Testicular toxicity evaluation of arsenic-containing binary compound semiconductors, gallium arsenide and indium arsenide, in hamsters

Changes in Organ Weight, Sperm Quality and Testosterone Levels After Aluminum (Al) and Indium (In) Administration to Wistar Rats

BACKGROUND

Aluminum and indium are widely used in industrial manufacturing, in pharmaceutical products, in medical treatments, and in food packaging, so they could reach organisms by different way. In order to clarify whether these elements are dangerous, we already demonstrated the ultrastructural modifications observed in the testicles, the epididymides, and the seminal vesicles of rat. Their pro-oxidative effect was also confirmed concomitantly to a decrease in anti-oxidant defenses in the blood, the testicles, and the liver. Thus, it seemed very logic to evaluate damages in the reproductive organs, especially on the exocrine and endocrine functions of the testicles.

METHODS

Aluminum and indium were intraperitoneally administered to male Wistar rats. Sperm solution was obtained from cauda epididymides. Motility, viability, density, and malformation of spermatozoa solution were assessed. Serum total unconjugated testosterone concentrations were measured using RIA technique.

RESULTS

Our results showed a decrease in weight of the testicles, epididymides, and seminal vesicles of indium-treated rats and an increase in the weight of their kidneys. A decrease in motility, viability, and density of epididymides stored sperm as well as generation of many spermatozoa malformations was also observed especially in indium-treated rats. Testosterone levels were increased in indium but were enhanced in aluminum group. This confirmed our previous studies showing that aluminum and indium are toxic for the testicular tissues. This could be explained by the generation of reactive oxygen species (ROS) affecting strongly the exocrine and the endocrine functions of the testicles.

CONCLUSION

Aluminum and indium are disturbing elements for the exocrine and endocrine functions of rat testicles.

Histological and ultrastructural changes observed in testicles, epididymides, seminal vesicles and liver of rat after intraperitoneal administration of aluminum and indium

BACKGROUND

Aluminum (Al) and indium (In) have been largely used in medicine, pharmacy, dentistry, manufacturing, engineering, clothing as well as food processing and packaging. Our previous study showed that In was accumulated as electron-dense materials in lysosomes of Sertoli and Leydig testicular cells and the liver ones, when administered to male rats as soluble form. For this reason, we have undertaken to confirm whether Al have the same behavior as In and to enlarge this behavior to other organs of the male reproductive system: epididymis and seminal vesicle.

METHODS

Experiments were performed on 24 adult male Wistar rat weighing approximately 250 g. Animals were divided to 3 groups, received Al, In or saline solution as 7 chronic intraperitoneal injections over a period of two weeks and were sacrificed 24 h after the last injection. For ultrastructure study we used The Transmission Electron Microscopy (TEM).

RESULTS

The TEM showed the presence of electron-dense granules in lysosomes of testicular cells (Sertoli and Leydig cells), and in the principal epididymal and seminal vesicle cells of Al and In treated rats. Impairments were observed in the endoplasmic reticulum and mitochondria and many vacuoles were identified in the cells cytoplasm. Our results concluded that lysosomes of Leydig and Sertoli cells, principal epididymis, and seminal vesicle cells as well as liver cells, played a central role in the extraction and concentration of Al and In under insoluble form after their introduction into the body as a soluble route. This mechanism intended to protect the organism against exogenous toxic and non-recognized mineral elements after their intrusion into the body.

CONCLUSION

It looks important to proceed with the study of Al and In impact on the endocrine and exocrine functions of the male rat reproductive system.

Effects of heavy metals on reproduction owing to infertility

The reproductive performance of most of the species is adversely affected by hazardous heavy metals like lead, cadmium, mercury, arsenic, zinc, and copper. Heavy metals are liberated in the environment by natural sources like rock weathering, volcanic eruption, and other human activities like industrial discharge, mineral mining, automobile exhaust, and so forth. Heavy metals alter several reproductive functions in both males and females like a decrease in sperm count, motility, viability, spermatogenesis, hormonal imbalance, follicular atresia, and delay in oocyte maturation, and so forth, and thus, forms an important aspect of reproductive toxicology. The present review compiles toxicity aspects of various heavy metals and their efficacy and mechanism of action in mammals.

