The Protective Role of MLCP-Mediated ERM Dephosphorylation in Endotoxin-Induced Lung Injury in Vitro and in Vivo

The goal of this study was to investigate the role of MLC phosphatase (MLCP) in a LPS model of acute lung injury (ALI). We demonstrate that ectopic expression of a constitutively-active (C/A) MLCP regulatory subunit (MYPT1) attenuates the ability of LPS to increase endothelial (EC) permeability. Down-regulation of MYPT1 exacerbates LPS-induced expression of ICAM1 suggesting an anti-inflammatory role of MLCP. To determine whether MLCP contributes to LPS-induced ALI in vivo, we utilized a nanoparticle DNA delivery method to specifically target lung EC. Expression of a C/A MYPT1 reduced LPS-induced lung inflammation and vascular permeability. Further, increased expression of the CS1β (MLCP catalytic subunit) also reduced LPS-induced lung inflammation, whereas the inactive CS1β mutant increased vascular leak. We next examined the role of the cytoskeletal targets of MLCP, the ERM proteins (Ezrin/Radixin/Moesin), in mediating barrier dysfunction. LPS-induced increase in EC permeability was accompanied by PKC-mediated increase in ERM phosphorylation, which was more prominent in CS1β depleted cells. Depletion of Moesin and Ezrin, but not Radixin attenuated LPS-induced increases in permeability. Further, delivery of a Moesin phospho-null mutant into murine lung endothelium attenuated LPS-induced lung inflammation and vascular leak suggesting that MLCP opposes LPS-induced ALI by mediating the dephosphorylation of Moesin and Ezrin

Histone deacetylases in vascular permeability and remodeling associated with acute lung injury

Acute lung injury (ALI) is a severe progressive disorder that arises from a wide range of causes such as toxins or inflammation, resulting in significant morbidity and mortality. There are no effective therapeutic options apart from mechanical ventilation strategies. While the mechanisms that govern the clinically relevant process of increased endothelial cell (EC) permeability and remodeling associated with ALI are under intense investigation, our knowledge of the processes that determine barrier enhancement or preservation are far from completion. Recently, epigenetic mechanisms have emerged as a major regulator of enduring changes in cell behavior and the therapeutic potential of inhibiting histone deacetylases (HDACs) for the treatment of cardiovascular and inflammatory diseases has gained remarkable attention. Although HDACs have been shown to play an important role in regulating EC barrier function, the involved HDAC subtypes and mechanisms remain undefined. Further investigation of the HDAC signaling may provide therapeutic approaches for the prevention and treatment of ALI

Trafficking dynamics of VEGFR1, VEGFR2, and NRP1 in human endothelial cells.

The vascular endothelial growth factor (VEGF) family of cytokines are key drivers of blood vessel growth and remodeling. These ligands act via multiple VEGF receptors (VEGFR) and co-receptors such as Neuropilin (NRP) expressed on endothelial cells. These membrane-associated receptors are not solely expressed on the cell surface, they move between the surface and intracellular locations, where they can function differently. The location of the receptor alters its ability to 'see' (access and bind to) its ligands, which regulates receptor activation; location also alters receptor exposure to subcellularly localized phosphatases, which regulates its deactivation. Thus, receptors in different subcellular locations initiate different signaling, both in terms of quantity and quality. Similarly, the local levels of co-expression of other receptors alters competition for ligands. Subcellular localization is controlled by intracellular trafficking processes, which thus control VEGFR activity; therefore, to understand VEGFR activity, we must understand receptor trafficking. Here, for the first time, we simultaneously quantify the trafficking of VEGFR1, VEGFR2, and NRP1 on the same cells-specifically human umbilical vein endothelial cells (HUVECs). We build a computational model describing the expression, interaction, and trafficking of these receptors, and use it to simulate cell culture experiments. We use new quantitative experimental data to parameterize the model, which then provides mechanistic insight into the trafficking and localization of this receptor network. We show that VEGFR2 and NRP1 trafficking is not the same on HUVECs as on non-human ECs; and we show that VEGFR1 trafficking is not the same as VEGFR2 trafficking, but rather is faster in both internalization and recycling. As a consequence, the VEGF receptors are not evenly distributed between the cell surface and intracellular locations, with a very low percentage of VEGFR1 being on the cell surface, and high levels of NRP1 on the cell surface. Our findings have implications both for the sensing of extracellular ligands and for the composition of signaling complexes at the cell surface versus inside the cell

Zinc-Dependent Histone Deacetylases in Lung Endothelial Pathobiology

A monolayer of endothelial cells (ECs) lines the lumen of blood vessels and, as such, provides a semi-selective barrier between the blood and the interstitial space. Compromise of the lung EC barrier due to inflammatory or toxic events may result in pulmonary edema, which is a cardinal feature of acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS). The EC functions are controlled, at least in part, via epigenetic mechanisms mediated by histone deacetylases (HDACs). Zinc-dependent HDACs represent the largest group of HDACs and are activated by Zn2+. Members of this HDAC group are involved in epigenetic regulation primarily by modifying the structure of chromatin upon removal of acetyl groups from histones. In addition, they can deacetylate many non-histone histone proteins, including those located in extranuclear compartments. Recently, the therapeutic potential of inhibiting zinc-dependent HDACs for EC barrier preservation has gained momentum. However, the role of specific HDAC subtypes in EC barrier regulation remains largely unknown. This review aims to provide an update on the role of zinc-dependent HDACs in endothelial dysfunction and its related diseases. We will broadly focus on biological contributions, signaling pathways and transcriptional roles of HDACs in endothelial pathobiology associated mainly with lung diseases, and we will discuss the potential of their inhibitors for lung injury prevention

