Acid ceramidase expression reduces IFNγ secretion by mouse CD4 T cells and is crucial for maintaining B-cell numbers in mice.

Acid ceramidase (Ac) is a lysosomal enzyme catalyzing the generation of sphingosine from ceramide, and Ac inhibitors are currently being investigated as potential cancer therapeutics. Yet, the role of the Ac in immune responses, particularly anti-viral immunity, is not fully understood. To investigate the impact of Ac expression on various leukocyte populations, we generated a tamoxifen-inducible global knockout mouse model for the Ac (iAc-KO).

Synthesis and Characterization of Ceramide-Containing Liposomes as Membrane Models for Different T Cell Subpopulations.

A fine balance of regulatory (T) and conventional CD4 T cells (T) is required to prevent harmful immune responses, while at the same time ensuring the development of protective immunity against pathogens. As for many cellular processes, sphingolipid metabolism also crucially modulates the T/T balance. However, our understanding of how sphingolipid metabolism is involved in T cell biology is still evolving and a better characterization of the tools at hand is required to advance the field.

The Manifold Roles of Sphingolipids in Viral Infections.

Sphingolipids are essential components of eukaryotic cells. In this review, we want to exemplarily illustrate what is known about the interactions of sphingolipids with various viruses at different steps of their replication cycles. This includes structural interactions during entry at the plasma membrane or endosomal membranes, early interactions leading to sphingolipid-mediated signal transduction, interactions with internal membranes and lipids during replication, and interactions during virus assembly and budding.

Inhibition of acid sphingomyelinase increases regulatory T cells in humans.

Genetic deficiency for acid sphingomyelinase or its pharmacological inhibition has been shown to increase Foxp3 regulatory T-cell frequencies among CD4 T cells in mice. We now investigated whether pharmacological targeting of the acid sphingomyelinase, which catalyzes the cleavage of sphingomyelin to ceramide and phosphorylcholine, also allows to manipulate relative CD4 Foxp3 regulatory T-cell frequencies in humans. Pharmacological acid sphingomyelinase inhibition with antidepressants like sertraline, but not those without an inhibitory effect on acid sphingomyelinase activity like citalopram, increased the frequency of Foxp3 regulatory T cell among human CD4 T cells .