μM CdCl2 Research Articles

BIOINDICATION OF WATER POLLUTION IN THE SOMES RIVER USING BIOCHEMICAL AND PHYSIOLOGICAL PARAMETERS OF THE GREEN ALGA SCENEDESMUS OPOLIENSIS P. RICHTER

Cultures of Scenedesmus opoliensis P. Richter, used as single-species test systems, were exposed to differently polluted water samples collected from distinct sectors of the Somes River, in order to identify physiological and biochemical markers suitable for a reliable bioindication of changes in the quality of aquatic environments. Algal cultures grown in Bold’s basal nutrient medium were used as control, and another reference consisted of cultures exposed to 25 µM CdCl2. Environmental stress exerted by water pollution induced changes in the antioxidative protection of algal cells. When only small amounts of hydrogen peroxide were generated, the activities of ascorbate peroxidase and of superoxide dismutase were enhanced, while the activity of these enzymes declined when hydrogen peroxide accumulated in cells. Vitamin C content of algal cells increased moderately, but significantly under water pollution. The chlorophylls to carotenoids ratio and net oxygen production decreased, while membrane lipid peroxidation increased in polluted water. Cell density was more affected than dry biomass. From among the parameters of induced chlorophyll fluorescence, potential quantum efficiency and vitality index exhibited the most sensitive changes in accordance with the pollution of aquatic environment. The above mentioned parameters of Scenedesmus opoliensis may be useful biochemical and physiological markers of water pollution.

Protective effects of N-acetylcysteine against cadmium-induced damage in cultured rat normal liver cells.

In this study, the protective effects of N-acetylcysteine (NAC), a precursor of reduced glutathione, were studied by measuring the viability, the levels of antioxidant enzymes, and by analyzing the cell cycle in cadmium (Cd)-treated rat liver cells. The cells were treated with 150 µM CdCl2 alone or co-treated with 150 µM CdCl2 and 5 mM NAC (2 h pre-, simultaneous or 2 h post-treatment) for 24 h. The viability of the cells treated with 150 µM CdCl2 alone decreased to 40.1%, while that of the cells co-treated with 5 mM NAC (pre-, simultaneous and post-treatment) significantly increased to 83.7, 86.2 and 83.7%, respectively in comparison to the control cells (100%). The catalase enzyme level decreased to undetectable level in the cells treated with CdCl2 alone, while it significantly increased in the co-treated cells (pre-, simultaneous and post-treatment) to 40.1, 34.3 and 13.2%, respectively. In the cells treated with CdCl2 alone, the glutathione peroxidase enzyme level decreased to 78.3%, while it increased in the co-treated cells (pre-, simultaneous, and post-treatment) to 84.5, 83.3 and 87.9%, respectively. The glutathione reductase enzyme level decreased to 56.1% in the cells treated with cadmium alone, but significantly increased in the cells co treated with NAC (pre-, simultaneous and post-treatment) to 79.5, 78.5 and 78.2%, respectively. Cd caused cell cycle arrest at the S and G2/M phases. The co-treatment with NAC inhibited cell cycle arrest by shifting the cells to the G1 phase. These results clearly show the protective effects of NAC against Cd-induced damage in rat liver cells.

Real‐time visualization of oxidative stress in a floating macrophyte Lemna minor L. exposed to cadmium, copper, menadione, and AAPH

