The pulmonary and hepatic immune microenvironment and its contribution to the early systemic inflammation following blunt chest trauma

OBJECTIVE: Blunt chest trauma is accompanied by an early increase in plasma cytokine concentrations. However, the local sources of these mediators are poorly defined. We investigated the impact of blunt chest trauma on the inflammatory mediator milieu in different compartments (lung tissue, bronchoalveolar lavage, liver tissue, Kupffer cells, plasma) along with the time course of trauma-induced pulmonary endothelial barrier dysfunction to elucidate potential relationships. In addition, the correlation between intratracheally instilled interleukin-6 and its systemic release were studied. DESIGN: Prospective, randomized, controlled animal study. SETTING: Basic science laboratory of a university affiliated level 1 trauma center. SUBJECTS: Male C3H/HeN mice, 8-9 wks old, n = 141. INTERVENTIONS: Blunt chest trauma induced by a focused blast wave, intravenous injection of Evans blue, and intratracheal instillation of recombinant human interleukin-6. MEASUREMENTS AND MAIN RESULTS: Two hours after blunt chest trauma, plasma interleukin-6 was markedly increased. Simultaneously, interleukin-6, tumor necrosis factor-alpha, macrophage inflammatory protein-2, monocyte chemotactic polypeptide-1 and neutrophil/monocyte accumulation in bronchoalveolar lavage and interleukin-6, monocyte chemotactic polypeptide-1, and myeloperoxidase activity in lung tissue were significantly increased. This was accompanied by a coinciding elevation in the Evans blue lung-plasma ratio. Recombinant human interleukin-6, instilled intratracheally before blunt chest trauma, was detected in a dose-dependent manner in the plasma of the mice. Additionally, Kupffer cell interleukin-6, tumor necrosis factor-alpha, and interleukin-10 production was significantly augmented as early as 30 mins after the insult. CONCLUSIONS: These results indicate that early increased cytokine concentrations in the lung, particularly interleukin-6, are important mediator sources as their local peak coincides with the systemic inflammatory response and is accompanied by a simultaneous impaired function of the pulmonary endothelial barrier. A direct relationship between their local and systemic concentrations can be established. Furthermore, this is the first study to show that Kupffer cells are activated early after blunt chest trauma.     

Pulmonary contusion causes impairment of macrophage and lymphocyte immune functions and increases mortality associated with a subsequent septic challenge

OBJECTIVE AND DESIGN: Pulmonary contusion is frequently followed by acute respiratory distress syndrome, pneumonia, and sepsis. However, immunologic alterations of circulating and resident immune cell populations contributing to the posttraumatic immunosuppression are poorly understood. We therefore characterized the influence of pulmonary contusion on peripheral blood mononuclear cells, peritoneal macrophages, splenocytes, and splenic macrophages. To address the significance of the immunosuppression associated with lung contusion, we investigated how the consecutive addition of moderate or severe sepsis affected survival after blunt chest trauma. SUBJECTS: Male C3H/HeN mice (n = 10 per group) were anesthetized and subjected to chest trauma or sham procedure. MEASUREMENTS: The cytokine release of cultured peripheral blood mononuclear cells, peritoneal macrophages, splenocytes, and splenic macrophages and plasma levels of tumor necrosis factor-alpha and interleukin-6 from those animals were quantified. Sepsis was induced via cecal ligation and puncture 24 hrs after lung contusion. MAIN RESULTS: Two hours after blunt chest trauma, plasma tumor necrosis factor-alpha and interleukin-6 were markedly increased, as was peripheral blood mononuclear cell cytokine production, lung myeloperoxidase activity, and lung chemokine concentrations. At 24 hrs and, in part, already at 2 hrs, cytokine release from peritoneal macrophages, splenic macrophages, and splenocytes was significantly suppressed. Furthermore, pulmonary contusion when followed by moderate sepsis significantly diminished survival rate when compared with chest trauma or moderate sepsis alone. CONCLUSIONS: These results indicate that pulmonary contusion causes severe immunodysfunction of splenocytes, macrophages, and monocytes in different local compartments and systemically. Moreover, this immunosuppression is associated with an increased susceptibility to infectious complications, which results in a decreased survival rate if blunt chest trauma is followed by a septic insult.     

