Production and delivery of a recombinant modified superoxide dismutase protein to a rodent ARDS model by vibrating mesh nebulisation

Acute respiratory distress syndrome (ARDS) is a life-threatening disease and is characterised by increased permeability of the alveolar-capillary membrane, pulmonary oedema and the acute onset of hypoxemia. During the acute phase of ARDS, neutrophil infiltration into the alveolar space results in uncontrolled release of reactive oxygen species and proteases that overwhelm antioxidant defences and leads to lung cell injury. It has been shown that overexpression of pulmonary extracellular superoxide dismutase attenuates endotoxin-induced acute lung injury (Hassett, P et al. Intensive Care Med. 2011; 37:1680-7). In our study, fusion proteins incorporating human Cu-Zn-superoxide dismutase protein (rhSODp) were expressed in Escherichia coli (E. coli) BL21 using co-overproduction of GroEL-GroES chaperones. Fusion proteins exhibited high superoxide dismutase activity in fused and unfused formats, and protected human bronchial epithelial cells from oxidative damage. The rhSODp protein retained activity post-nebulisation and exhibited no adverse effects in an in vivo rat lung. When administered via instillation or nebulisation to the lung of an E. coli induced pneumonia rat, rhSODp improved arterial oxygenation and lactate levels compared to vehicle controls. Basic lung compliance was improved when the protein was delivered by instillation. Lung white cell infiltration was reduced by treatment with instilled and nebulised rhSODp and attenuation of CINC-1 and IFN-γ pro-inflammatory cytokine production was observed. The results provide a basis for further investigation of the therapeutic potential of non-fused rhSODp protein in the treatment of ARDS.