Toll-like receptor-mediated production of IL-1Ra is negatively regulated by GSK3 via the MAPK ERK1/2

SHP2 inhibition and adjuvant therapy synergistically target KIT-mutant GISTs via ERK1/2-regulated GSK3β/cyclin D1 pathway

BACKGROUND

Most gastrointestinal stromal tumours (GISTs) are driven by KIT proto-oncogene, receptor tyrosine kinase (KIT). Targeted treatment with imatinib has been successful in primary GIST patients. However, resistance and relapse gradually develop due to secondary KIT mutations. Identifying novel therapeutic targets for advanced GIST with KIT mutants is critical.

METHODS

Clustered regularly interspaced palindromic repeats (CRISPR)/Cas9 gene editing, immunoblotting, immunoprecipitation and cell-based assays were used to characterise the role of Src homology region 2 domain-containing phosphatase 2 (SHP2) in GIST. Immunoblotting, cell cycle analysis, transcriptome analysis and rescue experiments were performed to investigate the molecular mechanisms underlying SHP2 inhibition. Synergistic effects of SHP2 inhibition with approved KIT tyrosine kinase inhibitors (TKIs) were demonstrated using cell proliferation assay, spheroid formation assay, cell cycle analysis and immunoblotting. The combination of SHP2 inhibition and imatinib was further evaluated in GIST mouse models.

RESULTS

In KIT-mutant GIST, SHP2 was hyperactive and coprecipitated with KIT. Activated SHP2 transduced signals from KIT to the downstream MAPK/ERK pathway. SHP2 inhibition significantly reduced cell viability and arrested cell at G0/G1 phase in GIST cells. Mechanistically, SHP2 regulated the MAPK/ERK, GSK3β/cyclin D1 and mTORC1 pathways in GIST. Specifically, SHP2 inhibition relieved GSK3β self-inhibition, leading to a reduction in cyclin D1 via phosphorylation at Thr286 and subsequent G0/G1 cell cycle arrest. Rescue experiments confirmed that cyclin D1 is functional and critical for cell proliferation. Additionally, SHP2 inhibition synergised with approved KIT TKIs in inhibiting GIST cells. In GIST mouse models, SHP2 inhibitor (SHP099) combined with imatinib significantly inhibited proliferation of imatinib-sensitive and -insensitive GIST cells.

CONCLUSIONS

SHP2 functioned as a key signal transducer for the MAPK/ERK signalling pathway and regulated the cell cycle through GSK3β/cyclin D1/Rb pathway. SHP2 inhibition demonstrates significant efficacy towards GIST cells and synergises with approved TKIs. Therefore, SHP2 represents a promising therapeutic target for advanced GIST.

KEY POINTS

SHP2 plays a pivotal role as a signal transducer in the MAPK/ERK signaling pathway. SHP2 controls the cell cycle via the GSK3β/cyclin D1/Rb pathway in oncogenic KIT-driven GIST. Inhibition of SHP2 synergizes with adjuvant therapy drugs in inhibiting KIT-driven GIST with primary and secondary mutations both in vitro and in vivo.

Assessing the impact of circulating inflammatory cytokines and proteins as drivers and therapeutic targets in epilepsy: A Mendelian randomization study

BACKGROUND

Previous research has demonstrated that neuroinflammation is a key element in the progress of epilepsy. Nevertheless, it is currently unidentified which inflammatory factors and proteins increase or decrease the risk of epilepsy.

METHODS

We adopted Mendelian randomization techniques to explore the causal relationship between circulating inflammatory factors and proteins and various epilepsy. Our principal approach was inverse variance weighting, supplemented by several sensitivity analyses to guarantee the robustness of our findings.

RESULTS

Studies have identified associations between epilepsy and specific inflammatory factors and proteins: three inflammatory factors and six proteins are linked to epilepsy in general; one inflammatory factor and four proteins are associated with focal epilepsy with no documented lesions; two inflammatory factors and three proteins are related to focal epilepsy, excluding cases with hippocampal sclerosis; two inflammatory factors and two proteins are connected to juvenile myoclonic epilepsy; two inflammatory factors and five proteins are linked to juvenile absence epilepsy; four inflammatory proteins are associated with childhood absence epilepsy; two inflammatory factors are related to focal epilepsy overall; two inflammatory factors and two proteins are connected to generalized epilepsy; and two inflammatory proteins are linked to generalized epilepsy with tonic-clonic seizures. Additionally, six inflammatory factors may play a downstream role in focal epilepsy.

CONCLUSION

Our study uncovers various inflammatory factors and proteins that influence the risk of epilepsy, offering instructive insights to the diagnosis and therapy of the condition.

NLRP3-mediated autophagy dysfunction links gut microbiota dysbiosis to tau pathology in chronic sleep deprivation

Emerging evidence indicates that sleep deprivation (SD) can lead to Alzheimer's disease (AD)-related pathological changes and cognitive decline. However, the underlying mechanisms remain obscure. In the present study, we identified the existence of a microbiota-gut-brain axis in cognitive deficits resulting from chronic SD and revealed a potential pathway by which gut microbiota affects cognitive functioning in chronic SD. Our findings demonstrated that chronic SD in mice not only led to cognitive decline but also induced gut microbiota dysbiosis, elevated NLRP3 inflammasome expression, GSK-3β activation, autophagy dysfunction, and tau hyperphosphorylation in the hippocampus. Colonization with the "SD microbiota" replicated the pathological and behavioral abnormalities observed in chronic sleep-deprived mice. Remarkably, both the deletion of NLRP3 in NLRP3 -/- mice and specific knockdown of NLRP3 in the hippocampus restored autophagic flux, suppressed tau hyperphosphorylation, and ameliorated cognitive deficits induced by chronic SD, while GSK-3β activity was not regulated by the NLRP3 inflammasome in chronic SD. Notably, deletion of NLRP3 reversed NLRP3 inflammasome activation, autophagy deficits, and tau hyperphosphorylation induced by GSK-3β activation in primary hippocampal neurons, suggesting that GSK-3β, as a regulator of NLRP3-mediated autophagy dysfunction, plays a significant role in promoting tau hyperphosphorylation. Thus, gut microbiota dysbiosis was identified as a contributor to chronic SD-induced tau pathology via NLRP3-mediated autophagy dysfunction, ultimately leading to cognitive deficits. Overall, these findings highlight GSK-3β as a regulator of NLRP3-mediated autophagy dysfunction, playing a critical role in promoting tau hyperphosphorylation.

A Protective Role of Canonical Wnt/β-Catenin Pathway in Pathogenic Bacteria-Induced Inflammatory Responses

Inflammation is a complex host defensive response against various disease-associated pathogens. A baseline extent of inflammation is supposed to be tightly associated with a sequence of immune-modulated processes, resulting in the protection of the host organism against pathogen invasion; however, as a matter of fact is that an uncontrolled inflammatory cascade is the main factor responsible for the host damage, accordingly suggesting a significant and indispensable involvement of negative feedback mechanism in modulation of inflammation. Evidence accumulated so far has supported a repressive effect of the canonical Wnt/β-catenin pathway on microbial-triggered inflammation via diverse mechanisms, although that consequence is dependent on the cellular context, types of stimuli, and cytokine environment. It is of particular interest and importance to comprehend the precise way in which the Wnt/β-catenin pathway is activated, due to its essential anti-inflammatory properties. It is assumed that an inflammatory milieu is necessary for initiating and activating this signaling, implying that Wnt activity is responsible for shielding tissues from overwhelming inflammation, thus sustaining a balanced physiological condition against bacterial infection. This review gathers the recent efforts to elucidate the mechanistic details through how Wnt/β-catenin signaling modulates anti-inflammatory responses in response to bacterial infection and its interactions with other inflammatory signals, which warrants further study for the development of specific interventions for the treatment of inflammatory diseases. Further clinical trials from different disease settings are required.

Impact of Enzymatically Extracted High Molecular Weight Fucoidan on Lipopolysaccharide-Induced Endothelial Activation and Leukocyte Adhesion

The endothelial cell lining creates an interface between circulating blood and adjoining tissue and forms one of the most critical barriers and targets for therapeutical intervention. Recent studies suggest that fucoidans, sulfated and fucose-rich polysaccharides from brown seaweed, show multiple promising biological effects, including anti-inflammatory properties. However, their biological activity is determined by chemical characteristics such as molecular weight, sulfation degree, and molecular structure, which vary depending on the source, species, and harvesting and isolation method. In this study, we investigated the impact of high molecular weight (HMW) fucoidan extract on endothelial cell activation and interaction with primary monocytes (MNCs) in lipopolysaccharide (LPS)-induced inflammation. Gentle enzyme-assisted extraction combined with fractionation by ion exchange chromatography resulted in well-defined and pure fucoidan fractions. FE_F3, with a molecular weight ranging from 110 to 800 kDa and a sulfate content of 39%, was chosen for further investigation of its anti-inflammatory potential. We observed that along with higher purity of fucoidan fractions, the inflammatory response in endothelial mono- and co-cultures with MNCs was reduced in a dose-dependent manner when testing two different concentrations. This was demonstrated by a decrease in IL-6 and ICAM-1 on gene and protein levels and a reduced gene expression of TLR-4, GSK3β and NF-kB. Expression of selectins and, consequently, the adhesion of monocytes to the endothelial monolayer was reduced after fucoidan treatment. These data indicate that the anti-inflammatory effect of fucoidans increases with their purity and suggest that fucoidans might be useful in limiting the inflammatory response of endothelial cells in cases of LPS-induced bacterial infection.

