Prompt inhibition of fMLP-induced Ca2+ mobilization by parenteral lipid emulsions in human neutrophils

Lipopeptide PAM3CYS4 Synergizes N-Formyl-Met-Leu-Phe (fMLP)-Induced Calcium Transients in Mouse Neutrophils

N-Formyl-Met-Leu-Phe (fMLP), a mimic of N-formyl oligopeptides that are released from bacteria, is a potent leukocyte chemotactic factor. It induces intracellular calcium ([Ca]i) transient that is important for various neutrophil biological functions, e.g., adhesion, ROS, and cytokine productions. Toll-like receptors (TLRs), an essential part of host innate immunity, regulate neutrophil activities, but their role in [Ca]i signaling is less clear. In the present study, we examined the effect of several TLR ligands, including Pam3Cys4 (TLR1/2), lipopolysaccharide (LPS, TLR4), and lipoteichoic acid (LTA, TLR2/6), on calcium signaling and on the fMLP-induced [Ca]i transients in mouse neutrophils loaded with Fura-2/AM. We found that unlike fMLP, the three TLR ligands tested did not elicit any detectable Ca flux. However, Pam3Cys4, but not LPS or LTA, markedly synergized the fMLP-induced [Ca]i transients, and had no effect on the host component keratinocyte-derived cytokine (KC)- or C5a-induced calcium flux. The effect of Pam3Cys4 on the fMLP-induced [Ca]i transients is by enhancing extracellular Ca influx, not intracellular Ca release. Surprisingly, deletion of TLR2 or MyD88 in neutrophils had no impact on the Pam3Cys4's effect, suggesting a TLR2-MyD88-independent mechanism. Finally, using the pan PKC activator and inhibitor, we demonstrated that PKC negatively regulated fMLP-induced [Ca]i transients and that inhibition of PKC did not prohibit Pam3Cys4's synergistic effect on the fMLP-induced calcium influx. In conclusion, the present study identified a novel synergistic effect of Pam3Cys4 on fMLP-induced [Ca]i transients, a process important for many neutrophil biological functions.

Toxicity of a Soybean Oil Emulsion on Human Lymphocytes and Neutrophils

BACKGROUND

The incorporation of lipid emulsions in parenteral diets is a requirement for energy and essential fatty acid supply to critically ill patients. In this study, the toxicity of a lipid emulsion rich (60%) in triacylglycerol of omega-6 polyunsaturated fatty acids on leukocytes from healthy volunteers was investigated.

METHODS

Eleven volunteers were recruited, and blood samples were collected before infusion of a soybean oil emulsion, immediately afterwards, and 18 hours later. The cells were studied immediately after isolation and again after 24 hours or 48 hours in culture. The following determinations were made: composition and concentration of fatty acids in plasma, lymphocytes and neutrophils, lymphocyte proliferation, levels of cell viability, DNA fragmentation, phosphatidylserine externalization, mitochondrial depolarization, reactive oxygen species production, and neutral lipid accumulation.

RESULTS

Soybean oil emulsion decreased lymphocyte proliferation and provoked neutrophil and lymphocyte apoptosis and necrosis. Evidence is presented herein that soybean oil emulsion is less toxic to neutrophils than to lymphocytes. The mechanism of cell death induced by this oil emulsion was characterized by mitochondrial membrane depolarization and neutral lipid accumulation but did not alter reactive oxygen species production.

CONCLUSIONS

Soybean oil emulsion given as a single dose of 500 mL promotes lymphocyte and neutrophil death that may enhance the susceptibility of the patients to infections.

Immune activation by medium-chain triglyceride-containing lipid emulsions is not modulated by n-3 lipids or toll-like receptor 4

BACKGROUND

Saturated medium-chain triglycerides (MCT) as part of the parenteral lipid regimen (50% MCT and 50% long chain triglycerides (LCT)) activate the immune system in vitro. Fish oil (FO)-derived n-3 fatty acids (FA) inhibit saturated FA-induced immune activation via a toll-like receptor (TLR)-4 mediated mechanism. We hypothesized that effects of parenteral MCTs on immune cells involve TLR-4 signaling and that these effects are modulated by n-3 FA that are present in FO.

