[Cell biology of heavy metal toxicity in vascular tissue]

The role of taurine through endoplasmic reticulum in physiology and pathology

Taurine is a sulfur-containing amino acid found in many cell organelles that plays a wide range of biological roles, including bile salt production, osmoregulation, oxidative stress reduction, and neuromodulation. Taurine treatments have also been shown to ameliorate the onset and development of many diseases, including hypertension, fatty liver, neurodegenerative diseases and ischemia-reperfusion injury, by exerting antioxidant, anti-inflammatory, and antiapoptotic effects. The endoplasmic reticulum (ER) is a dynamic organelle involved in a wide range of cellular functions, including lipid metabolism, calcium storage and protein stabilization. Under stress, the disruption of the ER environment leads to the accumulation of misfolded proteins and a characteristic stress response called the unfolded protein response (UPR). The UPR protects cells from stress and helps to restore cellular homeostasis, but its activation promotes cell death under prolonged ER stress. Recent studies have shown that ER stress is closely related to the onset and development of many diseases. This article reviews the beneficial effects and related mechanisms of taurine by regulating the ER in different physiological and pathological states, with the aim of providing a reference for further research and clinical applications.

Protection of cultured vascular endothelial cells against cadmium cytotoxicity by simultaneous treatment or pretreatment with manganese

Cadmium is a heavy metal that pollutes the environment and foods and is a risk factor for vascular disorders. We have previously demonstrated that pretreatment of vascular endothelial cells with zinc and copper protects the cells against cadmium cytotoxicity. In contrast, cadmium cytotoxicity was potentiated in cells following exposure to lead, thereby indicating that in vascular endothelial cells, cadmium cytotoxicity can be differentially modified by the co-occurrence of other heavy metals. In this study, we revealed that simultaneous treatment or pretreatment with manganese protects vascular endothelial cells against cadmium cytotoxicity. Intracellular accumulation of cadmium was observed to be reduced by simultaneous treatment with manganese, although not by pretreatment. The mRNA expression of metal transporters that regulate the uptake of both cadmium and manganese (ZIP8, ZIP14, and DMT1) remained unaffected by either simultaneous treatment or pretreatment with manganese, and simultaneous treatment with manganese suppressed the cadmium-induced expression of metallothionein but pretreatment with manganese did not exhibit such suppressive effect. Thus, the protection of vascular endothelial cells against cadmium cytotoxicity conferred by simultaneous treatment with manganese is assumed to be partially attributed to a reduction in the intracellular accumulation of cadmium, whereas the effects of pretreatment with manganese are independent of both the reduced intracellular accumulation of cadmium and the induction of metallothionein. These observations accordingly indicate that the protective effects of manganese are mediated via alternative (as yet unidentified) mechanisms.

[Elucidation and Application of Novel Action of Therapeutic Agents for Diabetic Neuropathy]

Epalrestat is the only aldose reductase inhibitor that is currently available for diabetic peripheral neuropathy. Oxidative stress impairs endothelial cells, thereby leading to numerous pathological conditions. Increasing antioxidative ability is important to prevent cellular toxicity induced by reactive oxygen species. Epalrestat increases antioxidant defense factors such as glutathione and γ-glutamylcysteine ligase in vascular endothelial cells through activation of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2). This increases suppression of oxidative stress-induced cellular toxicity. Cadmium is an industrial and environmental pollutant that targets the vascular endothelium. The vascular system is critically affected by cadmium toxicity. Therapeutic treatment against cadmium toxicity is chelation therapy that promotes metal excretion; however, cadmium chelators can cause renal toxicity. Therefore, safe and efficient therapeutic agents are required. Epalrestat suppresses cadmium-induced cytotoxicity in vascular endothelial cells through activation of Nrf2. In addition, epalrestat affects the intracellular levels of cadmium, cadmium transporter Zrt-Irt-like protein 8 (ZIP8), and metallothionein (MT). The upregulation of ZIP8 and MT may be involved in the suppression of cadmium-induced cytotoxicity by epalrestat. Drug repurposing is a new strategy for drug discovery in which the pharmacological action of existing medicines whose safety and pharmacokinetics have already been confirmed clinically and whose use has been approved is examined comprehensively at the molecular level. The results can be applied to the development of existing drugs for use as medicines for the treatment of other diseases. This review provides useful findings for future expansion of indications as research leading to drug repurposing of epalrestat.

