Proanthocyanidins inhibit the apoptosis and aging of nucleus pulposus cells through the PI3K/Akt pathway delaying intervertebral disc degeneration

Bradykinin protects nucleus pulposus cells from tert-butyl hydroperoxide-induced damage and delays intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is a leading cause of degenerative spinal disorders, involving complex biological processes. This study investigates the role of the kallikrein-kinin system (KKS) in IVDD, focusing on the protective effects of bradykinin (BK) on nucleus pulposus cells (NPCs) under oxidative stress. Clinical specimens were collected, and experiments were conducted using human and rat primary NPCs to elucidate BK's impact on tert-butyl hydroperoxide (TBHP)-induced oxidative stress and damage. The results demonstrate that BK significantly inhibits TBHP-induced NPC apoptosis and restores mitochondrial function. Further analysis reveals that this protective effect is mediated through the BK receptor 2 (B2R) and its downstream PI3K/AKT pathway. Additionally, BK/PLGA sustained-release microspheres were developed and validated in a rat model, highlighting their potential therapeutic efficacy for IVDD. Overall, this study sheds light on the crucial role of the KKS in IVDD pathogenesis and suggests targeting the B2R as a promising therapeutic strategy to delay IVDD progression and promote disc regeneration.

POSTN knockdown suppresses IL-1β-induced inflammation and apoptosis of nucleus pulposus cells via inhibiting the NF-κB pathway and alleviates intervertebral disc degeneration

The aim of this study is to investigate the effects of POSTN on IL-1β induced inflammation, apoptosis, NF-κB pathway and intervertebral disc degeneration (IVDD) in Nucleus pulposus (NP) cells (NPCs). NP tissue samples with different Pfirrmann grades were collected from patients with different degrees of IVDD. Western blot and immunohistochemical staining were used to compare the expression of POSTN protein in NP tissues. Using the IL-1β-induced IVDD model, NPCs were transfected with lentivirus-coated si-POSTN to down-regulate the expression of POSTN and treated with CU-T12-9 to evaluate the involvement of NF-κB pathway. Western blot, immunofluorescence, and TUNEL staining were used to detect the expression changes of inflammation, apoptosis and NF-κB pathway-related proteins in NPCs. To investigate the role of POSTN in vivo, a rat IVDD model was established by needle puncture of the intervertebral disc. Rats were injected with lentivirus-coated si-POSTN, and H&E staining and immunohistochemical staining were performed. POSTN expression is positively correlated with the severity of IVDD in human. POSTN expression was significantly increased in the IL-1β-induced NPCs degeneration model. Downregulation of POSTN protects NPCs from IL-1β-induced inflammation and apoptosis. CU-T12-9 treatment reversed the protective effect of si-POSTN on NPCs. Furthermore, lentivirus-coated si-POSTN injection partially reversed NP tissue damage in the IVDD model in vivo. POSTN knockdown reduces inflammation and apoptosis of NPCs by inhibiting NF-κB pathway, and ultimately prevents IVDD. Therefore, POSTN may be an effective target for the treatment of IVDD.

Progress in the study of molecular mechanisms of intervertebral disc degeneration

Degenerative intervertebral disc disease (IVDD) is one of the main spinal surgery, conditions, which markedly increases the incidence of low back pain and deteriorates the patient's quality of life, and it imposes significant social and economic burdens. The molecular pathology of IVDD is highly complex and multilateral however still not ompletely understood. New findings indicate that IVDD is closely associated with inflammation, oxidative stress, cell injury and extracellular matrix metabolismdysregulation. Symptomatic management is the main therapeutic approach adopted for IVDD, but it fails to address the basic pathological changes and the causes of the disease. However, research is still focusing on molecular aspects in terms of gene expression, growth factors and cell signaling pathways in an attempt to identify specific molecular targets for IVDD treatment. The paper summarizes the most recent achievements in molecularunderstanding of the pathogenesis of IVDD and gives evidence-based recommendations for clinical practice.

