Studies on the cell biology of interendothelial cell gaps

Combined ROS Sensitive Folate Receptor Targeted Micellar Formulations of Curcumin Effective Against Rheumatoid Arthritis in Rat Model

Introduction

Rheumatoid arthritis (RA) is an inflammatory immune-mediated disease that involves synovitis, cartilage destruction, and even joint damage. Traditional agents used for RA therapy remain unsatisfactory because of their low efficiency and obvious adverse effects. Therefore, we here established RA microenvironment-responsive targeted micelles that can respond to the increase in reactive oxygen species (ROS) levels in the joint and improve macrophage-specific targeting of loaded drugs.

Methods

We here prepared ROS-responsive folate-modified curcumin micelles (TK-FA-Cur-Ms) in which thioketal (TK) was used as a ROS-responsive linker for modifying polyethylene glycol 5000 (PEG5000) on the micellar surface. When micelles were in the ROS-overexpressing inflammatory microenvironment, the PEG5000 hydration layer was shed, and the targeting ligand FA was exposed, thereby enhancing cellular uptake by macrophages through active targeting. The targeting, ROS sensitivity and anti-inflammatory properties of the micelles were assessed in vitro. Collagen-induced arthritis (CIA) rats model was utilized to investigate the targeting, expression of serum inflammatory factors and histology change of the articular cartilage by micelles in vivo.

Results

TK-FA-Cur-Ms had a particle size of 90.07 ± 3.44 nm, which decreased to 78.87 ± 2.41 nm after incubation with H2O2. The micelles exhibited in vitro targeting of RAW264.7 cells and significantly inhibited inflammatory cytokine levels. Pharmacodynamic studies have revealed that TK-FA-Cur-Ms prolonged the drug circulation and exhibited augmented cartilage-protective and anti-inflammatory effects in vivo.

Conclusion

The unique ROS-responsive targeted micelles with targeting, ROS sensitivity and anti-inflammatory properties were successfully prepared and may offer an effective therapeutic strategy against RA.

Lung endothelium, tau, and amyloids in health and disease

Lung endothelia in the arteries, capillaries, and veins are heterogeneous in structure and function. Lung capillaries in particular represent a unique vascular niche, with a thin yet highly restrictive alveolar-capillary barrier that optimizes gas exchange. Capillary endothelium surveys the blood while simultaneously interpreting cues initiated within the alveolus and communicated via immediately adjacent type I and type II epithelial cells, fibroblasts, and pericytes. This cell-cell communication is necessary to coordinate the immune response to lower respiratory tract infection. Recent discoveries identify an important role for the microtubule-associated protein tau that is expressed in lung capillary endothelia in the host-pathogen interaction. This endothelial tau stabilizes microtubules necessary for barrier integrity, yet infection drives production of cytotoxic tau variants that are released into the airways and circulation, where they contribute to end-organ dysfunction. Similarly, beta-amyloid is produced during infection. Beta-amyloid has antimicrobial activity, but during infection it can acquire cytotoxic activity that is deleterious to the host. The production and function of these cytotoxic tau and amyloid variants are the subject of this review. Lung-derived cytotoxic tau and amyloid variants are a recently discovered mechanism of end-organ dysfunction, including neurocognitive dysfunction, during and in the aftermath of infection.

Lamellipodia dynamics and microrheology in endothelial cell paracellular gap closure

Vascular endothelial cells (ECs) form a semipermeable barrier separating vascular contents from the interstitium, thereby regulating the movement of water and molecular solutes across small intercellular gaps, which are continuously forming and closing. Under inflammatory conditions, however, larger EC gaps form resulting in increased vascular leakiness to circulating fluid, proteins, and cells, which results in organ edema and dysfunction responsible for key pathophysiologic findings in numerous inflammatory disorders. In this study, we extend our earlier work examining the biophysical properties of EC gap formation and now address the role of lamellipodia, thin sheet-like membrane projections from the leading edge, in modulating EC spatial-specific contractile properties and gap closure. Micropillars, fabricated by soft lithography, were utilized to form reproducible paracellular gaps in human lung ECs. Using time-lapse imaging via optical microscopy, rates of EC gap closure and motility were measured with and without EC stimulation with the barrier-enhancing sphingolipid, sphingosine-1-phosphate. Peripheral ruffle formation was ubiquitous during gap closure. Kymographs were generated to quantitatively compare the lamellipodia dynamics of sphingosine-1-phosphate-stimulated and -unstimulated ECs. Utilizing atomic force microscopy, we characterized the viscoelastic behavior of EC lamellipodia. Our results indicate decreased stiffness and increased liquid-like behavior of expanding lamellipodia compared with regions away from the cellular edge (lamella and cell body) during EC gap closure, results in sync with the rapid kinetics of protrusion/retraction motion. We hypothesize this dissipative EC behavior during gap closure is linked to actomyosin cytoskeletal rearrangement and decreased cross-linking during lamellipodia expansion. In summary, these studies of the kinetic and mechanical properties of EC lamellipodia and ruffles at gap boundaries yield insights into the mechanisms of vascular barrier restoration and potentially a model system for examining the druggability of lamellipodial protein targets to enhance vascular barrier integrity.

CU06-1004 alleviates vascular hyperpermeability in a murine model of hereditary angioedema by protecting the endothelium

BACKGROUND

Over-release of the vasoactive peptide bradykinin (BK) due to mutation in the SERPING1 gene is the leading cause of hereditary angioedema (HAE). BK directly activates endothelial cells and increases vascular permeability by disrupting the endothelial barrier, leading to angioedema affecting face, lips, extremities, gastrointestinal tract, and larynx. Although various pharmacological treatment options for HAE became available during the last decade, they are presently limited and pose a major economic burden on patients. To identify additional therapeutic options for HAE, we evaluated the effect of CU06-1004, an endothelial dysfunction blocker, on BK-induced vascular hyperpermeability and the HAE murine model.

METHODS

To investigate the effect of CU06-1004 on BK-induced vascular hyperpermeability in vivo, we pre-administrated WT mice with the drug and then induced vascular leakage through intravenous injection of BK and observed vascular alternation. Then, SERPING1 deficient mice were used for a HAE murine model. For an in vitro model, the HUVEC monolayer was pre-treated with CU06-1004 and then stimulated with BK.

RESULTS

Bradykinin disrupted the endothelial barrier and formed interendothelial cell gaps, leading to hyperpermeability in vivo and in vitro. However, CU06-1004 treatment protected the endothelial barrier by suppressing Src and myosin light chain activation via BK and alleviated hyperpermeability.

CONCLUSION

Our study shows that CU06-1004 oral administration significantly reduced vascular hyperpermeability in the HAE murine model by protecting the endothelial barrier function against BK stimulation. Therefore, protecting endothelium against BK with CU06-1004 could serve as a potential prophylactic/therapeutic approach for HAE patients.