Induction of ZIP8, a ZIP transporter, via NF-κB signaling by the activation of IκBα and JNK signaling in cultured vascular endothelial cells exposed to cadmium

Cadmium is an environmental pollutant that adversely affects various organs in the human body and is a well-known risk factor for cardiovascular diseases. These disorders are caused by the dysfunction of the vascular endothelial cells that cover the luminal surface of blood vessels. The ZIP transporter ZIP8 is one of the primary importers of cadmium, and its expression appears to be important for the sensitivity of vascular endothelial cells to cadmium. In the present study, we investigated the influence of ZIP8 on cadmium-induced cytotoxicity in vascular endothelial cells, the induction of ZIP8 expression by cadmium, and its action mechanism in vascular endothelial cells. The study revealed that: (1) cadmium cytotoxicity in vascular endothelial cells was potentiated by the overexpression of ZIP8, and the intracellular accumulation of cadmium in the cells was increased; (2) cadmium highly induced the expression of ZIP8, but not other ZIPs; (3) lead and methylmercury moderately induced ZIP8 expression, but the other tested metals did not; (4) the induction of ZIP8 expression by cadmium was mediated by both NF-κB and JNK signaling, and the accumulation of NF-κB in the nucleus was regulated by JNK signaling. Particularly, it was found that cadmium activated NF-κB to transfer it into nuclei and activated JNK to stabilize NF-κB in nuclei, resulting in the induction of ZIP8 expression. This induction appears to be crucial for cadmium cytotoxicity in vascular endothelial cells.

Immunomodulation by heavy metals as a contributing factor to inflammatory diseases and autoimmune reactions: Cadmium as an example

Cadmium (Cd) represents a unique hazard because of the long biological half-life in humans (20-30 years). This metal accumulates in organs causing a continuum of responses, with organ disease/failure as extreme outcome. Some of the cellular and molecular alterations in target tissues can be related to immune-modulating potential of Cd. This metal may cause adverse responses in which components of the immune system function as both mediators and effectors of Cd tissue toxicity, which, in combination with Cd-induced alterations in homeostatic reparative activities may contribute to tissue dysfunction. In this work, current knowledge concerning inflammatory/autoimmune disease manifestations found to be related with cadmium exposure are summarized. Along with epidemiological evidence, animal and in vitro data are presented, with focus on cellular and molecular immune mechanisms potentially relevant for the disease susceptibility, disease promotion, or facilitating development of pre-existing pathologies.

Comparison of blood lead concentrations in patients with acute ischemic stroke and healthy subjects

BACKGROUND AND OBJECTIVES

Stroke is the main cause of mortality and long-term disability in the general population. With the increased application of metals in industries and human environment, lead has become a health hazard. In this study, we aimed to evaluate the relationship between the blood concentration of lead and the incidence of acute stroke.

MATERIALS AND METHODS

We performed this study during 2016-17 at Vali-e-Asr Hospital in Birjand, Iran, among 80 ischemic stroke patients visiting the hospital and 80 healthy gender- and age-matched controls. Blood lead concentration (BLC) was measured using graphite furnace atomic absorption spectrometry.

RESULTS

BLC medians in the case and control groups were 20.65 [5.37-34.87] μg/dL and 2.65 [1.75-13.85] μg/dL, respectively (p < 0.05). The case group had significantly lower mean levels of HDL and phosphors, whereas the mean levels of white blood cells and uric acid were higher in this group. After adjusting for lipid profile and fasting blood sugar, multiple logistic regression indicated that the serum levels of uric acid and BLC were significant for predicting ischemic stroke. It is estimated that the odds ratio of ischemic stroke increases by 1.04 per 1 μg/dl increase in BLC.

