Ulinastatin Ameliorates IL-1β-Induced Cell Dysfunction in Human Nucleus Pulposus Cells via Nrf2/NF-κB Pathway

A2AR regulate inflammation through PKA/NF-κB signaling pathways in intervertebral disc degeneration

BACKGROUND

Reduction of inflammatory damage and inhibition of nucleus pulposus (NP) apoptosis are considered to be the main effective therapy idea to reverse the intervertebral disc degeneration (IDD) and alleviate the chronic low back pain. The adenosine A2A receptor (A2AR), as a member of G protein-coupled receptor families, plays an important role in the anti-inflammation and relieving pain. So far, the impact of A2AR on IDD therapy is unclear. The aim of this study was to explore the role of Adenosine A2A receptor (A2AR) in the intervertebral disc degeneration (IDD) and clarify potential mechanism.

MATERIALS AND METHODS

IL-1β and acupuncture was used to establish IDD model rats. A2AR agonist CGS-21680 and A2AR antagonist SCH442416 were used to investigate the therapeutical effects for IDD. Histological examination, western blotting analysis and RT-PCR were employed to evaluate the the association between A2AR and cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway.

RESULTS

A2AR activity of the intervertebral disc tissues was up-regulated in feedback way, and cAMP, PKA and CREB expression were also increased. But in general, IL-1β-induced IDD promoted the significant up-regulation the expression of inflammatory factors. The nucleus pulposus (NP) inflammation was exacerbated in result of MMP3 and Col-II decline through activating NF-κB signaling pathway. A2AR agonist CGS-21680 exhibited a disc protective effect through significantly increasing A2AR activity, then further activated cAMP/PKA signaling pathway with attenuating the release of TNF-α and IL-6 via down-regulating NF-κB. In contrast, SCH442416 inhibited A2AR activation, consistent with lower expression levels of cAMP and PKA, further leading to the acceleration of IDD.

CONCLUSIONS

The activation of A2AR can prevent inflammatory responses and mitigates degradation of IDD thus suggest a potential novel therapeutic strategy of IDD.

Ephrin B2 (EFNB2) potentially protects against intervertebral disc degeneration through inhibiting nucleus pulposus cell apoptosis

Nucleus pulposus (NP) cell apoptosis is a significant indication of accelerated intervertebral disc degeneration; however, the precise mechanism is unelucidated as of yet. Ephrin B2 (EFNB2), the only gene down-regulated in the three degraded intervertebral disc tissue microarray groups (GSE70362, GSE147383 and GSE56081), was screened for examination in this study. Subsequently, EFNB2 was verified to be down-regulated in degraded NP tissue samples. Interleukin-1 (IL-1β) treatment of NP cells to simulate the IDD environment indicated that IL-1β treatment decreased EFNB2 expression. In degenerative NP cells stimulated by IL-1β, EFNB2 knockdown significantly increased the rate of apoptosis as well as the apoptosis-related molecules cleaved-caspase-3 and the Bax to Bcl-2 ratio. EFNB2 was found to promote AKT, PI3K, and mTOR phosphorylation; the PI3K/AKT signaling role was investigated using the PI3K inhibitor LY294002. EFNB2 overexpression significantly increased PI3K/AKT pathway activity in IL-1β-stimulated NP cells than the normal control. Moreover, EFNB2 partially alleviated NP cell apoptosis induced by IL-1β, reduced the cleaved-cas3 level, and decreased the Bax/Bcl-2 ratio after the addition of the inhibitor LY294002. Additionally, EFNB2 overexpression inhibited the ERK1/2 phosphorylation; the effects of EFNB2 overexpression on ERK1/2 phosphorylation, degenerative NP cell viability, and cell apoptosis were partially reversed by ERK signaling activator Ceramide C6. EFNB2 comprehensively inhibited the apoptosis of NP cells by activating the PI3K/AKT signaling and inhibiting the ERK signaling, obviating the exacerbation of IDD. EFNB2 could be a potential target to protect against degenerative disc changes.

