Microtubules are required for NF-kappaB nuclear translocation in neuroblastoma IMR-32 cells: modulation by zinc

NFAT activation by FKBP52 promotes cancer cell proliferation by suppressing p53

FK506-binding protein 52 (FKBP52) is a member of the FKBP family of proline isomerases. FKBP52 is up-regulated in various cancers and functions as a positive regulator of steroid hormone receptors. Depletion of FKBP52 is known to inhibit cell proliferation; however, the detailed mechanism remains poorly understood. In this study, we found that FKBP52 depletion decreased MDM2 transcription, leading to stabilization of p53, and suppressed cell proliferation. We identified NFATc1 and NFATc3 as transcription factors that regulate MDM2 We also found that FKBP52 associated with NFATc3 and facilitated its nuclear translocation. In addition, calcineurin, a well-known Ca2+ phosphatase essential for activation of NFAT, plays a role in MDM2 transcription. Supporting this notion, MDM2 expression was found to be regulated by intracellular Ca2+ Taken together, these findings reveal a new role of FKBP52 in promoting cell proliferation via the NFAT-MDM2-p53 axis, and indicate that inhibition of FKBP52 could be a new therapeutic tool to activate p53 and inhibit cell proliferation.

Anti-Inflammatory and Cancer-Preventive Potential of Chamomile (Matricaria chamomilla L.): A Comprehensive In Silico and In Vitro Study

BACKGROUND AND AIM

Chamomile tea, renowned for its exquisite taste, has been appreciated for centuries not only for its flavor but also for its myriad health benefits. In this study, we investigated the preventive potential of chamomile (Matricaria chamomilla L.) towards cancer by focusing on its anti-inflammatory activity.

METHODS AND RESULTS

A virtual drug screening of 212 phytochemicals from chamomile revealed β-amyrin, β-eudesmol, β-sitosterol, apigenin, daucosterol, and myricetin as potent NF-κB inhibitors. The in silico results were verified through microscale thermophoresis, reporter cell line experiments, and flow cytometric determination of reactive oxygen species and mitochondrial membrane potential. An oncobiogram generated through comparison of 91 anticancer agents with known modes of action using the NCI tumor cell line panel revealed significant relationships of cytotoxic chamomile compounds, lupeol, and quercetin to microtubule inhibitors. This hypothesis was verified by confocal microscopy using α-tubulin-GFP-transfected U2OS cells and molecular docking of lupeol and quercetin to tubulins. Both compounds induced G2/M cell cycle arrest and necrosis rather than apoptosis. Interestingly, lupeol and quercetin were not involved in major mechanisms of resistance to established anticancer drugs (ABC transporters, TP53, or EGFR). Performing hierarchical cluster analyses of proteomic expression data of the NCI cell line panel identified two sets of 40 proteins determining sensitivity and resistance to lupeol and quercetin, further pointing to the multi-specific nature of chamomile compounds. Furthermore, lupeol, quercetin, and β-amyrin inhibited the mRNA expression of the proinflammatory cytokines IL-1β and IL6 in NF-κB reporter cells (HEK-Blue Null1). Moreover, Kaplan-Meier-based survival analyses with NF-κB as the target protein of these compounds were performed by mining the TCGA-based KM-Plotter repository with 7489 cancer patients. Renal clear cell carcinomas (grade 3, low mutational rate, low neoantigen load) were significantly associated with shorter survival of patients, indicating that these subgroups of tumors might benefit from NF-κB inhibition by chamomile compounds.

CONCLUSION

This study revealed the potential of chamomile, positioning it as a promising preventive agent against inflammation and cancer. Further research and clinical studies are recommended.

Emerging insights into the role of IL-1 inhibitors and colchicine for inflammation control in type 2 diabetes

Type 2 diabetes mellitus (T2DM), a prevalent chronic metabolic disorder, is closely linked to persistent low-grade inflammation, significantly contributing to its development and progression. This review provides a comprehensive examination of the inflammatory mechanisms underlying T2DM, focusing on the role of the NLRP3 inflammasome and interleukin-1β (IL-1β) in mediating inflammatory responses. We discuss the therapeutic potential of IL-1 inhibitors and colchicine, highlighting their mechanisms in inhibiting the NLRP3 inflammasome and reducing IL-1β production. Recent studies indicate that these agents could effectively mitigate inflammation, offering promising avenues for the prevention and management of T2DM. By exploring the intricate connections between metabolic disturbances and chronic inflammation, this review underscores the need for novel anti-inflammatory strategies to address T2DM and its complications.

Therapeutic potential of colchicine in cardiovascular medicine: a pharmacological review

Colchicine is an ancient herbal drug derived from Colchicum autumnale. It was first used to treat familial Mediterranean fever and gout. Based on its unique efficacy as an anti-inflammatory agent, colchicine has been used in the therapy of cardiovascular diseases including coronary artery disease, atherosclerosis, recurrent pericarditis, vascular restenosis, heart failure, and myocardial infarction. More recently, colchicine has also shown therapeutic efficacy in alleviating cardiovascular complications of COVID-19. COLCOT and LoDoCo2 are two milestone clinical trials that confirm the curative effect of long-term administration of colchicine in reducing the incidence of cardiovascular events in patients with coronary artery disease. There is growing interest in studying the anti-inflammatory mechanisms of colchicine. The anti-inflammatory action of colchicine is mediated mainly through inhibiting the assembly of microtubules. At the cellular level, colchicine inhibits the following: (1) endothelial cell dysfunction and inflammation; (2) smooth muscle cell proliferation and migration; (3) macrophage chemotaxis, migration, and adhesion; (4) platelet activation. At the molecular level, colchicine reduces proinflammatory cytokine release and inhibits NF-κB signaling and NLRP3 inflammasome activation. In this review, we summarize the current clinical trials with proven curative effect of colchicine in treating cardiovascular diseases. We also systematically discuss the mechanisms of colchicine action in cardiovascular therapeutics. Altogether, colchicine, a bioactive constituent from an ancient medicinal herb, exerts unique anti-inflammatory effects and prominent cardiovascular actions, and will charter a new page in cardiovascular medicine.

EGCG sensitizes chemotherapeutic-induced cytotoxicity by targeting the ERK pathway in multiple cancer cell lines

Epigallocatechin-3-gallate (EGCG), a major polyphenol component of green tea, presents anticancer efficacy. However, its exact mechanism of action is not known. In this study, we evaluated the effect of EGCG alone or in combination with current chemotherapeutics [gemcitabine, 5-flourouracil (5-FU), and doxorubicin] on pancreatic, colon, and lung cancer cell growth, as well as the mechanisms involved in the combined action. EGCG reduced pancreatic, colon, and lung cancer cell growth in a concentration and time-dependent manner. EGCG strongly induced apoptosis and blocked cell cycle progression. Moreover, EGCG enhanced the growth inhibitory effect of 5-FU and doxorubicin. Of note, EGCG enhanced 5-FU's and doxorubicin's effect on apoptosis, but not on cell cycle. Mechanistically, EGCG reduced ERK phosphorylation concentration-dependently, and sensitized gemcitabine, 5-FU, and doxorubicin to further suppress ERK phosphorylation in multiple cancer cell lines. In conclusion, EGCG presents a strong anticancer effect in pancreatic, colon, and lung cancer cells and is a robust combination partner for multiple chemotherapeutics as evidenced by reducing cancer cell growth, in part, by inhibiting the ERK pathway.

