarin-Associated Hemorrhagic Transformation After Experimental Stroke

Therapeutic exploitation of ferroptosis

Pathological breakdown of membrane lipids through excessive lipid peroxidation (LPO) was first described in the mid-20th century and is now recognized as a form of regulated cell death, dubbed ferroptosis. Accumulating evidence unveils how metabolic regulation restrains peroxidation of phospholipids within cellular membranes, thereby impeding ferroptosis execution. Unleashing these metabolic breaks is currently therapeutically explored to sensitize cancers to ferroptosis inducing anti-cancer therapies. Reversely, these natural ferroptotic defense mechanisms can fail resulting in pathological conditions or diseases such as ischemia-reperfusion injury, multi-organ dysfunction, stroke, infarction, or neurodegenerative diseases. This minireview outlines current ferroptosis-inducing anti-cancer strategies and highlights the detection as well as the therapeutic targeting of ferroptosis in preclinical experimental settings. Herein, we also briefly summarize observations related to LPO, iron and redox deregulation in patients that might hint towards ferroptosis as a contributing factor.

Ferroptosis as a Therapeutic Target in Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a cerebrovascular disorder with significant mortality and morbidity. Neural injury in SAH is mediated through a variety of pathophysiological processes. Currently available treatments are either nonspecific in targeting the basic pathophysiological mechanisms that result in neural damage in SAH, or merely focus on vasospasm. Ferroptosis is a type of programmed iron dependent cell death, which has received attention due to its possible role in neural injury in SAH. Herein, we review how intracellular iron overload mediates the production of reactive free radicals and lipid peroxidation through a variety of biochemical pathways in SAH. This in turn results in induction of ferroptosis, as well as exacerbation of vasospasm. We also discuss several therapeutic agents that have been shown to inhibit ferroptosis through targeting different steps of the process. Such agents have proven effective in ameliorating vasospasm, neural damage, and neurobehavioral outcomes in animal models of SAH. Human studies to test the safety and efficacy of intrathecal or parenteral administration of the inhibitors of ferroptosis in improving outcomes of SAH patients are warranted. There are currently a few ongoing clinical trials pursuing this therapeutic concept, the results of which will be critical to determine the value of ferroptosis as a novel therapeutic target in SAH.

Arachidonic acid metabolism in health and disease

Arachidonic acid (AA), an n-6 essential fatty acid, is a major component of mammalian cells and can be released by phospholipase A2. Accumulating evidence indicates that AA plays essential biochemical roles, as it is the direct precursor of bioactive lipid metabolites of eicosanoids such as prostaglandins, leukotrienes, and epoxyeicosatrienoic acid obtained from three distinct enzymatic metabolic pathways: the cyclooxygenase pathway, lipoxygenase pathway, and cytochrome P450 pathway. AA metabolism is involved not only in cell differentiation, tissue development, and organ function but also in the progression of diseases, such as hepatic fibrosis, neurodegeneration, obesity, diabetes, and cancers. These eicosanoids are generally considered proinflammatory molecules, as they can trigger oxidative stress and stimulate the immune response. Therefore, interventions in AA metabolic pathways are effective ways to manage inflammatory-related diseases in the clinic. Currently, inhibitors targeting enzymes related to AA metabolic pathways are an important area of drug discovery. Moreover, many advances have also been made in clinical studies of AA metabolic inhibitors in combination with chemotherapy and immunotherapy. Herein, we review the discovery of AA and focus on AA metabolism in relation to health and diseases. Furthermore, inhibitors targeting AA metabolism are summarized, and potential clinical applications are discussed.

12/15-lipoxygenase inhibition attenuates neuroinflammation by suppressing inflammasomes

Introduction

Lipoxygenases (LOXs) have essential roles in stroke, atherosclerosis, diabetes, and hypertension. 12/15-LOX inhibition was shown to reduce infarct size and brain edema in the acute phase of experimental stroke. However, the significance of 12/15-LOX on neuroinflammation, which has an essential role in the pathophysiology of stroke, has not been clarified yet.

Methods

In this study, ischemia/recanalization (I/R) was performed by occluding the proximal middle cerebral artery (pMCAo) in mice. Either the 12/15-LOX inhibitor (ML351, 50 mg/kg) or its solvent (DMSO) was injected i.p. at recanalization after 1 h of occlusion. Mice were sacrificed at 6, 24, and 72-h after ischemia induction. Infarct volumes were calculated on Nissl-stained sections. Neurological deficit scoring was used for functional analysis. Lipid peroxidation was determined by the MDA assay, and the inflammatory cytokines IL-6, TNF-alpha, IL-1beta, IL-10, and TGF-beta were quantified by ELISA. The inflammasome proteins NLRP1 and NLRP3, 12/15-LOX, and caspase-1 were detected with immunofluorescence staining.