Lactic acid promotes nucleus pulposus cell senescence and corresponding intervertebral disc degeneration via interacting with Akt

The accumulation of metabolites in the intervertebral disc is considered an important cause of intervertebral disc degeneration (IVDD). Lactic acid, which is a metabolite that is produced by cellular anaerobic glycolysis, has been proven to be closely associated with IVDD. However, little is known about the role of lactic acid in nucleus pulposus cells (NPCs) senescence and oxidative stress. The aim of this study was to investigate the effect of lactic acid on NPCs senescence and oxidative stress as well as the underlying mechanism. A puncture-induced disc degeneration (PIDD) model was established in rats. Metabolomics analysis revealed that lactic acid levels were significantly increased in degenerated intervertebral discs. Elimination of excessive lactic acid using a lactate oxidase (LOx)-overexpressing lentivirus alleviated the progression of IVDD. In vitro experiments showed that high concentrations of lactic acid could induce senescence and oxidative stress in NPCs. High-throughput RNA sequencing results and bioinformatic analysis demonstrated that the induction of NPCs senescence and oxidative stress by lactic acid may be related to the PI3K/Akt signaling pathway. Further study verified that high concentrations of lactic acid could induce NPCs senescence and oxidative stress by interacting with Akt and regulating its downstream Akt/p21/p27/cyclin D1 and Akt/Nrf2/HO-1 pathways. Utilizing molecular docking, site-directed mutation and microscale thermophoresis assays, we found that lactic acid could regulate Akt kinase activity by binding to the Lys39 and Leu52 residues in the PH domain of Akt. These results highlight the involvement of lactic acid in NPCs senescence and oxidative stress, and lactic acid may become a novel potential therapeutic target for the treatment of IVDD.

DNMT3a-mediated methylation of PPARγ promote intervertebral disc degeneration by regulating the NF-κB pathway

Intervertebral disc degeneration (IVDD) is a common chronic musculoskeletal disease that causes chronic low back pain and imposes an immense financial strain on patients. The pathological mechanisms underlying IVDD have not been fully elucidated. The development of IVDD is closely associated with abnormal epigenetic changes, suggesting that IVDD progression may be controlled by epigenetic mechanisms. Consequently, this study aimed to investigate the role of epigenetic regulation, including DNA methyltransferase 3a (DNMT3a)-mediated methylation and peroxisome proliferator-activated receptor γ (PPARγ) inhibition, in IVDD development. The expression of DNMT3a and PPARγ in early and late IVDD of nucleus pulposus (NP) tissues was detected using immunohistochemistry and western blotting analyses. Cellularly, DNMT3a inhibition significantly inhibited IL-1β-induced apoptosis and extracellular matrix (ECM) degradation in rat NP cells. Pretreatment with T0070907, a specific inhibitor of PPARγ, significantly reversed the anti-apoptotic and ECM degradation effects of DNMT3a inhibition. Mechanistically, DNMT3a modified PPARγ promoter hypermethylation to activate the nuclear factor-κB (NF-κB) pathway. DNMT3a inhibition alleviated IVDD progression. Conclusively, the results of this study show that DNMT3a activates the NF-κB pathway by modifying PPARγ promoter hypermethylation to promote apoptosis and ECM degradation. Therefore, we believe that the ability of DNMT3a to mediate the PPARγ/NF-κB axis may provide new ideas for the potential pathogenesis of IVDD and may become an attractive target for the treatment of IVDD.

