Diverse Profiles of Ricin-Cell Interactions in the Lung Following Intranasal Exposure to Ricin

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.

Early disruption of the alveolar-capillary barrier in a ricin-induced ARDS mouse model: neutrophil-dependent and -independent impairment of junction proteins

“…Early neutrophil accumulation has been observed in the lung tissue of ARDS patients (14), and a poor prognosis in septic ARDS was found to correlate with elevated neutrophil counts in BALF 39). Rapid and high level recruitment of neutrophils to the lungs has been well documented in pulmonary ricinosis animal models (7,20,30,33,35). Since the administration of anti-ricin Ab treatment at 24 h postexposure to ricin resulted in significantly reduced levels of pulmonary EBD (see Fig.…”

“…In pulmonary ricinosis, the toxin enzymatically inactivates ribosomes by a unique 28S rRNA ribosomal depurination mechanism, thereby inducing death of inflammatory cells, dendritic cells, macrophages, lung parenchymal cells, blood endothelial cells, and alveolar epithelial cells (35). At the clinical level, pulmonary exposure to ricin induces neutrophil influx to the lungs accompanied by a cytokine storm and the generation of a severe edema in the alveoli and pulmonary interstitium, which in turn leads to respiratory failure and death (11,35,44). Recently, we have shown that the clinical manifestations of ricin-induced respiratory damage in swine comply fully with the accepted diagnostic criteria for ARDS (18).…”

Quantitative profiling of the in vivo enzymatic activity of ricin reveals disparate depurination of different pulmonary cell types

“…Although this mode of exposure may not accurately replicate inhalatory exposures, we have demonstrated in the past that intranasal exposure of mice to ricin, brings about extensive pulmonary damage, including the generation of an acute edematous lung inflammation and damage of lung cell subtypes (Gal et al, 2014;Sapoznikov et al, 2015). Ribosome depurination quantitation was accomplished by developing a method for measuring depurination levels, utilizing a primary extension assay previously described (Iordanov et al, 1997).…”

“…Toxins were prepared as previously described (Gal et al, 2014;Sapoznikov et al, 2015;Sabo et al, 2015). Briefly, seeds of Ricinus communis or Abrus precatorius were homogenized in a Waring blender in 5% acetic acid/phosphate buffer (Na2 HPO4, pH 7.4) the homogenate was centrifuged and the clarified supernatant containing the toxin was subjected to ammonium sulphate precipitation (60% and 80% saturation, for ricin and abrin, respectively).…”

Equal Neutralization Potency of Antibodies Raised against Abrin Subunits

“…Crude ricin was prepared from seeds of endemic Ricinus communis, essentially as described before [9]. Briefly, seeds were homogenized in a Waring blender in 5% acetic acid/phosphate buffer (Na 2 HPO 4 , pH-7.4), the homogenate was centrifuged and the clarified supernatant containing the toxin was subjected to ammonium sulfate precipitation (60% saturation).…”