Beta-secretase activity increases with aging in human, monkey, and mouse brain

Amyloid beta protein (A beta) accumulates in the brains of aging humans, amyloid precursor protein (APP) transgenic mouse lines, and rhesus monkeys. We tested the hypothesis that aging was associated with increased activity of the beta-site amyloid precursor protein cleaving enzyme (beta-secretase, BACE) in brain. We evaluated BACE activity, BACE protein, and formic acid-extractable A beta levels in cohorts of young (4 months old) and old (14 to 18 months old) nontransgenic mice (n = 16) and Tg2576 APP transgenic mice (n = 17), young (4.4 to 12.7 years old) and old (20.9 to 30.4 years old) rhesus monkeys (n = 17), and a wide age range (18 to 92 years old) of nondemented human brains (n = 25). Aging was associated with increased brain A beta levels in each cohort. Furthermore BACE activity increased significantly with age in mouse, monkey, and human brains, independent of brain region. BACE protein levels, however, were unchanged with age. BACE activity correlated with formic acid-extractable A beta levels in transgenic mouse, nontransgenic mouse, and human cortex, but not in monkey brain. These data suggest that an age-related increase of BACE activity contributes to the increased production and accumulation of brain A beta, and potentially predisposes to Alzheimer's disease in humans.

Immunohistochemical Localization of Endothelin-Converting Enzyme-1 in Neuroendocrine Tumors and Normal Human Tissue

Endothelin-converting enzyme-1 (ECE-1) is the key enzyme of endothelin biosynthesis, catalyzing the final step in the process. In this study, we investigated the cellular distribution of ECE-1 in 19 normal human tissues and 16 neuroendocrine tumors using immunohistochemical staining with antigen retrieval. ECE-1 was expressed in vessel endothelial cells as well as nearly all epithelial cells, glands and duct cells in normal human tissues including the esophagus, stomach, small intestine, appendix, colon, liver, gallbladder, pancreas, endometrium, cervix, breast, skin, prostate, urinary bladder, lung, kidney, sympathetic ganglion, thyroid gland, and adrenal gland. The most interesting finding was that ECE-1 was expressed in normal neuroendocrine cells. ECE-1 was also expressed in all 16 neuroendocrine tumors, including three paragangliomas, five pheochromocytomas, three carcinoid tumors, four medullary carcinomas of the thyroid, and one islet cell tumor of the pancreas. In conclusion, ECE-1 is enriched in neuroendocrine cells and neuroendocrine tumors, suggesting an important biologic role for the enzyme in the neuroendocrine system.

Competitive binding inhibition enzyme-linked immunosorbent assay that uses the secreted aspartyl proteinase of Candida albicans as an antigenic marker for diagnosis of disseminated candidiasis

The secreted aspartyl proteinases (Saps) of Candida albicans have been implicated as virulence factors associated with adherence and tissue invasion. The potential use of proteinases as markers of invasive candidiasis led us to develop a competitive binding inhibition enzyme-linked immunosorbent assay (ELISA) to detect Sap in clinical specimens. Daily serum and urine specimens were collected from rabbits that had been immunosuppressed with cyclophosphamide and cortisone acetate and infected intravenously with 10(7) C. albicans blastoconidia. Disseminated infection was confirmed by organ culture and histopathology. Although ELISA inhibition was observed when serum specimens from these rabbits were used, more significant inhibition, which correlated with disease progression, occurred when urine specimens were used. Urine collected as early as 1 day after infection resulted in significant ELISA inhibition (mean inhibition +/- standard error [SE] compared with preinfection control urine, 15.7% +/- 2.7% [P < 0.01]), and inhibition increased on days 2 through 5 (29.4% +/- 4.8% to 44.5% +/- 3.5% [P < 0.001]). Urine specimens from immunosuppressed rabbits infected intravenously with Candida tropicalis, Candida parapsilosis, Candida krusei, Cryptococcus neoformans, Aspergillus fumigatus, or Staphylococcus aureus were negative in the assay despite culture-proven dissemination. Nonimmunosuppressed rabbits receiving oral tetracycline and gentamicin treatment were given 2 x 10(8) C. albicans blastoconidia orally or intraurethrally to establish colonization of the gastrointestinal tract or bladder, respectively, without systemic dissemination; urine specimens from these rabbits also gave negative ELISA results. Dissemination to the kidney and spleen occurred in one rabbit challenged by intragastric inoculation, and urine from this rabbit demonstrated significant inhibition in the ELISA (mean inhibition +/- SE by day 3 after infection, 32.9% +/- 2.7% [P < 0.001]). The overall test sensitivity was 83%, the specificity was 92%, the positive predictive value was 84%, the negative predictive value was 91%, and the efficiency was 89% (166 urine samples from 33 rabbits tested). The specificity, positive predictive value, and efficiency could be increased to 97, 95, and 92%, respectively, if at least two positive test results were required for a true positive designation. The ELISA was sensitive and specific for the detection of Sap in urine specimens from rabbits with disseminated C. albicans infection, discriminated between colonization and invasive disease, reflected disease progression and severity, and has the potential to be a noninvasive means to diagnose disseminated candidiasis.

