p38 activation through Toll-like receptors modulates IFN-gamma-induced expression of the Tap-1 gene only in macrophages

Inducible TAP1 Negatively Regulates the Antiviral Innate Immune Response by Targeting the TAK1 Complex

The innate immune response is critical for host defense and must be tightly controlled, but the molecular mechanisms responsible for its negative regulation are not yet completely understood. In this study, we report that transporter 1, ATP-binding cassette, subfamily B (TAP1), a virus-inducible endoplasmic reticulum-associated protein, negatively regulated the virus-triggered immune response. In this study, we observed upregulated expression of TAP1 following virus infection in human lung epithelial cells (A549), THP-1 monocytes, HeLa cells, and Vero cells. The overexpression of TAP1 enhanced virus replication by inhibiting the virus-triggered activation of NF-κB signaling and the production of IFNs, IFN-stimulated genes, and proinflammatory cytokines. TAP1 depletion had the opposite effect. In response to virus infection, TAP1 interacted with the TGF-β-activated kinase (TAK)1 complex and impaired the phosphorylation of TAK1, subsequently suppressing the phosphorylation of the IκB kinase complex and NF-κB inhibitor α (IκBα) as well as NF-κB nuclear translocation. Our findings collectively suggest that TAP1 plays a novel role in the negative regulation of virus-triggered NF-κB signaling and the innate immune response by targeting the TAK1 complex.

TLR8-dependent TNF-(alpha) overexpression in Fanconi anemia group C cells

Tumor necrosis factor alpha (TNF-alpha) production is abnormally high in Fanconi anemia (FA) cells and contributes to the hematopoietic defects seen in FA complementation group C-deficient (Fancc(-/-)) mice. Applying gene expression microarray and proteomic methods to studies on FANCC-deficient cells we found that genes encoding proteins directly involved in ubiquitinylation are overrepresented in the signature of FA bone marrow cells and that ubiquitinylation profiles of FA-C and complemented cells were substantially different. Finding that Toll-like receptor 8 (TLR8) was one of the proteins ubiquitinylated only in mutant cells, we confirmed that TLR8 (or a TLR8-associated protein) is ubiquitinylated in mutant FA-C cells and that TNF-alpha production in mutant cells depended upon TLR8 and the canonical downstream signaling intermediates interleukin 1 receptor-associated kinase (IRAK) and IkappaB kinase-alpha/beta. FANCC-deficient THP-1 cells and macrophages from Fancc(-/-) mice overexpressed TNF-alpha in response to TLR8 agonists but not other TLR agonists. Ectopically expressed FANCC point mutants were capable of fully complementing the mitomycin-C hypersensitivity phenotype of FA-C cells but did not suppress TNF-alpha overproduction. In conclusion, FANCC suppresses TNF-alpha production in mononuclear phagocytes by suppressing TLR8 activity and this particular function of FANCC is independent of its function in protecting the genome from cross-linking agents.

Chronic exposure to high levels of atrazine alters expression of genes that regulate immune and growth-related functions in developing Xenopus laevis tadpoles

Atrazine is the most commonly detected pesticide in ground and surface waters, with seasonal spikes that often exceed the Environmental Protection Agency's "Recommended Water Quality Criterion" of 350 parts per billion (ppb). Although numerous studies have shown atrazine produces adverse effects on growth, development, immune and endocrine system functions in a wide range of species, few describe gene expression changes concurrent with atrazine-induced changes in phenotype during development. In this report, developing Xenopus laevis tadpoles were chronically exposed to 400 ppb atrazine, an environmentally relevant concentration. Affymetrix microarrays and Taqman qRT-PCR were used to define gene expression changes that underlie atrazine-induced phenotypic alterations. Atrazine significantly reduced survival and growth (weight, length and fat body size) in male and female tadpoles. Microarray analysis showed atrazine altered expression of 44 genes in male tadpoles (18 upregulated, 26 downregulated) and 77 genes in female tadpoles (23 upregulated, 54 downregulated). Classification of the genes into functional groups showed the majority of genes were associated with the following biological functions: growth and metabolism, proteolysis, fibrinogen complex formation and immune regulation. Seven genes associated with immune system function, specifically defense molecules present in the skin (e.g. magainin II, levitide A, preprocarulein, skin granule protein), were significantly downregulated in female tadpoles. These results support the idea that environmental contaminants such as atrazine compromise important gene pathways during frog development that may, ultimately, be relevant to global amphibian decline.

