N-acetylcysteine attenuates acute lung injury induced by fat embolism. Crit Care Med. 2008;36:565-571. [PMID: 18216605 DOI: 10.1097/01.ccm.0000299737.24338.5c]

Fat embolism syndrome after trauma: What you need to know

ABSTRACT

Fat embolism syndrome refers to a systemic condition caused by the circulation of fat droplets in the bloodstream, reaching various target organs typically after major bone fractures or related surgical procedures. Although most cases resolve spontaneously, severe instances can lead to significant respiratory failure, neurological damage, and even mortality. Therefore, appropriate prevention, timely diagnosis, and management are crucial for trauma patients at risk. The objective of this review article is to explore the definition, epidemiology, risk factors, clinical presentation, and pathophysiology of fat embolism syndrome. Furthermore, it aims to examine current recommendations for the accurate diagnosis, prevention, and treatment of it, providing a comprehensive guide for the effective management of patients prone to this condition.

Ursodeoxycholic acid protects against lung injury induced by fat embolism syndrome

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a life‐threatening disease with a high mortality rate, which was a common complication of fat embolism syndrome (FES). Ursodeoxycholic acid (UDCA) has been reported to exert potent anti‐inflammatory effects under various conditions. In vivo, perinephric fat was injected via tail vein to establish a rat FES model, the anti‐inflammatory effects of UDCA on FES‐induced lung injury were investigated through histological examination, ELISA, qRT‐PCR, Western blot and immunofluorescence. In vitro, human lung microvascular endothelial cells (HPMECs) were employed to understand the protective effects of UDCA. The extent of ALI/ARDS was evaluated and validated by reduced PaO₂/FiO₂ ratios, increased lung wet/dry (W/D) ratios and impaired alveolar‐capillary barrier, up‐regulation of ALI‐related proteins in lung tissues (including myeloperoxidase [MPO], vascular cell adhesion molecule 1 [VCAM‐1], intercellular cell adhesion molecule‐1 [ICAM‐1]), elevated protein concentration and increased proinflammatory cytokines levels (TNF‐α and IL‐1β) in bronchoalveolar lavage fluid (BALF). Pre‐treatment with UDCA remarkably alleviated these pathologic and biochemical changes of FES‐induced ALI/ARDS; our data demonstrated that pre‐treatment with UDCA attenuated the pathologic and biochemical changes of FES‐induced ARDS, which provided a possible preventive therapy for lung injury caused by FES.

Targeting Neutrophils to Treat Acute Respiratory Distress Syndrome in Coronavirus Disease

This review describes targeting neutrophils as a potential therapeutic strategy for acute respiratory distress syndrome (ARDS) associated with coronavirus disease 2019 (COVID-19), a pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Neutrophil counts are significantly elevated in patients with COVID-19 and significantly correlated with disease severity. The neutrophil-to-lymphocyte ratio can serve as a clinical marker for predicting fatal complications related to ARDS in patients with COVID-19. Neutrophil-associated inflammation plays a critical pathogenic role in ARDS. The effector functions of neutrophils, acting as respiratory burst oxidants, granule proteases, and neutrophil extracellular traps, are linked to the pathogenesis of ARDS. Hence, neutrophils can not only be used as pathogenic markers but also as candidate drug targets for COVID-19 associated ARDS.

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-1β (IL-1β) 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-1β 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-1β release and iNOS upregulation. Blockade of could be used to treat FE-induced pulmonary damage.

N-acetylcysteine tiherapeutically protects against pulmonary fibrosis in a mouse model of silicosis

Silicosis is a lethal pneumoconiosis disease characterized by chronic lung inflammation and fibrosis. The present study was to explore the effect of against crystalline silica (CS)-induced pulmonary fibrosis. A total of 138 wild-type C57BL/6J mice were divided into control and experimental groups, and killed on month 0, 1, 2, 3, 4, and 5. Different doses of N-acetylcysteine (NAC) were gavaged to the mice after CS instillation to observe the effect of NAC on CS induced pulmonary fibrosis and inflammation. The pulmonary injury was evaluated with Hematoxylin and eosin/Masson staining. Reactive oxygen species level was analyzed by DCFH-DA labeling. Commercial ELISA kits were used to determine antioxidant activity (T-AOC, glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) and cytokines (TNF-α, IL-1β, IL-4, and IL-6). The expression of oxidising enzymes (NOX2, iNOS, SOD2, and XO) were detected by real time PCR. Immunohistochemistry (IHC) staining was performed to examine epithelial-mesenchymal transition-related markers. The mice treated with NAC presented markedly reduced CS-induced pulmonary injury and ameliorated CS-induced pulmonary fibrosis and inflammation. The level of malondialdehyde was reduced, while the activities of GSH-PX, SOD, and T-AOC were markedly enhanced by NAC. We also found the down-regulation of oxidising enzymes (NOX2, iNOS, SOD2, and XO) after NAC treatment. Moreover, E-cadherin expression was increased while vimentin and Cytochrome C expressions were decreased by NAC. These encouraging findings suggest that NAC exerts pulmonary protective effects in CS-induced pulmonary fibrosis and might be considered as a promising agent for the treatment of silicosis.

