Aminopeptidase A Research Articles

Preliminary study on plasma proteins in pregnant and non-pregnant female dogs

In this study, we used a combined approach based on 2-dimensional electrophoresis (2-DE), difference in gel electrophoresis (DIGE), and mass spectrometry (MS) to identify the plasma protein composition in pregnant female dogs and compared it with non-pregnant female dogs. We used the plasma samples obtained from four female dogs during I, II, and III thirds of pregnancy, three days after parturition, as well as from four non-pregnant female dogs in diestrus phase. Analysis of 2-DE gel image exhibited of 249 protein spots. The intensity of staining of 35 spots differed significantly (P < 0.05) between the non-pregnant and pregnant female dogs. We used matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI TOF MS) to identify 47 spots corresponding to 52 different proteins. Five identified protein spots, including zinc finger BED domain-containing protein 5, hemoglobin subunit beta-2, integrator complex subunit 7, apolipoprotein A-I, and glutamyl aminopeptidase were differentially presented in the plasma of pregnant and non-pregnant female dogs. To the best of our knowledge, this is the first report on the plasma protein profile of pregnant and non-pregnant female dogs. In this study, we identified proteins that have not been previously identified in dogs. Our findings showed that numerous protein spots were differentially presented in the plasma of female dogs during normal pregnancy. Although we identified only a limited number of differentially presented proteins, our study demonstrated that the plasma protein profile changed during pregnancy in female dogs, which suggests its importance in maintaining pregnancy. Further studies are necessary to define complete plasma protein profile of pregnant female dogs and to identify all proteins that are differentially presented in the pregnant animals compared with the non-pregnant ones. In addition, studies are warranted to explain the role of those proteins in maintaining the pregnancy and their usefulness in detection of early pregnancy. Furthermore, our results indicated that DIGE technique is useful in the comparison of samples originated from different states and time points in dogs.

Deficiency of the Angiotensinase Aminopeptidase A Increases Susceptibility to Glomerular Injury.

Aminopeptidase A (APA) is expressed in glomerular podocytes and tubular epithelia and metabolizes angiotensin II (AngII), a peptide known to promote glomerulosclerosis. In this study, we tested whether APA expression changes in response to progressive nephron loss or whether APA exerts a protective role against glomerular damage and during AngII-mediated hypertensive kidney injury. At advanced stages of FSGS, fawn-hooded hypertensive rat kidneys exhibited distinctly increased APA staining in areas of intact glomerular capillary loops. Moreover, BALB/c APA-knockout (KO) mice injected with a nephrotoxic serum showed persistent glomerular hyalinosis and albuminuria 96 hours after injection, whereas wild-type controls achieved virtually full recovery. We then tested the effect of 4-week infusion of AngII (400 ng/kg per minute) in APA-KO and wild-type mice. Although we observed no significant difference in achieved systolic BP, AngII-treated APA-KO mice developed a significant rise in albuminuria not observed in AngII-treated wild-type mice along with increased segmental and global sclerosis and/or collapse of juxtamedullary glomeruli, microcystic tubular dilation, and tubulointerstitial fibrosis. In parallel, AngII treatment significantly increased the kidney AngII content and attenuated the expression of podocyte nephrin in APA-KO mice but not in wild-type controls. These data show that deficiency of APA increases susceptibility to glomerular injury in BALB/c mice. The augmented AngII-mediated kidney injury observed in association with increased intrarenal AngII accumulation in the absence of APA suggests a protective metabolizing role of APA in AngII-mediated glomerular diseases.

Sex differences in the aging pattern of renin\u2013angiotensin system serum peptidases

BackgroundSerum peptidases, such as angiotensin-converting enzyme (ACE), angiotensin-converting enzyme-2 (ACE2), neutral endopeptidase (NEP), aminopeptidase N (APN), and aminopeptidase A (APA), are important elements of the renin–angiotensin system (RAS). Dysregulation of these enzymes has been associated with hypertension and cardiovascular risk. In the present study, serum activities of RAS peptidases were analyzed to evaluate the existence of sexual differences, with a possible different pattern in pre- and post-andropausal/post-menopausal participants.MethodsOne hundred and eighteen healthy men and women between 41 and 70 years of age (58 women and 60 men) were recruited to participate in the study. Serum RAS-regulating enzymes were measured by spectrofluorimetry. Enzymatic activity was recorded as units of enzyme per milliliter of serum (U/mL).ResultsSignificantly lower serum APA activity was observed in men with respect to women; no sex differences were detected for ACE, ACE2, NEP, or APN. Significantly lower APA and ACE serum activity were observed in older men compared to older women. In contrast, younger (<55 years) men had significantly higher values of NEP serum activity than younger women. Significantly lower ACE serum activity was detected in older men compared to younger men. In women, significantly higher ACE2 serum activity was observed in older women compared to younger women.ConclusionsThese results suggest a differential effect of aging on the activity of RAS enzymes in men and women, especially with respect to the breakpoint of andropausia/menopausia, on the critical serum enzymatic activities of the RAS, which could correlate with sexual differences in cardiovascular risk.

