Regulation of CREB activation by p38 mitogen activated protein kinase during human primary erythroblast differentiation

G9a Inhibition Promotes Neuroprotection through GMFB Regulation in Alzheimer's Disease

Epigenetic alterations are a fundamental pathological hallmark of Alzheimer's disease (AD). Herein, we show the upregulation of G9a and H3K9me2 in the brains of AD patients. Interestingly, treatment with a G9a inhibitor (G9ai) in SAMP8 mice reversed the high levels of H3K9me2 and rescued cognitive decline. A transcriptional profile analysis after G9ai treatment revealed increased gene expression of glia maturation factor β (GMFB) in SAMP8 mice. Besides, a H3K9me2 ChIP-seq analysis after G9a inhibition treatment showed the enrichment of gene promoters associated with neural functions. We observed the induction of neuronal plasticity and a reduction of neuroinflammation after G9ai treatment, and more strikingly, these neuroprotective effects were reverted by the pharmacological inhibition of GMFB in mice and cell cultures; this was also validated by the RNAi approach generating the knockdown of GMFB/Y507A.10 in Caenorhabditis elegans. Importantly, we present evidence that GMFB activity is controlled by G9a-mediated lysine methylation as well as we identified that G9a directly bound GMFB and catalyzed the methylation at lysine (K) 20 and K25 in vitro. Furthermore, we found that the neurodegenerative role of G9a as a GMFB suppressor would mainly rely on methylation of the K25 position of GMFB, and thus G9a pharmacological inhibition removes this methylation promoting neuroprotective effects. Then, our findings confirm an undescribed mechanism by which G9a inhibition acts at two levels, increasing GMFB and regulating its function to promote neuroprotective effects in age-related cognitive decline.

Stress signaling boosts interferon-induced gene transcription in macrophages

Promoters of antimicrobial genes function as logic boards, integrating signals of innate immune responses. One such set of genes is stimulated by interferon (IFN) signaling, and the expression of these genes [IFN-stimulated genes (ISGs)] can be further modulated by cell stress-induced pathways. Here, we investigated the global effect of stress-induced p38 mitogen-activated protein kinase (MAPK) signaling on the response of macrophages to IFN. In response to cell stress that coincided with IFN exposure, the p38 MAPK-activated transcription factors CREB and c-Jun, in addition to the IFN-activated STAT family of transcription factors, bound to ISGs. In addition, p38 MAPK signaling induced activating histone modifications at the loci of ISGs and stimulated nuclear translocation of the CREB coactivator CRTC3. These actions synergistically enhanced ISG expression. Disrupting this synergy with p38 MAPK inhibitors improved the viability of macrophages infected with Listeria monocytogenes. Our findings uncover a mechanism of transcriptional synergism and highlight the biological consequences of coincident stress-induced p38 MAPK and IFN-stimulated signal transduction.

Resveratrol blocks retrotransposition of LINE-1 through PPAR α and sirtuin-6

The retroelement long interspersed element-1 (LINE-1 or L1) comprises about 17% of the human genome. L1 retrotransposition is known to cause genomic instability and related disorders, and resveratrol suppresses this retrotransposition; however, the underlying mechanism is still not elucidated. Recent observations showed that low-molecular-weight compounds might induce L1 retrotransposition through unknown mechanisms. This study aimed to determine polyphenol resveratrol (RV)'s effect on L1-RTP (retrotransposition) in somatic cells. Surprisingly, RV completely blocked L1-RTP. Experiments using the PPARα inhibitor GW6471 or siRNA-mediated PPARα depletion showed that RV-mediated L1-RTP's inhibition depended on peroxisome proliferator-activated receptor α (PPARα). We demonstrated that RV inhibits p38 and cAMP response element binding protein phosphorylation, which are involved in MAPK signaling, and the L1-ORF1 protein's chromatin recruitment. Furthermore, RV increased the expression of sirtuin-6 (SIRT6), which inhibited the activation of L1. The sirtuins family, SIRT1, SIRT6, and SIRT7, but not SIRT3, are involved in RV-mediated inhibition of L1-RTP. Overall, our findings suggest that RV directly modulates PPARα-mediated L1-RTP in somatic cells and that MAPK signaling interacts with SIRT6 closely and may play a role in preventing human diseases such as cancer.

