CD44 is protective during hyperoxia-induced lung injury

Alveolar-capillary endocytosis and trafficking in acute lung injury and acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is associated with high morbidity and mortality but lacks specific therapeutic options. Diverse endocytic processes play a key role in all phases of acute lung injury (ALI), including the initial insult, development of respiratory failure due to alveolar flooding, as a consequence of altered alveolar-capillary barrier function, as well as in the resolution or deleterious remodeling after injury. In particular, clathrin-, caveolae-, endophilin- and glycosylphosphatidyl inositol-anchored protein-mediated endocytosis, as well as, macropinocytosis and phagocytosis have been implicated in the setting of acute lung damage. This manuscript reviews our current understanding of these endocytic pathways and subsequent intracellular trafficking in various phases of ALI, and also aims to identify potential therapeutic targets for patients with ARDS.

Genetic heterogeneity of liver cancer stem cells

Cancer cell heterogeneity is a serious problem in the control of tumor progression because it can cause chemoresistance and metastasis. Heterogeneity can be generated by various mechanisms, including genetic evolution of cancer cells, cancer stem cells (CSCs), and niche heterogeneity. Because the genetic heterogeneity of CSCs has been poorly characterized, the genetic mutation status of CSCs was examined using Exome-Seq and RNA-Seq data of liver cancer. Here we show that different surface markers for liver cancer stem cells (LCSCs) showed a unique propensity for genetic mutations. Cluster of differentiation 133 (CD133)-positive cells showed frequent mutations in the IRF2, BAP1, and ERBB3 genes. However, leucine-rich repeat-containing G protein-coupled receptor 5-positive cells showed frequent mutations in the CTNNB1, RELN, and ROBO1 genes. In addition, some genetic mutations were frequently observed irrespective of the surface markers for LCSCs. BAP1 mutations was frequently observed in CD133-, CD24-, CD13-, CD90-, epithelial cell adhesion molecule-, or keratin 19-positive LCSCs. ASXL2, ERBB3, IRF2, TLX3, CPS1, and NFATC2 mutations were observed in more than three types of LCSCs, suggesting that common mechanisms for the development of these LCSCs. The present study provides genetic heterogeneity depending on the surface markers for LCSCs. The genetic heterogeneity of LCSCs should be considered in the development of LCSC-targeting therapeutics.

Whole lung proteome of an acute epithelial injury mouse model in comparison to spatially resolved proteomes

Epithelial injury is one of the major drivers of acute pulmonary diseases. Recurring injury followed by aberrant repair is considered as the primary cause of chronic lung diseases, such as idiopathic pulmonary fibrosis (IPF). Preclinical in vivo models allow studying early disease-driving mechanisms like the recently established adeno-associated virus-diphtheria toxin receptor (AAV-DTR) mouse model of acute epithelial lung injury, which utilises AAV mediated expression of the human DTR. We performed quantitative proteomics of homogenised lung samples from this model and compared the results to spatially resolved proteomics data of epithelial cell regions from the same animals. In whole lung tissue proteins involved in cGAS-STING and interferon pathways, proliferation, DNA replication and the composition of the provisional extracellular matrix were upregulated upon injury. Besides epithelial cell markers SP-A, SP-C and Scgb1a1, proteins involved in cilium assembly, lipid metabolism and redox pathways were among downregulated proteins. Comparison of the bulk to spatially resolved proteomics data revealed a large overlap of protein changes and striking differences. Together our study underpins the broad usability of bulk proteomics and pinpoints to the benefit of sophisticated proteomic analyses of specific tissue regions or single cell types.

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.

A specific low-density neutrophil population correlates with hypercoagulation and disease severity in hospitalized COVID-19 patients

SARS coronavirus 2 (SARS-CoV-2) is a novel viral pathogen that causes a clinical disease called coronavirus disease 2019 (COVID-19). Although most COVID-19 cases are asymptomatic or involve mild upper respiratory tract symptoms, a significant number of patients develop severe or critical disease. Patients with severe COVID-19 commonly present with viral pneumonia that may progress to life-threatening acute respiratory distress syndrome (ARDS). Patients with COVID-19 are also predisposed to venous and arterial thromboses that are associated with a poorer prognosis. The present study identified the emergence of a low-density inflammatory neutrophil (LDN) population expressing intermediate levels of CD16 (CD16Int) in patients with COVID-19. These cells demonstrated proinflammatory gene signatures, activated platelets, spontaneously formed neutrophil extracellular traps, and enhanced phagocytic capacity and cytokine production. Strikingly, CD16Int neutrophils were also the major immune cells within the bronchoalveolar lavage fluid, exhibiting increased CXCR3 but loss of CD44 and CD38 expression. The percentage of circulating CD16Int LDNs was associated with D-dimer, ferritin, and systemic IL-6 and TNF-α levels and changed over time with altered disease status. Our data suggest that the CD16Int LDN subset contributes to COVID-19-associated coagulopathy, systemic inflammation, and ARDS. The frequency of that LDN subset in the circulation could serve as an adjunct clinical marker to monitor disease status and progression.