MATERIALS AND METHODS

To test this hypothesis we assessed effects of addition of various commercially available mixed parenteral lipid emulsions, n-3 FA and of TLR-4 inhibition on MCT-induced human immune cell activation by evaluation of the expression of leukocyte membrane activation markers and reactive oxygen species (ROS) production.

RESULTS

All MCT-containing lipid emulsions activated leukocytes by inducing changes in expression of membrane markers and stimulus induced ROS production, whereas MCT-free lipid emulsions lacked this effect. Moreover, addition of n-3 FA to LCT/MCT did not prevent MCT-induced immune activation. TLR-4 inhibitors did not distinctly modulate MCT-induced changes in immune function.

CONCLUSION

Taken together, these findings suggest that leukocyte activation by parenteral MCTs does not involve TLR-4 signaling and is not modulated by n-3 FA in FO-, but is exerted via different signaling pathways.

Effects of lipid emulsions in parenteral nutrition of esophageal cancer surgical patients receiving enteral nutrition: a comparative analysis

Background: Olive oil-based lipid emulsion (LE) and medium chain triglyceride/long chain triglyceride (MCT/LCT) emulsion are both LEs with low ω-6 polyunsaturated fat acids (PUFAs) content. However, which one of these LEs is associated with a lower infection risk in patients receiving parenteral nutrition (PN) remains unclear. The aim of the study was to compare the effects of the two LEs in PN in esophageal cancer patients undergoing surgery. Methods: Patients with resectable esophageal carcinoma were recruited and allocated randomly to two groups. The test group was given enteral nutrition (EN) with PN containing olive oil-based LE after tumor resection for ≥7 days, and the patients in the control group were supported by EN with MCT/LCT emulsion-based PN after surgery for the same time period. Immunological markers and inflammatory indicators were tested and perioperative clinical outcomes were determined. The trial was registered in the Chinese Clinical Trial Register, number ChiCTR-TRC-13003562. 94 Patients were recruited, and grouped (olive oil-based LE, n = 46 and MCT/LCT, n = 48), matched for sex, age, body mass index, histological type, TNM stage, and nutrition risk screening (NRS) 2002 score. Results: There were no differences in perioperative fever (>38 °C), infectious complications, length of hospital stay (>14 days), length of critical care stay (>2 days), time for oral food intake, and in-hospital mortality between the two groups. The test group showed a higher increase in IgG level compared with the MCT/LCT group (p = 0.028). There was no difference in other immunological markers and inflammatory indicators between the two groups. Conclusion: PN containing olive oil-based or MCT/LCT LEs had similar effects on perioperative outcome, cell-mediated immune function and inflammatory response in esophageal cancer patients who had undergone surgery and were receiving EN.

Cationic surfactants in the form of nanoparticles and micelles elicit different human neutrophil responses: a toxicological study

Cationic surfactants are an ingredient commonly incorporated into nanoparticles for clinical practicability; however, the toxicity of cationic surfactants in nanoparticles is not fully elucidated. We aimed to evaluate the inflammatory responses of cationic nanobubbles and micelles in human neutrophils. Soyaethyl morpholinium ethosulfate (SME) and hexadecyltrimethyl-ammonium bromide (CTAB) are the two cationic surfactants employed in this study. The zeta potential of CTAB nanobubbles was 80 mV, which was the highest among all formulations. Nanobubbles, without cationic surfactants, showed no cytotoxic effects on neutrophils in terms of inflammatory responses. Cationic nanobubbles caused a concentration-dependent cytotoxicity of degranulation (elastase release) and membrane damage (release of lactate dehydrogenase, LDH). Among all nanoparticles and micelles, CTAB-containing nanosystems showed the greatest inflammatory responses. A CTAB nanobubble diluent (1/150) increased the LDH release 80-fold. Propidium iodide staining and scanning electron microscopy (SEM) verified cell death and morphological change of neutrophils treated by CTAB nanobubbles. SME, in a micelle form, strengthened the inflammatory response more than SME-loaded nanobubbles. Membrane interaction and subsequent Ca(2+) influx were the mechanisms that triggered inflammation. The information obtained from this work is beneficial in designing nanoparticulate formulations for balancing clinical activity and toxicity.

