A murine skeletal muscle ischemia-reperfusion injury model: differential pathology in BALB/c and DBA/2N mice.

Ischemia-reperfusion injuries can occur with diseases such as myocardial infarction and stroke and during surgical procedures such as organ transplantation and correction of aortic aneurysms. We developed a murine model to mimic abdominal aortic aneurysm repair with cross-clamping of the aorta distal to the renal artery. After model development, we compared the normal complement BALB/c mouse with the C5-deficient DBA/2N mouse. To assess quantitative differences, we measured neuromuscular function up to 72 h after ischemia with a subjective clinical scoring system, as well as plasma chemistries, hematology, and histopathology. There were significant increases in clinical scores and creatine phosphokinase, lactate dehydrogenase, and muscle histopathology scores in BALB/c mice compared with those in DBA/2N mice and sham-surgery mice. Muscle histopathology scores of the cranial tibialis and quadriceps correlated well with clinical signs, creatine phosphokinase, and lactate dehydrogenase, and indicated the greatest pathology in these muscle groups. We developed a murine model of skeletal muscle ischemia-reperfusion injury that can utilize the benefits of murine genetic and transgenic models to assess therapeutic principles of this model. Additionally, we have shown a significant reduction in clinical signs, plasma muscle enzyme concentrations, and muscle pathology in the C5-deficient DBA/2N mouse in this model.

Expression of vascular cell adhesion molecule-1 by vascular endothelial cells in immune and nonimmune inflammatory reactions in the skin.

Expression of VCAM-1 was compared with that of E-selectin in cytokine-induced lesions and in delayed-type hypersensitivity reactions to tuberculin purified protein derivative (PPD) in pig skin. Lumenally expressed Ags were quantified by measuring localization in skin of i.v. injected (111)In-mAb 10.2C7 (anti-vascular cell adhesion molecule-1 (anti-VCAM-1), (125)I-mAb 1.2B6 (anti-E-selectin), and (99m)Tc-MOPC21 (control IgG1). Anti-VCAM-1 mAb uptake was greater following intradermal (i.d.) injection of TNF-alpha than following injection of IL-1, while the two cytokines induced similar uptake of anti-E-selectin. In immunologically naive pigs there was no detectable increase in anti-VCAM-1 after i.d. injection of PPD, although anti-E-selectin uptake was increased at 3 and 6 h. In contrast, i.d. injection of PPD in sensitized pigs led to increased uptake of both anti-VCAM-1 and anti-E-selectin at 6, 8, 24, and 48 h, each of which was significantly greater than the uptake of control IgG1 into the same lesions (each p < 0.01). Anti-TNF-alpha mAb abolished the increased uptake of anti-VCAM-1 3 and 8 h following i.d. injection of PPD in sensitized pigs and significantly inhibited uptake at 24 h (p = 0.0025), but did not significantly reduce uptake of anti-E-selectin. We conclude that in this delayed-type hypersensitivity model 1) E-selectin expression by endothelial cells follows sequential Ag nonspecific and immune-specific phases, 2) increased VCAM-1 expression by endothelial cells is only seen in sensitized animals, and 3) expression of VCAM-1 appears to be relatively more dependent on TNF-alpha than E-selectin. Differential expression of E-selectin and VCAM-1 may influence the leukocytic infiltrate during the course of nonspecific and immune-specific inflammatory reactions.

Endothelial activation in monosodium urate monohydrate crystal-induced inflammation: in vitro and in vivo studies on the roles of tumor necrosis factor alpha and interleukin-1.

