Abstract / Summary
Osteoarthritis (OA) is a chronic degenerative and debilitating disease. Reactive oxygen species (ROS) and oxidative stress play key roles in OA. NADPH oxidase 4 (NOX4) represents a major ROS source in chondrocytes. Nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) activation results in the activation of heme oxygenase-1 (HO-1), which can suppress NOX4 activity. Hydrogen gas (H 2 ) exerts antioxidant, anti-inflammatory, and anti-apoptotic effects. This research aimed to explore whether H 2 can suppress NOX4 via activation of the Nrf2/HO-1 pathway and thereby reduce oxidative stress to delay OA progression. An in-vivo OA model was established in male rats through anterior cruciate ligament transection coupled with medial meniscus resection, and an in-vitro OA model was constructed via IL-1β (10 ng/mL) stimulation of human primary chondrocytes. H 2 intervention was performed by intraperitoneal injection of hydrogen-rich saline (in vivo) and incubation with hydrogen-rich medium (in vitro). Nrf2 overexpression plasmids and siRNA knockdown techniques were used in vitro experiments. Detection methods included histological evaluation, apoptosis assays, CCK-8 assay, ROS fluorescence detection, ELISA, immunohistochemistry, qRT-PCR, and western blotting to quantify oxidative stress, inflammatory, and apoptosis factors, as well as extracellular matrix (ECM) and pathway-related proteins. In vivo results showed that H 2 reduced OARSI scores, alleviated cartilage destruction, decreased TUNEL-positive cells, and downregulated MMP-1 and MMP-13 expression. In vitro results demonstrated that H 2 restored chondrocyte viability; reduced levels of ROS, 8-OHdG, and HNE; downregulated cleaved caspase-3 and Bax while upregulating Bcl-2; inhibited iNOS, COX-2, and IL-6 expression; promoted upregulation of collagen II and downregulation of MMP-1 and MMP-13. H 2 also promoted the expression of Nrf2 and HO-1 while suppressing NOX4 expression both in vivo and in vitro. Nrf2 knockdown eliminated the protective influence of H 2 . This research shows that Nrf2 is a crucial mediator of the effects of H 2 , which can activate the Nrf2/HO-1/NOX4 signaling pathway to decrease ROS production and reduce oxidative stress, apoptosis, inflammation, and ECM catabolism, thereby delaying OA progression. Mechanistically, H 2 promoted Nrf2 nuclear translocation and inhibited NF-κB signaling via a Nrf2-dependent mechanism.