TGF-B Activates eNOS and Regulates Vasomotor Function by an endoglin-and Alk-1 Dependent Mechanism


Mechanism of Disease $50,000 Research Grant Award

Dr. Michelle Letarte
Toronto Hospital for Sick Children, Canada



According to Dr. Letarte, “The genes mutated in HHT are endoglin and ALK1. The products of these genes, the endoglin and ALK1 proteins, are receptors for a potent factor called TGF-ß. We now have recent evidence that this TGF-ß factor may control the dilatation of blood vessels. We hypothesize that this normal process of regulation of vessel dilatation by TGF-ß is defective in HHT and can eventually lead to the clinical manifestations of disease. We will use the mouse models of HHT1 and HHT2 and test blood vessels isolated from these mice to see how they respond to TGF-ß compared to those of normal mice. We will then identify the molecules and pathways responsible for the effects of TGF-ß in cells from mice and patients with HHT. Our experiments should provide a better understanding of the mechanisms responsible for the early events in the disease and pave the way to novel therapeutic interventions.

Research study objectives:

  • To measure the effects of TGF-b1 on eNOS-dependent vasodilation in small resistance arteries isolated from Eng+/- (HHT1 model) and control mice, using a perfusion myograph.
  • To test whether TGF-b1 regulation of eNOS-dependent vasodilation is similarly altered in HHT2. Vasodilation will be measured on small resistance arteries from alk1+/- and control mice.
  • To characterize the mechanism of TGF-b1-induced eNOS activation in murine endothelial cells (normal and deficient endoglin) and in human umbilical vein endothelial cells (HUVEC) from newborns with a molecular diagnostic of HHT1 or HHT2. We will measure the effects of TGF-b1 on eNOS enzymatic activity, eNOS-Hsp90 association, and eNOS phosphorylation using specific anti-phospho-eNOS antibodies. We will test for the association of ALK1 with eNOS and/or Hsp90 and see if its overexpression in endothelial cells amplifies the activation of eNOS by TGF-b1.


Dr. Letarte states, “We are very grateful to the Cure HHT for awarding us this grant and thank all of you for your kind donations. Our daily efforts are devoted to understanding the underlying mechanisms of HHT through basic research. We could not do it without your generous financial and moral support.”