Effectiveness of liposomal-N-acetylcysteine against LPS-induced lung injuries in rodents

Acute lung injury (ALI) and its most severe form, the acute respiratory distress syndrome (ARDS) are frequent complications in critically ill patients and are responsible for significant morbidity and mortality. So far, experimental evidence supports the role of oxidants and oxidative injury in the pathogenesis of ALI/ARDS. In this study, the antioxidant effects of conventional N-acetylcysteine (NAC) and liposomally entrapped N-acetylcysteine (L-NAC) were evaluated in experimental animals challenged with lipopolysaccharide (LPS). Rats were pretreated with empty liposomes, NAC, or L-NAC (25mg/kg body weight, iv); 4h later were challenged with LPS (E. coli, LPS 0111:B4) and sacrificed 20h later. Challenge of saline (SAL)-pretreated animals with LPS resulted in lung injury as evidenced by increases in wet lung weight (edema), increases in lipid peroxidation (marker of oxidative stress), decreases of lung angiotensin-converting enzyme (ACE) (injury marker for pulmonary endothelial cells) and increases in the pro-inflammatory eicosanoids, thromboxane B(2) and leukotriene B(4). The LPS challenge also increased pulmonary myeloperoxidase activity and chloramine concentrations indicative of neutrophil infiltration and activation of the inflammatory response. Pretreatment of animals with L-NAC resulted in significant increases in the levels of non-protein thiols and NAC levels in lung homogenates (p<0.05) and bronchoalveolar lavage fluids (p<0.001), respectively. L-NAC was significantly (p<0.05) more effective than NAC or empty liposomes in attenuating the LPS-induced lung injuries as indicated by the aforementioned injury markers. Our results suggested that the delivery of NAC as a liposomal formulation improved its prophylactic effectiveness against LPS-induced lung injuries.     

Prophylaxis against lipopolysaccharide-induced liver injuries by lipoic acid in rats

Lipopolysaccharide (LPS) is a major cell wall molecule of Gram-negative bacteria known to stimulate the synthesis and secretion of several metabolites, such as reactive oxygen species, from phagocytes that play an important role in the pathogenesis of tissue injuries. In this study, the prophylactic effect of the antioxidant lipoic acid was evaluated in an animal acute organ injury model. Animals were pre-treated intraperitoneally with lipoic acid (50 mg kg(-1) body weight) or saline; 3 h later, pretreated animals were challenged intravenously with LPS (Escherichia coli 0111:B4, 1.0 mg kg(-1) body weight) or saline and killed 21 h later. Saline-pretreated animals challenged with LPS were extensively damaged in the liver, as evidenced by an increase in plasma alanine and aspartate aminotransferase activities. Also, LPS injection to saline-pretreated animals resulted in significant increases in plasma tumour necrosis factor-alpha (TNFalpha) and nitric oxide (NO) concentrations, suggestive of activation of the proinflammatory response. The LPS challenge to saline-pretreated animals also increased hepatic myeloperoxidase activity as well as protease and chloramine levels, suggestive of neutrophil infiltration and activation of the inflammatory response. In addition, the involvement of oxidative stress was evident, because a significant increase in lipid peroxidation was observed in the livers of saline-pretreated animals challenged with LPS. The administration of lipoic acid prior to LPS challenge resulted in a significant alleviation of liver injuries, evidenced by a general reversal of the altered biochemical indices toward normal among treated animals. These results indicate that lipoic acid may serve as a potentially effective prophylactic pharmacological agent in alleviating LPS-induced tissue injuries.     

Pharmacological alteration of oxygen-induced lung toxicity.

