Tumor Necrosis Factor-alpha Stimulation Research Articles

Features of endothelial dysfunction in umbilical cord vessels of women with gestational diabetes

Background and aimsGestational diabetes (GDM) is associated with increased oxidative stress and overexpression of inflammatory cytokines, both of which might lead to endothelial dysfunction and vascular disease. As such, GDM could be viewed as a sort of ‘short lived’ metabolic syndrome. As umbilical cord vessels represent a suitable model for the study of vascular alterations brought about by GDM, the aim of the present work was to characterize the phenotype of human umbilical vein endothelial cells (HUVECs) chronically exposed to hyperglycaemia and to a pro-inflammatory environment during pregnancy so as to identify molecular modifications of cellular homoeostasis eventually impacting on endothelial dysfunction. Methods and resultTissue specimens and HUVECs were obtained from umbilical cords of GDM and control women. As compared to controls, GD-HUVEC exhibited enhanced monocyte adhesion and vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) expression and exposure on plasma membrane after tumour necrosis factor-alpha (TNF-α) stimulation (Western blot, flow cytometer). As compared to control cells, GD-HUVEC in basal conditions exhibited enhanced monocyte adhesion, nitric oxide synthase (NOS) expression and activity (eNOS Real-Time polymerase chain reaction, Western Blot for eNOS total protein and monomers/dimers ratio, conversion of [3H]-L-arginine in [3H]-L-citrulline), increased O2– generation together with increased NT levels (immunofluorescence) and reduced NO bioavailability (guanosine 3′,5′-monophosphate (cGMP) production, EIA). Furthermore, immunohistochemistry revealed increased eNOS and NT immunoreactivity in GD umbilical cords. ConclusionEndothelial cells exposed in vivo even transiently to hyperglycaemia, oxidative stress and inflammation exhibit durable pro-atherogenic modifications.

Spinal release of tumour necrosis factor activates c-Jun N-terminal kinase and mediates inflammation-induced hypersensitivity.

BackgroundMounting evidence points to individual contributions of tumour necrosis factor-alpha (TNF) and the c-Jun N-terminal kinase (JNK) pathway to the induction and maintenance of various pain states. Here we explore the role of spinal TNF and JNK in carrageenan-induced hypersensitivity. As links between TNF and JNK have been demonstrated in vitro, we investigated if TNF regulates spinal JNK activity in vivo.MethodsTNF levels in lumbar cerebrospinal fluid (CSF) were measured by enzyme-linked immunosorbent assay, spinal TNF gene expression by real-time polymerase chain reaction and TNF protein expression, JNK and c-Jun phosphorylation by western blotting. The role of spinal TNF and JNK in inflammation-induced mechanical and thermal hypersensitivity was assessed by injecting the TNF inhibitor etanercept and the JNK inhibitors SP600125 and JIP-1 intrathecally (i.t.). TNF-mediated regulation of JNK activity was examined by assessing the effect of i.t. etanercept on inflammation-induced spinal JNK activity.ResultsTNF levels were increased in CSF and spinal cord following carrageenan-induced inflammation. While JNK phosphorylation followed the same temporal pattern as TNF, c-jun was only activated at later time points. Intrathecal injection of TNF and JNK inhibitors attenuated carrageenan-induced mechanical and thermal hypersensitivity. TNF stimulation induced JNK phosphorylation in cultured spinal astrocytes and blocking the spinal actions of TNF in vivo by i.t. injection of etanercept reduced inflammation-induced spinal JNK activity.ConclusionsHere we show that spinal JNK activity is dependent on TNF and that both TNF and the JNK signalling pathways modulate pain-like behaviour induced by peripheral inflammation.

Negative Elongation Factor Is Required for the Maintenance of Proviral Latency but Does Not Induce Promoter-Proximal Pausing of RNA Polymerase II on the HIV Long Terminal Repeat

