The occurrence of cholestatic liver injury is accompanied by the alterations of hepatocyte polarization and bile acid homeostasis. Located in epithelial cells, tight junctions(TJs)are a special barrier structure which are important in maintaining permeability and bile acid homeostasis. Based on the fully analysis and discussion of TJs, the latest therapeutic drugs for cholestasis were summaried, which may provide new perspectives and potential therapeutic agents for the treatment of cholestatic liver injury.

Sphingomyelin phosphodiesterase 3 (SMPD3) encodes neutral sphingomyelinase 2 (nSMase2), which plays an important role in tumor development as a key enzyme regulating cell growth variation and inducing apoptosis with the important messenger molecule ceramide. On one hand, the common epigenetic alteration of SMPD3 methylation mediates carcinogenesis through the disruption of gene expression by regulating cell proliferation, differentiation, and apoptosis. Meanwhile, SMPD3 also induces apoptosis and cell cycle arrest in tumor cells through its hydrolysis products. On the other hand, SMPD3 is also closely related to pro-cancer processes such as exosome secretion, inflammatory response, and tumor cell proliferation. In this paper, the biological action of SMPD3 in tumor diseases was reviewed to enhance the understanding of the role of SMPD3 in the development of different tumors and provide broader ideas for basic research and clinical diagnosis and treatment of tumor diseases.