Ceramide activates the stress-activated protein kinases

Area of Science:

• Cellular signaling pathways
• Molecular biology
• Biochemistry

Background:

• Tumor necrosis factor alpha (TNF alpha) is a key inflammatory cytokine.
• TNF alpha activates stress-activated protein kinases (SAPKs/JNKs) and NF-kappa B.
• Ceramide is a lipid mediator implicated in cellular signaling.

Purpose of the Study:

• To investigate the role of ceramide as a second messenger in TNF alpha signaling.
• To determine the effects of ceramide on SAPK/JNK and NF-kappa B activation.
• To compare the effects of ceramide with TNF alpha on specific cellular responses.

Main Methods:

• Treatment of HL-60 cells with TNF alpha, C2-ceramide, and sphingomyelinase.
• Assay of JNK/SAPK and ERK1/2 kinase activities.
• Measurement of NF-kappa B DNA binding and transcriptional activity.
• Analysis of c-jun gene expression.

Main Results:

• Exogenous sphingomyelinase and C2-ceramide stimulated JNK/SAPK activity, mimicking TNF alpha.
• TNF alpha weakly stimulated ERK1/2, while C2-ceramide inhibited them.
• TNF alpha stimulated NF-kappa B activity, but ceramide and sphingomyelinase did not.
• All tested agents (TNF alpha, sphingomyelinase, C2-ceramide) induced c-jun expression.

Conclusions:

• Ceramide acts as a second messenger for TNF alpha-induced SAPK activation and c-jun expression.
• Ceramide is not involved in TNF alpha-mediated NF-kappa B activation.
• These findings elucidate a specific role for ceramide in TNF alpha signaling pathways.