Anti-human skeletal muscle glycolipid antibodies in unstable angina.

BACKGROUND: We studied whether the level of anti-skeletal muscle glycolipid antibodies (AGA), a marker of acute rejection in heart transplantation, may be associated with an adverse prognosis in unstable angina. METHODS AND RESULTS: The in-hospital evolution of 50 patients with unstable angina (Braunwald class III B) was assessed. We determined the incidence of death, myocardial infarction, and refractory angina. Blood was collected at admission and 24 hours later for determination of AGA levels by enzyme-linked immunosorbent assay. Twenty-three patients showed a decrease in the AGA level at 24 hours after admission. Ten in-hospital cardiac events occurred in these patients (43.4%) as compared with 4 (14.8%) in the 27 patients who did not show a decrease (P =.025). In patients with previous myocardial infarction (n = 26), the AGA assay was a powerful predictor of outcome. In this subgroup, 66.6% of patients who had decreased AGA levels (8 of 12) had cardiac events as compared with 14.2% (2 of 14) of those who did not have that decrease (P =.001). CONCLUSIONS: We conclude that a decrease of AGA levels 24 hours after admission is associated with a complicated in-hospital course. This finding may provide new insights in the phenomenon of plaque instability involved in the development of acute coronary syndromes.

Anti-skeletal muscle glycolipid antibodies in human heart transplantation as predictors of acute rejection: comparison with other risk factors.

In forty-five patients who underwent orthotopic heart transplantation, the titer of anti-human skeletal muscle glycolipid antibodies (AGA) present in the sera at the moment of transplantation was correlated with the number of histologically diagnosed cellular grade 3A and humoral acute rejection episodes during the first 120 days after transplantation. Determination of a cutoff value of 0.800 for the AGA level was determined by a receiver operating characteristic curve. Thirteen of 19 patients (68.4%) with an AGA titer above 0.800 developed 24 severe rejection episodes, and of the 26 patients with an AGA titer below 0.800, only 4 (15.3%) presented 6 severe rejection episodes during that time. This was especially evident for the humoral rejection episodes, which were diagnosed in only 1 of the 26 patients with AGA below 0.800 and in 7 of the 19 with AGA above 0.800. Comparison by univariate analysis of other well-known risk factors for a greater number of rejection episodes during the early posttransplant period with the AGA level at the moment of transplantation revealed that the latter distinguished a greater number of patients at risk than the other factors, such as a female donor, the lymphocyte direct cross-match, or the status of the patients at transplantation; the odds ratios were 6.33 for the AGA level, 3.17 for the direct cross-match, and 2.76 for the status at transplantation. By multiple logistic regression analysis, the only relevant risk factors in our group of patients were the AGA level (P=0.0009) and the status at transplantation (P=0.0285). These results indicate that determination of the AGA level at the moment of transplantation could represent a useful method for distinguishing which patients are at risk for a greater number of rejection episodes during the early posttransplant period, with a greater sensitivity than other risk factors.

Anti-skeletal muscle glycolipid antibodies in human heart transplantation as markers of acute rejection. Correlation with endomyocardial biopsy.

In seventeen patients the result of the histological study of 153 endomyocardial biopsies (EMB) was compared with the ELISA titer of anti-human skeletal muscle glycolipid antibodies (AGA) present in serum samples collected simultaneously with the EMB procedure during the first four months following cardiac transplantation. The glycolipids were extracted from the quadriceps femoralis of blood group O patients. In the serum samples corresponding to the histological rejection grades with myocyte necrosis (greater than or equal to 2, International Society for Heart and Lung Transplantation grading) the AGA titer was significantly higher (P<0.005) than in the less severe rejection grades. The follow-up in each patient showed that the AGA titer raised in the serum samples collected immediately after, before, or coincidentally with a histological diagnosis of rejection grade 2 or 3A. In only one rejection grade 3A case was a false-negative result observed. Determination of the cut-off of the AGA level versus rejection grades 2 and 3A was determined by a relative-operating characteristic curve. An optical density (OD) of 0.040 showed maximum efficiency with sensitivity 53% and specificity 79%. Four patients who had AGA with an OD above 0.040 at the time of transplant had a significantly higher number of rejection grade 2 and 3A episodes than eleven patients with low pre-transplant AGA titers (P<0.05). These results indicate that search of anti-skeletal muscle glycolipid antibodies may represent a useful noninvasive method for monitoring heart rejection, and suggest that its investigation prior transplant may be a predictor of the number of grades 2 and 3A rejection episodes.

Presence of antiheart and antiskeletal muscle glycolipid autoantibodies in the sera of patients with chagasic cardiopathy.

OBJECTIVE: To characterize biochemically and isolate the skeletal and heart muscle cell epitope recognized by the autoantibodies present in the serum of chronically infected Trypanosoma cruzi patients. Secondly, to use that epitope in an immunoenzymatic assay for determining differences in antibody titre among Chagas' and other protozoan and heart diseases and between asymptomatic and cardiopathic chagasic patients. DESIGN: Isolated human skeletal and heart muscle cells were treated with organic solvents, pronase, neuraminidase and sodium metaperiodate before immunofluorescence assay. Glycolipids were extracted from human skeletal muscle for ELISA. PATIENTS: Sera were collected from 155 patients with positive serology for T cruzi infection; 44 healthy blood bank donors; and from patients after heart transplantation (16 patients), during the first month after cardiac infarction (eight) or cardiotomy (10), dilated myocardiopathy (21), leishmaniasis (12), acute toxoplasmosis (four) and hyperthyroid ophthalmopathy (five). MAIN RESULTS: Immunofluorescence assay revealed that the chagasic sera recognized epitopes that appeared to be glycolipid in nature. ELISA showed that the chagasic sera contained a higher titre of antiskeletal muscle glycolipid antibodies than the control sera and that, in the chagasic population, antibody titre was significantly higher in patients with heart failure than in asymptomatic subjects or in those presenting only electrocardiographic abnormalities. CONCLUSIONS: The skeletal and heart muscle epitope recognized by antibodies present in the sera of chagasic patients has the characteristics of a glycolipid. ELISA with glycolipids extracted from human skeletal muscle indicated that chagasic patients presented a higher antibody titre and that patients with heart failure showed a titre significantly higher than those who were asymptomatic or with electrocardiographic abnormalities, suggesting that those antibodies could be immunological markers and even predictors of heart failure in Chagas' disease.

