Chromium-induced kidney disease

Disease-associated metabolic pathways affected by heavy metals and metalloid

Increased exposure to environmental heavy metals and metalloids and their associated toxicities has become a major threat to human health. Hence, the association of these metals and metalloids with chronic, age-related metabolic disorders has gained much interest. The underlying molecular mechanisms that mediate these effects are often complex and incompletely understood. In this review, we summarize the currently known disease-associated metabolic and signaling pathways that are altered following different heavy metals and metalloids exposure, alongside a brief summary of the mechanisms of their impacts. The main focus of this study is to explore how these affected pathways are associated with chronic multifactorial diseases including diabetes, cardiovascular diseases, cancer, neurodegeneration, inflammation, and allergic responses upon exposure to arsenic (As), cadmium (Cd), chromium (Cr), iron (Fe), mercury (Hg), nickel (Ni), and vanadium (V). Although there is considerable overlap among the different heavy metals and metalloids-affected cellular pathways, these affect distinct metabolic pathways as well. The common pathways may be explored further to find common targets for treatment of the associated pathologic conditions.

Case-only approach applied in environmental epidemiology: 2 examples of interaction effect using the US National Health and Nutrition Examination Survey (NHANES) datasets

INTRODUCTION

By substituting the general 'susceptibility factor' concept for the conventional 'gene' concept in the case-only approach for gene-environment interaction, the case-only approach can also be used in environmental epidemiology. Under the independence between the susceptibility factor and environmental exposure, the case-only approach can provide a more precise estimate of an interaction effect.

METHODS

Two analysis examples of the case-only approach in environmental epidemiology are provided using the 2015-2016 and 2017-2018 US National Health and Nutritional Examination Survey (NHANES): (i) the negative interaction effect between blood chromium level and glycohemoglobin level on albuminuria and (ii) the positive interaction effect between blood cobalt level and old age on albuminuria. The second part of the methods (theoretical backgrounds) summarized the logic and equations provided in previous studies about the case-only approach.

RESULTS

(i) When a 1 μg/L difference of both blood chromium level (mcg/L) and a 1% difference in blood glycohemoglobin level coincide, the multiplicative interaction contrast ratio (ICR_c/nc) was 0.72 (95% CI 0.35-1.60), with no statistical significance. However, when only the cases were analyzed, the case-only ICR (ICR_CO) was 0.59 (95% CI 0.28-0.95), with a statistical significance (a negative interaction effect). (ii) When a 1 μg/L difference of both blood cobalt levels and a 1-year difference in age coincide, the multiplicative interaction contrast ratio (ICR_c/nc) was 1.13 (95% CI 0.99-1.37), with no statistical significance. However, when only the cases were analyzed, the case-only ICR (ICR_CO) was 1.21 (95% CI 1.06-1.51), with a statistical significance (a positive interaction effect).

DISCUSSION

The discussion suggested the theoretical background and previous literature about the possible protective interaction effect between blood chromium levels and blood glycohemoglobin levels on the incidence of albuminuria and the possible aggravating interaction effect between blood cobalt levels and increasing ages on the incidence of albuminuria. If the independence assumption between a susceptibility factor and environmental exposure in a study with cases and non-cases is kept, the case-only approach can provide a more precise interaction effect estimate than conventional approaches with both cases and non-cases.

Prenatal and early childhood critical windows for the association of nephrotoxic metal and metalloid mixtures with kidney function

INTRODUCTION

As renal development and maturation processes begin in utero and continue through early childhood, sensitive developmental periods arise during which metal exposures can program subclinical nephrotoxicity that manifests later in life. We used novel dentine biomarkers of established nephrotoxicants including arsenic (As), cadmium (Cd), lead (Pb), chromium (Cr), and lithium (Li), and their mixtures, to identify critical windows of exposure-associated kidney function alterations in preadolescents.

METHODS

Participants included 353 children in the Programming Research in Obesity Growth, Environment and Social Stressors (PROGRESS) longitudinal birth cohort study based in Mexico City. Estimated glomerular filtration rate (eGFR) was assessed in 8-12 year old children using serum cystatin C measures. Pre- and postnatal metal(loid) concentrations were assessed in weekly increments by analyzing deciduous teeth with laser ablation-inductively coupled plasma-mass spectrometry. We used reverse distributed lag models (rDLMs) and lagged Weighted Quantile Sum (L-WQS) regression to examine time-varying associations between weekly perinatal metal(loid) exposure or metal(loid) mixtures and preadolescent eGFR while adjusting for age, sex, BMI z-score, SES and prenatal tobacco smoke exposure.

RESULTS

We identified a critical window of susceptibility to Pb exposure, in the late 3rd trimester (5 weeks prior to birth) during which higher Pb exposure was associated with children's increased eGFR. When all elements were assessed as a mixture, we identified late 2nd/early 3rd trimester (weeks 8-17 of gestation) as a window of vulnerability associated with decreased eGFR, with Li and Cr contributing the greatest weights to the association. When stratified by sex, we observed stronger effects among boys than girls.