Zinc and the modulation of Nrf2 in human neuroblastoma cells

Zinc plays a key role in the modulation of neuronal redox homeostasis. A decreased zinc availability is associated with neuronal NADPH oxidase and nitric oxide synthase activation, deregulation of redox signaling, and impaired glutathione synthesis. The present work tested the hypothesis that zinc is necessary in the neuronal defense response against dopamine (DA)-induced oxidative stress, in particular through heme oxygenase-1 (HO-1) upregulation. DA showed higher cytotoxicity when zinc availability was low. Human IMR-32 neuroblastoma cells responded to high DA concentrations (100 μM) by upregulating HO-1. This upregulation involved Nrf2 translocation to the nucleus, degradation of the Bach-1 repressor, and Nrf2-DNA binding, but it was independent of ERK1/2 activation. DA-mediated induction of HO-1 expression was dependent on the concentration of zinc in the medium. IMR-32 cells incubated in zinc deficient medium showed an impaired response to DA, with lower HO-1 mRNA and protein levels than control DA-challenged cells. This altered HO-1 upregulation was reversed by zinc supplementation. In the presence of DA, Nrf2 nuclear translocation and Bach-1 degradation were lower in zinc deficient cells. The mechanisms involved include: i) impaired Nrf2-tubulin interactions and ii) alterations in the proteasome-mediated degradation of Bach-1 secondary to a decreased ubiquitylation. Results suggest that zinc is crucial in the neuronal response to DA-induced oxidative stress in part through its role in the modulation of the Nrf2-and Bach-1-driven upregulation of HO-1 expression.

Colchicine as a Novel Therapy for Suppressing Chemokine Production in Patients With an Acute Coronary Syndrome: A Pilot Study

PURPOSE

Existing literature reports that colchicine inhibits inflammasome activation and downstream inflammatory cytokine production and stabilizes coronary plaque. However, colchicine's effect on chemokines, which orchestrate multiple atheroinflammatory pathways, is unknown.

METHODS

Patients with acute coronary syndrome (ACS) were randomly assigned to colchicine (1.5 mg PO) (n = 12; mean age, 65.2 years) or no treatment (n = 13; mean age, 62.2 years). Blood samples were collected during cardiac catheterization within 24 hours of colchicine administration from the coronary sinus, aortic root, and right atrium. Patients with colchicine-naive stable angina (SAP) (n = 13; mean age, 66.8 years) were additionally sampled. Serum chemokine levels were analyzed with ELISA. In parallel, monocytes from healthy donors were isolated and subjected to colchicine treatment.

FINDINGS

Transcoronary (TC) levels of chemokine ligand 2 (CCL2) and C-X3-C motif chemokine ligand 1 (CX3CL1) were significantly elevated in patients with ACS versus patients with SAP (P < 0.01). TC chemokine ligand 5 (CCL5) levels were not significantly (P = 0.084) elevated in patients with ACS versus patients with SAP. Colchicine treatment markedly reduced TC levels of CCL2, CCL5, and CX3CL1 in patients with ACS (P < 0.05). In vitro colchicine suppressed CCL2 gene expression in stimulated monocytes (P < 0.05). Colchicine treatment reduced the intracellular concentration of all 3 chemokines (P < 0.01) and impaired monocyte chemotaxis (P < 0.05).

IMPLICATIONS

Here, we report for the first time that short-term colchicine therapy significantly reduces the local production of coronary chemokines, in part by attenuating production of these mediators by monocytes. These data provide further evidence of colchicine's beneficial role in patients with ACS.

Epigallocatechin-3-Gallate (EGCG) Suppresses Pancreatic Cancer Cell Growth, Invasion, and Migration partly through the Inhibition of Akt Pathway and Epithelial-Mesenchymal Transition: Enhanced Efficacy when Combined with Gemcitabine

Most pancreatic cancers are usually diagnosed at an advanced stage when they have already metastasized. Epigallocatechin-3-gallate (EGCG), a major polyphenolic constituent of green tea, has been shown to reduce pancreatic cancer growth, but its effect on metastasis remains elusive. This study evaluated the capacity of EGCG to inhibit pancreatic cancer cell migration and invasion and the underlying mechanisms. EGCG reduced pancreatic cancer cell growth, migration, and invasion in vitro and in vivo. EGCG prevented "Cadherin switch" and decreased the expression level of TCF8/ZEB1, β-Catenin, and Vimentin. Mechanistically, EGCG inhibited the Akt pathway in a time-dependent manner, by suppressing IGFR phosphorylation and inducing Akt degradation. Co-treatment with catalase or N-Acetyl-L-cysteine did not abrogate EGCG's effect on the Akt pathway or cell growth. Moreover, EGCG synergized with gemcitabine to suppress pancreatic cancer cell growth, migration, and invasion, through modulating epithelial-mesenchymal transition markers and inhibiting Akt pathway. In summary, EGCG may prove beneficial to improve gemcitabine sensitivity in inhibiting pancreatic cancer cell migration and invasion, to some extent through the inhibition of Akt pathway and epithelial-mesenchymal transition.

Biological Actions of the Hsp90-binding Immunophilins FKBP51 and FKBP52

Immunophilins are a family of proteins whose signature domain is the peptidylprolyl-isomerase domain. High molecular weight immunophilins are characterized by the additional presence of tetratricopeptide-repeats (TPR) through which they bind to the 90-kDa heat-shock protein (Hsp90), and via this chaperone, immunophilins contribute to the regulation of the biological functions of several client-proteins. Among these Hsp90-binding immunophilins, there are two highly homologous members named FKBP51 and FKBP52 (FK506-binding protein of 51-kDa and 52-kDa, respectively) that were first characterized as components of the Hsp90-based heterocomplex associated to steroid receptors. Afterwards, they emerged as likely contributors to a variety of other hormone-dependent diseases, stress-related pathologies, psychiatric disorders, cancer, and other syndromes characterized by misfolded proteins. The differential biological actions of these immunophilins have been assigned to the structurally similar, but functionally divergent enzymatic domain. Nonetheless, they also require the complementary input of the TPR domain, most likely due to their dependence with the association to Hsp90 as a functional unit. FKBP51 and FKBP52 regulate a variety of biological processes such as steroid receptor action, transcriptional activity, protein conformation, protein trafficking, cell differentiation, apoptosis, cancer progression, telomerase activity, cytoskeleton architecture, etc. In this article we discuss the biology of these events and some mechanistic aspects.

Discovery of a Novel Microtubule Targeting Agent as an Adjuvant for Cancer Immunotherapy

For an activating immunotherapy such as adjuvants, a compound that can prolong immune stimulation may enhance efficacy. We leveraged data from two prior high throughput screens with NF-κB and interferon reporter cell lines to identify 4H-chromene-3-carbonitriles as a class of compounds that prolonged activation in both screens. We repurchased 23 of the most promising candidates. Out of these compounds we found #1 to be the most effective agent in stimulating the release of cytokines and chemokines from immune cells, including murine primary bone marrow derived dendritic cells. Mechanistically, #1 inhibited tubulin polymerization, and its effect on immune cell activation was abolished in cells mutated in the beta-tubulin gene (TUBB) encoding the site where colchicine binds. Treatment with #1 resulted in mitochondrial depolarization followed by mitogen-activated protein kinase activation. Because tubulin polymerization modulating agents have been used for chemotherapy to treat malignancy and #1 activated cytokine responses, we hypothesized that #1 could be effective for cancer immunotherapy. Intratumoral injection of #1 delayed tumor growth in a murine syngeneic model of head and neck cancer. When combined with PD-1 blockade, tumor growth slowed in the injected tumor nodule and there was an abscopal effect in an uninjected nodule on the contralateral flank, suggesting central antitumor immune activation. Thus, we identified a new class of tubulin depolymerizing agent that acts as both an innate and an adaptive immune activating agent and that limits solid tumor growth when used concurrently with a checkpoint inhibitor.