The toxicology of gallium oxide in comparison with gallium arsenide and indium oxide

Gallium arsenide (GaAs) and indium oxide (In₂O₃) are used in electronic industries at high and increasing tonnages since decades. Gallium oxide (Ga₂O₃) is an emerging wide-bandgap transparent conductive oxide with as yet little industrial use. Since GaAs has received critical attention due to the arsenic ion, it seemed reasonable to compare its toxicology with the respective endpoints of Ga₂O₃ and In₂O₃ toxicology in order to find out if and to what extent arsenic contributes. In addition, the toxicology of Ga₂O₃ has not yet been adequately reviewed, Therefore, this review provides the first evaluation of all available toxicity data on Ga₂O₃. The acute toxicity of all three compounds is rather low. Subchronic inhalation studies in rats and mice revealed persistent pulmonary alveolar proteinosis (PAP) and/or alveolar histiocytic infiltrates down to the lowest tested concentration in rats and mice, i.e. 0.16 mg Ga₂O₃/m³. These are also the predominant effects after GaAs and In₂O₃ exposure at similarly low levels, i.e. 0.1 mg/m³ each. Subchronic Ga₂O₃ exposure caused a minimal microcytic anemia with erythrocytosis in rats (at 6.4 mg/m³ and greater) and mice (at 32 and 64 mg/m³), a decrease in epididymal sperm motility and concentration as well as testicular degeneration at 64 mg/m³. At comparable concentrations the hematological effects and male fertility of GaAs were much stronger. The stronger effects of GaAs are due to its better solubility and presumed higher bioavailability. The database for In₂O₃ is too small and subchronic testing was at very low levels to allow conclusive judgements if blood/blood forming or degrading and male fertility organs/tissues would also be targets.

RNA Sequencing Analyses Reveal the Potential Mechanism of Pulmonary Injury Induced by Gallium Arsenide Particles in Human Bronchial Epithelioid Cells

Extensive use of gallium arsenide (GaAs) has led to increased exposure to humans working in the semiconductor industry. This study employed physicochemical characterization of GaAs obtained from a workplace, cytotoxicity analysis of damage induced by GaAs in 16HBE cells, RNA-seq and related bioinformatic analysis, qRT-PCR verification and survival analysis to comprehensively understand the potential mechanism leading to lung toxicity induced by GaAs. We found that GaAs-induced abnormal gene expression was mainly related to the cellular response to chemical stimuli, the regulation of signalling, cell differentiation and the cell cycle, which are involved in transcriptional misregulation in cancer, the MAPK signalling pathway, the TGF-β signalling pathway and pulmonary disease-related pathways. Ten upregulated genes (FOS, JUN, HSP90AA1, CDKN1A, ESR1, MYC, RAC1, CTNNB1, MAPK8 and FOXO1) and 7 downregulated genes (TP53, AKT1, NFKB1, SMAD3, CDK1, E2F1 and PLK1) related to GaAs-induced pulmonary toxicity were identified. High expression of HSP90AA1, RAC1 and CDKN1A was significantly associated with a lower rate of overall survival in lung cancers. The results of this study indicate that GaAs-associated toxicities affected the misregulation of oncogenes and tumour suppressing genes, activation of the TGF-β/MAPK pathway, and regulation of cell differentiation and the cell cycle. These results help to elucidate the molecular mechanism underlying GaAs-induced pulmonary injury.

