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Inflammasome activation is of central importance for the process of generation of overwhelming inflammatory response and the pathogenesis of sepsis. The intrinsic molecular mechanism for controlling inflammasome activation is still poorly understood. Here we investigated the role of p120-catenin expression in macrophages in regulating nucleotide-binding oligomerization domain (NOD) and leucine-rich repeat (LRR)- and pyrin domain-containing proteins 3 (NLRP3) inflammasome activation. Depletion of p120-catenin in murine bone marrow-derived macrophages enhanced caspase-1 activation and secretion of active interleukin (IL)-1β in response to ATP stimulation following LPS priming. Coimmunoprecipitation analysis showed that p120-catenin deletion promoted NLRP3 inflammasome activation by accelerating the assembly of the inflammasome complex comprised of NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and pro-caspase-1. Depletion of p120-catenin also increased the production of mitochondrial reactive oxygen species. Pharmacological inhibition of mitochondrial reactive oxygen species nearly completely abolished NLRP3 inflammasome activation, caspase-1 activation, and the production of IL-1β in p120-catenin-depleted macrophages. Furthermore, p120-catenin ablation significantly disrupted mitochondrial function, evidenced by decreased mitochondrial membrane potential and lower production of intracellular ATP. In alveolar macrophage-depleted mice challenged with cecal ligation and puncture, pulmonary transplantation of p120-catenin-deficient macrophages dramatically enhanced the accumulation of IL-1β and IL-18 in bronchoalveolar lavage fluid. These results demonstrate that p120-catenin prevents NLRP3 inflammasome activation in macrophages by maintaining mitochondrial homeostasis and reducing the production of mitochondrial reactive oxygen species in response to endotoxin insult. Thus, inhibition of NLRP3 inflammasome activation by stabilization of p120-catenin expression in macrophages may be a novel strategy to prevent an uncontrolled inflammatory response in sepsis.

Patients with type 2 diabetes exhibit severe impairments in insulin signalling in the brain and are five times more likely to develop Alzheimer’s disease. However, what leads to these impairments is not fully understood. Here, we show reduced expression of endothelial cell caveolin-1 (Cav-1) in the db/db (Leprdb) mouse model of type 2 diabetes. This reduction correlated with alterations in insulin receptor expression and signalling in brain microvessels as well as brain parenchyma. These findings were recapitulated in the brains of endothelial cell-specific Cav-1 knock-out (Tie2Cre; Cav-1fl/fl) mice. Lack of Cav-1 in endothelial cells led to reduced response to insulin as well as reduced insulin uptake. Furthermore, we observed that Cav-1 was necessary for the stabilization of insulin receptors in lipid rafts. Interactome analysis revealed that insulin receptor interacts with Cav-1 and caveolae-associated proteins, insulin-degrading enzyme and the tight junction protein Zonula Occludence-1 in brain endothelial cells. Restoration of Cav-1 in Cav-1 knock-out brain endothelial cells rescued insulin receptor expression and localization. Overall, these results suggest that Cav-1 regulates insulin signalling and uptake by brain endothelial cells by modulating IR-α and IR-β localization and function in lipid rafts. Furthermore, depletion of endothelial cell–specific Cav-1 and the resulting impairment in insulin transport leads to alteration in insulin signalling in the brain parenchyma of type 2 diabetics.

Mechanical ventilation is a life-sustaining therapy for patients with respiratory failure but can cause further lung damage known as ventilator-induced lung injury (VILI). However, the intrinsic molecular mechanisms underlying recovery of VILI remain unknown. Phagocytosis of apoptotic cells (also known as efferocytosis) is a key mechanism orchestrating successful resolution of inflammation. Here we show the positive regulation of macrophage Toll-like receptor (TLR) 4 in efferocytosis and resolution of VILI. Mice were depleted of alveolar macrophages and then subjected to injurious ventilation (tidal volume, 20 mL/kg) for 4 h. On day 1 after mechanical ventilation, Tlr4+/+ or Tlr4−/− bone marrow-derived macrophages (BMDMs) were intratracheally administered to alveolar macrophage-depleted mice. We observed that mice depleted of alveolar macrophages exhibited defective resolution of neutrophilic inflammation, exuded protein, lung edema, and lung tissue injury after ventilation, whereas these delayed responses were reversed by administration of Tlr4+/+ BMDMs. Importantly, these proresolving effects by Tlr4+/+ BMDMs were abolished in mice receiving Tlr4−/− BMDMs. The number of macrophages containing apoptotic cells or bodies in bronchoalveolar lavage fluid was much less in mice receiving Tlr4−/− BMDMs than that in those receiving Tlr4+/+ BMDMs. Macrophage TLR4 deletion facilitated a disintegrin and metalloprotease 17 maturation and enhanced Mer cleavage in response to mechanical ventilation. Heat shock protein 70 dramatically increased Mer tyrosine kinase surface expression, phagocytosis of apoptotic neutrophils, and rescued the inflammatory phenotype in alveolar macrophage-depleted mice receiving Tlr4+/+ BMDMs, but not Tlr4−/− BMDMs. Our results suggest that macrophage TLR4 promotes resolution of VILI via modulation of Mer-mediated efferocytosis.

CXCL10 is an interferon-inducible chemokine that can recruit CXCR3+leukocytes to the central nervous system, leading to neuroinflammation, demyelination, and neuronal losses. How CXCL10 promotes leukocyte extravasation and diapedesis across the blood-brain barrier – formed by brain endothelial cells – is poorly understood. Here, we report that CXCL10 mediates CD4+ T cell migration through the brain endothelial cell cytoplasm (transcellular), but not cell-cell junctions (paracellular), via the vesicular trafficking protein Caveolin-1. Caveolin-1 promotes CXCL10 aggregation into cytoplasmic stores in brain endothelial cellsin vitroto provide the local, high concentration necessary for recruitment of CXCR3+ leukocytes. This process also requires LFA-1 activity. In the absence of Caveolin-1, endothelial CXCL10 is secreted, and the local signaling cues are lost. Consistent with ourin vitrodata, genetic ablation of Caveolin-1 in endothelial cells reduces the severity of active experimental autoimmune encephalomyelitis (EAE), a murine model for multiple sclerosis, by decreasing the infiltration of CXCR3+ T cells into the CNS. Moreover, loss of Caveolin-1 protects against the adoptive transfer of autoreactive T cells. Our findings establish a novel mechanism by which brain endothelial cells utilize Caveolin-1 dependent CXCL10 intracellular stores to license T cells for transcellular migration across the blood-brain barrier.

Chronic, non-healing skin wounds such as diabetic foot ulcers (DFUs) are common in patients with type 2 diabetes. Here, we investigated the role of chemokine CCL28 and its receptor CCR10 in downregulation of endothelial nitric oxide synthase (eNOS) in association with delayed skin wound healing in the db/db mouse model of type 2 diabetes. We observed reduced eNOS expression and elevated CCL28/CCR10 levels in dorsal skin of db/db mice and subdermal leg biopsies from human subjects with type 2 diabetes. Further interrogation revealed that overexpression of CCR10 reduced eNOS expression, NO bioavailability, and tube formation of human dermal microvascular endothelial cells (HDMVECs) in vitro which was recapitulated in mouse dorsal skin. In addition, incubation of HDMVECs with CCL28 led to internalization of the CCR10/eNOS complex and co-localization with lysosome-associated membrane protein-1. Finally, topical application of myristoylated CCR10 binding domain 7 amino acid (Myr-CBD7) peptide prevented CCR10-eNOS interaction and subsequent eNOS downregulation, enhanced eNOS/NO levels, eNOS/VEGF-R2+ microvessel density, and blood perfusion, reduced inflammatory cytokine levels, and importantly, decreased wound healing time in db/db mice. Thus, endothelial cell CCR10 activation in genetically obese mice with type 2 diabetes promotes eNOS depletion and endothelial dysfunction, and targeted disruption of CCR10/eNOS interaction improves wound healing

