Lead nephropathy, gout, and hypertension

Lead exerts a depression of neurotransmitter release through a blockade of voltage dependent calcium channels in chromaffin cells

The present work, using chromaffin cells of bovine adrenal medullae (BCCs), aims to describe what type of ionic current alterations induced by lead (Pb2+) underlies its effects reported on synaptic transmission. We observed that the acute application of Pb2+ lead to a drastic depression of neurotransmitters release in a concentration-dependent manner when the cells were stimulated with both K+ or acetylcholine, with an IC50 of 119,57 μM and of 5,19 μM, respectively. This effect was fully recovered after washout. Pb2+ also blocked calcium channels of BCCs in a time- and concentration-dependent manner with an IC50 of 6,87 μM. This blockade was partially reversed upon washout. This compound inhibited the calcium current at all test potentials and shows a shift of the I-V curve to more negative values of about 8 mV. The sodium current was not blocked by acute application of high Pb2+ concentrations. Voltage-dependent potassium current was also shortly affected by high Pb2+. Nevertheless, the calcium- and voltage-dependent potassium current was drastically depressed in a dose-dependent manner, with an IC50 of 24,49 μM. This blockade was related to the prevention of Ca2+ influx through voltage-dependent calcium channels coupled to Ca2+-activated K+-channels (BK) instead a direct linking to these channels. Under current-clamp conditions, BCCs exhibit a resting potential of -52.7 mV, firing spontaneous APs (1-2 spikes/s) generated by the opening of Na+ and Ca2+-channels, and terminated by the activation of K+ channels. In spite of the effect on ionic channels exerted by Pb2+, we found that Pb2+ didn't alter cellular excitability, no modification of the membrane potential, and no effect on action potential firing. Taken together, these results point to a neurotoxic action evoked by Pb2+ that is associated with changes in neurotransmitter release by blocking the ionic currents responsible for the calcium influx.

Early transcriptomic signatures and biomarkers of renal damage due to prolonged exposure to embedded metal

BACKGROUND

Prolonged exposure to toxic heavy metals leads to deleterious health outcomes including kidney injury. Metal exposure occurs through both environmental pathways including contamination of drinking water sources and from occupational hazards, including the military-unique risks from battlefield injuries resulting in retained metal fragments from bullets and blast debris. One of the key challenges to mitigate health effects in these scenarios is to detect early insult to target organs, such as the kidney, before irreversible damage occurs.

METHODS

High-throughput transcriptomics (HTT) has been recently demonstrated to have high sensitivity and specificity as a rapid and cost-effective assay for detecting tissue toxicity. To better understand the molecular signature of early kidney damage, we performed RNA sequencing (RNA-seq) on renal tissue using a rat model of soft tissue-embedded metal exposure. We then performed small RNA-seq analysis on serum samples from the same animals to identify potential miRNA biomarkers of kidney damage.

RESULTS

We found that metals, especially lead and depleted uranium, induce oxidative damage that mainly cause dysregulated mitochondrial gene expression. Utilizing publicly available single-cell RNA-seq datasets, we demonstrate that deep learning-based cell type decomposition effectively identified cells within the kidney that were affected by metal exposure. By combining random forest feature selection and statistical methods, we further identify miRNA-423 as a promising early systemic marker of kidney injury.

CONCLUSION

Our data suggest that combining HTT and deep learning is a promising approach for identifying cell injury in kidney tissue. We propose miRNA-423 as a potential serum biomarker for early detection of kidney injury.

Low-level exposure to lead, mercury, arsenic, and cadmium, and blood pressure among 8-17-year-old participants of the 2009-2016 National Health and Nutrition Examination Survey

BACKGROUND

Dysregulation of systolic, diastolic blood pressure (SBP, DBP), and pulse pressure (PP) in children may predict elevated blood pressure (BP) in adulthood. Toxicant exposure is widely studied as a risk factor for high BP in adults, but not in children. We assessed the joint associations between lead (Pb), mercury (Hg), arsenic (As), and cadmium (Cd) exposure and SBP, DBP, and PP among 8-17 year-old participants (n = 1642) of the 2009-2016 National Health and Nutrition Examination Survey (NHANES).

METHODS

Participants with at least two BP measures were included. Urinary As and Cd were adjusted for urinary creatinine concentrations. Blood Pb, Hg, and urinary As, Cd were natural log-transformed. Bayesian Kernel Machine Regression (BKMR) analyses were conducted to assess the associations between the toxicant mixture and BP measures. Multivariable regression models assessed the associations between individual toxicants, and the four toxicants simultaneously with each of the outcomes. Interactions with sodium intake were tested.

RESULTS

Exposure to all toxicants was low, with median (5%, 95%) level: Pb, 0.57 (0.26, 1.60) μg/dL; Hg, 0.37 (0.19, 2.12) μg/L; As, 5.61 (1.37, 33.2) μg/g creatinine, Cd, 0.06 (0.03, 0.23) μg/g creatinine. Toxicant mixture showed a statistically significant, inverse association with DBP, but not other BP measures. Linear regressions revealed no association between toxicants, individually or together, and BP measures. No evidence of interaction of sodium intake with any of the toxicants was observed.

CONCLUSIONS

In a nationally representative sample of 8-17 year-olds, we found suggestive inverse association of the mixture of low-level Pb, Hg, As, and Cd, with DBP. Longitudinal studies with multiple toxicants are needed to understand the interactive effects of toxicants on children's BP.