CONCLUSIONS

Using tooth-matrix biomarkers, we identified discrete developmental exposure windows wherein Pb and metal(loid) mixtures were associated with altered preadolescent kidney function.

Renal hypoxia-HIF-PHD-EPO signaling in transition metal nephrotoxicity: friend or foe?

The kidney is the main organ that senses changes in systemic oxygen tension, but it is also the key detoxification, transit and excretion site of transition metals (TMs). Pivotal to oxygen sensing are prolyl-hydroxylases (PHDs), which hydroxylate specific residues in hypoxia-inducible factors (HIFs), key transcription factors that orchestrate responses to hypoxia, such as induction of erythropoietin (EPO). The essential TM ion Fe is a key component and regulator of the hypoxia–PHD–HIF–EPO (HPHE) signaling axis, which governs erythropoiesis, angiogenesis, anaerobic metabolism, adaptation, survival and proliferation, and hence cell and body homeostasis. However, inadequate concentrations of essential TMs or entry of non-essential TMs in organisms cause toxicity and disrupt health. Non-essential TMs are toxic because they enter cells and displace essential TMs by ionic and molecular mimicry, e. g. in metalloproteins. Here, we review the molecular mechanisms of HPHE interactions with TMs (Fe, Co, Ni, Cd, Cr, and Pt) as well as their implications in renal physiology, pathophysiology and toxicology. Some TMs, such as Fe and Co, may activate renal HPHE signaling, which may be beneficial under some circumstances, for example, by mitigating renal injuries from other causes, but may also promote pathologies, such as renal cancer development and metastasis. Yet some other TMs appear to disrupt renal HPHE signaling, contributing to the complex picture of TM (nephro-)toxicity. Strikingly, despite a wealth of literature on the topic, current knowledge lacks a deeper molecular understanding of TM interaction with HPHE signaling, in particular in the kidney. This precludes rationale preventive and therapeutic approaches to TM nephrotoxicity, although recently activators of HPHE signaling have become available for therapy.

Inflammatory Injury and Mitophagy in the Cock Heart Induced by the Oral Administration of Hexavalent Chromium

As a highly toxic heavy metal, chromium has caused a certain threat to public health and livestock breeding in recent years. In poultry, as one of our most commonly consumed meat product, its health issues will seriously threaten the safety of human life. As previous studies have confirmed, when cells are stimulated by the external environment, mitochondria, as an organelle that provides energy to the cells, can cause damage and autophagy. The purpose of this study is to confirm whether Cr(VI) can cause mitophagy in cock heart. We first randomly divided 32 cocks into four groups to explore the mechanism of this effect. The cocks were then separately exposed to four different dose levels, namely, the control level and 10, 30, and 50 mg/kg levels, via daily oral intake into the body through mixed feeding for 45 days. After 45 days, we sampled and detected pathological changes and the levels of inflammatory factors (IL-6, TNF-α, and IFN-γ), mitochondrial membrane potential (MMP), adenosine triphosphatases (ATPases), and mitophagy-related proteins (LC3, p62/SQTM1, TOMM20, and Parkin). We found that IL-6, TNF-α, IFN-γ, and LC3II contents increased with the increase in Cr(VI) concentration. However, MMP, ATPases, p62/SQTM1, and TOMM20 levels decreased with the increase in Cr(VI) concentration. At the same time, Cr(VI) exposure caused heart tissue damages and Parkin translocation. In conclusion, our results proved that inflammatory damage, mitochondrial function damage, and mitophagy in cock heart tissues were dependent on Cr(VI) concentration.

The Groundwater Geochemistry and the Human Health Risk Assessment of Drinking Water in an Area with a High Prevalence of Chronic Kidney Disease of Unknown Etiology (CKDu), Sri Lanka

