leupeptins and phosphoramidon

Designer natriuretic peptides (NPs) represent an active area of drug development. In canine and human studies, the designer natriuretic peptide CD-NP demonstrated more desirable therapeutic potential than recombinant B-type NP (BNP), which is known as nesiritide and is approved for treatment of acute decompensated heart failure. However, why CD-NP is more effective than BNP is not known. We previously reported that CD-NP is a poorer activator of human guanylyl cyclase-A (GC-A) and a better activator of human guanylyl cyclase-B than BNP. Here, guanylyl cyclase bioassays were used to compare the susceptibility of CD-NP verses ANP, BNP, CNP and DNP to inactivation by human kidney membranes. The half time (t(1/2)) for CD-NP inactivation was increased by factors of 13, 3 and 4 compared to ANP, BNP and CNP, respectively, when measured in the same assay. Surprisingly, DNP failed to undergo complete inactivation and was the most degradation resistant of the peptides tested. The neutral endopeptidase (NEP) inhibitor, phosphoramidon, blocked inactivation of CNP and CD-NP, but not BNP or DNP. In contrast, the general serine and cysteine protease inhibitor, leupeptin, completely blocked the degradation of BNP and CD-NP, but did not block CNP inactivation unless phosphoramidon was included in the assay. Thus, NPs with shorter carboxyl tails (ANP and CNP) are degraded by phosphoramidon-sensitive proteases and NPs with extended carboxyl tails (BNP, DNP and CD-NP) are resistant to NEP degradation and degraded by leupeptin-sensitive proteases. We conclude that DNP and CD-NP are highly resistant to proteolysis and that proteolytic resistance contributes to the beneficial cardiovascular properties of CD-NP. We suggest that this property may be exploited to increase the half-life of NP-based drugs.

Topics: Atrial Natriuretic Factor; Cells, Cultured; Cysteine Proteinase Inhibitors; Elapid Venoms; Glycopeptides; HEK293 Cells; Humans; Hydrolysis; Intercellular Signaling Peptides and Proteins; Kidney; Leupeptins; Natriuretic Peptide, Brain; Natriuretic Peptide, C-Type; Neprilysin; Peptides; Receptors, Atrial Natriuretic Factor; Serine Proteinase Inhibitors

Most early-onset forms of Alzheimer's disease are due to missense mutations located on two homologous proteins named presenilin 1 and 2 (PS1 and PS2). Several lines of evidence indicate that PS1 and PS2 undergo various post-transcriptional events including endoproteolytic cleavages, giving rise to 28-30 kD N-terminal (NTF) and 18-20 kD C-terminal (CTF) fragments that accumulate in vivo. Whether the biological activity of presenilins is borne by the processed fragments or their holoprotein precursor remains in question. We have examined the putative control of beta APP maturation by CTF-PS1/PS2 and the catabolic process of the latter proteins by the multicatalytic complex, proteasome.. We transiently and stably transfected HEK293 cells with CTF-PS1 or CTF-PS2 cDNA. We examined these transfectants for their production of A beta 40, A beta 42, and APP alpha by immunoprecipitation using specific polyclonals. The effect of a series of proteases inhibitors on the immunoreactivity of CTF-PS1/PS2 was examined by Western blot. Finally, the influence of proteasome inhibitors on the generation of beta APP fragments by CTF-expressing cells was assessed by combined immunoprecipitation and densitometric analyses.. We showed that transient and stable transfection of CTF-PS1 and CTF-PS2 cDNAs in human cells leads to increased secretion of APP alpha and A beta, the maturation products of beta APP. Furthermore, we demonstrated that two proteasome inhibitors, lactacystin and Z-IE(Ot-Bu)A-Leucinal, prevent the degradation of both CTFs. Accordingly, we established that proteasome inhibitors drastically potentiate the phenotypic increased production of APP alpha and A beta elicited by CTF-PS1/PS2.. Our data establish that the C-terminal products of PS1 and PS2 maturation exhibit biological activity and in particular control beta APP maturation upstream to alpha-and beta/gamma-secretase cleavages. This function is directly controlled by the proteasome that modulates the intracellular concentration of CTFs.

