Low doses of cadmium chloride and methallothionein-1-bound cadmium display different accumulation kinetics and induce different genes in cells of the human nephron

Multifactorial Screening Reveals New Insight into Early Cadmium Exposure and Garlic Interactions in Dicentrarchus labrax

Environmental pollutants and especially metal trace elements remain an unmitigated threat to the overall life support system. Their chemical stability and accumulation pattern in the ecosystem make them a persistent hazard. This study aims to characterize the early cadmium (Cd) histological and hematological alterations and their corresponding plasma indicators in the Mediterranean sea bass (Dicentrarchus labrax). We also assessed garlic potential to prevent cadmium toxicity. For this purpose, 200 fish of 55 g mean weight were separated into 3 cylindroconical fiberglass tanks of 500-L capacity, each with a stocking density of 4 kg m-3. The fish were regularly hand-fed 0% (control group), 2%, and 6% garlic-supplemented diets to apparent satiation twice a day for 1 month. At the end of the experiment, we injected 22.2 mM cadmium (CdCl2) intraperitoneally to the experimental groups and a placebo solution (9% NaCl) to the control groups; liver, kidney, heart, and blood tissue alterations were monitored with a full screening of their plasmatic indicators, 24 h before and 48 h after Cd injection. Subsequently, whole blood count and blood smears were performed to follow up on Cd-induced vascular damages. Our data showed that Cd induced thrombotic thrombocytopenic purpura, leading to widespread bleeding and cellular alterations in the targeted tissues. These alterations were associated with an obvious normochromic normocytic anemia in favor of microangiopathic hemolytic anemia. Cd injection has also seriously inhibited the overall enzymatic activities triggering a metabolic shift. Although garlic supplementation had little effect on cadmium-induced alterations, it significantly reduced biomass dispersion. Our data is the first evidence of the cadmium versatile toxicity involving vascular alterations as a central and a leading cause of the overall parenchymal lesions. Cd toxicity was associated with a specific enzymatic signature, which must be considered during the interpretation.

Cadmium-Induced Renal Cell Toxicity Is Associated With MicroRNA Deregulation

Cadmium is an environmental pollutant well known for its nephrotoxic effects. Nevertheless, mechanisms underlying nephrotoxicity continue to be elucidated. MicroRNAs (miRNAs) have emerged in recent years as modulators of xenobiotic-induced toxicity. In this context, our study aimed at elucidating whether miRNAs are involved in renal proximal tubular toxicity induced by cadmium exposure. We showed that cadmium exposure, in 2 distinct renal proximal tubular cell models (renal proximal tubular epithelial cell [RPTEC]/human telomerase reverse transcriptase [hTERT] and human kidney-2), resulted in cytotoxicity associated with morphological changes, overexpression of renal injury markers, and induction of apoptosis and inflammation processes. Cadmium exposure also resulted in miRNA modulation, including the significant upregulation of 38 miRNAs in RPTEC/hTERT cells. Most of these miRNAs are known to target genes whose coding proteins are involved in oxidative stress, inflammation, and apoptosis, leading to tissue remodeling. In conclusion, this study provides a list of dysregulated miRNAs which may play a role in the pathophysiology of cadmium-induced kidney damages and highlights promising cadmium molecular biomarkers that warrants to be further evaluated.

Levels and determinants of adipose tissue cadmium concentrations in an adult cohort from Southern Spain

This study was conceived as a first step to evaluate the suitability of adipose tissue cadmium (Cd) concentrations as a biomarker for the assessment of long-term exposure. Specifically, the aim of this work was to explore the socio-demographic, dietary, and lifestyle determinants of adipose tissue Cd concentrations. The study population is a subsample of GraMo cohort. Adipose tissue samples were intraoperatively collected from 226 adult volunteers recruited in two public hospitals from Granada, Spain. Cd concentrations in adipose tissue were analyzed by High-Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS). Data on socio-demographic characteristics, lifestyle, diet and health status were collected by face-to-face interviews. Predictors of Cd concentrations were assessed by multivariable linear regression with a stepwise variable selection. We found detectable levels of Cd in the adipose tissue of all the study participants, with a mean concentration (±standard deviation) of 12.66 ± 18.91 μg/kg. Smoking habit at recruitment was associated with increased adipose tissue Cd concentrations (β for smokers = 0.669 p < 0.001; β for former smokers = 0.502, p < 0.001; reference = non-smokers). Age was positively associated with Cd concentrations (β = 0.014, p < 0.001), and men showed lower concentrations than women (β = -0.424, p < 0.001). Obesity, measured as Body Mass Index (BMI), showed an inverse association with Cd concentrations (β = -0.038, p < 0.001). Egg consumption ≥2 portions/week (β = 0.241, p = 0.025) was positively associated with Cd concentrations. Perceived exposure to paints was also positively associated with Cd concentrations. The observed associations with age, smoking habit, BMI, and egg and meat consumption did not substantially change after sex/gender stratification. Our results are consistent with currently-known Cd sources and suggest other potential pathways, which might be population-specific. As a whole, our findings underline the potential relevance of adipose tissue as a biological matrix for exposure characterization to Cd, as well as for the assessment of long-term clinical implications of the exposure, particularly in obesity-related diseases.

