Patterns of immunocytochemical staining for ferritin and transferrin in the human spinal cord following traumatic injury

Fibroblast growth factor 21 inhibits ferroptosis following spinal cord injury by regulating heme oxygenase-1

JOURNAL/nrgr/04.03/01300535-202407000-00037/figure1/v/2023-11-20T171125Z/r/image-tiff

Interfering with the ferroptosis pathway is a new strategy for the treatment of spinal cord injury. Fibroblast growth factor 21 can inhibit ferroptosis and promote neurofunctional recovery, while heme oxygenase-1 is a regulator of iron and reactive oxygen species homeostasis. The relationship between heme oxygenase-1 and ferroptosis remains controversial. In this study, we used a spinal cord injury rat model to show that the levels of fibroblast growth factor 21 in spinal cord tissue decreased after spinal cord injury. In addition, there was a significant aggravation of ferroptosis and a rapid increase in heme oxygenase-1 expression after spinal cord injury. Further, heme oxygenase-1 aggravated ferroptosis after spinal cord injury, while fibroblast growth factor 21 inhibited ferroptosis by downregulating heme oxygenase-1. Thus, the activation of fibroblast growth factor 21 may provide a potential treatment for spinal cord injury. These findings could provide a new potential mechanistic explanation for fibroblast growth factor 21 in the treatment of spinal cord injury.

Application of Deferoxamine in Tissue Regeneration Attributed to Promoted Angiogenesis

Deferoxamine, an iron chelator used to treat diseases caused by excess iron, has had a Food and Drug Administration-approved status for many years. A large number of studies have confirmed that deferoxamine can reduce inflammatory response and promote angiogenesis. Blood vessels play a crucial role in sustaining vital life by facilitating the delivery of immune cells, oxygen, and nutrients, as well as eliminating waste products generated during cellular metabolism. Dysfunction in blood vessels may contribute significantly to the development of life-threatening diseases. Anti-angiogenesis therapy and pro-angiogenesis/angiogenesis strategies have been frequently recommended for various diseases. Herein, we describe the mechanism by which deferoxamine promotes angiogenesis and summarize its application in chronic wounds, bone repair, and diseases of the respiratory system. Furthermore, we discuss the drug delivery system of deferoxamine for treating various diseases, providing constructive ideas and inspiration for the development of new treatment strategies.

Lipoxin A4 protects primary spinal cord neurons from Erastin-induced ferroptosis by activating the Akt/Nrf2/HO-1 signaling pathway

Ferroptosis is an iron‐dependent programmed cell death, which participates in the pathogenesis of spinal cord injury (SCI). Our previous study has revealed that Lipoxin A4 (LXA4) exerts a protective role in SCI. Here, we investigated whether LXA4 can protect SCI through inhibiting neuronal ferroptosis. We treated primary spinal cord neurons with Erastin (ferroptosis activator) to induce ferroptosis. Erastin treatment reduced cell viability and enhanced cell death of primary spinal cord neurons, which was rescued by ferrostatin‐1 (ferroptosis inhibitor). Moreover, Erastin repressed glutathione peroxidase 4 (GPX4) expression and the levels of glutathione and cysteine in primary spinal cord neurons. Erastin also enhanced the expression of ferroptosis biomarkers (PTGS2 and ACSL4) and the levels of reactive oxygen species (ROS) in primary spinal cord neurons. The influence conferred by Erastin was effectively abolished by LXA4 treatment. Furthermore, LXA4 enhanced the protein expression of p‐AKT, nuclear factor (erythroid‐derived 2)‐like 2 (Nrf2) and haem‐oxygenase‐1 (HO‐1) in primary spinal cord neurons. LXA4‐mediated inhibition of ferroptosis of primary spinal cord neurons was prohibited by LY294002 (AKT inhibitor), brusatol (Nrf2 inhibitor) or zinc protoporphyrin (HO‐1 inhibitor). In conclusion, this work demonstrated that LXA4 exerted a neuroprotective effect in Erastin‐induced ferroptosis of primary spinal cord neurons by activating the Akt/Nrf2/HO‐1 signaling pathway. Thus, this work provides novel insights into the mechanisms of action of LXA4 in ferroptosis of primary spinal cord neurons and indicates that LXA4 may be a potential therapeutic agent for SCI.

