SPHK-2 Promotes the Particle-Induced Inflammation of RAW264.7 by Maintaining Consistent Expression of TNF-α and IL-6

Abstract

Aseptic implant loosening is a devastating long-term complication of total joint arthroplasty. It is mainly initiated by the interaction of wear debris and macrophages. However, how does the chronic inflammation persist and how to stop it is poorly understood. Sphingosine kinases (SPHKs) are an essential feature of immunosuppressive M2 polarisation in macrophages and a promoter for chronic inflammation. In this study, RAW 264.7 macrophages were exposed to stimulation with titanium particles (0.1 mg/ml), and the subsequent expression of SPHKs and pro-inflammatory cytokines was evaluated. The effect of inhibitors of SPHKs (FTY720, PF543, and ABC294640) on titanium particle-challenged macrophages was analysed. As for results, the amount of sphingosine kinase (SPHK)-1 and SPHK-2 in RAW264.7 macrophages increased in the presence of titanium particles in a time-dependent manner. Two inhibitors of SPHKs (FTY720 and ABC294640) suppressed titanium particle-induced tumour necrosis factor (TNF)-α and interleukin (IL)-6 production in RAW264.7 macrophages. These findings suggest that persistent stimulation with titanium particles may lead to a consistent release of TNF-α and IL-6 via SPHK-2 activity, which may lead to aseptic implant loosening. Appropriate regulation of SPHK-2 may serve as a potential new strategy in the treatment of aseptic implant loosening.

The Immunosuppressant Fingolimod (FTY720) for the Treatment of Mechanical Force-Induced Abnormal Scars

“…Qin et al reported that FTY720 is effective in reducing brain inflammation by directing microglia after chronic cerebral hypoperfusion to M2 polarization [47]. FTY720 has been reported to suppress TNFα and IL6 production in RAW264.7 macrophages [48]. The results of the present study are in agreement with these previous reports.…”

Cellular stress promotes NOD1/2‐dependent inflammation via the endogenous metabolite sphingosine‐1‐phosphate

“…Previous studies reported that sphingosine kinases/S1P are required for ER and mitochondrial unfolded protein responses and contribute to protection against ER, mitochondrial, and oxidative stress (Lee et al, 2015;Qi et al, 2015;Kim & Sieburth, 2018;Kim & Sieburth, 2019). SPHK2 is required for inflammatory responses in macrophages upon ureteral obstruction and titanium particle stimulation (Ghosh et al, 2018;Yang et al, 2018). It inhibits IL6 production at late time points upon LPS stimulation (Weigert Our studies complement the current knowledge about immune roles of SPHKs by showing that S1P, a product of SPHKs, modulates cytokine responses during stress-induced inflammation.…”

SPHK Inhibitors and Zoledronic Acid Suppress Osteoclastogenesis and Wear Particle-Induced Osteolysis

“…The average diameter of the Ti particles is 3.2 ± 2.7 μm. The Ti particle storage solution is washed with 70% ethanol and autoclaved to remove endotoxins, according to the previously published methods ( Yang et al, 2018 ; Xian et al, 2020 ; Chen et al, 2021 ). After sterility is ensured, the Limulus assistant kit (Xiamen Houshiji, Fujian, China) is used to determine the endotoxin, and endotoxins <0.01 Eu can be used for experiments in vivo and in vitro .…”

“…Our previous studies have found that SPHKs are important mediators that regulate the inflammatory response of macrophages induced by wear particles. The upregulation of SPHKs enables macrophages to synthesize and continuously release inflammatory factors, causing local persistent inflammation and immune function damage, eventually leading to loosening of the prosthesis ( Yang et al, 2018 ). SPHK2 generates sphingosine-1-phosphate (S1P) as an isoenzyme ( Hait et al, 2009 ).…”