The safety of the EDTA lead-mobilization test

Pb exposure triggers MAPK-dependent inflammation by activating oxidative stress and miRNA-155 expression in carp head kidney

Lead (Pb) is a toxic heavy metal and an aquatic pollutant. Various amounts of heavy metals are released into the environment through industrial discharge, causing excessive contamination of aquatic ecosystems. The head kidney is a unique immune organ of the bony fish and plays an important role in the metabolism of heavy metals. Studies of toxic Pb exposure that have investigated the head kidney of carp are limited. This study was carried out to explore the potential immunotoxicity effects of Pb and the specific related mechanisms in the carp head kidney. Pb poisoning was shown to induce the production of reactive oxygen species (ROS) and increase the expression levels of phosphorylated proteins related to the MAPK pathway, including p38, extracellular signal-regulated protein kinase (ERK), and c-Jun N-terminal kinase (JNK). We also found that microRNA-155 played a key role in regulating the production of inflammatory factors TNF-α, IL-1β, and IL-6, and the pre-miRNA-155 inhibitor reversed the Pb-induced inflammation. In conclusion, these in vitro and in vivo findings suggest that oxidative stress and the MAPKs are involved in the Pb-induced inflammasome response, and the production of microRNA-155 aggravated the occurrence of inflammation in carp head kidney.

A comparative study of edetate calcium disodium and dimercaptosuccinic acid in the treatment of lead poisoning in adults

BACKGROUND

We evaluated the efficacy of two antidotes, edetate calcium disodium (CaNa₂EDTA) and dimercaptosuccinic acid (DMSA), for the treatment of lead poisoning in adults.

METHODS

Thirty-seven patients with blood lead concentrations >40 μg/dL and positive CaNa₂EDTA lead mobilization were randomized to receive 1050 mg/m²/day of oral DMSA (n = 21) or 500 mg/m²/day of intravenous CaNa₂EDTA (n = 16) over two five-day courses separated by a 10-day rest period. Efficacy of treatment was evaluated by blood lead assays on the first day of the two courses and 14 days after the end of treatment and baseline CaNa₂EDTA lead mobilization test and 14 days after the end of treatment.

RESULTS AND CONCLUSION

Both treatments significantly reduced the prevalence of clinical symptoms, blood lead levels and CaNa₂EDTA lead mobilization and were well tolerated. DMSA had a greater impact on reducing blood lead concentrations (p = .005) and CaNa₂EDTA on lead mobilization (p = .04). Comparison of equimolar doses showed that CaNa₂EDTA was more effective than DMSA (p < .001).

Lead Nephropathy: Revisiting an Overlooked Cause of Kidney Disease

Despite the recognition of lead nephropathy as a consequence of environmental and occupational lead exposure, lead nephropathy still appears to be underrecognized by physicians as a cause and promoter of chronic kidney disease (CKD), especially in people with more apparent causative factors such as diabetes and hypertension. This review focuses on the clinical, pathophysiological and epidemiological perspectives of lead nephropathy with the objective of promoting the awareness of this important but overlooked cause of CKD among physicians. Literature was reviewed using available medical journals and online literature search through Google, Pubmed, Medline, Medscape and HINARI databases. The key words employed were: Lead Nephropathy, Environmental and Occupational lead exposure and chronic kidney disease. Lead nephropathy which is a tubulointerstitial nephritis, may present acutely or chronically in association with hypertension. The clinical diagnosis of lead nephropathy is complex, because the symptoms are varied and non-specific especially with subclinical nephrotoxicity. The recognition of lead nephropathy can be enhanced if physicians have a high index of suspicion in the assessment of patients with renal disease. It is recommended that the evaluation of environmental and occupational nephrotoxins like lead be incorporated into programs for the prevention of CKD, especially in developing countries where lead exposure and toxicity still remain largely unchecked and the prevalence and burden of CKD is increasing.

Effect of chelation therapy on progressive diabetic nephropathy in patients with type 2 diabetes and high-normal body lead burdens

BACKGROUND

A previous study in type 2 diabetic patients with high-normal body lead burdens showed that EDTA chelation therapy for 3 months slows progressive diabetic nephropathy during a 12-month follow-up. The effect of a longer course of therapy on kidney function decrease over a longer follow-up is not known.

