Viscosity Of Cystic Fibrosis Sputum Research Articles

Dornase alfa and progression of lung disease in cystic fibrosis

Obstruction, infection, and inflammation lead to progressive and irreversible lung destruction in cystic fibrosis (CF). Neutrophil-derived DNA contributes to thick, viscous secretions. Dornase alfa hydrolyzes DNA, reducing the viscosity of CF sputum. Clinical trials have shown that dornase alfa improves forced expiratory volume in one second (FEV1). Immediate improvement is important, but long term survival requires slowing the rate of lung function decline. Demonstrating changes in rate of decline requires long term studies with many patients, which are impractical for clinical trials. Observational studies such as the Epidemiologic Study of Cystic Fibrosis (ESCF) can address rate of decline in lung function, and is being used to evaluate the long-term effectiveness of dornase alfa. CF patients age 8–38 years when initially treated with dornase alfa (index event) were compared to patients not treated (for 2 years before and 2 years after index). In a preliminary analysis, FEV1 at index for the dornase alfa group (n = 2,706) was 80.5% predicted, and for the comparator group (n = 3,991) 86.7% predicted. The estimated rate of FEV1 decline before index for the dornase alfa group was −2.81 and for the comparator group −0.85% predicted/year. After index, the rate of decline for the dornase alfa group was −1.53% predicted/year (46% reduction, P < 0.001), with no change in the comparator group. These preliminary results suggest that initiating dornase alfa is associated with both an acute improvement in FEV1 and a slowing of the rate of FEV1 decline. Analysis is ongoing to further evaluate this association. Pediatr Pulmonol. 2008; 43:S24–S28. © 2008 Wiley-Liss, Inc.

Pharmacology, clinical efficacy and safety of recombinant human DNase in cystic fibrosis

Recombinant human DNase (rhDNase) is a mucolytic agent that is primarily used to improve mucociliary clearance in cystic fibrosis (CF). rhDNase is a recombinant human enzyme that is synthesized in a Chinese hamster ovary cell line. rhDNase enzymatically cleaves extracellular DNA into molecules of shorter length. CF sputum shows high concentrations of DNA released by disintegrating inflammatory cells. Free DNA contributes to the abnormally high viscosity of CF sputum and therefore forms an important target in the treatment of CF lung disease. Clinical studies have shown that daily nebulization of rhDNase is associated with an increase in lung function and a decrease in the frequency of exacerbations in patients with CF.

Anionic poly(amino acid)s dissolve F-actin and DNA bundles, enhance DNase activity, and reduce the viscosity of cystic fibrosis sputum

Bundles of F-actin and DNA present in the sputum of cystic fibrosis (CF) patients but absent from normal airway fluid contribute to the altered viscoelastic properties of sputum that inhibit clearance of infected airway fluid and exacerbate the pathology of CF. Previous strategies to remove these filamentous aggregates have focused on DNase to enzymatically depolymerize DNA to constituent monomers and gelsolin to sever F-actin to small fragments. The high densities of negative surface charge on DNA and F-actin suggest that the bundles of these filaments, which alone exhibit a strong electrostatic repulsion, may be stabilized by multivalent cations such as histones, antimicrobial peptides, and other positively charged molecules prevalent in airway fluid. This study reports that bundles of DNA or F-actin formed after addition of histone H1 or lysozyme are efficiently dissolved by soluble multivalent anions such as polymeric aspartate or glutamate. Addition of poly-aspartate or poly-glutamate also disperses DNA and actin-containing bundles in CF sputum and lowers the elastic moduli of these samples to levels comparable to those obtained after treatment with DNase I or gelsolin. Addition of poly-aspartic acid also increased DNase activity when added to samples containing DNA bundles formed with histone H1. When added to CF sputum, poly-aspartic acid significantly reduced the growth of bacteria, suggesting activation of endogenous antibacterial factors. These findings suggest that soluble multivalent anions have potential alone or in combination with other mucolytic agents to selectively dissociate the large bundles of charged biopolymers that form in CF sputum.

Gelsolin activates DNase I in vitro and cystic fibrosis sputum.