Association of IL-4 with pachychoroid neovasculopathy

The purpose of this study was to identify the inflammatory cytokines that were associated with pachychoroid neovasculopathy (PNV). Seventy-five eyes of 75 patients with PNV, 145 eyes of 145 patients with neovascular age-related macular degeneration without pachyvessels, and 150 eyes of 150 normal subjects were examined for the levels of intraocular cytokines. In eyes with PNV, the levels of IL-1α, IL-1β, IL-2, IL-4, IL-10, and VEGF were significantly higher than that of the controls. Logistic regression analysis showed that the highest association with the pachyvessels was found for IL-4, IL-2, and IL-1α. In eyes with PNV, the levels of IL-4, IL-2, IL-5, IL-13, IL-1α, and IL-1β were significantly higher in eyes with both increased choroidal thickness and choroidal vessel diameter. The strongest correlation with the choroidal thickness and vessel diameter was observed for IL-4. In PNV eyes with polypoidal lesions, the levels of IL-4, IL-17, and TNFβ were significantly correlated with the number of polypoidal lesions. Of these cytokines, IL-4 was especially associated with the thickness of the choroidal vessels and the formation of polypoidal lesions. We conclude that IL-4 is most likely involved in establishing the clinical characteristics of PNV and polypoidal vascular remodeling.

Delivery of germacrone (GER) using macrophages-targeted polymeric nanoparticles and its application in rheumatoid arthritis

Macrophages can transform into M1 (pro-inflammatory) and M2 (anti-inflammatory) phenotypes, which mediate the immune/inflammatory response in rheumatoid arthritis (RA). Activated M1 phenotype macrophages and overexpression of folate (FA) receptors are abundant in inflammatory synovium and joints and promote the progression of RA. Germacrone (GER) can regulate the T helper 1 cell (Th1)/the T helper 2 cell (Th2) balance to delay the progression of arthritis. To deliver GER to inflammatory tissue cells to reverse M1-type proinflammatory cells and reduce inflammation, FA receptor-targeting nanocarriers loaded with GER were developed. In activated macrophages, FA-NPs/DiD showed significantly higher uptake efficiency than NPs/DiD. In vitro experiments confirmed that FA-NPs/GER could promote the transformation of M1 macrophages into M2 macrophages. In adjuvant-induced arthritis (AIA) rats, the biodistribution profiles showed selective accumulation at the inflammatory site of FA-NPs/GER, and significantly reduced the swelling and inflammation infiltration of the rat's foot. The levels of pro-inflammatory cytokines (TNF-α, IL-1β) in the rat's inflammatory tissue were significantly lower than other treatment groups, which indicated a significant therapeutic effect in AIA rats. Taken together, macrophage-targeting nanocarriers loaded with GER are a safe and effective method for the treatment of RA.

Microvascular fluid flow in ex vivo and engineered lungs

In recent years, it has become common to experiment with ex vivo perfused lungs for organ transplantation and to attempt regenerative pulmonary engineering using decellularized lung matrices. However, our understanding of the physiology of ex vivo organ perfusion is imperfect; it is not currently well understood how decreasing microvascular barrier affects the perfusion of pulmonary parenchyma. In addition, protocols for lung perfusion and organ culture fluid-handling are far from standardized, with widespread variation on both basic methods and on ideally controlled parameters. To address both of these deficits, a robust, noninvasive, and mechanistic model is needed which is able to predict microvascular resistance and permeability in perfused lungs while providing insight into capillary recruitment. Although validated mathematical models exist for fluid flow in native pulmonary tissue, previous models generally assume minimal intravascular leak from artery to vein and do not assess capillary bed recruitment. Such models are difficult to apply to both ex vivo lung perfusions, in which edema can develop over time and microvessels can become blocked, and to decellularized ex vivo organomimetic cultures, in which microvascular recruitment is variable and arterially perfused fluid enters into the alveolar space. Here, we develop a mathematical model of pulmonary microvascular fluid flow which is applicable in both instances, and we apply our model to data from native, decellularized, and regenerating lungs under ex vivo perfusion. The results provide substantial insight into microvascular pressure-flow mechanics, while producing previously unknown output values for tissue-specific capillary-alveolar hydraulic conductivity, microvascular recruitment, and total organ barrier resistance.NEW & NOTEWORTHY We present a validated model of pulmonary microvascular fluid mechanics and apply this model to study the effects of increased capillary permeability in decellularized and regenerating lungs. We find that decellularization alters microvascular steady-state mechanics and that re-endothelialization partially rescues key biologic parameters. The described model provides powerful insight into intraorgan microvascular dynamics and may be used to guide regenerative engineering experiments. We include all data and derivations necessary to replicate this work.

Carbonic Anhydrase IX and Hypoxia Promote Rat Pulmonary Endothelial Cell Survival During Infection

Low tidal volume ventilation protects the lung in mechanically ventilated patients. The impact of the accompanying permissive hypoxemia and hypercapnia on endothelial cell recovery from injury is poorly understood. Carbonic anhydrase IX (CA IX) is expressed in pulmonary microvascular endothelial cells (PMVECs), where it contributes to CO2 and pH homeostasis, bioenergetics and angiogenesis. We hypothesized that CA IX is important for PMVEC survival, and CA IX expression and release from PMVECs are increased during infection. While plasma CA IX was unchanged in human and rat pneumonia, there was a trend towards increasing CA IX in bronchoalveolar fluid of mechanically ventilated critically ill pneumonia patients and a significant increase in CA IX in lung tissue lysate of rat pneumonia. To investigate functional implications of the lung CA IX increase, we generated PMVEC cell lines harboring domain-specific CA IX mutations. Using these cells, we found that infection promotes intracellular expression, release and metalloproteinase-mediated extracellular cleavage of CA IX in PMVECs. Intracellular domain deletion uniquely impaired CA IX membrane localization. Loss of the CA IX intracellular domain promoted cell death following infection, suggesting the important role of intracellular domain in PMVEC survival. We also found that hypoxia improves survival, whereas hypercapnia reverses the protective effect of hypoxia, during infection. Thus, we report that: (1) CA IX increases in rat pneumonia lung; and, (2) the CA IX intracellular domain and hypoxia promote PMVEC survival during infection.

Blood vessels are primary targets for 2,3,7,8-tetrachlorodibenzo-p-dioxin in pre-cardiac edema formation in larval zebrafish

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has adverse effects on the development and function of the heart in zebrafish eleutheroembryos (embryos and larvae). We previously reported that TCDD reduced blood flow in the mesencephalic vein of zebrafish eleutheroembryos long before inducing pericardial edema. In the present study, we compared early edema (pre-cardiac edema), reduction of deduced cardiac output and reduction of blood flow in the dorsal aorta and cardinal vein caused by TCDD. In the same group of eleutheroembryos, TCDD (1.0 ppb) caused pre-cardiac edema and circulation failure at the cardinal vein in the central trunk region with the similar time courses from 42 to 54 h post fertilization (hpf), while the same concentration of TCDD did not significantly affect aortic circulation in the central trunk region or cardiac output. The dependence of pre-cardiac edema on TCDD concentration (0-2.0 ppb) at 55 hpf correlated well with the dependence of blood flow through the cardinal vein on TCDD concentration. Several treatments that markedly inhibited TCDD-induced pre-cardiac edema such as knockdown of aryl hydrocarbon receptor nuclear translocator-1 (ARNT1) and treatment with ascorbic acid, an antioxidant, did not significantly prevent the reduction of cardiac output at 55 hpf caused by 2.0 ppb TCDD. TCDD caused hemorrhage and extravasation of Evans blue that was intravascularly injected with bovine serum albumin, suggesting an increase in endothelium permeability to serum protein induced by TCDD. The results suggest that the blood vessels are primary targets of TCDD in edema formation in larval zebrafish.