CONCLUSION

This study showed that lead can be a risk factor for ischemic stroke. Since it does not have any beneficial effects on the health of individuals, screening serum concentrations of lead can be considered as a preventive strategy for those at risk of stroke.

Aqueous bark extract of Terminalia arjuna protects against cadmium-induced hepatic and cardiac injuries in male Wistar rats through antioxidative mechanisms

Cadmium (Cd) is one of the most ubiquitous toxic heavy metal in the environment. The present study was conducted to evaluate the protective role of aqueous bark extract of Terminalia arjuna (TA) against Cd induced oxidative damage in hepatic and cardiac tissues as the TA bark extract has folkloric medicinal use in the treatment of various hepatic and cardiac disorders. Male Wistar rats were divided into 4 groups. The control group was treated with normal saline as the vehicle; the second group orally administered with TA (20 mg/kg bw) daily for 15 days; the third group injected with Cd-acetate (0.44 mg/kg bw, s.c.) every alternate day for a period of 15 days; and the fourth group was administered with TA, 60 min prior to Cd treatment. The biomarkers of organ damage were significantly increased in the Cd treated groups. Besides, a significant alteration in the tissue levels of biomarkers of oxidative stress, the activities and the levels of antioxidant enzymes was observed following treatment with Cd. Additionally, some of the enzymes were found to be inhibited uncompetitively by Cd when tested in an in vitro system. Furthermore, evidence gathered from studies on the histological parameters and mitochondrial membrane potential in both the tissues argue in favour of the possible protective role of TA against Cd induced damage. Finally, gas chromatography-mass spectrometry revealed the presence of eight major bioactive phytochemicals in aqueous bark extract of TA having potent free radical scavenging property. The results indicate that the extract could protect hepatic and cardiac tissues against Cd-induced oxidative stress mediated damages through antioxidant mechanism(s).

Association between heavy metal levels and acute ischemic stroke

Background

Few studies have examined the relationship between the amounts of heavy metal and stroke incidence. The aim of this study was to explore the relationship between levels of heavy metals, including Pb, Hg, As, and Cd, in patients with acute ischemic stroke (AIS).

Methods

We selected patients with first-ever AIS onset within 1 week as our study group. Healthy controls were participants without a history of stroke or chronic disease, except hypertension. The serum levels of Pb, Hg, As, and Cd in participants in the experimental and control groups were determined. All participants received a 1-g infusion of edetate calcium disodium (EDTA). Urine specimens were collected for 24 h after EDTA infusion and measured for heavy metal levels.

Results

In total, 33 patients with AIS and 39 healthy controls were enrolled in this study. The major findings were as follows: (1) The stroke group had a significantly lower level of serum Hg (6.4 ± 4.3 μg/L vs. 9.8 ± 7.0 μg/L, P = 0.032, OR = 0.90, 95% CI = 0.81–0.99) and a lower level of urine Hg (0.7 ± 0.7 μg/L vs. 1.2 ± 0.6 μg/L, P = 0.006, OR = 0.27, 95% CI = 0.11–0.68) than the control group. (2) No significant difference in serum Pb (S-Pb), As (S-As), and Cd (S-Cd) levels and urine Pb (U-Pb), As (U-As) and Cd (U-Cd) levels was observed in either group.

Conclusions

Our study found low levels of serum and urine Hg in first-ever patients with AIS, providing new evidence of dysregulated heavy metals in patients with AIS.

Electronic supplementary material

The online version of this article (10.1186/s12929-018-0446-0) contains supplementary material, which is available to authorized users.

