Associations Among Nitric Oxide and Enkephalinases With Fibromyalgia Symptoms.

BACKGROUND: Fibromyalgia (FM) is a complex syndrome of uncertain etiology, characterized by the presence of widespread pain. Both nitric oxide and enkephalinases modulate pain perception. OBJECTIVES: The aim of this study was to evaluate the relationships among serum nitric oxide levels, oxytocinase activity, and enkephalin-degrading aminopeptidase (EDA) activity with pain-related clinical manifestations in women with FM. METHODS: We performed an observational case study in a population of 58 women diagnosed with FM. Serum nitric oxide levels were analyzed by an ozone chemiluminescence-based assay. Both serum oxytocinase and EDA activities were fluorometrically determined. Pain threshold and pain magnitude were evaluated using the PainMatcher. The pressure pain thresholds were measured using a digital pressure algometer. We used a visual analog scale, the Central Sensitization Inventory, the Revised Fibromyalgia Impact Questionnaire, and the Beck Anxiety Inventory to assess the global level of pain, the symptoms associated with the central sensitization syndrome, the severity of FM, and the anxiety level, respectively. RESULTS: Multiple linear regression analysis adjusted by age, body mass index, and menopause status revealed significant associations between nitric oxide levels and dominant occiput pressure pain thresholds, nondominant occiput pressure pain thresholds, and FM effects. Significant associations of oxytocinase activity with the visual analog scale and dominant knee pressure pain thresholds were also found. Moreover, results showed a significant association between high EDA activity levels and dominant second-rib pressure pain thresholds. DISCUSSION: Our data have shown significant relationships of serum nitric oxide levels and oxytocinase and EDA activities with some body pressure pain thresholds, the daily activity level, and the global intensity of pain in women with FM. These results suggest that pain, which is the main symptom of this syndrome, may be related to alterations in nitric oxide levels and in oxytocinase and EDA activities in patients with FM.

Aminopeptidases in Cardiovascular and Renal Function. Role as Predictive Renal Injury Biomarkers.

Aminopeptidases (APs) are metalloenzymes that hydrolyze peptides and polypeptides by scission of the N-terminus amino acid and that also participate in the intracellular final digestion of proteins. APs play an important role in protein maturation, signal transduction, and cell-cycle control, among other processes. These enzymes are especially relevant in the control of cardiovascular and renal functions. APs participate in the regulation of the systemic and local renin-angiotensin system and also modulate the activity of neuropeptides, kinins, immunomodulatory peptides, and cytokines, even contributing to cholesterol uptake and angiogenesis. This review focuses on the role of four key APs, aspartyl-, alanyl-, glutamyl-, and leucyl-cystinyl-aminopeptidases, in the control of blood pressure (BP) and renal function and on their association with different cardiovascular and renal diseases. In this context, the effects of AP inhibitors are analyzed as therapeutic tools for BP control and renal diseases. Their role as urinary biomarkers of renal injury is also explored. The enzymatic activities of urinary APs, which act as hydrolyzing peptides on the luminal surface of the renal tubule, have emerged as early predictive renal injury biomarkers in both acute and chronic renal nephropathies, including those induced by nephrotoxic agents, obesity, hypertension, or diabetes. Hence, the analysis of urinary AP appears to be a promising diagnostic and prognostic approach to renal disease in both research and clinical settings.

Altered Serum Oxytocinase and Enkephalin-Degrading Aminopeptidase Activities in Patients With Fibromyalgia.

OBJECTIVES: Fibromyalgia (FM) is a chronic pain condition of unclear etiology. We have analyzed, for the first time, the activity of a broad spectrum of aminopeptidases (APs) in patients with FM and controls to investigate whether they are involved in the pathophysiology of this syndrome. METHOD: In this case-control study, we fluorometrically measured specific AP activities in serum samples of 75 patients with FM and 29 healthy controls. The predictive value of AP activities in FM was determined by receiver operating characteristic (ROC) analysis. RESULTS: Oxytocinase activity was higher in patients with FM than in controls (p < .001). A subgroup of patients with FM (n = 18; 24%) showed low levels of enkephalin-degrading aminopeptidase (EDA) activity when compared with the healthy controls (p < .001) and with the rest of FM patients (p < .001). There were no significant differences in the activity levels of aminopeptidase A, aminopeptidase B, aspartyl aminopeptidase, insulin-regulated aminopeptidase, pyroglutamyl aminopeptidase, or aminopeptidase N between FM patients and controls. According to ROC analysis, oxytocinase activity may be a good marker for differentiating individuals with FM from healthy subjects. CONCLUSIONS: Our findings show that serum oxytocinase activity is increased in patients with FM, which could alter the metabolism of peptides with analgesic effects such as oxytocin and enkephalins. The determination of serum oxytocinase activity may aid in FM diagnosis. Additionally, we have identified a subpopulation of FM patients with abnormally low serum EDA activity.

