Microarray analysis of gene expression patterns in human proximal tubule cells over a short and long time course of cadmium exposure

Integrative analysis to explore the biological association between environmental skin diseases and ambient particulate matter

Although numerous experimental studies have suggested a significant association between ambient particulate matter (PM) and respiratory damage, the etiological relationship between ambient PM and environmental skin diseases is not clearly understood. Here, we aimed to explore the association between PM and skin diseases through biological big data analysis. Differential gene expression profiles associated with PM and environmental skin diseases were retrieved from public genome databases. The co-expression among them was analyzed using a text-mining-based network analysis software. Activation/inhibition patterns from RNA-sequencing data performed with PM_2.5-treated normal human epidermal keratinocytes (NHEK) were overlapped to select key regulators of the analyzed pathways. We explored the adverse effects of PM on the skin and attempted to elucidate their relationships using public genome data. We found that changes in upstream regulators and inflammatory signaling networks mediated by MMP-1, MMP-9, PLAU, S100A9, IL-6, and S100A8 were predicted as the key pathways underlying PM-induced skin diseases. Our integrative approach using a literature-based co-expression analysis and experimental validation not only improves the reliability of prediction but also provides assistance to clarify underlying mechanisms of ambient PM-induced dermal toxicity that can be applied to screen the relationship between other chemicals and adverse effects.

Potential protective roles of curcumin against cadmium-induced toxicity and oxidative stress

Curcumin, used as a spice and traditional medicine in India, exerts beneficial effects against several diseases, owing to its antioxidant, analgesic, and anti-inflammatory properties. Evidence indicates that curcumin might protect against heavy metal-induced organ toxicity by targeting biological pathways involved in anti-oxidation, anti-inflammation, and anti-tumorigenesis. Curcumin has received considerable attention owing to its therapeutic properties, and the mechanisms underlying some of its actions have been recently investigated. Cadmium (Cd) is a heavy metal found in the environment and used extensively in industries. Chronic Cd exposure induces damage to bones, liver, kidneys, lungs, testes, and the immune and cardiovascular systems. Because of its long half-life, exposure to even low Cd levels might be harmful. Cd-induced toxicity involves the overproduction of reactive oxygen species (ROS), resulting in oxidative stress and damage to essential biomolecules. Dietary antioxidants, such as chelating agents, display the potential to reduce Cd accumulation and metal-induced toxicity. Curcumin scavenges ROS and inhibits oxidative damage, thus resulting in many therapeutic properties. This review aims to address the effectiveness of curcumin against Cd-induced organ toxicity and presents evidence supporting the use of curcumin as a protective antioxidant.

Developmental toxicity of cadmium in infants and children: a review

Several millions of people are exposed to cadmium worldwide due to natural and anthropogenic activities that led to their widespread distribution in the environment and have shown potential adverse effects on the kidneys, liver, heart and nervous system. Recently human and animal-based studies have been shown that In utero and early life exposure to cadmium can have serious health issues that are related to the risk of developmental disabilities and other outcomes in adulthood. Since, cadmium crosses the placental barrier and reaches easily to the fetus, even moderate or high-level exposure of this metal during pregnancy could be of serious health consequences which might be reflected either in the children’s early or later stages of life. Mortality from various diseases including cancer, cardiovascular, respiratory, kidney and neurological problems, correlation with In utero or early life exposure to cadmium has been found in epidemiological studies. Animal studies with strong evidence of various diseases mostly support for the human studies, as well as suggested a myriad mechanism by which cadmium can interfere with human health and development. More studies are needed to establish the mechanism of cadmium-induced toxicity with environmentally relevant doses in childhood and later life. In this review, we provide a comprehensive examination of the literature addressing potential long- term health issues with In utero and early life exposure to cadmium, as well as correlating with human and animal exposure studies.

Effect of plasma selenium, red blood cell cadmium, total urinary arsenic levels, and eGFR on renal cell carcinoma

High total urinary arsenic concentrations and low estimated glomerular filtration rate (eGFR) increase the risk of renal cell carcinoma (RCC). This study aimed to determine whether other metals or metalloids can affect RCC. A total of 401 patients with RCC and 774 age- and sex-matched controls were recruited between November 2006 and December 2012 in Taiwan. Surgical resection or image-guided biopsy of renal tumors was performed to pathologically verify RCC. High-performance liquid chromatography linked to a hydride generator and atomic absorption spectrometer were used to measure the urinary arsenic species concentrations. Inductively coupled plasma mass spectrometry was used to determine plasma selenium and red blood cell cadmium and lead concentration. Plasma selenium levels were inversely related to RCC, whereas red blood cell cadmium levels were directly related to RCC. The odds ratio (OR) and 95% confidence interval (CI) were 0.14 (95% CI, 0.10-0.20) and 1.33 (95% CI, 1.03-1.72), respectively. A low plasma selenium level tended to interact with high total urinary arsenic levels or with high red blood cell cadmium concentration to increase the OR of RCC. In particular, low eGFR multiplicatively interacted with high red blood cell cadmium concentration to increase the OR of RCC (P_interaction=0.003). This study was the first to find a significant multiplicative interaction between eGFR and the red blood cell cadmium levels on the increased OR of RCC.

