effect of glutathione on the cadmium chelation

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the compounds to other organs and exacerbating the

toxicity.5 However, many investigators have reported

animal studies that demonstrate a possible protective

role of antioxidants, especially sulfhydryl amino acids,

on cadmium intoxication.6-9 Although the exact

mechanism is poorly understood, it is known that

cadmium exerts at least some of its toxic effectsvia the binding of sulfhydryl groups, subsequent

denaturing of proteins and/or inactivation of enzymes.10

Sulfhydryl group amino acids have antioxidant

affects themselves and their sulfhydryl base may

compete to bind cadmium with other tissue proteins.10

Glutathione is a tripeptide ofg-glutamylcysteinyl-

glycine, available for intravenous administration. In

our previous study,11 we reported that intravenous

administration of glutathione increased not only

cysteine levels but also the pool of sulfhydryl group

amino acids (sum of cysteine, cystine, and methio-nine). Therefore, we hypothesized that cadmium

chelation should be safer and more effective when the

chelating agent is administered with glutathione.In order to support this hypothesis, we measured

the blood cadmium level, renal excretion of cadmium,

a proximal tubule injury marker (b2-microglobulin),

and glomerular injury markers (proteinuria, hema-

turia), during intravenous administration of Ca-

EDTA with and without glutathione in a patient with

chronic cadmium intoxication.

Material and method

Case report

A 54-year-old male presented to the toxicology clinic

at Soonchunhyang Cheonan hospital on 4 October

2008. The chief complaint was generalized bone pain,

worse at night and relieved during the day time

especially by walking. The history was significant for

the patient working at a factory producing compres-

sors for air conditioners over the past 24 years (from

1977.3 to 2001.5). In May 2001, abnormally high

blood levels of cadmium were noted during a regularscreening test by a doctor employed by the industry to

monitor workers. The patient reported that, at that

time, he had intractable bone pain, insomnia, and

general weakness. The patient was then immediately

entered into a program for the treatment of cadmium

intoxication, and he no longer worked at the factory.

During the first visit to the outpatient toxicology

clinic, the patient was exhausted, looked chronically-

ill and very thin, with a body weight of 49.5 kg and a

height of 172 cm. The blood pressure was 100/60

mm Hg, with a weak pulse pressure (60/min), and the

respiratory rate was 20/min. The results of the routine

blood chemistry, CBC, and urinalysis are summarized

in Table 1.

Experimental treatmentIn an attempt to provide new aggressive treatment, we

designed a protocol for Ca-EDTA chelation with

glutathione. With the patients consent, we adminis-

tered 500 mg of Ca-EDTA and 50 mg/kg of

glutathione alone or together in 1 L of normal saline

over 24 hours using a drop factor and repeated the

treatment for 12 consecutive days. The first 3 days

were used for the determination of basal levels (only

saline administration, basal group); the second 3 days

for Ca-EDTA only (EDTA group), the third 3 days

for Ca-EDTA with glutathione (EDTA with

glutathione group), and the last 3 days for glutathione

only (glutathione group). Blood samples and 24-hour

urine were obtained everyday to measure creatinine,

cadmium, and b2-microglobulin levels. One month

later, the same protocol was repeated and six blood

and urine samples obtained for each group (Figure 1).

Assay

The cadmium levels were measured by a flameless

atomic Absorption Spectrophotometer (AAS 800

Perkin-Elmer, Germany). b2-microglobulin was

measured by the radioimmune assay method (SPAC-S

b2-microglobulin micro kit, Daiichi Co., Japan).

Statistics

The data is presented as mean + standard deviation.

The parameters were compared with the Kruskal-

Wallis test among groups and ap < 0.05 was considered

significant.

Results

The blood cadmium level was higher when EDTAwas infused together with glutathione (7.44 + 0.73

mg/L, p < 0.01, Mann-Whitney U) compared to the

basal level of 4.6 + 0.44 mg/L (Figure 2). However,

there was no significant difference between the basal

level and the glutathione alone (5.55 + 0.90 mg/L) or

the EDTA alone (5.53 + 1.03 mg/L; Figure 2). The

basal renal cadmium excretion was 23.4 + 15.81

mg/g creatinine. It increased to 89.23 + 58.52 mg/g

creatinine (p < 0.01) when EDTA was given with glu-

tathione. The renal cadmium excretion was 9.87 +

80 Human and Experimental Toxicology 30(1)


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3.02 mg/g creatinine for glutathione alone, and 20.52

+ 12.42 mg/g creatinine for EDTA alone (Figure 3).

The protein/creatinine ratio in the urine was 109.39

+ 17.29 mg/g in the basal state, 117.43 + 14.17mg/g with glutathione and calcium EDTA adminis-

tration, 117.44 + 28.67 mg/g for EDTA administra-

tion alone, and 108.81 + 13.95 mg/g for

glutathione alone (p > 0.05, Kruskal-Wallis analysis).

