High-molecular-weight hyaluronan is a novel inhibitor of pulmonary vascular leakiness

Hyaluronan and Reactive Oxygen Species Signaling—Novel Cues from the Matrix?

Hyaluronan (HA) is a naturally occurring non-sulfated glycosaminoglycan (GAG) localized to the cell surface and the tissue extracellular matrix (ECM). It is composed of disaccharides containing glucuronic acid and N-acetylglucosamine, is synthesized by the HA synthase (HAS) enzymes and is degraded by hyaluronidase (HYAL) or reactive oxygen and nitrogen species (ROS/RNS) actions. HA is deposited as a high molecular weight (HMW) polymer and degraded to low molecular weight (LMW) fragments and oligosaccharides. HA affects biological functions by interacting with HA-binding proteins (hyaladherins). HMW HA is anti-inflammatory, immunosuppressive, and antiangiogenic, whereas LMW HA has pro-inflammatory, pro-angiogenetic, and oncogenic effects. ROS/RNS naturally degrade HMW HA, albeit at enhanced levels during tissue injury and inflammatory processes. Thus, the degradation of endothelial glycocalyx HA by increased ROS challenges vascular integrity and can initiate several disease progressions. Conversely, HA exerts a vital role in wound healing through ROS-mediated HA modifications, which affect the innate immune system. The normal turnover of HA protects against matrix rigidification. Insufficient turnover leads to increased tissue rigidity, leading to tissue dysfunction. Both endogenous and exogenous HMW HA have a scavenging capacity against ROS. The interactions of ROS/RNS with HA are more complex than presently perceived and present an important research topic.

The role of hyaluronan in endothelial glycocalyx and potential preventative lifestyle strategy with advancing age

The endothelial glycocalyx (EG) is a gel-like structure that forms a layer in between the surface of the endothelium and lumen. EG was once thought to be merely a structural support for the endothelium. However, in recent years, the importance of EG as a first line of defense and a key regulator to endothelial integrity has been illuminated. With advanced age, EG deterioration becomes more noticeable and at least partially associated with endothelial dysfunction. Hyaluronan (HA), one of the critical components of the EG, has distinct properties and roles to the maintenance of EG and endothelial function. Therefore, given the intimate relationship between the EG and endothelium during the aging process, HA may serve as a promising therapeutic target to prevent endothelial dysfunction.

CPAP-induced airway hyper-reactivity in mice is modulated by hyaluronan synthase-3

BACKGROUND

Continuous positive airway pressure (CPAP) is a primary mode of respiratory support for preterm infants. Animal studies have shown long-term detrimental effects on lung/airway development, particularly airway (AW) hyper-reactivity, as an unfortunate consequence of neonatal CPAP. Since the hyaluronan (HA) synthesizing enzyme hyaluronan synthase-3 (HAS3) is involved in various adult pulmonary disorders, the present study used a neonatal mouse model to investigate the role of HAS3 in CPAP-induced AW hyper-reactivity.

METHODS

Male and female neonatal mice were fitted with a custom-made mask for delivery of daily CPAP 3 h/day for 7 days. At postnatal day 21 (2 weeks after CPAP ended), airway (AW) hyper-reactivity and HAS3 expression were assessed with and without in vitro HAS3 siRNA treatment.

RESULTS

MRIs of 3-day-old mice confirmed that CPAP increased lung volume with incrementing inflation pressures. CPAP increased AW reactivity in both male and female mice, which was associated with increased airway smooth muscle and epithelial HAS3 immunoreactivity. CPAP did not affect HA accumulation, but HAS3 siRNA reversed CPAP-induced AW hyper-reactivity and reduced HAS3 expression.

CONCLUSIONS

These data in mice implicate a role for HAS3 in long-term effects of CPAP in the developing airway in the context of preterm birth and CPAP therapy.

IMPACT

Neonatal CPAP increases airway smooth muscle and epithelial HAS3 expression in mice. CPAP-induced airway hyper-reactivity is modulated by HAS3. These data enhance our understanding of the role mechanical forces play on lung development. These data are a significance step toward understanding CPAP effects on developing airway. These data may impact clinical recognition of the ways that CPAP may contribute to wheezing disorders of former preterm infants.

Hyaluronic acid restored protein permeability across injured human lung microvascular endothelial cells

Lung endothelial permeability is a key pathological feature of acute respiratory distress syndrome. Hyaluronic acid (HA), a major component of the glycocalyx layer on the endothelium, is generated by HA synthase (HAS) during inflammation and injury and is critical for repair. We hypothesized that administration of exogenous high molecular weight (HMW) HA would restore protein permeability across human lung microvascular endothelial cells (HLMVEC) injured by an inflammatory insult via upregulation of HAS by binding to CD44. A transwell coculture system was used to study the effects of HA on protein permeability across HLMVEC injured by cytomix, a mixture of IL‐1β, TNFα, and IFNγ, with or without HMW or low molecular weight (LMW) HA. Coincubation with HMW HA, but not LMW HA, improved protein permeability following injury at 24 h. Fluorescence microscopy demonstrated that exogenous HMW HA partially prevented the increase in “actin stress fiber” formation. HMW HA also increased the synthesis of HAS2 mRNA expression and intracellular HMW HA levels in HLMVEC following injury. Pretreatment with an anti‐CD44 antibody or 4‐methylumbelliferone, a HAS inhibitor, blocked the therapeutic effects. In conclusion, exogenous HMW HA restored protein permeability across HLMVEC injured by an inflammatory insult in part through upregulation of HAS2.

Role of extracellular vesicles in severe pneumonia and sepsis

INTRODUCTION

Extracellular vesicles (EV) released constitutively or following external stimuli from structural and immune cells are now recognized as important mediators of cell-to-cell communication. They are involved in the pathogenesis of pneumonia and sepsis, leading causes of acute respiratory distress syndrome (ARDS) where mortality rates remain up to 40%. Multiple investigators have demonstrated that one of the underlying mechanisms of the effects of EVs is through the transfer of EV content to host cells, resulting in apoptosis, inflammation, and permeability in target organs.

AREAS COVERED

The current review focuses on preclinical research examining the role of EVs released into the plasma and injured alveolus during pneumonia and sepsis.

EXPERT OPINION

Inflammation is associated with elevated levels of circulating EVs that are released by activated structural and immune cells and can have significant proinflammatory, procoagulant, and pro-permeability effects in critically ill patients with pneumonia and/or sepsis. However, clinical translation of the use of EVs as biomarkers or potential therapeutic targets may be limited by current methodologies used to identify and quantify EVs accurately (whether from host cells or infecting organisms) and lack of understanding of the role of EVs in the reparative phase during recovery from pneumonia and/or sepsis.

Therapeutic Effects of Hyaluronic Acid Against Cytotoxic Extracellular Vesicles Released During Pseudomonas Aeruginosa Pneumonia

ABSTRACT

Extracellular vesicles (EVs) have now been recognized as important mediators of cellular communication during injury and repair. We previously found that plasma EVs isolated from ex vivo perfused human lungs injured with Escherichia coli bacterial pneumonia were inflammatory, and exogenous administration of high molecular weight (HMW) hyaluronic acid (HA) as therapy bound to these EVs, decreasing inflammation and injury. In the current study, we studied the role of EVs released during severe Pseudomonas aeruginosa (PA) pneumonia in mice and determined whether intravenous administration of exogenous HMW HA would have therapeutic effects against the bacterial pneumonia. EVs were collected from the bronchoalveolar lavage fluid (BALF) of mice infected with PA103 by ultracentrifugation and analyzed by NanoSight and flow cytometry. In a cytotoxicity assay, administration of EVs released from infected mice (I-EVs) decreased the viability of A549 cells compared to EV isolated from sham control mice (C-EVs). Either exogenous HMW HA or an anti-CD44 antibody, when co-incubated with I-EVs, significantly improved the viability of the A549 cells. In mice with PA103 pneumonia, administration of HMW HA improved pulmonary edema and bacterial count in the lungs and decreased TNF-α and caspase-3 levels in the supernatant of lung homogenates. In conclusion, EVs isolated from BALF of mice with P. aeruginosa pneumonia were cytotoxic and inflammatory, and intravenous HMW HA administration was protective against P. aeruginosa pneumonia.

Protection and rebuilding of the endothelial glycocalyx in sepsis - Science or fiction?

