Biomedical subjects

Blake C Beehler

Publications and source records attributed to Blake C Beehler.

7 recordsLinked to original sources

PubMed2006

Discovery of potent, orally-active, and muscle-selective androgen receptor modulators based on an N-aryl-hydroxybicyclohydantoin scaffold.

A novel, N-aryl-bicyclohydantoin selective androgen receptor modulator scaffold was discovered through structure-guided modifications of androgen receptor antagonists. A prototype compound (7R,7aS)-10b from this series is a potent and highly tissue-selective agonist of the androgen receptor. After oral dosing in a rat atrophied levator ani muscle model, (7R,7aS)-10b demonstrated efficacy at restoring levator ani muscle mass to that of intact controls and exhibited >50-fold selectivity for muscle over prostate.

Administration, Oral↗

PubMed2006

Pharmacological and x-ray structural characterization of a novel selective androgen receptor modulator: potent hyperanabolic stimulation of skeletal muscle with hypostimulation of prostate in rats.

A novel, highly potent, orally active, nonsteroidal tissue selective androgen receptor (AR) modulator (BMS-564929) has been identified, and this compound has been advanced to clinical trials for the treatment of age-related functional decline. BMS-564929 is a subnanomolar AR agonist in vitro, is highly selective for the AR vs. other steroid hormone receptors, and exhibits no significant interactions with SHBG or aromatase. Dose response studies in castrated male rats show that BMS-564929 is substantially more potent than testosterone (T) in stimulating the growth of the levator ani muscle, and unlike T, highly selective for muscle vs. prostate. Key differences in the binding interactions of BMS-564929 with the AR relative to the native hormones were revealed through x-ray crystallography, including several unique contacts located in specific helices of the ligand binding domain important for coregulatory protein recruitment. Results from additional pharmacological studies effectively exclude alternative mechanistic contributions to the observed tissue selectivity of this unique, orally active androgen. Because concerns regarding the potential hyperstimulatory effects on prostate and an inconvenient route of administration are major drawbacks that limit the clinical use of T, the potent oral activity and tissue selectivity exhibited by BMS-564929 are expected to yield a clinical profile that provides the demonstrated beneficial effects of T in muscle and other tissues with a more favorable safety window.

Aging↗

PubMed2006

Reduction of skeletal muscle atrophy by a proteasome inhibitor in a rat model of denervation.

The ubiquitin-proteasome system is the primary proteolytic pathway implicated in skeletal muscle atrophy under catabolic conditions. Although several studies showed that proteasome inhibitors reduced proteolysis under catabolic conditions, few studies have demonstrated the ability of these inhibitors to preserve skeletal muscle mass and architecture in vivo. To explore this, we studied the effect of the proteasome inhibitor Velcade (also known as PS-341 and bortezomib) in denervated skeletal muscle in rats. Rats were given vehicle or Velcade (3 mg/kg po) daily for 7 days beginning immediately after induction of muscle atrophy by crushing the sciatic nerve. At the end of the study, the rats were euthanized and the soleus and extensor digitorum longus (EDL) muscles were harvested. In vehicle-treated rats, denervation caused a 33.5 +/- 2.8% and 16.2 +/- 2.7% decrease in the soleus and EDL muscle wet weights (% atrophy), respectively, compared to muscles from the contralateral (innervated) limb. Velcade significantly reduced denervation-induced atrophy to 17.1 +/- 3.3% in the soleus (P < 0.01), a 51.6% reduction in atrophy associated with denervation, with little effect on the EDL (9.8 +/- 3.2% atrophy). Histology showed a preservation of muscle mass and preservation of normal cellular architecture after Velcade treatment. Ubiquitin mRNA levels in denervated soleus muscle at the end of the study were significantly elevated 120 +/- 25% above sham control levels and were reduced to control levels by Velcade. In contrast, testosterone proprionate (3 mg/kg sc) did not alleviate denervation-induced skeletal muscle atrophy but did prevent castration-induced levator ani atrophy, while Velcade was without effect. These results show that proteasome inhibition attenuates denervation-induced muscle atrophy in vivo in soleus muscles. However, this mechanism may not be operative in all types of atrophy.

Animals↗

PubMed2004

Retinoic acid signalling specifies intermediate character in the developing telencephalon.

The organisation of the telencephalon into its major structures depends on its early regionalisation along the dorsoventral axis. Previous studies have provided evidence that sonic hedgehog (SHH) is required for the generation of telencephalic cells of ventral character, and that sequential WNT and fibroblast growth factor (FGF) signalling specifies cells of dorsal telencephalic character. However, the signalling mechanisms that specify telencephalic cells of an intermediate character remain to be defined. We provide evidence here that retinoic acid has a crucial role in specifying telencephalic progenitor cells of intermediate character.

