Evaluation of the maternal and developmental toxicity of 6-methylmercaptopurine riboside in rats.

Thiopurine prodrugs (azathioprine, AZA, and 6-mercaptopurine, 6MP) are embryotoxic to rodents and rabbits. Little is known about the developmental toxicity of 6-methylmercaptopurine riboside (6MMPr), a thiopurine drug metabolite that is thought to mediate its liver toxicity. A limb bud assay found that 6MMPr impairs the in vitro morphogenetic differentiation of mouse limb extremities, being more potent than 6MP in the assay. This study evaluated the embryotoxicity of 6MMPr (0, 7.5, 15, 30 mg/kg bw sc) in rats after single-dose exposure in mid organogenesis (GD10). One group of pregnant rats was similarly treated with 6MP (15 mg/kg bw sc). After C-section (GD21), fetuses were weighed, and examined for external abnormalities. One third of each litter was examined for soft-tissue abnormalities while the remaining fetuses were cleared and stained for skeleton evaluation. 6MMPr caused a dose-dependent maternal weight loss followed by recovery before term pregnancy. Except for a nonsignificant increase in embryolethality and slight reduction in fetal weight at 30 mg/kg bw, no indication of embryotoxicity was noted at this dose or at lower doses of 6MMPr. In contrast, 6MP led to nearly 98 % of post-implantation losses in the presence of slight-to-mild maternal toxicity. These results are consistent with the notion that maternal treatment with 6MMPr affects embryo development, causing a nonsignificant increase in embryolethality and a slight reduction in fetal weight at 30 mg/kg bw. However, there was no increase in abnormalities at this dose, which was severely toxic to the dams, as reflected in the maternal weight gain data.

Evaluation of the developmental toxicity of solvents, metals, drugs, and industrial chemicals using a freshwater snail (Biomphalaria glabrata) assay.

A freshwater snail assay was employed to assess the embryotoxicity of solvents including acetone, methanol, ethanol, isopropanol, dimethyl-sulfoxide, glycerin, metals/metalloids including mercuric chloride (HgCl2), cadmium chloride (CdCl2,), antimony salts Sb+3 and Sb+5, drugs including colchicine, hydroxyurea, cyclophosphamide, an industrial chemical sodium azide (SA), an anionic surfactant dodecyl sodium sulfate-(DSS), H2O2 and sodium chloride (NaCl). The assay consists of exposing Biomphalaria glabrata egg masses (EM) to the substances for 96-hr and following up embryo/snail development for lethality, abnormal morphology (teratogenicity), and day of hatching up to day 10 or 14 after spawning. Based upon concentration-response relationships, LC50%s (embryolethality), EC50%s (teratogenicity) and IC50%s (hatching retardation) and 95%CIs were determined for tested chemicals. The LOECs indicated that HgCl2 (37 nM) and CdCl2 (140 nM) are potent embryotoxic agents in snails. Teratogenic indices (TI = LC50/EC50) for almost all tested chemicals were lower than or close to unity suggesting that these compounds were not teratogenic in this assay. The snail assay may be adequately performed in a cost-effective standardized protocol which enables testing a number of environmental chemicals over a broad concentration range. The snail assay needs to undergo further validation to be recognized for an internationally harmonized hazard identification in ecotoxicity risk assessment.

The impact of tobacco additives on cigarette smoke toxicity: a critical appraisal of tobacco industry studies. / O impacto dos aditivos do tabaco na toxicidade da fumaça do cigarro: uma avaliação crítica dos estudos patrocinados pela indústria do fumo.

