Regulation of plasminogen activator inhibitor-1 and urokinase by hyaluronan fragments in mouse macrophages

Hyaluronic Acid Interacting Molecules Mediated Crosstalk between Cancer Cells and Microenvironment from Primary Tumour to Distant Metastasis

Hyaluronic acid (HA) is a prominent component of the extracellular matrix, and its interactions with HA-interacting molecules (HAIMs) play a critical role in cancer development and disease progression. This review explores the multifaceted role of HAIMs in the context of cancer, focusing on their influence on disease progression by dissecting relevant cellular and molecular mechanisms in tumour cells and the tumour microenvironment. Cancer progression can be profoundly affected by the interactions between HA and HAIMs. They modulate critical processes such as cell adhesion, migration, invasion, and proliferation. The TME serves as a dynamic platform in which HAIMs contribute to the formation of a unique niche. The resulting changes in HA composition profoundly influence the biophysical properties of the TME. These modifications in the TME, in conjunction with HAIMs, impact angiogenesis, immune cell recruitment, and immune evasion. Therefore, understanding the intricate interplay between HAIMs and HA within the cancer context is essential for developing novel therapeutic strategies. Targeting these interactions offers promising avenues for cancer treatment, as they hold the potential to disrupt critical aspects of disease progression and the TME. Further research in this field is imperative for advancing our knowledge and the treatment of cancer.

Glycosaminoglycans' Ability to Promote Wound Healing: From Native Living Macromolecules to Artificial Biomaterials

Glycosaminoglycans (GAGs) are important for the occurrence of signaling molecules and maintenance of microenvironment within the extracellular matrix (ECM) in living tissues. GAGs and GAG-based biomaterial approaches have been widely explored to promote in situ tissue regeneration and repair by regulating the wound microenvironment, accelerating re-epithelialization, and controlling ECM remodeling. However, most approaches remain unacceptable for clinical applications. To improve insights into material design and clinical translational applications, this review highlights the innate roles and bioactive mechanisms of native GAGs during in situ wound healing and presents common GAG-based biomaterials and the adaptability of application scenarios in facilitating wound healing. Furthermore, challenges before the widespread commercialization of GAG-based biomaterials are shared, to ensure that future designed and constructed GAG-based artificial biomaterials are more likely to recapitulate the unique and tissue-specific profile of native GAG expression in human tissues. This review provides a more explicit and clear selection guide for researchers designing biomimetic materials, which will resemble or exceed their natural counterparts in certain functions, thereby suiting for specific environments or therapeutic goals.

The Study of the Extracellular Matrix in Chronic Inflammation: A Way to Prevent Cancer Initiation?

Bidirectional communication between cells and their microenvironment has a key function in normal tissue homeostasis, and in disease initiation, progression and a patient's prognosis, at the very least. The extracellular matrix (ECM), as an element of all tissues and cellular microenvironment, is a frequently overlooked component implicated in the pathogenesis and progression of several diseases. In the inflammatory microenvironment (IME), different alterations resulting from remodeling processes can affect ECM, progressively inducing cancer initiation and the passage toward a tumor microenvironment (TME). Indeed, it has been demonstrated that altered ECM components interact with a variety of surface receptors triggering intracellular signaling that affect cellular pathways in turn. This review aims to support the notion that the ECM and its alterations actively participate in the promotion of chronic inflammation and cancer initiation. In conclusion, some data obtained in cancer research with the employment of decellularized ECM (dECM) models are described. The reported results encourage the application of dECM models to investigate the short circuits contributing to the creation of distinct IME, thus representing a potential tool to avoid the progression toward a malignant lesion.

Deregulated hyaluronan metabolism in the tumor microenvironment drives cancer inflammation and tumor-associated immune suppression

Hyaluronan (HA) is known to be a prominent component of the extracellular matrix in tumors, and many solid cancers are characterized by aberrant HA metabolism resulting in increased production in tumor tissue. HA has been implicated in regulating a variety of cellular functions in tumor cells and tumor-associated stromal cells, suggesting that altered HA metabolism can influence tumor growth and malignancy at multiple levels. Importantly, increased HA production in cancer is associated with enhanced HA degradation due to high levels of expression and activity of hyaluronidases (Hyal). Understanding the complex molecular and cellular mechanisms involved in abnormal HA metabolism and catabolism in solid cancers could have important implications for the design of future cancer therapeutic approaches. It appears that extensive crosstalk between immune cells and HA-enriched stroma contributes to tumor growth and progression in several ways. Specifically, the interaction of tumor-recruited Hyal2-expressing myeloid-derived suppressor cells (MDSCs) of bone marrow origin with HA-producing cancer-associated fibroblasts and epithelial tumor cells results in enhanced HA degradation and accumulation of small pro-inflammatory HA fragments, which further drives cancer-related inflammation. In addition, hyaluronan-enriched stroma supports the transition of tumor-recruited Hyal2⁺MDSCs to the PD-L1⁺ tumor-associated macrophages leading to the formation of an immunosuppressive and tolerogenic tumor microenvironment. In this review, we aim to discuss the contribution of tumor-associated HA to cancer inflammation, angiogenesis, and tumor-associated immune suppression. We also highlight the recent findings related to the enhanced HA degradation in the tumor microenvironment.

Targeting of Glycosaminoglycans in Genetic and Inflammatory Airway Disease

In the lung, glycosaminoglycans (GAGs) are dispersed in the extracellular matrix (ECM) occupying the interstitial space between the capillary endothelium and the alveolar epithelium, in the sub-epithelial tissue and in airway secretions. In addition to playing key structural roles, GAGs contribute to a number of physiologic processes ranging from cell differentiation, cell adhesion and wound healing. Cytokine and chemokine–GAG interactions are also involved in presentation of inflammatory molecules to respective receptors leading to immune cell migration and airway infiltration. More recently, pathophysiological roles of GAGs have been described. This review aims to discuss the biological roles and molecular interactions of GAGs, and their impact in the pathology of chronic airway diseases, such as cystic fibrosis and chronic obstructive pulmonary disease. Moreover, the role of GAGs in respiratory disease has been heightened by the current COVID-19 pandemic. This review underlines the essential need for continued research aimed at exploring the contribution of GAGs in the development of inflammation, to provide a better understanding of their biological impact, as well as leads in the development of new therapeutic agents.

Glycocalyx Impairment in Vascular Disease: Focus on Inflammation

The glycocalyx is a complex polysaccharide-protein layer lining the lumen of vascular endothelial cells. Changes in the structure and function of the glycocalyx promote an inflammatory response in blood vessels and play an important role in the pathogenesis of many vascular diseases (e.g., diabetes, atherosclerosis, and sepsis). Vascular endothelial dysfunction is a hallmark of inflammation-related diseases. Endothelial dysfunction can lead to tissue swelling, chronic inflammation, and thrombosis. Therefore, elimination of endothelial inflammation could be a potential target for the treatment of vascular diseases. This review summarizes the key role of the glycocalyx in the inflammatory process and the possible mechanism by which it alleviates this process by interrupting the cycle of endothelial dysfunction and inflammation. Especially, we highlight the roles of different components of the glycocalyx in modulating the inflammatory process, including components that regulate leukocyte rolling, L-selectin binding, inflammasome activation and the signaling interactions between the glycocalyx components and the vascular cells. We discuss how the glycocalyx interferes with the development of inflammation and the importance of preventing glycocalyx impairment. Finally, drawing on current understanding of the role of the glycocalyx in inflammation, we consider a potential strategy for the treatment of vascular diseases.

