(563.15) Global PER1 knockout Dahl Salt Sensitive rats show increased expression of renal Edn1 mRNA and Endothelin-1 peptide

Poster Board Number: E210

Alexandria Juffre (University of Florida, University of Florida), Hannah Costello (University of Florida, University of Florida), G. Ryan Crislip (University of Florida), Lauren Douma (University of Florida), Kit-Yan Cheng (University of Florida), Phillip Bratanatawira (University of Florida), Adrian Zietara (Medical College of Wisconsin, Medical College of Wisconsin), Lashodya Dissanayake (University of South Florida, University of South Florida), Alexander Staruschenko (University of South Florida, University of South Florida), Michelle Gumz (University of Florida, University of Florida)

Background:  Previously, we showed that global knockout of the circadian clock protein PERIOD1 (PER1) in Dahl Salt Sensitive (SS) rats resulted in worsening of the SS hypertensive phenotype (1). PER1 KO rats also exhibited evidence of renal injury and increased plasma aldosterone levels after three weeks on  a high salt diet (4% NaCl). Because we previously showed that PER1 negatively regulates the peptide hormone Endothelin-1 (ET-1) via transcriptional control of the ET-1-encoding gene Edn1, we wanted to investigate ET-1 regulation in this novel rat model. Interestingly, Edn1 is also positively regulated by aldosterone through the mineralocorticoid receptor (MR).  

Hypothesis: Given that ET-1 signaling can be pro-hypertensive and profibrotic in the kidney, we hypothesized that ET-1 peptide levels in the kidney may be upregulated as part of the phenotype of the PER1 KO SS rats. 

Methods:  Protein and total RNA were isolated from the kidney samples of control and PER1 KO SS rats on normal diet (0.4% NaCl) or after three weeks on a high salt (4% NaCl) diet. Renal ET-1 peptide and plasma aldosterone levels were measured by ELISA and quantitative PCR was performed to quantify the renal mRNA levels of ET-1 and its receptors ETA and ETB, MR, and GR. Renal MR protein levels were measured by Western Blot and quantified by relative densitometry. Data were evaluated for genotype or diet differences using ANOVA.  

Results:  Renal ET-1 peptide levels were significantly higher in PER1 KO rats on high salt diet when compared to control SS rats (p=0.0003), as were plasma aldosterone levels (p=0.0156). There was also a significant genotype difference in Edn1 mRNA levels, with increased levels in PER1 KO rats on a high salt diet (p=0.0389). In contrast, significant differences were not observed in the mRNA levels of ET-1 receptors Ednra and Ednrb between genotypes or diets. Importantly, quantification of renal MR protein levels showed marked increase with genotype and treatment effects (genotype: p=0.0002, treatment: p=0.0133).  

Conclusions:  These data suggest that PER1 KO results in increased ET-1 in the kidney, due to increased transcription of the Edn1 gene, with increased plasma aldosterone and renal MR protein levels. This apparent negative regulation of ET-1 by PER1, coupled with increased MR and aldosterone levels, is likely to contribute to the hypertensive and renal injury phenotype of PER1 KO SS rats on a high salt diet. Together these data show an important role for PER1 and its target ET-1 in salt-sensitive hypertension and the accompanying renal injury. 

Reference: 

1 Spires DR, Zietara A, Levchenko V, Gumz ML, Staruschenko A. Knockout of Per1 Exacerbates the Hypertensive Phenotype of the Dahl Salt Sensitive Rat. FASEB J. 2020;34(S1):1.

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Funding: lt;/bgt; 1R01DK109570-01A1