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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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Cell counts at different time points following ricin intoxication. Lung cells isolated from mice at different time points after intranasal exposure to ricin-AF488 and then stained for different cell surface markers were analyzed by FACS (five to ten mice per group). (A) MΦs, (B) DCs, (C) B cells, (D) endothelial cells, (E) epithelial cells and (F) total lung cells (open bars) and neutrophils (filled bars); * p < 0.05.
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toxins-07-04817-f004: Cell counts at different time points following ricin intoxication. Lung cells isolated from mice at different time points after intranasal exposure to ricin-AF488 and then stained for different cell surface markers were analyzed by FACS (five to ten mice per group). (A) MΦs, (B) DCs, (C) B cells, (D) endothelial cells, (E) epithelial cells and (F) total lung cells (open bars) and neutrophils (filled bars); * p < 0.05.

Mentions: To appreciate the correlation between binding kinetics and alterations in the lung cell populations, we performed a quantitative analysis of pulmonary cells following ricin intoxication. Evaluation of the alterations in MΦs allowed us to determine that a two-fold reduction occurred as early as 18 h after intoxication (Figure 4A) in line with our finding that ricin binding to this cell type occurred early (Figure 2A). Likewise, a two-fold reduction in the DCs population could be discerned already at 18 h after intoxication (Figure 4B). Profiling of the B cell and endothelial cell populations, both of which were found to bind toxin at late time points (Figure 2C,E), demonstrated that a two-fold reduction in these cells was reached at 48 h and 72 h after intoxication, respectively (Figure 4C,D). In the case of epithelial cells, although binding of toxin occurred early after intoxication (Figure 2D), a significant decrease in their number was evidenced only later: epithelial cell counts dropped from (3.3 ± 0.8) × 106 down to (1.2 ± 0.5) × 106 at 48 h after intoxication (Figure 4E). In spite of the cytotoxic effect of ricin and the marked elimination observed for various cell types, the overall number of cells comprising the lungs increased over time. Thus, at 6 h after intoxication, the number of lung cells (48.5 ± 6) × 106 increased to (65.6 ± 6) × 106, while 48 h after intoxication, numbers reached (95 ± 13) × 106 cells (Figure 4F). This striking rise in cell number correlated with the concomitant recruitment of neutrophils to the lungs. Neutrophil counts (~2 × 106 cells) were tripled 6 h after exposure to ricin, and at 48–72 h after intoxication, the size of this cell population was nearly equal to the number of cells comprising the entire lungs in naive mice (Figure 4F).


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)

Cell counts at different time points following ricin intoxication. Lung cells isolated from mice at different time points after intranasal exposure to ricin-AF488 and then stained for different cell surface markers were analyzed by FACS (five to ten mice per group). (A) MΦs, (B) DCs, (C) B cells, (D) endothelial cells, (E) epithelial cells and (F) total lung cells (open bars) and neutrophils (filled bars); * p < 0.05.
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toxins-07-04817-f004: Cell counts at different time points following ricin intoxication. Lung cells isolated from mice at different time points after intranasal exposure to ricin-AF488 and then stained for different cell surface markers were analyzed by FACS (five to ten mice per group). (A) MΦs, (B) DCs, (C) B cells, (D) endothelial cells, (E) epithelial cells and (F) total lung cells (open bars) and neutrophils (filled bars); * p < 0.05.
Mentions: To appreciate the correlation between binding kinetics and alterations in the lung cell populations, we performed a quantitative analysis of pulmonary cells following ricin intoxication. Evaluation of the alterations in MΦs allowed us to determine that a two-fold reduction occurred as early as 18 h after intoxication (Figure 4A) in line with our finding that ricin binding to this cell type occurred early (Figure 2A). Likewise, a two-fold reduction in the DCs population could be discerned already at 18 h after intoxication (Figure 4B). Profiling of the B cell and endothelial cell populations, both of which were found to bind toxin at late time points (Figure 2C,E), demonstrated that a two-fold reduction in these cells was reached at 48 h and 72 h after intoxication, respectively (Figure 4C,D). In the case of epithelial cells, although binding of toxin occurred early after intoxication (Figure 2D), a significant decrease in their number was evidenced only later: epithelial cell counts dropped from (3.3 ± 0.8) × 106 down to (1.2 ± 0.5) × 106 at 48 h after intoxication (Figure 4E). In spite of the cytotoxic effect of ricin and the marked elimination observed for various cell types, the overall number of cells comprising the lungs increased over time. Thus, at 6 h after intoxication, the number of lung cells (48.5 ± 6) × 106 increased to (65.6 ± 6) × 106, while 48 h after intoxication, numbers reached (95 ± 13) × 106 cells (Figure 4F). This striking rise in cell number correlated with the concomitant recruitment of neutrophils to the lungs. Neutrophil counts (~2 × 106 cells) were tripled 6 h after exposure to ricin, and at 48–72 h after intoxication, the size of this cell population was nearly equal to the number of cells comprising the entire lungs in naive mice (Figure 4F).

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