NF-κB p65 serine 467 phosphorylation sensitizes mice to weight gain and TNFα-or diet-induced inflammation

Phosphorylation of Serine 536 of p65(RelA) Downregulates Inflammatory Responses

Nuclear factor-κB (NF-κB) is a transcription factor that regulates the expression of various genes involved in inflammatory diseases and immune responses. Recently, a novel transcriptional regulatory mechanism of NF-κB involving the phosphorylation of serine 536 (534 in mice; S534) of its p65 subunit was reported; however, further research is required to elucidate the physiological role of S534 phosphorylation. Therefore, we generated S534A knock-in (KI) mice, in which the S534 of p65 was substituted with alanine. Similar to the wild-type (WT) mice, S534A KI mice developed normally. After stimulation with tumor necrosis factor α (TNFα), mouse embryonic fibroblasts (MEFs) derived from S534A KI mice exhibited increased target gene expression compared with that in the WT MEFs, which was induced by long-term binding of p65 to DNA. According to comprehensive gene expression analysis after stimulation with TNFα, the expression of genes p65ted to inflammatory and immune responses was increased, and the expression of genes p65ted to lipolysis was decreased in S534A KI MEFs. Analyses of a periodontal disease model established using WT and S534A KI mice revealed that alveolar bone resorption was enhanced in S534A KI mice owing to an increase in the number of osteoclasts, which was not attributed to the differentiation of osteoclast precursor cells but to an increased expression of interleukin-1β and receptor activator of NF-κB ligand in the periodontal tissue. Hence, phosphorylation of S536 negatively regulates inflammatory responses in vitro and in vivo.

Open questions in the NF-κB field

A variety of stress signals leads to activation of the inducible transcription factor NF-κB, one of the master regulators of the innate immune response. Despite a wealth of information available on the NF-κB core components and its control by different activation pathways and negative feedback loops, several levels of complexity hamper our understanding of the system. This has also contributed to the limited success of NF-κB inhibitors in the clinic and explains some of their unexpected effects. Here we consider the molecular and cellular events generating this complexity at all levels and point to a number of unresolved questions in the field. We also discuss potential future experimental and computational strategies to provide a deeper understanding of NF-κB and its coregulatory signaling networks.

[Mechanisms of age-related changes in the morphology of the pulp system of the first lower molars]

OBJECTIVE

To study the coupling of age-related systemic changes in inflammation-mediated apoptosis with the features of the anatomy of the pulp system of the first mandibular molars in patients with chronic pulpitis and periodontitis.

MATERIAL AND METHODS

The study included 55 patients of both sexes from 18 to 75 years of age in three age groups - young (18-44 years) (n=17), middle (45-59 years) (n=18), elderly (60-74 years) (n=20) with indications for endodontic treatment. Diagnostic measures were supplemented with New Tom 3G cone-beam tomography. The concentration of anitapoptotic protein Bcl-XL and tumor necrosis factor-a (TNF-a) was determined in the blood, and the level of the nuclear transcription factor NF-KB subunit p65 was determined in the lysates of mononuclear cells.

RESULTS

As a result of the analysis of the sections, significant obliteration of the pulp was revealed throughout and an increase in the frequency of occurrence of slit-shaped channels in the distal root of the first molar of the mandible in elderly patients.

CONCLUSION

The pathogenetic factors leading to a change in the morphology of the pulp system include old age and an imbalance in the system of anti-inflammatory cytokine transcription mechanisms, which contributes to increased apoptosis and the protracted nature of inflammation.

Mutual regulation of metabolic processes and proinflammatory NF-κB signaling

The nuclear factor kappa B (NF-κB) signaling system, a key regulator of immunologic processes, also affects a plethora of metabolic changes associated with inflammation and the immune response. NF-κB-regulating signaling cascades, in concert with NF-κB-mediated transcriptional events, control the metabolism at several levels. NF-κB modulates apical components of metabolic processes including metabolic hormones such as insulin and glucagon, the cellular master switches 5' AMP-activated protein kinase and mTOR, and also numerous metabolic enzymes and their respective regulators. Vice versa, metabolic enzymes and their products also exert multilevel control of NF-κB activity, thereby creating a highly connected regulatory network. These insights have resulted in the identification of the noncanonical IκB kinase kinases IκB kinase ɛ and TBK1, which are upregulated by overnutrition, and may therefore be suitable potential therapeutic targets for metabolic syndromes. An inhibitor interfering with the activity of both kinases reduces obesity-related metabolic dysfunctions in mouse models and the encouraging results from a recent clinical trial indicate that targeting these NF-κB pathway components improves glucose homeostasis in a subset of patients with type 2 diabetes.

