Release of von Willebrand factor antigen (vWF:Ag) and eicosanoids during acute injury to the isolated rat lung

Injury of the renal microvascular endothelium alters barrier function after ischemia

The role of renal microvascular endothelial cell injury in the pathophysiology of ischemic acute renal failure (ARF) remains largely unknown. No consistent morphological alterations have been ascribed to the endothelium of the renal microvasculature as a result of ischemia-reperfusion injury. Therefore, the purpose of this study was to examine biochemical markers of endothelial injury and morphological changes in the renal microvascular endothelium in a rodent model of ischemic ARF. Circulating von Willebrand factor (vWF) was measured as a marker of endothelial injury. Twenty-four hours after ischemia, circulating vWF peaked at 124% over baseline values (P = 0.001). The FVB-TIE2/GFP mouse was utilized to localize morphological changes in the renal microvascular endothelium. Immediately after ischemia, there was a marked increase in F-actin aggregates in the basal and basolateral aspect of renal microvascular endothelial cells in the corticomedullary junction. After 24 h of reperfusion, the pattern of F-actin staining was more similar to that observed under physiological conditions. In addition, alterations in the integrity of the adherens junctions of the renal microvasculature, as demonstrated by loss of localization in vascular endothelial cadherin immunostaining, were observed after 24 h of reperfusion. This observation temporally correlated with the greatest extent of permeability defect in the renal microvasculature as identified using fluorescent dextrans and two-photon intravital imaging. Taken together, these findings indicate that renal vascular endothelial injury occurs in ischemic ARF and may play an important role in the pathophysiology of ischemic ARF.

Low tidal volume reduces epithelial and endothelial injury in acid-injured rat lungs

Using a rat model of acid-induced lung injury, we tested the hypothesis that tidal volume reduction at the same level of PEEP (10 cm H(2)O) would diminish the degree of pulmonary edema by attenuating injury to the alveolar epithelial and endothelial barriers. Tidal volume reduction from 12 to 6 to 3 ml/kg significantly reduced the rate of lung water accumulation from 690 microl/h to 310 microl/h to 210 microl/h. Ventilation with either 6 or 3 ml/kg reduced endothelial injury equally as measured by plasma vWf:Ag and permeability to albumin. Plasma RTI40, a marker of type I epithelial cell injury, decreased 46% when tidal volume was reduced from 12 to 6 ml/kg and decreased an additional 33% with 3 ml/kg (p < 0.05). The rate of alveolar epithelial fluid clearance was significantly faster in the 3-ml/kg group (24 +/- 7%/h) compared with 6 ml/kg (15 +/- 11%/h) and 12 ml/kg (3 +/- 6%/h). We conclude that low tidal volume ventilation protects both the alveolar epithelium and the endothelium in this model of acute lung injury. The additional decrease in pulmonary edema with a tidal volume of 3 ml/kg is partly accounted for by greater protection of the alveolar epithelium.

Evaluation of plasma von Willebrand factor as a biomarker for acute arterial damage in rats

Plasma von Willebrand factor (vWF) was evaluated as a potential biomarker of acute arterial damage in rats after a vasotoxic dose of the dopaminergic vasodilator, fenoldopam (FP). Male Sprague-Dawley rats were given FP or isotonic saline by subcutaneous injection, and plasma vWF was measured at 2, 6, and 24 hours after challenge. Mean plasma vWF values increased in FP-treated rats compared to controls at 2 hours (167 vs 122%; p < 0.05) and 6 hours postdose (172 vs 130%; p < 0.01) but were comparable to control values after 24 hours. Mesenteric arterial lesions were observed microscopically in all FP-treated rats 24 hours postdose but were not present in rats at 1, 2, 4, 6, or 8 hours after FP challenge. Further, plasma vWF concentrations increased in saline-treated rats after only the minimal perturbation of repeated venipuncture. These results indicate an early, minimal, and transient release of vWF that precedes the onset of morphologically evident vascular damage. The minimal increases in plasma vWF concentrations were of limited predictive value, may be more reflective of an acute-phase reactant response, and were not considered a reliable biomarker of acute FP-induced arterial damage in the rat.