Recent advances and prospects of hyaluronan as a multifunctional therapeutic system

Hyaluronan (HA) is a naturally occurring non-sulfated glycosaminoglycan (GAG), cell-surface-associated biopolymer and is the key component of tissue extracellular matrix (ECM). Along with remarkable physicochemical properties, HA also has multifaceted biological effects that include but not limited to ECM organization, immunomodulation, and various cellular processes. Environmental cues such as tissue injury, infection or cancer change downstream signaling functionalities of HA. Unlike native HA, the fragments of HA have diversified effects on inflammation, cancer, fibrosis, angiogenesis and autoimmune response. In this review, we aim to discuss HA as a therapeutic delivery system development process, source, biophysical-chemical properties, and associated biological pathways (especially via cell surface receptors) of native and fragmented HA. We also tried to address an overview of the potential role of HA (native HA vs fragments) in the modulation of inflammation, immune response and various cancer targeting delivery applications. This review will also highlight the HA based therapeutic systems, medical devices and future perspectives of various biomedical applications were discussed in detail.

Immunomodulatory Role of the Extracellular Matrix Within the Liver Disease Microenvironment

Chronic liver disease when accompanied by underlying fibrosis, is characterized by an accumulation of extracellular matrix (ECM) proteins and chronic inflammation. Although traditionally considered as a passive and largely architectural structure, the ECM is now being recognized as a source of potent damage-associated molecular pattern (DAMP)s with immune-active peptides and domains. In parallel, the ECM anchors a range of cytokines, chemokines and growth factors, all of which are capable of modulating immune responses. A growing body of evidence shows that ECM proteins themselves are capable of modulating immunity either directly via ligation with immune cell receptors including integrins and TLRs, or indirectly through release of immunoactive molecules such as cytokines which are stored within the ECM structure. Notably, ECM deposition and remodeling during injury and fibrosis can result in release or formation of ECM-DAMPs within the tissue, which can promote local inflammatory immune response and chemotactic immune cell recruitment and inflammation. It is well described that the ECM and immune response are interlinked and mutually participate in driving fibrosis, although their precise interactions in the context of chronic liver disease are poorly understood. This review aims to describe the known pro-/anti-inflammatory and fibrogenic properties of ECM proteins and DAMPs, with particular reference to the immunomodulatory properties of the ECM in the context of chronic liver disease. Finally, we discuss the importance of developing novel biotechnological platforms based on decellularized ECM-scaffolds, which provide opportunities to directly explore liver ECM-immune cell interactions in greater detail.

An aberrant STAT pathway is central to COVID-19

COVID-19 is caused by SARS-CoV-2 infection and characterized by diverse clinical symptoms. Type I interferon (IFN-I) production is impaired and severe cases lead to ARDS and widespread coagulopathy. We propose that COVID-19 pathophysiology is initiated by SARS-CoV-2 gene products, the NSP1 and ORF6 proteins, leading to a catastrophic cascade of failures. These viral components induce signal transducer and activator of transcription 1 (STAT1) dysfunction and compensatory hyperactivation of STAT3. In SARS-CoV-2-infected cells, a positive feedback loop established between STAT3 and plasminogen activator inhibitor-1 (PAI-1) may lead to an escalating cycle of activation in common with the interdependent signaling networks affected in COVID-19. Specifically, PAI-1 upregulation leads to coagulopathy characterized by intravascular thrombi. Overproduced PAI-1 binds to TLR4 on macrophages, inducing the secretion of proinflammatory cytokines and chemokines. The recruitment and subsequent activation of innate immune cells within an infected lung drives the destruction of lung architecture, which leads to the infection of regional endothelial cells and produces a hypoxic environment that further stimulates PAI-1 production. Acute lung injury also activates EGFR and leads to the phosphorylation of STAT3. COVID-19 patients' autopsies frequently exhibit diffuse alveolar damage (DAD) and increased hyaluronan (HA) production which also leads to higher levels of PAI-1. COVID-19 risk factors are consistent with this scenario, as PAI-1 levels are increased in hypertension, obesity, diabetes, cardiovascular diseases, and old age. We discuss the possibility of using various approved drugs, or drugs currently in clinical development, to treat COVID-19. This perspective suggests to enhance STAT1 activity and/or inhibit STAT3 functions for COVID-19 treatment. This might derail the escalating STAT3/PAI-1 cycle central to COVID-19.

An aberrant STAT pathway is central to COVID-19

COVID-19 is caused by SARS-CoV-2 infection and characterized by diverse clinical symptoms. Type I interferon (IFN-I) production is impaired and severe cases lead to ARDS and widespread coagulopathy. We propose that COVID-19 pathophysiology is initiated by SARS-CoV-2 gene products, the NSP1 and ORF6 proteins, leading to a catastrophic cascade of failures. These viral components induce signal transducer and activator of transcription 1 (STAT1) dysfunction and compensatory hyperactivation of STAT3. In SARS-CoV-2-infected cells, a positive feedback loop established between STAT3 and plasminogen activator inhibitor-1 (PAI-1) may lead to an escalating cycle of activation in common with the interdependent signaling networks affected in COVID-19. Specifically, PAI-1 upregulation leads to coagulopathy characterized by intravascular thrombi. Overproduced PAI-1 binds to TLR4 on macrophages, inducing the secretion of proinflammatory cytokines and chemokines. The recruitment and subsequent activation of innate immune cells within an infected lung drives the destruction of lung architecture, which leads to the infection of regional endothelial cells and produces a hypoxic environment that further stimulates PAI-1 production. Acute lung injury also activates EGFR and leads to the phosphorylation of STAT3. COVID-19 patients' autopsies frequently exhibit diffuse alveolar damage (DAD) and increased hyaluronan (HA) production which also leads to higher levels of PAI-1. COVID-19 risk factors are consistent with this scenario, as PAI-1 levels are increased in hypertension, obesity, diabetes, cardiovascular diseases, and old age. We discuss the possibility of using various approved drugs, or drugs currently in clinical development, to treat COVID-19. This perspective suggests to enhance STAT1 activity and/or inhibit STAT3 functions for COVID-19 treatment. This might derail the escalating STAT3/PAI-1 cycle central to COVID-19.

Modulation of Fibrinolytic System Components in Mesothelial Cells by Hyaluronan

← Objective

Hyaluronan (HA) is an important extracellular matrix component and is involved in fluid homeostasis, tissue repair, and response to infections. Previous studies have shown that supplementation of dialysis fluid with high molecular weight HA may have a positive impact on peritoneal solute and fluid transport characteristics. In the present study, we investigated the impact of HA on the synthesis of tissue-type plasminogen activator (t-PA) and its inhibitor, plasminogen activator inhibitor type 1 (PAI-1) in cultured human peritoneal mesothelial cells (MC).

← Methods

Cultured human peritoneal MC isolated from omental tissue were used for the experiments. Concentrations of t-PA and PAI-1 antigens were measured in conditioned media of confluent MC using ELISA. Northern blot analysis was performed to investigate mRNA expression of t-PA, PAI-1, and low-density lipoprotein receptor-related protein.

← Results

Hyaluronan in a concentration as suggested for supplementation of dialysis fluid (10 mg/dL) did not have a significant impact on the synthesis of t-PA or PAI-1 in human MC. However, incubation of MC with higher concentrations of HA (30 – 1000 mg/dL) resulted in a concentration- and time- (8 – 48 hours) dependent decrease in t-PA antigen release and mRNA expression. In contrast, PAI-1 antigen secretion was distinctly but not significantly increased in the presence of HA.

← Conclusion

The expression of t-PA and PAI-1 in MC was not affected by low concentrations of HA. Therefore, it is reasonable to assume that supplementation of dialysis fluid with HA (10 mg/dL) will not decrease mesothelial fibrinolytic activity. Only high concentrations (> 50 mg/dL) may disturb the balance between intraperitoneal generation and degradation of fibrin by decreasing t-PA synthesis.

