OS057. Pathophysiological role of elevated tissue transglutaminase in autoantibody-induced features of preeclampsia in pregnant mice

Introduction Preeclampsia (PE) is highly associated with the presence of autoantibodies that activate the major angiotensin receptor, AT1R. These autoantibodies (termed AT1-AA) cause most features of PE when introduced into pregnant mice and are believed to contribute to disease pathogenesis. Tissue transglutaminase (tTG) is a prominent member of a family of enzymes that crosslink proteins by catalyzing the formation of an isopeptide bond between the amide group of glutamine and the free amino group of lysine and is believed to play a role in AT1R activation. Objectives To test the hypothesis that tTG plays a role in autoantibody-mediated AT1R activation and thereby contributes to the pathophyhsiology of PE. Methods Western blotting was used to quantify tTG in placentas of normotensive pregnant women and those with PE. Immunohistochemistry was used to determine cellular localization of tTG, AT1R and glutamyl-lysine isopeptides in placenta tissue. Co-immunoprecipitation experiments were used to explore the possible association of tTG and AT1R. Finally, in an effort to determine the role of tTG in AT1-AA-induced features of PE in vivo, we treated autoantibody-injected pregnant mice with cystamine, a potent tTG inhibitor. Results Western blot analysis showed elevated tTG in placentas of women with PE. Immunohistochemical analysis revealed that increased levels of tTG, glutamyl- lysine isopeptides, AT1R co-localized in the microvillous membrane of PE placentas. Immunoprecipitation of tTG from human trophoblast cell (HTR) lysates resulted in the co-immunoprecipitation of AT1R, thereby providing evidence for an interaction between tTG and AT1R in HTR cells. Finally, we found that cystamine treatment significantly attenuated key features associated with PE including hypertension and proteinuria in the PE-IgG-injected pregnant mice. Conclusion Taken together, we identified a previously unrecognized role of elevated tTG in PE likely by activating or stabilizing AT1Rs. These studies provide novel mechanisms of autoantibody-induced AT1R activation by elevated placental tTG, highlight the role of tTG in the pathogenesis of PE and suggest novel therapeutic strategies for the disease.