Biomedical subjects
Publications and source records attributed to D Fuchs.
Iron is essential for growing microorganisms and tumour cells, and is also crucial for the proliferation of immune cells. In this review, Günter Weiss, Helmut Wachter and Dietmar Fuchs focus on the complex network of interactions that link iron metabolism with cellular immune effector functions involving cytokines and nitric oxide, and draw a suitable model for the pathogenesis of anaemia of chronic disease.
Pteridines are ubiquitous in living organisms, but little is known about their biological functions. Different pteridines were tested for their ability to modulate luminol-dependent chemiluminescence induced by chloramine-T at pH = 7.5 and at a concentration of 100 microM for each pteridine. We observed striking differences between the compounds; whereas reduced pteridine species were generally potent scavengers, aromatic pteridines were weak to strong enhancers of the chemiluminescence. Taking into account the detailed chemical structure of the molecules, by multiple linear regression analysis a simple index was constructed that allows prediction of the effects of the different pteridines with high accuracy (linear correlation coefficient between predicted and observed values r = 0.89). The effects of different pteridines on free radical-induced chemiluminescence might bear biological significance since, for example, certain pteridines take part in enzymic reactions involving free-radical intermediates, or are related to the activation of macrophages in close relationship with the oxidative burst.
To get a measure of the extent of induction of nitric oxide synthase in infection with human immunodeficiency virus type-1 (HIV-1) in vivo, we estimated serum nitrite plus nitrate concentrations in 110 HIV-1 infected individuals compared to 76 blood donors. To monitor cytokine action and to measure induction of pteridine synthesis, we determined in parallel neopterin, biopterin, soluble tumor necrosis factor-alpha receptor 55 and 75, and beta 2-microglobulin. Serum nitrite plus nitrate concentrations were elevated in patients as compared to blood donor controls. In sera of patients, nitrite plus nitrate levels correlated significantly with neopterin, soluble tumor necrosis factor receptor 55 and 75, and beta 2-microglobulin. Nitrite plus nitrate levels were higher and correlations were stronger in groups of patients with lower CD4+ cell count. These results suggest that cytokine-mediated nitric oxide synthesis occurs in individuals with HIV-1 infection.
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As part of an in vivo titration study of the macaque simian immunodeficiency virus (SIVmac) strain 251/spl, macaques were inoculated intravenously with various dilutions of this infectious SIVmac. Seven animals received dilutions from 10(-3) to 10(-6) of SIVmac251/spl. Two monkeys infected with the 10(-3) dilution of SIVmac exhibited a productive infection as indicated by seroconversion, detection of genomic RNA and proviral DNA and positive virus isolation. These animals showed a cytotoxic T cell (CTL) response against different SIVmac proteins without any measurable T cell proliferation. The five macaques receiving higher virus dilutions did not seroconvert and were negative for both viral RNA and for infectious virus, although proviral DNA was detected in their peripheral blood mononuclear cells. In contrast to the animals receiving the 10(-3) virus dilution, these five silently infected monkeys developed an SIV-specific proliferative T cell response but SIV-specific CTL could not be observed. The SIV-specific T cell proliferation of the silently infected animals could be boosted by a second low-dose exposure with a 10(-4) or 10(-5) dilution of SIVmac251/spl. The virological status of the animals was not changed following this second virus inoculation. Four months later these macaques were challenged intravenously with 2 ml of a 10(-4) dilution of SIVmac251/32H containing 10 monkey ID50. After this challenge all SIV-pre-exposed animals and three naive controls became productively infected. In addition, all infected animals developed typical signs of an immunodeficiency within 6 months after infection. These observations indicate that macaques infected silently by a low-dose exposure to infectious virus generated a virus-specific cellular immune response. However, SIV-specific T cell proliferation alone could not protect the monkeys against an intravenous challenge with SIVmac and the subsequent development of AIDS-like symptoms.
Soluble tumour necrosis factor receptors (sTNF-Rs) play a role as modulators of the biological function of tumour necrosis factor-alpha (TNF-alpha) in an agonist/antagonist pattern. In various pathologic states the production and release of sTNF-Rs may mediate host response and determine the course and outcome of disease by interacting with TNF-alpha and competing with cell surface receptors. The determination of sTNF-Rs in body fluids such as plasma or serum is a new tool to gain information about immune processes and provides valuable insight into a variety of pathological conditions. Regarding its immediate clinical use, sTNF-Rs levels show high accuracy in the follow-up and prognosis of various diseases. In HIV infection and sepsis, sTNF-Rs concentrations strongly correlate with the clinical stage and the progression of disease and can be of predictive value. Determination of sTNF-Rs also gives useful information for monitoring cancer and autoimmune diseases. The information provided is often even superior to that obtained with classical disease markers, probably due to the direct involvement of the "TNF system" in the pathogenetic mechanisms in these patients. The available data imply that the measurement of sTNF-Rs, especially of the sTNF-R 75kD type, is a useful adjunct for quantification of the Th1-type immune response, similar to other immune activation markers such as neopterin and beta 2-microglobulin. Endogenous sTNF-Rs concentrations appear to reflect the activation state of the TNF-alpha/TNF receptor system.