The role of the negative elongation factor (NELF) in maintaining HIV latency was investigated following small hairpin RNA (shRNA) knockdown of the NELF-E subunit, a condition that induced high levels of proviral transcription in latently infected Jurkat T cells. Chromatin immunoprecipitation (ChIP) assays showed that latent proviruses accumulate RNA polymerase II (RNAP II) on the 5' long terminal repeat (LTR) but not on the 3' LTR. NELF colocalizes with RNAP II, and its level increases following proviral induction. RNAP II pause sites on the HIV provirus were mapped to high resolution by ChIP with high-throughput sequencing (ChIP-Seq). Like cellular promoters, RNAP II accumulates at around position +30, but HIV also shows additional pausing at +90, which is immediately downstream of a transactivation response (TAR) element and other distal sites on the HIV LTR. Following NELF-E knockdown or tumor necrosis factor alpha (TNF-α) stimulation, promoter-proximal RNAP II levels increase up to 3-fold, and there is a dramatic increase in RNAP II levels within the HIV genome. These data support a kinetic model for proviral transcription based on continuous replacement of paused RNAP II during both latency and productive transcription. In contrast to most cellular genes, HIV is highly activated by the combined effects of NELF-E depletion and activation of initiation by TNF-α, suggesting that opportunities exist to selectively activate latent HIV proviruses.

EZH2, a Potential Regulator of Dental Pulp Inflammation and Regeneration

IntroductionDental pulp has limited capability to regenerate, which happens in the early stage of pulpitis. An ambiguous relationship exists; inflammation may impair or support pulp regeneration. Epigenetics, which is involved in cell proliferation and inflammation, could regulate human dental pulp cell (HDPCs) regeneration. The aim of this study was to determine the role of the epigenetic mark, enhancer of zeste homolog 2 (EZH2), in the inflammation, proliferation, and regeneration of dental pulp. We used trimethylated histone H3 lysine 27(H3K27me3) and its lysine demethylase 6B (KDM6B) to monitor functional effects of altered EZH2 levels. MethodsWe detected epigenetic marks (EZH2, H3K27me3, and KDM6B) in pulp tissue by immunohistochemistry and immunofluorescence. EZH2 levels in HDPCs in inflammatory responses or differentiation were analyzed by quantitative polymerase chain reaction and Western blot. Quantitative polymerase chain reaction was used to assess the effects of EZH2 inhibition on interleukins in HDPCs upon tumor necrosis factor alpha stimulation. Cell proliferation was tested by cell counting kit-8, cell cycle, and apoptosis analysis. HDPC differentiation was investigated by quantitative polymerase chain reaction, alkaline phosphatase activity, and oil red O staining. ResultsEZH2 and H3K27me3 were decreased, whereas KDM6B was increased in infected pulp tissue and cells, which were similar to HDPC differentiation. EZH2 inhibition suppressed IL-1b, IL-6, and IL-8 messenger RNA (mRNA) in HDPCs upon inflammatory stimuli and impeded HDPC proliferation by decreasing cell number, arresting cell cycle, and increasing apoptosis. Suppressed EZH2 impaired adipogenesis, peroxisome proliferator-activated receptor r (PPAR-r), and CCAAT-enhancer binding protein a (CEBP/a) mRNA in adipogenic induction while enhancing alkaline phosphatase activity, Osx, and bone sialoprotein (BSP) mRNA in mineralization induction of HDPCs. ConclusionsEZH2 inhibited HDPC osteogenic differentiation while enhancing inflammatory response and proliferation, suggesting its role in pulp inflammation, proliferation, and regeneration.

Exhaustive exercise increases the TNF-α production in response to flagellin via the upregulation of toll-like receptor 5 in the large intestine in mice

Although intense exercise may induce temporary immune depression, it is unclear whether exercise stimulates tumor necrosis factor-alpha (TNF-α) production in response to flagella protein flagellin (FG), which binds to toll-like receptor 5 (TLR5) and induces the production of pro-inflammatory cytokines. Male C3H/HeN mice were administered FG (1mg/kg, i.v.) after exhaustive exercise (EX), and the plasma TNF-α concentrations were examined. The production of TNF-α and the TLR5 expression in both RAW264 and Caco2 cells were measured under FG conditions in vitro. Although the plasma TNF-α concentrations were observed to significantly increase in both the EX and non-EX (N-EX) mice (p<0.01, respectively) following FG injection, the TNF-α levels in the EX mice were significantly higher than those observed in the N-EX mice (p<0.01). Epinephrine (Ep) treatment accelerated the FG-induced TNF-α production and TLR5 expression on the Caco2, but not RAW264 cells. Interestingly, a high Ep-induced TLR5 expression was observed on the Caco2 cell surface, which was inhibited by an inhibitor of phosphoinositide3-kinase (PI3K), Ly294002, as well as a β-adrenergic blocker, propranolol. In addition, the EX-induced TNF-α production observed in response to FG was also attenuated by pretreatment with propranolol. Our findings suggest that exhaustive exercise upregulates the production of TNF-α in response to FG via a high expression of TLR5 on the intestinal cell surface following the stimulation of β-adrenergic receptors with exercise.