The effect of eight selected drugs on oxygen-induced pulmonary injury was evaluated in the rat. Several drug treatments, including meclofenamate (5 mg/kg/day), aminophylline (15 mg/kg/day), and vitamin C (20 and 50 mg/kg/every 12 hr) were found not to alter the survival of rats in 96 to 98% oxygen. Although vitamin E deficiency has repeatedly been shown to aggravate oxygen toxicity, pharmacologic doses of vitamin E (20 and 50 mg/kg/every 12 hr) in animals maintained on a normal diet did not offer protection against oxygen-induced lung toxicity. For the remaining drug treatments, the activity of pulmonary antioxidant defense systems [superoxide dimutase (SOD), catalase (CA), glutathione peroxidase (GP), and reduced glutathione (GSH)] were analyzed to explore the possible mechanism of pharmacological alteration of oxygen toxicity. Lungs from rats treated with dexamethasone (0.4 mg/kg/day) were found to have greater oxygen-induced lung damage and significantly lower pulmonary antioxidant activity. Rats pretreated with propylthiouracil (10 mg/kg/day) showed less oxygen-induced lung damage and greater pulmonary GSH levels and CA activity. Indomethacin pretreatment did not affect the course of oxygen toxicity or the activity of pulmonary antioxidant defense systems. GSH levels were lower in lungs of rats pretreated with levothyroxine (16.7 mg/kg/day), which produced an accelerated development of pulmonary oxygen toxicity. It was concluded that modification of the activity of the pulmonary antioxidant defense systems provides a plausible mechanism in explaining pharmacological alteration of oxygen-induced pulmonary injury.     

S-nitroso human serum albumin given after LPS challenge reduces acute lung injury and prolongs survival in a rat model of endotoxemia

Endotoxemia leads to the induction of inducible nitric oxide synthase (NOS-2) and increased expression of numerous inflammatory mediators contributing to endotoxin-induced acute lung injury. We tested the hypothesis that supplementation of nitric oxide (NO) by the novel NO donor S-nitroso human serum albumin (S-NO-HSA) given after lipopolysaccharide (LPS) challenge may reduce NOS-2 expression, lung inflammation and acute lung injury. Rats were divided into four groups: sham-operated (no treatment), LPS, LPS+HSA (human serum albumin), and LPS+S-NO-HSA. LPS was administered intravenously (20 mg kg(-1)) resulting in acute lung injury and a high mortality rate within 6 h (>90%). LPS-induced lung injury was characterized by an increased lung edema (lung wet/dry weight ratio), pulmonary neutrophil infiltration (myeloperoxidase activity, MPO) as well as a robust inflammatory response [increased expression of intercellular adhesion molecule-1 (ICAM-1), NOS-2, and cyclooxygenase-2 (COX-2)]. Infusion of S-NO-HSA or HSA was started 2 h after LPS and continued for 4 h (total dose of 72 mg kg(-1)) at a rate of 300 mug kg(-1) min(-1). S-NO-HSA but not HSA prolonged survival of endotoxemic rats, reduced the hypotensive response to LPS, minimized LPS-induced lung edema and injury, normalized MPO activity as well as diminished lung expression of pro-inflammatory molecules such as ICAM-1, NOS-2, and COX-2. Continuous supplementation of NO by S-NO-HSA after LPS challenge prevents induction of NOS-2, provides significant protection of endotoxin-induced acute lung injury, and prevents early mortality in endotoxic shock in rats. Our results suggest a potential therapeutic role for S-NO-HSA in endotoxemia.     

Ruscogenin inhibits lipopolysaccharide-induced acute lung injury in mice: involvement of tissue factor, inducible NO synthase and nuclear factor (NF)-κB

Acute lung injury is still a significant clinical problem with a high mortality rate and there are few effective therapies in clinic. Here, we studied the inhibitory effect of ruscogenin, an anti-inflammatory and anti-thrombotic natural product, on lipopolysaccharide (LPS)-induced acute lung injury in mice basing on our previous studies. The results showed that a single oral administration of ruscogenin significantly decreased lung wet to dry weight (W/D) ratio at doses of 0.3, 1.0 and 3.0 mg/kg 1 h prior to LPS challenge (30 mg/kg, intravenous injection). Histopathological changes such as pulmonary edema, coagulation and infiltration of inflammatory cells were also attenuated by ruscogenin. In addition, ruscogenin markedly decreased LPS-induced myeloperoxidase (MPO) activity and nitrate/nitrite content, and also downregulated expression of tissue factor (TF), inducible NO synthase (iNOS) and nuclear factor (NF)-κB p-p65 (Ser 536) in the lung tissue at three doses. Furthermore, ruscogenin reduced plasma TF procoagulant activity and nitrate/nitrite content in LPS-induced ALI mice. These findings confirmed that ruscogenin significantly attenuate LPS-induced acute lung injury via inhibiting expressions of TF and iNOS and NF-κB p65 activation, indicating it as a potential therapeutic agent for ALI or sepsis.     

