Ras participates in the activation of p38 MAPK by interleukin-1 by associating with IRAK, IRAK2, TRAF6, and TAK-1

TRPV4 mediates IL-1-induced Ca2+ signaling, ERK activation and MMP expression

Ca2+ permeation through TRPV4 in fibroblasts is associated with pathological matrix degradation. In human gingival fibroblasts, IL-1β binding to its signaling receptor (IL-1R1) induces activation of extracellular regulated kinase (ERK) and MMP1 expression, processes that require Ca2+ flux across the plasma membrane. It is not known how IL-1R1, which does not conduct Ca2+, generates Ca2+ signals in response to IL-1. We examined whether TRPV4 mediates the Ca2+ fluxes required for ERK signaling in IL-1 stimulated gingival fibroblasts. TRPV4 was immunostained in fibroblasts of human gingival connective tissue and in focal adhesions of cultured mouse gingival fibroblasts. Human gingival fibroblasts treated with IL-1β showed no change of TRPV4 expression but there was increased MMP1 expression. In mouse, gingival fibroblasts expressing TRPV4, IL-1 strongly increased [Ca2+]i. Pre-incubation of cells with IL-1 Receptor Antagonist blocked Ca2+ entry induced by IL-1 or the TRPV4 agonist GSK101. Knockout of TRPV4 or expression of a non-Ca2+-conducting TRPV4 pore-mutant or pre-incubation with the TRPV4 inhibitor RN1734, blocked IL-1-induced Ca2+ transients and expression of the mouse interstitial collagenase, MMP13. Treatment of mouse gingival fibroblasts with GSK101 phenocopied Ca2+ and ERK responses induced by IL-1; these responses were absent in TRPV4-null cells or cells expressing a non-conducting TRPV4 pore-mutant. Immunostained IL-1R1 localized with TRPV4 in adhesions within cell extensions. While TRPV4 immunoprecipitates analyzed by mass spectrometry showed no association with IL-1R1, TRPV4 associated with Src-related proteins and Src co-immunoprecipitated with TRPV4. Src inhibition reduced IL-1-induced Ca2+ responses. The functional linkage of TRPV4 with IL-1R1 expands its repertoire of innate immune signaling processes by mediating IL-1-driven Ca2+ responses that drive matrix remodeling in fibroblasts. Thus, inhibiting TRPV4 activity may provide a new pharmacological approach for blunting matrix degradation in inflammatory diseases.

Small Heterodimer Partner Modulates Macrophage Differentiation during Innate Immune Response through the Regulation of Peroxisome Proliferator Activated Receptor Gamma, Mitogen-Activated Protein Kinase, and Nuclear Factor Kappa B Pathways

Hepatic macrophages act as the liver's first line of defense against injury. Their differentiation into proinflammatory or anti-inflammatory subpopulations is a critical event that maintains a delicate balance between liver injury and repair. In our investigation, we explored the influence of the small heterodimer partner (SHP), a nuclear receptor primarily associated with metabolism, on macrophage differentiation during the innate immune response. During macrophage differentiation, we observed significant alterations in Shp mRNA expression. Deletion of Shp promoted M1 differentiation while interfering with M2 polarization. Conversely, overexpression of SHP resulted in increased expression of peroxisome proliferator activated receptor gamma (Pparg), a master regulator of anti-inflammatory macrophage differentiation, thereby inhibiting M1 differentiation. Upon lipopolysaccharide (LPS) injection, there was a notable increase in the proinflammatory M1-like macrophages, accompanied by exacerbated infiltration of monocyte-derived macrophages (MDMs) into the livers of Shp myeloid cell specific knockout (Shp-MKO). Concurrently, we observed significant induction of tumor necrosis factor alpha (Tnfa) and chemokine (C-C motif) ligand 2 (Ccl2) expression in LPS-treated Shp-MKO livers. Additionally, the mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NF-κB) pathways were activated in LPS-treated Shp-MKO livers. Consistently, both pathways were hindered in SHP overexpression macrophages. Finally, we demonstrated that SHP interacts with p65, thereby influencing macrophage immune repones. In summary, our study uncovered a previously unrecognized role of SHP in promoting anti-inflammatory macrophage differentiation during the innate immune response. This was achieved by SHP acting as a regulator for the Pparg, MAPK, and NF-κB pathways.

Network pharmacology-based analysis in determining the mechanisms of Huoxin pill in protecting against myocardial infarction

CONTEXT

Huoxin pill (HXP) is a commonly used TCM prescription for treatment of cardiovascular diseases. However, its mechanism in protecting against myocardial infarction (MI) remains unknown.

OBJECTIVE

We performed a network pharmacology analysis to explore the bioactive ingredients, therapeutic effects, and mechanisms of HXP in protecting against MI.

MATERIALS AND METHODS

HPLC was used to identify major bioactive compounds, and overlap with MI target genes were visualised. 10-Week old C57BL/6 mice were randomly assigned as: Sham-operated control, MI + Phosphate buffered saline (PBS), and MI + HXP (3 mg/mL and 9 mg/mL) treatment groups, received oral gavage administration once every two-days starting from 1-week prior to MI, and subsequently MI models were established for one-week before sacrifice.

RESULTS

AKT1, VEGFA, TNF and RELA were identified as core target proteins among eighty-five candidate bioactive compounds identified in HXP with overlapping MI-related genes. HXP protection against MI was mainly via regulation of inflammatory pathways, notably TNF signalling pathway. Mouse models of MI and cardiac myoblasts demonstrated that HXP improved MI-induced injury via improving regulation of inflammatory response.

DISCUSSION AND CONCLUSION

Stellasterol, deoxycholic acid, kaempferol, and quercetin are important active compounds contained in HXP with anti-inflammatory properties in the therapeutic treatment of MI. Due to the straightforward nature and effectiveness of taking oral HXP medications, our findings provide a theoretical basis for the clinical application of HXP in treating patients with angina or myocardial ischaemia. Future research into the combination of surgical procedures or medications that restore blood flow together with HXP as supportive medication would be worthwhile.

The Role of DNA Damage Response in Dysbiosis-Induced Colorectal Cancer

The high incidence of colorectal cancer (CRC) in developed countries indicates a predominant role of the environment as a causative factor. Natural gut microbiota provides multiple benefits to humans. Dysbiosis is characterized by an unbalanced microbiota and causes intestinal damage and inflammation. The latter is a common denominator in many cancers including CRC. Indeed, in an inflammation scenario, cellular growth is promoted and immune cells release Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS), which cause DNA damage. Apart from that, many metabolites from the diet are converted into DNA damaging agents by microbiota and some bacteria deliver DNA damaging toxins in dysbiosis conditions as well. The interactions between diet, microbiota, inflammation, and CRC are not the result of a straightforward relationship, but rather a network of multifactorial interactions that deserve deep consideration, as their consequences are not yet fully elucidated. In this paper, we will review the influence of dysbiosis in the induction of DNA damage and CRC.

Ras Isoforms from Lab Benches to Lives-What Are We Missing and How Far Are We?

The central protein in the oncogenic circuitry is the Ras GTPase that has been under intense scrutiny for the last four decades. From its discovery as a viral oncogene and its non-oncogenic contribution to crucial cellular functioning, an elaborate genetic, structural, and functional map of Ras is being created for its therapeutic targeting. Despite decades of research, there still exist lacunae in our understanding of Ras. The complexity of the Ras functioning is further exemplified by the fact that the three canonical Ras genes encode for four protein isoforms (H-Ras, K-Ras4A, K-Ras4B, and N-Ras). Contrary to the initial assessment that the H-, K-, and N-Ras isoforms are functionally similar, emerging data are uncovering crucial differences between them. These Ras isoforms exhibit not only cell-type and context-dependent functions but also activator and effector specificities on activation by the same receptor. Preferential localization of H-, K-, and N-Ras in different microdomains of the plasma membrane and cellular organelles like Golgi, endoplasmic reticulum, mitochondria, and endosome adds a new dimension to isoform-specific signaling and diverse functions. Herein, we review isoform-specific properties of Ras GTPase and highlight the importance of considering these towards generating effective isoform-specific therapies in the future.

Mechanisms by which mastitis affects reproduction in dairy cow: A review

Reproductive performance is a key factor in determining the profitability of dairy farm, which is affected by many factors such as environment and diseases. Mastitis is a common and important disease, which has caused huge economic losses to the dairy industries worldwide. Mammary gland infection causes immune responses, resulting in the abnormal secretion of cytokines and hormones and abnormal function of the reproductive system such as the ovary, corpus luteum, uterus and embryo. Cows with mastitis have delayed oestrus, decreased pregnancy rate and increased risk of abortion. The adverse effects of mastitis on reproductive performance are affected by many factors, such as occurrence time, pathogen and cow factors. This paper primarily reviews the progress in the effects and mechanisms of mastitis on reproductive performance, with emphasis on maternal transcriptome, genomic analysis, epigenetic modification, microbiota, inflammatory regulation and immune evasion mechanism of mastitis, aiming to provide directions for the prevention and control of mastitis in the future.