Mammalian Glutamyl Aminopeptidase Genes (ENPEP) and Proteins: Comparative Studies of a Major Contributor to Arterial Hypertension.

Glutamyl aminopeptidase (ENPEP) is a member of the M1 family of endopeptidases which are mammalian type II integral membrane zinc-containing endopeptidases. ENPEP is involved in the catabolic pathway of the renin-angiotensin system forming angiotensin III, which participates in blood pressure regulation and blood vessel formation. Comparative ENPEP amino acid sequences and structures and ENPEP gene locations were examined using data from several mammalian genome projects. Mammalian ENPEP sequences shared 71-98% identities. Five N-glycosylation sites were conserved for all mammalian ENPEP proteins examined although 9-18 sites were observed, in each case. Sequence alignments, key amino acid residues and predicted secondary and tertiary structures were also studied, including transmembrane and cytoplasmic sequences and active site residues. Highest levels of human ENPEP expression were observed in the terminal ileum of the small intestine and in the kidney cortex. Mammalian ENPEP genes contained 20 coding exons. The human ENPEP gene promoter and first coding exon contained a CpG island (CpG27) and at least 6 transcription factor binding sites, whereas the 3′-UTR region contained 7 miRNA target sites, which may contribute to the regulation of ENPEP gene expression in tissues of the body. Phylogenetic analyses examined the relationships of mammalian ENPEP genes and proteins, including primate, other eutherian, marsupial and monotreme sources, using chicken ENPEP as a primordial sequence for comparative purposes.

High aminopeptidase A activity contributes to blood pressure control in ob/ob mice by AT2 receptor-dependent mechanism.

Obesity is assumed to be a major cause of human essential hypertension; however, the mechanisms responsible for weight-related increase in blood pressure (BP) are not fully understood. The prevalence of hypertension induced by obesity has grown over the years, and the role of the renin-angiotensin-aldosterone system (RAAS) in this process continues to be elucidated. In this scenario, the ob/ob mice are a genetic obesity model generally used for metabolic disorder studies. These mice are normotensive even though they present several metabolic conditions that predispose them to hypertension. Although the normotensive trait in these mice is associated with the poor activation of sympathetic nervous system by the lack of leptin, we demonstrated that ob/ob mice present massively increased aminopeptidase A (APA) activity in the circulation. APA enzyme metabolizes angiotensin (ANG) II into ANG III, a peptide associated with intrarenal angiotensin type 2 (AT2) receptor activation and induction of natriuresis. In these mice, we found increased ANG-III levels in the circulation, high AT2 receptor expression in the kidney, and enhanced natriuresis. AT2 receptor blocking and APA inhibition increased BP, suggesting the ANG III-AT2 receptor axis as a complementary BP control mechanism. Circulating APA activity was significantly reduced by weight loss independently of leptin, indicating the role of fat tissue in APA production. Therefore, in this study we provide new data supporting the role of APA in BP control in ob/ob mouse strain. These findings improve our comprehension about obesity-related hypertension and suggest new tools for its treatment.NEW & NOTEWORTHY In this study, we reported an increased angiotensin III generation in the circulation of ob/ob mice caused by a high aminopeptidase A activity. These findings are associated with an increased natriuresis found in these mice and support the role of renin-angiotensin-aldosterone system as additional mechanism regulating blood pressure in this genetic obese strain.