Results

Infarct volumes, neurological deficit scores, and lipid peroxidation were significantly attenuated in ML351-treated groups at 6, 24, and 72-h. ELISA results revealed that the pro-inflammatory cytokines IL-1beta, IL-6, and TNF-alpha were significantly decreased at 6-h and/or 24-h of I/R, while the anti-inflammatory cytokines IL-10 and TNF-alpha were increased at 24-h or 72-h of ML351 treatment. NLRP1 and NLRP3 immunosignaling were enhanced at three time points after I/R, which were significantly diminished by the ML351 application. Interestingly, NLRP3 immunoreactivity was more pronounced than NLRP1. Hence, we proceeded to study the co-localization of NLRP3 immunoreactivity with 12/15-LOX and caspase-1, which indicated that NLRP3 was co-localized with 12/15-LOX and caspase-1 signaling. Additionally, NLRP3 was found in neurons at all time points but in non-neuronal cells 72 h after I/R.

Discussion

These results suggest that 12/15-LOX inhibition suppresses ischemia-induced inflammation in the acute and subacute phases of stroke via suppressing inflammasome activation. Understanding the mechanisms underlying lipid peroxidation and its associated pathways, like inflammasome activation, may have broader implications for the treatment of stroke and other neurological diseases characterized by neuroinflammation.

Functional Characterization of Transgenic Mice Overexpressing Human 15-Lipoxygenase-1 (ALOX15) under the Control of the aP2 Promoter

Arachidonic acid lipoxygenases (ALOX) have been implicated in the pathogenesis of inflammatory, hyperproliferative, neurodegenerative, and metabolic diseases, but the physiological function of ALOX15 still remains a matter of discussion. To contribute to this discussion, we created transgenic mice (aP2-ALOX15 mice) expressing human ALOX15 under the control of the aP2 (adipocyte fatty acid binding protein 2) promoter, which directs expression of the transgene to mesenchymal cells. Fluorescence in situ hybridization and whole-genome sequencing indicated transgene insertion into the E1-2 region of chromosome 2. The transgene was highly expressed in adipocytes, bone marrow cells, and peritoneal macrophages, and ex vivo activity assays proved the catalytic activity of the transgenic enzyme. LC-MS/MS-based plasma oxylipidome analyses of the aP2-ALOX15 mice suggested in vivo activity of the transgenic enzyme. The aP2-ALOX15 mice were viable, could reproduce normally, and did not show major phenotypic alterations when compared with wildtype control animals. However, they exhibited gender-specific differences with wildtype controls when their body-weight kinetics were evaluated during adolescence and early adulthood. The aP2-ALOX15 mice characterized here can now be used for gain-of-function studies evaluating the biological role of ALOX15 in adipose tissue and hematopoietic cells.

TJ-M2010-5, a novel CNS drug candidate, attenuates acute cerebral ischemia-reperfusion injury through the MyD88/NF-κB and ERK pathway

Background: Cerebral ischemia-reperfusion injury (CIRI) inevitably occurs after vascular recanalization treatment for ischemic stroke. The accompanying inflammatory cascades have a major impact on outcome and regeneration after ischemic stroke. Evidences have demonstrated that TLR/MyD88/NF-κB signaling contributes to CIRI. This study aimed to investigate the druggability of MyD88 in the central nervous system (CNS) and the neuroprotective and anti-neuroinflammatory effects of the MyD88 inhibitor TJ-M2010-5 on CIRI. Methods: A middle cerebral artery occlusion (MCAO) model was used to simulate CIRI in mice. BV-2 cells were stimulated with oxygen glucose deprivation/reoxygenation (OGD/R) or lipopolysaccharide, and SH-SY5Y cells were induced by OGD/R in vitro. Neurological deficit scores and cerebral infarction volumes were evaluated. Immunofluorescence staining was performed to measure neuronal damage and apoptosis in the brain. The anti-neuroinflammatory effect of TJ-M2010-5 was evaluated by analyzing the expression of inflammatory cytokines, activation of microglia, and infiltration of peripheral myeloid cells. The expression of proteins of the MyD88/NF-κB and ERK pathway was detected by Simple Western. The concentrations of TJ-M2010-5 in the blood and brain were analyzed by liquid chromatography-mass spectrometry. Results: The cerebral infarction volume decreased in mice treated with TJ-M2010-5, with the most prominent decrease being approximately 80% of the original infarction volume. Neuronal loss and apoptosis were reduced following TJ-M2010-5 treatment. TJ-M2010-5 inhibited the infiltration of peripheral myeloid cells and the activation of microglia. TJ-M2010-5 also downregulated the expression of inflammatory cytokines and inhibited the MyD88/NF-κB and ERK pathway. Furthermore, TJ-M2010-5 showed good blood-brain barrier permeability and no neurotoxicity. Conclusion: TJ-M2010-5 has an excellent therapeutic effect on CIRI as a novel CNS drug candidate by inhibiting excessive neuroinflammatory responses.

Cepharanthine Attenuates Early Brain Injury after Subarachnoid Hemorrhage in Mice via Inhibiting 15-Lipoxygenase-1-Mediated Microglia and Endothelial Cell Ferroptosis

Background

Ferroptosis is a newly identified form of programmed cell death caused by iron-dependent lipid peroxidation. Our study was designed to determine the expression patterns and role of 15-lipoxygenase-1 (ALOX15) in subarachnoid hemorrhage (SAH) and to investigate whether cepharanthine (CEP) can inhibit ferroptosis by inhibiting ALOX15 in specific cell types.

