The Effects of Aquaporin-1 in Pulmonary Edema Induced by Fat Embolism Syndrome.

This study was designed to investigate the role of aquaporin1 (AQP1) in the pathologic process of pulmonary edema induced by fat embolism syndrome (FES) and the effects of a free fatty acid (FFA) mixture on AQP1 expression in pulmonary microvascular endothelial cells (PMVECs). In vivo, edema was more serious in FES mice compared with the control group. The expression of AQP1 and the wet-to-dry lung weight ratio (W/D) in the FES group were significantly increased compared with the control group. At the same time, inhibition of AQP1 decreased the pathological damage resulting from pulmonary edema. Then we performed a study in vitro to investigate whether AQP1 was induced by FFA release in FES. The mRNA and protein level of AQP1 were increased by FFAs in a dose- and time-dependent manner in PMVECs. In addition, the up-regulation of AQP1 was blocked by the inhibitor of p38 kinase, implicating the p38 MAPK pathway as involved in the FFA-induced AQP1 up-regulation in PMVECs. Our results demonstrate that AQP1 may play important roles in pulmonary edema induced by FES and can be regarded as a new therapy target for treatment of pulmonary edema induced by FES.

Changes of leptin concentration in plasma in patients with spinal cord injury: a meta-analysis.

OBJECTIVE: The aim of this study was to investigate changes of leptin concentration in plasma in patients with spinal cord injury to come to a single concept by using a Meta-analysis. SETTING: Systematic Review. METHODS: Searching relevant articles was performed in Ovid data base, Medline (PubMed) EMBASE, Google Scholar, Cochrane and Scopus up to February 2013. Five articles were selected using two independent reviewers. Analysis were performed using SPSS version 18 and Comparative Meta-analysis software version 2.0. RESULTS: The combined analysis with confidence interval of 95% using comprehensive meta-analysis showed significant higher leptin levels in patients with spinal cord injury in comparison with able bodies (P<0.0001). The effect of spinal lesion level on plasma leptin concentration was also statistically significant (P<0.0001). Body mass index was positively related to plasma leptin concentration in both groups (P<0.0001). CONCLUSION: This Meta analysis approves increased level of leptin in spinal cord injured patients which can be due to fat distribution changes and sympathetic dysfunction in these patients. Our results also showed that patients with higher spinal lesion level have higher plasma leptin concentration.

Lipid emboli distribution in cardiac surgery is dependent on the state of emulsification.

OBJECTIVE: Lipid embolizations from retransfused shed blood during cardiac surgery have been shown to enter the circulation and end up in different organs. The purpose of this investigation was to evaluate differences in the kinetics and deposition between emulsified and non-emulsified lipid emboli in a porcine model. DESIGN: Twelve animals were anesthetized and put on cardiopulmonary bypass. A shed-blood phantom (6 animals given emulsified and 6 given non-emulsified lipids) was produced from arterial blood, saline, and tritium-labeled triolein. The phantom was infused into the cardiopulmonary bypass circuit. Arterial and venous blood samples were taken at short intervals. Tissue samples were taken post-mortem from examined organs and prepared for scintillation counting. Levels of radioactivity were used to measure lipid emboli content in blood and tissue. RESULTS: Emulsified lipid emboli generated a 5-fold higher embolic load in the arterial and a 12-fold higher in the venous circulation, compared with non-emulsified lipid emboli. Emulsified lipid micro emboli resulted in a 2-15-fold higher tissue deposition in investigated organs compared with non-emulsified lipid micro emboli. CONCLUSIONS: This study shows that the state of emulsion significantly alter the kinetics and tissue deposition of lipid emboli. Emulsified lipid emboli give higher embolic load in the arterial and venous circulation, and higher tissue deposition versus non-emulsified lipid emboli. In both groups, the embolic load was higher in the arterial circulation than on the venous side.

Effects of the ALX/FPR2 receptors of lipoxin A4 on lung injury induced by fat embolism syndrome in rats.

