Acute kidney injury in the rat causes cardiac remodelling and increases angiotensin-converting enzyme 2 expression.

Patients with kidney failure are at high risk of a cardiac death and frequently develop left ventricular hypertrophy (LVH). The mechanisms involved in the cardiac structural changes that occur in kidney failure are yet to be fully delineated. Angiotensin-converting enzyme (ACE) 2 is a newly described enzyme that is expressed in the heart and plays an important role in cardiac function. This study assessed whether ACE2 plays a role in the cardiac remodelling that occurs in experimental acute kidney injury (AKI). Sprague-Dawley rats had sham (control) or subtotal nephrectomy surgery (STNx). Control rats received vehicle (n = 10), and STNx rats received the ACE inhibitor (ACEi) ramipril, 1 mg kg(-1) day(-1) (n = 15) or vehicle (n = 13) orally for 10 days after surgery. Rats with AKI had polyuria (P < 0.001), proteinuria (P < 0.001) and hypertension (P < 0.001). Cardiac structural changes were present and characterized by LVH (P < 0.001), fibrosis (P < 0.001) and increased cardiac brain natriuretic peptide (BNP) mRNA (P < 0.01). These changes occurred in association with a significant increase in cardiac ACE2 gene expression (P < 0.01) and ACE2 activity (P < 0.05). Ramipril decreased blood pressure (P < 0.001), LVH (P < 0.001), fibrosis (P < 0.01) and BNP mRNA (P < 0.01). These changes occurred in association with inhibition of cardiac ACE (P < 0.05) and a reduction in cardiac ACE2 activity (P < 0.01). These data suggest that AKI, even at 10 days, promotes cardiac injury that is characterized by hypertrophy, fibrosis and increased cardiac ACE2. Angiotensin-converting enzyme 2, by promoting the production of the antifibrotic peptide angiotensin(1-7), may have a cardioprotective role in AKI, particularly since amelioration of adverse cardiac effects with ACE inhibition was associated with normalization of cardiac ACE2 activity.

Developmental expression of ACE2 in the SHR kidney: a role in hypertension?

The abnormal development of the intrarenal renin-angiotensin system (RAS) is thought contribute to adult-onset hypertension in the spontaneously hypertensive rat (SHR). Angiotensin-converting enzyme 2 (ACE2) is a novel enzyme with complementary actions to that of ACE. Recent studies have shown that ACE2 expression is reduced in the adult SHR. However, its regulation in pre-hypertensive animals is unknown. In this study, we examine the developmental expression of ACE2 in the rodent kidney and its temporal expression, as it relates to the development of hypertension in the SHR model. Kidneys from SHR and normotensive Wistar Kyoto (WKY) rats (n=8-12/group) at birth, 6 weeks of age, and adulthood (80 days) were examined. Gene expression and activity of ACE2 were determined by real-time reverse transcription-polymerase chain reaction and quenched fluorescence assays, respectively. Renal expression was localized by in situ hybridization and immunohistochemistry. The expression and ACE2 activity are significantly increased in the SHR kidney at birth. With the onset of hypertension, the tubular expression of ACE2 falls in SHR compared to WKY and remains reduced in the adult SHR kidney. Glomerular expression is paradoxically increased in the SHR glomerulus. The overall developmental pattern of ACE2 expression in the SHR kidney is also modified, with declining expression over the course of renal development. The developmental pattern of ACE2 expression in the SHR kidney is altered before the onset of hypertension, consistent with the key role of the RAS in the pathogenesis of adult-onset hypertension. Further research is required to distinguish the contribution of these changes to the development and progression of hypertension in this model.

Lateralized cognitive dysfunction in patients with systemic lupus erythematosus.

