Objective: To investigate whether glutamate cysteine ligase modulatory (GCLM) subunit gene polymorphism is associated with susceptibility to chronic obstructive pulmonary disease (COPD), and to study the relationship between polymorphism of GCLM gene with plasma gamma-glutamylcysteine synthetase (gamma-GCS) activity.
Methods: Blood samples of 104 stable phase COPD smokers (COPD group), 124 healthy smokers (C group) and 132 healthy never-smokers (H group) were collected, and then the genotypes of GCLM -588C/T and GCLM -23C/T polymorphism sites were detected by polymerase chain reaction (PCR) and restriction fragment length polymorphism analysis (RFLP). The plasma gamma-GCS activity was measured by coupled enzyme procedure.
Results: (1) The distribution of -588CC, -588CT, -588TT genotypes were corresponding to -23GG, -23GT, -23TT respectively in all of the individuals. (2) The frequencies of -588CC genotype and -588 C allele were significantly lower in COPD group (62.3% and 79.2%) than in C group (84.7% and 91.9%) and H group (78.8% and 89.0%, P < 0.01). (3) In smokers, GCLM -588 T allele carried a higher risk to COPD, the odds ratio (OR value) to C allele was 3.0, and with a 95% confidence interval 1.7 - 5.3. (4) The plasma gamma-GCS activity was increased in C group [(282 +/- 58) U/mg.prot] and COPD group [(224 +/- 54) U/mg.prot] as compared with H group [(157 +/- 26) U/mg.prot, P < 0.01], and were higher in healthy smokers than in COPD smokers (P < 0.01). (5) The smokers with -588CC genotype had higher gamma-GCS activity than CT or TT genotype [(292 +/- 54), (225 +/- 45) U/mg.prot, P < 0.01 in C group and (245 +/- 52), (188 +/- 36) U/mg.prot, P < 0.01 in COPD group], but the difference did not exist in H group [(158 +/- 27), (153 +/- 25) U/mg.prot, P > 0.05].
Conclusion: The polymorphism of GCLM -588C/T and -23G/T sites were associated with susceptibility to COPD, and were associated with plasma gamma-GCS activity.