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426: Vascular endothelial growth factor-C enhances experimental obliterative bronchiolitis by inducing lymphangiogenesis
The Journal of Heart and Lung Transplantation Volume 26, Number 2S
Abstracts
Table 1 hIL-10 Levels (mean, pg/ml, Pig IL-10 group) Hours EVLP
0h
6h
9h
12 h
Perfusate BAL
0 0
0 37.10
13.58 300.33
42.26 1384
Table 2 Pig Lung Function After 12 hours EVLP
IL-10 Empty Control
Compliance (ml/cmH2O)
PVR (dynes ⴛ sec ⴛ cmⴚ5)
Delta PO2 (mmHg)
27 ⫾ 2 13 ⫾ 5.6 24.3 ⫾ 5.5
631.7 ⫾ 166 1219 ⫾ 140 791.1 ⫾ 140
460 ⫾ 71 113 ⫾ 9.8 404 ⫾ 138
424 ANTI-CD20 PREVENTS ALLOANTIBODY PRODUCTION AND ATTENUATES CARDIAC ALLOGRAFT VASCULOPATHY IN MONKEYS TREATED WITH ANTI-CD154 S.S. Kelishadi,1 T. Zhang,1 B.N. Nguyen,1 G. Wu,1 E. Welty,1 C.J. Avon,1 S. Pfeiffer,1 C. Schroder,1 A. Azimzadeh,1 R.N. Pierson, III,1 1Cardiac Surgery, University of Maryland School of Medicine and Baltimore VAMC, Baltimore, MD Purpose: Blockade of CD40-154 prolongs cardiac allograft survival in cynomolgus macaques, but cardiac allograft vasculopathy (CAV) causes graft failure, and is closely associated with appearance of anti-donor antibody (Ab). We hypothesized that depletion of CD20⫹ B-cells might interfere with formation of anti-donor plasma cells and alloantibodies, and thus prevent CAV. Methods and Materials: Thirty MLR-mismatched heterotopic cardiac cynomolgus allograft recipients were treated with anti-CD154 high intensity monotherapy (␣CD154; n⫽17, 6 with ATG) or ␣CD154 with additional ␣CD20 (20mg/kg q wk for 4 weeks: ␣CD154⫹␣CD20; n⫽13, 11 with ATG). Some animals received an additional donor thymus graft or bone marrow infusion. Acute rejection was usually treated with steroids; graft survival was censored at 90 days. Results: 10 animals died with beating grafts, mainly with ATG-associated lung pathology, and are excluded from the survival analysis. Graft survival with ␣CD154⫹␣CD20 (median ⬎90d) and proportion of grafts surviving to 90 days (5/5) was significantly increased relative to ␣CD154 (median 43d, IQR(25-75) 35-82d, p⬍0.007; 3/15 ⬎90d). With ␣CD154, 15/15 (100%) developed anti-donor IgM and 14/15 (93%) IgG, usually weeks before graft failure, whereas no IgG was detected in samples analyzed to date from the ␣CD154⫹␣CD20 group, and weak IgM was transiently detected in only one animal. All ␣CD154 grafts had severe CAV (score ⱖ3 on 0-4 scale), in many instances with fibrosis and unscorable vessels due to infarction. In stark contrast, ␣CD154⫹␣CD20 was associated with CAVⱕ 1 in 4 of 5 grafts, and CAV 2 in the 5th, and preserved myocardial architecture. Conclusions: Using ␣CD20 with ␣CD154 is associated with decreased elaboration of alloAb, prolonged graft survival to ⬎90 days, and significant attenuation of CAV. Concomitant thymus transplant or ATG induction did not appear to be necessary to this effect; ATG is associated with significant morbidity. These findings suggest that ␣CD20 may reduce the incidence of CAV, perhaps by inhibiting alloAb. 425 VAD-ASSOCIATED THROMBOEMBOLISM: POSSIBLE ROLE FOR INTRINSIC COAGULATION CASCADE S. Kallam,1 R.N. Sangrampurkar,1 Z. Kon,1 R.N. Pierson,1 B.P. Griffith,1 R.S. Poston,1 1Cardiac Surgery, University of Maryland Medical Center, Baltimore, MD
