Passive immunization against cachectin/tumor necrosis factor protects mice from lethal effect of endotoxin

A highly specific polyclonal rabbit antiserum directed against murine cachectin/tumor necrosis factor (TNF) was prepared. When BALB/c mice were passively immunized with the antiserum or with purified immune globulin, they were protected against the lethal effect of the endotoxin lipopolysaccharide produced by Escherichia coli. The prophylactic effect was dose-dependent and was most effective when the antiserum was administered prior to the injection of the endotoxin. Antiserum to cachectin/TNF did not mitigate the febrile response of endotoxin-treated animals, and very high doses of endotoxin could overcome the protective effect. The median lethal dose of endotoxin in mice pretreated with 50 microliters of the specific antiserum was approximately 2.5 times greater the median lethal dose for controls given nonimmune serum. The data suggest that cachectin/TNF is one of the principal mediators of the lethal effect of endotoxin.     

A macrophage factor inhibits adipocyte gene expression: an in vitro model of cachexia

Certain infections and malignancies in mammals cause the development of a condition known as cachexia in which the animal continues to lose weight, often while consuming an adequate diet. When macrophages are stimulated with an endotoxin, they produce a factor or factors, termed cachectin, that inhibits the activity of fat-producing (lipogenic) enzymes in cultured adipocytes. This effect may reflect one of the physiological bases for cachexia. In the present study, clones of complementary DNA from genes whose expression is increased during the differentiation of adipocytes were used to study the molecular basis of cachectin's actions. In the presence of cachectin, the expression of the corresponding genes was reversibly and specifically inhibited. Furthermore, when mature adipocytes were exposed to cachectin, the messenger RNA's of those genes diminished and rapidly approached the levels present before differentiation.     

Tumor necrosis factor (cachectin) as an essential mediator in murine cerebral malaria

Tumor necrosis factor, or cachectin (TNF-alpha), a protein with a wide range of biological activities, is produced mainly by macrophages and may be important in inflammatory processes. The role of TNF-alpha in the pathogenesis of cerebral malaria was investigated in a murine model. Most CBA mice infected with Plasmodium berghei anka die between days 6 and 14 with acute neurological manifestations unrelated to the level of parasitemia, whereas mice of some other strains have malaria of the same severity that ends in death after 3 to 4 weeks without neurological manifestations. The activity of serum TNF-alpha was considerably increased in CBA/Ca mice with cerebral malaria but not in Plasmodium berghei-infected mice that did not develop this complication. One injection of rabbit antibody to TNF-alpha on day 4 or 7 fully protected infected mice from cerebral malaria without modifying the parasitemia, whereas immunoglobulins from normal rabbit had no effect. In mice with cerebral malaria, the cerebral vessels showed focal accumulations of packed macrophages often containing infected erythrocytes; this lesion was not seen in mice treated with antibody to TNF-alpha or in untreated mice without cerebral malaria. These findings indicate that TNF-alpha has an important role in the pathogenesis of cerebral malaria in this murine model and suggest that local accumulation and activation of macrophages may lead to the predominance of lesions in the central nervous system.     

Cachectin/TNF and IL-1 induced by glucose-modified proteins: role in normal tissue remodeling

Proteins undergo a series of nonenzymatic reactions with glucose over time to form advanced glycosylation end products (AGEs). Macrophages have a receptor that recognizes the AGE moiety and mediates the uptake and degradation of AGE proteins. This removal process is associated with the production and secretion of cachectin (tumor necrosis factor) and interleukin-1, two cytokines with diverse and seemingly paradoxical biological activities. The localized release and action of these cytokines could account for the coordinated removal and replacement of senescent extracellular matrix components in normal tissue homeostasis.     

Suppression of prolactin in pigs by Escherichia coli endotoxin

An endotoxin produced by Escherichia coli caused a decrease in prolactin concentrations in the plasma of sows when given at low dosages 2 days postpartum. Five to tenfold increases occurred in the plasma cortisol concentrations. Piglet growth, used as an indicator of milk secretion by the sows, was significantly depressed after the endotoxin administration. Some cases of lactation failure in the periparturient sow may thus be due to endotoxins suppressing prolactin concentrations. This appears to be the first report of a bacterial endotoxin having an effect on prolactin in any species.     

