Aloin Regulates Matrix Metabolism and Apoptosis in Human Nucleus Pulposus Cells via the TAK1/NF-κB/NLRP3 Signaling Pathway

Homoplantaginin alleviates intervertebral disc degeneration by blocking the NF-κB/MAPK pathways via binding to TAK1

Intervertebral disc degeneration (IVDD) is a common degenerative disease which is closely related to low back pain (LBP) and brings huge economic and social burdens. In this study, we explored the therapeutic effects of Homoplantaginin (Hom) for IVDD due to its convincing anti-inflammatory and antioxidant functions. TNF-α was used to simulate the inflammatory environment for nucleus pulposus (NP) cells in vitro. We verified that Hom could alleviate the TNF-α-induced inflammation and disturbance of ECM homeostasis through blocking the NF-κB/MAPK signaling pathways. Subsequently, we screened the binding targets of Hom and confirmed that Hom could directly bind to TAK1 and inhibit its phosphorylation to down-regulate the inflammation-related pathways. The therapeutic effects of Hom on IVDD were further validated through a needle puncture rat model in vivo. Overall, Hom was a promising small molecule for IVDD early intervention, possessing huge clinical translational value.

Pyroptosis: A spoiler of peaceful coexistence between cells in degenerative bone and joint diseases

BACKGROUND

As people age, degenerative bone and joint diseases (DBJDs) become more prevalent. When middle-aged and elderly people are diagnosed with one or more disorders such as osteoporosis (OP), osteoarthritis (OA), and intervertebral disc degeneration (IVDD), it often signals the onset of prolonged pain and reduced functionality. Chronic inflammation has been identified as the underlying cause of various degenerative diseases, including DBJDs. Recently, excessive activation of pyroptosis, a form of programed cell death (PCD) mediated by inflammasomes, has emerged as a primary driver of harmful chronic inflammation. Consequently, pyroptosis has become a potential target for preventing and treating DBJDs.

AIM OF REVIEW

This review explored the physiological and pathological roles of the pyroptosis pathway in bone and joint development and its relation to DBJDs. Meanwhile, it elaborated the molecular mechanisms of pyroptosis within individual cell types in the bone marrow and joints, as well as the interplay among different cell types in the context of DBJDs. Furthermore, this review presented the latest compelling evidence supporting the idea of regulating the pyroptosis pathway for DBJDs treatment, and discussed the potential, limitations, and challenges of various therapeutic strategies involving pyroptosis regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In summary, an interesting identity for the unregulated pyroptosis pathway in the context of DBJDs was proposed in this review, which was undertaken as a spoiler of peaceful coexistence between cells in a degenerative environment. Over the extended course of DBJDs, pyroptosis pathway perpetuated its activity through crosstalk among pyroptosis cascades in different cell types, thus exacerbating the inflammatory environment throughout the entire bone marrow and joint degeneration environment. Correspondingly, pyroptosis regulation therapy emerged as a promising option for clinical treatment of DBJDs.

M6A methylation-regulated autophagy may be a new therapeutic target for intervertebral disc degeneration

Degeneration of intervertebral discs is considered one of the most important causes of low back pain and disability. The intervertebral disc (IVD) is characterized by its susceptibility to various stressors that accelerate the senescence and apoptosis of nucleus pulposus cells, resulting in the loss of these cells and dysfunction of the intervertebral disc. Therefore, how to reduce the loss of nucleus pulposus cells under stress environment is the main problem in treating intervertebral disc degeneration. Autophagy is a kind of programmed cell death, which can provide energy by recycling substances in cells. It is considered to be an effective method to reduce the senescence and apoptosis of nucleus pulposus cells under stress. However, further research is needed on the mechanisms by which autophagy of nucleus pulposus cells is regulated under stress environments. M6A methylation, as the most extensive RNA modification in eukaryotic cells, participates in various cellular biological functions and is believed to be related to the regulation of autophagy under stress environments, may play a significant role in nucleus pulposus responding to stress. This article first summarizes the effects of various stressors on the death and autophagy of nucleus pulposus cells. Then, it summarizes the regulatory mechanism of m6A methylation on autophagy-related genes under stress and the role of these autophagy genes in nucleus pulposus cells. Finally, it proposes that the methylation modification of autophagy-related genes regulated by m6A may become a new treatment approach for intervertebral disc degeneration, providing new insights and ideas for the clinical treatment of intervertebral disc degeneration.