The endothelial glycocalyx (eGC), a delicate carbohydrate-rich structure lining the luminal surface of the vascular endothelium, is vital for maintenance of microvascular homeostasis. In sepsis, damage of the eGC triggers the development of vascular hyperpermeability with consecutive edema formation and organ failure. While there is evidence that protection or rebuilding of the eGC might counteract sepsis-induced vascular leakage and improve outcome, approved therapeutics are not yet available. This narrative review aims to outline possible therapeutic strategies to ameliorate organ dysfunction caused by eGC impairment.

Therapeutic effects of high molecular weight hyaluronic acid in severe Pseudomonas aeruginosa pneumonia in ex vivo perfused human lungs

We previously reported that extracellular vesicles (EVs) released during Escherichia coli (E. coli) bacterial pneumonia were inflammatory, and administration of high molecular weight hyaluronic acid (HMW HA) suppressed several indices of acute lung injury (ALI) from E. coli pneumonia by binding to these inflammatory EVs. The current study was undertaken to study the therapeutic effects of HMW HA in ex vivo perfused human lungs injured with Pseudomonas aeruginosa (PA)103 bacterial pneumonia. For lungs with baseline alveolar fluid clearance (AFC) <10%/h, HMW HA 1 or 2 mg was injected intravenously after 1 h (n = 4-9), and EVs released during PA pneumonia were collected from the perfusate over 6 h. For lungs with baseline AFC > 10%/h, HMW HA 2 mg was injected intravenously after 1 h (n = 6). In vitro experiments were conducted to evaluate the effects of HA on inflammation and bacterial phagocytosis. For lungs with AFC < 10%/h, administration of HMW HA intravenously significantly restored AFC and numerically decreased protein permeability and alveolar inflammation from PA103 pneumonia but had no effect on bacterial counts at 6 h. However, HMW HA improved bacterial phagocytosis by human monocytes and neutrophils and suppressed the inflammatory properties of EVs released during pneumonia on monocytes. For lungs with AFC > 10%/h, administration of HMW HA intravenously improved AFC from PA103 pneumonia but had no significant effects on protein permeability, inflammation, or bacterial counts. In the presence of impaired alveolar epithelial transport capacity, administration of HMW HA improved the resolution of pulmonary edema from Pseudomonas PA103 bacterial pneumonia.

The S100 Protein Family as Players and Therapeutic Targets in Pulmonary Diseases

The S100 protein family consists of over 20 members in humans that are involved in many intracellular and extracellular processes, including proliferation, differentiation, apoptosis, Ca₂⁺ homeostasis, energy metabolism, inflammation, tissue repair, and migration/invasion. Although there are structural similarities between each member, they are not functionally interchangeable. The S100 proteins function both as intracellular Ca²⁺ sensors and as extracellular factors. Dysregulated responses of multiple members of the S100 family are observed in several diseases, including the lungs (asthma, chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, cystic fibrosis, pulmonary hypertension, and lung cancer). To this degree, extensive research was undertaken to identify their roles in pulmonary disease pathogenesis and the identification of inhibitors for several S100 family members that have progressed to clinical trials in patients for nonpulmonary conditions. This review outlines the potential role of each S100 protein in pulmonary diseases, details the possible mechanisms observed in diseases, and outlines potential therapeutic strategies for treatment.

Hyaluronan (HA) Immobilized on Surfaces via Self-Assembled Monolayers of HA-Binding Peptide Modulates Endothelial Cell Spreading and Migration through Focal Adhesion

The extracellular matrix (ECM) modulates a multitude of cell functions, and this regulation is provided by key ECM components forming a complex network. Hyaluronic acid (HA) is an abundant component of the ECM that binds to proteins and influences various activities of endothelial cells (ECs). Although the effect of soluble HA on cell spreading has been studied, the impact of peptide-bound HA has not yet been investigated in great detail. We aim to comprehensively study the roles of immobilized HA on the regulation of EC behavior compared to the more conventional use of soluble HA. A 2D model surface formed by self-assembled monolayers (SAMs) of a HA-binding peptide (Pep-1) is used as an anchor for HA immobilization. Mixed SAMs, consisting of thiolated Pep-1 and 1-octanethiol, are prepared and characterized by using ellipsometry and contact angle measurement. Full density Pep-1 SAMs are more hydrophilic and bind more HA than mixed SAMs. Cell spreading and migration are enhanced by immobilized low molecular weight (LMW) HA, which also facilitates cell alignment and elongation under laminar flow conditions and potentially drives directional migration. This effect is not mediated by the expression of CD44, and immobilized LMW HA is found to accelerate the assembly of focal adhesions. Such biomimetic surfaces provide new insights into the role of HA in regulating the spreading and phenotype of endothelial cells.

Loss of Endothelial Glycocalyx Hyaluronan Impairs Endothelial Stability and Adaptive Vascular Remodeling After Arterial Ischemia

We recently reported that loss of hyaluronan (HA) from the endothelial glycocalyx leads to loss of vessel stability in specific microcirculatory vascular beds. Here we hypothesized that such derangements in the glycocalyx may also impair the adaptive response to vascular ischemia. Endothelial specific conditional hyaluronan synthase 2-KO (Has2-cKO) mice revealed reduced endothelial HA expression and lower hindlimb perfusion at baseline compared to control mice. After a single ligation of the common femoral artery in these mice, we observed dysregulated angiogenesis in the gastrocnemius muscle which did not restore capillary perfusion. Mechanistically, decreased endothelial binding of the pericyte-derived molecule angiopoietin1 (Ang1) could be observed in the Has2-cKO mouse. In vitro angiogenesis assays with an endothelial cell-pericyte coculture confirmed such disturbed Ang1-TIE2 signaling resulting in excessive angiogenesis upon loss of HA. These data could be of relevance to diabetes patients, where we confirm loss of endothelial HA in the microcirculation of muscle tissue, indicating that this may contribute to the known disturbed adaptation to ischemia in these patients. In summary, loss of endothelial HA results in impaired microvascular perfusion and endothelial stability in ischemic gastrocnemius muscle. Endothelial HA is a potential target to improve angiogenic therapy in diabetic patients with critical limb ischemia.

Cancer Metastasis: The Role of the Extracellular Matrix and the Heparan Sulfate Proteoglycan Perlecan

Cancer metastasis is the dissemination of tumor cells to new sites, resulting in the formation of secondary tumors. This process is complex and is spatially and temporally regulated by intrinsic and extrinsic factors. One important extrinsic factor is the extracellular matrix, the non-cellular component of tissues. Heparan sulfate proteoglycans (HSPGs) are constituents of the extracellular matrix, and through their heparan sulfate chains and protein core, modulate multiple events that occur during the metastatic cascade. This review will provide an overview of the role of the extracellular matrix in the events that occur during cancer metastasis, primarily focusing on perlecan. Perlecan, a basement membrane HSPG is a key component of the vascular extracellular matrix and is commonly associated with events that occur during the metastatic cascade. Its contradictory role in these events will be discussed and we will highlight the recent advances in cancer therapies that target HSPGs and their modifying enzymes.

Extracellular Superoxide Dismutase Regulates Early Vascular Hyaluronan Remodeling in Hypoxic Pulmonary Hypertension

Chronic hypoxia leads to pathologic remodeling of the pulmonary vasculature and pulmonary hypertension (PH). The antioxidant enzyme extracellular superoxide dismutase (SOD3) protects against hypoxia-induced PH. Hyaluronan (HA), a ubiquitous glycosaminoglycan of the lung extracellular matrix, is rapidly recycled at sites of vessel injury and repair. We investigated the hypothesis that SOD3 preserves HA homeostasis by inhibiting oxidative and enzymatic hyaluronidase-mediated HA breakdown. In SOD3-deficient mice, hypoxia increased lung hyaluronidase expression and activity, hyaluronan fragmentation, and effacement of HA from the vessel wall of small pulmonary arteries. Hyaluronan fragmentation corresponded to hypoxic induction of the cell surface hyaluronidase-2 (Hyal2), which was localized in the vascular media. Human pulmonary artery smooth muscle cells (HPASMCs) demonstrated hypoxic induction of Hyal2 and SOD-suppressible hyaluronidase activity, congruent to our observations in vivo. Fragmentation of homeostatic high molecular weight HA promoted HPASMC proliferation in vitro, whereas pharmacologic inhibition of hyaluronidase activity prevented hypoxia- and oxidant-induced proliferation. Hypoxia initiates SOD3-dependent alterations in the structure and regulation of hyaluronan in the pulmonary vascular extracellular matrix. These changes occurred soon after hypoxia exposure, prior to appearance of PH, and may contribute to the early pathogenesis of this disease.

