Application of hybrid anaerobic reactor: Treatment of increasing cyanide containing effluents and microbial composition identification

The study endeavors the anaerobic treatment of cyanide-containing effluents using the hybrid anaerobic reactor, with self-immobilized granules under high up-flow velocities. Comparison of one-year time-course analyses of HARs treating high strength effluents containing cyanide and control indicates the importance of wastewater characteristics in development and maintenance of microbiome. Efforts were directed towards associating process performance with microbial dynamics. Presence of cyanide results in the accumulation of intermediates paralleled with a drop in abundance of sensitive aceticlastic methanogens. HAR appear to have better resilience than other identified digesters because of shielding effects and enhanced granule-wastewater contact. The predominance of Methanobacteriales in the presence of cyanide can be linked to its tolerance. It was found that methane yield is positively correlated with abundance of aceticlastic guilds (R = 0.830, CI = 0.01). Tolerant bacterial groups were also identified. The study advances our knowledge related to less energy intensive technology with the focus on the development of efficient HAR.

Suppression of ferroportin expression by cadmium stimulates proliferation, EMT, and migration in triple-negative breast cancer cells

Cadmium (Cd) has been linked to a variety of cancers, including breast cancer; however, the molecular mechanism of its carcinogenic activity is not fully understood. To this end, the present study investigated the roles of ferroportin (FPN), a prognostic marker of breast cancer, in Cd-induced stimulation of cell proliferation and cell migration. Triple-negative MDA-MB-231 cells were treated with 1-3 μM Cd. The cells exhibited significant reduction in FPN expression and concomitant increase in iron concentration. Cells treated with Cd for 8 weeks displayed elevated proliferative and migratory activities which were inversely related with FPN expression. Reduced FPN expression also resulted in EMT as indicated by an increase in the expression of E-cadherin, and a decrease in the expression of N-cadherin, Twist and Slug. Further investigation revealed that Cd suppressed FPN expression at least partially by activating TGF-β, a known regulator of FPN expression. Taken together, these results indicate that Cd-induced stimulation of MDA-MB-231 cell proliferation, EMT, and migration is brought about by suppression of FPN expression and associated disruption of iron homeostasis.

Epithelial-mesenchymal transition in breast epithelial cells treated with cadmium and the role of Snail

Epidemiological and experimental studies have implicated cadmium (Cd) with breast cancer. In breast epithelial MCF10A and MDA-MB-231 cells, Cd has been shown to promote cell growth. The present study examined whether Cd also promotes epithelial-mesenchymal transition (EMT), a hallmark of cancer progression. Human breast epithelial cells consisting of non-cancerous MCF10A, non-metastatic HCC 1937 and HCC 38, and metastatic MDA-MB-231 were treated with 1 or 3 μM Cd for 4 weeks. The MCF10A epithelial cells switched to a more mesenchymal-like morphology, which was accompanied by a decrease in the epithelial marker E-cadherin and an increase in the mesenchymal markers N-cadherin and vimentin. In both non-metastatic HCC 1937 and HCC 38 cells, treatment with Cd decreased the epithelial marker claudin-1. In addition, E-cadherin also decreased in the HCC 1937 cells. Even the mesenchymal-like MDA-MB-231 cells exhibited an increase in the mesenchymal marker vimentin. These changes indicated that prolonged treatment with Cd resulted in EMT in both normal and cancer-derived breast epithelial cells. Furthermore, both the MCF10A and MDA-MB-231 cells labeled with Zcad, a dual sensor for tracking EMT, demonstrated a decrease in the epithelial marker E-cadherin and an increase in the mesenchymal marker ZEB-1. Treatment of cells with Cd significantly increased the level of Snail, a transcription factor involved in the regulation of EMT. However, the Cd-induced Snail expression was completely abolished by actinomycin D. Luciferase reporter assay indicated that the expression of Snail was regulated by Cd at the promotor level. Snail was essential for Cd-induced promotion of EMT in the MDA-MB-231 cells, as knockdown of Snail expression blocked Cd-induced cell migration. Together, these results indicate that Cd promotes EMT in breast epithelial cells and does so by modulating the transcription of Snail.

Cadmium stimulates metastasis-associated phenotype in triple-negative breast cancer cells through integrin and β-catenin signaling

Cadmium (Cd) is a carcinogenic heavy metal which is implicated in breast cancer development. While the mechanisms of Cd-induced breast cancer initiation and promotion have been studied, the molecular processes involved in breast cancer progression remain to be investigated. The purpose of the present study was to evaluate the influence of Cd on metastasis-associated phenotypes, such as cell adhesion, migration, and invasion in triple-negative breast cancer cells. Treatment of MDA-MB-231 cells with 1μM Cd increased cell spreading and cell migration. This was associated with the activation of integrin β1, FAK, Src, and Rac1. Treatment with Cd also inhibited GSK3β activity and induced T-cell factor/lymphoid enhancer factor (TCF/LEF) transcription, indicating the involvement of β-catenin signaling. Furthermore, treatment with 3μM Cd for 4weeks increased the expression of β-catenin and enhanced TCF/LEF-mediated transcription. Furthermore, enhanced expressions of integrins α5 and β1, paxillin, and vimentin indicated that prolonged Cd treatment reorganized the cytoskeleton, which aided malignancy, as evidenced by enhanced matrix metalloprotease 2/9 (MMP2/9) secretion and cell invasion. Prolonged Cd treatment also caused an increase in cell growth. Together, these results indicate that Cd alters key signaling processes involved in the regulation of cytoskeleton to enhance cancer cell migration, invasion, adhesion, and proliferation.

Anti-glycation and anti-oxidative effects of a phenolic-enriched maple syrup extract and its protective effects on normal human colon cells

Oxidative stress and free radical generation accelerate the formation of advanced glycation endproducts (AGEs) which are linked to several chronic diseases. Published data suggest that phenolic-rich plant foods, show promise as natural anti-AGEs agents due to their anti-oxidation capacities. A phenolic-enriched maple syrup extract (MSX) has previously been reported to show anti-inflammatory and neuroprotective effects but its anti-AGE effects remain unknown. Therefore, herein, we investigated the anti-glycation and anti-oxidation effects of MSX using biochemical and biophysical methods. MSX (500 μg mL^-1) reduced the formation of AGEs by 40% in the bovine serum albumin (BSA)-fructose assay and by 30% in the BSA-methylglyoxal (MGO) assay. MSX also inhibited the formation of crosslinks typically seen in the late stage of glycation. Circular dichroism and differential scanning calorimeter analyses demonstrated that MSX maintained the structure of BSA during glycation. In the anti-oxidant assays, MSX (61.7 μg mL^-1) scavenged 50% of free radicals (DPPH assay) and reduced free radical generation by 20% during the glycation process (electron paramagnetic resonance time scan). In addition, the intracellular levels of hydrogen peroxide induced reactive oxygen species were reduced by 27-58% with MSX (50-200 μg mL^-1) in normal/non-tumorigenic human colon CCD-18Co cells. Moreover, in AGEs and MGO challenged CCD-18Co cells, higher cellular viabilities and rapid extracellular signal-regulated kinase (ERK) phosphorylation were observed in MSX treated cells, indicating its protective effects against AGEs-induced cytotoxicity. Overall, this study supports the biological effects of MSX, and warrants further investigation of its potential as a dietary agent against diseases mediated by oxidative stress and inflammation.

Effects of a Standardized Phenolic-Enriched Maple Syrup Extract on β-Amyloid Aggregation, Neuroinflammation in Microglial and Neuronal Cells, and β-Amyloid Induced Neurotoxicity in Caenorhabditis elegans

Published data supports the neuroprotective effects of several phenolic-containing natural products, including certain fruit, berries, spices, nuts, green tea, and olive oil. However, limited data are available for phenolic-containing plant-derived natural sweeteners including maple syrup. Herein, we investigated the neuroprotective effects of a chemically standardized phenolic-enriched maple syrup extract (MSX) using a combination of biophysical, in vitro, and in vivo studies. Based on biophysical data (Thioflavin T assay, transmission electron microscopy, circular dichroism, dynamic light scattering, and zeta potential), MSX reduced amyloid β1-42 peptide (Aβ1-42) fibrillation in a concentration-dependent manner (50-500 μg/mL) with similar effects as the neuroprotective polyphenol, resveratrol, at its highest test concentration (63.5 % at 500 μg/mL vs. 77.3 % at 50 μg/mL, respectively). MSX (100 μg/mL) decreased H2O2-induced oxidative stress (16.1 % decrease in ROS levels compared to control), and down-regulated the production of lipopolysaccharide (LPS)-stimulated inflammatory markers (22.1, 19.9, 74.8, and 87.6 % decrease in NOS, IL-6, PGE2, and TNFα levels, respectively, compared to control) in murine BV-2 microglial cells. Moreover, in a non-contact co-culture cell model, differentiated human SH-SY5Y neuronal cells were exposed to conditioned media from BV-2 cells treated with MSX (100 μg/mL) and LPS or LPS alone. MSX-BV-2 media increased SH-SY5Y cell viability by 13.8 % compared to media collected from LPS-BV-2 treated cells. Also, MSX (10 μg/mL) showed protective effects against Aβ1-42 induced neurotoxicity and paralysis in Caenorhabditis elegans in vivo. These data support the potential neuroprotective effects of MSX warranting further studies on this natural product.

