De novo characterization of Japanese scallop Mizuhopecten yessoensis transcriptome and analysis of its gene expression following cadmium exposure

Background

Japanese scallop has been cultured on a large-scale in China for many years. However, serious marine pollution in recent years has resulted in considerable loss to this industry. Moreover, due to the lack of genomic resources, limited research has been carried out on this species. To facilitate the understanding at molecular level immune and stress response mechanism, an extensive transcriptomic profiling and digital gene expression (DGE) database of Japanese scallop upon cadmium exposure was carried out using the Illumina sequencing platform.

Results

RNA-seq produced about 112 million sequencing reads from the tissues of adult Japanese scallops. These reads were assembled into 194,839 non-redundant sequences with open reading frame (ORF), of which 14,240 putative amino acid sequences were assigned biological function annotation and were annotated with gene ontology and eukaryotic orthologous group terms. In addition, we identified 720 genes involved in response to stimulus and 302 genes involved in immune-response pathways. Furthermore, we investigated the transcriptomic changes in the gill and digestive gland of Japanese scallops following cadmium exposure using a tag-based DGE system. A total of 7,556 and 3,002 differentially expressed genes were detected, respectively, and functionally annotated with KEGG pathway annotations.

Conclusion

This study provides a comprehensive transcripts sequence resource for the Japanese scallop and presents a survey of gene expression in response to heavy metal exposure in a non-model marine invertebrate via the Illumina sequencing platform. These results may contribute to the in-depth elucidation of the molecular mechanisms involved in bivalve responses to marine pollutants.

Hg- and Cd-induced modulation of lipid packing and monolayer fluidity in biomimetic erythrocyte model systems

The public health consequences that are associated with the low level exposure of various human populations to Cd(2+) and Hg(2+) are incompletely understood. In order to assess if interactions between these inorganic pollutants and erythrocyte biomembranes may contribute to their chronic toxicity, we have used a Langmuir trough to probe the effect of HgCl2 and CdCl2 on the packing and elasticity properties of biomimetic lipid monolayers using different lipid mixtures. These lipid films were deposited at room temperature on a biologically relevant subphase (1mM phosphate, 100mM NaCl at pH 7.4) in the absence and presence of 100μM HgCl2, CdCl2 and 1:1 mixtures thereof. The interactions of heavy metals with the lipids were monitored as changes in the surface pressure (π)-area (A) isotherms. In addition, metal induced changes to the elastic properties of the model systems were analyzed by area and compressibility data of phosphatidylcholine (PC) systems containing 0, 15, 30, 45 and 100% phosphatidylethanolamine (PE) and phosphatidylserine (PS). These mixtures revealed changes in lateral lipid packing as indicated by area expansion as well as enhanced film rigidity. The results demonstrate that both heavy metals affected the various lipid matrices, but metal mixtures showed the strongest impact. Based on these data, the adverse interaction of Hg(2+) and Cd(2+) with lipid bilayer membranes is identified as a feasible mechanism by which these toxic metals exert toxicity in mammalian cells. Interestingly, these metal interactions were found to depend on the lipid composition.

Effect of cadmium chloride on secretion of 17β-estradiol by the ovarian follicles of common carp, Cyprinus carpio

