Inhibition of ferroptosis-like cell death attenuates neuropathic pain reactions induced by peripheral nerve injury in rats

Repressing iron overload ameliorates central post-stroke pain via the Hdac2-Kv1.2 axis in a rat model of hemorrhagic stroke

JOURNAL/nrgr/04.03/01300535-202412000-00027/figure1/v/2024-04-08T165401Z/r/image-tiff Thalamic hemorrhage can lead to the development of central post-stroke pain. Changes in histone acetylation levels, which are regulated by histone deacetylases, affect the excitability of neurons surrounding the hemorrhagic area. However, the regulatory mechanism of histone deacetylases in central post-stroke pain remains unclear. Here, we show that iron overload leads to an increase in histone deacetylase 2 expression in damaged ventral posterolateral nucleus neurons. Inhibiting this increase restored histone H3 acetylation in the Kcna2 promoter region of the voltage-dependent potassium (Kv) channel subunit gene in a rat model of central post-stroke pain, thereby increasing Kcna2 expression and relieving central pain. However, in the absence of nerve injury, increasing histone deacetylase 2 expression decreased Kcna2 expression, decreased Kv current, increased the excitability of neurons in the ventral posterolateral nucleus area, and led to neuropathic pain symptoms. Moreover, treatment with the iron chelator deferiprone effectively reduced iron overload in the ventral posterolateral nucleus after intracerebral hemorrhage, reversed histone deacetylase 2 upregulation and Kv1.2 downregulation, and alleviated mechanical hypersensitivity in central post-stroke pain rats. These results suggest that histone deacetylase 2 upregulation and Kv1.2 downregulation, mediated by iron overload, are important factors in central post-stroke pain pathogenesis and could serve as new targets for central post-stroke pain treatment.

HIF-1α Induced by Hypoxia Promotes Peripheral Nerve Injury Recovery Through Regulating Ferroptosis in DRG Neuron

Peripheral nerve injury (PNI) usually has a poor effect on functional recovery and severely declines the patient's quality of life. Our prior findings indicated that hypoxia remarkably promoted nerve regeneration of rats with sciatic nerve transection. However, the underlying molecular mechanisms of hypoxia in functional recovery of PNI still remain elusive. In this research, we tried to explain the functional roles and mechanisms of hypoxia and the hypoxia-inducible factor-1α (HIF-1α) in PNI. Our results indicated that hypoxia promoted proliferation and migration of dorsal root ganglia (DRG) and increased the expression of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF). Mechanistically, hypoxia suppressed ferroptosis through activating HIF-1α in DRG neurons. Gain and loss of function studies were performed to evaluate the regulatory roles of HIF-1α in ferroptosis and neuron recovery. The results revealed that up-regulation of HIF-1α enhanced the expression of solute carrier family membrane 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) and increased the contents of cysteine and glutathione, while inhibiting the accumulation of reactive oxygen species (ROS). Our findings provided novel light on the mechanism of ferroptosis involved in PNI and manifest hypoxia as a potential therapeutic strategy for PNI recovery.

HDAC inhibitors as a potential therapy for chemotherapy-induced neuropathic pain

Cancer, a chronic disease characterized by uncontrolled cell development, kills millions of people globally. The WHO reported over 10 million cancer deaths in 2020. Anticancer medications destroy healthy and malignant cells. Cancer treatment induces neuropathy. Anticancer drugs cause harm to spinal cord, brain, and peripheral nerve somatosensory neurons, causing chemotherapy-induced neuropathic pain. The chemotherapy-induced mechanisms underlying neuropathic pain are not fully understood. However, neuroinflammation has been identified as one of the various pathways associated with the onset of chemotherapy-induced neuropathic pain. The neuroinflammatory processes may exhibit varying characteristics based on the specific type of anticancer treatment delivered. Neuroinflammatory characteristics have been observed in the spinal cord, where microglia and astrocytes have a significant impact on the development of chemotherapy-induced peripheral neuropathy. The patient's quality of life might be affected by sensory deprivation, loss of consciousness, paralysis, and severe disability. High cancer rates and ineffective treatments are associated with this disease. Recently, histone deacetylases have become a novel treatment target for chemotherapy-induced neuropathic pain. Chemotherapy-induced neuropathic pain may be treated with histone deacetylase inhibitors. Histone deacetylase inhibitors may be a promising therapeutic treatment for chemotherapy-induced neuropathic pain. Common chemotherapeutic drugs, mechanisms, therapeutic treatments for neuropathic pain, and histone deacetylase and its inhibitors in chemotherapy-induced neuropathic pain are covered in this paper. We propose that histone deacetylase inhibitors may treat several aspects of chemotherapy-induced neuropathic pain, and identifying these inhibitors as potentially unique treatments is crucial to the development of various chemotherapeutic combination treatments.

