Although the etiology of rheumatoid interstitial lung disease (RILD) remains unknown, bronchoalveolar lavage (BAL) has been useful in studying potentially pathogenic mechanisms in this disorder. Previous investigations in patients with rheumatoid arthritis (RA) and RILD revealed abnormal BAL T-lymphocyte subpopulations and a significant elevation in BAL neutrophils. Because neutrophils have been implicated as important effector cells in inflammatory disorders such as ARDS and idiopathic pulmonary fibrosis, we evaluated BAL fluid in patients with RA for neutrophil chemotactic and activating properties and for evidence of neutrophil activation. The BAL fluid from patients with RILD contained significant neutrophil chemotactic activity derived from both lipid and nonlipid components. Evidence for neutrophil stimulation in the lower respiratory tract of patients with RILD was suggested by elevations in both myeloperoxidase activity and immunologically determined levels of human neutrophil elastase in BAL fluid. Free uninhibited elastolytic activity, however, was not demonstrated, suggesting that adequate protease inhibitor levels were present to inhibit active elastase activity. In addition to elevated myeloperoxidase activity, a potential role for neutrophil-derived oxidant injury was indirectly suggested by the enhanced release of superoxide anion (O2-) from resting normal human blood neutrophils challenged with concentrated BAL fluid from patients with RA and interstitial lung disease. Significant correlations were found between physiologic parameters and the percentage of BAL neutrophils, as well as levels of neutrophil-derived mediators. For example, levels of human neutrophil elastase were strongly correlated with diminished diffusion capacity (r = -0.73, p less than 0.001) and reduced forced vital capacity (r = -0.63, p less than 0.006).(ABSTRACT TRUNCATED AT 250 WORDS)

We examined the effect of fibrinolysis depression on thrombin-induced pulmonary microembolism in awake sheep prepared with chronic lung lymph fistulas. Fibrinolysis was depressed by an intravenous infusion (100 mg) of tranexamic acid [trans-4-(Aminomethyl)cyclohexanecarboxylic acid]. Pulmonary microembolism was induced by an intravenous infusion of alpha-thrombin (80 NIH U/kg) in normal (n = 7) and in tranexamic acid-treated (n = 6) sheep. Thrombin immediately increased pulmonary lymph flow (Qlym) in both groups. The increased Qlym was not associated with a change in the lymph-to-plasma protein concentration (L/P) ratio in the control group and with a small decrease in the tranexamic acid-treated group. The increases in Qlym and pulmonary transvascular protein clearance (Qlym X L/P ratio) in the tranexamic acid-treated group were greater and sustained at four- to fivefold above base line for 10 h after the thrombin and remained elevated at twofold above base line even at 24 h. In contrast, Qlym and protein clearance were transiently increased in the control group. The mean pulmonary arterial pressure (Ppa) and pulmonary vascular resistance (PVR) increased after thrombin in tranexamic acid-treated group; the increases in Ppa and PVR in the control group were transient. Protein reflection coefficient as determined by the filtration independent method decreased after thrombin in tranexamic acid-treated sheep (n = 5), indicating an increased vascular permeability to proteins. We conclude that prolongation of microthrombi retention in the pulmonary circulation results in an increased vascular permeability to proteins. Both increased vascular permeability and vascular hydrostatic pressure are important determinants of the increases in Qlym and transvascular protein clearance after thrombin-induced pulmonary microembolism.

We compared pulmonary vascular responses with thrombin-induced pulmonary microembolism in awake sheep pretreated with ibuprofen or meclofenamate. Control sheep with lung lymph fistulas (n = 6) were challenged with 80 U/kg of alpha-thrombin, the native enzyme. Two groups of similarly prepared sheep received the cyclooxygenase inhibitors, ibuprofen (n = 4) or meclofenamate (n = 4), before the thrombin challenge. Thrombin-induced pulmonary microembolism in control sheep increased pulmonary lymph flow and lymph protein clearance (lymph flow X lymph-to-plasma protein concentration ratio). These lymph changes were associated with sustained increases in mean pulmonary arterial pressure (Ppa) and pulmonary vascular resistance (PVR) and a decrease in circulating neutrophil count. The steady-state pulmonary hemodynamic and lymph responses to thrombin persisted after cyclooxygenase inhibition with meclofenamate, although the increases in pulmonary lymph flow and lymph protein clearance were delayed. In contrast, ibuprofen reduced pulmonary lymph flow, lymph protein clearance, Ppa, and PVR responses. Neutrophil count in control and meclofenamate groups remained below base line after thrombin, whereas neutrophil count returned to base line in the ibuprofen group within 90 min after thrombin. Ibuprofen resulted in a greater decrease in vitro neutrophil adherence to pulmonary endothelium induced by serum generated by clotting whole blood with alpha-thrombin as compared with meclofenamate. Results indicate that ibuprofen attenuates the increases in Ppa and PVR and markedly attenuates the increase in pulmonary transvascular protein clearance after thrombin. The protective effect of ibuprofen may be due to reduction of neutrophil sequestration in lung.

We examined the mechanism of the neutrophil (PMN)-dependent increase in pulmonary vascular permeability to protein after thrombin-induced pulmonary microembolism. Humoral factors that activate PMNs after thrombin-induced pulmonary microembolism were characterized in pulmonary lymph obtained from unanesthetized sheep challenged with intravenous infusion of alpha-thrombin. Time-dependent increases in PMN migration, aggregation, and superoxide anion (O2-) generation were induced by the pulmonary lymph obtained within 20 minutes after thrombin infusion. The pulmonary lymph neutrophil activating factors present in ether extracts of lymph had retention times of leukotriene B4 (LTB4) and monohydroxyeicosatetraenoic acids (HETEs) by high-performance liquid chromatography. The postthrombin lymph samples containing the LTB4 and HETEs increased PMN O2- generation and endothelial monolayer permeability to 125I-albumin in the presence of PMNs layered on the endothelial monolayers. Control lymph samples replete with LTB4, 5-HETE, and 15-HETE induced increases in PMN O2- generation and endothelial monolayer permeability to 125I-albumin in the presence of PMNs layered on the endothelial monolayers. Maximal increases in PMN O2- production and endothelial permeability occurred when LTB4, 5-HETE, and 15-HETE were coincubated with PMNs, indicating a synergistic action of these mediators in inducing PMN activation. Endothelial monolayer permeability to 125I-albumin did not increase with postthrombin lymph samples obtained after pretreatment with the 5-lipoxygenase inhibitor, L-651,392. The results indicate that lipoxygenase products generated in the lungs after thrombin-induced microembolism contribute to increased endothelial permeability secondary to PMN activation.