Effect of surfactant on pulmonary expression of type IIA PLA(2) in an animal model of acute lung injury

Mechanism of Anti-Inflammatory Activity of TLR4-Interacting SPA4 Peptide

The TLR4-interacting SPA4 peptide suppresses inflammation. We assessed the structural and physicochemical properties and binding of SPA4 peptide to TLR4-MD2. We also studied the changes at the whole transcriptome level, cell morphology, viability, secreted cytokines and chemokines, and cell influx in cell systems and mouse models challenged with LPS and treated with SPA4 peptide. Our results demonstrated that the SPA4 peptide did not alter the cell viability and size and only moderately affected the transcriptome of the cells. Computational docking and rendering suggested that the SPA4 peptide intercalates with LPS-induced TLR4-MD2 complex. Results with alanine mutations of D-2 amino acid and NYTXXXRG-12-19 motif of SPA4 peptide suggested their role in binding to TLR4 and in reducing the cytokine response against LPS stimulus. Furthermore, therapeutically administered SPA4 peptide significantly suppressed the secreted levels of cytokines and chemokines in cells and bronchoalveolar lavage fluids of LPS-challenged mice. The results suggest that the SPA4 peptide intercalates with LPS-induced TLR4 complex and signaling for the suppression of inflammation.

3, 4-dihydroxybenzalacetone attenuates lipopolysaccharide-induced inflammation in acute lung injury via down-regulation of MMP-2 and MMP-9 activities through suppressing ROS-mediated MAPK and PI3K/AKT signaling pathways

3, 4-Dihydroxybenzalacetone (DBL) is a constituent of Phellinus linteus. This study demonstrated the protective effect of DBL on lipopolysaccharide (LPS)-induced acute lung injuries in mice. Pretreatment with DBL significantly improved LPS-induced histological alterations in lung tissues. In addition, DBL markedly reduced the total cell number, the leukocytes, the protein concentrations, and decreased the release of nitrite, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and the activities of matrix metalloproteinase (MMP)-2 and -9 in the bronchoalveolar lavage fluid. DBL also inhibited the W/D ratio and myeloperoxidase activity in the lung tissues. Western blot analysis indicated DBL efficiently blocked the protein expressions of inducible nitric oxide synthase, cyclooxygenase-2, MMP-2, MMP-9, and the phosphorylation of mitogen-activated protein kinase (MAPK), phosphoinositide-3-kinase (PI3K), AKT, Toll-like receptor 4 (TLR4) and nuclear factor (NF)-κB. Moreover, DBL enhanced the expression of anti-oxidant proteins, such as superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx). Based on our results, DBL might be a potential target for attenuating tissue oxidative injuries and nonspecific pulmonary inflammation.

Hydrostatin-SN1, a Sea Snake-Derived Bioactive Peptide, Reduces Inflammation in a Mouse Model of Acute Lung Injury

Snake venom has been used for centuries as a traditional Chinese medicine. Hydrostatin-SN1 (H-SN1), a bioactive peptide extracted from the Hydrophis cyanocinctus venom gland T7 phage display library, was reported to have the ability to reduce inflammation in a dextran sulfate sodium-induced murine colitis model. In this study, we sought to investigate the inhibitory potential of H-SN1 on inflammation in a murine model of lipopolysaccharide (LPS)-induced acute lung injury (ALI), and elucidate the anti-inflammatory mechanism in LPS-stimulated RAW 264.7 cells. In vivo, C57BL/6 male mice were intratracheally instilled with LPS or physiological saline with concurrent intraperitoneal injection of H-SN1 or saline alone. Lung histopathologic changes, lung wet-to-dry weight ratio, and myeloperoxidase activity in lung tissues were assessed. Total cell number, the protein concentration, and cytokine levels were determined in the bronchial alveolar lavage fluid. In vitro, RAW 264.7 cells were treated with various concentrations of H-SN1 for 2 h followed by incubation with or without 1 μg/ml LPS for 0.5 or 24 h. The mRNA expression of inflammatory cytokines was determined via RT-PCR and protein levels in the supernatants were measured via ELISA. Extracellular-signal related kinase 1/2 (ERK1/2) and nuclear factor-κB (NF-κB) pathways were analyzed via western blot. H-SN1 improved pulmonary edema status, decreased vascular permeability, suppressed pro-inflammatory cytokine production, and lessened lung morphological injury. H-SN1 also dose-dependently inhibited the mRNA expression and release of TNF-α, IL-6, and IL-1β in LPS-stimulated RAW 264.7 cells. Moreover, H-SN1 inhibited the LPS-induced phosphorylation of ERK1/2 and the nuclear translocation of NF-κB. Our results suggest that H-SN1 could attenuate LPS-induced ALI in mice, which is associated with the anti-inflammatory effect of H-SN1. The mechanism might involve inhibiting the production of inflammatory cytokines by, at least in part, interfering with the ERK1/2 and NF-κB signaling pathways.

Bioactive Components from Qingwen Baidu Decoction against LPS-Induced Acute Lung Injury in Rats

Qingwen Baidu Decoction (QBD) is an extraordinarily “cold” formula. It was traditionally used to cure epidemic hemorrhagic fever, intestinal typhoid fever, influenza, sepsis and so on. The purpose of this study was to discover relationships between the change of the constituents in different extracts of QBD and the pharmacological effect in a rat model of acute lung injury (ALI) induced by lipopolysaccharide (LPS). The study aimed to discover the changes in constituents of different QBD extracts and the pharmacological effects on acute lung injury (ALI) induced by LPS. The results demonstrated that high dose and middle dose of QBD had significantly potent anti-inflammatory effects and reduced pulmonary edema caused by ALI in rats (p < 0.05). To explore the underlying constituents of QBD, we assessed its influence of six different QBD extracts on ALI and analyzed the different constituents in the corresponding HPLC chromatograms by a Principal Component Analysis (PCA) method. The results showed that the pharmacological effect of QBD was related to the polarity of its extracts, and the medium polarity extracts E2 and E5 in particular displayed much better protective effects against ALI than other groups. Moreover, HPLC-DAD-ESI-MSⁿ and PCA analysis showed that verbascoside and angoroside C played a key role in reducing pulmonary edema. In addition, the current study revealed that ethyl gallate, pentagalloylglucose, galloyl paeoniflorin, mudanpioside C and harpagoside can treat ALI mainly by reducing the total cells and infiltration of activated polymorphonuclear leukocytes (PMNs).

