Relative effects of aspirin on platelet aggregation and prostaglandin-mediated coronary vasodilatation in the dog

Prostaglandin E2 accelerated recovery of chemotherapy-induced intestinal damage by increasing expression of cyclin D

Intestinal stem cells (ISCs) play a crucial role in maintaining intestinal homeostasis upon chemotherapy and radiotherapy. It has been documented that prostaglandin E2 (PGE2) treatment improved hematopoietic stem cell function in vitro and in vivo, while the relationship between PGE2 and intestinal stem cells remains unclear. Presently, mice were exposed to PGE1, dmPGE2 and indomethacin. Numbers and function of ISCs were assessed by analyzing Olfm4⁺ ISCs. Intestinal protection of dmPGE2 was investigated on a 5-fluorouracil (5FU)-induced intestinal damage mouse model. The results showed that dmPGE2 treatment, but not PGE1, increased numbers of Olfm4⁺ ISCs in dose- and time-dependent manners. Indomethacin treatment decreased numbers of Olfm4⁺ ISCs. The beneficial effects of short-term dmPGE2 treatment on intestine were supported in a 5FU-induced intestinal damage model. Our data showed that 5FU treatment significantly decreased numbers of Olfm4⁺ ISCs and goblet cells in intestine, which could be ameliorated by dmPGE2 treatment. dmPGE2 treatment accelerated the recovery of 5FU-induced ISC injury via increasing expression of cyclin D1 and D2 in intestine. Furthermore, dmPGE2 treatment-induced expression of cyclin D1 and D2 might be mediated by up-regulation of FOXM1 expression in intestine. These findings feature PGE2 as an effective protector against chemotherapy-induced intestinal damage.

NSAIDs and Cardiovascular Diseases: Role of Reactive Oxygen Species

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most commonly used drugs worldwide. NSAIDs are used for a variety of conditions including pain, rheumatoid arthritis, and musculoskeletal disorders. The beneficial effects of NSAIDs in reducing or relieving pain are well established, and other benefits such as reducing inflammation and anticancer effects are also documented. The undesirable side effects of NSAIDs include ulcers, internal bleeding, kidney failure, and increased risk of heart attack and stroke. Some of these side effects may be due to the oxidative stress induced by NSAIDs in different tissues. NSAIDs have been shown to induce reactive oxygen species (ROS) in different cell types including cardiac and cardiovascular related cells. Increases in ROS result in increased levels of oxidized proteins which alters key intracellular signaling pathways. One of these key pathways is apoptosis which causes cell death when significantly activated. This review discusses the relationship between NSAIDs and cardiovascular diseases (CVD) and the role of NSAID-induced ROS in CVD.

Evaluation of prognostic factors, survival rates, and treatment protocols for immune-mediated hemolytic anemia in dogs: 151 cases (1993-2002)

OBJECTIVE

To evaluate prognostic factors, survival, and treatment protocols for immune-mediated hemolytic anemia (IMHA) in dogs.

DESIGN

Retrospective study.

ANIMALS

151 dogs with IMHA not associated with underlying infectious or neoplastic disease.

PROCEDURE

lnformation recorded from review of medical records included signalment at the time of initial evaluation; vaccination history; 30-, 60-, and 365-day follow-up outcomes; laboratory data; results of imaging studies; and necropsy findings. Dogs were grouped according to the presence of spherocytes, autoagglutination, a regenerative erythrocyte response, and treatments received (azathioprine, azathioprine plus ultralow-dose aspirin, azathioprine plus mixed-molecular-weight heparin [mHEP], or azathioprine plus ultralow-dose aspirin plus mHEP) for comparisons. All dogs received glucocorticoids.

RESULTS

Cocker Spaniels, Miniature Schnauzers, neutered dogs, and female dogs were overrepresented. Alterations in certain clinicopathologic variables were associated with increased mortality rate. Rates of survival following treatment with azathioprine, azathioprine plus ultralow-dose aspirin, azathioprine plus mHEP, and azathioprine plus ultralow-dose aspirin plus mHEP were 74%, 88%, 23%, and 70%, respectively, at hospital discharge; 57%, 82%, 17%, and 67%, respectively, at 30 days; and 45%, 69%, 17%, and 64%, respectively, at 1 year. In comparison, mean survival rates at discharge and at 30 days and 1 year after evaluation collated from 7 published reviews of canine IMHA were 57%, 58%, and 34%, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Treatment with a combination of glucocorticoids, azathioprine, and ultralow-dose aspirin significantly improved short- and long-term survival in dogs with IMHA.