Measuring human beta-secretase (BACE1) activity using homogeneous time-resolved fluorescence

The human beta-secretase enzyme, BACE1, mediates a critical step in the production of A beta(40) and A beta(42) peptides which are responsible for the severe neuronal cell death and insoluble amyloid plaques of Alzheimer's disease (AD). Several lines of evidence suggest that potent BACE1 inhibitors represent an attractive A beta-lowering strategy for AD. We designed a simple homogeneous time-resolved fluorescence (HTRF) assay which utilizes the fluorescence resonance energy transfer (FRET) pair europium and allophycocyanin for measuring BACE1 enzymatic activity in a high-throughput manner. Robust FRET was observed when an 18-amino-acid APP Swedish-synthetic peptide that was N-terminally labeled with europium cryptate and C-terminally biotinylated was incubated with streptavidin-coupled cross-linked allophycocyanin (SA-XL665). Purified BACE1 enzyme caused a time- and concentration-dependent linear change in FRET at low nanomolar enzyme concentrations. This assay was used to compare the autoprocessed "mature" BACE1 enzyme (sautoBACe1) and the soluble proBACE1 for activity and inhibition by selected peptidic BACE inhibitors. sautoBACE1 displayed only a modest increase in activity compared to sproBACE1 and this activity was uninhibited by the BACE1 prodomain peptide. Interestingly, the BACE1 prodomain peptide was able to partially inhibit sproBACE1 activity. IC(50s) for a P10-P4' statine BACE1 inhibitor, OM99-2, and OM-003 determined using the HTRF assay were in good agreement with those reported in the literature. The primary advantages of the HTRF-formatted BACE1 protease assay include appropriate reflection of native BACE1 activity, high sensitivity, low variability, and intrinsic quench correction afforded by ratiometric measurements made between EuK and SA-XL665 fluorophores.

Differential expression of Candida albicans secreted aspartyl proteinase and phospholipase B genes in humans correlates with active oral and vaginal infections

The in vivo expression of Candida albicans secreted aspartyl proteinase (SAP1-SAP8) and phospholipase B (PLB1 and PLB2) genes was analyzed in 137 human subjects with oral and vaginal candidiasis or carriage. Total RNA was isolated from whole unstimulated saliva or vaginal swabs, and the expression of SAP1-8 and PLB1-2 was evaluated by reverse-transcriptase polymerase chain reaction using specific primer sets. A spectrum of SAP gene expression profiles was obtained from different C. albicans strains during symptomatic disease and asymptomatic carriage. SAP2 and SAP5 were the most common genes expressed during both infection and carriage. SAP1, SAP3, SAP4, SAP7, SAP8, and PLB1 expression was correlated with oral disease, whereas SAP1, SAP3, and SAP6-SAP8 expression was correlated with vaginal disease. Furthermore, SAP1, SAP3, and SAP8 were preferentially expressed in vaginal, rather than oral, infections. This study demonstrates the differential expression of the hydrolytic enzyme genes in humans and correlates the expression of specific Candida species virulence genes with active disease and anatomical location.

