Nuclear Nox4-derived reactive oxygen species in myelodysplastic syndromes

A role for intracellular ROS production has been recently implicated in the pathogenesis and progression of a wide variety of neoplasias. ROS sources, such as NAD(P)H oxidase (Nox) complexes, are frequently activated in AML (acute myeloid leukemia) blasts and strongly contribute to their proliferation, survival, and drug resistance. Myelodysplastic syndromes (MDS) comprise a heterogeneous group of disorders characterized by ineffective hematopoiesis, with an increased propensity to develop AML. The molecular basis for MDS progression is unknown, but a key element in MDS disease progression is the genomic instability. NADPH oxidases are now recognized to have specific subcellular localizations, this targeting to specific compartments for localized ROS production. Local Nox-dependent ROS production in the nucleus may contribute to the regulation of redox-dependent cell growth, differentiation, senescence, DNA damage, and apoptosis. We observed that Nox1, 2, and 4 isoforms and p22phox and Rac1 subunits are expressed in MDS/AML cell lines and MDS samples, also in the nuclear fractions. Interestingly, Nox4 interacts with ERK and Akt1 within nuclear speckle domain, suggesting that Nox4 could be involved in regulating gene expression and splicing factor activity. These data contribute to the elucidation of the molecular mechanisms used by nuclear ROS to drive MDS evolution to AML

Specific ablation of phospholipase Cγ1 in forebrain causes manic-like behavior

It is well known that manic episodes are one of the major diagnostic symptoms in a spectrum of neuropsychiatric disorders that include schizophrenia, obsessive-compulsive disorder and bipolar disorder (BD). Despite a possible association between BD and the gene encoding phospholipase Cγ1 (PLCG1), its etiological basis remains unclear. Here, we report that mice lacking phospholipase Cγ1 (PLCγ1) in the forebrain (Plcg1f/f; CaMKII) exhibit hyperactivity, decreased anxiety-like behavior, reduced depressive-related behavior, hyperhedonia, hyperphagia, impaired learning and memory and exaggerated startle responses. Inhibitory transmission in hippocampal pyramidal neurons and striatal dopamine receptor D1-expressing neurons of Plcg1-deficient mice was significantly reduced. The decrease in inhibitory transmission is likely due to a reduced number of γ-aminobutyric acid (GABA)-ergic boutons, which may result from impaired localization and/or stabilization of postsynaptic CaMKII (Ca2+/calmodulin-dependent protein kinase II) at inhibitory synapses. Moreover, mutant mice display impaired brain-derived neurotrophic factor-tropomyosin receptor kinase B-dependent synaptic plasticity in the hippocampus, which could account for deficits of spatial memory. Lithium and valproate, the drugs presently used to treat mania associated with BD, rescued the hyperactive phenotypes of Plcg1f/f; CaMKII mice. These findings provide evidence that PLCγ1 is critical for synaptic function and plasticity and that the loss of PLCγ1 from the forebrain results in manic-like behavior

Epigenetic Regulation of Nuclear PI-PLC beta1 Signalling Pathway in Low-Risk MDS Patients During Azacitidine Treatment

Myelodysplastic syndromes (MDS) are a heterogeneous group of hematological malignancies characterized by epigenetic abnormalities and therefore treated with demethylating agents [1]. PI-PLCbeta1 has been reported to be a specific target for demethylating therapy in high-risk MDS patients, since azacitidine treatment can be associated with a PI-PLCbeta1 specific promoter demethylation and induction of both PI-PLCbeta1 gene and protein expression [1]. In the present study we investigated the role of epigenetic regulation of PI-PLCbeta1, mainly focusing on the functional role of azacitidine on the structure of the PI-PLCbeta1 promoter. We firstly examined the effect of azacitidine on PI-PLCbeta1 promoter methylation and gene expression in low-risk MDS. Moreover, we studied the expression of key molecules involved in the nuclear inositide signalling pathway, such as Cyclin D3. We also studied the correlation between the demethylating effect of azacitidine and the degree of recruitment to PI-PLCbeta1 promoter of some transcription factors implicated in hematopoietic stem cell proliferation and differentiation, as well as of the Methyl-CpG binding domain proteins (MBDs), which specifically interact with methylated DNA. Taken together, our results hint at a specific involvement of PI-PLCbeta1 in epigenetic mechanisms, and are particularly consistent with the hypothesis of a role for PI-PLCbeta1 in azacitidine- induced myeloid differentiation

