Cadmium intoxication of pregnant rats and fetuses: interactions of copper supplementation

Effects of cadmium on liver function in turtle Mauremys reevesii

This research was designed to investigate the effects of cadmium (Cd) on liver function in turtle Mauremys reevesii. Turtles were divided into 4 groups at random. The turtles were injected intraperitoneally with Cd at 0, 7.5, 15, 30 mg kg-1 Cd chloride separately. Liver index was calculated. The activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and the content of TP in liver were examined with biochemical methods. The results indicated that the liver index of turtles changed obviously only at higher dose and longer time. The activities of ALT and AST in liver increased with prolongation of exposure time in a dose-dependent manner. TP content in liver was lower than that in the control. In summary, Cd had an obvious toxic effect on liver tissues of freshwater turtle Mauremys reevesii, and it was dose dependent with the extension of exposure time. But the results also showed that the turtle had strong tolerance to Cd.

Telomeres, oxidative stress, and timing for spontaneous term and preterm labor

Telomeres are nucleoprotein complexes located at the distal ends of chromosomes. In adults, progressive telomere shortening occurs throughout the lifetime and is thought to contribute to progressive aging, physiological senescence, multiorgan dysfunction, and ultimately, death. As discussed in this review, multiple lines of evidence provide support for the biological plausibility that a telomere-based clock mechanism also determines the length of gestation, leading to the onset of labor (parturition). After telomere expansion at the beginning of pregnancy, the telomere lengths in the gestational tissues (ie, the placenta and fetal membranes) progressively shorten throughout the remainder of pregnancy. The rate of telomere shortening can be accelerated by conditions that affect the mother and result in oxidative stress. Preterm births in the United States are associated with multiple risk factors that are linked with increased oxidative stress. Antioxidant vitamins (ie, vitamins E and C) mitigate the effects of oxidative stress and delay or prevent telomere shortening. Clinical trials with vitamins E and C and with multivitamins started during the periconception period have been associated with reduced rates of preterm births. In the United States, African-American women have a 2-3-fold higher rate of preterm birth. African-American women have multiple risk factors for premature birth, all of which are distinct and potentially additive with regard to epigenetic telomere shortening. The "weathering effect" is the hypothesis to explain the increased rates of chronic illness, disabilities, and early death observed in African-Americans. With regard to pregnancy, accelerated weathering with the associated telomere shortening in the gestational tissues would not only explain the preterm birth disparity but could also explain why highly educated, affluent African-American women continue to have an increased rate of preterm birth. These studies suggest that the racial disparities in preterm birth are potentially mediated by telomere shortening produced by lifetime or even generational exposure to the effects of systemic racism and socioeconomic marginalization. In conclusion, this review presents multiple lines of evidence supporting a novel hypothesis regarding the biological clock mechanism that determines the length of pregnancy, and it opens the possibility of new approaches to prevent or reduce the rate of spontaneous preterm birth.

Predictors of toxic metal exposures among US women of reproductive age

BACKGROUND

Arsenic, cadmium, lead, and mercury are ubiquitous toxicants that may be especially harmful to unborn children. We therefore sought to identify temporal trends and predictors of toxic metal biomarkers among US women of reproductive age, including those who were pregnant and/or breastfeeding.

METHODS

Interviews and examinations were performed among a representative sample of women, aged 20-44 years, as part of the 2003-2014 National Health and Nutrition Examination Surveys. A range of sociodemographic, lifestyle, and dietary factors were evaluated as predictors of urinary inorganic arsenic, urinary cadmium, blood mercury, and blood lead concentrations.

RESULTS

Levels of all four toxic metal biomarkers declined during the study period. Older age, racial/ethnic minorities, and a birthplace outside of the US were independently associated with higher toxic metal concentrations. Associations were similar for women who were pregnant or breastfeeding and those who were not.