Enhanced activity of liposomal polymyxin B against Pseudomonas aeruginosa in a rat model of lung infection

The bactericidal effectiveness of liposomal polymyxin B against Pseudomonas aeruginosa was investigated in an animal model of pulmonary infection. Polymyxin B was incorporated into liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol (Chol) (2:1). Lung infection was induced in rats following intratracheal instillation of 10(7) colony-forming units (CFU) of P. aeruginosa (ATCC 27853) embedded in agar beads. Starting on day 3 post-infection, animals were treated daily, for 3 consecutive days, with saline, empty liposomes, free polymyxin B, or liposomal polymyxin B (2mg polymyxin B/kg body weight) by intratracheal instillation; animals were killed 24hr after the third drug instillation. Treatment of infected animals with liposomal polymyxin B significantly reduced the pulmonary bacterial counts (3.7+/-0.4log CFU/paired lungs) as compared with that of free polymyxin B (5.1+/-0.2log CFU/paired lungs). Treatment of infected animals with empty liposomes gave pulmonary bacterial counts similar to those obtained from the saline-treated group. Pulmonary infection with P. aeruginosa also resulted in lung injury as evidenced by increases in wet lung weight and decreases in angiotensin converting enzyme activity as well as increases in myeloperoxidase activity, an index of the inflammatory response. Treatment with free polymyxin B ameliorated the lung injuries induced by the microorganism, a protective effect that was more pronounced in the liposomal polymyxin B-treated group. The levels of polymyxin B in the lungs of the infected animals treated with the liposomal suspension were significantly higher (42.8+/-6.2 microg/paired lungs) compared with those treated with the free drug (8.2+/-0.4 microg/paired lungs). These data suggest that direct delivery of liposomal polymyxin B to the lung can be effective in the treatment of pulmonary infection with P. aeruginosa by enhancing retention of the antibiotic in the lung.     

Protective effects of pravastatin in murine lipopolysaccharide-induced acute lung injury

1. The present study was designed to determine whether pravastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, could attenuate acute lung injury (ALI) induced by lipopolysaccharide (LPS) in BALB/c mice. 2. Acute lung injury was induced successfully by intratracheal administraiton of LPS (3 microg/g) in BALB/c mice. Pravastatin (3, 10 and 30 mg/kg, i.p.) was administered to mice 24 h prior to and then again concomitant with LPS exposure. 3. Challenge with LPS alone produced a significant increase in lung index and the wet/dry weight ratio compared with control animals. Pulmonary microvascular leakage, as indicated by albumin content in the bronchoalveolar lavage fluid (BALF) and extravasation of Evans blue dye albumin into lung tissue, was apparently increased in LPS-exposed mice. Lipopolysaccharide exposure also produced a significant lung inflammatory response, reflected by myeloperoxidase activity and inflammatory cell counts in BALF. Furthermore, histological examination showed that mice exposed to LPS also exhibited prominent inflammatory cell infiltration and occasional alveolar haemorrhage. 4. Pravastatin (3, 10 or 30 mg/kg, i.p.) produced a significant reduction in multiple indices of LPS-induced pulmonary vascular leak and inflammatory cell infiltration into lung tissue. Elevated tumour necrosis factor (TNF)-alpha levels in lung tissue homogenates of ALI mice were significantly decreased after administration of 10 or 30 mg/kg pravastatin. 5. These findings confirm significant protection by pravastatin against LPS-induced lung vascular leak and inflammation and implicate a potential role for statins in the management of ALI. The inhibitory effect of pravastatin was associated with its effect in decreasing TNF-alpha.     