Therapeutic Effects of Hyaluronic Acid in Bacterial Pneumonia in Ex Vivo Perfused Human Lungs

Rationale: Recent studies have demonstrated that extracellular vesicles (EVs) released during acute lung injury (ALI) were inflammatory.Objectives: The current study was undertaken to test the role of EVs induced and released from severe Escherichia coli pneumonia (E. coli EVs) in the pathogenesis of ALI and to determine whether high-molecular-weight (HMW) hyaluronic acid (HA) administration would suppress lung injury from E. coli EVs or bacterial pneumonia.Methods:E. coli EVs were collected from the perfusate of an ex vivo perfused human lung injured with intrabronchial E. coli bacteria for 6 hours by ultracentrifugation and then given intrabronchially or intravenously to naive human lungs. One hour later, HMW HA was instilled into the perfusate (n = 5-6). In separate experiments, HMW HA was given after E. coli bacterial pneumonia (n = 6-10). In vitro experiments were conducted to evaluate binding of EVs to HMW HA and uptake of EVs by human monocytes.Measurements and Main Results: Administration of HMW HA ameliorated the impairment of alveolar fluid clearance, protein permeability, and acute inflammation from E. coli EVs or pneumonia and reduced total bacteria counts after E. coli pneumonia. HMW HA bound to E. coli EVs, inhibiting the uptake of EVs by human monocytes, an effect associated with reduced TNFα (tumor necrosis factor α) secretion. Surprisingly, HMW HA increased E. coli bacteria phagocytosis by monocytes.Conclusions: EVs induced and released during severe bacterial pneumonia were inflammatory and induced ALI, and HMW HA administration was effective in inhibiting the uptake of EVs by target cells and decreasing lung injury from E. coli EVs or bacterial pneumonia.

Endothelial Glycocalyx Shedding Occurs during Ex Vivo Lung Perfusion: A Pilot Study

Background

Damage to the endothelium has been established as a key pathological process in lung transplantation and ex vivo lung perfusion (EVLP), a new technology that provides a platform for the assessment of injured donor lungs. Damage to the lung endothelial glycocalyx, a structure that lines the endothelium and is integral to vascular barrier function, has been associated with lung dysfunction. We hypothesised that endothelial glycocalyx shedding occurs during EVLP and aimed to establish a porcine model to investigate the mechanism underlying glycocalyx breakdown during EVLP.

Methods

Concentrations of endothelial glycocalyx breakdown products, syndecan-1, hyaluronan, heparan sulphate, and CD44, were measured using the ELISA and matrix metalloproteinase (MMP) activity by zymography in the perfusate of both human (n = 9) and porcine (n = 4) lungs undergoing EVLP. Porcine lungs underwent prolonged EVLP (up to 12 hours) with perfusion and ventilation parameters recorded hourly.

Results

During human EVLP, endothelial glycocalyx breakdown products in the perfusate increased over time. Increasing MMP-2 activity over time was positively correlated with levels of syndecan-1 (r = 0.886; p=0.03) and hyaluronan (r = 0.943; p=0.02). In the porcine EVLP model, hyaluronan was the only glycocalyx product detectable during EVLP (1 hr: 19 (13–84) vs 12 hr: 143 (109–264) ng/ml; p=0.13). Porcine hyaluronan was associated with MMP-9 activity (r = 0.83; p=0.02) and also with dynamic compliance (r = 0.57; p=0.03).

Conclusion

Endothelial glycocalyx products accumulate during both porcine and human EVLP, and this accumulation parallels an accumulation of matrix-degrading enzyme activity. Preliminary evidence in our porcine EVLP model suggests that shedding may be related to organ function, thus warranting additional study.

Roles of exosomes in liver metastases: Novel diagnosis and treatment choices

Tumors tend to metastasize to the liver. Premetastatic niche formation is a vital step in liver metastasis. Tumor-derived exosomes can influence premetastatic niche formation from three aspects: vascular leakiness and angiogenesis, recruitment of nonresident cells, and changes in local resident cells. Exosomes from other tissues, such as mesenchymal stem cell-derived exosomes and engineered exosomes, also have therapeutic potential, but further research on these exosomes is required. Based on the mechanism of premetastatic niche formation, we summarize the therapeutic and diagnostic potential of exosomes in inhibiting liver metastases in this review in an attempt to provide new avenues for the prevention and treatment of liver metastases.

High Molecular Weight Hyaluronan Suppresses Macrophage M1 Polarization and Enhances IL-10 Production in PM2.5-Induced Lung Inflammation

PM_2.5 is particulate matter with a diameter of 2.5 μm or less. Airway macrophages are the key players regulating PM_2.5-induced inflammation. High molecular weight hyaluronan (HMW-HA) has previously been shown to exert protective effects on PM_2.5-induced acute lung injury and inflammation. However, little is known about the detailed mechanism. In this study, we aimed to determine whether HMW-HA alleviates PM_2.5-induced pulmonary inflammation by modulating macrophage polarization. The levels of M1 biomarkers TNF-α, IL-1β, IL-6, CXCL1, CXCL2, NOS2 and CD86, as well as M2 biomarkers IL-10, MRC1, and Arg-1 produced by macrophages were measured by ELISA, qPCR, and flow cytometry. In addition, the amount of M1 macrophages in lung tissues was examined by immunofluorescence of CD68 and NOS2. We observed a decline in PM_2.5-induced M1 polarization both in macrophages and lung tissues when HMW-HA was administered simultaneously. Meanwhile, western blot analysis revealed that PM_2.5-induced JNK and p38 phosphorylation was suppressed by HMW-HA. Furthermore, in vitro and in vivo studies showed that co-stimulation with HMW-HA and PM_2.5 promoted the expression and release of IL-10, but exhibited limited effects on the transcription of MRC1 and ARG1. In conclusion, our results demonstrated that HMW-HA ameliorates PM_2.5-induced lung inflammation by repressing M1 polarization through JNK and p38 pathways and promoting the production of pro-resolving cytokine IL-10.

The receptor for hyaluronan-mediated motility (RHAMM) expression in neonatal bronchiolar epithelium correlates negatively with lung air content

INTRODUCTION

Hyaluronan (HA) and the receptor for hyaluronan-mediated motility (RHAMM) may play an important role in lung development. We examined the expression of HA content and RHAMM during postnatal lung development by analyzing human lung specimens from newborn infants with a variety of lung diseases at different gestational (GA) and postnatal (PNA) ages.

MATERIALS AND METHODS

Ninety-four patients were evaluated. Immunohistochemical RHAMM expression was studied with digital image analysis, followed by hierarchical cluster analysis of both these data and clinical data to define subgroups. The air content of the lung was determined by computerized analysis. HA content was estimated by radiometric assay.

RESULTS

Cluster analysis defined six distinct patient groups (Group 1-2: 34-41 weeks GA; Group 3-5: 23-27 weeks GA; Group 6: mixed population). Group 1-5 showed individual patterns in RHAMM expression and HA content (Group 1: high RHAMM/low HA; Group 2: low RHAMM/low HA; Group 3: low RHAMM/low HA; Group 4: low RHAMM/high HA; Group 5: high RHAMM/high HA). HA content decreased with increasing PNA independently of GA. Negative correlation was observed between air content and RHAMM expression in the bronchiolar epithelium irrespective of clustered groups. Lung hypoplasia appeared in two distinctive groups, with significant differences in lung development and RHAMM expression.

CONCLUSIONS

RHAMM expression may show dynamic changes during pathological processes in the neonatal lung. The distribution of RHAMM in the lung tissue is heterogeneous with a predominance to the bronchiolar epithelium. We found a negative correlation between lung air content and RHAMM expression in bronchiolar epithelium.

Sphingolipids Signaling in Lamellipodia Formation and Enhancement of Endothelial Barrier Function

Sphingolipids, first described in the brain in 1884, are important structural components of biological membranes of all eukaryotic cells. In recent years, several lines of evidence support the critical role of sphingolipids such as sphingosine, sphingosine-1-phosphate (S1P), and ceramide as anti- or pro-inflammatory bioactive lipid mediators in a variety of human pathologies including pulmonary and vascular disorders. Among the sphingolipids, S1P is a naturally occurring agonist that exhibits potent barrier enhancing property in the endothelium by signaling via G protein-coupled S1P1 receptor. S1P, S1P analogs, and other barrier enhancing agents such as HGF, oxidized phospholipids, and statins also utilize the S1P/S1P1 signaling pathway to generate membrane protrusions or lamellipodia, which have been implicated in resealing of endothelial gaps and maintenance of barrier integrity. A better understanding of sphingolipids mediated regulation of lamellipodia formation and barrier enhancement of the endothelium will be critical for the development of sphingolipid-based therapies to alleviate pulmonary disorders such as sepsis-, radiation-, and mechanical ventilation-induced acute lung injury.

