Li Guan

Extracellular Histones Play an Inflammatory Role in Acid Aspiration-induced Acute Respiratory Distress Syndrome

Background:Systemic inflammation is a key feature in acid aspiration-induced acute respiratory distress syndrome (ARDS), but the factors that trigger inflammation are unclear. The authors hypothesize that extracellular histones, a newly identified inflammatory mediator, play important roles in the pathogenesis of ARDS. Methods:The authors used a hydrochloric acid aspiration-induced ARDS model to investigate whether extracellular histones are pathogenic and whether targeting histones are protective. Exogenous histones and antihistone antibody were administered to mice. Heparin can bind to histones, so the authors studied whether heparin could protect from ARDS using cell and mouse models. Furthermore, the authors analyzed whether extracellular histones are clinically involved in ARDS patients caused by gastric aspiration. Results:Extracellular histones in bronchoalveolar lavage fluid of acid-treated mice were significantly higher (1.832 ± 0.698) at 3 h after injury than in sham-treated group (0.63 ± 0.153; P = 0.0252, n = 5 per group). Elevated histones may originate from damaged lung cells and neutrophil infiltration. Exogenous histones aggravated lung injury, whereas antihistone antibody markedly attenuated the intensity of ARDS. Notably, heparin provided a similar protective effect against ARDS. Analysis of plasma from ARDS patients (n = 21) showed elevated histones were significantly correlated with the degree of ARDS and were higher in nonsurvivors (2.723 ± 0.2933, n = 7) than in survivors (1.725 ± 0.1787, P = 0.006, n = 14). Conclusion:Extracellular histones may play a contributory role toward ARDS by promoting tissue damage and systemic inflammation and may become a novel marker reflecting disease activity. Targeting histones by neutralizing antibody or heparin shows potent protective effects, suggesting a potentially therapeutic strategy.

Induction of heme oxygenase-1 with hemin attenuates hippocampal injury in rats after acute carbon monoxide poisoning

Carbon monoxide (CO) poisoning is a major cause of brain injury and mortality; delayed neurological syndrome (DNS) is encountered in survivors of acute CO exposure. The toxic effects of CO have been attributed to oxidative stress induced by hypoxia. Heme oxygenase-1 (HO-1) is the inducible heme oxygenase isoform, and its induction acts as an important cellular defense mechanism against oxidative stress, cellular injury and disease. In this study, we examined the functional roles of HO-1 induction in a rat model of CO-exposured hippocampal injury. We report that acute CO exposure produces severe hippocampal injury in rats. However, hemin pretreatment reduced both the CO-induced rise in hippocampal water content and levels of neuronal damage in the hippocampus; survival rates at 24 h were significantly improved. Upregulation of HO-1 by hemin pretreatment resulted in a significant decrease in hippocampal levels of malondialdehyde (MDA), a marker of oxidative stress; levels of pro-apoptotic caspase-3 were also reduced. In contrast, inhibition of HO activity by administration of tin protoporphyrin IX (SnPP, a specific inhibitor of HO) abolished the neuroprotective effects of HO-1 induction. These data suggested that the upregulation of endogenous HO-1 expression therefore plays a pivotal protective role in CO neurotoxicity. Though the precise mechanisms underlying hemin-mediated HO-1 induction and neuroprotection are not known, these may involve the anti-oxidant and anti-apoptotic effects of HO-1 enzyme activity.

Protection of echinacoside against acute lung injury caused by oleic acid in rats

