Cytochrome P450scc-dependent metabolism of 7-dehydrocholesterol in placenta and epidermal keratinocytes

Andrzej T. Slominski, Tae Kang Kim, Jianjun Chen, Minh N. Nguyen, Wei Li, Charles Yates, Trevor Sweatman, Zorica Janjetovic, Robert C. Tuckey

Research output: Contribution to journalArticle

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Abstract

The discovery that 7-dehydrocholesterol (7DHC) is an excellent substrate for cytochrome P450scc (CYP11A1) opens up new possibilities in biochemistry. To elucidate its biological significance we tested ex vivo P450scc-dependent metabolism of 7DHC by tissues expressing high and low levels of P450scc activity, placenta and epidermal keratinocytes, respectively. Incubation of human placenta fragments with 7DHC led to its conversion to 7- dehydropregnenolone (7DHP), which was inhibited by dl-aminoglutethimide, and stimulated by forskolin. Final proof for P450scc involvement was provided in isolated placental mitochondria where production of 7DHP was almost completely inhibited by 22R-hydroxycholesterol. 7DHC was metabolized by placental mitochondria at a faster rate than exogenous cholesterol, under both limiting and saturating conditions of substrate transport, consistent with higher catalytic efficiency (kcat/Km) with 7DHC as substrate than with cholesterol. Ex vivo experiments showed five 5,7-dienal intermediates with MS spectra of dihydroxy and mono-hydroxy-7DHC and retention time corresponding to 20,22(OH)27DHC and 22(OH)7DHC. The chemical structure of 20,22(OH)27DHC was defined by NMR. 7DHP was further metabolized by either placental fragments or placental microsomes to 7-dehydroprogesterone as defined by UV, MS and NMR, and to an additional product with a 5,7-dienal structure and MS corresponding to hydroxy-7DHP. Furthermore, epidermal keratinocytes transformed either exogenous or endogenous 7DHC to 7DHP. 7DHP inhibited keratinocytes proliferation, while the product of its pholytic transformation, pregcalciferol, lost this capability. In conclusion, tissues expressing P450scc can metabolize 7DHC to biologically active 7DHP with 22(OH)7DHC and 20,22(OH)27DHC serving as intermediates, and with further metabolism to 7-dehydroprogesterone and (OH)7DHP.

Original languageEnglish (US)
Pages (from-to)2003-2018
Number of pages16
JournalInternational Journal of Biochemistry and Cell Biology
Volume44
Issue number11
DOIs
StatePublished - Nov 1 2012

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Cholesterol Side-Chain Cleavage Enzyme
Keratinocytes
Metabolism
Placenta
Mitochondria
Substrates
Cholesterol
Nuclear magnetic resonance
7-dehydrocholesterol
Aminoglutethimide
Tissue
Biochemistry
7-dehydropregnenolone
Colforsin
Microsomes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Cell Biology

Cite this

Cytochrome P450scc-dependent metabolism of 7-dehydrocholesterol in placenta and epidermal keratinocytes. / Slominski, Andrzej T.; Kim, Tae Kang; Chen, Jianjun; Nguyen, Minh N.; Li, Wei; Yates, Charles; Sweatman, Trevor; Janjetovic, Zorica; Tuckey, Robert C.

In: International Journal of Biochemistry and Cell Biology, Vol. 44, No. 11, 01.11.2012, p. 2003-2018.

Research output: Contribution to journalArticle

Slominski, Andrzej T. ; Kim, Tae Kang ; Chen, Jianjun ; Nguyen, Minh N. ; Li, Wei ; Yates, Charles ; Sweatman, Trevor ; Janjetovic, Zorica ; Tuckey, Robert C. / Cytochrome P450scc-dependent metabolism of 7-dehydrocholesterol in placenta and epidermal keratinocytes. In: International Journal of Biochemistry and Cell Biology. 2012 ; Vol. 44, No. 11. pp. 2003-2018.
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AU - Nguyen, Minh N.

AU - Li, Wei

AU - Yates, Charles

AU - Sweatman, Trevor

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AU - Tuckey, Robert C.

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