The secreted aspartyl proteinases Sap1 and Sap2 cause tissue damage in an in vitro model of vaginal candidiasis based on reconstituted human vaginal epithelium

Secreted aspartyl proteinases (Saps) contribute to the ability of Candida albicans to cause mucosal and disseminated infections. A model of vaginal candidiasis based on reconstituted human vaginal epithelium (RHVE) was used to study the expression and role of these C. albicans proteinases during infection and tissue damage of vaginal epithelium. Colonization of the RHVE by C. albicans SC5314 did not cause any visible epithelial damage 6 h after inoculation, although expression of SAP2, SAP9, and SAP10 was detected by reverse transcriptase PCR. However, significant epithelial damage was observed after 12 h, concomitant with the additional expression of SAP1, SAP4, and SAP5. Additional transcripts of SAP6 and SAP7 were detected at a later stage of the artificial infection (24 h). Similar SAP expression profiles were observed in three samples isolated from human patients with vaginal candidiasis. In experimental infection, secretion of antigens Sap1 to Sap6 by C. albicans was confirmed at the ultrastructural level by using polyclonal antisera raised against Sap1 to Sap6. Addition of the aspartyl proteinase inhibitors pepstatin A and the human immunodeficiency virus proteinase inhibitors ritonavir and amprenavir strongly reduced the tissue damage of the vaginal epithelia by C. albicans cells. Furthermore, SAP null mutants lacking either SAP1 or SAP2 had a drastically reduced potential to cause tissue damage even though SAP3, SAP4, and SAP7 were up-regulated in these mutants. In contrast the vaginopathic potential of mutants lacking SAP3 or SAP4 to SAP6 was not reduced compared to wild-type cells. These data provide further evidence for a crucial role of Sap1 and Sap2 in C. albicans vaginal infections.

Aspartic proteinase napsin is a useful marker for diagnosis of primary lung adenocarcinoma

Napsin A is an aspartic proteinase expressed in lung and kidney. We have reported that napsin A is expressed in type II pneumocytes and in adenocarcinomas of the lung. The expression of napsin was examined in 118 lung tissues including 16 metastases by in situ hybridisation. Napsin was expressed in the tumour cell compartment in 33 of 39 adenocarcinomas (84.6%), in two of 11 large cell carcinomas and in one lung metastasis of a renal cell carcinoma. Expression of napsin was found to be associated with a high degree of differentiation in adenocarcinoma. Immunohistochemistry was performed for three proteins currently used as markers for lung adenocarcinoma : surfactant protein-A, surfactant protein-B and thyroid transcription factor-1. Thyroid transcription factor-1 showed the same sensitivity (84.6%) as napsin for adenocarcinoma, whereas surfactant protein-A and surfactant protein-B showed lower sensitivities. Among these markers, napsin showed the highest specificity (94.3%) for adenocarcinoma in nonsmall cell lung carcinoma. We conclude that napsin is a promising marker for the diagnosis of primary lung adenocarcinoma.

Characterization of an aspartic proteinase activity in buckwheat (Fagopyrum esculentum Moench) seeds

The pepstatin A sensitive acidic proteolytic activity of total protein extracts of buckwheat seeds has been analyzed in developing, mature, and germinating seeds by activity measurements as well as by electrophoretic and immunochemical techniques. Immunoblot analysis using cross-reactive antibodies raised against barley phytepsin suggested that specific proteolytic activity could be attributed to a 47 kDa heterodimeric polypeptide, composed of two subunits: 31 and 16 kDa polypeptides. The analysis of time course expression revealed that the 47 kDa heterodimer accumulated during seed maturation starting from 12 days after pollination and was also present at the beginning of germination. Milk-clotting activity of this proteinase was also indicated.

