Dermal Exposure to Vesicating Nettle Agent Phosgene Oxime: Clinically Relevant Biomarkers and Skin Injury Progression in Murine Models

Phosgene oxime (CX), categorized as a vesicating chemical threat agent, causes effects that resemble an urticant or nettle agent. CX is an emerging potential threat agent that can be deployed alone or with other chemical threat agents to enhance their toxic effects. Studies on CX-induced skin toxicity, injury progression, and related biomarkers are largely unknown. To study the physiologic changes, skin clinical lesions and their progression, skin exposure of SKH-1 and C57BL/6 mice was carried out with vapor from 10 μl CX for 0.5-minute or 1.0-minute durations using a designed exposure system for consistent CX vapor exposure. One-minute exposure caused sharp (SKH-1) or sustained (C57BL/6) decrease in respiratory and heart rate, leading to mortality in both mouse strains. Both exposures caused immediate blanching, erythema with erythematous ring (wheel) and edema, and an increase in skin bifold thickness. Necrosis was also observed in the 0.5-minute CX exposure group. Both mouse strains showed comparative skin clinical lesions upon CX exposure; however, skin bifold thickness and erythema remained elevated up to 14 days postexposure in SKH-1 mice but not in C57BL/6 mice. Our data suggest that CX causes immediate changes in the physiologic parameters and gross skin lesions resembling urticaria, which could involve mast cell activation and intense systemic toxicity. This novel study recorded and compared the progression of skin injury to establish clinical biomarkers of CX dermal exposure in both the sexes of two murine strains relevant for skin and systemic injury studies and therapeutic target identification. SIGNIFICANCE STATEMENT: Phosgene oxime (CX), categorized as a vesicating agent, is considered as a potent chemical weapon and is of high military and terrorist threat interest since it produces rapid onset of severe injury as an urticant. However, biomarkers of clinical relevance related to its toxicity and injury progression are not studied. Data from this study provide useful clinical markers of CX skin toxicity in mouse models using a reliable CX exposure system for future mechanistic and efficacy studies.

Dabrafenib- and trametinib-associated glomerular toxicity: A case report

RATIONALE

Combined treatment with dabrafenib, a B-RAF inhibitor, and trametinib, a mitogen-activated protein kinase inhibitor, is an effective option for patients with metastatic melanoma. A few cases of acute kidney injury associated with tubulointerstitial nephritis and 1 case of nephrotic syndrome have been reported in patients on this drug combination; however, progressive renal injury has not been reported. In this case study, we report a patient with metastatic melanoma who developed glomerular capillary endothelial toxicity and progressive glomerular sclerosis during combination therapy.

PATIENT CONCERN

Our patient was an 80-year-old woman with a history of type 2 diabetes and chronic kidney disease.

DIAGNOSIS AND INTERVENTION

She was diagnosed with metastatic melanoma and commenced combination therapy with dabrafenib and trametinib.

OUTCOMES

Her renal function progressively deteriorated; by month 20 after treatment commencement, her serum creatinine level had increased from 1.59 to 3.74 mg/dL. The first kidney biopsy revealed marked glomerular and endothelial cell damage. Her medication was stopped, but no improvement was evident. At 5 months after the first biopsy, her serum creatinine level had increased to 5.46 mg/dL; a second kidney biopsy revealed focal segmental glomerular sclerosis and marked tubulointerstitial fibrosis. She was started on hemodialysis.

LESSONS

We describe a patient with a metastatic melanoma who developed progressive kidney failure during treatment with dabrafenib and trametinib. The most prominent microscopy findings were glomerular endothelial damage in the initial kidney biopsy and accelerated glomerular sclerosis and tubulointerstitial fibrosis in the follow-up biopsy. We hypothesize that a decreased renal reserve and impairment of kidney repair capacity caused by inhibition of B-RAF, a downstream mediator of vascular endothelial growth factor, may explain the progressive kidney injury.

Drug delivery of 6-bromoindirubin-3'-glycerol-oxime ether employing poly(D,L-lactide-co-glycolide)-based nanoencapsulation techniques with sustainable solvents

BACKGROUND

Insufficient solubility and stability of bioactive small molecules as well as poor biocompatibility may cause low bioavailability and are common obstacles in drug development. One example of such problematic molecules is 6-bromoindirubin-3'-glycerol-oxime ether (6BIGOE), a hydrophobic indirubin derivative. 6BIGOE potently modulates the release of inflammatory cytokines and lipid mediators from isolated human monocytes through inhibition of glycogen synthase kinase-3 in a favorable fashion. However, 6BIGOE suffers from poor solubility and short half-lives in biological aqueous environment and exerts cytotoxic effects in various mammalian cells. In order to overcome the poor water solubility, instability and cytotoxicity of 6BIGOE, we applied encapsulation into poly(D,L-lactide-co-glycolide) (PLGA)-based nanoparticles by employing formulation methods using the sustainable solvents Cyrene™ or 400 g/mol poly(ethylene glycol) as suitable technology for efficient drug delivery of 6BIGOE.

RESULTS

For all preparation techniques the physicochemical characterization of 6BIGOE-loaded nanoparticles revealed comparable crystallinity, sizes of about 230 nm with low polydispersity, negative zeta potentials around - 15 to - 25 mV, and biphasic release profiles over up to 24 h. Nanoparticles with improved cellular uptake and the ability to mask cytotoxic effects of 6BIGOE were obtained as shown in human monocytes over 48 h as well as in a shell-less hen's egg model. Intriguingly, encapsulation into these nanoparticles fully retains the anti-inflammatory properties of 6BIGOE, that is, favorable modulation of the release of inflammation-relevant cytokines and lipid mediators from human monocytes.

CONCLUSIONS

Our formulation method of PLGA-based nanoparticles by applying sustainable, non-toxic solvents is a feasible nanotechnology that circumvents the poor bioavailability and biocompatibility of the cargo 6BIGOE. This technology yields favorable drug delivery systems for efficient interference with inflammatory processes, with improved pharmacotherapeutic potential.

Toxic blister agents: Chemistry, mode of their action and effective treatment strategies

Since their use during the First World War, Blister agents have posed a major threat to the individuals and have caused around two million casualties. Major incidents occurred not only due to their use as chemical warfare agents but also because of occupational hazards. Therefore, a clear understanding of these agents and their mode of action is essential to develop effective decontamination and therapeutic strategies. The blister agents have been categorised on the basis of their chemistry and the biological interactions that entail post contamination. These compounds have been known to majorly cause blisters/bullae along with alkylation of the contaminated DNA. However, due to the high toxicity and restricted use, very little research has been conducted and a lot remains to be clearly understood about these compounds. Various decontamination solutions and detection technologies have been developed, which have proven to be effective for their timely mitigation. But a major hurdle seems to be the lack of proper understanding of the toxicological mechanism of action of these compounds. Current review is about the detailed and updated information on physical, chemical and biological aspects of various blister agents. It also illustrates the mechanism of their action, toxicological effects, detection technologies and possible decontamination strategies.

Activation of (un)regulated cell death as a new perspective for bispyridinium and imidazolium oximes

Oximes, investigated as antidotes against organophosphates (OP) poisoning, are known to display toxic effects on a cellular level, which could be explained beyond action on acetylcholinesterase as their main target. To investigate this further, we performed an in vitro cell-based evaluation of effects of two structurally diverse oxime groups at concentrations of up to 800 μM, on several cell models: skeletal muscle, kidney, liver, and neural cells. As indicated by our results, compounds with an imidazolium core induced necrosis, unregulated cell death characterized by a cell burst, increased formation of reactive oxygen species, and activation of antioxidant scavenging. On the other hand, oximes with a pyridinium core activated apoptosis through specific caspases 3, 8, and/or 9. Interestingly, some of the compounds exhibited a synergistic effect. Moreover, we generated a pharmacophore model for each oxime series and identified ligands from public databases that map to generated pharmacophores. Several interesting hits were obtained including chemotherapeutics and specific inhibitors. We were able to define the possible structural features of tested oximes triggering toxic effects: chlorine atoms in combination with but-2(E)-en-1,4-diyl linker and adding a second benzene ring with substituents such as chlorine and/or methyl on the imidazolium core. Such oximes could not be used in further OP antidote development research, but could be introduced in other research studies on new specific targets. This could undoubtedly result in an overall improved wider use of unexplored oxime database created so far in OP antidotes field of research in a completely new perspective.

