Inhibition of Early Response Genes Prevents Changes in Global Joint Metabolomic Profiles in Mouse Post-Traumatic Osteoarthritis

Abstract

Osteoarthritis (OA) is the most common degenerative joint disease, and joint injury increases the risk of OA by 10-fold. Although the injury event itself damages joint tissues, a substantial amount of secondary damage is mediated by the cellular responses to the injury. Cellular responses include the production and activation of proteases (MMPs, ADAMTSs, Cathepsins), the production of inflammatory cytokines, and we hypothesize, changes to the joint metabolome. The trajectory of cellular responses is driven by the transcriptional activation of early response genes, which requires Cdk9-dependent RNA Polymerase II phosphorylation. Flavopiridol is a potent and selective inhibitor of Cdk9 kinase activity, which prevents the transcriptional activation of early response genes. To model post-traumatic osteoarthritis, we subjected mice to noninvasive ACL-rupture joint injury. Following injury, mice were treated with flavopiridol to inhibit Cdk9-dependent transcriptional activation, or vehicle control. Global joint metabolomics were analyzed 1 hour after injury. We found that injury induced metabolomic changes, including increases in Vitamin D3 metabolism and others. Importantly, we found that inhibition of primary response gene activation at the time of injury largely prevented the global changes in the metabolomics profiles. Cluster analysis of joint metabolomes identified groups of injury-induced and drug-responsive metabolites, which may offer novel targets for cell-mediated secondary joint damage. Metabolomic profiling provides an instantaneous snapshot of biochemical activity representing cellular responses, and these data demonstrate the potential for inhibition of early response genes to alter the trajectory of cell-mediated degenerative changes following joint injury.

Cannabinoid-based therapy as a future for joint degeneration. Focus on the role of CB2 receptor in the arthritis progression and pain: an updated review

“…AEA and 2-AG levels were augmented in the synovial fluid of dogs with OA [ 115 ]. AEA was also elevated in the joint in a posttraumatic OA mouse model [ 116 ]. In contrast to those in healthy volunteers, AEA and 2-AG have been detected in the synovial fluid of OA and RA patients [ 72 ].…”

Metabolism and global protein glycosylation are differentially expressed in healthy and osteoarthritic equine carpal synovial fluid

“…Although these pathways did not remain significant after FDR correction, this is likely a reflection of the small sample size as acknowledged in previous synovial fluid metabolomic studies 34 . Alterations in inflammatory pathways have been reported in human RA, OA 7 and in rodent OA models, 35 and tryptophan metabolism has been studied as a biomarker for RA using urine tryptophan metabolites 36 . Histamine was not altered in equine OA; however, imidazole‐4‐acetate, which has histamine as a precursor, was significantly elevated in OA joints.…”

Alterations in Anandamide Synthesis and Degradation during Osteoarthritis Progression in an Animal Model

“…Preclinical and clinical studies have suggested that the endocannabinoid system may be useful to treat various diseases, including the diseases related to chronic pain. In the course of several diseases, an elevated level of the ECS components was reported in preclinical models [ 33 ] and in clinical trials [ 34 , 35 ]. Bishay et al demonstrated that aged mice have lower AEA levels in particular brain structures compared with that in young mice, which resulted in stronger nociceptive development after spared nerve injury and weaker response for R-flurbiprofen [ 36 ].…”