Triglyceride-rich lipoprotein modulates endothelial vascular cell adhesion molecule (VCAM)-1 expression via differential regulation of endoplasmic reticulum stress.

Circulating triglyceride-rich lipoproteins (TGRL) from hypertriglyceridemic subjects exacerbate endothelial inflammation and promote monocyte infiltration into the arterial wall. We have recently reported that TGRL isolated from human blood after a high-fat meal can elicit a pro- or anti-atherogenic state in human aortic endothelial cells (HAEC), defined as up- or down-regulation of VCAM-1 expression in response to tumor necrosis factor alpha (TNFα) stimulation, respectively. A direct correlation was found between subjects categorized at higher risk for cardiovascular disease based upon serum triglycerides and postprandial production of TGRL particles that increased VCAM-1-dependent monocyte adhesion to inflamed endothelium. To establish how TGRL metabolism is linked to VCAM-1 regulation, we examined endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) pathways. Regardless of its atherogenicity, the rate and extent of TGRL internalization and lipid droplet formation by HAEC were uniform. However, pro-atherogenic TGRL exacerbated ER membrane expansion and stress following TNFα stimulation, whereas anti-atherogenic TGRL ameliorated such effects. Inhibition of ER stress with a chemical chaperone 4-phenylbutyric acid decreased TNFα-induced VCAM-1 expression and abrogated TGRL’s atherogenic effect. Activation of ER stress sensors PKR-like ER-regulated kinase (PERK) and inositol requiring protein 1α (IRE1α), and downstream effectors including eukaryotic initiation factor-2α (eIF2α), spliced X-box-binding protein 1 (sXBP1) and C/EBP homologous protein (CHOP), directly correlated with the atherogenic activity of an individual’s TGRL. Modulation of ER stress sensors also correlated with changes in expression of interferon regulatory factor 1 (IRF-1), a transcription factor of Vcam-1 responsible for regulation of its expression. Moreover, knockdown studies using siRNA defined a causal relationship between the PERK/eIF2α/CHOP pathway and IRF-1-mediated VCAM-1 expression. We conclude that ER stress and the UPR contribute to the regulation of Vcam-1 transcription as a function of the atherogenic nature of TGRL.

252 : Analysis of a cross-talk between various chemokines and bone marrow-derived stem cells in patients with pancreatic cancer

Various experimental studies suggest that pancreatic malignancies may originate from stem cells. Recently we reported that in patients with pancreatic tumors intensified trafficking of selected populations of bone marrow (BM)-derived stem cells (SCs) is observed, and this is associated with activity of the complement cascade (Starzynska et al. JCMM 2013). Unfortunately the mechanisms responsible for this “selective” mobilization of BMSCs are not fully known. However, it is hypothesized that various chemokines may participate in this process. In this study we analyzed levels of interleukins (IL-1, IL-6, IL-8, IL-10, IL-12, IL-17 and IL-23) together with granulocyte-colony stimulating factor (G-CSF) and tumor necrosis factor-alpha (TNF α ) in patients with pancreatic neoplasms ( n = 26) and control individuals ( n = 32), and verified whether these molecules are associated with previously observed phenomenon of selective BMSCs egress in patients with pancreatic neoplasms. Our results demonstrated that in patients with pancreatic neoplasms significantly (up to 3 times) higher levels of IL-6, IL-8, IL-10 and TNFα are observed (in all cases at least P P = 0.002). No significant differences in IL-1, IL-12 nor G-CSF levels were stated. In our study, IL-6, IL-8 and TNFα levels negatively correlated with the absolute numbers of circulating hematopoietic stem cells (HSCs) and endothelial progenitor cells (EPCs) (in all cases at least P r = 0.57; P P α may be involved into orchestration of intensified BMSCs trafficking in patients with pancreatic tumors. Clinical value of these molecules must be assessed in further studies. Supported by MNiSW Grant (402 423038).