Single cell transcriptomic analysis of murine lung development on hyperoxia-induced damage

During late lung development, alveolar and microvascular development is finalized to enable sufficient gas exchange. Impaired late lung development manifests as bronchopulmonary dysplasia (BPD) in preterm infants. Single-cell RNA sequencing (scRNA-seq) allows for assessment of complex cellular dynamics during biological processes, such as development. Here, we use MULTI-seq to generate scRNA-seq profiles of over 66,000 cells from 36 mice during normal or impaired lung development secondary to hyperoxia with validation of some of the findings in lungs from BPD patients. We observe dynamic populations of cells, including several rare cell types and putative progenitors. Hyperoxia exposure, which mimics the BPD phenotype, alters the composition of all cellular compartments, particularly alveolar epithelium, stromal fibroblasts, capillary endothelium and macrophage populations. Pathway analysis and predicted dynamic cellular crosstalk suggest inflammatory signaling as the main driver of hyperoxia-induced changes. Our data provides a single-cell view of cellular changes associated with late lung development in health and disease.

Hyperoxia and Lungs: What We Have Learned From Animal Models

Although oxygen (O₂) is essential for aerobic life, it can also be an important source of cellular damage. Supra-physiological levels of O₂ determine toxicity due to exacerbated reactive oxygen species (ROS) production, impairing the homeostatic balance of several cellular processes. Furthermore, injured cells activate inflammation cascades, amplifying the tissue damage. The lung is the first (but not the only) organ affected by this condition. Critically ill patients are often exposed to several insults, such as mechanical ventilation, infections, hypo-perfusion, systemic inflammation, and drug toxicity. In this scenario, it is not easy to dissect the effect of oxygen toxicity. Translational investigations with animal models are essential to explore injuring stimuli in controlled experimental conditions, and are milestones in understanding pathological mechanisms and developing therapeutic strategies. Animal models can resemble what happens in critical care or anesthesia patients under mechanical ventilation and hyperoxia, but are also critical to explore the effect of O₂ on lung development and the role of hyperoxic damage on bronchopulmonary dysplasia. Here, we set out to review the hyperoxia effects on lung pathology, contributing to the field by describing and analyzing animal experimentation's main aspects and its implications on human lung diseases.

Regulatory mechanisms of neutrophil migration from the circulation to the airspace

The neutrophil, a short-lived effector leukocyte of the innate immune system best known for its proteases and other degradative cargo, has unique, reciprocal physiological interactions with the lung. During health, large numbers of ‘marginated’ neutrophils reside within the pulmonary vasculature, where they patrol the endothelial surface for pathogens and complete their life cycle. Upon respiratory infection, rapid and sustained recruitment of neutrophils through the endothelial barrier, across the extravascular pulmonary interstitium, and again through the respiratory epithelium into the airspace lumen, is required for pathogen killing. Overexuberant neutrophil trafficking to the lung, however, causes bystander tissue injury and underlies several acute and chronic lung diseases. Due in part to the unique architecture of the lung’s capillary network, the neutrophil follows a microanatomic passage into the distal airspace unlike that observed in other end-organs that it infiltrates. Several of the regulatory mechanisms underlying the stepwise recruitment of circulating neutrophils to the infected lung have been defined over the past few decades; however, fundamental questions remain. In this article, we provide an updated review and perspective on emerging roles for the neutrophil in lung biology, on the molecular mechanisms that control the trafficking of neutrophils to the lung, and on past and ongoing efforts to design therapeutics to intervene upon pulmonary neutrophilia in lung disease.

CD44 and RHAMM expression patterns in the human developing lung

BACKGROUND

The hyaluronan (HA) receptors CD44 and RHAMM (CD168) are involved in cellular proliferation, differentiation, and motility. As previously investigated, HA and RHAMM expression in human neonatal lungs correlates to gestational age (GA) and air content.

METHODS

CD44 immunofluorescence was analyzed in postmortem lung samples from infants (n = 93; 22-41 GA) by digital image analysis together with clinical data, including RHAMM expression, lung air, and HA content by hierarchical clustering.

RESULTS

Five groups were defined according to RHAMM/CD44 expression, GA, and postnatal age (PNA): extremely to very preterm (EVP; 22-31 GA; Groups 1-2), moderately preterm to term (MPT; 31-41 GA; Groups 3-4), and mixed preterm to term (27-40 GA; Group 5). CD44 correlated linearly with RHAMM in MPT (r = 0.600; p < 0.004). In EVP, high CD44 and low RHAMM corresponded with high PNA and lung air content independently of HA and GA (Group 1 vs 2; p < 0.05). In MPT, high and low CD44 corresponded with low and high RHAMM independently of GA, HA, and lung air content (Group 3 vs 4; p < 0.001). No correlation between CD44 and GA/PNA at death was observed.