Associations between exposure to heavy metals and the risk of chronic kidney disease: a systematic review and meta-analysis

We performed a systematic review and meta-analysis to examine the relationship between heavy metals (HMs) exposure and the risk of chronic kidney disease (CKD). Databases of Web of Science, Embase, MEDLINE, and Scopus were searched through June 2020 to identify studies assessing the relationships between exposure to HMs (i.e. cadmium, lead, arsenic, mercury) and the risk of CKD, evaluated by decreased estimated glomerular filtration rate (eGFR) and/or increased proteinuria risks in adults (≥18 years). Data were pooled by random-effects models and expressed as weighted mean differences and 95% confidence intervals. The risk of bias was assessed by the Newcastle-Ottawa scale (NOS). Twenty-eight eligible articles (n = 107,539 participants) were included. Unlike eGFR risk (p = 0.10), Cadmium exposure was associated with an increased proteinuria risk (OR = 1.35; 95% CI: 1.13, 1.61; p < 0.001; I² = 79.7%). Lead exposure was associated with decreased eGFR (OR = 1.12; 95%CI: 1.03, 1.22; p = 0.008; I² = 87.8%) and increased proteinuria (OR = 1.25; 95% CI: 1.04, 1.49; p = 0.02; I² = 79.6) risks. Further, arsenic exposure was linked to a decreased eGFR risk (OR = 1.55; 95% CI: 1.05, 2.28; p = 0.03; I² = 89.1%) in contrast to mercury exposure (p = 0.89). Only two studies reported the link between arsenic exposure and proteinuria risk, while no study reported the link between mercury exposure and proteinuria risk. Exposure to cadmium, lead, and arsenic may increase CKD risk in adults, albeit studies were heterogeneous, warranting further investigations. Our observations support the consideration of these associations for preventative, diagnostic, monitoring, and management practices of CKD.

Effects of ambient PM2.5 and particle-bound metals on the healthy residents living near an electric arc furnace: A community- based study

Fine particulate matter (PM_2.5) emitted from electric arc furnaces (EAFs) poses health concerns. However, little research has been done on the impact of EAF on the health of community residents. This cross-sectional study conducted a PM_2.5 exposure assessment and health examination of community residents living near an EAF. A total of 965 residents aged 40-90 years were recruited. The residents' exposure to PM_2.5 was categorized according to the distance of their residence from the EAFs (<500, 500-1000, 1000-1500, 1500-2000, and > 2000 m). Average ambient PM_2.5 concentrations were estimated using a hybrid kriging/land-use regression (LUR) model. In addition, we selected two air-sampling sites to monitor the 2-year levels of PM_2.5 and particle-bound metals. A spot urine sample and blood samples were collected and ten heavy metal concentrations in the blood were analyzed. Inflammation- and oxidative stress-related biomarkers were measured. The associations between environmental factors and a biochemical examination were estimated using a generalized linear model. Active air sampling and hybrid kriging/LUR model simulation indicated increased levels of PM_2.5 near the EAF. The metal concentrations in PM_2.5 included Fe, Pb, Mn, Ni, As, Cu, Ni, Zn, and Al, which also significantly increased near the EAF. PM_2.5 levels were significantly associated with an increased total cholesterol-high-density lipoprotein (TC/HDL) ratio. High levels of PM_2.5 and malondialdehyde were associated with a 1.72-fold increased risk of TC/HDL ratio ≥ 4 (95% CI: 1.12-2.65) after adjusting for potential confounding factors. Blood Pb levels were significantly associated with increased systolic and diastolic blood pressure and decreased estimated glomerular filtration rate but negatively associated with distance from the EAF. The results show that people living near EAFs should pay more attention to adverse health problems, including atherogenic dyslipidemia, hypertension, and chronic kidney disease associated with exposure to PM_2.5 and particle-bound metals.

Wastewater-based estimation of the prevalence of gout in Australia

Allopurinol, a first-line gout treatment drug in Australia, was assessed as a wastewater-based epidemiology biomarker of gout via quantification of the urinary metabolite, oxypurinol in wastewater. The in-sewer stability of oxypurinol was examined using laboratory-scale sewer reactors. Wastewater from 75 wastewater treatment plants across Australia, covering approximately 52% (12.2 million) of the country's population, was collected on the 2016 census day. Oxypurinol was quantified in the wastewater samples and population-weighted mass loads calculated. Pearson and Spearman rank-order correlations were applied to investigate any link between allopurinol, other selected wastewater biomarkers, and socio-economic indicators. Oxypurinol was shown to be stable in sewer conditions and suitable as a WBE biomarker. Oxypurinol was detected in all wastewater samples. The estimated consumption of allopurinol ranged from 1.9 to 32 g/day/1000 people equating to 4.8 to 80 DDD/day/1000 people. The prevalence of gout across all tested sewer catchments was between 0.5% to 8%, with a median of 2.9% nationally. No significant positive correlation was observed between allopurinol consumption and alcohol consumption, mean age of catchment population, remoteness or higher socioeconomic status. There was a significant positive correlation with selective analgesic drug use. Wastewater analysis can be used to study gout prevalence and can provide additional insights on population level risk factors when triangulated with other biomarkers.

Renal function in relation to low-level environmental lead exposure

BACKGROUND

Numerous studies suggested that occupational or environmental exposure to lead adversely affects renal function. However, most studies lost relevance because of the substantially lower current environmental lead exposure and all relied on serum creatinine to estimate glomerular filtration. We investigated the association of estimated glomerular filtration rate (eGFR), estimated from serum creatinine, cystatin C or both, with blood lead (BPb) using the baseline measurements of the ongoing Study for Promotion of Health in Recycling Lead (SPHERL; NCT02243904) in newly hired workers prior to significant occupational lead exposure.

METHODS

Among 447 men (participation rate, 82.7%), we assessed the association of eGFR and the urinary albumin-to-creatinine ratio (ACR) with BPb across thirds of the BPb distribution using linear regression analysis. Fully adjusted models accounted for age, blood pressure, body mass index, the waist-to-hip ratio, smoking, the total-to-high-density-lipoprotein ratio, plasma glucose, serum γ-glutamyltransferase and antihypertensive drug treatment.

RESULTS

Age averaged 28.7 (SD, 10.2) years (range, 19.1-31.8). Geometric mean BPb concentration was 4.34 μg/dL (5th-95th percentile interval, 0.9-14.8). In unadjusted and adjusted analyses, eGFR estimated from serum creatinine [mean (SD), 105.26 (15.2) mL/min/1.73 m2], serum cystatin C [mean (SD), 127.8 (13.8) mL/min/1.73 m2] or both [mean (SD), 111.9 (14.8) mL/min/1.73 m2] was not associated with BPb (P  ≥  0.36), whereas ACR [geometric mean, 4.32 mg/g (5th-95th percentile interval, 1.91-12.50)] was lower with higher BPb.

