Low molecular weight hyaluronan from stretched lung enhances interleukin-8 expression

Multivalent, calcium-independent binding of surfactant protein A and D to sulfated glycosaminoglycans of the alveolar epithelial glycocalyx

Lung surfactant collectins, surfactant protein A (SP-A) and D (SP-D), are oligomeric C-type lectins involved in lung immunity. Through their carbohydrate recognition domain, they recognize carbohydrates at pathogen surfaces and initiate lung innate immune response. Here, we propose that they may also be able to bind to other carbohydrates present in typical cell surfaces, such as the alveolar epithelial glycocalyx. To test this hypothesis, we analyzed and quantified the binding affinity of SP-A and SP-D to different sugars and glycosaminoglycans (GAGs) by microscale thermophoresis (MST). In addition, by changing the calcium concentration, we aimed to characterize any consequences on the binding behavior. Our results show that both oligomeric proteins bind with high affinity (in nanomolar range) to GAGs, such as hyaluronan (HA), heparan sulfate (HS) and chondroitin sulfate (CS). Binding to HS and CS was calcium-independent, as it was not affected by changing calcium concentration in the buffer. Quantification of GAGs in bronchoalveolar lavage (BAL) fluid from animals deficient in either SP-A or SP-D showed changes in GAG composition, and electron micrographs showed differences in alveolar glycocalyx ultrastructure in vivo. Taken together, SP-A and SP-D bind to model sulfated glycosaminoglycans of the alveolar epithelial glycocalyx in a multivalent and calcium-independent way. These findings provide a potential mechanism for SP-A and SP-D as an integral part of the alveolar epithelial glycocalyx binding and interconnecting free GAGs, proteoglycans, and other glycans in glycoproteins, which may influence glycocalyx composition and structure.NEW & NOTEWORTHY SP-A and SP-D function has been related to innate immunity of the lung based on their binding to sugar residues at pathogen surfaces. However, their function in the healthy alveolus was considered as limited to interaction with surfactant lipids. Here, we demonstrated that these proteins bind to glycosaminoglycans present at typical cell surfaces like the alveolar epithelial glycocalyx. We propose a model where these proteins play an important role in interconnecting alveolar epithelial glycocalyx components.

Development of Therapeutic Agent for Osteoarthritis via Inhibition of KIAA1199 Activity: Effect of Ipriflavone In Vivo

This study aimed to clarify the effects of ipriflavone, which effectively reduces KIAA1199 activity, on osteoarthritis (OA) development and progression in an in vivo OA mouse model. The OA model mice were divided into the ipriflavone (200 mg/kg/day) group and the control group. OA onset and progression were evaluated with the Mankin score, and KIAA1199 expression and hyaluronan (HA) accumulation were analyzed by immunostaining. The molecular weight of HA in the cartilage tissue and serum HA concentration were analyzed by chromatography and competitive HA enzyme-linked immunoassay. The effects of ipriflavone on the bovine cartilage explant culture under the influence of IL-1β were also investigated. In the ipriflavone group, Safranin-O stainability was well-preserved, resulting in significant reduction of the Mankin score (p = 0.027). KIAA1199 staining positivity decreased and HA stainability was preserved in the ipriflavone group. The serum HA concentration decreased, and the molecular weight of HA in the cartilage tissue increased in the ipriflavone group. The results of the cartilage explant culture indicated that ipriflavone could reduce GAG losses and increase the molecular weight of HA. Thus, ipriflavone may have an inhibitory effect on OA development/progression. Ipriflavone could be a therapeutic drug for OA by targeting KIAA1199 activity.

Hyaluronan regulates sperm-induced inflammatory response by enhancing sperm attachment to bovine endometrial epithelial cells via CD44: in-silico and in-vitro approaches

Recently, we reported that sperm induce cluster of differentiation 44 (CD44) expression and Toll-like receptor 2 (TLR2)-mediated inflammatory response in bovine uterus. In the present study, we hypothesized that the interaction between CD44 of bovine endometrial epithelial cells (BEECs) and hyaluronan (HA) affects sperm attachment and thereby enhancing TLR2-mediated inflammation. To test our hypothesis, at first, in-silico approaches were employed to define the binding affinity of HA for CD44 and TLR2. Further, an in-vitro experiment using the sperm-BEECs co-culture model was applied to investigate the effect of HA on sperm attachment and inflammatory response. Here, low molecular weight (LMW) HA at different concentrations (0, 0.1, 1, or 10 µg/mL) was incubated with BEECs for 2 h followed by the co-culture without- or with non-capacitated washed sperm (10⁶/ml) for additional 3 h was performed. The present in-silico model clarified that CD44 is a high-affinity receptor for HA. Moreover, TLR2 interactions with HA oligomer (4- and 8-mers) target a different subdomain (h-bonds) compared to TLR2-agonist (PAM3) which targets a central hydrophobic pocket. However, the interaction of LMW HA (32-mers) with TLR2 revealed no stability of HA at any pocket of TLR2. Notably, the immunofluorescence analysis revealed the HA localization in both endometrial stroma and epithelia of ex-vivo endometrial explant. Moreover, ELISA showed significant levels of HA in BEECs culture media. Importantly, BEECs pretreatment with HA prior to sperm exposure increased the number of attached sperm to BEECs, and upregulated the transcriptional levels of pro-inflammatory genes (TNFA, IL-1B, IL-8, and PGES) in BEECs in response to sperm. However, BEECs treated with HA only (no sperm exposure) did not show any significant effect on the transcript abundance of pro-inflammatory genes when compared to the non-treated BEECs. Altogether, our findings strongly suggest a possible cross-talk between sperm and endometrial epithelial cells via HA and HA binding receptors (CD44 and TLR2) to induce a pro-inflammatory response in bovine uterus.

Low-Molecular-Weight Hyaluronic Acid Contributes to Noise-Induced Cochlear Inflammation

INTRODUCTION

Our previous work indicated that the activation of the Toll-like receptor (TLR) 4 signaling pathway contributed to noise-induced cochlear inflammation. Previous studies have reported that low-molecular-weight hyaluronic acid (LMW-HA) accumulates during aseptic trauma and promotes inflammation by activating the TLR4 signaling pathway. We hypothesized that LMW-HA or enzymes synthesizing or degrading HA might be involved in noise-induced cochlear inflammation.

METHODS

The present study included two arms. The first arm was the noise exposure study, in which TLR4, proinflammatory cytokines, HA, hyaluronic acid synthases (HASs), and hyaluronidases (HYALs) in the cochlea as well as auditory brainstem response (ABR) thresholds were measured before and after noise exposure. The second arm was analysis of HA delivery-induced reactions, in which control solution, high-molecular-weight HA (HMW-HA), or LMW-HA was delivered into the cochlea by cochleostomy or intratympanic injection. Then, the ABR threshold and cochlear inflammation were measured.

RESULTS

After noise exposure, the expression of TLR4, proinflammatory cytokines, HAS1, and HAS3 in the cochlea significantly increased over the 3rd to 7th day post-noise exposure (PE3, PE7). The expression of HYAL2 and HYAL3 dramatically decreased immediately after noise exposure, gradually increased thereafter to levels significantly greater than the preexposure level on PE3, and then rapidly returned to the preexposure level on PE7. The expression of HA, HAS2, and HYAL1 in the cochlea remained unchanged after exposure. After cochleostomy or intratympanic injection, both the hearing threshold shifts and the expression of TLR4, TNF-α, and IL-1β in the cochleae of the LMW-HA group were obviously greater than those of the control group and HMW-HA group. The expression of proinflammatory cytokines in the LMW-HA and control groups on the 7th day (D7) after cochleostomy tended to increase compared to that on the 3rd day (D3), whereas levels in the HMW-HA group tended to decrease on D7 compared to D3.

CONCLUSION

HAS1, HAS3, HYAL2, and HYAL3 in the cochlea are involved in acoustic trauma-induced cochlear inflammation through the potential proinflammatory function of LMW-HA.

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.