The cellular and molecular basis of major depressive disorder: towards a unified model for understanding clinical depression

Major depressive disorder (MDD) is considered a serious public health issue that adversely impacts an individual's quality of life and contributes significantly to the global burden of disease. The clinical heterogeneity that exists among patients limits the ability of MDD to be accurately diagnosed and currently, a symptom-based approach is utilized in many cases. Due to the complex nature of this disorder, and lack of precise knowledge regarding the pathophysiology, effective management is challenging. The aetiology and pathophysiology of MDD remain largely unknown given the complex genetic and environmental interactions that are involved. Nonetheless, the aetiology and pathophysiology of MDD have been the subject of extensive research, and there is a vast body of literature that exists. Here we overview the key hypotheses that have been proposed for the neurobiology of MDD and highlight the need for a unified model, as many of these pathways are integrated. Key pathways discussed include neurotransmission, neuroinflammation, clock gene machinery pathways, oxidative stress, role of neurotrophins, stress response pathways, the endocannabinoid and endovanilloid systems, and the endogenous opioid system. We also describe the current management of MDD, and emerging novel therapies, with particular focus on patients with treatment-resistant depression (TRD).

Propofol attenuates monocyte-endothelial adhesion via modulating connexin43 expression in monocytes

AIMS

Monocyte-endothelial adhesion is considered to be the primary initiator of inflammatory vascular diseases, such as atherosclerosis. Connexin 43 (Cx43) has been reported to play an important part in this process, however, the underlying mechanisms are not fully understood. Intravenous anesthetics, propofol is commonly used in the perioperative period and in the intensive care unit, and considered to have good anti-inflammatory and antioxidant effects. Thus, we speculate that propofol could influence monocyte-endothelial adhesion, and explore whether its possible mechanism is relative with Cx43 expression in U937 monocytes influencing cell adhesion of U937 monocytes to human umbilical vein endothelial cells (HUVEC).

MAIN METHODS

Cx43-siRNAs or pc-DNA-Cx43 were used to alter Cx43 expression in U937 monocytes. Propofol was given as pretreatments to U937 monocytes. Then, cell adhesion, ZO-1, LFA-1, VLA-4, COX and MCP-1 were determined. PI3K/AKT/NF-κB signaling pathway was explored to clarify the possible mechanism.

KEY FINDINGS

Alternation of Cx43 expression affects cell adhesion and adhesion molecules significantly, such as ZO-1, LFA-1, VLA-4, COX-2 and MCP-1, the mechanism of which is relative with Cx43 influencing the activation of PI3K/AKT/NF-κB signaling pathway. Preconditioning with propofol at its clinically relevant anesthesia concentration attenuates cell adhesion. Propofol not only decreases Cx43 expression in U937 monocytes, but also depresses the activation of PI3K/AKT/NF-κB signaling pathway.

SIGNIFICANCE

Modulation Cx43 expression in U937 monocytes could affect cell adhesion via regulating the activation of PI3K/AKT/NF-κB signaling pathway. Propofol attenuates cell adhesion via inhibiting Cx43 and its downstream signaling pathway of PI3K/AKT/NF-κB.

