Risk of bleeding associated with combined use of selective serotonin reuptake inhibitors and antiplatelet therapy following acute myocardial infarction

Background:

Patients prescribed antiplatelet treatment to prevent recurrent acute myocardial infarction are often also given a selective serotonin reuptake inhibitor (SSRI) to treat coexisting depression. Use of either treatment may increase the risk of bleeding. We assessed the risk of bleeding among patients taking both medications following acute myocardial infarction.

Methods:

We conducted a retrospective cohort study using hospital discharge abstracts, physician billing information, medication reimbursement claims and demographic data from provincial health services administrative databases. We included patients 50 years of age or older who were discharged from hospital with antiplatelet therapy following acute myocardial infarction between January 1998 and March 2007. Patients were followed until admission to hospital due to a bleeding episode, admission to hospital due to recurrent acute myocardial infarction, death or the end of the study period.

Results:

The 27 058 patients in the cohort received the following medications at discharge: acetylsalicylic acid (ASA) (n = 14 426); clopidogrel (n = 2467), ASA and clopidogrel (n = 9475); ASA and an SSRI (n = 406); ASA, clopidogrel and an SSRI (n = 239); or clopidogrel and an SSRI (n = 45). Compared with ASA use alone, the combined use of an SSRI with antiplatelet therapy was associated with an increased risk of bleeding (ASA and SSRI: hazard ratio [HR] 1.42, 95% confidence interval [CI] 1.08–1.87; ASA, clopidogrel and SSRI: HR 2.35, 95% CI 1.61–3.42). Compared with dual antiplatelet therapy alone (ASA and clopidogrel), combined use of an SSRI and dual antiplatelet therapy was associated with an increased risk of bleeding (HR 1.57, 95% CI 1.07–2.32).

Interpretation:

Patients taking an SSRI together with ASA or dual antiplatelet therapy following acute myocardial infarction were at increased risk of bleeding.Antiplatelet agents such as acetylsalicylic acid (ASA) and clopidogrel are a mainstay of therapy following acute myocardial infarction. These agents are effective in reducing the risk of recurrent acute myocardial infarction and other cardiovascular events, with the potential for additive benefit when used in combination.^1–3 The risk of bleeding associated with their use, however, is of concern.^4–6 This risk may be increased further by the frequent concomitant use of other medications associated with an increased risk of bleeding, such as anticoagulant therapy⁷ and selective serotonin reuptake inhibitors (SSRIs).Up to 20% of patients with cardiovascular disease experience depression and are most often prescribed an SSRI.^8–13 The vast majority of these patients also use antiplatelet therapy. The risk of bleeding associated with combining SSRI therapy with single or dual antiplatelet therapy is uncertain. Two large clinical trials that examined SSRI use following acute myocardial infarction did not specifically report on the risk of bleeding,^14,15 and earlier studies suggested no increase in risk associated with SSRI therapy combined with single-agent antiplatelet therapy.^16,17SSRI use itself has been associated with an increased risk of bleeding, particularly during the first month of use.¹⁸ The inhibition of serotonin transporters by SSRIs is thought to be responsible for the risk of bleeding.¹⁹ Platelets release serotonin at sites of bleeding and vascular damage; however, they do not synthesize serotonin and instead acquire it from the blood and store it.^19,20 By this mechanism, SSRIs may also worsen the bleeding caused by ASA and clopidogrel.^19,20 Inhibition of cytochrome P450 by certain SSRIs has also been associated with increased risk of drug interaction causing bleeding;²¹ however, data on this issue are scarce.We examined the risk of bleeding associated with the use of SSRIs when combined with single and dual antiplatelet therapy among patients following acute myocardial infarction.     

Splice variant-specific cellular function of the formin INF2 in maintenance of Golgi architecture

INF2 is a unique formin that can both polymerize and depolymerize actin filaments. Mutations in INF2 cause the kidney disease focal and segmental glomerulosclerosis. INF2 can be expressed as two C-terminal splice variants: CAAX and non-CAAX. The CAAX isoform contains a C-terminal prenyl group and is tightly bound to endoplasmic reticulum (ER). The localization pattern and cellular function of the non-CAAX isoform have not been studied. Here we find that the two isoforms are expressed in a cell type-dependent manner, with CAAX predominant in 3T3 fibroblasts and non-CAAX predominant in U2OS, HeLa, and Jurkat cells. Although INF2-CAAX is ER localized in an actin-independent manner, INF2-non-CAAX localizes in an actin-dependent meshwork pattern distinct from ER. INF2-non-CAAX is loosely attached to this meshwork, being extracted by brief digitonin treatment. Suppression of INF2-non-CAAX causes fragmentation of the Golgi apparatus. This effect is counteracted by treatment with the actin monomer-sequestering drug latrunculin B. We also find discrete patches of actin filaments in the peri-Golgi region, and these patches are reduced upon INF2 suppression. Our results suggest that the non-CAAX isoform of INF2 serves a distinct cellular function from that of the CAAX isoform.     

