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Studies on the role of acid sphingomyelinase and ceramide in the LPS‐induced TNFa secretion by macrophages
Author(s) -
Rozenova Krasimira Aleksandrova,
Deevska Gergana,
NikolovaKarakashian Maria
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.lb263
Subject(s) - acid sphingomyelinase , ceramide , tumor necrosis factor alpha , secretion , western blot , sphingomyelin phosphodiesterase , biology , chemistry , microbiology and biotechnology , biochemistry , immunology , gene , apoptosis
The objective of this study is to decipher the role of ASMase in LPS‐triggered TNFα production. ASMase deficient (ASMase (‐/‐)) and wild‐type (ASMase (+/+)) mice and macrophages were stimulated with LPS and TNFα levels in serum and medium were monitored by ELISA and western blot analysis. The data revealed that ASMase deficiency is linked to increased production of soluble TNFα in response to LPS but does not affect MAP kinases activity or the rate of TNFα mRNA synthesis. These results suggest that ASMase affects post‐transcriptional processing of TNFα. 26kDa TNFα precursor (proTNFα), is cleaved to the 17kDa soluble form (sTNFα) by the TNFα converting enzyme (TACE). Substantial portion of the un‐cleaved proTNFα appeared to be rapidly degraded in the endosomes/lysosomes as judged by the increase of proTNFα in the presence of lysomotropic agent ammonium chloride. These data suggest that TACE is a rate‐limiting step in TNFα secretion. Notably, TACE activity is 2‐3 fold greater in ASMase(‐/‐) macrophages as compared to control cells, and it is inhibited by the addition of ceramide. Further studies revealed that the level of TACE mRNA was not affected but ASMase deficiency influences the sub‐cellular distribution of TNFα and TACE. Together, these results suggest that the rate of post‐translational processing of TNFα is important regulator of TNFα secretion and it is modulated by ASMase activity.