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Biomedical subjects

A M Lefer

Publications and source records attributed to A M Lefer.

At least 19 recordsLinked to original sources

Splanchnic vascular endothelial dysfunction in rat endotoxemia: role of superoxide radicals.

Intravenous lipopolysaccharide, 30 mg/kg, results in rapid systemic hypotension in anesthetized rats. Interaction of lipopolysaccharide with the vascular endothelium and blood borne cells results in the elaboration of cytokines and oxygen-derived free radicals, all of which can be injurious to normal endothelial function. To evaluate endothelial function, superior mesenteric artery rings were isolated from endotoxemic rats just prior to death. Endotoxemia significantly blunted superior mesenteric artery ring vasorelaxations to acetylcholine and to A23187 but not to NaNO2. Contraction of superior mesenteric artery rings from endotoxemic rats induced by U46619 was not altered. Treatment with human superoxide dismutase or U74006F, an aminosteroid, significantly preserved vasorelaxation to acetylcholine and A23187. However, the hydroxyl radical scavenger N-(2-mercaptopropionyl)-glycine did not protect the endothelium. Thus, intravenous lipopolysaccharide can induce endothelial dysfunction in superior mesenteric artery rings. Furthermore, because superoxide dismutase but not N-(2-mercaptopropionyl)-glycine preserves endothelial function, it is likely that superoxide radicals mediate the endothelial dysfunction observed in endotoxemic rats.

Acetylcholine

Activated neutrophils aggravate endothelial dysfunction after reperfusion of the ischemic feline myocardium.

Endothelial dysfunction, as evidenced by decreased stimulated release of endothelium-derived relaxing factor (EDRF), occurs after reperfusion of the ischemic myocardium. To better understand this endothelial dysfunction, isolated cat hearts were perfused under constant flow by the Langendorff procedure with Krebs-Henseleit solution devoid of blood cells. Following global ischemia (90 minutes) and reperfusion (20 minutes), coronary vasorelaxation to the endothelium-dependent vasodilator acetylcholine (ACh) was 70 +/- 3% of initial values (p less than 0.01) compared with 90 +/- 4% in nonischemic control perfused hearts. No decrement occurred in response to the endothelium-independent vasodilator nitroglycerin (NTG). Coronary artery rings isolated from the ischemic left circumflex coronary artery showed a similar degree of endothelial dysfunction to ACh, with normal relaxation in response to NaNO2. Autologous cat neutrophils (100 million cells), activated with 100 nmol/L f-met-leu-phe infused into the heart directly before and throughout reperfusion, resulted in a further decrement in ACh-induced vasodilation, to 55 +/- 5% of initial response, with no effect on NTG-induced vasodilation. Similar results were obtained with coronary artery rings isolated from perfused cat hearts and exposed to neutrophils. This neutrophil-enhanced endothelial dysfunction was inhibited by human superoxide dismutase as well as by an antibody to the adherence glycoprotein complex CD-18 (i.e., MAbR 15.7). Therefore endothelial dysfunction occurs initially upon reperfusion of the previously ischemic heart and is aggravated by superoxide radicals produced by activated neutrophils.

Animals

Anti-ischaemic and endothelial protective actions of recombinant human osteogenic protein (hOP-1).

Osteogenic protein one (hOP-1), a member of the transforming growth factor-beta (TGF-beta) supergenic family, was studied for its anti-ischaemic properties in rats subjected to myocardial ischaemia and reperfusion. Ten minutes after ligation (i.e., just prior to reperfusion) of the left coronary artery, 2 or 20 micrograms/rat recombinant human (hOP-1) or its vehicle, was given intravenously. hOP-1 at 20 micrograms significantly reduced reperfusion injury 24 h later compared to rats receiving only vehicle (i.e., 0.9% NaCl). hOP-1 was also found to preserve rat coronary endothelial function (i.e., release of endothelium-derived relaxing factor, EDRF) in perfused hearts following global ischaemia and reperfusion. Moreover, hOP-1 also significantly inhibited adherence of rat neutrophils to rat vascular endothelium in vitro. Thus, hOP-1 exerts significant anti-ischaemic effects. Some of this cardioprotection may be related to the ability of hOP-1 to preserve endothelial function and inhibit neutrophil adherence to the endothelium.