Cadmium (Cd(2+)) is a common environmental pollutant present in wastes associated with mining, smelting and electroplating. It is a major constituent of the tobacco smoke. Exposure of this heavy metal has been linked to wide range of detrimental effects on mammalian reproduction particularly on ovarian steroidogenesis. Low doses of Cd(2+) are reported to stimulate ovarian luteal progesterone synthesis whereas high doses inhibited it. Cd(2+) exposure is also reported to inhibit gonadal function in fish. In the present study the effects of cadmium chloride (CdCl(2)) on the secretion of gonadotropin-induced 17β-estradiol was examined in female common carp Cyprinus carpio. Vitellogenic stage fish were exposed to physiological safe dose of CdCl(2) for 0, 24, 48 and 96 h and serum and ovarian 17β-estradiol levels were estimated. In the in vitro experiments, vitellogenic follicles were incubated with CdCl(2) and a dose- and time-dependent effects on steroid production were estimated induced by LH. Exposure of fish with CdCl(2) gradually attenuated serum and ovarian 17β-estradiol levels with increasing time and maximum inhibition was noticed after 96 h. Administration of CdCl(2) to the incubations significantly inhibited LH-induced release of 17β-estradiol in vitro. To clarify the mechanism of attenuated production of 17β-estradiol, in vitro effects of CdCl(2) on LH induced P450 aromatase activity (conversion of testosterone to 17β-estradiol) and cytochrome P450arom gene expression in carp ovarian follicles were evaluated. Results show that LH-stimulated P450 aromatase activity and P450arom gene expression in ovarian follicles were significantly inhibited by CdCl(2). The present study further demonstrated that LH-induced stimulation of ovarian steroidogenic factor-1 (SF-1) which activates aromatase enzyme, is strongly inhibited by cadmium chloride treatment.

Cadmium induced physio-biochemical and molecular response in Brassica juncea

Cadmium is a hazardous heavy metal; its presence in the agricultural soil constrains the crop productivity and restricts crop plants from reaching their full genetic potential. In the present study, two Brassica juncea cultivars (Pusa Bold and Pusa Jaikisan), were exposed to different concentrations of cadmium (Cd) as cadmium chloride (CdCl2) (50 microM, 100 microM, 150 microM, and 200 microM). The effect of cadmium on seed germination ratio, changes in the root and shoot length, plant dry weight, moisture content, metal tolerance index, antioxidant enzyme activity and lipid peroxidation were studied. The consequence of cadmium stress at the molecular level was studied using a key gene Phytochelatin Synthase (PCS). The results of our study suggested that, exposure of cadmium affected the seed germination, growth rate, biomass content and antioxidant enzyme activities in the root, shoot and leaves of both the cultivars. Transcript expression of PCS was increased with increasing CdCl2 concentration in both the cultivars. Based on the results, it was concluded that, Brassica juncea Cv Pusa Jaikisan is more tolerant to cadmium toxicity than the Pusa Bold. These findings could be used to develop heavy metal stress tolerant plants and more importantly, detoxification of heavy metals in the soil.

Unique reporter-based sensor platforms to monitor signalling in cells

Introduction

In recent years much progress has been made in the development of tools for systems biology to study the levels of mRNA and protein, and their interactions within cells. However, few multiplexed methodologies are available to study cell signalling directly at the transcription factor level.

Methods

Here we describe a sensitive, plasmid-based RNA reporter methodology to study transcription factor activation in mammalian cells, and apply this technology to profiling 60 transcription factors in parallel. The methodology uses two robust and easily accessible detection platforms; quantitative real-time PCR for quantitative analysis and DNA microarrays for parallel, higher throughput analysis.

Findings

We test the specificity of the detection platforms with ten inducers and independently validate the transcription factor activation.

Conclusions

We report a methodology for the multiplexed study of transcription factor activation in mammalian cells that is direct and not theoretically limited by the number of available reporters.

SNF1-related protein kinases type 2 are involved in plant responses to cadmium stress

Cadmium ions are notorious environmental pollutants. To adapt to cadmium-induced deleterious effects plants have developed sophisticated defense mechanisms. However, the signaling pathways underlying the plant response to cadmium are still elusive. Our data demonstrate that SnRK2s (for SNF1-related protein kinase2) are transiently activated during cadmium exposure and are involved in the regulation of plant response to this stress. Analysis of tobacco (Nicotiana tabacum) Osmotic Stress-Activated Protein Kinase activity in tobacco Bright Yellow 2 cells indicates that reactive oxygen species (ROS) and nitric oxide, produced mainly via an l-arginine-dependent process, contribute to the kinase activation in response to cadmium. SnRK2.4 is the closest homolog of tobacco Osmotic Stress-Activated Protein Kinase in Arabidopsis (Arabidopsis thaliana). Comparative analysis of seedling growth of snrk2.4 knockout mutants versus wild-type Arabidopsis suggests that SnRK2.4 is involved in the inhibition of root growth triggered by cadmium; the mutants were more tolerant to the stress. Measurements of the level of three major species of phytochelatins (PCs) in roots of plants exposed to Cd(2+) showed a similar (PC2, PC4) or lower (PC3) concentration in snrk2.4 mutants in comparison to wild-type plants. These results indicate that the enhanced tolerance of the mutants does not result from a difference in the PCs level. Additionally, we have analyzed ROS accumulation in roots subjected to Cd(2+) treatment. Our data show significantly lower Cd(2+)-induced ROS accumulation in the mutants' roots. Concluding, the obtained results indicate that SnRK2s play a role in the regulation of plant tolerance to cadmium, most probably by controlling ROS accumulation triggered by cadmium ions.