Lung Hyaluronasome: Involvement of Low Molecular Weight Ha (Lmw-Ha) in Innate Immunity

Hyaluronic acid (HA) is a major component of the extracellular matrix. It is synthesized by hyaluronan synthases (HAS) into high-molecular-weight chains (HMW-HA) that exhibit anti-inflammatory and immunomodulatory functions. In damaged, infected, and/or inflamed tissues, HMW-HA are degraded by hyaluronidases (HYAL) or reactive oxygen species (ROS) to give rise to low-molecular-weight HAs (LMW-HAs) that are potent pro-inflammatory molecules. Therefore, the size of HA regulates the balance of anti- or pro-inflammatory functions. The activities of HA depend also on its interactions with hyaladherins. HA synthesis, degradation, and activities through HA/receptors interactions define the hyaluronasome. In this review, a short overview of the role of high and low-molecular-weight HA polymers in the lungs is provided. The involvement of LMW-HA in pulmonary innate immunity via the activation of neutrophils, macrophages, dendritic cells, and epithelial cells is described to highlight LMW-HA as a therapeutic target in inflammatory respiratory diseases. Finally, the possibilities to counter LMW-HA’s deleterious effects in the lungs are discussed.

Mechanisms of Mechanical Force Induced Pulmonary Vascular Endothelial Hyperpermeability

Mechanical ventilation is a supportive therapy for patients with acute respiratory distress syndrome (ARDS). However, it also inevitably produces or aggravates the original lung injury with pathophysiological changes of pulmonary edema caused by increased permeability of alveolar capillaries which composed of microvascular endothelium, alveolar epithelium, and basement membrane. Vascular endothelium forms a semi-selective barrier to regulate body fluid balance. Mechanical ventilation in critically ill patients produces a mechanical force on lung vascular endothelium when the endothelial barrier was destructed. This review aims to provide a comprehensive overview of molecular and signaling mechanisms underlying the endothelial barrier permeability in ventilator-induced lung jury (VILI).

Intragraft Hyaluronan Increases in Association With Acute Lung Transplant Rejection

Supplemental Digital Content is available in the text.

Background.

Acute perivascular rejection (AR) is common in lung recipients and increases the risk for chronic lung allograft dysfunction (CLAD). Hyaluronan (HA), an extracellular matrix constituent, accumulates in experimental AR and can act as an innate immune agonist, breaking tolerance and potentiating alloimmunity. We previously demonstrated HA accumulates in CLAD after human-lung transplantation. We sought to determine if HA accumulates in the bronchoalveolar lavage fluid (BALF) concurrent with AR in lung recipients.

Methods.

The cohort consisted of 126 first adult lung recipients at 5 transplant centers with a total of 373 BALF samples collected within the first posttransplant year. All samples were paired with a lung biopsy from the same bronchoscopy. BALF HA (ng/mL) was quantified by ELISA and log-transformed for analysis. Linear-mixed effect models, adjusted for potential confounders, were used to estimate the association between BALF HA concentration and the presence of AR on biopsy. The association between early posttransplant BALF HA levels and the development of CLAD was explored utilizing tertiles of maximum BALF HA level observed within the first 6 months of transplant.

Results.

In analyses adjusted for potential confounders, BALF HA concentration was significantly increased in association with AR (change in means on log-scale 0.31; 95% CI, 0.01-0.60; P = 0.044). When considered on the original scale (ng/mL), BALF HA concentrations were 1.36 times (36%) higher, on average, among samples with, versus without, AR. The cumulative incidence of CLAD was numerically higher in individuals in the highest tertiles of BALF HA level within the first 6 months after transplant, as compared with those in the lowest tertile; however, this difference was not statistically significant (P = 0.32).

Conclusions.

These results demonstrate accumulation of HA in clinical AR and suggest a mechanism by which innate and adaptive immune activation might interact in the development of AR and CLAD.

A 28-day clinical trial of aerosolized hyaluronan in alpha-1 antiprotease deficiency COPD using desmosine as a surrogate marker for drug efficacy

INTRODUCTION

A previous 2-week clinical trial of aerosolized hyaluronan (HA) in COPD showed a rapid reduction in lung elastic fiber breakdown, as measured by sputum levels of the unique elastin crosslinks, desmosine and isodesmosine (DID). To further assess the therapeutic efficacy of HA and the utility of DID as surrogate markers for the development of pulmonary emphysema, we have conducted a 28-day randomized, double-blind, placebo-controlled, phase 2 trial of HA involving 27 subjects with alpha-1 antiprotease deficiency COPD.

METHODS

The study drug consisted of a 3 ml inhalation solution containing 0.03% HA with an average molecular weight of 150 kDa that was self-administered twice daily. DID levels were measured in urine, sputum, and plasma using tandem mass spectrometry.

RESULTS

Free urine DID in the HA group showed a significant negative correlation with time between days 14 and 35 (r = -1.0, p = 0.023) and was statistically significantly decreased from baseline at day 35 (15.4 vs 14.2 ng/mg creatinine, p = 0.035). A marked decrease in sputum DID was also seen in the HA group between days 1 and 28 (0.96 vs 0.18 ng/mg protein), but the difference was not significant, possibly due to the small number of adequate specimens. Plasma DID remained unchanged following HA treatment and no significant reductions in urine, sputum, or plasma DID were seen in the placebo group.

CONCLUSIONS

The results support additional clinical trials to further evaluate the therapeutic effect of HA and the use of DID as a real-time marker of drug efficacy.

Mechanobiological Principles Influence the Immune Response in Regeneration: Implications for Bone Healing

A misdirected or imbalanced local immune composition is often one of the reasons for unsuccessful regeneration resulting in scarring or fibrosis. Successful healing requires a balanced initiation and a timely down-regulation of the inflammation for the re-establishment of a biologically and mechanically homeostasis. While biomaterial-based approaches to control local immune responses are emerging as potential new treatment options, the extent to which biophysical material properties themselves play a role in modulating a local immune niche response has so far been considered only occasionally. The communication loop between extracellular matrix, non-hematopoietic cells, and immune cells seems to be specifically sensitive to mechanical cues and appears to play a role in the initiation and promotion of a local inflammatory setting. In this review, we focus on the crosstalk between ECM and its mechanical triggers and how they impact immune cells and non-hematopoietic cells and their crosstalk during tissue regeneration. We realized that especially mechanosensitive receptors such as TRPV4 and PIEZO1 and the mechanosensitive transcription factor YAP/TAZ are essential to regeneration in various organ settings. This indicates novel opportunities for therapeutic approaches to improve tissue regeneration, based on the immune-mechanical principles found in bone but also lung, heart, and skin.

Extracellular matrix remodelling in COPD

The extracellular matrix (ECM) of the lung plays several important roles in lung function, as it offers a low resistant pathway that allows the exchange of gases, provides compressive strength and elasticity that supports the fragile alveolar-capillary intersection, controls the binding of cells with growth factors and cell surface receptors and acts as a buffer against retention of water.COPD is a chronic inflammatory respiratory condition, characterised by various conditions that result in progressive airflow limitation. At any stage in the course of the disease, acute exacerbations of COPD may occur and lead to accelerated deterioration of pulmonary function. A key factor of COPD is airway remodelling, which refers to the serious alterations of the ECM affecting airway wall thickness, resistance and elasticity. Various studies have shown that serum biomarkers of ECM turnover are significantly associated with disease severity in patients with COPD and may serve as potential targets to control airway inflammation and remodelling in COPD. Unravelling the complete molecular composition of the ECM in the diseased lungs will help to identify novel biomarkers for disease progression and therapy.

