Modelling the interactions between TLR4 and IFNβ pathways

Affected inflammation-related signaling pathways in snake envenomation: A recent insight

Snake envenomation is well known to cause grievous pathological signs, including haemorrhagic discharge, necrosis, and respiratory distress. However, inflammatory reactions are also common envenoming manifestations that lead to successive damage, such as oedema, ulceration, lymphadenectasis, systemic inflammatory response syndrome (SIRS) and even multiple organ dysfunction syndrome (MODS). Interference with the inflammatory burst is hence important in the clinical treatment of snake envenomation. Here, we summarize the typical snake toxins (or venoms) that cause inflammatory reactions and the underlying signaling pathways. In brief, inflammatory reactions are usually triggered by snake venom phospholipase A2 (svPLA2), snake venom metalloprotease (SVMP), snake venom serine protease (SVSP) and C-type lectin/snaclec (CTL) as well as disintegrin (DIS) via multiple signaling pathways. They are nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 (NLRP3), nuclear factor kappa-B (NF-κB), mitogen-activated protein kinase (MAPK), janus kinase/signal transducer and activator of transcription (JAK-STAT) and phosphoinositide 3-Kinase/protein kinase B (PI3K/PKB also called PI3K-AKT) signaling pathways. Activation of these pathways promotes the expression of pro-inflammatory molecules such as cytokines, especially interleukin-1β (IL-1β) which causes further inflammatory cascades and manifestations, such as swelling, fever, pain, and severe complications. Remarkably, almost half of introduced snake toxins (or venoms) have anti-inflammatory effects through blocking these pathways and suppressing the expression of pro-inflammatory molecules. Investigation of affected inflammation-related signaling pathways is meaningful to achieve better clinical treatment.

Requirement of scavenger receptors for activation of the IRF-3/IFN-β/STAT-1 pathway in TLR4-mediated production of NO by LPS-activated macrophages

Production of nitric oxide (NO) by LPS-activated macrophages is due to a complex cellular signaling initiated by TLR4 that leads to the transcription of IFN-β, which activates IRF-1 and STAT-1, as well as to the activation of NF-κB, required for iNOS transcription. High concentrations of LPS can also be uptaken by scavenger receptors (SRs), which, in concert with TLR4, leads to inflammatory responses. The mechanisms by which TLR4 and SRs interact, and the pathways activated by this interaction in macrophages are not elucidated. Therefore, our main goal was to evaluate the role of SRs, particularly SR-A, in LPS-stimulated macrophages for NO production. We first showed that, surprisingly, LPS can induce the expression of iNOS and the production of NO in TLR4^-/- mice, provided exogenous IFN-β is supplied. These results indicate that LPS stimulate receptors other than TLR4. The inhibition of SR-A using DSS or neutralizing antibody to SR-AI showed that SR-A is essential for the expression of iNOS and NO production in stimulation of TLR4 by LPS. The restoration of the ability to express iNOS and produce NO by addition of rIFN-β to inhibited SR-A cells indicated that the role of SR-AI in LPS-induced NO production is to provide IFN-β, probably by mediating the internalization of LPS/TLR4, and the differential inhibition by DSS and neutralizing antibody to SR-AI suggested that other SRs are also involved. Our results reinforce that TLR4 and SR-A act in concert in LPS activation and demonstrated that, for the production of NO, it does mainly by synthesizing IRF-3 and also by activating the TRIF/IRF-3 pathway for IFN-β production, essential for LPS-mediated transcription of iNOS. Consequently STAT-1 is activated, and IRF-1 is expressed, which together with NF-κB from TLR4/MyD88/TIRAP, induce iNOS synthesis and NO production. SUMMARY SENTENCE: TLR4 and SRs act in concert activating IRF-3 to transcribe IFN-β and activate STAT-1 to produce NO by LPS-activated macrophages.

