Ferroptosis: a new regulatory mechanism in neuropathic pain

RIN1 regulates ferroptosis and nociceptive perception via the Nrf2/HO-1 pathway in chronic constriction injury

Neuropathic pain (NP) has been a major focus of clinical research for decades. This study investigates the function of RAS- and RAB-interacting protein 1 (RIN1) in modulating NP and explore the involvement of the nuclear factor-2 erythroid factor-2 (Nrf2) and heme oxygenase 1 (HO-1) pathway in this context. A rat model of CCI was generated. The presence of mechanical and thermal hypersensitivity, as well as spontaneous pain behaviors, confirmed the successful modeling. Intrathecal injection of AAV9-shRNA targeting RIN1 attenuated nociception, reduced microglial activation in the L4-L6 spinal cord, and decreased the expression levels of c-Fos, GFAP, and IBA-1. Furthermore, the levels of NMDAR, PKC, Src, enzymes linked to neural hypersensitivity, was inhibited by RIN1 silencing. RIN1 was found to interact to Nrf2 protein, inhibiting its nuclear translocation and transcriptional activation. The RIN1 knockdown activated the Nrf2/HO-1 pathway, reducing oxidative stress and ROS levels in the spinal cord, while increasing the expression of Nrf2-target genes, including Nqo1, Gclc, and Gclm, which are key players in cellular antioxidant defense. Additionally, ferroptosis, characterized by mitochondrial damage and elevated Fe2+ levels, was reduced in RIN1 knockdown rats. Treatment with Nrf2 or HO-1 activators improved pain sensitivity and reduced inflammation, while inhibition of Nrf2 activity attenuated the protective effects of RIN1 silencing. In vitro, RIN1 silencing reduced activation LPS-treated of mouse BV2 microglial cells, leading to a decrease in the secretion of pro-inflammatory cytokines (IL-6, TNFα, and IL-1β), reduced microglial ferroptosis, and decreased the cytotoxicity of BV2 cells to co-cultured neurons. These effects were mediated by the Nrf2 pathway, as Nrf2 antagonism reversed the effects of RIN1 knockdown. These findings suggest that RIN1 plays a critical role in spinal cord hypersensitivity and pain perception by inhibiting the Nrf2/HO-1 pathway, influencing neuroinflammation and ferroptosis. Targeting RIN1 could provide a potential therapeutic strategy for managing NP and neuroinflammation.

Role of efferocytosis in chronic pain -- From molecular perspective

The complex nature of pain pathophysiology complicates the establishment of objective diagnostic criteria and targeted treatments. The heterogeneous manifestations of pain stemming from various primary diseases contribute to the complexity and diversity of underlying mechanisms, leading to challenges in treatment efficacy and undesirable side effects. Recent evidence suggests the presence of apoptotic cells at injury sites, the distal dorsal root ganglia (DRG), spinal cord, and certain brain regions, indicating a potential link between the ineffective clearance of dead cells and debris and pain persistence. This review highlights recent research findings indicating that efferocytosis plays a significant yet often overlooked role in lesion expansion while also representing a potentially reversible impairment that could be targeted therapeutically to mitigate chronic pain progression. We examine recent advances into how efferocytosis, a process by which phagocytes clear apoptotic cells without triggering inflammation, influences pain initiation and intensity in both human diseases and animal models. This review summarizes that efferocytosis contributes to pain progression from the perspective of defective and inefficient efferocytosis and its subsequent secondary necrocytosis, cascade inflammatory response, and the shift of phenotypic plasticity and metabolism. Additionally, we investigate the roles of newly discovered genetic alterations or modifications in biological signaling pathways in pain development and chronicity, providing insights into innovative treatment strategies that modulate efferocytosis, which are promising candidates and potential avenues for further research in pain management and prevention.