Gene Expression Analysis of Murine Lungs Following Pulmonary Exposure to Asian Sand Dust Particles

The respiratory health impact of Asian sand dust events originating in the deserts of China has become a concern within China and in its neighboring countries. We examined the effects of Asian sand dust particles (ASDPs) on gene expression in the murine lung using microarray analysis and elucidated the components responsible for lung inflammation. Male ICR mice were intratracheally administrated ASDPs, heat-treated ASDPs (ASDP-F, lipopolysaccaride [LPS], or β-glucan free), or kaolin particles. We performed microarray analysis for murine lungs, the results of which were confirmed by quantitative reverse transcription–polymerase chain reaction (RT-PCR). We also assessed the protein expression and histologic changes. Exposure to ASDP, ASDP-F, or kaolin upregulated (>2-fold) 112, 36, or 9 genes, respectively, compared with vehicle exposure. In particular, ASDP exposure markedly enhanced inflammatory response–related genes, including chemokine (C-X-C motif) ligand 1/keratinocyte-derived chemokine, chemokine (C-X-C motif) ligand 2/macrophage inflammatory protein-2, chemokine (C-C motif) ligand 3/macrophage inflammatory protein-1α, and chemokine (C-X-C motif) ligand 10/interferon-gamma–inducible protein-10 (>6-fold). The results were correlated with those of the quantitative RT-PCR and the protein expression analyses in overall trend. In contrast, exposure to ASDP-F attenuated the enhanced expression of these proinflammatory molecules. Kaolin exposure increased the expression of genes and proteins for the chemokines. In histopathologic changes, exposure to ASDP prominently enhanced pulmonary neutrophilic inflammation, followed by kaolin and ASDP-F exposure in the order. Taken together, exposure to ASDP causes pulmonary inflammation via the expression of proinflammatory molecules, which can be attributed to LPS and β-glucan absorbed in ASDPs. Furthermore, microarray analysis should be effective for identifying potentially novel genes, sensitive biomarkers, and pathways involved in the health effects of the exposure to environmental particles (e.g., ASDPs).

Eupatorium lindleyanum DC. sesquiterpenes fraction attenuates lipopolysaccharide-induced acute lung injury in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Eupatorium lindleyanum DC. is widely used for its efficiency in treating cough, tracheitis and tonsillitis. Acute lung injury (ALI) induced by lipopolysaccharide (LPS) in mice was used to investigate therapeutic effects and possible mechanism of the sesquiterpenes fraction of E. lindleyanum DC. (EUP-SQT).

MATERIALS AND METHODS

Mice were orally administrated with EUP-SQT (15, 30 and 60mg/kg) per day for 7 days consecutively before LPS challenge. The lung specimens and bronchoalveolar lavage fluid (BALF) were harvested for histopathological examinations and biochemical analysis at 6h and 24h after LPS challenge. The level of complement 3 (C3) and complement 3c (C3c) in serum was quantified by a sandwich ELISA kit.

RESULTS

Pretreatment with EUP-SQT could significantly decrease lung wet-to-dry weight (W/D) ratio, nitric oxide (NO) and protein concentration in BALF, which was exhibited together with the lowered myeloperoxidase (MPO) activity, the increased superoxide dismutase (SOD) activity and down-regulation the level of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in ALI model. Additionally, EUP-SQT attenuated lung histopathological changes and significantly reduced complement deposition with decreasing the level of C3 and C3c in serum.

CONCLUSIONS

These results showed that EUP-SQT significantly attenuated LPS-induced ALI via reducing productions of pro-inflammatory mediators and decreasing the level of complement, indicating it as a potential therapeutic agent for ALI.

C1P Attenuates Lipopolysaccharide-Induced Acute Lung Injury by Preventing NF-κB Activation in Neutrophils

Recently, ceramide-1-phosphate (C1P) has been shown to modulate acute inflammatory events. Acute lung injury (Arnalich et al. 2000. Infect. Immun. 68: 1942-1945) is characterized by rapid alveolar injury, lung inflammation, induced cytokine production, neutrophil accumulation, and vascular leakage leading to lung edema. The aim of this study was to investigate the role of C1P during LPS-induced acute lung injury in mice. To evaluate the effect of C1P, we used a prophylactic and therapeutic LPS-induced ALI model in C57BL/6 male mice. Our studies revealed that intrapulmonary application of C1P before (prophylactic) or 24 h after (therapeutic) LPS instillation decreased neutrophil trafficking to the lung, proinflammatory cytokine levels in bronchoalveolar lavage, and alveolar capillary leakage. Mechanistically, C1P inhibited the LPS-triggered NF-κB levels in lung tissue in vivo. In addition, ex vivo experiments revealed that C1P also attenuates LPS-induced NF-κB phosphorylation and IL-8 production in human neutrophils. These results indicate C1P playing a role in dampening LPS-induced acute lung inflammation and suggest that C1P could be a valuable candidate for treatment of ALI.

Eriodictyol, a plant flavonoid, attenuates LPS-induced acute lung injury through its antioxidative and anti-inflammatory activity

Acute lung injury (ALI) is characterized by excessive inflammatory responses and oxidative injury in the lung tissue. It has been suggested that anti-inflammatory or antioxidative agents could have therapeutic effects in ALI, and eriodictyol has been reported to exhibit antioxidative and anti-inflammatory activity in vitro. The aim of the present study was to investigate the effect of eriodictyol on lipopolysaccharide (LPS)-induced ALI in a mouse model. The mice were divided into four groups: Phosphate-buffered saline-treated healthy control, LPS-induced ALI, vehicle-treated ALI (LPS + vehicle) and eriodictyol-treated ALI (LPS + eriodictyol). Eriodictyol (30 mg/kg) was administered orally once, 2 days before the induction of ALI. The data showed that eriodictyol pretreatment attenuated LPS-induced ALI through its antioxidative and anti-inflammatory activity. Furthermore, the eriodictyol pretreatment activated the nuclear factor erythroid-2-related factor 2 (Nrf2) pathway in the ALI mouse model, which attenuated the oxidative injury and inhibited the inflammatory cytokine expression in macrophages. In combination, the results of the present study demonstrated that eriodictyol could alleviate the LPS-induced lung injury in mice by regulating the Nrf2 pathway and inhibiting the expression of inflammatory cytokines in macrophages, suggesting that eriodictyol could be used as a potential drug for the treatment of LPS-induced lung injury.