Bioengineering the Blood-gas Barrier

The pulmonary blood-gas barrier represents a remarkable feat of engineering. It achieves the exquisite thinness needed for gas exchange by diffusion, the strength to withstand the stresses and strains of repetitive and changing ventilation, and the ability to actively maintain itself under varied demands. Understanding the design principles of this barrier is essential to understanding a variety of lung diseases, and to successfully regenerating or artificially recapitulating the barrier ex vivo. Many classical studies helped to elucidate the unique structure and morphology of the mammalian blood-gas barrier, and ongoing investigations have helped to refine these descriptions and to understand the biological aspects of blood-gas barrier function and regulation. This article reviews the key features of the blood-gas barrier that enable achievement of the necessary design criteria and describes the mechanical environment to which the barrier is exposed. It then focuses on the biological and mechanical components of the barrier that preserve integrity during homeostasis, but which may be compromised in certain pathophysiological states, leading to disease. Finally, this article summarizes recent key advances in efforts to engineer the blood-gas barrier ex vivo, using the platforms of lung-on-a-chip and tissue-engineered whole lungs. © 2020 American Physiological Society. Compr Physiol 10:415-452, 2020.

Liposomal glutathione as a promising candidate for immunological rheumatoid arthritis therapy

Nano-medicine can passively accumulate in chronic inflammatory tissues via the enhanced permeability and retention phenomenon, or by being conjugated with a ligand that can bind to receptors over expressed by cells inside chronic inflammatory tissues, contributing to reduced systemic side-effects and increased efficacy. This article highlights the utilization of nanomedicine for potential treatment of rheumatoid arthritis. Rheumatoid arthritis was induced in rat model via 2 weeks intradermal injection of pristane at the base of the tail in a daily dose of 150 μl. Susceptible rat strains developed severe arthritis with a sudden onset 3 weeks post pristane injection. Three weeks post pristane administration; rats were treated intravenously with glutathione or liposomal-glutathione in a dose of 5 mg/kg daily for 30 days. Concomitant supplementation with the aforementioned antioxidants effect on proinflammatory marker C-reactive protein (CRP) was assessed. On the other hand, oxidative stress biomarker malondialdehyde (MDA) and rheumatoid factor (RF) compared with pristane treated group was also investigated. The results elucidated that glutathione and liposomal -glutathione significantly reduced rheumatoid factor, malondialdehyde and C-reactive protein levels with the superiority of liposomal -glutathione in this side reflecting its pronounced effect as anti-rheumatoid agent.

Secreted Protein Acidic and Rich in Cysteine Mediated Biomimetic Delivery of Methotrexate by Albumin-Based Nanomedicines for Rheumatoid Arthritis Therapy

Rheumatoid arthritis (RA) is one of the most common chronic autoimmune diseases. Despite considerable advances in clinical treatment of RA, suboptimal response to therapy and treatment discontinuation are still unresolved challenges due to systemic toxicity. It is of crucial importance to actively target and deliver therapeutic agents to inflamed joints in order to promote in situ activity and decrease systemic toxicity. In this study, we found that SPARC (secreted protein acidic and rich in cysteine) was overexpressed in the synovial fluid and synovium of RA patients as well as mice with collagen-induced arthritis (CIA), which has been scarcely reported. Building upon the SPARC signature of RA joint microenvironment and the intrinsic high affinity of SPARC for albumin, we fabricated methotrexate-loaded human serum albumin nanomedicines (MTX@HSA NMs) and explored them as biomimetic drug delivery systems for RA therapy. Upon intravenous injection of chlorin e6-labeled MTX@HSA NMs into CIA mice, the fluorescence/magnetic resonance dual-modal imaging revealed higher accumulations and longer retention of MTX@HSA NMs in inflamed joints with respect to free MTX molecules. In vivo therapeutic evaluations suggested that the MTX@HSA NMs were able to attenuate the progression of RA with better efficacy and fewer side effects even at half  dose of administrated MTX in comparison with free MTX. By unraveling the mechanism driving the efficient accumulation of MTX@HSA NMs in RA joints and showing their ability to improve the safety and therapeutic efficacy of MTX, our work sheds light on the development of innovative anti-RA nanomedicines with a strong potential for clinical translation.

ORAI channels in cellular remodeling of cardiorespiratory disease

Cardiorespiratory disease, which includes systemic arterial hypertension, restenosis, atherosclerosis, pulmonary arterial hypertension, asthma, and chronic obstructive pulmonary disease (COPD) are highly prevalent and devastating diseases with limited therapeutic modalities. A common pathophysiological theme to these diseases is cellular remodeling, which is contributed by changes in expression and activation of ion channels critical for either excitability or growth. Calcium (Ca²⁺) signaling and specifically ORAI Ca²⁺ channels have emerged as significant regulators of smooth muscle, endothelial, epithelial, platelet, and immune cell remodeling. This review details the dysregulation of ORAI in cardiorespiratory diseases, and how this dysregulation of ORAI contributes to cellular remodeling.

Cortical Actin Dynamics in Endothelial Permeability

The pulmonary endothelial cell forms a critical semi-permeable barrier between the vascular and interstitial space. As part of the blood-gas barrier in the lung, the endothelium plays a key role in normal physiologic function and pathologic disease. Changes in endothelial cell shape, defined by its plasma membrane, determine barrier integrity. A number of key cytoskeletal regulatory and effector proteins including non-muscle myosin light chain kinase, cortactin, and Arp 2/3 mediate actin rearrangements to form cortical and membrane associated structures in response to barrier enhancing stimuli. These actin formations support and interact with junctional complexes and exert forces to protrude the lipid membrane to and close gaps between individual cells. The current knowledge of these cytoskeletal processes and regulatory proteins are the subject of this review. In addition, we explore novel advancements in cellular imaging that are poised to shed light on the complex nature of pulmonary endothelial permeability.

Recent advances in the understanding of endothelial barrier function and fluid therapy

Elucidation of the structural basis of endothelial barrier function and the study of transcapillary fluid exchange dynamics are areas of active research. There has been significant enhancement in our understanding of the ultrastructural basis of endothelial barrier function. The role of glycocalyx has received special attention. Experimental evidence has called for a revision in the classic Starling principle of transcapillary exchange. The glycocalyx model provides a potential structural mechanism for the revised Starling principle. This knowledge can provide the framework for understanding the volume expansion effect of fluid therapy and the physiological basis of fluid therapy.

