Inhibition of sphingomyelin synthase 1 activity promotes an epithelial-mesenchymal transition (EMT) in differentiated collecting duct cells

YAMILA ROMINA BRANDÁN; EDITH DEL VALLE GUAYTIMA; NICOLÁS OCTAVIO FAVALE; LUCILA GISEL PESCIO; NORMA BEATRIZ STERIN-SPEZIALE; MARÍA GABRIELA MÁRQUEZ

Cuidad Autónoma de Buenos Aires

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

SOCIEDADES DE BIOCIENCIAS

In Epithelial-Mesenchymal Transition (EMT), contrary to Mesenchymal-Epithelial Transition (MET), cells lose their epithelial phenotype and acquire the characteristics of mesenchymal cells. EMT normally occurs during embryonic development, and in adult tissues is activated during inflammation, tissue regeneration, and it has also been related with fibrosis and cancer. The sphingomyelin (SM) synthase 1 (SMS1) participates during the final step of SM synthesis. In previous works, we have demonstrated that the inhibition of SMS1 activity induces the loss of cell-cell adhesions of collecting ducts (CD), and it also affects their morphology. Taking into account that these characteristics are similar to those described for EMT, we investigate whether the SMS1 inhibition could induce this process. To this end, primary cultures of differentiated CD cells were incubated for 24 h with D609, a SMS1 inhibitor. By immunocytochemistry and immunoblot we analyzed the expression of the mesenchymal cells markers: vimentin and α-smooth muscle actin (α-SMA). In basal conditions, CD cells formed monolayers with low expression of vimentin, and almost null in α-SMA. Overlapping cells with fibroblastoid morphology, which strongly express both proteins, were also observed. After D609 treatment, the number of CD expressing vimentin and α-SMA increased, denoting a de novo synthesis of α-SMA. The amount of overlapping cells was also increased. The immunoblot analysis showed a correlative increased in the level of both proteins. Tacking into account the changes observed in cell morphology and de novo synthesis of α-SMA, we suggest that the inhibition of SMS1 activity could alter the equilibrium between EMT-MET, generating myofibroblasts from preexisting CD cells, because of the inability to form cell-cell adhesions. In this context, we propose that SM synthesis is important to keep the EMT-MET equilibrium, and we highlight the activity of SMS1 as a modulator of this process.