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Abstract: PO2139

NPFFR2 in the Kidney via Novel Transcriptional and Posttranslational Mechanisms Triggers Molecular Responses to Salt

Session Information

Category: Hypertension and CVD

  • 1403 Hypertension and CVD: Mechanisms

Authors

  • Asico, Laureano D., The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, United States
  • Rozyyev, Selim, Children's National Health System, Washington, District of Columbia, United States
  • Hunt, Jessica, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, United States
  • Domingo, Ron Jako D., University of Maryland at College Park, College Park, Maryland, United States
  • Armando, Ines, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, United States
  • Jose, Pedro A., The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, United States
Background

Hypertension and salt sensitivity is dependent on NaCl intake. The kidney maintains sodium (Na) balance and blood pressure homeostasis. Neuropeptide FF (NPFF), is involved in nociception, hormonal modulation, and body temperature control. NPFF and its receptors, NPFFR1 and NPFFR2, are found in the kidney and have prohypertensive properties.

Methods

Renal restricted bolus or chronic infusion of NPFF raised blood pressure and reduced Na excretion (n=4) in C57Bl/6 mice. Silencing NPFFR1 had no effect but, silencing NPFFR2 raised UNaV (3 fold). NPFFR2 with the D1 dopamine receptor interacts. Both coimmunoprecipitated (coIP) and colocalized in human renal proximal tubule cells (hRPTCs) and whole kidney. NPFF and the D1R/D5R agonist fenoldopam (FEN) antagonized cAMP production (2.54±0.1 pmol/mg/min for FEN vs. 1.23±0.2 for vehicle vs. 1.11± 0.2 for both, n=4) and Na transport (1.78±0.1 fold with FEN, 1±0.11 for vehicle, and 1.1±0.2 for both, n=4) in hRPTCs. Mice fed a 4% NaCl diet increased (>2.5 fold) the coIP between renal NPFFR2 and D1R, enabling the D1R to limit NPFFR2 effects. A normal (145 μM) to low (90 μM) NaCl raised both promoter activity (~2.5 fold, n=3), mRNA and protein expression (n=4; 0–8 hr). A normal to high (175 μM) Na concentration reduced promoter activity (−0.5 fold), mRNA and protein expression of NPFFR2 (0–8 hr). The increased coIP between prohypertensive NPFFR2 and antihypertensive D1R, resulted in an increased receptor antagonism to cAMP response and Na transport (vs FEN or NPFF treatment [1 mM/30 min], n=4).

Results

We found a “Sodium Response Element” (NaRE), homolog of “Dehydration Responsive Element” (“TACCGACAT”) in Arabidopsis thaliana genome, at the NPFFR2 promoter. We measured NPFFR2 promoter activity to test NaRE response to Na. The NPFFR2 promoter responded to low (4.1±0.05 fold increase,) and high (0.52±0.5 fold decrease) Na with wild type NaRE, but not in the absence of NaRE (mutant NPFFR2). Using a selective NaRE blocker, (antigene RNA) on mouse kidneys, showed no increased NPFFR2 response to low Na intake (<0.04 G Na/day) but a decreased systolic blood pressure caused by the low Na diet (65±0.6 mm Hg vs. 83.3±1.3, n=4).

Conclusion

Our data identified NaRE and novel transcriptional and posttranslational mechanisms by which mammalian genes respond to sodium.

Funding

  • NIDDK Support