Cellular senescence is a homeostatic biological process that functions to irreversibly halt the proliferation of dividing cell types. It has a central role in embryonic development, as well as prevents tumorigenesis and limits tissue damage following injury. However, a growing body of evidence suggests senescence to be associated with neurodegenerative disorders including Alzheimer’s disease, Parkinson’s Disease, amyotrophic lateral sclerosis, Down syndrome, and multiple sclerosis. To investigate the role of cellular senescence in Parkinson’s Disease (PD), a team of researchers led by Dinesh Kumar Verma, Ph.D., of Delaware State University used StressMarq’s α-synuclein preformed fibrils (α-syn PFF) to perform a series of in vitro and in vivo studies centered on monitoring the expression of known senescence markers. Their data, published in Cells, showed that α-syn PFF-induced pathology could be linked to cellular senescence in PD brains, indicating senescent cells to be viable therapeutic targets.

α-syn PFF induces in vitro expression of cellular senescence markers

Initially, Verma et al. used α-syn PFF to treat immortalized rat dopaminergic N27 cells, which they then lysed for Western blot analysis of known senescence markers. These included HMGB1, Lamin B1, and SATB1, which were reduced following α-syn PFF treatment, and p21, which was increased – all classic hallmarks of senescence. Similar experiments performed in primary cells showed α-syn PFF to trigger the expression of senescence markers in astrocytes and microglia, with less pronounced effects in primary cortical neurons. Importantly, increased levels of GFAP (an astrocyte marker) and Iba-1 (a microglial marker) demonstrated the activation of these cell types to be a consequence of α-syn PFF treatment; such activation has been reported to trigger a pro-inflammatory response known as the senescence associated secretory phenotype (SASP), which contributes to age-related neurodegeneration. In addition, decreased levels of β-III-tubulin over time suggested α-syn PFF to cause the loss of cortical neurons.

In vivo results mirror in vitro data

After performing further Western blot experiments with human PD postmortem midbrain tissues (which also had reduced levels of HMGB1, Lamin B1, and SATB1, and increased levels of p21), Verma et al. used α-syn PFF to inject a mouse model of PD before isolating the brain tissue for analysis. Western blot data again matched previous results, although inconsistencies for SATB1 prevented its inclusion in the subsequent immunohistochemical (IHC) evaluation. In alignment with previous findings, the IHC data confirmed α-syn PFF treatment to reduce HMGB1 and LaminB1 expression and increase levels of p21 in the murine brain, while at the same time activating astrocytes and microglial cells, and causing the loss of cortical neurons. These data corroborate the findings of other groups working on establishing a role for senescence in neurodegeneration and provide additional support for therapeutic targeting of senescent cells to treat conditions such as PD.

Future perspectives

With cellular senescence becoming a primary focus of neurodegenerative disease research, tools that enable its investigation are essential. StressMarq’s Mouse Alpha Synuclein Pre-formed Fibrils (catalog# SPR-324) have proven utility for these types of studies and promise to help drive the development of novel senolytic drugs, as demonstrated by the authors of this study. Other α-synuclein products in our range include our Anti-Alpha Synuclein (pSer129) Antibody (catalog# SMC-600) and our Anti-Alpha Synuclein Antibody (catalog# SPC-800), both of which are validated for applications including Western blot, ELISA, and IHC and available as conjugated to multiple fluorescent tags.

C57/BL6 mice were injected with sonicated recombinant mouse Alpha Synuclein Monomers (catalog# SPR-323) or Active Mouse Recombinant Alpha Synuclein Pre-formed Fibrils (catalog# SPR-324) at 8 weeks of age. Mice were unilaterally injected in the dorsal striatum (bregma AP + 0.2 mm, L +/- 2.0 mm, V – 3.0 mm) and sacrificed 30 days post-injection. (A) 1.25 uL mouse alpha synuclein monomers, (B) 2.5 uL mouse alpha synuclein monomers, (C) 2.5 ug alpha synuclein PFFs, (D) 5 ug alpha synuclein PFFs. Inset: PBS (negative control). Primary antibody: Anti-Alpha Synuclein (pSer129) Antibody (catalog# SMC-600) at 1:10,000. Secondary antibody: anti-rabbit HRP. Mice injected with PFFs displayed alpha synuclein staining in the striatum and cortex and contralateral to the injection site. Courtesy of: Porsolt.

Article reference:

Alpha-Synuclein Preformed Fibrils Induce Cellular Senescence in Parkinson’s Disease Models, Verma DK et al, Cells. 2021;10(7):1694