Abstract 15153: Inhibition of the Tumor Suppressor Wwox Expression Alters Mitochondrial Dynamics in PASMC

Introduction: Pulmonary arterial hypertension (PAH) contributes to the morbidity and mortality of several patients with different pulmonary and cardiac diseases. Among other factors, the pathogenesis of PAH involves exaggerated pulmonary artery smoot muscle cell (PASMC) hyperproliferation, resistance to apoptosis and energy metabolism shift associated with alterations in mitochondrial metabolism and dynamics. The WW domain-containing oxidoreductase gene ( WWOX ) is a tumor suppressor gene that has the ability to interact with a large number of proteins, exerting its activity through a wide variety of molecular actions in specific cells. WWOX loss affects cell proliferation, motility, and deregulates expression of genes involved in cell cycle regulation, metabolism, and DNA damage in a variety of cancers. Considering that a similar phenotype is observed in cancer cells and PAH, we sought to investigate whether the loss of WWOX in PASMC is associated abnormalities of mitochondrial metabolism and dynamics in PAH. Methods and Results: In PASMC, inhibition of WWOX expression by short-interfering RNA (siRNA) decreased oxygen consumption by 30% when compared with siRNA control. Dysregulation of mitochondrial bioenergetics in WWOX-silenced PASMC was attributed to modulation of the oxidative state of mitochondrial electron transport chain proteins, showing that succinate dehydrogenase (SDH)(complex II) expression decreased by 15% in relation to siRNA control. JC-1 and mitotraker red CMXROS staining demonstrated that WWOX- silenced PASMC had hyperpolarized and fragmented mitochondria that generated more reactive oxygen species than the control. Changes in mitochondrial dynamics were detected with increased phosphorylation levels of the fission protein, dynamin-related protein 1 (DRP-1) and, decreased Mitofusin 2 and 1 protein levels, positive regulators of mitochondrial fusion. Conclusion: Loss of WWOX expression causes changes in PASMC mitochondrial metabolism and dynamics stimulating these cells to use different resources as a way to reprogram their metabolism and ensure their survival. These alterations may contribute, for example, to the stimulation of vascular remodeling, which consequently promote the pathogenesis of PAH.