17β-Estradiol Inhibites Tumor Necrosis Factor-α Induced Apoptosis of Human Nucleus Pulposus Cells via the PI3K/Akt Pathway

The Role of Sex Hormones in Cartilaginous Tissues: A Scoping Review

Background

The use of sex hormones in the clinic for the management of musculoskeletal conditions is increasingly common. Despite this, the role of sex hormones in various joint tissues such as the intervertebral disc (IVD), temporomandibular joint (TMJ), and articular cartilage remains poorly understood. Here, we employ a database search strategy to critically examine the available literature in this field through a scoping review.

Methods

Using a 4-step protocol, primary research articles pertaining to sex hormones and the IVD, TMJ, or articular cartilage were identified and reviewed by two independent reviewers. ~3900 articles were identified in our initial search, and after review, ~140 were identified to be relevant to our tissues of interest and the effects of sex hormones.

Results

Within all joint tissues investigated here, there were limited investigations on the effects of testosterone. Studies reported here for these tissues indicate that sex hormones are likely beneficial in the context of age-associated joint diseases, but there are important limitations to how this translates to the clinic given that various animal models can display distinct responses to sex hormone exposure. Direct comparisons of sex hormone therapies are limited between biological sexes, but evidence indicates that the molecular responses are likely similar. Current evidence indicates that sex hormone exposure likely has anti-inflammatory effects within joint tissues at the level of gene and protein expression, but the mechanism is unknown.

Conclusion

Sex hormones such as testosterone and estrogen play an important role in inflammatory signaling within joint tissues, which could lead to novel interventions within the clinic for joint degeneration. However, understanding the biological mechanisms of hormones in these distinct tissues, between sexes, and with age is imperative for their proper implementation.

Low back pain and osteoarthritis pain: a perspective of estrogen

Low back pain (LBP) is the world's leading cause of disability and is increasing in prevalence more rapidly than any other pain condition. Intervertebral disc (IVD) degeneration and facet joint osteoarthritis (FJOA) are two common causes of LBP, and both occur more frequently in elderly women than in other populations. Moreover, osteoarthritis (OA) and OA pain, regardless of the joint, are experienced by up to twice as many women as men, and this difference is amplified during menopause. Changes in estrogen may be an important contributor to these pain states. Receptors for estrogen have been found within IVD tissue and nearby joints, highlighting the potential roles of estrogen within and surrounding the IVDs and joints. In addition, estrogen supplementation has been shown to be effective at ameliorating IVD degeneration and OA progression, indicating its potential use as a therapeutic agent for people with LBP and OA pain. This review comprehensively examines the relationship between estrogen and these pain conditions by summarizing recent preclinical and clinical findings. The potential molecular mechanisms by which estrogen may relieve LBP associated with IVD degeneration and FJOA and OA pain are discussed.

Asymmetric distribution of Modic changes in patients with lumbar disc herniation

PURPOSE

This study aims to report a new distribution pattern of Modic changes (MCs) in patients with lumbar disc herniation (LDH) and investigate the prevalence, correlative factors and clinical outcomes of asymmetric Modic changes (AMCs).

METHODS

The study population consisted of 289 Chinese Han patients who were diagnosed with LDH and single-segment MCs from January 2017 to December 2019. Demographic, clinical and imagological information was collected. Lumbar MRI was performed to assess MCs and intervertebral discs. The visual analogue score (VAS) and Oswestry disability index (ODI) were evaluated in patients undergoing surgery preoperatively and at the final follow-up. Correlative factors contributing to AMCs were analysed by multivariate logistic regression.

RESULTS

The study population included 197 patients with AMCs and 92 patients with symmetric Modic changes (SMCs). The incidence of leg pain (P < 0.001) and surgical treatment (P = 0.027) in the AMC group was higher than that in the SMC group. The VAS of low back pain was lower (P = 0.048), and the VAS of leg pain was higher (P = 0.036) in the AMC group than in the SMC group preoperatively. Multivariate logistic regression analysis revealed that leg pain (OR = 2.169, 95% CI = 1.218 ~ 3.864) and asymmetric LDH (OR = 7.342, 95% CI = 4.170 ~ 12.926) were independently associated with AMCs. The receiver operating characteristic curve showed an AUC of 0.765 (P < 0.001).

CONCLUSION

AMCs were a more common phenomenon than SMCs in this study. The asymmetric and symmetric distribution of MCs was closely related to LDH position. AMCs were related to leg pain and higher pain levels. Surgery can achieve satisfactory clinical improvement for asymmetric and symmetric MCs.

Molecular Basic of Pharmacotherapy of Cytokine Imbalance as a Component of Intervertebral Disc Degeneration Treatment

Intervertebral disc degeneration (IDD) and associated conditions are an important problem in modern medicine. The onset of IDD may be in childhood and adolescence in patients with a genetic predisposition. With age, IDD progresses, leading to spondylosis, spondylarthrosis, herniated disc, spinal canal stenosis. One of the leading mechanisms in the development of IDD and chronic back pain is an imbalance between pro-inflammatory and anti-inflammatory cytokines. However, classical therapeutic strategies for correcting cytokine imbalance in IDD do not give the expected response in more than half of the cases. The purpose of this review is to update knowledge about new and promising therapeutic strategies based on the correction of the molecular mechanisms of cytokine imbalance in patients with IDD. This review demonstrates that knowledge of the molecular mechanisms of the imbalance between pro-inflammatory and anti-inflammatory cytokines may be a new key to finding more effective drugs for the treatment of IDD in the setting of acute and chronic inflammation.