The Leucine-Rich Repeat Region of CARMIL1 Regulates IL-1-Mediated ERK Activation, MMP Expression, and Collagen Degradation

CARMILs are large, multidomain, membrane-associated proteins that regulate actin assembly and Rho-family GTPases, but their role in inflammatory signaling is not defined. Tandem mass tag mass spectrometry indicated that, in fibroblasts, CARMIL1 associates with interleukin (IL)-1 signaling molecules. Immunoprecipitation of cells transfected with CARMIL1 mutants showed that the leucine-rich repeat (LRR) region of CARMIL1 associates with IL-1 receptor type 1 (IL-1R1) and IL-1 receptor-associated kinase (IRAK). Knockout of CARMIL1 by CRISPR-Cas9 reduced IL-1-induced ERK activation by 72% and MMP3 expression by 40%. Compared with CARMIL1 wild-type (WT), cells expressing mutant CARMIL1 lacking its LRR domain exhibited 45% lower ERK activation and 40% lower MMP3 expression. In fibroblasts transduced with a cell-permeable, TAT CARMIL1 peptide that competed with IL-1R1 and IRAK binding to the LRR of CARMIL1, collagen degradation was reduced by 43%. As the LRR of CARMIL1 evidently regulates IL-1 signaling, CARMIL1 could become a target for anti-inflammatory drug development.

Highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) induces IL-6 production through TAK-1/JNK/AP-1 and TAK-1/NF-κB signaling pathways

Porcine reproductive and respiratory syndrome virus (PRRSV) mainly infects monocyte/macrophage lineage and regulates the production of cytokines to influence host immune responses. Interleukin-6 (IL-6) is originally identified as a B-cell stimulatory factor and has important functions in regulating immune response, hemopoiesis, and inflammation. In this study, we verified that highly pathogenic PRRSV (HP-PRRSV) infection up-regulated IL-6 production in vivo and in vitro. Subsequently, we demonstrated that HP-PRRSV infection activated JNK and NF-κB signaling pathways to enhance IL-6 expression. We further showed that TAK-1 was important in the activation of JNK and NF-κB pathways following HP-PRRSV infection. Moreover, AP-1 and NF-κB binding motifs were found in the cloned porcine IL-6 (pIL-6) promoter, and deletion of these motifs abrogated the activation of pIL-6 promoter by HP-PRRSV, suggesting that IL-6 expression is dependent on AP-1 and NF-κB activation. These findings imply that IL-6 induced by HP-PRRSV infection is dependent on the activation of TAK-1/JNK/AP-1 and TAK-1/NF-κB signaling pathways.

ROS Generation in Microglia: Understanding Oxidative Stress and Inflammation in Neurodegenerative Disease

Neurodegenerative disorders, such as Alzheimer's disease, are a global public health burden with poorly understood aetiology. Neuroinflammation and oxidative stress (OS) are undoubtedly hallmarks of neurodegeneration, contributing to disease progression. Protein aggregation and neuronal damage result in the activation of disease-associated microglia (DAM) via damage-associated molecular patterns (DAMPs). DAM facilitate persistent inflammation and reactive oxygen species (ROS) generation. However, the molecular mechanisms linking DAM activation and OS have not been well-defined; thus targeting these cells for clinical benefit has not been possible. In microglia, ROS are generated primarily by NADPH oxidase 2 (NOX2) and activation of NOX2 in DAM is associated with DAMP signalling, inflammation and amyloid plaque deposition, especially in the cerebrovasculature. Additionally, ROS originating from both NOX and the mitochondria may act as second messengers to propagate immune activation; thus intracellular ROS signalling may underlie excessive inflammation and OS. Targeting key kinases in the inflammatory response could cease inflammation and promote tissue repair. Expression of antioxidant proteins in microglia, such as NADPH dehydrogenase 1 (NQO1), is promoted by transcription factor Nrf2, which functions to control inflammation and limit OS. Lipid droplet accumulating microglia (LDAM) may also represent a double-edged sword in neurodegenerative disease by sequestering peroxidised lipids in non-pathological ageing but becoming dysregulated and pro-inflammatory in disease. We suggest that future studies should focus on targeted manipulation of NOX in the microglia to understand the molecular mechanisms driving inflammatory-related NOX activation. Finally, we discuss recent evidence that therapeutic target identification should be unbiased and founded on relevant pathophysiological assays to facilitate the discovery of translatable antioxidant and anti-inflammatory therapeutics.

Regeneration Enhances Metastasis: A Novel Role for Neurovascular Signaling in Promoting Melanoma Brain Metastasis

Neural repair after stroke involves initiation of a cellular proliferative program in the form of angiogenesis, neurogenesis, and molecular growth signals in the surrounding tissue elements. This cellular environment constitutes a niche in which regeneration of new blood vessels and new neurons leads to partial tissue repair after stroke. Cancer metastasis has similar proliferative cellular events in the brain and other organs. Do cancer and CNS tissue repair share similar cellular processes? In this study, we identify a novel role of the regenerative neurovascular niche induced by stroke in promoting brain melanoma metastasis through enhancing cellular interactions with surrounding niche components. Repair-mediated neurovascular signaling induces metastatic cells to express genes crucial to metastasis. Mimicking stroke-like conditions in vitro displays an enhancement of metastatic migration potential and allows for the determination of cell-specific signals produced by the regenerative neurovascular niche. Comparative analysis of both in vitro and in vivo expression profiles reveals a major contribution of endothelial cells in mediating melanoma metastasis. These results point to a previously undiscovered role of the regenerative neurovascular niche in shaping the tumor microenvironment and brain metastatic landscape.

TranscriptAchilles: a genome-wide platform to predict isoform biomarkers of gene essentiality in cancer

BACKGROUND

Aberrant alternative splicing plays a key role in cancer development. In recent years, alternative splicing has been used as a prognosis biomarker, a therapy response biomarker, and even as a therapeutic target. Next-generation RNA sequencing has an unprecedented potential to measure the transcriptome. However, due to the complexity of dealing with isoforms, the scientific community has not sufficiently exploited this valuable resource in precision medicine.

FINDINGS

We present TranscriptAchilles, the first large-scale tool to predict transcript biomarkers associated with gene essentiality in cancer. This application integrates 412 loss-of-function RNA interference screens of >17,000 genes, together with their corresponding whole-transcriptome expression profiling. Using this tool, we have studied which are the cancer subtypes for which alternative splicing plays a significant role to state gene essentiality. In addition, we include a case study of renal cell carcinoma that shows the biological soundness of the results. The databases, the source code, and a guide to build the platform within a Docker container are available at GitLab. The application is also available online.

CONCLUSIONS

TranscriptAchilles provides a user-friendly web interface to identify transcript or gene biomarkers of gene essentiality, which could be used as a starting point for a drug development project. This approach opens a wide range of translational applications in cancer.

Regulation of IL-1 signaling through control of focal adhesion assembly

IL-1 signaling is adhesion-restricted in many cell types, but the mechanism that drives it is not defined. We screened for proteins recruited to nascent adhesions in IL-1-treated human fibroblasts with tandem mass tag-mass spectrometry. We used fibronectin bead preparations to enrich 10 actin-associated proteins. There was a 1.2 times log 2-fold enrichment of actin capping protein (ACP) at 30 min after IL-1 stimulation. Knockdown (KD) of ACP by siRNA reduced IL-1-induced ERK activation(by 56%, matrix metalloproteinase-3 (MMP-3) expression by 48%, and MMP-9 expression by 62% (in all reductions, P < 0.01). Confocal or structured illumination microscopy showed that ACP was diffused throughout the cytosol but strongly accumulated at the ruffled border of spreading cells. ACP colocalized with nascent paxillin- and vinculin-containing adhesions at the ruffled border, but not with mature adhesions in the center. ACP KD promoted the formation of large, stable adhesions. Immunoprecipitation and proximity ligation analysis showed that ACP was associated with the IL-1 signal transduction proteins myeloid differentiation factor 88 (MyD88) and IL-1 receptor-associated kinase (IRAK) at the ruffled border of the leading edge. IL-1-induced phospho-ERK and MyD88 or IRAK colocalized at the leading edge. We concluded that ACP is required for recruitment and function of IL-1 signaling complexes in nascent adhesions at the leading edge of the cell.-Wang, Q., Delcorde, J., Tang, T., Downey, G. P., McCulloch, C. A. Regulation of IL-1 signaling through control of focal adhesion assembly.

