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Biomedical subjects

Huan Yang

Publications and source records attributed to Huan Yang.

53 records · Page 3Linked to original sources
PubMed2003

Activation of gene expression in human neutrophils by high mobility group box 1 protein.

High mobility group box 1 (HMGB1) protein, a DNA binding protein that stabilizes nucleosomes and facilitates transcription, was recently identified as a late mediator of endotoxin lethality. High serum HMGB1 levels in patients with sepsis are associated with increased mortality, and administration of HMGB1 produces acute inflammation in animal models of lung injury and endotoxemia. Neutrophils occupy a critical role in mediating the development of endotoxemia-associated acute lung injury, but previously it was not known whether HMGB1 could influence neutrophil activation. In the present experiments, we demonstrate that HMGB1 increases the nuclear translocation of NF-kappaB and enhances the expression of proinflammatory cytokines in human neutrophils. These proinflammatory effects of HMGB1 in neutrophils appear to involve the p38 MAPK, phosphatidylinositol 3-kinase/Akt, and ERK1/2 pathways. The mechanisms of HMGB1-induced neutrophil activation are distinct from endotoxin-induced signals, because HMGB1 leads to a different profile of gene expression, pattern of cytokine expression, and kinetics of p38 activation compared with LPS. These findings indicate that HMGB1 is an effective stimulus of neutrophil activation that can contribute to development of a proinflammatory phenotype in diseases characterized by excessively high levels of HMGB1.

Biological Transport↗
PubMed2003

[Antitumour study with combined IL-2 gene therapy and radiation for head and neck squamous cell carcinoma].

OBJECTIVE: To assess the efficacy of combination therapy with IL-2 gene transfer and radiation in an immunocompetent murine model that parallel more closely the clinical therapy of head and neck Squamous cell carcinoma(HNSCC). METHOD: Tumors were established in the floor of mouth in C3H/HeJ mice with SCC VII cell line. Lipid-DNA complexed (lipoplexes) by using polycationic liposome-Mediated transduction for HNSCC were transducted in tumor-bearing mouse by direct intratumoral gene transfer. The local tumor radiation with 2 Gy were done in second day. Tumor size were measured before and after the treatment as compared to different single treatment groups and the controls. After tumors were subcultured, the supernatants were collected for IL-2 expression by enzyme-linked immunosorbent assay (ELISA). Natural killer (NK) cell activity and cytotoxic T-lymphocyte (CTL) activity were also assayed by LDH method. CD4+ and CD8+ T-lymphcyte in tumour tissues were examined by immunohistochemistry. RESULT: HNSCC tumor growth was significantly inhibited after a combined IL-2 gene and radiation therapy as compared to the controls. Increased secreted levels of IL-2 protein expression were found in combined and single IL-2 gene treated groups. The combination and IL-2 gene treated groups produced greater activation of CTL and NK than the other groups. The significant CD4+ and CD8+ T lymphocyte infiltration was distributed in tumor tissues after IL-2 gene therapy. CONCLUSION: Combined IL-2 gene therapy and radiation could significantly inhibited HNSCC tumor growth in the murine model and efficiently induced antitumor immunity of the host.

Animals↗
PubMed2003

[Studies of mouse interleukin-2 gene therapy for head, and neck sequamous cell carcinoma using polycationic liposome-mediated transduction].

OBJECTIVE: To investigate the immunological mechanism of mouse IL-2 gene therapy and the optimal lipid to DNA ratios of lipid-DNA complexed (lipoplexes) by using polycationic liposome-mediated Tumors were established in the transduction for head and neck squamous cell carcinoma (HNSCC). METHODS: floor of mouth in C3H/HeJ immunocompetent mice with SCCVII cell line. Lipoplexes with various lipid to DNA ratios (L:D) and naked DNA were transducted in vivo by direct intratumoral gene transfer and in vitro. The supernatants of SCCVII cell and tumour tissues were collected for IL-2 expression by enzyme-linked immunosorbent assay. Natural killer (NK) cell activity and cytotoxic T-lymphocyte (CTL) activity were also The optimal L:D ratio for IL-2 expression in vitro was not assayed by lactate dehydrogenase method. RESULTS: consistent with that in vivo. By use of lipoplexes with L:D = 3:1, higher IL-2 expression of tumor tissues and greater activities of NK cell and CTL of murine spleen were noted in the treated group as compared with those A comparison of naked plasmid and lipid-complexed found in naked DNA and empty plasmid (EP). CONCLUSION: DNA revealed that lipoplexes were more effective for intratumoral gene transfer to HNSCC. The results indicate that the formulation and dosage of polycationic L:D complexes play a key role in determining the level of intratumoral transgene expression.