Exosomes From Muscle-Derived Stem Cells Repair Peripheral Nerve Injury by Inhibiting Ferroptosis via the Keap1-Nrf2-Ho-1 Axis

Currently, the clinical outcomes of peripheral nerve injuries are suboptimal, highlighting the urgent need to understand the mechanisms of nerve injury to enhance treatment strategies. Muscle-derived stem cells (MDSCs) are a diverse group of multipotent cells that hold promise for peripheral nerve regeneration due to their strong antioxidant and regenerative properties. Our research has revealed that severe ferroptosis occurs in the sciatic nerve and ipsilateral dorsal root ganglion following sciatic nerve injury. Interestingly, we have observed that MDSC-derived exosomes effectively suppress cell ferroptosis and enhance cell viability in Schwann cells and dorsal root ganglion cells. Treatment with exosomes led to increased expression of BDNF and P62 in Schwann cells, decreased expression of Keap1, Nrf2, and HO-1 in Schwann cells, and upregulated dorsal root ganglion cells. Rats treated with exosomes exhibited improvements in sciatic nerve function, sensitivity to stimuli, and reduced muscle atrophy, indicating a positive impact on post-injury recovery. In conclusion, our findings demonstrate the occurrence of ferroptosis in the sciatic nerve and dorsal root ganglion post-injury, with MDSC exosomes offering a potential therapeutic strategy by inhibiting ferroptosis, activating the Keap1-Nrf2-HO-1 pathway, and optimizing the post-injury repair environment.

Alleviating Recombinant Tissue Plasminogen Activator-induced Hemorrhagic Transformation in Ischemic Stroke via Targeted Delivery of a Ferroptosis Inhibitor

Intravenous thrombolysis with recombinant tissue plasminogen activator (rtPA) is the primary treatment for ischemic stroke. However, rtPA treatment can substantially increase blood-brain barrier (BBB) permeability and susceptibility to hemorrhagic transformation. Herein, the mechanism underlying the side effects of rtPA treatment is investigated and demonstrated that ferroptosis plays an important role. The ferroptosis inhibitor, liproxstatin-1 (Lip) is proposed to alleviate the side effects. A well-designed macrocyclic carrier, glucose-modified azocalix[4]arene (GluAC4A), is prepared to deliver Lip to the ischemic site. GluAC4A bound tightly to Lip and markedly improved its solubility. Glucose, modified at the upper rim of GluAC4A, imparts BBB targeting to the drug delivery system owing to the presence of glucose transporter 1 on the BBB surface. The responsiveness of GluAC4A to hypoxia due to the presence of azo groups enabled the targeted release of Lip at the ischemic site. GluAC4A successfully improved drug accumulation in the brain, and Lip@GluAC4A significantly reduced ferroptosis, BBB leakage, and neurological deficits induced by rtPA in vivo. These findings deepen the understanding of the side effects of rtPA treatment and provide a novel strategy for their effective mitigation, which is of great significance for the treatment and prognosis of patients with ischemic stroke.

GPX4, ferroptosis, and diseases

GPX4 (Glutathione peroxidase 4) serves as a crucial intracellular regulatory factor, participating in various physiological processes and playing a significant role in maintaining the redox homeostasis within the body. Ferroptosis, a form of iron-dependent non-apoptotic cell death, has gained considerable attention in recent years due to its involvement in multiple pathological processes. GPX4 is closely associated with ferroptosis and functions as the primary inhibitor of this process. Together, GPX4 and ferroptosis contribute to the pathophysiology of several diseases, including sepsis, nervous system diseases, ischemia reperfusion injury, cardiovascular diseases, and cancer. This review comprehensively explores the regulatory roles and impacts of GPX4 and ferroptosis in the development and progression of these diseases, with the aim of providing insights for identifying potential therapeutic strategies in the future.

Electroacupuncture suppresses neuronal ferroptosis to relieve chronic neuropathic pain

Growing evidence supports the analgesic efficacy of electroacupuncture (EA) in managing chronic neuropathic pain (NP) in both patients and NP models induced by peripheral nerve injury. However, the underlying mechanisms remain incompletely understood. Ferroptosis, a novel form of programmed cell death, has been found to be activated during NP development, while EA has shown potential in promoting neurological recovery following acute cerebral injury by targeting ferroptosis. In this study, to investigate the detailed mechanism underlying EA intervention on NP, male Sprague-Dawley rats with chronic constriction injury (CCI)-induced NP model received EA treatment at acupoints ST36 and GV20 for 14 days. Results demonstrated that EA effectively attenuated CCI-induced pain hypersensitivity and mitigated neuron damage and loss in the spinal cord of NP rats. Moreover, EA reversed the oxidative stress-mediated spinal ferroptosis phenotype by upregulating reduced expression of xCT, glutathione peroxidase 4 (GPX4), ferritin heavy chain (FTH1) and superoxide dismutase (SOD) levels, and downregulating increased expression of acyl-CoA synthetase long-chain family member 4 (ACSL4), malondialdehyde levels and iron overload. Furthermore, EA increased the immunofluorescence co-staining of GPX4 in neurons cells of the spinal cord of CCI rats. Mechanistic analysis unveiled that the inhibition of antioxidant pathway of Nrf2 signalling via its specific inhibitor, ML385, significantly countered EA's protective effect against neuronal ferroptosis in NP rats while marginally diminishing its analgesic effect. These findings suggest that EA treatment at acupoints ST36 and GV20 may protect against NP by inhibiting neuronal ferroptosis in the spinal cord, partially through the activation of Nrf2 signalling.

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.

Stress/cell death pathways, neuroinflammation, and neuropathic pain

Neuropathic pain is a common and debilitating modality of chronic pain induced by a lesion or disease of the somatosensory nervous system. Albeit the elucidation of numerous pathophysiological mechanisms and the development of potential treatment compounds, safe and reliable therapies of neuropathic pain remain poor. Multiple stress/cell death pathways have been shown to be implicated in neuroinflammation during neuropathic pain. Here, we summarize the current knowledge of stress/cell death pathways and present an overview of the roles and molecular mechanisms of stress/cell death pathways in neuroinflammation during neuropathic pain, covering intrinsic and extrinsic apoptosis, autophagy, mitophagy, ferroptosis, pyroptosis, necroptosis, and phagoptosis. Small molecule compounds that modulate stress/cell death pathways in alleviating neuropathic pain are discussed mainly based on preclinical neuropathic pain models. These findings will contribute to in-depth understanding of the pathological processes during neuropathic pain as well as bridge the gap between basic and translational research to uncover new neuroprotective interventions.

