Hemopexin alleviates cognitive dysfunction after focal cerebral ischemia-reperfusion injury in rats

Free heme induces neuroinflammation and cognitive impairment by microglial activation via the TLR4/MyD88/NF-κB signaling pathway

BACKGROUND

Red blood cells (RBCs) transfusion is related to perioperative neurocognitive disorders. The toxic effect of free heme has been identified in many pathologies. However, the underlying mechanisms of RBCs transfusion or free heme in cognitive impairment have not been clearly explored. Therefore, this research was conducted to determine the mechanism of free heme-induced neuroinflammation and cognitive impairment.

METHODS

Rats were received intraperitoneal injection of hemin alone or combined with intracerebroventricular injection of Hemopexin (HPX), and MWM test was conducted to measure cognitive function. The amount of heme-HPX complexes was evaluated by flow cytometry for CD91 + cells. The microglial inflammatory response in rat brain was observed by immunofluorescence staining of Iba-1, and the inflammatory factors of TNF-α, IL-1β and IL-6 in rat brain and BV2 cells were detected by ELISA analysis. Furthermore, neuronal apoptosis in HT22 cells alone and in HT22 + BV2 coculture system was detected by flow cytometry and immunofluorescence staining. Finally, western blot was conducted to detect TLR4/MyD88/NF-κB proteins in rat brain and BV2 cells treated with hemin or combined with pathway inhibitors. Additionally, the M1 surface marker CD86 was observed in BV2 cells to further confirm neuroinflammation.

RESULTS

Intraperitoneal injection of hemin induced cognitive impairment, increase of CD91 + cells, up-regulation of TNF-α and IL-1β, down-regulation of IL-6, activation of microglia, and activation of the TLR4/MyD88/NF-κB signaling pathway in rat brain. Significantly, intracerebroventricular injection of HPX reduced the above effects. Hemin induced boost of TNF-α, IL-1β and IL-6 in BV2 cells, as well as apoptosis in HT22 cells. Notably, when HT22 cells were cocultured with BV2 cells, apoptosis was significantly increased. Hemin also induced activation of the TLR4/MyD88/NF-κB signaling pathway and increased the M1 surface marker CD86 in BV2 cells, and inhibiting this pathway reduced the inflammatory responses.

CONCLUSIONS

Free heme induces cognitive impairment, and the underlying mechanism may involve neuronal apoptosis and microglial inflammation via the TLR4/MyD88/NF-κB signaling pathway. HPX may have potential therapeutic effects. Video Abstract.

Molecular biomarkers of diffuse axonal injury: recent advances and future perspectives

INTRODUCTION

Diffuse axonal injury (DAI), with high mortality and morbidity both in children and adults, is one of the most severe pathological consequences of traumatic brain injury. Currently, clinical diagnosis, disease assessment, disability identification, and postmortem diagnosis of DAI is mainly limited by the absent of specific molecular biomarkers.

AREAS COVERED

In this review, we first introduce the pathophysiology of DAI, summarized the reported biomarkers in previous animal and human studies, and then the molecular biomarkers such as β-Amyloid precursor protein, neurofilaments, S-100β, myelin basic protein, tau protein, neuron-specific enolase, Peripherin and Hemopexin for DAI diagnosis is summarized. Finally, we put forward valuable views on the future research direction of diagnostic biomarkers of DAI.

EXPERT OPINION

In recent years, the advanced technology has ultimately changed the research of DAI, and the numbers of potential molecular biomarkers was introduced in related studies. We summarized the latest updated information in such studies to provide references for future research and explore the potential pathophysiological mechanism on diffuse axonal injury.

Identification of serum exosomal metabolomic and proteomic profiles for remote ischemic preconditioning

BACKGROUND

Remote ischemic preconditioning (RIPC) refers to a brief episode of exposure to potential adverse stimulation and prevents injury during subsequent exposure. RIPC has been shown to increase tolerance to ischemic injury and improve cerebral perfusion status. Exosomes have a variety of activities, such as remodeling the extracellular matrix and transmitting signals to other cells. This study aimed to investigate the potential molecular mechanism of RIPC-mediated neuroprotection.