Early-Life Exposure to Cadmium Triggers Distinct Zn-Dependent Protein Expression Patterns and Impairs Brain Development

The objective of this study was to determine if the brain development impairment induced by early-life exposure to cadmium (Cd) could result from changes in the expression pattern of distinct zinc (Zn)-dependent proteins. For this purpose, adult female rats receiving either tap water, Cd, Zn, or Cd + Zn in their drinking water during gestation and lactation periods were used. After birth, the male offspring were screened for locomotors and sensorial defects. At postnatal day 21 (PND 21), the male pups were sacrificed and their brains, liver, and plasma were taken for chemical, biochemical, and molecular analyses. Our results show that exposure to Cd significantly increased the metal accumulation and decreased Zn concentrations in the brain of male pups from Cd-treated mothers. Besides, Cd exposure reduced significantly the locomotor activity of the offspring in open-field test, the body weight, and the cranio-caudal length at PND21. Insulin-like growth factor-I (IGF-1) levels in the plasma and liver were also decreased in male pups from Cd-treated mothers. Cd-induced brain development disruption was accompanied by a significant increase of the superoxide dismutase (SOD) activity, induction of the metallothionein (MT) synthesis, and, at the molecular level, by an upregulation of Zrt-,Irt-related protein 6 (ZIP6) gene and a significant downregulation of the expression of the Zn transporter 3 (ZnT3) and brain-derived neurotrophic factor (BDNF) genes in the brain. No significant changes on the expression of genes encoding other Zn-dependent proteins and factors such as ZnT1, ZIP12, NF-κB, and Zif268. Interestingly, Zn supplementation provided a total or partial correction of the changes induced by the Cd exposure. These data indicated that changes in expression of ZnT3 and ZIP6 as well as alteration of other transcription factors, such as BDNF, or Zn-dependent proteins, such as SOD and MTs, in response to Cd exposure might be an underlying mechanism of Cd-induced brain development impairment.

Zinc deficiency affects the STAT1/3 signaling pathways in part through redox-mediated mechanisms

Zinc deficiency affects the development of the central nervous system (CNS) through mechanisms only partially understood. We previously showed that zinc deficiency causes CNS oxidative stress, damaging microtubules and impairing protein nuclear shuttling. STAT1 and STAT3 transcription factors, which require nuclear import for their functions, play major roles in CNS development. Thus, we investigated whether zinc deficiency disrupts STAT1 and STAT3 signaling pathways in the developing fetal CNS, characterizing the involvement of oxidative stress and the cytoskeleton in the adverse effects. Maternal (gestation day 0–19) marginal zinc deficiency (MZD) reduced STAT1 and STAT3 tyrosine phosphorylation and their nuclear translocation in the embryonic day 19 (E19) rat brain. Similar effects were observed in zinc depleted IMR-32 neuroblastoma cells, with an associated decrease in STAT1- and STAT3-dependent gene transactivation. Zinc deficiency caused oxidative stress (increased 4-hydroxynonenal-protein adducts) in E19 brain and IMR-32 cells, which was prevented in cells by supplementation with 0.5 mM α-lipoic acid (LA). In zinc depleted IMR-32 cells, the low tyrosine phosphorylation of STAT1, but not that of STAT3, recovered upon incubation with LA. STAT1 and STAT3 nuclear transports were also restored by LA. Accordingly, chemical disruption of the cytoskeleton partially reduced STAT1 and STAT3 nuclear levels. In summary, the redox-dependent tyrosine phosphorylation, and oxidant-mediated disruption of the cytoskeleton are involved in the deleterious effects of zinc deficit on STAT1 and STAT3 activation and nuclear translocation. Therefore, disruption of the STAT1 and STAT3 signaling pathways may in part explain the deleterious effects of maternal MZD on fetal brain development.

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Zinc deficits impair STAT1/STAT3 signaling in fetal brain and neuroblastoma cells.

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Zinc deficiency inhibits STAT1 and STAT3 tyrosine phosphorylation and nuclear translocation.

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Zinc deficiency causes oxidative stress (high HNE-protein adducts) in fetal brain and cells.

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Lipoic acid reverts zinc deficiency-associated decreased STAT1/STAT3 nuclear shuttling.

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Zinc deficiency-associated oxidative stress impairs STAT1/STAT3 modulation.

Cytoplasmic hnRNPK interacts with GSK3β and is essential for the osteoclast differentiation

Osteoclast differentiation is a complex and finely regulated physiological process that involves a variety of signaling pathways and factors. Recent studies suggested that the Ser9 phosphorylation of Glycogen synthase kinase-3β (GSK3β) is required for the osteoclast differentiation. However, the precise underlying mechanism remains unclear. We have previously identified the heterogeneous nuclear ribonucleoprotein K (hnRNPK) as a putative GSK3β interactor. In the present study, we demonstrate that, during the RANKL-induced osteoclast differentiation, the PI3K/Akt-mediated Ser9 phosphorylation of GSK3β provokes the nuclear-cytoplasmic translocation of hnRNPK in an ERK-dependent manner, enhancing the cytoplasmic co-localization and interaction of GSK3β and hnRNPK. We show that hnRNPK is essential for the osteoclast differentiation, and is involved in several reported functions of GSK3β, including the activation of NF-κB, the expression of NFATc1, and the acetylation of tubulin, all known to be critical for osteoclast differentiation and functions. We find that hnRNPK is localized in the actin belt, and is important for the mature osteoclast formation. Taken together, we demonstrate here the critical role of hnRNPK in osteoclast differentiation, and depict a model in which the cytoplasmic hnRNPK interacts with GSK3β and regulates its function.

Role of JNK and NF-κB in mediating the effect of combretastatin A-4 and brimamin on endothelial and carcinoma cells

PURPOSE

The 4,5-diarylimidazole brimamin is an analog of the natural vascular-disrupting agent combretastatin A-4 (CA-4) with improved water solubility, tolerance by animals and efficacy in multidrug-resistant tumors. Here, we aimed at identifying the major mechanisms underlying the in vitro and in vivo actions of brimamin on endothelial and carcinoma cells, including vascularization.

METHODS

The contribution of specific signaling kinases to the effects of brimamin on cytoskeleton organization and the viability and differentiation of endothelial cells was assessed by MTT and tube formation assays in the presence or absence of specific kinase inhibitors. Changes in DNA affinity and expression of NF-κB in endothelial and carcinoma-derived cells and their solid tumors (xenografts) treated with brimamin were ascertained by electrophoretic mobility shift assays and Western blotting. The anti-vascular effect of brimamin in solid tumors was verified by CD31 immunostaining.

RESULTS

We found that brimamin can inhibit tubulin polymerization and cause a reorganization of F-actin in Ea.hy926 endothelial cells. Its inhibitory effect on tube formation was found to depend on functional Rho kinase and JNK. JNK inhibition was found to suppress the induction of endothelial cell apoptosis by brimamin. In CA-4-refractory human BxPC-3 pancreas carcinoma-derived and triple-negative MDA-MB-231 breast carcinoma-derived cells brimamin was found to inhibit growth and to induce apoptosis at low nanomolar concentrations by blocking NF-κB activation in a dose-dependent manner. Brimamin was also found to reduce the in vivo growth rate and vascularization of MDA-MB-231 xenografts in mice. Residual tumor cells of these treated xenografts showed a relatively low expression of the p65 subunit of NF-κB.

CONCLUSIONS

Our data indicate that cellular JNK and Rho kinase activities are crucial for the cytotoxic and cytoskeleton reorganizing effects of brimamin on endothelial cells. In addition, we found that in resistant carcinoma cells and xenografts brimamin can induce down-regulation of anti-apoptotic NF-κB expression and signaling. Its chemical properties and efficacy against clinically relevant cancer entities make brimamin a promising candidate vascular-disrupting agent.

Down-regulation of Stathmin Is Required for the Phenotypic Changes and Classical Activation of Macrophages

Macrophages are important cells of innate immunity with specialized capacity for recognition and elimination of pathogens and presentation of antigens to lymphocytes for adaptive immunity. Macrophages become activated upon exposure to pro-inflammatory cytokines and pathogenic stimuli. Classical activation of macrophages with interferon-γ (IFNγ) and lipopolysaccharide (LPS) triggers a wide range of signaling events and morphological changes to induce the immune response. Our previous microtubule (MT) proteomic work revealed that the stathmin association with MTs is considerably reduced in activated macrophages, which contain significantly more stabilized MTs. Here, we show that there is a global decrease in stathmin levels, an MT catastrophe protein, in activated macrophages using both immunoblotting and immunofluorescent microscopy. This is an LPS-specific response that induces proteasome-mediated degradation of stathmin. We explored the functions of stathmin down-regulation in activated macrophages by generating a stable cell line overexpressing stathmin-GFP. We show that stathmin-GFP overexpression impacts MT stability, impairs cell spreading, and reduces activation-associated phenotypes. Furthermore, overexpressing stathmin reduces complement receptor 3-mediated phagocytosis and cellular activation, implicating a pivotal inhibitory role for stathmin in classically activated macrophages.