Independent transcriptional reprogramming and apoptosis induction by cisplatin

Neither the molecular mechanisms whereby cancer cells intrinsically are or become resistant to the DNA-damaging agent cisplatin nor the signaling pathways that account for cisplatin cytotoxicity have thus far been characterized in detail. In an attempt to gain further insights into the molecular cascades elicited by cisplatin (leading to resistance or underpinning its antineoplastic properties), we comparatively investigated the ability of cisplatin, C2-ceramide and cadmium dichloride, alone or in the presence of an array of mitochondrion-protective agents, to trigger the permeabilization of purified mitochondria. In addition, we compared the transcriptional response triggered by cisplatin, C2-ceramide and cadmium dichloride in non-small cell lung carcinoma A549 cells. Finally, we assessed the capacity of cisplatin, C2-ceramide and cadmium dichloride to reduce the clonogenic potential of a battery of yeast strains lacking proteins involved in the regulation of cell death, DNA damage signaling and stress management. This multipronged experimental approach revealed that cisplatin elicits signaling pathways that are for the most part "private," i.e., that manifest limited overlap with the molecular cascades ignited by other inducers of mitochondrial apoptosis, and triggers apoptosis mainly in a transcription-independent fashion. Indeed, bona fide cisplatin-response modifiers that we have recently identified by a functional genome-wide siRNA screen are either not transcriptionally regulated during cisplatin-induced cell death or their transcriptional modulation reflects the activation of an adaptive response promoting cisplatin resistance.

[Influence of activator and inhibitors of Ca2+ channels on proliferative activity in Tetrahymena pyriformis infusoria]

It was determined that change in DNA content in macronuclei occurs in the T. pyriformis infusoria under the influence of an activator (caffeine) and inhibitors of Ca2+ channels (verapamil), NiCl2, and CdCl2. Caffeine (10 mM) stimulates DNA synthesis. Verapamil (5 microM), CdCl2 (125 microM), and NiCl2 (100 microM) decrease DNA content in macronuclei by 30 min after proliferative stimulation. By 4 h of incubation, there is, on average, 10% less DNA in macronuclei of Tetrahymena preprocessed with verapamil than in the control cells. The cells preprocessed with CdCl2 and NiCl2 differ from the control cells by lower DNA content almost at all studied periods, but they restore the level of nuclear DNA by 4 h. It is assumed that transmission of proliferative signals in the T. pyriformis has a Ca2+ -dependent character.

Ovarian toxicity induced by dietary cadmium in hen

To investigate the toxicity of cadmium (Cd) on female reproduction in birds, this study was conducted to determine the changes in biochemical parameters of serum and ovary tissue caused by dietary cadmium in hens. Ninety 50-day-old hyline white hens were randomly divided into three groups (30 hens per group): a control group was fed with basal diet, a low dose group was fed with basal diet containing 140 mg/kg CdCl(2) and a high dose group was fed with basal diet containing 210 mg/kg CdCl2. After being treated with Cd for 20, 40 and 60 days, ovary and serum samples were collected and examined for Cd content, histological evaluations, malondialdehyde (MDA) content, glutathione peroxidase (GPx) content, activities of superoxide dismutase (SOD), nitric oxide (NO) content, nitric oxide synthase (NOS) activity, and serum estradiol and progestogen levels. The results showed that the content of Cd, MDA, NO and the activity of NOS in ovary and serum were increased (P < 0.05), while the level of GPx and the activity of SOD were decreased (P < 0.05) in low dose and high dose groups. A time- and dose-dependent correlation was observed between serum and ovary tissue cadmium levels. The number of apoptotic cells in the ovary was increased in the Cd treatment group (P < 0.05). Extensive damage was observed in the ovary. The level of estradiol and progestogen in the serum of low dose and high dose groups was decreased significantly (P < 0.05). It indicated that Cd exposure resulted in oxidative damage of hens' ovary tissue by altering antioxidant defense enzyme systems, lipid peroxidation, apoptosis and endocrine disturbance which may be possible underlying reproductive toxicity mechanisms induced by Cd.

