phosphoramidon and Disease-Models--Animal

There is increasing evidence that deficient clearance of β-amyloid (Aβ) contributes to its accumulation in late-onset Alzheimer disease (AD). Several Aβ-degrading enzymes, including neprilysin (NEP), insulin-degrading enzyme, and endothelin-converting enzyme reduce Aβ levels and protect against cognitive impairment in mouse models of AD. The activity of several Aβ-degrading enzymes rises with age and increases still further in AD, perhaps as a physiological response to minimize the buildup of Aβ. The age- and disease-related changes in expression of more recently recognized Aβ-degrading enzymes (e.g. NEP-2 and cathepsin B) remain to be investigated, and there is strong evidence that reduced NEP activity contributes to the development of cerebral amyloid angiopathy. Regardless of the role of Aβ-degrading enzymes in the development of AD, experimental data indicate that increasing the activity of these enzymes (NEP in particular) has therapeutic potential in AD, although targeting their delivery to the brain remains a major challenge. The most promising current approaches include the peripheral administration of agents that enhance the activity of Aβ-degrading enzymes and the direct intracerebral delivery of NEP by convection-enhanced delivery. In the longer term, genetic approaches to increasing the intracerebral expression of NEP or other Aβ-degrading enzymes may offer advantages.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Disease Models, Animal; Genetic Therapy; Glycopeptides; Humans; Insulysin; Mice; Mice, Transgenic; Microglia; Neprilysin; Protease Inhibitors; Stem Cell Transplantation; Thiorphan

Serotoninergic activation which decreases brain Aβ peptides is considered beneficial in mouse models for Alzheimer's disease (AD), but the mechanisms involved remain unclear. Because growing evidence suggested that the stimulation of proteases digesting Aβ, especially the endopeptidase neprilysin (NEP) may be effective for AD therapy/prevention, we explored the involvement of serotonin precursors and derivatives in NEP regulation. We found that 5-hydroxyindolacetic acid (5-HIAA), the final metabolite of serotonin, considered until now as a dead-end and inactive product of serotonin catabolism, significantly reduces brain Aβ in the transgenic APPSWE mouse model for AD-related Aβ pathology and in the phosphoramidon-induced cerebral NEP inhibition mouse model. 5-HIAA treatment improves memory performance in APPSWE mice. Furthermore, 5-HIAA and its precursors increase NEP level in vivo and in neuroblastoma cells. Inhibition of ERK 1/2 cascade by 5-HIAA or SCH772984 enhanced NEP levels, suggesting MAP-kinase pathway involvement in 5-HIAA-induced regulation of NEP expression. Our results provide the first demonstration that 5-HIAA is an active serotonin metabolite that increases brain Aβ degradation/clearance and improves symptoms in the APPSWE mouse model for AD.

Topics: 5-Hydroxytryptophan; Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Antipsychotic Agents; Brain; Cell Line, Tumor; Disease Models, Animal; Enzyme Inhibitors; Female; Gene Expression Regulation; Glycopeptides; Humans; Hydroxyindoleacetic Acid; Male; Mice; Mice, Transgenic; Neprilysin; Signal Transduction; Spatial Behavior

Intranasal administration is emerging as a reliable and non-invasive method to bypass the blood-brain barrier and deliver drugs to the brain. This approach has been primarily used to explore therapeutic avenues for neurological diseases. However, intranasal administration could also be used to create animal models of brain disease. Beta-amyloid peptide (Aβ) accumulation is a key feature of Alzheimer's disease (AD), and the most common models of AD are transgenic mice expressing mutant human genes linked to familial AD. An alternative model of amyloidosis utilizes intracerebroventricular infusion of thiorphan or phosphoramidon to block the activity of key Aβ degrading enzymes (NEP, NEP2) resulting in accumulation of Aβ. Here, we demonstrate that intranasal administration of phosphoramidon produces significantly elevated cerebral Aβ levels in wild-type mice. Furthermore, intranasal phosphoramidon administration in double knockout mice lacking NEP and NEP2 also showed increased levels of Aβ(40). These data show that intranasal delivery of drugs can be used to model AD and suggest that other phosphoramidon-sensitive peptidases are degrading Aβ in NEP/NEP2-deficient mice.

