Sharona Even-Ram

Publications (27) View all

• Article: Cells exposed to sublethal oxidative stress selectively attract monocytes/macrophages via scavenger receptors and MyD88-mediated signaling.

  Anat Geiger-Maor, Inbar Levi, Sharona Even-Ram, Yoav Smith, Dawn M Bowdish, Gabriel Nussbaum, Jacob Rachmilewitz
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  ABSTRACT: The innate immune system responds to endogenous molecules released during cellular stress or those that have undergone modifications normally absent in healthy tissue. These structures are detected by pattern-recognition receptors, alerting the immune system to "danger." In this study, we looked for early signals that direct immune cells to cells undergoing stress before irreversible damage takes place. To avoid detecting signals emanating from apoptotic or necrotic cells we exposed fibroblasts to sublethal oxidative stress. Our results indicate that both nonenzymatic chemical reactions and aldehyde dehydrogenase-2-mediated enzymatic activity released signals from fibroblasts that selectively attracted CD14(+) monocytes but not T, NK, and NKT cells or granulocytes. Splenocytes from MyD88(-/-) mice did not migrate, and treatment with an inhibitory peptide that blocks MyD88 dimerization abrogated human monocyte migration. Monocyte migration was accompanied by downmodulation of CD14 expression and by the phosphorylation of IL-1R-associated kinase 1, a well-known MyD88-dependent signaling molecule. The scavenger receptor inhibitors, dextran sulfate and fucoidan, attenuated monocyte migration toward stressed cells and IL-1R-associated kinase 1 phosphorylation. Surprisingly, although monocyte migration was MyD88 dependent, it was not accompanied by inflammatory cytokine secretion. Taken together, these results establish a novel link between scavenger receptors and MyD88 that together function as sensors of oxidation-associated molecular patterns and induce monocyte motility. Furthermore, the data indicate that MyD88 independently regulates monocyte activation and motility.
  The Journal of Immunology 01/2012; 188(3):1234-44. · 5.79 Impact Factor
• Article: Derivation, propagation and controlled differentiation of human embryonic stem cells in suspension.

  Debora Steiner, Hanita Khaner, Malkiel Cohen, Sharona Even-Ram, Yaniv Gil, Pavel Itsykson, Tikva Turetsky, Maria Idelson, Einat Aizenman, Rita Ram, Yael Berman-Zaken, Benjamin Reubinoff
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  ABSTRACT: Undifferentiated human embryonic stem cells (hESCs) are currently propagated on a relatively small scale as monolayer colonies. Culture of hESCs as floating aggregates is widely used for induction of differentiation into embryoid bodies. Here we show that hESC lines can be derived from floating inner cell masses in suspension culture conditions that do not involve feeder cells or microcarriers. This culture system supports prolonged propagation of the pluripotent stem cells as floating clusters without their differentiation into embryoid bodies. HESCs cultivated as aggregates in suspension maintain the expression of pluripotency markers and can differentiate into progeny of the three germ layers both in vitro and in vivo. We further show the controlled differentiation of hESC clusters in suspension into neural spheres. These results pave the way for large-scale expansion and controlled differentiation of hESCs in suspension, which would be valuable in basic and applied research.
  Nature Biotechnology 03/2010; 28(4):361-4. · 29.50 Impact Factor
• Article: Human embryonic stem cells suppress T cell responses via arginase I-dependent mechanism.

  Nurit Yachimovich-Cohen, Sharona Even-Ram, Yoel Shufaro, Jacob Rachmilewitz, Benjamin Reubinoff
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  ABSTRACT: Human embryonic stem cells (hESCs) can proliferate extensively in culture and give rise to progeny of the three germ layers. Several reports suggested that mouse and hESCs may attenuate immune responses. In this study, we focused on the mechanism by which hESCs inhibit T cell responses. Using coculture experiments, we demonstrate that hESCs inhibit cytokine secretion and T cell proliferation in response to potent T cell activators. Furthermore, we show that hESCs downmodulate the TCR-associated CD3-zeta chain. These effects are maintained when hESCs are replaced by their conditioned media and can be restored by the addition of L-arginine to hESC-conditioned media or by treatment of hESCs with a specific arginase inhibitor. Moreover, we show arginase-I expression and activity in hESCs. We further demonstrate that mouse ESCs (mESCs) similarly inhibit T cell activation via arginase I, suggesting an evolutionary conserved mechanism of T cell suppression by ESCs. In addition, we demonstrate that arginase I expression is not limited to ESCs in culture, but can also be detected in the inner cell mass and the trophectoderm of preimplantation mouse embryos and hESC-derived trophectoderm cells. Finally, T cells infiltrating ESC-derived teratomas have significantly lower levels of CD3-zeta chain. Collectively, the data indicate a role for ESC-arginase I activity in the attenuation of T cell activation.
  The Journal of Immunology 02/2010; 184(3):1300-8. · 5.79 Impact Factor
• Article: Protection of thrombin receptor expression under hypoxia.

