J. Dieter Geratz

Amidino-substituted aromatic heterocycles as probes of the specificity pocket of trypsin-like proteases

Abstract A number of amidino-substituted heterocycles were synthesized and examined for their inhibitory effect against arginine-directed esteroproteases, including human and bovine thrombin (EC 3.4.21.5), human factor Xa and plasmin (EC 3.4.21.7), bovine trypsin (EC 3.4.21.4), porcine pancreatic Kallikrein (EC 3.4.21.8), and boar acrosin (EC 3.4.21.10). Inhibition was competitive and reversible in all cases, and the K i values were taken to reflect binding conditions in the specificity pockets of the enzymes. A remarkably potent blocking agent was found in 5-amidinoindole. Compared to the established inhibitor benzamidine, it proved one to two orders of magnitude more effective against the majority of the proteases, the exceptions being trypsin and plasmin. Improved hydrophobic interaction, fortuitous hydrogen bonding, and charge transfer complex formation were considered in accounting for the considerable activity of the compound. Placement of the amidino moiety in the 6-position rather than in the 5-position on the indole ring resulted in a striking loss of inhibitory potency against human and bovine thrombin, factor Xa, and Kallikrein, yet slightly improved the affinity with respect to acrosin. Tightness of binding of the inhibitors to the enzymes was pH dependent and was significantly reduced below pH 7.0.

Control of glucan-induced systemic granulomatosis by cyclosporine A

This study has shown that cyclosporine A (CyA), under certain conditions, is a powerful inhibitor of intravascular and extravascular monocyte/macrophage accumulation. Experiments were carried out in Lewis rats in which intravenous injection of particulate glucan calls forth a striking granulomatous response in lung, liver, and spleen and produces a marked stimulation of splenic erythro- and myelopoiesis. In agreement with the results of others, there was also a considerable elevation in monocyte/macrophage chemoattractant levels in the bronchoalveolar lavage fluid, which is held to be a key reaction in the pathogenesis of the histologic lesions. Treatment of the animals with subcutaneous injections of CyA prevented the rise in the chemoattractant activity and suppressed the granulomatous organ infiltration as well as the splenic hemopoiesis. The findings supply new insights into the activities of CyA and would support its clinical use in macrophage-dominated diseases.