The liver fibrosis niche: Novel insights into the interplay between fibrosis-composing mesenchymal cells, immune cells, endothelial cells, and extracellular matrix

Liver fibrosis is a hepatic wound-healing response caused by chronic liver diseases that include viral hepatitis, alcoholic liver disease, non-alcoholic steatohepatitis, and cholestatic liver disease. Liver fibrosis eventually progresses to cirrhosis that is histologically characterized by an abnormal liver architecture that includes distortion of liver parenchyma, formation of regenerative nodules, and a massive accumulation of extracellular matrix (ECM). Despite intensive investigations into the underlying mechanisms of liver fibrosis, developments of anti-fibrotic therapies for liver fibrosis are still unsatisfactory. Recent novel experimental approaches, such as single-cell RNA sequencing and proteomics, have revealed the heterogeneity of ECM-producing cells (mesenchymal cells) and ECM-regulating cells (immune cells and endothelial cells). These approaches have accelerated the identification of fibrosis-specific subpopulations among these cell types. The ECM also consists of heterogenous components. Their production, degradation, deposition, and remodeling are dynamically regulated in liver fibrosis, further affecting the functions of cells responsible for fibrosis. These cellular and ECM elements cooperatively form a unique microenvironment: a fibrotic niche. Understanding the complex interplay between these elements could lead to a better understanding of underlying fibrosis mechanisms and to the development of effective therapies.

Retrospective immunohistological study of autopsied lungs in patients with acute exacerbation of interstitial pneumonia managed with extracorporeal membrane oxygenation

Background

Acute exacerbation of interstitial pneumonia (AE-IP) is a life-threatening pulmonary condition that involves various pathogeneses. In patients with AE-IP who need mechanical ventilation with high driving pressure and oxygen concentration, veno-venous extracorporeal membrane oxygenation (V-V ECMO) may diminish alveolar epithelial damage by decreasing ventilator settings. The pathophysiological benefit of this therapeutic option is not well investigated.

Methods

We retrospectively collected 15 autopsied patients with AE-IP who were treated with mechanical ventilation in the intensive care unit (ICU) at Hiroshima University Hospital (Hiroshima, Japan) between 2010 and 2016. The patients were grouped by whether they were managed with mechanical ventilation only (the ventilator group, n=6) or with mechanical ventilation and V-V ECMO (the ECMO group, n=9).

Results

The median age of the ventilator and ECMO group patients were similar (65 and 64 years, respectively). The severity score APACHE II in the ECMO group (35.0) is significantly higher than that of ventilator group (14.5) (P=0.006). Ventilator days were significantly shorter in the ventilator group (17.5 days) than in the ECMO group (30.0 days) (P=0.04). Compared with the ECMO group, the ventilator group had a stronger Masson-trichrome stain grade (4 vs. 6, P=0.04) and higher immunoreactivity grades for Krebs von den Lungen-6 (4 vs. 6, P=0.04) and IL-8 (3 vs. 6, P=0.02). Between the ventilator and ECMO groups, the immunoreactivity grades of angiopoietin 2 (4 vs. 1, P=0.08) and receptor for advanced glycation end products (2 vs. 1, P=0.52) did not differ.

Conclusions

The lungs of mechanically ventilated AE-IP patients treated with V-V ECMO had decreased fibrosis, endothelial injury, and inflammation. This finding suggests the lung-protective efficacy of adjunctive V-V ECMO therapy.

Hyaluronic acid inhibition by 4-methylumbelliferone reduces the expression of cancer stem cells markers during hepatocarcinogenesis

Hyaluronic acid (HA) is a glycosaminoglycan of extracellular matrix related to cell surface which interacts with various cell types. To understand the role of HA during hepatocarcinogenesis, we assessed the effect of the inhibition of HA deposition and its association with heterogeneous hepatocellular carcinoma (HCC) cells. In this study, we used transgenic mice C57BL/6J-Tg(Alb1HBV)44Bri/J (HBV-TG) and normal C57BL/6 J (WT) for in vivo study, while HCC cells Huh7 and JHH6 as in vitro models. Both models were treated with an HA inhibitor 4-methylumbelliferone (4MU). We observed that 4MU treatments in animal model down-regulated the mRNA expressions of HA-related genes Has3 and Hyal2 only in HBV-TG but not in normal WT. As observed in vivo, in HCC cell lines, the HAS2 mRNA expression was down-regulated in Huh7 while HAS3 in JHH6, both with or without the presence of extrinsic HA. Interestingly, in both models, the expressions of various cancer stem cells (CD44, CD90, CD133, and EpCAM) were also decreased. Further, histological analysis showed that 4MU treatment with dose 25 mg/kg/day reduced fibrosis, inflammation, and steatosis in vivo, in addition to be pro-apoptotic. We concluded that the inhibition of HA reduced the expressions of HA-related genes and stem cells markers in both models, indicating a possible modulation of cells-to-cells and cells-to-matrix interaction.

Strain-induced inflammation in pulmonary alveolar tissue due to mechanical ventilation

Inflammation is the body's attempt at self-protection to remove harmful stimuli, including damaged cells, irritants, or pathogens and begin the healing process. In this study, strain-induced inflammation in pulmonary alveolar tissue under high tidal volume is investigated through a combination of an inflammation model and fluid structure interaction (FSI) analysis. A realistic three-dimensional organ model for alveolar sacs is built, and FSI is employed to evaluate strain distribution in alveolar tissue for different tidal volume (TV) values under the mechanical ventilation (MV) condition. The alveolar tissue is treated as a hyperelastic solid and provides the environment for the tissue constituents. The influence of different strain distributions resulting from different tidal volumes is investigated. It is observed that strain is highly distributed in the inlet area. In addition, strain versus time curves in different locations through the alveolar model reveals that middle layers in the alveolar region would undergo higher levels of strain during breathing under the MV condition. Three different types of strain distributions in the alveolar region from the FSI simulation are transferred to the CA model to study population dynamics of cell constituents under MV for different TVs; 200, 500 and 1000 mL, respectively. The CA model results suggests that strain distribution plays a significant role in population dynamics. An interplay between strain magnitude and distribution appears to influence healing capability. Results suggest that increasing TV leads to an exponential rise in tissue damage by inflammation.

Interplay of extracellular matrix and leukocytes in lung inflammation

During inflammation, leukocytes influx into lung compartments and interact with extracellular matrix (ECM). Two ECM components, versican and hyaluronan, increase in a range of lung diseases. The interaction of leukocytes with these ECM components controls leukocyte retention and accumulation, proliferation, migration, differentiation, and activation as part of the inflammatory phase of lung disease. In addition, bronchial epithelial cells from asthmatic children co-cultured with human lung fibroblasts generate an ECM that is adherent for monocytes/macrophages. Macrophages are present in both early and late lung inflammation. Matrix metalloproteinase 10 (MMP10) is induced in alveolar macrophages with injury and infection and modulates macrophage phenotype and their ability to degrade collagenous ECM components. Collectively, studies outlined in this review highlight the importance of specific ECM components in the regulation of inflammatory events in lung disease. The widespread involvement of these ECM components in the pathogenesis of lung inflammation make them attractive candidates for therapeutic intervention.

An in situ hybridization study of Hyaluronan synthase (Has) mRNA in developing mouse molar and incisor tooth germs

Hyaluronan (HA) is a major constituent molecule in most extracellular matrices and is synthesized by Hyaluronan synthase (Has). In the present study, we examined expression patterns of Has1, -2, -3 mRNA in developing mouse molar and incisor tooth germs from embryonic day (E) 11.5 to postnatal day (P) 7, focusing on Hertwig's epithelial root sheath (HERS) and the apical bud in particular. Has1 mRNA expression was not detected in all tooth germs examined. Has2 mRNA was expressed in the surrounding mesenchyme from E12.0 to 18.0 in both molar and incisor tooth germs, but disappeared after birth. Meanwhile, Has3 mRNA was exclusively expressed within the enamel organ, especially in the inner enamel epithelium (IEE), stellate reticulum (SR), and stratum intermedium (SI) until the early bell stage at E16.0. Has3 mRNA disappeared as IEE differentiated into differentiating ameloblasts (dABs), but remained in SI until the root developmental stage of the molar tooth germ at P7. Has3 mRNA was also expressed in HERS until P7. In incisors, Has3 mRNA was expressed in the apical bud, especially in the transit-amplifying (TA) cell region from E16.0 to P7, and in the papillary layer (PL) adjacent to the mature enamel. These gene expression patterns suggested that Has3 is the main control factor for prenatal and postnatal HA synthesis of the tooth germ, and may in part regulate crown and root formation of the tooth germ, maintenance of stem cell niches in the apical bud as well as mineral transport in PL.

