The role of cereblon-AMPK (AMP-activated protein kinase) axis in osteoarthritis and development of disease-modifying osteoarthritis drugs

Abstract

Osteoarthritis (OA), now recognized as a whole-joint disease, involves cartilage destruction, subchondral bone sclerosis, osteophyte formation, and synovial inflammation. Currently, there are no pharmacological interventions that effectively modulate OA progression. Recent studies suggest that abnormal energy metabolism in joint tissues is a critical risk factor for OA, with dysregulation of AMP-activated protein kinase (AMPK) implicated in its pathogenesis. However, the mechanisms driving this dysregulation remain unclear. In this research, I investigated the pathological mechanisms of metabolic dysfunction-mediated OA to identify potential therapeutic targets and develop novel candidates for disease-modifying osteoarthritis drugs (DMOADs). In part Ⅰ, I demonstrate that the cereblon-AMPK axis plays a critical catabolic role within the pathogenesis of OA. Elevated cereblon expression levels were observed in both human and mouse cartilage affected by OA. Adenoviral overexpression of cereblon in mouse joint tissues exacerbated cartilage destruction induced by destabilization of the medial meniscus (DMM) surgery. Conversely, in DMM model mice, cartilage destruction was inhibited in both global (OARSI grade difference; -2.50 [95% CI: -3.00 to -1.17]) and cartilage- specific (-2.17 [95% CI: -3.14 to -1.06]) cereblon-deficient mice compared to wild-type (WT) mice. The inhibitory effects became more pronounced in mice fed a high-fat diet (HFD) compared to those on a regular diet (RD). Moreover, specific degradation of cereblon via intra-articular (IA) injection of the proteolysis- targeting chimera (PROTAC) system, TD-165, considerably inhibited OA cartilage destruction (-2.47 [95% CI: -3.22 to -1.56]). Mechanistically, cereblon was found to downregulate AMPK activity in chondrocytes within OA cartilage. These findings suggest that the cereblon-AMPK axis holds promising potential as a therapeutic target in preclinical models of OA. In part Ⅱ, I explored the potential of the selected rhodanine derivatives (R-501, R-502, R-503) as DMOADs in various animal OA models. All three rhodanine derivatives suppressed OA progression caused by DMM surgery, as well as by the overexpression of hypoxia inducible factor-2α (HIF-2α) or Zrt- and Irt-like protein 8 (ZIP8). In DMM-operated mice, IA injection of R-501 reduced the median OARSI grade from 3.78 (IQR 3.00-5.00) to 1.89 (IQR 0.94-2.00, p = 0.0001). R-502 and R-503 also reduced the grade from 3.67 (IQR 2.11-4.56) to 2.00 (IQR 1.00-2.00, p = 0.0030) and 2.00 (IQR 1.83-2.67, p = 0.0378), respectively. Mechanistically, the rhodanine derivatives inhibited the nuclear localization and transcriptional activity of HIF- 2α in chondrocytes and fibroblast-like synoviocytes (FLS). They did not bind to Zn2+ or disrupt cellular Zn2+ homeostasis in chondrocytes or FLS; instead, they suppressed the nuclear localization and transcriptional activity of the Zn2+-dependent transcription factor, metal regulatory transcription factor 1 (MTF1). Although HIF-2α, ZIP8, and interleukin-1β are known to upregulate matrix-degrading enzymes in chondrocytes and FLS, the rhodanine derivatives appeared to inhibit these effects. Collectively, this study demonstrates that the cereblon-AMPK axis plays a pivotal role in OA especially under HFD conditions, and that targeting this axis offers a promising approach for addressing metabolic OA. This study additionally characterized novel rhodanine derivatives as potential DMOADs. Keywords Osteoarthritis, Cartilage, Chondrocytes, Mice, Cereblon, AMPK, Rhodanine, DMOADs