Cadmium promotes the proliferation of triple-negative breast cancer cells through EGFR-mediated cell cycle regulation

Cadmium (Cd) is a carcinogenic metal which is implicated in breast cancer by epidemiological studies. It is reported to promote breast cancer cell growth in vitro through membrane receptors. The study described here examined Cd-mediated growth of non-metastatic human breast cancer derived cells that lack receptors for estrogen, progesterone, and HER2. Treatment of triple-negative HCC 1937 cells with 0.1-0.5 μM Cd increased cell growth by activation of AKT and ERK. Accelerated cell cycle progression was achieved by increasing the levels of cyclins A, B, and E, as well as those of CDKs 1 and 2. Although triple negative cells lack estrogen receptor, they express high levels of EGFR. Therefore, further studies on HCC 1937 and another triple-negative cell line, HCC 38, were conducted using specific siRNA and an inhibitor of EGFR to determine whether EGFR was responsible for mediating the effect of Cd. The results revealed that in both cell types EGFR was not only activated upon Cd treatment, but was also essential for the downstream activation of AKT and ERK. Based on these observations, it is concluded that, in breast cancer cells lacking estrogen receptor, sub-micromolar concentration of Cd can promote cell proliferation. Furthermore, that EGFR plays a critical role in this process.

Requirement of ERα and basal activities of EGFR and Src kinase in Cd-induced activation of MAPK/ERK pathway in human breast cancer MCF-7 cells

Cadmium (Cd) is a common environmental toxicant and an established carcinogen. Epidemiological studies implicate Cd with human breast cancer. Low micromolar concentrations of Cd promote proliferation of human breast cancer cells in vitro. The growth promotion of breast cancer cells is associated with the activation of MAPK/ERK pathway. This study explores the mechanism of Cd-induced activation of MAPK/ERK pathway. Specifically, the role of cell surface receptors ERα, EGFR, and Src kinase was evaluated in human breast cancer MCF-7 cells treated with 1-3μM Cd. The activation of ERK was studied using a serum response element (SRE) luciferase reporter assay. Receptor phosphorylation was detected by Western blot analyses. Cd treatment increased both the SRE reporter activity and ERK1/2 phosphorylation in a concentration-dependent manner. Cd treatment had no effect on reactive oxygen species (ROS) generation. Also, blocking the entry of Cd into the cells with manganese did not diminish Cd-induced activation of MAPK/ERK. These results suggest that the effect of Cd was likely not caused by intracellular ROS generation, but through interaction with the membrane receptors. While Cd did not appear to activate either EGFR or Src kinase, their inhibition completely blocked the Cd-induced activation of ERK as well as cell proliferation. Similarly, silencing ERα with siRNA or use of ERα antagonist blocked the effects of Cd. Based on these results, it is concluded that not only ERα, but also basal activities of EGFR and Src kinase are essential for Cd-induced signal transduction and activation of MAPK/ERK pathway for breast cancer cell proliferation.

The membrane estrogen receptor GPR30 mediates cadmium-induced proliferation of breast cancer cells

Cadmium (Cd) is a nonessential metal that is dispersed throughout the environment. It is an endocrine-disrupting element which mimics estrogen, binds to estrogen receptor alpha (ERalpha), and promotes cell proliferation in breast cancer cells. We have previously published that Cd promotes activation of the extracellular regulated kinases, erk-1 and -2 in both ER-positive and ER-negative human breast cancer cells, suggesting that this estrogen-like effect of Cd is not associated with the ER. Here, we have investigated whether the newly appreciated transmembrane estrogen receptor, G-protein coupled receptor 30 (GPR30), may be involved in Cd-induced cell proliferation. Towards this end, we compared the effects of Cd in ER-negative human SKBR3 breast cancer cells in which endogenous GPR30 signaling was selectively inhibited using a GPR30 interfering mutant. We found that Cd concentrations from 50 to 500 nM induced a proliferative response in control vector-transfected SKBR3 cells but not in SKBR3 cells stably expressing interfering mutant. Similarly, intracellular cAMP levels increased about 2.4-fold in the vector transfectants but not in cells in which GPR30 was inactivated within 2.5 min after treatment with 500 nM Cd. Furthermore, Cd treatment rapidly activated (within 2.5 min) raf-1, mitogen-activated protein kinase kinase, mek-1, extracellular signal regulated kinases, erk-1/2, ribosomal S6 kinase, rsk, and E-26 like protein kinase, elk, about 4-fold in vector transfectants. In contrast, the activation of these signaling molecules in SKBR3 cells expressing the GPR30 mutant was only about 1.4-fold. These results demonstrate that Cd-induced breast cancer cell proliferation occurs through GPR30-mediated activation in a manner that is similar to that achieved by estrogen in these cells.

Rapid activation of ERK1/2 and AKT in human breast cancer cells by cadmium

Cadmium (Cd), an endocrine disruptor, can induce a variety of signaling events including the activation of ERK1/2 and AKT. In this study, the involvement of estrogen receptors (ER) in these events was evaluated in three human breast cancer cell lines, MCF-7, MDA-MB-231, and SK-BR-3. The Cd-induced signal activation patterns in the three cell lines mimicked those exhibited in response to 17 beta-estradiol. Specifically, treatment of MCF-7 cells, that express ER alpha, ER beta and GPR30, to 0.5-10 microM Cd for only 2.5 min resulted in transient phosphorylation of ERK1/2. Cd also triggered a gradual increase and sustained activation of AKT during the 60 min treatment period. In SK-BR-3 cells, that express only GPR30, Cd also caused a transient activation of ERK1/2, but not of AKT. In contrast, in MDA-MB-231 cells, that express only ER beta, Cd was unable to cause rapid activation of either ERK1/2 or AKT. A transient phosphorylation of ER alpha was also observed within 2.5 min of Cd exposure in the MCF-7 cells. While the estrogen receptor antagonist, ICI 182,780, did not prevent the effect of Cd on these signals, specific siRNA against hER alpha significantly reduced Cd-induced activation of ERK1/2 and completely blocked the activation of AKT. It is concluded that Cd, like estradiol, can cause rapid activation of ERK1/2 and AKT and that these signaling events are mediated by possible interaction with membrane ER alpha and GPR30, but not ER beta.

Cadmium induces cell cycle arrest in rat kidney epithelial cells in G2/M phase

Cadmium (Cd) has been reported to cause cell cycle arrest in various cell types by p53-dependent and -independent mechanisms. This study was designed to investigate cell cycle progression in kidney cells that are the target of chronic Cd toxicity. Rat renal proximal tubular epithelial cells, NRK-52E, were treated with up to 20 microM CdCl2 in DMEM containing 10% calf serum for up to 24 h. Flow cytometric analysis revealed time- and concentration-dependent increases in cells in G2/M phase of the cell cycle. As compared to the control cells, the cells exposed to 20 microM Cd showed a doubling of the number of cells in this phase after 24 h. The cell cycle arrest was associated with a decrease in protein levels of both cyclins A and B. Further investigation into the mechanism revealed that Cd treatment led to down-modulation of cyclin-dependent kinases, Cdk1 and Cdk2, apparently by elevating the expression of cyclin kinase inhibitors, KIP1/p27 and WAF1/p21. Furthermore, the wild-type p53 DNA-binding activity was up-regulated. Based on these observations, it appears that Cd causes G2/M phase arrest in NRK-52E cells via elevation of p53 activity, increasing the expression of cyclin kinase inhibitors p27 and p21, and decreasing the expression of cyclin-dependent kinases Cdk1 and 2, and of cyclins A and B.

