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Genetic polymorphisms in glutathione S-transferase and COPD development and severity
Natasa Petrovic1, Marija Stankovic2, Andrija Tomovic 3, Vesna Dopudja1, Marina Andjelic4, Aleksandra Nikolic2, Aleksandra Divac2, Dragica Radojkovic2
1Department of Pulmonology, Zvezdara University Medical Centre, Dimitrija Tucovica 161, Belgrade, Serbia
2Institute of Molecular Genetics and Genetic Engineering, Vojvode Stepe 444a, Belgrade, Serbia
3Friedrich Miescher Institute for Biomedical Research, Part of the Novartis Research Foundation, Maulbeerstrasse 66, CH Basel, Switzerland
4Department of Endocrinology, Zvezdara University Medical Centre, Dimitrija Tucovića 161, Belgrade
Introduction
Chronic obstructive pulmonary disease (COPD) is directly associated with cigarette smoking. However, only a small proportion of smokers develop this disease which indicates that a difference in susceptibility to tobacco smoke injury might be related to genetic factors. Glutathione S-transferase (GST) supergene family encodes izoenzymes that appear to be crucial in protection against oxidative stress by detoxifying various toxic substrates in tobacco smoke. Polymorphisms of GSTM1, GSTT1 and GSTP1, responsible for enzyme deficiency or altered enzyme activity, may influence kinetic of activation and detoxification of various toxic substrates in tobacco smoke causing oxidant-antioxidant imbalance as one of the major hypotheses in the pathogenesis of smoke-related COPD.
Results and conclusions
No statistical significance difference between patient and control group and among patients, when analyzed COPD severity, was observed if polymorphisms were studied separately. Statistical significance was observed for combination of GSTM1 null and GSTP1 Ile/Val or Val/Val genotype in COPD group in comparison with control subjects (37% vs. 24%, OR=1.9, p=0.050) (Table 2).
Table 2. The distributions of single and associated GSTs genotypes in COPD and control group.
Polymorphism
Genotype
COPD, n (%)
Controls, n (%)
OR (95%CI)
p-value
GSTM1
deletion
Non-null
35 (41)
53 (53)
Null
51 (59)
47 (47)
1.6 ( )
0.09
GSTT1
65 (76)
76 (76)
21 (24)
24 (24)
1.0 ( )
0.95
GSTP1
Ile105Val
Ile/Ile
36 (42)
45 (45)
Ile/Val
40 (46)
46 (46)
1.1 ( )*
0.67*
Val/Val
10 (12)
9 (9)
GSTM1-GSTP1 association
Non-null-Ile/Ile
54 (63)
Null-Ile/Val or Val/Val
32 (37)
1.9 ( )
0.05
Aims
In order to investigate relationship between GSTM1 null, GSTT1 null and GSTP1 Ile105Val genetic polymorphisms, single and in combination, in COPD susceptibility and severity an association case-control study was designed.
*presence of at least one Val allele versus Ile/Ile was tested.
Patients
A total number of 86 COPD patients and 100 control subjects were included in this study. The diagnosis of COPD was established according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD). The control group encompassed subjects who had no clinical evidence of COPD and showed normal pulmonary function according to GOLD. The main characteristics and clinical parameters of COPD patients and control subjects are shown in Table 1.
Interestingly, the frequency of the same combination of GSTM1 null genotype and presence of at least one Val allele of GSTP1 gene variant was higher in severe/very severe (46%) than in mild/moderate (21%) patient group and showed statistical significance (OR=3.2, p =0.02) (Table 3).
Table 1. The main characteristics of COPD patients and control group.
COPD group
Control group
Subjects, n 86
100
Sex, male/female
58/28
35/65
Age, years*
60±15
51±14
Smokers, % 72 50
FEV1† % pred.*
45±21
110±17
FEV1/FVC‡*
48±16
82±8
Table 3. Analysis of single and combined GSTs genotypes and COPD severity.
Polymorphism
Genotype
FEV1% pred.
OR (95%CI)
p-value
<50%, n (%)
≥50%, n (%)
GSTM1
deletion
Non-null
20 (35)
15 (52)
Null
37 (65)
14 (48)
2.0 ( )
0.14
GSTT1
42 (74)
23 (79)
15 (26)
6 (21)
1.4 ( )
0.57
GSTP1
Ile105Val
Ile/Ile
16 (55)
Ile/Val
30 (53)
10 (35)
2.3 ( )*
0.07*
Val/Val
7 (12)
3 (10)
GSTM1-GSTP1 association
Non-null-Ile/Ile
31 (54)
23 (79)
Null-Ile/Val or Val/Val
26 (46)
3.2 ( )
0.02
*data are presented as mean±SD,
†forced expiratory volume in one second,
‡forced vital capacity.
Methods
Detections of GSTM1 null and GSTT1 null genotypes were performed by multiplex PCR, while GSTP1 Ile105Val polymorphism was analyzed by PCR-RFLP method. Statistical difference in single and combined genotypes distributions between COPD patients and control subjects were assessed by the 2 test. Odds ratio (OR) and 95% confidence interval (CI) were calculated. A p-value of less than 0.05 was considered significant.
To analyze potential role of GSTs polymorphisms in COPD severity, patients were classified as mild/moderate (FEV ≥50% pred), 29 patients, and severe/very severe (FEV<50% pred), 57 patients, and distributions of single and associated genotypes were tested among these two groups.
Statistical analysis was performed by Statistical Package for Social Science (SPSS) software.
*presence of at least one Val allele versus Ile/Ile was tested.
According to our results the association of GSTM1 and GSTP1 polymorphisms is a statistically significant risk factor for development of COPD as well as COPD severity. In this study we demonstrated importance of associated analysis of GSTs polymorphisms.Certain combination of GSTM1-GSTP1 polymorphisms could result in increased oxidative stress which is a crucial characteristic of COPD pathogenesis.
In conclusion, COPD is a complex disease in which many genes, as well as smoking, are involved, but more data on other populations are needed to confirm this association which could be used as predictive factor in development of this disease and its prognosis.