Low Molecular Weight Hyaluronan Induces an Inflammatory Response in Ovarian Stromal Cells and Impairs Gamete Development In Vitro

The ovarian stroma, the microenvironment in which female gametes grow and mature, becomes inflamed and fibrotic with age. Hyaluronan is a major component of the ovarian extracellular matrix (ECM), and in other aging tissues, accumulation of low molecular weight (LMW) hyaluronan fragments can drive inflammation. Thus, we hypothesized that LMW hyaluronan fragments contribute to female reproductive aging by stimulating an inflammatory response in the ovarian stroma and impairing gamete quality. To test this hypothesis, isolated mouse ovarian stromal cells or secondary stage ovarian follicles were treated with physiologically relevant (10 or 100 μg/mL) concentrations of 200 kDa LMW hyaluronan. In ovarian stromal cells, acute LMW hyaluronan exposure, at both doses, resulted in the secretion of a predominantly type 2 (Th2) inflammatory cytokine profile as revealed by a cytokine antibody array of conditioned media. Additional qPCR analyses of ovarian stromal cells demonstrated a notable up-regulation of the eotaxin receptor Ccr3 and activation of genes involved in eosinophil recruitment through the IL5-CCR3 signaling pathway. These findings were consistent with an age-dependent increase in ovarian stromal expression of Ccl11, a major CCR3 ligand. When ovarian follicles were cultured in 10 or 100 μg/mL LMW hyaluronan for 12 days, gametes with compromised morphology and impaired meiotic competence were produced. In the 100 μg/mL condition, LMW hyaluronan induced premature meiotic resumption, ultimately leading to in vitro aging of the resulting eggs. Further, follicles cultured in this LMW hyaluronan concentration produced significantly less estradiol, suggesting compromised granulosa cell function. Taken together, these data demonstrate that bioactive LMW hyaluronan fragments may contribute to reproductive aging by driving an inflammatory stromal milieu, potentially through eosinophils, and by directly compromising gamete quality through impaired granulosa cell function.

Absence of differences among low, middle, and high molecular weight hyaluronan in activating murine immune cells in vitro

Hyaluronan (HA) effects on immune response are suggested to be dependent on HA molecular weight (MW), as low MW HA should activate immune cells in contrast to high MW HA. However, some current studies do not support this conception and emphasize the importance of the form of preparation of HA, particularly with respect to its purity and origin. We compared the activation of mouse immune cells by HA samples (100kDa, 500kDa, and 997kDa) prepared from HA originating from rooster comb, and HA samples (71kDa, 500kDa, and 1000kDa) prepared from pharmacological grade HA originating from Streptococcus equi. Interestingly, in contrast to established theory, only middle and high MW HA originating from rooster comb induced the production of tumor necrosis factor-α by macrophages and in whole blood. Further, all tested preparations of HA failed to induce the expression of inducible nitric oxide synthase, the production of nitric oxide, or the expression of cyclooxygenase 2 in macrophages and splenocytes. Importantly, all HA samples originating from rooster comb were found to be contaminated by endotoxin (up to 1.23EU/ml). Hence, low MW HA did not reveal itself to have significantly higher immunostimulatory activity compared to HA of higher MW.

COPD Exacerbations Are Associated With Proinflammatory Degradation of Hyaluronic Acid

BACKGROUND

COPD is characterized by chronic airway inflammation and remodeling, with serious modifications of the extracellular matrix (ECM). Hyaluronic acid (HA) is an abundant ECM molecule in the lung with various biologic functions that depend on its molecular weight (MW). High-MW HA exhibits antiinflammatory and immunosuppressive effects, whereas low-MW HA is proinflammatory. In this study, we investigated whether acute exacerbations of COPD (AECOPDs), which affect patient quality of life and survival, are associated with altered HA turnover in BAL.

METHODS

We used BAL from patients with stable COPD (n = 53) or during AECOPD (n = 44) matched for demographics and clinical characteristics and BAL from control subjects (n = 15). HA, HA synthase-1 (HAS-1), and hyaluronidase (HYAL) values were determined by enzyme-linked immunosorbent assay, and HYAL activity was determined by HA zymography. The MW of HA was analyzed by agarose electrophoresis.

RESULTS

Levels of HA, HAS-1, and HYAL were significantly increased in BAL of patients with stable COPD and during exacerbations compared with control subjects. HYAL activity was significantly increased in BAL of patients with AECOPD, resulting in an increase of low-MW HA during exacerbations. In patients with AECOPD, we also observed a significant negative correlation of HA and HYAL levels with FEV1 % predicted but not with diffusing capacity of lung for carbon monoxide % predicted, indicating that increased HA degradation may be more associated with airway obstruction than with emphysema.

CONCLUSIONS

AECOPDs are associated with increased HYAL activity in BAL and subsequent degradation of HA, which may contribute to airway inflammation and subsequent lung function decline during exacerbations.

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.

In vitro analysis of the effects on wound healing of high- and low-molecular weight chains of hyaluronan and their hybrid H-HA/L-HA complexes

BACKGROUND

Recent studies have reported the roles of Hyaluronic acid (HA) chains of diverse length in wound repair, especially considering the simultaneous occurrence in vivo of both high- (H-HA) and low-molecular weight (L-HA) hyaluronan at an injury site. It has been shown that HA fragments (5 ≤ MW ≤ 20 kDa) usually trigger an inflammatory response that, on one hand, is the first signal in the activation of a repair mechanism but on the other, when it's overexpressed, it may promote unwanted side effects. The present experimental research has aimed to investigate H-HA, L-HA and of a newly developed complex of the two (H-HA/L-HA) for stability (e.g. hyaluronidases digestion), for their ability to promote wound healing of human keratinocytes in vitro and for their effect on cellular biomarker expression trends.

RESULTS

Time-lapse video microscopy studies proved that the diverse HA was capable of restoring the monolayer integrity of HaCat. The H-HA/L-HA complex (0.1 and 1%w/v) proved faster in regeneration also in co-culture scratch test where wound closure was achieved in half the time of H-HA stimulated cells and 2.5-fold faster than the control. Gene expression was evaluated for transformation growth factor beta 1 (TGF-β1) proving that L-HA alone increased its expression at 4 h followed by restoration of similar trends for all the stimuli. Depending on the diverse stimulation (H-HA, L-HA or the complex), metalloproteinases (MMP-2, -9, -13) were also modulated differently. Furthermore, type I collagen expression and production were evaluated. Compared to the others, persistence of a significant higher expression level at 24 h for the H-HA/L-HA complex was found.

CONCLUSIONS

The outcomes of this research showed that, both at high and low concentrations, hybrid complexes proved to perform better than HA alone thus suggesting their potential as medical devices in aesthetic and regenerative medicine.

Interactions between Hyaluronan and Its Receptors (CD44, RHAMM) Regulate the Activities of Inflammation and Cancer

The glycosaminoglycan hyaluronan (HA), a major component of extracellular matrices, and cell surface receptors of HA have been proposed to have pivotal roles in cell proliferation, migration, and invasion, which are necessary for inflammation and cancer progression. CD44 and receptor for HA-mediated motility (RHAMM) are the two main HA-receptors whose biological functions in human and murine inflammations and tumor cells have been investigated comprehensively. HA was initially considered to be only an inert component of connective tissues, but is now known as a “dynamic” molecule with a constant turnover in many tissues through rapid metabolism that involves HA molecules of various sizes: high molecular weight HA (HMW HA), low molecular weight HA, and oligosaccharides. The intracellular signaling pathways initiated by HA interactions with CD44 and RHAMM that lead to inflammatory and tumorigenic responses are complex. Interestingly, these molecules have dual functions in inflammations and tumorigenesis. For example, the presence of CD44 is involved in initiation of arthritis, while the absence of CD44 by genetic deletion in an arthritis mouse model increases rather than decreases disease severity. Similar dual functions of CD44 exist in initiation and progression of cancer. RHAMM overexpression is most commonly linked to cancer progression, whereas loss of RHAMM is associated with malignant peripheral nerve sheath tumor growth. HA may similarly perform dual functions. An abundance of HMW HA can promote malignant cell proliferation and development of cancer, whereas antagonists to HA-CD44 signaling inhibit tumor cell growth in vitro and in vivo by interfering with HMW HA-CD44 interaction. This review describes the roles of HA interactions with CD44 and RHAMM in inflammatory responses and tumor development/progression, and how therapeutic strategies that block these key inflammatory/tumorigenic processes may be developed in rodent and human diseases.