Nonplatelet effects of aspirin during acute coronary occlusion: electrophysiologic and cation alterations in ischemic myocardium

BACKGROUND

Mortality after acute myocardial ischemia has been reduced by aspirin (ASA) but mechanisms other than the antiplatelet effect have not been established. This article evaluates an antiarrhythmic action during sympathetic stimulation in the intact anesthetized dog with and without ischemia.

METHODS AND RESULTS

The ventricular fibrillation threshold (VFT) was examined before and after epinephrine (E) in normals (group I). A VFT reduction during E was normalized after 1 week of ASA (P<.01). Regional myocardial ischemia for 1 hour resulted in similar hypoperfusion in controls of group II and after ASA. Action potential responses in isolated superfused ischemic tissue showed prolonged repolarization (APD90) in response to E, which was normalized after ASA (P<.01). To assess the antiarrhythmic role of the anion in group III, Na salicylate was given. During 1 hour of ischemia, the VF incidence was reduced and cation abnormalities diminished in ischemic myocardium compared with untreated ischemia.

CONCLUSIONS

ASA antagonizes the reduction of the VFT induced by catecholamine in normals as well as the repolarization abnormality elicited by E during acute ischemia. The salicylate anion appears to be the active component in view of the efficacy in preventing VF during the early ischemic period.

Effect of high dose aspirin on coronary hemodynamics during pacing-induced myocardial ischemia

The effects of aspirin on coronary hemodynamics and transcardiac concentrations of thromboxane B2 (the stable metabolite of thromboxane A2) were determined at rest and during pacing-induced myocardial ischemia in 11 patients with coronary disease. Control coronary sinus pacing increased both arterial thromboxane B2 (331 +/- 70 to 623 +/- 132 pg/ml, p less than 0.02) and coronary sinus thromboxane B2 (184 +/- 3 to 403 +/- 156 pg/ml, p less than 0.05), but positive transmyocardial gradients developed in only three patients. After 650 mg of oral aspirin, more than 90% inhibition of in vitro thromboxane B2 production was demonstrated and circulating thromboxane B2 was undetectable at rest and during pacing in all patients. Despite these changes in thromboxane B2 concentrations, coronary blood flow was unchanged by aspirin at rest (107 +/- 14 versus 112 +/- 13 ml/min, p = NS) and during pacing (189 +/- 29 versus 181 +/- 25 ml/min, p = NS). Myocardial lactate extraction was also unchanged at rest (24 +/- 7 versus 19 +/- 5%, p = NS) and during pacing (5 +/- 6 versus 9 +/- 5%, p = NS). No change occurred in the anginal threshold. Thus, aspirin does not have the vasoconstrictive properties that have been reported with another cyclo-oxygenase inhibitor, indomethacin. These findings also suggest that thromboxane A2 production does not play a major role in the pathogenesis of stress-induced ischemia. Nonetheless, intracoronary thromboxane A2 production in some patients may potentiate platelet activation and coronary thrombosis. Such patients may benefit from long-term aspirin therapy and can be treated with aspirin without risk of adverse coronary hemodynamic effects.

Anti-thrombotic effect of very low doses of acetyl salicylic acid in rats

The anti-thrombotic effect of acetyl salicylic acid (ASA) was studied using the following experimental model: a silk thread was inserted in an extracorporeal shunt between the right carotid artery and the opposite jugular vein. A thrombus developed around the thread which was weighed at 10 minutes intervals. ASA inhibits the development of the thrombus at a dose of 3.1 mg/kg. When the dose was increased the anti-thrombotic effect disappeared. These results suggest that ASA may be an effective antithrombotic agent in man if the dosage is based on pharmacological data.

The injury-spasm (ischemia-induced hemostatic vasoconstrictive) and vascular autoregulatory hypothesis of ischemic disease. Resistance vessel-spasm hypothesis of ischemic disease

THe injury-spasm concept assumes that severe myocardial ischemia secondary to stenotic coronary artery disease causes spasm of resistance vessels through ischemic tissue injury. In this communication the concept is developed further and is now extended to include other diseases. It is suggested that relative arterial insufficiency, as traditionally understood, is an invalid concept and that disorders usually attributed to it, including congestive heart failure and peripheral vascular disease, should be attributed to injury-spasm. Because a basic reaction to injury is to prevent bleeding, injury-spasm is identified as an exaggerated form of hemostatic vasoconstriction, and spasm is related to distorted vascular autoregulatory activities of resistance vessels. It is asserted that blood platelets probably are not involved int he initiation of ischemic attacks, and instead of a platelet thromboxane/vessel prostacyclin vasomotor balance of epicardial coronary arteries, the vasoconstrictive/vasodilative balance is centered in resistance vessels and is based on autoregulatory processes such as the hemostatic injury-spasm reaction and reactive hyperemia.

