Delayed myelosuppression with acute exposure to hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and environmental degradation product hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX) in rats

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), a widely used munitions compound, and hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), its N-nitroso product of anaerobic microbial nitroreduction, are contaminants of military sites. Previous studies have shown MNX to be the most acutely toxic among the nitroreduced degradation products of RDX and to cause mild anemia at high dose. The present study compares hematotoxicity with acute oral exposure to MNX with parent RDX. Both RDX and MNX caused a modest decrease in blood hemoglobin and ~ 50% loss of granulocytes (NOAELs = 47 mg/kg) in female Sprague–Dawley rats observed 14 days post-exposure. We explored the possibility that blood cell loss observed after 14 days was delayed in onset because of toxicity to bone marrow (BM) progenitors. RDX and MNX decreased granulocyte/macrophage-colony forming cells (GM-CFCs) at 14, but not 7, days (NOAELs = 24 mg/kg). The earliest observed time at which MNX decreased GM-CFCs was 10 days post-exposure. RDX and MNX likewise decreased BM burst-forming units-erythroid (BFU-Es) at 14, but not 7, days. Granulocyte–erythrocyte–monocyte–megakaryocyte (GEMM)-CFCs were unaffected by RDX and MNX at 7 days suggesting precursor depletion did not account for GM-CFC and BFU-E loss. MNX added to the culture media was without effect on GM-CFC formation indicating no direct inhibition. Flow cytometry showed no differential loss of BM multilineage progenitors (Thy1.1⁺) or erythroid (CD71⁺) precursors with MNX suggesting myeloid and erythroid lineages were comparably affected. Collectively, these data indicate that acute exposure to both RDX and MNX caused delayed suppression of myelo- and erythropoiesis with subsequent decrease of peripheral granulocytes and erythrocytes.     

Up-and-down procedure (UDP) determinations of acute oral toxicity of nitroso degradation products of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), a widely used military explosive and soil and ground water contaminant of munitions manufacturing and artillery training sites, undergoes microbial nitroreductase metabolism to hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX). Human occupational and accidental exposures to RDX, as well as acute oral exposures in rats, result in seizures, but little is known about the toxicity of the RDX degradation products. The main objective of the present study was to determine the oral LD50 of the most potent RDX N-nitroso product in female Sprague-Dawley rats using the recently validated up-and-down procedure (UDP). With only 26 rats, MNX was identified as the most potent metabolite and a maximum likelihood estimate of 187 mg kg(-1) (95% confidence interval 118-491 mg kg(-1)) for its LD50 was established and found equivalent to that of RDX determined with the same protocol. CNS toxicity, manifested as forelimb clonic seizures progressing to generalized clonic-tonic seizures, was the critical adverse effect. Further, confirmation of the UDP LD50 for MNX with a fixed-dose design enabled identification of 94 mg kg(-1) as the highest nonlethal dose. An ED50 of 57 mg kg(-1) was determined for neurotoxicity, while splenic hemosiderosis and decreased blood hematocrit and hemoglobin concentration occurred with a threshold at 94 mg kg(-1) in 14-day survivors. These studies, while providing new toxicity data necessary for the management of RDX-contaminated sites, illustrate the efficiency of the UDP for comparative acute toxicity determinations and its value in guiding further characterization of dose dependency of identified adverse effects.     

Synthesis of [O‐methyl‐11C]‐4‐(1,3‐dimethoxy‐2‐propylamino)‐2,7‐dimethyl‐8‐(2,4‐dichlorophenyl)[1,5‐a]pyrazolo‐1,3,5‐triazine ([11C]DMP696): a potential PET ligand for CRF1 receptors

Synthesis of [O‐methyl‐¹¹C]‐4‐(1,3‐dimethoxy‐2‐propylamino)‐2,7‐dimethyl‐8‐(2,4‐dichlorophenyl)[1,5‐a]pyrazolo‐1,3,5‐triazine ([¹¹C]DMP696), a highly selective CRF₁ antagonist has been achieved. The total time required for the synthesis of [¹¹C]DMP696 is 30 min from EOB using [¹¹C]methyl triflate in THF, with a 16% yield (EOS) and >99% chemical and radiochemical purities along with a specific activity of >2000 Ci/mmol (EOS). Copyright © 2004 John Wiley & Sons, Ltd.     

