Genomic regulation of Krüppel-like-factor family members by corticosteroid receptors in the rat brain.

Hippocampal mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) mediate glucocorticoid hormone (GC) action in the hippocampus. These receptors bind to glucocorticoid responsive elements (GREs) within target genes, eliciting transcriptional effects in response to stress and circadian variation. Until recently, little was known about the genome-wide targets of hippocampal MRs and GRs under physiological conditions. Following on from our genome-wide MR and GR ChIP-seq and Ribo-Zero RNA-seq studies on rat hippocampus, we investigated the Krüppel-like factors (KLFs) as targets of MRs and GRs throughout the brain under circadian variation and after acute stress. In particular, Klf2, Klf9 and Klf15 are known to be stress and/or GC responsive and play a role in neurobiological processes including synaptic plasticity and neuronal differentiation. We found increased binding of MR and GR to GREs within Klf2, Klf9 and Klf15 in the hippocampus, amygdala, prefrontal cortex, and neocortex after acute stress and resulting from circadian variation, which was accompanied by upregulation of corresponding hnRNA and mRNA levels. Adrenalectomy abolished transcriptional upregulation of specific Klf genes. These results show that MRs and GRs regulate Klf gene expression throughout the brain following exposure to acute stress or in response to circadian variation, likely alongside other transcription factors.

Genome-wide chromosomal association of Upf1 is linked to Pol II transcription in Schizosaccharomyces pombe.

Although the RNA helicase Upf1 has hitherto been examined mostly in relation to its cytoplasmic role in nonsense mediated mRNA decay (NMD), here we report high-throughput ChIP data indicating genome-wide association of Upf1 with active genes in Schizosaccharomyces pombe. This association is RNase sensitive, correlates with Pol II transcription and mRNA expression levels. Changes in Pol II occupancy were detected in a Upf1 deficient (upf1Δ) strain, prevalently at genes showing a high Upf1 relative to Pol II association in wild-type. Additionally, an increased Ser2 Pol II signal was detected at all highly transcribed genes examined by ChIP-qPCR. Furthermore, upf1Δ cells are hypersensitive to the transcription elongation inhibitor 6-azauracil. A significant proportion of the genes associated with Upf1 in wild-type conditions are also mis-regulated in upf1Δ. These data envisage that by operating on the nascent transcript, Upf1 might influence Pol II phosphorylation and transcription.

Distinct regulation of hippocampal neuroplasticity and ciliary genes by corticosteroid receptors.

Glucocorticoid hormones (GCs) - acting through hippocampal mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) - are critical to physiological regulation and behavioural adaptation. We conducted genome-wide MR and GR ChIP-seq and Ribo-Zero RNA-seq studies on rat hippocampus to elucidate MR- and GR-regulated genes under circadian variation or acute stress. In a subset of genes, these physiological conditions resulted in enhanced MR and/or GR binding to DNA sequences and associated transcriptional changes. Binding of MR at a substantial number of sites however remained unchanged. MR and GR binding occur at overlapping as well as distinct loci. Moreover, although the GC response element (GRE) was the predominant motif, the transcription factor recognition site composition within MR and GR binding peaks show marked differences. Pathway analysis uncovered that MR and GR regulate a substantial number of genes involved in synaptic/neuro-plasticity, cell morphology and development, behavior, and neuropsychiatric disorders. We find that MR, not GR, is the predominant receptor binding to >50 ciliary genes; and that MR function is linked to neuronal differentiation and ciliogenesis in human fetal neuronal progenitor cells. These results show that hippocampal MRs and GRs constitutively and dynamically regulate genomic activities underpinning neuronal plasticity and behavioral adaptation to changing environments.

Dronedarone: an alternative to amiodarone?

OBJECTIVE: To review the safety and efficacy of the newly approved, mixed-activity antiarrhythmic dronedarone (classes I-IV) versus its parent compound comparator, amiodarone (class III, with mixed activity). DATA SOURCES: A MEDLINE/PUBMED (January 1966 to March 2010) and International Pharmaceutical Abstract (January 1975 to March 2010) search of English language papers in addition to a bibliographic search of retrieved papers. STUDY SELECTION: All human studies of dronedarone, alone or in combination with amiodarone, were reviewed. DATA SYNTHESIS: Approved in July 2009, dronedarone is a new antiarrhythmic agent indicated to reduce the risk of hospitalization for cardiac events in patients with paroxysmal or persistent atrial fibrillation or atrial flutter. Dronedarone has been viewed as a potential therapeutic alternative for amiodarone because of a lower risk for pulmonary, thyroid, and dermatologic adverse effects. Compared with amiodarone, dronedarone has poor bioavailability and a shorter terminal disposition half-life, which dictates a twice-daily dosing regimen. Furthermore, dronedarone failed to demonstrate superiority over amiodarone with respect to recurrence of atrial fibrillation in a comparative efficacy analysis. Dronedarone therapy is more costly and increases overall tablet burden. No dosage adjustments are required with dronedarone for renal impairment. Use of dronedarone is contraindicated in the presence of severe hepatic impairment. No serious organ-related toxicities (i.e., thyroid and pulmonary system) have been reported with use of dronedarone. CONCLUSION: Dronedarone as a niche drug may be a reasonable theoretical alternative for patients who cannot tolerate amiodarone or have underlying comorbidities that contraindicate amiodarone use (e.g., pulmonary, thyroid disease). However, dronedarone has not been studied in the vast majority of indications and patient populations in which amiodarone has been studied.