Baicalein and 12/15-lipoxygenase in the ischemic brain

12/15-Lipooxygenase Inhibition Reduces Microvessel Constriction and Microthrombi after Subarachnoid Hemorrhage in Mice

Background and Purpose

Impaired cerebral circulation, induced by blood vessel constrictions and microthrombi, leads to delayed cerebral ischemia after subarachnoid hemorrhage (SAH). 12/15-Lipooxygenase (12/15-LOX) overexpression has been implicated in worsening early brain injury outcomes following SAH. However, it is unknown if 12/15-LOX is important in delayed pathophysiological events after SAH. Since 12/15-LOX produces metabolites that induce inflammation and vasoconstriction, we hypothesized that 12/15-LOX leads to microvessel constriction and microthrombi formation after SAH, and thus 12/15-LOX is an important target to prevent delayed cerebral ischemia.

Methods

SAH was induced in C57BL/6 and 12/15-LOX-/- mice of both sexes by endovascular perforation. Expression of 12/15-LOX was assessed in brain tissue slices and in vitro. C57BL/6 mice were administered either ML351 (12/15-LOX inhibitor) or vehicle. Mice were evaluated for daily neuroscore and euthanized on day five to assess cerebral 12/15-LOX expression, vessel constrictions, platelet activation, microthrombi, neurodegeneration, infarction, cortical perfusion, and for development of delayed deficits. Finally, the effect of 12/15-LOX inhibition on platelet activation was assessed in SAH patient samples using a platelet spreading assay.

Results

In SAH mice, 12/15-LOX was upregulated in brain vascular cells and there was an increase in 12-S-HETE. Inhibition of 12/15-LOX improved brain perfusion on days 4-5 and attenuated delayed pathophysiological events, including microvessel constrictions, microthrombi, neuronal degeneration, and infarction. Additionally, 12/15-LOX inhibition reduced platelet activation in human and mouse blood samples.

Conclusions

Cerebrovascular 12/15-LOX overexpression plays a major role in brain dysfunction after SAH by triggering microvessel constrictions and microthrombi formation, which reduces brain perfusion. Inhibiting 12/15-LOX may be a therapeutic target to improve outcomes after SAH.

Application of natural products in regulating ferroptosis in human diseases

BACKGROUND

Ferroptosis is a type of cell death caused by excessive iron-induced peroxidation. It has been found to be involved in a variety of diseases, and natural products can be used to target ferroptosis in treatments. Natural products are biologically active compounds extracted or synthesized from nature. It is an important resource for the discovery of skeletons with a high degree of structural diversity and a wide range of bioactivities, which can be developed directly or used as a starting point for the optimization of new drugs.

PURPOSE

In this review, we aim to discuss the interactions between natural products and ferroptosis in the treatment of human diseases.

METHODS

Literature was searched in Pubmed, Science Direct, and Web of Science databases for the 11-year period from 2012 to 2023 using the search terms "natural products", "ferroptosis", "human disease", "neurodegenerative disease", "cardiovascular disease", and "cancer".

RESULTS

In this research, the roles of natural products and ferroptosis were investigated. We suggest that natural products, such as terpenoids, flavonoids, polyphenols, alkaloids, and saponins, can be used in therapeutic applications for human diseases, as well as in ferroptosis. Additionally, the main mechanisms of ferroptosis were summarized and discussed. Furthermore, we propose that natural products can be utilized to enhance the sensitivity of cancer cells to ferroptosis, thus helping to overcome drug resistance and inhibit metastasis. Moreover, natural products have the potential to modulate the expression levels of ferroptosis-related factors. Finally, the future directions of this field were highlighted.

CONCLUSION

The potential of natural products which focus on ferroptosis to treat human illnesses, particularly cancer, is very encouraging for human wellbeing.

[What is the Initiating Reaction for the Lipid Radical Chain Reaction System That Can Induce Ferroptotic Cell Death at the Lower Oxygen Content?]

The neural cell death in cerebral infarction is suggested to be ferroptosis-like cell death, involving the participation of 15-lipoxygenase (15-LOx). Ferroptosis is induced by lipid radical species generated through the one-electron reduction of lipid hydroperoxides, and it has been shown to propagate intracellularly and intercellularly. At lower oxygen concentration, it appeared that both regiospecificity and stereospecificity of conjugated diene moiety in lipoxygenase-catalysed lipid hydroperoxidation are drastically lost. As a result, in the reaction with linoleic acid, the linoleate 9-peroxyl radical-ferrous lipoxygenase complex dissolves into the linoleate 9-peroxyl radical and ferrous 15-lipoxygenase. Subsequently, the ferrous 15-lipoxygenase then undergoes one-electron reduction of 13-hydroperoxy octadecadienoic acid, generating an alkoxyl radical (pseudoperoxidase reaction). A part of the produced lipid alkoxyl radicals undergoes cleavage of C-C bonds, liberating small molecular hydrocarbon radicals. Particularly, in ω-3 polyunsaturated fatty acids, which are abundant in the vascular and nervous systems, the liberation of small molecular hydrocarbon radicals was more pronounced compared to ω-6 polyunsaturated fatty acids. The involvement of these small molecular hydrocarbon radicals in the propagation of membrane lipid damage is suggested.

Progress of Ferroptosis in Ischemic Stroke and Therapeutic Targets

Ferroptosis is an iron-dependent form of programmed cell death (PCD) and ischemic stroke (IS) has been confirmed to be closely related to ferroptosis. The mechanisms of ferroptosis were summarized into three interrelated aspects: iron metabolism, lipid peroxide metabolism, as well as glutathione and amino acid metabolism. What's more, the causal relationship between ferroptosis and IS has been elucidated by several processes. The disruption of the blood-brain barrier, the release of excitatory amino acids, and the inflammatory response after ischemic stroke all lead to the disorder of iron metabolism and the antioxidant system. Based on these statements, we reviewed the reported effects of compounds and drugs treating IS by modulating key molecules in ferroptosis. Through detailed analysis of the roles of these key molecules, we have also more clearly demonstrated the essential effect of ferroptosis in the occurrence of IS so as to provide new targets and ideas for the therapeutic targets of IS.

The role of ferroptosis in central nervous system damage diseases

Ferroptosis is a form of cell death, i.e., programmed cell death characterized by lipid peroxidation and iron dependence, which has unique morphological and biochemical properties. This unique mode of cell death is driven by iron-dependent phospholipid peroxidation and regulated by multiple cell metabolic pathways, including redox homeostasis, iron metabolism, mitochondrial activity, and the metabolism of amino acids, lipids, and sugars. Many organ injuries and degenerative pathologies are caused by ferroptosis. Ferroptosis is closely related to central nervous system injury diseases and is currently an important topic of research globally. This research examined the relationships between ferroptosis and the occurrence and treatment of central nervous system injury diseases. Additionally, ferroptosis was assessed from the aspect of theory proposal, mechanism of action, and related signaling pathways per recent research. This review provides a relevant theoretical basis for further research on this theory, the prospect of its development, and the prevention and treatment of such diseases.