Animals↗

PubMed2004

Selective retinoic acid receptor ligands for rheumatoid arthritis.

Retinoids, modulators of retinoic acid receptors (RARs), have been studied for over 20 years as potential therapeutic agents for rheumatoid arthritis (RA). Early successes at the in vitro and in vivo levels were overshadowed by disappointing clinical trials that yielded poor efficacy and unacceptable side effects. A greater understanding of retinoid biology has led to the development of many synthetic retinoids that selectively modulate the RAR isotypes. RAR selective retinoids have a high potential for improved pharmacology with reduced toxicity, thereby renewing interest for the use of retinoids in RA.

Arthritis, Rheumatoid↗

PubMed2003

Effects of the thyroid hormone receptor agonist GC-1 on metabolic rate and cholesterol in rats and primates: selective actions relative to 3,5,3'-triiodo-L-thyronine.

Current drug therapies for obesity are ineffective, and existing treatments for lipid disorders can be further improved. Thyroid hormones affect both conditions, although currently available nonselective thyromimetics are not clinically useful for such treatment due to cardiac side effects. Recent studies suggest that thyroid hormone receptor subtype beta (TRbeta) selective agonists have a profile in which cholesterol can be reduced with minimal tachycardia. The purpose of this study was to determine whether modest (5-10%) increases in metabolic rate could also be observed with minimal tachycardia after TRbeta stimulation. For these studies, the TRbeta selective agonist, GC-1, was used to assess selectivity for lipid-lowering and metabolic rate changes relative to tachycardia. Studies in cholesterol-fed rats (7 d treatment) showed that GC-1 reduced cholesterol (ED(50) = 190 nmol/kg x d) approximately 30 times more potently than it induced tachycardia (ED(15) = 5451 nmol/kg x d). T(3) showed no potency difference between cholesterol lowering and tachycardia. GC-1 showed approximately 10-fold selectivity for increasing metabolic rate (ED(5) = 477 nmol/kg x d) relative to tachycardia compared with T(3), which showed no selectivity. In cynomolgus monkeys treated for 7 d, significant cholesterol-lowering and lipoprotein (a) reduction was noted for both T(3) and GC-1, whereas no tachycardia was observed for GC-1, unlike T(3). T(3) and GC-1 caused a significant (approximately 4%) reduction in body weight in these animals. Therefore, selective TRbeta activation may be a potentially usefully treatment for obesity and reduction of low density lipoprotein cholesterol and reduction of the atherogenic risk factor lipoprotein (a).

Acetates↗

PubMed2003

Inhibition of disease progression by a novel retinoid antagonist in animal models of arthritis.

OBJECTIVE: To investigate the usefulness of a novel retinoic acid receptor (RAR) antagonist (BMS-189453) in animal models of arthritis. METHODS: BMS-189453 was tested in HIG-82 rabbit synovial fibroblasts to determine its ability to repress collagenase (matrix metalloproteinase-1, MMP-1) mRNA expression in vitro. Cells were stimulated with phorbol myristate acetate or interleukin 1 beta and mRNA quantified by slot-blot analysis. In vivo, BMS-189453 was evaluated in 2 animal models of arthritis: collagen induced arthritis (CIA) in mice and streptococcal cell wall induced arthritis (SCWA) in rats. Clinical scores for arthritis were recorded weekly. At the end of each study, limbs were evaluated histologically. In CIA, these results were correlated with mRNA levels for collagenase-3 (MMP-13) and stromelysin-1 (MMP-3) as determined by Northern blot. RESULTS: BMS-189453 reduced MMP-1 expression in HIG-82 synovial fibroblasts in culture. BMS-189453 treatment blocked the clinical progression of arthritis beyond soft tissue inflammation in the CIA model. In the SCWA model, BMS-189453 treatment resulted in significantly reduced swelling with no notable progression to joint distortion/destruction. Histological evaluation of the joints from animals in both models confirmed this result. Analysis of mRNA from the CIA paws showed that BMS-189453 prevented the overexpression of MMP-13 and MMP-3 in arthritic joints. CONCLUSION: Improvement in clinical and histologic variables in 2 separate animal models, along with simultaneous reduction in MMP expression in the affected joint, suggests that RAR antagonists such as BMS-189453 may be useful as agents to treat rheumatoid arthritis and for determining the role of MMP in disease progression. This is the first study to show the clinical potential of RAR antagonists in arthritis.

Animals↗