Role for tumor necrosis factor-alpha in UVB-induced conversion of 7-dehydrocholesterol to 1alpha,25-dihydroxyvitamin D3 in cultured keratinocytes

The Journal of Steroid Biochemistry and Molecular Biology
Bodo LehmannM Meurer

Abstract

UVB irradiation of cultured human keratinocytes induces both the conversion of 7-dehydrocholesterol (7-DHC) to calcitriol (1alpha,25(OH)(2)D(3)) and the release of tumor necrosis factor-alpha (TNF-alpha) in these cells. Calcitriol synthesis in human keratinocytes was reduced in the presence if a neutralizing polyclonal antibody directed against human TNF-alpha. On the other hand, we found a 1.7-fold higher stimulatory effect of UVB on liberation of TNF-alpha in cultured keratinocytes enriched with 7-DHC compared with irradiated cell cultures in absence of 7-DHC. These observations argue in favor of a synergetic relationship between generation of TNF-alpha and calcitriol in UVB irradiated keratinocytes. In addition, we found that TNF-alpha potently increases the conversion rate of Vitamin D(3) (cholecalciferol) to calcitriol in this cell system. The UVB-triggered formation of both TNF-alpha and calcitriol in cultured keratinocytes was wavelength-, time- and dose-dependent. Maximum formation of TNF-alpha and calcitriol was found at 300 nm and UVB doses of 30 mJ/cm2. The enhancement of both the formation of TNF-alpha and calcitriol in keratinocytes by UVB may be of relevance for regulation of growth and apoptosis in light-exposed ...Continue Reading

Citations

Jan 16, 2007·The Journal of Steroid Biochemistry and Molecular Biology·K M DixonR S Mason
Oct 22, 2009·Tidsskrift for den Norske lægeforening : tidsskrift for praktisk medicin, ny række·Inge LindsethIngvild Felling Meyer
Apr 14, 2009·Annales de dermatologie et de vénéréologie·C MaireP Thomas
Jul 26, 2005·The Journal of Steroid Biochemistry and Molecular Biology·K M DixonR S Mason
Jan 18, 2008·BioEssays : News and Reviews in Molecular, Cellular and Developmental Biology·Trevor G Marshall

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