Dalteparin: only protective in hepatic ischemia-reperfusion or also capable of preventing injury in liver hyperperfusion syndrome?
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Animals↗
Biomedical subjects
Michael D Menger
Publications and source records attributed to Michael D Menger.
Impact of severity of local soft-tissue trauma on long-term manifestation of microcirculatory and microlymphatic dysfunctions.
BACKGROUND: The present study aimed at quantitatively evaluating the impact of severity of local trauma on manifestation of soft-tissue injury-associated microcirculatory and microlymphatic dysfunctions in a chronic model that allowed repeated analyses by intravital fluorescence microscopy. METHODS: C57BL/6 mice were chronically instrumented with dorsal skinfold chambers and subjected to mild (180 J/m2, n = 6), moderate (270 J/m2, n = 6), or severe trauma (450 J/m2, n = 6; 540 J/m2, n = 6). Nontraumatized animals served as controls (sham; n = 8). Intravital microscopy was performed before and at 5 minutes, 1 hour, 8 hours, 24 hours, 3 days, and 5 days after trauma, and included the analysis of (1) blood and lymph microvessel rupture, (2) hematoma formation and lymph leakage, (3) arteriolar and venular constriction, (4) capillary perfusion failure, (5) arteriolar and venular leukocyte adhesion, and (6) interstitial edema formation. RESULTS: Mild trauma did not induce any changes of microcirculatory and microlymphatic functions. Moderate trauma did not affect lymphatics but provoked arteriolar constriction, capillary perfusion failure, leukocyte-endothelial cell interactions, and minor blood vessel ruptures with hematoma formation. These alterations, however, recovered within the first 24 hours after trauma. Severe trauma also did not affect the lymphatic microvasculature, but resulted in massive hematoma formation, arteriolar constriction, and capillary perfusion failure, which was associated with marked arteriolar and venular leukocyte recruitment and edema formation, and which did not recover to normal over a 5-day observation period. CONCLUSION: Only severe trauma of > 450 J/m2 provokes irreversible microcirculatory dysfunction in soft tissue, however, without affecting the integrity of lymphatic microvessels. Of interest, trauma-induced microcirculatory alterations are neither dominated solely by microcirculatory dysfunction nor by leukocytic inflammation. Instead, both pathologies develop in parallel, generating a vicious circle, which may be responsible for the compromised healing of severely traumatized soft tissue frequently observed in clinical practice.
Animals↗
Systemic hypothermia increases PAI-1 expression and accelerates microvascular thrombus formation in endotoxemic mice.
INTRODUCTION: Hypothermia during sepsis significantly impairs patient outcome in clinical practice. Severe sepsis is closely linked to activation of the coagulation system, resulting in microthrombosis and subsequent organ failure. Herein, we studied whether systemic hypothermia accelerates microvascular thrombus formation during lipopolysacharide (LPS)-induced endotoxemia in vivo, and characterized the low temperature-induced endothelial and platelet dysfunctions. METHODS: Ferric-chloride induced microvascular thrombus formation was analyzed in cremaster muscles of hypothermic endotoxemic mice. Flow cytometry, ELISA and immunohistochemistry were used to evaluate the effect of hypothermia on endothelial and platelet function. RESULTS: Control animals at 37 degrees C revealed complete occlusion of arterioles and venules after 759 +/- 115 s and 744 +/- 112 s, respectively. Endotoxemia significantly (p < 0.05) accelerated arteriolar and venular occlusion in 37 degrees C animals (255 +/- 35 s and 238 +/- 58 s, respectively). This was associated with an increase of circulating endothelial activation markers, agonist-induced platelet reactivity, and endothelial P-selectin and plasminogen activator inhibitor (PAI)-1 expression. Systemic hypothermia of 34 degrees C revealed a slight but not significant reduction of arteriolar (224 +/- 35 s) and venular (183 +/- 35 s) occlusion times. Cooling of the endotoxemic animals to 31 degrees C core body temperature, however, resulted in a further acceleration of microvascular thrombus formation, in particular in arterioles (127 +/- 29 s, p < 0.05 versus 37 degrees C endotoxemic animals). Of interest, hypothermia did not affect endothelial receptor expression and platelet reactivity, but increased endothelial PAI-1 expression and, in particular, soluble PAI-1 antigen (sPAI-Ag) plasma levels. CONCLUSION: LPS-induced endotoxemia accelerates microvascular thrombus formation in vivo, most probably by generalized endothelial activation and increased platelet reactivity. Systemic hypothermia further enhances microthrombosis in endotoxemia. This effect is associated with increased endothelial PAI-1 expression and sPAI-Ag in the systemic circulation rather than further endothelial activation or modulation of platelet reactivity.