Animals↗
PubMed2002

Nicotinic acetylcholine receptor alpha7 subunit is an essential regulator of inflammation.

Excessive inflammation and tumour-necrosis factor (TNF) synthesis cause morbidity and mortality in diverse human diseases including endotoxaemia, sepsis, rheumatoid arthritis and inflammatory bowel disease. Highly conserved, endogenous mechanisms normally regulate the magnitude of innate immune responses and prevent excessive inflammation. The nervous system, through the vagus nerve, can inhibit significantly and rapidly the release of macrophage TNF, and attenuate systemic inflammatory responses. This physiological mechanism, termed the 'cholinergic anti-inflammatory pathway' has major implications in immunology and in therapeutics; however, the identity of the essential macrophage acetylcholine-mediated (cholinergic) receptor that responds to vagus nerve signals was previously unknown. Here we report that the nicotinic acetylcholine receptor alpha7 subunit is required for acetylcholine inhibition of macrophage TNF release. Electrical stimulation of the vagus nerve inhibits TNF synthesis in wild-type mice, but fails to inhibit TNF synthesis in alpha7-deficient mice. Thus, the nicotinic acetylcholine receptor alpha7 subunit is essential for inhibiting cytokine synthesis by the cholinergic anti-inflammatory pathway.

Acetylcholine↗
PubMed2002

Ethyl pyruvate prevents lethality in mice with established lethal sepsis and systemic inflammation.

Sepsis, a potentially fatal clinical syndrome, is mediated by an early (e.g., tumor necrosis factor and IL-1) and late [e.g., high mobility group B-1 (HMGB1)] proinflammatory cytokine response to infection. Specifically targeting early mediators has not been effective clinically, in part because peak mediator activity often has passed before therapy can be initiated. Late-acting downstream effectors, such as HMGB1, that mediate sepsis lethality may be more relevant therapeutic targets. Ethyl pyruvate (EP) recently was identified as an experimental therapeutic that significantly protects against lethal hemorrhagic shock. Here, we report that EP attenuates lethal systemic inflammation caused by either endotoxemia or sepsis even if treatment begins after the early tumor necrosis factor response. Treatment with EP initiated 24 h after cecal puncture significantly increased survival (vehicle survival = 30% vs. EP survival = 88%, P < 0.005). EP treatment significantly reduced circulating levels of HMGB1 in animals with established endotoxemia or sepsis. In macrophage cultures, EP specifically inhibited activation of p38 mitogen-activated protein kinase and NF-kappaB, two signaling pathways that are critical for cytokine release. This report describes a new strategy to pharmacologically inhibit HMGB1 release with a small molecule that is effective at clinically achievable concentrations. EP now warrants further evaluation as an experimental "rescue" therapeutic for sepsis and other potentially fatal systemic inflammatory disorders.

Animals↗
PubMed2002

Resistance to experimental autoimmune myasthenia gravis in IL-6-deficient mice is associated with reduced germinal center formation and C3 production.

To provide direct genetic evidence for a role of IL-6 in experimental autoimmune myasthenia gravis (EAMG), IL-6 gene KO (IL-6(-/-)) mice in the C57BL/6 background were immunized with Torpedo californica acetylcholine receptor (AChR) and evaluated for EAMG. Only 25% of AChR-immunized IL-6(-/-) mice developed clinical EAMG compared to 83% of C57BL/6 (wild-type) mice. A significant reduction in the secondary anti-AChR Ab of IgG, IgG(2b), and IgG(2c), but not the primary or secondary IgM response was observed in AChR-immunized IL-6(-/-) mice, suggesting a possible defect in T cell help and class switching to anti-AChR IgG(2) isotype. The AChR-specific lymphocyte proliferative response, IFN-gamma, and IL-10 production were suppressed in AChR-immunized IL-6(-/-) mice. EAMG resistance in IL-6(-/-) mice was associated with a significant reduction in germinal center formation and decreased serum complement C3 levels. The data provide the first direct genetic evidence for a key role of IL-6 in the autoimmune response to AChR and in EAMG pathogenesis.

Animals↗
PubMed2002

HMGB-1, a DNA-binding protein with cytokine activity, induces brain TNF and IL-6 production, and mediates anorexia and taste aversion.

