Abstract: SA-PO236
Sphingosine 1-Phosphate (S1P) as a Novel Paracrine Mediator of Classic and Regenerative Functions of Macula Densa Cells
Session Information
- Glomerular: Cell Biology
November 04, 2017 | Location: Hall H, Morial Convention Center
Abstract Time: 10:00 AM - 10:00 AM
Category: Glomerular
- 1003 Glomerular: Cell Biology
Authors
- Schiessl, Ina M, University of Southern California, Los Angeles, California, United States
- Riquier-brison, Anne, University of Southern California, Los Angeles, California, United States
- Desposito, Dorinne, University of Southern California, Los Angeles, California, United States
- Peti-Peterdi, Janos, University of Southern California, Los Angeles, California, United States
Background
Macula densa (MD) cells play a key role in the regulation of renal hemodynamics. Newly emerging non-classic MD functions include the release of tissue remodeling factors and the recruitment of renal progenitor cells. S1P-signaling contributes to cell migration and proliferation and regulates renal vascular development. Also, in vitro studies demonstrated that S1P-signalling acutely regulates glomerular hemodynamics. Hence, we hypothesized that S1P may be synthesized locally in the MD, and that MD-derived S1P may contribute to classic and regenerative cell functions.
Methods
To investigate if S1P signaling regulates glomerular hemodynamics in vivo, we evaluated the acute effects of the S1P analogue FTY720 [1 mg/kg] on single nephron GFR (snGFR) using intravital multiphoton microscopy (MPM) of C57BL6 mice. Cell proliferation was determined using Ki67 staining of frozen kidney sections from mice treated with L-NAME [500mg/L, per os] for one week with or without daily FTY720 injections [3 mg/kg]. The expression and regulation of known S1P synthesizing or activating enzymes in MD cells was studied using MD gene profiling with the translating ribosome affinity purification (TRAP) technique. To isolate translated mRNA from MD cells, adult nNOS-eGFR-L10a mice were used, which were either treated with low salt/enalapril [100 mg/L] or a normal diet for 2 weeks.
Results
FTY720 administration reduced afferent arteriole diameter by 10 % (n=7, p=.0232) and snGFR by 24% (n=11, p=.0013). In the L-NAME injury model, we found significantly more Ki67+ proliferating cells in FTY720-treated kidneys compared to control (8.3±1.3 vs. 5.1±0.7 cells/area, n=12, p<.05). Screening the MD gene profile for S1P-relevant enzymes revealed the expression of sphingosine kinase 1, ceramide synthases (CS) 1, 2, 4 and 6, and a 2-fold upregulation in response to MD-stimulating treatment for CS 4 and 6 (p<.05) as well as a 2.5-fold reduction of sphingosine-1-phosphate phosphatase 2 mRNA abundance (p<0.01).
Conclusion
Our data show that S1P acutely decreases glomerular blood flow and snGFR in vivo, enhances kidney cell proliferation, and that MD cells express and regulate several S1P synthesizing or activating enzymes. This suggests that MD cell-derived S1P may act as a paracrine regulator of classic and new tissue regenerative MD cell functions.
Funding
- NIDDK Support