The CD44-HA axis and inflammation in atherosclerosis: A temporal perspective

Cardiovascular disease (CVD) due to atherosclerosis is a disease of chronic inflammation at both the systemic and the tissue level. CD44 has previously been implicated in atherosclerosis in both humans and mice. This multi-faceted receptor plays a critical part in the inflammatory response during the onset of CVD, though little is known of CD44's role during the latter stages of the disease. This review focuses on the role of CD44-dependent HA-dependent effects on inflammatory cells in several key processes, from disease initiation throughout the progression of atherosclerosis. Understanding how CD44 and HA regulate inflammation in atherogenesis is key in determining the utility of the CD44-HA axis as a therapeutic target to halt disease and potentially promote disease regression.

Instillation of hyaluronan reverses acid instillation injury to the mammalian blood gas barrier

Acid (HCl) aspiration during anesthesia may lead to acute lung injury. There is no effective therapy. We hypothesized that HCl instilled intratracheally in C57BL/6 mice results in the formation of low-molecular weight hyaluronan (L-HA), which activates RhoA and Rho kinase (ROCK), causing airway hyperresponsiveness (AHR) and increased permeability. Furthermore, instillation of high-molecular weight hyaluronan (H-HA; Yabro) will reverse lung injury. We instilled HCl in C57BL/6 wild-type (WT), myeloperoxidase gene-deficient (MPO^-/-) mice, and CD44 gene-deficient (CD44^-/-) mice. WT mice were also instilled intranasally with H-HA (Yabro) at 1 and 23 h post-HCl. All measurements were performed at 1, 5, or 24 h post-HCl. Instillation of HCl in WT but not in CD44^-/- resulted in increased inflammation, AHR, lung injury, and L-HA in the bronchoalveolar lavage fluid (BALF) 24 h post-HCl; L-HA levels and lung injury were significantly lower in HCl-instilled MPO^-/- mice. Isolated perfused lungs of HCl instilled WT but not of CD44^-/- mice had elevated values of the filtration coefficient ( K_f). Addition of L-HA on the apical surface of human primary bronchial epithelial cell monolayer decreased barrier resistance ( R_T). H-HA significantly mitigated inflammation, AHR, and pulmonary vascular leakage at 24 h after HCl instillation and mitigated the increase of K_f and R_T, as well as ROCK2 phosphorylation. Increased H- and L-HA levels were found in the BALF of mechanically ventilated patients but not in healthy volunteers. HCl instillation-induced lung injury is mediated by the L-HA-CD44-RhoA-ROCK2 signaling pathway, and H-HA is a potential novel therapeutic agent for acid aspiration-induced lung injury.

Proteoglycans as Immunomodulators of the Innate Immune Response to Lung Infection

Proteoglycans (PGs) are complex, multifaceted molecules that participate in diverse interactions vital for physiological and pathological processes. As structural components, they provide a scaffold for cells and structural organization that helps define tissue architecture. Through interactions with water, PGs enable molecular and cellular movement through tissues. Through selective ionic interactions with growth factors, chemokines, cytokines, and proteases, PGs facilitate the ability of these soluble ligands to regulate intracellular signaling events and to influence the inflammatory response. In addition, recent findings now demonstrate that PGs can activate danger-associated molecular patterns (DAMPs) and other signaling pathways to influence production of many of these soluble ligands, indicating a more direct role for PGs in influencing the immune response and tissue inflammation. This review will focus on PGs that are selectively expressed during lung inflammation and will examine the novel emerging concept of PGs as immunomodulatory regulators of the innate immune responses in lungs.

Injured lung endothelium: mechanisms of self-repair and agonist-assisted recovery (2017 Grover Conference Series)

The lung endothelium is vulnerable to both exogenous and endogenous insults, so a properly coordinated efficient repair system is essential for the timely recovery of the lung after injury. The agents that cause endothelial injury and dysfunction fall into a broad range from mechanical forces such as pathological cyclic stretch and shear stress to bacterial pathogens and their virulent components, vasoactive agonists including thrombin and histamine, metabolic causes including high glucose and oxidized low-density lipoprotein (OxLDL), circulating microparticles, and inflammatory cytokines. The repair mechanisms employed by endothelial cells (EC) can be broadly categorized into three groups: (1) intrinsic mechanism of recovery regulated by the cross-talk between small GTPases as exemplified by Rap1-mediated EC barrier recovery from Rho-mediated thrombin-induced EC hyperpermeability; (2) agonist-assisted recovery facilitated by the activation of Rac and Rap1 with subsequent inhibition of Rho signaling as observed with many barrier protective agonists including oxidized phospholipids, sphingosine 1-phosphate, prostacyclins, and hepatocyte growth factor; and (3) self-recovery of EC by the secretion of growth factors and other pro-survival bioactive compounds including anti-inflammatory molecules such as lipoxins during the resolution of inflammation. In this review, we will discuss the molecular and cellular mechanisms of pulmonary endothelium repair that is critical for the recovery from various forms of lung injuries.

Hyaluronan content governs tissue stiffness in pancreatic islet inflammation

We have identified a novel role for hyaluronan (HA), an extracellular matrix polymer, in governing the mechanical properties of inflamed tissues. We recently reported that insulitis in type 1 diabetes of mice and humans is preceded by intraislet accumulation of HA, a highly hygroscopic polymer. Using the double transgenic DO11.10 × RIPmOVA (DORmO) mouse model of type 1 diabetes, we asked whether autoimmune insulitis was associated with changes in the stiffness of islets. To measure islet stiffness, we used atomic force microscopy (AFM) and developed a novel "bed of nails"-like approach that uses quartz glass nanopillars to anchor islets, solving a long-standing problem of keeping tissue-scale objects immobilized while performing AFM. We measured stiffness via AFM nanoindentation with a spherical indenter and found that insulitis made islets mechanically soft compared with controls. Conversely, treatment with 4-methylumbelliferone, a small-molecule inhibitor of HA synthesis, reduced HA accumulation, diminished swelling, and restored basal tissue stiffness. These results indicate that HA content governs the mechanical properties of islets. In hydrogels with variable HA content, we confirmed that increased HA leads to mechanically softer hydrogels, consistent with our model. In light of recent reports that the insulin production of islets is mechanosensitive, these findings open up an exciting new avenue of research into the fundamental mechanisms by which inflammation impacts local cellular responses.

The Biomechanical Effects of Resuscitation Colloids on the Compromised Lung Endothelial Glycocalyx

BACKGROUND

The endothelial glycocalyx is an important component of the vascular permeability barrier, forming a scaffold that allows serum proteins to create a gel-like layer on the endothelial surface and transmitting mechanosensing and mechanotransduction information that influences permeability. During acute inflammation, the glycocalyx is degraded, changing how it interacts with serum proteins and colloids used during resuscitation and altering its barrier properties and biomechanical characteristics. We quantified changes in the biomechanical properties of lung endothelial glycocalyx during control conditions and after degradation by hyaluronidase using biophysical techniques that can probe mechanics at (1) the aqueous/glycocalyx interface and (2) inside the glycocalyx. Our goal was to discern the location-specific effects of albumin and hydroxyethyl starch (HES) on glycocalyx function.

METHODS

The effects of albumin and HES on the mechanical properties of bovine lung endothelial glycocalyx were studied using a combination of atomic force microscopy and reflectance interference contrast microscopy. Logistic regression was used to determine the odds ratios for comparing the effects of varying concentrations of albumin and HES on the glycocalyx with and without hyaluronidase.

RESULTS

Atomic force microscopy measurements demonstrated that both 0.1% and 4% albumin increased the thickness and reduced the stiffness of glycocalyx when compared with 1% albumin. The effect of HES on glycocalyx thickness was similar to albumin, with thickness increasing significantly between 0.1% and 1% HES and a trend toward a softer glycocalyx at 4% HES. Reflectance interference contrast microscopy revealed a concentration-dependent softening of the glycocalyx in the presence of albumin, but a concentration-dependent increase in stiffness with HES. After glycocalyx degradation with hyaluronidase, stiffness was increased only at 4% albumin and 1% HES.

