Expression of vitamin D 3 25-hydroxylase (CYP27) mRNA after induction by vitamin D 3 or UVB radiation in keratinocytes of human skin equivalents - a preliminary study

Abstract

The presence of both 1alpha-hydroxylase activity and 25-hydroxylase activity is a biochemical prerequisite for the enzymatic generation of 1alpha,25(OH)2D3 from vitamin D3 in keratinocytes. In contrast to 1alpha-hydroxylase, however, activity of a 25-hydroxylase in keratinocytes has not previously been demonstrated. In this study, using RT-PCR we detected vitamin D3 25-hydroxylase mRNA in human keratinocytes. The expression of vitamin D3 25-hydroxylase mRNA in keratinocytes was identical to that of CYP27 expressed in mitochondria of human hepatoma HepG2 cells. CYP27 mRNA in keratinocytes is not constitutively expressed but is inducible both by vitamin D3 (780 nM) and by UVB radiation (300 nm, 30 mJ/cm2).

Multiple sclerosis and vitamin D: an update

“…It is either stored in fat or converted by 25-hydroxylase (25-OHase) enzyme in the liver to 25OHD. Interestingly, the presence of 25-OHase activity has also been demonstrated outside the liver in kidney, in keratinocytes in skin, and in parathyroid cells (Lehmann et al, 1999;Gascon-Barre et al, 2001;Correa et al, 2002).…”

Vitamin D3and the immune system: maintaining the balance in health and disease

“…Sources and metabolism 1,25-Dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ), the biologically active form of vitamin D 3 , is well known for its effects on mineral homeostasis and bone metabolism. This secosteroid hormone can be obtained by nutritional uptake (for example, fortified dairy products, fatty fish and their liver oils); however, UVB-mediated photosynthesis in the skin serves as the main source of vitamin D 3 .…”

“…This secosteroid hormone can be obtained by nutritional uptake (for example, fortified dairy products, fatty fish and their liver oils); however, UVB-mediated photosynthesis in the skin serves as the main source of vitamin D 3 . Upon sunlight exposure, photolytic cleavage of 7-dihydrocholesterol in the skin results in the formation of previtamin D 3 , which is subsequently converted by a spontaneous thermal isomerisation into vitamin D 3 1 . Once in the blood circulation, vitamin D 3 and its metabolites are bound to a carrier molecule, vitamin D 3 binding protein.…”

“…Upon sunlight exposure, photolytic cleavage of 7-dihydrocholesterol in the skin results in the formation of previtamin D 3 , which is subsequently converted by a spontaneous thermal isomerisation into vitamin D 3 1 . Once in the blood circulation, vitamin D 3 and its metabolites are bound to a carrier molecule, vitamin D 3 binding protein. Two subsequent hydroxylation steps are required to convert the hormone into its biologically active form 2 .…”

“…Two subsequent hydroxylation steps are required to convert the hormone into its biologically active form 2 . The first activation step, the hydroxylation of vitamin D 3 at the carbon-25 position, occurs primarily in the liver and is catalysed by D 3 -25-hydroxylase (25CYP2D25). Interestingly, 25-hydroxylase activity has also been reported to be present in kidney, parathyroid cells and keratinocytes 3 -5 .…”