IL-10 delays the degeneration of intervertebral discs by suppressing the p38 MAPK signaling pathway

Inhibition of TNFR1 Attenuates LPS Induced Apoptosis and Inflammation in Human Nucleus Pulposus Cells by Regulating the NF-KB and MAPK Signalling Pathway

Intervertebral disc degeneration (IDD) is accompanied by nucleus pulposus (NP) cell apoptosis, inflammation, and extracellular matrix degradation. Tumour necrosis factor receptor 1 (TNFR1) is a receptor of TNF-α, and is deeply involved in the processes of IDD. However, the effect of TNFR1 inhibition on IDD is not clear. Herein, we report that TNFR1 was increased in LPS-treated HNPCs. The aim of this study was to investigate the potential therapeutic effect of TNFR1 siRNA and selective antagonists of TNFR1 (GSK1995057) on HNPC damage. The results showed that the blockade of TNFR1 by TNFR1 siRNA and GSK1995057 effectively suppressed the cell viability loss, apoptosis, and inflammation induced by LPS in HNPCs. Furthermore, we found that TNFR1 siRNA and GSK1995057 inhibited activation of the NF-KB and MAPK signalling pathways in LPS-stimulated HNPCs. In summary, the blockade of TNFR1 effectively suppressed LPS-induced apoptosis and inflammation in HNPCs through the NF-KB and MAPK signalling pathways. This revealed that the blockade of TNFR1 may provide a potential therapeutic treatment for IDD.

Protein regulation strategies of the mouse spleen in response to Babesia microti infection

BACKGROUND

Babesia is a protozoan parasite that infects red blood cells in some vertebrates. Some species of Babesia can induce zoonoses and cause considerable harm. As the largest immune organ in mammals, the spleen plays an important role in defending against Babesia infection. When infected with Babesia, the spleen is seriously injured but still actively initiates immunomodulatory responses.

METHODS

To explore the molecular mechanisms underlying the immune regulation and self-repair of the spleen in response to infection, this study used data-independent acquisition (DIA) quantitative proteomics to analyse changes in expression levels of global proteins and in phosphorylation modification in spleen tissue after Babesia microti infection in mice.

RESULTS

After mice were infected with B. microti, their spleens were seriously damaged. Using bioinformatics methods to analyse dynamic changes in a large number of proteins, we found that the spleen still initiated immune responses to combat the infection, with immune-related proteins playing an important role, including cathepsin D (CTSD), interferon-induced protein 44 (IFI44), interleukin-2 enhancer-binding factor 2 (ILF2), interleukin enhancer-binding factor 3 (ILF3) and signal transducer and activator of transcription 5A (STAT5A). In addition, some proteins related to iron metabolism were also involved in the repair of the spleen after B. microti infection, including serotransferrin, lactoferrin, transferrin receptor protein 1 (TfR1) and glutamate-cysteine ligase (GCL). At the same time, the expression and phosphorylation of proteins related to the growth and development of the spleen also changed, including protein kinase C-δ (PKC-δ), mitogen-activated protein kinase (MAPK) 3/1, growth factor receptor-bound protein 2 (Grb2) and P21-activated kinase 2 (PAK2).

CONCLUSIONS

Immune-related proteins, iron metabolism-related proteins and growth and development-related proteins play an important role in the regulation of spleen injury and maintenance of homeostasis. This study provides an important basis for the diagnosis and treatment of babesiosis.

Multiscale Regulation of the Intervertebral Disc: Achievements in Experimental, In Silico, and Regenerative Research

Intervertebral disc (IVD) degeneration is a major risk factor of low back pain. It is defined by a progressive loss of the IVD structure and functionality, leading to severe impairments with restricted treatment options due to the highly demanding mechanical exposure of the IVD. Degenerative changes in the IVD usually increase with age but at an accelerated rate in some individuals. To understand the initiation and progression of this disease, it is crucial to identify key top-down and bottom-up regulations' processes, across the cell, tissue, and organ levels, in health and disease. Owing to unremitting investigation of experimental research, the comprehension of detailed cell signaling pathways and their effect on matrix turnover significantly rose. Likewise, in silico research substantially contributed to a holistic understanding of spatiotemporal effects and complex, multifactorial interactions within the IVD. Together with important achievements in the research of biomaterials, manifold promising approaches for regenerative treatment options were presented over the last years. This review provides an integrative analysis of the current knowledge about (1) the multiscale function and regulation of the IVD in health and disease, (2) the possible regenerative strategies, and (3) the in silico models that shall eventually support the development of advanced therapies.