CONCLUSIONS

At the BPb levels observed in this study, there was no evidence for an association between renal function and lead exposure.

Urinary KIM-1: a novel biomarker for evaluation of occupational exposure to lead

Chronic occult lead poisoning often develops ensuing occupational lead exposure. Early diagnosis of lead poisoning is critical for timely discontinuation of lead exposure and for prognosis. This study explored the value of urinary kidney injury molecule-1 (KIM-1) in diagnosing renal injury induced by lead at an early stage. We retrospectively analyzed 92 workers exposed to occupational lead and demonstrated a better correlation ship between blood lead levels and urine excretion of KIM-1 than other traditional renal injury biomarkers following creatinine adjustment. Receiver operating characteristic curve analysis of the ability of diverse biomarkers for predicting kidney injury in lead-exposed workers demonstrated that the order of predicting accuracy of the studied biomarkers is as follows: urinary KIM-1-to-creatinine ratio > urinary N-acetyl-β-(D)-glucosaminidase-to-creatinine ratio > urinary β2-microglobulin-to-creatinine ratio > urinary α1-microglobulin-to-creatinine ratio, with the Youden index being 16.59 ng/g, 14.01 U/g, 0.15 mg/g, and 4.63 mg/g, respectively. Collectively, our findings suggest that short-period occupational lead exposure may cause injury of renal tubules. Urinary excretion of KIM-1 correlates with blood lead levels better than other traditional renal injury biomarkers, including N-acetyl-β-(D)-glucosaminidase, α1-microglobulin, and β2-microglobulin. Longitudinal surveillance of urinary KIM-1 may aid for early diagnosis of renal tubular injury in workers with occupational lead exposure.

Environmental lead exposure accelerates progressive diabetic nephropathy in type II diabetic patients

Whether environmental lead exposure has a long-term effect on progressive diabetic nephropathy in type II diabetic patients remains unclear. A total of 107 type II diabetic patients with stage 3 diabetic nephropathy (estimated glomerular filtration rate (eGFR) range, 30-60 mL/min/1.73 m(2)) with normal body lead burden (BLB) (<600  μ g/72 hr in EDTA mobilization tests) and no history of exposure to lead were prospectively followed for 2 years. Patients were divided into high-normal BLB (>80  μ g) and low-normal BLB (<80  μ g) groups. The primary outcome was a 2-fold increase in the initial creatinine levels, long-term dialysis, or death. The secondary outcome was a change in eGFR over time. Forty-five patients reached the primary outcome within 2 years. Although there were no differences in baseline data and renal function, progressive nephropathy was slower in the low-normal BLB group than that in the high-normal BLB group. During the study period, we demonstrated that each 100  μ g increment in BLB and each 10  μ g increment in blood lead levels could decrease GFR by 2.2 mL/min/1.72 m(2) and 3.0 mL/min/1.72 m(2) (P = 0.005), respectively, as estimated by generalized equations. Moreover, BLB was associated with increased risk of achieving primary outcome. Environmental exposure to lead may have a long-term effect on progressive diabetic nephropathy in type II diabetic patients.

Assessment of some renal indices in people occupationally exposed to lead

Exposure to lead has been reported to have adverse health implications. An assessment of renal function in people occupationally exposed to lead was carried out using the following biochemical markers urea, creatinine, sodium, potassium, chloride and bicarbonate. A total of 53 test subjects (mean age 30.9 ± 7.7) were randomly selected among some workers occupationally exposed to lead in Osogbo city and 42 apparently healthy subjects (mean age 30.1 ± 1.2) were used as controls. The plasma urea, creatinine, chloride and bicarbonate concentration were determined using modified Berthelot method, Jaffe's reaction, Schales and Schales method and back titration methods, respectively. The plasma sodium and potassium concentrations were determined using flame emission spectrophotometry while blood lead level was also determined using atomic absorption spectrophotometry. The result showed significant increases in mean plasma concentration of creatinine (84.9 ± 13.6-97.4 ± 28.7 μmol/L), sodium (131.9 ± 3.9-134.8 ± 3.7 mmol/L) and chloride (98.2 ± 4.0-100.4 ± 3.9 mmol/L) in test subjects when compared with controls (p < 0.05). Furthermore, significant increases (p < 0.01) were observed in mean plasma concentration of urea (4.7 ± 1.2-5.7 ± 1.3 mmol/L) and blood lead levels (18.5 ± 3.5-69.7 ± 13.2 mg/L) in test subjects in comparison with controls. In contrast, there were no significant differences observed when mean plasma potassium and bicarbonate levels in test subjects were compared with controls (p > 0.05). These results indicate that occupational exposure to lead may compromise renal function.

Effect of lead toxicity on coenzyme Q levels in rat tissues

Lead is a persistent and common environmental contaminant, which chiefly plays a significant role in modern industry. Coenzyme Q acts as electron and proton carrier in mitochondria and functions as an antioxidant in its reduced form (ubiquinol). To investigate the hazardous effects of lead on the coenzyme Q level, rats were injected i.p. with lead acetate (5 mg/kg b.wt. daily for 6 weeks). Our results showed that the levels of both oxidized (ubiquinone) and reduced (ubiquinol) forms of coenzyme Q(9) and Q(10) in serum, brain, liver and kidney of lead-treated rats are quite different depending on the organ tissue type.

Interplay of reactive oxygen species and nitric oxide in the pathogenesis of experimental lead-induced hypertension

1. Lead is a common environmental and industrial toxin that can cause a variety of acute and chronic illnesses. For example, chronic exposure to low levels of lead has been shown to raise arterial pressure and promote renal and cardiovascular complications. 2. Several mechanisms have been identified by which chronic lead exposure can cause hypertension and cardiovascular disease. In recent years, increasing evidence has emerged pointing to the role of oxidative stress as a major mediator of lead-induced hypertension. 3. The present article provides an overview of the published studies on this subject.

