Dependent NF-κB Activation Research Articles

PSMC5 regulates microglial polarization and activation in LPS-induced cognitive deficits and motor impairments by interacting with TLR4

Luteolin is a flavonoid found in high concentrations in celery and green pepper, and acts as a neuroprotectant. PSMC5 (proteasome 26S subunit, ATPase 5) protein levels were reduced after luteolin stimulation in activated microglia. We aimed to determine whether regulating PSMC5 expression could inhibit neuroinflammation, and investigate the underlying mechanisms.BV2 microglia were transfected with siRNA PSMC5 before the addition of LPS (lipopolysaccharide, 1.0 µg/ml) for 24 h in serum free DMEM. A mouse model of LPS-induced cognitive and motor impairment was established to evaluate the neuroprotective effects of shRNA PSMC5. Intracerebroventricular administration of shRNA PSMC5 was commenced 7 days prior to i.p. injection of LPS (750 μg/kg). Treatments and behavioral experiments were performed once daily for 7 consecutive days. Behavioral tests and pathological/biochemical assays were performed to evaluate LPS-induced hippocampal damage. Molecular dynamics simulation was used to confirm the interaction between PSMC5 and TLR4 (Toll-like receptor 4) in LPS-stimulated BV2 microglia. SiRNA PSMC5 inhibited BV2 microglial activation, and suppressed the release of inflammatory factors (IL-1β, COX-2, PGE2, TNF-α, and iNOS) upon after LPS stimulation in BV2 microglia. LPS increased IκB-α and p65 phosphorylation, which was attenuated by siRNA PSMC5. Behavioral tests and pathological/biochemical assays showed that shRNA PSMC5 attenuated LPS-induced cognitive and motor impairments, and restored synaptic ultrastructure and protein levels in mice. ShRNA PSMC5 reduced pro-inflammatory cytokine (TNF-α, IL-1β, PGE2, and NO) levels in the serum and brain, and relevant protein factors (iNOS and COX-2) in the brain. Furthermore, shRNA PSMC5 upregulated the anti-inflammatory mediators interleukin IL-4 and IL-10 in the serum and brain, and promoted a pro-inflammation-to-anti-inflammation phenotype shift in microglial polarization. Mechanistically, shRNA PSMC5 significantly alleviated LPS-induced TLR4 expression. The polarization of LPS-induced microglial pro-inflammation phenotype was abolished by TLR4 inhibitor and in the TLR-4−/− mouse, as in shRNA PSMC5 treatment. PSMC5 interacted with TLR4 via the amino sites Glu284, Met139, Leu127, and Phe283. PSMC5 site mutations attenuated neuroinflammation and reduced pro-inflammatory factors by reducing TLR4-related effects, thereby reducing TLR4-mediated MyD88 (myeloid differentiation factor 88)-dependent activation of NF-κB. PSMC5 could be an important therapeutic target for treatment of neurodegenerative diseases involving neuroinflammation-associated cognitive deficits and motor impairments induced by microglial activation.Graphical

Inhibition of Both IRAK1 and IRAK4 Is Required for Complete Suppression of NF-Kb Signaling across Multiple Receptor-Mediated Pathways in MDS and AML