Differential Cytokine Signatures of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and Influenza Infection Highlight Key Differences in Pathobiology

BACKGROUND

Several inflammatory cytokines are upregulated in severe coronavirus disease 2019 (COVID-19). We compared cytokines in COVID-19 versus influenza to define differentiating features of the inflammatory response to these pathogens and their association with severe disease. Because elevated body mass index (BMI) is a known risk factor for severe COVID-19, we examined the relationship of BMI to cytokines associated with severe disease.

METHODS

Thirty-seven cytokines and chemokines were measured in plasma from 135 patients with COVID-19, 57 patients with influenza, and 30 healthy controls. Controlling for BMI, age, and sex, differences in cytokines between groups were determined by linear regression and random forest prediction was used to determine the cytokines most important in distinguishing severe COVID-19 and influenza. Mediation analysis was used to identify cytokines that mediate the effect of BMI and age on disease severity.

RESULTS

Interleukin-18 (IL-18), IL-1β, IL-6, and tumor necrosis factor-α (TNF-α) were significantly increased in COVID-19 versus influenza patients, whereas granulocyte macrophage colony-stimulating factor, interferon-γ (IFN-γ), IFN-λ1, IL-10, IL-15, and monocyte chemoattractant protein 2 were significantly elevated in the influenza group. In subgroup analysis based on disease severity, IL-18, IL-6, and TNF-α were elevated in severe COVID-19, but not in severe influenza. Random forest analysis identified high IL-6 and low IFN-λ1 levels as the most distinct between severe COVID-19 and severe influenza. Finally, IL-1RA was identified as a potential mediator of the effects of BMI on COVID-19 severity.

CONCLUSIONS

These findings point to activation of fundamentally different innate immune pathways in severe acute respiratory syndrome coronavirus 2 and influenza infection, and emphasize drivers of severe COVID-19 to focus both mechanistic and therapeutic investigations.

GSK3β is involved in promoting Alzheimer's disease pathologies following chronic systemic exposure to Porphyromonas gingivalis lipopolysaccharide in amyloid precursor proteinNL-F/NL-F knock-in mice

In line with the strong association between periodontitis and Alzheimer's disease (AD) clinically, preclinical studies have shown that systemic exposure to Porphyromonas gingivalis (Pg) initiates AD pathologies. However, the involvement of periodontitis in promoting AD pathologies is unclear. In the present study, we provided evidence that chronic systemic exposure to lipopolysaccharide derived from Pg (PgLPS, 1 mg/kg, daily, intraperitoneally) prompted neuroinflammation and tau hyperphosphorylation in 10-month-old of amyloid precursor protein (APP) knock-in mice, a model of AD, carrying the Swedish and Beyreuther/Iberian mutation (APP^NL-F/NL-F). The learning and memory function were assessed using the passive avoidance test. The production of APP, Amyloid (A)β_1-42, cytokines, synaptic proteins and the activation of glycogen synthase kinase (GSK)-3β as well as phosphorylation of tau were analyzed by immunohistochemistry, Western blotting or an enzyme-linked immunosorbent assay (ELISA) in the cortex of APP^NL-F/NL-F mice. We found that systemic exposure of PgLPS for three consecutive weeks induced learning and memory deficits with significantly reduced postsynaptic density protein (PSD95). Increased hyperphosphorylation of tau in multiple residues, including Ser202, Thr231 and Ser396, but not the accumulation of Aβ_1-42 was detected in the neurons of APP^NL-F/NL-F mice. Furthermore, PgLPS increased the GSK3β activity by reducing its phosphorylation of the serine residue at position 9 (Ser9) and promoted neuroinflammation by increasing the expression of interleukin-1β (IL-1β) and tumor necrosis factor (TNF-α) while decreasing that of interleukin-10 (IL-10) and transforming growth factor (TGFβ) in the cortex of APP^NL-F/NL-F mice. Moreover, the PgLPS-increased GSK3β activity was detected in both microglia and neurons, while the PgLPS-increased TNF-α expression was mainly detected in the microglia in the cortex of APP^NL-F/NL-F mice. In in vitro studies, PgLPS (1 µg/ml) stimulation increased the mRNA and protein level of TNF-α in MG6 microglia, which were significantly inhibited by the GSK3β-specific inhibitor TWS119. In contrast, the tau hyperphosphorylation and activation of GSK3β in N2a neurons were enhanced after treatment with conditioned medium from PgLPS-stimulated microglia, which was attenuated after pre-treatment with TNF-α inhibitor. Taken together, these findings indicate that GSK3β is involved in prompting microglia (TNF-α)-dependent tau hyperphosphorylation in neurons, resulting in learning and memory deficits in APP^NL-F/NL-F mice without changes in the Aβ expression during chronic systemic exposure to PgLPS. We propose that dampening GSK3β activation may help delay the periodontitis-promoted pathological progression of AD.

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.

GSK3 Restrains Germinal Center B Cells to Form Plasma Cells

B cells in the germinal center (GC) are programmed to form plasma cells (PCs) or memory B cells according to signals received by receptors that are translated to carry out appropriate activities of transcription factors. However, the precise mechanism underlying this process to complete the GC reaction is unclear. In this study, we show that both genetic ablation and pharmacological inhibition of glycogen synthase kinase 3 (GSK3) in GC B cells of mice facilitate the cell fate decision toward PC formation, accompanied by acquisition of dark zone B cell properties. Mechanistically, under stimulation with CD40L and IL-21, GSK3 inactivation synergistically induced the transcription factors Foxo1 and c-Myc, leading to increased levels of key transcription factors required for PC differentiation, including IRF4. This GSK3-mediated alteration of transcriptional factors in turn facilitated the dark zone transition and consequent PC fate commitment. Our study thus reveals the upstream master regulator responsible for interpreting external cues in GC B cells to form PCs mediated by key transcription factors.

Glycogen synthase kinase-3β inhibition alleviates activation of the NLRP3 inflammasome in myocardial infarction

Inflammasome-promoted sterile inflammation following cardiac damage is critically implicated in heart dysfunction after myocardial infarction (MI). Glycogen synthase kinase-3 (GSK-3β) is a prominent mediator of the inflammatory response, and high GSK-3 activity is associated with various heart diseases. We investigated the regulatory mechanisms of GSK-3β in activation of the nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome in a rat model with successful induction of MI on days 2-28. An in vitro investigation was performed using newborn rat/human cardiomyocytes and fibroblast cultures under typical inflammasome stimulation and hypoxia treatment. GSK-3β inhibition markedly improved myocardial dysfunction and prevented remodeling, with parallel reduction in the parameters of NLRP3 inflammasome activation after MI. GSK-3β inhibition reduced NLRP3 inflammasome activation in cardiac fibroblasts, but not in cardiomyocytes. GSK-3β's interaction with activating signal cointegrator (ASC) as well as GSK-3β inhibition reduced ASC phosphorylation and oligomerization at the tissues and cellular levels. Taken together, these data show that GSK-3β directly mediates NLRP3 inflammasome activation, causing cardiac dysfunction in MI.

Modulation of LPS-induced inflammatory cytokine production by a novel glycogen synthase kinase-3 inhibitor

Sepsis is a serious condition that can lead to long-term organ damage and death. At the molecular level, the hallmark of sepsis is the elevated expression of a multitude of potent cytokines, i.e. a cytokine storm. For sepsis involving gram-negative bacteria, macrophages recognize lipopolysaccharide (LPS) shed from the bacteria, activating Toll-like-receptor 4 (TLR4), and triggering a cytokine storm. Glycogen synthase kinase-3 (GSK-3) is a highly active kinase that has been implicated in LPS-induced cytokine production. Thus, compounds that inhibit GSK-3 could be potential therapeutics for sepsis. Our group has recently described a novel and highly selective inhibitor of GSK-3 termed COB-187. In the present study, using THP-1 macrophages, we evaluated the ability of COB-187 to attenuate LPS-induced cytokine production. We found that COB-187 significantly reduced, at the protein and mRNA levels, cytokines induced by LPS (e.g. IL-6, TNF-α, IL-1β, CXCL10, and IFN-β). Further, the data suggest that the inhibition could be due, at least in part, to COB-187 reducing NF-κB (p65/p50) DNA binding activity as well as reducing IRF-3 phosphorylation at Serine 396. Thus, COB-187 appears to be a potent inhibitor of the cytokine storm induced by LPS.

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.

