Nigericin Induces Paraptosis-Like Cell Death Instead of Pyroptosis in Corneal Keratocytes

The purpose of this study was to examine the nature of the underlying molecular mechanisms of cell death in human keratocytes treated with nigericin, a known pyroptosis inducer. Human keratocytes were exposed to nigericin, and cell death was assessed through morphological analysis and detection of related molecular markers. Proteomic profiling was performed to identify cell death-related proteins, with key findings validated by western blot. Additionally, organelle disruptions were examined using immunostaining techniques. Pyroptosis-like cell death was observed morphologically in cultured keratocytes. Moreover, an elevated release of IL-1beta was detected, accompanied by a significant loss of mitochondrial membrane potential. However, nigericin treatment induced a form of non-inflammatory cell death characterized by extensive vacuolation, resembling paraptosis. This was accompanied by the absence of caspase-3 activation and endoplasmic reticulum (ER) stress markers, along with increased accumulation of the autophagic marker LC3-II. Proteomic analysis revealed the absence of key components of the canonical pyroptosis pathway, including proteins involved in inflammasome assembly and the gasdermin (GSDM) family. These results were further confirmed by western blot. Significant alterations were also observed in the Golgi apparatus, mitochondria, and lysosomes following nigericin treatment. These findings suggest that nigericin triggers a paraptosis-like cell death in human keratocytes, rather than pyroptosis, as keratocytes lack the canonical executors of pyroptosis. This highlights an alternative mechanism of cell death in the cornea, warranting further exploration to understand its role and potential therapeutic implications.