Endothelial angiotensin II generation induced by placenta-derived factors from preeclampsia

Hypersensitivity to angiotensin II contributes to the increased vasoconstriction in preeclampsia. In this study, we determined whether placenta-derived factors could affect endothelial cell angiotensin II generation.Our results showed that more angiotensin II was produced by endothelial cells treated with preeclampsia placental conditioned medium than the cells treated with normal conditioned medium or untreated controls. To determine which pathway, angiotensin-converting enzyme or nonangiotensin-converting enzyme angiotensin-generating enzyme/chymase, might be involved in preeclampsia conditioned medium induced angiotensin II generation, angiotensin-converting enzyme inhibitor captopril and chymotrypsin inhibitors were applied to the cell culture either separately or in combination. We found that chymotrypsin inhibitor, but not captopril, could attenuate the increased angiotensin II generation. To further test specific effects of the protease on endothelial cell angiotensin II generation, endothelial cells were grown in cell culture inserts and chymotrypsin was added to the upper chamber of the cell culture (apical exposure). The medium in the lower chamber (basal direction) was collected and measured for angiotensin II. Our results showed that apical exposure of endothelial cells to the protease resulted in a concentration-dependent increase in basal release of angiotensin II. Angiotensin II receptor-1 expression was also upregulated in cells treated with preeclampsia conditioned medium or chymotrypsin. This data suggest that placenta-derived factors may activate chymase-angiotensin pathway in endothelial cells. Moreover, increased endothelial cell basal release of angiotensin II in response to the protease stimulation further suggests that angiotensin II levels in the circulation may not necessarily reflect angiotensin II generation within the vascular wall.