Activated neutrophil by endothelin-1 caused tissue damage in human umbilical cord.

Immunostaining of human neutrophils incubated with endothelin-1 (ET-1) showed intense and spreading pattern of anti human granulocyte elastase within the cytosol. That reflected neutrophil activation followed by the release of granule contents by ET-1. In contrast, PBS (phosphate buffered saline) treated neutrophils showed localized and faintly stained granules. Intracellular calcium in fura-2 loaded neutrophils was measured at 340/380 nm. A dose and time dependent increase in intracellular calcium by ET-1 occurred in human single neutrophil. Elastase activity assay was done with chromogenic substrate S2484. ET-1 induces dose and time dependent increase in elastase activity in neutrophil suspensions like ionophore A23187. A similar time dependent increase in elastase activity was retained even after repeated wash and ET-1 treatment. That confirmed the viability of most of the neutrophils after each treatment. In umbilical cord preparations, ET-1 treated neutrophils could migrate from the venous lumen into the tissue matrix of the umbilical cords. Hematoxylin and eosin staining revealed a massive tissue destruction in ET-1 activated neutrophil treated cords when compared to sham control and untreated neutrophil injected cords. Immunostaining with monoclonal anti human elastase revealed an intense staining in former sections when compared to the others. We suggest that ET-1 activated neutrophil might play a major role in endothelial injury and tissue damage in conditions with high blood level of endothelin.