Chronic kidney disease of unknown etiology (CKDu) has become an alarming health issue in Sri Lanka. The disease is more notable among farming communities and people who consume groundwater as their main source of drinking water. To assess the possible links between drinking water chemistry and expansion of CKDu, the study was compared with hydrogeochemical data of drinking water sources in a CKDu prevalent area (Girandurukotte GND, Badulla District) and a reference area (Dambethalawa GND, Ampara District) in Sri Lanka. Based on the results, nephrotoxic heavy metal (Cd, Cr, Pb, and As) concentrations were significantly higher in the CKDu prevalent site than the reference area, compromised the harmful consequences to the people in the CKDu hotspot. Results of the inverse distance weighted (IDW) interpolation tool indicated the nephrotoxic heavy metals contents including Cd, Pb, As, and Cr in CKDu hotspot were changed in the ranges of 9.78–187.25 μg/L, 0.08–0.66 μg/L, 20.76–103.30 μg/L, and 0.03–0.34 μg/L. The random distribution patterns were shown by the result in Moran’s index values. Noteworthy, the results have emphasized a strong association between fluoride and water hardness. The frequency of occurrence above the threshold limit of fluoride was 28% in non-CKDu water samples, while 81% in CKDu prevalent sites. The hardness values in the CKDu prevalent site indicated “moderately hard water,” while the non-CKDu area indicated the “soft water.” Furthermore, this paper quantified overall water quality and heavy metal contamination and assessed the human health risks associated with drinking water. According to the results of the water quality index, 90% of the samples in the CKDu prevalent area were classified as “poor water” and “very poor water” for drinking purposes, while 73.33% of the samples in the non-CKDu area were “good” and “excellent” for drinking usage. Calculated chronic daily intake (CDIoral) and hazard quotient (HQoral) of nephrotoxicants were higher in CKDu hotspot than the non-CKDu site. Besides, the hazard index (HI) values obtained for the CKDu prevalent area exceeding the acceptable limit (HI = 1) indicated potential health risks to the people in those areas. This study suggests that long-term exposure to nephrotoxic heavy metals, water hardness, and fluoride present in drinking water may threaten human health and affect kidney functions. Therefore, regular monitoring and better management of water supplies in CKDu prevalent areas are essential to determine the contamination load and reduce the health impacts due to excessive and long-term exposure to the nephrotoxicants.

Nephroprotective Effect of the Herbal Composition BNO 2103 in Rats with Renal Failure

(1) Background: this research aims at studying the nephroprotective properties of BNO 2103 in a model of chromate-induced renal failure in rats and at proving the possibility of using BNO 2103 in clinical practice for the complex treatment of chronic kidney disease (CKD). (2) Methods: fifty rats divided into five groups were studied. The drugs BNO 2103, Prednisolone and Lespephril were administered within 20 days. The excretory function and the functional state of kidneys, blood biochemical parameters and indicators of nitrogen metabolism were determined. (3) Results: under the influence of BNO 2103, there was a significant improvement in renal excretory function, in nitrogen metabolism and blood biochemical parameters compared with the control pathology group. BNO 2103 also outperformed the comparators in most indicators. (4) Conclusions: BNO 2103 has demonstrated nephroprotective, hypoazotemic and diuretic effects; and can be used to implement to the combined therapy of CKD.

Hexavalent chromium intoxication induces intrinsic and extrinsic apoptosis in human renal cells

Hexavalent chromium [Cr(VI)], is a well-known toxic form of the heavy metal chromium in the natural environment. Clinical evidence has indicated that exposure to Cr(VI) can cause severe renal damage. The production of reactive oxygen species (ROS) due to intracellular reduction of Cr(VI) is the main mechanism underlying the induction of cellular dysfunction and apoptosis. The present study aimed to investigate in detail the apoptotic pathways induced by Cr(VI)-exposure in a human immortalized proximal tubular epithelial cell line HK-2, in order to understand the mechanism involved therein. Exposure to 10 µM potassium dichromate (K₂Cr₂O₇), a toxic compound of Cr(VI), significantly decreased cell viability after 24 and 48 h of incubation and induced intracellular ROS generation. The expression levels of markers that activate the apoptotic pathway including cleaved caspase-3 and poly (ADP-ribose) polymerase were significantly upregulated in K₂Cr₂O₇-exposed HK-2 cells. In addition, the induction of intrinsic and extrinsic apoptotic markers was detected in K₂Cr₂O₇-exposed HK-2 cells. In summary, the present study described for the first time the novel apoptotic mechanism of Cr(VI)-toxicity in human renal cells which may be beneficial in designing optimal clinical treatment for renal damage caused by acute Cr(VI) toxicity.

Chronic kidney disease of unknown aetiology in Sri Lanka and the exposure to environmental chemicals: a review of literature

Chronic kidney disease of unknown aetiology (CKDu) has emerged as a serious health issue in Sri Lanka. The disease has been recorded in the North Central Province of the country. While studies have elicited many hypotheses concerning the pathogenicity of CKDu, none adequately explains the cause of CKDu and the measures needed to minimise its occurrence. Nephrotoxic heavy metal (oid)s such as cadmium, arsenic, lead, and chromium are present in biological samples of people from endemic areas. This review appraises evidence on the effects of long-term exposure to low concentration of nephrotoxic heavy metals, which could be the principal cause of CKDu. Although a considerable variation exists in metal concentrations in patients' blood and urine, higher levels of heavy metals were consistently observed in affected areas. This review finds that the populations in the endemic areas are exposed to heavy metal (oid)s at low concentrations, which are considered as safe levels; nevertheless, it influences the incidence of CKDu. Recent global studies on chronic kidney disease (CKD) revealed a low concentration of heavy metals in diseased patients. Research findings indicated that CKDu patients in Sri Lanka demonstrated similar blood levels of Cd, Pb, and higher concentrations of Cr than that have been reported globally. Further studies on the influence of combinations of nephrotoxic heavy metals at low concentrations on reduced glomerular filtration rate and other renal biomarkers could explain CKDu pathogenicity.

