Neutral proteases of human granulocytes. IV. Interaction between human granulocyte collagenase and plasma protease inhibitors.

Purified human granulocyte collagenase was inactivated by serum through the formation of complexes with alpha 1-antitrypsin and alpha 2-macroglobulin. A molar combining ratio of 1:1 was observed for each inhibitor. The affinity of alpha 2-macroglobulin was about 10 times that of alpha 1-antitrypsin for granulocyte collagenase. The molar concentration of alpha 1-antitrypsin in the blood exceeds that of alpha 2-macroglobulin by about 12 times, so that the inhibitors may be equally important for defence against granulocyte collagenase.     

Antibacterial activity of cationic proteins from human granulocytes.

Human granulocytes contain several cationic proteins with a molecular weight of approximately 25,000, almost identical amino acid composition, and complete immunologic identity. These proteins possess a chymotrypsin-like protease activity at a neutral pH. The antibacterial activity of the cationic proteins has been studied. Bactericidal activities are found against both Gram-positive (Streptococcus faecalis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) organisms. Gram-positive bacteria are, however, the most sensitive. The pH-optimum is near neutrality, and the microbicidal activity shows an inverse relationship to the ionic strength, indicating an ionic interaction between the cationic proteins and the bacterial surface. The microbicidal effect of the cationic proteins is generally independent of the chymotrypsin-like activity of the same proteins since the activity against several bacterial species is heat stable while the chymotrypsin-like activity is heat labile. The surface properties of S. aureus that are determined by protein A do not seem to influence the susceptibility to cationic proteins. The properties of the Gram-negative envelope of E. coli that determine the susceptibility to the lytic action of serum do not influence the sensitivity to the action of cationic proteins. The present study shows that cationic proteins of human granulocytes represent one potential microbicidal mechanism that is independent of hydrogen peroxide and myeloperoxidase.     

Influence of plasma protease inhibitors and the secretory leucocyte protease inhibitor on leucocyte elastase-induced consumption of selected plasma proteins in vitro in man

Cleavage of C3, fibronectin, antithrombin III and alpha 2-antiplasmin in human plasma following the addition of increasing amounts of human leucocyte elastase was studied using an in vitro model. The cleavage was correlated with the degree of saturation of the plasma protease inhibitors alpha 2-macroglobulin and alpha 1-protease inhibitor and also with varying amounts of secretory leucocyte protease inhibitor. When alpha 1-protease inhibitor approached saturation, there was a prompt cleavage of all the four plasma proteins studied. The secretory leucocyte protease inhibitor was needed in a concentration of 6 mumol/l in the present model to block this consumption completely. This concentration also gave some protection of alpha 1-protease inhibitor and alpha 2-macroglobulin.     

Prorenin-renin conversion by the contact activation system in human plasma: role of plasma protease inhibitors

Acid-pretreated normal human plasma generates renin activity at 0 degree C and neutral pH by the activation of prorenin. The activation is caused by kallikrein generated from prekallikrein by activated factor XII. Nonacidified plasma also generates renin at 0 degree C, but at a lower rate (cold-promoted activation). In normal plasma, 14% +/- 1% of prorenin (mean +/- SEM, n = 30) was activated during incubation at 0 degree C for 7 days (range 6% to 26%). Cold-promoted activation of prorenin was within the normal range in plasma deficient in factor XI, X, IX, VIIIC, VII, V, prothrombin, or high mol wt kininogen. Cold-promoted activation of prorenin was less than or equal to 1% in plasma deficient in factor XII or prekallikrein. Reconstitution of these plasmas with highly purified factor XII or prekallikrein restored normal prorenin activation. Correction of high mol wt kininogen deficiency had no effect. Thus cold-promoted activation of prorenin depends on the presence of factor XII and prekallikrein, whereas the other clotting factors are not essential. The influence of the inhibitors C1 esterase-inhibitor, alpha 2-macroglobulin, antithrombin III, and alpha 1-antitrypsin on the activation of prorenin was studied in factor XII-deficient plasma from which one or more of these inhibitors had been selectively removed by immunoadsorption. Factor XII was subsequently added, and the generation of renin at 37 degrees C was observed after complete factor XII-high mol wt kininogen-mediated activation of prekallikrein induced by dextran sulfate. No activation of prorenin was observed at 37 degrees C after depletion of C1 esterase inhibitor, alpha 2-macroglobulin, antithrombin III, or alpha 1-antitrypsin. When prekallikrein was activated in plasma depleted of both C1 esterase-inhibitor and alpha 2-macroglobulin, 6% of prorenin was activated in 2 hours at 37 degrees C. After additional depletion of antithrombin III, the activation increased to 47%. These results indicate that the contact activation system is capable of activating prorenin in plasma at physiologic pH and temperature when the three most important kallikrein inhibitors, C1 esterase-inhibitor, alpha 2-macroglobulin, and antithrombin III, are absent.     