Differential effects of hyaluronan synthase 3 deficiency after acute vs chronic liver injury in mice

Background

Hyaluronan (HA) is a ubiquitous extracellular matrix (ECM) glycosaminoglycan synthesized by three different enzymes, hyaluronan synthase (HAS)1, 2, and 3. HA synthesis mediated by HAS3 promotes inflammation and is pathogenic in animal models of human lung and intestinal disease. Liver fibrosis is a common endpoint to chronic liver injury and inflammation for which there is no cure. Although plasma HA is a commonly used biomarker for liver disease, if and how HA contributes to disease pathogenesis remains unclear. Here, we tested the hypothesis that HA synthesized by HAS3 enhances inflammation and fibrosis. To test this hypothesis, we exposed wild-type or Has3−/− mice to carbon tetrachloride (CCl₄) once (acute) or ten (chronic) times.

Results

HAS3-deficient mice exhibited increased hepatic injury and inflammatory chemokine production 48 h after acute CCl₄; this was associated with a threefold reduction in plasma HA levels and alterations in the proportions of specific molecular weight HA polymer pools. Hepatic accumulation of fibrosis-associated transcripts was also greater in livers from HAS3-deficient mice compared to controls after acute CCl₄ exposure. Surprisingly, fibrosis was not different between genotypes. Hepatic matrix metalloproteinase (MMP)13 mRNA and MMP13 activity was greater in livers from Has3-null mice after chronic CCl₄; this was prevented by a MMP13-specific inhibitor. Collectively, these data suggest that Has3, or more likely HA produced by HAS3, limits hepatic inflammation after acute injury and attenuates MMP13-mediated matrix metabolism after chronic injury.

Conclusions

These data suggest that HA should be investigated further as a novel therapeutic target for acute and chronic liver disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13069-016-0041-5) contains supplementary material, which is available to authorized users.

N-Acetylcysteine Inhibits Ventilation-Induced Collagen Accumulation in the Rat Lung

Mechanical ventilation is the most important life supportive therapy for patients with acute respiratory distress syndrome (ARDS). However, increasing evidence from clinical studies suggests that mechanical ventilation can cause lung fibrosis, which may significantly contribute to morbidity and mortality. Recent studies also found fibroproliferation occurred in early stage of ARDS with poor outcome. We have hypothesized that mechanical ventilation-induced lung injury may be a major contributor to lung fibrosis, and antioxidant could be a potential therapeutic agent for the treatment to mechanic ventilation induced fibroproliferation. We therefore used Sprague-Dawley rats that were ventilated with large tidal volume (20 ml/kg) or low tidal volume (7 ml/kg). We analyzed the time course of collagen level in the lung and the effect of N-acetylcysteine (NAC), a thiol antioxidant, on mechanical ventilation-induced collagen accumulation. In addition, normal human lung fibroblasts (NHLF) were exposed to mechanical stretch, which mimics ventilator-induced lung inflation, to evaluate the collagen secretion in culture medium. We found that ventilation-induced collagen accumulation occurred even after 2-hour ventilation. Pretreatment with NAC (140 mg/kg) inhibited collagen accumulation in lungs of rats ventilated with large tidal volume. Moreover, mechanical stretch caused the accumulation of collagen in the culture medium of NHLF, the magnitude of which was decreased with the pretreatment with NAC (1 mM). These results indicate that mechanical ventilation can induce collagen accumulation within 2 hours. NAC alleviated the collagen accumulation induced by mechanical ventilation with high tidal volume. Therefore, NAC can be considered as a good candidate in preventing ventilation-induced lung fibrosis.

Chemokine Involvement in Fetal and Adult Wound Healing

Significance: Fetal wounds heal with a regenerative phenotype that is indistinguishable from surrounding skin with restored skin integrity. Compared to this benchmark, all postnatal wound healing is impaired and characterized by scar formation. The biologic basis of the fetal regenerative phenotype can serve as a roadmap to recapitulating regenerative repair in adult wounds. Reduced leukocyte infiltration, likely mediated, in part, through changes in the chemokine milieu, is a fundamental feature of fetal wound healing. Recent Advances: The contributions of chemokines to wound healing are a topic of active investigation. Recent discoveries have opened the possibility of targeting chemokines therapeutically to treat disease processes and improve healing capability, including the possibility of achieving a scarless phenotype in postnatal wounds. Critical Issues: Successful wound healing is a complex process, in which there is a significant interplay between multiple cell types, signaling molecules, growth factors, and extracellular matrix. Chemokines play a crucial role in this interplay and have been shown to have different effects in various stages of the healing process. Understanding how these chemokines are locally produced and regulated during wound healing and how the chemokine milieu differs in fetal versus postnatal wounds may help us identify ways in which we can target chemokine pathways. Future Directions: Further studies on the role of chemokines and their role in the healing process will greatly advance the potential for using these molecules as therapeutic targets.

Hyaluronan ameliorates LPS-induced acute lung injury in mice via Toll-like receptor (TLR) 4-dependent signaling pathways

Toll-like receptor-4 (TLR4) signaling has been implicated in innate immunity and acute inflammation following acute lung injury (ALI). As such, modulating inflammatory response through TLR4 represents an attractive therapeutic approach to treat ALI. Increasing evidence demonstrates that hyaluronan (HA) can modulate TLR4 activation and has shown early promise as a therapeutic agent in ALI. However, the mechanism associated with HA has not been fully elucidated. In the current study, we sought to determine the effects of HA on lipopolysaccharide (LPS)-induced inflammatory response and gain insights into the mechanism of action in mice with intratracheal instillation of LPS. Our results demonstrate that in contrast to mice challenged with LPS, pretreatment with HA significantly inhibited inflammatory cell recruitment, attenuated lung injury and suppressed the level of cytokine/chemokine in bronchial alveolar lavage fluid (BALF). Investigation of the mechanism responsible for inhibition of LPS activation showed HA treatment significantly inhibited the nuclear translocation of NF-κB p65 and protein expression of myeloid differentiation primary response protein (MyD88) and TIR-domain-containing adapter-inducing interferon-β (TRIF) and p38 MAPK, JNK and ERK activation in lung tissue. Furthermore, we compared the protection effect of HA in TLR4-deficient mice with those of genetically matched wild type (WT) mice in an acute model of lung injury. However, in TLR4-deficient mice, HA pretreatment before LPS instillation fail to affect the LPS response. Therefore, our findings suggest that HA pretreatment attenuated LPS-induced ALI and the anti-inflammatory function of HA was partial dependent on TLR4, which shed new light on potential elements that regulate the lung injury response.

Toll-like receptor 4-interacting SPA4 peptide suppresses the NLRP3 inflammasome in response to LPS and ATP stimuli

Inflammation is induced because of interplay among multiple signaling pathways and molecules during infectious and noninfectious tissue injuries. Crosstalk between Toll-like receptor-4 signaling and the neuronal apoptosis inhibitor protein, major histocompatibility class 2 transcription activator, incompatibility locus protein from Podospora anserina, and telomerase-associated protein (NACHT), leucine-rich repeat (LRR), and pyrin domain-containing protein 3 (NLRP3) inflammasome against pathogen- or damage-associated molecular patterns can cause exaggerated inflammation. We previously established that the Toll-like receptor-4-interacting SPA4 peptide suppresses gram-negative bacterial lipopolysaccharide (Toll-like receptor-4 ligand)-induced nuclear factor-κB and inflammatory response. In the present study, we hypothesized that the SPA4 peptide exerts its anti-inflammatory effects by suppressing the crosstalk between Toll-like receptor-4 signaling and the NLRP3 inflammasome. We evaluated binding of the lipopolysaccharide-ligand to cell-surface Toll-like receptor-4 in the presence or absence of adenosine triphosphate (an NLRP3 inflammasome inducer) by flow cytometry. The expression and activity of NLRP3 inflammasome-related parameters were studied in cells challenged with lipopolysaccharide and adenosine triphosphate using molecular and immunologic methods. The cells were challenged with lipopolysaccharide and treated with SPA4 peptide before (pre-adenosine triphosphate) or after (post-adenosine triphosphate) secondary challenge with adenosine triphosphate. Our data demonstrate that the Toll-like receptor-4-interacting SPA4 peptide does not affect the binding of lipopolysaccharide to Toll-like receptor-4 in the presence or absence of adenosine triphosphate. We also found that the SPA4 peptide inhibits mRNA and cellular protein levels of pro-interleukin-1β and NLRP3, formation of the NLRP3 inflammasome, caspase activity, and release of interleukin-1β. Furthermore, the SPA4 peptide treatment reduced the secreted levels of interleukin-1β from cells overexpressing Toll-like receptor-4 compared with cells expressing the dominant-negative form of Toll-like receptor-4. Together our results suggest that the SPA4 peptide exerts its anti-inflammatory activity by suppressing Toll-like receptor-4-priming of the NLRP3 inflammasome.