STUDY DESIGN

A 12-month run-in phase, then a randomized single-blind study with a 27-month intervention.

SETTING & PARTICIPANTS

University medical center; 50 patients (serum creatinine, 1.5-3.9 mg/dL) with high-normal body lead burden (≥80-<600 μg) were randomly assigned to the treatment and control groups.

INTERVENTION

The treatment group received weekly chelation therapy for 3 months to reduce their body lead burden to <60 μg and then as needed for 24 months to maintain this level. The control group received placebo for 3 months and then weekly for 5 weeks at 6-month intervals for 24 months.

OUTCOMES

The primary end point was change in estimated glomerular filtration rate (eGFR) over time. A secondary end point was a 2-fold increase in baseline serum creatinine level or the requirement for renal replacement therapy.

MEASUREMENTS

Body lead burdens were assessed by EDTA mobilization tests and eGFR was calculated using the equation for Chinese patients with type 2 diabetes.

RESULTS

Mean baseline eGFRs in the treatment and control groups were similar. After 3 months of chelation therapy, the change in eGFR in the treatment group (+1.0 ± 4.8 mL/min/1.73 m(2)) differed significantly from that in the control group (-1.5 ± 4.8 mL/min/1.73 m(2); P = 0.04). In the subsequent 24-month intervention, the yearly rate of decrease in eGFR (5.6 ± 5.0 mL/min/1.73 m(2) per year) in the treatment group was slower than that (9.2 ± 3.6 mL/min/1.73 m(2) per year; P = 0.04) in the control group. 17 (68%) control-group patients and 9 (36%) treatment-group patients achieved the secondary end point.

LIMITATIONS

Small sample size, not double blind.

CONCLUSIONS

A 27-month course of EDTA chelation therapy retards the progression of diabetic nephropathy in type 2 diabetic patients with high-normal body lead burdens.

Lead-related nephrotoxicity: a review of the epidemiologic evidence

Chronic kidney disease (CKD) represents a major global public health concern. Efforts to prevent and/or slow progression of CKD are essential. Lead nephropathy, characterized by chronic tubulointerstitial nephritis, is a well-known risk of chronic, high-level lead exposure. However, in recent years, lead exposure has declined sharply, particularly in developed countries. We reviewed epidemiologic research in general, occupational, and patient populations to assess whether lead, at current exposure levels, still contributes to nephrotoxicity. Other pertinent topics, such as risk in children, genetic susceptibility, and co-exposure to cadmium, are also considered. The data reviewed indicate that lead contributes to nephrotoxicity, even at blood lead levels below 5 microg/dl. This is particularly true in susceptible populations, such as those with hypertension (HTN), diabetes, and/or CKD. Low socioeconomic status is a risk factor for both lead exposure and diseases that increase susceptibility. Future public health risk for lead-related nephrotoxicity may be most significant in those rapidly developing countries where risk factors for CKD, including obesity and secondary HTN and diabetes mellitus, are increasing more rapidly than lead exposure is declining. Global efforts to reduce lead exposure remain important. Research is also needed to determine whether specific therapies, such as chelation, are beneficial in susceptible populations.

Changes in brain biogenic amines and haem biosynthesis and their response to combined administration of succimers and Centella asiatica in lead poisoned rats

This study was designed to investigate the therapeutic potential of meso 2,3-dimercaptosuccinic acid (DMSA) and one of its monoesters, monoisoamyl DMSA (MiADMSA), individually or when administered in combination with an extract of Centella asiatica against experimental lead intoxication in rats. Biochemical variables indicative of alterations in the central nervous system and haem biosynthesis were investigated to determine the toxicity in male Wistar rats. Thirty five rats were exposed to 0.2% lead acetate for 10 weeks, followed by 10 days of treatment with DMSA and MiADMSA (50 mg kg(-1), i.p., once daily) alone and in combination with C. asiatica (200 mg kg(-1), p.o., once daily). Biochemical variables indicative of oxidative stress and brain biogenic amines, along with lead concentration in blood and brain, were measured. Lead exposure caused a significant depletion of blood and brain delta-aminolevulinic acid dehydratase (ALAD) activity, an important enzyme of the haem biosynthesis pathway, and glutathione (GSH) level. These changes were accompanied by a marked increase in reactive oxygen species (ROS) level, thiobarbituric acid reactive substances (TBARS), delta-aminolevulinic acid synthase (ALAS) and oxidized glutathione (GSSG) activity in blood and brain. Significant depletion of brain noradrenaline (norepinephrine, NE), 5-hydroxytryptamine (5-HT), dopamine (DA) and acetylcholinesterase (AChE) also were observed following lead exposure. Also seen was a significant depletion in brain glutathione peroxidase (GPx), glutathione S-transferase (GST) and monoamine oxidase activity, as well as blood and brain superoxide dismutase (SOD) activity. These biochemical changes were correlated with an increased uptake of lead in blood and brain. Combined administration of MiADMSA and C. asiatica was most effective in reducing these alterations, including biogenic amines, besides reducing body lead burden, compared with individual treatment with MiADMSA. Certain other biochemical variables responded favourably to combination therapy and monotherapy with MiADMSA. Thus, supplementation of C. asiatica during chelation could be recommended for achieving optimum effects of chelation therapy.