Identification and verification of ferroptosis-related genes in diabetic foot using bioinformatics analysis

Ferroptosis is a novel form of cell death that plays a key role in several diseases, including inflammation and tumours; however, the role of ferroptosis-related genes in diabetic foot remains unclear. Herein, diabetic foot-related genes were downloaded from the Gene Expression Omnibus and the ferroptosis database (FerrDb). The least absolute shrinkage and selection operator regression algorithm was used to construct a related risk model, and differentially expressed genes were analysed through immune infiltration. Finally, we identified relevant core genes through a protein-protein interaction network, subsequently verified using immunohistochemistry. Comprehensive analysis showed 198 genes that were differentially expressed during ferroptosis. Based on functional enrichment analysis, these genes were primarily involved in cell response, chemical stimulation, and autophagy. Using the CIBERSORT algorithm, we calculated the immune infiltration of 22 different types of immune cells in diabetic foot and normal tissues. The protein-protein interaction network identified the hub gene TP53, and according to immunohistochemistry, the expression of TP53 was high in diabetic foot tissues but low in normal tissues. Accordingly, we identified the ferroptosis-related gene TP53 in the diabetic foot, which may play a key role in the pathogenesis of diabetic foot and could be used as a potential biomarker.

Electroacupuncture Alleviates Neuropathic Pain by Suppressing Ferroptosis in Dorsal Root Ganglion via SAT1/ALOX15 Signaling

Neuropathic pain affects globally about 7-10% of the general population. Electroacupuncture (EA) effectively relieves neuropathic pain symptoms without causing any side effects; however, the underlying molecular mechanisms remain unclear. We established a chronic constriction injury (CCI)-induced rat model of neuropathic pain. RNA sequencing was used to screen for differentially expressed genes in the dorsal root ganglion after CCI and EA treatment. We identified gene markers of ferroptosis spermidine/spermine N1-acetyltransferase 1 (Sat1) and arachidonate 15-lipoxygenase (Alox15) to be dysregulated in the CCI-induced neuropathic pain model. Furthermore, EA relieved CCI-induced pain as well as ferroptosis-related symptoms in the dorsal root ganglion, including lipid peroxidation and iron overload. Finally, SAT1 knockdown also alleviated mechanical and thermal pain hypersensitivity and reversed ferroptosis damage. In conclusion, we showed that EA inhibited ferroptosis by regulating the SAT1/ALOX15 pathway to treat neuropathic pain. Our findings provide insight into the mechanisms of EA and suggest a novel therapeutic target for neuropathic pain.

Bone marrow-derived mesenchymal stem cells attenuate complete Freund's adjuvant-induced inflammatory pain by inhibiting the expression of P2X3

Bone marrow-derived mesenchymal stem cells (BMSCs) show a good property for pain treatment by modulating inflammatory response. However, the underlying therapeutic effect and related mechanism of BMSCs on inflammatory pain remain unclear. Therefore, we explored the function and potential mechanism of BMSCs performing in a complete Freund's adjuvant (CFA)-induced inflammatory pain model in this study. Here, BMSCs were injected into the CFA-treated rats, and we used behavioural tests to evaluate the changes in hypersensitivity. High-throughput sequencing was used to screen out the hub genes. Molecular biology experiments were performed to detect the level of P2X3 or inflammatory mediators in rats and observed the distribution of P2X3 in neural cells. Furthermore, the function of the P2X3 was explored via inhibitor and activator experiments. Finally, we found that BMSCs alleviated hyperalgesia and spinal levels of pro-inflammatory factors in CFA-treated rats. High-throughput sequencing showed that P2X3 and P2X7 were identified as hub genes, and only the expression level of P2X3 was significantly down-regulated after BMSCs treatment. Immunohistochemistry showed that P2X3 mainly colocalized with microglia and astrocytes. The levels of P2X3 and pro-inflammatory factors were all significantly reduced after BMSC injection. Moreover, similar attenuation was found in the CFA-treated rats after injecting the P2X3 inhibitor, and a P2X3 antagonist reversed the attenuation induced by the BMSCs. These findings suggest that BMSCs exerted a therapeutic effect on inflammatory pain by inhibiting the expression of P2X3 and the excessive production of inflammatory mediators was associated with an increased P2X3 level and BMSC therapy reverse these effects.

