Stress-induced generation of N-acylethanolamines in mouse epidermal JB6 P⁺ cells

It has long been known that N-acylethanolamine phospholipids [N-acylphosphatidylethanolamine (N-acyl PE)] and N-acyl-ethanolamines (NAEs) accumulate in mammalian tissues undergoing degenerative membrane changes associated with necrosis. Here we studied the effects of stress factors (UVB irradiation and serum deprivation) on the endogenous levels of N-acyl PE and NAE in mouse epidermal JB6 P⁺ cells. We found that 16:0, 18:0, 18:1, n-9 and 18:1, n-7 are the predominant amide-linked fatty acids in both N-acyl PE and NAE in these cells. UVB irradiation and serum deprivation resulted in significantly increased levels of N-acyl PE and NAE, especially 18:1, n-9 N-acyl PE and NAE. WE challenge increased the cellular content of anandamide (20:4, n-6 NAE), but this increase was the lowest of all NAEs measured. Serum deprivation resulted in a decreased cellular anandamide level, as well as a decrease in 20:4, n-6 N-acyl PE. Interestingly, the replacement of serum-free medium with medium containing 5% (v/v) fetal calf serum after 36 h of serum deprivation restored N-acyl PE and NAE levels almost completely within 4-8 h. These data suggest the involvement of N-acyl PE and NAE in cellular responses to stress.