Montelukast attenuates lipopolysaccharide-induced cardiac injury in rats

This study investigates the possible protective effects of montelukast (MNT) against lipopolysaccharide (LPS)-induced cardiac injury, in comparison to dexamethasone (DEX), a standard anti-inflammatory. Male Sprague Dawley rats (160–180 g) were assigned to five groups ( n = 8/group): (1) control; (2) LPS (10 mg/kg, intraperitoneal (i.p.)); (3) LPS + MNT (10 mg/kg, per os (p.o.)); (4) LPS + MNT (20 mg/kg, p.o.); and (5) LPS + DEX (1 mg/kg, i.p.). Twenty-four hours after LPS injection, heart/body weight (BW) ratio and percent survival of rats were determined. Serum total protein, creatine kinase muscle/brain (CK-MB), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) activities were measured. Heart samples were taken for histological assessment and for determination of malondialdehyde (MDA) and glutathione (GSH) contents. Cardiac tumor necrosis factor α (TNF-α) expression was evaluated immunohistochemically. LPS significantly increased heart/BW ratio, serum CK-MB, ALP, and LDH activities and decreased percent survival and serum total protein levels. MDA content increased in heart tissues with a concomitant reduction in GSH content. Immunohistochemical staining of heart specimens from LPS-treated rats revealed high expression of TNF-α. MNT significantly reduced percent mortality and suppressed the release of inflammatory and oxidative stress markers when compared with LPS group. Additionally, MNT effectively preserved tissue morphology as evidenced by histological evaluation. MNT (20 mg/kg) was more effective in alleviating LPS-induced heart injury when compared with both MNT (10 mg/kg) and DEX (1 mg/kg), as evidenced by decrease in positive staining by TNF-α immunohistochemically, decrease MDA, and increase GSH content in heart tissue. This study demonstrates that MNT might have cardioprotective effects against the inflammatory process during endotoxemia. This effect can be attributed to its antioxidant and/or anti-inflammatory properties.

D(-)-Salicin inhibits the LPS-induced inflammation in RAW264.7 cells and mouse models

D(-)-Salicin is a traditional medicine which has been known to exhibit anti-inflammation and other therapeutic activities. The present study aimed to investigate whether D(-)-Salicin inhibited the LPS-induced inflammation in vivo and in vitro. We evaluated the effect of D(-)-Salicin on cytokines (TNF-α, IL-1β, IL-6 and IL-10) in vivo and in vitro by enzyme-linked immunosorbent assay and signaling pathways (MAPKs and NF-κB) in vivo by Western blot. The results showed that D(-)-Salicin markedly decreased TNF-α, IL-1β and IL-6 concentrations and increased IL-10 concentration. In addition, western blot analysis indicated that D(-)-Salicin suppressed the activation of MAPKs and NF-κB signaling pathways stimulated by LPS. To examine whether D(-)-Salicin ameliorated LPS-induced lung inflammation, inhibitors of MAPKs and NF-κB signaling pathways were administrated intraperitoneally to mice. Interference with specific inhibitors revealed that D(-)-Salicin-mediated cytokine suppression was through MAPKs and NF-κB pathways. In the mouse model of acute lung injury, histopathologic examination indicted that D(-)-Salicin suppressed edema induced by LPS. So it is suggest that D(-)-Salicin might be a potential therapeutic agent against inflammatory diseases.

The total alkaloids of Aconitum tanguticum protect against lipopolysaccharide-induced acute lung injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Aconitum tanguticum has been widely used as a remedy for infectious diseases in traditional Tibetan medicine in China. The total alkaloids of Aconitum tanguticum (TAA) are the main active components of Aconitum tanguticum and have been demonstrated to be effective in suppressing inflammation. Our aim was to investigate the protective effects of TAA on acute lung injury (ALI) induced by lipopolysaccharide (LPS) in rats.

MATERIALS AND METHODS

TAA was extracted in 95% ethanol and purified in chloroform. After vacuum drying, the TAA powder was dissolved in dimethyl sulfoxide. Adult male Sprague-Dawley rats were randomly divided into six groups. Rats were given dexamethasone (DXM, 4 mg/kg) or TAA (60 mg/kg, 30 mg/kg) before LPS injection. The PaO2and PaO2/FiO2 values, lung wet/dry (W/D) weight ratio and histological changes in lung tissue were measured. The cell counts, protein concentration, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in bronchoalveolar lavage fluid (BALF), and myeloperoxidase (MPO) activity in lung tissue were determined at 6, 12 or 24 h after LPS treatment. In addition, the NF-κ B activation in lung tissue was analyzed by western blot.

RESULTS

In ALI rats, TAA significantly reduced the lung W/D ratio and increased the value of PaO2 or PaO2/FiO2 at 6, 12 or 24 h after LPS challenge. TAA also reduced the total protein concentration and the number of total cells, neutrophils or lymphocytes in BALF. In addition, TAA decreased MPO activity in the lung and attenuated histological changes in the lung. Furthermore, TAA inhibited the concentration of TNF-α, IL-6 and IL-1β in BALF at 6, 12 or 24 h after LPS treatment. Further study demonstrated that TAA significantly inhibited NF-κ B activation in lung tissue.

CONCLUSIONS

The current study proved that TAA exhibited a potent protective effect on LPS-induced ALI in rats through its anti-inflammatory activity.