An update on animal models of intervertebral disc degeneration and low back pain: Exploring the potential of artificial intelligence to improve research analysis and development of prospective therapeutics

Animal models have been invaluable in the identification of molecular events occurring in and contributing to intervertebral disc (IVD) degeneration and important therapeutic targets have been identified. Some outstanding animal models (murine, ovine, chondrodystrophoid canine) have been identified with their own strengths and weaknesses. The llama/alpaca, horse and kangaroo have emerged as new large species for IVD studies, and only time will tell if they will surpass the utility of existing models. The complexity of IVD degeneration poses difficulties in the selection of the most appropriate molecular target of many potential candidates, to focus on in the formulation of strategies to effect disc repair and regeneration. It may well be that many therapeutic objectives should be targeted simultaneously to effect a favorable outcome in human IVD degeneration. Use of animal models in isolation will not allow resolution of this complex issue and a paradigm shift and adoption of new methodologies is required to provide the next step forward in the determination of an effective repairative strategy for the IVD. AI has improved the accuracy and assessment of spinal imaging supporting clinical diagnostics and research efforts to better understand IVD degeneration and its treatment. Implementation of AI in the evaluation of histology data has improved the usefulness of a popular murine IVD model and could also be used in an ovine histopathological grading scheme that has been used to quantify degenerative IVD changes and stem cell mediated regeneration. These models are also attractive candidates for the evaluation of novel anti-oxidant compounds that counter inflammatory conditions in degenerate IVDs and promote IVD regeneration. Some of these compounds also have pain-relieving properties. AI has facilitated development of facial recognition pain assessment in animal IVD models offering the possibility of correlating the potential pain alleviating properties of some of these compounds with IVD regeneration.

Intervertebral disc degeneration and how it leads to low back pain

The purpose of this review was to evaluate data generated by animal models of intervertebral disc (IVD) degeneration published in the last decade and show how this has made invaluable contributions to the identification of molecular events occurring in and contributing to pain generation. IVD degeneration and associated spinal pain is a complex multifactorial process, its complexity poses difficulties in the selection of the most appropriate therapeutic target to focus on of many potential candidates in the formulation of strategies to alleviate pain perception and to effect disc repair and regeneration and the prevention of associated neuropathic and nociceptive pain. Nerve ingrowth and increased numbers of nociceptors and mechanoreceptors in the degenerate IVD are mechanically stimulated in the biomechanically incompetent abnormally loaded degenerate IVD leading to increased generation of low back pain. Maintenance of a healthy IVD is, thus, an important preventative measure that warrants further investigation to preclude the generation of low back pain. Recent studies with growth and differentiation factor 6 in IVD puncture and multi-level IVD degeneration models and a rat xenograft radiculopathy pain model have shown it has considerable potential in the prevention of further deterioration in degenerate IVDs, has regenerative properties that promote recovery of normal IVD architectural functional organization and inhibits the generation of inflammatory mediators that lead to disc degeneration and the generation of low back pain. Human clinical trials are warranted and eagerly anticipated with this compound to assess its efficacy in the treatment of IVD degeneration and the prevention of the generation of low back pain.

Irisin Ameliorates Intervertebral Disc Degeneration by Activating LATS/YAP/CTGF Signaling

Unbalanced metabolism of an extracellular matrix (ECM) in nucleus pulposus cells (NPCs) is widely acknowledged as the primary cause of intervertebral disc degeneration (IDD). Irisin, a novel myokine, is cleaved from fibronectin type III domain-containing 5 (FNDC5) and has recently been proven to regulate the metabolism of ECM. However, little is known about its potential on NPCs and the development of IDD. Therefore, this study sought to examine the protective effects and molecular mechanism of irisin on IDD in vivo and in vitro. Decreased expression levels of FNDC5 and anabolism markers (COL2A1 and ACAN) but increased levels of catabolism markers (ADAMTS4) were found in degenerative nucleus pulposus (NP) tissues. In a punctured-induced rat IDD model, irisin treatment was found to significantly slow the development of IDD, and in TNF-α-stimulated NPCs, irisin treatment partly reversed the disorder of ECM metabolism. In mechanism, RNA-seq results suggested that irisin treatment affected the Hippo signaling pathway. Further studies revealed that with irisin treatment, the phosphorylation levels of key factors (LATS and YAP) were downregulated, while the expression level of CTGF was upregulated. Moreover, CTGF knockdown partially eliminated the protective effects of irisin on the metabolism of ECM in NPCs, including inhibiting the anabolism and promoting the catabolism. Taken together, this study demonstrated that the expression levels of FNDC5 were decreased in degenerative NP tissues, while irisin treatment promoted the anabolism, inhibited the catabolism of the ECM in NPCs, and delayed the progression of IDD via LATS/YAP/CTGF signaling. These results shed light on the protective actions of irisin on NPCs, leading to the development of a novel therapeutic target for treating IDD.

