Purpose: Sirtuin1 (Sirt1) is an NAD(+)-dependent deacetylase involved in development, cell survival, stress resistance, energy metabolism, and aging. It is expressed in the mammalian central nervous system (CNS) and is activated during processes associated with neuroprotection. The retinal degeneration 10 (rd10) mouse model of retinitis pigmentosa (RP) was used to investigate the possible role of Sirt1 in this type of retinal degeneration.
Methods: Eyes from control and rd10 mice were used. Sirt1 mRNA was detected by in situ hybridization, and its abundance was estimated by semiquantitative RT-PCR. The presence of Sirt1 protein was investigated by immunohistofluorescence and Western blot analysis. The apoptosis of photoreceptor cells was analyzed by terminal dUTP transferase nick-end labeling (TUNEL). Immunolabeling for Sirt1, apoptosis-inducing factor (Aif), and caspase-12 (Casp-12) was performed on retinal tissue sections.
Results: Sirt1 mRNA and immunoreactivity were observed in normal adult mouse eyes. In the control retina, Sirt1 was immunolocalized mostly to the nucleus. In rd10 mice with retinal degeneration, changes in Sirt1 immunolabeling were observed only in the retinal outer nuclear layer (ONL). The pathologic pattern of Sirt1 immunoreactivity correlated with the start of retinal degeneration in rd10 mice.
Conclusions: The results suggest a link between Sirt1 production and retinal degeneration in rd10 mice. The anti-apoptotic, neuroprotective role of Sirt1 in the mouse retina is based on the involvement of Sirt1 in double DNA strand-break repair mechanisms and in maintaining energy homeostasis in photoreceptor cells. The results suggest that the neuroprotective properties of Sirt1 may gradually weaken in rd10 mouse photoreceptor cells.