The C-type lectin receptor Mincle is functionally expressed by murine bone cells and can mediate inflammatory responses to Staphylococcus aureus 2257334

Abstract

It is now apparent that osteoblasts (OBs) and osteoclasts (OCs) have immune functions that play a critical role in shaping host responses and the abnormal bone remodeling associated with Staphylococcus aureus (SA) infection. Both express pattern recognition receptors (PRR) to perceive pathogens and initiate the production of mediators that can exacerbate inflammatory bone loss. Macrophage-inducible C-type lectin (Mincle) is a tyrosine activation motif—coupled PRR for microbial glycolipids that has been suggested to play an important role in host responses against Gram positive bacteria in the lungs. However, the ability of Mincle to serve a similar function in bone tissue has not been investigated. RNA sequence analysis was used to assess changes in the transcriptome of murine bone marrow-derived OCs and primary OBs following SA challenge. Additionally, bone cells were either treated with a Mincle-neutralizing antibody, an isotype control antibody, or were left untreated, prior to being stimulated with Mincle-specific ligands or SA infection. Cell supernatants and whole cell protein lysates were subsequently collected to quantify changes in the production of immune mediators by immunoblot analysis and ELISA. RNA Tag-Seq analysis of SA infected OCs and OBs revealed elevated expression of mRNA encoding Mincle and its key downstream signaling components. We found robust levels of Mincle protein in murine OCs and OBs and demonstrated the inducible expression of this molecule in human OBs. The functional nature of Mincle expression by OCs and OBs was confirmed by the ability of Mincle agonists to elicit inflammatory cytokine production. Importantly, we showed that such responses to SA are attenuated following Mincle blockade. These studies show that bone cells functionally express Mincle and indicate that this C-type lectin can mediate, at least in part, the inflammatory responses of OBs to SA challenge. NIAID R01AI170012 Innate Immune Responses and Host Defense: Cellular Mechanisms (INC)