Associations between blood cadmium concentration and kidney function in the U.S. population: Impact of sex, diabetes and hypertension

BACKGROUND

Exposure to cadmium has been associated with nephropathy and implicated in the development of diabetes and hypertension. The role of environmental metal exposure may be an underexplored risk factor for decreased kidney function among people with diabetes and/or hypertension. The objective of this study was to examine the association of blood concentration of cadmium with kidney function parameters and evaluate sex, diabetes, and hypertension as effect modifiers of the association.

METHODS

This study used data from 12,577 adult participants in the National Health and Nutrition Examination Survey (NHANES) 2007-2012 cycles. We used multivariable linear and logistic regression models to conduct a cross-sectional analysis of the association between cadmium exposure quartiles and estimated glomerular filtration rate (eGFR), urine albumin to creatinine ratio (UACR), low eGFR (defined as eGFR <60 mL/minute/1.73 m²), and albuminuria (defined as UACR ≥ 30 mg/g). Models were adjusted for confounders and interaction terms were evaluated for cadmium concentration and sex, diabetes, and hypertension. Final models were stratified by sex and indices of existing diabetes and hypertension status.

RESULTS

The mean eGFR was 94.3 mL/minute/1.73 m² (SD 21.5) and the geometric mean of UACR was 7.9 mg/g (95% CI 7.6-8.2 mg/g). Blood cadmium concentration was inversely associated with eGFR and positively associated with UACR. We found significant effect modification of the association of eGFR with cadmium, predominantly for sex and hypertension. The strength of the association between cadmium quartiles and eGFR was more pronounced among females compared to males. Among females with hypertension and diabetes, eGFR was lower on average by 4.9 mL/minute/1.73 m² (95% CI -10.1 to 0.29) in the highest versus lowest cadmium quartile, and in females with hypertension alone, eGFR was lower on average by 5.8 mL/minute/1.73 m² (95% CI -8.2 to -3.3) in the highest versus lowest cadmium quartile. Among those in the highest exposure quartile, higher mean UACR was observed among participants with hypertension compared to those without.

CONCLUSIONS

Our results confirm that cadmium exposure is associated with decreased glomerular filtration and increased urine protein excretion, and provide evidence that the magnitude of these associations differ by sex and may vary based on preexisting diabetes and hypertension. Future prospective sex-specific investigations are necessary to address concerns of reverse causality and efforts should be made to reduce smoking and environmental contamination from cadmium to protect human health.

The stress response of human proximal tubule cells to cadmium involves up-regulation of haemoxygenase 1 and metallothionein but not cytochrome P450 enzymes

Enzymes of the cytochrome P450 (CYP) super-family are implicated in cadmium (Cd) -induced nephrotoxicity, however, direct evidence is lacking. This study investigated the endogenous expression of various CYP proteins together with the stress-response proteins, heme oxygenase-1 (HO-1) and metallothionein (MT) in human kidney sections and in cadmium-exposed primary cultures of human proximal tubular epithelial cells (PTC). By immunohistochemistry, the CYP members 2B6, 4A11 and 4F2 were prominently expressed in the cortical proximal tubular cells and to a lesser extent in distal tubular cells. Low levels of CYPs 2E1 and 3A4 were also detected. In PTC, in the absence of Cd, CYP2E1, CYP3A4, CYP4F2 and MT were expressed, but HO-1, CYP2B6 and CYP4A11 were not detected. A range of cadmium concentrations (0-100μM) were utilized to induce stress conditions. MT protein was further induced by as little as 0.5μM cadmium, reaching a 6-fold induction at 20μM, whereas for HO-1, a 5μM cadmium concentration was required for initial induction and at 20μM cadmium reached a 15-fold induction. The expression of CYP2E1, CYP3A4, and CYP4F2 were not altered by any cadmium concentrations tested at 48h. Cadmium caused a reduction in cell viability at concentrations above 10μM. In conclusion although cultured PTC, do express CYP proteins, (CYP2E1, CYP3A4, and CYP4F2), Cd-induced cell stress as indicted by induction of HO-1 and MT does not alter expression of these CYP proteins at 48h.