Plasma levels of von Willebrand factor antigen in acute bronchitis and in a normal population

von Willebrand factor (vWF) is a large glycoprotein secreted predominantly by endothelial cells in both the systemic and pulmonary circulations and has a central role in the formation of the platelet plug. It has been put forward as a possible marker of endothelial cell injury, but is not ideal in that it is not specific for either the pulmonary or systemic circulation and may be released as part of the acute phase response from otherwise healthy endothelial cells. We undertook two studies (i) to assess within-subject to assess within-subject variation in plasma von Willebrand factor antigen (vWF:Ag) levels over time and to assess between-subject variation in a healthy patient population, and (ii) as part of a descriptive study of acute bronchitis, to assess whether plasma vWF:Ag levels altered in such a common and minor insult. A random sample of patients aged 45-74 years were taken from a local general practice. vWF:Ag levels were measured on three occasions, and spirometry was performed. The descriptive study was undertaken on patients in the general practice diagnosed with acute bronchitis without pre-existing pulmonary disease. Plasma vWF:Ag was measured on presentation and 14 and 42 days later. In 219 randomly selected patients the mean plasma vWF:Ag was similar at all three visits, the within-subject standard deviation being 0.09 U ml(-1) and 1.12 U ml(-1) respectively). There was no correlation between plasma vWF:Ag and C-reactive protein on presentation. We conclude that there is relatively little variation in an individual's plasma vWF:Ag level but that levels increase significantly with age. The observed elevation occurring with acute bronchitis is a true phenomenon; the absence of an associated acute phase response suggests that endothelial cell injury is the mechanism for the rise. These observations are important in the context of vWF as a marker of endothelial cell damage, as a common and supposedly minor insult such as acute bronchitis may markedly raise plasma levels.

Pathogenesis of hemorrhage induced by proteinase H from eastern diamondback rattlesnake (Crotalus adamanteus) venom

The pathogenesis of hemorrhage of a purified hemorrhagic toxin, proteinase H from Crotalus adamanteus venom, was studied. Female, white CD-1 mice were injected intramuscularly with sublethal doses of the hemorrhagic toxin and tissue samples were obtained at 10 min, 1, 3 and 24 hr following injection. Severe local hemorrhage was observed grossly within 10 min. Hemorrhage was observed in the connective tissue of skeletal muscle and within adjacent adipose tissue. Many larger vessels were congested with erythrocytes and platelets. By 3 hr inflammatory cell infiltration was observed and necrosis of some muscle cells was evident. Transmission electron microscopy showed that the capillary endothelium was ruptured, leading to hemorrhage per rhexis. Capillary basal laminae were disorganized and often wholly or partially absent.

Distribution of von Willebrand factor in capillary endothelial cells of rat lungs with pulmonary fibrosis

To determine the value of von Willebrand factor (vWF) antigen as a marker of endothelial injury in radiation-induced fibrosis of rat lungs, we studied endothelial immunoreactivity to antibodies against vWF using the indirect immunoperoxidase technique combined with morphometric analysis. Using immunoelectron microscopy of LR White embedded lung samples to detect vWF, immunogold-labelled Weibel Palade bodies were found in endothelial cells of capillary endothelium. The irradiated lungs showed a statistically significant elevation of vWF expression, ie, vWF positive endothelia per unit area, and a significant increase of vWF expression per unit of parenchyma as well. The results suggest that vWF antigen expression and the number of vWF positive structures is modulated under condition of injury in radiation-induced fibrosis.

Cellular fibronectin and von Willebrand factor concentrations in plasma of rats treated with monocrotaline pyrrole

The monocrotaline pyrrole (MCTP)-treated rat is a useful model for the study of certain chronic pulmonary vascular diseases. A single, i.v. administration of a low dose of MCTP causes pneumotoxicity, pulmonary vascular remodeling, sustained increases in pulmonary arterial pressure, and right ventricular hypertrophy in rats. The pulmonary vascular lesions are characterized by endothelial cell alterations, platelet and fibrin microvascular thrombosis, pulmonary edema, and thickening of the intimal and medial layers of the vessel wall. These lesions suggest that some dysfunction of the hemostatic system occurs in the lungs of rats treated with MCTP. We evaluated the concentrations of two adhesion proteins, cellular fibronectin (cFn) and von Willebrand factor (vWF), in the plasma of rats treated with MCTP. We hypothesized that changes in these factors occur along with markers of pneumotoxicity and ventricular hypertrophy and that such changes might contribute to the genesis of the vascular lesions. Enzyme-linked immunosorbent assays were used to measure cFn and vWF concentrations in the plasma of rats after MCTP treatment. Rats treated with a single i.v. injection of 3.5 mg MCTP/kg body weight had delayed and progressive lung injury characterized at 5 days post-treatment by increases in the lung-to-body weight ratio and in lactate dehydrogenase activity and protein concentration in cell-free bronchoalveolar lavage fluid (BALF). Values for these markers were further increased at 8 days and reached a plateau thereafter. The number of nucleated cells within the BALF was increased at 8 and 14 days. Right ventricular hypertrophy, an indirect marker of pulmonary hypertension, was evident at 14 days. The cFn concentration was increased in plasma in rats at 8 and 14 days after treatment with MCTP. There was no difference between the vWF concentration in plasma of rats treated with MCTP and those treated with vehicle at any time. We conclude that an increase in plasma cFn concentration occurs prior to the onset of right ventricular hypertrophy and that this change is consistent with a role for cFn in the genesis of vascular remodeling and pulmonary hypertension in the MCTP-treated rat. The lung vascular injury and pulmonary hypertension in this model were not reflected in altered vWF concentration in the plasma.