High-mobility group protein-1 (HMG-1 also termed HMGB-1), a DNA-binding protein, regulates gene transcription and stabilizes nucleosome formation. HMG-1 was recently implicated as a cytokine, because it is a late-acting mediator of endotoxin lethality that induces the release of pro-inflammatory cytokines from monocytes. Here it is shown that administration of HMG-1 into the cerebral ventricles decreases food intake (food intake=4.6g/mouse in controls vs 1.6g/mouse after 1 microg HMG-1 i.c.v.; P <0.05). Intracerebroventricular HMG-1 induced an increased in TNF and IL-6 expression in the brain, and mediated taste aversion with potencies equivalent to LPS. In a model of endotoxemia, passive immunization with anti-HMG-1 antibodies attenuated the development of hypophagia, indicating that HMG-1 is a mediator of sickness behaviour associated with endotoxemia.

Animals↗
PubMed2002

Pharmacological stimulation of the cholinergic antiinflammatory pathway.

Efferent activity in the vagus nerve can prevent endotoxin-induced shock by attenuating tumor necrosis factor (TNF) synthesis. Termed the "cholinergic antiinflammatory pathway," inhibition of TNF synthesis is dependent on nicotinic alpha-bungarotoxin-sensitive acetylcholine receptors on macrophages. Vagus nerve firing is also stimulated by CNI-1493, a tetravalent guanylhydrazone molecule that inhibits systemic inflammation. Here, we studied the effects of pharmacological and electrical stimulation of the intact vagus nerve in adult male Lewis rats subjected to endotoxin-induced shock to determine whether intact vagus nerve signaling is required for the antiinflammatory action of CNI-1493. CNI-1493 administered via the intracerebroventricular route was 100,000-fold more effective in suppressing endotoxin-induced TNF release and shock as compared with intravenous dosing. Surgical or chemical vagotomy rendered animals sensitive to TNF release and shock, despite treatment with CNI-1493, indicating that an intact cholinergic antiinflammatory pathway is required for antiinflammatory efficacy in vivo. Electrical stimulation of either the right or left intact vagus nerve conferred significant protection against endotoxin-induced shock, and specifically attenuated serum and myocardial TNF, but not pulmonary TNF synthesis, as compared with sham-operated animals. Together, these results indicate that stimulation of the cholinergic antiinflammatory pathway by either pharmacological or electrical methods can attenuate the systemic inflammatory response to endotoxin-induced shock.

Animals↗
PubMed2002

HMGB1 B box increases the permeability of Caco-2 enterocytic monolayers and impairs intestinal barrier function in mice.

BACKGROUND & AIMS: High mobility group (HMG) B1 is a nonhistone nuclear protein that was recently identified as a late-acting mediator of lipopolysaccharide-induced lethality in mice. The proinflammatory actions of HMGB1 have been localized to a region of the molecule called the B box. METHODS: To determine whether HMGB1 or B box are capable of causing derangements in intestinal barrier function, we incubated cultured Caco-2 human enterocytic monolayers with recombinant human HMGB1 or a 74-residue truncated form of the protein consisting of the B box domain. RESULTS: Both HMGB1 and B box increased the permeability of Caco-2 monolayers to fluorescein isothiocyanate-labeled dextran (FD4) in a time- and dose-dependent fashion. The increase in permeability was reversible following removal of the recombinant protein. Exposure of Caco-2 cells to B box resulted in increased expression of inducible nitric oxide synthase messenger RNA and increased production of NO. When we used various pharmacologic strategies to inhibit NO production or scavenge NO or peroxynitrite (ONOO(-)), we abrogated B box-induced hyperpermeability. Administration of B box to wild-type mice increased both ileal mucosal permeability to FD4 and bacterial translocation to mesenteric lymph nodes. These effects were not observed in inducible nitric oxide synthase knockout mice. CONCLUSIONS: These data support the view that HMGB1 and B box are capable of causing alterations in gut barrier function via a mechanism that depends on the formation of NO and ONOO(-).

Animals↗
PubMed2002

Globin attenuates the innate immune response to endotoxin.

Hemoglobin is an endotoxin (lipopolysaccharide; LPS)-binding protein that synergistically increases the release of proinflammatory cytokines from the innate immune system in response to LPS. It has been suggested that this activity of hemoglobin facilitates the recognition of Gram-negative bacteria in a wound, thereby maximizing immune efficiency. This synergy may be important to the pathogenesis of a broad spectrum of clinical conditions because elevated hemoglobin levels frequently are observed in patients after the transfusion of red cells, trauma, cardiopulmonary bypass surgery, hemolysis, in addition to other disorders. To determine the molecular basis of the specific hemoglobin-LPS synergy, in this article we tested the effects of globin itself on macrophage responses to LPS. Paradoxically, these studies revealed that globin suppressed tumor necrosis factor (TNF) synthesis in LPS-stimulated murine and human macrophage cultures. LPS comigrated with globin on non-denaturing electrophoretic gels, giving direct evidence for binding. Globin specifically inhibited LPS activity in the standard Limulus assay but did not inhibit interleukin-1beta-mediated TNF synthesis. Iron supplementation of macrophage cultures significantly increased interleukin-1beta-induced TNF release. Intraperitoneal administration of globin protected mice against both LPS-induced lethality and experimentally induced bacterial infection. Thus, the heme-iron moiety of hemoglobin, and not the binding of LPS to globin, enhanced macrophage responses to LPS.

