Cadmium induces cytotoxicity in human bronchial epithelial cells through upregulation of eIF5A1 and NF-kappaB

Immunohistochemical, histopathological, and biochemical studies of the NF-ҡB P65 marker in rat ovaries experimentally intoxicated by cadmium and the protective effect of the purslane plant extract

The aim of this study is to describe the existence of the inflammatory marker nuclear factor kappa light chain B lymphocyte protein (NF-ҡB P65) in the tissue as a response to cadmium (CdCl₂) toxicity. Next is to describe the disappearance of the NF-ҡB P65 in response to the purslane plant treatment to explore its anti-inflammatory effect, also describing the histopathological and biochemical changes that occurred from CdCl₂ toxicity and the purslane plant tissue protections. There are four experimental groups, 32 rats (n = 8) intraperitoneally injected with CdCl₂ and orally administered with purslane plant extract (according to groups) for 30 days: group one (control), group two (purslane extract 2 g/kg bw), group three (CdCl₂ 3.5 mg/kg bw), group four (CdCl₂ 3.5 mg/kg bw + purslane plant extract 2 g/kg bw). The biochemical findings showed that ovaries and brain tissue homogenates in group three showed malondialdehyde increase and reduction in catalase, total antioxidant capacity, and acetylcholine esterase. A reduction in serum LH, FSH, and estradiol were also recorded. These parameters became normal in group four. The histopathological findings exhibited that group three showed ovarian and cerebral hemorrhage and lung pneumonia. Tissues of group four were protected and no pathological lesions were detected. The immunohistochemical results showed that the inflammatory marker NF-ҡB P65 in group three was strongly detected in the spleen and moderately detected in the ovaries, brain, and lung but negatively detected in the tissues of group four. In conclusion, CdCl₂ induced ovarian toxicity and the NF-ҡB P65 existence was increased. Purslane plant protected rats from CdCl₂ toxicity and decrease NF-ҡB P65.

Recent insights into eukaryotic translation initiation factors 5A1 and 5A2 and their roles in human health and disease

The eukaryotic translation initiation factor 5A1 (eIF5A1) and its homolog eIF5A2 are the only two human proteins containing the unique post-translational modification-hypusination, which is essential for the function of these two proteins. eIF5A1 was initially identified as a translation initiation factor by promoting the first peptide bond formation of protein during translation; however, recent results suggest that eIF5A1 also functions as a translation elongation factor. It has been shown that eIF5A1 is implicated in certain human diseases, including diabetes, several human cancer types, viral infections and diseases of neural system. Meanwhile, eIF5A2 is overexpressed in many cancers, and plays an important role in the development and progression of cancers. As multiple roles of these two factors were observed among these studies, therefore, it remains unclear whether they act as oncogene or tumor suppressor. In this review, the recent literature of eIF5As and their roles in human diseases, especially in human cancers, will be discussed.

Cadmium telluride quantum dot-exposed human bronchial epithelial cells: a further study of the cellular response by proteomics

Quantum dots (QDs) are luminescent nanoparticles with superior versatility. In this regard, cadmium telluride (CdTe) QDs have been widely used for various bioimaging applications. Although these nano-Cd containing particles can be capped with shells to reduce their cytotoxicity, these shells would be gradually disintegrated after a certain period of time, thereby inevitably exerting nanotoxicity. Previously, we showed that treatment of human bronchial epithelial BEAS-2B cells with uncapped CdTe QDs (520Q, 580Q and 730Q with emission maximum at 520, 580 and 730 nm, respectively) elicited dose-dependent cytotoxicity for 520Q and 580Q (<5 nm), while 730Q (>5 nm) elicited negligible cytotoxicity. In order to gain a more global perspective on the action mechanism of these nano-Cd particles, here, we further characterized the proteome response of BEAS-2B when challenged with the above QDs. Interestingly, among the three nano-Cd particles, we observed that 520Q and 580Q treatment altered the BEAS-2B proteome significantly in a very similar magnitude while 730Q has no obvious impact at all, as compared with the untreated control. Notably, the treatment of BEAS-2B with glutathione before nano-Cd particles abrogated the induction/repression of differentially expressed proteins and prevented cell death. Taken together, our findings show that uncapped CdTe nanoparticles (520Q and 580Q) induce oxidative stress in human bronchial epithelial cells, and the similarly altered protein signatures also suggest potential mitotoxicity and common cellular and detoxification responses upon exposure of lung cells to these two QDs. On the other hand, 730Q may exert a more noticeable effect after long-term exposure, but not upon transient exposure.

