RAR activity is proadipogenic as illustrated with the use of TTNPB to preferentially activate RAR (Fig. The two retinoid agonists, LG268 and TTNPB, had a similar antiproliferative action, reducing the cell density by 50% and 70%, respectively. In contrast, RXRatg and RARatg had no influence around the proliferation of P19 cells. RARatg had also been reported to have no effect on the proliferation of breast carcinoma MCF-7 cells, even if used at 10?M . Open in a separate windows FIG. 2. RAR and RXR agonists reduce the proliferation and stemness character of P19-MLC2v-GFP cells. (A) Cell proliferation. Cell monolayers were treated for 48?h with no inducer (NI) or with the indicated retinoid, and stained with crystal violet. Absorbance values are expressed as the meansSEM of three impartial studies. (B) Cell stemness. Cells were subjected to the mesodermal protocol in the absence (NI) or presence of the indicated retinoid inducer from D2 to D3, and analyzed for Oct3/4 expression Verucerfont at D3. Cells were also collected at D0 (undifferentiated cells) and at D2 (before retinoid treatment) for comparison. An immunoblot specimen and the densitograms (meansSEM) obtained from three impartial cell series. Oct3/4 signal was normalized to tubulin and reported relatively to the corresponding NI-D3 condition. The inducer treatment was significantly different from the NI-D3 condition (*), and the retinoid treatment was significantly different from the atRA reference treatment (#) (indicate stimulatory effects, and lines ending with a small indicate inhibitory effects. Activation of RAR and RXR by atRA concurrently induces adipogenesis and myogenesis. Treatments favoring RAR over RXR signaling preferentially induce adipogenesis Verucerfont over myogenesis (TTNPB and atRA?+?RXRatg treatments). Treatments favoring RXR over RAR signaling permit both differentiation routes (LG268 and atRA?+?RARatg treatments). Inhibitors of p38 (p38i) and ERK (ERKi) signaling have differential effects on mesodermal differentiation depending upon the cellular retinoid status. P38i enhances myogenesis and adipogenesis when RAR and RXR are activated, inhibits both differentiation routes under the predominance of RXR signaling, and increases the antimyogenic action of RAR when RAR signaling predominates. ERKi increases Verucerfont myogenesis when Verucerfont RAR and RXR are activated, but has no influence on myogenesis or on adipogenesis when either RAR or RXR signaling predominates. This study shows that favoring RAR activity over RXR activity has proadipogenic and antimyogenic impacts (Fig. 8). RAR activity is usually proadipogenic as illustrated with the use of TTNPB to preferentially activate RAR (Fig. 3 and Supplementary Table S2: treatment 3) and with the use of atRA in conjunction with RXRatg to preferentially deactivate RXR (Fig. 7 and Supplementary Table S2: treatment 4). The crucial role of RAR in adipogenesis was revealed by comparing atRA and atRA+RARatg treatments when p38 signaling was inhibited (Fig. 7 and Supplementary Table S2: treatments 10 and 12). Indeed, in the presence of the p38 inhibitor, RARatg abolished atRA-induced adipogenesis in P19 cells. This is in accordance with the work of Monteiro em et al. /em , showing the inhibitory action of another RAR antagonist on atRA-induced adipogenesis in an ES cell line . However, in that work in contrast to ours, the demonstration was not conditional to the inhibition of p38. For the first time is revealed a concurrent antimyogenic action of RAR signaling and this, in either absence or presence of p38 inhibitor (Fig. 8). Indeed, in both p38 situations, the SKM+CM and CM yields were null or reduced with the use of TTNPB or atRA+RXRatg compared to the corresponding atRA treatment (Figs 4 and ?and77 and Supplementary Table S2: treatments 3 and 4 versus 2, and treatment 11 versus Rabbit polyclonal to ZBTB49 10). The antimyogenic effect of TTNPB was greater than that of atRA+RXRatg, which could be due to the stability of TTNPB in cell culture. TTNPB was indeed reported to be more stable than atRA, which led to a more prolonged stimulatory action on RAR compared to atRA . Favoring RXR over RAR activation in the absence of p38.