Kaempferol regulates MAPKs and NF-κB signaling pathways to attenuate LPS-induced acute lung injury in mice

Recent studies show that mitogen-activated protein kinases (MAPKs) and nuclear factor-kappa B (NF-κB) signaling pathways are two pivotal roles contributing to the development of lipopolysaccharide (LPS)-induced acute lung injury (ALI). The present study aimed to investigate the protective effect of kaempferol (Kae), a naturally occurring flavonoid compound, on ALI and explore its possible mechanisms. Male BALB/c mice with ALI, induced by intranasal instillation of LPS, were treated or not with Kae (100mg/kg, intragastrically) 1h prior to LPS exposure. Kae treatment attenuated pulmonary edema of mice with ALI after LPS challenge, as it markedly decreased the lung W/D ratio of lung samples, protein concentration and the amounts of inflammatory cells in BALF. Similarly, LPS mediated overproduction of proinflammatory cytokines in BALF, including TNF-α, IL-1β and IL-6, was strongly reduced by Kae. Histological studies demonstrated that Kae substantially inhibited LPS-induced alveolar wall thickness, alveolar hemorrhage and leukocytes infiltration in lung tissue with evidence of reduced myeloperoxidase (MPO) activity. Kae also efficiently increased superoxide dismutase (SOD) activity of lung sample when compared with LPS group, which was obviously reduced by LPS administration. In addition, Western blot analysis indicated that the activation of MAPKs and NF-κB signaling pathways stimulated by LPS was significantly blocked by Kae. Taken together, our results suggest that Kae exhibits a protective effect on LPS-induced ALI via suppression of MAPKs and NF-κB signaling pathways, which may involve the inhibition of tissue oxidative injury and pulmonary inflammatory process.     

泻心汤有效组分不同配伍对内毒素肺损伤大鼠NF-κB及IκB表达的影响

目的研究泻心汤有效组分及其配伍对内毒素肺损伤大鼠NF-κB及IκB表达的影响。方法大鼠灌胃给予黄芩总黄酮提取物(TFL)、大黄总游离蒽醌提取物(TFA)、大黄总结合蒽醌提取物(TCA)、TFL与TFA配伍高、低剂量(A高A低)、TFL与TCA配伍(B)及醋酸地塞米松(Dex)4d,末次给药后1h股静脉注射脂多糖(LPS)建立大鼠内毒素肺损伤模型,1、2、4h各组分别处死6只动物,收集肺组织,免疫印记(Western blot)检测核因子κB(NF-κB)、κB抑制因子(IκB)的蛋白表达。结果大黄总游离蒽醌、A高及Dex在1、2、4h均能够明显抑制NF-κB p65的核转位(P<0.01),所有给药组在2、4h均能够明显抑制胞质中的IκBα的降解(P<0.01)。结论泻心汤有效组分及其配伍对内毒素肺损伤大鼠保护作用与抑制NF-κB的核转位及IκB的降解有关。     

Dexamethasone treatment attenuates early seawater instillation-induced acute lung injury in rabbits.

There is very little evidence on the value of giving corticoids in cases of seawater drowning induced acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Therefore, this study aimed to investigate whether dexamethasone treatment can attenuate seawater instillation-induced acute lung injury in rabbits. Seawater (4 ml/kg body weight) was instilled into the lower trachea of ventilated, anesthetized rabbits. Then these rabbits were assigned randomly 20 min later to receive intravenous injection of 1mg/kg body weight of dexamethasone (dissolving in 2 ml of normal saline) or 2 ml of normal saline. All animals demonstrated immediate drops in arterial oxygen tension (PaO2) and the total thoracic compliance, which were significantly improved after 2 h of dexamethasone treatment. Histopathological study also indicated that dexamethasone treatment markedly attenuated lung histopathological changes, alveolar hemorrhage and inflammatory cells infiltration with evidence of decreasing of myeloperoxidase (MPO) activity and tumor necrosis factor-alpha (TNF-alpha) concentration in lung tissue. In addition, dexamethasone treatment reduced extravascular lung water and lung epithelial-endothelial barrier permeability, up-regulated the expression of surfactant protein-A (SP-A) and alpha-epithelial Na+ channel, and increased Na+/K+-adenosine triphosphatase (Na+/K+-ATPase) activity and Na+/K+-ATPase-alpha1 protein abundance. Thus, these data indicate that dexamethasone treatment might be of benefit in patients with seawater aspiration-induced ALI.     