Topics: Administration, Intranasal; Alzheimer Disease; Amyloid beta-Peptides; Animals; Disease Models, Animal; Glycopeptides; Humans; Mice; Mice, Knockout; Neprilysin; Protease Inhibitors

Leptin, a multifunctional hormone that regulates food intake and energy expenditure, has emerged recently as an important modulator of inflammatory cascades associated with wound healing. In this study, we applied the animal model of buccal mucosal ulcer to investigate the role of endothelin-1 (ET-1) and leptin in soft oral tissue repair. Using groups of rats with experimentally induced buccal mucosal ulcers we show that ulcer onset was characterized by a marked increase in the mucosal level of ET-1 and leptin. However, while the ET-1 level gradually declined with healing, the mucosal level of leptin increased reaching maximum expression on the 4th day of healing. Therapeutic administration of phosphoramidon, an inhibitor of ECE-1 activity, not only led to a 53.2% drop in the ET-1, but also produced a dose-dependent reduction (up to 50.9%) in the mucosal level of leptin and up to 42.3% decline in the rate of ulcer healing. A marked drop (54.2%) in the mucosal level of leptin and the reduction (46.8%) in the rate of ulcer healing was also attained in the presence of ETA receptor antagonist BQ610 administration, but not the ETB receptor antagonist BQ788. Moreover, administration of ERK inhibitor, PD98059 in the presence of ETB receptor antagonist, but not the ETA receptor antagonist, caused the reduction the mucosal leptin level as well as a decline in the rate of ulcer healing. Our findings are the first to implicate the requirement for both ET-1 and leptin in orderly progression of the events of soft oral tissue repair. We also show that ET-1 is a key factor in up-regulation of leptin production associated with oral mucosal ulcer healing , and that the effect of ET-1 on leptin production is a consequence of ETA receptor activation and subsequent signaling through MAPK/ERK.

Topics: Acetic Acid; Animals; Aspartic Acid Endopeptidases; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Endothelin-Converting Enzymes; Flavonoids; Glycopeptides; Leptin; Metalloendopeptidases; Mitogen-Activated Protein Kinase Kinases; Mouth Mucosa; Oligopeptides; Oral Ulcer; Piperidines; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptor, Endothelin B; Time Factors; Up-Regulation; Wound Healing

Several metallopeptidases have been implicated in both term and preterm parturition. We hypothesize that endotoxin-induced preterm delivery can be prevented by the administration of a metallopeptidase inhibitor.. We used an animal model of endotoxin-induced preterm delivery in timed pregnancy C57Bl/6 mice. Test animals received lipopolysaccharide followed by phosphoramidon, either every 1.5 or every 3 hours. Control mice received lipopolysaccharide followed by buffer injections at the same intervals. The primary outcome was a preterm delivery rate.. The rate of preterm delivery for the control animals was 88.0% compared with the treatment groups of 45.5% for the mice that received phosphoramidon every 3 hours and 30.8% for the group that received it every 1.5 hours (P<.01).. The administration of a metallopeptidase inhibitor resulted in a decreased rate of preterm delivery in this animal model.

Topics: Animals; Disease Models, Animal; Female; Glycopeptides; Metalloendopeptidases; Mice; Mice, Inbred C57BL; Obstetric Labor, Premature; Pregnancy; Protease Inhibitors