Methods

A mouse model of SAH was developed by the endovascular perforation method. bEend.3 endothelial cells and BV2 microglial cells as well as RSL3 and hemin were used to simulate SAH in vitro. Mice and cell lines were treated with CEP and a group of specific oxygenase inhibitors to explore the protection effect from ferroptosis. Lipid peroxidation staining with BODIPY 581/591 C11 and transmission electron microscopy were used to identify ferroptosis in vitro and in vivo.

Results

In the present study, the accumulation of lipid peroxide, a defect in the glutathione peroxidase 4 (GPx4)/glutathione (GSH) antioxidant system, highly expressed ALOX15 in microglia and endothelium, and ferroptotic changes in microglial mitochondria confirmed the occurrence of ferroptosis after SAH in vivo. Further, CEP was shown to inhibit ferroptosis and improve neurological function by downregulating the expression of ALOX15. During in vitro experiments, we investigated the important role ALOX15 in RSL3-induced endothelial ferroptosis. In addition, we found that M2-type microglia are more sensitive to RSL3-induced ferroptosis than M1-type microglia and that hemin probably induced ferroptosis in M2-type microglia by increasing ALOX15 levels and decreasing GPx4 levels. The effect of CEP treatment was also demonstrated in vitro.

Conclusions

In summary, to the best of our knowledge, this is the first study demonstrating that ferroptosis occurred in the microglia and endothelium after SAH, and this process was facilitated by increased ALOX15 levels. More importantly, treatment with CEP could inhibit ferroptosis through downregulating the expression of ALOX15.

Ferroptosis in Intracerebral Hemorrhage: A Panoramic Perspective of the Metabolism, Mechanism and Theranostics

Iron is one of the most crucial elements in the human body. In recent years, a kind of programmed, non-apoptotic cell death closely related to iron metabolism-called ferroptosis- has aroused much interest among many scientists. Ferroptosis also interacts with other pathways involved in cell death including iron abnormality, the cystine/glutamate antiporter and lipid peroxidation. Together these pathological pathways exert great impacts on intracerebral hemorrhage (ICH), a lethal cerebrovascular disease with a high incidence rate and mortality rate. Furthermore, the ferroptosis also affects different brain cells (neurons and neuroglial cells) and different organelles (mitochondria and endoplasmic reticulum). Clinical treatments for ferroptosis in ICH have been closely investigated recently. This perspective provides a comprehensive summary of ferroptosis mechanisms after ICH and its interaction with other cell death patterns. Understanding the role of ferroptosis in ICH will open new windows for the future treatments and preventions for ICH and other intracerebral diseases.

Stem Cell-Derived Exosomes: a New Strategy of Neurodegenerative Disease Treatment

Short-term symptomatic treatment and dose-dependent side effects of pharmacological treatment for neurodegenerative diseases have forced the medical community to seek an effective treatment for this serious global health threat. Therapeutic potential of stem cell for treatment of neurodegenerative disorders was identified in 1980 when fetal nerve tissue was used to treat Parkinson's disease (PD). Then, extensive studies have been conducted to develop this treatment strategy for neurological disease therapy. Today, stem cells and their secretion are well-known as a therapeutic environment for the treatment of neurodegenerative diseases. This new paradigm has demonstrated special characteristics related to this treatment, including neuroprotective and neurodegeneration, remyelination, reduction of neural inflammation, and recovery of function after induced injury. However, the exact mechanism of stem cells in repairing nerve damage is not yet clear; exosomes derived from them, an important part of their secretion, are introduced as responsible for an important part of such effects. Numerous studies over the past few decades have evaluated the therapeutic potential of exosomes in the treatment of various neurological diseases. In this review, after recalling the features and therapeutic history, we will discuss the latest stem cell-derived exosome-based therapies for these diseases.

Baicalein, Baicalin, and Wogonin: Protective Effects against Ischemia-Induced Neurodegeneration in the Brain and Retina

Ischemia is a common pathological condition present in many neurodegenerative diseases, including ischemic stroke, retinal vascular occlusion, diabetic retinopathy, and glaucoma, threatening the sight and lives of millions of people globally. Ischemia can trigger excessive oxidative stress, inflammation, and vascular dysfunction, leading to the disruption of tissue homeostasis and, ultimately, cell death. Current therapies are very limited and have a narrow time window for effective treatment. Thus, there is an urgent need to develop more effective therapeutic options for ischemia-induced neural injuries. With emerging reports on the pharmacological properties of natural flavonoids, these compounds present potent antioxidative, anti-inflammatory, and antiapoptotic agents for the treatment of ischemic insults. Three major active flavonoids, baicalein, baicalin, and wogonin, have been extracted from Scutellaria baicalensis Georgi (S. baicalensis); all of which are reported to have low cytotoxicity. They have been demonstrated to exert promising pharmacological capabilities in preventing cell and tissue damage. This review focuses on the therapeutic potentials of these flavonoids against ischemia-induced neurotoxicity and damage in the brain and retina. The bioactivity and bioavailability of baicalein, baicalin, and wogonin are also discussed. It is with hope that the therapeutic potential of these flavonoids can be utilized and developed as natural treatments for ischemia-induced injuries of the central nervous system (CNS).

