Molecular mechanisms affecting LPS‐induced endothelial cells (EC) hyperpermeability

Abstract

LPS decreases transendothelial electrical resistance (TER), increases endothelium permeability for large molecules, and leads to sizeable gap formation in cells grown on glass coverslips. Forskolin suppresses LPS‐induced drop in TER and gap formation in EC monolayer, concomitant with the decrease in LPS‐induced myosin light chain (MLC) phosphorylation. Both protein kinase A activator 6‐Bnz‐cAMP and Epac activator O‐Me‐cAMP have similar effect on LPS‐induced TER changes and gap formation; however, only 6‐Bnz‐cAMP decreases LPS‐induced MLC phosphorylation and increases phosphorylation of VASP. Inhibition of MLC phosphorylation with Rho kinase inhibitor Y27632 significantly suppresses LPS‐induced gap formation. VASP depletion with siRNA exacerbates LPS‐induced changes in TER. These data suggest that MLC‐dependent actomyosin contraction contributes to LPS‐induced barrier dysfunction, whereas VASP‐dependent organization of actin near cell membrane plays barrier‐protective role. We next studied the role of p38 pathway in LPS‐induced pulmonary edema. p38 inhibitor SB203580 significantly suppresses LPS‐induced gap formation and permeability for large molecules, indicative of barrier‐disruptive role of p38 pathway. HSP27 depletion by siRNA exacerbates LPS‐induced changes in TER and gap formation, suggesting barrier‐protective role of this protein. This work was supported by HL‐067307.