Animals↗
Protective effect of fasudil, a Rho-kinase inhibitor, on chemokine expression, leukocyte recruitment, and hepatocellular apoptosis in septic liver injury.
Rho-kinase signaling regulates important features of inflammatory reactions. Herein, we investigated the effect and mechanisms of action of the Rho-kinase inhibitor fasudil in endotoxemic liver injury. C57/BL/6 mice were challenged with lipopolysaccharide (LPS) and D-galactosamine, with or without pretreatment with the Rho-kinase inhibitor fasudil. Six hours after endotoxin challenge, leukocyte-endothelium interactions in the hepatic microvasculature were studied by use of intravital fluorescence microscopy and tumor necrosis factor alpha (TNF-alpha); CXC chemokines as well as liver enzymes and apoptosis were determined. Administration of fasudil reduced LPS-induced leukocyte adhesion in postsinusoidal venules and sequestration in sinusoids. Moreover, we found that fasudil abolished extravascular infiltration of leukocytes as well as production of TNF-alpha and CXC chemokines in the liver of endotoxemic mice. Liver enzymes and hepatocellular apoptosis were markedly reduced, and sinusoidal perfusion was improved significantly in endotoxemic mice pretreated with fasudil. Our novel data document that fasudil is a potent inhibitor of endotoxin-induced expression of TNF-alpha and CXC chemokines as well as leukocyte infiltration and hepatocellular apoptosis in the liver. Based on the present findings, it is suggested that inhibition of the Rho-kinase signaling pathway may be a useful target in the treatment of septic liver injury.
1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
Fibronectin binding proteins contribute to the adherence of Staphylococcus aureus to intact endothelium in vivo.
Staphylococcal adhesins mediate attachment to matrix proteins and endothelial cells in vitro, yet, their role in primary adherence to the physiologic vessel wall has not been studied in vivo, and complex endocarditis models yielded ambiguous results. Recently, we developed a hamster model to study interaction kinetics of S. aureus with intact microvasculature using intravital fluorescence microscopy (Laschke et al. J Infect Dis 2005; 191: 435-443) providing the basis for this study. S. aureus Cowan 1 wild type (WT) log phase cells adhered to postcapillary venules to a significantly larger extent compared to stationary phase staphylococci, a finding in congruence with the fact that the staphylococcal adhesin repertoire largely depends on the growth phase. In comparison, the adherence rate of the fnbA deleted mutant (DU5895) to the vessel wall was significantly reduced to approximately 40% of WT. These DU5895 attachment rates were similar to those of an S. carnosus strain (TM300). In contrast, upon heterologous complementation of TM300 with either fnbA and fnbB, adherence of these transformants to the microvasculature increased, an increase found to be significant for fnbA transformant single cocci and clusters at 30 and 60 min when compared to S. carnosus TM300 WT. In conclusion, these results demonstrate that staphylococcal FnBPs significantly contribute to primary interaction with intact endothelium under physiologic conditions. Accordingly, this attribution of staphylococcal FnBPs provide a rationale for novel intervention strategies such as the use of anti-FnBP antibodies in endovascular S. aureus disease.