CONCLUSIONS

A linear correlation between CD44 and RHAMM expression occurs during the late saccular phase of lung development at birth, whereas postnatal influences on CD44 and RHAMM expression in extremely to very preterm infants cannot be excluded.

IMPACT

The interplay between CD44 and RHAMM, two receptors of hyaluronic acid, can be dependent on the lung developmental stage at birth. This is the second study that analyzes the distribution pattern of CD44 in the human lung during development and the first study performed with quantitative analysis of CD44 expression together with RHAMM expression in the human lung. Our results suggest a relationship in a subset of infants between CD44 and RHAMM expression, which appears at birth during the late saccular stage but not during the earlier stages of lung development.

Curcumin may be a potential adjuvant treatment drug for colon cancer by targeting CD44

Despite the considerable advances in treatment method development, the mortality rate related to colon cancer still ranks the fifth in all tumor-related diseases. Recently, there has been growing evidences supporting the existence of colon cancer stem cells (CSCs) might be one of the main causes for initiation, progression and recurrence of colon cancer. Curcumin has been shown to possess anticancer activities. It has also been suggested that curcumin was effective against colon CSCs by coupling with CD44, a robust marker and functional important molecule for colorectal CSC. In the present study, we confirmed that curcumin can inhibit the proliferation, colony formation, migration and tumor sphere formation of colon cancer cells. Results from real-time PCR and western blotting had suggested that curcumin could down-regulate the expression of CD44. Moreover, results from flow cytometry had further revealed that curcumin could decrease the proportion of CD44⁺ colon cancer cells. After the expression of CD44 had been knocked down by using siRNA, the inhibition effects of curcumin against CD44⁺ colon cancer cells were observed to be reduced significantly. Moreover, it had been observed that the cellular uptake of curcumin was significantly higher in CD44⁺ colon cancer cells. Results from flow cytometry had shown that curcumin could induce apoptosis in CD44⁺ colon cancer cells. Altogether, our results suggested that curcumin might be an adjuvant drug for the treatment of colorectal cancer by targeting CD44.

Neutrophils mitigate the systemic host response during endotoxemia in mice

Recent studies have suggested that neutrophils can exert anti-inflammatory effects. To determine the role of neutrophils in the acute response to lipopolysaccharide (LPS), a component of the Gram-negative bacterial cell wall, we challenged neutrophil-depleted and control mice with LPS and analyzed the plasma concentrations of biomarkers indicative of the cytokine and chemokine network, activation of coagulation and the vascular endothelium, and cellular injury. We here show that neutrophils serve an anti-inflammatory role upon LPS administration, as reflected by sustained elevations of multiple cytokines and chemokines, and enhanced release of nucleosomes in mice depleted of neutrophils, compared with control mice.

Cancer Stem Cells in Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma is one of the most common cancers and the second leading cause of cancer-related deaths worldwide. Only a small proportion of patients benefit from curative treatment and the prognosis is very poor for the majority of cases due to late presentation, resistance to chemotherapy and high recurrence rate. In recent years, progress in stem cell biology allowed us to explain that hierarchically organized cancer stem cells (CSCs) drive histological and functional heterogeneity of hematological malignancies and solid tumors.

METHODS AND RESULTS

Also referred to as tumor-initiating cells, CSCs have been isolated from both hepatocellular carcinoma (HCC) cell lines and primary tumors by using hepatic progenitor markers. Although there is still no consensus on cancer stem cell phenotype in HCC, single or combined use of CSC markers defines a minor population of tumor cells with the capacity of self-renewing and the ability to recapitulate the original tumor heterogeneity.

CONCLUSIONS

This review focuses on the biological features of CSCs and their potential as diagnostic/prognostic tools and therapeutic targets in HCC.

Human amnion epithelial cells modulate the inflammatory response to ventilation in preterm lambs

Ventilation of preterm neonates causes pulmonary inflammation that can contribute to lung injury, propagate systemically and result in long-term disease. Modulation of this initial response may reduce lung injury and its sequelae. We aimed to determine the effect of human amnion epithelial cells (hAECs) on immune activation and lung injury in preterm neonatal lambs. Preterm lambs received intratracheal hAECs (90x106) or vehicle, prior to 2 h of mechanical ventilation. Within 5 min of ventilation onset, lambs also received intravenous hAECs (90x106) or vehicle. Lung histology, bronchoalveolar lavage (BAL) cell phenotypes, and cytokine profiles were examined after 2 h of ventilation, and in unventilated controls. Histological indices of lung injury were higher than control, in vehicle-treated ventilated lambs but not in hAEC-treated ventilated lambs. Ventilation-induced pulmonary leukocyte recruitment was greater in hAEC-treated lambs than in vehicle-treated lambs. Lung IL-1β and IL-6 mRNA expression was higher in vehicle- and hAEC-treated ventilated lambs than in controls but IL-8 mRNA levels were greater than control only in vehicle-treated ventilated lambs. Numbers of CD44+ and CD21+ lymphocytes and macrophages from the lungs were altered in vehicle- and hAEC-treated ventilated lambs. Numbers of CD8+ macrophages were lower in hAEC-treated ventilated lambs than in vehicle-treated ventilated lambs. Indices of systemic inflammation were not different between vehicle- and hAEC-treated lambs. Human amnion epithelial cells modulate the pulmonary inflammatory response to ventilation in preterm lambs, and reduce acute lung injury. Immunomodulatory effects of hAECs reduce lung injury in preterm neonates and may protect against longer-term respiratory disease.