Caveolae, the cave-like structures abundant in endothelial cells (ECs), are important for multiple signaling processes such as production of nitric oxide and caveolae-mediated intracellular trafficking. Using superresolution microscopy, fluorescence resonance energy transfer, and biochemical analysis, we observed that the EphB1 receptor tyrosine kinase constitutively interacts with caveolin-1 (Cav-1), the key structural protein of caveolae. Activation of EphB1 with its ligand Ephrin B1 induced EphB1 phosphorylation and the uncoupling EphB1 from Cav-1 and thereby promoted phosphorylation of Cav-1 by Src. Deletion of Cav-1 scaffold domain binding (CSD) motif in EphB1 prevented EphB1 binding to Cav-1 as well as Src-dependent Cav-1 phosphorylation, indicating the importance of CSD in the interaction. We also observed that Cav-1 protein expression and caveolae numbers were markedly reduced in ECs from EphB1-deficient (EphB1−/−) mice. The loss of EphB1 binding to Cav-1 promoted Cav-1 ubiquitination and degradation, and hence the loss of Cav-1 was responsible for reducing the caveolae numbers. These studies identify the crucial role of EphB1/Cav-1 interaction in the biogenesis of caveolae and in coordinating the signaling function of Cav-1 in ECs.

Increased permeability of vascular lung tissues is a hallmark of acute lung injury and is often caused by edemagenic insults resulting in inflammation. Vascular endothelial (VE)-cadherin undergoes internalization in response to inflammatory stimuli and is recycled at cell adhesion junctions during endothelial barrier re-establishment. Here, we hypothesized that phospholipase D (PLD)-generated phosphatidic acid (PA) signaling regulates VE-cadherin recycling and promotes endothelial barrier recovery by dephosphorylating VE-cadherin. Genetic deletion of PLD2 impaired recovery from protease-activated receptor-1–activating peptide (PAR-1–AP)-induced lung vascular permeability and potentiated inflammation in vivo. In human lung microvascular endothelial cells (HLMVECs), inhibition or deletion of PLD2, but not of PLD1, delayed endothelial barrier recovery after thrombin stimulation. Thrombin stimulation of HLMVECs increased co-localization of PLD2-generated PA and VE-cadherin at cell-cell adhesion junctions. Inhibition of PLD2 activity resulted in prolonged phosphorylation of Tyr-658 in VE-cadherin during the recovery phase 3 h post-thrombin challenge. Immunoprecipitation experiments revealed that after HLMVECs are thrombin stimulated, PLD2, VE-cadherin, and protein-tyrosine phosphatase nonreceptor type 14 (PTPN14), a PLD2-dependent protein-tyrosine phosphatase, strongly associate with each other. PTPN14 depletion delayed VE-cadherin dephosphorylation, reannealing of adherens junctions, and barrier function recovery. PLD2 inhibition attenuated PTPN14 activity and reversed PTPN14-dependent VE-cadherin dephosphorylation after thrombin stimulation. Our findings indicate that PLD2 promotes PTPN14-mediated dephosphorylation of VE-cadherin and that redistribution of VE-cadherin at adherens junctions is essential for recovery of endothelial barrier function after an edemagenic insult.

Transcytosis of macromolecules through lung endothelial cells is the primary route of transport from the vascular compartment into the interstitial space. Endothelial transcytosis is mostly a caveolae-dependent process that combines receptor-mediated endocytosis, vesicle trafficking via actin-cytoskeletal remodeling, and SNARE protein directed vesicle fusion and exocytosis. Herein, we review the current literature on caveolae-mediated endocytosis, the role of actin cytoskeleton in caveolae stabilization at the plasma membrane, actin remodeling during vesicle trafficking, and exocytosis of caveolar vesicles. Next, we provide a concise summary of experimental methods employed to assess transcytosis. Finally, we review evidence that transcytosis contributes to the pathogenesis of acute lung injury. © 2020 American Physiological Society. Compr Physiol 10:491-508, 2020.

Chemokines and their receptors play important roles in vascular homeostasis, development, and angiogenesis. Little is known regarding the molecular signaling mechanisms activated by CCL28 chemokine via its primary receptor CCR10 in endothelial cells (ECs). Here, we test the hypothesis that CCL28/CCR10 signaling plays an important role in regulating skin wound angiogenesis through endothelial nitric oxide synthase (eNOS)-dependent Src, PI3K, and MAPK signaling. We observed nitric oxide (NO) production in human primary ECs stimulated with exogenous CCL28, which also induced direct binding of CCR10 and eNOS resulting in inhibition of eNOS activity. Knockdown of CCR10 with siRNA lead to reduced eNOS expression and tube formation suggesting the involvement of CCR10 in EC angiogenesis. Based on this interaction, we engineered a myristoylated 7 amino acid CCR10-binding domain (Myr-CBD7) peptide and showed that this can block eNOS interaction with CCR10, but not with calmodulin, resulting in upregulation of eNOS activity. Importantly, topical administration of Myr-CBD7 peptide on mouse dermal wounds not only blocked CCR10-eNOS interaction, but also enhanced expression of eNOS, CD31, and IL-4 with reduction of CCL28 and IL-6 levels associated with improved wound healing. These results point to a potential therapeutic strategy to upregulate NO bioavailability, enhance angiogenesis, and improve wound healing by disrupting CCL28-activated CCR10-eNOS interaction.

Introduction: Schistosomiasis-associated Pulmonary Arterial Hypertension (Sch-PAH) is a life-threatening complication of chronic S. mansoni infection, which can evolve to heart failure and death. During PAH, hyperproliferation of apoptosis-resistant endothelial cells (ECs) has been extensively reported, but therapeutic approaches to reverse this pathological phenotype remain clinically challenging. Hypothesis: Thus, our hypothesis is that antigenic molecules from S. mansoni eggs amplify the secretion of inhibitor of apoptosis protein 2 (c-IAP2), leading to generation of an abnormal EC memory of survival and the development of PAH. Methods/Results: Previously, we showed that depletion of the anti-apoptotic protein Caveolin-1 (Cav-1) via shedding of extracellular vesicles (EVs) leads to the survival of an abnormal EC phenotype through an unclear mechanism. Analysis of survival-associated genes in isolated murine lung ECs from Flk1 +/GFP ;Cav1 -/- mice, revealed high expression of the anti-apoptotic genes BIRC3 and BIRC5 (which encodes cIAP2 and survivin, respectively) when compared to control ECs. Interesting, exposure to 1 μg/mL of the major S. mansoni egg antigen Sm-p40 induced time-dependent phosphorylation of Cav-1 at residue Tyr14 in human lung microvascular EC (HMVEC-L: 228.2 +/- 38.28% of control; pS. mansoni -infected mice confirmed a significant decrease in Cav-1 expression unique to the egg-dependent granuloma area, indicating that local inflammatory response due to egg-derived antigenic molecules is essential for reprogramming and survival of an abnormal EC phenotype during Sch-PAH. Conclusions: Our data suggest that S. mansoni -induced Cav-1 depletion promotes the secretion of the anti-apoptotic c-IAP2 protein, which may be critical for prolonged survival of a pathogenic EC phenotype during the development of Sch-PAH.