Subarachnoid hemorrhage (SAH) leads to the development of vasospasm in which endothelin-1 plays a very important role. The effect of its vasoconstricting action is hypoxia of the nervous tissue, which stimulates the release of growth factors. Vascular endothelial growth factor (VEGF) released in excessive amounts from hypoxically altered cerebrovascular endothelial cells is the most potent angiogenic factor and may enhance angiogenesis after SAH. If endothelin-1 is mainly responsible for vasospasm after SAH, it is possible that early administration of endothelin converting enzyme inhibitor or endothelin receptor antagonist may protect neurons against. The aim of the study was to establish whether prolonged vasospasm and endothelial cell hypoxia stimulate VEGF expression and, in consequence, promote angiogenesis in the central nervous system after subarachnoid hemorrhage. Investigations were also performed to determine whether the administration of phosphoramidon, an endothelin-converting enzyme (ECE) inhibitor, and BQ-123, an endothelin receptor ET(A) antagonist, suppresses angiogenesis and VEGF expression. Experiments were carried out in male Wistar rats injected with phosphoramidon or BQ-123 into the cisterna magna following the induction of subarachnoid hemorrhage. The brains were removed 48 h after the hemorrhage for histopathological and immunohistochemical examinations of VEGF expression and angiogenesis in the cerebral hemispheres, brainstem, and cerebellum. Statistical analysis was performed using nonparametric Wilcoxon test (P<0.05). The results obtained have shown for the first time a close correlation between endothelial hypoxia after SAH in cerebral microvessels and enhanced angiogenesis. There is also an increase in VEGF expression in cerebral vessels and neurons within the cerebral hemispheres, brainstem, and cerebellum. The administration of phosphoramidon or BQ-123 has been found to inhibit angiogenesis. Angiogenesis in the chronic phase of SAH-induced vasospasm is the result of prolonged narrowing of vessels due to excessive secretion of endothelin by damaged endothelial cells. Present results obtained indicate that it is possible to reduce or prevent the late effects of SAH, i.e., neuronal hypoxia and cerebral edema, through the inhibition of endothelin-1 induced vasospasm.

Topics: Animals; Antihypertensive Agents; Cell Count; Cerebral Cortex; Disease Models, Animal; Endothelial Growth Factors; Glycopeptides; Immunohistochemistry; Intercellular Signaling Peptides and Proteins; Lymphokines; Male; Neovascularization, Physiologic; Peptides, Cyclic; Protease Inhibitors; Rats; Rats, Wistar; Subarachnoid Hemorrhage; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

The aim of this study was to investigate whether the blocking of endothelin-converting enzyme (ECE) activity offers a new approach to inhibiting the development of cerebral vasospasm after subarachnoid hemorrhage (SAH) by preventing transformation of big endothelin-1 (big ET-1) to vasoactive endothelin-1 (ET-1). The effect of potential ECE inhibitors was determined in vitro by measurement of isometric contractions, induced by big ET-1, in isolated rat basilar arteries. Intact and de-endothelialized endothelium (E+ and E-, respectively) segments were examined after preincubation with the putative ECE inhibitors: phosphoramidon (10(-4) M), and [22D-Val]big ET-1 [16-38] (10(-5) M and 10(-6) M). Additionally, the effect of [D-Val22]big ET-1 [16-38] was investigated in rabbits after intracisternal application in order to inhibit the contraction of the basilar artery induced by (2x10(-6) M) big ET-1. Application of 10(-4)-M phosphoramidon resulted in a statistically significant decrease in big ET-1-induced contraction in E+ and E- segments; 10(-5)-M and 10(-6)-M [22D-Val]big ET-1 [16-38] in E- segments produced no statistically significant effect. The application of 10(-6)-M [22D-Val]big ET-1 [16-38] in E+ segments caused increased contractions, as shown by the shift to the left of the concentration-effect curve (CEC). In the rabbit group pretreated with [D-Val22]big ET-1 [16-38] (2x10(-5) M) (n=8), the angiographically measured diameter of the basilar artery increased from 0.63+/-0.12 mm to 0.66+/-0.12 mm. In the control group (n=8), this diameter decreased from 0.71+/-0.13 mm to 0.57+/-0.15 mm. This corresponded to an increase in vessel diameter of 5.24+/-9.89% in the treatment group and a decrease of 19.54+/-15.81% in the control group (P=0.002). The present study indicates the existence of functional ECE activity in rat basilar artery, which differs in the endothelium and the smooth muscle layer. These results demonstrate that [D-Val22]big ET-1 [16-38] has a potent ECE-inhibitory effect, preventing cerebral vasospasm in rabbit basilar artery by inhibiting the transformation of big ET-1 to vasoactive ET-1 after intracisternal application in vivo, whereas no inhibitory effect was detectable in rat basilar artery in vitro. Therefore, further studies of the biochemical nature of cerebrovascular ECE activity are required.