Divergent profile between hypothalamic and plasmatic aminopeptidase activities in WKY and SHR. Influence of beta-adrenergic blockade.

AIMS: Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) differ in their renin-angiotensin system function and sympathetic tone. The metabolism of angiotensins and vasopressin depends on the action of certain aminopeptidases whose activity may be influenced by the autonomic nervous system. Their regulation may differ between WKY and SHR in hypothalamus and plasma according to the sympathetic tone. We analyzed aminopeptidases responsible for the hydrolysis of certain angiotensins, vasopressin, cholecystokinin or enkephalins in hypothalamus and plasma of WKY and SHR in untreated controls rats and under beta-adrenoceptor blockade. Systolic blood pressure, food intake, water intake and diuresis were measured as parameters modulated by the autonomic nervous system and the above mentioned peptides. MAIN METHODS: Glutamyl-, aspartyl-, cystinyl- and alanyl-aminopeptidase activities were analyzed fluorimetrically in plasma and hypothalamus of control and propranolol-treated (100mg/kg/day administered in drinking water for 1month) WKY and SHR, using arylamide derivatives as substrates. KEY FINDINGS: An opposite response of aminopeptidases to propranolol treatment between plasma and hypothalamus was observed in either WKY and SHR. Furthermore, the behavior of aminopeptidases was inversed between WKY and SHR either in hypothalamus and plasma: while the activity increased in hypothalamus and decreased in plasma of WKY, it decreased in hypothalamus and increased in plasma of SHR. SIGNIFICANCE: These results revealed an inverse response of aminopeptidases between hypothalamus and plasma and also an opposite behavior of these enzymes between WKY and SHR in hypothalamus and plasma. These observations support the involvement of the sympathetic system in the modulation of aminopeptidase activities.

Serum protease activity in chronic kidney disease patients: The GANI_MED renal cohort.

Serum or plasma proteases have been associated with various diseases including cancer, inflammation, or reno-cardiovascular diseases. We aimed to investigate whether the enzymatic activities of serum proteases are associated with the estimated glomerular filtration rate (eGFR) in patients with different stages of chronic kidney disease (CKD). Our study population comprised 268 participants of the "Greifswald Approach to Individualized Medicine" (GANI_MED) cohort. Enzymatic activity of aminopeptidase A, aminopeptidase B, alanyl (membrane) aminopeptidase, insulin-regulated aminopeptidase, puromycin-sensitive aminopeptidase, leucine aminopeptidase 3, prolyl-endopeptidase (PEP), dipeptidyl peptidase 4 (DPP4), angiotensin I-converting enzyme, and angiotensin I-converting enzyme 2 (ACE2) proteases was measured in serum. Linear regression of the respective protease was performed on kidney function adjusted for age and sex. Kidney function was modeled either by the continuous Modification of Diet in Renal Disease (MDRD)-based eGFR or dichotomized by eGFR < 15 mL/min/1.73 m2 or <45 mL/min/1.73 m2, respectively. Results with a false discovery rate below 0.05 were deemed statistically significant. Among the 10 proteases investigated, only the activities of ACE2 and DPP4 were correlated with eGFR. Patients with lowest eGFR exhibited highest DPP4 and ACE2 activities. DPP4 and PEP were correlated with age, but all other serum protease activities showed no associations with age or sex. Our data indicate that ACE2 and DPP4 enzymatic activity are associated with the eGFR in patients with CKD. This finding distinguishes ACE2 and DPP4 from other serum peptidases analyzed and clearly indicates that further analyses are warranted to identify the precise role of these serum ectopeptidases in the pathogenesis of CKD and to fully elucidate underlying molecular mechanisms. Impact statement • Renal and cardiac diseases are very common and often occur concomitantly, resulting in increased morbidity and mortality. Understanding of molecular mechanisms linking both diseases is limited, available fragmentary data point to a role of the renin-angiotensin system (RAS) and, in particular, Ras-related peptidases. • Here, a comprehensive analysis of serum peptidase activities in patients with different stages of chronic kidney disease (CKD) is presented, with special emphasis given to RAS peptidases • The serum activities of the peptidases angiotensin I-converting enzyme 2 and dipeptidyl peptidase 4 were identified as closely associated with kidney function, specifically with the estimated glomerular filtration rate. The findings are discussed in the context of available data suggesting protective roles for both enzymes in reno-cardiac diseases. • The data add to our understanding of pathomechanisms underlying development and progression of CKD and indicate that both enzymes might represent potential pharmacological targets for the preservation of renal function.