An ultra-sensitive digital imaging system was employed to visualize oxidative stress in intact L. minor plants exposed to Cd, Cu, menadione, AAPH, and ascorbate in real time. The increase of ROS production was assessed by measuring the rate of fluorescence intensity increases of the test medium supplemented with a fluorescing probe (dichlorofluorescein diacetate). The addition of 100 μM CdCl₂ or 100 μM CuSO₄ to the growth medium resulted in a significant increase of medium fluorescence. Additionally, CuSO₄ caused a significantly higher fluorescence intensity than CdCl₂ did. A strong positive correlation (R² = 0.99) between menadione concentration and fluorescence intensity was observed. The positive correlation between AAPH concentration and fluorescence intensity was not as strong as in the case of menadione (R² = 0.81). Menadione induced a stronger oxidative stress than similar concentration of AAPH. The addition of 100 μM ascorbate to L. minor treated with 50 μM menadione significantly reduced the fluorescence intensity increase. A linear trend of the fluorescence increase was observed in all treatments, indicating that chemical-induced oxidative stress is a gradual process and that the applied concentrations of the chemicals caused a constant increased production of ROS with different intensities, depending on the treatment. This is the combined result of a gradual diminishing of antioxidant reserves and accumulating oxidative damage. The observed rates of ROS production were slower than those in the studies using cell cultures.

A Combined Zinc/Cadmium Sensor and Zinc/Cadmium Export Regulator in a Heavy Metal Pump

Heavy metal pumps (P1B-ATPases) are important for cellular heavy metal homeostasis. AtHMA4, an Arabidopsis thaliana heavy metal pump of importance for plant Zn(2+) nutrition, has an extended C-terminal domain containing 13 cysteine pairs and a terminal stretch of 11 histidines. Using a novel size-exclusion chromatography, inductively coupled plasma mass spectrometry approach we report that the C-terminal domain of AtHMA4 is a high affinity Zn(2+) and Cd(2+) chelator with capacity to bind 10 Zn(2+) ions per C terminus. When AtHMA4 is expressed in a Zn(2+)-sensitive zrc1 cot1 yeast strain, sequential removal of the histidine stretch and the cysteine pairs confers a gradual increase in Zn(2+) and Cd(2+) tolerance and lowered Zn(2+) and Cd(2+) content of transformed yeast cells. We conclude that the C-terminal domain of AtHMA4 serves a dual role as Zn(2+) and Cd(2+) chelator (sensor) and as a regulator of the efficiency of Zn(2+) and Cd(2+) export. The identification of a post-translational handle on Zn(2+) and Cd(2+) transport efficiency opens new perspectives for regulation of Zn(2+) nutrition and tolerance in eukaryotes.

Effects of long-term cadmium exposure on growth and metabolomic profile of tomato plants

The response of tomato plants to long-term cadmium exposure was evaluated after a 90-days long culture in hydroponic conditions (0, 20, and 100 μM CdCl 2). Cadmium preferentially accumulated in roots, and to a lower extent in upper parts of plants. Absolute quantification of 28 metabolites was obtained through 1H NMR, HPLC-PDA, and colorimetric methods. The principal component analysis showed a clear separation between control and Cd treated samples. Proline and total ascorbate amounts were reduced in Cd-treated leaves, whereas α-tocopherol, asparagine, and tyrosine accumulation increased, principally in 100 μM Cd treated leaves. Carotenoid and chlorophyll contents decreased only in 100 μM Cd-mature-leaves, which correlate with a reduced expression of genes essential for isoprenoid and carotenoid accumulations. Our results show that tomato plants acclimatize during long-term exposure to 20 μM Cd. On the contrary, 100 μM Cd treatment results in drastic physiological and metabolic perturbations leading to plant growth limitation and fruit set abortion.

Cadmium-induced lignification restricts soybean root growth

The effects of cadmium (Cd), a well-known environmental pollutant with high toxicity to plants, were tested on root growth, cell viability, phenylalanine ammonia-lyase (PAL) soluble plus cell wall-bound peroxidase (POD) activities, hydrogen peroxide (H 2O 2) levels, and the content and monomeric composition of lignin in soybean ( Glycine max) roots. Three-day-old seedlings were cultivated in half-strength Hoagland’s solution (pH 6.0), with or without 25–100 μM CdCl 2 in a growth chamber (25 °C, 12/12-h light/dark photoperiod, irradiance of 280 μmol m −2 s −1) for 24 h. In general, root length and the fresh and dry weights decreased followed by loss of cell viability after Cd treatment. PAL activity, soluble and cell wall-bound POD activities, and H 2O 2 and lignin contents increased significantly after Cd exposure. The lignin monomeric composition of Cd-exposed roots revealed a significant increase of p-hydroxyphenyl (H) and syringyl (S) units. These results suggest that the effects caused by Cd may be due to excessive production of monolignols forming lignin, which solidifies the cell wall and restricts root growth.

