Uncoupling of Cytochrome P450 2B6 and stimulation of reactive oxygen species production in pharmacogenomic alleles affected by interethnic variability

Cytochrome P450 mediated substrate metabolism is generally characterized by the formation of reactive intermediates. In vitro and in vivo reaction uncoupling, results in the accumulation and dissociation of reactive intermediates, leading to increased ROS formation. The susceptibility towards uncoupling and altered metabolic activity is partly modulated by pharmacogenomic alleles resulting in amino acid substitutions. A large variability in the prevalence of these alleles has been demonstrated in CYP2B6, with some being predominantly unique to African populations. The aim of this study is to characterize the uncoupling potential of recombinant CYP2B6*1, CYP2B6*6 and CYP2B6*34 metabolism of specific substrates. Therefore, functional effects of these alterations on enzyme activity were determined by quantification of bupropion, efavirenz and ketamine biotransformation using HPLC-MS/MS. Determination of H2O2 levels was performed by the AmplexRed/horseradish peroxidase assay. Our studies of the amino acid substitutions Q172H, K262R and R487S revealed an exclusive use of the peroxide shunt for the metabolism of bupropion and ketamine by CYP2B6*K262R. Ketamine was also identified as a trigger for the peroxide shunt in CYP2B6*1 and all variants. Concurrently, ketamine acted as an uncoupler for all enzymes. We further showed that the expressed CYP2B6*34 allele results in the highest H2O2 formation. We therefore conclude that the reaction uncoupling and peroxide shunt are directly linked and can be substrate specifically induced with K262R carriers being most likely to use the peroxide shunt and R487S carrier being most prone to reaction uncoupling. This elucidates the functional diversity of pharmacogenomics in drug metabolism and safety.

Circulating microRNA as a marker for predicting liver disease progression in patients with chronic hepatitis B

INTRODUCTION

Hepatitis B virus (HBV) constitutes an important risk factor for cirrhosis and hepatocellular carcinoma (HCC). The link between circulating microRNAs and HBV has been previously reported, although not as a marker of liver disease progression in chronic hepatitis B (CHB). The aim of this study was to characterize miRNA expression profiles between CHB with and without cirrhosis or HCC.

METHODS:

A total of 12 subjects were recruited in this study. We employed an Affymetrix Gene Chip miRNA 3.0 Array to provide universal miRNA coverage. We compared microRNA expression profiles between CHB with and without cirrhosis/HCC to discover possible prognostic markers associated with the progression of CHB.

RESULTS:

Our results indicated 8 differently expressed microRNAs, of which miRNA-935, miRNA-342, miRNA-339, miRNA-4508, miRNA-3615, and miRNA-3200 were up-regulated, whereas miRNA-182 and miRNA-4485 were down-regulated in patients with CHB who progressed to cirrhosis/HCC as compared to those without progression.

CONCLUSIONS:

We demonstrated the differential expression of miRNA-935, miRNA-342, miRNA-339, miRNA-4508, miRNA-3615, miRNA-3200, miRNA-182, and miRNA-4485 between patients with HBV without cirrhosis/HCC and those who had progressed to these more severe conditions. These miRNAs may serve as novel and non-invasive prognostic markers for early detection of CHB-infected patients who are at risk of progression to cirrhosis and/or HCC.

Interleukin 1 receptor type 2 gene polymorphism is associated with reduced risk of preterm birth

OBJECTIVE

Interleukin 1 receptor type 2 (IL1R2) regulates the inflammatory pathway that results in preterm delivery. We aim to investigate the impact of IL1R2 gene polymorphisms on the risk of preterm delivery.

METHOD

A total of 664 women with spontaneous preterm and term deliveries were genotyped for IL1R2 gene polymorphisms (rs2072476A/G, rs2071008G/T, rs2072474C/T) using Sequenom MassARRAY platform.

RESULTS

Ethnic-specific analysis revealed a significant association between the G allele of IL1R2 rs2072476 polymorphism and reduced risk of PTB in the Indian ethnic subgroup (OR: 3.7, 95% CI: 1.3-11.3, p = 0.017). The odds of G allele occurring among Indian women with term delivery (>37 weeks) was three times higher than those with preterm delivery (<37 weeks). Genotype analysis showed a significant association between the GG genotype of IL1R2 rs2072476 polymorphism and term delivery in the Indian women.

CONCLUSION

This study shows disparity in the occurrence of preterm birth due to the differences in the genotype of the women. Particularly, Indian women with the minor allele of IL1R2 rs2072476 polymorphisms were more likely to deliver at term (>37 weeks). These findings suggest the possible influence of maternal IL1R2 gene polymorphism on the risk of preterm delivery.

Progesterone Receptor (PGR) gene polymorphism is associated with susceptibility to preterm birth

BACKGROUND

Preterm birth (PTB) is the major cause of death in newborn and the second major cause of death in children less than 5 years old worldwide. Genetic polymorphism has been implicated as a factor for the occurrence of preterm birth. The aim of this study is to evaluate whether polymorphism in the progesterone receptor (PGR) is associated with susceptibility to preterm birth.

METHODS

A total of 135 women with preterm and 532 women with term deliveries were genotyped for PGR gene polymorphisms (rs660149, rs471767, rs10895068) using Sequenom MassARRAY platform.

RESULTS

The G allele of PGR rs660149 polymorphism was significantly associated with susceptibility to PTB in the Malay women. The odds of G allele occurring among Malay women with preterm delivery was twice that of Malay women with term delivery (OR 2.3, 95 % CI (1.2-4.5, P = 0.011). Alternatively, no significant association was observed between PGR rs660149 polymorphisms and susceptibility to PTB in Chinese and Indian women.

CONCLUSIONS

This study shows that variability in the occurrence of PTB across ethnicities in Malaysia is partly due to differences in genetic background. We therefore suggest that in addition to life style and environmental factors, genetic factor should be greatly considered in this population. Prior information on the genetic composition of women may help in the identification and management of women at risk of preterm birth complication.

Role of pharmacodiagnostic of CYP2C9 variants in the optimization of warfarin therapy in Malaysia: a 6-month follow-up study

1. A retrospective study was conducted to explore the importance of CYP2C9 genotyping for the initiation and maintenance therapy of warfarin in clinical practice. A total of 191 patients on warfarin therapy in a local hospital were recruited after written informed consent. Their medical records were reviewed and no intervention of warfarin dose was performed. 2. A total of 5 ml of blood were taken from each subject for DNA extraction and identification of 1, 2, 3 and 4 CYP2C9 alleles, using a nested-allele-specific-multiplex-polymerase chain reaction (PCR). Half the patients were Malays and the remaining were Chinese. 3. Two genotypes were detected; 93.2% had CYP2C9 1/1 and 6.8% were CYP2C9 1/3. Warfarin doses were higher in patients with CYP2C91/1. Patients with the 1/3 genotype experienced a higher rate of serious and life-threatening bleeding; 15.4 versus 6.2 per 100 patients per 6 months. 4. The observation clearly highlights the inadequacy of the current dosing regimens and the need to move toward a more individualized approach to warfarin therapy. Prospective clinical studies are now being conducted to assess dosing algorithms that incorporate the contribution of the genotype to allow the individualization of warfarin dose.