Activation of Toll-Like Receptor 3 Induces Interleukin-1 Receptor Antagonist Expression by Activating the Interferon Regulatory Factor 3

Toll-like receptor 3 (TLR3) is a sensor of endogenous cell necrosis during the process of acute inflammation. Interleukin (IL)-1 receptor antagonist (IL-1Ra) is an anti-inflammatory cytokine and can negatively regulate the pathogenesis of inflammation. However, whether and how activation of TLR3 can regulate IL-1Ra expression has not been clarified. Here, we show that poly(I:C) induces IL-1Ra expression in primarily cultured human fibroblast-like synoviocytes and other types of cells. Induction of IL-1Ra by poly(I:C) was dependent on TLR3, but was independent of melanoma differentiation--associated protein 5 or retinoic acid-inducible gene I. Interferon regulatory factor 3 (IRF3) directly binds to the IL-1Ra promoter and promotes IL-1Ra expression in response to poly(I:C) stimulation. Induction of IL-1Ra by poly(I:C) was abolished by the inhibition of the NF-κB signaling, attenuated by the inhibition of the PI3K-Akt signaling, enhanced by inhibition of the ERK1/2 or MSK1/2 activation, but was independent of the p38 MAPK signaling. Treatment with poly(I:C) or Sendai virus elevated the levels of serum IL-1Ra in wild-type, but not in TLR3-/- or IRF3-/- mice. Our findings may provide new insights into the intrinsic anti-inflammatory function of TLR3 and double-stranded RNA-induced IL-Ra expression by TLR3 and its regulation.

Glycogen synthase kinase-3 inhibitor as a multi-targeting anti-rheumatoid drug

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease that causes swelling, bone erosion, and joint disorder. Patients with RA therefore suffer from pain and physiological disability, and have a decreased quality of life. During the progression of RA, many different types of cells and inflammatory factors influence each other with an important role. A better understanding of the pathology of RA should therefore lead to the development of effective anti-rheumatoid drugs, such as the anti-TNFα antibody. Glycogen synthase kinase-3 (GSK-3) is a cytoplasmic serine/threonine protein kinase that is involved in a large number of key cellular processes and is dysregulated in a wide variety of diseases, including inflammation and osteoporosis. The accumulated evidence has suggested that GSK-3 could be involved in multiple steps in the progression of RA. In the present review, the mechanisms of the pathogenesis of RA are summarized, and recent developments and potential new drugs targeting GSK-3 are discussed.

GSK3β inhibition attenuates LPS-induced IL-6 expression in porcine adipocytes

IL-6 is not only a proinflammatory cytokine associated with inflammatory responses but also a regulator on the energy and glucose metabolism in adipose tissue. Glycogen synthase kinase 3β (GSK3β) has fundamental roles in the regulation of pro- and anti-inflammatory cytokines production. However, the regulatory role for GSK3β in the pig inflammatory response in adipocytes remains unknown. We show here that SB216763 and LPS increased the phosphorylation of GSK3β (Ser9), and decreased the phosphorylation of GS (Ser641) in adipocytes. The activity of porcine GSK3β was inhibited by SB216763, an inhibitor of GSK3β, attenuated the production of IL-6 in LPS-stimulated adipocytes. Additionally, the essential core region of the pig IL-6 promoter located at -191 bp to -59 bp, and an NF-κBp65 element in this region was responsible for IL-6 promoter activity. The transcription activity of NF-κBp65 was activated by LPS stimulation, and the GSK3β inhibition repressed LPS-induced luciferase activity of the IL-6 promoter. Furthermore, LPS increased p65 binding to the NF-κB site, and GSK3β inhibition had no effect on the association of NF-κBp65 with IL-6 gene promoter after LPS treatment. These results demonstrate that GSK3β has important regulatory roles in the LPS-induced inflammatory response of IL-6 production in pig adipocytes.

TNFα disrupts blood brain barrier integrity to maintain prolonged depressive-like behavior in mice

Recovery from major depressive disorder is difficult, particularly in patients who are refractory to antidepressant treatments. To examine factors that regulate recovery, we developed a prolonged learned helplessness depression model in mice. After the induction of learned helplessness, mice were separated into groups that recovered or did not recover within 4 weeks. Comparisons were made between groups in hippocampal proteins, inflammatory cytokines, and blood brain barrier (BBB) permeability. Compared with mice that recovered and control mice, non-recovered mice displaying prolonged learned helplessness had greater hippocampal activation of glycogen synthase kinase-3 (GSK3), higher levels of tumor necrosis factor-α (TNFα), interleukin-17A, and interleukin-23, increased permeability of the blood brain barrier (BBB), and lower levels of the BBB tight junction proteins occludin, ZO1, and claudin-5. Treatment with the GSK3 inhibitor TDZD-8 reduced inflammatory cytokine levels, increased tight junction protein levels, and reversed impaired recovery from learned helplessness, demonstrating that prolonged learned helplessness is reversible and is maintained by abnormally active GSK3. In non-recovered mice with prolonged learned helpless, stimulation of sphingosine 1-phosphate receptors by Fingolimod or administration of the TNFα inhibitor etanercept repaired the BBB and reversed impaired recovery from prolonged learned helplessness. Thus, disrupted BBB integrity mediated in part by TNFα contributes to blocking recovery from prolonged learned helplessness depression-like behavior. Overall, this report describes a new model of prolonged depression-like behavior and demonstrates that stress-induced GSK3 activation contributes to disruption of BBB integrity mediated by inflammation, particularly TNFα, which contributes to impaired recovery from prolonged learned helplessness.

Identification of immune-related genes in gill cells of Japanese eels (Anguilla japonica) in adaptation to water salinity changes

The changes in ambient salinity influence ion and water homeostasis, hormones secretion, and immune response in fish gills. The physiological functions of hormones and ion transporters in the regulation of gill-osmoregulation have been widely studied, however the modulation of immune response under salinity changes is not determined. Using transcriptome sequencing, we obtained a comprehensive profile of osmo-responsive genes in gill cells of Japanese eel (Anguilla japonica). Herein, we applied bioinformatics analysis to identify the immune-related genes that were significantly higher expressed in gill pavement cells (PVCs) and mitochondrial-rich cells (MRCs) in freshwater (FW) than seawater (SW) adapted fish. We validated the data using the real-time qPCR, which showed a high correlation between the RNA-seq and real-time qPCR data. In addition, the immunohistochemistry results confirmed the changes of the expression of selected immune-related genes, including C-reactive protein (CRP) in PVCs, toll-like receptor 2 (TLR2) in MRCs and interleukin-1 receptor type 2 (IL-1R2) in both PVCs and MRCs. Collectively our results demonstrated that those immune-related genes respond to salinity changes, and might trigger related special signaling pathways and network. This study provides new insights into the impacts of ambient salinity changes on adaptive immune response in fish gill cells.

Glycogen synthase kinase-3 (GSK3) regulates TNF production and haemocyte phagocytosis in the immune response of Chinese mitten crab Eriocheir sinensis

Glycogen synthase kinase-3 (GSK3) is a serine/threonine protein kinase firstly identified as a regulator of glycogen synthesis. Recently, it has been proved to be a key regulator of the immune reaction. In the present study, a GSK3 homolog gene (designated as EsGSK3) was cloned from Chinese mitten crab, Eriocheir sinensis. The open reading frame (ORF) was 1824 bp, which encoded a predicted polypeptide of 607 amino acids. There was a conserved Serine/Threonine Kinase domain and a DNA binding domain found in EsGSK3. Phylogenetic analysis showed that EsGSK3 was firstly clustered with GSK3-β from oriental river prawn Macrobrachium nipponense in the invertebrate branch, while GSK3s from vertebrates formed the other distinct branch. EsGSK3 mRNA transcripts could be detected in all tested tissues of the crab including haepatopancreas, eyestalk, muscle, gonad, haemocytes and haematopoietic tissue with the highest expression level in haepatopancreas. And EsGSK3 protein was mostly detected in the cytoplasm of haemocyte by immunofluorescence analysis. The expression levels of EsGSK3 mRNA increased significantly at 6 h after Aeromonas hydrophila challenge (p < 0.05) in comparison with control group, and then gradually decreased to the initial level at 48 h (p > 0.05). The mRNA expression of lipopolysaccharide-induced tumor necrosis factor (TNF)-α factor (EsLITAF) was also induced by A. hydrophila challenge. However, the mRNA expression of EsLITAF and TNF-α production was significantly suppressed after EsGSK3 was blocked in vivo with specific inhibitor lithium, while the phagocytosis of crab haemocytes was significantly promoted. These results collectively demonstrated that EsGSK3 could regulate the innate immune responses of E. sinensis by promoting TNF-α production and inhibiting haemocyte phagocytosis.

Phosphodiesterase 4B negatively regulates endotoxin-activated interleukin-1 receptor antagonist responses in macrophages

Activation of TLR4 by lipopolysaccharide (LPS) induces both pro-inflammatory and anti-inflammatory cytokine production in macrophages. Type 4 phosphodiesterases (PDE4) are key cAMP-hydrolyzing enzymes, and PDE4 inhibitors are considered as immunosuppressors to various inflammatory responses. We demonstrate here that PDE4 inhibitors enhance the anti-inflammatory cytokine interleukin-1 receptor antagonist (IL-1Ra) secretion in LPS-activated mouse peritoneal macrophages, and this response was regulated at the transcriptional level rather than an increased IL-1Ra mRNA stability. Studies with PDE4-deficient macrophages revealed that the IL-1Ra upregulation elicited by LPS alone is PKA-independent, whereas the rolipram-enhanced response was mediated by inhibition of only PDE4B, one of the three PDE4 isoforms expressed in macrophages, and it requires PKA but not Epac activity. However, both pathways activate CREB to induce IL-1Ra expression. PDE4B ablation also promoted STAT3 phosphorylation (Tyr⁷⁰⁵) to LPS stimulation, but this STAT3 activation is not entirely responsible for the IL-1Ra upregulation in PDE4B-deficient macrophages. In a model of LPS-induced sepsis, only PDE4B-deficient mice displayed an increased circulating IL-1Ra, suggesting a protective role of PDE4B inactivation in vivo. These findings demonstrate that PDE4B negatively modulates anti-inflammatory cytokine expression in innate immune cells, and selectively targeting PDE4B should retain the therapeutic benefits of nonselective PDE4 inhibitors.