FK506 Induces the TGF-β1/Smad 3 Pathway Independently of Calcineurin Inhibition to Prevent Intervertebral Disk Degeneration

Background

Intervertebral disk (IVD) degeneration is the most common cause of lower back pain. Inhibiting inflammation is a key strategy for delaying IVD degeneration. Tacrolimus (FK506) is a potent immunosuppressive agent that is also beneficial to chondrocytes via alleviating inflammation. However, the potential function of FK506 in IVD and the underlying mechanisms remain unknown. The current study is aim at exploring the underlying mechanism of FK506 in preventing IVD degeneration.

Methods

Cell morphology was imaged using an optical microscope. mRNA levels of nucleus pulposus (NP) matrix components were determined by qRT-PCR, and protein expression NP matrix components was assessed by western blotting. A rat caudal IVD degeneration model was established to test for FK506 in vivo.

Results

FK506 improved the morphology of NP cells and the cell function at both the mRNA and protein level. FK506 could attenuate NP degeneration induced by IL-1β. Furthermore, FK506 exerted its function via TGFβ/Smad3 activation instead of through calcineurin inhibition. Inhibition of the TGF-β pathway prevented the protective effect of FK506 on IVD degeneration. In an in vivo study, FK506 injection reversed the development of rat caudal IVD degeneration influenced by Smad3.

Conclusion

Our current study demonstrates the positive effect of FK506 on delaying the degeneration of IVD via the TGFβ/Smad3 pathway.

Animal models of regenerative medicine for biological treatment approaches of degenerative disc diseases

Degenerative disc disease (DDD) is a painful, chronic and progressive disease, which is characterized by inflammation, structural and biological deterioration of the intervertebral disc (IVD) tissues. DDD is specified as cell-, age-, and genetic-dependent degenerative process that can be accelerated by environmental factors. It is one of the major causes of chronic back pain and disability affecting millions of people globally. Current treatment options, such as physical rehabilitation, pain management, and surgical intervention, can provide only temporary pain relief. Different animal models have been used to study the process of IVD degeneration and develop therapeutic options that may restore the structure and function of degenerative discs. Several research works have depicted considerable progress in understanding the biological basis of disc degeneration and the therapeutic potentials of cell transplantation, gene therapy, applications of supporting biomaterials and bioactive factors, or a combination thereof. Since animal models play increasingly significant roles in treatment approaches of DDD, we conducted an electronic database search on Medline through June 2020 to identify, compare, and discuss publications regarding biological therapeutic approaches of DDD that based on intradiscal treatment strategies. We provide an up-to-date overview of biological treatment strategies in animal models including mouse, rat, rabbit, porcine, bovine, ovine, caprine, canine, and primate models. Although no animal model could profoundly reproduce the clinical conditions in humans; animal models have played important roles in specifying our knowledge about the pathophysiology of DDD. They are crucial for developing new therapy approaches for clinical applications.

Calcitonin inhibits intervertebral disc degeneration by regulating protein kinase C

Intervertebral disc degeneration (IVDD) is the most critical factor that causes low back pain. Molecular biotherapy is a fundamental strategy for IVDD treatment. Calcitonin can promote the proliferation of chondrocytes, stimulate the synthesis of matrix and prevent cartilage degeneration. However, its effect and the underlying mechanism for IVDD have not been fully revealed. Chondrogenic specific matrix components’ mRNA expression of nucleus pulposus cell (NPC) was determined by qPCR. Protein expression of NPC matrix components and protein kinase C was determined by Western blotting. A rat caudal intervertebral disc degeneration model was established and tested for calcitonin in vivo. IL‐1 induced NPC change via decreasing protein kinase C (PKC)‐ε phosphorylation, while increasing PKC‐δ phosphorylation. Calcitonin treatment could prevent or reverse IL‐1‐induced cellular change on PKC signalling associated with degeneration. The positive effect of calcitonin on IVDD in vivo was verified on a rat caudal model. In summary, this study, for the first time, elucidated the important role of calcitonin in the regulation of matrix components in the nucleus of the intervertebral disc. Calcitonin can delay degeneration of the intervertebral disc nucleus by activating the PKC‐ε pathway and inhibiting the PKC‐δ pathway.

