The Dkk3 gene encodes a vital intracellular regulator of cell proliferation

Members of the Dickkopf (Dkk) family of Wnt antagonists interrupt Wnt-induced receptor assembly and participate in axial patterning and cell fate determination. One family member, DKK3, does not block Wnt receptor activation. Loss of Dkk3 expression in cancer is associated with hyperproliferation and dysregulated ss-catenin signaling, and ectopic expression of Dkk3 halts cancer growth. The molecular events mediating the DKK3-dependent arrest of ss-catenin-driven cell proliferation in cancer cells are unknown. Here we report the identification of a new intracellular gene product originating from the Dkk3 locus. This Dkk3b transcript originates from a second transcriptional start site located in intron 2 of the Dkk3 gene. It is essential for early mouse development and is a newly recognized regulator of ss-catenin signaling and cell proliferation. Dkk3b interrupts nuclear translocation ss-catenin by capturing cytoplasmic, unphosphorylated ss-catenin in an extra-nuclear complex with ss-TrCP. These data reveal a new regulator of one of the most studied signal transduction pathways in metazoans and provides a novel, completely untapped therapeutic target for silencing the aberrant ss-catenin signaling that drives hyperproliferation in many cancers

Teriflunomide treatment for multiple sclerosis modulates T cell mitochondrial respiration with affinity-dependent effects

International audienceInterference with immune cell proliferation represents a successful treatment strategy in T cell-mediated autoimmune diseases such as rheumatoid arthritis and multiple sclerosis (MS). One prominent example is pharmacological inhibition of dihydroorotate dehydrogenase (DHODH), which mediates de novo pyrimidine synthesis in actively proliferating T and B lymphocytes. Within the TERIDYNAMIC clinical study, we observed that the DHODH inhibitor teriflunomide caused selective changes in T cell subset composition and T cell receptor repertoire diversity in patients with relapsing-remitting MS (RRMS). In a preclinical antigen-specific setup, DHODH inhibition preferentially suppressed the proliferation of high-affinity T cells. Mechanistically, DHODH inhibition interferes with oxidative phosphorylation (OXPHOS) and aerobic glycolysis in activated T cells via functional inhibition of complex III of the respiratory chain. The affinity-dependent effects of DHODH inhibition were closely linked to differences in T cell metabolism. High-affinity T cells preferentially use OXPHOS during early activation, which explains their increased susceptibility toward DHODH inhibition. In a mouse model of MS, DHODH inhibitory treatment resulted in preferential inhibition of high-affinity autoreactive T cell clones. Compared to T cells from healthy controls, T cells from patients with RRMS exhibited increased OXPHOS and glycolysis, which were reduced with teriflunomide treatment. Together, these data point to a mechanism of action where DHODH inhibition corrects metabolic disturbances in T cells, which primarily affects profoundly metabolically active high-affinity T cell clones. Hence, DHODH inhibition may promote recovery of an altered T cell receptor repertoire in autoimmunity

K(2P)18.1 translates T cell receptor signals into thymic regulatory T cell development

It remains largely unclear how thymocytes translate relative differences in T cell receptor (TCR) signal strength into distinct developmental programs that drive the cell fate decisions towards conventional (Tconv) or regulatory T cells (Treg). Following TCR activation, intracellular calcium (Ca2+) is the most important second messenger, for which the potassium channel K(2P)18.1 is a relevant regulator. Here, we identify K(2P)18.1 as a central translator of the TCR signal into the thymus-derived Treg (tTreg) selection process. TCR signal was coupled to NF-kappa B-mediated K(2P)18.1 upregulation in tTreg progenitors. K(2P)18.1 provided the driving force for sustained Ca2+ influx that facilitated NF-kappa B- and NFAT-dependent expression of FoxP3, the master transcription factor for Treg development and function. Loss of K(2P)18.1 ion-current function induced a mild lymphoproliferative phenotype in mice, with reduced Treg numbers that led to aggravated experimental autoimmune encephalomyelitis, while a gain-of-function mutation in K(2P)18.1 resulted in increased Treg numbers in mice. Our findings in human thymus, recent thymic emigrants and multiple sclerosis patients with a dominant-negative missense K(2P)18.1 variant that is associated with poor clinical outcomes indicate that K(2P)18.1 also plays a role in human Treg development. Pharmacological modulation of K(2P)18.1 specifically modulated Treg numbers in vitro and in vivo. Finally, we identified nitroxoline as a K(2P)18.1 activator that led to rapid and reversible Treg increase in patients with urinary tract infections. Conclusively, our findings reveal how K(2P)18.1 translates TCR signals into thymic T cell fate decisions and Treg development, and provide a basis for the therapeutic utilization of Treg in several human disorders.Peer reviewe

