TNF-ALPHA RELEASE IN MONOCYTES AFTER EXPOSURE TO CALCIUM HYDROXIDE TREATED ESCHERICHIA-COLI LPS

Lipopolysaccharide (LPS), a cell wall component of Gram negative anaer obic bacteria, has been implicated in the pathogenesis of periapical d isease resulting from infected root canals. Calcium hydroxide [Ca(OH)( 2)] has been shown to be an effective medicament in such infections, r educing the microbial titre within the canal, It has been proposed tha t the therapeutic effect of Ca(OH)(2) may also be the result of direct inactivation of LPS. The aim of this study was to investigate whether the toxic potential of an Escherichia col LPS could be reduced or eli minated by Ca(OH)(2). Four concentrations of E. coli LPS ranging from 1-1000 ng/ml sterile water were incubated in duplicate either with 25 mg Ca(OH)(2) or sterile water alone. Controls consisted of Ca(OH)(2) w ithout LPS or sterile water only. Monocytes were collected from periph eral blood by centrifuging through a gradient and plated to a specific density. Adherent monocytes were incubated for 4 days at 37 degrees C with 5% CO2 in M199 medium with 10% autologous serum. The different L PS solutions were added to the wells on day 5. After 4 h the supernata nts were collected and quantitatively assayed for TNF-alpha using a co mmercial ELISA kit. Statistical analysis was performed with ANOVA. Res ults indicated that Ca(OH)(2) is able to eliminate the ability of an E . coli LPS to stimulate TNF-alpha production in peripheral blood monoc ytes (P<0.0001).