  E Landau, R Tirosh, A Pinson, S Banai, S Even-Ram, M Maoz, S Katzav, R Bar-Shavit
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  ABSTRACT: Thrombin receptor (ThR) plays a significant role in myocyte contractility and hypertrophy. Heart myocyte ischemic damage, caused by insufficient blood supply, is the leading cause of heart infarction. Here we demonstrate that when primary myocyte cultures are subjected to hypoxic stress, ThR mRNA levels are reduced markedly. This takes place also in vivo in a model of ischemic pig heart, exhibiting reduced levels of ThR compared with normal heart sections. Prior activation of ThR however, by either thrombin receptor-activating peptide (TRAP) or by alpha-thrombin resulted in full protection of ThR mRNA levels under hypoxia. The effect appeared specific to ThR because the addition of TRAP did not affect the hypoxic damage as shown by the levels of lactic dehydrogenase release and up-regulated GLUT-1, a glucose transporter gene. This protection effect took place not only in primary myocytes but also in NIH3T3 fibroblasts. ThR protection occurs via specific cell signaling events because activation of the receptor by TRAP, following interruption of the signaling cascade by calphostin C, a protein kinase C inhibitor, resulted in loss of ThR mRNA protection. Because Ras and Src are part of the ThR signaling cascade, the introduction of either dominant ras or src oncogenes to NIH3T3 murine fibroblasts gave rise to similar protection of ThR mRNA levels under hypoxic conditions without the exogenous addition of TRAP. Likewise, ThR mRNA protection was obtained after transfection with proto-oncogene vav. The 95-kDa protein Vav undergoes tyrosine phosphorylation after ThR activation, serving thus as part of the receptor machinery cascade. We therefore conclude that the initiation of the signaling cascades either exogenously by TRAP or within the cell via src or ras, as well as via vav oncogene interconnecting G-binding protein to the tyrosine kinase pathway, ultimately results in ThR protection under hypoxia. We present hereby, a novel concept of activated receptors, which under minimal oxygen tension protect their otherwise decaying mRNA. Maintaining the level of ThR that plays an active role in normal myocyte function may provide a significant repair mechanism in ischemic tissue, assisting in the regaining of normal myocyte functions.
  Journal of Biological Chemistry 02/2000; 275(4):2281-7. · 4.77 Impact Factor
• Article: Thrombin receptor overexpression in malignant and physiological invasion processes.

  S Even-Ram, B Uziely, P Cohen, S Grisaru-Granovsky, M Maoz, Y Ginzburg, R Reich, I Vlodavsky, R Bar-Shavit
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  ABSTRACT: Although the involvement of soluble and matrix-immobilized proteases in tumor cell invasion and metastasis is well recognized, the role of proteolytically activated cell surface receptors has not been elucidated. We report here that thrombin receptor, a member of the protease-activated receptor family, is preferentially expressed in highly metastatic human breast carcinoma cell lines and breast carcinoma biopsy specimens. Introduction of thrombin receptor antisense cDNA considerably inhibited the invasion of metastatic breast carcinoma cells in culture through a reconstituted basement membrane. During placental implantation of the human embryo, thrombin receptor is transiently expressed in the invading cytotrophoblasts. These results emphasize the involvement of thrombin receptor in cell invasion associated with tumor progression and normal embryonic development.
  Nature Medicine 09/1998; 4(8):909-14. · 22.46 Impact Factor