Protection of renal tubular cells against the cytotoxicity of cadmium by glycine

Glycine treatment is reported to protect against the nephrotoxicity of cadmium (Cd) in rats. The purpose of the present study was to explore the mechanism of this protection using a renal epithelial cell line, LLC-PK(1). The cells were incubated with 10-30 microM Cd in serum-free DMEM and cytotoxicity was evaluated by LDH leakage into the incubation medium. Under these conditions, 20 and 30 microM Cd concentrations were cytotoxic. As compared to the non-Cd-exposed cells, the LDH release was elevated more than six-fold in cells exposed to 30 microM Cd for 24h. Co-treatment with 5-50mM glycine was cytoprotective in a concentration-dependent manner. Prior treatment with 50 mM glycine for 16 h, or co-treatment for 24h, reduced LDH leakage due to 30 microM Cd exposure by 60 and 66%, respectively. Co-incubation with 50 mM alanine was also protective but only about half as effective as with glycine. During the first 4h, prior to the onset of any significant cell membrane damage, the Cd-exposed cells accumulated 0.55 microg Cd/mg protein. Glycine pre-treatment or co-treatment reduced Cd accumulation by about one-quarter or one-half, respectively. To delineate the mechanism of glycine's effect on Cd accumulation, the efflux of Cd was studied after a 30 min pulse exposure. The results suggested that pre-treatment reduced Cd accumulation by increasing its efflux from the cells. In contrast, co-treatment reduced Cd efflux, suggesting that the co-treatment lowered Cd accumulation by suppressing its uptake. When co-incubated, Cd and glycine formed a complex that was apparently responsible for the marked reduction in Cd uptake. It is concluded that, regardless of the mode of treatment, glycine is cytoprotective against Cd and that it may do so by lowering the intracellular Cd burden.

Cadmium-Induced Apoptosis in Rat Kidney Epithelial Cells Involves Decrease in Nuclear Factor-Kappa B Activity

Renal epithelial cells undergo apoptosis upon exposure to cadmium (Cd). Transcription factors, such as nuclear factor-kappa B (NF-kappaB), mediate the expression of a number of genes involved in apoptosis. The present study was designed to examine the involvement of this transcription factor in Cd-induced apoptosis. Rat kidney proximal tubular epithelial cells, NRK-52E, were incubated with up to 20 microM CdCl2 in serum-free medium for 5 h followed by incubation in serum-containing medium (without Cd) for an additional 12 h. The cells accumulated 582 +/- 19 ng Cd/mg protein after 5-h exposure to 20 microM Cd. As a result of Cd exposure, the DNA-binding activity of the p65 subunit of NF-kappaB was decreased in a concentration- and time-dependent manner. The activity of tumor necrosis factor-alpha-induced inhibitor of kappa B (IkappaB) kinase alpha was also inhibited by Cd. In addition, the phosphorylation of IkappaB-alpha and NF-kappaB p65, as well as the levels of NF-kappaB target gene products, cIAP-1 and cIAP-2, were reduced. Pretreatment of the cells with the antioxidant U83836E or butylated hydroxytoluene preserved the DNA-binding activity and blocked the Cd-induced decease in IkappaB-alpha phosphorylation. Cd exposure caused the activation of caspase-3, -7, and -9 and DNA fragmentation. By flow cytometry, 14.6 and 30.5% apoptosis was detected at 6 and 12 h after stopping the Cd exposure. Overexpression of NF-kappaB p65 by transient transfection protected the cells from the Cd-induced apoptosis. Conversely, attenuation of NF-kappaB activity by pretreatment with SN50, an NF-kappaB nuclear translocation inhibitor, potentiated apoptosis. These results suggest that Cd-induced apoptosis involves suppression of NF-kappaB activity which may be mediated by oxidative stress.

Excretion of urinary cadmium, copper, and zinc in cadmium-exposed and nonexposed subjects, with special reference to urinary excretion of beta2-microglobulin and metallothionein

The objectives of this study were to examine the association between urinary excretion of cadmium (U-Cd), copper (U-Cu), and zinc (U-Zn) and the severity of two different indicators of renal toxicity (urinary excretion of beta2-microglobulin [U-beta2-MG] and metallothionein [U-MT]) in Cd-exposed subjects compared to controls, and to assess the physiologic mechanisms by which the exposure to environmental Cd affects U-Cd, U-Cu, and U-Zn. The target population included 3508 Cd-exposed and 294 nonexposed participants who received a health survey conducted among the population of the Kakehashi River basin. Increases of U-Cd, U-beta2-MG, and U-MT in the Cd-exposed population were observed relative to excretion of these substances in controls. Regression analysis using a general linear model revealed that the correlations between U-Cd or U-Cu, and U-beta2-MG and between U-Cd, U-Cu or U-Zn, and U-MT were statistically significant in both sexes, but the correlation between U-Zn and U-beta2-MG excretion was significant only in men. These results suggest U-Cd and U-Cu is affected by dysfunction in renal tubular absorption (indicated by U-beta2-MG), whereas not only U-Cd and U-Cu but also U-Zn appear to be a function of renal cellular desquamation (indicated by U-MT).

Renal cortical mitochondrial dysfunction upon cadmium metallothionein administration to Sprague-Dawley rats

A bolus dose of cadmium metallothionein (CdMT) produces renal proximal tubular dysfunction because it accumulates in the tubular epithelial cells and undergoes rapid degradation, releasing Cd. Morphologically, mitochondria appear to be the target organelle. The present study examined changes in renal cortical mitochondrial function following CdMT administration and investigated whether some of these effects could be ascribed to Cd2+ accumulation in the mitochondria. Sprague-Dawley rats were injected ip with 0.3 mg Cd as CdMT/kg and the animals were sacrificed after 6, 8, or 12 h. Two- to threefold increases in urinary protein excretion and LDH activity were evident at 8 h, with marked elevations (11- and 29-fold) thereafter. Renal cortical mitochondria were swollen and rounded at 12 h. The mitochondrial Cd level was 399 pmol/mg protein at 6 h and did not change significantly during the next 6 h; however, mitochondrial respiratory function declined with time. At 12 h, state 3 oxygen consumption, respiratory control ratio (RCR), and ADP:O (P/O) ratio were 48, 49, and 76% of control values, respectively, indicating inhibition of electron transfer and oxidative phosphorylation. The direct effect of Cd on mitochondrial function was examined by incubating mitochondria from untreated rats with 0.1-2 microM CdCl2. Rapid uptake of Cd resulted in concentration-dependent effects on respiration. After 1 min of incubation with 2 microM Cd, the mitochondria contained 262 microgCd/mg protein and state 3 respiration and RCR values were 75 and 33% of control levels, respectively. Thus, renal proximal tubular cell damage following a bolus dose of CdMT involves perturbations in mitochondrial respiration, brought on by the accumulation of Cd.

Gray matter T2 hypointensity is related to plaques and atrophy in the brains of multiple sclerosis patients

Cortical and subcortical gray matter hypointensities on T2-weighted MR images (T2WI) occur commonly in MS brains and have been related to disease duration, clinical course, and the level of neurologic disability. These hypointensities have been reported to occur in the thalamus, basal ganglia, and rolandic cortex. We assessed whether T2 hypointensity is associated with the severity of white matter plaques and atrophy of MS brains. In 114 MS patients, hypointensity of the thalamus, putamen, caudate, and sensorimotor cortex was ordinally rated against age- and gender-matched normal controls on 1.5-T MRI fast spin-echo axial T2WI. Regional and global T2 hyperintense and T1 hypointense parenchymal lesion loads were ordinally rated. Enlargement of subarachnoid and ventricular spaces (atrophy) was ordinally rated vs. age- and gender-matched normal controls. T2 hypointensity was highly, positively correlated with many other MRI variables. Regression modeling showed that T2 hypointensity was related to total atrophy, total T2 lesion load, third ventricular enlargement, parietal atrophy, and to a lesser extent, frontal T1 lesions and cerebellar T2 lesions, but not related to gadolinium enhancement. Ordinal ratings of T2 lesions and central atrophy showed high correlations with quantitative computerized assessments. We conclude that gray matter hypointensity on T2WI may reflect pathologic iron deposition and brain degeneration in MS. This T2 hypointensity is associated with brain atrophy and other MR markers of tissue damage. Further study is warranted to determine if T2 hypointensity is predictive of disease course in MS and is a useful surrogate outcome measure in therapeutic trials.