CircEYA3 aggravates intervertebral disc degeneration through the miR-196a-5p/EBF1 axis and NF-κB signaling

Intervertebral disc degeneration (IDD) is a well-established cause of disability, and extensive evidence has identified the important role played by regulatory noncoding RNAs, specifically circular RNAs (circRNAs) and microRNAs (miRNAs), in the progression of IDD. To elucidate the molecular mechanism underlying IDD, we established a circRNA/miRNA/mRNA network in IDD through standardized analyses of all expression matrices. Our studies confirmed the differential expression of the transcription factors early B-cell factor 1 (EBF1), circEYA3, and miR-196a-5p in the nucleus pulposus (NP) tissues of controls and IDD patients. Cell proliferation, apoptosis, and extracellular mechanisms of degradation in NP cells (NPC) are mediated by circEYA3. MiR-196a-5p is a direct target of circEYA3 and EBF1. Functional analysis showed that miR-196a-5p reversed the effects of circEYA3 and EBF1 on ECM degradation, apoptosis, and proliferation in NPCs. EBF1 regulates the nuclear factor kappa beta (NF-кB) signalling pathway by activating the IKKβ promoter region. This study demonstrates that circEYA3 plays an important role in exacerbating the progression of IDD by modulating the NF-κB signalling pathway through regulation of the miR196a-5p/EBF1 axis. Consequently, a novel molecular mechanism underlying IDD development was elucidated, thereby identifying a potential therapeutic target for future exploration.

Macrophage migration inhibitory factor (MIF) promotes intervertebral disc degeneration through the NF-κB pathway, and the MIF inhibitor CPSI-1306 alleviates intervertebral disc degeneration in a mouse model

Lumbar intervertebral disc degeneration(IDD) is a prevalent inflammatory disease caused by many proinflammatory factors, such as TNF and IL-1β. Migration inhibitory factor (MIF) is an upstream inflammatory factor widely expressed in vivo that is associated with a variety of inflammatory diseases or malignant tumors and has potential therapeutic value in many diseases. We explored the role of MIF in intervertebral disc degeneration by regulating the content of exogenous MIF or the expression of MIF in cells. Upon inducing degeneration of nucleus pulposus (NP) cells with IL-1β, we found that the increase in intracellular and exogenous MIF promoted the catabolism induced by proinflammatory factors in NP cells, while silencing of the MIF gene alleviated the degeneration to some extent. In a mouse model, the intervertebral disc degeneration of MIF-KO mice was significantly less than that of wild-type mice. To explore the treatment of intervertebral disc degeneration, we selected the small-molecular MIF inhibitor CPSI-1306. CPSI-1306 had a therapeutic effect on intervertebral disc degeneration in the mouse model. In summary, we believe that MIF plays an important role in intervertebral disc degeneration and is a potential therapeutic target for the treatment of intervertebral disc degeneration.

Protective effects of aloin on asthmatic mice by activating Nrf2/HO-1 pathway and inhibiting TGF-β/Smad2/3 pathway

BACKGROUND

Asthma is a severe chronic respiratory disease affecting all age groups with increasing prevalence. Anti-inflammatory strategies are promising options for the treatment of asthma. Although the inhibitory effect of aloin on inflammation has been demonstrated in various diseases, its effect on asthma remains unknown.

METHODS

A mice asthma model was established by treating with ovalbumin (OVA). The effects and mechanism of aloin on the OVA-treated mice were determined by enzyme-linked--immunosorbent serologic assay, biochemical examination, hematoxylin and eosin and Masson's staining, and Western blot assay.

RESULTS

OVA treatment in mice significantly increased the number of total cells, neutrophils, eosinophils, and macrophages and the concentration of interleukin (IL)-4, IL-5, and IL-13, which were attenuated with the administration of aloin. The content of malondialdehyde was enhanced in OVA-treated mice, with the decreased levels of superoxide dismutase and glutathione, which were reversed with aloin treatment. Aloin treatment reduced the airway resistance of OVA-induced mice. The inflammatory cell infiltration around small airways was accompanied by the thickening and contraction of bronchial walls and pulmonary collagen deposition in OVA-treated mice; however, these conditions were ameliorated with aloin treatment. Mechanically, aloin upregulated the expression of nuclear factor erythroid 2-related factor 2 (Nrf2)-heme oxygenase 1 (HO-1) pathway but inhibited the level of transforming growth factor beta-SMAD2/3 genes (TGF-β/Smad2/3) axis in OVA-induced mice.

CONCLUSION

Aloin treatment lessened airway hyperresponsiveness, airway remodeling, inflammation, and oxidative stress in OVA-treated mice, and was closely related to the activation of Nrf2/HO-1 pathway and the weakening of TGF-β/Smad2/3 pathway.

