The HSP90 Inhibitor, AUY-922, Ameliorates the Development of Nitrogen Mustard-Induced Pulmonary Fibrosis and Lung Dysfunction in Mice.

Increased levels of heat shock protein 90 (HSP90) have been recently implicated in the pathogenesis of pulmonary fibrosis and the use of HSP90 inhibitors constitutes a potential therapeutic approach. Similarly, acute exposure to nitrogen mustard (NM) is related to the development of chronic lung injury driven by TNF-α, TGF-ß, ERK and HSP90. Thus, we developed a murine model of NM-induced pulmonary fibrosis by instilling C57BI/6J mice with 0.625 mg/kg mechlorethamine hydrochloride. After 24 h, mice began receiving AUY-922, a second generation HSP90 inhibitor, at 1 mg/kg 2 times per week or 2 mg/kg 3 times per week, for either 10 or 30 days. AUY-922 suppressed the NM-induced sustained inflammation, as reflected in the reduction of leukocyte and protein concentrations in bronchoalveolar lavage fluid (BALF), and inhibited the activation of pro-fibrotic biomarkers, ERK and HSP90. Furthermore, AUY-922 maintained normal lung function, decreased the overexpression and accumulation of extracellular matrix proteins, and dramatically reduced histologic evidence of fibrosis in the lungs of mice exposed to NM. The HSP90 inhibitor, AUY-922, successfully blocked the adverse effects associated with acute exposures to NM, representing a promising approach against NM-induced pulmonary fibrosis.

Ebselen oxide attenuates mechlorethamine dermatotoxicity in the mouse ear vesicant model.

Mechlorethamine (HN2) is an alkylating agent and sulfur mustard mimetic. Topical exposure to HN2 is associated with tissue blistering. Previous work in our laboratory has shown that ebselen (EB-1) possesses anti-vesicant, anti-inflammatory, anti-bacterial, anti-fungal, and cytoprotective properties, both in vivo and in vitro. We recently reported that ebselen oxide (EB-2), an analog of EB-1 with a tetravalent selenium atom, also possesses anti-bacterial and anti-fungal activity and confers cytoprotection against HN2 in vitro. The purpose of the present study was to determine the vesicant countermeasure potential of EB-2 using the mouse ear vesicant model (MEVM). Compared to control ears, mouse ears exposed to a single dose of HN2 (0.500 µmol/ear) showed an increase in wet weights, ear thickness, hyperplasia, vesication, and inflammatory cell infiltration after 24 h. Fluorescence microscopy of terminal deoxynucleotidyl transferase (TdT) dUTP nick end labeling (TUNEL)-stained sections showed that the occurrence of apoptosis extended from the epidermis of the HN2-treated side, all the way to the contralateral epidermis. In contrast, HN2-exposed ears treated topically with EB-2 at a test dose of 0.250 mg/ear showed a significant decrease in wet weight (12% less vs. HN2 alone), morphometric thickness (13% less vs. HN2 alone), and vesication. In addition, TUNEL staining revealed that HN2 ears treated with EB-2 (0.250 mg/ear) showed a decrease in apoptosis as compared to the HN2 group. EB-2 also reduced the abundance of matrix metalloproteinase-9 (MMP-9) in ear tissues exposed to HN2. Taken together, our study demonstrates that EB-2 is an efficacious countermeasure to HN2.

Efficacy of anti-inflammatory, antibiotic and pleiotropic agents in reversing nitrogen mustard-induced injury in ex vivo cultured rabbit cornea.

Vesicating agent, Sulfur mustard (SM), causes devastating eye injury; however, there are no effective antidotes available. Using nitrogen mustard (NM), a bi-functional analog of SM, we have earlier reported that NM-induced corneal injury in ex vivo rabbit cornea organ culture model parallels corneal injury reported with SM. Using this model, we have demonstrated the therapeutic efficacy of dexamethasone (DEX), doxycycline (DOX) and silibinin (SB) in reversing NM (2h exposure)-induced corneal injuries when added immediately after washing NM. In the present study, we further examined the efficacy of similar/higher doses of these agents when added immediately, 2, or 4h after washing NM following its 2h exposure. All three treatment agents caused a reversal in established NM-induced injury biomarkers when added immediately or 2h after washing NM following its 2h exposure; however, when treatments were carried out 4h after washing NM, there was no significant effect. Together, our results further show the beneficial effect of these agents in reversing NM-induced corneal injury and indicate the time window for effective treatment. This could be useful towards future development of targeted therapeutics against vesicant-induced ocular injury.

