Abstract
Atopic dermatitis is characterized by increased skin innervation. The expression of neurotrophin-4 is enhanced in the epidermal keratinocytes of lesions with atopic dermatitis and may be related to hyperinnervation in these lesions. Prostaglandin E2 (PGE2) levels are increased in lesions with atopic dermatitis; thus, PGE2 may be involved in the development of this disease. We examined the in vitro effects of PGE2 on neurotrophin-4 production in human keratinocytes. PGE2 and EP1/EP3 agonist sulprostone increased neurotrophin-4 secretion and mRNA levels without altering its mRNA stability. Antisense Sp1 oligodeoxynucleotide and Sp1 inhibitor mithramycin A suppressed PGE2 and sulprostone-induced neurotrophin-4 expression, indicating the requirement for Sp1 for expression. PGE2 or sulprostone markedly enhanced the phosphorylation, DNA binding, and transcriptional activity of Sp1 and modestly increased Sp1 mRNA and protein levels. PGE2 or sulprostone induced the membrane translocation of protein kinase Cα and the phosphorylation of extracellular signal-regulated kinase (ERK). PGE2-induced increases in neurotrophin-4 expression, Sp1 transcriptional and DNA-binding activity, Sp1 mRNA and protein levels, and ERK phosphorylation were suppressed by antisense EP3 oligodeoxynucleotide, inhibitors of phosphatidylinositol-specific phospholipase C, conventional protein kinase C, and mitogen-activated protein kinase/ERK kinase 1 (MEK1). These results suggest that PGE2 enhances neurotrophin-4 production by activating Sp1 via the EP3/phosphatidylinositol-specific phospholipase C/protein kinase Cα/MEK1/ERK pathway. PGE2 may promote innervation in skin lesions with atopic dermatitis via the induction of neurotrophin-4.
Footnotes
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This work was partly supported by aid from the KANAE Medical Research Foundation.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.105.091645.
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ABBREVIATIONS: PGE2, prostaglandin E2; NT-4, neurotrophin-4; p75NTR, p75 neurotrophin receptor; AP-1, activator protein-1; ERK, extracellular signal-regulated kinase; PKC, protein kinase C; MEK, mitogen-activated protein kinase/ERK kinase; 1-OH PGE1, prostaglandin E1 alcohol; Gö6976, 12-(2-cyanoethyl)-6,7,12,13-tetrahydro-13-methyl-5-oxo-5H-indolo(2,3-a)pyrrolo(3,4-c)-carbazole; PD98059, 2′-amino-3′-methoxyflavone; H-89, N-[2-((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide; U73122, 1-[6-((17β-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)-hexyl]-1H-pyrrole-2,5-dione; PI-PLC, phosphatidylinositol-specific phospholipase C; KBM, keratinocyte basal medium; RT, reverse transcription; PCR, polymerase chain reaction; EMSA, electrophoretic mobility shift assay; PKA, protein kinase A; KGM, keratinocyte growth medium; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; phRL-TK, promoter-linked Renilla luciferase vector; Luc, luciferase.
- Received June 28, 2005.
- Accepted August 2, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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