This study was designed to determine whether there is a lateralized pattern of cognitive dysfunction in patients with systemic lupus erythematosus (SLE). Fifty right-handed patients with SLE, but no history of cerebrovascular disease participated in the study. Thirty right-handed healthy subjects matched for age and education served as controls. SLE and healthy control subjects underwent a three-hour neuropsychological evaluation designed to measure attention, memory, visual spatial skills, verbal skills reasoning, psychomotor speed, and motor function. A cognitive disability index was created to identify cognitive impairment. Percentile tables based on the performance of all subjects were constructed for 20 component scores. Any subject with five or more component scores below the 25th percentile was designated impaired. Using this criterion, cognitive impairment was identified in 50% of patients with SLE and 20% of healthy controls. Patients with SLE were impaired on measures of psychomotor speed/fluency, verbal speed/fluency and verbal memory. This pattern of performance on neuropsycholgical testing was consistent with left hemisphere brain dysfunction. The observed deficits were not clearly attributable to vascular lesions and suggest immune-mediated effects on specific brain regions in a subgroup of patients with SLE.

Chronic liver injury in rats and humans upregulates the novel enzyme angiotensin converting enzyme 2.

BACKGROUND: Angiotensin converting enzyme (ACE) 2 is a recently identified homologue of ACE that may counterregulate the actions of angiotensin (Ang) II by facilitating its breakdown to Ang 1-7. The renin-angiotensin system (RAS) has been implicated in the pathogenesis of cirrhosis but the role of ACE2 in liver disease is not known. AIMS: This study examined the effects of liver injury on ACE2 expression and activity in experimental hepatic fibrosis and human cirrhosis, and the effects of Ang 1-7 on vascular tone in cirrhotic rat aorta. METHODS: In sham operated and bile duct ligated (BDL) rats, quantitative reverse transcriptase-polymerase chain reaction was used to assess hepatic ACE2 mRNA, and western blotting and immunohistochemistry to quantify and localise ACE2 protein. ACE2 activity was quantified by quenched fluorescent substrate assay. Similar studies were performed in normal human liver and in hepatitis C cirrhosis. RESULTS: ACE2 mRNA was detectable at low levels in rat liver and increased following BDL (363-fold; p < 0.01). ACE2 protein increased after BDL (23.5-fold; p < 0.05) as did ACE2 activity (fourfold; p < 0.05). In human cirrhotic liver, gene (>30-fold), protein expression (97-fold), and activity of ACE2 (2.4 fold) were increased compared with controls (all p < 0.01). In healthy livers, ACE2 was confined to endothelial cells, occasional bile ducts, and perivenular hepatocytes but in both BDL and human cirrhosis there was widespread parenchymal expression of ACE2 protein. Exposure of cultured human hepatocytes to hypoxia led to increased ACE2 expression. In preconstricted rat aorta, Ang 1-7 alone did not affect vascular tone but it significantly enhanced acetylcholine mediated vasodilatation in cirrhotic vessels. CONCLUSIONS: ACE2 expression is significantly increased in liver injury in both humans and rat, possibly in response to increasing hepatocellular hypoxia, and may modulate RAS activity in cirrhosis.

Identification of angiotensin converting enzyme 2 in the rodent retina.

PURPOSE: An active renin-angiotensin system has been found in the retina of rats and humans. Angiotensin-converting enzyme 2 (ACE2) is a recently discovered enzymatic homologue of Angiotensin-converting enzyme (ACE) that may be an important new component of the renin-angiotensin system (RAS). This study assesses the involvement of ACE2 in the normal and diabetic rodent retina and its modulation by ACE inhibition. METHODS: Sprague-Dawley rats were randomised into three groups, control, diabetes, and diabetes plus ramipril, with diabetes induced with the cell toxin streptozocin and the study run for 24 weeks. ACE2 and ACE gene levels were measured using quantitative real-time polymerase chain reaction (QRT-PCR), ACE2 protein expression was confirmed by Western blotting, and ACE and ACE2 catalytic activity were measured using specific activity assays in the rat retina. Localisation of ACE2 mRNA and protein were determined by in situ hybridisation and immunohistochemistry, respectively. RESULTS: ACE mRNA levels were decreased to approximately 50% in the diabetic retina, but ACE2 mRNA levels were not significantly changed. ACE but not ACE2 gene expression was influenced by ramipril treatment. Following immunostaining, both ACE2 and ACE protein were localised predominantly to the inner nuclear layer (INL) but also to photoreceptors. In the diabetic retina, ACE enzyme activity was decreased, whereas ACE2 enzyme activity was increased. CONCLUSIONS: This study has identified ACE2 gene and catalytically active protein in the rodent retina. In diabetes, the major changes were a decrease in ACE but an increase in ACE2 enzymatic activity. The ACE inhibitor ramipril did not reduce ACE2 enzymatic activity.