IRF-1 Intervention in the Classical ROS-Dependent Release of NETs during LPS-Induced Acute Lung Injury in Mice

Previously, we demonstrated that neutrophil extracellular traps (NETs) play an essential role in lipopolysaccharide (LPS)-induced acute lung injury. However, the underlying mechanism is unclear. In this study, we showed that knockout of interferon regulatory factor 1 (IRF-1) in mice strongly attenuated the generation of NETs and reactive oxygen species (ROS) production in neutrophils from bronchoalveolar lavage fluid and alleviated LPS-induced lung injury and systemic inflammation. Our in vitro experiments demonstrated that LPS-stimulated platelets induce NET release through two distinct processes: an ROS-independent early/rapid NETosis and a later ROS-dependent classical NETosis. Notably, the classical ROS-dependent pathway plays a dominant role in the generation of NETs. Furthermore, we showed that IRF-1 knockout does not affect the formation of NETs in early/rapid NETosis, but significantly attenuates ROS production and the generation of NETs in classical NETosis, which determines the total levels of NETs released by LPS-stimulated platelets. In conclusion, IRF-1 deficiency plays a key role in moderating the excessive NETs formed via ROS in the classical pathway and retaining the protective role of the low-NET levels generated in early/rapid NETosis, which may serve as a novel target in acute lung injury/acute respiratory distress syndrome.

Critical Differences between Microscopic (MIFE) and Macroscopic (MAFE) Fat Embolism during Liposuction and Gluteal Lipoinjection

BACKGROUND

Liposuction and gluteal lipoinjection are two of the most frequent surgical procedures in body contouring surgery, and two of the most important complications are microscopic (MIFE) and macroscopic (MAFE) fat embolism. Despite a high index of morbidity and mortality, few reports exist about these complications, and although they have the same causal agent, their etiopathogenesis, clinical evolution, treatment, prognosis, and prevention are totally different. Therefore, the authors performed a comprehensive review of the literature to exhaustively analyze both pathologic conditions and present the differences between them.

METHODS

A detailed search was carried out in PubMed of studies on humans from 1946 to March of 2017 in any language and including the keywords microscopic fat embolism and macroscopic fat embolism with either liposuction or gluteal lipoinjection. The articles found were selected according to the search criteria and were analyzed to provide the final data and recommendations.

RESULTS

Of the 1245 and 26 articles that were found on complications related to liposuction and gluteal lipoinjection, respectively, only 41 on liposuction and microscopic fat embolism and seven on gluteal lipoinjection and microscopic fat embolism met the specific criteria for inclusion in the analysis. Only two articles on liposuction and two on gluteal lipoinjection referred to macroscopic fat embolism as a complication.

CONCLUSION

Although microscopic fat embolism and macroscopic fat embolism are pathologic conditions with high morbidity and mortality rates in association with liposuction and gluteal lipoinjection, few reports about them exist; therefore, the authors made recommendations based on this study for their diagnosis, prevention, and treatment.

N-acetylcysteine (NAC) ameliorates Epstein-Barr virus latent membrane protein 1 induced chronic inflammation

Chronic inflammation results when the immune system responds to trauma, injury or infection and the response is not resolved. It can lead to tissue damage and dysfunction and in some cases predispose to cancer. Some viruses (including Epstein-Barr virus (EBV)) can induce inflammation, which may persist even after the infection has been controlled or cleared. The damage caused by inflammation, can itself act to perpetuate the inflammatory response. The latent membrane protein 1 (LMP1) of EBV is a pro-inflammatory factor and in the skin of transgenic mice causes a phenotype of hyperplasia with chronic inflammation of increasing severity, which can progress to pre-malignant and malignant lesions. LMP1 signalling leads to persistent deregulated expression of multiple proteins throughout the mouse life span, including TGFα S100A9 and chitinase-like proteins. Additionally, as the inflammation increases, numerous chemokines and cytokines are produced which promulgate the inflammation. Deposition of IgM, IgG, IgA and IgE and complement activation form part of this process and through genetic deletion of CD40, we show that this contributes to the more tissue-destructive aspects of the phenotype. Treatment of the mice with N-acetylcysteine (NAC), an antioxidant which feeds into the body’s natural redox regulatory system through glutathione synthesis, resulted in a significantly reduced leukocyte infiltrate in the inflamed tissue, amelioration of the pathological features and delay in the inflammatory signature measured by in vivo imaging. Reducing the degree of inflammation achieved through NAC treatment, had the knock on effect of reducing leukocyte recruitment to the inflamed site, thereby slowing the progression of the pathology. These data support the idea that NAC could be considered as a treatment to alleviate chronic inflammatory pathologies, including post-viral disease. Additionally, the model described can be used to effectively monitor and accurately measure therapies for chronic inflammation.