ERBB2-PTGS2 axis promotes intervertebral disc degeneration by regulating senescence of nucleus pulposus cells

Intervertebral disc degeneration (IDD) is considered one of the main causes of low back pain and lumbar disc herniation. Various studies have shown that disc cell senescence plays a critical role in this process. however, its role in IDD is yet unclear. In this study, we explored the role of senescence-related genes (SR-DEGs) and its underlying mechanism in IDD. A total of 1325 differentially expressed genes (DEGs) were identified using Gene Expression Omnibus (GEO) database GSE41883. 30 SR-DEGs were identified for further functional enrichment and pathway analysis, and two hub SR-DEGs (ERBB2 and PTGS2) were selected to construct transcription factor (TF)-gene interaction and TF-miRNA coregulatory networks, and 10 candidate drugs were screened for the treatment of IDD. Last but not least, in vitro experiments show that ERBB2 expression decreased and PTGS2 expression increased in human nucleus pulposus (NP) cell senescence model treated with TNF-α. After lentivirus-mediated overexpression of ERBB2, the expression of PTGS2 decreased and the senescence level of NP cells decreased. Overexpression of PTGS2 reversed the anti-senescence effects of ERBB2. The findings in this study suggested that ERBB2 overexpression further reduced NP cell senescence by inhibiting PTGS2 levels, which ultimately alleviated IDD. Taken together, our findings provide new insights into the roles of senescence-related genes in IDD and highlight a novel target of ERBB2-PTGS2 axis for therapeutic strategies.

The mechanisms and functions of TNF-α in intervertebral disc degeneration

Low back pain (LBP) is one of the most common health problems in people's lives, which brings a massive burden to clinicians, and the leading cause of LBP is intervertebral disc degeneration (IDD). IDD is mainly caused by factors such as aging, mechanical stress, and lack of nutrition. The pathological mechanism of IDD is very complex, involving inflammatory response, cell metabolism disorder, and so on. Unfortunately, in the current treatment of IDD, only relieving symptoms as the primary means of relieving a patient's pain cannot effectively inhibit or reverse the progression of IDD. Tumor necrosis factor-α (TNF-α) is a multifunctional pro-inflammatory factor involved in many diseases' pathological processes. With the in-depth study of the pathological mechanism of IDD, more and more evidence has shown that TNF-α is an essential activator of IDD, which is related to the metabolic disorder, inflammatory responses, apoptosis, and other pathological processes of extracellular dissociation in the intervertebral disc. Therefore, anti-TNF-α therapy is an effective therapeutic target for alleviating IDD, especially in inhibiting extracellular matrix degradation and reducing inflammatory responses. This article reviews the pathological role of TNF-α in IDD and the latest research progress of TNF-α inhibitors in treating IDD.

Nutrient metabolism of the nucleus pulposus: A literature review

Cells take in, consume, and synthesize nutrients for numerous physiological functions. This includes not only energy production but also macromolecule biosynthesis, which will further influence cellular signaling, redox homeostasis, and cell fate commitment. Therefore, alteration in cellular nutrient metabolism is associated with pathological conditions. Intervertebral discs, particularly the nucleus pulposus (NP), are avascular and exhibit unique metabolic preferences. Clinical and preclinical studies have indicated a correlation between intervertebral degeneration (IDD) and systemic metabolic diseases such as diabetes, obesity, and dyslipidemia. However, a lack of understanding of the nutrient metabolism of NP cells is masking the underlying mechanism. Indeed, although previous studies indicated that glucose metabolism is essential for NP cells, the downstream metabolic pathways remain unknown, and the potential role of other nutrients, like amino acids and lipids, is understudied. In this literature review, we summarize the current understanding of nutrient metabolism in NP cells and discuss other potential metabolic pathways by referring to a human NP transcriptomic dataset deposited to the Gene Expression Omnibus, which can provide us hints for future studies of nutrient metabolism in NP cells and novel therapies for IDD.

Innovative immune mechanisms and antioxidative therapies of intervertebral disc degeneration

Intervertebral disc degeneration (IDD) is the basic pathological process of many degenerative diseases of the spine, characterized by series of symptoms, among which low back pain (LBP) is the most common symptom that patients suffer a lot, which not only makes patients and individual families bear a huge pain and psychological burden, but also consumes a lot of medical resources. IDD is usually thought to be relevant with various factors such as genetic predisposition, trauma and aging, and IDD progression is tightly relevant with structural and functional alterations. IDD processes are caused by series of pathological processes, including oxidative stress, matrix decomposition, inflammatory reaction, apoptosis, abnormal proliferation, cell senescence, autophagy as well as sepsis process, among which the oxidative stress and inflammatory response are considered as key link in IDD. The production and clearance of ROS are tightly connected with oxidative stress, which would further simulate various signaling pathways. The phenotype of disc cells could change from matrix anabolism-to matrix catabolism- and proinflammatory-phenotype during IDD. Recent decades, with the relevant reports about oxidative stress and inflammatory response in IDD increasing gradually, the mechanisms researches have attracted much more attention. Consequently, this study focused on the indispensable roles of the oxidative stress and inflammatory response (especially macrophages and cytokines) to illustrate the origin, development, and deterioration of IDD, aiming to provide novel insights in the molecular mechanisms as well as significant clinical values for IDD.