Chlorogenic acid prevents hepatotoxicity in arsenic-treated mice: role of oxidative stress and apoptosis.

Arsenic is a potent and toxic heavy metal found in the environment that causes health problems, including liver disease, in humans and animals. Chlorogenic acid (CA) is the most abundant caffeoylquinic acid isomer present in plants. This study aims to assess how CA protects the liver tissue following sodium arsenite (NaAsO2)-induced toxicity in mice. Male Swiss mice were allocated into 5 groups: Control, intragastrically administered CA (200 mg/kg), intragastrically administered NaAsO2 (5 mg/kg), and two groups administered with CA (100 and 200 mg/kg) and NaAsO2. CA was administered 30 min before NaAsO2 and all the mice were treated daily for 28 days. To investigate the biochemical, histopathological, immunohistochemical, and molecular changes, blood and liver samples were collected. NaAsO2 treatment increased the liver function biomarkers such as alanine transaminase, aspartate transaminase, alkaline phosphatase, and total bilirubin. Lipid and nitric oxide production was elevated. Glutathione content and the activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase decreased, indicating a disturbance in redox homeostasis. Histopathological examination revealed a granular degeneration of hepatocytes, infiltration of inflammatory cells, and centrilobular hepatocyte necrosis. Furthermore, tumor necrosis factor-α and interleukin-1ß were upregulated upon NaAsO2 treatment, suggesting the induction of inflammation. Moreover, NaAsO2 triggered apoptosis in the liver by upregulating Bax and caspase-3 and downregulating Bcl-2. However, CA abrogated the biochemical, molecular, and histological changes, reflecting its hepatoprotective role in response to NaAsO2 treatment. Our findings demonstrate that CA could be a potential therapeutic to minimize NaAsO2-induced hepatic injury.

KML001, an arsenic compound, as salvage chemotherapy in refractory biliary tract cancers: A prospective study.

BACKGROUND: Sodium meta-arsenite (NaAsO2, KML001) is a potential oral anticancer agent acting on telomerase and telomere length. This prospective study evaluated its safety, tolerability, and effectiveness as salvage chemotherapy in patients with advanced biliary tract cancer (BTC) resistant to gemcitabine-based chemotherapy. METHODS: Forty-four patients (21 women and 23 men) with advanced BTC and failure history of gemcitabine-based chemotherapy, performance status (PS) 0-2, normal cardiac, hepatic, and renal function were enrolled. Daily dose of KML001 (7.5 mg. p.o.) was administered to eligible subjects for 24 weeks divided into six treatment cycles. Response was evaluated bimonthly using CT. RESULTS: After an average of 1.5 months of treatment (range: 0.5-10.0), 3 patients (6.8%) obtained progression-free status, 23 patients (52.3%) had disease progression, and 18 patients (40.9%) dropped out before evaluation. One patient (2.3%) completed six treatment cycles without progression. During the treatment, morphine dosage kept the same or decreased in 20 patients (47.6%). Nine patients (20.5%) experienced grade-3 adverse events (AEs), while no patient experienced grade-4 AEs. The most common AEs were liver enzyme elevation (11/44, 25%) and anemia (10/44, 22.7%). KML001 was discontinued in six patients (13.6%) due to AEs, including liver toxicity (n = 3), QTc prolongation (n = 2), and abdominal pain (n = 1). CONCLUSIONS: KML001 did not have enough anticancer effect on patients with advanced BTC resistant to gemcitabine. However, KML001 was safe and well-tolerable in terms of AEs and pain control when used as salvage therapy. Further studies are needed to establish arsenic agents as a reliable treatment option in patients with BTC.

[Study on congenital cardiac anomalies induced by arsenic exposure before and during maternal pregnancy in fetal rats].

