Taurine (Tau) is an exceptionally abundant free amino acid in the cytosol of inflammatory cells and especially in neutrophils. Taurine protects cells from self-destruction during processes that generate oxidants. The major function of Tau in leukocytes is to trap chlorinated oxidants (HOCl). Taurine reacts with HOCl to produce the long-lived compound taurine chloramine (TauCl). Previously, we have shown that other products of the neutrophil chlorinating system are able to modify functions of macrophages. In this study, we investigated in vitro the influence of TauCl on the generation of inflammatory mediators by activated macrophages. We have found that TauCl inhibited the generation of nitric oxide, prostaglandin E2, tumor necrosis factor alpha, and interleukin-6, but TauCl slightly enhanced the release of IL-1 alpha. The formation of nitrites by interferon-gamma-activated macrophages was inhibited by TauCl in a dose-dependent manner. Taurine chloramine also reduced the level of inducible nitric oxide synthase (iNOS) mRNA in macrophages, in a similar concentration-dependent manner. Although our experiments do not exclude a direct effect of TauCl on enzymatic activity of iNOS, the inhibition of iNOS expression seems to be the major mechanism responsible for suppression of NO formation. Finally, we discuss the biological role of TauCl in vivo. We suggest that at the site of inflammation TauCl works as a specific signaling molecule of activated neutrophils that coordinates the generation of inflammatory mediators in macrophages.

Cytokine-dependent regulation of tissue inhibitors of metalloproteinases (TIMPs) expression provides an important mechanism for controlling the activity of matrix metalloproteinases. We present data indicating that during inflammatory processes TIMP-1 and TIMP-3 may be involved in the proteolytic remodeling of subendothelial basement membrane of the brain microvascular system, a key step during leukocyte migration into the brain perivascular tissue. In brain endothelial cells the expression of TIMP-1 is dramatically up-regulated by major proinflammatory cytokines, with the combination of interleukin-1L L (IL-1L L) and tumor necrosis factor-K K (TNFK K) exhibiting the strongest synergistic stimulation. Simultaneously, IL-1L L/TNFK K almost completely blocks TIMP-3 expression. Both synergistic effects are dose-dependent within the concentration range 0.05^5 ng/ml of both cytokines and correlate with the expression of inducible nitric oxide synthase, an endothelial cell activation marker. Down-regulation of TIMP-3 expression is also detected in astrocytes treated with TNFK K or IFN-Q Q, whereas oncostatin M as well as TNFK K up-regulate TIMP-1 mRNA level. We propose that the cytokine-modified balance between TIMP-1 and TIMP-3 expression provides a potential mechanism involved in the regulation of microvascular basement membrane proteolysis.z 1999 Federation of European Biochemical Societies.

Gingipains are cysteine proteinases produced by Porphyromonas gingivalis, a major causative bacterium of adult periodontitis. They consist of arginine-specific (HRgpA and RgpB) and lysine-specific (Kgp) proteinases. Gingipains strongly affect the host defense system by degrading some cytokines, components of the complement system, and several immune cell receptors. In an in vitro model, gingipains were shown to degrade soluble tumor necrosis factor alpha (TNF-␣). However, since membrane TNF-␣ shows strong biological activity, especially in local inflammatory lesions, it was worth investigating whether gingipains might also destroy membrane TNF-␣ and limit its biological activities. To avoid a possible influence of gingipains on ADAM17, the secretase of TNF-␣, the majority of experiments were performed using ADAM17 ؊/؊ fibroblasts stably transfected with cDNA of human pro-TNF-␣ (ADAM17 ؊/؊ TNF ؉ ). Arginine-specific gingipains (Rgp's) strongly diminished the level of TNF-␣ on the cell surface as measured by flow cytometry, and this process was not accompanied by an increased concentration of soluble TNF-␣ in the culture medium. Degradation of membrane TNF-␣ by Rgp's correlated with a strong decrease in TNF-␣-mediated biological activities of ADAM17 ؊/؊ TNF ؉ cells. First, the activation state of transcription factor NF-B was suppressed; second, the cells were no longer able to induce apoptosis in HL-60 cells. Kgp was also able to cleave membrane TNF-␣, but its effect was much weaker than that of Rgp's. Gingipains also limited the binding of native TNF-␣ to the target cells. Thus, gingipains are able not only to cleave soluble TNF-␣ but also to destroy the membrane form of the cytokine, which may additionally dysregulate the cytokine network.