Oxidative Stress Aggravates Apoptosis of Nucleus Pulposus Cells through m6A Modification of MAT2A Pre-mRNA by METTL16

The process of intervertebral disc degeneration (IVDD) is complex, and its mechanism is considered multifactorial. Apoptosis of oxidative stressed nucleus pulposus cells (NPCs) should be a fundamental element in the pathogenesis of IVDD. In our pilot study, we found that the expression of MAT2A decreased, and METTL16 increased in the degenerative nucleus pulposus tissues. Previous studies have shown that the balance of splicing, maturation, and degradation of MAT2A pre-mRNA is regulated by METTL16 m⁶A modification. In the current study, we aimed to figure out whether this mechanism was involved in the aberrant apoptosis of NPCs and IVDD. Human NPCs were isolated and cultured under oxidative stress. An IVDD animal model was established. It showed that significantly higher METTL16 expression and lower MAT2A expression were seen in either the NPCs under oxidative stress or the degenerative discs of the animal model. MAT2A was inhibited with siRNA in vitro or cycloleucine in vivo. METTL16 was overexpressed with lentivirus in vitro or in vivo. Downregulation of MAT2A or upregulation of METTL16 aggravated nucleus pulposus cell apoptosis and disc disorganization. The balance of splicing, maturation, and degradation of MAT2A pre-mRNA was significantly inclined to degradation in the NPCs with the overexpression of METTL16. Increased apoptosis of NPCs under oxidative stress could be rescued by reducing the expression of METTL16 using siRNA with more maturation of MAT2A pre-mRNA. Collectively, oxidative stress aggravates apoptosis of NPCs through disrupting the balance of splicing, maturation, and degradation of MAT2A pre-mRNA, which is m⁶A modified by METTL16.

Influence of Gestational Hormones on the Bacteria-Induced Cytokine Response in Periodontitis

Periodontitis is an inflammatory disease that affects the supporting structures of teeth. The presence of a bacterial biofilm initiates a destructive inflammatory process orchestrated by various inflammatory mediators, most notably proinflammatory cytokines, which are upregulated in the gingival crevicular fluid, leading to the formation of periodontal pockets. This represents a well-characterized microbial change during the transition from periodontal health to periodontitis; interestingly, the gestational condition increases the risk and severity of periodontal disease. Although the influence of periodontitis on pregnancy has been extensively reviewed, the relationship between pregnancy and the development/evolution of periodontitis has been little studied compared to the effect of periodontitis on adverse pregnancy outcomes. This review is aimed at summarizing the findings on the pregnancy-proinflammatory cytokine relationship and discussing its possible involvement in the development of periodontitis. We address (1) an overview of periodontal disease, (2) the immune response and possible involvement of proinflammatory cytokines in the development of periodontitis, (3) how bone tissue remodelling takes place with an emphasis on the involvement of the inflammatory response and metalloproteinases during periodontitis, and (4) the influence of hormonal profile during pregnancy on the development of periodontitis. Finally, we believe this review may be helpful for designing immunotherapies based on the stage of pregnancy to control the severity and pathology of periodontal disease.

Liraglutide Protects Nucleus Pulposus Cells Against High-Glucose Induced Apoptosis by Activating PI3K/Akt/ mTOR/Caspase-3 and PI3K/Akt/GSK3β/Caspase-3 Signaling Pathways

Background and Objective: Diabetes mellitus (DM) is reportedly a significant risk factor for intervertebral disc degeneration (IDD). Incretin system and particularly glucagon-like peptide 1 (GLP-1) because of its glucose-lowering effects has become an important target in therapeutic strategies of type 2 diabetes (T2D). Liraglutide is a GLP-1 receptor (GLP-1R) agonist with glucoregulatory and insulinotropic functions as well as regulatory functions on cell proliferation, differentiation, and apoptosis. However, little is known on the roles and signaling pathways of apoptosis protecting effects of liraglutide in IDD. This study aimed to investigate the potential protective effects of liraglutide against high glucose-induced apoptosis of nucleus pulposus cells (NPCs) and the possible involved signaling pathways.

Methods: The human NPCs were incubated with 100 nM liraglutide alone or in combination with LY294002 (PI3K inhibitor), rapamycin (mTOR inhibitor), and SB216763 (GSK3β inhibitor) in a high glucose culture for 48 h. The four groups were assessed further for apoptosis and genes expressions. The apoptotic effect was evaluated by flow cytometry and further confirmed by cell death detection enzyme-linked immunoassay plus (ELISAPLUS). The gene and protein expression levels were assessed by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting techniques. The results were comparatively assessed between the four groups.

Results: The results confirmed the presence of GLP-1R in the NPCs indicating that liraglutide inhibited the high glucose-induced apoptosis, which was blocked by silencing GLP-1R with siRNA. Moreover, liraglutide stimulated the phosphorylation of Akt, mTOR and GSK3β. Treatment with LY294002 significantly increased the apoptosis of NPCs and reduced the levels of their downstream substrates (p-AKT, p-mTOR, and p-GSK3β). Further assessments revealed that activation of mTOR and GSK3β was almost completely inhibited by rapamycin and SB216763, respectively, which significantly increased the caspase-3 levels.

Conclusion: Liraglutide could protect NPCs against high glucose-induced apoptosis by activating the PI3K/AKT/mTOR/caspase-3 and PI3K/AKT/GSK3β/caspase-3 signaling pathways.

