Background
Inflammation and pulmonary injury caused by mechanical ventilation is a complex process in which long pentraxin 3 (PTX3) is suggested to play an important role. The effect of mechanical stretch on PTX3 mRNA and protein expression in human alveolar epithelial cells (A549) was investigated.
Material and Method
Immortalized A549 cells were exposed to tightly controlled and physiologically relevant cyclic mechanical stretch. A549 cells grown on collagen I BioFlex plates were exposed to square cyclic stretch at 0.3 Hz using the Flexercell system with 6% or 20% elongation of cells. In another group, cells were pretreated with small interfering RNA directed against PTX3 before stretch. After stretching, conditioned media and cells were collected and analyzed by Western blotting. Real-time PCR of cDNA generated from the stretched cells was performed. Apoptosis and viability of the cells following treatment were assessed using standard procedures.
Results
Mechanical cyclic stretch of 20% elongation led to increased PTX3 gene expression, increased release of PTX3 protein, and induced apoptosis and necrosis in A549 cells. Expression of PTX3 highly correlated with the severity of apoptosis. However, the results suggest that PTX3 expression was significantly reduced by pretreatment of the A549 cells with small interfering RNA of PTX3.
Conclusions
PTX3 may be an important mediator of lung tissue damage associated with mechanical stretch. Determining the production and regulation of PTX3 during mechanical ventilation may be critical in preventing or reducing ventilator-induced lung injury.

Keywords: Pulmonary Alveoli - metabolism, Epithelial Cells - metabolism, DNA Primers, Cell Line, Transformed, C-Reactive Protein - metabolism, Base Sequence, RNA, Small Interfering, Serum Amyloid P-Component - metabolism