Encapsulation of oxime K027 into cucurbit[7]uril: In vivo evaluation of safety, absorption, brain distribution and reactivation effectiveness

Oxime-based acetylcholinesterase reactivators (briefly oximes) regenerate organophosphate-inactivated acetylcholinesterase and restore its function. Poor blood-brain-barrier passage and fast elimination from blood limit their actual use in treatment of patients exposed to organophosphates. Previous in vitro results implicated further testing of cucurbit[7]uril as a delivery vehicle for bisquaternary oximes. The present paper focuses on cell toxicity, in vivo safety and influence of cucurbit[7]uril on oxime pharmacokinetics and pharmacodynamics. Neither the K027 nor the complex caused any cell toxicity, changes in blood biochemistry or hepato- or nephrotoxicity in tested concentrations. The encapsulation of K027 increased and accelerated the blood-brain-barrier penetration. The peripheral oxime exposure also increased, supporting the suggestion that cucurbit[7]uril protects the circulating oxime from rapid renal clearance. Contrary to the comparable in vitro reactivation power of K027 and the encapsulated K027, we failed to confirm this in vivo. In theory, this might result from the non-specific binding of molecules to the cucurbit[7]uril or the interaction of K027 with cucurbit[7]uril being too strong for acetylcholinesterase reactivation. Precise explanation requires additional in silico, in vitro and also in vivo experiments.

An unusual double radical homolysis mechanism for the unexpected activation of the aldoxime nerve-agent antidotes by polyhalogenated quinoid carcinogens under normal physiological conditions

We have recently shown that the pyridinium aldoximes, best-known as therapeutic antidotes for chemical warfare nerve-agents, could markedly detoxify the carcinogenic tetrachloro-1,4-benzoquinone (TCBQ) via an unusual double Beckmann fragmentation mechanism. However, it is still not clear why pralidoxime (2-PAM) cannot provide full protection against TCBQ-induced biological damages even when 2-PAM was in excess. Here we show, unexpectedly, that TCBQ can also activate pralidoxime to generate a reactive iminyl radical intermediate in two-consecutive steps, which was detected and unequivocally characterized by the complementary application of ESR spin-trapping, HPLC/MS and nitrogen-15 isotope-labeling studies. The same iminyl radical was observed when TCBQ was substituted by other halogenated quinones. The end product of iminyl radical was isolated and identified as its corresponding reactive and toxic aldehyde. Based on these data, we proposed that the reaction of 2-PAM and TCBQ might be through the following two competing pathways: a nucleophilic attack of 2-PAM on TCBQ forms an unstable transient intermediate, which can decompose not only heterolytically to form 2-CMP via double Beckmann fragmentation, but also homolytically leading to the formation of a reactive iminyl radical in double-steps, which then via H abstraction and further hydrolyzation to form its corresponding more toxic aldehyde. Analogous radical homolysis mechanism was observed with other halogenated quinones and pyridinium aldoximes. This study represents the first detection and identification of reactive iminyl radical intermediates produced under normal physiological conditions, which provides direct experimental evidence to explain only the partial protection by 2-PAM against TCBQ-induced biological damages, and also the potential side-toxic effects induced by 2-PAM and other pyridinium aldoxime nerve-agent antidotes.

Impact of O-alkyl-pyridineamidoximes on the soil environment

Pyridine derivatives such as oximes and amidoximes are widely used in pharmaceutical, analytical and coordination chemistry. Increasing interest in this group of compounds as well as their complexing properties and surface activity resulted in their introduction into the environment and change of the ecosystem functioning. Based on this phenomenon, the evaluation of impact O-alkyl-pyridineamidoximes on the soil environment was determined by analysis of changes of metal mobility in soil and plant seed germination. The obtained results indicate that O-propyl-pyridineamidoximes may change the mobility of metals in soil and influence the germination and development of plants. The introduction of these compounds to soil resulted in the reduction of metal (Cu, Pb, Fe) mobility in the soil matrix. This effect resulted in the retention of metals in the soil and inhibition of their mobility. This phenomenon suggests the possibility of using the analyzed compounds in the remediation process as a stabilizing factor. Pyridineamidoximes at a concentration below 100 mg/kg of soil did not influence the seed germination and plant development.

Targeting of CDK9 with indirubin 3'-monoxime safely and durably reduces HIV viremia in chronically infected humanized mice

Successful propagation of HIV in the human host requires entry into a permissive cell, reverse transcription of viral RNA, integration into the human genome, transcription of the integrated provirus, and assembly/release of new virus particles. Currently, there are antiretrovirals against each of these viral steps, except for provirus transcription. An inhibitor of HIV transcription could both increase potency of treatment and suppress drug-resistant strains. Cellular cyclin-dependent kinase 9 (CDK9) serves as a cofactor for the HIV Tat protein and is required for effective transcription of the provirus. Previous studies have shown that the CDK9 inhibitor Indirubin 3’-monoxime (IM) inhibits HIV transcription in vitro and in short-term in vivo studies of HIV acute infection in humanized mice (PBMC-NSG model), suggesting a therapeutic potential. The objective of this study is to evaluate the toxicity, pharmacokinetics and long-term antiviral activity of IM during chronic HIV infection in humanized mice (HSC-NSG model). We show that IM concentrations above EC₅₀ values are rapidly achieved and sustained for > 3 h in plasma, and that non-toxic concentrations durably reduce HIV RNA levels. In addition, IM enhanced the antiviral activity of antiretrovirals from the reverse transcriptase, protease and integrase inhibitor classes in in vitro infectivity assays. In summary, IM may enhance current antiretroviral treatments and could help achieve a “functional cure” in HIV patients by preventing expression of proviruses.

Antifouling activity of bromotyrosine-derived sponge metabolites and synthetic analogues

Eighteen brominated sponge-derived metabolites and synthetic analogues were analyzed for antilarval settlement of Balanus improvisus. Only compounds exhibiting oxime substituents including bastadin-3 (4), -4 (1), -9 (2), and -16 (3), hemibastadin-1 (6), aplysamine-2 (5), and psammaplin A (10) turned out to inhibit larval settling at 1 to 10 microM. Analogues of hemibastadin-1 (6) were synthesized and tested for structure activity studies. Debromohemibastadin-1 (8) inhibited settling of B. improvisus, albeit at lower concentrations than hemibastadin-1 (6). Both 6 and 8 also induced cyprid mortality. 5,5'-dibromohemibastadin-1 (7) proved to be nontoxic, but settlement inhibition was observed at 10 microM. Tyrosinyltyramine (9), lacking the oxime function, was not antifouling active and was non-toxic at 100 microM. Hemibastadin-1 (6) and the synthetic products showed no general toxicity when tested against brine shrimp larvae. In contrast to the lipophilic psammaplin A (10), the hydrophilic sulfated psammaplin A derivative (11) showed no antifouling activity even though it contains an oxime group. We therefore hypothesize that the compound needs to cross membranes (probably by diffusion) and that the target for psammaplin A lies intracellularly.

Tin(IV) cyanoximates: synthesis, characterization, and cytotoxicity

In recent years, numerous organotin(IV) derivatives have exhibited remarkable cytotoxicity against several types of cancer. However, the properties of the cyanoxime-containing organotin(IV) complexes are unknown. Previously, it has been shown that cyanoximes displayed an interesting spectrum of biological activity ranging from growth-regulation to antimicrobial and pesticide detoxification actions. The work presented here attempts to combine the useful properties of both groups of compounds and investigate the likely antiproliferating activity of the new substances. A series of 19 organotin(IV) complexes, with nine different cyanoxime ligands, were anaerobically prepared by means of the heterogeneous metathesis reaction between the respective organotin(IV) halides (Cl, Br) and ML (M=Ag, Tl; L=cyanoximate anion), using an ultrasound in the CH3CN at room temperature. The compounds were characterized using spectroscopic methods (UV-visible, IR, 1H,13C NMR, 119Sn Mössbauer) and X-ray analysis. The crystal structures of the complexes revealed the formation of two types of tin(IV) cyanoximates: mononuclear five-coordinated compounds of R4-xSnLx composition (R=Me, Et, n-Bu, Ph; x=1, 2; L=cyanoximate anion), and the tetranuclear R8Sn4(OH)2O2L2 species (R=n-Bu, Ph). The latter complex contains a planar [Sn4(OH)2O2]2- core, consisting of three adjacent rhombs with bridging oxo and hydroxo groups. The tin(IV) atoms are five-coordinated and have distorted trigonal-pyramidal surrounding. This is the first instance when the organic anions were found to act as monodentate O-bound planar oxime ligands. All of the compounds were studied in vitro for antiproliferating activity, using human cervical cancer HeLa and WiDR colon cancer cell lines; cisplatin was used as a positive control substance. The two dibutyltin(IV) cyanoximates showed cytotoxicity similar and greater to that of cisplatin.

