Ultrastructural evaluation of lithium-induced autophagic and mitochondrial stress in 3D endometrial and neuroblastoma spheroids

Lithium chloride (LiCl), a widely used mood stabilizer, has been reported to modulate selective autophagy pathways, including mitophagy. However, its ultrastructural effects in three-dimensional (3D) tumor models remain incompletely characterized. In this study, we examined the subcellular alterations induced by LiCl in 3D spheroid cultures derived from Ishikawa endometrial cancer and SH-SY5Y neuroblastoma cells. Spheroids were treated with 1, 10, or 50 mM LiCl and analyzed using transmission electron microscopy (TEM). The analysis revealed double-membrane-bound vesicles surrounding degenerating mitochondria, along with cytoplasmic vacuolization and membrane remodeling. These morphological features are suggestive of mitophagic activity, accompanied by stress-related ultrastructural remodeling. Although molecular validation (e.g., LC3B or PINK1/Parkin Western blotting) was not performed, the observed ultrastructural profiles are consistent with organelle-selective autophagy. These findings underscore the dose-dependent cellular responses to LiCl and support the value of 3D cancer spheroids as models to explore non-canonical autophagy-related stress pathways. Future studies incorporating molecular markers such as LC3B, PINK1, Parkin, and Lamin B1 will be essential to confirm these observations.