HDAC6 mediates HIV-1 tat-induced proinflammatory responses by regulating MAPK-NF-kappaB/AP-1 pathways in astrocytes

Human immunodeficiency virus (HIV)-1 transactivator of transcription (Tat) is a viral protein that induces extensive neuroinflammation by up-regulating proinflammatory mediators, including cytokines, chemokines, and adhesion molecules. Histone deacetylase 6 (HDAC6) has been implicated in the transcriptional regulation of inflammatory genes. In this study, we investigated the possible role of HDAC6 in HIV-1 Tat-induced up-regulation of proinflammatory mediators in astrocytes. HIV-1 Tat augmented HDAC6 expression, which was correlated with a reduction in acetylated α-tubulin in CRT-MG human astroglioma cells and primary mouse astrocytes. Knockdown and pharmacological inhibition of HDAC6 significantly inhibited HIV-1 Tat-induced expression of CCL2, CXCL8, and CXCL10 chemokines; adhesion molecules; and subsequent adhesion of monocytes to astrocytes. HDAC6 knockdown attenuated HIV-1 Tat-induced activation of mitogen-activated protein kinase species, including ERK, JNK, and p38. Furthermore, HDAC6 knockdown suppressed HIV-1 Tat-induced activation of NF-κB and AP-1. Thus, HDAC6 is involved in HIV-1 Tat-induced expression of proinflammatory genes by regulating mitogen-activated protein kinase-NF-κB/AP-1 pathways and serves as a molecular target for HIV-1 Tat-mediated neuroinflammation GLIA 2015;63:1953-1965.

Biological relevance of Hsp90-binding immunophilins in cancer development and treatment

Immunophilins are a family of intracellular receptors for immunosuppressive drugs. Those immunophilins that are related to immunosuppression are the smallest proteins of the family, i.e., FKBP12 and CyPA, whereas the other members of the family have higher molecular weight because the show additional domains to the drug-binding site. Among these extra domains, the TPR-domain is perhaps the most relevant because it permits the interaction of high molecular weight immunophilins with the 90-kDa heat-shock protein, Hsp90. This essential molecular chaperone regulates the biological function of several protein-kinases, oncogenes, protein phosphatases, transcription factors and cofactors . Hsp90-binding immunophilins where first characterized due to their association with steroid receptors. They regulate the cytoplasmic transport and the subcellular localization of these and other Hsp90 client proteins, as well as transcriptional activity, cell proliferation, cell differentiation and apoptosis. Hsp90-binding immunophilins are frequently overexpressed in several types of cancers and play a key role in cell survival. In this article we analyze the most important biological actions of the best characterized Hsp90-binding immunophilins in both steroid receptor function and cancer development and discuss the potential use of these immunophilins for therapeutic purposes as potential targets of specific small molecules.

Influence of intracellular zinc on cultures of rat cardiac neural crest cells

BACKGROUND

Developmental zinc (Zn) deficiency increases the incidence of heart anomalies in rat fetuses, in regions and structures derived from the outflow tract. Given that the development of the outflow tract requires the presence of cardiac neural crest cells (cNCC), we speculated that Zn deficiency selectively kills cNCC and could lead to heart malformations.

METHODS

Cardiac NCC were isolated from E10.5 rat embryos and cultured in control media (CTRL), media containing 3 μM of the cell permeable metal chelator N, N, N', N'-tetrakis (2-pyridylmethyl) ethylene diamine (TPEN), or in TPEN-treated media supplemented with 3 μM Zn (TPEN + Zn). Cardiac NCC were collected after 6, 8, and 24 h of treatment to assess cell viability, proliferation, and apoptosis.

RESULTS

The addition of TPEN to the culture media reduced free intracellular Zn pools and cell viability as assessed by low ATP production, compared to cells grown in control or Zn-supplemented media. There was an accumulation of reactive oxygen species, a release of mitochondrial cytochrome c into the cytoplasm, and an increased cellular expression of active caspase-3 in TPEN-treated cNCC compared to cNCC cultured in CTRL or TPEN + Zn media.

CONCLUSION

Zn deficiency can result in oxidative stress in cNCC, and subsequent decreases in their population and metabolic activity. These data support the concept that Zn deficiency associated developmental heart defects may arise in part as a consequence of altered cNCC metabolism.

Analysis of dermal papilla cell interactome using STRING database to profile the ex vivo hair growth inhibition effect of a vinca alkaloid drug, colchicine

Dermal papillae (DPs) control the formation of hair shafts. In clinical settings, colchicine (CLC) induces patients' hair shedding. Compared to the control, the ex vivo hair fiber elongation of organ cultured vibrissa hair follicles (HFs) declined significantly after seven days of CLC treatment. The cultured DP cells (DPCs) were used as the experimental model to study the influence of CLC on the protein dynamics of DPs. CLC could alter the morphology and down-regulate the expression of alkaline phosphatase (ALP), the marker of DPC activity, and induce IκBα phosphorylation of DPCs. The proteomic results showed that CLC modulated the expression patterns (fold>2) of 24 identified proteins, seven down-regulated and 17 up-regulated. Most of these proteins were presumably associated with protein turnover, metabolism, structure and signal transduction. Protein-protein interactions (PPI) among these proteins, established by Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database, revealed that they participate in protein metabolic process, translation, and energy production. Furthermore, ubiquitin C (UbC) was predicted to be the controlling hub, suggesting the involvement of ubiquitin-proteasome system in modulating the pathogenic effect of CLC on DPC.

Parthenolide and costunolide reduce microtentacles and tumor cell attachment by selectively targeting detyrosinated tubulin independent from NF-κB inhibition

Introduction

Detyrosinated tubulin, a post-translational modification of α-tubulin and a hallmark of stable microtubules, has gained recent attention given its association with tumor progression, invasiveness, and chemoresistance. We also recently reported that epithelial-to-mesenchymal transition (EMT) promotes tubulin detyrosination through tubulin tyrosine ligase (TTL) suppression. Furthermore, detyrosinated tubulin-enriched membrane protrusions, termed microtentacles (McTN), facilitate tumor cell reattachment to endothelial layers. Given the induction of EMT associated with inflammation and cancer progression, we tested anti-inflammatory nuclear factor-kappaB (NF-κB) inhibitors on a panel of human breast carcinoma cells to examine their effects on detyrosinated tubulin to identify more specific tubulin-directed anti-cancer treatments.

Methods

Using metastatic human breast carcinoma cells MDA-MB-157, MDA-MB-436, and Bt-549, we measured the impact of NF-κB inhibitors parthenolide, costunolide, and resveratrol on detyrosinated tubulin using protein expression analysis and immunofluorescence. A luciferase reporter assay and a viability screen were performed to determine if the effects were associated with their NF-κB inhibitory properties or were a result of apoptosis. Real-time monitoring of cell-substratum attachment was measured utilizing electrical impedance across microelectronic sensor arrays. We compared the selectivity of the NF-κB inhibitors to specifically target detyrosinated tubulin with traditional tubulin-targeted therapeutics, paclitaxel and colchicine, throughout the study.

Results

Sesquiterpene lactones, parthenolide and costunolide, selectively decrease detyrosinated tubulin independent of their inhibition of NF-κB. Live-cell scoring of suspended cells treated with parthenolide and costunolide show reduction in the frequency of microtentacles and inhibition of reattachment. Structural analysis shows that parthenolide and costunolide can decrease detyrosinated microtubules without significantly disrupting the overall microtubule network or cell viability. Paclitaxel and colchicine display indiscriminate disruption of the microtubule network.

Conclusions

Our data demonstrate that selective targeting of detyrosinated tubulin with parthenolide and costunolide can reduce McTN frequency and inhibit tumor cell reattachment. These actions are independent of their effects on NF-κB inhibition presenting a novel anti-cancer property and therapeutic opportunity to selectively target a stable subset of microtubules in circulating tumor cells to reduce metastatic potential with less toxicity in breast cancer patients.