Arachidonic Acid Metabolites in Neurologic Disorders

BACKGROUND & OBJECTIVE

Arachidonic acid (ARA) is essential for the fluidity, selective permeability, and flexibility of the cell membrane. It is an important factor for the function of all cells, particularly in the nervous system, immune system, and vascular endothelium. ARA, after docosahexaenoic acid, is the second most common polyunsaturated fatty acid in the phospholipids of the nerve cell membrane. ARA metabolites have many kinds of physiologic roles. The major action of ARA metabolites is the promotion of the acute inflammatory response, mediated by the production of pro-inflammatory mediators such as PGE2 and PGI2, followed by the formation of lipid mediators, which have pro-resolving effects. Another important action of ARA derivatives, especially COX, is the regulation of vascular reactivity through PGs and TXA2. There is significant involvement of ARA metabolites in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and neuropsychiatric disorders. ARA derivatives also make an important contribution to acute stroke, global ischemia, subarachnoid hemorrhage, and anticoagulation- related hemorrhagic transformation.

CONCLUSION

In this review, we discuss experimental and human study results of neurologic disorders related to ARA and its metabolites in line with treatment options.

Mechanisms of neuronal cell death in ischemic stroke and their therapeutic implications

Ischemic stroke caused by arterial occlusion is the most common type of stroke, which is among the most frequent causes of disability and death worldwide. Current treatment approaches involve achieving rapid reperfusion either pharmacologically or surgically, both of which are time-sensitive; moreover, blood flow recanalization often causes ischemia/reperfusion injury. However, even though neuroprotective intervention is urgently needed in the event of stroke, the exact mechanisms of neuronal death during ischemic stroke are still unclear, and consequently, the capacity for drug development has remained limited. Multiple cell death pathways are implicated in the pathogenesis of ischemic stroke. Here, we have reviewed these potential neuronal death pathways, including intrinsic and extrinsic apoptosis, necroptosis, autophagy, ferroptosis, parthanatos, phagoptosis, and pyroptosis. We have also reviewed the latest results of pharmacological studies on ischemic stroke and summarized emerging drug targets with a focus on clinical trials. These observations may help to further understand the pathological events in ischemic stroke and bridge the gap between basic and translational research to reveal novel neuroprotective interventions.

Lipoxygenase inhibitor ML351 dysregulated an innate inflammatory response leading to impaired cardiac repair in acute heart failure

The presistent increase of 12/15 lipoxygenase enzyme activity is correlated with uncontrolled inflammation, leading to organ dysfunction. ML351, a potent 12/15 lipoxygenase (12/15LOX) inhibitor, was reported to reduce infarct size and inflammation in a murine ischemic stroke model. In the presented work, we have applied three complementary experimental approaches, in-vitro, ex-vivo, and in-vivo, to determine whether pharmacological inhibition of 12/15LOX could dampen the inflammatory response in adult mice after Kdo2-Lipid A (KLA) as an endotoxin stimulator or post myocardial infarction (MI). Male C57BL/6 (8-12 weeks) mice were subjected to permanent coronary ligation thereby inducing acute heart failure (MI-d1 and MI-d5) for in-vivo studies. 12/15LOX antagonist ML351 (50 mg/kg) was subcutaneously injected 2 h post-MI, while MI-controls received saline. For ex-vivo experiments, ML351 (25 mg/kg) was injected as bolus after 5 min of inflammatory stimulus (KLA 1 μg/g) injection. Peritoneal macrophages (PMɸ) were harvested after 4 h post KLA. For in-vitro studies, PMɸ were treated with KLA (100 ng/mL), ML351 (10 µM), or KLA + ML351 for 4 h, and inflammatory response was evaluated. In-vivo, 5LOX expression was reduced after ML351 administration, inducing a compensatory increase of 12LOX that sensitized PMɸ toward a proinflammatory state. This was marked by higher inflammatory cytokines and dysregulation of the splenocardiac axis post-MI. ML351 treatment increased CD11b⁺ and Ly6C^high populations in spleen and Ly6G⁺ population in heart, with a decrease in F4/80⁺ macrophage population at MI-d1. In-vitro results indicated that ML351 suppressed initiation of inflammation while ex-vivo results suggested ML351 overactivated inflammation consequently delaying the resolution process. Collectively, in-vitro, ex-vivo, and in-vivo results indicated that pharmacological blockade of lipoxygenases using ML351 impaired initiation of inflammation thereby dysregulated acute immune response in cardiac repair.