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Purpose: Thromboembolism (TE) in ventricular assist device (VAD) patients often follow acute bursts in thrombin production. The purpose of this study was to further investigate the factors that lead to this dysregulated thrombin metabolism. Methods and Materials: Blood from 20 consecutive VAD patients was assayed for factor XIIa activity (intrinsic cascade), reaction time and maximum amplitude of tissue factor activated thrombelastography (TEG-r and TEG-MA, extrinsic cascade and platelet activity), F1.2 level (thrombin generation) and plasminogen activator inhibitor-1 (PAI-1) levels (fibrinolysis). TE was defined as clinical stroke or asymptomatic ⬎2-fold rise in S100 level. Each assay was compared: 1) before and after VAD implantation and 2) for 24 hours preceding TE vs. other postoperative timepoints. Results: PAI-1 was the only marker that was elevated chronically after VAD implantation. Just prior to TE, significant elevations were noted in F1.2 (1.20 vs. 0.34nmol/mg, p⫽0.0001) and XIIa (2.48 vs. 1.45ng/ml, p⫽0.002). ROC analysis identified discrete cutoff values for both F1.2 (0.5nmol/L/mg) and XIIa (2ng/ml) that strongly predicted TE (p⬍0.0001, Fischer’s exact test). Factor XIIa activity significantly correlated with F1.2 (R ⫽ 0.59, p ⫽ 0.0003) and S100 (Figure 1) (R ⫽ 0.52, p ⫽ 0.003) but not with PAI-1 (R ⫽ 0.07). Conclusions: VAD recipients demonstrate compromised fibrinolysis in the setting of acute bursts in thrombin generation that are associated with increased risk of TE. The significant correlation of factor XIIa activity with both TE and thrombin production suggests that the intrinsic cascade may prove to be a novel antithrombotic target in these high risk patients.
426 VASCULAR ENDOTHELIAL GROWTH FACTOR-C ENHANCES EXPERIMENTAL OBLITERATIVE BRONCHIOLITIS BY INDUCING LYMPHANGIOGENESIS R. Krebs,1 J.M. Tikkanen,1 A.I. Nyka ¨ nen,1 S. Yla ¨ -Herttuala,2 1 1 1 P.K. Koskinen, K.B. Lemstro ¨ m, Transplantation Laboratory, University of Helsinki, Helsinki, Finland; 2A.I.Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland Purpose: The role of vascular endothelial growth factor-C (VEGF-C) in the development of obliterative airway disease (OAD) as a manifestation of chronic rejection was investigated in the rat tracheal allograft model. Methods and Materials: Tracheal allografts were transplanted heterotopically from DA- to WF-rats into the greater omentum. Syngeneic controls were performed from DA to DA rats. Expression of VEGF-C and VEGFR-3 protein and lymphatic vessel marker LYVE-1 was analysed
S214
Abstracts
from normal, syngeneic, and allogeneic tracheal transplants. Adenovirally mediated mouse VEGF-C (AdVEGF-C) gene transfer was used to over-express VEGF-C while AdLacZ-treated allografts served as controls. Cyclosporine A (CyA) was used for background immunosuppression. Tracheal allografts were removed 10 and 30 days after transplantation. Results: An increase in VEGFR-3-positive inflammatory cells was shown in 10d allografts (p⬍0.01; n⫽8⫹8) and an increase in VEGF-C-positive inflammatory cells was observed at 10d (p⬍0.005; n⫽3⫹5) and 30d (p⬍0.01; n⫽5⫹5) allografts when compared to syngrafts. In contrast to syngrafts, allografts