Publications

Higher organisms rely on a closed cardiovascular circulatory system with blood vessels supplying vital nutrients and oxygen to distant tissues. Not surprisingly, vascular pathologies rank among the most life-threatening diseases. At the crux of most of these vascular pathologies are (dysfunctional) endothelial cells (ECs), the cells lining the blood vessel lumen. ECs display the remarkable capability to switch rapidly from a quiescent state to a highly migratory and proliferative state during vessel sprouting. This angiogenic switch has long been considered to be dictated by angiogenic growth factors (eg, vascular endothelial growth factor) and other signals (eg, Notch) alone, but recent findings show that it is also driven by a metabolic switch in ECs. Furthermore, these changes in metabolism may even override signals inducing vessel sprouting. Here, we review how EC metabolism differs between the normal and dysfunctional/diseased vasculature and how it relates to or affects the metabolism of other cell types contributing to the pathology. We focus on the biology of ECs in tumor blood vessel and diabetic ECs in atherosclerosis as examples of the role of endothelial metabolism in key pathological processes. Finally, current as well as unexplored EC metabolism-centric therapeutic avenues are discussed.

Background— The cell-associated proteoglycan syndecan-1 (Synd1) closely regulates inflammation and cell-matrix interactions during wound healing and tumorigenesis. The present study investigated whether Synd1 may also regulate cardiac inflammation, matrix remodeling, and function after myocardial infarction (MI). Methods and Results— First, we showed increased protein and mRNA expression of Synd1 from 24 hours on, reaching its maximum at 7 days after MI and declining thereafter. Targeted deletion of Synd1 resulted in increased inflammation and accelerated, yet functionally adverse, infarct healing after MI. In concordance, adenoviral gene expression of Synd1 protected against exaggerated inflammation after MI, mainly by reducing transendothelial adhesion and migration of leukocytes, as shown in vitro. Increased inflammation in the absence of Synd1 resulted in increased monocyte chemoattractant protein-1 expression, increased activity of matrix metalloproteinase-2 and -9, and decreased activity of tissue transglutaminase, associated with increased collagen fragmentation and disorganization. Exaggerated inflammation and adverse matrix remodeling in the absence of Synd1 increased cardiac dilatation and impaired systolic function, whereas gene overexpression of Synd1 reduced inflammation and protected against cardiac dilatation and failure. Conclusions— Increased expression of Synd1 in the infarct protects against exaggerated inflammation and adverse infarct healing, thereby reducing cardiac dilatation and dysfunction after MI in mice.

Abstract The transforming and tumor growth–promoting properties of Axl, a member of the Tyro3, Axl, and Mer (TAM) family of receptor tyrosine kinases (TAMRs), are well recognized. In contrast, little is known about the role of the TAMR ligand growth arrest–specific gene 6 (Gas6) in tumor biology. By using Gas6-deficient (Gas6−/−) mice, we show that bone marrow–derived Gas6 promotes growth and metastasis in different experimental cancer models, including one resistant to vascular endothelial growth factor inhibitors. Mechanistic studies reveal that circulating leukocytes produce minimal Gas6. However, once infiltrated in the tumor, leukocytes up-regulate Gas6, which is mitogenic for tumor cells. Consistent herewith, impaired tumor growth in Gas6−/− mice is rescued by transplantation of wild-type bone marrow and, conversely, mimicked by transplantation of Gas6−/− bone marrow into wild-type hosts. These findings highlight a novel role for Gas6 in a positive amplification loop, whereby tumors promote their growth by educating infiltrating leukocytes to up-regulate the production of the mitogen Gas6. Hence, inhibition of Gas6 might offer novel opportunities for the treatment of cancer.

<b>Rationale:</b> Acute respiratory distress syndrome is defined by the presence of systemic hypoxia and consequent on disordered neutrophilic inflammation. Local mechanisms limiting the duration and magnitude of this neutrophilic response remain poorly understood. <b>Objectives:</b> To test the hypothesis that during acute lung inflammation tissue production of proresolution type 2 cytokines (IL-4 and IL-13) dampens the proinflammatory effects of hypoxia through suppression of HIF-1α (hypoxia-inducible factor-1α)-mediated neutrophil adaptation, resulting in resolution of lung injury. <b>Methods:</b> Neutrophil activation of IL4Ra (IL-4 receptor α) signaling pathways was explored <i>ex vivo</i> in human acute respiratory distress syndrome patient samples, <i>in vitro</i> after the culture of human peripheral blood neutrophils with recombinant IL-4 under conditions of hypoxia, and <i>in vivo</i> through the study of IL4Ra-deficient neutrophils in competitive chimera models and wild-type mice treated with IL-4. <b>Measurements and Main Results:</b> IL-4 was elevated in human BAL from patients with acute respiratory distress syndrome, and its receptor was identified on patient blood neutrophils. Treatment of human neutrophils with IL-4 suppressed HIF-1α-dependent hypoxic survival and limited proinflammatory transcriptional responses. Increased neutrophil apoptosis in hypoxia, also observed with IL-13, required active STAT signaling, and was dependent on expression of the oxygen-sensing prolyl hydroxylase PHD2. <i>In vivo</i>, IL-4Ra-deficient neutrophils had a survival advantage within a hypoxic inflamed niche; in contrast, inflamed lung treatment with IL-4 accelerated resolution through increased neutrophil apoptosis. <b>Conclusions:</b> We describe an important interaction whereby IL4Rα-dependent type 2 cytokine signaling can directly inhibit hypoxic neutrophil survival in tissues and promote resolution of neutrophil-mediated acute lung injury.