Endothelial adhesiveness for blood neutrophils is inhibited by transforming growth factor-beta

Adhesion of blood cells to endothelial cells is an essential component of all inflammatory responses. The capacity of the endothelium to support adhesion of neutrophils is increased by cytokines such as tumor necrosis factor-alpha, interleukin-1, and endotoxin. Another cytokine, transforming growth factor-beta (TGF-beta), was a strong inhibitor of basalneutrophil adhesion and also decreased the adhesive response of endothelial cells to tumor necrosis factor-alpha (TNF-alpha). The ability of cells to respond to TGF-beta was related to the duration of culture of endothelial cells after explantation from umbilical veins. TGF-beta is likely to serve an anti-inflammatory role at sites of blood vessel injury undergoing active endothelial regeneration.     

Evidence for the prion hypothesis: induction of the yeast [PSI+] factor by in vitro- converted Sup35 protein

Starting with purified, bacterially produced protein, we have created a [PSI(+)]-inducing agent based on an altered (prion) conformation of the yeast Sup35 protein. After converting Sup35p to its prion conformation in vitro, we introduced it into the cytoplasm of living yeast using a liposome transformation protocol. Introduction of substoichiometric quantities of converted Sup35p greatly increased the rate of appearance of the well-characterized epigenetic factor [PSI+], which results from self-propagating aggregates of cellular Sup35p. Thus, as predicted by the prion hypothesis, proteins can act as infectious agents by causing self-propagating conformational changes.     

Acidic mammalian chitinase in asthmatic Th2 inflammation and IL-13 pathway activation

Chitin is a surface component of parasites and insects, and chitinases are induced in lower life forms during infections with these agents. Although chitin itself does not exist in humans, chitinases are present in the human genome. We show here that acidic mammalian chitinase (AMCase) is induced via a T helper-2 (Th2)-specific, interleukin-13 (IL-13)-mediated pathway in epithelial cells and macrophages in an aeroallergen asthma model and expressed in exaggerated quantities in human asthma. AMCase neutralization ameliorated Th2 inflammation and airway hyperresponsiveness, in part by inhibiting IL-13 pathway activation and chemokine induction. AMCase may thus be an important mediator of IL-13-induced responses in Th2-dominated disorders such as asthma.     

鱼类神经坏死病毒衣壳蛋白MCP和鮰爱德华氏菌外膜蛋白ompN1融合基因的原核表达

目前在针对鱼类神经坏死病毒的疫苗研究中，主要是将神经坏死病毒某些蛋白作为抗原进行注射免疫，但是传统的注射免疫并不能有效地激发黏膜免疫。笔者将鱼类神经坏死病毒的衣壳蛋白（MCP）与鮰爱德华氏菌的跨粘膜蛋白ompN1融合表达，拟制备能够抵抗神经坏死病毒的粘膜疫苗；利用从NCBI GenBank库里获得的鱼类神经坏死病毒的外壳蛋白MCP和鮰爱德华氏菌的外膜蛋白ompN1的基因序列，将两者进行序列优化与全基因合成，分别构建原核表达载体:MCP-ompN1 pET28a和MCP pET28a和ompN1 pET28a，并在大肠杆菌内分别诱导表达融合蛋白MCP-ompN1，MCP，ompN1后，再利用包涵体纯化及透析复性获得MCP-ompN1，MCP，ompN1蛋白。SDS-PAGE结果显示，原核表达纯化得到了较纯的MCP-ompN1 融合蛋白，Western Blotting结果表明，纯化得到的MCP-ompN1 融合蛋白不仅具有MCP抗原性，还具有ompN1抗原性。本实验通过原核表达纯化得到了鱼类神经坏死病毒衣壳蛋白MCP和鮰爱德华氏菌外膜蛋白ompN1的融合蛋白MCP-ompN1，为进一步验证融合蛋白MCP-ompN1能否作为抵抗神经坏死病毒的粘膜疫苗奠定了基础。