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.

Inhibition of circulating dipeptidyl peptidase 4 activity in patients with metastatic prostate cancer.

Cancer is responsible for many deaths and is a major source of healthcare expenditures. The identification of new, non-invasive biomarkers might allow improvement of the direct diagnostic or prognostic ability of already available tools. Here, we took the innovative approach of interrogating the activity of exopeptidases in the serum of cancer patients with the aim of establishing a distinction based on enzymatic function, instead of simple protein levels, as a means to biomarker discovery. We first analyzed two well-characterized mouse models of prostate cancer, each with a distinct genetic lesion, and established that broad exopeptidase and targeted aminopeptidase activity tests reveal proteolytic changes associated with tumor development. We also describe new peptide-based freeze-frame reagents uniquely suited to probe the altered balance of selected aminopeptidases, as opposed to the full array of exopeptidases, and/or their modulators in patient serum or plasma. One particular proteolytic activity was impaired in animals with aggressive disease relative to cancer-free littermates. We identified the protease in question as dipeptidyl peptidase 4 (DPP4) by analyzing selected knockout mice and evaluating the effect of specific inhibitors. DPP4 activity was also reduced in the sera of patients with metastatic prostate cancer relative to patients with localized disease or healthy controls. However, no significant differences in DPP4 serum levels were observed, which established the loss of activity as the result of impaired enzymatic function. Biochemical analysis indicated that reduced activity was the result not of post-translational modifications or allosteric changes, but instead of a low-molecular-weight inhibitor. After we adjusted for age and total prostate-specific antigen, reduced DPP4 activity remained a significant predictor of cancer status. The results of this proof-of-principle study suggest that DPP4 activity might be a potential blood-based indicator of the presence of metastatic cancer of prostatic origin, either by itself or, more likely, as a means to improve the sensitivity and specificity of existing markers.

Circulating aminopeptidase activities in men and women with essential hypertension.

Essential hypertension is one of the major contributors to premature morbidity and mortality due to the incresased risk for coronary heart disease, stroke, renal disease, peripheral vascular disease and vascular dementia for both men and women. However, its basic causes remain unknown. In the present work we studied the activity of several proteolytic regulatory enzymes related to renin-angiotensin-system (RAS) (aminopeptidase A, APA; aminopeptidase N, APN; aminopeptidase B, APB; and insulin-regulated aminopeptidase, IRAP); with oxytocin regulation (oxytocinase); with the metabolism of GnRH and TRH (pyrrolidone carboxypeptidase, Pcp); and with enkephalins metabolism (enkephalindegrading activity, EDA), to elucidate their role in the mechanisms responsible of essential hypertension and to discuss the possible gender differences. Serum samples of 53 individuals with essential hypertension and 60 healthy volunteers were collected and used to assay enzyme activities, gonad hormones testosterone and estradiol, TSH and free thyroxin (fT4). Differences were observed in APA, APN, Pcp and EDA specific activities, and in serum gonad hormone levels between hypertensive and control groups. Only Pcp activity showed gender differences. Regarding the RAS, APA is reduced while APN is increased, suggesting increased levels of angiotensin II and a facilitation of the conversion of angiotensin III in angiotensin IV. Thus, the changes in several RAS-regulating specific activities and other enzyme activities involved in the neuroendocrine modulation of gonad and stress-related functions are related to essential hypertension with minor gender differences. Therefore, aminopeptidases constitute new elements for the knowledge of the causes of essential hypertension and an alternative as therapeutic targets against the illness.

Metabolites of PPI-2458, a selective, irreversible inhibitor of methionine aminopeptidase-2: structure determination and in vivo activity.