OBJECTIVE: To investigate the effects of arsenic exposure before and during maternal pregnancy on heart development of fetal rats. METHODS: According to body weight, thirty-two female SD rats (30 to 40 days of age) were randomly divided into control group, low dose group, middle dose group and high dose group with 8 rats per group. They were allowed free access to drinking water with 0, 37.5, 75 and 150 mg/L of sodium arsenite (NaAsO2) for 6 weeks, respectively. Then all the female rats and adult male SD rats were caged together for mating. Once female rats were determined to be pregnant, they would continue to drink deionized distilled water containing different concentrations of sodium arsenite for another 2 weeks. On embryonic day 16, rats were sacrificed to harvest fetuses. Female rats' weight changes, abortions, absorbed fetus number, growth and development of fetal rats were observed. Hematoxylin-eosin staining of serial cardiac slices was performed in embryos to observe cardiac morphology and structure. Fur arsenic contents of female rats were determined with the method of atomic fluorescence spectrometry. RESULTS: Subchronic arsenic exposure caused slow weight growth in female rats. There were two cases of abortion in middle dose group and high dose group, respectively. Compared with these of control group, fetal and placental weight decreased (P < 0.05), and the incidence of fetal absorption increased (P < 0.05) in all arsenic-treated groups. Cardiac malformations in fetal rats including ventricular septal defect, atrial septal defect and tetralogy of Fallot were observed in low, middle and high dose group. The incidence of cardiac malformations increased with the increase of arsenic concentrations in drinking water. Compared with that of control group, the incidence of cardiac malformations remarkably increased in both middle and high dose groups (P < 0.05). Fur arsenic contents increased with the increase of arsenic concentrations in drinking water (P < 0.01). CONCLUSION: Arsenic exposure before and during maternal pregnancy could cause abnormal cardiac development in fetal rats, and increased the risk of congenital heart disease.

Analysis of neuroglobin mRNA expression in rat brain due to arsenite-induced oxidative stress.

Arsenic (As) in drinking water is a toxicant causing several health problems including nervous system disturbance. Neuroglobin (Ngb) is a tissue globin in nervous system playing protective role against oxidative stress in many injuries. This study was to investigate how long arsenite exposure (sodium arsenite 7.5 mg/kg/day) could induce oxidative stress in blood and brain of rats and to determine whether Ngb expression in rat brain changed due to oxidative stress. Results showed that superoxide dismutase (SOD) activity and malondialdehyde (MDA) level in serum and brain homogenates and reactive oxygen species (ROS) generation in red blood cells (RBCs) did not change in the rats exposed to arsenite for 8 weeks. In the rats exposed to arsenite for 16 weeks, SOD activity decreased (serum: P < 0.05; brain homogenates: P < 0.01) and MDA level increased (P < 0.01) in serum and brain homogenates; ROS production increased (P < 0.01) in RBC. When oxidative stress occurred, Ngb mRNA expression did not change in whole brain, cerebral cortex, midbrain, and hippocampus; however, Ngb mRNA expression increased significantly (P < 0.05) in cerebellum compared to the control group. This study suggests that arsenite exposure for 16 weeks can lead to oxidative stress of blood and brain of rats. Ngb may play a protective role in cerebellum when oxidative stress occurs due to arsenite exposure.

Phase I clinical trial of KML001 monotherapy in patients with advanced solid tumors.

BACKGROUND: We evaluated the tolerability, pharmacokinetics (PK) and preliminary efficacy of KML001, an oral trivalent arsenical, as a monotherapy in patients with advanced solid tumors. RESEARCH DESIGN AND METHODS: With a standard 3 + 3 design for dose-escalation stage, the planned dose levels of KML001 were 5, 7.5, 10, 12.5, and 15 mg/day for 28 days. Once the maximum tolerated dose was determined, 22 subjects were additionally enrolled for dose-expansion stage. PK analysis was performed in the 5, 10, and 15 mg/day cohort at the dose-escalation stage and also at the dose-expansion stage. Moreover, response was assessed using the standard RECIST 1.1. RESULTS: A total of 45 Korean subjects were enrolled. No DLT was reported at the dose-escalation stage. Three DLTs, two cases of prolonged QTc interval and one of neutropenia, were reported in the 12.5 mg/day cohort at the dose-expansion stage. Higher total daily doses up to 12.5 mg/day of KML001 resulted in higher trough plasma concentrations. Among the 18 subjects who completed 2 cycles of therapy, 15 had progressive disease and 3 had stable disease. CONCLUSIONS: Doses equal to or greater than 10 mg/day KML001 alone were tolerable and produced plasma concentrations higher than biologically relevant targets.