Prediction of the number of activated genes in multiple independent Cd(+2)- and As(+3)-induced malignant transformations of human urothelial cells (UROtsa)

BACKGROUND

Many toxic environmental agents such as cadmium and arsenic are found to be epidemiologically linked to increasing rates of cancers. In vitro studies show that these toxic agents induced malignant transformation in human cells. It is not clear whether such malignant transformation induced by a single toxic agent is driven by a common set of genes. Although the advancement of high-throughput technology has facilitated the profiling of global gene expression, it remains a question whether the sample size is sufficient to identify this common driver gene set.

RESULTS

We have developed a statistical method, SOFLR, to predict the number of common activated genes using a limited number of microarray samples. We conducted two case studies, cadmium and arsenic transformed human urothelial cells. Our method is able to precisely predict the number of stably induced and repressed genes and the number of samples to identify the common activated genes. The number of independent transformed isolates required for identifying the common activated genes is also estimated. The simulation study further validated our method and identified the important parameters in this analysis.

CONCLUSIONS

Our method predicts the degree of similarity and diversity during cell malignant transformation by a single toxic agent. The results of our case studies imply the existence of common driver and passenger gene sets in toxin-induced transformation. Using a pilot study with small sample size, this method also helps microarray experimental design by determining the number of samples required to identify the common activated gene set.

Actin cytoskeleton redox proteome oxidation by cadmium

Epidemiological studies associate environmental cadmium (Cd) exposure with the risk of lung diseases. Although mechanisms are not fully elucidated, several studies demonstrate Cd effects on actin and actin-associated proteins. In a recent study of Cd at concentrations similar to environmental exposures, we found that redox-dependent inflammatory signaling by NF-κB was sensitive to the actin-disrupting agent, cytochalasin D. The goal of the present study was to use mass spectrometry-based redox proteomics to investigate Cd effects on the actin cytoskeleton proteome and related functional pathways in lung cells at low environmental concentrations. The results showed that Cd under conditions that did not alter total protein thiols or glutathione redox state caused significant oxidation of peptidyl Cys of proteins regulating actin cytoskeleton. Immunofluorescence microscopy of lung fibroblasts and pulmonary artery endothelial cells showed that low-dose Cd exposure stimulated filamentous actin formation and nuclear localization of destrin, an actin-depolymerizing factor. Taken together, the results show that redox states of peptidyl Cys in proteins associated with actin cytoskeleton pathways are selectively oxidized in lung by Cd at levels thought to occur from environmental exposure.

Short and long term gene expression variation and networking in human proximal tubule cells when exposed to cadmium

Cadmium (Cd²⁺) is a known nephrotoxin causing tubular necrosis during acute exposure and potentially contributing to renal failure in chronic long-term exposure. To investigate changes in global gene expression elicited by cadmium, an in-vitro exposure system was developed from cultures of human renal epithelial cells derived from cortical tissue obtained from nephrectomies. These cultures exhibit many of the qualities of proximal tubule cells. Using these cells, a study was performed to determine the cadmium-induced global gene expression changes after short-term (1 day, 9, 27, and 45 μM) and long-term cadmium exposure (13 days, 4.5, 9, and 27 μM). These studies revealed fundamental differences in the types of genes expressed during each of these time points. The obtained data was further analyzed using regression to identify cadmium toxicity responsive genes. Regression analysis showed 403 genes were induced and 522 genes were repressed by Cd²⁺ within 1 day, and 366 and 517 genes were induced and repressed, respectively, after 13 days. We developed a gene set enrichment analysis method to identify the cadmium induced pathways that are unique in comparison to traditional approaches. The perturbation of global gene expression by various Cd²⁺ concentrations and multiple time points enabled us to study the transcriptional dynamics and gene interaction using a mutual information-based network model. The most prominent network module consisted of INHBA, KIF20A, DNAJA4, AKAP12, ZFAND2A, AKR1B10, SCL7A11, and AKR1C1.