Animals

Low doses of superoxide dismutase and a stable prostacyclin analogue protect in myocardial ischemia and reperfusion.

The effects of low dose human superoxide dismutase and low dose taprostene, a stable analogue of prostacyclin, were investigated separately and together in a model of myocardial ischemia (1.5 h) with reperfusion (4.5 h) in open chest, anesthetized cats. Taprostene (60 ng/kg per min), human superoxide dismutase (0.25 mg/kg per h), both agents together, or their vehicle, were infused intravenously in cats starting 0.5 h after occlusion of the left anterior descending coronary artery. Neither low dose taprostene nor low dose human superoxide dismutase exerted any endothelial or myocardial protection in this model. However, the two agents together showed a significant endothelial and myocardial protection in cats with myocardial ischemia and reperfusion. Compared with cats that were untreated or received only taprostene or human superoxide dismutase, cats receiving both agents exhibited a lower plasma creatine kinase activity at every time point observed after reperfusion, a reduced area of cardiac necrosis (7 +/- 2% vs. 21 +/- 5% area at risk, p less than 0.001), lower myeloperoxidase activity in the ischemic region (p less than 0.01) and a significant preservation of vasorelaxant responses of left anterior descending coronary rings to endothelium-dependent vasodilators, acetylcholine (p less than 0.001) and A-23187 (p less than 0.001). Taprostene appears to act additively with human superoxide dismutase to inhibit neutrophil adherence and activation and to inactivate superoxide radicals, and thus reduce cellular injury 4.5 h after reperfusion of the ischemic heart. Use of this agent may allow low doses of superoxide dismutase to be used more effectively in early myocardial ischemia.

Animals

Beneficial effects of SPM-5185, a cysteine-containing NO donor in myocardial ischemia-reperfusion.

Intravenous administration of SPM-5185 [N-nitratopivaloyl-S-(N'-acetylalanyl)-cysteine ethyl ester], a cysteine-containing nitric oxide (NO) donor, or SPM-5267 [pivaloyl-S-(N'-acetylalanyl)-cysteine ethyl ester], an analogue of SPM-5185 that lacks the NO moiety, was studied in a feline myocardial ischemia-reperfusion model. Administration of SPM-5185 (1 mg/kg), followed by a 2-mg.kg-1.h-1 infusion starting 10 min before reperfusion, resulted in significant protection 4.5 h postreperfusion. In the myocardial ischemia (MI)+SPM-5267 group, 38 +/- 4% of the area at risk was necrotic, whereas the necrotic area/area at risk was only 7 +/- 2% in the MI+SPM-5185 group (P less than 0.01). Moreover, SPM-5185 treatment markedly attenuated the endothelial dysfunction observed in the left anterior descending coronary artery after reperfusion by 50%. These beneficial effects occurred despite the absence of a significant change in myocardial oxygen demand, as measured by the pressure-rate index. In vitro experiments demonstrated that SMP-5185, but not SPM-5267, decreased adherence of neutrophils to the coronary vascular endothelium and decreased production of superoxide radicals. Therefore, a likely mechanism of the observed cardioprotection by SPM-5185 involves attenuation of polymorphonuclear leukocyte-induced endothelial dysfunction.

Animals

Cardiac venous endothelial dysfunction after myocardial ischemia and reperfusion in dogs.

Endothelial dysfunction is a prominent occurrence in coronary arteries after myocardial ischemia and reperfusion. However, this has not been studied in coronary veins. Endothelium-dependent vasorelaxation was studied in cardiac venous rings obtained from dogs subjected to 60 min of coronary artery occlusion followed by 270 min of reperfusion, as well as from dogs subjected to sham ischemia-reperfusion. Myocardial ischemia resulted in a 96 +/- 2% decrease in coronary flow to the ischemic area 60 min after occlusion of the left anterior descending (LAD) coronary artery, which led to a significant degree of cardiac necrosis (i.e., 32.9 +/- 3.9% of area at risk). Cardiac venous rings isolated from sham ischemia-reperfusion dogs relaxed 68 +/- 3% to 200 microM ADP, 65 +/- 3% to 2 microM A23187, and 76 +/- 4% to 200 microM sodium nitrite (NaNO2). Corresponding values for cardiac venous rings isolated from ischemic-reperfused dogs were 32 +/- 3% for 200 microM ADP (P less than 0.01 vs. sham), 31 +/- 3% for 2 microM A23187 (P less than 0.01 vs. sham), and 74 +/- 3% for 200 microM NaNO2 (NS from sham). In rings from control dogs, vasorelaxation to ADP and A23187 was markedly inhibited by 4 mM NG-methyl-L-arginine (L-NMMA) and 10 methylene blue and restored after NG-nitro-L-arginine by 3 mM L-arginine. These results demonstrate that a significant degree of endothelial dysfunction occurred in cardiac venous rings after ischemia and reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals

The role of L-arginine in ameliorating reperfusion injury after myocardial ischemia in the cat.

BACKGROUND: Myocardial ischemia followed by reperfusion results in endothelial dysfunction characterized by a reduced release of endothelium-derived relaxing factor (EDRF). Because EDRF has been characterized as nitric oxide, we examined the ability of L-arginine, the substrate for nitric oxide synthesis, to protect in a feline model of myocardial ischemia plus reperfusion. METHODS AND RESULTS: The effects of L-arginine were investigated in a 6-hour model of myocardial ischemia and reperfusion in pentobarbital-anesthetized cats. A bolus administration (30 mg/kg) of L-arginine, or its enantiomer D-arginine, was given followed by a continuous infusion of 10 mg/kg/min for 1 hour starting 10 minutes before reperfusion. Myocardial ischemia plus reperfusion in cats receiving D-arginine resulted in severe myocardial injury and endothelial dysfunction characterized by marked myocardial necrosis, high cardiac myeloperoxidase activity in ischemic cardiac tissue, and loss of acetylcholine- and A-23187-induced endothelium-dependent relaxation in coronary artery rings. In contrast, myocardial ischemia plus reperfusion cats treated with L-arginine exhibited a reduced area of cardiac necrosis (16 +/- 2% versus 41 +/- 5% of area at risk, p less than 0.01), lower myeloperoxidase activity in the ischemic region (0.3 +/- 0.08 versus 0.8 +/- 0.10 units/100 mg tissue, p less than 0.05), and significant preservation of acetylcholine- (p less than 0.01) and A-23187- (p less than 0.01) induced endothelial-dependent relaxation. CONCLUSIONS: These results demonstrate the ability of L-arginine to reduce necrotic injury in a cat model of myocardial ischemia plus reperfusion, and this reduction in infarct size is associated with the preservation of endothelial function and attenuation of neutrophil accumulation in ischemic cardiac tissue.

Animals

Coronary endothelial and cardiac protective effects of a monoclonal antibody to intercellular adhesion molecule-1 in myocardial ischemia and reperfusion.

BACKGROUND: Intercellular adhesion molecule-1 (ICAM-1) is a major ligand on endothelial cells for adherence of activated polymorphonuclear leukocytes (PMNs). The major purpose of this study was to study the effects of RR1/1, a monoclonal antibody against ICAM-1 (i.e., MAb RR1/1), on myocardial injury and endothelial dysfunction associated with myocardial ischemia and reperfusion. METHODS AND RESULTS: Either MAb RR1/1 (2 mg/kg, n = 7), an antibody that was found to bind selectively to endothelial cells in the cat, or MAb R3.1 (2 mg/kg, n = 7), a nonbinding control antibody, was given as an intravenous bolus 10 minutes before reperfusion. Two hundred eighty minutes later, hearts were excised. The left ventricle area-at-risk (AAR) was similar in MAb RR1/1 (29 +/- 2%) and MAb R3.1 (30 +/- 3%) groups. In MAb R3.1-treated cats, 90 minutes of myocardial ischemia plus 4.5 hours of reperfusion induced a significant myocardial injury (necrotic tissue/AAR, 28 +/- 2%), high myeloperoxidase activity (0.65 +/- 0.16 units/100 mg ischemic tissue), and a marked decrease in endothelium-dependent vasorelaxation in isolated left anterior descending coronary arteries (vasorelaxation to acetylcholine, 29 +/- 3%) with no change in endothelium-independent vasorelaxation (relaxation to NaNO2, 91 +/- 3%). However, cats treated with MAb RR1/1 developed significantly less myocardial necrosis (10 +/- 2% of the AAR, p less than 0.01), lower myeloperoxidase activity in ischemic myocardial tissue (0.2 +/- 0.03 units/100 mg ischemic tissue, p less than 0.01), and enhanced vasorelaxant responses to endothelial-dependent relaxation to acetylcholine (53 +/- 5%) compared with ischemic/reperfused cats treated with Mab R3.1. Furthermore, addition of MAb RR1/1 in vitro significantly inhibited unstimulated PMN adherence to ischemic-reperfused coronary artery endothelium. CONCLUSIONS: These results suggest that ICAM-1-dependent PMN adherence plays an important role in reperfusion injury, and that PMN adherence and infiltration contribute significantly to coronary endothelial dysfunction.

