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Advanced Neurology Drosophila Sirtuin 1 and Alzheimer’s disease

exacerbates, the rough eye phenotype in correlation with Sirt1 RNAi /+ flies significantly increased the expression
AD model flies (Figure 1 A‑H). To investigate whether the of these apoptotic genes by up to 2.0-, 1.79-, and 1.39-
rough eye phenotype in AD model flies is associated with fold, respectively, compared to control flies (Figure 4K).
excessive cell death in the eyes, we conducted AO staining These findings support our earlier observations that Sirt1
in the respective larval eye imaginal discs (Figure 4 A‑I) overexpression plays an antiapoptotic role and indicate
of control (GMR-GAL4/+), AD model flies (GMR-GAL4- that Sirt1 is a crucial modulator of AD-related pathologies
UAS-Tau /+;+/+ and GMR-Aβ 42 k52 /+;GMR-Aβ 42 k53 /+), in Drosophila.
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and AD model flies with Sirt1 overexpression (GMR- To further investigate whether the increased expression
GAL4-UAS-Tau /UAS-Sirt1;+/+ and GMR-Aβ 42 k52 / of apoptotic genes (Grim, Reaper, and Hid) was linked
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UAS-Sirt1;GMR-Aβ 42 k53 /+) or Sirt1 downregulation to changes in the expression of Drosophila inhibitor of
(GMR-GAL4-UAS-Tau /+;UAS-Sirt1 RNAi /+ and GMR- apoptosis (DIAP1), we analyzed DIAP1 expression levels
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Aβ k52 /+;GMR-Aβ k53 /UAS-Sirt1 RNAi ) backgrounds.
42 42 through qRT-PCR in the heads of 10-day-old adult flies
We observed excessive cell death (AO-positive cells) from both control and experimental groups. Figure 4L
posterior to the MF in the third instar larval eyes of AD shows that DIAP1 expression was significantly reduced
model flies (Figure 4D and G) compared to age-matched to 0.55 in elav-Gal4/+;+/+;UAS-ArcAβ /+ AD model flies
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experimental control flies (GMR-GAL4/+ and GMR-GAL4/ compared to control flies (1.0). Sirt1 overexpression in the
UAS-Sirt1;+/+), which showed fewer AO-positive cells AD genetic background increased DIAP1 expression up
associated with developmental apoptosis (Figure 4A and B). to 16.09 in elav-Gal4/+;UAS-Sirt1/+;UAS-ArcAβ /+ flies
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Further, AO staining in AD model flies with Sirt1 compared to AD model flies, whereas Sirt1 downregulation
overexpression (GMR-GAL4-UAS-Tau /UAS-Sirt1;+/+ significantly reduced DIAP1 expression to 0.44 in elav-
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and GMR-Aβ 42 k52 /UAS-Sirt1;GMR-Aβ 42 k53 /+) showed a Gal4/+;UAS-ArcAβ /+;UAS-Sirt1 RNAi /+ flies compared to
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significant reduction in AO-positive cells posterior to the AD model flies (Figure 4L). Therefore, it was confirmed
MF (Figure 4E and H). In contrast, downregulation of that the rescue observed in the eye phenotype was linked
Sirt1 in GMR-GAL4-UAS-Tau /+;UAS-Sirt1 RNAi /+ and to reduced cell death due to Sirt1 overexpression.
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GMR-Aβ 42 k52 /+;GMR-Aβ 42 k53 /UAS-Sirt1 RNAi did not show
any significant changes in cell death compared to their 3.5. Sirt1 plays a neuroprotective effect by altering
respective AD model flies (Figure 4F and I). Overexpression JNK signaling pathways
or downregulation of Sirt1 in the GMR-GAL4 (experimental JNK is a key component of the mitogen-activated protein
control) background (GMR-GAL4/UAS-Sirt1;+/+ and kinase (MAPK) pathway 47-49 and has been extensively
GMR-GAL4/+;UAS-Sirt1 RNAi /+) showed no visible changes studied in the context of cell death in Drosophila. In
in cell death (Figure 4B and C) compared to the undriven Drosophila, the sole JNK is Bsk. Several earlier studies
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control GMR-GAL4/+ (Figure 4A). These results indicate have indicated that AD correlates with increased
that Sirt1 overexpression exerts a protective effect against phosphorylated JNK expression, which also colocalizes
apoptosis in Drosophila. with Aβ. 50-52 In addition, Aβ peptides can induce JNK
In flies, apoptosis is primarily regulated by three signaling activation. 53-55 As shown above, AD model
proapoptotic genes: Grim, Reaper, and Hid 44,45 . These flies exhibited increased cell death in eye cells, and JNK
genes are transcriptionally regulated in response to death- signaling is strongly correlated with cell death signaling
inducing signals and link signaling pathways to the cell pathways. Therefore, to analyze the potential genetic
death mechanism 45,46 . interaction between Drosophila JNK (Bsk), Drosophila
Sirtuin1, and AD-associated genes (Tau ) in flies, we
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To further confirm the AO staining results, we analyzed conducted a genetic interaction study. In this study, we
the mRNA expression levels of the proapoptotic genes Grim, observed the rough eye phenotype, abnormal bristles,
Reaper, and Hid through qRT-PCR in the heads of 10-day- and ommatidial disarrangement in GMR-GAL4-UAS-
old adult flies from both control and experimental groups. Tau /+;+/+ flies. These pathologies were exacerbated
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The expression levels of Grim, Reaper, and Hid in when Bsk was downregulated using UAS-Bsk RNAi (single/
elav-Gal4/+;+/+;UAS-ArcAβ /+ flies (Figure 4K) were double copy) in GMR-GAL4-UAS-Tau /+;UAS-Bsk RNAi /
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significantly increased by 4.16-, 3.24-, and 1.73-fold, TM6B and GMR-GAL4-UAS-Tau /+;UAS-Bsk RNAi /UAS-
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respectively, compared to control flies (1.0). Overexpression sk RNAi , (Figure 5B and C). We further noted significant
of Sirt1 in elav-Gal4/+;UAS-Sirt1/+;UAS-ArcAβ /+ flies improvements in these pathologies in GMR-GAL4-UAS-
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significantly reduced the expression levels of Grim, Reaper, Tau /+;+/+ flies when Sirt1 was overexpressed and Bsk
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and Hid by 1.42-, 1.65-, and 0.44-fold, respectively, whereas was downregulated (single/double copy) in the AD model
Sirt1 downregulation in elav-Gal4/+;UAS-ArcAβ /+;UAS- flies (i.e., GMR-GAL4-UAS-Tau /UAS-Sirt1;UAS-Bsk RNAi /
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Volume 3 Issue 4 (2024) 9 doi: 10.36922/an.4291