Cadmium affects toxicokinetics of pyrene in the collembolan Folsomia candida

Since toxicity is time dependent, short-term toxicity tests may overlook mixture effects, because chemical accumulation within an organism takes time. We therefore studied the effects of cadmium on the toxicokinetics of pyrene and its metabolites in the soil-dwelling collembolan Folsomia candida exposed through Lufa 2.2 soil. Single pyrene was rapidly taken up and steady state was reached within the 337-h exposure period. Simultaneous exposure to cadmium significantly decreased the pyrene uptake and elimination rate, resulting in a prolonged half life. Kinetics of the first phase metabolite OH-pyrene was also significantly influenced by cadmium. Cadmium increased the hydroxylation rate of pyrene but slowed down its further metabolization, again resulting in a prolonged half life. We showed that pyrene accumulation and metabolization are significantly influenced by the presence of cadmium. Our results suggest that mixture effects may be dependent on exposure time.

Expression analysis of four peroxiredoxin genes from Tamarix hispida in response to different abiotic stresses and Exogenous Abscisic Acid (ABA)

Peroxiredoxins (Prxs) are a recently discovered family of antioxidant enzymes that catalyze the reduction of peroxides and alkyl peroxides. In this study, four Prx genes (named as ThPrxII, ThPrxIIE, ThPrxIIF, and Th2CysPrx) were cloned from Tamarix hispida. Their expression profiles in response to stimulus of NaCl, NaHCO(3), PEG, CdCl(2) and abscisic acid (ABA) in roots, stems and leaves of T. hispida were investigated using real-time RT-PCR. The results showed that the four ThPrxs were all expressed in roots, stems and leaves. Furthermore, the transcript levels of ThPrxIIE and ThPrxII were the lowest and the highest, respectively, in all tissue types. All the ThPrx genes were induced by both NaCl and NaHCO(3) and reached their highest expression levels at the onset of stress in roots. Under PEG and CdCl(2) stress, the expression patterns of these ThPrxs showed temporal and spatial specificity. The expressions of the ThPrxs were all differentially regulated by ABA, indicating that they are all involved in the ABA signaling pathway. These findings reveal a complex regulation of Prxs that is dependent on the type of Prx, tissue, and the signaling molecule. The divergence of the stress-dependent transcriptional regulation of the ThPrx gene family in T. hispida may provide an essential basis for the elucidation of Prx function in future work.

Role of the RNA-binding protein Nrd1 in stress granule formation and its implication in the stress response in fission yeast

We have previously identified the RNA recognition motif (RRM)-type RNA-binding protein Nrd1 as an important regulator of the posttranscriptional expression of myosin in fission yeast. Pmk1 MAPK-dependent phosphorylation negatively regulates the RNA-binding activity of Nrd1. Here, we report the role of Nrd1 in stress-induced RNA granules. Nrd1 can localize to poly(A)-binding protein (Pabp)-positive RNA granules in response to various stress stimuli, including heat shock, arsenite treatment, and oxidative stress. Interestingly, compared with the unphosphorylatable Nrd1, Nrd1^DD (phosphorylation-mimic version of Nrd1) translocates more quickly from the cytoplasm to the stress granules in response to various stimuli; this suggests that the phosphorylation of Nrd1 by MAPK enhances its localization to stress-induced cytoplasmic granules. Nrd1 binds to Cpc2 (fission yeast RACK) in a phosphorylation-dependent manner and deletion of Cpc2 affects the formation of Nrd1-positive granules upon arsenite treatment. Moreover, the depletion of Nrd1 leads to a delay in Pabp-positive RNA granule formation, and overexpression of Nrd1 results in an increased size and number of Pabp-positive granules. Interestingly, Nrd1 deletion induced resistance to sustained stresses and enhanced sensitivity to transient stresses. In conclusion, our results indicate that Nrd1 plays a role in stress-induced granule formation, which affects stress resistance in fission yeast.

