Reduction of endothelial injury after hypothermic lung preservation by initial leukocyte-depleted reperfusion

OBJECTIVES

Leukocyte depletion has been shown to ameliorate the effects of reperfusion injury in many organ systems. The aim of this study was to investigate the effects of leukocyte depletion on functional and endothelial markers of pulmonary performance after cold ischemic injury.

METHOD

Groups of 6 rat lungs were flushed with University of Wisconsin solution and then stored at 4 degrees C for 4 hours. They then underwent sanguine reperfusion for 30 minutes, during which time functional measures (gas exchange, pulmonary artery, and airway pressures) were made and after which the lungs underwent estimation of endothelial permeability by measurement of the capillary filtration coefficient (in grams per centimeter of water per minute per grams of wet lung tissue) by a gravimetric technique. Four groups were studied: group 1 underwent no reperfusion, group 2 underwent 30 minutes of reperfusion, group 3 underwent 30 minutes of leukocyte-deplete reperfusion with an in-line leukocyte filter (PALL), and group 4 underwent 10 minutes of leukocyte-depleting reperfusion followed by 20 minutes of normal reperfusion.

RESULTS

The capillary filtration coefficient increased between group 1 and group 2 animals (1.05 +/- 0.32 to 3.07 +/- 0.47 [mean +/- SEM]; P <.01). Complete leukocyte depletion caused the greatest diminution in the capillary filtration coefficient (0.392 +/- 0.07, P <.001), but initial leukocyte depletion (group 4) also showed a significant diminution (0.74 +/- 0.3, P <.01). Complete or initial leukocyte depletion caused no significant change in functional measures of pulmonary performance. Complete leukocyte depletion produced less pulmonary leukostasis, as assessed by means of myeloperoxidase activity.

CONCLUSION

Initial and continued leukocyte depletion are associated with amelioration of reperfusion-induced endothelial injury after cold ischemic injury.

Differential time scale of fluid and solute permeability following hypothermic lung preservation

BACKGROUND

Assessment of the quality of lung graft preservation by simple functional measures in some laboratory models may fail to detect endothelial injury. The effects of hypothermic preservation in isolation were investigated by measuring the pulmonary capillary filtration coefficient (Kf) and the albumin surface area product (PS) at various cold ischemic intervals.

METHODS

Rat lungs were flushed with University of Wisconsin solution at 4 degrees C. Following storage at 4 degrees C, lungs for Kf measurement were subjected to a change in pulmonary arterial pressure. Kf was calculated from the change in rate of weight gain as a function of hydrostatic stress. PS lungs were exposed to Tris buffered Ringer's solution containing 1125 albumin (20 microM) in an isogravimetric state. Following a vascular flush the lungs were homogenized and underwent scintillation counting. Using the Kedem-Katchalsky equation PS was calculated.

RESULTS

The Kf for the control, 4-hour, and 7-hour groups were 0.778, 1.816, 4.853 g/ cm H2O/min/100 g wet lung tissue, respectively. There was a significant increase in Kf with each time increment (P,0.01). The Kf for the 24-hour group was 5.587 g/cm H2O/min/100 g wet lung tissue; not an additional significant increase. PS for the control and 4-hour groups (0.0115 and 0.0101 cm3/g wet lung tissue/minute, respectively) were not significantly different. After 7 hours there was a significant increase to 0.171 cm3/g wet lung tissue/min. PS could not be measured after 24 hours.

CONCLUSIONS

Significant endothelial injury occurs after 4 hours of cold ischemic preservation. There is progressive injury with time. Increase in water permeability is not secondary to increase in albumin permeability.

Protein interactions in the herpes simplex virus type 1 VP16-induced complex: VP16 peptide inhibition and mutational analysis of host cell factor requirements

The herpes simplex virus VP16 protein functions as a potent transcriptional activator and targets DNA sites with the consensus TAATGARAT present in all the viral immediate-early gene promoters. To do so, VP16 directs assembly of a multiprotein complex involving two cellular proteins, host cell factor (HCF) and the Oct-1 DNA-binding transcription factor. To investigate the importance of specific protein-protein interactions to formation of this VP16-induced complex (VIC), we used oligopeptides to prevent VIC assembly. Linear and cyclic peptides corresponding to a region of VP16 previously implicated in complex formation were potent inhibitors of VIC assembly. To further characterize the protein interactions involved, we cloned a human cDNA encoding the minimal VP16 interaction domain of HCF, containing amino acids 1 to 380 [HCF (1-380)]. The REHAYS-based peptides active in preventing VIC assembly were found to specifically block binding of VP16 to HCF (1-380), without affecting VP16-Oct-1 binding. The inhibitory activity of these VP16 peptides was strictly sequence specific for the EHAY residues. Site-directed mutagenesis of the HCF (1-380) domain revealed residues E102 and K105 to be critical determinants in support of VIC formation. Alteration of a single residue in HCF, K105, was shown to virtually abolish complex assembly. Interestingly however, none of the HCF mutants that were impaired in their ability to support complex formation exhibited defects in direct VP16 binding, supporting loss of function at a higher order in complex assembly.