Quantitative Assessment of the Post-translational Modifications of Human Serum Albumin by Dimethyl Trisulfide

Some bacteria, such as Fusobacterium nucleatum, act as dimethyl trisulfide (DMTS) producers in the host in vivo. DMTS acts as a sulfane sulfur donor and chemically modifies the sulfhydryl groups. This study explored the post-translational modifications of human serum albumin using DMTS. Quantitative assessments were conducted on mixed disulfides of mercaptoalbumin with mercaptomethane (Alb-SS-CH3) and albumin hydropersulfide (Alb-SSH) as post-translationally modified species. The hydropersulfide group was alkylated with iodoacetamide, resulting in the formation of an albumin-mercaptoacetamide mixed disulfide. The mixed disulfides were subsequently reduced with tris(2-carboxyethyl)phosphine, and the liberated mercaptomethane and mercaptoacetamide were fluorescently labeled with 4-fluoro-7-sulfamoylbenzofurazan (ABD-F). Quantification was performed using HPLC with fluorescence detection. Using this methodology, we examined the formation of Alb-SS-CH3 and Alb-SSH via the reaction between 4% human serum albumin and DMTS at 10-100 µM concentrations. Approximately two molecules of Alb-SS-CH3 and one molecule of Alb-SSH were generated from one DMTS molecule. Moreover, hydrogen sulfide was identified as an intermediate, suggesting its generation and subsequent reaction with intraprotein disulfide bonds, leading to the production of Alb-SSH. These results suggest the production of DMTS in humans in vivo should be involved in the elevation of Alb-SS-CH3 and Alb-SSH contents in plasma samples.

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.

Targeting ferroptosis opens new avenues for the development of novel therapeutics

Ferroptosis is an iron-dependent form of regulated cell death with distinct characteristics, including altered iron homeostasis, reduced defense against oxidative stress, and abnormal lipid peroxidation. Recent studies have provided compelling evidence supporting the notion that ferroptosis plays a key pathogenic role in many diseases such as various cancer types, neurodegenerative disease, diseases involving tissue and/or organ injury, and inflammatory and infectious diseases. Although the precise regulatory networks that underlie ferroptosis are largely unknown, particularly with respect to the initiation and progression of various diseases, ferroptosis is recognized as a bona fide target for the further development of treatment and prevention strategies. Over the past decade, considerable progress has been made in developing pharmacological agonists and antagonists for the treatment of these ferroptosis-related conditions. Here, we provide a detailed overview of our current knowledge regarding ferroptosis, its pathological roles, and its regulation during disease progression. Focusing on the use of chemical tools that target ferroptosis in preclinical studies, we also summarize recent advances in targeting ferroptosis across the growing spectrum of ferroptosis-associated pathogenic conditions. Finally, we discuss new challenges and opportunities for targeting ferroptosis as a potential strategy for treating ferroptosis-related diseases.

Pharmacological Inhibition of Ferroptosis as a Therapeutic Target for Neurodegenerative Diseases and Strokes

Emerging evidence suggests that ferroptosis, a unique regulated cell death modality that is morphologically and mechanistically different from other forms of cell death, plays a vital role in the pathophysiological process of neurodegenerative diseases, and strokes. Accumulating evidence supports ferroptosis as a critical factor of neurodegenerative diseases and strokes, and pharmacological inhibition of ferroptosis as a therapeutic target for these diseases. In this review article, the core mechanisms of ferroptosis are overviewed and the roles of ferroptosis in neurodegenerative diseases and strokes are described. Finally, the emerging findings in treating neurodegenerative diseases and strokes through pharmacological inhibition of ferroptosis are described. This review demonstrates that pharmacological inhibition of ferroptosis by bioactive small-molecule compounds (ferroptosis inhibitors) could be effective for treatments of these diseases, and highlights a potential promising therapeutic avenue that could be used to prevent neurodegenerative diseases and strokes. This review article will shed light on developing novel therapeutic regimens by pharmacological inhibition of ferroptosis to slow down the progression of these diseases in the future.

Baicalein Suppresses NLRP3 and AIM2 Inflammasome-Mediated Pyroptosis in Macrophages Infected by Mycobacterium tuberculosis via Induced Autophagy

Mycobacterium tuberculosis (Mtb) continues to pose a significant threat to global health because it causes granulomas and systemic inflammatory responses during active tuberculosis (TB). Mtb can induce macrophage pyroptosis, which results in the release of IL-1β and causes tissue damage, thereby promoting its spread. In the absence of anti-TB drugs, host-directed therapy (HDT) has been demonstrated to be an effective strategy against TB. In this study, we used an in vitro Mtb-infected macrophage model to assess the effect of baicalein, derived from Scutellariae radix, on pyroptosis induced in Mtb-infected macrophages. Further, we investigated the molecular mechanisms underlying the actions of baicalein. The results of the study suggest that baicalein inhibits pyroptosis in Mtb-infected macrophages by downregulating the assembly of AIM2 and NLRP3 inflammasome and promoting autophagy. Further research has also shown that the mechanism by which baicalein promotes autophagy may involve the inhibition of the activation of the Akt/mTOR pathway and the inhibition of the AIM2 protein, which affects the levels of CHMP2A protein required to promote autophagy. Thus, our data show that baicalein can inhibit Mtb infection-induced macrophage pyroptosis and has the potential to be a new adjunctive HDT drug. IMPORTANCE Current strategies for treating drug-resistant tuberculosis have limited efficacy and undesirable side effects; hence, research on new treatments, including innovative medications, is required. Host-directed therapy (HDT) has emerged as a viable strategy for modulating host cell responses in order to enhance protective immunity against infections. Baicalein, extracted from Scutellariae radix, was shown to inhibit pyroptosis caused by Mycobacterium tuberculosis-infected macrophages and was associated with autophagy. Our findings reveal that baicalein can be used as an adjunctive treatment for tuberculosis or other inflammatory diseases by regulating immune function and enhancing the antibacterial ability of the host. It also provides a new idea for exploring the anti-inflammatory mechanism of baicalein.

Ferroptosis, Acyl Starvation, and Breast Cancer

To maintain their growth rate, cancer cells must secure a supply of fatty acids, which are necessary for building cell membranes and maintaining energy processes. This is one of the reasons why tissues with intensive fatty acid metabolism, such as the mammary gland, are more likely to develop tumors. One natural or induced defense process against cancer is ferroptosis, which interferes with normal fatty acid metabolism. This leads to the oxidation of polyunsaturated fatty acids, which causes a rearrangement of the metabolism and damages cell membranes. As a consequence of this oxidation, there is a shortage of normal polyunsaturated fatty acids, which disturbs the complicated metabolism of fatty acids. This imbalance in metabolism, resulting from the deficiency of properly structured fatty acids, is called, by these authors, "acyl starvation." When cancer cells are exposed to alternating hypoxia and reoxygenation, they often develop resistance to neoadjuvant therapies. Blocking the stearoyl-CoA desaturase - fatty acid-binding protein 4 - fatty acid translocase axis appears to be a promising pathway in the treatment of breast cancer. On the one hand, the inhibition of desaturase leads to the formation of toxic phospholipid hydroperoxides in ferroptosis, whereas on the other hand, the inhibition of fatty acid-binding protein 4 and translocase leads to a reduced uptake of fatty acids and disruption of the cellular transport of fatty acids, resulting in intracellular acyl starvation. The disruption in the metabolism of fatty acids in cancer cells may augment the effectiveness of neoadjuvant therapy. SIGNIFICANCE STATEMENT: Regulation of the metabolism of fatty acids in cancer cells seems to be a promising therapeutic direction. Studies show that the induction of ferroptosis in cancer cells, combined with use of neoadjuvant therapies, effectively inhibits the proliferation of these cells. We link the process of ferroptosis with apoptosis and SCD1-FABP4-CD36 axis and propose the term "acyl starvation" for the processes leading to FA deficiency, dysregulation of FA metabolism in cancer cells, and, most importantly, the appearance of incorrect proportions FAs.