The effect of magnolol on the Toll-like receptor 4/nuclear factor kappa B signaling pathway in lipopolysaccharide-induced acute lung injury in mice

Magnolol, a hydroxylated biphenyl compound isolated from Magnolia officinalis has been reported to have anti-inflammatory properties. The purpose of this study was to evaluate the effect of magnolol on acute lung injury induced by lipopolysaccharide in mice. Male BALB/c mice were pretreated with dexamethasone or magnolol 1 h before intranasal instillation of lipopolysaccharide (LPS). 7 h after LPS administration, the myeloperoxidase in lung tissues, lung wet/dry weight ratio and inflammatory cells in the bronchoalveolar lavage fluid were determined. The levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in the bronchoalveolar lavage fluid were measured by enzyme-linked immunosorbent assay (ELISA). The extent of phosphorylation of nuclear factor of inhibitory kappa B alpha (IκB-α), nuclear factor kappa-B (NF-κB) p65 and the expression of Toll-like receptor-4 (TLR4) were detected by western blot. The results showed that magnolol markedly attenuated the histological alterations in the lung; reduced the number of total cells, neutrophils, and macrophages in the bronchoalveolar lavage fluid; decreased the wet/dry weight ratio of lungs in the bronchoalveolar lavage fluid; down-regulated the level of pro-inflammatory mediators, including TNF-α, IL-1β and IL-6; inhibited the phosphorylation of IκB-α, NF-κB p65 and the expression of TLR4, caused by LPS. Taken together, our results suggest that anti-inflammatory effects of magnolol against the LPS-induced acute lung injury may be due to its ability of inhibition TLR4 mediated NF-κB signaling pathways. Magnolol may be a promising potential therapeutic reagent for acute lung injury treatment.     

Effect of Apremilast on LPS-induced immunomodulation and inflammation via activation of Nrf2/HO-1 pathways in rat lungs

Lipopolysaccharides (LPS), the lipid component of gram-negative bacterial cell wall, is recognized as the key factor in acute lung inflammation and is found to exhibit severe immunologic reactions. Phosphodiesterase-4 (PDE-4) inhibitor: “apremilast (AP)” is an immune suppressant and anti-inflammatory drug which introduced to treat psoriatic arthritis. The contemporary experiment designed to study the protective influences of AP against LPS induced lung injury in rodents. Twenty-four (24) male experimental Wistar rats selected, acclimatized, and administered with normal saline, LPS, or AP + LPS respectively from 1 to 4 groups. The lung tissues were evaluated for biochemical parameters (MPO), Enzyme Linked Immunosorbent Assay (ELISA), flowcytometry assay, gene expressions, proteins expression and histopathological examination. AP ameliorates the lung injuries by attenuating immunomodulation and inflammation. LPS exposure upregulated IL-6, TNF-α, and MPO while downregulating IL-4 which were restored in AP pretreated rats. The changes in immunomodulation markers by LPS were reduced by AP treatment. Furthermore, results from the qPCR analysis represented an upregulation in IL-1β, MPO, TNF-α, and p38 whereas downregulated in IL-10 and p53 gene expressions in disease control animals while AP pretreated rats exhibited significant reversal in these expressions. Western blot analysis suggested an upregulation of MCP-1, and NOS-2, whereas HO-1, and Nrf-2 expression were suppressed in LPS exposed animals, while pretreatment with AP showed down regulation in the expression MCP-1, NOS-2, and upregulation of HO-1, and Nrf-2 expression of the mentioned intracellular proteins. Histological studies further affirmed the toxic influences of LPS on the pulmonary tissues. It is concluded that, LPS exposure causes pulmonary toxicities via up regulation of oxidative stress, inflammatory cytokines and stimulation of IL-1β, MPO, TNF-α, p38, MCP-1, and NOS-2 while downregulation of IL-4, IL-10, p53, HO-1, and Nrf-2 at different expression level. Pretreatment with AP controlled the toxic influences of LPS by modulating these signaling pathways.     