In a number of mammalian cell types, pteridine biosynthesis from guanosine 5'-triphosphate and formation of nitric oxide from L-arginine are induced by gamma interferon (IFN-gamma) and bacterial lipopolysaccharide (LPS). We assessed the possibility of using such metabolic alterations for the in vitro detection of pyrogens. Products from gram-negative and gram-positive bacteria and related synthetic compounds were tested for their potential to induce either of these pathways. Stimulation of pteridine biosynthesis was monitored as the formation of neopterin in the human myelomonocytic cell line THP-1. The formation of nitric oxide was determined as nitrite in murine J774A.1 macrophage cultures. The substances tested included toxic and detoxified parts of LPS and lipid A from Escherichia coli, Salmonella typhimurium, Salmonella minnesota, and Klebsiella pneumoniae as well as lipoteichoic acid and toxic shock syndrome toxin 1 from Staphylococcus aureus. Furthermore, two cell wall compounds from Mycobacterium tuberculosis, trehalose 6,6'-dimycolate and N-acetylmuramyl-L-alanyl-D-isoglutamine, which are active components of Freund's adjuvant, were used. When applied as a single stimulus, only the whole LPS molecule potently stimulated neopterin or nitrite formation. Lipid A and products from gram-positive bacteria were weakly active. For neopterin formation, lipid A required the presence of fetal calf serum. Besides detoxified LPS and independently from the presence of serum, all bacterial compounds tested strongly increased the effects mediated by IFN-gamma. Our results show that bacterial pyrogens can be detected by monitoring the formation of neopterin or nitrite. This may provide a basis for the development of an in vitro assay for the detection of pyrogenic contamination with the aim of replacing the currently used animal test.
By superinfection of human immunodeficiency virus type 2 (HIV-2) strain HIV-2ben-infected macaques with simian immunodeficiency virus (SIV) strain SIVmac, we investigated the mutual influences of an apathogenic and a pathogenic virus in vivo. Four rhesus and two cynomolgus monkeys were infected with HIV-2ben in 1988 and 1989, respectively. Virus could be reisolated from five of six animals 6 weeks after infection. The monkeys remained healthy over the next 2 to 3 years. PCR for viral RNA became negative, and virus could no longer be reisolated by coculture. All six macaques were superinfected with the pathogenic SIVmac251/32H. Subsequently, five monkeys became persistently viremic, while one animal was protected against the SIVmac infection. In the peripheral blood mononuclear cells and cocultures of the five viremic animals, DNA from both HIV-2 and SIVmac was present. The plasma contained RNA from both viruses. Thus, superinfection with SIVmac activated HIV-2. A proliferative T-cell response against both HIV-2 and SIVmac was measured in all animals after superinfection. Such a response was regularly seen after infection with the apathogenic HIV-2 but never when the pathogenic SIVmac alone was administered. While naive control monkeys inoculated with SIVmac251/32H regularly develop AIDS-like symptoms soon after infection and have to be killed, none of the preinfected animals has developed AIDS-like symptoms, but two of six animals developed tumors. After the SIVmac challenge, however, apoptotic lymphocytes were detected in the peripheral blood mononuclear cells of all animals. Thus, the presence of an apathogenic viral variant seems to retard the disease occurring after infection with a pathogenic virus rather than to confirm total protection. This partial protection appears to depend on a specific proliferative T-cell response early after infection.
In previous experiments, animals infected with SIVmac239 containing a point mutation in the vpr and nef genes developed AIDS-like symptoms after early reversion of the vpr and nef genes. Here we show that two animals in which the nef gene but not the vpr gene had reverted in the first few months did not develop disease during a 3-year observation period even after reversion to a functional vpr gene 70 weeks postinfection. To study the influence of a stable vpr mutation on virus load and pathogenesis, a 43-bp deletion was introduced into the vpr gene of SIVmac239on, a nef-open mutant of SIVmac239. Four rhesus monkeys were inoculated with the vpr deletion mutant (SIV delta vpr), and two control animals were infected with SIVmac239on. Both control animals had persistent antigenemia, high cell-associated virus loads, and elevated neopterin levels. They had to be euthanized 20 and 30 weeks postinfection because of AIDS-related symptoms. However, all four rhesus monkeys inoculated with SIV delta vpr showed only transiently detectable antigenemia. The cell-associated virus loads were high in three of the four animals. Two animals with AIDS-like symptoms had to be euthanized 71 and 73 weeks postinfection. The two remaining monkeys infected with SIV delta vpr were still alive 105 weeks postinfection. In contrast to the SIVmac239on-infected animals, SIV delta vpr-infected animals had strong humoral immune responses and intermittent cellular immune responses to SIV antigens. Our data show that a functional vpr gene is not necessary for pathogenesis. However, vpr-deficient SIVmac239 variants might be slightly attenuated, allowing some animals to resist progression to disease for an extended period of time.
