Lipoteichoic Acid Is a Potent Inducer of Cytokine Production in Rat and Human Kupffer Cells In Vitro

Abstract

Background

: Kupffer cells have been proposed to be a major cellular origin of pro-inflammatory mediators in sepsis. However, the cytokine response of Kupffer cells to gram-positive bacteria and their endotoxins peptidoglycan (PepG) and lipoteichoic acid (LTA) has never previously been studied.

Materials and Methods

: Primary cultures of rat and human Kupffer cells were exposed to live Staphylococcus aureus (S. aureus) (4.0 × 10¹ to 4.0 × 10⁷ CFU/mL culture medium), as well as highly purified PepG and LTA (0-100 μg/mL). Lipopolysaccharide (LPS) at 1 μg/mL was used for control. In parallel experiments, whole blood obtained from the same rats was stimulated in a similar manner. Accumulation of the proinflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in plasma or culture supernatants were assessed by enzyme immuno assays. TNF-α and IL-6 mRNA were analyzed by real-time RT-PCR.

Results

: PepG and LTA, as well as live S. aureus, induced the production of TNF-α and IL-6 in Kupffer cells from both species in a time- and dose-dependent manner. Whereas PepG was a more potent inducer of TNF-α and IL-6 in whole blood, the opposite seemed to be the case in Kupffer cells. In fact, a 100-fold lower concentration of LTA (1 μg/mL) than of PepG (100 μg/mL) was sufficient to induce a substantial production of both TNF-α and IL-6 in the Kupffer cells. TNF-α and IL-6 mRNA were induced correspondingly.

Conclusion

: Our results support the contention that gram-positive bacteria may activate cytokine production in Kupffer cells during bacteremia and suggest that LTA is important in this interaction.