Because actin can form a complex in vitro containing both gelsolin and DNase I, gelsolin and DNase I have been assumed to bind independently to actin. Although this assumption is consistent with the known crystalline structures of gelsolin with one actin and of actin with DNase I, which suggest that the binding sites on actin for both gelsolin and DNase I are distinct and separate, we propose that a second actin binding site on gelsolin competes with DNase I for actin. Since actin is an inhibitor of DNase I, competition at the second binding site results in activation of DNase I by gelsolin. Covalent cross-linking experiments confirm that DNase I prevents dimerization of actin by gelsolin, consistent with displacement of one actin from gelsolin by DNase I. Activation of DNase I by gelsolin is a novel function for a cytoskeletal protein and could have broad implications for biology, such as a role in initiating apoptosis. These results also may explain why both gelsolin and DNase I decrease sputum viscosity in cystic fibrosis (CF). While the activity of DNase I had originally been attributed to fragmentation of DNA, subsequent data suggested that both gelsolin and DNase I may affect viscosity by depolymerizing filamentous actin. The current results alternatively suggest aht dissociation of the actin-DNase I complex by gelsolin in CF sputum results in activation of the nuclease activity of constitutive DNase I. The nuclease activity of DNase I alone is therefore sufficient to explain the effects of both gelsolin and DNase I on CF sputum.

Tyloxapol inhibits NF-kappa B and cytokine release, scavenges HOCI, and reduces viscosity of cystic fibrosis sputum.

Cystic fibrosis (CF) patients develop progressive cytokine-mediated inflammatory lung disease, with abundant production of thick, tenacious, protease- and oxidant-rich purulent airway secretions that are difficult to clear even with physiotherapy. In the search for a potential treatment, we have tested tyloxapol, an alkylaryl polyether alcohol polymer detergent previously used as a mucolytic agent in adult chronic bronchitis. Tyloxapol inhibits activation of the transcription factor nuclear factor-kappa B (NK-kappa B), reduces resting secretion of the cytokine interleukin-8 (IL-8) in cultured human monocytes, and inhibits lipopolysaccharide (LPS)-stimulated release of tumor necrosis factor-alpha (TNF-alpha), IL-1 beta, IL-6, IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), and the eiconsanoids thromboxane A2 and leukotriene B4 (LTB4). We have previously shown that tyloxapol is a potent antioxidant for hydroxyl radicals ( OH). Tyloxapol (0.05 to 0.1% wt/vol) effectively scavenges the oxidant hypochlorous acid (HOCl; 1 to 7.5 mM) in vitro, and protects from HOCl-mediated lung injury in rats. Tyloxapol also reduces the viscosity of CF sputum (from 463 +/- 133 to 128 +/- 52 centipoise). We conclude that tyloxapol is potentially useful as a new antiinflammatory therapy for CF lung disease, and could possibly promote clearance of secretions in the CF airway.

Reduction in Viscosity of Cystic Fibrosis Sputum in Vitro by Gelsolin

Obstruction of airways by viscous sputum causes lung damage in patients with cystic fibrosis (CF). Sputum samples from CF patients were shown to contain filamentous actin. Human plasma gelsolin, a protein that severs actin filaments, rapidly decreased the viscosity of CF sputum samples in vitro. Gc globulin and deoxyribonuclease I, proteins that sequester monomeric actin but do not sever actin filaments, were less efficient than gelsolin in diminishing sputum viscosity. These results suggest that gelsolin may have therapeutic potential as a mucolytic agent in CF patients.

Recombinant human DNase I reduces the viscosity of cystic fibrosis sputum.

Respiratory distress and progressive lung destruction in cystic fibrosis can be attributed to bacterial persistence and the accumulation of viscous purulent secretions in the airways. More than 30 yr ago it was suggested that the large amounts of DNA in purulent secretions contribute to its viscosity and that bovine pancreatic DNase I could reduce the viscosity. To evaluate the potential clinical utility of recombinant human DNase I (rhDNase) in the treatment of cystic fibrosis, we have cloned, sequenced, and expressed rhDNase. Catalytic amounts of rhDNase greatly reduce the viscosity of purulent cystic fibrosis sputum, transforming it within minutes from a nonflowing viscous gel to a flowing liquid. The reduction in viscosity is associated with a decrease in size of DNA in the sputum. Inhalation of a rhDNase aerosol may be a simple direct approach that will help individuals with cystic fibrosis and other patients with pneumonia or bronchitis to clear their airways of purulent secretions.

Effect of tolazoline hydrochloride on sputum viscosity in cystic fibrosis : E. A. Feather and G. Russell. Thorax 25:732 (November) 1970

Effect of tolazoline hydrochloride on sputum viscosity in cystic fibrosis : E. A. Feather and G. Russell. Thorax 25:732 (November) 1970

Sputum viscosity in cystic fibrosis of the pancreas and other pulmonary diseases

Studies of sputum viscosity from patients with cystic fibrosis and other diseases showed that in cystic fibrosis mucoid sputum was less viscous than that produced by patients with other respiratory diseases. Unlike bronchitic sputum, the viscosity of cystic fibrosis sputum increased markedly with purulence. Evidence is discussed to suggest that factors in addition to sputum viscosity may be of importance in initiating pulmonary disease in cystic fibrosis.