Endothelial Rap1B mediates T-cell exclusion to promote tumor growth: a novel mechanism underlying vascular immunosuppression.

Overcoming vascular immunosuppression: lack of endothelial cell (EC) responsiveness to inflammatory stimuli in the proangiogenic environment of tumors, is essential for successful cancer immunotherapy. The mechanisms through which Vascular Endothelial Growth Factor A(VEGF-A) modulates tumor EC response to exclude T-cells are not well understood. Here, we demonstrate that EC-specific deletion of small GTPase Rap1B, previously implicated in normal angiogenesis, restricts tumor growth in endothelial-specific Rap1B-knockout (Rap1BiΔEC) mice. EC-specific Rap1B deletion inhibits angiogenesis, but also leads to an altered tumor microenvironment with increased recruitment of leukocytes and increased activity of tumor CD8+ T-cells. Depletion of CD8+ T-cells restored tumor growth in Rap1BiΔEC mice. Mechanistically, global transcriptome and functional analyses indicated upregulation of signaling by a tumor cytokine, TNF-α, and increased NF-κB transcription in Rap1B-deficient ECs. Rap1B-deficiency led to elevated proinflammatory chemokine and Cell Adhesion Molecules (CAMs) expression in TNF-α stimulated ECs. Importantly, CAM expression was elevated in tumor ECs from Rap1BiΔEC mice. Significantly, Rap1B deletion prevented VEGF-A-induced immunosuppressive downregulation of CAM expression, demonstrating that Rap1B is essential for VEGF-A-suppressive signaling. Thus, our studies identify a novel endothelial-endogenous mechanism underlying VEGF-A-dependent desensitization of EC to proinflammatory stimuli. Significantly, they identify EC Rap1B as a potential novel vascular target in cancer immunotherapy.

Clinical Spectrum and Outcomes of Neonatal Necrotizing Enterocolitis.

BACKGROUND/AIM: The objective of the study was analysis of risk factors associated with outcome of necrotizing enterocolitis (NEC) in infants in a single-center study. PATIENTS AND METHODS: All consecutive infants hospitalized for NEC over a period of 6 years were retrospectively analyzed for clinical course, infections, treatment and outcome. RESULTS: Out of 76 patients, surgical management was applied in 56 (53 exploratory laparotomy, three initial peritoneal drain placement) and in 20 there was only a conservative approach. Segmental intestinal resection was performed in 41 patients. Survival from NEC in our cohort was 79%. We found that independent adverse risk factors of outcome of newborns and infants with NEC were gut perforation, infection, abdominal wall erythema, and development of acute kidney injury. CONCLUSION: We underline the value of both surgical and conservative approach with careful management in this cohort of patients.

Endothelial Rap1 (Ras-Association Proximate 1) Restricts Inflammatory Signaling to Protect From the Progression of Atherosclerosis.

OBJECTIVE: Small GTPase Rap1 (Ras-association proximate 1) is a novel, positive regulator of NO release and endothelial function with a potentially key role in mechanosensing of atheroprotective, laminar flow. Our objective was to delineate the role of Rap1 in the progression of atherosclerosis and its specific functions in the presence and absence of laminar flow, to better define its role in endothelial mechanisms contributing to plaque formation and atherogenesis. Approach and Results: In a mouse atherosclerosis model, endothelial Rap1B deletion exacerbates atherosclerotic plaque formation. In the thoracic aorta, where laminar shear stress-induced NO is otherwise atheroprotective, plaque area is increased in Athero-Rap1BiΔEC (atherogenic endothelial cell-specific, tamoxifen-inducible Rap1A+Rap1B knockout) mice. Endothelial Rap1 deficiency also leads to increased plaque size, leukocyte accumulation, and increased CAM (cell adhesion molecule) expression in atheroprone areas, whereas vascular permeability is unchanged. In endothelial cells, in the absence of protective laminar flow, Rap1 deficiency leads to an increased proinflammatory TNF-α (tumor necrosis factor alpha) signaling and increased NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) activation and elevated inflammatory receptor expression. Interestingly, this increased signaling to NF-κB activation is corrected by AKTVIII-an inhibitor of Akt (protein kinase B) translocation to the membrane. Together, these data implicate Rap1 in restricting Akt-dependent signaling, preventing excessive cytokine receptor signaling and proinflammatory NF-κB activation. CONCLUSIONS: Via 2 distinct mechanisms, endothelial Rap1 protects from the atherosclerosis progression in the presence and absence of laminar flow; Rap1-stimulated NO release predominates in laminar flow, and restriction of proinflammatory signaling predominates in the absence of laminar flow. Our studies provide novel insights into the mechanisms underlying endothelial homeostasis and reveal the importance of Rap1 signaling in cardiovascular disease.

