Inhibiting Adrenomedullin signaling to prevent mammalian brain endothelial cell abnormalities and brain arteriovenous malformation - Project Summary/Abstract Maintenance of neurovascular health is critical for a properly functioning central nervous system (CNS). Neurovascular disorders not only affect the CNS vasculature – accompanying damage to CNS tissue can lead to neurological dysfunction, compromised quality of life, and even death. Brain arteriovenous malformation (AVM) is a human neurovascular disease characterized by enlarged, tortuous, often tangled vessels that shunt blood directly from artery to vein and promote abnormally high-velocity and high-pressure blood flow. Effective clinical treatments for brain AVM are limited to invasive surgical procedures; thus, there is a critical need for prevention and treatment strategies that can be delivered to patients pharmacologically. Recent sequencing data from a mouse model of brain AVM and from human brain AVM tissue independently showed increased Adrenomedullin (encodes a secreted vasodilatory peptide) expression in endothelial cells (ECs) from brain AVM, as compared to controls. This proposal will test whether inhibition of Adrenomedullin signaling, using a small molecule inhibitor in vivo and in vitro, can prevent EC abnormalities and features of brain AVM. We will use in vivo and in vitro approaches to examine whether Adrenomedullin signaling is required for vascular abnormalities associated with Rbpj-deficient brain AVM in mice and for cellular perturbations caused by RBPJ deficiency in cultured human brain ECs. The rationale is as follows: (i-ii) using a genetically inducible mouse model of brain AVM (endothelial deletion of Rbpj from postnatal day (P) 1) and an siRNA based in vitro system for cultured human brain ECs (si-RBPJ), we recently showed that endothelial Rbpj/RBPJ deficiency upregulates Adrenomedullin in both mouse (isolated at P14) and human brain ECs; (iii) we showed that Rbpj occupies chromatin regions mapping to Adrenomedullin, suggesting that Adrenomedullin is a direct binding target of Rbpj; (iv) published sequencing data from another lab showed increased Adrenomedullin expression in human brain AVM tissue. We will test the hypothesis that pharmacological inhibition of Adrenomedullin signaling prevents molecular and cellular abnormalities, including those that contribute to brain AVM, in Rbpj/RBPJ-deficient brain ECs. This hypothesis will be addressed in two specific aims that will determine whether inhibition of Adrenomedullin signaling, via in vivo or in vitro administration of the small-molecule inhibitor NSC16311, (Aim 1) attenuates brain AVM formation in endothelial-Rbpj deficient mice and (Aim 2) prevents cellular abnormalities in cultured, RBPJ-deficient human brain ECs. These studies will advance our long-term research objectives, which are to understand molecular and cellular mechanisms of brain AVM pathogenesis, including how different signaling molecules are involved, and to identify molecular targets that may lead to new, highly effective, pharmacologically based treatments for brain AVM. Our hope is to offer therapeutic options that alleviate symptoms of brain AVM, including neurological complications associated with this neurovascular disease.
