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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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Effect of exposure to ricin on alveolar type I (ATI) and ATII cells. Lungs were harvested at different time points after intranasal exposure to unlabeled ricin. (A) ATI and (B) ATII cells were analyzed by FACS 48 and 72 h after intoxication (five mice per group). * p < 0.05. (C) Immunofluorescence analysis of pro-surfactant C (pro-SPC) (red), T1α (yellow) and DAPI (blue) staining of lung tissue from naive (left) and 48 h post-intoxication (right) mice. Scale bars indicate 20 µm.
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toxins-07-04817-f005: Effect of exposure to ricin on alveolar type I (ATI) and ATII cells. Lungs were harvested at different time points after intranasal exposure to unlabeled ricin. (A) ATI and (B) ATII cells were analyzed by FACS 48 and 72 h after intoxication (five mice per group). * p < 0.05. (C) Immunofluorescence analysis of pro-surfactant C (pro-SPC) (red), T1α (yellow) and DAPI (blue) staining of lung tissue from naive (left) and 48 h post-intoxication (right) mice. Scale bars indicate 20 µm.

Mentions: Lung alveolar epithelial cells are of two types, respiratory alveolar type I (ATI) and surfactant-secreting alveolar type II (ATII) cells [14], the latter being dispersed between the ATI cells. ATI and ATII cells can be differentiated by specific labeling of podoplanin (T1α) [15] and pro-surfactant C (pro-SPC) [16], respectively. FACS analysis demonstrated that ATII cells (CD45−, CD31−, pro-SPC+), but not ATI cells (CD45−, CD31−, T1α+) (Figure S3), were depleted from the intoxicated lung at 48 h after exposure (Figure 5A,B). This unexpected finding, that epithelial elimination in the intoxicated lung was restricted to ATII cells, was also manifested by immunohistochemical analysis (Figure 5C). TUNEL staining for apoptosis was prevalent in pro-SPC labeled cells, suggesting that apoptosis of ATII cells precedes their elimination (Figure 6A). It should be mentioned that at 24 h after ricin intoxication, but not at later time points, pro-SPC+ ring structures were detected in the damaged parenchyma (Figure 6B). Moreover, pro-SPC expression, undetected in the bronchial epithelia of naive lungs, was readily visualized in the bronchial epithelia of intoxicated lungs (Figure 6C). This incongruous de novo expression of the surfactant precursor presumably reflects an attempt to restore pulmonary functionality by means of synthesizing surfactant.


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)

Effect of exposure to ricin on alveolar type I (ATI) and ATII cells. Lungs were harvested at different time points after intranasal exposure to unlabeled ricin. (A) ATI and (B) ATII cells were analyzed by FACS 48 and 72 h after intoxication (five mice per group). * p < 0.05. (C) Immunofluorescence analysis of pro-surfactant C (pro-SPC) (red), T1α (yellow) and DAPI (blue) staining of lung tissue from naive (left) and 48 h post-intoxication (right) mice. Scale bars indicate 20 µm.
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Related In: Results  -  Collection

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

toxins-07-04817-f005: Effect of exposure to ricin on alveolar type I (ATI) and ATII cells. Lungs were harvested at different time points after intranasal exposure to unlabeled ricin. (A) ATI and (B) ATII cells were analyzed by FACS 48 and 72 h after intoxication (five mice per group). * p < 0.05. (C) Immunofluorescence analysis of pro-surfactant C (pro-SPC) (red), T1α (yellow) and DAPI (blue) staining of lung tissue from naive (left) and 48 h post-intoxication (right) mice. Scale bars indicate 20 µm.
Mentions: Lung alveolar epithelial cells are of two types, respiratory alveolar type I (ATI) and surfactant-secreting alveolar type II (ATII) cells [14], the latter being dispersed between the ATI cells. ATI and ATII cells can be differentiated by specific labeling of podoplanin (T1α) [15] and pro-surfactant C (pro-SPC) [16], respectively. FACS analysis demonstrated that ATII cells (CD45−, CD31−, pro-SPC+), but not ATI cells (CD45−, CD31−, T1α+) (Figure S3), were depleted from the intoxicated lung at 48 h after exposure (Figure 5A,B). This unexpected finding, that epithelial elimination in the intoxicated lung was restricted to ATII cells, was also manifested by immunohistochemical analysis (Figure 5C). TUNEL staining for apoptosis was prevalent in pro-SPC labeled cells, suggesting that apoptosis of ATII cells precedes their elimination (Figure 6A). It should be mentioned that at 24 h after ricin intoxication, but not at later time points, pro-SPC+ ring structures were detected in the damaged parenchyma (Figure 6B). Moreover, pro-SPC expression, undetected in the bronchial epithelia of naive lungs, was readily visualized in the bronchial epithelia of intoxicated lungs (Figure 6C). This incongruous de novo expression of the surfactant precursor presumably reflects an attempt to restore pulmonary functionality by means of synthesizing surfactant.

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