Synergistic protection in lung ischemia-reperfusion injury with calcineurin and thrombin inhibition.
BACKGROUND
Ischemia-reperfusion injury impairs lung transplant outcomes. The transcription factors, activator protein-1, and nuclear factor kappa B, are activated early in reperfusion and drive the development of injury. Thrombin inhibition with hirudin, and calcineurin inhibition with tacrolimus have independently been shown to ameliorate lung ischemia-reperfusion injury by reducing activator protein-1 and nuclear factor kappa B activation, respectively. However, high doses were required to achieve protection using individual agents, raising concerns about potential toxicities. We sought to determine if low-dose combination therapy reduced injury through synergistic inhibition of pretranscriptional signaling events.


METHODS
Rats were pretreated with either intravenous hirudin or tacrolimus at low doses or high doses, or both at low doses, prior to undergoing left lung ischemia and reperfusion. Lungs were assessed for markers of lung injury, including bronchoalveolar lavage cytokine-chemokine content and transcription factor transactivation of activator protein-1 and nuclear factor kappa B.


RESULTS
High-dose monotherapy with hirudin or tacrolimus reduced lung injury and transactivation of activator protein-1 and nuclear factor kappa B activation, respectively, whereas low-dose monotherapy with either agent did not alter transcription factor activation or lung injury compared with positive controls. Low-dose combination therapy was more protective than high-dose monotherapy with either drug, and correlated with a reduction in activation of both transcription factors and their associated cytokines.


CONCLUSIONS
The significant decrease in lung injury severity and transcription factor activation with combined pathway inhibition suggests pretranscriptional signaling redundancy between the calcineurin and thrombin dependent pathways in lung reperfusion injury.
McCourtie
Anton S
AS
Department of Surgery, Division of Cardiothoracic Surgery, University of Washington Medical Center, Seattle, Washington, USA.
Merry
Heather E
HE
Wolf
Patrick S
PS
FitzSullivan
Elizabeth
E
Keech
John C
JC
Farivar
Alexander S
AS
Mulligan
Michael S
MS
D000818:Animals; D065095:Calcineurin Inhibitors; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D024764:Hirudin Therapy; D008168:Lung / Q000098:blood supply*; D051381:Rats; D020318:Rats, Long-Evans; D015427:Reperfusion Injury / Q000517:prevention & control*; D016559:Tacrolimus / Q000627:therapeutic use*; D013917:Thrombin / Q000037:antagonists & inhibitors*
D065095:Calcineurin Inhibitors; D013917:Thrombin; D016559:Tacrolimus