Association between hospital and surgeon procedure volume and outcomes of total hip replacement in the United States medicare population.

BACKGROUND: The mortality and complication rates of many surgical procedures are inversely related to hospital procedure volume. The objective of this study was to determine whether the volumes of primary and revision total hip replacements performed at hospitals and by surgeons are associated with rates of mortality and complications. METHODS: We analyzed claims data of Medicare recipients who underwent elective primary total hip replacement (58,521 procedures) or revision total hip replacement (12,956 procedures) between July 1995 and June 1996. We assessed the relationship between surgeon and hospital procedure volume and mortality, dislocation, deep infection, and pulmonary embolus in the first ninety days postoperatively. Analyses were adjusted for age, gender, arthritis diagnosis, comorbid conditions, and income. Analyses of hospital volume were adjusted for surgeon volume, and analyses of surgeon volume were adjusted for hospital volume. RESULTS: Twelve percent of all primary total hip replacements and 49% of all revisions were performed in centers in which ten or fewer of these procedures were carried out in the Medicare population annually. In addition, 52% of the primary total hip replacements and 77% of the revisions were performed by surgeons who carried out ten or fewer of these procedures annually. Patients treated with primary total hip replacement in hospitals in which more than 100 of the procedures were performed per year had a lower risk of death than those treated with primary replacement in hospitals in which ten or fewer procedures were performed per year (mortality rate, 0.7% compared with 1.3%; adjusted odds ratio, 0.58; 95% confidence interval, 0.38, 0.89). Patients treated with primary total hip replacement by surgeons who performed more than fifty of those procedures in Medicare beneficiaries per year had a lower risk of dislocation than those who were treated by surgeons who performed five or fewer of the procedures per year (dislocation rate, 1.5% compared with 4.2%; adjusted odds ratio, 0.49; 95% confidence interval, 0.34, 0.69). Patients who had revision total hip replacement done by surgeons who performed more than ten such procedures per year had a lower rate of mortality than patients who were treated by surgeons who performed three or fewer of the procedures per year (mortality rate, 1.5% compared with 3.1%; adjusted odds ratio, 0.65; 95% confidence interval, 0.44, 0.96). CONCLUSIONS: Patients treated at hospitals and by surgeons with higher annual caseloads of primary and revision total hip replacement had lower rates of mortality and of selected complications. These analyses of Medicare claims are limited by a lack of key clinical information such as operative details and preoperative functional status.

Metalloendopeptidases EC 3.4.24.15 and EC 3.4.24.16 and bradykinin B2 receptors do not play important roles in renal wrap hypertension in rabbits.

1. The aim of the present study was to determine the effects of the metalloendopeptidase (EP) 24.15 and 24.16 inhibitor N-[1-(R,S)-carboxy-3-phenylpropyl]-Ala-Aib-Tyr-p-aminobenzoate (JA-2) on haemodynamics and renal function in conscious rabbits with two-kidney, two-wrapped hypertension. We have also examined the role of endogenous bradykinin in the maintenance phase of this form of renovascular hypertension and whether inhibition of bradykinin degradation contributes to any potential effects of JA-2. 2. In two preliminary operations, rabbits were equipped with transit-time ultrasound flow probes for measuring cardiac output (CO) and renal blood flow (RBF) and had both kidneys wrapped in cellophane. Starting 4 weeks after the last operation, rabbits underwent four studies (3-5 days apart), during which they were treated with combinations of the bradykinin B2 receptor antagonist icatibant or its vehicle (1 mL/kg bodyweight 0.9% w/v NaCl) and JA-2 or its vehicle (1 mL/kg of a 5% w/v 2-hydroxypropyl-beta-cyclodextrin, 2.5% v/v dimethylsulphoxide solution). Renal function was monitored using standard renal clearance methods. 3. Icatibant (10 microg/kg) had no significant effects on systemic haemodynamic variables (mean arterial pressure, heart rate or CO), renal haemodynamic variables (RBF or glomerular filtration rate), urine flow or sodium excretion. At 5 mg/kg plus 3 mg/kg per h, JA-2 also did not affect any of these variables, either after icatibant vehicle treatment or after icatibant treatment. 4. Our data do not support major roles for endogenous bradykinin or bradykinin degradation by EP 24.15/24.16 in the control of systemic and renal haemodynamics or renal excretory function in two-kidney, two-wrapped hypertension in rabbits.