OBJECTIVE: There is relatively little direct evidence for the roles of interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) in activating endothelium in vivo. The aim of this study was to use in vitro and in vivo models to investigate the contribution of these cytokines to both E-selectin expression and the recruitment of polymorphonuclear cells (PMN) in monosodium urate monohydrate (MSU) crystal-induced inflammation. METHODS: MSU crystals were incubated with freshly isolated mononuclear cells, after which the harvested supernatants were tested for their ability to induce E-selectin expression during coculture with human umbilical vein endothelial cells. Subsequent experiments were performed with the addition of neutralizing anticytokine antibodies/antisera. The role of TNF alpha was then studied in an MSU crystal-induced monarthritis model, in the presence or absence of anti-TNF alpha (5 mg/kg intravenously). 99mtechnetium (99mTc)-labeled PMN cells and (111)indium (111In)-labeled anti-E-selectin monoclonal antibody (MAb) 1.2B6 were intravenously administered 4 hours after intraarticular injection to quantify PMN recruitment and E-selectin expression in inflamed joints. RESULTS: MSU crystals were a potent stimulus for IL-1 and TNF alpha production by monocytes in vitro, and these cytokines fully accounted for MSU crystal-stimulated, monocyte-mediated endothelial activation. In the MSU crystal-induced monarthritis model, TNF alpha blockade was very effective in suppressing both E-selectin expression and PMN emigration into the inflamed joints, as judged by gamma-camera image analysis and postmortem tissue counting following the intravenous injection of 99mTc-PMN and 111In-anti-E-selectin MAb. CONCLUSION: IL-1 and TNF alpha appear to be the only factors released by monocytes following incubation with MSU crystals, which induce E-selectin expression in vitro. Anti-TNF alpha is effective in suppressing endothelial activation and PMN recruitment in vivo E-selectin imaging can be used to assess the endothelial response to therapy and may prove useful for clinical studies.

The interaction of alpha 1-proteinase inhibitor and tissue kallikrein in controlling allergic ovine airway hyperresponsiveness.

We reported previously that the development of airway hyperresponsiveness (AHR) 24 h after antigen challenge in allergic sheep was associated with increased tissue kallikrein activity (TK) and decreased alpha-1-proteinase inhibitor (alpha 1-PI) activity in bronchoalveolar fluid (BAL). The inverse correlation between TK and alpha 1-PI in these experiments suggested that administration of alpha 1-PI might reduce TK activity and block AHR. To test this hypothesis, airway responsiveness, as determined by calculating the cumulative carbachol breath units (BU) that increased specific lung resistance by 400% (PC400), was measured before and 24 h after aerosol challenge with Ascaris suum antigen in seven sheep hypersensitive to this antigen. On the next day, 30 min before the 24 h PC400 measurement, the sheep were treated with either aerosol alpha 1-PI (Prolastin, 10 mg/5 ml) or denatured (DN) prolastin (10 mg/5 ml), which had only 10% of its original activity. BAL was also performed before and 24 h after challenge for the measurement of TK and alpha 1-PI activity. Treatment with DN-Prolastin at 24 h after antigen challenge did not block antigen-induced AHR: PC400 fell from a baseline (mean +/- SE) of 26.0 +/- 3.2 BU to 11.2 +/- 1.5 BU after challenge (p < 0.05). This AHR was associated with increased TK (363%, p < 0.05) and decreased alpha 1-PI activity (65%, p < 0.05). Prolastin treatment at 24 h blocked the AHR: PC400 was 21.0 +/- 2.8 before and 23.2 +/- 3.7 after challenge (p < 0.05 versus DN-Prolastin) and the changes in BAL TK (28% increase) and alpha 1-PI activities (15% increase) were not different from baseline (both p < 0.05 versus DN-Prolastin). There was a significant inverse correlation between alpha 1-PI activity and TK activity in BAL, as well as the changes between baseline and 24 h in alpha 1-PI activity and TK activity in BAL Pretreatment (30 min before antigen challenge) with Prolastin also protected against the antigen-induced AHR. The effect of Prolastin was also seen against aerosol challenge with high-molecular-weight kininogen (HMWK), a substrate of TK. HMWK caused bronchoconstriction which was blocked by Prolastin (p < 0.05), and the bradykinin B2 antagonist, NPC-567 (indicating that kinins were generated), but not DN-Prolastin or the elastase inhibitor, ICI 200, 355. Although the negative association between alpha 1-PI activity and TK activity identified in this study does not prove cause and effect, our findings do raise the possibility that in vivo alpha 1-PI may regulate TK activity and allergen-induced AHR.

Contribution of specific cell-adhesive glycoproteins to airway and alveolar inflammation and dysfunction.

