Randy W. Scott

The role of bactericidal/permeability-increasing protein in the treatment of primate bacteremia and septic shock

Human neutrophil azurophilic granules contain an ∼55-kDa protein, known as bactericidal/permeabilityincreasing protein (BPI), which possesses a high-affinity binding domain for the lipid A component of lipopolysaccharide (LPS). Thein vivo LPS neutralizing activity of exogenous BPI was studied in a model of lethalEscherichia coli bacteremia. Five baboons were treated with BPI (5 mg/kg bolus injection followed by a 95 μg/kg/min BPI infusion over 4 hr), while four additional animals received a genetically engineered variant of BPI (NCY103). Five animals received a placebo treatment and served as controls. Both wild-type rhBPI and NCY103 significantly (P<0.05) decreased blood levels of LPS throughout an 8-hr evaluation period following live bacterial challenge. Two hours followingE. coli administration, LPS levels peaked in the controls, at 6.86±3.22 ng/ml, whereas LPS levels were 3.39±2.1 ng/ml in the BPI group and 2.04±1.18 ng/ml in the NCY103 group. Tumor necrosis factor-alpha (TNF-α) and interleukin-6 levels likewise were attenuated in the treatment groups, whereas circulating sTNFR I was significantly (P<0.05) reduced only in the BPI group. Leukocytopenia and granulocytopenia were significantly (P<0.02) lessened in the BPI group, by an average of 59% leukocytopenia and 65% granulocytopenia, respectively. This study supports the concept ofE. coli LPS neutralization by BPIin vivo and demonstrates that a moderate (70%) reduction in peak LPS-LAL activity is sufficient to alter some hematologic and cytokine manifestations of bacteremia.

Structure of the Human Protease Nexin Gene and Expression of Recombinant Forms of PN-I

Protease nexin (PN-I) is a member of the serpin family of serine protease inhibitors that are characterized by the formation of an irreversible complex with the catalytic site of their target serine proteases.1 PN-I is known to inhibit a number of biologically relevant serine proteases such as thrombin, urokinase, plasmin, and plasminogen activators.2–4 The significance of regulatory inhibitors in controlling the activity of the serine proteases has only begun to be appreciated in the areas of cell movement, blood coagulation, fibrinolysis, extracellular matrix modulation, and mitosis.5–8 Recently PN-I has been shown to be identical to glial derived nexin, which has been reported to possess neurite extension activity on peripheral nerve cells 3,9–11 Native PN-I is a glycoprotein of approximately 45,000 daltons that is secreted by various fibroblasts and extravascular cells.12 Multiple forms of PN-I have been described which differ in their behavior on SDS-PAGE, pH gradient gels, and heparin affinity chromatography.4’13 Although glycosylation differences can most certainly account for some of these differences, we have identified two species of human PN-I which we have designated αPN-I and βPN-I that differ by a net change of three amino acids.14