NF-κB p65 dimerization and DNA-binding is important for inflammatory gene expression

Increasing evidence shows that many transcription factors execute important biologic functions independent from their DNA-binding capacity. The NF-κB p65 (RELA) subunit is a central regulator of innate immunity. Here, we investigated the relative functional contribution of p65 DNA-binding and dimerization in p65-deficient human and murine cells reconstituted with single amino acid mutants preventing either DNA-binding (p65 E/I) or dimerization (p65 FL/DD). DNA-binding of p65 was required for RelB-dependent stabilization of the NF-κB p100 protein. The antiapoptotic function of p65 and expression of the majority of TNF-α–induced genes were dependent on p65’s ability to bind DNA and to dimerize. Chromatin immunoprecipitation with massively parallel DNA sequencing experiments revealed that impaired DNA-binding and dimerization strongly diminish the chromatin association of p65. However, there were also p65-independent TNF-α–inducible genes and a subgroup of p65 binding sites still allowed some residual chromatin association of the mutants. These sites were enriched in activator protein 1 (AP-1) binding motifs and showed increased chromatin accessibility and basal transcription. This suggests a mechanism of assisted p65 chromatin association that can be in part facilitated by chromatin priming and cooperativity with other transcription factors such as AP-1.—Riedlinger, T., Liefke, R., Meier-Soelch, J., Jurida, L., Nist, A., Stiewe, T., Kracht, M., Schmitz, M. L. NF-κB p65 dimerization and DNA-binding is important for inflammatory gene expression.

Long noncoding RNA-antisense noncoding RNA in the INK4 locus accelerates wound healing in diabetes by promoting lymphangiogenesis via regulating miR-181a/Prox1 axis

BACKGROUND

Slow lymphangiogenesis is one crucial reason for the impaired wound healing process in diabetes. Accumulative evidence showed that long noncoding RNA-antisense noncoding RNA in the INK4 locus (ANRIL) could influence lymphangiogenesis. Besides, miR-181a has been reported to regulate Prox1 that is essential for lymphangiogenesis. However, the relationship between ANRIL and miR-181a as well as the definitive function of ANRIL in lymphangiogenesis is not clear.

METHODS

The diabetic mouse model was set up to assess the wound healing rate in vivo. Quantitative real-time polymerase chain reaction was performed to measure the expressions of ANRIL, miR-181a, and Prox1. Western blot analysis was used to assess the expressions of vascular endothelial growth factor receptor-3, lymphatic vessel hyaluronan receptor-1, Prox1, and epithelial-mesenchymal transition (EMT)-related proteins. Flow cytometry was used to assess the cell apoptosis. Wound healing assay was used to determine the effect of ANRIL on cell migration. Tube-formation assay and immunofluorescence staining were performed to determine tube-formation capacity of human dermal lymphatic endothelial cells (LECs).

RESULTS

ANRIL and Prox1 were downregulated, whereas miR-181a was upregulated in the diabetic wound healing mouse model and high glucose (HG)-induced LECs. The wound healing rate and EMT were inhibited during the diabetic wound healing process. Dual-luciferase assay proved that miR-181a could bind Prox1 to repress its expression, whereas ANRIL could sponge miR-181a to recover Prox1 expression. Overexpression of ANRIL or inhibition of miR-181a rescued the impairments of survival, migration, EMT formation, and tube formation of LECs caused by HG.

CONCLUSION

ANRIL could promote lymphangiogenesis during the diabetic wound healing process via sponging miR-181a to enhance Prox1 expression, which might help design new therapy to improve the wound healing efficacy for diabetes.

The Direct and Indirect Roles of NF-κB in Cancer: Lessons from Oncogenic Fusion Proteins and Knock-in Mice

NF-κB signaling pathways play an important role in the regulation of cellular immune and stress responses. Aberrant NF-κB activity has been implicated in almost all the steps of cancer development and many of the direct and indirect contributions of this transcription factor system for oncogenesis were revealed in the recent years. The indirect contributions affect almost all hallmarks and enabling characteristics of cancer, but NF-κB can either promote or antagonize these tumor-supportive functions, thus prohibiting global NF-κB inhibition. The direct effects are due to mutations of members of the NF-κB system itself. These mutations typically occur in upstream components that lead to the activation of NF-κB together with further oncogenesis-promoting signaling pathways. In contrast, mutations of the downstream components, such as the DNA-binding subunits, contribute to oncogenic transformation by affecting NF-κB-driven transcriptional output programs. Here, we discuss the features of recently identified oncogenic RelA fusion proteins and the characterization of pathways that are regulating the transcriptional activity of NF-κB by regulatory phosphorylations. As NF-κB’s central role in human physiology prohibits its global inhibition, these auxiliary or cell type-specific NF-κB regulating pathways are potential therapeutic targets.