There is increasing interest in the role of the IRAK kinases as targets in the treatment of MDS and AML (reviewed in J Bennett and DT Starczynowski, Curr Opin Hematol 2022). IRAK1 and IRAK4 lie downstream of multiple receptors that stimulate the canonical NF-κB signaling pathway upstream of TRAF6 via the myddosome complex. While TRAF6 is necessary to preserve the tonic NF-κB signaling that is required for hematopoietic stem cell (HSC) homeostasis (J Fang et. al. Cell Reports 2018), overactivity of the NF-κB signaling pathway has been implicated in both MDS and AML (reviewed in MCJ Bosman et. al., Crit Rev Oncol/Hematol 2016; JJ Trowbridge and DT Starczynowski, J Exp Med 2021). The requirement for both IRAK1 and IRAK4 in this pathway has been explored using both genetic and pharmacologic technologies. The use of genetic loss-of-function approaches revealed that deletion and/or inhibition of IRAK4 results in a compensatory increase in IRAK1 protein and activation (data unpublished), suggesting that high potency antagonism of both kinases will be required for optimal inhibition of NF-κB-mediated transcriptional responses in disease-propagating MDS and AML cells. In this report, we use a pharmacological approach in which a series of IRAK inhibitors of varying relative potency at IRAK1:IRAK4 were examined for both inhibition of NF-κB activation in AML cells and inhibition of leukemic progenitor cell function in vitro. We find that potency and efficacy for antagonism at NF-κB requires effective inhibition of both IRAK1 and IRAK4. We also find that the relative potency of NF-κB inhibition correlates with suppression of leukemic progenitor cell function in vitro, providing pharmacological validation that inhibition of both IRAK1 and IRAK4 are necessary for optimal inhibition of NF-κB and effect on leukemia progenitor cell function. We utilized an NF-κB reporter system expressed in human AML cells (THP1) to measure NF-κB dependent activation in response to a variety of IRAK4, IRAK1, or IRAK1/4 antagonists. The cells are highly responsive to both TLR agonists as well as to IL-1b, which allows for measurement of IRAK-mediated antagonism of multiple receptor-mediated pathways. Using the IRAK4-selective antagonists PF-06650833 and BAY 1834845 we find that both compounds fully suppress signaling through TLR2 (IC50vs. Pam3CSK4 = 7.2 and 150 nM, respectively). The IRAK4 antagonists inhibit signaling through the IL-1R with similar relative potency (IC50vs. IL-1b = 5.7 and 81 nM), but do not fully suppress signaling through this receptor (Span = 75% and 59%, respectively). Interestingly, the IRAK1 selective covalent inhibitor JH-X-119-01 does not inhibit signaling against either the TLR or the IL-1 receptor agonist. Together these data imply that neither IRAK4 nor IRAK1 inhibition alone is sufficient to fully inhibit NF-κB-mediated signaling through multiple receptor mediated pathways. For this reason, we then examined the activity of a series of IRAK4/IRAK1 inhibitors in AML cells. This allowed us to study the effect of adding in additional inhibitory activity at IRAK1 on the background of high potency IRAK4 inhibitors. Using two reference compounds with varying IRAK1:IRAK4 potency, we then compared the relative ability to inhibit TLR-agonist or IL-1b-agonist stimulated NF-κB activity in AML. KME-2780 has an IRAK1:IRAK4 potency ratio of 36 whereas KME-3859 has an IRAK1:IRAK4 potency ratio of 100. Unlike what we observed with the IRAK4-selective antagonists, both compounds can completely suppress NF-κB signaling through IL-1b, with relative potencies apparently determined by their activity at IRAK1: (IC50vs. Pam3CSK4 = 6.3 and 73.8 nM for KME- 2780 and KME-3859, respectively); (IC50vs. IL-1b = 9.3 and 227 nM for KME- 2780 and KME-3859, respectively). Finally, we examined the correlation between potency in the biochemical kinase assay at IRAK1 or IRAK4, activity in the NF-κB reporter assay, and leukemic progenitor cell activity in the colony forming assay for a series of KME compounds in AML and MDS cells. We find a correlation between kinase activity for both IRAK1 and IRAK4 and NF-κB activity that extends to the leukemia colony forming assays. This suggests that NF-κB signaling contributes to leukemia progenitor cell function and that optimal inhibition requires potent antagonism of both IRAK1 and IRAK4 in the setting of MDS and AML.

Overcoming Acquired Epigenetic Resistance to BTK Inhibitors.

In diffuse large B-cell lymphoma, we show that primary resistance to BTK inhibitors is due to epigenetic rather than genetic changes that circumvent the BTK blockade. We also observed this resistance mechanism in chronic lymphocytic leukemia, suggesting that epigenetic alterations may contribute more to BTK inhibitor resistance than currently thought.See related commentary by Pasqualucci, p. 555. This article is highlighted in the In This Issue feature, p. 549.

Osteoblast lineage cells and periodontal ligament fibroblasts regulate orthodontic tooth movement that is dependent on Nuclear Factor-kappa B (NF-kB) activation.

To investigate the role of NF-κB in osteoblast lineage cells and periodontal ligament (PDL) fibroblasts during orthodontic tooth movement (OTM). Transgenic mice that expressed a dominant negative mutant of the inhibitor of kB kinase (IKK-DN) with lineage specific expression in osteoblastic cells and PDL fibroblasts driven by a response element in the collagen1α1 promoter and matched wild-type (WT) mice were examined. A 10-12 g force was applied by a NiTi coil and maintained for 5 or 12 days. OTM distance, PDL width, and bone volume fraction were measured using micro computed tomography. Osteoclast numbers were counted in tartrate-resistant acid phosphatase-stained sections. Activation of nuclear factor kappa B (NF-kB) was assessed by nuclear localization of p65, and the receptor activator of nuclear factor-κB ligand (RANKL) was measured by immunofluorescence and compared to control specimens with no orthodontic force. OTM-induced NF-kB activation (p65 nuclear localization) in WT mice was largely blocked in transgenic (TG) mice. OTM was significantly reduced in the TG mice compared to WT mice along with reduced osteoclastogenesis, narrower PDL width, higher bone volume fraction, and reduced RANKL expression. Osteoblast lineage cells and PDL fibroblasts are key contributors to alveolar bone remodeling in OTM through IKKβ dependent NF-κB activation.