Increased risk of cancer mortality associated with cadmium exposures in older Americans with low zinc intake

Cadmium (Cd) exposure has been associated with increased cancer risk, and zinc (Zn) appears to reduce that risk. However, little is known about the combined influence of Cd and Zn on cancer risk. The aim of this study was to examine relationships between Cd exposure, Zn intake, and cancer mortality risks. The analyses used 5204 subjects aged 50 yr or older from the Third National Health and Nutrition Examination Survey (NHANES III, 1988-1994) and the mortality follow-up through December 31, 2006. Cox proportional hazards models were used to test associations. In total, 569 cancer deaths were recorded during an average follow-up of 12.4 yr, including 155 from lung, 61 from prostate, and 26 from breast cancer. A positive association between Cd and cancer mortality risk was identified for both genders. Despite limited cause-specific deaths, the increased risk associated with Cd was significant for lung cancer in men. All-cause cancer mortality risk was significantly elevated among women with Zn intakes below the recommended dietary allowance (RDA) compared with women who met the RDA. The effect of low dietary Zn was not observed in men. Similar trends for prostate and breast cancer deaths were not significant. There was a significant inverse association between cancer deaths and the Zn-to-Cd ratio for both genders. Cd exposure is an important independent risk factor of cancer mortality in older Americans and the risk appears exaggerated in those with inadequate dietary Zn. Additional studies are required to elucidate the mechanism(s) by which Zn participates in the carcinogenic influence of Cd.

Increased nuclear thioredoxin-1 potentiates cadmium-induced cytotoxicity

Cadmium (Cd) is a widely dispersed environmental agent that causes oxidative toxicity through mechanisms that are sensitive to thioredoxin-1 (Trx1). Trx1 is a cytoplasmic protein that translocates to nuclei during oxidative stress. Recent research shows that interaction of Trx1 with actin plays a critical role in cell survival and that increased nuclear Trx-1 potentiates proinflammatory signaling and death in cell and mouse models. These observations indicate that oxidative toxicity caused by low-dose Cd could involve disruption of actin-Trx1 interaction, nuclear Trx1 translocation, and potentiation of proinflammatory cell death mechanisms. In this study, we investigated the role of nuclei-localized Trx1 in Cd-induced inflammation and cytotoxicity using in vitro and in vivo models. The results show that Cd stimulated nuclear translocation of Trx1 and p65 of NF-κB. Elevation of Trx1 in nuclei in in vitro cells and kidney of transgenic mice potentiated Cd-stimulated NF-κB activation and cell death. Cd-stimulated Trx1 nuclear translocation and NF-κB activation were inhibited by cytochalasin D, an inhibitor of actin polymerization, suggesting that actin regulates Trx1 nuclear translocation and NF-κB activation by Cd. A nuclear-targeted dominant negative form of Trx1 blocked Cd-stimulated NF-κB activation and decreased cell death. Addition of zinc, known to antagonize Cd toxicity by increasing metallothionein, had no effect on Cd-stimulated nuclear translocation of Trx1 and NF-κB activation. Taken together, the results show that nuclear translocation and accumulation of redox-active Trx1 in nuclei play an important role in Cd-induced inflammation and cell death.

Gene expression databases for kidney epithelial cells

The 21st century has seen an explosion of new high-throughput data from transcriptomic and proteomic studies. These data are highly relevant to the design and interpretation of modern physiological studies but are not always readily accessible to potential users in user-friendly, searchable formats. Data from our own studies involving transcriptomic and proteomic profiling of renal tubule epithelia have been made available on a variety of online databases. Here, we provide a roadmap to these databases and illustrate how they may be useful in the design and interpretation of physiological studies. The databases can be accessed through http://helixweb.nih.gov/ESBL/Database.

Brain transcriptomic response of threespine sticklebacks to cues of a predator

Predation pressure represents a strong selective force that influences the development and evolution of living organisms. An increasing number of studies have shown that both environmental and social factors, including exposure to predators, substantially shape the structure and function of the brain. However, our knowledge about the molecular mechanisms underlying the response of the brain to environmental stimuli is limited. In this study, we used whole-genome comparative oligonucleotide microarrays to investigate the brain transcriptomic response to cues of a predator in the threespine stickleback, Gasterosteus aculeatus. We found that repeated exposure to olfactory, visual and tactile cues of a predator (rainbow trout, Oncorrhynchus mykiss) for 6 days resulted in subtle but significant transcriptomic changes in the brain of sticklebacks. Gene functional analysis and gene ontology enrichment revealed that the majority of the transcripts differentially expressed between the fish exposed to cues of a predator and the control group were related to antigen processing and presentation involving the major histocompatibility complex, transmission of synaptic signals, brain metabolic processes, gene regulation and visual perception. The top four identified pathways were synaptic long-term depression, RAN signaling, relaxin signaling and phototransduction. Our study demonstrates that exposure of sticklebacks to cues of a predator results in the activation of a wide range of biological and molecular processes and lays the foundation for future investigations on the molecular factors that modulate the function and evolution of the brain in response to stressors.