Deaths resulting from hypocalcemia after administration of edetate disodium: 2003-2005

From 2003 to 2005, deaths of 3 individuals as a result of cardiac arrest caused by hypocalcemia during chelation therapy were reported to the Centers for Disease Control and Prevention. Two were children, both of whom were treated with edetate disodium. At the time of this writing, the adult case was still under investigation. No previous cases of death resulting from hypocalcemia during chelation have been reported. From our experience and review of the literature, we suggest that health care providers who are unfamiliar with chelation consult an expert before undertaking treatment and that hospital formularies evaluate whether stocking edetate disodium is necessary, given the risk for hypocalcemia and the availability of less toxic alternatives.

Follow-up of patients affected by manganese-induced Parkinsonism after treatment with CaNa2EDTA

In the period of 1998-2004, seven workers affected by manganese-induced Parkinsonism were diagnosed, studied and treated with CaNa2EDTA at our Occupational Health Ward. Biological markers, as well as magnetic resonance imaging and clinical examinations, were used to assess the disease trend. Those workers still employed were immediately removed from exposure. Our results seem to confirm that very good clinical, biological and neuroradiological results can be obtained by timely removal from exposure and chelating treatment, and that amelioration can persist in time. Manganism is, however, a severe condition that can also progress independent of further exposure. Therefore, chelating treatment can be a great aid in overt manganism, but particular attention must be paid to primary prevention, as this disease should now be totally preventable and definitely merits eradication.

Beneficial role of monoesters of meso-2,3-dimercaptosuccinic acid in the mobilization of lead and recovery of tissue oxidative injury in rats

We investigated the therapeutic efficacy of meso-2,3-dimercaptosuccinic acid (DMSA) and two of its analogues, monomethyl dimercaptosuccinic acid (MmDMSA) and mono-cyclohexyl dimercaptosuccinic acid (MchDMSA) in reducing lead concentration in blood and soft tissues, and in recovering lead induced oxidative stress in rats. Male wistar rats were exposed to lead acetate in drinking water for 20 weeks, followed by 5 days of oral treatment with DMSA (100mg/kg, oral, once daily), MmDMSA or MchDMSA (50 and 100mg/kg). Biochemical variables indicative of oxidative stress along with lead, zinc and copper concentration were evaluated in blood and other soft tissues. Exposure to lead caused a significant decrease in blood delta-aminolevulinic acid dehydratase (ALAD) activity and glutathione (GSH) level. These changes were accompanied by inhibition of kidney ALAD and an increase in delta-aminolevulinic acid synthatase (ALAS) activity in liver and kidneys. Also seen were a pronounced depletion of brain GSH, glutathione peroxidase (GPx), glutathione-S-transferase (GST) and decreased superoxide dismutase (SOD) activity and an increase in thiobarbituric acid reactive substances (TBARS) and reactive oxygen species (ROS) levels. These biochemical changes were correlated with an increased uptake of lead in blood and soft tissues. Blood and kidneys zinc concentration decreased significantly following lead exposure while, copper concentration remained unchanged. No effect of chelation on hepatic zinc concentration was noted, only liver copper concentration showed significant depletion on treatment with DMSA and MmDMSA (100mg/kg). Treatment with DMSA, MmDMSA and MchDMSA provided significant recovery in altered biochemical variables and brain DNA damage besides significant depletion of tissue lead burden. Among the chelating agents used, MchDMSA and MmDMSA provided better recovery in altered biochemical variables and depletion of lead concentration in tissues compared to DMSA. The above results suggest DMSA monoesters to be a better treatment option than DMSA in eliciting recovery to the altered biochemical variables and in the depletion of body lead burden.

