Contribution of S6K1/MAPK signaling pathways in the response to oxidative stress: activation of RSK and MSK by hydrogen peroxide

Trobareu correccions de l'article a: http://dx.doi.org/10.1371/annotation/0b485bd9-b1b2-4c60-ab22-3ac5d271dc59Cells respond to different kind of stress through the coordinated activation of signaling pathways such as MAPK or p53. To find which molecular mechanisms are involved, we need to understand their cell adaptation. The ribosomal protein, S6 kinase 1 (S6K1), is a common downstream target of signaling by hormonal or nutritional stress. Here, we investigated the initial contribution of S6K1/MAPK signaling pathways in the cell response to oxidative stress produced by hydrogen peroxide (H2O2). To analyze S6K1 activation, we used the commercial anti-phospho-Thr389-S6K1 antibody most frequently mentioned in the bibliography. We found that this antibody detected an 80-90 kDa protein that was rapidly phosphorylated in response to H2O2 in several human cells. Unexpectedly, this phosphorylation was insensitive to both mTOR and PI3K inhibitors, and knock-down experiments showed that this protein was not S6K1. RSK and MSK proteins were candidate targets of this phosphorylation. We demonstrated that H2O2 stimulated phosphorylation of RSK and MSK kinases at residues that are homologous to Thr389 in S6K1. This phosphorylation required the activity of either p38 or ERK MAP kinases. Kinase assays showed activation of RSK and MSK by H2O2. Experiments with mouse embryonic fibroblasts from p38 animals" knockout confirmed these observations. Altogether, these findings show that the S6K1 signaling pathway is not activated under these conditions, clarify previous observations probably misinterpreted by non-specific detection of proteins RSK and MSK by the anti-phospho-Thr389-S6K1 antibody, and demonstrate the specific activation of MAPK signaling pathways through ERK/p38/RSK/MSK by H2O2

Myeloid p38α signaling promotes intestinal IGF‐1 production and inflammation‐associated tumorigenesis

Abstract The protein kinase p38α plays a key role in cell homeostasis, and p38α signaling in intestinal epithelial cells protects against colitis‐induced tumorigenesis. However, little is known on the contribution of p38α signaling in intestinal stromal cells. Here, we show that myeloid cell‐specific downregulation of p38α protects mice against inflammation‐associated colon tumorigenesis. The reduced tumorigenesis correlates with impaired detection in the colon of crucial chemokines for immune cell recruitment. We identify insulin‐like growth factor‐1 (IGF‐1) as a novel mediator of the p38α pathway in macrophages. Moreover, using genetic and pharmacological approaches, we confirm the implication of IGF‐1 produced by myeloid cells in colon inflammation and tumorigenesis. We also show a correlation between IGF‐1 pathway activation and the infiltration of myeloid cells with active p38α in colon samples from patients with ulcerative colitis or colon cancer. Altogether, our results uncover an important role for myeloid IGF‐1 downstream of p38α in colitis‐associated tumorigenesis and suggest the interest in evaluating IGF‐1 therapies for inflammation‐associated intestinal diseases, taking into consideration IGF‐1 signaling and immune cell infiltration in patient biopsies

Pt and Pd on activated carbon for oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

The liquid phase transformation of 5-hydroxymethylfurfuraldehyde (5-HMF) towards 2,5-furandicarboxylicacid (2,5-FDCA) using Pt and Pd catalysts supported on activated carbon and with the presence of CaCO3 andNaOH, is reported. The catalysts were characterized using different techniques, such as: H2 chemisorptionat room temperature, X ray photoelectronic spectroscopy (XPS) and thermogravimetric analysis (TGA).The results indicate that the particle size followed the order: PtCl/C < PdCl/C < PdN/C, which is closelyrelated to the catalytic behavior. It was found that the metal particles are present in the Pd0 and Pt0 form.PtCl/C was most active catalyst using CaCO3 as weak base.Fil: Sanabria, Lyda. Universidad Pedagógica y Tecnológica de Colombia Uptc; ColombiaFil: Lederhos, Cecilia Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Quiroga, Monica Esther. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica ; ArgentinaFil: Cubillos Lobo, Jairo Antonio. Universidad Pedagógica y Tecnológica de Colombia Uptc; ColombiaFil: Rojas, Agustin Hugo. Universidad Pedagógica y Tecnológica de Colombia Uptc; ColombiaFil: Martinez, Jose. Universidad Pedagógica y Tecnológica de Colombia Uptc; Colombi

The mTOR/S6K1 signaling pathway is not activated in response to the oxidative stress produced by H₂O₂.

<p>MCF7 cells were transfected with the indicated siRNAs 72 h before treatment with 0.4 mM H₂O₂ for 30 min. Cell lysates were analyzed by Western blot with the indicated antibodies. Molecular weight markers are indicated on the left. NT means non-targeting control.</p

Effect of rapamycin and wortmannin on phosphorylation of p85 protein by H₂O₂.

<p>MCF7 cells were treated with 0.4 mM H₂O₂ for 30 min. Where indicated, MCF7 cells were pre-incubated with 100 nM wortmannin or 20 nM rapamycin for 60 min before treatment with H₂O₂. Cell lysates were analyzed by Western blot with the indicated antibodies. Molecular weight markers are indicated on the left.</p

Activation of the MAPK signaling pathways in response to H₂O_2..

<p>Experiments of time and dose course were performed in MCF7 cells with 0.4 mM H₂O₂ (A) or for 30 min (B), respectively. Human cells were treated with 0.4 mM H₂O₂ for 30 min (C). Cell lysates were analyzed by Western blot with the indicated antibodies. NSB means non-specific band recognized by the antibody. Molecular weight markers are indicated on the left.</p

Phosphorylation of p85, RSK and MSK proteins was sensitive to inhibitors of the MAPK signaling pathways.

<p>(A) MCF7 cells were treated with 0.4 mM H₂O₂ for 30 min. Where indicated, cells were pre-incubated with 5 µM SB203580 (S), 5 µM U0126 (U), 100 nM wortmannin (W) or 20 nM rapamycin (R) for 60 min before treatment with H₂O₂. Cell lysates were analyzed by Western blot with the indicated antibodies. NSB means non-specific band recognized by the antibody. Molecular weight markers are indicated on the left. (B) Histograms represent the phosphorylation ratio of the indicated proteins. All bands were standardized with respect to mTOR levels. Values are the means ± SEM of the percentage of respective control for at least three independent experiments. Asterisks indicate values that are significantly different (*, p<0.05; **, p<0.01; ***, p<0.001) from the corresponding control value.</p