Metabolite profiling of [14C]hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in Yucatan miniature pigs

The study reported herein examined the metabolism of 14C-labeled hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) resulting from a single oral gavage of 5 ml/kg to male and female Yucatan miniature pigs (43 mg/kg, 56 microCi/kg in 0.5% carboxymethylcellulose in water). Blood, urine, and feces were collected at selected times of 1, 6, 12, and 24 h postdose. At 24 h postdose, liver samples were collected. Blood, plasma, liver, and excreta were analyzed for total RDX-derived radioactivity and metabolites were identified. Urine was the major route of elimination of 14C-RDX-derived radioactivity in both males and females. Relatively low levels of radioactivity were found in gastrointestinal contents and in feces, suggesting nearly complete absorption of 14C-RDX following an oral dose. Analysis of urine by liquid chromatography-mass spectrometry (LC/MS) identified quantifiable levels of two ring-cleavage metabolites, 4-nitro-2,4-diazabutanal and 4-nitro-2,4-diaza-butanamide, as well as parent RDX. The 4-nitro-2,4-diazabutanal, was seen in earlier studies of aerobic metabolism of RDX. The 4-nitro-2,4-diaza-butanamide, an amide, was not previously reported but was tentatively identified in this study. Analysis by a more sensitive method (LC/MS/MS) also showed trace amounts of the RDX metabolites 1-nitroso-3,5-dinitro-1,3,5-triazacyclohexane (MNX) (in both male and female urine) and 1-nitro-3,5-dinitroso-1,3,5-triazacyclohexane (DNX) (in male urine). Analysis of plasma by LC/MS/MS also revealed quantifiable levels of RDX and trace levels of MNX, DNX, and 1,3,5-trinitroso-1,3,5-triazacyclohexane (TNX). None of the liver extracts showed quantifiable levels of RDX or any identifiable metabolites. Most of the radioactivity was in the form of water-soluble high-molecular-weight compounds. RDX when given orally to pigs was rapidly metabolized by loss of two nitro groups followed by ring cleavage.     

叔丁基对苯二酚上调Nrf2调控的基因表达并减轻环磷酰胺导致的小鼠血液毒性

血液毒性（或称骨髓抑制）是癌症化疗最常见的剂量限制毒副作用,而转录因子Nrf2控制着包括骨髓在内的许多组织对化学刺激的敏感性。本文研究了叔丁基对苯二酚（tBHQ）对小鼠外周血细胞中Nrf2调控的基因表达和环磷酰胺（CTX）导致的血液毒性的影响。CTX处理导致了小鼠外周血有核细胞的凋亡和白细胞减少,伴随着骨髓造血细胞的动员。tBHQ处理则可以在体外和体内激活RAW264.7小鼠巨噬细胞和外周血细胞中Nrf2信号和下游基因如血红素氧化酶1和谷胺酸半胱氨酸连接酶催化亚基等的表达同时,tBHQ预处理可以减轻CTX导致的小鼠外周血有核细胞的凋亡和白细胞减少,说明Nrf2可能在减轻CTX血液毒性中发挥作用。本文的研究有助于加深对化疗所致血液毒性的了解,并提示Nrf2可能作为减轻化疗毒副作用的化疗保护剂的药物靶标。     

Genotoxicity assessment of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)