Application of path analysis to urinary findings of cadmium-induced renal dysfunction

In order to identify some causal relations among various urinary indices of cadmium-induced renal dysfunction, such as glucose, total protein, amino nitrogen, beta 2-microglobulin (beta 2-m), metallothionein (MT), and cadmium (Cd), we applied path analysis method to previous epidemiological studies targeting the residents of the Cd-polluted Kakehashi River basin of Ishikawa Prefecture, Japan. We obtained a diagram-termed path model, representing some causal relations among the above urinary indices. It shows that urinary Cd is located at the beginning point in the diagram, and Cd-induced renal dysfunction develops in the following order: Cd exposure-->increase of beta 2-m and/or MT excretion-->increase of amino-N and/or total protein excretion-->increase of glucose excretion. It was proved mathematically, that in the case of both males and females, increased excretions of beta 2-m and/or MT were the most sensitive urinary indices of the early stage of chronic Cd-induced renal dysfunction.

Early-onset Moyamoya syndrome in a patient with Down syndrome: case report and review of the literature

Moyamoya disease is a chronic occlusive cerebrovascular disorder. It can occur as a primary disease or as a syndrome associated with a variety of conditions. Usually it takes 1 to 2 years to develop a classic moyamoya pattern. We report a 20-month-old girl with Down syndrome and moyamoya syndrome who presented with seizure and hemiparesis. To our knowledge, this is the youngest case reported with moyamoya syndrome and Down syndrome. The prognosis and current treatment of moyamoya syndrome and its relation to Down syndrome are reviewed. There is some reason to speculate that the abnormalities associated with Down syndrome might create a vulnerability for the development of moyamoya syndrome.

Magnetic resonance imaging findings in bilateral Bell's palsy

Bell's palsy (idiopathic facial paralysis) is the most common cause of unilateral peripheral facial neuropathy. Bilateral involvement occurs in less than 10% of cases. The authors describe a 20-year-old man with bilateral idiopathic facial weakness. Brain magnetic resonance imaging (MRI) showed abnormal bilateral enhancement of the proximal intracanalicular segments of VII/VIII nerve complexes. The enhancement was most prominent in the leptomeningeal regions. There was no facial nerve swelling. Three months later he had improving residual bifacial weakness. To the authors' knowledge, this is the first report of abnormal MRI findings in bilateral Bell's palsy.

Orbital involvement as the initial manifestation of sarcoidosis: magnetic resonance imaging findings

A 74-year-old man had diplopia, painful right ophthalmoplegia, proptosis, conjunctival injection, and facial skin lesions. Magnetic resonance imaging (MRI) revealed infiltration of the right intraorbital adipose tissue. Lesions were mixed low- and high-signal on T2-weighted images and enhanced on fat-suppressed T1-weighted postcontrast images. A skin biopsy revealed numerous noncaseating granulomas consistent with sarcoidosis. Treatment with corticosteroids and chlorambucil led to a full clinical recovery. Sarcoidosis should be considered in the evaluation of orbital pseudotumor in elderly patients, even if no systemic manifestations of sarcoidosis are present.

Fatigue in multiple sclerosis and its relationship to depression and neurologic disability

We studied multiple sclerosis fatigue (MSF) and its relationship to depression and disability. Seventy-one patients [50 relapsing-remitting, 21 secondary progressive] were grouped by Fatigue Severity Scale (FSS) into MS-fatigue (MSF) (FSS>/=5; n=46) or MS-nonfatigue (MSNF) (FSS</=4; n=20). Forty-one patients were grouped into MS-depression (MSD) (n=15) or MS-nondepression (MSND) (n=26) by interview. Higher expanded disability status scale (EDSS) scores were noted in MSF than MSNF patients (P=0.0003); EDSS scores correlated with FSS scores (rho=0.43, P=0.003). However, fatigue was present in 58% (n=29) of relapsing-remitting patients and in 52% (n=26) of patients with mild physical disability (EDSS<3.5). Hamilton/Beck depression severity scores were higher in MSF than MSNF patients and correlated with FSS scores (P<0.05). MSD had higher FSS scores than MSND patients (P=0.008). After controlling for EDSS, depression severity continued to correlate with FSS scores (rho=0.37, P=0.02). After controlling for depression, FSS scores no longer correlated with EDSS scores (rho=0.27, P=0.09). Thus, MSF is independent of physical disability, but is associated with depression, suggesting that common mechanisms play a role in MSF and MSD including psychological factors or brain lesions in specific neuroanatomic pathways. Further study is warranted to determine if antidepressant medications improve fatigue in MS.

Brain MRI lesions and atrophy are related to depression in multiple sclerosis

It is unclear whether brain MRI lesions are associated with depression in multiple sclerosis (MS). Neurological dysfunction in depressed (n= 19) and non-depressed (n = 29) MS patients was rated by expanded disability status scale (EDSS). EDSS was weakly predictive of the presence of (p = 0.03) and severity of (p = 0.01) depression. After correcting for EDSS, the presence of depression was predicted by superior frontal and superior parietal hypointense TI lesions (p<0.01); the severity of depression was predicted by superior frontal, superior parietal and temporal TI lesions, lateral and third ventricular enlargement, and frontal atrophy (p<0.01). Depression was not related to bright T2 lesions or enhancement. We conclude that atrophy and cortical-subcortical disconnection due to frontal and parietal white matter destructive lesions may contribute to depression in MS.

MRI T2 shortening ('black T2') in multiple sclerosis: frequency, location, and clinical correlation

Abnormal iron deposition occurs in the brains of patients with multiple sclerosis (MS) and may cause MRI T2 shortening ('black T2'; BT2). The frequency, distribution and clinical significance of BT2 in MS is unknown. Analysis of brain MRI scans of 114 MS patients showed BT2 in thalamus (n = 65; 57%), putamen (n = 48; 42%), caudate (n = 27; 24%) and Rolandic cortex (n = 9; 8%). BT2 was significantly related to longer disease duration and advancing neurological disability. Wheelchair-bound patients had worse BT2 in thalamus (p < 0.05), putamen (p < 0.001) and Rolandic cortex (p < 0.05). Patients with secondary progressive disease (n = 34) had worse BT2 in thalamus, putamen and caudate (all p < 0.05) than those with relapsing remitting disease (n = 80). BT2 is proposed as a clinically relevant finding relating to neuronal degeneration in MS.

Fatigue in multiple sclerosis: cross-sectional correlation with brain MRI findings in 71 patients

Fatigue is an unexplained but common and disabling symptom in MS. We assessed fatigue in 71 patients with MS and identified MS-fatigue (MSF) and MS-nonfatigue (MSNF) groups. Fatigue severity did not correlate with regional or global MRI plaque load or atrophy assessed by conventional sequences. No significant differences were noted in any MRI measures between MSF and MSNF groups. We suggest that brain MRI disease topography or severity does not explain fatigue in MS and that fatigue is likely due to mechanisms poorly characterized by conventional MRI.

MRI findings in 32 consecutive lipomas using conventional and advanced sequences

Intracranial lipomas are histologically benign and usually incidental magnetic resonance imaging findings that must be differentiated from ominous lesions. The authors describe 32 lipomas in 30 patients using conventional spin-echo (CSE) T1-weighted images (T1WI), CSE proton density (PDWI), CSE T2-weighted images (T2WI), fast spin-echo (FSE) T2WI, and FSE fluid-attenuated inversion recovery (FLAIR). Lipomas occurred most commonly in the trigonal choroid plexus, cerebral convexity, pericallosal, and quadrigeminal cistern regions. Lipomas were hyperintense on CSE T1WI and of variable appearance on CSE PDWI and CSE T2WI. Lipomas were isointense to hyperintense on FSE T2WI and hyperintense on FLAIR. Chemical shift artifact (CSA) usually was present on either CSE PDWI or CSE T2WI but was not seen on FSE images. One patient had intracranial hypotension associated with a large convexity lipoma. The authors conclude that lipomas appear different on CSE T2WI than on FSE T2WI. CSE PDWI and CSE T2WI are complementary in detecting CSA. The lack of CSA being detected in lipomas on FSE images most likely relates to inherent bandwidth differences compared with those of CSE. The hyperintense appearance of lipomas on FSE FLAIR and FSE T2WI may be confused with subacute hematomas. The authors recommend that if CSE technique by itself is used to exclude lipomas (in centers that are not using FSE), then T1WI, PDWI, and T2WI usually are sufficient. For centers using FSE routinely, fat saturation or CSE sequences also may be needed to exclude lipomas. Finally, the authors' series suggests that intracranial lipomas may occur in lateral locations more frequently than reported previously.

