The zinc finger domain of IKKγ (NEMO) protein in health and disease

Caspase 6 promotes innate immune activation by functional crosstalk between RIPK1-IκBα axis in liver inflammation

BACKGROUND

Caspase 6 is an essential regulator in innate immunity, inflammasome activation and host defense. We aimed to characterize the causal mechanism of Caspase 6 in liver sterile inflammatory injury.

METHODS

Human liver tissues were harvested from patients undergoing ischemia-related hepatectomy to evaluate Caspase 6 expression. Subsequently, we created Caspase 6-knockout (Caspase 6KO) mice to analyze roles and molecular mechanisms of macrophage Caspase 6 in murine models of liver ischemia/reperfusion (IR) injury.

RESULTS

In human liver biopsies, Caspase 6 expression was positively correlated with more severe histopathological injury and higher serum ALT/AST level at one day postoperatively. Moreover, Caspase 6 was mainly elevated in macrophages but not hepatocytes in ischemic livers. Unlike in controls, the Caspase 6-deficient livers were protected against IR injury, as evidenced by inhibition of inflammation, oxidative stress and iron overload. Disruption of macrophage NF-κB essential modulator (NEMO) in Caspase 6-deficient livers deteriorated liver inflammation and ferroptosis. Mechanistically, Caspase 6 deficiency spurred NEMO-mediated IκBα phosphorylation in macrophage. Then phosphorylated-inhibitor of NF-κBα (p-IκBα) co-localized with receptor-interacting serine/ threonine-protein kinase 1 (RIPK1) in the cytoplasm to degradate RIPK1 under inflammatory conditions. The disruption of RIPK1-IκBα interaction preserved RIPK1 degradation, triggering downstream apoptosis signal-regulating kinase 1 (ASK1) phosphorylation and inciting NIMA-related kinase 7/NOD-like receptor family pyrin domain containing 3 (NEK7/NLRP3) activation in macrophages. Moreover, ablation of macrophage RIPK1 or ASK1 diminished NEK7/NLRP3-driven inflammatory response and dampened hepatocyte ferroptosis by reducing HMGB1 release from macrophages.

CONCLUSIONS

Our findings underscore a novel mechanism of Caspase 6 mediated RIPK1-IκBα interaction in regulating macrophage NEK7/NLRP3 function and hepatocytes ferroptosis, which provides therapeutic targets for clinical liver IR injury. Video Abstract.

LncRNA Gm26917 regulates inflammatory response in macrophages by enhancing Annexin A1 ubiquitination in LPS-induced acute liver injury

Long noncoding RNAs (lncRNAs) are defined as transcripts of more than 200 nucleotides that have little or no coding potential. LncRNAs function as key regulators in diverse physiological and pathological processes. However, the roles of lncRNAs in lipopolysaccharide (LPS)-induced acute liver injury (ALI) are still elusive. In this study, we report the roles of lncRNA Gm26917 induced by LPS in modulating liver inflammation. As key components of the innate immune system, macrophages play critical roles in the initiation, progression and resolution of ALI. Our studies demonstrated that Gm26917 localized in the cytoplasm of hepatic macrophages and globally regulated the expression of inflammatory genes and the differentiation of macrophages. In vivo study showed that lentivirus-mediated gene silencing of Gm26917 attenuated liver inflammation and protected mice from LPS-induced ALI. Furthermore, mechanistic study showed that the 3'-truncation of Gm26917 interacted with the N-terminus of Annexin A1, a negative regulator of the NF-κB signaling pathway. We also found that Gm26917 knockdown suppressed NF-κB activity by decreasing the ubiquitination of Annexin A1 and its interaction with NEMO. In addition, expression of Gm26917 in inflammatory macrophages was regulated by the transcription factor forkhead box M1 (FOXM1). LPS treatment dramatically increased the binding of FOXM1 to the promoter region of Gm26917 in macrophages. In summary, our findings suggest that lncRNA Gm26917 silencing protects against LPS-induced liver injury by regulating the TLR4/NF-κB signaling pathway in macrophages.