Effects of ML351 and tissue plasminogen activator combination therapy in a rat model of focal embolic stroke

Thrombolytic stroke therapy with tissue plasminogen activator (tPA) is limited by risks of hemorrhagic transformation (HT). We have reported that a new 12/15-lipoxygenase (12/15-LOX) inhibitor ML351 reduced tPA related HT in mice subjected to experimental stroke under anticoagulation. In this study, we asked whether ML351 can ameliorate tPA induced HT in an embolic stroke model. Rats were subjected to embolic middle cerebral artery occlusion with 2 or 3 hr ischemia and tPA infusion, with or without ML351. Regional cerebral blood flow was monitored 2 hr after ischemia and continuously monitored for 1 hr after treatment for determining reperfusion. Hemoglobin was determined in brain homogenates and infarct volume was quantified at 24 hr after stroke.12/15-LOX, cluster of differentiation 68(CD68), immunoglobulin G (IgG), and tight junction proteins expression was detected by immunohistochemistry. ML351 significantly reduced tPA related hemorrhage after stroke without affecting its thrombolytic efficacy. ML351 also reduced blood-brain barrier disruption and improved preservation of junction proteins. ML351 and tPA combination improved neurological deficit of rats even though ML351 did not further reduce the infarct volume compared to tPA alone treated animals. Pro-inflammatory cytokines were suppressed by ML351 both in vivo and in vitro experiments. We further showed that ML351 suppressed the expression of c-Jun-N-terminal kinase (JNK) in brains and microglia cultures, whereas exogenous 12-HETE attenuated this effect in vitro. In conclusion, ML351 and tPA combination therapy is beneficial in ameliorating HT after ischemic stroke. This protective effect is probably because of 12/15-LOX inhibition and suppression of JNK-mediated microglia/macrophage activation.

The future of neuroprotection in stroke

Investigators acknowledge the limitations of rodent or non-human primate stroke models, hundreds of putative neuroprotectants have been evaluated in preclinical models, but not one has entered the clinical realm. Initial studies focused on the neuron, but in recent years the focus has widened to also include other neural cells including astrocytes, pericytes and endothelial cells, which together form the neurovascular unit. Some new developments raise renewed hope for neuroprotection: the appearance of new compounds with multiple mechanisms of action, or the promulgation of new standards for a rigorous preclinical testing. At the bedside in the last 5 years, uric acid and nerinetide are the only compounds tested for clinical efficacy in randomised controlled trials (RCTs), where all patients had to receive reperfusion therapies, either intravenous thrombolysis and/or mechanical thrombectomy. In addition, otaplimastat, 3K3A-activated protein C (APC), intra-arterial verapamil and intra-arterial hypothermia were also assessed in combination with reperfusion therapy, but in RCTs that only included feasibility or safety outcomes. Some of these compounds yielded promising results which are discussed in this review. Altogether, a deeper knowledge of the mechanisms involved in the ischaemic death process at the neurovascular unit, an improved preselection and evaluation of drugs at the preclinical stage and the testing of putative neuroprotectants in enriched clinical studies of patients receiving reperfusion therapies, might prove more effective than in the past to reverse a dismal situation that has lasted already too long.

Inhibiting ferroptosis: A novel approach for stroke therapeutics

Stroke ranks as the second leading cause of death across the globe. Despite advances in stroke therapeutics, no US Food and Drug Administration (FDA)-approved drugs that can minimize neuronal injury and restore neurological function are clinically available. Ferroptosis, a regulated iron-dependent form of nonapoptotic cell death, has been shown to contribute to stroke-mediated neuronal damage. Inhibitors of ferroptosis have also been validated in several stroke models of ischemia or intracerebral hemorrhage. Herein, we review the therapeutic activity of inhibitors of ferroptosis in stroke models. We further summarize previously reported neuroprotectants that show protective effects in stroke models that have been recently validated as ferroptosis inhibitors. These findings reveal new mechanisms for neuroprotection and highlight the importance of ferroptosis during stroke processes.

The Protective Role of Immunomodulators on Tissue-Type Plasminogen Activator-Induced Hemorrhagic Transformation in Experimental Stroke: A Systematic Review and Meta-Analysis

Background: Recanalization with tissue plasminogen activator (tPA) is the only approved agent available for acute ischemic stroke. But delayed treatment of tPA may lead to lethal intracerebral hemorrhagic transformation (HT). Numerous studies have reported that immunomodulators have good efficacy on tPA-induced HT in ischemic stroke models. The benefits of immunomodulators on tPA-associated HT are not clearly defined. Here, we sought to conduct a systematic review and meta-analysis of preclinical studies to further evaluate the efficacy of immunomodulators.

Methods: The PubMed, Web of Science, and Scopus electronic databases were searched for studies. Studies that reported the efficacy of immunomodulators on tPA-induced HT in animal models of stroke were included. Animals were divided into two groups: immunomodulators plus tPA (intervention group) or tPA alone (control group). The primary outcome was intracerebral hemorrhage, and the secondary outcomes included infarct volume and neurobehavioral score. Study quality was assessed by the checklist of CAMARADES. We used standardized mean difference (SMD) to assess the impact of interventions. Regression analysis and subgroup analysis were performed to identify potential sources of heterogeneity and evaluate the impact of the study characteristics. The evidence of publication bias was evaluated using trim and fill method and Egger’s test.

Results: We identified 22 studies that met our inclusion criteria involving 516 animals and 42 different comparisons. The median quality checklist score was seven of a possible 10 (interquartile range, 6–8). Immunomodulators improved cerebral hemorrhage (1.31 SMD, 1.09–1.52); infarct volume (1.35 SMD, 0.95–1.76), and neurobehavioral outcome (0.9 SMD, 0.67–1.13) in experimental stroke. Regression analysis and subgroup analysis indicated that control of temperature and time of assessment were important factors that influencing the efficacy of immunomodulators.