Monokine-induced lung injury in rats: similarities to monocrotaline-induced pneumotoxicity

Previous studies have shown that abnormal alveolar macrophages and biological activity resembling the macrophage-derived mediator interleukin-1 (IL-1) can be detected in bronchoalveolar lavage fluid from rats with monocrotaline-induced lung injury and pulmonary hypertension. To determine if monokines might play a pathogenic role in this model, the present study evaluated the effects of a murine monokine preparation enriched in IL-1 bioactivity on selected events characterizing the early pneumotoxic response to monocrotaline, including pulmonary edema and protein extravasation, pulmonary vascular hyperreactivity, and enhanced lung tissue activity of the rate-limiting enzyme in polyamine biosynthesis, ornithine decarboxylase (ODC). Intravenous injection of the monokine preparation containing 200 units/kg IL-1 (quantified by lymphocyte activating factor assay) into intact rats produced pulmonary edema within 3 hr manifested by increases in the lung wet-to-dry weight ratio and in the extent of pulmonary albumin extravasation. The edema had resolved within 24 hr of monokine administration as indicated by a return to control levels of the wet-to-dry weight ratio and albumin extravasation index. The monokine preparation also increased the transfer of albumin across monolayers of cultured porcine pulmonary vascular endothelial cells. While salt solution-perfused rat lungs isolated from animals treated 3 hr previously with the monokine preparation were hyporesponsive to angiotensin II, preparations derived from animals treated 24 hr previously were markedly hyperresponsive to the vasoconstrictor actions of the peptide. Pressor responses to potassium chloride and prostaglandin F2a were unaffected by exposure to the monokine preparation. Lung ODC activity in monokine-exposed animals did not differ from control at 3, 6, or 24 hr after treatment. In contrast, a 24-hr exposure of cultured pulmonary vascular endothelial cells to the monokine preparation increased ODC activity approximately 100-fold. These observations indicate that a monokine preparation containing IL-1 bioactivity causes transient pulmonary edema and pulmonary vascular hyperreactivity and increases ODC activity in pulmonary vascular endothelial cells. Because the monokine preparation mimics certain aspects of monocrotaline-induced pneumotoxicity in the rat, it is reasonable to postulate that monokines could play a pathogenic role in this and similar animal models of lung injury and pulmonary hypertension.     

多西环素减轻小鼠内毒素性急性肺损伤的作用及机制研究

目的：探讨多西环素对内毒素性急性肺损伤的影响及机制。方法：将昆明小鼠随机分为：生理盐水对照组、多西环素组、内毒素脂多糖（LPS）急性肺损伤模型组及多西环素干预组。注射LPS24h后处死动物,行支气管肺泡灌洗（BALF）,计数灌洗液中白细胞数量及测定总蛋白含量。用ELISA分别测定肺组织匀浆上清液中TNF-a、基质金属蛋白酶-9（MMP-9）和金属蛋白酶组织抑制剂-1（TIMP-1）的含量。同时取肺组织进行病理学观察,测定肺组织湿/干重比值。结果：多西环素显著减少LPS所致BALF中白细胞数量、总蛋白浓度和肺组织湿/干重比值（P〈0.01）。多西环素能降低肺组织匀浆上清液中TNF-a和MMP-9含量（P〈0.01）,轻度上调TIMP-1的含量。多西环素能显著减轻LPS所致肺组织出血、肺水肿及炎性细胞浸润等肺损伤改变。结论：多西环素可减轻LPS所致急性肺损伤,其机制可能与抑制TNF-α等促炎因子释放及下调MMP-9/TIMP-1比值有关。     

p38MAPK inhibition attenuates LPS-induced acute lung injury involvement of NF-kappaB pathway