CONCLUSION

US women of reproductive age were exposed to lower levels of toxic metals in 2013-2014 compared to 2003-2004. However, because the long-term health effects of early life exposures are unclear, public health efforts to address toxic metals should pay particular attention to older, nonwhite, and foreign-born women if they are pregnant or planning to become pregnant.

Copper attenuates early and late biochemical alterations induced by inorganic mercury in young rats

Mercury (Hg), a divalent metal, produces adverse effects predominantly in the renal and central nervous systems. The aim of this study was to determine the effectiveness of copper (Cu) in prevention of mercuric mercury (Hg²⁺)-mediated toxic effects as well as the role metallothioneins (MT) play in this protective mechanism in young rats. Wistar rats were treated subcutaneously with saline (Sal) or CuCl₂.2H₂O (Cu 2.6 mg/kg/day) from 3 to 7 days old and with saline or HgCl₂ (Hg 3.7 mg/kg/day) from 8 to 12 days old. The experimental groups were (1) Sal-Sal, (2) Cu-Sal, (3) Sal-Hg, and (4) Cu-Hg. MTs and metal contents were determined at 13 and 33 days of age. Porphobilinogen synthase (PBG-synthase) activity as well as renal and hepatic parameters were measured at 33 days. At 13 day, Hg²⁺ exposure increased hepatic MT, Hg, zinc (Zn) and iron (Fe) levels, in kidney elevated Cu and Hg and decreased renal Fe concentrations, accompanied by elevated blood Hg levels. At 33 days, Hg²⁺ exposure inhibited renal PBG-synthase activity, increased serum urea levels and lowered Fe and Mg levels. Copper partially prevented the rise in blood Hg and liver Fe noted at 13 days; and completely blocked urea rise and diminished renal PBG-synthase activity inhibition at 33 days. In 13-day-old rats, Cu exposure redistributed the Hg in the body, decreasing hepatic and blood levels while increasing renal levels, accompanied by elevated renal and hepatic MT levels in Hg²⁺-exposed animals. These results suggest that hepatic MT might bind to hepatic and blood Hg for transport to the kidney in order to be excreted.

ABBREVIATIONS

MT: metallothioneins; PBG-synthase: porphobilinogen synthase.

Copper or/and arsenic induce oxidative stress-cascaded, nuclear factor kappa B-dependent inflammation and immune imbalance, trigging heat shock response in the kidney of chicken

Excessive amount of copper (Cu) and inorganic arsenic (iAs) coexists in drinking water in many regions, this is associated with high risk of nephropathy, defined as chronic structural and functional disorders of the kidney. However, the underlying mechanisms are not well understood. In this study, a total of 72 day-old Hy-line chickens were exposed to 300 mg/kg copper sulphate or/and 30 mg/kg arsenic trioxide for 12 weeks. Indicators of oxidative stress, inflammation and heat shock proteins (HSPs) production were analyzed in kidney. The results showed that, when the toxicant was administrated alone, there is an antagonism between redox homeostasis during the first 4 weeks, which follows a collapse of antioxidant system manifested by damaged biomembrane structure. What's worse, oxidative damage-cascaded histopathological lesions were accompanied by increases of proinflammatory mediators and an imbalance of "Th1/Th2 drift" (Th, helper T cell) regulated by nuclear factor kappa B (NF-κB). Simultaneously, intense heat shock response went with the organism. The above-mentioned renal lesions and indicators changes were time-dependent, more complex and deteriorated effects were observed in Cu/iAs combined groups compared with the others. This study supports Cu and iAs have a synergistic type on the nephro-toxicological process additively. In conclusion, oxidative stress and inflammatory induced by Cu or/and iAs are potential mechanisms in their nephrotoxicity, increased heat shock response may play a renoprotection function in tissues damage.