The Footprints of Oxidative Stress and Mitochondrial Impairment in Arsenic Trioxide-Induced Testosterone Release Suppression in Pubertal and Mature F1-Male Balb/c Mice via the Downregulation of 3β-HSD, 17β-HSD, and CYP11a Expression

Exposure to arsenic (AS) causes abnormalities in the reproductive system; however, the precise cellular pathway of AS toxicity on steroidogenesis in developing F1-male mice has not been clearly defined. In this study, paternal mice were treated with arsenic trioxide (As₂O₃; 0, 0.2, 2, and 20 ppm in drinking water) from 5 weeks before mating until weaning and continued for male offspring from weaning until maturity (in vivo). Additionally, Leydig cells (LCs) were isolated from the testes of sacrificed F1-intact mature male mice and incubated with As₂O₃ (0, 1, 10, and 100 μM) for 48 h (in vitro). Biomarkers of mitochondrial impairment, oxidative stress, and several steroidogenic genes, including the steroidogenic acute regulatory (StAR) protein, cytochrome P450 side-chain cleaving enzyme (P450scc; Cyp11a), 3β-hydroxysteroid dehydrogenase (3β-HSD), and 17β-hydroxysteroid dehydrogenase (17β-HSD), were evaluated. High doses of As₂O₃ interrupted testosterone (T) biosynthesis and T-related gene expression in these experimental models. Altogether, overconsumption of As₂O₃ can cause testicular and LC toxicity through mitochondrial-related pathways and oxidative stress indices as well as downregulation of androgenic-related genes in mice and isolated LCs. These results could lead to the development of preventive/therapeutic procedures against As₂O₃-induced reproductive toxicity. Graphical Abstract Mohammad Mehdi Ommati and Reza Heidari contributed equally to this study.

A Materials Roadmap to Functional Neural Interface Design

Advancement in neurotechnologies for electrophysiology, neurochemical sensing, neuromodulation, and optogenetics are revolutionizing scientific understanding of the brain while enabling treatments, cures, and preventative measures for a variety of neurological disorders. The grand challenge in neural interface engineering is to seamlessly integrate the interface between neurobiology and engineered technology, to record from and modulate neurons over chronic timescales. However, the biological inflammatory response to implants, neural degeneration, and long-term material stability diminish the quality of interface overtime. Recent advances in functional materials have been aimed at engineering solutions for chronic neural interfaces. Yet, the development and deployment of neural interfaces designed from novel materials have introduced new challenges that have largely avoided being addressed. Many engineering efforts that solely focus on optimizing individual probe design parameters, such as softness or flexibility, downplay critical multi-dimensional interactions between different physical properties of the device that contribute to overall performance and biocompatibility. Moreover, the use of these new materials present substantial new difficulties that must be addressed before regulatory approval for use in human patients will be achievable. In this review, the interdependence of different electrode components are highlighted to demonstrate the current materials-based challenges facing the field of neural interface engineering.

The toxicology of indium oxide

Indium oxide (In₂O₃) is a technologically important semiconductor essentially used, doped with tin oxide, to form indium tin oxide (ITO). It is poorly soluble in all so far tested physiologic media. After repeated inhalation, In₂O₃ particles accumulate in the lungs. Their mobilization can cause significant systemic exposure over long periods of time. An increasing number of cases of severe lung effects (characterized by pulmonary alveolar proteinosis, emphysema and/or interstitial fibrosis) in workers of the ITO industry warrants a review of the toxicological hazards also of In₂O₃. The database on acute and chronic toxicity/carcinogenicity/genotoxicity/reproductive toxicity as well skin/eye irritation and sensitization is very limited or even lacking. Short-term and subchronic inhalation studies in rats and mice revealed persistent alveolar proteinosis, inflammation and early indicators of fibrosis in the lungs down to concentrations of 1 mg/m³. Epidemiological and medical surveillance studies, serum/blood indium levels in workers as well as data on the exposure to airborne indium concentrations indicate a need for measures to reduce exposure at In₂O₃ workplaces.