Tumor necrosis factor-α induces claudin-3 upregulation in kidney tubular epithelial cells through NF-κB and CREB1.

Claudins are essential for tight junction formation and paracellular transport, and they affect key cellular events including proliferation and migration. The properties of tight junctions are dynamically modulated by a variety of inputs. We previously showed that the inflammatory cytokine tumor necrosis factor-α (TNFα), a major pathogenic factor in kidney disease, alters epithelial permeability by affecting the expression of claudin-1, -2, and -4 in kidney tubular cells. Here, we explored the effect of TNFα on claudin-3 (Cldn-3), a ubiquitous barrier-forming protein. We found that TNFα elevated Cldn-3 protein expression in tubular epithelial cells (LLC-PK1 and IMCD3) as early as 3 h post treatment. Bafilomycin A and bortezomib, inhibitors of lysosomal and proteasomes, respectively, reduced Cldn-3 degradation. However, TNFα caused a strong upregulation of Cldn-3 in the presence of bafilomycin, suggesting an effect independent from lysosomes. Blocking protein synthesis using cycloheximide prevented Cldn-3 upregulation by TNFα, verifying the contribution of de novo Cldn-3 synthesis. Indeed, TNFα elevated Cldn-3 mRNA levels at early time points. Using pharmacological inhibitors and siRNA-mediated silencing, we determined that the effect of TNFα on Cldn-3 was mediated by extracellular signal regulated kinase (ERK)-dependent activation of NF-κB and PKA-induced activation of CREB1. These two pathways were turned on by TNFα in parallel and both were required for the upregulation of Cldn-3. Because Cldn-3 was suggested to modulate cell migration and epithelial-mesenchymal transition (EMT), and TNFα was shown to affect these processes, Cldn-3 upregulation may modulate regeneration of the tubules following injury.

Oral administration of polyphenol-rich Sargassum horneri suppresses particulate matter exacerbated airway inflammation in murine allergic asthma: Relevance to the TLR mediated NF-κB pathway inhibition

• Polyphenol rich Sargassum horneri extract (SHE) attenuates inflammatory responses in asthmatic mice. • SHE attenuates particulate matter (PM)-induced histopathological changes in lung. • SHE suppresses PM-induced TLR2/4/7 activation and downstream signaling cascade along the NF-κB pathway in lung. Particulate matter (PM) is known to exacerbate airway inflammatory responses in asthma patients and to worsen asthma symptoms. Hypothesizing that attenuating airway inflammation might delay the exacerbation of PM-induced asthma symptoms, we investigated polyphenol-containing Sargassum horneri extract’s (SHE’s) anti-inflammatory efficacy and its underlying mechanism against PM–exacerbated inflammatory response using an asthma mouse model. SHE attenuated the PM–aggravated granulocytes infiltration into the airway and suppressed the PM-exacerbated mRNA expression of TLRs (TLR2/4/7), leading to the reduction of MyD88 dependent NF-κB activation in lungs of asthmatic mice. This resulted in attenuated PM-exacerbated mRNA expression of pro-inflammatory cytokines (IL-1β, TNF-α, TGF-β, IL-6), pro-allergic cytokines (TSLP, IL-25, IL-33), and a chemokine (IL-8) in lungs of asthmatic mice. Taken together, we conclude that SHE mitigates the PM-exacerbated airway inflammatory response of asthmatic mice via modulating TLR2/4/7 mediated MyD88 dependent NF-κB pathway and might make a natural candidate against the PM exacerbated severe asthma.

Pro-inflammatory activation following demyelination is required for myelin clearance and oligodendrogenesis.

Remyelination requires innate immune system function, but how exactly microglia and macrophages clear myelin debris after injury and tailor a specific regenerative response is unclear. Here, we asked whether pro-inflammatory microglial/macrophage activation is required for this process. We established a novel toxin-based spinal cord model of de- and remyelination in zebrafish and showed that pro-inflammatory NF-κB-dependent activation in phagocytes occurs rapidly after myelin injury. We found that the pro-inflammatory response depends on myeloid differentiation primary response 88 (MyD88). MyD88-deficient mice and zebrafish were not only impaired in the degradation of myelin debris, but also in initiating the generation of new oligodendrocytes for myelin repair. We identified reduced generation of TNF-α in lesions of MyD88-deficient animals, a pro-inflammatory molecule that was able to induce the generation of new premyelinating oligodendrocytes. Our study shows that pro-inflammatory phagocytic signaling is required for myelin debris degradation, for inflammation resolution, and for initiating the generation of new oligodendrocytes.