Molluscum Contagiosum Virus Protein MC005 Inhibits NF-κB Activation by Targeting NEMO-Regulated IκB Kinase Activation

Molluscum contagiosum virus (MCV), the only known extant human-adapted poxvirus, causes a long-duration infection characterized by skin lesions that typically display an absence of inflammation despite containing high titers of live virus. Despite this curious presentation, MCV is very poorly characterized in terms of host-pathogen interactions. The absence of inflammation around MCV lesions suggests the presence of potent inhibitors of human antiviral immunity and inflammation. However, only a small number of MCV immunomodulatory genes have been characterized in detail. It is likely that many more remain to be discovered, given the density of such sequences in other poxvirus genomes. NF-κB activation occurs in response to both virus-induced pattern recognition receptor (PRR) signaling and cellular activation by virus-induced proinflammatory cytokines like tumor necrosis factor and interleukin-1. Activated NF-κB drives cytokine and interferon gene expression, leading to inflammation and virus clearance. We report that MC005, which has no orthologs in other poxvirus genomes, is a novel inhibitor of PRR- and cytokine-stimulated NF-κB activation. MC005 inhibited NF-κB proximal to the IκB kinase (IKK) complex, and unbiased affinity purification revealed that MC005 interacts with the IKK subunit NEMO (NF-κB essential modulator). MC005 binding to NEMO prevents the conformational priming of the IKK complex that occurs when NEMO binds to ubiquitin chains during pathway activation. These data reveal a novel mechanism of poxvirus inhibition of human innate immunity, validate current dynamic models of NEMO-dependent IKK complex activation, and further clarify how the human-adapted poxvirus MCV can so effectively evade antiviral immunity and suppress inflammation to persist in human skin lesions.IMPORTANCE Poxviruses adapt to specific hosts over time, evolving and tailoring elegantly precise inhibitors of the rate-limiting steps within the signaling pathways that control innate immunity and inflammation. These inhibitors reveal new features of the antiviral response, clarify existing models of signaling regulation while offering potent new tools for approaching therapeutic intervention in autoimmunity and inflammatory disease. Molluscum contagiosum virus (MCV) is the only known extant poxvirus specifically adapted to human infection and appears adept at evading normal human antiviral responses, yet it remains poorly characterized. We report the identification of MCV protein MC005 as an inhibitor of the pathways leading to the activation of NF-κB, an essential regulator of innate immunity. Further, identification of the mechanism of inhibition of NF-κB by MC005 confirms current models of the complex way in which NF-κB is regulated and greatly expands our understanding of how MCV so effectively evades human immunity.

Upregulation of p38 pathway accelerates proliferation and migration of MDA-MB-231 breast cancer cells

Tumor cells capture the signaling pathways used by normal tissue to promote their own survival and dissemination and among them, the NF-κB and MAPK pathways (ERK, JNK and p38). MAPK activation has ambiguous effects on tumor cell fate depending on cell type, cancer stage and the engaged MAPK isoforms. A synthetic peptide named LyeTx II, derived from the venom of the Brazilian spider Lycosa erythrognatha, was capable of increasing MDA-MB-231 aggressive breast cancer cell proliferation as indicated by MTT and BrdU (5-bromo-2'-deoxyuridine) incorporation assay and cell migration. A correlation has been established between the accelerated proliferation and migration observed in the presence of LyeTx II and the upregulation of p38 MAPK phosphorylation. The use of the selective inhibitor of p38α/β (SB203580) abrogated the peptide effect in MDA-MB-231 cells. Besides, an augment of the canonical NF-κB pathway activation considered as crucial in cancer progression was noted after cell incubation with LyeTx II. Importantly, activation of p38 and NF-κB pathways was dependent on TAK1 activity. Together, these data suggest that TAK1-p38 pathway may represent an interesting target for treatment of aggressive breast cancers.

Lactobacillus paracasei modulates LPS-induced inflammatory cytokine release by monocyte-macrophages via the up-regulation of negative regulators of NF-kappaB signaling in a TLR2-dependent manner

The application of the probiotic lactobacillus is suggested in the treatment of some inflammatory diseases of intestines due to its potential ability to attenuate inflammation. However, the mechanism is not completely understood. In PBMCs, Lactobacillus paracasei (L. Paracasei) down-regulated the LPS-induced production of TNF-α and IL-6. Using a macrophage-like differentiated THP-1 cell line induced by PMA, we investigated the effect of L. paracasei on the production of pro-inflammatory cytokines by monocyte-macrophages. Treatment of the differentiated THP-1 cells with L. paracasei either concurrently with or before LPS challenge attenuated the LPS-induced secretion of TNF-α and IL-1β. This effect was due to a decrease in IκB phosphorylation and NF-κB nuclear translocation. Furthermore, treatment of the differentiated THP-1 cells with L. paracasei induced the expression of negative regulators of the NF-κB signaling pathway, including the deubiquitinating enzyme A20, suppressor of cytokine signaling (SOCS) 1, SOCS3, and IL-1 receptor-associated kinase (IRAK) 3. Pretreatment with an IRAK4 inhibitor suppressed the L. paracasei-induced expression of these negative regulators and further increased the LPS-mediated expressions of TNF-α and IL-1β. Moreover, treatment with an antibody against Toll-like receptor (TLR) 2 reversed the effect of L. paracasei on inducing negative regulators and inhibiting TNF-α and IL-1β productions. Our findings suggest that L. paracasei inhibits the production of pro-inflammatory cytokines by monocyte-macrophages via the induction of negative regulators of the NF-κB signaling pathway in a TLR2-IRAK4-dependent manner.

Ginkgolides and bilobalide protect BV2 microglia cells against OGD/reoxygenation injury by inhibiting TLR2/4 signaling pathways

Ginkgolide and bilobalide are major trilactone constituent of Ginkgo biloba leaves and have been shown to exert powerful neuroprotective properties. The aims of this study were to observe the inhibitory effects of ginkgolide and bilobalide on the activation of microglial cells induced by oxygen-glucose deprivation and reoxygenation (OGD/R) and the specific mechanisms by which these effects are mediated. For detecting whether ginkgolide and bilobalide increased cell viability in a dose-dependent manner, BV2 cells were subjected to oxygen-glucose deprivation for 4 h followed by 3 h reoxygenation with various concentrations of drugs (6.25, 12.5, 25, 50, and 100 μg/ml). The extent of apoptosis effect of OGD/R with or without ginkgolide and bilobalide treatment were also measured by Annexin V-FITC/PI staining. Similarly, the levels of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, IL-8, and IL-10 were detected using a specific Bio-Plex Pro™ Reagent Kit. The effects of ginkgolide and bilobalide on protein levels of TLR2/4, MyD88, p-TAK1, p-IKKβ, p-IkBα, NF-κB p65, Bcl-2, Bax, Bak, RIP3, cleaved-Caspase-3, cleaved PARP-1 and cellular localization of NF-κB p65 were evaluated by Western blot and double-labeled immunofluorescence staining, respectively. OGD/R significantly decreased the cell viability and increased the release of IL-1β, IL-6, IL-8, IL-10, TNF-α in BV2 microglia cells; these effects were suppressed by ginkgolide and bilobalide. Meanwhile, ginkgolide and bilobalide also attenuated the OGD/R-induced increases in TLR2, TLR4, MyD88, Bak, RIP3 levels and reversed cleaved caspase-3/caspase-3, Bax/Bcl-2 and cleaved PARP-1/PARP-1 ratio. Furthermore, ginkgolide and bilobalide also downregulated p-TAK1, p-IkBα, and p-IKKβ and inhibited the OGD/R-induced transfer of NF-κB p65 from cytoplasm to nucleus in BV2 microglia cells. The results showed that ginkgolide and bilobalide can inhibit OGD/R-induced production of inflammatory factors in BV2 microglia cells by regulating the TLRs/MyD88/NF-κB signaling pathways and attenuating inflammatory response. The possible mechanism of anti-inflammatory and neuroprotective effects of ginkgolides results from the synergistic reaction among each monomer constituents.

Overexpression of CD14, TLR4, and MD-2 in HEK 293T cells does not prevent induction of in vitro endotoxin tolerance

TLR4 and MD-2 are necessary for conferring cellular responsiveness to LPS. Prior exposure to LPS induces a transient state of cell refractoriness to subsequent LPS re-stimulation, known as `endotoxin tolerance'. While induction of LPS tolerance has been reported to correlate with down-regulation of cell surface expression of TLR4/MD-2, other mechanisms of LPS tolerance have been revealed that target intracellular intermediates downstream of the TLR4/MD-2 complex. In this study, we sought to examine whether endotoxin tolerance could be induced under conditions where expression of TLR4 and MD-2 proteins is not affected by LPS. Human HEK 293T cells are completely unresponsive to LPS, but acquire high LPS sensitivity following transient transfection with CD14, TLR4, and MD-2 (293T/CD14/TLR4/MD-2 cells), as judged by NF-κB activation, ERK 1/2 phosphorylation, and TNFα gene expression. Prior exposure of 293T/CD14/TLR4/MD-2 cells to LPS resulted in a significant decrease of LPS-mediated responses, yet failed to affect expression levels of TLR4 and MD-2. Thus, altered expression and/or function of intracellular mediators downstream of the TLR4/MD-2 complex play an important role in mediating LPS tolerance.