Adhesins, Bacterial↗
Antithrombin is as effective as heparin and hirudin to prevent formation of microvascular thrombosis in a murine model.
A recently published post-hoc analysis of a trial using high-dose antithrombin (AT) in septic patients (KyberSept) revealed significant reduction of lethality when no concomitant heparin was administered, whereas patients with the combination of heparin and AT did not benefit in terms of survival. Therefore, it seems feasible to study the capability of AT in prevention of microvascular thrombus formation to avoid concomitant application of heparin and AT. Using fluorescence microscopy and a light/dye-injury mouse ear model, the kinetics of thrombus formation were analyzed quantitatively in vivo upon single iv bolus of saline (control), heparin (100 IU/kg), hirudin (1 mg/kg) or AT (25, 50, 100 or 250 IU/kg) (N = 7 animals per group each). In controls, light/dye-injury induced complete thrombotic occlusion in all arterioles and venules studied. Heparin and hirudin prevented thrombotic vessel occlusion in 62% and 43% of arterioles and 11% and 28% of venules. AT-250 was found to be more effective than heparin and hirudin, because thrombus formation was completely banned in all arterioles and venules. AT-100 and AT-50 were also capable of significantly blocking thrombus formation in both arterioles and venules. In blood vessels, which finally clogged, the time for development of complete vessel occlusion was delayed after heparin, hirudin and AT-25, but in particular after AT-50 and AT-100. In conclusion, AT-mediated antithrombotic activity has been characterized in a model of phototoxicity-induced microvascular thrombosis formation, demonstrating that AT delays and prevents thrombus formation in arterioles and venules at least comparably effective as heparin and hirudin.
Animals↗
Immunostimulatory CpG-oligodeoxynucleotides (CpG-ODN) induce early hepatic injury, but provide a late window for protection against endotoxin-mediated liver damage.
BACKGROUND/AIMS: An impaired immunologic response to infection has been recognized as a major defect in the pathogenesis of sepsis and multi-organ failure. Sepsis-associated liver dysfunction and damage are main determinants for the course of the disease. CpG-motif-containing DNA-sequences (CpG-ODN) were previously shown to confer protection in models of infection by stimulating both innate and specific immune responses. Herein, we studied the effect of CpG-ODN in lipopolysaccharide (LPS)-associated hepatotoxicity. METHODS: Sprague Dawley rats pre-treated at day 6 with either CpG-ODN or inert DNA were challenged with E. coli LPS and subsequently studied for liver injury at 6 and 16 h using in vivo fluorescence microscopy and immunohistochemistry. Western blot protein analysis served for assessment of expression of TLR4, TNF receptor-associated factor 6 (TRAF6), NFkappaB and caspase-3. To evaluate CpG-ODN effects during non-septic conditions, additional animals were solely exposed to CpG-ODN and studied after 1 and 6 days. RESULTS: CpG-ODN application induced marked hepatic microcirculatory deterioration and liver dysfunction at day 1, however, with almost complete recovery to normal at day 6. Interestingly, CpG-ODN pre-treatment decreased LPS-induced leukocyte-endothelial cell interaction, sinusoidal perfusion failure and caspase-3-dependent apoptotic cell death. Although Kupffer cell phagocytic activity was not affected, CpG-ODN pre-treatment in LPS-challenged animals attenuated hepatic protein expression of TRAF6 and NFkappaB and increased TLR4 by almost 100%. CONCLUSIONS: CpG-containing DNA-sequences induce early hepatic injury, but mediate long-term protection against LPS hepatotoxicity. The mechanism of protection is based on the induction of cross-tolerance, probably via inhibition of the downstream TRAF6-NFkappaB signaling pathway and upregulation of the TLR4 surface receptor.
Adjuvants, Immunologic↗
Beyond the epithelial mucosa barrier: monitoring of microvascular perfusion dysfunction in critically endangered intestinal transplants(1,2).
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Animals↗
Microcirculatory alterations in ischemia-reperfusion injury and sepsis: effects of activated protein C and thrombin inhibition.