Pulmonary contusion induces alveolar type 2 epithelial cell apoptosis: role of alveolar macrophages and neutrophils

Alveolar type 2 (AT-2) cell apoptosis is an important mechanism during lung inflammation, lung injury, and regeneration. Blunt chest trauma has been shown to activate inflammatory cells such as alveolar macrophages (AMs) or neutrophils (polymorphonuclear granulocytes [PMNs]), resulting in an inflammatory response. The present study was performed to determine the capacity of different components/cells of the alveolar compartment (AMs, PMNs, or bronchoalveolar lavage [BAL] fluids) to induce apoptosis in AT-2 cells following blunt chest trauma. To study this, male Sprague-Dawley rats were subjected to either sham procedure or blunt chest trauma induced by a single blast wave. Various time points after injury (6 h to 7 d), the lungs were analyzed by immunohistochemistry, for AT-2 cells, or with antibodies directed against caspase 3, caspase 8, Fas, Fas ligand (FasL), BAX, and BCL-2. Bronchoalveolar lavage concentrations of TNF-alpha, IL-1beta, and soluble FasL were determined by enzyme-linked immunosorbent assay. Furthermore, cultures of AT-2 cells isolated from healthy rats were incubated with supernatants of AMs, PMNs, or BAL fluids obtained from either trauma or sham-operated animals in the presence or absence of oxidative stress. Annexin V staining or TUNEL (terminal deoxynucleotidyl transferase) assay was used to detect apoptotic AT-2 cells. Histological evaluation revealed that the total number of AT-2 cells was significantly reduced at 48 h following trauma. Fas, FasL, active caspase 8, and active caspase 3 were markedly up-regulated in AT-2 cells after chest trauma. BAX and BCL-2 did not show any significant changes between sham and trauma. IL-1beta, but not TNF-alpha, levels were markedly increased at 24 h after the injury, and soluble FasL concentrations were significantly enhanced at 6, 12, 24, and 48 h after the insult. Apoptosis of AT-2 cells incubated with supernatants from cultured AMs, isolated at 48 h following chest trauma was markedly increased when compared with shams. In contrast, no apoptosis was induced in AT-2 cells incubated with supernatants of activated PMNs or BAL fluids of traumatized animals. In summary, blunt chest trauma induced apoptosis in AT-2 cells, possibly involving the extrinsic death receptor pathway. Furthermore, mediators released by AMs appeared to be involved in the induction of AT-2 cell apoptosis.     

Blunt chest trauma induces delayed splenic immunosuppression

Severe blunt chest trauma is frequently associated with multiple organ failure and sepsis. Posttraumatic immunosuppression seems to play a major role in their development. However, the immunologic alterations following pulmonary contusion are insufficiently elucidated. Specifically, it remains unknown whether immunocompetent cells located distant from the site of the impact are affected. We therefore aimed to characterize the influence of pulmonary contusion on lymphocytes and splenic macrophages. Male C3H/HeN mice (n = 8-10/group) were anesthetized and subjected to trauma or sham procedure. Blunt chest trauma was induced by a blast wave focused on the thorax. Two or 24 h later, splenocytes and splenic macrophages were isolated and stimulated for 48 h. The cytokine release (IFN-gamma, IL-2, IL-3, IL-10, IL-12, IL-18) from splenocytes as well as from splenic macrophages (TNF-alpha, IL-10, IL-12, IL-18) and plasma levels of TNF-alpha and IL-6 were quantified by ELISA. The results indicate that at 2 h after blunt chest trauma, plasma TNF-alpha and IL-6 were markedly increased. At the same time, no differences in splenocyte cytokine production were detectable. However, at 24 h a significantly depressed cytokine release was observed in trauma animals. Furthermore, splenic macrophages showed a significantly decreased production of TNF-alpha, IL-10, and IL-12 at 24 h and markedly increased release of IL-18 at 2 h after trauma. These results indicate that blunt chest trauma causes severe immunodysfunction of lymphocytes and splenic macrophages. Thus, lung contusion as a localized type of trauma causes dysfunction of immunocompetent cell populations, which are located distant from the site of injury.     