Human beta-secretase activity in yeast detected by a novel cellular growth selection system

Sequential processing of the transmembrane amyloid precursor protein (APP) by the beta-secretase BACE and by the gamma-secretase causes secretion of Abeta peptides. Extracellular aggregation of these peptides in the brain is a major hallmark of Alzheimer's disease. For therapeutic purposes and the development of specific inhibitors, it is important to characterize these secretases. We have established a cellular growth selection system for functional expression of human BACE in the yeast Saccharomyces cerevisiae. A fragment of APP bearing the beta-site, the transmembrane domain and the cytosolic tail was fused to the C-terminus of the yeast enzyme invertase, which is normally secreted to allow cell growth in the presence of sucrose as the sole carbon source. The resulting invertase-APP fusion protein was expressed as a type-I transmembrane protein in intracellular compartments of yeast cells lacking endogenous invertase. In these cells, co-expression of human BACE restored cell growth on selective plates upon cleavage of the invertase-APP fusion protein. The cellular growth selection system presented here can be generally applied to screen for secretases that specifically cleave membrane-bound substrates. Furthermore, this system provides the basis for a high-throughput screen for identifying secretase inhibitors that are active in eukaryotic cells.

Double radial immunodiffusion as a tool to identify pregnancy-associated glycoproteins in ruminant and nonruminant placentae

Pregnancy-associated glycoproteins (PAGs) are antigens synthesized in the superficial layers of the ruminant trophoblast. Initially, they were identified either as proteins released into the maternal bloodstream (where they have applications in pregnancy diagnosis) (PAG1) or as molecules binding to the LH receptor (PAG2). In this study, double radial immunodiffusion was used to test the ability of antisera raised against different PAG molecules (bovine, ovine and caprine) to react with placental extracts from nonruminants (rabbit, cat, mouse, pig, and wild pig) and ruminants (cow, ewe, and goat). Placental extracts from all nonruminants tested except rabbit reacted with anti bovine PAG2 (anti-boPAG2). Extracts of ruminant placentas reacted with different antisera, confirming the expression of various PAG molecules. According to the time at which the placentas were collected (early or middle pregnancy), the reaction differed as regards the thickness, position, and number of precipitation lines, suggesting that PAG expression varies as pregnancy progresses. Bos indicus and Bos taurus placental extracts exhibited different reactions with anti-boPAG2: a single precipitation line in the former case and two lines in the latter. This suggests differential expression of boPAG2 related glycoproteins in these two subspecies.

Environmental allergens and asthma in urban elementary schools

BACKGROUND

Asthma in school children is rising, and indoor allergens are very common triggers of asthma attacks; however, the risk of the school environment on asthma has not been well studied.

OBJECTIVE

To determine the presence and the levels of common aeroallergens in schools, where asthma prevalence rates are high.

METHODS

Settled dust samples were collected from 12 Baltimore City public elementary schools, and they were analyzed for the following allergens: cockroaches (Bla g 1/2), dust mites (Der f 1/p 1), dog (Can f 1), cat (Fel d 1), and mouse (Mus m 1). School asthma prevalence rates were correlated with allergen levels, and association between allergen levels and other risk factors present in the schools' environment was examined.

RESULTS

The mean and range levels were 1.49 U/g (0 to 8) for Bla g 1/2; 0.38 microg/g (0 to 11.9) for the Der f 1/p 1; 1.44 microg/g (0.1 to 9.6) for Can f 1; 1.66 microg/g (0.2 to 12) for Fel d 1; and 6.24 microg/g (0.3 to 118.3) for Mus m 1. Dust mite, cat and dog allergens were significantly in rooms with carpet and/or area rugs, compared to rooms with bare floors (P < 0.05). Asthma prevalence rates varied from 11.8 to 20.8% between schools and positively correlation with the mean levels of Bla g 1/2 in the schools (P = 0.001).

CONCLUSIONS

Common allergens that are known to trigger asthma were detected in all school environments, where asthma prevalence rates were high. However, the overall allergen levels were low, indicating that other factors, including exposures in the homes of asthmatic patients, may have more relevance to sensitization and symptoms than school exposures.