Review: Molecular mechanisms of endotoxin tolerance

The phenomenon of endotoxin tolerance has been widely investigated, but to date, the molecular mechanisms of endotoxin tolerance remain to be resolved clearly. The discovery of the Toll-like receptor (TLR) family as the major receptors for lipopolysaccharide (LPS) and other bacterial products has prompted a resurgence of interest in endotoxin tolerance mechanisms. Changes of cell surface molecules, signaling proteins, pro-inflammatory and anti -inflammatory cytokines and other mediators have been examined. During tolerance expression of LPS-binding protein (LBP), CD14, myeloid differentiation protein-2 (MD-2) and TLR2 are unchanged or up-regulated, whereas TLR4 is transiently suppressed or unchanged. Proximal post-receptor signaling proteins that are altered in tolerance include augmented degradation of interleukin-1 receptor-associated kinase (IRAK), and decreased TLR4-myeloid differentiation factor 88 (MyD88) and IRAK-MyD88 association. Tolerance has also been shown to be associated with decreased Gi protein content and activity, decreased protein kinase C (PKC) activity, reduction in mitogen-activated protein kinase (MAP kinase) activity, and reduced activator protein-1 (AP-1) and nuclear factor kappa B (NF-κB) induced gene transactivation. However, not all signaling proteins and pathways are suppressed in tolerance and induction of specific anti-inflammatory proteins and signaling pathways may serve important counter inflammatory functions. The latter include induction of IRAK-M and suppressor of cytokine-signaling-1 (SOCS-1), phosphoinositide-3-kinase (PI3K) signaling, and increased or maintained expression of inhibitor-κB (IκB) isoforms. Also at the nuclear level, increase in the NFκB subunit p50 homodimer expression and increased activation of peroxisome-proliferatoractivated receptors-γ (PPARγ) have been linked to tolerance phenotype. Although there are species and cellular variations in manifestation of the LPS tolerant phenotype, it is clear that the tolerance phenomena have evolved as a complex orchestrated counter regulatory response to inflammation.

Model Predicts That MKP1 and TAB1 Regulate p38α Nuclear Pulse and Its Basal Activity through Positive and Negative Feedback Loops in Response to IL-1

Interleukin-1 mediates inflammation and stress response through nuclear activity of p38α. Although IL-1 receptor is not degraded, p38α activation is transient. IL-1 also causes cell migration and EMT by modulating cell-cell junctions. Although molecules involved in p38 activation are known, mechanism of the transient nuclear response and its basal activity remains unknown. By mathematical modeling of IL1/p38 signaling network, we show that IL-1 induces robust p38α activation both in the nucleus and in the cytoplasm/membrane. While nuclear response consists of an acute phase, membrane response resembles a step change. Following stimulation, p38α activity returns to a basal level in absence of receptor degradation. While nuclear pulse is controlled by MKP1 through a negative feedback to pp38, its basal activity is controlled by both TAB1 and MKP1 through a positive feedback loop. Our model provides insight into the mechanism of p38α activation, reason for its transient nuclear response, and explanation of the basal activity of MKK3/6 and p38α, which has been experimentally observed by other groups.

Human oral isolate Lactobacillus fermentum AGR1487 induces a pro-inflammatory response in germ-free rat colons

Lactobacilli are thought to be beneficial for human health, with lactobacilli-associated infections being confined to immune-compromised individuals. However, Lactobacillus fermentum AGR1487 negatively affects barrier integrity in vitro so we hypothesized that it caused a pro-inflammatory response in the host. We compared germ-free rats inoculated with AGR1487 to those inoculated with another L. fermentum strain, AGR1485, which does not affect in vitro barrier integrity. We showed that rats inoculated with AGR1487 had more inflammatory cells in their colon, higher levels of inflammatory biomarkers, and increased colonic gene expression of pro-inflammatory pathways. In addition, our in vitro studies showed that AGR1487 had a greater capacity to activate TLR signaling and induce pro-inflammatory cytokines in immune cells. This study indicates the potential of strains of the same species to differentially elicit inflammatory responses in the host and highlights the importance of strain characterization in probiotic approaches to treat inflammatory disorders.

Poxvirus Protein MC132 from Molluscum Contagiosum Virus Inhibits NF-B Activation by Targeting p65 for Degradation

Molluscum contagiosum virus (MCV) is unique in being the only known extant, human-adapted poxvirus, yet to date, it is very poorly characterized in terms of host-pathogen interactions. MCV causes persistent skin lesions filled with live virus, but these are generally immunologically silent, suggesting the presence of potent inhibitors of human antiviral immunity and inflammation. Fewer than five MCV immunomodulatory genes have been characterized in detail, but it is likely that many more remain to be discovered given the density of such sequences in all well-characterized poxviruses. Following virus infection, NF-B activation occurs in response to both pattern recognition receptor (PRR) signaling and cellular activation by virus-elicited proinflammatory cytokines, such as tumor necrosis factor (TNF). As such, NF-B activation is required for virus detection, antiviral signaling, inflammation, and clearance of viral infection. Hence, we screened a library of MCV genes for effects on TNF-stimulated NF-B activation. This revealed MC132, a unique protein with no orthologs in other poxviral genomes, as a novel inhibitor of NF-B. Interestingly, MC132 also inhibited PRR- and virus-activated NF-B, since MC132 interacted with the NF-B subunit p65 and caused p65 degradation. Unbiased affinity purification to identify host targets of MC132 revealed that MC132 acted by targeting NF-B p65 for ubiquitin-dependent proteasomal degradation by recruiting p65 to a host Cullin-5/Elongin B/Elongin C complex. These data reveal a novel mechanism for poxviral inhibition of human innate immunity and further clarify how the human-adapted poxvirus MCV can so effectively evade antiviral immunity to persist in skin lesions.

Effect of NADPH oxidase inhibitor-apocynin on the expression of Src homology-2 domain-containing phosphatase-1 (SHP-1) exposed renal ischemia/reperfusion injury in rats

This study was designed to evaluate whether NADPH oxidase inhibitor (apocynin) preconditioning induces expression of Src homology-2 domain-containing phosphatase-1 (SHP-1) to protect against renal ischemia/reperfusion (I/R) injury (RI/RI) in rats. Rats were pretreated with 50 mg/kg apocynin, then subjected to 45 min ischemia and 24 h reperfusion. The results indicated that apocynin preconditioning improved the recovery of renal function and nitroso-redox balance, reduced oxidative stress injury and inflammation damage, and upregulated expression of SHP-1 as compared to RI/RI group. Therefore our study demonstrated that apocynin preconditioning provided a protection to the kidney against I/R injury in rats partially through inducing expression of SHP-1.

Regulatory effects of AT₁R-TRAF6-MAPKs signaling on proliferation of intermittent hypoxia-induced human umbilical vein endothelial cells

Endothelial dysfunction induced by intermittent hypoxia (IH) participates in obstructive sleep apnea syndrome (OSAS)-associated cardiovascular disorders. Myeloid differentiation primary response 88 (MyD88) and tumor necrosis factor receptor-associated factor 6 (TRAF6) regulate numerous downstream adaptors like mitogen-activated protein kinases (MAPKs) and the subsequent oxidative stress and inflammatory responses. This study aimed to characterize the role of MyD88/TRAF6 in IH-treated cell function and its associated signaling. Human umbilical vein endothelial cells (HUVECs) were randomly exposed to IH or normoxia for 0, 2, 4 and 6 h. Western blotting was used to detect the expression pattern of target gene proteins [angiotensin 1 receptor (AT1R), p-ERK1/2, p-p38MAPK, MyD88 and TRAF6], and the relationships among these target genes down-regulated by the corresponding inhibitors were studied. Finally, the influence of these target genes on proliferation of HUVECs was also assessed by EdU analysis. Protein levels of AT1R, TRAF6 and p-ERK1/2 were increased after IH exposure, with a slight rise in MyD88 and a dynamic change in p-p38MAPK. The down-regulation of TRAF6 by siRNA reduced ERK1/2 phosphorylation during IH without any effects on AT1R. Blockade of AT1R with valsartan decreased TRAF6 and p-ERK1/2 protein expression after IH exposure. ERK1/2 inhibition with PD98059 suppressed only AT1R expression. IH promoted HUVECs proliferation, which was significantly suppressed by the inhibition of TRAF6, AT1R and ERK1/2. The findings demonstrate that TRAF6 regulates the proliferation of HUVECs exposed to short-term IH by modulating cell signaling involving ERK1/2 downstream of AT1R. Targeting the AT1R-TRAF6-p-ERK1/2 signaling pathway might be helpful in restoring endothelial function.

Geniposide plays an anti-inflammatory role via regulating TLR4 and downstream signaling pathways in lipopolysaccharide-induced mastitis in mice

Geniposide is a medicine isolated from Gardenia jasminoides Ellis, which is a traditional Chinese herb that is widely used in Asia for the treatment of inflammation, brain diseases, and hepatic disorders. Mastitis is a highly prevalent and important infectious disease. In this study, we used a lipopolysaccharide (LPS)-induced mouse mastitis model and LPS-stimulated primary mouse mammary epithelial cells (mMECs) to explore the anti-inflammatory effect and the mechanism of action of geniposide. Using intraductal injection of LPS as a mouse model of mastitis, we found that geniposide significantly reduced the infiltration of inflammatory cells and downregulated the production of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). To further investigate the anti-inflammatory mechanism, we used LPS-stimulated mMECs as an in vitro mastitis model. The results of enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR) showed that geniposide inhibited the expression of TNF-α, IL-1β, and IL-6 in a dose-dependent manner. Western blot analysis demonstrated that geniposide could suppress the phosphorylation of inhibitory kappa B (IκBα), nuclear factor-κB (NF-κB), p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK). Geniposide also inhibited the expression of toll-like receptor 4 (TLR4) in the LPS-stimulated mMECs. In conclusion, geniposide exerted its anti-inflammatory effect by regulating TLR4 expression, which affected the downstream NF-κB and mitogen-activated protein kinase (MAPK) signaling pathways. Thus, geniposide may be a potential drug for mastitis therapy.