Abstract P152: Aminopeptidase A in the Brain Exerts Cardiovascular Action via Degradation of Kallidin to Bradykinin

Objective: Aminopeptidase A (APA) degrades of various sympathomodulatory peptides such as angiotensin (Ang) II, cholecystkinin-8, neurokinin B and kallidin. APA activity is increased in the brain of hypertensive rats. A centrally acting APA inhibitor prodrug is currently under investigation in clinical trial for treatment of hypertension. In previous reports, a role of APA in the brain on cardiovascular regulation was researched focus on only renin-angiotensin system. We previously reported that intracerebroventricular(icv) administration of APA increased blood pressure and that this pressor response was partially blocked by angiotensin receptor blocker. In this study, we evaluated a role of APA on cardiovascular regulation focusing on peptides other than Ang II. Method: Eleven weeks old Wistar Kyoto rats were used. We icv administrated 800 ng/8 μL of APA after pretreatment of following drugs, i) 8μL of artificial cerebrospinal fluid (aCSF) as a control, ii) 80 nmol/8 μL of amastatin which is a non-specific aminopeptidase inhibitor, iii) 1 nmol/8 μL of HOE-140 which is a bradykinin receptor blocker to evaluate the involvement of degradation of kallidin to bradykinin by APA. Result: i) Icv administration of APA after pretreatment of aCSF increased blood pressure rapidly. Blood pressure reached a peak within 1 minute. The elevated blood pressure decreased gradually and reached baseline blood pressure in 10 minutes. A peak pressor response is 25.5±1.4 mmHg (n=5). ii) Icv pretreatment of amastatin or HOE-140 did not change the blood pressure. A peak pressor response induced by APA is 13.1±4.1 mmHg (n=6, p&lt;0.05 vs aCSF). iii) Icv pretreatment of HOE-140 did not change the blood pressure. A peak pressor response induced by APA is 21.2±1.8 mmHg (n=4, p&lt;0.05 vs aCSF). Conclusion: 1) Icv administration of APA increased blood pressure by APA enzymatic activity. 2) Cardiovascular regulation of APA in the brain is due to not only degradation of Ang II to Ang III but also degradation of kallidin to bradykinin. Clinical implication: We think inhibition of APA in the brain may be a unique therapeutic target which affects several cardiovascular peptides in the brain.

MPS 18-01 MODE OF ACTION OF RB150, AN AMINOPEPTIDASE A INHIBITOR PRODRUG AS A CENTRALLY-ACTING ANTIHYPERTENSIVE AGENT IN DOCA-SALT HYPERTENSIVE RATS

Objective: In the brain, angiotensin III (AngIII) generated from angiotensin II (AngII) by aminopeptidase A (APA) exerts a tonic stimulatory action on the control of blood pressure (BP) in hypertensive rats. Inhibition of brain APA by RB150, an orally active prodrug of the specific and selective APA inhibitor, blocks brain AngIII formation and normalizes BP in hypertensive rats. Since following blockade of brain AngIII formation by RB150, no AngII accumulation was observed, we aimed to delineate if this treatment induces the activation of another metabolic pathway of brain AngII, in particular angiotensin converting enzyme type 2 (ACE2) which converts AngII into angiotensin 1–7 (Ang1–7). Design and Method: For this purpose, RB150 and MLN4760, an ACE2 inhibitor, were administered by intracerebroventricular (ICV) route after insertion of an intracerebral cannula to alert DOCA-salt rats, a model of salt-dependent hypertension. Mean arterial blood pressure (MABP) was recorded via an arterial femoral catheter. Maximal MABP decrease and area under the curve (AUC) of the variations in MABP were calculated. Results: ICV administration of RB150 (100 μg) significantly decreased MABP compared to vehicle (−23 ± 3 mmHg vs −6 ± 2 mmHg; AUC: 17.6 ± 2 vs 2.1 ± 3). Administration of MLN4760 (10 μg) didn’t induce any significant change of MABP compared to vehicle (−10 ± 3 mmHg; AUC: 1.4 ± 2). Co-administration of MLN4760 (10 μg) with RB150 (100 μg) partially inhibits RB150-induced BP decrease. Conclusions: In conclusion, ICV administration of the ACE2 inhibitor alone has no effect on BP indicating that in DOCA-salt rats, brain Ang1–7 does not exert a tonic stimulatory effect on the control of BP. However, when conversion of brain AngII into AngIII is blocked by RB150, there is an activation of the conversion by ACE2 of brain AngII into Ang1–7, which by acting on the Mas receptor, may participate to the RB150-induced BP decrease in hypertensive rats.