CONCLUSIONS

Albumin and HES induced markedly different effects on glycocalyx mechanics and had notably different effects after glycocalyx degradation by hyaluronidase. We conclude that HES is not comparable with albumin for studies of vascular permeability and glycocalyx-dependent signaling. Characterizing the molecular and biomechanical effects of resuscitation colloids on the glycocalyx should clarify their indicated uses and permit a better understanding of how HES and albumin affect vascular function.

The Consequences of Overlapping G-Quadruplexes and i-Motifs in the Platelet-Derived Growth Factor Receptor β Core Promoter Nuclease Hypersensitive Element Can Explain the Unexpected Effects of Mutations and Provide Opportunities for Selective Targeting of Both Structures by Small Molecules To Downregulate Gene Expression

The platelet-derived growth factor receptor β (PDGFR-β) signaling pathway is a validated and important target for the treatment of certain malignant and nonmalignant pathologies. We previously identified a G-quadruplex-forming nuclease hypersensitive element (NHE) in the human PDGFR-β promoter that putatively forms four overlapping G-quadruplexes. Therefore, we further investigated the structures and biological roles of the G-quadruplexes and i-motifs in the PDGFR-β NHE with the ultimate goal of demonstrating an alternate and effective strategy for molecularly targeting the PDGFR-β pathway. Significantly, we show that the primary G-quadruplex receptor for repression of PDGFR-β is the 3'-end G-quadruplex, which has a GGA sequence at the 3'-end. Mutation studies using luciferase reporter plasmids highlight a novel set of G-quadruplex point mutations, some of which seem to provide conflicting results on effects on gene expression, prompting further investigation into the effect of these mutations on the i-motif-forming strand. Herein we characterize the formation of an equilibrium between at least two different i-motifs from the cytosine-rich (C-rich) sequence of the PDGFR-β NHE. The apparently conflicting mutation results can be rationalized if we take into account the single base point mutation made in a critical cytosine run in the PDGFR-β NHE that dramatically affects the equilibrium of i-motifs formed from this sequence. We identified a group of ellipticines that targets the G-quadruplexes in the PDGFR-β promoter, and from this series of compounds, we selected the ellipticine analog GSA1129, which selectively targets the 3'-end G-quadruplex, to shift the dynamic equilibrium in the full-length sequence to favor this structure. We also identified a benzothiophene-2-carboxamide (NSC309874) as a PDGFR-β i-motif-interactive compound. In vitro, GSA1129 and NSC309874 downregulate PDGFR-β promoter activity and transcript in the neuroblastoma cell line SK-N-SH at subcytotoxic cell concentrations. GSA1129 also inhibits PDGFR-β-driven cell proliferation and migration. With an established preclinical murine model of acute lung injury, we demonstrate that GSA1129 attenuates endotoxin-mediated acute lung inflammation. Our studies underscore the importance of considering the effects of point mutations on structure formation from the G- and C-rich sequences and provide further evidence for the involvement of both strands and associated structures in the control of gene expression.

Actin dynamics in the regulation of endothelial barrier functions and neutrophil recruitment during endotoxemia and sepsis

Sepsis is a leading cause of death worldwide. Increased vascular permeability is a major hallmark of sepsis. Dynamic alterations in actin fiber formation play an important role in the regulation of endothelial barrier functions and thus vascular permeability. Endothelial integrity requires a delicate balance between the formation of cortical actin filaments that maintain endothelial cell contact stability and the formation of actin stress fibers that generate pulling forces, and thus compromise endothelial cell contact stability. Current research has revealed multiple molecular pathways that regulate actin dynamics and endothelial barrier dysfunction during sepsis. These include intracellular signaling proteins of the small GTPases family (e.g., Rap1, RhoA and Rac1) as well as the molecules that are directly acting on the actomyosin cytoskeleton such as myosin light chain kinase and Rho kinases. Another hallmark of sepsis is an excessive recruitment of neutrophils that also involves changes in the actin cytoskeleton in both endothelial cells and neutrophils. This review focuses on the available evidence about molecules that control actin dynamics and regulate endothelial barrier functions and neutrophil recruitment. We also discuss treatment strategies using pharmaceutical enzyme inhibitors to target excessive vascular permeability and leukocyte recruitment in septic patients.

Endothelial dysfunction mediated by interleukin-18 in patients with ischemic heart disease undergoing coronary artery bypass grafting surgery

When medication management or percutaneous coronary intervention is not successful in patients with advanced ischemic heart disease, surgical revascularisation-predominantly coronary artery bypass grafting (CABG)-is considered the gold standard. However, CABG surgery can lead to ischemia/reperfusion injury, which is characterized by a strong inflammatory response. Interleukin (IL)-18, is a strong inflammatory mediator, that is released from cardiomyocytes and can be found in the systemic circulation of patients during and immediately after CABG surgery. The existing damage of endothelial glycocalyx in patients with ischemic heart disease is further impaired concurrently during the surgery due to the anaesthesia-surgical technique used and intravascular fluid loading. This results in the increased incidence of adverse events, including myocardial infarction. IL-18 leads to the activation of lymphocyte cytotoxicity via cytotoxic mediators (Fas ligand, Tumour necrosis factor (TNF)-related apoptosis-inducing ligand, perforin, and granulysin). We hypothesize that IL-18 is released locally in the heart and the systemic circulation in patients undergoing CABG surgery and may be correlated with the level of activity of circulating lymphocytes. In turn, this may lead to lymphocyte-mediated cytotoxicity directed toward damaged and activated endothelial cells. Shear stress glycocalyx, as well as damaged and activated endothelial cells then become the main the source of pro-inflammatory cytokines, chemokines, and adhesion molecules. These attract activated lymphocytes to adhere to the endothelium or enter the subintimal layer, increasing existing or initiating the formation of new plaques, which leads to the development of myocardial infarction during or shortly after surgery. To evaluate our hypothesis, we will measure the local concentration of IL-18 in the sinus coronarius and systemic circulation. These values will then be correlated with immunological and biochemical parameters, predominantly with the concentration of degradation products of glycocalyx and cytotoxic mediators in activated lymphocytes. If our hypothesis is correct, measuring the IL-18 concentration that is responsible for glycocalyx deterioration, may become a useful tool for predicting myocardial infarction occurrence in patients undergoing CABG surgery.

Protective Function of Ahnak1 in Vascular Healing after Wire Injury

AIM

Vascular remodeling following injury substantially accounts for restenosis and adverse clinical outcomes. In this study, we investigated the role of the giant scaffold protein Ahnak1 in vascular healing after endothelial denudation of the murine femoral artery.

METHODS

The spatiotemporal expression pattern of Ahnak1 and Ahnak2 was examined using specific antibodies and real-time quantitative PCR. Following wire-mediated endothelial injury of Ahnak1-deficient mice and wild-type (WT) littermates, the processes of vascular healing were analyzed.

RESULTS

Ahnak1 and Ahnak2 showed a mutually exclusive vascular expression pattern, with Ahnak1 being expressed in the endothelium and Ahnak2 in the medial cells in naïve WT arteries. After injury, a marked increase of Ahnak1- and Ahnak2-positive cells at the lesion site became evident. Both proteins showed a strong upregulation in neointimal cells 14 days after injury. Ahnak1-deficient mice showed delayed vascular healing and dramatically impaired re-endothelialization that resulted in prolonged adverse vascular remodeling, when compared to the WT littermates.

CONCLUSION

The large scaffold and adaptor proteins Ahnak1 and Ahnak2 exhibit differential expression patterns and functions in naïve and injured arteries. Ahnak1 plays a nonredundant protective role in vascular healing.