This study was designed to investigate the inflammatory responses in fat embolism syndrome (FES) and the relationship of ALX/FPR2 receptors and lipoxin A4 (LXA4) in FES models. In this model, lung injury score, lung tissue wet-to-dry (W/D) ratio and total protein concentration in bronchoalveolar lavage fluid (BALF) were increased compared with those of the control group. Meanwhile, the number of leukocytes and neutrophils was significantly increased in the FES group, as was the myeloperoxidase (MPO) activity and mRNA expression. In addition, the release of TNF-α and IL-1ß was increased. Then, we explored whether LXA4 and ALX/FPR2 were involved in the pathological process of FES. The LXA4 concentration in the experimental groups was markedly higher than that in the control group. At the same time, the protein and mRNA levels of ALX/FPR2 were upregulated in the rat model of FES. Moreover, rats treated with BML-111, an agonist for the ALX/FPR2 receptor of LXA4, showed a lower inflammatory response than mice treated with fat alone. However, the role of BML-111 in fat emboli (FE)-induced acute lung injury (ALI) was attenuated by BOC-2, an antagonist of the ALX/FPR2 receptor of LXA4. Our results demonstrated that the inflammatory response may play an important role in the pathogenesis of FES and that the activation of the ALX/FPR2 receptor for LXA4 can decrease the inflammatory response and may be a therapeutic target for FE-induced ALI.

Is lipoxin A4 an effective treatment on fat embolism syndrome by attenuating pro-inflammatory response?

Fat embolism syndrome (FES) is characterized by high mortality and lack of effective treatment, the symptomatic therapy is most used to relieve clinical symptoms. Some studies have shown that inflammation is one of the main pathogeneses of FES. Lipoxin A4 is an endogenous-derived anti-inflammatory substance which was discovered recently. It can alleviate inflammatory response and promote inflammation resolution, and is referred as brake signal of inflammation. Therefore we hypothesize that lipoxin A4 may have a remission and therapeutic effect on FES by attenuating FES-induced inflammatory responses.

VEGF mediates fat embolism-induced acute lung injury via VEGF receptor 2 and the MAPK cascade.

Fat embolism (FE) is a lethal medical emergency often caused by fracture of long bones and amputation of limbs. Vascular endothelial growth factor (VEGF) promotes angiogenesis and increases vascular permeability. We tested the hypothesis that VEGF plays a critical role in FE-induced acute respiratory distress syndrome (ARDS) and acute lung injury (ALI). Fat tissues were collected from male Sprague-Dawley rats, and animal oil was extracted and mixed with water to form fatty micelles. The micelles were then injected into the tail vein to produce FE and ALI in rats. Lung weight gain was measured as the index of pulmonary edema. The expression of pulmonary VEGF was evaluated by real-time PCR and western blot analysis. Inducible nitric oxide synthase (iNOS) and phosphorylation of mitogen-activated protein kinase (MAPK) were determined by western blot analyses. Interleukin-1ß (IL-1ß) was quantified by ELISAs. Hematoxylin and eosin staining was used to evaluate the pathological damage of ALI. In this study, we found that animal oil-induced FE significantly increased pulmonary VEGF expression and MAPK phosphorylation. We also evaluated the inflammatory response after FE and found that iNOS and IL-1ß significantly increased after FE. Systemic administration of SU-1498, an antagonist of VEGF receptor 2 (VEGFR-2), significantly attenuated the FE-induced inflammatory response and histological damage. This study suggested that VEGF is involved in FE-induced ARDS via the VEGFR-2 and MAPK cascades, which induce IL-1ß release and iNOS upregulation. Blockade of could be used to treat FE-induced pulmonary damage.

The kinetics of lipid micro-emboli during cardiac surgery studied in a porcine model.