Animals

Antishock and endothelial protective actions of a NO donor in mesenteric ischemia and reperfusion.

Splanchnic artery occlusion (SAO) of the celiac, superior mesenteric, and inferior mesenteric arteries for 2 hr, followed by a 2-hr reperfusion period in cats produces a severe form of circulatory shock characterized by endothelial dysfunction, increased lysosomal leakage, and severe hypotension resulting from release of proteases, oxygen-derived free radicals, and other humoral mediators into the circulation. Administration of 0.75 mg/kg/hr of C873754, a nitric oxide (NO) donor, 10 min prior to reperfusion, significantly attenuated the accumulation of plasma cathepsin D from 12 +/- 3 U/ml in the SAO + vehicle group to 5 +/- 1 U/ml (P < 0.05) in the C87-3754 treated SAO group. A similar attenuation of plasma myocardial depressant factor (MDF) activity was observed in the C87-3754 treated cats (P < 0.02). Administration of C87-3754 significantly increased short term (i.e., 2-hr) survival rate (P < 0.05, compared to the vehicle group). Moreover, C87-3754 attenuated the SAO shock induced decline in release of endothelium-derived relaxing factor (EDRF) from isolated superior mesenteric artery (SMA) rings stimulated by acetylcholine and A23187. Additionally, C87-3754 significantly decreased PMN adherence to the superior mesenteric venous endothelium in vitro. Thus, treatment with the NO donor, C87-3754 reduced the accumulation of humoral mediators into the plasma while significantly attenuating endothelial dysfunction and improving short term survival.

Animals

Protective actions of S-nitroso-N-acetylpenicillamine (SNAP) in a rat model of hemorrhagic shock.

The anti-shock effects of an organic nitric oxide donor, S-nitroso-N-acetylpenicillamine (SNAP), were tested in a rat model of hemorrhagic shock. Administration of SNAP at a dose of 10 mcg/kg injection followed by 10 mcg/kg/h infusion neither significantly decreased mean arterial blood pressure (MABP) nor significantly altered bleedout volumes in hemorrhagic rats, indicating that SNAP did not modify the severity of the shock protocol. However, hemorrhaged rats treated with SNAP maintained post-reinfusion MABP at significantly higher values than hemorrhaged rats receiving 0.9% NaCl (final MABP 81 +/- 3.0 mmHg vs. 54 +/- 1.1 mmHg, respectively; p < 0.001). SNAP also significantly increased survival times following hemorrhagic shock (113 +/- 4 min in SNAP treated rats compared with 70 +/- 4.5 min in vehicle treated rats, p < 0.001). The overall survival rates were 87.5% when treated with SNAP and 0% with 0.9% NaCl (p < 0.01). In hemorrhagic shock rats receiving only vehicle, a significant accumulation of neutrophils in intestinal tissue occurred as indicated by a higher MPO activity in intestinal tissue (MPO activity, 1.26 +/- 0.31 vs. 0.14 +/- 0.05U/100 mg in sham hemorrhagic shock rats, p < 0.02). Administration of SNAP significantly attenuated the neutrophil accumulation in the intestinal tissue (MPO activity, 0.42 +/- 0.09U/100 mg, p < 0.05 compared with hemorrhagic rats receiving only the vehicle). Moreover, endothelial dysfunction of superior mesenteric artery rings occurred in hemorrhagic shock rats given only 0.9% NaCl.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals

Mechanisms of the cardioprotective actions of WEB-2170, bepafant, a platelet activating factor antagonist, in myocardial ischemia and reperfusion.