Preventive and curative effect of melatonin on mammary carcinogenesis induced by dimethylbenz[a]anthracene in the female Sprague–Dawley rat

INTRODUCTION: It has been well documented that the pineal hormone, melatonin, which plays a major role in the control of reproduction in mammals, also plays a role in the incidence and growth of breast and mammary cancer. The curative effect of melatonin on the growth of dimethylbenz [a]anthracene-induced (DMBA-induced) mammary adenocarcinoma (ADK) has been previously well documented in the female Sprague–Dawley rat. However, the preventive effect of melatonin in limiting the frequency of cancer initiation has not been well documented. METHODS: The aim of this study was to compare the potency of melatonin to limit the frequency of mammary cancer initiation with its potency to inhibit tumor progression once initiation, at 55 days of age, was achieved. The present study compared the effect of preventive treatment with melatonin (10 mg/kg daily) administered for only 15 days before the administration of DMBA with the effect of long-term (6-month) curative treatment with the same dose of melatonin starting the day after DMBA administration. The rats were followed up for a year after the administration of the DMBA. RESULTS: The results clearly showed almost identical preventive and curative effects of melatonin on the growth of DMBA-induced mammary ADK. Many hypotheses have been proposed to explain the inhibitory effects of melatonin. However, the mechanisms responsible for its strong preventive effect are still a matter of debate. At least, it can be envisaged that the artificial amplification of the intensity of the circadian rhythm of melatonin could markedly reduce the DNA damage provoked by DMBA and therefore the frequency of cancer initiation. CONCLUSION: In view of the present results, obtained in the female Sprague–Dawley rat, it can be envisaged that the long-term inhibition of mammary ADK promotion by a brief, preventive treatment with melatonin could also reduce the risk of breast cancer induced in women by unidentified environmental factors

A comprehensive analysis of coherent rainfall patterns in China and potential drivers. Part II: intraseasonal variability

The causes of subseasonal precipitation variability in China are investigated using observations and reanalysis data for extended winter (November–April) and summer (May–October) seasons from 1982 to 2007. For each season, the three dominant regions of coherent intraseasonal variability are identified with Empirical Orthogonal Teleconnection (EOT) analysis. While previous studies have focused on particular causes for precipitation variability or on specific regions, here a comprehensive analysis is carried out with an objective method. Furthermore, the associated rainfall anomaly timeseries are tied to specific locations in China, which facilitates their interpretation. To understand the underlying processes associated with spatially coherent patterns of rainfall variability, fields from observations and reanalysis are regressed onto EOT timeseries. The three dominant patterns in winter together explain 43% of the total space–time variance and have their origins in midlatitude disturbances that appear two pentads in advance. Winter precipitation variability along the Yangtze River is associated with wave trains originating over the Atlantic and northern Europe, while precipitation variability in southeast China is connected to the Mediterranean storm track. In summer, all patterns have a strong relationship with the Boreal Summer Intraseasonal Oscillation and are modulated by the seasonal cycle of the East Asian summer monsoon. The wet and dry phases of the regional patterns can substantially modulate the frequency of daily rainfall across China. The discovered links between weather patterns, precursors, and effects on local and remote precipitation may provide a valuable basis for hydrological risk assessments and the evaluation of numerical weather prediction models

GABAB receptor signalling of OPCs attenuates a brust of OPC proliferation and oligodendrocyte formation at the onset of chronic TLE