OBJECTIVE: To study the kinetics of lipid micro-emboli during cardiac surgery. DESIGN: Eleven pigs were studied. Seven of these were put on extracorporeal circulation. A shed blood phantom consisted of blood, saline and radioactive triolein was added to the circuit. Both venous and arterial blood samples were taken at short intervals. Four animals were used to study renal kinetics without extracorporeal circulation. The same kind of shed blood phantom was infused into the ascending aorta. Samples were taken from the renal artery and vein. All samples were analyzed for radioactivity by scintillation counting. RESULTS: A median 130-fold increase in radioactivity was seen in the blood and was quickly eliminated. Systemic first-pass wedging was found to be 62%. The first-pass elimination in the kidney was 77%. No radioactivity was found in urine. CONCLUSIONS: This study shows that the turnover of lipid micro-emboli is fast, and that the majority of the emboli are trapped on their first passage through the capillary system. No evidence was found of a renal excretion of these lipid emboli.

Proton magnetic resonance spectroscopic findings of cerebral fat embolism induced by triolein emulsion in cats.

BACKGROUND: In experimental studies, embolization of the cerebral hemisphere with triolein emulsion has revealed reversible magnetic resonance imaging (MRI) findings in the subacute stage. PURPOSE: To investigate the changes in the major metabolites, by proton magnetic resonance spectroscopy (MRS), in a cerebral fat embolism induced by a triolein emulsion. MATERIAL AND METHODS: The internal carotid arteries of 19 cats were injected with a triolein emulsion, and multivoxel MRS was performed 30 min, 1 day, and 7 days later. In the control group, six cats were injected with normal saline. The MR spectra were evaluated for N-acetyl aspartate (NAA), creatine (Cr), and choline (Cho), along with the presence of lipid and lactate. Semiquantitative analyses of NAA/Cr, Cho/Cr, NAA/Cho, and lipid/Cr ratios compared the median values of the ipsilateral metabolite ratios with those of the contralateral side and in the control group for each point in time. RESULTS: The NAA/Cr, Cho/Cr, and NAA/Cho ratios in the ipsilateral cerebral hemisphere of the embolized group after 30 min, 1 day, and 7days were not significantly different from the contralateral hemisphere of the embolized and control groups (P>0.05). The lipid/Cr ratio in the ipsilateral cerebral hemisphere of the embolized group was significantly higher when compared with the control group (P=0.012 at 30 min, P=0.001 on day 1, and P=0.018 on day 7). CONCLUSION: Cerebral fat embolism induced by a triolein emulsion resulted in no significant change in the major metabolites of the brain in the acute stage, except for an elevated lipid/Cr ratio, which suggests the absence of any significant hypoxic-ischemic changes in the lesions embolized using a fat emulsion.

Clinical and pathological features of fat embolism with acute respiratory distress syndrome.

FES (fat embolism syndrome) is a clinical problem, and, although ARDS (acute respiratory distress syndrome) has been considered as a serious complication of FES, the pathogenesis of ARDS associated with FES remains unclear. In the present study, we investigated the clinical manifestations, and biochemical and pathophysiological changes, in subjects associated with FES and ARDS, to elucidate the possible mechanisms involved in this disorder. A total of eight patients with FES were studied, and arterial blood pH, PaO(2) (arterial partial pressure of O(2)), PaCO(2) (arterial partial pressure of CO(2)), biochemical and pathophysiological data were obtained. These subjects suffered from crash injuries and developed FES associated with ARDS, and each died within 2 h after admission. In the subjects, chest radiography revealed that the lungs were clear on admission, and pulmonary infiltration was observed within 2 h of admission. Arterial blood pH and PaO(2) declined, whereas PaCO(2) increased. Plasma PLA(2) (phospholipase A(2)), nitrate/nitrite, methylguanidine, TNF-alpha (tumour necrosis factor-alpha), IL-1beta (interleukin-1beta) and IL-10 (interleukin-10) were significantly elevated. Pathological examinations revealed alveolar oedema and haemorrhage with multiple fat droplet depositions and fibrin thrombi. Fat droplets were also found in the arterioles and/or capillaries in the lung, kidney and brain. Immunohistochemical staining identified iNOS (inducible nitric oxide synthase) in alveolar macrophages. In conclusion, our clinical analysis suggests that PLA(2), NO, free radicals and pro-inflammatory cytokines are involved in the pathogenesis of ARDS associated with FES. The major source of NO is the alveolar macrophages.