showed a significantly elevated number of LYVE-1-positive vessels at 30d (p⬍0.05; n⫽6⫹6). Adenovirus-mediated mouse VEGF-C gene transfer into heterotopic tracheal allografts resulted in 80% reduction of epithelial necrosis at 10d (-gal: 29,4 %; VEGF-C: 6,1 %; p⬍0.05; n⫽9⫹9) and in a more than three-fold increase in airway occlusion at 30d compared to allografts treated with virus expressing -gal (-gal: 17,3 %; VEGF-C: 57,7 %; p⬍0.01; n⫽7⫹9). Additionally, significant increases of LYVE-1-positive vessels (p⬍0.05; n⫽7⫹9) and of CD8-positive cells (p⬍0.05; n⫽6⫹9) were observed in AdVEGF-Ctreated allografts at 30d. Conclusions: This study suggests that VEGF-C enhances the posttransplantory inflammatory response via induction of lymphangiogenesis, thereby augmenting the development of OAD. Thus, appropriate inhibition of the VEGF-C signalling pathway may provide a therapeutic strategy for prevention of bronchiolitis obliterans syndrome. 427 THE EFFECTS OF HORMONE RESUSCITATION ON TRANSPLANTABLE ORGANS IN THE BRAIN DEAD DONOR A. Hing,1 M. Hicks,1 L. Gao,1 S.C. Faddy,1 P. Tran,2 S.H. Kesteven,3 A.F. Sharland,2 G.J. Stewart,2 P.S. Macdonald,1 1Transplant Program, The Victor Chang Cardiac Research Institute, Sydney, NSW, Australia; 2The Collaborative Transplant Research Group, The University of Sydney, Sydney, NSW, Australia; 3Cardiovascular Mechanics Program, The Victor Chang Cardiac Research Institute, Sydney, NSW, Australia Purpose: Hormone Resuscitation (HR) of the brain dead donor has been advocated to increase donor organ quality and utilization. We are unaware of any prospective, randomized trials testing HR and its effects on organs. This study investigated the effects of HR on the heart, lung, kidney, liver and pancreas. Methods and Materials: A porcine model of the brain dead organ donor was used. One hour after brain death (BD) induction, animals were commenced on norepinephrine (NE; n⫽9), HR (triiodothyronine, methylprednisolone, vasopressin and insulin; n⫽9) or continued on IV fluids alone (FL; n⫽9) to maintain hemodynamics. Hemodynamics, organ blood flows, and blood/physiological markers of organ function were assessed. Results: At 6 hours post-BD, and despite NE animals receiving 3.5⫾1.5 g/kg/min norepinephrine, mean arterial pressure (MAP) was highest in HR compared with FL and NE animals (64⫾5 vs 38⫾12 & 36⫾14 mmHg; p⬍0.05). Cardiac output was higher in HR animals compared with NE (5.4⫾1.4 vs 1.9⫾1.5 L/min; p⬍0.05) and cardiac contractility (preload recruitable stroke work) was superior in HR and NE animals compared with FL. Troponin I release was similar between groups. With lung function, PaO2/FiO2 was higher in HR and FL animals compared with NE (470⫾95 & 464⫾63 vs 345⫾106; p⬍0.05) and Aa gradient was higher in the NE animals compared with both HR and FL (311⫾101 vs 192⫾91 & 199⫾62 mmHg; p⬍0.05). Renal arterial flow was higher in HR than NE animals (204⫾96 vs 41⫾42 mL/min; p⬍0.05), as was creatinine clearance (132⫾54 vs 40⫾34 mL/min; p⬍0.05). There were no differences in hepatic arterial or portal venous flow and there were no differences in liver function tests (ALT, AST and bilirubin) or bile production. There were also no differences between groups in amylase or lipase release.
