Hyaluronan (hyaluronic acid) in lung lavage of asbestos-exposed humans and sheep

Clinical utility of hyaluronic acid values in serum and bronchoalveolar lavage fluid as tumor marker for bronchogenic carcinoma

Various authors have proposed the use of hyaluronic acid (HA) as a tumor marker. In order to analyze its usefulness as a marker in bronchogenic carcinoma, the most common carcinoma in men, we determined the HA values in serum and bronchoalveolar lavage fluid (BAL). We performed prospective studies on two groups of patients: 81 diagnosed as having bronchial carcinoma and 34 with benign respiratory diseases.

HA values were higher in patients with cancer than in those with benign diseases (serum: 79.8 ng/ml vs 63.7 ng/ml; BAL: 927 ng/mg vs 522 ng/mg). Also, the percentage of patients with levels exceeding the established cutoff was greater in the group with cancer than in the group with benign diseases (serum: 24.6 vs 17.6; BAL: 25.3 vs 3). Statistically significant differences in these percentages were found in BAL (p<0.01). Patients with extended small cell carcinoma had higher HA values (p=0.04) than those with limited disease, and the percentage of patients with abnormal HA values was larger in the group with extended disease than in the group with limited disease (p=0.004). The serial determinations of HA values in serum reflected the clinical evolution after treatment in 73% of the small cell carcinomas. Most of the patients with benign diseases whose HA values exceeded the cutoff level suffered from acute infectious dis-eases. Once these cases were excluded, the specificity of HA value determination in the diagnosis of carcinoma was very high (serum 96%, BAL 100%). The determination of HA levels in serum or BAL did not have any prognostic value in this study.

We conclude that the HA levels in serum and BAL could be of interest as a tumor marker, especially in patients with small cell carcinoma.

Pulmonary toxicity and global gene expression changes in response to sub-chronic inhalation exposure to crystalline silica in rats

Exposure to crystalline silica results in serious adverse health effects, most notably, silicosis. An understanding of the mechanism(s) underlying silica-induced pulmonary toxicity is critical for the intervention and/or prevention of its adverse health effects. Rats were exposed by inhalation to crystalline silica at a concentration of 15 mg/m³, 6 hr/day, 5 days/week for 3, 6 or 12 weeks. Pulmonary toxicity and global gene expression profiles were determined in lungs at the end of each exposure period. Crystalline silica was visible in lungs of rats especially in the 12-week group. Pulmonary toxicity, as evidenced by an increase in lactate dehydrogenase (LDH) activity and albumin content and accumulation of macrophages and neutrophils in the bronchoalveolar lavage (BAL), was seen in animals depending upon silica exposure duration. The most severe histological changes, noted in the 12-week exposure group, consisted of chronic active inflammation, type II pneumocyte hyperplasia, and fibrosis. Microarray analysis of lung gene expression profiles detected significant differential expression of 38, 77, and 99 genes in rats exposed to silica for 3-, 6-, or 12-weeks, respectively, compared to time-matched controls. Among the significantly differentially expressed genes (SDEG), 32 genes were common in all exposure groups. Bioinformatics analysis of the SDEG identified enrichment of functions, networks and canonical pathways related to inflammation, cancer, oxidative stress, fibrosis, and tissue remodeling in response to silica exposure. Collectively, these results provided insights into the molecular mechanisms underlying pulmonary toxicity following sub-chronic inhalation exposure to crystalline silica in rats.

The Rise and Fall of Hyaluronan in Respiratory Diseases

In normal airways, hyaluronan (HA) matrices are primarily located within the airway submucosa, pulmonary vasculature walls, and, to a lesser extent, the alveoli. Following pulmonary injury, elevated levels of HA matrices accumulate in these regions, and in respiratory secretions, correlating with the extent of injury. Animal models have provided important insight into the role of HA in the onset of pulmonary injury and repair, generally indicating that the induction of HA synthesis is an early event typically preceding fibrosis. The HA that accumulates in inflamed airways is of a high molecular weight (>1600 kDa) but can be broken down into smaller fragments (<150 kDa) by inflammatory and disease-related mechanisms that have profound effects on HA pathobiology. During inflammation in the airways, HA is often covalently modified with heavy chains from inter-alpha-inhibitor via the enzyme tumor-necrosis-factor-stimulated-gene-6 (TSG-6) and this modification promotes the interaction of leukocytes with HA matrices at sites of inflammation. The clearance of HA and its return to normal levels is essential for the proper resolution of inflammation. These data portray HA matrices as an important component of normal airway physiology and illustrate its integral roles during tissue injury and repair among a variety of respiratory diseases.

