Phosphodiesterase 2 Mediates Redox-Sensitive Endothelial Cell Proliferation and Angiogenesis by Thrombin via Rac1 and NADPH Oxidase 2

Abstract

Abstract-Cyclic nucleotide phosphodiesterases (PDEs) control the levels of the second messengers cAMP and cGMP in many cell types including endothelial cells. Although PDE2 has the unique property to be activated by cGMP but to hydrolyze cAMP, its role in endothelial function is only poorly understood. Reactive oxygen species (ROS) have been recognized as signaling molecules controlling many endothelial functions. We thus investigated whether PDE2 would link to ROS generation and proliferative responses in human umbilical vein endothelial cells in response to thrombin. Thrombin stimulated the GTPase Rac1, known to activate NADPH oxidases, and enhanced ROS formation, whereas PDE2 inhibition or depletion by short hairpin (sh)RNA prevented these responses. Similar observations were made with 8-Br-cGMP or atrial natriuretic peptide. In agreement, thrombin elevated cGMP but decreased cAMP levels, whereas db-cAMP or forskolin diminished Rac1 activity and ROS production. Subsequently, PDE2 overexpression activated Rac1, increased ROS generation, and enhanced proliferation and in vitro capillary formation. These responses were not observed in the presence of inactive Rac1 or shRNA against the NADPH oxidase subunit NOX2. Inhibition or depletion of PDE2 also prevented thrombin-induced proliferation and capillary formation. Importantly, downregulation of PDE2 by lentiviral shRNA or PDE2 inhibition prevented vessel sprouting from mouse aortic explants and in vivo angiogenesis in a mouse model, respectively. In summary, PDE2 promotes activation of NADPH oxidase-dependent ROS production and subsequent endothelial proliferation and angiogenesis. Targeting PDE2 may provide a new therapeutic approach in diseases associated with endothelial dysfunction, oxidative stress, vascular proliferation, and angiogenesis.

Knockdown of lung phosphodiesterase 2A attenuates alveolar inflammation and protein leak in a two-hit mouse model of acute lung injury

“…These results serve to confirm the emerging idea that PDE2A is a key proinflammatory enzyme that enhances the cellular and humoral inflammation associated with common forms of tissue injury (14,41,44,52).…”

“…cAMP is a key defensive signaling molecule in the injured lung, opposing LPS-and ROS-mediated cell death, preserving endothelial and epithelial intercellular junctions, and enhancing edema clearance (16,21,23,26,28,38). For example, increased PDE2A expression in human umbilical vein endothelium was recently reported to increase thrombin-induced NADPH oxidase activity and ROS production by a loss of cAMP inhibition of rac1 activity (14). cAMP also serves as a critical regulator of lung macrophage function suppressing cytokine and chemokine production as well as iNOS expression (40).…”

Hyaluronic Acid Promotes Angiogenesis by Inducing RHAMM-TGFβ Receptor Interaction via CD44-PKCδ

“…VEGF activates Rac1 via vav-2 (Garrett et al, 2007) and activation of Rac1 is involved in the hypoxia-induced production of angiogenesis-promoting factors (Xue et al, 2006). Thrombin-induced angiogenesis requires Rac1 and NADPH oxidase 2 (Diebold et al, 2009). Inhibition of Rac1 reduces VEGF-induced tyrosine phosphorylation of VEGFR-2 (Ushio- Fukai et al, 2002).…”

Rho GTPases, oxidation, and cell redox control

“…101 In particular, Rac1 and Rac2 are involved in the activation of NOX1, NOX2, and NOX3. [101][102][103] This function of Rac, first demonstrated in neutrophils and other phagocytic cells and later expanded to non-phagocytic cells, 104 is important in both physiological 105 and pathophysiological [106][107][108] settings. Rac1 has been shown to associate with many enzymes necessary for maintaining redox homeostasis in cells.…”

“…In contrast to the vast amount of literature documenting Rac-mediated ROS production, [101][102][103][104][105][106][107][108] relatively few studies have investigated the role of ROS/RNS in regulating Rac activity. Nagase et al have demonstrated ROS-mediated activation of Rac1 in rat cardiomyocytes.…”