Effect of high-density lipoprotein on lipopolysaccharide-induced alveolar bone resorption in rats

OBJECTIVE: To determine whether treatments with high-density lipoprotein (HDL) may alter the lipopolysaccharide (LPS)-induced alveolar bone resorption in rats. MATERIALS AND METHODS: Rats were injected with 500 mug of LPS from Escherichia coli at the alveolar mucosa of lower right first molar once every 2 days for 8 days. The negative and positive control were injected with phosphate buffered saline (PBS) and LPS alone, respectively. In HDL-treated animals various concentration of HDL were injected immediately before, after the third or the final LPS injection. The bone sections were stained with tartrate-resistant acid phosphatase (TRAP) and the numbers of both osteoclasts and preosteoclasts and the levels of alveolar bone resorption were assessed. RESULTS: The numbers of both osteoclasts and preosteoclasts and the levels of alveolar bone resorption in animals treated with HDL before or during LPS injections were lower than those in the positive control, but higher than those in the negative control, regardless of HDL doses. Similar results were also observed in animals treated with 250 and 500 mug of HDL after the final LPS injection. Only treatments with 1000 mug of HDL after LPS injections completely reduced the number of both osteoclasts and preosteoclasts, but only partially decreased the alveolar bone resorption. CONCLUSION: HDL treatments partially reduced the LPS-induced alveolar bone resorption in vivo in rats, suggesting that HDL may neutralize the ability of LPS to induce alveolar bone resorption.