The mitochondrial UPR induced by ATF5 attenuates intervertebral disc degeneration via cooperating with mitophagy

Intervertebral disc degeneration (IVDD) is an aging disease that results in a low quality of life and heavy socioeconomic burden. The mitochondrial unfolded protein response (UPRmt) take part in various aging-related diseases. Our research intents to explore the role and underlying mechanism of UPRmt in IVDD. Nucleus pulposus (NP) cells were exposed to IL-1β and nicotinamide riboside (NR) served as UPRmt inducer to treat NP cells. Detection of ATP, NAD + and NADH were used to determine the function of mitochondria. MRI, Safranin O-fast green and Immunohistochemical examination were used to determine the degree of IVDD in vivo. In this study, we discovered that UPRmt was increased markedly in the NP cells of human IVDD tissues than in healthy controls. In vitro, UPRmt and mitophagy levels were promoted in NP cells treated with IL-1β. Upregulation of UPRmt by NR and Atf5 overexpression inhibited NP cell apoptosis and further improved mitophagy. Silencing of Pink1 reversed the protective effects of NR and inhibited mitophagy induced by the UPRmt. In vivo, NR might attenuate the degree of IDD by activating the UPRmt in rats. In summary, the UPRmt was involved in IVDD by regulating Pink1-induced mitophagy. Mitophagy induced by the UPRmt might be a latent treated target for IVDD.

Esculetin Alleviates IL-1β-Evoked Nucleus Pulposus Cell Death, Extracellular Matrix Remodeling, and Inflammation by Activating Nrf2/HO-1/NF-kb

Inflammation, extracellular matrix metabolic dysfunction, and oxidative stress are key pathogenic characteristics of intervertebral disk degeneration (IVDD), a major pathogenic cause of low back pain. Esculetin possesses anti-injury, anti-inflammation, and antinociceptive properties. This study aimed to explore its role in IVDD. In this research, esculetin exhibited little cytotoxicity to human nucleus pulposus cells (NPCs). Moreover, esculetin increased cell viability under IL-1β stimulation but attenuated IL-1β-induced cell apoptosis and caspase-3 activity. Furthermore, IL-1β-evoked increases in intracellular reactive oxygen species and malondialdehyde (MDA) levels, and decreases in superoxide dismutase (SOD) activity were reversed after esculetin treatment, indicating the antioxidative stress efficacy of esculetin. Esculetin alleviated the inhibitory effects of IL-1β on the transcription and protein expression of anabolic biomarkers (collagen II and aggrecan), accompanied by decreases in expression and release of catabolic biomarkers MMP-3 and MMP-13 from NPCs. Moreover, IL-1β exposure enhanced the expression levels of the inflammatory mediator nitric oxide and inflammatory cytokine IL-6 and TNF-α, which were overturned after esculetin treatment. Additionally, esculetin activated the nuclear factor-erythroid 2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) to inhibit the activation of nuclear factor κB (NF-κB) signaling in NPCs. Importantly, suppression of Nrf2 signaling reversed the protective efficacy of esculetin against IL-1β-mediated oxidative injury, matrix metabolism disruption, and inflammatory response in NPCs. Together, esculetin may alleviate IL-1β-induced dysfunction in NPCs by regulating the Nrf2/HO-1/NF-kb signaling, indicating its potential as a promising therapeutic agent against IVDD.

Clinical Efficacy of Ulinastatin Combined with Azithromycin in the Treatment of Severe Pneumonia in Children and the Effects on Inflammatory Cytokines and Oxidative Stress: A Retrospective Cohort Study

Purpose

This retrospective cohort study aimed to evaluate the clinical efficacy of ulinastatin (UTI) and azithromycin (AZM) combination therapy in treating severe pneumonia in children and its impact on inflammatory cytokines and oxidative stress.