Association of tibia lead and blood lead with end-stage renal disease: a pilot study of African-Americans

The association between body lead burden and kidney disease remains controversial. Fifty-five African-American end-stage renal disease (ESRD) cases and 53 age- and sex-matched African-American controls without known renal disease were recruited from Tulane University-affiliated dialysis clinics and out-patient clinics, respectively. Blood lead was measured via atomic absorption spectrophotometry and tibia lead (a measure of body lead) was measured via (109)Cd-based K shell X-ray fluorescence. Median blood lead levels were significantly higher among ESRD cases (6 microg/dL) compared to their control counterparts (3 microg/dL; P<0.001). Although no participants had overt lead poisoning (blood lead > or = 25 microg/dL), seven cases but no controls had blood lead levels above 10 microg/dL (P=0.006). The median tibia lead level was 17 micrograms of lead per gram of bone mineral (microg/g) and 13 microg/g among ESRD cases and their control counterparts, respectively (P=0.134). Four ESRD cases (7%), but no controls, had a tibia lead level above 40 microg/g (P=0.115) while a similar proportion of cases and controls had tibia lead between 20 and 39 microg/g (33% and 32%, respectively; P=0.726). After adjustment for potential confounders, the odds ratios of ESRD associated with a tibia lead > or = 20 microg/g and each four-fold higher tibia lead (e.g., 5-20 microg/g) were 1.55 (95% CI: 0.55, 4.41) and 1.88 (95% CI: 0.53, 6.68), respectively. These findings support the need for prospective cohort studies of body lead burden and renal disease progression.

Lead toxicity and chelation therapy

PURPOSE

Common sources of lead exposure, the primary clinical effects of lead toxicity, and current recommendations for managing lead toxicity, including chelation therapy, are reviewed.

SUMMARY

Common sources of lead exposure in children and adults include industrial and mining activities, paint, dust, soil, water, air, the workplace, food, trinkets, ethnic folk remedies, and cosmetics. The absorption and biological fate of lead are affected by a variety of factors, including an individual's nutritional status, health, and age. Children with a blood lead concentration of >10 microg/dL and adults with a blood lead concentration of > or = 45 mug/dL should undergo further evaluation. Symptoms and time to onset of symptoms postexposure may vary, and it can be difficult to identify the early, subtle neurologic effects of lead toxicity. The classic symptoms of lead toxicity generally correlate with blood lead concentrations of 25-50 microg/dL in children and 40-60 microg/dL in adults. Management of lead toxicity requires extensive risk assessment and caregiver education. Chelation is generally not indicated for adults with blood lead concentrations of < 45 microg/dL because of the potential risk of adverse drug events and concerns about remobilized lead, and chelation for children with blood lead concentrations of < 45 microg/dL remains controversial. Dimercaprol, edetate calcium disodium, and succimer are the three agents primarily used for chelation.

CONCLUSION

Lead toxicity remains a significant public health concern. Elimination of elevated blood lead levels in children can be accomplished by educating appropriate health care providers and caregivers, recognizing potential lead sources, and adopting aggressive prevention and case management measures.

Blood Lead Below 0.48 μmol/L (10 μg/dL) and Mortality Among US Adults

Background— Blood lead levels above 0.48 μmol/L (10 μg/dL) in adults have been associated with increased risk of cardiovascular, cancer, and all-cause mortality. The objective of the present study was to determine the association between blood lead levels below 0.48 μmol/L and mortality in the general US population.

Methods and Results— Blood lead levels were measured in a nationally representative sample of 13 946 adult participants of the Third National Health and Nutrition Examination Survey recruited in 1988 to 1994 and followed up for up to 12 years for all-cause and cause-specific mortality. The geometric mean blood lead level in study participants was 0.12 μmol/L (2.58 μg/dL). After multivariate adjustment, the hazard ratios (95% CI) for comparisons of participants in the highest tertile of blood lead (≥0.17 μmol/L [≥3.62 μg/dL]) with those in the lowest tertile (<0.09 μmol/L [<1.94 μg/dL]) were 1.25 (1.04 to 1.51; P trend across tertiles=0.002) for all-cause mortality and 1.55 (1.08 to 2.24; P trend across tertiles=0.003) for cardiovascular mortality. Blood lead level was significantly associated with both myocardial infarction and stroke mortality, and the association was evident at levels >0.10 μmol/L (≥2 μg/dL). There was no association between blood lead and cancer mortality in this range of exposure.

Conclusions— The association between blood lead levels and increased all-cause and cardiovascular mortality was observed at substantially lower blood lead levels than previously reported. Despite the marked decrease in blood lead levels over the past 3 decades, environmental lead exposures remain a significant determinant of cardiovascular mortality in the general population, constituting a major public health problem.

Environmental exposure to lead and progressive diabetic nephropathy in patients with type II diabetes

Studies indicate that environmental exposure to lead is associated with reduced renal function. Whether lead affects progressive diabetic nephropathy is unclear. Eighty-seven patients with type II diabetes and diabetic nephropathy (serum creatinine of 1.5-3.9 mg/dl) with normal body lead burden and no lead exposure history were observed over a 12-month period. Thirty subjects with high normal body lead burdens (80-600 microg) were randomly assigned to a chelation and control group. For 3 months, the 15 chelation-group patients underwent lead-chelation therapy with calcium disodium ethylenediaminetetraacetic acid weekly until body lead burden fell <60 microg, and the 15 control group subjects received a weekly placebo. During the following 12 months, renal function was regularly assessed at 3-month intervals. The primary outcome was an elevation of serum creatinine to 1.5 times baseline value during the observation period. A secondary outcome was temporal changes in renal function following chelation therapy. Twenty-six patients achieved the primary outcome. Basal blood lead levels and body lead burden were the most important risk factors in predicting progressive diabetic nephropathy. Following chelation, the rates of decline in glomerular filtration rates in the chelation group and the control group, respectively, were 5.0+/-5.7 ml and 11.8+/-7.0 ml/min/year/1.73 m(2) of body surface area (P=0.0084) during follow-up, although both groups had similar rates of progression of renal function during the 12-month observation period. We concluded that low-level environmental lead exposure accelerates progressive diabetic nephropathy and lead-chelation therapy can decrease its rate of progression.

