Initiation of signal transduction of the respiratory burst of prawn haemocytes triggered by CpG oligodeoxynucleotides

Phagocytosis is important in the immune system of the prawn and is believed to be a defence parameter. Previous studies have demonstrated that CpG oligonucleotides enhance the activation of the prophenoloxidase activating system of the prawn through either the G-protein/protein kinase C (PKC) or the cAMP pathway. This study investigated the influence of CpG ODN on the respiratory burst used as the indicator of phagocytic activity and on the initiation of the signal pathway in haemocytes of Macrobrachium rosenbergii. When haemocytes were treated in vitro with 50 microg ml(-1) of ODN2006 for 15 min, the increase of nitroblue-tetrazolium (NBT) reduction suggested that the respiratory burst of haemocytes can be enhanced by ODN2006 stimulation. In an attempt to determine which signal transduction pathway is involved in the enhancement effect, haemocytes were separately treated with activators or inhibitors of specific signalling components. The results showed that the NBT reduction of haemocytes increased after treatment with sodium fluoride (a G-protein activator) and decreased after treatment with GDP-beta-S (a G-protein inhibitor). When ODN2006-stimulated haemocytes were treated with GDP-beta-S, the inductive effect was significantly reduced. In haemocytes treated with 8-bromo-cAMP (a PKA activator), the NBT reduction was not significantly different from the control. The addition of phosphodiesterase-inhibiting caffeine, which inhibits the degradation of cAMP, decreased the NBT reduction of ODN2006-stimulated haemocytes; however, the addition of phenol-12-myristate-13-acetate (PMA) significantly increased the NBT reduction. When PMA-stimulated haemocytes were treated with chelerythrine (a PKC inhibitor), the induced NBT reduction was significantly reduced. Furthermore, the study of ODN2006-stimulated haemocytes treated with chelerythrine showed that the enhancement effect of ODN2006 on the NBT reduction was significantly decreased. All results suggest that the enhancement of the respiratory burst of prawn haemocytes is induced by ODN2006 via a PKC-activating signalling pathway, but negatively regulated via the cAMP pathway.     

Signal transduction of the prophenoloxidase activating system of prawn haemocytes triggered by CpG oligodeoxynucleotides

Intracellular phenoloxidase (PO) activity in haemocyte lysate supernatant (HLS) of giant freshwater prawn (Macrobrachium rosenbergii) was shown to be enhanced by CpG oligodeoxynucleotide (ODN) 2006, but not by so-ODN13. When haemocytes were treated in vitro with 50 microg/ml of ODN2006 for 30 min, the increases in both intra- and extracellular stimulated PO activity (POS) and extracellular total PO activity (POT) and the reduction of POT suggest that the PO activity of haemocytes is enhanced by ODN2006 stimulation, but new prophenoloxidase (proPO) is not synthesised. In an attempt to determine which signal transduction pathway is involved in the activation of the proPO system, haemocytes were separately treated with activators or inhibitors of specific signalling components. The results show that there was an increase in both intra- and extracellular POT of haemocytes treated with sodium fluoride (a G-protein activator); the addition of phosphokinase A (PKA)-activating 8-bromo-cAMP to haemocytes only increased intracellular POT, and the addition of either phorbol-12-myristate-13-acetate (PMA; a phosphokinase C (PKC) activator) or caffeine (a phosphodiesterase inhibitor) only increased extracellular POT. When PMA-stimulated haemocytes were treated with chelerythrine (a PKC inhibitor), the induced extracellular POT was significantly reduced. Furthermore, the study of ODN2006-stimulated haemocytes treated with chelerythrine or palmitoyl-DL-carnitine (a PKC inhibitor) showed that the enhancement effects of ODN2006 on the intra- and extracellular POS and extracellular POT were significantly decreased. ODN-stimulated haemocytes treated with genistein (an inhibitor of protein tyrosine kinase) showed a further increase in extracellular POT, but the other PO activities remained the same as those of the ODN-stimulated group. These results suggest that the activation of the proPO system of prawn haemocytes, including degranulation and PO activity, is induced by ODN2006 via a PKC-activating signalling pathway, but negatively regulated via the tyrosine kinase pathway.     

