Fig. 1. Toll-like receptor 4 (TLR4) is a susceptible gene of increased pulmonary permeability and edema in ventilator-induced lung injury. (A ) Pulmonary permeability, as quantified by the amount of Evans Blue albumin (EBA) fluxing across pulmonary vascular barriers, by using mouse lung turbidity correction factor and expressed as permeability index calculated by dividing the EBA absorbance in lung tissue over plasma (see Materials and Methods). In TLR4-wild-type (WT) mice, high tidal volume ventilation (HTV) elicited significant increase in permeability compared with both control (CON) and low tidal volume ventilation (LTV) mice. In contrast, in TLR4-mutant mice, HTV did not increase pulmonary permeability compared with both LTV and CON mice groups. (B ) Pulmonary edema, as measured by lung wet/dry ratio, was significantly elevated in TLR4-WT mice after 4 h of HTV compared with LTV and unventilated CON mice. In contrast, HTV increased wet/dry ratio in TLR4-mutant mice was significantly attenuated compared with HTV in TLR4-WT mice. All data are presented as mean ± SD. *P < 0.05 compared with CON; # P < 0.05 compared with LTV. n = 5 in all groups.