Auto repair workers exposed to PM2.5 particulate matter in Barranquilla, Colombia: telomere length and hematological parameters

Exposure to 2.5 µm particulate matter (PM_2.5) in automotive repair shops is associated with risks to health. We evaluated the effects of occupational exposure to PM_2.5 among auto repair-shop workers. Blood and urine samples were collected from 110 volunteers from Barranquilla, Colombia: 55 active workers and 55 controls. PM_2.5 concentrations were assessed at each of the sampling sites and chemical content was analyzed by SEM-EDS electron microscopy. The biological samples obtained were peripheral blood (hematological profiling, DNA extraction) and urine (malondialdehyde concentration). Telomere length was assessed by qPCR and polymorphisms in the glutathione transferase genes GSTT1 and GSTM1 by PCR-RFLP, with confirmation by allelic exclusion. White blood cell (WBC), lymphocyte (LYM%) and platelet (PLT) counts and the malondialdehyde concentration were higher (4.10 ± 0.93) in the exposed group compared to the control group (1.56 ± 0.96). TL was shorter (5071 ± 891) in the exposed individuals compared to the control group (6271 ± 805). White blood cell (WBC) and platelet counts were positively associated with exposure. Age and TBARS were correlated with TL in exposed individuals. The GSTT1 gene alleles were not in Hardy-Weinberg (H-W) equilibrium. The GSTM1 gene alleles were in H-W equilibrium and allelic exclusion analysis confirmed the presence of heterozygous GSTM1 genotypes. SEM-EDS analysis showed the presence of potentially toxic elements, including Mg, Al, Fe, Mn, Rh, Zn, and Cu. Auto repair shop workers showed effects that may be associated with exposure to mixtures of pollutants present in PM_2.5. The GSTM1 and GSTT1 genes had independent modulatory effects.

The mercapturic acid pathway

The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.

Distribution of xenobiotic metabolising enzyme genotypes in different Tunisian populations

BACKGROUND

The N-acetyltransferase 2 (NAT2) and glutathione transferase enzymes play a crucial role in the metabolism of xenobiotics. Genetic polymorphisms affecting these enzymes can modify their activities with an effect on individual susceptibility for different pathologies. These metabolic phenotypes occur with varying prevalence in different populations.

AIM

This study sought to analyse the prevalence of important allelic variants of NAT2, GSTM1 and GSTT1 in different Tunisian populations and compare them to other previously reported data.

SUBJECTS AND METHODS

A total of 253 unrelated subjects from different Tunisian populations participated in this study. Subjects were examined with respect to the frequency of slow NAT2, GSTM1*0 and GSTT1*0 genotypes.

RESULTS

The frequency of 'slow' NAT2, GSTM1*0 and GSTT1*0 genotypes in the Tunisian population were, respectively, estimated at 23.3%, 53.75% and 29.24%. The frequency of slow NAT2 and GSTM1*0 genotypes were significantly different between the North, Centre and South of Tunisia. However, this study doesn't report any significant differences in the genotype distribution between Cosmopolitan, Arab and Berber populations.

CONCLUSIONS

In conclusion, these data indicate that the Tunisian population is highly heterogenic and, therefore, a strict definition of the populations involved in studies investigating the clinical effect of polymorphisms is required.

GSTM1 and GSTM5 Genetic Polymorphisms and Expression in Age-Related Macular Degeneration

PURPOSE

Previously, two cytosolic antioxidant enzymes, Glutathione S-transferase Mu 1 (GSTM1) and Mu 5 (GSTM5), were reduced in retinas with age-related macular degeneration (AMD). This study compared genomic copy number variations (gCNV) of these two antioxidant enzymes in AMD versus controls.

METHODS

Genomic copy number (gCN) assays were performed using Taqman Gene Copy Number Assays (Applied Biosystems, Darmstadt, Germany) in technical quadruplicate for both GSTM1 and GSTM5. Peripheral leukocyte RNA levels were compared with controls in technical triplicates. Statistical comparisons were performed in SAS v9.2 (SAS Institute Inc., Cary, NC).

RESULTS

A large percentage of patients in both AMD and age-matched control groups had no copies of GSTM1 (0/0). The mean gCN of GSTM1 was 1.40 (range 0-4) and 1.61 (range 0-5) for AMD and control, respectively (p = 0.29). A greater percentage of control patients had > 3 gCNs of GSTM1 compared with AMD, respectively (15.3% versus 3.0%, p = 0.004). The gCN of GSTM5 was 2 in all samples except one control sample. The relative quantification of GSTM1 and GSTM5 mRNA from peripheral blood leukocytes in patients showed significant differences in relative expression in AMD versus control (p < 0.05). Peripheral blood leukocyte mRNA and gCN were not significantly correlated (p = 0.27).

CONCLUSION

Since high copy numbers of GSTM1 are found more frequently in controls than in AMD, it is possible that high copy number leads to increased retinal antioxidant defense. Genomic polymorphisms of GSTM1 and GSTM5 do not significantly affect the peripheral blood leukocyte mRNA levels.

Haplotype differences for copy number variants in the 22q11.23 region among human populations: a pigmentation-based model for selective pressure

Two gene clusters are tightly linked in a narrow region of chromosome 22q11.23: the macrophage migration inhibitory factor (MIF) gene family and the glutathione S-transferase theta class. Within 120 kb in this region, two 30-kb deletions reach high frequencies in human populations. This gives rise to four haplotypic arrangements, which modulate the number of genes in both families. The variable patterns of linkage disequilibrium (LD) between these copy number variants (CNVs) in diverse human populations remain poorly understood. We analyzed 2469 individuals belonging to 27 human populations with different ethnic origins. Then we correlated the genetic variability of 22q11.23 CNVs with environmental variables. We confirmed an increasing strength of LD from Africa to Asia and to Europe. Further, we highlighted strongly significant correlations between the frequency of one of the haplotypes and pigmentation-related variables: skin color (R(2)=0.675, P<0.001), distance from the equator (R(2)=0.454, P<0.001), UVA radiation (R(2)=0.439, P<0.001), and UVB radiation (R(2)=0.313, P=0.002). The fact that all MIF-related genes are retained on this haplotype and the evidences gleaned from experimental systems seem to agree with the role of MIF-related genes in melanogenesis. As such, we propose a model that explains the geographic and ethnic distribution of 22q11.23 CNVs among human populations, assuming that MIF-related gene dosage could be associated with adaptation to low UV radiation.