Age-related increases in LPS-stimulated nitric oxide production from cultured rat bone marrow cells

Objective: To understand bone metabolism during senescence, we examined age-related change in nitric oxide (NO) production from bone marrow cells stimulated by lipopolysaccharide (LPS). Methods: We evaluated the age-related change in the NO production and expression of iNOS protein and mRNA of LPS-stimulated bone marrow cells collected from the tibiae of young and retired female and young and retired male rats. In addition, we used flow cytometry to assess changes in the distribution of CD14, a cell surface receptor of LPS. Results: The results revealed that NO production from bone marrow cells stimulated with LPS changed with aging. The NO levels in old rats were significantly higher (P<0.05) than those in young rats. Polymerase chain reaction (PCR) analysis indicated that the LPS-induced expression of iNOS mRNA was augmented in retired rats. Although the distribution pattern of the bone marrow cells was similar between young and retired rats, the percentage of CD14-positive cells in specific populations differed between the age groups. Specifically, in the granule-containing bone marrow cells, the percentage of CD14-positive cells was increased in retired rats. Conclusion: Our results indicate that LPS-stimulated NO production from rat bone marrow cells increased with age and that the difference in responsiveness might be due to changes in the percentage of CD14-positive cells in the bone marrow.