Distinctive roles of receptor‐interacting protein kinases 1 and 3 in caspase‐independent cell death of L929

Upon tumour necrosis factor alpha (TNFα) stimulation, cells respond actively by way of cell survival, apoptosis or programmed necrosis. The receptor-interacting proteins 1 (RIP1) and 3 (RIP3) are responsible for TNFα-mediated programmed necrosis. To delineate the differential contributions of RIP3 and RIP1 to programmed necrosis, L929 cells were stimulated with TNFα, carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone (zVAD) or zVAD along with TNFα following RNA interference against RIP1 and RIP3, respectively. RIP1 silencing did not protect cells from TNFα-mediated cell death, while RIP3 down-regulation made them refractory to TNFα. The heat shock protein 90 inhibitor geldanamycin (GA) down-regulated both RIP1 and RIP3 expression, which rendered cells resistant to zVAD/TNFα-mediated cell death but not to TNFα-mediated cell death alone. Therefore, the protective effect of GA on zVAD/TNFα-stimulated necrosis might be attributed to RIP3, not RIP1, down-regulation. Pretreatment of L929 cells with rapamycin mitigated zVAD-mediated cell death, while the autophagy inhibitor chloroquine did not affect necrotic cell death. Meanwhile, necrotic cell death by zVAD and TNFα was caused by reactive oxygen species generation and effectively diminished by lipid-soluble butylated hydroxyanisole. Taken together, the results indicate that RIP1 and RIP3 can independently mediate death signals being transduced by two different death stimuli, zVAD and TNFα.

Deciphering the role of 75kDa SirT1 fragment in osteoarthritis

s / Osteoarthritis and Cartilage 21 (2013) S9–S62 S49 Fig. Molecular networks generated from the genes differentially expressed by age. The molecular networks generated from genes differentially expressed in meniscus by age (top: up-regulated genes; bottom: down-regulated genes) using GRANITE. The colors are based on the database from which the network is extracted. ellipse 1⁄4 protein; square 1⁄4 transcription factor 79 DECIPHERING THE ROLE OF 75KDA SIRT1 FRAGMENT IN OSTEOARTHRITIS M. Dvir-Ginzberg y, H. Oppenheimer y, H. Meir y, O. Gabay z, K. Zaal z, C. Sanchez x, A. Haze k, L. Kandel k, M. Leibergall k. yHebrew Univ. of Jerusalem, Jerusalem, Israel; zNIAMS, NIH, MD, USA; xHebrew Univ. of Jerusalem, University of Liege, Liege, Belgium; kHebrew Univ. of JerusalemHadassah Med. Center, Jerusalem, Israel Objective: SirT1 is a nuclear NAD-dependent deacetylase associated with cellmetabolismand survival. In joints, recent evidence shows that it regulates cartilage homeostasis and is involved in the inflammatory phase of osteoarthritis (OA). It is widely held that the inflammatory cytokines tumor necrosis factor alpha (TNFa), and interleukin 1b (IL-1b) may elicit chondrocyte death associated with the deterioration of articular cartilage (AC) in OA. Exposing human chondrocytes to both cytokines leads to cathepsin B-mediated cleavage of the nuclear full-length SirT1 (FLSirT1; 110kDa) to generate a stable but enzymatically inactive 75kDa fragment of SirT1 (75SirT1). Here we aim to elucidate the biological andbiochemical role of 75kDa SirT1 fragment in-vivo and in-vitro Methods: Using immunoblot analyses we aimed to detect cathepsin B, FLSirT1 and/or 75SirT1 in OA and normal human chondrocytes. Confocal imaging of SirT1 was used tomonitor its subcellular trafficking following TNFa stimulation of human chondrocytes. Coimmunofluorescent staining for cathepsin B, mitochondrial cytochrome oxidase subunit IV and lysosome-associated membrane protein 1 together with SirT1was performed. Human chondrocytes were tested for apoptosis by fluorescence-activated cell sorter analysis and immunoblotting for caspases 3 and 8. Human chondrocyte mitochondrial extracts were obtained and analyzed for 75SirT1-cytochrome C association. In-vivo assays of heterozygous haploinsufficient (SirT1+/-) and wildtype (WT; SirT1+/+) 129/J mice aged 1 or 9 months were systematically compared for musculoskeletal features, scored for osteoarthritis (OA) severity, and monitored for chondrocyte apoptosis in articular cartilage. Protein extracts from articular chondrocytes were isolated and immunoblotted for SirT1 and active caspase 3. Results: Confocal imaging, immunoprecipitation assays and immunoblot analyses following TNFa challenge of human chondrocytes exhibited that 75SirT1 was generated and exported to the cytoplasm wherein it colocalized with the mitochondrial membrane and associates with cytochrome C. Additionally, levels of cathepsin B and 75SirT1 were elevated in OA versus normal chondrocytes. Subjecting human chondrocytes to TNFa and a cathepsin B inhibitor (ALLN), enhanced levels of apoptotic cell and cleaved caspase 3. Immunoblot assays comparing medial tibial plateau articular cartilage (MTP-AC) of heterozygous haploinsufficient (SirT1+/-) and wild-type (WT; SirT1+/+) 129/J mice revealed reduced levels of FLSirT1 in both strains at 9 months compared to their 1 month equivalent. WT 9-monthold strains presented the 75SirT1 fragments in immunoblot assays, whereas age-matched SirT1+/-mice possessed undetected 75SirT1 levels. Interestingly, 9 month-old SirT1+/mice exhibited increased OA severity andaugmented levels of apoptosis comparedwithage-matchedWTmice. Conclusion: Despite 75SirT1 being enzymatically impaired our results show that it is relatively stable and participates in promoting chondrocyte survival following exposure to proinflammatory cytokines or during articular cartilage maturation. 80 ASYMPTOMATIC INDIVIDUALS WITH RADIOGRAPHIC EVIDENCE OF KNEE OSTEOARTHRITIS WALK WITH DIFFERENT KNEE MECHANICS PATTERNS THAN SYMPTOMATIC INDIVIDUALS WITH THE SAME RADIOGRAPHIC EVIDENCE J.L. Astephen Wilson, G. Hatfield, W.D. Stanish, C.L. HubleyKozey. Dalhousie Univ., Halifax, NS, Canada

