Distinct haplogenotypes of the dopamine D2 receptor gene are associated with non-smoking behaviour and daily cigarette consumption.

INTRODUCTION: Dopamine systems in the CNS are decisively implicated in the motivational and rewarding properties of nicotine. The dopamine D2 receptor (DRD2) plays a pivotal role by promoting these properties, making this gene a good candidate for association studies. Several single nucleotide polymorphisms (SNPs) have been described to influence the expression of DRD2. The amount of expressed DRD2 will finally be the result of the sum and/or interaction of several functional polymorphisms located at the respective DNA strand forming a distinct haplotype. Thus, the knowledge about the distribution of the haplotypes in groups of subjects, differing by their smoking behaviour, would result in a better understanding of the putative associations compared to single SNP investigations. METHODS: 218 healthy subjects grouped for being never smokers, former smokers, and current smokers, were genotyped for the following polymorphisms: -141 ins(I)/del(D), STRPi2 (intron 2), C957T (exon 7), A1385G (exon 8), and TaqIA. Regular immoderate alcohol consumption was an exclusion criterion. RESULTS: In the total study group four haplotypes represented 90% of the haplotypes, with I-T-A-A2, I-C-G-A2, I-C-A-A1, and D-C-G-A2 accounting for around 50%, 20%, 10%, and 10%, respectively. I-C-G-A2 homozygosity was significantly higher in never smokers compared to ever smokers (current+former smokers) (chi2=36.585, df=1, p<0.001). There was a significant difference in the daily cigarette consumption of current smokers with respect to the haplogenotype (chi2=3211.9, df=18, p=0.003). Current smokers with a haplogenotype containing at least one I-T-A-A2 allele showed a significant smaller daily cigarette consumption (15.1+/-7.93) compared to subjects with a genotype not bearing this allele (20.1+/-6.79; T=-2.06, df=61, p=0.044). CONCLUSION: We have demonstrated an association of the distinct haplogenotype I/I-C/C-G/G-A2/A2 of the DRD2 gene with a reduced risk to become a smoker in Caucasians of German origin. This protection may result from an association of this haplotype with a reduced activation of the dopaminergic neurotransmission by nicotine. Moreover, in current smokers, higher daily cigarette consumption is associated with those haplogenotypes that do not contain the I-T-A-A2 haplotype.

Functional cortical effects of novel allelic variants of the serotonin transporter gene-linked polymorphic region (5-HTTLPR) in humans.

INTRODUCTION: Genetic variations of the serotonin transporter-linked polymorphic region (5-HTTLPR) have been implicated in the pathogenesis of several psychiatric disorders. Recent evidence indicates that the biallelic polymorphic region (S and L allele) contains additional variations affecting the mRNA expression. METHODS: According to recent preclinical and clinical studies, the loudness dependence of auditory evoked potentials (LD) was investigated as surrogate parameter for the central serotonergic activity in 185 healthy subjects subdivided according to newly identified 5-HTTLPR genotypes. RESULTS: Individuals homozygous for the L (A) allele showed the lowest LD of all genotypes suggesting a high serotonergic neurotransmission. The other observed genotypes (L (A)/L (G), S/L (A), S/L (G), S/S) had an LD which was similar to each other but higher compared to the L (A)/L (A) genotype. DISCUSSION: The data provide a rationale to subdivide the L allele of the 5-HTTLPR into L (A) and L (G) alleles in terms of their serotonin activity as indicated by the LD. The present IN VIVO measurements provide a basis for grouping the L (G) and S alleles for further investigations.

2,9-Dimethyl-beta-carbolinium, a neurotoxin occurring in human brain, is a potent inducer of apoptosis as 1-methyl-4-phenylpyridinium.

The causes of neurodegeneration are not well understood. However, the role of environmental and endogenous toxins is receiving much attention. In this study, we compared the synthetic neurotoxin 1-methyl-4-phenyl-pyridinium with beta-carbolines occurring in human brain. Methylation of both nitrogens is necessary to convert a beta-carboline into a potent inhibitor of mitochondrial complex I. The respective beta-carboline, 2,9-dimethyl-beta-carbolinium ion is neurotoxic in rats. To investigate the underlying mechanisms, we incubated mouse neuroblastoma 2A cells with 2,9-dimethyl-beta-carbolinium ion, and compared the findings with effects of norharman, the precursor beta-carboline of methylated derivatives, and with 1-methyl-4-phenyl-pyridinium. 2,9-Dimethyl-beta-carbolinium ion caused a significant increase of reactive oxygen species (higher efficiency than 1-methyl-4-phenyl-pyridinium) and of mitochondrial membrane potential within the first minutes. After 60 min, the membrane potential dissipated. Concomitantly, the levels of glutathione increased in 2,9-dimethyl-beta-carbolinium ion but not in 1-methyl-4-phenyl-pyridinium treated cells. After 24 h effector caspases 3 and 7 were activated and the number of apoptotic cells increased as revealed by fluorescence-activated cell sorting cytometry. When incubated longer (48 h), cells underwent late apoptosis/secondary necrosis as shown by fluorescence-activated cell sorting analysis and confirmed qualitatively by an electron microscopy study. The effects of 2,9-dimethyl-beta-carbolinium ion on apoptotic changes were similar to those induced by 1-methyl-4-phenyl-pyridinium(,) while norharman showed only a weak potency at the very high doses. To investigate whether 2,9-dimethyl-beta-carbolinium ion is neurotoxic under in vivo conditions and whether only dopaminergic neurones are affected we conducted a dose-response study. Three weeks after injection of 2,9-dimethyl-beta-carbolinium ion in the substantia nigra we found a dose-dependent decrease of dopamine and its metabolites in the striatum of rats. The levels of 5-hydroxytryptamine were diminished although the decrease was less. The levels of noradrenaline increased after some doses. The findings strongly suggest an important role of endogenous beta-carbolines in neurodegeneration with apoptosis as the predominant mechanism.