&lt;div&gt;Abstract&lt;p&gt;Protein phosphatase 2A (PP2A) complexes counteract many oncogenic kinase pathways. In cancer cells, PP2A function can be compromised by several mechanisms, including sporadic mutations in its scaffolding A and regulatory B subunits or more frequently through overexpression of cellular PP2A inhibitors. Here, we identify a novel genetic mechanism by which PP2A function is recurrently affected in human cancer, involving haploinsufficiency of &lt;i&gt;PPP2R4&lt;/i&gt;, a gene encoding the cellular PP2A activator PTPA. Notably, up to 70% of cancer patients showed a heterozygous deletion or missense mutations in &lt;i&gt;PPP2R4&lt;/i&gt;. Cancer-associated PTPA mutants exhibited decreased abilities to bind the PP2A-C subunit or activate PP2A and failed to reverse the tumorigenic phenotype induced by PTPA suppression, indicating they function as null alleles. In &lt;i&gt;Ppp2r4&lt;/i&gt; gene-trapped (gt) mice showing residual PTPA expression, total PP2A activity and methylation were reduced, selectively affecting specific PP2A holoenzymes. Both PTPA&lt;sup&gt;gt/gt&lt;/sup&gt; and PTPA&lt;sup&gt;+/gt&lt;/sup&gt; mice showed higher rates of spontaneous tumors, mainly hematologic malignancies and hepatocellular adenomas and carcinomas. These tumors exhibited increased c-Myc phosphorylation and increased Wnt or Hedgehog signaling. We observed a significant reduction in lifespan in PTPA&lt;sup&gt;+/gt&lt;/sup&gt; mice compared with wild-type mice. In addition, chemical-induced skin carcinogenesis was accelerated in PTPA&lt;sup&gt;+/gt&lt;/sup&gt; compared with wild-type mice. Our results provide evidence for &lt;i&gt;PPP2R4&lt;/i&gt; as a haploinsufficient tumor suppressor gene, defining a high-penetrance genetic mechanism for PP2A inhibition in human cancer. &lt;i&gt;Cancer Res; 77(24); 6825–37. ©2017 AACR&lt;/i&gt;.&lt;/p&gt;&lt;/div&gt;

NIPP1 (nuclear inhibitor of protein phosphatase 1) is a ubiquitously expressed nuclear scaffold protein that has been implicated in both transcription and RNA processing. Among its protein ligands are a protein kinase, a protein phosphatase, two splicing factors, and a transcriptional regulator, and the binding of these proteins to NIPP1 is tightly regulated by phosphorylation. To study the function of NIPP1 in vivo, we have used homologous recombination to generate mice that are deficient in NIPP1. NIPP1(-/+) mice developed normally. However, NIPP1(-/-) embryos showed severely retarded growth at embryonic day 6.5 (E6.5) and were resorbed by E8.5. This early embryonic lethality was not associated with increased apoptosis but correlated with impaired cell proliferation. Blastocyst outgrowth experiments and the RNA interference-mediated knockdown of NIPP1 in cultured cells also revealed an essential role for NIPP1 in cell proliferation. In further agreement with this function, no viable NIPP1(-/-) cell lines were obtained by derivation of embryonic stem (ES) cells from blastocysts of NIPP1(-/+) intercrosses or by forced homogenotization of heterozygous ES cells at high concentrations of Geneticin. We conclude that NIPP1 is indispensable for early embryonic development and cell proliferation.

Reduced VEGF levels cause motor neuron degeneration in mice, whereas VEGF delivery exerts therapeutic effects in ALS mouse models, at least partly by direct neurotrophic effects. VEGF also exerts potent therapeutic effects in chemotherapy-induced sensory neuropathies, which have been attributed to its vessel growth and perfusion-promoting effects.\nTo test whether the therapeutic effect of VEGF is due to a direct effect on sensory nerves, VEGF was subplantarly delivered to rats with Taxol-induced neuropathy. VEGF treatment significantly reduced sensory neuropathy comparable to archetypical growth factors. VEGF also protected sensory neurons in vitro against Taxol induced tubulin hyperacetylation, neuronal stress and cell death.\nMice overexpressing the VEGF-receptor (VEGFR) Flk1 in neurons developed a milder sensory deficit after Taxol challenge, whereas mice overexpressing a dominant-negative Flk1 in neurons performed worse and failed to respond to VEGF delivery. Also in vitro, DRG neurons with Flk1 overexpression were more protected against Taxol induced hyperacetylation and neuronal stress. The positive effects of VEGF were counteracted by TSA and Tubacin, which suggests that VEGF protects sensory neurons in these Taxol models at least partly via HDAC6.\nDelivery of VEGFR inhibitors, an anti-angiogenic treatment for cancer, to WT mice induced mechanical allodynia. Furthermore, when delivered to mice with Taxol-induced neuropathy, VEGFR inhibition aggravated the sensory deficits. Overall, these data indicate that VEGF exerts direct neurotrophic effects on sensory neurons through its Flk1 receptor and that VEGFR-inhibitors should be applied with care.