Mechanisms of imporvement following functional inhibition of nitrosative stress after brun and smoke-induced acute lung injury

Severe trauma, caused by flame burn and smoke (B + S) inhalation induces acute lung injury (ALI) and results in the loss of pulmonary function. A cascade of molecular and cellular events initiates the formation of reactive oxygen/nitrogen species (ROS/RNS) that in turn drives an inflammatory response and consequently cell death through hyper-activation of poly (ADP-ribose) polymerase (PARP-1). The purpose of this study was to investigate and counteract pulmonary dysfunction associated with nitrosative stress generated after B + S inhalation injury in an ovine and murine model of ALI. \r\nIn our time course experiment, sheep were sacrificed at 4, 8, 12, 18 and 24 hours post B + S injury. From 4 through 24 hours, there was a progressive increase in airway obstruction and lung edema formation. Furthermore, injury was associated with increased ROS/RNS generation, pro-inflammatory cytokine expression and neutrophil accumulation. Additionally, PARP-1 enzymatic activity increased in parallel with Hoechst 3324 nuclear staining in sheep lung sections.\r\nTreatment after ALI with a hydrogen sulfide (H2S) donor compound, a peroxynitrite scavenger, was tested to determine the effect on mortality, pulmonary shunt fraction and gas exchange. The H2S donor increased animal survival. Additionally the rapid decline in PaO2/FiO2, reduced the pulmonary shunt fraction and elevated airway pressures were improved. Likewise, the lung histological assessment demonstrated marked increase in aerated areas in lung sections.\r\nBurn and smoke injury generates reactive oxygen species and nitrogen species and influences inflammatory cytokine expression. Pro- and anti-inflammatory cytokine protein levels were measured in the lung parenchyma as well as 3-nitrotyrosine and protein carbonyl formation (indices of RNS and ROS generation, respectively). In our murine study, treatment with the H2S donor significantly reduced the pro- inflammatory cytokine level and increased the anti-inflammatory cytokine concentration in the lung. Additionally, ROS and RNS generation were significantly lowered. \r\nThese results demonstrate the effectiveness of inhibiting nitrosative stress after burn and smoke injury using a H2S donor and a possible mechanism for improved outcomes may be the altered the expression pattern of pro- and anti-inflammatory cytokines and ROS generation which may contribute to dysfunctional outcomes after B+ S inhalation injury.\r\n\r\n