Patients and Methods

This retrospective cohort study was conducted from January 1, 2019, to January 1, 2021, involving pediatric patients diagnosed with severe mycoplasma pneumonia (SMPP). The pediatric patients were divided into two groups: those receiving UTI and AZM combination therapy (treatment group) and those receiving azithromycin alone (control group). We compared the two groups regarding clinical data, disease outcomes, inflammatory cytokines, and oxidative stress levels.

Results

Baseline characteristics did not significantly differ between the two groups. UTI, in combination with AZM, significantly improved blood oxygen levels, inflammatory infection markers, and relevant clinical symptoms in patients with SMPP on the 3rd day of treatment. Additionally, it significantly reduced the levels of inflammatory cytokines TNF-a, IL-6, IL-1β, and IL-10, as well as oxidative stress markers GSH and SOD.

Conclusion

Combining UTI and AZM can rapidly alleviate clinical symptoms and effectively control the progression of patients with SMPP. Therefore, this treatment approach deserves consideration for clinical promotion and utilization.

MSC-Derived Exosomes Ameliorate Intervertebral Disc Degeneration By Regulating the Keap1/Nrf2 Axis

Bone marrow mesenchymal stem cell derived exosomes (BMSC-exos) are a crucial means of intercellular communication and can regulate a range of biological processes by reducing inflammation, decreasing apoptosis and promoting tissue repair. The process of intervertebral disc degeneration (IVDD) is accompanied by increased reactive oxygen species (ROS) because of a decrease in the expression of Nrf2, a critical transcription factor that resists excessive ROS. Our study demonstrated that BMSC-exos decreased ROS production by inhibiting Keap1 and promoting Nrf2 expression, attenuating the apoptosis, inflammation, and degeneration of nucelus pulposus (NP) cells. BMSC-exos promoted an increase in Nrf2 and nuclear translocation, while NF-κB expression was downregulated during this process. Additionally, the expression of antioxidative proteins was elevated after treatment with BMSC-exos. In vivo, we found more NP tissue retention in the BMSC-exos-treated group, along with more expression of Nrf2 and antioxidant-related proteins. Our findings demonstrated for the first time that BMSC-exos could restore the down-regulated antioxidant response system in degenerating NP cells by modulating the Keap1/Nrf2 axis. BMSC-exos could be used as an immediate ROS modulator in the treatment of intervertebral disc degeneration. When BMSC-exos were uptaken by NPCs, the expression of Keap1 decreased and this led to increased expression of Nrf2. Nuclear translocation of Nrf2 then promoted the synthesis of antioxidants against ROS and inhibited NF-kB signalling. Cellular inflammation, apoptosis, and ECM-related indicators were further reduced. Together, the process of IVDD was alleviated.

Fucoidan-functionalized gelatin methacryloyl microspheres ameliorate intervertebral disc degeneration by restoring redox and matrix homeostasis of nucleus pulposus

Loss of extracellular matrix (ECM) and dehydration of the nucleus pulposus (NP) are major pathological characteristics of intervertebral disc degeneration (IVDD), the leading cause of low back pain. Excessive reactive oxygen species (ROS) induced by proinflammatory cytokines substantially contribute to IVDD pathogenesis. This study aimed to examine the potential of fucoidan in protecting the matrix metabolism of NP cells and its therapeutic efficacy in the prevention of IVDD. In an inflammatory environment induced by interleukin (IL)-1β, fucoidan treatments demonstrated a dose-dependent enhancement of ECM production in NP cells, while concurrently reducing the expression of matrix degradation enzymes. The protective effect of fucoidan was mediated through the activation of nuclear factor erythroid 2-related factor 2 (NRF2) and subsequent induction of antioxidant enzymes, whereas silencing Nrf2 abrogated the protection of fucoidan on NP cells against IL-1β-induced oxidative stress. Moreover, a novel fucoidan-functionalized gelatin methacryloyl microsphere (Fu@GelMA-MS) was synthesized. The in vivo application of Fu@GelMA-MS via in situ injection in a rat caudal IVD model effectively conserved the ECM components and maintained the hydration of the NP tissue, thereby preventing IVDD caused by puncture. Collectively, fucoidan-functionalized hydrogel microspheres represent a promising strategy for the regeneration of NP and the treatment of IVDD.