Relaxant effect of pharmacological interventions increasing heart cyclic AMP and its protein kinase.

After 1 min of treatment with different positive inotropic interventions, cyclic nucleotide levels (cAMP and cGMP) and cAMP-dependent protein kinase activity were determined in heart homogenates. Glucagon, norepinephrine, and isoproterenol increased cAMP from 0.503 +/- 0.025 pmol/mg wet weight to 1.051 +/- 0.099, 0.900 +/- 0.064, and 0.982 +/- 0.138, respectively. Simultaneously, cAMP-dependent protein kinase activity ratio rose from 0.21 +/- 0.02 to 0.45 +/- 0.04 with glucagon, 0.33 +/- 0.02 with norepinephrine, and 0.34 +/- 0.02 with isoproterenol. The ratio between maximal velocities of contraction and relaxation (+T/-T) was significantly decreased by these interventions, whereas time to peak tension (TTP) was shortened by norepinephrine and isoproterenol. High calcium, ouabain, and paired stimulation did not affect cAMP-dependent protein kinase activity and +T/-T. Our results suggest that inotropic interventions increasing cAMP levels might primarily affect intracellular mechanisms causing relaxation.

Influence of acid-base alterations on myocardial sensitivity to catecholamines.

The influence of "respiratory" and "metabolic" acid-base alterations on the myocardial sensitivity to catecholamines was studied in the isolated rat atria. The ability of noradrenaline for increasing the atrial rate was enhanced during alkalosis and conversely, it was decreased by acidosis. These changes in sensitivity shifted the concentration-effect curve for noradrenaline to the right by about 0.5 log unit when the pH was lowered from 7.60 to 7.00. No changes in the maximum attainable response were detected. Essentially the same shifts of the concentration-effect curves were obtained with changes in pH brought about by altering the pCO2 or at constant pCO2. The decrease in the pH produced a similar shift to the right of the concentration-effect curve for isoprenaline, after the extraneuronal uptake inhibition by hydrocortisone and also in atria tissue with low content of endogenous noradrenaline (reserpine-pretreated and newborn rats). The ability of isoprenaline for increasing cyclic AMP levels in atrial tissue was also enhanced by alkalosis and decreased by acidosis. However, the shift to the right of the concentration-effect curve for cyclic AMP induced by the decrease in the pH was greater than the shift detected in the chronotropic-effect curve. In addition a decrease in the maximum increment of cyclic AMP was detected under acidosis, in spite of equal maximal chronotropic response. Our results support the hypothesis that the alterations in the sensitivity to catecholamines induced by the changes in pH are not due to a release of endogenous noradrenaline nor to alterations of the mechanisms which remove catecholamines from the biophase. The fact that cyclic AMP response to catecholamines was also reduced by acidosis strongly suggests that the mechanism(s) involved is located in the earlier steps of the events leading to the chronotropic effect of the beta-agonists.

Relaxing effect of pharmacologic interventions increasing cAMP in rat heart.

The relationship between cAMP and relaxation was studied in the isolated rat heart beating at constant rate and perfused at constant coronary flow. After treatment during 1 min with different positive inotropic interventions, cyclic nucleotide levels (cAMP and cGMP) and cAMP-dependent protein kinase activity were determined in heart homogenates. Glucagon, norepinephrine, and isoproterenol increased cAMP from 0.503 +/- 0.025 pmol/mg wet wt to 1.051 +/- 0.099, 0.900 +/- 0.064, and 0.982 +/- 0.138, respectively. Simultaneously glucagon, norepinephrine, and isoproterenol increased cAMP-dependent protein kinase activity ratio from 0.21 +/- 0.02 to 0.45 +/- 0.04, 0.33 +/- 0.02, and 0.34 +/- 0.02, respectively. The ratio between maximal velocities of contraction and relaxation (+T/-T) was significantly decreased by these interventions, whereas time to peak tension (TTP) was shortened by norepinephrine and isoproterenol. High calcium, ouabain, and paired stimulation did not affect cAMP levels, TTP, or +T/-T. A striking correlation was found between cAMP-dependent protein kinase activity and relaxation induces, i.e., TTP, -T, or +T/-T (r = +/- 0.7 to -0.9). Results suggest that inotropic interventions increasing cAMP levels might be primarily affecting intracellular mechanisms causing relaxation.

The mechanical and biochemical effects of pentoxifylline on the perfused rat heart.

Perfusion of the isolated rat heart at constant heart rate and coronary flow with the inhibitor of cyclic nucleotide phosphodiesterase, pentoxifylline (10(-4) moles/l), produced no significant effect on the maximum rate and the peak of contraction, but increased the maximum rate of relaxation. cAMP level and cAMP-dependent protein kinase activity were increased in the absence of changes in cGMP. The results were identical in hearts of reserpinized rats.