Association of serum chromium levels with malnutrition in hemodialysis patients

BACKGROUND

Chromium is an essential trace metal that reduces oxidative stress and inflammation. In patients undergoing maintenance hemodialysis (MHD), a correlation among chromium exposure, inflammation, and malnutrition remains unclear. This study examined the possible effects of serum chromium levels (SCLs) in MHD patients.

METHODS

Initially, 732 MHD patients in dialysis centers were recruited. A total of 647 patients met the inclusion criteria and were stratified by SCL into four equal-sized groups: first quartile (< 0.29 μg/L), second quartile (0.29-0.56 μg/L), third quartile (0.57-1.06 μg/L), and fourth quartile (> 1.06 μg/L). Demographic, biochemical, and dialysis-related data were obtained for analyses. The analysis included nutritional and inflammatory markers.

RESULTS

As compared with the highest quartile group, more subjects in the lowest quartile group were of an older age; had lower hemoglobin and creatinine levels; had a higher prevalence of DM and malnutrition (serum albumin level < 3.6 g/dL); and higher serum transferrin saturation and ferritin levels. A stepwise multiple linear regression analysis revealed a significant negative correlation between malnutrition and SCL (β coefficient = - 0.129, p = 0.012) and negative associations among body mass index (β coefficient = - 0.010, p = 0.041), ferritin (β coefficient = - 0.107, p = 0.001) and SCL. A multivariate logistic regression analysis also demonstrated a negative correlation between malnutrition and SCL. With a 10-fold increase in SCL, the risk ratio of malnutrition was 0.49 (95% confidence interval: 0.25-0.96; p = 0.039).

CONCLUSIONS

SCL is significantly associated with malnutrition in MHD patients. Further evaluation of the relationship between clinical outcomes (morbidity/mortality) and SCL is necessitated.

Molecular and epigenetic mechanisms of Cr(VI)-induced carcinogenesis

Chromium (Cr) is a naturally occurring metallic element found in the Earth's crust. While trivalent chromium ([Cr(III)] is considered non-carcinogenic, hexavalent chromium [Cr(VI)] has long been established as an IARC class I human carcinogen, known to induce cancers of the lung. Current literature suggests that Cr(VI) is capable of inducing carcinogenesis through both genetic and epigenetic mechanisms. Although much has been learned about the molecular etiology of Cr(VI)-induced lung carcinogenesis, more remains to be explored. In particular, the explicit epigenetic alterations induced by Cr(VI) in lung cancer including histone modifications and miRNAs, remain understudied. Through comprehensive review of available literature found between 1973 and 2019, this article provides a summary of updated understanding of the molecular mechanisms of Cr(VI)-carcinogenesis. In addition, this review identifies potential research gaps in the areas of histone modifications and miRNAs, which may prompt new niches for future research.

Redox regulation in tumor cell epithelial-mesenchymal transition: molecular basis and therapeutic strategy

Epithelial–mesenchymal transition (EMT) is recognized as a driving force of cancer cell metastasis and drug resistance, two leading causes of cancer recurrence and cancer-related death. It is, therefore, logical in cancer therapy to target the EMT switch to prevent such cancer metastasis and recurrence. Previous reports have indicated that growth factors (such as epidermal growth factor and fibroblast growth factor) and cytokines (such as the transforming growth factor beta (TGF-β) family) are major stimulators of EMT. However, the mechanisms underlying EMT initiation and progression remain unclear. Recently, emerging evidence has suggested that reactive oxygen species (ROS), important cellular secondary messengers involved in diverse biological events in cancer cells, play essential roles in the EMT process in cancer cells by regulating extracellular matrix (ECM) remodeling, cytoskeleton remodeling, cell–cell junctions, and cell mobility. Thus, targeting EMT by manipulating the intracellular redox status may hold promise for cancer therapy. Herein, we will address recent advances in redox biology involved in the EMT process in cancer cells, which will contribute to the development of novel therapeutic strategies by targeting redox-regulated EMT for cancer treatment.

Metabolic adaptability in hexavalent chromium-treated renal tissue: an in vivo study

Background

Hexavalent chromium [Cr(VI)], an environmental pollutant that originates mostly from anthropogenic sources, is a serious threat to human health. After entering into cells, Cr(VI) is capable of producing excessive free radicals and causing tissue damage. The present study aims to reveal the toxic manifestation of Cr(VI) on the metabolic activity of renal tissue.