Brain fatty acid and transcriptome profiles of pig fed diets with different levels of soybean oil

BACKGROUND

The high similarity in anatomical and neurophysiological processes between pigs and humans make pigs an excellent model for metabolic diseases and neurological disorders. Lipids are essential for brain structure and function, and the polyunsaturated fatty acids (PUFA) have anti-inflammatory and positive effects against cognitive dysfunction in neurodegenerative diseases. Nutrigenomics studies involving pigs and fatty acids (FA) may help us in better understanding important biological processes. In this study, the main goal was to evaluate the effect of different levels of dietary soybean oil on the lipid profile and transcriptome in pigs' brain tissue.

RESULTS

Thirty-six male Large White pigs were used in a 98-day study using two experimental diets corn-soybean meal diet containing 1.5% soybean oil (SOY1.5) and corn-soybean meal diet containing 3.0% soybean oil (SOY3.0). No differences were found for the brain total lipid content and FA profile between the different levels of soybean oil. For differential expression analysis, using the DESeq2 statistical package, a total of 34 differentially expressed genes (DEG, FDR-corrected p-value < 0.05) were identified. Of these 34 DEG, 25 are known-genes, of which 11 were up-regulated (log2 fold change ranging from + 0.25 to + 2.93) and 14 were down-regulated (log2 fold change ranging from - 3.43 to -0.36) for the SOY1.5 group compared to SOY3.0. For the functional enrichment analysis performed using MetaCore with the 34 DEG, four pathway maps were identified (p-value < 0.05), related to the ALOX15B (log2 fold change - 1.489), CALB1 (log2 fold change - 3.431) and CAST (log2 fold change + 0.421) genes. A "calcium transport" network (p-value = 2.303e-2), related to the CAST and CALB1 genes, was also identified.

CONCLUSION

The results found in this study contribute to understanding the pathways and networks associated with processes involved in intracellular calcium, lipid metabolism, and oxidative processes in the brain tissue. Moreover, these results may help a better comprehension of the modulating effects of soybean oil and its FA composition on processes and diseases affecting the brain tissue.

ACSL4 and the lipoxygenases 15/15B are pivotal for ferroptosis induced by iron and PUFA dyshomeostasis in dopaminergic neurons

Ferroptosis, an iron-dependent regulated cell death triggered by high lipid peroxide levels, has been implicated in several neurodegenerative diseases, including Parkinson's disease (PD). Brain regions such as the striatum are highly rich in both peroxidation susceptible PUFAs and iron, which accumulate at a greater rate than age in PD. The exact molecular pathways and patho-physiological conditions promoting cell death in the dopaminergic neurons that are particularly susceptible in PD remain elusive. In the current work, we show that modifying the PUFA composition in membranes of dopaminergic neurons using arachidonic acid (AA) can determine ferroptosis susceptibility. Furthermore, cotreatment with iron (Fe), increases AA-containing phospholipid association and synergistically promotes high lipid peroxidation to facilitate ferroptosis. Ex vivo analysis with organotypic brain slices, confirm that AA + Fe induces cell death in the nigrostriatal pathway and can be rescued by the anti-ferroptotic drug Ferrostatin-1. Prevention of ferroptotic AA + Fe induced cell death through inhibition of ACSL4, ALOX15 or ALOX15B provides mechanistic support of this lipid peroxidation pathway being involved in dopaminergic neuronal death and novel potential pharmacological targets for neuroprotective strategies in PD.

Baicalein-functionalized collagen scaffolds direct neuronal differentiation toward enhancing spinal cord injury repair

Spinal cord injury (SCI) repair remains a major challenge in clinics. Though neural stem cells (NSCs) have shown great potentials in SCI treatment, their applications were hampered since they primarily differentiate into astrocytes rather than neurons in the injured area, indicating a high demand for effective strategies to direct neuronal differentiation. Baicalein is a clinical drug with multiple pharmacological activities, while its effects on NSCs have rarely been reported. In the current work, inspired by a similarity of the metabolic reprogramming required in neuronal differentiation and that involved in chemoresistance reversal of cancer cells induced by baicalein, we studied the role of baicalein in NSC differentiation and discovered its promotion effects on neuronal differentiation. Based on this observation, baicalein-functionalized collagen scaffolds (BFCSs) were developed and applied for SCI treatment. The BFCSs released the payload in a sustained way and possessed comparable physical properties to the commonly used collagen. Both in vitro studies with primary NSCs and in vivo studies in SCI rats showed that the BFCSs containing a low amount of baicalein can facilitate not only neurogenesis and axon extension, but also reduce astrocyte production and glial scar formation. More importantly, the BFCS implantation led to improvement in the motor functional recovery of SCI rats. Thus, the BFCSs provided a potential strategy to induce neuronal differentiation towards facilitating SCI repair, as well as for the treatment of other central nervous system injuries.

Ferroptosis: mechanisms and advances in ocular diseases

As an essential trace element in the body, iron is critical for the maintenance of organismal metabolism. Excessive iron facilitates reactive oxygen species generation and inflicts damage on cells and tissues. Ferroptosis, a newly identified iron-dependent type of programmed cell death, has been implicated in a broad set of metabolic disorders. Ferroptosis is mainly characterized by excess iron accumulation, elevated lipid peroxides and reactive oxygen species, and reduced levels of glutathione and glutathione peroxidase 4. The vast emerging literature on ferroptosis has shown that numerous diseases, such as cancers, neurodegeneration, and autoimmune diseases, are associated with ferroptosis. Meanwhile, recent studies have confirmed the relationship between ferroptosis and eye diseases including keratopathy, cataract, glaucoma, retinal ischemia-reperfusion injury, age-related macular degeneration, retinitis pigmentosa, diabetic retinopathy, and retinoblastoma, indicating the critical role of ferroptosis in ocular diseases. In this article, we introduce the primary signaling pathways of ferroptosis and review current advances in research on ocular diseases involving iron overload and ferroptosis. Furthermore, several unanswered questions in the area are raised. Addressing these unanswered questions promises to provide new insights into preventing, controlling, and treating not only ocular diseases but also a variety of other diseases in the near future.