Topics: Animals; Aspartic Acid Endopeptidases; Basilar Artery; Disease Models, Animal; Endothelin-Converting Enzymes; Endothelins; Glycopeptides; In Vitro Techniques; Male; Metalloendopeptidases; Muscle Contraction; Muscle, Smooth, Vascular; Protease Inhibitors; Rabbits; Rats; Rats, Sprague-Dawley; Subarachnoid Hemorrhage; Vasospasm, Intracranial

Chagas' disease is an important cause of cardiomyopathy. Endothelin-1, a vasoactive peptide has been implicated in the pathogenesis of chagasic cardiomyopathy. C57BL/6 x 129sv and CD1 mice were thus, infected with trypomastigotes of Trypanosoma cruzi (Brazil strain) and these infected mice were compared with infected mice treated with phosphoramidon. This compound inhibits endothelin-converting enzyme and neutral endopeptidases and does not affect the growth of the parasite in culture. Phosphoramidon was given in a dose of 10mg/kg for the initial 15 days post-infection None of the C57Bl/6 x 129sv mice died as a result of infection. However, there was marked myocardial inflammation and fibrosis in infected, untreated mice. The hearts of the infected, phosphoramidon-treated mice showed significantly less pathology. Cardiac magnetic resonance imaging of infected mice revealed right ventricular dilation that was less severe in those treated with phosphoramidon. Phosphoramidon-treated CD1 mice survived the acute infection. Transthoracic echocardiography demonstrated left ventricular dilation and reduced percent fractional shortening and relative wall thickness. These alterations were also attenuated as a result of phosphoramidon treatment. These data suggest that endothelin-1 contributes to the pathogenesis of chagasic cardiomyopathy and interventions that inhibit the synthesis of endothelin-1 and/or neutral endopeptidase might have a protective effect on myocardial structure and function in murine Chagas' disease.

Topics: Animals; Chagas Cardiomyopathy; Disease Models, Animal; Echocardiography; Gene Expression Regulation; Glycopeptides; Heart; Magnetic Resonance Imaging; Male; Mice; Mice, Inbred Strains; Myocardium; Protease Inhibitors; Reverse Transcriptase Polymerase Chain Reaction; Trypanosoma cruzi

Renal ischemia is of clinical interest because of its role in renal failure and also renal graft rejection. To evaluate the effect of the combination of N-acetylcysteine (NAC), a potent antioxidant, sodium nitroprusside (SNP), a nitric oxide donor, and phosphoramidon (P), an endothelin converting enzyme inhibitor, on tissue protection against ischemia-reperfusion injury, we studied the biochemical and morphological changes due to 90 min of renal ischemia-reperfusion in the rat model. Ninety min of ischemia caused very severe injury and the animals could not survive after 4 days without any treatment. Whereas, animals in the treated groups survived i.e. the NAC group (25%), NAC + SNP group (43%) and in the NAC + SNP + P group (100%), 2 weeks after 90 min of ischemia. A significant increase in the serum levels of creatinine and urea nitrogen was shown in the untreated group and to a much lesser extent in the treated group, especially in the NAC + SNP + P group. The protective effect was also supported by light microscopic studies on renal tissue sections. We also measured the activities of antioxidant enzymes in tissue homogenates. With the exception of Mn-superoxide dismutase, the activities of antioxidant enzymes (catalase, glutathione peroxidase, CuZn-superoxide dismutase) were decreased in the untreated kidney. The administration of NAC alone and NAC + SNP protected against the loss of activities. Treatment with a combination of NAC, SNP and P showed a synergistic effect as evidenced by the best protection. These results suggest that pre-administration of a combination of antioxidant (NAC) with endothelin derived vasodilators (sodium nitroprusside and Phosphoramidon) attenuates renal ischemia-reperfusion injury, e.g. in donor kidney for transplantation, by protecting cells against free radical damage.

Topics: Acetylcysteine; Animals; Antioxidants; Catalase; Disease Models, Animal; Drug Therapy, Combination; Glutathione Peroxidase; Glycopeptides; Ischemic Preconditioning; Kidney; Male; Nitroprusside; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Superoxide Dismutase; Time Factors