Pulmonary vascular dysfunction secondary to pulmonary arterial hypertension: insights gained through retrograde perfusion

Here, we tested the hypothesis that severe pulmonary arterial hypertension impairs retrograde perfusion. To test this hypothesis, pulmonary arterial hypertension was induced in Fischer rats using a single injection of Sugen 5416 followed by 3 wk of exposure to 10% hypoxia and then 2 wk of normoxia. This Sugen 5416 and hypoxia regimen caused severe pulmonary arterial hypertension, with a Fulton index of 0.73 ± 0.07, reductions in both the pulmonary arterial acceleration time and pulmonary arterial acceleration to pulmonary arterial ejection times ratio, and extensive medial hypertrophy and occlusive neointimal lesions. Whereas the normotensive circulation accommodated large increases in forward and retrograde flow, the hypertensive circulation did not. During forward flow, pulmonary artery and double occlusion pressures rose sharply at low perfusion rates, resulting in hydrostatic edema. Pulmonary arterial hypertensive lungs possessed an absolute intolerance to retrograde perfusion, and they rapidly developed edema. Retrograde perfusion was not rescued by maximal vasodilation. Retrograde perfusion was preserved in lungs from animals treated with Sugen 5416 and hypoxia for 1 and 3 wk, in lungs from animals with a milder form of hypoxic hypertension, and in normotensive lungs subjected to high outflow pressures. Thus impaired retrograde perfusion coincides with development of severe pulmonary arterial hypertension, with advanced structural defects in the microcirculation.

Protective role of FKBP51 in calcium entry-induced endothelial barrier disruption

Pulmonary artery endothelial cells (PAECs) express a cation current, I_SOC (store-operated calcium entry current), which when activated permits calcium entry leading to inter-endothelial cell gap formation. The large molecular weight immunophilin FKBP51 inhibits I_SOC but not other calcium entry pathways in PAECs. However, it is unknown whether FKBP51-mediated inhibition of I_SOC is sufficient to protect the endothelial barrier from calcium entry-induced disruption. The major objective of this study was to determine whether FKBP51-mediated inhibition of I_SOC leads to decreased calcium entry-induced inter-endothelial gap formation and thus preservation of the endothelial barrier. Here, we measured the effects of thapsigargin-induced I_SOC on the endothelial barrier in control and FKBP51 overexpressing PAECs. FKBP51 overexpression decreased actin stress fiber and inter-endothelial cell gap formation in addition to attenuating the decrease in resistance observed with control cells using electric cell-substrate impedance sensing. Finally, the thapsigargin-induced increase in dextran flux was abolished in FKBP51 overexpressing PAECs. We then measured endothelial permeability in perfused lungs of FKBP51 knockout (FKBP51^–/–) mice and observed increased calcium entry-induced permeability compared to wild-type mice. To begin to dissect the mechanism underlying the FKBP51-mediated inhibition of I_SOC, a second goal of this study was to determine the role of the microtubule network. We observed that FKBP51 overexpressing PAECs exhibited increased microtubule polymerization that is critical for inhibition of I_SOC by FKBP51. Overall, we have identified FKBP51 as a novel regulator of endothelial barrier integrity, and these findings are significant as they reveal a protective mechanism for endothelium against calcium entry-induced disruption.

Tamoxifen-Related Thrombosis: An Experimental Study in Rat Venous Microvascular Anastomosis Model

Tamoxifen is an estrogen receptor modulator and has been shown to increase risk for microvascular flap complications. This study aimed to investigate the clinical and histopathological effects of tamoxifen use in venous microvascular anastomosis model in rats. The role of vitamin E combination therapy and discontinuing tamoxifen therapy preoperatively were also evaluated.Forty rats were equally divided into 4 groups as follows: group 1 was given saline by oral gavage, group 2 was given tamoxifen citrate, group 3 was given tamoxifen citrate and vitamin E, and in group 4, tamoxifen citrate was given everyday except between days 12 and 16. In each group, femoral veins were dissected in each side and end-to-end anastomosis was performed in one side. Clinical and histopathological evaluations were performed. The ratio of total endothelial area to total vein area in a cross-sectional view of the vein was evaluated and compared.All veins with anastomosis in postoperative 15 minutes were found to be patent. In postoperative 1 week in groups 1 to 4, visible thrombus were present in 1, 3, 2, and 3 samples, respectively. Vitamin E group showed similar histopathological findings with control group. The ratio of endothelial layer to total vein cross-sectional area was increased in groups 2 and 4 in all samples. The increase was statistically significant between groups 2NA and 3NA (P = 0.023) and 2A and 1A (P = 0.006).Chronic tamoxifen consumption in the presence of anastomosis have led to prominent endothelial proliferation in rat femoral veins. Vitamin E combination therapy reversed this endothelial proliferation and should be focused in future studies.

Single cell cloning generates lung endothelial colonies with conserved growth, angiogenic, and bioenergetic characteristics

Pulmonary artery, capillary, and vein endothelial cells possess distinctive structures and functions, which represent a form of vascular segment specific macroheterogeneity. However, within each of these segmental populations, individual cell functional variability represents a poorly characterized microheterogeneity. Here, we hypothesized that single cell clonogenic assays would reveal microheterogeneity among the parent cell population and enable isolation of highly representative cells with committed parental characteristics. To test this hypothesis, pulmonary microvascular endothelial cells (PMVECs) and pulmonary arterial endothelial cells (PAECs) were isolated from different Sprague Dawley rats. Serum stimulated proliferation of endothelial populations and single cell clonogenic potential were evaluated. In vitro Matrigel assays were utilized to analyze angiogenic potential and the Seahorse assay was used to evaluate bioenergetic profiles. PMVEC populations grew faster and had a higher proliferative potential than PAEC populations. Fewer PMVECs were needed to form networks on Matrigel when compared with PAECs. PMVECs primarily utilized aerobic glycolysis, while PAECs relied more heavily on oxidative phosphorylation, to support bioenergetic demands. Repeated single cell cloning and expansion of PAEC colonies generated homogeneous first-generation clones that were highly reflective of the parental population in terms of growth, angiogenic potential, and bioenergetic profiles. Repeated single cell cloning of the first-generation clones generated second-generation clones with increased proliferative potential while maintaining other parental characteristics. Second-generation clones were highly homogeneous populations. Thus, single cell cloning reveals microheterogeneity among the parent cell population and enables isolation of highly representative cells with parental characteristics.

Therapeutic effects of lornoxicam-loaded nanomicellar formula in experimental models of rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is a chronic inflammatory disease treated by nonsteroidal anti-inflammatory drugs (NSAIDs) including lornoxicam (LX). Nanocarriers have been used to increase the efficacy and reduce the side effects of various drugs. The objective of the present study was to compare the therapeutic efficacy of systemic administration of lornoxicam-loaded nanomicellar formula (LX-NM) with that of free LX.

Materials and methods

The LX-loaded mixed polymeric nanomicellar formula was prepared by direct equilibrium technique. Two rat models were used in the study: carrageenan-induced acute edema and Freund’s complete adjuvant (FCA)-induced chronic arthritis.

Results

The inhibitory effect of LX-NM on carrageenan-induced edema was higher than free LX for the same dose (1.3 mg/kg, i.p.). LX-NM (0.325 mg/kg, i.p.) produced effects comparable to that of diclofenac, which served as a standard. In the FCA model, daily treatment with LX-NM (0.325 mg/kg, i.p.) starting on day 14 significantly reduced the percentage of edema and increased weight growth. However, the same dose of LX failed to confer any significant change. Additionally, LX-NM significantly attenuated the rise of tumor necrosis factor-α (TNF-α), interleukin-1β, prostaglandin E2, nuclear factor-κβ, malondialdehyde and nitric oxide serum levels. In contrast, LX failed to show any significant reduction in elevated serum biomarkers except for TNF-α.

