Implication of sphingosine kinase (sk) activity in osmotic stress during postnatal renal development

GUAYTIMA EDITH; BRANDAN YAMILA; CORTEZ MARIA MERCEDES; STERIN-SPEZIALE NORMA B; MARQUEZ MARIA GABRIELA

Entre Rios

Congreso; LIV REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIONES EN BIOQUÍMICA Y BIOLOGÍA MOLECULAR (SAIB); 2018

SOCIEDAD ARGENTINA DE INVESTIGACIONES EN BIOQUÍMICA Y BIOLOGÍA MOLECULAR (SAIB)

Sphingosine 1 phosphate (S1P), the product of SK activity, regulates cell proliferation and survival. In neonatal rats, the renal papilla osmolality is much lower than in adults and increases dramatically after weaning. Previously, we demonstrated that the developmental regulation of SK expression and activity leads sphingolipid metabolism to the formation of S1P in the neonatal period, consistent with the immature-proliferative stage of neonatal renal papilla. Here, we evaluated the implication of SK activity in renal papilla collecting duct (CD) cells of 10-day-old rats subjected to osmotic stress. Taking advantage of the fact that CD cells in primary cultures retain many characteristics of their behavior in intact tissue, primary cultures of neonatal CD cells in hypertonic medium (HT) were performed. D,L-threo-dihydrosphingosine (tDHS) was used as an SK activity inhibitor. We analyzed by immunofluorescence the DBA lectin staining, a CD marker, and the cell morphology and proliferation. While cultured cells displayed an elongated morphology with regular intensity for DBA staining in isotonic medium, osmotic stress induced a more mature phenotype, reflected by a morphological change from an elongated to a hexagonal shape, and a greater positive DBA signal. When cells were subjected to HT in the presence of tDHS, cell-cell adhesion was impaired and a decreased intensity of DBA staining was observed. The proliferation decreased in cells subjected to HT, even in the absence of tDHS, with respect to the isotonic situation. These results suggest that SK activity is essential to maintain the epithelial phenotype in CD cells subjected to osmotic stress.