Lasting DNA Damage and Aberrant DNA Repair Gene Expression Profile Are Associated with Post-Chronic Cadmium Exposure in Human Bronchial Epithelial Cells

Cadmium (Cd) is a widespread environmental pollutant and carcinogen. Although the exact mechanisms of Cd-induced carcinogenesis remain unclear, previous acute/chronic Cd exposure studies have shown that Cd exerts its cytotoxic and carcinogenic effects through multiple mechanisms, including interference with the DNA repair system. However, the effects of post-chronic Cd exposure remain unknown. Here, we establish a unique post-chronic Cd-exposed human lung cell model (the "CR0" cells) and investigate the effects of post-chronic Cd exposure on the DNA repair system. We found that the CR0 cells retained Cd-resistant property even though it was grown in Cd-free culture medium for over a year. The CR0 cells had lasting DNA damage due to reduced DNA repair capacity and an aberrant DNA repair gene expression profile. A total of 12 DNA repair genes associated with post-chronic Cd exposure were identified, and they could be potential biomarkers for identifying post-chronic Cd exposure. Clinical database analysis suggests that some of the DNA repair genes play a role in lung cancer patients with different smoking histories. Generally, CR0 cells were more sensitive to chemotherapeutic (cisplatin, gemcitabine, and vinorelbine tartrate) and DNA damaging (H₂O₂) agents, which may represent a double-edged sword for cancer prevention and treatment. Overall, we demonstrated for the first time that the effects of post-chronic Cd exposure on human lung cells are long-lasting and different from that of acute and chronic exposures. Findings from our study unveiled a new perspective on Cd-induced carcinogenesis-the post-chronic exposure of Cd. This study encourages the field of post-exposure research which is crucial but has long been ignored.

Existence of Internal N7-Methylguanosine Modification in mRNA Determined by Differential Enzyme Treatment Coupled with Mass Spectrometry Analysis

The recent discovery of reversible chemical modifications on mRNA has opened a new era of post-transcriptional gene regulation in eukaryotes. Among the 15 types of modifications identified in mRNA of eukaryotes, N7-methylguanosine (m⁷G) is unique owing to its presence in the 5' cap structure. It remains unknown whether m⁷G is also present internally in mRNA, and this is largely attributed to the lack of an appropriate analytical method to differentiate internal m⁷G in mRNA from that in the 5' cap. To address this analytical challenge, we developed a novel strategy of combining differential enzymatic digestion with liquid chromatography-tandem mass spectrometry analysis to quantify the levels of these two types of m⁷G modifications in mRNA. In particular, we found that S1 nuclease and phosphodiesterase I exhibit differential activities toward internal and 5'-terminal m⁷G. By using this method, we found that internal m⁷G was present in mRNA of cultured human cells as well as plants and rat tissue. In addition, our results showed that plants contain higher levels of internal m⁷G in mRNA than mammals. We also observed that exposure of rice to cadmium (Cd) stimulated marked diminution in the levels of m⁷G at both the 5' cap and internal positions of mRNA, which was correlated with the Cd-induced elevated expression of m⁷G-decapping enzymes. Taken together, we reported here a strategy to distinguish internal and 5'-terminal m⁷G in mRNA, and by using this method, we demonstrated the prevalence of internal m⁷G modification in mRNA, which we believe will stimulate future functional studies of m⁷G on post-transcriptional gene regulation in eukaryotes.