Cadmium Handling, Toxicity and Molecular Targets Involved during Pregnancy: Lessons from Experimental Models

Even decades after the discovery of Cadmium (Cd) toxicity, research on this heavy metal is still a hot topic in scientific literature: as we wrote this review, more than 1440 scientific articles had been published and listed by the PubMed.gov website during 2017. Cadmium is one of the most common and harmful heavy metals present in our environment. Since pregnancy is a very particular physiological condition that could impact and modify essential pathways involved in the handling of Cd, the prenatal life is a critical stage for exposure to this non-essential element. To give the reader an overview of the possible mechanisms involved in the multiple organ toxic effects in fetuses after the exposure to Cd during pregnancy, we decided to compile some of the most relevant experimental studies performed in experimental models and to summarize the advances in this field such as the Cd distribution and the factors that could alter it (diet, binding-proteins and membrane transporters), the Cd-induced toxicity in dams (preeclampsia, fertility, kidney injury, alteration in essential element homeostasis and bone mineralization), in placenta and in fetus (teratogenicity, central nervous system, liver and kidney).

Acute mercury exposition of virgin, pregnant, and lactating rats: Histopathological kidney and liver evaluations

This work investigated the effects of mercury chloride (HgCl₂ ) acute exposure on virgin, pregnant and lactating rats by determination of renal and hepatic morphological and ultrastructural parameters and the expression of oxidative stress and stress tolerance markers, due to kidney and liver are the organs that more accumulate inorganic mercury. Adult Wistar rats virgin (90 days old), pregnant (18^th gestation day) and lactating (7^th lactation day) were injected once with HgCl₂ (5 mg/kg) or saline (controls). We observed that HgCl₂ exposure of virgin rats caused significant inflammatory infiltration and severe morphological variations, like glomeruli atrophy, dilatation of Bowman's capsule, tubular degeneration and hepatocytes alteration. Moreover, virgin rats presented mitochondrial modification, important oxidative stress and increase in stress tolerance proteins at both kidney and liver level, compared with virgin controls. In detail, virgin rats exposed to HgCl₂ presented significantly elevated level of inducible nitric oxide synthase, heat shock protein 27 and glucose regulated proteins 75 expressions at both renal tubular and hepatocytes level, respect untreated virgin rats. Interestingly, pregnant and lactating rats exposed to HgCl₂ presented weak renal and liver morphological alterations, showing weak inflammatory infiltration and no significant difference in structural mitochondrial transmembrane protein, oxidative stress markers and stress tolerance proteins expressions respect controls (virgin, pregnant and lactating rats). Although, both control and HgCl₂ -exposed pregnant and lactating rats showed renal glomeruli greater in diameter respect virgin rats. In conclusion, we believe that virgin rats are more sensitive to HgCl₂ toxicity respect pregnant and lactating rats. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1500-1512, 2017.

Lectin histochemistry for detecting cadmium-induced changes in the glycosylation pattern of rat placenta

Cadmium (Cd) is an industrial and environmental pollutant that produces toxic effects on gametogenesis, pre- and post-implantation embryos, and the placenta. Because the effects of acute Cd intoxication on the placenta are not well understood, we investigated changes in its glycosylated components in Cd treated dams at days 4, 7, 10 and 15 of gestation using lectin histochemistry. CdCl₂ was administered to pregnant rats; control animals received sterile normal saline. Placentas were processed for DBA, Con A, SBA, PNA, UEA-I, RCA-I and WGA lectin histochemistry to evaluate changes in the carbohydrate pattern of the placenta that might modify cell interactions and contribute to embryonic alterations. Lectin binding was analyzed in the yolk sac; trophoblast giant cells; trophoblast I, II and III; spongiotrophoblast cells and endovascular trophoblast cells in the chorioallantoic placenta. Our lectin binding patterns showed that Cd caused alteration of SBA and DBA labeling of trophoblast-derived cells, which suggested increased expressions of α and β GalNAc. Cd also caused decreased UEA-1 binding affinity, which indicated fewer α-L-Fuc residues in placentas of Cd treated dams. The nonreactivity in trophoblast I of the control placentas incubated with Con-A contrasted with the labeling in placentas of experimental dams, which indicated increased expression of terminal α-D-Man, and α-D-Glc residues. We found that Cd altered the reactivity of placenta to several lectins, which indicated modification of the glycotype presented by the fetal component of the placenta. We report that Cd exerts a deleterious effect on the glycosylation pattern of the placenta.