Integration of Rap1 and Calcium Signaling.

Ca2+ is a universal intracellular signal. The modulation of cytoplasmic Ca2+ concentration regulates a plethora of cellular processes, such as: synaptic plasticity, neuronal survival, chemotaxis of immune cells, platelet aggregation, vasodilation, and cardiac excitation-contraction coupling. Rap1 GTPases are ubiquitously expressed binary switches that alternate between active and inactive states and are regulated by diverse families of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Active Rap1 couples extracellular stimulation with intracellular signaling through secondary messengers-cyclic adenosine monophosphate (cAMP), Ca2+, and diacylglycerol (DAG). Much evidence indicates that Rap1 signaling intersects with Ca2+ signaling pathways to control the important cellular functions of platelet activation or neuronal plasticity. Rap1 acts as an effector of Ca2+ signaling when activated by mechanisms involving Ca2+ and DAG-activated (CalDAG-) GEFs. Conversely, activated by other GEFs, such as cAMP-dependent GEF Epac, Rap1 controls cytoplasmic Ca2+ levels. It does so by regulating the activity of Ca2+ signaling proteins such as sarcoendoplasmic reticulum Ca2+-ATPase (SERCA). In this review, we focus on the physiological significance of the links between Rap1 and Ca2+ signaling and emphasize the molecular interactions that may offer new targets for the therapy of Alzheimer's disease, hypertension, and atherosclerosis, among other diseases.

[Iatrogenic pleuropneumonia complicating central venous cannulation in a very low birth weight infant]. / Jatrogenna pleuropneumonia jako powilkanie cewnikowania zyl centralnych u noworodka.

BACKGROUND: Central venous cannulation is necessary for long-term parenteral nutrition in premature infants. Peripherally inserted long catheters are commonly used in these patients but even this relatively simple technique can end in serious complications. We present a case in which perforation of the vena cava and migration of the catheter to the intrapleural space resulted in multiple organ failure and death. CASE REPORT: A 700 g bw. infant, born at 28 weeks of gestation, was referred to our centre because of suspected bowel perforation. In the referring hospital, the infant had a central venous catheter inserted peripherally. The catheter migrated to the right intrapleural space, and parenteral formula was delivered over several hours to the right pleura, resulting in hydrothorax with serious compression of the lung and atelectasis. Emergency laparotomy did not reveal any pathology and a chest tube was inserted into the right pleura; the effusion fluid contained a large number fat particles. The child's condition worsened and he died 16 days after surgery because of multiple organ failure and sepsis. CONCLUSION: Accidental migrations of central venous catheters to the pleural space have been described by many authors. It can result in severe pneumonia, cardiac tamponade or sepsis and is often fatal. We conclude that central venous catheters in premature infants should be inserted under ultrasonography or fluoroscopy. Catheters should never be forced along vessels; their size ought to be adjusted to age, and a free outflow of blood should be obtained before they are used.

[Iatrogenic pleuropneumonia as a complication of nutritional treatment of preterm-delivery newborn]. / Jatrogenna pleuropneumonia jako powiklanie leczenia zywieniowego u noworodka urodzonego przedwczesnie.

Our study presents a case of pleuropneumonia caused by a leak of nutritional formula to pleural cavity, which was caused by perforation of the oesophagus. The child was born in 28 hbd with 1400 g birth weight and was fed with mother's milk by a nasogastric tube. From day 11 of life general state of the neonate worsened and on chest X-ray the contrast showed leaking into the right pleural cavity and the end of gastric tube was seen in the right lung area. With this diagnosis the child was admitted to the University Hospital in Bydgoszcz. The child was conservatively treated and in two contrast X-ray examinations there was no pathology of the oesophagus. CT of chest showed pleural empyema which was repeatedly punctured. On the 19th day of hospitalization thoracotomy with resection of interior pulmomery lobe was performed. From the 14th day after surgery, the child was again enterally fed and in good general state. He was discharged on the 51st day of hospitalization. This case should pay our attention to the fact that respiratory distress syndrome of preterm-delivery newborns may be caused by iatrogenic proceedings not only infections and lack of surfactant. Some complications can be accomplished with the nutrition treatment in every dimension.