IL-1β-mediated inflammatory responses in intervertebral disc degeneration: Mechanisms, signaling pathways, and therapeutic potential

Intervertebral disc degeneration (IDD) has been widely recognized as the primary cause of low back pain and is one of the major chronic diseases imposing a severe socioeconomic burden worldwide. IDD is a degenerative process characterized by inflammatory responses, and its underlying pathological mechanisms remain complex. Genetic, developmental, biochemical, and biomechanical factors contribute to the development of IDD. There is a pressing need for an effective non-surgical treatment, mainly due to the lack of comprehensive understanding of the specific mechanisms involved and the effective therapeutic targets for IDD. Recently, interleukin (IL)-1β has been recognized as an essential inflammatory factor and a key mediator of the inflammatory process in IDD. Current studies have found that IL-1β is mainly involved in IDD by affecting the metabolism of the extracellular matrix and regulating cell death (RCD), such as apoptosis, pyroptosis, and ferroptosis (a new form of RCD). Although analysis of clinical samples from different laboratories confirmed how IL-1β is induced in IDD, its specific signal transduction pathway, and the inflammatory role mediated in IDD remains unclear. This review describes the molecules and mechanisms involved in IL-1β-mediated inflammatory responses, and their roles in resolving the inflammatory process in IDD. Understanding the signaling pathways involved in IL-1β may lead to a new class of targets that promote remission for IDD patients. This review aims to provide a framework for the treatment of IDD by analyzing the signaling mechanism and function related to IL-1β, especially in terms of inflammation, matrix metabolism, and cell death regulation.

Baicalin suppresses interleukin-1β-induced apoptosis, inflammatory response, oxidative stress, and extracellular matrix degradation in human nucleus pulposus cells

OBJECTIVE

To explore the effect of baicalin on human nucleus pulposus cells (NPCs) in response to interleukin (IL)-1β stimulation.

METHODS

Viability of NPCs was measured by cell counting kit-8 (CCK-8) assay. TUNEL staining assay and flow cytometry were performed to detect apoptotic cell death of NPCs. Western blot analysis was conducted to detect the expression levels of proteins. Enzyme-linked immunosorbent assay (ELISA) was applied for the determination of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor alpha (TNF-α), and IL-6. Oxidative stress indicators including reactive oxygen species (ROS) production, malondialdehyde (MDA) level, and superoxide dismutase (SOD) activity were measured.

RESULTS

Baicalin attenuated IL-1β-caused cell viability reduction and apoptosis in NPCs. IL-1β-induced increase in Bax expression and decrease in Bcl-2 expression were attenuated by baicalin treatment. IL-1β-induced production of iNOS, COX-2, IL-6, and TNF-α in NPCs was inhibited by baicalin treatment. Baicalin treatment reversed IL-1β-induced increase in ROS production and MDA level, as well as decrease in SOD activity. Furthermore, baicalin treatment elevated the expression levels of Col II and Aggrecan and downregulated the expression levels of MMP3, MMP13, and ADAMTS5 in IL-1β-induced NPCs. A total of 402 related targets of baicalin and 134 related targets of intervertebral disk degeneration were found, and nine intersection targets were screened out. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that mitogen-activated protein kinase (MAPK) pathway was found to be involved in the effects of baicalin.

CONCLUSIONS

Baicalin exhibited protective effects on IL-1β-caused cell viability reduction, apoptosis, oxidative stress, inflammation, and extracellular matrix degradation in NPCs. In addition, we found c-Jun N-terminal kinase (JNK) and p38 MAPK pathways as targets of baicalin through bioinformatic analysis.