Isobaric Tagging for Relative and Absolute Protein Quantification (iTRAQ)-Based Quantitative Proteomics Analysis of Differentially Expressed Proteins 1 Week After Spinal Cord Injury in a Rat Model

Background

Spinal cord injury (SCI) is a devastating trauma of the central nervous system (CNS), with high levels of morbidity, disability, and mortality. One week after SCI may be a critical time for treatment. Changes in protein expression have crucial functions in nervous system diseases, although the effects of changes occurring 1 week after SCI on patient outcomes are unclear.

Material/Methods

Protein expression was examined in a rat contusive SCI model 1 week after SCI. Differentially expressed proteins (DEPs) were identified by isobaric tagging for relative and absolute protein quantification (iTRAQ)-coupled liquid chromatography tandem-mass spectrometry (LC-MS/MS) proteomics analysis. Gene Ontology (GO) analysis was performed to identify the biological processes, molecular functions, and cellular component terms of the identified DEPs, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) was used to identify key enriched pathways. Protein–protein interaction (PPI) networks were analyzed to identify the top 10 high-degree core proteins.

Results

Of the 295 DEPs identified, 204 (69.15%) were upregulated and 91 (30.85%) were downregulated 1 week after injury. The main cellular components, molecular functions, biological processes, and pathways identified may be crucial mechanisms involved in SCI. The top 10 high-degree core proteins were complement component C3 (C3), alpha-2-HS-glycoprotein (Ahsg), T-kininogen 1 (Kng1), Serpinc1 protein (Serpinc1), apolipoprotein A-I (Apoa1), serum albumin (Alb), disulfide-isomerase protein (P4hb), transport protein Sec61 subunit alpha isoform 1 (Sec61a1), serotransferrin (Tf), and 60S ribosomal protein L15 (Rpl15).

Conclusions

The proteins identified in this study may provide potential targets for diagnosis and treatment 1 week after SCI.

Mechanisms underlying the promotion of functional recovery by deferoxamine after spinal cord injury in rats

Deferoxamine, a clinically safe drug used for treating iron overload, also repairs spinal cord injury although the mechanism for this action remains unknown. Here, we determined whether deferoxamine was therapeutic in a rat model of spinal cord injury and explored potential mechanisms for this effect. Spinal cord injury was induced by impacting the spinal cord at the thoracic T10 vertebra level. One group of injured rats received deferoxamine, a second injured group received saline, and a third group was sham operated. Both 2 days and 2 weeks after spinal cord injury, total iron ion levels and protein expression levels of the proinflammatory cytokines tumor necrosis factor-α and interleukin-1β and the pro-apoptotic protein caspase-3 in the spinal cords of the injured deferoxamine-treated rats were significantly lower than those in the injured saline-treated group. The percentage of the area positive for glial fibrillary acidic protein immunoreactivity and the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells were also significantly decreased both 2 days and 2 weeks post injury, while the number of NeuN-positive cells and the percentage of the area positive for the oligodendrocyte marker CNPase were increased in the injured deferoxamine-treated rats. At 14–56 days post injury, hind limb motor function in the deferoxamine-treated rats was superior to that in the saline-treated rats. These results suggest that deferoxamine decreases total iron ion, tumor necrosis factor-α, interleukin-1β, and caspase-3 expression levels after spinal cord injury and inhibits apoptosis and glial scar formation to promote motor function recovery.

eIF5A1/RhoGDIα pathway: a novel therapeutic target for treatment of spinal cord injury identified by a proteomics approach