Pentose Pathway Activation Is Superior to Increased Glycolysis for Therapeutic Angiogenesis in Peripheral Arterial Disease

Background In endothelial cells (ECs), glycolysis, regulated by PFKFB3 (6‐phosphofructo‐2‐kinase/fructose‐2,6‐biphosphatase, isoform‐3), is the major metabolic pathway for ATP generation. In preclinical peripheral artery disease models, VEGF165a (vascular endothelial growth factor165a) and microRNA‐93 both promote angiogenesis. Methods and Results Mice following hind‐limb ischemia (HLI) and ECs with, and without, hypoxia and serum starvation were examined with, and without, microRNA‐93 and VEGF165a. Post‐HLI perfusion recovery was monitored. EC metabolism was studied using seahorse assay, and the expression and activity of major metabolism genes were assessed. Reactive oxygen species levels and EC permeability were evaluated. C57Bl/6J mice generated a robust angiogenic response to HLI, with ECs from ischemic versus nonischemic muscle demonstrating no increase in glycolysis. Balb/CJ mice generated a poor angiogenic response post‐HLI; ischemic versus nonischemic ECs demonstrated significant increase in glycolysis. MicroRNA‐93‐treated Balb/CJ mice post‐HLI showed better perfusion recovery, with ischemic versus nonischemic ECs showing no increase in glycolysis. VEGF165a‐treated Balb/CJ mice post‐HLI showed no improvement in perfusion recovery with ischemic versus nonischemic ECs showing significant increase in glycolysis. ECs under hypoxia and serum starvation upregulated PFKFB3. In ECs under hypoxia and serum starvation, VEGF165a versus control significantly upregulated PFKFB3 and glycolysis, whereas miR‐93 versus control demonstrated no increase in PFKFB3 or glycolysis. MicroRNA‐93 versus VEGF165a upregulated glucose‐6‐phosphate dehydrogenase expression and activity, activating the pentose phosphate pathway. MicroRNA‐93 versus control increased reduced nicotinamide adenine dinucleotide phosphate and virtually eliminated the increase in reactive oxygen species. In ECs under hypoxia and serum starvation, VEGF165a significantly increased and miR‐93 decreased EC permeability. Conclusions In peripheral artery disease, activation of the pentose phosphate pathway to promote angiogenesis may offer potential therapeutic advantages

The protective role of MLCP-mediated ERM dephosphorylation in endotoxin-induced lung injury in vitro and in vivo

The goal of this study was to investigate the role of MLC phosphatase (MLCP) in a LPS model of acute lung injury (ALI). We demonstrate that ectopic expression of a constitutively-active (C/A) MLCP regulatory subunit (MYPT1) attenuates the ability of LPS to increase endothelial (EC) permeability. Down-regulation of MYPT1 exacerbates LPS-induced expression of ICAM1 suggesting an anti-inflammatory role of MLCP. To determine whether MLCP contributes to LPS-induced ALI in vivo, we utilized a nanoparticle DNA delivery method to specifically target lung EC. Expression of a C/A MYPT1 reduced LPS-induced lung inflammation and vascular permeability. Further, increased expression of the CS1 beta (MLCP catalytic subunit) also reduced LPS-induced lung inflammation, whereas the inactive CS1 beta mutant increased vascular leak. We next examined the role of the cytoskeletal targets of MLCP, the ERM proteins (Ezrin/Radixin/Moesin), in mediating barrier dysfunction. LPS-induced increase in EC permeability was accompanied by PKC-mediated increase in ERM phosphorylation, which was more prominent in CS1 beta-depleted cells. Depletion of Moesin and Ezrin, but not Radixin attenuated LPS-induced increases in permeability. Further, delivery of a Moesin phospho-null mutant into murine lung endothelium attenuated LPS-induced lung inflammation and vascular leak suggesting that MLCP opposes LPS-induced ALI by mediating the dephosphorylation of Moesin and Ezrin.NIH [HL101902]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Previous estimates of VEGFR trafficking parameters are not consistent with HUVEC observations.

A, VEGFR2 and NRP1 trafficking parameters as previously estimated using a computational model and published experimental data from porcine aortic endothelial cells overexpressing human VEGFR2 and NRP1 [16]; and VEGFR1 parameters as then assumed based on VEGFR2 parameters for computational models incorporating all three receptors [33]. B, Model-predicted levels (“Sim”) of VEGFR1, VEGFR2 and NRP1 at steady state on the cell surface and in intracellular endosomes (Rab4a/5a and Rab11a) using the 2015–2017 trafficking parameters based mainly on PAEC data. Experimental data comparisons (“Exp”) for surface receptor levels are for HUVECs from this study. C, Simulations (lines) and experimental data (dots) for whole-cell VEGFR1, VEGFR2, and NRP1 over time following CHX treatment. The schematic shows how CHX inhibition of protein synthesis is represented in the model.</p

S2 Fig -

Simulated dimerization of VEGFR1 (A) and VEGFR2 (B) on HUVECs, by subcellular location, depending on the underlying coupling rate constant. Note that the local coupling rate constant is then adjusted by surface area as noted above; for example, for a base coupling rate constant of 10−4 1/(#/μm2)/s, the local coupling rate at the surface would be 10−7 1/(#/cell)/s. (PDF)</p

Theoretical estimate of the effective affinity (K_d,eff) of NRP1 coupling to VEGFR1, assuming 2:2 binding, compared to the 1:1 binding affinity (K_d), as dependent on the local current unbound NRP1 levels and the 1:1 binding affinity.

Theoretical estimate of the effective affinity (Kd,eff) of NRP1 coupling to VEGFR1, assuming 2:2 binding, compared to the 1:1 binding affinity (Kd), as dependent on the local current unbound NRP1 levels and the 1:1 binding affinity.</p