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.

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.

Low molecular weight hyaluronan-pulsed human dendritic cells showed increased migration capacity and induced resistance to tumor chemoattraction

We have shown that ex vivo pre-conditioning of bone marrow-derived dendritic cells (DC) with low molecular weight hyaluronan (LMW HA) induces antitumor immunity against colorectal carcinoma (CRC) in mice. In the present study we investigated the effects of LMW HA priming on human-tumor-pulsed monocytes-derived dendritic cells (DC/TL) obtained from healthy donors and patients with CRC. LMW HA treatment resulted in an improved maturation state of DC/TL and an enhanced mixed leucocyte reaction activity in vivo. Importantly, pre-conditioning of DC/TL with LMW HA increased their ability to migrate and reduced their attraction to human tumor derived supernatants. These effects were associated with increased CCR7 expression levels in DC. Indeed, a significant increase in migratory response toward CCL21 was observed in LMW HA primed tumor-pulsed monocyte-derived dendritic cells (DC/TL/LMW HA) when compared to LWM HA untreated cells (DC/TL). Moreover, LMW HA priming modulated other mechanisms implicated in DC migration toward lymph nodes such as the metalloproteinase activity. Furthermore, it also resulted in a significant reduction in DC migratory capacity toward tumor supernatant and IL8 in vitro. Consistently, LMW HA dramatically enhanced in vivo DC recruitment to tumor-regional lymph nodes and reduced DC migration toward tumor tissue. This study shows that LMW HA--a poorly immunogenic molecule--represents a promising candidate to improve human DC maturation protocols in the context of DC-based vaccines development, due to its ability to enhance their immunogenic properties as well as their migratory capacity toward lymph nodes instead of tumors.

Mechanical ventilation-associated lung fibrosis in acute respiratory distress syndrome: a significant contributor to poor outcome

One of the most challenging problems in critical care medicine is the management of patients with the acute respiratory distress syndrome. Increasing evidence from experimental and clinical studies suggests that mechanical ventilation, which is necessary for life support in patients with acute respiratory distress syndrome, can cause lung fibrosis, which may significantly contribute to morbidity and mortality. The role of mechanical stress as an inciting factor for lung fibrosis versus its role in lung homeostasis and the restoration of normal pulmonary parenchymal architecture is poorly understood. In this review, the authors explore recent advances in the field of pulmonary fibrosis in the context of acute respiratory distress syndrome, concentrating on its relevance to the practice of mechanical ventilation, as commonly applied by anesthetists and intensivists. The authors focus the discussion on the thesis that mechanical ventilation-or more specifically, that ventilator-induced lung injury-may be a major contributor to lung fibrosis. The authors critically appraise possible mechanisms underlying the mechanical stress-induced lung fibrosis and highlight potential therapeutic strategies to mitigate this fibrosis.

Biological responses of three-dimensional cultured fibroblasts by sustained compressive loading include apoptosis and survival activity

Pressure ulcers are characterized by chronicity, which results in delayed wound healing due to pressure. Early intervention for preventing delayed healing due to pressure requires a prediction method. However, no study has reported the prediction of delayed healing due to pressure. Therefore, this study focused on biological response-based molecular markers for the establishment of an assessment technology to predict delayed healing due to pressure. We tested the hypothesis that sustained compressive loading applied to three dimensional cultured fibroblasts leads to upregulation of heat shock proteins (HSPs), CD44, hyaluronan synthase 2 (HAS2), and cyclooxygenase 2 (COX2) along with apoptosis via disruption of adhesion. First, sustained compressive loading was applied to fibroblast-seeded collagen sponges. Following this, collagen sponge samples and culture supernatants were collected for apoptosis and proliferation assays, gene expression analysis, immunocytochemistry, and quantification of secreted substances induced by upregulation of mRNA and protein level. Compared to the control, the compressed samples demonstrated that apoptosis was induced in a time- and load- dependent manner; vinculin and stress fiber were scarce; HSP90α, CD44, HAS2, and COX2 expression was upregulated; and the concentrations of HSP90α, hyaluronan (HA), and prostaglandin E₂ (PGE₂) were increased. In addition, the gene expression of antiapoptotic Bcl2 was significantly increased in the compressed samples compared to the control. These results suggest that compressive loading induces not only apoptosis but also survival activity. These observations support that HSP90α, HA, and, PGE₂ could be potential molecular markers for prediction of delayed wound healing due to pressure.

Hyaluronan contributes to bronchiolitis obliterans syndrome and stimulates lung allograft rejection through activation of innate immunity

RATIONALE

Although innate immunity is increasingly recognized to contribute to lung allograft rejection, the significance of endogenous innate ligands, such as hyaluronan (HA) fragments, in clinical or experimental lung transplantation is uncertain.

OBJECTIVES

To determine if HA is associated with clinical bronchiolitis obliterans syndrome (BOS) in lung transplant recipients, and evaluate the effect of low- or high-molecular-weight HA on experimental lung allograft rejection, including dependence on innate signaling pathways or effector cells.

METHODS

HA concentrations were measured in bronchoalveolar lavage and plasma samples from lung recipients with or without established BOS. BOS and normal lung tissues were assessed for HA localization and expression of HA synthases. Murine orthotopic lung recipients with established tolerance were treated with low- or high-molecular-weight HA under varied experimental conditions, including Toll-like receptor (TLR) 2/4 and myeloid differentiation protein 88 deficiency and neutrophil depletion.

MEASUREMENTS AND MAIN RESULTS

HA localized within areas of intraluminal small airways fibrosis in BOS lung tissue. Moreover, transcripts for HA synthase enzymes were significantly elevated in BOS versus normal lung tissues and both lavage fluid and plasma HA concentrations were increased in recipients with BOS. Treatment with low-molecular-weight HA abrogated tolerance in murine orthotopic lung recipients in a TLR2/4- and myeloid differentiation protein 88-dependent fashion and drove expansion of alloantigen-specific T lymphocytes. Additionally, TLR-dependent signals stimulated neutrophilia that promoted rejection. In contrast, high-molecular-weight HA attenuated basal allograft inflammation.

CONCLUSIONS

These data suggest that accumulation of HA could contribute to BOS by directly activating innate immune signaling pathways that promote allograft rejection and neutrophilia.

Ventilation-induced lung injury

Mechanical ventilation (MV) is, by definition, the application of external forces to the lungs. Depending on their magnitude, these forces can cause a continuum of pathophysiological alterations ranging from the stimulation of inflammation to the disruption of cell-cell contacts and cell membranes. These side effects of MV are particularly relevant for patients with inhomogeneously injured lungs such as in acute lung injury (ALI). These patients require supraphysiological ventilation pressures to guarantee even the most modest gas exchange. In this situation, ventilation causes additional strain by overdistension of the yet non-injured region, and additional stress that forms because of the interdependence between intact and atelectatic areas. Cells are equipped with elaborate mechanotransduction machineries that respond to strain and stress by the activation of inflammation and repair mechanisms. Inflammation is the fundamental response of the host to external assaults, be they of mechanical or of microbial origin and can, if excessive, injure the parenchymal tissue leading to ALI. Here, we will discuss the forces generated by MV and how they may injure the lungs mechanically and through inflammation. We will give an overview of the mechanotransduction and how it leads to inflammation and review studies demonstrating that ventilator-induced lung injury can be prevented by blocking pathways of mechanotransduction or inflammation.

