Phosphorylation of serine 468 by GSK-3beta negatively regulates basal p65 NF-kappaB activity

LGR4 is essential for maintaining β-cell homeostasis through suppression of RANK

Pancreatic β-cell stress contributes to diabetes progression. This study demonstrates that Leucine-rich repeat-containing G-protein-coupled-receptor-4 (LGR4) is critical for maintaining β-cell health and is modulated by stressors. In vitro , Lgr4 knockdown decreases proliferation and survival in rodent β-cells, while overexpression protects against cytokine-induced cell death in rodent and human β-cells. Mechanistically, LGR4 suppresses Receptor Activator of Nuclear Factor Kappa B (NFκB) (RANK) and its subsequent activation of NFκB to protect β-cells. β-cell-specific Lgr4 -conditional knockout (cko) mice exhibit normal glucose homeostasis but increased β-cell death in both sexes and decreased proliferation only in females. Male Lgr4 cko mice under stress display reduced β-cell proliferation and a further increase in β-cell death. Upon aging, both male and female Lgr4 cko mice display impaired β-cell homeostasis, however, only female mice are glucose intolerant with decreased plasma insulin. We show that LGR4 is required for maintaining β-cell health under basal and stress-induced conditions, through suppression of RANK.

Teaser

LGR4 receptor is critical for maintaining β-cell health under basal and stressed conditions, through suppression of RANK.

CLK2 mediates IκBα-independent early termination of NF-κB activation by inducing cytoplasmic redistribution and degradation

Activation of the NF-κB pathway is strictly regulated to prevent excessive inflammatory and immune responses. In a well-known negative feedback model, IκBα-dependent NF-κB termination is a delayed response pattern in the later stage of activation, and the mechanisms mediating the rapid termination of active NF-κB remain unclear. Here, we showed IκBα-independent rapid termination of nuclear NF-κB mediated by CLK2, which negatively regulated active NF-κB by phosphorylating the RelA/p65 subunit of NF-κB at Ser180 in the nucleus to limit its transcriptional activation through degradation and nuclear export. Depletion of CLK2 increased the production of inflammatory cytokines, reduced viral replication and increased the survival of the mice. Mechanistically, CLK2 phosphorylated RelA/p65 at Ser180 in the nucleus, leading to ubiquitin‒proteasome-mediated degradation and cytoplasmic redistribution. Importantly, a CLK2 inhibitor promoted cytokine production, reduced viral replication, and accelerated murine psoriasis. This study revealed an IκBα-independent mechanism of early-stage termination of NF-κB in which phosphorylated Ser180 RelA/p65 turned off posttranslational modifications associated with transcriptional activation, ultimately resulting in the degradation and nuclear export of RelA/p65 to inhibit excessive inflammatory activation. Our findings showed that the phosphorylation of RelA/p65 at Ser180 in the nucleus inhibits early-stage NF-κB activation, thereby mediating the negative regulation of NF-κB.

Therapeutic Potential Effect of Glycogen Synthase Kinase 3 Beta (GSK-3β) Inhibitors in Parkinson Disease: Exploring an Overlooked Avenue

Parkinson's disease (PD) is a progressive neurodegenerative disease of the brain due to degeneration of dopaminergic neurons in the substantia nigra (SN). Glycogen synthase kinase 3 beta (GSK-3β) is implicated in the pathogenesis of PD. Therefore, the purpose of the present review was to revise the mechanistic role of GSK-3β in PD neuropathology, and how GSK-3β inhibitors affect PD neuropathology. GSK-3 is a conserved threonine/serine kinase protein that is intricate in the regulation of cellular anabolic and catabolic pathways by modulating glycogen synthase. Over-expression of GSK-3β is also interconnected with the development of different neurodegenerative diseases. However, the underlying mechanism of GSK-3β in PD neuropathology is not fully clarified. Over-expression of GSK-3β induces the development of PD by triggering mitochondrial dysfunction and oxidative stress in the dopaminergic neurons of the SN. NF-κB and NLRP3 inflammasome are activated in response to dysregulated GSK-3β in PD leading to progressive neuronal injury. Higher expression of GSK-3β in the early stages of PD neuropathology might contribute to the reduction of neuroprotective brain-derived neurotrophic factor (BDNF). Thus, GSK-3β inhibitors may be effective in PD by reducing inflammatory and oxidative stress disorders which are associated with degeneration of dopaminergic in the SN.

Oxoaporphine Pr(III) complex inhibits hepatocellular carcinoma progression and metastasis by disrupting tumor cell-macrophage crosstalk

Tumor cells and macrophages communicate through the secretion of various cytokines to jointly promote the malignant development of cancers. We synthesized and characterized an oxoaporphine Pr(III) complex (PrL3(NO3)3) and found that it inhibits hepatocellular carcinoma (HCC) progression and metastasis by disrupting HCC cell-macrophage crosstalk. PrL3(NO3)3 treatment upregulated CD86, TNF-α, and IL-1β and downregulated CD163, CD206, CCL2, and VEGFA in macrophages. Our mRNA-Seq results demonstrated that PrL3(NO3)3 inhibited macrophage M2-like polarization by inhibiting the AMPK pathway and activating the NF-κB pathway by upregulating RelA/p65 Ser536 phosphorylation. This kind of macrophage polarization significantly inhibited HCC cell proliferation, migration, and invasion. In addition, PrL3(NO3)3 inhibited the migration, invasion, and chemotaxis of HCC cells by downregulating the expression of EMT-related markers and CCL2. hTFtarget database analysis revealed that PrL3(NO3)3 inhibited NF-κB nuclear translocation by upregulating RelA/p65 Ser536 phosphorylation in HCC cells, thereby downregulating the expression of Snail and CCL2. HCC tissue microarray analysis revealed that downregulation of RelA/p65 Ser536 phosphorylation is a driving event in HCC malignant progression. In conclusion, PrL3(NO3)3 effectively inhibits HCC cell-macrophage crosstalk by upregulating RelA/p65 Ser536 phosphorylation. This is the first report of a lanthanide complex exerting regulatory effects on both tumors and tumor-associated macrophages, providing a new strategy for the development of effective antitumor drugs.

Bik promotes proteasomal degradation to control low-grade inflammation

Although chronic low-grade inflammation does not cause immediate clinical symptoms, over the longer term, it can enhance other insults or age-dependent damage to organ systems and thereby contribute to age-related disorders, such as respiratory disorders, heart disease, metabolic disorders, autoimmunity, and cancer. However, the molecular mechanisms governing low-level inflammation are largely unknown. We discovered that Bcl-2-interacting killer (Bik) deficiency causes low-level inflammation even at baseline and the development of spontaneous emphysema in female but not male mice. Similarly, a single nucleotide polymorphism that reduced Bik levels was associated with increased inflammation and enhanced decline in lung function in humans. Transgenic expression of Bik in the airways of Bik-deficient mice inhibited allergen- or LPS-induced lung inflammation and reversed emphysema in female mice. Bik deficiency increased nuclear but not cytosolic p65 levels because Bik, by modifying the BH4 domain of Bcl-2, interacted with regulatory particle non-ATPase 1 (RPN1) and RPN2 and enhanced proteasomal degradation of nuclear proteins. Bik deficiency increased inflammation primarily in females because Bcl-2 and Bik levels were reduced in lung tissues and airway cells of female compared with male mice. Therefore, controlling low-grade inflammation by modifying the unappreciated role of Bik and Bcl-2 in facilitating proteasomal degradation of nuclear proteins may be crucial in treating chronic age-related diseases.