Experimental studies in ischemia-reperfusion and sepsis indicate that activated protein C (APC) has direct anti-inflammatory effects at a cellular level. In vivo, however, the mechanisms of action have not been characterized thus far. Intravital multifluorescence microscopy represents an elegant way of studying the effect of APC on endotoxin-induced leukocyte-endothelial-cell interaction and nutritive capillary perfusion failure. These studies have clarified that APC effectively reduces leukocyte rolling and leukocyte firm adhesion in systemic endotoxemia. Protection from leukocytic inflammation is probably mediated by a modulation of adhesion molecule expression on the surface of leukocytes and endothelial cells. Of interest, the action of APC and antithrombin in endotoxin-induced leukocyte-endothelial-cell interaction differs in that APC inhibits both rolling and subsequent firm adhesion, whereas antithrombin exclusively reduces the firm adhesion step. The biological significance of this differential regulation of inflammation remains unclear, since both proteins are capable of reducing sepsis-induced capillary perfusion failure. To elucidate whether the action of APC and antithrombin is mediated by inhibition of thrombin, the specific thrombin inhibitor hirudin has been examined in a sepsis microcirculation model. Strikingly, hirudin was not capable of protecting from sepsis-induced microcirculatory dysfunction, but induced a further increase of leukocyte-endothelial-cell interactions and aggravated capillary perfusion failure when compared with nontreated controls. Thus, the action of APC on the microcirculatory level in systemic endotoxemia is unlikely to be caused by a thrombin inhibition-associated anticoagulatory action.
Animals↗
Sustained hypothermia accelerates microvascular thrombus formation in mice.
Cold is supposed to be associated with alterations in blood coagulation and a pronounced risk for thrombosis. We studied the effect of clinically encountered systemic hypothermia on microvascular thrombosis in vivo and in vitro. Ferric chloride-induced microvascular thrombus formation was analyzed in cremaster muscle preparations from hypothermic mice. Additionally, flow cytometry and Western blot analysis was used to evaluate the effect of hypothermia on platelet activation. To test whether preceding hypothermia predisposes for enhanced thrombosis, experiments were repeated after hypothermia and rewarming to 37 degrees C. Control animals revealed complete occlusion of arterioles and venules after 742 +/- 150 and 824 +/- 172 s, respectively. Systemic hypothermia of 34 degrees C accelerated thrombus formation in arterioles and venules (279 +/- 120 and 376 +/- 121 s; P < 0.05 vs. 37 degrees C). This was further pronounced after cooling to 31 degrees C (163 +/- 57 and 281 +/- 71 s; P < 0.05 vs. 37 degrees C). Magnitude of thrombin receptor activating peptide (TRAP)-induced platelet activation increased with decreasing temperatures, as shown by 1.8- and 3.0-fold increases in mean fluorescence after PAC-1 binding to glycoprotein (GP)IIb-IIIa and 1.6- and 2.9-fold increases of fibrinogen binding on incubation at 34 degrees C and 31 degrees C. Additionally, tyrosine-specific protein phosphorylation in platelets was increased at hypothermic temperatures. In rewarmed animals, kinetics of thrombus formation were comparable to those in normothermic controls. Concomitantly, spontaneous and TRAP-enhanced GPIIb-IIIa activation did not differ between rewarmed platelets and those maintained continuously at 37 degrees C. Moderate systemic hypothermia accelerates microvascular thrombosis, which might be mediated by increased GPIIb-IIIa activation on platelets but does not cause predisposition with increased risk for microvascular thrombus formation after rewarming.
Animals↗
Is hemoglobin in hemoglobin vesicles infused for isovolemic hemodilution necessary to improve oxygenation in critically ischemic hamster skin?