Proinsulin processing in the diabetic Goto-Kakizaki rat

The biosynthesis and processing of proinsulin was investigated in the diabetic Goto-Kakizaki (GK) rat. Immunofluorescence microscopy comparing GK and Wistar control rat pancreata revealed marked changes in the distribution of alpha-cells and pronounced beta-cell heterogeneity in the expression patterns of insulin, prohormone convertases PC1, PC2, carboxypeptidase E (CPE) and the PC-binding proteins 7B2 and ProSAAS. Western blot analyses of isolated islets revealed little difference in PC1 and CPE expression but PC2 immunoreactivity was markedly lower in the GK islets. The processing of the PC2-dependent substrate chromogranin A was reduced as evidenced by the appearance of intermediates. No differences were seen in the biosynthesis and post-translational modification of PC1, PC2 or CPE following incubation of islets in 16.7 mM glucose, but incubation in 3.3 mM glucose resulted in decreased PC2 biosynthesis in the GK islets. The rates of biosynthesis, processing and secretion of newly synthesized (pro)insulin were comparable. Circulating insulin immunoreactivity in both Wistar and GK rats was predominantly insulin 1 and 2 in the expected ratios with no (pro)insulin evident. Thus, the marked changes in islet morphology and PC2 expression did not impact the rate or extent of proinsulin processing either in vitro or in vivo in this experimental model.

Cockroach extract antigen increases bronchial airway epithelial permeability

BACKGROUND

The bronchial epithelial cells of airways are subject to recurrent environmental injury throughout the life of an individual. Recently, a high incidence of asthma has been reported in inner-city children. The increased incidence of asthma in inner-city children is thought to be caused, in part, by frequent exposure to allergens of the common household pest the cockroach.

OBJECTIVE

We sought to investigate whether cockroach extract antigen (CrAg) induces vascular permeability factor, also known as vascular endothelial growth factor (VEGF), and whether it increases permeability in bronchial airway epithelial cells (BAECs).

METHODS

We estimated CrAg-induced VEGF release in BAECs by using an ELISA and VEGF mRNA expression by using an RT-PCR reaction. The influence of CrAg on BAEC barrier function was estimated by measuring electrical resistance with an electric cell substrate impedance-sensing system.

RESULTS

Our results demonstrate that CrAg induces VEGF release in BAECs in a time-dependent manner. The VEGF induction was also confirmed by means of VEGF mRNA expression in CrAg-stimulated BAECs. CrAg decreased electrical resistance across BAEC monolayers. The maximum decrease in electrical resistance was noticed 6 hours after activation and reached a plateau thereafter. Neutralizing antibodies to VEGF significantly inhibited the decrease in BAEC electrical resistance caused by CrAg.

CONCLUSIONS

These data suggest that CrAg induces VEGF release in BAECs and alters bronchial airway permeability.

Elevated expression of beta-site amyloid precursor protein cleaving enzyme 2 in brains of patients with Down syndrome

The gene encoding the beta-site amyloid precursor protein cleaving enzyme 2 (BACE2) has been determined to be located on the long arm of chromosome 21 at 21q22.3. BACE2 cleaves the amyloid precursor protein at the beta-secretase site and is thought to contribute to amyloid beta protein production. In the present study, changes in the expression of BACE2 were investigated immunohistochemically in the frontal cortex of patients with Down syndrome (DS). The immunoreactivity for BACE2 was detected in neurofibrillary tangle-bearing neurons from the elderly DS brains with Alzheimer-type neuropathology, but were not detected in those of DS brains without Alzheimer-type neuropathology or of control brains of any age. This suggests the possibility that the elevated expression of BACE2 is involved in the Alzheimer-type neuropathology of DS.

Localization of beta-secretase memapsin 2 in the brain of Alzheimer's patients and normal aged controls

Chronic accumulation of beta-amyloid in the brain has been shown to result in complex molecular and cellular changes that accompany neurodegeneration in Alzheimer's disease (AD). In this study, we examined the expression of a newly identified beta-secretase, memapsin 2 (M2) or beta-site APP cleaving enzyme in deparaffinized sections from 10 AD patients and 10 aged matched controls and in frozen samples of parietal cortex from 11 AD and 8 controls. M2 is mainly expressed in neurons, with high levels in CA4 to CA2 regions and transentorhinal cortex and low or intermediate levels in CA1, subiculum, and granule cells of the dentate gyrus. The majority of AD brains showed an increase of M2 expression in the CA1, but a decrease in the transentorhinal cortex. A subset of controls and AD patients had high M2 expression in parietal neocortex. Double-staining revealed that senile plaques are not directly associated with the soma of M2-expressing neurons. Neurofibrillary tangles were associated with lower M2 expression in AD. These data indicate that beta-secretase M2 may not be straightforwardly involved in amyloid plaque formation in AD brain.