Using various animal models of toxic or antigenic-induced airway inflammation, we have demonstrated that adhesion molecules play an important role in the recruitment, retention, and site-specific activation of inflammatory cells within the airways. Furthermore, we have shown that cytokines may contribute to inflammatory responses in the airways by enhancing the expression of adhesion molecules on respiratory epithelial cells.

A prodrug of a 2,6-disubstituted 4-(2-arylethenyl)phenol is a selective and orally active 5-lipoxygenase inhibitor.

BI-L-226, a 2,6-disubstituted 4-(2-arylethenyl)phenol, is a potent and selective 5-lipoxygenase inhibitor which shows excellent inhibition of antigen-induced leukotriene generation in the lung of cynomolgus monkeys by aerosol administration, although little activity has been observed by the p.o. route. The facile synthesis of the succinate ester BI-L-357, however, results in a prodrug which has p.o. activity between 10 to 30 mg/kg in an ex vivo whole blood model of leukotriene B4 generation in both squirrel and cynomolgus monkeys. In addition, the prodrug is effective in inhibiting pulmonary leukotriene C4 production in antigen-challenged cynomolgus monkeys in the same dose range. Plasma levels of the parent compound in the monkey after p.o. administration of 30 mg/kg are 25-fold higher than the IC50 needed for in vitro inhibition of leukotriene B4 in whole blood. Absolute bioavailability of the parent compound was 50%. The prodrug concept therefore extends the potential of this class of compounds to inflammation sites mediated by 5-lipoxygenase not readily treated by topical administration.

The role of 5-lipoxygenase products in preclinical models of asthma.

BACKGROUND: The action of 5-lipoxygenase on arachidonic acid generates potent inflammatory mediators that may contribute to the pathophysiology of asthma. METHODS: Using the potent and selective 5-lipoxygenase inhibitor BI-L-239, we have examined the role of 5-lipoxygenase products in three animal models of asthma. RESULTS: In vitro BI-L-239 inhibited 5-lipoxygenase product generation from human lung mast cells, alveolar macrophages, and peripheral blood leukocytes with a concentration that would provide 50% inhibition values of 28 to 340 nmol/L. A 36-fold selectivity for immunoreactive leukotriene C4 versus immunoreactive prostaglandin D2 inhibition was demonstrated in mast cells. In anesthetized cynomolgus monkeys, inhaled BI-L-239 provided dose-dependent inhibition of the inhaled Ascaris-induced immunoreactive leukotriene C4 release (maximum, 73%; bronchoalveolar lavage [BAL], 20 minutes), late-phase bronchoconstriction (maximum, 41%; +6 to 8 hours), and neutrophil infiltration (maximum, 63%; BAL, +8 hours). In conscious sheep, inhaled BI-L-239 provided dose-dependent inhibition of the inhaled Ascaris-induced late-phase bronchoconstriction (maximum, 66%; +6 to 8 hours) and increase in airway responsiveness (maximum, 82%; carbachol, +24 hours). The acute bronchoconstriction was shortened, and neutrophil infiltration diminished (maximum, 61%; BAL, +8 hours) in this model. Finally in conscious actively sensitized guinea pigs pretreated with pyrilamine and indomethacin, inhaled BI-L-239 attenuated acute bronchoconstriction (maximum, 80%; +5 to 15 minutes), leukocyte infiltration (58%; BAL, +3 days) and increase in airway responsiveness (100%; methacholine, +3 days) induced by three alternate-day ovalbumin inhalations. CONCLUSIONS: In conclusion, results in these three animal models indicate that 5-lipoxygenase products may be major contributors to the bronchoconstriction (especially late phase), leukocyte infiltration, and airway hyperresponsiveness that characterize asthma.

Control of inflammatory processes by adhesion glycoproteins.

Cell surface adhesive glycoproteins are principal regulators of nearly all aspects of immune/inflammatory responses. Using monoclonal antibodies to individual adhesion molecules, the expression and contribution of specific molecules in the pathogenesis of allergen-induced airway hyperresponsiveness in monkeys has been studied. Results confirm the importance of cell adhesion and demonstrate that antagonism of a single adhesion molecule may provide a novel therapeutic approach.

Efficacy of monoclonal antibodies against adhesion molecules in animal models of asthma.