Ferroptosis: a new regulatory mechanism in neuropathic pain

Neuropathic pain (NP) is pain caused by damage to the somatosensory system. It is a common progressive neurodegenerative disease that usually presents with clinical features such as spontaneous pain, touch-evoked pain, nociceptive hyperalgesia, and sensory abnormalities. Due to the complexity of the mechanism, NP often persists. In addition to the traditionally recognized mechanisms of peripheral nerve damage and central sensitization, excessive iron accumulation, oxidative stress, neuronal inflammation, and lipid peroxidation damage are distinctive features of NP in pathophysiology. However, the mechanisms linking these pathological features to NP are not fully understood. The complexity of the pathogenesis of NP greatly limits the development of therapeutic approaches for NP. Ferroptosis is a novel form of cell death discovered in recent years, in which cell death is usually accompanied by massive iron accumulation and lipid peroxidation. Ferroptosis-inducing factors can affect glutathione peroxidase directly or indirectly through different pathways, leading to decreased antioxidant capacity and accumulation of lipid reactive oxygen species (ROS) in cells, ultimately leading to oxidative cell death. It has been shown that ferroptosis is closely related to the pathophysiological process of many neurological disorders such as NP. Possible mechanisms involved are changes in intracellular iron ion levels, alteration of glutamate excitability, and the onset of oxidative stress. However, the functional changes and specific molecular mechanisms of ferroptosis during this process still need to be further explored. How to intervene in the development of NP by regulating cellular ferroptosis has become a hot issue in etiological research and treatment. In this review, we systematically summarize the recent progress of ferroptosis research in NP, to provide a reference for further understanding of its pathogenesis and propose new targets for treatment.

Astrocyte senescence-like response related to peripheral nerve injury-induced neuropathic pain

BACKGROUND

Peripheral nerve damage causes neuroinflammation, which plays a critical role in establishing and maintaining neuropathic pain (NeP). The mechanisms contributing to neuroinflammation remain poorly elucidated, and pharmacological strategies for NeP are limited. Thus, in this study, we planned to explore the possible link between astrocyte senescence and NeP disorders following chronic sciatic nerve injury.

METHODS

An NeP animal model was established by inducing chronic constrictive injury (CCI) to the sciatic nerve in adult rats. A senolytic drug combination of dasatinib and quercetin was gavaged daily from the first postoperative day until the end of the study. Paw mechanical withdrawal threshold (PMWT) and paw thermal withdrawal latency (PTWL) were evaluated to assess behaviors in response to pain in the experimental rats. Senescence-associated β-galactosidase staining, western blot analysis, and immunofluorescence were applied to examine the levels of proinflammatory factors and severity of the senescence-like response in the spinal cord. Lipopolysaccharide (LPS) was administered to induce senescence of spinal astrocytes in primary cultures in vitro, to explore the potential impacts of senescence on the secretion of proinflammatory factors. Furthermore, single-cell RNA sequencing (scRNA-seq) was conducted to identify senescence-related molecular responses in spinal astrocytes under neuropathic pain.

RESULTS

Following sciatic nerve CCI, rats exhibited reduced PMWT and PTWL, increased levels of spinal proinflammatory factors, and an enhanced degree of senescence in spinal astrocytes. Treatment with dasatinib and quercetin effectively attenuated spinal neuroinflammation and mitigated the hypersensitivities of the rats subjected to sciatic nerve CCI. Mechanistically, the dasatinib-quercetin combination reversed senescence in LPS-stimulated primary cultured astrocytes and decreased the levels of proinflammatory factors. The scRNA-seq data revealed four potential senescence-related genes in the spinal astrocyte population, and the expression of clusterin (CLU) protein was validated via in vitro experiments.

CONCLUSION

The findings indicate the potential role of astrocyte senescence in neuroinflammation following peripheral nerve injury, and suggest that targeting CLU activation in astrocytes might provide a novel therapeutic strategy to treat NeP.

The emerging role of pyroptosis in neuropathic pain

Neuropathic pain caused by somatosensory system injuries is notoriously difficult to treat. Previous research has shown that neuroinflammation and cell death have been implicated in the pathophysiology of neuropathic pain. Pyroptosis is a form of programmed cell death associated with inflammatory processes, as it can enhance or sustain the inflammatory response by releasing pro-inflammatory cytokines. This review presents the current knowledge on pyroptosis and its underlying mechanisms, including the canonical and noncanonical pathways. Moreover, we discuss recent findings on the role of pyroptosis in neuropathic pain and its potential as a therapeutic target. In conclusion, this review highlights the potential significance of pyroptosis as a promising target for developing innovative therapies to treat neuropathic pain.

Inhibition of spinal ferroptosis-like cell death alleviates hyperalgesia and spontaneous pain in a mouse model of bone cancer pain

Bone cancer pain (BCP) impairs patients' quality of life. However, the underlying mechanisms are still unclear. This study investigated the role of spinal interneuron death using a pharmacological inhibitor of ferroptosis in a mouse model of BCP. Lewis lung carcinoma cells were inoculated into the femur, resulting in hyperalgesia and spontaneous pain. Biochemical analysis revealed that spinal levels of reactive oxygen species and malondialdehyde were increased, while those of superoxide dismutase were decreased. Histological analysis showed the loss of spinal GAD65+ interneurons and provided ultrastructural evidence of mitochondrial shrinkage. Pharmacologic inhibition of ferroptosis using ferrostatin-1 (FER-1, 10 mg/kg, intraperitoneal for 20 consecutive days) attenuated ferroptosis-associated iron accumulation and lipid peroxidation and alleviated BCP. Furthermore, FER-1 inhibited the pain-associated activation of ERK1/2 and COX-2 expression and prevented the loss of GABAergic interneurons. Moreover, FER-1 improved analgesia by the COX-2 inhibitor Parecoxib. Taken together, this study shows that pharmacological inhibition of ferroptosis-like cell death of spinal interneurons alleviates BCP in mice. The results suggest that ferroptosis is a potential therapeutic target in patients suffering on BCP and possibly other types of pain.