Sesn2 Serves as a Regulator between Mitochondrial Unfolded Protein Response and Mitophagy in Intervertebral Disc Degeneration

Mitochondrial unfold protein response (UPR^mt) can induce mitophagy to protect cell from unfold protein. However, how UPR^mt induces mitophagy to protect cell is not yet clear. Herein, Sesn2 was considered to be a key molecule that communicated UPR^mt and mitophagy in the intervertebral disc. Silencing of Sesn2 was able to reverse the protective effects of Nicotinamide riboside (NR) on nucleus pulposus (NP) cells and inhibit mitophagy induced by UPR^mt. UPR^mt upregulated Sesn2 through Eif2ak4/eIF2α/Atf4, and further induced mitophagy. Sesn2 promoted the translocation of cytosolic Parkin and Sqstm1 to the defective mitochondria respectively, thereby enhancing mitophagy. The translocation of cytosolic Sqstm1 to the defective mitochondria was dependent on Parkin. The two functional domains of Sesn2 were necessary for the interaction of Sesn2 with Parkin and Sqstm1. The cytosolic interaction of Sesn2 between Parkin and Sqstm1 was independent on Pink1 (named as PINK1 in human) but the mitochondrial translocation was dependent on Pink1. Sesn2-/- mice showed a more severe degeneration and NR did not completely alleviate the intervertebral disc degeneration (IVDD) of Sesn2-/- mice. In conclusion, UPR^mt could attenuate IVDD by upregulation of Sesn2-induced mitophagy. This study will help to further reveal the mechanism of Sesn2 regulating mitophagy, and open up new ideas for the prevention and treatment of IVDD.

Disc regeneration by injectable fucoidan-methacrylated dextran hydrogels through mechanical transduction and macrophage immunomodulation

Modulating a favorable inflammatory microenvironment that facilitates the recovery of degenerated discs is a key strategy in the treatment of intervertebral disc (IVD) degeneration (IDD). More interestingly, well-mechanized tissue-engineered scaffolds have been proven in recent years to be capable of sensing mechanical transduction to enhance the proliferation and activation of nucleus pulposus cells (NPC) and have demonstrated an increased potential in the treatment and recovery of degenerative discs. Additionally, existing surgical procedures may not be suitable for IDD treatment, warranting the requirement of new regenerative therapies for the restoration of disc structure and function. In this study, a light-sensitive injectable polysaccharide composite hydrogel with excellent mechanical properties was prepared using dextrose methacrylate (DexMA) and fucoidan with inflammation-modulating properties. Through numerous in vivo experiments, it was shown that the co-culture of this composite hydrogel with interleukin-1β-stimulated NPCs was able to promote cell proliferation whilst preventing inflammation. Additionally, activation of the caveolin1-yes-associated protein (CAV1-YAP) mechanotransduction axis promoted extracellular matrix (ECM) metabolism and thus jointly promoted IVD regeneration. After injection into an IDD rat model, the composite hydrogel inhibited the local inflammatory response by inducing macrophage M2 polarization and gradually reducing the ECM degradation. In this study, we propose a fucoidan-DexMA composite hydrogel, which provides an attractive approach for IVD regeneration.

lncRNA ZFAS1 promotes intervertebral disc degeneration by upregulating AAK1

We investigated the function of lncRNA zinc finger antisense 1 (ZFAS1) in intervertebral disc degeneration (IDD) progression in vitro and in vivo. Nucleus pulposus (NP) tissues were obtained from 20 patients with IDD. IL-1β was used to stimulate primary NP cells to establish the IDD models in vitro. Gene expression was determined by RT-qPCR. 5-Ethynyl-2'-deoxyuridine and flow cytometry were performed to determine cell proliferation and apoptosis, and western blotting was conducted to measure the apoptosis- and extracellular matrix (ECM)-related protein expression. Luciferase reporter assay was used to examine the interactions between the genes. We also investigated the effect of ZFAS1 in a mouse model of IDD induced by needle punctures. Our results showed that ZFAS1 expression was elevated in degenerative NP tissues and IL-1β-treated NP cells. ZFAS1 knockdown inhibited NP cell apoptosis and ECM degradation induced by IL-1β. Mechanically, ZFAS1 sponged miR-4711-5p and adaptor-associated kinase 1 (AAK1) was targeted by miR-4711-5p. Furthermore, AAK1 overexpression partially eliminated the impact of ZFAS1 depletion on NP cell proliferation, apoptosis, and ECM degradation. More importantly, the results of the in vivo studies confirmed the effect of silencing ZFAS1 on alleviating the symptoms of IDD mice. Overall, silencing ZFAS1 inhibits IDD progression by reducing NP cell apoptosis and ECM degradation through the miR-4711-5p/AAK1 axis.