Hexahydro-1,3,5-trinitro-1,3,5-triazine, a polynitramine compound, commonly known as RDX, has been used as an explosive in military munitions formulations since World War II. There is considerable data available regarding the toxicity and carcinogenicity of RDX. It has been classified as a possible carcinogen (U.S. Environmental Protection Agency, Integrated Risk Information System, 2005, www.epa.gov/IRIS/subst/0313.htm). In order to better understand its gentoxic potential, the authors conducted the in vitro mouse lymphoma forward mutation and the in vivo mouse bone marrow micronucleus assays. Pure RDX (99.99%) at concentrations ranging from 3.93 to 500 microg/ml showed no cytotoxicity and no mutagenicity in forward mutations at the thymidine kinase (TK) locus in L5178Y mouse lymphoma cells, with and without metabolic activation. This finding was also confirmed by repeat assays under identical conditions. In addition, RDX did not induce micronuclei in mouse bone marrow cells when tested to the maximum tolerated dose of 250 mg/kg in male mice. These results show that RDX was not mutagenic in these in vitro and in vivo mammalian systems.     

Exploring isoxazoles and pyrrolidinones decorated with the 4,6‐dimethoxy‐1,3,5‐triazine unit as human farnesyltransferase inhibitors

Unprecedented triazinyl‐isoxazoles were afforded via an effective cycloaddition reaction between nitrile oxides and the scarcely described 2‐ethynyl‐4,6‐dimethoxy‐1,3,5‐triazine as dipolarophile. The biological evaluation of the newly synthesized compounds showed that the inhibition of human farnesyltransferase by zinc complexation could be improved with triazine‐isoxazole moieties. The replacement of the isoxazole unit by a pyrrolidin‐2‐one was detrimental to the inhibitory activity while the pyrrolidin‐2‐thione derivatives conserved the biological potential. The potential of selected compounds to disrupt protein farnesylation in Chinese hamster ovary (CHO) cells transfected with pEGFP‐CAAX was also evaluated.     

Cancer mode of action,weight of evidence,and proposed cancer reference value for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX, CAS No. 121-82-4) is a component of munitions formulations, and has been detected in groundwater samples collected at various US military sites. Clean up target levels for RDX may be derived based on consideration of acceptable cumulative human exposure as expressed in toxicity reference values. Evaluations of the cancer weight of evidence and possible modes of action (MOA) for RDX-induced cancer were conducted. It was concluded that the available data provide suggestive evidence of human carcinogenic potential for RDX. While a mutagenic/genotoxic MOA for RDX is unlikely, no alterative MOA is strongly supported by the available data. A nonlinear (threshold) approach to the assessment of human cancer risk was recommended, and a recommended chronic cancer reference dose of 0.08 mg/kg/day was derived. For comparison only, computations using a linear approach were also conducted, yielding a cancer risk specific dose of 0.000235 mg/kg/day for 1 in 10⁵ risk; this value is 2.6-fold higher the current US EPA risk specific dose for 1 in 10⁵ risk. Thus, cleanup standards based on human health risk from RDX exposure could potentially depend on the willingness of risk managers to accept a nonlinear MOA and nonlinear toxicity risk value derivation.     

Synthesis and Biological Evaluation of Novel 6‐Hydrazinyl‐2,4‐bismorpholino pyrimidine and 1,3,5‐Triazine Derivatives as Potential Antitumor Agents

A series of 6‐hydrazinyl‐2,4‐bismorpholino pyrimidine and 1,3,5‐triazine derivatives ( 5a – 5l and 8a – 8o ) were synthesized and their chemical structures as well as the relative stereochemistry were confirmed. All the synthesized compounds were evaluated for antiproliferative activity against three cancer cell lines (H460, HT‐29, and MDA‐MB‐231). Several potent compounds were further evaluated against two other cell lines (U87MG, H1975). Most of the prepared compounds, particularly compounds 5c and 5j with IC₅₀ values (0.07 and 0.05 µM, respectively) in the nM range, exhibited moderate to excellent antiproliferative activity and high selectivity against the H460 cancer cell line as compared with compound 1 . The most promising compound 5j , possessing a cyano group at the 3‐position of the benzene ring, showed strong antiproliferative activity against H460, HT‐29, and MDA‐MB‐231 cell lines with IC₅₀ values of 0.05, 6.31, and 6.50 µM, which were 4.6‐ to 190.4‐fold more active than compound 1 (9.52, 29.24, and 36.21 µM), respectively.     