Ferroptosis in Endometriosis: Traditional Chinese Medicine Interventions and Mechanistic Insights

Endometriosis (EMS) is a chronic, estrogen-dependent inflammatory disease affecting 5-10% of women of reproductive age, characterized by the growth of endometrial tissue on the outside of the uterus. The dysregulation of iron metabolism leads to the accumulation of iron ions at the lesion sites, resulting in oxidative stress and pro-inflammatory responses that promote the progression of EMS. The mechanisms underlying ferroptosis in EMS primarily involve iron accumulation, lipid peroxidation, and loss of glutathione peroxidase 4 activity. These mechanisms confer resistance to ferroptosis within the ectopic tissues and facilitate cell survival and proliferation. Traditional Chinese medicine (TCM) has demonstrated therapeutic potential for modulating ferroptosis. Studies have shown that TCM monomers may regulate ferroptosis by modulating iron transport proteins and anti-oxidant defense mechanisms. TCM formulas employ distinct treatment strategies depending on the stage of EMS: in the early stages, they promote ferroptosis to control lesion growth, whereas in the later stages, they inhibit ferroptosis to reduce oxidative stress and inflammation in order to improve reproductive health and slow disease progression. This study provides a new perspective on potential therapeutic strategies for the management of EMS by summarizing the role of ferroptosis in its pathological mechanisms and reviewing findings on the use of TCM in regulating ferroptosis.

Hypoxia-inducible factor-1 as targets for neuroprotection : from ferroptosis to Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disease characterized by motor paralysis, tremor,and cognitive impairment. Risk factors such as brain hypoxia caused by aging and abnormal expression of HIF-1α areconsidered to be key to the development of PD, including α-synuclein accumulation and ferroptosis. However, therelationship between HIF-1α signaling and ferroptosis in PD has not been elucidated. The stable expression of HIF-1αinhibits the pathological development of PD. Aging aggravates PD pathology by promoting α-synuclein accumulationand oxidative stress.

METHODS

The literature on lipid peroxidation, oxidative stress, iron metabolism and other key factors in Parkinson'sdisease in recent years was reviewed through a variety of literature search channels, such as PubMed and Elsevier.

RESULTS

HIF-1α mediated ferroptosis through oxidative stress and GPX4-GSH system. HIF-1α mediates ferroptosisthrough Keap1-Nrf2-ARE, Grx3 and Grx4. HIF-1α mediates ferroptosis through iron metabolism.

CONCLUSION

This article reviews the oxygen-dependent regulatory mechanism of HIF-1α and its role in cerebralhypoxia homeostasis. Studies in the past decade have shown that Hif-1α mediated ferroptosis is important in PD.HIF-1α has a dual role, depending on the degree of cellular hypoxia and the environment. The equilibrium complexityneeds to be explained, and the role of ferroptosis needs to be investigated. The literature shows that the stabilizationof HIF-1α with PHD inhibitors and the combination of antioxidants and iron chelators are potential therapeuticdirections. In the future, the optimal use time and dose of inhibitors should be studied to improve the efficacy.

Mechanisms and Therapeutic Potential of GPX4 in Pain Modulation

Pain, a complex symptom encompassing both sensory and emotional dimensions, constitutes a significant global public health issue. Oxidative stress is a pivotal factor in the complex pathophysiology of pain, with glutathione peroxidase 4 (GPX4) recognized as a crucial antioxidant enzyme involved in both antioxidant defense mechanisms and ferroptosis pathways. This review systematically explores GPX4's functions across various pain models, including neuropathic, inflammatory, low back, and cancer-related pain. Specifically, the focus includes GPX4's physiological roles, antioxidant defense mechanisms, regulation of ferroptosis, involvement in signal transduction pathways, and metabolic regulation. By summarizing current research, we highlight the potential of GPX4-targeted therapies in pain management.

