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Diverse profiles of ricin-cell interactions in the lung following intranasal exposure to ricin.

Sapoznikov A, Falach R, Mazor O, Alcalay R, Gal Y, Seliger N, Sabo T, Kronman C - Toxins (Basel) (2015)

Bottom Line: Neutrophils, which were massively recruited to the intoxicated lung, were refractive to toxin binding.The differential binding and cell-elimination patterns observed may stem from dissimilar accessibility of the toxin to different cells in the lung and may also reflect unequal interactions of the toxin with different cell-surface receptors.The multifaceted interactions observed in this study between ricin and the various cells of the target organ should be considered in the future development of efficient post-exposure countermeasures against ricin intoxication.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona 74100, Israel. anitas@iibr.gov.il.

ABSTRACT
Ricin, a plant-derived exotoxin, inhibits protein synthesis by ribosomal inactivation. Due to its wide availability and ease of preparation, ricin is considered a biothreat, foremost by respiratory exposure. We examined the in vivo interactions between ricin and cells of the lungs in mice intranasally exposed to the toxin and revealed multi-phasic cell-type-dependent binding profiles. While macrophages (MΦs) and dendritic cells (DCs) displayed biphasic binding to ricin, monophasic binding patterns were observed for other cell types; epithelial cells displayed early binding, while B cells and endothelial cells bound toxin late after intoxication. Neutrophils, which were massively recruited to the intoxicated lung, were refractive to toxin binding. Although epithelial cells bound ricin as early as MΦs and DCs, their rates of elimination differed considerably; a reduction in epithelial cell counts occurred late after intoxication and was restricted to alveolar type II cells only. The differential binding and cell-elimination patterns observed may stem from dissimilar accessibility of the toxin to different cells in the lung and may also reflect unequal interactions of the toxin with different cell-surface receptors. The multifaceted interactions observed in this study between ricin and the various cells of the target organ should be considered in the future development of efficient post-exposure countermeasures against ricin intoxication.

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In vivo binding of ricin to cells of the mouse lung. Lung cells isolated 3 h after intranasal exposure to ricin-AF488 were analyzed by fluorescence activated cell sorting (FACS) for bound toxin direct toxin-fluorescence (A) or by staining of the cells with anti-ricin antibody, RAF5 (B).
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toxins-07-04817-f001: In vivo binding of ricin to cells of the mouse lung. Lung cells isolated 3 h after intranasal exposure to ricin-AF488 were analyzed by fluorescence activated cell sorting (FACS) for bound toxin direct toxin-fluorescence (A) or by staining of the cells with anti-ricin antibody, RAF5 (B).

Mentions: To characterize the interactions between ricin and cells of the lung, mice were intranasally exposed to fluorescently-labeled ricin at a lethal dose of 2 LD50. We monitored toxin-associated cells by examining the forward scatter (FSC) profile of pulmonary cells isolated 3 h after intoxication. Intoxication led to the labeling of a defined population of cells, mainly of hematopoietic (CD45+) origin (Figure 1A). Since fluorescent toxin identifies both internal and external cell-associated toxin, ricin binding was monitored by an additional technique, utilizing purified anti-ricin antibody, RAF5, for tagging the toxin. It should be noted that when this technique is employed, the detection of cell-associated ricin reflects a primary interaction between the antibody and the toxin, which occurred at the cell exterior. Indeed, monitoring toxin-associated cells by this technique revealed a distinctly different pattern, attesting to the binding of the toxin mainly to parenchymal (CD45−) cells (Figure 1B). Identification of ricin binding to CD45+ cells mostly by toxin fluorescence and not by antibodies indicates that in these cells, the bulk of cell-associated toxin has already been internalized. In contrast, ricin-bound CD45− cells were mainly detectable by antibodies, indicating that in these cells, ricin was associated with the exterior surface of the cells. Toxin/cell interactions in CD45− cells could not be observed by the direct fluorescent-toxin monitoring technique, suggesting that this technique is less sensitive than the antibody-tagging technique.