The Journal of Heart and Lung Transplantation February 2007
Conclusions: These results demonstrate that HR can improve MAP, and cardiac, pulmonary and renal function in the donor and does not appear to have any detrimental effects on the liver or pancreas. This study supports the use of HR to resuscitate the brain-dead donor to improve donor organ quality. 428 LIPOPOLYSACCHARIDE PRECONDITIONING IS PROTECTIVE IN LUNG ISCHEMIA REPERFUSION INJURY H.E. Merry,1 A.S. McCourtie,1 P.S. Wolf,1 A.S. Farivar,1 M.S. Mulligan,1 1Cardiothoracic Surgery, University of Washington, Seattle, WA Purpose: In lung transplantation, donor lungs are procured from ventilated patients who are frequently colonized with bacteria. How bacterial colonization influences subsequent ischemia-reperfusion injury and graft function is poorly understood. Exposure to bacterial products at sufficient levels can cause lung injury. However, recent work in other organ systems suggests that low-dose lipopolysaccharide (LPS) pretreatment may confer protection in ischemia-reperfusion injury through replication of ischemic preconditioning responses. This appears to occur via modulation of innate immune responses, specifically Toll-like receptor 4 (TLR-4) activation. Methods and Materials: Long-Evans rats received intratracheal LPS over a wide range of doses (2ng-1000ng) 24 hours prior to left lung ischemia and reperfusion. Lungs were analyzed for cytokine production, total and nuclear protein expression. Results: There was up to a 70% reduction in vascular permeability with LPS pretreatment (p⬍0.001) after 90 minutes of ischemia and 4 hours of reperfusion. Protection from LPS was maintained across a wide range of doses, although the degree of protection was decreased at the extremes of dosing (2ng, 1000ng). This protection was associated with altered pro-inflammatory signaling, with a significant (p⬍0.01) reduction in MAPK activation. Additionally, we have demonstrated that the mechainsm of this protection is associated with alterations in TLR-4 adapter protein recruitment. Conclusions: LPS pretreatment is protective in an experimental model of lung ischemia reperfusion injury. Understanding how LPS alters ischemia-reperfusion injury and the thresholds of bacterial colonization that are safe in donor lungs will have significant implications for donor management and selection.
Abstracts
Table 1 hIL-10 Levels (mean, pg/ml, Pig IL-10 group) Hours EVLP
0h
6h
9h
12 h
Perfusate BAL
0 0
0 37.10
13.58 300.33
42.26 1384
Table 2 Pig Lung Function After 12 hours EVLP
IL-10 Empty Control
Compliance (ml/cmH2O)
PVR (dynes ⴛ sec ⴛ cmⴚ5)
Delta PO2 (mmHg)
27 ⫾ 2 13 ⫾ 5.6 24.3 ⫾ 5.5
631.7 ⫾ 166 1219 ⫾ 140 791.1 ⫾ 140
460 ⫾ 71 113 ⫾ 9.8 404 ⫾ 138
424 ANTI-CD20 PREVENTS ALLOANTIBODY PRODUCTION AND ATTENUATES CARDIAC ALLOGRAFT VASCULOPATHY IN MONKEYS TREATED WITH ANTI-CD154 S.S. Kelishadi,1 T. Zhang,1 B.N. Nguyen,1 G. Wu,1 E. Welty,1 C.J. Avon,1 S. Pfeiffer,1 C. Schroder,1 A. Azimzadeh,1 R.N. Pierson, III,1 1Cardiac Surgery, University of Maryland School of Medicine and Baltimore VAMC, Baltimore, MD Purpose: Blockade of CD40-154 prolongs cardiac allograft survival in cynomolgus macaques, but cardiac allograft vasculopathy (CAV) causes graft failure, and is closely associated with appearance of anti-donor antibody (Ab). We hypothesized that depletion of CD20⫹ B-cells might interfere with formation of anti-donor plasma cells and alloantibodies, and thus prevent CAV. Methods and Materials: Thirty MLR-mismatched heterotopic cardiac cynomolgus allograft recipients