EIF5A1 promotes epithelial ovarian cancer proliferation and progression

Epithelial ovarian cancer (EOC) is one of the most common gynecological cancers and has the highest mortality rate thereof. We found abundant eukaryotic translation initiation factor 5A1 (EIF5A1) in 54 EOC tissues, and high EIF5A1 levels predicted poor survival. EIF5A1 ectopic expression enhanced EOC cell proliferative, migration, and invasive capabilities, while EIF5A1 knockdown suppressed them. Most importantly, GC7 (N1-guanyl-1,7-diaminoheptane, an EIF5A1 hypusination inhibitor) could reverse the effect of EIF5A1 upregulation on EOC cell proliferation, migration, and invasion and mutant type EIF5A1K50A plasmid [bearing a single point mutation (K50 → A50) that prevents hypusination] had no effects on these malignant behaviors. Our findings imply that EIF5A1 is a vital regulator of EOC proliferation and progression and is a potential prognostic marker and therapeutic target in EOC.

Progressive silencing of the zinc transporter Zip8 (Slc39a8) in chronic cadmium-exposed lung epithelial cells

Cadmium (Cd), a non-essential metal, stealthily enters the cells by utilizing the essential metal importing pathways. The zinc transporters Zip8, Zip14, and divalent metal transporter 1 (Dmt1) are now emerging as several important metal transporters involved in cellular Cd incorporation and their expressions have been shown to be down-regulated in several Cd-resistant (CdR) cell lines, however, the involvement of these transporters during the development of Cd-resistance in lung cells is unclear. In this study, we therefore check the expression of these metal transporters in our previously established rat lung epithelial cells (LECs) and show that the level of Zip8 is progressively silenced when LECs are adapted to increasing concentrations of CdCl2 (from 1 to 20 μM). Subsequent measurement of the cellular Cd content indicated that CdR LECs exhibit a marked decrease of Cd accumulation, possibly due to the loss of Zip8 expression. We investigate the possibility that epigenetic silencing of the Zip8 gene by DNA hypermethylation is involved in the down-regulation of Zip8 expression. CdR LECs show a higher mRNA level of DNA methyltransferase 3b (Dnmt3b) than parental cells. Treatment of CdR LECs with 5-aza-2'-deoxycytidine, an inhibitor of DNA methyltransferases, reverted the expression of Zip8 and sensitivity to Cd in these cells, indicating the critical role of Zip8 for Cd import. Taken together, our results demonstrate that the progressive silencing of Zip8 expression is involved in the acquisition of resistance against Cd in lung cells, representing an adaptive survival mechanism that resists Cd-induced cytotoxicity.

Low-dose cadmium exposure induces peribronchiolar fibrosis through site-specific phosphorylation of vimentin

Exposure to cadmium (Cd) has been associated with development of chronic obstructive lung disease (COPD). The mechanisms and signaling pathways whereby Cd causes pathological peribronchiolar fibrosis, airway remodeling, and subsequent airflow obstruction remain unclear. We aimed to evaluate whether low-dose Cd exposure induces vimentin phosphorylation and Yes-associated protein 1 (YAP1) activation leading to peribronchiolar fibrosis and subsequent airway remodeling. Our data demonstrate that Cd induces myofibroblast differentiation and extracellular matrix (ECM) deposition around small (<2 mm in diameter) airways. Upon Cd exposure, α-smooth muscle actin (α-SMA) expression and the production of ECM proteins, including fibronectin and collagen-1, are markedly induced in primary human lung fibroblasts. Cd induces Smad2/3 activation and the translocation of both Smad2/3 and Yes-associated protein 1 (YAP1) into the nucleus. In parallel, Cd induces AKT and cdc2 phosphorylation and downstream vimentin phosphorylation at Ser³⁹ and Ser⁵⁵, respectively. AKT and cdc2 inhibitors block Cd-induced vimentin fragmentation and secretion in association with inhibition of α-SMA expression, ECM deposition, and collagen secretion. Furthermore, vimentin silencing abrogates Cd-induced α-SMA expression and decreases ECM production. Vimentin-deficient mice are protected from Cd-induced peribronchiolar fibrosis and remodeling. These findings identify two specific sites on vimentin that are phosphorylated by Cd and highlight the functional significance of vimentin phosphorylation in YAP1/Smad3 signaling that mediates Cd-induced peribronchiolar fibrosis and airway remodeling.