Diverse profiles of ricin-cell interactions in the lung following intranasal exposure to ricin.

Sapoznikov A, Falach R, Mazor O, Alcalay R, Gal Y, Seliger N, Sabo T, Kronman C - Toxins (Basel) (2015)

In vivo binding of ricin to cells of the mouse lung. Lung cells isolated 3 h after intranasal exposure to ricin-AF488 were analyzed by fluorescence activated cell sorting (FACS) for bound toxin direct toxin-fluorescence (A) or by staining of the cells with anti-ricin antibody, RAF5 (B).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663535&req=5

toxins-07-04817-f001: In vivo binding of ricin to cells of the mouse lung. Lung cells isolated 3 h after intranasal exposure to ricin-AF488 were analyzed by fluorescence activated cell sorting (FACS) for bound toxin direct toxin-fluorescence (A) or by staining of the cells with anti-ricin antibody, RAF5 (B).
Mentions: To characterize the interactions between ricin and cells of the lung, mice were intranasally exposed to fluorescently-labeled ricin at a lethal dose of 2 LD50. We monitored toxin-associated cells by examining the forward scatter (FSC) profile of pulmonary cells isolated 3 h after intoxication. Intoxication led to the labeling of a defined population of cells, mainly of hematopoietic (CD45+) origin (Figure 1A). Since fluorescent toxin identifies both internal and external cell-associated toxin, ricin binding was monitored by an additional technique, utilizing purified anti-ricin antibody, RAF5, for tagging the toxin. It should be noted that when this technique is employed, the detection of cell-associated ricin reflects a primary interaction between the antibody and the toxin, which occurred at the cell exterior. Indeed, monitoring toxin-associated cells by this technique revealed a distinctly different pattern, attesting to the binding of the toxin mainly to parenchymal (CD45−) cells (Figure 1B). Identification of ricin binding to CD45+ cells mostly by toxin fluorescence and not by antibodies indicates that in these cells, the bulk of cell-associated toxin has already been internalized. In contrast, ricin-bound CD45− cells were mainly detectable by antibodies, indicating that in these cells, ricin was associated with the exterior surface of the cells. Toxin/cell interactions in CD45− cells could not be observed by the direct fluorescent-toxin monitoring technique, suggesting that this technique is less sensitive than the antibody-tagging technique.

Bottom Line: Neutrophils, which were massively recruited to the intoxicated lung, were refractive to toxin binding.The differential binding and cell-elimination patterns observed may stem from dissimilar accessibility of the toxin to different cells in the lung and may also reflect unequal interactions of the toxin with different cell-surface receptors.The multifaceted interactions observed in this study between ricin and the various cells of the target organ should be considered in the future development of efficient post-exposure countermeasures against ricin intoxication.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona 74100, Israel. anitas@iibr.gov.il.

ABSTRACT
Ricin, a plant-derived exotoxin, inhibits protein synthesis by ribosomal inactivation. Due to its wide availability and ease of preparation, ricin is considered a biothreat, foremost by respiratory exposure. We examined the in vivo interactions between ricin and cells of the lungs in mice intranasally exposed to the toxin and revealed multi-phasic cell-type-dependent binding profiles. While macrophages (MΦs) and dendritic cells (DCs) displayed biphasic binding to ricin, monophasic binding patterns were observed for other cell types; epithelial cells displayed early binding, while B cells and endothelial cells bound toxin late after intoxication. Neutrophils, which were massively recruited to the intoxicated lung, were refractive to toxin binding. Although epithelial cells bound ricin as early as MΦs and DCs, their rates of elimination differed considerably; a reduction in epithelial cell counts occurred late after intoxication and was restricted to alveolar type II cells only. The differential binding and cell-elimination patterns observed may stem from dissimilar accessibility of the toxin to different cells in the lung and may also reflect unequal interactions of the toxin with different cell-surface receptors. The multifaceted interactions observed in this study between ricin and the various cells of the target organ should be considered in the future development of efficient post-exposure countermeasures against ricin intoxication.

Show MeSH
Related in: MedlinePlus