Production of IL-6 and TNF-alpha by the macrophage-like cell line RAW 264.7 after treatment with a cell wall extract of Candida albicans

Commercial naphthenic acids and the organic fraction of oil sands process water downregulate pro-inflammatory gene expression and macrophage antimicrobial responses

This is the first report showing that the organic fraction of oil sands process water (OSPW-OF), and commercial naphthenic acids (C-NAs), cause immunotoxicity. The exposure of mouse bone marrow-derived macrophages (BMDM) to different amounts of C-NAs or OSPW-OF, did not affect cell viability in vitro. We examined whether exposure of BMDM to C-NAs or OSPW-OF affected various antimicrobial responses of these cells. A dose-dependent decrease in nitric oxide response was observed after treatment of BMDM with OSPW-OF, but not with C-NAs. Although OSPW-OF and C-NAs both down-regulated the respiratory burst response of BMDM, the suppression of the production of reactive oxygen intermediates was more pronounced in cells treated with OSPW-OF. Treatment with OSPW-OF or C-NAs reduced BMDM phagocytosis of zymosan and latex beads. The decrease of BMDM antimicrobial response after exposure to OSPW-OF or C-NAs, was accompanied by decreased pro-inflammatory cytokine gene expression. Oral exposure of mice to OSPW-OF caused down-regulation in the expression of genes encoding pro-inflammatory cytokines IFNγ, IL-1β and CSF-1. Our findings indicated that OSPW causes immunotoxic effects that may impair the ability of an exposed host to defend against infectious disease. Furthermore, given the differences between the effects of OSPW-OF and C-NAs, C-NAs should not be assumed to be a direct surrogate for the immunotoxic chemical species in OSPW.

The Importance of the Phagocytes' Innate Response in Resolution of the Infection Induced by a Low Virulent Candida albicans Mutant

We have reported that a Candida albicans mkc1Delta/mkc1Delta mutant, deleted in the Mkc1p mitogen-activated protein kinase, an essential element of the cell integrity signalling pathway, has reduced virulence in a murine model of systemic infection. We analyse here the immunological basis for this feature in view of its failure to vaccinate. Firstly, the influence of the Th response was analysed by infecting different knockout mice, revealing the importance of interferon-gamma in the resolution of mkc1 systemic infection. Secondly, the role of innate immunity was studied. The infection of neutropenic mice revealed that the candidacidal activity of neutrophils is crucial during the first 3 days of infection for the mutant strain. Macrophages played a critical role in the clearance of infection. Although a similar anti-Candida activity was found for both fungal strains with naïve macrophages, activated macrophages discriminated between both strains. In vitro experiments revealed that the mutant strain displayed a greater susceptibility to nitric oxide (NO), a reduced inhibitory effect on macrophage NO production and an increased capacity of macrophage stimulation by cell wall extracts. The importance of NO in systemic infection with the mutant strain was confirmed by the strong increase in the susceptibility of aminoguanidine (an iNOs inhibitor)-treated mice.

NK cells mediate increase of phagocytic activity but not of proinflammatory cytokine (interleukin-6 [IL-6], tumor necrosis factor alpha, and IL-12) production elicited in splenic macrophages by tilorone treatment of mice during acute systemic candidiasis

The participation of NK cells in the activation of splenic macrophages or in resistance to systemic candidiasis is still a matter of debate. We had previously reported that there is a correlation between natural killer cell activation and resistance to systemic candidiasis. In those experiments we had used tilorone to boost NK cell activity in mice. Here we show a mechanism elicited by tilorone in splenic macrophages which could explain their effect on mouse survival during acute disseminated Candida albicans infection. The results demonstrate that tilorone treatment elicits, by a direct effect, the production of proinflammatory cytokines (interleukin-6 [IL-6], tumor necrosis factor alpha [TNF-alpha], and IL-12) by splenic macrophages. In addition, it increases the capacity of splenic macrophages to phagocytize C. albicans through activation of NK cells. We also demonstrate that the presence of NK cells is essential for maintaining a basal level of phagocytic activity, which characterizes splenic macrophages of naïve control mice. The results demonstrate that it is possible to identify two phenotypically and functionally peculiar cell populations among splenic macrophages: (i). cells of the "stimulator/secretor phenotype," which show high levels of major histocompatibility complex (MHC) class II surface expression, are poorly phagocytic, and synthesize the proinflammatory cytokines IL-6, TNF-alpha, and IL-12, and (ii). cells of the "phagocytic phenotype," which express low levels of MHC class II molecules, are highly phagocytic, and do not secrete proinflammatory cytokines.