New insights into the role of GSK-3β in the brain: from neurodegenerative disease to tumorigenesis

Glycogen synthase kinase 3 (GSK-3) is a serine/threonine kinase widely expressed in various tissues and organs. Unlike other kinases, GSK-3 is active under resting conditions and is inactivated upon stimulation. In mammals, GSK-3 includes GSK-3 α and GSK-3β isoforms encoded by two homologous genes, namely, GSK3A and GSK3B. GSK-3β is essential for the control of glucose metabolism, signal transduction, and tissue homeostasis. As more than 100 known proteins have been identified as GSK-3β substrates, it is sometimes referred to as a moonlighting kinase. Previous studies have elucidated the regulation modes of GSK-3β. GSK-3β is involved in almost all aspects of brain functions, such as neuronal morphology, synapse formation, neuroinflammation, and neurological disorders. Recently, several comparatively specific small molecules have facilitated the chemical manipulation of this enzyme within cellular systems, leading to the discovery of novel inhibitors for GSK-3β. Despite these advancements, the therapeutic significance of GSK-3β as a drug target is still complicated by uncertainties surrounding the potential of inhibitors to stimulate tumorigenesis. This review provides a comprehensive overview of the intricate mechanisms of this enzyme and evaluates the existing evidence regarding the therapeutic potential of GSK-3β in brain diseases, including Alzheimer's disease, Parkinson's disease, mood disorders, and glioblastoma.

GSK3 Is a Central Player in Retinal Degenerative Diseases but a Challenging Therapeutic Target

Glycogen synthase kinase 3 (GSK3) is a key regulator of many cellular signaling processes and performs a wide range of biological functions in the nervous system. Due to its central role in numerous cellular processes involved in cell degeneration, a rising number of studies have highlighted the interest in developing therapeutics targeting GSK3 to treat neurodegenerative diseases. Although recent works strongly suggest that inhibiting GSK3 might also be a promising therapeutic approach for retinal degenerative diseases, its full potential is still under-evaluated. In this review, we summarize the literature on the role of GSK3 on the main cellular functions reported as deregulated during retinal degeneration, such as glucose homeostasis which is critical for photoreceptor survival, or oxidative stress, a major component of retinal degeneration. We also discuss the interest in targeting GSK3 for its beneficial effects on inflammation, for reducing neovascularization that occurs in some retinal dystrophies, or for cell-based therapy by enhancing Müller glia cell proliferation in diseased retina. Together, although GSK3 inhibitors hold promise as therapeutic agents, we highlight the complexity of targeting such a multitasked kinase and the need to increase our knowledge of the impact of reducing GSK3 activity on these multiple cellular pathways and biological processes.

Transglutaminase 2 mediates UVB-induced matrix metalloproteinase-1 expression by inhibiting nuclear p65 degradation in dermal fibroblasts

Matrix metalloproteinases (MMPs) play a key role in tissue remodelling by cleaving extracellular matrix (ECM) components. In the skin, UV irradiation increases expression of MMPs that causes dysregulation of ECM homeostasis in dermis, leading to acceleration of skin aging. However, the mediator(s) that links UV irradiation to the upregulation of MMPs have not been fully defined. Previously, we showed that UVB irradiation activated transglutaminase 2 (TG2) in keratinocytes, eliciting an inflammatory response by activating NF-κB signalling. In this study, we reported the role of TG2 in mediating the UVB-induced expression of MMP-1. In human dermal fibroblasts, UVB irradiation enhanced the expression and activity of TG2, which in turn promotes the expression of MMP-1. Analyses of MMP-1 promoter showed that activation of the NF-κB signalling pathway, rather than AP-1, was responsible for the TG2-mediated upregulation of MMP-1. Moreover, Western blot analysis revealed that TG2 increased the activity of NF-κB by inhibiting degradation of p65 in the nucleus. Furthermore, ex vivo skin from TG2-knockout mice exhibited significantly reduced levels of MMP-1 compared to that from wild-type mice. These results indicate that TG2 functions as a mediator for the UVB-induced expression of MMP-1 in dermal fibroblasts, providing a new target for preventing skin photodamage.

Glycogen Synthase Kinase-3: A Focal Point for Advancing Pathogenic Inflammation in Depression

Increasing evidence indicates that the host immune response has a monumental role in the etiology of major depressive disorder (MDD), motivating the development of the inflammatory hypothesis of depression. Central to the involvement of chronic inflammation in MDD is a wide range of signaling deficits induced by the excessive secretion of pro-inflammatory cytokines and imbalanced T cell differentiation. Such signaling deficits include the glutamatergic, cholinergic, insulin, and neurotrophin systems, which work in concert to initiate and advance the neuropathology. Fundamental to the communication between such systems is the protein kinase glycogen synthase kinase-3 (GSK-3), a multifaceted protein critically linked to the etiology of MDD and an emerging target to treat pathogenic inflammation. Here, a consolidated overview of the widespread multi-system involvement of GSK-3 in contributing to the neuropathology of MDD will be discussed, with the feed-forward mechanistic links between all major neuronal signaling pathways highlighted.

Paraquat induces redox imbalance and disrupts glutamate and energy metabolism in the hippocampus of prepubertal rats

Paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride; PQ) is a widely used herbicide in Brazilian crops, despite its banishment in many other countries. The present study investigated the effects of repeated dose of PQ on glutamate system, energy metabolism and redox parameters in the hippocampus of prepubertal rats. Twenty-two-day-old rats received daily intraperitoneal injections of PQ (10 mg/Kg) during 5 consecutive days and the effects of the pesticide were assessed 24 h after the last injection. The PQ exposure provoked cytotoxicity associated to decreased cell viability and increased glutamate excitotoxicity, as demonstrated by decreased 14C-glutamate uptake and increased ⁴⁵Ca²⁺ uptake. Downregulated glutamine synthetase (GS) activity, further supports disrupted glutamate metabolism compromising the glutamate-glutamine cycle. Downregulated ¹⁴C-2-Deoxy-D-glucose indicates energy failure and upregulated lactate dehydrogenase (LDH) suggests the relevance of lactate as energy fuel. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) upregulation suggest Krebs cycle replenishment and piruvate production. In addition, PQ disturbed the redox status inducing lipid peroxidation, evaluated by increased TBARS and imbalanced antioxidant system. Downregulated glutathione reductase (GR), gamma-glutamyltransferase (GGT), glutathione-S-transferase (GST) and glucose-6-P-dehydrogenase (G6PD) activities together with upregulated superoxide dismutase (SOD) and catalase activities corroborate the oxidative imbalance. The mechanisms underlying PQ-induced neurotoxicity involves the modulation of GSK-3β, NF-κB and NMDA receptors. These neurochemical and oxidative events observed may contribute to neuroinflammation and neurotoxic effects of PQ on hippocampal cells.

Interplay of Opposing Effects of the WNT/β-Catenin Pathway and PPARγ and Implications for SARS-CoV2 Treatment

The Coronavirus disease 2019 (COVID-19), caused by the novel coronavirus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), has quickly reached pandemic proportions. Cytokine profiles observed in COVID-19 patients have revealed increased levels of IL-1β, IL-2, IL-6, and TNF-α and increased NF-κB pathway activity. Recent evidence has shown that the upregulation of the WNT/β-catenin pathway is associated with inflammation, resulting in a cytokine storm in ARDS (acute respire distress syndrome) and especially in COVID-19 patients. Several studies have shown that the WNT/β-catenin pathway interacts with PPARγ in an opposing interplay in numerous diseases. Furthermore, recent studies have highlighted the interesting role of PPARγ agonists as modulators of inflammatory and immunomodulatory drugs through the targeting of the cytokine storm in COVID-19 patients. SARS-CoV2 infection presents a decrease in the angiotensin-converting enzyme 2 (ACE2) associated with the upregulation of the WNT/β-catenin pathway. SARS-Cov2 may invade human organs besides the lungs through the expression of ACE2. Evidence has highlighted the fact that PPARγ agonists can increase ACE2 expression, suggesting a possible role for PPARγ agonists in the treatment of COVID-19. This review therefore focuses on the opposing interplay between the canonical WNT/β-catenin pathway and PPARγ in SARS-CoV2 infection and the potential beneficial role of PPARγ agonists in this context.

