Inhibition of lipopolysacharide induced osteoclast formation and bone resorption in vitro and in vivo in mice by cystatin C

Abstract

BACKGROUND We recently reported that the signaling pathway downstream RANK in RANKL-induced osteoclastogenesis is inhibited by cysteine proteinase inhibitors (CPIs) (Strålberg et al., FASEB J, 2013). Here, we demonstrate that osteoclastogenesis stimulated by LPS E.coli in RANKL-primed mouse bone marrow macropages (BMM) is inhibited by CPIs cystatin C, E-64, and Z-RLVG-CHN 2. The inhibitory effect is associated with decreased gene and protein expression, and an active uptake of fluorescent tagged cystatin C dependent on LPS-stimulation. Osteoclast formation was inhibited by all three CPIs in cathepsin K deficient mice. Also, the cathepsin K inhibitor L-006235 did not inhibit osteoclast formation. LPS-stimulated osteoclast formation in skull bones of adult mouse was inhibited by E-64. CONCLUSIONS All together, these data show that: ü Cysteine proteinase inhibitors are important in LPS-induced osteoclastogenesis both in vitro and in vivo ü Osteoclast progenitors take up Cystatin C by a process facilitated by RLprimed LPS-stimulation ü inhibition of osteoclast formation by cysteine proteinase inhibitors is not explained by inhibition of cathepsin K Disclosure of Interest: None Declared RESULTS Printed by A) RL-primed LPS-induced osteoclast differentiation is inhibited by CPIs Cystatin C, E-64, and Z-RLVG-CHN 2 B) CPIs inhibit LPS-induced mRNA and protein expression of Cfos and Nfatc1 C) CPIs inhibit LPS-induced mRNA and protein expression of Acp5, Calcr, and Ctsk E) LPS potentiates the intracellular uptake of CysC in RL-primed osteoclast progenitors F) The cathepsin K inhibitor L-006235 does not inhibit osteoclast formation G) LPS-induced osteoclast formation in skull bones is inhibited by E-64 in vivo