METHODS

Sixty adult male military personnel participants were divided into the control group (n = 30) and the RIPC group (n = 30). We analyzed the differential metabolites and proteins in the serum exosomes of RIPC participants and control subjects.

RESULTS

Eighty-seven differentially expressed serum exosomal metabolites were found between the RIPC and control groups, which were enriched in pathways related to tyrosine metabolism, sphingolipid metabolism, serotonergic synapses, and multiple neurodegeneration diseases. In addition, there were 75 differentially expressed exosomal proteins between RIPC participants and controls, which involved the regulation of insulin-like growth factor (IGF) transport, neutrophil degranulation, vesicle-mediated transport, etc. Furthermore, we found differentially expressed theobromine, cyclo gly-pro, hemopexin (HPX), and apolipoprotein A1 (ApoA1), which are associated with neuroprotective benefits in ischemia/reperfusion injury. In addition, five potential metabolite biomarkers, including ethyl salicylate, ethionamide, piperic acid, 2, 6-di-tert-butyl-4-hydroxymethylphenol and zerumbone, that separated RIPC from control individuals were identified.

CONCLUSION

Our data suggest that serum exosomal metabolites are promising biomarkers for RIPC, and our results provide a rich dataset and framework for future analyses of cerebral ischemia‒reperfusion injury under ischemia/reperfusion conditions.

Shielding Effect of Ryanodine Receptor Modulator in Rat Model of Autism

Introduction

A neurodevelopmental disorder, autism is typically identified with three primary behavioral consequences, such as social impairment, communication problems, and limited or stereotypical behavior. Because of its co-morbidity and lack of therapeutic options, autism is a global economic burden. A short chain of fatty acid, propionic acid is formed biologically by the gut microbiome. Propionic acid levels that are too high can cause leaky intestines, which can lead to autism-like symptoms.

Methods

To induce autism, male Albino Wistar rats were given propionic acid (250 mg/kg/po on the 21st, 22nd, and 23rd postnatal days). Rats also received a ryanodine receptor antagonist (Ruthenium red: 3 mg/kg/po; postnatal 21st to 50th day) to see what influence it had on propionic acid-induced autism. Anxiety, social behavior, and repeated behaviors were all assessed, as well as oxidative stress, inflammatory indicators, neuro signaling proteins, and blood-brain barrier permeability.

Results

Ruthenium red was found to counter the propionic acid-induced increases in anxiety, repetitive behavior prefrontal cortex levels of IL-6, TNF-α, TBARS, Evans blue leakage, and water content along with decreases in social behavior, IL-10, and GSH followed by hippocampus CREB and BDNF levels.

Conclusion

Ryanodine receptor antagonists presented a neuroprotective effect in propionic acid-induced conditions like autism by modulatory effects on social and repetitive behavior, oxidative stress, neuroinflammation, and neuroprotein changes. Ryanodine receptors can be further explored in depth to manage autism as a condition.

Highlights

Ruthenium red can reduce the propionic acid-induced anxiety of rats with autism.Ruthenium red can improve the propionic acid-induced changes in repetitive behavior of rats with autism.Ruthenium red can reduce the propionic acid-induced social behavior dysfunction in rats with autism.

Plain Language Summary

Autism is a complex heterogeneous neurodevelopmental disorder mainly diagnosed with social behavior dysfunction, communication problems, and repetitive behavior. Due to high comorbidity and multiple unknown factors involvement, its exact etiology remains unclear, and so no successful treatment is available. Among the environmentally produced models of autism in rats, the most common is created by propionic acid (PPA). With short-chain type fatty acid, PPA is one of the mediators for the cycle of cell metabolism. This study attempted to study the effect of a ryano-dine receptor antagonist (Ruthenium red) on PPA-induced Anxiety, social behavior dysfunction, and repeated behaviors in rats with autism. The results showed the modulatory effects of Ruthenium red PPA-induced conditions including social and repetitive behavior, oxidative stress, neuroinflammation, and neuroprotein changes in rats with autism.

Protective Effect of Nimodipine Against Valproic-acid Induced Biochemical and Behavioral Phenotypes of Autism

Objective

Present study was designed to investigate behavioral and biochemical role of nimodipine in prenatal valproic acid (Pre-VPA) induced autism in rats.