Exploration and identification of six novel ferroptosis-related hub genes as potential gene signatures for peripheral nerve injury

Specific biomarkers of ferroptosis after peripheral nerve injury (PNI) are still under debate. In this study, 52 differentially expressed ferroptosis-related genes (DE-FRGs) were retrieved from publicly accessible sequencing data of intact and injured samples of rats with sciatic nerve crush injury. Functional enrichment analyses revealed that adipogenesis, mitochondrial gene sets, and pathways of MAPK, p53, and CD28 family were predominantly engaged in ferroptosis after PNI. Next, Cdkn1a, Cdh1, Hif1a, Hmox1, Nfe2l2, and Tgfb1 were investigated as new ferroptosis-associated hub genes after PNI. Subsequently, clustering correlation heatmap shows six hub genes are linked to mitochondria. The immunofluorescence assay at 0, 1, 4, 7, and 14 days indicated the temporal expression patterns of Tgfb1, Hmox1, and Hif1a after PNI were consistent with ferroptosis validated by PI and ROS staining, while Cdh1, Cdkn1a, and Nfe2l2 were the opposite. In summary, this study identified six hub genes as possible ferroptosis-related biomarkers for PNI, which may offer therapeutic targets for peripheral nerve regeneration and provide a therapeutic window for ferroptosis.

Methyl Ferulic Acid Alleviates Neuropathic Pain by Inhibiting Nox4-induced Ferroptosis in Dorsal Root Ganglia Neurons in Rats

Neuropathic pain is a disease that has become one of the major public health problems and a global burden. Nox4-induced oxidative stress can lead to ferroptosis and neuropathic pain. Methyl ferulic acid (MFA) can inhibit the Nox4-induced oxidative stress. This study aimed to estimate whether methyl ferulic acid alleviates neuropathic pain by inhibiting the expression of Nox4 and its induction of ferroptosis. Adult male Sprague-Dawley rats were subjected to spared nerve injury (SNI) model to induce neuropathic pain. After the establishment of the model, methyl ferulic acid was given 14 days by gavage. Nox4 overexpression was induced by microinjection of the AAV-Nox4 vector. All groups measured paw mechanical withdrawal threshold (PMWT), paw thermal withdrawal latency (PTWL), and paw withdrawal cold duration (PWCD). The expression of Nox4, ACSL4, GPX4, and ROS was investigated by Western blot and immunofluorescence staining. The changes in iron content were detected by a tissue iron kit. The morphological changes in mitochondria were observed by transmission electron microscopy. In the SNI group, the paw mechanical withdrawal threshold, the paw withdrawal cold duration decreased, the paw thermal withdrawal latency did not change, the Nox4, ACSL4, ROS, and iron content increased, the GPX4 decreased, and the number of abnormal mitochondria increased. Methyl ferulic acid can increase PMWT and PWCD but does not affect PTWL. Methyl ferulic acid can inhibit Nox4 protein expression. Meanwhile, ferroptosis-related protein ACSL4 expression was decreased, GPX4 expression was increased, ROS, iron content and abnormal mitochondrial number were decreased. By overexpressing Nox4, the PMWT, PWCD, and ferroptosis of rats were more severe than those of the SNI group, but they could be reversed after treatment with methyl ferulic acid. In conclusion, methyl ferulic acid can alleviate neuropathic pain, which is related to Nox4-induced ferroptosis.

Intrathecal liproxstatin-1 delivery inhibits ferroptosis and attenuates mechanical and thermal hypersensitivities in rats with complete Freund’s adjuvant-induced inflammatory pain

Previous studies have confirmed the relationship between iron-dependent ferroptosis and a peripheral nerve injury-induced neuropathic pain model. However, the role of ferroptosis in inflammatory pain remains inconclusive. Therefore, we aimed to explore whether ferroptosis in the spinal cord and dorsal root ganglion contributes to complete Freund’s adjuvant (CFA)-induced painful behaviors in rats. Our results revealed that various biochemical and morphological changes were associated with ferroptosis in the spinal cord and dorsal root ganglion tissues of CFA rats. These changes included iron overload, enhanced lipid peroxidation, disorders of anti-acyl-coenzyme A synthetase long-chain family member 4 and glutathione peroxidase 4 levels, and abnormal morphological changes in mitochondria. Intrathecal treatment of liproxstatin-1 (a ferroptosis inhibitor) reversed these ferroptosis-related changes and alleviated mechanical and thermal hypersensitivities in CFA rats. Our study demonstrated the occurrence of ferroptosis in the spinal cord and dorsal root ganglion tissues in a rodent model of inflammatory pain and indicated that intrathecal administration of ferroptosis inhibitors, such as liproxstatin-1, is a potential therapeutic strategy for treating inflammatory pain.

Role of ferroptosis inhibitors in the management of diabetes

Ferroptosis, the iron-dependent, lipid peroxide-mediated cell death, has garnered attention due to its critical involvement in crucial physiological and pathological cellular processes. Indeed, several studies have attributed its role in developing a range of disorders, including diabetes. As accumulating evidence further the understanding of ferroptotic mechanisms, the impact this specialized mode of cell death has on diabetic pathogenesis is still unclear. Several in vivo and in vitro studies have highlighted the association of ferroptosis with beta-cell death and insulin resistance, supported by observations of marked alterations in ferroptotic markers in experimental diabetes models. The constant improvement in understanding ferroptosis in diabetes has demonstrated it as a potential therapeutic target in diabetic management. In this regard, ferroptosis inhibitors promise to rescue pancreatic beta-cell function and alleviate diabetes and its complications. This review article elucidates the key ferroptotic pathways that mediate beta-cell death in diabetes, and its complications. In particular, we share our insight into the cross talk between ferroptosis and other hallmark pathogenic mediators such as oxidative and endoplasmic reticulum stress regulators relevant to diabetes progression. Further, we extensively summarize the recent developments on the role of ferroptosis inhibitors and their therapeutic action in alleviating diabetes and its complications.