Chemical assessment of lead, cadmium, nitrate, and nitrite intakes with daily diets of children and adolescents from orphanages in Krakow, Poland

The aim of this study has been to measure the level of lead, cadmium, nitrates, and nitrites in the daily diets of children and adolescents from orphanages located in Krakow (Poland). Diets were collected over four seasons of 2009. The content of cadmium and lead was measured with flameless atomic absorption spectrometry. Nitrates and nitrites in diets were measured using the Griess colorimetric method. In all orphanages, the average intake of lead with daily diets, regardless of the season, ranged from 1.11 ± 0.15 to 22.59 ± 0.07 μg/kg bw/week. The average cadmium intake by children and adolescents ranged between 3.09 ± 0.21 and 20.36 ± 2.21 μg/kg bw/week and, for all orphanages, exceeded the tolerable weekly intake (TWI) level. Daily intake of nitrates and nitrites ranged respectively from 27 to 289 % and from 9 to 99 % of the acceptable daily intake (ADI). The youngest children, with lower body mass, were particularly sensitive to the excessive intakes of cadmium and nitrates.

Effects of sub-chronic Cd exposure on levels of copper, selenium, zinc, iron and other essential metals in rat renal cortex

Cd (Cd) is a nephrotoxic environmental pollutant that causes generalized proximal tubule dysfunction. Even though the specific mechanisms by which Cd damages the kidney have yet to be fully elucidated, there is evidence to suggest that some of these nephrotoxic effects may result from the ability of Cd to alter the levels and function of metals such as Cu, Se, Zn and Fe within the kidney. In order to further explore this issue, we examined the effects of subchronic Cd exposure on tissue levels of a panel of metals (Ca, Cu, Fe, K, Mg, Na, Se and Zn) in the rat renal cortex. Adult male Sprague-Dawley rats were treated with CdCl₂ (0.6 mg Cd/kg body weight in isotonic saline by subcutaneous injection, 5 days per week for 6, 9 or 12 weeks). At each time point, 24 h urine samples were collected and assayed for levels of protein, creatinine, β₂ microglobulin and cystatin C. Samples of renal cortex were removed and assayed for levels of the metals of interest by inductively-coupled mass spectrometry at Michigan State University. Results showed that at 9 and 12 weeks, Cd caused significant increases in urine volume and urinary protein with no change in creatinine excretion. Increases in the excretion of the urinary biomarkers β₂ microglobulin and cystatin C were evident after 6 weeks of Cd exposure. Results of the metal analyses showed that Cd caused significant increases in tissue levels of Cu and Se at all of the time points examined. Tissue levels of Zn were transiently elevated at 6 weeks but declined to control levels at 9 and 12 weeks. Cd caused a significant decrease in levels of Fe at 9 and 12 weeks. Cd had no effects on any of the other metals. Tissue levels of Cd were 530 ± 52, 863 ± 23, 837 ± 23 ppm dry weight at 6, 9 and 12 weeks, respectively. These results indicate that the early stages of Cd nephrotoxicity are associated with alterations in renal tissue levels of Cu, Se, Zn and Fe. The fact that the changes in levels of the metals occurred during the early stages of Cd toxicity raises the possibility that the alterations in renal cortical metal content may play some role in the pathophysiology or Cd-induced injury.

