Flora Brozzi - Academia.edu (original) (raw)

Papers by Flora Brozzi

Diabetologia, Jan 23, 2015

Proinflammatory cytokines contribute to beta cell damage in type 1 diabetes in part through activ... more Proinflammatory cytokines contribute to beta cell damage in type 1 diabetes in part through activation of endoplasmic reticulum (ER) stress. In rat beta cells, cytokine-induced ER stress involves NO production and consequent inhibition of the ER Ca(2+) transporting ATPase sarco/endoplasmic reticulum Ca(2+) pump 2 (SERCA2B). However, the mechanisms by which cytokines induce ER stress and apoptosis in mouse and human pancreatic beta cells remain unclear. The purpose of this study is to elucidate the role of ER stress on cytokine-induced beta cell apoptosis in these three species and thus solve ongoing controversies in the field. Rat and mouse insulin-producing cells, human pancreatic islets and human EndoC-βH1 cells were exposed to the cytokines IL-1β, TNF-α and IFN-γ, with or without NO inhibition. A global comparison of cytokine-modulated gene expression in human, mouse and rat beta cells was also performed. The chemical chaperone tauroursodeoxycholic acid (TUDCA) and suppression of...

Cell death & disease, 2013

We have recently shown that the crosstalk between mild endoplasmic reticulum (ER) stress and low ... more We have recently shown that the crosstalk between mild endoplasmic reticulum (ER) stress and low concentrations of the pro-inflammatory cytokine interleukin (IL)-1β exacerbates beta cell inflammatory responses via the IRE1α/XBP1 pathway. We presently investigated whether mild ER stress also sensitizes beta cells to cytokine-induced apoptosis. Cyclopiazonic acid (CPA)-induced ER stress enhanced the IL-1β apoptosis in INS-1E and primary rat beta cells. This was not prevented by XBP1 knockdown (KD), indicating the dissociation between the pathways leading to inflammation and cell death. Analysis of the role of pro- and anti-apoptotic proteins in cytokine-induced apoptosis indicated a central role for the pro-apoptotic BH3 (Bcl-2 homology 3)-only protein Bim (Bcl-2-interacting mediator of cell death), which was counteracted by four anti-apoptotic Bcl-2 (B-cell lymphoma-2) proteins, namely Bcl-2, Bcl-XL, Mcl-1 and A1. CPA+IL-1β-induced beta cell apoptosis was accompanied by increased exp...

† These authors contributed equally to the work. The brain-spliced isoform of Myosin Va (BR-MyoVa... more † These authors contributed equally to the work. The brain-spliced isoform of Myosin Va (BR-MyoVa) plays an important role in the transport of dense core secretory granules (SGs) to the plasma membrane in hormone and neuropeptide-producing cells. The molecular composition of the protein complex that recruits BR-MyoVa to SGs and regulates its function has not been identified to date.

Italian Journal of …, 2010

The Ca 2+ binding protein of the EFhand type, S100B, is an intracellular regulator and an extra c... more The Ca 2+ binding protein of the EFhand type, S100B, is an intracellular regulator and an extra cellular signal. Within cells S100B interacts with several proteins thereby regulating energy metabolism, Ca 2+ homeostasis, protein phosphorylation and degradation, and cell locomotion, proliferation and differentiation. Once secreted/released, S100B exerts autocrine and paracrine effects on responsive cells by engaging the receptor for advanced glycation end products. How ever, recent evidence suggests that S100B might also activate basic fi broblast growth factor receptor 1 via prior binding to basic fi broblast growth factor.

Journal of Biological Chemistry, 2014

Background: Cytokine-induced IRE1␣ activation regulates adaptive/pro-apoptotic endoplasmic reticu... more Background: Cytokine-induced IRE1␣ activation regulates adaptive/pro-apoptotic endoplasmic reticulum (ER) stress transition in type 1 diabetes (T1D). Results: The IRE1␣-binding protein NMI modulates JNK activation and apoptosis in beta cells. Conclusion: NMI induction is a novel negative feedback mechanism regulating ER stress and apoptosis in cytokine-exposed beta cells. Significance: Clarifying cytokine modulation of ER stress may provide information to protect beta cells in early T1D.

Type 1 diabetes (T1D) is an autoimmune disease with a strong inflammatory component. The cytokine... more Type 1 diabetes (T1D) is an autoimmune disease with a strong inflammatory component. The cytokines interleukin-1β and interferon-γ contribute to beta cell apoptosis in T1D. These cytokines induce endoplasmic reticulum stress and the unfolded protein response (UPR), contributing to loss of beta cells. IRE1α, one of the UPR mediators, triggers insulin degradation and inflammation in beta cells and is critical for the transition from ″physiological″ to ″pathological″ UPR. The mechanisms regulating IRE1α activation, and its signalling for beta cell ″adaptation″, ″stress response″ or ″apoptosis″ remain to be clarified. To address these questions we combined MAPPIT (MAmmalian Protein-Protein Interaction Trap)-based IRE1α interactome and functional genomic analysis of human and rodent beta cells exposed to pro-inflammatory cytokines to identify novel cytokine-induced regulators of IRE1α. Based on this approach, we identified N-myc interactor (NMI) as an IRE1α-interacting/modulator protein ...