Attenuation of Nitrogen Mustard-Induced Pulmonary Injury and Fibrosis by Anti-Tumor Necrosis Factor-α Antibody.

Nitrogen mustard (NM) is a bifunctional alkylating agent that causes acute injury to the lung that progresses to fibrosis. This is accompanied by a prominent infiltration of macrophages into the lung and upregulation of proinflammatory/profibrotic cytokines including tumor necrosis factor (TNF)α. In these studies, we analyzed the ability of anti-TNFα antibody to mitigate NM-induced lung injury, inflammation, and fibrosis. Treatment of rats with anti-TNFα antibody (15 mg/kg, iv, every 9 days) beginning 30 min after intratracheal administration of NM (0.125 mg/kg) reduced progressive histopathologic alterations in the lung including perivascular and peribronchial edema, macrophage/monocyte infiltration, interstitial thickening, bronchiolization of alveolar walls, fibrin deposition, emphysema, and fibrosis. NM-induced damage to the alveolar-epithelial barrier, measured by bronchoalveolar lavage (BAL) protein and cell content, was also reduced by anti-TNFα antibody, along with expression of the oxidative stress marker, heme oxygenase-1. Whereas the accumulation of proinflammatory/cytotoxic M1 macrophages in the lung in response to NM was suppressed by anti-TNFα antibody, anti-inflammatory/profibrotic M2 macrophages were increased or unchanged. Treatment of rats with anti-TNFα antibody also reduced NM-induced increases in expression of the profibrotic mediator, transforming growth factor-ß. This was associated with a reduction in NM-induced collagen deposition in the lung. These data suggest that inhibiting TNFα may represent an efficacious approach to mitigating lung injury induced by mustards.

The protective effect of melatonin and S-methylisothiourea treatments in nitrogen mustard induced lung toxicity in rats.

OBJECTIVES: Mustard is highly toxic to the lung. Its toxic effects are associated with inflammatory cell accumulation and increased pro-inflammatory cytokines as well as reactive oxygen and nitrogen species. In this study, we aimed to investigate the efficiency of melatonin (MEL) and S-methylisothiourea (SMT) on mechlorethamine (MEC) induced lung toxicity. METHODS: Thirty-six male rats were randomly divided into four groups: control, MEC, MEC+MEL, and MEC+SMT. Control group was given saline only via transdermal route. Other groups were exposured to a single dose of MEC (3.5 mg/kg) via transdermal route. MEL (100 mg/kg) was administered intraperitoneally 30 min after the application of MEC, and after the same dose of MEL was given every 12 h for a total of six doses. SMT (50 mg/kg) was also given intraperitoneally 30 min after the application of MEC. RESULTS: MEC injection resulted in alveolar epithelial injury, hemorrhage, inflammation, edema and interalveolar septal thickening in the lung tissues. The tissue TNF-α, IL-1ß, and nitrate/nitrite (NOx) levels were found significantly different for all groups (p<0.001). TNF-α and IL-1ß levels increased significantly with MEC exposure, and MEL and SMT ameliorated these increases in lung tissues. MEC also elevated NOx levels in lung tissue. Melatonin showed meaningful protection against lung injury. But protection of SMT was weaker. CONCLUSION: Inflammation plays an important role in the MEC induced lung toxicity as well as oxidative and nitrosative stress. Melatonin has also anti-inflammatory properties similar to SMT, as well as anti-oxidant properties. But melatonin treatment was found more efficient than SMT treatment.

Ebselen reduces the toxicity of mechlorethamine in A-431 cells via inhibition of apoptosis.