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.

Interfacial biology of in-stent restenosis

Percutaneous angioplasty is a nonsurgical method able to restore patency in atherosclerotic blood vessels through the expansion of a balloon. The clinical outcome of this technique has been significantly enhanced by the combined deployment of a stent. Although stents are successful in the majority of cases, a large percentage of patients (20-30%) still suffer a second vessel lumen reduction known as in-stent restenosis. In-stent restenosis is recognized to be caused by the mechanical and foreign body challenges elicited by the device. Drug-eluting stents have been recently made available to tackle restenosis, but their short clinical history and high costs may limit their future use. The present review links the most recent biologic findings related to in-stent restenosis to the devices' phyisico-chemical features in an attempt to demonstrate that a new generation of stents may be developed without the need of drug elution.

Hyaluronan fragments induce IFNβ via a novel TLR4-TRIF-TBK1-IRF3-dependent pathway

Background

The extracellular matrix plays a critical role in insuring tissue integrity and water homeostasis. However, breakdown products of the extracellular matrix have emerged as endogenous danger signals, designed to rapidly activate the immune system against a potential pathogen breach. Type I interferons play a critical role in the immune response against viral infections. In the lungs, hylauronan (HA) exists as a high molecular weight, biologically inert extracellular matrix component that is critical for maintaining lung function. When lung tissue is injured, HA is broken down into lower molecular weight fragments that alert the immune system to the breach in tissue integrity by activating innate immune responses. HA fragments are known to induce inflammatory gene expression via TLR-MyD88-dependent pathways.

Methods

Primary peritoneal macrophages from C57BL/6 wild type, TLR4 null, TLR3 null, MyD88 null, and TRIF null mice as well as alveolar and peritoneal macrophage cell lines were stimulated with HA fragments and cytokine production was assessed by rt-PCR and ELISA. Western blot analysis for IRF3 was preformed on cell lysates from macrophages stimulate with HA fragments

Results

We demonstrate for the first time that IFNβ is induced in murine macrophages by HA fragments. We also show that HA fragments induce IFNβ using a novel pathway independent of MyD88 but dependent on TLR4 via TRIF and IRF-3.

Conclusions

Overall our findings reveal a novel signaling pathway by which hyaluronan can modulate inflammation and demonstrate the ability of hyaluronan fragments to induce the expression of type I interferons in response to tissue injury even in the absence of viral infection. This is independent of the pathway of the TLR2-MyD88 used by these matrix fragments to induce inflammatory chemokines. Thus, LMW HA may be modifying the inflammatory milieu simultaneously via several pathways.

Induction of brain microvascular endothelial cell urokinase expression by Cryptococcus neoformans facilitates blood-brain barrier invasion

The invasive ability of the blood-borne fungal pathogen Cryptococcus neoformans can be enhanced through interactions with host plasma components, such as plasminogen. Previously we showed by in vitro studies that plasminogen coats the surface of C. neoformans and is converted to the active serine protease, plasmin, by host plasminogen activators. Viable, but not formaldehyde- or sodium azide-killed, cryptococcal strains undergo brain microvascular endothelial cell-dependent plasminogen-to-plasmin activation, which results in enhanced, plasmin-dependent cryptococcal invasion of primary bovine brain microvascular endothelial cells and fungal ability to degrade plasmin substrates. In the present work, brain microvascular endothelial cells cultured with viable, but not killed, cryptococcal strains led to significant increases in both urokinase mRNA transcription and cell-associated urokinase protein expression. Soluble urokinase was also detected in conditioned medium from brain microvascular endothelial cells cultured with viable, but not killed, C. neoformans. Exposure of plasminogen pre-coated viable C. neoformans to conditioned medium from strain-matched brain microvascular endothelial cell-fungal co-cultures resulted in plasminogen-to-plasmin activation and plasmin-dependent cryptococcal invasion. siRNA-mediated silencing of urokinase gene expression or the use of specific inhibitors of urokinase activity abrogated both plasminogen-to-plasmin activation on C. neoformans and cryptococcal-brain microvascular endothelial cell invasion. Our results suggest that pathogen exploitation of the host urokinase-plasmin(ogen) system may contribute to C. neoformans virulence during invasive cryptococcosis.

Impact of intraperitoneal pressure of a CO2 pneumoperitoneum on the surgical peritoneal environment

BACKGROUND

Animal experiments have suggested that a high intraperitoneal pressure (IPP) might adversely affect the surgical peritoneal environment. The present experimental study investigates the impact of IPP of a CO(2) pneumoperitoneum on human peritoneum.

METHODS

Patients undergoing laparoscopic surgery were subjected to either low (8 mmHg) or standard (12 mmHg) IPP. Normal peritoneum was collected from the parietal wall at the beginning of surgery and every 60 min thereafter. Expression levels of 168 genes that encode extracellular matrix proteins, adhesion molecules or inflammatory cytokine signaling molecules were measured in peritoneal tissues using real-time polymerase chain reaction (PCR)-based assay panels. Human peritoneal mesothelial cells (HPMCs) and human peritoneal fibroblasts (HPFBs) were incubated in a CO(2) insufflation chamber for 1 h at 12 or 8 mmHg. Hyaluronan (HA) synthesis and mRNA expression levels of hyaluronic acid synthases (HAS) and hyaluronidases (Hyal) in HPMCs and HPFBs were measured at 0, 4, 8, 12, 24 and 48 h after CO(2) gas exposure by ELISA and real-time PCR, respectively.

RESULTS

Expression levels of connective tissue growth factor (CTGF), matrix metalloproteinase-9, E-selectin, chemokine (C-X-C motif) ligand 2 (CXCL-2), Hyal-1 and Hyal-2 were significantly higher and those of HAS-1, HAS-3, thrombospondin-2 (TSP-2) and interleukin-10 were significantly lower in the 12 mmHg group compared with the 8 mmHg group. HA synthesis was significantly lower in the 12 mmHg group compared with the 8 mmHg group in HPMCs and HPFBs throughout the time course.

CONCLUSIONS

A low IPP (8 mmHg) may be better than the standard IPP (12 mmHg) to minimize the adverse impact on the surgical peritoneal environment during a CO(2) pneumoperitoneum.

PAI-1 in tissue fibrosis

Fibrosis is defined as a fibroproliferative or abnormal fibroblast activation-related disease. Deregulation of wound healing leads to hyperactivation of fibroblasts and excessive accumulation of extracellular matrix (ECM) proteins in the wound area, the pathological manifestation of fibrosis. The accumulation of excessive levels of collagen in the ECM depends on two factors: an increased rate of collagen synthesis and or decreased rate of collagen degradation by cellular proteolytic activities. The urokinase/tissue type plasminogen activator (uPA/tPA) and plasmin play significant roles in the cellular proteolytic degradation of ECM proteins and the maintenance of tissue homeostasis. The activities of uPA/tPA/plasmin and plasmin-dependent MMPs rely mostly on the activity of a potent inhibitor of uPA/tPA, plasminogen activator inhibitor-1 (PAI-1). Under normal physiologic conditions, PAI-1 controls the activities of uPA/tPA/plasmin/MMP proteolytic activities and thus maintains the tissue homeostasis. During wound healing, elevated levels of PAI-1 inhibit uPA/tPA/plasmin and plasmin-dependent MMP activities, and, thus, help expedite wound healing. In contrast to this scenario, under pathologic conditions, excessive PAI-1 contributes to excessive accumulation of collagen and other ECM protein in the wound area, and thus preserves scarring. While the level of PAI-1 is significantly elevated in fibrotic tissues, lack of PAI-1 protects different organs from fibrosis in response to injury-related profibrotic signals. Thus, PAI-1 is implicated in the pathology of fibrosis in different organs including the heart, lung, kidney, liver, and skin. Paradoxically, PAI-1 deficiency promotes spontaneous cardiac-selective fibrosis. In this review, we discuss the significance of PAI-1 in the pathogenesis of fibrosis in multiple organs.