The cardioprotective effects of WEB-2170, a specific platelet activating factor (PAF) receptor antagonist, were investigated in a feline model of myocardial ischemia (MI) and reperfusion. Either WEB-2170 (1-mg/kg bolus plus 2 mg/kg/hr) or its vehicle (0.9% NaCl) was administered 1 hr after left anterior descending coronary artery occlusion (i.e., 30 min before reperfusion). The cardiac area-at-risk (AAR) was similar in MI-reperfused (MI + R) cats given either WEB-2170 (31.5 +/- 3.6%) or vehicle (27.8 +/- 2.8%). However, in cats receiving only the vehicle, 1.5 hr of ischemia plus 4.5 hr of reperfusion resulted in significant myocardial injury (necrotic tissue/AAR, 37.7 +/- 4.5%), high plasma creatine kinase activity (29.4 +/- 4.1 I.U./micrograms of protein) and a marked decrease in endothelium-dependent relaxation in isolated left anterior descending coronary arteries to acetylcholine (33 +/- 4% of U-46619-induced vasocontraction) with no change in endothelium-independent relaxation to NaNO2 (91 +/- 1%). In contrast, MI + R cats treated with WEB-2170 developed significantly less myocardial necrosis (necrotic tissue/AAR, 12.0 +/- 2.8%, P less than .001), lower plasma creatine kinase activity (16.5 +/- 4.1 I.U./micrograms of protein, P less than .01) and enhanced vascular relaxation to acetylcholine (53 +/- 4.1%, P less than .01) compared to MI + R cats given only the vehicle. Furthermore, the addition of WEB-2170 to PMN suspensions in vitro significantly inhibited (P less than .01) PAF-induced polymorphonuclear leukocyte (PMN) adherence to endothelial cells (12 +/- 2.4 cells/field vs. 27 +/- 2.6 in the control group).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals

Effects of adenosine, an adenosine-A1 antagonist, and their combination in splanchnic occlusion shock in rats.

Splanchnic artery occlusion (SAO) with reperfusion results in a severe form of circulatory shock. To study the possible involvement of adenosine in this shock state, we have examined the effects of adenosine, an adenosine A1-receptor antagonist, and their combination in a rat model of SAO shock. Pentobarbital-anesthetized rats were subjected to a 90-min occlusion of both the celiac and superior mesenteric arteries followed by reperfusion. Rats given only the vehicle for adenosine (i.e., 0.9% NaCl) developed severe hypotension following reperfusion, and the survival rate was less than 30% 2 hr after reperfusion. Final plasma free amino-nitrogen concentrations, cathepsin D and myocardial depressant factor (MDF) activities were significantly elevated in rats receiving only the vehicle. Infusion of adenosine (i.e., 30 micrograms/kg/min, i.v.), starting 45 min postocclusion, did not significantly improve the survival rate but did attenuate the accumulation of MDF. Eighty percent (i.e., 4 of 5) rats given KF15372, an adenosine A1-antagonist, 45 min postocclusion (500 micrograms/kg), survived 2 hr. KF15372 also attenuated the increased plasma free amino-nitrogen and MDF. Seventy-five percent (i.e., 6 of 8) rats treated with KF15372 and adenosine survived 2 hr. This combined treatment significantly attenuated the increased plasma levels of free amino-nitrogen, cathepsin D, and MDF. These results suggest that endogenous adenosine plays a significant role in the pathogenesis of shock following SAO and reperfusion, and that blockade of the adenosine A1-receptor could be beneficial in shock states.

Adenosine

Cardioprotection and attenuation of endothelial dysfunction by organic nitric oxide donors in myocardial ischemia-reperfusion.