Cigarette production involves a number of substances and materials other than just tobacco, paper and a filter. Tobacco additives include flavorings, enhancers, humectants, sugars, and ammonium compounds. Although companies maintain that tobacco additives do not enhance smoke toxicity and do not make cigarettes more attractive or addictive, these claims are questioned by independent researchers. This study reviewed the studies on the effects of tobacco additives on smoke chemistry and toxicity. Tobacco additives lead to higher levels of formaldehyde and minor changes in other smoke analytes. Toxicological studies (bacterial mutagenicity and mammalian cytoxicity tests, rat 90 days inhalation studies and bone-marrow cell micronucleus assays) found that tobacco additives did not enhance smoke toxicity. Rodent assays, however, poorly predicted carcinogenicity of tobacco smoke, and were clearly underpowered to disclose small albeit toxicologically relevant differences between test (with tobacco additives) and control (without tobacco additives) cigarettes. This literature review led to the conclusion that the impact of tobacco additives on tobacco smoke harmfulness remains unclear.

O impacto dos aditivos do tabaco na toxicidade da fumaça do cigarro: uma avaliação crítica dos estudos patrocinados pela indústria do fumo / El impacto de los aditivos del tabaco en la toxicidad del humo del cigarrillo: una evaluación crítica de los estudios de la industria del tabaco / The impact of tobacco additives on cigarette smoke toxicity: a critical appraisal of tobacco industry studies

Resumo: A produção de cigarros envolve uma série de substâncias e materiais além do próprio tabaco, do papel e do filtro. Os aditivos do tabaco incluem conservantes, flavorizantes, intensificadores, umectantes, açúcares e compostos de amônio. Embora as empresas produtoras de tabaco aleguem que os aditivos não aumentam a toxicidade da fumaça e não tornam os cigarros mais atraentes ou viciantes, tais alegações são contestadas por pesquisadores independentes. Os autores realizaram uma revisão dos estudos sobre os efeitos dos aditivos sobre a composição química e toxicidade da fumaça. Os aditivos elevam os níveis de formaldeído e causam pequenas alterações nos níveis de outros analitos medidos na fumaça. Estudos toxicológicos (testes de mutagenicidade e de citotoxicidade em células de mamíferos, estudos da exposição por 90 dias por via inalatória em ratos e ensaios do micronúcleo em células da medula óssea) indicaram que os aditivos do tabaco não aumentam a toxicidade da fumaça. Entretanto, é conhecido que os estudos em roedores falham em predizer o potencial carcinogênico da fumaça do cigarro, e os testes realizados tiveram poder estatístico insuficiente para detectar diferenças pequenas, porém relevantes do ponto de vista toxicológico, entre cigarros experimentais (com aditivos) e controles (sem aditivos). Em conclusão, esta revisão da literatura mostrou que o impacto dos aditivos na toxicidade da fumaça do tabaco ainda permanece por ser esclarecido.

Resumen: La producción de cigarrillos involucra un número de sustancias y materiales diferentes al tabaco en sí, papel y filtro. Los aditivos del tabaco incluyen aromas artificiales, potenciadores del sabor, humectantes, azúcares, y compuestos de amonio. A pesar de que las compañías sostienen que los aditivos del tabaco no aumentan la toxicidad del humo y no hacen los cigarrillos más atractivos y adictivos, estas afirmaciones son cuestionadas por investigadores independientes. Este trabajo ha revisado los estudios sobre los efectos de los aditivos del tabaco en la química del humo y su toxicidad. Los aditivos del tabaco conllevan niveles más altos de formaldehído y otros cambios menores en los análisis realizados del humo. Estudios toxicológicos (tests de mutagenicidad en bacterias y citotoxicidad en mamíferos, ensayos de inhalación en ratas 90 días y células del micronúcleo de la médula ósea) mostraron que los aditivos del tabaco no aumentaron la toxicidad del humo. Los ensayos de roedores, sin embargo, no predijeron adecuadamente la carcinogenicidad del humo del tabaco, y no eran claramente suficientes para dar a conocer, sin embargo, las pequeñas, pero toxicológicamente relevantes, diferencias entre el test (con/aditivos del tabaco) y control (sin/aditivos del tabaco) en cigarrillos. Esta revisión de la literatura nos lleva a la conclusión de que el impacto dañino de los aditivos del tabaco en el humo continúa estando poco claro.

