Leukocyte Sequestration in Pulmonary Microvessels and Lung Injury following Systemic Complement Activation in Rabbits

Abstract

Inflammatory reactions are associated with sequestration of leukocytes in the lung. Complement activation leads to accumulation of leukocytes in alveolar septa and alveoli, to lung edema and hemorrhage. Although in organs other than the lung leukocytes interact with the vascular endothelium only in postcapillary venules, alveolar capillaries are considered to be the site of leukocyte sequestration in the lung. However, pulmonary venules and arterioles have not been investigated systematically after complement activation so far. A closed thoracic window was implanted in anesthetized rabbits; leukocytes and red blood cells were stained, and the movement of these cells was measured in superficial pulmonary arterioles, venules and alveolar capillaries using fluorescence video microscopy before and 30 and 60 min after infusion of cobra venom factor (CVF). Erythrocyte velocity and macrohemodynamic conditions did not change after CVF infusion and were not different from the sham-treated controls. The number of sticking leukocytes increased significantly compared to baseline and control: by 150% in arterioles and in venules and by 740% in alveolar capillaries within 60 min after CVF infusion. The width of alveolar septa in vivo was significantly enlarged after CVF infusion, indicating interstitial pulmonary edema. At the end of the experiments, myeloperoxidase activity was higher in the CVF group, showing leukocyte sequestration in the whole organ. It is concluded that complement activation by CVF induces leukocyte sequestration in lung arterioles, venules and alveolar capillaries and leads to mild lung injury.

Intravital microscopy of the lung: minimizing invasiveness

“…However, physiological motion of the chest from breathing and a beating heart greatly impairs image acquisition and thus prevents the extensive quantitative analysis of dynamic phenomena observed in the [30] 1925 Lung clamping Light microscopy Cat, rabbit [22] 1930 Manual tracking of lung movements using a mobile microscope Light microscopy Dog, frog, alligator [31] 1933 Lung clamping Light microscopy Rabbit, cat, dog [21] 1934 Curare Light microscopy Cat [48] 1969 Suction Light microscopy Dog [23] 1993 Implanted thoracic window Videomicroscopy Rabbit [58] 1998 Implanted thoracic window Videomicroscopy Rabbit [37] 1999 Apnea Confocal Rat [36] 1999 Apnea Confocal Rat [24] 2000 Suction Videomicroscopy Rat [50] 2000 Suction Confocal Mouse [38] 2001 Apnea Videomicroscopy Rat [45] 2004 Suction Videomicroscopy Mouse [25] 2008 Apnea Videomicroscopy Mouse [26] 2009 Slow breathing; apnea; implanted thoracic window lungs of living animals. For this reason, and for several centuries, the investigation of dynamic phenomena at a microscopic scale in the lungs of a living animal has been uniquely based on the subjective interpretation of the experimenter's observation.…”

“…In some cases, mice are ventilated with pure oxygen in order to compensate the likely hypoxia resulting from a slower breathing frequency [28,29]. Animals may also be treated with pancuronium bromide to avoid all muscle-related chest motion during assisted mechanical ventilation [24,58].…”

“…In order to protect the lungs from the outside environment, and to avoid collapse as well as stabilization, several groups fix a rigid transparent chest window on big mammals like cats [21,59], rabbits [23,58], rats [24,60,61], and less frequently mice [45]. A variant consists in the use of a soft window, generally a polymer membrane, sealed over the thoracotomy [25,26,56].…”

Direct Leukocyte Migration across Pulmonary Arterioles and Venules into the Perivascular Interstitium of Murine Lungs during Bleomycin Injury and Repair

“…[21][22][23][24] However, leukocytes within the pulmonary circulation migrate into lung parenchymal tissue predominantly via al-veolar capillaries and to a lesser extent the postcapillary venules. 20,22,[25][26][27][28][29][30][31][32][33] Although leukocyte transmigration at the alveolar-capillary level has been widely studied, little is really known about the routes or mechanisms of leukocyte accumulation within perivascular spaces. Nonetheless, marked leukocyte accumulation within perivascular interstitia is known to occur under pulmonary pathological conditions such as acute lung injury.…”

Role of P-Selectin in Platelet Sequestration in Pulmonary Capillaries during Endotoxemia

“…Microhemodynamics and platelet kinetics were analyzed offline from the video recordings using a digital image-processing system (Optimas, Bioscan, Edmonds, Wach., USA), as described previously [12, 13]. The inner wall of the alveoli was outlined and the respective alveolar surface area was planimetrically determined by the image analysis system.…”