Confounding of the relation between homocysteine and peripheral arterial disease by lead, cadmium, and renal function

Homocysteine levels are associated with peripheral arterial disease (PAD) in observational studies. Lead and cadmium are risk factors for PAD that affect thiol metabolism, and they may partly explain the association of homocysteine with PAD. To evaluate the roles of lead and cadmium exposure in confounding the association between homocysteine and PAD, the authors performed a cross-sectional study among 4,447 persons aged > or = 40 years who participated in the 1999-2002 National Health and Nutrition Examination Survey (NHANES). PAD was defined as an ankle-brachial blood pressure index less than 0.90 in at least one leg. After adjustment for sociodemographic variables, the odds ratio for PAD in the highest quintile of homocysteine compared with the lowest was 1.92 (p(trend) = 0.004). Adjusting for blood lead and cadmium levels reduced this odds ratio to 1.37 (p(trend) = 0.13), and further adjusting for estimated glomerular filtration rate and smoking reduced it to 0.89 (p(trend) = 0.87). Adjustment for other risk factors did not affect this association. In the general population, the association of homocysteine level with PAD can be completely explained by confounding due to smoking, increased blood lead and cadmium levels, and impaired renal function. The association of lead and cadmium with PAD risk deserves further investigation.

Lead and other trace metals in preeclampsia: a case-control study in Tehran, Iran

To assess the effects of environmental exposures to trace metals on the incidence of preeclampsia, concentrations of lead (Pb), antimony (Sb), manganese (Mn), mercury, cadmium, cobalt and zinc in umbilical cord blood (UCB) and mother whole blood (MWB) were measured in 396 postpartum women without occupational exposure to metals in Tehran, Iran, using inductively coupled plasma mass spectrometry. Mother's ages ranged from 15 to 49 (mean 27) years. Preeclampsia was diagnosed in 31 subjects (7.8%). Levels of Pb, Sb and Mn in UCB were significantly higher in preeclampsia cases [mean+/-SD of 4.30+/-2.49 microg/dl, 4.16+/-2.73 and 46.87+/-15.03 microg/l, respectively] than in controls [3.52+/-2.09 microg/dl, 3.17+/-2.68 and 40.32+/-15.19 microg/l, respectively] (P<0.05). The logistic regression analysis revealed that one unit increase in the common logarithms of UCB concentration of Pb, Sb or Mn led to increase in the risk of preeclampsia several-fold; unit risks (95% CI) were 12.96 (1.57-107.03), 6.11 (1.11-33.53) and 34.2 (1.81-648.04) for Pb, Sb and Mn, respectively (P<0.05). These findings suggest that environmental exposure to Pb, Sb and Mn may increase the risk of preeclampsia in women without occupational exposure; levels of metals in UCB to be sensitive indicators of female reproductive toxicity as compared with those in mother MWB. Further studies are necessary to confirm these findings, especially on Sb and Mn.

Lead blood concentrations and renal function evaluation: study in an exposed Mexican population

The relation of blood Pb concentrations and renal dysfunction has been reported in association with interstitial fibrosis, tubular atrophy, and decreased glomerular filtration. In this report information about blood Pb concentrations and renal function tests in a population from Oaxaca, Mexico is analyzed. The main changes found were that males had higher blood Pb concentrations than females (P<0.0012); the leading variables associated with this were occupation (glazed pottery workers, P=0.0001) and the use of glazed pottery for preparing meals (P=0.0000). Variables that better explain uric acid variability were blood Pb concentrations, sex, weight, and height (r2=0.23). Hyperuricemia was associated with blood Pb concentrations above 40 microg/dL (OR=1.74, 95% CI, 1.12-2.61). SCr was associated with sex, age, and blood Pb, with coefficient r2=0.12. Our findings might be related to inadequate control of oven emissions, a situation that will require further analysis and the implementation of preventive measurements for the nonoccupational exposed population.

Associations among lead dose biomarkers, uric acid, and renal function in Korean lead workers

Recent research suggests that both uric acid and lead may be nephrotoxic at lower levels than previously recognized. We analyzed data from 803 current and former lead workers to determine whether lead biomarkers were associated with uric acid and whether previously reported associations between lead dose and renal outcomes were altered after adjustment for uric acid. Outcomes included uric acid, blood urea nitrogen, serum creatinine, measured and calculated creatinine clearances, and urinary N-acetyl-ss-d-glucosaminidase (NAG) and retinol-binding protein. Mean (+/- SD) uric acid, tibia lead, and blood lead levels were 4.8 +/- 1.2 mg/dL, 37.2 +/- 40.4 microg/g bone mineral, and 32.0 +/- 15.0 microg/dL, respectively. None of the lead measures (tibia, blood, and dimercaptosuccinic-acid-chelatable lead) was associated with uric acid, after adjustment for age, sex, body mass index, and alcohol use. However, when we examined effect modification by age on these relations, both blood and tibia lead were significantly associated (ss = 0.0111, p < 0.01 and ss = 0.0036, p = 0.04, respectively) in participants in the oldest age tertile. These associations decreased after adjustment for blood pressure and renal function, although blood lead remained significantly associated with uric acid (ss = 0.0156, p = 0.01) when the population was restricted to the oldest tertile of workers with serum creatinine greater than the median (0.86 mg/dL). Next, in models of renal function in all workers, uric acid was significantly (p < 0.05) associated with all renal outcomes except NAG. Finally, in the oldest tertile of workers, associations between lead dose and NAG were unchanged, but fewer associations between the lead biomarkers and the clinical renal outcomes remained significant (p less than or equal to 0.05) after adjustment for uric acid. In conclusion, our data suggest that older workers comprise a susceptible population for increased uric acid due to lead. Uric acid may be one, but not the only, mechanism for lead-related nephrotoxicity.