Conclusion

LX-NM is an alternative delivery system that is simply prepared at low costs. It showed a superior therapeutic efficacy against RA compared to free LX. Thus, LX-NM can be considered as a promising candidate for treatment of RA and similar inflammatory disorders.

Exposure of Stored Packed Erythrocytes to Nitric Oxide Prevents Transfusion-associated Pulmonary Hypertension

BACKGROUND

Transfusion of packed erythrocytes stored for a long duration is associated with increased pulmonary arterial pressure and vascular resistance. Prolonged storage decreases erythrocyte deformability, and older erythrocytes are rapidly removed from the circulation after transfusion. The authors studied whether treating stored packed ovine erythrocytes with NO before transfusion could prevent pulmonary vasoconstriction, enhance erythrocyte deformability, and prolong erythrocyte survival after transfusion.

METHODS

Ovine leukoreduced packed erythrocytes were treated before transfusion with either NO gas or a short-lived NO donor. Sheep were transfused with autologous packed erythrocytes, which were stored at 4°C for either 2 ("fresh blood") or 40 days ("stored blood"). Pulmonary and systemic hemodynamic parameters were monitored before, during, and after transfusion. Transfused erythrocytes were labeled with biotin to measure their circulating lifespan. Erythrocyte deformability was assessed before and after NO treatment using a microfluidic device.

RESULTS

NO treatment improved the deformability of stored erythrocytes and increased the number of stored erythrocytes circulating at 1 and 24 h after transfusion. NO treatment prevented transfusion-associated pulmonary hypertension (mean pulmonary arterial pressure at 30 min of 21 ± 1 vs. 15 ± 1 mmHg in control and NO-treated packed erythrocytes, P < 0.0001). Washing stored packed erythrocytes before transfusion did not prevent pulmonary hypertension.

CONCLUSIONS

NO treatment of stored packed erythrocytes before transfusion oxidizes cell-free oxyhemoglobin to methemoglobin, prevents subsequent NO scavenging in the pulmonary vasculature, and limits pulmonary hypertension. NO treatment increases erythrocyte deformability and erythrocyte survival after transfusion. NO treatment might provide a promising therapeutic approach to prevent pulmonary hypertension and extend erythrocyte survival.

The ARP 2/3 complex mediates endothelial barrier function and recovery

Pulmonary endothelial cell (EC) barrier dysfunction and recovery is critical to the pathophysiology of acute respiratory distress syndrome. Cytoskeletal and subsequent cell membrane dynamics play a key mechanistic role in determination of EC barrier integrity. Here, we characterizAQe the actin related protein 2/3 (Arp 2/3) complex, a regulator of peripheral branched actin polymerization, in human pulmonary EC barrier function through studies of transendothelial electrical resistance (TER), intercellular gap formation, peripheral cytoskeletal structures and lamellipodia. Compared to control, Arp 2/3 inhibition with the small molecule inhibitor CK-666 results in a reduction of baseline barrier function (1,241 ± 53 vs 988 ± 64 ohm; p < 0.01), S1P-induced barrier enhancement and delayed recovery of barrier function after thrombin (143 ± 14 vs 93 ± 6 min; p < 0.01). Functional changes of Arp 2/3 inhibition on barrier integrity are associated temporally with increased intercellular gap area at baseline (0.456 ± 0.02 vs 0.299 ± 0.02; p < 0.05) and thirty minutes after thrombin (0.885 ± 0.03 vs 0.754 ± 0.03; p < 0.05). Immunofluorescent microscopy reveals reduced lamellipodia formation after S1P and during thrombin recovery in Arp 2/3 inhibited cells. Individual lamellipodia demonstrate reduced depth following Arp 2/3 inhibition vs vehicle at baseline (1.83 ± 0.41 vs 2.55 ± 0.46 µm; p < 0.05) and thirty minutes after S1P treatment (1.53 ± 0.37 vs 2.09 ± 0.36 µm; p < 0.05). These results establish a critical role for Arp 2/3 activity in determination of pulmonary endothelial barrier function and recovery through formation of EC lamellipodia and closure of intercellular gaps.

IL-4 Causes Hyperpermeability of Vascular Endothelial Cells through Wnt5A Signaling

Microvascular leakage due to endothelial barrier dysfunction is a prominent feature of T helper 2 (Th2) cytokine mediated allergic inflammation. Interleukin-4 (IL-4) is a potent Th2 cytokine, known to impair the barrier function of endothelial cells. However, the effectors mediating IL-4 induced cytoskeleton remodeling and consequent endothelial barrier dysfunction remain poorly defined. Here we have used whole genome transcriptome profiling and gene ontology analyses to identify the genes and processes regulated by IL-4 signaling in human coronary artery endothelial cells (HCAEC). The study revealed Wnt5A as an effector that can mediate actin cytoskeleton remodeling in IL-4 activated HCAEC through the regulation of LIM kinase (LIMK) and Cofilin (CFL). Following IL-4 treatment, LIMK and CFL were phosphorylated, thereby indicating the possibility of actin stress fiber formation. Imaging of actin showed the formation of stress fibers in IL-4 treated live HCAEC. Stress fiber formation was notably decreased in the presence of Wnt inhibitory factor 1 (WIF1). Non-invasive impedance measurements demonstrated that IL-4 increased the permeability and impaired the barrier function of HCAEC monolayers. Silencing Wnt5A significantly reduced permeability and improved the barrier function of HCAEC monolayers upon IL-4 treatment. Our study identifies Wnt5A as a novel marker of IL-4 activated vascular endothelium and demonstrates a critical role for Wnt5A in mediating IL-4 induced endothelial barrier dysfunction. Wnt5A could be a potential therapeutic target for reducing microvascular leakage and edema formation in Th2 driven inflammatory diseases.

Molecular pathophysiology of cerebral edema

Advancements in molecular biology have led to a greater understanding of the individual proteins responsible for generating cerebral edema. In large part, the study of cerebral edema is the study of maladaptive ion transport. Following acute CNS injury, cells of the neurovascular unit, particularly brain endothelial cells and astrocytes, undergo a program of pre- and post-transcriptional changes in the activity of ion channels and transporters. These changes can result in maladaptive ion transport and the generation of abnormal osmotic forces that, ultimately, manifest as cerebral edema. This review discusses past models and current knowledge regarding the molecular and cellular pathophysiology of cerebral edema.

N-cadherin coordinates AMP kinase-mediated lung vascular repair

Injury to the pulmonary circulation compromises endothelial barrier function and increases lung edema. Resolution of lung damage involves restoring barrier integrity, a process requiring reestablishment of endothelial cell-cell adhesions. However, mechanisms underlying repair in lung endothelium are poorly understood. In pulmonary microvascular endothelium, AMP kinase α1 (AMPKα1) stimulation enhances recovery of the endothelial barrier after LPS-induced vascular damage. AMPKα1 colocalizes to a discrete membrane compartment with the adhesion protein neuronal cadherin (N-cadherin). This study sought to determine N-cadherin's role in the repair process. Short-hairpin RNA against full-length N-cadherin or a C-terminally truncated N-cadherin, designed to disrupt the cadherin's interactions with intracellular proteins, were expressed in lung endothelium. Disruption of N-cadherin's intracellular domain caused translocation of AMPK away from the membrane and attenuated AMPK-mediated restoration of barrier function in LPS-treated endothelium. AMPK activity measurements indicated that lower basal AMPK activity in cells expressing the truncated N-cadherin compared with controls. Moreover, the AMPK stimulator 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) failed to increase AMPK activity in cells expressing the modified N-cadherin, indicating uncoupling of a functional association between AMPK and the cadherin. Isolated lung studies confirmed a physiologic role for this pathway in vivo. AMPK activation reversed LPS-induced increase in permeability, whereas N-cadherin inhibition hindered AMPK-mediated repair. Thus N-cadherin coordinates the vascular protective actions of AMPK through a functional link with the kinase. This study provides insight into intrinsic repair mechanisms in the lung and supports AMPK stimulation as a modality for treating vascular disease.