Lutein alleviates arsenic-induced reproductive toxicity in male mice via Nrf2 signaling

This study aims to investigate the mechanisms involved in the action of lutein (LU) alleviating arsenic-induced reproductive toxicity using mice model. Forty male Kunming mice were received following treatments by gavage: normal saline solution (control), arsenic trioxide (ATO; 5 mg/kg/day), LU (40 mg/kg/day), and ATO + LU (5 mg/kg/day + 40 mg/kg/day). At the end, the mice were killed by cervical dislocation and weighed. Pathological examination was done on the testis. The biomedical parameters including superoxide dismutase (SOD), glutathione (GSH), total antioxidative capability, malondialdehyde (MDA), 8-hydroxydeoxyguanosine (8-OHdG), and reproductive indexes were analyzed. The messenger RNA (mRNA) and protein expression of Nrf2, heme oxygenase 1 (HO-1), glutathione S-transferase (GST), nicotinamide adenine dinucleotide phosphate dehydrogenase, quinone 1 (NQO1) in testis were detected by real-time polymerase chain reaction and Western blot. We found that there was a decrease in sperm count; testis somatic index; the activities of SOD, GSH, total antioxidative capacity ( p < 0.01, respectively) in ATO-treated mice, while there was an increase in the levels of sperm abnormalities, MDA, and 8-OHdG than control ( p < 0.01, respectively). The groups treated with ATO + LU showed recovery of the measured parameters between those of ATO or saline-treated group. The antagonized interaction between ATO and LU was statistically significant ( p < 0.01). Mice treated with ATO + LU also showed greater mRNA expression of Nrf2, HO-1, NQO1, and GST than ATO or saline-treated groups. These findings suggest that LU alleviates reproductive toxicity induced by arsenic in male mice via Nrf2 signaling, which implicates a possible mechanism of LU in preventing the reproductive injury, and elucidates that consuming the rich plant sources of LU will alleviate the reproductive toxicity induced by chemicals.

Oxidative stress in blood and testicle of rat following intraperitoneal administration of aluminum and indium

Aluminum (Al) and indium (In) have embryotoxic, neurotoxic and genotoxic effects, oxidative stress being one of the possible mechanisms involved in their cytotoxicity. We have recently demonstrated that indium intraperitoneal (ip) administration induced histological disorganization of testicular tissue. In the present research we aimed at investigating the effect of Al and In ip administration on systemic and testicular oxidative stress status. Studies were performed on Wistar rats ip injected with Al, In or physiological solution for two weeks. Our results showed that In significantly decreased the absolute weight of testicles. Measurements of lactate dehydrogenase (LDH) and paraoxonase (PON) activities showed that In induced a significant augmentation in the first parameter but no changes were observed in the second. Both Al and In caused oxidative stress in testicles by increasing malondialdehyde (MDA) and protein carbonyls (PC) production. Concomitantly, thiol group (-SH) and glutathione (GSH) level were enhanced in the testicles. In the blood, while concentrations of MDA was not changed, those of GSH was significantly decreased in the Al and In groups. Our results indicated that Al and In cause oxidative stress both in blood and testicles but In has cytotoxic effect as well as negative impact on testicle weights. These findings could explain the testicular histological alterations previously described after In ip administration.

Effects of the presence of indium on the mammary gland ultrastructure, body weight, food intake and plasmatic prolactin concentration

Several studies have demonstrated the toxic effect of indium. This element induces impairments in many organs such as spleen, lungs and testicles after its systemic administration. Teratogenic and embryotoxic effects of this element have also been established. In the present study, we attempt to investigate the histological and the ultrastructural consequences of the presence of this element in mammary gland tissue using conventional transmission electron microscopy and to evaluate the incidences of its presence on the food intake, body weight and prolactin plasmatic concentration of lactating female rats. Our study showed that this element induced a significant decrease in food intake and body weight, and caused some cellular damage in the glandular epithelial cell such as cytoplasmic vacuolization and expansion of the ergastoplasm. The ultrastructural observations also showed many electron-dense surcharges in the lysosomes of the glandular epithelial cells. The electron probe microanalysis showed that these deposits are composed of indium and phosphorus. The lysosomes, known for their protective role of sequestrating foreign elements to avoid their diffusion in the blood, failed to stop the toxic effect of indium.