Dose of intravenous lipids and rate of bacterial clearance in preterm infants with blood stream infections

BACKGROUND

Intravenous lipid emulsion (IVLE) is an integral part of the total parenteral nutrition (TPN) regimen in neonates. The use of IVLE during sepsis is the subject of controversy because it may interfere with phagocytosis of microbes by macrophages and may lead to significant hypertriglyceridemia.

OBJECTIVE

This paper aims to study the rate of clearance of bacteria in relation to dose of IVLE administered to preterm infants with blood stream infections (BSIs).

METHODS

Preterm infants (mean gestational age ± SD, 32.0 ± 2.5 weeks) with culture-proven BSI and receiving TPN were randomized to two groups. The first group (n = 22) was given the usual dose of IVLE according to a standard protocol (starting from 0.5 g kg(-1) day(-1) and gradually increased by 1 g kg(-1) day(-1) to a maximum of 3.5 g kg(-1) day(-1)); in the second group (n = 20), IVLE were restricted at a dose of 1 g kg(-1) day(-1). Samples for blood cultures were withdrawn every 24 h until a negative culture was obtained. CRP was measured daily until its normalization. Serum triglycerides were monitored daily.

RESULTS

The rate of bacterial clearance was significantly more rapid in the restricted-dose IVLE group compared to the standard-dose group [72 (48-120) versus 144 (72-168) h, p = 0.001]. Daily weight increment was significantly greater in the standard-dose IVLE group compared to the restricted-dose IVLE group [25 (6.9-31.9) versus 0.9 (-3.3-11.7) g, p = 0.0001]. The duration of antibiotic use was significantly reduced in the restricted-dose IVLE group compared with the standard-dose IVLE group (10.0 ± 4.5 vs 14.9 ± 5.1 days; p = 0.003). The durations of TPN, mechanical ventilation, and hospitalization were not significantly different between groups.

CONCLUSIONS

Restriction of the dose of IVLE to 1 g kg(-1) day(-1) in preterm infants with BSI is associated with earlier negative blood cultures and reduced duration of antibiotic therapy but was associated with a lower daily weight increments.

Unsaturated long-chain fatty acids induce the respiratory burst of human neutrophils and monocytes in whole blood

Background

It is increasingly recognized that infectious complications in patients treated with total parenteral nutrition (TPN) may be caused by altered immune responses. Neutrophils and monocytes are the first line of defence against bacterial and fungal infection through superoxide anion production during the respiratory burst. To characterize the impact of three different types of lipid solutions that are applied as part of TPN formulations, we investigated the unstimulated respiratory burst activation of neutrophils and monocytes in whole blood.

Methods

Whole blood samples were incubated with LCT (Intralipid^®), LCT/MCT (Lipofundin^®) and LCT-MUFA (ClinOleic^®) in three concentrations (0.06, 0.3 and 0.6 mg ml^-1) for time periods up to one hour. Hydrogen peroxide production during the respiratory burst of neutrophils and monocytes was measured by flow cytometry.

Results

LCT and LCT-MUFA induced a hydrogen peroxide production in neutrophils and monocytes without presence of a physiological stimulus in contrast to LCT/MCT.

Conclusion

We concluded that parenteral nutrition containing unsaturated oleic (C18:1) and linoleic (C18:2) acid can induce respiratory burst of neutrophils and monocytes, resulting in an elevated risk of tissue damage by the uncontrolled production of reactive oxygen species. Contradictory observations reported in previous studies may in part be the result of different methods used to determine hydrogen peroxide production.

Comparative effects of olive oil-based and soyabean oil-based emulsions on infection rate and leucocyte count in critically ill patients receiving parenteral nutrition