The effects of two nitric oxide (NO) donors were evaluated in a 6-h model of feline myocardial ischemia-reperfusion. After 80 min of a 90-min ischemic period, SIN-1 or C87-3754 or their respective controls (i.e., 0.9% NaCl or C88-3934, a control compound which does not release NO) were given i.v. as a bolus (0.1 mg/kg) and infused at 1 mg/kg/h for the entire 4.5-h reperfusion period. Administration of the active NO donors significantly decreased the necrotic area/area-at-risk ratio from 29 +/- 3% in the vehicle group to 9 +/- 2 and 11 +/- 5% in the SIN-1 and C87-3754 groups, respectively (P less than .001). The inactive NO donor C88-3934 failed to reduce infarct size (31 +/- 3%). Neither NO donor reduced the accumulation of neutrophils in the necrotic area when compared to their respective control groups, but both agents significantly attenuated coronary endothelial dysfunction as shown by a vasorelaxation to acetylcholine of 62 +/- 2 and 64 +/- 3% in the SIN-1- and C87-3754-treated arteries, as compared to only a 27 +/- 3 and 34 +/- 4% vasorelaxation in the vehicle and inactive NO donor groups, respectively (P less than .001). Our studies show that SIN-1 and C87-3754 exert beneficial effects in a 6-h model of myocardial ischemia-reperfusion. Both NO donors decreased myocardial necrosis and decreased the reperfusion-induced endothelial dysfunction without significantly altering the pressure-rate index (i.e., an index of myocardial oxygen demand).

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5

Mechanisms of the protective effects of transforming growth factor-beta in reperfusion injury.

TGF-beta appears to be an important regulatory peptide in cellular physiology. Although all of its actions are not presently known, TGF-beta functions as a cell-switching molecule. In the case of ischemia-reperfusion states, TGF-beta has been shown to exert remarkably effective protective effects. These effects appear to pertain to preservation of endothelial function, particularly to maintenance of EDRF formation by the endothelium. The endothelial protection may be related to actions of TGF-beta opposing the endothelial-destabilizing actions of both TNF and superoxide radicals. However, other important mechanisms will undoubtedly be brought to light with further study of TGF-beta in these situations.

Animals

Endothelial dysfunction in myocardial ischemia and reperfusion: role of oxygen-derived free radicals.

Myocardial ischemia followed by reperfusion results in endothelial dysfunction in cats. This dysfunction is characterized by a loss of endothelium-derived relaxing factor (EDRF) release in response to endothelium-dependent dilators. This loss of endothelium-dependent relaxation (EDR) occurs significantly at 2.5 min post-reperfusion and the dysfunction progresses until it is complete at 20 min post-reperfusion. This reduced EDR is prevented by superoxide dismutase, but not by hydroxyl radical scavengers. In contrast, neutrophil accumulation in the heart, as measured by cardiac myeloperoxidase (MPO) activity, does not reach significant levels until 3 h post-reperfusion, and significant myocardial necrosis does not occur until 4.5 h post-reperfusion. No significant changes in EDR, MPO or cardiac necrosis occurred during the 90 min of ischemia. Thus, endothelial dysfunction is an early and specific marker of reperfusion injury preceding neutrophil involvement and cardiac necrosis. Superoxide radicals appear to play a key role in the decreased EDR observed early after reperfusion.

Animals

Role of endothelial dysfunction in the pathogenesis of reperfusion injury after myocardial ischemia.

Endothelial dysfunction occurs after myocardial ischemia and reperfusion characterized by a marked reduction in endothelium-dependent relaxation (EDR) due to reduced release or action of endothelium-derived relaxing factor (EDRF). This reduced EDR occurs in coronary rings isolated from cats 2.5 min after reperfusion and in isolated perfused cat hearts 2.5 min after reperfusion. No decrease in EDR occurs before reperfusion in either preparation, suggesting that this impairment in EDR occurs during reperfusion. The decrease in EDR occurs soon after the generation of superoxide radicals by the reperfused coronary endothelium. Accumulation of neutrophils and myocardial cell injury does not occur until 3-4.5 h after reperfusion. Thus, endothelial generation of superoxide radicals acts as a trigger mechanism for endothelial dysfunction which is then amplified by neutrophil adherence and diapedesis into the ischemic region enhancing post-reperfusion ischemic injury. Agents that preserve endothelial function or inhibit neutrophil activation (e.g., superoxide dismutase, prostacyclin analogs, TGF-beta, antibodies to adhesive proteins) can protect against endothelial dysfunction and myocardial injury, if administered before reperfusion.

Animals