Glycogen synthase kinase 3β in Toll-like receptor signaling

Toll-like receptors (TLRs) play a critical role in the innate immune response against pathogens. Each TLR recognizes specific pathogen-associated molecular patterns, after which they activate the adaptor protein MyD88 or TRIF-assembled signaling complex to produce immune mediators, including inflammatory cytokines and type I IFNs. Although the activation of TLR is important for host defense, its uncontrolled activation can damage the host. During the past decade, numerous studies have demonstrated that GSK3β is a key regulator of inflammatory cytokine production in MyD88-mediated TLR signaling via TLR2 and TLR4. Recently, GSK3β has also been implicated in the TRIF-dependent signaling pathway via TLR3. In this review, we describe current advances on the regulatory role of GSK3β in immune responses associated with various TLRs. A better understanding of the role of GSK3β in TLR signaling might lead to more effective anti-inflammatory interventions. [BMB Reports 2016; 49(6): 305-310]

Interleukin-1 receptor antagonist mediates toll-like receptor 3-induced inhibition of trophoblast adhesion to endometrial cells in vitro

STUDY QUESTION

Is interleukin-1 receptor antagonist (IL-1RA) involved in the toll-like receptor 3 (TLR 3)-induced inhibition of trophoblast cells' adhesion to endometrial cells in vitro?

SUMMARY ANSWER

IL-1RA mediates the TLR 3-induced inhibition of trophoblast cells' adhesion to endometrial cells in vitro.

WHAT IS KNOWN ALREADY

It is well documented that endometrial TLR 3 activation leads to impairment of trophoblast binding to endometrial cells in vitro. IL-1RA is known as an anti-implantation factor, as its injection significantly reduced implantation rates in mice by an effect on endometrial receptivity.

STUDY DESIGN, SIZE, DURATION

Poly I:C was used as a TLR3 specific ligand and endometrial cells were either treated or not with Poly I:C (treated versus control) in vitro. IL-1RA was applied to block IL-1 signal transduction. IL-1RA was knocked down by Accell Human IL1RN siRNA. Flagellin was used to stimulate TLR 5. SP600125 (JNK) was applied to inhibit the mitogen-activated protein kinases (MAPK) pathway. BAY11 -7082 was used to inhibit the nuclear factor-κB (NF-κB) pathway. The experiments were performed in three replicates on three separate days.

PARTICIPANTS/MATERIALS, SETTING, METHODS

An in vitro assay was developed using RL95-2 (an endometrial cell line) and JAr (a trophoblast cell line) cells. Initially, the production of IL-1RA in RL95-2 cells in response to TLR 3 activation was measured. To determine whether the TLR 3-induced inhibition of trophoblast binding was mediated through IL-1RA: (i) we evaluated the effect of IL-1RA on the attachment of trophoblast cells to endometrial cells; (ii) we knocked down TLR3-induced IL-1RA gene expression by IL-1RA Small interfering RNA (siRNA) and evaluated trophoblast attachment to endometrial cells. Finally, to clarify through which pathway TLR 3-induced inhibition of trophoblast binding occurs: (i) activation of NF-κB and MAPK was detected by transfecting the cells with secreted placental alkaline phosphatase reporter plasmids bearing promoter sequences for each transcription factor; (ii) the inhibitors for NF-κB and MAPK were used to block signaling; (iii) it was then investigated whether addition of these inhibitors could restore the TLR 3-induced impairment of trophoblast attachment to the endometrial cells.

MAIN RESULTS AND THE ROLE OF CHANCE

Our results showed that addition of polyinosinic:polycytidylic acid (Poly I:C) to RL95-2 cells significantly increased the production of IL-1RA (P < 0.05). Addition of human recombinant IL-1RA to RL95-2 cells remarkably decreased the adhesion rate of trophoblast cells to endometrial cells (P < 0.05). In addition, suppression of TLR3-induced IL-1RA gene expression in RL95-2 cells significantly restored trophoblast cells attachment to endometrial cells in the presence of Poly I:C (P < 0.05). Only TLR3 and not TLR5 induced MAPK activation (P < 0.05). TLR3 ligation did not affect NF-κB activation. Of NF-kB and MAPK inhibitors, only MAPK's inhibitor could achieve restoration of spheroid adhesion to endometrial cells (P < 0.05).

LIMITATIONS, REASONS FOR CAUTION

This study has been only done in vitro. Future in vivo studies will confirm our data.

WIDER IMPLICATIONS OF THE FINDINGS

The findings of this study have a potential clinical application in introducing IL-1RA as one of the diagnostic infertility markers in the endometrium, which can affect the process of embryo adhesion at the time of implantation. Moreover, based on the novel data obtained in the current study, blocking and regulating the MAPK pathway by its inhibitors can be used as a new strategy to prevent and treat virus-induced infertility cases in ART techniques.

STUDY FUNDING/COMPETING INTEREST

This study was partially funded by a Marie Curie IIF-253948 grant to I.C. and was partially funded by the author's institutions. The authors have no conflict of interest to declare.

Lithium chloride antileukemic activity in acute promyelocytic leukemia is GSK-3 and MEK/ERK dependent

We recently identified that the MEK/ERK1/2 pathway synergized with retinoic acid (RA) to restore both transcriptional activity and RA-induced differentiation in RA-resistant acute promyelocytic leukemia (APL) cells. To target the MEK/ERK pathway, we identified glycogen synthase kinase-3β (GSK-3β) inhibitors including lithium chloride (LiCl) as activators of this pathway in APL cells. Using NB4 (RA-sensitive) and UF-1 (RA-resistant) APL cell lines, we observed that LiCl as well as synthetic GSK-3β inhibitors decreased proliferation, induced apoptosis and restored, in RA-resistant cells, the expression of RA target genes and the RA-induced differentiation. Inhibition of the MEK/ERK1/2 pathway abolished these effects. These results were corroborated in primary APL patient cells and translated in vivo using an APL preclinical mouse model in which LiCl given alone was as efficient as RA in increasing survival of leukemic mice compared with untreated mice. When LiCl was combined with RA, we observed a significant survival advantage compared with mice treated by RA alone. In this work, we demonstrate that LiCl, a well-tolerated agent in humans, has antileukemic activity in APL and that it has the potential to restore RA-induced transcriptional activation and differentiation in RA-resistant APL cells in an MEK/ERK-dependent manner.

Phagocytosed Clofazimine Biocrystals Can Modulate Innate Immune Signaling by Inhibiting TNFα and Boosting IL-1RA Secretion

Clofazimine (CFZ) is an FDA-approved leprostatic and anti-inflammatory drug that massively accumulates in macrophages, forming insoluble, intracellular crystal-like drug inclusions (CLDIs) during long-term oral dosing. Interestingly, when added to cells in vitro, soluble CFZ is cytotoxic because it depolarizes mitochondria and induces apoptosis. Accordingly, we hypothesized that, in vivo, macrophages detoxify CFZ by sequestering it in CLDIs. To test this hypothesis, CLDIs of CFZ-treated mice were biochemically isolated and then incubated with macrophages in vitro. The cell biological effects of phagocytosed CLDIs were compared to those of soluble CFZ. Unlike soluble CFZ, phagocytosis of CLDIs did not lead to mitochondrial destabilization or apoptosis. Rather, CLDIs altered immune signaling response pathways downstream of Toll-like receptor (TLR) ligation, leading to enhanced interleukin-1 receptor antagonist (IL-1RA) production, dampened NF-κB activation and tissue necrosis factor alpha (TNFα) production, and ultimately decreased TLR expression levels. In aggregate, our results constitute evidence that macrophages detoxify soluble CFZ by sequestering it in a biocompatible, insoluble form. The altered cellular response to TLR ligation suggests that CLDI formation may also underlie CFZ's anti-inflammatory activity.

Glycogen synthase kinase-3 controls IL-10 expression in CD4(+) effector T-cell subsets through epigenetic modification of the IL-10 promoter

The serine/threonine kinase glycogen synthase kinase-3 (GSK3) plays an important role in balancing pro- and anti-inflammatory cytokines. We have examined the role of GSK3 in production of IL-10 by subsets of CD4(+) T helper cells. Treatment of naive murine CD4(+) T cells with GSK3 inhibitors did not affect their production of IL-10. However, treatment of Th1 and Th2 cells with GSK3 inhibitors dramatically increased production of IL-10. GSK3 inhibition also led to upregulation of IL-10 among Th1, Th2, and Th17 subsets isolated from human blood. The encephalitogenic potential of GSK3 inhibitor treated murine Th1 cells was significantly reduced in adoptive transfer experiments by an IL-10-dependent mechanism. Analysis of the murine IL-10 promoter in response to inhibition of GSK3 in Th1 cells showed modification to a transcriptionally active state indicated by changes in histone H3 acetylation and methylation. Additionally, GSK3 inhibition increased expression of the transcription factors c-Maf, Nfil3, and GATA3, correlating with the increase in IL-10. These findings are important in the context of autoimmune disease since they show that it is possible to reprogram disease-causing cells through GSK3 inhibition.