Methods

Male Swiss albino mice were treated orally with potassium dichromate (K₂Cr₂O₇) at a dose of 10 mg/kg body weight for a period of 30 days. Important tricarboxylic acid (TCA) cycle enzyme activities like isocitrate dehydrogenase, succinate dehydrogenase and malate dehydrogenase, as well as the activities of enzymes involved in oxidative phosphorylation such as Nicotinamide adenine dinucleotide (NADH) dehydrogenase, were measured. Additionally, transaminase and protease (pronase, cathepsin and trypsin) activities, tissue protein and free amino nitrogen were estimated in renal tissue. Glucose-6-phosphatase, glucose-6-phosphate dehydrogenase and alkaline phosphatase activities, as well as lactic acid, pyruvic acid and chromium contents, of kidneys were determined following standard protocols. Kidney histology was performed by hematoxylin and eosin staining.

Results

Cr(VI) suppresses the rate-limiting enzymes of the TCA cycle and oxidative phosphorylation indicating an inhibition of renal ATP production. It decreases protease activity by eliminating the protein substrates and alters the gluconeogenic pathway. Cr(VI) worsens the normophysiological attributes of renal tissue by enhancing the activity of alkaline phosphatase, pointing towards kidney disease. Histopathological observations confirmed these biochemical results through the presence of chronic tubular nephritis and altered glomerular structure. Cr(VI) retention occurs to a greater extent in renal tissue, which intensifies the toxic manifestation of this pollutant in the kidney.

Conclusions

Cr(VI) disrupts the metabolic interaction between carbohydrates and proteins in mammalian renal tissue.

Nephritic cell damage and antioxidant status in rats exposed to leachate from battery recycling industry

Limited studies have assessed the toxic effect of sub-acute and sub-chronic exposure of leachate (mixture of metals) in mammalian kidney. The sub-acute and sub-chronic exposure of mature male Wistar-strain albino rats (200–220 g) were given by oral administration with leachate from Elewi Odo municipal battery recycling industry (EOMABRIL) for period of 7 and 60 days respectively, at different concentrations (20%, 40%, 60%, 80% and 100%). This was to evaluate its toxic effects on male renal functions using biomarkers of oxidative stress and nephro-cellular damage. Control groups were treated equally, but given distilled water instead of the leachate. All the groups were fed with the same standard food and had free access to drinking water. Following the exposure, results showed that the treatment induced systemic toxicity at the doses tested by causing a significant (p<0.05) alteration in enzymatic antioxidants-catalase (CAT) and superoxide dismutase (SOD) in the kidneys which resulted into elevated levels of malonaldehyde (MDA). Reduced glutathione (GSH) levels were found to be significantly (p<0.05) depleted relative to the control group. Considerable renal cortical congestion and numerous tubules with protein casts were observed in the lumen of EOMABRIL-treated rats. These findings conclude that possible mechanism by which EOMABRIL at the investigated concentrations elicits nephrotoxicity could be linked to the individual, additive, synergistic or antagonistic interactions of this mixture of metals with the renal bio-molecules, alteration of kidney detoxifying enzymes and necrosis of nephritic tubular epithelial cells.

Environmental exposure to arsenic and chromium in children is associated with kidney injury molecule-1

Environmental hazards from natural or anthropological sources are widespread, especially in the north-central region of Mexico. Children represent a susceptible population due to their unique routes of exposure and special vulnerabilities. In this study we evaluated the association of exposure to environmental kidney toxicants with kidney injury biomarkers in children living in San Luis Potosi (SLP), Mexico. A cross-sectional study was conducted with 83 children (5-12 years of age) residents of Villa de Reyes, SLP. Exposure to arsenic, cadmium, chromium, fluoride and lead was assessed in urine, blood and drinking water samples. Almost all tap and well water samples had levels of arsenic (81.5%) and fluoride (100%) above the permissible levels recommended by the World Health Organization. Mean urine arsenic (45.6ppb) and chromium (61.7ppb) were higher than the biological exposure index, a reference value in occupational settings. Using multivariate adjusted models, we found a dose-dependent association between kidney injury molecule-1 (KIM-1) across chromium exposure tertiles [(T1: reference, T2: 467pg/mL; T3: 615pg/mL) (p-trend=0.001)]. Chromium upper tertile was also associated with higher urinary miR-200c (500 copies/μl) and miR-423 (189 copies/μL). Arsenic upper tertile was also associated with higher urinary KIM-1 (372pg/mL). Other kidney injury/functional biomarkers such as serum creatinine, glomerular filtration rate, albuminuria, neutrophil gelatinase-associated lipocalin and miR-21 did not show any association with arsenic, chromium or any of the other toxicants evaluated. We conclude that KIM-1 might serve as a sensitive biomarker to screen children for kidney damage induced by environmental toxic agents.

