Inhibition of sphingosine 1-phosphate (S1P) receptor 1/2/3 ameliorates biological dysfunction in rheumatoid arthritis fibroblast-like synoviocyte MH7A cells through Gαi/Gαs rebalancing

Microglia-mediated pericytes migration and fibroblast transition via S1P/S1P3/YAP signaling pathway after spinal cord injury

Platelet-derived growth factor receptor β positive (PDGFRβ+) pericytes detach from the microvascular wall and migrate into the injury center following spinal cord injury (SCI), which has been widely regarded as the main source of fibrotic scar, but the mechanism of migration and fibroblast transition remains elusive. Here we show the associated spatiotemporal distribution between microglia and pericytes at three and seven days post-injury (dpi). The increased expression of Sphingosine kinase-1 (SPHK1) in microglia significantly raised the concentration of Sphingosine-1-phosphate (S1P) in the spinal cord, which promotes migration and fibroblast transition of pericyte. In vitro experiments, we found the elevated Sphingosine 1-phosphate receptor 3 (S1P3), the S1P/S1PR3 axis inhibited the phosphorylation of YAP and promoted its nuclear translocation, which contributed to the formation of alpha-smooth muscle actin (α-SMA) and collagen type I (COL1) protein, This process can be blocked by an S1P3 specific inhibitor TY52156 in vitro. The S1P/S1P3/YAP pathway might be a potential target for treatment in SCI.

Protective effects of Typhonii Rhizoma in rheumatoid arthritis rats revealed by integrated metabolomics and network pharmacology

Rheumatoid arthritis (RA) is an autoimmune disease with a 0.5% prevalence worldwide. Inflammation, periosteal proliferation and joint destruction are the main clinical symptoms of RA. Typhonii Rhizoma (TR) is the dry tuber of the Araceae plant Typhonium giganteum Engl, and possesses many uses such as dispelling obstructive wind-phlegm and relieving pain. It is used for the clinical treatment of arthromyodynia and RA. However, the mechanism of action remains unclear. In this study, we first evaluated the effects of TR in type II collagen-induced RA model rats. Secondly, in serum metabolomics, TR could ameliorate 11 potential metabolites in RA model rats and reversed RA through pentose and glucuronate interconversions, sphingolipid metabolism, glycerophospholipid metabolism and tryptophan metabolism. To further explore the mechanisms of TR, 40 chemical constituents were used to establish a component-target interaction network. Some key genes were verified by in vitro pharmacological tests by integrating the results from the network pharmacology and metabolomics. The verification results showed that the mechanisms of TR against RA may be related to the inhibition of the production of inflammatory cytokines and the expression and function of HIF1-α. This study serves as a theoretical basis for the treatment of RA with TR.

Geniposide augments apoptosis in fibroblast-like synoviocytes by restoring hypoxia-enhanced JNK-BNIP3-mediated autophagy

BACKGROUND

As the main effector cells of chronic inflammation and hyperplasia of synovium, fibroblast-like synoviocytes (FLSs) show abnormal proliferation and insufficient apoptosis in the hypoxic microenvironment, which is due to the increase of BNIP3-mediated autophagy. This study aimed to explore the mechanism of geniposide (GE) on hypoxia-induced hyper-proliferative FLSs with a focus on autophagy and the JNK-BNIP3 pathway.

METHODS

The dynamic changes of autophagy, apoptosis, and hypoxia-related proteins in adjuvant arthritis (AA) rats were detected by immunohistochemistry and Western blot. The proliferation, autophagy, apoptosis, and mitochondrial state of FLSs were detected by CCK-8, flow cytometry, immunofluorescence, and transmission electron microscopy, respectively. Western blot, qRT-PCR, and co-immunoprecipitation were used to detect the expression of the JNK-BNIP3 pathway.