Prostaglandins and ischemic heart disease

There is an abundance of information suggesting that prostaglandins are involved in the development and clinical expression of atherosclerosis. Many studies demonstrate a relationship between prostaglandins and the risk factors for peripheral and coronary artery disease. Thus, part of the mechanism by which hyperlipidemia, diabetes mellitus, smoking, hypertension, sex hormones, age, heredity, emotional stress and diet contribute to the development and progression of atherosclerosis may be through an imbalance between thromboxane A2 and prostaglandin I2. Recent studies show a temporal relationship between acute ischemic events (specifically, unstable angina) and a transcardiac increase in thromboxane B2, while others demonstrate a salutary effect of disaggregatory and vasodilatory prostaglandins in such patients. If prostaglandins and thromboxane prove important in ischemic vascular disease, attention will be directed at the correction of their pathologic imbalance. This may be accomplished by dietary manipulation as well as by the development of prostaglandin receptor antagonists or inhibitors of specific prostaglandin pathways.

Release of prostaglandins and thromboxane into the coronary circulation in patients with ischemic heart disease

Endogenous modulators of platelet aggregability and vascular tone may play a part in coronary-artery disease. We therefore measured the release of prostaglandins and thromboxane into the coronary circulation in patients with various kinds of cardiac disease. Simultaneous coronary-sinus (CS) and ascending-aortic (AO) blood samples were obtained from 60 patients for measurement of 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha, a prostaglandin I2 metabolite) and of thromboxane B2 (TxB2). Samples from 45 of these patients were also tested for prostaglandin E2 (PGE2) and lactate. Patients with unstable angina pectoris who reported chest pain within 24 hours of study had higher TxB2 CS/AO ratios (5.8 +/- 2.8, mean +/- S.D.) than patients whose most recent anginal pain was more than 96 hours before study (1.3 +/- 0.6; P less than 0.05), than those with nonischemic chest pain (1.2 +/- 0.4; P less than 0.05), or with valvular or congenital nonischemic heart disease (1.2 +/- 0.6; P less than 0.05). Those whose most recent anginal pain occurred 24 to 96 hours before study were distributed bimodally: the majority had low TxB2 CS/AO ratios (range, 0.5 to 2.1) like the patients in the three aforementioned groups, whereas a few had markedly elevated values (range, 10.5 to 46.6). The 6-keto-PGF1 alpha and PGE2 CS/AO ratios and myocardial lactate extraction were not significantly different among the five groups. These data suggest that local thromboxane release is associated with recent episodes of angina in patients with unstable angina pectoris, but whether this release is a cause or an effect is not yet known.

Lack of effect of aspirin on myocardial infarct size in the dog

Pretreatment with platelet-inhibitory doses of aspirin (3 mg/kg body weight) has been shown to augment epicardial collateral flow by more than 50 percent (p less than 0.05) 4 hours after ligation of the left anterior descending coronary artery in dogs. To determine whether this favorable influence of aspirin is sufficient to decrease the amount of infarcted tissue, either intravenous aspirin, 3 mg/kg (n = 17), or saline solution (n = 17) was administered to dogs 10 minutes before occlusion of the left anterior descending coronary artery. Administration of saline solution or aspirin was repeated every 24 hours. By 72 hours, 5 dogs in each treatment group had died. Survivors were killed at 72 hours. The portion of the left ventricle at risk of infarction was delineated by perfusion of the aortic root with Evans blue and simultaneous perfusion of the distal left anterior descending coronary artery with saline solution under equal physiologic pressures. Slices of the stained heart were incubated with triphenyltetrazolium to identify gross infarct (with histologic confirmation). Total mass of left ventricle, myocardium at risk, and infarct size were measured in each dog. A direct relation was found between the mass at risk and the mass infarcted (r = 0.84, p less than 0.001). Aspirin-treated dogs did not differ from control dogs in percent ventricle at risk (mean +/- standard error 37 +/- 2 versus 40 +/- 2), percent infarct weight/left ventricle (29 +/- 3 versus 31 +/- 2) or percent infarct weight/weight of ventricle at risk (78 +/- 4 versus 77 +/- 3). Thus, despite aspirin's ability to inhibit platelet aggregation and to increase epicardial collateral flow by more than 50 percent, aspirin treatment failed to reduce infarct size in this dog model.