The natural product fumagillin exhibits potent antiproliferative and antiangiogenic properties. The semisynthetic analog PPI-2458, [(3R,4S,5S,6R)-5-methoxy-4-[(2R,3R)-2-methyl-3-(3-methylbut-2-enyl)oxiran-2-yl]-1-oxaspiro[2.5]octan-6-yl] N-[(2R)-1-amino-3-methyl-1-oxobutan-2-yl]carbamate, demonstrates rapid inactivation of its molecular target, methionine aminopeptidase-2 (MetAP2), and good efficacy in several rodent models of cancer and inflammation with oral dosing despite low apparent oral bioavailability. To probe the basis of its in vivo efficacy, the metabolism of PPI-2458 was studied in detail. Reaction phenotyping identified CYP3A4/5 as the major source of metabolism in humans. Six metabolites were isolated from liver microsomes and characterized by mass spectrometry and nuclear resonance spectroscopy, and their structures were confirmed by chemical synthesis. The synthetic metabolites showed correlated inhibition of MetAP2 enzymatic activity and vascular endothelial cell growth. In an ex vivo experiment, MetAP2 inhibition in white blood cells, thymus, and lymph nodes in rats after single dosing with PPI-2458 and the isolated metabolites was found to correlate with the in vitro activity of the individual species. In a phase 1 clinical study, PPI-2458 was administered to patients with non-Hodgkin lymphoma. At 15 mg administered orally every other day, MetAP2 in whole blood was 80% inactivated for up to 48 hours, although the exposure of the parent compound was only ∼10% that of the summed cytochrome P450 metabolites. Taken together, the data confirm the participation of active metabolites in the in vivo efficacy of PPI-2458. The structures define a metabolic pathway for PPI-2458 that is distinct from that of TNP-470 ([(3R,4S,5S,6R)-5-methoxy-4-[(2R,3R)-2-methyl-3-(3-methylbut-2-enyl)oxiran-2-yl]-1-oxaspiro[2.5]octan-6-yl] N-(2-chloroacetyl)carbamate). The high level of MetAP2 inhibition achieved in vivo supports the value of fumagillin-derived therapeutics for angiogenic diseases.

Neoadjuvant chemotherapy modifies serum angiotensinase activities in women with breast cancer.

PURPOSE: The aim of this study was to investigate the putative changes in serum angiotensinase activities (aminopeptidase N, APN; aminopeptidase B, APB; aminopeptidase A, APA; aspartyl aminopeptidase, ASAP) involved in the renin-angiotensin system (RAS) in women with breast cancer treated or not with a neoadjuvant therapy of paclitaxel and anthracycline and in healthy women volunteers. METHODS: We fluorometrically analysed serum APN, APB, APA and ASAP activities using their corresponding aminoacyl-ß-naphthylamides as substrates in women with breast cancer treated with a neoadjuvant therapy of paclitaxel and anthracycline. RESULTS: When compared with healthy controls, women with breast cancer not treated with neoadjuvant chemotherapy, showed a decrease in angiotensinase activity, which support the putative increase of angiotensin II (Ang II) levels, indicating that the tumour process would favour the development of the disease. Also, an increase in APN and APB activities was observed, which support a role for angiotensin IV (Ang IV). In women treated with a neoadjuvant therapy, we described an increase in ASAP and APA activities, supporting the idea that this treatment increases Ang II catabolism. The resulting decrease in Ang II level could lead to an inhibition of the tumour growth. CONCLUSION: Present results show changes in serum angiotensinase activities in women with breast cancer and in women with breast cancer treated with a neoadjuvant therapy of paclitaxel and anthracycline. Therefore, considerable attention should be focused on the development of RAS blockade therapy as a new strategy for breast cancer treatment.

Renin angiotensin system-regulating aminopeptidase activities in serum of pre- and postmenopausal women with breast cancer.

Angiotensin peptides regulate vascular tone and natriohydric balance through the renin angiotensin system (RAS) and are related with the angiogenesis which plays an important role in the metastatic pathway. Estrogen influences the aminopeptidases (APs) involved in the metabolism of bioactive peptides of RAS through several pathways. We analyze RAS-regulating AP activities in serum of pre- and postmenopausal women with breast cancer to evaluate the putative value of these activities as biological markers of the development of breast cancer. We observed an increase in aminopeptidase N (APN) and aminopeptidase B (APB) activities in women with breast cancer; however, a decrease in aspartyl-aminopeptidase (AspAP) activity in premenopausal women. These results suggest a slow metabolism of angiotensin II (Ang II) to angiotensin III (Ang III) in premenopausal women and a rapid metabolism of Ang III to angiotensin IV (Ang IV) in pre- and postmenopausal women with breast cancer. An imbalance in the signals activated by Ang II may produce abnormal vascular growth with different response between pre- and postmenopausal women depending on the hormonal profile and the development of the disease.