Partial contribution of the Keap1-Nrf2 system to cadmium-mediated metallothionein expression in vascular endothelial cells

Cadmium is an environmental electrophile that modifies protein reactive thiols such as Kelch-like ECH-associated protein 1 (Keap1), a negative regulator of nuclear factor-erythroid 2-related factor 2 (Nrf2). In the present study, we investigated a role of the Keap1-Nrf2 system in cellular response to cadmium in vascular endothelial cells. Exposure of bovine aortic endothelial cells to cadmium resulted in modification of Keap1 and Nrf2 activation, thereby up-regulating not only its typical downstream proteins but also metallothionein-1/2. Experiments with siRNA-mediated knockdown of Nrf2 or Keap1 supported participation of the Keap1-Nrf2 system in the modulation of metallothionein-1/2 expression. Furthermore, chromatin immunoprecipitation assay showed that Nrf2 was recruited to the antioxidant response element of the promoter region of the bovine metallothionein-2 gene in the presence of cadmium. These results suggest that the transcription factor Nrf2 plays, at least in part, a role in the changes in metallothionein expression mediated by exposure to cadmium.

[Activation of cellular defense mechanism by organic-inorganic hybrid molecules]

Organic-inorganic hybrid molecules can exhibit biological activities by controlling the activities of their individual components. These molecules can be applied as seed/lead compounds in drug development, and can be used as molecular probes in chemical biology for the elucidation of the molecular mechanisms of biological systems. In this review, we introduce copper diethyldithiocarbamate (Cu10), a copper complex, as a compound that activates nuclear factor erythroid 2-related factor 2 (Nrf2) and induces metallothionein, which are the key cellular defense factors against toxic metals and oxidative stress in vascular endothelial cells. It was found that neither the complexes with the same ligand and other metal ions (including zinc and iron) nor the ligand alone was inactive. Therefore, both copper ion and the ligand of Cu10 are essential components for the biological functioning of the complex. In addition, Cu10 may be useful in clarifying the molecular mechanism underlying metallothionein induction in vascular endothelial cells.

Cellular defense mechanisms against lead toxicity in the vascular system

Lead is a toxic heavy metal that can cause a range of health problems. In this context, the vascular system is a particular target of the deleterious effects of lead. Lead exerts its toxicity through substitution of other divalent cations such as calcium and zinc, resulting in disruption of homeostasis. Based on the evidence that lead up-regulates endoplasmic reticulum (ER) chaperone glucose-regulated protein 78 (GRP78) and/or antioxidant proteins such as hemeoxygenase-1, it is believed that the heavy metal is able to induce ER and/or oxidative stress in cells. These events also suggest that the unfolded protein response (UPR) system and the antioxidant defense system Kelch-like ECH-associated protein 1-nuclear factor (NF)-E2-related factor 2 (Keap1-Nrf2) play a critical role in adaptive response to lead. In this review, we summarize recent progress in lead toxicity in terms of cellular defense systems, including stress proteins and transcription factors involved in the vascular system.

Bismuth protects against arsenite-induced inhibition of proteoglycan synthesis in cultured vascular endothelial cells

Chronic ingestion of arsenic is associated with an increased risk of vascular disease such as atherosclerosis. Previously, we showed that arsenite inhibits the synthesis of general proteoglycans (PGs), which are key molecules in the progression of atherosclerosis, in vascular endothelial cells. In the present study, we investigated the effect of several metals on arsenite-induced inhibitory effect in endothelial cells. The results indicate that, after 24-hr incubation, the inhibition of PG synthesis caused by sodium arsenite was protected by bismuth nitrate but not zinc sulfate, manganese chloride, nickel chloride or cobalt chloride. The accumulation of arsenic in the cell layer was significantly decreased by bismuth after 12-hr incubation and that of bismuth was also decreased by arsenite. It was therefore suggested that the protective effect of bismuth against the inhibitory effect of arsenite on PG synthesis in vascular endothelial cells may be due, at least in part, to the decrease in cellular arsenic accumulation.