Challenge of Drosophila melanogaster with Cryptococcus neoformans and role of the innate immune response

We found that the ingestion of Cryptococcus neoformans by Drosophila melanogaster resulted in the death of the fly but that the ingestion of Saccharomyces cerevisiae or the nonpathogenic Cryptococcus kuetzingii or Cryptococcus laurentii did not. The C. neoformans protein kinase A and RAS signal transduction pathways, previously shown to be involved in virulence in mammals, also played a role in killing DROSOPHILA: Mutation of the Toll immune response pathway, the predominant antifungal pathway of the fly, did not play a role in Drosophila defense following ingestion of the yeast. However, the Toll pathway was necessary for the clearance of C. neoformans introduced directly into the hemolymph of D. melanogaster and for the survival of systemically infected flies.     

Inhibitors of pathogen intercellular signals as selective anti-infective compounds

Long-term antibiotic use generates pan-resistant super pathogens. Anti-infective compounds that selectively disrupt virulence pathways without affecting cell viability may be used to efficiently combat infections caused by these pathogens. A candidate target pathway is quorum sensing (QS), which many bacterial pathogens use to coordinately regulate virulence determinants. The Pseudomonas aeruginosa MvfR-dependent QS regulatory pathway controls the expression of key virulence genes; and is activated via the extracellular signals 4-hydroxy-2-heptylquinoline (HHQ) and 3,4-dihydroxy-2-heptylquinoline (PQS), whose syntheses depend on anthranilic acid (AA), the primary precursor of 4-hydroxy-2-alkylquinolines (HAQs). Here, we identified halogenated AA analogs that specifically inhibited HAQ biosynthesis and disrupted MvfR-dependent gene expression. These compounds restricted P. aeruginosa systemic dissemination and mortality in mice, without perturbing bacterial viability, and inhibited osmoprotection, a widespread bacterial function. These compounds provide a starting point for the design and development of selective anti-infectives that restrict human P. aeruginosa pathogenesis, and possibly other clinically significant pathogens.     

Robustness of prevalence estimates derived from misclassified data from administrative databases

Because primary data collection can be expensive, researchers are increasingly using information collected in medical administrative databases for scientific purposes. This information, however, is typically collected for reasons other than research, and many such databases have been shown to contain substantial proportions of misclassification errors. For example, many administrative databases contain fields for patient diagnostic codes, but these are often missing or inaccurate, in part because physician reimbursement schemes depend on medical acts performed rather than any diagnosis. Errors in ascertaining which individuals have a given disease bias not only prevalence estimates, but also estimates of associations between the disease and other variables, such as medication use. We attempt to estimate the prevalence of osteoarthritis (OA) among elderly Quebeckers using a government administrative database. We compare a naive estimate relying solely on the physician diagnoses of OA listed in the database to estimates from several different Bayesian latent class models which adjust for misclassified physician diagnostic codes via use of other available diagnostic clues. We find that the prevalence estimates vary widely, depending on the model used and assumptions made. We conclude that any inferences from these databases need to be interpreted with great caution, until further work estimating the reliability of database items is carried out.     

Time-resolved fluoroimmunoassay of potato virus M with monoclonal antibodies

Mouse monoclonal antibodies (MAbs) specific for potato virus M (PVM) were prepared and the properties of three of them were studied. MAb M4C1 is IgG2b, it binds with high affinity to PVM coat protein, to purified virus preparations and recognises PVM in infected potato leaves and tubers. MAb M6D5 is IgG2a and also reacts with PVM coat protein, purified PVM and with PVM in potato leaf and tuber extracts. In double-antibody sandwich ELISA (DAS ELISA) MAbs M4C1 and M6D5 reacted with all 17 PVM isolates tested. MAb M7 is IgG2b and recognises PVM only in indirect dot ELISA on nitrocellulose filters and viral coat protein on Western blots. MAbs against PVM were used as capture antibodies and europium-labelled MAbs as conjugates in time-resolved fluoroimmunoassay (EuTRFIA). The standard EuTRFIA curve of PVM detection is approximately linear over a range of PVM concentrations from 0.5 ng/ml to 1000 ng/ml. The lowest PVM concentration detectable in EuTRFIA was 0.5 ng/ml and correspondingly 6 ng/ml in DAS ELISA. The use of the europium chelate label allows PVM detection in potato leaf and tuber sap at dilutions greater than 10^--⁴ with very low background fluorescence. EuTRFIA with MAbs, with either one or two incubations is about 10–20 times more sensitive for PVM detection than is DAS ELISA. PVM and PVX, mixed with healthy potato tuber sap, were simultaneously tested in a single sample at concentrations lower than 10 ng/ml by double-label TRFIA using europium-labelled MAbs to PVM and samarium-labelled MAbs to PVX.     