An immune-stimulating proteoglycan from the medicinal mushroom Huaier up-regulates NF-κB and MAPK signaling via Toll-like receptor 4

Trametes robiniophila Murr. (Huaier) is a mushroom with a long history of use as a medicinal ingredient in China and exhibits good clinical efficacy in cancer management. However, the antitumor components of Huaier and the underlying molecular mechanisms remain poorly understood. Here, we isolated a proteoglycan with a molecular mass of ∼5.59 × 104 Da from Huaier aqueous extract. We named this proteoglycan TPG-1, and using FTIR and additional biochemical analyses, we determined that its total carbohydrate and protein compositions are 43.9 and 41.2%, respectively. Using biochemical assays and immunoblotting, we found that exposing murine RAW264.7 macrophages to TPG-1 promotes the production of nitric oxide (NO), tumor necrosis factor α (TNFα), and interleukin-6 (IL-6) through Toll-like receptor 4 (TLR4)-dependent activation of NF-κB and mitogen-activated protein kinase (MAPK) signaling. Of note, the TPG-1 treatment significantly inhibited the tumorigenesis of human hepatoma HepG2 cells likely at least in part by increasing serum levels of TNFα and promoting leukocyte infiltration into tumors in nude mice. TPG-1 also exhibited good antitumor activity in hepatoma H22-bearing mice and had no obvious adverse effects in these mice. We conclude that TPG-1 exerts antitumor activity partially through an immune-potentiating effect due to activation of the TLR4-NF-κB/MAPK signaling cassette. Therefore, TPG-1 may be a promising candidate drug for cancer immunotherapy. This study has identified the TPG-1 proteoglycan as an antitumor agent and provided insights into TPG-1's molecular mechanism, suggesting a potential utility for applying this agent in cancer therapy.

Abstract B103: Altering the mevalonate pathway to enhance CD8+ T-cell responses

Abstract Inhibitors of the mevalonate pathway have been found to induce inflammatory reactions and delay the progression of cancer. Emerging evidence suggests these inhibitors sensitise immune cells to signalling from the myeloid differentiation primary response gene 88 (MyD88) and in turn enhance NF-κB dependent activation of antigen presenting cells (APCs), an essential element in inducing an immune response. To further explore the adjuvant effect of these inhibitors, we designed a vaccine comprising an inhibitor of the mevalonate pathway conjugated to a tumor-specific peptide. We hypothesized that immunisation with these vaccines would elicit functional peptide-specific CD8+ T-cells. Using an in vivo mouse model, we found the vaccine generates greater peptide-specific cytotoxicity against targeT-cells bearing a human papillomavirus antigen than its unconjugated components, a chemical control vaccine or peptide alone. Moreover, the vaccine delayed outgrowth of an antigen-expressing tumor. Using human PBMCs, we obtained preliminary evidence that a similar vaccine can promote greater in vitro activation of CD8+ T-cells specific for a cytomegalovirus antigen than peptide alone. These results suggest that inhibitors of the mevalonate pathway can act as adjuvants in eliciting cytotoxic T-cell responses, and may have utility for the treatment or prevention of viral infections or neoplasia. Citation Format: Olivia K. Burn, Astrid Authier-Hall, Collin Brooks, Regan Anderson, Andrew Marshall, Gavin Painter, Robert Weinkove, Ian Hermans. Altering the mevalonate pathway to enhance CD8+ T-cell responses [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr B103.

Neuroinflammation is induced by tongue-instilled ZnO nanoparticles via the Ca2+-dependent NF-\u03baB and MAPK pathways

BackgroundThe extensive biological applications of zinc oxide nanoparticles (ZnO NPs) in stomatology have created serious concerns about their biotoxicity. In our previous study, ZnO NPs were confirmed to transfer to the central nervous system (CNS) via the taste nerve pathway and cause neurodegeneration after 30 days of tongue instillation. However, the potential adverse effects on the brain caused by tongue-instilled ZnO NPs are not fully known.MethodsIn this study, the biodistribution of Zn, cerebral histopathology and inflammatory responses were analysed after 30 days of ZnO NPs tongue instillation. Moreover, the molecular mechanisms underlying neuroinflammation in vivo were further elucidated by treating BV2 and PC12 cells with ZnO NPs in vitro.ResultsThis analysis indicated that ZnO NPs can transfer into the CNS, activate glial cells and cause neuroinflammation after tongue instillation. Furthermore, exposure to ZnO NPs led to a reduction in cell viability and induction of inflammatory response and calcium influx in BV2 and PC12 cells. The mechanism underlying how ZnO NPs induce neuroinflammation via the Ca2+-dependent NF-κB, ERK and p38 activation pathways was verified at the cytological level.ConclusionThis study provided a new way how NPs, such as ZnO NPs, induce neuroinflammation via the taste nerve translocation pathway, a new mechanism for ZnO NPs-induced neuroinflammation and a new direction for nanomaterial toxicity analysis.