were treated with anti-CD154 high intensity monotherapy (␣CD154; n⫽17, 6 with ATG) or ␣CD154 with additional ␣CD20 (20mg/kg q wk for 4 weeks: ␣CD154⫹␣CD20; n⫽13, 11 with ATG). Some animals received an additional donor thymus graft or bone marrow infusion. Acute rejection was usually treated with steroids; graft survival was censored at 90 days. Results: 10 animals died with beating grafts, mainly with ATG-associated lung pathology, and are excluded from the survival analysis. Graft survival with ␣CD154⫹␣CD20 (median ⬎90d) and proportion of grafts surviving to 90 days (5/5) was significantly increased relative to ␣CD154 (median 43d, IQR(25-75) 35-82d, p⬍0.007; 3/15 ⬎90d). With ␣CD154, 15/15 (100%) developed anti-donor IgM and 14/15 (93%) IgG, usually weeks before graft failure, whereas no IgG was detected in samples analyzed to date from the ␣CD154⫹␣CD20 group, and weak IgM was transiently detected in only one animal. All ␣CD154 grafts had severe CAV (score ⱖ3 on 0-4 scale), in many instances with fibrosis and unscorable vessels due to infarction. In stark contrast, ␣CD154⫹␣CD20 was associated with CAVⱕ 1 in 4 of 5 grafts, and CAV 2 in the 5th, and preserved myocardial architecture. Conclusions: Using ␣CD20 with ␣CD154 is associated with decreased elaboration of alloAb, prolonged graft survival to ⬎90 days, and significant attenuation of CAV. Concomitant thymus transplant or ATG induction did not appear to be necessary to this effect; ATG is associated with significant morbidity. These findings suggest that ␣CD20 may reduce the incidence of CAV, perhaps by inhibiting alloAb. 425 VAD-ASSOCIATED THROMBOEMBOLISM: POSSIBLE ROLE FOR INTRINSIC COAGULATION CASCADE S. Kallam,1 R.N. Sangrampurkar,1 Z. Kon,1 R.N. Pierson,1 B.P. Griffith,1 R.S. Poston,1 1Cardiac Surgery, University of Maryland Medical Center, Baltimore, MD
S213
Purpose: Thromboembolism (TE) in ventricular assist device (VAD) patients often follow acute bursts in thrombin production. The purpose of this study was to further investigate the factors that lead to this dysregulated thrombin metabolism. Methods and Materials: Blood from 20 consecutive VAD patients was assayed for factor XIIa activity (intrinsic cascade), reaction time and maximum amplitude of tissue factor activated thrombelastography (TEG-r and TEG-MA, extrinsic cascade and platelet activity), F1.2 level (thrombin generation) and plasminogen activator inhibitor-1 (PAI-1) levels (fibrinolysis). TE was defined as clinical stroke or asymptomatic ⬎2-fold rise in S100 level. Each assay was compared: 1) before and after VAD implantation and 2) for 24 hours preceding TE vs. other postoperative timepoints. Results: PAI-1 was the only marker that was elevated chronically after VAD implantation. Just prior to TE, significant elevations were noted in F1.2 (1.20 vs. 0.34nmol/mg, p⫽0.0001) and XIIa (2.48 vs. 1.45ng/ml, p⫽0.002). ROC analysis identified discrete cutoff values for both F1.2 (0.5nmol/L/mg) and XIIa (2ng/ml) that strongly predicted TE (p⬍0.0001, Fischer’s exact test). Factor XIIa activity significantly correlated with F1.2 (R ⫽ 0.59, p ⫽ 0.0003) and S100 (Figure 1) (R ⫽ 0.52, p ⫽ 0.003) but not with PAI-1 (R ⫽ 0.07). Conclusions: VAD recipients demonstrate compromised fibrinolysis in the setting of acute bursts in thrombin generation that are associated with increased risk of TE. The significant correlation of factor XIIa activity with both TE and thrombin production suggests that the intrinsic cascade may prove to be a novel antithrombotic target in these high risk patients.