Nanomedicine delivers promising treatments for rheumatoid arthritis

An increased understanding in the pathophysiology of chronic inflammatory diseases, such as rheumatoid arthritis, reveals that the diseased tissue and the increased presence of macrophages and other overexpressed molecules within the tissue can be exploited to enhance the delivery of nanomedicine. Nanomedicine can passively accumulate into chronic inflammatory tissues via the enhanced permeability and retention phenomenon, or be surface conjugated with a ligand to actively bind to receptors overexpressed by cells within chronic inflammatory tissues, leading to increased efficacy and reduced systemic side-effects. This review highlights the research conducted over the past decade on using nanomedicine for potential treatment of rheumatoid arthritis and summarizes some of the major findings and promising opportunities on using nanomedicine to treat this prevalent and chronic disease.

Autologous transfusion of stored red blood cells increases pulmonary artery pressure

RATIONALE

Transfusion of erythrocytes stored for prolonged periods is associated with increased mortality. Erythrocytes undergo hemolysis during storage and after transfusion. Plasma hemoglobin scavenges endogenous nitric oxide leading to systemic and pulmonary vasoconstriction.

OBJECTIVES

We hypothesized that transfusion of autologous blood stored for 40 days would increase the pulmonary artery pressure in volunteers with endothelial dysfunction (impaired endothelial production of nitric oxide). We also tested whether breathing nitric oxide before and during transfusion could prevent the increase of pulmonary artery pressure.

METHODS

Fourteen obese adults with endothelial dysfunction were enrolled in a randomized crossover study of transfusing autologous, leukoreduced blood stored for either 3 or 40 days. Volunteers were transfused with 3-day blood, 40-day blood, and 40-day blood while breathing 80 ppm nitric oxide.

MEASUREMENTS AND MAIN RESULTS

The age of volunteers was 41 ± 4 years (mean ± SEM), and their body mass index was 33.4 ± 1.3 kg/m(2). Plasma hemoglobin concentrations increased after transfusion with 40-day and 40-day plus nitric oxide blood but not after transfusing 3-day blood. Mean pulmonary artery pressure, estimated by transthoracic echocardiography, increased after transfusing 40-day blood (18 ± 2 to 23 ± 2 mm Hg; P < 0.05) but did not change after transfusing 3-day blood (17 ± 2 to 18 ± 2 mm Hg; P = 0.5). Breathing nitric oxide decreased pulmonary artery pressure in volunteers transfused with 40-day blood (17 ± 2 to 12 ± 1 mm Hg; P < 0.05).

CONCLUSIONS

Transfusion of autologous leukoreduced blood stored for 40 days was associated with increased plasma hemoglobin levels and increased pulmonary artery pressure. Breathing nitric oxide prevents the increase of pulmonary artery pressure produced by transfusing stored blood. Clinical trial registered with www.clinicaltrials.gov (NCT 01529502).

Sodium entry through endothelial store-operated calcium entry channels: regulation by Orai1

Orai1 interacts with transient receptor potential protein of the canonical subfamily (TRPC4) and contributes to calcium selectivity of the endothelial cell store-operated calcium entry current (ISOC). Orai1 silencing increases sodium permeability and decreases membrane-associated calcium, although it is not known whether Orai1 is an important determinant of cytosolic sodium transitions. We test the hypothesis that, upon activation of store-operated calcium entry channels, Orai1 is a critical determinant of cytosolic sodium transitions. Activation of store-operated calcium entry channels transiently increased cytosolic calcium and sodium, characteristic of release from an intracellular store. The sodium response occurred more abruptly and returned to baseline more rapidly than did the transient calcium rise. Extracellular choline substitution for sodium did not inhibit the response, although 2-aminoethoxydiphenyl borate and YM-58483 reduced it by ∼50%. After this transient response, cytosolic sodium continued to increase due to influx through activated store-operated calcium entry channels. The magnitude of this sustained increase in cytosolic sodium was greater when experiments were conducted in low extracellular calcium and when Orai1 expression was silenced; these two interventions were not additive, suggesting a common mechanism. 2-Aminoethoxydiphenyl borate and YM-58483 inhibited the sustained increase in cytosolic sodium, only in the presence of Orai1. These studies demonstrate that sodium permeates activated store-operated calcium entry channels, resulting in an increase in cytosolic sodium; the magnitude of this response is determined by Orai1.

A unique pulmonary microvascular endothelial cell niche revealed by Weibel-Palade bodies and Griffonia simplicifolia

Pulmonary endothelium displays considerable heterogeneity along the vascular axis, from arteries to capillaries to veins. Griffonia simplicifolia is a lectin that recognizes pulmonary microvascular endothelium with preference over extra-alveolar endothelium in both arteries and veins, yet the precise vascular location where this phenotypic shift occurs is poorly resolved. We gelatin-filled the circulation and agarose-loaded the airways and then labeled the lung with Griffonia lectin to enable visualization of the endothelial transition zone. Endothelium in vessels with internal diameters less than 38 μm were uniformly Griffonia positive, whereas vessels with internal diameters greater than 60 μm were always Griffonia negative. Two populations of endothelium were identified in vessels ranging from 38 to 60 μm in diameter, including some that were positive and others that were negative for binding to G. simplicifolia. To better resolve this endothelial transition zone, we performed morphology studies to measure the distribution of Weibel-Palade bodies (WPbs), since WPbs are present in conduit vessel endothelium and absent in capillary endothelium. WPbs were found in endothelium with vascular dimensions as small as 18 μm in diameter but were not found in capillaries. Thus, we identify with precision that the endothelial phenotype transition from a cell that does not interact with Griffonia lectin to one that does occurs in blood vessels with internal diameters of approximately 38 μm, and we reveal an unappreciated vascular zone, between 18 and 38 μm in diameter, where endothelium both is Griffonia positive and possesses WPbs.