Synthesis and biodistribution studies of two novel radioiodinated areno‐annelated estra‐1,3,5(10),16‐tetraene‐3‐ols as promising estrogen receptor radioligands

Two novel radioiodinated areno‐annelated estra‐1,3,5(10),16‐tetraenes, [¹²⁵I]2‐iodo‐1′‐methoxybenzo[4′,3′:16,17]estra‐1,3,5(10),16‐tetraene‐3‐ol ( 2 ‐[ ¹²⁵ I ]‐ MEBE ) and [¹²⁵I]4‐iodo‐1′‐methoxybenzo[4′,3′:16,17]estra‐1,3,5(10),16‐tetraene‐3‐ol, ( 4 ‐[ ¹²⁵ I ]‐ MEBE ) were synthesized for evaluation as potential ligands for the estrogen receptor. Radioiodination of 1′‐methoxybenzo[4′,3′:16,17]estra‐1,3,5(10),16‐tetraene‐3‐ol at the A ring was accomplished by electrophilic aromatic substitution using [¹²⁵I] sodium iodide and chloramine‐T as oxidant. After purification by reverse phase HPLC, the two radioisomers ( 2 ‐[ ¹²⁵ I ]‐ MEBE and 4 ‐[ ¹²⁵ I ]‐ MEBE ) were obtained in a radiochemical yield of 42 and 48%, respectively, in a radiochemical purity of greater than 95% and a high specific activity. The effect of the site of radioiodination (C₂ vs C₄) on the biological behaviour of the molecules was evaluated through biodistribution studies in immature female Sprague‐Dawley rats. Both 2 ‐[ ¹²⁵ I ]‐ MEBE and 4 ‐[ ¹²⁵ I ]‐ MEBE are stable in vivo and are mainly excreted through the hepatobiliary pathway. Both localize in the uterus and ovaries via a receptor‐mediated process, where the 2 ‐[ ¹²⁵ I ]‐ MEBE isomer has the higher specific ER binding and uterus selectivity. The favourable in vitro/in vivo stability and biodistribution profiles suggest that these radioligands are good candidates for further exploration of their potential clinical application. Copyright © 2006 John Wiley & Sons, Ltd.     

6‐Ethyl‐N,N′‐bis(3‐hydroxyphenyl)[1,3,5]triazine‐2,4‐diamine (RS‐0466) Enhances the Protective Effect of Brain‐Derived Neurotrophic Factor on Amyloid β‐Induced Cytotoxicity in Cortical Neurones

Abstract: Amyloid β peptide in the senile plaques of patients with Alzheimer's disease is considered to be responsible for the pathology of Alzheimer's disease. We have previously reported that 6‐ethyl‐N,N′‐bis(3‐hydroxyphenyl)[1,3,5]triazine‐2,4‐diamine, RS‐0466, is capable of significantly inhibiting amyloid β‐induced cytotoxicity in HeLa cells. To determine various profiles of RS‐0466, we investigated whether RS‐0466 would enhance the neuroprotective effect of brain‐derived neurotrophic factor on amyloid β_1–42‐induced cytotoxicity in rat cortical neurones. Consistent with previous observations, brain‐derived neurotrophic factor ameliorated amyloid β_1–42‐induced cytotoxicity. Furthermore, co‐application of RS‐0466 enhanced the neuroprotective effect of brain‐derived neurotrophic factor. RS‐0466 also reversed amyloid β_1–42‐induced decrease of brain‐derived neurotrophic factor‐triggered phosphorylated Akt. These results raise the possibility that RS‐0466 or one of its derivatives has potential to enhance the neuroprotective effect of brain‐derived neurotrophic factor, and could serve as a therapeutic agent for patients with Alzheimer's disease.     