Dependence of cadmium-metallothionein nephrotoxicity on glutathione

Acute cadmium-metallothionein (CdMT) injection is frequently used as a model to study the mechanism of chronic Cd-induced nephrotoxicity. The purpose of this study was to investigate the relationship between glutathione (GSH) status and the ability of CdMT, either administered as a bolus dose or infused over a 24-h period by an osmotic minipump, to cause nephrotoxicity. GSH levels were modulated by pretreatment with either buthionine sulfoximine (BSO) or GSH. BSO enhanced while GSH suppressed acute CdMT nephrotoxicity. An infused dose of CdMT (150 microg Cd/kg) that was well tolerated when delivered over a 24-h period became nephrotoxic when GSH synthesis was inhibited by BSO. With depletion of GSH, as little as 0.4 microg Cd/g renal cortex was sufficient to cause nephrotoxicity after an acute dose of CdMT. While BSO had no effect on renal Cd accumulation, pretreatment with GSH reduced renal cortical Cd accumulation by 36%. CdMT nephrotoxicity was enhanced by depleting renal GSH, but without increasing renal Cd accumulation, which suggests that intracellular GSH is directly involved in protection against CdMT nephrotoxicity. Reduced Cd accumulation in the renal cortex following GSH pretreatment suggests an additional extracellular mechanism of GSH protection. It is concluded that GSH status is an important determinant of CdMT nephrotoxicity, with low GSH levels enhancing and high GSH levels reducing its toxicity, and that the mechanism appears to involve both intracellular and extracellular sites.

Measurement of cadmium-induced metallothionein in urine by ELISA and prevention of overestimation due to polymerization

Urinary metallothionein (MT) is a biological marker of cadmium (Cd) exposure and Cd-induced renal dysfunction. The MT is prone to oxidation due to high cysteine content and forms polymers, which can result in overestimation of the protein by immunochemical methods. The objectives of the present study were to develop an enzyme-linked immunosorbent assay (ELISA) for the measurement of MT in urine and to find ways by which the protein could either be preserved in its monomeric form or converted to this form before analysis to avoid overestimation. Urine specimens analyzed were either from rats repeatedly injected with Cd or from individuals chronically exposed to cadmium through their diets. The MT in rat urine remained in the monomeric form if the urine was collected at 4 degrees C but did not if it was collected at room temperature. The MT was also polymerized if the urine was subjected to repeated freezing and thawing. Overestimation of MT in rat urine occurred (as much as 12-fold) if the MT was polymerized. Addition of 5mM mercaptoethanol to freshly collected rat urine retarded MT polymerization, and addition of 50mM mercaptoethanol converted the polymerized MT to its monomeric form. Analysis of MT in frozen human urine samples revealed that if the urines were not treated with mercaptoethanol, the estimates of MT concentration were up to 11-fold higher than in the treated samples. We conclude that the polymerization of MT in rat and human urines is a serious problem and results in overestimation of the protein by ELISA and that this problem could be overcome by the addition of mercaptoethanol to the urine samples prior to analysis.

Protection against chronic cadmium toxicity by caloric restriction

Exposure to cadmium (Cd) can result in nephrotoxicity and osteotoxicity. Because Cd-induced nephrotoxicity involves oxidative stress and caloric restriction decreases oxidative stress, we examined whether reduced caloric intake will protect against Cd-induced nephrotoxicity. In addition, the protection against the osteotoxicity was also examined. Male and female Sprague-Dawley rats were provided drinking water containing 100 mg Cd/l. Since fluid intake relative to the body weight was higher in females as compared to the males, the Cd concentration in their water was reduced to 80 mg/l after 3 months and 65 mg/l after 6.5 months. During the 27 month exposure period the males and females consumed a total of about 5 g Cd/kg body weight. Food was restricted to 20 g/day after the first 3 months. During the unrestricted food intake period Cd exposure reduced the bone density in females by 23%, with a partial recovery and stabilization during the caloric restriction phase. Hepatic and renal Cd accumulation and corresponding metallothionein (MT) levels were very similar in both sexes. The reported critical Cd concentration for nephrotoxicity was reached by 9 months. Renal MT levels were maximum at this time. Despite a 1.5-fold increase in renal Cd concentration over the next 18 months, there was no significant increase in renal MT levels. In spite of high renal Cd levels and lack of availability of sufficient MT, there was no sign of nephrotoxicity, as measured by urinary protein and glucose excretion. It is concluded that caloric restriction prevents Cd-induced nephrotoxicity and also appears to control the osteotoxicity of Cd.

Thrombotic thrombocytopenic purpura: brain CT and MRI findings in 12 patients

Clinical-neuroimaging analysis of 12 thrombotic thrombocytopenic purpura (TTP) patients revealed a variety of brain lesions. These included reversible cerebral edema lesions with MRI features of reversible posterior leukoencephalopathy syndrome (RPLS). Most of the RPLS patients had hypertension and renal dysfunction, suggesting RPLS due to hypertensive encephalopathy. Prompt treatment usually led to neurologic recovery and disappearance of edematous lesions. Those with infarcts or hematomas had a poorer outcome. TTP should be added to the expanding spectrum of RPLS and hypertensive encephalopathy.

Protection against chronic cadmium toxicity by glycine

A Japanese drug containing glycine, glycyrrhizin, and cysteine (Stronger Neo-Minophagen C) has been reported to protect against chronic cadmium (Cd) toxicity. The present study was conducted to evaluate which of the three constituents of this drug was the main antagonist for Cd toxicity and whether the mechanism of protection involved antioxidant action. Adult female Sprague-Dawley rats were injected sc with 5 micromol CdCl2/kg per day, five times per week, for 15 weeks. Four groups of Cd-injected animals received co-treatments with either 10 mg glycyrrhizin/kg, 100 mg glycine/kg, 5 mg cysteine/kg, or with a mixture of all three compounds, five times per week, starting from week 7. An additional Cd-injected group was co-treated with vitamin E (100 mg/kg, five times per week, starting from week 7) as a positive control. Only those animals that received vitamin E, Minophagen mixture, or glycine were protected against Cd-induced hepatotoxicity as well as nephrotoxicity. All three co-treatments suppressed Cd-induced hepatic and renal lipid peroxidation. We conclude that the reported beneficial effects of Stronger Neo-Minophagen C are due to glycine, which appears to protect against chronic Cd toxicity by reducing oxidative stress.

Oxidative stress as a mechanism of chronic cadmium-induced hepatotoxicity and renal toxicity and protection by antioxidants

The role of oxidative stress in chronic cadmium (Cd) toxicity and its prevention by cotreatment with antioxidants was investigated. Adult female Sprague-Dawley rats were injected sc with 5 micromol CdCl2/kg/day, 5 times a week, for up to 22 weeks. Serum alanine amino transferase and lactate dehydrogenase activities were elevated after 9 weeks of Cd administration, indicating hepatic damage. Renal toxicity, indicated by elevation in urinary lactate dehydrogenase activity and protein, was also observed around this time. Chronic Cd administration resulted in a gradual rise in hepatic as well as renal cortex glutathione levels. In spite of this, lipid peroxidation increased in both tissues, particularly during the second half of the Cd exposure period. Depletion of glutathione following buthionine sulfoximine administration at the end of Week 5, or inhibition of catalase by aminotriazole at the end of Week 7, resulted in the development of acute nephrotoxicity within 6 h. Coadministration of antioxidants, N-acetylcysteine (50-100 mg/kg, sc), or vitamin E (100-150 mg/kg, sc) with Cd, starting from the early phases of Cd exposure, controlled Cd-induced lipid peroxidation and protected the animals against hepatic as well as renal toxicity. A Japanese hepatoprotective drug, Stronger Neo-Minophagen C, containing glycyrrhizin, glycine, and cysteine, was also effective in reducing the chronic Cd nephrotoxicity. In conclusion, oxidative stress appears to play a major role in chronic Cd-induced hepatic and renal toxicity since inhibition of components of the antioxidant defense system accelerated and administration of antioxidants protected against Cd toxicity.