Spinal cord injury (SCI) is frequently accompanied by a degree of spontaneous functional recovery. The underlying mechanisms through which such recovery is generated remain elusive. In this study, we observed a significant spontaneous motor function recovery 14 to 28 days after spinal cord transection (SCT) in rats. Using a comparative proteomics approach, caudal to the injury, we detected difference in 20 proteins. Two of these proteins, are eukaryotic translation initiation factor 5A1 (eIF5A1) that is involved in cell survival and proliferation, and Rho GDP dissociation inhibitor alpha (RhoGDIα), a member of Rho GDI family that is involved in cytoskeletal reorganization. After confirming the changes in expression levels of these two proteins following SCT, we showed that in vivo eIF5A1 up-regulation and down-regulation significantly increased and decreased, respectively, motor function recovery. In vitro, eIF5A1 overexpression in primary neurons increased cell survival and elongated neurite length while eIF5A1 knockdown reversed these results. We found that RhoGDIα up-regulation and down-regulation rescues the effect of eIF5A1 down-regulation and up-regulation both in vivo and in vitro. Therefore, we have identified eIF5A1/RhoGDIα pathway as a new therapeutic target for treatment of spinal cord injured patients.

CSF proteomics of secondary phase spinal cord injury in human subjects: perturbed molecular pathways post injury

Recovery of sensory and motor functions following traumatic spinal cord injury (SCI) is dependent on injury severity. Here we identified 49 proteins from cerebrospinal fluid (CSF) of SCI patients, eight of which were differentially abundant among two severity groups of SCI. It was observed that the abundance profiles of these proteins change over a time period of days to months post SCI. Statistical analysis revealed that these proteins take part in several molecular pathways including DNA repair, protein phosphorylation, tRNA transcription, iron transport, mRNA metabolism, immune response and lipid and ATP catabolism. These pathways reflect a set of mechanisms that the system may adopt to cope up with the assault depending on the injury severity, thus leading to observed physiological responses. Apart from putting forward a picture of the molecular scenario at the injury site in a human study, this finding further delineates consequent pathways and molecules that may be altered by external intervention to restrict neural degeneration.

Detection of endogenous iron deposits in the injured mouse spinal cord through high-resolution ex vivo and in vivo MRI

The main aim of this study was to employ high-resolution MRI to investigate the spatiotemporal development of pathological features associated with contusive spinal cord injury (SCI) in mice. Experimental mice were subjected to either sham surgery or moderate contusive SCI. A 16.4-T small-animal MR system was employed for nondestructive imaging of post-mortem, fixed spinal cord specimens at the subacute (7 days) and more chronic (28-35 days) stages post-injury. Routine histological techniques were used for subsequent investigation of the observed neuropathology at the microscopic level. The central core of the lesion appeared as a dark hypo-intense area on MR images at all time points investigated. Small focal hypo-intense spots were also observed spreading through the dorsal funiculi proximal and distal to the site of impact, an area that is known to undergo gliosis and Wallerian degeneration in response to injury. Histological examination revealed these hypo-intense spots to be high in iron content as determined by Prussian blue staining. Quantitative image analysis confirmed the increased presence of iron deposits at all post-injury time points investigated (p<0.05). Distant iron deposits were also detectable through live imaging without the use of contrast-enhancing agents, enabling the longitudinal investigation of this pathology in individual animals. Further immunohistochemical evaluation showed that intracellular iron deposits localised to macrophages/microglia, astrocytes and oligodendrocytes in the subacute phase of SCI, but predominantly to glial fibrillary acidic protein-positive, CC-1-positive astrocytes at later stages of recovery. Progressive, widespread intracellular iron accumulation is thus a normal feature of SCI in mice, and high-resolution MRI can be effectively used to detect and monitor these neuropathological changes with time.

Plasma iron levels appraised 15 days after spinal cord injury in a limb movement animal model

STUDY DESIGN

Experimental, controlled trial.

OBJECTIVES

The purpose of this study was to evaluate plasma iron and transferrin levels in a limb movement animal model with spinal cord injury (SCI).

SETTING

Universidade Federal de São Paulo, Departamento de Psicobiologia.