Iron Metabolism and Ferroptosis in Peripheral Nerve Injury

Peripheral nerve injury (PNI) is a major clinical problem that may lead to different levels of sensory and motor dysfunction including paralysis. Due to the high disability rate and unsatisfactory prognosis, the exploration and revealment of the mechanisms involved in the PNI are urgently required. Ferroptosis, a recently identified novel form of cell death, is an iron-dependent process. It is a unique modality of cell death, closely associated with iron concentrations, generation of reactive oxygen species, and accumulation of the lipid reactive oxygen species. These processes are regulated by multiple cellular metabolic pathways, including iron overloading, lipid peroxidation, and the glutathione/glutathione peroxidase 4 pathway. Furthermore, ferroptosis is accompanied by morphological changes in the mitochondria, such as increased membrane density and shrunken mitochondria; this association between ferroptosis and mitochondrial damage has been detected in various diseases, including spinal cord injury and PNI. The inhibition of ferroptosis can promote the repair of damaged peripheral nerves, reduce mitochondrial damage, and promote the recovery of neurological function. In this review, we intend to discuss the detailed mechanisms of ferroptosis and summarize the current researches on ferroptosis with respect to nerve injury. This review also aims at providing new insights on targeting ferroptosis for PNI treatment.

An update on the therapeutic implications of long-chain acyl-coenzyme A synthetases in nervous system diseases

Long-chain acyl-coenzyme A synthetases (ACSLs) are a family of CoA synthetases that activate fatty acid (FA) with chain lengths of 12-20 carbon atoms by forming the acyl-AMP derivative in an isozyme-specific manner. This family mainly includes five members (ACSL1, ACSL3, ACSL4, ACSL5, and ACSL6), which are thought to have specific and different functions in FA metabolism and oxidative stress of mammals. Accumulating evidence shows that the dysfunction of ACSLs is likely to affect cell proliferation and lead to metabolic diseases in multiple organs and systems through different signaling pathways and molecular mechanisms. Hence, a central theme of this review is to emphasize the therapeutic implications of ACSLs in nervous system disorders.

Characterization of Ferroptosis-Related Molecular Subtypes with Immune Infiltrations in Neuropathic Pain

Background

Neuropathic pain (NP) caused by a lesion or disease of the somatosensory nervous system is a common chronic pain condition that has a major impact on quality of life. However, NP pathogenesis remains unclear. The purpose of this study was to identify differentially expressed genes (DEGs) and specific and meaningful gene targets for the diagnosis and treatment of NP.

Methods

Data from rat spinal nerve ligations and the sham group were downloaded from the Gene Expression Omnibus (GEO) database. Based on the single-sample gene set enrichment analysis (ssGSEA) method, 29 immune gene sets were identified in each sample, and these samples were correlated with the immune infiltration phenotype. LASSO regression modeling was used to screen key genes to identify diagnostic gene markers. According to GSEA and GSVA, NP is concentrated in a large number of immune-related pathways and genes. Additionally, we used the DGIdb database and correlation test to construct gene-drug and transcription factor interaction networks for differentially expressed genes relevant to NP-related ferroptosis. We used WGCNA to identify gene co-expression modules of NP, and explored the relationship between gene networks and phenotypes. Finally, we crossed core genes with diagnostic markers and analyzed gene correlation with molecular subtypes and immune cells.

Results

We identified 224 DEGs, including 191 upregulated genes and 33 downregulated genes. APC co-stimulation, CCR, cytolytic activity, humid-promoting, neutrophils, NK cells, and RGS4, CXCL2, DRD4 and other 7 genes related to ferroptosis were involved in NP development. Key genes of RGS4 and HIF-1 signaling pathway were screened.

Conclusion

This study contributes to our understanding of the neuroimmune mechanism of neuropathic pain, provides a reference for NP biomarkers and drug targets. Ferroptosis may be the next research direction to explore NP mechanism.

Targeting Ferroptosis Attenuates Inflammation, Fibrosis, and Mast Cell Activation in Chronic Prostatitis

Purpose

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a common urological disorder. Although ferroptosis is closely associated with inflammation, oxidative stress, and neuropathic pain, its role in CP/CPPS has not yet been elucidated. Therefore, we sought to explore the role and mechanism of ferroptosis in the prostatitis development.

Methods

The experimental autoimmune prostatitis (EAP) was established through intradermal immunization of prostate extract. Iron chelator deferoxamine (DFO) and free radical scavenger edaravone (EDA) were applied to evaluate the effects of ferroptosis inhibition on oxidative stress, ferroptosis, inflammation, fibrosis, and mast cell activation in the context of CP/CPPS.

Results

Increased generation of lipid peroxidation products (ROS and MDA) and decreased activities of antioxidant enzymes (SOD and CAT) suggested an aberrant oxidative stress status in EAP model. Elevated iron concentration was observed in the EAP model. Meanwhile, we discovered significant biological performances associated with ferroptosis in CP/CPPS, including the downregulation of the system Xc^-/GPX4 axis and the upregulation of the ACSL4/LPCAT3 axis. EAP rats performed serious leukocyte infiltration, advanced inflammatory grade, and abnormal expression of inflammatory mediators. Abundant collagen deposition, enhanced RhoA, ROCK1, and α-SMA protein levels indicated that EAP rats were prone to suffer from stromal fibrosis compared with control group. An elevated number of degranulated mast cells and corresponding marker TPSB2 represented that mast cell-sensitized pain was amplified in the EAP model. Furthermore, reduction of NRF2/HO-1 indicated a vulnerability of EAP towards ferroptosis response. However, application of DFO and EDA had partially reversed the adverse influences mentioned above.