Quantitation of endothelial cell specific protein E-9 employing a single monoclonal antibody in an indirect sandwich ELISA

An indirect enzyme-linked immunosorbent assay is described for the quantitation of protein E-9 which is specifically expressed on human vascular endothelial cells. The assay capitalizes on the dimeric structure of the E-9 protein by utilizing a single monoclonal antibody as both the capture and detection reagent. Detection is achieved by conjugating the Mab with biotin and is followed by the addition of streptavidin peroxidase to provide high sensitivity. Bound activity is measured by enhanced chemiluminescence utilizing standard Amerlite chemistry. The optimised assay is reproducible and is highly sensitive. Using this assay it was possible to detect the presence of E-9 protein in tissue culture media of endothelial cells and in serum samples--in one case even at 1/100 dilution. In vitro, X irradiation resulted in a greater than two-fold increase (P < or = 0.005) in the level of E-9 protein in culture supernatants of human umbilical vein endothelial cells (HUVEC). There are potential applications for measurements of E-9 protein in body fluids and tissue extracts from patients with a vast variety of diseases characterised by vascular endothelial damage and/or activation.

Neutrophil and nonneutrophil-mediated injury in intestinal ischemia-reperfusion

OBJECTIVE

The role of polymorphonuclear neutrophils (PMN) was examined in local and remote organ injury after intestinal ischemia-reperfusion.

SUMMARY BACKGROUND DATA

PMN have been found to mediate the local injury in low flow intestinal ischemia-reperfusion. However, in complete intestinal ischemia-reperfusion, prevention of PMN adhesion by monoclonal antibodies to CD11b and CD18 reduces remote but not local intestinal injury. The role of PMN was further investigated in this setting.

METHODS

In a rat model of 1-hour complete intestinal ischemia and 4-hour reperfusion. PMN were manipulated in the following four ways: (1) inhibition of oxygen-free radicals using manganese superoxide dismutase and catalase (SOD/CAT), (2) antagonism of PMN elastase using secretory leukocyte protease inhibitor (SLPI), (3) neutropenia using PMN antisera, and (4) inhibition of activation and adhesion using interleukin-1 receptor antagonist (IL-1ra) and tumor necrosis factor binding protein (TNFbp). Lung injury was quantified by the pulmonary permeability index, which is the ratio of bronchoalveolar lavage to blood concentration of radiolabeled bovine serum albumin, and PMN sequestration by myeloperoxidase (MPO) activity. Liver injury was estimated by PMN counts using quantitative histologic examination and by serum glutamic pyruvic transaminase (SGPT). Local injury was quantified by MPO activity and histologic grading.

RESULTS

Neutropenia reduced the pulmonary permeability 80% from 11.0 +/- 0.5 x 10(-3) with saline treatment to 5.50 +/- 0.12 x 10(-3); IL-1ra, to 5.62 +/- 0.44 x 10(-3); and TNFbp, to 4.32 +/- 0.18 x 10(-3) (all p < 0.05). Pulmonary MPO rose from 0.03 +/- 0.01 U/g to 0.25 +/- 0.03 U/g (p < 0.05). This was reduced by neutropenia, 0.01 +/- 0.003 U/g, but not by inhibition of oxygen-free radicals or PMN elastase. IL-1ra inhibited PMN sequestration, reducing MPO to 0.12 +/- 0.01 (p < 0.05). Liver injury was 60% dependent on PMN. Ischemia-reperfusion increased SGPT from 20.3 +/- 0.7 IU/L in the sham-treated animals to 97.0 +/- 3.1 IU/L in the experimental animals. Neutropenia reduced this to 48.1 +/- 3.9 IU/L; IL-1ra, to 44.7 +/- 3.7 IU/L; SOD/CAT, to 64.0 +/- 3.38 IU/L; and SLPI, to 57.1 +/- 3.4 IU/L (p < 0.05 in all cases). Local injury was severe and unaffected by manipulation of the PMN.

CONCLUSIONS

These data suggest that PMN and their products mediate most of the lung, part of the liver, and none of the local gut injury after intestinal ischemia-reperfusion.