1α,25-Dihydroxyvitamin D3 (1α,25(OH)2D3), the active form of vitamin D, suppresses keratinocyte proliferation, promotes keratinocyte differentiation, and induces involucrin expression. Peroxisome proliferation-activated receptors (PPARs) are ligand-activated transcription factors. It has been reported that PPARs stimulate keratinocyte differentiation and regulate the expression of differentiation molecules.
Keratinocytes treated with 1α,25(OH)2D3 induced PPARγ, which was followed by increased involucrin expression. In this study, we investigated whether PPARγ is involved in the 1α,25(OH)2D3-induced involucrin expression in human keratinocytes.
Subconfluent keratinocytes were treated with 10−7 M 1α,25(OH)2D3 for the indicated times, and PPAR and involucrin mRNA expression were determined by real-time RT-PCR. The levels of PPARs, involucrin, p38, and phospho-p38 proteins were assayed by Western blotting, and the DNA binding activities of PPARγ and AP-1 were investigated by electrophoretic mobility shift assays (EMSA). To examine the role of PPARγ in 1α,25(OH)2D3 responses, recombinant adenovirus carrying a dominant-negative form of PPARγ (Axdn-PPARγ) was constructed and transfected into keratinocytes. The p38 inhibitor SB203580 was added to the cultures to evaluate the involvement of p38 in involucrin expression.
1α,25(OH)2D3 induced PPARγ expression and stimulated PPARγ activity. The introduction of dn-PPARγ inhibited the expression of involucrin mRNA and protein induced by 1α,25(OH)2D3, and suppressed AP-1 DNA binding activity. 1α,25(OH)2D3 also triggered the phosphorylation of p38, which contributes to involucrin induction. Moreover, dn-PPARγ prevented the 1α,25(OH)2D3-induced phosphorylation of p38.
These results suggest that PPARγ regulates involucrin expression by controlling the AP-1 signal and p38 activation in 1α,25(OH)2D3-induced keratinocyte differentiation.
Abbreviations:1α,25(OH)2D3 (1α,25-dihydroxyvitamin D3), AP-1 (activator protein-1), Ax (adenovirus vector), m.o.i. (multiplicity of infection), PPAR (peroxisome proliferator-activated receptor), VDR (vitamin D receptor), VDRE (vitamin D response elements)
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- Epidermal differentiation: the bare essentials.J Cell Biol. 1990; 111: 2807-2814
- Identification of a DNA sequence responsible for binding of the 1,25-dihydroxyvitamin D3 receptor and 1,25-dihydroxyvitamin D3 enhancement of mouse secreted phosphoprotein 1 (SPP-1 or osteopontin) gene expression.Proc Natl Acad Sci USA. 1990; 87: 9995-9999
- Effect of 1 alpha, 25-dihydroxyvitamin D3 on the morphologic and biochemical differentiation of cultured human epidermal keratinocytes grown in serum-free conditions.J Invest Dermatol. 1986; 86: 709-714
- Fetal epidermal differentiation and barrier development in vivo is accelerated by nuclear hormone receptor activators.J Invest Dermatol. 1999; 113: 788-795
- Peroxisome proliferator-activated receptors in cutaneous biology.Br J Dermatol. 2003; 149: 229-236
- Modulation of keratinocyte gene expression and differentiation by PPAR-selective ligands and tetradecylthioacetic acid.J Invest Dermatol. 2001; 116: 702-712
- Peroxisome-proliferator-activated receptor (PPAR)-gamma activation stimulates keratinocyte differentiation.J Invest Dermatol. 2004; 123: 305-312
- Troglitazone improves psoriasis and normalizes models of proliferative skin disease: ligands for peroxisome proliferator-activated receptor-gamma inhibit keratinocyte proliferation.Arch Dermatol. 2000; 136: 609-616
- Topical treatment with thiazolidinediones, activators of peroxisome proliferator-activated receptor-gamma, normalizes epidermal homeostasis in a murine hyperproliferative disease model.Exp Dermatol. 2006; 15: 154-160
- TGF-beta is not involved in early phase growth inhibition of keratinocytes by 1alpha, 25(OH)2vitamin D3.J Dermatol Sci. 2004; 36: 41-50
- A dominant-negative peroxisome proliferator-activated receptor gamma (PPARgamma) mutant is a constitutive repressor and inhibits PPARgamma-mediated adipogenesis.J Biol Chem. 2000; 275: 5754-5759
- STAT5a/PPARgamma pathway regulates involucrin expression in keratinocyte differentiation.J Invest Dermatol. 2007; 1: 1
- All-trans-retinoic acid induces interleukin-8 via the nuclear factor-kappaB and p38 mitogen-activated protein kinase pathways in normal human keratinocytes.J Invest Dermatol. 2004; 123: 1078-1085
- Expression and localization of peroxisome proliferator-activated receptors and nuclear factor kappaB in normal and lesional psoriatic skin.J Invest Dermatol. 2003; 121: 1104-1117
- Apoptosis signal-regulating kinase 1 (ASK1) is an intracellular inducer of keratinocyte differentiation.J Biol Chem. 2001; 276: 999-1004
- The vitamin D response element of the involucrin gene mediates its regulation by 1,25-dihydroxyvitamin D3.J Invest Dermatol. 2002; 119: 1109-1113
- 1alpha,25-dihydroxyvitamin D3 induced differentiation of cultured human keratinocytes is accompanied by a PKC-independent regulation of AP-1 DNA binding activity.J Invest Dermatol. 2000; 114: 1174-1179
- 1alpha,25-dihydroxyvitamin D3 stimulates activator protein 1 DNA-binding activity by a phosphatidylinositol 3-kinase/Ras/MEK/extracellular signal regulated kinase 1/2 and c-Jun N-terminal kinase 1-dependent increase in c-Fos, Fra1, and c-Jun expression in human keratinocytes.J Invest Dermatol. 2003; 120: 561-570
- Dashti S. p38 Mitogen-activated protein kinases on the body surface—a function for p38 delta.J Invest Dermatol. 2003; 120: 823-828
- Differential expression of peroxisome proliferator-activated receptor subtypes during the differentiation of human keratinocytes.J Invest Dermatol. 1998; 111: 1116-1121
- Activation of peroxisome proliferator-activated receptor-gamma reverses squamous metaplasia and induces transitional differentiation in normal human urothelial cells.Am J Pathol. 2004; 164: 1789-1798
- Peroxisome proliferator-activated receptor-gamma: from adipogenesis to carcinogenesis.J Mol Endocrinol. 2001; 27: 1-9
- Rosiglitazone and retinoic acid induce uncoupling protein-1 (UCP-1) in a p38 mitogen-activated protein kinase-dependent manner in fetal primary brown adipocytes.J Biol Chem. 2003; 278 (Epub 2002 October 31): 263-269
Published online: July 12, 2010
Accepted: October 26, 2007
Received in revised form: September 18, 2007
Received: June 12, 2007
© 2007 Japanese Society for Investigative Dermatology. Published by Elsevier Inc. All rights reserved.