Basic aminopeptidase activity is an emerging biomarker in collagen-induced rheumatoid arthritis.

The objective of this study was to investigate the catalytic activity of basic aminopeptidase (APB) and its association with periarticular edema and circulating tumor necrosis factor (TNF)-alpha and type II collagen (CII) antibodies (AACII) in a rat model of rheumatoid arthritis (RA) induced by CII (CIA). Edema does not occur in part of CII-treated, even when AACII is higher than in control. TNF-alpha is detectable only in edematous CII-treated. APB in synovial membrane is predominantly a membrane-bound activity also present in soluble form and with higher activity in edematous than in non-edematous CII-treated or control. Synovial fluid and blood plasma have lower APB in non-edematous than in edematous CII-treated or control. In peripheral blood mononuclear cells (PBMCs) the highest levels of APB are found in soluble form in control and in membrane-bound form in non-edematous CII-treated. CII treatment distinguishes two categories of rats: one with arthritic edema, high AACII, detectable TNF-alpha, high soluble and membrane-bound APB in synovial membrane and low APB in the soluble fraction of PBMCs, and another without edema and with high AACII, undetectable TNF-alpha, low APB in the synovial fluid and blood plasma and high APB in the membrane-bound fraction of PBMCs. Data suggest that APB and CIA are strongly related.

Oxidative stress and aminopeptidases in Parkinson's disease patients with and without treatment.

BACKGROUND/OBJECTIVE: Mitochondrial dysfunction, oxidative stress and protein metabolism impairment are the main molecular events underlying the pathogenesis of Parkinson's disease (PD). However, only few studies have addressed the changes produced by these phenomena in the blood of PD patients. Our purpose was to compare oxidative stress between newly diagnosed PD patients (ntPD) and PD patients under treatment (tPD). We also analyzed changes in plasma activity of several aminopeptidases (AP) involved in the metabolism of various active peptides. METHODS: Plasma lipid peroxide (LPO) and lactate (LAC) concentrations were measured by colorimetric methods, and plasma AP activities were determined by fluorometric assay. RESULTS: LPO and LAC concentrations were significantly elevated in ntPD and tPD patients versus controls, but there were no differences between the PD groups. Alanine-, cystine- and aspartate-AP activities were significantly lower in tPD versus ntPD patients. Nondenaturing electrophoresis and Western blot results confirmed these findings. CONCLUSIONS: The plasma LPO and LAC levels were high in both PD groups, indicating that they are elevated at an early stage of PD and are not affected by anti-PD treatment. The higher AP activities in ntPD versus tPD patients suggest that anti-PD treatment may improve protein metabolism while not altering oxidative stress. A therapy directed to reduce oxidative stress and normalize AP activity may be useful in the treatment of PD.

Hypothalamic and plasmatic angiotensin metabolism in L-NAME treated rats.

In order to study the interaction between the renin-angiotensin system (RAS) and nitric oxide (NO), we analyzed the activity of aspartyl- (AspAP), glutamyl- (GluAP), alanyl- (AlaAP), and cystinylaminopeptidase (CysAP) enzymes involved in the RAS cascade, in the hypothalamus, and plasma of normotensive adult male rats after the inhibition of NO production with the NO synthase inhibitor L-NAME (L-N (G)-nitroarginine methyl ester). L-NAME treatment produced a significant increase of systolic blood pressure (SBP). In plasma, while GluAP activity decreased significantly, suggesting a lower Ang III formation, the other aminopeptidases did not change after L-NAME treatment. In hypothalamus, the activities of AspAP and CysAP were not affected after L-NAME treatment. In contrast, GluAP and AlaAP increased significantly. These results suggested mainly a higher formation of Ang III, but also higher levels of Ang IV in the hypothalamus of L-NAME treated rats. Both peptides have hypertensive properties at central level. On the contrary, Ang III may counteract the hypertensive action of Ang II at the periphery. Therefore, the increased SBP in L-NAME treated rats may be due in part to the increased activity of GluAP and AlaAP in hypothalamus and to a decreased activity of GluAP in plasma.