Rho-kinase regulation of TNF-α-induced nuclear translocation of NF-κB RelA/p65 and M-CSF expression via p38 MAPK in mesangial cells

The small GTPase Rho and its downstream effector, Rho-associated coiled-coil containing protein kinase (Rho-kinase), regulate a number of cellular processes, including organization of the actin cytoskeleton, cell adhesion, and migration. While pharmacological inhibitors of Rho-kinase signaling are known to block renal inflammation, the molecular basis for this effect is unclear. Here, we provide evidence that proinflammatory TNF-α promotes mesangial expression of macrophage colony-stimulating factor (M-CSF), a key regulator for the growth and differentiation of mononuclear phagocytes, in a Rho-kinase-dependent manner. Consistent with this observation, TNF-α-mediated renal expression of M-CSF in insulin-resistant db/db mice was downregulated by Rho-kinase inhibition. Small interfering RNA-facilitated knockdown of Rho-kinase isoforms ROCK1 and ROCK2 indicated that both isoforms make comparable contributions to regulation of M-CSF expression in mesangial cells. From a mechanistic standpoint, Western blotting and EMSA showed that Rho-kinase and its downstream target p38 MAPK regulate nuclear translocation of NF-κB RelA/p65 and subsequent DNA binding activity, with no significant effects on IκBα degradation and RelA/p65 phosphorylation. Moreover, we showed that Rho-kinase-mediated cytoskeletal organization is required for the nuclear uptake of RelA/p65. Collectively, these findings identify Rho-kinase as a critical regulator of chemokine expression and macrophage proliferation.

NF-κB transcriptional activity is modulated by FK506-binding proteins FKBP51 and FKBP52: a role for peptidyl-prolyl isomerase activity

Hsp90 binding immunophilins FKBP51 and FKBP52 modulate steroid receptor trafficking and hormone-dependent biological responses. With the purpose to expand this model to other nuclear factors that are also subject to nuclear-cytoplasmic shuttling, we analyzed whether these immunophilins modulate NF-κB signaling. It is demonstrated that FKBP51 impairs both the nuclear translocation rate of NF-κB and its transcriptional activity. The inhibitory action of FKBP51 requires neither the peptidylprolyl-isomerase activity of the immunophilin nor its association with Hsp90. The TPR domain of FKBP51 is essential. On the other hand, FKBP52 favors the nuclear retention time of RelA, its association to a DNA consensus binding sequence, and NF-κB transcriptional activity, the latter effect being strongly dependent on the peptidylprolyl-isomerase activity and also on the TPR domain of FKBP52, but its interaction with Hsp90 is not required. In unstimulated cells, FKBP51 forms endogenous complexes with cytoplasmic RelA. Upon cell stimulation with phorbol ester, the NF-κB soluble complex exchanges FKBP51 for FKBP52, and the NF-κB biological effect is triggered. Importantly, FKBP52 is functionally recruited to the promoter region of NF-κB target genes, whereas FKBP51 is released. Competition assays demonstrated that both immunophilins antagonize one another, and binding assays with purified proteins suggest that the association of RelA and immunophilins could be direct. These observations suggest that the biological action of NF-κB in different cell types could be positively regulated by a high FKBP52/FKBP51 expression ratio by favoring NF-κB nuclear retention, recruitment to the promoter regions of target genes, and transcriptional activity.

A zinc transporter gene required for development of the nervous system

The essentiality of zinc for normal brain development is well established. It has been suggested that primary and secondary zinc deficiencies can contribute to the occurrence of numerous human birth defects, including many involving the central nervous system. In a recent study, we searched for zinc transporter genes that were critical for neurodevelopment. We confirmed that ZIP12 is a zinc transporter encoded by the gene slc39a12 that is highly expressed in the central nervous systems of human, mouse, and frog (Xenopus tropicalis).Using loss-of-function methods, we determined that ZIP12 is required for neuronal differentiation and neurite outgrowth and necessary for neurulation and embryonic viability. These results highlight an essential need for zinc regulation during embryogenesis and nervous system development. We suggest that slc39a12 is a candidate gene for inherited neurodevelopmental defects in humans.

A novel autosomal recessive GJA1 missense mutation linked to Craniometaphyseal dysplasia

Craniometaphyseal dysplasia (CMD) is a rare sclerosing skeletal disorder with progressive hyperostosis of craniofacial bones. CMD can be inherited in an autosomal dominant (AD) trait or occur after de novo mutations in the pyrophosphate transporter ANKH. Although the autosomal recessive (AR) form of CMD had been mapped to 6q21-22 the mutation has been elusive. In this study, we performed whole-exome sequencing for one subject with AR CMD and identified a novel missense mutation (c.716G>A, p.Arg239Gln) in the C-terminus of the gap junction protein alpha-1 (GJA1) coding for connexin 43 (Cx43). We confirmed this mutation in 6 individuals from 3 additional families. The homozygous mutation cosegregated only with affected family members. Connexin 43 is a major component of gap junctions in osteoblasts, osteocytes, osteoclasts and chondrocytes. Gap junctions are responsible for the diffusion of low molecular weight molecules between cells. Mutations in Cx43 cause several dominant and recessive disorders involving developmental abnormalities of bone such as dominant and recessive oculodentodigital dysplasia (ODDD; MIM #164200, 257850) and isolated syndactyly type III (MIM #186100), the characteristic digital anomaly in ODDD. However, characteristic ocular and dental features of ODDD as well as syndactyly are absent in patients with the recessive Arg239Gln Cx43 mutation. Bone remodeling mechanisms disrupted by this novel Cx43 mutation remain to be elucidated.

Decreased zinc availability affects glutathione metabolism in neuronal cells and in the developing brain

A deficit in zinc (Zn) availability can increase cell oxidant production, affect the antioxidant defense system, and trigger oxidant-sensitive signals in neuronal cells. This work tested the hypothesis that a decreased Zn availability can affect glutathione (GSH) metabolism in the developing rat brain and in neuronal cells in culture, as well as the capacity of human neuroblastoma IMR-32 cells to upregulate GSH when challenged with dopamine (DA). GSH levels were low in the brain of gestation day 19 (GD19) fetuses from dams fed marginal Zn diets throughout gestation and in Zn-deficient IMR-32 cells. γ-Glutamylcysteine synthetase (GCL), the first enzyme in the GSH synthetic pathway, was altered by Zn deficiency (ZD). The protein and mRNA levels of the GCL modifier (GCLM) and catalytic (GCLC) subunits were lower in the Zn-deficient GD19 fetal brain and in IMR-32 cells compared with controls. The nuclear translocation of transcription factor nuclear factor (erythroid-derived 2)-like 2, which controls GCL transcription, was impaired by ZD. Posttranslationally, the caspase-3-dependent GCLC cleavage was high in Zn-deficient IMR-32 cells. Cells challenged with DA showed an increase in GCLM and GCLC protein and mRNA levels and a consequent increase in GSH concentration. Although Zn-deficient cells partially upregulated GCL subunits after exposure to DA, GSH content remained low. In summary, results show that a low Zn availability affects the GSH synthetic pathway in neuronal cells and fetal brain both at transcriptional and posttranslational levels. This can in part underlie the GSH depletion associated with ZD and the high sensitivity of Zn-deficient neurons to pro-oxidative stressors.

Zinc and the modulation of redox homeostasis

Zinc, a redox-inactive metal, has been long viewed as a component of the antioxidant network, and growing evidence points to its involvement in redox-regulated signaling. These actions are exerted through several mechanisms based on the unique chemical and functional properties of zinc. Overall, zinc contributes to maintaining the cell redox balance through various mechanisms including: (i) the regulation of oxidant production and metal-induced oxidative damage; (ii) the dynamic association of zinc with sulfur in protein cysteine clusters, from which the metal can be released by nitric oxide, peroxides, oxidized glutathione, and other thiol oxidant species; (iii) zinc-mediated induction of the zinc-binding protein metallothionein, which releases the metal under oxidative conditions and acts per se as a scavenging oxidant; (iv) the involvement of zinc in the regulation of glutathione metabolism and of the overall protein thiol redox status; and (v) a direct or indirect regulation of redox signaling. Findings of oxidative stress, altered redox signaling, and associated cell/tissue dysfunction in cell and animal models of zinc deficiency highlight the relevant role of zinc in the preservation of cell redox homeostasis. However, although the participation of zinc in antioxidant protection, redox sensing, and redox-regulated signaling is accepted, the molecules, targets, and mechanisms involved are still partially known and the subject of active research.

