Immunosuppressive Effect of Subchronic Exposure to a Mixture of Eight Heavy Metals, Found as Groundwater Contaminants in Different Areas of India, Through Drinking Water in Male Rats

Immunotoxicity is an important health hazard of heavy metal exposure. Because the risk of combined exposure in the population cannot be neglected, we examined whether subchronic exposure to a mixture of metals (arsenic, cadmium, lead, mercury, chromium, nickel, manganese, and iron) via drinking water at contemporary Indian groundwater contamination levels and at concentrations equivalent to the WHO maximum permissible limit (MPL) in drinking water can induce immunotoxicity in male rats. Data on groundwater contamination with metals in India were collected from literature and metals were selected on the basis of their frequency of occurrence and contamination level above the MPL. Male albino Wistar rats were exposed to the mixture at 0, 1, 10, and 100 times the mode concentrations (the most frequently occurring concentration) of the individual metals in drinking water for 90 days. In addition, one group was exposed to the mixture at a concentration equal to the MPL of the individual metal and another group was used as positive control for immune response studies. The end points assessed were weights of organs, hematological indices, humoral and cell-mediated immune responses, and histopathology of skin and spleen. The MPL and 1× doses did not significantly affect any of the parameters and none of the doses induced any significant changes after 30 days of exposure. The mixture at 10× and 100× doses increased the relative weight of the spleen, but that of thymus, adrenals, and popliteal lymphnodes were increased with the 100× dose. After 90 days, 10× and 100× doses decreased serum protein and globulin contents and increased the albumin:globulin ratio; the albumin level was decreased only with the 100× dose. After 60 days, the total erythrocyte count (TEC), hemoglobin (Hb) level, and packed cell volume (PCV) were decreased with the 100× dose, whereas after 90 days, 10× and 100× doses reduced the TEC, total leukocyte count, Hb level, PCV, mean corpuscular volume, and mean corpuscular hemoglobin. With the 100× dose, the lymphocyte count was decreased after 60 and 90 days, but the neutrophil number was increased after 90 days. Antibody titer was decreased after 75 days with the 100× dose, but after 90 days, it was decreased with both the 10× and 100× doses. In delayed-type hypersensitivity response, these two doses decreased ear thickness after 24 and 48 h and skin biopsies showed a dose-dependent decrease in inflammatory changes. Histologically, the spleen revealed depletion of lymphoid cells and atrophic follicles with reduced follicular activity with higher doses. The findings suggest that hematopoietic and immune systems are toxicologically sensitive to the mixture, which could lead to anemia and suppression of humoral and cell-mediated immune responses in male rats at 10 and 100 times the mode concentrations of the individual components in contaminated groundwater.     

Effects of Subchronic Exposure via Drinking Water to a Mixture of Eight Water-Contaminating Metals: A Biochemical and Histopathological Study in Male Rats

In the current study, we examined whether subchronic exposure via drinking water to low doses of a mixture of metals (arsenic, cadmium, lead, mercury, chromium, manganese, iron, and nickel), found as contaminants in various water sources of India, and to concentrations equivalent to WHO maximum permissible limits (MPL) in drinking water for individual metals, can alter systemic physiology of male rats. Data on water contamination with metals in India were collected from the literature and metals were selected on the basis of their frequency of occurrence and contamination level above MPL. Male Wistar rats were exposed to the mixture at 0, 1, 10, and 100 times the mode concentrations (the most frequently occurring concentration) of the individual metals via drinking water for 90 days. One more group of rats was exposed to the mixture at a concentration equivalent to the MPL (WHO) in drinking water for individual metals. Toxic potential of the mixture was evaluated by assessing general toxicological end points, serum chemistry and histopathology of vital organs. The mixture decreased body weight and water consumption and increased weights of brain, liver, and kidneys with 10× and 100× doses. After 30 days of exposure, no appreciable changes were found in any blood clinical markers. After 60 days, only the 100× dose, while after 90 days both 10× and 100× doses increased activities of aspartate aminotransferase and alkaline phosphatase and levels of urea nitrogen and creatinine and decreased total protein and albumin levels, but alanine aminotransferase activity and glucose level were not affected. At 10× and 100× exposure levels, qualitatively similar, but dose-dependent vascular, degenerative, and necrotic changes were observed in brain, liver, and kidney. The results indicate that subchronic exposure to the metal mixture affected general health of male rats by altering the functional and structural integrity of kidney, liver, and brain at 10 and 100 times the mode concentrations of the individual metals in Indian water sources, but exposure at mode concentrations of contemporary water contamination levels or at concentrations equivalent to the MPL for individual metals in drinking water may not cause any health hazards in male rats.     

