Abstract
Triptolide (TP), an active component isolated from Tripterygiumwilfordii Hook F, has therapeutic potential against rheumatoid arthritis (RA). However, the underlying molecular mechanism has not been fully elucidated. The aim of this study is to investigate the mechanisms of TP acting on RA by combining bioinformatics analysis with experiment validation. The human protein targets of TP and the human genes of RA were found in the PubChem database and NCBI, respectively. These two dataset were then imported into Ingenuity Pathway Analysis (IPA) software online, and then the molecular network of TP on RA could be set up and analyzed. After that, both in vitro and in vivo experiments were done to further verify the prediction. The results indicated that the main canonical signal pathways of TP protein targets networks were mainly centered on cytokine and cellular immune signaling, and triggering receptors expressed on myeloid cells (TREM)-1 signaling was searched to be the top one shared signaling pathway and involved in the cytokine and cellular immune signaling. Further in vitro experiments indicated that TP not only remarkably lowered the levels of TREM-1 and DNAX-associated protein (DAP)12, but also significantly suppressed the activation of janus activating kinase (JAK)2 and signal transducers and activators of transcription (STAT)3. The expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 in lipopolysaccharides (LPS)-stimulated U937 cells also decreased after treatment with TP. Furthermore, TREM-1 knockdown was able to interfere with the inhibition effects of TP on these cytokines production. In vivo experiments showed that TP not only significantly inhibited the TREM-1 mRNA and DAP12 mRNA expression, and activation of JAK2 and STAT3 in ankle of rats with collagen-induced arthritis (CIA), but also remarkably decreased production of TNF-α, IL-1β and IL-6 in serum and joint. These findings demonstrated that TP could modulate the TREM1 signal pathway to inhibit the inflammatory response in RA.
Highlights
Rheumatoid arthritis (RA) is a complicated disease caused by various factors, such as environmental and genetic factors [1], and is characterized by an overactive immune system and synovial inflammation in multiple joints which will lead to irreversible joint destruction and severe disability in the absence of adequate treatment [2]
Many cytokines and chemokines are found in RA patients’ synovial fluid, such as interleukin (IL)-1α, IL-3, IL-2, IL-4, IL-6, IL-8, IL-17, interferon (IFN) γ, tumor necrosis factor (TNF) β, transforming growth factor (TGF) β, granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage inflammatory protein-3α (MIP-3α) (CCL20) [3,4]. These cytokines and chemokines are able to activate nuclear factor-κB (NF-κB), boost cyclo-oxygenase-2 (COX-2) production, induce nitric oxide synthase, synthesis of prostaglandin E2 (PGE2) and nitric oxide (NO), which result in the inflammation in synovial accompanied by arthrosis, swelling, hyperplasia, angiogenesis, bone destruction, and arthritic decay [5,6,7]
Triggering Receptors Expressed on Myeloid Cells (TREM)-1 Signaling Was an Important Signaling Pathway of Triptolide (TP) on Inflammatory Response in Rheumatoid Arthritis (RA)
Summary
Rheumatoid arthritis (RA) is a complicated disease caused by various factors, such as environmental and genetic factors [1], and is characterized by an overactive immune system and synovial inflammation in multiple joints which will lead to irreversible joint destruction and severe disability in the absence of adequate treatment [2]. Many cytokines and chemokines are found in RA patients’ synovial fluid, such as interleukin (IL)-1α, IL-3, IL-2, IL-4, IL-6, IL-8, IL-17, interferon (IFN) γ, tumor necrosis factor (TNF) β, transforming growth factor (TGF) β, granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage inflammatory protein-3α (MIP-3α) (CCL20) [3,4]. These cytokines and chemokines are able to activate nuclear factor-κB (NF-κB), boost cyclo-oxygenase-2 (COX-2) production , induce nitric oxide synthase (iNOS), synthesis of prostaglandin E2 (PGE2) and nitric oxide (NO), which result in the inflammation in synovial accompanied by arthrosis, swelling, hyperplasia, angiogenesis, bone destruction, and arthritic decay [5,6,7]. These evidences implicate that RA is even more complex than initially predicted
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