Peroxisome proliferators activate Kupffer cells in vivo

Area of Science:

• Hepatology
• Toxicology
• Immunology

Background:

• Peroxisome proliferators are known to increase cell replication and cause liver tumors in rodents.
• Kupffer cells, the liver's resident macrophages, release mitogenic stimuli upon activation, potentially promoting hepatocyte proliferation.

Purpose of the Study:

• To investigate the effect of peroxisome proliferators nafenopin and WY-14,643 on Kupffer cell activation in vivo.
• To explore the role of Kupffer cell activation in the mechanism of peroxisome proliferator-induced liver cell replication.

Main Methods:

• Assessed Kupffer cell phagocytosis by monitoring colloidal carbon uptake in isolated, perfused rat livers following in vivo drug treatment.
• Administered nafenopin and WY-14,643 to rats and measured colloidal carbon uptake rates at various time points.
• Evaluated functional parameters of Kupffer cells, including plasma nitrite levels.

Main Results:

• Nafenopin and WY-14,643 significantly increased colloidal carbon uptake rates in a time- and dose-dependent manner.
• Nafenopin treatment elevated phagocytosis rates by approximately 40% at 5 hours and 100% at 24 hours post-administration.
• WY-14,643 treatment resulted in a 1.8-fold increase in colloidal carbon uptake, and WY-14,643 also increased plasma nitrite levels.

Conclusions:

• This study clearly demonstrates that nafenopin and WY-14,643 activate Kupffer cell phagocytosis in vivo.
• The findings suggest that Kupffer cell activation plays a significant role in the stimulation of cell replication induced by peroxisome proliferators.
• Cell-to-cell communication involving activated Kupffer cells may be a key mechanism in peroxisome proliferator-induced hepatocarcinogenesis.