Cordycepin induced eryptosis in mouse erythrocytes through a Ca2+-dependent pathway without caspase-3 activation

Cordyceps sinensis is a prized traditional Chinese medicine and its major component cordycepin is found to have anti-leukemia activities. However, its cytotoxicity in erythrocytes was unclear. To examine the effect of cordycepin on the induction of eryptosis (an apoptosis-like process in enucleated erythrocytes), flow cytometric assays based on membrane integrity and asymmetry were employed. For comparison, analyses were performed in parallel with two other anti-leukemia agents, indirubin 3'-monoxime (IDM) and As2O3. We found that at the IC50 against leukemia HL-60, cordycepin elicited eryptosis while IDM and As2O3 showed no erythrotoxicity in mouse erythrocytes. Mechanistically, cordycepin increased the [Ca2+]i and activated mu-calpain protease in a dose-dependent manner. Yet, no caspase-3 activation was observed in the cordycepin-treated erythrocytes. When extracellular Ca2+ was depleted, both the cordycepin-induced eryptosis and mu-calpain cleavage were suppressed. Our study therefore demonstrated for the first time that cordycepin induces eryptosis through a calcium-dependent pathway in the absence of mitochondria and caspase-3 activation.

A randomized, controlled trial of asoprisnil, a novel selective progesterone receptor modulator, in women with uterine leiomyomata

OBJECTIVE

To determine efficacy and safety of asoprisnil in patients with leiomyomata.

DESIGN

Phase 2, multicenter, prospective, randomized, double-blind, placebo-controlled, parallel-group study.

SETTING

Twenty-eight sites in the United States and 1 in Canada.

PATIENT(S)

One hundred twenty-nine women with leiomyomata.

INTERVENTION(S)

Asoprisnil (5, 10, or 25 mg) or placebo orally daily for 12 weeks.

MAIN OUTCOME MEASURE(S)

Uterine bleeding changes by using daily bleeding diaries, hemoglobin concentrations, dominant leiomyoma and uterus volume measured sonographically, patient-reported symptoms related to bloating and pelvic pressure, endometrial thickness and morphology, hormonal parameters, and standard safety measures.

RESULT(S)

Asoprisnil suppressed uterine bleeding in 28%, 64%, and 83% of subjects at 5, 10, and 25 mg, respectively, and reduced leiomyoma and uterine volumes. Median percentage decrease from baseline in leiomyoma volume was statistically significant at 25 mg compared with placebo after 4 and 8 weeks of treatment; by week 12, leiomyoma volume was reduced by 36%. There was a significant reduction in bloating with the two highest doses and in pelvic pressure with 25 mg by week 12. Asoprisnil was associated with follicular-phase estrogen concentration and minimal hypoestrogenic symptoms.

CONCLUSION(S)

After 12-week treatment, asoprisnil controlled uterine bleeding while reducing leiomyoma volume and the associated pressure symptoms. Asoprisnil was well tolerated.

Toxicodynamic Modeling of Highly Toxic Organophosphorus Compounds

Although the in vitro effect of organophosphorus (OP) compounds on acetylcholine-esterase (AChE) has been studied extensively, the hypothesis that OP inhibition of AChE is the primary mechanism of acute in vivo OP toxicity has been controversial. For example, a recent review (Pope and Liu, 2004) suggested that OP compounds have direct toxic effects on other enzymes, ACh receptors, and receptor/ channel complexes that are independent of AChE inhibition. The purpose of this report is to examine the hypothesis that AChE inhibition is the mechanism of acute toxicity of OP compounds by mathematically modeling the in vivo lethal effects of highly toxic OP compounds and determining the amount of variation in OP toxicity that is explained by AChE inhibition.

An α,β-unsaturated oxime identified as a strong contact allergen

The aim of this study was to examine the possible skin sensitizing effect of oximes, employing an alpha,beta-unsaturated oxime as the model compound. Oximes are not frequently used as biologically active compounds. However, they have been shown to possess both anti-inflammatory and anti-allergic activities. Furthermore, in a recent study, a number of oximes and oxime-ethers of hydroxylated benzaldehydes and acetophenones were found to be powerful antioxidants suggested to be used in consumer products such as cosmetics and food. Although there are only few reports on the sensitizing effect of oximes, their ability to be hydrolyzed to the corresponding ketones or aldehydes makes them potential contact allergens. The oxime investigated in this study was demonstrated to be a strong contact allergen in both mice and guinea pigs, capable of sensitize the control animals after only one dermal exposure. In order to elucidate the mechanisms for the formation of the complete antigen, a variety of analogues with different reactivity were tested. The results indicate that alpha,beta-unsaturated oximes can react with proteins via several different pathways. Most likely, a metabolic transformation is involved. Due to the strong allergenic effect of the oxime investigated, we strongly advise against the use of such oximes in consumer products until a better understanding of their interactions with biological macromolecules has been obtained.

Antidotal treatment of GF-agent intoxication in mice with bispyridinium oximes

It was shown that intoxications with GF-agent are rather resistant to convential oxime therapy; therefore, the development of new oximes in an effort to improve this unsatisfactory situation continues. Upon screening in vitro reactivation test for oximes, that were either newly synthesized at our department, or those that have never been tested for reactivation of GF-inhibited acetylcholinesterase (AChE), three oximes {(1,4-bis(4-hydroxyiminomethylpyridinium)butane dibromide) (K033); (1-(2-hydroxyiminomethylpyridinium)-3-(3-carbamoylpyridinium)-2-oxa-propane dichloride) (HS-6); and (1-(2-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium)-but-2-ene dibromide) (BI-6)} with the highest reactivation potency were chosen for in vivo testing in our study. 1,3-Bis(4-hydroxyiminomethylpyridinium)-2-oxa-propane dibromide) (obidoxime); (1-(2-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium)-2-oxa-propane dichloride) (HI-6); and (1,1-bis(4-hydroxyiminomethylpyridinium)-methane dibromide) (methoxime) were chosen for comparison as a standard antidotal treatment. All the oximes were applied at the same proportion of their LD50 value (5%), and because of the different acute toxicity of the oximes, the molar concentrations of their solutions for intramuscular (i.m.) administration were considerably different. The highest therapeutic ratio was achieved for therapeutic regimen consisting of HI-6 and atropine. The significantly (P < 0.05) lowest effectivity in treatment of supralethal GF-agent poisoning in comparison with all the other therapeutic regimens, was surprisingly observed for methoxime. HS-6, K033 and BI-6 as well as obidoxime were comparably effective antidotes against GF-agent intoxication and their therapeutic ratios were similar.

In vitro reactivation of tabun-inhibited acetylcholinesterase using new oximes--K027, K005, K033 and K048

Four new AChE oximes for reactivation of acetylcholinesterase inhibited with tabun - K027 [1-(4-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium) propane dibromide], K005 [1,3-bis(2-hydroxyiminomethylpyridinium) propane dibromide], K033 [1,4-bis(2-hydroxyiminomethylpyridinium) butane dibromide] and K048 [1-(4-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium) butane dibromide] were prepared. Their efficacies to reactivate tabun-inhibited acetylcholinesterase were studied and compared with the currently used acetylcholinesterase reactivators (pralidoxime, obidoxime and HI-6). Reactivator K048 seems to be promising reactivator of tabun-inhibited AChE. Its reactivation potency is significantly higher than the efficacy of HI-6 and pralidoxime, and comparable with the potency of the obidoxime at human relevant doses.