Cylindromatosis (CYLD) inhibits Streptococcus pneumonia-induced plasminogen activator inhibitor-1 expression via interacting with TRAF-6

Streptococcus pneumoniae (S. p) remains one of the foremost causes of community-acquired pneumonia. Recent studies have shown that S. p lung infection is associated with plasminogen activator inhibitor-1 (PAI-1) expression, which inhibits acute lung injury. Such effects by S. p were negatively regulated by cylindromatosis (CYLD). The current study explored the underlying mechanisms. We showed that S. p-induced PAI-1 expression requires tumor necrosis factor receptor-associated factor 6 (TRAF-6) signaling. Si-RNA-mediated knockdown of TRAF-6 remarkably inhibited S. p-induced PAI-1 expression. Reversely, over-expression of wild type (wt-) TRAF-6 further potentiated PAI-1 expression in S. p-treated cells. We provided evidences to support that CYLD-mediated anti-PAI-1 activity might be through direct regulation of TRAF-6. Our results from co-immunoprecipitation (co-IP) and confocal microscopy assays confirmed a direct association between the CYLD and TRAF-6 in A549 cells. Over-expression of wt-CYLD remarkably inhibited TRAF-6 ubiquitination and subsequent PAI-1 expression. Introducing a mutated CYLD, on the other hand, enhanced TRAF-6 ubiquitination and PAI-1 expression. Together, these results indicate that TRAF-6 mediates S. p-induced PAI-1 expression, and CYLD inhibits PAI-1 expression probably through deubiquitinating TRAF-6. The current study provided molecular insights of CYLD-mediated activities in S. p-induced PAI-1 expression and possible acute lung injury.

Pellino1-mediated TGF-β1 synthesis contributes to mechanical stress induced cardiac fibroblast activation

Activation of cardiac fibroblasts is a key event in the progression of cardiac fibrosis that leads to heart failure. However, the molecular mechanisms underlying mechanical stress-induced cardiac fibroblast activation are complex and poorly understood. This study demonstrates that Pellino1, an E3 ubiquitin ligase, was activated in vivo in pressure overloaded rat hearts and in cultured neonatal rat cardiac fibroblasts (NRCFs) exposed to mechanical stretch in vitro. Suppression of the expression and activity of Pellino1 by adenovirus-mediated delivery of shPellino1 (adv-shpeli1) attenuated pressure overload-induced cardiac dysfunction and cardiac hypertrophy and decreased cardiac fibrosis in rat hearts. Transfection of adv-shpeli1 also significantly attenuated mechanical stress-induced proliferation, differentiation and collagen synthesis in NRCFs. Pellino1 silencing also abrogated mechanical stretch-induced polyubiquitination of tumor necrosis factor-alpha receptor association factor-6 (TRAF6) and receptor-interacting protein 1 (RIP1) and consequently decreased the DNA binding activity of nuclear factor-kappa B (NF-κB) in NRCFs. In addition, Pellino1 silencing prevented stretch-induced activation of p38 and activator protein 1 (AP-1) binding activity in NRCFs. Chromatin Immunoprecipitation (ChIP) and luciferase reporter assays showed that Pellino1 silencing prevented the binding of NF-κB and AP-1 to the promoter region of transforming growth factor-β1 (TGF-β1) thus dampening TGF-β1 transactivation. Our data reveal a previously unrecognized role of Pellino1 in extracellular matrix deposition and cardiac fibroblast activation in response to mechanical stress and provides a novel target for treatment of cardiac fibrosis and heart failure.

Cholesterol selectively regulates IL-5 induced mitogen activated protein kinase signaling in human eosinophils

Eosinophils function contributes to human allergic and autoimmune diseases, many of which currently lack curative treatment. Development of more effective treatments for eosinophil-related diseases requires expanded understanding of eosinophil signaling and biology. Cell signaling requires integration of extracellular signals with intracellular responses, and is organized in part by cholesterol rich membrane microdomains (CRMMs), commonly referred to as lipid rafts. Formation of these organizational membrane domains is in turn dependent upon the amount of available cholesterol, which can fluctuate widely with a variety of disease states. We tested the hypothesis that manipulating membrane cholesterol content in primary human peripheral blood eosinophils (PBEos) would selectively alter signaling pathways that depend upon membrane-anchored signaling proteins localized within CRMMs (e.g., mitogen activated protein kinase [MAPK] pathway), while not affecting pathways that signal through soluble proteins, like the Janus Kinase/Signal Transducer and Activator of Transcription [JAK/STAT] pathway. Cholesterol levels were increased or decreased utilizing cholesterol-chelating methyl-β-cyclodextrin (MβCD), which can either extract membrane cholesterol or add exogenous membrane cholesterol depending on whether MβCD is preloaded with cholesterol. Human PBEos were pretreated with MβCD (cholesterol removal) or MβCD+Cholesterol (MβCD+Chol; cholesterol delivery); subsequent IL-5-stimulated signaling and physiological endpoints were assessed. MβCD reduced membrane cholesterol in PBEos, and attenuated an IL-5-stimulated p38 and extracellular-regulated kinase 1/2 phosphorylation (p-p38, p-ERK1/2), and an IL-5-dependent increase in interleukin-1β (IL-1β) mRNA levels. In contrast, MβCD+Chol treatment elevated PBEos membrane cholesterol levels and basal p-p38, but did not alter IL-5-stimulated phosphorylation of ERK1/2, STAT5, or STAT3. Furthermore, MβCD+Chol pretreatment attenuated an IL-5-induced increase in cell survival at 48 hours, measured as total cellular metabolism. The reduction in cell survival following cholesterol addition despite unaltered STAT phosphorylation contradicts the current dogma in which JAK/STAT activation is sufficient to promote eosinophil survival, and suggests an additional, unidentified mechanism critically regulates IL-5-mediated human PBEos survival.

RasGRP3 limits Toll-like receptor-triggered inflammatory response in macrophages by activating Rap1 small GTPase

Host immune cells can detect and destruct invading pathogens via pattern-recognition receptors. Small Rap GTPases act as conserved molecular switches coupling extracellular signals to various cellular responses, but their roles as regulators in Toll-like receptor (TLR) signalling have not been fully elucidated. Here we report that Ras guanine nucleotide-releasing protein 3 (RasGRP3), a guanine nucleotide-exchange factor activating Ras and Rap1, limits production of proinflammatory cytokines (especially IL-6) in macrophages by activating Rap1 on activation by low levels of TLR agonists. We demonstrate that RasGRP3, a dominant member of RasGRPs in macrophages, impairs TLR3/4/9-induced IL-6 production and relieves dextrane sulphate sodium-induced colitis and collagen-induced arthritis. In RasGRP3-deficient RAW264.7 cells obtained by CRISPR-Cas9 genome editing, TLR3/4/9-induced activation of Rap1 was inhibited while ERK1/2 activation was enhanced. Our study suggests that RasGRP3 limits inflammatory response by activating Rap1 on low-intensity pathogen infection, setting a threshold for preventing excessive inflammatory response.

Toll like receptors (TLRs) couple microbial sensing to initiation of immune responses, which are essential for defense against pathogens but may cause immunopathology when activated excessively. Here the authors show that RasGRP3 sets a threshold of TLR activation to prevent immunopathology.

The same and not the same: heterogeneous functional activation of prostate tumor cells by TLR ligation

Background

Many types of tumors are organized in a hierarchy of heterogeneous cell populations with different molecular signature. Such heterogeneity may be associated with different responsiveness to microenvironment stimuli. In the present study, the effects of lipopolysaccharide (LPS) and lipoteichoic acid (LTA), as well-known mediators of inflammation, on cancerous behavior of three prostate tumor cells, LNCaP, PC3 and DU145, were investigated.

Methods

Expression of TLR1-10, CD14 and MyD88 transcripts was investigated by RT-PCR. Protein expression of TLR2 and 4 was scrutinized by flow cytometry, immunofluorescent staining and Western blotting. Experiments were set up to assess the effects of LPS and LTA at different concentrations and times on cell proliferation, extracellular matrix invasion, adhesion and cytokine production.

Results

We showed that prostate cancer cell lines differentially express TLR1-10, MyD88 and CD14 transcripts. DU145 failed to express TLR4 gene. Positively-identified TLR2 protein in all prostate cancer cells and TLR4 protein in PC3 and LNCaP by Western blotting was not accompanied by cell surface expression, as judged by flow cytometry. Immunofluorescent staining clearly demonstrated predominantly perinuclear localization of TLR2 and TLR4. LTA activation of all prostate cancer cells significantly increased cell proliferation. Regardless of lacking TLR4, DU145 cells proliferated in response to LPS treatment. While LPS caused increased invasiveness of LNCaP, invasive capacity of PC3 was significantly reduced after LPS or LTA stimulation. Stimulation of all prostate tumor cells with LTA was associated with increased cell adhesion and IL-8 production. IL-6 production, however, was differentially regulated by LPS stimulation in prostate tumor cells.

