Hypoxia-Sensitive COMMD1 Integrates Signaling and Cellular Metabolism in Human Macrophages and Suppresses Osteoclastogenesis

Highlights

• COMMD1 is a negative regulator of osteoclast differentiation

• COMMD1 suppresses bone loss in RA and inflammatory arthritis and osteolysis models

• COMMD1 negatively regulates E2F1-dependent metabolic pathways in macrophages

• Hypoxia suppresses COMMD1 expression to augment osteoclastogenesis

Summary

Hypoxia augments inflammatory responses and osteoclastogenesis by incompletely understood mechanisms. We identified COMMD1 as a cell-intrinsic negative regulator of osteoclastogenesis that is suppressed by hypoxia. In human macrophages, COMMD1 restrained induction of NF-κB signaling and a transcription factor E2F1-dependent metabolic pathway by the cytokine RANKL. Downregulation of COMMD1 protein expression by hypoxia augmented RANKL-induced expression of inflammatory and E2F1 target genes and downstream osteoclastogenesis. E2F1 targets included glycolysis and metabolic genes including CKB that enabled cells to meet metabolic demands in challenging environments, as well as inflammatory cytokine-driven target genes. Expression quantitative trait locus analysis linked increased COMMD1 expression with decreased bone erosion in rheumatoid arthritis. Myeloid deletion of Commd1 resulted in increased osteoclastogenesis in arthritis and inflammatory osteolysis models. These results identify COMMD1 and an E2F-metabolic pathway as key regulators of osteoclastogenic responses under pathological inflammatory conditions and provide a mechanism by which hypoxia augments inflammation and bone destruction.