Association of maternal serum cadmium level during pregnancy with risk of preterm birth in a Chinese population

Cadmium (Cd) was a developmental toxicant that induces fetal malformation and growth restriction in mice. However, epidemiological studies about the association of maternal serum Cd level with risk of preterm birth were limited. This study was to investigate whether maternal serum Cd level during pregnancy is associated with risk of preterm birth in a Chinese population. Total 3254 eligible mother-and-singleton-offspring pairs were recruited. Maternal serum Cd level was measured by GFAAS. Based on tertiles, maternal serum Cd concentration was classified as low (LCd, <0.65 μg/L), medium (MCd, 0.65-0.94 μg/L) and high (HCd, ≥0.95 μg/L). Odds ratio (OR) for preterm birth was estimated using multiple logistic regression models. Results showed the rate of preterm birth among LCd, M-Cd and HCd was 3.5%, 3.8%, and 9.4%, respectively. Subjects with HCd had a significantly higher risk for preterm birth (OR: 2.86; 95%CI: 1.95, 4.19; P < 0.001) than did those with LCd. Adjusted OR for preterm birth was 3.02 (95%CI: 2.02, 4.50; P < 0.001) among subjects with HCd compared to subjects with LCd. Taken together, the above results suggest that maternal serum Cd level during pregnancy is positively associated with risk of preterm birth.

Possible protective role of elderberry fruit lyophilizate against selected effects of cadmium and lead intoxication in Wistar rats

The objective of this study was the investigation whether the administration of the elderberry fruit lyophilizate under exposure to cadmium(Cd) and (Pb) lead may protect against some effects of their toxic action in Wistar rats. Rats were fed with diets containing Cd (Cd 0.025 mg/kg b.m.) or Pb (Pb 0.025 mg /kg b.m.) with the addition of the freeze-dried elderberry fruits (BEF) in the amount of 5 %. BEF added to the diet with Cd significantly decreased the activity of AST and ALT compared to the rats fed with the control diet with Cd (C + Cd). Activity of glutathione peroxidase was significantly higher in the blood of rats fed with BEF diet compared with animals fed with BEF + Cd, BEF + Pb, and C + Pb diets. Addition of BEF to the diets with Cd or Pb significantly decreased the uric acid concentration compared to the level of this parameter in the serum of animals fed with control diets containing Cd or Pb. The level of the Cd significantly decreased in the livers of rodents fed with BEF + Cd diet as compared to the concentration of this metal in the livers of rats fed with C + Cd diet. Elderberry fruit lyophilizate did not protect against the increased concentration of Cd or Pb in kidneys and bones of experimental rats; however, it improved the function of livers and kidneys, especially of rats intoxicated with Cd.

Malondialdehyde and heavy metal concentrations in tissues of wild boar (Sus scrofa L.) from central Croatia

The aim of this research was to assess the degree of heavy metal (cadmium, lead and mercury) contamination of wild boars from central Croatia and thereby conduct further tests to connect the contamination to oxidative stress occurrence. The highest cadmium concentration was noticed in the kidneys of older boars, the lead concentration was approximately the same in the liver and kidneys, but it was much higher than the concentration in the muscles, while the highest mercury concentration was measured in the kidneys of all wild boars. The correlation between the malondialdehyde (MDA) and the heavy metal concentrations was higher in tissue samples taken from younger animals (1 to 3 years of age) than in the tissue samples taken from older animals (5 to 6 years of age). In the kidneys of all wild boars there was a statistically significant connection between the MDA and cadmium concentration; in the kidneys of younger wild boars there was a statistically significant connection between the MDA and lead concentration. Further research on this topic should focus on MDA potential to find its use, not only as a contamination biomarker in the area of ecotoxicology, but also in the evaluation of the hygienic acceptability of animal products.

Mammalian metallothioneins: properties and functions

Metallothioneins (MT) are a family of ubiquitous proteins, whose role is still discussed in numerous papers, but their affinity to some metal ions is undisputable. These cysteine-rich proteins are connected with antioxidant activity and protective effects on biomolecules against free radicals, especially reactive oxygen species. In this review, the connection between zinc(II) ions, reactive oxygen species, heavy metal ions and metallothioneins is demonstrated with respect to effect of these proteins on cell proliferation and a possible negative role in resistance to heavy metal-based and non-heavy metal-based drugs.