Topics: Acetylcysteine; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Cysteine Endopeptidases; Cysteine Proteinase Inhibitors; Enzyme Inhibitors; Glycopeptides; Humans; Leucine; Leupeptins; Membrane Proteins; Multienzyme Complexes; Oligopeptides; Pepstatins; Presenilin-1; Presenilin-2; Proteasome Endopeptidase Complex; Recombinant Proteins; Sulfones; Transfection

Escherichia coli endotoxin (0.1 to 1000 micrograms/ml) stimulated the release of neutrophil chemotactic activity (P < 0.001) and induced bronchial epithelial cell (BEC) cytotoxicity assessed by lactate dehydrogenase release (P < 0.001). Endotoxin (100 micrograms/ml) inhibited BEC accumulation (P < 0.001). In the present study, we investigated the role of proteolytic activity of BECs per se in response to endotoxin. Several structurally and functionally different antiproteases, alpha 1 protease inhibitor, soybean trypsin inhibitor, two chloromethyl ketone derivatives (N-tosyl-L-lysine chloromethyl ketone and methoxysuccinyl-Ala-Ala-Pro-Val chloromethyl ketone), and L-658,758, a neutrophil elastase inhibitor, attenuated the release of neutrophil chemotactic activity and lactate dehydrogenase (P < 0.01). alpha 1-Protease inhibitor and N-tosyl-L-lysine chloromethyl ketone attenuated the inhibition of BEC accumulation by endotoxin (P < 0.001). The proteolytic enzyme activity measured by synthetic substrates revealed that endotoxin significantly augmented the serine proteolytic activity in the cell layers. Culture supernatant fluids and cell lysates of BECs in the presence of endotoxin solubilized 14C-labeled casein. These data suggest that responses of BECs to endotoxin may involve activation of cellular proteolytic activity.

Topics: Bronchi; Cell Line; Chemotaxis, Leukocyte; Endopeptidases; Endotoxins; Epithelium; Escherichia coli; Glycopeptides; Leupeptins; Neutrophils; Protease Inhibitors

1. We have previously shown that atrial natriuretic peptide causes bronchodilatation and reduces bronchial reactivity when administered intravenously or by inhalation to asthmatic patients. We wished to determine the direct effect of exogenously applied atrial natriuretic peptide on isolated airway and the role of proteases important in atrial natriuretic peptide degradation in other organ systems. 2. The ability of atrial natriuretic peptide (alpha-human atrial natriuretic peptide 28-amino acid) to relax precontracted tissues and to protect against methacholine-induced contraction was studied in human and bovine tissue. The role of neutral endopeptidase-24.11 and other proteases in regulating the effect of atrial natriuretic peptide on bronchial smooth muscle was also examined by studying the influence of phosphoramidon, a protease inhibitor, whose actions include the inhibition of neutral endopeptidase-24.11, and the protease inhibitors leupeptin, aprotinin and soybean trypsin inhibitor on the airway response to atrial natriuretic peptide. 3. In human and bovine tissue atrial natriuretic peptide (10(-6) mol/l) caused a slight relaxation of methacholine-contracted tissue [mean (SEM) percentage inhibition of contraction of 13.2 (3.02)% and 9.41 (2.63)% respectively] and evoked a significant rightward shift of the cumulative concentration-response curve to methacholine [pD2 5.15 (0.23) and 4.85 (0.1) compared with control values of 6.14 (0.1) and 5.85 (0.16), respectively]. 4. Phosphoramidon potentiated atrial natriuretic peptide-induced relaxation of methacholine-induced tone and the ability of atrial natriuretic peptide to protect against methacholine-induced contraction. The combination of leupeptine, aprotinin and soybean trypsin inhibitor did not significantly alter the bronchial response to atrial natriuretic peptide in either human or bovine tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Aprotinin; Atrial Natriuretic Factor; Bronchi; Bronchoconstriction; Cattle; Culture Techniques; Glycopeptides; Humans; Leupeptins; Methacholine Chloride; Protease Inhibitors; Trypsin Inhibitors