NTP technical report on the toxicity studies of Butanal oxime (CAS No. 110-69-0) administered in drinking water and by gavage to F344/N rats and B6C3F1 mice

Butanal oxime is used as a volatile antiskinning agent in paints, inks, and similar products. Butanal oxime was chosen for toxicology testing as a representative of the aldoxime class. Male and female F344/N rats and B6C3F1 mice received butanal oxime (99 percent pure) in drinking water for 15 days or by gavage in 0.5 percent methylcellulose for 14 weeks. Animals were evaluated for clinical pathology, reproductive system effects, and histopathology. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and mouse peripheral blood erythrocytes. In the 15-day studies, groups of five male and five female rats and mice received 0, 312, 625, 1,250, 2,500, or 5,000 ppm butanal oxime in drinking water, resulting in average daily doses of approximately 40, 70, or 100 mg butanal oxime/kg body weight to male and female rats; 45, 90, 130, 200, or 300 mg/kg to male mice; and 45, 85, 100, 130, or 170 mg/kg to female mice. Due to body weight loss and lack of water consumption, all male and female rats receiving 2,500 or 5,000 ppm were removed from the study on day 9; average daily doses were not calculated for these groups. All other rats and mice survived until the end of the studies. Mean body weights of 1,250 ppm male and female rats and 2,500 and 5,000 ppm male and female mice were significantly less than those of the controls. Male mice receiving 5,000 ppm and females receiving 2,500 or 5,000 ppm lost weight during the study. Water consumption by rats and mice receiving 1,250 ppm or greater was less than that by the controls. Thinness in 2,500 and 5,000 ppm rats and mice was the only clinical finding of toxicity. Spleen weights were significantly decreased in 2,500 and 5,000 ppm female mice. No chemical-related lesions were observed grossly; histologic examinations were not performed. In the 14-week studies, groups of 10 male and 10 female rats and mice received butanal oxime by gavage at doses of 0, 25, 50, 100, 200, or 600 mg/kg, 5 days per week for 14 weeks. All 600 mg/kg rats died or were killed moribund during the first week of the study; in the 600 mg/kg mouse groups, seven males and nine females died, were killed moribund, or were killed accidentally before the end of the study. Mean body weights of 100 and 200 mg/kg male rats, 600 mg/kg male mice, and female mice administered 50 mg/kg or greater were less than those of the controls. Clinical findings of toxicity in 600 mg/kg rats included loss of coordination, wobbly gait, shaking, blinking, constant grooming and scratching of the face, head weaving, burying of the face in bedding, lethargy, and prostration; in 600 mg/kg mice, clinical findings included ataxia, loss of balance after rearing, squinting, and burying of the face in the bedding. Hematology results of the 14-week gavage studies indicate that butanal oxime induces a methemoglobinemia and a responsive anemia in rats and mice. Spleen weights of 100 and 200 mg/kg male rats, female rats administered 50 mg/kg or greater, and 200 and 600 mg/kg male mice were increased, as were the liver weights of 200 mg/kg female rats and mice. In animals that died early due to butanal oxime administration, hepatocellular necrosis was the primary pathologic finding. Degeneration of the nasal olfactory epithelium was observed in dosed rats and mice that died early as well as in animals that survived to the end of the studies. Additional chemical-related nasal findings were respiratory epithelial changes in male rats and suppurative exudate in male and female mice. Increased incidences and/or severities of splenic hematopoietic cell proliferation and pigmentation (hemosiderin) as well as bone marrow hyperplasia were also observed in dosed groups, particularly in the 200 and 600 mg/kg groups, and were indicative of erythrocyte damage. Butanal oxime (3 to 10,000 ug/plate) was mutagenic in S. typhimurium strain TA1535 in the presence of 5 percent or 10 percent rat liver S9; an equivocal response was seen in TA100 with 30 percent rat S9, and no mutagenic activity was seen in TA98, with or without rat or hamster liver S9. Butanal oxime induced chromosomal aberrations in cultured Chinese hamster ovary cells, with and without S9. Significant increases in the frequencies of micronucleated normochromatic erythrocytes were observed in vivo in peripheral blood of male and female mice administered 25 to 600 mg/kg butanal oxime for 14 weeks by gavage. Synonyms: Butanaloxime; butylaldoxime; butyraldehyde oxime; n-butyraldehyde oxime; butyraldoxime; n-butyraldoxime Trade names: Exkin 1, Exkin No. 1 Anti-Skinning Agent, Skino #1, Troykyd Anti-Skin BTO

Cholinesterase reactivation in vivo with a novel bis-oxime optimized by computer-aided design

Recently, several bis-pyridiniumaldoximes linked by a variable-length alkylene chain were rationally designed in our laboratories as cholinesterase reactivators. Extensive in vitro tests of these oximes with acetylcholinesterase inhibited by two different organophosphate agents, echothiophate and diisopropylfluorophosphate, revealed one compound with particularly good reactivation kinetics and affinity for phosphorylated acetylcholinesterase (AChE). This compound, designated "ortho-7", with a heptylene chain bridging two aldoximes ortho to a pyridinium ring nitrogen, was chosen for detailed comparison with the classic reactivator pyridine-2-aldoxime methochloride (2-PAM). In vitro, ortho-7 reactivated AChE selectively, without restoring activity of the related enzyme butyrylcholinesterase (BChE). For in vivo studies, rats were injected with ortho-7 or 2-PAM before or after organophosphate exposure, and the activities of AChE and BChE were determined at multiple intervals in blood and solid tissues. Ortho-7 behaved nearly as well in the animal as in vitro, reactivating AChE to the same extent as 2-PAM in all peripheral tissues studied (serum, red blood cell, and diaphragm), but at doses up to 100-fold smaller. Like other oxime reactivators, ortho-7 did not reactivate brain AChE after systemic administration. Nonetheless, this agent could be useful in combination therapy for organophosphate exposure, and it may provide a platform for development of additional, even more effective reactivators.

Developmental toxicity studies of methyl ethyl ketoxime (MEKO) in rats and rabbits

The developmental toxicity of methyl ethyl ketoxime (MEKO), an industrial antioxidant used primarily as an antiskinning agent in alkyd paint, was investigated in rats and rabbits. Following preliminary dose range finding studies, groups of 25 pregnant rats or 18 pregnant rabbits were dosed by gavage with aqueous solutions of MEKO at 0, 60, 200, or 600 mg/kg (rats) or 0, 8, 14, 24, or 40 mg/kg (rabbits) on gestation days 6-15 or 6-18, respectively. In rats, dose-dependent clinical signs of maternal toxicity including reduced body weight gains were noted at 200 and 600 mg/kg. At 60 mg/kg and above enlarged spleens were observed at necropsy. The preliminary study found methemoglobin formation and reticulocytosis indicative of anemia at these dose levels. No treatment-related gestational effects, malformations or developmental variations were observed in the rats. In rabbits, 3 females aborted and 8 females were found dead at 40 mg/kg between gestation days 11 and 24. Clinical signs of maternal toxicity were present in surviving doses at this dose level. Body weight gains were reduced at 24 and 40 mg/kg. The preliminary study indicated maternal hematological effects in the rabbits similar to the rats at dose levels as low as 10 mg/kg. MEKO was not considered to have produced any treatment-related gestational effects, malformations or developmental variations in the rabbit at dose levels at or below 24 mg/kg. Because of excessive maternal mortality and abortions at the 40 mg/kg dose level, only 6 rabbits produced litters. The severe maternal toxicity and limited number of litters precluded a full assessment of developmental toxicity at 40 mg/kg. Nonetheless, MEKO did not appear to be teratogenic to the rabbit at this dose level.

The unusual effect of pKM101 on the mutagenicity of acetaldehyde oxime in Salmonella typhimurium

Acetaldehyde oxime was found to induce more revertants in Salmonella typhimurium strain TA1535 than in TA100 in the absence of S9 metabolic activation. TA100 was originally constructed from TA1535 by the addition of the plasmid pKM101, carrying mucAB which generally enhances sensitivity to the mutagenic effects of chemicals. The role of pKM101 in lowering the sensitivity to acetaldehyde oxime was explored by: (1) increasing the incubation time of the selective agar plates from 2 to 3 days; (2) using a new strain, isogenic to TA100, constructed by introducing pKM101 into the TA1535 isolate used in these experiments; (3) by testing a strain constructed by inserting into TA1535 a plasmid carrying mucAB but otherwise unrelated to pKM101. Each of these alterations increased the number of revertants per plate in the presence of acetaldehyde oxime, indicating that the apparent nonmutagenicity of this chemical in TA100 is due to multiple factors.

Synthesis of anthelmintically active N-methylated amidoxime analogues of the cyclic octadepsipeptide PF1022A

The N-methylated amidoxime analogues of the cyclic octadepsipeptide PF1022A represent novel derivatives with activity against Trichinella spiralis Owen and Nippostrongylus brasiliensis Lane in vitro and against parasitic nematodes in mice and sheep. Some of them show better activity against Hymenolepis nana Siebold, Heterakis spumosa Schneider and Heligmosomoides polygyrus Dujardin in mice than the natural product PF1022A. In particular an improved efficacy against Haemonchus contortus Rudolphi and Trichostrongylus colubriformis Giles in sheep compared to the potent cyclic octadepsipeptide PF1022A and its mono-thionated derivative has been observed. Here we report on a specific modification at the N-methyl amide linkage by using the mono-thionated PF1022A, resulting in novel anthelmintically active backbone analogues of PF 1022A.