Can iron, zinc, copper and selenium status be a prognostic determinant in COVID-19 patients?

In severe COVID-19, the levels of iron (Fe), copper (Cu), zinc (Zn) and selenium (Se), do not only regulate host immune responses, but modify the viral genome, as well. While low serum Fe concentration is an independent risk factor for the increased death rate, Zn controls oxidative stress, synthesis of inflammatory cytokines and viral replication. Therefore, Zn deficiency associates with a worse prognosis. Although Cu exposure inactivates the viral genome and exhibits spike protein dispersal, increase in Cu/Zn due to high serum Cu levels, are correlated with enhanced risk of infections. Se levels are significantly higher in surviving COVID-19 patients. Meanwhile, both Zn and Se suppress the replication of SARS-CoV-2. Since the balance between the deficiency and oversupply of these metals due to a reciprocal relationship, has decisive effect on the prognosis of the SARS-CoV-2 infection, monitoring their concentrations may facilitate improved outcomes for patients suffering from COVID-19.

Procyanidins from Hawthorn (Crataegus Pinnatifida) Alleviates Lipid Metabolism Disorder via Inhibiting Insulin Resistance and Oxidative Stress, Normalizing Gut Microbiota Structure and Intestinal Barrier, Further Suppressing Hepatic Inflammation and Lipid Accumulation

Recently, lipid metabolism disorder (LMD) has been regarded as a risky factor leading to multiple diseases and affecting human health. Procyanidins have been reported to be the potential therapy for...

The NFκB Antagonist CDGSH Iron-Sulfur Domain 2 Is a Promising Target for the Treatment of Neurodegenerative Diseases

Proinflammatory response and mitochondrial dysfunction are related to the pathogenesis of neurodegenerative diseases (NDs). Nuclear factor κB (NFκB) activation has been shown to exaggerate proinflammation and mitochondrial dysfunction, which underlies NDs. CDGSH iron-sulfur domain 2 (CISD2) has been shown to be associated with peroxisome proliferator-activated receptor-β (PPAR-β) to compete for NFκB and antagonize the two aforementioned NFκB-provoked pathogeneses. Therefore, CISD2-based strategies hold promise in the treatment of NDs. CISD2 protein belongs to the human NEET protein family and is encoded by the CISD2 gene (located at 4q24 in humans). In CISD2, the [2Fe-2S] cluster, through coordinates of 3-cysteine-1-histidine on the CDGSH domain, acts as a homeostasis regulator under environmental stress through the transfer of electrons or iron-sulfur clusters. Here, we have summarized the features of CISD2 in genetics and clinics, briefly outlined the role of CISD2 as a key physiological regulator, and presented modalities to increase CISD2 activity, including biomedical engineering or pharmacological management. Strategies to increase CISD2 activity can be beneficial for the prevention of inflammation and mitochondrial dysfunction, and thus, they can be applied in the management of NDs.

Toddalolactone Protects Lipopolysaccharide-Induced Sepsis and Attenuates Lipopolysaccharide-Induced Inflammatory Response by Modulating HMGB1-NF-κB Translocation

Toddalolactone (TA-8) is a main compound isolated from Toddalia asiatica (L.) Lam., and its anti-inflammatory activity and anti-inflammatory mechanism are less studied. In the present study, we investigated the anti-inflammatory effects of TA-8. Our experimental results showed that TA-8 inhibited the production of pro-inflammatory cytokines by both lipopolysaccharide (LPS)-activated RAW 264.7 cells and septic mice. Moreover, TA-8 suppressed the NF-κB transcriptional activity, reduced the nuclear translocation and phosphorylation of NF-κB, blocked the translocation of HMGB1 from the nucleus to cytosol, and decreased LPS-induced up-regulation of TLR4 and IKBKB expression, and decreased IκBα phosphorylation. In addition, the administration of TA-8 decreased LPS-induced liver damage markers (AST and ALT), attenuated infiltration of inflammatory cells and tissue damage of lung, liver, and kidney, and improved survival in septic mice. Taken together, these results suggested that toddalolactone protects LPS-induced sepsis and attenuates LPS-induced inflammatory response by modulating HMGB1-NF-κB translocation. TA-8 could potentially be a novel anti-inflammatory and immunosuppressive drug candidate in the treatment of sepsis and septic shock.