Clinical signs, risk factors, and outcomes associated with bromide toxicosis (bromism) in dogs with idiopathic epilepsy.

OBJECTIVE: To evaluate clinical signs, risk factors, and outcomes associated with bromide toxicosis (bromism) in dogs with idiopathic epilepsy treated with potassium or sodium bromide. DESIGN: Retrospective case-control study. ANIMALS: 83 clinically ill epileptic dogs with (cases; n = 31) and without (controls; 52) bromism. PROCEDURES: Medical records were reviewed for information regarding signalment, epilepsy history, treatment, diet, clinicopathologic test results, concurrent diseases, clinical signs, and outcome. Case and control dogs were matched by the veterinary hospitals from which they were referred and by month of admission. A presumptive diagnosis of bromism was made in case dogs when treatment for primary clinical signs was limited to induction of diuresis or reduction in the dose of bromide administered, and this diagnosis was supported by serum bromide concentrations. Potential risk factors for bromism were identified via univariate and subsequent multivariate logistic regression analyses. RESULTS: Common clinical signs of bromism included alterations in consciousness, ataxia, and upper and lower motor neuron tetraparesis and paraparesis. The multivariate analysis identified bromide dose at admission to the hospital as the only factor significantly associated with bromism. In all dogs with bromism, treatment via dose reduction or facilitated renal excretion of bromide resulted in rapid clinical improvement, although breakthrough seizures happened during treatment in 8 of 31 (26%) dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Bromism is a clinically heterogeneous, dose-dependent neurotoxicosis that is largely reversible with treatment. Regular serial monitoring of serum bromide concentrations is recommended to optimize anticonvulsant treatment in dogs with idiopathic epilepsy.

Involvement of proinflammatory cytokines and metallothionein in the repairing of arsenic-mediated uterine tissue damage by curcumin.

Background Curcumin is extensively used as a therapeutic intervention for treating several ailments. The antioxidant curcumin has an anti-inflammatory and chelating property with arsenic to exhibit a strong therapeutic effect on reproductive organs. This study was undertaken to describe the protective effect of noninvasive administration of curcumin against sodium-arsenite-mediated uterine hazards in female Wistar rats. Methods Twenty-four female Wistar rats were randomly divided into four groups. The treatment was continued for 8 days and given orally sodium arsenite (10 mg/kg body weight) in combination with curcumin (20 mg/kg body weight). Results Our evaluation revealed that 8 days of sodium arsenite (10 mg/kg body weight) treatment reduced the activities of the uterine enzymatic antioxidants superoxide dismutase, catalase, and peroxidase. Blood levels of vitamin B12 and folic acid decreased followed by an increased serum lactate dehydrogenase, homocysteine level, and hepatic metallothionein-1 in arsenic-treated rats. Necrosis of uterine tissue along with the disruption of ovarian steroidogenesis was marked in arsenic-treated rats with an upregulation of uterine NF-κB and IL-6 along with a raised level of serum TNF-α. Oral administration of curcumin (20 mg/kg body weight/day) in arsenic-treated rats significantly reinstated these alterations of the antioxidant system followed by an improvement of ovarian steroidogenesis and the circulating level of B12 and folate along with the downregulation of serum homocysteine, metallothionein-1, and cytokines. Conclusions The findings of this study clearly and strongly elucidated that arsenic-induced oxidative stress in uterus is linked to an alteration of inflammation-signaling biomarkers and these have been protected through the co-administration of curcumin due to its anti-inflammatory, free radical scavenging, and antioxidant activity by the possible regulation of an S-adenosine methionine pool.

