Senescence and Lipid Droplet Accumulation are Involved in the Onset of Neurodegenerative Diseases

Recent research on senescence is revealing that senescence is related to lipid droplet and lysosomal dysfunction, which impair cell function. Here are some of the papers showing that these processes leads to neurodegenerative diseases.

Cellular senescence, a state of irreversible growth arrest, is closely linked to neurodegeneration through the accumulation of damaged cells in the nervous system. Lipid droplets, which store excess lipids, can accumulate in aging or stressed cells, contributing to cellular dysfunction and exacerbating neurodegenerative processes. Lysosomal dysfunction plays a central role in both lipid accumulation and the removal of cellular waste, and its impairment leads to the accumulation of toxic substances that further drive neurodegeneration. Together, these mechanisms create a cycle of cellular damage that accelerates the progression of neurodegenerative diseases such as Alzheimer's and Parkinson's.

Point of Interest
- Parkinson's disease (PD) is associated with the loss of dopaminergic neurons, with genetic and environmental factors contributing to its progression.

- Mutations in the lysosomal enzyme β-glucocerebrosidase cause lipid accumulation that drives cellular senescence in dopaminergic neurons in PD.

- Lipid droplet aggregation and lysosomal dysfunction may trigger cellular senescence leading to neurodegeneration in PD.

Point of Interest
- Senescent glia in aging Drosophila brains originate from neuronal mitochondrial dysfunction and express AP1, a senescence-associated transcription factor.

- AP1⁺ senescent glia cause lipid accumulation in non-senescent glia and increase senescence markers.

- Targeting AP1 in senescent glia extends lifespan, but increases oxidative damage in the brain and neuronal mitochondrial function remains poor.

Point of Interest
- Alzheimer's disease risk genes influence macrophage and microglial responses in lipid-rich tissues such as the brain.

- DLAMs are macrophage subpopulations with similar transcriptional activation states found in aging brains and other diseased lipid-rich tissues.

- Targeting BHLHE40/41, transcriptional regulators of DALM, may improve cholesterol clearance and lysosomal function in Alzheimer's disease therapies.

Co-staining with Lipid droplet and SA-β-Gal in fixed cells

*Cellular senescence was induced in A549 cells by DOX (0.2 μM DOX for 3 days → normal medium for 3 days)

1. A549 (2 x 10⁴) cells were seeded onto µ-slide 8 well plates (ibidi) and cultured overnight in a 37°C CO₂ incubator. 
2. The supernatant was removed, washed once with PBS, and fixed in 4% paraformaldehyde (PFA)/PBS solution for 30 minutes at room temperature. 
3. The supernatant was removed and the cells were washed once with PBS. 
4. 15 µM SPiDER Blue + 0.1 µM Lipi-Deep Red prepared in Assay buffer was added and incubated at 37°C for 30 min.
5. The supernatant was removed, washed once with PBS, and 200 µl of PBS was added and observed under a confocal laser microscope (60x magnification).

Imaging analysis of lipid droplet accumulation in senescent cells was performed using normal A549 cells (CTRL)  and cells induced senescence by Doxorubicin treatment (DOX). SA-β-Gal was detected as a senescence marker with Cellular Senescence Detection Kit - SPiDER Blue, and lipid droplets were detected with Lipi-Deep Red. As a result, the signal of Lipi-Deep Red was increased in SA-β-Gal-positive senescent cells.

[Detection conditions]

SPiDE Blue: 405 nm (Ex), 400–550 nm (Em), 1.0%, 600V
Lipi-Deep Red: 633 nm (Ex), 650–700 nm (Em), 1.0%, 650V

Multiple staining with oxidative stress-related markers using Doxorubicin-induced senescent cells（flow cytometry)

Using A549 cells induced to senescence by doxorubicin (DOX) and normal cells (CTRL), changes in oxidative stress-related markers in senescent cells were analyzed by flow cytometry with multiple staining. SA-βGal as a senescence marker was detected by Cellular Senescence Detection Kit - SPiDER Blue, total ROS as an oxidative stress marker was detected by ROS Assay Kit - Photo-oxidation Resistant DCFH-DA-, and γH2AX as a DNA damage marker was detected by DNA Damage Detection Kit - γH2AX-Red. As a result, total ROS and γH2AX were increased in SA-βGal-positive senescent cells, and the increase in oxidative stress-related markers associated with cellular senescence could be detected by multiple staining.


  Flow cytometry：SONY SA3800
　 SPiDER Blue: PacificBlue 　
    ROS Assay Kit: FITC
    γH2AX - Red: Cy3

＜Experimental Procedure>
 *Cellular senescence was induced in A549 cells by DOX (0.2 μM DOX for 3 days → normal medium for 3 days)
 The detail procedure for this experiment, please refer to the product page: SPiDER Blue.