Integrated Analysis of Transcriptome mRNA and miRNA Profiles Reveals Self-Protective Mechanism of Bovine MECs Induced by LPS

Many studies have investigated the molecular crosstalk between mastitis-pathogens and cows by either miRNA or mRNA profiles. Here, we employed both miRNA and mRNA profiles to understand the mechanisms of the response of bovine mammary epithelial cells (bMECs) to lipopolysaccharide (LPS) by RNA-Seq. The total expression level of miRNAs increased while mRNAs reduced after LPS treatment. About 41 differentially expressed mRNAs and 45 differentially expressed miRNAs involved in inflammation were screened out. We found the NFκB-dependent chemokine, CXCL1, CXCL3, CXCL6, IL8, and CX3CL1 to be strongly induced. The anti-apoptosis was active because BCL2A1 and BIRC3 significantly increased with a higher expression. The effects of anti-microbe and inflammation were weakly activated because TNF, IL1, CCL20, CFB, S100A, MMP9, and NOS2A significantly increased but with a low expression, IL6 and β-defensin decreased. These activities were supervised by the NFKBIA to avoid excessive damage to bMECs. The bta-let-7a-5p, bta-miR-30a-5p, bta-miR-125b, and bta-miR-100 were essential to regulate infection process in bMECs after LPS induction. Moreover, the lactation potential of bMECs was undermined due to significantly downregulated SOSTDC1, WNT7B, MSX1, and bta-miR-2425-5p. In summary, bMECs may not be good at going head-to-head with the pathogens; they seem to be mainly charged with sending out signals for help and anti-apoptosis for maintaining lives after LPS induction.

Differences in Lipopolysaccharides-Induced Inflammatory Response Between Mouse Embryonic Fibroblasts and Bone Marrow-Derived Macrophages

Mouse embryonic fibroblasts (MEFs) are commonly used in research on the molecular mechanism(s) of inflammation because of its good response to inflammatory stimuli. However, the difference in inflammatory reaction between MEFs and macrophages, a classical inflammatory cell type, has not been identified. In this study, we report that both mRNA and protein levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in MEFs upon lipopolysaccharides (LPS) stimulation were significantly lower than those in bone marrow-derived macrophages (BMDMs). MAPK, NF-κB, and IRF3 pathways control the expression and production of inflammatory activated in LPS-stimulated MEFs, but showed different activation patterns in comparison with LPS-stimulated BMDMs. Upon LPS stimulation, activation of the MAPK pathway was slow and remarkably weaker in MEFs than that in BMDMs, whereas more pronounced activation of both NF-κB and IRF3 pathways was observed in MEFs compared to BMDMs. This difference in the activation of MAPK, NF-κB, and IRF3 pathways may result in different production of IL-6 and TNF-α between MEFs and BMDMs. We further revealed that substantial differences in more additional inflammatory response-related cytokines exist between LPS-stimulated MEFs and BMDMs. In conclusion, MEFs exhibit good responsiveness to LPS as a target cell for inflammation-related research. However, MEFs cannot replace macrophages because of substantial differences in their inflammatory reactivity.

Regulation of signal transduction by spatial parameters: a case in NF-κB oscillation

NF-κB is a transcription factor regulating expression of more than 500 genes, and its dysfunction leads to the autoimmune and inflammatory diseases. In malignant cancer cells, NF-κB is constitutively activated. Thus the elucidation of mechanisms for NF-κB regulation is important for the establishment of therapeutic treatment caused by incorrect NF-κB responses. Cytoplasmic NF-κB translocates to the nucleus by the application of extracellular stimuli such as cytokines. Nuclear NF-κB is known to oscillate with the cycle of 1.5-4.5 h, and it is thought that the oscillation pattern regulates the expression profiles of genes. In this review, first we briefly describe regulation mechanisms of NF-κB. Next, published computational simulations on the oscillation of NF-κB are summarised. There are at least 60 reports on the computational simulation and analysis of NF-κB oscillation. Third, the importance of a 'space' for the regulation of oscillation pattern of NF-κB is discussed, showing altered oscillation pattern by the change in spatial parameters such as diffusion coefficient, nuclear to cytoplasmic volume ratio (N/C ratio), and transport through nuclear membrane. Finally, simulations in a true intracellular space (TiCS), which is an intracellular 3D space reconstructed in a computer with organelles such as nucleus and mitochondria are discussed.