A series of test compounds were evaluated for an ability to reduce the toxicity of the nitrogen mustard mechlorethamine (HN2) in vitro. The test compounds included resveratrol, pterostilbene, vitamin C, ebselen, ebselen diselenide, and ebselen-sulfur. Among them, ebselen demonstrated the highest degree of protection against HN2 toxicity. To this end, pretreatment of the cells with ebselen offered protection against the toxicant whereas no protection was observed when cells were first incubated with HN2 and then treated with ebselen. Significant increases in caspase 3 and caspase 9 activities were observed in response to HN2, and ebselen was found to reduce these effects. Taken together, the data presented here indicate that ebselen is an effective countermeasure to nitrogen mustard in vitro, which is worthy of future investigation in vivo.

Prophylactic efficacy of amifostine and its analogues against sulphur mustard toxicity.

The successful implication of the chemical weapons convention stimulated research with a new vigour on the destruction of the stockpiled sulphur mustard (SM). A prophylactic agent for SM will be very useful for personnel engaged in the destruction of SM and during inspections by the Organisation for the Prohibition of Chemical Weapons. Due to simple method of preparation, SM can be used clandestinely during war or by terrorist groups. Inspite of research over several decades no satisfactory prophylactic or treatment regimen has evolved for SM. Amifostine an organophosphorothioate, originally developed as a radioprotector, and its analogues were evaluated as a prophylactic agent for SM. Three analogues by varying the chain length and substitution at the sulphur atom were synthesised and coded as DRDE-06, DRDE-07 and DRDE-08. LD(50) of amifostine and its analogues were estimated through intraperitoneal (i.p.) route. For the protection studies, amifostine and its analogues were administered i.p. in mice, 30 min before dermal (percutaneous) application of SM. The dose of the prophylactic agent was 0.2 LD(50) (i.p.) and that of SM was 152 mg/kg (undiluted) equal to 19-fold LD(50) of SM. Amifostine and one of its analogues, DRDE-07 gave significant protection. Further studies were carried out using amifostine and DRDE-07, and both of them significantly protected mice against SM (155 mg/kg, in PEG 300, equal to 19 LD(50)) when they were administered i.p. either 30 min before or simultaneously. LD(50) of amifostine and DRDE-07 were also estimated through the oral route (1049 or 1248 mg/kg, respectively). Prophylactically administered amifostine and DRDE-07 (0.2 LD(50), p.o.) significantly protected the mice against dermally applied SM (155 mg/kg, in PEG 300, equal to 19 LD(50)). The protection offered by DRDE-07 was better than that of amifostine by the oral route. DRDE-07 (0.2 LD(50), p.o.) also protected significantly with respect to the decrease in body weight and the depletion of GSH induced by SM. DNA damage induced by SM was also significantly reduced by amifostine and DRDE-07 (0.2 LD(50), p.o.). Further studies are in progress on the various pharmacological and toxicological properties of DRDE-07.

Protective effect of povidone-iodine ointment against skin lesions induced by sulphur and nitrogen mustards and by non-mustard vesicants.

Mustard gas (sulphur mustard, SM) is a powerful vesicant employed as a chemical weapon. The present study demonstrates the effect of povidone iodine (PI) ointment against skin toxicity caused by SM. Gross and histopathological examinations showed that application of PI up to 20 min following exposure to the vesicant resulted in marked skin protection. The shorter the interval between exposure and treatment the better was the protection achieved. PI was also effective against other mustards such as carboxybutyl chloroethyl sulphide (CBCS) and mechlorethamine. The fact that PI protected the skin against agents which cannot be oxidized such as iodoacetic acid, divinylsulphone and cantharidine showed that the antidotal effect of PI was unrelated to oxidation of the nitrogen and sulphur atoms of the mustards. PI ointment is proposed as an efficient protective agent against skin toxicity caused by mustards and other alkylators.

The Fanconi anemia complementation group C protein corrects DNA interstrand cross-link-specific apoptosis in HSC536N cells.