Environmental toxin-induced acute kidney injury

Human beings are exposed to various potentially toxic agents and conditions in their natural and occupational environments. The kidney, due to its concentrating ability and excretory function, is highly vulnerable to the effects of environmental toxins. Identifying the precise cause and mechanisms of environmentally induced renal injury remains a challenge for which various scientific disciplines need to be involved. Investigations in this field are confronted with the apparent infinite types of toxins, their mutual interaction, handling/metabolization by the body, ways of exposure, etc. Although interdisciplinary efforts and persistence are required to identify, mechanistically unravel and tackle environmental toxin-induced pathologies, research eventually pays off in ameliorated working/living conditions and development of preventive/therapeutic strategies. This review was compiled to particularly emphasize the need for a maintained awareness of environmental threats in general and those targeting the kidney. Different mechanisms of renal toxicity are illustrated and discussed, thereby focusing on three types of environmental toxins, namely aristolochic acid, melamine and heavy metals.

The RPTEC/TERT1 Cell Line as an Improved Tool for In Vitro Nephrotoxicity Assessments

In earlier studies, we have characterized a newly developed cell line derived from the renal proximal tubule epithelial cells (RPTEC) of a healthy human male donor in order to provide an improved in vitro model with which to investigate human diseases, such as cancer, that may be promoted by toxicant exposure. The RPTEC/TERT1 cell line has been immortalized using the human telomerase reverse transcriptase (hTERT) catalytic subunit and does not exhibit chromosomal abnormalities (Evercyte Laboratories). We have previously conducted single-compound and binary mixture experiments with the common environmental carcinogens, cadmium (Cd), and benzo[a]pyrene (B[a]P). Cells exhibited cytotoxic and compound-specific responses to low concentrations of B[a]P and Cd. We detected responses after exposure consistent with what is known regarding these cells in a normal, healthy kidney including significant gene expression changes, BPDE-DNA adducts in the presence of B[a]P, and indications of oxidative stress in the presence of Cd. The RPTEC/TERT1 cell line was also amenable to co-exposure studies due to its sensitivity and compound-specific properties. Here, we review our earlier work, compare our findings with commonly used renal cell lines, and suggest directions for future experiments. We conclude that the RPTEC/TERT1 cell line can provide a useful tool for future toxicological and mixture studies.

Chronic cadmium exposure in vitro induces cancer cell characteristics in human lung cells

Cadmium is a known human lung carcinogen. Here, we attempt to develop an in vitro model of cadmium-induced human lung carcinogenesis by chronically exposing the peripheral lung epithelia cell line, HPL-1D, to a low level of cadmium. Cells were chronically exposed to 5 μM cadmium, a noncytotoxic level, and monitored for acquired cancer characteristics. By 20 weeks of continuous cadmium exposure, these chronic cadmium treated lung (CCT-LC) cells showed marked increases in secreted MMP-2 activity (3.5-fold), invasion (3.4-fold), and colony formation in soft agar (2-fold). CCT-LC cells were hyperproliferative, grew well in serum-free media, and overexpressed cyclin D1. The CCT-LC cells also showed decreased expression of the tumor suppressor genes p16 and SLC38A3 at the protein levels. Also consistent with an acquired cancer cell phenotype, CCT-LC cells showed increased expression of the oncoproteins K-RAS and N-RAS as well as the epithelial-to-mesenchymal transition marker protein Vimentin. Metallothionein (MT) expression is increased by cadmium, and is typically overexpressed in human lung cancers. The major MT isoforms, MT-1A and MT-2A were elevated in CCT-LC cells. Oxidant adaptive response genes HO-1 and HIF-1A were also activated in CCT-LC cells. Expression of the metal transport genes ZNT-1, ZNT-5, and ZIP-8 increased in CCT-LC cells culminating in reduced cadmium accumulation, suggesting adaptation to the metal. Overall, these data suggest that exposure of human lung epithelial cells to cadmium causes acquisition of cancer cell characteristics. Furthermore, transformation occurs despite the cell's ability to adapt to chronic cadmium exposure.