Background: Sensitivity of Kupffer cells to endotoxin [lipopolysaccharide (LPS)] and overproduction of tumor necrosis factor-α (TNF-α) are critical for progression of alcoholic liver injury. Therefore, suppression of TNF-α should prove useful for treatment of alcoholic liver injury. However, a transient increase of intracellular calcium ([Ca2+]i) is required for LPS-induced TNF-α production by the macrophage cell line. The phosphodiesterase III inhibitor olprinone has been shown to suppress [Ca2+]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 μmol/liter). After addition of LPS (10 μg/ml) to culture media, [Ca2+]i was measured using a fluorescent indicator, fura-2.
Results: LPS increased [Ca2+]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 μg/ml)-induced TNF-α 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.