Peripheral gene expression profiling of CCK-4-induced panic in healthy subjects.

Progress in understanding the genetic basis of panic attacks may extend current knowledge on susceptibility to panic and pathogenesis of panic disorder. In the present study we applied the microarray Illumina platform for whole genome expression profiling in healthy subjects participating in the CCK-4-induced panic test. The study sample consisted of 31 male and female healthy volunteers, who were categorized according to predefined criteria as "panickers" or "non-panickers" to a CCK-4 challenge. The gene expression profiles were measured on peripheral blood cells at baseline and at 120 min post-CCK-4 injection using Illumina Human-6 v2 BeadChips. The fold change was used to demonstrate rate of changes in average gene expressions between studied groups. Statistical analyses were performed using the false discovery rate (FDR). Gene expression profiling 2 hr post-CCK-4 challenge showed changes in transcriptional levels of 226 genes. A total of 61 genes were differentially expressed between panickers and non-panickers with most of them related to immune, enzymatic or stress regulation systems. Other distinctive mRNA transcripts were from the genes known to be related to phenotypes associated with increased occurrence of panic attacks, such as asthma, diabetes, or myocardial ischemia. Our findings provide preliminary evidence for genetic substrates of panic attacks on the transcriptional level and indicate potential biological proximity between acute panicogenesis and several somatic conditions.

Determination of thiopurine S-methyltransferase (TPMT) activity by comparing various normalization factors: reference values for Estonian population using HPLC-UV assay.

Thiopurine S-methyltransferase (TPMT; EC 2.1.1.67) is the key enzyme in the metabolism of thiopurine drugs. Determination of TPMT activity has been used for the individualization of thiopurine dose. We developed HPLC-UV assay for the determination of TPMT activity in human erythrocytes using 6-mercaptopurine as a substrate. Various extraction and chromatographic conditions were compared. In-house developed extraction with acetonitrile provided the lowest limit of quantification. TPMT activity was determined in 99 previously genotyped healthy Estonians. TPMT activity was expressed as the formation of 6-methylmercaptopurine ng/ml/h and normalized either to haemoglobin, haematocrit, erythrocyte count or protein content. The receiver-operating characteristic curve analysis revealed similar accuracy values for TPMT activity in predicting heterozygous and wild type individuals for each method of calculation. In healthy Estonians, TPMT activity varied from 21.5 to 129.6 ng/ml/h. For heterozygous individuals (n = 18), TPMT activity was 48.1 +/- 11.7 ng/ml/h. Wild type individuals (n = 81) revealed significantly higher TPMT activity 79.3 +/- 20.7 ng/ml/h (P < 0.001). This sensitive HPLC assay for quantitative determination of TPMT activity could easily be used in clinical settings. Under constant experimental conditions for haemolysate preparation no normalization is required.

Serotonin transporter promoter region polymorphisms do not influence treatment response to escitalopram in patients with major depression.

Several studies and meta-analyses have implicated a polymorphism in the promoter region of the serotonin transporter (5-HTT) gene, 5-HTTLPR in treatment outcomes of selective serotonin re-uptake inhibitors in patients with major depression. In this study we investigated the impact of 5-HTTLPR and a functional SNP rs25531 on the treatment outcomes to escitalopram in depressive patients. The study sample consisted of 135 outpatients with major depressive disorder (mean age 31.1+/-11.6 years, 68% females) treated with escitalopram 10-20 mg/day for 12 weeks. There were no significant associations between 5-HTT promoter region polymorphisms and response rate or mean change of depressive symptoms during escitalopram treatment. However we showed that patients carrying S allele of 5-HTTLPR may have increased risk for some side effects, including headache, induced by escitalopram medication.

Thiopurine S-methyltransferase (TPMT) pharmacogenetics: three new mutations and haplotype analysis in the Estonian population.

BACKGROUND: Thiopurine methyltransferase (TPMT) is a cytoplasmic enzyme involved in the metabolism of thiopurine drugs. To date, at least 25 single nucleotide polymorphisms have been reported in the TPMT gene, 23 of these are associated with reduced enzyme activity. METHODS: The aim of the present study was to sequence the whole coding region of TPMT (exons 3-10) to identify known and novel TPMT sequence variants amongst healthy Estonians. Erythrocyte TPMT activity was also measured to carry out a genotype-phenotype comparison. RESULTS: A total of 21 subjects were heterozygous for known TPMT alleles (*2, *3A, *3C, *9, *12). Several other previously described intronic and exon polymorphisms were identified. Three novel mutations were detected -30T>A in exon 3, 10A>G in intron 3, and 145A>G in intron 10. Association analysis revealed four markers (114T>A, 94T>A, 460G>A, 719A>G) whose frequencies were significantly different in intermediate (enzyme activity or=140 ng/mL/h) methylators (p<0.001). Haplotype analysis found one haplotype to be associated with intermediate TPMT activity. CONCLUSIONS: Our results point to several markers that predict reduced enzyme activity. None of the identified markers were associated with high enzyme activity.