Cell surface adhesive glycoproteins are principal regulators of nearly all aspects of immune/inflammatory responses. Using monoclonal antibodies to individual adhesion molecules, the expression and contribution of specific molecules in the pathogenesis of allergen-induced airway hyperresponsiveness in monkeys has been deciphered. Results confirm the importance of cell adhesion and demonstrate that antagonism of a single adhesion molecule may provide a novel therapeutic approach.

Human eosinophil major basic protein augments bronchoconstriction induced by intravenous agonists in guinea pigs.

The direct effect of intratracheal (IT) administration of human major basic protein (MBP) on pulmonary inspiratory pressure (PIP), and the effect on agonist-induced change in PIP, were determined in anesthetized, ventilated guinea pigs. 500 micrograms MBP increased PIP from 24.1 +/- 4.3 to 49.8 +/- 7.4 cmH2O (p < 0.002, n = 10). Maximum PIP was achieved within 30 min after 500 micrograms MBP. The direct PIP response to 250 micrograms MBP was not different from vehicle. The PIP responses to intravenous (IV) acetylcholine (Ach) and 5-hydroxytryptamine (5-HT) were measured before and after administration of 250 micrograms MBP (n = 12). MBP caused a modest, but significant potentiation of the increase in PIP induced by 1, 3 and 10 micrograms/kg Ach (24, 32 and 28%, respectively, p < 0.02) and to 1 microgram/kg 5-HT (43% p < 0.02). We conclude that MBP at a dose that does not directly affect inspiratory pressure is capable of augmenting the PIP response to IV Ach and 5-HT in vivo.

Antigen-induced acute and late-phase responses in primates.

We have examined the proinflammatory cell influx as well as the levels of eosinophil and neutrophil-derived granule proteins in BAL fluid obtained from monkeys undergoing acute and late-phase (dual) or single acute bronchoconstriction following antigen inhalation. Prior to antigen inhalation, there was a significantly higher number (and percentage) of eosinophils in BAL fluid from dual responder monkeys as compared with single responders. The late-phase response (LPR) (6 to 8 h postantigen) was associated with a decrease in the number of BAL eosinophils and an increase in the levels of BAL fluid EPO that returned to baseline levels by 24 h postantigen inhalation. In contrast, the number of BAL neutrophils prior to antigen inhalation were low. Concurrent with the LPR, the number of BAL neutrophils and the concentration of EPO in BAL fluid were significantly increased above that occurring in single responders. Chronic treatment (7 days) with dexamethasone significantly reduced the number of BAL eosinophils and the BAL levels of EPO prior to antigen inhalation in dual responder (LPR) monkeys and significantly blocked the dual response and both the associated neutrophil influx into the airways and an increase in BAL fluid EPO during the LPR. We conclude that, in this primate model, eosinophil activation and a large influx of neutrophils into the airways is associated with the occurrence of the antigen-induced late-phase airway obstructive response.

The role of intercellular adhesion molecule-1 in chronic airway inflammation.

We have examined the role of intercellular adhesion molecule-1 (ICAM-1) in chronic airway inflammation and airway hyperresponsiveness in a primate model of asthma. Airway cellular composition was assessed by bronchoalveolar lavage (BAL) and airway responsiveness was measured as the bronchoconstrictor response to inhaled methacholine. In animals with chronic airway inflammation (increased BAL eosinophils) and sustained airway hyperresponsiveness, a 7 day dosing scheme with a murine anti-human ICAM-1 monoclonal antibody (R6.5, 2 mg/kg/day; i.v.) did not reduce the existing airway inflammation or airway hyperresponsiveness. In contrast, a similar dosing scheme with dexamethasone (0.2 mg/kg/day, i.m.) was found to significantly reduce both the airway eosinophilia and hyperresponsiveness. However, one week after cessation of dexamethasone treatment, the airway inflammation and hyperresponsiveness returned to pre-treatment levels. In further experiments where animals were first treated with dexamethasone (7 days) followed by a 7 day treatment with R6.5, the reoccurrence of airway inflammation and subsequent increase in airway responsiveness was prevented. We conclude that the efficacy of ICAM-1 is primarily associated with inhibition of the influx of inflammatory cells into the airways and subsequent reduction in airway responsiveness. These data suggest that in lungs with pre-existing inflammation the modulation of ICAM-1 following treatment with glucocorticoids may be a novel and more selective long-term treatment for control of the chronic airway inflammation and hyperresponsiveness associated with bronchial asthma.