426 VASCULAR ENDOTHELIAL GROWTH FACTOR-C ENHANCES EXPERIMENTAL OBLITERATIVE BRONCHIOLITIS BY INDUCING LYMPHANGIOGENESIS R. Krebs,1 J.M. Tikkanen,1 A.I. Nyka ¨ nen,1 S. Yla ¨ -Herttuala,2 1 1 1 P.K. Koskinen, K.B. Lemstro ¨ m, Transplantation Laboratory, University of Helsinki, Helsinki, Finland; 2A.I.Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland Purpose: The role of vascular endothelial growth factor-C (VEGF-C) in the development of obliterative airway disease (OAD) as a manifestation of chronic rejection was investigated in the rat tracheal allograft model. Methods and Materials: Tracheal allografts were transplanted heterotopically from DA- to WF-rats into the greater omentum. Syngeneic controls were performed from DA to DA rats. Expression of VEGF-C and VEGFR-3 protein and lymphatic vessel marker LYVE-1 was analysed
S214
Abstracts
from normal, syngeneic, and allogeneic tracheal transplants. Adenovirally mediated mouse VEGF-C (AdVEGF-C) gene transfer was used to over-express VEGF-C while AdLacZ-treated allografts served as controls. Cyclosporine A (CyA) was used for background immunosuppression. Tracheal allografts were removed 10 and 30 days after transplantation. Results: An increase in VEGFR-3-positive inflammatory cells was shown in 10d allografts (p⬍0.01; n⫽8⫹8) and an increase in VEGF-C-positive inflammatory cells was observed at 10d (p⬍0.005; n⫽3⫹5) and 30d (p⬍0.01; n⫽5⫹5) allografts when compared to syngrafts. In contrast to syngrafts, allografts showed a significantly elevated number of LYVE-1-positive vessels at 30d (p⬍0.05; n⫽6⫹6). Adenovirus-mediated mouse VEGF-C gene transfer into heterotopic tracheal allografts resulted in 80% reduction of epithelial necrosis at 10d (-gal: 29,4 %; VEGF-C: 6,1 %; p⬍0.05; n⫽9⫹9) and in a more than three-fold increase in airway occlusion at 30d compared to allografts treated with virus expressing -gal (-gal: 17,3 %; VEGF-C: 57,7 %; p⬍0.01; n⫽7⫹9). Additionally, significant increases of LYVE-1-positive vessels (p⬍0.05; n⫽7⫹9) and of CD8-positive cells (p⬍0.05; n⫽6⫹9) were observed in AdVEGF-Ctreated allografts at 30d. Conclusions: This study suggests that VEGF-C enhances the posttransplantory inflammatory response via induction of lymphangiogenesis, thereby augmenting the development of OAD. Thus, appropriate inhibition of the VEGF-C signalling pathway may provide a therapeutic strategy for prevention of bronchiolitis obliterans syndrome. 427 THE EFFECTS OF HORMONE RESUSCITATION ON TRANSPLANTABLE ORGANS IN THE BRAIN DEAD DONOR A. Hing,1 M. Hicks,1 L. Gao,1 S.C. Faddy,1 P. Tran,2 S.H. Kesteven,3 A.F. Sharland,2 G.J. Stewart,2 P.S. Macdonald,1 1Transplant Program, The Victor Chang Cardiac Research Institute, Sydney, NSW, Australia; 2The Collaborative Transplant Research Group, The University of Sydney, Sydney, NSW, Australia; 3Cardiovascular Mechanics Program, The Victor Chang Cardiac Research Institute, Sydney, NSW, Australia Purpose: Hormone Resuscitation (HR) of the brain dead donor has been advocated to increase donor organ quality and utilization. We are unaware of any prospective, randomized trials testing HR and its effects on organs. This study investigated the effects of HR on the heart, lung, kidney, liver and pancreas. Methods and Materials: A porcine model of the brain dead organ donor was used. One hour after brain death (BD) induction, animals were commenced on norepinephrine (NE; n⫽9), HR (triiodothyronine, methylprednisolone, vasopressin and insulin; n⫽9) or continued on IV fluids alone (FL; n⫽9) to maintain