Effect of intraperitoneal and intravenous administration of cholecystokinin-8 and apolipoprotein AIV on intestinal lymphatic CCK-8 and apo AIV concentration.

CCK and apolipoprotein AIV (apo AIV) are gastrointestinal satiety signals whose synthesis and secretion by the gut are stimulated by fat absorption. Intraperitoneally administered CCK-8 is more potent in suppressing food intake than a similar dose administered intravenously, but the reason for this disparity is unclear. In contrast, both intravenous and intraperitoneally administered apo AIV are equally as potent in inhibiting food intake. When we compared the lymphatic concentration of CCK-8 and apo AIV, we found that neither intraperitoneally nor intravenously administered CCK-8 or apo AIV altered lymphatic flow rate. Interestingly, intraperitoneal administration of CCK-8 produced a significantly higher lymphatic concentration at 15 min than did intravenous administration. Intraperitoneal injection of apo AIV also yielded a higher lymphatic concentration at 30 min than did intravenous administration. Intraperitoneal administration of CCK-8 and apo AIV also resulted in a much longer period of elevated CCK-8 and apo AIV peptide concentration in lymph than intravenous administration. Furthermore, enzymatic activity of dipeptidyl peptidase IV (DPPIV) and aminopeptidase was higher in plasma than in lymph during fasting, and so, satiation peptides, such as CCK-8 and apo AIV in the lymph, are protected from degradation by the significantly lower DPPIV and aminopeptidase activity levels in lymph than in plasma. Therefore, the higher potency of intraperitoneally administered CCK-8 compared with intravenously administered CCK-8 in inhibiting food intake may be explained by both its higher concentration in lymph and the prolonged duration of its presence in the lamina propria.

Prospective evaluation of aminopeptidase activities in plasma and peripheral organs of streptozotocin-induced diabetic rats.

The cleavage of peptides by aminopeptidase enzyme types could be among the mechanisms related to certain disruptions on mediator and modulatory functions in diabetes mellitus. In order to examine this hypothesis, we measured representative aminopeptidase activities in tissues of peripheral organs of control and streptozotocin-diabetic rats. None of the examined aminopeptidase activities differed between diabetics and controls in plasma, ileum, stomach or lung. Soluble and membrane-associated alanyl, and membrane-associated cystyl aminopeptidase activities were higher in the kidney of diabetics. Decreased activity was observed in soluble and membrane-associated aspartyl and soluble dipeptidyl-peptidase IV, while increased activity was observed in soluble alanyl, arginyl, and cystyl aminopeptidases in the pancreas of diabetics. In the jejunum, soluble cystyl aminopeptidase increased in diabetics. Soluble arginyl and type-1-pyroglutamyl aminopeptidase and membrane-associated dipeptidyl-peptidase IV activities increased in the liver of diabetics. Membrane-associated dipeptidyl-peptidase IV and alanyl aminopeptidase activities in the spleen were higher in diabetics than in controls. Membrane-associated alanyl aminopeptidase activity also increased in the heart of diabetics. All these changes in streptozotocin-treated rats were avoided by the administration of insulin. Our comparative analysis of a diverse array of aminopeptidase activities supported the proposal that the regulation of peptide cleavage by these enzyme types is associated with the effects of streptozotocin-diabetes mellitus on peripheral organs.

Acute hypotensive transfusion reaction during liver transplantation in a patient on angiotensin converting enzyme inhibitors from low aminopeptidase P activity.

Acute hypotensive transfusion reactions are newly characterized transfusion reactions in which hypotension is the prominent feature. The pathophysiology of acute hypotensive transfusion reactions is related to the bradykinin function and its metabolism. A liver transplant recipient on treatment with an angiotensin converting enzyme inhibitor developed sudden hypotension, that is, systolic pressure of 60 mm Hg, after receiving 200 mL of a blood product mixture without significant surgical blood loss. He responded to the resuscitation measure, although hypotension developed again after a challenge transfusion of 200 mL of the blood mixture. A severe hypotensive reaction to the blood transfusion and diffuse bleeding from the dissection surfaces forced the transplantation to be aborted after the common bile duct had been divided. We hypothesized that the patient had an acute hypotensive transfusion reaction due to disordered bradykinin metabolism. Analysis of his blood showed low levels of both angiotensin converting enzyme and aminopeptidase P enzyme activity, confirming that the patient experienced an acute hypotensive transfusion reaction that was due to the use of the angiotensin converting enzyme inhibitor and was precipitated by an abnormality in the metabolic enzyme pathway. It is recommended to discontinue angiotensin converting enzyme inhibitors and switch to a different class of antihypertensive medications for patients with a high Model for End-Stage Liver Disease score on the waiting list for liver transplantation.

