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Abstract

Background:

Omapatrilat (Vanlev) is a new vasopeptidase inhibitor. It simultaneously inhibits two key enzymes involved in the regulation of cardiovascular function, neutral endopeptidase and angiotensin-converting enzyme. Omapatrilat contains a free thiol group that can potentially act as a nitric oxide (NO)-carrier. In this study, we explored the ability Omapatrilat-NO to donate NO to the cytosol of by acting as a substrate for the enzyme cell-surface protein disufide isomerase.

Methods: These dynamic microscopy studies, were conducted on live human umbilical vein endothelial cells in vitro, with the aid of fluorescent intracellular NO-probe dansylhomocysteine. With this compound the kinetics of cell-surface protein disulfide isomerase-catalyzed NO transfer from S-nitrosothiols, like Omapatrrilat-NO can be directly evaluated. The levels of cell-surface protein disulfide isomerase protein, were also monitored as a function of Omapatrilat by Western blotting.

Results:

The estimated KM of cell-surface protein disulfide isomerase for Omapatrilat-NO, in the presence of 10 micromolar Omapatrilat was 40 micromolar. When the kinetics were repeated after a 24 h pretreatment of the cells with 10 micromolar Omapatrilat, the KM decreased by 30-fold to 1.4 micromolar. Western blot analysis of secreted protein disulfide isomerase, indicated that the amount of protein also increased by nearly 5-fold upon a 24h incubation with Omapatrilat.

Conclusion:

These studies show that the NO derivative of Omapatrilat is stable and can donate its NO to the cytosol through the action of the enzyme cell-surface protein disufide isomerase. These studies also demonstrate that Omapatrilat can affect the affinity of the enzyme as well as upregulating its excreteion by and unknown mechanism. The results presented here indicate that apart from vasopeptidase inhibiton, Omapatrilat could potentially act as a vasodilator by its ability to carry NO and to positively affect the enzyme resposible for the release of S-nitrosothiol-bound NO into the cells comprizing the vasculature.

S-Nitroso derivative of omapatrilat, Endothelial NO-metabolism, Cell surface protein-disufide isomerase
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© American Journal of Hypertension, Ltd. 2001
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