Introduction: Dysfunctional bone morphogenetic protein receptor 2 (BMPR2) and endothelial nitric oxide synthase (eNOS) have been implicated in the pathogenesis of pulmonary arterial hypertension (PAH), a life-threatening disease characterized by pulmonary vascular remodeling, elevated right ventricular systolic pressure (RVSP), and right ventricular hypertrophy (RVH). Although the incidence of this disease is three times higher in females, males with PAH usually have a worse prognosis. The mechanism behind this sex-associated difference remains undetermined. Objective: Determine whether BMPR2 +/R899X loss-of-function mutation contributes to sex-associated differences in PAH, including the degree of vascular remodeling, RVSP, and RVH. Methods: Wild-type (WT) and BMPR2 +/R899X mice (male/female) were exposed to hypoxia (Hx) or normoxia (Nx) for 4 weeks, when the RVSP and RVH were measured. Lung tissue was used for western blot and histological analysis. Results/Discussion: Hx exposure elevated RVSP, inducing RVH in both groups, with a greater effect in BMPR2 +/R899X mice compared to WT (RVSP: 45.0+/- 2.2 and 34.9 +/- 1.3 mmHg, respectively). A higher RVSP was observed in BMPR2 +/R899X female mice, with males exhibiting more pronounced RVH, suggesting females might have a protective mechanism against severe RVH. Lung histology revealed no differences in vessel thickness/area between sexes, which may indicate that the RVSP differences are unlikely a response to vascular remodeling. Hx exposure increased the amount of α-SMA+ microvessels and eNOS expression in BMPR2 +/R899X females compared to males, but further experiments are required to determine whether elevated eNOS reflects higher function or an oxidative stress-driven endothelial cell phenotype. Conclusion: This work is uncovering the translational relevance of BMPR2 +/R899X mutation in the sex-linked differences in PAH incidence, severity, and outcome.

Pannexin 1 (Panx1), an ATP-efflux pathway, has been linked with inflammation in pulmonary capillaries. However, the physiological roles of endothelial Panx1 in the pulmonary vasculature are unknown. Endothelial transient receptor potential vanilloid 4 (TRPV4) channels lower pulmonary artery (PA) contractility and exogenous ATP activates endothelial TRPV4 channels. We hypothesized that endothelial Panx1–ATP–TRPV4 channel signaling promotes vasodilation and lowers pulmonary arterial pressure (PAP). Endothelial, but not smooth muscle, knockout of Panx1 increased PA contractility and raised PAP in mice. Flow/shear stress increased ATP efflux through endothelial Panx1 in PAs. Panx1-effluxed extracellular ATP signaled through purinergic P2Y2 receptor (P2Y2R) to activate protein kinase Cα (PKCα), which in turn activated endothelial TRPV4 channels. Finally, caveolin-1 provided a signaling scaffold for endothelial Panx1, P2Y2R, PKCα, and TRPV4 channels in PAs, promoting their spatial proximity and enabling signaling interactions. These results indicate that endothelial Panx1–P2Y2R–TRPV4 channel signaling, facilitated by caveolin-1, reduces PA contractility and lowers PAP in mice.

Potassium channels are important regulators of cellular homeostasis and targeting these proteins pharmacologically is unveiling important mechanisms in cancer cell biology. Here we demonstrate that pharmacological stimulation of the Kv11.1 potassium channel activity results in mitochondrial reactive oxygen species (ROS) production and fragmentation in breast cancer cell lines and patient-derived organoids independent of breast cancer subtype. mRNA expression profiling revealed that Kv11.1 activity significantly altered expression of genes controlling the production of ROS and endoplasmic-reticulum (ER) stress. Characterization of the transcriptional signature of breast cancer cells treated with Kv11.1 potassium channel activators strikingly revealed an adaptive response to the potentially lethal augmentation of ROS by increasing Nrf2-dependent transcription of antioxidant genes. Nrf2 in this context was shown to promote survival in breast cancer, whereas knockdown of Nrf2 lead to Kv11.1-induced cell death. In conclusion, we found that the Kv11.1 channel activity promotes oxidative stress in breast cancer cells and that suppression of the Nrf2-mediated anti-oxidant survival mechanism strongly sensitized breast cancer cells to a lethal effect of pharmacological activation of Kv11.1.

Introduction: Schistosomiasis-associated Pulmonary Arterial Hypertension (Sch-PAH) is a life-threatening complication of chronic Schistosoma mansoni infection. Sch-PAH is marked by obliteration and remodeling of the pulmonary vasculature in response to S. mansoni eggs. Remodeled and occluded vessels increase vascular resistance and can lead to heart failure and death. Currently, there are no target therapies for the treatment of Sch-PAH. Hypothesis: S. mansoni egg-derived antigens alter pulmonary endothelial cell (EC) Caveolin-1 (Cav-1) expression and phosphorylation contributing to the loading and shedding of extracellular vesicles (EVs), which in turn stimulates abnormal EC survival leading to Sch-PAH. Methods/Results: Immunohistology and western blot analysis of lungs from S. mansoni -infected mice revealed a significant decrease in Cav-1 expression in the egg-dependent granuloma area when compared to uninfected control animals, indicating that local S. mansoni -associated molecules and inflammatory mediators contribute to Cav-1 depletion. Previously we showed that upon vascular injury, Cav-1 deficiency leads to the survival of an abnormal EC phenotype through an unclear mechanism. Analysis of survival-associated genes in isolated lung ECs from Flk1 +/GFP ; Cav1 -/- mice, revealed a high expression of the anti-apoptotic BIRC2 and BIRC5 (known as c-IAP2 and surviving, respectively) when compared to control ECs. Interesting, in vitro exposure to the major S. mansoni egg antigen, Sm-p40 (1 μg/mL), induced time-dependent phosphorylation of Cav-1 Tyr14 in human lung microvascular ECs (HMVEC-L; 228.2 +/- 38.28% of control; p Conclusions: This work is uncovering the biological role and potential translational relevance of pathogen-induced EC-Cav-1 depletion via shedding of EVs during Sch-PAH.

Objective— To determine whether pulmonary arterial hypertension is associated with endothelial cell (EC)–Cav-1 (caveolin-1) depletion, EC-derived extracellular vesicle cross talk with macrophages, and proliferation of Cav-1 depleted ECs via TGF-β (transforming growth factor-β) signaling. Approach and Results— Pulmonary vascular disease was induced in Sprague-Dawley rats by exposure to a single injection of VEGFRII (vascular endothelial growth factor receptor II) antagonist SU5416 (Su) followed by hypoxia (Hx) plus normoxia (4 weeks each–HxSu model) and in WT (wild type; Tie2.Cre − ; Cav1 lox/lox ) and EC- Cav1 −/− (Tie2.Cre + ; Cav1 fl/fl ) mice (Hx: 4 weeks). We observed reduced lung Cav-1 expression in the HxSu rat model in association with increased Cav-1+ extracellular vesicle shedding into the circulation. Whereas WT mice exposed to hypoxia exhibited increased right ventricular systolic pressure and pulmonary microvascular thickening compared with the group maintained in normoxia, the remodeling was further increased in EC- Cav1 −/− mice indicating EC Cav-1 expression protects against hypoxia-induced pulmonary hypertension. Depletion of EC Cav-1 was associated with reduced BMPRII (bone morphogenetic protein receptor II) expression, increased macrophage-dependent TGF-β production, and activation of pSMAD2/3 signaling in the lung. In vitro, in the absence of Cav-1, eNOS (endothelial NO synthase) dysfunction was implicated in the mechanism of EC phenotype switching. Finally, reduced expression of EC Cav-1 in lung histological sections from human pulmonary arterial hypertension donors was associated with increased plasma concentration of Cav-1, extracellular vesicles, and TGF-β, indicating Cav-1 may be a plasma biomarker of vascular injury and key determinant of TGF-β–induced pulmonary vascular remodeling. Conclusions— EC Cav-1 depletion occurs, in part, via Cav-1+ extracellular vesicle shedding into the circulation, which contributes to increased TGF-β signaling, EC proliferation, vascular remodeling, and pulmonary arterial hypertension.