Prognostic value of CD44 expression in patients with hepatocellular carcinoma: meta-analysis

Background

CD44 has been reported to be involved with tumor growth and metastasis and has also been implicated as a CSC marker in hepatocellular carcinoma (HCC). However, the prognostic value of CD44 still remains controversial; hence, we investigated the correlation between CD44 and the clinicopathological features of HCC by meta-analysis.

Methods

Identification and review of publications assessing clinical or prognostic significance of CD44 expression in HCC until November 1, 2015. A meta-analysis was performed to clarify the association between CD44 expression and clinical outcomes.

Results

A total of 14 publications met the criteria and comprised 2235 cases. Analysis of these data showed that CD44 expression was not significantly associated with the tumor differentiation (OR 1.48, 95 % confidence interval [CI] 0.85–2.60, P = 0.17), AFP level of HCC patients (OR 0.83, 95 % CI 0.52–1.33, P = 0.45), or disease-free survival (relative risk [RR] 1.15, 95 % CI, 0.85–1.54; P = 0.36). However, in the identified studies, CD44 expression was highly correlated with tumor TNM classification (OR 2.38, 95 % CI 1.23–4.60; P = 0.01) and decreased overall survival (RR 1.49, 95 % CI, 1.26–1.76; P < 0.00001).

Conclusions

This meta-analysis shows CD44 expression in HCC is connected with decreased overall and thus marks a worse prognosis.

Liver cancer stem cell markers: Progression and therapeutic implications

Cancer stem cells (CSCs) are a small subpopulation in cancer, have been proposed to be cancer-initiating cells, and have been shown to be responsible for chemotherapy resistance and cancer recurrence. The identification of CSC subpopulations inside a tumor presents a new understanding of cancer development because it implies that tumors can only be eradicated by targeting CSCs. Although advances in liver cancer detection and treatment have increased the possibility of curing the disease at early stages, unfortunately, most patients will relapse and succumb to their disease. Strategies aimed at efficiently targeting liver CSCs are becoming important for monitoring the progress of liver cancer therapy and for evaluating new therapeutic approaches. Herein, we provide a critical discussion of biological markers described in the literature regarding liver cancer stem cells and the potential of these markers to serve as therapeutic targets.

Aggravation of Allergic Airway Inflammation by Cigarette Smoke in Mice Is CD44-Dependent

Background

Although epidemiological studies reveal that cigarette smoke (CS) facilitates the development and exacerbation of allergic asthma, these studies offer limited information on the mechanisms involved. The transmembrane glycoprotein CD44 is involved in cell adhesion and acts as a receptor for hyaluronic acid and osteopontin. We aimed to investigate the role of CD44 in a murine model of CS-facilitated allergic airway inflammation.

Methods

Wild type (WT) and CD44 knock-out (KO) mice were exposed simultaneously to house dust mite (HDM) extract and CS. Inflammatory cells, hyaluronic acid (HA) and osteopontin (OPN) levels were measured in bronchoalveolar lavage fluid (BALF). Proinflammatory mediators, goblet cell metaplasia and peribronchial eosinophilia were assessed in lung tissue. T-helper (Th) 1, Th2 and Th17 cytokine production was evaluated in mediastinal lymph node cultures.

Results

In WT mice, combined HDM/CS exposure increased the number of inflammatory cells and the levels of HA and OPN in BALF and Th2 cytokine production in mediastinal lymph nodes compared to control groups exposed to phosphate buffered saline (PBS)/CS, HDM/Air or PBS/Air. Furthermore, HDM/CS exposure significantly increased goblet cell metaplasia, peribronchial eosinophilia and inflammatory mediators in the lung. CD44 KO mice exposed to HDM/CS had significantly fewer inflammatory cells in BALF, an attenuated Th2 cytokine production, as well as decreased goblet cells and peribronchial eosinophils compared to WT mice. In contrast, the levels of inflammatory mediators were similar or higher than in WT mice.

Conclusion

We demonstrate for the first time that the aggravation of pulmonary inflammation upon combined exposure to allergen and an environmental pollutant is CD44-dependent. Data from this murine model of concomitant exposure to CS and HDM might be of importance for smoking allergic asthmatics.