Glycogen synthase kinase 3β ubiquitination by TRAF6 regulates TLR3-mediated pro-inflammatory cytokine production

TRAF6 is critical for the production of inflammatory cytokines in various TLR-mediated signalling pathways. However, it is poorly understood how TRAF6 regulates TLR3 responses. Here we demonstrate that GSK3β interacts with TRAF6 and positively regulates the TLR3-mediated signalling. Suppression of GSK3β expression or its kinase activity drastically reduces the production of inflammatory cytokines and the induction of c-Fos by decreasing ERK and p38 phosphorylation. GSK3β physically associates with TRAF6 in a TLR3 ligand poly I:C-dependent manner. TRAF6 is determined to be a direct E3 ligase for GSK3β, and TRAF6-mediated GSK3β ubiquitination is essential for poly I:C-dependent cytokine production by promoting the TLR3 adaptor protein TRIF-assembled signalling complex.

GSK3β is a molecular hub implicated in regulation of cell metabolism, migration, proliferation and survival. Here the authors show that GSK3β regulates inflammatory cytokine production by promoting the assembly of a signalling platform downstream of TLR3, a sensor of viral infection.

Cytokine-induced monocyte MMP-1 is negatively regulated by GSK-3 through a p38 MAPK-mediated decrease in ERK1/2 MAPK activation

Elucidation of the signal transduction events leading to the production of MMPs by monocytes/macrophages may provide insights into the mechanisms involved in the destruction of connective tissue associated with chronic inflammatory lesions. Here, we show that GSK-3 is a negative regulator of cytokine-induced MMP-1 production by monocytes. Inhibition of monocyte GSK-3 pharmacologically with SB216763 or GSK-3β siRNA caused a significant enhancement of MMP-1 by TNF-α- and GM-CSF-activated monocytes, indicating that induction of MMP-1 by TNF-α and GM-CSF involved phosphorylation/inactivation of GSK-3. TNF-α- and GM-CSF-induced phosphorylation of GSK-3 and subsequent MMP-1 production was blocked with the PKC inhibitor Gö6976 but not by the AKT1/2 inhibitor AKT VIII, showing that cytokine phosphorylation of GSK-3 occurs primarily through a PKC pathway. Inhibition of GSK-3 resulted in decreased phosphorylation of p38 MAPK with a corresponding increase in phosphorylation of ERK1/2 MAPK. Enhanced MMP-1 production by treatment with SB216763 was a result of increased ERK1/2 activation, as demonstrated by inhibition of MMP-1 by PD98059, a specific ERK1/2 inhibitor. Conversely, the p38 MAPK inhibitor SB203580 enhanced cytokine activation of ERK1/2 and the production of MMP-1 similar to that of SB216763. These findings demonstrate that the degree of cytokine-mediated phosphorylation/inhibition of GSK-3 determines the level of MMP-1 production through a mechanism involving decreased activation of p38 MAPK, a negative regulator of ERK1/2 required for cytokine-induced production of MMP-1 by monocytes.

Fractional factorial design to investigate stromal cell regulation of macrophage plasticity

Understanding the regulatory networks which control specific macrophage phenotypes is essential in identifying novel targets to correct macrophage mediated clinical disorders, often accompanied by inflammatory events. Since mesenchymal stromal cells (MSCs) have been shown to play key roles in regulating immune functions predominantly via a large number of secreted products, we used a fractional factorial approach to streamline experimental evaluation of MSC mediated inflammatory macrophage regulation. Our macrophage reprogramming metrics, human bone marrow MSC attenuation of macrophage pro-inflammatory M1 TNFα secretion and simultaneous enhanced expression of the M2 macrophage marker, CD206, were used as analysis endpoints. Objective evaluation of a panel of MSC secreted mediators indicated that PGE2 alone was sufficient in facilitating macrophage reprogramming, while IL4 only provided partial reprogramming. Inhibiting stromal cell PGE2 secretion with Indomethacin, reversed the macrophage reprogramming effect. PGE2 reprogramming was mediated through the EP4 receptor and indirectly through the CREB signaling pathway as GSK3 specific inhibitors induced M1 macrophages to express CD206. This reprogramming pathway functioned independently from the M1 suppression pathway, as neither CREB nor GSK3 inhibition reversed PGE2 TNF-α secretion attenuation. In conclusion, fractional factorial experimental design identified stromal derived PGE2 as the factor most important in facilitating macrophage reprogramming, albeit via two unique pathways.

Protective effects of pretreatment with oleanolic acid in rats in the acute phase of hepatic ischemia-reperfusion injury: role of the PI3K/Akt pathway

Oleanolic acid (OA) has been used to treat liver disorders, but whether it can attenuate hepatic ischemia-reperfusion- (IR-) associated liver dysfunction remains unexplored. In the present study, 160 male Sprague-Dawley rats were equally divided into five groups: group SH received neither hepatic IR nor drugs; group IR received hepatic IR without drugs; group CM and group OA received 0.5% sodium carboxymethylcellulose and 100 mg/kg OA, intragastrically, once a day for seven days before the hepatic IR, respectively; on the basis of treatment in group OA, group OA+wortmannin further received 15 μg/kg of PI3K inhibitor wortmannin, intraperitoneally, 30 min before the hepatic IR. Then each group was equally divided into four subgroups according to four time points (preoperation, 0 h, 3 h, and 6 h after reperfusion). Serum ALT activity, IL-1β concentration, and hepatic phosphorylation of PI3K, Akt, and GSK-3β protein expression were serially studied. We found that OA pretreatment improved histological status and decreased serum ALT and IL-1β levels. It also increased p-PI3K, p-Akt, and p-GSK-3β protein expression at all the four time points. Prophylactic wortmannin partially reversed OA's protective effects. The data indicate that OA pretreatment protects liver from IR injury during the acute phase partially through PI3K/Akt-mediated inactivation of GSK-3β.

GSK3β and the control of infectious bacterial diseases

Glycogen synthase kinase 3β (GSK3β) has been shown to be a crucial mediator of the intensity and direction of the innate immune system response to bacterial stimuli. This review focuses on: (i) the central role of GSK3β in the regulation of pathogen-induced inflammatory responses through the regulation of pro- and anti-inflammatory cytokine production, (ii) the extensive ongoing efforts to exploit GSK3β for its therapeutic potential in the control of infectious diseases, and (iii) the increasing evidence that specific pathogens target GSK3β-related pathways for immune evasion. A better understanding of complex bacteria-GSK3β interactions is likely to lead to more effective anti-inflammatory interventions and novel targets to circumvent pathogen colonization and survival.

A20 is critical for the induction of Pam3CSK4-tolerance in monocytic THP-1 cells

A20 functions to terminate Toll-like receptor (TLR)-induced immune response, and play important roles in the induction of lipopolysacchride (LPS)-tolerance. However, the molecular mechanism for Pam3CSK4-tolerance is uncertain. Here we report that TLR1/2 ligand Pam3CSK4 induced tolerance in monocytic THP-1 cells. The pre-treatment of THP-1 cells with Pam3CSK4 down-regulated the induction of pro-inflammatory cytokines induced by Pam3CSK4 re-stimulation. Pam3CSK4 pre-treatment also down-regulated the signaling transduction of JNK, p38 and NF-κB induced by Pam3CSK4 re-stimulation. The activation of TLR1/2 induced a rapid and robust up-regulation of A20, suggesting that A20 may contribute to the induction of Pam3CSK4-tolerance. This hypothesis was proved by the observation that the over-expression of A20 by gene transfer down-regulated Pam3CSK4-induced inflammatory responses, and the down-regulation of A20 by RNA interference inhibited the induction of tolerance. Moreover, LPS induced a significant up-regulation of A20, which contributed to the induction of cross-tolerance between LPS and Pam3CSK4. A20 was also induced by the treatment of THP-1 cells with TNF-α and IL-1β. The pre-treatment with TNF-α and IL-1β partly down-regulated Pam3CSK4-induced activation of MAPKs. Furthermore, pharmacologic inhibition of GSK3 signaling down-regulated Pam3CSK4-induced A20 expression, up-regulated Pam3CSK4-induced inflammatory responses, and partly reversed Pam3CSK4 pre-treatment-induced tolerance, suggesting that GSK3 is involved in TLR1/2-induced tolerance by up-regulation of A20 expression. Taken together, these results indicated that A20 is a critical regulator for TLR1/2-induced pro-inflammatory responses.

Sustained elevation of Snail promotes glial-mesenchymal transition after irradiation in malignant glioma

BACKGROUND

Ionizing irradiation is an effective treatment for malignant glioma (MG); however, a higher rate of recurrence with more aggressive phenotypes is a vital issue. Although epithelial-mesenchymal transition (EMT) is involved in irradiation-induced cancer progression, the role for such phenotypic transition in MG remains unknown.

METHODS

To investigate the mechanism of irradiation-dependent tumor progression in MG, we performed immunohistochemistry (IHC) and qRT-PCR using primary and recurrent MG specimens, MG cell lines, and primary culture cells of MG. siRNA technique was used for MG cell lines.