A randomized trial of the Hawaii SunSmart program's impact on outdoor recreation staff.

BACKGROUND: Skin cancer is the most common form of cancer in the United States and one of the most preventable. Prevention programs for children at outdoor recreation sites may influence not only the youth, but the staff, or caregivers, as well. By teaching children about sun protection, staff may also change their sun protection behaviors. OBJECTIVE: We report on the impact of a childhood skin cancer prevention program (SunSmart) on staff at outdoor recreation sites where a child-focused intervention was conducted. METHODS: The intervention included staff training, on-site activities delivered by staff, distribution of sunscreen, and the promotion of sun-safe environments. It was hypothesized that by teaching children about sun protection, staff would change their sun protection behaviors. A randomized trial at 14 recreation sites (n = 176 staff) in Hawaii tested the efficacy of education only, and education plus environmental changes, compared with a control condition. RESULTS: Results showed significant positive changes in knowledge, sun protection habits, norms, and sun protection policies. The education plus environment group was not superior to education alone. CONCLUSION: Changes in staff behavior and attitudes are important for their own health, as positive role models, and for the dissemination of skin cancer control programs.

Prevalence of migraine in patients with systemic lupus erythematosus.

OBJECTIVE: To determine the prevalence of migraine in patients with systemic lupus erythematosus (SLE), and to examine the relationships between headache type and other clinical, serologic, and treatment features of the disease. BACKGROUND: Headaches are common in SLE and are a significant source of patient disability. The exact prevalence of headaches in patients with SLE is unknown. The classification of headache syndromes in SLE is also unclear. Previous studies were based on small numbers of patients and the headache types and criteria to define headache types varied widely. METHODS: Four hundred fourteen patients meeting American College of Rheumatology criteria for the diagnosis of SLE were sent the University of California, San Diego Migraine Questionnaire. Patients who completed the questionnaire had their medical records reviewed for constitutional, respiratory, cardiac, vascular, skin, musculoskeletal, other neuropsychiatric, hematologic, renal, and immunologic manifestations of the disease. Recent corticosteroid, nonsteroidal anti-inflammatory drug, antimalarial, and immunosuppressive medications were also recorded. RESULTS: One hundred eighty-six patients completed the questionnaire. Sixty-two percent of patients reported headaches: 39% met diagnostic criteria for migraine and 23% met criteria for nonmigrainous headache. Of the patients with migraine, 56% met criteria for migraine without aura and 44% met criteria for migraine with aura. There were no significant associations between headache type and other clinical, serologic, or treatment features of the disease. CONCLUSIONS: There is a high prevalence of migraine in patients with SLE, and patients should be routinely evaluated for migraine symptoms.

Lyme disease and preventive behaviors in residents of Nantucket Island, Massachusetts.

BACKGROUND: To determine the age-specific prevalence of Lyme disease and whether preventive behaviors on Nantucket Island correlate with Lyme disease, we surveyed island residents. METHODS: A survey with questions on Lyme disease symptoms, history, and preventive behaviors was mailed to all residents. Respondents were stratified by likelihood of having had Lyme disease. A subsample was selected for examination, and then classified according to the Lyme disease national surveillance case definition. RESULTS: The overall lifetime prevalence of Lyme disease for Nantucket residents was 15% (CI, 10%-19.8%): 19% among females, and 11% among males. The prevalence was highest among age groups 0-16 and 30-49 years. Overall, 86% of the population practiced at least one behavior. The most frequently reported preventive behavior was checking oneself for ticks (80%), followed by wearing protective clothing (53%), avoiding tick areas (34%), and using tick repellent (11%). Younger individuals practiced fewer preventive behaviors than older individuals (p=0.001). Although males reported greater tick exposure than females, females uniformly practiced preventive behaviors more frequently (p=0.001). The practice of preventive behaviors was not associated with a history of Lyme disease, but finding more than 5 ticks per year on oneself was (p=0.001). CONCLUSION: Lyme disease is highly prevalent on Nantucket Island. Young people are particularly at risk and health education should emphasize preventive behaviors less frequently practiced: using tick repellent, avoiding tick areas, and wearing protective clothing.