Endocrine Disruption Alters Developmental Energy Allocation and Performance in Rana temporaria.

Environmental change exposes wildlife to a wide array of environmental stressors that arise from both anthropogenic and natural sources. Many environmental stressors with the ability to alter endocrine function are known as endocrine disruptors, which may impair the hypothalamus-pituitary-thyroid axis resulting in physiological consequences to wildlife. In this study, we investigated how the alteration of thyroid hormone (TH) levels due to exposure to the environmentally relevant endocrine disruptor sodium perchlorate (SP; inhibitory) and exogenous L-thyroxin (T4; stimulatory) affects metabolic costs and energy allocation during and after metamorphosis in a common amphibian (Rana temporaria). We further tested for possible carry-over effects of endocrine disruption during larval stage on juvenile performance. Energy allocated to development was negatively related to metabolic rate and thus, tadpoles exposed to T4 could allocate 24% less energy to development during metamorphic climax than control animals. Therefore, the energy available for metamorphosis was reduced in tadpoles with increased TH level by exposure to T4. We suggest that differences in metabolic rate caused by altered TH levels during metamorphic climax and energy allocation to maintenance costs might have contributed to a reduced energetic efficiency in tadpoles with high TH levels. Differences in size and energetics persisted beyond the metamorphic boundary and impacted on juvenile performance. Performance differences are mainly related to strong size-effects, as altered TH levels by exposure to T4 and SP significantly affected growth and developmental rate. Nevertheless, we assume that juvenile performance is influenced by a size-independent effect of achieved TH. Energetic efficiency varied between treatments due to differences in size allocation of internal macronutrient stores. Altered TH levels as caused by several environmental stressors lead to persisting effects on metamorphic traits and energetics and, thus, caused carry-over effects on performance of froglets. We demonstrate the mechanisms through which alterations in abiotic and biotic environmental factors can alter phenotypes at metamorphosis and reduce lifetime fitness in these and likely other amphibians.

Sodium phosphates and colonoscopy: renal failure.

Sodium phosphate solutions used for bowel cleansing before colonoscopy increase the risk of renal failure, especially in the elderly or in patients treated with angiotensin-converting enzyme inhibitors or other drugs that can affect renal function.

Antioxidant supplementation upregulates calbindin expression in cerebellar Purkinje cells of rat pups subjected to post natal exposure to sodium arsenite.

Optimal cytoplasmic calcium (Ca2+) levels have been associated with adequate cell functioning and neuronal survival. Altered intracellular Ca2+ levels following impaired Ca2+ homeostasis could induce neuronal degeneration or even cell death. There are reports of arsenite induced oxidative stress and the associated disturbances in intracellular calcium homeostasis. The present study focused on determining the strategies that would modulate tissue redox status and calcium binding protein (CaBP) (Calbindin D28k-CB) expression affected adversely by sodium arsenite (NaAsO2) exposure (postnatal) of rat pups. NaAsO2 alone or along with antioxidants (AOXs) (alpha lipoic acid or curcumin) was administered by intraperitoneal (i.p.) route from postnatal day (PND) 1-21 (covering rapid brain growth period - RBGP) to experimental groups and animals receiving sterile water by the same route served as the controls. At the end of the experimental period, the animals were subjected to euthanasia and the cerebellar tissue obtained therefrom was processed for immunohistochemical localization and western blot analysis of CB protein. CB was diffusely expressed in cell body as well as dendritic processes of Purkinje cells (PCs) along the PC Layer (PCL) in all cerebellar folia of the control and the experimental animals. The multilayered pattern of CB +ve cells along with their downregulated expression and low packing density was significantly evident in the arsenic (iAs) alone exposed group as against the controls and AOX supplemented groups. The observations are suggestive of AOX induced restoration of CaBP expression in rat cerebellum following early postnatal exposure to NaAsO2.

Human gastric cells resistant to (-)-epigallocatechin gallate show cross-resistance to several environmental pollutants.