No abstract

Tumor necrosis factor-a converting enzyme (ADAM17) is a major metalloproteinase involved in the shedding of several membrane-bound cytokines and cytokine receptors. Interplay of cytokines and their soluble receptors might be an important regulatory element in the network of interactions responsible for maintaining homeostasis in the immune system. ADAM17 thus has the potential to participate in a broad range of immune reactions. We studied the mechanisms of ADAM17 activation in endothelial cells and found that pro-inflammatory cytokines (tumor necrosis factor-a, interleukin-1b, interferon-c) and growth factors (epidermal growth factor, vascular endothelial growth factor) are able to upregulate transcription of ADAM17 and expression of ADAM17 protein. This process might constitute an important mechanism of regulation of ADAM17 activity. Stimulation of transcription, rather than increased ADAM17 mRNA stability, was responsible for increased levels of ADAM17 mRNA. Importantly, the increase in ADAM17 was accompanied by increased shedding of TNFReceptor I (p55) in tumor necrosis factor-a-stimulated endothelial cells. Therefore, ADAM17-dependent depletion of membrane-bound tumor necrosis factor receptors from endothelial cells might constitute a mechanism of selfprotection in states of prolonged immunostimulation.

Bacterial cancer therapy is a concept more than 100 years old -yet, all things considered, it is still in early development. While the use of many passive therapeutics is hindered by the complexity of tumor biology, bacteria offer unique features that can overcome these limitations. Microbial metabolism, motility and sensitivity can lead to site-specific treatment, highly focused on the tumor and safe to other tissues. Activation of tumor-specific immunity is another important mechanism of such therapies. Several bacterial strains have been evaluated as cancer therapeutics so far, Salmonella Typhimurium being one of the most promising. S. Typhimurium and its derivatives have been used both as direct tumoricidal agents and as cancer vaccine vectors. VNP20009, an attenuated mutant of S. Typhimurium, shows significant native toxicity against murine tumors and was studied in a first-in-man phase I clinical trial for toxicity and anticancer activity. While proved to be safe in cancer patients, insufficient tumor colonization of VNP20009 was identified as a major limitation for further clinical development. Antibody-fragment-based targeting of cancer cells is one of the few approaches proposed to overcome this drawback.

No abstract

Protamine, the only registered antidote of unfractionated heparin (UFH), may produce a number of adverse effects, such as anaphylactic shock or serious hypotension. We aimed to develop an alternative UFH antidote as efficient as protamine, but safer and easier to produce. As a starting material, we have chosen generally non-toxic, biocompatible, widely available, inexpensive, and easy to functionalize polysaccharides. Our approach was to synthesize, purify and characterize cationic derivatives of dextran, hydroxypropylcellulose, pullulan and γ-cyclodextrin, then to screen them for potential heparin-reversal activity using an in vitro assay and finally examine efficacy and safety of the most active polymers in Wistar rat and BALB/c mouse models of experimentally induced arterial and venous thrombosis. Efficacy studies included the measurement of thrombus formation, activated partial thromboplastin time, bleeding time, and anti-factor Xa activity; safety studies included the measurement of hemodynamic, hematologic and immunologic parameters. Linear, high molecular weight dextran substituted with glycidyltrimethylammonium chloride groups at a ratio of 0.65 per glucose unit (Dex40-GTMAC3) is the most potent and the safest UFH inhibitor showing activity comparable to that of protamine while possessing lower immunogenicity. Cationic polysaccharides of various structures neutralize UFH. Dex40-GTMAC3 is a promising and potentially better UFH antidote than protamine.