Oxidative Stress Biomarkers in the Digestive Gland of Theba pisana Exposed to Heavy Metals

The in vivo toxic effects of sublethal treatment of 40 and 80% of 48-h LD₅₀ of topically applied trace metals [copper (Cu), lead (Pb), and zinc (Zn)] on oxidative stress biomarkers in the digestive gland of Theba pisana were examined. Oxidative individual perturbations were assessed by measuring nonenzymatic (glutathione; GSH) and enzymatic (catalase, CAT; glutathione peroxidase, GPx; and glutathione-S-transferase, GST) antioxidants in digestive gland of the snails. Lipid peroxidation (LPO) was also evaluated as a marker of cell damage. The results indicated that the copper ion was the most potent metal against this snail, followed by zinc and lead, for which the corresponding LD₅₀ values were 37.88, 261.72, and 652.55 μg/snail, respectively. The no-observed effect concentration (NOEC) values for Cu, Zn, and Pb were 10, 50, and 500 μg/snail, respectively, and the corresponding lowest-observed effect concentration (LOEC) values were 50, 100, and 1000 μg/snail. All trace metals resulted in a significant increase in the level of LPO, whereas a significant decline in the content of GSH was observed when compared with untreated controls. Treatment with both sublethal doses of the metals caused significant increase in CAT activity, except in the case of 40% LD₅₀ Zn and 80% LD₅₀ Cu, which exhibited no alteration in CAT when compared to control animals. GPx was significantly increased in snails exposed to 40% LD₅₀ Cu and Pb as well as 80% LD₅₀ Cu. However, an opposite effect was observed in snails exposed to 80% LD₅₀ Pb and in either 40 or 80% LD₅₀ of Zn-intoxicated animals. Treatment with Pb at two sublethal doses significantly increased GST activity, whereas treatment the animal with Cu caused significant inhibition in this enzyme. Snails exposed to 40% LD₅₀ Zn showed significant enhancement of GST, whereas snails exposed to 80% LD₅₀ showed ignificantly reduced GST activity. Biphasic responses were observed for CAT, GPx, and GST activities in snails exposed to Cu, Pb, and Zn, respectively. This study suggests that upregulation of the antioxidant enzyme activities, elevation of LPO, and the reduction in GSH content is related to oxidative stress in this species that could be useful as biomarkers for the evaluation of contaminated terrestrial ecosystems.     

Whey Protein Protects Liver Mitochondrial Function Against Oxidative Stress in Rats Exposed to Acrolein

Acrolein (AC) is one of the most toxic environmental pollutants, often associated with incomplete combustion of petrol, wood, and plastic, oil frying, and tobacco smoking, that causes oxidative damage to DNA and mitochondria. Considering that little is known about the protective effects of whey protein (WP) against AC-induced liver toxicity, the aim of our study was to learn more about them in respect to liver mitochondrial oxidative stress, respiratory enzymes, Krebs cycle enzymes, and adenosine triphosphate (ATP). To do that, we treated Sprague Dawley rats with daily doses of AC alone (5 mg/kg bw in 0.9 % NaCl solution), WP alone (200 mg/kg bw, in 0.9 % NaCl solution), or their combination by oral gavage for six days a week over 30 days. As expected, the AC group showed a drop in glutathione levels and antioxidant, transport chain, and tricarboxylic acid cycle enzyme activities and a significant rise in mitochondrial lipid peroxidation and protein carbonyl levels. Co-treatment with WP mitigated oxidative stress and improved enzyme activities. Judging by the measured parameters, WP reduced AC toxicity by improving bioenergetic mechanisms and eliminating oxidative stress.Key words: antioxidants, glutathione, oxidative phosphorylation enzymes, tricarboxylic acid cycle enzymes     