Methods

Valproic acid was utilized to induce autistic phenotypes in Wistar rats. The rats were assessed for social behavior. Hippocampus and prefrontal cortex (PFC) were utilized for various biochemical assessments, whereas cerebellum was used to assess blood brain barrier (BBB) permeability.

Results

Pre-VPA rats showed reduction social interaction. Pre-VPA administration were decreased PFC levels of interleukin- 10 (IL-10), and glutathione along with hippocampus cAMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF). Also, the animals have shown increase in PFC levels of IL-6, tumor necrosis factor-α, thiobarbituric acid reactive substance, Evans blue leakage and water content. Nimodipine countered Pre-VPA administered reduction in social interaction, CREB, BDNF, inflammation, oxidative stress, BBB permeability.

Conclusion

Pre-VPA has induced autistic phenotype, which were attenuated by nimodipine in rats. Nimodipine and other calcium channel blockers should further investigate to check the management of autism.

Dexmedetomidine suppresses the isoflurane-induced neurological damage by upregulating Heme Oxygenase-1 via activation of the mitogen-activated protein kinase kinase 1/extracellular regulated protein kinases 1/nuclear factor erythroid 2-related factor 2 axis in aged rats

Dexmedetomidine (DEX) displays a neuroprotective role in aged rats with isoflurane (ISO)-induced cognitive impairment through antioxidant, and anti-inflammatory, and anti-apoptotic effects. Therefore, the present study was performed to define the molecular mechanism of DEX on ISO-induced neurological impairment in aged rats in relation to the MEK1/ERK1/Nrf2/HO-1 axis. The study enrolled elderly patients undergoing ISO anesthesia. Patient cognitive function following treatment with DEX was evaluated using mini-mental state examination (MMSE). The results revealed that DEX supplementation of anesthesia contributed to higher MMSE scores in patients one week post treatment. Rat model of neurological impairment was also induced in 18-month-age Wistar rats by ISO, followed by DEX treatment. Based on the results of Morris water maze experiment, ELISA, and TUNEL and hematoxylin-eosin staining, in vivo experiments confirmed that DEX could reduce the oxidative stress and neurological damage induced by ISO in rats. DEX activated the nuclear factor erythroid 2-related factor (Nrf2)/Heme Oxygenase 1 (HO-1) pathway. DEX upregulated the expression of Nrf2 and HO-1 by activating the MEK1/ERK1 pathway, whereby attenuating the ISO-caused oxidative stress and neurological damage in rats. Collectively, DEX suppresses the ISO-induced neurological impairment in the aged rats by promoting HO-1 through activation of the MEK1/ERK1/Nrf2 axis.

Anti-apoptosis effects of codonolactone on cerebral ischemia-reperfusion injury

Codonolactone is the main biologically active ingredient in Atractylodes lancea. Studies have shown various functions of codonolactone, while its protective effect against neurotoxicity caused by ischemic stroke is unclear. This study investigated the roles of codonolactone in inflammation, oxidative stress and apoptosis after cerebral ischemia-reperfusion (I/R) injury. Rats with codonolactone treatment, I/R treatment and the sham operation group were used in this study. After reperfusion for 24 hours, nerve damage was detected by nerve staining, and the neurological deficits of the rats were analyzed. The contents of superoxide dismutase (SOD), malondialdehyde (MDA), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in rat brain tissues were also determined. Western blot analysis was performed to determine the expression levels of Akt/Nrf2 pathway-associated proteins. Compared with the I/R group, the cerebral blood flow, infarct volume, brain water content, coronary blood flow and neurological deficits in the codonolactone treatment group, especially with the 80 mg/kg dosage, were significantly reduced. Codonolactone could significantly reduce the expression levels of caspase-3 and Bax, and significantly increase the expression levels of Bcl-2 after I/R. In addition, codonolactone could significantly reduce MDA content and the expression levels of TNF-α and IL-1β in ischemic brain tissues. It also significantly increased SOD activity, the expression levels of heme oxygenase-1 (HO-1) and the phosphorylation of Akt and Nrf2. Codonolactone ameliorated the cerebral I/R injury by improving anti-oxidant, anti-inflammatory activities and reducing apoptosis. Besides, the Akt/Nrf2 pathway was involved in the pharmacological action of the codonolactone.