Hyaluronic Acid Hydrogel Functionalized with Self-Assembled Micelles of Amphiphilic PEGylated Kartogenin for the Treatment of Osteoarthritis

Synthetic hyaluronic acid (HA) containing a covalently integrated drug is capable of releasing therapeutic molecules and is an attractive candidate for the intra-articular treatment of osteoarthritis (OA). Herein, self-assembled PEGylated kartogenin (PEG/KGN) micelles consisting of hydrophilic polyethylene glycol (PEG) and hydrophobic KGN, which has been shown to induce chondrogenesis in human mesenchymal stem cells, were prepared by covalent crosslinking. HA hydrogels containing PEG/KGN micelles (HA/PEG/KGN) were prepared by covalently bonding PEG chains to HA. The physicochemical properties of the HA/PEG/KGN conjugate gels were investigated using Fourier transform infrared spectroscopy, ¹H NMR, dynamic light scattering (DLS), and scanning electron microscopy (SEM). HA/PEG/KGN gels exhibited larger micelles in aqueous solution than PEG/KGN. SEM images of PEG/KGN micelles showed a dark core and a bright shell, whereas PEG/KGN micelles covalently integrated into HA had an irregular oval shape. Covalent integration of PEG/KGN micelles in HA hydrogels significantly reduced drug release rates and provided sustained release over a prolonged period of time. HA/PEG/KGN hydrogels were degradable enzymatically by collagenase and hyaluronidase in vitro. Injection of HA/PEG/KGN hydrogels into articular cartilage significantly suppressed the progression of OA in rats compared with free-HA hydrogel injection. These results suggest that the HA/PEG/KGN hydrogels have greater potency than free-HA hydrogels against OA as biodegradable synthetic therapeutics.

Identifying immune mechanisms mediating the hypertension during preeclampsia

Preeclampsia (PE) is a pregnancy-associated disorder that affects 5-8% of pregnancies and is a major cause of maternal, fetal, and neonatal morbidity and mortality. Hallmark characteristics of PE are new onset hypertension after 20 wk gestation with or without proteinuria, chronic immune activation, fetal growth restriction, and maternal endothelial dysfunction. However, the pathophysiological mechanisms that lead to the development of PE are poorly understood. Recent data from studies of both clinical and animal models demonstrate an imbalance in the subpopulations of CD4+ T cells and a role for these cells as mediators of inflammation and hypertension during pregnancy. Specifically, it has been proposed that the imbalance between two CD4+ T cell subtypes, regulatory T cells (Tregs) and T-helper 17 cells (Th17s), is involved in the pathophysiology of PE. Studies from our laboratory highlighting how this imbalance contributes to vasoactive factors, endothelial dysfunction, and hypertension during pregnancy will be discussed in this review. Therefore, the purpose of this review is to highlight hypertensive mechanisms stimulated by inflammatory factors in response to placental ischemia, thereby elucidating a role.

Treatment with the hyaluronic Acid synthesis inhibitor 4-methylumbelliferone suppresses LPS-induced lung inflammation

Exposure to bacterial endotoxins, such as lipopolysaccharide (LPS), can lead to the induction of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). To date, there are no known effective treatments for LPS-induced inflammation. In the current study, we investigated the potential use of the hyaluronic acid (HA) synthesis inhibitor 4-methylumbelliferone (4-MU) on LPS-induced acute lung inflammation. Culturing LPS-activated immune cells with 4-MU led to reduced proliferation, reduced cytokine production, and an increase in apoptosis when compared to untreated cells. Treatment of mice with 4-MU led to protection from LPS-induced lung injury. Specifically, 4-MU treatment led to a reduction in LPS-induced hyaluronic acid synthase (HAS) messenger RNA (mRNA) levels, reduction in lung permeability, and reduction in proinflammatory cytokine production. Taken together, these results suggest that use of 4-MU to target HA production may be an effective treatment for the inflammatory response following exposure to LPS.

The role of hyaluronan in the pathobiology and treatment of respiratory disease

Hyaluronan, a ubiquitous naturally occurring glycosaminoglycan, is a major component of the extracellular matrix, where it participates in biological processes that include water homeostasis, cell-matrix signaling, tissue healing, inflammation, angiogenesis, and cell proliferation and migration. There are emerging data that hyaluronan and its degradation products have an important role in the pathobiology of the respiratory tract. We review the role of hyaluronan in respiratory diseases and present evidence from published literature and from clinical practice supporting hyaluronan as a novel treatment for respiratory diseases. Preliminary data show that aerosolized exogenous hyaluronan has beneficial activity against airway inflammation, protects against bronchial hyperreactivity and remodeling, and disrupts the biofilm associated with chronic infection. This suggests a role in airway diseases with a predominant inflammatory component such as rhinosinusitis, asthma, chronic obstructive pulmonary disease, cystic fibrosis, and primary ciliary dyskinesia. The potential for hyaluronan to complement conventional therapy will become clearer when data are available from controlled trials in larger patient populations.

Aberrant Splicing of Estrogen Receptor, HER2, and CD44 Genes in Breast Cancer

Breast cancer (BC) is the most common cause of cancer-related death among women under the age of 50 years. Established biomarkers, such as hormone receptors (estrogen receptor [ER]/progesterone receptor) and human epidermal growth factor receptor 2 (HER2), play significant roles in the selection of patients for endocrine and trastuzumab therapies. However, the initial treatment response is often followed by tumor relapse with intrinsic resistance to the first-line therapy, so it has been expected to identify novel molecular markers to improve the survival and quality of life of patients. Alternative splicing of pre-messenger RNAs is a ubiquitous and flexible mechanism for the control of gene expression in mammalian cells. It provides cells with the opportunity to create protein isoforms with different, even opposing, functions from a single genomic locus. Aberrant alternative splicing is very common in cancer where emerging tumor cells take advantage of this flexibility to produce proteins that promote cell growth and survival. While a number of splicing alterations have been reported in human cancers, we focus on aberrant splicing of ER, HER2, and CD44 genes from the viewpoint of BC development. ERα36, a splice variant from the ER1 locus, governs nongenomic membrane signaling pathways triggered by estrogen and confers 4-hydroxytamoxifen resistance in BC therapy. The alternative spliced isoform of HER2 lacking exon 20 (Δ16HER2) has been reported in human BC; this isoform is associated with transforming ability than the wild-type HER2 and recapitulates the phenotypes of endocrine therapy-resistant BC. Although both CD44 splice isoforms (CD44s, CD44v) play essential roles in BC development, CD44v is more associated with those with favorable prognosis, such as luminal A subtype, while CD44s is linked to those with poor prognosis, such as HER2 or basal cell subtypes that are often metastatic. Hence, the detection of splice variants from these loci will provide keys to understand the pathogenesis, predict the prognosis, and choose specific therapies for BC.

Targeting ECM Disrupts Cancer Progression

Metastatic complications are responsible for more than 90% of cancer-related deaths. The progression from an isolated tumor to disseminated metastatic disease is a multistep process, with each step involving intricate cross talk between the cancer cells and their non-cellular surroundings, the extracellular matrix (ECM). Many ECM proteins are significantly deregulated during the progression of cancer, causing both biochemical and biomechanical changes that together promote the metastatic cascade. In this review, the influence of several ECM proteins on these multiple steps of cancer spread is summarized. In addition, we highlight the promising (pre-)clinical data showing benefits of targeting these ECM macromolecules to prevent cancer progression.

Hyperglycemia-Induced Changes in Hyaluronan Contribute to Impaired Skin Wound Healing in Diabetes: Review and Perspective

Ulcers and chronic wounds are a particularly common problem in diabetics and are associated with hyperglycemia. In this targeted review, we summarize evidence suggesting that defective wound healing in diabetics is causally linked, at least in part, to hyperglycemia-induced changes in the status of hyaluronan (HA) that resides in the pericellular coat (glycocalyx) of endothelial cells of small cutaneous blood vessels. Potential mechanisms through which exposure to high glucose levels causes a loss of the glycocalyx on the endothelium and accelerates the recruitment of leukocytes, creating a proinflammatory environment, are discussed in detail. Hyperglycemia also affects other cells in the immediate perivascular area, including pericytes and smooth muscle cells, through exposure to increased cytokine levels and through glucose elevations in the interstitial fluid. Possible roles of newly recognized, cross-linked forms of HA, and interactions of a major HA receptor (CD44) with cytokine/growth factor receptors during hyperglycemia, are also discussed.