Dissecting the Regulatory Strategies of NF-κB RelA Target Genes in the Inflammatory Response Reveals Differential Transactivation Logics

Nuclear factor κB (NF-κB) RelA is the potent transcriptional activator of inflammatory response genes. We stringently defined a list of direct RelA target genes by integrating physical (chromatin immunoprecipitation sequencing [ChIP-seq]) and functional (RNA sequencing [RNA-seq] in knockouts) datasets. We then dissected each gene’s regulatory strategy by testing RelA variants in a primary-cell genetic-complementation assay. All endogenous target genes require RelA to make DNA-base-specific contacts, and none are activatable by the DNA binding domain alone. However, endogenous target genes differ widely in how they employ the two transactivation domains. Through model-aided analysis of the dynamic time-course data, we reveal the gene-specific synergy and redundancy of TA1 and TA2. Given that post-translational modifications control TA1 activity and intrinsic affinity for coactivators determines TA2 activity, the differential TA logics suggests context-dependent versus context-independent control of endogenous RelA-target genes. Although some inflammatory initiators appear to require co-stimulatory TA1 activation, inflammatory resolvers are a part of the NF-κB RelA core response.

Ngo et al. developed a genetic complementation system for NF-κB RelA that reveals that NF-κB target-gene selection requires high-affinity RelA binding and transcriptional activation domains for gene induction. The synergistic and redundant functions of two transactivation domains define pro-inflammatory and inflammation-response genes.

Norrin mediates tumor-promoting and -suppressive effects in glioblastoma via Notch and Wnt

Glioblastoma multiforme (GBM) contains a subpopulation of cells, GBM stem cells (GSCs), that maintain the bulk tumor and represent a key therapeutic target. Norrin is a Wnt ligand that binds Frizzled class receptor 4 (FZD4) to activate canonical Wnt signaling. Although Norrin, encoded by NDP, has a well-described role in vascular development, its function in human tumorigenesis is largely unexplored. Here, we show that NDP expression is enriched in neurological cancers, including GBM, and its levels positively correlated with survival in a GBM subtype defined by low expression of ASCL1, a proneural factor. We investigated the function of Norrin and FZD4 in GSCs and found that it mediated opposing tumor-suppressive and -promoting effects on ASCL1lo and ASCL1hi GSCs. Consistent with a potential tumor-suppressive effect of Norrin suggested by the tumor outcome data, we found that Norrin signaling through FZD4 inhibited growth in ASCL1lo GSCs. In contrast, in ASCL1hi GSCs Norrin promoted Notch signaling, independently of WNT, to promote tumor progression. Forced ASCL1 expression reversed the tumor-suppressive effects of Norrin in ASCL1lo GSCs. Our results identify Norrin as a modulator of human brain cancer progression and reveal an unanticipated Notch-mediated function of Norrin in regulating cancer stem cell biology. This study identifies an unanticipated role of Norrin in human brain cancer progression. In addition, we provide preclinical evidence suggesting Norrin and canonical Wnt signaling as potential therapeutic targets for GBM subtype-restricted cancer stem cells.

The role of glycogen synthase kinase 3 (GSK3) in cancer with emphasis on ovarian cancer development and progression: A comprehensive review

Glycogen synthase kinase 3 (GSK3) is a monomeric serine-threonine kinase discovered in 1980 in a rat skeletal muscle. It has been involved in various cellular processes including embryogenesis, immune response, inflammation, apoptosis, autophagy, wound healing, neurodegeneration, and carcinogenesis. GSK3 exists in two different isoforms, GSK3α and GSK3β, both containing seven antiparallel beta-plates, a short linking part and an alpha helix, but coded by different genes and variously expressed in human tissues. In the current review, we comprehensively appraise the current literature on the role of GSK3 in various cancers with emphasis on ovarian carcinoma. Our findings indicate that the role of GSK3 in ovarian cancer development cannot be decisively determined as the currently available data support both prooncogenic and tumor-suppressive effects. Likewise, the clinical impact of GSK3 expression on ovarian cancer patients and its potential therapeutic implications are also limited. Further studies are needed to fully elucidate the pathophysiological and clinical implications of GSK3 activity in ovarian cancer.

Transcriptional repression of NFKBIA triggers constitutive IKK- and proteasome-independent p65/RelA activation in senescence

The IκB kinase (IKK)‐NF‐κB pathway is activated as part of the DNA damage response and controls both inflammation and resistance to apoptosis. How these distinct functions are achieved remained unknown. We demonstrate here that DNA double‐strand breaks elicit two subsequent phases of NF‐κB activation in vivo and in vitro, which are mechanistically and functionally distinct. RNA‐sequencing reveals that the first‐phase controls anti‐apoptotic gene expression, while the second drives expression of senescence‐associated secretory phenotype (SASP) genes. The rapidly activated first phase is driven by the ATM‐PARP1‐TRAF6‐IKK cascade, which triggers proteasomal destruction of inhibitory IκBα, and is terminated through IκBα re‐expression from the NFKBIA gene. The second phase, which is activated days later in senescent cells, is on the other hand independent of IKK and the proteasome. An altered phosphorylation status of NF‐κB family member p65/RelA, in part mediated by GSK3β, results in transcriptional silencing of NFKBIA and IKK‐independent, constitutive activation of NF‐κB in senescence. Collectively, our study reveals a novel physiological mechanism of NF‐κB activation with important implications for genotoxic cancer treatment.

MiR-155/GSK-3β mediates anti-inflammatory effect of Chikusetsusaponin IVa by inhibiting NF-κB signaling pathway in LPS-induced RAW264.7 cell

It has been demonstrated that Chikusetsusaponin IVa (CsIVa) possesses abundant biological activities. Herein, using LPS to establish acute inflammation model of mouse liver and cell line inflammation model, we investigated whether miR-155/GSK-3β regulated NF-κB signaling pathway, and CsIVa exerted anti-inflammatory effects by regulating miR-155/GSK-3β signaling pathway. Our results showed that LPS induced high expression of miR-155 and miR-155 promoted macrophage activation through GSK-3β. In addition, CsIVa inhibited inflammatory responses in LPS-induced mouse liver and RAW264.7 cells. Furthermore, we demonstrated that CsIVa improved the inflammatory response in LPS-induced RAW264.7 cells by inhibiting miR-155, increasing GSK-3β expression, and inhibiting NF-κB signaling pathway. In conclusion, our study reveals that CsIVa suppresses LPS-triggered immune response by miR-155/GSK-3β-NF-κB signaling pathway.

CDDO-Me Distinctly Regulates Regional Specific Astroglial Responses to Status Epilepticus via ERK1/2-Nrf2, PTEN-PI3K-AKT and NFκB Signaling Pathways

2-Cyano-3,12-dioxo-oleana-1,9(11)-dien-28-oic acid methyl ester (CDDO-Me) is a triterpenoid analogue of oleanolic acid. CDDO-Me shows anti-inflammatory and neuroprotective effects. Furthermore, CDDO-Me has antioxidant properties, since it activates nuclear factor-erythroid 2-related factor 2 (Nrf2), which is a key player of redox homeostasis. In the present study, we evaluated whether CDDO-Me affects astroglial responses to status epilepticus (SE, a prolonged seizure activity) in the rat hippocampus in order to understand the underlying mechanisms of reactive astrogliosis and astroglial apoptosis. Under physiological conditions, CDDO-Me increased Nrf2 expression in the hippocampus without altering activities (phosphorylations) of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), phosphatidylinositol-3-kinase (PI3K), and AKT. CDDO-Me did not affect seizure activity in response to pilocarpine. However, CDDO-Me ameliorated reduced astroglial Nrf2 expression in the CA1 region and the molecular layer of the dentate gyrus (ML), and attenuated reactive astrogliosis and ML astroglial apoptosis following SE. In CA1 astrocytes, CDDO-Me inhibited the PI3K/AKT pathway by activating PTEN. In contrast, CDDO-ME resulted in extracellular signal-related kinases 1/2 (ERK1/2)-mediated Nrf2 upregulation in ML astrocytes. Furthermore, CDDO-Me decreased nuclear factor-κB (NFκB) phosphorylation in both CA1 and ML astrocytes. Therefore, our findings suggest that CDDO-Me may attenuate SE-induced reactive astrogliosis and astroglial apoptosis via regulation of ERK1/2-Nrf2, PTEN-PI3K-AKT, and NFκB signaling pathways.