IKKε-Mediated Tumorigenesis Requires K63-Linked Polyubiquitination by a cIAP1/cIAP2/TRAF2 E3 Ubiquitin Ligase Complex

IκB kinase ε (IKKε, IKBKE) is a key regulator of innate immunity and a breast cancer oncogene, amplified in ~30% of breast cancers, that promotes malignant transformation through NF-κB activation. Here, we show that IKKε is modified and regulated by K63-linked polyubiquitination at lysine 30 and lysine 401. Tumor necrosis factor alpha and interleukin-1β stimulation induces IKKε K63-linked polyubiquitination over baseline levels in both macrophages and breast cancer cell lines, and this modification is essential for IKKε kinase activity, IKKε-mediated NF-κB activation, and IKKε-induced malignant transformation. Disruption of K63-linked ubiquitination of IKKε does not affect its overall structure but impairs the recruitment of canonical NF-κB proteins. A cIAP1/cIAP2/TRAF2 E3 ligase complex binds to and ubiquitinates IKKε. Altogether, these observations demonstrate that K63-linked polyubiquitination regulates IKKε activity in both inflammatory and oncogenic contexts and suggests an alternative approach to targeting this breast cancer oncogene.

Shikonin induces programmed necrosis-like cell death through the formation of receptor interacting protein 1 and 3 complex

An alternative cell demise programmed necrosis has also been proposed when apoptotic machinery is impaired or blocked during tumor necrosis factor alpha (TNFα) stimulation. Shikonin (SKN), an herbal extract from the Chinese plant, has been reported to induce either apoptosis or necrosis depending on cell types or its concentrations. In this presentation, SKN caused cell death of NIH3T3 in a dose-dependent manner. Intriguingly, SKN-mediated cell death was in part protected by necrostatin-1 (Nec-1), a specific inhibitor of programmed necrosis, but not zVAD a pan-caspase inhibitor. SKN directly mediated cell death via receptor interacting protein1 and 3 (RIP1-RIP3) complex formation, which is required for TNFα-mediated programmed necrosis. Additionally, SKN-caused cell death was reversed by a reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC) whereas TNFα-mediated necrosis was successfully protected by butylated hydroxyanisole (BHA), implying that ROS may be differentially derived from death inducing agents. Concurrently with the protective effect of the ROS scavenger or Nec-1 on TNFα or SKN, the RIP1-RIP3 complex was significantly affected in the presence of those agents. Here, it is highlighted that SKN as well as TNFα can directly mediate cell death via a pronecrotic complex, but ROS were generated via different routes depending on cell death-inducing agents.

