Inflammatory response in human alveolar epithelial cells after TiO2 NPs or ZnO NPs exposure: Inhibition of surfactant protein A expression as an indicator for loss of lung function.

The increasing use of metal oxide nanoparticles (MONPs) as TiO2 NPs or ZnO NPs has led to environmental release and human exposure. The respiratory system, effects on lamellar bodies and surfactant protein A (SP-A) of pneumocytes, can be importantly affected. Exposure of human alveolar epithelial cells (A549) induced differential responses; a higher persistence of TiO2 in cell surface and uptake (measured by Atomic Force Microscopy) and sustained inflammatory response (by means of TNF-α, IL-10, and IL-6 release) and ROS generation were observed, whereas ZnO showed a modest response and low numbers in cell surface. A reduction in SP-A levels at 24 h of exposure to TiO2 NPs (concentration-dependent) or ZnO NPs (the higher concentration) was also observed, reversed by blocking the inflammatory response (by the inhibition of IL-6). Loss of SP-A represents a relevant target of MONPs-induced inflammatory response that could contribute to cellular damage and loss of lung function.

Pulmonary surfactant protein A isolation as a by-product of porcine pulmonary surfactant production

A pulmonary surfactant reduces surface tension at the air/liquid interface of the alveoli and stabilizes alveoli at low lung volumes. Surfactant deficiency and dysfunction were shown to be present in a number of pulmonary diseases, and surfactant replacement therapy is the common clinical conduct. The hydrophilic SP-A (surfactant protein A) is absent when solvent extraction was used during exogenous surfactant production. Addition of SP-A to the surfactant preparation increases the surface activity and completely counteracts inhibition by blood proteins. SP-A recognizes and binds to carbohydrate structures on the surfaces of pathogenic micro-organisms, and acts as opsonins or cross-linking molecules by binding to a variety of cells that participate in the pulmonary immune response. The purification procedure yielded 206 mg of high-purity SP-A/kg of porcine lung, as judged by gel filtration, SDS/PAGE and Western blotting. The electrophoretic profiles obtained showed that pure SP-A consists of proteins of wide molecular mass in the range 26-36 kDa and a dimer in the range 56-60 kDa. The Western-blot results displayed the same band pattern profile after incubating the membrane using a commercially available polyclonal anti-SP-A antibody produced in goat. Gel-filtration experiments confirmed the molecular mass of SP-A in 10 mM NaCl solution. The isolated SP-A showed mannose-binding ability, representative of its functionality.