Coexposure to Borrelia burgdorferi and Babesia microti does not worsen the long-term outcome of lyme disease.

Previous studies suggest that concurrent Lyme disease and babesiosis produce a more sever illness than either disease alone. The majority of babesiosis infections, however, are subclinical. Our objective was to characterize on the basis of a total-population survey of Nantucket Island, Massachusetts, whether coexposure to Lyme disease and babesiosis causes more severe illness or poorer long-term outcomes than Lyme disease alone. In this retrospective cohort study, residents indicating a history of Lyme disease were compared with randomly selected population controls on a standardized medical history, blinded physical examination, and serological studies for Borrelia burgdorferi and Babesia microti. Serological evidence of exposure to babesiosis was not associated with increased severity of acute Lyme disease. The groups did not differ with regard to the prevalence of constitutional, musculoskeletal, or neurological symptoms a mean of 6 years after acute Lyme disease. Prior Lyme disease and serological exposure to B. microti are not associated with poorer long-term outcomes or more persistent symptoms Lyme disease alone.

Bradykinin analogues with beta-amino acid substitutions reveal subtle differences in substrate specificity between the endopeptidases EC 3.4.24.15 and EC 3.4.24.16.

The closely related zinc metalloendopeptidases EC 3.4.24.15 (EP24.15) and EC 3.4.24.16 (EP24.16) cleave many common substrates, including bradykinin (BK). As such, there are few substrate-based inhibitors which are sufficiently selective to distinguish their activities. We have used BK analogues with either alanine or beta-amino acid (containing an additional carbon within the peptide backbone) substitutions to elucidate subtle differences in substrate specificity between the enzymes. The cleavage of the analogues by recombinant EP24.15 and EP24.16 was assessed, as well as their ability to inhibit the two enzymes. Alanine-substituted analogues were generally better substrates than BK itself, although differences between the peptidases were observed. Similarly, substitution of the four N-terminal residues with beta-glycine enhanced cleavage in some cases, but not others. beta-Glycine substitution at or near the scissile bond (Phe5-Ser6) completely prevented cleavage by either enzyme: interestingly, these analogues still acted as inhibitors, although with very different affinities for the two enzymes. Also of interest, beta-Gly8-BK was neither a substrate nor an inhibitor of EP24.15, yet could still interact with EP24.16. Finally, while both enzymes could be similarly inhibited by the D-stereoisomer of beta-C3-Phe5-BK (IC50 approximately 20 microM, compared to 8 microM for BK), EP24.16 was relatively insensitive to the L-isomer (IC50 12 approximately microM for EP24.15, >40 microM for EP24.16). These studies indicate subtle differences in substrate specificity between EP24.15 and EP24.16, and suggest that beta-amino acid analogues may be useful as templates for the design of selective inhibitors.

Design and synthesis of inhibitors incorporating beta -amino acids of metalloendopeptidase EC 3.4.24.15.

