Serotonin transporter gene and response to lithium augmentation in depression.

BACKGROUND: The serotonin (5-HT) transporter gene-linked polymorphic region (5-HTTLPR) is associated with better response to selective serotonin reuptake inhibitors in Caucasian patients carrying the long (l)-allele. In contrast, augmentation of antidepressant drugs with pindolol has been shown to improve responsiveness to antidepressants in short (s)-allele carriers. Lithium augmentation is a well-established strategy for overcoming treatment resistance. In this study, the 5-HTTLPR allele variant's effect on lithium augmentation was analyzed in antidepressant-nonresponsive patients. METHODS: We measured remission rates during lithium augmentation in 50 depressed patients genotyped for the 5-HTTLPR. All patients took part in phase II of the German Algorithm Project, a prospective study for the evaluation of a standardized stepwise drug treatment regimen. For statistical analysis, the Cox regression model including several clinical factors besides the 5-HTTLPR was used. RESULTS: Only the genotype of the 5-HTTLPR (P<0.006) showed a signficant influence on remission. Patients homozygous for the s-allele had a more favorable response compared with those heterozygous (hazard ratio=6.9; P=0.005) or homozygous for the l allele (hazard ratio=4.5; P=0.003). CONCLUSION: The findings support a differential effect of the 5-HTTLPR gene on primary treatment with antidepressants and treatment augmentation. Similar to the observations with pindolol, s/s-allele patients showed a higher benefit from lithium augmentation than did patients carrying other 5-HTTLPR genotypes. Thus, the s/s genotype might predict an individual's risk of antidepressant nonresponsiveness and sensitivity to augmentative drugs such as lithium.

Investigation of the association between 5-HT3A receptor gene polymorphisms and efficiency of antiemetic treatment with 5-HT3 receptor antagonists.

OBJECTIVES: Acute cytostatic drug induced nausea and vomiting is provoked by a release of endogenous serotonin that mediates its effect by binding to the 5-hydroxytryptamine type 3 (5-HT3) receptors. The most effective antiemetic drugs are the 5-HT3 receptor antagonists. Nevertheless about 30% of the patients do not respond satisfactorily. Five 5-HT3 receptor genes (5-HT(3A-E)) with high sequence homology have been identified. Two subunits, the 5-HT3A and 5-HT3B are expressed in anatomical structures known to be involved in the mechanism of acute cytostatic drug induced emesis. METHODS: We included 242 cancer patients at their first day of chemotherapy to investigate the influence of genetic polymorphisms of the 5-HT3A receptor gene on the intensity of nausea and vomiting which was documented using standardized interviews and visual analog scales. RESULTS: Sequencing of the entire 5-HT3A receptor gene of all patients revealed 21 polymorphisms, two of them were amino acid substitutions (Ala33Thr, Met257Ile). Linkage disequilibrium analysis revealed that 15 polymorphisms of the 5-HT3A receptor gene are partially linked to each other. However, none of the haplotypes was significantly associated with the intensity of cytostatic induced nausea and vomiting. CONCLUSION: Polymorphisms and haplotype analysis of the 5-HT3A receptor gene may not serve as a pharmacogenetic predictor of the antiemetic treatment with 5-HT3 receptor antagonists in cancer patients.

Variations in the 5-hydroxytryptamine type 3B receptor gene as predictors of the efficacy of antiemetic treatment in cancer patients.

PURPOSE: Serotonin (5-hydroxytryptamine type 3 [5-HT3]) receptor antagonists have substantially reduced but not eliminated nausea and vomiting in patients undergoing cancer chemotherapy. They act through specific binding to the 5-HT3A, 5-HT3B receptor complex. The 5-HT3B subunit seems to be most important for its functionality. We hypothesized that patients with genetic variations in the 5-HT3B receptor gene might respond differently to antiemetic treatment. PATIENTS AND METHODS: We included 242 cancer patients on their first day of chemotherapy. Nausea and vomiting were documented before and twice during the chemotherapy using standardized interviews and visual analog scales. We sequenced the entire 5-HT3B receptor gene, including the 5' flanking region and at least a 20-base pair intronic sequence of each intron-exon splice site of all patients. RESULTS: Approximately 30% of all patients suffered from nausea or vomiting. Sequencing of the 5-HT3B receptor gene revealed 13 polymorphisms: two of them were amino acid exchanges (Tyr129Ser, Ala223Thr) and two were deletion variants. In both observation periods, patients homozygous for the -100_-102delAAG deletion variant of the promotor region experienced vomiting more frequently than did all the other patients. CONCLUSION: A more efficient antiemetic treatment with 5-HT3 receptor antagonists might be possible on a pharmacogenetic basis. However, only a small fraction of the therapeutic failure is explained by the -AAG deletion variant of the 5-HT3B receptor gene. Additional clinical and biochemical studies are needed to confirm the association.

Patient-tailored antiemetic treatment with 5-hydroxytryptamine type 3 receptor antagonists according to cytochrome P-450 2D6 genotypes.