Protective effect of pretreatment with cilostazol on cytotoxicity of cadmium and arsenite in cultured vascular endothelial cells

Cilostazol, an antiplatelet drug, exhibits antiatherogenic effects. The purpose of the present study was to determine the effect of cilostazol on the cytotoxicity of cadmium (Cd) and arsenite (iAs(III)), which involved in the pathogenesis of vascular disorders such as atherosclerosis, in cultured vascular endothelial cells. Cytotoxicity was evaluated by the lactate dehydrogenase leakage assay and morphological observation. Cd (10 µM) -induced cytotoxicity was prevented by pretreatment with cilostazol (30 and 100 µM) and simultaneous treatment with cilostazol (100 µM). On the other hand, iAs(III)-induced cytotoxicity was blocked by pretreatment with cilostazol (30 and 100 µM) but not simultaneous treatment with cilostazol. The mRNA level and the protein level of metallothionein (MT) were significantly increased by cilostazol in the cells. These results suggested, therefore, that pretreatment with cilostazol effectively prevents the cytotoxicity of Cd and iAs(III) in cultured vascular endothelial cells, at least in part through the induction of MT synthesis.

An adsorptive transfer technique coupled with brdicka reaction to reveal the importance of metallothionein in chemotherapy with platinum based cytostatics

The drugs based on platinum metals represent one of the oldest, but also one of the most effective groups of chemotherapeutic agents. Thanks to many clinical studies it is known that resistance of tumor cells to drugs is a frequent cause of chemotherapy failure. With regard to platinum based drugs, multidrug resistance can also be connected with increased expression of low-molecular weight protein metallothionein (MT). This study aimed at investigating the interactions of MT with cisplatin or carboplatin, using the adsorptive transfer technique coupled with differential pulse voltammetry Brdicka reaction (AdTS DPV Brdicka reaction), and a comparison of in vitro results with results obtained in vivo. The results obtained from the in vitro study show a strong affinity between platinum based drugs and MT. Further, we analyzed extracts of neuroblastoma cell lines treated with cisplatin or carboplatin. It is clear that neuroblastoma UKF-NB-4 cisplatin-resistant and cisplatin-sensitive cell lines unlikely respond to the presence of the platinum-based cytostatics cisplatin and carboplatin. Finally, we determined the level of MT in samples from rabbits treated with carboplatin and patients with retinoblastoma treated with the same drug.

Cadmium toxicity at low concentration on rabbit spermatozoa motility, morphology and membrane integrity in vitro

In this study the effect of cadmium on various parameters of spermatozoa motility, morphology as well as on the spermatozoa membrane integrity in rabbits was analyzed in vitro, experimental concentrations ranging from 0.62 to 0.98 micro g CdCl(2)/mL. Pooled rabbit (n = 5) semen was cultured in vitro with cadmium and subsequently diluted to various experimental concentrations apart from control which received no cadmium exposure. Using computer assisted semen analysis method (CASA) we detected decrease of total motility with in the higher concentration range at Time 0. However, with increasing time (after 1 and 2 h of culture), cadmium exerted deleterious effect leading to significant motility reduction in comparison to control. A similar trend was exhibited in case of progressive motility, too. Most of the spermatozoa distance and velocity parameters detected no significant change in comparison to control at the beginning of culture (Time 0), although the toxic effect became significant (P < 0.05) with the passage of culture time (Times 1 and 2 h) in all concentrations. Analysis of spermatozoa morphology detected significant (P < 0.05) alterations at higher concentrations. At higher concentrations acrosomal changes, head without flagellum/separated flagellum, broken flagellum and other abnormalities were significantly higher (P < 0.05), while knob-twisted flagellum and small heads differed significantly (P < 0.05) in comparison to control at all concentrations. In regards to flagellum torso, flagellum ball and retention of cytoplasmic drop statistically higher values (P < 0.05) were noted at the maxium experimental concentration only. Annexin analysis for detection of spermatozoa with disordered membranes revealed higher occurrence of positive spermatozoa in cadmium exposed groups. Annexin-positive reactions suggested alterations in anterior part of head (acrosome) and in flagellum (mitochondrial segment) of spermatozoa. This paper underlines that cadmium is highly toxic for rabbit spermatozoa, as visualized by the toxic effects on parameters of spermatozoa motility, morphology and membrane integrity. The toxic effect is more drastic at higher concentrations. This study also indicates that cadmium requires a minimum one hour incubation time to exert its deletorious effects on various parameters of spermatozoa, particularly at low concentrations.