Extracellular Vesicles from Caveolin-Enriched Microdomains Regulate Hyaluronan-Mediated Sustained Vascular Integrity

Defects in vascular integrity are an initiating factor in several disease processes. We have previously reported that high molecular weight hyaluronan (HMW-HA), a major glycosaminoglycan in the body, promotes rapid signal transduction in human pulmonary microvascular endothelial cells (HPMVEC) leading to barrier enhancement. In contrast, low molecular weight hyaluronan (LMW-HA), produced in disease states by hyaluronidases and reactive oxygen species (ROS), induces HPMVEC barrier disruption. However, the mechanism(s) of sustained barrier regulation by HA are poorly defined. Our results indicate that long-term (6–24 hours) exposure of HMW-HA induced release of a novel type of extracellular vesicle from HLMVEC called enlargeosomes (characterized by AHNAK expression) while LMW-HA long-term exposure promoted release of exosomes (characterized by CD9, CD63, and CD81 expression). These effects were blocked by inhibiting caveolin-enriched microdomain (CEM) formation. Further, inhibiting enlargeosome release by annexin II siRNA attenuated the sustained barrier enhancing effects of HMW-HA. Finally, exposure of isolated enlargeosomes to HPMVEC monolayers generated barrier enhancement while exosomes led to barrier disruption. Taken together, these results suggest that differential release of extracellular vesicles from CEM modulate the sustained HPMVEC barrier regulation by HMW-HA and LMW-HA. HMW-HA-induced specialized enlargeosomes can be a potential therapeutic strategy for diseases involving impaired vascular integrity.

Exploring the tumor microenvironment with nanoparticles

Recent developments in nanotechnology have brought new approaches to cancer diagnosis and therapy. While enhanced permeability and retention effect (EPR) promotes nanoparticle (NP) extravasation, the abnormal tumor vasculature, high interstitial pressure and dense stroma structure limit homogeneous intratumoral distribution of NP and compromise their imaging and therapeutic effect. Moreover, heterogeneous distribution of NP in nontumor-stroma cells damages the nontumor cells, and interferes with tumor-stroma crosstalk. This can lead to inhibition of tumor progression, but can also paradoxically induce acquired resistance and facilitate tumor cell proliferation and metastasis. Overall, the tumor microenvironment plays a crucial, yet controversial role in regulating NP distribution and their biological effects. In this review, we summarize recent studies on the stroma barriers for NP extravasation, and discuss the consequential effects of NP distribution in stroma cells. We also highlight design considerations to improve NP delivery and propose potential combinatory strategies to overcome acquired resistance induced by damaged stroma cells.

Hyaluronan in wound healing: rediscovering a major player

Wound healing involves a series of carefully modulated steps, from initial injury and blood clot to the final reconstituted tissue or scar. A dynamic reciprocity exists throughout between the wound, blood elements, extracellular matrix, and cells that participate in healing. Multiple cytokines and signal transduction pathways regulate these reactions. A major component throughout most of the process is hyaluronan, a straight-chain carbohydrate extracellular matrix polymer. Hyaluronan occurs in multiple forms, chain length being the only distinguishing characteristic between them. Levels of hyaluronan in its high-molecular-weight form are prominent in the earliest stages of wound repair. Progressively more fragmented forms occur in a manner not previously appreciated. We outline here steps in the wound healing cascade in which hyaluronan participates, as well as providing a review of its metabolism. Although described by necessity in a series of quantum steps, the healing process is constituted by a smooth continuum of overlapping reactions. The prevalence of hyaluronan in the wound (initially termed "hexosamine-containing mucopolysaccharide"), particularly in its early stages, was pointed out over half a century ago by the Harvard surgeon J. Engelbert Dunphy. It appears we are now returning to where we started.

Hyaluronan - a functional and structural sweet spot in the tissue microenvironment

Transition from homeostatic to reactive matrix remodeling is a fundamental adaptive tissue response to injury, inflammatory disease, fibrosis, and cancer. Alterations in architecture, physical properties, and matrix composition result in changes in biomechanical and biochemical cellular signaling. The dynamics of pericellular and extracellular matrices, including matrix protein, proteoglycan, and glycosaminoglycan modification are continually emerging as essential regulatory mechanisms underlying cellular and tissue function. Nevertheless, the impact of matrix organization on inflammation and immunity in particular and the consequent effects on tissue healing and disease outcome are arguably under-studied aspects of adaptive stress responses. Herein, we review how the predominant glycosaminoglycan hyaluronan (HA) contributes to the structure and function of the tissue microenvironment. Specifically, we examine the evidence of HA degradation and the generation of biologically active smaller HA fragments in pathological settings in vivo. We discuss how HA fragments versus nascent HA via alternate receptor-mediated signaling influence inflammatory cell recruitment and differentiation, resident cell activation, as well as tumor growth, survival, and metastasis. Finally, we discuss how HA fragmentation impacts restoration of normal tissue function and pathological outcomes in disease.

Hyaluronan in the healthy and malignant hematopoietic microenvironment

The fate of both endogenous and transplanted stem cells is dependent on the functional status of the regulatory local microenvironment, which is compromised by disease and therapeutic intervention. The glycosaminoglycan hyaluronan (HA) is a critical component of the hematopoietic microenvironment. We summarize recent advances in our understanding of the role of HA in regulating mesenchymal stem cells, osteoblasts, fibroblasts, macrophages, and endothelium in bone marrow (BM) and their crosstalk within the hematopoietic microenvironment. HA not only determines the volume, hydration, and microfluidics of the BM interstitial space, but also, via interactions with specific receptors, regulates multiple cell functions including differentiation, migration, and production of regulatory factors. The effects of HA are dependent on the polymer size and are influenced by the formation of complexes with other molecules. In healthy BM, HA synthases and hyaluronidases form a molecular network that maintains extracellular HA levels within a discrete physiological window, but HA homeostasis is often perturbed in pathological conditions, including hematological malignancies. Recent studies have suggested that HA synthases may have functions beyond HA production and contribute to the intracellular regulatory machinery. We discuss a possible role for HA synthases, intracellular and extracellular HA in the malignant BM microenvironment, and resistance to therapy.

Hyaluronan regulation of endothelial barrier function in cancer

Vascular integrity or the maintenance of blood vessel continuity is a fundamental process regulated by endothelial cell-cell junctions. Defects in endothelial barrier function are an initiating factor in several disease processes including tumor angiogenesis and metastasis. The glycosaminoglycan, hyaluronan (HA), maintains vascular integrity through specific mechanisms including HA-binding protein signaling in caveolin-enriched microdomains, a subset of lipid rafts. Certain disease states, including cancer, increase enzymatic hyaluronidase activity and reactive oxygen species generation, which break down high molecular weight HA (HMW-HA) to low molecular weight fragments (LMW-HA). LMW-HA can activate specific HA-binding proteins during tumor progression to promote disruption of endothelial cell-cell contacts. In contrast, exogenous administration of HMW-HA promotes enhancement of vascular integrity. This review focuses on the roles of HA in regulating angiogenic and metastatic processes based on its size and the HA-binding proteins present. Further, potential therapeutic applications of HMW-HA in treating cancer are discussed.

Hyaluronan fragments as mediators of inflammation in allergic pulmonary disease

Asthma is frequently caused and/or exacerbated by sensitization to allergens, which are ubiquitous in many indoor and outdoor environments. Severe asthma is characterized by airway hyperresponsiveness and bronchial constriction in response to an inhaled allergen, leading to a disease course that is often very difficult to treat with standard asthma therapies. As a result of interactions among inflammatory cells, structural cells, and the intercellular matrix of the allergic lung, patients with sensitization to allergens may experience a greater degree of tissue injury followed by airway wall remodeling and progressive, accumulated pulmonary dysfunction as part of the disease sequela. In addition, turnover of extracellular matrix (ECM) components is a hallmark of tissue injury and repair. This review focuses on the role of the glycosaminoglycan hyaluronan (HA), a component of the ECM, in pulmonary injury and repair with an emphasis on allergic asthma. Both the synthesis and degradation of the ECM are critical contributors to tissue repair and remodeling. Fragmented HA accumulates during tissue injury and functions in ways distinct from the larger native polymer. There is gathering evidence that HA degradation products are active participants in stimulating the expression of inflammatory genes in a variety of immune cells at the injury site. In this review, we will consider recent advances in the understanding of the mechanisms that are associated with HA accumulation and inflammatory cell recruitment in the asthmatic lung.