Fanconi anemia (FA) cells are hypersensitive to cytotoxicity, cell cycle arrest, and chromosomal aberrations induced by DNA cross-linking agents, such as mitomycin C (MMC) and nitrogen mustard (HN2). Although MMC hypersensitivity is complemented in a subset of FA cells (complementation group C [FA-C]) by wild-type FAC cDNA, the cytoprotective mechanism is unknown. In the current study, we tested the hypothesis that FAC protein functions in the suppression of DNA interstand cross-link (ISC)-induced cell cycle arrest and apoptosis. Comparison of HN2-induced cell cycle arrest and apoptosis with those of its non-cross-linking analogs, diethylaminoethyl chloride and 2-dimethylaminoethyl chloride, delineated the DNA ISC specificity of FAC-mediated cytoprotection. Overexpression of wild-type FAC cDNA in FA-C lymphoblasts (HSC536N cell line) prevented HN2-induced growth inhibition, G2 arrest, and DNA fragmentation that is characteristic of apoptosis. In contrast cytoprotection was not conferred against the effects of the non-cross-linking mustards. Our data show that DNA ISCs induce apoptosis more potently than do DNA monoadducts and suggest that FAC suppresses specifically DNA ISC-induced apoptosis in the G2 phase of the cell cycle.

N-acetylcysteine protects lymphocytes from nitrogen mustard-induced apoptosis.

The ability of the antioxidant N-acetylcysteine to prevent apoptosis induced in lymphocytes by nitrogen mustard (HN2) was investigated. HN2 caused a concentration-dependent induction of apoptosis on C3H murine spleen cells, as identified by two criteria: morphological features revealed by microscopical observations and DNA fragmentation visualized by the characteristic "ladder" pattern observed upon agarose gel electrophoresis, as well as by hypodiploid DNA-containing cells revealed by the flow cytometric analysis of propidium iodide labelled cells. The antioxidant N-acetylcysteine (NAC) was found to markedly reduce the occurrence of HN2-induced apoptosis in these cells. This protective effect will still obtained when NAC was added 30 min after HN2. In contrast, the pretreatment of spleen cells with this antioxidant did not provide any significant protection. We also showed that lymphocytes protected by NAC are still able to respond to a mitogenic stimulation. To gain some insight into the mechanisms underlying the cytoprotective action of NAC against HN2, we tested whether or not poly(ADP-ribose) polymerase (PARP, EC 2.4.2.30), a nuclear enzyme that participates in the triggering of apoptosis induced by alkylating agents, is involved. We report that 6(5H)-phenanthridinone, a potent PARP inhibitor, did not affect the ability of NAC to prevent HN2-induced apoptosis under our experimental conditions. Thus, the exact mechanism by which NAC protects lymphocytes from HN2 cytotoxicity has yet to be determined.

Influence of diltiazem on the ocular irritative response to nitrogen mustard.

Application of nitrogen mustard to the eye of rabbits causes an anterior segment irritation and a biphasic elevation of intraocular pressure. This intraocular pressure response is composed of an initial peak, produced by neuropeptides released by excited sensory nerves, and a second, slower rise due to prostaglandins. We studied the effect of diltiazem, a calcium antagonist that selectively blocks chemical excitation of sensory nerves, on the inflammatory response to nitrogen mustard. In adult rabbits, intraocular pressure was determined by pneumatonometry; pupil diameter and palpebral opening were measured with a ruler while conjunctival vasodilation, edema and secretion were scored in subjective units (0-8). Aqueous humor protein content was analysed at the end of the experiment. Bilateral application of 1% nitrogen mustard evoked within the first 6 hr an intraocular pressure elevation followed by ocular hypotony, miosis, palpebral closure, conjunctival vasodilation, edema and an elevation of aqueous proteins. Topical application of 10 mM diltiazem, prior to administration of nitrogen mustard elicited by itself a transient, small intraocular pressure increase and reduced significantly the acute intraocular pressure elevation and conjunctival vasodilation evoked by the irritant; delayed conjunctival edema and palpebral closure were also attenuated by 10 mM diltiazem. The decrease of miotic response and of aqueous humor protein content was not significant. Diltiazem at 2.8 mM was effective only in reducing significantly conjunctival edema and vasodilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of mustard toxicity by tacrine.

Compounds containing the chloroethyl group are potent inhibitors of DNA synthesis and cell growth. Tacrine, a choline carrier inhibitor, was found to protect both HeLa cells and rat thymocytes against the effects of nitrogen mustard. DNA synthesis was restored from 13 to 71% of the control value and cell viability restored from 27 to 57% of the control value by exposure of the cells to an equimolar concentration of tacrine immediately prior to nitrogen mustard. In contrast, tacrine was unable to significantly protect rat thymocytes against the toxic effects of sulphur mustard. These results have implications for the clinical use of nitrogen mustard.

