Heinz-Werner Kleemann

Interaction of renin inhibitors with the intestinal uptake system for oligopeptides and β-lactam antibiotics

The interaction of two renin inhibitors, S 86,2033 and S 86,3390, with the uptake system for beta-lactam antibiotics and small peptides in the brush border membrane of enterocytes from rabbit small intestine was investigated using brush border membrane vesicles. Both renin inhibitors inhibited the uptake of the orally active cephalosporin cephalexin into brush border membrane vesicles from rabbit small intestine in a concentration-dependent manner. 1.1 mM of S 86,3390 and 2.5 mM of S 86,2033 led to a half-maximal inhibition of the H(+)-dependent uptake of cephalexin. Both renin inhibitors were stable against peptidases of the brush border membrane. The uptake of cephalexin into brush border membrane vesicles (1 min of incubation) was competitively inhibited by S 86,2033 and S 86,3390 suggesting a direct interaction of these compounds with the intestinal peptide uptake system. The renin inhibitors are transported across the brush border membrane into the intravesicular space as was shown by equilibrium uptake studies dependent upon the medium osmolarity. The uptake of S 86,3390 was stimulated by an inwardly directed H(+)-gradient and occurred with a transient accumulation against a concentration gradient (overshoot phenomenon). The renin inhibitors S 86,2033 and 86,3390 also caused a concentration-dependent inhibition in the extent of photoaffinity labeling of the putative peptide transport protein of apparent Mr 127,000 in the brush border membrane of small intestinal enterocytes. In conclusion, these studies show that renin inhibitors specifically interact with the intestinal uptake system shared by small peptides and beta-lactam antibiotics.

Inhibition of diacylglycerol–sensitive TRPC channels by synthetic and natural steroids

TRPC channels are a family of nonselective cation channels that regulate ion homeostasis and intracellular Ca2+ signaling in numerous cell types. Important physiological functions such as vasoregulation, neuronal growth, and pheromone recognition have been assigned to this class of ion channels. Despite their physiological relevance, few selective pharmacological tools are available to study TRPC channel function. We, therefore, screened a selection of pharmacologically active compounds for TRPC modulating activity. We found that the synthetic gestagen norgestimate inhibited diacylglycerol-sensitive TRPC3 and TRPC6 with IC50s of 3–5 µM, while half-maximal inhibition of TRPC5 required significantly higher compound concentrations (>10 µM). Norgestimate blocked TRPC-mediated vasopressin-induced cation currents in A7r5 smooth muscle cells and caused vasorelaxation of isolated rat aorta, indicating that norgestimate could be an interesting tool for the investigation of TRP channel function in native cells and tissues. The steroid hormone progesterone, which is structurally related to norgestimate, also inhibited TRPC channel activity with IC50s ranging from 6 to 18 µM but showed little subtype selectivity. Thus, TRPC channel inhibition by high gestational levels of progesterone may contribute to the physiological decrease of uterine contractility and immunosuppression during pregnancy.

3N-methylbiphenylsulfonylurea and -carbamate substituted imidazo[4,5-b]pyridines. Potent antagonists of the ANG II AT1 receptors.

The synthesis and the SAR study of imidazo[4,5-b]pyridine biphenyl sulfonylureas and -carbamates as highly potent AT1-selective ANG II receptor antagonists are described. Several members of this new class of antagonists efficiently inhibited the ANG II-induced pressor response in pithed rats after iv and intraduodenal (id) administration.

Cariporide, a selective Na+/H+ exchange inhibitor, decreases liver fibrosis in the bile duct ligated rat

Results: We demonstrate 1) That both core tumour and non-tumourderived sequences inhibit the global antiviral effects of IFNa on VSV and EMCV replication in Ratl and HuH7 cells and sensitize Ref cells to transformation, in cooperation with ras oncogene. 2) That tumour and nontumour derived cores show, however, a quite distinct pattern of biological effects on IFNa signaling: inhibition of global antiviral effect of IFNa in tumour-derived expressing cells is much less pronounced, compared with non tumour-derived and reference lb cores.Expression of tumour-derived, and not non-tumour-derived nor reference lb cores, induces transactivafion of 0interferon sensitive response element0 (ISRE); tumour-derived core also increases phosphorylation of Statl and Stat 2, compared with nontumour-derived and reference lb proteins.Tumour-derived core show a markedly increased transforming activity in REF cells, in cooperation with ras oncogene, compared with non-tumour-derived and reference lb cores. Conclusion: Our data 1) support a role for HCV core in the resistance to global antiviral effect of IFNa (despite ISRE activation) and cell transformation in REF cells. 2) demonstrate a distinct pattern of biological effects of tumour and non-tumour-derived cores on interferon signaling and cell transformation, correlated with the hypothesis of selection of core mutants in clonaly expanding liver cells. Data obtained with 3 additional tumour and non-tumour-derived core sequences will be discussed.