Naringin alleviates H2O2-induced apoptosis via the PI3K/Akt pathway in rat nucleus pulposus-derived mesenchymal stem cells

Purpose: To investigate the protective effect of naringin (Nar) on H₂O₂-induced apoptosis of nucleus pulposus-derived mesenchymal stem cells (NPMSC) and the potential mechanism in this process. Methods: Rat NPMSC were cultured in MSC culture medium or culture medium with different concentrations of H₂O₂. Nar or the combination of Nar and LY294002 was added into the culture medium to investigate the effects of Nar. Cell viability was evaluated by cell counting kit-8 (CCK-8) assay. The apoptosis rate was determined using Annexin V/PI dual staining and terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) assays. Additionally, the levels of reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were analyzed by flow cytometry. ATP level in NPMSC was analyzed via ATP detection kit. Mitochondrial ultrastructure change was observed through transmission electron microscope (TEM). Levels of apoptosis-associated molecules (cleaved caspase-3, Bax and Bcl-2) were evaluated via RT-PCR and western blot, respectively. Results: The cells isolated from NP met the criteria for MSC. H₂O₂ significantly promoted NPMSC apoptosis in a dose and time-dependent manner. Nar showed no cytotoxicity effect on NPMSC up to a concentration of 100 μM for 24 h. Nar exhibited protective effects against H₂O₂-induced NPMSC apoptosis including apoptosis rate, expressions of proapoptosis and antiapoptosis related genes and protein. Nar could also alleviate H₂O₂-induced mitochondrial dysfunction of increased mitochondrial ROS production, reduced MMP, decreased intracellular ATP and mitochondrial ultrastructure change. However, these protected effects were inhibited after LY294002 treatment. Conclusions: Our results demonstrated that Nar efficiently attenuated H₂O₂-induced NPMSC apoptosis and mitochondrial dysfunction. The activation of ROS-mediated PI3K/Akt pathway may be the potential mechanism in this process.

Kupffer Cell-Derived TNF-α Triggers the Apoptosis of Hepatic Stellate Cells through TNF-R1/Caspase 8 due to ER Stress

Purpose

To investigate the roles of ER stress in Kupffer cells (KCs) and KC-derived TNF-α in the apoptosis of hepatic stellate cells (HSCs).

Methods

A rat model of liver fibrosis was established. Liver and blood serum samples were collected. Liver function assays, Masson staining, Sirius Red staining, ELISAs, and TUNEL and immunohistochemical staining were performed. Liver function, liver fibrosis, KC phenotype, inflammatory factors, and number of active HSCs were investigated. KCs were isolated, treated with tunicamycin, and then, cocultured with primary hepatic stellate cells. ELISAs, immunofluorescence staining, flow cytometry, and Western blotting were performed. KC phenotype, inflammatory factors, HSC apoptosis, and TNF-R1/caspase 8 pathway activity were examined.

Result

s. ER stress in KCs reduced the levels of liver function markers, reduced the degree of liver fibrosis, and increased the number of KCs with the M1 phenotype and the expression of TNF-α. The increase in KC-derived TNF-α reduced the number of active HSCs and increased the activity of TNF-R1/caspase 8. Furthermore, ER stress in KCs promoted the polarization of KCs towards the M1 phenotype and increased the expression of TNF-α. The increase in KC-derived TNF-α triggered the apoptosis of HSCs and the activation of TNF-R1/caspase 8 in vitro, which was consistent with the in vivo results.

Conclusion

ER stress in KCs promotes the polarization of these cells towards the M1 phenotype and increases the expression of TNF-α. Then, the increase in KC-derived TNF-α triggers the apoptosis of HSCs through TNF-R1/caspase 8.

[Endoplasmic reticulum stress enhances tumor necrosis factor-α expression in rat Kupffer cells to trigger hepatic stellate apoptosis cell through TNFR/caspase-8 pathway]

OBJECTIVE

To investigate the role of endoplasmic reticulum (ER)-stress of Kupffer cells (KCs) and KCs-derived tumor necrosis factor-α (TNF-α) in medicating apoptosis of hepatic stellate cell (HSC).

METHODS

Sixty male SD rats were randomized into control group, model group, ER- stress group, depletion group and KCs block group (n=15). The 4 groups of rats were given intraperitoneal injections (twice a week for 8 weeks) of normal saline (2 mg/kg); 40% CCl4 solution (in peanut oil, 2 mg/kg); 40% CCl4 solution (2 mg/kg) and tunicamycin (1 mg/kg); and 40% CCl4 solution (2 mg/kg) and tunicamycin (1 mg/kg) followed by clodronate liposomes (50 mg/kg), respectively. After the treatments, samples of the liver tissue and serum were collected from the rats from the 4 groups to isolate KC cells, which were co-cultured with LX2 cells. In the depletion group, the rats were injected with anti-rat TNFR mAb (0.35 mg/kg) via the portal vein before isolating the KCs. Liver function examination, Eirius red staining, ELISA, immuno- histochemical staining, and RT-PCR were performed to assess the liver function, liver fibrosis, KC phenotypes, expression of the in fl ammatory factors, and the number of active HSC was detected. The isolated KCs were treated with tunicamycin before co-culture with LX2 cells, and ELISA, RT-PCR and Western blot were performed to examine KC phenotypes, in fl ammatory factors, LX2 cell apoptosis and TNFR/caspase8 pathway activity.

RESULTS

Compared with the rats in the control group, the rats in the model group had significantly increased ALT and AST levels, Sirius red staining-positive area, and Desmin-positive cells (activated HSCs) (P &lt; 0.05) with significantly lowered number of CD16-positive KCs (M1), and TNF-α protein and mRNA expression (P &lt; 0.05). Compared with those in the model group, the rats in ER-stress group showed significantly decreased ALT and AST levels, Sirius red staining positivity and Desmin-positive cells (P &lt; 0.05) and increased number of CD16-positive KCs and TNF-α expressions (P &lt; 0.05). In the depletion group, compared with the ER-stress group, the rats had significantly increased ALT and AST levels of, Sirius red staining positivity and Desmin-positive cells (P &lt; 0.05) and reduced CD16- positive KCs and TNF-αexpressions (P &lt; 0.05). In the cell co-culture experiment, the model group showed significantly reduced TUNEL-positive LX2 cells, CD16-positive cells, and expressions of TNFR1, cleaved caspase- 8 and cleaved caspase- 3 in the KCs (P &lt; 0.05) with increased Desmin-positive LX2 cells (P &lt; 0.05). Compared with the model group, the ER- stress group exhibited significantly increased TUNEL-positive LX2 cells, CD16-positive cells and expressions of TNFR, cleaved caspase-8 and cleaved caspase-3 in the KCs (P &lt; 0.05) and decreased Desmin-positive LX2 cells (P &lt; 0.05). In the depletion group, blocking TNFR resulted in significantly decreased expressions of cleaved caspase-8 and cleaved caspase-3 compared with those in ER- stress group (P &lt; 0.05) although there was no significant changed in TNFR expression.