Montelukast reduces sepsis-induced lung and renal injury in rats

This study was undertaken to examine the effects of montelukast (MNT) on lung and kidney injury in lipopolysaccharide (LPS) induced systemic inflammatory response. Rats were randomized into 5 groups (n = 8 rats/group): (i) Control; (ii) LPS treated (10 mg/kg body mass, by intraperitoneal (i.p.) injection); (iii) LPS + MNT (10 mg/kg, per oral (p.o.)); (iv) LPS + MNT (20 mg/kg, p.o); (v) LPS + dexamethasone (DEX; 1 mg/kg, i.p.). Twenty-four hours after sepsis was induced, the lung or kidney:body mass ratio and percent survival of rats were determined. Creatinine, blood urea nitrogen (BUN), albumin, total protein, and LDH activity were measured. Lung and kidney samples were taken for histological assessment and for determination of their malondialdehyde (MDA) and glutathione (GSH) contents. The expression of tumour necrosis factor α (TNF-α) in tissue was evaluated immunohistochemically. LPS significantly increased the organ:body mass ratio, serum creatinine, BUN, and LDH, and decreased serum albumin and total protein levels. MDA levels increased in lung and kidney tissues after treatment with LPS, and there was a concomitant reduction in GSH levels. Immunohistochemical staining of lung and kidney specimens from LPS-treated rats revealed high expression levels of TNF-α. MNT suppresses the release of inflammatory and oxidative stress markers. Additionally, MNT effectively preserved tissue morphology as evidenced by histological evaluation. These results demonstrate that MNT could have lung and renoprotective effects against the inflammatory process during endotoxemia. This effect can be attributed to its antioxidant and (or) anti-inflammatory properties.

Rabdosia japonica var. glaucocalyx Flavonoids Fraction Attenuates Lipopolysaccharide-Induced Acute Lung Injury in Mice

Rabdosia japonica var. glaucocalyx (Maxim.) Hara, belonging to the Labiatae family, is widely used as an anti-inflammatory and antitumor drug for the treatment of different inflammations and cancers. Aim of the Study. To investigate therapeutic effects and possible mechanism of the flavonoids fraction of Rabdosia japonica var. glaucocalyx (Maxim.) Hara (RJFs) in acute lung injury (ALI) mice induced by lipopolysaccharide (LPS). Materials and Methods. Mice were orally administrated with RJFs (6.4, 12.8, and 25.6 mg/kg) per day for 7 days, consecutively, before LPS challenge. Lung specimens and the bronchoalveolar lavage fluid (BALF) were isolated for histopathological examinations and biochemical analysis. The level of complement 3 (C3) in serum was quantified by a sandwich ELISA kit. Results. RJFs significantly attenuated LPS-induced ALI via reducing productions of the level of inflammatory mediators (TNF- α , IL-6, and IL-1 β ), and significantly reduced complement deposition with decreasing the level of C3 in serum, which was exhibited together with the lowered myeloperoxidase (MPO) activity and nitric oxide (NO) and protein concentration in BALF. Conclusions. RJFs significantly attenuate LPS-induced ALI via reducing productions of proinflammatory mediators, decreasing the level of complement, and reducing radicals.

Rutin decreases lipopolysaccharide-induced acute lung injury via inhibition of oxidative stress and the MAPK-NF-κB pathway

Acute lung injury (ALI) is a serious disease with unacceptably high mortality and morbidity rates. Up to now, no effective therapeutic strategy for ALI has been established. Rutin, quercetin-3-rhamnosyl glucoside, expresses a wide range of biological activities and pharmacological effects, such as anti-inflammatory, antihypertensive, anticarcinogenic, vasoprotective, and cardioprotective activities. Pretreatment with rutin inhibited not only histopathological changes in lung tissues but also infiltration of polymorphonuclear granulocytes into bronchoalveolar lavage fluid in lipopolysaccharide (LPS)-induced ALI. In addition, LPS-induced inflammatory responses, including increased secretion of proinflammatory cytokines and lipid peroxidation, were inhibited by rutin in a concentration-dependent manner. Furthermore, rutin suppressed phosphorylation of NF-κB and MAPK and degradation of IκB, an NF-κB inhibitor. Decreased activities of antioxidative enzymes such as superoxide dismutase, catalase, glutathione peroxidase, and heme oxygenase-1 caused by LPS were reversed by rutin. At the same time, we found that ALI amelioration by chelation of extracellular metal ions with rutin is more efficacious than with deferoxamine. These results indicate that the protective mechanism of rutin is through inhibition of MAPK-NF-κB activation and upregulation of antioxidative enzymes.

Tyrosol exhibits negative regulatory effects on LPS response and endotoxemia

Tyrosol, a phenolic compound, was isolated from wine, olive oil and other plant-derived products. In the present study, we first investigated the negative regulatory effects of tyrosol on cytokine production by lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages in vitro, and the results showed that tyrosol reduced tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) secretion. This inspired us to further study the effects of tyrosol in vivo. Tyrosol significantly attenuated TNF-α, IL-1β and IL-6 production in serum from mice challenged with LPS, and consistent with the results in vitro. In the murine model of endotoxemia, mice were treated with tyrosol prior to or after LPS challenge. The results showed that tyrosol significantly increased mice survival. We further investigated signal transduction ways to determine how tyrosol works. The data revealed that tyrosol shocked LPS-induced mitogen activated protein kinases (MAPKs) and nuclear transcription factor-κB (NF-κB) signal transduction pathways in RAW 264.7 macrophages. These observations indicated that tyrosol exerted negative regulatory effects on LPS response in vitro and in vivo through suppressing NF-κB and p38/ERK MAPK signaling pathways.

Stevioside protects LPS-induced acute lung injury in mice

Stevioside, a diterpene glycoside component of Stevia rebaudiana, has been known to exhibit anti-inflammatory properties. To evaluate the effect and the possible mechanism of stevioside in lipopolysaccharide (LPS)-induced acute lung injury, male BALB/c mice were pretreated with stevioside or dexamethasone 1 h before intranasal instillation of LPS. Seven hours later, tumor necrosis factor-α, interleukin-1β, and interleukin-6 in bronchoalveolar lavage fluid (BALF) were measured by using enzyme-linked immunosorbent assay. The number of total cells, neutrophils, and macrophages in the BALF were also determined. The right lung was excised for histological examination and analysis of myeloperoxidase activity and nitrate/nitrite content. Cyclooxygenase 2 (COX-2), inducible NO synthase (iNOS), nuclear factor-kappa B (NF-κB), inhibitory kappa B protein were detected by western blot. The results showed that stevioside markedly attenuated the LPS-induced histological alterations in the lung. Stevioside inhibited the production of pro-inflammatory cytokines and the expression of COX-2 and iNOS induced by LPS. In addition, not only was the wet-to-dry weight ratio of lung tissue significantly decreased, the number of total cells, neutrophils, and macrophages in the BALF were also significantly reduced after treatment with stevioside. Moreover, western blotting showed that stevioside inhibited the phosphorylation of IκB-α and NF-κB caused by LPS. Taken together, our results suggest that anti-inflammatory effect of stevioside against the LPS-induced acute lung injury may be due to its ability of inhibition of the NF-κB signaling pathway. Stevioside may be a promising potential therapeutic reagent for acute lung injury treatment.