Biochemical parameters of bronchoalveolar lavage fluid in fat embolism.

OBJECTIVE: To identify diagnostic markers distinguishing between acute lung injury/acute respiratory distress syndrome (ALI/ARDS) due to fat embolism syndrome (FES) and that due to other causes, and to investigate whether phospholipase A2 and platelet-activating factor (PAF) play a role in the pathogenesis of ALI due to FES. DESIGN AND SETTING: A prospective study in a 14-bed ICU. PATIENTS: We studied 13 patients with FES, 11 with ALI/ARDS from other causes (6 without trauma, ALI/ARDS group 1; 7 with trauma, ALI/ARDS group 2) and 5 without cardiopulmonary disease. MEASUREMENTS AND RESULTS: We compared broncholveolar lavage (BAL) fluid alterations in the respective groups. Total BAL protein in FES group was significantly higher compared to in ALI/ARDS group 1 and controls but ALI/ARDS group 2. Higher total phospholipids were found than in other groups. The alterations in individual phospholipid classes were similar to those in ALI/ARDS patients. However, total cholesterol, lipid esters, and monoglycerides were significantly higher in FES than in other groups. The level of PAF in FES was significantly higher and there was an inverse correlation between PAF and PAF-acetylhydrolase. Phospholipase A2 activity was significantly higher in both FES and ALI/ARDS groups than in control. CONCLUSIONS: The levels of neutral lipids and especially cholesterol and cholesterol esters in BAL can be used to distinguish patients with FES from ALI/ARDS due to other predisposing factors. Phospholipase A(2) may be involved in the development, and PAF-acetylhydrolase in the downregulation of inflammation in FES.

Fat distribution and changes in the blood brain barrier in a rat model of cerebral arterial fat embolism.

This study was designed to determine the distribution of fat which reaches the brain by the internal carotid artery, and the consequent alterations in the blood brain barrier, in a rat model of cerebral arterial fat embolism. The distribution of the blood flow in this model was determined by the injection of radiolabelled microspheres. Over 44% were trapped in the brain, 43% in the extracerebral tissues of the head and neck, and 7% in the lungs. Over 30% of radiolabelled triolein was present within the brain 30 min after injection, and 4% still remained after 17 days. Approximately 25% of the triolein which went to the brain moved through the cerebral vessels and left within the first 15 min. The majority of the triolein distributed to the ipsilateral cerebral hemisphere, with significantly less to the contralateral cerebral hemisphere, brain stem and cerebellum. The blood brain barrier opened, as measured by uptake of 99mTc, within the first 15 min and remained open for at least 3 days. A significant percentage of fat reaching the brain persists for days, and causes rapid and long-lasting damage to the blood brain barrier.

Fat embolism and related effects during reamed and unreamed intramedullary nailing in a pig model.

OBJECTIVES: To determine whether reamed or unreamed femoral intramedullary nailing is more adverse to pulmonary function, the authors compared three populations of healthy pigs, analyzing the biochemical and hemodynamic effects related to fat embolism. Likewise, the authors histologically evaluated the presence of bone marrow fat embolism in lungs, heart, kidney, brain, and retina. DESIGN: Randomized, experimental model. SETTING: Laboratory. PARTICIPANTS: Twenty-five male Duroc Jersey adult healthy pigs divided in three groups. INTERVENTION: Reamed and unreamed intramedullary nailing. OUTCOME MEASUREMENTS: Biochemical, hemodinamical, and histologic analysis. METHODS: In the first group of ten pigs, a reamed nail was inserted; in the second group of ten specimens, the authors placed an unreamed nail; and in the third group of five animals (control), only the surgical approach was made without opening the medullary cavity. RESULTS: The authors did not find statistically significant differences in pulmonary function between the reamed and unreamed group in the hemodynamic, biochemical, and histopathologic parameters evaluated. The histologic analysis of the lung tissue revealed a statistically significant difference between the nailed groups and the control (P < 0.04). CONCLUSIONS: In this animal model, the results indicate that pulmonary changes and fat embolization during intramedullary nailing occur to the same degree in reamed and in unreamed femurs.