Nebulized hyaluronan ameliorates lung inflammation in cystic fibrosis mice

RATIONALE

Chronic lung inflammation with increased susceptibility to bacterial infections cause much of the morbidity and mortality in patients with cystic fibrosis (CF), the most common severe, autosomal recessively inherited disease in the Caucasian population. Exogenous inhaled hyaluronan (HA) can exert a protective effect against injury and beneficial effects of HA have been shown in experimental models of chronic respiratory diseases. Our objective was to examine whether exogenous administration of nebulized HA might interfere with lung inflammation in CF.

STUDY DESIGN/METHODS

F508del homozygous mice (Cftr(F508del) ) and transgenic mice overexpressing the ENaC channel β-subunit (Scnn1b-Tg) were treated with nebulized HA (0.5 mg/mouse/day for 7 days). Tumor necrosis factor-alpha (TNFα), macrophage inflammatory protein-2 (MIP-2), myeloperoxidase (MPO) levels, and macrophage infiltration were assessed on lung tissues. IB3-1 and CFBE41o-epithelial cell lines were cultured with HA (24 hr, 100 µg/ml) and Reactive Oxygen Species (ROS), Tissue Transglutaminase (TG2) SUMOylation and Peroxisome Proliferator Activated Receptor gamma (PPARγ) and phospho-p42/p44 levels were measured by dichlorodihydrofluorescein assay, or fluorescence resonance energy transfer (FRET) microscopy or immunoblots.

RESULTS

Nebulized HA reduced TNFα expression (P < 0.005); TNFα, MIP-2, and MPO protein levels (P < 0.05); MPO activity (P < 0.05); and CD68+ cells counts (P < 0.005) in lung tissues of Cftr(F508del) and Scnn1b-Tg mice, compared with saline-treated mice. HA reduced ROS, TG2 SUMOylation, TG2 activity, phospho-p42-44, and increased PPARγ protein in both IB3-1 and CFBE41o cells (P < 0.05).

CONCLUSIONS

Nebulized HA is effective in controlling inflammation in vivo in mice CF airways and in vitro in human airway epithelial cells. We provide the proof of concept for the use of inhaled HA as a potential anti-inflammatory drug in CF therapy.

Hyaluronan with dextran added to therapeutic lung surfactants improves effectiveness in vitro and in vivo

Surfactants in current clinical use are largely ineffective in treating acute lung injury (ALI)/ acute respiratory distress syndrome. In part, this ineffectiveness is due to inactivation of surfactant by serum leakage into the alveoli. Previously, we reported that adding hyaluronan and some nonionic polymers to synthetic lipids combined with native SP-B and SP-C enhanced surface activity. In this study, we first tested two therapeutic lung surfactants and then retested after adding hyaluronan, polyethylene glycol or dextran alone or in two-polymer combinations including hyaluronan in the absence or presence of serum. Surface activities were measured in a modified bubble surfactometer. Results indicate that the inhibition threshold (defined as the amount of serum required to produce a minimum surface tension above 10 mN/m after 5 minutes of cycling) was 35 times higher with hyaluronan plus dextran added to Infasurf than with Infasurf alone, and better than all other mixtures tested. The threshold for Survanta with hyaluronan plus polyethylene glycol was 7 times higher than Survanta alone. We next tested selected surfactant mixtures in an animal model that mimicked ALI. All measurements of lung function showed significant improvement (P ≤ .05) with hyaluronan, or with hyaluronan and dextran added to Infasurf compared to Infasurf alone. Also, for these two groups, lung function was still improving at the end of the experiment. We conclude that certain polymers added to clinical surfactants can greatly increase resistance to inactivation in vitro, while in vivo, both Infasurf mixtures containing hyaluronan tended to normalize measures of lung function unlike other mixtures tested.

Corticosteroid administration reduces the concentration of hyaluronan in bronchoalveolar lavage in a murine model of eosinophilic airway inflammation

OBJECTIVE

To analyze the effect of corticosteroid administration on the concentration of hyaluronan (HA) in bronchoalveolar lavage (BAL) in a murine model of eosinophilic airway inflammation and to study the mechanisms involved.

MATERIALS AND METHODS

Untreated-mice or mice treated with 1 μg/g/day betamethasone (Bm) or 0.25 μg/g/day(-1) budesonide (Bd) were sensitized and challenged with Dermatophagoides pteronyssinus (Dp) or saline (control group). The concentration of HA in BAL was determined by ELISA. In vitro migration assays were performed using a Boyden chamber and the expression of HA synthases (HAS) was analyzed by RT-PCR.

RESULTS

We found a significant increase (P < 0.01) in the levels of HA in BAL from Dp-treated mice that was prevented by Bm or Bd. Corticosteroids also inhibited the increase in HAS expression, and the phosphorylation of Akt and ERK in the lungs of challenged mice. Finally, we found that low molecular weight HA induces the chemotaxis of BAL cells in vitro through a mechanism mediated by CD44.

CONCLUSION

We conclude that corticosteroids prevent the increase in HA in BAL from Dp-challenged mice. This effect is associated with reduced expression of HAS and reduced phosphorylation of Akt and ERK in the lungs of challenged mice.

Hyaluronic acid as a rescue therapy for trinitrobenzene sulfonic acid-induced colitis through Cox-2 and PGE2 in a Toll-like receptor 4-dependent way

We hypothesized whether systemic administration of high-molecular-weight hyaluronic acid (HMW HA) could rescue trinitrobenzene sulfonic acid (TNBS)-induced colitis through Toll-like receptor 4 (TLR4) signal. C3H/HeN mice and C3H/HeJ mice were used. Mice were divided into four groups: control, 50% ethanol treatment group, TNBS treatment group, and TNBS plus HA treatment group. The weight changes, clinical scores, macroscopic scores, and histological scores were recorded. Cyclooxygenase 2 (Cox-2) and prostaglandin E(2) (PGE(2)) expressions were measured both in colons and peritoneal macrophages from these mice. HA was a rescue therapy for the colitis induced by TNBS only in C3H/HeN mice. The clinical score, macroscopic score, and histological score were much lower in C3H/HeN mice receiving TNBS plus HA treatment. Cox-2 and PGE(2) expressions only increased in C3H/HeN mice. These Cox-2 expressing cells were macrophages. HA can also promote the production of Cox-2 and PGE(2) in peritoneal macrophages from C3H/HeN mice. Our data demonstrated that HMW HA can rescue TNBS-induced colitis through inducing Cox-2 and PGE(2) expressions in a TLR4-dependent way. Macrophages may be the effector cells of HMW HA.

Bench-to-bedside review: Damage-associated molecular patterns in the onset of ventilator-induced lung injury

Mechanical ventilation (MV) has the potential to worsen pre-existing lung injury or even to initiate lung injury. Moreover, it is thought that injurious MV contributes to the overwhelming inflammatory response seen in patients with acute lung injury or acute respiratory distress syndrome. Ventilator-induced lung injury (VILI) is characterized by increased endothelial and epithelial permeability and pulmonary inflammation, in which the innate immune system plays a key role. A growing body of evidence indicates that endogenous danger molecules, also termed damage-associated molecular patterns (DAMPs), are released upon tissue injury and modulate the inflammatory response. DAMPs activate pattern recognition receptors, may induce the release of proinflammatory cytokines and chemokines, and have been shown to initiate or propagate inflammation in non-infectious conditions. Experimental and clinical studies demonstrate the presence of DAMPs in bronchoalveolar lavage fluid in patients with VILI and the upregulation of pattern recognition receptors in lung tissue by MV. The objective of the present article is to review research in the area of DAMPs, their recognition by the innate immune system, their role in VILI, and the potential utility of blocking DAMP signaling pathways to reduce VILI in the critically ill.

