norisoboldine and Arthritis--Rheumatoid

Norisoboldine (NOR), an isoquinoline alkaloid with very poor oral bioavailability, was previously proven to have a unique anti-arthritis activity in rats by inducing intestinal Treg cells. Herein, we explored its underlying mechanism in view of aryl hydrocarbon receptor (AhR).. The differentiation of regulatory T cells (Treg cells) and IL-17-producing T cells (Th17 cells) from naïve T cells was analyzed in vitro. The key role of AhR was ascertained using siRNA transfection. AhR agonistic effect was verified based on the activation of downstream signaling pathway and target genes. The correlation between AhR activation and Treg cell induction as well as pathological changes of joints was confirmed in collagen-induced arthritis (CIA) mouse model.. NOR promoted intestinal Treg cell differentiation and function in an AhR-dependent manner. It acted as an AhR agonist, as evidenced by induction of CYP1A1 expression and activity, promotion of AhR/Hsp90 dissociation and AhR nuclear translocation, induction of XRE reporter activity, and facilitation of AhR/XRE binding. In CIA mice, NOR exerted substantial anti-arthritic effect through enhancing AhR activation in intestinal tissues and inducing intestinal Treg cell generation, which could be largely abolished by resveratrol (a antagonist of AhR). An adoptive transfer of Treg cells from NOR-treated mice could successfully alleviate arthritis symptoms in CIA mice.. Oral NOR induces the generation of intestinal Treg cells by the activation of AhR, and thereby exerts anti-arthritic effect.

Topics: Active Transport, Cell Nucleus; Alkaloids; Animals; Arthritis, Rheumatoid; Cell Differentiation; Cell Nucleus; Cytochrome P-450 CYP1A1; Gene Expression Regulation, Enzymologic; HSP90 Heat-Shock Proteins; Intestines; Ligands; Male; Mice; Receptors, Aryl Hydrocarbon; Signal Transduction; T-Lymphocytes, Regulatory; Th17 Cells

Interleukin-6 (IL-6) is a pleiotropic cytokine secreted by macrophages and others and it has been proven to be a potential therapeutic target of RA. Norisoboldine (NOR) is the main isoquinoline alkaloid constituent in the dry roots of Lindera aggregata (Sims) Kosterm. (L. strychnifolia Vill.), which has long been used in traditional Chinese medicine for treating RA and other diseases. Our previous studies indicated that NOR was able to attenuate inflammation and joint destruction in collagen II-induced arthritis of mice. To further recognize the anti-rheumatoid potentials of NOR, the present study addressed whether and how NOR interfered with IL-6 production from fibroblast-like synoviocytes (FLS), key effector cells in the development and progression of RA. FLS, obtained from the synovial tissues of rats with adjuvant arthritis, showed incremental release of IL-6 after stimulated with IL-1β in vitro. NOR (10, 30, and 60 µM) could reduce the production of IL-6 in a concentration-dependent manner. It also down-regulated the phosphorylations of mitogen-activated protein kinases (MAPKs), protein kinase C (PKC), and transcriptional factor nuclear factor-κB (NF-κB)-p65 (ser 276) as well as cAMP response element-binding protein (CREB) in FLS. By using specific inhibitors, PKC was shown to be the upstream protein of MAPKs, and p38 MAPK was at the upstream of CREB. It was concluded that preventing IL-6 release from FLS might be an important mechanism for NOR displaying anti-RA property, and the action of NOR was relative to inhibition of PKC/MAPKs/p65/CREB pathways.

Topics: Alkaloids; Animals; Arthritis, Rheumatoid; Cyclic AMP Response Element-Binding Protein; Fibroblasts; Interleukin-6; NF-kappa B; Protein Kinase C; Rats; Signal Transduction; Synovial Membrane