Caenorhabditis elegans as a model in developmental toxicology

A number of practical advantages have made the nematode Caenorhabditis elegans a useful model for genetic and developmental biological research. These same advantages, along with conservation of disease and stress response pathways, availability of mutant and transgenic strains, and wealth of biological information, have led to the increased use of C. elegans in toxicological studies. Although the potential to study the mechanisms of developmental toxicology in C. elegans is promising, embryonic and larval growth tests to identify compounds that affect the nematode have remained the primary use of C. elegans in developmental toxicology. Here, we describe a C. elegans larval growth and development assay for medium- and high-throughput screening using the COPAS Biosort flow cytometer and provide descriptions of the data and subsequent analysis.

Effect of copper and cadmium ions on heart function and calpain activity in blue mussel Mytilus edulis

The heart rate and calpain activity of blue mussels Mytilus edulis from the sublittoral zone, exposed to different levels of water-borne copper and cadmium, was investigated in a long-term experiment. The content of cadmium and copper in the blue mussel was determined using flame and graphite Atomic absorption spectroscopy. The observed concentrations ranged from 2.5 to 89.1 μg/g dry weight for cadmium and from 6.1 to 51.0 μg/g dry weight for copper in the control and highest concentration, respectively. Initially, increase in cardiac activity in response to copper and Cadmium exposure was observed under all pollutant concentrations (5-250 and 10-500 μg/L, respectively). The calpain-like activity in gills and hepatopancreas of the mussels treated with metals changed in dose- and time-dependent manner: from a sharp rise at the 250 μg/L concentration of copper on the first day to a significant decrease under the effect of Cadmium in the concentration of 500 μg/L on the third day of the experiment. These results suggest that: (i) heart rate oscillation may reflect active adaptation of blue mussels to contamination and (ii) animals have different sensitivity to copper and Cadmium according to the role of the metals in the mussels' life activity.

Glutathione level of Desulfovibrio desulfuricans IMV K-6 under the influence of heavy metal salts

Glutathione is the metal stress protector and changes of its level in the sulfate-reducing bacteria cells under the influence of heavy metal salts have not been studied yet. CdCl2, Pb(NO3)2, CuCl2, and ZnCl2 influence on the total glutathione level in cell-free extracts of sulfate-reducing bacteria Desulfovibrio desulfuricans IMV K-6 was studied. The research has been carried out using Ellman, Lowry methods, statistical processing of the results. It was shown that the glutathione level depends on the heavy metal salts concentration in the medium. The total glutathione level was the highest under the influence of Pb(NO3)2. Other salts were also toxic to bacteria because glutathione level increased in bacterial cells after addition of these salts to the medium. On the basis of the results of our work the range of heavy metal salts influence on D. desulfuricans IMV K-6 cells glutathione level has been formed for the first time: Pb(NO3)2 > CuCl2 > CdCl2 > ZnCl2.