Traffic, 2012

Oncology Reports, 2006

The challenging possibility of selectively inducing mitotic death in tumor cells by combining gen... more The challenging possibility of selectively inducing mitotic death in tumor cells by combining genotoxic agents with the inhibition of G2 checkpoints of the cell cycle is the subject of intensive investigation. We show that very low concentrations (3.5 and 5 nM) of okadaic acid induce mitotic death in two glioblastoma cell lines, in the absence of genotoxic agents. At the concentrations used, the main target of okadaic acid action is protein phosphatase 2A (PP2A), an enzyme deeply involved in the negative control of cell-cycle progression. The peculiar susceptibility of glioblastoma cells to induction of mitotic death by very low concentrations of okadaic acid must be related to an impairment of PP2A activity and to a specific deficiency in some cell-cycle checkpoints. In addition to its ability to induce abnormal mitoses in actively proliferating glioblastoma cells, okadaic acid possesses the ability to force semi-confluent glioblastoma cells to the M phase of the cell cycle, where they show the same abnormalities observed in actively proliferating glioblastoma cells. In semiconfluent cells the induction of mitotic death involves the activity of both the extracellular signal regulated kinases (ERKs) and the M-phase promoting factor: okadaic acid overstimulates ERK activity, and PD98059 (inhibitor of ERK activation) as well as roscovitine (S)-isomer (specific inhibitor of M-phase promoting factor activity) counteract the induction of mitotic death. Our results show that, without the use of genotoxic agents, it is possible to induce mitotic death in glioblastoma cells by activating the same uncontrolled pathways responsible for the uncontrolled proliferation.

Diabetologia, 2011

Aims/hypothesis This study used proteomics and biochemical approaches to identify novel glucose-r... more Aims/hypothesis This study used proteomics and biochemical approaches to identify novel glucose-regulated proteins and to unveil their role in pancreatic beta cell function. Translationally controlled tumour protein (TCTP) was identified to be one such protein, and further investigations into its function and regulation were carried out. Methods Global protein profiling of beta cell homogenates following glucose stimulation was performed using twodimensional gel electrophoresis. Proteins were identified by mass spectroscopy analysis. Immunoblotting was used to investigate alterations in TCTP protein levels in response to glucose stimulation or cell stress induced by palmitate. To investigate the biological function of TCTP, immunolocalisation, gene knockdown and overexpression of Tctp (also known as Tpt1) were performed. Apoptosis was measured in Tctp knockdown or Tctp-overexpressing cells. Glucosestimulated insulin secretion was carried out in Tctp knockdown cells.

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 2009

The Ca 2+ -binding protein of the EF-hand type, S100B, exerts both intracellular and extracellula... more The Ca 2+ -binding protein of the EF-hand type, S100B, exerts both intracellular and extracellular functions. Recent studies have provided more detailed information concerning the mechanism(s) of action of S100B as an intracellular regulator and an extracellular signal. Indeed, intracellular S100B acts as a stimulator of cell proliferation and migration and an inhibitor of apoptosis and differentiation, which might have important implications during brain, cartilage and skeletal muscle development and repair, activation of astrocytes in the course of brain damage and neurodegenerative processes, and of cardiomyocyte remodeling after infarction, as well as in melanomagenesis and gliomagenesis. As an extracellular factor, S100B engages RAGE (receptor for advanced glycation end products) in a variety of cell types with different outcomes (i.e. beneficial or detrimental, pro-proliferative or pro-differentiative) depending on the concentration attained by the protein, the cell type and the microenvironment. Yet, RAGE might not be the sole S100B receptor, and S100B's ability to engage RAGE might be regulated by its interaction with other extracellular factors. Future studies using S100B transgenic and S100B null mice might shed more light on the functional role(s) of the protein. j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / b b a m c r Growth phase (astrocytes) [35]

Journal of Biological Chemistry, 2009

S100B is a Ca(2+)-binding protein of the EF-hand type that is abundantly expressed in astrocytes ... more S100B is a Ca(2+)-binding protein of the EF-hand type that is abundantly expressed in astrocytes and has been implicated in the regulation of several intracellular activities, including proliferation and differentiation. We show here that reducing S100B levels in the astrocytoma cell line GL15 and the Müller cell line MIO-M1 by small interference RNA technique results in a rapid disassembly of stress fibers, collapse of F-actin onto the plasma membrane and reduced migration, and acquisition of a stellate shape. Also, S100B-silenced GL15 and MIO-M1 Müller cells show a higher abundance of glial fibrillary acidic protein filaments, which mark differentiated astrocytes, compared with control cells. These effects are dependent on reduced activation of the phosphatidylinositol 3-kinase (PI3K) downstream effectors, Akt and RhoA, and consequently elevated activity of GSK3beta and Rac1 and decreased activity of the RhoA-associated kinase. Also, rat primary astrocytes transiently down-regulate S100B expression when exposed to the differentiating agent dibutyryl cyclic AMP and re-express S100B at later stages of dibutyryl cyclic AMP-induced differentiation. Moreover, reducing S100B levels results in a remarkably slow resumption of S100B expression, suggesting the S100B might regulate its own expression. Finally, we show that S100B interacts with Src kinase, thereby stimulating the PI3K/Akt and PI3K/RhoA pathways. These results suggest that S100B might contribute to reduce the differentiation potential of cells of the astrocytic lineage and participate in the astrocyte activation process in the case of brain insult and in invasive properties of glioma cells.