Treatment of chronic cadmium nephrotoxicity by N-acetyl cysteine

Chronic cadmium (Cd)-induced nephrotoxicity is believed to be irreversible at advanced stages and no treatment is currently available. This study examined the beneficial effect of N-acetyl cysteine (NAC) on Cd-induced nephrotoxicity. Female Sprague-Dawley rats were injected s.c. with 5 micromol CdCl2/kg per day, five times/week for up to 26 weeks. Nephrotoxicity was detected after 10 weeks by elevation in urinary lactate dehydrogenase activity and protein. NAC co-administration from week 13 prevented the progression of nephrotoxicity. In these animals, with low-level nephrotoxicity, discontinuation of Cd exposure at the end of week 22 resulted in gradual recovery over the next several weeks, without the need for treatment with NAC. On the other hand, discontinuation of NAC co-treatment at the end of week 22 resulted in quick progression of nephrotoxicity, indicating that NAC protection was short-lived. Resumption of NAC treatment and cessation of Cd exposure after 26 weeks resulted in rapid recovery from advanced nephrotoxicity. It is concluded that protection from Cd-induced nephrotoxicity is possible by continued co-administration of NAC and that recovery from advanced nephrotoxicity can also be achieved with NAC, provided that Cd exposure is stopped.

Cytotoxicity of cadmium and characteristics of its transport in cardiomyocytes

Cadmium (Cd) is reported to produce cardiotoxicity at doses and exposure conditions that cause no effect in kidney or liver. The purpose of the present investigation was to examine the cytotoxicity of Cd to neonatal rat cardiomyocytes in primary culture and to elucidate the transport characteristics of Cd in these cells at a nontoxic concentration. Cd concentrations of 0.1 microM and higher that are well tolerated by hepatocytes and renal cortical epithelial cells were toxic to the cardiomyocyte. The plot of initial uptake rate of Cd at various concentrations was nonlinear suggesting that, in addition to simple diffusion, other processes may also be involved. These processes required metabolic energy as pretreatment with dinitrophenol or sodium fluoride inhibited 58 and 59% of the Cd uptake, respectively. The uptake of Cd was also affected by the incubation temperature and lowering the temperature from 37 to 4 degreesC reduced Cd uptake over 30 min by 61%. Cd uptake required interaction with membrane sulfhydryl groups; pretreatment with p-chloromercuribenzenesulfonic acid or mercuric chloride reduced Cd uptake by 46 and 58%, respectively. Cd utilized the transport pathways for calcium (Ca), zinc (Zn), and copper (Cu). Coincubation with 1.26 mM Ca competitively inhibited Cd uptake by 77%. In the presence of Ca, 30 microM Zn or Cu further inhibited Cd accumulation competitively by as much as 63 and 32%, respectively. Cd could enter the cardiomyocytes through Ca channels and Ca channel blocker, verapamil, inhibited up to 76% of Cd uptake. From the above results it can be concluded that Cd is highly toxic to the cardiomyocytes. A majority of Cd enters these cells through transport processes that exist for Ca, Zn, and Cu. The transport processes utilized by Cd are temperature sensitive and dependent on metabolic energy. Furthermore, these involve membrane sulfhydryl groups and include Ca channels.

Nephrotoxicity of cadmium-metallothionein: protection by zinc and role of glutathione

Chronic cadmium (Cd) exposure can cause renal proximal tubular dysfunction resulting from the release of Cd metallothionein (CdMT) from the liver and its accumulation and degradation in the renal tubular epithelial cells. Pretreatment with zinc (Zn) can protect against acute CdMT nephrotoxicity. While induction of MT by Zn plays a part in Zn protection, other factors, such as glutathione (GSH), may also be involved because protection is offered even in MT-null mice. The present study was designed to investigate the involvement of GSH in Zn protection against acute CdMT nephrotoxicity. The study was carried out in MT-null mice to remove the induction of MT by Zn as a confounding variable. Three approaches were used to modulate renal cortex GSH levels: buthionine sulfoximine (BSO) was administered to inhibit GSH synthesis, and GSH and Zn were administered to increase the GSH levels. Both GSH and Zn were effective in protecting against CdMT nephrotoxicity. Elevation in renal cortex GSH levels, however, was not essential for Zn protection, as a low dose of Zn that caused no significant increase in renal GSH also protected against CdMT. On the other hand, maintenance of normal GSH status was essential for Zn protection, as inhibition of GSH synthesis abolished this protection. Both GSH and Zn reduced the accumulation of Cd as well as MT in the renal cortex, with Zn causing greater reduction in Cd accumulation than that of MT. The relative intracellular distribution of Cd was unaltered. These results suggest that in MT-null mice Zn protects against CdMT nephrotoxicity by possibly displacing some of the Cd from CdMT as well as reducing the uptake of CdMT, and that this protection requires the maintenance of normal GSH status.

Mercury uptake by LLC-PK1 cells: dependence on temperature and membrane potential

The purpose of this study was to investigate the mechanism of inorganic mercury (Hg) uptake in LLC-PK1 cells, a renal tubular epithelial cell line, and to compare the results with those reported previously by us in rat renal cortical epithelial (RCE) cells in primary culture. The LLC-PK1 cells were cultured for 3-12 days, incubated with 1 microM HgCl2 in Hanks' balanced salt solution at 4 or 37 degrees C for 30 min, and washed with phosphate-buffered saline containing BAL to remove the cell membrane-bound Hg. The uptake of Hg was higher in nonconfluent cultures than in confluent cultures and higher at 37 than at 4 degrees C. In confluent culture (Day 8) Hg uptake at 4 degrees C was only 27% of that at 37 degrees C. The initial accumulation of Hg (5 min) from different concentrations of HgCl2 (0.5-50 microM) was linear and did not show a tendency toward saturation, suggesting that a carrier-mediated process was not involved. Pretreatment of cells with 10 microM FCCP, a metabolic inhibitor and a proton ionophore, 0.5 mm DIDS, an anion transport inhibitor, or 0.5 mM ouabain, a Na+/K+-ATPase inhibitor, resulted in 72, 60, and 57% reduction in Hg uptake, respectively. Furthermore, replacement of 137 mm NaCl in the incubation medium with 137 mM KCl or LiCl or 274 mM mannitol caused 30, 45, and 87% reduction in Hg uptake, respectively. These results suggest that in LLC-PK1 cells, as in RCE cells, Hg uptake is inversely related to cell density and is influenced by membrane fluidity, membrane potential, and HCO3-/Cl- transporter.

Mercury uptake by primary cultures of rat renal cortical epithelial cells. II. Effects of pH, halide ions, and alkali metal ions

The effects of pH, halide ions, and alkali metal ions on the uptake of inorganic mercury (Hg) were investigated in confluent primary cultures of rat renal cortical epithelial cells. The cells were incubated with 1 microM Hg in phosphate buffer at pH 5.5, 6.4, or 7.4 for 30 min at 37 degrees C. Incubation of cells at pH 5.5 resulted in a 22% increase in total Hg accumulation over those cells that were incubated at pH 7.4. Almost all of this increase was accounted for in the membrane fraction. In contrast, there was a 33% reduction in internalized Hg in cells incubated at pH 5.5. This may be explained by the conversion of hydroxide forms of Hg (Hg(OH)Cl and Hg(OH)2) to the chloride forms (HgCl2, HgCl3-, and HgCl4(2-) at a lower pH (decreased OH-) condition. In the presence of halide ions, the cells internalized Hg in the relative order of affinity of the halide ions for Hg2+ (i.e., F- < Cl- < Br- < I-). Br- and I- resulted in a 67 and 142% increase in internalized Hg over that by Cl-. The relatively high membrane binding and internalization of Hg in the presence of Br- and I- was possibly due to the formation of highly lipophilic complexes of Hg (i.e., HgBr2 and HgI2). The replacement of NaCl in the incubation medium by KCl caused a 36% decrease in internalized Hg. LiCl had a similar effect on the internalization of Hg. The above results suggest that in rat renal proximal tubules Hg uptake involves Na(+)- and H(+)-dependent mechanisms.

Mercury uptake by primary cultures of rat renal cortical epithelial cells. I. Effects of cell density, temperature, and metabolic inhibitors

Factors affecting the renal uptake of inorganic mercury were investigated using primary cultures of rat renal cortical epithelial (RCE) cells under protein- and amino acid-free conditions. The cells were isolated from kidneys of adult rats and cultured. Confluence of culture (cell density), monitored morphologically and by total protein content, was achieved on Day 5. The RCE cells were incubated with 1 microM Hg at 37 degrees C for 30 min, followed by washing with phosphate-buffered saline containing various chelating agents (i.e., EGTA, PEN, DMSA, and BAL) to remove the surface-bound, noninternalized Hg. A substantial portion of Hg was bound to the cell surface. The removal of Hg from these binding sites was dependent on the stability constants of the chelating agents for Hg and lipophilic BAL removed the most Hg. Hg accumulation by the cells was dependent on cell density and decreased as the cell culture became confluent, possibly due to the formation of tight junctions resulting in a majority of the Hg transport occurring through the apical membrane. As measured after BAL washing, metabolic inhibitors, NaF, DNP, and ouabain decreased Hg accumulation by 28% and low temperature (4 degrees C) decreased it by 62%. Dependence of Hg uptake on metabolic energy and temperature suggests that a part of Hg is transported via active transport system. The pronounced decrease of Hg uptake at 4 degrees C indicates that, in addition to active transport, Hg transport also involves simple diffusion, some of which is dependent on membrane fluidity. It is concluded that Hg transport in RCE cells through the apical membrane occurs mainly by diffusion, and to a smaller extent by active transport.