Role of ZIP8 in regulating cell morphology and NF-κB/Snail2 signaling

ZIP8 is a recently identified membrane transporter which facilitates uptake of many substrates including both essential and toxic divalent metals (e.g. zinc, manganese, iron, cadmium) and inorganic selenium. Many ZIP8 regulated downstream signals and pathways remain to be elucidated. In this study, we investigated ZIP8 regulatory roles in downstream targets in ZIP8-gain and loss cells and in ZIP8 overexpressed lungs. Our results show that the overexpression of ZIP8 in mouse fibroblast cells (MEF) induces significant morphological change and re-organization of filament actin (F-actin), along with increased cell proliferation and migration rate. In ZIP8 knockout chronic myelogenous leukemia HAP1 cells, significant clonal morphological change with increased cell-cell adhesion was observed. In the ZIP8 overexpressed lung, F-actin was aberrantly enriched around the tracheal branch. In these ZIP8 gain and loss cell lines and ZIP8 transgenic lungs, we identified two relevant transcription factors, NF-κB and Snail2, whose activation is dependent on the ZIP8 level. They were both significantly upregulated in ZIP8 overexpressed cells and lungs. Expression of NF-κB and Snail2 targets, COL1A2 and E-cadherin, was also correspondingly elevated. Taken together, our results suggest that ZIP8 is a new regulator for cell morphology and cytoskeleton which involves NF-κB and Snail2.

Simulation of the Dynamics of Primary Immunodeficiencies in B Cells

Primary immunodeficiencies (PIDs) are a group of over 300 hereditary, heterogeneous, and mainly rare disorders that affect the immune system. Various aspects of immune system and PID proteins and genes have been investigated and facilitate systems biological studies of effects of PIDs on B cell physiology and response. We reconstructed a B cell network model based on data for the core B cell receptor activation and response processes and performed semi-quantitative dynamic simulations for normal and B cell PID failure modes. The results for several knockout simulations correspond to previously reported molecular studies and reveal novel mechanisms for PIDs. The simulations for CD21, CD40, LYN, MS4A1, ORAI1, PLCG2, PTPRC, and STIM1 indicated profound changes to major transcription factor signaling and to the network. Significant effects were observed also in the BCL10, BLNK, BTK, loss-of-function CARD11, IKKB, MALT1, and NEMO, simulations whereas only minor effects were detected for PIDs that are caused by constitutively active proteins (PI3K, gain-of-function CARD11, KRAS, and NFKBIA). This study revealed the underlying dynamics of PID diseases, confirms previous observations, and identifies novel candidates for PID diagnostics and therapy.

All-atom molecular dynamics comparison of disease-associated zinc fingers

An important regulatory domain of NF-[Formula: see text]B Essential Modulator (NEMO) is a ubiquitin-binding zinc finger, with a tetrahedral CYS3HIS1 zinc-coordinating binding site. Two variations of NEMO's zinc finger are implicated in various disease states including ectodermal dysplasia and adult-onset glaucoma. To discern structural and dynamical differences between these disease states, we present results of 48-[Formula: see text]s of molecular dynamics simulations for three zinc finger systems each in two states, with and without zinc-bound and correspondingly appropriate cysteine thiol/thiolate configurations. The wild-type protein, often studied for its role in cancer, maintains the most rigid and conformationally stable zinc-bound configuration compared with the diseased counterparts. The glaucoma-related protein has persistent loss of secondary structure except within the dominant conformation. Conformational overlap between wild-type and glaucoma isoforms indicate a competitive binding mechanism may be substantial in the malfunctioning configuration, while the alpha-helical disruption of the ectodermal dysplasia suggests a loss of binding selectivity is responsible for aberrant function.