MiR-702-5p ameliorates diabetic encephalopathy in db/db mice by regulating 12/15-LOX

The purpose of this study was to investigate the effect of miR-702-5p on diabetic encephalopathy (DE) and the interaction of miR-702-5p/12/15-LOX in the central nervous system (CNS). In this study, db/db mice were used as DE animal model and HT22 cells were treated with high-glucose (HG). Based on the bioinformatics prediction of possible binding sites between miR-702-5p and 12/15-LOX, we found that the expression of miR-702-5p was significantly down-regulated while 12/15-LOX up-regulated in vivo and in vitro, and the expression changes were inversely correlated. In vivo, diabetic mice with cognitive dysfunction and hippocampal neuronal damage had a concomitant increase in amyloid precursor protein (APP), amyloid beta(Aβ), tau, BAX protein expressions; by contrast, Bcl-2 protein expression was significantly decreased. Overexpression of miR-702-5p significantly reduced the histopathological damage of the hippocampus, improved the learning and memory function of db/db mice, down-regulated 12/15-LOX, APP, Aβ, tau, BAX protein expressions significantly and up-regulated the expression of Bcl-2. In vitro, miR-702-5p mimic reversed the decline in cell viability and the increase in cell apoptosis induced by HG. Simultaneously, reduced 12/15-LOX, APP, Aβ, BAX protein expressions, and increased Bcl-2 protein expression were detected in the miR-702-5p mimic group. Moreover, combined administration of miR-702-5p mimic and 12/15-LOX overexpression lentivirus significantly reversed the protective effect of up-regulation of miR-702-5p. In conclusion, miR-702-5p has a neuroprotective effect on DE, and this effect was achieved by inhibiting 12/15-LOX. However, miR-702-5p had an endogenous regulatory effect on 12/15-LOX rather than a direct targeting relationship.

12/15-Lipoxygenase debilitates mitochondrial health in intermittent hypobaric hypoxia induced neuronal damage: An in vivo study

High altitude cerebral edema does not fall in routine definition of hypoxia and requires alternative therapeutic strategies. 12/15-Lipoxygenase (12/15 LOX), a key proinflammatory lipid peroxidative enzyme which site specifically inserts into cellular and subcellular membranes and plays an instrumental role in hypobaric hypoxia induced neuropathogenesis. Mitochondria, the master regulator organelles for oxygen consumption and ATP generation are sensitive to intracellular oxygen perturbations and are associated with activation of apoptosis based cell death cascades that seal the fate of the cell. The mechanistic involvement of 12/15 LOX in mitochondria mediated cell death in brain microenvironment during hypobaric hypoxia conditions can be an interesting preposition. In the present study, we have investigated underlying involvement of 12/15 LOX in hypobaric hypoxia (HH) induced disturbance in mitochondrial integrity and its relation with neuronal apoptosis. Male Balb/c mice subjected to simulated HH condition for three consecutive days showed robust increase in intra-hippocampal 12(S)HETE (12/15 LOX metabolite), which was significantly reduced following baicalein (12/15 LOX Inhibitor) treatment. The elevated level of 12(S)HETE following hypobaric hypoxia condition correlated with simultaneous increase in expression of 12/15 LOX in neurons and microglia lining the hippocampal CA3 region. Further, 12/15 LOX gets embedded onto the periphery of mitochondria following HH and a strong correlation has been observed with loss of mitochondrial integrity as evident from increased cytochrome-c in the cytosolic compartment and a subsequent upregulated activity of Caspase-3 and Caspase-9 as well as Bax/Bcl-2 expression ratio. The observed effects seen under HH were reversed upon treatment with baicalein suggesting a critical role of 12/15 LOX in HH induced mitochondrial damage Further, the hypobaric hypoxia-mediated increase in hippocampal pAKT and pmTOR protein expression were significantly ameliorated following 12/15 LOX inhibition, suggesting a mitochondrial involvement. We hereby demonstrate the contribution of 12/15 LOX in disorienting mitochondrial integrity with subsequent release of cytochrome-c in cytosol which drives the neuronal cells to intrinsic mode of cell death during hypobaric hypoxia. The protective role of baicalein by inhibition of 12/15 LOX dependent neuronal cell death and preservation of mitochondrial integrity suggests it to be a plausible therapeutic target in CNS related disorders.

Design, synthesis, and structure-activity relationship study of O-prenylated 3-acetylcoumarins as potent inhibitors of soybean 15-lipoxygenase

In this work, the design, synthesis, and structure-activity relationships of a novel array of geranyloxy and farnesyloxy 3-acetylcoumarins were reported as potent soybean 15-lipoxygenase inhibitors. Among the prepared coumarins, 7-farnesyloxy-3-acetylcoumarin (12b) was found to be the most potent inhibitor by IC50  = 0.68 μM while O-geranyl substituents at positions 5 and 6 of 3-acetylcoumarin (10a and 11a) were not inhibitors. Using docking studies, the binding affinity and the preferred pose of synthetic compounds were considered. It was found that lipoxygenase inhibitory activity and prenyl length chain were directly related. The hydrophobic cavity of the enzyme was more effectively occupied by the farnesyl moiety of the potent inhibitor 12b rather than other derivatives. Also, with this pose of farnesyl chain in 7-farnesyloxy-3-acetylcoumarins, the acetyl group could be directed to the hydrophilic pocket in the active site.

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).

Baicalein 5,6-Dimethyl Ether Prevents Memory Deficits in the Scopolamine Zebrafish Model by Regulating Cholinergic and Antioxidant Systems

Baicalein 5,6-dimethyl ether, a bioactive flavonoid isolated for the first time from Alnus rugosa, was explored for its capability to relieve memory deficits and decrease oxidative stress. We examined the neuropharmacological effects of baicalein 5,6-dimethyl ether on scopolamine (Sco)-induced zebrafish (Danio rerio) anxiety, amnesia, and brain oxidative stress and attempted to elucidate the underlying mechanisms. Anxiety-like behavior, exploratory behavior, and memory performance were measured using novel tank-diving test (NTT), Y-maze, and novel object recognition (NOR) tests. For 10 days, baicalein 5,6-dimethyl ether (1, 3, and 5 µg/L) was administered through immersion, whereas Sco (100 μM) was delivered 30 min before behavioral tests. Treatment with baicalein 5,6-dimethyl ether reduced anxiety and memory impairment, and increased exploratory behavior in specific tests, along with significant protection from neuronal oxidative stress in the brain tissue of Sco-treated zebrafish. Antioxidant and anti-acetylcholinesterase (AChE) activities of baicalein 5,6-dimethyl ether in the Sco-induced zebrafish were further confirmed using in vivo assays. In Sco-treated zebrafish, baicalein 5,6-dimethyl ether regulated cholinergic function by inhibiting AChE activity. Baicalein 5,6-dimethyl ether may be a promising candidate compound for treating anxiety and amnesia by restoring cholinergic activity and reducing brain oxidative stress, according to our findings.

