Nitidine chloride inhibits fibroblast like synoviocytes-mediated rheumatoid synovial inflammation and joint destruction by targeting KCNH1

Highlights

• NC treatment reduced synovial inflammation and joint destruction of RA.

• KCNH1 is the new targeting gene of NC on RA FLS.

• KCNH1 is involved in the regulation of abnormal biological behavior of RA FLS.

Abstract

Objective

Nitidine chloride (NC), a natural small molecular compound from traditional Chinese herbal medicine zanthoxylum nitidum, has been shown to exhibit anti-tumor effect. However, its role in autoimmune diseases such as rheumatoid arthritis (RA) is unknown. Here, we investigate the effect of NC in controlling fibroblast-like synoviocytes (FLS)-mediated synovial inflammation and joint destruction in RA and further explore its underlying mechanism(s).

Methods

FLSs were separated from synovial tissues obtained from patients with RA. Protein expression was analyzed by Western blot or immunohistochemistry. Gene expression was measured using quantitative RT-PCR. ELISA was used to measure the levels of cytokines and MMPs. Cell proliferation was detected using EdU incorporation. Migration and invasion were evaluated by Boyden chamber assay. RNA sequencing analysis was used to identify the target of NC. Collagen-induced arthritis (CIA) model was used to evaluate the in vivo effect of NC.

Results

NC treatment reduced the proliferation, migration, invasion, and lamellipodia formation but not apoptosis of RA FLSs. We also demonstrated the inhibitory effect of NC on TNF-α-induced expression and secretion of IL-6, IL-8, CCL-2, MMP-1 and MMP-13. Furthermore, we identified KCNH1, a gene that encodes ether-à-go-go-1 channel, as a novel targeting gene of NC in RA FLSs. KCNH1 expression was increased in FLSs and synovial tissues from patients with RA compared to healthy controls. KCNH1 knockdown or NC treatment decreased the TNF-α-induced phosphorylation of AKT. Interestingly, NC treatment ameliorated the severity of arthritis and reduced synovial KCNH1 expression in mice with CIA.

Conclusions

Our data demonstrate that NC treatment inhibits aggressive and inflammatory actions of RA FLSs by targeting KCNH1 and sequential inhibition of AKT phosphorylation. Our findings suggest that NC might control FLS-mediated rheumatoid synovial inflammation and joint destruction, and be a novel therapeutic agent for RA.

Introduction

Rheumatoid arthritis (RA) is a common autoimmune disease characterized by persistent joint inflammation and destruction. Fibroblast-like synoviocytes (FLSs), the predominant joint-lining cells, play important roles in promoting synovial inflammation and joint destruction of RA. In addition to secreting a number of proinflammatory cytokines, RA FLSs exhibit aggressive behavior to cartilage and bone [1], [2], [3]. Increasing evidence indicates that selectively targeting RA FLS might be promising for improving rheumatoid joint damage [4], [5], [6].

Conventional and biological disease-modifying antirheumatic drugs (DMARDs) have brough great improvement for patients with RA, but their clinical use is limited due to insufficient efficacy, potentially serious toxicity and high cost [7]. Thus, it is still necessary to explore alternative therapeutic drugs for RA. It is well known that natural compounds purified from herbal medicines usually exhibit the advantages of wide sources, a low toxicity profile and relatively low prices [8]. Therefore, exploring new herbal medicine–based antirheumatic drugs that target RA FLS might provide novel pharmaceutical drugs for RA.

Nitidine chloride (NC) is a natural bioactive small molecular compound purified from zanthoxylum nitidum, a traditional Chinese herbal medicine which has inhibitory effect on pain and swelling of joint [9]. It has shown that NC exhibits a wide range of biological effects such as anti-malarial, anti-virus, and anti-tumor cells [9], [10], [11]. Increasing evidence indicates that NC has a role in modulating the migratory and invasive behavior in some cancer cells. For instance, NC suppresses the migration and invasion of osteosarcoma cells [12]. NC treatment inhibits the proliferation and invasion of renal cancer cells [13], [14]. Interestingly, a previous study shows the inhibitory effect of NC on LPS-induced inflammatory cytokines production in RAW 264.7 cells [15]. However, to date, it is still unknown whether NC has therapeutic potential for inflammatory arthritis including RA.

In the present study, we investigated the effect of NC on inflammation, proliferation and aggression of RA FLS, and subsequently explored the underlying mechanisms by which this agent inhibits abnormal RA FLS functions. Moreover, we used the collagen-induced arthritis (CIA) mouse model to evaluate the in vivo effect of NC on improvement of the severity of arthritis.