Acute Lung Injury Regulation by Hyaluronan

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS), have high mortality rates with few treatment options. An important regulatory factor in the pathology observed in ALI/ARDS is a disruption of the pulmonary endothelial barrier which, in combination with epithelial barrier disruption, causes leakage of fluid, protein and cells into lung airspaces. Degradation of the glycosaminoglycan, hyaluronan (HA), is involved in reduction of the endothelial glycocalyx, disruption of endothelial cell-cell contacts and activation of HA binding proteins upregulated in ALI/ARDS which promote a loss of pulmonary vascular integrity. In contrast, exogenous administration of high molecular weight HA has been shown to be protective in several models of ALI. This review focuses on the dichotomous role of HA to both promote and inhibit ALI based on its size and the HA binding proteins present. Further, potential therapeutic applications of high molecular weight HA in treating ALI/ARDS are discussed.

Role of hyaluronan and hyaluronan-binding proteins in lung pathobiology

Hyaluronan (HA) has diverse functions in normal lung homeostasis and pulmonary disease. HA constitutes the major glycosaminoglycan in lung tissue, with HA degradation products, produced by hyaluronidase enzymes and reactive oxygen species, being implicated in several lung diseases, including acute lung injury, asthma, chronic obstructive pulmonary disease, and pulmonary hypertension. The differential activities of HA and its degradation products are due, in part, to regulation of multiple HA-binding proteins, including cluster of differentiation 44 (CD44), Toll-like receptor 4 (TLR4), HA-binding protein 2 (HABP2), and receptor for HA-mediated motility (RHAMM). Recent research indicates that exogenous administration of high-molecular-weight HA can serve as a novel therapeutic intervention for lung diseases, including lipopolysaccharide (LPS)-induced acute lung injury, sepsis/ventilator-induced lung injury, and airway hyperreactivity. This review focuses on the regulatory role of HA and HA-binding proteins in lung pathology and discusses the capacity of HA to augment and inhibit various lung diseases.

Hyaluronan as an immune regulator in human diseases

Accumulation and turnover of extracellular matrix components are the hallmarks of tissue injury. Fragmented hyaluronan stimulates the expression of inflammatory genes by a variety of immune cells at the injury site. Hyaluronan binds to a number of cell surface proteins on various cell types. Hyaluronan fragments signal through both Toll-like receptor (TLR) 4 and TLR2 as well as CD44 to stimulate inflammatory genes in inflammatory cells. Hyaluronan is also present on the cell surface of epithelial cells and provides protection against tissue damage from the environment by interacting with TLR2 and TLR4. Hyaluronan and hyaluronan-binding proteins regulate inflammation, tissue injury, and repair through regulating inflammatory cell recruitment, release of inflammatory cytokines, and cell migration. This review focuses on the role of hyaluronan as an immune regulator in human diseases.

Hyaluronan fragments promote inflammation by down-regulating the anti-inflammatory A2a receptor

The tissue microenvironment plays a critical role in regulating inflammation. Chronic inflammation leads to an influx of inflammatory cells and mediators, extracellular matrix turnover, and increased extracellular adenosine. Low molecular weight (LMW) fragments of hyaluronan (HA), a matrix component, play a critical role in lung inflammation and fibrosis by inducing inflammatory gene expression at the injury site. Adenosine, a crucial negative regulator of inflammation, protects tissues from immune destruction via the adenosine A2a receptor (A2aR). Therefore, these two extracellular products of inflammation play opposing roles in regulating immune responses. As such, we wanted to determine the effect of LMW HA on A2aR function. In this article, we demonstrate that LMW HA causes a rapid, significant, and sustained down-regulation of the A2aR. CD44 was found to be necessary for LMW HA to down-modulate the A2aR as was protein kinase C signaling. We also demonstrate that LMW HA induces A2aR down-regulation during inflammation in vivo, and that this down-regulation can be blocked by treatment with an HA-blocking peptide. Because adenosine plays a critical role in limiting inflammation, our data provide a novel mechanism whereby LMW HA itself may further augment inflammation. By defining the pro- and anti-inflammatory properties of extracellular matrix components, we will be better able to identify specific pharmacologic targets as potential therapies.

Immunolocalization of lymphatic vessels in human fetal knee joint tissues

We immunolocalized lymphatic and vascular blood vessels in 12- and 14-week-old human fetal knee joint tissues using a polyclonal antibody to a lymphatic vascular endothelium specific hyaluronan receptor (LYVE-1) and a monoclonal antibody to podoplanin (mAb D2-40). A number of lymphatic vessels were identified in the stratified connective tissues surrounding the cartilaginous knee joint femoral and tibial rudiments. These tissues also contained small vascular vessels with entrapped red blood cells which were imaged using Nomarsky DIC microscopy. Neither vascular nor lymphatic vessels were present in the knee joint cartilaginous rudiments. The menisci in 12-week-old fetal knees were incompletely demarcated from the adjacent tibial and femoral cartilaginous rudiments which was consistent with the ongoing joint cavitation process at the femoral-tibial junction. At 14 weeks of age the menisci were independent structural entities; they contained a major central blood vessel containing red blood cells and numerous communicating vessels at the base of the menisci but no lymphatic vessels. In contrast to the 12-week-old menisci, the 14-week meniscal rudiments contained abundant CD-31 and CD-34 positive but no lymphatic vessels. Isolated 14-week-old meniscal cells also were stained with the CD-31 and CD 34 antibodies; CD-68 +ve cells, also abundant in the 14-week-old menisci, were detectable to a far lesser degree in the 12-week menisci and were totally absent from the femoral and tibial rudiments. The distribution of lymphatic vessels and tissue macrophages in the fetal joint tissues was consistent with their roles in the clearance of metabolic waste and extracellular matrix breakdown products arising from the rapidly remodelling knee joint tissues.

Emerging concepts in cardiac matrix biologyThis article is one of a selection of papers published in a special issue on Advances in Cardiovascular Research

The cardiac extracellular matrix, far from being merely a static support structure for the heart, is now recognized to play central roles in cardiac development, morphology, and cell signaling. Recent studies have better shaped our understanding of the tremendous complexity of this active and dynamic network. By activating intracellular signal cascades, the matrix transduces myocardial physical forces into responses by myocytes and fibroblasts, affecting their function and behavior. In turn, cardiac fibroblasts and myocytes play active roles in remodeling the matrix. Coupled with the ability of the matrix to act as a dynamic reservoir for growth factors and cytokines, this interplay between the support structure and embedded cells has the potential to exert dramatic effects on cardiac structure and function. One of the clearest examples of this occurs when cell–matrix interactions are altered inappropriately, contributing to pathological fibrosis and heart failure. This review will examine some of the recent concepts that have emerged regarding exactly how the cardiac matrix mediates these effects, how our collective vision of the matrix has changed as a result, and the current state of attempts to pharmacologically treat fibrosis.