After a long-term culture in (-)-epigallocatechin gallate (EGCG, 20 microM), a major constituent of green tea, human gastric AGS cells developed 2.2-fold resistance to EGCG. The resistant AGS (AGS-R) cells were cross-resistant to several N-methylcarbamate insecticides, which are among the major control agents for pest insects in Taiwan. The AGS-R cells also showed protective effects against both the cytotoxicity and DNA damage induced by one of the mutagenic derivatives of N-methylcarbamate insecticide, N-nitroso methomyl, which is known to target the mammalian gastric tract. Therefore, acquisition of resistance by AGS cells through chronic exposure to EGCG implies that the tea-drinking habit of the Taiwanese is probably beneficial for the health of the gastric tract. In addition, AGS-R cells were cross-resistant to sodium arsenite and hydrogen peroxide, indicating that tolerance to oxidative stress might play a role in the development of resistance described in this investigation.

Bromide supplementation exacerbated the renal dysfunction, injury and fibrosis in a mouse model of Alport syndrome.

A seminal study recently demonstrated that bromide (Br-) has a critical function in the assembly of type IV collagen in basement membrane (BM), and suggested that Br- supplementation has therapeutic potential for BM diseases. Because salts of bromide (KBr and NaBr) have been used as antiepileptic drugs for several decades, repositioning of Br- for BM diseases is probable. However, the effects of Br- on glomerular basement membrane (GBM) disease such as Alport syndrome (AS) and its impact on the kidney are still unknown. In this study, we administered daily for 16 weeks 75 mg/kg or 250 mg/kg (within clinical dosage) NaBr or NaCl (control) via drinking water to 6-week-old AS mice (mouse model of X-linked AS). Treatment with 75 mg/kg NaBr had no effect on AS progression. Surprisingly, compared with 250 mg/kg NaCl, 250 mg/kg NaBr exacerbated the progressive proteinuria and increased the serum creatinine and blood urea nitrogen in AS mice. Histological analysis revealed that glomerular injury, renal inflammation and fibrosis were exacerbated in mice treated with 250 mg/kg NaBr compared with NaCl. The expressions of renal injury markers (Lcn2, Lysozyme), matrix metalloproteinase (Mmp-12), pro-inflammatory cytokines (Il-6, Il-8, Tnf-α, Il-1ß) and pro-fibrotic genes (Tgf-ß, Col1a1, α-Sma) were also exacerbated by 250 mg/kg NaBr treatment. Notably, the exacerbating effects of Br- were not observed in wild-type mice. These findings suggest that Br- supplementation needs to be carefully evaluated for real positive health benefits and for the absence of adverse side effects especially in GBM diseases such as AS.

Optimization of alginate purification using polyvinylidene difluoride membrane filtration: Effects on immunogenicity and biocompatibility of three-dimensional alginate scaffolds.

Sodium alginate is an effective biomaterial for tissue engineering applications. Non-purified alginate is contaminated with protein, lipopolysaccharide, DNA, and RNA, which could elicit adverse immunological reactions. We developed a purification protocol to generate biocompatible alginate based on (a) activated charcoal treatment, (b) use of hydrophobic membrane filtration (we used hydrophobic polyvinylidene difluoride membranes to remove organic contaminants), (c) dialysis, and finally (d) ethanol precipitation. Using this approach, we could omit pre-treatment with chloroform and significantly reduce the quantities of reagents used. Purification resulted in reduction of residual protein by 70% down to 0.315 mg/g, DNA by 62% down to 1.28 µg/g, and RNA by 61% down to less than 10 µg/g, respectively. Lipopolysaccharide levels were reduced by >90% to less than 125 EU/g. Purified alginate did not induce splenocyte proliferation in vitro. Three-dimensional scaffolds generated from purified alginate did not elicit a significant foreign body reaction, fibrotic overgrowth, or macrophage infiltration 4 weeks after implantation. This study describes a simplified and economical alginate purification method that results in alginate purity, which meets clinically useful criteria.