Ulinastatin attenuates spinal cord injury by targeting AMPK/NLRP3 signaling pathway

The AMPK and NLRP3 inflammasome signaling pathways are reported to participant in the inflammatory responses following spinal cord injury (SCI). Ulinastatin (ULI) is a urinary trypsin inhibitor with excellent anti-inflammatory effects, but the functions of ULI on SCI are rarely reported. Hence, this study was designed to investigate whether ULI could modulate SCI through regulating the AMPK/NLRP3 signaling pathway. Cell Counting Kit-8 (CCK-8) assays were used to investigate whether ULI had cytotoxic effects on BV-2 cells. Basso-Beattie-Bresnahan (BBB) scale, spinal cord water content detection, hematoxylin-eosin (HE) and Nissl stainings were used to investigate the protective effects of ULI on rat SCI. The expressions of inflammatory cytokines were detected by ELISA and RT-qPCR. The expressions of key proteins of AMPK and NLRP3 inflammasome were analyzed by western blot. The CCK-8 assays indicated that ULI did not significantly influence the viability of BV-2 cells at various concentrations below 10,000 U/ml. It was witnessed that ULI could dramatically inhibit the activation of NLRP3 inflammasome via activating the AMPK signaling pathway, thus relieving inflammatory responses. Besides, the in vivo experiment suggested that treatment with ULI remarkably relieve spinal cord edema, ameliorated spinal cord tissue architecture, and improved neurological function following SCI. The findings indicate that ULI significantly ameliorates neurological function following SCI by regulating the AMPK/NLRP3 inflammasome signaling pathway.

The role of nerve fibers and their neurotransmitters in regulating intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) has been the major contributor to chronic lower back pain (LBP). Abnormal apoptosis, senescence, and pyroptosis of IVD cells, extracellular matrix (ECM) degradation, and infiltration of immune cells are the major molecular alternations during IVDD. Changes at tissue level frequently occur at advanced IVD tissue. Ectopic ingrowth of nerves within inner annulus fibrosus (AF) and nucleus pulposus (NP) tissue has been considered as the primary cause for LBP. Innervation at IVD tissue mainly included sensory and sympathetic nerves, and many markers for these two types of nerves have been detected since 1940. In fact, in osteoarthritis (OA), beyond pain transmission, the direct regulation of neuropeptides on functions of chondrocytes have attracted researchers' great attention recently. Many physical and pathological similarities between joint and IVD have shed us the light on the neurogenic mechanism involved in IVDD. Here, an overview of the advances in the nervous system within IVD tissue will be performed, with a discussion on in the role of nerve fibers and their neurotransmitters in regulating IVDD. We hope this review can attract more research interest to address neuromodulation and IVDD itself, which will enhance our understanding of the contribution of neuromodulation to the structural changes within IVD tissue and inflammatory responses and will help identify novel therapeutic targets and enable the effective treatment of IVDD disease.