Skeletal muscle atrophy-induced hemopexin accelerates onset of cognitive impairment in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is an unmet medical need worldwide, and physical inactivity is a risk factor for AD. Performing physical exercise is difficult at old age, and thus, decline in physical movement may be a cause of age-associated lowering of the brain function. This study aimed to elucidate the molecular mechanism and onset of the skeletal muscle atrophy-induced acceleration of AD.

METHODS

Pre-symptomatic young 5XFAD or non-transgenic wildtype mice were used. The bilateral hindlimbs were immobilized by placing them in casts for 14 days. Cognitive function was evaluated using the object recognition and spatial memory tests. Further, the hindlimb muscles were isolated for organ culture. Conditioned media (CM) of each muscle was separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Protein expressions in the CM were analysed by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry analysis. The expression levels of candidate proteins were quantified using ELISA. After continuous intracerebroventricular (i.c.v.) infusion of recombinant hemopexin, cognitive function was evaluated. Gene microarray analysis of the hippocampus was performed to investigate the molecules involved in the accelerated memory deficit. Real-time reverse transcription polymerase chain reaction and histological analysis confirmed the expression.

RESULTS

Casting for 2 weeks reduced skeletal muscle weight. Object recognition memory in the cast-attached 5XFAD mice (n = 7, training vs. test, P = 0.3390) was impaired than that in age-matched wildtype (n = 7, training vs. test, P = 0.0523) and non-cast 5XFAD mice (n = 7, training vs. test, P = 0.0473). On 2D-PAGE, 88 spots were differentially expressed in muscle CM. The most increased spot in the cast-attached 5XFAD CM was hemopexin. Hemopexin levels in the skeletal muscle (n = 3, P = 0.0064), plasma (n = 3, P = 0.0386), and hippocampus (n = 3, P = 0.0164) were increased in cast-attached 5XFAD mice than those in non-cast 5XFAD mice. Continuous i.c.v. infusion of hemopexin for 2 weeks induced memory deficits in young 5XFAD mice (n = 4, training vs. test, P = 0.6764). Lipocalin-2 (Lcn2) messenger RNA (mRNA), neuroinflammation-associated factor, was increased in the hippocampus in hemopexin-infused 5XFAD mice than in control mice. LCN2 protein in the hippocampus was localized in the neurons, but not glial cells. Lcn2 mRNA levels in the hippocampus were also increased by cast-immobilization of the hindlimbs (n = 6, P = 0.0043).

CONCLUSIONS

These findings provide new evidence indicating that skeletal muscle atrophy has an unbeneficial impact on the occurrence of memory impairment in young 5XFAD mice, which is mediated by the muscle secreted hemopexin.

Apelin receptor homodimer inhibits apoptosis in vascular dementia

Apelin receptor (APJ), a member of family A of the G protein-coupled receptors (GPCRs), is a potential pharmaceutical target for diseases of the nervous system. Our previous work revealed that human APJ can form a homodimer that has different functional characteristics than the monomer. To investigate the effects of APJ homodimers on neuroprotection in vascular dementia (VD), we established VD model in rats and treated the animals by injecting apelin-13 into the lateral ventricle. In addition, we established an oxygen-glucose deprivation/reoxygenation (OGD/R) model in SH-SY5Y cells treated with apelin-13. After apelin-13 stimulation in the VD rat, the level of APJ and APJ homodimer were elevated. Furthermore, APJ homodimer decreased the level of cleaved caspase-3 and cleaved caspase-9 via the Gα_i3 and Gα_q signaling pathway, thereby increasing the number of neurons and inhibiting apoptosis. Consequently, APJ homodimers may serve as a unique mechanism for neuroprotection against VD and provide new pharmaceutical targets for VD.

