Effects of echinacoside on the regulation of mitochondrial fission induced by TBK1/Drp1 in rheumatoid arthritis.

Background: Dysregulated mitochondrial fission in synovial tissue is a key contributor to the progression of rheumatoid arthritis (RA), and echinacoside (ECH) has been shown to modulate this process in a mouse model of RA.

Objectives: This study aimed to investigate the effects of echinacoside (ECH) on the proliferation and inflammatory response of human fibroblast-like synoviocytes (MH7A cells), and to elucidate the potential underlying mechanisms.

Material and methods: The expression and co-localization of TANK-binding kinase 1 (TBK1) and phosphorylated dynamin-related protein 1 (p-Drp1) in synovial tissues from patients with and without RA were analyzed. MH7A cells were exposed to either ECH or 0.1% dimethyl sulfoxide (DMSO). Cell proliferation was detected using Cell Counting Kit-8 (CCK-8) assay and reactive oxygen species (ROS) expression was detected with dichlorofluorescin (DCFH) staining. The levels of interleukin (IL)-6, IL-8, tumor necrosis factor alpha (TNF-α), cyclooxygenase (COX)-2, IL-1β, TANK-binding kinase 1 (TBK1), and Drp1 and the oxidative stress markers NF-E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO1) were measured using quantitative real-time polymerase chain reaction (qPCR). The mitochondrial morphology was detected with transmission electron microscopy (TEM), and the expression levels of p-TBK1 (S172), TBK1, p-Drp1 (S616), p-Drp1 (S637), and Drp1 were assessed using western blotting.

Results: Compared to tissue from non-RA patients, RA synovial tissue exhibited higher expression and co-localization of TBK1 and phosphorylated Drp1 (p-Drp1). Following ECH treatment, MH7A cell proliferation and inflammatory cytokine secretion were reduced, while the expression of antioxidant stress markers was significantly increased. Furthermore, ECH treatment led to reduced levels of ROS, mitochondrial fragmentation and dysregulated mitochondrial fission in MH7A cells, along with decreased expression of p-TBK1 (Ser172) and p-Drp1 (Ser616), while p-Drp1 (Ser637) levels were increased.

Conclusions: Echinacoside regulates abnormal mitochondrial fission via the TBK1/Drp1 pathway, reducing the proliferation and inflammatory response of MH7A cells.