Lead-induced oxidative stress and hematological alterations and their response to combined administration of calcium disodium EDTA with a thiol chelator in rats

The therapeutic efficacy of calcium disodium ethylenediaminetetracetic acid (CaNa(2)EDTA) and the two thiol chelators, 2,3-dimercaptopropane 1-sulfonate (DMPS) and monoisoamyl dimercaptosuccinic acid (MiADMSA) was studied, both individually and in combination, in reducing lead concentration in blood and soft tissues and in restoring lead induced altered biochemical variables in rats. Exposure to subacute dose of lead implicated a critical role of reactive oxygen species (ROS) and oxidative stress in altering the normal values of these variables. Exposure to lead caused a significant inhibition of blood delta-aminolevulinic acid dehydratase (ALAD), an important enzyme in the haem synthesis pathway and glutathione (GSH) level. These changes were also accompanied by inhibition of ALAD activity in kidney, delta-aminolevulinic acid synthase (ALAS) activities in liver and changes in platelet counts in whole blood suggesting disturbed haem synthesis pathway. Lead exposure also led to a pronounced depletion of brain GSH contents, superoxide dismutase (SOD) activity, an increase in thiobarbituric acid reactive substances (TBARS), and activity of glutathione S-transferase (GST). Specific activities of membrane-bound enzymes, acetylcholinesterase (AChE) and monoamine oxidase (MAO), were significantly inhibited on lead exposure. These biochemical changes were correlated with increased uptake of lead in blood and soft tissues. Post lead exposure treatment with MiADMSA in particular provided significant recovery in altered biochemical variables besides significant depletion of tissue lead burden. Treatment with CaNa(2)EDTA and DMPS individually had only moderate beneficial effects on tissue oxidative stress, although they were equally effective in the removal of tissue lead burden. Tissue zinc and copper levels did not depict any significant depletion, although changes like marked depletion of zinc following CaNa(2)EDTA and copper after MiADMSA administration were of some concern. Combined administration of CaNa(2)EDTA, particularly with MiADMSA, was the most effective treatment protocol compared to all other treatments. It can be concluded from our present results that combined therapy with CaNa(2)EDTA and MiADMSA proved significantly better in restoring biochemical and clinical variables over monotherapy with these chelating agents against subacute lead exposure in adult rats.

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.

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.

Therapeutic efficacy of combined meso 2,3-dimercaptosuccinic acid and calcium disodium edetate treatment during acute lead intoxication in rats

1. The therapeutic ability of Ca disodium EDTA and meso 2,3-dimercaptosuccinic acid (DMSA) was studied, both individually and when given in combination, in reducing lead concentration in blood and other soft tissues, and in restoring lead induced altered biochemical variables in acute lead intoxicated rats. 2. Combined treatment with the above two chelating agents was more beneficial in reducing blood and hepatic lead compared to treatment with these drugs alone. Kidney lead concentration however, remained high following combined treatment, indicating the possibility of extra renal burden following treatment. 3. Lead sensitive biochemical variables also responded more favourably to combined treatment than treatment with these drugs alone. However, clinical biochemical indices indicate caution regarding the use of this new treatment regimen, and further investigation is required.

Lead nephropathy, gout, and hypertension

The EDTA (calcium disodium edetate) lead mobilization test revealed lead as the probable cause of renal disease in industrial lead workers and in patients with gout or essential hypertension. The data reviewed here demonstrate persistence of lead nephropathy in the contemporary scene despite the introduction of modern industrial and environmental exposure standards. Renal function and biopsy studies showed that lead nephropathy is a chronic tubulointerstitial renal disease with modest proteinuria which frequently presents with hyperuricemia, gout and hypertension. Only evaluation of body lead stores by either the EDTA lead mobilization test or by x-ray fluorescence is helpful in diagnosing lead nephropathy. While chelation therapy is safe and helpful in reversing early lead nephropathy, the best treatment is prevention. These studies further raise the possibility that chronic environmental lead poisoning and associated renal disease and hypertension may be a more widespread problem than suspected. Assessment of the true extent of chronic lead poisoning requires large scale epidemiological studies.