RESULTS

The excessive accumulation of BNIP3 in the synovium of AA rats was accompanied by inhibition of apoptosis and an increase in autophagy. GE inhibited the expression of BNIP3, enhanced apoptosis, decreased autophagy, and improved chronic inflammation and hyperplasia of synovium. The amount of autophagy under different oxygen concentrations was the key to mediating the different survival rates of FLSs, and the inhibition of autophagy triggered apoptosis. GE suppressed the proliferation of FLSs and down-regulated autophagy, leading to the accumulation of ROS and the decrease of mitochondrial membrane potential, induced the increase of apoptosis, and suppressed the accumulation of BNIP3 and the hyperphosphorylation of JNK.

CONCLUSION

GE inhibited autophagy by restoring the hypoxia-induced activated JNK-BNIP3 pathway, inducing mitochondrial oxidative damage, augmented apoptosis, and decreased survival rate of FLSs.

Silence of S1PR4 Represses the Activation of Fibroblast-like Synoviocytes by Regulating IL-17/STAT3 Signaling Pathway

Rheumatoid arthritis (RA) is a chronic inflammatory disease with persistent inflammation and progressive joint damage. However, the underlying pathological mechanisms of RA are still unclear. Fibroblast‑like synoviocytes (FLSs) play an important role in the pathogenesis of RA by the regulation of proliferation and apoptosis, and the release of multiple pro-inflammatory factors. The lipid mediator sphingosine-1-phosphate receptor 4 (S1PR4) is one of the sphingolipid sphingosine-1-phosphate (S1P) receptors, which affects the function of immune cells. However, the role of S1PR4 in the activation of FLSs and the development of RA is unknown. In this study, we found that the expression of S1PR4 was significantly increased in RA-FLSs. The silence of S1PR4 decreases the proliferation, migration, proinflammation, and promotes the apoptosis of RA-FLSs, accompanied with repressing interleukin-17 (IL-17)/signal transducer and activator of transcription 3 (STAT3) signal pathway. However, the regulatory effects of S1PR4 silencing on RA-FLSs were partly abolished by additional recombinant human (rh) IL-17A treatment. Therefore, our study demonstrated that S1PR4 silencing might inhibit proliferation, migration, proinflammation, and promote apoptosis of RA-FLSs partly by repressing IL-17, which suggests that inhibitors for S1PR4 might be a potentially promising strategy for the treatment of RA.

The interplay between fibroblast-like synovial and vascular endothelial cells leads to angiogenesis via the sphingosine-1-phosphate-induced RhoA-F-Actin and Ras-Erk1/2 pathways and the intervention of geniposide

The changes of fibroblast-like synoviocytes (FLSs) and vascular endothelial cells (VECs) biological functions are closely related to angiogenesis in rheumatoid arthritis (RA). Nevertheless, how the crosstalk between FLSs and VECs interferes with RA is far from being clarified. Herein, we studied the effect of the reciprocal interactions between FLSs and VECs on angiogenesis and mechanism of geniposide (GE). After administration of GE, improvement of synovial hyperplasia in adjuvant arthritis rats was accompanied by downregulation of SphK1 and p-Erk1/2. The dynamic interaction between FLSs and VECs triggers the release of S1P by activating p-Erk1/2 and SphK1, then activating RhoA-F-actin and Ras-Erk1/2 pathways. When exposed to the inflammatory microenvironment mediated by FLSs-VECs crosstalk, proliferation, migration, and permeability of VECs were enhanced, the angiogenic factors were imbalanced. Meanwhile, the proliferation and secretory ability of FLSs increased. Interestingly, depletion of S1P or blocking of the activation of SphK1 by GE and PF-543 prevented the changes. In conclusion, S1P released during FLSs-VECs crosstalk changed their biological functions by activating RhoA-F-actin and Ras-Erk1/2 pathways. GE acted on p-Erk1/2 and SphK1, inhibited the secretion of S1P, and blocked the interplay between FLSs and VECs. These results provide new insights into the mechanism of angiogenesis in RA.