Immune regulation of 25-hydroxyvitamin D-1alpha-hydroxylase in human monocytic THP1 cells: mechanisms of interferon-gamma-mediated induction.
Level 5 - mechanism / opinion, no new human data
In vitro laboratory study using a human cell line
PubMed 16787983 · doi:10.1210/jc.2006-0678
What was done
Human monocytic THP1 cells were evaluated in undifferentiated states or differentiated into macrophages using phorbol myristate acetate (PMA). Cells were activated with interferon-gamma (IFNgamma) alone or combined with secondary stimuli such as lipopolysaccharide (LPS) or PMA. 1alpha-Hydroxylase mRNA expression was quantified by real-time RT-PCR. Signaling pathways were probed with specific pharmacological inhibitors, and phosphorylation of STAT1alpha and C/EBPbeta was assessed by Western blotting.
What was found
The abstract reports no numerical values or effect sizes. In undifferentiated THP1 cells, IFNgamma required a secondary stimulus like LPS to induce 1alpha-hydroxylase expression. In PMA-differentiated THP1 macrophages, IFNgamma alone induced 1alpha-hydroxylase at higher levels. Induction required concurrent activation of the JAK-STAT, MAPK, and NF-kappaB pathways, with an essential role for C/EBPbeta and histone remodeling involving histone deacetylases and histone acetylase p300.
Why it matters
This study maps the intracellular signaling pathways required for extrarenal vitamin D activation in monocytes and macrophages, clarifying the molecular mechanisms driving excess 1,25-dihydroxyvitamin D3 production in granulomatous diseases such as sarcoidosis.
Limits
This is an in vitro study using a single immortalized human cell line (THP1), which may not fully reflect primary human macrophage biology or in vivo granuloma pathology. The abstract provides no quantitative values, confidence intervals, or sample sizes.
Cited by
- supports Circulating 25-hydroxyvitamin D is converted into active 1,25-dihydroxyvitamin D not only in the kidneys but also locally within white blood cells.