Recent studies have focused on the contribution of capillary endothelial TRPV4 channels to pulmonary pathologies, including lung edema and lung injury. However, in pulmonary hypertension (PH), small pulmonary arteries are the focus of the pathology, and endothelial TRPV4 channels in this crucial anatomy remain unexplored in PH. Here, we provide evidence that TRPV4 channels in endothelial cell caveolae maintain a low pulmonary arterial pressure under normal conditions. Moreover, the activity of caveolar TRPV4 channels is impaired in pulmonary arteries from mouse models of PH and PH patients. In PH, up-regulation of iNOS and NOX1 enzymes at endothelial cell caveolae results in the formation of the oxidant molecule peroxynitrite. Peroxynitrite, in turn, targets the structural protein caveolin-1 to reduce the activity of TRPV4 channels. These results suggest that endothelial caveolin-1–TRPV4 channel signaling lowers pulmonary arterial pressure, and impairment of endothelial caveolin-1–TRPV4 channel signaling contributes to elevated pulmonary arterial pressure in PH. Thus, inhibiting NOX1 or iNOS activity, or lowering endothelial peroxynitrite levels, may represent strategies for restoring vasodilation and pulmonary arterial pressure in PH.

Pannexin 1 (Panx1) is an ATP-efflux channel that controls endothelial function in the systemic circulation. However, the roles of endothelial Panx1 in resistance-sized pulmonary arteries (PAs) are unknown. Extracellular ATP dilates PAs through activation of endothelial TRPV4 (transient receptor potential vanilloid 4) ion channels. We hypothesized that endothelial Panx1–ATP– TRPV4 channel signaling promotes vasodilation and lowers pulmonary arterial pressure (PAP). Endothelial, but not smooth muscle, knockout of Panx1 or TRPV4 increased PA contractility and raised PAP. Panx1-effluxed extracellular ATP signaled through purinergic P2Y2 receptor (P2Y2R) to activate protein kinase Cα (PKCα), which in turn activated endothelial TRPV4 channels. Finally, caveolin-1 provided a signaling scaffold for endothelial Panx1, P2Y2R, PKCα, and TRPV4 channels in PAs, promoting their spatial proximity and enabling signaling interactions. These results indicate that endothelial Panx1–P2Y2R–TRPV4 channel signaling, facilitated by caveolin-1, reduces PA contractility and lowers PAP.

Ventilator-induced lung injury is associated with an increase in mortality in patients with respiratory dysfunction, although mechanical ventilation is an essential intervention implemented in the intensive care unit. Intrinsic molecular mechanisms for minimizing lung inflammatory injury during mechanical ventilation remain poorly defined. We hypothesize that Yes-associated protein (YAP) expression in endothelial cells protects the lung against ventilator-induced injury. Wild-type and endothelial-specific YAP-deficient mice were subjected to a low (7 mL/kg) or high (21 mL/kg) tidal volume ( VT) ventilation for 4 h. Infiltration of inflammatory cells into the lung, vascular permeability, lung histopathology, and the levels of inflammatory cytokines were measured. Here, we showed that mechanical ventilation with high VT upregulated YAP protein expression in pulmonary endothelial cells. Endothelial-specific YAP knockout mice following high VT ventilation exhibited increased neutrophil counts and protein content in bronchoalveolar lavage fluid, Evans blue leakage, and histological lung injury compared with wild-type littermate controls. Deletion of YAP in endothelial cells exaggerated vascular endothelial (VE)-cadherin phosphorylation, downregulation of vascular endothelial protein tyrosine phosphatase (VE-PTP), and dissociation of VE-cadherin and catenins following mechanical ventilation. Importantly, exogenous expression of wild-type VE-PTP in the pulmonary vasculature rescued YAP ablation-induced increases in neutrophil counts and protein content in bronchoalveolar lavage fluid, vascular leakage, and histological lung injury as well as VE-cadherin phosphorylation and dissociation from catenins following ventilation. These data demonstrate that YAP expression in endothelial cells suppresses lung inflammatory response and edema formation by modulating VE-PTP-mediated VE-cadherin phosphorylation and thus plays a protective role in ventilator-induced lung injury.

Background: Pulmonary hypertension (PH) is a degenerative disorder that is characterized by elevated vascular resistance and pulmonary arterial pressure (PAP). Endothelial transient receptor potential vanilloid 4 (TRPV4 EC ) ion channels represent an important Ca 2+ influx signaling mechanism that promotes vasodilation of small pulmonary arteries (PAs). Scaffolding protein caveolin-1 (Cav-1) has been shown to precipitate with TRPV4 channels in pulmonary endothelial cells in culture. Hypothesis: We hypothesized that the endothelial Cav-1-TRPV4 channel signaling in small PAs lowers PAP, and is impaired in PH. Methods: Inducible endothelium-specific KO mice for TRPV4 channel or Cav-1 were used to study the role of Cav-1-TRPV4 signaling in the regulation of resting PAP. Endothelium-specific P2Y2 receptor KO mice were used to test if Cav-1 provides a signaling scaffold for purinergic activation of TRPV4 EC channels. Endothelial Cav-1-TRPV4 signaling was assessed in PAs from two PH mouse models and PH patients. The role of NADPH oxidase (NOX1)- and inducible nitric oxide synthase (iNOS)-mediated peroxynitrite (PN), an oxidant molecule, in impairing Cav-1-TRPV4 signaling in PH was evaluated using NOX1-/- and iNOS-/- mice and pharmacological inhibitors. Results: We show that endothelial Cav-1-TRPV4 signaling in small PAs lowers resting PAP, and protects against the pathogenesis of PH. Endothelial Cav-1 provides a signaling scaffold for the activation of TRPV4 channels by endogenous purinergic receptor signaling. Moreover, TRPV4 EC channel activity and Cav-1-TRPV4 signaling are impaired in small PAs from two mouse models of PH and PH patients. Elevated levels of NOX1 and iNOS enzymes in caveolae resulted in PN formation close to Cav-1 in PH. Elevated PN targeted Cav-1 to lower Cav-1-TRPV4 signaling, thereby contributing to impaired vasodilation and increased PAP. Pharmacological inhibition of NOX1, iNOS, or PN rescued TRPV4 EC channel activity and vasodilation in PH. Conclusion: This study provides novel evidence that endothelial Cav-1-TRPV4 signaling lowers PAP and is impaired in PH. Inhibiting NOX1 or iNOS activity, or lowering endothelial PN levels may represent a novel strategy for restoring TRPV4 EC channel activity, vasodilation, and PAP.

Hippocampal neurogenesis plays an important role in learning and memory function throughout life. Declines in this process have been observed in both aging and Alzheimer’s disease (AD). Type 2 Diabetes mellitus (T2DM) is a disorder characterized by insulin resistance and impaired glucose metabolism. T2DM often results in cognitive decline in adults, and significantly increases the risk of AD development. The pathways underlying T2DM-induced cognitive deficits are not known. Some studies suggest that alterations in hippocampal neurogenesis may contribute to cognitive deterioration, however, the fate of neurogenesis in these studies is highly controversial. To address this problem, we utilized two models of T2DM: (1) obesity-independent MKR transgenic mice expressing a mutated form of the human insulin-like growth factor 1 receptor (IGF-1R) in skeletal muscle, and (2) Obesity-dependent db/db mice harboring a mutation in the leptin receptor. Our results show that both models of T2DM display compromised hippocampal neurogenesis. We show that the number of new neurons in the hippocampus of these mice is reduced. Clone formation capacity of neural progenitor cells isolated from the db/db mice is deficient. Expression of insulin receptor and epidermal growth factor receptor was reduced in hippocampal neurospheres isolated from db/db mice. Results from this study warrant further investigation into the mechanisms underlying decreased neurogenesis in T2DM and its link to the cognitive decline observed in this disorder.