CONCLUSIONS

ER stress of KCs promotes the transformation of KCs towards M1 phenotype and increases the expression of TNF-α, which triggers the apoptosis of HSCs through the TNFR/caspase-8 pathway.

17β-Estradiol Prevents Extracellular Matrix Degradation by Downregulating MMP3 Expression via PI3K/Akt/FOXO3 Pathway

STUDY DESIGN

In vitro studies of the role of 17β-estradiol (E2) and its possible targets in intervertebral disc degeneration (IDD).

OBJECTIVE

To define the regulatory role of E2 in IDD and the potential mechanisms.

SUMMARY OF BACKGROUND DATA

IDD has intricate etiology that is influenced by multiple risk factors. However, the underlying molecular mechanisms of occurrence and progression of IDD are not well elucidated. The degradation of extracellular matrix (ECM) has been extensively observed in IDD. E2 was found to inhibit ECM degradation in human nuleus pulposus cells (HNPCs), but the molecular mechanism remained to be determined.

METHODS

Western blot and qPCR was performed to quantify the expression of target proteins in HNPCs. Luciferase reporter gene assay was applied to detect the effects of E2 and forkhead box O-3 (FOXO3) on matrix metalloproteinases (MMP)-3 promoter activity. Chromatin immunoprecipitation assay analyzed the binding of FOXO3 to MMP-3 and the effect of E2 on this process.

RESULTS

We identified the upregulation of collagen II and aggrecan by E2 independent of time and concentration. And E2 downregulated MMP-3 expression in human nucleus pulposus cells. The phosphorylation of FOXO3 led to the reduction of MMP-3 promoter activity. Furthermore, 17β-estradiol-induced the activation of PI3K/Akt pathway is required for FOXO3 phosphorylated.

CONCLUSION

E2 prevents the degradation of ECM by upregulating collagen II and aggrecan expression via reducing MMP-3 expression in HNPCs, and PI3K/Akt/FOXO3 pathway is dispensable for MMP-3 downregulated. Therefore, E2 protects against IDD by preventing ECM degradation.

LEVEL OF EVIDENCE

3.

Resveratrol Combined with 17β-Estradiol Prevents IL-1β Induced Apoptosis in Human Nucleus Pulposus Via The PI3K/AKT/Mtor and PI3K/AKT/GSK-3β Pathway

BACKGROUNDS

Nucleus pulposus (NP) apoptosis is mainly charged for the pathological process of Intervertebral disc degeneration (IVDD). Our previous study revealed that Resveratrol (RSV) combined with 17β-estradiol (E2) was more effective in cutting down IL-1β induced NP cell apoptosis via PI3K/AKT pathway. The present study further evaluated the effect of RSV and E2 in the anti-apoptosis process of IVDD.

METHODS

Human nucleus pulposus (NP) cells culture system and IL-1β inducing apoptosis model were constructed in this research. RSV and E2 were used to inhibit apoptosis. FACS (Fluorescence-activated cell sorting) and CCK-8 (Cell Counting Kit-8) assays were respectively used to determine apoptotic incidence and cell viability of NP cells. Quantitative RT-PCR was used to determine expression of target genes in mRNA level, and western blot analysis was performed to detect the changes of related protein expression.

RESULTS

RSV combined with E2 attenuated IL-1β-induced cell apoptosis and recovered cell viability. Blockers for mTOR and GSK-3β abated the effect of RSV and E2. RSV combined with E2 obviously increased activated P-mTOR and P-GSK-3β, which contributes to the downregulation of caspase-3. Activated P-NF-kappa B was not involved in the anti-apoptosis process of RSV and E2.

CONCLUSION

Combination of Resveratrol and 17β-estradiol efficiently resisted IL-1β induced apoptosis of NP cell, mainly through PI3K/AKT/mTOR/caspase-3 and PI3K/AKT/GSK-3β pathway.

The role of estrogen in intervertebral disc degeneration

Intervertebral disc degeneration (IVDD) is a main contributor to low back and radicular pain, which imposes heavy economic burdens on society. However, the etiology and mechanism of IVDD are complex and still not completely clear. In particular, the role of estrogen in IVDD has not received much attention in recent research, although estrogen plays a crucial role in the metabolic dysfunction of others musculoskeletal structures, such as bone, muscle, and tendon. In this review, we attempt to describe the role of estrogen in IVDD and to summarize the proposed mechanisms in vivo and in vitro, as well as, to outline several interesting questions in this field.

The protective effects of PI3K/Akt pathway on human nucleus pulposus mesenchymal stem cells against hypoxia and nutrition deficiency

BACKGROUND

To study the effects of hypoxia and nutrition deficiency mimicking degenerated intervertebral disc on the biological behavior of human nucleus-derived pulposus mesenchymal stem cells (hNP-MSCs) and the role of PI3K/Akt pathway in the process in vitro.