Fibroblast growth factor receptor 3 activates a network of profibrotic signaling pathways to promote fibrosis in systemic sclerosis

Aberrant activation of fibroblasts with progressive deposition of extracellular matrix is a key feature of systemic sclerosis (SSc), a prototypical idiopathic fibrotic disease. Here, we demonstrate that the profibrotic cytokine transforming growth factor β selectively up-regulates fibroblast growth factor receptor 3 (FGFR3) and its ligand FGF9 to promote fibroblast activation and tissue fibrosis, leading to a prominent FGFR3 signature in the SSc skin. Transcriptome profiling, in silico analysis and functional experiments revealed that FGFR3 induces multiple profibrotic pathways including endothelin, interleukin-4, and connective tissue growth factor signaling mediated by transcription factor CREB (cAMP response element-binding protein). Inhibition of FGFR3 signaling by fibroblast-specific knockout of FGFR3 or FGF9 or pharmacological inhibition of FGFR3 blocked fibroblast activation and attenuated experimental skin fibrosis in mice. These findings characterize FGFR3 as an upstream regulator of a network of profibrotic mediators in SSc and as a potential target for the treatment of fibrosis.

Regorafenib enhances antitumor immunity via inhibition of p38 kinase/Creb1/Klf4 axis in tumor-associated macrophages

BACKGROUND

Regorafenib and other multikinase inhibitors may enhance antitumor efficacy of anti-program cell death-1 (anti-PD1) therapy in hepatocellular carcinoma (HCC). Its immunomodulatory effects, besides anti-angiogenesis, were not clearly defined.

METHODS

In vivo antitumor efficacy was tested in multiple syngeneic liver cancer models. Murine bone marrow-derived macrophages (BMDMs) were tested in vitro for modulation of polarization by regorafenib and activation of cocultured T cells. Markers of M1/M2 polarization were measured by quantitative reverse transcription PCR (RT-PCR), arginase activity, flow cytometry, and ELISA. Knockdown of p38 kinase and downstream Creb1/Klf4 signaling on macrophage polarization were confirmed by using knockdown of the upstream MAPK14 kinase, chemical p38 kinase inhibitor, and chromatin immunoprecipitation.

RESULTS

Regorafenib (5 mg/kg/day, corresponding to about half of human clinical dosage) inhibited tumor growth and angiogenesis in vivo similarly to DC-101 (anti-VEGFR2 antibody) but produced higher T cell activation and M1 macrophage polarization, increased the ratio of M1/M2 polarized BMDMs and proliferation/activation of cocultured T cells in vitro, indicating angiogenesis-independent immunomodulatory effects. Suppression of p38 kinase phosphorylation and downstream Creb1/Klf4 activity in BMDMs by regorafenib reversed M2 polarization. Regorafenib enhanced antitumor efficacy of adoptively transferred antigen-specific T cells. Synergistic antitumor efficacy between regorafenib and anti-PD1 was associated with multiple immune-related pathways in the tumor microenvironment.

CONCLUSION

Regorafenib may enhance antitumor immunity through modulation of macrophage polarization, independent of its anti-angiogenic effects. Optimization of regorafenib dosage for rational design of combination therapy regimen may improve the therapeutic index in the clinic.

Alanyl-glutamine Heals Indomethacin-induced Gastric Ulceration in Rats Via Antisecretory and Anti-apoptotic Mechanisms

OBJECTIVES

Alanylglutamine (AG) is a dipeptide that fuels enterocytes and has a coadjuvant role during gut healing. The current study aimed to investigate the potential ulcer-healing effect of AG in indomethacin-induced gastropathy.

METHODS

Animals (n = 10 rats/group) were randomly allocated into 5 groups. Gastric ulcerated rats were administered AG, AG + dexamethasone, or pantoprazole after indomethacin exposure.

RESULTS

Comparable to pantoprazole, AG inhibited H-KATPase pump, and elevated the pH of gastric juice. Moreover, the dipeptide increased the serum/mucosal contents of glucagon-like peptide-1 (GLP-1), pS473-Akt, and cyclin-D1. On the contrary, AG abated serum tumor necrosis factor-α and gastric mucosal content of pS45-β catenin, pS9-GSK3β, pS133-CREB, pS536-NF-κB, H2O2, claudin-1, and caspase-3. The administration of dexamethasone before AG hampered its effect on almost all the measured parameters.

CONCLUSIONS

AG confers its antiulcerogenic/antisecretory potentials by repressing the proton pump to increase the gastric juice pH via boosting p-CREB, p-Akt, p-GSK-3β, and GLP-1. Also, it inhibits apoptosis through suppressing nuclear factor-kappa B/tumor necrosis factor-α/H2O2/claudin-1 cue. This trajectory contributes to loosen the tight junction priming AG-mediated GLP-1/β-catenin/cyclin-D1 that results in pronounced increase in gastric mucosa proliferation. Therefore, the crosstalk between multiple pathways orchestrates the action of AG against gastric ulceration.

