Inhibitory Effects of Oxyradicals on Surfactant Function: Utilizing in Vitro Fenton Reaction

Abstract

The inhibitory effects of reactive oxygen species (ROS) on the surface tension-lowering abilities of three surfactants were compared: natural lung surfactant (NLS), KL4 surfactant containing synthetic peptide resembling the hydrophobic/hydrophilic domains of SP-B in an aqueous dispersion of phospholipids, and Survanta (SUR) containing SP-B and SP-C. The inhibitory concentrations of Fenton reactants (i.e. 0.65 mM FeCl2, 0.65 mM EDTA, 30 mM H2O2), deduced from dose-response plots of FeCl2 on minimum surface tension (MST) of SUR, were used to assess the Fenton effect on biophysical properties of various surfactants. Neither H2O2 (30 mM) nor FeCl2 with EDTA (both 0.65 mM) alone affected surfactant function, but when mixed together significantly increased (p < 0.01) the MST of SUR compared with KL4 (p < 0.05) in a FeCl2 concentration-dependent manner. This effect on NLS was not significant (p = 0.05) at similar phospholipid concentrations. Also, the range of increases in surface adsorption in mN/m at equilibrium surface tension (EST) was 27-40 for SUR, 36-44 for KL4, and 24-25 for NLS. We speculate that the presence of SP-A and the catalase content in NLS may have protective effects on inactivation of NLS by ROS. We conclude that the in vitro Fenton effect could be a valuable test system for comparing the inactivation range of surfactants by oxyradicals.

Pulmonary Surfactant Protein-A (SP-A) Restores the Surface Properties of Surfactant after Oxidation by a Mechanism That Requires the Cys6 Interchain Disulfide Bond and the Phospholipid Binding Domain

“…2A), where the increased absorbance produced by the Fenton reaction on BLES was approximately double H-BLES and triple the BLES control (BLES versus F-BLES p Ͻ 0.001, BLES versus H-BLES p Ͻ 0.001). These findings are consistent with and expand on previously published results reporting elevations in primary (conjugated dienes) and secondary lipid peroxidation products (thiobarbituric acid-reactive substances) after incubation of various surfactants with in vitro reactive oxygen species generating systems (21,22,38,39).…”

“…For oxidation by the Fenton reaction, BLES was incubated with 0.65 mM FeCl 2 , 0.65 mM sodium EDTA, and 30 mM H 2 O 2 in buffer A. These conditions approximate those used by a number of other investigators who conclude that they represent high physiological ranges (21)(22)(23).…”

The Future of Exogenous Surfactant Therapy

“…• Alterations in alveolar surfactant aggregates, whereby the most active large aggregate forms of surfactant are reduced in activity and/or percent content, while less active small aggregate forms of surfactant become more prevalent 72,80,[85][86][87][88][89][90][91][92][93] • Biophysical inhibition and/or chemical alteration of components in the alveolar surfactant film induced by cell membrane lipids, 75,79,83,[94][95][96] meconium, 97 or other substances present during the innate pulmonary inflammatory response, such as proteases, 98 phospholipases, 23,99,100 or reactive oxygen/nitrogen species 84,[101][102][103] • Altered synthesis, secretion, or composition of active surfactant due to injury-induced changes in alveolar type II pneumocytes, which are the primary cells of lung surfactant metabolism [104][105][106][107] All of the above mechanistic pathways of surfactant dysfunction are potentially present in the complex pathology of ALI/ARDS lung injury, and abnormalities in surfactant activity, large aggregate content, or composition have been well documented in bronchoalveolar lavage from patients with ALI/ARDS. 92,93,[108][109][110][111][112][113] Regardless of mechanism, the practical consequences of surfactant dysfunction in ALI/ARDS are not dissimilar to those in RDS.…”

A Pharmacoeconomic Analysis of In-Hospital Costs Resulting from Reintubation in Preterm Infants Treated with Lucinactant, Beractant, or Poractant Alfa

“…Compared with the amount of SP-B protein found in animalderived surfactants, the concentration of sinapultide in lucinactant is consistently much higher than the SP-B concentration in beractant. 34 In addition, lucinactant appears to be more resistant to inactivation by plasma proteins and oxidant species than other exogenous surfactants [35][36][37][38] and has also been shown to reduce plasma protein and neutrophil influx into the alveolar space in vivo and to modulate the inflammatory processes in vitro. 39,40 These factors may have resulted in improved overall lung function, potentially leading to lower rates of reintubation.…”