Role of Nrf2 and HO-1 in intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is a common age-related disease with clinical manifestations of lumbar and leg pain and limited mobility. The pathogenesis of IDD is mainly mediated by the death of intervertebral disc (IVD) cells and the imbalance of extracellular matrix (ECM) synthesis and degradation. Oxidative stress and inflammatory reactions are the important factors causing this pathological change. Therefore, the regulation of reactive oxygen species and production of inflammatory factors may be an effective strategy to delay the progression of IDD. In recent years, nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream regulated protein heme oxygenase-1 (HO-1) have received special attention due to their antioxidant, anti-inflammatory and anti-apoptotic protective effects. Recent studies have elucidated the important role of these two proteins in the treatment of IDD disease. However, Nrf2 and HO-1 have not been systematically reported in IDD-related diseases. Therefore, this review describes the biological characteristics of Nrf2 and HO-1, the relationship between Nrf2- and HO-1-regulated oxidative stress and the inflammatory response and IDD, and the progress in research on some extracts targeting Nrf2 and HO-1 to improve IDD. Understanding the role and mechanism of Nrf2 and HO-1 in IDD may provide novel ideas for the clinical treatment and development of Nrf2- and HO-1-targeted drugs.

The Nrf2 antioxidant defense system in intervertebral disc degeneration: Molecular insights

Intervertebral disc degeneration (IDD) is a common degenerative musculoskeletal disorder and is recognized as a major contributor to discogenic lower back pain. However, the molecular mechanisms underlying IDD remain unclear, and therapeutic strategies for IDD are currently limited. Oxidative stress plays pivotal roles in the pathogenesis and progression of many age-related diseases in humans, including IDD. Nuclear factor E2-related factor 2 (Nrf2) is a master antioxidant transcription factor that protects cells against oxidative stress damage. Nrf2 is negatively modulated by Kelch-like ECH-associated protein 1 (Keap1) and exerts important effects on IDD progression. Accumulating evidence has revealed that Nrf2 can facilitate the transcription of downstream antioxidant genes in disc cells by binding to antioxidant response elements (AREs) in promoter regions, including heme oxygenase-1 (HO-1), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and NADPH quinone dehydrogenase 1 (NQO1). The Nrf2 antioxidant defense system regulates cell apoptosis, senescence, extracellular matrix (ECM) metabolism, the inflammatory response of the nucleus pulposus (NP), and calcification of the cartilaginous endplates (EP) in IDD. In this review, we aim to discuss the current knowledge on the roles of Nrf2 in IDD systematically.

Insights into the activity of a protein that regulates gene expression and protects cells against oxidative stress could yield novel treatments for lower back pain. Intervertebral disc degeneration (IDD) is a common cause of lower back pain, but the molecular mechanisms underlying IDD are unclear, meaning treatment options are limited. Oxidative stress is implicated in IDD, and scientists have begun exploring the role of nuclear factor E2-related factor 2 (Nrf2), a master regulator of the body’s antioxidant responses, in regulating IDD progression. In a review of recent research, Weishi Li at Peking University Third Hospital, Beijing, China, and co-workers point out that boosting the activity of Nrf2-related signaling pathways alleviates oxidative stress in intervertebral disc cells. The researchers suggest that therapies based on non-coding RNAs may prove valuable in activating Nrf2 in IDD patients.

The protective effects of dezocine on interleukin-1β-induced inflammation, oxidative stress and apoptosis of human nucleus pulposus cells and the possible mechanisms

Intervertebral disc degeneration (IDD) is a natural problem linked to the inflammation. We aimed to investigate the role of dezocine (DEZ) in the development of IDD. Human nucleus pulposus cells (HNPCs) induced by interleukin (IL)-1β was used as a cellular model of IDD. After treatment with DEZ, HNPCs viability was evaluated with a CCK-8 assay. Then, the levels of inflammatory factors, including IL-6 and tumor necrosis factor-α (TNF-α), and oxidative stress-related markers, including reactive oxygen species (ROS), malondialdehyde (MDA) and reduced glutathione (GSH), were tested by RT-qPCR or kits. TUNEL staining was employed to detect cell apoptosis and Western blot was used to determine the expression of proteins related to inflammation, oxidative stress, apoptosis, endoplasmic reticulum stress (ERS) and MAPK signaling. Afterward, PMA, a MAPK signaling pathway agonist, was adopted for exploring the regulatory effects of DEZ on MAPK pathway. Results indicated that DEZ enhanced cell viability of HNPCs after IL-1β exposure. DEZ alleviated the inflammation and oxidative stress, evidenced by decreased levels of IL-6, TNF-α, ROS, MDA, p-NF-κB p65, NF-κB p65 in nucleus, cox-2 and increased levels of NF-κB p65 in cytoplasm, GSH, SOD1 and SOD2. Moreover, DEZ notably inhibited IL-1β-induced apoptosis of HNPCs. Furthermore, DEZ suppressed the levels of ERS-related proteins. The levels of related proteins in MAPK signaling including p-P38 and p-ERK1/2 were remarkably reduced after DEZ administration. By contrast, PMA crippled the impacts of DEZ on inflammation, oxidative stress and apoptosis of HNPCs induced by IL-1β. Collectively, DEZ ameliorates IL-1β-induced HNPCs injury via inhibiting MAPK signaling.

