Objectives A family of histone deacetylases (HDACs) mediates chromatin remodeling, and repression of gene expression. Deacetylation of histones within the HIV-1 long terminal repeat (LTR) by HDACs plays a key role in the maintenance of latency, whereas acetylation of histones about the LTR is linked to proviral expression and escape of HIV from latency. Global HDAC inhibition may adversely affect host gene expression, leading to cellular toxicities. Potent inhibitors selective for HDACs that maintain LTR repression could be ideal antilatency therapeutics. Methods We investigated the ability of selective HDAC inhibitors to de-repress the HIV-1 LTR in both a cell line model of latency and in resting CD4+ T cells isolated from patients who were aviremic on antiretroviral therapy (ART). Results We found that inhibition of class I HDACs increased acetylation of histones at the LTR, but that LTR chromatin was unaffected by class II HDAC inhibitors. In a latently infected cell line, inhibitors selective for class I HDACs were more efficient activators of the LTR than inhibitors that target class II HDACs. Class I HDAC inhibitors were strikingly efficient inducers of virus outgrowth from resting CD4+ T cells of aviremic patients, whereas HIV was rarely recovered from patient’s cells exposed to class II HDAC inhibitors. Conclusions Further development of selective HDAC inhibitors as part of a clinical strategy to target persistent HIV infection is warranted.

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Radioligand binding studies have detected alpha1A- and alpha1B-adrenergic receptors (AR) in rat heart, but the ligands available for these studies lack the sensitivity and specificity needed to map possible differences in alpha1-AR subtype expression. We therefore used competitive reverse transcriptase-polymerase chain reaction (RT-PCR) techniques to measure steady-state amounts of alpha1-AR messenger RNA (mRNA) subtypes in tissue dissected from several regions of rat heart. We detected mRNA for alpha1A-, alpha1B-, and alpha1D-AR in each region. Irrespective of the alphaAR subtype, the total number of alpha1-AR transcripts has the following regional rank order: left ventricular papillary muscle > left ventricle > left atrium > apex > right ventricle > ventricular septum > right atria. Among the regions, the fractional contribution of alpha1A-, alpha1B-, and alpha1D-AR mRNA to the total amount of alpha1-AR displays considerable variability. The alpha1B-AR mRNA accounts for >50% of the total alpha1-AR mRNA in all regions except the ventricular septum. There are also significant percentages of alpha1A-AR in each region, especially in the papillary muscle (48%) and ventricular septum (48%). The alpha1D-AR mRNA transcripts are found in comparatively low numbers; their highest levels (18% of total) were found in the right ventricle. These differences in alpha1-AR mRNA expression may contribute to the observed regional differences in myocardial responses to alpha1-AR agonists and antagonists.

The spiral modiolar artery supplies blood and essential nutrients to the cochlea. Our previous functional study indicates the α1A–adrenergic receptor subtype mediates vasoconstriction of the gerbil spiral modiolar artery. Although the gerbil cochlea is often used as a model in hearing research, the molecular and pharmacological characteristics of the cloned gerbil α1a-adrenergic receptor have not been determined. Thus we cloned, expressed and characterized the gerbil α1a-adrenergic receptor and then compared its molecular and pharmacological properties to those of other mammalian α1a-adrenergic receptors. The cDNA clone contained 1404 nucleotides, which encoded a 467 amino acid peptide with a deduced sequence having 96.8, 96.4 and 91.6% identity to rat, mouse and human α1a-receptors, respectively. We transiently transfected the α1a-adrenergic receptor into COS-1 cells and determined its pharmacological characteristics by [3H]prazosin binding. Unlabeled prazosin had a Ki of 0.89 ± 0.1 nM. The α1A-adrenergic receptor-selective antagonists, 5-methylurapidil and WB-4101, bound with high affinity and had Ki values of 4.9 ± 1 and 1.0 ± 0.1 nM, respectively. BMY-7378, an α1D-adrenergic receptor-selective antagonist, bound with low affinity (260 ± 60 nM). The 91.6% amino acid sequence identity and Kis of the cloned gerbil α1a-adrenergic receptor are similar to those of the human α1a-adrenergic receptor clone. These results show that the gerbil α1a-adrenergic receptor is representative of the human α1a-adrenergic receptor, lending validity to the use of the gerbil spiral modiolar artery as a model in studies of vascular disorders of the cochlea.

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