Conclusion: Our findings suggested that immunomodulators had a favorable effect on tPA-associated intracerebral hemorrhage, cerebral infarction, and neurobehavioral impairments in animal models of ischemic stroke.

Ferroptosis, a Regulated Neuronal Cell Death Type After Intracerebral Hemorrhage

Ferroptosis is a term that describes one form of regulated non-apoptotic cell death. It is triggered by the iron-dependent accumulation of lipid peroxides. Emerging evidence suggests a link between ferroptosis and the pathophysiological processes of neurological disorders, including stroke, degenerative diseases, neurotrauma, and cancer. Hemorrhagic stroke, also known as intracerebral hemorrhage (ICH), belongs to a devastating illness for its high level in morbidity and mortality. Currently, there are few established treatments and limited knowledge about the mechanisms of post-ICH neuronal death. The secondary brain damage after ICH is mainly attributed to oxidative stress and hemoglobin lysate, including iron, which leads to irreversible damage to neurons. Therefore, ferroptosis is becoming a common trend in research of neuronal death after ICH. Accumulative data suggest that the inhibition of ferroptosis may effectively prevent neuronal ferroptosis, thereby reducing secondary brain damage after ICH in animal models. Ferroptosis has a close relationship with oxidative damage and iron metabolism. This review reveals the pathological pathways and regulation mechanism of ferroptosis following ICH and then offers potential intervention strategies to mitigate neuron death and dysfunction after ICH.

Phthalide derivative CD21 alleviates cerebral ischemia-induced neuroinflammation: Involvement of microglial M2 polarization via AMPK activation

Microglia can be activated to become the classic phenotype (M1) or alternative phenotype (M2), which play an important role in regulating neuroinflammatory response and tissue repair after ischemic stroke. CD21, a novel phthalide derivative, is a potential neuroprotectant against ischemic brain injury. The present study further investigated the effects of CD21 on post-ischemic microglial polarization and the underlying mechanisms. Transient middle cerebral artery occlusion (tMCAO) was used as a mouse model of ischemic stroke, while BV2 cells stimulated with conditioned medium collected from oxygen-glucose deprivation-treated HT22 cells were used in in vitro ischemic studies. The current results showed that CD21 dose-dependently and significantly improved neurological outcomes in tMCAO mice. Biochemical analyses revealed that CD21 decreased the expression of M1 phenotype markers (CD86, interleukin-1β and inducible nitric oxide synthase) and increased the expression of M2 phenotype markers (CD206, interleukin-10 and YM1/2) in both ischemic brain tissues and BV2 cells. Meanwhile, CD21 decreased the production of proinflammatory cytokines (interleukin-1β, interleukin-6 and tumor necrosis factor-α), promoted the release of the antiinflammatory cytokine (interleukin-10), and enhanced the phosphorylation of adenosine 5'-monophosphate-activated protein kinase (AMPK) in ischemic brain tissue and BV2 cells. Furthermore, the AMPK inhibitor (compound C) reversed these effects of CD21 in BV2 cells. These findings indicate that CD21 alleviates post-ischemic neuroinflammation through induction of microglial M2 polarization that is at least in part medicated by AMPK activation, suggesting that CD21 may be a promising candidate for protecting against ischemic brain injury.

Opening the time window

The recently completed EXTEND trial tested the idea that tissue plasminogen activator thrombolysis can be safely extended up to 9 h after stroke onset if automated perfusion imaging indicates the presence of a salvageable penumbra. This important trial contributes to an ongoing paradigm shift for stroke therapy. Combined with the introduction of endovascular therapy, image-guided patient selection is expanding the toolbox of the stroke practitioner. At the same time, pushing the limits of reperfusion has raised important questions about mechanisms to pursue for combination therapy as well as potential approaches to mitigate side effects and optimize treatments for patients with various co-morbidities.

The lipoxygenase pathway of Tupaia belangeri representing Scandentia. Genomic multiplicity and functional characterization of the ALOX15 orthologs in the tree shrew

The tree shrew (Tupaia belangeri) is a rat-sized mammal, which is more closely related to humans than mice and rats. However, the use of tree shrew to explore the patho-mechanisms of human inflammatory disorders has been limited since nothing is known about eicosanoid metabolism in this mammalian species. Eicosanoids are important lipid mediators exhibiting pro- and anti-inflammatory activities, which are biosynthesized via lipoxygenase and cyclooxygenase pathways. When we searched the tree shrew genome for the presence of cyclooxygenase and lipoxygenase isoforms we found copies of functional COX1, COX2 and LOX genes. Interestingly, we identified four copies of ALOX15 genes, which encode for four structurally distinct ALOX15 orthologs (tupALOX15a-d). To explore the catalytic properties of these enzymes we expressed tupALOX15a and tupALOX15c as catalytically active proteins and characterized their enzymatic properties. As predicted by the Evolutionary Hypothesis of ALOX15 specificity we found that the two enzymes converted arachidonic acid predominantly to 12S-HETE and they also exhibited membrane oxygenase activities. However, their reaction kinetic properties (K_M for arachidonic acid and oxygen, T- and pH-dependence) and their substrate specificities were remarkably different. In contrast to mice and humans, tree shrew ALOX15 isoforms are highly expressed in the brain suggesting a role of these enzymes in cerebral function. The genomic multiplicity and the tissue expression patterns of tree shrew ALOX15 isoforms need to be considered when the results of in vivo inflammation studies obtained in this animal are translated into the human situation.