The Pseudomonas aeruginosa exoenzyme Y impairs endothelial cell proliferation and vascular repair following lung injury

Exoenzyme Y (ExoY) is a Pseudomonas aeruginosa toxin that is introduced into host cells through the type 3 secretion system (T3SS). Once inside the host cell cytoplasm, ExoY generates cyclic nucleotides that cause tau phosphorylation and microtubule breakdown. Microtubule breakdown causes interendothelial cell gap formation and tissue edema. Although ExoY transiently induces interendothelial cell gap formation, it remains unclear whether ExoY prevents repair of the endothelial cell barrier. Here, we test the hypothesis that ExoY intoxication impairs recovery of the endothelial cell barrier following gap formation, decreasing migration, proliferation, and lung repair. Pulmonary microvascular endothelial cells (PMVECs) were infected with P. aeruginosa strains for 6 h, including one possessing an active ExoY (PA103 exoUexoT::Tc pUCPexoY; ExoY(+)), one with an inactive ExoY (PA103ΔexoUexoT::Tc pUCPexoY(K81M); ExoY(K81M)), and one that lacks PcrV required for a functional T3SS (ΔPcrV). ExoY(+) induced interendothelial cell gaps, whereas ExoY(K81M) and ΔPcrV did not promote gap formation. Following gap formation, bacteria were removed and endothelial cell repair was examined. PMVECs were unable to repair gaps even 3-5 days after infection. Serum-stimulated growth was greatly diminished following ExoY intoxication. Intratracheal inoculation of ExoY(+) and ExoY(K81M) caused severe pneumonia and acute lung injury. However, whereas the pulmonary endothelial cell barrier was functionally improved 1 wk following ExoY(K81M) infection, pulmonary endothelium was unable to restrict the hyperpermeability response to elevated hydrostatic pressure following ExoY(+) infection. In conclusion, ExoY is an edema factor that chronically impairs endothelial cell barrier integrity following lung injury.

Clinical syndromes associated with acquired antithrombin deficiency via microvascular leakage and the related risk of thrombosis

Antithrombin (AT) is a 65kDa glycoprotein belonging to a group of inhibitory factors known as serpins (serine protease inhibitors). It plays a critical role in the inhibition of coagulation and inflammation processes within the environment of the vascular endothelium. Inadequate levels of functional AT in plasma results in an increased risk of thrombotic events, both venous and arterial. AT deficiency can be inherited or acquired. Congenital AT deficiency is the most severe inherited thrombophilic condition with an odds ratio of 20 for the increased risk of venous thrombosis. Acquired AT deficiency occurs in a variety of physiologic and pathologic medical conditions with similar risks of increased thrombosis. In this article, we review clinical settings characterized by an acquired AT deficiency largely or partly subsequent to protein microvascular leakage. Other different mechanisms of AT depletion are implied in some clinical conditions together with endothelial loss, and, therefore, outlined. In addition, we provide a description of the current knowledge on the specific mechanisms underlying endothelial AT leakage and on the consequences of this protein decrease, specifically looking at thrombosis. We identify potential directions of research that might prove useful in patients with acquired AT deficiency.

Novel concepts of acute lung injury and alveolar-capillary barrier dysfunction

In this review we summarize recent major advances in our understanding on the molecular mechanisms, mediators, and biomarkers of acute lung injury (ALI) and alveolar-capillary barrier dysfunction, highlighting the role of immune cells, inflammatory and noninflammatory signaling events, mechanical noxae, and the affected cellular and molecular entities and functions. Furthermore, we address novel aspects of resolution and repair of ALI, as well as putative candidates for treatment of ALI, including pharmacological and cellular therapeutic means.

HIF-dependent regulation of AKAP12 (gravin) in the control of human vascular endothelial function

Hypoxia has been widely implicated in many pathological conditions, including those associated with inflammation and tumorigenesis. A number of recent studies have implicated hypoxia in the control of vasculogenesis and permeability, the basis for which is not fully understood. Here we examine the transcriptional regulation of angiogenesis and permeability by hypoxia in endothelial cells. Guided by a global profiling approach in cultured endothelial cells, these studies revealed the selective induction of human gravin (protein kinase A anchoring protein 12) by hypoxia. Analysis of the cloned gravin promoter identified a functional hypoxia-responsive region including 2 binding sites for hypoxia-inducible factor (HIF). Site-directed mutagenesis identified the most distal HIF-binding site as essential for the induction of gravin by hypoxia. Further studies examining gravin gain and loss of function confirmed strong dependence of gravin in control of microvascular endothelial tube formation, wherein gravin functions as a "braking" system for angiogenesis. Additional studies in confluent endothelia revealed that gravin functionally couples to control endothelial barrier function in response to protein kinase A (PKA) agonists. Taken together, these results demonstrate transcriptional coordination of gravin by HIF-1α and amplified PKA-dependent endothelial responses. These findings provide an important link between hypoxia and metabolic conditions associated with inflammation and angiogenesis.

Pseudomonas aeruginosa exotoxin Y-mediated tau hyperphosphorylation impairs microtubule assembly in pulmonary microvascular endothelial cells

Pseudomonas aeruginosa uses a type III secretion system to introduce the adenylyl and guanylyl cyclase exotoxin Y (ExoY) into the cytoplasm of endothelial cells. ExoY induces Tau hyperphosphorylation and insolubility, microtubule breakdown, barrier disruption and edema, although the mechanism(s) responsible for microtubule breakdown remain poorly understood. Here we investigated both microtubule behavior and centrosome activity to test the hypothesis that ExoY disrupts microtubule dynamics. Fluorescence microscopy determined that infected pulmonary microvascular endothelial cells contained fewer microtubules than control cells, and further studies demonstrated that the microtubule-associated protein Tau was hyperphosphorylated following infection and dissociated from microtubules. Disassembly/reassembly studies determined that microtubule assembly was disrupted in infected cells, with no detectable effects on either microtubule disassembly or microtubule nucleation by centrosomes. This effect of ExoY on microtubules was abolished when the cAMP-dependent kinase phosphorylation site (Ser-214) on Tau was mutated to a non-phosphorylatable form. These studies identify Tau in microvascular endothelial cells as the target of ExoY in control of microtubule architecture following pulmonary infection by Pseudomonas aeruginosa and demonstrate that phosphorylation of tau following infection decreases microtubule assembly.

Interaction of membrane/lipid rafts with the cytoskeleton: impact on signaling and function: membrane/lipid rafts, mediators of cytoskeletal arrangement and cell signaling

The plasma membrane in eukaryotic cells contains microdomains that are enriched in certain glycosphingolipids, gangliosides, and sterols (such as cholesterol) to form membrane/lipid rafts (MLR). These regions exist as caveolae, morphologically observable flask-like invaginations, or as a less easily detectable planar form. MLR are scaffolds for many molecular entities, including signaling receptors and ion channels that communicate extracellular stimuli to the intracellular milieu. Much evidence indicates that this organization and/or the clustering of MLR into more active signaling platforms depends upon interactions with and dynamic rearrangement of the cytoskeleton. Several cytoskeletal components and binding partners, as well as enzymes that regulate the cytoskeleton, localize to MLR and help regulate lateral diffusion of membrane proteins and lipids in response to extracellular events (e.g., receptor activation, shear stress, electrical conductance, and nutrient demand). MLR regulate cellular polarity, adherence to the extracellular matrix, signaling events (including ones that affect growth and migration), and are sites of cellular entry of certain pathogens, toxins and nanoparticles. The dynamic interaction between MLR and the underlying cytoskeleton thus regulates many facets of the function of eukaryotic cells and their adaptation to changing environments. Here, we review general features of MLR and caveolae and their role in several aspects of cellular function, including polarity of endothelial and epithelial cells, cell migration, mechanotransduction, lymphocyte activation, neuronal growth and signaling, and a variety of disease settings. This article is part of a Special Issue entitled: Reciprocal influences between cell cytoskeleton and membrane channels, receptors and transporters. Guest Editor: Jean Claude Hervé.

