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Use of ricin A-chain to selectively deplete Kupffer cells
M E Zenilman1, M Fiani, P Stahl
1Department of Surgery, Washington University School of Medicine, St. Louis, Missouri 63110.
Abstract:
We used the A-chain of the toxin ricin (RTA) as a toxin specific to Kupffer cells in mice. RTA is specifically taken up by the mannose receptor present exclusively in macrophages. Kupffer cells were quantitated by shifts in beta-glucuronidase clearance and microscopic counts of cells which phagocytosed India ink. When compared to saline controls, 20 mg/kg of RTA intraperitoneally (divided over 4 days) or intraportally (single doses) significantly prolonged the t 1/2 half-life of beta-glucuronidase by 270 +/- 37 and 210 +/- 8%, respectively. Kupffer cell numbers were significantly decreased by 27 +/- 8 and 33 +/- 16%. This effect persisted for at least 3 days after toxin administration. Despite effects on Kupffer cell number, minimal histological damage to liver, spleen, lung, and heart was noted. Higher doses of RTA or doses potentiated by ureteral ligation to prevent renal clearance resulted in prohibitive mortalities and histologic liver damage. Doses of Hura crepitans inhibitor, a toxin similar to RTA but not mannose-receptor specific, did not affect Kupffer cell numbers. We conclude that RTA given both intraperitoneally and intraportally at low doses is toxic specifically to Kupffer cells. Kupffer cell numbers can be indirectly measured by beta-glucuronidase clearance.
Insights
Ricin toxin A-chain (RTA) selectively targets Kupffer cells in mice via the mannose receptor. Low-dose RTA administration reduces Kupffer cell populations without significant organ damage, offering a specific method for Kupffer cell depletion.
Area of Science:
- Immunology
- Toxicology
- Hepatology
Background:
- Kupffer cells are liver-resident macrophages crucial for immune responses.
- Targeting Kupffer cells specifically is challenging due to their unique markers.
- Ricin toxin A-chain (RTA) binds to the mannose receptor, expressed on macrophages.
Purpose of the Study:
- To investigate the Kupffer cell-specific toxicity of RTA in mice.
- To evaluate RTA's efficacy in depleting Kupffer cells using different administration routes.
- To assess the safety and histological impact of RTA treatment on other organs.
Main Methods:
- Ricin toxin A-chain (RTA) was administered intraperitoneally and intraportally to mice.
- Kupffer cell populations were quantified by measuring beta-glucuronidase clearance and India ink phagocytosis.
- Histological examination of liver, spleen, lung, and heart was performed.
Main Results:
- Low-dose RTA significantly prolonged beta-glucuronidase half-life, indicating Kupffer cell depletion (270% and 210% increase).
- Kupffer cell numbers decreased by 27-33% after RTA administration, with effects lasting at least 3 days.
- Minimal histological damage was observed in major organs at effective RTA doses.
Conclusions:
- RTA is a potent and specific toxin for Kupffer cells when administered at low doses.
- Beta-glucuronidase clearance serves as an indirect measure of Kupffer cell number.
- RTA offers a promising tool for targeted Kupffer cell depletion in research settings.