Polymyxin B-induced bronchial neutrophilia does not alter airway responsiveness to methacholine in cynomolgus monkeys.

The purpose of this study was to develop a primate model of chronic bronchial neutrophilia to investigate the role of neutrophils in the pathogenesis of airway hyperresponsiveness. Ten adult male cynomolgus monkeys (Macaca fascicularis) were anaesthetized and intubated for each study. Six animals each received a total of seven inhalation treatments with polymyxin B (200 micrograms) over a 24 day period. Four control animals received an identical treatment regime with vehicle inhalations. Airway cellular composition was assessed by bronchoalveolar lavage (BAL). Airway responsiveness was assessed by methacholine cumulative dose response determinations. There were no significant changes in airway cellular composition or airway responsiveness in the control group. In contrast, Polymyxin B inhalation resulted in an influx of neutrophils (PMN) into the lungs which peaked at day 10 of the study (%PMN in BAL fluid rose from 5 +/- 2 to 51 +/- 8, P less than 0.001) and persisted out to day 24 (41 +/- 8, P less than 0.01). Increases in PMNs were associated with an increase in BAL levels of myeloperoxidase (MPO levels in BAL fluid increased from 2 +/- 3 to 180 +/- 23 OD P less than 0.05). Although airway PMN percentages and MPO concentrations were chronically elevated, airway responsiveness did not change. These results suggest that the neutrophil does not play a functional role in the onset of hyperresponsive airways in primates.

The onset and recovery from airway hyperresponsiveness: relationship with inflammatory cell infiltrates and release of cytotoxic granule proteins.

Previous studies from our laboratory have demonstrated a temporal relationship between eosinophil influx into the airways and the onset of airway hyperresponsiveness to inhaled methacholine. The purpose of the present study was to extend this observation by evaluating changes in airway cellular composition and measuring the levels of granulocyte-derived mediators recovered in BAL fluid during the onset and recovery from antigen-induced airway hyperresponsiveness. Airway cellular composition, airway responsiveness to inhaled methacholine and the levels of BAL fluid EPO and MPO were monitored over a 32 day study in eight adult male Ascaris suum sensitive cynomolgus monkeys. Repeated Ascaris suum inhalation (nine challenges during days 0-21) resulted in a selective, sustained airway eosinophilia that was temporally related with the onset and maintenance of airway hyperresponsiveness (r = 0.67, P less than 0.001). The level of BAL eosinophil-derived EPO was increased and remained elevated concurrent with the increase in airway eosinophils and airway responsiveness. During the recovery phase (days 22-32) the actual number of eosinophils remained elevated, while BAL EPO levels were significantly decreased. The recovery phase was also associated with a transient increase in the number of BAL neutrophils and MPO concentration. We conclude that the number and state of activation of airway eosinophils directly correlate with the onset and maintenance of airway hyperresponsiveness. Recovery from airway hyperresponsiveness is associated with a decrease in eosinophil activation and a transient increase in the number of activated neutrophils.

Is platelet activating factor (PAF) an important mediator in bronchial asthma?

The development of selective PAF receptor antagonists may provide a novel approach to the treatment of human bronchial asthma. In preclinical animal models of human asthma, PAF receptor antagonists have been found to be efficacious in blocking antigen-induced changes in lung function. However, the majority of these models involve acute inflammatory events and transient changes in lung function and, therefore, their relevance to human asthma is questionable. In a recent study with a primate model of chronic airway inflammation and hyperresponsiveness, we have shown that treatment with a PAF receptor antagonist had no effect on reducing chronic inflammation and hyperresponsiveness. Similarly, recent studies in human asthmatics with PAF receptor antagonists have failed to show efficacy in blocking allergen-induced airway responses or to have any steroid sparing effects in patients with ongoing asthma. Thus, it seems that PAF may not be a key mediator which can be blocked and thereby provide therapy for bronchial asthma.