TRIM28 Fosters Microglia Ferroptosis via Autophagy Modulation to Enhance Neuropathic Pain and Neuroinflammation

This study explores the molecular underpinnings of neuropathic pain (NPP) and neuroinflammation, focusing on the role of TRIM28 in the regulation of autophagy and microglia ferroptosis. Leveraging transcriptomic data associated with NPP, we identified TRIM28 as a critical regulator of ferroptosis. Through comprehensive analysis, including Gene Ontology enrichment and protein-protein interaction network assessments, we unveiled GSK3B as a downstream target of TRIM28. Experimental validation confirmed the capacity of TRIM28 to suppress GSK3B expression and attenuate autophagic processes in microglia. We probed the consequences of autophagy and ferroptosis on microglia physiology, iron homeostasis, oxidative stress, and the release of proinflammatory cytokines. In a murine model, we validated the pivotal role of TRIM28 in NPP and neuroinflammation. Our analysis identified 20 ferroptosis regulatory factors associated with NPP, with TRIM28 emerging as a central orchestrator. Experimental evidence affirmed that TRIM28 governs microglial iron homeostasis and cell fate by downregulating GSK3B expression and modulating autophagy. Notably, autophagy was found to influence oxidative stress and proinflammatory cytokine release through the iron metabolism pathway, ultimately fueling neuroinflammation. In vivo experiments provided conclusive evidence of TRIM28-mediated pathways contributing to heightened pain sensitivity in neuroinflammatory states. The effect of TRIM28 on autophagy and microglia ferroptosis drives NPP and neuroinflammation. These findings offer promising avenues for identifying novel therapeutic targets to manage NPP and neuroinflammation.

Identification of Cytisine Derivatives as Agonists of the Human Delta Opioid Receptor by Supercomputer-Based Virtual Drug Screening and Transcriptomics

Delta opioid receptors (DORs) are rising as therapeutic targets, not only for the treatment of pain but also other neurological disorders (e.g., Parkinson's disease). The advantage of DOR agonists compared to μ-opioid receptor agonists is that they have fewer side effects and a lower potential to induce tolerance. However, although multiple candidates have been tested in the past few decades, none have been approved for clinical use. The current study focused on searching for new DOR agonists by screening a chemical library containing 40,000 natural and natural-derived products. The functional activity of the top molecules was evaluated in vitro through the cyclic adenosine monophosphate accumulation assay. Compound 3 showed promising results, and its activity was further investigated through transcriptomic methods. Compound 3 inhibited the expression of TNF-α, prevented NF-κB translocation to the nucleus, and activated the G-protein-mediated ERK1/2 pathway. Additionally, compound 3 is structurally different from known DOR agonists, making it a valuable candidate for further investigation for its anti-inflammatory and analgesic potential.

Vitamin D3 Attenuates Neuropathic Pain via Suppression of Mitochondria-Associated Ferroptosis by Inhibiting PKCα/NOX4 Signaling Pathway

AIMS

Neuropathic pain remains a significant unmet medical challenge due to its elusive mechanisms. Recent clinical observations suggest that vitamin D (VitD) holds promise in pain relief, yet its precise mechanism of action is still unclear. This study explores the therapeutical role and potential mechanism of VitD3 in spared nerve injury (SNI)-induced neuropathic pain rat model.

METHODS

The analgesic effects and underlying mechanisms of VitD3 were evaluated in SNI and naïve rat models. Mechanical allodynia was assessed using the Von Frey test. Western blotting, immunofluorescence, biochemical assay, and transmission electron microscope (TEM) were employed to investigate the molecular and cellular effects of VitD3.