Hyaluroan-regulated lymphatic permeability through S1P receptors is crucial for cancer metastasis

Disruption of cancer lymphatic vessel barrier function occurs has been reported to involve in cancer lymphatic metastasis. Hyaluronan (HA), a major glycosaminoglycan component of the extracellular matrix, is associated with cancer metastasis. We investigated the effect of high/low molecular weight hyaluronan (HMW-HA/LMW-HA) on regulation of barrier function and tight junctions in cancer lymphatic endothelial cell (LEC) monolayer. Results showed that LMW-HA increased the permeability of cancer LEC monolayers and induced disruption of Zonula Occludens-1 (ZO-1)-mediated intercellular tight junction and actin stress fiber formation. HMW-HA treatment decreased permeability in cancer LEC monolayers and cortical actin ring formation. As reported, sphingosine 1-phosphate (S1P) receptors are involved in vascular integrity. After silencing of lymphatic vessel endothelial hyaluronan receptor (LYVE-1), upregulation of S1P receptors (S1P1 and S1P3) induced by HMW-HA/LMW-HA were inhibited, respectively. With S1P3 silenced, the disruption of ZO-1 as well as stress fiber formation and the ROCK1/RhoA signaling pathway induced by LMW-HA was not observed in cancer LEC. These results suggested that S1P receptors may play an important role in HMW-HA-/LMW-HA-mediated regulation of cancer lymphatic vessel integrity, which might be the initial step of cancer lymphatic metastasis and a useful intervention of cancer progression.

Asthma is not only an airway disease, but also a vascular disease

Multiple studies have identified an expansion and morphological dysregulation of the bronchial vascular network in the airways of asthmatics. Increased number, size and density of blood vessels, as well as vascular leakage and plasma engorgement, have been reported in the airways of patients with all grades of asthma from mild to fatal. This neovascularisation is an increasingly commonly reported feature of airway remodelling; however, the pathophysiological impact of the increased vasculature in the bronchial wall and its significance to pulmonary function in asthma are unrecognised at this time. Multiple factors capable of influencing the development and persistence of the vascular network exist within asthmatic airway tissue. These include structural components of the altered extracellular matrix (ECM), imbalance of proteases and their endogenous inhibitors, release of active matrikines and the dysregulated levels of both soluble and matrix sequestered growth factors. This review will explore the features of the asthmatic airway which influence the development and persistence of the increased vascular network, as well as the effect of enhanced tissue perfusion on chronic inflammation and airway dynamics. The response of cells of the airways to the altered vascular profile and the subsequent influence on the features of airway remodelling will also be highlighted. We will explore the failure of current asthma therapeutics in "normalising" this vascular remodelling. Finally, we will summarize the outcomes of recent clinical trials which provide hope that anti-angiogenic therapies may be a potent asthma-resolving class of drugs and provide a new approach to asthma management in the future.

Transactivation of the receptor-tyrosine kinase ephrin receptor A2 is required for the low molecular weight hyaluronan-mediated angiogenesis that is implicated in tumor progression

Angiogenesis or the formation of new blood vessels is important in the growth and metastatic potential of various cancers. Therefore, understanding the mechanism(s) by which angiogenesis occurs can have important therapeutic implications in numerous malignancies. We and others have demonstrated that low molecular weight hyaluronan (LMW-HA, ∼2500 Da) promotes endothelial cell (EC) barrier disruption and angiogenesis. However, the mechanism(s) by which this occurs is poorly defined. Our data indicate that treatment of human EC with LMW-HA induced CD44v10 association with the receptor-tyrosine kinase, EphA2, transactivation (tyrosine phosphorylation) of EphA2, and recruitment of the PDZ domain scaffolding protein, PATJ, to the cell periphery. Silencing (siRNA) CD44, EphA2, PATJ, or Dbs (RhoGEF) expression blocked LMW-HA-mediated angiogenesis (EC proliferation, migration, and tubule formation). In addition, silencing EphA2, PATJ, Src, or Dbs expression blocked LMW-HA-mediated RhoA activation. To translate our in vitro findings, we utilized a novel anginex/liposomal targeting of murine angiogenic endothelium with either CD44 or EphA2 siRNA and observed inhibition of LMW-HA-induced angiogenesis in implanted Matrigel plugs. Taken together, these results indicate LMW-HA-mediated transactivation of EphA2 is required for PATJ and Dbs membrane recruitment and subsequent RhoA activation required for angiogenesis. These results suggest that targeting downstream effectors of LMW-HA could be a useful therapeutic intervention for angiogenesis-associated diseases including tumor progression.

Chondroprotective Effect of Kartogenin on CD44-Mediated Functions in Articular Cartilage and Chondrocytes

OBJECTIVE

A recent report identified the small molecule kartogenin as a chondrogenic and chondroprotective agent. Since changes in hyaluronan metabolism occur during cartilage degeneration in osteoarthritis, we began studies to determine whether there was a connection between extracellular hyaluronan, CD44-hyaluronan interactions and the effects of kartogenin on articular chondrocytes.

METHODS

Chondrocytes cultured in monolayers, bioengineered neocartilages, or cartilage explants were treated with kartogenin with or without stimulation by IL-1β. Accumulation of matrix was visualized by a particle exclusion assay or by safranin O staining and release of sulfated glycosaminoglycans was determined. Production of aggrecanases and aggrecan G1-ITEGE neoepitope, fragmentation of CD44 and the SMAD1/5/8 signaling pathway were evaluated by western blotting.

RESULTS

Kartogenin treatment enhanced chondrocyte pericellular matrix assembly and retention in the presence of IL-1β. The chondroprotective effects of kartogenin on IL-1β-induced release of sulfated glycosaminoglycans from articular cartilage explants, reduction in safranin O staining of neocartilage discs as well as a reduction in aggrecan G1-ITEGE neoepitope in chondrocyte and explant cartilage cultures were observed. Kartogenin partially blocked the IL-1β-induced increased expression of ADAMTS-5. Additionally, kartogenin-treated articular chondrocytes exhibited a decrease in CD44 proteolytic fragmentation. However, kartogenin treatment did not enhance proteoglycan in control, non-IL-1β-treated cultures. Similarly, kartogenin enhanced the SMAD1 phosphorylation but only following pretreatment with IL-1β.

CONCLUSION

These studies provide novel information on the chondroprotective function of kartogenin in adult articular cartilage. The effects of kartogenin are significant after activation of chondrocytic chondrolysis, which may occur following disruption of homeostasis maintained by hyaluronan-CD44 interactions.

TH17- and IL-17- mediated autoantibodies and placental oxidative stress play a role in the pathophysiology of pre-eclampsia

Pre-eclampsia is a multisystem disorder of pregnancy that affects 5-8% of pregnancies. The pathophysiologic mechanisms that lead to the development of pre-eclampsia are poorly understood. Higher than normal levels of circulating TH17 is observed in preeclamptic women compared to women with normal pregnancy. TH17 cells are a subset of CD4+ T helper cells that are characterized by their secretion of IL-17. Recent studies suggest a role for TH17 cells and IL-17 in the pathophysiology of pre-eclampsia. In this review, we will discuss the known function of TH17 cells and IL-17 in immunity and vascular function. We will then review the role of IL-17 and TH17 cells in normal pregnancy and their association with pre-eclampsia, followed by a discussion of the literature to examine a potential role for IL-17 and TH17 cells in mediating pathophysiology in pre-eclampsia.

GRP78 is a novel receptor initiating a vascular barrier protective response to oxidized phospholipids

Vascular integrity and the maintenance of blood vessel continuity are fundamental features of the circulatory system maintained through endothelial cell-cell junctions. Defects in the endothelial barrier become an initiating factor in several pathologies, including ischemia/reperfusion, tumor angiogenesis, pulmonary edema, sepsis, and acute lung injury. Better understanding of mechanisms stimulating endothelial barrier enhancement may provide novel therapeutic strategies. We previously reported that oxidized phospholipids (oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine [OxPAPC]) promote endothelial cell (EC) barrier enhancement both in vitro and in vivo. This study examines the initiating mechanistic events triggered by OxPAPC to increase vascular integrity. Our data demonstrate that OxPAPC directly binds the cell membrane-localized chaperone protein, GRP78, associated with its cofactor, HTJ-1. OxPAPC binding to plasma membrane-localized GRP78 leads to GRP78 trafficking to caveolin-enriched microdomains (CEMs) on the cell surface and consequent activation of sphingosine 1-phosphate receptor 1, Src and Fyn tyrosine kinases, and Rac1 GTPase, processes essential for cytoskeletal reorganization and EC barrier enhancement. Using animal models of acute lung injury with vascular hyperpermeability, we observed that HTJ-1 knockdown blocked OxPAPC protection from interleukin-6 and ventilator-induced lung injury. Our data indicate for the first time an essential role of GRP78 and HTJ-1 in OxPAPC-mediated CEM dynamics and enhancement of vascular integrity.