Strenuous exercise triggers a life-threatening response in mice susceptible to malignant hyperthermia.

In humans, hyperthermic episodes can be triggered by halogenated anesthetics [malignant hyperthermia (MH) susceptibility] and by high temperature [environmental heat stroke (HS)]. Correlation between MH susceptibility and HS is supported by extensive work in mouse models that carry a mutation in ryanodine receptor type-1 (RYR1Y522S/WT) and calsequestrin-1 knockout (CASQ1-null), 2 proteins that control Ca2+ release in skeletal muscle. As overheating episodes in humans have also been described during exertion, here we subjected RYR1Y522S/WT and CASQ1-null mice to an exertional-stress protocol (incremental running on a treadmill at 34°C and 40% humidity). The mortality rate was 80 and 78.6% in RYR1Y522S/WT and CASQ1-null mice, respectively, vs. 0% in wild-type mice. Lethal crises were characterized by hyperthermia and rhabdomyolysis, classic features of MH episodes. Of importance, pretreatment with azumolene, an analog of the drug used in humans to treat MH crises, reduced mortality to 0 and 12.5% in RYR1Y522S/WT and CASQ1-null mice, respectively, thanks to a striking reduction of hyperthermia and rhabdomyolysis. At the molecular level, azumolene strongly prevented Ca2+-dependent activation of calpains and NF-κB by lowering myoplasmic Ca2+ concentration and nitro-oxidative stress, parameters that were elevated in RYR1Y522S/WT and CASQ1-null mice. These results suggest that common molecular mechanisms underlie MH crises and exertional HS in mice.-Michelucci, A., Paolini, C., Boncompagni, S., Canato, M., Reggiani, C., Protasi, F. Strenuous exercise triggers a life-threatening response in mice susceptible to malignant hyperthermia.

Na+ influx via Orai1 inhibits intracellular ATP-induced mTORC2 signaling to disrupt CD4 T cell gene expression and differentiation.

T cell effector functions require sustained calcium influx. However, the signaling and phenotypic consequences of non-specific sodium permeation via calcium channels remain unknown. α-SNAP is a crucial component of Orai1 channels, and its depletion disrupts the functional assembly of Orai1 multimers. Here we show that α-SNAP hypomorph, hydrocephalus with hopping gait, Napahyh/hyh mice harbor significant defects in CD4 T cell gene expression and Foxp3 regulatory T cell (Treg) differentiation. Mechanistically, TCR stimulation induced rapid sodium influx in Napahyh/hyh CD4 T cells, which reduced intracellular ATP, [ATP]i. Depletion of [ATP]i inhibited mTORC2 dependent NFκB activation in Napahyh/hyh cells but ablation of Orai1 restored it. Remarkably, TCR stimulation in the presence of monensin phenocopied the defects in Napahyh/hyh signaling and Treg differentiation, but not IL-2 expression. Thus, non-specific sodium influx via bonafide calcium channels disrupts unexpected signaling nodes and may provide mechanistic insights into some divergent phenotypes associated with Orai1 function.

Recombinant CC16 protein inhibits the production of pro-inflammatory cytokines via NF-κB and p38 MAPK pathways in LPS-activated RAW264.7 macrophages.

Accumulating evidence indicates that Clara cell protein-16 (CC16) has anti-inflammatory functions, although the involved molecular pathways have not been completely elucidated. Here, we evaluated the effect of recombinant rat CC16 (rCC16) on the expression of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and IL-8 in lipopolysaccharide (LPS)-stimulated mouse macrophages (RAW264.7 cells) and explored the underlying molecular mechanisms. It was found that rCC16 inhibited LPS-induced TNF-α, IL-6, and IL-8 expression at both the messenger ribonucleicacid (mRNA) level and protein level in a concentration-dependent manner, as demonstrated by real-time reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay. Such suppressive effects were accompanied by the inhibition of transcriptional activity and the deoxyribonucleic acid binding activity of nuclear factor (NF)-κB but not activator protein (AP)-1. Western blot analysis further revealed that rCC16 inhibited the increase of nuclear NF-κB and the reduction of cytosolic NF-κB, the phosphorylation and reduction of NF-κB inhibitory protein IκBα, and the p38 mitogen-activated protein kinase (MAPK)-dependent NF-κB activation by phosphorylation at Ser276 of its p65 subunit. Furthermore, rCC16 was found to have no effect on the phosphorylation of c-Jun N-terminal kinase, c-Jun, or the nuclear translocation of c-Jun. In addition, reduction of TNF-α, IL-6, and IL-8 were reversed when the level of endogenous uteroglobin-binding protein was reduced by RNA interference in rCC16- and LPS-treated RAW264.7 cells. Our data suggest that rCC16 suppresses LPS-mediated inflammatory mediator TNF-α, IL-6, and IL-8 production by inactivating NF-κB and p38 MAPK but not AP-1 in RAW264.7 cells.