The bradykinin-degrading aminopeptidase P is increased in women taking the oral contraceptive pill.

INTRODUCTION: The renin-angiotensin and kininogen-kinin hormonal systems are critically involved in regulating blood pressure and are candidates in contributing to oral contraceptive pill (OCP)-induced hypertension. Angiotensin-converting enzyme (ACE) and aminopeptidase P (AP-P) are key enzymes in these systems and are both involved in the degradation of the vasodilator bradykinin. METHODS: Circulating ACE and AP-P levels were measured by activity assay using selective fluorogenic peptide substrates in plasma samples from the Leeds Family Study. In addition, the effect of progesterone on the expression of AP-P and ACE was examined in cells. RESULTS: Women on the OCP had higher age-adjusted plasma AP-P (mean [95% confidence interval]) (0.27 [0.23-0.32] nmol/min/ml (n = 53)) compared with women not on the OCP (0.17 [0.16-0.19] nmol/min/ml (n = 133), p < 0.001) or males (0.19 [0.17-0.20] nmol/min/ml (n = 209), p<0.001). There were no differences in the age-adjusted plasma ACE levels among the three groups. In HepG2 cells, progesterone treatment increased the AP-P protein and mRNA expression, whereas no effect of progesterone treatment was observed for ACE. CONCLUSION: Increased AP-P may result in increased breakdown of bradykinin. These data suggest that progesterone-induced increases in AP-P may contribute to the development of OCP-induced hypertension in susceptible Women.

Plasma aminopeptidase activities in Parkinson's disease.

Parkinson's disease (PD) is an age-related neurodegenerative disease characterized by a progressive motor disorder, but frequently is accompanied by autonomic symptoms such as hypotension. Together with the decrease of dopamine, significant decreases in aminopeptidase activities have been reported in PD brains. However, up to date there are no studies about changes of aminopeptidase activities in plasma of PD patients. We studied plasma activities of alanyl-, aspartyl-(AspAP), cystinyl-(CysAP) and glutamyl-aminopeptidase (GluAP) in two groups of subjects: control (n=41) and PD (n=48). Plasma activities of AspAP, CysAP, and GluAP showed significant decreases of 24.9% (p<0.05), 39.4% (p<0.01) and 33.3% (p<0.01), respectively, in PD group. These aminopeptidases are involved in the metabolism of circulating peptides such as the ones of the renin-angiotensin system. The importance of aminopeptidases in striatal dopamine content and in neuroendocrine system in PD is discussed.

Insulin-regulated aminopeptidase/placental leucil Aminopeptidase (IRAP/P-lAP) and angiotensin IV-forming activities are modified in serum of rats with breast cancer induced by N-methyl-nitrosourea.

BACKGROUND: In previous reports, changes in oxytocinase activity in human breast cancer tissue and in the serum of N-methyl-nitrosourea (NMU)-induced rat mammary tumors were described. Insulin-regulated aminopeptidase (IRAP) has been identified with oxytocinase and has also been referred to as placental leucine aminopeptidase (P-LAP). MATERIALS AND METHODS: The IRAP/P-LAP activity in rat serum was assayed to analyze the putative role that IRAP/P-LAP may play in regulating mammary gland carcinogenesis induced by NMU. Furthermore, as it has been recently described that IRAP/P-LAP is the angiotensin IV (Ang IV) receptor AT4, the activities of Ang IV-forming aminopeptidase N (APN) and aminopeptidase B (APB) were also assayed. RESULTS: Changes in serum IRAP/P-LAP and Ang IV-forming APB activities were found in rats with mammary tumors induced by NMU. Both activities were greatly increased, although the Ang IV-forming APN activity was not modified. CONCLUSION: These changes in aminopeptidase activities may reflect the local functional status of their substrates, which can be selectively activated or inhibited in the affected tissue as a result of specific conditions brought about by the tumor. Thus, these enzymatic activities may be involved in the promotion and progression of breast cancer through oxytocin (OT), vasopressin (AVP) and/or renin-angiotensin system (RAS) misregulation.