Soyabean oil-based emulsions high in linoleic acid used in parenteral nutrition (PN) could interfere with immune function and may increase the risk of septic complications. Olive oil-based emulsions, high in oleic acid, could have fewer immune effects. We compared the effects of a soyabean oil-based emulsionv. an olive oil-based emulsion on infection rate, appearance of new infection episodes, leucocyte count (peak and evolution), acute-phase proteins, and major health outcomes in intensive care unit (ICU) adult patients receiving PN. The study was designed as an observational, retrospective, single-centre, cohort study in a general ICU. Patients in the SOYA cohort (n16) received a soyabean oil-based emulsion and patients in the OLIVE cohort (n23), an olive oil-based emulsion. Both cohorts had similar basal characteristics and received a similar energy load. The SOYA cohort received an oleic acid:linoleic acid ratio of 0·43 and the OLIVE cohort 2·99 (P < 0·001). No differences were observed in infection rate and appearance, acute-phase proteins, and major health outcomes. At the end of PN, blood leucocyte count decreased by 3·25 × 109cells/l in the SOYA cohort and increased by 4·51 × 109cells/l in the OLIVE cohort from baseline values (P = 0·036). Peak leucocyte count presented a trend for a higher value in the OLIVE cohortv. the SOYA cohort (18·86v. 15·28 × 109cells/l;P = 0·078). The use of an olive oil-based emulsion in PN had no effect on infection, acute-phase proteins, major health outcomes, and presented higher leucocyte count at the end of PN and a trend to higher peak leucocyte count when compared with soyabean oil-based emulsion in ICU patients.

Immune modulation by parenteral lipid emulsions

Total parenteral nutrition is the final option for nutritional support of patients with severe intestinal failure. Lipid emulsions constitute the main source of fuel calories and fatty acids (FAs) in parenteral nutrition formulations. However, adverse effects on patient outcomes have been attributed to the use of lipids, mostly in relation to impaired immune defenses and altered inflammatory responses. Over the years, this issue has remained in the limelight, also because technical advances have provided no safeguard against the most daunting problems, ie, infectious complications. Nevertheless, numerous investigations have failed to produce a clear picture of the immunologic characteristics of the most commonly used soybean oil-derived lipid emulsions, although their high content of n-6 polyunsaturated FAs (PUFAs) has been considered a drawback because of their proinflammatory potential. This concern initiated the development of emulsions in which part of the n-6 FA component is replaced by less bioactive FAs, such as coconut oil (rich in medium-chain saturated FAs) or olive oil (rich in the n-9 monounsaturated FA oleic acid). Another approach has been to use fish oil (rich in n-3 PUFA), the FAs of which have biological activities different from those of n-6 PUFAs. Recent studies on the modulation of host defenses and inflammation by fish-oil emulsions have yielded consistent data, which indicate that these emulsions may provide a tool to beneficially alter the course of immune-mediated conditions. Although most of these lipids have not yet become available on the US market, this review synthesizes available information on immunologic characteristics of the different lipids that currently can be applied via parenteral nutrition support.

Olive oil in parenteral nutrition

PURPOSE OF REVIEW

A lipid emulsion for use in parenteral nutrition containing a significant proportion of olive oil in place of soybean oil (ClinOleic; Baxter, Maurepas, France) is now available. The purpose of this review is to provide background information about the rationale for this emulsion, to collate and synthesize the literature about it, and to highlight recent studies in which it has been used.

RECENT FINDINGS

ClinOleic offered significant advantage over soybean oil-based emulsions in terms of glucose metabolism in preterm infants. ClinOleic was recently used for the first time in malnourished haemodialysis, trauma and burn patients and was found to be safe and well tolerated. In burn patients ClinOleic was associated with better liver function.

SUMMARY

ClinOleic is safe and well tolerated in preterm infants, and in home parenteral nutrition, haemodialysis, trauma and burn patients and may offer advantages with regard to liver function, oxidative stress and immune function. ClinOleic may offer significant advantage over soybean oil-based emulsions in terms of glucose metabolism in preterm infants. More clinical studies of ClinOleic are required and these should include evaluation of oxidative stress markers and immune function as well as of clinical outcomes.

Olive oil-based lipid emulsion's neutral effects on neutrophil functions and leukocyte-endothelial cell interactions

BACKGROUND

Infection remains a drawback of parenteral nutrition (PN), probably related, among other factors, to immunosuppressive effects of its lipid component. Newer preparations may have lesser immunosuppressive impact. This study examines the effects of an olive oil-based lipid emulsion (long-chain triacylglycerols-monounsaturated fatty acids [LCT-MUFA]; ClinOleic) on various functions of human neutrophils in vitro and on rat leukocyte-endothelial cell interactions in vivo compared with LCT (Intralipid) and 50% LCT-50% medium-chain triacylglycerols (MCT; Lipofundin) mixture.