Lipid abnormalities associated with protease inhibitors.

Treatment for HIV infection in the past 3 years has significantly improved the prognosis of people infected with HIV. Protease inhibitors have played a critical role in this improved prognosis. Recent findings indicate, however, that protease inhibitors may cause significant alterations in lipid metabolism. This study reviewed the incidence of lipid abnormalities associated with the use of three different protease inhibitor therapies and identified that 56% of those who were assessed had abnormal elevated lipids. Following initiation of the protease inhibitor, a significant increase in cholesterol was found in 80% of the patients on norvir/saquinavir, 51% of patients on indinavir, and 47% of patients on nelfinavir. These lipid alterations have added a new and unexpected health risk for HIV-infected persons. The risks of therapy with protease inhibitors may have a greater life-threatening potential than the disease itself. This article will review the published findings suggestive of protease inhibitor hyperlipidemia and will highlight the findings of these events in a clinical setting. The purpose of this article is to alert the nursing community of this potential serious side effects and to make recommendations that may be put into practice so that complications may be reduced.     

The contribution of plasma protease inhibitors to antiplasmin activity in man.

1. Human plasma contains a variety of proteins that are capable of inhibiting plasmin activity. Whole plasma possesses 'rapid' and 'progressive' plasmin-neutralizing activity: this study assesses the contribution of individual protease inhibitors to this plasmin-neutralizing property of plasma. 2. Rapid and progressive antiplasmin activities of human plasma correlate with alpha2-macroglobulin and alpha1-antitrypsin concentrations respectively. 3. Fluctuations in the amounts of the other measured inhibitors (antithrombin III, Cl in activator and inter-alpha-tryspin inhibitor) did not influence the measured antiplasmin activity.     

Granulocyte collagenase, elastase and plasma protease inhibitors in purulent sputum.

Sputum was collected from patients with purulent chronic bronchitis. Immuno-chemical techniques using rabbit antiserum against human granulocyte collagenase and elastase showed the presence of both enzymes. Also the serum protease ingibitors alpha1-antitrypsin and alpha2-macroglobulin were demonstrated. Their protease inhibiting capacity was saturated. Granulocyte elastase and collagenase occurred not only in complexes with the inhibitors, but also as free enzymes. All sputa showed free proteolytic, elastolytic and collagenolytic activity. The concentration of collagenase was equal in the sol phase and in the gel phase of the sputa, but most of the elastase was bound to the gel phase.     

Comparison of the reactions of neutral granulocyte proteases with the major plasma protease inhibitors and with antiplasmin.

Reaction mixtures of human serum and increasing amounts of granulocyte collagenase, elastase and chymotrypsin-like enzyme were studied by crossed immunoelectrophoresis utilizing antibodies against alpha1-antitrypsin, alpha1-antichymotrypsin, and antiplasmin. The increasing complex formation of alpha1-antitrypsin and alpha 1-antichymotrypsin with the different granulocyte proteases was not accompanied by any changes in the electrophoretic mobility or precipitate pattern of antiplasmin until the protease binding capacity of serum was saturated. The antiplasmin component in the reaction mixtures of human serum and granulocyte collagenase or elastase was not precipitated by antibodies against the proteases. The results indicate that none of the granulocyte proteases are bound by antiplasmin and that these enzymes do not activate plasminogen in serum.     

Morphine binding to human plasma proteins.

The interaction of (N-methyl-14C) morphine with purified human albumin and gamma globulin and with human plasma was studied by equilibrium dialysis. Morphine binds to albumin and, to a lesser extent, to gamma globulin, but probably does not bind to plasma lipoproteins. The per cent of drug bound to protein was dependent on protein concentration but independent of drug concentration in the therapeutic range of plasma morphine concentration. In this range, 34.0% to 37.5% of the drug is bound to human plasma, largely to the albumin fraction. This study is compared to an earlier one on the interaction of methadone with plasma proteins. It is likely that the lower lipid solubility of morphine compared to methadone is related to its decreased affinity for plasma proteins.     

Pharmacokinetic enhancement of inhibitors of the human immunodeficiency virus protease by coadministration with ritonavir.

Coadministration with the human immunodeficiency virus (HIV) protease inhibitor ritonavir was investigated as a method for enhancing the levels of other peptidomimetic HIV protease inhibitors in plasma. In rat and human liver microsomes, ritonavir potently inhibited the cytochrome P450 (CYP)-mediated metabolism of saquinavir, indinavir, nelfinavir, and VX-478. The structural features of ritonavir responsible for CYP binding and inhibition were examined. Coadministration of other protease inhibitors with ritonavir in rats and dogs produced elevated and sustained plasma drug levels 8 to 12 h after a single dose. Drug exposure in rats was elevated by 8- to 46-fold. A > 50-fold enhancement of the concentrations of saquinavir in plasma was observed in humans following a single codose of ritonavir (600 mg) and saquinavir (200 mg). These results indicate that ritonavir can favorably alter the pharmacokinetic profiles of other protease inhibitors. Combination regimens of ritonavir and other protease inhibitors may thus play a role in the treatment of HIV infection. Because of potentially substantial drug level increases, however, such combinations require further investigation to establish safe regimens for clinical use.     

alpha1-Antichymotrypsin interaction with cationic proteins from granulocytes.

