Genetic susceptibility in pharmacodynamic and pharmacokinetic pathways underlying drug-induced arrhythmia and sudden unexplained deaths

ABSTRACT: Drug-induced arrhythmia is an adverse drug reaction that can be potentially fatal since it is mostly related to drug-induced QT prolongation, a known risk factor for Torsade de Pointes and sudden cardiac death (SCD). Several risk factors have been described in association to these drug-induced events, such as preexistent cardiac disease and genetic variation. Our objective was to study the genetic susceptibility in pharmacodynamic and pharmacokinetic pathways underlying suspected drug-induced arrhythmias and sudden unexplained deaths in 32 patients. The genetic component in the pharmacodynamic pathway was studied by analysing 96 genes associated with higher risk of SCD through massive parallel sequencing. Pharmacokinetic-mediated genetic susceptibility was investigated by studying the genes encoding cytochrome P450 enzymes using mediumthroughput genotyping. Pharmacodynamic analysis showed three probably pathogenic variants and 45 variants of uncertain significance in 28 patients, several of them previously described in relation to mild or late onset cardiomyopathies. These results suggest that genetic variants in cardiomyopathy genes, in addition to those related with channelopathies, could be relevant to drug-induced cardiotoxicity and contribute to the arrhythmogenic phenotype. Pharmacokinetic analysis showed three patients that could have an altered metabolism of the drugs they received involving CYP2C19 and/or CYP2D6, probably contributing to the arrhythmogenic phenotype. The study of genetic variants in both pharmacodynamic and pharmacokinetic pathways may be a useful strategy to understand the multifactorial mechanism of drug-induced events in both clinical practice and forensic field. However, it is necessary to comprehensively study and evaluate the contribution of the genetic susceptibility to drug-induced cardiotoxicity. (AU)

Genetic susceptibility in pharmacodynamic and pharmacokinetic pathways underlying drug-induced arrhythmia and sudden unexplained deaths.

Drug-induced arrhythmia is an adverse drug reaction that can be potentially fatal since it is mostly related to drug-induced QT prolongation, a known risk factor for Torsade de Pointes and sudden cardiac death (SCD). Several risk factors have been described in association to these drug-induced events, such as preexistent cardiac disease and genetic variation. Our objective was to study the genetic susceptibility in pharmacodynamic and pharmacokinetic pathways underlying suspected drug-induced arrhythmias and sudden unexplained deaths in 32 patients. The genetic component in the pharmacodynamic pathway was studied by analysing 96 genes associated with higher risk of SCD through massive parallel sequencing. Pharmacokinetic-mediated genetic susceptibility was investigated by studying the genes encoding cytochrome P450 enzymes using medium-throughput genotyping. Pharmacodynamic analysis showed three probably pathogenic variants and 45 variants of uncertain significance in 28 patients, several of them previously described in relation to mild or late onset cardiomyopathies. These results suggest that genetic variants in cardiomyopathy genes, in addition to those related with channelopathies, could be relevant to drug-induced cardiotoxicity and contribute to the arrhythmogenic phenotype. Pharmacokinetic analysis showed three patients that could have an altered metabolism of the drugs they received involving CYP2C19 and/or CYP2D6, probably contributing to the arrhythmogenic phenotype. The study of genetic variants in both pharmacodynamic and pharmacokinetic pathways may be a useful strategy to understand the multifactorial mechanism of drug-induced events in both clinical practice and forensic field. However, it is necessary to comprehensively study and evaluate the contribution of the genetic susceptibility to drug-induced cardiotoxicity.

Characterization of the Trypanosoma cruzi Cdc2p-related protein kinase 1 and identification of three novel associating cyclins.

Several Cdc2p-related protein kinases (CRKs) have been described in trypanosomatids but their role in the control of the cell cycle nor their biological functions have been addressed. In Trypanosoma cruzi two CRKs have been identified, TzCRK1 and TzCRK3. In this work we further characterize T. cruzi CRK1 and report the identification of three novel associating cyclins. We demonstrate that CRK1 levels and localization do not vary during the cell cycle, and show that it is localized in the cytoplasm, discrete regions of the nucleus, and is highly concentrated in the mitochondrion DNA (kinetoplast), suggesting a putative control function in this organelle. Using purified anti-CRK1 IgGs, we immunoprecipitated from the soluble fraction of T. cruzi epimastigote forms a protein kinase activity which is not inhibited by CDK inhibitors. In addition, we co-precipitated with p13Suc1p beads a kinase activity that was inhibited by the CDK inhibitor flavopiridol and olomoucine. Lastly, using the yeast two-hybrid system we identified three novel cyclin-like proteins able to associate with TzCRK1, and demonstrate that two of these cyclins also bind the T. cruzi CRK3 protein, indicating that these two CRKs are cyclin-dependent kinases.