Involvement of ADAM10 in acrolein-induced astrocytic inflammation

Acrolein is a neurotoxin produced through lipid peroxidation in the brain affected by ischemic stroke, which results in neuronal cell injury and inflammation. However the mechanism underlying acrolein-induced brain inflammation remains unclear. Therefore we examined how acrolein leads to astrocytic inflammation. It was found that acrolein increased the levels of NLRP3 and cleaved caspase-1, which led to the maturation of interleukin-1β (IL-1β). ELISA assay results, which showed that acrolein increased the secreted IL-1β, further supported acrolein-induced astrocytic inflammation. Acrolein increased ADAM10 protein levels and the cleavage of N-cadherin. The ADAM10 inhibitor, GI 254023X blocked N-cadherin cleavage by acrolein, suggesting that ADAM10 is an upstream of N-cadherin. Furthermore, we found that acrolein activated p38 MAPK and NF-κB p65, while pretreatment with p38 MAPK inhibitor, SB203580 and GI 254023X inhibited NF-κB p65 activation and NLRP3 inflammasome. This suggests that p38 MAPK mediates the activation of NF-κB p65, which is associated with NLRP3 expression. Finally, we showed that acrolein induced cell toxicity and decrease of EAAT1 expression, suggesting that acrolein may induce a loss of glutamate uptake function. In conclusion, we demonstrate that acrolein induces astrocytic inflammation through NLRP3 inflammasome, which is regulated by ADAM10 and attributed to p38 MAPK-activated NF-κB p65 activity.

Ovatodiolide suppresses inflammatory response in BEAS-2B cells by regulating the CREB/AQP5 pathway, and sensitizes nasopharyngeal carcinoma cells to radiation therapy

Due to the radiosensitivity of the airway epithelium, radiation-induced sinusitis or bronchitis is not uncommon, and makes mitigation of resulting inflammatory airway diseases a principal goal of many investigations. This study examined whether Ovatodiolide (Ova) sensitizes the human metastatic nasopharyngeal cancer (NPC) cell line, NPC-BM2, to irradiation using viability, clonogenicity and Western blot assays. Concurrently, we used varying concentrations of histamine and/or Ova to determine the anti-inflammatory potential of Ovatodiolide on normal bronchus epithelial BEAS-2B cells, as well as on the subcellular distribution of Aquaporin 5 (AQP5) and expression levels of p-CREB, AQP5, p38 MAPK, NF-κB, PI3K, Akt and ERK proteins. We demonstrated that Ova in synergism with irradiation inhibited NPC-BM2 cell viability and suppressed their clonogenicity. Immunofluorescence analysis revealed low-dose (≤ 2.5 μM) Ova reversed histamine-induced suppression of AQP5 expression, and abrogated histamine-enhanced NF-κB nuclear translocation, indicating Ova modulates the p38 MAPK/NF-κB signaling pathway and elicits p-CREB/AQP5-mediated antihistamine effects. Similarly, Ova deregulates the PI3K/Akt/ERK signaling in BEAS-2B cells, suggesting its cytoprotective potential. In conclusion, this study highlights the radio-sensitizing anticancer efficacy of Ova in human metastatic NPC cells, as well as its putative cytoprotective role in normal bronchial cells, for airway surface liquid maintenance and homeostasis during or after radiotherapy.

Long glucocorticoid-induced leucine zipper regulates human thyroid cancer cell proliferation

Long glucocorticoid-induced leucine zipper (L-GILZ) has recently been implicated in cancer cell proliferation. Here, we investigated its role in human thyroid cancer cells. L-GILZ protein was highly expressed in well-differentiated cancer cells from thyroid cancer patients and differentiated thyroid cancer cell lines, but poorly expressed in anaplastic tumors. A fusion protein containing L-GILZ, when overexpressed in an L-GILZ-deficient 8505C cell line derived from undifferentiated human thyroid cancer tissue, inhibited cellular proliferation in vitro. In addition, when this protein was injected into nude mice, in which cells from line 8505C had been transplanted, xenograft growth was reduced. Since the mitogen-activated protein kinase (MAPK) pathway is frequently hyperactivated in thyroid cancer cells as a result of the BRAF^V600E or Ras mutation, we sought to further investigate the role of L-GILZ in the MAPK pathway. To this end, we analyzed L-GILZ expression and function in cells treated with MAPK inhibitors. We used 8505C cells, which have the BRAF^V600E mutation, or the CAL-62 cell line, which harbors a Ras mutation. The cells were treated with the BRAF-specific drug vemurafenib (PLX4032) or the MEK1/2 inhibitor, U0126, respectively. Treatment with these agents inhibited MAPK activation, reduced cell proliferation, and upregulated L-GILZ expression. L-GILZ silencing reversed the antiproliferative activity of the MAPK inhibitors, consistent with an antiproliferative role. Treatment with MAPK inhibitors led to the phosphorylation of the cAMP/response element-binding protein (CREB), and active CREB bound to the L-GILZ promoter, contributing to its transcription. We suggest that the CREB signaling pathway, frequently deregulated in thyroid tumors, is involved in L-GILZ upregulation and that L-GILZ regulates thyroid cancer cell proliferation, which may have potential in cancer treatment.