The pathogenesis of acute lung injury/acute respiratory distress syndrome (ARDS) is complex and involves multiple signal transduction processes. It is believed that p38MAPK (mitogen-activated protein kinase) is one of the most kinases in inflammatory signaling. At present study, we demonstrated the role of p38MAPK in lipopolysaccharide (LPS)-induced acute lung injury with pharmacologic p38MAPK inhibition by SB203580. SB203580, p38MAPK specific inhibitor, was injected (10 mg/kg, i.v.) 30 min before LPS administration (5 mg/kg, i.v.). The hematoxylin-eosin staining of lung tissues showed that p38MAPK inhibition significantly attenuated the pulmonary inflammatory responses induced by LPS. Moreover, SB203580 can also inhibit the inflammatory cytokine release, and reduce the mortality rate of LPS-induced acute lung injury. Further, western blot analysis that showed SB203580 administration can inhibit the activation of NF-kappaB, which was associated with the inhibition of IkappaBalpha degradation in cytoplasm. These data suggest that p38MAPK signaling may be involved in the activation of NF-kappaB, and activation of p38MAPK signaling may be one of the mechanisms of acute lung injury.     

Sclareol ameliorate lipopolysaccharide-induced acute lung injury through inhibition of MAPK and induction of HO-1 signaling

Sclareol is a natural fragrance compound that is used widely in the cosmetic and food industries. This study examined the effect of sclareol on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice. Mice were treated with sclareol 1 h before an intratracheal (I.T.) LPS challenge to induce an ALI model. The effects on lung tissue and lung injury were evaluated 6 h after LPS induction. Pretreatment with sclareol noticeably improved the LPS-induced histological alterations and edema in lung tissue. Sclareol also inhibited the release of pro-inflammatory mediators. Differences in nitric oxide (NO), tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and IL-10 were found in the bronchoalveolar lavage fluid (BALF) 6 h after LPS-induced lung injury. This study also found a reduced number of total cells and reduced protein concentrations in the BALF. There were also changes in the pulmonary wet/dry (W/D) weight ratio, antioxidant enzyme activity, and myeloperoxidase activity in lung tissues. Sclareol effectively blocked the phosphorylation of mitogen-activated protein kinases (MAPKs) and impeded the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). The compound boosted the expression of heme oxygenase-1 (HO-1) and inhibited the breakdown of nuclear factor-kappa B (NF-κB) and inhibitor of kappa B (IκBα). To the best of the authors' knowledge, this study is the first to demonstrate that sclareol effectively inhibits acute lung edema, and the results suggest that sclareol may be a potential agent for the treatment of ALI. The potential therapeutic benefits may include the attenuation of LPS-induced pulmonary inflammation due to sclareol's effects on several pathways, including NF-κB, MAPKs and HO-1, as well as the regulation of antioxidant enzyme activity.     

Mechanistic target of rapamycin-mediated autophagy is involved in the alleviation of lipopolysaccharide-induced acute lung injury in rats

Acute lung injury (ALI) is a complex clinical syndrome with high morbidity and mortality rates. Autophagy is an adaptive process that plays a complex role in ALI. The aim of this study was to investigate the effects of autophagy on lipopolysaccharide (LPS)-induced lung injury by establishing a rat ALI model and to further explore the possible mechanisms involved. Rats were pretreated with the autophagy inhibitor 3-methyladenine (3-MA) or the autophagy activator rapamycin before they were challenged with the intratracheal instillation of LPS (5 mg/kg). The level of autophagy in the lung tissue was detected. Lung injury and vascular permeability were assessed. The role of the mechanistic target of rapamycin (mTOR)-mediated Unc-51-like kinase 1 (ULK1) and the class III PI3 kinase VPS34 in autophagy regulation was examined. LPS challenge induced autophagy and rapamycin pretreatment enhanced autophagy activity in LPS-induced ALI rats. LPS caused severe lung injury and high pulmonary vascular permeability, which could be alleviated by enhancing autophagy. In addition, the inhibition of mTOR upregulated the expression of ULK1 and VPS34 and thus increased LPS-induced autophagy. Autophagy plays a protective role in LPS-induced ALI, and enhancing autophagy via the inhibition of mTOR alleviates lung injury and pulmonary barrier function. Moreover, mTOR negatively mediates ULK1 and VPS34 to regulate LPS-induced autophagy in rats.     

