Discovery of aminofurazan-azabenzimidazoles as inhibitors of Rho-kinase with high kinase selectivity and antihypertensive activity.

The discovery, proposed binding mode, and optimization of a novel class of Rho-kinase inhibitors are presented. Appropriate substitution on the 6-position of the azabenzimidazole core provided subnanomolar enzyme potency in vitro while dramatically improving selectivity over a panel of other kinases. Pharmacokinetic data was obtained for the most potent and selective examples and one (6n) has been shown to lower blood pressure in a rat model of hypertension.

Expression and functional role of Rho-kinase in rat urinary bladder smooth muscle.

(1) The involvement of Rho-kinase (ROCK) in the contractile mechanisms mediating smooth muscle contraction of the rat urinary bladder was investigated using expression studies and the ROCK inhibitor Y-27632. (2) Both isoforms of ROCK (ROCK I and ROCK II) were detected in high levels in rat urinary bladder. (3) Y-27632 (10 micro M) significantly attenuated contractions of rat urinary bladder strips evoked by the G-protein coupled receptor agonists carbachol (58.1+/-10.5% at 0.3 micro M) and neurokinin A (68.6+/-12.7% at 1 micro M) without affecting contractions to potassium chloride (10-100 mM). In addition, basal tone was reduced by 47.8+/-2.0% by 10 micro M Y-27632 in the absence of stimulation. (4) Contractions of urinary bladder strips evoked by the P2X receptor agonist alpha,beta-methylene ATP (alpha,beta-mATP; 10 micro M) were also attenuated by Y-27632 (30.0+/-7.2% at 10 micro M). (5) Y-27632 (10 micro M) significantly attenuated contractions evoked by electrical field stimulation (2-16 Hz). The effect of Y-27632 on the tonic portion of the neurogenic response (4-16 Hz) was not significantly different from the effect of atropine (1 micro M) alone. (6) While the mechanism underlying the ability of Y-27632 to inhibit alpha,beta-mATP-evoked contractions remains undetermined, the results of the present study clearly demonstrate a role for ROCK in the regulation of rat urinary bladder smooth muscle contraction and tone.

Induction and superinduction of growth arrest and DNA damage gene 45 (GADD45) alpha and beta messenger RNAs by histone deacetylase inhibitors trichostatin A (TSA) and butyrate in SW620 human colon carcinoma cells.

Histone deacetylase (HDAC) inhibitors such as trichostatin (TSA) and butyrate have been shown to inhibit cancer cell proliferation, induce apoptosis and regulate the expression of genes involved in cell cycle. Although the precise mechanism underlying HDAC inhibitor-induced cell growth arrest is not fully understood, induction of cell cycle related genes such as p21(cip/waf), is thought to be important. Here we showed that in the SW620 human colon cancer cell line, TSA and butyrate induced the growth arrest and DNA damage gene 45alpha (GADD45alpha) and GADD45beta. Furthermore, GADD45beta and p21(cip/waf) messenger RNA were induced in the absence of protein synthesis, indicating that both genes were immediate target genes for TSA. Cyclohexamide and TSA super-induced the expression of GADD45alpha and beta, but not p21(cip/waf). Interestingly while mitogen-activated kinase (MEK) inhibitor PD98059 and p38 kinase inhibitor SB242235 were unable to affect GADD45 induction, two serine/threonine protein kinase inhibitors (H7 and H8) as well as curcumin completely blocked the super-induction. Concomitant to the inhibition of GADD45 induction, H7 and H8 also blocked TSA-induced apoptosis. Taken together, these results suggest that GADD45 induction may play important role in TSA-induced cellular effects.

Novel Rho kinase inhibitors with anti-inflammatory and vasodilatory activities.

Increased Rho kinase (ROCK) activity contributes to smooth muscle contraction and regulates blood pressure homeostasis. We hypothesized that potent and selective ROCK inhibitors with novel structural motifs would help elucidate the functional role of ROCK and further explore the therapeutic potential of ROCK inhibition for hypertension. In this article, we characterized two aminofurazan-based inhibitors, GSK269962A [N-(3-{[2-(4-amino-1,2,5-oxadiazol-3-yl)-1-ethyl-1H-imidazo[4, 5-c]pyridin-6-yl]oxy}phenyl)-4-{[2-(4-morpholinyl)ethyl]-oxy}benzamide] and SB-7720770-B [4-(7-{[(3S)-3-amino-1-pyrrolidinyl]carbonyl}-1-ethyl-1H-imidazo[4,5-c]pyridin-2-yl)-1,2,5-oxadiazol-3-amine], as members of a novel class of compounds that potently inhibit ROCK enzymatic activity. GSK269962A and SB-772077-B have IC50 values of 1.6 and 5.6 nM toward recombinant human ROCK1, respectively. GSK269962A also exhibited more than 30-fold selectivity against a panel of serine/threonine kinases. In lipopolysaccharide-stimulated monocytes, these inhibitors blocked the generation of inflammatory cytokines, such as interleukin-6 and tumor necrosis factor-alpha. Furthermore, both SB-772077-B and GSK269962A induced vasorelaxation in preconstricted rat aorta with an IC50 of 39 and 35 nM, respectively. Oral administration of either GSK269962A or SB-772077-B produced a profound dose-dependent reduction of systemic blood pressure in spontaneously hypertensive rats. At doses of 1, 3, and 30 mg/kg, both compounds induced a reduction in blood pressure of approximately 10, 20, and 50 mm Hg. In addition, administration of SB-772077-B also dramatically lowered blood pressure in DOCA salt-induced hypertensive rats. SB-772077-B and GSK269962A represent a novel class of ROCK inhibitors that have profound effects in the vasculature and may enable us to further evaluate the potential beneficial effects of ROCK inhibition in animal models of cardiovascular as well as other chronic diseases.

Identification of novel isoform-selective inhibitors within class I histone deacetylases.

Histone deacetylases (HDACs) represent an expanding family of protein modifying-enzymes that play important roles in cell proliferation, chromosome remodeling, and gene transcription. We have previously shown that recombinant human HDAC8 can be expressed in bacteria and retain its catalytic activity. To further explore the catalytic activity of HDACs, we expressed two additional human class I HDACs, HDAC1 and HDAC3, in baculovirus. Recombinant HDAC1 and HDAC3 fusion proteins remained soluble and catalytically active and were purified to near homogeneity. Interestingly, trichostatin (TSA) was found to be a potent inhibitor for all three HDACs (IC50 value of approximately 0.1-0.3 microM), whereas another HDAC inhibitor MS-27-275 (N-(2-aminophenyl)-4-[N-(pyridin-3-methyloxycarbonyl)-aminomethyl]benzamide) preferentially inhibited HDAC1 (IC50 value of approximately 0.3 microM) versus HDAC3 (IC50 value of approximately 8 microM) and had no inhibitory activity toward HDAC8 (IC50 value >100 microM). MS-27-275 as well as TSA increased histone H4 acetylation, induced apoptosis in the human colon cancer cell line SW620, and activated the simian virus 40 early promoter. HDAC1 protein was more abundantly expressed in SW620 cells compared with that of HDAC3 and HDAC8. Using purified recombinant HDAC proteins, we identified several novel HDAC inhibitors that preferentially inhibit HDAC1 or HDAC8. These inhibitors displayed distinct properties in inducing histone acetylation and reporter gene expression. These results suggest selective HDAC inhibitors could be identified using recombinantly expressed HDACs and that HDAC1 may be a promising therapeutic target for designing HDAC inhibitors for proliferative diseases such as cancer.