Disturbed flow-mediated PKCζ–PIASy association is critical for p53 SUMOylation and induces p53 nuclear export and endothelial cell apoptosis.

Cardiac fibroblasts become activated and differentiate to smooth muscle-like myofibroblasts in response to hypertension and myocardial infarction (MI), resulting in extracellular matrix (ECM) remodeling, scar formation and impaired cardiac function. cAMP and cGMP-dependent signaling have been implicated in cardiac fibroblast activation and ECM synthesis. Dysregulation of cyclic nucleotide phosphodiesterase (PDE) activity/expression is also associated with various diseases and several PDE inhibitors are currently available or in development for treating these pathological conditions. The objective of this study is to define and characterize the specific PDE isoform that is altered during cardiac fibroblast activation and functionally important for regulating myofibroblast activation and ECM synthesis. We have found that Ca2+/calmodulin-stimulated PDE1A isoform is specifically induced in activated cardiac myofibroblasts stimulated by Ang II and TGF-β in vitro as well as in vivo within fibrotic regions of mouse, rat, and human diseased hearts. Inhibition of PDE1A function via PDE1-selective inhibitor or PDE1A shRNA significantly reduced Ang II or TGF-β-induced myofibroblast activation, ECM synthesis, and pro-fibrotic gene expression in rat cardiac fibroblasts. Moreover, the PDE1 inhibitor attenuated isoproterenol-induced interstitial fibrosis in mice. Mechanistic studies revealed that PDE1A modulates unique pools of cAMP and cGMP, predominantly in perinuclear and nuclear regions of cardiac fibroblasts. Further, both cAMP-Epac-Rap1 and cGMP-PKG signaling was involved in PDE1A-mediated regulation of collagen synthesis. These results suggest that induction of PDE1A plays a critical role in cardiac fibroblast activation and cardiac fibrosis, and targeting PDE1A may lead to regression of the adverse cardiac remodeling associated with various cardiac diseases.

Conflict of interest: JT is a cofounder of Principia Biopharma, which has licensed the p90RSK inhibitor FMK-MEA.

Background: The incidence of cardiovascular disease (CVD) is higher in HIV + patients than it is in the average population, and combination antiretroviral therapy (cART) is a recognized risk factor for CVD. However, the molecular mechanisms that link cART and CVD are currently unknown. Our study explores the role of the activation of p90RSK, a reactive oxygen species (ROS)-sensitive kinase, in engendering senescent phenotype in macrophages and accelerating atherogenesis in patients undergoing cART. Methods: Peripheral whole blood from cART-treated HIV + individuals and non-treated HIV − individuals was treated with H 2 O 2 (200 μM) for 4 minutes, and p90RSK activity in CD14 + monocytes was measured. Plaque formation in the carotids were also analyzed in these individuals. Macrophage senescence was determined by evaluating their efferocytotic ability, antioxidation-related molecule expression, telomere length, and inflammatory gene expression. The involvement of p90RSK-NRF2 signaling in cART-induced senescence was assessed by p90RSK specific inhibitor (FMK-MEA) or dominant negative p90RSK (DN-p90RSK), and NRF2 activator (NRF2A). Further, the severity of atherosclerosis was determined in myeloid cell-specific wild type and DN-p90RSK transgenic mice. Results: Monocytes from HIV + patients exhibited higher levels of p90RSK activity and were also more sensitive to ROS than monocytes from HIV − individuals. A multiple linear regression analysis involving cART, Reynolds CV risk score, and basal p90RSK activity revealed that cART and basal p90RSK activity were the two significant determinants of plaque formation. Many of the antiretroviral drugs individually activated p90RSK, which simultaneously triggered all components of the macrophage senescent phenotype. cART inhibited antioxidant response element reporter activity via ERK5 S496 phosphorylation. NRF2A reversed the H 2 O 2-induced over-activation of p90RSK in cART-treated macrophages by countering the induction of senescent phenotype. Lastly, the data obtained from our gain-or loss-of-function mice conclusively showed the crucial role of p90RSK in inducing senescent phenotype in macrophages and atherogenesis. Conclusions: cART increased monocyte/macrophage sensitivity to ROS in HIV + individuals by suppressing NRF2-ARE activity via p90RSK-mediated ERK5 S496 phosphorylation, which coordinately elicited senescent phenotypes and pro-inflammatory responses. As such, our report underscores the importance of p90RSK regulation in monocytes/macrophages as a viable biomarker and therapeutic target for preventing CVD, especially in HIV + patients treated with cART.

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