An evaluation of changes and recovery in the olfactory epithelium in mice after inhalation exposure to methylethylketoxime

Methylethylketoxime, also known as MEKO or 2-butanone oxime (CAS No. 96-29-7), is a clear, colorless to light yellow liquid at room temperature. It is an industrial antioxidant used as an antiskinning agent in alkyd paint, an industrial blocking agent for urethane polymers, and a corrosion inhibitor in industrial boilers, and can be found in some adhesives and silicone caulking products. Male CD-1 mice were exposed 6 h/day, 5 days/wk, for 1, 2, 4, or 13 wk via whole-body inhalation exposures to MEKO vapor concentrations of 0, 3 +/- 0.1, 10 +/- 0.3, 30 +/- 1, or 100 +/- 2 ppm (10 mice/group/interval). Satellite animals were removed after 1, 2, 4, or 13 wk of exposure and allowed to recover for 4 or 13 wk (5 mice/group/interval). After termination, the nasal turbinates were evaluated microscopically, and cross-sectional nasal maps of the lesions were prepared. At the end of the 1-, 2-, 4-, and 13-wk exposure periods, degeneration of the olfactory epithelium lining the dorsal meatus was seen in the anterior region of the nasal cavity. In a few instances, the olfactory epithelium covering the tips of the nasoturbinal scrolls projecting into the dorsal region of the nasal cavity was also degenerated. Large areas of olfactory epithelium lying laterally and posteriorly were unaffected. In general, approximately 10% or less of the total olfactory tissue was affected. In several instances, the degenerated olfactory epithelium was reepithelialized by squamous/squamoid and/or respiratory types of epithelium. Degeneration, which was dose related in incidence and severity, was seen in mice exposed to 30 and 100 ppm after 1 wk of exposure and in several mice exposed to 10 ppm after 13 wk of exposure. The incidence and severity of the degeneration present after 1 wk of exposure did not increase with the longer exposures. The olfactory degeneration was reversible. Recovery was complete within 4 wk following exposures at 10 ppm and nearly complete within 13 wk after exposures at 30 and 100 ppm. A no-observed-effect level (NOEL) for the olfactory degeneration was considered to be 3 ppm.

A chronic inhalation toxicity/oncogenicity study of methylethylketoxime in rats and mice

To evaluate the oncogenic potential of methylethylketoxime (MEKO), CD-1 mice (50/sex/group) and F-344 rats (50/sex/group) were coexposed 6 h/day, 5 days/wk for 18 mo (mice) or 26 mo (rats) via whole-body inhalation exposures to target vapor concentrations of 0, 15, 75, and 375 ppm (actual concentrations of 0, 15 +/- 1, 75 +/- 2, or 374 +/- 10 ppm). Satellite groups of rats and mice (10/sex/group/interval) were exposed for 12 mo (mice) and 3, 12, or 18 mo (rats) to evaluate chronic toxicity. Methyl ethyl ketone (MEK), a possible hydrolysis product of MEKO, was present at less than 1%. Treatment-related effects included increased body weight (male rats only), methemoglobin formation, hematology and clinical chemistry changes, increased liver weight, and increased spleen and testes weights (rats only). A high incidence of cataracts and corneal dystrophy occurred in both control and MEKO-exposed rats, with an earlier appearance and slightly higher incidence for these ocular lesions in MEKO-exposed animals compared to controls. Degenerative and reparative changes of the olfactory epithelium in the nasal turbinates, primarily limited to the dorsal meatus, occurred in both rats (75 and 374 ppm) and mice (15, 75, and 374 ppm). In addition, in the mice, liver changes included increased incidences of pigment in reticuloendothelial cells, centilobular hypertrophy, granulomatous inflammation, and a slightly increased incidence of necrosis (75 and 374 ppm). An increase in hepatocellular carcinomas occurred in male mice at 374 ppm. Additional MEKO-related findings in the rat included congestion of the spleen with pigment in reticuloendothelial cells and extramedullary hematopoiesis and a decreased incidence of lymphoreticular mononuclear cell leukemia. Effects observed in the liver of the rats included decreases in the incidence of both peribiliary fibrosis and hyperplasia/proliferation of the biliary duct, an increase of spongiosis hepatis in males, and an increase in the incidence of intracytoplasmic vacuoles and hepatocellular basophilic foci. The effects on the liver were generally most profound in the high-exposure groups and, with the exception of the spongiosis hepatis, occurred in both sexes. An increase in hepatocellular adenomas occurred in the male rats at 75 and 374 ppm, and hepatocellular carcinomas in the male rats at 374 ppm. In both species, the liver tumors appeared relatively late in the life of the animals, with no significant increase in tumors at 12 mo of exposure in mice and at 18 mo of exposure in rats. Lifespan shortening was not observed, as MEKO-exposed animals survived generally as well as, or slightly better than, the controls.

Determination of therapeutic doses of bisquaternary oximes in large animals

This report presents a non-lethal method for estimating a range of therapeutic doses of bisquaternary oximes that serve as antidotes against organophosphorus poisoning. We have estimated therapeutic oxime doses that are equivalent in their relative toxicity rather than selecting arbitrary fractions of their LD(50). Thus, toxic signs of the oximes HI-6, HLö-7, Toxogonin, AB-8 and AB-13 were monitored quantitatively in baboon monkeys and beagle dogs. Using Toxogonin as a reference oxime, a calculated unit of equivalent dose (CED) was defined as the oxime dose equal to the ratio between its minimal toxic dose (MTD) and the therapeutic ratio (TR) of Toxogonin i.e. CED = MTD/TR. Assuming that the tails of dose-response curves of toxicity for bisquaternary oximes are shallow and similar to one another, one could substitute the ED(10) for the MTD. The ED(10) values for bisquaternary oximes were estimated using the log-log model following experimental observations and quantitative scoring of toxic signs in dogs and monkeys. The MTD values then were calculated using the ED(10) values and the experimental therapeutic dose of the reference oxime Toxogonin. The following CED values were obtained for AB-8, AB-13, Toxogonin, HI-6 and HLö-7 in dogs (d) and monkeys (m): 98.7, 74.2, 30.0, 14.5 and 12.1 (d) and 281.9, 232.1, 41.7, 192.9 and 92.9 (m) micromol kg(-1), respectively. The antidotal efficacy of these oximes against poisoning by the nerve agent tabun was determined in dogs and monkeys. These dose-dependent efficacy data were obtained at 0.3 x CED, 1 x CED and 3 x CED of oximes in combination with atropine. These data provide comparative therapeutic values using oxime doses based on their relative toxicity. The highest antidotal efficacy against tabun in dogs was obtained for toxogonin, whereas HLö-7 and AB-13 were most efficacious in monkeys.

Brasofensine NeuroSearch

Brasofensine (NS-2214) is a dopamine reuptake inhibitor under development by NeuroSearch for the potential treatment of Parkinson's disease (PD) [178224]. The compound entered phase II trials in Denmark in November 1996, and phase I trials in the US in January 1996 [195505], [206604]. Bristol-Myers Squibb (BMS) had been codeveloping the compound until June 1999, when it decided to withdraw from the collaboration due to financial restraints of further regulatory requirements (such as additional toxicology documentation) [318365], [329665]. NeuroSearch was seeking licensing agreements with one or more international pharmaceutical companies to accelerate the development and marketing of brasofensine [187758] and had plans to meet with new potential partners for discussions concerning brasofensine licensing in late 1999 [337221]. A more complete evaluation of the effects of brasofensine was anticipated to be obtained through controlled trials, of at least 3 months duration, comparing it with a placebo and the marketed anti-Parkinson's drug, L-DOPA [317406]. In addition, further animal (monkey) tests were planned in order to document the safety of the drug in long-term treatment. These studies were expected to be discussed with the US FDA in October 1999 and, if satisfactory, the 3-month clinical trials were planned to commence in mid-2000 [337221]. At a meeting with the FDA during 1999, NeuroSearch presented plans for developing brasofensine alone. These were found to be satisfactory on condition that further preclinical studies were performed prior to any more clinical development [371542]. In August 2000, Lehman Brothers predicted worldwide sales of US $45 million in 2002 and US $175 million in 2003 [389229]. In February 1999, Lehman Brothers predicted the drug had a 35% probability of reaching market, with an estimated first launch date in 2002. The analysts predicted peak sales would occur in 2009, with sales of $250 million at that time [319225].