Regulation of Cancer Cell Responsiveness to Ionizing Radiation Treatment by Cyclic AMP Response Element Binding Nuclear Transcription Factor

Cyclic AMP response element binding (CREB) protein is a member of the CREB/activating transcription factor (ATF) family of transcription factors that play an important role in the cell response to different environmental stimuli leading to proliferation, differentiation, apoptosis, and survival. A number of studies highlight the involvement of CREB in the resistance to ionizing radiation (IR) therapy, demonstrating a relationship between IR-induced CREB family members' activation and cell survival. Consistent with these observations, we have recently demonstrated that CREB and ATF-1 are expressed in leukemia cell lines and that low-dose radiation treatment can trigger CREB activation, leading to survival of erythro-leukemia cells (K562). On the other hand, a number of evidences highlight a proapoptotic role of CREB following IR treatment of cancer cells. Since the development of multiple mechanisms of resistance is one key problem of most malignancies, including those of hematological origin, it is highly desirable to identify biological markers of responsiveness/unresponsiveness useful to follow-up the individual response and to adjust anticancer treatments. Taking into account all these considerations, this mini-review will be focused on the involvement of CREB/ATF family members in response to IR therapy, to deepen our knowledge of this topic, and to pave the way to translation into a therapeutic context.

Bacterial flagellin induces IL-6 expression in human basophils

Binding of allergen to IgE on basophils positively affects allergic inflammation by releasing inflammatory mediators. Recently, basophils were shown to express pattern-recognition receptors, such as toll-like receptors (TLRs), for recognizing microbe-associated molecular patterns (MAMPs) that are independent of allergen-IgE binding. In this study, we investigated whether MAMP alone can induce IL-6 production in a human basophil cell line, KU812. Stimulation with flagellin in the absence of allergen-IgE association induced IL-6 expression in KU812 cells, while stimulation with lipoteichoic acid, peptidoglycan, or poly I:C did not under the same condition. Flagellin-induced IL-6 expression was also observed in human primary basophils. Flow cytometric analysis showed that KU812 cells expressed flagellin-recognizing TLR5 both on the cell surface and in the cytoplasm while TLR2 and TLR3 were observed only in the cytoplasm. We further demonstrated that although flagellin augmented the phosphorylation of mitogen-activated protein kinases including p38 kinase, ERK, and JNK, flagellin-induced IL-6 production was attenuated by inhibitors for p38 kinase and ERK, but not by JNK inhibitors. In addition, flagellin enhanced phosphorylation of signaling molecules including CREB, PKCδ, and AKT. The inhibitors for PKA and PKC also showed inhibitory effects. Interestingly, flagellin-induced IL-6 production was further enhanced by pretreatment with inhibitors for PI3K, implying that PI3K negatively affects the flagellin-induced IL-6 production. Furthermore, DNA binding activities of NF-κB, AP-1, and CREB, which play pivotal roles in the induction of IL-6 gene expression, were increased by flagellin. These results suggest that flagellin alone is sufficient to induce IL-6 gene expression via TLR5 signaling pathways in human basophils.

Inhibition of phosphodiesterase-4 promotes oligodendrocyte precursor cell differentiation and enhances CNS remyelination

The increasing effectiveness of new disease-modifying drugs that suppress disease activity in multiple sclerosis has opened up opportunities for regenerative medicines that enhance remyelination and potentially slow disease progression. Although several new targets for therapeutic enhancement of remyelination have emerged, few lend themselves readily to conventional drug development. Here, we used transcription profiling to identify mitogen-activated protein kinase (Mapk) signalling as an important regulator involved in the differentiation of oligodendrocyte progenitor cells (OPCs) into oligodendrocytes. We show in tissue culture that activation of Mapk signalling by elevation of intracellular levels of cyclic adenosine monophosphate (cAMP) using administration of either dibutyryl-cAMP or inhibitors of the cAMP-hydrolysing enzyme phosphodiesterase-4 (Pde4) enhances OPC differentiation. Finally, we demonstrate that systemic delivery of a Pde4 inhibitor leads to enhanced differentiation of OPCs within focal areas of toxin-induced demyelination and a consequent acceleration of remyelination. These data reveal a novel approach to therapeutic enhancement of remyelination amenable to pharmacological intervention and hence with significant potential for translation.