Activation of the cardiac endothelin system in left ventricular hypertrophy before onset of heart failure in TG(mREN2)27 rats

OBJECTIVE

To characterize the cardiac angiotensin and endothelin (ET) system in compensated left ventricular hypertrophy due to long standing arterial hypertension and to assess the role of angiotensin and ET converting enzymes in mediating the observed changes of angiotensin and ET levels, respectively.

METHODS

We studied the left ventricular renin-angiotensin system (RAS) and ET system in 20-week-old male transgenic hypertensive TG(mREN2)27 rats, a model of the monogenic renin-dependent form of severe hypertension. Age-matched Sprague-Dawley rats served as controls.

RESULTS

TG(mREN2)27 rats exhibited left ventricular hypertrophy without signs of congestion. Transgene overexpression led to an activation of the tissue RAS with increased angiotensin II levels in spite of unchanged angiotensin converting enzyme (ACE) activity and ACE mRNA levels. ET-1 production was markedly increased in TG(mREN2)27 rats indicating that the ET-system was activated. Cardiac ET-1 in TG(mREN2)27 originated most likely from increased preproET-1 production because preproET-1 mRNA levels were increased but ET converting enzyme gene expression and activity were unchanged. Furthermore, ET-1 binding sites were significantly increased in TG(mREN2)27 rats without changes in K(D) values and ET(A)/ET(B) receptor ratios. ET(A) receptor gene expression was not altered whereas ET(B) receptor mRNA levels were up-regulated twofold in TG(mREN2)27 rats suggesting that ET(A) and ET(B) receptor expression may be regulated differentially.

CONCLUSIONS

Cardiac ET and angiotensin systems are co-activated in compensated cardiac hypertrophy before onset of heart failure, and thus may be involved in the mechanism by which cardiac remodelling and progression of left ventricular dysfunction occur in TG(mREN2)27 rats.

Endothelin converting enzyme-1 expression in endometrial adenocarcinomas

Endothelin-1 (ET-1) is a potent mitogen in various precursor tumor cells, including endometrial adenocarcinoma. It is proposed that ET-1 produced by endometrial adenocarcinoma may participate in the angiogenesis of this carcinoma in vivo. Endothelin converting enzyme-1 (ECE-1) is the key enzyme that synthesizes ET-1. In this study, we tried to demonstrate the expression of ECE-1 in endometrial carcinomas. Deparaffinized tissue sections from patients with endometrial adenocarcinoma were analyzed by immunohistochemistry for the presence of ECE-1. Our study showed that the expression of ECE-1 was markedly increased in 9 of 15 (60%) well-differentiated endometrial adenocarcinomas; in contrast, only 2 out of 10 (20%) control specimens showed a mild labeling. With new selective inhibitory molecules emerging, research is currently evaluating the possible inhibition of ECE-1 as an alternative approach for the treatment of endometrial as well as other carcinomas.

Prostaglandin F(2alpha) regulation of the bovine corpus luteum endothelin system during the early and midluteal phase

Recent evidence in the cow suggests that endothelin-1 (ET-1) plays a role during prostaglandin (PG) F(2alpha)-induced luteal regression. We have examined the effects of treatment with PGF(2alpha) during the early and midluteal phases on three components of the endothelin system: endothelin-converting enzyme-1 (ECE-1), ET type A receptor (ET(A)), and ET-1 in the bovine corpus luteum (CL). Cyclic beef cows were injected (0 h) on Day 4 or 10 with either saline or the PGF(2alpha) analogue Lutalyse (15 mg). The CL were collected at 2 (n = 11), 10 (n = 23), 24 (n = 15), or 48 h (n = 12) after treatment. The cows in which CL were removed after 10 h comprised of two experimental groups. The first group (n = 11) received one injection; the second group (n = 12) received two injections, one at 0 h and one at 8 h. The cows in which CL were collected after 24 and 48 h received one injection every 8 h. Semiquantitative reverse transcriptase-polymerase chain reaction was used to evaluate the mRNA encoding ECE-1, ET(A), and ET-1. The ECE-1 and ET(A) proteins were evaluated by semiquantitative Western blot analysis. The ET-1 was the most likely component of the endothelin system target for PGF(2alpha) regulation during the midluteal phase. The ET(A) and ECE-1 genes were constitutively expressed in the Day 4 and Day 10 CL. A practical application of this observation is that it may be possible to target the ET-1 gene as a way to manipulate the luteolytic action of PGF(2alpha).