Hyaluronan: From Biomimetic to Industrial Business Strategy

Hyaluronan (hyaluronic acid) is a naturally occurring polysaccharide of a linear repeating disaccharide unit consisting of β-(1→4)-linked D-glucopyranuronic acid and β-(1→3)-linked 2-acetamido-2-deoxy-D-glucopyranose, which is present in extracellular matrices, the synovial fluid of joints, and scaffolding that comprises cartilage.

In its mechanism of synthesis, its size, and its physico-chemical properties, hyaluronan is unique amongst other glycosaminoglycans. The network-forming, viscoelastic and its charge characteristics are important to many biochemical properties of living tissues. It is an important pericellular and cell surface constituent; its interaction with other macromolecules such as proteins, participates in regulating cell behavior during numerous morphogenic, restorative, and pathological processes in the body. The knowledge of HA in diseases such as various forms of cancers, arthritis and osteoporosis has led to new impetus in research and development in the preparation of biomaterials for surgical implants and drug conjugates for targeted delivery.

A concise and focused review on hyaluronan is timely. This review will cover the following important aspects of hyaluronan: (i) biological functions and synthesis in nature; (ii) current industrial production and potential biosynthetic processes of hyaluronan; (iii) chemical modifications of hyaluronan leading to products of commercial significance; and (iv) and the global market position and manufacturers of hyaluronan.

Hyaluronic acid: evaluation as a potential delivery vehicle for vitronectin:growth factor complexes in wound healing applications

We have previously reported that novel vitronectin:growth factor (VN:GF) complexes significantly increase re-epithelialization in a porcine deep dermal partial-thickness burn model. However, the potential exists to further enhance the healing response through combination with an appropriate delivery vehicle which facilitates sustained local release and reduced doses of VN:GF complexes. Hyaluronic acid (HA), an abundant constituent of the interstitium, is known to function as a reservoir for growth factors and other bioactive species. The physicochemical properties of HA confer it with an ability to sustain elevated pericellular concentrations of these species. This has been proposed to arise via HA prolonging interactions of the bioactive species with cell surface receptors and/or protecting them from degradation. In view of this, the potential of HA to facilitate the topical delivery of VN:GF complexes was evaluated. Two-dimensional (2D) monolayer cell cultures and 3D de-epidermised dermis (DED) human skin equivalent (HSE) models were used to test skin cell responses to HA and VN:GF complexes. Our 2D studies revealed that VN:GF complexes and HA stimulate the proliferation of human fibroblasts but not keratinocytes. Experiments in our 3D DED-HSE models showed that VN:GF complexes, both alone and in conjunction with HA, led to enhanced development of both the proliferative and differentiating layers in the DED-HSE models. However, there was no significant difference between the thicknesses of the epidermis treated with VN:GF complexes alone and VN:GF complexes together with HA. While the addition of HA did not enhance all the cellular responses to VN:GF complexes examined, it was not inhibitory, and may confer other advantages related to enhanced absorption and transport that could be beneficial in delivery of the VN:GF complexes to wounds.

Mechanical stretch induces epithelial-mesenchymal transition in alveolar epithelia via hyaluronan activation of innate immunity

Epithelial injury is a central event in the pathogenesis of many inflammatory and fibrotic lung diseases like acute respiratory distress syndrome, pulmonary fibrosis, and iatrogenic lung injury. Mechanical stress is an often underappreciated contributor to lung epithelial injury. Following injury, differentiated epithelia can assume a myofibroblast phenotype in a process termed epithelial to mesenchymal transition (EMT), which contributes to aberrant wound healing and fibrosis. We demonstrate that cyclic mechanical stretch induces EMT in alveolar type II epithelial cells, associated with increased expression of low molecular mass hyaluronan (sHA). We show that sHA is sufficient for induction of EMT in statically cultured alveolar type II epithelial cells and necessary for EMT during cell stretch. Furthermore, stretch-induced EMT requires the innate immune adaptor molecule MyD88. We examined the Wnt/β-catenin pathway, which is known to mediate EMT. The Wnt target gene Wnt-inducible signaling protein 1 (wisp-1) is significantly up-regulated in stretched cells in hyaluronan- and MyD88-dependent fashion, and blockade of WISP-1 prevents EMT in stretched cells. In conclusion, we show for the first time that innate immunity transduces mechanical stress responses through the matrix component hyaluronan, and activation of the Wnt/β-catenin pathway.

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.

Therapeutic effects of hyaluronan on smoke-induced elastic fiber injury: does delayed treatment affect efficacy?

Aerosolized hyaluronan (HA) has been previously shown to prevent cigarette smoke-induced airspace enlargement and elastic fiber injury in mice when given concurrently with smoke. In the present study, a more stringent test of the therapeutic potential of HA was performed by delaying treatment with this agent for 1 month. After treatment with cigarette smoke for 3 h per day for 5 days per week for 1 month, mice (DBA/2J) began receiving aerosolized HA (0.1%) for 1 h prior to smoke exposure (controls were given aerosolized water). The results indicate that much of the damage to the lung elastic fibers occurred within the first several months of smoke exposure, as measured by levels of desmosine and isodesmosine (DID) in bronchoalveolar lavage fluid (BALF). In contrast to previously published studies, where concurrent administration of aerosolized HA significantly reduced BALF DID levels within 3 months of smoke exposure, the same effect was not seen until 6 months when HA treatment was delayed. However, despite the prolonged breakdown of elastic fibers in the current study, a significant reduction in airspace enlargement was observed after only 2 months of HA treatment. These findings provide further support for testing this agent in patients with pre-existing chronic obstructive pulmonary disease.

Low molecular weight hyaluronic acid effects on murine macrophage nitric oxide production

Hyaluronic acid (HA) is increasingly used for a number of medical device applications. Since the chemical structure of HA is identical no matter its bacterial or animal origin, it should be the ideal biomaterial. However, short term transient inflammatory reactions are common, while rare long-term adverse events may correlate with subclinical chronic inflammation. Concern has been raised that low molecular weight components or degradation fragments from implanted HA may directly stimulate inflammatory reactions. This study examined a panel of HA molecular weights from the unitary disaccharide up to 1.7 x 10(6) Dalton lengths, in which endotoxin was assayed at a very low level (less than 0.03 EU/mg). The murine cell line RAW 264.7, rat splenocytes, and rat adherent differentiated primary macrophages were assayed for nitric oxide production under a variety of inflammatory conditions plus or minus HA. Under the highest inflammatory states, nitric oxide production was mildly suppressed by HMW-HA while slightly augmented by LMW-HA at mg/mL concentrations. However, at micromolar concentrations fragments below 5000 Daltons, thought to have drug-like qualities, were without effect. These data support the hypothesis that if endotoxin is reduced to an extremely low level, LMW-HA may not directly provoke normal tissue macrophage-mediated inflammatory reactions.

Role of Apoptosis in Amplifying Inflammatory Responses in Lung Diseases

Apoptosis is an important contributor to the pathophysiology of lung diseases such as acute lung injury (ALI) and chronic obstructive pulmonary disease (COPD). Furthermore, the cellular environment of these acute and chronic lung diseases favors the delayed clearance of apoptotic cells. This dysfunctional efferocytosis predisposes to the release of endogenous ligands from dying cells. These so-called damage-associated molecular patterns (DAMPs) play an important role in the stimulation of innate immunity as well as in the induction of adaptive immunity, potentially against autoantigens. In this review, we explore the role of apoptosis in ALI and COPD, with particular attention to the contribution of DAMP release in augmenting the inflammatory response in these disease states.