Hepatocyte toxicity of mechlorethamine and other alkylating anticancer drugs. Role of lipid peroxidation.

The alkylating anticancer drugs, mechlorethamine (HN2), chlorambucil, cyclophosphamide, carmustine and lomustine readily induced cytotoxicity in isolated rat hepatocytes. Hepatocyte glutathione (GSH) was depleted rapidly following addition of the drugs. Lipid peroxidation ensued following GSH depletion and before cytotoxicity occurred. Furthermore, cytotoxicity was delayed by the antioxidants butylated hydroxyanisole (BHA) and alpha-tocopherol, the ferric iron chelator desferoxamine or the radical trap 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) even when added 10 min later. HN2 was much less toxic to hepatocytes under nitrogen and caused much less lipid peroxidation than under aerobic conditions. Cytotoxicity induced by HN2 was also prevented by choline, suggesting that a choline carrier is responsible for HN2 uptake in the hepatocytes. Various sulfur compounds acted as antidotes for HN2 cytotoxicity. Thiosulfate was still effective when added 30 min after HN2. Depletion of GSH in the hepatocytes markedly increased their susceptibility to HN2. However, BHA, desferoxamine or TEMPO protected these hepatocytes from HN2. This suggests that antioxidants could prove useful in preventing the increased risk of hepatotoxicity if GSH-depleting agents are used to overcome tumor resistance to nitrogen mustards.

In vitro inhibition of nitrogen mustard efficacy by postincubation of treated cells in serum protein.

Lettre-Ehrlich cells were loaded with sufficient HN2 to produce about a 98% cell kill. Postincubation of the HN2-loaded cells in PBS resulted in the loss of about 40% of their HN2 without changing the cytolytic effect, supporting the proposal that only bound drug was effective. Postincubation of the HN2-loaded cells in PBS which contained 2% bovine serum albumin or in cell-free mouse ascitic fluid (1.8% protein) resulted in the same relative cellular HN2 loss as well as a 79% decrease in the cell kill. The cytolytic effect of HN2 is believed to be dependent on the degree to which the drug crosslinks DNA in 2 sequential reactions. It seems likely that such crosslinking occurred in nearly all of the PBS-postincubated cells, as they were nearly all killed. By analogy, albumin postincubation apparently blocked the competition of such crosslinking.

Protective effects of 2-[(aminopropyl)amino] ethanethiol against bleomycin and nitrogen mustard-induced mutagenicity in V79 cells.

This study examines the effects of the radioprotector 2-[(aminopropyl)amino] ethanethiol (WR-1065) on bleomycin (BLM) and nitrogen mustard- (HN2) induced cytotoxicity, DNA damage, and mutagenesis at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in V79 Chinese hamster cells. The anti-mutagenic effect of WR-1065 on cis-diamminedichloroplatinum (cis-DDP) and radiation- (XRT) induced HGPRT mutations was also evaluated for comparative purposes. WR-1065 (4 mM) was added prior to exposure of cells to therapy agents. All exposure times were 30 min. and both cell survival and mutagenesis were assayed. WR-1065 was effective in protecting against both effects. The induction of mutants corrected for background by BLM, HN2, cis-DDP, or XRT was linear in all cases. Mutation frequencies without WR-1065 were 78 X 10(-6) per unit BLM, 66 X 10(-7) per microgram HN2, 25 X 10(-7) per microgram cis-DDP; and 87 X 10(-7) per Gy of XRT. With WR-1065, these were reduced to 37 X 10(-6) per unit BLM, 40 X 10(-7) per microgram HN2, 1 X 10(-7) per microgram cis-DDP, and 44 X 10(-7) per Gy of XRT. Mutation protection factors (MPF), a ratio of the corresponding slopes of the mutation induction curves, with and without WR-1065 were: BLM, MPF = 2.8; HN2, MPF = 3.4; cis-DDP, MPF = 7.1; and XRT, MPF = 5.1. Single-strand-break (SSB) formation in DNA by BLM or HN2, assayed by alkaline elution, was protected against by WR-1065. WR-1065 did not induce SSB in control cells. The reduction of the mutagenic effects of agents used in radiation and chemotherapy by radioprotectors may be an important additional benefit for consideration in their use in cancer treatment.