A new twist in trypanosome RNA metabolism: cis-splicing of pre-mRNA.

It has been known for almost a decade and a half that in trypanosomes all mRNAs are trans-spliced by addition to the 5' end of the spliced leader (SL) sequence. During the same time period the conviction developed that classical cis-splicing introns are not present in the trypanosome genome and that the trypanosome gene arrangement is highly compact with small intergenic regions separating one gene from the next. We have now discovered that these tenets are no longer true. Poly(A) polymerase (PAP) genes in Trypanosoma brucei and Trypanosoma cruzi are split by intervening sequences of 653 and 302 nt, respectively. The intervening sequences occur at identical positions in both organisms and obey the GT/AG rule of cis-splicing introns. PAP mRNAs are trans-spliced at the very 5' end as well as internally at the 3' splice site of the intervening sequence. Interestingly, 11 nucleotide positions past the actual 5' splice site are conserved between the T. bruceiand T. cruzi introns. Point mutations in these conserved positions, as well as in the AG dinucleotide of the 3' splice site, abolish intron removal in vivo. Our results, together with the recent discovery of cis-splicing introns in Euglena gracilis, suggest that both trans- and cis-splicing are ancient acquisitions of the eukaryotic cell.

The 'eye test' in recognition of late-onset Alzheimer's disease.

A rapid and specific diagnostic test for Alzheimer's disease (AD), the prevalent cause of dementia in the elderly, is currently unavailable. The aim of this study was to verify the validity of the recently proposed 'Eye Test' in the identification of AD patients, based on their supposed greater mydriatic response to cholinergic antagonists. We tested the pupillary response to the instillation of 0.01% tropicamide in 48 subjects: 15 patients with probable or possible Alzheimer's disease, five patients with vascular dementia (VD), 16 elderly controls (EC) and 12 young controls (YC). Mean pupil dilation in the treated eye at 30 and 40 min after drops instillation was not significantly different among the four groups. The mean change in anisocoria at 30 min was significantly greater in the AD group (0.90 mm, S.D. 0.83) than in the YC group (0.21 mm, S.D. 0.46), but no significant difference was found among the AD group, the EC group and the VD group. Our results, therefore, do not support the potential usefulness of the pupillary response to dilute tropicamide for identifying individuals with AD.

[Level of protection against tetanus in an outpatient population]. / Livello di protezione contro il tetano in una popolazione ambulatoriale.

Protection levels against tetanus toxin were estimated in 332 patients, at our Laboratory, by means of the passive haemagglutination with turkey erythrocyte test. The testing showed that the protection level decreases with age, it is higher among males in those over 30 yrs; roughly 10% of those who were not vaccinated were protected. Furthermore, it has been demonstrated that in some cases the protection level remains high even after a long period of time since the last vaccination, whereas a certain percentage of the recently vaccinated patients is not protected; consequently the effectiveness of the vaccination must be checked by measuring the antibody titers.

Coagulation and platelet activation after retinal vein occlusions.

The role played by coagulation and platelet activation in the pathogenesis of retinal vein occlusions (RVO) has been evaluated by measuring beta-thromboglobulin (B-TG), circulating platelet aggregates (CPA), thromboxane B2 (TxB2) and fibrinopeptide A (FPA) in 25 patients less than 40 years old, investigated after the acute phase of RVO. FPA nd B-TG were significantly higher than in healthy subjects; CPA and TxB2 were not different. These abnormalities, found in patients free from apparent generalized vascular disease, suggest that a thrombophilic state characterized by coagulation and platelet activation is present in a high proportion of young patients with RVO.

[Retinal vascular changes and haemostatic function in young patients (author's transl)]. / Les altérations vasculaires rétiniennes des jeunes et les fonctions hémostatiques.

Haemostatic function was studied in 40 patients between one and 12 months from the occurrence of retinal vein occlusion (RVO); 25 patients aged 40 years, or less and 15 were more than 45 years old. The following tests were performed : plasma beta-thromboglobuline (beta-TG) fibrinopeptide A (FpA), PTT, spontaneous in vitro platelet aggregation (SpA), circulating platelet aggregates (CPA), platelet retention (PR) to glass beads, serum thromboxane B2 (TxB2). In the group of older patients, there was a significant increase of beta-TG, FpA, PR, SPA, TxB2, and a reduction in the PTT. CPA was not significantly changed. In the group of younger patients (less than 40 yrs) only FpA and beta TG levels showed significant differences from the control group of age-matched healthy subjects. These findings suggest that the alterations present in older patients are likely to be secondary to generalized vascular damage, whereas a state of activation of the coagulation system appears to be present in younger patients with RVO.