Identification and expression analysis of cobia (Rachycentron canadum) Toll-like receptor 9 gene

Cobia culture is hindered by bacterial infection (Photobacterium damselae subsp. piscicida) and in order to study the effect of P. damselae subsp. piscicida challenge and CpG ODN stimulation on cobia Toll like receptor 9 (RCTLR9), we used PCR to clone RCTLR9 gene and qRT-PCR to quantify gene expression. The results indicated that RCTLR9 cDNA contains 3141 bp. It encodes 1047 amino acids containing 16 typical structures of leucine-rich repeats (LRRs) including an LRRTYP, LRRCT and a motif involved in PAMP binding was identified at position 240–253 amino acid. Broad expression of RCTLR9 was found in larval, juvenile and adult stages irrespective of the tissues. In larval stage, RCTLR9 mRNA expression decreased at 5 d and then increased at 10 dph. At juvenile stage cobia, the expression was significantly high (p < 0.05) in spleen and intestine compared to gill, kidney, liver and skin. However, at adult stage, the significant high expression was found in gill and intestine. Cobia challenged with P. damselae subsp. piscicida showed significant increase in RCTLR9 expression at 24 h post challenge in intestine, spleen and liver, while in kidney the expression was peak at 12 h and later it decreased at 24 h. The highest expression was 40 fold increase in spleen and the lowest expression was ∼3.6 fold increase in liver. Cobia stimulated with CpG oligonucleotides showed that the induction of these genes was CpG ODN type and time dependent. In spleen and liver, CpG ODNs 1668 and 2006 injected group showed high expression of RCTLR9, IL-1β, chemokine CC compared to other groups. Meanwhile, CpG ODN 2006 has induced high expression of IgM. The CpG ODNs 2395 have induced significant high expression of Mx in spleen and liver. These results demonstrates the potential of using CpG ODN to enhance cobia resistance to P. damselae subsp. piscicida infection and use as an adjuvant in vaccine development.     

Increased intracellular Cl− concentration mediates Trichomonas vaginalis-induced inflammation in the human vaginal epithelium

Trichomonas vaginalis is a primary urogenital parasite that causes trichomoniasis, a common sexually transmitted disease. As the first line of host defense, vaginal epithelial cells play critical roles in orchestrating vaginal innate immunity and modulate intracellular Cl⁻ homeostasis via the cystic fibrosis transmembrane conductance regulator (CFTR), an anion channel that plays positive roles in regulating nuclear factor-κB (NF-κB) signalling. However, the association between T. vaginalis infection and intracellular Cl⁻ disequilibrium remains elusive. This study showed that after T. vaginalis infection, CFTR was markedly down-regulated by cysteine proteases in vaginal epithelial cells. The intracellular Cl⁻ concentration ([Cl⁻]_i) was consequently elevated, leading to NF-κB signalling activation via serum- and glucocorticoid-inducible kinase-1. Moreover, heightened [Cl⁻]_i and activated NF-κB signalling could be sustained in a positive feedback regulatory manner resulting from decreased intracellular cAMP through NF-κB-mediated up-regulation of phosphodiesterase 4. The results conclusively revealed that the intracellular Cl⁻ of the human vaginal epithelium could be dynamically modulated by T. vaginalis, which contributed to mediation of epithelial inflammation in the human vagina.     

Microarray analyses of the effects of NF-κB or PI3K pathway inhibitors on the LPS-induced gene expression profile in RAW264.7 cells: Synergistic effects of rapamycin on LPS-induced MMP9-overexpression

Lipopolysaccharide (LPS) activates a broad range of signalling pathways including mainly NF-κB and the MAPK cascade, but recent evidence suggests that LPS stimulation also activates the PI3K pathway. To unravel the specific roles of both pathways in LPS signalling and gene expression profiling, we investigated the effects of different inhibitors of NF-κB (BAY 11-7082), PI3K (wortmannin and LY294002) but also of mTOR (rapamycin), a kinase acting downstream of PI3K/Akt, in LPS-stimulated RAW264.7 macrophages, analyzing their effects on the LPS-induced gene expression profile using a low density DNA microarray designed to monitor the expression of pro-inflammatory genes. After statistical and hierarchical cluster analyses, we determined five clusters of genes differentially affected by the four inhibitors used. In the fifth cluster corresponding to genes upregulated by LPS and mainly affected by BAY 11-7082, the gene encoding MMP9 displayed a particular expression profile, since rapamycin drastically enhanced the LPS-induced upregulation at both the mRNA and protein levels. Rapamycin also enhanced the LPS-induced NF-κB transactivation as determined by a reporter assay, phosphorylation of the p38 and Erk1/2 MAPKs, and counteracted PPAR activity. These results suggest that mTOR could negatively regulate the effects of LPS on the NF-κB and MAPK pathways. We also performed real-time RT-PCR assays on mmp9 expression using rosiglitazone (agonist of PPARγ), PD98059 (inhibitor of Erk 1/2) and SB203580 (inhibitor of p38^MAPK), that were able to counteract the rapamycin mediated overexpression of mmp9 in response to LPS. Our results suggest a new pathway involving mTOR for regulating specifically mmp9 in LPS-stimulated RAW264.7 cells.     