Enrichment of CD44 in basal-type breast cancer correlates with EMT, cancer stem cell gene profile, and prognosis

Cluster of differentiation 44 (CD44) is a transmembrane glycoprotein that serves as the receptor for the extracellular matrix component hyaluronic acid. CD44 has been reported to play key roles in cell proliferation, motility, and survival, but its role in breast cancer remains controversial. In this study, we conducted a meta-analysis. A total of 23 published Gene Expression Omnibus databases were included to evaluate the association between CD44 mRNA expression and clinicopathological characteristics or prognosis of the patients with breast cancer. Our analysis revealed that CD44 expression was associated with clinicopathological features, including the histological grade, estrogen receptor status, progesterone receptor status, and human epidermal growth factor receptor-2 status. Higher levels of CD44 expression were observed in the basal subtype of breast cancer both at the mRNA and protein levels (odds ratio [OR] =2.08, 95% confidence interval [CI]: 1.72–2.52; OR =2.11, 95% CI: 1.67–2.68). Patients with CD44 overexpression exhibited significantly worse overall survival (hazard ratio =1.27; 95% CI: 1.04–1.55). Whole gene profile analysis revealed that CD44 expression was enriched in basal-type breast cancer and correlated with epithelial–mesenchymal transition and cancer stem cell gene profiles. In summary, our analyses indicated that CD44 potentially might be a prognostic marker for breast cancer and thus can serve as a therapeutic target for basal-type breast cancer.

The role of CD44 in epithelial-mesenchymal transition and cancer development

CD44, a multi-structural and multifunctional transmembrane glycoprotein, was initially identified as a receptor for hyaluronan that participates in both physiological and pathological processes. CD44 is found to be closely linked to the development of various solid tumors. Molecular studies have revealed that high CD44 expression was correlated with the phenotypes of cancer stem cells and epithelial–mesenchymal transition, thereby contributing to tumor invasion, metastasis, recurrence, and chemoresistance. Correspondingly, blockade of CD44 has been demonstrated to be capable of attenuating the malignant phenotype, slowing cancer progression, and reversing therapy resistance. Clinical analyses showed that high CD44 expression is associated with poor survival of various cancer patients, indicating that CD44 can be a potential prognostic marker. In this review, we summarize recent research progress of CD44 on tumor biology and the clinical significance of CD44.

The role of platelet MyD88 in host response during gram-negative sepsis

BACKGROUND

Beside their role in hemostasis, platelets serve as sentinel cells in host defense during infection. In sepsis, platelets have been implicated in both beneficial (antibacterial) and detrimental responses (thrombosis and organ damage). Toll-like receptors and their common adaptor, myeloid differentiation factor 88 (MyD88), are essential for pathogen recognition and protective immunity. Platelets express functional Toll-like receptors and MyD88, which participate in platelet responsiveness to bacterial agonists.

OBJECTIVE

Considering the pivotal involvement of platelets and MyD88 in the host response to bacteria, we studied the role of platelet MyD88 in gram-negative sepsis using intravenous and airway infections with the common human sepsis pathogen Klebsiella pneumoniae.

METHODS

Platelet-specific Myd88(-/-) mice were generated by crossing mice with a conditional Myd88 flox allele with mice expressing Cre recombinase controlled by the platelet factor 4 promoter. In a reverse approach, full Myd88(-/-) mice were transfused with wild-type platelets.

RESULTS

In both settings, platelet MyD88 did not impact on bacterial growth or dissemination. In addition, platelet MyD88 did not influence hallmark sepsis responses such as thrombocytopenia, coagulation or endothelial activation, or distant organ injury. Platelet MyD88 played no role in lung pathology during pneumonia-derived sepsis.

CONCLUSION

Despite known literature, platelet MyD88-dependent TLR signaling does not contribute to the host response during gram-negative sepsis.

The where, when, how, and why of hyaluronan binding by immune cells

Hyaluronan is made and extruded from cells to form a pericellular or extracellular matrix (ECM) and is present in virtually all tissues in the body. The size and form of hyaluronan present in tissues are indicative of a healthy or inflamed tissue, and the interactions of hyaluronan with immune cells can influence their response. Thus, in order to understand how inflammation is regulated, it is necessary to understand these interactions and their consequences. Although there is a large turnover of hyaluronan in our bodies, the large molecular mass form of hyaluronan predominates in healthy tissues. Upon tissue damage and/or infection, the ECM and hyaluronan are broken down and an inflammatory response ensues. As inflammation is resolved, the ECM is restored, and high molecular mass hyaluronan predominates again. Immune cells encounter hyaluronan in the tissues and lymphoid organs and respond differently to high and low molecular mass forms. Immune cells differ in their ability to bind hyaluronan and this can vary with the cell type and their activation state. For example, peritoneal macrophages do not bind soluble hyaluronan but can be induced to bind after exposure to inflammatory stimuli. Likewise, naïve T cells, which typically express low levels of the hyaluronan receptor, CD44, do not bind hyaluronan until they undergo antigen-stimulated T cell proliferation and upregulate CD44. Despite substantial knowledge of where and when immune cells bind hyaluronan, why immune cells bind hyaluronan remains a major outstanding question. Here, we review what is currently known about the interactions of hyaluronan with immune cells in both healthy and inflamed tissues and discuss how hyaluronan binding by immune cells influences the inflammatory response.

