High-performance liquid chromatographic separation of aprotinin-like inhibitors and their determination in very small amounts

Aprotinin stimulates angiogenesis and human endothelial cell migration through the growth factor pleiotrophin and its receptor protein tyrosine phosphatase beta/zeta

Pleiotrophin is an 18 kDa secreted polypeptide growth factor with direct pro-angiogenic and tumorigenic properties. Pleiotrophin is a substrate for proteolytic enzymes, such as plasmin, leading to proteolytic fragments with distinct activities on endothelial cell activation in vitro or angiogenesis in vivo. Aprotinin is a naturally occurring broad spectrum protease inhibitor, used widely in cardiac surgery due to its ability to inhibit plasmin and reduce perioperative bleeding. Since we have seen that aprotinin inhibits proteolysis of pleiotrophin by plasmin, the aim of the present study was to evaluate the possible role of pleiotrophin in the effects of aprotinin on angiogenesis and human endothelial cell migration. Our data demonstrate that aprotinin, in a concentration-dependent manner, is angiogenic in the chicken embryo chorioallantoic membrane assay in vivo and induces human endothelial cell migration in vitro. Aprotinin inhibits pleiotrophin proteolysis and induces expression and secretion of pleiotrophin through an AP-1-dependent transcriptional activation of the pleiotrophin gene, and pleiotrophin seems to mediate the stimulatory effects of aprotinin on cell migration through its receptor protein tyrosine phosphatase beta/zeta. The stimulatory effect of aprotinin on pleiotrophin expression and cell migration may explain, at least partly, the problems observed with the clinical use of aprotinin.

Identification of proteinase 3 as the major caseinolytic activity in acute human wound fluid

Wound fluid contains several proteinases that are important in the repair process. In this study, we analyzed caseinolytic activity in wound fluid obtained from acute (burn) wounds. Caseinolytic activity in wound fluid increased markedly 2 d after injury and appeared on casein zymographs as a series of bands or a smear ranging from 30 to 100 kDa. Most of the enzyme activity was inhibited by the synthetic human neutrophil elastase inhibitor MDL 27,367 but not by the naturally occurring inhibitor of elastase, human secretory leukoproteinase inhibitor. Fractionation of wound fluid indicated that a single enzyme accounted for approximately 80% of the caseinolytic activity. This enzyme degraded the elastase substrate methoxysuccinyl-ala-ala-pro-val-p-nitroanilide at a slow rate. The above findings suggested that the enzyme responsible for caseinolytic activity might be proteinase 3, an elastase-related enzyme whose physiologic functions are poorly understood. Consistent with the above possibility, we found that monoclonal antibodies against proteinase 3 removed caseinolytic activity from wound fluid, and that purified proteinase 3 had a similar caseinolytic profile and inhibitor sensitivity to burn fluid.

Isolation and N-terminal sequence of multiple forms of granulins in human urine

Three molecular forms of granulins (also known as epithelins) were isolated, for the first time, in human urine. Their N-terminal sequences, which have also been determined, are identical to those of granulins A and B, previously isolated from human leukocytes, and of granulin F, never isolated before but whose primary structure is known on the basis of the cDNA sequence. The urinary molecules, which show a molecular weight of about 6.5 kDa, are most likely produced by a posttranslational proteolytic processing occurring at the level of the kidney, which appears to be the organ richest in granulin precursor mRNA. The molecular events underlying the precursor processing are unknown, even though the involvement of the protease kallikrein, an enzyme thought to be responsible for the processing of several polypeptidic growth factor precursors, could be hypothesized. Granulins, however, do not show antikallikrein activity. The presence in human urine of isoform F, previously not identified from other human sources, seems to support the hypothesis that mature forms of granulins are generated by an organ-specific precursor processing, on the basis of particular physiological requirements, and to suggest also that this isoform may play "in vivo" an important and specific role in the epithelial cells of the human kidney.