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San Sebastián de los Reyes, Spain

Sardina J.L.,University of Salamanca | Lopez-Ruano G.,University of Salamanca | Sanchez-Abarca L.I.,Hospital Clinico Universitario Of Salamanca | Perez-Simon J.A.,Hospital Clinico Universitario Of Salamanca | And 5 more authors.
Cell Death and Differentiation | Year: 2010

Transient reactive oxygen species (ROS) production is currently proving to be an important mechanism in the regulation of intracellular signalling, but reports showing the involvement of ROS in important biological processes, such as cell differentiation, are scarce. In this study, we show for the first time that ROS production is required for megakaryocytic differentiation in K562 and HEL cell lines and also in human CD34 cells. ROS production is transiently activated during megakaryocytic differentiation, and such production is abolished by the addition of different antioxidants (such as N-acetyl cysteine, trolox, quercetin) or the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor diphenylene iodonium. The inhibition of ROS formation hinders differentiation. RNA interference experiments have shown that a p22 phox-dependent NADPH oxidase activity is responsible for ROS production. In addition, the activation of ERK, AKT and JAK2 is required for differentiation, but the activation of phosphatidylinositol 3-kinase and c-Jun N-terminal kinase seems to be less important. When ROS production is prevented, the activation of these signalling pathways is partly inhibited. Taken together, these results show that NADPH oxidase ROS production is essential for complete activation of the main signalling pathways involved in megakaryocytopoiesis to occur. We suggest that this might also be important for in vivo megakaryocytopoiesis. © 2010 Macmillan Publishers Limited All rights reserved.

Dorronsoro A.,Foundation for Stem Cell Research | Ferrin I.,Foundation for Stem Cell Research | Salcedo J.M.,Foundation for Stem Cell Research | Jakobsson E.,Foundation for Stem Cell Research | And 6 more authors.
European Journal of Immunology | Year: 2014

Although mesenchymal stromal cells (MSCs) possess the capacity to modulate immune responses, little is known about the mechanisms that underpin these processes. In this study, we show that immunosupression is mediated by activation of nuclear factor kappa B (NF-κB) in human MSCs. This pathway is activated by TNF-α that is generated following TCR stimulation of T cells. Inhibition of NF-κB through silencing of IκB kinase β or the TNF-α receptor abolishes the immunosuppressive capacity of MSCs. Our data also indicate that MSC-associated NF-κB activation primarily leads to inhibition of T-cell proliferation with little effect on expression of the activation markers CD69 and CD25. Thus, our data support the hypothesis that the TNF-α/NF-κB signalling pathway is required for the initial priming of immunosuppressive function in human MSCs. Interestingly, drugs that interfere with NF-κB activation significantly antagonise the immunoregulatory effect of MSCs, which could have important implications for immunosuppression regimens in the clinic. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dorronsoro A.,Foundation for Stem Cell Research | Lang V.,Foundation for Stem Cell Research | Jakobsson E.,Foundation for Stem Cell Research | Ferrin I.,Foundation for Stem Cell Research | And 5 more authors.
Cell Death and Disease | Year: 2013

The zinc-finger protein A20 is a key player in the negative feedback regulation of the nuclear factor kappa-light-chain-enhancer of activated B-cell (NF-κB) pathway in response to multiple stimuli. Tumor necrosis factor alpha (TNFα), a cytokine with pleiotropic effects on cellular proliferation and differentiation, dramatically increases A20 expression in all tissues. As TNFα inhibits adipocyte differentiation, we have determined the contribution of A20 to the adipogenic capacity of human mesenchymal stromal cells (MSCs). Here we show that A20 is constitutively expressed in MSCs, which previously has been observed only in cells that are either tumor or immune cells (T/B lymphocytes). TNFα stimulation induced a rapid degradation of A20 protein mediated exclusively by the proteasome in MSCs and not by caspases. This degradation is concomitant to the induction of its own mRNA, which suggests that a tight regulation of NF-κB signaling in MSCs is fundamental. On one hand, we demonstrate that the knockdown of A20-mediated transcript dramatically decreases the adipogenic capacity of MSCs, which correlates with the phenotype observed in the presence of TNFα. On the other hand, A20 overexpression blocks NF-κB activation and drives to increased adipogenesis, even in the presence of TNFα treatment. In conclusion, our data demonstrate that the presence of A20 allows MSCs to differentiate into adipocytes by maintaining NF-κB signaling at a basal state. © 2013 Macmillan Publishers Limited All rights reserved.

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