Integrated genomic analyses in bronchopulmonary dysplasia

OBJECTIVE

To identify single-nucleotide polymorphisms (SNPs) and pathways associated with bronchopulmonary dysplasia (BPD) because O2 requirement at 36 weeks' postmenstrual age risk is strongly influenced by heritable factors.

STUDY DESIGN

A genome-wide scan was conducted on 1.2 million genotyped SNPs, and an additional 7 million imputed SNPs, using a DNA repository of extremely low birth weight infants. Genome-wide association and gene set analysis was performed for BPD or death, severe BPD or death, and severe BPD in survivors. Specific targets were validated via the use of gene expression in BPD lung tissue and in mouse models.

RESULTS

Of 751 infants analyzed, 428 developed BPD or died. No SNPs achieved genome-wide significance (P < 10(-8)), although multiple SNPs in adenosine deaminase, CD44, and other genes were just below P < 10(-6). Of approximately 8000 pathways, 75 were significant at false discovery rate (FDR) <0.1 and P < .001 for BPD/death, 95 for severe BPD/death, and 90 for severe BPD in survivors. The pathway with lowest FDR was miR-219 targets (P = 1.41E-08, FDR 9.5E-05) for BPD/death and phosphorous oxygen lyase activity (includes adenylate and guanylate cyclases) for both severe BPD/death (P = 5.68E-08, FDR 0.00019) and severe BPD in survivors (P = 3.91E-08, FDR 0.00013). Gene expression analysis confirmed significantly increased miR-219 and CD44 in BPD.

CONCLUSIONS

Pathway analyses confirmed involvement of known pathways of lung development and repair (CD44, phosphorus oxygen lyase activity) and indicated novel molecules and pathways (adenosine deaminase, targets of miR-219) involved in genetic predisposition to BPD.

Divergent Temporal Expression of Hyaluronan Metabolizing Enzymes and Receptors with Craniotomy vs. Controlled-Cortical Impact Injury in Rat Brain: A Pilot Study

Traumatic brain injury (TBI) triggers many secondary changes in tissue biology, which ultimately determine the extent of injury and clinical outcome. Hyaluronan [hyaluronic acid (HA)] is a protective cementing gel present in the intercellular spaces whose degradation has been reported as a causative factor in tissue damage. Yet little is known about the expression and activities of genes involved in HA catabolism after TBI. Young adult male Sprague-Dawley rats were assigned to three groups: naïve control, craniotomy, and controlled-cortical impact-induced TBI (CCI-TBI). Four animals per group were sacrificed at 4 h, 1, 3, and 7 days post-CCI. The mRNA expression of hyaluronan synthases (HAS1-3), hyaluronidases (enzymes for HA degradation, HYAL 1–4, and PH20), and CD44 and RHAMM (membrane receptors for HA signaling and removal) were determined using real-time PCR. Compared to the naïve controls, expression of HAS1 and HAS2 mRNA, but not HAS3 mRNA increased significantly following craniotomy alone and following CCI with differential kinetics. Expression of HAS2 mRNA increased significantly in the ipsilateral brain at 1 and 3 days post-CCI. HYAL1 mRNA expression also increased significantly in the craniotomy group and in the contralateral CCI at 1 and 3 days post-CCI. CD44 mRNA expression increased significantly in the ipsilateral CCI at 4 h, 1, 3, and 7 days post-CCI (up to 25-fold increase). These data suggest a dynamic regulation and role for HA metabolism in secondary responses to TBI.

Significance of CD44 expression in head and neck cancer: a systemic review and meta-analysis

BACKGROUND

CD44 has been reported to be involved with tumor growth and metastasis and has also been implicated as a CSC marker in head and neck squamous cell cancer (HNSCC). However, the prognostic value of CD44 still remains controversial; hence, we investigated the correlation between CD44 and the clinicopathological features of HNSCC by meta-analysis.

METHODS

A comprehensive search was performed using PubMed, ISI web of Science and China National Knowledge Infrastructure (CNKI) up to April 2013. Only studies with immunohistochemical staining of HNSCC were considered. Data on TNM classification, tumor grade, disease free survival and 3- or 5-year overall survival rate were extracted.