Glycogen synthase kinase 3β in tumorigenesis and oncotherapy (Review)

Glycogen synthase kinase 3β (GSK 3β), a multifunctional serine and threonine kinase, plays a critical role in a variety of cellular activities, including signaling transduction, protein and glycogen metabolism, cell proliferation, cell differentiation, and apoptosis. Therefore, aberrant regulation of GSK 3β results in a broad range of human diseases, such as tumors, diabetes, inflammation and neurodegenerative diseases. Accumulating evidence has suggested that GSK 3β is correlated with tumorigenesis and progression. However, GSK 3β is controversial due to its bifacial roles of tumor suppression and activation. In addition, overexpression of GSK 3β is involved in tumor growth, whereas it contributes to the cell sensitivity to chemotherapy. However, the underlying regulatory mechanisms of GSK 3β in tumorigenesis remain obscure and require further in‑depth investigation. In this review, we comprehensively summarize the roles of GSK 3β in tumorigenesis and oncotherapy, and focus on its potentials as an available target in oncotherapy.

Glycogen synthase kinase (GSK)-3 and the double-strand RNA-dependent kinase, PKR: When two kinases for the common good turn bad

Glycogen synthase kinase (GSK)-3α/β and the double-stranded RNA-dependent kinase PKR are two sentinel kinases that carry-out multiple similar yet distinct functions in both the cytosol and the nucleus. While these kinases belong to separate signal transduction cascades, they demonstrate an uncanny propensity to regulate many of the same proteins either through direct phosphorylation or by altering transcription/translation, including: c-MYC, NF-κB, p53 and TAU, as well as each another. A significant number of studies centered on the GSK3 kinases have led to the identification of the GSK3 interactome and a number of substrates, which link GSK3 activity to metabolic control, translation, RNA splicing, ribosome biogenesis, cellular division, DNA repair and stress/inflammatory signaling. Interestingly, many of these same pathways and processes are controlled by PKR, but unlike the GSK3 kinases, a clear picture of proteins interacting with PKR and a complete listing of its substrates is still missing. In this review, we take a detailed look at what is known about the PKR and GSK3 kinases, how these kinases interact to influence common cellular processes (innate immunity, alternative splicing, translation, glucose metabolism) and how aberrant activation of these kinases leads to diseases such as Alzheimer's disease (AD), diabetes mellitus (DM) and cancer.

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GSK3α/β and PKR are major regulators of cellular homeostasis and the response to stress/inflammation and infection.

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GSK3α/β and PKR interact with and/or modify many of the same proteins and affect the expression of similar genes.

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A balance between AKT and PKR nuclear signaling may be responsible for regulating the activation of nuclear GSK3β.

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GSK3α/β- and PKR-dependent signaling influence major molecular mechanisms of the cell through similar intermediates.

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Aberrant activation of GSK3α/β and PKR is highly involved in cancer, metabolic disorders, and neurodegenerative diseases.

GSK3: A Kinase Balancing Promotion and Resolution of Inflammation

GSK3 has been implicated for years in the regulation of inflammation and addressed in a plethora of scientific reports using a variety of experimental (disease) models and approaches. However, the specific role of GSK3 in the inflammatory process is still not fully understood and controversially discussed. Following a detailed overview of structure, function, and various regulatory levels, this review focusses on the immunoregulatory functions of GSK3, including the current knowledge obtained from animal models. Its impact on pro-inflammatory cytokine/chemokine profiles, bacterial/viral infections, and the modulation of associated pro-inflammatory transcriptional and signaling pathways is discussed. Moreover, GSK3 contributes to the resolution of inflammation on multiple levels, e.g., via the regulation of pro-resolving mediators, the clearance of apoptotic immune cells, and tissue repair processes. The influence of GSK3 on the development of different forms of stimulation tolerance is also addressed. Collectively, the role of GSK3 as a kinase balancing the initiation/perpetuation and the amelioration/resolution of inflammation is highlighted.

Classic and Novel Signaling Pathways Involved in Cancer: Targeting the NF-κB and Syk Signaling Pathways

The nuclear factor kappa B (NF-κB) consists of a family of transcription factors involved in the regulation of a wide variety of biological responses. Growing evidence support that NF-κB plays a major role in oncogenesis as well as its well-known function in the regulation of immune responses and inflammation. Therefore, we made a review of the diverse molecular mechanisms by which the NF-κB pathway is constitutively activated in different types of human cancers and the potential role of various oncogenic genes regulated by this transcription factor in cancer development and progression. We also discussed various pharmacological approaches employed to target the deregulated NF-κB signaling pathway and their possible therapeutic potential in cancer therapy. Moreover, Syk (Spleen tyrosine kinase), non-receptor tyrosine kinase which mediates signal transduction downstream of a variety of transmembrane receptors including classical immune-receptors like the B-cell receptor (BCR), which can also activate the inflammasome and NF-κB-mediated transcription of chemokines and cytokines in the presence of pathogens would be discussed as well. The highlight of this review article is to summarize the classic and novel signaling pathways involved in NF-κB and Syk signaling and then raise some possibilities for cancer therapy.

MicroRNA-34 Family Enhances Wound Inflammation by Targeting LGR4

Venous ulcers are the most common type of human chronic nonhealing wounds and are stalled in a constant and excessive inflammatory state. The molecular mechanisms underlying the chronic wound inflammation remain elusive. Moreover, little is known about the role of regulatory RNAs, such as microRNAs, in the pathogenesis of venous ulcers. We found that both microRNA (miR)-34a and miR-34c were upregulated in the wound-edge epidermal keratinocytes of venous ulcers compared with normal wounds or the skin. In keratinocytes, miR-34a and miR-34c promoted inflammatory chemokine and cytokine production. In wounds of wild-type mice, miR-34a-mimic treatment enhanced inflammation and delayed healing. To further explore how miR-34 functions, LGR4 was identified as a direct target mediating the proinflammatory function of miR-34a and miR-34c. Interestingly, impaired wound closure with enhanced inflammation was also observed in Lgr4 knockout mice. Mechanistically, the miR-34-LGR4 axis regulated GSK-3β-induced p65 serine 468 phosphorylation, changing the activity of the NF-κB signaling pathway. Collectively, the miR-34-LGR4 axis was shown to regulate keratinocyte inflammatory response, the deregulation of which may play a pathological role in venous ulcers.

Curcumin: a therapeutic strategy in cancers by inhibiting the canonical WNT/β-catenin pathway

Numerous studies have presented that curcumin could have a positive effect in the prevention of cancer and then in tumor therapy. Several hypotheses have highlighted that curcumin could decreases tumor growth and invasion by acting on both chronic inflammation and oxidative stress. This review focuses on the interest of use curcumin in cancer therapy by acting on the WNT/β-catenin pathway to repress chronic inflammation and oxidative stress. In the cancer process, one of the major signaling pathways involved is the WNT/β-catenin pathway, which appears to be upregulated. Curcumin administration participates to the downregulation of the WNT/β-catenin pathway and thus, through this action, in tumor growth control. Curcumin act as PPARγ agonists. The WNT/β-catenin pathway and PPARγ act in an opposed manner. Chronic inflammation, oxidative stress and circadian clock disruption are common and co-substantial pathological processes accompanying and promoting cancers. Circadian clock disruption related to the upregulation of the WNT/β-catenin pathway is involved in cancers. By stimulating PPARγ expression, curcumin can control circadian clocks through the regulation of many key circadian genes. The administration of curcumin in cancer treatment would thus appear to be an interesting therapeutic strategy, which acts through their role in regulating WNT/β-catenin pathway and PPARγ activity levels.