塞来昔布对急性肺损伤大鼠肺组织NF-κB和iNOS的影响

【摘要】目的探讨脂多糖（LPS）所致大鼠急性肺损伤时环氧化酶-2（COX-2）抑制剂塞来昔布对肺组织的核因子-κB（NF-κB）p65和诱导型一氧化氮合酶（iNOS）表达的影响。方法将60只大鼠随机分为对照组、LPS组、治疗组和塞来昔布组,每组15只。LPS组尾静脉注射LPS（5mg/kg）复制急性肺损伤模型;治疗组注射LPS复制急性肺损伤模型后30min用塞来昔布灌胃（20mg/kg）;塞来昔布组不造模,于相同时间点用相同剂量塞来昔布灌胃;对照组不造模、不给药,给等量的生理盐水;各组均于3h后放血处死动物。采用蛋白质印迹（Western blot）和逆转录-聚合酶链反应（RT-PCR）方法分别检测肺组织COX-2、NF-κB p65、iNOS蛋白及NF-κB p65、iNOS mRNA的表达。结果LPS组与对照组相比COX-2、NF-κB p65和iNOS蛋白及NF-κB p65、iNOS mRNA表达均显著升高（P<0.01）;治疗组NF-κB p65、iNOS mRNA和蛋白表达较LPS组明显降低（P<0.01）。结论选择性COX-2抑制剂塞来昔布对急性肺损伤大鼠有保护作用。     

Inhibitory effects of flavonoids extracted from licorice on lipopolysaccharide-induced acute pulmonary inflammation in mice

Airway inflammation plays important roles in the pathogenesis of acute respiratory distress syndrome (ARDS), asthma and chronic obstructive pulmonary disease (COPD), and anti-inflammatory treatment effectively improves the symptoms of these diseases. To develop the potentially therapeutic compounds for the treatment of pulmonary inflammation, we investigated the effects of licorice flavonoids (LF) extracted from the roots of Glycyrrhiza uralensis (licorice) on lipopolysaccharide (LPS)-induced acute pulmonary inflammation in mice. Acute pulmonary inflammation was induced by intracheal instillation with LPS, treatment with LF at dosages of 3, 10 and 30 mg/kg significantly reduced the LPS-induced inflammatory cells, including neutrophils, macrophages and lymphocytes accumulation in bronchoalveolar lavage fluids (BALF), among these inflammatory cells, LF predominately inhibited neutrophil infiltration, and the maximal effect (30 mg/kg) was as comparable as dexamethasone treatment at 1 mg/kg. Consistent with its effects on neutrophil infiltration, LF treatment significantly increased LPS-induced BALF superoxide dismutase activity, and significantly decreased lung myeloperoxidase activity as well. Furthermore, treatment with LF at 30 mg/kg significantly reduced LPS-induced lung TNFα and IL-1β mRNA expression at 6 h and 24 h after LPS instillation, respectively. Finally, LF at different dosages not only significantly decreased the elevation of lung water content, but also markedly attenuated LPS-induced histological alteration. Therefore, we suggest that LF effectively attenuates LPS-induced pulmonary inflammation through inhibition of inflammatory cells infiltration and inflammatory mediator release which subsequently reduces neutrophil recruitment into lung and neutrophil-mediated oxidative injury, and this study provides with the potential rationale for development of anti-inflammatory compounds from flavonoid extracts of licorice.