Antitumor activity of hyaluronic acid synthesis inhibitor 4-methylumbelliferone in prostate cancer cells

4-Methylumbelliferone (4-MU) is a hyaluronic acid (HA) synthesis inhibitor with anticancer properties; the mechanism of its anticancer effects is unknown. We evaluated the effects of 4-MU on prostate cancer cells. 4-MU inhibited proliferation, motility, and invasion of DU145, PC3-ML, LNCaP, C4-2B, and/or LAPC-4 cells. At IC(50) for HA synthesis (0.4 mmol/L), 4-MU induced >3-fold apoptosis in prostate cancer cells, which could be prevented by the addition of HA. 4-MU induced caspase-8, caspase-9, and caspase-3 activation, PARP cleavage, upregulation of Fas-L, Fas, FADD and DR4, and downregulation of bcl-2, phosphorylated bad, bcl-XL, phosphorylated Akt, phosphorylated IKB, phosphorylated ErbB2, and phosphorylated epidermal growth factor receptor. At IC(50), 4-MU also caused >90% inhibition of NF-kappaB reporter activity, which was prevented partially by the addition of HA. With the exception of caveolin-1, HA reversed the 4-MU-induced downregulation of HA receptors (CD44 and RHAMM), matrix-degrading enzymes (MMP-2 and MMP-9), interleukin-8, and chemokine receptors (CXCR1, CXCR4, and CXCR7) at the protein and mRNA levels. Expression of myristoylated-Akt rescued 4-MU-induced apoptosis and inhibition of cell growth and interleukin-8, RHAMM, HAS2, CD44, and MMP-9 expression. Oral administration of 4-MU significantly decreased PC3-ML tumor growth (>3-fold) when treatment was started either on the day of tumor cell injection or after the tumors became palpable, without organ toxicity, changes in serum chemistry, or body weight. Tumors from 4-MU-treated animals showed reduced microvessel density ( approximately 3-fold) and HA expression but increased terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells and expression of apoptosis-related molecules. Therefore, the anticancer effects of 4-MU, an orally bioavailable and relatively nontoxic agent, are primarily mediated by inhibition of HA signaling.

Effects of MMP-9 inhibition by doxycycline on proteome of lungs in high tidal volume mechanical ventilation-induced acute lung injury

Background

Although mechanical ventilation (MV) is a major supportive therapy for patients with acute respiratory distress syndrome, it may result in side effects including lung injury. In this study we hypothesize that MMP-9 inhibition by doxycycline might reduce MV-related lung damage. Using a proteomic approach we identified the pulmonary proteins altered in high volume ventilation-induced lung injury (VILI). Forty Wistar rats were randomized to an orally pretreated with doxycycline group (n = 20) or to a placebo group (n = 20) each of which was followed by instrumentation prior to either low or high tidal volume mechanical ventilation. Afterwards, animals were euthanized and lungs were harvested for subsequent analyses.

Results

Mechanical function and gas exchange parameters improved following treatment with doxycycline in the high volume ventilated group as compared to the placebo group. Nine pulmonary proteins have shown significant changes between the two biochemically analysed (high volume ventilated) groups. Treatment with doxycycline resulted in a decrease of pulmonary MMP-9 activity as well as in an increase in the levels of soluble receptor for advanced glycation endproduct, apoliporotein A-I, peroxiredoxin II, four molecular forms of albumin and two unnamed proteins. Using the pharmacoproteomic approach we have shown that treatment with doxycycline leads to an increase in levels of several proteins, which could potentially be part of a defense mechanism.

Conclusion

Administration of doxycycline might be a significant supportive therapeutic strategy in prevention of VILI.

Toll-like receptor 4 mediates neutrophil sequestration and lung injury induced by endotoxin and hyperinflation

OBJECTIVE

To address the role of Toll-like receptor 4 signaling in mediating neutrophil recruitment and lung injury induced by lipopolysaccharide challenge coupled to lung hyperinflation, using Toll-like receptor 4 knockout (tlr4) mice. Infiltration of polymorphonuclear neutrophils into the lung is an important feature of ventilator-induced lung injury associated with pneumonia, but the mechanisms involved in neutrophil recruitment are poorly understood.

DESIGN

Experimental animal model.

SETTING

University laboratory.

SUBJECTS

tlr4 and wild-type C57BL/6 mice.

INTERVENTIONS

Wild-type or tlr4 mice were challenged by intratracheal instillation of lipopolysaccharide (0.3 mg/kg) for 2 hrs and then subjected to normal (7 mL/kg) or high (28 mL/kg) tidal volume ventilation for another 2 hrs. In other studies, neutrophils from wild-type or tlr4 mice were pretreated with lipopolysaccharide for 30 mins and then infused into the isolated lung preparation for 30 mins as the lungs were ventilated with 25 cm H2O peak inspiratory pressure.

MEASUREMENTS AND MAIN RESULTS

Lipopolysaccharide-challenged wild-type mice ventilated with a 28 mL/kg tidal volume exhibited 12-fold increase in neutrophil sequestration, 6-fold increase in bronchoalveolar lavage albumin concentration, and 1.6-fold increase in lung water content compared with unchallenged mice exposed to normal tidal volume ventilation. However, tlr4 mice showed negligible neutrophil sequestration, microvascular barrier breakdown, or edema formation. Mechanical ventilation alone or combined with lipopolysaccharide caused activation of circulating neutrophils and pulmonary endothelium in wild-type mice, whereas this was prevented in tlr4 mice.

CONCLUSIONS

High tidal volume ventilation during pneumonia/sepsis induces lung neutrophil sequestration and injury via the Toll-like receptor 4-dependent signaling pathway. The results suggest an important role of Toll-like receptor 4 in the mechanism of lung neutrophil sequestration and acute lung injury when pneumonia/sepsis is coupled to lung hyperinflation.

The enzymatic degradation of hyaluronan is associated with disease progression in experimental pulmonary hypertension

Hyaluronan (HA) degradation fragments have been linked to inflammation in a wide range of lung diseases. In idiopathic pulmonary arterial hypertension, HA accumulation has been associated with advanced disease. In this study, we investigated the potential role of HA degradation in the early stages of disease by examining HA distribution, molecular mass, synthesis, and enzymatic degradation at different stages of disease progression in a rat model of monocrotaline (MCT)-induced pulmonary hypertension (PH). At 28 days post-MCT, severe PH was associated with increased total lung HA (P = 0.04). In contrast, a significant decrease in total lung HA was observed on day 10, before the onset of PH (P = 0.02). Molecular mass analysis revealed a loss of high molecular mass (HMM) HA at 10 and 24 days post-MCT, followed by an increase in HMM HA at 28 days. Expression of HA synthase 2 (HAS2) was elevated in MCT-challenged animals at 24 and 28 days, consistent with increased synthesis of HMM HA. Analysis by Morgan Elson assay and zymography demonstrated increased hyaluronidase-1 activity in the lungs of MCT-challenged rats, indicating that the observed increases in HAS2 expression and HA synthesis were counterbalanced, in part, by enhanced degradation. The present data demonstrate that, in the MCT model, early-stage PH is associated with enhanced hyaluronidase-1 activity, while both degradation and synthesis are increased at later stages. Thus an early increase in the generation of proinflammatory HA fragments may play a role in the onset and progression of pulmonary arterial hypertension.

Recent advances and new opportunities in lung mechanobiology

Lung function is inextricably linked to mechanics. On short timescales every breath generates dynamic cycles of cell and matrix stretch, along with convection of fluids in the airways and vasculature. Perturbations such airway smooth muscle shortening or surfactant dysfunction rapidly alter respiratory mechanics, with profound influence on lung function. On longer timescales, lung development, maturation, and remodeling all strongly depend on cues from the mechanical environment. Thus mechanics has long played a central role in our developing understanding of lung biology and respiratory physiology. This concise review focuses on progress over the past 5 years in elucidating the molecular origins of lung mechanical behavior, and the cellular signaling events triggered by mechanical perturbations that contribute to lung development, homeostasis, and injury. Special emphasis is placed on the tools and approaches opening new avenues for investigation of lung behavior at integrative cellular and molecular scales. We conclude with a brief summary of selected opportunities and challenges that lie ahead for the lung mechanobiology research community.