Baicalin attenuates LPS-induced alveolar type II epithelial cell A549 injury by attenuation of the FSTL1 signaling pathway via increasing miR-200b-3p expression

In China, baicalin is the main active component of Scutellaria baicalensis, which has been used in the treatment of inflammation-related diseases, such as inflammation-induced acute lung injury. However, its specific mechanism remains unclear. This study examined the protective effect of baicalin on LPS-induced inflammation injury of alveolar epithelial cell line A549 and explored its protective mechanism. Compared with the LPS-induced group, the proliferation inhibition rates of alveolar type II epithelial cell line A549 intervened by different concentrations of baicalin decreased significantly, as did the levels of inflammatory factors IL-6, IL-1β, prostaglandin 2 and TNF-α in the supernatant. The expression levels of inflammatory proteins inducible NO synthase (iNOS), NF-κB65, phosphorylated ERK (p-ERK1/2), and phosphorylated c-Jun N-terminal kinase (p-JNK1) significantly decreased, as did the protein expression of follistatin-like protein 1 (FSTL1). In contrast, expression of miR-200b-3p significantly increased in a dose-dependent manner. These results suggested that baicalin could significantly inhibit the expression of inflammation-related proteins and improve LPS-induced inflammatory injury in alveolar type II epithelial cells. The mechanism may be related to the inhibition of ERK/JNK inflammatory pathway activation by increasing the expression of miR-200b-3p. Thus, FSTL1 is the regulatory target of miR-200b-3p.

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.

Crosstalk between Oxidative Stress and Ferroptosis/Oxytosis in Ischemic Stroke: Possible Targets and Molecular Mechanisms

Oxidative stress is a key cause of ischemic stroke and an initiator of neuronal dysfunction and death, mainly through the overproduction of peroxides and the depletion of antioxidants. Ferroptosis/oxytosis is a unique, oxidative stress-induced cell death pathway characterized by lipid peroxidation and glutathione depletion. Both oxidative stress and ferroptosis/oxytosis have common molecular pathways. This review summarizes the possible targets and the mechanisms underlying the crosstalk between oxidative stress and ferroptosis/oxytosis in ischemic stroke. This knowledge might help to further understand the pathophysiology of ischemic stroke and open new perspectives for the treatment of ischemic stroke.

Regulation of Tissue Inflammation by 12-Lipoxygenases

Lipoxygenases (LOXs) are lipid metabolizing enzymes that catalyze the di-oxygenation of polyunsaturated fatty acids to generate active eicosanoid products. 12-lipoxygenases (12-LOXs) primarily oxygenate the 12th carbon of its substrates. Many studies have demonstrated that 12-LOXs and their eicosanoid metabolite 12-hydroxyeicosatetraenoate (12-HETE), have significant pathological implications in inflammatory diseases. Increased level of 12-LOX activity promotes stress (both oxidative and endoplasmic reticulum)-mediated inflammation, leading to damage in these tissues. 12-LOXs are also associated with enhanced cellular migration of immune cells-a characteristic of several metabolic and autoimmune disorders. Genetic depletion or pharmacological inhibition of the enzyme in animal models of various diseases has shown to be protective against disease development and/or progression in animal models in the setting of diabetes, pulmonary, cardiovascular, and metabolic disease, suggesting a translational potential of targeting the enzyme for the treatment of several disorders. In this article, we review the role of 12-LOXs in the pathogenesis of several diseases in which chronic inflammation plays an underlying role.

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.

Positive and Negative Regulation of Ferroptosis and Its Role in Maintaining Metabolic and Redox Homeostasis

Ferroptosis is a recently recognized regulated form of cell death characterized by accumulation of lipid-based reactive oxygen species (ROS), particularly lipid hydroperoxides and loss of activity of the lipid repair enzyme glutathione peroxidase 4 (GPX4). This iron-dependent form of cell death is morphologically, biochemically, and also genetically discrete from other regulated cell death processes, which include autophagy, apoptosis, necrosis, and necroptosis. Ferroptosis is defined by three hallmarks, defined as the loss of lipid peroxide repair capacity by GPX4, the bioavailability of redox-active iron, and oxidation of polyunsaturated fatty acid- (PUFA-) containing phospholipids. Experimentally, it can be induced by many compounds (e.g., erastin, Ras-selective lethal small-molecule 3, and buthionine sulfoximine) and also can be pharmacologically inhibited by iron chelators (e.g., deferoxamine and deferoxamine mesylate) and lipid peroxidation inhibitors (e.g., ferrostatin and liproxstatin). The sensitivity of a cell towards ferroptotic cell death is tightly associated with the metabolism of amino acid, iron, and polyunsaturated fatty acid metabolism, and also with the biosynthesis of glutathione, phospholipids, NADPH, and coenzyme Q10. Ferroptosis sensitivity is also governed by many regulatory proteins, which also link ferroptosis to the function of key tumour suppressor pathways. In this review, we highlight the discovery of ferroptosis, the mechanism of ferroptosis regulation, and its association with other cellular metabolic processes.

Ferroptosis: mechanisms, biology and role in disease

The research field of ferroptosis has seen exponential growth over the past few years, since the term was coined in 2012. This unique modality of cell death, driven by iron-dependent phospholipid peroxidation, is regulated by multiple cellular metabolic pathways, including redox homeostasis, iron handling, mitochondrial activity and metabolism of amino acids, lipids and sugars, in addition to various signalling pathways relevant to disease. Numerous organ injuries and degenerative pathologies are driven by ferroptosis. Intriguingly, therapy-resistant cancer cells, particularly those in the mesenchymal state and prone to metastasis, are exquisitely vulnerable to ferroptosis. As such, pharmacological modulation of ferroptosis, via both its induction and its inhibition, holds great potential for the treatment of drug-resistant cancers, ischaemic organ injuries and other degenerative diseases linked to extensive lipid peroxidation. In this Review, we provide a critical analysis of the current molecular mechanisms and regulatory networks of ferroptosis, the potential physiological functions of ferroptosis in tumour suppression and immune surveillance, and its pathological roles, together with a potential for therapeutic targeting. Importantly, as in all rapidly evolving research areas, challenges exist due to misconceptions and inappropriate experimental methods. This Review also aims to address these issues and to provide practical guidelines for enhancing reproducibility and reliability in studies of ferroptosis. Finally, we discuss important concepts and pressing questions that should be the focus of future ferroptosis research.

High-fat diet activates liver iPLA2γ generating eicosanoids that mediate metabolic stress

High-fat (HF) diet-induced obesity precipitates multiple metabolic disorders including insulin resistance, glucose intolerance, oxidative stress, and inflammation, resulting in the initiation of cell death programs. Previously, we demonstrated murine germline knockout of calcium-independent phospholipase A₂γ (iPLA₂γ) prevented HF diet-induced weight gain, attenuated insulin resistance, and decreased mitochondrial permeability transition pore (mPTP) opening leading to alterations in bioenergetics. To gain insight into the specific roles of hepatic iPLA₂γ in mitochondrial function and cell death under metabolic stress, we generated a hepatocyte-specific iPLA₂γ-knockout (HEPiPLA₂γKO). Using this model, we compared the effects of an HF diet on wild-type versus HEPiPLA₂γKO mice in eicosanoid production and mitochondrial bioenergetics. HEPiPLA₂γKO mice exhibited higher glucose clearance rates than WT controls. Importantly, HF-diet induced the accumulation of 12-hydroxyeicosatetraenoic acid (12-HETE) in WT liver which was decreased in HEPiPLA₂γKO. Furthermore, HF-feeding markedly increased Ca²⁺ sensitivity and resistance to ADP-mediated inhibition of mPTP opening in WT mice. In contrast, ablation of iPLA₂γ prevented the HF-induced hypersensitivity of mPTP opening to calcium and maintained ADP-mediated resistance to mPTP opening. Respirometry revealed that ADP-stimulated mitochondrial respiration was significantly reduced by exogenous 12-HETE. Finally, HEPiPLA₂γKO hepatocytes were resistant to calcium ionophore-induced lipoxygenase-mediated lactate dehydrogenase release. Collectively, these results demonstrate that an HF diet increases iPLA₂γ-mediated hepatic 12-HETE production leading to mitochondrial dysfunction and hepatic cell death.

