Pornchai Sithisarankul

DNA adducts in urothelial cells: Relationship with biomarkers of exposure to arylamines and polycyclic aromatic hydrocarbons from tobacco smoke

Markers of exposure to polycyclic aromatic hydrocarbons (urinary 1‐hydroxypyrene‐glucuronide) and aromatic amines (4‐aminobiphenyl‐hemoglobin adducts), as well as urinary mutagenicity, were measured in 47 healthy smokers and 50 non‐smokers. DNA adducts were determined by P32‐postlabeling in the exfoliated bladder cells of 39 healthy subjects. Both 1‐hydroxypyrene‐glucuronide (1‐OHPG) and 4‐aminobiphenyl adducts (4‐ABP‐Hb) were associated with smoking habits, but only 4‐ABP‐Hb adducts were associated with consumption of black, air‐cured tobacco. The levels of 2 DNA adducts (numbers 2 and 4) in urothelial cells were clearly associated with 4‐ABP‐Hb adducts, in all subjects and in smokers. Levels of one of these DNA adducts (number 2) were also associated with 1‐hydroxypyrene‐glucuronide in urines, but in smokers the association was not statistically significant. Overall, these observations constitute further evidence of a role of arylamines in tobacco‐induced bladder cancer.

delta-Aminolevulinic acid dehydratase genotype modifies four hour urinary lead excretion after oral administration of dimercaptosuccinic acid.

OBJECTIVES: Previous research suggests that binding of lead by delta-aminolevulinic acid dehydratase (ALAD) may vary by ALAD genotype. This hypothesis was tested by examining whether ALAD genotype modifies urinary lead excretion (DMSA chelatable lead) after oral administration of dimercaptosuccinic acid (DMSA). METHODS: 57 South Korean lead battery manufacturing workers were given 5 mg/kg oral DMSA and urine was collected for four hours. Male workers were randomly selected from two ALAD genotype strata (ALAD1-1, ALAD1-2) from among all current workers in the two plants (n = 290). Subjects with ALAD1-1 (n = 38) were frequency matched with subjects with ALAD1-2 (n = 19) on duration of employment in the lead industry. Blood lead, zinc protoporphyrin, and plasma aminolevulinic acid concentrations, as well as ALAD genotype, duration of exposure, current tobacco use, and weight were examined as predictors or effect modifiers of levels of DMSA chelatable lead. RESULTS: Blood lead concentrations ranged from 11 to 53 micrograms/dl, with a mean (SD) of 25.4 (10.2) micrograms/dl. After 5 mg/kg DMSA orally, the workers excreted a mean (SD) 85.4 (45.0) micrograms lead during a four hour urine collection (range 16.5-184.1 micrograms). After controlling for blood lead concentrations, duration of exposure, current tobacco use, and body weight, subjects with ALAD1-2 excreted, on average, 24 micrograms less lead during the four hour urine collection than did subjects with ALAD1-1 (P = 0.05). ALAD genotype seemed to modify the relation between plasma delta-aminolevulinic acid (ALA) and DMSA chelatable lead. Workers with ALAD1-2 excreted more lead, after being given DMSA, with increasing plasma ALA than did workers with ALAD1-1 (P value for interaction = 0.01). CONCLUSIONS: DMSA chelatable lead may partly reflect the stores of bioavailable lead, and the current data indicate that subjects with ALAD1-2 have lower stores than those with ALAD1-1. These data provide further evidence that the ALAD genotype modifies the toxicokinetics of lead-for example, by differential binding of current lead stores or by differences in long-term retention and deposition of lead.

Aminolevulinic acid dehydratase genotype mediates plasma levels of the neurotoxin, 5-aminolevulinic acid, in lead-exposed workers.