Differences in cytokine stimulation between methicillin-susceptible and methicillin-resistant Staphylococcus aureus in an experimental endocarditis model

The present study focused on the impact of methicillin resistance of Staphylococcus aureus on cytokine production by monocytes. Cytokine stimulation was studied by 20 heat-killed isolates, 10 methicillin-susceptible Staphylococcus aureus (MSSA) and 10 methicillin-resistant Staphylococcus aureus (MRSA). Bacterial endocarditis was induced in 27 male rabbits by challenge with 1 MSSA isolate and 1 MRSA isolate. Blood was sampled for estimation of tumor necrosis factor-alpha (TNF-α) and malondialdehyde (MDA) and stimulation of monocytes. MSSA induced greater stimulation of TNF-α than MRSA, as shown after addition of a Toll-like receptor-4 (TLR4) antagonist. Survival of rabbits challenged by MRSA was prolonged compared to those challenged by MSSA. Serum MDA was greater after MSSA stimulation. Serum of animals challenged by MRSA stimulated greater release of interleukin (IL)-8 and IL-10 compared with MSSA: the opposite was observed for TNF-α. It is concluded that MSSA and MRSA induce a different pattern of TNF-α stimulation through a TLR4-independent mechanism, leading to shorter survival in experimental endocarditis.

Intermolecular Binding between TIFA-FHA and TIFA-pT Mediates Tumor Necrosis Factor Alpha Stimulation and NF-κB Activation

Intermolecular Binding between TIFA-FHA and TIFA-pT Mediates Tumor Necrosis Factor Alpha Stimulation and NF-κB Activation

Epstein-Barr Virus BGLF4 Kinase Downregulates NF-κB Transactivation through Phosphorylation of Coactivator UXT

Epstein-Barr virus (EBV) BGLF4 is a member of the conserved herpesvirus kinases that regulate multiple cellular and viral substrates and play an important role in the viral lytic cycles. BGLF4 has been found to phosphorylate several cellular and viral transcription factors, modulate their activities, and regulate downstream events. In this study, we identify an NF-κB coactivator, UXT, as a substrate of BGLF4. BGLF4 downregulates not only NF-κB transactivation in reporter assays in response to tumor necrosis factor alpha (TNF-α) and poly(I·C) stimulation, but also NF-κB-regulated cellular gene expression. Furthermore, BGLF4 attenuates NF-κB-mediated repression of the EBV lytic transactivators, Zta and Rta. In EBV-positive NA cells, knockdown of BGLF4 during lytic progression elevates NF-κB activity and downregulates the activity of the EBV oriLyt BHLF1 promoter, which is the first promoter activated upon lytic switch. We show that BGLF4 phosphorylates UXT at the Thr3 residue. This modification interferes with the interaction between UXT and NF-κB. The data also indicate that BGLF4 reduces the interaction between UXT and NF-κB and attenuates NF-κB enhanceosome activity. Upon infection with short hairpin RNA (shRNA) lentivirus to knock down UXT, a spontaneous lytic cycle was observed in NA cells, suggesting UXT is required for maintenance of EBV latency. Overexpression of wild-type, but not phosphorylation-deficient, UXT enhances the expression of lytic proteins both in control and UXT knockdown cells. Taking the data together, transcription involving UXT may also be important for EBV lytic protein expression, whereas BGLF4-mediated phosphorylation of UXT at Thr3 plays a critical role in promoting the lytic cycle.

Intermolecular Binding between TIFA-FHA and TIFA-pT Mediates Tumor Necrosis Factor Alpha Stimulation and NF-κB Activation

The forkhead-associated (FHA) domain recognizes phosphothreonine (pT) with high specificity and functional diversity. TIFA (TRAF-interacting protein with an FHA domain) is the smallest FHA-containing human protein. Its overexpression was previously suggested to provoke NF-κB activation, yet its exact roles in this signaling pathway and the underlying molecular mechanism remain unclear. Here we identify a novel threonine phosphorylation site on TIFA and show that this phosphorylated threonine (pT) binds with the FHA domain of TIFA, leading to TIFA oligomerization and TIFA-mediated NF-κB activation. Detailed analysis indicated that unphosphorylated TIFA exists as an intrinsic dimer and that the FHA-pT9 binding occurs between different dimers of TIFA. In addition, silencing of endogenous TIFA resulted in attenuation of tumor necrosis factor alpha (TNF-α)-mediated downstream signaling. We therefore propose that the TIFA FHA-pT9 binding provides a previously unidentified link between TNF-α stimulation and NF-κB activation. The intermolecular FHA-pT9 binding between dimers also represents a new mechanism for the FHA domain.

