Prevention of ischemia reperfusion injury by positive pulmonary venous pressure in isolated rat lung.

Pulmonary ischemia-reperfusion (I/R) without tissue hypoxia induces inflammatory cytokine mRNA expression in the lung under the condition of 0 mm Hg pulmonary venous pressure (0PVP), which might be a cause of I/R injury. Our aim is to determine whether the pulmonary vascular endothelium expresses cytokine mRNAs and their corresponding proteins or develops I/R injury when positive PVP is maintained during ischemia to provide a positive stretch to the endothelium throughout the ischemic period. In isolated, perfused, and ventilated rat lungs, the right and left pulmonary arteries were isolated, and the left lung was selectively occluded for 60 min and then reperfused for 30 min. During ischemia, the left atrial pressure was maintained at 5 mm Hg (5PVP) or 0PVP. TNF-alpha, IL-1beta, IL-6, and IL-10 mRNA expression in the lungs was evaluated by RT-PCR and in situ hybridization, and the production and localization of corresponding proteins were determined by staining with fluorescence-labeled antibodies against the cytokines and an antibody against CD34. Pulmonary vascular/epithelial permeability was evaluated by measuring albumin content in bronchoalveolar lavage (BAL) fluid and wet/dry ratio. At 5PVP, there were no increases in the left lung perfusion pressure, albumin content in BAL fluid, wet/dry ratio, or expression of cytokine mRNAs and their corresponding proteins on the vascular endothelium by I/R. In contrast, at 0PVP, the increased expression of cytokine mRNAs and their corresponding proteins on the vascular endothelium by I/R was verified. The finding that the application of 5PVP during ischemia abolished the expression of cytokine mRNAs and their corresponding proteins as well as the I/R injury gives us new insights in the study of lung preservation for transplantation.

Venous hypertension, inflammation and valve remodeling.

OBJECTIVES: To identify possible mechanisms for destruction of valves in chronic venous hypertension and the results of treatment with an anti-inflammatory micronized purified flavonoid fraction. MATERIAL AND METHODS: The saphenous vein valves in a rat model of venous hypertension caused by a femoral arterial-venous fistula were studied. Studies included femoral venous pressure, valve morphology, femoral venous reflux and selected molecular inflammatory markers as examined by immunohistochemistry. The effects of treatment with the anti-inflammatory micronized purified flavonoid fraction (S 5628, Servier, 50 and 100 mg/kg/day) were investigated. RESULTS: The femoral venous pressure was elevated close to arterial values for a period of 3 weeks. We then examined the morphology of the veins and selected molecular inflammatory markers were assessed. The results show that in this model venous reflux develops in response to venous hypertension. This can be inhibited by the administration of the anti-inflammatory micronized purified flavonoid fraction (S 5628, Servier, 50 and 100 mg/kg/day). The valve becomes incompetent by a combination of venous dilation and shortening of the valve leaflets. This is not inhibited by treatment with S 5628. The valve leaflets are infiltrated with granulocytes, monocytes and T-lymphocytes, and the endothelial cells express enhanced levels of P-selectin and ICAM-1. Cells in the valves are subject to extensive apoptosis although no enhancement of MMP 2,9 expression could be detected at the three-week time point examined in this study. CONCLUSIONS: These results indicate that in this model chronic elevation of venous pressure is associated with an inflammatory reaction in venous valves, a process that may lead to their dysfunction, reflux, and upstream elevation of venous pressure. These effects are mitigated by the anti-inflammatory micronized purified flavonoid fraction in a dose dependent manner.