Serine/Threonine Kinase 17A Is a Novel Candidate for Therapeutic Targeting in Glioblastoma

STK17A is a relatively uncharacterized member of the death-associated protein family of serine/threonine kinases which have previously been associated with cell death and apoptosis. Our prior work established that STK17A is a novel p53 target gene that is induced by a variety of DNA damaging agents in a p53-dependent manner. In this study we have uncovered an additional, unanticipated role for STK17A as a candidate promoter of cell proliferation and survival in glioblastoma (GBM). Unexpectedly, it was found that STK17A is highly overexpressed in a grade-dependent manner in gliomas compared to normal brain and other cancer cell types with the highest level of expression in GBM. Knockdown of STK17A in GBM cells results in a dramatic alteration in cell shape that is associated with decreased proliferation, clonogenicity, migration, invasion and anchorage independent colony formation. STK17A knockdown also sensitizes GBM cells to genotoxic stress. STK17A overexpression is associated with a significant survival disadvantage among patients with glioma which is independent of age, molecular phenotype, IDH1 mutation, PTEN loss, and alterations in the p53 pathway and partially independent of grade. In summary, we demonstrate that STK17A provides a proliferative and survival advantage to GBM cells and is a potential target to be exploited therapeutically in patients with glioma.     

Magnetic Resonance Spectroscopy of live Drosophila melanogaster using Magic Angle Spinning

High-Resolution Magic Angle Spinning (HRMAS) proton magnetic resonance spectroscopy (¹H-MRS) is a novel non-destructive technique that improves spectral line-widths and allows high-resolution spectra to be obtained from extracts, intact cells, cell cultures, and more importantly intact tissue to investigate relationships between metabolites and cellular processes. In vivo HRMAS ¹H-MRS studies have yet to be reported in the live fruit fly Drosophila melanogaster.Drosophila, as a simpler genetic organism, allows the multiple biological functions and various evolutionarily conserved signaling pathways to be examined at the whole organism level and it is a useful model for investigating genetics and physiology. To this end, we developed and implemented an in vivo HRMAS ¹H-MRS method to investigate live Drosophila at 14.1 T. Here, we outline an HRMAS ¹H-MRS protocol for the molecular characterization of Drosophila with a conventional MR spectrometer equipped with an HRMAS probe. This technique is a novel, in vivo, non-destructive Drosophila metabolite measurement approach, which enables the identification of disease biomarkers and thus may contribute to novel therapeutic development.Download video file.^{(85M, mp4)}     

Genomic analysis reveals that Pseudomonas aeruginosa virulence is combinatorial

Background

Pseudomonas aeruginosa is a ubiquitous environmental bacterium and an important opportunistic human pathogen. Generally, the acquisition of genes in the form of pathogenicity islands distinguishes pathogenic isolates from nonpathogens. We therefore sequenced a highly virulent strain of P. aeruginosa, PA14, and compared it with a previously sequenced (and less pathogenic) strain, PAO1, to identify novel virulence genes.

Results

The PA14 and PAO1 genomes are remarkably similar, although PA14 has a slightly larger genome (6.5 megabses [Mb]) than does PAO1 (6.3 Mb). We identified 58 PA14 gene clusters that are absent in PAO1 to determine which of these genes, if any, contribute to its enhanced virulence in a Caenorhabditis elegans pathogenicity model. First, we tested 18 additional diverse strains in the C. elegans model and observed a wide range of pathogenic potential; however, genotyping these strains using a custom microarray showed that the presence of PA14 genes that are absent in PAO1 did not correlate with the virulence of these strains. Second, we utilized a full-genome nonredundant mutant library of PA14 to identify five genes (absent in PAO1) required for C. elegans killing. Surprisingly, although these five genes are present in many other P. aeruginosa strains, they do not correlate with virulence in C. elegans.

Conclusion

Genes required for pathogenicity in one strain of P. aeruginosa are neither required for nor predictive of virulence in other strains. We therefore propose that virulence in this organism is both multifactorial and combinatorial, the result of a pool of pathogenicity-related genes that interact in various combinations in different genetic backgrounds.