Induction of Oxidative Stress in the Epididymis of Rats After Subchronic Exposure to Epichlorohydrin

This study investigated the effects of epichlorohydrin (ECH) on spermatogenesis and antioxidant system in rats. An increase in the incidence of clinical signs, gross pathology and histopathology findings in the epididymidis, and sperm abnormalities and a decrease in the testicular spermatid counts, epididymal sperm counts, and sperm motility were observed at 30 mg/kg/day. Oxidative stress in the epididymal tissue was detected at ≥3.3 mg/kg/day. The results show that graded doses of ECH elicit depletion of antioxidant defense system and that the adverse effects on male reproductive function in ECH-treated rats may be due to the induction of oxidative stress.     

褪黑素对饮水氟染毒大鼠脑组织氧化应激的影响

目的研究不同浓度饮水氟染毒对大鼠脑氧化应激状态的影响及褪黑素(MEL)的干预作用。方法将清洁级初断乳Wistar大鼠34只随机分为5组,分别为对照组(蒸馏水,8只),60、120mg/L氟单独染毒组(各7只),60mg/L氟+5mg/kg褪黑素联合染毒组和120mg/L氟+5mg/kg褪黑素联合染毒组(各6只)。各组大鼠饮用相应浓度的氟化钠溶液;从第7周开始腹腔注射褪黑素溶液,连续染毒10周。染毒结束后,取脑组织测定氟含量和谷胱甘肽(GSH)、超氧化物歧化酶(SOD)、丙二醛(MDA)水平以及单纯氟染毒组大鼠血清褪黑素水平。结果与对照组比较,120mg/L氟单独染毒组以及60mg/L氟+5mg/kg褪黑素联合染毒组和120mg/L氟+5mg/kg褪黑素联合染毒组大鼠脑组织中氟含量均较高,差异有统计学意义(P0.01)。氟单独染毒各组之间比较,GSH、SOD、MDA含量差异无统计学意义。与相同浓度氟单纯染毒组比较,60mg/L氟+5mg/kgMEL联合染毒组大鼠脑组织中GSH含量和SOD活力均较高,但差异无统计学意义;120mg/L氟+5mg/kgMEL联合染毒组大鼠脑组织中GSH含量较高,SOD活力较低,差异均无统计学意义。各组大鼠脑组织中MDA含量间比较,差异无统计学意义。与对照组比较,60mg/L氟单独染毒组大鼠脑组织中褪黑素浓度略有升高,120mg/L氟单独染毒组大鼠脑组织中褪黑素浓度有下降趋势,但差异均无统计学意义(P0.05)。结论氟能透过血脑屏障在脑中蓄积,产生一定程度的氧化损伤,小剂量的褪黑素干预未能见到明显的抗氧化作用。     

Induction of Oxidative Stress in the Reproductive System of Rats after Subchronic Exposure to 2,3,7,8-Tetrachlorodibenzo-P-Dioxin

No abstract available.     

