Stimulation of the ceramide pathway partially mimics lipopolysaccharide-induced responses in murine peritoneal macrophages.
Recent studies have suggested that lipolysaccharide (LPS) stimulates cells by mimicking the second-messenger function of ceramide, a lipid generated in the cell by the action of sphingomyelinase (SMase). To examine this possibility further, we compared the abilities of LPS, SMase, and/or ceramide analogs to induce cytokine secretion, modulate gene expression, and induce endotoxin tolerance in macrophages. SMase and LPS induced secretion of tumor necrosis factor alpha (TNF-alpha) to comparable degrees; however, unlike LPS, SMase failed to stimulate detectable interferon activity. Cell-permeable analogs of ceramide induced the expression of many LPS-inducible genes; however, the expression of interferon-inducible protein 10 (IP-10) and interferon consensus sequence-binding protein (ICSBP) mRNAs was significantly lower than that induced by LPS. Both SMase-induced TNF-alpha secretion and LPS-induced TNF-alpha secretion were inhibited by pretreatment with a serine/threonine phosphatase inhibitor, calyculin A. Macrophages preexposed in vitro to LPS to induce a well-characterized state of endotoxin tolerance secreted little or no TNF-alpha upon secondary challenge with either LPS or SMase, whereas macrophages preexposed to SMase secreted high levels of TNF-alpha upon secondary stimulation with LPS or SMase. Collectively, these results suggest that ceramide activates a subset of LPS-induced signaling pathways in murine peritoneal exudate macrophages.
Barber
S A
SA
Department of Microbiology and Immunology, Uniformed Services University of Health Sciences, Bethesda, Maryland 20814, USA.
Detore
G
G
McNally
R
R
Vogel
S N
SN
D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis; D002518:Ceramides / Q000737:chemistry / Q000378:metabolism*; D054357:Chemokine CXCL10; D019743:Chemokines, CXC; D016207:Cytokines / Q000096:biosynthesis; D004791:Enzyme Inhibitors / Q000494:pharmacology; D050835:Interferon Regulatory Factors; D007372:Interferons / Q000032:analysis; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008262:Macrophage Activation / Q000502:physiology*; D017737:Macrophages, Peritoneal / Q000187:drug effects*; D008387:Marine Toxins; D051379:Mice; D008809:Mice, Inbred C3H; D010080:Oxazoles / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D012097:Repressor Proteins; D015290:Second Messenger Systems; D013108:Sphingomyelin Phosphodiesterase / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis; D000099185:Interferon Regulatory Factor-8
D002352:Carrier Proteins; D002518:Ceramides; D054357:Chemokine CXCL10; D019743:Chemokines, CXC; D016207:Cytokines; D004791:Enzyme Inhibitors; D050835:Interferon Regulatory Factors; D007372:Interferons; D008070:Lipopolysaccharides; D008387:Marine Toxins; D010080:Oxazoles; D010749:Phosphoprotein Phosphatases; D012097:Repressor Proteins; D013108:Sphingomyelin Phosphodiesterase; D014409:Tumor Necrosis Factor-alpha; D000099185:Interferon Regulatory Factor-8; C059041:calyculin A