Antioxidant Potential of Spirulina platensis Mitigates Oxidative Stress and Reprotoxicity Induced by Sodium Arsenite in Male Rats.

The present study aimed to examine the protective role of Spirulina platensis (S. platensis) against arsenic-induced testicular oxidative damage in rats. Arsenic (in the form of NaAsO2 at a dose of 6.3 mg/kg body weight for 8 weeks) caused a significant accumulation of arsenic in testicular tissues as well as a decrease in the levels of testicular superoxide dismutase (SOD), catalase (CAT), reduced glutathione, and zinc. Moreover, it significantly decreased plasma testosterone, luteinizing hormone (LH), triiodothyronine (T3), and thyroxine (T4) levels and reduced sperm motility and sperm count. Arsenic (AS) led to a significant increase in testicular malondialdehyde (MDA), tumour necrosis factor alpha (TNF-α), nitric oxide (NO), and sperm abnormalities. S. platensis at a dose of 300 mg/kg was found to attenuate As-induced oxidative stress, testicular damage, and sperm abnormalities by its potent antioxidant activity. S. platensis may represent a potential therapeutic option to protect the testicular tissue from arsenic intoxication.

Effect of sodium arsenite on reproductive organs of female Wistar rats.

The present study was performed to investigate the subchronic effect of sodium arsenite on female Wistar rats. Mature female rats were divided into 4 groups of 12 animals each. Group I received distilled water, whereas the other 3 groups received sodium arsenite at 10, 30, and 50 µg/L doses for 60 days through drinking water. Half of the animals from each group were dissected after 30 days and the remaining after 60 days. A disruption in estrous cycle was observed with prolonged diestrous and metestrous phases. A significant increase in ovarian surface epithelium and follicular atresia was observed in treated rats (p ≤ .05). A significant decrease (p ≤ .05) in the uterine myometrium was observed. A significant increase (p ≤ .05) in the levels of lipid peroxidation along with decrease in the activities of antioxidant enzymes was observed. The results revealed that subchronic exposure of sodium arsenite causes degenerative changes in reproductive organs and induces oxidative stress in female rats.

Sodium arsenite-induced stress-related gene expression in normal human epidermal, HaCaT, and HEL30 keratinocytes.

Arsenic is a carcinogen that poses a significant health risk in humans. Based on evidence that arsenic has differential effects on human, rodent, normal, and transformed cells, these studies addressed the relative merits of using normal human epidermal keratinocytes (NHEK) and immortalized human (HaCaT) and mouse (HEL30) keratinocytes when examining stress-induced gene expression that may contribute to carcinogenesis. We hypothesize that redox-related gene expression is differentially modulated by arsenic in normal versus immortalized keratinocytes. To test the hypothesis, we exposed keratinocytes to sodium arsenite for 4 or 24 hr, at which time serine threonine kinase-25 (stk25) and nicotine adenine dinucleotide phosphate [nad(p)h] quinone oxidoreductase gene expression were measured. The effect of glutathione reduction on arsenite-induced cytotoxicity and gene expression in NHEK also was evaluated by addition of l-buthionine-[S,R]-sulfoximine (BSO) to culture media. Results indicate the term LC(50) for arsenite is approximately 10-15 microM in NHEK and HEL30 keratinocytes and 30 microM in HaCaT keratinocytes. Compared with HaCaT and HEL30 keratinocytes, a nontoxic concentration of arsenite (2.5 microM) increases stk25 and nad(p)h quinone oxidoreductase gene expression in NHEK, an effect partially attenuated by BSO. These data indicate that NHEK and HaCaT/HEL30 keratinocytes have similar sensitivities toward arsenite-induced cytotoxicity but unique gene expression responses. They also suggest that arsenite modulates gene expression in NHEK involved in cellular signaling and other aspects of intermediary metabolism that may contribute to the carcinogenic process.

Health effects assessment for environmental perchlorate contamination: the dose response for inhibition of thyroidal radioiodine uptake in humans.