The aim of this study was to test the influence of hemoglobin, encapsulated in phospholipid vesicles as an oxygen carrier, given in the course of isovolemic hemodilution to improve oxygenation in critically ischemic hamster flap tissue. Capillary hemodynamics and macromolecular leakage were investigated with intravital microscopy and analyzed off-line with the CapImage software. Partial tissue oxygen tension was measured with fluorescence quenching electrodes. The occurrence of apoptosis was assessed with the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. Vesicles with (HbV) or without (V) encapsulated Hb were suspended in 6% hydroxyethyl starch (HES) used for the 33% blood exchange. In the ischemic tissue, hemodilution led to an increase in functional capillary density by 31% for HES (P < 0.01 vs. other groups), 66% for V-HES, and 62% for HbV-HES (all P < 0.01 vs. control). Capillary diameters behaved inversely proportional to capillary microhemodynamics. The 20% increase in macromolecular leakage found over time in control animals was completely abolished in the vesicles groups (P < 0.01) but not with HES. Oxygen tension was improved from 10.7 to 16.0 mmHg after HbV-HES (P < 0.01 vs. baseline and other groups). Compared with the other groups, apoptosis was significantly reduced after HbV-HES (P < 0.01). We conclude that the encapsulation of Hb was essential to attenuate hypoxia and subsequent cell death in the critically ischemic tissue. However, the effect was partly attributed to the rheological changes exerted by the vesicles.
Acute Disease↗
Pifithrin-alpha induced p53 inhibition does not affect liver regeneration after partial hepatectomy in mice.
BACKGROUND/AIMS: Beside its well-known function as tumour suppressor gene, p53 is supposed to positively regulate cell division and cell differentiation. Because hepatocyte proliferation has been reported to be reduced by blockade of p53 function in vitro, we examined in the present study the impact of p53 inhibition on hepatocyte proliferation in vivo. METHODS: Mice treated with either pifithrin-alpha (PFT), a p53-inactivating agent, or the equivalent volume of vehicle, were subjected to 70% hepatectomy. In addition to assessment of liver mass restitution we examined p53 and p21 protein expression as well as PCNA expression and BrdU incorporation by using Western blot and immunohistochemical techniques. Extent of apoptosis was assessed by TUNEL assay. RESULTS: PFT lowered nuclear but not cytoplasmic p53, and did not inhibit protein expression of regeneration-associated p21. PCNA protein expression as well as PCNA and BrdU immunohistochemistry did not differ between regenerating livers of either PFT- or vehicle-treated animals. Moreover, TUNEL analysis of regenerated liver tissue revealed comparable numbers of apoptotic cells in both groups. CONCLUSIONS: Pharmacological inhibition of p53 did not impair liver regeneration in mice, implying that p53 is functionally redundant in that p53-independent pathways compensate for the blockade of p53 and sufficiently support the process of hepatocyte replication in liver regeneration.
Animals↗
Arteriolovenular shunting critically determines shutdown of microcirculation upon cryotherapy in tumor-bearing rat liver.
BACKGROUND: Tissue destruction by cryosurgery not only is mediated by direct cell damage, but also involves secondary mechanisms, such as ischemia due to shutdown of the microcirculation. Clinicians favor repetitive cryoapplication, although there is no proven evidence for a more effective tumor eradication. METHODS: The aims of this study were (1) to establish a rat liver tumor model that allows for intravital microscopic analysis of hepatic tumor microcirculation and (2) to elucidate critical determinants of shutdown of microvascular perfusion after single and repetitive cryotherapy. In WAG-Rji rats (n = 14), syngeneic colon carcinoma cells (CC531) were implanted into the left liver lobe. Hepatic and tumor microcirculation were studied by intravital microscopy. RESULTS: Two weeks after implantation, the tumors had developed a microvasculature with a capillary density markedly (P < .05) lower compared with the sinusoidal density of normal liver. However, at the tumor margin, venule diameters were significantly enlarged (P < .05), with high red blood cell velocities and arteriolovenular shunts. Both freeze procedures (temperature at the tumor margin: -32.4 degrees C +/- 1.6 degrees C and -36.4 degrees C +/- 2.0 degrees C) resulted in a complete shutdown of intratumoral and peritumoral capillary and hepatic sinusoidal perfusion. In contrast, some large venules showed maintenance of blood flow initially after freezing (15 minutes); however, this was abolished during the subsequent 2-hour observation period. CONCLUSIONS: Enlarged high-flow venules at the tumor margin, which participate in arteriolovenular shunting, critically determine the shutdown of the microcirculation upon cryotherapy. Repetitive freezing is not more effective than a single-freeze procedure to achieve complete tumor microcirculatory stasis.