Expression of an Arabidopsis Ca 2+/H + antiporter CAX1 variant in petunia enhances cadmium tolerance and accumulation

Phytoremediation is a cost-effective and minimally invasive technology to cleanse soils contaminated with heavy metals. However, few plant species are suitable for phytoremediation of metals such as cadmium (Cd). Genetic engineering offers a powerful tool to generate plants that can hyperaccumulate Cd. An Arabidopsis CAX1 mutant (CAXcd), which confers enhanced Cd transport in yeast, was ectopically expressed in petunia to evaluate whether the CAXcd expression would enhance Cd tolerance and accumulation in planta. The CAXcd-expressing petunia plants showed significantly greater Cd tolerance and accumulation than the controls. After being treated with either 50 or 100 μM CdCl 2 for 6 weeks, the CAXcd-expressing plants showed more vigorous growth compared with controls, and the transgenic plants accumulated significantly more Cd (up to 2.5-fold) than controls. Moreover, the accumulation of Cd did not affect the development and morphology of the CAXcd-expressing petunia plants until the flowering and ultimately the maturing of seeds. Therefore, petunia has the potential to serve as a model species for developing herbaceous, ornamental plants for phytoremediation.

Heat shock-induced ascorbic acid accumulation in leaves increases cadmium tolerance of rice (Oryza sativa L.) seedlings

Ascorbic acid (AsA) is the most abundant antioxidant in plants and plays a role in responding to oxidative stress. It has been shown that AsA plays a role in protecting against abiotic stresses. Rice seedlings stressed with 5 μM CdCl2 showed typical Cd toxicity (chlorosis and increase in malondialdehyde content). Rice seedlings pretreated with heat shock at 45°C (HS) or H2O2 under non-HS conditions resulted in the increase in ascorbic acid (AsA) content and the AsA/dehydroascorbate ratio in rice leaves. Exogenous application of AsA or L-galactonone-1, 4-lactone (GalL), a biosynthetic precursor of AsA, under non-HS conditions, which resulted in an increase in AsA content in leaves, enhanced subsequent Cd tolerance of rice seedlings. Pretreatment with imidazole, an inhibitor of NADPH oxidase, under HS conditions significantly decreased H2O2 and AsA contents in leaves and reduced subsequent Cd tolerance of rice seedlings. We also observed that pretreatment with lycorine, which is known to inhibit the conversion of GalL to AsA, significantly inhibited HS-induced AsA accumulation in leaves and reduced HS-induced protection against subsequent Cd stress of rice stress. It appears that HS- or H2O2-induced protection against subsequent Cd stress of rice seedlings is mediated through AsA. The time-course analyses of HS in rice seedlings demonstrated that the accumulation of H2O2 preceded the increase in AsA. Based on the data obtained in this study, it could be concluded that the early accumulation of H2O2 during HS signals the increase in AsA content, which in turn protects rice seedlings from oxidative damage caused by Cd.

Effect of salicylic acid pretreatment on cadmium toxicity in wheat

Cadmium (100, 400 and 1000 μM CdCl2) treatments resulted in the inhibition of root dry biomass, root elongation and increased Cd accumulation in wheat (Triticum aestivum L.) roots. Further, these treatments decreased relative water content, chlorophyll content, 14CO2-fixation, activities of phosphoenolpyruvate carboxylase and ribulose-1,5-bisphosphate carboxylase and abscisic acid content while increased malondialdehyde, hydrogen peroxide and free proline contents. Chloroplast and root ultrastructure was also changed. Pretreatment of seeds with SA (500 μM) for 20 h resulted in amelioration of these effects.