Critical Role of Hemopexin Mediated Cytoprotection in the Pathophysiology of Sickle Cell Disease

Circulating hemopexin is the primary protein responsible for the clearance of heme; therefore, it is a systemic combatant against deleterious inflammation and oxidative stress induced by the presence of free heme. This role of hemopexin is critical in hemolytic pathophysiology. In this review, we outline the current research regarding how the dynamic activity of hemopexin is implicated in sickle cell disease, which is characterized by a pathological aggregation of red blood cells and excessive hemolysis. This pathophysiology leads to symptoms such as acute kidney injury, vaso-occlusion, ischemic stroke, pain crises, and pulmonary hypertension exacerbated by the presence of free heme and hemoglobin. This review includes in vivo studies in mouse, rat, and guinea pig models of sickle cell disease, as well as studies in human samples. In summary, the current research indicates that hemopexin is likely protective against these symptoms and that rectifying depleted hemopexin in patients with sickle cell disease could improve or prevent the symptoms. The data compiled in this review suggest that further preclinical and clinical research should be conducted to uncover pathways of hemopexin in pathological states to evaluate its potential clinical function as both a biomarker and therapy for sickle cell disease and related hemoglobinopathies.

Increase in Blood-Brain Barrier (BBB) Permeability Is Regulated by MMP3 via the ERK Signaling Pathway

BACKGROUND

The blood-brain barrier (BBB) regulates the exchange of molecules between the brain and peripheral blood and is composed primarily of microvascular endothelial cells (BMVECs), which form the lining of cerebral blood vessels and are linked via tight junctions (TJs). The BBB is regulated by components of the extracellular matrix (ECM), and matrix metalloproteinase 3 (MMP3) remodels the ECM's basal lamina, which forms part of the BBB. Oxidative stress is implicated in activation of MMPs and impaired BBB. Thus, we investigated whether MMP3 modulates BBB permeability.

METHODS

Experiments included in vivo assessments of isoflurane anesthesia and dye extravasation from brain in wild-type (WT) and MMP3-deficient (MMP3-KO) mice, as well as in vitro assessments of the integrity of monolayers of WT and MMP3-KO BMVECs and the expression of junction proteins.

RESULTS

Compared to WT mice, measurements of isoflurane usage and anesthesia induction time were higher in MMP3-KO mice and lower in WT that had been treated with MMP3 (WT+MMP3), while anesthesia emergence times were shorter in MMP3-KO mice and longer in WT+MMP3 mice than in WT. Extravasation of systemically administered dyes was also lower in MMP3-KO mouse brains and higher in WT+MMP3 mouse brains, than in the brains of WT mice. The results from both TEER and Transwell assays indicated that MMP3 deficiency (or inhibition) increased, while MMP3 upregulation reduced barrier integrity in either BMVEC or the coculture. MMP3 deficiency also increased the abundance of TJs and VE-cadherin proteins in BMVECs, and the protein abundance declined when MMP3 activity was upregulated in BMVECs, but not when the cells were treated with an inhibitor of extracellular signal related-kinase (ERK).

CONCLUSION

MMP3 increases BBB permeability following the administration of isoflurane by upregulating the ERK signaling pathway, which subsequently reduces TJ and VE-cadherin proteins in BMVECs.

Methylphenidate exerts neuroprotective effects through the AMPK signaling pathway

PURPOSE

Cerebral ischemia is the main cause of permanent adult disabilities worldwide. This study investigated the reparative effects and potential mechanisms of methylphenidate (MPH), a medication for the treatment of attention-deficit/hyperactivity disorder.

METHODS

In vitro oxygen-glucose deprivation/reperfusion (OGD/R) and in vivo cerebral ischemia-reperfusion models were established. Sprague-Dawley (SD) rats were randomly divided into four groups (n = 20): Sham, Model, and MPH (0.5 and 1 mg/kg). Rats in MPH groups were treated with 0.5 or 1 mg/kg MPH via intraperitoneal injection for 7 days. Rats in the Sham and Model groups were treated with PBS during the same period. Cell viability was measured using MTT assay. Apoptosis was detected by Annexin V/PI staining. Protein expression was detected by Western blot. The volume of cerebral infarction was detected by triphenyltetrazolium chloride (TTC) staining. The DNA damage in ischemic brain tissues was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay.

RESULTS

MPH treatment significantly reduced OGD/R-induced cell damage, shown by the increased cell viability and decreased apoptotic rate. p-AMPK and p-ACC protein expression increased in the OGD/R model after MPH treatment. The addition of AMPK inhibitor largely abolished the neuroprotective effects of MPH, evidenced by the reduced cell viability, increased apoptotic rate, and decreased protein expression of p-AMPK as well as p-ACC. Moreover, MPH treatment significantly alleviated the cerebral ischemia-reperfusion injury and decreased apoptosis in brain tissues, which may be associated with the AMPK/ACC pathway.