Vimentin and PSF act in concert to regulate IbeA+ E. coli K1 induced activation and nuclear translocation of NF-κB in human brain endothelial cells

BACKGROUND

IbeA-induced NF-κB signaling through its primary receptor vimentin as well as its co-receptor PSF is required for meningitic E. coli K1 penetration and leukocyte transmigration across the blood-brain barrier (BBB), which are the hallmarks of bacterial meningitis. However, it is unknown how vimentin and PSF cooperatively contribute to IbeA-induced cytoplasmic activation and nuclear translocation of NF-κB, which are required for bacteria-mediated pathogenicities.

METHODOLOGY/PRINCIPAL FINDINGS

IbeA-induced E. coli K1 invasion, polymorphonuclear leukocyte (PMN) transmigration and IKK/NF-κB activation are blocked by Caffeic acid phenethyl ester (CAPE), an inhibitor of NF-κB. IKKα/β phosphorylation is blocked by ERK inhibitors. Co-immunoprecipitation analysis shows that vimentin forms a complex with IκB, NF-κB and tubulins in the resting cells. A dissociation of this complex and a simultaneous association of PSF with NF-κB could be induced by IbeA in a time-dependent manner. The head domain of vimentin is required for the complex formation. Two cytoskeletal components, vimentin filaments and microtubules, contribute to the regulation of NF-κB. SiRNA-mediated knockdown studies demonstrate that IKKα/β phosphorylation is completely abolished in HBMECs lacking vimentin and PSF. Phosphorylation of ERK and nuclear translocation of NF-κB are entirely dependent on PSF. These findings suggest that vimentin and PSF cooperatively contribute to IbeA-induced cytoplasmic activation and nuclear translocation of NF-κB activation. PSF is essential for translocation of NF-κB and ERK to the nucleus.

CONCLUSION/SIGNIFICANCE

These findings reveal previously unappreciated facets of the IbeA-binding proteins. Cooperative contributions of vimentin and PSF to IbeA-induced cytoplasmic activation and nuclear translocation of NF-κB may represent a new paradigm in pathogen-induced signal transduction and lead to the development of novel strategies for the prevention and treatment of bacterial meningitis.

Alterations of the extracellular matrix of lung during zinc deficiency

Suboptimal intake of Zn is one of the most common nutritional problems worldwide. Previously, we have shown that Zn deficiency (ZD) produces oxidative and nitrosative stress in the lung of rats. We analyse the effect of moderate ZD on the expression of several intermediate filaments of the cytoskeleton, as well as the effect of restoring Zn during the refeeding period. Adult male rats were divided into three groups: Zn-adequate control (CO) group; ZD group; Zn-refeeding group. CerbB-2 and proliferating cell nuclear antigen (PCNA) expression was increased in the ZD group while the other parameters did not change. During the refeeding time, CerbB-2, cytokeratins, vimentin and PCNA immunostaining was higher than that in the CO group. The present findings indicate that the overexpression of some markers could lead to the fibrotic process in the lung. Perhaps ZD implications must be taken into account in health interventions because an inflammation environment is associated with ZD in the lung.

Spatio-temporal modelling of the NF-κB intracellular signalling pathway: the roles of diffusion, active transport, and cell geometry

The nuclear factor kappa B (NF-κB) intracellular signalling pathway is central to many stressful, inflammatory, and innate immune responses. NF-κB proteins themselves are transcription factors for hundreds of genes. Experiments have shown that the NF-κB pathway can exhibit oscillatory dynamics-a negative feedback loop causes oscillatory nuclear-cytoplasmic translocation of NF-κB. Given that cell size and shape are known to influence intracellular signal transduction, we consider a spatio-temporal model of partial differential equations for the NF-κB pathway, where we model molecular movement by diffusion and, for several key species including NF-κB, by active transport as well. Through numerical simulations we find values for model parameters such that sustained oscillatory dynamics occur. Our spatial profiles and animations bear a striking resemblance to experimental images and movie clips employing fluorescent fusion proteins. We discover that oscillations in nuclear NF-κB may occur when active transport is across the nuclear membrane only, or when no species are subject to active transport. However, when active transport is across the nuclear membrane and NF-κB is additionally actively transported through the cytoplasm, oscillations are lost. Hence transport mechanisms in a cell will influence its response to activation of its NF-κB pathway. We also demonstrate that sustained oscillations in nuclear NF-κB are somewhat robust to changes in the shape of the cell, or the shape, location, and size of its nucleus, or the location of ribosomes. Yet if the cell is particularly flat or the nucleus sufficiently small, then oscillations are lost. Thus the geometry of a cell may partly determine its response to NF-κB activation. The NF-κB pathway is known to be constitutively active in several human cancers. Our spatially explicit modelling approach will allow us, in future work, to investigate targeted drug therapy of tumours.

Microtubule assembly affects bone mass by regulating both osteoblast and osteoclast functions: stathmin deficiency produces an osteopenic phenotype in mice

Cytoskeleton microtubules regulate various cell signaling pathways that are involved in bone cell function. We recently reported that inhibition of microtubule assembly by microtubule-targeting drugs stimulates osteoblast differentiation and bone formation. To further elucidate the role of microtubules in bone homeostasis, we characterized the skeletal phenotype of mice null for stathmin, an endogenous protein that inhibits microtubule assembly. In vivo micro-computed tomography (µCT) and histology revealed that stathmin deficiency results in a significant reduction of bone mass in adult mice concurrent with decreased osteoblast and increased osteoclast numbers in bone tissues. Phenotypic analyses of primary calvarial cells and bone marrow cells showed that stathmin deficiency inhibited osteoblast differentiation and induced osteoclast formation. In vitro overexpression studies showed that increased stathmin levels enhanced osteogenic differentiation of preosteoblast MC3T3-E1 cells and mouse bone marrow-derived cells and attenuated osteoclast formation from osteoclast precursor Raw264.7 cells and bone marrow cells. Results of immunofluorescent studies indicated that overexpression of stathmin disrupted radial microtubule filaments, whereas deficiency of stathmin stabilized the microtubule network structure in these bone cells. In addition, microtubule-targeting drugs that inhibit microtubule assembly and induce osteoblast differentiation lost these effects in the absence of stathmin. Collectively, these results suggest that stathmin, which alters microtubule dynamics, plays an essential role in maintenance of postnatal bone mass by regulating both osteoblast and osteoclast functions in bone. \

Curcumin recognizes a unique binding site of tubulin

Although curcumin is known for its anticarcinogenic properties, the exact mechanism of its action or the identity of the target receptor is not completely understood. Studies on a series of curcumin analogues, synthesized to investigate their tubulin binding affinities and tubulin self-assembly inhibition, showed that: (i) curcumin acts as a bifunctional ligand, (ii) analogues with substitution at the diketone and acetylation of the terminal phenolic groups of curcumin are less effective, (iii) a benzylidiene derivative, compound 7, is more effective than curcumin in inhibiting tubulin self-assembly. Cell-based studies also showed compound 7 to be more effective than curcumin. Using fluorescence spectroscopy we show that curcumin binds tubulin 32 Å away from the colchicine-binding site. Docking studies also suggests that the curcumin-binding site to be close to the vinblastine-binding site. Structure-activity studies suggest that the tridented nature of compound 7 is responsible for its higher affinity for tubulin compared to curcumin.