Lead-induced hypertension: role of oxidative stress

Chronic, low-level lead exposure causes hypertension in both animals and humans. The pathogenesis of lead-induced hypertension is multifactorial, including such diverse mechanisms as: inactivation of endogenous nitric oxide and downregulation of soluble guanylate cyclase by reactive oxygen species (ROS), leading to a functional deficiency in nitric oxide; heightened sympathetic activity and plasma norepinephrine together with depressed vascular and elevated renal beta-adrenergic receptor density; elevated plasma angiotensin-converting enzyme (ACE) activity, plasma renin activity (PRA), angiotensin II (Ang-II), and aldosterone levels; increased kininase I and kininase II activities; lead-induced inhibition of vascular smooth muscle Na(+)-K+ ATPase, leading to a rise in cellular Na+ and, hence, Ca2+; and a possible rise in endothelin and thromboxane generation. In this article, we present an overview of the epidemiology and proposed underlying mechanisms of lead-induced hypertension.

A Review of Chronic Lead Intoxication: An Unrecognized Cause of Chronic Kidney Disease

Chronic lead nephropathy occurs as a result of years of lead exposure. This disease has been prevalent throughout human history. It is important that primary care providers and internists recognize this disorder because it can contribute to progressive loss of kidney function. Diagnosis is made by a thorough history in combination with physical examination. A history of lead intoxication often requires knowledge of the various sources of lead exposure. Laboratory tests, many previously known and some newly described, are available to further support this diagnosis. Therapy to reduce lead burden may be useful when employed early in the disease; new data sheds more light on which patients should be treated and when such patients should undergo chelation therapy. In particular, treatment with calcium EDTA chelation may benefit certain patients with chronic kidney disease by slowing the progression to end-stage renal disease.

Associations of lead biomarkers with renal function in Korean lead workers

AIMS

To compare associations of lead biomarkers with renal function in current and former lead workers.

METHODS

Cross sectional analysis of first year results from a longitudinal study of 803 lead workers and 135 controls in South Korea. Clinical renal function was assessed by blood urea nitrogen (BUN), serum creatinine, and measured and calculated creatinine clearance. Urinary N-acetyl-beta-D-glucosaminidase (NAG) and retinol-binding protein were also measured.

RESULTS

Mean (SD) tibia lead, blood lead, and DMSA chelatable lead levels in lead workers were 37.2 (40.4) micro g/g bone mineral, 32.0 (15.0) micro g/dl, and 767.8 (862.1) micro g/g creatinine, respectively. Higher lead measures were associated with worse renal function in 16/42 models. When influential outliers were removed, higher lead measures remained associated with worse renal function in nine models. An additional five associations were in the opposite direction. Effect modification by age was observed. In 3/16 models, associations between higher lead measures and worse clinical renal function in participants in the oldest age tertile were significantly different from associations in those in the youngest age tertile which were in the opposite direction. Mean urinary cadmium (CdU) was 1.1 micro g/g creatinine (n = 191). Higher CdU levels were associated with higher NAG.

CONCLUSIONS

These data suggest that lead has an adverse effect on renal function in the moderate dose range, particularly in older workers. Associations between higher lead measures and lower BUN and serum creatinine and higher creatinine clearances may represent lead induced hyperfiltration. Environmental cadmium may also have an adverse renal impact, at least on NAG.

Blood lead and chronic kidney disease in the general United States population: results from NHANES III

BACKGROUND

High lead exposure is associated with hypertension and renal dysfunction but the effect of low-level environmental exposure is not as well studied.

METHODS

We examined the association between blood lead and renal function among a representative sample of the civilian noninstitutionalized United States population with and without hypertension, age 20 years old or older, participating in the Third National Health and Nutrition Examination Survey (NHANES III) (N=15211). Elevated serum creatinine was defined as >or=99th percentile of each race-sex specific distribution for healthy young adults and chronic kidney disease (CKD) as a glomerular filtration rate (GFR) <60 mL/min estimated using the Modification of Diet in Renal Disease (MDRD) formula.

RESULTS

Among persons with and without hypertension, mean blood lead was 4.21 and 3.30 ug/dL, respectively, the prevalence of elevated serum creatinine was 11.5% and 1.8%, respectively, and CKD was 10.0% and 1.1%, respectively. Among persons with hypertension, a graded association was present between higher quartile of blood lead and a higher odds ratio of both an elevated serum creatinine and CKD. Comparing the highest to lowest quartile of blood lead, the multivariate adjusted odds ratio (95% CI) of an elevated serum creatinine and CKD were 2.41 (1.46, 3.97) and 2.60 (1.52, 4.45), respectively. The analogous adjusted odds ratios (95% CI) among normotensives were 1.09 (0.53, 2.22) and 1.09 (0.41, 2.89), respectively. Associations were consistent when modeling lead as a continuous variable and in all subgroups except smokers.

CONCLUSION

In the United States population with hypertension, exposure to lead, even at low levels, is associated with CKD. Reduction of lead exposure may reduce the burden of CKD in the community.

Blood lead level is associated with elevated blood pressure in blacks

Chronic lead exposure has been associated with elevated blood pressure in epidemiological studies. It is not known whether the previously observed relation between blood lead and hypertension persists after significant reductions have been made in environmental lead contamination. We examined the relation between blood lead levels and blood pressure in a representative sample of 14 952 whites and blacks aged 18 years or older who participated in the Third National Health and Nutrition Examination Survey. Blood lead was measured by atomic absorption spectrophotometry and blood pressure by standard sphygmomanometry. Mean blood lead levels were significantly higher for black men and women (5.4 and 3.4 microg/dL, respectively) compared with white men and women (4.4 and 3.0 microg/dL, respectively). After multivariate adjustment for important covariables, each standard deviation higher blood lead (3.3 microg/dL) was associated with a 0.82 (95% confidence interval [CI], 0.19 to 1.44) mm Hg and a 1.55 (95% CI, 0.47 to 2.64) mm Hg higher systolic blood pressure among black men and women, respectively. In contrast, blood lead level was not associated with blood pressure among white men or women. The multivariate-adjusted odds ratio (95% CI) of hypertension associated with a 1-SD higher level of blood lead was 1.08 (95% CI, 0.99 to 1.19) for black men and 1.39 (95% CI, 1.21 to 1.61) for black women. These findings suggest that increased levels of blood lead remain an important environmental risk factor for elevated blood pressure in blacks.

Environmental lead exposure and progression of chronic renal diseases in patients without diabetes

BACKGROUND

Previous research suggests that environmental lead exposure correlates with age-related decreases in renal function.