Animals↗
Prevention of core cell damage in isolated islets of Langerhans by low temperature preconditioning.
AIM: To study the core cell damage in isolated islets of Langerhans and its prevention by low temperature preconditioning (26 degrees). METHODS: Islets were cultured at 37 degrees for 7-14 d after isolation, and then at 26 degrees for 2, 4 and 7 d before additional culture at 37 degrees for another 7 d. Core cell damage in the isolated islets was monitored by video-microscopy and analyzed quantitatively by use of a computer-assisted image analysis system. The analysis included daily measurement of the diameter and the area of the isolated islets and the area of the core cell damage that developed in those islets over time during culture. Histology and TdT-mediated dUTP-biotin nick end labeling (TUNEL) assay were used to characterize the cell damage and to monitor islet function. RESULTS: Microscopic analysis showed that during the 7 to 14 d of culture at 37 degrees, core cell damage occurred in the larger islets with diameters >200 microm, which included both necrotic and apoptotic cell death. Low temperature (26 degrees) culture could prevent core cell damage of isolated islets. The 7-d culture procedure at 26 degrees could inhibit most of the core cell (excluding diameters >300 microm) damages when the islets were re-warmed at 37 degrees. CONCLUSION: Our results indicate that core cell damage within isolated islets of Langerhans correlates with the size of islets. Low temperature (26 degrees) culture can prevent core cell damage in isolated islets, and successfully precondition these islets for incubation at 37 degrees. These novel findings may help to understand the pathophysiology of early loss of islet tissue after transplantation, and may provide a new strategy to improve graft function in the clinical setting of islet transplantation.
Animals↗
Initial hepatic microcirculation correlates with early graft function in human orthotopic liver transplantation.
Microcirculatory disturbances are an initial causative determinant in hepatic ischemia/reperfusion injury. The aim of this study was to assess sinusoidal perfusion during human liver transplantation using orthogonal polarization spectral imaging and to evaluate the significance of intraoperative microcirculation for early postoperative graft function. Hepatic microcirculation was measured in 27 recipients undergoing full-size liver transplantation and compared to a group of 32 healthy living-related liver donors. The microvascular parameters were correlated with postoperative aspartate aminotransferase and bilirubin levels. Hepatic perfusion following liver transplantation was found to be significantly decreased when compared with the control group. Volumetric blood flow within the individual sinusoids increased due to sinusoidal dilatation and enhanced flow velocity. Regression analysis of postoperative aspartate aminotransferase and bilirubin with microvascular parameters revealed significant correlations. The extent of volumetric blood flow increased within the first 30 minutes after reperfusion and showed a significant correlation with postoperative aspartate aminotransferase release and bilirubin elimination. In conclusion, postischemic hepatic microvascular perfusion was analyzed in vivo, demonstrating significant microvascular impairment during liver transplantation. Sinusoidal hyperperfusion appears to confer protection against postischemic liver injury, as given by the correlation with aspartate aminotransferase and bilirubin levels. Thus, these findings may have therapeutic importance with respect to mechanisms mediating postischemic reactive hyperemia.
Adolescent↗
Local platelet trapping as the cause of thrombocytopenia after hepatic cryotherapy.