Synthesis of New N‐Substituted 5‐Arylidene‐2,4‐thiazolidinediones as Anti‐Inflammatory and Antimicrobial Agents

A novel series of 5‐arylidene ‐ 2,4‐thiazolidinediones (TZDs) 2a – p was synthesized from the condensation of 3‐((2‐phenylthiazol‐4‐yl)methyl)thiazolidine‐2,4‐dione with different benzaldehyde derivatives. All the structures were confirmed by their spectral (IR, ¹H NMR, ¹³C NMR and mass) and elemental analytical data. The new molecules were evaluated in vivo as anti‐inflammatory agents in an acute experimental inflammation, evaluating the acute phase bone marrow response and phagocyte activity. All compounds, excepting one, reduced the absolute leukocytes count due to the lower neutrophil percentage. Phagocytary index was decreased by the same molecules, while only half of them reduced the phagocytary activity. The effect was superior to meloxicam, the reference anti‐inflammatory drug, for the majority of the TZD derivatives. The new molecules were also investigated for their antimicrobial properties on Gram‐positive and Gram‐negative bacteria and one fungal strain. Two compounds ( 2e and 2n ) manifested growth inhibition capacity on all the tested strains.     

Labelled compounds of interest as antitumour agents – VIII. Synthesis of 2H‐isotopomers of pentamethylmelamine and of a potential prodrug thereof

Treatment of 2‐chloro‐4,6‐(dimethylamino)‐1,3,5‐triazine with trideuteromethylamine gave 4,6‐(dimethylamino)‐2‐trideuteromethyl‐1,3,5‐triazine, an isotopomer of the experimental anticancer agent pentamethylmelamine (PMM). Mitsunobu coupling with 1,2‐dimethyl‐3‐hydroxymethyl‐5‐methoxy‐indole‐4,7‐dione gave 1,2‐dimethyl‐3‐(N‐(4,6‐bis(dimethylamino)‐1,3,5‐triazin‐2‐yl)‐N‐trideuteromethylaminomethyl)‐5‐methoxyindole‐4,7‐dione. This conjugate is a potential reductively triggered prodrug of PMM. Copyright © 2002 John Wiley & Sons, Ltd.     

Cardioprotective effect of novel sulphonamides‐1,3,5‐triazine conjugates against ischaemic–reperfusion injury via selective inhibition of MMP‐9

Diseases affecting cardiovascular system are ranked as a top most cause of morbidity and mortality. Herein, a novel class sulphonamides‐1,3,5‐triazine conjugates have been synthesized and tested for inhibitory activity against MMP‐2 and MMP‐9. The results of the study showed that these molecules efficiently inhibit MMP‐9 than MMP‐2, revealing compound 8e as the most potent inhibitor (IC₅₀ = 2.34 ± 0.56 nm ). Due to involvement of MMP‐9 in many cardiovascular diseases, particularly in myocardial ischaemia (MI), compound 8e was further subjected for the determination of the protective effect on isoproterenol (ISO)‐induced myocardial injury in rats.     

Synthesis,Docking, In Vitro and In Vivo Antimalarial Activity of Hybrid 4‐aminoquinoline–1,3,5‐triazine Derivatives Against Wild and Mutant Malaria Parasites

A new series of hybrid 4‐aminoquinoline–1,3,5‐triazine derivatives was synthesized by a four‐step reaction. Target compounds were screened for in vitro antimalarial activity against chloroquine‐sensitive (3D‐7) and chloroquine‐resistant (RKL‐2) strains of Plasmodium falciparum. Compounds exhibited, by and large, good antimalarial activity against the resistant strain, while two of them, that is 8g and 8a, displayed higher activity against both the strains of P. falciparum. Additionally, docking study was performed on both wild (1J3I.pdb) and quadruple mutant (N51I, C59R, S108 N, I164L, 3QG2.pdb) type pf‐DHFR‐TS to highlight the structural features of hybrid molecules.     

