Activation of acid sphingomyelinase and its inhibition by the nitric oxide/cyclic guanosine 3′,5′-monophosphate pathway: Key events in Escherichia coli-elicited apoptosis of dendritic cells

Sestina Falcone, Cristiana Perrotta, Clara De Palma, Addolorata Pisconti, Clara Sciorati, Annalisa Capobianco, Patrizia Rovere-Querini, Angelo A. Manfredi, Emilio Clementi

Research output: Contribution to journalArticlepeer-review

Abstract

Depletion of dendritic cells (DCs) via apoptosis contributes to sepsis-induced immune suppression. The mechanisms leading to DC apoptosis during sepsis are not known. In this study we report that immature DCs undergo apoptosis when treated with high numbers of Escherichia coli. This effect was mimicked by high concentrations of LPS. Apoptosis was accompanied by generation of ceramide through activation of acid sphingomyelinase (A-SMase), was prevented by inhibitors of this enzyme, and was restored by exogenous ceramide. Compared with immature DCs, mature DCs expressed significantly reduced levels of A-SMase, did not generate ceramide in response to E. coli or LPS, and were insensitive to E. coli- and LPS-triggered apoptosis. However, sensitivity to apoptosis was restored by addition of exogenous A-SMase or ceramide. Furthermore, inhibition of A-SMase activation and ceramide generation was found to be the mechanism through which the immune-modulating messenger NO protects immature DCs from the apoptogenic efects of E. coli and LPS. NO acted through formation of cGMP and stimulation of the cGMP-dependent protein kinase. The relevance of A-SMase and its inhibition by NO/cGMP were confirmed in a mouse model of LPS-induced sepsis. DC apoptosis was significantly higher in inducible NO synthase-deficient mice than in wild-type animals and was significantly reduced by treatment ex vivo with NO, cGMP, or the A-SMase inhibitor imipramine. Thus, A-SMase plays a central role in E. coli/LPS-induced DC apoptosis and its inhibition by NO, and it might be a target of new therapeutic approaches to sepsis.

Original languageEnglish
Pages (from-to)4452-4463
Number of pages12
JournalJournal of Immunology
Volume173
Issue number7
Publication statusPublished - Oct 1 2004

ASJC Scopus subject areas

  • Immunology

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