Cadmium Uptake, Translocation, and Tolerance in AHA1OX Arabidopsis thaliana

Information on cadmium (Cd) uptake and transport is essential to understand better the physiology of Cd tolerance in plants. In this study, Cd uptake, translocation, and tolerance were investigated in AHA1 (Arabidopsis plasma membrane H(+)-ATPase gene) overexpressed plants. Exposed to 10 µM CdCl(2), AHA1OX showed a higher root elongation, accumulated more Cd, and maintained better integrity of nucleus membrane of root tips in comparison to the control plant (WT), suggesting that AHA1OX was more Cd tolerant than WT. To investigate Cd tolerance mechanism of AHA1OX plants, we measured the activity of plasma membrane H(+)-ATPase and the secretion of citrate. Results indicated that treatment with 10 µM of Cd stimulated the activity of plasma membrane H(+)-ATPase and the secretion of citrate, while 30 µM of Cd inhibited them. AHA1OX had higher activity of H(+)-ATPase and secretion of citrate than WT. Addition of citrate enhanced root-to-shoot translocation of Cd significantly. A higher root-to-shoot Cd translocation was observed in AHA1OX than in WT plants. Treatment with low temperature or metabolic inhibitor (carbonyl cyanide m-chlorophenylhydrazone) inhibited Cd uptake and translocation. The study of Cd forms using sequential extraction indicated that Cd was mainly present as a protein-bound form, and AHA1OX had more water-soluble Cd than WT. Taken together, our results suggested that the Cd tolerance of AHA1OX was associated with its root-to-shoot Cd translocation and secretion of citrate, which converts Cd(2+) into less toxic and more easily transportable forms in plant cells.

Differential induction of MAP kinase signalling pathways by cadmium in primary cultures of mouse embryo limb bud cells

While it is well accepted that mammalian embryos may develop abnormally in response to harmful environmental stresses, the molecular changes that embryonic cells undergo are not always clear. In the present study we examined the induction of mitogen-activated protein kinase (MAPK) pathways by cadmium chloride (CdCl 2) in micromass cultures of limb bud cells from day 11 BALB/c mouse embryos. CdCl 2 exposure was found to cause a marked reduction in both cell survival and differentiation in these cultures. To study stress signalling pathways, cells were lysed and were examined for the phosphorylation of three MAPKs. It was shown that 4 μM CdCl 2 treatment of limb bud cells caused the phosphorylation of c-Jun N-terminal kinase (JNK), but not p38 or extracellular signal-regulated kinase (ERK), over a 120 min period. The results indicate a specific activation of the JNK pathway in response to CdCl 2-induced toxicity in mouse limb bud cells.

Cadmium effects on human fetal spinal cord

The biological effects of Cadmium (Cd) on the central nervous system is poorly understood; it is thought that during brain development, when the blood-brain barrier is not well established, Cd may enter the brain and exerts its toxic effects. It has also been suggested that several diseases such as Parkinson disease, amyotrophic lateral sclerosis (ALS) as well as malformations such as spina bifida and forelimb ectrodactyly may be related to Cd exposure. In this study we evaluated the role of Cd in affecting motor neurons and glial cells of the ventral horns of human fetal spinal cord. Sections of human fetal spinal cord (9-12 weeks) were exposed for 24 h to 10 and 100 μM CdCl2. Morphology was evaluated by Haematoxilyn-Eosin staining; distribution and number of motor neurons as well as of glial cells were studied by immunohistochemistry and by Western blot; apoptosis were investigated by TUNEL assay and by Western blot. The cell density in the ventral horns, after CdCl2 treatments, appeared dramatically decreased and the number of apoptotic cells became higher in comparison to control specimens as demonstrated by the high expression level of three different apoptotic markers (NGFR p75, caspase 8 and PARP). The number and the distribution of motor neurons, expressing β tubulin III and positive to choline acetyltransferase, appeared significantly decreased after the treatment with different concentrations of CdCl2. Activation and increase of glial cells were confirmed by the high expression level of Glial Fibrillary Acidic Protein (GFAP). In this study we demonstrate the role of Cd, one of the most diffuse environmental pollutant linked to industrial development, in inducing apoptosis of motor neurons in the ventral horns of human fetal spinal cord. Motor neurons death is accompanied by a surrounding intense glyosis leading to a significant overthrow of the morphological architecture of spinal cord during its development.