HNO suppresses LPS-induced inflammation in BV-2 microglial cells via inhibition of NF-κB and p38 MAPK pathways

Both hydrogen sulfide (H2S) and nitric oxide (NO) are important gaseous mediators. We and others previously reported that these two gases react with each other to generate a new mediator, nitroxyl (HNO), and regulate cardiovascular functions. In this study, we demonstrated for the first time that the interaction between the two gases also existed in microglia. The biological functions of HNO in microglial cells were further studied with Angeli⿿s salt (AS), an HNO donor. We found that AS attenuated lipopolysaccharide (LPS)-evoked production of reactive oxygen species (ROS) and pro-inflammatory cytokines (e.g. IL-1β and TNFα) through downregulating the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). HNO significantly reduced the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and the activation of nuclear factor-κB (NF-κB) through suppression of phosphorylation p65 and IκBα. The above effects were abolished by l-cysteine, an HNO scavenger, but were not mimicked by nitrite, another product of AS during generating HNO. A Cys-179-to-Ala mutation in inhibitory κB kinase β (IKKβ) mimicked the effect of HNO on LPS-induced NF-κB activation. Interestingly, AS abolished the inflammation in cells overexpressing WT-IKKβ, but had no significant effect in cells overexpressing C179A-IKKβ. These data suggest that HNO may act on C179 to prevent IKKβ-dependent inflammation. Taken together, our data demonstrated for the first time that H2S interacts with NO to generate HNO in microglial cells. HNO produces anti-inflammatory effects through suppressing the IKKβ dependent NF-κB activation and p38 MAPK pathways.

Luteolin inhibits viral-induced inflammatory response in RAW264.7 cells via suppression of STAT1/3 dependent NF-κB and activation of HO-1

Luteolin is a common dietary flavonoid present in Chinese herbal medicines that has been reported to have important anti-inflammatory properties. Previous studies have shown that luteolin is an anti-inflammatory and anti-oxidative agent.In this study, the anti-virus inflammatory capacity of luteolin and its molecular mechanisms of action were analyzed. The cytotoxic effects of luteolin were assessed in the presence or absence of pseudorabies virus (PRV) via LDH and MTT assays. The results showed that luteolin (<10μM) had no toxic effects and there were tendencies toward higher cell survival.In PRV-infected RAW264.7 cells, luteolin potently inhibited the production of NO, iNOS, COX-2 and inflammatory cytokine production. Luteolin did not inhibit the phosphorylation of ERK 1/2, p38, and JNK 1/2 either. We found that PRV-induced NF-κB activation is regulated through inhibition of STAT1and STAT3 phosphorylation in response to luteolin. Additionally, luteolin caused the induction of HO-1 via upregulation of Nrf2, both of which are involved in the secretion of proinflammatory mediators. The blockade of HO-1 expression with SnPP, a HO-1 inhibitor, attenuated HO-1 induction by luteolin and thus mitigated its anti-inflammatory effects during PRV-infected RAW264.7 cells. Taken together, our data indicate that luteolin diminishes the proinflammatory mediators NO, inflammatory cytokines and the expression of their regulatory genes, iNOS and COX-2, in PRV-infected RAW264.7 cells by inhibiting STAT1/3 dependent NF-κB activation and inducing Nrf2mediated HO-1 expression.

Bromodomain and extra-terminal domain bromodomain inhibition prevents synovial inflammation via blocking IκB kinase–dependent NF-κB activation in rheumatoid fibroblast-like synoviocytes