RESULTS

In 22 cases of clinically recurrent MG, the expression of the mesenchymal markers vimentin and CD44 was found to be increased by IHC. In paired identical MG of 7 patients, the expression of collagen, MMPs, and YKL-40 were also elevated in the recurrent MGs, suggesting the The Cancer Genome Atlas-based mesenchymal subtype. Among EMT regulators, sustained elevation of Snail was observed in MG cells at 21 days after irradiation. Cells exhibited an upregulation of migration, invasion, numbers of focal adhesion, and MMP-2 production, and all of these mesenchymal features were abrogated by Snail knockdown. Intriguingly, phosphorylation of ERK1/2 and GSK-3β were increased after irradiation in a Snail-dependent manner, and TGF-β was elevated in both fibroblasts and macrophages but not in MG cells after irradiation. It was noteworthy that irradiated cells also expressed stemness features such as SOX2 expression and tumor-forming potential in vivo.

CONCLUSIONS

We here propose a novel concept of glial-mesenchymal transition after irradiation in which the sustained Snail expression plays an essential role.

The role of glycogen synthase kinase 3-β in immunity and cell cycle: implications in esophageal cancer

Esophageal cancer (EC) is one of the most aggressive gastrointestinal malignancies, possessing an insidious onset and a poor prognosis. Numerous transcription factors and inflammatory mediators have been reported to play a pivotal role in the initiation and progression of this cancer. However, the specifics of the signaling network responsible for said factors, especially which elements are the critical regulators, are still being elucidated. Glycogen synthesis kinases 3 (GSK3)β was originally regarded as a kinase regulating glucose metabolism. Accumulating evidence demonstrated that it also played an essential role in a variety of cellular processes including proliferation, differentiation, inflammation, motility, and survival by regulating various transcription factors such as c-Jun, AP-1, β-catenin, CREB, and NF-κB. Aberrant regulation of GSK3β has been shown to promote cell growth in some cancers, while suppressing it in others, and thus may play an important role in the development of EC. This review will discuss our current understanding of GSK3β signaling, and its control of the expression and activation of various transcription factors that mediate the inflammatory response. We will also explore some of the known mediators of EC progression, and based on current literature, elucidate the potential roles and implications of GSK3 in this disease.

The role of JAK-3 in regulating TLR-mediated inflammatory cytokine production in innate immune cells

The role of JAK-3 in TLR-mediated innate immune responses is poorly understood, although the suppressive function of JAK3 inhibition in adaptive immune response has been well studied. In this study, we found that JAK3 inhibition enhanced TLR-mediated immune responses by differentially regulating pro- and anti- inflammatory cytokine production in innate immune cells. Specifically, JAK3 inhibition by pharmacological inhibitors or specific small interfering RNA or JAK3 gene knockout resulted in an increase in TLR-mediated production of proinflammatory cytokines while concurrently decreasing the production of IL-10. Inhibition of JAK3 suppressed phosphorylation of PI3K downstream effectors including Akt, mammalian target of rapamycin complex 1, glycogen synthase kinase 3β (GSK3β), and CREB. Constitutive activation of Akt or inhibition of GSK3β abrogated the capability of JAK3 inhibition to enhance proinflammatory cytokines and suppress IL-10 production. In contrast, inhibition of PI3K enhanced this regulatory ability of JAK3 in LPS-stimulated monocytes. At the transcriptional level, JAK3 knockout lead to the increased phosphorylation of STATs that could be attenuated by neutralization of de novo inflammatory cytokines. JAK3 inhibition exhibited a GSK3 activity-dependent ability to enhance phosphorylation levels and DNA binding of NF-κB p65. Moreover, JAK3 inhibition correlated with an increased CD4(+) T cell response. Additionally, higher neutrophil infiltration, IL-17 expression, and intestinal epithelium erosion were observed in JAK3 knockout mice. These findings demonstrate the negative regulatory function of JAK3 and elucidate the signaling pathway by which JAK3 differentially regulates TLR-mediated inflammatory cytokine production in innate immune cells.

Neuroprotective effects of pretreatment with propofol in LPS-induced BV-2 microglia cells: role of TLR4 and GSK-3β

Surgery often leads to neuroinflammation, which mainly acts as the activation of microglia cells. Propofol is always used for induction and maintenance of anesthesia prior to surgical trauma, whereas whether or not it could attenuate neuroinflammation used prophylactically is not well defined. In the present study, we incubated BV-2 microglia cells with 1 μg/ml lipopolysaccharide (LPS) to mimic neuroinflammation in vitro. Firstly, cell viability was measured using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay and the data indicated that propofol would not reduce cell viability unless its concentration reached 300 μM. Secondly, BV-2 microglia cells were pretreated with 30 μM propofol (clinically relevant concentration), and then stimulated with LPS. The results showed that the production of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-10 was considerably increased by LPS, but the change could be markedly attenuated by pretreatment with propofol. Meanwhile, pretreatment with propofol inhibited LPS-induced augmentation of toll-like receptor 4 (TLR4) expression at both mRNA and protein levels and further upregulated LPS-induced inactivation of glycogen synthase kinase-3β (GSK-3β) in BV-2 microglia cells. These results indicated, at least in part, that pretreatment with propofol can protect BV-2 microglia cells against LPS-induced inflammation. Downregulation of TLR4 expression and inactivation of GSK-3β may be involved in its protective effect.

Inhibition of GSK3 abolishes bacterial-induced periodontal bone loss in mice

The tissue destruction that characterizes periodontitis is driven by the host response to bacterial pathogens. Inhibition of glycogen synthase kinase 3β (GSK3β) in innate cells leads to suppression of Toll-like receptor (TLR)-initiated proinflammatory cytokines under nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 transcriptional control and promotion of cyclic adenosine monophosphate response element-binding (CREB)-dependent gene activation. Therefore, we hypothesized that the cell permeable GSK3-specific inhibitor, SB216763, would protect against alveolar bone loss induced by the key periodontal pathogen, Porphyromonas gingivalis (P. gingivalis), in a murine model. B6129SF2/J mice either were infected orally with P. gingivalis ATCC 33277; or treated with SB216763 and infected with P. gingivalis; sham infected; or exposed to vehicle only (dimethyl sulfoxide [DMSO]); or to GSK3 inhibitor only (SB216763). Alveolar bone loss and local (neutrophil infiltration and interleukin [IL]-17) and systemic (tumor necrosis factor [TNF], IL-6, Il-1β and IL-12/IL-23 p40) inflammatory indices also were monitored. SB216763 unequivocally abrogated mean P. gingivalis-induced bone resorption, measured at 14 predetermined points on the molars of defleshed maxillae as the distance from the cementoenamel junction to the alveolar bone crest (p < 0.05). The systemic cytokine response, the local neutrophil infiltration and the IL-17 expression were suppressed (p < 0.001). These data confirm the relevance of prior in vitro phenomena and establish GSK3 as a novel, efficacious therapeutic preventing periodontal disease progression in a susceptible host. These findings also may have relevance to other chronic inflammatory diseases and the systemic sequelae associated with periodontal infections.

Role of glycogen synthase kinase-3 beta in the inflammatory response caused by bacterial pathogens

Glycogen synthase kinase 3β (GSK3β) plays a fundamental role during the inflammatory response induced by bacteria. Depending on the pathogen and its virulence factors, the type of cell and probably the context in which the interaction between host cells and bacteria takes place, GSK3β may promote or inhibit inflammation. The goal of this review is to discuss recent findings on the role of the inhibition or activation of GSK3β and its modulation of the inflammatory signaling in monocytes/macrophages and epithelial cells at the transcriptional level, mainly through the regulation of nuclear factor-kappaB (NF-κB) activity. Also included is a brief overview on the importance of GSK3 in non-inflammatory processes during bacterial infection.

MT1-MMP regulates the PI3Kδ·Mi-2/NuRD-dependent control of macrophage immune function

Macrophages play critical roles in events ranging from host defense to obesity and cancer, where they infiltrate affected tissues and orchestrate immune responses in tandem with the remodeling of the extracellular matrix (ECM). Despite the dual roles played by macrophages in inflammation, the functions of macrophage-derived proteinases are typically relegated to tissue-invasive or -degradative events. Here we report that the membrane-tethered matrix metalloenzyme MT1-MMP not only serves as an ECM-directed proteinase, but unexpectedly controls inflammatory gene responses wherein MT1-MMP(-/-) macrophages mount exaggerated chemokine and cytokine responses to immune stimuli both in vitro and in vivo. MT1-MMP modulates inflammatory responses in a protease-independent fashion in tandem with its trafficking to the nuclear compartment, where it triggers the expression and activation of a phosphoinositide 3-kinase δ (PI3Kδ)/Akt/GSK3β signaling cascade. In turn, MT1-MMP-dependent PI3Kδ activation regulates the immunoregulatory Mi-2/NuRD nucleosome remodeling complex that is responsible for controlling macrophage immune response. These findings identify a novel role for nuclear MT1-MMP as a previously unsuspected transactivator of signaling networks central to macrophage immune responses.

