OBJECTIVE: Our poor understanding of how inflammatory mediators can affect 
osteoblast behavior led us to investigate the tumor necrosis factor 
(TNF)α-induced focal adhesion kinase (FAK) and Src phosphorylation.
MATERIAL AND METHODS: MC3T3-E1 pre-osteoblast cells were harvested at specific 
time points after either TNFα treatment or RAW267 stimulated conditioned medium, 
and thereafter cell extracts were prepared for Immunoblotting assay. ELISA 
detected TNFα content at conditioned medium. Tumor necrosis 
factor-α-neutralizing antibodies also were used.
RESULTS: It was possible to show that TNFα provokes attenuation at 
Y-phosphorylation of both FAK (at Y397 ) and Src (at Y416 ) proteins (P < 0.05), 
suggesting a decrease in their activities. The very similar profile was observed 
when osteoblasts were incubated with conditioned medium from lipopolysaccharide 
(LPS)-stimulated macrophages, it being significantly different than control (FAK 
and Src, P < 0.05). Nevertheless, in order to validate these findings, we 
decided to pre-incubate osteoblasts with anti-TNFα neutralizing antibody 
(2 μg ml(-1) ) prior exposing to conditioned medium. Importantly, our results 
revealed that there was a diminution on those conditioned medium effects when 
the same biological parameters were evaluated (P < 0.05). Moreover, we also 
showed that TNFα impairs osteoblast adhesion, suggesting an interesting role on 
osteoblast performance.
CONCLUSIONS: Altogether, these results suggest that LPS-stimulated macrophage 
mediators attenuate both FAK and Src activations in osteoblast, suggesting a 
novel role for TNFα on osteoblast performance.