thymosin-beta(4) and Cystic-Fibrosis

A high-performance liquid chromatography (HPLC) methodology is presented. Using bovine and rabbit F- and G-actin, this methodology results in both fractions as being well-resolved peaks, which were confirmed by dot blot immunoassay and fluorescence microscopy. F- and G-actin were incubated with thymosin β4 (Tβ4) and DNase and then analyzed by HPLC, which indicated that Tβ4 and DNase inhibit G-actin polymerization and that Tβ4 depolymerizes F-actin in a dose- and time-dependent manner. The F- and G-actin content in sputum from healthy controls and cystic fibrosis (CF) patients were measured by HPLC before and after incubation with Tβ4, DNase, and gelsolin. These data demonstrate higher quantities of F-actin in the sputum of CF patients compared to healthy individuals, and also demonstrate a significantly increased F/G-actin ratio in CF sputum. Further, Tβ4, DNase, and gelsolin each increase the depolymerization of F-actin in CF sputum in a dose-dependent fashion that is additive when these agents are combined.

Topics: Actins; Chromatography, High Pressure Liquid; Cystic Fibrosis; Humans; Sputum; Thymosin

Mucus clearance is the first line of pulmonary defense against inhaled irritants, microorganisms, and allergens. In health, the gel-forming mucins are the principal polymeric components of airway mucus but in cystic fibrosis (CF), the necrotic death of inflammatory and epithelial cells releases a network of copolymerized extracellular DNA and filamentous (F-) actin-producing secretions that are similar to pus and difficult to clear by cilia or airflow. The large amounts of F-actin in CF sputum suggested that thymosin beta4 (Tbeta4) or gelsolin could depolymerize the secondary polymer network of CF sputum. Dose-dependent CF sputum rheology and polymer structure were measured before and after the addition of excipient, dornase alfa, Tbeta4, gelsolin, and Tbeta4 or gelsolin with dornase for 30 min. Sputum was also incubated with Tbeta4 30 microg/mL, gelsolin 10 microg/mL or excipient for 0, 5, 10, 15, 20, or 60 min. There was a dose-dependent decrease in cohesivity with Tbeta4 and a time-dependent decrease in cohesivity at 30 microg/mL. With the combination of dornase alfa and Tbeta4 at 1.5 microg/mL, there was a 65% decrease in elasticity (P = 0.013). There was a time-dependent decrease in cohesivity (P = 0.0004) and elasticity (P = 0.047) with gelsolin and a dose-dependent fall in cohesivity (P = 0.0008). An apparent synergy of Tbeta4 or gelsolin on actin and dornase on DNA may be explained by the combined effect of actin depolymerization and DNA filament severing or by virtue of actin depolymerization increasing the effectiveness of dornase alfa.

Topics: Actins; Adolescent; Adult; Cystic Fibrosis; DNA; Gelsolin; Humans; Mucins; Pseudomonas aeruginosa; Pseudomonas Infections; Rheology; Sputum; Thymosin

Filamentous actin (F-actin) forms polymers that contribute to the abnormal biophysical properties of sputum. Thymosin beta4 (Tbeta4) is the major monomeric actin-sequestering peptide in cells and can depolymerize F-actin. Tbeta4 could potentially decrease sputum viscoelasticity and adhesivity and improve sputum clearance.. Sputum was collected during pulmonary function testing from 17 subjects during a cystic fibrosis (CF) center visit. Sputum rheology, cough and ciliary transportability, and interfacial tension were measured before and after the addition of dornase alfa at 30 microg/mL; Tbeta4 at 0.3, 3, 30, and 150 microg/mL; and Tbeta4 with dornase alfa at 1.5 microg/mL each. Sputum was separately incubated with Tbeta4 at 30 microg/mL for 0, 10, 20, or 60 min.. There was a direct relationship between actin filament length and sputum cohesivity. There was a dose-dependent threshold decrease in cohesivity with Tbeta4 and a time-dependent decrease in cohesivity over 60 min at 30 microg/mL. With the combination of dornase alfa and Tbeta4 at 1.5 microg/mL each, there was a 70% decrease in G*s and a 65% decrease in G' at 1 rad/s (p = 0.013). There was a 44% increase in cough transportability of sputum in vitro (p = 0.037) and a 71% increase in mucociliary transportability of sputum in vitro (p = 0.013) relative to control with the combination of dornase alfa and Tbeta4, but no significant change with dornase alfa or Tbeta4 alone at any concentration.. Actin polymer filament length is correlated with sputum cohesivity. Tbeta4 depolymerizes CF sputum actin in both a dose-dependent and a time-dependent manner. An apparent synergy of Tbeta4 on actin and dornase on DNA may be explained by the combined effect of actin depolymerization and DNA filament severing or by virtue of actin depolymerization increasing the effectiveness of dornase alfa.

Topics: Actins; Adolescent; Adult; Cystic Fibrosis; Deoxyribonuclease I; DNA; Female; Humans; Lung; Male; Microscopy, Confocal; Respiratory Function Tests; Rheology; Sputum; Thymosin; Time Factors