Fat embolism syndrome: What have we learned over the years?

Although its original clinical description dates from the nineteenth century, fat embolism syndrome remains a diagnostic challenge for clinicians. Fat emboli occur in all patients with long-bone fractures, but only few of them develop a multisystem disorder affecting the lung, brain, and skin, also known as fat embolism syndrome (FES). The incidence of FES varies and is often underestimated. Mechanical and biochemical theories have been proposed for the pathophysiology of FES. Clinical manifestations consist of respiratory and cerebral dysfunction and a petechial rash. Diagnosis of FES is difficult and based mainly on clinical criteria. FES is a self-limiting disease and treatment needs to be mainly supportive. Surgical treatment of the coexistent injuries is still obscured by controversies and the treatment methods used provide inconclusive results. In this context, prevention focuses on the early identification of predisposing factors.

Detrimental role of the airway mucin Muc5ac during ventilator-induced lung injury

Acute lung injury (ALI) is associated with high morbidity and mortality in critically ill patients. At present, the functional contribution of airway mucins to ALI is unknown. We hypothesized that excessive mucus production could be detrimental during lung injury. Initial transcriptional profiling of airway mucins revealed a selective and robust induction of MUC5AC upon cyclic mechanical stretch exposure of pulmonary epithelia (Calu-3). Additional studies confirmed time- and stretch-dose-dependent induction of MUC5AC transcript or protein during cyclic mechanical stretch exposure in vitro or during ventilator-induced lung injury in vivo. Patients suffering from ALI showed a 58-fold increase in MUC5AC protein in their bronchoalveolar lavage. Studies of the MUC5AC promoter implicated nuclear factor κB in Muc5ac induction during ALI. Moreover, mice with gene-targeted deletion of Muc5ac⁻/⁻ experience attenuated lung inflammation and pulmonary edema during injurious ventilation. We observed that neutrophil trafficking into the lungs of Muc5ac⁻/⁻ mice was selectively attenuated. This implicates that endogenous Muc5ac production enhances pulmonary neutrophil trafficking during lung injury. Together, these studies reveal a detrimental role for endogenous Muc5ac production during ALI and suggest pharmacological strategies to dampen mucin production in the treatment of lung injury.

Pulmonary fat embolism and related effects during femoral intramedullary surgery: An experimental study in dogs

The aim of the present study was to develop an animal model of pulmonary fat embolism (PFE) caused by femoral intramedullary procedures, and to investigate the initial changes in the hemodynamics, cytokines and risk factors of PFE. Sixteen dogs were randomly divided into two groups: Group A (intramedullary reaming and bone cement injection, n=8) and Group B (surgical approach without opening the medullary cavity, n=8). The hemodynamics, arterial blood gases and relevant cytokines were evaluated, and the lungs were examined using Oil Red O staining. In the animals of Group A, the heart rate, central venous pressure, mean pulmonary arterial pressure, pulmonary capillary wedge pressure and extravascular lung water (EVLW) were increased compared with the baseline levels, while the mean arterial pressure was decreased immediately following the reaming and bone cement infusion (P<0.05). Furthermore, there was a significant reduction in the pH and the arterial oxygen tension (PaO₂), and a significant increase in the arterial carbon dioxide tension (PaCO₂; P<0.05 for all) following the bilateral intramedullary surgery. The EVLW was correlated with the PaO₂ (P<0.001) and PaCO₂ (P=0.046). Following surgery, there was a significant increase in tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 levels in Group A (P<0.05). However, there were no significant changes in these parameters in Group B. The parameters tested, with the exception of pH, were significantly different in Group A compared with those in Group B (P<0.05) following the bilateral intramedullary surgery. Oil Red O staining was positive for all animals in Group A and negative for those in Group B. Femoral intramedullary surgery may induce PFE and subsequently affect hemodynamics and arterial blood gases. EVLW was correlated with the PaO₂ (P<0.001) and the PaCO₂ (P=0.046). These results demonstrated that EVLW and cytokines may serve as predictors of the development of fat embolism syndrome (FES).

Acute lung injury and acute respiratory distress syndrome: experimental and clinical investigations

Acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) can be associated with various disorders. Recent investigation has involved clinical studies in collaboration with clinical investigators and pathologists on the pathogenetic mechanisms of ALI or ARDS caused by various disorders. This literature review includes a brief historical retrospective of ALI/ARDS, the neurogenic pulmonary edema due to head injury, the long-term experimental studies and clinical investigations from our laboratory, the detrimental role of NO, the risk factors, and the possible pathogenetic mechanisms as well as therapeutic regimen for ALI/ARDS.