Hypoxaemia affects male reproduction: a case study of how to differentiate between primary and secondary hypoxic testicular toxicity due to chemical exposure

Classification for fertility is based on two conditions, namely on evidence of an adverse effect on sexual function and fertility and that the effect is not secondary to other toxic effects. To decide on an adverse effect is a relatively simple day-to-day decision in toxicology but whether this effect is secondary often leads to serious controversy. As the seminiferous epithelium operates on the verge of hypoxia, oxygen deficit can lead to secondary impairment of testicular function. This is well known from healthy mountaineers exposing themselves to high altitude. They have reduced blood oxygen content that goes in parallel with impairment of testicular function and this effect remains for some time in spite of a compensatory polycythaemia. Similar findings are described for experimental animals exposed to hypobaric oxygen/high altitude. In addition, testicular function is affected in severe diseases in humans associated with systemic oxygen deficit like chronic obstructive pulmonary disease, sickle cell disease or beta-thalassaemia as well as in transgenic animals simulating haemolytic anaemia or sickle cell disease. The problem of insufficient oxygen supply as the underlying cause for testicular impairment has received relatively little attention in toxicology, mainly because blood oxygen content is generally not measured in these animal experiments. The difficulties associated with the decision whether testicular toxicity is primary or secondary to hypoxia are exemplified by the results of inhalation studies with nickel subsulphide and gallium arsenide (GaAs). Both of these particulate substances lead to severe lung toxicity that might impair oxygen uptake, but testicular toxicity is only observed with GaAs. This may first be explained by different effects on the blood: nickel subsulphide inhalation leads to a compensatory erythropoiesis that may mitigate pulmonary lack of oxygen uptake. In contrast, GaAs exposure is associated with microcytic haemolytic anaemia thereby aggravating any possible oxygen undersupply. Furthermore, the predominant pulmonary effect caused by GaAs (but not by nickel subsulphide) is alveolar proteinosis. Pulmonary alveolar proteinosis is also known as a severe disease in humans associated with hypoxaemia. Therefore, we conclude that the testicular effects observed after GaAs are secondary to hypoxaemia caused by the combination of pulmonary proteinosis and haemolytic anaemia. This publication tries to raise awareness to the severe consequences of hypoxaemia on testicular function that may already be caused by reduced oxygen pressure at high altitude without any chemical exposure.

Environmental exposure to arsenic may reduce human semen quality: associations derived from a Chinese cross-sectional study

BACKGROUND

Recent observations in in vitro and in vivo models suggest that arsenic (As) is an endocrine disruptor at environmentally-relevant levels. When exposed to As, male rats and mice show steroidogenic dysfunction that can lead to infertility. However, the possible effects of As on human male semen quality remain obscure.

METHODS

We monitored the profile of As species in the urine of a reproductive-age human cohort and assessed its association with semen quality. Men (n = 96) were recruited in an infertility clinic from July 2009 to August 2010 in the Affiliated Hospital of Chongqing Institute for Population and Family Planning. Five urinary As species were analyzed by high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Clinical information on the semen volume, sperm concentration and motility was employed to catalogue and evaluate semen quality according to WHO guidelines. As species concentrations in addition to other continuous variables were dichotomized by the medians and modelled as categorical variables in order to explore using the binary logistic regression possible associations between As exposure and semen quality.

RESULTS

Urinary concentrations (geometric mean ± SD, μg g(-1) creatinine) of different As species were 7.49 (± 24.8) for AsB, 20.9 (± 13.7) for DMA, 2.77 (± 3.33) for MMA, and 4.03 (± 3.67) for Asi (Asi(III )and Asi(V)). DMA concentrations above the median were significantly associated with below-reference sperm concentrations (P = 0.02) after adjusting for age, body mass index (BMI), abstinence, smoking and drinking habits. In addition, smoking was positively associated with MMA.

CONCLUSION

Reduced parameters in human semen quality are positively associated with As exposure in a reproductive-age Chinese cohort.