Conclusion

The data shows that cancer cells originated from the same histologically origin exhibit heterogeneous response to the same TLR ligand. Therefore, a thorough and comprehensive judgment on how and to what extent a particular cancer is affected by TLR agonist could not be inferred by studying an individual cell line.

Role of gut microbiota in a zebrafish model with chemically induced enterocolitis involving toll-like receptor signaling pathways

BACKGROUND/AIMS

It is believed that inflammatory bowel disease (IBD) involves a breakdown in interactions between the resident commensal microbiota and the host immune response. Recent studies have revealed that gut physiology and pathology relevant to human IBD can be rapidly modeled in zebrafish larvae with a number of advantages compared with murine models. The objective of this study was to evaluate the role of gut microbiota in zebrafish models with IBD-like enterocolitis.

METHODS

IBD-like enterocolitis was induced by exposing larval zebrafish to 2, 4, 6-trinitrobenzene sulfonic acid (TNBS). Assays were performed using larval zebrafish collected at 8 and 10 days postfertilization (dpf ).

RESULTS

In the absence of gut microbiota, the TNBS-induced enterocolitis was less extensive. The expression of toll-like receptor 3 (TLR3) and the TLRs signaling pathway molecules MyD88 and TRIF, the activation of NF-κB, and the production of inflammatory cytokine tumor necrosis factor-α were stimulated in TNBS-treated zebrafish but there was no corresponding alteration in germ-free fish. With microbial colonization, all results reverted to a pattern similar to that observed in conventionally reared zebrafish.

CONCLUSION

We described the key role of gut microbiota in the etiology of a chemically induced larval zebrafish IBD-like model, showing an involvement of TLR signaling pathways.

Protective effect of tea polyphenols on renal ischemia/reperfusion injury via suppressing the activation of TLR4/NF-κB p65 signal pathway

Tea polyphenols (TP) was investigated in rats for its protective effect on renal ischemia/reperfusion injury (RIRI). Rats were randomized into groups as follows: (I) sham group (n=10); (II) RIRI group (n=10); (III) RIRI+TP (100mg/kg) group (n=5); (IV) RIRI+TP (200mg/kg) group (n=5); (V) RIRI+TP+ Astragalus mongholicus aqueous extract (AMAE) (300 mg/kg+100mg/kg) group (n=5). For the IRI+TP groups, rats were orally given with tea polyphenols (100, 200 and 300 mg/kg body weight) once daily 10 days before induction of ischemia, followed by renal IRI. For the sham group and RIRI group, rats were orally given with equal volume of saline once daily 10 days before induction of ischemia, followed by renal IRI. Results showed that tea polyphenol pretreatment significantly suppressed ROS level and MDA release. On the other hand, in rats subjected to ischemia-reperfusion, the activities of endogenous antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GSH-Px) showed recovery, whereas the levels of urea nitrogen and serum creatinine were reduced by administration of tea polyphenols orally for 10 days prior to ischemia-reperfusion. Moreover, tea polyphenol pretreatment significantly decreased TLR4 and NF-κB p65 protein expression levels in RIRI rats. At the same time, tea polyphenol pretreatment attenuated the increased level of serum IL-1β, IL-6, ICAM-1 and TNF-α, and enhanced IL-10 production in RIRI rats. Furthermore, tea polyphenol pretreatment significantly decreased renal epithelial tubular cell apoptosis induced by renal ischemia/reperfusion, alleviating renal ischemia/reperfusion injury. These results cumulatively indicate that tea polyphenol pretreatment could suppress the TLR4/NF-κB p65 signaling pathway, protecting renal tubular epithelial cells against ischemia/reperfusion-induced apoptosis, which implies that antioxidants may be a potential and effective agent for prevention of the ischemic/reperfusion injury through the suppression extrinsic apoptotic signal pathway induced by TLR4/NF-κB p65 signal pathway. Moreover, supplement of AMAE can increased renal protection effect of TP.

IL-1α expression in pancreatic ductal adenocarcinoma affects the tumor cell migration and is regulated by the p38MAPK signaling pathway

The interplay between the tumor cells and the surrounding stroma creates inflammation, which promotes tumor growth and spread. The inflammation is a hallmark for pancreatic adenocarcinoma (PDAC) and is to high extent driven by IL-1α. IL-1α is expressed and secreted by the tumor cells and exerting its effect on the stroma, i.e. cancer associated fibroblasts (CAF), which in turn produce massive amount of inflammatory and immune regulatory factors. IL-1 induces activation of transcription factors such as nuclear factor-κβ (NF-κβ), but also activator protein 1 (AP-1) via the small G-protein Ras. Dysregulation of Ras pathways are common in cancer as this oncogene is the most frequently mutated in many cancers. In contrast, the signaling events leading up to the expression of IL-1α by tumor cells are not well elucidated. Our aim was to examine the signaling cascade involved in the induction of IL-1α expression in PDAC. We found p38MAPK, activated by the K-Ras signaling pathway, to be involved in the expression of IL-1α by PDAC as blocking this pathway decreased both the gene and protein expression of IL-1α. Blockage of the P38MAPK signaling in PDAC also dampened the ability of the tumor cell to induce inflammation in CAFs. In addition, the IL-1α autocrine signaling regulated the migratory capacity of PDAC cells. Taken together, the blockage of signaling pathways leading to IL-1α expression and/or neutralization of IL-1α in the PDAC microenvironment should be taken into consideration as possible treatment or complement to existing treatment of this cancer.

MyD88 and its divergent toll in carcinogenesis

Toll-like and interleukin-1 (IL-1) family receptors recognize microbial or endogenous ligands and inflammatory mediators, respectively, and with the exception of Toll-like receptor 3 (TLR3), signal via the adaptor molecule myeloid differentiation factor 88 (MyD88). MyD88 is involved in oncogene-induced cell intrinsic inflammation and in cancer-associated extrinsic inflammation, and as such MyD88 contributes to skin, liver, pancreatic, and colon carcinogenesis, as well as sarcomagenesis. MyD88 is also protective, for example in oncogenic virus carcinogenesis or, acting downstream of IL-18R to strengthen mucosal repair, in azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced colon carcinogenesis. Here, we discuss the mechanisms of the divergent effects of MyD88 and the balance of its protumor role in cancer-enhancing inflammation and immunity and its antitumor role in tissue homeostasis, repair, and immunity against the tumor or oncogenic pathogens.

Inducible HSP70 antagonizes IL-1β cytocidal effects through inhibiting NF-kB activation via destabilizing TAK1 in HeLa cells

Background

Despite several reports describing the HSP70-mediated cytoprotection against IL-1, the precise mechanism for this phenomenon remains to be determined.

Methods/Principal Findings

Here we used HeLa cells, a human epithelial carcinoma cell line, to evaluate the role of inducible HSP70 in response of IL-1β stimulation. We found that inducible HSP70 antagonized the cytotoxicity of IL-1β and improved the survival of HeLa cells. Further investigation demonstrated that increased expression level of inducible HSP70 reduced the complex of TAK1 and HSP90, and promoted the degradation of TAK1 protein via proteasome pathway. By overexpression and RNAi knockdown, we showed that inducible HSP70 modulated the NF-kB but not MAPKs signalings through influencing the stability of TAK1 protein in HeLa cells. Moreover, overexpression of HSP70 attenuated the production of iNOS upon IL-1β stimulation, validating that inducible HSP70 serves as a cytopretective factor to antagonize the cytocidal effects of IL-1β in HeLa cells.

Conclusions/Significance

Our observations provide evidence for a novel signaling mechanism involving HSP70, TAK1, and NF-κB in the response of IL-1β cytocidal effects. This research also provides insight into mechanisms by which HSP70 exerts its cytoprotective action upon toxic stimuli in tumor cells.

Baicalin attenuates proinflammatory cytokine production in oxygen-glucose deprived challenged rat microglial cells by inhibiting TLR4 signaling pathway

Baicalin, a flavonoid compound isolated from Scutellariae radix, has been shown to possess a number of pharmacological effects. The aim of the present study was to observe the inhibitory effects of baicalin on the activation of microglial cells induced by oxygen-glucose deprivation (OGD) and the specific mechanisms by which these effects are mediated. Cultured rat primary microglial cells were exposed to baicalin at final concentrations of 10 μg/ml, 20 μg/ml and 40 μg/ml during 4h of OGD. The effects of baicalin on (i) cell viability; (ii) secretion of proinflammatory cytokines; (iii) Tlr4 mRNA expression; (iv) p-c-jun, p-ERK1/2, p-JNK, p-p38, TRAF6 and p-IκB-α levels; and (v) co-localization of TLR4 and MyD88 were evaluated using the Cell Counting Kit-8 (CCK-8), enzyme-linked immunosorbent assays (ELISA), reverse transcription-polymerase chain reaction (RT-PCR), western blot and double-labeled immunofluorescence staining, respectively. OGD increased cell viability and release of TNF-α, IL-1β, IL-6 and IL-8, these effects were suppressed by baicalin. Baicalin also attenuated the OGD-induced increases in Tlr4 mRNA expression. In addition, high dose of baicalin reduced TRAF6 levels remarkably. Furthermore, baicalin also downregulated phosphorylation of IκB-α, c-jun, ERK1/2, JNK, p38 and inhibited the OGD-induced transfer of MyD88 from cytoplasm to membrane in microglial cells. The results show that baicalin can inhibit OGD-induced production of inflammatory factors in microglial cells by attenuating inflammatory factors and regulating the TLR4 signaling pathways.