Detoxification effects of phytonutrients against environmental toxicants and sharing of clinical experience on practical applications

According to the Food and Health Bureau and Trade and Industry Department of the Hong Kong Government, 90 % of the total food supply in Hong Kong was imported from the Mainland China. In addition, the hidden or illegal use of prohibited pesticides, food adulteration (e.g., using industrial salt in food processing, using gutter oil as cooking oil), and pollutions were periodically reported by the media. Excessive exposure to toxic heavy metals or persistent organic pollutants (POPs) from diet or environmental is inevitable amid industrialization and pollution. Understanding of the detoxification ability among nutrients in plant-based food (i.e., phytonutrients in green tea, onion, garlic, coriander, and turmeric) offers therapeutic and preventive effects against the poisoning effects due to these pollutants. Oxidative stress and pro-inflammatory actions are the common mechanisms for heavy metals or POPs toxicities, while phytonutrients counteracts these cellular insults by anti-oxidation, upregulation of anti-inflammatory pathways, and chelation.

NF-κB signaling maintains the survival of cadmium-exposed human renal glomerular endothelial cells

The kidney is one of the primary organs targeted by cadmium (Cd), a widely distributed environmental pollutant. The glomerular endothelium is the major component of the glomerular filtration barrier. However, the effects of Cd on glomerular endothelial cells remain largely unknown. For this purpose, we aimed to determine the effects of low dose Cd on the survival of human renal glomerular endothelial cells (HRGECs). Cultured HRGECs were exposed to 4 µM cadmium chloride (CdCl₂) and examined at different time-points. We found that Cd activates the nuclear factor-κB (NF-κB) pathway without inducing the apoptosis of HRGECs. Pre-treating the cells with pyrrolidine dithiocarbamate (PDTC), a potent NF-κB inhibitor, prior to Cd exposure triggered extensive cell death (73.5%). In addition, Cd activates the c-Jun N-terminal kinase (JNK) pathway, and inhibition of the NF-κB pathway significantly elevates Cd-induced JNK phosphorylation in HRGECs (p<0.01). The combination treatment of PDTC and SP600125, a JNK pathway inhibitor, increased the survival of Cd-stimulated HRGECs compared with those cells treated with PDTC alone (p<0.05). Taken together, these findings demonstrate that the NF-κB pathway plays an essential role in maintaining the survival of Cd-exposed HRGECs.

Microcystin-LR induces mitochondria-mediated apoptosis in human bronchial epithelial cells

The present study aimed to investigate the toxicity of microcystin-LR (MC-LR) and to explore the mechanism of MC-LR-induced apoptosis in human bronchial epithelial (HBE) cells. HBE cells were treated with MC-LR (1, 10, 20, 30 and 40 µg/ml) alone or with MC-LR (0, 2.5, 5 and 10 µg/ml) and Z-VAD-FMK (0, 10, 20, 40, 60, 80, 100, 120 and 140 µM), which is a caspase inhibitor, for 24 and 48 h. Cell viability was assessed via an MTT assay and the half maximal effective concentration of MC-LR was determined. The optimal concentration of Z-VAD-FMK was established as 50 µm, which was then used in the subsequent experiments. MC-LR significantly inhibited cell viability and induced apoptosis of HBE cells in a dose-dependent manner, as detected by an Annexin V/propidium iodide assay. MC-LR induced cell apoptosis, excess reactive oxygen species production and mitochondrial membrane potential collapse, upregulated Bax expression and downregulated B-cell lymphoma-2 expression in HBE cells. Moreover, western blot analysis demonstrated that MC-LR increased the activity levels of caspase-3 and caspase-9 and induced cytochrome c release into the cytoplasm, suggesting that MC-LR-induced apoptosis is associated with the mitochondrial pathway. Furthermore, pretreatment with Z-VAD-FMK reduced MC-LR-induced apoptosis by blocking caspase activation in HBE cells. Therefore, the results of the present study suggested that MC-LR is capable of significantly inhibiting the viability of HBE cells by inducing apoptosis in a mitochondria-dependent manner. The present study provides a foundation for further understanding the mechanism underlying the toxicity of MC-LR in the respiratory system.