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) manifests as non-cardiogenic pulmonary edema, respiratory distress and refractory hypoxemia, which is caused by increased permeability of damaged pulmonary capillary endothelia. ARDS is the ultimate stage clinical syndrome of ALI [1] and the leading cause of death in intensive care units with a very high mortality rate of 40% or more [2]. The common predisposing causes of ALI/ARDS are trauma, aspiration and sepsis, which can trigger a series of pathologic events including aggregation and activation of neutrophils, release of proteases and lipid mediators, production of free radicals and cytokines, finally leading to occurrence of ALI/ARDS [3]. However, there are no specific pharmacologic intervention for prevention and treatment by now [4]. The present strategies and future perspectives of the treatment for ALI/ARDS, focus on the ventilatory, pharmacological and cell therapies [5–7]: (1) improving ventilation, such as lung protective mechanical ventilation, positive end expiratory pressure ventilation, inverse ratio ventilation and high frequency ventilation; (2) drug therapy, such as inhaled nitric oxide, aerosolized prostacyclin, surfactant, antiinflammatory drugs and antioxidants; and (3)cell and cell-based gene therapy, such as endothelial progenitor cells (EPCs) and embryonic stem (ES) cells. The markedly high mortality of ARDS indicates that the key mechanism of the pathogenesis is not very clear. Thus, future studies should focus on newer forms of therapy and early phase of the pathogenesis of the disease. OA-induced ALI is a well-known model of chemical ARDS and extensive studies on it have been made for decades [8]. Oxidative stress has been shown to play an important role in this model in recent several studies [9,10]. The reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase-dependent pathway from activated polymorphonuclear leukocytes and endothelial cells was considered to contribute much to the generation of reactive oxygen species (ROS) in OA-induced ALI [11]. One of the mechanisms of OA-induced ALI is that the intravenous administration of OA can induce neutrophil activation through aggregation and attachment to endothelial cells [12]. Then the activated neutrophils may generate much free radicals including ROS and reactive nitrogen species (RNS) [13]. The free radicals may cause tissue injury directly, such as lipid peroxidation, destroying of construction integrity and disfunction of the biomembranes. Moreover, the free radicals can serve as signals to activate both neutrophils and endothelial cells in a positive feedback

N-acetyl-heparin attenuates acute lung injury caused by acid aspiration mainly by antagonizing histones in mice.

Acute lung injury (ALI) is the leading cause of death in intensive care units. Extracellular histones have recently been recognized to be pivotal inflammatory mediators. Heparin and its derivatives can bind histones through electrostatic interaction. The purpose of this study was to investigate 1) the role of extracellular histones in the pathogenesis of ALI caused by acid aspiration and 2) whether N-acetyl-heparin (NAH) provides more protection than heparin against histones at the high dose. ALI was induced in mice via intratracheal instillation of hydrochloric acid (HCl). Lethality rate, blood gas, myeloperoxidase (MPO) activity, lung edema and pathological changes were used to evaluate the degree of ALI. Heparin/NAH was administered intraperitoneally, twice a day, for 3 days or until death. Acid aspiration caused an obvious increase in extracellular histones. A significant correlation existed between the concentration of HCl aspirated and the circulating histones. Heparin/NAH (10 mg/kg) improved the lethality rate, blood gas, MPO activity, lung edema and pathological score. At a dose of 20 mg/kg, NAH still provided protection, however heparin tended to aggravate the injury due to hemorrhagic complications. The specific interaction between heparin and histones was verified by the binding assay. In summary, high levels of extracellular histones can be pathogenic in ALI caused by acid aspiration. By neutralizing extracellular histones, heparin/NAH can offer similar protection at the moderate doses. At the high dose, NAH provides better protection than heparin.

Pulmonary endothelial activation caused by extracellular histones contributes to neutrophil activation in acute respiratory distress syndrome