Dose-response relationship between total cadmium intake and prevalence of renal dysfunction using general linear models

To determine the maximum allowable intake limits for chronic dietary exposure to cadmium (Cd), the dose-response relationship between total Cd intake and prevalence of renal dysfunction was examined using general linear models considering the effect of age as a confounder. The target population comprised 1850 Cd-exposed and 294 non-exposed inhabitants of Ishikawa, Japan. They were divided into 96 subgroups by sex, age (four categories) cadmium concentrations in rice (three categories) and length of residence (four categories). As indicators of the cadmium-induced renal dysfunction, glucose, total protein, amino nitrogen, beta 2-microglobulin and metallothionein in urine were employed. General linear models were fitted statistically to the relationship among prevalence of renal dysfunction, sex, age and total Cd intake. Prevalence of abnormal urinary findings other than glucosuria had significant associations with total Cd intake. When total Cd intake corresponding to the mean prevalence of each abnormal urinary finding in the non-exposed subjects was calculated using general linear models, total Cd intakes corresponding to glucosuria, proteinuria, aminoaciduria (men only) and proteinuria with glucosuria were determined to be ca. 2.2-3.8 g and those corresponding to prevalence of metallothioneinuria were calculated as ca. 1.5-2.6 g. The low-molecular-weight protein in urine was confirmed to be a more sensitive indicator of renal dysfunction, and these total Cd intake values were close to those calculated previously by simple regression analysis, suggesting them to be reasonable values as the maximum allowable intake of Cd.

Metal transport in cells: cadmium uptake by rat hepatocytes and renal cortical epithelial cells

The toxic metals appear to use the transport pathways that exist for biologically essential metals. In this regard interactions between the toxic and essential metals are possible. This report summarizes recent findings on the transport of cadmium in rat hepatocytes and renal cortical epithelial cells in the presence or absence of certain essential metals. The transport of cadmium in hepatocytes does not require energy and, therefore, is not an active process. It occurs primarily (80%) by temperature-sensitive processes, i.e., ion channels and carriers, that involve interaction with sulfhydryl groups. These processes apparently exist for the transport of essential metals like copper, zinc and calcium. The remaining 20% of the cadmium in hepatocytes is transported via a temperature-insensitive process, possibly by diffusion. In comparison with the hepatocytes, a smaller fraction (30%) of the cadmium transport through the basolateral membrane and none from the apical membrane of the renal cortical epithelial cells is temperature-sensitive. Total accumulation through the basolateral membrane is about twice that through the apical membrane. A majority of the cadmium transport in the renal cells is by diffusion. As in hepatocytes, copper, zinc and mercury antagonize cadmium transport through the apical membranes of the renal cells. The relative antagonism by copper is the same (25%); however, the antagonism by zinc (16%) and mercury (10%) is 4- to 6-fold lower than in hepatocytes. It appears that the relative contribution of various transport pathways available for cadmium uptake is different in each cell type and apparently depends on the morphological and functional differences between the cell membranes.

The nephrotoxicity of intravenously administered cadmium-metallothionein: effect of dose, mode of administration, and preexisting renal cadmium burden

Exogenously administered cadmium-metallothionein (Cd-MT) is highly nephrotoxic, producing renal damage similar to that seen following chronic Cd exposure. However, nephrotoxicity following Cd-MT administration occurs at a much lower renal Cd concentration than that following chronic Cd exposure. In the present study, the sensitivity of female rats to bolus and infused doses of Cd-MT was evaluated. The Cd-MT was administered via the jugular vein either as a bolus or infused over a 24-hr period via osmotic minipumps in naive rats and in rats which had been pretreated with 5 microM CdCl2/kg, sc, five times/week, for 9 weeks. Renal toxicity was evaluated by urinary lactate dehydrogenase, protein, and MT excretion. In naive rats, a bolus dose of 0.15 mg Cd/kg as Cd-MT was nephrotoxic. In comparison, a two-fold higher infused dose was required to cause nephrotoxicity. In Cd-pretreated rats, a bolus dose of 0.45 mg Cd/kg as Cd-MT was necessary to produce nephrotoxicity, presumably because Cd pretreatment yielded renal MT levels that were about 15 times higher than the levels in naive animals. Although a bolus dose of 3 mg Cd/kg as CdCl2 resulted in a renal Cd concentration about 1.5 times that found after administration of 0.15 mg Cd/kg as Cd-MT, it did not produce any nephro-toxicity. The results of this study suggest that a renal Cd concentration, which is nephrotoxic if the Cd-MT is administered as a bolus dose, is well tolerated if the Cd-MT is delivered at a sustained level over a 24-hr period. Furthermore, the preexisting renal Cd burden reduces the sensitivity to nephrotoxicity of Cd-MT, presumably due to elevated MT levels available for sequestration of incoming Cd. We conclude that mere accumulation of Cd in the kidney does not necessarily result in nephrotoxicity; instead, the circulating Cd-MT level, as well as the intracellular MT concentration, appear to be the more important determinants of nephrotoxicity.

Cadmium uptake by primary cultures of rat renal cortical epithelial cells: influence of cell density and other metal ions

The uptake and accumulation of 1-5 microM cadmium (Cd) was studied in primary cultures of rat renal cortical epithelial cells under protein-free conditions at 4 or 37 degrees C for up to 30 min. The cells were isolated from female rats by collagenase digestion and cultured for 3-7 days. Confluency of the culture, monitored morphologically as well as by total protein content, was achieved on Day 5. Cd accumulation at 1 microM concentration demonstrated an inverse relationship to the cell density; the Cd level in Day 5 culture was only 45% of that in Day 3 culture. In subconfluent cultures (Days 3 and 4) the Cd accumulation was temperature sensitive; on Day 3 the cells accumulated one-third less Cd at 4 degrees C than at 37 degrees C. In comparison, the confluent cells (Day 5) had the same Cd accumulation regardless of the incubation temperature. In these cells, preincubation with cyanide also had no significant effect on Cd accumulation, implying a lack of energy requirement for Cd uptake. As the transport of Cd may involve processes that exist for the essential metal ions, the effect of 30 microM zinc (Zn) and copper (Cu) on the accumulation of 1 microM Cd was studied in Day 5 cultures. Coincubation with Zn caused a 16% reduction in Cd levels at 37 degrees C and even greater reduction (44% of control) at 4 degrees C. Similarly, Cu inhibited Cd accumulation by 26 and 45% at 37 and 4 degrees C, respectively, as compared to the temperature-matched controls. The Vmax for the initial Cd uptake (1 min) was 125 pmol/mg protein/min and the Km was 7 microM. Both Zn and Cu exhibited competitive inhibition kinetics and doubled the Km for Cd uptake. The Ki for Zn and Cu was 23 and 30 microM, respectively. Mercury (Hg) and lead (Pb) were also tested for their ability to affect Cd accumulation. As compared to the controls, 1 microM Hg caused an 11% reduction in Cd level at 37 degrees C. In contrast, 1 microM Pb enhanced Cd accumulation by 20%. However, neither Hg nor Pb had any significant effect on Cd accumulation at 4 degrees C. All four metals had no significant effect on the efflux of Cd from the cells. Thus, these metals affected Cd accumulation by changing its uptake rather than its efflux.(ABSTRACT TRUNCATED AT 400 WORDS)

Dose-response relationship between total cadmium intake and metallothioneinuria using logistic regression analysis

The dose-response relationship for environmental cadmium exposure was assessed using logistic regression analysis. The prevalence of metallothioneinuria was employed as a response variable, while age and total cadmium intake, calculated from the average cadmium concentration in rice and duration of residence in the cadmium-polluted area, were used as explanatory variables. The target population comprised of 1843 cadmium-exposed and 240 non-exposed inhabitants of Ishikawa, Japan. The individuals were divided into 96 subgroups by sex, age (4 categories), cadmium concentrations in rice (3 categories) and length of residence in the polluted area (4 categories). Only total cadmium intake had a significant association with the prevalence of metallothioneinuria. In the non-exposed subjects total cadmium intakes corresponding to 2.5% prevalence of metallothioneinuria were calculated. Based on metallothionein levels expressed as either microgram/l urine or microgram/g creatinine, the total intakes were: 2.221 or 2.207 g in men and 2.365 or 0.319 g in women, respectively. Most of these values were similar to those reported by us previously, employing simple regression analysis. It is concluded, therefore, that a maximum allowable intake of about 2 g cadmium is a reasonable estimate for preventing the cadmium-induced renal dysfunction.