RESULTS

Ferroptosis was observed in the spinal cord following SNI. Intrathecal administration of VitD3, the active form of VitD, activated the vitamin D receptor (VDR), suppressed ferroptosis, and alleviated mechanical nociceptive behaviors. VitD3 treatment preserved spinal GABAergic interneurons, and its neuroprotective effects were eliminated by the ferroptosis inducer RSL3. Additionally, VitD3 mitigated aberrant mitochondrial morphology and oxidative metabolism in the spinal cord. Mechanistically, VitD3 inhibited SNI-induced activation of spinal PKCα/NOX4 signaling. Inhibition of PKCα/NOX4 signaling alleviated mechanical pain hypersensitivity, accompanied by reduced ferroptosis and mitochondrial dysfunction in SNI rats. Conversely, activation of PKCα/NOX4 signaling in naïve rats induced hyperalgesia, ferroptosis, loss of GABAergic interneurons, and mitochondrial dysfunction in the spinal cord, all of which were reversed by VitD3 treatment.

CONCLUSIONS

Our findings provide evidence that VitD3 attenuates neuropathic pain by preserving spinal GABAergic interneurons through the suppression of mitochondria-associated ferroptosis mediated by PKCα/NOX4 signaling, probably via VDR activation. VitD, alone or in combination with existing analgesics, presents an innovative therapeutic avenue for neuropathic pain.

Daphnetin Ameliorates Neuropathic Pain via Regulation of Microglial Responses and Glycerophospholipid Metabolism in the Spinal Cord

Neuropathic pain (NP) is a common type of chronic pain caused by a lesion or disease of the somatosensory nervous system. This condition imposes a considerable economic burden on society and patients. Daphnetin (DAP) is a natural product isolated from a Chinese medicinal herb with various pharmacological activities, such as anti-inflammatory and analgesic properties. However, the underlying mechanisms of these effects are not fully understood. In the present study, we aimed to investigate DAP's anti-inflammatory and analgesic effects and explore the underlying mechanisms of action. The NP model was established as chronic constrictive injury (CCI) of the sciatic nerve, and pain sensitivity was evaluated by measuring the mechanical withdrawal threshold (MWT) and thermal withdrawal threshold (TWT). The activation of microglia in the spinal dorsal horn was measured via immunofluorescence staining. Protein levels were measured using a western blot assay. Using a mass-spectrometry proteomics platform and an LC-MS/MS-based metabolomics platform, proteins and metabolites in spinal cord tissues were extracted and analyzed. DAP treatment ameliorated the MWT and TWT in CCI rats. The expression of IL-1β, IL-6, and TNF-α was inhibited by DAP treatment in the spinal cords of CCI rats. Moreover, the activation of microglia was suppressed after DAP treatment. The elevation in the levels of P2X4, IRF8, IRF5, BDNF, and p-P38/P38 in the spinal cord caused by CCI was inhibited by DAP. Proteomics and metabolomics results indicated that DAP ameliorated the imbalance of glycerophospholipid metabolism in the spinal cords of CCI rats. DAP can potentially ameliorate NP by regulating microglial responses and glycerophospholipid metabolism in the CCI model. This study provides a pharmacological justification for using DAP in the management of NP.

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.

Neuroinflammation and Neurodegenerative Diseases: How Much Do We Still Not Know?

The term "neuroinflammation" defines the typical inflammatory response of the brain closely related to the onset of many neurodegenerative diseases (NDs). Neuroinflammation is well known, but its mechanisms and pathways are not entirely comprehended. Some progresses have been achieved through many efforts and research. Consequently, new cellular and molecular mechanisms, diverse and conventional, are emerging. In listing some of those that will be the subject of our description and discussion, essential are the important roles of peripheral and infiltrated monocytes and clonotypic cells, alterations in the gut-brain axis, dysregulation of the apelinergic system, alterations in the endothelial glycocalyx of the endothelial component of neuronal vascular units, variations in expression of some genes and levels of the encoding molecules by the action of microRNAs (miRNAs), or other epigenetic factors and distinctive transcriptional factors, as well as the role of autophagy, ferroptosis, sex differences, and modifications in the circadian cycle. Such mechanisms can add significantly to understanding the complex etiological puzzle of neuroinflammation and ND. In addition, they could represent biomarkers and targets of ND, which is increasing in the elderly.