Emerging role and therapeutic implications of p53 in intervertebral disc degeneration

Lower back pain (LBP) is a common degenerative musculoskeletal disease that imposes a huge economic burden on both individuals and society. With the aggravation of social aging, the incidence of LBP has increased globally. Intervertebral disc degeneration (IDD) is the primary cause of LBP. Currently, IDD treatment strategies include physiotherapy, medication, and surgery; however, none can address the root cause by ending the degeneration of intervertebral discs (IVDs). However, in recent years, targeted therapy based on specific molecules has brought hope for treating IDD. The tumor suppressor gene p53 produces a transcription factor that regulates cell metabolism and survival. Recently, p53 was shown to play an important role in maintaining IVD microenvironment homeostasis by regulating IVD cell senescence, apoptosis, and metabolism by activating downstream target genes. This study reviews research progress regarding the potential role of p53 in IDD and discusses the challenges of targeting p53 in the treatment of IDD. This review will help to elucidate the pathogenesis of IDD and provide insights for the future development of precision treatments.

N-Acetylserotonin Protects Rat Nucleus Pulposus Cells Against Oxidative Stress Injury by Activating the PI3K/AKT Signaling Pathway

BACKGROUND

Current studies suggest that the pathogenesis of intervertebral disc degeneration (IDD) is related to oxidative stress damage in nucleus pulposus cells (NPCs). N-acetylserotonin (NAS) is an effective scavenger of reactive oxygen species, but its role in IDD and its underlying mechanisms are not yet clear. Therefore, the aim of this study was to investigate the effect of NAS on oxidative stress injury in NPCs and its mechanism.

METHODS

NP tissue of rat intervertebral disc was collected and NPCs were isolated. NPCs were treated with H2O2 to simulate the state of oxidative stress. The effects of NAS on cell viability, apoptosis, senescence, extracellular matrix (ECM), redox status and PI3K/AKT signal pathway were evaluated by cell counting kit-8, western blot, immunofluorescence, flow cytometry and SA-β-gal staining. Finally, the changes of the above indexes were further observed after the inhibition of PI3K pathway by LY294002.

RESULTS

Flow cytometry showed that NAS reduced H2O2-induced apoptosis of NPCs. SA-β-Gal staining showed that H2O2-induced senescence of NP cells was reversed by NAS. Immunofluorescence staining showed that NAS inhibited H2O2-induced ECM degradation. Western blotting analysis revealed that NAS significantly decreased apoptosis, senescence and ECM degradation. Further analysis showed that NAS treatment activated the PI3K/AKT pathway in H2O2-stimulated NPCs. However, these protected effects were inhibited after LY294002 treatment.

CONCLUSIONS

The results of the present study suggest that NAS inhibits H2O2-induced NPCs degeneration by activating PI3K/AKT pathway, suggesting that NAS has the potential to treat IDD.

Aging, cell senescence, the pathogenesis and targeted therapies of intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) refers to the aging and degenerative diseases of intervertebral disc components such as nucleus pulposus, annulus fibrosus, and cartilage endplate, and is the main cause of chronic low back pain. Over the past few years, many researchers around the world concerned that the degeneration of nucleus pulposus (NP) cells plays the main role in IVDD. The degeneration of NP cells is caused by a series of pathological processes, including oxidative stress, inflammatory response, apoptosis, abnormal proliferation, and autophagy. Interestingly, many studies have found a close relationship between the senescence of NP cells and the progression of NP degeneration. The classical aging pathways also have been confirmed to be involved in the pathological process of IVDD. Moreover, several anti-aging drugs have been used to treat IVDD by inhibiting NP cells senescence, such as proanthocyanidins, resveratrol and bone morphogenetic protein 2. Therefore, this article will systematically list and discuss aging, cell senescence, the pathogenesis and targeted therapies of IVDD, in order to provide new ideas for the treatment of IVDD in the future.

Role of signal transduction pathways in IL-1β-induced apoptosis: Pathological and therapeutic aspects

BACKGROUND

Interleukin-1β (IL-1β) is a pro-inflammatory cytokine mainly produced by monocytes and macrophages with a wide range of biological effects. Evidence has shown that IL-1β plays a vital role in the process of apoptosis; however, the specific mechanisms, by which IL-1β induces apoptosis, vary due to different cellular and experimental conditions. Therefore, this present reviewstudy aimed to systematically review the association between the molecular mechanisms of IL-1β-induced apoptosis in pathological processes and the role of signaling pathways. This article also sought to briefly investigate the potential of signaling pathway-targeted therapy in the prevention and treatment of disease.