Divergent effects of activated neutrophils on inflammation, Kupffer cell/splenocyte activation, and lung injury following blunt chest trauma

Polymorphonuclear granulocytes (PMNs) have been attributed a primarily deleterious role in the pathogenesis of acute lung injury (ALI). However, evidence exists that PMNs might also act beneficially in certain types of ALI. In this regard, we investigated the role of activated neutrophils in the pathophysiology of lung contusion-induced ALI. We used the model of blunt chest trauma accompanied by PMN-depletion in male C3H/HeN mice. Animals received 25 μg/g body weight PMN-depleting antibody Gr-1 intravenously 48 h before trauma. Bronchoalveolar lavage (BAL) and lung tissue interleukin 6 (IL-6) were similarly elevated in PMN-depleted and control animals after trauma, whereas macrophage inflammatory protein 2 and monocyte chemoattractant protein 1 in BAL and lungs, IL-10 in BAL, and lung keratinocyte chemoattractant (KC) were even further increased in the absence of PMNs. Plasma IL-6 and KC were also increased in response to the insult and even further in the absence of PMNs. Chest trauma induced an enhanced release of IL-6, tumor necrosis factor α, macrophage inflammatory protein 2, monocyte chemoattractant protein 1, and IL-10 from isolated KU, which was blunted in the absence of PMNs. In the presence of PMNs, BAL protein was further increased at 30 h when compared with the 3-h time point, which was not the case in the absence of PMNs. Taken together, in response to lung trauma, activated neutrophils control inflammation including mediator release from distant immune cells but simultaneously mediate pulmonary tissue damage. Thus, keeping in mind potential inflammatory adverse effects, modulation of neutrophil activation or trafficking might be a reasonable therapeutic approach in chest trauma-induced lung injury.     

Role of activated neutrophils in chest trauma-induced septic acute lung injury

More than 50% of severely injured patients have chest trauma. Second insults frequently result in acute lung injury (ALI), with sepsis being the main underlying condition. We aimed to develop a standardized, reproducible, and clinically relevant double-hit mouse model of ALI induced by chest trauma and polymicrobial sepsis and to investigate the pathophysiologic role of activated neutrophils. Lung contusion was applied to C57Bl/6 mice via a focused blast wave. Twenty-four hours later, sepsis was induced by cecal ligation and puncture. For polymorphonuclear leukocyte (PMN) depletion, animals received intravenous injections of PMN-depleting antibody. In response to blunt chest trauma followed by sepsis as well as after sepsis alone, a significant local and systemic inflammatory response with increased cytokine/chemokine levels in lung and plasma was observed. In contrast, lung apoptosis was markedly elevated only after a double hit. Intra-alveolar neutrophils and total bronchoalveolar lavage protein concentrations were markedly increased following isolated chest trauma or the combined insult, but not after sepsis alone. Lung myeloperoxidase activity was enhanced only in response to the double hit accompanied by histological disruption of the alveolar architecture, lung congestion, and marked cellular infiltrates. Neutrophil depletion significantly diminished lung interleukin 1β and interleukin 6 concentrations and reduced the degree of septic ALI. Here we have established a novel and highly reproducible mouse model of chest trauma-induced septic ALI characterizing a clinical relevant double-hit scenario. In particular, the depletion of neutrophils substantially mitigated the extent of lung injury, indicating a pathomechanistic role for neutrophils in chest trauma-induced septic ALI.     

Protective effect of hydrogen sulfide in a murine model of acute lung injury induced by combined burn and smoke inhalation

Acute lung injury results in a severe inflammatory response, which leads to priming and activation of leucocytes, release of reactive oxygen and reactive nitrogen species, destruction of pulmonary endothelium, extravasation of protein-rich fluid into the interstitium and formation of oedema. Recently, H2S (hydrogen sulfide) has been shown to decrease the synthesis of pro-inflammatory cytokines, reduce leucocyte adherence to the endothelium and subsequent diapedesis of these cells from the microvasculature in in vivo studies, and to protect cells in culture from oxidative injury. In the present study, we hypothesized that a parenteral formulation of H2S would reduce the lung injury induced by burn and smoke inhalation in a novel murine model. H(2)S post-treatment significantly decreased mortality and increased median survival in mice. H2S also inhibited IL (interleukin)-1beta levels and significantly increased the concentration of the anti-inflammatory cytokine IL-10 in lung tissue. Additionally, H2S administration attenuated protein oxidation following injury and improved the histological condition of the lung. In conclusion, these results suggest that H2S exerts protective effects in acute lung injury, at least in part through the activation of anti-inflammatory and antioxidant pathways.     

Esophageal perforation due to blunt chest trauma: Difficult diagnosis because of coexisting severe disturbance of consciousness

Esophageal perforation due to blunt trauma is a rare clinical condition, and the diagnosis is often difficult because patients have few specific symptoms. Delayed diagnosis may result in a fatal clinical course due to mediastinitis and subsequent sepsis. In this article, we describe a 26-year-old man with esophageal perforation due to blunt chest trauma resulting from a motor vehicle accident. Because a severe disturbance of consciousness masked the patient's trauma-induced thoracic symptoms, we required 11 h to diagnose the esophageal perforation. Therefore, the patient developed septic shock due to mediastinitis. However, his subsequent clinical course was good because of prompt combined therapy involving surgical repair and medical treatment after the diagnosis.     