Detection of immunoreactive napsin A in human urine

Human napsin A is an aspartic proteinase highly expressed in kidney and lung. To elucidate whether napsin A is excreted in the urine we have performed an immunochemical study using anti-napsin A polyclonal antibody. As a result an immunoreactive band at approx. 38 kDa was detected which corresponds to the molecular mass of recombinant active human napsin A. A deglycosylation study showed that excreted napsin A is N-glycosylated on apparently all of the three potential glycosylation sites. Immunoreactive napsin A was also observed in urine from patients with a transplanted kidney whose kidney function appeared half to fully normal. On the other hand, no or very low immunostaining was detected in samples from patients with diseased kidneys. The urinary excretion pattern correlates well with the enzymatic activity of napsin A. These data show that human napsin A is excreted as functional proteinase in the urine. Furthermore, immunochemical studies suggest a relation between urinary excretion of napsin A and renal function. More specifically, lack of urinary excretion of napsin A could potentially serve as a tool for the detection of kidney dysfunction.

Human endothelin converting enzyme-2 (ECE2): characterization of mRNA species and chromosomal localization

Generation of the functionally pleiotropic members of the endothelin vasoactive peptide family is critically catalyzed by unique type II metalloproteases, termed endothelin converting enzymes (ECE). Isolation of human ECE-2 (EC 3.4.24.71) cDNAs revealed deduced open reading frames of 787 and 765 amino acids with approximately 60% identity with human ECE-1. Characterization of mRNA variants revealed mRNA structural diversity at the 5'-terminus. Two mRNA species exist containing distinct first and second exons. Furthermore, in one of these species, an in-frame deletion of the intracytoplasmic domain removed 29 amino acids. Because of the previously reported human genetic diseases ascribed to germline mutations of member genes of the endothelin family, ECE2 was localized in human chromosomes with fluorescence in situ hybridization and radiation hybrid mapping to 3q28-q29 and SHGC-20171/D3S1571, respectively.

Coexpression of endothelin-converting enzyme-1 and endothelin-1 in different stages of human atherosclerosis

BACKGROUND

Endothelin-converting enzyme (ECE)-1 activates endothelin-1 (ET-1) and may thus contribute to the regulation of vascular tone and cell growth during atherosclerosis.

METHODS AND RESULTS

To evaluate ECE-1 immunoreactivity concerning big ET-1/ET-1, we performed qualitative and quantitative immunohistochemistry in normal internal mammary arteries (n=10), in coronary arteries with adaptive intimal fibrosis (n=10), in aortic fatty streaks (n=10), and in distinct regions of advanced carotid plaques (n=15). Furthermore, we determined ECE-1 activity in the control specimens and in the inflammatory intimal regions of carotid plaques. Double immunolabeling showed that ECE-1 was present in endothelial cells, vascular smooth muscle cells, and macrophages. All ET-1(+) cells were simultaneously ECE-1(+). Most importantly, there were significantly more ET-1(+) cells in the intima and media when atherosclerosis was in an inflammatory stage than when it was in a noninflammatory stage. Moreover, ECE-1 activity was upregulated in the intima of carotid plaques, although immunohistochemically, there were no significant differences between the number of ECE(+) cells in the different compartments of the arterial wall.

CONCLUSION

Together with ET-1, ECE-1 is abundantly present in human arteries and at different stages of atherosclerotic plaque evolution. The upregulation of the ECE-1/ET-1 system is closely linked to the presence of chronic inflammation and is present in very early stages of plaque evolution. Therefore, enhanced production of active ET-1 may substantially contribute to cell growth and the regulation of vascular tone in advanced atherosclerotic lesions and in the very early stages of plaque evolution, when a plaque is still imperceptible clinically.