Epoxyquinol B,a Naturally Occurring Pentaketide Dimer,Inhibits NF-κB Signaling by Crosslinking TAK1

Several epoxyquinoids interfere with NF-κB signaling by targeting IKKβ or NF-κB. We report that epoxyquinol B (EPQB), classified as an epoxyquiniod, inhibits NF-κB signaling through inhibition of the TAK1 complex, a factor upstream of IKKβ and NF-κB. cDNA microarray analysis revealed that EPQB decreased TNF-α-induced expression of NF-κB target genes. EPQB covalently bound to a recombinant TAK1-TAB1 fusion protein in vitro, and inhibited its kinase activity. Furthermore, in vitro/in situ treatment with EPQB resulted in a ladder-like hypershift of TAK1 protein bands. We reported recently that EPQB crosslinks proteins via cysteine residues by opening its two epoxides, and our current results suggest that EPQB inhibits NF-κB signaling by crosslinking TAK1 itself or TAK1 through other proteins.     

A GpC-Rich Oligonucleotide Acts on Plasmacytoid Dendritic Cells To Promote Immune Suppression

Short synthetic oligodeoxynucleotides (ODNs) rich in CpG or GpG motifs have been considered as potential modulators of immunity in clinical settings. In this study, we show that a synthetic GpC-ODN conferred highly suppressive activity on mouse splenic plasmacytoid dendritic cells, demonstrable in vivo in a skin test assay. The underlying mechanism involved signaling by noncanonical NF-κB family members and TGF-β-dependent expression of the immunoregulatory enzyme IDO. Unlike CpG-ODNs, the effects of GpC-ODN required TLR7/TRIF-mediated but not TLR9/MyD88-mediated events, as do sensing of viral ssRNA and the drug imiquimod. Induction of IDO by a GpC-containing ODN could also be demonstrated in human dendritic cells, allowing those cells to assist FOXP3(+) T cell generation in vitro. Among potentially therapeutic ODNs, this study identifies GpC-rich sequences as novel activators of TLR7-mediated, IDO-dependent regulatory responses.     

Mustard NPR1, a mammalian IκB homologue inhibits NF-κB activation in human GBM cell lines

NF-κB activity is tightly regulated by IκB class of proteins. IκB proteins possess ankyrin repeats for binding to and inhibiting NF-κB. The regulatory protein, NPR1 from Brassica juncea possesses ankyrin repeats with sequence similarity to IκBα subgroup. Therefore, we examined whether stably expressed BjNPR1 could function as IκB in inhibiting NF-κB in human glioblastoma cell lines. We observed that BjNPR1 bound to NF-κB and inhibited its nuclear translocation. Further, BjNPR1 expression down-regulated the NF-κB target genes iNOS, Cox-2, c-Myc and cyclin D1 and reduced the proliferation rate of U373 cells. Finally, BjNPR1 decreased the levels of pERK, pJNK and PKCα and increased the Caspase-3 and Caspase-8 activities. These results suggested that inhibition of NF-κB activation by BjNPR1 can be a promising therapy in NF-κB dependent pathologies.     

Role of nitric oxide and nuclear factor-κB in the CYP2E1 potentiation of tumor necrosis factor α hepatotoxicity in mice

Induction of CYP2E1 by pyrazole (PY) potentiated the hepatotoxicity induced by TNFα in mice. We evaluated the role of nitrosative and oxidative stress and the NF-κB activation pathway in this liver injury. The iNOS inhibitor N-(3-aminomethyl)benzylacetamindine (1400W) or the antioxidant N-acetyl-l-cysteine (NAC) prevented this liver injury. TNFα plus PY treatment triggered radical stress in the liver with increased lipid peroxidation and decreased glutathione and caused mitochondrial damage as reflected by elevated membrane swelling and cytochrome c release. The radical stress and mitochondrial damage were prevented by 1400W and NAC. TNFα plus PY treatment elevated 3-nitrotyrosine adduct formation and induced NOS2 in the liver; 1400W and NAC blocked these changes. A lower extent of liver injury and oxidative stress was found in NOS2^?/? mice treated with TNFα plus PY compared with wild-type controls. Neither 1400W nor NAC modified CYP2E1 activity or protein. Activation of JNK and p38MAPK was weaker in TNFα plus PY-treated NOS2^?/? mice and 1400W and NAC blocked the activation of JNK and p38MAPK in wild-type mice. IKKα/β protein levels were decreased by TNFα plus PY treatment, whereas IκBα and IκBβ protein levels were elevated compared with saline, PY, or TNFα alone. NF-κB DNA binding activity was increased by TNFα alone but lowered by TNFα plus PY. All these changes were blocked by 1400W and NAC. NF-κB activation products such as Bcl-2, Bcl-X_L, cFLIP_S, cFLIP_L, and Mn-SOD were reduced by TNFα plus PY and restored by 1400W or NAC. We conclude that TNFα plus CYP2E1 induces oxidative/nitrosative stress, which plays a role in the activation of JNK or p38MAPK and mitochondrial damage. These effects combine with the blunting of the NF-κB activation pathways and the synthesis of protective factors to cause liver injury.