Cardiopulmonary,histological, and inflammatory alterations after lung contusion in a novel mouse model of blunt chest trauma

Severe blunt chest trauma remains an important injury with high morbidity and mortality. However, the associated immunological alterations are poorly understood. Existing big animal models require large-scale settings, are often too expensive, and research products for immunological studies are limited. In this study we aimed to establish a new model of blunt, isolated and bilateral chest trauma in mice and to characterize its effects on physiological and inflammatory variables. Male C3H/HeN mice (n = 9-10/group) were anesthetized and a femoral artery was catheterized. The animals were subjected to trauma or sham procedure and monitored for 180 min. Blunt chest trauma was induced by a blast wave focused on the thorax. Trauma intensity was optimized by varying the exposure distance. Blood pressure, heart rate, respiratory rate, arterial blood gases and plasma cytokine levels were measured. Macroscopic and microscopic examinations were performed. In addition, outcome was evaluated in a 10-day survival study. Chest trauma caused a drop (P < 0.05) in blood pressure and heart rate, which partly recovered. Blood gases revealed hypoxemia and hypercarbia (P < 0.05) 180 min after trauma. There was marked damage to the lungs but none to abdominal organs. Histologically, the characteristic signs of a bilateral lung contusion with alveolar and intrabronchial hemorrhage were found. Plasma interleukin-6 and tumor necrosis factor alpha were considerably increased after 180 min. Blunt chest trauma resulted in an early mortality of 10% without subsequent death. On the basis of these findings, this novel mouse model of blunt chest trauma appears suitable for detailed studies on immunological effects of lung contusion.     

The role of C5a in the innate immune response after experimental blunt chest trauma

The inflammatory response after severe blunt chest trauma often leads to acute lung injury and acute respiratory distress syndrome which are associated with high mortality rates. Whereas the role of innate immunity in acute lung injury has been broadly investigated, the immune response after blunt chest trauma is still poorly understood. Therefore, the role of complement and neutrophils was determined in bilateral lung injury induced by a single blast wave. The following time-points were investigated posttrauma: sham, 1, 6, 12, and 24 h. There was a time-dependent systemic activation of complement as determined by CH-50 and presence of C5a-dependent chemotactic plasma activity. Moreover, factor H, a complement regulatory protein, was increased systemically and locally after injury. Anti-C5a treatment immediately after trauma ameliorated these peaks. After an initial systemic leukopenic phase, a marked leukocytosis occurred. The latter was normalized by C5a blockade. In parallel, white blood cell count in bronchioalveolar lavage fluids was increased as a function of time and was significantly decreased by anti-C5a treatment. Trauma-induced lung injury was also associated with dramatic changes in neutrophil function, namely early enhanced chemotaxis and phagocytosis, followed by prolonged functional defects-all of which were ameliorated by anti-C5a treatment. Furthermore, blockade of C5a ameliorated the buildup of the proinflammatory cytokine TNF-alpha, diminished the increase of cytokine-induced neutrophil chemoattractant 1, and altered the levels of the anti-inflammatory cytokine IL-10.These data suggest that blunt chest trauma leads to systemic activation of complement and robust C5a generation, which causes perturbations in defensive functions of neutrophils. Thus, C5a might represent a potential target for therapeutic immunomodulation to prevent immune dysfunctions post-trauma and thereby, perhaps, the progression to acute respiratory distress syndrome.     

Spontaneous occlusion of splenic and renal pseudoaneurysm after blunt abdominal trauma: a case report and literature review

Pseudoaneurysms caused by blunt abdominal trauma are rarely observed in solid organs. The preferred therapy for pseudoaneurysm after blunt abdominal trauma is often angiography and embolization. Here, we report a case of a spontaneous occlusion of splenic pseudoaneurysm and renal pseudoaneurysm after blunt abdominal trauma. Angiography and embolization were not required, and contrast-enhanced multi-detector computed tomography was used to monitor the patient. This case shows that spontaneous occlusion can be one of the possible outcomes of intraparenchymal splenic pseudoaneurysm and renal pseudoaneurysm after blunt abdominal trauma.     