Whole bowel irrigation in an acute oral lead intoxication

An 89-year-old man acutely ingested approximately three ounces of a ceramic glaze preparation with a 30% lead oxide content. A blood lead level of 18 micrograms/mL was reported from a sample drawn within 1 hour of ingestion and just prior to gastric lavage. Following lavage, an abdominal radiograph demonstrated lead throughout the small intestine. Whole bowel irrigation was then undertaken and subsequent x-rays demonstrated clearing of all lead in the small bowel. At 16 and 24 hours post-ingestion, blood lead levels rose to 39 micrograms/dL and 42 micrograms/dL, respectively, and the patient then underwent a 5-day course of chelation therapy. This is the first reported case of the use of whole bowel irrigation in an acute lead ingestion. The use of decontamination techniques in acute lead ingestions is reviewed.

Environmental lead exposure and the kidney

Lead and its components remain widely distributed in the environment and in some workplaces. Lead serves no useful physiological function, yet is potentially toxic to several organ systems. For many years human health effects have been recognized after heavy lead exposure. Recently more subtle human effects have been suggested invoking nervous system, reproductive and kidney function. Assessing lead body burden and dose-response relationships of this metal by blood lead determination, porphyrin assessments, chelation testing or bone lead studies may be difficult. Quantitative assessment of subtle changes in kidney function by routine BUN, creatinine, or urinalysis also poses problems. There is now mounting evidence that chronic low level environmental lead exposure may subtly effect kidney function. This paper first examines the history of lead and kidney function and then examines critically the evidence associating low-level environmental lead exposure and effects on renal function.

Lead intoxication in paint removal workers on the Sydney Harbour Bridge

Lead intoxication is far more prevalent than is recognized by those persons who are exposed to lead fumes and dust in industry, as the early symptoms of intoxication are subtle and non-specific. The levels of lead in blood are a poor reflection of lead stores in the body and their potential toxicity, but are used frequently as the only test for screening of lead intoxication. Chelation of lead with calcium-EDTA is a more sensitive test to detect those persons who are at risk of toxicity. Industrial workers who are exposed regularly to lead must be screened on a periodic basis and a diagnosis of lead poisoning must be considered if substantial morbidity is to be avoided. We report six cases of men with significant lead intoxication who were employed on the Sydney Harbour Bridge, all of whom have benefited symptomatically from calcium-EDTA chelation therapy.

Lead intoxication

Lead intoxication was recognised as early as 2000 BC and the widespread use of lead has been a cause of endemic chronic plumbism in several societies throughout history. In the twentieth century, lead intoxication is still a common problem. In children it is largely due to ingestion of pica and environmental exposure, whereas adult groups at greatest risk are the industrially exposed: thus, screening of these workers should be undertaken at regular intervals. The clinical features of lead intoxication are nonspecific and often go unrecognised. The early manifestations are largely neuropsychiatric, followed by more significant disturbances of the central and peripheral nervous systems, symptomatic gastrointestinal, musculoskeletal, haematological and endocrine abnormalities. The association of lead poisoning with renal disease is well documented and must be considered, particularly if there is associated hypertension and/or gout. Blood lead concentrations are an unreliable predictor of body lead stores as they are indicative only of recent exposure. Haematological parameters have been used to assess those at risk of toxicity, but although more reliable than blood concentrations, they also fail to predict those patients at risk of toxicity. The recommended assessment for patients with suspected lead intoxication is a calcium disodium edetate chelation test, which is a sensitive marker for assessing body stores and subsequent intoxication. In children the dosage should be 50 mg/kg up to 1000 mg, and in adults 1000 mg administered intravenously or 2000 mg intramuscularly in divided doses 12 hours apart with subsequent 72 hour urinary lead estimations. Lead excretion levels greater than 350 micrograms/72 hours should be considered as suggestive of intoxication, particularly if supported by historical, clinical or biochemical evidence of lead exposure. Treatment of patients with positive chelation tests involves symptomatic treatment and a course of chelation therapy utilising calcium disodium edetate in doses similar to those used for testing, and in the more severely intoxicated patient, the addition of dimercaprol in doses of 75 mg/m2 every 4 hours to a total of 300 mg/m2/day. The safety of these treatment regimens is well documented.