OP.6D.03] MODE OF ACTION OF RB150, AN AMINOPEPTIDASE A INHIBITOR PRODRUG AS A CENTRALLY-ACTING ANTIHYPERTENSIVE AGENT IN DOCA-SALT HYPERTENSIVE RATS

Objective: In the brain, angiotensin III (AngIII) generated from angiotensin II (AngII) by aminopeptidase A (APA) exerts a tonic stimulatory action on the control of blood pressure (BP) in hypertensive rats. Inhibition of brain APA by RB150 (also known as QGC001), an orally active prodrug of the specific and selective APA inhibitor EC33, blocks brain AngIII formation and normalizes BP in hypertensive rats. Thus, RB150 has emerged as the prototype of a new class of centrally-acting antihypertensive agents and is currently evaluated in a phase II clinical trial in hypertensive patients. Since following blockade of brain AngIII formation by RB150, no AngII accumulation was observed, we aimed to delineate if this treatment induces the activation of another metabolic pathway of brain AngII, in particular angiotensin converting enzyme type 2 (ACE2) which converts AngII into angiotensin 1–7 (Ang1-7). Design and method: For this purpose, RB150 and MLN4760, an ACE2 inhibitor, were administered by intracerebroventricular (ICV) route after insertion of an intracerebral cannula to alert DOCA-salt rats, a model of salt-dependent hypertension. Mean arterial blood pressure (MABP) was recorded via an arterial femoral catheter. Maximal MABP decrease and area under the curve (AUC) of the variations in MABP were calculated. Results: ICV administration of RB150 (100 μg) significantly decreased MABP compared to vehicle (−23 ± 3 mmHg vs −6 ± 2 mmHg; AUC: 17.6 ± 2 vs 2.1 ± 3). Administration of MLN4760 (10 μg) didn’t induce any significant change of MABP compared to vehicle (−10 ± 3 mmHg; AUC: 1.4 ± 2). Experiments in progress show that a co-administration of MLN4760 (10 μg) with RB150 (100 μg) partially inhibits the RB150-induced BP decrease. Conclusions: In conclusion, ICV administration of the ACE2 inhibitor alone has no effect on BP indicating that in DOCA-salt rats, brain Ang1-7 does not exert a tonic stimulatory effect on the control of BP. However, when conversion of brain AngII into AngIII is blocked by RB150, there is an activation of the conversion by ACE2 of brain AngII into Ang1-7, which by acting on the Mas receptor, may participate to the RB150-induced BP decrease in hypertensive rats.

OP.8C.06] CENTRAL ANTIHYPERTENSIVE EFFECTS OF CHRONIC TREATMENT WITH RB150/QGC001, AN ORALLY ACTIVE AMINOPEPTIDASE A INHIBITOR PRODRUG IN DOCA-SALT HYPERTENSIVE RATS

Objective: Hyperactivity of the brain renin-angiotensin system (RAS) is implicated in the development and maintenance of arterial hypertension (HTA). We previously showed that angiotensin III (AngIII) is one of the main effector peptides of the brain RAS, exerting a tonic stimulatory control over blood pressure (BP) in alert hypertensive rats. Therefore, aminopeptidase A (APA) the enzyme generating brain AngIII, represents a new therapeutic target for the treatment of HTA. This led to the development of RB150 (also known as QGC001), a prodrug of the specific and selective APA inhibitor, EC33. When given orally, RB150 is able to cross the blood-brain-barrier, to inhibit brain APA activity and to decrease BP in two experimental models of HTA. We investigate here the effects of repeated oral administrations of RB150 (50 mg/kg/day) over 10 days on BP in conscious DOCA-salt rats to assess if a tolerance to the antihypertensive RB150 effect occurs after chronic treatment. Design and method: For this purpose, 5 hours after RB150 administration, we measured daily variations in systolic BP (sBP) by the tail-cuff method, plasma arginine-vasopressin (AVP) levels by radioimmunoassay and metabolic parameters Results: Chronic oral treatment with RB150 significantly decreased sBP compared with saline over the 10 days treatment period, without significantly altering heart rate. The maximal decrease in sBP (−29.6 ± 6 mmHg) was observed on the second day and the average RB150-induced decrease in sBP over 10 days was not significantly changed (−21 ± 5 mmHg), showing no tolerance to the antihypertensive effect of RB150 after repeated administrations. Chronic oral treatment with RB150 reduced by 59% the increase in plasma AVP levels observed in DOCA-salt rats compared with normotensive rats receiving saline. The administration of RB150 increased significantly diuresis by 39% and natriuresis by 34% without modification of plasma sodium and potassium levels when compared to DOCA-salt rats receiving saline over a 10 days analysis. This may participate to the blood pressure decrease by reducing the size of fluid compartment. Conclusions: Our results further confirm the interest of developing RB150 as a novel centrally-acting agent for the treatment of HTA.