Dual Antiplatelet Therapy Increases Hemorrhagic Transformation Following Thrombolytic Treatment in Experimental Stroke

Background and Purpose- Dual antiplatelet treatment poses a risk for increased hemorrhagic transformation (HT) following intravenous thrombolysis and mechanical thrombectomy. The aim of this study was to implement a model of experimental stroke with tissue-type plasminogen activator (tPA)-associated HT in mice on dual antiplatelet treatment to enable mechanistic studies and also to allow for an initial assessment of therapeutic approaches to limit HT. Methods- Male C57BL6 mice were fed with Aspirin and Clopidogrel via drinking water for 3 days. Subsequently, mice were subjected to 2-hour transient middle cerebral artery occlusion, and tPA was infused when indicated. HT was quantified by measuring hemorrhaged areas in brain sections with ImageJ. TTC staining was used to determine infarct size. Platelet function was tested in vitro using flow cytometry and in vivo with standard tail bleeding tests. Results- Both flow cytometry and tail bleeding volumes indicated significantly reduced platelet function following Aspirin and Clopidogrel treatment. While tPA administered 2 hours after onset of middle cerebral artery occlusion did not cause bleeding in control mice (0.51±0.13 mm2), HT significantly increased by 18.9±5.4 mm2 (P=0.0045) in Aspirin and Clopidogrel mice treated with tPA. HT in aspirin and clopidogrel mice not treated with tPA was nonsignificantly elevated by 8.0±4.6 mm² (P=0.3784) compared with controls. Infarct sizes did not differ between groups. The HT persisted when the tPA dosage was reduced. Conclusions- We successfully established a translational stroke model of tPA treatment under dual antiplatelet treatment. The impaired platelet function led to an increased risk for HT in tPA-treated mice. Reducing the dosage of tPA did not prevent this hemorrhagic complication.

12/15 Lipoxygenase as a Therapeutic Target in Brain Disorders

Lipoxygenases are a family of lipid-oxidizing enzymes, which generate eicosanoids and related compounds from arachidonic acid and other polyunsaturated fatty acids. These metabolites play important roles in physiology and pathogenesis of host defense mechanisms, cardiovascular diseases, cancer, inflammatory, allergic and neurodegenerative diseases. The 12/15-lipoxygenase (LOX) is special in that it can directly oxidize lipid membranes containing polyunsaturated fatty acids, without the preceding action of a phospholipase, leading to the direct attack on membranous organelles, such as mitochondria. The cytotoxic activity of human 12/15-LOX is up-regulated in neurons and endothelial cells especially after a stroke and thought to contribute to both neuronal cell death and blood-brain barrier leakage. The discovery of inhibitors that selectively target recombinant 12/15-LOX in vitro, as well as possessing activity against the murine orthologous ex vivo, could potentially support a novel therapeutic strategy for the treatment of stroke and other brain disorders related to 12/15-LOX. Here we reviewed 12/15-LOX chemistry shortly, and the diseases in which 12/15-LOX has a role in their pathophysiology and recent advances of 12/15-LOX inhibitors as a treatment option for neurological diseases.

Contributions of 12/15-Lipoxygenase to Bleeding in the Brain Following Ischemic Stroke

Ischemic strokes are caused by one or more blood clots that typically obstruct one of the major arteries in the brain, but frequently also result in leakage of the blood-brain barrier and subsequent hemorrhage. While it has long been known that the enzyme 12/15-lipoxygenase (12/15-LOX) is up-regulated following ischemic strokes and contributes to neuronal cell death, recent research has shown an additional major role for 12/15-LOX in causing this hemorrhagic transformation. These findings have important implications for the use of 12/15-LOX inhibitors in the treatment of stroke.

Role of the 12-lipoxygenase pathway in diabetes pathogenesis and complications

12-lipoxygenase (12-LOX) is one of several enzyme isoforms responsible for the metabolism of arachidonic acid and other poly-unsaturated fatty acids to both pro- and anti-inflammatory lipid mediators. Mounting evidence has shown that 12-LOX plays a critical role in the modulation of inflammation at multiple checkpoints during diabetes development. Due to this, interventions to limit pro-inflammatory 12-LOX metabolites either by isoform-specific 12-LOX inhibition, or by providing specific fatty acid substrates via dietary intervention, has the potential to significantly and positively impact health outcomes of patients living with both type 1 and type 2 diabetes. To date, the development of truly specific and efficacious inhibitors has been hampered by homology of LOX family members; however, improvements in high throughput screening have improved the inhibitor landscape. Here, we describe the function and role of human 12-LOX, and mouse 12-LOX and 12/15-LOX, in the development of diabetes and diabetes-related complications, and describe promise in the development of strategies to limit pro-inflammatory metabolites, primarily via new small molecule 12-LOX inhibitors.