The first intermediate substrate in the heme synthetic pathway, 5-aminolevulinic acid (ALA), is neurotoxic in animal models and may be responsible for some of the adverse neurologic outcomes in lead poisoning and porphyria in adult humans. ALA is a substrate for the enzyme aminolevulinic acid dehydratase (ALAD; EC 4.2.1.24), which is encoded by the ALAD gene containing 2 co-dominant alleles, 1 and 2. We measured plasma ALA (ALAP) and urinary ALA (ALAU) in 65 Korean lead workers, of whom 44 were homozygous for ALADI (ALAD1-1 genotype) and 21 were heterozygous for ALAD (ALAD1-2 genotype). ALAP in subjects with the ALAD1-1 genotype was significantly higher than in those with the ALAD1-2 genotype (Wilcoxon rank sum test, P = 0.01). No difference between ALAD genotypes was found for age, zinc protoporphyrin (ZPP), blood lead levels (PbB), ALAU, or ALAU adjusted for creatinine. ALAP was significantly correlated with ZPP (Spearmans r = 0.38, P = 0.002) and with PbB (r = 0.34, P = 0.006), and marginally with employment duration (r = 0.22, P = 0.08). ALAP remained significantly elevated (P = 0.032) in ALAD1-1 subjects after adjustment for PbB and age by multiple linear regression. These results suggest that ALAD1-1 subjects respond differently and may be more susceptible than ALAD1-2 subjects to the ALA-mediated neurotoxic effects of lead.

Age, gender, and other predictors of the wasting syndrome among HIV-1-infected injecting drug users.

We conducted a study to identify predictors of the wasting syndrome among human immunodeficiency virus 1 (HIV-1)-seropositive injecting drug users. We enrolled 113 cases (defined as an unexplained loss of > 10% baseline weight) and 226 controls (defined as < 5% weight loss or any weight gain) from a HIV-1-seropositive cohort of injecting drug users (N = 630) into a nested case-control study. Crude predictors of wasting included: older age [odds ratio (OR) for a 1-year difference = 1.06], female gender (OR = 1.66), more years spent injecting drugs (OR for 1-year difference = 1.05), presence of diarrhea (OR = 3.78), lower percentage of CD4 T-lymphocytes (OR for 10-unit difference = 0.73), and higher log beta 2-microglobulin concentration (OR for 1 log difference = 11.3). After adjusting for CD4 cell level, beta 2-microglobulin concentration, diarrhea, gender, length and frequency of drug use, age, the presence of thrush, and education, independent predictors of weight loss in HIV-seropositive injecting drug users were female gender (OR = 2.23) and increasing age (OR for 1-year difference = 1.06). Frequency and duration of drug use were not strongly associated with the odds of developing wasting syndrome in this HIV-1-seropositive cohort. These data indicate that HIV wasting syndrome in injecting drug users is distinct from complications of drug use.

Urinary 5-aminolevulinic acid (ALA) adjusted by creatinine : A surrogate for plasma ALA?

5-Aminolevulinic acid (ALA) is the first intermediate substrate in the heme synthetic pathway and is the substrate of aminolevulinic acid dehydratase (ALAD, porphobilinogen synthase). Because lead effectively inhibits ALAD activity, resulting in accumulation of ALA in urine and blood, urinary ALA (ALAU) has been used as a biomarker for lead exposure or early biologic effect of lead. Intraindividual variation in urinary excretion of ALA requires the use of 24-hour urine samples or adjustment of single urine samples by other normalizing variables, such as urinary creatinine concentration. Previous studies of ALAU concentration have used various adjustment methods; however, few have compared creatinine-adjusted ALAU concentration with ALA concentration in plasma (ALAP) from subjects with low (< 30 micrograms/dL) to moderate (< 60 micrograms/dL) levels of blood lead. To determine if creatinine-adjusted ALAU is associated with ALAP, we measured ALAU, ALAP, and urinary creatinine in 65 Korean lead workers with blood lead concentrations in the range of 14-60 micrograms/dL. ALAU, ALAU/creatinine, or ALAU/log creatinine all correlated with ALAP. However, ALAU/creatinine correlated more closely with ALAP based on Spearmans r (rs = 0.40, P, = 0.0009), supporting the use of ALA/creatinine in single urine samples as a surrogate for ALAP.