Pulmonary overexpression of inhibitor κBα decreases the severity of ventilator-induced lung injury in a rat model

Background: Activation of the nuclear factor-κB (NF-κB) pathway is central to the pathogenesis of lung injury and inflammation. We determined whether targeted overexpression of inhibitor-κBα (IκBα) in the lung could decrease the severity of ventilator-induced lung injury (VILI). Methods: Anaesthetized adult male Sprague–Dawley rats were randomly allocated to undergo intratracheal instillation of: (i) vehicle alone (surfactant, n=10); (ii) 1×10¹⁰ adeno-associated virus encoding IκBα (AAV-IκBα, n=10); (iii) 5×10¹⁰ AAV-IκBα (n=10); and (iv) 1×10¹⁰ AAV-Null (n=5). This was followed by 4 h of injurious mechanical ventilation. Subsequent experiments examined the effect of IκBα overexpression in animals undergoing ‘protective’ mechanical ventilation. Results: IκBα overexpression increased survival duration at both the lower [3.8 h (0.4)] and higher [3.6 h (0.7)] doses compared with vehicle [2.7 h (1.0)] or the null transgene [2.2 h (0.8)]. IκBα overexpression reduced the alveolar–arterial oxygen gradient (kPa) at both the lower [53 (21)] and higher [52 (19)] doses compared with vehicle [75 (8.5)] or the null transgene [70 (15)], decreased alveolar neutrophil infiltration, and reduced alveolar concentrations of interleukin (IL)-1β and IL-10. The lower IκBα dose was as effective as the higher dose. IκBα overexpression had no effect in the setting of protective lung ventilation. Conclusions: Inhibition of pulmonary NF-κB activity by IκBα overexpression reduced the severity of VILI in a rat model.