RESULTS

Thirty studies with 2102 patients met the inclusion criteria for the meta-analysis. Fifteen studies used anti-pan-CD44 antibody, 9 used anti-CD44-v6 antibody, 2 used anti-CD44-v3 and 2 used anti-CD44s antibody, 1 used anti-CD44-v9, and 1 used anti-CD44-v6,-v3 and -v4-5 simultaneously. The total percentage of CD44 expression was 57.8%, with 49.3% in oral cancer patients, 66.4% in pharynx and 54.7% in larynx cancer patients expressing CD44. No significant correlation between clinical features and CD44 expression was revealed for oral cancer patients, but CD44 was shown to be associated with advanced T categories (larynx: RR = 1.33, 95% CI 1.01-1.76; larynx & pharynx RR = 1.21, 95% CI 1.08-1.35), worse N categories (larynx: RR = 2.53, 95% CI 1.99-3.21; larynx & pharynx RR = 1.95, 95% CI 1.35-2.82), higher tumor grades (larynx & pharynx RR = 1.71, 95% CI 1.04-2.79) and 5-year OS rates (larynx: RR = 0.62, 95% CI 0.47-0.83; larynx & pharynx RR = 0.66, 95% CI 0.47-0.94) in patients with laryngeal and pharyngolaryngeal cancer. In stratified analysis, pan-CD44 and CD44-v6 expression were both correlated with 5-year OS rate of patients with laryngeal (CD44: RR = 0.66, 95% CI 0.46-0.95; CD44-v6 RR = 0.53, 95% CI 0.37-0.77) and pharyngolaryngeal cancer (CD44: RR = 0.56, 95% CI 0.34-0.93; CD44-v6 RR = 0.53, 95% CI 0.37-0.77).

CONCLUSIONS

Our analysis suggested that CD44 is related to worse T category, N category, tumor grade and prognosis, in pharyngeal and laryngeal cancer, but no clear association was revealed between CD44 expression and oral cancer.

Cyclin-dependent kinase inhibition reduces lung damage in a mouse model of ventilator-induced lung injury

Mechanical ventilation (MV) has the potential to induce lung damage in healthy lungs or aggravate existing lung injury. Polymorphonuclear neutrophil (PMN) recruitment plays an important role in driving the inflammatory response in ventilator-induced lung injury (VILI). The cyclin-dependent kinase inhibitor r-roscovitine has been shown to induce apoptosis in PMNs. In this study, we investigated the potential of r-roscovitine treatment in reducing lung damage in a mouse model of VILI. Mice were tracheotomized and subjected to lung-protective MV with lower (∼7.5 mL/kg) or lung-injurious MV with higher (∼15 mL/kg) tidal volume (VT). R-roscovitine treatment enhanced apoptosis in PMNs in vitro. Ventilator-induced lung injury was associated with pulmonary PMN influx in low and high VT MV. During lung-injurious MV, r-roscovitine treatment reduced the number of PMNs and lowered levels of the lung damage markers RAGE (receptor for advanced glycation end products) and total immunoglobulin M in bronchoalveolar lavage fluid. R-roscovitine did not affect cytokine or chemokine levels in the bronchoalveolar space, neither during lung-protective nor lung-injurious MV. Thus, r-roscovitine treatment reduces lung damage in VILI, possibly dependent on increased apoptosis of PMNs.

Endogenous protein C has a protective role during Gram-negative pneumosepsis (melioidosis)

BACKGROUND

Activated protein C (APC) exerts anticoagulant effects via inactivation of factors Va and VIIIa and cytoprotective effects via protease activated receptor (PAR)1. Inhibition of endogenous APC in endotoxemia and sepsis results in exacerbation of coagulation and inflammation, with consequent enhanced lethality.

OBJECTIVES

We here sought to dissect the distinct roles of the anticoagulant and cytoprotective functions of endogenous APC in severe Gram-negative pneumonia-derived sepsis (melioidosis).

METHODS

We infected wild-type (WT) mice with Burkholderia pseudomallei, a common sepsis pathogen in southeast Asia, and treated them with antibodies inhibiting both the anticoagulant and cytoprotective functions of APC (MPC1609) or the anticoagulant functions of APC (MAPC1591) only. Additionally, we administered SEW2871 (stimulating the S1P1-pathway downstream from PAR1) to control and MPC1609-treated mice.

RESULTS

MPC1609, but not MAPC1591, significantly worsened survival, increased coagulation activation, facilitated bacterial growth and dissemination and enhanced the inflammatory response. The effects of MPC1609 could not be reversed by SEW2871, suggesting that S1P1 does not play a major role in this model.

CONCLUSIONS

These results suggest that the mere inhibition of the anticoagulant function of APC does not interfere with its protective role during Gram-negative pneumosepsis, suggesting a more prominent role for cytoprotective effects of APC .

AMP-activated protein kinase activation by 5-aminoimidazole-4-carbox-amide-1-β-D-ribofuranoside (AICAR) reduces lipoteichoic acid-induced lung inflammation

Adenosine monophosphate-activated protein (AMP)-activated kinase (AMPK) is a highly conserved kinase that plays a key role in energy homeostasis. Activation of AMPK was shown to reduce inflammation in response to lipolysaccharide in vitro and in vivo. 5-Aminoimidazole-4-carbox-amide-1-β-D-ribofuranoside (AICAR) is intracellularly converted to the AMP analog ZMP, which activates AMPK. Lipoteichoic acid (LTA) is a major component of the cell wall of Gram-positive bacteria that can trigger inflammatory responses. In contrast to lipopolysaccharide, little is known on the effects of AMPK activation in LTA-triggered innate immune responses. Here, we studied the potency of AMPK activation to reduce LTA-induced inflammation in vitro and in lungs in vivo. Activation of AMPK in vitro reduced cytokine production in the alveolar macrophage cell line MH-S. In vivo, AMPK activation reduced LTA-induced neutrophil influx, as well as protein leak and cytokine/chemokine levels in the bronchoalveolar space. In conclusion, AMPK activation inhibits LTA-induced lung inflammation in mice.

