[The change in Toll-like receptor 4 gene expression in skeleton of endotoxemia mice]

To explore the changes in gene expression of bone in endotoxemia in mice.

Lipopolysaccharide (LPS) was injected intraperitoneally to reproduce an endotoxemia model in mice. Forty-eight mice were randomly divided into eight groups: normal group, 4, 6, 8, 12, 24, 48 and 72 hours after LPS injection groups, with 6 mice in each group. To evaluate endotoxemia whole blood was collected for leukocytic count, eye sockets blood was obtained for liver and renal functions tests. mRNA expression level of Toll-like receptor 4 (TLR4) in bone was determined by reverse transcription-polymerase chain reaction (RT-PCR) assay. The pathological changes of bone and tissue slides were prepared with hematoxylin and eosin (HE) staining for observing under microscope.

Compared with normal group, leukocyte count of 4-hour LPS-treated group was significantly decreased (P<0.01). However, after 4 hours, leukocyte count became higher gradually and remained at high level at 72 hours compared with that of normal group (P<0.05). Compared with normal group, alanine aminotransferase (ALT) level reached to a high level in LPS-treated groups at 4 hours and 6 hours (both P<0.05), and then decreased gradually showing a tendency to return to normal level after 8 hours (P>0.05). Blood urea nitrogen (BUN) was increased at 6 hours (P<0.05), reaching to the highest level at 8 hours (P<0.05) and tended to become normal level after 12 hours (P>0.05). Six hours after LPS treatment, the expression of TLR4 mRNA was enhanced (P<0.01) and reached the peak at 24 hours (P<0.01), and it remained at a high level at 72 hours (P<0.05). However, there were no significant pathological changes in bone structure after LPS treatment.

Expression level of TLR4 mRNA in bone is significantly increased in endotoxemia mice.