[Pulmonary lipids in fatal burns (author's transl)]. / Uber das Verhalten der Lungenfette nach vitalen Verbrennungen.

The pulmonary lipids were investigated at autopsy in 22 deaths from burns (3 scalds among them) by means of histological examination, thin-layer chromatography and gas liquid chromatography. Leaving out of consideration 4 cases with concomitant mechanical trauma 7 out of 18 burned victims showed fat embolism of the lungs, the degree varying from slight (4) to medium (3). Cases surviving for a short period showed fat embolism more frequently than those with a rapidly fatal course. The extracted pulmonary lipids were separated by thin-layer chromatography into 5 fractions (phospholipids, cholesterol, fatty acids, triglycerides, cholesterol esters) and evaluated densitometrically. The triglyceride fraction was increased in cases of fat embolism after burns, as well as in control cases of post-traumatic fat embolism. For further lipid characterisation the fatty acids were determined by gas chromatography. Calculation of the amounts of the individual fatty acids showed that in cases of at least medium intensity the ratio of oleic acid/linoleic acid and oleic acid/stearic acid is shifted towards oleic acid.

[Pathomorphological changes in lungs in acute periods of myocardial infarction]. / Patomorfolohichni zminy lehen' v hostromu periodi infarktu miokarda.

With the aid of morphological methods of investigation, the structure of the lungs was studied in those deceased persons having been ill with myocardial infarction and also in rats simulated with acute coronary failure. Comparison of results of studies made in autopsy and experimental material has shown that in the lungs occur certain stereotype structural changes which reflect abnormalities of lipid metabolism and manifest itself by fat microembolism of vessels of the microcirculatory bed and by accumulation of unemulsified fats in the interalveolar septa and alveolar lumens.

[The diagnosis of fat embolism in lungs altered by putrefaction]. / K diagnostike zhirovoiu émbolii gnilostno izmenennykh legkikh.

The results of biochemical analysis of rabbit lungs in case of death due to fat embolism and mechanical asphyxia (control) are presented. Reliable difference in lipid quantities was evident both immediately after death and in different putrefaction periods (this difference was 9-10 times greater in case of pulmonary fat embolism than in controls). The significant reduction in water content of the lungs in case of fat embolism as compared to controls was detected. Histological analysis of the putrefactive lungs can't detect fat embolism. Biochemical analysis makes it possible to diagnose fat embolism of the lungs in case of their marked putrefactive changes.

Transient blood brain barrier disruption induced by oleic acid is mediated by nitric oxide.

The blood brain barrier (BBB) maintains cerebral microenvironmental homeostasis. Transient disruption of the BBB after brain fat embolism in clinical cases and animal models has been reported but the precise mechanism underlying this occurrence is unclear. In the present study, we investigated BBB alterations in rats treated oleic acid (OA) delivered intra-arterially. Following OA treatment, transient brain edema, extravasation of Evans blue and Fluorescein isothiocyanate (FITC)-labeled dextran, and loss of laminin in the affected brain area were observed. Activation of matrix metalloproteinase (MMP)-2, -3, and -13 was found in the cerebral vessels 2 h after OA administration. Expression of intercellular adhesion molecule (ICAM)-1 in the vessels and neutrophil infiltration into the brain tissue was also observed. Inducible nitric oxide synthase (iNOS) was expressed in the neutrophils and nitrotyrosine was produced mainly in the vessels. Inhibitor of iNOS activity suppressed the loss of laminin, leakage of FITC-labeled dextran and Evans blue, and activation of MMP-2 and -13. Protein level of aquaporin (AQ)-4 was increased after OA administration but was not affected by treatment with iNOS inhibitor. In conclusion, we suggest that nitric oxide (NO) contributes to OA-induced MMP activation, BBB disruption and the development of transient brain edema.