A deficit in zinc availability can cause alterations in tubulin thiol redox status in cultured neurons and in the developing fetal rat brain

Zinc (Zn) deficiency during early development can result in multiple brain abnormalities and altered neuronal functions. In rats, a gestational deficit of Zn can affect the fetal brain cytoskeleton and signaling cascades involved in cellular processes that are central to brain development. In this paper, we tested the hypothesis that oxidative stress is involved in Zn deficiency-induced altered tubulin dynamics and the associated dysregulation of transcription factor NF-κB. For this purpose, we used two cell culture models (rat cortical neurons, human IMR-32 neuroblastoma cells) and an animal model of Zn deficiency. A low rate of in vitro tubulin polymerization, an increase in tubulin oligomers, and a higher protein cysteine oxidation were observed in the Zn-deficient neuronal cells and in gestation day 19 fetal brains obtained from dams fed marginal-Zn diets throughout pregnancy. These alterations could be prevented by treating the Zn-deficient cells with the reducing agent tris(2-carboxyethyl)phosphine or by the presence of N-acetylcysteine (NAC) and α-lipoic acid (LA). Consistent with the above, Zn deficiency-induced tubulin-mediated alterations in transcription factor NF-κB nuclear translocation were prevented by treating IMR-32 cells with LA and NAC. Binding of the NF-κB protein p50, dynein, and karyopherin α (components of the NF-κB transport complex) to β-tubulin as well as the expression of NF-κB-dependent genes (Bcl-2, cyclin D1, and c-myc) was also restored by the addition of LA and NAC to Zn-deficient cells. In conclusion, a deficit in Zn viability could affect early brain development through: (1) an induction of oxidative stress, (2) tubulin oxidation, (3) altered tubulin dynamics, and (4) deregulation of signals (e.g., NF-κB) involved in critical developmental events.

Disruption of microtubules sensitizes the DNA damage-induced apoptosis through inhibiting nuclear factor κB (NF-κB) DNA-binding activity

The massive reorganization of microtubule network involves in transcriptional regulation of several genes by controlling transcriptional factor, nuclear factor-kappa B (NF-κB) activity. The exact molecular mechanism by which microtubule rearrangement leads to NF-κB activation largely remains to be identified. However microtubule disrupting agents may possibly act in synergy or antagonism against apoptotic cell death in response to conventional chemotherapy targeting DNA damage such as adriamycin or comptothecin in cancer cells. Interestingly pretreatment of microtubule disrupting agents (colchicine, vinblastine and nocodazole) was observed to lead to paradoxical suppression of DNA damage-induced NF-κB binding activity, even though these could enhance NF-κB signaling in the absence of other stimuli. Moreover this suppressed NF-κB binding activity subsequently resulted in synergic apoptotic response, as evident by the combination with Adr and low doses of microtubule disrupting agents was able to potentiate the cytotoxic action through caspase-dependent pathway. Taken together, these results suggested that inhibition of microtubule network chemosensitizes the cancer cells to die by apoptosis through suppressing NF-κB DNA binding activity. Therefore, our study provided a possible anti-cancer mechanism of microtubule disrupting agent to overcome resistance against to chemotherapy such as DNA damaging agent.

The role of zinc in the modulation of neuronal proliferation and apoptosis

Although a requirement of zinc (Zn) for normal brain development is well documented, the extent to which Zn can modulate neuronal proliferation and apoptosis is not clear. Thus, we investigated the role of Zn in the regulation of these two critical events. A low Zn availability leads to decreased cell viability in human neuroblastoma IMR-32 cells and primary cultures of rat cortical neurons. This occurs in part as a consequence of decreased cell proliferation and increased apoptotic cell death. In IMR-32 cells, Zn deficiency led to the inhibition of cell proliferation through the arrest of the cell cycle at the G₀/G₁ phase. Zn deficiency induced apoptosis in both proliferating and quiescent neuronal cells via the intrinsic apoptotic pathway. Reductions in cellular Zn triggered a translocation of the pro-apoptotic protein Bad to the mitochondria, cytochrome c release, and caspase-3 activation. Apoptosis is the resultant of the inhibition of the prosurvival extracellular-signal-regulated kinase, the inhibition of nuclear factor-kappa B, and associated decreased expression of antiapoptotic proteins, and to a direct activation of caspase-3. A deficit of Zn during critical developmental periods can have persistent effects on brain function secondary to a deregulation of neuronal proliferation and apoptosis.

Zinc deficiency and neurodevelopment: the case of neurons

Zinc is essential for normal brain development. Gestational severe zinc deficiency can lead to overt fetal brain malformations. Although not teratogenic, suboptimal zinc nutrition during gestation can have long-term effects on the offspring's nervous system. This article will review current knowledge on the role of zinc in modulating neurogenesis and neuronal apoptosis as well as the proposed underlying mechanisms. A decrease in neuronal zinc causes cell cycle arrest, which in part involves a deregulation of select signals (ERK1/2, p53, and NF-kappaB). Zinc deficiency also induces apoptotic neuronal death through the intrinsic (mitochondrial) pathway, which can be triggered by the activation of the zinc-regulated enzyme caspase-3, and as a consequence of abnormal regulation of prosurvival signals (ERK1/2 and NF-kappaB). Alterations in the finely tuned processes of neurogenesis, neuronal migration, differentiation, and apoptosis, which involve the developmental shaping of the nervous system, could have a long-term impact on brain health. Zinc deficiency during gestation, even at the marginal levels observed in human populations, could increase the risk for behavioral/neurological disorders in infancy, adolescence, and adulthood.

Iron in neuronal function and dysfunction

Iron (Fe) is an essential element for many metabolic processes, serving as a cofactor for heme and nonheme proteins. Cellular iron deficiency arrests cell growth and leads to cell death; however, like most transition metals, an excess of intracellular iron is toxic. The ability of Fe to accept and donate electrons can lead to the formation of reactive nitrogen and oxygen species, and oxidative damage to tissue components; contributing to disease and, perhaps, aging itself. It has also been suggested that iron-induced oxidative stress can play a key role in the pathogenesis of several neurodegenerative diseases. Iron progressively accumulates in the brain both during normal aging and neurodegenerative processes. However, iron accumulation occurs without the concomitant increase in tissue ferritin, which could increase the risk of oxidative stress. Moreover, high iron concentrations in the brain have been consistently observed in Alzheimer's disease (AD) and Parkinson's disease (PD). In this regard, metalloneurobiology has become extremely important in understanding the role of iron in the onset and progression of neurodegenerative diseases. Neurons have developed several protective mechanisms against oxidative stress, among them the activation of cellular signaling pathways. The final response will depend on the identity, intensity, and persistence of the oxidative insult. The characterization of the mechanisms involved in high iron induced in neuronal dysfunction and death is central to understanding the pathology of a number of neurodegenerative disorders.

Gestational zinc deficiency affects the regulation of transcription factors AP-1, NF-κB and NFAT in fetal brain

Transcription factors AP-1, nuclear factor κB (NF-κB) and NFAT are central to brain development by regulating the expression of genes that modulate cell proliferation, differentiation, apoptosis and synaptic plasticity. This work investigated the consequences of feeding zinc-deficient and marginal zinc diets to rat dams during gestation on the modulation of AP-1, NF-κB and NFAT in fetal brain. Sprague-Dawley rats were fed from gestation day (GD) 0 a control diet ad libitum (25 μg zinc/g diet, C), a zinc-deficient diet ad libitum (0.5 μg zinc/g diet, ZD), the control diet in the amounts eaten by the ZD rats (restrict fed, RF) or a diet containing a marginal zinc concentration ad libitum (10 μg zinc/g diet, MZD) until GD 19. AP-1-DNA binding was higher (50-190%) in nuclear fraction isolated from ZD, RF and MZD fetal brains compared to controls. In MZD fetal brain, high levels of activation of the upstream mitogen-activated protein kinases JNK and p38 and low levels of ERK phosphorylation were observed. Total levels of NF-κB and NFAT activation were higher or similar in the ZD and MZD groups than in controls, respectively. However, NF-κB- and NFAT-DNA binding in nuclear fractions was markedly lower in ZD and MZD fetal brain than in controls (50-80%). The latter could be related to zinc deficiency-associated alterations of the cytoskeleton, which is required for NF-κB and NFAT nuclear transport. In summary, suboptimal zinc nutrition during gestation could cause long-term effects on brain function, partially through a deregulation of transcription factors AP-1, NF-κB and NFAT.