Conclusion

We first demonstrated that ferroptosis might be a crucial factor of chronic prostatitis progression. Inhibition of ferroptosis using DFO and EDA represented a promising approach for treating prostatitis by ameliorating inflammation, fibrosis, and mast cell activation.

The Role of Vascular-Immune Interactions in Modulating Chemotherapy Induced Neuropathic Pain

Chemotherapy causes sensory disturbances in cancer patients that results in neuropathies and pain. As cancer survivorships has dramatically increased over the past 10 years, pain management of these patients is becoming clinically more important. Current analgesic strategies are mainly ineffective and long-term use is associated with severe side effects. The issue being that common analgesic strategies are based on ubiquitous pain mediator pathways, so when applied to clinically diverse neuropathic pain and neurological conditions, are unsuccessful. This is principally due to the lack of understanding of the driving forces that lead to chemotherapy induced neuropathies. It is well documented that chemotherapy causes sensory neurodegeneration through axonal atrophy and intraepidermal fibre degeneration causing alterations in pain perception. Despite the neuropathological alterations associated with chemotherapy-induced neuropathic pain being extensively researched, underlying causes remain elusive. Resent evidence from patient and rodent studies have indicated a prominent inflammatory cell component in the peripheral sensory nervous system in effected areas post chemotherapeutic treatment. This is accompanied by modulation of auxiliary cells of the dorsal root ganglia sensory neurons such as activation of satellite glia and capillary dysfunction. The presence of a neuroinflammatory component was supported by transcriptomic analysis of dorsal root ganglia taken from mice treated with common chemotherapy agents. With key inflammatory mediators identified, having potent immunoregulatory effects that directly influences nociception. We aim to evaluate the current understanding of these immune-neuronal interactions across different cancer therapy drug classes. In the belief this may lead to better pain management approaches for cancer survivors.

Transcriptome Profiles of IncRNA and mRNA Highlight the Role of Ferroptosis in Chronic Neuropathic Pain With Memory Impairment

Background: Chronic neuropathic pain is commonly associated with memory loss, which increases the risk of dementia, lowers life quality and spending. On the other hand, the molecular processes are unknown, and effective therapies have yet to be discovered. Long non-coding RNAs (lncRNAs) are emerging potential therapeutic targets for chronic pain, but their role in chronic pain-induced memory impairment is unknown. Methods: We established a CCI-induced memory impairment rat model. To investigate and validate the gene expression alterations in the hippocampus of CCI-induced memory impairment, we used RNA-Seq, bioinformatics analysis, qRT-PCR, western blot, immunostaining, Nissl staining, and Diaminobenzidine-enhanced Perls' stain. Results: CCI rats displayed long-term memory deficits in the Y maze and novel objective recognition tests, and chronic mechanical and thermal pain hypersensitivity in the hind paws. We found a total of 179 differentially expressed mRNAs (DEmRNAs) (81 downregulated and 98 upregulated) and 191 differentially expressed long noncoding RNAs (DElncRNAs) (87 downregulated and 105 upregulated) between the hippocampus CA1 of CCI-induced memory impairment model and the sham control, using RNA-Seq expression profiles. The most enriched pathways involving oxidation and iron metabolism were explored using a route and function pathway analysis of DEmRNAs and DElncRNAs. We also discovered that ATF3 was considerably overexpressed in the hippocampal CA1 area, and gene markers of ferroptosis, such as GPX4, SLC7A11, SLC1A5, and PTGS2, were dysregulated in the CCI-induced memory impairment paradigm. Furthermore, in the hippocampus CA1 of CCI-induced memory impairment, lipid peroxidation and iron overload were considerably enhanced. Fer-1 treatment reversed ferroptosis damage of CCI with memory impairment model. Finally, in CCI-induced memory impairment, a competing RNA network analysis of DElncRNAs and DEmRNAs was performed to investigate the putative regulatory link of DElncRNAs on DEmRNAs via miRNA sponging. Conclusion: Using RNA-Seq, we created a genome-wide profile of the whole hippocampus of a rat model of CCI-induced memory impairment. In the hippocampus, pathways and function analyses revealed numerous intriguing genes and pathways involved in ferroptosis and memory impairment in response to chronic pain stress. As a result, our research may aid in the identification of potential and effective treatments for CCI-induced memory impairment.

Sirtuin 2 Alleviates Chronic Neuropathic Pain by Suppressing Ferroptosis in Rats

Neuropathic pain (NP) is chronic and associated with poor effects of general analgesia. It affects patients’ health and quality of life. The apoptotic process of lipid peroxidation caused by iron overload is called ferroptosis, which may be associated with nervous system disease. A recent study has found that sirtuin 2 (SIRT2) achieves a neuroprotective effect by suppressing ferroptosis. Herein, we aimed to examine whether SIRT2 regulated spared nerve injury (SNI)-induced NP by suppressing ferroptosis in rats. A rat model of NP was induced in adult male Sprague-Dawley rats weighing 200–250 g. Mechanical allodynia was observed from the first day after SNI and continued for 14 days. Compared with age-matched control rats, the expression of SIRT2 and ferroportin 1 (FPN1) decreased in the L4-6 spinal cord of the SNI-induced NP rats. In addition, we observed that the levels of both iron and anti-acyl-coenzyme A synthetase long-chain family member 4 (ACSL4) were significantly increased in the spinal cord after SNI, while the expression of glutathione peroxidase 4 (GPX4) was decreased. Furthermore, an intrathecal injection of SIRT2 overexpressed recombinant adenovirus, which upregulated the expression of SIRT2, attenuated mechanical allodynia, enhanced the level of FPN1, inhibited intracellular iron accumulation, and reduced oxidant stress levels, thereby reversing the changes to ACSL4 and GPX4 expression in the SNI rats. This evidence suggests that SIRT2-targeted therapeutics may help relieve the symptoms of chronic NP.