Effect of N-acetylcysteine (NAC) on acute lung injury and acute kidney injury in hemorrhagic shock

AIM OF THE STUDY

N-acetylcysteine (NAC) has been investigated to attenuate organ injury in various experimental and clinical studies. However, results in hemorrhagic shock (HS) were controversial. We determined the effects of continuous administration of NAC on acute lung injury (ALI) and acute kidney injury (AKI) in HS model.

METHODS

Twenty male Sprague-Dawley rats were used. Pressure controlled HS model defined by mean arterial pressure (MAP) 40±2 mmHg for 90 min followed by resuscitation and observation was used. Rats (n=10 per group) were randomized into 2 groups with NAC or dextrose. Intravenous NAC was given continuously from 15 min after induction of HS to the end of observation period (2 h). We measured serum IL-6, nitrite/nitrate concentration. NF-κB p65 DNA binding activity, expressions of cytoplasmic phosphorylated IκB-α (p-IκB-α) and IκB-α, malondialdehyde (MDA) and histopathological injury scores in lung and kidney were also evaluated.

RESULTS

MAP did not show any difference during the study period. NAC decreased histopathologic scores in both lung and kidney. Lung and kidney MDA levels were significantly lower in the NAC group compared to control group. Serum nitrite/nitrate and IL-6 were also significantly lower in the NAC group. The levels of lung cytoplasmic p-IκB-α expression was mitigated by NAC, and NF-κB p65 DNA binding activity was also significantly decreased in the NAC group.

CONCLUSIONS

Continuous infusion of NAC attenuated inflammatory response and acute lung and kidney injury after hemorrhagic shock in rats.

Acute respiratory distress syndrome and lung injury: Pathogenetic mechanism and therapeutic implication

To review possible mechanisms and therapeutics for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). ALI/ARDS causes high mortality. The risk factors include head injury, intracranial disorders, sepsis, infections and others. Investigations have indicated the detrimental role of nitric oxide (NO) through the inducible NO synthase (iNOS). The possible therapeutic regimen includes extracorporeal membrane oxygenation, prone position, fluid and hemodynamic management and permissive hypercapnic acidosis etc. Other pharmacological treatments are anti-inflammatory and/or antimicrobial agents, inhalation of NO, glucocorticoids, surfactant therapy and agents facilitating lung water resolution and ion transports. β-adrenergic agonists are able to accelerate lung fluid and ion removal and to stimulate surfactant secretion. In conscious rats, regular exercise training alleviates the endotoxin-induced ALI. Propofol and N-acetylcysteine exert protective effect on the ALI induced by endotoxin. Insulin possesses anti-inflammatory effect. Pentobarbital is capable of reducing the endotoxin-induced ALI. In addition, nicotinamide or niacinamide abrogates the ALI caused by ischemia/reperfusion or endotoxemia. This review includes historical retrospective of ALI/ARDS, the neurogenic pulmonary edema due to head injury, the detrimental role of NO, the risk factors, and the possible pathogenetic mechanisms as well as therapeutic regimen for ALI/ARDS.

Protective effects of hydrogen-rich saline in a rat model of traumatic brain injury via reducing oxidative stress

BACKGROUND

Hydrogen gas (H(2)) has been considered as a novel antioxidant to selectively reduce the toxic reactive oxygen species (ROS) such as hydroxyl radical (•OH) without affecting the other signal ROS. Our recent study shows that H(2) inhalation is beneficial to traumatic brain injury (TBI) via reducing oxidative stress. In contrast to H(2), hydrogen-rich saline (HS) may be more suitable for clinical application. The present study was designed to investigate whether HS has a protective effect against TBI via reducing oxidative stress in rats.

METHODS

TBI model was induced by controlled cortical impact injury. Different dosages of HS were intraperitoneally administered at 5 min after TBI operation. We then measured the brain edema, blood-brain barrier (BBB) breakdown, neurological dysfunction and injury volume in all animals. In addition, the oxidative products and antioxidant enzymes in brain tissues were detected.

RESULTS

TBI-challenged rats exhibited significant brain injuries characterized by the increase of BBB permeability, brain edema, and lesion volume as well as neurological dysfunction, which were dose-dependently ameliorated by HS treatment. Moreover, we found that HS treatment increased the endogenous antioxidant enzymatic activities and decreased the oxidative product levels in brain tissues of TBI-challenged rats.

CONCLUSION

Hydrogen-rich saline can exert a protective effect against TBI via reducing oxidative stress. Molecular hydrogen may be a more effective therapeutic strategy for TBI patients.

Niacinamide mitigated the acute lung injury induced by phorbol myristate acetate in isolated rat's lungs

BACKGROUND

Phorbol myristate acetate (PMA) is a strong neutrophil activator and has been used to induce acute lung injury (ALI). Niacinamide (NAC) is a compound of B complex. It exerts protective effects on the ALI caused by various challenges. The purpose was to evaluate the protective effects of niacinamide (NAC) on the PMA-induced ALI and associated changes.