METHODS

This is a literature review article. The present discourse aim is first to scrutinize and assess the available literature on IL-1β and apoptosis. The relevant studies using the keywords of "IL-1β-induced apoptosis" and "signaling pathways" were searched in the databases of PubMed, Scopus, Google Scholar, and Web of Science. Gathered relevant material, and extracted information was then assessed.

RESULTS

IL-1β can induce apoptosis in various types of cells under different external stimuli via the mitochondrial pathway, death receptor pathway and endoplasmic reticulum pathway, and that the different pathways are often interconnected. The NF-kB signaling pathway, p38MAPK, and JNK signaling pathways mainly play a proapoptotic part, and the ERK1/2 pathway has a bidirectional role in regulating apoptosis, while activation of the PI3K-Akt signaling pathway can inhibit apoptosis.

CONCLUSION

This review indicates that IL-1β-induced apoptosis plays an important role in pathogenesis and development of pathology of many inflammatory diseases. Elucidating the role of the signaling pathways will aid the development of targeted therapeutic treatments.

Nutritional deficiency induces nucleus pulposus cell apoptosis via the ATF4-PKM2-AKT signal axis

Background

The intervertebral disc is the largest avascular tissue in the human body. The nucleus pulposus (NP) consumes glucose and oxygen to generate energy to maintain cellular metabolism via nutrients that diffuse from the cartilage endplate. The microenvironment in the intervertebral disc becomes nutritionally deficient during degeneration, and nutritional deficiency has been shown to inhibit the viability and proliferation of NP cells.

Methods

To investigate the molecular mechanism by which nutritional deficiency reduces viability and decreases proliferation, we created an in vitro model by using decreasing serum concentration percentages.

Results

In this study, we found that nutritional deficiency reduced NP cell viability and increased cell apoptosis and that the upregulation of ATF4 expression and the downregulation of PKM2 expression were involved in this process. Moreover, we found that PKM2 inhibition can reduce the cell apoptosis induced by ATF4 silence under nutritional deficiency.

Conclusion

Our findings revealed that PKM2 inhibition reduces the cell apoptosis induced by ATF4 silence under nutritional deficiency by inhibiting AKT phosphate. Revealing the function and mechanism of NP cell development under nutritional deficiency will provide new insights into the etiology, diagnosis, and treatment of intervertebral disc and related diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05853-1.

The Impact of Oxidative Stress and AKT Pathway on Cancer Cell Functions and Its Application to Natural Products

Oxidative stress and AKT serine-threonine kinase (AKT) are responsible for regulating several cell functions of cancer cells. Several natural products modulate both oxidative stress and AKT for anticancer effects. However, the impact of natural product-modulating oxidative stress and AKT on cell functions lacks systemic understanding. Notably, the contribution of regulating cell functions by AKT downstream effectors is not yet well integrated. This review explores the role of oxidative stress and AKT pathway (AKT/AKT effectors) on ten cell functions, including apoptosis, autophagy, endoplasmic reticulum stress, mitochondrial morphogenesis, ferroptosis, necroptosis, DNA damage response, senescence, migration, and cell-cycle progression. The impact of oxidative stress and AKT are connected to these cell functions through cell function mediators. Moreover, the AKT effectors related to cell functions are integrated. Based on this rationale, natural products with the modulating abilities for oxidative stress and AKT pathway exhibit the potential to regulate these cell functions, but some were rarely reported, particularly for AKT effectors. This review sheds light on understanding the roles of oxidative stress and AKT pathway in regulating cell functions, providing future directions for natural products in cancer treatment.