The role of TSPO in regulating hyperosmolarity-induced inflammatory response in human corneal epithelial cells via PPARγ

The mitochondrial translocator protein (TSPO) is critically involved in the regulation of inflammatory responses. However, the specific functions and molecular mechanisms of TSPO in the pathogenesis of Dry Eye Disease (DED) remain unclear. This study aims to investigate whether TSPO regulates the inflammatory response in an in vitro hyperosmolar model via the Peroxisome Proliferator-activated Receptor γ (PPARγ) signaling pathway and to explore their relationship. The research employed a hyperosmolar-stressed human corneal epithelial cell (HCE-T) model and utilized various techniques, including Western blotting, quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR), and immunofluorescence for comprehensive analysis. The results indicate that knocking down TSPO under hyperosmolar stimulation conditions significantly increased PPARγ expression levels while stabilizing mitochondrial membrane potential. Mechanistic studies revealed that further knockdown of PPARγ following hyperosmolar stimulation and TSPO knockdown led to upregulation of TSPO expression and exacerbated cell Apoptosis. This finding suggests that PPARγ may exert feedback regulatory effects on TSPO. The observed phenotypic reversal after gene knockdown suggests that TSPO may influence cellular inflammatory responses and Apoptosis via the mitochondrial pathway through regulation of PPARγ. In conclusion, this study's findings indicate that mutual regulation between TSPO and PPARγ may constitute an important signaling pathway in the inflammatory response associated with DED. The dynamic balance within this pathway may contribute to maintaining homeostasis in corneal epithelial cells. Based on the current in vitro findings, these insights enhance our understanding of the pathogenesis underlying dry eye and suggest potential targets for developing new treatment strategies.