Differential Health Effects of Constant versus Intermittent Exposure to Formaldehyde in Mice: Implications for Building Ventilation Strategies

Formaldehyde, an air pollutant in the indoor environment, may have severe effects on human health. The aim of this study is to compare the health effects caused by intermittent exposure to formaldehyde (based on real monitoring) to those caused by exposures at constant concentration. Health effects explored in this study including the oxidative stress, histopathological changes, inflammatory responses, etc. Mice were divided into three groups and exposed to intermittent concentration formaldehyde (0.8 ppm for 12 h and 0 ppm for another 12 h), or constant concentration formaldehyde (0.4 ppm for 24 h) or zero concentration formaldehyde (reference) per day for 7, 14, and 28 days. Following these exposures, bronchoalveolar lavage fluid (BALF), lung tissue and lung tissue homogenate were prepared to measure biomarkers of oxidative stress (ROS, MDA, GSH), histopathological changes, inflammatory responses (EOS, NEU, LYM, IL-4, IL-5, IL-13, IL-6, IL-17A, NF-κB, IL-1β) and apoptosis (caspase-3). Compared to the constant exposure, intermittent exposure to fluctuating formaldehyde concentrations resulted in more profound increases in numbers of inflammatory cells in the BALF, greater biological alterations including apoptosis. The findings imply that with the same average indoor formaldehyde concentrations over the same time, a ventilation strategy to avoid higher peak concentrations would lead to lower health risks.

Electroacupuncture Suppresses the NF-κB Signaling Pathway by Upregulating Cylindromatosis to Alleviate Inflammatory Injury in Cerebral Ischemia/Reperfusion Rats

Electroacupuncture (EA) may reduce inflammatory injury by inhibiting nuclear factor-kappa B (NF-κB) signaling pathway activation after ischemic stroke. Thus, we explored temporal and spatial expression of cylindromatosis (CYLD), a negative feedback inhibitor of the NF-κB signaling pathway, to learn whether CYLD is essential for EA and reduction of inflammatory injury after focal cerebral ischemia/reperfusion. A middle cerebral artery occlusion/reperfusion (MCAO/R) model was established in male Sprague-Dawley (SD) rats and CYLD gene interference was used to investigate a potential role of neuroprotection. Rats were treated with EA (1 mA, 20 Hz for 5 min, 2 Hz for 30 min) at Baihui (GV 20), Hegu (LI 4) and Taichong (LR 3) acupoints, once daily, beginning 2 h after focal cerebral ischemia. Microglial activation and co-expression of CYLD and NF-κB were measured with immunofluorescence. Neuronal CX3CL1 expression was assayed to investigate the role of EA in the interaction between neurons and microglia via upregulation of CYLD. Then, CYLD, NF-κB p65 and p-IκBα protein expression was measured with Western blot. CYLD was mainly expressed in neurons of the peri-ischemic area after MCAO/R in rats and EA upregulated CYLD mRNA and protein from 24 to 72 h after focal cerebral ischemia/reperfusion. In addition, CYLD overexpression was positively correlated to neurobehavior and negatively connected with infarct volume and pro-inflammatory cytokines (TNF-α and IL-1β). Upregulation of CYLD by EA prevented NF-κB nuclear translocation and inhibition of neuronal CX3CL1 expression, which repressed activation of microglia. Finally, CYLD silencing significantly weakened suppression of the NF-κB signaling pathway by EA. In conclusion, upregulation of CYLD may underlie how EA could alleviate inflammatory injury after focal cerebral ischemia/reperfusion.

