Morphological Changes in Articular Cartilage and Free-Radical Lipid Peroxidation in Rats with Posttraumatic Osteoarthrosis

Sirt1 overexpression inhibits chondrocyte ferroptosis via Ftl deacetylation to suppress the development of osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is a chronic degenerative joint disorder characterized by an imbalance in chondrocyte metabolism. Ferroptosis has been implicated in the pathogenesis of OA. The role of Sirt1, a deacetylase, in mediating deacetylation during ferroptosis in OA chondrocytes remains underexplored. This study aimed to elucidate the mechanisms by which Sirt1 influences chondrocyte ferroptosis in the development of OA.

MATERIALS AND METHODS

In vitro and in vivo models of OA were established using IL-1β-induced mouse chondrocytes and a destabilization of the medial meniscus (DMM) mouse model, respectively. Ferroptosis was evaluated through measurements of cell viability, lactate dehydrogenase (LDH) release, intracellular levels of Fe2+, glutathione (GSH), malondialdehyde (MDA), lipid reactive oxygen species (ROS), propidium iodide staining, and Western blot analysis. The underlying mechanisms were further investigated using quantitative real-time polymerase chain reaction, Western blotting, immunoprecipitation (IP), co-immunoprecipitation (Co-IP), and glutathione-S-transferase pulldown assays. In vivo validation was performed via Safranin O staining.

RESULTS

IL-1β induced ferroptosis and increased histone acetylation, effects that were partially reversed by Sirt1 overexpression. Mechanistically, Sirt1 overexpression upregulated ferritin light polypeptide (Ftl) expression by deacetylating Ftl at the K181 residue. Ftl knockdown inhibited the ferroptosis-enhancing effect of Sirt1 overexpression in chondrocytes. In vivo studies showed that Sirt1 overexpression mitigated the progression of OA and reduced ferroptosis in the DMM-induced OA mouse model.

CONCLUSION

Our findings confirm that Sirt1 overexpression promotes Ftl expression through deacetylation at the K181 site, thereby suppressing chondrocyte ferroptosis and attenuating the progression of OA. These results suggest a potential therapeutic target for OA treatment.

New insight of the pathogenesis in osteoarthritis: the intricate interplay of ferroptosis and autophagy mediated by mitophagy/chaperone-mediated autophagy

Ferroptosis, characterized by iron accumulation and lipid peroxidation, is a form of iron-driven cell death. Mitophagy is a type of selective autophagy, where degradation of damaged mitochondria is the key mechanism for maintaining mitochondrial homeostasis. Additionally, Chaperone-mediated autophagy (CMA) is a biological process that transports individual cytoplasmic proteins to lysosomes for degradation through companion molecules such as heat shock proteins. Research has demonstrated the involvement of ferroptosis, mitophagy, and CMA in the pathological progression of Osteoarthritis (OA). Furthermore, research has indicated a significant correlation between alterations in the expression of reactive oxygen species (ROS), adenosine monophosphate (AMP)-activated protein kinase (AMPK), and hypoxia-inducible factors (HIFs) and the occurrence of OA, particularly in relation to ferroptosis and mitophagy. In light of these findings, our study aims to assess the regulatory functions of ferroptosis and mitophagy/CMA in the pathogenesis of OA. Additionally, we propose a mechanism of crosstalk between ferroptosis and mitophagy, while also examining potential pharmacological interventions for targeted therapy in OA. Ultimately, our research endeavors to offer novel insights and directions for the prevention and treatment of OA.

Lipid peroxidation in osteoarthritis: focusing on 4-hydroxynonenal, malondialdehyde, and ferroptosis

Osteoarthritis (OA) is a multifactorial and increasingly prevalent degenerative disease that affects the whole joint. The pathogenesis of OA is poorly understood and there is a lack of therapeutic interventions to reverse the pathological process of this disease. Accumulating studies have shown that the overproduction of reactive oxygen species (ROS) and ROS-induced lipid peroxidation are involved in the pathogenesis of OA. 4-Hydroxy-2-nonenal (4-HNE) and malondialdehyde (MDA) have received considerable attention for their role in cartilage degeneration and subchondral bone remodeling during OA development. Ferroptosis is a form of cell death characterized by a lack of control of membrane lipid peroxidation and recent studies have suggested that chondrocyte ferroptosis contributes to OA progression. In this review, we aim to discuss lipid peroxidation-derived 4-HNE and MDA in the progression of OA. In addition, the therapeutic potential for OA by controlling the accumulation of lipid peroxidation and inhibiting chondrocyte ferroptosis are discussed.

The Role Played by Ferroptosis in Osteoarthritis: Evidence Based on Iron Dyshomeostasis and Lipid Peroxidation

Ferroptosis, a recently discovered regulated cell death modality, is characterised by iron-dependent accumulation of lipid hydroperoxides, which can reach lethal levels but can be specifically reversed by ferroptosis inhibitors. Osteoarthritis (OA), the most common degenerative joint disease, is characterised by a complex pathogenesis involving mechanical overload, increased inflammatory mediator levels, metabolic alterations, and cell senescence and death. Since iron accumulation and oxidative stress are the universal pathological features of OA, the role played by ferroptosis in OA has been extensively explored. Increasing evidence has shown that iron dyshomeostasis and lipid peroxidation are closely associated with OA pathogenesis. Therefore, in this review, we summarize recent evidence by focusing on ferroptotic mechanisms and the role played by ferroptosis in OA pathogenesis from the perspectives of clinical findings, animal models, and cell research. By summarizing recent research advances that characterize the relationship between ferroptosis and OA, we highlight avenues for further research and potential therapeutic targets.