Distribution of DNA Adducts and Corresponding Tissue Damage of Sprague–Dawley Rats with Percutaneous Exposure to Sulfur Mustard

Abstract

Sulfur mustard (SM) is a highly reactive alkylation vesicant and cytotoxic agent that has been recognized as an animal and human carcinogen. Although the exact mechanism of toxicology is vague, DNA alkylation seems to be responsible for the triggering of apoptosis. In this study, after male adult Sprague-Dawley rats were cutaneous exposed to a low concentration of SM at parts-per-million levels, their lungs, livers, pancreases, spleens, marrow, and brains were collected at 11 different time points and analyzed. N7-[2-[(2-hydroxyethyl)thio]-ethyl]guanine (N7-HETEG), N3-[2-[(2-hydroxyethyl)thio]-ethyl]adenine (N3-HETEA), and bis[2-(guanin-7-yl)ethyl]sulfide (Bis-G) as the biomarkers for DNA damage were measured in the vital tissues by isotope dilution ultraperformance liquid chromatography tandem mass spectrometry (ID-UPLC-MS/MS). At the same time, general variations and pathological changes were monitored and detected to evaluate the tissue damage. Time- and dose-dependent data showed that SM had strong permeability and reactivity and that three SM-DNA adducts were detected in all investigated tissues only after 10 min after exposure. Obvious dose-dependency was observed except in the brain and pancreas. Most times to peak (tmax) of all three adducts were less than 3 h, while half-lifetimes (t1/2) were less than 24 h. We also suggested that the lipophilic SM can easily pass through the blood-brain barrier and can be stored in the fatty organs. To the best of our knowledge, the abundant adducts in marrow were found and reported for the first time. The surveillance of N7-HETEG in vivo, which was the most abundant adduct, may be the most efficient indicator to validate SM exposure even without any symptoms. Bis-G can be regarded as a biomarker of effect, which is directly related to the extent of damage. The most abundant Bis-G was found in the most sensitive tissues, marrow, spleen, and lung, which is in good accordance with histopathologic results. General variations and pathological changes were evaluated as well. After cutaneous exposure to SM, the body weights of rats heavily decreased in the first 4 days and were inversely proportional to the applied doses, and then recovered at the last experimental day except for those of the rats at the highest dosing level, in which the relative weights of rat spleens were obviously lost. Moreover, we found remarkable histological changes of the lung and skin, such as encephalemia, at the very beginning of the sampling procedure, and plentiful mononuclear cells in marrow appeared 6 h after exposure. The micronucleus test of marrow cells showed that the micronucleus rate had a positively dose-dependent effect.

Analysis of Different Fates of DNA Adducts in Adipocytes Post-sulfur Mustard Exposure in Vitro and in Vivo Using a Simultaneous UPLC-MS/MS Quantification Method

“…By comparison, our previous work reported that the maximum level of N 7 -HETEG in the liver from a 10 mg/kg dose exposed rat was approximately 98 ± 62 per 10 6 bases. 25 There were multiple magnitude differences between the adduct levels in the ATs and other tissues. These results were different from the comparative results in vitro and may be a result of a more complex physiological environment in vivo.…”

“…25 SM has lipophilic properties. 26 It has been suggested that the accumulation of SM in adipose or hydrophobic environments (such as lipids) and the subsequent biological effects may be crucial for the distribution of and damage caused by SM.…”

From the Cover: Catalytic Antioxidant Rescue of Inhaled Sulfur Mustard Toxicity

“…Depletion of white blood cells is a well reported facet of SM toxicity, and it has been suggested that the SM-mediated immune suppression may be one of the most threatening effects of exposure (Anderson et al, 2006;Hassan et al, 2006;Yue et al, 2015). These studies also found SM exposure to produce a leukopenia that was primarily influenced by depressed lymphocyte counts.…”

“…Catalytic antioxidant administration attenuated leukopenia at each time point studied with the largest effects on the neutrophil and lymphocyte counts. The finding that white blood cells are restored with catalytic antioxidant treatments is highly significant due to the previous research which has shown bone marrow to be an important target of SM damage (Yue et al, 2015). Leukocytes are believed to have an important role in the pathogenic response to inhaled vesicants (McClintock et al, 2002;Weinberger et al, 2011).…”

Emerging targets for treating sulfur mustard–induced injuries

“…These ions are potent alkylating molecules that react with nucleotides, proteins, and lipids. Because of its strong alkylating properties, primarily due to activity at guanine residues, SM forms DNA adducts and cross‐links . SM is partially absorbed from the skin into the dermis, where it can form DNA adducts or enter systemically and react with other organs, including the lung .…”