Effects of exogenous hydrogen sulfide on brain metabolism and early neurological function in rabbits after cardiac arrest

Purpose

Some of the neuroprotective effects of hydrogen sulfide (H₂S) have been attributed to systemic hypometabolism and hypothermia. However, systemic metabolism may vary more dramatically than brain metabolism after cardiac arrest (CA). The authors investigated the effects of inhaled exogenous hydrogen sulfide on brain metabolism and neurological function in rabbits after CA and resuscitation.

Methods

Anesthetized rabbits were randomized into a sham group, a sham/H₂S group, a CA group, and a CA/H₂S group. Exogenous 80?ppm H₂S was administered to the sham/H₂S group and the CA/H₂S group which suffered 3?min of untreated CA by asphyxia and resuscitation. Effects on brain metabolism (cerebral extraction of oxygen (CEO₂), arterio-jugular venous difference of glucose [AJVD(glu)] and lactate clearance), S100B, viable neuron counts, neurological dysfunction score, and survival rate were evaluated.

Results

CEO₂, AJVD(glu), and lactate increased significantly after CA. Inhalation of 80?ppm H₂S significantly increased CEO₂ (25.04?±?7.11 vs. 16.72?±?6.12?%) and decreased AJVD(glu) (0.77?±?0.29 vs. 1.18?±?0.38?mmol/L) and lactate (5.11?±?0.43 vs. 6.01?±?0.64?mmol/L) at 30?min after resuscitation when compared with the CA group (all P?<?0.05). In addition, neurologic deficit scores, viable neuron counts, and survival rate were significantly better whereas S100B was decreased after H₂S inhalation.

Conclusions

The present study reveals that inhalation of 80?ppm H₂S reduced neurohistopathological damage and improves early neurological function after CA and resuscitation in rabbits. The increased CEO₂ and decreased AJVD(glu) and enhanced lactate clearance may be involved in the protective effects.     

Alveolar macrophage phagocytosis is enhanced after blunt chest trauma and alters the posttraumatic mediator release

Blunt chest trauma is known to induce a pulmonary invasion of short-lived polymorphonuclear neutrophils and apoptosis of alveolar epithelial type 2 (AT2) cells. Apoptotic cells are removed by alveolar macrophages (AMΦ). We hypothesized that chest trauma alters the phagocytic response of AMΦ as well as the mediator release of AMΦ during phagocytosis. To study this, male Sprague-Dawley rats were subjected to blunt chest trauma. Phagocytosis assays were performed in AMΦ isolated 2 or 24 h after trauma with apoptotic cells or opsonized beads. Phagocytosis of apoptotic AT2 cells by unstimulated AMΦ was significantly increased 2 h after trauma. At 24 h, AMΦ from traumatized animals, stimulated with phorbol-12-myristate-13-acetate, ingested significantly more apoptotic polymorphonuclear neutrophils than AMΦ from sham animals. Alveolar macrophages after trauma released significantly higher levels of tumor necrosis factor α, macrophage inflammatory protein 1α, and cytokine-induced neutrophil chemoattractant 1 when they incorporated latex beads, but significantly lower levels of interleukin 1β and macrophage inflammatory protein 1α when they ingested apoptotic cells. In vivo, phagocytosis of intratracheally instilled latex beads was decreased in traumatized rats. The bronchoalveolar lavage concentrations of the phagocytosis-supporting surfactant proteins A and D after blunt chest trauma were slightly decreased, whereas surfactant protein D mRNA expression in AT2 cells was significantly increased after 2 h. These findings indicate that chest trauma augments the phagocytosis of apoptotic cells by AMΦ. Phagocytosis of opsonized beads enhances and ingestion of apoptotic cells downregulates the immunologic response following lung contusion. Our data emphasize the important role of phagocytosis during posttraumatic inflammation after lung contusion.     

