Ex Vivo Effect of Varespladib on Secretory Phospholipase A2 Alveolar Activity in Infants with ARDS

Background

Secretory phospholipase A2 (sPLA2) plays a pivotal role in acute respiratory distress syndrome (ARDS). This enzyme seems an interesting target to reduce surfactant catabolism and lung tissue inflammation. Varespladib is a specifically designed indolic sPLA2 inhibitor, which has shown promising results in animals and adults. No specific data in pediatric ARDS patients are yet available.

Methods

We studied varespladib in broncho-alveolar lavage (BAL) fluids obtained ex vivo from pediatric ARDS patients. Clinical data and worst gas exchange values during the ARDS course were recorded. Samples were treated with saline or 10–40–100 µM varespladib and incubated at 37°C. Total sPLA2 activity was measured by non-radioactive method. BAL samples were subjected to western blotting to identify the main sPLA isotypes with different sensitivity to varespladib. Results was corrected for lavage dilution using the serum-to-BAL urea ratio and for varespladib absorbance.

Results

Varespladib reduces sPLA2 activity (p<0.0001) at 10,40 and 100 µM; both sPLA2 activity reduction and its ratio to total proteins significantly raise with increasing varespladib concentrations (p<0.001). IC₅₀ was 80 µM. Western blotting revealed the presence of sPLA2-IIA and –IB isotypes in BAL samples. Significant correlations exist between the sPLA2 activity reduction/proteins ratio and PaO₂ (rho = 0.63;p<0.001), PaO₂/FiO₂ (rho = 0.7; p<0.001), oxygenation (rho = −0.6; p<0.001) and ventilation (rho = −0.4;p = 0.038) indexes.

Conclusions

Varespladib significantly inhibits sPLA2 in BAL of infants affected by post-neonatal ARDS. Inhibition seems to be inversely related to the severity of gas exchange impairment.