We studied the effect of substance P (SP) on the electric properties of cultured canine tracheal epithelium and its possible modulation by neutral endopeptidase (NEP) by Ussing's short-circuited technique in vitro. Addition of SP (5 x 10(-6) M) to the mucosal side increased short-circuit current (SCC) from 5.1 +/- 0.9 to 10.3 +/- 2.2 microA/cm2 (mean +/- SE; p less than 0.01), which was accompanied by increases in transepithelial potential difference and conductance. The effect of the mucosal SP on SCC was dose-dependent, with the maximal increase from the baseline value being 5.8 +/- 1.0 microA/cm2 observed at 5 x 10(-5) M. The NEP inhibitor phosphoramidon (10(-5) M) did not affect these responses. On the other hand, SCC was not altered by the addition of SP to the submucosal side. However, it was increased dose-dependently in the presence of phosphoramidon (10(-5) M) but not in the presence of captopril, bestatin or leupeptin. This stimulatory effect of submucosal SP was abolished by furosemide, diphenylamine-2-carboxylate and Cl-free medium, but not by amiloride. These results suggest that SP may selectively stimulate Cl secretion across the airway epithelium and that this effect may be modulated by submucosal NEP.

Topics: Amiloride; Animals; Anti-Bacterial Agents; Biological Transport, Active; Captopril; Cells, Cultured; Complement C1; Dogs; Dose-Response Relationship, Drug; Electric Conductivity; Female; Furosemide; Glycopeptides; In Vitro Techniques; Ion Channel Gating; Leucine; Leupeptins; Male; Membrane Potentials; Neprilysin; Substance P; Time Factors; Trachea

To study the effect of atrial natriuretic factor (ANF) on airway ciliary motility, we measured ciliary beat frequency by a photoelectric method in response to ANF in cultured tracheal epithelial cells from rabbits. Addition of ANF but not [Tyr8]ANF-(5-27) decreased ciliary beat frequency in a dose-dependent fashion; the maximal decrease from the baseline value was 24.1 +/- 1.5% (+/- SE, P less than 0.001), and a half-maximal inhibitory concentration (IC50) was 3 x 10(-12) M. Inhibition of neutral endopeptidase activity by phosphoramidon (10(-6) M) or thiorphan (10(-6) M) potentiated the effect of ANF so that the dose-response curve for ANF was shifted to lower concentrations by approximately 0.5 log units (P less than 0.05, in each case). The inhibition of ciliary motility induced by ANF was not affected by the blockade of arachidonic acid metabolism with indomethacin, piroxicam, or nordihydroguaiaretic acid, but it was blocked by methylene blue, a soluble guanylate cyclase inhibitor, and was potentiated by M & B 22948, a guanosine 3',5'-cyclic monophosphate (cGMP) phosphodiesterase inhibitor. The intracellular cGMP levels were increased by ANF, an effect that was further potentiated by phosphoramidon or thiorphan. These results suggest that ANF inhibits ciliary motility presumably through a guanylate cyclase-dependent regulatory pathway and that neutral endopeptidase may play a role in modulating the ANF effect on airway mucociliary transport function.

Topics: Animals; Atrial Natriuretic Factor; Captopril; Cells, Cultured; Cilia; Enzyme Inhibitors; Epithelium; Glycopeptides; Indomethacin; Kinetics; Leucine; Leupeptins; Male; Masoprocol; Methylene Blue; Movement; Piroxicam; Purinones; Rabbits; Thiorphan; Trachea

Topics: Animals; Antipain; Cattle; Chickens; Cytosol; Female; Glycopeptides; Leupeptins; Liver; Male; Molybdenum; Organophosphorus Compounds; Oviducts; Protease Inhibitors; Rats; Receptors, Estrogen; Receptors, Glucocorticoid; Receptors, Progesterone; Receptors, Steroid; Uterus