川芎嗪干预钝性肺挫伤急性期大鼠肺组织细胞的凋亡

背景：急性胸部撞击后所致的肺挫伤（钝性肺挫伤）常引起呼吸功能异常和继发性炎性反应,并参与全身炎性反应综合征和多器官功能障碍综合征,其发病原因及致病机制亟待明确。目的：观察胸部撞击所致钝性肺挫伤急性期细胞凋亡的变化及其川芎嗪对其的影响。方法：健康雄性SD大鼠随机分为正常对照组、模型组、川芎嗪治疗组,后两组制备胸部撞击伤模型,川芎嗪治疗组建模后立即腹腔注射川芎嗪80mg／kg1次。在创伤发生后1,2,3h观察肺组织病理形态学及细胞凋亡的改变、检测肺水肿程度和肺血管通透性改变,免疫组织化学检测肺组织Bcl-2、Bax和Caspase-3的表达及血液中肿瘤坏死因子α水平变化。结果与结论：模型组肿瘤坏死因子α水平在创伤后1h即显著增加,创伤后2h及3h间急剧增加（P〈0．05）;创伤后2h及3h肺组织细胞凋亡指数及肺组织损伤程度显著增高（均P〈0．05）;肺血管通透性及肺水肿程度增加（P〈0．05）;Caspase-3表达显著增高（P〈0．05）,Bcl-2／Bax比值显著降低（P〈0．05）。川芎嗪治疗组在相应时间点相对于模型组肿瘤坏死因子α水平显著降低（P〈0．05）,肺组织内细胞凋亡指数及肺组织损伤程度降低（P〈0．05）,肺血管通透性及肺水肿程度减轻（P〈0．05）;Caspase-3表达下降（P〈0．05）,Bcl-2／Bax比值增加（P〈0．01）。结果提示,川芎嗪可通过抑制肿瘤坏死因子CI表达,下调Caspase-3的表达并提高Bcl-2／Bax的比值,以降低胸部撞击所致肺组织急性期的异常凋亡并减轻胸部撞击所致急性期肺挫伤。     

CT in blunt chest trauma: Pulmonary, tracheobronchial, and diaphragmatic injuries

Routine use of CT in the initial evaluation of blunt chest trauma is controversial. CT, however, has been shown to be useful in the diagnosis of unsuspected chest injuries and in directing therapeutic interventions. This review discusses the CT findings in patients with pulmonary, tracheobronchial, and diaphragmatic injuries after blunt chest trauma.     

Distribution and function of alveolar cells in multiply injured patients with trauma-induced ARDS

To determine whether alveolar cells are involved in the pathogenesis of adult respiratory distress syndrome (ARDS), we assessed the distribution and function of alveolar cells from 30 polytraumatized patients with trauma-induced respiratory failure, 5 of whom also had lung contusion. Cells were obtained by bronchoalveolar lavage performed daily begining on the day of trauma and continuing for 14 days. Neutrophils constituted about 60% of lavage cells in ARDS patients with lung contusion 0–2 days after polytrauma and about 50% in ARDS patients without lung contusion. In ARDS patients with lung contusion the neutrophil fraction decreased to 52% 3–6 days after trauma and to 40% 7–14 days after trauma. In patients without lung contusion the neutrophil fraction increased to 77% and then decreased to 60% at these times. Total cell counts in ARDS patients with lung contusion were more than twice as high as in patients without lung contusion 0–2 days after trauma. The difference in total cell counts decreased during days 3–6 and disappeared by day 7. In all patients morphologically altered alveolar cells were observed 4 days and more after trauma. In non-survivors significantly more altered cells were found. The chemiluminescence-response pattern of the alveolar cells was enhanced throughout the study and correlated with the neutrophil fraction (r=0.6). The neutrophil fraction also correlated with the pulmonary vascular resistance during the first two days after trauma (r=0.53). We conclude that alveolar cells are involved in the pathogenesis of trauma-induced ARDS and that the alveolar cell distribution is different in patients with and without lung contusion during the development of posttraumatic respiratory failure.Part of this paper was presented as a poster at the VII^th International Symposium on Intensive Care and Emergency Medicine, Brussels, Belgium, March 1987     

Inhaled milrinone attenuates experimental acute lung injury

Purpose  To test whether inhalation of the phosphodiesterase 3 inhibitor milrinone may attenuate experimental acute lung injury (ALI). Methods  In rats, ALI was induced by infusion of oleic acid (OA). After 30 min, milrinone was inhaled either as single dose, or repeatedly in 30 min intervals. In mice, ALI was induced by intratracheal instillation of hydrochloric acid, followed by a single milrinone inhalation. Results  Four hours after OA infusion, ALI was evident as lung inflammation, protein-rich edema and hypoxemia. A single inhalation of milrinone attenuated the increase in lung wet-to-dry weight ratio and myeloperoxidase activity, and reduced protein concentration, neutrophil counts and TNF-α levels in bronchoalveolar lavage. This effect was further pronounced when milrinone was repeatedly inhaled. In mice with acid-induced ALI, milrinone attenuated hypoxemia and prevented the increase in lung myeloperoxidase activity. Conclusions  Inhalation of aerosolized milrinone may present a novel therapeutic strategy for the treatment of ALI.