Identification of 25-hydroxyvitamin D3 1alpha-hydroxylase gene expression in macrophages

Kidney Int. 2000 Aug;58(2):559-68. doi: 10.1046/j.1523-1755.2000.00202.x.


Background: The 25-hydroxyvitamin D3 1alpha-hydroxylase (1alpha-hydroxylase) is almost exclusively expressed in the kidney. However, 1alpha-hydroxylase activities have been observed in some extrarenal tissues, including inflammatory cells of the monocyte/macrophage lineage. In sarcoidosis, macrophage 1alpha-hydroxylase causes overproduction of 1,25-(OH)2D3, resulting in hypercalcemia. In this study, we investigated the regulation of macrophage 1alpha-hydroxylase at a molecular level.

Methods: We used the human monocytic cell line THP-1, which can be differentiated into macrophage-like cells by treatment with phorbol ester. The expression of 1alpha-hydroxylase in THP-1 cells was examined by Northern blotting and immunoblotting using an antibody raised against a synthetic peptide corresponding to the 14 C-terminal amino acids of 1alpha-hydroxylase. We investigated the regulation of 1alpha-hydroxylase mRNA expression by RNase protection assay.

Results: Northern blot and immunoblot analyses confirmed the expression of 1alpha-hydroxylase in THP-1 cells at the mRNA and protein levels. Although parathyroid hormone and calcitonin, known stimulators of renal 1alpha-hydroxylase, did not affect the expression of 1alpha-hydroxylase mRNA, 8-Br-cAMP (5 x 10-4 mol/L) increased the expression of 1alpha-hydroxylase mRNA in THP-1 cells (198 +/- 9%). 1,25-(OH)2D3, known as a suppressor of renal 1alpha-hydroxylase, did not affect the expression of 1alpha-hydroxylase mRNA. By contrast, 1,25-(OH)2D3 markedly increased the expression of 25-hydroxyvitamin D3 24-hydroxylase mRNA. Interferon-gamma (2000 IU/mL) increased the expression of 1alpha-hydroxylase mRNA in differentiated THP-1 cells (922 +/- 25%).

Conclusions: The present results suggest that 1alpha-hydroxylase activity in macrophages is mediated by the same enzyme as in kidney. Interferon-gamma treatment increases macrophage 1alpha-hydroxylase levels via directly increasing gene expression of this enzyme.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies
  • Antineoplastic Agents / pharmacology
  • Blotting, Northern
  • Blotting, Western
  • Calcitonin / pharmacology
  • Calcitriol / pharmacology
  • Calcium Channel Agonists / pharmacology
  • Cell Differentiation / physiology
  • Cell Line
  • Cholestanetriol 26-Monooxygenase
  • Cloning, Molecular
  • Cyclic AMP / pharmacology
  • DNA, Complementary
  • Dactinomycin / pharmacology
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Enzymologic / physiology*
  • Humans
  • Interferon-gamma / pharmacology
  • Macrophages / cytology
  • Macrophages / enzymology*
  • Nucleic Acid Synthesis Inhibitors / pharmacology
  • Parathyroid Hormone / pharmacology
  • RNA, Messenger / analysis
  • Ribonucleases
  • Steroid Hydroxylases / analysis
  • Steroid Hydroxylases / genetics*
  • Steroid Hydroxylases / immunology


  • Antibodies
  • Antineoplastic Agents
  • Calcium Channel Agonists
  • DNA, Complementary
  • Nucleic Acid Synthesis Inhibitors
  • Parathyroid Hormone
  • RNA, Messenger
  • Dactinomycin
  • Interferon-gamma
  • Calcitonin
  • Cyclic AMP
  • Steroid Hydroxylases
  • CYP27A1 protein, human
  • Cholestanetriol 26-Monooxygenase
  • Ribonucleases
  • Calcitriol