Role of CD44 as a marker of cancer stem cells in head and neck cancer

In recent years, many studies have shown that some types of tumors are characterized by the presence of cells with stem-like characteristics, called cancer stem cells (CSCs). These are considered cells that initiate the tumor and are probably responsible for tumor recurrence. CSCs have the capacity for self-renewal, the potential to give rise to one or more cell types within the tumor, and the ability to drive, in a continuous manner, the proliferation of malignant cells. The failure of current cancer therapies can be attributed to the relative ineffectiveness of drugs against CSCs, which remain viable while retaining their full ability to reproduce the tumor. The development of new strategies is currently hampered by the lack of reliable markers to identify CSCs. One promising surface marker of CSCs in head and neck cancer is the CD44 molecule, which has been shown in preliminary studies to have high specificity, although there are discrepant data because its prognostic value may depend on the specific tumor location. More rigorous studies are needed to investigate the usefulness of CD44 expression in head and neck tumors for possible clinical applicability.

Differential roles of MyD88 and TRIF in hematopoietic and resident cells during murine gram-negative pneumonia

BACKGROUND

Pneumonia is frequently caused by gram-negative pathogens, among which Klebsiella pneumoniae prominently features. Recognition of pathogen-associated molecular patterns by Toll-like receptors (TLRs) is important for an appropriate immune response during infection. TLR signaling can proceed via 2 distinct routes that are dependent on the adaptor proteins Myeloid differentiation primary response gene (88) (MyD88) and TIR-domain-containing adaptor-inducing interferon-β (TRIF). The aim of the study was to determine the relative contribution of MyD88 and TRIF signaling in resident and hematopoietic cells to host defense during pneumonia.

METHODS

Bone marrow chimeras of MyD88 deficient/wild type and TRIF mutant/wild type mice were created and infected with K. pneumoniae via the airways.

RESULTS

MyD88 in both resident and hematopoietic cells contributed to survival and antibacterial defense in late-stage infection, whereas only TRIF in hematopoietic cells was protective. On the other hand, resident MyD88 and hematopoietic TRIF contributed to distant cellular injury. Resident MyD88 was pivotal for early chemokine release and neutrophil recruitment in the bronchoalveolar space.

CONCLUSIONS

MyD88- and TRIF-dependent signaling has a differential contribution to host defense in different cell types that changes from early- to late-stage gram-negative pneumonia.

Synchronizing allelic effects of opposing quantitative trait loci confirmed a major epistatic interaction affecting acute lung injury survival in mice

Increased oxygen (O₂) levels help manage severely injured patients, but too much for too long can cause acute lung injury (ALI), acute respiratory distress syndrome (ARDS) and even death. In fact, continuous hyperoxia has become a prototype in rodents to mimic salient clinical and pathological characteristics of ALI/ARDS. To identify genes affecting hyperoxia-induced ALI (HALI), we previously established a mouse model of differential susceptibility. Genetic analysis of backcross and F₂ populations derived from sensitive (C57BL/6J; B) and resistant (129X1/SvJ; X1) inbred strains identified five quantitative trait loci (QTLs; Shali1-5) linked to HALI survival time. Interestingly, analysis of these recombinant populations supported opposite within-strain effects on survival for the two major-effect QTLs. Whereas Shali1 alleles imparted the expected survival time effects (i.e., X1 alleles increased HALI resistance and B alleles increased sensitivity), the allelic effects of Shali2 were reversed (i.e., X1 alleles increased HALI sensitivity and B alleles increased resistance). For in vivo validation of these inverse allelic effects, we constructed reciprocal congenic lines to synchronize the sensitivity or resistance alleles of Shali1 and Shali2 within the same strain. Specifically, B-derived Shali1 or Shali2 QTL regions were transferred to X1 mice and X1-derived QTL segments were transferred to B mice. Our previous QTL results predicted that substituting Shali1 B alleles onto the resistant X1 background would add sensitivity. Surprisingly, not only were these mice more sensitive than the resistant X1 strain, they were more sensitive than the sensitive B strain. In stark contrast, substituting the Shali2 interval from the sensitive B strain onto the X1 background markedly increased the survival time. Reciprocal congenic lines confirmed the opposing allelic effects of Shali1 and Shali2 on HALI survival time and provide unique models to identify their respective quantitative trait genes and to critically assess the apparent bidirectional epistatic interactions between these major-effect loci.

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.