Induction of lymphocyte apoptosis in a murine model of acute lung injury--modulation by lipid emulsions.

Acute lung injury (ALI) and sepsis are the major causes of mortality in intensive care units. Lymphocytes apoptosis is a hallmark feature of late detrimental sepsis. Parenteral nutrition in critically ill patients is based on lipid emulsions, but the impact of ALI and lipid emulsions on lymphocytes has not been defined. The effects of intravenously infused conventional soybean oil (SO)-based and new olive oil (OO)-based emulsions on splenic and blood lymphocytes were investigated in a murine model of endotoxin-induced ALI. After LPS challenge and infusion of lipid emulsions, apoptosis of lymphocytes and lung injury were assessed by flow cytometry, Western blot, and histology. Induction of ALI led to a time-dependent decline in splenic and circulating lymphocyte numbers and an increase in apoptosis, with engagement of the extrinsic apoptotic pathway. Both SO- and OO-based emulsions promoted the apoptosis of splenic lymphocytes before induction of ALI. The OO-based emulsions exhibited lower proapoptotic activity than did SO-based emulsions, an observation paralleled by the induction of survival factors. Induction of ALI increased the mortality of mice receiving SO-based emulsions compared with OO-based emulsions and normal saline. Splenic lymphocyte apoptosis is apparent in murine ALI, which may be linked to detrimental outcome. Infusion of lipid emulsions per se provoked splenic lymphocyte apoptosis. Infusion of SO-based emulsions further augmented the apoptosis of splenic and circulating lymphocytes in ALI and led to increased mortality in mice. These findings may be of relevance for patients experiencing ALI that require parenteral nutrition.

Immunomodulation by n-3- versus n-6-rich lipid emulsions in murine acute lung injury--role of platelet-activating factor receptor.

OBJECTIVE: Cytokines, platelet-activating factor (PAF), and eicosanoids control local and systemic inflammation. Conventional soybean oil-based lipid emulsions used for parenteral nutrition may aggravate the leukocyte inflammatory response or adhesion to the vessel wall. Fish oil-based lipid emulsions, in contrast, may exert an anti-inflammatory effect. DESIGN: We investigated the impact of lipid emulsions on leukocyte invasion, protein leakage, and cytokines in two murine models of acute inflammation. SETTING: Research laboratory of a university hospital. SUBJECTS: Wild-type mice and PAF-receptor knockout mice. INTERVENTIONS: Mice received an infusion of normal saline, fish oil- or soybean oil-based lipid emulsions before lipopolysaccharide challenge. MEASUREMENTS AND MAIN RESULTS: Preinfusion with soybean oil resulted in increased leukocyte invasion, myeloperoxidase activity, and protein leakage and exaggerated release of tumor necrosis factor (TNF)-alpha as well as macrophage inflammatory protein (MIP)-2 into the alveolar space after intratracheal lipopolysaccharide challenge. In contrast, preinfusion with fish oil reduced leukocyte invasion, myeloperoxidase activity, protein leakage, and TNF-alpha as well as MIP-2 generation. Corresponding profiles were found in plasma following intraperitoneal lipopolysaccharide application: Soybean oil increased but fish oil decreased the TNF-alpha and MIP-2 formation. When PAF-receptor-deficient mice were challenged with lipopolysaccharide, leukocyte invasion, lung tissue myeloperoxidase, cytokine generation, and alveolar protein leakage corresponded to those observed in wild-type animals. Fish oil and soybean oil lost their diverging effects on leukocyte transmigration, myeloperoxidase activity, leakage response, and cytokine generation in these knockout mice. Similarly, the differential impact of both lipid emulsions on these lipopolysaccharide-provoked changes was suppressed after pretreating animals with a PAF-receptor antagonist. CONCLUSIONS: Fish oil- vs. soybean oil-based lipid infusions exert anti- vs. proinflammatory effects in murine models of acute inflammation. The PAF/PAF-receptor-linked signaling appears to be a prerequisite for this differential profile.

[Effect of different fat emulsions on acute lung injury induced by endotoxin].

OBJECTIVE: To assess the effect of Clinoleic 20% (olive oil-based, n-9) and Lipoven 20% (soy bean-based, n-6) lipid emulsions on inflammatory parameters in a murine acute lung injury (ALI) model induced by lipopolysaccharide (LPS) of E. coli O111:B4. METHODS: Male Balb/C mice were infused for three days with 0.9% NaCl, Clinoleic 20%, or Lipoven 20% respectively, and sacrificed either at 8 hours or 24 hours after intra-tracheal introduction of LPS. Survival rate, lung wet/dry weight ratio (W/D), lung tissue myeloperoxidase (MPO) activity were determined, and tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-2 (MIP-2) in bronchoalveolar lavage fluid (BALF) were determined with enzyme linked immunosorbent assay (ELISA). Serum free fatty acids [arachidonic acid (AA), oleic acid, linoleic acid] were determined by gas chromatography. Leukocytes in BALF were counted under light microscope. RESULTS: Lipoven significantly decreased survival rate at 24 hours after intra-tracheal LPS challenge compared to corresponding controls (both P<0.01). No significant difference was observed between Clinoleic and NaCl groups. MPO activity was obviously increased in lipids groups than that in NaCl group at 24 hours (both P<0.01), and no difference was found between two lipids groups. LPS markedly induced an increase in leukocyte infiltration, W/D ratio, lung MPO activity, release of TNF-alpha as well as MIP-2 into alveolar space in both lipids and NaCl groups. Pre-infusion with Lipoven gave rise to heavier leukocyte infiltration at 24 hours, which was blunted in Clinoleic group and NaCl group (both P<0.01). In contrast to Clinoleic and NaCl groups, Lipoven increased production of TNF-alpha at 24 hours and MIP-2 at 8 hours in LPS-treated mice (all P<0.01). Notably, lipid emulsions increased LPS-induced MPO activity, but no difference in effects was found in both Lipoven and Clinoleic groups. Clinoleic significantly reduced free AA at 8 and 24 hours compared with Lipoven (both P<0.01). There were no differences in lung tissues edema, serum oleic acid and linoleic acid among three groups. CONCLUSION: In murine model of ALI, although LPS caused an increase in alveolar leucocytic infiltration, MPO activity, cytokine generation in both lipids and NaCl groups, Lipoven 20%, n-6 lipid emulsion induces a severer inflammatory reaction. It is speculated that by increasing AA, Lipoven 20% may aggravate ALI, whereas Clinoleic 20%, n-9 lipid emulsion possibly offers an alternative choice in producing less impact on inflammatory lung injury.