Background

Lipid droplets (LDs), once seen solely as lipid storage organelles, are now recognised for their multifunctional roles in regulating cell physiology. They have also been increasingly implicated in neurodegenerative diseases. Aberrant accumulation of TAR DNA-binding protein 43 (TDP-43), a prominent feature of Motor Neurone Disease (MND), is associated with inflammation and lipid dyshomeostasis. This study investigates the emerging, yet unexplored, connection between LD biology and TDP-43-mediated neurodegeneration. 

Methods

Neuroblastoma SH-SY5Y cells with doxycycline-inducible overexpression of TDP-43 wildtype, the disease-associated Q331K mutation, or empty vector control were treated with or without 100nM of JAK1 inhibitor Baricitinib. Following a 48-hour post-induction period, cells were analysed using immunofluorescence to assess lipid droplets.

Results

We observed a significant decrease in the total area of LD expression (p<0.0001; Mann-Whitney Test) and the average size of LDs in both our neuronal models of TDP-43 proteinopathy (i.e., TDP-43 WT (p=0.0004) and TDP-43 Q331K (p<0.0001)) compared to control cells. This reduction in LDs correlated with increased cytotoxicity as quantified by lactate dehydrogenase (LDH) assay. Notably, Baricitinib treatment significantly reverted the LD phenotype and mitigated neurotoxicity.

Conclusion

Our findings demonstrate phenotypic alterations in LDs in association with TDP-43 proteinopathy. The pronounced rescue of the LD phenotype to control levels with Baricitinib suggests that activation of the JAK/STAT signalling pathway driven by aberrant TDP-43 functions in neurons, may disrupt lipid homeostasis. This study lays the groundwork for new insights into the roles of LDs in neurodegenerative diseases.