The role of the PM2.5-associated metals in pathogenesis of child Mycoplasma Pneumoniae infections: a systematic review

The peak occurrence of Mycoplasma pneumoniae (M. pneumoniae) infections in childhood and haze episodes is concurrent. Together, the prevalence of macrolide-resistant M. pneumoniae varies among countries might also be related to the concentration of ambient fine particulate mass (aerodynamic diameter ≤2.5 μm, PM2.5). Numerous cohort studies have identified consistent associations between ambient PM2.5 and cardiorespiratory morbidity and mortality. PM2.5 is a carrier of the heavy metals. The relationship between PM2.5-associated metals and M. pneumoniae infections in childhood has been increasingly drawing public attention. First, we reviewed original articles and review papers in Pubmed and Web of Science regarding M. pneumoniae and PM2.5-associated metal and analyzed the structural basis of PM2.5-associated metal interaction with M. pneumoniae. Then, the possible mechanisms of action between them were conjectured. Mechanisms of oxidative stress induction and modulation of the host immune system and inflammatory responses via Toll-like receptors (TLRs) and/or the nuclear factor-kappa B (NF-κB) pathway are postulated to be the result of PM2.5-associated metal complex interaction with M. pneumoniae. In addition, a heavy metal effect on M. pneumoniae-expressed community-acquired respiratory distress syndrome (CARDS) toxin, and activation of the aryl hydrocarbon receptor (AhR) and TLRs to induce the differentiation of T helper (Th) cells are also regarded as important reasons for the influence of the heavy metals on the severity of M. pneumoniae pneumonia and the initial onset and exacerbation of M. pneumoniae associated asthma. PM2.5-associated metals via complex mechanisms can exert a great impact on the host through interaction with M. pneumoniae.

Proteome profiling of cadmium-induced apoptosis by antibody array analyses in human bronchial epithelial cells

Protein array technology is a powerful platform for the simultaneous determination of the expression levels of a number of proteins as well as post-translational modifications such as phosphorylation. Here, we screen and report for the first time, the dominant signaling cascades and apoptotic mediators during the course of cadmium (Cd)-induced cytotoxicity in human bronchial epithelial cells (BEAS-2B) by antibody array analyses. Proteins from control and Cd-treated cells were captured on Proteome Profiler™ Arrays for the parallel determination of the relative levels of protein phosphorylation and proteins associated with apoptosis. Our results indicated that the p38 MAPK- and JNK-related signal transduction pathways were dramatically activated by Cd treatment. Cd potently stimulates the phosphorylations of p38α (MAPK14), JNK1/2 (MAPK8/9), and JUN; while the phosphorylations of Akt1, ERK1/2 (MAPK3/1), GSK3β, and mTOR were suppressed. Moreover, there was an induction of proapoptotic protein BAX, release of cytochrome c (CYCS) from mitochondria, activation of caspase-3/9 (CASP3/9); as well as decreased expression of cell cycle checkpoint proteins (TP53, p21, and p27) and several inhibitors of apoptosis proteins (IAPs) [including cIAP-1/2 (BIRC2/3), XIAP (BIRC4), and survivin (BIRC5)]. Pretreatment of cells with the thiol antioxidant glutathione or p38 MAPK/JNK inhibitors before Cd treatment effectively abrogated ROS activation of p38 MAPK/JNK pathways and apoptosis-related proteins. Taken together, our results demonstrate that Cd causes oxidative stress-induced apoptosis; and the p38 MAPK/JNK and mitochondrial pathways are more importantly participated for signal transduction and the induction of apoptosis in Cd-exposed human lung cells.