Cadmium has contrasting effects on polyethylene glycol – Sensitive and resistant cell lines in the Mediterranean halophyte species Atriplex halimus L.

Beside a direct toxicity, cadmium impact on plants involves both a secondary-induced water stress and an oxidative stress. Proliferating cell lines of Atriplex halimus were selected for their sensitivity or resistance to polyethylene glycol (PEG 10,000, 20%) and then exposed to 100 μM CdCl 2 in the simultaneous presence or absence of PEG 20% or 150 mM NaCl. The PEG resistant cell line exhibited a higher growth in the presence of Cd than the sensitive line, although Cd acccumulation was higher in the former than in the latter. Exogenous PEG induced an increase in Cd concentration in the sensitive but not in the resistant cell line while NaCl induced a decrease in Cd accumulation in both cell lines. In the presence of Cd alone, the water content (WC) was higher and the osmotic potential was lower in PEG-sensitive than in PEG resistant line. The presence of PEG in the Cd-containing medium increased the WC and decreased the osmotic potential in PEG-resistant line comparatively to Cd stress alone, while an inverse trend was observed for the sensitive line. The PEG-resistant cell line displayed a higher ability to cope with oxidative stress in relation to an increase of endogenous antioxidants (glutathione and ascorbic acid), a high constitutive superoxide dismutase (EC 1.15.1.1) activity and an efficient Cd-induced increase in glutathione reductase (GR) (EC 1.6.4.1) and ascorbate peroxidase (APX) (EC 1.11.1.11). Cadmium tolerance in PEG-resistant line is thus not related to any strategy of Cd exclusion or osmotic adjustment but to tolerance mechanisms allowing the tissue to restrict the deleterious impact of accumulated Cd.

Silicon supplementation ameliorated the inhibition of photosynthesis and nitrate metabolism by cadmium (Cd) toxicity in Cucumis sativus L.

The effects of silicon (Si) application on plant growth, pigments, photosynthetic parameters, chlorophyll a (Chl a) fluorescence parameters and nitrogen metabolism were studied in Cucumis sativus L. under cadmium (Cd) toxicity. Compared with the control, 100 μM CdCl 2 treatment caused dramatic accumulation of Cd in cucumber leaves, greatly induced chlorosis, and the transmission electron microscope (TEM) analysis indicated that Cd treatment cucumber chloroplast showed obvious swollen, thylakoids and chloroplast membrane were seriously damaged, and could not be observed clearly. Application of Si reversed the chlorosis, protected the chloroplast from disorganization, and significantly increased the pigments contents, which might be mainly responsible for the higher photosynthetic rate and accumulation of biomass under Cd stress. Further investigation of chlorophyll a fluorescence indicated that Cd treatment decreasing photosynthesis was not due to stomatal restriction, while was closely related integrity damage or function lost of the photosynthetic machinery which can be concluded from the higher intercellular CO 2 concentration (Ci) and lower F v/ F m and ΦPSII. Application of Si alleviated the inhibited level of photosynthesis and F v/ F m and ΦPSII by Cd, which might imply that Si plays important roles in protecting photosynthetic machinery from damaging. The Cd treatment also greatly inhibited the enzymes of nitrogen metabolism including nitrogen reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH), and Si supply decreased the inhibiting effects of Cd.