Hormonal Mechanisms Underlying Aberrant Sexual Differentiation in Male Rats Prenatally Exposed to Alcohol, Stress, or Both

The male offspring of rats exposed to restraint stress, alcohol, or both during late pregnancy show normally masculinized genitalia; however, sexual differentiation of behavior is dissociated from the external morphology. In contrast to controls, males exposed prenatally to stress, alcohol, or a combination of these factors exhibited the female lordotic pattern. Thus, all 3 prenatal treatments led to incomplete behavioral defeminization. Behavioral masculinization was not altered by fetal alcohol exposure alone, but a significant number of males that experienced prenatal stress alone failed to copulate. A more severe disruption of behavioral masculinization occurred when stress and alcohol were combined. Very few males exposed to the combination treatment mated with females. This study attempted to relate the effects of these treatments on sexual behavior to the postparturitional surge in plasma testosterone (T) that is known to influence the process of sexual differentiation. Prenatally stressed males, like control males showed a large, brief surge in plasma T that peaked 1 hr after delivery. Altered defeminization and masculinization were seen in prenatally stressed males, despite a normal postparturitional T surge. Fetal alcohol exposure, with or without concomitant stress, depressed T to the same extent right after birth and led to a similarly blunted T surge 1 hr later. Thus, equal disruption of the neonatal T pattern occurred in alcohol-alone males, who showed normal male copulatory behavior, and in alcohol-plus-stress males, whose behavior was severely attenuated. The results suggest that consideration of abnormal exposure to T during prenatal ontogeny may be required to understand the atypical sexual behaviors associated with these treatments.     

不同粒径纳米二氧化钛对大鼠氧化应激的影响

目的探讨不同粒径的纳米二氧化钛(TiO2)对大鼠氧化应激的影响。方法将50只SD大鼠随机分为空白对照组、溶剂对照组以及200、25和15 nm 3种粒径的TiO2染毒组。每天以40 mg TiO2进行皮肤染毒,连续染毒7 d,股动脉取血,检测血清中丙二醛(MDA)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和8-羟基脱氧鸟苷(8-OHdG)等指标。结果200、25和15 nm TiO2染毒组雌性大鼠血清SOD活性分别为(22.73±5.10)、(18.13±6.02)和(12.87±4.23)U/ml,空白对照和溶剂对照组分别为(28.77±3.05)和(24.43±5.92)U/ml,25 nm TiO2染毒组SOD活性较空白对照组下降(P0.05),15 nm TiO2染毒组较空白对照、溶剂对照和200 nm TiO2染毒组均下降(P0.05),而雄性大鼠各组间SOD活性无明显变化(P0.05);200、25和15 nm TiO2染毒组雌性大鼠血清8-OHdG分别为(7.91±0.66)、(8.02±0.93)和(8.93±0.56)ng/ml,空白对照和溶剂对照组分别为(7.24±0.69)和(7.66±0.69)ng/ml,15 nm TiO2染毒组8-OHdG含量较空白对照、溶剂对照组均升高(P0.05),而雄性大鼠各组间8-OHdG无明显变化(P0.05);CAT活性、MDA含量各组间差异无统计学意义(P0.05)。结论 25 nm和15 nm级TiO2皮肤染毒可引起大鼠氧化应激反应,该反应与TiO2的粒径大小有关,并具有性别差异。     

牛磺酸对急性甲基汞致大鼠脑氧化损伤的影响

目的观察牛磺酸对甲基汞致大鼠脑氧化损伤的影响。方法24只大鼠,分成3组,每组8只。第1组为对照组,第2组单纯染甲基汞组,第3组为牛磺酸预处理组。第1、2组皮下注射0．9％氯化钠溶液,第3组皮下注射2mmol／kg的牛磺酸。2h后,第1组腹腔注射0．9％氯化钠溶液,第2、3组腹腔注射25μmol／kg的氯化甲基汞溶液。染毒后24h处死大鼠,切取大脑皮质,测定大鼠大脑皮质汞含量,谷胱甘肽（GSH）和丙二醛（MDA）含量,谷胱甘肽过氧化物酶（GSH—Px）和超氧化物歧化酶（SOD）活力。结果染甲基汞24h后,与对照组比较,单纯染甲基汞组大鼠大脑皮质汞含量显著升高（P〈0．01）,GSH含量显著降低（P〈0．01）,MDA含量明显升高（P〈0．05）,而GSH—Px和SOD活力均明显下降（P〈0．05）;与单纯染甲基汞组比较,牛磺酸干预组大鼠大脑皮质汞含量差异无统计学意义（P〉0．05）,GSH含量明显升高（P〈0．05）和MDA含量明显下降（P〈0．05）,而GSH—Px活力显著回升（P〈0．01）和SOD活力明显回升（P〈0．05）。结论牛磺酸对急性甲基汞致大鼠脑氧化损伤有一定拮抗作用。     

