Inhibition of p38 mitogen-activated protein kinase down-regulates the inflammatory osteolysis response to titanium particles in a murine osteolysis model.

The p38 mitogen-activated protein kinase (p38 MAPK) pathway is involved in the osteoclast differentiation. The aim of the study was to investigate whether SB203580, a p38 MAPK inhibitor, inhibits wear-debris-induced inflammatory osteolysis in mice. Forty-five mice were implanted with calvaria bone from syngeneic littermates; then, titanium (Ti) particles were injected into established air pouches to provoke inflammatory osteolysis. At 14 days after bone/Ti implantation, pouch membranes with intact bone implants underwent histological and molecular analysis. SB203580 had less effect on MMP-9 and TNF-α expression under wear-debris-induced conditions. SB203580, by inhibiting the expression of p38 MAPK and phospho-p38 MAPK, inhibited Ti particle wear-debris-induced inflammatory osteolysis. It also remarkably decreased the number of tartrate-resistant acid phosphatase positive cells in Ti-particle-induced pouch tissues. Results suggest that p38 MAPK may be critical in a murine osteolysis model. SB203580 may notably inhibit wear-debris-induced inflammatory osteolysis by down-regulating expression of MMP-9 and TNF-α via the p38 MAPK pathway.