METHODS

Neutrophils isolated from healthy donors were incubated with concentrations (0.03-3 mmol/L) of lipid emulsions encompassing clinically relevant levels. In vivo leukocyte recruitment was studied with intravital microscopy within rat mesenteric microcirculation.

RESULTS

LCT-MUFA (3 mmol/L) did not alter the N-formyl-Met-Leu-Phe (FMLP)-induced rise in [Ca2+]i, oxidative burst, chemotaxis, and elastase release, whereas LCT-MCT decreased [Ca2+]i and chemotaxis and increased oxidative burst. FMLP-induced LTB4 production was augmented by lipid emulsions. Serum-opsonized zymosan-induced phagocytosis was unaltered by lipid emulsions. Basal and FMLP-induced CD11b expression was unaffected by lipid emulsions. Lipopolysaccharide (LPS)-induced TNF-alpha, IL-1beta and IL-8 mRNA, and protein expression was unaltered by LCT-MUFA, whereas LCT and LCT-MCT decreased IL-1beta mRNA and protein. LCT-MUFA did not alter apoptosis, but LCT increased apoptosis in absence and presence of GM-CSF. LPS (1 microg/mL)-induced increase in leukocyte rolling flux, adhesion, and emigration was inhibited by LCT and LCT-MCT but unaffected in LCT-MUFA-treated rats. Immunohistochemistry showed LPS-induced increase in P-selectin expression attenuated by LCT and LCT-MCT but not LCT-MUFA.

CONCLUSIONS

LCT-MUFA showed lower in vitro and in vivo impact on neutrophil function compared with LCT and LCT-MCT.

No evidence for oxidative stress in patients on home parenteral nutrition

BACKGROUND & AIMS

Patients on total parenteral nutrition depend on the composition of the nutritional formulation for maintenance of their oxidant-antioxidant balance. The present observational study was conducted to evaluate a substantial part of our patient population for evidence of oxidative stress.

METHODS

Venous blood samples were obtained from 41 patients on home parenteral nutrition (HPN) and 41 healthy controls. Glutathione in plasma and whole blood, glutathione peroxidase and superoxide dismutase in erythrocytes and total plasma antioxidant capacity were measured to assess the antioxidant status. Oxidant status was evaluated by measuring the production of reactive oxygen species by leukocytes. Oxidative damage was assessed by measuring lipid peroxidation and protein oxidation products.

RESULTS

Patients on HPN showed some signs of increased oxidative stress, however, there were no signs for oxidative damage, compared with healthy controls. In addition, activity of any underlying disease was not associated with increased oxidative stress.

CONCLUSIONS

The current treatment regime for patients on HPN at our center apparently prevents the development of significant oxidative damage, despite signs of some oxidative stress. Based on these data, adaptations in the composition of parenteral nutritional formulations do not seem mandatory.

INTRAVENOUS ANESTHESIA INHIBITS LEUKOCYTE-ENDOTHELIAL INTERACTIONS AND EXPRESSION OF CD11B AFTER HEMORRHAGE

Hemorrhage increases adhesion of leukocytes to the venular endothelium, mediated by increased expression of the Mac-1 integrin complex (CD18/CD11b) present on leukocytes. Anesthetic agents may possess anti-inflammatory properties. Hence, this study determined the effects of i.v. anesthesia on leukocyte adhesion after hemorrhage in relation to expression of CD11b.

METHODS

Male Wistar rats were (n = 57) anesthetized i.v. with propofol (Diprivan) and fentanyl, ketamine, or thiopental. During anesthesia, 10% of total blood volume was removed and intravital microscopy used to observe the rat mesentery and measure leukocyte (neutrophils) rolling and adhesion in postcapillary venules (15 - 25 microm). Flow cytometry was also used to determine CD11b expression on neutrophils from blood removed at the end of these experiments (n = 25) or blood incubated with anesthetic agents and activated with platelet activating factor ex vivo (0.1 micromol/L) (n = 24).