Synthesis, toxicological and pharmacological assessment of morpholinooximes

The synthesis, pharmacology and toxicology of four morpholine derivatives from 1-(2-arylmorpholino)-3-phenyl-3-propanonoxime and the synthesis of two anilides are described. The structures of the synthesized derivatives were proved by IR, 1H NMR and occasionally with 13C NMR. The acute toxicity of the compounds in mice was determined. A comparative pharmacological study of the in vivo effect on the central nervous system was realised by the following screening tests: pentobarbital induced sleeping time, locomotor activity and behaviour despair test for antidepressive activity. The most active compound was 1-(2-phenylmorpholino)-3-phenyl-3-propanonoxime (2b) which showed low toxicity and antidepressive activity at a dose of 1/10 LD50.

Design and synthesis of m1-selective muscarinic agonists: (R)-(-)-(Z)-1-Azabicyclo[2.2.1]heptan-3-one, O-(3-(3'-methoxyphenyl)-2-propynyl)oxime maleate (CI-1017), a functionally m1-selective muscarinic agonist

The synthesis and SAR of a series of (Z)-(+/-)-1-azabicyclo[2.2. 1]heptan-3-one, O-(3-aryl-2-propynyl)oximes are described. The biochemistry and pharmacology of 24Z (PD 142505) and its enantiomers are highlighted. 24Z is functionally an m1-selective muscarinic agonist. Efficacy and m1 selectivity reside in the R enantiomer, (R)-24Z (CI-1017).

Iron binding capacity of didox (3,4 dihydroxybenzohydroxamic acid) and amidox (3,4 dihydroxybenzamidoxime) two inhibitors of the enzyme ribonucleotide reductase

Ribonucleotide reductase is the rate limiting enzyme of deoxynucleoside triphosphate synthesis and is considered to be an excellent target of cancer chemotherapy. Didox and amidox are newly synthesized compounds, which inhibit this enzyme and have in vitro and in vivo antitumor activity. We have now investigated the capability of didox and amidox to interfere with the iron metabolism. We show by photometric and polarographic methods, that didox and amidox are capable of forming an iron complex. However, their cytotoxic action cannot be circumvented by addition of Fe-ammoniumcitrate, indicating the iron complexing capacity not to be responsible for the mechanism of action of these compounds. When L1210 leukemia cells were incubated with the didox-iron or amidox-iron complex itself, only slight changes of the 50% growth inhibitory capacity of the complex in comparison with didox or amidox alone could be shown. We conclude, that didox and amidox are capable of forming an iron complex, but in contrast to other agents, the anticancer activity cannot be contributed to this effect alone. Further studies will have to elucidate the molecular mechanism of action of these new and promising anticancer agents.

A comparison of the therapeutic efficacy of conventional and modern oximes against supralethal doses of highly toxic organophosphates in mice

1. The therapeutic efficacy of various oximes (pralidoxime, obidoxime, methoxime, HI-6, HLö-7, BI-6) against supralethal nerve agent poisoning (soman, sarin, cyclosin) in mice was tested. 2. New oxime BI-6, synthesized in our laboratory, is significantly more efficacious than conventional oximes but a little less efficacious than other H-oximes (HI-6, HLö-7). 3. H-oximes (HI-6, HLö-7) seem to be the most efficacious reactivators of nerve agent-inhibited acetylcholinesterase for antidotal treatment of supralethal nerve agent poisoning in mice.

Pharmacokinetic analysis for assessing developmental toxicity of a new synthetic acetolactate synthase inhibitor, LGC-40863, in rats

Effects of O-[2,6-bis[(4,6-dimethoxy-2pyrimidinyl)oxy]benzoyl]oxime (LGC-40863) on dams and embryonic development were examined at p.o. doses of 500, 1000 and 2000 mg/kg/day on days 6 to 15 of gestation in rats. No significant maternal or embryonic toxicity was observed at any of the doses. However, external fetal anomalies including brachycephaly, microcephaly, micrognathia, agnathia, lordosis and edema were observed at an incidence of 2.2% at the lowest dosage level but not at higher dosages. Because these malformations are not common as spontaneous variations in rats, we carried out a toxicokinetic study to clarify whether the fetal anomalies at 500 mg/kg are related to LGC-40863. During multiple p.o. administrations of LGC-40863 at the same doses used in the developmental toxicity study, LGC-40863 was not detected in the systemic circulation. Moreover, 3 months of multiple dosing did not alter its plasma level. In the pregnant rats receiving 500 mg/kg on 10 consecutive days of gestation, LGC-40863 was also undetectable. However, after i.v. administration, high levels of the drug were found in plasma, and these could be described by a two-compartment model. These results demonstrate that the bioavailability of LGC-40863 is negligible. To investigate a possible relevance of metabolite(s) to the fetal anomalies, we examined excretion of radioactivity after p.o. doses of 500 and 2000 mg/kg of LGC-40863 spiked with [14C]LGC-40863. For both doses, cumulative recovery up to 72 hr was approximately 80% and 9% in feces and urine, respectively, indicating dose linearity in the elimination kinetics. Overall, these toxicokinetic data suggest that the fetal anomalies observed at 500 mg/kg are not associated with LGC-40863 but are spontaneously generated. In conclusion, LGC-40863 had neither significant maternal nor developmental toxicity at any of the doses tested for p.o. exposure.

Iron binding capacity of didox (3,4-dihydroxybenzohydroxamic acid) and amidox (3,4-dihydroxybenzamidoxime) new inhibitors of the enzyme ribonucleotide reductase

Ribonucleotide reductase is the rate limiting enzyme of deoxynucleoside triphosphate synthesis and is considered to be an excellent target of cancer chemotherapy. Didox and amidox are newly synthesized compounds, which inhibit this enzyme and have in vitro and in vivo antitumor activity. We have now investigated the capability of didox and amidox to interfere with the iron metabolism. We show by photometric and polarographic methods, that didox and amidox are capable of forming an iron complex. However, their cytotoxic action cannot be completely circumvented by addition of Fe-ammoniumcitrate, indicating that the iron complexing capacity may not be responsible for the mechanism of action of these compounds. When L1210 leukemia cells were incubated with the didox-iron or amidox-iron complex itself, changes of the 50% growth inhibitory capacity of the complex in comparison with didox or amidox alone could be shown. We conclude, that didox and amidox are capable of forming iron complexes, but in contrast to other agents, the anticancer activity cannot be contributed to this effect alone. Future studies will have to elucidate the molecular mechanism of action of these new and promising anticancer agents.

Genotoxic properties of the newly synthesized antineoplastic agents amidox, didox and trimidox

Toxic and genotoxic effects of three polyhydroxy-substituted benzohydroxamates (amidox, didox and trimidox), having antineoplastic activities by the mechanism of the ribonucleotid reductase activity inhibition, were evaluated by reverse mutation assay on Salmonella typhimurium strains TA97, TA98, TA100, TA102. While amidox did not exhert any toxic effect, didox and trimidox were toxic. The toxicity of the test chemicals was dependent on the structure of their molecule and the repair capacity of the test strains. Trimidox exhibited the highest toxicity, and it was proved as a direct-acting frameshift mutagen. Its mutagenic effect was increased after a metabolic activation. Amidox and didox can be classified as frameshift promutagens.

Cytotoxicity of copper complexes of 2-furaldehyde oxime derivatives in murine and human tissue cultured cell lines

The copper complexes of furan oxime derivatives were found to be potent cytotoxic agents in both murine and human tissue cultured cell lines which were either suspended or solid tumors. The ED50 values were frequently improved over the clinically useful antineoplastic agents. These copper complexes of 2-furaldehyde oximes were effective inhibitors of L1210 lymphoid leukemia DNA synthesis followed by RNA synthesis. Purine synthesis regulatory enzyme activities were markedly reduced by the compounds with marginal inhibition of t-RNA polymerase, and nucleoside kinases activities. L1210 DNA topoisomerase II activity was markedly reduced with IC50 values better than the standard VP-16, etoposide. Yet, the copper complexes caused no further protein linked breaks than VP-16 did, but did block phosphorylation activation of the topoisomerase II enzyme.

