Inhibitors of sphingolipid synthesis modulate interferon (IFN)-gamma-induced intercellular adhesion molecule (ICAM)-1 and human leukocyte antigen (HLA)-DR expression on cultured normal human keratinocytes: possible involvement of ceramide in biologic action of IFN-gamma.
To elucidate the participation of sphingosine and ceramide in the biologic action of cytokines on epidermal keratinocytes, we studied whether inhibitors of sphingolipid synthesis modulate interferon (IFN)-gamma-induced intercellular adhesion molecule (ICAM)-1 and human leukocyte antigen (HLA)-DR expression on cultured normal human keratinocytes. Pretreatment of keratinocytes with L-cycloserine or fumonisin B1, but not 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP), significantly suppressed both ICAM-1 and HLA-DR expression induced by IFN-gamma. Because the synthesis of all kinds of sphingolipids is blocked by L-cycloserine and all except that of sphinganine by fumonisin B1, whereas PDMP inhibits the synthesis of glucosylceramide and glycosphingolipids, the result suggests the participation of ceramide and/or sphingosine in IFN-gamma-induced ICAM-1 and HLA-DR expression. Exogenous C2-ceramide reversed the effects of L-cycloserine and fumonisin B1. On the other hand, sphingosine reversed the effect of L-cycloserine, but not of fumonisin B1. These results indicate that ceramide participates in this pathway, as fumonisin B1, but not L-cycloserine, inhibits the synthesis of ceramide from sphingosine. In addition, reverse transcriptase polymerase chain reaction showed that L-cycloserine reduced the mRNA for ICAM-1, HLA-DR alpha, and HLA-DR beta induced by IFN-gamma, and C2-ceramide and sphingosine antagonized the effect of L-cycloserine. Furthermore, the degradation rate of fluorescent sphingomyelin into ceramide in keratinocytes was increased by IFN-gamma, suggesting that IFN-gamma activates sphingomyelin hydrolysis in keratinocytes. These observations suggest the possible role of ceramide in IFN-gamma-induced ICAM-1 and HLA-DR expression on keratinocytes. Ceramide may function as an endogenous modulator mediating the cytokine signals in keratinocytes.
Wakita
H
H
Department of Dermatology, Hamamatsu University School of Medicine, Japan.
Nishimura
K
K
Tokura
Y
Y
Furukawa
F
F
Takigawa
M
M
D001483:Base Sequence; D002478:Cells, Cultured; D002518:Ceramides / Q000502:physiology; D003523:Cycloserine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D037341:Fumonisins; D006684:HLA-DR Antigens / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics / Q000378:metabolism*; D007371:Interferon-gamma / Q000494:pharmacology*; D015603:Keratinocytes / Q000378:metabolism*; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D009183:Mycotoxins / Q000494:pharmacology; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000378:metabolism; D012016:Reference Values; D013107:Sphingolipids / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D013109:Sphingomyelins / Q000378:metabolism; D013110:Sphingosine / Q000494:pharmacology
D002518:Ceramides; D037341:Fumonisins; D006684:HLA-DR Antigens; D015335:Molecular Probes; D009183:Mycotoxins; D012333:RNA, Messenger; D013107:Sphingolipids; D013109:Sphingomyelins; D018799:Intercellular Adhesion Molecule-1; C056933:fumonisin B1; D007371:Interferon-gamma; D003523:Cycloserine; D013110:Sphingosine