Effects of Tumor Necrosis Factor Alpha on the Expression of Programmed Cell Death Factor 5 in Arthritis

A large-scale Boolean model of the rheumatoid arthritis fibroblast-like synoviocytes predicts drug synergies in the arthritic joint

Rheumatoid arthritis (RA) is a complex autoimmune disease with an unknown aetiology. However, rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS) play a significant role in initiating and perpetuating destructive joint inflammation by expressing immuno-modulating cytokines, adhesion molecules, and matrix remodelling enzymes. In addition, RA-FLS are primary drivers of inflammation, displaying high proliferative rates and an apoptosis-resistant phenotype. Thus, RA-FLS-directed therapies could become a complementary approach to immune-directed therapies by predicting the optimal conditions that would favour RA-FLS apoptosis, limit inflammation, slow the proliferation rate and minimise bone erosion and cartilage destruction. In this paper, we present a large-scale Boolean model for RA-FLS that consists of five submodels focusing on apoptosis, cell proliferation, matrix degradation, bone erosion and inflammation. The five-phenotype-specific submodels can be simulated independently or as a global model. In silico simulations and perturbations reproduced the expected biological behaviour of the system under defined initial conditions and input values. The model was then used to mimic the effect of mono or combined therapeutic treatments and predict novel targets and drug candidates through drug repurposing analysis.

Effects of Modified Glucosamine on the Chondrogenic Potential of Circulating Stem Cells under Experimental Inflammation

Glucosamine (GlcN) is a glycosaminoglycan (GAGs) constituent in connective tissues. It is naturally produced by our body or consumed from diets. In the last decade, in vitro and in vivo trials have demonstrated that the administration of GlcN or its derivates has a protective effect on cartilage when the balance between catabolic and anabolic processes is disrupted and cells are no longer able to fully compensate for the loss of collagen and proteoglycans. To date, these benefits are still controversial because the mechanism of action of GlcN is not yet well clarified. In this study, we have characterized the biological activities of an amino acid (AA) derivate of GlcN, called DCF001, in the growth and chondrogenic induction of circulating multipotent stem cells (CMCs) after priming with tumor necrosis factor-alpha (TNFα), a pleiotropic cytokine commonly expressed in chronic inflammatory joint diseases. In the present work, stem cells were isolated from the human peripheral blood of healthy donors. After priming with TNFα (10 ng/mL) for 3 h, cultures were treated for 24 h with DCF001 (1 μg/mL) dissolved in a proliferative (PM) or chondrogenic (CM) medium. Cell proliferation was analyzed using a Corning^® Cell Counter and trypan blue exclusion technique. To evaluate the potentialities of DCF001 in counteracting the inflammatory response to TNFα, we measured the amount of extracellular ATP (eATP) and the expression of adenosine-generating enzymes CD39/CD73, TNFα receptors, and NF-κB inhibitor IκBα using flow cytometry. Finally, total RNA was extracted to perform a gene expression study of some chondrogenic differentiation markers (COL2A1, RUNX2, and MMP13). Our analysis has shed light on the ability of DCF001 to (a) regulate the expression of CD39, CD73, and TNF receptors; (b) modulate eATP under differentiative induction; (c) enhance the inhibitory activity of IκBα, reducing its phosphorylation after TNFα stimulation; and (d) preserve the chondrogenic potentialities of stem cells. Although preliminary, these results suggest that DCF001 could be a valuable supplement for ameliorating the outcome of cartilage repair interventions, enhancing the efficacy of endogenous stem cells under inflammatory stimuli.

Corresponding Changes of Autophagy-Related Genes and Proteins in Different Stages of Knee Osteoarthritis: An Animal Model Study

Objective

To investigate the effect of autophagy expression levels of different weight‐bearing states and different stages of osteoarthritis in animal models, as well as the corresponding mechanisms.

Methods

We used the male Sprague–Dawley (SD) rats (12‐week‐old, SPF) to establish the OA animal models by modified Hulth method, and grouped animal models according to the length of time after surgery and different weight‐bearing areas. RT‐qPCR was carried out for detection of autophagy‐related genes such as Atg7, Atg12, P62, etc. Western blot analysis was used to detect the expression levels of corresponding autophagy‐related proteins such as LC3B, P62, etc. T test was performed for statistical analysis to compare different groups, while the differences were deemed statistically significant with P < 0.05. Transmission electron microscopy was used to observe the autophagosome to demonstrate the level of autophagy expression and the status of the chondrocytes.

Results

The results of the RT‐qPCR testing showed that when the weight‐bearing cartilage of the 4‐week group (relatively mild) was compared with that of the 10‐week group (relatively severe), there were statistically significant differences in all the genes tested, in detail: Atg3 (P < 0.01), Atg7 (P < 0.01), Atg12 (P < 0.01), P62 (P < 0.0001). The expression of autophagy‐related mRNA in the 4‐week group is increased compared with that of the 10‐week group. As for the expression of proteins, Western blotting showed that in the comparison between the 4‐ and the 10‐week groups, statistically significant results include Atg12 (P < 0.01) in the non‐weight‐bearing area, with decreased autophagy in the 10‐week group compared with that of the 4‐week group, while expression of LC3B (P < 0.05) protein was significantly higher in the 4‐week group than in the control in the non‐weight‐bearing area. The expression of LC3B (P < 0.0001) and P62 (P < 0.05) in the 10‐week group were higher than that of the control. Transmission electron microscope showed that autophagy in the weight‐bearing area is stronger than that in the non‐weight‐bearing area, and autophagy in the 4‐week group is stronger than in the 10‐week group for the weight‐bearing area.

Conclusions

The expression of autophagy varies during different stages of osteoarthritis, in which the autophagy is stronger in the early stage of osteoarthritis, and gradually decreases with the progression of the disease. Autophagy in different weight‐bearing areas may also be different.

Silencing SGK1 alleviates osteoarthritis through epigenetic regulation of CREB1 and ABCA1 expression

AIM

Osteoarthritis (OA) is the most common joint disorder and a leading cause of disability. While early proactive management is crucial in alleviating symptoms in OA patients, currently available therapeutic approaches are yet to achieve an ideal level of efficacy. The path to the development of a potent treatment begins with the thorough understanding of the pathophysiology of OA. The present study aims to explore the mechanism by which SGK1 is involved in OA progression.

METHODS

Firstly, the potential target gene of SGK1 was screened and SGK1 expression was determined in OA through bioinformatics analysis. Mouse OA model was then established and chondrocytes were extracted, after which inflammation was induced with lipopolysaccharide (LPS). Following LPS treatment, the chondrocytes were transfected with synthesized plasmids to explore the impact of SGK1, CREB1, and ABCA1 on apoptosis, proliferation and inflammation in OA. ChIP-PCR and dual-luciferase reporter gene assay were conducted to determine the binding relation between SGK1 and CREB1 as well as between CREB1 and ABCA1.

RESULTS

OA mice presented with high expression of SGK1. Interestingly, we found that SGK1 inhibited CREB1 expression in chondrocytes, thereby inducing inflammation and suppressing chondrocyte proliferation. CREB1 was found to have a positive correlation with ABCA1 expression, while down-regulation of CREB1 resulted in the inhibition of cell proliferation and aggravated inflammation, which could be reversed by overexpressed ABCA1.

CONCLUSION

Taken altogether, silencing of SGK1 alleviated OA through epigenetic regulation of CREB1 and ABCA1 expression. These findings may provide novel insight into SGK1-based strategy for OA treatment.