Role of hypoxia-inducible factor 1, α subunit and cAMP-response element binding protein 1 in synergistic release of interleukin 8 by prostaglandin E2 and nickel in lung fibroblasts

Numerous epidemiological studies have linked exposure to particulate matter (PM) air pollution with acute respiratory infection and chronic respiratory and cardiovascular diseases. We have previously shown that soluble nickel (Ni), a common component of PM, alters the release of CXC chemokines from cultured human lung fibroblasts (HLF) in response to microbial stimuli via a pathway dependent on disrupted prostaglandin (PG)E2 signaling. The current study sought to identify the molecular events underlying Ni-induced alterations in PGE2 signaling and its effects on IL-8 production. PGE2 synergistically enhances Ni-induced IL-8 release from HLF in a concentration-dependent manner. The effects of PGE2 were mimicked by butaprost and PGE1-alcohol and inhibited with antagonists AH6809 and L-161,982, indicating PGE2 signals via PGE2 receptors 2 and 4. PGE2 and forskolin stimulated cAMP, but it was only in the presence of Ni-induced hypoxia-inducible factor 1, α subunit (HIF1A) that these agents stimulated IL-8 release. The Ni-induced HIF1A DNA binding was enhanced by PGE2 and mediated, in part, by activation of p38 MAPK. Negation of cAMP-response element binding protein 1 or HIF1A using short interfering RNA blocked the synergistic interactions between Ni and PGE2. The results of the current study provide novel information on the ability of atmospheric hypoxia-mimetic metals to disrupt the release of immune-modulating chemokines by HLF in response to PGE2. Moreover, in the presence of HIF1A, cAMP-mediated signaling pathways may be altered to exacerbate inflammatory-like processes in lung tissue, imparting a susceptibility of PM-exposed populations to adverse respiratory health effects.

Novel avenues of drug discovery and biomarkers for diabetes mellitus

Globally, developed nations spend a significant amount of their resources on health care initiatives that poorly translate into increased population life expectancy. As an example, the United States devotes 16% of its gross domestic product to health care, the highest level in the world, but falls behind other nations that enjoy greater individual life expectancy. These observations point to the need for pioneering avenues of drug discovery to increase life span with controlled costs. In particular, innovative drug development for metabolic disorders such as diabetes mellitus becomes increasingly critical given that the number of diabetic people will increase exponentially over the next 20 years. This article discusses the elucidation and targeting of novel cellular pathways that are intimately tied to oxidative stress in diabetes mellitus for new treatment strategies. Pathways that involve wingless, β-nicotinamide adenine dinucleotide (NAD(+)) precursors, and cytokines govern complex biological pathways that determine both cell survival and longevity during diabetes mellitus and its complications. Furthermore, the role of these entities as biomarkers for disease can further enhance their utility irrespective of their treatment potential. Greater understanding of the intricacies of these unique cellular mechanisms will shape future drug discovery for diabetes mellitus to provide focused clinical care with limited or absent long-term complications.

Diabetes mellitus: channeling care through cellular discovery

Diabetes mellitus (DM) impacts a significant portion of the world's population and care for this disorder places an economic burden on the gross domestic product for any particular country. Furthermore, both Type 1 and Type 2 DM are becoming increasingly prevalent and there is increased incidence of impaired glucose tolerance in the young. The complications of DM are protean and can involve multiple systems throughout the body that are susceptible to the detrimental effects of oxidative stress and apoptotic cell injury. For these reasons, innovative strategies are necessary for the implementation of new treatments for DM that are generated through the further understanding of cellular pathways that govern the pathological consequences of DM. In particular, both the precursor for the coenzyme beta-nicotinamide adenine dinucleotide (NAD(+)), nicotinamide, and the growth factor erythropoietin offer novel platforms for drug discovery that involve cellular metabolic homeostasis and inflammatory cell control. Interestingly, these agents and their tightly associated pathways that consist of cell cycle regulation, protein kinase B, forkhead transcription factors, and Wnt signaling also function in a broader sense as biomarkers for disease onset and progression.