To explore the roles of the bromodomain (Brd) and extra-terminal domain (BET) of chromatin adaptors in regulating synovial inflammation in RA. Fibroblast-like synoviocytes (FLSs) were isolated from synovial tissue from RA patients. A specific BET inhibitor, JQ1, and short hairpin RNA (shRNA) for Brd2 or Brd4 were used to evaluate the role of the BET Brd in inflammatory responses. Protein expression was measured by western blot or immunofluorescence staining. Nuclear factor kappa B (NF-κB) gene activity was detected by luciferase assay. The secretion and gene expression of cytokines and MMPs were evaluated by ELISA and real-time PCR, respectively. FLS proliferation was detected by BrdU incorporation. Four Brd proteins, including Brd2, Brd3, Brd4 and Brdt, were expressed in FLSs from patients with RA and OA; however, the expression of Brd2 and Brd4 was increased in RA compared with that in OA. Treatment with JQ1, Brd2 shRNA or Brd4 shRNA decreased the production of pro-inflammatory cytokines (TNFα, IL-1β, IL-6 and IL-8), MMPs expression (MMP-1, MMP-3 and MMP-13) and proliferation by RA FLSs. BET inhibition downregulated TNFα-induced NF-κB-dependent transcription and expression of the NF-κB target genes. JQ1 suppressed the phosphorylation of IκB kinaseβ and IκBα, and nuclear translocation of p65. Intraperitoneal injection of JQ1 in mice with collagen-induced arthritis reduced synovial inflammation, joint destruction and serum levels of the anti-CII antibodies TNFα and IL-6. This study implicates BET Brds as important regulators of IκB kinase/NF-κB-mediated synovial inflammation of RA and identifies BET proteins as novel therapeutic targets in inflammatory arthritis.

CgIκB3, the third novel inhibitor of NF-kappa B (IκB) protein, is involved in the immune defense of the Pacific oyster, Crassostrea gigas.

Inhibitor of NF-κB (IκB), the important regulator of NF-κB/Rel signaling pathway, plays the crucial role in immune response of both vertebrates and invertebrates. Here, a novel homologue of IκB was cloned from Crassostrea gigas, and designated as CgIκB3. The complete CgIκB3 cDNA was 1282 bp in length, including a 942 bp open reading frame (ORF), a 51 bp 5' UTR and a 289 bp 3' UTR. The ORF encodes a putative protein of 313 amino acids with a predicted molecular weight of approximately 34.7 kDa. Sequence analysis reveals that CgIκB3 contains a conserved degradation motif but with only five ankyrin repeats. Neither a PEST domain nor a C-terminal casein kinase II phosphorylation site was identified through either alignment or bioinformatic prediction. Phylogenetic analysis suggested that CgIκB3 shares common ancestor with CgIκB1 rather CgIκB2, and theoretically it may originate from one duplication event prior to divergence of CgIκB1 and CgIκB2. Tissue expression analyses demonstrated that CgIκB3 mRNA is the most abundant in gills and heart. The expression following PAMP infection showed that CgIκB3 was significantly up-regulated in a similar pattern when challenged with LPS, HKLM or HKVA, respectively. Moreover, similar to CgIκB1 and CgIκB2, CgIκB3 can also inhibit Rel dependent NF-κB activation in HEK293 cells in a dose-dependent manner. In summary, these findings suggest that CgIκB3 can be as the functional inhibitor of NF-κB/Rel and involved in the host defense of C. gigas. The discovery of the third IκB emphasizes the complexity and importance of the regulation on NF-κB activation.

Abstract 5109: The CARMA3-Bcl10-MALT1 signalosome mediates NF-κB activation and cellular invasion in AGTR1-positive breast cancer