Dermal Stem Cells Can Differentiate Down an Endothelial Lineage

In this study, we have demonstrated that cells of neural crest origin located in the dermal papilla (DP) exhibit endothelial marker expression and a functional activity. When grown in endothelial growth media, DP primary cultures upregulate expression of vascular endothelial growth factor receptor 1 (FLT1) mRNA and downregulate expression of the dermal stem cell marker α-smooth muscle actin. DP cells have demonstrated functional characteristics of endothelial cells, including the ability to form capillary-like structures on Matrigel, increase uptake of low-density lipoprotein and upregulate ICAM1 (CD54) in response to tumour necrosis factor alpha (TNF-α) stimulation. We confirmed that these observations were not due to contaminating endothelial cells, by using DP clones. We have also used the WNT1cre/ROSA26R and WNT1cre/YFP lineage-tracing mouse models to identify a population of neural crest-derived cells in DP cultures that express the endothelial marker PECAM (CD31); these cells also form capillary-like structures on Matrigel. Importantly, cells of neural crest origin that express markers of endothelial and mesenchymal lineages exist within the dermal sheath of the vibrissae follicle.

Inflammatory stress exacerbates hepatic cholesterol accumulation via disrupting cellular cholesterol export

Both inflammation and cholesterol accumulation play important roles in the development of non-alcoholic fatty liver disease. This study was undertaken to investigate whether inflammation aggravated cholesterol accumulation via disrupting hepatic cholesterol export and we explored the underlying mechanisms. We used casein injection in C57BL/6J mice, and tumor necrosis factor alpha (TNF-α) stimulation in human hepatoblastoma cell line (HepG2) cells to induce inflammation. Intracellular cholesterol level was examined by Oil Red O staining and quantitative analysis. Bile acid level was quantified by colorimetric analysis. (3)[H] cholesterol assay by scintillation counting was performed to evaluate the cholesterol efflux. The mRNA and protein expression was examined by real-time polymerase chain reaction and Western blot. Inflammation increased cholesterol accumulation in livers of C57BL/6J mice and in HepG2 cells. High-fat diet in mice and low-density lipoprotein (LDL) loading in HepG2 cells increased bile acid synthesis and cholesterol efflux, enhanced the mRNA and protein expression of liver X receptor α (LXRα), peroxisome proliferator-activated receptors (PPARα, γ), cholesterol 7α-hydroxylase (CYP7A1) and ATP-binding cassette transporter A1 (ABCA1). However, inflammation reduced bile acid synthesis and cholesterol efflux even in high-fat-diet-fed mice and HepG2 cells in the presence of LDL loading. The enhanced effects of these genes and proteins expression due to high-fat diet and LDL loading were inhibited by inflammation both in vivo and in vitro. Inflammation disrupted PPAR-LXR-CYP7A1/ABCA1-mediated bile acid synthesis and cholesterol efflux resulting in exacerbated cholesterol accumulation in livers of C57BL/6J mice and HepG2 cells.

Highly pathogenic porcine reproductive and respiratory syndrome virus impairs LPS- and poly(I:C)-stimulated tumor necrosis factor-alpha release by inhibiting ERK signaling pathway

