Environmental Pollutant Ozone Causes Damage to Lung Surfactant Protein B (SP-B)

Abstract

Lung surfactant protein B (SP-B) is an essential protein found in the surfactant fluid at the air–water interface of the lung. Exposure to the air pollutant ozone could potentially damage SP-B and lead to respiratory distress. We have studied two peptides, one consisting of the N-terminus of SP-B [SP-B(1–25)] and the other a construct of the N- and C-termini of SP-B [SP-B(1–25,63–78)], called SMB. Exposure to dilute levels of ozone (∼2 ppm) of monolayers of each peptide at the air–water interface leads to a rapid reaction, which is evident from an increase in the surface tension. Fluorescence experiments revealed that this increase in surface tension is accompanied by a loss of fluorescence from the tryptophan residue at the interface. Neutron and X-ray reflectivity experiments show that, in contrast to suggestions in the literature, the peptides are not solubilized upon oxidation but rather remain at the interface with little change in their hydration. Analysis of the product material reveals that no cleavage of the peptides occurs, but a more hydrophobic product is slowly formed together with an increased level of oligomerization. We attributed this to partial unfolding of the peptides. Experiments conducted in the presence of phospholipids reveal that the presence of the lipids does not prevent oxidation of the peptides. Our results strongly suggest that exposure to low levels of ozone gas will damage SP-B, leading to a change in its structure. The implication is that the oxidized protein will be impaired in its ability to interact at the air–water interface with negatively charged phosphoglycerol lipids, thus compromising what is thought to be its main biological function.

Cobalt(III)‐Mediated Permanent and Stable Immobilization of Histidine‐Tagged Proteins on NTA‐Functionalized Surfaces

“…The other concern is the sensitivity of proteins toward oxidants, which is difficult to generalize and has to be considered case by case. Although some proteins, including cysteine‐rich proteins, are prone to oxidation and can lose their activity upon treatment with H 2 O 2 , other proteins, such the extracellular matrix proteins, can resist oxidants and are regulated by oxidative stress . Therefore, the herein‐presented method is restricted to proteins that are not sensitive to oxidation.…”

“…Although some proteins,i ncluding cysteine-rich proteins,a re prone to oxidation andc an lose their activity upon treatmentw ith H 2 O 2 ,o ther proteins, such the extracellular matrix proteins,can resist oxidants and are regulated by oxidatives tress. [43][44][45][46][47] Therefore, the herein-presented methodi s restricted to proteins that are not sensitive to oxidation. To demonstrate that the oxidation of Co 2 + to Co 3 + with 10 mm H 2 O 2 is compatible with the immobilization of activep roteins, we used His6-tagged ProteinA, which binds IgG antibodies and is widely used to immobilize antibodies in an oriented fashion.…”

Is phosphatidylglycerol essential for terrestrial life?

“…Presumably, the stiffening effect of cholesterol is therefore modulated by PG and restricted to areas that contain less of it. This may contribute to the observation of a fluidising effect of the presence of PG in model systems of LS [37].…”

“…The concentration of PG in LS is around 10 %, which is considerably higher than the concentration of PG in the membranes of mammalian cells [12,[33][34][35] and of lung cells in particular [36]. Studies of ozone-based damage have shown that PG has a fluidising effect on LS [37].…”

Stability of an amphipathic helix-hairpin surfactant peptide in liposomes

“…animal-derived, lung surfactants with native SP-B and SP-C have not been published except that package inserts mention a shelf-life of 18 months during storage at a temperature of 2° to 8°C. Oxidation of SMB by exposure to the air pollutant ozone negatively affects its surface activity, probably by partial unfolding that impairs its interaction with negatively charged PG lipids at the air-water interface [31]. Exposure of mixed monolayers composed of POPC and DPPC to ozone does not lead to a loss of DPPC from the air-water interface, but surface activity changes significantly secondary to oxidative damage of the unsaturated POPC [32].…”