CONCLUSIONS

MPH exerted protective activities against oxidative stress in the OGD/R model and ameliorated brain damage of rats in the middle cerebral artery occlusion model, at least in part, through activating the AMPK pathway. These data demonstrated neuroprotective properties of MPH and highlighted it as a potential therapeutic agent against cerebral ischemia-reperfusion injury.

Ephedrine attenuates cerebral ischemia/reperfusion injury in rats through NF-κB signaling pathway

The inflammation and immune responses are critical in ischemic stroke and contribute to aggravated brain damage. Ephedrine was reported to play an important role in the control of inflammatory responses. This study was to investigate the repairing effects and potential mechanisms of ephedrine on cerebral ischemic injury in a rat model of focal cerebral ischemia. The rat model of cerebral ischemia/reperfusion injury was established using the middle cerebral artery occlusion (MCAO) method and then rats were treated with ephedrine (5 and 10 mg/kg) for 7 days. The neurobehavioral progression was assessed using the neurological scoring method. The pathology of brain tissue was evaluated by hematoxylin and eosin (H&E) staining. The infarct volume was examined by triphenyltetrazolium chloride (TTC) staining. The apoptosis in ischemic brain tissues was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Inflammatory factors were detected by enzyme-linked immunosorbent assay (ELISA). Gene quantification and protein expression were detected by real-time PCR and western blot, respectively. Ephedrine treatment significantly alleviated the cerebral ischemia/reperfusion injury, evidenced by decreased neurological deficit score, infarct volume and water content. Ephedrine also decreased autophagy and apoptosis in brain tissues. Moreover, ephedrine treatment significantly reduced inflammatory responses, associating with decreasing the protein expression of p-NF-κB. These results demonstrated neuroprotective properties of ephedrine and highlighted it as a new potential anti-inflammatory agent against injury of cerebral ischemia/reperfusion.

Motor Cortex and Hippocampus Display Decreased Heme Oxygenase Activity 2 Weeks After Ventricular Fibrillation Cardiac Arrest in Rats

Heme oxygenase (HO) and biliverdin reductase (BVR) activities are important for neuronal function and redox homeostasis. Resuscitation from cardiac arrest (CA) frequently results in neuronal injury and delayed neurodegeneration that typically affect vulnerable brain regions, primarily hippocampus (Hc) and motor cortex (mC), but occasionally also striatum and cerebellum. We questioned whether these delayed effects are associated with changes of the HO/BVR system. We therefore analyzed the activities of HO and BVR in the brain regions Hc, mC, striatum and cerebellum of rats subjected to ventricular fibrillation CA (6 min or 8 min) after 2 weeks following resuscitation, or sham operation. From all investigated regions, only Hc and mC showed significantly decreased HO activities, while BVR activity was not affected. In order to find an explanation for the changed HO activity, we analyzed protein abundance and mRNA expression levels of HO-1, the inducible, and HO-2, the constitutively expressed isoform, in the affected regions. In both regions we found a tendency for a decreased immunoreactivity of HO-2 using immunoblots and immunohistochemistry. Additionally, we investigated the histological appearance and the expression of markers indicative for activation of microglia [tumor necrosis factor receptor type I (TNFR1) mRNA and immunoreactivity for ionized calcium-binding adapter molecule 1 (Iba1])], and activation of astrocytes [immunoreactivity for glial fibrillary acidic protein (GFAP)] in Hc and mC. Morphological changes were detected only in Hc displaying loss of neurons in the cornu ammonis 1 (CA1) region, which was most pronounced in the 8 min CA group. In this region also markers indicating inflammation and activation of pro-death pathways (expression of HO-1 and TNFR1 mRNA, as well as Iba1 and GFAP immunoreactivity) were upregulated. Since HO products are relevant for maintaining neuronal function, our data suggest that neurodegenerative processes following CA may be associated with a decreased capacity to convert heme into HO products in particularly vulnerable brain regions.