METHODS

hP-MSCs were isolated from lumbar disc and were further identified by their immunophenotypes and multilineage differentiation. Then, cells were divided into the control group, hypoxia and nutrition deficiency group, the LY294002 group, and insulin-like growth factor 1 (IGF-1) group. Then cell apoptosis, the cell viability, the caspase 3 activity, and the expression of PI3K, Akt, and functional genes (aggrecan, collagen I, and collagen II) were evaluated.

RESULT

Our work showed that isolated cells met the criteria of International Society for cellular Therapy. Therefore, cells obtained from degenerated nucleus pulposus were definitely hNP-MSCs. Our results showed that hypoxia and nutrition deficiency could significantly increase cell apoptosis, the caspase 3 activity, and inhibit cell viability. Gene expression results demonstrated that hypoxia and nutrition deficiency could increase the relative expression of PI3K and Akt gene and inhibit the expression of functional genes. However, when the PI3K/Akt pathway was inhibited by LY294002, the cell apoptosis and caspase 3 activity significantly increased while the cell viability was obviously inhibited. Quantitative real-time PCR results showed that the expression of functional genes was more significantly inhibited. Our study further verified that the above-mentioned biological activities of hNP-MSCs could be significantly improved by IGF1.

CONCLUSIONS

PI3K/Akt signal pathway may have protective effects on human nucleus pulposus-derived mesenchymal stem cells against hypoxia and nutrition deficiency.

Intervertebral disc ageing and degeneration: The antiapoptotic effect of oestrogen

As an important part of the spinal column, the intervertebral disc (IVD) plays an important role in the intervertebral juncture and spinal movement in general. IVD degeneration (IVDD), which mimics disc ageing but at an accelerated rate, is a common and chronic process that results in severe spinal symptoms, such as lower back pain. It is generally assumed that lower back pain caused by IVDD can also develop secondary conditions, including spinal canal stenosis, spinal segmental instability, osteophyte formation, disc herniation and spinal cord and nerve root compression. Over the past few years, many researchers around the world have widely studied the relevance between oestrogen and IVDD, indicating that oestrogen can effectively alleviate IVDD development by inhibiting the apoptosis of IVD cells. Oestrogen can decrease IVD cell apoptosis in multiple ways, including the inhibition of the inflammatory cytokines IL-1β and TNF-α, reducing catabolism because of inhibition of matrix metalloproteinases, upregulating integrin α₂β₁ and IVD anabolism, activating the PI3K/Akt pathway, decreasing oxidative damage and promoting autophagy. In this article, we perform an overview of the literature regarding the antiapoptotic effect of oestrogen in IVDD.

17β‑Estradiol protects against interleukin‑1β‑induced apoptosis in rat nucleus pulposus cells via the mTOR/caspase‑3 pathway

Intervertebral disc degeneration (IVDD) is the main pathological basis of spinal degenerative diseases, and aberrant apoptosis of nucleus pulposus cells (NPCs) is the main cellular process that causes IVDD. In our previous studies, 17β-estradiol (E₂) was demonstrated to protect rat NPCs from interleukin-1β (IL-1β)-induced apoptosis via the PI3K/Akt signaling pathway. However, the downstream signaling pathway of PI3K/Akt is currently unclear. The present study aimed to explore the signaling pathways that are downstream of the PI3K/Akt pathway, including mTOR, NF-κB and glycogen synthase kinase-3β (GSK-3β). Annexin V/propidium iodide double staining was used to determine the incidence of apoptosis. Cell Counting kit-8 and MTS assays were used to determine the proliferation and viability of NPCs, respectively. Cellular binding was evaluated using a cell-collagen binding assay. Western blotting was used to determine the protein expression levels of mTOR, NF-κB and GSK-3β, and their phosphorylation levels, as well as the expression levels of active caspase-3. The results revealed that IL-1β induced NPC apoptosis and increased the early apoptotic rate of NPCs. However, E₂ reduced the early apoptosis of NPCs induced by IL-1β. In addition, E₂ suppressed the decrease in cell viability and binding ability caused by IL-1β cytotoxicity. Western blotting revealed that E₂ also reduced the expression of activated caspase-3, and increased the expression of activated mTOR. As a specific inhibitor of mTOR, rapamycin effectively attenuated the effects of E₂. These findings indicated that E₂ protected NPCs against apoptosis via activation of the mTOR/caspase-3 pathway.

Resveratrol inhibits IL-1β-mediated nucleus pulposus cell apoptosis through regulating the PI3K/Akt pathway

Nucleus pulposus (NP) cell apoptosis is a classical cellular character during intervertebral disc degeneration (IDD). Previous studies have shown that inflammatory cytokine-induced NP cell apoptosis plays an important role in disc degeneration. The present study was aimed to investigate whether resveratrol can suppress IL-1β-mediated NP cell apoptosis and the potential signal transduction pathway. Experimental rat NP cells were treated with culture medium containing IL-1β (20 ng/ml) for 7 days. Control NP cells were cultured in the baseline medium. Resveratrol was added along with culture medium to investigate its effects. The inhibitor LY294002 was used to study the role of the PI3K/Akt pathway. NP cell apoptosis was reflected by the caspase-3 activity, cell apoptosis ratio, and expression of apoptosis-related molecules (Bcl-2, Bax, caspase-3, cleaved caspase-3, and cleaved PARP). Compared with the control NP cells, IL-1β significantly increased caspase-3 activity, NP cell apoptosis ratio and mRNA/protein expression of Bax, caspase-3, cleaved caspase-3 and cleaved PARP, but decreased mRNA expression of Bcl-2. However, resveratrol partly suppressed the effects of IL-1β on those cell apoptosis-related parameters. Further analysis showed that IL-1β significantly decreased activity of the PI3K/Akt pathway whereas resveratrol partly increased activity of the PI3K/Akt pathway in NP cells treated with IL-1β. Additionally, when the inhibitor LY294002 was added along with the resveratrol, its protective effects against IL-1β-induced NP cell apoptosis were attenuated. In conclusion, resveratrol suppresses IL-1β-mediated NP cell apoptosis through activating the PI3K/Akt pathway. Resveratrol may be an effective drug to attenuate inflammatory cytokine-induced disc degenerative changes.