Caveolin-1 (Cav-1) is a scaffolding protein and a major component of caveolae/lipid rafts. Previous reports have shown that endothelial dysfunction in Cav-1-deficient (Cav-1−/−) mice is mediated by elevated oxidative stress through endothelial nitric oxide synthase (eNOS) uncoupling and increased NADPH oxidase. Oxidant stress is the net balance of oxidant generation and scavenging, and the role of Cav-1 as a regulator of antioxidant enzymes in vascular tissue is poorly understood. Extracellular SOD (SOD3) is a copper (Cu)-containing enzyme that is secreted from vascular smooth muscle cells/fibroblasts and subsequently binds to the endothelial cells surface, where it scavenges extracellular [Formula: see text] and preserves endothelial function. SOD3 activity is dependent on Cu, supplied by the Cu transporter ATP7A, but whether Cav-1 regulates the ATP7A-SOD3 axis and its role in oxidative stress-mediated vascular dysfunction has not been studied. Here we show that the activity of SOD3, but not SOD1, was significantly decreased in Cav-1−/−vessels, which was rescued by re-expression of Cav-1 or Cu supplementation. Loss of Cav-1 reduced ATP7A protein, but not mRNA, and this was mediated by ubiquitination of ATP7A and proteasomal degradation. ATP7A bound to Cav-1 and was colocalized with SOD3 in caveolae/lipid rafts or perinucleus in vascular tissues or cells. Impaired endothelium-dependent vasorelaxation in Cav-1−/−mice was rescued by gene transfer of SOD3 or by ATP7A-overexpressing transgenic mice. These data reveal an unexpected role of Cav-1 in stabilizing ATP7A protein expression by preventing its ubiquitination and proteasomal degradation, thereby increasing SOD3 activity, which in turn protects against vascular oxidative stress-mediated endothelial dysfunction.

Pulmonary hypertension is a chronic vascular disease characterized by pulmonary vasoconstriction and pulmonary arterial remodeling. Pulmonary arterial remodeling is mainly due to small pulmonary arterial wall thickening and lumen occlusion. Previous studies have described intravascular changes in lung sections using histopathology, but few were able to obtain a fine detailed image of the pulmonary vascular system. In this study, we used Microfil compounds to cast the pulmonary arteries in a rat model of monocrotaline-induced pulmonary hypertension. High-quality images that enabled quantification of distal pulmonary arterial branching based on the number of vessel bifurcations/junctions were demonstrated in this model. The branch and junction counts of distal pulmonary arteries significantly decreased in the monocrotaline group compared to the control group, and this effect was inversely proportional to the mean pulmonary artery pressure observed in each group. The patterns of pulmonary vasculature and the methods for pulmonary vessel casting are presented to provide a basis for future studies of pulmonary arterial remodeling due to pulmonary hypertension and other lung diseases that involve the remodeling of vasculature.

Cell surface G protein–coupled receptors (GPCRs), upon agonist binding, undergo serine–threonine phosphorylation, leading to either receptor recycling or degradation. Here, we show a new fate of GPCRs, exemplified by ER retention of sphingosine-1-phosphate receptor 1 (S1PR1). We show that S1P phosphorylates S1PR1 on tyrosine residue Y143, which is associated with recruitment of activated BiP from the ER into the cytosol. BiP then interacts with endocytosed Y143-S1PR1 and delivers it into the ER. In contrast to WT-S1PR1, which is recycled and stabilizes the endothelial barrier, phosphomimicking S1PR1 (Y143D-S1PR1) is retained by BiP in the ER and increases cytosolic Ca2+ and disrupts barrier function. Intriguingly, a proinflammatory, but non-GPCR agonist, TNF-α, also triggered barrier-disruptive signaling by promoting S1PR1 phosphorylation on Y143 and its import into ER via BiP. BiP depletion restored Y143D-S1PR1 expression on the endothelial cell surface and rescued canonical receptor functions. Findings identify Y143-phosphorylated S1PR1 as a potential target for prevention of endothelial barrier breakdown under inflammatory conditions.

Hippocampal neurogenesis plays an important role in learning and memory function throughout life. Declines in this process have been observed in both aging and Alzheimer's disease (AD). Type 2 Diabetes mellitus (T2DM) is a disorder characterized by insulin resistance and impaired glucose metabolism. T2DM often results in cognitive decline in adults, and significantly increases the risk of AD development. The pathways underlying T2DM-induced cognitive deficits are not known. Some studies suggest that alterations in hippocampal neurogenesis may contribute to cognitive deterioration, however, the fate of neurogenesis in these studies is highly controversial. To address this problem, we utilized two models of T2DM: (1) obesity-independent MKR transgenic mice expressing a mutated form of the human insulin-like growth factor 1 receptor (IGF-1R) in skeletal muscle, and (2) Obesity-dependent db/db mice harboring a mutation in the leptin receptor. Our results show that both models of T2DM display compromised hippocampal neurogenesis. We show that the number of new neurons in the hippocampus of these mice is reduced. Clone formation capacity of neural progenitor cells isolated from the db/db mice is deficient. Expression of insulin receptor and epidermal growth factor receptor was reduced in hippocampal neurospheres isolated from db/db mice. Results from this study warrant further investigation into the mechanisms underlying decreased neurogenesis in T2DM and its link to the cognitive decline observed in this disorder.

Uncontrolled inflammatory response during sepsis predominantly contributes to the development of multiorgan failure and lethality. However, the cellular and molecular mechanisms for excessive production and release of proinflammatory cytokines are not clearly defined. In this study, we show the crucial role of the GTPase Ras-related protein in brain (Rab)1a in regulating the nucleotide binding domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation and lung inflammatory injury. Expression of dominant negative Rab1 N124I plasmid in bone marrow–derived macrophages prevented the release of IL-1β and IL-18, NLRP3 inflammasome activation, production of pro–IL-1β and pro–IL-18, and attenuated TLR4 surface expression and NF-кB activation induced by bacterial LPS and ATP compared with control cells. In alveolar macrophage–depleted mice challenged with cecal ligation and puncture, pulmonary transplantation of Rab1a-inactivated macrophages by expression of Rab1 N124I plasmid dramatically reduced the release of IL-1β and IL-18, neutrophil count in bronchoalveolar lavage fluid, and inflammatory lung injury. Rab1a activity was elevated in alveolar macrophages from septic patients and positively associated with severity of sepsis and respiratory dysfunction. Thus, inhibition of Rab1a activity in macrophages resulting in the suppression of NLRP3 inflammasome activation may be a promising target for the treatment of patients with sepsis.

