Interleukin (IL)-1β and tumor necrosis factor (TNF)-α, in particular, control the degeneration of articular cartilage, making them prime targets for osteoarthritis (OA) therapeutic strategies. Advanced oxidation protein products (AOPPs) are prevalent in numerous diseases. Our previous work demonstrates that intra-articular injections of AOPPs accelerate regression of cartilage in OA models. Whether AOPPs exist in the course of OA and their effects on TNF-α and IL-1β expression in chondrocytes are still unclear. This study confirmed that AOPPs levels in human synovial fluid were positively associated with severity of OA. We also found AOPPs deposition in articular cartilage in anterior cruciate ligament transection (ACLT) induced rodent OA models. AOPPs increased expression of TNF-α and IL-1β in chondrocytes in vitro, which was inhibited by pre-treatment with SB202190 (p38-MAPK inhibitor) or apocynin (NADPH oxidase inhibitor) or NOX4 knockdown by siRNAs. Subsequently, we further verified in vivo that exogenous injection of AOPPs in OA mice up-regulated expression of TNF-α and IL-1β in cartilage, which was blocked by treatment with apocynin. In parallel, apocynin attenuated articular cartilage degeneration resulting in substantially lower OARSI scores. Specifically, apocynin reduced NOX4, p-P38, TNF-α and IL-1β and increased collagen II and glycosaminoglycan (GAG). This study demonstrated that AOPPs increased expression of TNF-α and IL-1β in chondrocytes via the NADPH oxidase4-dependent and p38-MAPK mediated pathway, and accelerated cartilage degeneration in OA progression. These findings suggest an endogenous pathogenic role of AOPPs in OA progression. Targeting AOPPs-triggered cellular mechanisms might be a promising therapeutic option for patients with OA.

Background: Intervertebral disc degeneration (IVDD) is closely associated with senescence. Annulus fibrosus (AF) cell senescence is a crucial driver of AF tissue tearing and fissures, thereby exacerbating IVDD. Increased advanced oxidative protein products (AOPPs) were found in human degenerative discs and aged rat discs and may be involved in IVDD. This study aimed to explore the mechanism of AOPPs-induced senescence in AF cells. Methods: The pathological effects of AOPPs in vivo were investigated using a rat lumbar disc persistent degeneration model and a rat caudal disc puncture model. Rat primary AF cells were selected as in vitro models, and AOPPs were used as direct stimulation to observe their pathological effects. Setanaxb (NOX1/4 inhibitor), apocynin (NADPH oxidase inhibitor) and adenovirus (ADV) packed NADPH oxidase 4 (NOX4) specific shRNAs were used for pathway inhibition, respectively. Finally, adeno-associated viruses (AAVs) packed with NOX4-specific blocking sequences were used to inhibit the in vivo pathway. Results: AOPPs accumulated in the rat lumbar and caudal degenerative discs. Intra-discal loading of AOPPs up-regulated the expression of NOX4, p53, p21, p16, IL-1β, and TNF-α, ultimately accelerating IVDD. Exposure of AOPPs to AF primary cells up-regulated NOX4 expression, induced phosphorylation of mitogen-activated protein kinases (MAPK), triggered senescence and increased IL-1β and TNF-α. Apocynin, setanaxib, and ADV pre-cultured AF cells abrogated AOPPs-induced senescence. AAV-mediated inhibition of NOX4 expression in vivo reduced the expression of p53, p21, p16, IL-1β and TNF-α in vivo and delayed IVDD. Conclusions: AOPPs induced AF cell senescence through a NOX4-dependent and MAPK-mediated pathway.

Background: Osteoarthritis (OA) and type 2 diabetes mellitus (T2DM) frequently coexist and share inflammatory and metabolic disturbances, but the immune-epigenetic features that may overlap between these conditions remain incompletely defined. Enhancer RNAs (eRNAs) are increasingly recognized as regulators of enhancer activity and transcriptional programs, whereas eRNA-associated signatures shared between OA-related and T2DM-related datasets remain largely unexplored. Methods: Transcriptomic datasets from OA joint tissues and controls (63 OA, 35 controls) were analyzed together with an independent T2DM dataset of CD14 ⁺ monocytes (5 T2DM, 5 controls) to explore overlapping molecular features across distinct disease-related contexts. Differential expression analysis, exploratory Weighted Gene Co-expression Network Analysis (WGCNA), CIBERSORT-based estimation, and pathway analyses were used to prioritize eRNA-associated features, transcription factors (TFs), candidate genes, and immune-associated transcriptional patterns. Public ATAC-seq, ChIP-seq, and scRNA-seq datasets, together with a high-glucose stress model in rat chondrocytes, were used to provide epigenomic, cellular, and preliminary experimental context for the candidate associations. Results: We identified 473 annotated dysregulated eRNA-associated features in OA, with associated genes enriched in skeletal development, extracellular matrix remodeling, and PI3K-Akt signaling. CIBERSORT-based and pathway analyses suggested immune-associated transcriptional alterations and inflammatory pathway activation in OA. Integrative analysis prioritized TOB1 as a candidate eRNA-associated feature related to JUN, CCNL1 , and inflammatory signaling within an inferred correlation-based network. Public ATAC-seq, ChIP-seq, and scRNA-seq datasets provided supportive epigenomic and cellular context for these candidate associations. Comparison with the T2DM monocyte dataset showed overlapping TNF-α/NF-κB and MAPK-related pathway alterations, with CCNL1 identified as a commonly downregulated candidate gene. In vitro , high-glucose stress was accompanied by reduced TOB1, JUN, and CCNL1 protein levels and increased TNF-α expression in chondrocytes. Conclusion: TOB1 was prioritized as a candidate eRNA-associated signal related to JUN, CCNL1 , and inflammatory signaling across OA-related and T2DM-related datasets. These findings provide a bioinformatics-driven and correlation-based framework supported by public epigenomic context and preliminary in vitro data, offering potential directions for future studies of immune-metabolic overlap between OA and T2DM.