Osteogenic protein-1 attenuates nucleus pulposus cell apoptosis through activating the PI3K/Akt/mTOR pathway in a hyperosmotic culture

BACKGROUND

Previous studies have indicated that osteogenic protein-1 has protective effects on the biological functions of intervertebral disc cells. Hyperosmolarity is an important physicochemical factor within the disc nucleus pulposus (NP) region, which obviously promotes NP cell apoptosis.

OBJECTIVE

To study the effects of osteogenic protein-1 (OP-1) on NP cell apoptosis induced by hyperosmolarity and the potential signaling transduction pathway.

METHODS

Rat NP cells were cultured in a hyperosmotic medium with or without OP-1 addition for 7 days. Inhibitor 294002 and inhibitor FK-506 were used to investigate the role of the PI3K/Akt/mTOR pathway in this process. NP cell apoptosis were evaluated by cell apoptosis ratio, activity of caspase-3/9 and gene/protein expression of apoptosis-related molecules (Bax, Bcl-2, caspase-3/cleaved caspase-3 and cleaved PARP).

RESULTS

OP-1 addition obviously decreased cell apoptosis ratio and caspase-3/9 activity, down-regulated gene/protein expression of pro-apoptosis molecules (Bax, caspase-3/cleaved casepase-3 and cleaved PARP), up-regulated gene/protein expression of anti-apoptosis molecule (Bcl-2) in a hyperosmotic culture. Moreover, OP-1 addition significantly increased protein expression of p-Akt and p-mTOR. Further analysis showed that addition of LY294002 and FK-506 partly attenuated these protective effects of OP-1 against NP cell apoptosis and activation of the PI3K/Akt/mTOR pathway in a hyperosmotic culture.

CONCLUSION

OP-1 can attenuate NP cell apoptosis through activating the PI3K/Akt/mTOR pathway in a hyperosmotic culture. The present study sheds a new light on the protective role of OP-1 in regulating disc cell biology and provides some theoretical basis for the application of OP-1 in retarding/regenerating disc degeneration.

Wogonin mitigates intervertebral disc degeneration through the Nrf2/ARE and MAPK signaling pathways

Intervertebral disc degeneration (IVDD) is a prevalent disease characterized by the progressive loss of the extracellular matrix in the local nucleus pulposus region. Metalloproteinases and pro-inflammatory cytokines play an important role in this process. Thus, anti-inflammatory strategies are an important component of IVDD treatment. Wogonin, a naturally existing monoflavonoid, has been reported to have potential anti-inflammatory effects in some inflammatory diseases. Hence, in our present study we investigated the protective effects and potential mechanisms of wogonin in rat nucleus pulposus cells that had been treated with interleukin-1beta (IL-1β) to induce severe IVDD. An in vivo rat caudal vertebrae needle-stab model was also designed and its validity was evaluated as an IVDD model. The results demonstrated that wogonin suppressed IL-1β-induced inflammatory mediators (iNOS, IL-6 and COX2) and matrix-degrading proteinases (MMP1, MMP3, MMP13 and ADAMTS4). Wogonin also upregulated some of the key components of the extracellular matrix, such as collagen II. Furthermore, we discovered that wogonin exerted anti-inflammatory effects by activating the Nrf2/HO-1-SOD2-NQO1-GCLC signaling axis. Moreover, the IL-1β-induced stimulation of the MAPK signaling pathway was reversed by wogonin treatment. The in vivo MRI and histological results also revealed that wogonin protected the nucleus pulposus from the progression of IVDD. Therefore, wogonin may be a potential agent for the treatment of IVDD.

Resveratrol attenuates high glucose-induced nucleus pulposus cell apoptosis and senescence through activating the ROS-mediated PI3K/Akt pathway

BACKGROUND

Diabetes mellitus is closely correlated with disc degeneration. Nucleus pulposus (NP) cell apoptosis and senescence are typical cellular features within the degenerative disc. Resveratrol is a newly identified phytoalexin that has protective effects on cartilaginous tissue.

OBJECTIVE

To investigate the whether resveratrol can protect against high glucose-induced NP cell apoptosis and senescence, and the potential mechanism in this process.

METHODS

Rat NP cells were cultured in either 10% FBS culture medium (control group) or 10% FBS with a high glucose concentration (0.2 M, experiment group) for 3 days. Resveratrol or the combination of resveratrol and LY294002 was added into the culture medium of experiment group to investigate the effects of resveratrol and the PI3K/Akt pathway.

RESULTS

High glucose significantly promoted NP cell apoptosis and NP cell senescence compared with the control group. Resveratrol exhibited protective effects against high glucose-induced NP cell apoptosis and senescence. Further analysis showed that resveratrol suppressed reactive oxygen species (ROS) generation and increased the activity of the PI3K/Akt pathway under the high glucose condition. However, the LY294002 had no significant effects on ROS content in the resveratrol-treated high glucose group.