Genotoxicity of N-nitroso-N-methylurea and acetone oxime in the transgenic Drosophila carrying the human gene encoding a subunit of glutathione S-transferase

The genotoxic effects of N-nitroso-N-methylurea (MNU) and acetone oxime (ACOX) were tested in the Somatic Mutation and Recombination Test (SMART) in Drosophila melanogaster. We have performed the same assay on transgenic flies expressing the human gene encoding a glutathione S-transferase alpha subunit (HGST). The SMART assay is used here to demonstrate genotoxicity and to determine the effect of human glutathione S-transferase on the genotoxic response. Three types of Drosophila strains were used: non-transgenic strains first described by Szabad (1986), transgenic strains derived from the Szabad strains but expressing the bacterial lacZ gene, and similarly derived transgenic strains expressing the HGST gene. MNU was highly genotoxic in both transgenic and non-transgenic flies. The non-transgenic lies were significantly more sensitive to the genotoxic effects of MNU compared to both types of transgenic flies. There were statistically significant differences between the transgenic HGST crosses and transgenic lacZ and non-transgenic control crosses but there was no significant difference between the genotoxic response to MNU in flies from the transgenic cross with lacZ and from the cross carrying three copies of HGST. ACOX also proved to be genotoxic to both non-transgenic and transgenic flies. However, flies carrying three copies of the gene were significantly more resistant to the genotoxic effect of ACOX than those transgenic flies with two or no copies of the human gene.

Reproductive toxicity evaluation of methylethyl ketoxime by gavage in CD rats

Methylethyl ketoxime (CAS No. 96-29-7; MEKO; 2-butanone oxime), an antioxidant agent used in paints, resins, and adhesives, was tested for reproductive toxicity in a two-generation study with CD (Sprague-Dawley) rats. Thirty-eight-week-old rats/sex/group (F0) were administered MEKO in water, by gavage, at 0, 10, 100, or 200 mg/kg/day (at a dosing volume of 2 ml/kg), 5 days/week for 10 weeks with vaginal cytology evaluation (VCE) of F0 females during the last 3 weeks of the prebreed period. Animals were mated within groups for 3 weeks with dosing during mating, gestation, and lactation for 7 days/week. F0 parents and F1 weanlings, 10/sex/dose, were necropsied (after a 2-week postwean VCE in F0 females) with hematologic evaluation (including methemoglobin) and histology of adult livers, spleens, and reproductive organs. F1 weanlings, 30/sex/dose, were dosed for 11 weeks and mated as described above. Because of poor reproductive performance, not treatment related, F1 animals with no F2a litters were rebred to produce F2b litters. F1 parents and F2a weanlings, 10/sex/dose, were necropsied and evaluated as described above. Inguinal mammary glands were examined histologically from all nonselected F1 and F2 (a and b) female weanlings. Adult toxicity was observed in both generations and both sexes at all doses. Treatment-related parental deaths occurred at 200 mg/kg/day. At 100 and 200 mg/kg/day, parents exhibited dose-related reduced body weights and weight gains, reduced feed consumption, clinical signs of toxicity, and anemia with concomitant extramedullary hematopoiesis and hemosiderosis in livers and spleens (and increased spleen weights). At 10 mg/kg/day, only adult liver and spleen histologic effects were present. There was no evidence of reproductive organ or mammary glad pathology or of reproductive or postnatal toxicity at any dose tested. There was no adult "no observable adverse effect level" (NOAEL) established; the NOAEL for reproductive and postnatal toxicity was at least 200 mg/kg/day for rats in this study.

Toxicological comparison of a muscarinic agonist given to rats by gavage or in the diet

Corneal opacities and urinary tract sepsis were previously observed by the authors in rats given muscarinic agonists mixed in the diet or by gavage. To explain the differential toxicity generated by each means of administration, toxicokinetics of the muscarinic agonist CI-979 were investigated. In addition, the muscarinic antagonist scopolamine was co-administered with CI-979 to evaluate the relationship of these effects to pharmacological mechanism of action of CI-979. Female rats were given CI-979 daily by gavage at 0, 1, 10 and 30 mg/kg body weight or in the diet at 0, 1, 10 and 50 mg/kg body weight for up to 14 days. Dose-related clinical signs of muscarinic stimulation, such as sialorrhoea and dacryorrhoea, were observed predominantly in rats given 10 and 30 mg/kg body weight CI-979 by gavage, and corresponded with the high plasma drug concentrations. In contrast, hydronephrosis, pyelonephritis, and inflammation and necrosis of the kidney, urinary bladder, urethra and urinary papilla were linked to sustained, albeit lower plasma drug concentrations attained by dietary administration of CI-979 at 10 and 50 mg/kg body weight. Comparable incidences of corneal opacities were induced by both means of administration, but lesions appeared more rapidly and were generally of greater severity when CI-979 was given in the diet. The induction of corneal lesions, as well as urinary sepsis, may not relate simply to maximum plasma concentrations or to areas under the curve per se, but rather may arise when plasma drug concentrations are sustained. Corneal opacification and development of urinary tract pathology were inhibited by scopolamine, suggesting that these effects were related to the muscarinic mechanism of action of CI-979.

Assessing the neurotoxic potential of methyl ethyl ketoxime in rats

The potential of methyl ethyl ketoxime (MEKO) to produce neurotoxicity following acute and subchronic exposure was studied in rats. A Functional Observational Battery, assessment of motor activity, and neuropathology evaluations were conducted in the context of acute and subchronic toxicity studies. Three independent studies are reported: a pilot time-effect study designed to determine the time course and time to peak effect following a single high dose of MEKO, a single-dose neurotoxicity study, and a subchronic (13-week) repeated-dose neurotoxicity study in rats. An acrylamide-positive control group was included in the acute and subchronic studies for comparison with MEKO. Following an acute oral exposure of MEKO at a dose level of 900 mg/kg, locomotor activity was decreased compared to control with maximum decreases occurring between 30 and 60 min following oral administration. In the acute study, transient treatment-related changes in ease of cage removal, ease of handling, and in posture and gait were observed 1 hr after dosing with 900 mg/kg MEKO, as were significant depressions in motor activity. Following a single 300 mg/kg dose, transient MEKO-related changes in gait and aerial righting reflex were noted 1 hr after dosing. All effects were reversible within 24 hr of dosing. The single 100 mg/kg dose of MEKO was without observable effects. No acrylamide-related behavioral effects were noted following a single 50 mg/kg dose. In the subchronic study, transient treatment-related changes in ease of cage removal, ease of handling, and in posture, gait, and aerial righting were observed at the 400 mg/kg/day dose level when assessments were conducted immediately after dose administration. No consistent behavioral effects were observed prior to daily dose administration even after 13 weeks of exposure, indicating a lack of cumulative behavioral effect. No consistent behavioral changes were noted at doses of 125 mg/kg/day and below. Significant dose-related decreases in red cell mass, and increases in methemoglobin levels, reticulocyte, leukocyte, Heinz body counts, and spleen weights occurred at subchronic MEKO doses of 40 mg/kg/day and higher. No MEKO-related neuropathological changes occurred. Animals receiving acrylamide at 20 mg/kg/day showed expected behavioral and neuropathological changes consistent with peripheral neuropathy. In conclusion, high doses of MEKO can produce transient and reversible changes in neurobehavioral function consistent with central nervous system (CNS) depression. No evidence of cumulative neurotoxicity was detected. The hematopoietic system was effected at doses which did not produce detectable changes in CNS function.

Formation of N-methyl protoporphyrin in chemically-induced protoporphyria. Studies with a novel porphyrogenic agent

1-[4-(3-Acetyl-2,4,6-trimethylphenyl)-2,6-cyclohexanedionyl]-O-eth yl propionaldehyde oxime (for short ATMP) is a novel porphyrogenic agent causing hepatic protoporphyria in the mouse. Mice given a single dose of the drug showed 24 h later a 70% inhibition of liver ferrochelatase and marked accumulation of protoporphyrin. These changes were not seen in similarly treated rats, guinea pigs, hamsters or chick embryos. A green pigment was isolated from the liver of mice treated with ATMP and identified by its electronic absorption spectrum and chromatographic properties on HPLC as N-methyl protoporphyrin. The ATMP pigment markedly inhibited the enzyme ferrochelatase in vitro, thus supporting its identification as N-methyl protoporphyrin. Two inhibitors of liver cytochrome P450, compound SKF 525-A and piperonyl butoxide, when given before ATMP, afforded protection against ATMP-induced porphyria and production of N-methyl protoporphyrin, suggesting a role of cytochrome P450 in the induction of the metabolic disorder. The most likely interpretation for these findings is therefore that ATMP is metabolized in the mouse to a reactive species, which in turn alkylates the haem moiety of liver cytochrome P450, thus producing N-methyl protoporphyrin. This inhibits ferrochelatase and, as a secondary response, protoporphyrin accumulates. This pathway of metabolism to the postulated reactive metabolite presumably does not occur to a significant extent in the other species examined and hence is the likely basis for the species difference in protoporphyria.