Abstract Angiotensin II (Ang II) is a potent vasoconstrictor and vascular pro-inflammatory mediator, known classically for its role in promoting arterial dysfunction. Many of these pathogenic effects result from activation of NF-κB in response to stimulation of the type-1 Ang II receptor (AGTR1), a G protein-coupled receptor. We previously discovered that a complex composed of three proteins, CARMA3, Bcl10 and MALT1 (CBM signalosome) mediates AGTR1-dependent activation of NF-κB in vascular cells. Despite its principal role in vascular pathobiology, we recently found that AGTR1 is aberrantly overexpressed in 10-20% of breast cancers (characterized as Luminal, ER+, PR+, Her2-). In this context, AGTR1 promotes cellular invasion and in vivo tumorigenesis, but the mechanisms driving this effect of AGTR1 have remained unclear. We hypothesized that stimulation of AGTR1 in this subset of breast tumors induces CBM-dependent NF-κB activation, thus contributing to tumorigenesis. To develop experimental models for studying the impact of AGTR1 in breast cancer (BC), we screened a panel of BC cell lines and found overexpression of endogenous AGTR1 in BT549 cells, among a few others, but no expression in most lines. To complement the BT549 line, we stably over-expressed exogenous AGTR1 in ZR75 cells (an AGTR1-, luminal line) to produce the ZR75-AGTR1 line. All BC lines tested, irrespective of AGTR1 status, expressed CARMA3, Bcl10 and MALT1. We found that Ang II treatment induces time-dependent phosphorylation of IκB, indicating NF-κB activation, in both BT549 and ZR75-AGTR1 cells, but not in control ZR75 cells. We then employed an NF-κB reporter assay to generate further evidence of NF-κB activation in ZR75-AGTR1 cells. We also demonstrated induction of several endogenous NF-κB target genes using real-time Q-PCR. Importantly, Ang II-dependent NF-κB activation is effectively blocked by pretreatment with losartan (AGTR1 antagonist) or with IKK-VI (IKKβ inhibitor), as well as by siRNA-mediated knockdown of Bcl10 or MALT1. These data indicate that Ang II dependent NF-κB activation in these cells is dependent on activation of AGTR1, proceeds through the canonical NF-κB machinery, and requires the CBM signalosome. Moreover, we showed that AGTR1 activation triggers a dramatic increase in migration and invasion of both BT549 and ZR75-AGTR1 cells, and that this response is completely blocked by siRNA-mediated Bcl10 knockdown. These results demonstrate for the first time that AGTR1 stimulation leads to NF-κB activation in a subset of breast cancer cells, and link this response to aggressive phenotypic behavior. These studies have significant clinical implications since AGTR1 antagonists, currently used for treatment of hypertension, might be effectively re-deployed for treatment of breast cancers that harbor AGTR1 overexpression. Inhibition of CBM-dependent signaling may also represent a novel treatment approach. Citation Format: Prasanna Ekambaram, Nathaniel Hubel, Jia-Ying Lee, Linda Klei, Vincent Concel, Philip Delekta, Scott Tomlins, Linda McAllister-Lucas, Peter Lucas. The CARMA3-Bcl10-MALT1 signalosome mediates NF-κB activation and cellular invasion in AGTR1-positive breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5109. doi:10.1158/1538-7445.AM2015-5109

Low Concentrations of Uncouplers of Oxidative Phosphorylation Prevent Inflammatory Activation of Endothelial Cells by Tumor Necrosis Factor.

In endothelial cells, mitochondria play an important regulatory role in physiology as well as in pathophysiology related to excessive inflammation. We have studied the effect of low doses of mitochondrial uncouplers on inflammatory activation of endothelial cells using the classic uncouplers 2,4-dinitrophenol and 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole, as well as the mitochondria-targeted cationic uncoupler dodecyltriphenylphosphonium (C12TPP). All of these uncouplers suppressed the expression of E-selectin, adhesion molecules ICAM1 and VCAM1, as well as the adhesion of neutrophils to endothelium induced by tumor necrosis factor (TNF). The antiinflammatory action of the uncouplers was at least partially mediated by the inhibition of NFκB activation due to a decrease in phosphorylation of the inhibitory subunit IκBα. The dynamic concentration range for the inhibition of ICAM1 expression by C12TPP was three orders of magnitude higher compared to the classic uncouplers. Probably, the decrease in membrane potential inhibited the accumulation of penetrating cations into mitochondria, thus lowering the uncoupling activity and preventing further loss of mitochondrial potential. Membrane potential recovery after the removal of the uncouplers did not abolish its antiinflammatory action. Thus, mild uncoupling could induce TNF resistance in endothelial cells. We found no significant stimulation of mitochondrial biogenesis or autophagy by the uncouplers. However, we observed a decrease in the relative amount of fragmented mitochondria. The latter may significantly change the signaling properties of mitochondria. Earlier we showed that both classic and mitochondria-targeted antioxidants inhibited the TNF-induced NFκB-dependent activation of endothelium. The present data suggest that the antiinflammatory effect of mild uncoupling is related to its antioxidant action.

RIP1 Kinase Is an Oncogenic Driver in Melanoma.

Although many studies have uncovered an important role for the receptor-binding protein kinase RIP1 in controlling cell death signaling, its possible contributions to cancer pathogenesis have been little explored. Here, we report that RIP1 functions as an oncogenic driver in human melanoma. Although RIP1 was commonly upregulated in melanoma, RIP1 silencing inhibited melanoma cell proliferation in vitro and retarded the growth of melanoma xenografts in vivo. Conversely, while inducing apoptosis in a small proportion of melanoma cells, RIP1 overexpression enhanced proliferation in the remaining cells. Mechanistic investigations revealed that the proliferative effects of RIP1 overexpression were mediated by NF-κB activation. Strikingly, ectopic expression of RIP1 enhanced the proliferation of primary melanocytes, triggering their anchorage-independent cell growth in an NF-κB-dependent manner. We identified DNA copy-number gain and constitutive ubiquitination by a TNFα autocrine loop mechanism as two mechanisms of RIP1 upregulation in human melanomas. Collectively, our findings define RIP1 as an oncogenic driver in melanoma, with potential implications for targeting its NF-κB-dependent activation mechanism as a novel approach to treat this disease.