hemodynamics. Hemodynamics, organ blood flows, and blood/physiological markers of organ function were assessed. Results: At 6 hours post-BD, and despite NE animals receiving 3.5⫾1.5 g/kg/min norepinephrine, mean arterial pressure (MAP) was highest in HR compared with FL and NE animals (64⫾5 vs 38⫾12 & 36⫾14 mmHg; p⬍0.05). Cardiac output was higher in HR animals compared with NE (5.4⫾1.4 vs 1.9⫾1.5 L/min; p⬍0.05) and cardiac contractility (preload recruitable stroke work) was superior in HR and NE animals compared with FL. Troponin I release was similar between groups. With lung function, PaO2/FiO2 was higher in HR and FL animals compared with NE (470⫾95 & 464⫾63 vs 345⫾106; p⬍0.05) and Aa gradient was higher in the NE animals compared with both HR and FL (311⫾101 vs 192⫾91 & 199⫾62 mmHg; p⬍0.05). Renal arterial flow was higher in HR than NE animals (204⫾96 vs 41⫾42 mL/min; p⬍0.05), as was creatinine clearance (132⫾54 vs 40⫾34 mL/min; p⬍0.05). There were no differences in hepatic arterial or portal venous flow and there were no differences in liver function tests (ALT, AST and bilirubin) or bile production. There were also no differences between groups in amylase or lipase release.
The Journal of Heart and Lung Transplantation February 2007
Conclusions: These results demonstrate that HR can improve MAP, and cardiac, pulmonary and renal function in the donor and does not appear to have any detrimental effects on the liver or pancreas. This study supports the use of HR to resuscitate the brain-dead donor to improve donor organ quality. 428 LIPOPOLYSACCHARIDE PRECONDITIONING IS PROTECTIVE IN LUNG ISCHEMIA REPERFUSION INJURY H.E. Merry,1 A.S. McCourtie,1 P.S. Wolf,1 A.S. Farivar,1 M.S. Mulligan,1 1Cardiothoracic Surgery, University of Washington, Seattle, WA Purpose: In lung transplantation, donor lungs are procured from ventilated patients who are frequently colonized with bacteria. How bacterial colonization influences subsequent ischemia-reperfusion injury and graft function is poorly understood. Exposure to bacterial products at sufficient levels can cause lung injury. However, recent work in other organ systems suggests that low-dose lipopolysaccharide (LPS) pretreatment may confer protection in ischemia-reperfusion injury through replication of ischemic preconditioning responses. This appears to occur via modulation of innate immune responses, specifically Toll-like receptor 4 (TLR-4) activation. Methods and Materials: Long-Evans rats received intratracheal LPS over a wide range of doses (2ng-1000ng) 24 hours prior to left lung ischemia and reperfusion. Lungs were analyzed for cytokine production, total and nuclear protein expression. Results: There was up to a 70% reduction in vascular permeability with LPS pretreatment (p⬍0.001) after 90 minutes of ischemia and 4 hours of reperfusion. Protection from LPS was maintained across a wide range of doses, although the degree of protection was decreased at the extremes of dosing (2ng, 1000ng). This protection was associated with altered pro-inflammatory signaling, with a significant (p⬍0.01) reduction in MAPK activation. Additionally, we have demonstrated that the mechainsm of this protection is associated with alterations in TLR-4 adapter protein recruitment. Conclusions: LPS pretreatment is protective in an experimental model of lung ischemia reperfusion injury. Understanding how LPS alters ischemia-reperfusion injury and the thresholds of bacterial colonization that are safe in donor lungs will have significant implications for donor management and selection.