Fig. 3.  Activation of nuclear factor-κB and mitogen-activated protein kinase (MAPK) in Toll-like receptor 4 (TLR4) wild-type (WT) mice after high tidal volume ventilation (HTV). A representative Western blot of expression of inhibitor of κB α (IκBα) (A ) and MAPK-extracellular signal-regulated kinase (ERK) phosphorylation, phosphorylated ERK (B ) in lungs isolated from TLR4-WT and TLR4-mutant mice from three independent experiments 4 h after spontaneous breathing with tracheotomy (control [CON]), mechanical ventilation with low tidal volume (LTV; 7 ml/kg), and HTV (20 ml/kg). All data are presented as mean ± SD. *P < 0.05 compared with CON in TLR4-WT mice. RDU = relative densitometry units.