Abstract: Cigarette production involves a number of substances and materials other than just tobacco, paper and a filter. Tobacco additives include flavorings, enhancers, humectants, sugars, and ammonium compounds. Although companies maintain that tobacco additives do not enhance smoke toxicity and do not make cigarettes more attractive or addictive, these claims are questioned by independent researchers. This study reviewed the studies on the effects of tobacco additives on smoke chemistry and toxicity. Tobacco additives lead to higher levels of formaldehyde and minor changes in other smoke analytes. Toxicological studies (bacterial mutagenicity and mammalian cytoxicity tests, rat 90 days inhalation studies and bone-marrow cell micronucleus assays) found that tobacco additives did not enhance smoke toxicity. Rodent assays, however, poorly predicted carcinogenicity of tobacco smoke, and were clearly underpowered to disclose small albeit toxicologically relevant differences between test (with tobacco additives) and control (without tobacco additives) cigarettes. This literature review led to the conclusion that the impact of tobacco additives on tobacco smoke harmfulness remains unclear.

Acute toxicity, cytotoxicity, genotoxicity and antigenotoxic effects of a cellulosic exopolysaccharide obtained from sugarcane molasses.

The acute toxicity, cytotoxicity, genotoxicity and antigenotoxic effects of BC were studied. Cytotoxicity of BC was evaluated in cultured C3A hepatoma cells (HepG2/C3A) using a lactate dehydrogenase (LDH) activity assay. Acute toxicity was tested in adults Wistar rats treated with a single dose of BC. The genotoxicity of BC was evaluated in vivo by the micronucleus assay. BC (0.33-170 µg/mL) added to C3A cell culture medium caused no elevation in LDH release over the background level recorded in untreated cell wells. The treatment with the BC in a single oral dose (2000 mg/kg body weight) caused no deaths or signs of toxicity. BC attenuated CP-induced and inhibition the incidence of MNPCE (female: 46.94%; male: 22.7%) and increased the ratio of PCE/NCE (female: 46.10%; male: 35.25%). There was no alteration in the LDH release in the wells where C3A cells were treated with increasing concentrations of BC compared to the wells where the cells received the cell culture medium only (background of approximately 20% cell death), indicated that in the dose range tested BC was not cytotoxic. BC was not cytotoxic, genotoxic or acutely toxic. BC attenuated CP-induced genotoxic and myelotoxic effects.

Estudo dos efeitos da co-exposição aos antineoplásicos hidroxiuréia e 6-mercaptopurina sobre o desenvolvimento embriofetal de ratos / [Study of the effects of co-exposure to hydroxyurea and 6- antineoplastic agents mercaptopurine on the embryo-fetal development of rats]

Os antineoplásicos hidroxiureia (HU) e 6-mercaptopurina (6MP) inibem a síntese do DNA. A HU inibe a enzima ribonucleotideo redutase (RR) que converte ribonucleotídeos em desoxirribonucleotídeos, resultando em bloqueio da síntese de DNA. A 6MP é ativada pela via HGPRT que origina nucleotídeos de 6-tioguanina, incorporados erroneamente ao DNA. HU e 6MP são teratógenos potentes em roedores e afetam o desenvolvimento da prole das mães expostas. Estudos indicam que os efeitos da co-administração desses fármacos não são explicados pela mera adição dos efeitos isolados, entretanto, o modo pelo qual eles interagem não está claro.Na primeira parte deste trabalho investigamos as relações dose-efeito embriotóxico da HU e 6-MP; na segunda, analisamos os efeitos das exposições sequenciais ou concomitantes aos dois fármacos sobre o desenvolvimento pré-natal. Avaliamos embrioletalidade, retardo do crescimento e indução de anomalias externas e esqueléticas fetais. Os experimentos envolveram: cruzamento dos animais; tratamento das ratas grávidas (DG11) com HU ou 6-MP; cesariana e retirada do útero (DG21); fixação dos fetos, diafanização e coloração do esqueleto; avaliação dos esqueletos. Na segunda parte deste estudo, selecionamos a dose máxima não teratogênica de HU (250 mg/kg ip) e uma dose embriotóxica de 6MP (24 mg/kg sc) e testamos os efeitos combinados desses fármacos, injetados concomitantemente, ou com intervalos de 2 ou 4 horas, em quatro grupos de ratas grávidas: Não tratadas; Tratadas com HU e veículo; Tratadas com veículo e 6MP; Tratadas com HU e 6MP. Os resultados mostraram que a administração concomitante de HU atenuou vários efeitos da 6MP, como as proporções de fetos mortos e malformados, a redução dos pesos fetal e placentário, e o aumento da incidência de anomalias externas e ósseas...

