MOLECULAR MECHANISM OF PDE3A SIGNALING IN HYPERTENSION WITH BRACHYDACTYLY (HTNB)

Objective: Hypertension with brachydactyly (HTNB) is a syndrome characterized by progressive hypertension, brachydactyly type E, and blood vessel hyperplasia. HTNB is caused by mutations in the gene encoding phosphodiesterase 3A (PDE3A). The mutations cause hypertension by increasing vascular smooth muscle cell (VSMC) proliferation and compromising relaxation of second-order mesenteric arteries. cAMP signaling occurs in defined cellular compartments where PDE3A hydrolyzes and thereby limits cAMP levels. The objective of this project is the elucidation of molecular mechanism of mutant PDE3A-induced hypertension to identify novel therapeutic strategies targeting PDE3A signaling compartments for the treatment of hypertension. Design and method: Experiments were performed with three models: thoracic aorta and second-order mesenteric artery VSMCs from wild-type and rat HTNB models, and VSMCs differentiated from human induced pluripotent stem cells carrying PDE3A mutations that cause HTNB (iPSC-VSMCs). RNA-seq, RT-qPCR and Western blotting were used to validate gene and protein expression differences of candidates. Intracellular Ca2+ signaling changes were analyzed by Ca2+ imaging. Results: RNA-seq and RT-qPCR results showed that several genes were differentially expressed between wild-type and HTNB VSMCs. For example, compared with wild-type, PDE3A expression was downregulated in blood vessels derived from HTNB rats, whether derived from thoracic aorta or second-order mesenteric arteries. The protein expression of regulatory subunits of protein kinase A (PKA) was decreased in the second-order mesenteric arteries of HTNB models but there was no significant change in the thoracic aorta. Ca2+ imaging of iPSC-VSMCs revealed greater contractility in cells carrying PDE3A mutations. Conclusions: Mutant PDE3A signaling may be a starting point for an innovative, PDE3A compartment-specific pharmacological concept for the treatment of hypertension.