METHODS

In all, 72 male Wistar rats aged 90 days were divided into four groups: (1) acute SCI (1 day, SCI1), (2) 3 days post-SCI (SCI3), (3) 7 days post-SCI (SCI7) and (4) 15 days post-SCI (SCI15). Each of these groups had corresponding control (CTRL) and SHAM groups. Plasma iron and transferrin levels of the different groups were analyzed using a one-way analysis of variance (ANOVA) followed by Tukey's test.

RESULTS

We found a significant reduction in iron plasma levels after SCI compared with the CTRL group: SCI1 (CTRL: 175±10.58 μg dl(-1); SCI: 108.28±11.7 μg dl(-1)), SCI3 (CTRL: 195.5±11.00 μg dl(-1); SCI: 127.88±12.63 μg dl(-1)), SCI7 (CTRL: 186±2.97 μg dl(-1); SCI: 89.2±15.39 μg dl(-1)) and SCI15 (CTRL: 163±5.48 μg dl(-1); SCI: 124.44±10.30 μg dl(-1)) (P<0.05; ANOVA). The SHAM1 group demonstrated a reduction in iron plasma after acute SCI (CTRL: 175±10.58 μg dl(-1); SHAM: 114.60±7.81 μg dl(-1)) (P<0.05; ANOVA).

CONCLUSION

Reduced iron metabolism after SCI may be one of the mechanisms involved in the pathogenesis of sleep-related movement disorders.

Iron regulatory proteins increase neuronal vulnerability to hydrogen peroxide

Iron regulatory protein (IRP)-1 and IRP2 inhibit ferritin synthesis by binding to an iron responsive element in the 5'-untranslated region of its mRNA. The present study tested the hypothesis that neurons lacking these proteins would be resistant to hydrogen peroxide (H(2)O(2)) toxicity. Wild-type cortical cultures treated with 100-300microM H(2)O(2) sustained widespread neuronal death, as measured by lactate dehydrogenase assay, and a significant increase in malondialdehyde. Both endpoints were reduced by over 85% in IRP2 knockout cultures. IRP1 gene deletion had a weaker and variable effect, with approximately 20% reduction in cell death at 300microM H(2)O(2). Ferritin expression after H(2)O(2) treatment was increased 1.9- and 6.7-fold in IRP1 and IRP2 knockout cultures, respectively, compared with wild-type. These results suggest that iron regulatory proteins, particularly IRP2, increase neuronal vulnerability to oxidative injury. Therapies targeting IRP2 binding to ferritin mRNA may attenuate neuronal loss due to oxidative stress.

Ferritin and ferritin isoforms II: protection against uncontrolled cellular proliferation, oxidative damage and inflammatory processes

Ferritin is a major iron storage protein involved in the regulation of iron availability. Each ferritin molecule comprises 24 subunits. Various combinations of H-subunits and L-subunits make up the 24-subunit protein structure and these ferritin isoforms differ in their H-subunit to L-subunit ratio, as well as in their metabolic properties. Ferritin is an acute-phase protein and its expression is up-regulated in conditions such as uncontrolled cellular proliferation, in any condition marked by excessive production of toxic oxygen radicals, and by infectious and inflammatory processes. Under such conditions ferritin up-regulation is predominantly stimulated by increased reactive oxygen radical production and by cytokines. The major function of ferritin in these conditions is to reduce the bio-availability of iron in order to stem uncontrolled cellular proliferation and excessive production of reactive oxygen radicals. Ferritin is not, however, indiscriminately up-regulated in these conditions as a marked shift towards a predominance in H-subunit rich ferritins occurs. Preliminary indications are that, while the L-subunit primarily fulfils the conventional iron storage role, the H-subunit functions primarily as rapid regulator of iron availability, and perhaps indirectly as regulator of other cellular processes. It is suggested that the optimum differential expression of the two subunits differ for different cells and under different conditions and that the expression of appropriate isoferritins offers protection against uncontrolled cellular proliferation, oxidative stress and against side effects of infectious and inflammatory conditions.