Serotonergic effects of smoking are independent from the human serotonin transporter gene promoter polymorphism: evidence from auditory cortical stimulus processing.

BACKGROUND: Cigarette smoking has been associated with mood enhancing properties and modulating effects on serotonin activity. The loudness dependence (LD) of the auditory-evoked N1/P2-component has been related to serotonergic neurotransmission, i. e. the allelic variants in the promoter of the 5-hydroxytryptamine-transporter (5-HTT) gene (SCL6A4). Moreover, smoking behavior has been associated to the 5-HTT-genotype. It was hypothesized that cigarette smoking modulates the LD and this effect was expected to interact with the 5-HTT-genotype. METHODS: 5-HTT-genotype and LD were determined in 63 healthy smokers and 114 nonsmokers. RESULTS: LD was significantly affected by smoking status (p = 0.008) and 5-HTT-genotype (p = 0.045) but not by smoking*genotype-interaction or daily cigarette consumption. Current smokers exhibited a significantly weaker LD compared to nonsmokers. 5-HTT-genotype showed no significant effect on smoking behavior. DISCUSSION: The results indicate a higher serotonergic activity in smokers as compared to nonsmokers independent of 5-HTT-genotype. Since former smokers and never smokers showed similar LDs, the serotonin enhancing effect of smoking seems to be a characteristic state, which may contribute to the maintenance of smoking behavior.

Numerical aberrations of chromosomes 1, 2, and 7 in astrocytomas studied by interphase cytogenetics.

For both juvenile astrocytomas and astrocytomas of adults, numerical and structural aberrations of chromosomes 1 and 7 have been described. To study the frequency of those aberrations in more detail and to exclude in vitro artifacts, we investigated directly prepared material from 18 juvenile and 26 astrocytomas of adults by fluorescence in situ hybridization with DNA probes specific for chromosome regions 1p36, 1q12, 2cen, and 7cen. Chromosome 2 was used as control in the hybridization with chromosome 7. To exclude tissue-specific alterations, we tested cerebral and cerebellar paraffin-embedded material from persons who had died from other diseases. In 13 of the juvenile astrocytomas, we found a loss of 1p36 in relation to 1q12 in 16 astrocytomas of adults, a gain of signals from 1p36 or both probes for chromosome 1 was seen. Gain of chromosome 7 was found in 25 cases. Unexpectedly, gain of chromosome 2 occurred in 32 cases. For both probes, there was no difference between astrocytomas of children and those of adults. Our data suggest that loss of 1p is an early event in the development of juvenile astrocytomas and that trisomy 7 is frequent in malignant tumors and tumors containing a potential of growing malignantly.

Genomic structure and chromosomal localization of the human interleukin 15 gene (IL-15).

Interleukin 15 (IL-15) is a novel cytokine whose biological activities are similar to those of interleukin 2 (IL-2). The genomic sequence of human IL-15 has been isolated based on its sequence homology with a cDNA clone encoding human IL-15. The human sequence is 14968 bp in length and includes all six protein-coding exons and five introns. The location of the introns in the human sequence is identical to their positions in the murine IL-15 gene. The same is true for the overall size of the gene, which was estimated to be at least 32 kb. Using Polymerase Chain Reaction (PCR) with gene-specific primers on a panel of human/rodent hybrid cell DNAs, as well as by fluorescence in situ hybridization the human IL-15 gene was mapped to chromosome 4 region q25-35.

Involvement of chromosome 22 in ependymomas.

We have karyotyped a total of twelve ependymomas using GTG-banding including seven for which preliminary results have already been published. One case showing hyperdiploid main line with two marker chromosomes was further analyzed by nonisotopic chromosome in situ suppression hybridization. It was shown that the marker chromosomes consisted of 1q, 14q and 1q, and 22q. The possible role of chromosome 22 in ependymomas and the usefulness of fluorescence in situ hybridization for cytogenetic analysis in tumor investigation are discussed.

[Aorto-intestinal fistula following bypass operation--a rare cause of gastrointestinal hemorrhage]. / Aortointestinale Fistel nach Bypassoperation--seltene Ursache der Gastrointestinalblutung.

A rare case of aorto-enteric fistula is reported. The age of the patient was 56 years. The fistula is a complication of abdominal aortic surgery. The early diagnosis (duodenoscopy) decides on life of the patient.