METHODS

The rat's lungs were isolated in situ and perfused with constant flow. A total of 60 isolated lungs were randomized into 6 groups to received Vehicle (DMSO 100 μg/g), PMA 4 μg/g (lung weight), cotreated with NAC 0, 100, 200 and 400 mg/g (lung weight). There were 10 isolated lungs in each group. We measured the lung weight and parameters related to ALI. The pulmonary arterial pressure and capillary filtration coefficient (Kfc) were determined in isolated lungs. ATP (adenotriphosphate) and PARP [poly(adenosine diphophate-ribose) polymerase] contents in lung tissues were detected. Real-time PCR was employed to display the expression of inducible and endothelial NO synthases (iNOS and eNOS). The neutrophil-derived mediators in lung perfusate were determined.

RESULTS

PMA caused increases in lung weight parameters. This agent produced pulmonary hypertension and increased microvascular permeability. It resulted in decrease in ATP and increase in PARP. The expression of iNOS and eNOS was upregulated following PMA. PMA increased the neutrophil-derived mediators. Pathological examination revealed lung edema and hemorrhage with inflammatory cell infiltration. Immunohistochemical stain disclosed the presence of iNOS-positive cells in macrophages and endothelial cells. These pathophysiological and biochemical changes were diminished by NAC treatment. The NAC effects were dose-dependent.

CONCLUSIONS

Our results suggest that neutrophil activation and release of neutrophil-derived mediators by PMA cause ALI and associated changes. NO production through the iNOS-producing cells plays a detrimental role in the PMA-induced lung injury. ATP is beneficial, while PARP plays a deteriorative effect on the PMA-induced ALI. NAC exerts protective effects on the inflammatory cascade leading to pulmonary injury. This B complex compound may be applied for clinical usage and therapeutic regimen.

Effects of phorbol myristate acetate and sivelestat on the lung injury caused by fat embolism in isolated lungs

Background

Fat embolism syndrome (FES) associated with acute lung injury (ALI) is a clinical condition following long bone fracture. We have reported 14 victims due to ALI with FES. Our laboratory has developed an animal model that produced fat emboli (FE). The major purpose of this study was to test whether neutrophil activation with phorbol myristate acetate (PMA) and inhibition with sivelestat (SVT) exert protection on the lung.

Methods

The lungs of Sprague-Dawley rats were isolated and perfused. FE was produced by addition of corn oil micelles into the lung perfusate. PMA and SVT were given simultaneously with FE. Parameters such as lung weight/body weight ratio, LW gain, exhaled nitric oxide (NO), protein concentration in bronchoalveolar lavage relating to ALI were measured. The neutrophil elastase (NE), myeloperoxidase, malondialdehyde and phopholipase A₂ activity were determined. We also measured the nitrate/nitrite, methyl guanidine (MG), and cytokines. Pulmonary arterial pressure and microvascular permeability were assessed. Lung pathology was examined and scored. The inducible and endothelial NO synthase (iNOS and eNOS) were detected.

Results

FE caused ALI and increased biochemical factors. The challenge also resulted in pulmonary hypertension and increased microvascular permeability. The NE appeared to be the first to reach its peak at 1 hr, followed by other factors. Coadministration with PMA exacerbated the FE-induced changes, while SVT attenuated the effects of FE.

Conclusions

The FE-induced lung changes were enhanced by PMA, while SVT had the opposite effect. Sivelestat, a neutrophil inhibitor may be a therapeutic choice for patients with acute respiratory distress syndrome (ARDS) following fat embolism.

N-Acetylcysteine modulates acute lung injury induced by Pseudomonas aeruginosa in rats

1. In critically ill patients, Pseudomonas aeruginosa-induced pneumonia and the lung injury associated with infection are major causes of mortality. The aim of the present study was to evaluate the protective properties of N-acetylcysteine (NAC) in rats infected with P. aeruginosa and the role of nitric oxide synthases (NOS) protein in this process. 2. Pneumonia was induced in rats by infecting them with P. aeruginosa intratracheally. One group of rats was treated with NAC (150 mg/kg per day, i.p., for 7 days). An untreated group served as the control. Samples were collected both before (0 h) and after infection (24 h). Bacterial loads in lung tissue, the lung wet : dry (W/D) ratio and pulmonary vascular permeability were assessed. Total cell and polymorphonuclear leucocyte cell counts in bronchoalveolar lavage fluid were determined. The expression of inducible (i) NOS and endothelial (e) NOS protein was analysed and correlated with indices of lung injury using Pearson's correlation analysis. 3. Bacterial load, lung injury indices and NOS expression increased after infection. Pretreatment with NAC mitigated lung injury although it did not significantly change bacterial loads. Furthermore, NAC treatment increased eNOS protein expression, but decreased iNOS expression, in lung tissues after infection. The expression of iNOS protein was positively correlated with indices of lung injury, whereas there was a negative correlation between eNOS expression and lung injury indices. 4. N-Acetylcysteine modulated P. aeruginosa-induced lung injury in rats. The results suggest that this effect maybe due to regulation of iNOS and eNOS protein expression by NAC.