Studies in hypotensive agents. Synthesis and hypotensive activity of 3,4-dihydro-1(2H)-benzoxepine oxime ethers and their derivatives

Substituted oximino-ethers of 3,4-dihydro-1(2H)-benzoxepines were synthezised from 3,4-dihydro-1(2H)benzoxepin-5-ones. The hypotensive activity of these compounds was evaluated on anaesthetized cats.

Lymphocyte labeling with technetium-99m-HMPAO: a radiotoxicity study using the micronucleus assay

The cytogenetic radiation damage to lymphocytes after in-vitro labeling of mixed leukocytes and isolated lymphocytes with 99mTc-hexamethylpropyleneamine oxime (HMPAO) was evaluated using the cytokinesis-blocked micronucleus assay. A direct assessment of the radiation damage to the lymphocytes after a labeling procedure of leukocytes separated from 46 ml blood with 740 MBq of 99mTc-HMPAO was not possible due to an almost complete impairment of the proliferative capacity. By starting with isolated lymphocytes, the number of micronuclei was studied versus the intracellular activity concentration in the range 0-3 MBq/10(7) lymphocytes for three donors. A comparison of these results with the dose response of the micronucleus incidence in lymphocytes after in-vitro irradiation with x-rays allowed an individual assessment of the x-ray dose, inducing the equivalent amount of clastogenic damage as the intracellular activity after 99mTc-HMPAO labeling. Based on an extrapolation of these data, the radiation damage of the lymphocytes due to self-irradiation in a labeling procedure of leukocytes with 740 MBq of 99mTc-HMPAO was estimated to be equivalent to 26 Gy of x-rays. Due to the observed almost complete inhibition of the proliferative capacity at this high dose level, the increased risk for a lymphoid malignancy after administration of isolated lymphocytes or mixed leukocytes labeled with 99mTc-HMPAO activities sufficient for scintigraphy can be regarded as small.

Toxicity of organophosphate nerve agents and related phosphonylated oximes compared to their anticholinesterase activity in neuron cultures

Oximes, such as pralidoxime and toxogonin, are important therapeutic agents for the treatment of organophosphate (OP) nerve agent poisoning. Oximes can react with these nerve agents to give intermediates, phosphonylated oximes, which may be equally toxic to the parent OP. The sc LD50s of a series of phosphonylated 2-butanone and 2,3-butanedione monoximes were compared to the sc LD50s of their parent OPs (tabun, sarin, and VX) in CD-1 mice. In every case the derivatives were significantly less toxic than their parent nerve agents. Times to death, and to signs of poisoning, were inversely proportional to the dose of test compound, and in all mortalities, blood serum acetylcholinesterase (AChE) was severely inhibited. The relative potencies of these compounds, as well as soman, cyclohexyl methylphosphonofluoridate, and diisopropyl fluorophosphate, as inhibitors of AChE in primary cultures of mouse embryo neurons, correlated with their in vivo toxicities. The results indicate that mouse embryo neuron cultures may be a useful model with which to study this class of compounds.

Comparison of oxidative damage to rat liver DNA and RNA by primary nitroalkanes, secondary nitroalkanes, cyclopentanone oxime, and related compounds

The hepatocarcinogen 2-nitropropane causes oxidative damage to liver DNA and RNA after administration to rats; increases in 8-hydroxydeoxyguanosine and formation of an unknown moiety (DX1) in DNA, plus increases in 8-hydroxyguanosine and the appearance of two unidentified peaks (RX1 and RX2) in RNA were observed by high-performance liquid chromatography of nucleosides from 2-nitropropane-treated rats using electrochemical detection (E. S. Fiala et al, Cancer Res., 49:5518-5522, 1989). In the present study, damage to Sprague-Dawley rat liver RNA and DNA was assessed to determine whether the characteristic pattern of oxidative nucleic acid damage caused by 2-nitropropane also occurred after i.p. administration of primary nitroalkanes, other secondary nitroalkanes, 2-methyl-2-nitropropane (a tertiary nitroalkane), and cyclopentanone oxime. All of the secondary nitroalkanes and cyclopentanone oxime significantly increased levels of 8-hydroxyguanine in both DNA and RNA and caused the appearance of DX1, RX1 and RX2. The primary nitroalkanes and the tertiary nitroalkane 2-methyl-2-nitropropane did not cause a similar pattern of nucleic acid damage. The rates of reprotonation of nitronates of the secondary nitroalkanes to the respective un-ionized neutral forms at pH 7.7 were more than 20-fold less than the rates of reprotonation of primary nitroalkane nitronates, suggesting that the anionic nitronates, rather than neutral compounds, are more immediately responsible for the DNA and RNA damage observed in vivo. Since 8-hydroxyguanine is a miscoding lesion in DNA, these results suggest the possibility, still to be rigorously tested, that hepatocarcinogenicity may be associated not only with 2-nitropropane but also with other secondary nitroalkanes as well as with those ketoximes that are capable of being converted to secondary nitroalkanes in vivo.

Sex and organ differences in oxidative DNA and RNA damage due to treatment of Sprague-Dawley rats with acetoxime or 2-nitropropane

The hepatocarcinogens 2-nitropropane and acetoxime have previously been found to induce a specific and qualitatively identical pattern of base damage in rat liver DNA and RNA, including the induction of increased levels of 8-hydroxyguanine. Because both 2-nitropropane and acetoxime are weaker carcinogens in female rats than male rats, we examined the ability of these chemicals to induce this pattern of damage in liver and kidney nucleic acids of male and female Sprague-Dawley rats 6 and 18 h after administration. Significantly lower levels of 8-hydroxydeoxyguanosine, 8-hydroxyguanosine and other presumed modified nucleosides discernible by high-performance liquid chromatography with electrochemical detection were found in liver nucleic acids of female rats at both time points. In addition, minimal alteration of nucleic acids was observed in the kidney, which is not a target organ for the carcinogenicity of either 2-nitropropane (2-NP) or acetoxime (ACO). These results support the hypothesis that the specific DNA alterations observed are relevant to the hepatocarcinogenicity of 2-NP and ACO.

Oxidative DNA and RNA damage in rat liver due to acetoxime: similarity to effects of 2-nitropropane

Acetoxime (ACO) and 2-nitropropane (2-NP), both industrially important chemicals and known hepatocarcinogens in rats, induced increased levels of 8-hydroxy-guanine in liver DNA and RNA of male Sprague-Dawley and F344 rats after either oral or i.p. administration. Both compounds also produced qualitatively the same patterns of other apparent modifications of liver DNA and RNA nucleosides, discernible by HPLC with electrochemical detection. Six hours after administration, the effects of 2-NP on liver nucleic acids were more pronounced in F344 rats than in Sprague-Dawley rats, suggesting that 2-NP may prove to be a stronger carcinogen in the F344 strain. The effects of ACO, a weaker carcinogen than 2-NP, were less than those of the nitroalkane in both rat strains. These results suggest that the hepatocarcinogenicity of ACO, like that of 2-NP, may depend on increased generation of reactive oxygen species capable of producing DNA and RNA base damage in rat liver. In addition, the data support the hypothesis that the hepatocarcinogenicity of ACO depends on its partial in vivo N-oxidation to 2-NP.

Induction of hyperplastic liver nodules in Wistar and MRC-Wistar rats by phenobarbital and the liver carcinogens acetoxime, 1-nitroso-5,6-dihydrouracil and 3-nitroso-2-oxazolidinone

We tested the ability of phenobarbital and two liver carcinogens, acetoxime and 1-nitroso-5,6-dihydrouracil (NDHU), to induce hyperplastic liver nodules (HLN) in MRC-Wistar and Wistar rats, using a system that included a single diethylnitrosamine (DEN) treatment, partial hepatectomy, and administration of the test compound in drinking water for 8 weeks. All three compounds induced significant HLN frequencies (number of HLN/cm2) in both rat strains. When the results for each strain were "normalized" for each compound and then combined, HLN frequency in MRC-Wistar rats was significantly lower (P less than 0.01) than that in Wistar rats. The weak liver carcinogen 3-nitroso-2-oxazolidinone (NOZ) did not induce a significant HLN frequency in MRC-Wistar rats. Acetoxime was highly volatile and was not mutagenic in the Ames test under a variety of conditions. The results for acetoxime are of interest because simple oximes are common constituents of oil paints. HLN induction by nitrosodihydrouracil is of interest because, unlike most liver carcinogens, this compound probably does not require metabolic activation and shows only a mild acute hepatoxicity.