Hemopexin as an Inhibitor of Hemolysis-Induced Complement Activation

Hemopexin is the main plasmatic scavenger of cell-free heme, released in the context of intravascular hemolysis or major cell injury. Heme is indispensable for the oxygen transport by hemoglobin but when released outside of the erythrocytes it becomes a danger-associated molecular pattern, contributing to tissue injury. One of the mechanisms of pro-inflammatory action of heme is to activate the innate immune complement cascade. Therefore, we hypothesized that injection of hemopexin will prevent hemolysis-induced complement activation. Human plasma-derived hemopexin is compatible with the heme clearance machinery of the mice. 100 or 500 mg/kg of hemopexin was injected in C57Bl/6 mice before treatment with phenylhydrazine (inducer of erythrocytes lysis) or with PBS as a control. Blood was taken at different timepoints to determine the pharmacokinetic of injected hemopexin in presence and absence of hemolysis. Complement activation was determined in plasma, by the C3 cleavage (western blot) and in the kidneys (immunofluorescence). Kidney injury was evaluated by urea and creatinine in plasma and renal NGAL and HO-1 gene expression were measured. The pharmacokinetic properties of hemopexin (mass spectrometry) in the hemolytic mice were affected by the target-mediated drug disposition phenomenon due to the high affinity of binding of hemopexin to heme. Hemolysis induced complement overactivation and signs of mild renal dysfunction at 6 h, which were prevented by hemopexin, except for the NGAL upregulation. The heme-degrading capacity of the kidney, measured by the HO-1 expression, was not affected by the treatment. These results encourage further studies of hemopexin as a therapeutic agent in models of diseases with heme overload.

(Z)-7,4′-Dimethoxy-6-hydroxy-aurone- 4-O-β-glucopyranoside alleviates cerebral ischemia-reperfusion injury in rats associating with the regulation of JAK1/STAT1 signaling pathway

Inflammatory responses have been demonstrated to contribute to the neuronal death following cerebral ischemia. This study was to investigate the repairing effects and potential mechanisms of (Z)-7,4′-dimethoxy-6-hydroxy-aurone-4-O-β-glucopyranoside (DHAG), a compound with neuroprotective effects, on cerebral ischemia-reperfusion (I/R) injury in rats. Cerebral I/R model was established with middle cerebral artery occlusion method in Sprague Dawley rats and then rats were treated with DHAG (1 and 2 mg/kg) for 7 days. The volume of cerebral infarction was detected by triphenyltetrazolium chloride staining. The apoptosis in ischemic brain tissues was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Oxidative stress markers and inflammatory factors were detected by enzyme-linked immunosorbent assay. Protein expression was detected by Western blot. DHAG treatment significantly alleviated the cerebral I/R injury and decreased apoptosis in brain tissues. Moreover, DHAG treatment significantly inhibited oxidative stress and reduced inflammatory responses, associating with decreasing the protein expression of phosphorylated Janus kinase 1/phosphorylated signal transducer and transcriptional activator 1. These results demonstrated neuroprotective properties of DHAG and highlighted it as a potential therapeutic agent against injury of cerebral IR.

What Is Next in This "Age" of Heme-Driven Pathology and Protection by Hemopexin? An Update and Links with Iron

This review provides a synopsis of the published literature over the past two years on the heme-binding protein hemopexin (HPX), with some background information on the biochemistry of the HPX system. One focus is on the mechanisms of heme-driven pathology in the context of heme and iron homeostasis in human health and disease. The heme-binding protein hemopexin is a multi-functional protectant against hemoglobin (Hb)-derived heme toxicity as well as mitigating heme-mediated effects on immune cells, endothelial cells, and stem cells that collectively contribute to driving inflammation, perturbing vascular hemostasis and blood–brain barrier function. Heme toxicity, which may lead to iron toxicity, is recognized increasingly in a wide range of conditions involving hemolysis and immune system activation and, in this review, we highlight some newly identified actions of heme and hemopexin especially in situations where normal processes fail to maintain heme and iron homeostasis. Finally, we present preliminary data showing that the cytokine IL-6 cross talks with activation of the c-Jun N-terminal kinase pathway in response to heme-hemopexin in models of hepatocytes. This indicates another level of complexity in the cell responses to elevated heme via the HPX system when the immune system is activated and/or in the presence of inflammation.