Transcranial Doppler detection of cerebral fat emboli and relation to paradoxical embolism: a pilot study

BACKGROUND

The fat embolism syndrome is clinically characterized by dyspnea, skin petechiae, and neurological dysfunction. It is associated mainly with long bone fracture and bone marrow fat passage to the systemic circulation. An intracardiac right-to-left shunt (RLS) could allow larger fat particles to reach the systemic circulation. Transcranial Doppler can be a useful tool to detect both RLS and the fat particles reaching the brain.

METHODS AND RESULTS

We prospectively studied patients with femur shaft fracture with RLS evaluation, daily transcranial Doppler with embolus detection studies, and neurological examinations to evaluate the relation of RLS and microembolic signals to the development of fat embolism syndrome. Forty-two patients were included; 14 had an RLS detected. Seven patients developed neurological symptoms; all of them had a positive RLS (P=<0.001). The patients with an RLS showed higher counts and higher intensities of microembolic signals (P=<0.05 and P=<0.01, respectively) compared with those who did not have an RLS identified. The presence of high microembolic signal counts and intensities in patients with RLS was strongly predictive of the occurrence of neurological symptoms (odds ratio, 204; 95% confidence interval, 11 to 3724; P<0.001) with a positive predictive value of 86% and negative predictive value of 97%.

CONCLUSIONS

In patients with long bone fractures, the presence of an RLS is associated with larger and more frequent microembolic signals to the brain detected by transcranial Doppler study and can predict the development of neurological symptoms.

Hydrogen gas improves survival rate and organ damage in zymosan-induced generalized inflammation model

Sepsis/multiple organ dysfunction syndrome is the leading cause of death in critically ill patients. Recently, it has been suggested that hydrogen gas (H2) exerts a therapeutic antioxidant activity by selectively reducing hydroxyl radical (•OH, the most cytotoxic reactive oxygen species). We have found that H2 inhalation significantly improved the survival rate and organ damage of septic mice with moderate or severe cecal ligation and puncture. In the present study, we investigated the effects of 2% H2 treatment on survival rate and organ damage in zymosan (ZY)-induced generalized inflammation model. Here, we found that 2% H2 inhalation for 60 min starting at 1 and 6 h after ZY injection, respectively, significantly improved the 14-day survival rate of ZY-challenged mice from 10% to 70%. Furthermore, ZY-challenged mice showed significant multiple organ damage characterized by the increase in serum biochemical parameters (aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, and creatinine), as well as lung, liver, and kidney histopathological scores at 24 h after ZY injection, which was significantly attenuated by 2% H2 treatment. In addition, we found that the beneficial effects of H2 treatment on ZY-induced organ damage were associated with the decreased levels of oxidative product, increased activities of antioxidant enzyme, and reduced levels of early and late proinflammatory cytokines in serum and tissues. In conclusion, this study provides evidence that H2 treatment protects against multiple organ damages in ZY-induced generalized inflammation model, suggesting the potential use of H2 as a therapeutic agent in the therapy of conditions associated with inflammation-related multiple organ dysfunction syndrome.

Impact of Escaped Bone Marrow Mesenchymal Stromal Cells on Extracardiac Organs after Intramyocardial Implantation in a Rat Myocardial Infarction Model

Cell escape occurs after intramyocardial injection for treatment of myocardial infarction (MI) and then the migrated cells might be entrapped by extracardiac organs. We investigated the fate of migrated bone marrow-derived mesenchymal stromal cells (MSCs) and their impact on lung, liver, and spleen. MI model was created by coronary artery ligation in female Lewis rats. Three weeks after the ligation, bromodeoxyuridine (BrdU)-labeled male MSCs were directly injected into the infarcted area in the cell transplantation group ( n = 22). The same volume of phosphate-buffered solution (PBS) was injected in the control group ( n = 21). In the sham group ( n = 10) intramyocardial injection of the same volume of PBS was performed in healthy rats. Four weeks later, echocardiography was performed and the cell retention was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). Immunohistochemistry study was performed to identify the migrated cells. Heart function was improved after the cell injection. qRT-PCR results showed the percentage of retained cells in heart, spleen, liver, and lung ranked 3.63 ± 0.48%, 0.77 ± 0.13%, 0.68 ± 0.10%, 0.62 ± 0.11%, respectively, after cell transplantation. The implanted MSCs that escaped to liver, spleen, and lung did not differentiate into fibroblast, myofibroblast, or alveolar epithelial cells. However, the migrated MSCs in liver expressed functional hepatocyte marker. In conclusion, cell migration after intramyocardial injection did not result in deterioration of lung, liver, and spleen function. Our study might pave the way for new safety investigation of emerging cell resources and their impact on target and untargeted organs.