Prime-O-glucosylcimifugin attenuates lipopolysaccharide-induced acute lung injury in mice

Prime-O-glucosylcimifugin is an active chromone isolated from Saposhnikovia root which has been reported to have various activities, such as anti-convulsant, anticancer, anti-inflammatory properties. The purpose of this study was to evaluate the effect of prime-O-glucosylcimifugin on acute lung injury (ALI) induced by lipopolysaccharide in mice. BALB/c mice received intraperitoneal injection of Prime-O-glucosylcimifugin 1h before intranasal instillation (i.n.) of lipopolysaccharide (LPS). Concentrations of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and interleukin (IL)-6 in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay (ELISA). Pulmonary histological changes were evaluated by hematoxylin-eosin, myeloperoxidase (MPO) activity in the lung tissue and lung wet/dry weight ratios were observed. Furthermore, the mitogen-activated protein kinases (MAPK) signaling pathway activation and the phosphorylation of IκBα protein were determined by Western blot analysis. Prime-O-glucosylcimifugin showed promising anti-inflammatory effect by inhibiting the activation of MAPK and NF-κB signaling pathway.

Licochalcone a inhibits lipopolysaccharide-induced inflammatory response in vitro and in vivo

Licochalcone A (Lico A), a flavonoid found in licorice root (Glycyrrhiza glabra), is known for its antimicrobial activity and its reported ability to inhibit cancer cell proliferation. In the present study, we found that Lico A exerted potent anti-inflammatory effects in in vitro and in vivo models induced by lipopolysaccharide (LPS). The concentrations of TNF-α, interleukin (IL)-6, and IL-1β in the culture supernatants of RAW 264.7 cells were determined at different time points following LPS administration. LPS (0.5 mg/kg) was instilled intranasally (i.n.) in phosphate-buffered saline to induce acute lung injury, and 24 h after LPS was given, bronchoalveolar lavage fluid was obtained to measure pro-inflammatory mediator and total cell counts. The phosphorylation of mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB) p65 protein was analyzed by Western blotting. Our results showed that Lico A significantly reduced the amount of inflammatory cells, the lung wet-to-dry weight (W/D) ratio, protein leakage, and myeloperoxidase activity and enhances oxidase dimutase activity in mice with LPS-induced acute lung injury (ALI). Enzyme-linked immunosorbent assay results indicated that Lico A can significantly down-regulate TNF-α, IL-6, and IL-1β levels in vitro and in vivo, and treatment with Lico A significantly attenuated alveolar wall thickening, alveolar hemorrhage, interstitial edema, and inflammatory cells infiltration in mice with ALI. In addition, we further demonstrated that Lico A exerts an anti-inflammation effect in an in vivo model of acute lung injury through suppression of NF-κB activation and p38/ERK MAPK signaling in a dose-dependent manner.

Polydatin up-regulates Clara cell secretory protein to suppress phospholipase A2 of lung induced by LPS in vivo and in vitro

Background

Lung injury induced by lipopolysaccharide (LPS) remains one of the leading causes of morbidity and mortality in children. The damage to membrane phospholipids leads to the collapse of the bronchial alveolar epithelial barrier during acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Phospholipase A₂ (PLA₂), a key enzyme in the hydrolysis of membrane phospholipids, plays an important traumatic role in pulmonary inflammation, and Clara cell secretory protein (CCSP) is an endogenous inhibitor of PLA₂. Our previous study showed that polydatin (PD), a monocrystalline extracted from a traditional Chinese medicinal herb (Polygonum cuspidatum Sieb, et Zucc), reduced PLA₂ activity and sPLA₂-IIA mRNA expression and mitigated LPS-induced lung injury. However, the potential mechanism for these effects has not been well defined. We have continued to investigate the effect of PD on LPS-induced expression of CCSP mRNA and protein in vivo and in vitro.

Results

Our results suggested that the CCSP mRNA level was consistent with its protein expression. CCSP expression was decreased in lung after LPS challenge. In contrast, PD markedly increased CCSP expression in a concentration-dependent manner. In particular, CCSP expression in PD-pretreated rat lung was higher than in rats receiving only PD treatment.

Conclusion

These results indicated that up-regulation of CCSP expression causing inhibition of PLA₂ activation may be one of the crucial protective mechanisms of PD in LPS-induced lung injury.

Nilotinib ameliorates lipopolysaccharide-induced acute lung injury in rats

The present study aimed to investigate the effect of the new tyrosine kinase inhibitor, nilotinib on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in rats and explore its possible mechanisms. Male Sprague-Dawley rats were given nilotinib (10mg/kg) by oral gavage twice daily for 1week prior to exposure to aerosolized LPS. At 24h after LPS exposure, bronchoalveolar lavage fluid (BALF) samples and lung tissue were collected. The lung wet/dry weight (W/D) ratio, protein level and the number of inflammatory cells in the BALF were determined. Optical microscopy was performed to examine the pathological changes in lungs. Malondialdehyde (MDA) content, superoxidase dismutase (SOD) and reduced glutathione (GSH) activities as well as nitrite/nitrate (NO(2)(-)/NO(3)(-)) levels were measured in lung tissues. The expression of inflammatory cytokines, tumor necrosis factor-α (TNF-α), transforming growth factor-β(1) (TGF-β(1)) and inducible nitric oxide synthase (iNOS) were determined in lung tissues. Treatment with nilotinib prior to LPS exposure significantly attenuated the LPS-induced pulmonary edema, as it significantly decreased lung W/D ratio, protein concentration and the accumulation of the inflammatory cells in the BALF. This was supported by the histopathological examination which revealed marked attenuation of LPS-induced ALI in nilotinib treated rats. In addition, nilotinib significantly increased SOD and GSH activities with significant decrease in MDA content in the lung. Nilotinib also reduced LPS mediated overproduction of pulmonary NO(2)(-)/NO(3)(-) levels. Importantly, nilotinib caused down-regulation of the inflammatory cytokines TNF-α, TGF-β(1) and iNOS levels in the lung. Taken together, these results demonstrate the protective effects of nilotinib against the LPS-induced ALI. This effect can be attributed to nilotinib ability to counteract the inflammatory cells infiltration and hence ROS generation and regulate cytokine effects.