p,p'-DDE对青春前期大鼠睾丸组织氧化应激及凋亡的影响

目的 研究p,p'-DDE对青春前期大鼠睾丸组织氧化应激及凋亡的影响.方法 将健康清洁级22日龄雄性SD大鼠25只按体重随机分为5组,分别为对照组(玉米油)、低(20 ms/kg)、中(60 mg/kg)、高(100 mg/kg)剂量P,p'-DDE染毒组和VitE干预组(100mg/kg p,p'-DDE+100mg/kg Vit E),每组5只.采用腹腔注射方式进行染毒,注射容积为10ml/kg,每隔1 d染毒1次,共10 d.染毒结束后,处死动物,取睾丸称重,并计算睾丸脏器系数;将睾丸制备组织切片和组织匀浆,分光光度计法测定大鼠睾丸组织超氧化物歧化酶(SOD)活力、丙二醛(MDA)含量和谷胱甘肽过氧化物酶(GSH-Px)活力,采用TUNEL法检测睾丸组织的细胞凋亡情况.结果 各组动物染毒前体重及染毒期间体重变化无差异.大鼠睾丸重量及其脏器系数间比较,差异无统计学意义(P＞0.05).与对照组比较,高、中、低剂量p,p'-DDE染毒组SOD活力降低,中、高剂量p,p'-DDE染毒组MDA含量升高,高剂量p,p'-DDE染毒组GSH-Px活力下降,差异均有统计学意义(P＜0.05).与高剂量p,p'-DDE染毒组比较,Vit E干预组SOD活力升高,差异有统计学意义(P＜0.05).Vit E干预组和高剂量p,p'-DDE染毒组MDA含量和GSH-Px活力间比较,差异无统计学意义(P＞0.05).高、中、低剂量p,p'-DDE染毒组和对照组均有睾丸细胞凋亡情况发生,对照组中凋亡细胞稀少;随着p,p'-DDE染毒剂量的升高,凋亡细胞数也逐渐增多,以精原细胞和精母细胞为主,伴有支持细胞.与对照组比较,高、中、低剂量P,p'-DDE染毒组的细胞凋亡指数均升高,差异有统计学意义(P＜0.05);Vit E干预组的细胞凋亡指数低于高剂量p,p'-DDE染毒组,差异有统计学意义(P＜0.05).结论 p,p'-DDE可通过引发睾丸组织氧化应激而诱导细胞凋亡.     

Lutein Can Alleviate Oxidative Stress,Inflammation, and Apoptosis Induced by Excessive Alcohol to Ameliorate Reproductive Damage in Male Rats

Chronic excessive alcohol intake may lead to male reproductive damage. Lutein is a carotenoid compound with antioxidant activity. The purpose of this study was to observe the effect of lutein supplementation on male reproductive damage caused by excessive alcohol intake. In this study, an animal model of excessive drinking (12 mL/(kg.bw.d)) for 12 weeks was established and supplemented with different doses of lutein (12, 24, 48 mg/(kg.bw.d)). The results showed that the body weight, sperm quality, sex hormones (FSH, testosterone), and antioxidant markers (GSH-Px) decreased significantly, while MDA and inflammatory factors (IL-6, TNF-α) increased significantly in the alcohol model group when compared to the normal control group. After 12 weeks of high-dose lutein supplementation with 48mg/(kg.bw.d), the spermatogenic ability, testosterone level, and the activity of marker enzymes reflecting testicular injury were improved. In addition, high-dose lutein supplementation downregulated the NF-κB and the pro-apoptosis biomarkers (Bax, Cytc and caspase-3), whereas it upregulated the expression of Nrf2/HO-1 and the anti-apoptotic molecule Bcl-2. These findings were fully supported by analyzing the testicular histopathology and by measuring germ cell apoptosis. In conclusion, lutein protects against reproductive injury induced by excessive alcohol through its antioxidant, anti-inflammatory, and anti-apoptotic properties.     