Mapping Cd²⁺-induced membrane permeability changes of single live cells by means of scanning electrochemical microscopy

Scanning Electrochemical Microscopy (SECM) is a powerful, non-invasive, analytical methodology that can be used to investigate live cell membrane permeability. Depth scan SECM imaging allowed for the generation of 2D current maps of live cells relative to electrode position in the x-z or y-z plane. Depending on resolution, one depth scan image can contain hundreds of probe approach curves (PACs). Individual PACs were obtained by simply extracting vertical cross-sections from the 2D image. These experimental PACs were overlaid onto theoretically generated PACs simulated at specific geometry conditions. Simulations were carried out using 3D models in COMSOL Multiphysics to determine the cell membrane permeability coefficients at different locations on the surface of the cells. Common in literature, theoretical PACs are generated using a 2D axially symmetric geometry. This saves on both compute time and memory utilization. However, due to symmetry limitations of the model, only one experimental PAC right above the cell can be matched with simulated PAC data. Full 3D models in this article were developed for the SECM system of live cells, allowing all experimental PACs over the entire cell to become usable. Cd(2+)-induced membrane permeability changes of single human bladder (T24) cells were investigated at several positions above the cell, displaced from the central axis. The experimental T24 cells under study were incubated with Cd(2+) in varying concentrations. It is experimentally observed that 50 and 100 μM Cd(2+) caused a decrease in membrane permeability, which was uniform across all locations over the cell regardless of Cd(2+) concentration. The Cd(2+) was found to have detrimental effects on the cell, with cells shrinking in size and volume, and the membrane permeability decreasing. A mapping technique for the analysis of the cell membrane permeability under the Cd(2+) stress is realized by the methodology presented.

Proteomic analysis of secreted proteins by human bronchial epithelial cells in response to cadmium toxicity

For years, many studies have been conducted to investigate the intracellular response of cells challenged with toxic metal(s), yet, the corresponding secretome responses, especially in human lung cells, are largely unexplored. Here, we provide a secretome analysis of human bronchial epithelial cells (BEAS-2B) treated with cadmium chloride (CdCl2 ), with the aim of identifying secreted proteins in response to Cd toxicity. Proteins from control and spent media were separated by two-dimensional electrophoresis and visualized by silver staining. Differentially-secreted proteins were identified by MALDI-TOF-MS analysis and database searching. We characterized, for the first time, the extracellular proteome changes of BEAS-2B dosed with Cd. Our results unveiled that Cd treatment led to the marked upregulation of molecular chaperones, antioxidant enzymes, enzymes associated with glutathione metabolic process, proteins involved in cellular energy metabolism, as well as tumor-suppressors. Pretreatment of cells with the thiol antioxidant glutathione before Cd treatment effectively abrogated the secretion of these proteins and prevented cell death. Taken together, our results demonstrate that Cd causes oxidative stress-induced cytotoxicity; and the differentially-secreted protein signatures could be considered as targets for potential use as extracellular biomarkers upon Cd exposure.

Heme oxygenase-1-mediated autophagy protects against pulmonary endothelial cell death and development of emphysema in cadmium-treated mice