A novel DAG-dependent mechanism links PKCα and cyclin B1 regulating the G2/M progression of cell cycle

Protein kinase C α has been reported to regulate cell cycle in several cell lines. Most of the reports describe a role for PKC α in G1/S transition but little is known about its possible involvement in G2/M progression. Our studies on the effects of PKC inhibitors, PKC α silencing and overexpression demonstrated a novel and positive role for PKC α in cyclin B1 regulation in human erythroleukemia cell line, K562. On the other hand, using PKC inhibitors and a PKC α inactive mutant, we could report that PKC α activity was not necessary for cyclin B1 regulation. Moreover, immunoprecipitation and immunocytochemistry experiments showed that these two proteins could physically interact each other and enter into the nuclei during G2/M progression. In order to better understand this mechanism, we investigated how PKC α could be attracted into the nuclei. We found a high increase of nuclear DAG during the G2/M phase. Then, using PMA and PLC inhibitors, we showed that PKC α translocation was due to the increase in nuclear DAG. Surprisingly, we saw the same effect on cyclin B1. Finally, in order to discover which PLC was involved, we silenced the nuclear localized PLCβ1 founding a decrease in PKC α and cyclin B1 nuclear amount. Taken together, our data demonstrate the existence of a novel DAG dependent mechanism linking PKC α and cyclin B1 which can regulate their entry into the nuclei during the G2/M phase of cell cycle

Nuclear phospholipase C β1 signaling, epigenetics and treatments in MDS.

Myelodysplastic syndromes (MDS), clonal hematopoietic stem-cell disorders mainly affecting older adult patients, show ineffective hematopoiesis in one or more of the lineages of the bone marrow. Most MDS are characterized by anemia, and a number of cases progresses to acute myeloid leukemia (AML). Indeed, the molecular mechanisms underlying the MDS evolution to AML are still unclear, even though the nuclear signaling elicited by PI-PLCβ1 has been demonstrated to play an important role in the control of the balance between cell cycle progression and apoptosis in MDS cells. Here we review both the role of epigenetic therapy on PI-PLCβ1 promoter and the changes in PI-PLCβ1 expression in MDS patients treated for anemia.Myelodysplastic syndromes (MDS), clonal hematopoietic stem-cell disorders mainly affecting older adult patients, show ineffective hematopoiesis in one or more of the lineages of the bone marrow. Most MDS are characterized by anemia, and a number of cases progresses to acute myeloid leukemia (AML). Indeed, the molecular mechanisms underlying the MDS evolution to AML are still unclear, even though the nuclear signaling elicited by PI-PLCβ1 has been demonstrated to play an important role in the control of the balance between cell cycle progression and apoptosis in MDS cells. Here we review both the role of epigenetic therapy on PI-PLCβ1 promoter and the changes in PI-PLCβ1 expression in MDS patients treated for anemia. © 2012 Elsevier Ltd

Nuclear Nox4 Interaction with Prelamin A is Associated with Nuclear Redox Control of Stem Cell Aging

Mesenchymal stem cells have emerged as an important tool that can be used for tissue regeneration thanks to their easy preparation, differentiation potential and immunomodulatory activity. However, an extensive culture of stem cells in vitro prior to clinical use can lead to oxidative stress that can modulate different stem cells properties, such as self-renewal, proliferation, differentiation and senescence. The aim of this study was to investigate the aging process occurring during in vitro expansion of stem cells, obtained from amniotic fluids (AFSC) at similar gestational age. The analysis of 21 AFSC samples allowed to classify them in groups with different levels of stemness properties. In summary, the expression of pluripotency genes and the proliferation rate were inversely correlated with the content of reactive oxygen species (ROS), DNA damage signs and the onset premature aging markers, including accumulation of prelamin A, the lamin A immature form. Interestingly, a specific source of ROS, the NADPH oxidase isoform 4 (Nox4), can localize into PML nuclear bodies (PML-NB), where it associates to prelamin A. Besides, Nox4 post translational modification, involved in PML-NB localization, is linked to its degradation pathway, as it is also for prelamin A, thus possibly modulating the premature aging phenotype occurrence

Differential activation of nuclear inositide-dependent signalling pathways during erythropoiesis and myelopoiesis induced by lenalidomide and azacitidine in myelodysplastic syndromes (MDS)