Objective— Disturbed flow (DF) is well-known to induce endothelial dysfunction and synergistically with plasma dyslipidemia facilitate plaque formation. Little is known, however, about the synergistic impact of DF and dyslipidemia on endothelial biomechanics. Our goal was to determine the impact of DF on endothelial stiffness and evaluate the role of dyslipidemia/oxLDL (oxidized low-density lipoprotein) in this process. Approach and Results— Endothelial elastic modulus of intact mouse aortas ex vivo and of human aortic endothelial cells exposed to laminar flow or DF was measured using atomic force microscopy. Endothelial monolayer of the aortic arch is found to be significantly stiffer than the descending aorta (4.2+1.1 versus 2.5+0.2 kPa for aortic arch versus descending aorta) in mice maintained on low-fat diet. This effect is significantly exacerbated by short-term high-fat diet (8.7+2.5 versus 4.5+1.2 kPa for aortic arch versus descending aorta). Exposure of human aortic endothelial cells to DF in vitro resulted in 50% increase in oxLDL uptake and significant endothelial stiffening in the presence but not in the absence of oxLDL. DF also increased the expression of oxLDL receptor CD36 (cluster of differentiation 36), whereas downregulation of CD36 abrogated DF-induced endothelial oxLDL uptake and stiffening. Furthermore, genetic deficiency of CD36 abrogated endothelial stiffening in the aortic arch in vivo in mice fed either low-fat diet or high-fat diet. We also show that the loss of endothelial stiffening in CD36 knockout aortas is not mediated by the loss of CD36 in circulating cells. Conclusions— DF facilitates endothelial CD36-dependent uptake of oxidized lipids resulting in local increase of endothelial stiffness in proatherogenic areas of the aorta.

We hypothesized that the maintenance of vascular homeostasis is critically dependent on the expression and reciprocal regulation of caveolin-1 (Cav-1) and endothelial nitric oxide synthase (eNOS) in endothelial cells (ECs). Skeletal muscle biopsies from subjects with type 2 diabetes showed 50% less Cav-1 and eNOS than those from lean healthy controls. The Cav-1:eNOS expression ratio was 200:1 in primary culture human ECs. Cav-1 small interfering RNA (siRNA) reduced eNOS protein and gene expression in association with a twofold increase in eNOS phosphorylation and nitrate production per molecule of eNOS, which was reversed in cells overexpressing Adv-Cav-1-GFP. Upon addition of the Ca2+ionophore A23187 to activate eNOS, we observed eNOS Ser1177 phosphorylation, its translocation to β-catenin-positive cell–cell junctions, and increased colocalization of eNOS and Cav-1 within 5 min. We also observed Cav-1 S-nitrosylation and destabilization of Cav-1 oligomers in cells treated with A23187 as well as insulin or albumin, and this could be blocked by L-NAME, PP2, or eNOS siRNA. Finally, caveola-mediated endocytosis of albumin or insulin was reduced by Cav-1 or eNOS siRNA, and the effect of Cav-1 siRNA was rescued by Adv-Cav-1-GFP. Thus, Cav-1 stabilizes eNOS expression and regulates its activity, whereas eNOS-derived NO promotes caveola-mediated endocytosis.

Haptoglobin (HP) is the major scavenger of cell-free hemoglobin in circulation. When haptoglobin is depleted, cell-free hemoglobin can lead to organ damage through direct oxidative injury, upregulation of inflammatory pathways, and depletion of nitric oxide. A common polymorphism in HP gives rise to structurally and functionally distinct phenotypes: HP 1-1, HP 2-1, and HP 2-2. In people of African descent, the HP 1-1 and 2-1 phenotypes have been associated with higher serum HP concentrations compared to the HP 2-2 phenotype (PMID 10807979). In hemolytic diseases, such as sickle cell disease (SCD), the consequence of the HP polymorphism is unclear but could influence cell-free hemoglobin processing and susceptibility to organ damage. We first investigated whether the HP isoforms are associated with HP concentrations at steady-state. Between 10/2009 and 6/2018, we recruited 431 SCD patients into a longitudinal registry at our institution during a routine clinic visit, which we defined as steady-state. Baseline clinical and laboratory data were collected at the time of enrolment. The median age of the cohort was 32 (interquartile range [IQR], 24 - 43) years, 43% were male, 76% were SCD SS or Sβ 0-thalassemia genotype, and 46% were on hydroxyurea at the time of enrolment. Genotyping of the HP polymorphisms by PCR demonstrated the HP 1-1 isoform in 30% (n = 129), the HP 2-1 isoform in 47% (n = 203), and the HP 2-2 isoform in 23% (n = 99) of the SCD cohort. Serum samples were available in 244 of the 431 SCD patients at steady-state. Serum concentrations of HP, measured by ELISA, were higher in those with the HP 1-1 isoform compared to the HP 2-1 or 2-2 isoform (Figure). In a linear regression model, independent variables associated with steady-state serum HP concentration included SCD SS or Sβ 0-thalassemia genotype (β -1.8; 95% CI: -2.5 to -1.0; P < 0.001), LDH (natural log β -0.9; 95% CI: -0.2 to -1.6; P = 0.018), hydroxyurea use (β 0.6; 95% CI: 0.1 to 1.1; P = 0.02), and HP 1-1 isoform (β 0.5, 95% CI: 0 to 1.1; P = 0.049), adjusting for age and sex. Between 9/2020 and 5/2021, we collected an additional 38 serum samples from SCD patients during a hospitalization for vaso-occlusive crisis (VOC) and serum samples from 7 SCD patients during a hospitalization for acute chest syndrome. The HP 1-1 isoform was associated with higher serum HP concentrations during VOC and during acute chest syndrome compared to the HP 2-1 or 2-2 isoforms (Figure). Interestingly, the serum HP trended higher from steady-state to VOC and to acute chest syndrome in SCD patients with the HP 1-1 isoform (β +1.1, P = 0.085) but trended lower in those with the HP 2-1 or 2-2 isoform (β -0.5, P = 0.099). Next we tested whether the HP 1-1 isoform is protective against multi-organ failure during hospitalizations for acute chest syndrome. For the longitudinal analysis, we focused on SCD patients with > 6 months of follow up at our institution (n = 391). A multiorgan failure event was defined as organ dysfunction involving at least 2 of the following organ systems: lung, kidney, liver, or central nervous system (PMID 8109600). With a median follow up of 6.8 (IQR, 3.5 - 8.9) years, we observed an acute chest syndrome episode complicated by multiorgan failure in 14% (53/391) of SCD patients. A significantly lower proportion of SCD patients with the HP 1-1 isoform developed a multiorgan failure event versus those with the 2-1 or 2-2 isoforms (5.7% vs. 17.2%, respectively; P < 0.001). On logistic regression analysis, acute chest syndrome with multiorgan failure was associated with the HP 1-1 isoform (OR 0.3, 95% CI: 0.1 to 0.6; P = 0.002) and baseline LDH (natural log OR 2.7, 95% CI: 1.2 - 6.3; P = 0.02), after adjusting for age, sex, SCD genotype and hydroxyurea use. In conclusion, we demonstrate that the HP 1-1 isoform is independently associated with higher serum HP concentrations at steady-state as well as during hospitalizations for VOC or acute chest syndrome compared to the HP 2-1 or 2-2 isoforms. Furthermore, the HP 1-1 isoform is protective against developing the devastating multiorgan failure syndrome during acute chest syndrome episodes. Our findings highlight the clinical significance of the HP isoforms and cell-free hemoglobin scavenging in SCD. Future studies assessing HP induction and scavenging function based on HP isoform may help elucidate high-risk patients for aggressive measures, such as rapid initiation of exchange transfusion therapy or HP replacement therapy. Figure 1 Figure 1. Disclosures Gordeuk: Modus Therapeutics: Consultancy; Novartis: Research Funding; Incyte: Research Funding; Emmaus: Consultancy, Research Funding; Global Blood Therapeutics: Consultancy, Research Funding; CSL Behring: Consultancy. Saraf: Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Research Funding; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Intravascular hemolysis releases cell-free hemoglobin and heme into the circulation. When haptoglobin and hemopexin are depleted, as observed in sickle cell anemia, cell-free hemoglobin and heme can cause direct oxidative injury, upregulation of inflammatory and immune response pathways, and depletion of nitric oxide. The kidneys are the primary route for clearance of non-scavenged cell-free hemoglobin and heme and are particularly susceptible to these deleterious pathways (PMID 31455889). In patients with sickle cell anemia, increased markers of hemolysis and hemoglobinuria are risk factors for kidney disease and kidney disease progression (PMID 24329963). Voxelotor is a small molecule allosteric modulator that binds and maintains sickle hemoglobin in the oxygenated state, thereby preventing hemoglobin S polymerization and red blood cell sickling. In a phase 3 study, voxelotor improved the degree of hemolysis, as reflected by a rise in hemoglobin concentration and a reduction in indirect bilirubin and reticulocyte percentage (PMID 31199090). The benefits of reducing hemolytic anemia with voxelotor on kidney function are unknown. We investigated whether GBT1118, an analogue of voxelotor with improved pharmacokinetic properties in transgenic sickle mice, would improve biomarkers of kidney damage and kidney function in sickle cell anemia. Transgenic sickle mice (Hb SS; Townes model, Jackson Laboratory) were treated with either GBT1118 (5 male, 5 female) or control (5 male, 5 female) chow from 12 to 24 weeks of age. Urine was collected using metabolic cages for 24 hours at 3 week intervals and blood was collected at baseline, 6 weeks, and 12 weeks of therapy. We compared markers of hemolysis (hemoglobin, reticulocyte percentage), reactive oxygen species (thibarbituric acid reactive substances [TBARS], kidney injury (kidney injury molecule-1 [KIM-1], nephrin), and kidney function (urine albumin and protein, serum blood urea nitrogen [BUN] and creatinine) at the respective time points using ANOVA and adjusting for gender. Mean and standard error values are provided. Consistent with the clinical results observed in the voxelotor phase 3 study, we observed significant improvements in the hemoglobin concentrations and reticulocyte percentages of Hb SS mice treated with GBT1118 versus control (Figure 1A and 1B). The hemoglobin occupancy of GBT1118 after 6 weeks (33 ± 2%) and 12 weeks (28 ± 2%) of therapy were also similar to what was observed in the phase 3 clinical study. An improvement in hemolysis led to reduced hemoglobinuria (6 weeks: treated = 0.07 ± 0.03 vs. control = 0.72 ± 0.2 ng/day, P = 0.004; 12 weeks: treated = 0.04 ± 0.03 vs. control = 1.06 ± 0.32 ng/day, P = 0.006) and less oxidant damage in the kidneys, assessed by urine TBARS concentration, in the treated versus control mice (6 weeks: treated = 31 ± 6 vs. control = 60 ± 10 nmol/day, P = 0.001; 12 weeks: treated = 29 ± 4 vs. control = 71 ± 9 nmol/day, P < 0.001). At 24 weeks of age, markers of glomerular (nephrin: treated = 3.5 ± 0.7 vs. control = 8.5 ± 1.6 ng/day) and tubular injury (KIM-1: treated = 169.6 ± 19.4 vs. control = 348.9 ± 48.2 pg/day) were significantly improved in the treated versus control Hb SS mice (P< 0.001) (Figure 1C). Albuminuria remained stable in the treated Hb SS mice and was relatively close in value to the degree of albuminuria observed in Hb AA mice (Figure 1D). In contrast, albuminuria progressively increased with older age in the control Hb SS mice. A similar pattern was observed for proteinuria (24 week: Hb SS treated = 2.02 ± 0.17 mg/day, Hb SS control = 3.65 ± 0.44 mg/day, Hb AA = 1.65 ± 0.27 mg/day). At 24 weeks of age, the treated Hb SS mice had serum BUN and creatinine values that were similar to what was observed at 12 weeks of age in the Hb SS mice and to the 24-week old Hb AA mice (Figure 1E, 1F). Furthermore, the values for serum BUN and creatinine were significantly lower in the treated versus control Hb SS mice at 24 weeks of age (P ≤ 0.04). In conclusion, we demonstrate that an improvement in hemolysis results in preserved kidney function in transgenic sickle mice. Our findings highlight the clinical importance of hemolytic anemia in the pathophysiology of sickle cell nephropathy. Our results also provide support for developing strategies to mitigate hemolysis in sickle cell anemia in order to provide a targeted approach to improve kidney disease, a devastating complication associated with high morbidity and mortality, in sickle cell anemia. Figure 1 Figure 1. Disclosures Gordeuk: Modus Therapeutics: Consultancy; Novartis: Research Funding; Incyte: Research Funding; Emmaus: Consultancy, Research Funding; Global Blood Therapeutics: Consultancy, Research Funding; CSL Behring: Consultancy. Saraf: Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Research Funding.

