ENG and preeclampsia: Moreover, endoglin activates eNOS [68,69] as well as interacts and modulates Activin receptor-like kinase-1 and -5 signaling [69], resulting in the potentiation of Smad1 and Smad2 and inhibition of Smad3 [69,70], thereby disrupting homeostasis and causing the development of preeclampsia [69].