Rap1a deficiency modifies cytokine responses and MAPK-signaling in vitro and impairs the in vivo inflammatory response

Rap1, which is closely related to ras, plays a key role in T-cell receptor (TCR)-signaling. TCR-stimulation without costimulation leads to constitutively activated rap1, which may mediate T-cell anergy via inhibition of ras-dependent induction of extracellular signal-regulated kinases (ERK). This activation is mediated by a second protein kinase b-Raf. Rap1-GTP is thought to activate ERK in a ras-independent manner by binding b-raf. Generally, T cells do not express b-raf while they express the adaptor protein raf-1, which is usually sequestered by rap1 leading to inhibition of ras-mediated ERK activation. In this study, we demonstrate that in rap1-deficient T cells, signaling by the ERK and p38 kinases is increased following activation by different stimuli leading to increased intracellular accumulation and secretion of cytokines. In addition, in a hypersensitivity model rap1-deficient mice demonstrated reduced contact dermatitis compared to wildtype mice, demonstrating the impact of rap1-deficiency on the inflammatory response in vivo.

Role of pro-inflammatory cytokines released from microglia in neurodegenerative diseases

Microglia are activated in response to a number of different pathological states within the CNS including injury, ischemia, and infection. Microglial activation results in their production of pro-inflammatory cytokines such as IL-1, IL-6, and TNF-α. While release of these factors is typically intended to prevent further damage to CNS tissue, they may also be toxic to neurons and other glial cells. Mounting evidence indicates that chronic microglial activation may also contribute to the development and progression of neurodegenerative disorders. Unfortunately, determining the role of pro-inflammatory cytokines in these disorders has been complicated by their dual roles in neuroprotection and neurodegeneration. The purpose of this review is to summarize current understanding of the involvement of cytokines in neurodegenerative disorders and their potential signaling mechanisms in this context. Taken together, recent findings suggest that microglial activation and pro-inflammatory cytokines merit interest as targets in the treatment of neurodegenerative disorders.

Homocysteine induces cardiomyocyte dysfunction and apoptosis through p38 MAPK-mediated increase in oxidant stress

Elevated plasma homocysteine (Hcy) is a risk factor for cardiovascular disease. While Hcy has been shown to promote endothelial dysfunction by decreasing the bioavailability of nitric oxide and increasing oxidative stress in the vasculature, the effects of Hcy on cardiomyocytes remain less understood. In this study we explored the effects of hyperhomocysteinemia (HHcy) on myocardial function ex vivo and examined the direct effects of Hcy on cardiomyocyte function and survival in vitro. Studies with isolated hearts from wild type and HHcy mice (heterozygous cystathionine-beta synthase deficient mice) demonstrated that HHcy mouse hearts had more severely impaired cardiac relaxation and contractile function and increased cell death following ischemia reperfusion (I/R). In isolated cultured adult rat ventricular myocytes, exposure to Hcy for 24 h impaired cardiomyocyte contractility in a concentration-dependent manner, and promoted apoptosis as revealed by terminal dUTP nick-end labeling and cleaved caspase-3 immunoblotting. These effects were associated with activation of p38 MAPK, decreased expression of thioredoxin (TRX) protein, and increased production of reactive oxygen species (ROS). Inhibition of p38 MAPK by the selective inhibitor SB203580 (5 μM) prevented all of these Hcy-induced changes. Furthermore, adenovirus-mediated overexpression of TRX in cardiomyocytes significantly attenuated Hcy-induced ROS generation, apoptosis, and impairment of myocyte contractility. Thus, Hcy may increase the risk for CVD not only by causing endothelial dysfunction, but also by directly exerting detrimental effects on cardiomyocytes.

Angiotensin II increases periostin expression via Ras/p38 MAPK/CREB and ERK1/2/TGF-β1 pathways in cardiac fibroblasts

AIMS

Angiotensin II (AngII) is involved in extracellular matrix (ECM) accumulation contributing to heart failure. Periostin, a 90 kDa ECM protein, is a key regulator of cardiac fibrosis, and its expression is significantly higher in failing hearts. We determined the modulatory effect of AngII on periostin level and explored the possible signal transduction mechanism.

METHODS AND RESULTS

AngII (400 ng/kg/min) or normal saline was infused subcutaneously for 28 days into rats; AngII antagonism was with losartan (10 mg/kg/day orally). AngII infusion induced cardiac fibrosis and increased periostin expression, which was attenuated by losartan. In cultured adult rat cardiac fibroblasts, AngII promoted the mRNA and protein expression of periostin. AngII provoked activation of cAMP response element-binding protein (CREB), and CREB small interfering RNA (siRNA) suppressed AngII-induced periostin expression. Inhibition of p38 mitogen-activated protein kinase (p38 MAPK) with SB202190 attenuated AngII-induced CREB activation and periostin expression. Transfection with Ras guanyl-releasing protein 1 siRNA or RasN17 dominant-negative plasmid prevented AngII-induced p38 MAPK phosphorylation and periostin expression. Transforming growth factor (TGF)-β1 antibody decreased the stimulatory effect of AngII on periostin expression. The extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor PD98059 attenuated AngII-induced TGF-β1 expression, Smad2/3 nuclear accumulation, and periostin expression.

CONCLUSION

The activation of the Ras/p38 MAPK/CREB pathway is required for AngII-induced periostin expression. ERK1/2 also participates in AngII-induced periostin expression by regulating TGF-β1/Smad signalling.

Ovarian cancer stem cells and inflammation

Epithelial ovarian cancer (EOC) is the fourth leading cause of cancer-related deaths in women in the United States and the leading cause of gynecologic cancer deaths. The major limiting factor in the treatment of ovarian cancer is recurrence and chemoresistance. Individuals who succumb to advanced-stage ovarian cancer inevitably become refractory to chemotherapy, resulting in disease progression and death. The source of recurrence and lack of response to chemotherapy is unknown. The focus of this review is to evaluate the question of recurrence and chemoresistance based on the concept of the cancer stem cells and inflammation.

Increased disease severity of parasite-infected TLR2-/- mice is correlated with decreased central nervous system inflammation and reduced numbers of cells with alternatively activated macrophage phenotypes in a murine model of neurocysticercosis

In a murine model for neurocysticercosis (NCC), intracranial inoculation of the helminth parasite Mesocestoides corti induces multiple Toll-like receptors (TLRs), among which TLR2 is upregulated first and to a relatively high extent. Here, we report that TLR2(-/-) mice displayed significantly increased susceptibility to parasite infection accompanied by increased numbers of parasites in the brain parenchyma compared to infection in wild-type (WT) mice. This coincided with an increased display of microglial nodule formations and greater neuropathology than in the WT. Parasite-infected TLR2(-/-) brains exhibited a scarcity of lymphocytic cuffing and displayed reduced numbers of infiltrating leukocytes. Fluorescence-activated cell sorter (FACS) analyses revealed significantly lower numbers of CD11b(+) myeloid cells, γδ T cells, αβ T cells, and B cells in the brains of parasite-infected TLR2(-/-) mice. This correlated with significantly reduced levels of inflammatory mediators, including tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), CCL2, CCL3, and interleukin-6 (IL-6) in the central nervous system (CNS) of TLR2(-/-) mice. As TLR2 has been implicated in immune regulation of helminth infections and as alternatively activated macrophages (AAMs) are thought to play a profound regulatory role in such infections, induction of AAMs in infected TLR2(-/-) mice was compared with that in WT mice. Parasite-infected WT brains showed larger numbers of macrophages/microglia (CD11b(+) cells) expressing AAM-associated molecules such as YM1, Fizz1 (found in inflammatory zone-1 antigen), and arginase 1 than TLR2(-/-) brains, consistent with a protective role of AAMs during infection. Importantly, these results demonstrate that TLR2-associated responses modulate the disease severity of murine NCC.

V3 versican isoform alters the behavior of human melanoma cells by interfering with CD44/ErbB-dependent signaling

Versican is a hyaluronan-binding, extracellular chondroitin sulfate proteoglycan produced by several tumor types, including malignant melanoma, which exists as four different splice variants. The short V3 isoform contains the G1 and G3 terminal domains of versican that may potentially interact directly or indirectly with the hyaluronan receptor CD44 and the EGFR, respectively. We have previously described that overexpression of V3 in MeWo human melanoma cells markedly reduces tumor cell growth in vitro and in vivo. In this study we have investigated the signaling mechanism of V3 by silencing the expression of CD44 in control and V3-expressing melanoma cells. Suppression of CD44 had the same effects on cell proliferation and cell migration than those provoked by V3 expression, suggesting that V3 acts through a CD44-mediated mechanism. Furthermore, CD44-dependent hyaluronan internalization was blocked by V3 expression and CD44 silencing, leading to an accumulation of this glycosaminoglycan in the pericellular matrix and to changes in cell migration on hyaluronan. Furthermore, ERK1/2 and p38 activation after EGF treatment were decreased in V3-expressing cells suggesting that V3 may also interact with the EGFR through its G3 domain. The existence of a EGFR/ErbB2 receptor complex able to interact with CD44 was identified in MeWo melanoma cells. V3 overexpression resulted in a reduced interaction between EGFR/ErbB2 and CD44 in response to EGF treatment. Our results indicate that the V3 isoform of versican interferes with CD44 and the CD44-EGFR/ErbB2 interaction, altering the signaling pathways, such as ERK1/2 and p38 MAPK, that regulate cell proliferation and migration.