Expression of catalase and glutathione S-transferase genes in Chironomus riparius on exposure to cadmium and nonylphenol

Antioxidant enzymes play important roles in the protection against oxidative damage caused by environmental pollutants by scavenging high levels of reactive oxygen species and have been quantified as oxidative stress markers. However, combining mRNA expressions of genes coding for detoxification enzymes along with enzyme activities will be more useful biomarkers of stress. Therefore, in this study the cDNA of the catalase gene from the aquatic midge, Chironomus riparius (CrCAT) was sequenced using 454 pyrosequencing. The 2139 bp CrCAT cDNA included an open reading frame of 1503 bp encoding a putative protein of 500 amino acids with a predicted molecular mass of 56.72 kDa. There was an 18 bp 5' and a long 618 bp 3' untranslated region with a polyadenylation signal site (AATAAA). The deduced amino acid sequence of CrCAT contained several highly conserved motifs including the proximal heme-ligand signature sequence RLFSYNDTX and the proximal active site signature FXRERIPERVVHAKGXGA. A comparative analysis showed the presence of conserved amino acid residues and all of the catalytic amino acids (His(70), Asn(143), and Tyr(353)) were conserved in all species. The CrCAT contained three potential glycosylation sites and a peroxisome targeting signal of 'AKM'. The mRNA was detected using RT-PCR at all developmental stages. The time-course expression of CrCAT was measured using quantitative real-time PCR after exposure to different concentration and durations of Paraquat (PQ), cadmium chloride (Cd) and nonylphenol (NP). The expression of CrCAT was significantly up regulated on exposure to 50 and 100mg/L PQ for 12 and 24h. Among the different concentrations and durations of Cd tested, significantly highest level of expression for CrCAT mRNA and catalase enzyme activity was observed on exposure to 10mg/L for 24h. In the case of NP, the highest level of CrCAT expression was observed after exposure to 100 μg/L for 24h. The expression profiles of three selected C. riparius glutathione S-transferase genes (CrGSTs) viz. CrGSTdelta3, CrGSTsigma4 and CrGSTepsilon1 was also studied on exposure to NP and were up or down regulated at different time points and concentrations. Significantly highest level of expression for CrGSTdelta3 was observed after 48 h and for CrGSTsigma4 and CrGSTepsilon1 after 24h exposure to 100 μg/L of NP. The results show that CrGSTs and CrCAT could be used as potential biomarkers in C. riparius for aquatic ecotoxicological studies.

Interrelationships between cadmium, zinc and antioxidants in the liver of the rat exposed orally to relatively high doses of cadmium and zinc

Zinc (Zn) reduces cadmium (Cd)-induced toxicity in the liver although it increases Cd tissue burden in some conditions; hence, the present study is designed to study the relationships between Cd, Zn and antioxidants in the liver of rats exposed to Cd. Livers of male rats which received orally relatively high doses of Cd (200 mg Cd/L as Cd chloride or Cd (200 mg/L)+Zn (500 mg Zn as Zn chloride) during five weeks, were investigated. Cd induced an accumulation of Cd and Zn in parallel to depletion in important variables (GSH, GSH/GSSG, CuZn-SOD and GPx activities) and to elevation in others (Cd/Zn and GSSG). Cd, did not affect CuZn SOD/GPx, nor Mn-SOD in the liver. Cd accumulation, Cd/Zn, CuZn SOD activity and CuZn SOD/GPx, was increased remarkably under Zn action. Zn supply ameliorated GSH level and partially reversed the decrease in GSH/GSSG, but it did not ameliorate GPx activity. Analysis showed high correlations between Cd and the majority of the variables, while Zn was positively correlated with only GSSG. We suggest from our results that Zn has indirect ameliorative effects on Cd-induced toxicity in the liver and that the increase in Cd retention is probably the key mechanism modulating, in the case of relatively high doses of Cd, the antioxidant response during exposure to Cd and Zn.

[Antimutagenic activity of wheat beta-purothionin Tk-AMP-BP]

Antimutagenic activity on human RD cells was studied for beta-purothionin Tk-AMP-BP isolated from seeds of wheat Triticum kiharae, which has a higher stress resistance. Cadmium chloride at 5 x 10(-6) M was used as a mutagen. The numbers of DNA breaks in mutagen-treated and intact cells were inferred from the single-stranded to double-stranded DNA ratio and expressed as protection coefficients. The protective effect was simultaneously assayed for aqueous plant extracts known to possess antioxidant properties. Wheat thionin was the most active among all of the antimutagens examined; its protection coefficient reached 85-88% at micromolar peptide concentrations (8-32 microg/ml). Thus, wheat beta-purothionin was for the first time demonstrated to be highly efficient in protecting human cell DNA from the damaging effect of cadmium chloride.

