Influence of medium-chain triglyceride-based lipid emulsion on rat polymorphonuclear cell functions.

Intravenous lipid emulsions are used as energy and essential fatty acids sources. There are controversial reports postulating in vitro and in vivo inhibitory effects of long-chain triglycerides (LCT) upon the blood polymorphonuclear leukocytes (PMNL) functions. In the present study the in vivo and in vitro effects of LCT and a physical mixture of medium- and long-chain triglycerides (MCT/LCT) emulsions were investigated on select PMNL functions, i.e., chemotaxis, phagocytosis, and bacterial killing. Blood from 20 rats was incubated with LCT, MCT, MCT/LCT, and saline, respectively. MCT-containing emulsions exhibited an inhibitory effect on all PMNL functions investigated, whereas LCT exerted an effect on the phagocytic index only. The administration of a parenteral supply of LCT, MCT/LCT, and saline for 30 h followed by saline infusion for 14 h in discontinuous mode did not influence any of the investigated PMNL functions. Similarly, continuous infusion over 44 h at increasing infusion rates up to 1.5 mL/h did not affect the PMNL functions. The obvious difference between in vitro and in vivo response of the PMNL model emphasizes the necessity for continuous monitoring of in vivo conditions. Appropriate interpretation of the data requires continuous circumspection and consideration of trials in a clinical setting.

Effect of total parenteral nutrition with different lipid emulsions of human monocyte and neutrophil functions.

Parenteral nutrition (TPN) with lipid emulsions is claimed to be associated with impaired monocyte (M) and neutrophil (N) functions. Long-chain triglycerides (LCT) and a mixture containing 50% medium-chain triglycerides (MCT) and 50% LCT, currently used in nutritional therapy with TPN, were evaluated for their ex vivo effects on human N and M chemotaxis, phagocytosis, bacterial killing, and oxidative metabolism by nitroblue tetrazolium reduction test. Cell functions were examined in a randomized, crossover, blind trial in 10 malnourished patients with gastric cancer. Prior to the operation (2 wk), central TPN (40 kcal/kg) with 25% of caloric energy provided as LCT or MCT/LCT emulsion was infused over 48 h. After the crossover period fat-free TPN was given over 48 h. Function tests were done for N and M before and after each lipid emulsion infusion. Every cell function test performed for each patient was controlled by another test done in healthy adult volunteers and the results were compared with the normal range of values previously established for a healthy adult population. All the patients completed the studies without complications. Crossover validity was statistically established. Bacterial killing was the only function reduced in neutrophils after LCT emulsion (% killed bacteria = 79.0 +/- 8.5 versus 67.4 +/- 19.2; P < 0.05), although this function remained within the normal range values in 80% of the patients. In conclusion, the lipid emulsions did not affect any monocyte functions and only moderately decreased neutrophil bacterial killing.

Application of a fluorochrome-lysostaphin assay to the detection of phagocytic and bactericidal disturbances in human neutrophils and monocytes.

The evaluation of phagocytic and microbicidal activities of the blood neutrophils has been recognized as one of the important tools for investigating phagocytic dysfunctions in patients with recurrent infections. In the present study, these activities were examined in neutrophils and monocytes from healthy adults and patients affected by primary phagocytic dysfunctions by using a modified fluorochromic microbicidal assay, discriminating simultaneously the extracellular adherence, ingestion and intracellular killing of Staphylococcus aureus Cowan I. The assay employs acridine orange staining, as described in Bellinati-Pires et al. (1989) (AO assay), but was modified by the addition of an alternative leukocyte treatment with 0.5 U/ml of lysostaphin (LS) for 5 min at 37 degrees C, after phagocytosis (AO-LS assay). The LS treatment was standardized to eliminate staphylococci adhered to the outer surface of the phagocytes without affecting the determination of intracellular live or dead bacteria, as demonstrated in normal neutrophils and monocytes. Our purpose in this study was to compare AO and AO-LS assays in order to evaluate the effect of LS on the determination of actually ingested staphylococci and to provide a means for improving the fluorochromic assay for detecting phagocytic defects, as well as bactericidal disturbances. By using the AO-LS assay, decreased ingestion of staphylococci by neutrophils in Chediak-Higashi Syndrome (CHS) was demonstrated. However, increased staphylococci adherence, as well as ingestion, was observed in neutrophils or monocytes from chronic granulomatous disease (CGD) patients, comparing AO and AO-LS assays. Bactericidal defect, which is a common feature in CHS and CGD, was detected in neutrophils or monocytes in both assays. We emphasize that such alterations were deduced by comparing the patients' results with those obtained from their respective normal controls and with the normal range of values previously established for 160 healthy adults. No alteration was observed in hyper IgE syndrome phagocytes. Despite the possible penetration of LS into the leukocytes, as stated in other studies, we concluded that a short period of phagocyte incubation with this enzyme increased the sensitivity of the fluorochromic assay to detect phagocytic defect without affecting the determination of the bactericidal activity. Moreover, comparations between AO and AO-LS assays may be important in the study of the initial pathways of staphylococci phagocyte interaction, including adherence by non-phagocytic receptors.