Gelsolin induces colorectal tumor cell invasion via modulation of the urokinase-type plasminogen activator cascade.

Gelsolin is a cytoskeletal protein which participates in actin filament dynamics and promotes cell motility and plasticity. Although initially regarded as a tumor suppressor, gelsolin expression in certain tumors correlates with poor prognosis and therapy-resistance. In vitro, gelsolin has anti-apoptotic and pro-migratory functions and is critical for invasion of some types of tumor cells. We found that gelsolin was highly expressed at tumor borders infiltrating into adjacent liver tissues, as examined by immunohistochemistry. Although gelsolin contributes to lamellipodia formation in migrating cells, the mechanisms by which it induces tumor invasion are unclear. Gelsolin's influence on the invasive activity of colorectal cancer cells was investigated using overexpression and small interfering RNA knockdown. We show that gelsolin is required for invasion of colorectal cancer cells through matrigel. Microarray analysis and quantitative PCR indicate that gelsolin overexpression induces the upregulation of invasion-promoting genes in colorectal cancer cells, including the matrix-degrading urokinase-type plasminogen activator (uPA). Conversely, gelsolin knockdown reduces uPA levels, as well as uPA secretion. The enhanced invasiveness of gelsolin-overexpressing cells was attenuated by treatment with function-blocking antibodies to either uPA or its receptor uPAR, indicating that uPA/uPAR activity is crucial for gelsolin-dependent invasion. In summary, our data reveals novel functions of gelsolin in colorectal tumor cell invasion through its modulation of the uPA/uPAR cascade, with potentially important roles in colorectal tumor dissemination to metastatic sites.

The helminth product ES-62 protects against septic shock via Toll-like receptor 4-dependent autophagosomal degradation of the adaptor MyD88.

Sepsis is one of the most challenging health problems worldwide. Here we found that phagocytes from patients with sepsis had considerable upregulation of Toll-like receptor 4 (TLR4) and TLR2; however, shock-inducing inflammatory responses mediated by these TLRs were inhibited by ES-62, an immunomodulator secreted by the filarial nematode Acanthocheilonema viteae. ES-62 subverted TLR4 signaling to block TLR2- and TLR4-driven inflammatory responses via autophagosome-mediated downregulation of the TLR adaptor-transducer MyD88. In vivo, ES-62 protected mice against endotoxic and polymicrobial septic shock by TLR4-mediated induction of autophagy and was protective even when administered after the induction of sepsis. Given that the treatments for septic shock at present are inadequate, the autophagy-dependent mechanism of action by ES-62 might form the basis for urgently needed therapeutic intervention against this life-threatening condition.

IL-33 exacerbates autoantibody-induced arthritis.

Rheumatoid arthritis pathogenesis comprises dysregulation in both innate and adaptive immunity. There is therefore intense interest in the factors that integrate these immunologic pathways in rheumatoid arthritis. In this paper, we report that IL-33, a novel member of the IL-1 family, can exacerbate anti-glucose-6-phosphate isomerase autoantibody-induced arthritis (AIA). Mice lacking ST2 (ST2(-/-)), the IL-33 receptor alpha-chain, developed attenuated AIA and reduced expression of articular proinflammatory cytokines. Conversely, treatment of wild-type mice with rIL-33 significantly exacerbated AIA and markedly enhanced proinflammatory cytokine production. However, IL-33 failed to increase the severity of the disease in mast cell-deficient or ST2(-/-) mice. Furthermore, mast cells from wild-type, but not ST2(-/-), mice restored the ability of ST2(-/-) recipients to mount an IL-33-mediated exacerbation of AIA. IL-33 also enhanced autoantibody-mediated mast cell degranulation in vitro and in synovial tissue in vivo. Together these results demonstrate that IL-33 can enhance autoantibody-mediated articular inflammation via promoting mast cell degranulation and proinflammatory cytokine production. Because IL-33 is derived predominantly from synovial fibroblasts, this finding provides a novel mechanism whereby a host tissue-derived cytokine can regulate effector adaptive immune response via enhancing innate cellular activation in inflammatory arthritis.

VAMP8 is essential in anaphylatoxin-induced degranulation, TNF-alpha secretion, peritonitis, and systemic inflammation.

VAMP8, a member of the soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (SNARE) family of fusion proteins, initially characterized in endosomal and endosomal-lysosomal fusion, may also function in regulated exocytosis. VAMP8 physiological function in inflammation has not been elucidated. In this paper, we show that deficiency of VAMP8 protects mice from anaphylatoxin (C5a)-induced neutropenia, peritonitis, and systemic inflammation. We show that, in vivo, VAMP8 deletion inhibits neutropenia and phagocyte recruitment. We also show that in macrophages, VAMP8 localizes on secretory granules and degranulation is inhibited in VAMP8-deficient macrophages. Moreover, VAMP8(-/-) mice show reduced systemic inflammation with inhibition of serum TNF-alpha levels, whereas IL-1beta, IL-6, and MIP1alpha release are not affected. In wild-type macrophages, TNF-alpha colocalizes with VAMP8-positive vesicles, and in VAMP8-deficient macrophages, the TNF-alpha release is inhibited. Furthermore, VAMP8 regulates the release of TNF-alpha and beta-hexosaminidase triggered by fMLP, and VAMP8(-/-) mice are protected from fMLP-induced peritonitis. These data demonstrate that the VAMP8 vesicle-associated-SNARE is required for the proper trafficking of secretory lysosomal granules for exocytosis in macrophages and for the release of the potent proinflammatory cytokine, TNF-alpha.

Inhibition of Fc epsilon RI-mediated mast cell responses by ES-62, a product of parasitic filarial nematodes.

Atopic allergy is characterized by an increase in IgE antibodies that signal through the high-affinity Fcepsilon receptor (FcepsilonRI) to induce the release of inflammatory mediators from mast cells. For unknown reasons, the prevalence of allergic diseases has recently increased steeply in the developed world. However, this increase has not been mirrored in developing countries, even though IgE concentrations are often greatly elevated in individuals from these countries, owing to nonspecific IgE induction by universally present parasitic worms. Here we offer one explanation for this paradox based on the properties of ES-62, a molecule secreted by filarial nematodes. We found that highly purified, endotoxin-free ES-62 directly inhibits the FcepsilonRI-induced release of allergy mediators from human mast cells by selectively blocking key signal transduction events, including phospholipase D-coupled, sphingosine kinase-mediated calcium mobilization and nuclear factor-kappaB activation. ES-62 mediates these effects by forming a complex with Toll-like receptor 4, which results in the sequestration of protein kinase C-alpha (PKC-alpha). This causes caveolae/lipid raft-mediated, proteasome-independent degradation of PKC-alpha, a molecule important for the coupling of FcepsilonRI to phospholipase D and mast cell activation. We also show that ES-62 is able to protect mice from mast cell-dependent hypersensitivity in the skin and lungs, indicating that it has potential as a novel therapeutic for allergy.