Simvastatin attenuates chromium-induced nephrotoxicity in rats

Background

Hexavalent Chromium (Cr (VI)) compounds are extremely toxic and have been demonstrated to induce nephrotoxicity associated with oxidative stress in humans and animals. The wide environmental distribution of these agents lead to an increase interest of preventive effects of its adverse effects.

Objectives

The propose of the present study was to determine the potential protective effects of simvastatin (SIMV) on Cr (VI)-induced nephrotoxicity in rat.

Materials and Methods

Forty-eight adult male Wistar rats (180-220 g BW) were randomly assigned to eight groups (n = 6). Group one received SIMV 20 mg/kg/day. Group two was given vehicle only. Groups three, five and seven received intraperitoneally (i.p) sodium dichromate (Cr (VI)) at doses of 8, 12 and 16 mg/kg body weight. Groups four, six and eight pretreated with the 20 mg/kg SIMV 30 minutes to prior administration of Cr (VI) at doses of 8, 12 and 16 mg/kg, respectively. The experiment repeated for eight consecutive days. Twenty-four hours after the last administration, animals were killed with overdose of sodium pentobarbital. Kidney tissues were excised for measuring malondialdehyde (MDA), glutathione (GSH) and histopathological examination.

Results

Chromium induced a dose dependent elevation of MDA and reduction of GSH levels. Histopathological manifestations were observed in Cr (VI)-treated rats. SIMV administration restored Cr (VI) produced biochemical and morphological changes in rat kidney. SIMV decreased MDA values and increased GSH levels in Cr (VI)-treated rats. SIMV clearly reversed the microscopic damage, demonstrating its protective effects against Cr (VI)-induced kidney injury.

Conclusions

This observation suggests that SIMV may have a protective effect against Cr (VI)-induced oxidative stress in rat kidney.

The role of ions, heavy metals, fluoride, and agrochemicals: critical evaluation of potential aetiological factors of chronic kidney disease of multifactorial origin (CKDmfo/CKDu) and recommendations for its eradication

The pollution of water and food through human waste and anthropogenic activities, including industrial waste and agricultural runoff, is a mounting problem worldwide. Water pollution from microbes causes identifiable diarrhoeal illnesses. The consumption of water contaminated with heavy metals, fluoride, and other toxins causes insidious illnesses that lead to protracted, non-communicable diseases and death. Chronic kidney disease of unusual/uncertain/unknown aetiology is one such example, began to manifest in the mid-1960s in several dry-zonal agricultural societies in developing economies that are located around the equator. In Sri Lanka, such a disease is affecting the North Central Province, the rice bowl of the country that first appeared in the mid-1990s. Several potential causes have been postulated, including heavy metals, fluoride, cyanobacterial and algae toxins, agrochemicals, and high salinity and ionicity in water, but no specific source or causative factor has been identified for CKD of multifactorial origin (CKDmfo). Three large studies conducted in the recent past failed to find any of the postulated components (heavy metals, cyanobacterial toxins, fluoride, salinity, or agrochemicals) at levels higher than those deemed safe by the World Health Organization and the US Environmental Protection Agency. At the reported low levels in water and with the heterogeneous geographical distribution, it is unrealistic to expect any of these components individually could cause this disease. However, the additive or synergistic effects of a combination of factors and components, even at lower exposure levels, together with malnutrition and harmful behaviours, and/or a yet-unidentified (or not investigated) toxin, can cause this epidemic. Because the cause is unknown, scientists need to work on broader hypotheses, so that key causative elements are not missed. Taken together the plausibility of multiple factors in the genesis of this disease, the appropriate terminology is CKDmfo, a name that also indicates the need for multi-disciplinary research programs to facilitate identifying the cause(s) and the need for multiple approaches to eradicate it. While some potential causes remain to be investigated, existing data point to polluted water as the main source of this disease. This article evaluates pros and cons of each hypothesis and highlights the importance of among others, providing clean water to all affected and surrounding communities. Available data do not support any of the postulated agents, chemicals, heavy metals, fluoride, salinity/ionicity, or individual agrochemical components, such as phosphate or glyphosate, as causative factors for CKDmfo in Sri Lanka. However, as the CKDmfo name implies, a combination of these factors (or an unknown toxin) together with harmful behaviour and chronic dehydration may cause this disease. Irrespective of the cause, prevention is the only way forward for eradication.

Occupation-related chromium toxicity a rare cause of renal failure and rhabdomyolysis

A 21-year-old gentleman, a worker in a mobile phone shop, was admitted with rhabdomyolysis, renal failure, and pulmonary edema requiring mechanical ventilation and hemodialysis. After extensive workup and ruling out other causes, heavy metal poisoning was considered. Investigations during the course of the hospital stay revealed chromium poisoning. With repeated hemodialysis, his parameters normalized and he was discharged home in a stable condition. Diagnosis of chromium toxicity needs high index of suspicion. A history of occupational exposure might offer a clue to diagnosis. With hemodialysis and supportive care, it is a potentially salvageable condition.