Effects of a single intraperitoneal administration of cadmium on femoral bone structure in male rats

BACKGROUND

Exposure to cadmium (Cd) is considered a risk factor for various bone diseases in humans and experimental animals. This study investigated the acute effects of Cd on femoral bone structure of adult male rats after a single intraperitoneal administration.

METHODS

Ten 4-month-old male Wistar rats were injected intraperitoneally with a single dose of 2 mg CdCl2/kg body weight and killed 36 h after the Cd had been injected. Ten 4-month-old males served as a control group. Differences in body weight, femoral weight, femoral length and histological structure of the femur were evaluated between the two groups of rats. The unpaired Student's t-test was used for establishment of statistical significance.

RESULTS

A single intraperitoneal administration of Cd had no significant effect on the body weight, femoral weight or femoral length. On the other hand, histological changes were significant. Rats exposed to Cd had significantly higher values of area, perimeter, maximum and minimum diameters of the primary osteons' vascular canals and Haversian canals. In contrast, a significant decrease in all variables of the secondary osteons was observed in these rats.

CONCLUSIONS

The results indicate that, as expected, a single intraperitoneal administration of 2 mg CdCl2/kg body weight had no impact on macroscopic structure of rat's femora; however, it affected the size of vascular canals of primary osteons, Haversian canals, and secondary osteons.

Disarrangement of actin filaments and Ca²⁺ gradient by CdCl₂ alters cell wall construction in Arabidopsis thaliana root hairs by inhibiting vesicular trafficking

Cadmium (Cd), one of the most toxic heavy metals, inhibits many cellular and physiological processes in plants. Here, the involvement of cytoplasmic Ca²⁺ gradient and actin filaments (AFs) in vesicular trafficking, cell wall deposition and tip growth was investigated during root (hair) development of Arabidopsis thaliana in response to CdCl₂ treatment. Seed germination and root elongation were prevented in a dose- and time-dependent manner by CdCl₂ treatment. Fluorescence labelling and non-invasive detection showed that CdCl₂ inhibited extracellular Ca²⁺ influx, promoted intracellular Ca²⁺ efflux, and disturbed the cytoplasmic tip-focused Ca²⁺ gradient. In vivo labelling revealed that CdCl₂ modified actin organization, which subsequently contributed to vesicle trafficking. Transmission electron microscopy revealed that CdCl₂ induced cytoplasmic vacuolization and was detrimental to organelles such as mitochondria and endoplasmic reticulum (ER). Finally, immunofluorescent labelling and Fourier transform infrared (FTIR) analysis indicated that configuration/distribution of cell wall components such as pectins and cellulose was significantly altered in response to CdCl₂. Our results indicate that CdCl₂ induces disruption of Ca²⁺ gradient and AFs affects the distribution of cell wall components in root hairs by disturbing vesicular trafficking in A. thaliana.

[Method of radiocapacity factor assessment in study of cross adaptations of plants]

Adaptation of plants to the action of gamma-irradiation and cadmium chloride has been studied in the experiments on water culture of maize plants. A new method of registration of the biological object state at the conditions of the stress-factor action - "the method of radiocapacity factor" based on the measurement of the culture medium radio-activity during the incubation process of vegetative objects has been developed. The method offered has allowed us to estimate in dynamics an integrated condition of the root system exposed to stimulating and inhibiting doses of acute gamma-irradiation. Application of the pattern of radio-adaptive response has allowed us to reveal it using both a conventional technique - by registering the values of growing parameters, and the radiocapacity factor method.

Lubiprostone reverses the inhibitory action of morphine on mucosal secretion in human small intestine

BACKGROUND AND AIMS

Treatments with morphine or opioid agonists cause constipation. Lubiprostone is approved for treatment of adult idiopathic constipation and constipation-predominant IBS in adult women. We tested whether lubiprostone can reverse morphine-suppression of mucosal secretion in human intestine and explored the mechanism of action.