Cadmium and cardiovascular diseases: cell biology, pathophysiology, and epidemiological relevance

Today cardiovascular diseases (CVDs) are the killer number one world wide. In 2004 an estimated 17.1 million people died due to CVDs and this number will further increase to an estimated 23.6 million by 2030. Importantly, currently known risk factors, like hypertension, and hypercholesterolemia, can only be made responsible for about 50-75% of all CVDs, highlighting the urgent need to search for and define new CVD risk factors. Cadmium (Cd) was shown to have the potential to serve as one such novel risk factor, as it was demonstrated-in vitro, in animal studies, and in human studies-that Cd causes atherosclerosis (the basis of most CVDs). Herein, we discuss the molecular and cellular biological effects of Cd in the cardiovascular system; we present concepts on the pathophysiology of Cd-caused atherosclerosis, and provide data that indicate an epidemiological relevance of Cd as a risk factor for CVDs.

Lead induces the expression of endoplasmic reticulum chaperones GRP78 and GRP94 in vascular endothelial cells via the JNK-AP-1 pathway

Lead, a ubiquitous heavy metal, is an important industrial and environmental pollutant that can target the vascular endothelium. To clarify the effects of lead on the unfolded protein response (UPR) and their significance in cytotoxicity, we examined the expression and function of endoplasmic reticulum (ER) chaperones glucose-regulated protein 78 (GRP78) and glucose-regulated protein 94 (GRP94) in vascular endothelial cells. We used bovine aortic endothelial cells as an in vitro model of the vascular endothelium. Exposure of vascular endothelial cells to lead nitrate resulted in a marked induction of GRP78 and GRP94 messenger RNA levels. In response to lead, the expression of GRP78 and GRP94 proteins also significantly increased in a dose- and time-dependent manner. In addition, small interfering RNA (siRNA)-mediated knockdown of GRP78 significantly enhanced lead-induced cytotoxicity. Compared with other metal(loid)s, including cadmium chloride, zinc sulfate, copper sulfate, and sodium arsenite, lead nitrate was found to be the most potent metal to induce these chaperones in endothelial cells. In the examined UPR pathways, lead increased the phosphorylation of inositol-requiring enzyme 1 (IRE1) and c-jun N-terminal kinase (JNK). Interestingly, the lead-induced upregulation of GRP78 and GRP94 was almost completely blocked by the JNK inhibitor SP600125 or activator protein-1 (AP-1) inhibitor curcumin. Taken together, these results suggest that lead induces ER stress, but the induction of GRP78 and GRP94 expression via the JNK-AP-1 pathway functions as a defense mechanism against lead-induced cytotoxicity in vascular endothelial cells.

Association of high body lead store with severe intracranial carotid atherosclerosis

OBJECTIVE

Lead is involved in the pathogenesis of atherosclerosis and hypertensive disease and may be related to cerebrovascular disease. We studied the association of body lead level with stroke subtypes and severity of cerebral atherosclerosis in order to identify the significance of lead exposure to cerebrovascular disease.

METHODS

From April, 2002 to March, 2005, we studied the lead level in all patients receiving digital subtraction angiography. Diameter stenosis at extracranial carotid, intracranial carotid and vertebrobasilar system was calculated according to the NASCET criteria. A blood sample and a mobilization test of 72-h urine sample were collected for lead measurement.