Integrated lipidomics in the secreted phospholipase A(2) biology

Mammalian genomes encode genes for more than 30 phospholipase A(2)s (PLA(2)s) or related enzymes, which are subdivided into several subgroups based on their structures, catalytic mechanisms, localizations and evolutionary relationships. More than one third of the PLA(2) enzymes belong to the secreted PLA(2) (sPLA(2)) family, which consists of low-molecular-weight, Ca(2+)-requiring extracellular enzymes, with a His-Asp catalytic dyad. Individual sPLA(2) isoforms exhibit unique tissue and cellular localizations and enzymatic properties, suggesting their distinct pathophysiological roles. Recent studies using transgenic and knockout mice for several sPLA(2) isoforms, in combination with lipidomics approaches, have revealed their distinct contributions to various biological events. Herein, we will describe several examples of sPLA(2)-mediated phospholipid metabolism in vivo, as revealed by integrated analysis of sPLA(2) transgenic/knockout mice and lipid mass spectrometry. Knowledge obtained from this approach greatly contributes to expanding our understanding of the sPLA(2) biology and pathophysiology.

Preventive effects of valnemulin on lipopolysaccharide-induced acute lung injury in mice

Valnemulin reportedly regulates inflammatory responses in addition to its in vitro antibacterial activity. In this study, we established a mouse model of lipopolysaccharide (LPS)-induced inflammatory lung injury and investigated the effect of valnemulin (100 mg/kg) on acute lung injury (ALI) 8 h after LPS challenge. We prepared bronchoalveolar lavage fluid (BALF) for measuring protein concentrations, cytokine levels, and superoxidase dismutase (SOD) activity, and collected lungs for assaying wet-to-dry weight (W/D) ratios, myeloperoxidase (MPO) activity, cytokine mRNA expression, and histological change. We found that the pre-administration of valnemulin significantly decreases the W/D ratio of lungs, protein concentrations, and the number of total cells, neutrophils, macrophages, and leukomonocytes, and histologic analysis indicates that valnemulin significantly attenuates tissue injury. Furthermore, valnemulin significantly increases LPS-induced SOD activity in BALF and decreases lung MPO activity as well. In addition, valnemulin also inhibits the production of tumor necrosis factor-alpha, interleukin-6, and interleukin-1beta, which is consistent with mRNA expression in lung. The results showed that valnemulin had a protective effect on LPS-induced ALI in mice.

Taraxacum officinale protects against lipopolysaccharide-induced acute lung injury in mice

AIM OF THE STUDY

Taraxacum officinale has been frequently used as a remedy for inflammatory diseases. In the present study, we investigated the in vivo protective effect of Taraxacum officinale on acute lung injury (ALI) induced by lipopolysaccharide (LPS) in mice.

MATERIALS AND METHODS

Taraxacum officinale at 2.5, 5 and 10 mg/kg was orally administered once per day for 5 days consecutively, followed by 500 microg/kg LPS was instilled intranasally. The lung wet/dry weight (W/D) ratio, protein concentration and the number of inflammatory cells in bronchoalveolar lavage fluid (BALF) were determined. Superoxidase dismutase (SOD) and myeloperoxidase (MPO) activities, and histological change in the lungs were examined. The levels of inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in the BALF were measured using ELISA.

RESULTS

We found that Taraxacum officinale decreased the lung W/D ratio, protein concentration and the number of neutrophils in the BALF at 24 h after LPS challenge. Taraxacum officinale decreased LPS-induced MPO activity and increased SOD activity in the lungs. In addition, histopathological examination indicated that Taraxacum officinale attenuated tissue injury of the lungs in LPS-induced ALI. Furthermore, Taraxacum officinale also inhibited the production of inflammatory cytokines TNF-alpha and IL-6 in the BALF at 6h after LPS challenge in a dose-dependent manner.

CONCLUSIONS

These results suggest that Taraxacum officinale protects against LPS-induced ALI in mice.

Animal models of human anthrax: the Quest for the Holy Grail

Anthrax is rare among humans, few data can be collected from infected individuals and they provide a fragmentary view of the dynamics of infection and human host-pathogen interactions. Therefore, the development of animal models is necessary. Anthrax has the particularity of being a toxi-infection, a combination of infection and toxemia. The ideal animal model would explore these two different facets and mimic human disease as much as possible. In the past decades, the main effort has been focused on modelling of inhalational anthrax and the perception of specific aspects of the infection has evolved in recent years. In this review, we consider criteria which can lead to the most appropriate choice of a given animal species for modelling human anthrax. We will highlight the positive input and limitations of different models and show that they are not mutually exclusive. On the contrary, their contribution to anthrax research can be more rewarding when taken in synergy. We will also present a reappraisal of inhalational anthrax and propose reflections on key points, such as portal of entry, connections between mediastinal lymph nodes, pleura and lymphatic drainage.

Phospholipase A2 subclasses in acute respiratory distress syndrome

Phospholipases A2 (PLA2) catalyse the cleavage of fatty acids esterified at the sn-2 position of glycerophospholipids. In acute lung injury-acute respiratory distress syndrome (ALI-ARDS) several distinct isoenzymes appear in lung cells and fluid. Some are capable to trigger molecular events leading to enhanced inflammation and lung damage and others have a role in lung surfactant recycling preserving lung function: Secreted forms (groups sPLA2-IIA, -V, -X) can directly hydrolyze surfactant phospholipids. Cytosolic PLA2 (cPLA2-IVA) requiring Ca2+ has a preference for arachidonate, the precursor of eicosanoids which participate in the inflammatory response in the lung. Ca(2+)-independent intracellular PLA2s (iPLA2) take part in surfactant phospholipids turnover within alveolar cells. Acidic Ca(2+)-independent PLA2 (aiPLA2), of lysosomal origin, has additionally antioxidant properties, (peroxiredoxin VI activity), and participates in the formation of dipalmitoyl-phosphatidylcholine in lung surfactant. PAF-AH degrades PAF, a potent mediator of inflammation, and oxidatively fragmented phospholipids but also leads to toxic metabolites. Therefore, the regulation of PLA2 isoforms could be a valuable approach for ARDS treatment.