Effects of cytokines and fluconazole on the activity of human monocytes against Candida albicans

This study evaluates the effects of cytokines, used singly and in combination, on the microbicidal activity of human monocyte-derived macrophages (MDM) against intracellular Candida albicans in the presence and absence of fluconazole. In the absence of fluconazole, the addition of tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), gamma interferon (IFN-gamma), or IL-4 had no effect on the growth of C. albicans. In contrast, the addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) resulted in decreased growth (P < 0.05), while the addition of IL-10 resulted in increased growth (P < 0.01). In the presence of fluconazole, only the addition of IFN-gamma resulted in an increase in the growth of C. albicans. In the presence or absence of fluconazole, all cytokine combinations except IFN-gamma plus GM-CSF caused significant decreases in growth (P < 0.01). IL-10 and IL-4 did not influence the activity of TNF-alpha or IL-1beta. In the absence or presence of C. albicans the addition of fluconazole, all of the cytokines studied, and combinations of fluconazole and selected cytokines caused increases in nitric oxide (NO) production (P < 0.01). Similar observations were made for superoxide (O(2)(-)) only in the presence of C. albicans. The greatest concentrations of NO and O(2)(-) were produced when C. albicans alone was present in the assays. Our results demonstrate that in the presence of low concentrations of fluconazole (0.1 times the MIC), selected cytokines and their combinations significantly increase the microbicidal activity of MDM against intracellular C. albicans.

Ultrasonication of pyrogenic microorganisms improves the detection of pyrogens in the Mono Mac 6 assay

The monocytic cell line Mono Mac 6 is sensitive to pyrogens. When exposed to pyrogens secretion of interleukin-6 is induced. However, some eukaryotic pyrogenic microorganisms are not detectable. The aim of this study is to introduce a pretreatment of samples to expand the detection range of the assay. The interleukin-6 inducing capacity of a broad spectrum of UV-killed and ultrasonicated microorganisms is examined in Mono Mac 6 cells. The interleukin-6 secretion is determined in a sandwich immunoassay (DELFIA). The Mono Mac 6 assay is able to detect UV-killed Bacillus subtilis, Staphylococcus aureus and Salmonella typhimurium, but neither Candida albicans nor Aspergillus niger. After ultrasonication of the microorganisms it is possible to detect C. albicans and A. niger. The interleukin-6 inducing ability of the examined microorganisms is in no case reduced after ultrasonic treatment. However, ultrasonication of S. aureus results in a 100-fold increase in the interleukin-6 response. Even after ultrasonication Streptococcus faecalis can not be detected. Ultrasonication is an easy and simple method for expanding the detection range in the Mono Mac 6 assay.

A comparative study of Mono Mac 6 cells, isolated mononuclear cells and Limulus amoebocyte lysate assay in pyrogen testing

Pyrogen induced secretion of interleukin 6 (IL-6) in Mono Mac 6 (MM6) cells was measured. The ability of the MM6 cell culture to detect pyrogens was compared to the Limulus amoebocyte lysate (LAL) test and isolated mononuclear cells (MNC). The detection limit of MM6 for lipopolysaccharide (LPS) and Staphylococcus aureus was comparable to that of MNC. Aspergillus niger and Candida albicans induced IL-6 in isolated MNC, but not in MM6. The detection limit for Salmonella typhimurium in the MM6 assay was comparable to that of the LAL assay. As expected, S. aureus and C. albicans did not show any LAL activity. A. niger and Influenza virus showed some activity in the LAL test, but could not be detected by MM6 cells. In conclusion, the MM6 assay is a good supplement to the current pyrogen assays for detection of LPS, S. aureus and S. typhimurium, but the MM6 assay could not detect A. niger, C. albicans and Influenza virus.