Cryosurgery has been shown to be an effective approach to destruction of unresectable hepatic tumors. However, hepatic cryoablation may also be associated with local and systemic side effects, including thrombocytopenia and clotting dysfunction. Although thrombocytopenia is known to relate to the magnitude of hepatocellular injury, its etiology is still unknown. With the use of whole-body scintigraphy after injection of indium-111-labeled platelets we here demonstrated in six patients undergoing cryoablation of hepatic tumors that manifestation of systemic thrombocytopenia after cryosurgery is associated with excessive platelet trapping and destruction within the cryolesion. We therefore conclude that local platelet trapping represents a major cause of cryothermia-induced systemic thrombocytopenia.
Aged↗
In vivo analysis of angiogenesis in endometriosis-like lesions by intravital fluorescence microscopy.
OBJECTIVE: To establish a novel endometriosis model that allows for repetitive in vivo analyses of angiogenesis in ectopic endometrial tissue. DESIGN: Intravital fluorescence microscopic study. SETTING: Institute for Clinical and Experimental Surgery, University of Saarland. ANIMAL(S): Female Syrian golden hamsters equipped with skinfold chambers. INTERVENTION(S): Large (0.5 mm2) and small (0.1 mm2) endometrial fragments were mechanically isolated and transplanted autologously into skinfold chambers of untreated hormonally synchronized or bilaterally ovariectomized hamsters. MAIN OUTCOME MEASURE(S): Angiogenesis, vascularization, and microhemodynamics were analyzed over a 14-day period. RESULT(S): In untreated controls, endometrial fragments developed complete microvascular networks during the experimental observation period. Interestingly, microvascular blood flow was higher in large than in small fragments. Histologic examinations revealed proliferating endometriosis-like lesions with dilated endometrial glands surrounded by a richly vascularized stroma. Vascularization of endometrial fragments in synchronized animals did not differ from that of untreated controls. In contrast, endometrial fragments in ovariectomized animals showed a delay in angiogenesis and a significantly decreased blood perfusion, indicating the essential role of ovarian estrogens for ectopic vascularization and perfusion of endometrial tissue. CONCLUSION(S): This novel model of endometrial tissue transplantation is a useful experimental approach, not only to focus on the in vivo pathogenesis of endometriosis but also to develop antiangiogenic strategies for the treatment of this disease.
Animals↗
Depletion of alveolar macrophages by clodronate-liposomes aggravates ischemia-reperfusion injury of the lung.
BACKGROUND: Macrophages play an important role in ischemia-reperfusion injury of various organs. Liposome-encapsulated dichloromethylene diphosphonate (clodronate-liposome) depletes local macrophages in vivo. However, the effect of this approach on alveolar macrophages in pulmonary ischemia-reperfusion injury has not yet been evaluated. METHODS: Clodronate-liposomes in Hanks' balanced salt solution (HBSS) or HBSS alone were given intratracheally to anesthetized male Lewis rats in the clodronate or the control group (n = 6/each group). After 3 days, we subjected the lungs to ischemia (37 degrees C, 60 minutes) and reperfusion (60 minutes) in an isolated blood-perfused rat lung model. Analysis during reperfusion included gas exchange, hemodynamics, and airway mechanics. At the end of reperfusion, we determined leukocyte recruitment and macrophage inflammatory protein-2 (MIP-2) in bronchoalveolar lavage fluid. RESULTS: In the clodronate group, 4 experiments had to be terminated within 10 minutes of reperfusion because of severe lung injury, whereas all lungs of the controls could be studied during the 60-minute reperfusion period (p < 0.05). Clodronate significantly decreased dynamic airway compliance (p < 0.05) and increased airway resistance. Besides a tendency toward greater pulmonary vascular resistance, this was associated with recruitment of polymorphonuclear neutrophils (p < 0.05) and increased MIP-2 concentrations in the bronchoalveolar lavage fluid (p < 0.05). CONCLUSIONS: Intratracheal administration of liposome-encapsulated clodronate does not benefit, but aggravates, warm ischemia-reperfusion injury of the lung, increasing MIP-2-associated alveolar neutrophil recruitment and airway mechanical dysfunction.
Animals↗