Clinical improvement in systemic sclerosis resulting from urokinase therapy explained by light and electron microscopy skin examination

OBJECTIVE

In our previous work, patients affected by SSc were treated with intravenous urokinase and showed clinical improvement. In this study we used microscopy to document ultrastructural alterations occurring in sclerodermic skin from SSc patients treated with urokinase.

METHODS

Ten patients with SSc were selected for this study. Skin biopsies were taken from the medial side of the right forearm on the third proximal on the volar surface. The patients were then treated with urokinase for 7 consecutive days. At the end of the treatment, the patients were examined and a new skin biopsy was taken close to the above-mentioned zone of the forearm for optic and electron microscopy examination.

RESULTS

The patients showed a gradual improvement of the skin after urokinase treatment. Raynaud's appeared to be less intense, and they had an increased articular range, with the restoration of movements that had previously been limited. Histological findings showed that, after treatment, skin alterations appeared attenuated, in particular the connective tissue showed a decreased density and inflammatory infiltrate was slight. Electron microscopy findings showed that collagen fibres appeared to have a more regular diameter, and the capillary vessels' lining was thicker, with fewer pinocytotic vesicles.

CONCLUSION

These observations show that urokinase treatment seems to be an interesting therapeutic strategy to consider for the treatment of SSc.

The 'sweet' and 'bitter' involvement of glycosaminoglycans in lung diseases: pharmacotherapeutic relevance

The extracellular matrix (ECM) plays a significant role in the structure and function of the lung. The ECM is a three-dimensional fibre mesh, comprised of various interconnected and intercalated macromolecules, among which are the glycosaminoglycans (GAG). GAG are long, linear and highly charged, heterogeneous polysaccharides that are composed of a variable number of repeating disaccharide units (macromolecular sugars) and most of them, as their name implies, have a sweet taste. In the lung, GAG support the structure of the interstitium, the subepithelial tissue and the bronchial walls, and are secreted in the airway secretions. Besides maintaining lung tissue structure, GAG also play an important role in lung function as they regulate hydration and water homeostasis, modulate the inflammatory response and influence lung tissue repair and remodelling. However, depending on their size and/or degree of sulphation, and their immobilization or solubilization in the ECM, specific GAG in the lung either live up to their sweet taste/name, supporting normal lung physiology, or they are associated to 'bitter' effects, related to lung pathology. The present review discusses the biological role of GAG in the lung as well as the involvement of these molecules in various respiratory diseases. Given the great structural diversity of GAG, understanding the changes in GAG expression that occur in lung diseases may lead to novel targets for pharmacological intervention in order to prevent and/or to treat a range of lung diseases.

Intact extracellular matrix and the maintenance of immune tolerance: high molecular weight hyaluronan promotes persistence of induced CD4+CD25+ regulatory T cells

The composition of the ECM provides contextual cues to leukocytes in inflamed and healing tissues. One example of this is HA, where LMW-HA, generated during active inflammation, is a TLR ligand and an endogenous "danger signal," and HMW-HA, predominant in healing or intact tissues, functions in an inverse manner. Our data suggest that HMW-HA actively promotes immune tolerance by augmenting CD4+CD25+ T(Reg) function, and LMW-HA does not. Using a human iT(Reg) model, we demonstrate that HMW-HA but not LMW-HA provides a costimulatory signal through cross-linking CD44 which promotes Foxp3 expression, a critical signaling molecule associated with T(Reg). This effect, in part, may be mediated by a role for intact HMW-HA in IL-2 production, as T(Reg) are highly IL-2-dependent for their survival and function. We propose that HMW-HA contributes to the maintenance of immune homeostasis in uninjured tissue and effectively communicates an "all-clear" signal to down-regulate the adaptive immune system through T(Reg) after tissue matrix integrity has been restored.

Anti-oxidant inhibition of hyaluronan fragment-induced inflammatory gene expression

Background

The balance between reactive oxygen species (ROS) and endogenous anti-oxidants is important in maintaining healthy tissues. Excessive ROS states occur in diseases such as ARDS and Idiopathic Pulmonary Fibrosis. Redox imbalance breaks down the extracellular matrix component hyaluronan (HA) into fragments that activate innate immune responses and perpetuate tissue injury. HA fragments, via a TLR and NF-κB pathway, induce inflammatory gene expression in macrophages and epithelial cells. NAC and DMSO are potent anti-oxidants which may help balance excess ROS states.

Methods

We evaluated the effect of H₂O₂, NAC and DMSO on HA fragment induced inflammatory gene expression in alveolar macrophages and epithelial cells.

Results

NAC and DMSO inhibit HA fragment-induced expression of TNF-α and KC protein in alveolar and peritoneal macrophages. NAC and DMSO also show a dose dependent inhibition of IP-10 protein expression, but not IL-8 protein, in alveolar epithelial cells. In addition, H₂O₂ synergizes with HA fragments to induce inflammatory genes, which are inhibited by NAC. Mechanistically, NAC and DMSO inhibit HA induced gene expression by inhibiting NF-κB activation, but NAC had no influence on HA-fragment-AP-1 mediated gene expression.

Conclusion

ROS play a central role in a pathophysiologic "vicious cycle" of inflammation: tissue injury generates ROS, which fragment the extracellular matrix HA, which in turn synergize with ROS to activate the innate immune system and further promote ROS, HA fragment generation, inflammation, tissue injury and ultimately fibrosis. The anti-oxidants NAC and DMSO, by inhibiting the HA induced inflammatory gene expression, may help re-balance excessive ROS induced inflammation.

The adenosine a2a receptor inhibits matrix-induced inflammation in a novel fashion

Endogenous mediators within the inflammatory milieu play a critical role in directing the scope, duration, and resolution of inflammation. High-molecular-weight extracellular matrix hyaluronan (HA) helps to maintain homeostasis. During inflammation, hyaluronan is broken down into fragments that induce chemokines and cytokines, thereby augmenting the inflammatory response. Tissue-derived adenosine, released during inflammation, inhibits inflammation via the anti-inflammatory A2 adenosine receptor (A2aR). We demonstrate that adenosine modulates HA-induced gene expression via the A2aR. A2aR stimulation inhibits HA fragment-induced pro-fibrotic genes TNF-alpha, keratinocyte chemoattractant (KC), macrophage inflammatory protein (MIP)-2, and MIP-1alpha while simultaneously synergizing with hyaluronan fragments to up-regulate the TH1 cytokine IL-12. Interestingly, A2aR stimulation mediates these affects via the novel cAMP-activated guanine nucleotide exchange factor EPAC. In addition, A2aR-null mice are more susceptible to bleomycin-induced lung injury, consistent with a role for endogenous adenosine in inhibiting the inflammation that may lead to fibrosis. Indeed, the bleomycin treated A2aR-null mice demonstrate increased lung inflammation, HA accumulation, and histologic damage. Overall, our data elucidate the opposing roles of tissue-derived HA fragments and adenosine in regulating noninfectious lung inflammation and support the pursuit of A2aR agonists as a means of pharmacologically inhibiting inflammation that may lead to fibrosis.

Fragments of extracellular matrix as mediators of inflammation

Classically, the extracellular matrix (ECM) was viewed as a supporting structure for stabilizing the location of cells in tissues and for preserving the architecture of tissues. This conception has changed dramatically over the past few decades with discoveries that ECM has profound influences on the structure, viability, and functions of cells. Much of the data supporting this new paradigm has been obtained from studies of normal and pathological structural cells such as fibroblasts, smooth muscle cells, and malignant cells, as, for example, breast cancer epithelial cells. However, there has also been recognition that effects of ECM on cells extend to inflammatory cells. In this context, attention has been drawn to fragments of ECM components. In this review, we present information supporting the concept that proteolytic fragments of ECM affect multiple functions and properties of inflammatory and immune cells. Our focus is particularly upon neutrophils, monocytes, and macrophages and fragments derived from collagens, elastin, and laminins. Hyaluronan fragments, although they are not products of proteolysis, are also discussed, as they are a notable example of ECM fragments that exhibit important effects on inflammatory cells. Further, we summarize some exciting recent developments in this field as a result of mouse models in which defined ECM fragments and their receptors are clearly implicated in inflammation in vivo. Thus, this review underscores the idea that proteolysis of ECM may well have implications that go beyond modifying the structural environment of cells and tissues.