Overexpression of c-Jun inhibits erastin-induced ferroptosis in Schwann cells and promotes repair of facial nerve function

Myelin undergoes various changes after nerve injury, and c‐Jun has a close relationship with Schwann cells (SCs). However, it remains unclear whether c‐Jun can be involved in nerve repair by regulating ferroptosis. To explore this, we first set up a facial nerve injury model and detected the changes of ferroptosis‐related proteins and c‐Jun by immunofluorescence and Western blot. Then, we cultured RSC 96 and pSCs, and studied the potential regulatory relationships by a combination of experimental methods such as CCK‐8, ELISA, immunofluorescence, qRT‐PCR, Western blot and viral transfection. Finally, we corroborated the role of c‐Jun through animal experiments. Our experiments revealed that ferroptosis occurs after facial nerve injury. Erastin decreased GPX4, c‐Jun proteins and GSH content, while PTGS2, NRF2, HO‐1 proteins, MDA, Fe²⁺ and ROS contents increased. This effect was inhibited after c‐Jun overexpression but was reversed after the addition of c‐Jun siRNA. Besides, we proved in vivo that c‐Jun could inhibit ferroptosis and promote the recovery of facial nerve function. In conclusion, our study identified the relationship between c‐Jun and ferroptosis during peripheral nerve injury repair, which provides new ideas for studying peripheral nerve injury and repair.

Construction of pH-responsive nanocarriers in combination with ferroptosis and chemotherapy for treatment of hepatocellular carcinoma

Background

Chemotherapy is widely used to treat hepatocellular carcinoma (HCC). Although sorafenib (SO) is the only chemotherapy drug approved by FDA for treatment of HCC, it is associated with several disadvantages including low water solubility, low bioavailability, lack of targeting and easily causes systemic toxicity. In recent years, nanocarriers have shown promise in drug delivery to effectively solve these problems. Herein, we used SO-loaded nanocarriers to overcome the defects of chemotherapy during treatment of HCC. Specifically, we encapsulated pH-sensitive hollow mesoporous Prussian blue nanoparticles (HMPB) with SO (an inhibitor of multi-kinase and accelerant of ferroptosis) to act as carriers and facilitate drug release. We also coated its surface with a layer of pH-responsive chitosan (CS) to block the drug and increase biocompatibility. Finally, we successfully constructed HP/SO/CS nanocomposites for targeted delivery of chemotherapeutic drugs, with the aim of initiating chemotherapy and ferroptosis for dual treatment of tumors. In vitro and in vivo experiments were performed for evaluation of the nanocomposites’ anti-tumor efficacy by using liver cancer cells and mice, respectively.

Results

The nanocomposites specifically targeted tumor cells through enhancing permeability and retention (EPR) effect. Results from in vitro experiments showed that the nanocarriers not only promoted cell apoptosis and reduced the number of cells for chemotherapy, but also promoted accumulation of reactive oxygen species (ROSs). In vivo experiments showed that mice in the nanocomposite-treated group exhibited the smallest tumor sizes and body weights, with no obvious damage to normal tissues and organs.

Conclusion

Taken together, these findings indicated that nanocarriers had an effective inhibitory effect on HCC cells. This safe and multifunctional treatment model was a valuable option for the treatment of HCC, as well as other cancers.

Graphical Abstract

Ferrostatin-1 Alleviates White Matter Injury Via Decreasing Ferroptosis Following Spinal Cord Injury

Spinal cord injury (SCI), a devastating neurological impairment, usually imposes a long-term psychological stress and high socioeconomic burden for the sufferers and their family. Recent researchers have paid arousing attention to white matter injury and the underlying mechanism following SCI. Ferroptosis has been revealed to be associated with diverse diseases including stroke, cancer, and kidney degeneration. Ferrostatin-1, a potent inhibitor of ferroptosis, has been illustrated to curb ferroptosis in neurons, subsequently improving functional recovery after traumatic brain injury (TBI) and SCI. However, the role of ferroptosis in white matter injury and the therapeutic effect of ferrostatin-1 on SCI are still unknown. Here, our results indicated that ferroptosis played a pivotal role in the secondary white matter injury, and ferrostatin-1 could reduce iron and reactive oxygen species (ROS) accumulation and downregulate the ferroptosis-related genes and its products of IREB2 and PTGS2 to further inhibit ferroptosis in oligodendrocyte, finally reducing white matter injury and promoting functional recovery following SCI in rats. Meanwhile, the results demonstrated that ferrostatin-1 held the potential of inhibiting the activation of reactive astrocyte and microglia. Mechanically, the present study deciphers the potential mechanism of white matter damage, which enlarges the therapeutic effects of ferrostatin-1 on SCI and even in other central nervous system (CNS) diseases existing ferroptosis.