RESULTS

Hemorrhage increased leukocyte adhesion (stationary count per 150 microm) in rats anesthetized with thiopental (baseline, 3.4 +/- 1.2; hemorrhage, 6.7 +/- 2.0; P < 0.05) but not in those receiving either ketamine (baseline, 3.6 +/- 1.3; hemorrhage, 3.3 +/- 1.3) or propofol/fentanyl (baseline, 6.2 +/- 2.0; hemorrhage, 5.8 +/- 0.8). Neutrophils collected from thiopental-treated rats had elevated CD11b expression with thiopental (mean fluorescence baseline, 67.5 +/- 1.3; hemorrhage, 83.6 +/- 5.3; P < 0.05) but not with propofol/fentanyl (mean fluorescence baseline, 69.1 +/- 1.3; hemorrhage, 65.9 +/- 1.6), and ketamine-treated rats (mean fluorescence baseline, 74.3 +/- 2.1; hemorrhage, 74.8 +/- 1.1). Ketamine also inhibited upregulation of CD11b with platelet activating factor ex vivo.

CONCLUSIONS

After hemorrhage, leukocyte adhesion and CD11b expression increased during thiopental anesthesia, but propofol/fentanyl and ketamine protected against hemorrhage-induced leukocyte adhesion. The anti-inflammatory effect of ketamine was mediated by direct inhibition of CD11b expression on leukocytes.

Lipid effects on neutrophil calcium signaling induced by opsonized particles: platelet activating factor is only part of the story

BACKGROUND & METHODS

Total parenteral nutrition is frequently used in clinical practice to improve the nutritional status of patients. However, the risk for infectious complications remains a drawback in which immune-modulating effects of the lipid component may play a role. To characterize these lipid effects we investigated neutrophil activation by opsonized yeast particles under influence of lipid emulsions derived from fish oil (VLCT), olive oil (LCT-MUFA), soybean oil (LCT), and a physical mixture of coconut and soybean oil (LCT-MCT).

RESULTS

Serum-treated zymosan (STZ) evoked a biphasic increase in cytosolic Ca2+ concentration ([Ca2+]c) with an initial slow rise that turned into a second fast rise until a plateau was reached. LCT-MCT (5 mM) pretreatment markedly increased the rate of [Ca2+]c rise during the initial phase, abolished the second phase and lowered the plateau. These effects of LCT-MCT were mimicked by the protein kinase C (PKC) activating phorbol ester PMA. LCT, LCT-MUFA and VLCT, on the other hand, decreased the rate of [Ca2+]c rise during both phases and lowered the plateau. The platelet-activating factor (PAF) receptor antagonist WEB 2086 inhibited the second phase, demonstrating that PAF acts as an intercellular messenger in STZ-induced Ca2+ mobilization, but did not interfere with the stimulatory effect of LCT-MCT or PMA on the initial rate of [Ca2+]c rise.

CONCLUSIONS

Structurally different lipids act only in part through PAF to distinctively modulate neutrophil calcium signaling in response to activation by opsonized particles.

Lipids and the immune response: from molecular mechanisms to clinical applications

PURPOSE OF REVIEW

This review critically evaluates recent studies investigating the effects of fatty acids on immune and inflammatory responses in both healthy individuals and in patients with inflammatory diseases, with some reference to animal studies where relevant. It examines recent findings describing the cellular and molecular basis for the modulation of immune function by fatty acids. The newly emerging area of diet-genotype interactions will also be discussed, with specific reference to the anti-inflammatory effects of fish oil.

RECENT FINDINGS

Fatty acids are participants in many intracellular signalling pathways. They act as ligands for nuclear receptors regulating a host of cell responses, they influence the stability of lipid rafts, and modulate eicosanoid metabolism in cells of the immune system. Recent findings suggest that some or all of these mechanisms may be involved in the modulation of immune function by fatty acids.

SUMMARY

Human studies investigating the relationship between dietary fatty acids and some aspects of the immune response have been disappointingly inconsistent. This review presents the argument that most studies have not been adequately powered to take into account the influence of variation (genotypic or otherwise) on parameters of immune function. There is well-documented evidence that fatty acids modulate T lymphocyte activation, and recent findings describe a range of potential cellular and molecular mechanisms. However, there are still many questions remaining, particularly with respect to the roles of nuclear receptors, for which fatty acids act as ligands, and the modulation of eicosanoid synthesis, for which fatty acids act as precursors.