Ceramide and Exosomes: A Novel Target in Cancer Biology and Therapy

Unique Roles of Sphingolipids in Selected Malignant and Nonmalignant Lesions of Female Reproductive System

Cancer develops as a result of the loss of self-control mechanisms by a cell; it gains the ability to induce angiogenesis, becomes immortal and resistant to cell death, stops responding to growth suppressor signals, and becomes capable of invasion and metastasis. Sphingolipids-a family of membrane lipids-are known to play important roles in the regulation of cell proliferation, the response to chemotherapeutic agents, and/or prevention of cancer. Despite the underlying functions of sphingolipids in cancer biology, their metabolism in different malignant tumors is poorly investigated. Some studies showed marked differences in ceramide content between the tumor and the respective healthy tissue. Interestingly, the level of this sphingolipid could be either low or elevated, suggesting that the alterations in ceramide metabolism in cancer tissue may depend on the biology of the tumor. These processes are indeed related to the type of cancer, its stage, and histology status. In this paper we present the unique roles of bioactive sphingolipid derivative in selected gynecologic malignant and nonmalignant lesions.

Lysosomal regulation of extracellular vesicle excretion during d-ribose-induced NLRP3 inflammasome activation in podocytes

The NLRP3 inflammasome is activated in the cytoplasm of cells and its products such as IL-1β are exported through a non-classical ER-Golgi pathway. Several mechanistically distinct models including exocytosis of secretory lysosomes, microvesicles (MVs) and extracellular vehicles (EVs) have been proposed for their release. In this study, we hypothesized that the NLRP3 inflammasome product, IL-1β in response to exogenously administrated and endogenously produced D-ribose stimulation is released via extracellular vesicles including EVs via a sphingolipid-mediated molecular mechanisms controlling lysosome and multivesicular body (MVB) interaction. First, we demonstrated that both endogenous and exogenous D-ribose induced NLRP3 inflammasome activation to produce IL-1β, which was released via EVs in podocytes. Then, we found that colocalization of marker MVB marker VPS16 with IL-1β within podocytes increased upon D-ribose stimulation, which was accompanied by decreased colocalization of lysosome marker Lamp-1 and VPS16, suggesting decrease in MVB inclusion of IL-1β due to reduced lysosome and MVB interaction. All these changes were mimicked and accelerated by lysosome v-ATPase inhibitor, bafilomycin. Moreover, ceramide in podocytes was found elevated upon D-ribose stimulation, and prior treatments of podocyte with acid sphingomyelinase (Asm) inhibitor, amitriptyline, acid ceramidase (AC) inducer, genistein, or AC CRISPR/cas9 activation plasmids were found to decrease D-ribose-induced ceramide accumulation, EVs release and IL-1β secretion due to reduced interactions of lysosome with MVBs. These results suggest that inflammasome-derived products such as IL-1β during D-ribose stimulation are released via EVs, in which lysosomal sphingolipid-mediated regulation of lysosome function plays an important role.