Targeting the Canonical WNT/β-Catenin Pathway in Cancer Treatment Using Non-Steroidal Anti-Inflammatory Drugs

Chronic inflammation and oxidative stress are common and co-substantial pathological processes accompanying and contributing to cancers. Numerous epidemiological studies have indicated that non-steroidal anti-inflammatory drugs (NSAIDs) could have a positive effect on both the prevention of cancer and tumor therapy. Numerous hypotheses have postulated that NSAIDs could slow tumor growth by acting on both chronic inflammation and oxidative stress. This review takes a closer look at these hypotheses. In the cancer process, one of the major signaling pathways involved is the WNT/β-catenin pathway, which appears to be upregulated. This pathway is closely associated with both chronic inflammation and oxidative stress in cancers. The administration of NSAIDs has been observed to help in the downregulation of the WNT/β-catenin pathway and thus in the control of tumor growth. NSAIDs act as PPARγ agonists. The WNT/β-catenin pathway and PPARγ act in opposing manners. PPARγ agonists can promote cell cycle arrest, cell differentiation, and apoptosis, and can reduce inflammation, oxidative stress, proliferation, invasion, and cell migration. In parallel, the dysregulation of circadian rhythms (CRs) contributes to cancer development through the upregulation of the canonical WNT/β-catenin pathway. By stimulating PPARγ expression, NSAIDs can control CRs through the regulation of many key circadian genes. The administration of NSAIDs in cancer treatment would thus appear to be an interesting therapeutic strategy, which acts through their role in regulating WNT/β-catenin pathway and PPARγ activity levels.

NF-κB/Rel Transcription Factors in Pancreatic Cancer: Focusing on RelA, c-Rel, and RelB

Regulation of Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)/Rel transcription factors (TFs) is extremely cell-type-specific owing to their ability to act disparately in the context of cellular homeostasis driven by cellular fate and the microenvironment. This is also valid for tumor cells in which every single component shows heterogenic effects. Whereas many studies highlighted a per se oncogenic function for NF-κB/Rel TFs across cancers, recent advances in the field revealed their additional tumor-suppressive nature. Specifically, pancreatic ductal adenocarcinoma (PDAC), as one of the deadliest malignant diseases, shows aberrant canonical-noncanonical NF-κB signaling activity. Although decades of work suggest a prominent oncogenic activity of NF-κB signaling in PDAC, emerging evidence points to the opposite including anti-tumor effects. Considering the dual nature of NF-κB signaling and how it is closely linked to many other cancer related signaling pathways, it is essential to dissect the roles of individual Rel TFs in pancreatic carcinogenesis and tumor persistency and progression. Here, we discuss recent knowledge highlighting the role of Rel TFs RelA, RelB, and c-Rel in PDAC development and maintenance. Next to providing rationales for therapeutically harnessing Rel TF function in PDAC, we compile strategies currently in (pre-)clinical evaluation.

Lemur tyrosine kinase 2 acts as a positive regulator of NF-κB activation and colon cancer cell proliferation

Lemur tyrosine kinase 2 (LMTK2) belongs to both protein kinase and tyrosine kinase families. LMTK2 is less studied and little is known about its function. Here we demonstrate that LMTK2 modulates NF-κB activity and functions to promote colonic tumorigenesis. We found that LMTK2 protein was abundant in colon cancer cells and LMTK2 knockdown (LMTK2-KD) inhibited proliferation of colon cancer cells through inactivating NF-κB. In unstimulated condition, LMTK2 modulated NF-κB through inhibiting phosphorylation of p65 at Ser468. Mechanistically, LMTK2 phosphorylated protein phosphatase 1A (PP1A) to prevent PP1A from dephosphorylating p-GSK3β(Ser9). The p-GSK3β(Ser9) could not phosphorylate p65 at Ser468, which maintained the basal NF-κB activity. LMTK2 also modulated TNFα-activated NF-κB. LMTK2-KD repressed TNFα-induced IKKβ phosphorylation, IκBα degradation and NF-κB activation, implying that LMTK2 modulates TNFα-activated NF-κB via IKK. These results suggest that LMTK2 modulates basal and TNFα-induced NF-κB activities in different mechanisms. Animal studies show that LMTK2-KD suppressed colon cancer cell xenograft growth, decreased PP1A phosphorylation and increased p-p65(Ser468). Our results reveal the role and underlying mechanism of LMTK2 in colonic tumorigenesis and suggest that LMTK2 may serve as a potential target for chemotherapy of colon cancer.

Mechanisms of NF-κB p65 and strategies for therapeutic manipulation

The transcription factor NF-κB is a critical regulator of immune and inflammatory responses. In mammals, the NF-κB/Rel family comprises five members: p50, p52, p65 (Rel-A), c-Rel, and Rel-B proteins, which form homo- or heterodimers and remain as an inactive complex with the inhibitory molecules called IκB proteins in resting cells. Two distinct NF-κB signaling pathways have been described: 1) the canonical pathway primarily activated by pathogens and inflammatory mediators, and 2) the noncanonical pathway mostly activated by developmental cues. The most abundant form of NF-κB activated by pathologic stimuli via the canonical pathway is the p65:p50 heterodimer. Disproportionate increase in activated p65 and subsequent transactivation of effector molecules is integral to the pathogenesis of many chronic diseases such as the rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis, and even neurodegenerative pathologies. Hence, the NF-κB p65 signaling pathway has been a pivotal point for intense drug discovery and development. This review begins with an overview of p65-mediated signaling followed by discussion of strategies that directly target NF-κB p65 in the context of chronic inflammation.

Hippocampal nuclear factor kappa B accounts for stress-induced anxiety behaviors via enhancing neuronal nitric oxide synthase (nNOS)-carboxy-terminal PDZ ligand of nNOS-Dexras1 coupling

Anxiety disorders are associated with a high social burden worldwide. Recently, increasing evidence suggests that nuclear factor kappa B (NF-κB) has significant implications for psychiatric diseases, including anxiety and depressive disorders. However, the molecular mechanisms underlying the role of NF-κB in stress-induced anxiety behaviors are poorly understood. In this study, we show that chronic mild stress (CMS) and glucocorticoids dramatically increased the expression of NF-κB subunits p50 and p65, phosphorylation and acetylation of p65, and the level of nuclear p65 in vivo and in vitro, implicating activation of NF-κB signaling in chronic stress-induced pathological processes. Using the novelty-suppressed feeding (NSF) and elevated-plus maze (EPM) tests, we found that treatment with pyrrolidine dithiocarbamate (PDTC; intra-hippocampal infusion), an inhibitor of NF-κB, rescued the CMS- or glucocorticoid-induced anxiogenic behaviors in mice. Microinjection of PDTC into the hippocampus reversed CMS-induced up-regulation of neuronal nitric oxide synthase (nNOS), carboxy-terminal PDZ ligand of nNOS (CAPON), and dexamethasone-induced ras protein 1 (Dexras1) and dendritic spine loss of dentate gyrus (DG) granule cells. Moreover, over-expression of CAPON by infusing LV-CAPON-L-GFP into the hippocampus induced nNOS-Dexras1 interaction and anxiety-like behaviors, and inhibition of NF-κB by PDTC reduced the LV-CAPON-L-GFP-induced increases in nNOS-Dexras1 complex and anxiogenic-like effects in mice. These findings indicate that hippocampal NF-κB mediates anxiogenic behaviors, probably via regulating the association of nNOS-CAPON-Dexras1, and uncover a novel approach to the treatment of anxiety disorders.