Intercellular adhesion molecule-1 (ICAM-1) mediates the firm adhesion of leukocytes to endothelial cells and initiates subsequent signaling that promotes their transendothelial migration (TEM). Vascular endothelial (VE)-cadherin plays a critical role in endothelial cell–cell adhesion, thereby controlling endothelial permeability and leukocyte transmigration. This study aimed to determine the molecular signaling events that originate from the ICAM-1–mediated firm adhesion of neutrophils that regulate VE-cadherin’s role as a negative regulator of leukocyte transmigration. We observed that ICAM-1 interacts with Src homology domain 2–containing phosphatase-2 (SHP-2), and SHP-2 down-regulation via silencing of small interfering RNA in endothelial cells enhanced neutrophil adhesion to endothelial cells but inhibited neutrophil transmigration. We also found that VE-cadherin associated with the ICAM-1–SHP-2 complex. Moreover, whereas the activation of ICAM-1 leads to VE-cadherin dissociation from ICAM-1 and VE-cadherin association with actin, SHP-2 down-regulation prevented ICAM-1–VE-cadherin association and promoted VE-cadherin–actin association. Furthermore, SHP-2 down-regulation in vivo promoted LPS-induced neutrophil recruitment in mouse lung but delayed neutrophil extravasation. These results suggest that SHP-2—via association with ICAM-1—mediates ICAM-1–induced Src activation and modulates VE-cadherin switching association with ICAM-1 or actin, thereby negatively regulating neutrophil adhesion to endothelial cells and enhancing their TEM.—Yan, M., Zhang, X., Chen, A., Gu, W., Liu, J., Ren, X., Zhang, J., Wu, X., Place, A. T., Minshall, R. D., Liu, G. Endothelial cell SHP-2 negatively regulates neutrophil adhesion and promotes transmigration by enhancing ICAM-1–VE-cadherin interaction.

Endothelial cell (EC) activation and vascular injury are hallmark features of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Caveolin-1 (Cav-1) is highly expressed in pulmonary microvascular ECs and plays a key role in maintaining vascular homeostasis. The aim of this study was to determine if the lung inflammatory response to Escherichia coli lipopolysaccharide (LPS) promotes priming of ECs via Cav-1 depletion and if this contributes to the onset of pulmonary vascular remodeling. To test the hypothesis that depletion of Cav-1 primes ECs to respond to profibrotic signals, C57BL6 wild-type (WT) mice ( Tie2.Cre−;Cav1fl/fl) were exposed to nebulized LPS (10 mg; 1 h daily for 4 days) and compared with EC-specific Cav1−/−( Tie2.Cre+;Cav1fl/fl). After 96 h of LPS exposure, total lung Cav-1 and bone morphogenetic protein receptor type II (BMPRII) expression were reduced in WT mice. Moreover, plasma albumin leakage, infiltration of immune cells, and levels of IL-6/IL-6R and transforming growth factor-β (TGF-β) were elevated in both LPS-treated WT and EC-Cav1−/−mice. Finally, EC-Cav1−/−mice exhibited a modest increase in microvascular thickness basally and even more so on exposure to LPS (96 h). EC-Cav1−/−mice and LPS-treated WT mice exhibited reduced BMPRII expression and endothelial nitric oxide synthase uncoupling, which along with increased TGF-β promoted TGFβRI-dependent SMAD-2/3 phosphorylation. Finally, human lung sections from patients with ARDS displayed reduced EC Cav-1 expression, elevated TGF-β levels, and severe pulmonary vascular remodeling. Thus EC Cav-1 depletion, oxidative stress-mediated reduction in BMPRII expression, and enhanced TGF-β-driven SMAD-2/3 signaling promote pulmonary vascular remodeling in inflamed lungs.

