Abstract
Purpose :
Endothelin 1 (Edn1) is a 21-amino acid peptide that potently induces vasoconstriction and plays a key role in retinal neuronal and vascular degeneration in glaucoma and diabetic retinopathy. Yet mechanisms that regulate Edn1 expression in retinal cells remain to be elucidated. Given that Edn1 production is associated with aging or cell senescence, we reasoned that molecules that regulate aging process may be involved in the regulation of Edn1 expression. Sirtuin (Sirt) 1 and Sirt6 are evolutionarily conserved nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylases and share homolog with yeast Sir2 protein that critically regulates lifespan of yeast. This study aims to test whether Sirt1 and Sirt6 can regulate Edn1 expression in retinal neuronal cells.
Methods :
Localization of Sirt1 and Sirt6 was determined by immunohistochemistry in mouse retinal sections. Differentiated R28 cells were transfected with siRNA to knockdown Sirt1 or Sirt6, with a non-targeting siRNA as control. Edn1 expression was assessed by quantitative PCR (qPCR).
Results :
Sirt6 was abundantly expressed in cells in the ganglion cell layer although weak immunoreactivity of Sirt6 was also noted in the inner nuclear layer and outer nuclear layer of the retina. In contrast, Sirt1 immunoreactivity was universally expressed in all cells. In differentiated R28 cells, Sirt1 siRNA reduced Sirt1 expression by 60.7% and 76.7% at 24 and 48 hours respectively, and raised Edn1 expression by 11.2% and 98.7%. Sirt6 siRNA reduced Sirt6 expression by 59.1% and 72.1% at 24 and 48 hours respectively, and resulted in the elevations of Edn1 by 130.2% and 306.6%.
Conclusions :
Although knockdown of either Sirt1 or Sirt6 induced Edn1 expression, Sirt6 siRNA had a much more pronounced effect on Edn1 expression, suggesting that Sirt6 had the primary role in regulating Edn1 expression in retinal neuronal cells. Considering Sirt6 but not Sirt1 was predominantly expressed in retinal ganglion cells (RGCs), our study suggests that Sirt6 may be potentially involved in maintaining RGC health by inhibiting Edn1 expression.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.