The b2-microglobulin/creatinine ratio in the urine

was 3378.48 + 1814.20 ng/mg in the basal state,

5674.94 + 2600.93 ng/mg for glutathione with cal-

cium EDTA administration, 4767.45 + 1359.81 ng/mg for glutathione administration alone, and

7178.45 + 2359.81 ng/mg for EDTA alone (p >

0.05, Kruskal-Wallis analysis). There was no signifi-

cant change in the serum creatinine levels. In addition,

Table 1. Laboratory findings at the beginning and 6 months after chelation therapy

Basal Before 2nd session After 6 months

CBCWBC (/UL) 10,870 10,020 10,130Hemoglobulin 13.2 13.5 13.8

Hematocrit 39.5 40.1 42Platelet 225,000 237,000 247,000Blood chemistry

Albumin (g/dL) 4.5 4.4 4.2Glucose (mg/dL) 116 121 132Total bilirubin (mg/dL) 0.3 0.4 0.3AST(IU/L) 16 17 17ALT(IU/L) 26 22 14BUN (mg/dL) 25 14.6 12.3Creatinine (mg/dL) 0.9 0.9 0.9Calcium (mg/dL) 9.3 9.2 9.1Phosphate (mg/dL) 3.5 3.8 2.9

Urine analysis

Specific gravity 1.026 1.020 1.012pH 6.0 6.0 7.0Protein - - -RBC (/HPF) 1-4 1-4 1-4WBC (/HPF)


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microhematuria and proteinuria did not develop over

the6-month observation period (Table1). The asparate

aminotransferase (ALT) and blood urea nitrogen

(BUN) decreased after 6months, which meant the

safety of this protocol. The results of each session were

shown in Table 2.

Discussion

There are many patients with chronic cadmium intox-

ication worldwide that have renal disease, chronic

lung disease, and intractable bone pain. The severity

of the bone pain can be extreme. Due to the significant

discomfort of patients clinical toxicologists have been

investigating new effective treatment modalities that

are not only safe, but also reduce the risk for exacer-

bating end-organ toxicity, in patients with chronic

cadmium intoxication.

Chelation has notbeen recommended fora number of

reasons. First, there is no evidence that chelation in

chronically poisoned animals is associated with long-

term improvement.5

Second, most of the cadmium inchronically exposed patients is bound to intracellular

metallothionein, which greatly reduces its toxicity. Any

attempt to remove cadmium from these deposits risks

redistributing the cadmium to other organs.12 Finally,

many of the common chelating agents might not be

effective for removing significant amounts of cadmium.

The results of the present study showed that both the

blood cadmium levels (Figure 1) and amount of renal

excretion of cadmium (Figure 2) were significantly

higher when EDTA was administered with glutathione

compared to EDTA given alone. Therefore, glutathione

appears to assist the chelating activity of EDTA for cad-

mium deposits.Subsequent EDTAand glutathione ther-

apy has not been effective in our study. The preceding

glutathione with calciumEDTA application might have

mobilized most of the available cadmium.

We cannot explain the precise mechanism underly-ing this synergy. However, the sulfhydryl base of

glutathione may compete to bind cadmium with other

tissue proteins. Based on our preliminary study11

showing 50 mg/kg of glutathione to be safe and to

increase the SH containing amino acid (cysteine,

cystine, and methionine) levels for longer than 6

hours, this might be a useful clinical dose. However,

further study is necessary to determine the optimum

dose of glutathione for cadmium chelation in patients

with chronic cadmium intoxication.

There was no significant change in the serumcreatinine levels. In addition, microhematuria and pro-

teinuria did not develop over the 6-month observation

period (Figure 3). Taken together, no difference in the

b2-microglobulin/creatinine ratio in urine for this

chelation procedure suggests that glutathione could

diminish the nephrotoxic effect of EDTA. However,

it is not clear whether repeated chelation procedures

over long treatment duration would cause renal injury.

The final assessment of the clinical outcome should

be based on the degree of pain relief provided to the

patient; this is the most serious complaint of patients

with chronic cadmium intoxication. Although we didnot use objective measures of pain, 6 months after our

current chelation trial the patient still reported similar

levels of pain compared to before the chelation trial.

Figure 2. Comparison of serum cadmium concentration

among groups. *p < 0.01 Mann-Whitney test.

Figure 3. Comparison of urine cadmium concentrationamong groups. p < 0.01 Kruskal-Wallis analysis.

82 Human and Experimental Toxicology 30(1)


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However, the patient was comforted by the fact that

the cadmium was being eliminated from his body.

In conclusion, our results suggest that glutathione

administration with EDTA might provide a safe and

effective chelation treatment modality for patients

with cadmium intoxication.

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van den Hazel P, Stilianakis N, et al. Cadmium and

children: exposure and health effects. Acta Paediatr

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Environmental cadmium exposure, adverse effects and

preventive measures in Japan. Biometals 2004; 17:

581-587.

3. Jin T, Kong Q, Ye T, Wu X, Nordberg GF. Renal

dysfunction of cadmium-exposed workers residing in a

cadmium-polluted environment. Biometals 2004; 17:513-518.

4. Blainey JD, Adams RG, Brewer DB, Harvey TC.

Cadmium-induced osteomalacia. Br J Ind Med 1980;

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5. Goldfrank LR, Flomenbaum NE, Lewin NA, Howland

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emergency. 7th ed. McGraw Hill, NY USA, 2002:

p.1254-1259.

6. Sinha M, Manna P, Sil PC. Taurine protects the

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Table 2. The results of each session (mean)

1st session 2nd session

EDTA withglutathione Glutathione EDTA

EDTA withglutathione Glutathione EDTA

Serum cadmium (m

g/L) 7.45 5.7 5.65 7.43 5.40 5.40Urine cadmium (mg/g creatinine) 88.28 17.11 8.75 90.17 19.82 10.98Urine b2-microglobulin (ng/mg creatinine) 6353.94 6514.65 5422.95 5594.88 6856.28 5681.31Urine protein (mg/g creatinine) 123.93 133.18 103.62 110.94 93.84 115.99

G Hyo-wook et al. 83


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effect of glutathione on the cadmium chelation

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