CONCLUSION

Resveratrol can attenuate high glucose-induced NP cell apoptosis and senescence, and the activation of ROS-mediated PI3K/Akt pathway may be the potential mechanism in this process.

Long non-coding RNA phosphatase and tensin homolog pseudogene 1 suppresses osteosarcoma cell growth via the phosphoinositide 3-kinase/protein kinase B signaling pathway

Osteosarcoma is a common type of human carcinoma, which exhibits a high metastasis and recurrence rate. Previous studies have indicated that long non-coding RNA phosphatase and tensin homolog pseudogene 1 (lnPTENP1) has tumor suppressive action by modulating PTEN expression in different types of tumor cells. However, the potential mechanism by which lnPTENP1 has an effect in osteosarcoma cells remains elusive. In the present study, the role of lnPTENP1 in osteosarcoma cells was investigated and the possible mechanisms by which it functions were explored. It was revealed that lnPTENP1 transfection significantly inhibited osteosarcoma cell growth, proliferation, migration and invasion. LnPTENP1 transfection also significantly promoted apoptosis in Mg63 cells treated with tunicamycin. Further analysis revealed that lnPTENP1 transfection regulated osteosarcoma cell growth via the PI3K/AKT signaling pathway. In vivo assays revealed that lnPTENP1 transfection significantly inhibited osteosarcoma tumor growth and significantly increased the protein expression and phosphorylation levels of PI3K and AKT. In conclusion, the results of the present study indicated that lnPTENP1 may inhibit osteosarcoma cell growth via the PI3K/AKT signaling pathway, which may be a potential novel target for human osteosarcoma therapy.

Infliximab relieves blood retinal barrier breakdown through the p38 MAPK pathway in a diabetic rat model

AIM

To clarify the mechanism of infliximab treatment in diabetic macular edema (DME) and to provide a new alternative therapy for DME.

METHODS

Rats were randomly divided into the control group, the model group and the infliximab treatment group. A diabetic rat model was created. The concentration of TNF-α in the vitreous body was detected by ELISA. The expressions of B-Raf, p38, claudin-1 and occludin in the retina were detected by Western blot. The integrity of the blood retinal barrier (BRB) was measured using Evan's blue as a tracer.

RESULTS

After three months and six months of the diabetes model, the vitreous TNF-α level in the model group was higher than that of the control group. It was also higher in treated group than that of the control group but was lower than that of the model group. The differences among the three groups were statistically significant (at 3mo, F=857.098, P<0.001; 6mo, F=1261.897, P<0.001). The retina B-Raf and p38 levels in the model group were higher than that of the control group. They were also higher in treated group than that of the control group but were lower than that of the model group. The differences among the three groups were statistically significant (B-Raf at 3mo, F=106.596, P<0.001 and at 6mo, F=200.681, P<0.001; p38 at 3mo, F=41.662, P<0.001 and at 6mo, F=67.979, P<0.001). The retina claudin-1 and occludin levels in the model group were lower than that of the control group. They were also lower in treated group than that of the control group but were higher than that of the model group. The differences among three groups were statistically significant (claudin-1 at 3mo, F=139.088, P<0.001 and at 6mo, F=128.415, P<0.001; occludin at 3mo, F=92.733, P<0.001 and at 6mo, F=104.478, P<0.001). The retinal Evans blue leakage in the model group was higher than that of the control group. It was also higher in treated group than that of the control group but was lower than that of the model group. The differences among the three groups were statistically significant (at 3mo, F=447.946, P<0.001; at 6mo, F=1610.732, P<0.001).

CONCLUSION

In a diabetic rat model, infliximab may relieve TNF-α induced BRB breakdown via the B-Raf and p38 signaling pathway.

Protective role of 17β-estradiol on tumor necrosis factor-α-induced apoptosis in human nucleus pulposus cells

The molecular mechanisms underlying protection and pathogenesis in spinal degenerative diseases remain unclear. Tumor necrosis factor-α (TNF-α) has been demonstrated to induce apoptosis of intervertebral disc (IVD) cells during IVD degeneration, and 17β-estradiol (17β-E2) has a protective effect against IVD cell apoptosis. However, the underlying molecular mechanism by which 17β-E2 protects nucleus pulposus (NP) cells remains to be investigated. The aim of the present study was to evaluate whether 17β-E2 modulates apoptosis of human NP cells induced by TNF-α. In addition, the concentration-response effect of 17β-E2 on human NP cells was investigated. Human NP cells were cultured in complete medium, which was replaced every three days until the culture was ~80% confluent. Cells were treated with 100 ng/ml TNF-α for 48 h, with or without pretreatment with various concentrations of 17β-E2, and ICI 182,780, for 30 min. Morphologic alterations characteristic of apoptosis were observed by inverted phase-contrast microscopy and Hoechst 33258 staining; the apoptosis rate was analyzed by flow cytometry. A Cell Counting kit-8 assay was used to assess cell proliferation. Furthermore, caspase-3 activity was determined and proteins associated with apoptosis were analyzed by western blotting. The level of apoptosis and caspase-3 activity in human NP cells increased, whereas proliferation and the expression of poly ADP-ribose polymerase decreased following TNF-α treatment. These effects of TNF-α were abolished by pretreatment with 17β-E2 in a concentration-dependent manner. The results of the present study indicated that 17β-E2 serves a critical role in the survival of degenerative human NP cells.