Secretory group V phospholipase A2 regulates acute lung injury and neutrophilic inflammation caused by LPS in mice

We investigated the regulatory role of 14-kDa secretory group V phospholipase A(2) (gVPLA(2)) in the development of acute lung injury (ALI) and neutrophilic inflammation (NI) caused by intratracheal administration of LPS. Experiments were conducted in gVPLA(2) knockout (pla2g5(-/-)) mice, which lack the gene, and gVPLA(2) wild-type littermate control (pla2g5(+/+)) mice. Indices of pulmonary injury were evaluated 24 h after intratracheal administration of LPS. Expression of gVPLA(2) in microsections of airways and mRNA content in lung homogenates were increased substantially in pla2g5(+/+) mice after LPS-administered compared with saline-treated pla2g5(+/+) mice. By contrast, expression of gVPLA(2) was neither localized in LPS- nor saline-treated pla2g5(-/-) mice. LPS also caused 1) reduced transthoracic static compliance, 2) lung edema, 3) neutrophilic infiltration, and 4) increased neutrophil myeloperoxidase activity in pla2g5(+/+) mice. These events were attenuated in pla2g5(-/-) mice exposed to LPS or in pla2g5(+/+) mice receiving MCL-3G1, a neutralizing MAb directed against gVPLA(2), before LPS administration. Our data demonstrate that gVPLA(2) is an inducible protein in pla2g5(+/+) mice but not in pla2g5(-/-) mice within 24 h after LPS treatment. Specific inhibition of gVPLA(2) with MCL-3G1 or gene-targeted mice lacking gVPLA(2) blocks ALI and attenuates NI caused by LPS.

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.

Upregulation of hypoxia-induced mitogenic factor in bacterial lipopolysaccharide-induced acute lung injury

Hypoxia-induced mitogenic factor (HIMF), also known as FIZZ1 (found in inflammatory zone), plays important roles in lung inflammation. We found that intraperitoneal injection of lipopolysaccharide (LPS) induced intensive HIMF production exclusively in mouse lung, but not in the heart, liver, spleen or kidney. This HIMF production, at least partly, contributes to LPS-induced vascular cell adhesion molecule-1 (VCAM-1) upregulation and mononuclear cell sequestration to lung parenchyma, while protecting alveolar type II cells from LPS-resulted decrease in surfactant protein-C production and cell death. These data indicate that HIMF participates in LPS-induced acute lung injury and inflammation through modulating VCAM-1 and SP-C expression.

Effects of budesonide and N-acetylcysteine on acute lung hyperinflation, inflammation and injury in rats

Leukocyte activation and production of inflammatory mediators and reactive oxygen species are important in the pathogenesis of lipopolysaccharide (LPS)-induced acute lung injury. The present study investigated acute lung hyperinflation, edema, and lung inflammation 4 h after an intratracheal instillation of LPS (0.5, 2.5, 5, 10, 50, 100, 500, 1000, and 5000 microg/ml/kg). Effects of budesonide, an inhaled anti-inflammatory corticosteroids, and N-acetylcysteine (NAC), an antioxidant, were evaluated in Wistar rats receiving either low (2.5 microg/ml/kg) or high (50 microg/ml/kg) concentrations of LPS. This study demonstrates that LPS in a concentration-dependent pattern induces acute lung hyperinflation measured by excised lung gas volume (25-45% above control), lung injury indicated by increased lung weight (10-60%), and lung inflammation characterized by the infiltration of leukocytes (40-14000%) and neutrophils (80-17000%) and the production of cytokines (up to 2700%) and chemokines (up to 350%) in bronchoalveolar lavage fluid (BALF). Pretreatment with NAC partially prevented tumor necrosis factor alpha (TNFalpha) production induced by the low concentration of LPS, while pretreatment with budesonide totally prevented the increased production of TNFalpha, interleukin (IL)-1beta, IL-6, and monocyte chemoattractive protein (MCP)-1 after LPS challenge at both low and high concentrations. Budesonide failed to prevent BALF levels of macrophage inflammatory protein (MIP)-2 and cytokine-induced neutrophil chemoattractant 1 (GRO/CINC-1) as well as lung hyperinflation induced by both low and high concentrations of LPS. Pretreatment with budesonide totally prevented the formation of lung edema at the low concentration of LPS and had partial effects on acute lung injury and leukocyte influx at the high concentrations. Thus, our data indicate that therapeutic effects of budesonide and NAC are dependent upon the severity of the disease.

Postinjury serum secretory phospholipase A2 correlates with hypoxemia and clinical status at 72 hours

BACKGROUND

Although trauma patients often suffer direct lung damage, an equally destructive mechanism of lung injury involves postinjury systemic inflammation. We postulate that secretory phospholipase A(2) (sPLA(2)) release induced by trauma relates to systemic inflammation that compromises both lung function and clinical status after injury. The objectives of this study were: to relate Injury Severity Score to postinjury sPLA(2); to determine whether circulating sPLA(2) relates to pulmonary oxygenation and compliance; and to determine whether early or persistent increases in sPLA(2) are associated with abnormal chest x-ray at 72 hours after injury.

STUDY DESIGN

The prospective cohort study comprised 54 consecutive intensive care admissions in patients with traumatic injury admitted over a 6-month period from November 1, 1996, to May 1, 1997.

RESULTS

Postinjury peak sPLA(2) values were associated with increased ISS (r = 0.49, r(2) = 0.24, p < 0.001). Patients with elevated sPLA(2) had poor oxygenation compared with those with normal sPLA(2) levels (Pa0(2)/Fi0(2) ratio 164 +/- 16 versus 260 +/- 26 mmHg [mean +/- SEM], p < 0.01) and also required additional PEEP (5.5 +/- 0.9 versus 2.5 +/- 0.4 cm H(2)O, p = 0.01). Secretory PLA(2) levels in patients with abnormal chest x-ray 72 hours after injury were higher (1.08 +/- 0.2 versus 0.34 +/- 0.1 activity units, p < 0.001) than levels seen in patients with normal x-rays.

CONCLUSIONS

Increasing injury magnitude is associated with elevated sPLA(2) levels, and increased sPLA(2) is related to postinjury hypoxemia and clinical status.