Involvement of the G-Protein-Coupled Receptor 4 in the Increased Expression of RANK/RANKL/OPG System and Neurotrophins by Nucleus Pulposus Cells under the Degenerated Intervertebral Disc-Like Acidic Microenvironment

Intervertebral disc (IVD) degeneration is associated with local inflammation and increased expression of neurotrophins. Acidic microenvironment is believed to cause the progression of IVD degeneration. However, there is a paucity of information regarding the relationship between acidic microenvironment and the inflammation and expression of neurotrophins in IVD. G-protein-coupled receptor 4 (GPR4) is a pH-sensing receptor, which can activate the inflammation and increase the expression levels of nerve growth factor in acidic microenvironment. In this study, culture media with pH 7.2 (representing the normal IVD-like acidic condition) and pH 6.5 (degenerated IVD-like acidic condition) were prepared. The gene and protein expression levels of GPR4 in SD rat nucleus pulposus cells were determined under the acidic conditions. And cyclic AMP (cAMP), the second messenger of GPR4, was assayed. Furthermore, the expression levels of receptor activator of nuclear factor κ B (RANK), RANKL ligand (RANKL), osteoprotegerin (OPG), nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) were also determined. To clarify the involvement of GPR4 in the upregulation of the expression of RANK/RANKL/OPG system and neurotrophins, gene knockdown and forced expression of GPR4 and inhibiting its downstream cAMP accumulation and Ca²⁺ mobilization were performed. The alternation of the expression levels of matrix metalloproteinase-3 (MMP-3), MMP-13, and aggrecanase-2 (ADAMTS-5) were evaluated by RT-PCR and western blot. The results showed that GPR4 was expressed in rat nucleus pulposus cells, and the expression was upregulated under the degenerated IVD-like acidic microenvironment. cAMP accumulation levels were increased under the degenerated IVD-like acidic culture conditions. The expression levels of RANK, RANKL, OPG, NGF, and BNDF were significantly upregulated under the degenerated IVD-like acidic microenvironment. GPR4 knockdown and reduction of cAMP by the inhibitor SQ22536 abolished the upregulation of the expression of RANK, RANKL, OPG, NGF, and BNDF under the degenerated IVD-like acidic microenvironment. On the opposite, acidosis-induced cAMP accumulation and upregulation of RANK, RANKL, OPG, NGF, and BNDF were further promoted by GPR4 overexpression. The expression levels of MMP-3, MMP-13, and ADAMTS-5 were upregulated under the degenerated IVD-like acidic condition, which can be promoted or attenuated by GPR4 overexpression or knockdown, respectively. We concluded that GPR4-mediated cAMP accumulation was involved in the increased expression of RANK/RANKL/OPG system and neurotrophins by nucleus pulposus cells under the degenerated IVD-like acidic microenvironment.

MiR-423-5p Regulates Cells Apoptosis and Extracellular Matrix Degradation via Nucleotide-Binding, Leucine-Rich Repeat Containing X1 (NLRX1) in Interleukin 1 beta (IL-1β)-Induced Human Nucleus Pulposus Cells

BACKGROUND Disc degeneration is characterized partly by the degradation in the extracellular matrix (ECM) and excess apoptosis of nucleus pulposus (NP) cells. NLRX1 (nucleotide-binding, leucine-rich repeat containing X1) is different from the other nucleotide-binding-domain and leucine-rich-repeat proteins and mainly located to the mitochondrial. It negatively regulates NF-κB (nuclear factor kappa B) and apoptosis inhibition. However, how NLRX1 is regulated and exerts effects in disc degeneration is unclear. Thus, the study aimed to analyze the effects of NLRX1 on NP cells. MATERIAL AND METHODS NLRX1 expression was detected in interleukin (IL)-1β-induced NP cells by western blot and quantitative real-time polymerase chain reaction (qRT-PCR). Then, NLRX1 was overexpressed in IL-1β-induced NP cells to detect apoptosis-related proteins and the extracellular matrix (ECM) by western blot, along with the detection of apoptosis levels using flow cytometry. StarBase predicted miR-423-5p target 3'UTR of NLRX1. Dual luciferase reporter assay showed that miR-423-5p could bind to the 3'UTR of NLRX1. Besides, miR-423-5p significantly affected NLRX1 levels detected by qRT-qPCR. RESULTS The miR-423-5p overexpression markedly, and negatively regulated the protective effects of NLRX1 on IL-1β induced NP cells. Thus, our results suggested that miR-423-5p mediated the regulation of NLRX1 to affect apoptosis and ECM levels in IL-1β induced NP cells. CONCLUSIONS miR-423-5p and NLRX1 could be potential therapeutic targets for patients with disc degeneration.