Minimal Toxicity to Myeloid Progenitor Cells of Weekly24‐Hr Infusion of High‐Dose 5‐Fluorouracil: Direct Evidence from Colony Forming Unit‐Granulocyte andMonocyte (CFU‐GM) Clonogenic Assay

Although very high doses of 5‐fluorouracil was used in the weekly 24‐h infusion, high‐dose 5‐fluorouracil (2600 mg/m²/week) and leucovorin (500 mg/m²/week) protocol, myelosuppression was surprisingly low. The current study was conducted to investigate the possible mechanism underlying the low myelosuppression. To mimic the clinical situation, peripheral blood progenitor cells collected from 12 patients were used for colony forming unit‐granulocyte and monocyte clonogenic assay; and 2 representative modes of 5‐fluorouracil exposure (30 min. versus 24 hr) were examined for cytotoxic effects on human myeloid progenitor cells. Previous pharmacokinetic studies have estimated the concentrations of 5‐fluorouracil in the bone marrow to be 200–400 μM and 1–2 μM for the 30 min. infusion (600–900 mg/m²) and the 24 hr‐infusion (1000–2000 mg/m²) regimens, respectively. The results of our colony‐forming unit‐granulocyte and monocyte clonogenic assay showed that 24‐hr exposure to 5‐fluorouracil (2 μM) and 30 min. exposure to 5‐fluorouracil (100 μM) resulted in 27.2% and 78.2% inhibition of the colony formation, respectively. Our data provided direct evidence which may explain why myelotoxicity is significantly less in weekly 24 hr infusion of fluorouracil than in the conventional bolus regimens.     

The Synthesis of 1,3,5‐triazine Derivatives and JNJ7777120 Analogues with Histamine H4 Receptor Affinity and Their Interaction with PTEN Promoter

The involvement of histamine and H₄ receptor (H₄R) in cancer has been investigated recently using the H₄R agonists and antagonists. The scope of the research project was synthesis and exploration of the consequences of a group of compounds with histamine H₄ receptor (H₄R) affinity on the promoter of PTEN gene encoding the antitumor PTEN protein. The series of novel compounds based either on H₄R antagonists JNJ7777120 structure or 1,3,5‐triazine scaffold were synthesized, evaluated for histamine H₄R affinity and used in this study. Compounds 5 and 7 belonging to the group of JNJ7777120 analogues showed the highest interaction with the promoter of PTEN gene and weak affinity against H₄R with K_i value >100 μm . These compounds showed no significant effect on neuroblastoma IMR‐32 cells viability indicating no correlation between PTEN gene promoter affinity and antitumor activity. Compound 6 , another JNJ7777120 analogue, showed the highest effect on IMR‐32 viability with calculated IC₅₀ = 23.27 μm . The 1,3,5‐triazine derivatives exhibited generally low or medium interaction with PTEN gene promoter. However, the 1,3,5‐triazine derivative 11 with the para‐bromo substituent showed the highest affinity against H₄R with K_i value of 520 nm and may be considered as a new lead structure.     

Synthesis and in vitro Evaluation of 1,2,4‐Triazolo[1,5‐a][1,3,5]triazine Derivatives as Thymidine Phosphorylase Inhibitors

In our lead finding program, a series of 1,2,4‐triazolo[1,5‐a][1,3,5]triazine derivatives were synthesized, and their in vitro thymidine phosphorylase inhibitory potential was explored. Among the different derivatives, compounds having keto group (C = O) at C7 and thioketo group (C = S) at C5 positions showed varying degrees of TP inhibitory activity comparable with positive control, 7‐deazaxanthine ( 7‐DX , 2 ) (IC₅₀ value = 42.63 μm ). Enzyme inhibition kinetics study suggested that compound IVn behaved as a mixed‐type inhibitor of the enzyme with respect to thymidine (dThd) as a variable substrate. Compound IVn was also found to inhibit PMA‐induced MMP‐9 expression in MDA‐MB‐231 cells at sublethal concentrations. Computational docking study was performed to illustrate the enzyme inhibition kinetics and to explore the ligand–enzyme interactions.