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.

Ferroptosis: mechanisms and links with diseases

Ferroptosis is an iron-dependent cell death, which is different from apoptosis, necrosis, autophagy, and other forms of cell death. The process of ferroptotic cell death is defined by the accumulation of lethal lipid species derived from the peroxidation of lipids, which can be prevented by iron chelators (e.g., deferiprone, deferoxamine) and small lipophilic antioxidants (e.g., ferrostatin, liproxstatin). This review summarizes current knowledge about the regulatory mechanism of ferroptosis and its association with several pathways, including iron, lipid, and cysteine metabolism. We have further discussed the contribution of ferroptosis to the pathogenesis of several diseases such as cancer, ischemia/reperfusion, and various neurodegenerative diseases (e.g., Alzheimer's disease and Parkinson's disease), and evaluated the therapeutic applications of ferroptosis inhibitors in clinics.

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.

Using the Oxytosis/Ferroptosis Pathway to Understand and Treat Age-Associated Neurodegenerative Diseases

Oxytosis was first described over 30 years ago in nerve cells as a non-excitotoxic pathway for glutamate-induced cell death. The key steps of oxytosis, including glutathione depletion, lipoxygenase activation, reactive oxygen species accumulation, and calcium influx, were identified using a combination of chemical and genetic tools. A pathway with the same characteristics as oxytosis was identified in transformed fibroblasts in 2012 and named ferroptosis. Importantly, the pathophysiological changes seen in oxytosis and ferroptosis are also observed in multiple neurodegenerative diseases as well as in the aging brain. This led to the hypothesis that this pathway could be used as a screening tool to identify novel drug candidates for the treatment of multiple age-associated neurological disorders, including Alzheimer's disease (AD). Using this approach, we have identified several AD drug candidates, one of which is now in clinical trials, as well as new target pathways for AD.

Exploring the molecular approach of COX and LOX in Alzheimer's and Parkinson's disorder

Neuroinflammation is well established biomarker for the major neurodegenerative like Alzheimer's disease (AD) and Parkinson's disease (PD). Cytokines/chemokines excite phospholipase A2 and cyclooxygenases (COX), facilitating the release of arachidonic acid (AA) and docosahexaenoic acid (DHA) from membrane glycerophospholipids, in which the former is oxidized to produce pro-inflammatory eicosanoids (prostaglandins, leukotrienes and thromboxane's), which intensify the neuroinflammatory events in the brain. Similarly, resolvins and neuroprotectins are the metabolized products of docosahexaenoic acid, which exert an inhibitory effect on the production of eicosanoids. Furthermore, an oxidized product of arachidonic acid, lipoxin, is generated via 5-lipoxygenase (5-LOX) pathway, and contributes to the resolution of inflammation, along with anti-inflammatory actions. Moreover, DHA and its lipid mediators inhibit neuroinflammatory responses by blocking NF-κB, inhibiting eicosanoid production, preventing cytokine secretion and regulating leukocyte trafficking. Various epidemiological studies reported, elevated levels of COX-2 enzyme in patients with AD and PD, indicating its role in progression of the disease. Similarly, enhanced levels of 5-LOX and 12/15-LOX in PD models represent their role brain disorders, where the former is expressed in AD patients and the latter exhibits it involvement in PD. The present review elaborates the role of AA, DHA, eicosanoids and docosanoids, along with COX and LOX pathway which provides an opportunity to the researchers to understand the role of these lipid mediators in neurological disorders (AD and PD). The information gathered from the review will aid in facilitating the development of appropriate therapeutic options targeting COX and LOX pathway.

Baicalein Ameliorates Epilepsy Symptoms in a Pilocarpine-Induced Rat Model by Regulation of IGF1R

Treatment for epilepsy, particularly temporal lobe epilepsy, is challenging. Baicalein has multiple effects, including anti-inflammatory action. However, little is known about its efficacy in treatment of epilepsy. In this study, we established a pilocarpine-induced rat model and used it for assessment of baicalein efficacy in vivo. We predicted the pharmacological mechanism of baicalein by network pharmacology and RNA sequencing analyses. Pilocarpine epileptic rats treated with baicalein exhibited improved average seizure severity, seizure frequency, seizure duration, and survival time. Network pharmacology and RNA sequencing identified the differentially expressed genes between the baicalein treatment and epileptic groups. Insulin-like growth factor 1 receptor (IGF1R) was chosen as the top candidate target because of its overlapping findings in RNA sequencing and network pharmacology data. Western blotting, immunofluorescence, and polymerase chain reaction analyses showed that baicalein inhibited microglial proliferation, IGF1R, and inflammatory cytokine expression. Moreover, baicalein improved epilepsy symptoms. Inhibition of IGF1R function by blocking with AXL1717 enhanced baicalein treatment efficacy both in vivo and in vitro. In conclusion, baicalein exerted antiepileptic effects by regulation of IGF1R in a pilocarpine-induced rat model.

Crosstalk Between Autophagy and Ferroptosis and Its Putative Role in Ischemic Stroke

Autophagy is a conserved process to maintains homeostasis via the degradation of toxic cell contents, which can either promote cell survival or accelerate cellular demise. Ferroptosis is a recently discovered iron-dependent cell death pathway associated with the accumulation of lethal reactive lipid species. In the past few years, an increasing number of studies have suggested the crosstalk between autophagy and ferroptosis. Ischemic stroke is a complex brain disease regulated by several cell death pathways, including autophagy and ferroptosis. However, the potential links between autophagy and ferroptosis in ischemic stroke have not yet been explored. In this review, we briefly overview the mechanisms of ferroptosis and autophagy, as well as their possible connections in ischemic stroke. The elucidation of crosstalk between different cell death pathways may provide insight into new future ischemic stroke therapies.

Structural considerations on lipoxygenase function, inhibition and crosstalk with nitric oxide pathways

Lipoxygenases (LOX) are non-heme iron-containing enzymes that catalyze regio- and stereo-selective dioxygenation of polyunsaturated fatty acids (PUFA). Mammalian LOXs participate in the eicosanoid cascade during the inflammatory response, using preferentially arachidonic acid (AA) as substrate, for the synthesis of leukotrienes (LT) and other oxidized-lipid intermediaries. This review focus on lipoxygenases (LOX) structural and kinetic implications on both catalysis selectivity, as well as the basic and clinical implications of inhibition and interactions with nitric oxide (^•NO) and nitroalkenes pathways. During inflammation ^•NO levels are increasingly favoring the formation of reactive nitrogen species (RNS). ^•NO may act itself as an inhibitor of LOX-mediated lipid oxidation by reacting with lipid peroxyl radicals. Besides, ^•NO may act as an O₂ competitor in the LOX active site, thus displaying a protective role on lipid-peroxidation. Moreover, RNS such as nitrogen dioxide (^•NO₂) may react with lipid-derived species formed during LOX reaction, yielding nitroalkenes (NO₂FA). NO₂FA represents electrophilic compounds that could exert anti-inflammatory actions through the interaction with critical LOX nucleophilic amino acids. We will discuss how nitro-oxidative conditions may limit the availability of common LOX substrates, favoring alternative routes of PUFA metabolization to anti-inflammatory or pro-resolutive pathways.