Application of a sensitive new detection method has revealed widespread perchlorate contamination of groundwater in the southwestern United States, typically at 0.005-0.020 mg/L (5-20 ppb). Perchlorate is a competitive inhibitor of the process by which iodide is actively transported from the bloodstream into the thyroid. This inhibitory action of perchlorate is the basis of its pharmaceutical use (in the treatment of hyperthyroidism) as well as its potential toxicity. To establish the dose response in humans for perchlorate inhibition of thyroidal iodide uptake and any short-term effects on thyroid hormones, we gave perchlorate in drinking water at 0.007, 0.02, 0.1, or 0.5 mg/kg-day to 37 male and female volunteers for 14 days. In 24 subjects we performed 8- and 24-hr measurements of thyroidal (123)I uptake (RAIU) before exposure, on exposure days 2 (E2) and 14 (E14), and 15 days postexposure (P15). In another 13 subjects we omitted both E2 studies and the 8-hr P15 study. We observed a strong correlation between the 8- and 24-hr RAIU over all dose groups and measurement days. We found no difference between E2 and E14 in the inhibition of RAIU produced by a given perchlorate dose. We also found no sex difference. On both E2 and E14, the dose response was a negative linear function of the logarithm of dose. Based on the dose response for inhibition of the 8- and 24-hr RAIU on E14 in all subjects, we derived estimates of the true no-effect level: 5.2 and 6.4 micro g/kg-day, respectively. Given default body weight and exposure assumptions, these doses would be ingested by an adult if the drinking-water supply contained perchlorate at concentrations of approximately 180 and 220 micro g/L (ppb), respectively. On P15, RAIU was not significantly different from baseline. In 24 subjects we measured serum levels of thyroxine (total and free), triiodothyronine, and thyrotropin in blood sampled 16 times throughout the study. Only the 0.5 mg/kg-day dose group showed any effect on serum hormones: a slight downward trend in thyrotropin levels in morning blood draws during perchlorate exposure, with recovery by P15.

Expression of the constitutive and inducible forms of heat shock protein 70 in human proximal tubule cells exposed to heat, sodium arsenite, and CdCl(2).

We determined the expression of the constitutive (hsc 70) and inducible (hsp 70) forms of heat shock protein 70 mRNA and protein in human proximal tubule (HPT) cells exposed to lethal and sublethal concentrations of Cd(+2) under both acute and extended conditions of exposure. The HPT cells exhibited the classic heat shock response when subjected to a physical (heat) or chemical stress (sodium arsenite); hsc 70 mRNA and protein levels were constant or slightly increased, whereas hsp 70 mRNA and protein were greatly elevated. Acute exposure to 53.4 microM CdCl(2) for 4 hr failed to increase either hsc 70 mRNA or protein, a finding similar to that observed under classic conditions of stress. However, under identical conditions of acute exposure to Cd(2+), the expected increase in hsp 70 protein level was suppressed as compared to that found under classic conditions of physical or chemical stress. The decrease in hsp 70 protein level correlated to the reduced expression of mRNA from the hsp 70B gene. The expression of mRNA from the hsp 70A and hsp 70C genes was similar to that found when the cells were treated with heat shock or sodium arsenite. We modeled an extended exposure to Cd(2+) by treating the cells continuously with Cd(2+) at both lethal and sublethal levels over a 16-day time course. Chronic exposure to Cd(2+) failed to increase either hsc 70 mRNA or protein levels in the HPT cells at a nonlethal dosage level and decreased hsc 70 mRNA and protein levels late in the time course of lethal exposure. Under identical conditions, the expression of hsp 70 protein remained at basal levels that were only marginally detectable throughout the time course. Hsp 70A and hsp 70C mRNA levels were unaltered by extended exposure to Cd(2+), and hsp 70B mRNA was not detected during the 16-day time course. Cd(2+) is a poor inducer of hsc 70 and hsp 70 in the proximal tubule under both acute and long-term exposure. These results reinforce the fact that the expression of hsp 70 protein does not result from the transcription of a single gene, but is derived from what may be a complex interplay of several underlying genes.