Differentiation of C2D macrophage cells after adoptive transfer

C2D macrophage cells protect immunocompromised mice from experimentally induced pneumonias after intraperitoneal (i.p.) adoptive transfer. These macrophage cells are immature and display minimal activity in vitro. Therefore, we wanted to understand how adoptive transfer affected these cells. We believe that the in vivo environment affects the phenotypic and functional characteristics of macrophages that help maintain the physiological integrity of the host. To test this hypothesis, we characterized the trafficking patterns and cellular changes of the established macrophage C2D cell line after adoptive transfer. We examined phenotypic changes of the C2D macrophage cells in vivo with and without stimulation with gamma interferon (IFN-gamma). After in vivo i.p. adoptive transfer, C2D macrophage cells trafficked to the lungs, spleen, lymph nodes, and bone marrow of recipient mice. The cells were detected for as long as 2 months, and the cells expressed increased levels of CD11b, c-fms, and F4/80 on their surface, becoming more differentiated macrophages compared to cells maintained in vitro. Upon in vivo stimulation with IFN-gamma, c-fms levels decreased while Gr-1 levels increased compared to in vivo, unstimulated, phosphate-buffered saline-injected controls. These responses were independent of the genetic backgrounds of the recipient mice. These data support the hypothesis and indicate that C2D macrophage cells respond to in vivo signals that are absent during in vitro culture.

Interferon-stimulated genes response in endothelial cells following Hantaan virus infection

The regulation mechanism of interferon (IFN) and IFN-stimulated genes is a very complex procedure and is dependent on cell types and virus species. We observed molecular changes related to anti-viral responses in endothelial cells during Hantaan virus (HTNV) infection. We found that there are two patterns of gene expression, the first pattern of gene expression being characterized by early induction and short action, as in that of type I IFNs,' and the other being characterized by delayed induction and long duration, as those of IRF-7, MxA, and TAP-1/2. Even though there are significant differences in their induction folds, we found that all of IFN-alpha/beta, IRF- 3/7, MxA, and TAP-1/2 mRNA expressions reached the peak when the viral replication was most active, which took place 3 days of post infection (d.p.i.). In addition, an interesting phenomenon was observed; only one gene was highly expressed in paired genes such as IFN-alpha/beta' (3/277-folds), IRF-3/7 (2.2/29.4-folds), and TAP- 1/2 (26.2/6.1-folds). Therefore, IFN-beta, IRF-7, and TAP-1 seem to be more important for the anti-viral response in HTNV infection. MxA was increased to 296-folds at 3 d.p.i. and kept continuing 207-folds until 7 d.p.i.. The above results indicate that IFN-beta works for an early anti-viral response, while IRF7, MxA, and TAP-1 work for prolonged anti-viral response in HTNV infection.

The CNS role of Toll-like receptor 4 in innate neuroimmunity and painful neuropathy

Neuropathic pain remains a prevalent and persistent clinical problem because of our incomplete understanding of its pathogenesis. This study demonstrates for the first time, to our knowledge, a critical role for CNS innate immunity by means of microglial Toll-like receptor 4 (TLR4) in the induction phase of behavioral hypersensitivity in a mouse and rat model of neuropathy. We hypothesized that after L5 nerve transection, CNS neuroimmune activation and subsequent cytokine expression are triggered by the stimulation of microglial membrane-bound TLR4. To test this hypothesis, experiments were undertaken to assess tactile and thermal hypersensitivity in genetically altered (i.e., TLR4 knockout and point-mutant) mice after L5 nerve transection. In a complementary study, TLR4 antisense oligodeoxynucleotide (ODN) was administered intrathecally to L5 spinal nerve injured rats to reduce the expression of spinal TLR4. Both the genetically altered mice and the rats treated with TLR4 antisense ODN displayed significantly attenuated behavioral hypersensitivity and decreased expression of spinal microglial markers and proinflammatory cytokines as compared with their respective control groups. This finding shows that TLR4 contributes to the initiation of CNS neuroimmune activation after L5 nerve transection. Further understanding of this early, specific, innate CNS/microglial response and how it leads to sustained glial/neuronal hypersensitivity may point to new therapies for the prevention and treatment of neuropathic pain syndromes.