The cytotoxic chemotherapeutics hydroxyurea (HU) and 6-ercaptopurine (6MP) inhibit DNA synthesis. HU inhibits the enzyme ribonucleotide reductase (RR) which converts ribonucleotides into deoxyribonucleotide leading to blockage of DNA synthesis. 6MP is activated by HGPRT and undergoes kinase reactions forming 6-thioguanine nucleotides which are erroneously incorporated into DNA. HU and 6MP are potent teratogens in rodents and affect the development of the offspring ofexposed mothers. Some studies suggest that responses resulting from the combined administration of these drugs cannot be explained by the sum of individual effects however the way they interact is unclear. In the first part of this work we investigated the dose-embryotoxic response of HU and 6MP; in the second, we analyzed the effects of sequential and concurrent exposure to both drugs on prenatal development. Embryolethality, growth retardation and induction of fetal external and skeletalabnormalities were evaluated. All the experiments included: mating of males and females; treatment of pregnant females (GD11) with HU or 6MP; cesarean section and removal of gravid uterus (GD21); clearing and staining fetuses for skeleton evaluation. In the second part of this study, the maximumnon teratogenic dose of HU (250 mg/kg ip) and a clear embryotoxic dose of 6MP (24 mg/kg sc) were selected to be injected in the dams at intervals of 2 or 4 hours, or concurrently. Four experimental groups of pregnant females were constituted: Untreated; Treated with HU and vehicle; Treated with vehicle and 6MP; Treated with HU and 6MP. Concomitant administration of HU attenuated various effects of 6MP, such as the proportion of dead and malformed fetuses, the reduction of fetal and placental weights and the increase in incidence of external/skeletal abnormalities...

Toxicological evaluation of an ethanolic extract from Chiococca alba roots.

The roots of Chiococca alba have been employed to treat rheumatic disorders and for other therapeutic purposes in Brazil and elsewhere. This study was undertaken to evaluate the toxicological properties of an ethanolic extract from Chiococca alba roots (EE), including mutagenicity in the Salmonella assay and acute and subacute toxicity to mice. Single oral doses of EE caused hypoactivity, but no deaths were noted up to the highest dose tested (2000 mg/kg). EE (500 mg/kg p.o.) reduced mouse locomotion in the open field test. EE was markedly more toxic when given by intraperitoneal (i.p.) and subcutaneous (s.c.) routes. Acute approximate lethal doses (ALD) were 125 mg/kg (males) and 250 mg/kg (females) and 250 mg/kg (both sexes) by i.p. and s.c. routes, respectively. Deaths after single doses were preceded by hypoactivity, ataxia and lethargy. Repeated administration of EE by gavage for 14 days caused no deaths. Activity of liver monooxygenases (pentoxy- and ethoxyresorufin-O-dealkylases) was not altered by repeated treatment with EE (2000 mg/kg/day p.o.). Administration of EE by the i.p. route for 14 days decreased weight gain and caused anemia, neutrophilia and deaths. The no-observed-adverse-effect level (NOAEL) for subacute treatment by the i.p. route was as low as 15.6 mg of EE/kg body weight (wt)/day. EE was not mutagenic in the Salmonella/microsome assay with TA100, TA98, TA97a and TA1535 strains. In summary, EE was not mutagenic and presented a low acute and subacute toxicity by the oral route. Toxicities by parenteral routes, however, were more pronounced.