Apical oxidative hyaluronan degradation stimulates airway ciliary beating via RHAMM and RON

Hyaluronan (HA) is synthesized in high-molecular-weight form at the apical pole of airway epithelial cells, covering the luminal surface. When human airway epithelial cells grown and redifferentiated at the air-liquid interface (ALI) were exposed to xanthine/xanthine oxidase (X/XO), ciliary beat frequency (CBF) increased. This effect was blocked by superoxide dismutase (SOD) and catalase. Inhibition of hyaluronan synthesis inhibited the CBF response to X/XO, while addition of exogenous HA amplified it. A functionally blocking antibody to the receptor for hyaluronic acid-mediated motility (RHAMM) reduced the CBF response to X/XO. Since RHAMM has no transmembrane domain and thus cannot signal on its own, the association of RHAMM with recepteur d'origine nantais (RON), a member of the hepatocyte growth factor receptor family, was explored. Immunohistochemistry of human airway epithelium showed co-localization of RHAMM and RON at the apex of ciliated cells. Physical association of RHAMM and RON was confirmed with co-immunoprecipitations. Macrophage-stimulating protein (MSP), an agonist of RON, stimulated CBF. Genistein, a nonspecific tyrosine kinase inhibitor, and MSP beta chain (beta-MSP), a specific RON inhibitor, blocked the X/XO-induced CBF increase. HA present in the apical secretions of human airway epithelial cells was shown to degrade upon exposure to X/XO, a process inhibited by SOD. Low-molecular-weight HA fragments stimulated CBF, an effect blocked by anti-RHAMM antibody and genistein. These data suggest that high molecular form HA is broken down by reactive oxygen species to form low-molecular-weight fragments that signal via RHAMM and RON to stimulate CBF.

The complement component C5a induces the expression of plasminogen activator inhibitor-1 in human macrophages via NF-kappaB activation

BACKGROUND

Atherosclerosis is considered to be a chronic inflammatory disorder. Activation of the complement cascade is a major aspect of chronic inflammatory diseases. Complement components were identified in atherosclerotic plaques, and a correlation between adverse events and C5a plasma levels was found. These findings support the notion that complement activation contributes to development and progression of atherosclerotic lesions.

OBJECTIVES

We investigated whether complement components C3a and C5a regulate plasminogen activator inhibitor (PAI-1) in human macrophages.

METHODS

Human monocyte-derived macrophages (MDM) and human plaque macrophages were cultured and incubated with the complement component C5a.

RESULTS

C5a increased PAI-1 up to 11-fold in human MDM and up to 2.7-fold in human plaque macrophages. These results were confirmed at the mRNA level using real time-polymerase chain reaction. Pertussis toxin or anti-C5aR/CD88 antibody completely abolished the effect of recombinant human C5a on PAI-1 production, suggesting a role of the C5a receptor. Experiments with antitumor necrosis factor (TNF)-alpha antibodies and tiron showed that the effect of C5a was not mediated by TNF-alpha or oxidative burst. Furthermore C5a induced NF-kappaB binding to the cis element in human macrophages and the C5a-induced increase in PAI-1 was completely abolished by an NF-kappaB inhibitor.

CONCLUSIONS

We conclude that C5a upregulates PAI-1 in macrophages via NF-kappaB activation. We hypothesize that - if operative in vivo- this effect could favor thrombus development and thrombus stabilization in the lesion area. On the other hand one could speculate that C5a-induced upregulation of PAI-1 in plaque macrophages could act as a defense mechanism against plaque destabilization and rupture.

Hyaluronan fragments: an information-rich system

Hyaluronan is a straight chain, glycosaminoglycan polymer of the extracellular matrix composed of repeating units of the disaccharide [-D-glucuronic acid-beta1,3-N-acetyl-D-glucosamine-beta1,4-]n. Hyaluronan is synthesized in mammals by at least three synthases with products of varying chain lengths. It has an extraordinary high rate of turnover with polymers being funneled through three catabolic pathways. At the cellular level, it is degraded progressively by a series of enzymatic reactions that generate polymers of decreasing sizes. Despite their exceedingly simple primary structure, hyaluronan fragments have extraordinarily wide-ranging and often opposing biological functions. There are large hyaluronan polymers that are space-filling, anti-angiogenic, immunosuppressive, and that impede differentiation, possibly by suppressing cell-cell interactions, or ligand access to cell surface receptors. Hyaluronan chains, which can reach 2 x 10(4) kDa in size, are involved in ovulation, embryogenesis, protection of epithelial layer integrity, wound repair, and regeneration. Smaller polysaccharide fragments are inflammatory, immuno-stimulatory and angiogenic. They can also compete with larger hyaluronan polymers for receptors. Low-molecular-size polymers appear to function as endogenous "danger signals", while even smaller fragments can ameliorate these effects. Tetrasaccharides, for example, are anti-apoptotic and inducers of heat shock proteins. Various fragments trigger different signal transduction pathways. Particular hyaluronan polysaccharides are also generated by malignant cells in order to co-opt normal cellular functions. How the small hyaluronan fragments are generated is unknown, nor is it established whether the enzymes of hyaluronan synthesis and degradation are involved in maintaining proper polymer sizes and concentration. The vast range of activities of hyaluronan polymers is reviewed here, in order to determine if patterns can be detected that would provide insight into their production and regulation.

Threat matrix: low-molecular-weight hyaluronan (HA) as a danger signal

Whether or not T cell receptor engagement leads to full activation or tolerance is determined by the context in which the antigen is encountered. Antigen presented by activated APCs in the presence of costimulation leads to full T cell activation, while antigen presented by resting APCs leads to tolerance. Pathogen-associated molecular patterns in the form of toll-like receptor ligands play a critical role in activating APCs and promoting T cell activation. In this review we hypothesize that low-molecular-weight species of the extracellular matrix polymer hyaluronan also performs this function by acting as an endogenous danger signal.

Expression of urokinase-type plasminogen activator, urokinase-type plasminogen activator receptor and plasminogen activator inhibitors in patients with renal cell carcinoma: correlation with tumor associated macrophage and prognosis

PURPOSE

Urokinase-type plasminogen activator (uPA) has an important role in tumor progression through the degradation of extracellular matrix. In addition, uPA receptor (uPAR) and plasminogen activator inhibitors (PAIs), composed of PAI-1 and 2, are also known to affect such activities. Tumor associated macrophage (TAM) is an important regulator of tumor progression that is associated with the uPA system in various cancers. However, to our knowledge the clinical significance of PAI-2 and the relationship between the uPA system and TAM in human renal cell carcinoma (RCC) tissues have not been investigated. We investigated and clarified these issues.

MATERIALS AND METHODS

The subjects of the current study were 106 consecutive surgically resected specimens from patients with RCC. The expression of uPA, uPAR, PAI-1 and PAI-2 was determined by immunohistochemistry. We also examined the relationships among these molecules, survival and TAM.

RESULTS

The mean immunoreactive scores (range 0 to 6) of uPA, uPAR, PAI-1 and PAI-2 were 3.09, 2.22, 1.99 and 0.56, respectively. These scores correlated with the grade and presence of metastasis. The expression of uPA, uPAR and PAI-1 but not PAI-2 correlated negatively with cause specific survival. Of uPA family members multivariate analysis showed that PAI-1 independently influenced cause specific survival. TAM counts correlated with PAI-1 only (p <0.001).