Inositide-dependent signalling pathways regulated by phosphoinositide-specific phospholi- pase C (PI-PLC) beta1 have been demonstrated to play important roles in MDS pathogenesis and in cell differentiation (1). Moreover, the MDS therapy aims at inducing myeloid and/or erythroid differentiation of MDS stem cells. Indeed, azacitidine is a demethylating agent that can induce myeloid differentiation. On the other hand, lenalidomide may restore a normal erythropoiesis. The exact molecular mechanisms underlying the effect of azacitidine and lenalidomide in MDS cells are still unclear, although it is clear that these therapies regulate stem cell proliferation, differentiation and apoptosis (2). The combination of azacitidine and lenalidomide in MDS therapy is now under considera- tion, given the capability of both drugs to balance proliferation and differentiation processes (3). In this study we analyzed the molecular effect of this combination therapy on PI-PLC isoenzymes, not only studying PI-PLCbeta1, but also PI-PLCgamma1, that can be associated with erythropoiesis. We analyzed 44 patients diagnosed with high-risk MDS who were given azacitidine and lenalidomide. Given the limited number of cells, we quantified the expression of these molecules by Real-Time PCR analyses and immunocytochemical experiments. Moreover, we carried out cell cycle analyses and studied both PI-PLCbeta1 methylation status and the expression of Globin genes. In our case series, 28/44 patients were evaluable, with an overall response rate of 78.6% (22/28 cases). At a molecular level, a significant increase of PI-PLCbeta1 and/or PI-PLCgamma1 expression was associated with a favourable clinical response to the combination therapy. Responder cases also showed an increase of Beta-globin expression, hinting at a specific contri- bution of lenalidomide on erythroid activation, whilst the frequent demethylation of PI-PLCbeta1 promoter could be specifically linked to azacitidine. Taken together, our results show that the combination of azacitidine and lenalidomide can be important for activating PI-PLC isoenzymes, therefore regulating myeloid and erythroid dif- ferentiation in MDS cells

Nuclear Phosphoinositides as Key Determinants of Nuclear Functions

Polyphosphoinositides (PPIns) are signalling messengers representing less than five per cent of the total phospholipid concentration within the cell. Despite their low concentration, these lipids are critical regulators of various cellular processes, including cell cycle, differentiation, gene transcription, apoptosis and motility. PPIns are generated by the phosphorylation of the inositol head group of phosphatidylinositol (PtdIns). Different pools of PPIns are found at distinct subcellular compartments, which are regulated by an array of kinases, phosphatases and phospholipases. Six of the seven PPIns species have been found in the nucleus, including the nuclear envelope, the nucleoplasm and the nucleolus. The identification and characterisation of PPIns interactor and effector proteins in the nucleus have led to increasing interest in the role of PPIns in nuclear signalling. However, the regulation and functions of PPIns in the nucleus are complex and are still being elucidated. This review summarises our current understanding of the localisation, biogenesis and physiological functions of the different PPIns species in the nucleus

Response of high-risk MDS to azacitidine and lenalidomide is impacted by baseline and acquired mutations in a cluster of three inositide-specific genes

Specific myeloid-related and inositide-specific gene mutations can be linked to myelodysplastic syndromes (MDS) pathogenesis and therapy. Here, 44 higher-risk MDS patients were treated with azacitidine and lenalidomide and mutations analyses were performed at baseline and during the therapy. Results were then correlated to clinical outcome, overall survival (OS), leukemia-free-survival (LFS) and response to therapy. Collectively, 34/44 patients were considered evaluable for response, with an overall response rate of 76.25% (26/34 cases): 17 patients showed a durable response, 9 patients early lost response and 8 patients never responded. The most frequently mutated genes were ASXL1, TET2, RUNX1, and SRSF2. All patients early losing response, as well as cases never responding, acquired the same 3 point mutations during therapy, affecting respectively PIK3CD (D133E), AKT3 (D280G), and PLCG2 (Q548R) genes, that regulate cell proliferation and differentiation. Moreover, Kaplan–Meier analyses revealed that this mutated cluster was significantly associated with a shorter OS, LFS, and duration of response. All in all, a common mutated cluster affecting 3 inositide-specific genes is significantly associated with loss of response to azacitidine and lenalidomide therapy in higher risk MDS. Further studies are warranted to confirm these data and to further analyze the functional role of this 3-gene cluster