Ischemia followed by reperfusion has a number of clinically significant consequences. A number of pathophysiological processes appear to be involved in ischemia/reperfusion (I/R) injury. The mitogen activated protein kinases (MAPK) are integral components of the parallel MAP kinase cascades activated in response to a variety of cellular stress inducing ischemia/ATP depletion and inflammatory cytokines. Many studies suggest that members of the MAP kinase family in particular Jun N-terminal kinase (JNK) are activated in kidney following ischemia/reperfusion of this tissue. The present study underlines the therapeutic potential of the combination of N-acetyl cysteine (NAC), a potent antioxidant, sodium nitroprusside (SNP), a nitric oxide donor and phosphoramidon (P), an endothelin-1 converting enzyme inhibitor in ameliorating the MAPK induced damage during renal ischemia/reperfusion injury. Our previous results showed that 90 min of ischemia followed by reperfusion caused very severe injury and that the untreated animals had 100% mortality after the 3rd day whereas there was improved renal function and 100% survival of animals in the three drug combination treatment group. The present study, mainly on tissue sections, further supports the protection provided by the triple drug therapy. A higher degree of expression of all the three classes of MAPK, i.e. JNK, P38 MAP kinases and P-extracellular signal regulated kinases (ERKs) can be seen in kidneys subjected to ischemia/reperfusion insult. Pretreatment with a combination of N-acetyl cysteine, sodium nitroprusside, and phosphoramidon completely inhibits all three classes of MAPK and ameliorates AP-1 whereas individual or a combination of any two drugs is not as effective.

Topics: Acetylcysteine; Animals; Disease Models, Animal; Glycopeptides; Immunohistochemistry; Ischemia; Ischemic Preconditioning; JNK Mitogen-Activated Protein Kinases; Male; Mitogen-Activated Protein Kinases; Nitroprusside; Phosphorylation; Proto-Oncogene Proteins c-fos; Proto-Oncogene Proteins c-jun; Rats; Rats, Sprague-Dawley; Reperfusion; Reperfusion Injury; Survival Rate; Time Factors; Transcription Factor AP-1

To investigate whether tachykinins are released in the airways by stimulating the esophagus, airway plasma extravasation induced by intraesophageal hydrochloric acid (HCl) in the presence or absence of the neutral endopeptidase (NEP) inhibitor phosphoramidon and the neurokinin-1-receptor antagonist FK888 was studied in anesthetized guinea pigs. Airway plasma extravasation also was studied in the presence of the NEP inhibitor in guinea pigs pretreated with capsaicin or bilateral vagotomy. Propranolol and atropine were used in all animals to block adrenergic and cholinergic nerve effects. Airway plasma leakage was evaluated by measuring extravasated Evans blue dye. One normal HCl infusion into the esophagus significantly increased plasma extravasation in the trachea. Phosphoramidon significantly potentiated plasma extravasation induced by HCl infusion into the esophagus in the trachea and main bronchi, and FK888 significantly inhibited extravasation in a dose-related manner. In capsaicin-treated animals, airway plasma extravasation was completely inhibited even in the presence of phosphoramidon. Tracheal plasma extravasation potentiated by phosphoramidon was significantly inhibited in the bilaterally vagotomized animals. These results suggest that locally acting substances are released by intraesophageal HCl stimulation that cause airway plasma extravasation. These substances are generated through activation of neural pathways, including some that traffic through the vagus nerves that link the esophagus or airways.

Topics: Animals; Dipeptides; Disease Models, Animal; Dose-Response Relationship, Drug; Esophagus; Extravasation of Diagnostic and Therapeutic Materials; Glycopeptides; Guinea Pigs; Hydrochloric Acid; Indoles; Lung; Reference Values; Sensitivity and Specificity; Substance P; Vagotomy

We describe the pharmacological characteristics of SM-19712 (4-chloro-N-[[(4-cyano-3-methyl-1-phenyl-1H-pyrazol-5-yl)amino]carbonyl] benzenesulfonamide, monosodium salt). SM-19712 inhibited endothelin converting enzyme (ECE) solubilized from rat lung microsomes with an IC50 value of 42 nM and, at 10 - 100 microM, had no effect on other metalloproteases such as neutral endopeptidase 24.11 and angiotensin converting enzyme, showing a high specificity for ECE. In cultured porcine aortic endothelial cells, SM-19712 at 1 - 100 microM concentration-dependently inhibited the endogenous conversion of big endothelin-1 (ET-1) to ET-1 with an IC50 value of 31 microM. In anesthetized rats, either intravenous (1-30 mg/kg) or oral (10-30 mg/kg) administration of SM-19712 dose-dependently suppressed the pressor responses induced by big ET-1. In acute myocardial infarction of rabbits subjected to coronary occlusion and reperfusion, SM-19712 reduced the infarct size, the increase in serum concentration of ET-1 and the serum activity of creatinine phosphokinase. The present study demonstrates that SM-19712 is a structurally novel, nonpeptide, potent and selective inhibitor of ECE, and SM-19712 is a valuable new tool for elucidating the pathophysiological role of ECE.