Epilepsy is a neurological disorder characterized by hyperexcitability of neuronal circuits, manifesting in recurrent seizures. Despite the abundance of anti-epileptic drugs available, targeting neurons, as many as 30% of patients cannot achieve a seizure free state. Several studies suggest that the balance between excitatory and inhibitory neurotransmission (E/I balance) is disturbed in the epileptic brain, favouring excitation. Uniquely among glia cells, oligodendrocyte progenitor cells (OPCs) form synaptic connections with inhibitory as well as excitatory neurons making them promising candidates as potential novel targets of research. Through pairing, they even form close anatomical and functional relationships with interneurons and mirror their electrical activity. A recent study from our group demonstrates, that GABAB receptor (GABABR) mediated OPC-interneuron communication is crucial for determining interneuronal density and function during early development, thereby regulating E/I balance under healthy conditions. Moreover, in several epileptic paradigms OPCs have been shown to react to the induction of recurrent seizures. Therefore, the central aim of this study is to investigate the role of OPC-GABABR signaling in regulating the response of OPCs and interneurons following hyperexcit able network dysfunction in epilepsy. We induced epileptic condition in transgenic mice carrying OPC-specific GABABR cKO by em ploying the mouse model of temporal lobe epilepsy by intracortical kainate injections. Immuno histochemistry was performed in the acute phase directly following status epilepticus, as well as one week later at the onset of the chronic phase and two weeks later during the early chronic phase. Our results demonstrated that GABABR signaling on OPCs impedes a transient burst of OPC proliferation and oligodendrocyte formation at the cortical epileptic lesion at the onset of the chronic phase. While OPC proliferation und density only peaks transiently in OPC-GABABR cKO mice, the density of oligodendrocytes at the cortical lesion remains elevated during the early chronic phase. Therefore, we hypothesize that reduction of GABABR signaling might be beneficial in attenuating myelin damage observed during the chronic phase of epileptogenesis. Furthermore, we show that interneuronal susceptibility to excitotoxicity in GABABR cKO mice is reduced. While the contralateral cortex of control mice was slowly depleted of interneurons as epileptogenesis progressed, interneuronal density at the contralateral cortex was preserved in GABABR cKO mice. Therefore, reduction of GABABR activation of OPCs could potentially attenuate severity of epilepsy by preventing myelin damage and curtailing loss of inhibitory neurotransmission during the chronic phaseEpilepsie ist eine Erkrankung, welche durch Übererregbarkeit neuronaler Netzwerke gekennzeichnet ist und sich in wiederkehrenden Krampfanfällen manifestiert. Trotz der Vielzahl zu Verfügung stehender auf Neuronen wirkenden Antiepileptika, erreichen 30% der Patienten keine Anfallsfreiheit. Etliche Studien schlagen vor, dass das Gleichgewicht zwischen inhibitorischer und exzitatorischer Neurotransmission im epileptischen Gehirn zugunsten der Exzitation verschoben ist. Oligodendrozyten Vorläuferzellen (OPCs) besitzen die Eigenschaft, synaptische Verbindungen mit exzitatorischen sowie inhibitorischen Neuronen einzugehen. Sie gehen enge anatomische und funktionelle Verbindungen mit Interneuronen ein und spiegeln deren elektrische Aktivität wider. Eine kürzlich publizierte Studie unserer Arbeitsgruppe zeigt, dass GABAB Rezeptor (GABABR) vermittelte OPC-InterneuronKommunikation die Dichte und Funktion von Interneuronen und dadurch das Gleichgewicht von Exzitation und Inhibition entscheidend beeinflusst. In zahlreichen Epilepsiemodellen zeigte sich ein Einfluss von wiederkehrenden Krampfanfällen auf OPCs. Das zentrale Ziel dieser Arbeit ist daher, den Einfluss von OPC-GABABR vermittelter Signalübertragung auf die Dynamik von OPCs und Interneuronen im übererregbaren epileptischen Gehirn zu erforschen. Durch intrakortikale Kainate-Injektionen induzierten wir epileptische Bedingungen im Gehirn von transgenen Mäusen, welche Träger eines OPC-spezifischen cKOs des GABABRs sind. Immunohistochemie wurde unmittelbar nach Status epilepticus (akute Phase), sowie eine Woche später (Beginn der chronischen Phase) und zwei Wochen später (chronische Phase) durchgeführt. Unsere Ergebnisse zeigen, dass OPC-GABABR abhängige Signalübertragung zu Beginn der chronischen Phase einen vorübergehenden Schub von OPC-Proliferation und Oligodendrozytenbildung an der kortikalen epileptischen Läsion verhindert. Während die Dichte und Proliferation von OPCs in OPC-GABABR cKO-Mäusen nur kurzzeitig erhöht ist, bleibt die Dichte von Oligodendrozyten auch noch in der frühen chronischen Phase erhöht. Daher liegt die Vermutung nahe, dass eine Reduktion von OPC-GABABR abhängiger Signalübertragung die Ausprägung von Myelinschäden wie sie in der chronischen Phase beobachtet wurden, günstig beeinflussen könnte. Des Weiteren demonstrieren wir eoine reduzierte Anfälligkeit von Interneuronen für Exzitotoxizität in OPC-GABABR cKO Mäusen. Während die interneuronale Dichte im kontralateralen Kortex von Mäusen der Kontrollgruppe mit Fortschreiten der Erkrankung langsam abnahm, blieb die Dichte von Interneuronen im kontralateralen Kortex der cKO-Mäuse unbeeinträchtigt. Deswegen könnte eine Reduktion der OPC-GABABR abhängigen Signalübertragung den Verlauf von epileptischen Erkrankungen durch Verringerung von Myelinschäden und Erhalt der inhibitorischen Neurotransmission mildern