CONCLUSIONS

Our results suggest that PAI-1 is an important regulator of tumor progression and survival, and PAI-1 may modulate them via TAM. On the other hand, PAI-2 has a minimum role in survival. Our results may help discussions of treatment strategy in patients with RCC.

Post-transcriptional regulation of plasminogen activator inhibitor-1 by intracellular iron in cultured human lung fibroblasts--interaction of an 81-kDa nuclear protein with the 3'-UTR

The proteinase inhibitor, type-1 plasminogen activator inhibitor (PAI-1), is a major regulator of the plasminogen activator system involved in plasmin formation and fibrinolysis. The present study explores the effects of intracellular iron on the expression of PAI-1 and associated cell-surface plasmin activity in human lung fibroblasts; and reports the presence of a novel iron-responsive protein. ELISA revealed a dose-dependent increase in PAI-1 antigen levels expressed in the conditioned medium of cells treated with deferoxamine, in the three cell lines studied. A concomitant increase in mRNA levels was also observed by Northern analyses. Presaturation with ferric citrate quenched the effect of deferoxamine. Experiments with transcription and translation inhibitors on TIG 3-20 cells demonstrated that intracellular iron modulated PAI-1 expression at the post-transcriptional level with the requirement of de-novo protein synthesis. Electrophoretic mobility shift assay and UV crosslinking assays revealed the presence of an approximately 81-kDa nuclear protein that interacted with the 3'-UTR of PAI-1 mRNA in an iron-sensitive manner. Finally, we demonstrated that the increased PAI-1 is functional in suppressing cell-surface plasmin activity, a process that can affect wound healing and tissue remodeling.

Role of hepatic fibrin in idiosyncrasy-like liver injury from lipopolysaccharide-ranitidine coexposure in rats

Coadministration of nonhepatotoxic doses of the histamine 2-receptor antagonist ranitidine (RAN) and bacterial lipopolysaccharide (LPS) results in hepatocellular injury in rats, the onset of which occurs in 3 to 6 hours. This reaction resembles RAN idiosyncratic hepatotoxicity in humans. Early fibrin deposition occurs in livers of rats cotreated with LPS/RAN. Accordingly, we tested the hypothesis that the hemostatic system contributes to liver injury in LPS/RAN-treated rats. Rats were given either LPS (44.4 x 10(6) EU/kg) or its vehicle, then RAN (30 mg/kg) or its vehicle 2 hours later. They were killed 2, 3, 6, 12, or 24 hours after RAN treatment, and liver injury was estimated from serum alanine aminotransferase activity. A modest elevation in serum hyaluronic acid, which was most pronounced in LPS/RAN-cotreated rats, suggested altered sinusoidal endothelial cell function. A decrease in plasma fibrinogen and increases in thrombin-antithrombin dimers and in serum concentration of plasminogen activator inhibitor-1 occurred before the onset of liver injury. Hepatic fibrin deposition was observed in livers from LPS/RAN-cotreated rats 3 and 6 hours after RAN. Liver injury was abolished by the anticoagulant heparin and was significantly attenuated by the fibrinolytic agent streptokinase. Hypoxia, one potential consequence of sinusoidal fibrin deposition, was observed in livers of LPS/RAN-treated rats. In conclusion, the results suggest that the hemostatic system is activated after LPS/RAN cotreatment and that fibrin deposition in liver is important for the genesis of hepatic parenchymal cell injury in this model.

Elevated levels of plasminogen activator inhibitor-1 in pulmonary edema fluid are associated with mortality in acute lung injury

The alveolar fibrinolytic system is altered in acute lung injury (ALI). Levels of the fibrinolytic protease inhibitor, plasminogen activator inhibitor-1 (PAI-1), are too low in bronchoalveolar lavage to address its prognostic significance. This study was performed to assess whether PAI-1 antigen in undiluted pulmonary edema fluid levels can identify patients with ALI and predict their outcome. PAI-1 antigen levels in both plasma and edema fluid were higher in ALI compared with hydrostatic edema, and edema fluid PAI-1 values identified those with ALI with high sensitivity and specificity. Both the high plasma and edema fluid PAI-1 antigen values were associated with a higher mortality rate and fewer days of unassisted ventilation in patients with ALI. Differences in PAI-1 activity were concordant with levels of PAI-1 antigen. Although the fibrin-derived alveolar D-dimer levels were strikingly similar in both groups, ALI patients had a higher relative proportion of D-monomer. In conclusion, PAI-1 levels in edema fluid and plasma identify those with ALI that have a poor prognosis. The data indicate that fibrin turnover in early ALI is a consequence of a rapid fibrinogen influx and fractional fibrinolytic inhibition.

Inducible nitric oxide synthase expression inhibition by adenovirus E1A

Nitric oxide (NO) is an antiviral effector of the innate immune system. Viruses that can interfere with NO synthesis may be able to replicate more rapidly than viruses that cannot limit NO synthesis. We show that the adenovirus E1A protein inhibits NO production by decreasing expression of the inducible NO synthase (NOS2). The amino-terminal portion of E1A decreases transactivation of the NOS2 5'-flanking region, limiting the DNA binding activity of NF-kappaB and inhibiting NOS2 expression. E1A is thus able to deactivate a critical component of the host defense against viral infection. Viral inhibition of NO production is a mechanism that may enable certain viruses to evade the host innate immune system.

A blocking antibody to the hyaluronan receptor for endocytosis (HARE) inhibits hyaluronan clearance by perfused liver

Hyaluronan (HA) and chondroitin sulfate clearance from lymph and blood is mediated by the hyaluronan receptor for endocytosis (HARE). The purification and molecular cloning (Zhou, B., Weigel, J. A., Saxena, A., and Weigel, P. H. (2002) Mol. Biol. Cell 13, 2853-2868) of this cell surface receptor were finally achieved after we developed monoclonal antibodies (mAbs) against HARE. There are actually two independent isoreceptors for HA, which in rat are designated the 175-kDa HARE and 300-kDa HARE. Only one mAb (number 174) effectively and completely blocked the specific uptake of 125I-HA at 37 degrees C by rat liver sinusoidal endothelial cells. 125I-HA binding to both the 175-kDa and 300-kDa HARE proteins in a ligand blot assay was almost completely inhibited by <1 microg/ml mAb-174, whereas mouse IgG had little or no effect. MAb-174 also performed very well in Western analysis, indirect fluorescence microscopy, and a variety of immuno-procedures. Immunohistochemistry using mAb-174 localized HARE to the sinusoidal cells of rat liver, spleen, and lymph node. Western analysis using mAb-174 revealed that the sizes of both HARE glycoproteins were the same in these three tissues. 125I-HA was taken up and degraded by excised rat livers that were continuously perfused ex vivo with a recirculating medium. This HA clearance and metabolism by liver, which is a physiological function of HARE, was very effectively blocked by mAb-174 but not by mouse IgG. The results indicate that mAb-174 will be a useful tool to study the functions of HARE and the physiological significance of HA clearance.

Use of Iodinated Hyaluronan Derivatives to Study Hyaluronan Binding, Endocytosis, and Metabolism by Cultured Cells

We have described several simple procedures to determine whether cells have specific receptors or binding proteins for HA. The advantage of using the uniquely modified 125I-labeled HA as a probe is that low levels of binding can be detected. It has been straightforward and productive to use 125I-labeled HA to quantitate cell surface and intracellular binding sites to determine affinity constants for HA binding and to determine whether the cell type being studied can efficiently endocytose and degrade the HA. The 125I-labeled HA preparations and assays described here and in Chapter 26 provide a very useful array of methods for studying the biochemistry and cell biology of HA.