Topics: Acute Disease; Animals; Aspartic Acid Endopeptidases; Disease Models, Animal; Endothelin-1; Endothelin-Converting Enzymes; Enzyme Inhibitors; Glycopeptides; Lung; Male; Metalloendopeptidases; Myocardial Infarction; Pressoreceptors; Rabbits; Rats; Rats, Sprague-Dawley; Substrate Specificity; Sulfonamides; Sulfonylurea Compounds; Swine

An inhalation of ultrasonically nebulized distilled water (UNDW) induces bronchoconstriction only in asthmatics, but the mechanism underlying the response is not fully understood. We recently showed that bronchoconstriction occurs immediately after UNDW is inhaled 20min after an aerosolized antigen challenge in passively sensitized guinea-pigs.. This study was conducted to examine the role of tachykinins in this response.. Passively sensitized animals were anaesthetized and artificially ventilated, and changes in pressure at the airway opening (Pao) were measured as an overall index of airway narrowing. A tachykinin NK1 and NK2 dual receptor antagonist, FK224, and a tachykinin NK1 selective antagonist, FK888, were intravenously administered 15 min after the antigen challenge. The effects of capsaicin desensitization and a neutral endopeptidase inhibitor, phosphoramidon, were also examined.. FK224 and FK888 significantly (P < 0.05 and P < 0.05, respectively) reduced the time course curve of the increase in Pao caused by UNDW inhalation in a dose-dependent manner. The percentage increase in Pao from the preantigen challenge value at 1 min after the UNDW inhalation was 267.4+/-17.1, 358.0+/-33.7 and 412.4+/-27.6% with 10 mg/kg of FK224, 1.0 mg/kg of FK224 and vehicle, respectively, (P<0.01 between 10 mg/kg of FK224 and vehicle) and the value was 254.4+/-48.5% with 10 mg/kg of FK888, 327.1+/-57.6% with 1.0 mg/kg of FK888 and 418.5+/-39.0% with vehicle, respectively (P < 0.05 between 10 mg/kg of FK888 and vehicle). The capsaicin desensitization, but not phosphoramidon, significantly reduced the UNDW-induced increase in Pao.. These results suggest that tachykinins, at least substance P, are involved in a part of the UNDW-induced bronchoconstriction in our guinea-pig model.

Topics: Animals; Bronchoconstriction; Capsaicin; Dipeptides; Disease Models, Animal; Glycopeptides; Guinea Pigs; Indoles; Killer Cells, Natural; Male; Nebulizers and Vaporizers; Ovalbumin; Peptides, Cyclic; Respiration; Tachykinins; Water

Following the use of deep hypothermic circulatory arrest in cardiac surgery, cerebral blood flow and cerebral oxygen metabolism are impaired. These may result from abnormal cerebral vasospasm. Powerful vasoconstrictors including endothelins and thromboxane A2 could mediate these processes. We investigated possible involvement of these two factors by assessing the effects of (a) phosphoramidon-an inhibitor of endothelin converting enzyme, and (b) vapiprost (GR32191B)-a specific thromboxane A2-receptor antagonist, on the recovery of cerebral blood flow and cerebral oxygen metabolism following deep hypothermic circulatory arrest.. A total of 18 1-week-old piglets were randomised into three groups (n = 6 per group). At induction, the control group received saline; group PHOS received phosphoramidon 30 mg kg-1 intravenously. Group VAP received vapiprost 2 mg kg-1 at induction and at 30 min intervals thereafter. All groups underwent cardiopulmonary bypass cooling to 18 degrees C, exposed to 60 min of deep hypothermic circulatory arrest, rewarmed and reperfused for 1 h. Cerebral blood flow was measured with radio-labeled microspheres: cerebral oxygen metabolism was calculated at baseline before deep hypothermic circulatory arrest and at 1 h of reperfusion and rewarming.. In the control group, cerebral blood flow decreased to 40.2 +/- 2.0% of baseline after deep hypothermic circulatory arrest and cerebral oxygen metabolism decreased to 50.0 +/- 5.5% (P < 0.0005). The responses in group PHOS were similar. In group VAP, cerebral blood flow and cerebral oxygen metabolism were 64.3 +/- 10.6 and 80.1 +/- 9.8% of baseline, respectively, after deep hypothermic circulatory arrest. Thus, treatment with vapiprost significantly improved recovery of cerebral blood flow (P = 0.046) and cerebral oxygen metabolism (P = 0.020) following deep hypothermic circulatory arrest. No such improvement was seen after treatment with phosphoramidon.. Thromboxane A2 mediates impairments in cerebral perfusion and metabolism following deep hypothermic circulatory arrest. These changes were attenuated by blockade of thromboxane A2-receptors using vapiprost. Endothelins are not shown to be involved. Better knowledge of injury mechanisms will enable development of more effective cerebral protection strategies and allow safer application of deep hypothermic circulatory arrest.