Glassy dynamics, cell mechanics, and endothelial permeability

A key feature of all inflammatory processes is disruption of the vascular endothelial barrier. Such disruption is initiated in part through active contraction of the cytoskeleton of the endothelial cell (EC). Because contractile forces are propagated from cell to cell across a great many cell-cell junctions, this contractile process is strongly cooperative and highly nonlocal. We show here that the characteristic length scale of propagation is modulated by agonists and antagonists that impact permeability of the endothelial barrier. In the presence of agonists including thrombin, histamine, and H2O2, force correlation length increases, whereas in the presence of antagonists including sphingosine-1-phosphate, hepatocyte growth factor, and the rho kinase inhibitor, Y27632, force correlation length decreases. Intercellular force chains and force clusters are also evident, both of which are reminiscent of soft glassy materials approaching a glass transition.

Modeling serotonin uptake in the lung shows endothelial transporters dominate over cleft permeation

A four-region (capillary plasma, endothelium, interstitial fluid, cell) multipath model was configured to describe the kinetics of blood-tissue exchange for small solutes in the lung, accounting for regional flow heterogeneity, permeation of cell membranes and through interendothelial clefts, and intracellular reactions. Serotonin uptake data from the Multiple indicator dilution "bolus sweep" experiments of Rickaby and coworkers (Rickaby DA, Linehan JH, Bronikowski TA, Dawson CA. J Appl Physiol 51: 405-414, 1981; Rickaby DA, Dawson CA, and Linehan JH. J Appl Physiol 56: 1170-1177, 1984) and Malcorps et al. (Malcorps CM, Dawson CA, Linehan JH, Bronikowski TA, Rickaby DA, Herman AG, Will JA. J Appl Physiol 57: 720-730, 1984) were analyzed to distinguish facilitated transport into the endothelial cells (EC) and the inhibition of tracer transport by nontracer serotonin in the bolus of injectate from the free uninhibited permeation through the clefts into the interstitial fluid space. The permeability-surface area products (PS) for serotonin via the inter-EC clefts were ~0.3 ml·g⁻¹·min⁻¹, low compared with the transporter-mediated maximum PS of 13 ml·g⁻¹·min⁻¹ (with Km = ~0.3 μM and Vmax = ~4 nmol·g⁻¹·min⁻¹). The estimates of serotonin PS values for EC transporters from their multiple data sets were similar and were influenced only modestly by accounting for the cleft permeability in parallel. The cleft PS estimates in these Ringer-perfused lungs are less than half of those for anesthetized dogs (Yipintsoi T. Circ Res 39: 523-531, 1976) with normal hematocrits, but are compatible with passive noncarrier-mediated transport observed later in the same laboratory (Dawson CA, Linehan JH, Rickaby DA, Bronikowski TA. Ann Biomed Eng 15: 217-227, 1987; Peeters FAM, Bronikowski TA, Dawson CA, Linehan JH, Bult H, Herman AG. J Appl Physiol 66: 2328-2337, 1989) The identification and quantitation of the cleft pathway conductance from these studies affirms the importance of the cleft permeation.

Ultrasound-mediated drug delivery for cardiovascular disease

INTRODUCTION

Ultrasound (US) has been developed as both a valuable diagnostic tool and a potent promoter of beneficial tissue bioeffects for the treatment of cardiovascular disease. These effects can be mediated by mechanical oscillations of circulating microbubbles, or US contrast agents, which may also encapsulate and shield a therapeutic agent in the bloodstream. Oscillating microbubbles can create stresses directly on nearby tissue or induce fluid effects that effect drug penetration into vascular tissue, lyse thrombi or direct drugs to optimal locations for delivery.

AREAS COVERED

The present review summarizes investigations that have provided evidence for US-mediated drug delivery as a potent method to deliver therapeutics to diseased tissue for cardiovascular treatment. In particular, the focus will be on investigations of specific aspects relating to US-mediated drug delivery, such as delivery vehicles, drug transport routes, biochemical mechanisms and molecular targeting strategies.

EXPERT OPINION

These investigations have spurred continued research into alternative therapeutic applications, such as bioactive gas delivery and new US technologies. Successful implementation of US-mediated drug delivery has the potential to change the way many drugs are administered systemically, resulting in more effective and economical therapeutics, and less-invasive treatments.

Regulation and repair of the alveolar-capillary barrier in acute lung injury

Considerable progress has been made in understanding the basic mechanisms that regulate fluid and protein exchange across the endothelial and epithelial barriers of the lung under both normal and pathological conditions. Clinically relevant lung injury occurs most commonly from severe viral and bacterial infections, aspiration syndromes, and severe shock. The mechanisms of lung injury have been identified in both experimental and clinical studies. Recovery from lung injury requires the reestablishment of an intact endothelial barrier and a functional alveolar epithelial barrier capable of secreting surfactant and removing alveolar edema fluid. Repair mechanisms include the participation of endogenous progenitor cells in strategically located niches in the lung. Novel treatment strategies include the possibility of cell-based therapy that may reduce the severity of lung injury and enhance lung repair.

Human alveolar epithelial cells attenuate pulmonary microvascular endothelial cell permeability under septic conditions

Acute lung injury (ALI) and its most severe form, acute respiratory distress syndrome (ARDS), are characterised by high-protein pulmonary edema and severe hypoxaemic respiratory failure due to increased permeability of pulmonary microvascular endothelial cells (PMVEC). Alveolar epithelial cells (AEC) contribute importantly to normal alveolar function, and AEC dysfunction in ALI/ARDS is associated with worse outcomes. We hypothesized that AEC can modulate human PMVEC barrier function, and investigated the effects of AEC presence on human PMVEC barrier under septic conditions in vitro. PMVEC isolated from human lung were treated in vitro with septic stimulation (lipopolysaccharide [LPS], a mixture of clinically-relevant cytokines [cytomix], or plasma from patients with severe sepsis), and the trans-PMVEC leak of Evans Blue dye-labeled albumin assessed. PMVEC septic responses were compared in the presence/absence of co-cultured A549 epithelial cell line or primary human AEC. Septic stimulation with LPS, cytomix, or septic plasma induced marked PMVEC hyper-permeability (10.2±1.8, 8.9±2.2, and 3.7±0.2 fold-increase vs. control, respectively, p<0.01 for all). The presence of A549 cells or primary human AEC in a non-contact co-culture model attenuated septic PMVEC hyper-permeability by 39±4% to 100±3%, depending on the septic stimulation (p<0.05). Septic PMVEC hyper-permeability was also attenuated following treatment with culture medium conditioned by previous incubation with either naïve or cytomix-treated A549 cells (p<0.05), and this protective effect of A549 cell-conditioned medium was both heat-stable and transferable following lipid extraction. Cytomix-stimulated PMN-dependent PMVEC hyper-permeability and trans-PMVEC PMN migration were also inhibited in the presence of A549 cells or A549 cell-conditioned medium (p<0.05). Human AEC appear to protect human PMVEC barrier function under septic conditions in vitro, through release of a soluble mediator(s), which are at least partly lipid in nature. This study suggests a scientific and potential clinical therapeutic importance of epithelial-endothelial cross talk in maintaining alveolar integrity in ALI/ARDS.