Should we measure ambivalence to change?

Notch is a membrane inserted protein activated by the membrane-inserted γ-secretase proteolytic complex. The Notch pathway is a potential therapeutic target for the treatment of renal diseases but also controls the function of other cells, requiring cell-targeting of Notch antagonists. Toward selective targeting, we have developed the γ-secretase inhibitor-based prodrugs 13a and 15a as substrates for γ-glutamyltranspeptidase (γ-GT) and/or γ-glutamylcyclotransferase (γ-GCT) as well as aminopeptidase A (APA), which are overexpressed in renal diseases, and have evaluated them in experimental in vitro and in vivo models. In nondiseased mice, the cleavage product from Ac-γ-Glu-γ-secretase inhibitor prodrug 13a (γ-GT-targeting and γ-GCT-targeting) but not from Ac-α-Glu-γ-secretase inhibitor prodrug 15a (APA-targeting) accumulated in kidneys when compared to blood and liver. Potential nephroprotective effects of the γ-secretase inhibitor targeted prodrugs were investigated in vivo in a mouse model of acute kidney injury, demonstrating that the expression of Notch1 and cleaved Notch1 could be selectively down-regulated upon treatment with the Ac-γ-Glu-γ-secretase-inhibitor 13a.

Targeted γ-Secretase Inhibition To Control the Notch Pathway in Renal Diseases.

Notch is a membrane inserted protein activated by the membrane-inserted γ-secretase proteolytic complex. The Notch pathway is a potential therapeutic target for the treatment of renal diseases but also controls the function of other cells, requiring cell-targeting of Notch antagonists. Toward selective targeting, we have developed the γ-secretase inhibitor-based prodrugs 13a and 15a as substrates for γ-glutamyltranspeptidase (γ-GT) and/or γ-glutamylcyclotransferase (γ-GCT) as well as aminopeptidase A (APA), which are overexpressed in renal diseases, and have evaluated them in experimental in vitro and in vivo models. In nondiseased mice, the cleavage product from Ac-γ-Glu-γ-secretase inhibitor prodrug 13a (γ-GT-targeting and γ-GCT-targeting) but not from Ac-α-Glu-γ-secretase inhibitor prodrug 15a (APA-targeting) accumulated in kidneys when compared to blood and liver. Potential nephroprotective effects of the γ-secretase inhibitor targeted prodrugs were investigated in vivo in a mouse model of acute kidney injury, demonstrating that the expression of Notch1 and cleaved Notch1 could be selectively down-regulated upon treatment with the Ac-γ-Glu-γ-secretase-inhibitor 13a.

Abstract P059: A A Role of Aminopeptidase A in the Brain on Cardiovascular Regulation of Conscious Rat

Objective: Aminopeptidase A (APA) have important role in conversion of Ang II to Ang III. Intravenous APA administration lowers blood pressure in hypertensive rats. In contrast, APA inhibition in the brain lowers blood pressure in hypertensive rats. Therefore APA might have different role on cardiovascular regulation. However, a role of APA and Ang III on cardiovascular regulation especially in the brain has not been fully understood. Our purpose of present study was to investigate a role of APA and Ang III in the brain on cardiovascular regulation in conscious state. Method: 12-13 weeks old Wistar Kyoto rat (WKY) and 12-16 weeks old spontaneously hypertensive rat (SHR) were used. i) APA distribution in the brain was evaluated by immunohistochemistry. Protein expression of APA was evaluated by Western blotting. Enzymatic activity of APA was evaluated using L-glutamic acid γ-(4-nitroanilide) as a substrate. ii) WKY received icv administration of Ang II 25ng/2μL and Ang III 25ng/2μL. We recorded change in mean arterial pressure (MAP) in conscious and unrestraied state and measured induced drinking time. iii) SHR received icv administeration of recombinant APA 400ng/4μL. We recorded change in MAP in conscious and unrestraied state and measured induced drinking time. Result: i) APA was diffusely immunostained in the cells of brain stem including cardiovascular regulatory area such as rostral ventrolateral medulla. Protein expression and APA activity in the brain were similar between WKY (n=3) and SHR (n=3).ii) Icv administration of Ang II increased MAP by 33.8±3.8 mmHg and induced drinking behavior for 405±90 seconds (n=4). Icv administration of Ang III also increased MAP by 24.7±2.4 mmHg and induced drinking behavior for 258±62 seconds (n=3). These vasopressor activity and induced drinking behavior was completely blocked by pretretment of angiotensin receptor type 1 blocker.iii) Icv administration of APA increased MAP by 10.0±1.7 mmHg (n=3). Conclusion: These results suggested that Ang III in the brain increase blood pressure by Angiotensin type 1 receptor dependent mechanism and APA in the brain may involved in blood pressure regulation as a vasopressor enzyme.