Detection of GSK-3β activation index in pediatric chronic tonsillitis is an indicator for chronic recurrent inflammation

PURPOSE

Chronic tonsillitis (TC) is among the most common bacterial diseases in pediatric otolaryngology. We aimed to evaluate the expression of glycogen synthase kinase 3β (GSK-3β) in a cohort of children with chronic tonsillitis (TC), and the correlation between GSK-3β activity index and inflammatory profiles of TC.

MATERIALS AND METHODS

The expression of GSK-3β was comparably evaluated between children with TC (n = 26) and tonsillar hypertrophy (TH, n = 26). GSK-3β expression was detected by immunohistochemistry, RT-qPCR, and Western blot. The inflammatory profiles between the TC and TH groups were also evaluated.

RESULTS

We found that while GSK-3β was highly expressed in both TC and TH groups, no significant difference were detected at mRNA and protein levels between groups. The protein level of p-GSK-3β was significantly lower in the TC group as compared to the TH group. Additionally, the inflammatory markers, including NF-κB, T-bet, and IFN-γ were higher in the TC group compared to TH group. The GSK-3β activation index was positively correlated with the levels of NF-κB, T-bet, and IFN-γ in the TC group.

CONCLUSIONS

Our findings suggested that GSK-3β activation index was demonstrated to be a clinically applicable indicator for chronic recurrent inflammation in pediatric TC.

Crosstalk Between Peroxisome Proliferator-Activated Receptor Gamma and the Canonical WNT/β-Catenin Pathway in Chronic Inflammation and Oxidative Stress During Carcinogenesis

Inflammation and oxidative stress are common and co-substantial pathological processes accompanying, promoting, and even initiating numerous cancers. The canonical WNT/β-catenin pathway and peroxisome proliferator-activated receptor gamma (PPARγ) generally work in opposition. If one of them is upregulated, the other one is downregulated and vice versa. WNT/β-catenin signaling is upregulated in inflammatory processes and oxidative stress and in many cancers, although there are some exceptions for cancers. The opposite is observed with PPARγ, which is generally downregulated during inflammation and oxidative stress and in many cancers. This helps to explain in part the opposite and unidirectional profile of the canonical WNT/β-catenin signaling and PPARγ in these three frequent and morbid processes that potentiate each other and create a vicious circle. Many intracellular pathways commonly involved downstream will help maintain and amplify inflammation, oxidative stress, and cancer. Thus, many WNT/β-catenin target genes such as c-Myc, cyclin D1, and HIF-1α are involved in the development of cancers. Nuclear factor-kappaB (NFκB) can activate many inflammatory factors such as TNF-α, TGF-β, interleukin-6 (IL-6), IL-8, MMP, vascular endothelial growth factor, COX2, Bcl2, and inducible nitric oxide synthase. These factors are often associated with cancerous processes and may even promote them. Reactive oxygen species (ROS), generated by cellular alterations, stimulate the production of inflammatory factors such as NFκB, signal transducer and activator transcription, activator protein-1, and HIF-α. NFκB inhibits glycogen synthase kinase-3β (GSK-3β) and therefore activates the canonical WNT pathway. ROS activates the phosphatidylinositol 3 kinase/protein kinase B (PI3K/Akt) signaling in many cancers. PI3K/Akt also inhibits GSK-3β. Many gene mutations of the canonical WNT/β-catenin pathway giving rise to cancers have been reported (CTNNB1, AXIN, APC). Conversely, a significant reduction in the expression of PPARγ has been observed in many cancers. Moreover, PPARγ agonists promote cell cycle arrest, cell differentiation, and apoptosis and reduce inflammation, angiogenesis, oxidative stress, cell proliferation, invasion, and cell migration. All these complex and opposing interactions between the canonical WNT/β-catenin pathway and PPARγ appear to be fairly common in inflammation, oxidative stress, and cancers.

GSK-3β activation index is a potential indicator for recurrent inflammation of chronic rhinosinusitis without nasal polyps

Chronic rhinosinusitis without nasal polyps (CRSsNP) is one of the most common otorhinolaryngologic diseases worldwide. However, the underlying mechanism remains unclear. In this study, the expression of glycogen synthase kinase 3 (GSK-3) was quantitatively evaluated in patients with CRSsNP (n = 20) and healthy controls (n = 20). The mRNA levels of GSK-3α and GSK-3β were examined by qPCR, the immunoreactivities of GSK-3β and nuclear factor-κB (NF-κB) were examined by immunohistochemistry (IHC) staining, and the protein levels of GSK-3β, phospho-GSK-3β (p-GSK-3β, s9) and NF-κB were examined using Western blot analysis. We found that GSK-3 was highly expressed in both CRSsNP and control groups without significant difference in both GSK-3β mRNA and protein levels. However, when compared with healthy control group, the GSK-3β activation index, defined as the ratio of GSK-3β over p-GSK-3β, was significantly decreased, whereas the NF-κB protein abundance was significantly increased in CRSsNP group (P < 0.05). Strikingly, the GSK-3β activation index, was highly correlated with NF-κB protein level, as well as CT scores in CRSsNP group (P < 0.05). It was also highly correlated with the mRNA expressions of inflammation-related genes, including T-bet, IFN-γ and IL-4 in CRSsNP group (P < 0.05). Our findings suggest that GSK-3β activation index, reflecting the inhibitory levels of GSK-3β through phosphorylation, may be a potential indicator for recurrent inflammation of CRSsNP, and that the insufficient inhibitory phosphorylation of GSK-3β may play a pivotal role in the pathogenesis of CRSsNP.

Thermodynamic Aspects and Reprogramming Cellular Energy Metabolism during the Fibrosis Process

Fibrosis is characterized by fibroblast proliferation and fibroblast differentiation into myofibroblasts, which generate a relaxation-free contraction mechanism associated with excessive collagen synthesis in the extracellular matrix, which promotes irreversible tissue retraction evolving towards fibrosis. From a thermodynamic point of view, the mechanisms leading to fibrosis are irreversible processes that can occur through changing the entropy production rate. The thermodynamic behaviors of metabolic enzymes involved in fibrosis are modified by the dysregulation of both transforming growth factor β (TGF-β) signaling and the canonical WNT/β-catenin pathway, leading to aerobic glycolysis, called the Warburg effect. Molecular signaling pathways leading to fibrosis are considered dissipative structures that exchange energy or matter with their environment far from the thermodynamic equilibrium. The myofibroblastic cells arise from exergonic processes by switching the core metabolism from oxidative phosphorylation to glycolysis, which generates energy and reprograms cellular energy metabolism to induce the process of myofibroblast differentiation. Circadian rhythms are far-from-equilibrium thermodynamic processes. They directly participate in regulating the TGF-β and WNT/β-catenin pathways involved in energetic dysregulation and enabling fibrosis. The present review focusses on the thermodynamic implications of the reprogramming of cellular energy metabolism, leading to fibroblast differentiation into myofibroblasts through the positive interplay between TGF-β and WNT/β-catenin pathways underlying in fibrosis.

Dynamic phosphorylation of RelA on Ser42 and Ser45 in response to TNFα stimulation regulates DNA binding and transcription

The NF-κB signalling module controls transcription through a network of protein kinases such as the IKKs, as well as inhibitory proteins (IκBs) and transcription factors including RelA/p65. Phosphorylation of the NF-κB subunits is critical for dictating system dynamics. Using both non-targeted discovery and quantitative selected reaction monitoring-targeted proteomics, we show that the cytokine TNFα induces dynamic multisite phosphorylation of RelA at a number of previously unidentified residues. Putative roles for many of these phosphorylation sites on RelA were predicted by modelling of various crystal structures. Stoichiometry of phosphorylation determination of Ser45 and Ser42 revealed preferential early phosphorylation of Ser45 in response to TNFα. Quantitative analyses subsequently confirmed differential roles for pSer42 and pSer45 in promoter-specific DNA binding and a role for both of these phosphosites in regulating transcription from the IL-6 promoter. These temporal dynamics suggest that RelA-mediated transcription is likely to be controlled by functionally distinct NF-κB proteoforms carrying different combinations of modifications, rather than a simple ‘one modification, one effect’ system.