ExoU is a potent intracellular phospholipase

The combination of a large genome encoding metabolic versatility and conserved secreted virulence determinants makes Pseudomonas aeruginosa a model pathogen that can be used to study host-parasite interactions in many eukaryotic hosts. One of the virulence regulons that likely plays a role in the ability of P. aeruginosa to avoid innate immune clearance in mammals is a type III secretion system (TTSS). Upon cellular contact, the P. aeruginosa TTSS is capable of delivering a combination of at least four different effector proteins, exoenzyme S (ExoS), ExoT, ExoU, and ExoY. Two of the four translocated proteins, ExoS and ExoU, are cytotoxic to cells during infection and transfection. The mechanism of cytotoxicity of ExoS is unclear. ExoU, however, has recently been characterized as a member of the phospholipase A family of enzymes, possessing at least phospholipase A2 activity. Similar to ExoS, ExoT and ExoY, ExoU requires either a eukaryotic-specific modification or cofactor for its activity in vitro. The biologic effects of minimal expression of ExoU in yeast can be visualized by membrane damage to different organelles and fragmentation of the vacuole. In mammalian cells, the direct injection of ExoU causes irreversible damage to cellular membranes and rapid necrotic death. ExoU likely represents a unique enzyme and is the first identified phopholipase virulence factor that is translocated into the cytosol by TTSS.

Complementary DNA microarray analysis in acute lung injury induced by lipopolysaccharide and diesel exhaust particles

We have recently shown that diesel exhaust particles (DEP) synergistically enhance acute lung injury related to lipopoly-saccharide (LPS) in mice. The present study used cDNA microarray to elucidate the effects of DEP on the global pattern of LPS-related gene expression in the murine lung. The number of genes upregulated >/=2-fold as compared with their expression levels in the vehicle group was greater in the LPS group than in other groups, but treatment with DEP and LPS dramatically increased the number of the genes upregulated >/=6-fold. In particular, gene expression of metallothionein-1 and -2, S100 calcium-binding protein A9, lipocalin 2, and small inducible cytokine B family member 10 was higher by >/=20-fold in the DEP + LPS group than in the vehicle group. These results were concomitant with those obtained by real-time reverse transcription-polymerase chain reaction analysis in the overall trend. Our findings suggest that intense, focused expression of genes such as S100 calcium-binding protein A9, lipocalin 2, and small inducible cytokine B family member 10 relates to the synergistic aggravation of acute lung injury by LPS and DEP rather than weak, broad expression of various genes by exposure of LPS alone.

Protective effects of sphingosine 1-phosphate in murine endotoxin-induced inflammatory lung injury

Our prior in vitro studies indicate that sphingosine 1-phosphate (S1P), a phospholipid angiogenic factor, produces endothelial cell barrier enhancement through ligation of endothelial differentiation gene family receptors. We hypothesized that S1P may reduce the vascular leak associated with acute lung injury and found that S1P infusion produced a rapid and significant reduction in lung weight gain (more than 50%) in the isolated perfused murine lung. The effect of S1P was next assessed in a murine model of LPS-mediated microvascular permeability and inflammation with marked increases in parameters of lung injury at both 6 and 24 hours after intratracheal LPS. Each parameter assessed was significantly reduced by intravenous S1P (1 microM final) and in selected experiments by the S1P analogue FTY720 (0.1 mg/kg, intraperitoneally) delivered 1 hour after LPS. S1P produced an approximately 40-50% reduction in LPS-mediated extravasation of Evans blue dye albumin, bronchoalveolar lavage protein content, and lung tissue myeloperoxidase activity (reflecting phagocyte infiltration). Consistent with systemic barrier enhancement, S1P significantly decreased Evans blue dye albumin extravasation and myeloperoxidase content in renal tissues of LPS-treated mice. These studies indicate that S1P significantly decreases pulmonary/renal vascular leakage and inflammation in a murine model of LPS-mediated acute lung injury and may represent a novel therapeutic strategy for vascular barrier dysfunction.

Secretory Phospholipase A2

Secretory phospholipase A2 (sPLA2) is a growing family of structurally related, disulfide-rich, low molecular weight, lipolytic enzymes with a His-Asp catalytic dyad. sPLA2s are distributed in a wide variety of vertebrate and invertebrate animals, plants, bacteria, and viruses, and there are 10 catalytically active sPLA2 isozymes in mammals. Although the structural bases for mammalian sPLA2s have been well documented, their physiological functions are still subject to debate. Individual mammalian sPLA2s have distinct enzymatic properties and display distinct tissue expression patterns, suggesting that each enzyme acts on distinct phospholipid membrane moieties in vivo. In this article, we briefly review our latest understanding of the possible physiological functions of sPLA2s, in keeping with their diverse actions on mammalian and nonmammalian cell membranes.

Surfactant protein-A and phosphatidylglycerol suppress type IIA phospholipase A2 synthesis via nuclear factor-kappaB

We previously showed that surfactant inhibits the synthesis of type IIA secretory phospholipase A2 (sPLA2-IIA) by alveolar macrophages. These cells have been identified as the main source of this enzyme in an animal model of acute lung injury. The aim of the present study was to identify the surfactant components involved in the inhibition of sPLA2-IIA expression in alveolar macrophages and the signaling pathways that mediate this inhibition. Our results show that various surfactant preparations can inhibit sPLA2-IIA expression in endotoxin-stimulated alveolar macrophages. Both the surfactant protein (SP)-A and the surfactant phospholipid fraction inhibit this expression. The surfactant phospholipid dioleylphosphatidylglycerol (DOPG) abolishes sPLA2-IIA expression, whereas dipalmitoylphosphatidylcholine does not. Chromatographic analysis and confocal microscopy revealed that phosphatidylglycerol was rapidly incorporated and metabolized by alveolar macrophages and that its metabolites accumulate in the cytosol. Nuclear factor-kappaB (NF-kappaB) modulates sPLA2-IIA expression in endotoxin-activated alveolar macrophages, and surfactant preparations, surfactant phospholipid fraction, SP-A, and DOPG indeed suppressed NF-kappaB activation. In summary, our results show that SP-A and DOPG play a role in the surfactant-mediated inhibition of sPLA2-IIA expression in alveolar macrophages and that this inhibition occurs via a downregulation of NF-kappaB activation.