Structural Basis for Inhibition Promiscuity of Dual Specific Thrombin and Factor Xa Blood Coagulation Inhibitors

AbstractBackground: A major current focus of pharmaceutical research is the development of selective inhibitors of the blood coagulation enzymes thrombin or factor Xa to be used as orally bioavailable anticoagulant drugs in thromboembolic disorders and in the prevention of venous and arterial thrombosis. Simultaneous direct inhibition of thrombin and factor Xa by synthetic proteinase inhibitors as a novel approach to antithrombotic therapy could result in potent anticoagulants with improved pharmacological properties.Results: The binding mode of such dual specific inhibitors of thrombin and factor Xa was determined for the first time by comparative crystallography using human α-thrombin, human des-Gla (1–44) factor Xa and bovine trypsin as the ligand receptors. The benzamidine-based inhibitors utilize two different conformations for the interaction with thrombin and factor Xa/trypsin, which are evoked by the steric requirements of the topologically different S2 subsites of the enzymes. Compared to the unliganded forms of the proteinases, ligand binding induces conformational adjustments of thrombin and factor Xa active site residues indicative of a pronounced induced fit mechanism.Conclusion: The structural data reveal the molecular basis for a desired unselective inhibition of the two key components of the blood coagulation cascade. The 4-(1-methyl-benzimidazole-2-yl)-methylamino-benzamidine moieties of the inhibitors are able to fill both the small solvent accessible as well as the larger hydrophobic S2 pockets of factor Xa and thrombin, respectively. Distal fragments of the inhibitors are identified which fit into both the cation hole/aromatic box of factor Xa and the hydrophobic aryl binding site of thrombin. Thus, binding constants in the medium-to-low nanomolar range are obtained against both enzymes

Inhibition of tissue angiotensin-converting enzyme with quinapril reduces hypoxic pulmonary hypertension and pulmonary vascular remodeling

BACKGROUND: Angiotensin II may contribute to hypoxic pulmonary hypertension via its vasoconstrictor and growth-stimulatory effects on vascular smooth muscle cells (VSMCs). Therefore, the use of ACE inhibitors might reduce hypoxic pulmonary hypertension by decreasing pulmonary vasomotor tone or vascular remodeling. METHODS AND RESULTS: Pulmonary hemodynamics and vascular remodeling were compared in chronically hypoxic (FIO2 = 0.10) rats treated with 0, 1, and 10 mg.kg-1.d-1 quinapril, a potent tissue ACE inhibitor, both during and after the development of pulmonary hypertension. Quinapril reduced the development of pulmonary hypertension after 12 days of hypoxia from 26 +/- 1 to 19 +/- 1 mm Hg (P < .05). When started in established pulmonary hypertension, quinapril reduced pulmonary artery pressure and total pulmonary resistance index from 29 +/- 1 to 25 +/- 1 mm Hg and from 0.136 +/- 0.01 to 0.101 +/- 0.005 mm Hg .mL-1.min-1 per kg, respectively (P < .05). Chronically hypoxic rats showed a small pulmonary vasoconstrictor response that was not affected by quinapril. In contrast, percent medial thickness in alveolar duct blood vessels was reduced by quinapril treatment both in developing and in established pulmonary hypertension (10.0 +/- 0.2% versus 8.9 +/- 0.1% [P < .05] and 11.2 +/- 0.2% versus 9.1 +/- 0.2% [P < .05], respectively). 5'-Bromo-deoxyuridine-positive VSMCs were detected in 56 +/- 3% of hypoxic control pulmonary resistance vessels versus 41 +/- 3% of vessels after quinapril treatment (P < .05). CONCLUSIONS: Pulmonary ACE and angiotensin II contribute to the development and maintenance of hypoxic pulmonary hypertension in rats. ACE inhibition with quinapril reduces the development of hypoxic pulmonary hypertension and in part reverses established pulmonary hypertension, most likely via inhibition of pulmonary VSMC proliferation and/or growth.status: publishe

Serum protein N-glycan alterations of diethylnitrosamine-induced hepatocellular carcinoma mice and their evolution after inhibition of the placental growth factor

Placental growth factor (PlGF) inhibition produced promising results in reducing tumor burden in a diethylnitrosamine (DEN)-induced mouse model for hepatocellular carcinoma (HCC). The aim of this study was to non-invasively assess the improved histology by performing a serum glycomic analysis. To elucidate the molecular mechanism underlying the observed glycomic effects, we investigated the transcription and expression of E26 transformation-specific sequence 1 (Ets-1), a transcription factor essential for the glycomic and angiogenic changes in malignant transformation, including its different phosphorylated forms that result from activation of the MAP kinase and a Ca2+-dependent pathway. In addition, three Ets-1-dependent glycosyltransferase genes, Mgat4a, Mgat4b, and Mgat5, were also evaluated. HCC was induced in mice by weekly injections with DEN for 16, 20, 25, and 30 w. In the treatment study, mice were injected with DEN for 25 w and subsequently treated with PlGF antibodies (5D11D4) for 5 w. Finally, PlGF-/- mice were injected with DEN for 20, 25, and 30 w. Serum N-glycans were analyzed with DNA sequencer-assisted fluorophore-assisted capillary electrophoresis and compared with histology. Maximum altered N-glycan phenotype was reached after 20 w of DEN-injections, i.e., when the first neoplastic lesions started to appear. 5D11D4-treatment improved the glycomic phenotype in that 7 of the 11 altered glycans tended to normalize. The PlGF-/- mice also showed a normalization trend, although not to the same extent of the treatment group. Number of Ets1, Mgat4a, Mgat4b, and Mgat5 transcripts increased considerably in DEN-injected mice, however, a non-significant decrease was observed after 5D11D4-treatment. On the protein level, 5D11D4-treatment had a prominent effect on the MAP kinase pathway with a significant p38 activation, yet independent of Ets-1 function