Hexavalent chromium induces expression of mesenchymal and stem cell markers in renal epithelial cells

Cr(VI) causes severe kidney damage. The patient's renal function could gradually recover by spontaneous kidney regeneration. The molecular effect of Cr(VI) on recovery of kidney cells, however, has not been clearly elucidated. Here we show that Cr(VI) induces expression of mesenchymal and stem cell markers, cell markers, such as paxillin, vimentin, α-SMA, nanog, and CD133 of HK-2 cells. Moreover, Cr(VI) activates epithelial-to-mesenchymal transition (EMT). By revealing that levels of dihydrodiol dehydrogenase were promptly reduced following Cr(VI) challenge, our data suggested that DDH could be involved in a Cr(VI)-related oxidation to generate massive reactive oxygen species and H2 O2 , and to create intracellular hypoxia, which then increased levels of SUMO-1 activating enzyme subunit 2, and sumoylation of eukaryotic elongation factor-2, to mediate the subsequent molecular and cellular responses, e.g., expression of mesenchymal and stem cell markers. Pretreatment with vitamin C reduced Cr(VI)-related cellular effects. However, no evident effect was observed when vitamin C was added following Cr(VI) challenge.

Metal-on-metal hip prostheses and systemic health: a cross-sectional association study 8 years after implantation

There is public concern over the long term systemic health effects of metal released from hip replacement prostheses that use large-diameter metal-on-metal bearings. However, to date there has been no systematic study to determine which organs may be at risk, or the magnitude of any effect. We undertook a detailed cross-sectional health screen at a mean of 8 years after surgery in 35 asymptomatic patients who had previously received a metal-on-metal hip resurfacing (MoMHR) versus 35 individually age and sex matched asymptomatic patients who had received a conventional hip replacement. Total body bone mineral density was 5% higher (mean difference 0.05 g/cm², P = 0.02) and bone turnover was 14% lower (TRAP 5b, mean difference −0.56IU/L, P = 0.006; osteocalcin, mean difference −3.08 ng/mL, P = 0.03) in the hip resurfacing versus conventional hip replacement group. Cardiac ejection fraction was 7% lower (mean absolute difference −5%, P = 0.04) and left ventricular end-diastolic diameter was 6% larger (mean difference 2.7 mm, P = 0.007) in the hip resurfacing group versus those patients who received a conventional hip replacement. The urinary fractional excretion of metal was low (cobalt 5%, chromium 1.5%) in patients with MoMHR, but creatinine clearance was normal. Diuretic prescription was associated with a 40% increase in the fractional excretion of chromium (mean difference 0.5%, P = 0.03). There was no evidence of difference in neuropsychological, renal tubular, hepatic or endocrine function between groups (P>0.05). Our findings of differences in bone and cardiac function between patient groups suggest that chronic exposure to low elevated metal concentrations in patients with well-functioning MoMHR prostheses may have systemic effects. Long-term epidemiological studies in patients with well-functioning metal on metal hip prostheses should include musculoskeletal and cardiac endpoints to quantitate the risk of clinical disease.

Early markers of nephrotoxicity in patients with metal-on-metal hip arthroplasty

BACKGROUND

Metal ions released from arthroplasty devices are largely cleared in urine, leading to high exposure in renal tissues. Validated early markers of renal damage are routinely used to monitor workers in heavy metal industries, and renal risk can be quantified in these industries. It is unclear if the ion levels in patients with metal-on-metal hips are sufficient to cause renal damage.

QUESTION

Does metal-on-metal (MOM) bearing use over a 10-year period lead to elevation of early renal markers compared with the levels expected in subjects with no metal exposure?

METHODS

We retrospectively reviewed 31 patients who underwent MOM hip resurfacings 10 years earlier. Whole blood specimens were collected for metal ion analysis, serum for creatinine estimation, and urine for timed metal ion output and renal markers. The renal marker levels of 30 age- and gender-matched subjects with no metal exposure and no known renal problems or diabetes mellitus were used as controls for renal markers.

RESULTS

Median serum creatinine level in the MOM group was 1.1 mg/dL (interquartile range, 1.0-1.2 mg/dL) and median creatinine clearance was 79.2 mL/min. In this cohort, the number of patients with markers of renal damage above the reference range was comparable to the controls. None of the renal markers were associated with metal levels.

CONCLUSION

The absence of elevation of renal markers in this cohort 10 years after MOM bearing implantation is reassuring. However, we believe surveillance through further longer-term, large-scale controlled trials are needed to monitor this arthroplasty-induced low-intensity (but long-term) trace element exposure to rule out potential nephrotoxicity.