Zinc: the brain's dark horse

Zinc is a life-sustaining trace element, serving structural, catalytic, and regulatory roles in cellular biology. It is required for normal mammalian brain development and physiology, such that deficiency or excess of zinc has been shown to contribute to alterations in behavior, abnormal central nervous system development, and neurological disease. In this light, it is not surprising that zinc ions have now been shown to play a role in the neuromodulation of synaptic transmission as well as in cortical plasticity. Zinc is stored in specific synaptic vesicles by a class of glutamatergic or "gluzinergic" neurons and is released in an activity-dependent manner. Because gluzinergic neurons are found almost exclusively in the cerebral cortex and limbic structures, zinc may be critical for normal cognitive and emotional functioning. Conversely, direct evidence shows that zinc might be a relatively potent neurotoxin. Neuronal injury secondary to in vivo zinc mobilization and release occurs in several neurological disorders such as Alzheimer's disease and amyotrophic lateral sclerosis, in addition to epilepsy and ischemia. Thus, zinc homeostasis is integral to normal central nervous system functioning, and in fact its role may be underappreciated. This article provides an overview of zinc neurobiology and reviews the experimental evidence that implicates zinc signals in the pathophysiology of neuropsychiatric diseases. A greater understanding of zinc's role in the central nervous system may therefore allow for the development of therapeutic approaches where aberrant metal homeostasis is implicated in disease pathogenesis.

Influence of zinc deficiency on Akt-Mdm2-p53 and Akt-p21 signaling axes in normal and malignant human prostate cells

Phosphorylated Akt (p-Akt), a phosphoinositide-3-OH-kinase-activated protein kinase, is highly expressed in prostate tumors. p-Akt can indirectly hinder p53-dependent growth suppression and apoptosis by phosphorylating Mdm2. Alternatively, p-Akt can directly phosphorylate p21 and restrict it to the cytoplasm for degradation. Because the prostate is the highest zinc-accumulating tissue before the onset of cancer, the effects of physiological levels of zinc on Akt-Mdm2-p53 and Akt-p21 signaling axes in human normal prostate epithelial cells (PrEC) and malignant prostate LNCaP cells were examined in the present study. Cells were cultured for 6 days in low-zinc growth medium supplemented with 0 [zinc-deficient (ZD)], 4 [zinc-normal (ZN)], 16 [zinc-adequate (ZA)], or 32 [zinc-supplemented (ZS)] microM zinc. Zinc status of both cell types was altered in a dose-dependent manner, with LNCaP cells reaching a plateau at >16 microM zinc. For both cell types, p-Akt was higher in the ZD than in the ZN cells and was normalized to that of the ZN cells by treatment with a PI3K inhibitor, LY-294002. PTEN, an endogenous phosphatase targeting Akt dephosphorylation, was hyperphosphorylated (p-PTEN, inactive form) in ZD PrEC. Nuclear p-Mdm2 was raised, whereas nuclear p53 was depressed, by zinc deficiency in PrEC. Nuclear p21 and p53 were lowered by zinc deficiency in LNCaP cells. Higher percentages of ZD, ZA, and ZS than ZN LNCaP cells were found at the G(0)/G(1) phase of the cell cycle, with proportionally lower precentages at the S and G(2)/M phases. Hence, the increased p-PTEN in ZD PrEC would result in hyperphosphorylation of p-Akt and p-Mdm2, as well as reduction of nuclear p53 accumulation. For ZD LNCaP cells, Akt hyperphosphorylation was probably mediated through p21 phosphorylation and degradation, thus restricting p21 nuclear entry to induce cell cycle arrest. Thus zinc deficiency differentially modulated the Akt-Mdm2-p53 signaling axis in normal prostate cells vs. the Akt-p21 signaling axis in malignant prostate cells.

Making it to the synapse: measles virus spread in and among neurons

Measles virus (MV) is one of the most transmissible microorganisms known, continuing to result in extensive morbidity and mortality worldwide. While rare, MV can infect the human central nervous system, triggering fatal CNS diseases weeks to years after exposure. The advent of crucial laboratory tools to dissect MV neuropathogenesis, including permissive transgenic mouse models, the capacity to manipulate the viral genome using reverse genetics, and cell biology advances in understanding the processes that govern intracellular trafficking of viral components, have substantially clarified how MV infects, spreads, and persists in this unique cell population. This review highlights some of these technical advances, followed by a discussion of our present understanding of MV neuronal infection and transport. Because some of these processes may be shared among diverse viruses, comparisons are made to parallel studies with other neurotropic viruses. While a crystallized view of how the unique environment of the neuron affects MV replication, spread, and, ultimately, neuropathogenesis is not fully realized, the tools and ideas are in place for exciting advances in the coming years.

p150/glued modifies nuclear estrogen receptor function

Estrogen modulates gene expression through interactions with estrogen receptors (ERs) that bind chromosomal target genes. Recent studies have suggested an interaction between the cytoskeletal system and estrogen signaling; these have implicated a role of cytoplasmic microtubules in scaffolding ERalpha and enhancing nongenomic function; in addition, other experiments demonstrate that dynein light chain 1 may chaperone ERalpha to the nucleus, indirectly increasing transcriptional potency. Actin/myosin and dynein light chain 1 are also required for estrogen-mediated chromosomal movement that is required for transcriptional up-regulation of ERalpha targets. We present evidence that the dynactin component, p150/glued, directly influences the potency of nuclear ER function. Increasing the stoichiometric ratio of p150/glued and ERalpha by overexpression enhances estrogen responses. ERalpha enhancement by p150/glued does not appear to be influenced by shifts in subcellular localization because microtubule disruption fails to increase nuclear ERalpha. Rather, we find that modest amounts of p150/glued reside in the nucleus of cells, suggesting that it plays a direct role in nuclear transcription. Notably, p150/glued is recruited to the pS2 promoter in the presence of hormone, and, in MCF-7 cells, knockdown of p150/glued levels reduces estrogen-dependent transcription. Our results suggest that p150/glued modulates estrogen sensitivity in cells through nuclear mechanisms.

Stimulated nuclear translocation of NF-kappaB and shuttling differentially depend on dynein and the dynactin complex

Translocation from the cytoplasm to the nucleus is required for the regulation of gene expression by transcription factors of the nuclear factor kappa B (NF-kappaB) family. The p65:p50 NF-kappaB heterodimer that predominates in many cell types can undergo stimulated movement, following degradation of the IkappaB inhibitor, as well as shuttling in the absence of stimulation with IkappaB bound. Disruption of the dynactin complex and knockdown of endogenous dynein were used to investigate the nuclear translocation requirements for stimulated and shuttling movement of NF-kappaB. A differential dependence of these two modes of transport on the dynein molecular motor and dynactin was found. NF-kappaB used active dynein-dependent transport following stimulation while translocation during shuttling was mediated by a dynein-independent pathway that could be potentiated by dynactin disruption, consistent with a process of facilitated diffusion. Nuclear translocation and activation of NF-kappaB-dependent gene expression showed a dependence on endogenous dynein in a variety of cell types and in response to diverse activating stimuli, suggesting that dynein-dependent transport of NF-kappaB may be a conserved mechanism in the NF-kappaB activation pathway and could represent a potential point of regulation.

Actin-targeting natural compounds as tools to study the role of actin cytoskeleton in signal transduction

Actin cytoskeleton controls a vast range of cellular processes such as motility, cytokinesis, differentiation, vesicle transport, phagocytosis, muscle contraction. A growing literature clearly demonstrated that actin cytoskeleton can play a regulating role in several signalling pathways. Cells tightly regulate actin dynamics through numerous specific proteins in order to rapidly and locally respond to various stimuli. An obvious approach to determine the involvement of actin cytoskeleton in signalling pathways is the use of actin-targeting natural compounds. These drugs modulate actin dynamics, accelerating either polymerization or depolymerization, through various mechanisms. This review focus on the use of these actin-targeting drugs as tools to demonstrate the role of actin cytoskeleton in several signal transduction pathways such as those initiated from antigen receptor in T and B cells or those involving mitogen-activated protein kinases (MAPKs) or transcription factors NF-kappaB and SRF (serum response factor). In this last case (SRF), the use of various actin-targeting drugs participated in the elucidation of the molecular mechanism by which actin regulates SRF-mediated transcription.