Plasma peptidases as prognostic biomarkers in patients with first-episode psychosis

The plasma activity of nine aminopeptidases was monitored over a year in first-episode psychotic patients. We observed significant differences in aminopeptidase B (APB), aminopeptidase N (APN) and dipeptidyl peptidase IV (DPPIV), but not in puromycin-sensitive aminopeptidase (PSA), prolyl endopeptidase (PEP), cysteine aminopeptidase (Cys-AP), aspartate aminopeptidase (Asp-AP), glutamate aminopeptidase (Glu) or piroglutamate aminopeptidase (PGI) in these patients compared to controls, and also a progressive increase in plasma activity, correlated to changes in scores on clinical scales, Global Assessment of Functioning scale (GAF) and Hamilton Depression Rating Scale (HDRS), at 1 month of follow-up. At 1 month after diagnosis, the median score obtained by patients on the GAF was negatively associated with the plasma activity of APB and PEP measured at the beginning of the psychotic episode, indicating a role as a negative prognostic factor that can predict psychiatric symptomatology. In the case of HDRS, scores at 1 month after diagnosis were found to be positively associated with the initial plasma activity of DPPIV, APN and PSA, indicating that their initial elevation is a negative prognostic factor that can predict subsequent depressive symptomatology. Taken together, these results suggest a pathophysiological involvement of plasma peptidases and indicate that aminopeptidase activity can predict the course of first-episode psychosis patients, acting as a prognostic indicator.

Immunological detection of glutamyl aminopeptidase in urine samples from cisplatin-treated rats.

The aim of this work is to demonstrate if urinary excretion of glutamyl aminopeptidase (GluAp) can be quantified by immunological methods. Urine samples from control and cisplatin-treated rats (n = 10 each group) were obtained at 1, 8, and 15 days after cisplatin injection. GluAp was analyzed by kinetic fluorimetry, ELISA, and immunoblotting. Sensitivity and specificity was studied for fluorimetric activity and ELISA 24 h after cisplatin injection. We also analyzed the predictive value over renal dysfunction at the end of the experiment. GluAp was easily detected by immunoblotting and ELISA, and its urinary excretion was increased in cisplatin-treated rats (p < 0.01). Results obtained with ELISA were strongly correlated (r = 0.8186; p < 0.0001) with fluorimetric activity. Kinetic fluorimetry was the method with the highest AUC (AUC = 1) and the highest predictive value over serum creatinine (r = 0.7630; p = 0.0001) and body weight increase (r = -0.8721; p < 0.0001). GluAp can be detected in urine samples with immunological methods, making possible the development of an antibody-based kit for its determination. Its excretion correlates with the extent of renal dysfunction in cisplatin-treated rats, confirming its value as an early marker of renal damage that can be a diagnostic aid in renal diseases.

New insights into the role of sex steroid hormones in pregnancy: possible therapeutic approach by sex steroid hormones for the treatment of both preeclampsia and preterm labor.

Fetal peptide hormones are essential for the development of fetus, which increase in accordance with pregnancy term. Concentration of these hormones within the feto-placental unit is normally higher than that of maternal circulation. Since these hormones are biologically active, the leakage of these hormones into the maternal circulation is regulated by degradation activity by placental aminopeptidases, in order to maintain the balance between carriage of pregnancy and onset of labor.Because the concentration of these hormones, being regulated by the amount of endogenous production and by physiological degradation by enzymes in the blood and tissue, the balance between production and degradation is a definitive element for maintaining normal gestation and term delivery.The changes of the balance between fetal angiotensin II (A-II) and vasopressin (AVP) andA-II and AVP degrading enzymes, between aminopeptidase A (APA) and placental leucine aminopeptidase( P-LAP) - in the placenta and maternal blood due to fetal stress such as hypoxia - are the provable causes of preeclampsia or preterm labor.Induction of APA and P-LAP by estradiol benzoate (E2) and progesterone (P) from placenta has been demonstrated. They are involved in the regulation of fetal peptide hormones via placental aminopeptidases in homeostasis of pregnancy.Recently it was shown that both APA and P-LAP could be potentially safe and effective drugs for preeclampsia and preterm labor. The authors' proposed sex steroid treatment with dose increasing manner by gestational week (sex steroid treatment) for severe preeclampsia and preterm labor could be candidates replacing conventional treatments. In light of lacking safe and effective medication, the proposed sex steroid treatment is worthwhile for the prospective controlled studies for the treatment of both preeclampsia and preterm labor.