Topics: Animals; Animals, Newborn; Biphenyl Compounds; Brain; Cardiopulmonary Bypass; Cerebrovascular Circulation; Confidence Intervals; Disease Models, Animal; Endothelins; Glycopeptides; Heart Arrest, Induced; Heptanoic Acids; Hypothermia, Induced; Metalloendopeptidases; Oxygen; Random Allocation; Receptors, Thromboxane; Reference Values; Swine; Vascular Resistance

Tachykinins, found in sensory nerves, have effects in the airways which suggest that they may contribute to the pathogenesis of asthma. We aimed to find evidence for tachykinin involvement in the immediate airway response to allergen in a sheep model of experimental asthma. Twenty-four sheep were actively sensitized to Ascaris suum, then challenged with nebulized Ascaris extract in a dose-response fashion. Change in lung resistance (RL) in response to challenge was measured. Responder sheep (those with an increase in RL of > or = 100% over baseline) that had reproducible responses over three challenges were identified (n = 4 sheep) and a PC100 (number of breaths of extract required to induce a 100% increase in RL) was determined. The effect of the neutral endopeptidase inhibitor phosphoramidon, the NK-1 receptor-specific antagonist CP 96, 345 and capsaicin desensitization on the RL response to Ascaris challenge was then assessed. Administration of phosphoramidon before Ascaris decreased the PC100 to 31 +/- 7% of the PC100 seen with Ascaris alone (P < 0.05), whereas CP 96,345 and capsaicin desensitization increased the PC100 to 285 +/- 41% and 555 +/- 93% respectively (P < 0.05 for both). These findings suggest that endogenous tachykinins are released in response to allergen challenge and that they contribute to the immediate increase in RL.

Topics: Allergens; Animals; Anti-Inflammatory Agents, Non-Steroidal; Ascaris suum; Asthma; Biphenyl Compounds; Bronchial Hyperreactivity; Bronchoconstriction; Capsaicin; Disease Models, Animal; Drug Interactions; Glycopeptides; Immunization; Reference Values; Reproducibility of Results; Sheep; Tachykinins