Single-crystal cubic silicon carbide: an in vivo biocompatible semiconductor for brain machine interface devices

Single crystal silicon carbide (SiC) is a wide band-gap semiconductor which has shown both bio- and hemo-compatibility [1-5]. Although single crystalline SiC has appealing bio-sensing potential, the material has not been extensively characterized. Cubic silicon carbide (3C-SiC) has superior in vitro biocompatibility compared to its hexagonal counterparts [3, 5]. Brain machine interface (BMI) systems using implantable neuronal prosthetics offer the possibility of bi-directional signaling, which allow sensory feedback and closed loop control. Existing implantable neural interfaces have limited long-term reliability, and 3C-SiC may be a material that may improve that reliability. In the present study, we investigated in vivo 3C-SiC biocompatibility in the CNS of C56BL/6 mice. 3C-SiC was compared against the known immunoreactive response of silicon (Si) at 5, 10, and 35 days. The material was examined to detect CD45, a protein tyrosine phosphatase (PTP) expressed by activated microglia and macrophages. The 3C-SiC surface revealed limited immunoresponse and significantly reduced microglia compared to Si substrate.

Medical applications and toxicities of gallium compounds

Over the past two to three decades, gallium compounds have gained importance in the fields of medicine and electronics. In clinical medicine, radioactive gallium and stable gallium nitrate are used as diagnostic and therapeutic agents in cancer and disorders of calcium and bone metabolism. In addition, gallium compounds have displayed anti-inflammatory and immunosuppressive activity in animal models of human disease while more recent studies have shown that gallium compounds may function as antimicrobial agents against certain pathogens. In a totally different realm, the chemical properties of gallium arsenide have led to its use in the semiconductor industry. Gallium compounds, whether used medically or in the electronics field, have toxicities. Patients receiving gallium nitrate for the treatment of various diseases may benefit from such therapy, but knowledge of the therapeutic index of this drug is necessary to avoid clinical toxicities. Animals exposed to gallium arsenide display toxicities in certain organ systems suggesting that environmental risks may exist for individuals exposed to this compound in the workplace. Although the arsenic moiety of gallium arsenide appears to be mainly responsible for its pulmonary toxicity, gallium may contribute to some of the detrimental effects in other organs. The use of older and newer gallium compounds in clinical medicine may be advanced by a better understanding of their mechanisms of action, drug resistance, pharmacology, and side-effects. This review will discuss the medical applications of gallium and its mechanisms of action, the newer gallium compounds and future directions for development, and the toxicities of gallium compounds in current use.

In vivo distribution and fractionation of indium in rats after subcutaneous and oral administration of [114mIn]InAs

Two in vivo experiments were carried out in this study. In the first experiment five rats were given two subcutaneous injections of [(114m)In]InAs. Major sites of accumulation were spleen, liver and kidney. The intracellular distribution of indium was examined by differential centrifugation. The cytoplasmic fraction contained most of the indium activity followed by the mitochondrial fraction. Both outcomes are in close agreement with the results obtained in previous studies. Chromatographic separations on a preparative size exclusion column were carried out. It was shown that indium was mostly bound to high molecular mass compounds in serum and in the cytoplasmic fraction of spleen, liver and kidney. In a second experiment five rats were given four oral doses of [(114m)In]InAs over a short period. Prior to this experiment the in vitro solubility of cold InAs in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) was determined using graphite furnace atomic absorption spectroscopy. In the case of the SGF only 1.3% of an InAs suspension dissolved after 48 hours incubation at 37 degrees C. InAs was not soluble in SIF. Uptake of InAs after oral administration was minimal (<1%). Due to incomplete removal of traces of [(114m)In]InAs from the gastrointestinal tract, it was impossible to calculate accurately the in vivo distribution over the different organs. As the uptake and consequently the activity in the organs were very low, no further chromatographic separations could be carried out. Considering this very low uptake, it can be concluded that InAs will not accumulate in the body after oral exposure.