TNF Tolerance in Monocytes and Macrophages: Characteristics and Molecular Mechanisms

Tumor necrosis factor (TNF) tolerance in monocytes and macrophages means that preexposure to TNF reduces the sensitivity in these cells to a subsequent restimulation with this cytokine. Differential effects arise following preincubation with both low and high doses of TNF resulting in absolute as well as induction tolerance affecting specific immunologically relevant gene sets. In this review article, we summarize the relevance of TNF tolerance in vivo and the molecular mechanisms underlying these forms of tolerance including the role of transcription factors and signaling systems. In addition, the characteristics of cross-tolerance between TNF and lipopolysaccharide (LPS) as well as pathophysiological aspects of TNF tolerance are discussed. We conclude that TNF tolerance may represent a protective mechanism involved in the termination of inflammation and preventing excessive or prolonged inflammation. Otherwise, tolerance may also be a trigger of immune paralysis thus contributing to severe inflammatory diseases such as sepsis. An improved understanding of TNF tolerance will presumably facilitate the implementation of diagnostic or therapeutic approaches to more precisely assess and treat inflammation-related diseases.

GSK-3β inhibitor 6-bromo-indirubin-3'-oxime promotes both adhesive activity and drug resistance in colorectal cancer cells

Multi-targets inhibitor 6-bromo-indirubin-3'-oxime (BIO) has diverse biological effects on cancer cells. The key component of the β-catenin destruction complex glycogen synthase kinase 3β (GSK-3β), one of the major target for BIO, polyubiquitination and degradation of the main oncoprotein β-catenin in colorectal cancer (CRC). In the present study, we evaluated the effect of BIO on drug resistance and biological properties of CRC cells. Whole-genome transcriptional profiling revealed that differentially expressed genes were mainly centered on well-characterized signaling pathways including stem cell, cell adhesion and cell growth in BIO-treated CRC cells. BIO treatment downregulated migration and invasion abilities of CRC cells, accompanying with MMP-9 downregulated and E-cadherin upregulated CRC cells. BIO treatment decreased apoptosis induced by 5-Fu/DDP in CRC SW480 cells. In addition, BIO treatment reversed the 5-Fu-induced CD133+ cell downregulation trend in CRC SW620 cells. After incubation with BIO, the expression levels of EpCAM, TERT and DCAMKL-1 proteins were upregulated in CRC cells. BIO treatment downregulated the activity of GSK-3β, upregulated and transported β-catenin to the nucleus in CRC cells. Our findings reveal that BIO treatment upregulated stemness, adhesive and chemoresistance of CRC cells. GSK-3β inhibition and WNT/β-catenin activation by BIO, may partly result in the biological behavior alterations in CRC cells.

Thiadiazolidinone-8 Ameliorates Inflammation Associated with Experimental Colitis in Mice

Thiadiazolidinone-8 (TDZD-8) is an effective thiadiazolidinone derivate that is able to suppress the expression of inflammatory cytokines; it also presents tissue protective actions by glycogen synthase kinase (GSK)-3β inhibition, promoting thus an anti-inflammatory effect. Since inflammatory bowel disease is a chronic disease with reduced quality of life, where currently available therapies are only able to induce or maintain the patient in remission, it is crucial to investigate new pharmacological approaches. The main objective of this study was to evaluate the effect of TDZD-8 in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis. Male CD-1 mice with TNBS-induced colitis were treated with a daily dose of TDZD-8 5 mg/kg/day IP during 4 days. The anti-inflammatory properties of TDZD-8 in the TNBS-induced colitis were confirmed by suppression of pro-inflammatory mediators, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β and myeloperoxidase, as well as by the significant increase of the anti-inflammatory cytokine, IL-10. These treated mice also presented a reduction in fecal hemoglobin and alkaline phosphatase, suggesting a beneficial effect of TDZD-8. Furthermore, renal and hepatic biomarkers remained stabilized after treatment. In conclusion, TDZD-8 reduces the inflammatory response associated with TNBS-induced colitis in mice, and modulation of GSK-3β seems to be an interesting pharmacological target in colitis.

Upregulation of FcγRIIB by resveratrol via NF-κB activation reduces B-cell numbers and ameliorates lupus

Resveratrol, an anti-inflammatory agent, can inhibit pro-inflammatory mediators by activating Sirt1, which is a class III histone deacetylase. However, whether resveratrol can regulate inhibitory or anti-inflammatory molecules has been less studied. FcγRIIB, a receptor for IgG, is an essential inhibitory receptor of B cells for blocking B-cell receptor-mediated activation and for directly inducing apoptosis of B cells. Because mice deficient in either Sirt1 or FcγRIIB develop lupus-like diseases, we investigated whether resveratrol can alleviate lupus through FcγRIIB. We found that resveratrol enhanced the expression of FcγRIIB in B cells, resulting in a marked depletion of plasma cells in the spleen and notably in the bone marrow, thereby decreasing serum autoantibody titers in MRL/lpr mice. The upregulation of FcγRIIB by resveratrol involved an increase of Sirt1 protein and deacetylation of p65 NF-κB (K310). Moreover, increased binding of phosphor-p65 NF-κB (S536) but decreased association of acetylated p65 NF-κB (K310) and phosphor-p65 NF-κB (S468) to the −480 promoter region of Fcgr2b gene was responsible for the resveratrol-mediated enhancement of FcγRIIB gene transcription. Consequently, B cells, especially plasma cells, were considerably reduced in MRL/lpr mice, leading to improvement of nephritis and prolonged survival. Taken together, we provide evidence that pharmacological upregulation of FcγRIIB expression in B cells via resveratrol can selectively reduce B cells, decrease serum autoantibodies and ameliorate lupus nephritis. Our findings lead us to propose FcγRIIB as a new target for therapeutic exploitation, particularly for lupus patients whose FcγRIIB expression levels in B cells are downregulated.

Interactions between TGF-β1, canonical WNT/β-catenin pathway and PPAR γ in radiation-induced fibrosis

Radiation therapy induces DNA damage and inflammation leading to fibrosis. Fibrosis can occur 4 to 12 months after radiation therapy. This process worsens with time and years. Radiation-induced fibrosis is characterized by fibroblasts proliferation, myofibroblast differentiation, and synthesis of collagen, proteoglycans and extracellular matrix. Myofibroblasts are non-muscle cells that can contract and relax. Myofibroblasts evolve towards irreversible retraction during fibrosis process. In this review, we discussed the interplays between transforming growth factor-β1 (TGF-β1), canonical WNT/β-catenin pathway and peroxisome proliferator-activated receptor gamma (PPAR γ) in regulating the molecular mechanisms underlying the radiation-induced fibrosis, and the potential role of PPAR γ agonists. Overexpression of TGF-β and canonical WNT/β-catenin pathway stimulate fibroblasts accumulation and myofibroblast differentiation whereas PPAR γ expression decreases due to the opposite interplay of canonical WNT/β-catenin pathway. Both TGF-β1 and canonical WNT/β-catenin pathway stimulate each other through the Smad pathway and non-Smad pathways such as phosphatidylinositol 3-kinase/serine/threonine kinase (PI3K/Akt) signaling. WNT/β-catenin pathway and PPAR γ interact in an opposite manner. PPAR γ agonists decrease β-catenin levels through activation of inhibitors of the WNT pathway such as Smad7, glycogen synthase kinase-3 (GSK-3 β) and dickkopf-related protein 1 (DKK1). PPAR γ agonists also stimulate phosphatase and tensin homolog (PTEN) expression, which decreases both TGF-β1 and PI3K/Akt pathways. PPAR γ agonists by activating Smad7 decrease Smads pathway and then TGF-β signaling leading to decrease radiation-induced fibrosis. TGF-β1 and canonical WNT/β-catenin pathway promote radiation-induced fibrosis whereas PPAR γ agonists can prevent radiation-induced fibrosis.