Endopeptidase EC 3.4.24.15 (EP 24.15) is a thermolysin-like metalloendopeptidase which is expressed widely throughout the body, with the highest concentrations in the brain, pituitary and testis. While the precise role of EP 24.15 remains unknown, it is thought to participate in the regulated metabolism of a number of specific neuropeptides. Of the limited number of inhibitors described for EP 24.15, N-[1-(R,S)-carboxy-3-phenylpropyl]-Ala-Ala-Tyr-p-amino benzoate (CFP) is the most widely studied. CFP is a potent and specific inhibitor, but is unstable in vivo due to its cleavage between the alanine and tyrosine residues by the enzyme neprilysin (EP 24.11). The cpp-Ala-Ala N-terminal product of this cleavage is a potent inhibitor of angiotensin converting enzyme, which further limits the use of CFP in vivo. To generate specific inhibitors of EP 24.15 that are resistant to in vivo proteolysis by EP 24.11, beta-amino acids have been incorporated into the structure of CFP. We have prepared racemic mixtures of beta-amino acids containing proteogenic side chains, which are 9-fluorenylmethoxycarbonyl (Fmoc)-protected, and several analogues of CFP containing beta-amino acids have been synthesized by solid phase peptide synthesis. The results of stability and inhibitory studies of these new analogues show that the incorporation of beta-amino acids adjacent to the scissile bond can indeed stabilize the peptides against cleavage by EP 24.11 and still inhibit EP 24.15. The results obtained in these studies demonstrate the potential of these amino acids in the synthesis of peptidomimetics and in the design of new stable and specific therapeutics.

Neuropeptidases regulating gonadal function.

The generation and metabolism of bioactive peptides involves a series of highly ordered proteolytic events. This post-translational processing can occur either within the cell, at the cell surface or after secretion. In the central nervous system a number of extracellular peptidases have been implicated in the regulated processing of peptides, particularly in the regulation of neuroendocrine function. The aim of this study has been to identify the peptidases involved in the metabolism of gonadotropin-releasing hormone (GnRH) and to characterize the factors and the mechanisms by which the activity of these peptidases are regulated. We have shown that both prolylendopeptidase and the thimet oligopeptidase EC 3.4. 24.15 are involved in GnRH metabolism and that both oestrogen and thiol-based reductants could be involved in the physiological regulation of their activities.

Skin cancer prevention in outdoor recreation settings: effects of the Hawaii SunSmart Program.

CONTEXT: Skin cancer is the most common form of cancer in the United States, and it is one of the most preventable. Interventions for young children and their parents can help prevent future cases of skin cancer. OBJECTIVE: To determine whether a skin cancer prevention program implemented at outdoor recreation sites improved children's sun-protection behaviors and site sun-protection policies. DESIGN: Randomized trial of 14 outdoor recreation sites on the island of Oahu, Hawaii. The trial had three arms: control, education only, and education/environment. INTERVENTION: The education arm included staff training, on-site activities, take-home booklets, behavior-monitoring boards, and incentives. The education/environment arm included all education components plus provision of sunscreen and promotion of sun-safe environments. PARTICIPANTS: Children 6 to 8 years of age and their parents. OUTCOME MEASURES: Reports from parents of children's sun-protection behaviors and the sun-protection policies of recreation sites. The cohort for analysis from baseline to 6 weeks after testing had 383 participants; the cohort from 6 weeks after testing to 3 months of follow-up had 285 participants. RESULTS: Program implementation was high in the education only and the education/environment sites. Compared with control sites, children's sun-protection behaviors and, in particular, the use of sunscreen improved significantly at sites where the two interventions were implemented. In addition, sun-protection policies of recreation sites were markedly higher at intervention arm sites. The education/environment intervention was not superior to education alone. Changes were partly maintained at 3 months of follow-up. CONCLUSION: A creative, engaging, multicomponent skin cancer prevention program in outdoor recreation settings can lead to modest improvements in children's sun-protection behaviors.

Association between clinical factors, socioeconomic status, and organ damage in recent onset systemic lupus erythematosus.