Protection of murine L1210 leukemia and bone marrow progenitor cells against mechlorethamine and inhibition of choline uptake as a structure-activity relationship of 2-dimethylaminoethanol and its analogues.

The structure-activity relationships of 2-dimethylaminoethanol and its analogues as protectors against mechlorethamine cytotoxicity and as inhibitors of choline uptake were evaluated. Of a series of inhibitors and protectors, 2-dimethylaminoethanol was the most potent inhibitor of choline uptake and the most potent protector of both hematopoietic progenitor cells and murine L1210 leukemia cells. Two analogues that exhibited both potent protection and inhibition were 1-dimethylamino-2-propanol and 2-ethylmethylaminoethanol. 2-Di-n-butylaminoethanol, while protecting against mechlorethamine cytotoxicity, was not an inhibitor of choline uptake. 2-n-Butylmethylaminoethanol, while an inhibitor of choline uptake, was not a protector against mechlorethamine cytotoxicity. Addition of 2-dimethylaminoethanol to mechlorethamine in a mole ratio of 1000:1 did not improve survival of tumor-bearing mice beyond that of mice treated with mechlorethamine alone.

Inhibition of nitrogen mustard induced DNA repair synthesis by anthracyclines in human peripheral leukocytes.

DNA repair synthesis was induced by nitrogen mustard in human peripheral leukocytes. When the cells were treated with increasing doses of doxorubicin or daunorubicin a decrease of the DNA repair synthesis was recorded. Daunorubicin had a significantly higher inhibitory effect on the DNA repair synthesis compared to doxorubicin. The inhibitory effect by doxorubicin or daunorubicin on nitrogen mustard induced DNA repair synthesis was compared with the inhibitory effect on replicative DNA and RNA synthesis in human lymphoblasts. The inhibition of DNA repair synthesis was significantly lower than the inhibition of replicative DNA synthesis and RNA synthesis for both drugs.

Tetraalkylammonium ions: protection of murine L1210 leukemia and bone marrow progenitor cells in vitro against mechlorethamine cytotoxicity and inhibition of the choline transport system.

In the series of tetraalkylammonium ions from tetramethylammonium to tetra-n-heptylammonium, tetra-n-pentylammonium ion was a potent protector of both murine L1210 leukemia and bone marrow progenitor cells against mechlorethamine cytotoxicity. It was also a non-competitive inhibitor of choline uptake. Phosphonium analogs of the tetraalkylammonium ions were equal to their corresponding tetraalkylammonium ions in their protection against mechlorethamine cytotoxicity and in their inhibition of choline uptake. Treatment of tumor bearing L1210 leukemia mice with the combination of tetra-n-pentylammonium ion and mechlorethamine resulted in no major improvement in survival of the tumor-bearing mice compared to mechlorethamine treatment alone.

Cain's quinolinium (NSC 176319): protection of murine L1210 leukemia cells and bone marrow progenitor cells against mechlorethamine cytotoxicity and its application to combination chemotherapy.

Cain's Quinolinium; quinolinium, 6-amino-1-methyl-4[[[[[[(1-methyl-pyridinium-4-yl)amino]phenyl]amino]carbonyl]phenyl]amino] (NSC 176319), is a chemotherapeutic agent, which is equally cytotoxic in vitro to both murine L1210 leukemia cells and bone marrow progenitor cells. At non-toxic concentrations it equally protects L1210 cells and bone marrow progenitor cells against mechlorethamine cytotoxicity. However, treatment of murine L1210 leukemia bearing mice with the combination of Cain's Quinolinium and mechlorethamine at a mole ratio of 1:1 resulted in 100% long term survivors compared to 50% with Cain's Quinolinium alone or 0% with mechlorethamine alone.

Thiamine protection of murine L1210 leukemia cells against mechlorethamine cytotoxicity and its relation to the choline uptake system.

Thiamine is an inhibitor of choline transport by murine L1210 leukemia cells and a protector of these cells from growth inhibition by mechlorethamine in vitro. Combination chemotherapy of tumor bearing mice with thiamine and mechlorethamine increased the mechlorethamine dosage required for a 50 to 60 percent increase in survival time but did not improve survival over that obtained with mechlorethamine alone.