Neuroprotective effects of bajijiasu against cognitive impairment induced by amyloid-β in APP/PS1 mice

Alzheimer's disease (AD) is a progressive neurological degenerative disease. The main clinical manifestations of AD include progressive cognitive impairment and alteration of personality. Senile plaques, neuroinflammation, and destruction of synapse structure stability are the main pathological features of AD. Bajijiasu(BJJS) is extracted from Morinda Officinalis, a Chinese herb. In this study, we explored the effect of BJJS on AD from many aspects in APPswe/PSEN1ΔE9 (APP/PS1) double transgenic mice. The Morris water maze and novel object recognition tests results showed that BJJS could significantly improve the learning and memory abilities in APP/PS1 mice. BJJS treatment increased the level of insulin degradation enzyme (IDE) and neprilysin (NEP) and decreased the level of β-site app cleaving enzyme 1(BACE1) in the brain of APP/PS1 mice. BJJS-treated APP/PS1 mice appeared to have reductions of Aβ deposition and senile plaques, and showed higher levels of neurotrophic factors in the brain. We also found that BJJS had an inhibitory function on neuroinflammation in APP/PS1 mice. In addition, the synapse structure relevant proteins were elevated in the brain of BJJS-treated APP/PS1 mice. The present results indicated that BJJS could attenuate cognitive impairment via ameliorating the AD-related pathological alterations in APP/PS1 mice. These findings suggest that BJJS may be a potential therapeutic strategy in Alzheimer's disease.

Hematopoietic stem cell transplantation in 29 patients hemizygous for hypomorphic IKBKG/NEMO mutations

X-linked recessive ectodermal dysplasia with immunodeficiency is a rare primary immunodeficiency caused by hypomorphic mutations of the IKBKG gene encoding the nuclear factor κB essential modulator (NEMO) protein. This condition displays enormous allelic, immunological, and clinical heterogeneity, and therapeutic decisions are difficult because NEMO operates in both hematopoietic and nonhematopoietic cells. Hematopoietic stem cell transplantation (HSCT) is potentially life-saving, but the small number of case reports available suggests it has been reserved for only the most severe cases. Here, we report the health status before HSCT, transplantation outcome, and clinical follow-up for a series of 29 patients from unrelated kindreds from 11 countries. Between them, these patients carry 23 different hypomorphic IKBKG mutations. HSCT was performed from HLA-identical related donors (n = 7), HLA-matched unrelated donors (n = 12), HLA-mismatched unrelated donors (n = 8), and HLA-haploidentical related donors (n = 2). Engraftment was documented in 24 patients, and graft-versus-host disease in 13 patients. Up to 7 patients died 0.2 to 12 months after HSCT. The global survival rate after HSCT among NEMO-deficient children was 74% at a median follow-up after HSCT of 57 months (range, 4-108 months). Preexisting mycobacterial infection and colitis were associated with poor HSCT outcome. The underlying mutation does not appear to have any influence, as patients with the same mutation had different outcomes. Transplantation did not appear to cure colitis, possibly as a result of cell-intrinsic disorders of the epithelial barrier. Overall, HSCT can cure most clinical features of patients with a variety of IKBKG mutations.

Cu(I) Disrupts the Structure and Function of the Nonclassical Zinc Finger Protein Tristetraprolin (TTP)