Pulmonary exposure to cadmium, a major component of cigarette smoke, has a dramatic impact on lung function and the development of emphysema. Cigarette smoke exposure induces heme oxygenase-1 (HO-1), a cytoprotective enzyme. In this study, we employed a truncated mouse model of emphysema by intratracheal instillation of cadmium (CdCl2) solution (0.025% per 1 mg/kg body wt) in HO-1(+/+), HO-1(-/-), and overexpressing humanized HO-1 bacterial artificial chromosome (hHO-1BAC) mice. We evaluated the role of HO-1 in cadmium-induced emphysema in mice by analyzing histopathology, micro-computed tomography scans, and lung function tests. CdCl2-exposed HO-1(-/-) mice exhibited more severe emphysema compared with HO-1(+/+) or hHO-1BAC mice. Loss of pulmonary endothelial cells (PECs) from the alveolar capillary membrane is recognized to be a target in emphysema. PECs from HO-1(+/+), HO-1(-/-), and hHO-1BAC were employed to define the underlying molecular mechanism for the protection from emphysema by HO-1. Electron microscopy, expression of autophagic markers (microtubule-associated protein 1B-light chain 3 II, autophagy protein 5, and Beclin1) and apoptotic marker (cleaved caspase 3) suggested induction of autophagy and apoptosis in PECs after CdCl2 treatment. CdCl2-treated HO-1(-/-) PECs exhibited downregulation of autophagic markers and significantly increased cleaved caspase 3 expression and activity (∼4-fold higher). Moreover, hHO-1BAC PECs demonstrated upregulated autophagy and absence of cleaved caspase 3 expression or activity. Pretreatment of HO-1(+/+) PECs with rapamycin induced autophagy and resulted in reduced cell death upon cadmium treatment. Induction of autophagy following CdCl2 treatment was found to be protective from apoptotic cell death. HO-1 induced protective autophagy in PECs and mitigated cadmium-induced emphysema.

Cadmium induces histone H3 lysine methylation by inhibiting histone demethylase activity

Cadmium is an established human lung carcinogen with weak mutagenicity. However, the mechanisms underlying cadmium-induced carcinogenesis remain obscure. It has been suggested that epigenetic mechanisms may play a role in cadmium-induced carcinogenesis. In this study, we investigated the effects of cadmium on histone methylation and histone demethylases, and the role of histone methylation in transformation of immortalized normal human bronchial epithelial (BEAS-2B) cells. Exposure to 0.625, 1.25, 2.5, and 5.0 μM of cadmium for 6, 24, and 48 h increased global trimethylated histone H3 on lysine 4 (H3K4me3) and dimethylated histone H3 on lysine 9 (H3K9me2) in BEAS-2B cells compared with untreated cells, and most of these changes remained after the removal of cadmium (P < .05 or P < .01 for most modifications). Meanwhile, cadmium inhibited the activities of histone H3 on lysine 4 (H3K4) and histone H3 on lysine 9 (H3K9) demethylases which were detected by histone demethylation assay. However, there was no significant change in the protein levels of the H3K4 demethylase lysine-specific demethylase 5A (KDM5A) and the H3K9 demethylase lysine-specific demethylase 3A (KDM3A). Interestingly, during transformation of BEAS-2B cells by 20 weeks of exposure to 2.0 μM cadmium as assessed by anchorage-independent growth in soft agar, global H3K4me3, and H3K9me2 were significantly increased at 4 weeks (P < .05 or P < .01), whereas no significant change was observed at 8, 12, 16, and 20 weeks compared with control. Our study suggests that cadmium increases global H3K4me3 and H3K9me2 by inhibiting the activities of histone demethylases, and aberrant histone methylation that occurs early (48 h) and at 4 weeks is associated with cadmium-induced transformation of BEAS-2B cells at the early stage.

Sex differences in shotgun proteome analyses for chronic oral intake of cadmium in mice