锌诱导肾脏Ⅰ型金属硫蛋白改善糖尿病大鼠肾脏氧化应激

<正>锌是金属硫蛋白(metallothionein,MTs)基因表达的诱导因子[1]。MTs是富含半胱氨酸、可诱导的、多功能、小分子量金属结合蛋白,在抗氧化、维持微量元素自稳态、重金属解毒等方面有重要作用[2]。本研究以口服硫酸锌诱导糖尿病大鼠肾脏MT-1基因表达,探讨其对糖尿病肾病的保护作用。     

Changes in Sperm Characteristics and Induction of Oxidative Stress in the Testis and Epididymis of Experimental Rats by a Herbicide, Atrazine

To study the effects of atrazine on reproductive functions and testicular and epididymal antioxidant defense, rats were exposed to 0, 120, or 200 mg/kg body weight atrazine orally for 7 and 16 days. Animals exposed to the high-dose atrazine had their body weights, feed intake, and reproductive organs weights significantly reduced, whereas testicular weights remain unaffected independent of the dose used. In comparison to control, glutathione (GSH) and glutathione-S-transferase (GST) activities were elevated in the high-dose group, whereas the activity of superoxide dismutase (SOD), catalase (CAT); ascorbate (AA), and malondialdehyde (MDA) levels and hydrogen peroxide production were unchanged in the testis during the 7-day-exposure protocol. When atrazine treatment was increased to 16 days, GSH levels remained unchanged, but lipid peroxidation levels were significantly increased in both the testes and epididymides. This corresponded to the significant diminution in the activities of GST and SOD. CAT activities were unaffected in the testes and then dropped in the epididymides. γ-Glutamyl transferase (γ-GT) activities increased during both studies, whereas AA levels remained unaffected (p < 0.05). Atrazine exposure has a dose-dependent adverse effect on the testicular and epididymal sperm numbers, motility, viability, morphology, and daily sperm production. Although the testes of the atrazine-treated animals appear normal, few tubules had mild degeneration with the presence of defoliated cells. Likewise, no perceptible morphological changes were observed in the epididymis. The results suggest that atrazine impairs reproductive function and elicits a depletion of the antioxidant defense system in the testis and epididymis, indicating the induction of oxidative stress.     

铬化合物对大鼠不同组织DNA－蛋白质交联物形成的探讨

用铬酸钾对大鼠腹腔注射染毒，以敏感的（１２５）Ｉ－后标记新技术检测不同组织ＤＮＡ－蛋白质交联（ＤＰＣ）的形成情况。结果显示铬酸钾急性染毒后引起白细胞、肝和肾ＤＰＣ明显升高并有剂量反应关系（Ｐ＜０．０５），但无肺ＤＰＣ升高；小量多次染毒结果也与一次染毒相一致。表明ＤＰＣ能反映铬化合物对白细胞和内部器官的遗传毒性，可作为毒作用分子生物标记。结果中还发现白细胞ＤＰＣ的升高比其他组织更明显并与肝ＤＰＣ有相关性（ｒ＝０．９７，Ｐ＜０．０５）。提示白细胞ＤＰＣ可作为某些内部器官的替代物应用于人群生物监测。     