Tristetraprolin (TTP) is a nonclassical zinc finger (ZF) protein that plays a key role in regulating inflammatory response. TTP regulates cytokines at the mRNA level by binding to AU-rich sequences present at the 3'-untranslated region, forming a complex that is then degraded. TTP contains two conserved CCCH domains with the sequence CysX₈CysX₅CysX₃His that are activated to bind RNA when zinc is coordinated. During inflammation, copper levels are elevated, which is associated with increased inflammatory response. A potential target for Cu(I) during inflammation is TTP. To determine whether Cu(I) binds to TTP and how Cu(I) can affect TTP/RNA binding, two TTP constructs were prepared. One construct contained just the first CCCH domain (TTP-1D) and serves as a peptide model for a CCCH domain; the second construct contains both CCCH domains (TTP-2D) and is functional (binds RNA) when Zn(II) is coordinated. Cu(I) binding to TTP-1D was assessed via electronic absorption spectroscopy titrations, and Cu(I) binding to TTP-2D was assessed via both absorption spectroscopy and a spin filter/inductively coupled plasma mass spectrometry (ICP-MS) assay. Cu(I) binds to TTP-1D with a 1:1 stoichiometry and to TTP-2D with a 3:1 stoichiometry. The CD spectrum of Cu(I)-TTP-2D did not exhibit any secondary structure, matching that of apo-TTP-2D, while Zn(II)-TTP-2D exhibited a secondary structure. Measurement of RNA binding via fluorescence anisotropy revealed that Cu(I)-TTP-2D does not bind to the TTP-2D RNA target sequence UUUAUUUAUUU with any measurable affinity, while Zn(II)-TTP-2D binds to this site with nanomolar affinity. Similarly, addition of Cu(I) to the Zn(II)-TTP-2D/RNA complex resulted in inhibition of RNA binding. Together, these data indicate that, while Cu(I) binds to TTP-2D, it does not result in a folded or functional protein and that Cu(I) inhibits Zn(II)-TTP-2D/RNA binding.

Mechanism of the protective effects of the combined treatment with rhynchophylla total alkaloids and sinapine thiocyanate against a prothrombotic state caused by vascular endothelial cell inflammatory damage

The aim of the present study was to investigate the effect and the underlying mechanism of the combined treatment of rhynchophylla total alkaloids (RTA) and sinapine thiocyanate for protection against a prothrombotic state (PTS) associated with the tumor necrosis factor-alpha (TNF-α)-induced inflammatory injury of vascular endothelial cells (VECs). A TNF-α-induced VEC inflammatory injury model was established, and cell morphology of VECs was evaluated using scanning electron microscopy. In addition, reverse transcription-quantitative polymerase chain reaction and western blot analysis were performed to examine the mRNA and protein expression of coagulation-related factors, including nuclear factor-κB (NF-κB), transforming growth factor-β1 (TGF-β1), tissue factor (TF), plasminogen activator inhibitor (PAI-1), protease-activation receptors (PAR-1) and protein kinase C (PKC-α) in VECs. Combined treatment with RTA and sinapine thiocyanate was demonstrated to reduce, to a varying extent, the mRNA and protein expression of NF-κB, TGF-β1, TF, PAR-1, PKC-α and PAI-1. Furthermore, combined treatment with RTA and sinapine thiocyanate was able to downregulate the expression of coagulation-related factors in injured VECs, thereby inhibiting the PTS induced by vascular endothelial injury. The underlying mechanism is partially associated with the TF-mediated activation of the thrombin-receptor signaling pathway that suppresses coagulation during inflammation and balances fibrinolysis in order to inhibit fibrin generation and deposition.

Gene Co-Expression Network Analysis Unraveling Transcriptional Regulation of High-Altitude Adaptation of Tibetan Pig

Tibetan pigs have survived at high altitude for millennia and they have a suite of adaptive features to tolerate the hypoxic environment. However, the molecular mechanisms underlying the regulation of hypoxia-adaptive phenotypes have not been completely elucidated. In this study, we analyzed differentially expressed genes (DEGs), biological pathways and constructed co-expression regulation networks using whole-transcriptome microarrays from lung tissues of Tibetan and Duroc pigs both at high and low altitude. A total of 3,066 DEGs were identified and this list was over-represented for the ontology terms including metabolic process, catalytic activity, and KEGG pathway including metabolic pathway and PI3K-Akt signaling pathway. The regulatory (RIF) and phenotypic (PIF) impact factor analysis identified several known and several potentially novel regulators of hypoxia adaption, including: IKBKG, KLF6 and RBPJ (RIF1), SF3B1, EFEMP1, HOXB6 and ATF6 (RIF2). These findings provide new details of the regulatory architecture of hypoxia-adaptive genes and also insight into which genes may undergo epigenetic modification for further study in the high-altitude adaptation.