The effect of phosphoramidon on the increase in pulmonary inflation pressure (PIP) induced by endothelin-1 (ET-1) administered by aerosol in ovalbumin (OA)-sensitized and challenged guinea-pigs was investigated after pretreatment or not of the animals with the neutral endopeptidase inhibitor, phosphoramidon, the cyclooxygenase inhibitor, indomethacin or the platelet activating factor (PAF) antagonist, BN 50730. When guinea-pigs were pretreated by phosphoramidon (0.1 mM, aerosol for 15 min), a significant enhancement of PIP was observed after administration of ET-1 (1 or 3 micrograms ml-1, aerosol for 2 min), whereas these doses of the peptide were only slightly active in control animals. In sensitized and unchallenged guinea-pigs, ET-1 (1 or 3 micrograms.ml-1, aerosol for 2 min) induced, as in controls, a moderate increase in PIP. In contrast, aerosol exposure of OA in sensitized guinea-pigs developed an increased PIP following ET-1 (1 and 3 micrograms.ml-1, aerosol for 2 min) administration, that was non significantly affected by pretreatment of the animals with phosphoramidon after the dose of 3 micrograms ml-1 ET-1. Guinea-pigs exposed to phorphoramidon and treated with indomethacin (10 mg kg-1, i.v.) or BN 50730 (25 mg kg-1, per os) significantly reduced the increase in PIP upon administration of ET-1 (3 micrograms.ml-1, aerosol for 2 min). No inhibitory effect of indomethacin was noted when ET-1 (3 micrograms.ml-1, aerosol for 2 min) was administered to sensitized and OA-exposed guinea-pigs, pretreated or not with phosphoramidon. In contrast, BN 50730 significantly reduced the increase in PIP induced by ET-1 observed in sensitized and OA-exposed guinea-pigs. Moreover, this drug was moderately active in reducing the increase in PIP induced by ET-1, when the animals were pretreated by phosphoramidon. These results suggest that a phosphoramidon-sensitive endopeptidase-like enzyme, present in the airway tissue modulates the effect of ET-1. Furthermore, the increase in PIP to ET-1 observed in aerosol-sensitized and antigen-exposed guinea-pigs appears to be mediated by PAF rather than cyclooxygenase metabolites, even though the participation of other mediators in this process is open.

Topics: Aerosols; Animals; Azepines; Bronchi; Disease Models, Animal; Endothelins; Glycopeptides; Guinea Pigs; Immunization; Indomethacin; Lung; Male; Neprilysin; Ovalbumin; Platelet Activating Factor; Prostaglandin-Endoperoxide Synthases; Respiratory Function Tests; Tetrazoles; Thienopyridines; Time Factors; Triazoles

The protective effects of phosphoramidon, a dual inhibitor of endothelin-converting enzyme and neutral endopeptidase (E.C. 24.11), on renal function in ischemic acute renal failure were investigated in anesthetized rats. Intravenous infusion of phosphoramidon (0.03 and 0.1 mg/kg per min) significantly suppressed tubular sodium wasting (measured by fractional excretion of sodium) and proteinuria in the postischemic kidney without modifying functional parameters in the contralateral normal kidney. Phosphoramidon (0.1 mg/kg/min) was associated with increased glomerular filtration in the ischemic kidney. In comparison, SCH 42354, a highly selective inhibitor of neutral endopeptidase at 0.3 mg/kg/min, did not inhibit endothelin-converting enzyme or afford renal protection. The data suggest that the protective action of phosphoramidon against ischemic acute renal failure is most likely mediated by inhibition of endothelin formation.

Topics: Acute Kidney Injury; Animals; Aspartic Acid Endopeptidases; Disease Models, Animal; Endothelin-Converting Enzymes; Endothelins; Glomerular Filtration Rate; Glycopeptides; Infusions, Intravenous; Male; Metalloendopeptidases; Methionine; Neprilysin; Rats

There is increasing evidence that the conversion of big endothelin-1 (big ET-1) to endothelin-1 (ET-1) is specifically inhibited by the metalloproteinase inhibitor phosphoramidon. We investigated the effect of phosphoramidon on delayed cerebral vasospasm from subarachnoid hemorrhage (SAH) using a two-hemorrhage canine model. The magnitude of the vasospasm and the drug effect were determined angiographically. On SAH Day 7, diameter of the basilar artery decreased to about 55% of the control value obtained before SAH (on Day 0). Immunoreactive ET (IR-ET) in the cerebrospinal fluid (CSF) significantly increased after SAH (on Day 7). The intracisternal pretreatment of phosphoramidon potently suppressed the decrease in diameter of the basilar artery after SAH, i.e., observed decrease was only about 20%, compared with the value before SAH. In the phosphoramidon group, IR-ET in CSF markedly increased (on SAH Day 2), but the increased levels of IR-ET significantly declined on SAH Day 7. These results clearly indicate that phosphoramidon effectively prevents delayed cerebral vasospasm. Whether the prevention is due to the inhibition of conversion of big ET-1 to ET-1 is now under study.

Topics: Animals; Cerebral Veins; Chromatography, High Pressure Liquid; Disease Models, Animal; Dogs; Endothelins; Glycopeptides; Ischemic Attack, Transient; Radiography; Radioimmunoassay; Subarachnoid Hemorrhage