Assessment of water quality parameters in the stream Galyan, Trabzon, Turkey

This paper presents a comprehensive evaluation of drinking water quality from the stream Galyan and its tributary, the stream Kuştul, in Trabzon Province, Turkey. In this study, surface water quality data for 20 physical and chemical parameters were determined and collected from three monitoring stations of the understudy stream during April 2004 to March 2005. According to the Turkish Water Pollution Control Regulation, the stream Galyan water was classified, and the studied parameters were evaluated for the values proposed by Turkish Standard (TS) 266 and World Health Organization (WHO) guidelines. The results showed that TS 266 and WHO guidelines were exceeded for Fe (up to 860 microg/l) and Cr (up to 134.7 microg/l). Pearson's correlation was also used to determine the relationship of the studied parameters and as a result significant correlations were observed between some parameters.

Comparison of kidney injury molecule-1 and other nephrotoxicity biomarkers in urine and kidney following acute exposure to gentamicin, mercury, and chromium

Sensitive biomarkers are needed to detect kidney injury at the earliest stages. The objective of this study was to determine whether the appearance of kidney injury molecule-1 (Kim-1) protein ectodomain in urine and kidney injury molecule-1/hepatitis A viral cellular receptor-1 (Kim-1/Havcr1) gene expression in kidney tissue may be more predictive of renal injury after exposure to nephrotoxicants when compared to traditionally used biomarkers. Male Sprague-Dawley rats were injected with a range of doses of gentamicin, mercury (Hg; HgCl2), or chromium (Cr; K2Cr2O7). The results showed that increases in urinary Kim-1 and kidney Kim-1/Havcr1 gene expression paralleled the degree of severity of renal histopathology and were detected at lower doses of nephrotoxicants when compared to blood urea nitrogen (BUN), serum creatinine, and urinary N-acetyl-beta-D-glucosaminidase (NAG). In a time course study, urinary Kim-1 was elevated within 24 h after exposure to gentamicin (100 mg/kg), Hg (0.25 mg/kg), or Cr (5 mg/kg) and remained elevated through 72 h. NAG responses were nephrotoxicant dependent with elevations occurring early (gentamicin), late (Cr), or no change (Hg). At 72 h, after treatment with any of the three nephrotoxicants, there was increased Kim-1 immunoreactivity and necrosis involving approximately 50% of the proximal tubules; however, only urinary Kim-1 was significantly increased, while BUN, serum creatinine, and NAG were not different from controls. In rats treated with the hepatotoxicant galactosamine (1.1 mg/kg), serum alanine aminotransferase was increased, but no increase in urinary Kim-1 was observed. Urinary Kim-1 and kidney Kim-1/Havcr1 expression appear to be sensitive and tissue-specific biomarkers that will improve detection of early acute kidney injury following exposure to nephrotoxic chemicals and drugs.

Chronic interstitial nephropathy after plasma cutting in stainless steel

Chromium is nephrotoxic in experimental animals. In subjects with acute chromium intoxication acute nephritis has been reported and renal function has been affected in chromium exposed workers with a high urinary chromium concentration. Chronic kidney disease after long term occupational exposure to chromium has, however, not been reported previously. A case report is presented concerning a 48 year old man who was diagnosed with chronic interstitial nephropathy. He had worked for nine years as a plasma cutter of stainless steel and had thereby been exposed to smoke containing chromium. At the time of diagnosis his blood chromium concentration was seven times higher and his urinary chromium concentration six times higher than reference values. Taking into account the nephrotoxicity of chromium and the high chromium burden of this patient it is considered likely that his exposure to smoke from plasma cutting of stainless steel was the cause of his chronic interstitial nephropathy.

Oral bioavailability of chromium from a specific site

Analysis of soil from a specific site in New Jersey indicated a low level of sodium and chromium present as a calcium compound. Chromium was then administered orally to young, mature male rats at a level of 240 micrograms/kg for 14 days as chromium-contaminated soil, as CaCrO4, and as an equimolar mixture of the soil and calcium salts for 14 days. The rats were sacrificed 24 hr after the last dosing, and tissues were taken immediately for chromium analysis. Blood, muscle, and liver contained the highest levels of chromium in these animals, although kidney contained the highest concentration per gram of tissue. The total amount of chromium in the tissues was less than 2% of the administered chromium. In a study of the excretion of chromium, the animals were dosed orally for 8 days (with CaCrO4 or contaminated soil, each at the level of 240 mumole Cr/kg), and the chromium in feces and urine was determined on days 1, 2, 7, and 8. After cessation of dosing for 27 days, the same rats were dosed for 2 days at the same level, and chromium in urine and feces was determined for the 2 days. The animals administered the chromium in soil had higher levels of chromium in both urine and feces on all days compared to the group fed the CaCrO4. The total recovery of chromium in any of the 2-day periods was less than 50% of the chromium administered during that period.