Bacopaside I, acting as an aquaporin 1 inhibitor, ameliorates rheumatoid arthritis via suppressing aquaporin 1-mediated autophagy.

Abstract

Background: Aquaporin 1 (AQP1) is a promising target for regulating fibroblast-like synoviocyte (FLS) behaviors in rheumatoid arthritis (RA). Bacopaside I (BSI), the main active compound of the herbal medicine Bacopa monnieri with anti-RA effects, inhibits tumor cell growth by blocking AQP1, but its potential use in RA is unclear.

Purpose: To address BSI's anti-RA effects and elucidate its underlying mechanisms.

Methods: We investigated BSI's therapeutic effects on TNF-α-induced RA FLS and identified AQP1 as its direct target through molecular docking, cellular thermal shift assay (CETSA), and AQP1 knockdown experiments. We studied BSI's impacts on rat adjuvant-induced arthritis (AIA) and synovial proliferation, apoptosis, and autophagy in AIA rat synovium. We explored the role of autophagy inhibition in BSI's effects in vitro and in vivo by co-treating with the autophagy activator rapamycin (Rapa) and/or the inhibitor 3-methyladenine (3-MA).

Results: BSI suppressed proliferation, promoted apoptosis, and reduced autophagy in TNF-α-stimulated RA FLS. Notably, BSI's in vitro effects were reduced by Rapa and enhanced by 3-MA. The molecular docking and CETSA confirmed BSI's binding to AQP1, while AQP1 knockdown invalidated BSI's in vitro effects, further indicating AQP1 as the target of BSI. In vivo, BSI attenuated the severity of rat AIA, alongside reduced synovial proliferation, increased apoptosis, and decreased autophagy within AIA rat synovium. Moreover, Rapa co-treatment negated BSI's effects on synovial proliferation and apoptosis and abolished its anti-AIA activity.

Conclusions: BSI, as an AQP1 inhibitor, hindered AQP1-mediated autophagy, causing increased apoptosis, reduced proliferation in RA FLS, and relieved rat AIA symptoms.