OBJECTIVE: To determine the prevalence and socioeconomic and clinical predictors of early organ damage in a cohort of patients with systemic lupus erythematosus (SLE) of 2-7 years' duration randomly sampled at 5 centers and balanced by socioeconomic status and race. METHODS: The Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) Damage Index was measured in 200 patients who met the ACR criteria for SLE with a mean disease duration of 3.8 years. The SLICC/ACR scores for each organ system and the prevalence of damage within organ systems were assessed. Logistic regression analyses evaluated the simultaneous effects of age at diagnosis, disease duration, disease activity, and sociodemographic factors. RESULTS: Sixty-one percent of the patients had damage within 7 years of onset (mean 3.8 yrs). Neuropsychiatric (20.5%) and musculoskeletal (18.5%) systems were the most frequently involved, followed by renal (15.5%) and skin (12.5%) systems, all with median SLICC/ACR organ system scores of 1. In multivariate models, African-American race was associated with skin damage but not with damage in other specific organ systems. Socioeconomic status was not associated with organ system damage. Older age at diagnosis correlated with cardiovascular, musculoskeletal, gastrointestinal, ocular, and pulmonary damage. Clinical factors such as longer disease duration correlated with higher renal and cardiovascular damage, and greater disease activity at diagnosis of SLE correlated with greater renal, musculoskeletal, and pulmonary damage. CONCLUSION: There is evidence of organ system damage in SLE within a mean of 3.8 years after onset. We found little evidence for differences in early organ damage according to race or socioeconomic status. Damage to most organ systems was related to age at diagnosis of SLE and clinical factors such as disease duration.

A novel stable inhibitor of endopeptidases EC 3.4.24.15 and 3.4.24.16 potentiates bradykinin-induced hypotension.

We have developed a novel inhibitor of the metalloendopeptidases EC 3.4.24.15 (EP24.15) and EC 3.4.24.16 (EP24.16), N-[1-(R, S)-carboxy-3-phenylpropyl]-Ala-Aib-Tyr-p-aminobenzoate (JA2), in which alpha-aminoisobutyric acid (Aib) is substituted for an alanine in a well-described but unstable inhibitor, cFP-AAY-pAB. This substitution increases the resistance of the inhibitor to degradation without altering potency. In the present study, we investigated the effects of JA2 (5 mg/kg) on the responses of mean arterial pressure to bradykinin, angiotensin I, and angiotensin II in conscious rabbits. The depressor responses to both low (10 ng/kg) and high (100 ng/kg) doses of bradykinin were increased 7.0+/-2. 7-fold and 1.5+/-0.3-fold, respectively, during the 30 minutes after JA2 administration (mean+/-SEM, n=8). Bradykinin potentiation was undiminished 4 hours after JA2 injection. In contrast, the hypertensive effects of angiotensins I and II were unaltered, indicating that the bradykinin-potentiating effects were not due to angiotensin-converting enzyme inhibition. These data suggest that JA2 is not only a potent and specific inhibitor of EP24.15 and EP24. 16 but is also stable in vivo. Furthermore, the potentiation of bradykinin-induced hypotension by JA2 suggests for the first time a role for one or both of these peptidases in the metabolism of bradykinin in the circulation.

Development and characterization of novel potent and stable inhibitors of endopeptidase EC 3.4.24.15.

Solid-phase synthesis was used to prepare a series of modifications to the selective and potent inhibitor of endopeptidase EC 3.4.24.15 (EP24.15), N-[1(R, S)-carboxy-3-phenylpropyl]-Ala-Ala-Tyr-p-aminobenzoate (cFP), which is degraded at the Ala-Tyr bond, thus severely limiting its utility in vivo. Reducing the amide bond between the Ala and Tyr decreased the potency of the inhibitor to 1/1000. However, the replacement of the second alanine residue immediately adjacent to the tyrosine with alpha-aminoisobutyric acid gave a compound (JA-2) that was equipotent with cFP, with a K(i) of 23 nM. Like cFP, JA-2 inhibited the closely related endopeptidase EC 3.4.24.16 1/20 to 1/30 as potently as it did EP24.15, and did not inhibit the other thermolysin-like endopeptidases angiotensin-converting enzyme, endothelin-converting enzyme and neutral endopeptidase. The biological stability of JA-2 was investigated by incubation with a number of membrane and soluble sheep tissue extracts. In contrast with cFP, JA-2 remained intact after 48 h of incubation with all tissues examined. Further modifications to the JA-2 compound failed to improve the potency of this inhibitor. Hence JA-2 is a potent, EP24.15-preferential and biologically stable inhibitor, therefore providing a valuable tool for further assessing the biological functions of EP24.15.