RESULTS

In a total of 213 subjects, 19 were free of stroke (blood lead level=4.62+/-2.41 microg/dL, body lead store=39.04+/-20.91 microg) and 194 were stroke patients (4.89+/-2.75 microg/dL, 45.13+/-29.8 microg; all stroke vs. non-stroke, P>0.05). In the 153 subjects with atherosclerotic origin, body lead store but not blood lead level in the intracranial carotid system was significantly higher in > or =50% group than <50% group (blood lead: 5.61+/-3.02 microg/dL vs. 4.80+/-2.50 microg/dL, Student's t-test, P=0.129; body lead store: 51.7+/-27.0 microg vs. 41.9+/-23.5 microg, Student's t-test, P=0.038, multivariate logistic regression, odds ratio=1.02, 95% CI: 1.00-1.03, P=0.043). However, there was no significant association between lead level and stenotic severity in extracranial and vertebrobasilar systems (P>0.05).

CONCLUSION

Our study demonstrated that long-term lead exposure as measured by body lead store might carry a potential risk of intracranial carotid atherosclerosis.

The vascular system as a target of metal toxicity

Vascular system function involves complex interactions among the vascular endothelium, smooth muscle, the immune system, and the nervous system. The toxic metals cadmium (Cd), arsenic (As), and lead (Pb) can target the vascular system in a variety of ways, ranging from hemorrhagic injury to subtle pathogenic remodeling and metabolic changes. Acute Cd exposure results in hemorrhagic injury to the testis, although some strains of animals are resistant to this effect. A comparison of Cd-sensitive with Cd-resistant mouse strains showed that expression of the Slc39a8 gene, encoding the ZIP8 transporter, in the testis vasculature endothelium is responsible for this difference. Endogenously, ZIP8 is a Mn(2+)/HCO(3)(-)symporter that may also contribute to Cd damage in the kidney. Chronic Cd exposure is associated with various cardiovascular disorders such as hypertension and cardiomyopathy and it is reported to have both carcinogenic and anticarcinogenic activities. At noncytotoxic concentrations of 10-100nM, Cd can inhibit chemotaxis and tube formation of vascular endothelial cells. These angiostatic effects may be mediated through disruption of vascular endothelial cadherin, a Ca(2+)-dependent cell adhesion molecule. With regard to As, ingestion of water containing disease-promoting concentrations of As promotes capillarization of the liver sinusoidal endothelium. Because capillarization is a hallmark precursor for liver fibrosis and contributes to an imbalance of lipid metabolism, this As effect on hepatic endothelial cells may be a pathogenic mechanism underlying As-related vascular diseases. With regard to Pb, perinatal exposure may cause sustained elevations in adult blood pressure, and genetically susceptible animals may show enhanced sensitivity to this effect. Taken together, these data indicate that the vascular system is a critical target of metal toxicity and that actions of metals on the vascular system may play important roles in mediating the pathophysiologic effects of metals in specific target organs.

Role of zinc in hemostasis: a review

Zinc is a multi-functional element that is found in almost 300 enzymes where it performs catalytic, co-catalytic, and/or structural functions. In 1982, Gordon et al. (Am J Clin Ntr 35:849-857, 1982) found that a low zinc diet caused poor platelet aggregation and increased bleeding tendency in adult males. This fact drew interest to the role of zinc in blood clotting. It has been shown that hyperzincemia predisposes to increased coagulability, and hypozincemia to poor platelet aggregation and increased bleeding time. The blood clotting disturbances can be regressed by appropriate zinc intake management. Considering the importance of zinc as an essential element, its participation in regulation of the equilibrium between pro- and anti-thrombotic factors originating in platelets and endothelium prompted further investigations.

The effect of cadmium in combination with zinc and selenium on ovarian structure in Japanese quails

In this study the effect of cadmium, cadmium+selenium and cadmium+zinc administration on the ovarian structure in Japanese quails was studied. The morphometric analysis of the relative volume of primary follicles detected the highest value in control group with a similar value in the group with administration of cadmium with selenium. Lower relative volume is reported in group with cadmium and zinc administration and the group with simple cadmium administration (P < 0.05). The relative volume of growing follicles was very similar in all studied groups (11.33-15.35%), and the relative volume of stroma was very stable (82.59-86.45%). In the evaluation of the number of follicles undergoing atresia detected significantly higher number of atretic primary follicles as well as atretic growing follicles in the group with cadmium administration and cadmium with selenium administration in comparison with control group. In comparison of normal and atretic follicles we report the most negative effect of single cadmium administration on ovarian structure. Selenium co-administration shows protective effects but only the co-administration with zinc prevent significant cadmium ovarian alterations.