Toxicity of indium arsenide, gallium arsenide, and aluminium gallium arsenide

Gallium arsenide (GaAs), indium arsenide (InAs), and aluminium gallium arsenide (AlGaAs) are semiconductor applications. Although the increased use of these materials has raised concerns about occupational exposure to them, there is little information regarding the adverse health effects to workers arising from exposure to these particles. However, available data indicate these semiconductor materials can be toxic in animals. Although acute and chronic toxicity of the lung, reproductive organs, and kidney are associated with exposure to these semiconductor materials, in particular, chronic toxicity should pay much attention owing to low solubility of these materials. Between InAs, GaAs, and AlGaAs, InAs was the most toxic material to the lung followed by GaAs and AlGaAs when given intratracheally. This was probably due to difference in the toxicity of the counter-element of arsenic in semiconductor materials, such as indium, gallium, or aluminium, and not arsenic itself. It appeared that indium, gallium, or aluminium was toxic when released from the particles, though the physical character of the particles also contributes to toxic effect. Although there is no evidence of the carcinogenicity of InAs or AlGaAs, GaAs and InP, which are semiconductor materials, showed the clear evidence of carcinogenic potential. It is necessary to pay much greater attention to the human exposure of semiconductor materials.

The metabolism of inorganic arsenic oxides, gallium arsenide, and arsine: a toxicochemical review

The aim of this review is to compare the metabolism, chemistry, and biological effects to determine if either of the industrial arsenicals (arsine and gallium arsenide) act like the environmental arsenic oxides (arsenite and arsenate). The metabolism of the arsenic oxides has been extensively investigated in the past 4 years and the differences between the arsenic metabolites in the oxidation states +III versus +V and with one or two methyl groups added have shown increased importance. The arsenic oxide metabolism has been compared with arsine (oxidation state -III) and arsenide (oxidation state between 0 to -III). The different metabolites appear to have different strengths of reaction for binding arsenic (III) to thiol groups, their oxidation-reduction reactions and their forming an arsenic-carbon bond. It is unclear if the differences in parameters such as the presence or absence of methyl metabolites, the rates of AsV reduction compared to the rates of AsIII oxidation, or the competition of phosphate and arsenate for cellular uptake are large enough to change biological effects. The arsine rate of decomposition, products of metabolism, target organ of toxic action, and protein binding appeared to support an oxidized arsenic metabolite. This arsine metabolite was very different from anything made by the arsenic oxides. The gallium arsenide had a lower solubility than any other arsenic compound and it had a disproportionate intensity of lung damage to suggest that the GaAs had a site of contact interaction and that oxidation reactions were important in its toxicity. The urinary metabolites after GaAs exposure were the same as excreted by arsenic oxides but the chemical compounds responsible for the toxic effects of GaAs are different from the arsenic oxides. The review concludes that there is insufficient evidence to equate the different arsenic compounds. There are several differences in the toxicity of the arsenic compounds that will require substantial research.

Insertional mutagenesis in a homologue of a Pi transporter gene confers arsenate resistance on chlamydomonas

An arsenate-resistant mutant AR3 of Chlamydomonas reinhardtii is a recessive mutant generated by random insertional mutagenesis using the ARG7 gene. AR3 shows about 10-fold resistance against arsenate toxicity compared with the wild type. By using a flanking region of an inserted tag as a probe, we cloned the corresponding wild-type allele (PTB1) of a mutated gene, which could completely complement the arsenate-resistance phenotype of AR3. The size of PTB1 cDNA is about 6.0 kb and it encodes a putative protein comprising 1666 amino acid residues. This protein exhibits significant sequence similarity with the yeast Pho89 protein, which is known to be a Na(+)/Pi co-transporter, although the PTB1 protein carries an additional Gln- and Gly-rich large hydrophilic region in the middle of its primary structure. Analyses of arsenic accumulation and release revealed that PTB1-disrupted cells show arsenate resistance due to low arsenate uptake. These results suggest that the PTB1 protein is a factor involved in arsenate (or Pi) uptake. Kinetics of Pi uptake revealed that the activity of high-affinity Pi transport component in AR3 is more activated than that in the wild type.