PURPOSE: The use of serotonin 5-hydroxytryptamine type 3 receptor antagonists has substantially reduced, but not eliminated, nausea and vomiting in cancer chemotherapy. This study sought to investigate whether efficacy of antiemetic treatment with ondansetron and tropisetron depends on cytochrome P-450 2D6 (CYP2D6) genotype, hypothesizing that the rapid and particularly the ultrarapid metabolizers of these drugs are at risk of being undertreated. PATIENTS AND METHODS: Included in the study were 270 cancer patients receiving their first day of chemotherapy. Nausea and vomiting were documented using standardized interviews. The intensity of nausea was measured with visual analog scales before and twice during the chemotherapy. The relationship between the CYP2D6 genotypes and the tropisetron serum concentrations 3 and 6 hours after drug administration was analyzed in a subgroup of 42 patients. CYP2D6 genotyping was carried out by polymerase chain reaction-restriction fragment length polymorphism analysis. RESULTS: Genetically defined poor metabolizers had higher serum concentrations of tropisetron than all other patients (P <.03). Approximately 30% of all patients receiving chemotherapy experienced nausea and vomiting. Genetically defined ultrarapid meta-bolizers of CYP2D6 substrates had higher frequency of vomiting within the first 4 hours (P <.001) and within the period 5 to 24 hours (P <.03) after treatment than all the other patients; the tendency for nausea was similar. This difference was more pronounced in patients treated with tropisetron than in those treated with ondansetron. CONCLUSION: Antiemetic treatment with tropisetron or ondansetron could be improved by adjustment for the CYP2D6 genotype; approximately 50 subjects would have to be genotyped to protect one patient from severe emesis.

Validity of PCR with emphasis on variable number of tandem repeat analysis.

OBJECTIVES: Variable number of tandem repeat polymorphisms (VNTR) are frequently analyzed by PCR in genetic, epidemiologic and forensic studies. We wanted to explore the validity of these PCR analyses. DESIGN AND METHODS: The amplification of the different alleles of the 17- and the 44-bp VNTR of the serotonin transporter gene and the 39-bp VNTR of the glycoprotein Ibalpha gene was analyzed. We studied the effects of the parameters magnesium, dimethylsulfoxide, 7-deaza-dGTP, formamide, betaine, PCR temperatures and different types of polymerases. RESULTS: In all three VNTR polymorphisms selective amplification of one of the alleles of heterozygous individuals could be obtained by change of the magnesium concentration. This problem could be minimized by a combination of Taq- and Pwo-polymerases and by use of 7-deaza-dGTP. CONCLUSION: PCR analysis of all of these VNTRs may give reproducibly wrong results in truly heterozygous subjects due to selective amplification of only one of the alleles.

Correlation between serotonin uptake in human blood platelets with the 44-bp polymorphism and the 17-bp variable number of tandem repeat of the serotonin transporter.

Dysfunctions of the central serotonin (5-hydroxytryptamine, 5-HT) system seem to be associated with psychiatric disorders such as schizophrenia or depression. Previous studies suggested that a 44-bp insertion/deletion polymorphism of the 5-HT transporter (5-HTT) promoter region might influence the transcriptional activity of the 5-HTT gene, and the insertion variant resulted in increased 5-HTT expression and 5-HT uptake. Moreover, a 17-bp variable number of tandem repeat (VNTR) polymorphism of the second intron may act as a transcriptional regulator with allele dependent differential enhancer-like properties. Since the 5-HTT of human platelets shares many properties with the transporter of neural tissue, platelets are widely used as a surrogate tissue source, possibly reflecting central 5-HT metabolism. Therefore, we investigated the impact of the 44-bp polymorphism and the 17-bp VNTR for 5-HT uptake in platelets of 50 male subjects. We found no significant effect of the 44-bp polymorphism and of the 17-bp VNTR on maximum rate (Vmax) of 5-HT uptake. However, individuals homozygous for the 5-HTT intron 2 allele with 12 repeats (STin2.12) of the 17-bp VNTR appeared to have lower affinity of 5-HT uptake than individuals heterozygous for the STin2.10/STin2.9 allele. This was also observed for the combined analysis of both polymorphisms. In conclusion, we found no association between the different genotypes of the 44-bp polymorphism and the 17-bp VNTR and maximum rate of 5-HT uptake into platelets.

Simultaneous determination of ondansetron and tropisetron in human plasma using HPLC with UV detection.

A rapid and sensitive HPLC method for the simultaneous quantitation of ondansetron and tropisetron, two serotonin (5-HT) receptor antagonists frequently used in treatment and prevention of nausea and emesis, is described. The procedure involves liquid-liquid extraction of human plasma with dichloromethane coupled with reversed-phase HPLC and UV detection. The lower limits of quantification (LOQ) were 0.62 ng/mL for ondansetron and 1.25 ng/mL or tropisetron. Intra- and inter-assay coefficients of variation ranged from 1.5 to 7.5% and 5.3 to 13.7%, respectively. The sensitivity and precision were sufficient for determination of plasma concentrations after therapeutic administration of both drugs and the method can be used for the estimation of pharmacokinetic parameters.