BackgroundDuring the acute respiratory distress syndrome (ARDS), neutrophils play a central role in the pathogenesis, and their activation requires interaction with the endothelium. Extracellular histones have been recognized as pivotal inflammatory mediators. This study was to investigate the role of pulmonary endothelial activation during the extracellular histone-induced inflammatory response in ARDS.MethodsARDS was induced in male C57BL/6 mice by intravenous injection with lipopolysaccharide (LPS) or exogenous histones. Concurrent with LPS administration, anti-histone H4 antibody (anti-H4) or non-specific IgG was administered to study the role of extracellular histones. The circulating von Willebrand factor (vWF) and soluble thrombomodulin (sTM) were measured with ELISA kits at the preset time points. Myeloperoxidase (MPO) activity in lung tissue was measured with a MPO detection kit. The translocation of P-selectin and neutrophil infiltration were measured by immunohistochemical detection. For in vitro studies, histone H4 in the supernatant of mouse lung vascular endothelial cells (MLVECs) was measured by Western blot. The binding of extracellular histones with endothelial membrane was examined by confocal laser microscopy. Endothelial P-selectin translocation was measured by cell surface ELISA. Adhesion of neutrophils to MLVECs was assessed with a color video digital camera.ResultsThe results showed that during LPS-induced ARDS extracellular histones caused endothelial and neutrophil activation, as seen by P-selectin translocation, release of vWF, an increase of circulating sTM, lung neutrophil infiltration and increased MPO activity. Extracellular histones directly bound and activated MLVECs in a dose-dependent manner. On the contrary, the direct stimulatory effect of exogenous histones on neutrophils was very limited, as measured by neutrophil adhesion and MPO activity. With the contribution of activated endothelium, extracellular histones could effectively activating neutrophils. Both inhibiting the endothelial activation with an anti-toll like receptor (TLR) antibody and inhibiting the interaction of the endothelium with neutrophil using an anti-P-selectin antibody decreased the degree of neutrophil activation.ConclusionsExtracellular histones are pro-inflammatory mediators in LPS-induced ARDS in mice. In addition to direct action to neutrophils, extracellular histones promote neutrophil adhesion and subsequent activation by first activating the pulmonary endothelium via TLR signaling. Thus, endothelial activation is important for extracellular histone-induced inflammatory injury.

Dynamic Changes of Heme Oxygenase-1 in the Hippocampus of Rats After Acute Carbon Monoxide Poisoning

Heme oxygenase-1 (HO-1), an inducible enzyme, degrades heme to carbon monoxide (CO), iron, and bilirubin. We have investigated the relationship among HO-1 protein expression, HO activity, and CO concentrations in the hippocampus of CO-exposed rats. Western blotting and immunohistochemistry revealed that the enzyme is predominantly localized in hippocampal CA1 and CA3 pyramidal cells and in granule cells of the dentate gyrus. HO enzyme activity was reduced immediately following CO exposure, while expression of HO-1 protein was consistently upregulated in a time-dependent manner. Local CO concentrations in hippocampus rose immediately following exposure, but the elevation was maintained forxa0~20xa0h despite the decline in blood carboxyhemoglobin levels toward baseline. We suggest that CO initially inhibits HO enzyme activity, whereas at later time points the inhibition is released and local CO generation is maintained by the activity of the endogenous HO enzyme. And the noninducible form of heme oxygenase, HO-2, was not altered following CO administration. Together these results indicate that the HO/CO pathway in the rat hippocampus is induced by acute CO exposure; local CO production may play a regulatory role in brain injury following CO poisoning.

Hemorheological changes in cerebral circulation of rabbits with acute carbon monoxide poisoning

Carbon monoxide (CO) poisoning is a leading cause of poison-related morbidity and mortality. The severe complication of delayed neuropsychiatric sequelae seriously affects patients living quality, but its mechanism remains controversial. In this study, we established an animal model by intraperitoneal injection of CO in rabbits at regular interval and kept the carboxyhemoglobin (HbCO) level in blood above 50% for at least 24 h. We investigated the dynamic changes in the hemorheological and coagulative properties of blood taken from venae jugularis interna before CO injection and at 30 min, 1-5 days after the last CO exposure. We found that RBC count, hemoglobin (Hb) concentration, and hematocrit (Hct) increased on 1 day and remained high level till 5 day. Whole blood viscosities at different shear rates decreased significantly at 30 min and then increased 1 day later until day 4. RBC deformation index (DI) and aggregation index decreased at 30 min and recovered to normal on day 3. Plasma viscosity and fibrinogen augmented from 30 min until day 5. Prothrombin time (PT) and active partial thromboplastin time (APTT) prolonged remarkably at 30 min and went back to normal on 3 day, plasma [Ca2+] decreased at 30 min and approached to normal level on 3 day. The level of malondialdehyde (MDA) in RBCs at 30 min was significantly higher than that of control and recovered to normal on day 3. Our results suggest that the changes in hemorheology participate in the development of acute CO poisoning, which may play a role in delayed encephalopathy after acute CO poisoning.

Ginsenoside Rg1 enhances lymphatic transport of intrapulmonary silica via VEGF-C/VEGFR-3 signaling in silicotic rats.