METHODS

Two hundred two patients with chronic renal insufficiency (indicated by a serum creatinine level between 1.5 mg per deciliter and 3.9 mg per deciliter) who had a normal total-body lead burden and no history of exposure to lead were observed for 24 months. After the observation period, 64 subjects with an elevated body lead burden were randomly assigned to the chelation control groups. For three months, the patients in the chelation group received lead-chelation therapy with calcium disodium EDTA, and the control group received placebo. During the ensuing 24 months, repeated chelation therapy was administered weekly to 32 patients with high-normal body lead burdens (at least 80 microg but less than 600 microg) unless on repeated testing the body lead burden fell below 60 microg; the other 32 patients served as controls and received weekly placebo infusions for 5 weeks every 6 months. The primary end point was an increase in the serum creatinine level to 1.5 times the base-line value during the observation period. A secondary end point was the change in renal function during the intervention period.

RESULTS

The primary end point occurred in 24 patients during the observation period; the serum creatinine levels and body lead burden at base line were the most important risk factors. The glomerular filtration rate improved significantly by the end of the 27-month intervention period in patients receiving chelation therapy: the mean (+/-SD) change in the glomerular filtration rate in the patients in the chelation group was 2.1+/-5.7 ml per minute per 1.73 m2 of body-surface area, as compared with -6.0+/-5.8 ml per minute per 1.73 m2 of body-surface area in the controls (P<0.001). The rate of decline in the glomerular filtration rate in the chelation group was also lower than that in the controls during the 24-month period of repeated chelation therapy or placebo.

CONCLUSIONS

Low-level environmental lead exposure may accelerate progressive renal insufficiency in patients without diabetes who have chronic renal disease. Repeated chelation therapy may improve renal function and slow the progression of renal insufficiency.

Occupational risk factors for renal cell cancer: a case--control study in northern Italy

Relatively little is known about occupational and other risk factors for renal-cell carcinoma (RCC). Associations between RCC and occupations, exposures and other factors were investigated in a hospital-based case-control study in Bologna (central-northern Italy). Between 1986 and 1994, 324 histologically confirmed RCC cases were diagnosed at Policlinico S. Orsola-Malpighi in patients from the Province of Bologna. Corresponding control subjects admitted to the same hospital with any diagnosis except RCC were matched for sex, age, and residency. We studied the 249 cases and 238 controls for whom detailed information on occupational history, diet, smoking habits, alcohol and drug intake was obtained. At conditional logistic regression, among males (167 matched pairs), significant matched odds ratios (OR) were found, after adjusting for cigarette smoking and alcohol intake, for high body-mass index BMI (third quartile: OR, 4.91; confidence interval [95% CI], 1.56-15.5; last quartile: OR, 4.42; 95% CI, 1.48-13.18), railway workers (OR, 10.14; 95% CI, 1.46-70.17) and asbestos exposure (OR, 7.11; 95% CI, 1.46-34.51); nearly significant OR were found for managers (OR, 3.59; 95% CI, 0.82-15.59) and metal workers (OR, 2.21; 95% CI, 0.99-5.37). Among females (52 pairs), significant OR were found for BMI > 25.4 (OR, 8.46; 95% CI, 1.02-68.0). Railway workers (on or near to trains) may have increased risk of developing RCC, possibly due to asbestos exposure. Studies are required on possible risks encountered by railway (and metal) workers and by managers.

Environmental lead exposure and urate excretion in the general population

PURPOSE

Chronic occupational exposure to lead is related to low urate excretion and a high incidence of gout in lead workers. However, whether chronic low-level environmental lead exposure influences urate excretion in the general population remains unknown.

SUBJECTS AND METHODS

We studied 111 healthy subjects with normal renal function (serum creatinine level < or =1.4 mg/dL) and no previous lead exposure or systemic diseases. All subjects had their blood lead levels measured, received ethylenediaminetetraacetic acid mobilization tests to assess their body lead burdens, and were investigated for renal function and urate excretion to assess the relation between lead and urate excretion. We studied urate excretion before and after lead chelation therapy in 24 subjects with high-normal body lead burden (>78 mg and <600 mg).

RESULTS

Healthy subjects with gout (n = 27) manifested a higher body lead burden (84 +/- 42 mg vs. 45 +/- 30 mg, P <0.0001) and lower urate clearance (3.7 +/- 1.2 mL/min/1.73 m(2) vs. 6.0 +/- 2.8 mL/min/1.73 m(2), P <0.0001) than did those without gout (n = 84). Blood lead levels and body lead burden of all subjects were within the safe range. In analyses that adjusted for age, sex, body mass index, protein intake, and creatinine clearance, blood lead level was significantly related to serum urate level (beta coefficient [+/- SE] = 0.23 +/- 0.11, P = 0.03), and body lead burdens were related to all indices of urate excretion (serum urate: beta coefficient = 0.023 +/- 0.005, P <0.0001; daily urate excretion: beta coefficient = -1.55 +/- 0.40, P = 0.0002; urate clearance: beta coefficient = -0.030 +/- 0.006, P <0.0001; fractional urate excretion: beta coefficient= -0.034 +/- 0.006, P <0.0001). Following lead chelation therapy, urate clearance increased after body lead burden was reduced (3.4 +/- 1.2 mL/min/1.73 m(2) vs. 4.9 +/- 1.4 mL/min/1.73 m(2), P <0.005).

CONCLUSION

Chronic low-level environmental lead exposure may inhibit urate excretion in the general population, and lead chelation therapy reduces this inhibition. These findings support efforts to reduce sources of environmental lead exposure and suggest alternative approaches to hyperuricemia and gout in the general population.

Lead-related gout. A case report

Gout secondary to lead-induced nephropathy is a long-term complication of occupational lead exposure. We report a case of this now-rare condition. The patient was a 63-year-old man who had been a miner from 1950 to 1970. Thirty years after cessation of his exposure to lead, he experienced onset of inflammatory symmetric polyarthritis with joint deformities. Hyperuricemia, moderately severe renal failure, and tubular acidosis were found, indicating gouty polyarthritis. Blood lead levels were high, establishing that the cause was lead poisoning. EDTA chelation therapy was effective. Lead poisoning is frequently under-recognized because the clinical manifestations are often minimal and the diagnosis difficult to establish. We suggest that lead bound to bone may result in continued exposure to lead after cessation of industrial or environmental exposure. Chelating agents are valuable for the diagnosis and can ensure a full recovery.