高浓度矽尘接触对大鼠氧化应激的作用研究

目的探讨大鼠高浓度矽尘接触过程中是否存在氧化应激反应。方法选40只SPF级Wistar雄性大鼠随机分为4组,即高剂量染尘组（1 000mg/m^3）、中剂量染尘组（500mg/m^3）、低剂量染尘组（100mg/m^3）和对照组,选用自然动式染尘装置每天染尘2h。染尘49d后处死大鼠,测定肺组织匀浆超氧化物歧化酶（SOD）、总抗氧化能力（T-AOC）活性及丙二醛（MDA）、还原性谷胱甘肽（GSH）含量。结果长时间、高浓度矽尘接触降低大鼠肺组织的SOD（30.25±0.49）U/ml、T-AOC活性（7.93±0.74）kU/L和GSH（2.34±0.96）g/L含量,同时MDA（5.65±0.13）nmol/ml水平升高,与对照组比较,差异有统计学意义（P〈0.01）。结论大鼠高浓度矽尘接触过程早期炎症反应发生可能与机体氧化应急有关。     

Dose Addition in the Induction of Craniofacial Malformations in Zebrafish Embryos Exposed to a Complex Mixture of Food-Relevant Chemicals with Dissimilar Modes of Action

Background: Humans are exposed to combinations of chemicals. In cumulative risk assessment (CRA), regulatory bodies such as the European Food Safety Authority consider dose addition as a default and sufficiently conservative approach. The principle of dose addition was confirmed previously for inducing craniofacial malformations in zebrafish embryos in binary mixtures of chemicals with either similar or dissimilar modes of action (MOAs).Objectives: In this study, we explored a workflow to select and experimentally test multiple compounds as a complex mixture with each of the compounds at or below its no observed adverse effect level (NOAEL), in the same zebrafish embryo model.Methods: Selection of candidate compounds that potentially induce craniofacial malformations was done using in silico methods—structural similarity, molecular docking, and quantitative structure–activity relationships—applied to a database of chemicals relevant for oral exposure in humans via food (EuroMix inventory, n=1,598). A final subselection was made manually to represent different regulatory fields (e.g., food additives, industrial chemicals, plant protection products), different chemical families, and different MOAs.Results: A final selection of eight compounds was examined in the zebrafish embryo model, and craniofacial malformations were observed in embryos exposed to each of the compounds, thus confirming the developmental toxicity as predicted by the in silico methods. When exposed to a mixture of the eight compounds, each at its NOAEL, substantial craniofacial malformations were observed; according to a dose–response analysis, even embryos exposed to a 7-fold dilution of this mixture still exhibited a slight abnormal phenotype. The cumulative effect of the compounds in the mixture was in accordance with dose addition (added doses of the individual compounds after adjustment for relative potencies), despite different MOAs of the compounds involved.Discussion: This case study of a complex mixture inducing craniofacial malformations in zebrafish embryos shows that dose addition can adequately predicted the cumulative effect of a mixture of multiple substances at low doses, irrespective of the (expected) MOA. The applied workflow may be useful as an approach for CRA in general. https://doi.org/10.1289/EHP9888     

Redox and Essential Metal Status in The Brain of Wistar Rats Acutely Exposed To a Cadmium and Lead Mixture

Most Pb and Cd neurotoxicity studies investigate exposure to either of the toxic metals alone, while data on co-exposure are scarce. The aim of our study was to fill that gap by investigating acute combined effects of Pb and Cd on redox and essential metal status in the brain of Wistar rats. Animals were randomised in four groups of six to eight rats, which received 15 or 30 mg/kg of Cd, 150 mg/kg of Pb, or 150 mg/kg of Pb + 15 mg/kg of Cd by gavage. The fifth, control, group received distilled water only. Co-treatment with Pb and Cd induced significant increase in malondialdehyde (MDA) and thiobarbituric acid-reactive substances (TBARS) compared to control and groups receiving either metal alone. This is of special importance, as MDA presence in the brain has been implicated in many neurodegenerative disorders. The groups did not significantly differ in Zn, Cu, Mn, and Fe brain levels. Our findings highlight the importance of metal mixture studies. Neurotoxicity assessments of single chemicals do not provide a real insight into exposure to mixtures in real life. Further research should look into interactions between these metals to reveal complex molecular mechanisms of their neurotoxicity.