MAPK activation is involved in Cadmium-induced Hsp70 expression in HepG2 cells

Cadmium is one of the most toxic elements to which man can be exposed at work or in the environment. By far, the most salient toxicological property of Cd is its exceptionally long half-life in the human body. Once absorbed, Cd accumulates in the human body, particularly in the liver and other vital organs. The cellular actions of Cd are extensively documented, but the molecular mechanisms underlying these actions are still not resolved. It is known that Cd activates the activator protein-1 (AP-1), but no data about the pathway involved are reported for liver. The objective was to provide a greater insight into the effect of cadmium on mitogen-activated protein kinases (MAPK’s) involved in signal transduction, its relationship with AP-1 activation, and heat shock protein (Hsp) 70 expression, in HepG2 cells. AP-1 activation as a result of 5 μM CdCl2 exposure was increased 24.5-fold over control cells after 4 h treatment. To investigate the role of the extracellular signal-regulated protein kinases (ERK’s), c-Jun N-terminal kinases (JNK’s) and p38 kinases in cadmium-induced AP-1 activation, specific MAPKs inhibitors were used. AP-1 activation decreased by 74% with ERK inhibition, by 83% with p38 inhibition, while inhibition of JNK decreased by 70%. Only ERK and JNK participated in Hsp70 production, conferring cell protection against cadmium damage.

Effects of cadmium on plant growth and physiological traits in contrast wheat recombinant inbred lines differing in cadmium tolerance

Four wheat ( Triticum aestivum L.) lines differing in cadmium (Cd) tolerance previously identified from a recombinant inbred line population were subjected to 50 μM CdCl 2 from the three-leaf stage for 24 d, to investigate the responses of wheat seedlings to Cd toxicity. Under Cd stress, most growth parameters and root morphological traits were reduced, except for secondary root numbers and average root diameter. Cd enhanced leaf cell peroxidation due to increased malondialdehyde (MDA) content and reduced activities of superoxide dismutase (SOD) and catalase (CAT) in leaves. In addition, CAT activity decreased in the Cd-sensitive lines while increased in the tolerant lines. Leaf photosystem II (PSII) was damaged, since the maximum efficiency of PSII photochemistry (Fv/Fm) and potential efficiency of PSII photochemistry under dark-adapted (Fv/Fo) decreased, while the initial fluorescence (Fo) increased in all lines under Cd stress. Then, total soluble sugar concentration decreased while free amino acids concentration increased in both shoot and root. We concluded that Cd-tolerant lines accumulated less Cd in plant and contained low Cd concentration in shoot (less translocation of Cd to shoot), maintained higher CAT activity in leaf and higher PS II function than the Cd-sensitive lines under Cd toxicity, thus could be related to their tolerant capacity to Cd in the present study.

Effect of selenium on macro- and microelement distribution and physiological parameters of rape and wheat seedlings exposed to cadmium stress

Cadmium (Cd) exerts a detrimental effect on the metabolism of plants, whereas selenium (Se) may protect them against various stressors through its antioxidative activity. In this in vitro study we investigated the impact of Se (2 µM Na2SeO4) on the growth, nutrient (P, S, K, Ca, Mg, B, Mn, Fe and Zn) concentrations and cell integrity of rape (Brassica napus oleifera) and two wheat (Triticum aestivum) genotypes subjected to Cd stress (600 µM CdCl2). Rape accumulated both Cd and Se more than did wheat. In all plants, Cd markedly reduced the biomass, enhanced lipid peroxidation and diminished plasmalemma fluidity. A drop in the K uptake and the reduced plasmalemma permeability diminished the K efflux from the leaf cells. In contrast, Cd elevated S concomitantly with Zn, indicating an activity of detoxifying SH groups and SOD isoenzymes. When added alone, Se promoted the growth of all plants, it enhanced the accumulation of S, but the impact on other nutrients remained minor. In Cd-stressed plants, Se tended to counterbalance the Cd-induced changes in nutrients, it also reduced the lipid peroxidation and exerted positive effects on the cell membrane stability. The Cd stress and the protective role of Se were most evident in rape. The Finnish wheat genotype was less tolerant to Cd than the Polish one.

Ultrastructure analysis of cadmium-tolerant and -sensitive cell lines of cucumber (Cucumis sativus L.)