MHJ_0461 is a multifunctional leucine aminopeptidase on the surface of Mycoplasma hyopneumoniae.

Aminopeptidases are part of the arsenal of virulence factors produced by bacterial pathogens that inactivate host immune peptides. Mycoplasma hyopneumoniae is a genome-reduced pathogen of swine that lacks the genetic repertoire to synthesize amino acids and relies on the host for availability of amino acids for growth. M. hyopneumoniae recruits plasmin(ogen) onto its cell surface via the P97 and P102 adhesins and the glutamyl aminopeptidase MHJ_0125. Plasmin plays an important role in regulating the inflammatory response in the lungs of pigs infected with M. hyopneumoniae. We show that recombinant MHJ_0461 (rMHJ_0461) functions as a leucine aminopeptidase (LAP) with broad substrate specificity for leucine, alanine, phenylalanine, methionine and arginine and that MHJ_0461 resides on the surface of M. hyopneumoniae. rMHJ_0461 also binds heparin, plasminogen and foreign DNA. Plasminogen bound to rMHJ_0461 was readily converted to plasmin in the presence of tPA. Computational modelling identified putative DNA and heparin-binding motifs on solvent-exposed sites around a large pore on the LAP hexamer. We conclude that MHJ_0461 is a LAP that moonlights as a multifunctional adhesin on the cell surface of M. hyopneumoniae.

Structural and theoretical studies on rhodium and iridium complexes with 5-nitrosopyrimidines. Effects on the proteolytic regulatory enzymes of the renin–angiotensin system in human tumoral brain cells

The reactions of [RhCl(CO)(PPh3)2], [RhCl(CO)2]2 and [IrCl(CO)(PPh3)2] with different 5-nitrosopyrimidines afforded sixteen complexes which have been structurally characterized by elemental analysis, IR and NMR (1H and 13C) spectral methods and luminescence spectroscopy. The crystal and molecular structures of [RhIIICl(VIOH−1)2(PPh3)], [RhIIICl(DVIOH−1)2(PPh3)] and [RhII(DVIOH−1)2(PPh3)2] have been established from single crystal x-ray structure analyses. The three complexes are six-coordinated with both violurato ligands into an equatorial N5,O4-bidentate fashion, but with different mutually arrangements. Theoretical studies were driven on the molecular structure of [RhIIICl(VIOH−1)2(PPh3)] to assess the nature of the metal–ligand interaction as well as the foundations of the cis–trans (3L–2L) isomerism. An assortment of density functional (SOGGA11-X, B1LYP, B3LYP, B3LYP-D3 and wB97XD) has been used, all of them leading to a similar description of the target system. Thus, a topological analysis of the electronic density within AIM scheme and the study of the Mulliken charges yield a metal–ligand link of ionic character. Likewise, it has been proved that the cis–trans isomerism is mainly founded on that metal–ligand interaction with the relativistic effects playing a significant role. Although most of the compounds showed low direct toxicity against the human cell lines NB69 (neuroblastoma) and U373-MG (astroglioma), they differently modify in several ways the renin–angiotensin system (RAS)-regulating proteolytic regulatory enzymes aminopeptidase A (APA), aminopeptidase N (APN) and insulin-regulated aminopeptidase (IRAP). Therefore, these complexes could exert antitumor activity against both brain tumor types, acting through the paracrine regulating system mediated by tissue RAS rather than exerting a direct cytotoxic effect on tumor cells.