Rare Presentations of Epstein-Barr Virus--Associated Smooth Muscle Tumor in Children

Epstein-Barr virus (EBV) has oncogenic potential and has been implicated in the etiology of a wide range of malignancies. Certain EBV-driven neoplasms, such as smooth muscle tumors (SMTs), manifest typically in immunocompromised patients. In children, these neoplasms have been encountered in the setting of primary immune disorders, specifically severe combined and common variable immunodeficiency syndromes. Human immunodeficiency virus infection and posttransplant immunosuppression, in particular liver and kidney transplantation, likewise increase the risk in the pediatric population. The location of these neoplasms appears related to the type of immunodeficiency: in acquired immunodeficiency syndrome they are frequently located intracranially or intraspinally, whereas after transplant they usually involve the liver or lung. We report 2 distinct cases of EBV-related SMT, unique through their coassociated immunosuppressive state or location: the 1st occurred in a patient with immunodeficiency secondary to NEMO gene mutation following hematopoietic stem cell transplantation; the 2nd developed in the orbit after heart transplant.

Roles of Toll-Like Receptor 4, IκB Kinase, and the Proteasome in the Intestinal Alterations Caused by Sepsis

BACKGROUND

Lipopolysaccharide decreases intestinal contractility and induces the production of cytokines, which play an important role in the pathogenesis of sepsis.

AIM

The objective of the present study was to examine the role of Toll-like receptor 4, IκB kinase, and the proteasome in the intestinal alterations induced by lipopolysaccharide.

METHODS

Sepsis was induced in rabbits by intravenous injection of lipopolysaccharide. Contractility studies of rabbit duodenum were performed in an organ bath. Expressions of interleukin-1β, interleukin-6, interleukin-8, interleukin-10, IκB kinase-α, IκB kinase-β, IκB kinase-γ, and the proteasome mRNA were determined by RT-PCR on rabbit duodenum.

RESULTS

Neomycin and polymyxin B (Toll-like receptor 4 inhibitors), IKK NBD peptide (IκB kinase complex inhibitor), and MG-132 (proteasome inhibitor) blocked partially the effects of lipopolysaccharide on the acetylcholine-, prostaglandin E2-, substance P-, and KCl-induced contractions in the longitudinal and circular smooth muscle of rabbit duodenum. Lipopolysaccharide increased the mRNA expression of interleukin-6 and interleukin-8 in duodenal tissue, and this effect was partly reversed by neomycin, polymyxin B, IKK NBD peptide, and MG-132. IκB kinase-α, IκB kinase-β, IκB kinase-γ, and the proteasome mRNA expressions was not affected by lipopolysaccharide treatment.

CONCLUSIONS

Toll-like receptor 4, the IκB kinase complex, and the proteasome could be therapeutic targets in the treatment of sepsis symptoms in the intestine.

Toll signal transduction pathway in bivalves: complete cds of intermediate elements and related gene transcription levels in hemocytes of immune stimulated Mytilus galloprovincialis

Based on protein domain structure and organization deduced from mRNA contigs, 15 transcripts of the Toll signaling pathway have been identified in the bivalve, Mytilus galloprovincialis. Identical searches performed on publicly available Mytilus edulis ESTs revealed 11 transcripts, whereas searches performed in genomic and new transcriptome sequences of the Pacific oyster, Crassostrea gigas, identified 21 Toll-related transcripts. The remarkable molecular diversity of TRAF and IKK coding sequences of C. gigas, suggests that the sequence data inferred from Mytilus cDNAs may not be exhaustive. Most of the Toll pathway genes were constitutively and ubiquitously expressed in M. galloprovincialis, although at different levels, and clearly induced after in vivo injection with bacteria. Such over-transcription was more rapid and intense with Gram-negative than with Gram-positive bacteria. Injection of a fungus modulated the transcription of few Toll pathway genes, with the induction levels of TLR/MyD88 complex being always less intense. Purified LPS and β-glucans had marginal effect whereas peptidoglycans were ineffective. At the moment, we found no evidence of an IMD transcript in bivalves. In conclusion, mussels possess a complete Toll pathway which can be triggered either by Gram-positive or Gram-negative bacteria.