We investigated a possible association between markers of immune activation and disease activity in 52 patients with systemic lupus erythematosus (SLE). Serum concentrations of neopterin, beta-2-microglobulin, 55 kD-type soluble tumor necrosis factor receptor, soluble interleukin-2 receptor and soluble CD8 were compared to the Index of European Consensus Lupus Activity Measurement (ECLAM). All markers of immune activation, except sCD8, significantly correlated with ECLAM. Stepwise multiple linear regression analysis revealed erythrocyte sedimentation rate and neopterin to correlate best with ECLAM (multiple correlation coefficient = 0.74, P < 0.001). The study shows that serum neopterin concentrations are a useful independent index for disease activity in SLE. The finding of enhanced concentrations of various parameters of immune activation in patients confirm a role of the T cell and macrophage activation in the pathogenesis of SLE.
Concentrations of neopterin, which is produced by human monocytes/macrophages when stimulated by gamma-interferon, were measured in urine specimens from 72 patients with lung cancer at diagnosis. Other routine clinical and laboratory variables were concomitantly determined. Neither neopterin nor any other laboratory variable studied showed a significant correlation with clinical indicators of the disease (morphologic type, tumour stage, grading, lymph node status, presence of distant metastases). The cancer patients were followed up for up to 10 years, and the abilities of all variable to predict fatal outcome were assessed. In univariate survival analyses, all clinical indicators except morphologic type (P = 0.86) were significant predictors of survival (P < 0.002), but of all the laboratory variables studies, only neopterin was significantly predictive (P = 0.0013). By multivariate survival analysis, a combination of four variables was found to jointly predict survival: lymph node status (P = 0.003), multivariate model), tumour stage (P = 0.0006), grading (P = 0.0047) and neopterin (P = 0.0047). The data suggest that certain aspects of immune activation may have adverse consequences for the prognosis of patients with lung cancer.
Twenty-five haemophiliacs who had been infected with HIV in 1982 or 1983 were followed up from 1986 to 1993. The absolute number of the CD4+ and CD8+ cells, neopterin levels and more recently the percentage of activated, DR+ T lymphocytes were determined twice a year. In most patients a permanent decline in the CD4+ cell count was observed whereas in two HIV-infected haemophiliacs the absolute number of CD4+ cells did not change during the observation period. In these long-term non-progressor patients no clinical symptoms and no increased neopterin levels were observed. T cells subset and neopterin measurements were found to predict the development of AIDS. AIDS developed only in those patients who exhibited both a CD4+ cell count of < 350/microliter and a serum neopterin concentration of > 20 nmol/l. A negative correlation was observed between the percentage of activated. DR+ T lymphocytes and the CD4+ cell counts.
We have previously shown that neopterin enhances hydrogen peroxide and chloramine T activity in a luminol-dependent chemiluminescence assay and strengthens toxicity of these agents against bacteria at slightly alkaline pH (pH 7.5), while 7,8-dihydroneopterin was shown to be a scavenger independent of the pH value. Besides various oxidants, phenolic antioxidants were shown to specifically induce expression of the c-fos and c-jun mRNAs. Using an inducible cfosCAT reporter transactivation system we studied the function of the pteridine derivatives on c-fos transactivation. For the first time, we demonstrate that neopterin and 7,8-dihydroneopterin, particularly together with cyclic guanosine monophosphate, induce c-fos gene expression. In humans, interferon-gamma induces the release of neopterin and 7,8-dihydroneopterin and also the synthesis of nitric oxide radical which in turn stimulate the formation of cGMP. Thus, in certain situations all three substances, namely neopterin, 7,8-dihydroneopterin and cGMP, may be present locally and even in the circulation at the same time. Based on our findings this constellation would significantly enhance the risk of c-fos gene expression and therefore promote tumour growth and development.
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Granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) have recently been introduced in the treatment of chemotherapy-induced neutropenia. Effects of these CSFs on the cellular immune system were evaluated in 38 neutropenic gynecological cancer patients during chemotherapy. In addition to restoring the leukocyte count, GM-CSF--to a greater extent than G-CSF--also induced neopterin, a sensitive marker of macrophages activated by interferons. This effect was confirmed in vitro by investigating the effects of these CSFs on interferon-gamma-mediated pathways in THP-I human myelomonocytic cells. The results suggest activation of immune effector cells by GM-CSF.
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OBJECTIVES: Zinc metabolism is frequently abnormal in renal allograft recipients. These abnormalities may be immune mediated because zinc metabolism is affected by inflammation. METHODS: We determined urinary zinc and neopterin concentrations in 24 allograft recipients (18 kidney, 3 combined kidney-pancreas and 3 liver allografts) daily for 1-41 days. In addition, serum zinc concentrations were measured in 11 patients. RESULTS: Serum zinc was decreased and urinary zinc concentrations were increased in kidney as well as liver transplant recipients when compared with healthy controls. Urinary zinc concentrations were only slightly elevated in patients with uncomplicated post-transplant course, but the increase was more pronounced in renal allograft recipients with acute tubular necrosis. Urinary zinc concentrations were drastically increased during rejection of various organs. In addition, significant associations between urinary zinc and neopterin concentrations were observed. CONCLUSION: Our results suggest that enhanced urinary zinc excretion in allograft recipients is due to immune activation. The data indicate that cytokines play a role in zinc metabolism.