Roles of Proteoglycans and Glycosaminoglycans in Wound Healing and Fibrosis

A wound is a type of injury that damages living tissues. In this review, we will be referring mainly to healing responses in the organs including skin and the lungs. Fibrosis is a process of dysregulated extracellular matrix (ECM) production that leads to a dense and functionally abnormal connective tissue compartment (dermis). In tissues such as the skin, the repair of the dermis after wounding requires not only the fibroblasts that produce the ECM molecules, but also the overlying epithelial layer (keratinocytes), the endothelial cells, and smooth muscle cells of the blood vessel and white blood cells such as neutrophils and macrophages, which together orchestrate the cytokine-mediated signaling and paracrine interactions that are required to regulate the proper extent and timing of the repair process. This review will focus on the importance of extracellular molecules in the microenvironment, primarily the proteoglycans and glycosaminoglycan hyaluronan, and their roles in wound healing. First, we will briefly summarize the physiological, cellular, and biochemical elements of wound healing, including the importance of cytokine cross-talk between cell types. Second, we will discuss the role of proteoglycans and hyaluronan in regulating these processes. Finally, approaches that utilize these concepts as potential therapies for fibrosis are discussed.

Transcriptomics analysis of lungs and peripheral blood of crystalline silica-exposed rats

Minimally invasive approaches to detect/predict target organ toxicity have significant practical applications in occupational toxicology. The potential application of peripheral blood transcriptomics as a practical approach to study the mechanisms of silica-induced pulmonary toxicity was investigated. Rats were exposed by inhalation to crystalline silica (15 mg/m(3), 6 h/day, 5 days) and pulmonary toxicity and global gene expression profiles of lungs and peripheral blood were determined at 32 weeks following termination of exposure. A significant elevation in bronchoalveolar lavage fluid lactate dehydrogenase activity and moderate histological changes in the lungs, including type II pneumocyte hyperplasia and fibrosis, indicated pulmonary toxicity in the rats. Similarly, significant infiltration of neutrophils and elevated monocyte chemotactic protein-1 levels in the lungs showed pulmonary inflammation in the rats. Microarray analysis of global gene expression profiles identified significant differential expression [>1.5-fold change and false discovery rate (FDR) p < 0.01] of 520 and 537 genes, respectively, in the lungs and blood of the exposed rats. Bioinformatics analysis of the differentially expressed genes demonstrated significant similarity in the biological processes, molecular networks, and canonical pathways enriched by silica exposure in the lungs and blood of the rats. Several genes involved in functions relevant to silica-induced pulmonary toxicity such as inflammation, respiratory diseases, cancer, cellular movement, fibrosis, etc, were found significantly differentially expressed in the lungs and blood of the silica-exposed rats. The results of this study suggested the potential application of peripheral blood gene expression profiling as a toxicologically relevant and minimally invasive surrogate approach to study the mechanisms underlying silica-induced pulmonary toxicity.

Genes of innate immunity and the biological response to inhaled ozone

Ambient ozone has a significant impact on human health. We have made considerable progress in understanding the fundamental mechanisms that regulate the biological response to ozone. It is increasingly clear that genes of innate immunity play a central role in both infectious and noninfectious lung disease. The biological response to ambient ozone provides a clinically relevant environmental exposure that allows us to better understand the role of innate immunity in noninfectious airways disease. In this brief review, we focus on (1) specific cell types in the lung modified by ozone, (2) ozone and oxidative stress, (3) the relationship between genes of innate immunity and ozone, (4) the role of extracellular matrix in reactive airways disease, and (5) the effect of ozone on the adaptive immune system. We summarize recent advances in understanding the mechanisms that ozone contributes to environmental airways disease.

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.

