Background: Sensitivity of Kupffer cells to endotoxin [lipopolysaccharide (LPS)] and overproduction of tumor necrosis factor-alpha (TNF-alpha) are critical for progression of alcoholic liver injury. Therefore, suppression of TNF-alpha should prove useful for treatment of alcoholic liver injury. However, a transient increase of intracellular calcium ([Ca]i) is required for LPS-induced TNF-alpha production by the macrophage cell line. The phosphodiesterase III inhibitor olprinone has been shown to suppress [Ca]i level in vascular smooth muscle cells. Accordingly, the purpose of this study was to determine whether olprinone could prevent sensitization of Kupffer cells to endotoxin.
Methods: Kupffer cells were isolated by collagenase digestion and differential centrifugation. LPS was added to Kupffer cells 24 hr after incubation with or without olprinone (0.1 micromol/liter). After addition of LPS (10 microg/ml) to culture media, [Ca]i was measured using a fluorescent indicator, fura-2.
Results: LPS increased [Ca]i of Kupffer cells in control rats from basal levels (28 +/- 4 nmol/liter) to 280 +/- 14 nmol/liter. This increase was blunted by olprinone (91 +/- 8 nmol/liter). Similarly, olprinone diminished the LPS (1 microg/ml)-induced TNF-alpha production by Kupffer cells by 30% (2220 +/- 116 vs. 1386 +/- 199 pg/ml; p < 0.05).
Conclusions: These results indicate that olprinone decreases sensitivity of Kupffer cells to endotoxin.