The ectodysplasin pathway: from diseases to adaptations

The ectodysplasin (EDA) pathway, which is active during the development of ectodermal organs, including teeth, hairs, feathers, and mammary glands, and which is crucial for fine-tuning the developmental network controlling the number, size, and density of these structures, was discovered by studying human patients affected by anhidrotic/hypohidrotic ectodermal dysplasia. It comprises three main gene products: EDA, a ligand that belongs to the tumor necrosis factor (TNF)-α family, EDAR, a receptor related to the TNFα receptors, and EDARADD, a specific adaptor. This core pathway relies on downstream NF-κB pathway activation to regulate target genes. The pathway has recently been found to be associated with specific adaptations in natural populations: the magnitude of armor plates in sticklebacks and the hair structure in Asian human populations. Thus, despite its role in human disease, the EDA pathway is a 'hopeful pathway' that could allow adaptive changes in ectodermal appendages which, as specialized interfaces with the environment, are considered hot-spots of morphological evolution.

Lysine392, a K63-linked ubiquitination site in NEMO, mediates inflammatory osteoclastogenesis and osteolysis

PMMA particles released from bone implants are considered major contributor to osteolysis and subsequent implant failure. Although the ensuing inflammatory response has been described, the mechanisms underlying PMMA particulate-induced osteolysis remain enigmatic. In previous studies, we have established that activation of Nuclear factor kappa-B (NF-κB) and MAP kinase pathways plays a central role in the pathogenesis of inflammatory osteolysis. Specifically, we have shown that impeding IKK complex assembly, and thus subsequent NF-κB activation, dampens particle-induced osteolysis. The IKK complex consists of IKKα, IKKβ, and IKKγ, also known as NEMO. NEMO has no catalytic activity and serves as a scaffold protein facilitating assembly and distal activation of NF-κB signaling. In fact, blocking binding of NEMO with IKKα/β abolishes NF-κB activity. In the current study, we identify Lysine 392 residue in NEMO as crucial mediator of PMMA particle-induced inflammatory osteoclastogenesis and osteolysis. Using mice in which NEMO-K392R mutation has been introduced, we provide evidence that PMMA-induced osteoclasts and osteolytic responses are impaired. Furthermore, we show that this impairment is likely due to poor activation of NF-κB and Erk, but not other MAP kinases. Our findings suggest that NEMO Lysine392, a well-established K63-linked polyubiquitination site, is an important mediator of PMMA-induced osteolysis. Therefore, this NEMO motif should be considered as a target to combat PMMA particle-induced osteolysis.

No one can whistle a symphony alone – how different ubiquitin linkages cooperate to orchestrate NF-κB activity

Although it has been known for a long time that ubiquitylation has a major role in the activation and regulation of the nuclear factor kappa B (NF-κB) pathway, recent studies have revealed that the picture is a lot more complex than originally thought. NF-κB and ubiquitylation initially became linked when it was recognised that lysine (K)48-linked ubiquitin chains are involved in the processing of NF-κB precursors and the degradation of inhibitor of kappa B (IκB) proteins. Soon thereafter, it was reported that K63-linked chains were involved in the assembly of IκB kinase (IKK)-activating complexes and required for activation of the NF-κB signalling pathway. Recently, the discovery that atypical ubiquitin linkages, including linear and K11 linkages, are also involved in the activation of NF-κB has led to the need to re-evaluate existing models of how activation of this transcription factor is initiated and regulated. It is now becoming apparent that not only the canonical types of ubiquitin chains but possibly all linkage types have to be investigated in order to fully comprehend NF-κB activation. This can be considered a turning point in our view of the regulation of one of the most important pathways of gene induction. Hence, in this Commentary, we summarise the information that is currently available and incorporate it into a new model of NF-κB activation, thereby highlighting the emerging new challenges in understanding the role of ubiquitylation in NF-κB activation.