Human granulocytes contain cationic proteins with chymotrypsin-like activity. These proteases showed a higher relative affinity for alpha1-antichymotrypsin than for alpha1-antitrypsin but the highest affinity for alpha2-macroglobulin. The complexes between cationic protein and alpha1-antichymotrypsin migrate as beta-globulin on agarose gel electrophoresis.     

The effect of class-specific protease inhibitors on the stabilization of B-type natriuretic peptide in human plasma

Background: B-type natriuretic peptide (BNP) is a cardiac hormone that regulates hemodynamic equilibrium. In the circulation, its activity is controlled by proteolytic factors. Accurate measurement of BNP in a patient's plasma may be affected by degradation due to proteolysis. Objective: We report on the identification and performance of classes of protease inhibitors that stabilize BNP in plasma. Design and methods: Using the Bayer ADVIA Centaur® BNP assay, we measured the effect of arginine, serine and/or specific kallikrein protease inhibitors (PIs) on exogenous spiked or endogenous BNP in patient plasma. Results: Compared to controls without inhibitor, all PIs were capable, to varying degrees, of retarding the rate of proteolytic degradation. The kallikrein-specific inhibitor, -Phe–Phe–Arg–chloromethylketone (PPACK II) was most effective as a single constituent and was able to eliminate BNP degradation in patient samples for up to 6–10 days when stored at 2–8 °C. Conclusions: The stability of BNP was markedly increased in the presence of kallikrein-specific PPACK II and a broad spectrum of serine PIs. Use of these compounds offers a simple method of extending sample handling and storage of plasma samples containing BNP.     

Intracellular accumulation of human immunodeficiency virus protease inhibitors

Intracellular accumulation of the protease inhibitors (PIs) saquinavir (SQV), ritonavir (RTV), and indinavir (IDV) was determined in 50 human immunodeficiency virus-positive patients. Following extraction, PIs were quantified by mass spectrometry. Paired plasma and intracellular samples were collected over a full dosing interval from patients (13 on SQV, 6 on RTV, 8 on IDV, 16 on SQV plus RTV, 7 on IDV plus RTV) with a plasma viral load of <400 copies/ml. Data were expressed as intracellular/plasma drug concentration ratios. A hierarchy of intracellular accumulation was demonstrated by the following medians: 9.45 for SQV > 1.00 for RTV > 0.51 for IDV. Coadministration of RTV did not boost ratios of SQV or IDV within the cell or in plasma, although absolute plasma and intracellular SQV concentrations were increased by RTV. Seven individuals receiving SQV in hard-gel capsule form (median, 32 months) had higher intracellular/plasma drug ratios than all other patients receiving SQV (median, 17.62 versus 4.83; P = 0.04), despite consistently low plasma SQV concentrations. How this occurs may provide insight into the mechanisms that limit adequate drug penetration into sanctuary sites.     

Antiviral properties of aminodiol inhibitors against human immunodeficiency virus and protease.

A series of aminodiol inhibitors of human immunodeficiency virus type 1 (HIV-1) protease were identified by using an in vitro peptide cleavage assay. BMS 182,193, BMS 186,318, and BMS 187,071 protected cells against HIV-1, HIV-2, and simian immunodeficiency virus infections, with 50% effective doses ranging from 0.05 to 0.33 microM, while having no inhibitory effect on cells infected with unrelated viruses. These compounds were also effective in inhibiting p24 production in peripheral blood mononuclear cells infected with HIV-1 IIIB and against the zidovudine-resistant HIV-1 strain A018C. Time-of-addition studies indicated that BMS 182,193 could be added as late as 27 h after infection and still retain its antiviral activity. To directly show that the activity of these compounds in culture was due to inhibition of proteolytic cleavage, the levels of HIV-1 gag processing in chronically infected cells were monitored by Western blot (immunoblot) analysis. All compounds blocked the processing of p55 in a dose-dependent manner, with 50% effective doses of 0.4 to 2.4 microM. To examine the reversibility of BMS 186,318, chronically infected CEM-SS cells were treated with drug and virions purified from the culture medium. Incubation of HIV-1 particles in drug-free medium indicated that inhibition of p55 proteolysis was slowly reversible. The potent inhibition of HIV-1 during both acute and chronic infections indicates that these aminodiol compounds are effective anti-HIV-1 compounds.