Design, synthesis, and SAR study of isopropoxy allylbenzene derivatives as 15-lipoxygenase inhibitors

Objective(s):

Allylbenzenes have been recently developed as inhibitors of lipoxygenases. They decrease peroxidation activity via mimicking 1,4-unsaturated bonds of fatty acids by their allyl portion. We designed and synthesized new derivatives of allyl benzenes (6a-f) with isopropoxy and amide substituents at ortho and meta positions towards allyl group, respectively. The inhibitory potency of the synthetized allylbenzenes against soybean 15-lipoxygenase (SLO) and subsequently structure-activity relationships was assessed.

Materials and Methods:

3-allyl-4-isopropoxybenzenamine (5) as starting material was synthesized by coupling of 4-nitropheol with allyl bromide, performing Claisen rearrangement and finally reduction of the nitro moiety. Final products 6a-f were prepared via amidation of 5 with the desired acyl chloride.

Results:

Among the compounds, N-(3-allyl-4-isopropoxyphenyl)adamantan carboxamide (6f) potentially showed best inhibition (IC₅₀ = 1.35 µM) while 6a with cyclopropyl carboxamide moiety was the weakest inhibitor and 6e with phenyl carboxamide moiety showed no effect. Energy minimized 3D structures of the compounds were docked into the active site pocket of SLO. For the aliphatic amides, docking results showed compatibility between inhibitory potency and average Ki of the cluster conformers, in which their allyl moiety oriented towards SLO iron core. For the aliphatic analogs, by enlargement of the amide moiety size the inhibitory potency was increased.

Conclusion:

Docking results showed that orientation of the amide and allyl moieties of the inhibitors in the active site pocket is the major factor in inhibitory potency variation. Based on the mentioned orientation, for cycloaliphatic amides, by enlargement of the amide moiety both inhibition potency and calculated binding energy increases.

Ferroptosis in Neurological Diseases

Ferroptosis is mechanism for non-apoptotic, iron-dependent, oxidative cell death that is characterized by glutathione consumption and lipid peroxides accumulation. Ferroptosis is crucially involved in neurological diseases, including neurodegeneration, stroke and neurotrauma. This review provides detailed discussions of the ferroptosis mechanisms in these neurological diseases. Moreover, it summarizes recent drugs that target ferroptosis for neurological disease treatment. Furthermore, it compares the differences and relationships among the various cell death mechanisms involved in neurological diseases. Elucidating the ferroptosis role in the brain can improve the understanding of neurological disease mechanism and provide potential prevention and treatment interventions for acute and chronic neurological diseases.

Cepharanthine attenuates cerebral ischemia/reperfusion injury by reducing NLRP3 inflammasome-induced inflammation and oxidative stress via inhibiting 12/15-LOX signaling

Cepharanthine (CEP) is a potential candidate for treatment of cerebral ischemia/reperfusion (I/R) injury, due to its anti-inflammatory and anti-oxidative properties. To investigate the effect of CEP on cerebral I/R injury, we established a mouse model of transient middle cerebral artery occlusion (tMCAO) and a microglia cell model of oxygen and glucose deprivation/reoxygenation (OGD/R). Administration of CEP attenuated neurological deficits, reduced infarct volume and edema, and decreased microglia activation in MCAO mice. Immunofluorescence staining showed an up-regulation in NLR Family Pyrin Domain Containing 3 (NLRP3) immunoreactivity in Iba1-labled microglia together with total Iba1 and NLRP3 expression in the brain following tMCAO, while down-regulated by CEP treatment. In both tMCAO-induced mice and OGD/R-treated BV-2 cells, CEP exhibited dose-dependent inhibition on the expression of NLRP3, ASC and cleaved caspase-1. Importantly, CEP attenuated tMCAO or OGD/R-induced overproduction of M1 microglia-regulated pro-inflammation cytokines IL-1β and IL-18, suggesting that CEP might involve in suppressing microglia polarization to M1 phenotype in vivo and in vitro. Moreover, CEP dose-dependently inhibited tMCAO-induced arachidonate 15 lipoxygenase (ALOX15) together with Iba1-labled microglia. The subsequent ALOX15-mediated oxidative stress was decreased by CEP treatment in vivo and in vitro, as evidenced by reduced ROS generation and MDA level, and increased SOD activity. Taken together, we demonstrate that CEP attenuates cerebral I/R injury probably by inhibiting microglia activation and NLRP3 inflammasome-induced inflammation and reducing oxidative stress via suppressing 12/15-LOX signaling.

Baicalein mediates protection against Staphylococcus aureus-induced pneumonia by inhibiting the coagulase activity of vWbp

The emergence and spread of multidrug-resistant Staphylococcus aureus (S. aureus) necessitate the research on therapeutic tactics which are different from classical antibiotics in overcoming resistance andtreatinginfections. In S. aureus, von Willebrand factor-binding protein (vWbp) is one of the key virulence determinants because it mediates not only the activation of thrombin to convert fibrinogen to fibrin, thereby enabling S. aureus to escape from the host immune clearance, but also the adhesion of S. aureus to host cells. Thus, vWbp is regarded as a promising druggable target to treat S. aureus-associated infections. Here we identify that baicalein, a natural compound isolated from the Chinese herb Scutellaria baicalensis, can effectively block the coagulase activity of vWbp without inhibiting the growth of the bacteria. Through thermal shift and fluorescence quenching assays, we demonstrated that baicalein directly binds to vWbp. Molecular dynamics simulations and mutagenesis assays revealed that the Asp-75 and Lys-80 residues are necessary for baicalein binding to vWbp. Importantly, we demonstrated that baicalein treatment attenuates the virulence of S. aureus and protects mice from S. aureus-induced lethal pneumonia. In addition, baicalein can improve the therapeutic effect of penicillin G by 75% in vivo. These findings indicate that baicalein might be developed as a promising therapeutic agent against drug-resistant S. aureus infections.

Achieving Life through Death: Redox Biology of Lipid Peroxidation in Ferroptosis

Redox balance is essential for normal brain, hence dis-coordinated oxidative reactions leading to neuronal death, including programs of regulated death, are commonly viewed as an inevitable pathogenic penalty for acute neuro-injury and neurodegenerative diseases. Ferroptosis is one of these programs triggered by dyshomeostasis of three metabolic pillars: iron, thiols, and polyunsaturated phospholipids. This review focuses on: (1) lipid peroxidation (LPO) as the major instrument of cell demise, (2) iron as its catalytic mechanism, and (3) thiols as regulators of pro-ferroptotic signals, hydroperoxy lipids. Given the central role of LPO, we discuss the engagement of selective and specific enzymatic pathways versus random free radical chemical reactions in the context of the phospholipid substrates, their biosynthesis, intracellular location, and related oxygenating machinery as participants in ferroptotic cascades. These concepts are discussed in the light of emerging neuro-therapeutic approaches controlling intracellular production of pro-ferroptotic phospholipid signals and their non-cell-autonomous spreading, leading to ferroptosis-associated necroinflammation.