Effects of reactive oxygen species scavenger on the protective action of 100% oxygen treatment against sterile inflammation in mice

Sepsis/multiple organ dysfunction syndrome (MODS) is a major cause of high mortality in the intensive care unit. We have recently reported that 100% oxygen treatment is beneficial to mice with zymosan-induced sterile inflammation by increasing antioxidant enzymatic activities. Yet, the use of hyperoxia is hindered by concerns that it could exacerbate organ injury by increasing free radical formation. It is believed that systemic inflammation and overproduction of reactive oxygen species (ROS) contribute to the mechanism underlying sepsis/MODS. A ROS scavenger has been proven to protect against sepsis/MODS in some animal models. Therefore, we hypothesized that ROS scavenger pretreatment might enhance the protective action of 100% oxygen treatment against zymosan-induced sterile inflammation in mice. In the present study, we showed that 100% oxygen treatment prevented the abnormal changes in serum biochemical parameters, tissue oxygenation, and organ histopathology, and improved the 14-day survival rate in zymosan-stimulated mice, indicating that 100% oxygen treatment had a protective action on sterile inflammation. We found that pretreatment with a ROS scavenger (N-acetylcysteine, vitamin C, or dimethylthiourea) abolished this protective action of 100% oxygen treatment. We also showed that 100% oxygen treatment decreased the levels of serum proinflammatory cytokines (TNF-alpha, IL-6, and high-mobility group box 1), increased the level of serum anti-inflammatory cytokine (IL-10), and upregulated the activities of serum and tissue antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) in zymosan-stimulated mice, which were reversed by the pretreatment with a ROS scavenger (N-acetylcysteine, vitamin C, or dimethylthiourea). We thus conclude that ROS scavenger pretreatment partly abolishes the protective effects of 100% oxygen treatment on sterile inflammation in mice by regulating inflammatory cytokines as well as antioxidant enzymes.

Beneficial effects of hydrogen gas in a rat model of traumatic brain injury via reducing oxidative stress

Traumatic brain injury (TBI) is a leading cause of mortality and disability among the young population. It has been shown that hydrogen gas (H(2)) exerts a therapeutic antioxidant activity by selectively reducing hydroxyl radical (OH, the most cytotoxic ROS). Recently, we have found that H(2) inhalation significantly improved the survival rate and organ damage of septic mice. In the present study, we investigated the effectiveness of H(2) therapy on brain edema, blood-brain barrier (BBB) breakdown, neurological dysfunction and injury volume in TBI-challenged rats. In addition, we investigated the effects of H(2) treatment on the changes of oxidative products and antioxidant enzymes in brain tissue of TBI-challenged rats. Hydrogen treatment was given by exposure to 2% H(2) from 5 min to 5h after sham or TBI operation, respectively. Here, we found that TBI-challenged rats showed significant brain injuries characterized by the increase of BBB permeability, brain edema and lesion volume as well as neurological dysfunction, which was significantly attenuated by 2% H(2) treatment. In addition, we found that the decrease of oxidative products and the increase of endogenous antioxidant enzymatic activities in the brain tissue may be associated with the protective effects of H(2) treatment in TBI-challenged rats. The present study supports that H(2) inhalation may be a more effective therapeutic strategy for patients with TBI.

Experimental therapies in hypertrophic cardiomyopathy

The quintessential clinical diagnostic phenotype of human hypertrophic cardiomyopathy (HCM) is primary cardiac hypertrophy. Cardiac hypertrophy is also a major determinant of mortality and morbidity including the risk of sudden cardiac death (SCD) in patients with HCM. Reversal and attenuation of cardiac hypertrophy and its accompanying fibrosis is expected to improve morbidity as well as decrease the risk of SCD in patients with HCM.The conventionally used pharmacological agents in treatment of patients with HCM have not been shown to reverse or attenuate established cardiac hypertrophy and fibrosis. An effective treatment of HCM has to target the molecular mechanisms that are involved in the pathogenesis of the phenotype. Mechanistic studies suggest that cardiac hypertrophy in HCM is secondary to activation of various hypertrophic signaling molecules and, hence, is potentially reversible. The hypothesis is supported by the results of genetic and pharmacological interventions in animal models. The results have shown potential beneficial effects of angiotensin II receptor blocker losartan, mineralocorticoid receptor blocker spironolactone, 3-hydroxy-3-methyglutaryl-coenzyme A reductase inhibitors simvastatin and atorvastatin, and most recently, N-acetylcysteine (NAC) on reversal or prevention of hypertrophy and fibrosis in HCM. The most promising results have been obtained with NAC, which through multiple thiol-responsive mechanisms completely reversed established cardiac hypertrophy and fibrosis in three independent studies. Pilot studies with losartan and statins in humans have established the feasibility of such studies. The results in animal models have firmly established the reversibility of established cardiac hypertrophy and fibrosis in HCM and have set the stage for advancing the findings in the animal models to human patients with HCM through conducting large-scale efficacy studies.