CNBP acts as a key transcriptional regulator of sustained expression of interleukin-6

The transcription of inflammatory genes is an essential step in host defense activation. Here, we show that cellular nucleic acid-binding protein (CNBP) acts as a transcription regulator that is required for activating the innate immune response. We identified specific CNBP-binding motifs present in the promoter region of sustained inflammatory cytokines, thus, directly inducing the expression of target genes. In particular, lipopolysaccharide (LPS) induced cnbp expression through an NF-κB-dependent manner and a positive autoregulatory mechanism, which enables prolonged il-6 gene expression. This event depends strictly on LPS-induced CNBP nuclear translocation through phosphorylation-mediated dimerization. Consequently, cnbp-depleted zebrafish are highly susceptible to Shigella flexneri infection in vivo. Collectively, these observations identify CNBP as a key transcriptional regulator required for activating and maintaining the immune response.

Aerobic Glycolysis Hypothesis Through WNT/Beta-Catenin Pathway in Exudative Age-Related Macular Degeneration

Exudative age-related macular degeneration (AMD) is characterized by molecular mechanisms responsible for the initiation of choroidal neovascularization (CNV). Inflammatory processes are associated with upregulation of the canonical WNT/beta-catenin pathway in exudative AMD. We focus this review on the link between WNT/beta-catenin pathway activation and neovascular progression in exudative AMD through activation of aerobic glycolysis for production of angiogenic factors. Increased WNT/beta-catenin pathway involves hexokinase 2 (HK2) and pyruvate kinase M2 (PKM2). WNT/beta-catenin pathway stimulates PI3K/Akt pathway and then HIF-1alpha which activates glycolytic enzymes: glucose transporter (Glut), pyruvate dehydrogenase kinase 1 (PDK1), lactate dehydrogenase A (LDH-A), and monocarboxylate lactate transporter (MCT-1). This phenomenon is called aerobic glycolysis or the Warburg effect. Consequently, phosphorylation of PDK-1 inhibits the pyruvate dehydrogenase complex (PDH). Thus, a large part of pyruvate cannot be converted into acetyl-CoA in mitochondria and only a part of acetyl-CoA can enter the tricarboxylic acid cycle. Cytosolic pyruvate is converted into lactate through the action of LDH-A. In exudative AMD, high level of cytosolic lactate is correlated with increase of VEGF expression, the angiogenic factor of CNV. Photoreceptors in retina cells can metabolize glucose through aerobic glycolysis to protect them against oxidative damage, as cancer cells do.

Modulatory Role of Nurr1 Activation and Thrombin Inhibition in the Neuroprotective Effects of Dabigatran Etexilate in Rotenone-Induced Parkinson's Disease in Rats

Recently, it has been shown that both decreased nuclear receptor-related 1 (Nurr1) expression and thrombin accumulation are involved in the degeneration of dopaminergic neurons in Parkinson's disease (PD). The new anticoagulant dabigatran etexilate (DE) is a direct thrombin inhibitor that owns benzimidazole group, which has been proposed to activate Nurr1. In the present study, we examined the neuroprotective effects of DE in rotenone model of PD. Rotenone was injected subcutaneously at a dose of 1.5 mg/kg every other day for 21 days. An oral regimen of DE (15 mg/kg) was started after the 5th rotenone injection following the manifestations of PD. Treatment of PD rats with DE mitigated rotenone-induced neuronal degeneration and restored striatal dopamine level with motor recovery. As well, DE enhanced Nurr1 expression in substantia nigra along with increasing transcriptional activation of Nurr1-controlled genes namely tyrosine hydroxylase, vascular monoamine transporter, glial cell line-derived neurotrophic factor, and its receptor gene c-Ret, which are critical for development and maintenance of dopaminergic neurons. DE also suppressed thrombin accumulation in substantia nigra. Both effects probably contributed to repressing neurotoxic proinflammatory cytokines, which was manifested by decreased level of nuclear factor kappa beta and tumor necrosis factor alpha. In conclusion, the present results suggest that DE could possess significant neuroprotective and regenerative effects in a rotenone-induced PD animal model as consequence of Nurr1 activation and thrombin inhibition.

SCFFBXO17 E3 ligase modulates inflammation by regulating proteasomal degradation of glycogen synthase kinase-3β in lung epithelia

Glycogen synthase kinase-3β (GSK3β) has diverse biological roles including effects on cellular differentiation, migration, and inflammation. GSK3β phosphorylates proteins to generate phosphodegrons necessary for recognition by Skp1/Cullin-1/F-box (SCF) E3 ubiquitin ligases leading to subsequent proteasomal degradation of these substrates. However, little is known regarding how GSK3β protein stability itself is regulated and how its stability may influence inflammation. Here we show that GSK3β is degraded by the ubiquitin-proteasome pathway in murine lung epithelial cells through lysine 183 as an acceptor site for K48 polyubiquitination. We have identified FBXO17 as an F-box protein subunit that recognizes and mediates GSK3β polyubiquitination. Both endogenous and ectopically expressed FBXO17 associate with GSK3β, and its overexpression leads to decreased protein levels of GSK3β. Silencing FBXO17 gene expression increased the half-life of GSK3β in cells. Furthermore, overexpression of FBXO17 inhibits agonist-induced release of keratinocyte-derived cytokine (KC) and interleukin-6 (IL-6) production by cells. Thus, the SCF^FBXO17 E3 ubiquitin ligase complex negatively regulates inflammation by targeting GSK3β in lung epithelia.

Natural Compound Histone Deacetylase Inhibitors (HDACi): Synergy with Inflammatory Signaling Pathway Modulators and Clinical Applications in Cancer

The remarkable complexity of cancer involving multiple mechanisms of action and specific organs led researchers Hanahan and Weinberg to distinguish biological capabilities acquired by cancer cells during the multistep development of human tumors to simplify its understanding. These characteristic hallmarks include the abilities to sustain proliferative signaling, evade growth suppressors, resist cell death, enable replicative immortality, induce angiogenesis, activate invasion and metastasis, avoid immune destruction, and deregulate cellular energetics. Furthermore, two important characteristics of tumor cells that facilitate the acquisition of emerging hallmarks are tumor-promoting inflammation and genome instability. To treat a multifactorial disease such as cancer, a combination treatment strategy seems to be the best approach. Here we focus on natural histone deacetylase inhibitors (HDACi), their clinical uses as well as synergies with modulators of the pro-inflammatory transcription factor signaling pathways.

Application of Fragment-Based de Novo Design to the Discovery of Selective Picomolar Inhibitors of Glycogen Synthase Kinase-3 Beta

A systematic fragment-based de novo design procedure was developed and applied to discover new potent and selective inhibitors of glycogen synthase kinase-3 beta (GSK3β). Candidate inhibitors were generated to simultaneously maximize the biochemical potency and the specificity for GSK3β through three design steps: identification of the optimal molecular fragments for the three sub-binding regions, design of proper linking moieties to connect the fragmental building blocks, and final scoring of the generated molecules. By virtue of modifying the ligand hydration free energy term in the scoring function using hybrid scaled particle theory and the extended solvent-contact model, we identified several GSK3β inhibitors with biochemical potencies ranging from low nanomolar to picomolar levels. Among them, the two most potent inhibitors (12 and 27) are anticipated to serve as promising starting points of drug discovery for various diseases caused by GSK3β because of the high specificity for the inhibition of GSK3β.