Atypical porcine reproductive and respiratory syndrome (PRRS) characterized by high morbidity and mortality emerged in China in 2006. The causative agent was confirmed to be a highly pathogenic PRRS virus (HP-PRRSV). However, the pathogenesis of HP-PRRSV is still uncertain. Here, the ability of the highly pathogenic strains (HV and JX) to induce tumor necrosis factor alpha (TNF-α) was studied. Our results showed that HV and JX were weaker inducers of TNF-α than the conventional strain CH-1a. Moreover, HV infection was demonstrated to suppress extracellular signal-regulated kinase (ERK) phosphorylation at the early time points. Pharmacologic inhibition or activation of ERK revealed that TNF-α production in HV-infected macrophages was associated with the activation status of ERK. Furthermore, HV- and JX-infection could potently impair lipopolysaccharide (LPS)- and poly(I:C)-stimulated TNF-α release in a dose dependent manner whereas synergistic effects were observed at mRNA level. The observation suggested the involvement of posttranslational impact of HP-PRRSV on TNF-α production, which might be attributed to the reduced ERK1/2 phosphorylation in response to toll-like receptor (TLR)-ligation. Taken together, our results indicated that HP-PRRSV infection could impair TNF-α production by inhibiting ERK signaling pathway, which might partially contribute to the pathogenesis of HP-PRRSV.

The fatty acid oxidation product 15‐A3t‐Isoprostane is a potent inhibitor of NFκB transcription and macrophage transformation

Fatty acids such as eicosapentaenoic acid (EPA) have been shown to be beneficial for neurological function and human health. It is widely thought that oxidation products of EPA are responsible for biological activity, although the specific EPA peroxidation product(s) which exert these responses have not yet been identified. In this work we provide the first evidence that the synthesized representative cyclopentenone IsoP, 15-A(3t)-IsoP, serves as a potent inhibitor of lipopolysaccharide-stimulated macrophage activation. The anti-inflammatory activities of 15-A(3t)-IsoP were observed in response not only to lipopolysaccharide, but also to tumor necrosis factor alpha and IL-1b stimulation. Subsequently, this response blocked the ability of these compounds to stimulate nuclear factor kappa b (NFκB) activation and production of proinflammatory cytokines. The bioactivity of 15-A(3t)-IsoP was shown to be dependent upon an unsaturated carbonyl residue which transiently adducts to free thiols. Site directed mutagenesis of the redox sensitive C179 site of the Ikappa kinase beta subunit, blocked the biological activity of 15-A(3t)-IsoP and NFκB activation. The vasoprotective potential of 15-A(3t)-IsoP was underscored by the ability of this compound to block oxidized lipid accumulation, a critical step in foam cell transformation and atherosclerotic plaque formation. Taken together, these are the first data identifying the biological activity of a specific product of EPA peroxidation, which is formed in abundance in vivo. The clear mechanism linking 15-A(3t)-IsoP to redox control of NFκB transcription, and the compound's ability to block foam cell transformation suggest that 15-A(3t)-IsoP provides a unique and potent tool to provide vaso- and cytoprotection under conditions of oxidative stress.

The Phosphoinositide-3-Kinase–Akt Signaling Pathway Is Important for Staphylococcus aureus Internalization by Endothelial Cells

Internalization of Staphylococcus aureus in bovine endothelial cells (BEC) is increased by tumor necrosis factor alpha stimulation and NF-κB activation. Because the phosphoinositide-3-kinase (PI3K)-Akt signaling pathway also modulates NF-κB activity, we considered whether the internalization of S. aureus by BEC is associated with the activity of PI3K and Akt. We found a time- and multiplicity of infection-dependent phosphorylation of Akt on Ser473 in BEC infected with S. aureus. This phosphorylation was inhibited by LY294002 (LY), indicating the participation of PI3K. Inhibition of either PI3K with LY or wortmannin, or Akt with SH-5, strongly reduced the internalization of S. aureus. Transfection of BEC with a dominant-negative form of the Akt gene significantly decreased S. aureus internalization, whereas transfection with the constitutively active mutant increased the number of internalized bacterium. Inhibition of PDK1 activity with OSU-03012 did not affect the level of S. aureus internalization, demonstrating that phosphorylation of Akt on Thr308 is not important for this process. Compared to the untreated control, the adherence of S. aureus to the surface of BEC was unaltered when cells were transfected or incubated with the pharmacological inhibitors. Furthermore, Akt activation by internalized S. aureus triggered a time-dependent phosphorylation of glycogen synthase kinase-3α (GSK-3α) on Ser21 and GSK-3β on Ser9 that was partially inhibited with SH-5. Finally, treatment of BEC with LY prior to S. aureus infection inhibited the NF-κB p65 subunit phosphorylation on Ser536, indicating the involvement of PI3K. These results suggest that PI3K-Akt activity is important for the internalization of S. aureus and phosphorylation of GSK-3α, GSK-3β, and NF-κB.