Summary
The effect of supernatant from phorbol myristate acetate (PMA) stimulated human polymorphonuclear
granulocytes (PMN) on human factor VII was studied in vitro. The supernatant caused
a rapid loss in factor VII coagulant activity by the action of human leukocyte elastase
(HLE) and cathepsin G in the supernatant, as demonstrated by the use of specific inhibitors
of the two serine proteases, respectively. Preincubation of the supernatant with the
elastase inhibitor and the cathepsin G inhibitor preserved 80% and 25% of the clotting
activity, respectively. Calcium protected factor VII completely from the supernatant
mediated inactivation. Cathepsin G and HLE purified from PMN each destroyed the coagulant
activity of factor VII when added to a non-plasma system. There were, however, no
effect on factor VII activity when cathepsin G was added to plasma. Polyacrylamide
gel electrophoresis in the presence of SDS indicated that HLE and cathepsin G cleaved
the zymogen in the same manner, producing (a) peptide(s) of low molecular mass and
a single large product of 48 kDa. Preincubation of factor VII with calcium ions inhibited
the proteolytic action of HLE and cathepsin G. It is suggested that HLE and cathepsin
G from activated granulocytes may be partly responsible for the loss in factor VII
activity that is observed during sepsis.