Chemical composition, toxicity and mosquito repellency of Ocimum selloi oil.

Ocimum spp. (Lamiaceae) and their essential oils have been traditionally used to kill or repel insects, and also to flavor foods and oral products, in fragrances, in folk medicine and as condiments. In Brazil, Ocimum selloi has been used to treat stomachaches and as an anti-inflammatory remedy. This study was performed to provide data on the chemical composition, acute toxicity, mutagenicity, skin irritant potential and mosquito repellency of Ocimum selloi oil. GC/MS analysis of Ocimum selloi oil revealed that its major constituents were methyl-chavicol or estragole (55.3%), trans-anethole (34.2%), cis-anethole (3.9%) and caryophyllene (2.1%). Ocimum selloi oil given by gavage to adult Swiss Webster mice produced no adverse effects at doses as high as 1250 mg/kg body weight. Deaths and symptoms (e.g. hypoactivity, ataxia and lethargy) were observed at doses > or =1500 mg/kg body weight, being females apparently more susceptible than males. Genotoxicity of Ocimum selloi oil was evaluated in the Salmonella/microsome assay without and with S9 mixture. The oil, tested up to the toxicity limit (500-700 microg/plate), was not mutagenic to tester strains TA97a, TA98 and TA100. None of 30 volunteers of either sex exposed to undiluted Ocimum selloi oil (4-h patch test) showed a positive skin irritant reaction. A field test (six volunteers, each individual his/her own control) was carried out to evaluate mosquito (Anopheles braziliensis) repellency of Ocimum selloi oil diluted in ethanol (10% v/v). The median number of mosquito bites on volunteers' skin-recorded for 30 min after application of Ocimum selloi oil (2, range 0-3) was much lower than that noted after application of the solvent alone (19.5, 3-25) (Wilcoxon test, P<0.01). In conclusion, results showed that Ocimum selloi oil is an effective mosquito repellent that presents a low acute toxicity, poses no mutagenic risk and seems not to be irritating to human skin.

Fatores de risco ambientais para o câncer gástrico: a visäo do toxicologista / Environmental risk factors for gastric cancer: the toxicologist's standpoint

A carcinogênese é um processo altamente complexo do qual participam fatores de risco herdados e fatores de risco ambientais, tais como a alimentaçäo, o hábito de fumar, a ocupaçäo, e a exposiçäo a radiaçäo e a agentes químicos. A toxicologia experimental identifica as substâncias químicas potencialmente carcinogênicas e torna possível medidas regulatórias que objetivam reduzir a exposiçäo humana a elas. A carcinogênese pode ser vista como consistindo de três seqüências distintas: a iniciaçäo, a promoçäo e a progressäo. A conversäo neoplásica (iniciaçäo) ocorre quando um evento genético (mutaçöes, rearranjos cromossômicos, inserçöes ou deleçöes de genes e amplificaçäo de genes) resulta em ativaçäo de oncogenes e/ou em falta de expressäo - ou inativaçäo de produtos - de genes supressores de tumores. A promoçäo envolve a expansäo clonal das células "iniciadas" e exige a proliferaçäo celular. Estratégias efetivas para reduzir os riscos de câncer gástrico e os riscos de neoplasias de outras localizaçöes devem incluir o controle de carcinógenos conhecidos, assim como a quimioprevençäo, por meio de intervençöes racionais no processo carcinogênico. Neste sentido, o desafio a ser enfrentado pelo toxicologista envolve o desenvolvimento de ensaios preditivos melhores e mais baratos e a elucidaçäo dos mecanismos subjacentes à carcinogênese química.