Associations of blood lead, dimercaptosuccinic acid-chelatable lead, and tibia lead with neurobehavioral test scores in South Korean lead workers

The authors performed a cross-sectional study to evaluate associations between blood lead, tibia lead, and dimercaptosuccinic acid (DMSA)-chelatable lead and measures of neurobehavioral and peripheral nervous system function among 803 lead-exposed workers and 135 unexposed controls in South Korea. The workers and controls were enrolled in the study between October 1997 and August 1999. Central nervous system function was assessed with a modified version of the World Health Organization Neurobehavioral Core Test Battery. Peripheral nervous system function was assessed by measuring pinch and grip strength and peripheral vibration thresholds. After adjustment for covariates, the signs of the beta coefficients for blood lead were negative for 16 of the 19 tests and blood lead was a significant predictor of worse performance on eight tests. On average, for the eight tests that were significantly associated with blood lead levels, an increase in blood lead of 5 microg/dl was equivalent to an increase of 1.05 years in age. In contrast, after adjustment for covariates, tibia lead level was not associated with neurobehavioral test scores. Associations with DMSA-chelatable lead were similar to those for blood lead. In these currently exposed workers, blood lead was a better predictor of neurobehavioral performance than was tibia or DMSA-chelatable lead, mainly in the domains of executive abilities, manual dexterity, and peripheral motor strength.

Lead nitrate induced apoptosis in alveolar macrophages from rat lung

In this work we have attempted to characterize the programmed cell death (apoptosis) in alveolar macrophages exposed to various concentrations of lead nitrate. It was found that after 3 h of exposure a significant increase in superoxide anion production was observed, i.e. the number of trypan blue - exculding cells, was unchanged (< or = 95%) with any dose of lead employed. Agarose gel electrophoresis and diphenylamin reaction analysis revealed the occurrence of internucleosomal DNA fragmentation evaluated using cytological analysis by fluorescence dyes, suggesting that lead nitrate at low concentrations and short periods of exposure leads macrophages into apoptosis. However, time course studies showed that beyond 3 h, toxicity occurs, which could be attenuated by phosphodiesterase inhibitors, such as caffeine, suggesting a possible mechanism involving cAMP.

Health risk assessment of long-term exposure to non-genotoxic chemicals: application of biological indices

For chemical pollutants, health risk assessment of long-term exposure is usually best realized through an epidemiologic approach which attempts to link cumulative levels of exposure to the potential for occurrence of early adverse effects. For some chemicals, however, the frequency of peak exposures may be more relevant for assessing the health risk than the integrated dose. In very few circumstances, biological exposure indices directly reflect the cumulative dose (e.g. PCB in blood). More frequently they are indicators of short-term interval dose but provided they have been measured with a sufficient frequency, their integration over the duration of exposure may represent a valid surrogate of the cumulative dose. This has been clearly demonstrated for lead or cadmium in blood. The selection of the appropriate biological effect markers for the study of the dose-effect/dose-response relationships is frequently a controversial issue when information on the mechanism of action of the pollutant is insufficient. In this case, the study of the health significance of the observed biological changes may be required for assessing a meaningful no-adverse-effect level. For example, in adult male workers moderate exposure to lead may affect the synthesis of vasodilatory prostaglandins in the kidney but presently there is no indication that this effect should be taken into account to define the acceptable occupational exposure level to lead because it is not associated with an impairment of the hemodynamic response of the kidney to an acute protein load. On the contrary, a low-molecular-weight proteinuria induced by cadmium may be predictive of an increased age-related decline of the glomerular filtration rate. Although the use of early biological effect markers for the study of the dose-effect or dose-response relationships in humans is probably less affected by selection biases than morbidity data, the possibility of such an interference cannot be excluded. For example, in the general population, the tubulotoxic effects of cadmium may occur at a lower body burden of the metal than in adult male workers. Whatever the adverse biological effect considered, the application of an uncertainty factor remains justified when extrapolating a no-effect level from adult male workers to the general population.

The link between hypertension and nephrosclerosis

Nephrosclerosis is literally defined as hardening of the kidneys (Greek derivation: nephros, kidney; sklerosis, hardening). It is the result of scarring or replacement of the normal renal parenchyma by dense collagenous tissue. In practice, nephrosclerosis refers to diseases with predominant pathologic changes occurring in the preglomerular microvasculature and secondarily involving the glomeruli and interstitium. The relationship between mild to moderate hypertension and either nephrosclerosis or end-stage renal disease (ESRD) remains circumstantial, although these syndromes have long been associated in the medical literature. Nephrologists credit hypertension as the etiology of nephrosclerosis in 25% of patients initiating Medicare-supported renal replacement therapy, even though other processes may cause similar renal pathologic findings. Strikingly, serum creatinine values infrequently increase in patients with long-standing mild to moderate hypertension. Patients classified as having hypertensive ESRD typically present with advanced disease, making the processes that initiated the renal disease difficult to detect. Nephrologists are twice as likely to label an African-American patient as having hypertensive nephrosclerosis, compared with a white patient, when presented with identical clinical histories. This review proposes that many patients classified as having hypertensive nephrosclerosis actually have intrinsic renal parenchymal diseases, renal artery stenosis, unrecognized episodes of accelerated hypertension, or a primary renal microvascular disease. The familial clustering of ESRD attributed to hypertension in African-Americans and the identification of genes associated with renal injury in animals support the concept that inherited factors may predispose to renal failure. African-American families often have members with ESRD from disparate etiologies, including hypertensive ESRD. This suggests that common mechanisms, be they inherited or environmental, underlie the development of progressive renal failure in diverse forms of nephropathy. Identification of the mechanisms producing susceptibility to progressive renal disease would support the concept that mild to moderate elevations in blood pressure per se are uncommon causes of nephrosclerosis.