METHODS

Fresh segments of jejunum discarded during Roux-En-Y gastric bypass surgeries were used. Changes in short-circuit current (ΔIsc) were recorded in Ussing flux chambers as a marker for electrogenic chloride secretion during pharmacological interactions between morphine, prostaglandin receptor antagonists, chloride channel blockers and lubiprostone.

RESULTS

Morphine suppressed basal Isc. Lubiprostone reversed morphine suppression of basal Isc. Lubiprostone, applied to the mucosa in concentrations ranging from 3 nM to 30 μM, evoked increases in Isc in concentration-dependent manner when applied to the mucosal side of muscle-stripped preparations. Blockade of enteric nerves did not change stimulation of Isc by lubiprostone. Removal of chloride or application of bumetanide or NPPB suppressed or abolished responses to lubiprostone. Antagonists acting at CFTR channels and prostaglandin EP(4) receptors, but not at E(1), EP(1-3) receptors, partially suppressed stimulation of Isc by lubiprostone.

CONCLUSIONS

Antisecretory action of morphine results from suppression of excitability of secretomotor neurons in the enteric nervous system. Lubiprostone, which does not affect enteric neurons directly, bypasses the action of morphine by directly opening mucosal chloride channels.

RceIF5A, encoding an eukaryotic translation initiation factor 5A in Rosa chinensis, can enhance thermotolerance, oxidative and osmotic stress resistance of Arabidopsis thaliana

Eukaryotic translation initiation factor 5A (eIF5A) is the only cellular protein known to contain the unusual amino acid hypusine. It is a highly conserved protein found in all eukaryotic organisms. Although originally identified as a translation initiation factor, recent studies suggest that eIF5A is mainly involved in translation elongation, mRNA turnover and decay, cell proliferation, and programmed cell death. However, the precise cellular function of eIF5A remains largely unknown, especially in plants. Here, we report the identification and characterization of RceIF5A from Rosa chinensis. RceIF5A expression is up-regulated in Rosa chinensis under high temperature, and oxidative and osmotic stress conditions. We produced transgenic Arabidopsis that constitutively enhanced or suppressed expression of RceIF5A. The RceIF5A over-expression plants exhibited increased resistance to heat, and oxidative and osmotic stresses, while the suppressed expression plants (three AteIF5A isoforms in Arabidopsis were down-regulated) showed more susceptibility to these stresses. These results reveal a new physiological role for eIF5A in plants and contribute to the elucidation of the molecular mechanisms involved in the stress response pathway.

Cadmium induced mitochondrial redox changes in germinating pea seed

Mitochondria play an essential role in producing the energy required for seedling growth following imbibition. Heavy metals, such as cadmium impair mitochondrial functioning in part by altering redox regulation. The activities of two protein redox systems present in mitochondria, thioredoxin (Trx) and glutaredoxin (Grx), were analysed in the cotyledons and embryo of pea (Pisum sativum L.) germinating seeds exposed to toxic Cd concentration. Compared to controls, Cd-treated germinating seeds showed a decrease in total soluble protein content, but an increase in -SH content. Under Cd stress conditions, Grx and glutathione reductase (GR) activities as well as glutathione (GSH) concentrations decreased both in cotyledons and the embryo. Similar results were obtained with the Trx system: Trx and NADPH-dependent thioredoxin reductase (NTR) activities were not stimulated, whereas total NAD(P) contents diminished in the embryo. However, Cd enhanced the levels of all components of the Trx system in the cotyledons. On the other hand, Cd caused a significant increase in oxidative stress parameters such as the redox ratio of coenzymes (oxidized to reduced forms) and NAD(P)H oxidase activities. These results indicate that Cd induces differential redox responses on different seed tissues. We suggest that neither Grx system nor Trx one may improve the redox status of mitochondrial thiols in the embryo of germinating pea seeds exposed to Cd toxicity, but in the cotyledons the contribution of Trx/NTR/NADPH can be established in despite the vulnerability of the coenzyme pools due to enzymatic oxidation.