The Src family tyrosine kinase, fyn, is a negative regulator of inflammation‐induced apoptosis in the lung (1176.6)

Abstract

Endothelial cell apoptosis is an early event in the development of acute respiratory distress syndrome (ARDS). We hypothesized that the Src‐family tyrosine kinases (STK) would differentially regulate endothelial cell apoptosis. Human pulmonary microvascular endothelial cells (hPMVEC) were transfected with siRNA against fyn or yes and then treated with cytomix (LPS, TNF‐α, IL‐1β and INF‐γ) or vehicle. Following cytomix treatment knock‐down of fyn resulted in greater levels of caspase 3 activity and lower viable cell numbers, while knock‐down of yes resulted in lower levels of caspase 3 activity and greater viable cell numbers, than in scramble treated control hPMVEC. We then tested the hypothesis that mice deficient in fyn will have greater lung injury following exposure to LPS. Wild‐type and fyn‐/‐ mice were given LPS 10 mg/kg or saline before harvesting tissues or measuring static lung compliance. The fyn‐/‐ mice had lower static lung compliance 24 hours after LPS compared to the WT mice. LPS exposure also caused more cleaved‐caspase 3 and p21 expression in the lungs of fyn‐/‐ mice than in WT mice. Real time‐PCR results showed that following LPS treatment the mRNA levels for arginase I, iNOS, and COX‐2 were greater in the fyn knockout mice than in WT mice. Our results demonstrate that fyn is an important negative regulator of LPS‐induced iNOS expression and apoptosis in cultured endothelial cell and in a mouse model of inflammatory lung disease.