Environmental diseases related to cadmium exposure primarily develop owing to industrial wastewater pollution and/or contaminated food. In regions with high cadmium exposure in Japan, cadmium accumulation occurs primarily in the kidneys of individuals who are exposed to the metal. In contrast, in the itai-itai disease outbreak that occurred in the Jinzu River basin in Toyama Prefecture in Japan, cadmium primarily accumulated in the liver. On the other hand, high concentration of cadmium caused renal tubular disorder and osteomalacia (multiple bone fracture), probably resulting from the renal tubular dysfunction and additional pathology. In this study, we aimed to establish a mouse model of chronic cadmium intake. We administered cadmium-containing drinking water (32 mg/l) to female and male mice ad libitum for 11 weeks. Metal analysis using inductively coupled plasma mass spectrometry revealed that cadmium accumulated in the kidneys (927 x 10 + 185 ng/g in females and 661 x 10 + 101 ng/g in males), liver (397 x 10 + 199 ng/g in females and 238 x 10 + 652 ng/g in males), and thyroid gland (293 + 93.7 ng/g in females and 129 + 72.7 ng/g in males) of mice. Female mice showed higher cadmium accumulation in the kidney, liver, and thyroid gland than males did (p = 0.00345, p = 0.00213, and p = 0.0331, respectively). Shotgun proteome analyses after chronic oral administration of cadmium revealed that protein levels of glutathione S-transferase Mu2, Mu4, and Mu7 decreased in the liver, and those of A1 and A2 decreased in the kidneys in both female and male mice.

Zinc improves the immune function and the proliferation of lymphocytes in Cadmium-treated rats

The effects of Cadmium (Cd) exposure and the treatment with Zinc (Zn) on immune functions of splenocytes and cultured lymphocytes of rats were studied. The exposure of rats to Cd was at a dose of 2.2 mg/kg CdCl₂, injected subcutaneously four times weekly for 2 months. Rats were supplemented with Zn (2.2 mg/kg ZnCl₂, injected subcutaneously four times weekly for 2 months) one hour prior to Cd exposure. Spleens were removed and splenocytes were isolated and cultured. The proliferation capacity of lymphocytes and their homing to the spleen were studied. Ribonucleic acid (RNA) was extracted from stimulated lymphocytes in order to analyse gene expressions using RT-PCR. Accordingly, proliferation of lymphocytes was found to be suppressed in Cd-treated rats, both in vivo and in vitro. Zinc served to activate the proliferation of B and T lymphocytes in Cd-treated rats both in vivo and in vitro. Antigen-activated lymphocytes showed that Cd impaired the mRNA expression of CD68, Ccl22 and CXCL10. Zinc was not found to restore mRNA expression of these genes to the normal levels. Zinc was found to decrease the MDA level with replenishment of activity of key antioxidant enzymes and proteins in Cd-pre-treated animals significantly. Moreover, the histopathological examination of spleen samples also agreed with the molecular, immunological and redox findings. Hence, Zn is able to restore the normal structure, redox status and immunity in Cd-induced damage in the rat model system.

Oxidative stress and Ca(2+) signals involved on cadmium-induced apoptosis in rat hepatocyte

Cadmium (Cd) is an important industrial and environmental pollutant. In animals, the liver is the major target organ of Cd toxicity. In this study, rat hepatocytes were treated with 2.5∼10 μM Cd for various durations. Studies on nuclear morphology, chromatin condensation, and apoptotic cells demonstrate that Cd concentrations ranging within 2.5∼10 μM induced apoptosis. The early-stage marker of apoptosis, i.e., decreased mitochondrial membrane potential, was observed as early as 1.5 h at 5 μM Cd. Significant (P < 0.01) reactive oxygen species (ROS) production at 5 μM Cd and 0.75 h occurred prior to the decrease of the mitochondrial membrane potential, suggesting the involvement of ROS in mitochondrial membrane damage. Glutathione (GSH) level significantly decreased after cell treatment with 5 and 10 μM Cd after 12 h (P < 0.01). Meanwhile, the intracellular free Ca(2+) concentration ([Ca(2+)] i ) of Cd-exposed cells significantly increased (P < 0.01) at 1.5 h, and pretreatment with the calcium chelator Bapta-AM partially blocked Cd-induced apoptosis. This finding indicated that the elevation of [Ca(2+)] i may play an important role in apoptosis. Overall, these results showed that oxidative stress and Ca(2+) signaling were critical mediators of the Cd-induced apoptosis of rat hepatocytes.