Cadmium disposition and metallothionein induction in mice: strain-, sex-, age- and dose-dependent differences

The strain- and sex-related differences in tissue cadmium (Cd) and metallothionein (MT) levels were examined in young adult (4-6 months old) C3H/HeJ, DBA/2J, 129/J, CD-1 and A/J mice, 24 h after a subcutaneous (s.c.) injection of 5-30 mumol CdCl2/kg. In many cases the tissue Cd concentrations were inversely related to the tissue weights. Also, the strain and sex differences were more obvious at 20-30-mumol dose levels. At such doses the hepatosensitive C3H males had as much as 30% higher hepatic Cd concentrations as the resistant DBA males, but similar concentrations to the resistant A/J and CD-1 males. This observation suggests that tissue Cd level is not the only determinant of strain differences in hepatotoxicity in males. Among the females, the A/J had 30-47% higher hepatic Cd concentration than the other strains. Livers of male C3H, CD-1 and 129/J mice had 17-57% higher Cd concentrations than those of the females; the greatest difference was in the C3H strain in which only the males exhibited hepatotoxicity at the 30 mumol dose. In all animals the hepatic MT concentration increased with the increasing Cd concentration. However, the 129/J males and all the females reached a plateau in MT concentration at Cd concentrations of 20-30 micrograms/g liver. Even at the highest Cd concentration, the C3H males had MT concentrations similar to some of the hepatoresistant males, suggesting that their sensitivity to Cd was not due to compromised MT levels. The renal Cd concentration was similar in males of most strains but not in females. For example, at the 30-mumol dose 129/J females had a Cd concentration which was 70% higher than in the DBA females. Also, at this dose level the A/J, C3H and 129/J females had 30-50% more Cd than the males. The DBA and C3H males had approximately twice the MT concentration of the A/J and 129/J males at 10 micrograms Cd/g kidney. At similar Cd concentration, the DBA females also had 1.6-2.0 times the MT concentration of the other females. The renal MT levels in females were 1.4-2.9 times higher than in males. Strains susceptible to the testicular toxicity of Cd had up to three times greater testicular Cd accumulation than the resistant strains. However, there was no increase in testicular MT in any strain. The effect of age on Cd and MT levels was studied in 19-month-old A/J and DBA mice at the 25-mumol dose.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of cadmium, mercury and calcium accumulations by isolated hepatocytes of the small skate (Raja erinacea) and rat

1. Accumulation of calcium, cadmium and mercury by isolated hepatocytes of the small skate (Raja erinacea) and rat was examined at 14 and 37 degrees C, respectively. 2. Metal uptakes by both species were biphasic, with rat cells accumulating more metal than the skate cells. 3. Total accumulation after 30 min was in the order: mercury = cadmium much greater than calcium. 4. In both species calcium and cadmium accumulations were reduced at 4 degrees C, while mercury accumulation was not. 5. Cd accumulation was increased by Cu and Hg in both species. 6. Hg accumulation was inhibited by Cu in both species, and increased by Cd only in the rat cells.

Cadmium and mercury accumulation in rat hepatocytes: interactions with other metal ions

The uptake of essential metals, such as calcium, copper (Cu), iron (Fe), and zinc (Zn), occurs through processes that include energy-independent carrier mechanisms as well as ion channels. Since cadmium (Cd) and mercury (Hg) inhibit the uptake of these metals, this study examined whether the essential metals in turn affect Cd and Hg accumulation. The uptake of 3 microM Cd was inhibited by Cu, Fe, Zn, and Hg, with 100 microM Zn having the greatest effect. Kinetic analysis indicated that these metals inhibited Cd accumulation in a competitive manner. In comparison, neither the essential metals nor Cd had any significant effect on Hg accumulation. At 4 degrees C the accumulation of Cd was reduced to 20% of that at 37 degrees C, while Hg uptake remained unaffected. The efflux of Cd from the hepatocytes was biphasic, energy-independent, and not affected by Zn, Cu, or Fe. Thus the essential metals decreased Cd accumulation by inhibiting its uptake. On the other hand, Hg decreased Cd accumulation by both inhibiting its uptake and enhancing its efflux. As determined by the organic SH blockers, nearly two-thirds of the Cd entered the hepatocytes through processes involving the SH ligands. The uptake of Hg, however, was not affected by the SH blockers. Furthermore, the fraction of membrane-bound Hg at 3 microM concentration was 2.5 times greater than Cd, indicating that Hg is associated with additional binding sites not utilized by Cd. These results suggest that in hepatocytes Cd uptake occurs mainly through the SH-containing transport processes associated with the uptake of Zn and, to a smaller extent, Cu and Fe. Hg can inhibit Cd uptake by binding to these sites; however, its own uptake occurs via other processes that remain to be elucidated.

Lead nephrotoxicity and associated disorders: biochemical mechanisms

Lead may exert toxic effects on several organ systems, but those in the kidney are the most insidious. Acute lead nephropathy is characterized by proximal tubular dysfunction with the development of a Fanconi-type syndrome, alterations in mitochondrial structure and the development of cytosolic and nuclear inclusion bodies. Intracellular lead is associated with specific high affinity proteins and can also bind to metallothionein. Chronic lead nephropathy is irreversible and is typically accompanied by interstitial fibrosis, both hyperplasia and atrophy of the tubules, glomerulonephritis and, ultimately, renal failure. In addition, lead produces renal neoplasms in experimental animals. Chronic lead exposure is also implicated in the development of saturnine gout and hypertension. The metal interacts with renal membranes and enzymes and disrupts energy production, calcium metabolism, glucose homeostasis, ion transport processes and the renin-angiotensin system. This review summarizes the biochemical effects of lead on the kidney to understand the mechanisms of lead-induced nephropathy and other associated disorders.

Differences in cadmium and mercury uptakes by hepatocytes: role of calcium channels

Calcium uptake in cells occurs through specific membrane channels. Since cadmium and mercury inhibit calcium uptake, this study examined whether the calcium channels may also be involved in the uptake of these metals. Primary cultures of rat hepatocytes were incubated with 3 microM CdCl2 or HgCl2 in the absence or presence of four different organic calcium channel blockers or a calcium agonist. The calcium channel blockers had no significant effect on mercury accumulation. In comparison, the uptake of cadmium was inhibited by diltiazem and verapmil (50-250 microM) as well as by nifedipine and nitrendipine (25-100 microM), with a maximum inhibition of 31% after 30 min incubation with 250 microM verapamil. The calcium agonist vasopressin (20 nM) increased cadmium accumulation by 15%. This effect was blocked by 250 microM verapamil. Kinetic analysis showed that verapamil decreased the Vmax of cadmium uptake, without altering the Km, indicating a noncompetitive inhibition. The calcium channel blockers were ineffective at 4 degrees C. These data suggest that about a third of the cadmium enters hepatocytes through the calcium channels. The mechanism of mercury uptake, on the other hand, is very different as it does not appear to involve the calcium channels.

Dose-response relationship between dietary cadmium intake and metallothioneinuria in a population from a cadmium-polluted area of Japan

An epidemiological study to examine the dose-response relationship for environmental cadmium exposure was performed in 1843 cadmium-exposed and 240 non-exposed inhabitants of the Kakehashi River basin in Ishikawa, Japan. The average cadmium concentration in rice from each village was employed as an indicator of cadmium exposure and the individuals were grouped according to the length of residence in the polluted area. Metallothioneinuria was used as an index of renal tubular dysfunction produced by the chronic exposure to cadmium. A dose-related increase in metallothioneinuria was observed. The chronic total cadmium intake resulting in metallothioneinuria in this population was calculated to be approximately 2 g for both men and women. The cumulative lifetime dose of 2 g cadmium over a 50-year period, means an average daily intake of 110 micrograms. Thus, these values may be regarded as the maximum allowable lifetime and daily intake limits, respectively for chronic dietary exposure to cadmium.