Toll-like receptors, tissue injury, and tumourigenesis

Toll-like receptors (TLRs) belong to a class of molecules known as pattern recognition receptors, and they are part of the innate immune system, although they modulate mechanisms that impact the development of adaptive immune responses. Several studies have shown that TLRs, and their intracellular signalling components, constitute an important cellular pathway mediating the inflammatory process. Moreover, their critical role in the regulation of tissue injury and wound healing process as well as in the regulation of apoptosis is well established. However, interest in the role of these receptors in cancer development and progression has been increasing over the last years. TLRs are likely candidates to mediate effects of the innate immune system within the tumour microenvironment. A rapidly expanding area of research regarding the expression and function of TLRs in cancer cells and its association with chemoresistance and tumourigenesis, and TLR-based therapy as potential immunotherapy in cancer treatment is taking place over the last years.

MTA1 coregulator regulates LPS response via MyD88-dependent signaling

Although metastasis tumor antigen 1 (MTA1) contributes to the responsiveness of macrophages to LPS, the underlying mechanism remains unknown. Here, we investigated the role of MTA1 in the regulation of expression and function of MyD88, a proximal component of NF-κB signaling. We discovered that MTA1 targets MyD88 and that MyD88 is a NF-κB-responsive gene in LPS-stimulated macrophages. We found that MTA1 is required for MyD88-dependent stimulation of NF-κB signaling and expression of proinflammatory cytokines such as IL-1β, MIP2, and TNF-α as MTA1 depletion leads to a substantial reduction in the expression of NF-κB target genes. In addition, LPS-mediated stimulation of MyD88 transcription was accompanied by an enhanced recruitment of MTA1, RNA polymerase II, and p65RelA complex to the NF-κB consensus sites in the MyD88 promoter. Interestingly, the recruitment of both MTA1 and MyD88 expression is effectively blocked by NF-κB inhibitor parthenolide. Selective knockdown of MyD88 by a dominant negative mutant of MyD88 or selective siRNA also impairs the ability of LPS to stimulate the NF-κB target genes. These findings reveal an inherent coregulatory role of MTA1 upon the expression of MyD88 and suggest that MTA1 regulation of MyD88 may constitute at least one of the mechanisms by which MTA1 stimulates LPS-induced NF-κB signaling in stimulated macrophages.

C3G down-regulates p38 MAPK activity in response to stress by Rap-1 independent mechanisms: involvement in cell death

We present here evidences supporting a negative regulation of p38alpha MAPK activity by C3G in MEFs triggered by stress, which can mediate cell death or survival depending on the stimuli. Upon serum deprivation, C3G induces survival through inhibition of p38alpha activation, which mediates apoptosis. In contrast, in response to H2O2, C3G behaves as a pro-apoptotic molecule, as its knock-down or knock-out enhances survival through up-regulation of p38alpha activation, which plays an anti-apoptotic role under these conditions. Moreover, the C3G target, Rap-1, plays an opposite role, also through regulation of p38alpha MAPK activity. Our data also suggest that changes in the protein levels of some members of the Bcl-2 family could account for the regulation of cell death by C3G and/or Rap-1 through p38alpha MAPK. Bim/Bcl-xL ratio appears to be important in the regulation of cell survival, both upon serum deprivation and in response to H2O2. In addition, the increase in BNIP-3 levels induced by C3G knock-down in wt cells treated with H2O2 might play a role preventing cell death. Therefore, we can conclude that C3G is a negative regulator of p38alpha MAPK in MEFs, while Rap-1 is a positive regulator, but both, through the regulation of p38alpha activity, can promote cell survival or cell death depending on the stimuli.

Angiotensin II Type 1 Receptor–Activated Caspase-3 Through Ras/Mitogen-Activated Protein Kinase/Extracellular Signal-Regulated Kinase in the Rostral Ventrolateral Medulla Is Involved in Sympathoexcitation in Stroke-Prone Spontaneously Hypertensive Rats

In the rostral ventrolateral medulla (RVLM), angiotensin II-derived superoxide anions, which increase sympathetic nerve activity, induce a pressor response by activating the p38 mitogen-activated protein kinase (p38 MAPK) and extracellular signal-regulated kinase (ERK) pathway. The small G protein Ras mediates a caspase-3–dependent apoptotic pathway through p38 MAPK, ERK, and c-Jun N-terminal kinase. We hypothesized that angiotensin II type 1 receptors activate caspase-3 through the Ras/p38 MAPK/ERK/c-Jun N-terminal kinase pathway in the RVLM and that this pathway is involved in sympathoexcitation in stroke-prone spontaneously hypertensive rats (SHRSP), a model of human hypertension. The activities of Ras, p38 MAPK, ERK, and caspase-3 in the RVLM were significantly higher in SHRSP (14 to 16 weeks old) than in age-matched Wistar-Kyoto rats (WKY). The mitochondrial apoptotic proteins Bax and Bad in the RVLM were significantly increased in SHRSP compared with WKY. c-Jun N-terminal kinase activity did not differ between SHRSP and WKY. In SHRSP, intracerebroventricular infusion of a Ras inhibitor significantly reduced sympathetic nerve activity and improved baroreflex sensitivity, partially because of inhibition of the Ras/p38 MAPK/ERK, Bax, Bad, and caspase-3 pathway in the RVLM. Intracerebroventricular infusion of a caspase-3 inhibitor also inhibited sympathetic nerve activity and improved baroreflex sensitivity in SHRSP. Intracerebroventricular infusion of an angiotensin II type 1 receptor blocker in SHRSP partially inhibited the Ras/p38 MAPK/ERK, Bax, Bad, and caspase-3 pathway in the RVLM. These findings suggest that in SHRSP, angiotensin II type 1 receptor-activated caspase-3 acting through the Ras/p38 MAPK/ERK pathway in the RVLM might be involved in sympathoexcitation, which in turn plays a crucial role in the pathogenesis of hypertension.

Mesocestoides corti intracranial infection as a murine model for neurocysticercosis

Neurocysticercosis (NCC) is the most common parasitic disease of the central nervous system (CNS) caused by the larval form of the tapeworm Taenia solium. NCC has a long asymptomatic period with little or no inflammation, and the sequential progression to symptomatic NCC depends upon the intense inflammation associated with degeneration of larvae. The mechanisms involved in these progressive events are difficult to study in human patients. Thus it was necessary to develop an experimental model that replicated NCC. In this review, we describe studies of a murine model of NCC in terms of the release/secretion of parasite antigens, immune responses elicited within the CNS environment and subsequent pathogenesis. In particular, the kinetics of leukocyte subsets infiltrating into the brain are discussed in the context of disruption of the CNS barriers at distinct anatomical sites and the mechanisms contributing to these processes. In addition, production of various inflammatory mediators and the mechanisms involved in their induction by the Toll-like receptor signaling pathway are described. Overall, the knowledge gained from the mouse model of NCC has provided new insights for understanding the kinetics of events contributing to different stages of NCC and should aid in the formulation of more effective therapeutic approaches.

MyD88-deficient mice exhibit decreased parasite-induced immune responses but reduced disease severity in a murine model of neurocysticercosis

The symptomatic phase of neurocysticercosis (NCC), a parasitic disease of the central nervous system (CNS) in humans, is characterized by inflammatory responses leading to neuropathology and, in some cases, death. In an animal model of NCC in which mice were intracranially inoculated with the parasite Mesocestoides corti, the infection in mice lacking the myeloid differentiation primary response gene 88 (MyD88(-/-)) resulted in decreased disease severity and improved survival compared with that in wild-type (WT) mice. The CNS of MyD88(-/-) mice was more quiescent, with decreased microgliosis and tissue damage. These mice exhibited substantially reduced primary and secondary microglial nodule formations and lacked severe astrogliotic reactions, which were seen in WT mice. Significantly reduced numbers of CD11b(+) myeloid cells, alphabeta T cells, gammadelta T cells, and B cells were present in the brains of MyD88(-/-) mice in comparison with those of WT mice. This decrease in cellular infiltration correlated with a decrease in blood-brain barrier permeability, as measured by reduced fibrinogen extravasation. Comparisons of cytokine expression indicated a significant decrease in the CNS levels of several inflammatory mediators, such as tumor necrosis factor alpha, gamma interferon, CCL2, and interleukin-6, during the course of infection in MyD88(-/-) mice. Collectively, these findings suggest that MyD88 plays a prominent role in the development of the hyperinflammatory response, which in turn contributes to neuropathology and disease severity in NCC.