Extracellular superoxide dismutase in pulmonary fibrosis

Disruption of the oxidant/antioxidant balance in the lung is thought to be a key step in the development of many airway pathologies. Hence, antioxidant enzymes play key roles in controlling or preventing pulmonary diseases related to oxidative stress. The superoxide dismutases (SOD) are a family of enzymes that play a pivotal role protecting tissues from damage by oxidant stress by scavenging superoxide anion, which prevents the formation of other more potent oxidants such as peroxynitrite and hydroxyl radical. Extracellular SOD (EC-SOD) is found predominantly in the extracellular matrix of tissues and is ideally situated to prevent cell and tissue damage initiated by extracellularly produced ROS. EC-SOD has been shown to be protective in several models of interstitial lung disease, including pulmonary fibrosis. In addition, alterations in EC-SOD expression are also present in human idiopathic pulmonary fibrosis (IPF). This review discusses EC-SOD regulation in response to pulmonary fibrosis in animals and humans and reviews possible mechanisms by which EC-SOD may protect against fibrosis.

Inhibition of gelatinase B (matrix metalloproteinase-9) by dihydrolipoic acid

Alpha-lipoic acid (LA) is a disulphide-containing fatty acid that is absorbed from the diet and transported to tissues. Once it has been taken up by mammalian cells, LA is reduced to dihydrolipoic acid (DHLA), a vicinal dithiol, and rapidly effluxed into the extracellular milieu. We hypothesized that DHLA may be an effective inhibitor of human gelatinase B (GelB). Purified human GelB was incubated with 0 to 200 µmol/L DHLA, and residual enzyme activity was measured by HPLC using a fluorogenic substrate (matrix metalloproteinase substrate III). DHLA inhibited GelB in a dose-dependent fashion with an IC50of 20 µmol/L. Oxidation of DHLA resulted in a loss of DHLA's capacity to inhibit GelB. The DHLA-mediated inhibition of GelB was independent of the zinc concentration in the reaction buffer. DHLA had no inhibitory effect on gelatinase A. Zymographs of activated neutrophil lysates demonstrated that higher concentrations of DHLA also prevent the activation of GelB proenzyme. Bronchoalveolar lavage fluid from mice fed a diet enriched with LA showed significantly increased GelB inhibitory capacity (p = 0.0002 vs. regular diet). We conclude that DHLA can modulate neutrophil-derived GelB activity through direct inhibition of enzyme activity and by preventing the activation of GelB proenzyme.Key words: matrix metalloproteinases, pulmonary fibrosis, thiols, neutrophils, inflammation.

Hyaluronan and procollagen type III aminoterminal peptide in serum and bronchoalveolar lavage fluid from patients with pulmonary fibrosis

Previous studies of the collagen synthesis markers hyaluronan (hyaluronic acid) (HA) and procollagen type III aminoterminal peptide (PIIINP) in pulmonary fibrosis have reported elevated levels in bronchoalveolar lavage fluid (BALF) and suggested an association with disease activity. The objective of the present study was to evaluate whether HA and PIIINP in BALF and serum (S) correlated with paraclinical markers of disease activity (chest X-ray profusion score, pulmonary function tests (FEV1, FVC, TLC, DLCO)) in patients with pulmonary fibrosis. The material comprised 27 patients with biopsy-proven pulmonary fibrosis (12 cryptogenic and 15 due to connective tissue diseases) and 24 control subjects with normal lung function. BAL was performed in the right middle lobe with 250 ml saline. HA and PIIINP were measured in the cell-free BALF supernatant and in serum. Patients had higher BALF-HA (mean 86 +/- 17 (SEM) micrograms/l) than controls (39 +/- 2 micrograms/l (p < 0.01)), higher BALF-albumin (124 +/- 24 mg/l) than controls (58 +/- 4 mg/l (p < 0.01)) and higher BALF/S-HA ratio (2.4 +/- 0.6) than controls (1.2 +/- 0.6 (p < 0.05)). There were no significant differences respecting BALF-PIIINP, S-HA, or S-PIIINP. Patients (n = 14) with progressive disease had higher BALF-HA, higher BALF-albumin, higher S-PIIINP, and higher S-immunoglobulins than those with stable disease, but the differences did not reach statistical significance. Smokers (n = 18) had lower BALF-HA, lower S-HA, lower S-PIIINP, lower S-immunoglobulins, and higher lung function tests than non-smokers, but the differences did not reach statistical significance. In patients, significantly positive correlations were found between BALF-HA and BALF-albumin, between BALF-PIIINP and BALF-albumin, and a significantly negative correlation between S-PIIINP and TLC. None of the BALF or serum markers correlated with chest X-ray profusion score or any of the other lung function measurements. It is concluded that disease activity may be associated with elevated HA and PIIINP levels. Smoking may influence the immunological processes in pulmonary fibrosis and may be a confounder in studies of these patients.