Ginsenoside Rg1, extracted mainly from Panax ginseng, has been shown to exert strong pro-angiogenic activities in vivo. But it is unclear whether ginsenoside Rg1 could promote lung lymphangiogenesis to improve lymphatic transport of intrapulmonary silica in silicotic rats. Here we investigated the effect of ginsenoside Rg1 on lymphatic transport of silica during experimental silicosis, and found that ginsenoside Rg1 treatment significantly raised the silicon content in tracheobronchial lymph nodes and serum to reduce the silicon level in lung interstitium, meanwhile increased pulmonary lymphatic vessel density by enhancing the protein and mRNA expressions of vascular endothelial growth factor-C (VEGF-C) and vascular endothelial growth factor receptor-3 (VEGFR-3). The stimulative effect of ginsenoside Rg1 on lymphatic transport of silica was actively correlated with its pro-lymphangiogenic identity. And VEGFR-3 inhibitor SAR131675 blocked these above effects of ginsenoside Rg1. These findings suggest that ginsenoside Rg1 exhibits good protective effect against lung burden of silica during experimental silicosis through improving lymphatic transport of intrapulmonary silica, which is potentially associated with the activation of VEGF-C/VEGFR-3 signaling pathway.

Early Biomarkers in 1H Nuclear Magnetic Resonance Spectroscopy of Striatal Pathological Mechanisms after Acute Carbon Monoxide Poisoning in Rats.

OBJECTIVEnIn vivo Proton Magnetic Resonance Spectroscopy (1H-MRS) can be used to evaluate the levels of specific neurochemical biomarkers of pathological mechanisms in the brain.nnnMETHODSnWe conducted T2-Weighted Magnetic Resonance Imaging (MRI) and 1H-MRS with a 3.0-Tesla animal MRI system to investigate the early microstructural and metabolic profiles in vivo in the striatum of rats following carbon monoxide (CO) poisoning.nnnRESULTSnCompared to baseline, we found significant cortical surface deformation, cerebral edema changes, which were indicated by the unclear gray/white matter border, and lateral ventricular volume changes in the brain. A significant reduction in the metabolite to total creatine (Cr) ratios of N-acetylaspartate (NAA) was observed as early as 1 h after the last CO administration, while the lactate (Lac) levels increased marginally. Both the Lac/Cr and NAA/Cr ratios leveled off at 6 h and showed no subsequent significant changes. In addition, compared to the control, the choline (Cho)/Cr ratio was slightly reduced in the early stages and significantly increased after 6 h. In addition, a pathological examination revealed mild cerebral edema on cessation of the insult and more severe cerebral injury after additional CO poisoning.nnnCONCLUSIONnThe present study demonstrated that 1H-MRS of the brain identified early metabolic changes after CO poisoning. Notably, the relationship between the increased Cho/Cr ratio in the striatum and delayed neuropsychologic sequelae requires further research.

Salvianolic Acids Attenuate Rat Hippocampal Injury after Acute CO Poisoning by Improving Blood Flow Properties

Carbon monoxide (CO) poisoning causes the major injury and death due to poisoning worldwide. The most severe damage via CO poisoning is brain injury and mortality. Delayed encephalopathy after acute CO poisoning (DEACMP) occurs in forty percent of the survivors of acute CO exposure. But the pathological cause for DEACMP is not well understood. And the corresponding therapy is not well developed. In order to investigate the effects of salvianolic acid (SA) on brain injury caused by CO exposure from the view point of hemorheology, we employed a rat model and studied the dynamic of blood changes in the hemorheological and coagulative properties over acute CO exposure. Compared with the groups of CO and 20% mannitol + CO treatments, the severe hippocampal injury caused by acute CO exposure was prevented by SA treatment. These protective effects were associated with the retaining level of hematocrit (Hct), plasma viscosity, fibrinogen, whole blood viscosities and malondialdehyde (MDA) levels in red blood cells (RBCs). These results indicated that SA treatment could significantly improve the deformation of erythrocytes and prevent the damage caused by CO poisoning. Meanwhile, hemorheological indexes are good indicators for monitoring the pathological dynamic after acute CO poisoning.