The detection of dynamic conformational changes in proteins in live cells is challenging. Live-cell FRET (Forster Resonance Energy Transfer) is an example of a noninvasive technique that can be used to achieve this goal at nanometer resolution. FRET-based assays are dependent on the presence of fluorescent probes, such as CFP- and YFP-conjugated protein pairs. Here, we describe an experimental protocol in which live-cell FRET was used to measure conformational changes in caveolin-1 (Cav-1) oligomers on the surface of plasmalemma vesicles, or caveolae.

Macrophages are tissue-resident immune cells that are crucial for the initiation and maintenance of immune responses. Purinergic signaling modulates macrophage activity and impacts cellular plasticity. The ATP-activated purinergic receptor P2X7 (also known as P2RX7) has pro-inflammatory properties, which contribute to macrophage activation. P2X7 receptor signaling is, in turn, modulated by ectonucleotidases, such as CD39 (also known as ENTPD1), expressed in caveolae and lipid rafts. Here, we examined P2X7 receptor activity and determined impacts on ectonucleotidase localization and function in macrophages primed with lipopolysaccharide (LPS). First, we verified that ATP boosts CD39 activity and caveolin-1 protein expression in LPS-primed macrophages. Drugs that disrupt cholesterol-enriched domains - such as nystatin and methyl-β-cyclodextrin - decreased CD39 enzymatic activity in all circumstances. We noted that CD39 colocalized with lipid raft markers (flotillin-2 and caveolin-1) in macrophages that had been primed with LPS followed by treatment with ATP. P2X7 receptor inhibition blocked these ATP-mediated increases in caveolin-1 expression and inhibited the colocalization with CD39. Further, we found that STAT3 activation is significantly attenuated caveolin-1-deficient macrophages treated with LPS or LPS+BzATP. Taken together, our data suggest that P2X7 receptor triggers the initiation of lipid raft-dependent mechanisms that upregulates CD39 activity and could contribute to limit macrophage responses restoring homeostasis.

Some metabolic disorders, such as type 2 diabetes mellitus (T2DM) are risk factors for the development of cognitive deficits and Alzheimer’s disease (AD). Epidemiological studies suggest that in people with T2DM, the risk of developing dementia is 2.5 times higher than that in the non-diabetic population. The signaling pathways that underlie the increased risk and facilitate cognitive deficits are not fully understood. In fact, the cause of memory deficits in AD is not fully elucidated. The dentate gyrus of the hippocampus plays an important role in memory formation. Hippocampal neurogenesis is the generation of new neurons and glia in the adult brain throughout life. New neurons incorporate in the granular cell layer of the dentate gyrus and play a role in learning and memory and hippocampal plasticity. A large body of studies suggests that hippocampal neurogenesis is impaired in mouse models of AD and T2DM. Recent evidence shows that hippocampal neurogenesis is also impaired in human patients exhibiting mild cognitive impairment or AD. This review discusses the role of hippocampal neurogenesis in the development of cognitive deficits and AD, and considers inflammatory and endothelial signaling pathways in T2DM that may compromise hippocampal neurogenesis and cognitive function, leading to AD.

Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New Background Sevoflurane with its antiinflammatory properties has shown to decrease mortality in animal models of sepsis. However, the underlying mechanism of its beneficial effect in this inflammatory scenario remains poorly understood. Macrophages play an important role in the early stage of sepsis as they are tasked with eliminating invading microbes and also attracting other immune cells by the release of proinflammatory cytokines such as interleukin-1β, interleukin-6, and tumor necrosis factor-α. Thus, the authors hypothesized that sevoflurane mitigates the proinflammatory response of macrophages, while maintaining their bactericidal properties. Methods Murine bone marrow–derived macrophages were stimulated in vitro with lipopolysaccharide in the presence and absence of 2% sevoflurane. Expression of cytokines and inducible NO synthase as well as uptake of fluorescently labeled Escherichia coli (E. coli) were measured. The in vivo endotoxemia model consisted of an intraperitoneal lipopolysaccharide injection after anesthesia with either ketamine and xylazine or 4% sevoflurane. Male mice (n = 6 per group) were observed for a total of 20 h. During the last 30 min fluorescently labeled E. coli were intraperitoneally injected. Peritoneal cells were extracted by peritoneal lavage and inducible NO synthase expression as well as E. coli uptake by peritoneal macrophages was determined using flow cytometry. Results In vitro, sevoflurane enhanced lipopolysaccharide-induced inducible NO synthase expression after 8 h by 466% and increased macrophage uptake of fluorescently labeled E. coli by 70% compared with vehicle-treated controls. Inhibiting inducible NO synthase expression pharmacologically abolished this increase in bacteria uptake. In vivo, inducible NO synthase expression was increased by 669% and phagocytosis of E. coli by 49% compared with the control group. Conclusions Sevoflurane enhances phagocytosis of bacteria by lipopolysaccharide-challenged macrophages in vitro and in vivo via an inducible NO synthase–dependent mechanism. Thus, sevoflurane potentiates bactericidal and antiinflammatory host-defense mechanisms in endotoxemia.

Type 2 diabetes mellitus (T2DM) is a risk factor for the development of late-onset Alzheimer's disease (AD). However, the mechanism underlying the development of late-onset AD is largely unknown. Here we show that levels of the endothelial-enriched protein caveolin-1 (Cav-1) are reduced in the brains of T2DM patients compared with healthy aging, and inversely correlated with levels of β-amyloid (Aβ). Depletion of Cav-1 is recapitulated in the brains ofdb/db(Leprdb) diabetic mice and corresponds with recognition memory deficits as well as the upregulation of amyloid precursor protein (APP), BACE-1, a trending increase in β-amyloid Aβ42/40ratio and hyperphosphorylated tau (p-tau) species. Importantly, we show that restoration of Cav-1 levels in the brains of maledb/dbmice using adenovirus overexpressing Cav-1 (AAV-Cav-1) rescues learning and memory deficits and reduces pathology (i.e., APP, BACE-1 and p-tau levels). Knocking down Cav-1 using shRNA in HEK cells expressing the familial AD-linked APPswe mutant variant upregulates APP, APP carboxyl terminal fragments, and Aβ levels. In turn, rescue of Cav-1 levels restores APP metabolism. Together, these results suggest that Cav-1 regulates APP metabolism, and that depletion of Cav-1 in T2DM promotes the amyloidogenic processing of APP and hyperphosphorylation of tau. This may suggest that depletion of Cav-1 in T2DM underlies, at least in part, the development of AD and imply that restoration of Cav-1 may be a therapeutic target for diabetic-associated sporadic AD.SIGNIFICANCE STATEMENTMore than 95% of the Alzheimer's patients have the sporadic late-onset form (LOAD). The cause for late-onset Alzheimer's disease is unknown. Patients with Type 2 diabetes mellitus have considerably higher incidence of cognitive decline and AD compared with the general population, suggesting a common mechanism. Here we show that the expression of caveolin-1 (Cav-1) is reduced in the brain in Type 2 diabetes mellitus. In turn, reduced Cav-1 levels induce AD-associated neuropathology and learning and memory deficits. Restoration of Cav-1 levels rescues these deficits. This study unravels signals underlying LOAD and suggests that restoration of Cav-1 may be an effective therapeutic target.