New drug targets in depression: inflammatory, cell-mediated immune, oxidative and nitrosative stress, mitochondrial, antioxidant, and neuroprogressive pathways. And new drug candidates--Nrf2 activators and GSK-3 inhibitors

This paper reviews new drug targets in the treatment of depression and new drug candidates to treat depression. Depression is characterized by aberrations in six intertwined pathways: (1) inflammatory pathways as indicated by increased levels of proinflammatory cytokines, e.g. interleukin-1 (IL-1), IL-6, and tumour necrosis factor α. (2) Activation of cell-mediated immune pathways as indicated by an increased production of interferon γ and neopterin. (3) Increased reactive oxygen and nitrogen species and damage by oxidative and nitrosative stress (O&NS), including lipid peroxidation, damage to DNA, proteins and mitochondria. (4) Lowered levels of key antioxidants, such as coenzyme Q10, zinc, vitamin E, glutathione, and glutathione peroxidase. (5) Damage to mitochondria and mitochondrial DNA and reduced activity of respiratory chain enzymes and adenosine triphosphate production. (6) Neuroprogression, which is the progressive process of neurodegeneration, apoptosis, and reduced neurogenesis and neuronal plasticity, phenomena that are probably caused by inflammation and O&NS. Antidepressants tend to normalize the above six pathways. Targeting these pathways has the potential to yield antidepressant effects, e.g. using cytokine antagonists, minocycline, Cox-2 inhibitors, statins, acetylsalicylic acid, ketamine, ω3 poly-unsaturated fatty acids, antioxidants, and neurotrophic factors. These six pathways offer new, pathophysiologically guided drug targets suggesting that novel therapies could be developed that target these six pathways simultaneously. Both nuclear factor (erythroid-derived 2)-like 2 (Nrf2) activators and glycogen synthase kinase-3 (GSK-3) inhibitors target the six above-mentioned pathways. GSK-3 inhibitors have antidepressant effects in animal models of depression. Nrf2 activators and GSK-3 inhibitors have the potential to be advanced to phase-2 clinical trials to examine whether they augment the efficacy of antidepressants or are useful as monotherapy.

Neutrophils in periodontal inflammation

Neutrophils (also called polymorphonuclear leukocytes) are the most abundant leukocytes whose primary purpose as anti-microbial professional phagocytes is to kill extracellular pathogens. Neutrophils and macrophages are phagocytic cell types that along with other cells effectively link the innate and adaptive arms of the immune response, and help promote inflammatory resolution and tissue healing. Found extensively within the gingival crevice and epithelium, neutrophils are considered the key protective cell type in the periodontal tissues. Histopathology of periodontal lesions indicates that neutrophils form a 'wall' between the junctional epithelium and the pathogen-rich dental plaque which functions as a robust anti-microbial secretory structure and as a unified phagocytic apparatus. However, neutrophil protection is not without cost and is always considered a two-edged sword in that overactivity of neutrophils can cause tissue damage and prolong the extent and severity of inflammatory periodontal diseases. This review will cover the innate and inflammatory functions of neutrophils, and describe the importance and utility of neutrophils to the host response and the integrity of the periodontium in health and disease.

Phosphatidylinositol-3-kinase activity during in vitro dendritic cell generation determines suppressive or stimulatory capacity

Modulating PI3K at different stages of dendritic cells (DC) generation could be a novel means to balance the generation of immunosuppressive versus immunostimulatory DC. We show that PI3K inhibition during mouse DC generation in vitro results in cells that are potently immunosuppressive and characteristic of CD8alpha- CD11c+ CD11b+ DC. These DC exhibited low surface class I and class II MHC, CD40, and CD86 and did not produce TNF-alpha. In allogeneic MLR, these DC were suppressive. Although in these mixed cultures, there was no increase in the frequency of CD4+ CD25+ Foxp3+ cells, the Foxp3 content on a per cell basis was significantly increased. Sustained TLR9 signaling in the presence of PI3K inhibition during DC generation overrode the cells' suppressive phenotype.

Glycogen synthase kinase 3 involvement in the excessive proinflammatory response to LPS in patients with decompensated cirrhosis

BACKGROUND & AIMS

In decompensated cirrhosis, the early innate immune response to the Toll-like receptor 4 (TLR4) agonist, lipopolysaccharides (LPS), is characterized by a hyper-production of pro-inflammatory cytokines and hypo-production of the anti-inflammatory cytokine IL-10. In LPS-stimulated non-cirrhotic immune cells, the constitutively active glycogen synthase kinase (GSK) 3 favors pro- vs. anti-inflammatory cytokines, by acting on gene induction. However, in these cells, TLR4 dampens its own pro-inflammatory response by inducing early (within minutes) AKT-mediated phosphorylation of GSK3β (one of two GSK3 isoforms) on Ser9. Phosphorylation of GSK3β (Ser9) inhibits its activity, decreases pro-inflammatory cytokines, and increases IL-10. Thus, we investigated the role of GSK3 in LPS-induced cytokine production by peripheral blood mononuclear cells (PBMCs) or monocytes from patients with advanced cirrhosis and normal subjects.

METHODS

Cells were pre-incubated with or without GSK3 inhibitor (SB216763 or lithium chloride) for 1h and then stimulated with LPS. Cytokine production was assessed at mRNA and secreted proteins levels, by real-time RT-PCR at 1h and ELISA at 20 h, respectively. GSK3β phosphorylation was assessed using Western blotting.

RESULTS

In cirrhotic and normal PBMCs pretreated with GSK3 inhibitors, LPS-induced production of pro-inflammatory proteins TNF-α and IL-12p40 was significantly decreased while that of IL-10 was increased. LPS-induced, AKT-mediated phosphorylation of GSK3β on Ser9 found in normal monocytes, was abolished in cirrhotic cells.

CONCLUSIONS

GSK3 is involved in the early TLR4-mediated pro-inflammatory response in patients with decompensated cirrhosis. This was associated with a defect in AKT-mediated GSK3β phosphorylation resulting in unrestricted 'pro-inflammatory' activity of the enzyme.

Inhibition of Rac activity alleviates lipopolysaccharide-induced acute pulmonary injury in mice

BACKGROUND

Rac small GTPases play important roles in cytoskeleton and many cell functions including cell cycle, cell growth, cell adhesion and gene transcription. Here, we investigated the roles of Rac including Rac1 and Rac2 in lipopolysaccharide (LPS)-induced pulmonary injury.

METHODS

After LPS was intratracheally instilled to lungs in mice, Rac, CDC42 and RhoA activation assay by pull-down and West blot, inflammatory cell infiltration assay by counting cell numbers and lung histological examination, pro-inflammatory mediator mRNA expression assay by quantitative RT-PCR, measurement of myeloperoxidase (MPO) activity, Evans Blue and albumin accumulation by spectrophotometry were performed to evaluate the roles of Rac in pulmonary injury by using its specific inhibitor, NSC23766.

RESULTS

LPS challenge led to increases of both Rac1 and Rac2, but not CDC42 or RhoA activities in lungs, and intraperitoneal administration with NSC23766 inhibited both Rac1 and Rac2, but not CDC42 or RhoA activities. Treatment with NSC23766 at 1 or 3mg/kg not only reduced the inflammatory cells infiltration and MPO activities, but also inhibited pro-inflammatory mediators, tumor necrosis factor-α and interleukin-1β, mRNA expression. Moreover, in vitro neutrophil migration assay and in vivo microvascular permeability assay indicated that NSC23766 not only inhibited neutrophil transwell migration toward a chemoattractant, fMLP, but also reduced Evans Blue and albumin accumulation in LPS-challenged lungs. LPS activated both Rac1 and Rac2, but not CDC42 or RhoA activities in lungs, and specific inhibition of Rac activities by NSC23766 effectively alleviated LPS-induced injury.

GENERAL SIGNIFICANCE

Rac could be a potential target for therapeutic intervention of pulmonary inflammation.

Investigation of POPX2 phosphatase functions by comparative phosphoproteomic analysis

Identifying the substrates and biochemical pathway regulated by phosphatases has always been more challenging than finding those regulated by kinases. Here, we report the use of phosphoproteomic methods to analyse the pathways regulated by POPX2 (partner of PIX 2) phosphatase. POPX2 is a serine/threonine phosphatase, found in many cancer types. The levels of the POPX2 have been found to be up-regulated in the more invasive breast cancer cells compared with non-invasive ones. Our observations also suggest that POPX2 level is positively correlated with cell motility. Thus, finding substrates or pathways regulated by POPX2 will help to elucidate the regulatory mechanism of cancer cell motility and invasiveness. We have also developed and validated a protocol using electrostatic repulsion-hydrophilic interaction chromatography (ERLIC) to enrich the phosphopeptides followed by LC-MS/MS to allow comparison between the phosphoproteomes of control and POPX2 overexpressing cells. With this approach, we were able to identify a biochemical pathway through which POPX2 exerts its apparent cellular function: the regulation of activity of glycogen synthase kinase-3, which in turn modulates extracellular signal-regulated kinase and cell motility.