Brozopine Inhibits 15-LOX-2 Metabolism Pathway After Transient Focal Cerebral Ischemia in Rats and OGD/R-Induced Hypoxia Injury in PC12 Cells

The goal of this study was to elucidate the mechanisms of protection of Sodium (±)-5-bromo-2-(α-hydroxypentyl) benzoate (trade name: Brozopine, BZP) against cerebral ischemia in vivo and in vitro. To explore the protective effect of BZP on focal cerebral ischemia-reperfusion injury, we evaluated the effects of various doses of BZP on neurobehavioral score, cerebral infarction volume, cerebral swelling in MCAO rats (ischemia for 2 h, reperfusion for 24 h). In addition, the effects of various doses of BZP on OGD/R-induced-PC12 cells injury (hypoglycemic medium containing 30 mmol Na₂S₂O₄ for 2 h, reoxygenation for 24 h) were evaluated. Four in vivo and in vitro groups were evaluated to characterize targets of BZP: Control group, Model group, BZP group (10 mg/kg)/BZP group (30 μmol/L), C8E4 group (10 mg/kg)/C8E4 group (30 μmol/L). An ELISA kit was used to determine the levels of 15-HETE (a 15-LOX-2 metabolite) in vivo and in vitro. Rat nuclear factor κB subunit p65 (NF-κB p65), tumor necrosis factor (TNF-α), interleukin-6 (IL-6), and intercellular adhesion molecule-1 (ICAM-1) were also quantified in vivo and in vitro. The results showed that BZP improved focal cerebral ischemia-reperfusion injury in rats and PC12 cells treated with Na₂S₂O₄ in dose/concentration-dependent manners through inhibition of production of 15-HETE and expression of NF-κB, IL-6, TNF-α, and ICAM-1. In conclusion, BZP exerted protective effects against cerebral ischemia via inhibition of 15-LOX-2 activity.

Baicalein inhibits mitochondrial apoptosis induced by oxidative stress in cardiomyocytes by stabilizing MARCH5 expression

Abnormal mitochondrial fission and mitophagy participate in the pathogenesis of many cardiovascular diseases. Baicalein is a key active component in the roots of traditional Chinese medicinal herb Scutellaria baicalensis Georgi. It has been reported that baicalein can resist cardiotoxicity induced by several stress, but the mechanisms of baicalein operate in the protection of cardiomyocytes need to be researched further. Here we report that baicalein can promote cell survival under oxidative stress by up‐regulating the expression level of MARCH5 in cardiomyocytes. Pre‐treatment cells or mice with baicalein can stabilize the expression of MARCH5, which plays a crucial role in the regulation of mitochondrial network and mitophagy. Overexpressed MARCH5 is able to against H₂O₂ and ischaemia/reperfusion (I/R) stress by suppressing mitochondrial fission and enhancing mitophagy, and then attenuate cells apoptosis. Altogether, our present study investigated that baicalein exerts a protective effect through regulating KLF4‐MARCH5‐Drp1 pathway, our research also provided a novel theoretical basis for the clinical application of baicalein.

Insights into the Authentic Active Ingredients and Action Sites of Oral Exogenous Glutathione in the Treatment of Ischemic Brain Injury Based on Pharmacokinetic-Pharmacodynamic Studies

Glutathione (GSH) has been reported to be closely related to various diseases of the central nervous system, yet its authentic active ingredients and action sites remain unclear. In the present study, oral exogenous GSH significantly alleviated ischemic brain injury, but this result was inconsistent with its low bioavailability and blood-brain barrier (BBB) permeability. To ascertain the exposure of GSH-derived ingredients, including GSH, cysteine (CYS), glutamate (Glu), glycine (GLY), CYS-GLY, and γ-glutamylcysteine (γ-GC) were systematically studied both in vitro and in vivo. The outcomes demonstrated that oral GSH not only increases the GSH and CYS levels in rat striatum and cortex, but it also can decrease the rise of intracerebral Glu concentration caused by ischemia/reperfusion surgery. Then the influence of GSH on the BBB was investigated via measuring IgG leakage, intracerebral endotoxin, and tight-junction proteins. All indicators showed that GSH dosing can repair the destroyed BBB. Oral GSH greatly enhances the exposure of GSH, CYS, CYS-GLY, and γ-GC in rat duodenum, jejunum, ileum, and colon. Accumulating evidence reveals a close link between brain injury and gastrointestinal dysfunction. Our findings further suggest that oral GSH significantly improves intestinal inflammatory damage and barrier disruptions. In conclusion, oral GSH can have a direct therapeutic role in brain injury by stabilizing intracerebral levels of GSH, CYS, and Glu. It can also play an indirect therapeutic role by enhancing the intestinal exposure of GSH, CYS, CYS-GLY, and γ-GC and improving intestinal barrier disruptions. SIGNIFICANCE STATEMENT: The authentic active ingredients and action sites of exogenous glutathione (GSH) in the treatment of ischemic brain injury are unclear. We have shown that oral exogenous GSH not only stabilizes intracerebral levels of GSH, cysteine (CYS), and glutamate (Glu) to act directly on brain injury, but it can also exert an indirect therapeutic role by improving intestinal barrier disruptions. These findings have great significance for revealing the therapeutic effect of GSH on ischemic brain injury and for promoting its further development and clinical application.

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.

Impact of 12/15-Lipoxygenase on Brain Injury After Subarachnoid Hemorrhage

Background and Purpose- Subarachnoid hemorrhage (SAH) is a devastating form of stroke. Oxidative stress contributes to brain injury, but the mechanisms have been poorly studied. Here, we evaluated the role of 12/15-lipoxygenase (12/15-LOX), an enzyme known to cause cell death in ischemic stroke, on brain injury in a mouse model of SAH. Methods- C57Bl6 wild-type mice and Alox15 knockout mice were subjected to SAH using a direct blood injection technique. In SAH wild-type mice, half received the 12/15-LOX inhibitor ML351 and half received vehicle. Immunohistochemistry, brain edema, blood-brain barrier leakage and functional outcomes were assessed 1 and 3 days after SAH induction. Results- SAH led to increased 12/15-LOX in macrophages of the brain parenchyma, adjacent to the subarachnoid blood. Neuronal cell death after SAH was reduced by ML351 and in Alox15 knockout mice. Similarly, SAH induced brain edema, which was 12/15-LOX dependent. Finally, Alox15 gene knockout and inhibitor treatment in wild-type mice with SAH led to an improved behavioral outcome. Conclusions- 12/15-LOX is overexpressed in macrophages after SAH in mice, and inhibition of the 12/15-LOX pathway decreases brain injury and improves neurological outcome. This study suggests 12/15-LOX as a novel therapeutic target to limit brain injury after SAH.