Animals↗
PubMed2002

Mapping myasthenia gravis-associated T cell epitopes on human acetylcholine receptors in HLA transgenic mice.

Susceptibility to myasthenia gravis (MG) is positively linked to expression of HLA-DQ8 and DR3 molecules and negatively linked to expression of the DQ6 molecule. To elucidate the molecular basis of this association, we have induced experimental autoimmune MG (EAMG) in mice transgenic for HLA-DQ8, DQ6, and DR3, and in DQ8xDQ6 and DQ8xDR3 F(1) transgenic mice, by immunization with human acetylcholine receptor (H-AChR) in CFA. Mice expressing transgenes for one or both of the HLA class II molecules positively associated with MG (DQ8 and DR3) developed EAMG. T cells from DQ8 transgenic mice responded well to three cytoplasmic peptide sequences of H-AChR (alpha320-337, alpha304-322, and alpha419-437), of which the response to alpha320-337 was the most intense. DR3 transgenic mice also responded to this sequence very strongly. H-AChR- and alpha320-337 peptide-specific lymphocyte responses were restricted by HLA class II molecules. Disease resistance in DQ6 transgenic mice was associated with reduced synthesis of anti-AChR IgG, IgG(2b), and IgG(2c) Ab's and reduced IL-2 and IFN-gamma secretion by H-AChR- and peptide alpha320-337-specific lymphocytes. Finally, we show that DQ8 imparts susceptibility to EAMG and responsiveness to an epitope within the sequence alpha320-337 as a dominant trait.

Amino Acid Sequence↗
PubMed2002

HMGB1 as a cytokine and therapeutic target.

HMGB1 is an abundant nuclear and cytoplasmic protein present in mammalian cells. It is traditionally known as a DNA binding protein involved in maintenance of nucleosome structure and regulation of gene transcription. Beyond these intracellular roles, we recently discovered that HMGB1 is released from activated macrophages and functions as a late mediator of lethal endotoxemia. Addition of HMGB1 to macrophage cultures activates cytokine release. When released into the extracellular milieu, HMGB1 causes systemic inflammatory responses including acute lung injury, epithelial barrier dysfunction, and death. Passive immunization with anti-HMGB1 antibodies confers significant protection against lethality induced by LPS administration and sepsis caused by cecal perforation in mice. Truncation of HMGB1 into individual structural domains revealed that the HMGB1 A box, a DNA-binding motif, specifically antagonizes the activity of HMGB1 and rescues mice from lethal sepsis caused by cecal perforation. Thus, strategies that target HMGB1 with specific antibodies or antagonists have potential for treating lethal systemic inflammatory diseases characterized by excessive HMGB1 release.

Antibodies↗
PubMed2002

Combined IL-2 and IL-12 gene therapy for murine head and neck squamous cell carcinoma.

OBJECTIVE: To evaluate the efficacy of combined interleukin (IL)-2 gene and IL-12 gene therapy in murine model with head and neck squamous cell carcinoma (HNSCC). METHODS: HNSCC model was established in the mouth floor of C3H/HeJ mice with SCCVII cell line. Lipid-IL2 and lipid-IL12 plasmid complexes were introduced either alone or in combination into the tumor by direct intratumor gene injection. Tumor size was measured before and after the treatment to evaluate the response of the different treatment and control groups. Enzyme-linked immunosorbent assay (ELISA) was used to measure the IL-2 and IL-12 expression. Lactic dehydrogenase (LDH) assay was used to evaluate the activity of Cytotoxic T-Lymphocyte (CTL) and natural killer (NK) cells. RESULTS: Growth of HNSCC was significantly inhibited in combined IL-2 and IL-12 gene therapy group as compared with the other groups (P < 0.01). Increased level of IL-2 and IL-12 protein expression was found in both combined and single treatment groups. Greater activity of CTL and NK was also observed in these two groups as compared with the controls. CONCLUSION: Both IL-2 and IL-12 gene therapy is able to inhibit the growth of HNSCC and induce the host antitumor immune response efficiently in the murine model. Combination of the two in gene therapy may be additive or synergistic in antitumor effect.

