Role of the Interaction of Tumor Necrosis Factor-α and Tumor Necrosis Factor Receptors 1 and 2 in Bone-Related Cells

Tumor necrosis factor-alpha (TNF-alpha) is a pleiotropic cytokine expressed by macrophages, monocytes, and T cells, and its expression is triggered by the immune system in response to pathogens and their products, such as endotoxins. TNF-alpha plays an important role in host defense by inducing inflammatory reactions such as phagocytes and cytocidal systems activation. TNF-alpha also plays an important role in bone metabolism and is associated with inflammatory bone diseases. TNF-alpha binds to two cell surface receptors, the 55kDa TNF receptor-1 (TNFR1) and the 75kDa TNF receptor-2 (TNFR2). Bone is in a constant state of turnover; it is continuously degraded and built via the process of bone remodeling, which results from the regulated balance between bone-resorbing osteoclasts, bone-forming osteoblasts, and the mechanosensory cell type osteocytes. Precise interactions between these cells maintain skeletal homeostasis. Studies have shown that TNF-alpha affects bone-related cells via TNFRs. Signaling through either receptor results in different outcomes in different cell types as well as in the same cell type. This review summarizes and discusses current research on the TNF-alpha and TNFR interaction and its role in bone-related cells.

Automated summary

TNF-alpha is a cytokine expressed by immune cells and is involved in host defense and bone-related cell functions. This review summarizes current research on the interaction between TNF-alpha and its receptors in bone cells.