Kamna Nanda

Benign prostatic hyperplasia: an insight into current investigational medical therapies.

Benign prostatic hyperplasia (BPH) is a leading disorder of the elderly male population that is characterised by a progressive enlargement of prostatic tissue, resulting in obstruction of the proximal urethra and causing urinary flow disturbances. The pathophysiology of BPH associated with lower urinary tract symptoms is characterised by increased adrenergic tone (dynamic component) leading to smooth muscle contraction and prostatic overgrowth due to androgenic stimulation (static component); therefore, the therapeutic armamentarium of BPH can be broadly divided into antiadrenergic and antiandrogenic approaches. α1-Adrenoceptor antagonists and 5α-reductase inhibitors are well-established representatives of the two categories, respectively. Other antiandrogenic approaches involve gonadotropin-releasing hormone agonists and antagonists for the treatment of prostate hyperplasia. Apart from these approaches, new approaches with novel targets are emerging. The advent of new therapies is, however, more oriented towards the static component. These involve metabolic factors (hexokinase inhibitor), growth factors (vitamin D3 analogues), oxytocin antagonists and gonadotropin-releasing hormone Gi agonist-based therapies. Gene therapy and photodynamic therapies are other emerging therapies for relieving symptoms in BPH patients. With the initial success of upcoming targets, the unmet need to develop an efficacious and relatively safe therapeutic modality is discussed. Nevertheless, their long-term safety and efficacy needs to be evaluated in large-scale clinical trials. The future also belongs to combination therapies to combat both dynamic and static disease components and for extended indications such as micturition disorder and non-bacterial prostatitis.

RBx 6198 : A novel α1-adrenoceptor antagonist for the treatment of benign prostatic hyperplasia

The present study, investigates the effect of RBx 6198, 2-{3-[4-(2-Isopropoxy-phenyl)-piperazin-1-yl]-propyl}-3a, 4, 7, 7a-tetrahydro-isoindole-1, 3,-dione, a novel alpha(1)-adrenoceptor antagonist, in both in vitro and in vivo test systems. RBx 6198 is a potent (nanomolar affinity) alpha(1A)-adrenoceptor antagonist with demonstrable uroselectivity in anaesthesized dog model. In radioligand binding studies using human recombinant receptors, RBx 6198 exhibited high selectivity (approximately 50 fold) for the alpha(1A)-adrenoceptor subtype as compared to alpha(1B)-adrenoceptor subtype. In order to assess tissue selectivity, the antagonistic effect of RBx 6198 on the phenylephrine induced contractile response of isolated rat prostate, spleen and aorta was characterized. RBx 6198 was 8 fold more potent in inhibiting phenylephrine-evoked contractions of isolated tissues compared to tamsulosin. However, the compound was non-selective for alpha(1A) vs. alpha(1D)-adrenoceptor like tamsulosin. In anaesthetized beagle dogs RBx 6198 suppressed the intraurethral pressure response to phenylephrine to a greater extent than the mean arterial pressure response thereby demonstrating uroselectivity consistent with in vitro binding and functional data. RBx 6198 was 6.4 fold more uroselective as compared to tamsulosin after i.v. route dose administration. Taken together all results from preclinical studies, it is suggested that RBx 6198 is a novel alpha(1)-adrenoceptor antagonist that exhibited improved pharmacological profile over tamsulosin in both in vitro and in vivo.

Molecular cloning, stable expression and cellular localization of human α1-adrenergic receptor subtypes: effect of charcoal/dextran treated serum on expression and localization of α1D-adrenergic receptor

The cDNAs encoding for three subtypes of adrenergic receptors, α1A-, α1B- and α1D-ARs, were cloned and expressed in HEK 293 cells. Expression of α1A- and α1B-AR subtypes in HEK 293 cells was stable even with increased passages but that of α1D-AR was not. Cellular localization studies using immunofluorescence and flow cytometry revealed that expression of α1A- and α1B-ARs was primarily localized on the cell membrane whereas expression of α1D-AR was␣predominantly intracellular. Our studies clearly demonstrated that the culturing of the recombinant cell lines expressing α1D-AR in charcoal/dextran treated fetal bovine serum (FBS) resulted in targeting of α1D-AR to the cell membrane and thus, significantly improving its stability and availability for ligand binding studies.

Ratiometric Ca+2 measurement in human recombinant muscarinic receptor subtypes using the Flexstation scanning fluorometer

In modern drug discovery, numerous assay formats are available to screen and quantitate receptor-ligand interactions. Radioactive assays are “gold standard” because they are fast, easy, and reproducible; however, they are hazardous, produce radioactive waste, require special lab conditions, and are expensive on a large scale. Thus, it provides a lot of importance to the “mix & measure” assays that have an optical readout. Fluorescence techniques are likely to be among the most important detection approaches used for high throughput screening due to their high sensitivity and amenability to automation. The aim of the present study was to determine the functional antagonistic affinities of standard muscarinic antagonists in CHO cells over expressing m1, m3, and m5 receptors and to compare them with the respective binding affinities. This study was further extended to elucidate that Ca+2 measurement assays can serve as a functional screening tool for GPCRs. For this purpose, standard muscarinic receptor antagonists, namely, tolterodine, oxybutynin, and atropine were used. We determined and compard the IC50 values of these three standard inhibitors in fura 2 AM loaded m1, m3, and m5 overexpressing CHO cells and in radioligand binding assay. Both the assays exhibited comparable rank order potencies of the standard inhibitors. This study suggests that Ca+2 mobilization assays can be an alternate to radioligand binding assays.

Identification and synthesis of novel inhibitors of mycobacterium ATP synthase

A non-diaryl quinoline scaffold 6,7-dihydropyrazolo[1,5-a]pyrazin-4-one was identified by screening of diverse set of compounds against M. smegmatis ATP synthase. Herein, we disclose our efforts to develop the structure activity relationship against Mycobacterium tuberculosis (Mtb.H37Rv strain) around the identified hit 1. A scaffold hopping approach was used to identify compounds 14a, 14b and 24a with improved activity against MTb.H37Rv.

Functional screening of adrenergic receptors by measuring intracellular calcium using the FlexStation scanning fluorimeter.

In this study we test whether functional screening of compounds to adrenergic G protein-coupled receptors (GPCRs) would provide data that correlated significantly with radiolabeled binding data, thereby permitting researchers to replace expensive radioligand-binding experiments with non-radioactive screening. An increase in intracellular calcium levels represents an important second messenger signal for several recombinant GPCRs. In this study, we describe the affinities of three alpha adrenoceptor antagonists (terazosin, tamsulosin and alfuzosin), determined by monitoring the changes in intracellular calcium levels and comparing them with their radioligand-binding affinities. In addition to determining the functional affinities of the three alpha adrenoceptor antagonists, we evaluate their binding at two alpha adrenoceptor subtypes and optimized the assay for high-throughput screening.

WITHDRAWN: Derivatives of cis-1,2,3,6-tetrahydrophthalimide for the treatment of benign prostatic hyperplasia.

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