Abstract 407: Aminopeptidase A (APA)/Ang(2-10) and APA/AngIII are the Dominant Axes in the Metabolism of Angiotensin Peptides in Mice Plasma

ACE2 is considered an important enzyme in the degradation of Angiotensin (Ang) I (1-10) and especially of Ang II (1-8), as demonstrated by the rapid dissipation of this peptide when recombinant ACE2 is infused but the steady state level of ACE2 in plasma is low. We examined levels of multiple Ang peptides in plasma under steady state conditions in WT and ACE2KO mice on C57BL genetic background (n=4 and 5, respectively). Liquid chromatography mass-spectrometry-based approach which enables concurrent evaluation of ten different angiotensins at physiologic levels (pg/mL) was used for multiple peptide quantification. The levels of angiotensin peptides in WT mice were highest for Ang I (1-10) (1295±313 pg/mL), Ang (2-10) (657±173 pg/mL) and Ang III (2-8) (1047±178 pg/mL). In contrast, plasma levels of Ang II (1-8), the main effector peptide of the RAS, and Ang (1-7), the product of cleavage of Ang II by ACE2, were very low (7.8±2 and 3.5±0 pg/mL, respectively). In ACE2 KO mice, Ang II and Ang (1-7) levels were not significantly different from WT. Activity of Aminopeptidase A, an enzyme that converts Ang (1-10) to Ang (2-10) and cleaves Ang II (1-8) to Ang III (2-8), was significantly increased in ACE2KO (n=11) as compared to WT (n=17) (149±11 vs. 94±9 RFU/ul/hr, respectively, p&lt;0.001). This finding along with increased ratio of Ang (2-10)/Ang(1-8) (175±31 vs. 84±4, p&lt;0.01, respectively) suggests increased formation of Ang (2-10) from Ang (1-10) in ACE2KO mice by APA over the formation of Ang II (1-8) from Ang (1-10). These results show that plasma Ang II and Ang (1-7) levels in WT and ACE2KO mice are low relative to the high levels of Ang (2-10) and Ang III (2-8). ACE2 deficiency does not result in plasma Ang II accumulation or reduced Ang (1-7) levels and is associated with an increase in serum APA activity. We conclude that in mice plasma the APA/Ang(2-10) and APA/AngIII pathways, and not ACE2/Ang(1-7), are dominant in the metabolism of Ang I and Ang II under steady state conditions.

Identification and Characterization of Novel Inhibitors of Mammalian Aspartyl Aminopeptidase

Aspartyl aminopeptidase (DNPEP) has been implicated in the control of angiotensin signaling and endosome trafficking, but its precise biologic roles remain incompletely defined. We performed a high-throughput screen of ∼25,000 small molecules to identify inhibitors of DNPEP for use as tools to study its biologic functions. Twenty-three confirmed hits inhibited DNPEP-catalyzed hydrolysis of angiotensin II with micromolar potency. A counter screen against glutamyl aminopeptidase (ENPEP), an enzyme with substrate specificity similar to that of DNPEP, identified eight DNPEP-selective inhibitors. Structure-activity relationships and modeling studies revealed structural features common to the identified inhibitors, including a metal-chelating group and a charged or polar moiety that could interact with portions of the enzyme active site. The compounds identified in this study should be valuable tools for elucidating DNPEP physiology.

Altered glutamyl-aminopeptidase activity and expression in renal neoplasms.

BackgroundAdvances in the knowledge of renal neoplasms have demonstrated the implication of several proteases in their genesis, growth and dissemination. Glutamyl-aminopeptidase (GAP) (EC. 3.4.11.7) is a zinc metallopeptidase with angiotensinase activity highly expressed in kidney tissues and its expression and activity have been associated wtih tumour development.MethodsIn this prospective study, GAP spectrofluorometric activity and immunohistochemical expression were analysed in clear-cell (CCRCC), papillary (PRCC) and chromophobe (ChRCC) renal cell carcinomas, and in renal oncocytoma (RO). Data obtained in tumour tissue were compared with those from the surrounding uninvolved kidney tissue. In CCRCC, classic pathological parameters such as grade, stage and tumour size were stratified following GAP data and analyzed for 5-year survival.ResultsGAP activity in both the membrane-bound and soluble fractions was sharply decreased and its immunohistochemical expression showed mild staining in the four histological types of renal tumours. Soluble and membrane-bound GAP activities correlated with tumour grade and size in CCRCCs.ConclusionsThis study suggests a role for GAP in the neoplastic development of renal tumours and provides additional data for considering the activity and expression of this enzyme of interest in the diagnosis and prognosis of renal neoplasms.