Previously, a stable cell suspension culture of cucumber tolerant to cadmium (Cd) was established (Gzyl and Gwoźdź, Plant Cell Tissue Organ Cult 80:59–67, 2005). In this study, ultrastructures of Cd-tolerant and -sensitive cells were analyzed by transmission electron microscopy (TEM). Ultrastructural differences between cell lines exposed to 100 μM CdCl2 were observed both at cellular and organelle levels. Tolerant cells exposed to Cd exhibited well-preserved cellular structures in comparison with sensitive cells. Increased numbers of osmiophilic globules in the cytoplasm and nucleolus-associated bodies as well as electron dense material in vacuoles were observed in cadmium tolerant cells. In contrast, ultrastructure of sensitive cells following exposure to Cd exhibited distinct disturbances including vacuolation, disintegration of cytoplasm, and structural changes in both mitochondria and endoplasmic reticulum. TEM observations confirmed the adaptation of tolerant cells to Cd.

Effect of selenium on characteristics of rape chloroplasts modified by cadmium

Selenium appears to be an important protective agent that decreases cadmium-induced toxic effects in animals and plants. The aim of these studies was to investigate the changes of properties of chloroplast membranes obtained from Cd-treated rape seedlings caused by Se additions. Chloroplasts were isolated from leaves of 3-week-old rape plants cultured on Murashige-Skoog media supplied with 2 μM Na 2SeO 4 and/or 400 μM CdCl 2 under in vitro conditions. The following physicochemical characteristics of chloroplasts were chosen as indicators of Se-effects: average size, zeta potential, ultrastructure, lipid and fatty acid composition and fluidity of envelope membrane. The results suggest that Se can partly counterbalance the destructive effects of Cd. This protective action led to an increase of chloroplast size reduced by Cd treatment and rebuilt, to some extent, the chloroplast ultrastructure. Lipid and fatty acid composition of chloroplast envelopes modified by Cd showed a decrease in digalactosyl-diacylglycerol content and an increase of content of monogalactosyl-diacylglycerol and phospholipid fractions, as well as an increase of fatty acid saturation of all lipids studied. The change in fatty acid saturation correlated well with a decrease of membrane fluidity and with a diminishing of absolute values of zeta potential. The presence of selenium in cultured media caused a partial reversal of the detected changes, which was especially visible in properties related to the hydrophobic part of an envelope, i.e. fatty acid saturation and fluidity.

Activation of Nrf2 by cadmium and its role in protection against cadmium-induced apoptosis in rat kidney cells

Kidney is the primary target organ in chronic cadmium (Cd) toxicity, and oxidative stress plays an important role in this process. The nuclear transcription factor Nrf2 binds to antioxidant response elements (AREs) and regulates genes involved in protecting cells from oxidative damage. Whether kidney cells respond to Cd by activating Nrf2 is unknown. This study was designed to examine the Cd-induced activation of Nrf2 transcriptional activity in a stable rat kidney cell line, NRK-52E, and to investigate the protection this might offer against apoptosis. The cells were treated with 5–20 μM CdCl 2 for 5 h, followed by a recovery period of up to 24 h. A concentration-dependent increase (up to 2.9-fold) in the level of reactive oxygen species was noted upon termination of 5-h Cd treatment. The Nrf2-ARE binding activity also increased and peaked (6.1-fold) at 10 μM Cd concentration. Time-course study revealed that the binding activity increased at 1 h of Cd treatment and peaked 2 h post Cd treatment. Apoptosis was detected 6 h post treatment with Cd and a concentration- and time-dependent increase in the apoptotic cell population occurred during the next 18 h. Over-expression of Nrf2 by transient transfection conferred resistance against Cd-induced apoptosis. Conversely, suppression of Nrf2 expression by specific siRNA resulted in greater sensitivity of the cells to Cd by decreasing the levels of two antioxidant enzymes, hemeoxygenase-1 and glutamate-cysteine ligase. Taken together, these results suggest that in kidney cells the activation of Nrf2 is an adaptive intracellular response to Cd-induced oxidative stress, and that Nrf2 is protective against Cd-induced apoptosis.