Baicalin Attenuates Blood-Brain Barrier Disruption and Hemorrhagic Transformation and Improves Neurological Outcome in Ischemic Stroke Rats with Delayed t-PA Treatment: Involvement of ONOO--MMP-9 Pathway

Tissue plasminogen activator (t-PA) has a restrictive therapeutic window within 4.5 h after ischemic stroke with the risk of hemorrhagic transformation (HT) and neurotoxicity when it is used beyond the time window. In the present study, we tested the hypothesis that baicalin, an active compound of medicinal plant, could attenuate HT in cerebral ischemia stroke with delayed t-PA treatment. Male Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO) for 4.5 h and then continuously received t-PA infusion (10 mg/kg) for 0.5 h and followed by 19-h reperfusion. Baicalin (50, 100, 150 mg/kg) was administrated via femoral vein at 4.5 h after MCAO cerebral ischemia. Delayed t-PA infusion significantly increased the mortality rate, induced HT, blood-brain barrier (BBB) damage, and apoptotic cell death in the ischemic brains and exacerbated neurological outcomes in cerebral ischemia-reperfusion rats at 24 h after MCAO cerebral ischemia. Co-treatment of baicalin significantly reduced the mortality rates, ameliorated the t-PA-mediated BBB disruption and HT. Furthermore, baicalin showed to directly scavenge peroxynitrite and inhibit MMP-9 expression and activity in the ischemic brains with the delayed t-PA treatment. Baicalin had no effect on the t-PA fibrinolytic function indicated by t-PA activity assay. Taken together, baicalin could attenuate t-PA-mediated HT and improve the outcomes of ischemic stroke treatment possibly via inhibiting peroxynitrite-mediated MMP-9 activation.

Inhibition of 12/15-Lipoxygenase Protects Against β-Cell Oxidative Stress and Glycemic Deterioration in Mouse Models of Type 1 Diabetes

Islet β-cell dysfunction and aggressive macrophage activity are early features in the pathogenesis of type 1 diabetes (T1D). 12/15-Lipoxygenase (12/15-LOX) is induced in β-cells and macrophages during T1D and produces proinflammatory lipids and lipid peroxides that exacerbate β-cell dysfunction and macrophage activity. Inhibition of 12/15-LOX provides a potential therapeutic approach to prevent glycemic deterioration in T1D. Two inhibitors recently identified by our groups through screening efforts, ML127 and ML351, have been shown to selectively target 12/15-LOX with high potency. Only ML351 exhibited no apparent toxicity across a range of concentrations in mouse islets, and molecular modeling has suggested reduced promiscuity of ML351 compared with ML127. In mouse islets, incubation with ML351 improved glucose-stimulated insulin secretion in the presence of proinflammatory cytokines and triggered gene expression pathways responsive to oxidative stress and cell death. Consistent with a role for 12/15-LOX in promoting oxidative stress, its chemical inhibition reduced production of reactive oxygen species in both mouse and human islets in vitro. In a streptozotocin-induced model of T1D in mice, ML351 prevented the development of diabetes, with coincident enhancement of nuclear Nrf2 in islet cells, reduced β-cell oxidative stress, and preservation of β-cell mass. In the nonobese diabetic mouse model of T1D, administration of ML351 during the prediabetic phase prevented dysglycemia, reduced β-cell oxidative stress, and increased the proportion of anti-inflammatory macrophages in insulitis. The data provide the first evidence to date that small molecules that target 12/15-LOX can prevent progression of β-cell dysfunction and glycemic deterioration in models of T1D.

Inhibiting 12/15-lipoxygenase to treat acute stroke in permanent and tPA induced thrombolysis models

12/15-Lipoxygenase (12/15-LOX) contributes to the brain damage after middle cerebral artery occlusion (MCAO) in the acute phase of stroke. The aim of this study was to investigate the effects of a 12/15-LOX inhibitor, LOXBlock-1(LB1), in mice using a FeCl₃-induced permanent distal MCAO model and FeCl₃-induced ischemia/thrombolysis with tPA. In order to induce permanent distal MCAO, 30% FeCl₃ was used in C57BL6 mice. LB1 or DMSO treatments were applied intraperitoneally 2 h following MCAO. For FeCl₃-induced ischemia/thrombolysis experiments, 10% FeCl₃ was preferred so as to obtain reperfusion with tPA in CD1 mice. 4 h following ischemia either LB1 or DMSO and iv tPA was administered. Outcomes were NSS, weight loss, infarct volume, hemorrhage area and reperfusion rate. FeCl₃-induced distal MCAO caused an increase in 12/15-LOX signal in the ischemic cortex with an increase in MDA2 and AIF immunoreactivity. LB1 treatment, applied 2 h after ischemia, significantly decreased the infarct volume at 24 h of permanent distal MCAO. Weight loss was also significantly reduced in LB1 treated group. Distal MCAO and tPA application with LB1 or DMSO showed that treatment significantly decreased the infarct volume and the hemorrhage area. The reperfusion rate in the LB1-treated group was surprisingly higher than in the DMSO group and NSS results were significantly improved. These data suggest that LB1 can be used as an adjuvant agent to tPA. This study not only shows the effects of LB1 treatment in distal MCAO but also confirms that FeCl₃-induced MCAO model can be a useful tool to screen novel treatment options in stroke.