Animals↗
PubMed2002

HMGB1 as a DNA-binding cytokine.

HMGB1 (high mobility group box chromosomal protein 1), historically known as an abundant, nonhistone architectural chromosomal protein, is extremely conserved across species. As a nuclear protein, HMGB1 stabilizes nucleosomes and allows bending of DNA that facilitates gene transcription. Unexpectedly, recent studies identified extracellular HMGB1 as a potent macrophage-activating factor, signaling via the receptor for advanced glycation end-products to induce inflammatory responses. It is released as a late mediator during inflammation and participates in the pathogenesis of systemic inflammation after the early mediator response has resolved. HMGB1 occupies a critical role as a proinflammatory mediator passively released by necrotic but not apoptotic cells. Necrotic Hmgb1(-/-) cells mediate minimal inflammatory responses. Stimulated macrophages actively secrete HMGB1 to promote inflammation and in turn, stimulate production of multiple, proinflammatory cytokines. HMGB1 mediates endotoxin lethality, acute lung injury, arthritis induction, activation of macrophages, smooth muscle cell chemotaxis, and epithelial cell barrier dysfunction. HMGB1 is structurally composed of three different domains: two homologous DNA-binding sequences entitled box A and box B and a highly, negatively charged C terminus. The B box domain contains the proinflammatory cytokine functionality of the molecule, whereas the A box region has an antagonistic, anti-inflammatory effect with therapeutic potential. Administration of highly purified, recombinant A box protein or neutralizing antibodies against HMGB1 rescued mice from lethal sepsis, even when initial treatment was delayed for 24 h after the onset of infection, establishing a clinically relevant therapeutic window that is significantly wider than for other known cytokines.

Animals↗
PubMedDate not supplied

Anti-HMGB1 neutralizing antibody ameliorates gut barrier dysfunction and improves survival after hemorrhagic shock.

Intestinal barrier dysfunction occurs following hemorrhagic shock and resuscitation (HS/R). High-mobility group B1 (HMGB1) has been shown to increase the permeability of Caco-2 human enterocyte-like epithelial monolayers in vitro. In this study, we found that serum concentrations of HMGB1 were higher in blood samples obtained from 25 trauma victims with hemorrhagic shock than in 9 normal volunteers. We also studied whether treatment with anti-HMGB1 antibody can ameliorate HS/R-induced gut barrier dysfunction in mice. Animals were shocked by withdrawal of blood to maintain mean arterial pressure at 25 to 30 mmHg for 2 h. After resuscitation with shed blood plus Ringer's lactate solution, the mice were treated with either anti-HMGB1 antibody or nonimmune rabbit IgG. Serum HMGB1 concentrations were significantly higher in trauma victims than control mice. Treatment with anti-HMGB1 antibody improved survival at 24 h and ameliorated the development of ileal mucosal hyperpermeability to FITC-labeled dextran. At 24 h after HS/R, treatment with anti-HMGB1 antibody decreased bacterial translocation to mesenteric lymph nodes and was associated with lower circulating concentrations of IL-6 and IL-10. These data support the notion that HMGB1 is a mediator of HS/R-induced gut barrier dysfunction and suggest that anti-HMGB1 antibodies warrant further evaluation as a therapeutic to ameliorate the morbidity of HS/R in trauma patients.

Adolescent↗
PubMedDate not supplied

Structural basis for the proinflammatory cytokine activity of high mobility group box 1.

High mobility group box 1 (HMGB), a ubiquitous DNA-binding protein, has been implicated as a proinflammatory cytokine and late mediator of lethal endotoxemia. HMGB1 is released by activated macrophages. It amplifies and extends the inflammatory response by inducing cytokine release and mediating acute lung injury, anorexia, and the inflammatory response to tissue necrosis. The kinetics of HMGB1 release provide a wide therapeutic window for endotoxemia because extracellular levels of HMGB1 begin to increase 12 to 24 h after exposure to inflammatory stimuli. Here, we demonstrate that a DNA-binding domain of HMGB1, the B box, recapitulates the cytokine activity of full length HMGB1 and efficiently activates macrophages to release tumor necrosis factor (TNF) and other proinflammatory cytokines. Truncation of the B box revealed that the TNF-stimulating activity localizes to 20 amino acids (HMGB1 amino acids 89 to 108). Passive immunization of mice with antibodies raised against B box conferred significant protection against lethal endotoxemia or sepsis, induced by cecal perforation. These results indicate that a proinflammatory domain of HMGB1 maps to the highly conserved DNA-binding B box, making this primary sequence a suitable target in the design of therapeutics.

Animals↗