Tumour necrosis factor-alpha (TNF-alpha) is a potent pro-inflammatory agent produced primarily by activated monocytes and macrophages. TNF-alpha is synthesized as a precursor protein of M(r) 26,000 (26K) which is processed to a secreted 17K mature form by cleavage of an Ala-Val bond between residues 76-77. The enzyme(s) responsible for processing pro-TNF-alpha has yet to be identified. Here, we describe the capacity of a metalloproteinase inhibitor, GI 129471, to block TNF-alpha secretion both in vitro and in vivo. The inhibition is specific to TNF-alpha; the production of other secreted cytokines, such as the interleukins IL-1 beta, IL-2, or IL-6, is not inhibited. The mechanism of inhibition occurs at a post-translational step in TNF-alpha production. Our data suggest that TNF-alpha processing is mediated by a unique Zn2+ endopeptidase which is inhibited by GI 129471 and would represent a novel target for therapeutic intervention in TNF-alpha associated pathologies.

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Leukotrienes are derived from arachidonic acid and serve as mediators of inflammation and immediate hypersensitivity. Leukotriene B4 (LTB4) and leukotriene C4 (LTC4) act through G protein–coupled receptors LTB4 receptor (BLTR) and Cys-LTR, respectively. To investigate the physiological role of BLTR, we produced mice with a targeted disruption of the BLTR gene. Mice deficient for BLTR (BLTR−/−) developed normally and had no apparent hematopoietic abnormalities. Peritoneal neutrophils from BLTR−/− mice displayed normal responses to the inflammatory mediators C5a and platelet-activating factor (PAF) but did not respond to LTB4 for calcium mobilization or chemotaxis. Additionally, LTB4 elicited peritoneal neutrophil influx in control but not in BLTR−/− mice. Thus, BLTR is the sole receptor for LTB4-induced inflammation in mice. Neutrophil influx in a peritonitis model and acute ear inflammation in response to arachidonic acid was significantly reduced in BLTR−/− mice. In mice, intravenous administration of PAF induces immediate lethal anaphylaxis. Surprisingly, female BLTR−/− mice displayed selective survival (6 of 9; P = 0.002) relative to male (1 of 11) mice of PAF-induced anaphylaxis. These results demonstrate the role of BLTR in leukotriene-mediated acute inflammation and an unexpected sex-related involvement in PAF-induced anaphylaxis.

It is controversial whether mutations in cystic fibrosis transmembrane conductance regulator intrinsically dysregulate inflammation. We characterized passage 2 human tracheobronchial epithelial cell cultures morphologically and physiologically and determined whether cytokine production or nuclear factor-kappaB activation was systematically altered in cystic fibrosis (CF) cells. Non-CF and CF cells originating from a total of 33 and 25 lungs, respectively, were available for culture on plastic or at an air-liquid interface until well differentiated. Forskolin-stimulated short-circuit currents were present in representative polarized non-CF cultures and were absent in CF cultures, whereas uridine 5'-triphosphate-stimulated currents were present in both. Constitutive or interleukin (IL)-1beta-induced IL-8 or IL-6 secretion or nuclear factor-kappaB activity was not significantly different between non-CF and CF cells. The cytokines regulated upon activation, normal T cell expressed and secreted (RANTES) and IL-10 were not detectable. Stimulation with tumor necrosis factor-alpha or a synthetic toll-like receptor 2 agonist or variable doses and times of Staphylococcus aureus culture filtrate revealed a single dose- and time-dependent difference in IL-8 production by CF cells. Interestingly, although IL-8 secretion after stimulation with Pseudomonas aeruginosa filtrates was not greater in CF cells in the absence of human serum, it was variably greater in its presence. Thus, although exaggerated responses may develop under certain conditions, our results do not support an overall intrinsically hyperinflammatory phenotype in CF cells.