In vivo and in vitro modulation of carp (Cyprinus carpio L.) phagocyte oxidative burst activity by gallium

Since gallium is a metal ion used in semiconductor industry, the toxicological effects were previously evaluated in mammals but the ecotoxicological impacts remain unknown. In term of ecotoxicological risk assessment, the median lethal concentration (LC50 for 96 h of gallium to carp (Cyprinus carpio L.) and the oxidative response of carp phagocytes after the fish were exposed to sublethal levels of gallium were determined. The LC50 of gallium on C. carpio at 96 h was estimated as 96.25 +/- 14.3 mg/L. To determine the effect in vivo of gallium on the phagocyte response, fish were exposed for 96 h to 5 or 50 mg Ga(3+)/L. Carp maintained for 48 or 96 h in water containing 50 mg/L gallium had a significant fall in phagocyte oxidative burst activity in comparison with controls, as well as decreased leukocyte number in blood and increased cytotoxicity. To determine the effect in vitro of gallium on the phagocyte response, isolated phagocytes were exposed for 5 or 15 min to 50 nM, 500 nM, or 5, 50, 100, or 200 microM of Ga(3+). The oxidative burst was increased after in vitro incubation of phagocytes with 50 or 500 nM gallium for 15 min or with 500 nM gallium for 5 min. Moreover, for 50, 100, or 200 microM gallium, the oxidative burst activity of carp phagocytes was significantly decreased. Results indicate that the lethal toxicity of gallium for carp of gallium is not as high as for other metal ions. However, gallium was immunosuppressive for carp at the highest concentrations used (from 50 microM) in vivo and in vitro. At low concentrations, it could be an immunostimulant as observed in vitro.

Effect of arsenic trioxide on human hepatoma cell line BEL-7402 cultured in vitro

AIM: To study the effect of a varying concentrations of arsenic trioxide on human hepatoma cell line BEL-7402 cultured in vitro and its mechanism of action.

METHODS: The BEL-7402 cells were treated with arsenic trioxide (at the concentrations of 0.5, 1, 2 μmol/L, respectively) for 4 successive days. The cell growth and proliferation were observed by cell counting and cell-growth curve. Morphologic changes were studied with electronmicroscopy. Flow cytometry was used to assay cell-DNA distribution and the protein expression of Bcl-2 and Bax detected by immuno cytochemical method.

RESULTS: The cell growth was significantly inhibited by varying concentrations of arsenic trioxide as revealed by cell counting and cell-growth curve, which was dose- and time-dependent. Arsenic trioxide treatment at 0.5, 1 and 2 μmol/L resulted in a sub G1 cell peak, the apoptosis rate of the control group was 9.31% and that of 0.5 μmol/L arsenic trioxide 15.53%, no significant difference was seen between the two. The apoptosis rates of 1, 2 μmol/L arsenic trioxide were 19.10% and 21.87% respectively, which were much higher (both P < 0.05). Decrease of G₀/G₁ phase cells and increase of S phase cells were observed by flow cytometry, suggesting the inhibition effect of 0.5, 1, 2 μmol/L arsenic trioxide on BEL-7402 cell lay in the G₀/G₁ phase. Morphologic changes such as intact cell membrane, nucleic condensation, apoptotic body formation were seen under transmission electronmicrescopy, whereas the 0.5 mol/L arsenic trioxide-treated BEL-7402 cells showed decrease of nucleocytoplasmic ratio, round nucleus, well-differentiated organelles in the cytoplasm. The processes and microvilli on the cell surface of the experimental groups under scanning electron microscopy were significantly decreased. High expressions of Bcl-2 and Bax were detected in 1 and 2 μmol/L arsenic trioxide-treated cells, these were 46%, 87.33% and 83.08%, 95.83% respectively, among which that of Bax was more significant. Arsenic trioxide treatment at 0.5 μmol/L resulted in a higher expression level of Bcl-2 and lower expression level of Bax, which were 8.81% and 3.83% respectively, as compared with that of the control group (15.33%) (P₁ <0.01, P₂ < 0.01).

CONCLUSION: Arsenic trioxide not only inhibited proliferation but also induced apoptosis of human hepatoma cell line BEL-7402. The induced-apoptosis effect of 1, 2 μmol/L arsenic trioxide was related to the expression level of Bcl-2 and Bax.