Convergence of the mammalian target of rapamycin complex 1- and glycogen synthase kinase 3-β-signaling pathways regulates the innate inflammatory response

The PI3K pathway and its regulation of mammalian target of rapamycin complex 1 (mTORC1) and glycogen synthase kinase 3 (GSK3) play pivotal roles in controlling inflammation. In this article, we show that mTORC1 and GSK3-β converge and that the capacity of mTORC1 to affect the inflammatory response is due to the inactivation of GSK3-β. Inhibition of mTORC1 attenuated GSK3 phosphorylation and increased its kinase activity. Immunoprecipitation and in vitro kinase assays demonstrated that GSK3-β associated with a downstream target of mTORC1, p85S6K, and phosphorylated GSK3-β. Inhibition of S6K1 abrogated the phosphorylation of GSK3-β while increasing and decreasing the levels of IL-12 and IL-10, respectively, in LPS-stimulated monocytes. In contrast, the direct inhibition of GSK3 attenuated the capacity of S6K1 inhibition to influence the levels of IL-10 and IL-12 produced by LPS-stimulated cells. At the transcriptional level, mTORC1 inhibition reduced the DNA binding of CREB and this effect was reversed by GSK3 inhibition. As a result, mTORC1 inhibition increased the levels of NF-κB p65 associated with CREB-binding protein. Inhibition of NF-κB p65 attenuated rapamycin's ability to influence the levels of pro- or anti-inflammatory cytokine production in monocytes stimulated with LPS. These studies identify the molecular mechanism by which mTORC1 affects GSK3 and show that mTORC1 inhibition regulates pro- and anti-inflammatory cytokine production via its capacity to inactivate GSK3.

The phosphomimetic mutation of an evolutionarily conserved serine residue affects the signaling properties of Rho of plants (ROPs)

Plant ROP (Rho of plants) proteins form a unique subgroup within the family of Rho-type small G-proteins of eukaryotes. In this paper we demonstrate that the phosphomimetic mutation of a serine residue conserved in all Rho proteins affects the signaling properties of plant ROPs. We found that the S74E mutation in Medicago ROP6 and Arabidopsis ROP4 prevented the binding of these proteins to their plant-specific upstream activator the plant-specific ROP nucleotide exchanger (PRONE)-domain-containing RopGEF (guanine nucleotide exchange factor) protein and abolished the PRONE-mediated nucleotide exchange reaction in vitro. Structural modeling supported the hypothesis that potential phosphorylation of the S74 residue interferes with the binding of the PRONE-domain to the adjacent plant-specific R76 residue which plays an important role in functional ROP-PRONE interaction. Moreover, we show that while the binding of constitutively active MsROP6 to the effector protein RIC (ROP-interactive CRIB-motif-containing protein) was not affected by the S74E mutation, the capability of this mutated protein to bind and activate the RRK1 kinase in vitro was reduced. These observations are in agreement with the morphology of tobacco pollen tubes expressing mutant forms of yellow fluorescent protein (YFP):MsROP6. The S74E mutation in MsROP6 had no influence on pollen tube morphology and attenuated the phenotype of a constitutively active form of MsROP6. The presented Medicago and Arabidopsis data support the notion that the phosphorylation of the serine residue in ROPs corresponding to S74 in Medicago ROP6 could be a general principle for regulating ROP activation and signaling in plants.

Glycogen synthase kinase 3: a point of convergence for the host inflammatory response

The phosphatidylinositol 3-kinase (PI3K) pathway has been shown to play a central role in regulating the host inflammatory response. Recent studies characterizing the downstream effector molecules within the PI3K pathway have identified that the serine/threonine kinase, glycogen synthase kinase 3 (GSK3), plays a pivotal role in regulating the production of pro- and anti-inflammatory cytokines. In innate immune cells, GSK3 inactivation augments anti-inflammatory cytokine production while concurrently suppressing the production of pro-inflammatory cytokines. The role of GSK3 in T cell biology has also been studied in detail and is involved in regulating multiple downstream signaling processes mediated by the T cell receptor (TCR), the co-stimulatory molecule CD28, and the IL-17 receptor. In vivo studies assessing the therapeutic properties of GSK3 inhibitors have shown that the inactivation of GSK3 can protect the host from immune-mediated pathology and death. This review will highlight the immunological importance GSK3 plays within different signal transduction pathways of the immune system, the cellular mechanisms regulating the activity of GSK3, the role of GSK3 in innate and adaptive immune responses, and the in vivo use of GSK3 inhibitors to treat inflammatory mediated diseases in animals.

The role of glycogen synthase kinase 3 in regulating IFN-β-mediated IL-10 production

The ability of IFN-β to induce IL-10 production from innate immune cells is important for its anti-inflammatory properties and is believed to contribute to its therapeutic value in treating multiple sclerosis patients. In this study, we identified that IFN-β stimulates IL-10 production by activating the JAK1- and PI3K-signaling pathways. JAK1 activity was required for IFN-β to activate PI3K and Akt1 that resulted in repression of glycogen synthase kinase 3 (GSK3)-β activity. IFN-β-mediated suppression of GSK3-β promoted IL-10, because IL-10 production by IFN-β-stimulated dendritic cells (DC) expressing an active GSK3-β knockin was severely reduced, whereas pharmacological or genetic inhibition of GSK3-β augmented IL-10 production. IFN-β increased the phosphorylated levels of CREB and STAT3 but only CREB levels were affected by PI3K. Also, a knockdown in CREB, but not STAT3, affected the capacity of IFN-β to induce IL-10 from DC. IL-10 production by IFN-β-stimulated DC was shown to suppress IFN-γ and IL-17 production by myelin oligodendrocyte glycoprotein-specific CD4(+) T cells, and this IL-10-dependent anti-inflammatory effect was enhanced by directly targeting GSK3 in DC. These findings highlight how IFN-β induces IL-10 production and the importance that IL-10 plays in its anti-inflammatory properties, as well as identify a therapeutic target that could be used to increase the IL-10-dependent anti-inflammatory properties of IFN-β.

Mammalian target of rapamycin (mTOR) regulates TLR3 induced cytokines in human oral keratinocytes

Recent studies implicate the mammalian target of rapamycin (mTOR) pathway in the control of inflammatory responses following Toll-like receptor (TLR) stimulation in myeloid cells but its role in non-myeloid cells such as human keratinocytes is unknown. Here we show that TLR3 signaling can induce robust cytokine secretion including interleukin 1 beta (IL-1β), tumor necrosis factor alpha (TNFα), IL-12p70 and interferon beta (IFN-β), and our data reveal for the first time that inhibiting mTOR with rapamycin, suppresses these TLR3 induced responses but actually enhances bioactive IL-12p70 production in human oral keratinocytes. Rapamycin inhibited the phosphorylation of the 70-kDa ribosomal protein S6 kinase (p70S6K) and the 4E binding protein 1 (4EBP-1), and suppressed the mitogen activated protein kinase (MAPK) pathway by decreasing phosphorylation of c-Jun N-terminal kinase (JNK). We also show that TLR3 induces interferon regulatory factor 3 (IRF3) activation by Akt via an mTOR-p70S6K-4EBP1 pathway. Furthermore, we provide evidence that Poly I:C induced expression of IL-1β, TNFα, IL-12p70 and IFN-β was blocked by JNK inhibitor SP600125. TLR3 preferentially phosphorylated IKKα through mTOR to activate nuclear factor kappa beta (NF-κB) in human oral keratinocytes. Taken together, these data demonstrate p70S6K, p4EBP1, JNK, NF-κB and IRF3 are involved in the regulation of inflammatory mediators by TLR3 via the mTOR pathway. mTOR is a novel pathway modulating TLR3 induced inflammatory and antiviral responses in human oral keratinocytes.

Glycogen Synthase Kinase-3 regulates multiple myeloma cell growth and bortezomib-induced cell death

Background

Glycogen Synthase Kinase-3 (GSK-3) α and β are two serine-threonine kinases controlling insulin, Wnt/β-catenin, NF-κB signaling and other cancer-associated transduction pathways. Recent evidence suggests that GSK-3 could function as growth-promoting kinases, especially in malignant cells. In this study, we have investigated GSK-3α and GSK-3β function in multiple myeloma (MM).

Methods

GSK-3 α and β expression and cellular localization were investigated by Western blot (WB) and immunofluorescence analysis in a panel of MM cell lines and in freshly isolated plasma cells from patients. MM cell growth, viability and sensitivity to bortezomib was assessed upon treatment with GSK-3 specific inhibitors or transfection with siRNAs against GSK-3 α and β isoforms. Survival signaling pathways were studied with WB analysis.

Results

GSK-3α and GSK-3β were differently expressed and phosphorylated in MM cells. Inhibition of GSK-3 with the ATP-competitive, small chemical compounds SB216763 and SB415286 caused MM cell growth arrest and apoptosis through the activation of the intrinsic pathway. Importantly, the two inhibitors augmented the bortezomib-induced MM cell cytotoxicity. RNA interference experiments showed that the two GSK-3 isoforms have distinct roles: GSK-3β knock down decreased MM cell viability, while GSK-3α knock down was associated with a higher rate of bortezomib-induced cytotoxicity. GSK-3 inhibition caused accumulation of β-catenin and nuclear phospho-ERK1, 2. Moreover, GSK-3 inhibition and GSK-3α knockdown enhanced bortezomib-induced AKT and MCL-1 protein degradation. Interestingly, bortezomib caused a reduction of GSK-3 serine phosphorylation and its nuclear accumulation with a mechanism that resulted partly dependent on GSK-3 itself.

Conclusions

These data suggest that in MM cells GSK-3α and β i) play distinct roles in cell survival and ii) modulate the sensitivity to proteasome inhibitors.