Female reproductive toxicology of cadmium

The aim of this study was to determine effects of Cd on the structure of ovary, oviduct and uterus after an experimental administration. Animals were divided into three groups. In group A rabbits received cadmium i.p. and were killed after 48 h. In group C Cd was administered p.o. for 5 month. The group K was the control. Decreased relative volume of growing follicles and increased stroma after Cd administration were detected. The number of atretic follicles was significantly higher after administration of Cd. The most frequent ultrastructural alterations observed were undulation of external nuclear membrane, dilatation of perinuclear cistern and endoplasmic reticulum. In all studied types of cells mitochondria with altered structure were found. In the oviduct the highest amount of epithelium in the group with long-term Cd administration was found. Microscopic analysis showed oedematization of the oviduct tissue, caused by disintegration of the capillary wall. An electron microscopic analysis showed dilatation of perinuclear cistern. The intercellular spaces were enlarged and junctions between cells were affected. Mainly after a long-term cadmium administration nuclear chromatin disintegration was present. In the uterus a significant change was determined in the relative volume of glandular epithelium. Increase of stroma was a sign of uterus oedamatization caused by damage in the wall of blood vessels and subsequent diapedesis. After Cd administration alteration in uterus were less expressed, in comparison with ovary and oviduct. Alteration of nuclear chromatin contain following Cd administration suggests degenerative functional changes.

New concept for a toxicity assay based on multiple indexes from the wave shape of damped metabolic oscillation induced in living yeast cells (part II): application to analytical toxicology

An ideal toxicity assay should utilize multiple indexes obtained from transient changes of metabolic activities. Here, we demonstrate the possibility for a novel toxicity bioassay using the damped glycolytic oscillation phenomenon occurring in starved yeast cells. In a previous study, the phenomenon was characterized in detail. Under optimum conditions to induce the phenomenon, the wave shapes of the damped glycolytic oscillations were changed by the instantaneous addition of both glucose and chemicals and by changing the chemical concentration. We estimated the changes in the oscillation wave shapes as six indexes, i.e., the number of wave cycles, maximum amplitude, oscillation frequency, attenuation coefficient, initial peak height, and non-steady-state time. These index changes were obtained from several kinds of chemicals. The chemicals, especially those for acids (0.01-100 mM HCl and 0.01-50 mM citric acid), bases (0.001-50 mM KOH), heavy metal ions (1-1,000 mg L(-1); Cu(2+), Pb(2+), Cd(2+), Hg(2+)), respiratory inhibitors (3-500 mg L(-1) NaN(3)), dissolved oxygen removers (10-300 mg L(-1) NaSO(3)), surfactants (10-200 mg L(-1) benzalkonium chloride), and aldehyde (10-1,000 mg L(-1) acetaldehyde), showed characteristic patterns depending on each chemical and its concentration. These significant results demonstrate the possibilities of new methods for both toxicity qualification and quantification.

The vascular endothelium as a target of cadmium toxicity

Cadmium (Cd) is an important industrial and environmental pollutant that can produce a wide variety of adverse effects in humans and animals. A growing volume of evidence indicates that the vascular endothelium may be one of the primary targets of Cd toxicity in vivo. Studies over the past 20 years have shown that Cd, at relatively low, sublethal concentrations, can target vascular endothelial cells at a variety of molecular levels, including cell adhesion molecules, metal ion transporters and protein kinase signaling pathways. The purpose of this review is to summarize the results of these recent studies and to discuss the implications of these findings with regard to the mechanisms of Cd toxicity in specific organs including the lung, liver, kidney, testis and heart. In addition the possible roles of the vascular endothelium in mediating the tumor promoting and anticarcinogenic effects of Cd are discussed.