Fat embolism

Fat embolism refers to the presence of fat droplets within the peripheral and lung microcirculation with or without clinical sequelae. The pathologic consequences of fat embolism are well recognized. Fat embolism is most often associated with trauma and orthopedic injuries. Fat embolism syndrome (FES) is a serious manifestation of fat embolism that involves a cascade of clinical signs such as petechial rash, deteriorating mental status, and progressive respiratory insufficiency, usually occurring within 24 hours of injury. This article reviews the definition, epidemiology, etiology, pathophysiology, clinical presentation, diagnosis, management, and prognosis of FES.

Interleukin-6 as an early marker for fat embolism

BACKGROUND

Fat Embolism is a complication of long bone fractures, intramedullary fixation and joint arthroplasty. It may progress to fat embolism syndrome, which is rare but involves significant morbidity and can occasionally be fatal. Fat Embolism can be detected at the time of embolization by transoesophageal echocardiography or atrial blood sampling. Later, a combination of clinical signs and symptoms will point towards fat embolism but there is no specific test to confirm the diagnosis. We investigated serum Interleukin-6 (IL-6) as a possible early marker for fat embolism.

METHODS

An animal study was conducted to simulate a hip replacement in 31 adult male Sprague Dawley rats. The procedure was performed under general anesthesia and the animals divided into 3 groups: control, uncemented and cemented. Following surgery and recovery from anaesthesia, the rats allowed to freely mobilize in their cages. Blood was taken before surgery and at 6 hours, 12 hours and 24 hours to measure serum IL-6 levels. The rats were euthanized at 24 hours and lungs removed and stained for fat. The amount of fat seen was then correlated with serum IL-6 levels.

RESULTS

No rats in the control group had fat emboli. Numerous fat emboli were seen in both the uncemented and cemented implant groups. The interleukin levels were raised in all groups reaching a peak at 12 hours after surgery reaching 100 pg/ml in the control group and around 250 pg/ml in the uncemented and cemented implant groups. The IL-6 levels in the control group were significantly lower than any of the implant groups at 12 and 24 hours. At these time points, the serum IL-6 correlated with the amount of fat seen on lung histology.

CONCLUSION

Serum IL-6 is a possible early marker of fat embolism.

Resolution of established cardiac hypertrophy and fibrosis and prevention of systolic dysfunction in a transgenic rabbit model of human cardiomyopathy through thiol-sensitive mechanisms

BACKGROUND

Cardiac hypertrophy, the clinical hallmark of hypertrophic cardiomyopathy (HCM), is a major determinant of morbidity and mortality not only in HCM but also in a number of cardiovascular diseases. There is no effective therapy for HCM and generally for cardiac hypertrophy. Myocardial oxidative stress and thiol-sensitive signaling molecules are implicated in pathogenesis of hypertrophy and fibrosis. We posit that treatment with N-acetylcysteine, a precursor of glutathione, the largest intracellular thiol pool against oxidative stress, could reverse cardiac hypertrophy and fibrosis in HCM.

METHODS AND RESULTS

We treated 2-year-old beta-myosin heavy-chain Q403 transgenic rabbits with established cardiac hypertrophy and preserved systolic function with N-acetylcysteine or a placebo for 12 months (n=10 per group). Transgenic rabbits in the placebo group had cardiac hypertrophy, fibrosis, systolic dysfunction, increased oxidized to total glutathione ratio, higher levels of activated thiol-sensitive active protein kinase G, dephosphorylated nuclear factor of activated T cells (NFATc1) and phospho-p38, and reduced levels of glutathiolated cardiac alpha-actin. Treatment with N-acetylcysteine restored oxidized to total glutathione ratio, normalized levels of glutathiolated cardiac alpha-actin, reversed cardiac and myocyte hypertrophy and interstitial fibrosis, reduced the propensity for ventricular arrhythmias, prevented cardiac dysfunction, restored myocardial levels of active protein kinase G, and dephosphorylated NFATc1 and phospho-p38.

CONCLUSIONS

Treatment with N-acetylcysteine, a safe prodrug against oxidation, reversed established cardiac phenotype in a transgenic rabbit model of human HCM. Because there is no effective pharmacological therapy for HCM and given that hypertrophy, fibrosis, and cardiac dysfunction are common and major predictors of clinical outcomes, the findings could have implications in various cardiovascular disorders.