Limonin Inhibits IL-1β-Induced Inflammation and Catabolism in Chondrocytes and Ameliorates Osteoarthritis by Activating Nrf2

Osteoarthritis (OA), a degenerative disorder, is considered to be one of the most common forms of arthritis. Limonin (Lim) is extracted from lemons and other citrus fruits. Limonin has been reported to have anti-inflammatory effects, while inflammation is a major cause of OA; thus, we propose that limonin may have a therapeutic effect on OA. In this study, the therapeutic effect of limonin on OA was assessed in chondrocytes in vitro in IL-1β induced OA and in the destabilization of the medial meniscus (DMM) mice in vivo. The Nrf2/HO-1/NF-κB signaling pathway was evaluated to illustrate the working mechanism of limonin on OA in chondrocytes. In this study, it was found that limonin can reduce the level of IL-1β induced proinflammatory cytokines such as INOS, COX-2, PGE2, NO, TNF-α, and IL-6. Limonin can also diminish the biosynthesis of IL-1β-stimulated chondrogenic catabolic enzymes such as MMP13 and ADAMTS5 in chondrocytes. The research on the mechanism study demonstrated that limonin exerts its protective effect on OA through the Nrf2/HO-1/NF-κB signaling pathway. Taken together, the present study shows that limonin may activate the Nrf2/HO-1/NF-κB pathway to alleviate OA, making it a candidate therapeutic agent for OA.

Tissue Renin-Angiotensin System (tRAS) Induce Intervertebral Disc Degeneration by Activating Oxidative Stress and Inflammatory Reaction

Lumbar intervertebral disc degeneration (IDD) has been the major contributor to low back pain (LBP). IDD is an chronic inflammation process, with the activation of plentiful inflammation-related cytokines and ECM degradation-related enzymes. In the past few years, hypertension has been reported to correlate with LBP. In addition, the local tissue renin-angiotensin system (tRAS) has been identified in multiple tissues, including the spinal cord, skin, kidney, heart, and bone. Recently, tRAS has also been established in both bovine and human intervertebral disc tissues, especially in the degenerated disc tissue. However, the exact of tRAS and IDD remains unknown. In this present study, proteomic analysis, molecular biology analysis, and animal model were all used. Firstly, we revealed that tRAS was excessively activated in the human degenerated intervertebral disc tissue via proteomic analysis and molecular biology analysis. Then, in vitro experiment suggested that Ang II could decrease the cell viability of human NP cells and promote NP cell apoptosis, senescence, oxidative stress, and NLRP3 activation in human NP cells. In addition, Ang II could also trigger degeneration and fibrosis phenotype in human NP cells. Finally, the animal model demonstrated that the local activated ACE/Ang II axis in the NP tissue could accelerate IDD in aging spontaneously hypertensive rats (SHR). Collectively, the degenerated intervertebral disc tissue showed excessively activated tRAS, and local activated tRAS could induce NP cell senescence, apoptosis, oxidative stress, and inflammatory reaction to promote IDD. These biological effects of Ang II on human NP cells may provide novel insight into further treatment of IDD.