Association of High Levels Anti-β2GPI Antibodies with Myocardial Infarct Size and Cytokine Production in the Rat

Barshack I., George J., Keren P., Goldberg I., Kopolovic J., Keren G.
Department of Pathology, Sheba Medical Center
Department of Cardiology, Tel-Aviv Medical Center
Background: Anti-β2-glycoprotein I (β2GPI) antibodies (a subpopulation of antiphospholipid antibodies) are associated with a procoagulant state in humans and with enhanced atherosclerosis in experimental animal models. Moreover, the presesnce of high titers of anti-cardiolipin antibodies in relatively young patients is associated with higher incidence of subsequent myocardial infarction. Herein, we evaluated the role of preexisting high levels of anti-cardiolipin antibodies in determining the size of the infarct induced by permanent ligation of the left anterior descending artery (LAD).

Methods and Results: 11 Wistar rats were immunized and boosted with 10mcg of the phospholipid binding protein- β2GPI (a method commonly applied for induction of anti-phospholipid antibodies). A control group (n=9) were imunized and boosted with an irrelevant adjuvant. Upon induction of high anti-β2GPI antibody levels, myocardial infarction was induced by ligation of the LAD. Rats were sacrificed 7 days later, their lymph nodes collected for evaluation of cellular immunity to β2GPI and their hearts were removed for assessment of infarct size and for immunohistochemical stains for iNOS and TGF-beta.

B2GPI immunized rats exibited high levels of anti-cardiolipin antibodies (mean optical density of 1.3±0.3) as compared with the control group (mean optical density of 0.12±0.03; p<0.0001). Cellular imunity to B2GPI was also pronounced as evident by an increased thymidine uptake and by increased interferon-gamma secretion by the lymph node cells from B2GPI immunized rats. Myocardial infarct size was increased in rats induced to develop anti-β2GPI antibodies (mean size 23±9%) as compared with controls (17±12%;p<0.23). iNOS positive cells in the infarct area of B2GPI immunized rats were significantly increased in comparisosn to the control group (p<0.01). Similarly, TGF-beta cell expression was significantly increased in the infarct area of the immunized rats in comparison to the control group (22.65.1, 7±2.1 per 100 cells, respectively; p=0.01)

Conclusion: The presence of high levels of anti-cardiolipin antibodies is associated with higher expression of iNOS and TGF-beta in the infarct area and may enhance the infarct size in a rat model.