Activation of FXR pathway does not alter glial cell function

Abstract Background The nuclear receptor farnesoid-X-receptor (FXR; NR1H4) is expressed not only in the liver, gut, kidney and adipose tissue but also in the immune cells. FXR has been shown to confer protection in several animal models of inflammation, including experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). FXR agonists are currently tested in clinical trials for treatment of human metabolic diseases. The beneficial effect of FXR agonists in EAE suggests that FXR might represent a potential target in inflammatory-demyelinating CNS diseases, such as MS. In MS, oligodendrocytes not only undergo cell death but also contribute to remyelination. This repair mechanism is impaired due to a differentiation block of oligodendroglial progenitor cells. Activation of other nuclear receptors that heterodimerize with FXR promote oligodendroglial differentiation. Therefore, we wanted to address the functional relevance of FXR for glial cells, especially for oligodendroglial differentiation. Methods We isolated primary murine oligodendrocytes from FXR-deficient (FXR Ko) and wild-type (WT) mice and determined the effect of FXR deficiency and activation on oligodendroglial differentiation by analysing markers of oligodendroglial progenitor cells (OPCs) and mature oligodendrocytes (OLs) using qRT-PCR and immunocytochemistry. Additionally, we determined whether FXR activation modulates the pro-inflammatory profile of astrocytes or microglia and whether this may subsequently modulate oligodendroglial differentiation. These in vitro studies were complemented by histological analyses of oligodendrocytes in FXR Ko mice. Results FXR is expressed by OPCs and mature oligodendrocytes. However, lack of FXR did not affect oligodendroglial differentiation in vitro or in vivo. Furthermore, activation of FXR using the synthetic agonist GW4064 did not affect oligodendroglial differentiation, remyelination in an ex vivo model or the expression of pro-inflammatory molecules in astrocytes or microglia. Concordantly, no effects of supernatants from macrophages cultured in the presence of GW4064 were observed regarding a possible indirect impact on oligodendroglial differentiation. Conclusions Our data suggest that FXR is dispensable for oligodendroglial differentiation and that FXR agonists, such as GW4064, represent a potential therapeutic approach for MS which specifically targets peripheral immune cells including macrophages but not brain-resident cells, such as oligodendrocytes, astrocytes or microglia

High Metabolic Dependence on Oxidative Phosphorylation Drives Sensitivity to Metformin Treatment in MLL/AF9 Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a group of hematological cancers with metabolic heterogeneity. Oxidative phosphorylation (OXPHOS) has been reported to play an important role in the function of leukemic stem cells and chemotherapy-resistant cells and are associated with inferior prognosis in AML patients. However, the relationship between metabolic phenotype and genetic mutations are yet to be explored. In the present study, we demonstrate that AML cell lines have high metabolic heterogeneity, and AML cells with MLL/AF9 have upregulated mitochondrial activity and mainly depend on OXPHOS for energy production. Furthermore, we show that metformin repressed the proliferation of MLL/AF9 AML cells by inhibiting mitochondrial respiration. Together, this study demonstrates that AML cells with an MLL/AF9 genotype have a high dependency on OXPHOS and could be therapeutically targeted by metformin