Proteome analysis of up-regulated proteins in the rat spinal cord induced by transection injury

The inability of the CNS to regenerate in adult mammals propels us to reveal associated proteins involved in the injured CNS. In this paper, either thoracic laminectomy (as sham control) or thoracic spinal cord transection was performed on male adult rats. Five days after surgery, the whole spinal cord tissue was dissected and fractionated into water-soluble (dissolved in Tris buffer) and water-insoluble (dissolved in a solution containing chaotropes and surfactants) portions for 2-DE. Protein identification was performed by MS and further confirmed by Western blot. As a result, over 30 protein spots in the injured spinal cord were shown to be up-regulated no less than 1.5-fold. These identified proteins possibly play various roles during the injury and repair process and may be functionally categorized as several different groups, such as stress-responsive and metabolic changes, lipid and protein degeneration, neural survival and regeneration. In particular, over-expression of 11-zinc finger protein and glypican may be responsible for the inhibition of axonal growth and regeneration. Moreover, three unknown proteins with novel sequences were found to be up-regulated by spinal cord injury. Further characterization of these molecules may help us come closer to understanding the mechanisms that underlie the inability of the adult CNS to regenerate.

Lecithinized superoxide dismutase (PC-SOD) improved spinal cord injury-induced motor dysfunction through suppression of oxidative stress and enhancement of neurotrophic factor production

PC-SOD (lecithinized superoxide dismutase) is a derivative of human Cu, Zn-SOD conjugated with 4 molecules of lecithin, yet having the enzyme activity of scavenging superoxide anion (O2-). Intravenous administration of PC-SOD promoted the recovery from spinal cord injury (SCI)-induced motor dysfunction in a dose-dependent manner in rat model, when evaluated by BBB (Basso Beattie Bresnahan) score. Even when given at 24 h after SCI, PC-SOD (1 mg/kg) significantly improved motor dysfunction. Distribution study demonstrated that PC-SOD gradually accumulated to the injured site. Enzyme-linked immunoassay revealed that PC-SOD prevented quantitative loss of neurons, astrocytes, and oligodendrocytes. PC-SOD inhibited SCI-induced oxidative stress, such as the decrease of free sulfhydryl residue, acetylcholine esterase activity, and the increase of lipid peroxidation. PC-SOD increased the production of neuroprotective factors. HIF-1alpha gene expression increased following SCI, and PC-SOD further increased it. In conclusion, PC-SOD gradually accumulated and retained at the damaged site to scavenge excessive O2-, and suppressed neuronal death through reducing oxidative stress, increasing neuroprotective factor production and HIF-1alpha gene expression.

Quercetin promotes functional recovery following acute spinal cord injury

We tested the hypothesis that quercetin, a potent Fe(2+)-chelating flavonoid, would decrease secondary damage following spinal cord trauma. MRI studies using the relaxation of the T1 proton signal caused by Fe(2+) ions and the dose-dependent reversal of this effect by addition of quercetin in aqueous solution were used to guide us to the dosage of quercetin to be used in animal experimentations. Forty-four male Wistar rats were used in two experimental series to test the hypothesis that administration of quercetin improves recovery of motor function after acute traumatic spinal cord injury. Animals were subjected to laminectomy and subjected to an extradural 40-g force clip compression for 5 sec at T7. Quercetin or saline was administered intraperitoneally 1 h after injury and then every 12 hr thereafter. Recovery of motor function was assessed using BBB scores at weekly intervals for 4 weeks. A dose of 2.5 micromoles quercetin/kg body weight did not result in significantly better functional outcome, whereas doses ranging from 5 to 100 micromoles quercetin/kg body weight resulted in a significantly better functional outcome with half or more of the animals walking, although with deficit; in contrast, no animals walked in the group of saline-treated animals. No significant differences in behavioral outcome were seen amongst the doses ranging from 5 to 100 micromol/kg, nor was there a difference if animals were treated for 4 or 10 days. Therapeutic outcome was coincident with more efficient iron clearance, suggesting that one possible mechanism whereby quercetin decreases secondary damage is through iron chelation.